PIM International June 2018 by Inovar Communications

Vol. 12 No. 2 JUNE 2018

FOR THE METAL, CERAMIC AND CARBIDE INJECTION MOULDING INDUSTRIES

in this issue The processing of 17-4 PH MIM in China: company visits HIP for MIM: cost calculations Published by Inovar Communications Ltd

www.pim-international.com

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Publisher & editorial offices

Inovar Communications Ltd 11 Park Plaza Battlefield Enterprise Park Shrewsbury SY1 3AF, United Kingdom Tel: +44 (0)1743 211991 Fax: +44 (0)1743 469909 Email: info@inovar-communications.com www.pim-international.com Managing Director and Editor Nick Williams Tel: +44 (0)1743 211993 nick@inovar-communications.com

For the metal, ceramic and carbide injection moulding industries

Publishing Director Paul Whittaker Tel: +44 (0)1743 211992 paul@inovar-communications.com Assistant Editor Emily-Jo Hopson Tel: +44 (0)1743 211994 emily-jo@inovar-communications.com Consulting Editors Prof Randall M German Former Professor of Mechanical Engineering, San Diego State University, USA Dr Yoshiyuki Kato Kato Professional Engineer Office, Yokohama, Japan Professor Dr Frank Petzoldt Deputy Director, Fraunhofer IFAM, Bremen, Germany Dr David Whittaker DWA Consulting, Wolverhampton, UK Bernard Williams Consultant, Shrewsbury, UK Production Hugo Ribeiro, Production Manager Tel: +44 (0)1743 211991 hugo@inovar-communications.com

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Jon Craxford, Advertising Director Tel: +44 (0) 207 1939 749, Fax: +44 (0) 1743 469909 jon@inovar-communications.com Subscriptions Powder Injection Moulding International is published on a quarterly basis as either a free digital publication or via a paid print subscription. The annual print subscription charge for four issues is £145.00 including shipping. Accuracy of contents Whilst every effort has been made to ensure the accuracy of the information in this publication, the publisher accepts no responsibility for errors or omissions or for any consequences arising there from. Inovar Communications Ltd cannot be held responsible for views or claims expressed by contributors or advertisers, which are not necessarily those of the publisher. Advertisements Although all advertising material is expected to conform to ethical standards, inclusion in this publication does not constitute a guarantee or endorsement of the quality or value of such product or of the claims made by its manufacturer. Reproduction, storage and usage Single photocopies of articles may be made for personal use in accordance with national copyright laws. All rights reserved. Except as outlined above, no part of this publication may be reproduced or transmitted in any form or by any means, electronic, photocopying or otherwise, without prior permission of the publisher and copyright owner. Printed by Cambrian Printers, Aberystwyth, United Kingdom ISSN 1753-1497 (print) ISSN 2055-6667 (online) Vol. 12. No. 2 June 2018 © 2018 Inovar Communications Ltd

If you remember only two technologies, they should be MIM and AM... As previously highlighted in PIM International, there has been a noticeable increase in the appearance of the term Metal Injection Moulding in the industrial and business media over the past year, thanks in large part to the high levels of interest in ‘MIM-like’ metal Additive Manufacturing processes. This is resulting in some much-deserved and long overdue exposure for the industry and the technology. One recent example highlighted in this issue’s industry news section is McKinsey & Company’s statement in its recent Factory of the Future report that, “...if you only remember two technologies from this paper, they should be Additive Manufacturing and Metal Injection Moulding”. That the report not only highlighted MIM’s potential but also its high level of manufacturing readiness presents an opportunity for the MIM industry to promote itself to a new generation of designers and engineers. For the first time, these young engineers are leaving higher education with an understanding that it is possible to manufacture high-performance components from metal powders. As they embrace the dynamic world of Additive Manufacturing, it is vital that they recognise MIM as, at the very least, an affiliated technology. Nick Williams, Managing Director & Editor

Cover image MIM CPU cooling fans

(Courtesy Shenzhen Shindy Technology Co., Ltd, China)

June 2018 Powder Injection Moulding International

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In this issue

MIM 17-4 PH Stainless Steel: Processing, properties and best practice

Shenzhen Shindy Technology: Rapid product development and high-volume production drive innovation

In the Metal Injection Moulding industry, 17-4 PH stainless steel is one of the most popular materials thanks to its combination of strength, hardness and corrosion resistance. As a result of its success in MIM, it is also attracting interest for use in the growing number of ‘MIM-like’ Additive Manufacturing processes, including binder jetting and feedstock extrusion. Despite the alloy’s popularity, there remain limited data on the final properties that can be expected, as well as data relating to dimensional control and the impact of Hot Isostatic Pressing. In this article, Prof Randall German highlights best practice in the debinding and sintering of 17-4 PH, as well as presenting in-depth analysis of published data.

Shenzhen Shindy Technology Co., Ltd. is one of a new generation of young, capable and fast-growing Chinese MIM producers. Within a decade, the company has joined the top-tier of global MIM producers and has ambitious plans for further expansion. Dr Georg Schlieper visited the company and reports exclusively for PIM International on the growth of MIM in Shenzhen, the current status of MIM technology at ShindyTech and the challenges of very high volume production.

Hot Isostatic Pressing: A cost calculation study for MIM parts

Hot Isostatic Pressing has become an important post-processing option for the Metal Injection Moulding industry. Whilst the majority of MIM components do not require HIPing in order to meet performance specifications, high-performance applications in the automotive and aerospace sector rely on HIP to remove residual porosity. The use of HIP is also common for aesthetic applications, where reduced porosity delivers improved polishability. Magnus Ahlfors and colleagues from Quintus Technologies AB present cost calculations for the HIP of a MIM turbocharger impeller, along with the pros and cons of purchasing a HIP system.

Shanghai Future High-tech: Research & development as a route to continued MIM growth

China’s emergence as a leading player in the world of Metal Injection Moulding demonstrates how a globally competitive industry can be built over a relatively short period of time with diligence, entrepreneurial skill and a receptive end-user market. Dr Georg Schlieper recently visited Shanghai Future High-tech Co., Ltd., one of China’s leading MIM manufacturers, and reports exclusively for PIM International about the importance of research partnerships, the company’s achievements to-date and its future ambitions.

Regular features 7

Industry news

101

Events guide

102

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June 2018 Powder Injection Moulding International

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Industry News

Industry News To submit news for inclusion in Powder Injection Moulding International please contact Nick Williams, nick@inovar-communications.com

McKinsey report places MIM in top ten ‘technologies of the future’

the technology was found to be mature and to have a high readiness for industrial application. 44% of the experts surveyed stated that AM would have a high impact on manufacturing over the next 0–5 years, but the manufacturing readiness and maturity of the technology was 9 9 significantly lower. Future Factory of the Future The report found that the impact of moving from Global management consulting firm McKinsey & traditional milling and die casting processes to MIM could Company, New York City, New York, USA, has highlighted result in significant cost savings, as in the case of Bosch Metal Injection Moulding as second in its top ten advanced India, which saved 80% on the cost of a fuel control gear manufacturing technologies in a report on advanced as a result of the reduced material waste and processing manufacturing and industry 4.0, Factory of the Future. time offered by MIM. The company is now said to produce Based on the McKinsey Advanced Manufacturing & three million units a year using the technology. Assembly survey, the report found that Metal Injection While the technology is not competitive for the producMoulding and Additive Manufacturing (AM) were consisttion of large parts, MIM was found to be an increasingly voted as the technologies thethis most If you only rememberently two technologies If you from only this remember paper, they two technologies should with be additive from paper,potential they should be additive manufacturing and metal injection manufacturing molding. and metal injection molding. acceptable choice for manufacturers for annual part to improve manufacturing across a broad span of volumes over 5,000, at unit weights under 200 g and for industries and areas. “If you only The importance of technologies varies The importance bygeographic industry: ofspray-on technologies circuit varies production by industry: holdsremember spray-on circuit production holds geometrically complex components. great potential for the electronics great industry, potential and composite for the electronics adhesive industry, bonding and remains composite adhesive bonding remains two technologies from this paper, they should be Additive a focus for aerospace and defense. a focus However, for aerospace additive manufacturing and defense. However, and metaladditive manufacturing and metal www.mckinsey.com Manufacturing and Metal Injection Moulding,” stated injection molding were consistently injection voted as molding the technologies were consistently with the voted mostas potential the technologies with the most potential to further improve manufacturing a broad improve span manufacturing of industriesacross and geographic a broad span of industries and geographic McKinseytoacross &further Company. areas (Exhibit 5). (Exhibit 5). In the areas survey, 21% of experts surveyed by the consultancy rated MIM as having a high or very high impact on manufacturing over the next 0–5 years, and Exhibit 5 Exhibit 5 Top 10 advanced manufacturingTop technologies 10 advanced manufacturing technologies

Low readiness High readiness

Rank Technology

Description Rank Technology Build up parts1from aAdditive powder or resin layer by layer manufacturing

Description Overall impact1

Maturity2

Overall impact1

Additive manufacturing

Metal injection Inject a metal 2powderMetal and ainjection binding Inject a metal powder and a binding molding agent into a mold molding agent into a21 mold

Composite adhesive bonding

3 Adhesive bonding of Composite 2 or more adhesive precured composite parts to avoid bonding bulky joints

Adhesive bonding of 2 or more 10 composite parts to avoid precured bulky joints

Carbon composites production

Solid 3-D structures 4 of Carbon lightweight carbon fibers bound in composites layers at high heat, pressure, production and vacuum

Solid 3-D structures of lightweight carbon 10fibers bound in layers at high heat, pressure, and vacuum

5 of metal Spray-on Spray a thin film of metal onto a Spray-on circuit Spray a thin film onto circuit a circuit9 board instead of the production circuit board instead production of the traditional print-and-etch technique traditional print-and-etch technique

Lead-free soldering

Using a solder6 containing no lead to Using a solder containing no lead to Lead-free meet new environmental regulations meet 9new environmental regulations soldering

Combination mill/turn machines

Cutting machines drill holes in Cutting machines that drill holes in 7 that Combination stationary parts, thenmill/turn create profiles stationary parts, then create profiles 8 by spinning the partsmachines by spinning the parts

Cold spraying

8 accelerated Cold spraying Powder particles by a compressed-gas jet to thin metal film on an object

Ultrasonic welding

9 ultrasonic Ultrasonic High-frequency acoustic High-frequency ultrasonic acoustic applied to work pieces to vibrations applied to welding work pieces to vibrations 7 create a solid-state weld create a solid-state weld

Capacitive measurement

10 sensors Capacitive Use capacitance to sense measurement the shape/quality of metal objects, even within packaging

Build up parts from a powder or resin layer by layer 44

Powder particles accelerated by a compressed-gas jet to thin metal 8 film on an object

Use capacitance sensors to sense the shape/quality of metal objects, 7 even within packaging

Maturity2 44

Precision Molds & Molding

The top ten advanced manufacturing technologies SOURCE: McKinsey Advanced Manufacturing & Assembly SOURCE: survey McKinsey Advanced Manufacturing & Assembly Manufacturing survey according to the McKinsey Advanced & Assembly survey (Courtesy McKinsey & Company)

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1 Percent of experts rating the technology as having 1 Percent high or of very experts high impact rating the on manufacturing technology as having over the high next or0very - 5 years high impact on manufacturing over the next 0 - 5 years 2 Derived from the Manufacturing Readiness Level 2 assessment Derived from the Manufacturing Readiness Level assessment

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Low readiness High readiness

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June 2018 Powder Injection Moulding International

Industry News

formnext 2018: Alliance MIM highlights opportunities for the industry Germany’s Mesago Messe Frankfurt GmbH is actively looking to add MIM technology to the scope of its formnext exhibition series, dedicated to the “next generation of manufacturing technologies.” The event series, one of Europe’s fastest-growing trade fairs, was launched in 2015 with a primary focus on industrial Additive Manufacturing. Within three years it has more than doubled in size, attracting over 20,000 visitors and covering nearly 30,000 m2 of exhibition floor space in 2017. The event’s international, industrial-focused audience includes a significant proportion of visitors who are seeking metal powder-based AM solutions, be they Powder Bed Fusion technologies or ‘MIM-like’ binder and extrusion-based systems. Jean-Claude Bihr, General Manager of French MIM producer Alliance MIM SA, attended formnext in 2017 and told PIM International that he immediately saw the potential overlaps for the MIM industry. Alliance is now confirmed as an exhibitor for 2018. Bihr stated, “From feedstock extrusion to binder jetting, MIM-like technologies are the answer to the long-standing barrier of tooling cost and development time. These processes are fast and very versatile and, except for the shaping method, they are metallurgically exactly like MIM, thus the name MIM-like. Alliance MIM is therefore developing these technologies – both in-house and in collaboration with equipment suppliers – in order to be able to deliver from one to one million parts, with the first parts in less a than a week.” Bihr added, “This is why we believe that MIM-like technologies are a door opener for MIM technology. MIM-like technologies make MIM flexible and fast, whilst MIM makes MIM-like technologies scalable. The perfect association! Unlike Powder Bed Fusion processes, MIMlike technologies can be a solution not only for prototyping or very small series. They are also for small production batches, perhaps up to 2,000 units. As such, they are an ideal way to develop a series part at lower cost, ensuring a smooth transition between early production step and full-scale production by MIM.” “Because MIM and MIM-like processes share the same densification mechanism in the same furnace run, what is qualified for MIM may also be qualified for MIM-like processes. The powder is the same, just the way to shape is different.” Whilst MIM powder suppliers are already wellrepresented at formnext, it is believed that there is much potential for MIM part producers to gain a greater degree of exposure by taking advantage of the appetite amongst visitors for advanced metal powder-based manufacturing processes. Inovar Communications Ltd will once again be promoting PIM International from its booth at formnext 2018, alongside its other titles, Metal AM and PM Review. www.alliance-mim.com | www.formnext.com

Powder Injection Moulding International

June 2018

Vol. 12 No. 2

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U.S.A and SOUTH AMERICA Mr. Tom Pelletiers tpelletiers@scmmetals.com EU Dr. Dieter Pyraseh Dieter.Pyrasch@thyssenkrupp.com

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June 2018

Vol. 12 No. 2

Industry News

Metal Powder Products renamed MPP following acquisition of NetShape Technologies Metal Powder Products LLC, headquartered in Westfield, Indiana, USA, will be renamed MPP as part of its efforts to integrate with the recently acquired Metal Injection Moulding specialist NetShape Technologies. The company has undergone a rebranding exercise, with the launch of a new logo and updated website. MPP provides customengineered Metal Injection Moulding and Powder Metallurgy solutions for industrial applications. It is said to be a key company in the innovation of material formulation, sintering, densification and PM joining techniques, and has nine production facilities in the USA and

China. “The combination of Metal Powder Products and NetShape Technologies creates a world class manufacturing company that will allow MPP to provide exceptional value for our customers with solutions that utilise innovative

custom-engineered products,” stated Dennis McKeen, CEO of MPP. At its facilities, MPP specialises in the production of various components, including customengineered gears and sprockets, complex structural parts, high strength aluminium parts and components requiring unique mechanical and physical properties for use in high stress, wear and magnetic applications. www.mppinnovation.com

MIM medical components produced at one of MPP’s Metal Injection Moulding facilities (Courtesy MPP)

• Ultra--ne particle sizes for complex parts. • Clean, consistent chemistries. • Several size ranges to meet customer requirements. • Wide range of powder alloys available.

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June 2018 Powder Injection Moulding International

Industry News

GKN Sinter Metals identifies market for Metal Injection Moulding in highprecision sensor systems

This threaded MIM sensor fitting is a complex, micro-precision component with a particularly delicate design, weighing only 15 g (Courtesy GKN Sinter Metals)

GKN Sinter Metals, Radevormwald, Germany, has identified a new market for Metal Injection Moulding in the production of high-pressure sensor systems. In an article published on the GKN Sinter Metals blog, Christoph Adler, the company’s MIM Sales Manager, introduced what is said to be the first MIM pressuretemperature sensor and explained the technology’s suitability for this application. As the automotive market’s demands on sensor system efficiency rapidly increase, individual sensors are becoming smaller, more complex and difficult to produce using conventional manufacturing methods. The MIM process provides manufacturing flexibility for more sophisticated sensor housings and components by delivering three-dimensional shape capability combined with the performance of alloy steels, stainless steels and high-temperature alloys. This means that MIM can help solve some of the product challenges of modern sensor systems. The first MIM sensor system component produced by GKN Sinter Metals is a

micro-precision threaded fitting with an exceptionally intricate design, weighing just 15 g. This fitting is part of a pressure-temperature sensor; a sensor housing made of stainless steel which records temperature and pressure data. This component is fixed directly to the measurement point by its thread and measures the temperature of coolant and exhaust gases as well as the fuel system pressure in common rail injection systems. This type of sensor is fitted in various areas of a vehicle, including the fuel supply and air conditioning system. It must be completely leak-proof and respond effectively in very small spaces. MIM was selected by GKN Sinter Metals and the customer after assessing the criteria necessary for the fitting’s design: an extremely thin wall thickness and an intricate design with narrow drill holes. A specific solution was developed by carrying out simulations and assessments of filling behaviour to produce an optimised design. It was found that to produce the optimised design using conventional manufacturing processes would

Powder Injection Moulding International

June 2018

have made it very difficult to produce as a single part, resulting in a work-intensive assembly process for multiple parts after manufacturing. GKN Sinter Metals stated that to manufacture the part by conventional methods would also have been highly expensive and time-consuming, and resulted in a lower surface quality and reduced precision compared to MIM. MIM was found to be “the ideal solution” for the production of this fitting, stated Adler. The resulting surfaces met the design requirements and could be mapped by the forming die, while efficient tool maintenance guaranteed an accurate contour and sufficient part quality. The final MIM product has a housing wall of only 0.4 mm between the medium to be measured (in this case coolant) and the sensor, guaranteeing optimum responsiveness. The thinner the wall between the medium and the sensor, the more accurately results will be measured. Adler added that, while the first such MIM sensor component produced was for the automotive market, MIM could challenge sensor systems in other areas, such as for industrial applications, especially where stainless steel is used. In addition, he stated that he sees a future for MIM sensor components in the food and chemical industries. “Sensor housings and components made of stainless steel are sterile and have high resistance to chemicals and other aggressive media,” he explained. “The stainless steel alloys we use are unaffected by these aggressive environments. Because of this, I see great future potential for new sensor applications in MIM in the food and chemical industries.” Concluding, he stated that MIM is suitable wherever high demands are made on sensors, such as where they are exposed to high temperatures, long-term mechanical resistance, aggressive media and germs, and where superior material properties are required. www.gkn.com

Vol. 12 No. 2

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June 2018 Powder Injection Moulding International

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Industry News

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Vol. 12 No. 2

Industry News

Sandvik reports strong start to 2018 with record operating profits Sweden’s Sandvik AB has reported a strong start to the year in its first quarter 2018 Interim Report. Order intake and revenues during the period improved organically yearon-year by 7% and 14% respectively, with positive development reported in all business areas. Operating proﬁt also rose by 22% year-on-year to 4,271 million SEK, with the operating margin said to be at 18.0%. “The year got off to a strong start with a broad-based increase in customer activity resulting in growth in orders and revenues as well as increased earnings and margins compared with the year-earlier period,” stated Björn Rosengren, CEO and President of Sandvik. “In addition, we made further progress

in relation to our active portfolio management. I am pleased with the performance of the Group.” Sandvik Materials Technology reported an organic increase of 13% in orders and, excluding the impact of the large order received in the year-earlier period, orders increased by 27%. Sandvik Machining Solutions reported organic order growth of 8%. In Sandvik Mining and Rock Technology, orders improved organically by 4%, from the high level in the year-earlier period. “Underlying demand improved in all business areas and geographical regions, yielding a book-to-bill of 107%. The strong growth in revenues supported operating proﬁt, which increased by 22% to a record-high level of 4.3 billion SEK.”

In the three major regions, Asia displayed the strongest momentum with growth of 19%, supported by a signiﬁcant increase in China. Europe improved by 6% with strong development across most countries. North America posted stable development with 0% growth. However order intake increased by 8%, excluding the major order received in the yearearlier period. During the quarter, Sandvik announced an investment of around 200 million SEK in a new plant for manufacturing titanium and nickel ﬁne metal powders in Sandvik Materials Technology. It was stated that the new plant will complement the company’s existing stainless-steel powder offering and thereby strengthen its position in the market for metal powder and metal Additive Manufacturing. www.sandvik.com

Atomising Systems appoints USA and Americas distributor for its metal powders

MPIF announces new association Presidents

Atomising Systems Ltd. (ASL), Sheffield, UK, has selected Steward Advanced Materials LLC (SAM), Chattanooga, Tennessee, USA, to represent and distribute its gas and water atomised powders in the USA and Americas. ASL’s gas atomised powders are used in many diverse fields including MIM, Additive Manufacturing, brazing and thermal spray. The company’s antisatellite system and hot gas technology reportedly allow the production of free-flowing spherical gas atomised powders with median particle sizes from less than 10 microns up to 250 microns. As well as the more standard types, ASL produces many bespoke stainless steel grades, along with various nickel and cobalt-based alloys. The company’s high-pressure water atomisers are capable of producing spherical and

The Metal Powder Industries Federation has announced that Rodney Brennen has been appointed President of the Powder Metallurgy Parts Association (PMPA) and Michael Stucky has been appointed President of the Metal Injection Molding Association (MIMA). Brennen, Metco Industries, Inc., St. Marys, Pennsylvania, is a current member of the PMPA Board of Directors and MPIF Finance Committee. Brennen has over thirty years in the PM industry and is a past member of the Board of Directors of APMI International. Michael Stucky, Norwood Injection Technologies LLC, Dayton, Ohio, is Chairman of the MIMA Standards Committee and current member of the MIMA Board of Directors and MPIF Technical Board. He served as co-chairman for MIM2017 and MIM2018 international conferences. www.mpif.org

nonspherical powders with D50s <10 µm to >500 µm. ASL is producing a range of powders for PM, filter applications and other industry sectors. Also available is a versatile water atomising system with a 30 kg batch size, which produces powder for dental, precious metal and specialised trial production lots. Steward Advanced Materials LLC. was founded in 2002 as a division of Steward, Inc., a company which has been family-owned for 130 years. It provides highly engineered speciality metallic and ceramic materials for the global energy, industrial and consumer markets. According to ASL, it expects that SAM will be an ideal partner for the company and its portfolio of stainless steel and alloyed powders. www.atomising.co.uk www.stewardmaterials.com

June 2018 Powder Injection Moulding International

Industry News

Bosch diesel technology to drastically cut NOx emissions New developments from Germany’s Bosch Group could enable vehicle manufacturers to drastically reduce emissions of nitrogen oxides (NOx), resulting in levels up to ten times lower than those scheduled to come into force from 2020. Even in real driving emissions (RDE) testing, emissions from vehicles equipped with the new Bosch diesel technology are reported to be significantly below current limits of 168 milligrams of NOx per kilometre, resulting in as little as 13 milligrams of NOx. “There’s a future for diesel. Today, we want to put a stop, once and for all, to the debate about the demise of diesel technology,” stated Bosch CEO Dr Volkmar Denner, speaking at the company’s annual press conference. Bosch engineers are said to have achieved this breakthrough with a combination of advanced fuel-injection technology, a newly developed air management system and intelligent temperature management. As the measures to reduce NOx emissions do not significantly impact consumption, the diesel retains its comparative advantage in terms of fuel economy, CO2 emissions, and therefore climate-friendliness. “Bosch is pushing the boundaries of

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Bosch has tested its diesel technology in a full range of driving conditions and reports results of as little as 13 milligrams of NOx per km

what is technically feasible,” Denner added. “Equipped with the latest Bosch technology, diesel vehicles will be classed as low-emission vehicles and yet remain affordable.” MIM components are widely used in the current generation of automotive fuel injection systems. Since 2017, European legislation has required that new passenger car models tested according to an RDEcompliant mix of urban, extra-urban and freeway cycles emit no more than 168 milligrams of NOx per kilometre. As of 2020, this limit will be cut to 120 milligrams. It was reported that even when driving in particularly challenging urban conditions, where test parameters are well in excess of legal requirements, the average emissions of the Bosch test vehicles are as low as 40 milligrams per kilometre. Even with this technological advance, the diesel engine has not yet reached its full development potential, the company stated. Bosch now aims to use artificial intelligence to build on these latest advances, resulting in the development of a combustion engine that – with the exception of CO2 – has virtually no impact on the ambient air. “We firmly believe that the diesel engine will continue to play an important role in the options for future mobility. Until electromobility breaks through to the mass market, we will still need these highly efficient combustion engines,” Denner added. The CEO’s ambitious target for Bosch engineers is the development of a new generation of diesel and gasoline engines that produce no significant particulate or NOx emissions. Denner wants future combustion engines to be responsible for no more than one microgram of NOx per cubic metre of ambient air – the equivalent of one-fortieth, or 2.5%, of today’s limit of 40 micrograms per m3. www.bosch.com

June 2018

Vol. 12 No. 2

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Industry News

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The PM Technology and Business Forum, sponsored by the China PM Business website, has experienced significant growth over the past decade. In 2017, the conference drew five-hundred attendees, becoming the largest annual Powder Metallurgy and Metal Injection Moulding conference in China. The 2018 event will be held from June 21-23 in Yangzhou New Century Hotel in Yangzhou, Jiangsu Province, China, and is expected to attract a large number of PM and MIM parts and equipment manufacturers. Discussions during the event will focus on industry

trends including the development of hybrid and electric vehicles and their impact on the PM industry, fine control of manufacturing process costs for PM parts, automatic analysis of the whole PM production process and shortcuts and advice for those in the press and sinter PM industry looking to enter the MIM/ PIM industry. Technical sessions will also be held during the forum, with a number of industry experts invited to discuss and provide solutions on a range of production problems. www.fmyj.org www.pmbiz.com.cn

GKN shareholders vote to accept Melrose takeover Melrose Industries plc has succeeded in its takeover of GKN plc after receiving the support of GKN’s shareholders. The deal values GKN at £8.1 billion, and in an announcement published on March 29, Melrose stated it had received 52.4% of the vote. “We are delighted and grateful to have received support from GKN shareholders for our plan to create a UK industrial powerhouse with a market capitalisation of over £10 billion and a tremendous future,” stated Christopher Miller, Chairman of Melrose. “We are looking forward to working with GKN’s talented workforce and to delivering for customers and all stakeholders. Melrose has made commitments as to investment in R&D, skills and people and we are very excited about putting these into action.”

Following an initial proposal from Melrose to acquire GKN in January 2018, both companies had launched campaigns to convince GKN shareholders of their respective plans for the group, with both parties looking to sell the Powder Metallurgy business, which includes one of Europe’s largest Metal Injection Moulding operations. “Let me assure you that GKN is entering into very good hands,” added Miller. “We would like to thank our shareholders for their continued support of the Melrose strategy thus far. We are full of enthusiasm as we begin this next stage of the Melrose story and look forward to creating substantial value for our shareholders, old and new.” www.gkn.com www.melroseplc.net

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Powder Injection Moulding International

June 2018

Vol. 12 No. 2

Industry News

Metal powder specialist Carpenter Technology reveals senior leadership changes Carpenter Technology Corporation, USA, has announced senior operating leadership changes within the organisation. The company announced that Joe Haniford, CEO, will assume a new role as Vice President, Business Management Office and Global Advanced Engineering, as well the leadership of Environmental, Health and Safety. In his new role, Haniford will be focused on the “continued implementation of the Carpenter Operating Model and lean manufacturing principles across the company’s facilities.” This transition is said to be in-line with the strategic plan initiated when Haniford joined Carpenter in July 2015.

In addition, Mike Murtagh will be appointed Vice President and Group President of Carpenter’s Specialty Alloys Operations (SAO). Murtagh previously served as Carpenter’s Chief Technology Officer, a role which the company will now look to fill. Both leadership changes will be effective July 1, 2018. Tony Thene, President and CEO of Carpenter, stated, “Over the last three years, we have executed a concerted transformational strategy to strengthen our long-term growth profile and these organisational changes are consistent with our leadership transition plan. Joe has been an invaluable contributor to our success in elevating Carpenter through establishing manufacturing

and safety disciplines that have become the foundation of the Carpenter operating model.” “We thank him for his many contributions as Chief Operating Officer and I am pleased that Joe will continue to be part of the team,” he continued. “He will focus primarily on the further implementation of the Carpenter operating model across our facilities as we know we are still in the early stages of its execution.” Speaking on Murtagh’s new appointment, he added, “Since joining Carpenter as the Chief Technology Officer, Mike has demonstrated strong technical and manufacturing operations expertise and has played an important role in our continued transition to becoming an irreplaceable supply chain partner for our customers. Given Mike’s background, I believe he is the ideal candidate to assume the manufacturing and business responsibilities of our SAO segment.” www.cartech.com

INNOVATION THAT OPENS UP NEW PATHS. It’s our passion for details that makes USD Powder GmbH your reliable partner. From assistance in design and development to the selection of production techniques – we combine high-tech with German craftsmanship. iPowder® - our brand that stands for unique gas-water combined atomized metal powders enables you to produce small and big sized parts with complex shapes. As part of our portfolio we have developed austenitic and ferritic stainless steel, low and high alloy steel, nickel, cobalt and copper alloys as well as magnetic material. Visit us: www.usdpowder.de

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June 2018 Powder Injection Moulding International

Industry News

New air classifier helps optimise metal powder particle size distribution Blue Power Casting Systems GmbH, Walzbachtal, Germany, has introduced a new version of its AC 1000 air classifier for metal powders. The AC 1000 has been specially developed for the economic and flexible separation of small powder batches into fine and coarse fractions, especially those in the <25 μm range, where conventional screening methods no longer work. The company states that it is suited for use in research and development as well as for demanding PIM and AM projects with special requirements for particle size distribution. Specifically designed for small powder quantities and for frequent changes of alloys or desired particle sizes, the company stated that the development focus of the system was on simple handling, precisely controllable classification, high process stability and above all the fastest, safest cleaning possible to avoid metal losses and cross contamination by powder residues. Air flow has been optimised to be able to define the size distribution even more precisely and a central layout

of the operating touch screen, optimal accessibility of the components and simplified cleaning has improved the ergonomics of the system. The turbine unit can now be selectively raised by means of an integrated crane with pulley and cleaned of powder residues. Blue Power Casting The AC 1000 air classifier from Systems stated Blue Power Casting Systems the most significant advances are the optionally available or GS versions. The AC 1000 G enables separation under a protective gas atmosphere, greatly reducing potential oxidation in reactive metals. In addition, the GS version is explosion-proof version and can be used to safely process explosive metals such as aluminium, magnesium, zirconium or titanium alloys. www.bluepower-casting.com

Makin Metal Powders appoints Magnum Metals its North American sales agent

See us at 206 Booth 304 Call us for more informations at Tel.: +7 8313 26 62 10 +7 831 200 34 34 E-mail: ktnv@sintez-pm.com Fax: +7 8313 25 08 13 Web: www.sintez-cip.ru

Powder Injection Moulding International

Makin Metal Powders (UK) Ltd., Rochdale, UK, has appointed Magnum Metals, Nettleton, Mississippi, USA, as its North American sales agent. Magnum’s Barry Anshutz is said to have a long track record in the metal powder industry, having previously served as Vice President of Sales for Makin’s former sister company, United States Bronze Powders, Inc. Steve Ellis, Director of Supply Chain Operations at Makin, stated, “Magnum Metals has a first-class team and I am delighted they have agreed to represent us in the North American region. We look forward to working alongside them, utilising their significant market knowledge and excellent relationships, in order to offer our customers enhanced service and responsiveness whilst making the products and expertise of Makin even more accessible in this growing and important market.” Makin Metal Powders manufactures copper powder, bronze powder, tin powder, infiltrants and press-ready pre-mix powders along with other related alloys from its purpose-built 10,000m2 production facility in Rochdale, UK, and is part of China’s GRINM family of companies. www.makin-metals.com www.magnum-metals.net

June 2018

Vol. 12 No. 2

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Vol. 12 No. 2 ÂŠ 2018 Inovar Communications Ltd

June 2018 Powder Injection Moulding International

Industry News

MIM2018 conference concludes with record attendance and strong interest from the AM industry MIM2018, the International Conference on Injection Molding of Metals, Ceramics and Carbides, this year held in Irvine, California, March 5-7, concluded with record-breaking attendance. The yearly conference is organised by North America’s Metal Powder Industries Federation (MPIF), which stated that this year’s event saw the previous attendance record broken by over 15%, with over 180 attendees representing 104 companies from sixteen countries. Notable was a very high level of interest from professionals from the Additive Manufacturing industry.

The technical conference was launched with a keynote address by Benedikt Blitz, SMR Premium, who highlighted the recent developments in the world of remelted steels. In addition to technical sessions, thirty companies showcased their products and services during a tabletop exhibit, sponsored by PIM International, on Tuesday, March 6. Twenty-four exhibitors also provided ‘infomercials’ for their companies intermittently throughout the event. Following the successful launch of a student grant program at MIM2017, the Metal Injection Molding Association again provided seven students with a grant to attend

Dr David Whittaker to receive 2018 Ivor Jenkins Medal The UK’s Institute of Materials, Minerals and Mining (IOM3) has named Dr David Whittaker, CEng, FIMMM, as recipient of its 2018 Ivor Jenkins Medal. The prestigious award is presented to individuals in recognition of a significant contribution that has enhanced the scientific, industrial or technological understanding of materials processing or component production using Powder Metallurgy and particulate materials. Dr Whittaker has over 34 years’ experience in Powder Metallurgy technology, with a career split between industrial research and development and independent technical consultancy. In both roles, he has established international recognition for his high level of expertise. In the field of industrial research and development, Dr Whittaker has led world-leading PM product and process development programmes at the level of Technical Director for GKN Powder Metallurgy Division

and at T&N/Federal-Mogul. These programmes have included the design and development of press/sinter PM automotive connecting rods (a world first), process development for surface-densified PM transmission gears, variable valve timing system development and the development of assembled camshafts with powder metal lobes. As a consultant, he has pursued a wide range of assignments for a broad customer base, including

MIM2018 and make a technical presentation. Grant recipients were given the opportunity to attend the presentations, network with professionals in the field and gain exposure to the MIM industry. Each also provided a presentation on work underway at their universities. Prior to the conference, Rand German, Professor Emeritus of San Diego State University, presented his Powder Injection Molding tutorial to fifty students, a 30% increase over last year’s tutorial. According to the MPIF, the attendance breakdown this year consisted of 23% equipment & service providers, 17% powder & feedstock suppliers, 14% end users/consumers, 35% parts manufacturers and 11% other. MIM2019 will be held in Orlando, Florida, February 25–27, 2019. www.mimaweb.org

those in industry, trade associations, government and European Union organisations and academia. Dr Whittaker has written for leading technical journals and publications around the world, and since 2007 has served as Consulting Editor to Powder Injection Moulding International, Powder Metallurgy Review and Metal Additive Manufacturing magazines. He has been active with IOM3 as a member of the Powder Metallurgy Committee (1984 – 1990) and of the Particulate Engineering Committee (since 2010). www.iom3.org

Dr David Whittaker has been named as recipient of the 2018 Ivor Jenkins Medal

Powder Injection Moulding International

June 2018

Vol. 12 No. 2

So small. So strong. So fine. Delivering high strength and low agglomeration, our ultra-fine titanium powder is ideal for injection mold applications. Creating consistently high-quality parts always begins with exceptional source material. AP&C’s premium titanium powder is the result of our proprietary Advanced Plasma Atomization (APA) process that ensures highly spherical particles for exceptional mold filling and high-density final parts. And for MIM component production, that makes our titanium powder better than fine. It’s exceptional.

June 2018 Powder Injection Moulding International

Industry News

HyGear signs deal to supply major Powder Metallurgy company with hydrogen HyGear, Arnhem, the Netherlands, a supplier of industrial gases through on-site generation technology, has announced the signing of a longterm supply contract for industrial hydrogen to a leading global metallurgy company. The company will use the hydrogen in its largescale sintering process. Pure hydrogen gas is often used as an effective atmosphere for high-temperature sintering of metal powders. Hydrogen helps to maximise corrosion resistance, reducing surface oxides and removing impurities from various alloys. HyGear will install its widelyapplied Hy.GEN technology to deliver the base-line supply by generating hydrogen at the customer’s site. In

addition, its growing trailer fleet will be deployed to guarantee supply flexibility in cases of temporary demand increase. This set up offers the most cost-effective and reliable hydrogen supply for this critical application. “The signing of this contract helps us strengthen our presence in the metal industry, which is our third growing market after the flat glass and food industries. Although our technologies are not limited to certain industrial applications, we feel that our industry-focused roll out strategy leads to better understanding of our customers’ needs. It also allows us to tailor our solutions in such a way that we will always offer the most cost-effective

Hydrogen generation systems are installed at the customer’s site (Courtesy HyGear)

and reliable overall solution,” stated Niels Lanser, HyGear’s Director of Sales and Marketing “We are also performing research and development works to further reduce costs by recycling the gases used in the process. We are currently implementing this technology in the glass industry and our next step is to develop products dedicated to the metal industry as well,” added Lanser. www.hygear.com

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Powder Injection Moulding International

June 2018

Vol. 12 No. 2

Global Advanced Metals to manufacture tantalum powders for AM & MIM Global Advanced Metals Pty Ltd (GAM), a producer of tantalum products, has commissioned a Tekna TEKSPHERO plasma spheroidisation system for installation at its facility in Boyertown, Pennsylvania, USA. The equipment is part of a new process development facility for the manufacture of spherical tantalum and other refractory metal powders for Additive Manufacturing and Metal Injection Moulding. The TEKSPHERO equipment produces spherical powders from a variety of tantalum feed materials. Particle sizes range from 10–100 µm, in narrow or broad particle size distributions. Standard oxygen content is in the range of 600–1000 ppm, but low-oxygen (< 250 ppm) powders remain an option. Andrew O’Donovan, Chief Executive Officer, Global Advanced Metals, stated, “Our new process development facility enables us to create spherical tantalum powders that can be used for the 3D printing of prototypes and commercial parts. The ability to rapidly prototype and produce complex tantalum parts via AM offers designers new materials choices for applications in military, aerospace, medical and other demanding industries.” GAM is said to be the world’s only fully integrated tantalum supplier and has exclusive rights to the world’s largest industrial resources of tantalum ore, located in Western Australia. The company produces tantalum powders and other metallurgical products at its Pennsylvania, USA, and Aizu, Japan, plants for a range of industries. www.globaladvancedmetals. com

Industry News

Tiangong to increase PM tool production China’s Tiangong International Co., Ltd., Jiangsu, is reportedly planning to produce 5,000 tons of PM tool steels annually, as the domestic market continues to show rapid growth. According to the Chinese website Steelclik, the annual demand for Powder Metallurgy tool steel in China

UNILOG B8 Control Unit

is around 500 tons, growing at a rate of 30% to 40% per year. Currently, China is said to rely heavily on imports from producers in the US, Japan, Sweden and Russia. Tiangong’s investment in related equipment will see a first phase production of around 2,000 tons, rising to 5,000 tons per year. Established in 1981, the company manufactures a wide range of high speed steels, die steels and cutting tools. www.tiangong-tools.com

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June 2018 Powder Injection Moulding International

Industry News

Bohler-Uddeholm becomes Voestalpine High Performance Metals

AMG reports positive Q1 2018, highlights PM furnaces for aerospace applications

Bohler-Uddeholm Corporation, USA, has been rebranded as Voestalpine High Performance Metals Corporation. According to Voestalpine, the decision was taken to reflect the ownership structure of the company which has been in place since 2007 when Voestalpine AG acquired Bohler-Uddeholm AG. The name change was said to align the US brand globally with each of its sister companies. Voestalpine AG owns a number of global brands alongside Bohler-Uddeholm, including Eifeler and ASSAB. Voestalpine’s High Performance Metals Division is a global leader for tool steel and a leading provider of high-speed steel, valve steel and other products made of special steels, as well as powder materials, nickel-based alloys and titanium. It is focused on producing and processing high-performance materials and customerspecific services including heat treatment, high-tech surface treatments and Additive Manufacturing processes. Voestalpine AG added that Eifeler Coatings Technology will be rebranded as Voestalpine Eifeler Coatings in the coming months. www.voestalpine.com | www.bucorp.com

AMG Advanced Metallurgical Group N.V. has reported first quarter 2018 revenue of $308.4 million, a 20% increase from $258 million in the first quarter 2017. EBITDA for the first quarter 2018 was $44.5 million, a 35% increase from $33 million in the first quarter 2017. Net income attributable to shareholders increased 18% to $18.4 million in the first quarter 2018 from $15.6 million in the first quarter 2017. AMG Engineering, which operates under the ALD Vacuum Technologies brand, achieved EBITDA of $7.4 million during the first quarter 2018, a slight increase from $7.3 million in the first quarter 2017. AMG Engineering signed $104.8 million in new orders during the first quarter 2018, representing a 1.74x book to bill ratio, driven by strong orders of turbine blade coating and Powder Metallurgy furnaces for the aerospace market, heat treatment furnaces for the automotive market and induction heated quartz tube (IWQ) furnaces for fibre optic applications. Order backlog was $255.8 million as of March 31, 2018, an increase of 24% compared to December 31, 2017. AMG Critical Materials generated EBITDA of $37.1 million during the first quarter 2018, an increase of 44% from $25.7 million in the first quarter of 2017, thanks to strong financial performance in vanadium, silicon, titanium alloys, graphite, chrome and aluminium, driven by higher vanadium and silicon metal prices and strong sales volumes. Dr. Heinz Schimmelbusch, Chairman of the Management Board and CEO, stated “AMG achieved a considerable improvement in profitability during the quarter, driven by improved pricing and higher sales volumes in AMG Critical Materials. In addition, continuing strong demand for our industry leading vacuum furnace solutions resulted in the highest quarterly order intake in ten years and the highest order backlog in over nine years.” In the first quarter of 2018, AMG generated cash from operating activities of $24.8 million, an increase of $7 million compared to the same period in 2017. As a result of the strong cashflow generation, AMG’s net debt decreased by $0.9 million in the first quarter of 2018, despite capital expenditures of $22.6 million during the period. In summary, the Company is operating at record levels. www.amg-nv.com

PolyMIM GmbH is a manufacturer that offers two different binder systems for metal injection molding: • polyPOM – our catalytic binder system • polyMIM – our water soluble binder system These two binder systems have excellent characteristics during the production process and combine attractive prices with worldwide availability. Our portfolio includes products for mass production for the telecommunication and automotive industries as well as the high-end sector with our special alloys. Please be informed that PolyMIM is participating from 14 th to 18th of October at the Euro PM2018 in Bilbao, Spain. You’re Welcome to visit us at our exhibition booth #98 PolyMIM GmbH Am Gefach 55566 Bad Sobernheim, Germany Phone: +49 6751 85769-0 Fax: +49 6751 85769-5300 Mail: info@polymim.com

www.polymim.com

Powder Injection Moulding International

June 2018

Vol. 12 No. 2

Visit ExOne at IMTS in Chicago, IL from September 10 - 15, 2018 Booth 432308 (West Hall)

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June 2018 Powder Injection Moulding International

Industry News

Arcast launches VersaMelt inert gas atomiser, wins Lawrence Livermore contract Arcast, Oxford, Maine, USA, has launched a new metal powder atomiser designed for use at small companies and research establishments. The VersaMelt inert gas atomiser is reportedly capable of processing a number of metal alloy systems from a single atomiser platform. The system incorporates a multi-configurable melt chamber to allow conventional melting in a ceramic induction crucible, rod feed induction drip melting, tube feed cold crucible arc/plasma melting, and tilt-and-pour cold crucible arc/plasma melting. This is expected to enable it to accommodate a wide range of complex alloys, from tin to tungsten. Arcast stated that the atomiser is capable of producing ceramicfree titanium (or similar metal) using scrap or recycled powder as feedstock, with a nominal batch capacity of up to 3 kg (steel equivalent) per cycle and multiple cycles possible in a day. The unit is priced for the budgets of small companies and research establishments and has reportedly been designed as a tool for organisations contemplating

BorgWarner inaugurates new turbocharger production facility in Thailand

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Powder Injection Moulding International

entering the AM market. In line with this aim, it is designed to occupy minimal space (less than 4 x 4 x 4 m) and to consume as little water, gas and electricity as possible. Arcast has also been awarded a contract to supply a gas atomisation system for the production of fine, spherical, reactive metal powders to Lawrence Livermore National Security, LLC (LLNS) on behalf of the Department of Energy National Nuclear Security Administration (DOE/NNSA) and the the Lawrence Livermore National Laboratory (LLNL). This is a specialised system for handling a wide range of challenging metals and alloys that are of interest to the national laboratory and other government agencies. “We are very proud to have been chosen for this work and making a contribution to our country’s capabilities in these challenging areas of science,” stated Arcast. “We believe it was Arcast’s unique approach to handling reactive metals and our good value proposal that persuaded LLNS to choose us to supply this equipment.” Arcast states that it has installed a number of research machines in major public research and educational institutions globally, as well as in corporate laboratories. www.arcastinc.com

BorgWarner Inc., headquartered in Michigan, USA, has inaugurated a new manufacturing facility for its turbochargers in Rayong, Thailand. The 6,500 m2 facility is designed to meet increasing demand for turbocharging technologies in the Southeast Asian market. Robin Kendrick, President and General Manager, BorgWarner Turbo Systems, stated, “Thailand is a very important production base for Asian automakers and offers an excellent business environment. Many leading automakers have production facilities in Thailand. With our new facility in Rayong we serve them with localised manufacturing to meet their thriving demand while strengthening our leadership position.” Using the experience gained in its other production plants, the latest BorgWarner facility is said to have been designed following lean production principles, making the flow of people and materials along the production line clear and efficient. Production will takes place in a clean environment with an over-pressurised and air-conditioned airlock-enclosed shop floor to keep out any particles which might interfere with production processes. www.borgwarner.com

June 2018

Vol. 12 No. 2

Vol. 12 No. 2 ÂŠ 2018 Inovar Communications Ltd

June 2018 Powder Injection Moulding International

Industry News

ARC Group Worldwide posts improved Q3 sales, announces new CEO ARC Group Worldwide, Inc., Deland, Florida, USA, a leading global provider of advanced manufacturing solutions including Metal Injection Moulding and metal Additive Manufacturing, has reported its results for the period ending April 1, 2018, its fiscal third quarter 2018. Fiscal third quarter 2018 revenue from continuing operations was $21.5 million, compared to $18.4 million in the prior sequential period. The increase in revenue was primarily driven by MIM and plastics sales from customers in the aerospace, medical, firearm and defence markets. Separately, the company’s international performance continues to improve with revenues from its Hungarian MIM operations increasing 7.9% sequentially to $2.3 million. Gross profit from continuing operations was $1.1 million in the

Executive Officer, Drew M Kelley. Quasha stated, “While we still have a long way to go, we are making great progress. During our fiscal third quarter, we have seen a marked improvement over our prior quarter. Management’s focus on repositioning our sales team, cost reductions and inventory efficiency efforts all have begun to show meaningful positive impacts. At the same time, we have begun to see some of our key, strategic customers in the defence and firearm industry return to more normal levels of demand.” “Despite the improving conditions both internally and externally, management remains focused on returning the company to profitability and improving cash flow generation by driving existing product revenue, increasing operational efficiency and rightsizing the balance sheet. We expect to see continued progress over the coming quarters,” added Quasha. www.arcgroupworldwide.com

fiscal third quarter, compared to $0.4 million in the previous sequential quarter. The aforementioned revenue growth, along with ongoing cost reduction initiatives, were the primary drivers of gross profit improvement. This improvement was achieved despite expenses of $1.3 million incurred due to planned, ongoing inventory reductions, primarily in ARC’s Colorado MIM operation. EBITDA from continuing operations was $1.3 million in the fiscal third quarter compared to $0.2 million in the prior sequential quarter. EBITDA was positively impacted by increased revenues and lower costs. ARC also announced that Alan Quasha, Chairman of the Board of Directors of ARC, will assume the dual roles of Chairman and Chief Executive Officer with immediate effect, replacing the Interim Chief

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Powder Injection Moulding International

June 2018

Photo Arburg GmbH & Co KG

Vol. 12 No. 2

Industry News

Eisenmann opens new sales and service office in Japan German plant engineering specialist Eisenmann is set to establish a new presence in Japan with the opening of a sales and service office in Yokohama, Kanagawa Prefecture. This new opening underlines the company’s strategic goal of international growth and takes the total number of Eisenmann sites to twenty-six across fifteen countries. The Yokohama office will reportedly focus on building and strengthening Eisenmann’s business relationships with Japanese vehicle manufacturers and automotive component suppliers. Japanese OEMs account for approximately 30% of the global market for vehicles under six metric tons and have manufacturing facilities in many countries worldwide. However, capital expenditure decisions are significantly influenced by their corporate headquarters.

As Jeffrey Bowers, General Manager of Eisenmann Japan, explains, “The new office in Yokohama puts us in close geographical proximity to our local customers and allows us to engage more effectively with them. Japanese auto companies traditionally prefer to cooperate with locally based suppliers, but also pay close attention to quality and costeffectiveness. As a result, they are increasingly interested in innovative technologies from other countries.”

Eisenmann manufactures a range of furnaces for PM and MIM applications. The company’s rollertype furnaces offer high-temperature sintering in multiple zones with temperatures of up to 1350°C, atmosphere separation and precise setting of the temperature profile. Very low dew points are said to permit dependable sintering of alloying elements with a high oxygen affinity such as chromium, manganese or vanadium. An integrated rapid cooling module permits sinter-hardening of new PM steels with tight dimensional tolerances. www.eisenmann.com

Schematic of a furnace produced by Eisenmann (Courtesy Eisenmann)

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June 2018 Powder Injection Moulding International

Industry News

PyroGenesis receives ISO 9001:2008 certification for metal powder production PyroGenesis Canada Inc., Montreal, Canada, reports that it has received certification for the production of metal powders under a quality management system which complies with the requirements of ISO 9001:2008. This certification is an amendment to the company’s existing

ISO certification, and pertains specifically to metal powder production. It was received under the auspices of independent risk and standards company SAI Global. P Peter Pascali, President and CEO of PyroGenesis, stated, “As we all know, having an ISO certification

PM Tooling System The EROWA PM Tooling System is the standard interface of the press tools between the toolshop and the powder press machine. Its unrivalled resetting time also enables you to produce small series profitably. www.erowa.com

2018 RMET E D W PO Texas o nio, t n A San 018 7-20, 2 June 1

Powder Injection Moulding International

confirms that our management systems, manufacturing processes, and documentation procedures have met all the requirements for standardisation, quality assurance, traceability, and batch to batch consistency. This gives prospective customers assurances that our house is in order. In addition, such efficient quality management systems will ultimately save time and money, as well as improve efficiencies.” “We have found that many of our customers will only do business with vendors that are certified as ISO 9001 compliant,” he added, “and many requests for quotes are from companies that make ISO 9001 certification a ‘must-have.’ We are also in the process of applying to AS9100D for the aerospace industry, and ISO 13485 for the medical devices industry. In short, having this certification gives potential customers the additional confidence to accept PyroGenesis as a qualified vendor.” With its extensive plasma expertise, PyroGenesis is able to convert many metals and alloys into high-purity spherical powders, as its plasma torches use argon gas and the reactor is backfilled with argon. This ensures that the powders produced are not exposed to any oxygen during the production process and as a result, PyroGenesis is able to produce powders with extra low interstitial (ELI) such as Ti 6Al-4V ELI. The company’s standard offering includes commercially pure titanium (CPTi), grades 1, 2, and 3, and Ti 6Al-4V, grades 5 and 23. www.pyrogenesis.com

Submitting news... To submit news to PIM International please contact Nick Williams: nick@inovar-communications.com

June 2018

Vol. 12 No. 2

Industry News

Quintus establishes new application centre at its Swedish headquarters Quintus Technologies has opened a new Quintus application centre at its headquarters in Västerås, Sweden. Supported by a team of specialists, customers will have access to a range of equipment with the aim of developing production processes and methods to optimise productivity. In addition to meeting and training facilities, the centre is equipped with a Quintus Hot Isostatic Press (HIP). With typical pressures from 1,035 to 2,070 bar (15,000 to 30,000 psi) and temperatures up to 2,000°C (4,000°F), HIP can achieve 100% of maximum theoretical density and improve the ductility and fatigue resistance of critical, high-performance materials. The

centre also has a Fluid Cell Press, with an additional Deep Draw Press scheduled later this year, for sheet metal forming applications. At the application centre the Quintus team, together with the customer, can perform pre-studies, validate, simulate and verify processes and materials. Quintus also arranges technical seminars and can provide the training needed to implement new solutions and products. As an additional service, Quintus can offer material testing together with an external partner to evaluate the chemical composition, microstructure, porosity, mechanical properties and fatigue properties of the tested samples. www.quintustechnologies.com

The Quintus application center in Västerås, Sweden, will allow customers and partners to verify processes and materials before fullscale production

At the application centre, Quintus will also arrange technical seminars and can provide the training needed to implement new solutions and products

June 2018 Powder Injection Moulding International

Industry News

Toyota to phase out passenger car diesel engines in Europe in 2018 At an executive press meeting on the eve of the Geneva Motor Show, Switzerland, Toyota Motor Europe (TME) revealed that it will phase out all diesel engines from its range of European passenger cars in 2018. The company stated it will, however, continue to offer diesel engines in its Hilux, Proace and Land Cruiser models to meet customer demand. In 2017, Toyota stated that hybrid electric vehicle (HEV)’s represented 41% of TME’s total sales, an increase of 38% year-on-year to 406,000 units. In contrast, Toyota’s diesel mix on passenger cars was reported to be less than 10% in the same year. Johan van Zyl, President and CEO of Toyota Motor Europe, commented, “Toyota has been pioneering Hybrid Electric Vehicle technology for more than twenty years. For several years,

pim international 2016-09.pdf

HEV versions have been the dominant powertrain where offered. In our latest new model, the Toyota C-HR, HEVs accounted for 78% of sales last year.” During the presentation, Toyota shared the next step of its European powertrain strategy, introducing the new Auris model, to be built at Toyota Manufacturing UK’s Burnaston factory from next year. This range will be offered with a choice of three powertrains, including a 1.2 litre petrol engine and two HEV systems. “As part of our electrified vehicle strategy, we are progressively expanding our HEV offering with a second, more powerful 2.0l engine,” continued van Zyl. “Starting with the new generation Auris, this expanded HEV line-up is a natural reaction to our passenger car customers’ demands.”

The new Toyota Auris, which made its world debut at the 2018 Geneva Motor Show (Courtesy Toyota Motor Europe)

In February 2018, Toyota Motor Group reported sales of 1.52 million vehicles with electrified drivetrains globally in 2017, an increase of 8% over the previous year’s electric vehicle (EV) sales, putting the company three years ahead of the target it set in October 2015 to sell 1.5 million EVs in the year 2020. www.toyota-europe.com

30/08/2016

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Powder Injection Moulding International

June 2018

Sales Agent in Europe Burkard Metallpulververtrieb GmbH Tel. +49(0)5403 3219041 E-mail: burkard@bmv-burkard.com

Vol. 12 No. 2

Arburg plans 18,000 m2 capacity expansion with new assembly hall Arburg, Lossburg, Germany, states that it will expand its production capacity by 18,000 m2 with the construction of a new assembly hall, just two years after completing construction on its most recently opened production facility in 2016. Assembly Hall 23 is the planned result of what the company states is a ‘large two-digit-million-Euro’ investment, and is scheduled to begin construction in 2019 for completion in 2020. Michael Hehl, Arburg Managing Partner, commented, “At the international press conference held during our Technology Days in mid-March, I was already saying that while we here at Arburg have certainly built on many occasions, and a fair amount at that – we have never before engaged in quite as much construction work, nor progressed with it quite as vigorously as we have over the last five years.” The company stated that its investment in a new assembly hall is the result of a consistently performing global economy and the growing importance of delivering machines to customers on schedule and in the desired quantities. “We wish to sell even more of our machines as global demand for them rises, and we are seeking to manufacture them even more quickly,” Hehl concluded. www.arburg.com

Industry News

EPMA’s 31st General Assembly The European Powder Metallurgy Association’s 31st General Assembly, took place in Brussels, Belgium, March 22-23. The two-day event included Board, Council and Committee meetings, as well as EuroMIM, EuroPress&Sinter and EuroHIP meetings. Two keynote presentations were provided by Guy Thiran, Director General of

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Eurometaux on the topic of ‘Legislation and Lobbying’, and Sigrid de Vries, Secretary General of CLEPA (European Association of Automotive Suppliers) on the subject of ‘The Future of the Automotive Supply Industry’. The presentation by de Vries reviewed the state of the automotive industry and highlighted future threats and opportunities that lie ahead for the Powder Metallurgy supply chain sector. www.epma.com

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Industry News

International Symposium on Novel and Nano Materials heads to Lisbon The 15th International Symposium on Novel and Nano Materials (ISNNM) is set to take place in Lisbon, Portugal, July 1-6, 2018. Organised by the Korean Powder Metallurgy Institute, the event will include three days of conference sessions followed by technical tours and panel discussions. ISNNM will focus on nanomaterials research and includes sessions on: • Advanced Materials Processing • Novel Functional Materials

ISNNM 2018 will take place at the Tivoli Oriente Hotel in Lisbon, Portugal

• Advanced Powder Metallurgy • Mechanical Alloying • MIM & Additive Manufacturing • Nanocomposites & Nanoporous Materials • Energy Materials • Rare Earth & Recycling • Refractory Metals & Hard Materials • Characterisation & Modelling. All main aspects of the materials will be covered, including synthesis,

mechanism, microstructures, properties and applications. The symposium will provide the latest research results and a state-ofthe-art overview of technology in the rapidly evolving field of nanomaterials. Symposium sessions will also include invited lectures from internationally distinguished scientists discussing topics ranging from the most recently discovered materials to the latest production processes. www.isnnm.org

Isostatic Toll Services increases HIP capacity Isostatic Toll Services (ITS) has commissioned a new HIP system at its site in Olive Branch, Mississippi, USA. The new HIP system is reported to reach temperatures up to 1260°C and pressures up to 138 MPa. The company recently passed its NADCAP AC7102/6 audit re-certification for Hot Isostatic Pressing and is certified to ISO 9001 (Aerospace), ISO AS9100C (Aerospace) and ISO 13485 (Medical). It is also reported to have passed exhaustive on-site quality audits by MTU Aero Engines and Rolls Royce. “This exciting expansion has increased our maximum pressure from 15,000 to 20,000 psi while increasing our production capacity,” stated Braden Fleak, General Manager at Isostatic Toll Services. “All our HIP systems are dedicated to meeting the industry’s high standards for quality” www.isostatictollservices.com

Rickinson to retire from UK’s Institute of Materials Dr Bernie Rickinson, Chief Executive of the UK’s Institute of Materials, Minerals and Mining (IOM3), has announced he will retire from his role with the Institute at the end of 2018. As yet no successor has been announced, but IOM3 confirmed that recruitment consultants have been engaged. Rickinson became Chief Executive in 1997 and has since guided the organisation to its current position as a major UK engineering institution whose activities encompass the whole materials cycle, from exploration and extraction, through characterisation, processing, forming, finishing and application, to product recycling and land reuse.

IOM3 was formed from the merger of the Institute of Materials and the Institution of Mining and Metallurgy in June 2002. It merged with the Institute of Packaging (2006) and the Institute of Clay Technology (2006). In the Summer of 2009, the Institute reached an agreement with the Institute of Wood Science to transfer all its members and activities to IOM3. In November 2010, IOM3 also embraced the activities and membership of the Institute of Vitreous Enamellers. Commenting on his retirement, Rickinson advised that with the organisation’s 150th anniversary set for 2019, it will be important for a new Chief Executive to take full advantage of the opportunity for

Dr Bernie Rickinson, Chief Executive of the UK’s Institute of Materials (Courtesy IOM3) community visibility during the series of anniversary events planned by the Institute. IOM3 stated that it would like to “sincerely thank Bernie for his outstanding contribution to the Institute and to the engineering community throughout his twenty years of service.” www.iom3.org

June 2018 Powder Injection Moulding International

Industry News

Toyota develops neodymium reduced-rare earth magnet for electric motors Toyota Motor Corporation, Toyota City, Japan, has developed what it states is the world’s first neodymium-reduced, heat-resistant magnet. Neodymium (Nd) magnets are used in a variety of motors, including high-output motors found in electrified vehicles, and there is increasing interest in manufacturing them by the Metal Injection Moulding process. According to Toyota, the new magnet uses significantly less of the rare-earth element neodymium and can be used in high-temperature conditions. It is important that magnets used in automotive motors and other applications have high coercivity even at high temperatures. For this reason, approximately 30% of the elements used in magnets are rare earths. The rare earths terbium (Tb) and dysprosium (Dy) are generally added to Nd magnets to increase high-temperature coercivity. However, these metals are rare and expensive and are found in high-geopolitical risk locations. Because of this, Toyota stated that it has made considerable efforts to develop magnets that do not use these metals – the newly developed magnet is said to use no Tb or Dy at all. Although production volumes of neodymium are relatively high among rare earths, there are concerns that shortages will develop as electrified vehicles, including hybrid and battery electric vehicles, become increasingly popular. Therefore, a portion of the Nd in the magnet has also been replaced with lanthanum (La) and cerium (Ce), said to be lower-cost rare earths. According to Toyota, merely reducing the Nd and replacing it with La and Ce results in a decline in motor performance; as a result, the company states that it has adopted new technologies to suppress the deterioration of coercivity and heat resistance and developed a magnet with levels of heat resistance equivalent to typical Nd magnets,

while reducing the amount of Nd used by up to 50%. This new type of magnet is expected to be useful in expanding the use of electric motors in areas such as automobiles and robotics, as well as maintaining a balance between the supply and demand of valuable rare earth resources. Toyota stated that it plans to work on further enhancing the performance of the magnets and evaluate their application in products, while accelerating the development of mass production technologies. According to Toyota, its new Nd-reduced magnet is able to maintain coercivity even at high temperatures thanks to the combination of three new technologies: Grain refinement of magnet Toyota stated that it is now possible to retain high coercivity at high temperatures through the reduction of the size of the magnet grains to 10% or less of those found in conventional Nd magnets and an enlargement of the grain boundary area. Two-layered high-performance grain surface In a conventional Nd magnet, neodymium is spread evenly within the grains of the magnet and, in many cases, Toyota stated that the neodymium used is more than the necessary amount to maintain coercivity. Thus, it is possible to use Nd more efficiently by increasing the neodymium concentration on the surface of the magnet grains, which is necessary to increase coercivity,

and decreasing the concentration in the grain core. This results in the reduction of the overall amount of neodymium used in the new magnet. Specific ratio of lanthanum and cerium If neodymium is simply alloyed with lanthanum and cerium, its performance properties (heat resistance and coercivity) decline substantially, complicating the use of light rare earths. After evaluating various alloys, Toyota stated that it discovered a specific ratio at which La and Ce can be alloyed so that the deterioration of properties is suppressed. Toyota stated that the continued development of elemental technologies for motors, inverters, batteries and other components will require steady research and development and that it sees these technologies as essential for the increased adoption of electrified vehicles. This new magnet is expected to be put into use in electric power steering motors for automobiles and other applications in the first half of the 2020s. The company believes that it will have a wide range of applications in motors that require relatively high output, such as those required for electrified vehicle drive motors and generators, robots and various household appliances, as well as helping to reduce the risks posed by potential disruptions in rare earth supplies and price increases. Going forward, the company reported that it will proceed with further practical applications in mind, perform application assessments in motor vehicles and continue researching and developing technologies with the aim of achieving low-cost, stable production. www.toyota-global.com

Submitting news... To submit news to PIM International please contact Nick Williams: nick@inovar-communications.com

Powder Injection Moulding International

June 2018

Vol. 12 No. 2

Reinvent how you manufacture with RenAM 500Q

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For more information visit www.renishaw.com/renam500q

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June 2018 Powder Injection Moulding International

Time to rethink your components with MIM? STRONG ER, BETTER, FASTER,...

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Powder Injection Moulding International

June 2018

Vol. 12 No. 2

Industry News

Advances in the sintering of MIM magnesium alloys Martin Wolff and research colleagues at the Institute of Materials Research, Helmholtz-Zentrum Geesthacht, Germany, along with research colleagues at the University of Applied Sciences, Flensburg, and the Helmut Schmidt University, Hamburg, have been investigating the potential of Metal Injection Moulding to produce biomedical components such as screws, nails and bone plates from magnesium alloys, as well as for commercial 3C applications. They have also found that the Mg alloy feedstock developed for MIM can be used to produce filament for Fused Filament Fabrication (FFF), a process for the Additive Manufacturing of metals that is attracting increasing interest. In a paper presented at TMS 2018 – 147th Annual Meeting of The Minerals, Metals and Materials Society held in Phoenix, Arizona, March 11-15, 2018, the researchers reported on their most recent work to improve the full process chain for the MIM manufacture of Mg-alloys. This involved the production and testing of demonstrator parts for two new Mg alloys based on (1) Mg-2.6Nd-1.3Gd-0.5Zr-0.3Zn alloy powder, referred to as EZK400 and produced by gas atomisation and (2) Mg-8Al-1Zn alloy powder, referred to as AZ81. Feedstock for MIM was prepared using a binder based on polypropylene, stearic acid and paraffin wax, which was blended with the Mg alloy powders in a planetary mixer at 160°C. Tensile test and demonstrator specimens were injection moulded at up to 1500 bar, 65°C mould temperature and 135°C feedstock temperature. Solvent debinding of stearic acid and organic wax was done in hexane at 45°C for 10-15 h, followed by thermal debinding of the polymer backbone binder, which was done in Ar+5% H2 in a combination debinding and sintering furnace. Sintering time was set to 64 h, 32 h, 16 h, 8 h, 3 h and 1 h, which corresponds

to previous studies on sintering of Mg-Ca alloys. In order to optimise sintering of the new Mg alloys, the researchers avoided any additional oxygen pick-up by handling the powder and moulded specimens in a glove box under a protective argon atmosphere. Because it is well known that the binder systems used in MIM can influence the sintering performance, and hence the mechanical properties, of the Mg alloys, the researchers first undertook tests on sintering of binder-free Mg alloy compacts produced by conventional powder compaction. A sintering temperature of 635°C was selected for the EZK400 Mg alloy powder and a pure irregular coarse Mg powder was used as a getter material inside the crucible of the sintering furnace, which is the state of the art to aid sintering of Mg alloys. The powder compacts were sintered for different times and, because the EZK400 alloy is sintered with a permanent liquid phase, it was established that sintering time could be significantly reduced from the 64 h normally used in former experiments for Mg alloys. Results were given for mechanical

properties achieved for the pressed and sintered (P+S) samples at 1 h, 3h and 16 h at a fixed temperature of 635°C (Fig. 1). At 1 h, the EZK400 alloy was not fully consolidated and had a residual porosity of ca 7%, which resulted in low elongation of ca 1.1% and a UTS of 124 ±6 MPa. At 16 h sintering time, the UTS increased to 188 ±5 MPa and the elongation to 5.8%. Significant improvements were also seen for sintering at an economic time of 3 h, which resulted in a UTS of 166 ±4 MPa and elongation of 4.4%. Sintering of the EZK400 for 64 h resulted in low porosity (0.7%) in the sintered material. The researchers decided that, because sintering time can influence densification of the Mg alloy in a linear behaviour, they would also select a second set of parameters to try and optimise the sintering regime. Here the time was fixed at 3 h and the temperature was varied between 635°C and 643°C. The result was a significant improvement in mechanical properties when using the shorter sintering time of 3 h (Fig. 2). UTS of 188 ±4 MPa at 5 ±1% of elongation at fracture and 122 ±6 MPa yield strength were achieved. Additionally, it was found that sintering could be performed without the need for the Mg getter E Modulus Yield strength Ultimate tensile strength

MPa GPa

200 150

properties=f(TS)

100 50 0 635/1

635/3

Elongation at fracture 7 % 6 5 4 3 2 1 0 635/16

Process Parameter

Fig. 1 Mechanical properties of tensile test specimens produced by P+S, using a fixed sintering temperature of 635°C and varying sintering time. (Paper by M Wolff, et al, ‘Metal Injection Molding (MIM) of Mg-Alloys’. Published in: TMS 2018 - 147th Annual Meeting & Exhibition Supplemental Proceedings, pp 239-251, February 2018, Springer, Cham.)

June 2018 Powder Injection Moulding International

Industry News

E Modulus Yield strength Ultimate tensile strength MPa GPa

200

Elongation at fracture 7 % 6 5

properties=f(TS)

150

100

3 2 1

50 0

635/3

639/3

643/3

643/3_no.G

Process Parameter

Fig. 2 Mechanical properties of tensile test specimens produced by P+S, using a fixed sintering time of 3 h and various sintering temperatures. (Paper by M Wolff, et al, ‘Metal Injection Molding (MIM) of Mg-Alloys’. Published in: TMS 2018 - 147th Annual Meeting & Exhibition Supplemental Proceedings, pp 239-251, February 2018, Springer, Cham.)

material. The fast sintering time for the EZK400 Mg alloy was explained by the permanent rare earth rich liquid phase during sintering, which may help to reduce the MgO layer on the powder particles in accordance with the relationship of Gibbs free energy of oxide formation. However, analysis of the particle surface by XPS, IR-spectroscopy or µ-XRF, in combination with DSC and XRD-analyses, needs to be done in future research. The findings for the sintering of P+S EZK400 Mg alloy were then compared with results obtained for

demonstrator and dogbone shape tensile test parts produced by MIM. In comparison with P+S, the MIM parts exhibited significant shrinkage under the same conditions and yielded a smooth, silvery surface. MIM tensile test specimens gave a UTS of 164 MPa, yield strength of 123 MPa and elongation of 3.4%. The difference in UTS and elongation between the sintered MIM and P+S samples was said to be caused by the formation of additional secondary phases in the near grain boundary region.

These phases are assumed to be carbides, formed during thermal debinding of the brown part. Further work is needed to identify these phases and how they can be avoided during thermal debinding. Thermal debinding could also be done using a hydrogen atmosphere and even better mechanical properties could be achieved if a T4 solid solution and T6 ageing heat treatment was used to induce a homogeneous distribution of the new carbide phase in the microstructure. The researchers also found that the AZ81 Mg alloy powder could be successfully injection moulded and sintered. achieving a residual porosity of 4.4%. Tensile test MIM specimens revealed UTS of 240 ±6 MPa, yield strength of 118 ±2 MPa and elongation of 5.1 ±0.6%. The authors concluded that MIM processing of the new Mg alloys using only a 3 h sintering cycle can achieve economic and SF6-free production of small size complex shaped components. Sulphur hexafluoride (SF6) is a protective gas commonly used in the casting and forging industry and is said to be a 22,800 times more active climate changer than CO2. Hence the use of SF6 will be prohibited in foundries in the near future. www.hzg.de www.hs-flensburg.de www.hsu-hh.de

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June 2018

Vol. 12 No. 2

Vol. 12 No. 2 ÂŠ 2018 Inovar Communications Ltd

Industry News

June 2018 Powder Injection Moulding International

Industry News

Optimising the PIM processing of high performance titanium alloy by numerical simulation Whilst Powder Injection Moulding of Ti alloys is similar to the injection moulding of other metal or ceramic powders, much more attention needs to be paid to controlling processing parameters in order to produce defect-free high-performance parts. Numerical simulation can be a powerful tool to aid optimisation of PIM processing conditions, but reliable simulation also requires accurate characterisation of the PIM feedstock. For example, little work has been reported on simulations for Ti-PIM, especially in the area of systematically characterising material properties such as rheological and thermal properties for Ti alloy feedstock, which can be used in numerical simulations. A Korean research team from Pohang University of Science & Technology, Korean Aerospace University and CetaTech Inc., has been undertaking work on both experimental and numerical analysis of the PIM of Ti-6Al-4V powder alloys with the specific aim of systematically obtaining the required rheological and thermal properties data. The results of their most recent work was published in the online edition of the Journal of the Minerals, Metals and Materials Society (JOM), February 26, 2018 [1]. The authors stated in their paper that spherical prealloyed Ti-6Al-4V powder having a medium particle size (D50) of 24.5 µm was mixed with a binder consisting of paraffin wax, polypropylene, polyethylene and stearic acid. Previous work had been published by the authors on the optimisation of the powder and binder system [2]. Solid loading in the feedstock was 67 vol.% and mixing was done three times at 160°C using a twin-screw extruder allowing high shear mixing to produce a homogeneous feedstock.

The number of mixing operations was determined by observing the fluctuation of the viscosity of the feedstock at a specific shear rate using a plate-to-plate rheometer after each mixing. The material properties of the prepared feedstock such as viscosity, specific heat, thermal conductivity, pressure–volume– temperature (PVT) relation and no-flow temperature were then measured in sequence using a standard testing method for each material property. The obtained data could then be used to perform accurate injection moulding simulations. It was reported that a relationship was established between the shear rate and viscosity of the feedstock at the temperatures of 140°C, 160°C and 180°C, which showed that the feedstock had good flowability at the three temperatures. The density at the injection temperature and the typical injection pressure were used as input parameters in injection moulding filling simulation. The thermal properties of the feedstock were also characterised experimentally with the specific heat of the feedstock measured at temperatures ranging from 20°C to 180°C using differential scanning calorimetry experiments. Three peaks were found at 42°C, 56°C and 90°C, representing the melting points of the binder components in the feedstock. The thermal conductivity of the PIM Ti alloy feedstock at different temperatures (150°C, 165°C and 180°C) was measured using a line-sourced method. The PIM feedstock was found to have thermal conductivity values at these temperatures of ca 3.1 W/m K, 2.0 W/m K and 1.9 W/m K, respectively. The researchers compared the results for numerical simulation

Powder Injection Moulding International

June 2018

for the PIM filling stage with experimental production of shorttest tensile test specimens using an injection moulding temperature of 165°C, mould temperature of 50°C and moulding pressure of 61 MPa. Two-step debinding of the green PIM Ti alloy parts was followed by sintering in vacuum at 1250°C for 2 h and finally HIPing at 930°C and 100 MPa for 2 h to enhance density and improve mechanical properties. After HIPing, a density of 99.84% was achieved, with tensile strength of 973 MPa, yield strength of 902 MPa and 16% elongation. The authors attributed the increased mechanical properties to the relatively high solid loading, defect-free moulded samples and the carefully optimised debinding and densification conditions. The oxygen and carbon contents in the final sinter-HIPed part were 0.20% and 0.09%, respectively, which are quite low values for PIM Ti alloy parts. They concluded that results for simulation of filling showed good agreement with experimental results, demonstrating the accuracy of the characterised feedstock properties and the validity of the numerical models. www.postech.ac.kr www.kau.ac.kr www.cetatech.com

[1] ‘Experimental and Numerical Analysis of Injection Molding of Ti-6Al-4V Powders for High Performance Titanium parts’ by D. Lin, et al, the Journal of the Minerals, Metals and Materials Society (JOM), 26 February, 2018. Supplementary information to this article has been included in the on-line version including debinding conditions. [2] ‘Preparation of Ti-6Al-4V feedstock for titanium powder injection molding’ by D. Lin et al. Journal of Mechanical Science and Technology Vol. 30, No. 4, April 2016, pp 1859–1864.

Vol. 12 No. 2

U.S. Metal Powders, Inc. A M PA L | P O U D R E S H E R M I L L O N

Advanced Engineered Aluminum Powders

Shaping the Future Together United States Metal Powders, Inc. has been a global leader in the production and distribution of metal powders since 1918. Together with our partners and subsidiary companies, AMPAL and POUDRES HERMILLON, we are helping to shape the future of the metal injection molding industry (MIM). Dedicated Research, Leading Edge Technology, Global Production & Customization • Aluminum alloy powders • Nodular and spherical aluminum powders • Aluminum based premix powders

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June 2018 Powder Injection Moulding International A M PA L | P O U D R E S

HERMILLON

Industry News

Optimising feedstock for low pressure injection moulding of cemented carbide Low Pressure Powder Injection Moulding (LPIM) has been used for a number of years to produce tungsten carbide-cobalt (WC-Co) based parts having complex geometry and small section thickness with good surface finish, such as cutting tools and blades, drills, router bits, etc. A collaborative research project underway between the Department of Materials Engineering at the Science and Research Branch, Islamic Azad University in Tehran, Iran, and the Department of Mechanical and Materials Engineering at the Universiti Kebangsaan in Selangor, Malaysia, has been focusing on the use of low pressure PIM to produce micro precision parts, such as dentistry drills using submicron WC-Co

powders. The most recent results from the project were presented in a paper at the 6th International Conference on Powder Metallurgy for Automotive Parts (PM Auto 2018) held in Isfahan, Iran, April 16-18, 2018. Abdolali Fayyaz and co-authors Norhamidi Muhamad and Abu Bakar Sulong reported that a submicron WC-10Co-0.8VC powder composition was used, with vanadium carbide (VC) added as a grain growth inhibitor. This type of powder is normally used to produce precision drills with high surface quality for the dental sector. Particle size analysis using a Malvern Zetasizer nano zs gave an average particle size distribution in the powder of D50 = 0.67 µm. The submicron

carbide powder exhibited an irregular and angular shape, which increases viscosity of the feedstock compared with the spherical shaped powder normally used in MIM, and the powder was slightly agglomerated, which impacts on achieving an acceptable level of powder loading for PIM processing. In a previous report on experimental work in this research project, the authors showed that adequate powder loading in feedstock for PIM could be achieved by de-agglomerating the WC powder using ball milling. The WC-10Co-0.8VC powder was mixed with a binder, based on 65 wt.% paraffin wax, 30 wt.% polyethylene (PE) and 5 wt.% stearic acid, with powder loadings tested at 49 vol.%, 50 vol.% and 51 vol.%. The authors stated that the critical step of feedstock preparation was done by kneading the WC-Co-VC powder and binder mixture in a twin-screw Babender mixer with a mixing temperature

www.lidemimpowder.com Ms. Vivian Song Mob/Whatsapp:+86 13290511818 Email:lidepowder@gmail.com

Lide Powder Material MIM Powder: 304L 316L 17-4ph F75 D10:2-4um D50:8-11um D90:21-24um

Powder Injection Moulding International

June 2018

Vol. 12 No. 2

45 40 35 30 Torque (Nm)

of 140°C. This is above the highest melting temperature (125°C) and lower than the lowest decomposition temperature (165°C) of the selected binder components. Fig. 1 shows the variation of torque as a function of mixing time for the different powder loadings in the feedstock. The figure also shows that the torque becomes stable in a short time, demonstrating that uniform mixing can be achieved even with lower solid loading. Fig. 2 shows that the WC-Co-VC carbide powder particles are coated by the binder achieving a homogeneous final feedstock. The success of injection moulding green parts is highly dependent on the flow behaviour of the feedstock mixture and the binder system should provide sufficiently low viscosity to guarantee the complete filling of the mould cavity. The flow behaviour of different powder-binder feedstock mixtures was tested using a Shimadzu Capillary Rheometer. The authors studied the variations in viscosity at injection moulding temperatures of 90, 100 and 110°C for the three different powder loadings. For low pressure injection moulding the viscosity of feedstock at the moulding temperature is put in the range of 15-40 Pa.s. They found that the viscosity of the feedstock with a solid loading of 51 vol.% is high (82 PA.s) at low temperature (90°C), but that the viscosity of feedstock with 49 vol.% and 50 vol.% solid loading showed lower sensitivity to moulding temperature, making them more suitable for low pressure injection moulding of green parts without any defects even at the lower temperature of 90°C. Contact: a.fayyaz@srbiau.ac.ir, abdolali.fayyaz@gmail.com

Industry News

25 20

50 vol.%

10 5

49 vol.% 0 0:00:00 0:02:53 0:05:46 0:08:38 0:11:31 0:14:24 0:17:17 0:20:10 0:23:02 Time (HH:MM:SS)

Fig. 1 Torque variation vs mixing time of feedstock preparations containing different solid loadings of WC-Co-VC. (From paper by A Fayyaz, et al, presented at the 6th International Conference on Powder Metallurgy for Automotive Parts (PM Auto 2018), Isfahan, April 16-18, 2018)

1 μm

The 6th International Conference on Powder Metallurgy for Automotive Parts - PM Auto 2018 was jointly organised by Mashhad Powder Metallurgy Company, Sadjad University of Technology and the Technical University Vienna.

51 vol.%

EHT = 3.00kV WD = 4.9 mm

Signal A = SE2 Mag = 5.00 K X

Fig. 2 FESEM image of WC-10Co-0.8VC/paraffin wax based binder feedstock. (From paper by A Fayyaz, et al, presented at the 6th International Conference on Powder Metallurgy for Automotive Parts (PM Auto 2018), Isfahan, April 16-18, 2018)

June 2018 Powder Injection Moulding International

ALL ROADS LEAD TO ELNIK. Elnik Systems has been leading the ﬁeld of Batch Debinding and Sintering equipment since entry in the mid 1990’s. Our innovation keeps us at the cutting edge with products that work due to extensive in house testing. We also service our equipment with a well-trained and energetic service team. This dedication and excellence in customer service allows Elnik to be the only partner you will ever need for the MIM and Metal Additive manufacturing process.

MIM 17-4 PH stainless steel

MIM 17-4 PH Stainless Steel: Processing, properties and best practice In the Metal Injection Moulding industry, 17-4 PH stainless steel is one of the most popular materials thanks to its combination of strength, hardness and corrosion resistance. As a result of its success in MIM, it is also attracting interest for use in the growing number of ‘MIM-like’ Additive Manufacturing processes, including binder jetting and feedstock extrusion. Despite the alloy’s popularity, there remain limited data on the final properties that can be expected, as well as data relating to dimensional control and the impact of Hot Isostatic Pressing. In the following article, Prof Randall German highlights best practice in the debinding and sintering of 17-4 PH, as well as presenting in-depth analysis of published data.

Sintering is a means to fabricate complex, high-performance stainless steel components from powders via injection moulding, die compaction, binder jetting, paste extrusion and other binder-assisted routes. The sintering behaviour of 17-4 PH stainless steel depends on particle size, peak temperature, heating rate, atmosphere and hold time. Complications arise from alloy composition variations and retained carbon and oxygen. Some binders add carbon during burnout and some powders carry a high oxygen content. Carbon from the powder or binder, oxygen from the powder or atmosphere and nitrogen from the process atmosphere influence the microstructural phases, sintering behaviour and final properties. Carbon and nitrogen stabilise the face-centred cubic austenite phase, slowing sintering. On the other hand, body-centred cubic deltaferrite increases the sintering rate. Martensite forms on cooling from the sintering temperature and precipitation reactions induce a high hardness

and strength. However, retained delta-ferrite reduces strength. An added difficulty comes from the segregation of alloying ingredients during sintering, leading to heterogeneous microstructures with reduced properties. Doping additions, such as boron, reduce the sintering temperature and improve properties. Manipulation of densification and phases leads to competitive properties. However, in spite of good strength and hardness, impact toughness is low. Considerable data are collected on how 17-4 PH stainless steel sinters and typical mechanical sintered and heat treated properties, with comments on corrosion, wear and biocompatibility.

An introduction to 17-4 PH Stainless steels are ferrous alloys containing at least 12 wt.% chromium. They arose in the early 1900s, with the first patents in the 1910-1919 time frame. These alloys are categorised according to their main phase; austenitic, ferritic, martensitic and semi-austenitic. Some of the alloys are responsive to precipitation hardening. The precipitation hardened martensitic stainless steels range from 12 to 17 wt.% chromium, 4 to 8 wt.% nickel, and 0 to 4 wt.% copper, with possible additions of molybdenum, silicon, manganese, titanium and niobium. Of these, 17-4 PH is a popular variant, consisting of iron

Nb + Ta

Wrought

15.5

4.5

3.5

0.5

0.4

0.3

0.04

Powder

16.5

4.0

1 max

0.3

0.07 max

Table 1 Nominal composition for wrought and powder alloys in wt.% (allowed Cr, Ni, and Cu variations are ± 1 wt.%)

June 2018 Powder Injection Moulding International

MIM 17-4 PH stainless steel

Fig. 1 Scanning electron micrographs of (a) spherical gas atomised and (b) ligamental water atomised powders. The larger particles are nominally 20 µm in diameter

alloyed as outlined in Table 1 [1, 2]. This alloy also carries identifications such as UNS S17400, AISI 630, ASTM A564, MIM-17-4PH and AMS 5643. The compositional specifications do not include oxygen. However, oxygen is a significant factor in sintered products. A powder has a high initial surface area coated with oxides. Accordingly, the initial oxygen level varies with the powder production process. These oxides remove chromium from its corrosion inhibition role. High oxygen levels result in low mechanical properties and poor corrosion resistance [3, 4]. Indeed, isolation of the oxygen role in

temperature varies around 1405°C and the liquidus temperature is near 1440°C. Because of precipitation hardening, the mechanical properties are sensitive to heat treatment. The full density elastic modulus is from 196 to 204 GPa [5]. Depending on heat treatment, the hardness reaches 43 HRC, with a yield strength from 760 to 1240 MPa, tensile strength from 1000 to 1340 MPa and fracture elongation between 8 and 14%. This high hardness makes die compaction difficult, but binder-assisted compaction, as well as injection moulding, feedstock extrusion and binder jetting and related ideas, are successful.

“Applications for 17-4 PH arise from the combination of strength, hardness and corrosion resistance.” sintered 17-4 PH stainless steel is an area requiring further study. Applications for 17-4 PH arise from the combination of strength, hardness and corrosion resistance. It is not the best stainless steel in any of these categories, but, after heat treatment, the property combination is attractive for aerospace, medical, dental, nuclear and consumer products. Depending on the composition (due to the allowed variations in Fe, Ni, Cu and Cr), the solidus

Due to fluctuations in alloy composition and microstructural phases, the theoretical density and properties change accordingly. Density for wrought material is 7.66 to 8.00 g/cm3. For powder, the average pycnometer density is 7.77 g/cm3. In the as-sintered condition, the average theoretical density is 7.74 g/ cm3 but varies with delta-ferrite content. The density increases slightly with hardening heat treatments, progressively reaching 7.86 g/cm3 at

Powder Injection Moulding International

June 2018

maximum hardness. These changes reflect differences in atomic size and lattice packing associated with the different crystalline phases. High temperature neutron diffraction during sintering identifies lattice constants of 0.35833 nm and 0.28583 nm for the face-centred cubic and body-centred cubic phases, corresponding to densities of 7.80 and 7.68 g/cm3 [6]. Most studies on sintered 17-4 PH ignore these density shifts. For this report, the pycnometer value measured in each study is used to calculate fractional density or porosity, or, where not reported, the theoretical density is assumed to be 7.80 g/cm3.

Binder and debinding effects Many binder systems can be used for shaping stainless steel powders [7-40]. Injection moulding and extrusion binders commonly rely on 60% filler, 30% backbone and 10% surfactant. Paraffin wax is a common filler phase, but polyethylene glycol and polyoxymethylene are also widely used. Backbone polymers are more varied, but favour polypropylene, polyethylene, ethylene vinyl acetate, or polymethyl methacrylate. Stearic acid is the most common surfactant/ lubricant/plasticiser, but palm oil, beeswax, glycerin and similar waxy or oily molecules are also in use. Binder ingredients that produce a

Vol. 12 No. 2

carbon residue, such as cellulose or polystyrene, are generally avoided, since carbon has profound effects on sintering and sintered properties. Generally, simple, small and inexpensive binder ingredients are most successful. Additive Manufacturing relies on these same binders for extrusion, but also takes on variants such as sucrose, acrylic, latex, starch or other polymers sprayed onto the powder bed during the build process. Debinding has some influence on properties, especially if the final oxygen or carbon levels are increased. The common first stage debinding routes are depolymerisation or solvent extraction. For example, paraffin wax dissolves in heptane and polyethylene glycol dissolves in hot water [41]. Catalytic extraction of polyoxymethylene uses fuming nitric acid in the first stage of debinding [42, 43]. Subsequently, the remaining backbone binder is extracted by pyrolysis during heating to the sintering temperature. Comparative tests with different binders show that 10% sintered property loss occurs in systems retaining more oxygen (0.23% oxygen versus 0.02% oxygen) [19]. Moreover, corrosion resistance is degraded by residual oxygen [4]. Thermal debinding is often performed in hydrogen or hydrogennitrogen, but lower temperature air burnout is successful [17, 44]. Optimal binder removal incorporates holds during heating at 600 and 1000°C, using hydrogen [45]. If water atomised powder is added to gas atomised powder, the increase in oxygen from the water atomised powder helps to reduce residual carbon. The oxides react with carbon to form CO or CO2 vapour. Likewise, graphite additions, in roughly equal mass to the starting oxygen content, are effective in oxygen removal during sintering. For example, in MIM, starting with 0.2% O and 0.01% C results in 8% delta-ferrite, 0.03% oxygen and 0.015% C. Otherwise, residual carbon stabilises austenite during sintering, resulting in slower sintering; however, with typical hold times at the peak temperature, the slower sintering rate becomes meaningless [46-48].

MIM 17-4 PH stainless steel

Powder characteristics Three powder approaches are applied to sintered 17-4 PH stainless steel; prealloy powder, mixed powder and master alloy powder. Prealloyed implies that each particle is a microcasting with the same composition. Mixed powder implies a combination of iron, chromium, nickel and other particles, each being a single element [49]. Master alloy is a hybrid where small carbonyl iron powder is mixed with 33% alloy powder. The alloy powder has concentrated additives (51% Cr, 12% Cu, 12% Ni, 24% Fe, 0.7% Nb, with traces of Si and Mn). A few variants use tumbled or milled powders [50-52]. Prealloy powder is favoured for performance, while the master alloy is favoured for low cost. However, prolonged sintering is required to deliver competitive properties from mixed elemental powders. Prealloyed powders are gas or water atomised. Because of molten metal exposure to high pressure water, the oxygen content is higher in water atomised powder. Gas atomised powder is spherical. If adhering small satellite particles are avoided, then gas atomised powder delivers a desirable high packing density and good flow properties. The less spherical, lower packing density water atomised powder starts at a lower packing density. Fig. 1 shows micrographs of typical gas and water atomised powders with a nominal particle size of 20 µm. For injection moulding feedstock, the solids loading might be 62.5 vol.% for gas atomised powder and 55 vol.% for water atomised powder. Similar loadings are anticipated for extrusion Additive Manufacturing. The lower solids loading implies that more sintering densification is needed for the water atomised powder [45, 51, 53]. The typical 17-4 PH stainless steel powder has a median particle size of 10 to 12 µm, with a tap density of 4.3 g/cm3. Table 2 gives the characteristics of several powders in use, reflecting powders from ten producers [18, 39, 41, 44, 46, 53-67].

• Low weight • Good mechanical stability • Low heat capacity • high open porosity • dust- and particle-free surface • homogeneous shrinkage • Absorbtion of the binder into the pores during the debindering process • Very smooth surface ﬁnish • Compatibility to Molybdenum, CFC, RSiC • Good to very good thermal shock resistance • Handling and assembly with robots possible

Al2O3 ZrO2 LTCC Dentalceramics

MIM

Tel.: +49 (0) 96 45 - 88 300 cts@kerafol.com

June 2018 Powder Injection Moulding International

MIM 17-4 PH stainless steel

Powder type*

D10 Âľm

D50 Âľm

D90 Âľm

Distribution width SW

Pycnometer density g/cm3

Tap density g/cm3

wt.% oxygen

wt.% carbon

5.3

7.8

4.0

0.06

0.04

2.7

7.8

4.3

0.06

0.07

2.7

7.8

4.3

0.53

0.04

3.4

7.7

4.6

0.12

0.06

4.6

7.7

4.6

0.53

0.04

3.8

7.8

4.5

0.06

0.04

3.3

7.8

4.8

0.08

0.03

4.1

7.8

4.9

0.10

0.04

5.3

7.8

3.8

0.60

0.04

4.9

7.8

4.1

0.60

0.04

3.3

7.8

4.2

0.60

0.05

3.1

7.7

4.4

0.38

0.06

4.1

7.7

4.0

0.49

0.07

3.9

7.8

3.4

0.60

0.04

3.2

7.7

4.1

0.38

0.06

4.0

7.7

4.0

0.59

0.07

3.0

7.8

4.4

0.65

0.07

4.7

7.6

4.4

0.65

0.04

5.7

7.7

4.2

0.32

0.01

* WA = water atomised, GA = gas atomised

Table 2 Examples of 17-4 PH powder characteristics

Oxygen is higher in the water atomised powder, ranging up to 0.65%. In contrast, gas atomised powder oxygen content is generally lower, near 0.06%. Some oxygen is removed by reacting with residual carbon during sintering. Residual oxygen degrades corrosion

resistance. The sizes D10, D50 and D90 correspond to the 10%, 50% and 90% points on the cumulative mass-based particle size distribution. Due to doubtful accuracy, particle sizes are rounded to the nearest micrometre sizes. The parameter SW is an indication

Pycnometer density

7.8 g/cm

Tap density

4.3 g/cm3

D10 particle size

5 Âľm

D50 particle size

11 Âľm

D90 particle size

24 Âľm

Distribution width SW

5.7

Carbon content

0.05%

Oxygen content

0.3%

Table 3 Typical powder characteristics

Powder Injection Moulding International

June 2018

of the log-normal size distribution (narrow size distributions have a high value corresponding to a steep log-normal slope) [68].

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(1)

The average SW is similar to that found for many powders. The pycnometer density is the full density for the powder and this is influenced by Ni, Cu, Cr content, as well as C, O, N impurities and any pores inside the particles. The tap density is a precursor to the feedstock solids loading and the green density prior to sintering. Average powder characteristics from about sixty reports are summarised in Table 3. Stainless steel surface chemistry is rich in

ÂŠ 2018 Inovar Communications Ltd

Vol. 12 No. 2

MIM 17-4 PH stainless steel

carbon and oxygen, with upwards densities of 98.9 and 97.2% [71]. reveals significant impact from four of 40 atomic % of each species on However, this strength difference factors - particle size, starting oxygen the surface [4, 69]. The remaining is eliminated by sintering the content, sintering atmosphere and surface consists of Fe, Si, Cr and Cu, water atomised powder at a higher heat treatment. The dominant factor in decreasing order of abundance. CM For Furnaces, temperature. sintering temperature, accounting long recognized as an industrialisleader in performance-proven, high a water atomised powder, the surface Statistical analysis reveals for about 90% of the sintered density temperature fully continuous sintering furnaces for MIM, CIM and traditional press consists of Cr2O3, SiO2 and MnO [61]. no significant impact of powder The powder type, hold and sinter now OFFERS YOU A CHOICE,variation. for maximum productivity and Master alloy mixtures provide characteristics on sintered time, green density and starting elimination of costly down time. similar properties after sintering properties. Mixed gas and water carbon content are not significant to gas atomised powders [70]. For Chooseatomised powders are used to hydrogenfactors with respect sintered one of our exclusive BATCH atmosphere RapidtoTemp furnaces. example, hydrogen sintering at lower cost and improve interparticle density. As detailed in the following Designed for both debinding and sintering, these new furnaces assure economical, 1370°C for 75 min gives a tensile friction to resist slumping during sections, experiments designed to simple and efficient operation. strength of 956 MPa (master) and debinding [54, 71, 72]. A higher test these several factors touch on 954 MPa (gas atomised) with 3.8 and sinteringour temperature is required moulding, debinding, Hot OR... choose continuous high temperature sintering furnacessintering, with complete 4.2% elongation. The sintered density to attain the same density as the Isostatic Pressing (HIP) and heat automation and low hydrogen consumption. is essentially the same at 98%. proportion of water atomised treating parameters. It seems that For one binder, water atomised powder increases. often experiments CONTACT US for more information on ourthe fulldesign line ofoffurnaces withisyour powder with a higher oxygen level to isolate capabilities effects, but invariably choice of size, automation,able atmosphere and reacts with carbon residue from the theto interaction parameters and temperature ranges up 3100˚F / of 1700˚C. Sintering parameter binder, beneficially reducing sensiincomplete reporting hide underlying effects tivity to debinding parameters [45]. cause-effect relationships. InherA comparison of sintered (1300°C, ently, in sintering 17-4 PH stainless Several sintering parameters hydrogen) 14 µm gas atomised and steel, we must assume everything is E-Mail: interact to determine the sintered 14 µm water atomised powders important. Here, we treat the adjustinfo@cmfurnaces.com density, phases, microstructure shows tensile strength of 1280 MPa able parameters and report their Web 103 Dewey StreetonBloomfield, 07003-4237 and properties. Statistical (pure Site: gas atomised) and 1080 MPa influence the responseNJ parameters Tel: 973-338-6500 Fax: 973-338-1625 http://www.cmfurnaces.com analysis of eighty sintering studies (pure water atomised) with sintered of density and properties.

FURNACES INC.

It’s a matter of choice High temp lab and industrial furnace manufacturer to the world www.cmfurnaces.com info@cmfurnaces.com 103 Dewey Street Bloomfield, NJ 07003-4237 | Tel: 973-338-6500 | Fax: 973-338-1625

June 2018 Powder Injection Moulding International

MIM 17-4 PH stainless steel

Fractional density 1.00

1320Â°C

0.95 1270Â°C 0.90 1220Â°C

0.85 0.80

1120Â°C

0.75 0.70

Hold time (min)

Fig. 2 Data showing sintered density versus hold time after heating to various temperatures [81]. Heating is 2Â°C/min from 1010Â°C to the peak temperature. For a peak temperature of 1320Â°C, almost all densification occurs prior to the isothermal hold. The starting density is 55% using 10 Âľm gas atomised powder

Green density In Metal Injection Moulding and Additive Manufacturing, the green density is about 96% of the particle tap density. The relation between fractional sintered density fS, green density fG, and sintering shrinkage Y is as follows:

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đ?&#x2018;&#x201C;đ?&#x2018;&#x201C;đ?&#x2018;&#x201C;đ?&#x2018;&#x201C;đ??şđ??şđ??şđ??ş (1 â&#x2C6;&#x2019; đ?&#x2018;&#x152;đ?&#x2018;&#x152;đ?&#x2018;&#x152;đ?&#x2018;&#x152;)3

(2)

This equation assumes no mass loss during sintering. For stainless steel powder, the usual behaviour is that a higher green density produces a higher sintered density [73].Â However, contrary to this sense are results using mixed particle sizes to improve green density from 64 to 71% of theoretical. Surprisingly, the lowest green density produces the highest sintered density. This is because of the smaller median particle size for the lower green density. Reports from other studies, including Additive Manufacturing, find that a higher green density does not necessarily result in a significant sintered density gain [74].

Gas atomised spherical particles enable a higher solids loading and green density. Water atomised powders can approach similar high packing densities, sintering to nearly the same final density. In vacuum sintering (120 min hold at 1390Â°C), gas atomised powder at 65 vol.% solids loading reaches 98% density, while lower packing density water atomised powder (55 vol.% solids loading) reaches almost the same value at 97% [51]. The latter exhibited more shrinkage. Another study compares 9 Âľm water atomised powder with green densities ranging from 55 to 71% [46]. After sintering (60 min at 1365Â°C), a higher sintered density results from the lower green density. Thus, from a few direct comparison studies, there is little evidence of a dominant green density effect on sintered density, or even sintered properties. Efforts to improve tap density or green density seem to be counterproductive.

Furnace types A wide variety of sintering furnaces are used to sinter 17-4 PH [75, 76]. The options include laboratory tube,

Powder Injection Moulding International

June 2018

refractory metal batch, graphite batch, and continuous belt, pusher, or walking beam designs. Microwave sintering trials conclude that this is inferior to standard sintering, but the difference is not explainedÂ [77]. In a study on molybdenum and graphite furnaces sintering 316L stainless in argon, the final density, yield strength, tensile strength and ductility are essentially identicalÂ [76]. The same study compared nitrogen as the atmosphere with a slight density-property gain for the graphite furnace (yield strength 375 MPa versus 330 MPa). However, when vacuum or hydrogen sintering are applied to 17-4 PH, there is no evident furnace role. Sintering is dominated by other factors, especially the peak temperature. Note that some furnace types restrict the atmosphere options, but, to-date, the furnace type is not significant.

Particle size Initial particle bonding during sintering is by surface diffusion [78]. Smaller particles have more surface area and, therefore, naturally the initial bonding and strengthening is dependent on particle size. Surface diffusion induced bonding replaces the particle adhesion initially provided by the backbone polymer, so slow heating is a typical protocol to add strength as binder pyrolysis occurs. As the sinter bonds grow between particles, grain boundary diffusion becomes the controlling process. This requires neck growth to form a grain boundary between particles. As grain boundaries form, the rate of sintering shifts to an inverse grain size dependence. Once shrinkage starts, the initial particle size role becomes secondary and attention shifts to the grain size. Even so, particle size is easily monitored as a starting parameter while grain size is less frequently measured. In a study with median particle sizes (D50) varied from 5.8 to 12.2 Âľm, the sintered strength is essentially the same once the peak temperature exceeds 1250Â°C (60 min, hydrogen) [56, 64]. Sintered densities

ÂŠ 2018 Inovar Communications Ltd

Vol. 12 No. 2

of 98% or higher are attained for 11 to 12 µm powders when sintered at temperatures over 1288°C. A comparison of 8 and 10 µm particle sizes (vacuum sintered at 1330°C for 60 min) reports a slightly higher density (98.2%) with smaller particles [79]. This promotes a slightly higher yield strength (760 versus 728 MPa) and tensile strength (888 versus 870 MPa) on using the finer powder. Longer hold times or higher peak temperatures tend to offset the early particle size effect. Indeed, for a 60 µm particle size, sintered at 1340°C for 60 min in hydrogen, the density is lower at 92.3%, but the heat treated strength reaches 1100 MPa with a fracture elongation of 2% [80]. Sintering distortion is lowest with the smaller particle size and largest with the larger particle size; both increase with sintering temperature. This is one justification for smaller particles or even mixtures of different particle sizes or powder types. However, more careful experiments are required to sort out densification versus distortion in cycles optimised for each particle size. To date, the sintering cycle is held constant using differing particle size, but this over-sinters the small particles or under-sinters the large particles.

MIM 17-4 PH stainless steel

from 1010°C to 1320°C, near full density occurs with a 10 min hold [81, 82]; delivering a tensile strength of 1185 MPa [42].

Temperature When tested using dilatometry, the onset of sintering shrinkage is detected near 900°C [51]. The peak sintering shrinkage rate is near 1250°C [27, 47], but full-density sintering (say 98%) requires peak temperatures approaching 1300°C.

However, such high temperatures evaporate copper and chromium, with a potential loss of heat treatment response and corrosion resistance. Delta-ferrite formation is favoured by higher temperatures and this phase assists final densification due to faster diffusion. Data on the shrinkage and sintered density (60 min, hydrogen) versus temperature for a 10 µm water atomised powder are plotted in Fig. 3 [59]. Almost the same values were reported in a study with gas atomised powder [53]. At 1350°C, a density of 99% is reached,

Heating rate Sintering cycles involve heats and holds to allow binder burnout and impurity removal. Optimal holds are near 600°C for final polymer removal and near 1000°C for impurity reduction. The heating rate approach to the peak temperature ranges from 2 to 10°C/min. When the heating rate drops to 2°C/min, then almost all shrinkage occurs prior to the isothermal hold [81]. As a specific example, for 1270°C, the density on reaching that temperature is 88%, starting from a green density of 55%. Fig. 2 illustrates how the rate of densification declines quickly at the highest temperatures. Most of the densification occurs during heating, especially prior to reaching 1300°C. Indeed, with 2°C/min heating

June 2018 Powder Injection Moulding International

MIM 17-4 PH stainless steel

Shrinkage (%)

Relative density (%)

100 shrinkage

-4

density

-8

-12

-16

900

1000

1100

1200

1300

60 1400

Temperature (°C)

Fig. 3 Plot of sintering shrinkage and sintered density versus hold temperature, heating is at 5°C/min with a 60 min hold at the final temperature [59]

about the same as achieved with gas atomised powder [47] and, at 1300°C, the density is 96%, which compares favourably with a report of 97% for the same conditions [83]. Shrinkage for 60% green density is 15.4%, similar to another report at 15.7%. Such small differences in

dimensional change probably reflect differences in delta-ferrite content. A study starting at 55% green density reports 17.5% shrinkage, giving 98% sintered density. In this case, about 10% delta-ferrite remained. The sintering shrinkage curve is a reflection of atomic scale

Fig. 4 Microstructure of 17-4 PH water quenched from 1260°C during hydrogen sintering, showing emergence of white delta-ferrite colonies. The dark regions are pores with some small circular oxide inclusions

Powder Injection Moulding International

June 2018

atom motion. Mathematically, the dimensional change is treated as a viscous flow event, similar to how glass deforms at high temperature. For 17-4 PH, the viscosity during sintering is approximated as: 3.4∙107 exp(3305/T) Pa∙s,

where T is the absolute temperature [84-86]. This is an effective viscosity that includes many factors lumped into a single term. Quenched samples harvested during heating show fully austenitic structures from 780°C up to 1200°C and the emergence of delta-ferrite over 1220°C. Fig. 4 is an example of hydrogen sintered material quenched from 1260°C, showing colonies of deltaferrite. The pores are transforming to spherical shapes. Property adjustments are possible by mixing austenitic 316L powder with 17-4 PH powder, possibly delivering altered magnetic and mechanical properties [87]. This is an area lacking attention, probably due to the difficulty in qualifying products sintered from mixed stainless steel powders. Independent trials using 60 min holds in hydrogen are widespread and tend to report similar densities [53]. For example, 1350°C produces 99.4% density for gas atomised 10.7 µm powder. Other studies find equivalent densification at slightly lower temperatures for longer times. Fig. 5 maps interpolated timetemperature effects on sintered density for a gas atomised powder [57]. Generally, the sintering studies are in agreement with respect to the time-temperature trade-off. For example, the horizontal one hour trace in this figure shows progressive density gains with increasing sintering temperature. However, long hold times are less productive. A comparison of gas and water atomised powders at 1300°C and 1380°C found both powders sintered to a high density at the lower temperature [71]. Another study comparing 1345, 1360, or 1380°C at times of 60, 90, or 120 min concluded that 1380°C for 90 min resulted in the highest

Vol. 12 No. 2

Time (h) 5

MIM 17-4 PH stainless steel

Density (%) density, % 98.5 98.0 97.5 97.0 96.5 96.0 95.5

4 3

100 90

heat rate 10Â°C/min

80 gas atomised

milled water atomised

0 1240

1260

1280

1300

1320

1340

1360

50 800

900

Temperature (Â°C)

Hold times Typical sintering hold times at the peak temperature are in the 60 to 120 min range. Little gain comes from the long holds. For one hour, the horizontal line in Fig. 5 indicates a progressive density gain from 96.3% to 98.5% as the temperature increases from 1240 to 1360Â°C. With about 60 min hold the compacts almost reach full density. As porosity is eliminated, the rate of pore annihilation declines, partly due to exhaustion of porosity and partly due to loss of grain boundaries due to grain growth. Grain boundaries are the annihilation sites for vacancies during sintering. Pores are massive collections of vacancies. Dilatometry shows that the peak shrinkage rate during heating occurs while about 7% porosity remains (near

Vol. 12 No. 2 ÂŠ 2018 Inovar Communications Ltd

1100

1200

1300

1400

Temperature (Â°C)

Fig. 5 Map of computer interpolated sintered density contours versus time and temperature [57]

tensile strength (1275Â MPa, 36 HRC, 5% elongation) [88]. As previously mentioned, a problem with such a high sintering temperature is evaporative loss of chromium and copper; chromium vapour pressure is 4.5 times higher at 1380Â°C versus 1300Â°C and copper vapour pressure is double that of chromium.

1000

Fig. 6 Constant heating rate dilatometry data for three powder types, heating at 10Â°C/min [51]. The data illustrate how full density is approached during heating if the peak temperature reaches about 1350Â°C

1250Â°C) [47]. Longer holds evidence saturation; the densification has gone about as far as possible due to grain size increases and loss of grain boundaries. The results plotted in Figs. 2, 5 and 6 verify that, when 1320-1350Â°C is reached, the density is high and further gains with extended holds are small. This implies that, upon reaching the ideal sintering temperature range, only a few minutes of hold are required. Most of the densification occurs during heating [51, 81]. Sintering parameters play a role in compact densification. At first, surface diffusion induces particle bonding. Once necks with grain boundaries form, densification follows by grain boundary diffusion. The model for grain boundary diffusion controlled sintering gives the isothermal shrinkage as a function of the processing conditions as follows [78]: 100 đ?&#x2018;Ąđ?&#x2018;Ąđ?&#x2018;Ąđ?&#x2018;Ą đ?&#x203A;žđ?&#x203A;žđ?&#x203A;žđ?&#x203A;ž đ?&#x203A;żđ?&#x203A;żđ?&#x203A;żđ?&#x203A;ż ÎŠ đ?&#x2018;&#x201E;đ?&#x2018;&#x201E;đ?&#x2018;&#x201E;đ?&#x2018;&#x201E;đ??ľđ??ľđ??ľđ??ľ 1/3 â&#x2C6;&#x2020;đ??żđ??żđ??żđ??ż (3) = ďż˝ đ??ˇđ??ˇđ??ˇđ??ˇđ??ľđ??ľđ??ľđ??ľ exp ďż˝â&#x2C6;&#x2019; ďż˝ďż˝ 4 đ?&#x2018;&#x2026;đ?&#x2018;&#x2026;đ?&#x2018;&#x2026;đ?&#x2018;&#x2026; đ?&#x2018;&#x2021;đ?&#x2018;&#x2021;đ?&#x2018;&#x2021;đ?&#x2018;&#x2021; đ?&#x2018;&#x2DC;đ?&#x2018;&#x2DC;đ?&#x2018;&#x2DC;đ?&#x2018;&#x2DC; đ?&#x2018;&#x2021;đ?&#x2018;&#x2021;đ?&#x2018;&#x2021;đ?&#x2018;&#x2021; đ??şđ??şđ??şđ??ş đ??żđ??żđ??żđ??żđ?&#x2018;&#x201A;đ?&#x2018;&#x201A;đ?&#x2018;&#x201A;đ?&#x2018;&#x201A;

where Î&#x201D;L is the change in length from the initial size LO, t is the hold time, Îł is the solid-vapour surface energy, Î´ is the atom diameter

(assuming the grain boundary is five atoms wide), ÎŠ is the atomic volume, k = Boltzmannâ&#x20AC;&#x2122;s constant (1.38â&#x2C6;&#x2122;10-23Â J/K), T is the absolute temperature, G is the grain size, DB is the frequency factor for grain boundary diffusion, QB is the activation energy and R is the universal gas constant (8.31 J/(mol K)). Such an isothermal model is difficult to test; as illustrated already, since most of the sintering shrinkage occurs before reaching isothermal conditions. Temperature and grain size are dominant parameters in comparison with hold time. Trials to extract an apparent activation energy from shrinkage data result in values ranging from 312 to 350 kJ/mol [54, 81]. This is slightly higher than 167 kJ/mol reported for other stainless steels [78]. For 17-4 PH, the simultaneous surface diffusion acts to exhaust surface energy, but does not contribute to densification. The result is a high apparent activation energy; surface diffusion acts to form interparticle necks containing grain boundaries, but grain boundary diffusion is only monitored by shrinkage. Further, grain growth goes hand-in-hand with sintering densification, since mass transport across the grain boundary

June 2018 Powder Injection Moulding International

MIM 17-4 PH stainless steel

provides a means of estimating strength evolution during heating. Table 4 summarises the calculation parameters. Compact strength evolution involves both neck growth and densification. During densification, the number of particle-particle contacts increases, measured by the coordination number [90]. Initially the bond size determines strength [91], but densification induces new bonds and increases the load bearing cross-sectional area. Thus, sintered strength Ď&#x192; is predicted as follows:

(5)

đ?&#x2018;&#x2039;đ?&#x2018;&#x2039;đ?&#x2018;&#x2039;đ?&#x2018;&#x2039; 2 2 + 11 đ?&#x2018;&#x201C;đ?&#x2018;&#x201C;đ?&#x2018;&#x201C;đ?&#x2018;&#x201C;đ??şđ??şđ??şđ??ş đ?&#x2018;&#x201C;đ?&#x2018;&#x201C;đ?&#x2018;&#x201C;đ?&#x2018;&#x201C;đ?&#x2018;&#x2020;đ?&#x2018;&#x2020;đ?&#x2018;&#x2020;đ?&#x2018;&#x2020; đ?&#x153;&#x17D;đ?&#x153;&#x17D;đ?&#x153;&#x17D;đ?&#x153;&#x17D; = đ?&#x153;&#x17D;đ?&#x153;&#x17D;đ?&#x153;&#x17D;đ?&#x153;&#x17D;đ?&#x2018;&#x152;đ?&#x2018;&#x152;đ?&#x2018;&#x152;đ?&#x2018;&#x152; đ??śđ??śđ??śđ??ś ďż˝ ďż˝ ďż˝ ďż˝ 2 + 11 đ?&#x2018;&#x201C;đ?&#x2018;&#x201C;đ?&#x2018;&#x201C;đ?&#x2018;&#x201C;đ?&#x2018;&#x2020;đ?&#x2018;&#x2020;đ?&#x2018;&#x2020;đ?&#x2018;&#x2020; đ?&#x2018;&#x201C;đ?&#x2018;&#x201C;đ?&#x2018;&#x201C;đ?&#x2018;&#x201C;đ??şđ??şđ??şđ??ş đ??ˇđ??ˇđ??ˇđ??ˇ Fig. 7 Spherical particles form necks by surface diffusion early in sintering to provide strength to the compact without contributing to densification

produces grain growth while mass transport along the grain boundary produces densification. Finally, the activation energy extracted from densification data is complicated by phase changes during heating [89]. Surface diffusion provides compact shape retention by building bonds between particles as the backbone binder evaporates. The resulting open pore structure is captured in Fig. 7. Neck growth by surface diffusion under isothermal conditions is modelled as follows [78]:

34 đ?&#x2018;Ąđ?&#x2018;Ąđ?&#x2018;Ąđ?&#x2018;Ą đ?&#x203A;žđ?&#x203A;žđ?&#x203A;žđ?&#x203A;ž đ?&#x203A;żđ?&#x203A;żđ?&#x203A;żđ?&#x203A;ż 4 đ?&#x2018;&#x201E;đ?&#x2018;&#x201E;đ?&#x2018;&#x201E;đ?&#x2018;&#x201E;đ?&#x2018;&#x2020;đ?&#x2018;&#x2020;đ?&#x2018;&#x2020;đ?&#x2018;&#x2020; đ?&#x2018;&#x2039;đ?&#x2018;&#x2039;đ?&#x2018;&#x2039;đ?&#x2018;&#x2039; 7 đ??ˇđ??ˇđ??ˇđ??ˇđ?&#x2018;&#x2020;đ?&#x2018;&#x2020;đ?&#x2018;&#x2020;đ?&#x2018;&#x2020; đ?&#x2018;&#x2019;đ?&#x2018;&#x2019;đ?&#x2018;&#x2019;đ?&#x2018;&#x2019;đ?&#x2018;&#x2019;đ?&#x2018;&#x2019;đ?&#x2018;&#x2019;đ?&#x2018;&#x2019;đ?&#x2018;&#x2019;đ?&#x2018;&#x2019;đ?&#x2018;&#x2019;đ?&#x2018;&#x2019; ďż˝â&#x2C6;&#x2019; ďż˝ ďż˝ = ďż˝ (4) 4 đ?&#x2018;&#x2DC;đ?&#x2018;&#x2DC;đ?&#x2018;&#x2DC;đ?&#x2018;&#x2DC; đ?&#x2018;&#x2021;đ?&#x2018;&#x2021;đ?&#x2018;&#x2021;đ?&#x2018;&#x2021; đ??ˇđ??ˇđ??ˇđ??ˇ đ?&#x2018;&#x2026;đ?&#x2018;&#x2026;đ?&#x2018;&#x2026;đ?&#x2018;&#x2026; đ?&#x2018;&#x2021;đ?&#x2018;&#x2021;đ?&#x2018;&#x2021;đ?&#x2018;&#x2021; đ??ˇđ??ˇđ??ˇđ??ˇ

The neck diameter is X, particle diameter is D and X/D is the neck size ratio. In Fig. 7, the neck size ratio varies from 0.3 to 0.5, averaging 0.38. In this equation, t = isothermal hold time, Îł = surface energy, Î´ Â =Â atomic spacing, k = Boltzmannâ&#x20AC;&#x2122;s constant (1.38â&#x2C6;&#x2122;10-23 J/K), T is the absolute temperature in kelvin, DS is the surface diffusion frequency factor, QS = the activation energy for surface diffusion and R = universal gas constant (8.31 J/(mol K)). Data for 316L stainless steel provide a means to estimate surface diffusion neck growth since 17-4 PH is also austenitic during heating. In turn, neck growth by surface diffusion

As density increases, due to grain boundary diffusion, the sintered fractional density fS increases from the green fractional density fG. The yield strength for dense material Ď&#x192;Y is 1040 MPa, a typical value for dense 17-4 PH. The neck size ratio X/D is limited to a maximum of 0.51. At this Sintered strength (MPa) 1200 1000 800 600

Room temperature yield strength Surface energy

1400Â°C 1020 MPa 2 J/m

Atomic size

0.252 nm

Surface diffusion frequency factor

0.4 m2/s

Surface diffusion activation energy

250 kJ/mol

Table 4 Surface diffusion controlled strength evolution calculation parameters

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June 2018

Experiment

400

Model

200 0 500

Melting temperature

17-4 PH sintered strength evolution hydrogen, 60 min

700

900

1100

1300

Sintering temperature (Â°C)

Fig. 8 Comparison of measured tensile strength (square symbols) and surface diffusion predicted strength (model) evolution for 60 min sintering in hydrogen at various temperatures. Experimental data are scattered due to factors such as delta-ferrite content and grain size effects

ÂŠ 2018 Inovar Communications Ltd

Vol. 12 No. 2

point, neighbouring necks converge and pores are eliminated. The parameter C adjusts to the particular means for measuring strength; it is 1.0 for tensile and 1.6 for transverse tests. Combining equations leads to the plot of expected sintered strength (at room temperature) versus sintering temperature in Fig. 8. The symbols are experimental results taken from different 60 min sintering holds for 10 µm powders [44, 56, 92-94]. Since heat treatment adds complexity, only as-sintered data are included. Grain size data are generally not reported, but this is another factor, as is the formation of delta-ferrite. Note that these calculations provide a means for sensing the desired minimum temperature required during thermal debinding. Setting a goal of 20 MPa handling strength, the model finds that a peak temperature of 600°C is sufficient, a temperature often encountered in thermal debinding, as noted earlier.

Atmosphere The sintering atmosphere options include hydrogen, nitrogen, hydrogen-nitrogen, argon-hydrogen and vacuum. Nitrogen is a potent austenite stabiliser, so it plays a role in martensite formation and final properties [44-46]. The same atmospheres are also used in second stage debinding. Hydrogen or vacuum are common sintering atmospheres for 17-4 PH stainless steel [95]. Without added graphite, both chromium and silicon retain oxygen. If carbon is added, significant oxide reduction is possible. With respect to atmospheres, a -40°C dew point is possible. This corresponds to an inlet atmosphere with one part moisture for 10,000 parts hydrogen [75]. As oxides are reduced, the resulting reaction product increases dew point, halting further reduction. To compensate, the moisture must be flushed to continually replenish with fresh atmosphere. Thus, both atmosphere quality and atmosphere flow rate are factors. Often, neither parameter is reported.

MIM 17-4 PH stainless steel

Dew point

Atmosphere mositure content

-60°C

0.001 vol.% H2O

-50°C

0.004 vol.% H2O

-40°C

0.013 vol.% H2O

-30°C

0.038 vol.% H2O

-20°C

0.102 vol.% H2O

-10°C

0.257 vol.% H2O

0°C

0.602 vol.% H2O

Table 5 Relation between dew point and atmosphere moisture content Dew point (°C) 0

oxidising zone 1250°C

-10 -20

1120°C -30

reducing zone

-40 -50

Hydrogen (%)

Fig. 9 Plot of the oxidation-reduction boundary for chromium in a stainless steel versus atmosphere hydrogen-nitrogen composition for 1120 and 1250°C [96]. A high hydrogen content ensures reduction in an atmosphere containing higher levels of water vapour

The dew point is a measure of the temperature at which an atmosphere is chilled to produce condensation. A low dew point is required to reduce surface oxides. The relation between dew point and volume percent moisture is summarised in Table 5. As plotted in Fig. 9, oxide reduction is favoured by higher temperatures and higher hydrogen contents [96]. A low dew point ensures oxide reduction. After sintering, the cold surfaces oxidise to form a passive layer that is rich in iron, chromium and silicon [4]. This passive layer provides corrosion resistance. Sintering in hydrogen is sensible for carbon and oxygen removal, but vacuum sintering is quite successful.

Vacuum sintering causes evaporation of chromium and copper at high temperatures that is suppressed by an atmosphere. Sometimes the atmosphere pressure is below 0.1 MPa, using variants such as argon or hydrogen-argon. However, the sintered density is lowered by argon since it is insoluble and remains trapped in closed pores; a peak density of 95% is typical [95]. A comparison of hydrogen, vacuum and argon sintering (1350°C for 60 min) confirms argon as being inferior (94.6% dense) [97]. Nitrogen is soluble in austenite and, on cooling, forms Cr2N precipitates. Since the precipitate robs grain boundary areas of chromium,

June 2018 Powder Injection Moulding International

MIM 17-4 PH stainless steel

Atmosphere

Density (%)

Hardness (HRC)

Tensile strength (MPa)

Elongation (%)

Hydrogen

97.6

28 (HT 40)

820 (HT 1085)

7 (HT 4)

Vacuum

97.7

22 (HT 39)

810 (HT 1135)

8 (HT 7)

Dissociated ammonia

94.3

27 (HT 40)

1000 (HT 1265)

3 (HT 9)

Table 6 Comparative sintering atmosphere (1320°C, 120 min) effect on 10 µm water atomised 17-4 PH stainless steel as-sintered and heat treated (in parentheses)

localised rapid corrosion occurs. Indeed, rust is found within days after sintering in nitrogen. This difficulty is minimised by avoiding nitrogen in the sintering atmosphere or by cooling at 200°C/min below 900°C to suppress chromium nitride formation [98]. Trials with nitrogen additions to the sintering atmosphere fail to demonstrate any notable advantage [44, 46, 70]. Nitrogen is soluble in austenite at temperatures over about 1000°C. The equilibrium solubility depends on temperature and nitrogen partial pressure. Sintering a fine water atomised powder in an atmosphere of 96% hydrogen and 4% nitrogen at 1350°C results in about 0.1 wt.% nitrogen in solution. The final nitrogen content depends on the cooling rate near 900 to 1000°C, the region of maximum solubility. Adsorbed nitrogen has a

small negative impact. For example, the sintered density is 97.7 with 96% H2 - 4% N2 and 98.3% with pure H2 and 99.0% with vacuum [44]. In a test matrix of different powder types and sintering atmospheres the findings were mixed [70]. The highest yield strength and corrosion resistance came from master alloy powder sintered in hydrogen (1370°C, 75 min), but the highest ductility and tensile strength came from gas atomised powder sintered in nitrogen. On the other hand, comparison of vacuum, hydrogen and dissociated ammonia sintering (10 µm water atomised powder) results in a lower sinter density (1320°C, 120 min) from dissociated ammonia [94]. Summary properties are given in Table 6 for sintered and heat treated conditions (parenthetical values). A

Carbon (%)

Oxygen (%)

0.08 sintered oxygen

0.06

0.04

starting oxygen 0.32%

starting carbon

0.00

0.05

Additives

0.20

Several additives allow manipulation of sintering. For 17-4 PH stainless steel, the additives include molybdenum, graphite, boron, silicon, iron boride and nickel boride [59, 60, 94, 99-105]. Molybdenum additions provide some hardening and strengthening when sintering is in dissociated ammonia. Silicon (1%) and boron (0.2%) combine to deliver a heat treated tensile strength of 1200 MPa, but low ductility. Boron segregates to grain boundaries where it forms a liquid phase to lower the sintering temperature. For a gas atomised powder, 0.5 wt.% to 0.6 wt.% boron lowers the sintering temperature to 1250 to 1260°C. After heat treatment, boron doped material

0.15 0.10 0.05

sintered carbon

0.25

0.02

0.00 0.10

0.15

0.20

0.25

0.30

Added graphite (wt.%)

Fig. 10 Influence of added graphite on the sintered carbon and oxygen contents for water atomised 15 µm 17-4 PH stainless steel sintered in graphite vacuum furnace at 1320°C for 60 min [61]

Powder Injection Moulding International

June 2018

higher temperature, 1370°C for 75 min, gives the opposite result for gas atomised powder [70]. Sorting out such confusion between studies requires more of the details on residual oxygen, carbon, delta-ferrite and grain size. With dissociated ammonia, increasing the sintering temperature to 1350°C results in a high hardness and strength after heat treatment (HRC 44, 1350 MPa), but elongation remains low at 3%. Since nitrogen stabilises austenite, which produces martensite on cooling, it should be beneficial to heat treated properties. Graphite vacuum furnaces are quite successful in vacuum sintering. Graphite enables the creation of a low partial pressure of carbon monoxide inside the vacuum. Chromium oxide is reduced by CO when the partial pressure is a few hundred parts per million. For example, at 1300°C, a low CO partial pressure (0.001 atmosphere) is reducing to chromium.

Vol. 12 No. 2

reaches a hardness of 55 HRC and 1520 MPa tensile strength. Alternatives are nickel or iron borides; 1 wt.% FeB or 1 wt.% NiB deliver full density using vacuum sintering at 1285Â°C for 45Â min. These compositions heat treat to 1300 to 1400 MPa tensile strength and 50 to 52 HRC hardness, with about 7% fracture elongation. Of concern is that the liquid phase induced by boron probably gives more distortion during sintering. Graphite additions remove oxygen from water atomised powders. Starting with 0.32% oxygen (and 0.048% carbon), the addition of 0.26 wt.% graphite results in a final composition of 0.01% O and 0.03%Â C. Fig. 10 is a plot of the final carbon and oxygen levels as influenced by the added graphite content [61]. Notable are the high mechanical properties that result, giving 40 HRC, 1300 MPa tensile strength and 9% elongation after heat treatment. Some corrosion resistance is lost if the final carbon level exceeds 0.07%.

MIM 17-4 PH stainless steel

Distortion Conceptually, the sintering shrinkage is uniform if the particle packing in the green body is uniform. However, anisotropic shrinkage arises from several factors, including substrate friction along the shrinking bottom surface, gravity induced slumping or bending of unsupported regions, powder-binder separation in moulding and non-uniform heating. It is best to use a high green density to minimise distortion [65, 66]. Careful inspection shows sintering shrinkage is not uniform; variations of 0.9% are reported [106]. An issue during sintering is thermal softening. Sinter bonds between particles add strength, but high temperatures soften the material. Stainless steels decrease strength to reach zero measurable strength near 1400Â°C. For 17-4 PH, the full density yield strength (in MPa) at temperature Ď&#x192;T depends on the absolute temperature T (in K) as follows:

Ď&#x192;đ?&#x2018;&#x2021;đ?&#x2018;&#x2021;đ?&#x2018;&#x2021;đ?&#x2018;&#x2021; = 1200 â&#x2C6;&#x2019; 0.7 đ?&#x2018;&#x2021;đ?&#x2018;&#x2021;đ?&#x2018;&#x2021;đ?&#x2018;&#x2021;

(6)

Heating induces bonding followed by densification. Both effects strengthen the powder compact, but heating causes thermal softening of the alloy. This latter effect gives inherent strength loss and less distortion resistance. Substitution of Ď&#x192;T for Ď&#x192;Y in Equation 5 illustrates the susceptibility to distortion and damage during heating. Fig. 11 plots the in-situ strength versus temperature during sintering. Contrast these data with the earlier plot showing the room temperature strength after heating to those temperatures. Below about 1200Â°C, sinter bonding and densification improve strength at temperature, but, over 1200Â°C, thermal softening dominates, resulting in a net strength loss at temperature during densification. These calculations build from hot rupture data acquired during sintering using a model that

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Vol. 12 No. 2 ÂŠ 2018 Inovar Communications Ltd

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MIM 17-4 PH stainless steel

Strength at temperature (MPa)

Height (mm)

12.0

17-4 PH strength during sintering after 60 min hold at indicated temperature

10.0 8.0 6.0

Initial shape 1390°C, 0 h 1390°C, 2 h 1390°C, 4 h

4.0 10

0 400

2.0 0.0 600

800 1000 Temperature (°C)

1200

1400

Fig. 11 Strength evolution at various temperatures during sintering, showing the in situ strength after 60 min hold. The greatest resistance to distortion is near 1200°C. Strength loss at higher temperatures is due to thermal softening. Below 600°C the compacts are delicate since the binder has evaporated but surface diffusion has not induced significant particle bonding

evokes surface diffusion neck growth, thermal softening and component densification [107-109]. Based on experiments to extract the sintering response, using variations in time, temperature and heating rate, viscous flow models allow prediction of final size and shape [81, 82, 86]. The models employ finite element analysis. The calculations consistently show densification occurs prior to slumping. Example results are plotted in Fig. 12 for right circular cylinders in profile [81]. The geometry is initially 10 mm in diameter and 10 mm high. Gravity is acting in the vertical direction to cause compact distortion near the bottom. Initially shrinkage is uniform, but, late in sintering, distortion occurs. The shrunk bottom surface is pinned by the compact mass, leading to bowing into the “elephant foot” geometry predicted here. Thus, distortion is reduced by shorter hold times at the peak temperature. Further study is needed to optimise the densification and distortion maps versus peak temperature, hold time and heating rate.

Carbon control Carbon is an austenite stabiliser during sintering. Fig. 13 plots this effect showing the delta-ferrite formation versus carbon content for 17-4 PH [110]. A low retained carbon level, especially below 0.1 wt.%, ensures a higher strength and hardness [97]. Changes in carbon level impact phases, densification and mechanical properties. The carbon level depends on the starting powder, binder residuals, debinding cycle, sintering atmosphere, initial oxygen and peak sintering temperature. A large factor is the initial oxygen level, since carbon and oxygen react during sintering [17, 95]. For example, 0.03% carbon loss occurs in gas atomised powder sintered at 1343°C (60 min) in hydrogen [55]. On the other hand, carbon contamination arises from some binders, impacting densification, especially at lower sintering temperatures. Fig. 14 plots an example of sintered density variation with carbon level. These data are for 11 µm gas atomised powder sintered at various temperatures for 100 min,

Powder Injection Moulding International

June 2018

0.0

2.0

4.0

6.0

Radius (mm)

Fig. 12 Finite element analysis predictions on shape distortion for 10 mm right circular cylinders during sintering at 1390°C [81]. The left half of the cylinder is shown for the initial shape at the start and after hold times of 0, 2, and 4 hours where the carbon level is adjusted by the debinding conditions [47]. Further insight is offered in Fig. 15, a plot of heat treated tensile strength versus retained carbon for a variety of hydrogen and vacuum sintered compacts [97]. The tensile strength is for both the sintered (1300 to 1350°C for 60 min) and H900 heat treatment. As the carbon concentration reaches higher levels, a notable loss of strength is evident.

Delta-ferrite The role of delta-ferrite (δFe) is mixed. On the one hand, it enhances high temperature sintering, but, on the other hand, it reduces mechanical properties. During sintering, diffusion in this body-centred cubic δFe phase is faster than in the face-centred cubic austenite phase, contributing to some density gains, especially for sintering temperatures below 1300°C. Longer holds or higher temperatures offset any gains from delta-ferrite formation. In hydrogen sintering, δFe first forms between 1190 and 1220°C [46, 111]. If the sintering atmosphere

Vol. 12 No. 2

mperatures. 14 plots an exampleespecially of sintered variation with carbon level. These ome binders,Figure impacting densification, at density lower sintering a are for 11 Âľm gas atomized powder sintered at various temperatures for 100 min, where the s an example of sintered density variation with carbon level. These bon level is adjusted by the debinding conditions [47]. Further insight is in Figure 15, a | contents page | news | events | advertisersâ&#x20AC;&#x2122; index | contact | zed powder sintered at various temperatures for 100 min, where the offered t of heat treated tensile strength versus retained carboninfor a variety he debinding conditions [47]. Further insight is offered Figure 15, aof hydrogen and vacuum tered [97]. The tensilefor strength is for both the sintered (1300 to 1350Â°C for 60 min) rengthcompacts versus retained carbon a variety of hydrogen and vacuum dtensile H900 strength heat treatment. As the carbon concentration reaches higher levels, a notable loss of is for both the sintered (1300 to 1350Â°C for 60 min) ength is evident. the carbon concentration reaches higher levels, a notable loss of

MIM 17-4 PH stainless steel

Temperature (Â°C) contains nitrogen, austenite is ta-ferrite stabilised, 1550 e role of delta-ferrite (đ?&#x203A;żđ?&#x203A;żđ?&#x203A;żđ?&#x203A;żFe) isretarding mixed. OnÎ´Fe theformation one hand it enhances high temperature sintering, but and resulting in slower sintering. Yet the other hand it reduces mechanical properties. During sintering, diffusion in this body) is mixed. On the one hand it enhances high temperature sintering, but ntered cubic properties. đ?&#x203A;żđ?&#x203A;żđ?&#x203A;żđ?&#x203A;żFe phase isDuring fasterproducts than in the face-centered the sintered dodiffusion not show mechanical sintering, in thiscubic body-austenite phase, contributing to 1500 me density forproperty sintering temperatures below 1300Â°C. significant difference aster than gains, in the aespecially face-centered cubic austenite phase, contributing to Longer holds or higher mperatures offset any gains from delta-ferrite formation. when the nitrogen content Longer is low. holds or higher y for sintering temperatures below 1300Â°C. Liquid liquid + delta - ferrite s from delta-ferrite formation. Also, some binders leave a carbon 1450 hydrogen sintering đ?&#x203A;żđ?&#x203A;żđ?&#x203A;żđ?&#x203A;żFe first forms between 1190 and 1220Â°C [46, 111]. If the sintering residue to stabilise austenite and mosphere contains 1190 nitrogen, austenite is stabilized, st forms between [46, 111]. If theretarding sinteringđ?&#x203A;żđ?&#x203A;żđ?&#x203A;żđ?&#x203A;żFe formation, resulting in slower hinder and Î´Fe 1220Â°C formation. The relation liquid + austenite tering. Yet the sintered products do not show a significant property difference when the nitrogen n, austenite is stabilized, retarding đ?&#x203A;żđ?&#x203A;żđ?&#x203A;żđ?&#x203A;żFe Î´formation, resulting in slower liquid + 1400 and hinder delta-ferrite Fe (percent) + delta ntent is low. Also,between some binders leave a carbon residue to stabilize austenite đ?&#x203A;żđ?&#x203A;żđ?&#x203A;żđ?&#x203A;żFe - ferrite oducts do not show a significant property difference when the nitrogen austenite and between temperature T in Â°C đ?&#x203A;żđ?&#x203A;żđ?&#x203A;żđ?&#x203A;żFe for 0.1 wt.% and temperature T in Â°C for 0.1 wt. % mation. The relation delta-ferrite (percent) nders leave a carbon residue to stabilize austenite and hinder đ?&#x203A;żđ?&#x203A;żđ?&#x203A;żđ?&#x203A;żFe carbon[111]: is given as follows [111]: bon is given as follows delta - ferrite + een delta-ferrite đ?&#x203A;żđ?&#x203A;żđ?&#x203A;żđ?&#x203A;żFe (percent) and temperature T in Â°C for 0.1 wt. % 1350 austenite 11]: đ?&#x203A;żđ?&#x203A;żđ?&#x203A;żđ?&#x203A;żđ?&#x203A;żđ?&#x203A;żđ?&#x203A;żđ?&#x203A;żđ?&#x2018;&#x2019;đ?&#x2018;&#x2019;đ?&#x2018;&#x2019;đ?&#x2018;&#x2019; = â&#x2C6;&#x2019;0.00132 (đ?&#x2018;&#x2021;đ?&#x2018;&#x2021;đ?&#x2018;&#x2021;đ?&#x2018;&#x2021; â&#x2C6;&#x2019; 1190)2 + 0.602 (đ?&#x2018;&#x2021;đ?&#x2018;&#x2021;đ?&#x2018;&#x2021;đ?&#x2018;&#x2021; â&#x2C6;&#x2019; 1190) (7) (7) 1300 = â&#x2C6;&#x2019;0.00132 (đ?&#x2018;&#x2021;đ?&#x2018;&#x2021;đ?&#x2018;&#x2021;đ?&#x2018;&#x2021; â&#x2C6;&#x2019; 1190)2 + 0.602 (đ?&#x2018;&#x2021;đ?&#x2018;&#x2021;đ?&#x2018;&#x2021;đ?&#x2018;&#x2021; â&#x2C6;&#x2019; 1190) (7) e consequence ofOne the transformation Austenite consequence ofhas thebeen mentioned, that being a peak in the sintering inkage rate near 1250Â°C after delta-ferrite forms. Retained delta-ferrite after sintering reduces 1250 sformation has been mentioned, that a peak in the sintering transformation has being been mentioned, martensite content after heat treatment, resulting in lower hardness and strength. For this after delta-ferritethat forms. Retained after sintering reduces being a peakdelta-ferrite in the sintering son, it is important to control the đ?&#x203A;żđ?&#x203A;żđ?&#x203A;żđ?&#x203A;żFe content. Data on the in situ behavior is thin. In a water heat treatment, resulting in lower hardness and strength. For this shrinkage rate near 1250Â°C after mized powder the initial powder has 15.5 % đ?&#x203A;żđ?&#x203A;żđ?&#x203A;żđ?&#x203A;żFe and reaches 18.7 % after 0 thermal debinding. in situ behavior is thin. In a water trol the đ?&#x203A;żđ?&#x203A;żđ?&#x203A;żđ?&#x203A;żFe content. Data on the delta-ferrite forms. Retained ring heating to the sintering temperature, đ?&#x203A;żđ?&#x203A;żđ?&#x203A;żđ?&#x203A;żFe disappears by 750Â°C, reappears 1300Â°C, 0.08 0.00 before0.04 0.12 0.16 0.20 powder has 15.5 delta-ferrite % đ?&#x203A;żđ?&#x203A;żđ?&#x203A;żđ?&#x203A;żFe and reaches 18.7 % after thermal debinding. after sintering reduces ches 22 % at 1360Â°C, and peaks at nearly 40 % at 1380Â°C. ng temperature, đ?&#x203A;żđ?&#x203A;żđ?&#x203A;żđ?&#x203A;żFe disappears by 750Â°C, reappears before 1300Â°C, Carbon (wt.%) the martensite content after heat peaks at nearly 40 % at 1380Â°C. cooling đ?&#x203A;żđ?&#x203A;żđ?&#x203A;żđ?&#x203A;żFe reverts to austenite, with as little as 3 % remaining after sintering [6]. Dilatometry treatment, resulting in lower Fig. 13 Relative phase content at various sintering temperatures is indicated by ows about 0.3 % dimensional change, beyond that to sintering, associated with the đ?&#x203A;żđ?&#x203A;żđ?&#x203A;żđ?&#x203A;żFe to hardness strength. For thisdue[6]. tenite, with as little as 3 %and remaining after sintering Dilatometry the tie lines on the phase diagram for 17-4 PH stainless steel [110]. Illustrated tenite phase change on cooling. For gas atomized Âľm powder a common goal is to limit final reason, it isto important control12 with nal change, beyond that due sintering,toassociated thehere đ?&#x203A;żđ?&#x203A;żđ?&#x203A;żđ?&#x203A;żFe are to the tie lines at a carbon content of 0.036%. At this concentration, the Î´Fe12 content. Data on the in-situ ooling. For gas atomized Âľm powder a common goal is to first limitdelta-ferrite final forms near 1270Â°C. By 1325Â°C the structure is about half 12 behaviour are sparse. In a water austenite and half delta-ferrite. The relative content is verified by quenching atomised powder, the initial powder 12 during sintering has 15.5% Î´Fe and reaches 18.7% after thermal debinding. During heating to the sintering temperature, On cooling, Î´Fe reverts to austenite, the Î´Fe to austenite phase change Î´Fe disappears by 750Â°C, reappears with as little as 3% remaining after on cooling. For gas atomised 12 Âľm before 1300Â°C, reaches 22% at sintering [6]. Dilatometry shows about powder, a common goal is to limit 1360Â°C and peaks at nearly 40% at 0.3% dimensional change, beyond final Î´Fe content to 10% or less. The 1380Â°C. that due to sintering, associated with map in Fig. 16 helps in matching

Density (g/cm3) 7.8 7.7

Tensile strength (MPa) 1400

11 Îźm gas atomised powder

1200

7.6

1000

7.5 7.4 7.3 7.2

800 0.2% C 0.1% C

600

7.1 1240 1260 1280 1300 1320 1340 1360 1380 1400 Sintering temperature (Â°C)

Fig. 14 Sintered density for two different carbon levels using a gas atomised 11 Âľm powder. Hold time at each temperature was 100 min [47]

Vol. 12 No. 2 ÂŠ 2018 Inovar Communications Ltd

400 0.001

0.01

0.1

Final carbon (%)

Fig. 15 Tensile strength after sintering (vacuum and hydrogen) and heat treatment, plotted versus retained carbon content [97]. This plot ignores density, grain size and other factors, so only a range of properties is associated with each carbon level

June 2018 Powder Injection Moulding International

MIM 17-4 PH stainless steel

Hold time (h)

Porosity (%)

5 30%

4 3

40%

50%

delta-ferrite vol.%

10 9 porosity, water atomised 8 delta-ferrite 7 water atomised 6 5 porosity delta-ferrite 4 gas atomised water atomised 3 2 1 0 1250 1275 1300 1325 1350

density, % 98.5 98.0 97.5 97.0 96.5 96.0 95.5

20%

10%

1 0 1240 1260 1280 1300 1320 1340 1360 Sintering temperature (°C)

Fig. 17 Data for the sintered porosity and delta-ferrite content in heat treated 17-4 PH after sintering for 60 min at various hold temperatures in hydrogen [54]. The results include gas and water atomised powders

less than 10% δFe, such as follows: • 1320°C for up to 20 min • 1300°C for 40 to 60 min • 1270°C for 90 to 150 min • 1260°C for 100 to 300 min. No correlation is found between delta-ferrite in the sintered microstructure and final density. This means that the typical sintering hold

Sintered heat treated

Sintered HIP, heat treated

% gain

Hardness (HRC)

Yield strength (MPa)

979

1103

Tensile strength (MPa)

1050

1137

Property

Elongation (%)

Table 7 Mechanical property changes with Hot Isostatic Pressing, in H1025 condition Condition*

10 9 8 7 6 5 4 3 2 1 0

Temperature (°C)

Fig. 16 Sintering time and temperature maps showing the sintered density and delta-ferrite contents using gas atomised powder [57]

this goal [57]. This time-temperature map is overlaid with density contours corresponding to 95.5% to 98.5% (in 0.5% increments) and deltaferrite contours. Higher sintering temperatures and longer hold times induce more δFe. For example, at 1300°C, up to 10% δFe forms in 60 min sintering [54, 57]. The plot helps identify temperature-time windows producing at least 97% density with

Delta-ferrite (%)

times are sufficient to compensate for diffusion rate differences between austenite and delta-ferrite. In several cases, lower sintering temperature and longer time combinations give the highest density. Sintering in hydrogen followed by a H900 heat treatment cuts the delta-ferrite in half compared to that expected from Fig. 16 [54]. Fig. 17 plots, for both gas and water atomised powders, a comparison of delta-ferrite and residual porosity versus sintering temperature (60 min hold). The results are confusing. One study says 1300°C for 60 min delivers 10% delta-ferrite, while another study reports that over 1350°C is required. The missing parameter is the carbon content. If the target for retained delta-ferrite is 10%, then sintering a gas atomised powder in hydrogen at 1343°C results in 9.5% retained delta-ferrite [56].

Yield strength, MPa

Tensile strength, MPa

Elongation, %

Elastic modulus, GPa

H900

790 - 1131

880 - 1269

10 - 11

196 - 221

H1025

958

1089

292

H1100

952

1027

255

H1100+

965

H1100 at 316°C+

772

737 - 790

900 - 910

12 - 16

183

623

689

164

H1150 H1150 at 316°C

* solutionised 1040°C, aged at 482°C 60 min (H900), 552°C 240 min (H1025), 593°C 240 min (H1100), or 240 min 621°C (H1050) + HIP prior to heat treatment

Table 8 Heat treatment effects on sintered 17-4 PH stainless steel

Powder Injection Moulding International

June 2018

Vol. 12 No. 2

Hot Isostatic Pressing For applications sensitive to fatigue failure, a protocol is to remove lingering pores via Hot Isostatic Pressing (HIP). If sintering delivers at least 95% density, then Hot Isostatic Pressing is effective without a container; called containerless HIP. At lower densities, encapsulation is required to prevent gas intrusion into the pores. Both gas and water atomised powders sintered in hydrogen for 60 min at 1300°C reach the required density for containerless HIP densification. Lower sintering temperatures fail to close the pores, so density is unchanged by HIP. Hot Isostatic Pressing at 1120 to 1165°C for 180 to 240 min at 103 MPa reaches essentially full density [19, 43, 112, 113]. However, tensile properties after HIP and heat treatment are little changed from that prior to HIP. For example, yield strength increases from 899 MPa to 908 MPa and fracture elongation increases from 12.2 to 14.6%. It would appear HIP is of little justification for tensile properties. Besides density and tensile properties, testing after HIP involves impact toughness using subsize un-notched bars. Compared to sintered compacts, HIP increases toughness by 25 to 50%. However, impact toughness is still low at 10 J [43]. Test results from HIP full size notched Charpy bars are similar, near 10 to 11 J. Compare this with the industry standard of 140 J for un-notched subsize bars [2]. Data from another HIP study reports the tensile property gains listed in Table 7 [114]. Both materials were heat treated to H1025 (552°C for 4 hour).

MIM 17-4 PH stainless steel

reaching 1050 to 1100 MPa with 9% elongation. In some cases, water atomised powder is less responsive to heat treatment. Part of the effect is from how residual oxygen in water atomised powder reacts with carbon during sintering. Carbon and nitrogen influence the martensite transformation responsible for strength [45]. Unfortunately, most studies do not report final carbon, oxygen and nitrogen levels, but do report sintered density, tensile strength and ductility.

One study examines 1300°C vacuum sintered 10 µm powder and reports a benefit from longer aging time. Peak hardness (41.5 HRC), tensile strength (1320 MPa) and ductility (10%) came with 180 min aging at 482°C [97]. This is triple the usual H900 aging time. For reference, a peak heat treated tensile strength of 1485 MPa with 9% elongation is attainable without additives [56]. Comparative heat treatment effects are summarised in Table 8 [19, 3, 115, 116]. These include different

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Heat treatment For strength and hardness, the desire is a martensite structure with less than 10% delta-ferrite [1]. If this is attained in the as-sintered condition, a tensile strength of 900 to 1100 MPa with 4 to 5% elongation is typical. After solutionisation (1038°C for 30 min), heat treatment to the H900 condition (482°C, 60 min) improves the tensile strength and ductility,

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www.centorr.com June 2018 Powder Injection Moulding International

MIM 17-4 PH stainless steel

Time (h) 5

Grain size (Îźm) 25

3 2 1

grain size Îźm 70 60 50 40 30 20

17-4 PH stainless sintered 1120 to 1320Â°C 6 to 60 min

0 1240 1260 1280 1300 1320 1340 1360

Temperature (Â°C)

aging conditions and Hot Isostatic Pressing prior to aging. Two reports are at an elevated temperature. The tensile strength at 316Â°C is 689 to 772Â MPa with 7 to 9% elongation. One elastic modulus report is anomalously high compared to other findings that average about 196 GPa [43, 117]. Poissonâ&#x20AC;&#x2122;s ratio is 0.29 for full density and changes little with density.

Sintering involves a competition between densification, pore rounding, pore coarsening, grain growth and phase transformations. Pore coarsening is from Ostwald ripening, where small pores emit vacancies that migrate and coalesce into large pores. The sintered microstructure typically evidences martensite, some delta-ferrite and residual spherical

Fig. 19 Grain size versus the inverse square root of the fractional porosity (1/(1 â&#x20AC;&#x201C; f)Â˝) for a variety of sintering conditions [81,82]. The starting grain size is 7.6 Âľm

pores. The pores may be filled with process atmosphere or reaction products such as steam. Retained austenite is sensitive to strain, so it decreases during a tensile test. For this reason, post-test analysis is not accurate for quantifying the relative phases. Likewise, the cooling process allows for phase changes. Quenching during sintering or studies using in-situ neutron or X-ray analysis find differences from that obtained after furnace cooling [6, 84]. The sintered microstructures also evidence spherical inclusions identified as silica-based particles, possibly chromium-silicon oxides [51, 59]. These sites nucleate ductile dimple fracture, so they are evident at a high concentration on fracture surfaces. Grain growth during sintering results in progressive enlargement of the grains. The growth behaviour

Peak temperature, Â°C

Tensile strength, MPa

Elongation, %

1150

1433

13.8

1210

1419

13.8

1235

1463

13.3

1260

1373

12.6

1285

1319

7.4

1310

1245

5.5

Table 9 Wrought 17-4 PH tensile properties after heating to various sintering temperatures

Inverse square-root porosity

Fig. 18 Grain size map for various combinations of peak temperature and hold time [56]

Microstructure

Powder Injection Moulding International

June 2018

is a function of sintering time and temperature, usually expressed as follows:

đ??şđ??şđ??şđ??ş 3 = đ??şđ??şđ??şđ??şđ?&#x2018;&#x201A;đ?&#x2018;&#x201A;đ?&#x2018;&#x201A;đ?&#x2018;&#x201A;3 + đ??žđ??žđ??žđ??ž đ?&#x2018;Ąđ?&#x2018;Ąđ?&#x2018;Ąđ?&#x2018;Ą đ?&#x2018;&#x2019;đ?&#x2018;&#x2019;đ?&#x2018;&#x2019;đ?&#x2018;&#x2019;đ?&#x2018;&#x2019;đ?&#x2018;&#x2019;đ?&#x2018;&#x2019;đ?&#x2018;&#x2019;đ?&#x2018;&#x2019;đ?&#x2018;&#x2019;đ?&#x2018;&#x2019;đ?&#x2018;&#x2019; đ?&#x2018;&#x2019;đ?&#x2018;&#x2019;

đ?&#x2018;&#x201E;đ?&#x2018;&#x201E;đ?&#x2018;&#x201E;đ?&#x2018;&#x201E;đ??şđ??şđ??şđ??ş ďż˝ đ?&#x2018;&#x2026;đ?&#x2018;&#x2026;đ?&#x2018;&#x2026;đ?&#x2018;&#x2026; đ?&#x2018;&#x2021;đ?&#x2018;&#x2021;đ?&#x2018;&#x2021;đ?&#x2018;&#x2021;

(8)

Here G is the median grain size after sintering for time t at absolute temperature T, starting at a grain size GO, with R = gas constant 8.31Â J/Â (mol K), K = rate constant and QG = activation energy. Since the activation energy and rate constant are unknown for 17-4 PH, the normal protocol is to map grain size versus time and temperature. An example is given in Fig. 18 for gas atomised powder [57]. Grain growth and densification are inherently connected, since both depend on diffusion at the grain boundaries. Densification requires atomic motion along the grain boundary and grain growth requires atomic motion across the grain boundary. For this reason, the grain size G relates to the starting grain size (or particle size) GO and sintered fractional density f as follows [118]:

đ??şđ??şđ??şđ??ş =

0.6 đ??şđ??şđ??şđ??şđ?&#x2018;&#x201A;đ?&#x2018;&#x201A;đ?&#x2018;&#x201A;đ?&#x2018;&#x201A;

ďż˝1 â&#x2C6;&#x2019; đ?&#x2018;&#x201C;đ?&#x2018;&#x201C;đ?&#x2018;&#x201C;đ?&#x2018;&#x201C;

(9)

The factor 0.6 compensates for the starting green density, typically near 60%. Fig. 19 plots data for 8Â Âľm water atomised powder sintered with various

ÂŠ 2018 Inovar Communications Ltd

Vol. 12 No. 2

combinations of time (0 to 60 min) and temperature (1120 to 1320°C), plotted as per Equation 9 [81, 82]. The starting grain size GO is 7.6 µm, essentially the same as the particle size.

Mechanical properties Already several mentions of mechanical properties have arisen. The focus on mechanical properties derives from the fact that sintered 17-4 PH is mostly used for structural devices. Strength, hardness and elongation are favourite comparative properties, already used here to examine the influence from several processing factors. Fatigue, fracture toughness, yield strength and reduction in area also are concerns, but they are reported less frequently. Many reports assess sintered mechanical properties [27, 43, 44, 47, 51-56, 60, 65, 66, 71, 77, 80-83,

MIM 17-4 PH stainless steel

92, 94, 116-127]. In addition, Additive Manufacturing and Metal injection Moulding firms provide an abundance of unaudited property reports. This summary only includes studies where the powder, processing and similar details are reported. These generally involve a wide range of powder types, with a typical 12 µm median particle size. Forming includes die compaction, injection moulding, binder jetting

atmosphere includes vacuum, argon-hydrogen, nitrogen, hydrogen and nitrogen-hydrogen. Almost half of the studies perform postsintering heat treatments, usually solutionisation followed by aging at 482°C 60 min (H900). At this point, only H900 properties are included. A few studies compare sintered material with wrought material after passing the wrought material

“The focus on mechanical properties derives from the fact that sintered 17-4 PH is mostly used for structural devices.” and feedstock extrusion options. Sintering temperatures range from 900 to 1390°C (1310°C is typical), hold times range from 10 to 180 min (75 min is typical) and sintering

through a simulated sintering cycle [51, 121]. Heating to temperatures over 1235°C (when δFe probably forms) weakens the wrought material with significantly less

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T.D.(g/cm3) 4.80 4.70 4.80 4.70 4.90

S.S.A(m2/g) 0.34 0.34 0.34 0.35 0.36

S.D.(g/cm3) 7.90 7.70 7.80 7.70 7.95

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67 June 2018 Powder Injection Moulding International 2018/1/16 20:05

MIM 17-4 PH stainless steel

The industry standard gives a minimum tensile strength of 790Â MPa Tensile strength (MPa) 1010 150 1485 1063 and hardness of 27 HRC after sintering and 1070 MPa and 33Â HRC Hardness (HRC) 30 6 44 34 after heat treating, both with 4% Elongation (%) 8 5 21 9 elongation. For comparison, a survey medical grade 17-4 PH Density (%) 97.3 1.6 99.9 97.3 3 % (7.58 g/cm ). Statistical analysisofofsintered the studies behind these values attributes 6 (H900 heat treatment) reports density property variation to sintering parameters, but molding, debinding, and heat trea Table 10 Average properties for 17-4 PH stainless steel sintered to a density of at 97.4%, hardness at 37 HRC, yield recognized factors [42]. 94% or higher strength of 1090 MPa and tensile strength of 1196Â MPa [127]. The industry standard gives minimum tensile strength of 790 MPa and hardness Many factors influence the sintering, and 1070 MPa and 33 HRC after heat treating, both with 4 % elongation mechanical properties. Statistical ductility, as summarised in TableÂ 9 Average properties are calculated a survey of sintered medical grade 17-4 PH (H900 heat treatment) reports densit analysis shows a dominant factor for [121]. This property deterioration using 82 reports and the summary is hardness at 37 HRC, yield strengthtensile of 1090 MPa, Ď&#x192;and tensile strength of 1196 MPa strength comes from grain coarsening, given in Table 10. This includes only U is the fractional sintered density fS, accounting for 82% formation of contiguous delta-ferrite those reports where the sintered Many factors influence the mechanical properties. Statistical analysis shows a do of the variation: stringers on grain boundaries and density is 94% of theoretical or tensile strength Ď&#x192;U is the fractional sintered density fS, accounting for 82 % of the element segregation between phases. higher. Theg/cm limitation to 94% or analysis of the studies behind these values attributes 3). Statistical % (7.58 At the sintering temperature, Ni and higher density is the same as used (10) and heat tre = molding, 1148 đ?&#x2018;&#x201C;đ?&#x2018;&#x201C;đ?&#x2018;&#x201C;đ?&#x2018;&#x201C;đ?&#x2018;&#x2020;đ?&#x2018;&#x2020;đ?&#x2018;&#x2020;đ?&#x2018;&#x2020;đ?&#x2018; đ?&#x2018; đ?&#x2018; đ?&#x2018; debinding, property variation to sintering parameters,đ?&#x153;&#x17D;đ?&#x153;&#x17D;đ?&#x153;&#x17D;đ?&#x153;&#x17D;đ?&#x2018;&#x2C6;đ?&#x2018;&#x2C6;đ?&#x2018;&#x2C6;đ?&#x2018;&#x2C6; but Cu diffuse into austenite while Cr in the industry standard [2]. The final recognized factors [42]. and Si diffuse into delta-ferrite. Such column summarises the properties where N = 5.67, similar to other segregation is difficult to remove by using only results from heatgives treated The industry standard minimum tensile strength of 790 MPa and hardness where N =both 5.67, similar [68].AsAs example, Figure 20 p sintered metals metals [68]. anan example, a lower temperature post-sintering samples. For groups, theto other sintered sintering, and 1070 MPa and 33 HRC after heat treating, both with 4 % elongatio 3 tensile strength versus sintered density for a water atomized powder sintered 60 Fig. 20 plots the ultimate tensile heat treatment [123]; homogenisation mean density is 97.3% (7.58 g/cm ). a survey of sintered medical grade 17-4 PH (H900 heat treatment) reports dens [59, 92]. The increase in load bearing area due to densification is an important fac strength versus sintered density for at 1150Â°C is required [122]. Statistical analysis of the studies hardness at 37 HRC, yield strength of 1090 MPa, and tensile strength of 1196 MP a water powder sintered 60 Replica samples generally give behind these values attributes 60% density to strength. Although sintered is aatomised dominant factor with respect to streng min in hydrogen [59, 92]. The increase low scatter; standard deviations for ofoxygen, the property variation to sinteringplay a carbon, and nitrogen role [44, 47, 71]. Elongation to fracture result Many factors influence the mechanical properties. Statistical analysis shows ad in load bearing area due to densisintered tensile strength are reported parameters, but moulding, debinding the same plot. therecogfractionalfication sintered fS, factor accounting tensile U is is andensity important with for 82 % of th as Âą 4 to 48 MPa, elongation as ÂąÂ 0.4 and heat strength treatment Ď&#x192; are also respect to strength. Fracture also varies with sintered density,Although rangingsintered from 4 to 9 MPaâ&#x2C6;&#x161;m to 2% and hardness as Âą 2 HRC. nised factorstoughness [42]. đ?&#x153;&#x17D;đ?&#x153;&#x17D;đ?&#x153;&#x17D;đ?&#x153;&#x17D; = 1148 đ?&#x2018;&#x201C;đ?&#x2018;&#x201C;đ?&#x2018;&#x201C;đ?&#x2018;&#x201C;đ?&#x2018;&#x2020;đ?&#x2018;&#x2020;đ?&#x2018;&#x2020;đ?&#x2018;&#x2020;đ?&#x2018; đ?&#x2018; đ?&#x2018; đ?&#x2018; density is a đ?&#x2018;&#x2C6;đ?&#x2018;&#x2C6;đ?&#x2018;&#x2C6;đ?&#x2018;&#x2C6; dominant factor 98.5 to 99.2 % [66]. As a benchmark, fracture toughness forwith wrought 17-4 PH is 4 respect to strength, retained oxygen, In turn, hardness directly relates tocarbon strength. The ultimate tensile and nitrogen play a role [44, strength and HR Tensile strength (MPa) Elongation (%) correlate as follows: 47, 71]. Elongation to fracture where N = 5.67, similar to other sintered metals [68]. As an results example, Figure 20 p are included in the same plot. tensile strength versus sintered density for a water atomized powder sintered 6 1200 6 447 + 19also đ??ťđ??ťđ??ťđ??ťđ?&#x2018;&#x2026;đ?&#x2018;&#x2026;đ?&#x2018;&#x2026;đ?&#x2018;&#x2026;đ?&#x2018;&#x2026;đ?&#x2018;&#x2026;đ?&#x2018;&#x2026;đ?&#x2018;&#x2026; đ?&#x153;&#x17D;đ?&#x153;&#x17D;đ?&#x153;&#x17D;đ?&#x153;&#x17D;đ?&#x2018;&#x2C6;đ?&#x2018;&#x2C6;đ?&#x2018;&#x2C6;đ?&#x2018;&#x2C6; =toughness Fracture varies [59, 92]. The increase in load bearing area due to densification is an important fa 10 Îźm water with sintered density, ranging from to strength. Although5sintered density is a dominant factor with respect to stren atomised 1h, 1000 4 to 9 MPaâ&#x2C6;&#x161;m for densities of 98.5 to oxygen, carbon, and nitrogen play 99.2% a role[66]. [44,As47, 71]. Elongation to fracture resu hydrogen benchmark, In other words, hardness is equally sensitive toathose same fracture factors that determine the same plot. toughness for wrought 17-4 PH is strength and is dominated by sintering factors. 4 800 48Â MPaâ&#x2C6;&#x161;m [128]. Fracture toughness also varies with sintered density, ranging from 4 to 9 MPaâ&#x2C6;&#x161;m turn,to hardness directly The elastic modulus is reported in theIn186 207 GPa rangerelates [2, 43, 117], except fo 98.5 to 99.2 % [66]. As a benchmark, fractureThe toughnesstensile for wrought 17-4 PH is strength. giving values up to 292 Poissonâ&#x20AC;&#x2122;s ratioultimate is 0.29. 600 3 GPa [115]. to and HRC hardness correlate In turn, hardness directly relates tostrength strength. The ultimate tensile strength and H Fracture elongation is sensitive to as fractional follows: density and expresses that sensitivit correlate as follows: 400 2 parameter in the following relation [68]: Mean

Deviation

Maximum

200

Heat treated

19 đ??ťđ??ťđ??ťđ??ťđ?&#x2018;&#x2026;đ?&#x2018;&#x2026;đ?&#x2018;&#x2026;đ?&#x2018;&#x2026;đ?&#x2018;&#x2026;đ?&#x2018;&#x2026;đ?&#x2018;&#x2026;đ?&#x2018;&#x2026; đ?&#x153;&#x17D;đ?&#x153;&#x17D;đ?&#x153;&#x17D;đ?&#x153;&#x17D;đ?&#x2018;&#x2C6;đ?&#x2018;&#x2C6;đ?&#x2018;&#x2C6;đ?&#x2018;&#x2C6; = 447 đ?&#x2018;&#x201C;đ?&#x2018;&#x201C;đ?&#x2018;&#x201C;đ?&#x2018;&#x201C;+3/2 đ?&#x2018;?đ?&#x2018;?đ?&#x2018;?đ?&#x2018;? = ďż˝(1 + đ?&#x203A;˝đ?&#x203A;˝đ?&#x203A;˝đ?&#x203A;˝ đ?&#x153;&#x20AC;đ?&#x153;&#x20AC;đ?&#x153;&#x20AC;đ?&#x153;&#x20AC; 2 )

(11)

In other words, hardness is equally

In other words, hardness is equallysensitive sensitive to those factors to those samesame factors that that determin 0 determine sintered tensile strength by sintering factors. 70 80 strength90and is dominated 100 where Z is the elongation relative to full density material, andfactors. Îľ is the fractional p and is dominated by sintering Sintering density (%) The elastic modulus is reported in theThe 186 to 207 GPa range [2, except Î˛ = 300, with a full density ductility of 5 ductility data in Figure 20 correspond to elastic modulus is reported 43, in 117], giving values up to 292 GPa [115]. Poissonâ&#x20AC;&#x2122;s ratio is 0.29. 186 observed to 207 GPa in range [2, 43, 117], steels [96, 12 This sensitivity to porosity is lowerthe than other sintered

Fig. 20 Sintered strength (upper curve) and elongation (lower curve) of 10 except for one report giving values Fracture elongation to up fractional density and expresses that sensitivi Âľm water atomised 17-4 PH stainless steel powder after sinteringis 60sensitive min in to 292 GPa [115]. Poissonâ&#x20AC;&#x2122;s ratio parameter in the following relation [68]: hydrogen at temperatures from 900 to 1350Â°C [59, 92] is 0.29.

Powder Injection Moulding International

June 2018

đ?&#x2018;?đ?&#x2018;?đ?&#x2018;?đ?&#x2018;? =

đ?&#x2018;&#x201C;đ?&#x2018;&#x201C;đ?&#x2018;&#x201C;đ?&#x2018;&#x201C; 3/2

ďż˝(1 +Ltdđ?&#x203A;˝đ?&#x203A;˝đ?&#x203A;˝đ?&#x203A;˝ Vol. đ?&#x153;&#x20AC;đ?&#x153;&#x20AC;đ?&#x153;&#x20AC;đ?&#x153;&#x20AC; ) 12 No. 2 ÂŠ 2018 Inovar Communications

ws:

đ?&#x153;&#x17D;đ?&#x153;&#x17D;đ?&#x153;&#x17D;đ?&#x153;&#x17D;đ?&#x2018;&#x2C6;đ?&#x2018;&#x2C6;đ?&#x2018;&#x2C6;đ?&#x2018;&#x2C6; = 447 + 19 đ??ťđ??ťđ??ťđ??ťđ?&#x2018;&#x2026;đ?&#x2018;&#x2026;đ?&#x2018;&#x2026;đ?&#x2018;&#x2026;đ?&#x2018;&#x2026;đ?&#x2018;&#x2026;đ?&#x2018;&#x2026;đ?&#x2018;&#x2026;

rdness is equally sensitive to those same factors that determine sintered tensile minated by sintering factors.

Fracture elongation sensitive to 117], except for one report us is reported in the 186 to 207 GPaisrange [2, 43, Condition fractional density and expresses that o 292 GPa [115]. Poissonâ&#x20AC;&#x2122;s ratio is 0.29.

Test bar

Impact toughness, J

Notched, full-size*

21 - 41

Sintered, solutionised

Notched, full-size*

Sintered, solutionised

Notched, subsize

Sintered, solutionised

Un-notched, full-size

272

Sintered, solutionised

(12) Un-notched, subsize

153

Cast, heat treated sensitivity via the Î˛ parameter in the following relation [68]:and expresses thatSintered, n is sensitive to fractional density sensitivity via the Î˛ no treatment

ollowing relation [68]:

đ?&#x2018;?đ?&#x2018;?đ?&#x2018;?đ?&#x2018;? =

đ?&#x2018;&#x201C;đ?&#x2018;&#x201C;đ?&#x2018;&#x201C;đ?&#x2018;&#x201C; 3/2

ďż˝(1 + đ?&#x203A;˝đ?&#x203A;˝đ?&#x203A;˝đ?&#x203A;˝ đ?&#x153;&#x20AC;đ?&#x153;&#x20AC;đ?&#x153;&#x20AC;đ?&#x153;&#x20AC; 2 )

MIM 17-4 PH stainless steel

(11)

(12)

where Z is the elongation relative

Sintered, porosity. heat treated Notched, full-size* ngation relative to full density material, and Îľ is the fractional The to full density material and Îľ is the Î˛ = 300, with a full density ductility of 5.2 % in this case. gure 20 correspond to Sintered, heat treated Notched, subsize fractional porosity. The ductility data porosity is lower than observed in other sintered steels [96, 129]. in Fig. 20 correspond to Î˛ = 300, with a full density ductility of 5.2% in this case. This sensitivity to porosity is lower than observed in other sintered steels [96, 129]. Impact toughness evidences a high variability that depends on test conditions [43, 103, 116, 120]. There are at least four tests in use, notched and un-notched, and full size (10 by 10 mm) and subsize (5 by 10 mm). The standard Charpy test relies on a 2 mm deep notch in a full size bar. As evident in Table 11, the findings are highly scattered [5, 43, 103, 116, 120, 128]. This compilation includes comparative data for cast and wrought 17-4 PH. The heat treated condition is H900 and a few tests are in the solutionised condition. For comparison, the industry sets 140 J as the recommended value for subsize un-notched test bars, both as-sintered and heat treated. No test data are published to support this value, so caution is advised for applications sensitive to impact loading. Testing in use temperature, strain rate and surface finish conditions is advised to avoid surprises. Residual pores cause low impact toughness, but second phases (deltaferrite), segregation of impurities and inclusions are problems. Although the industry standard is 140 J, the sintered results are much lower, tending toward 20 J (H900). Higher aging temperatures improve the response, reaching up to 50 J for notched full-size bars aged at 610Â°C [116]. Like tensile tests, the fracture surface shows evidence of deltaferrite and ductile dimples nucleated at silica or chromia inclusions [39, 51,Â 130].

Vol. 12 No. 2 ÂŠ 2018 Inovar Communications Ltd

2 â&#x20AC;&#x201C; 49 1

Sintered, heat treated

Un-notched, full-size

Sintered, heat treated

Un-notched, subsize

14 to 25

Notched, full-size*

48 to 275

Wrought, solutionised

Un-notched, subsize

> 275

Wrought, heat treated

Notched, full-size*

15 to 37

Wrought, heat treated

Notched, subsize

Wrought, solutionsed

* Standard Charpy impact toughness geometry

Table 11 Comparative impact toughness reports

Powder, condition

Testing condition

Fatigue strength, MPa

Mixed elemental, H900

50% survival, R = -1

517

Gas atomised, H1150

50% survival, R = -1

405

Gas atomised, H1150

99% survival, R = -1

362

Gas atomised, H1150

50% survival, R = 0.1

517

Gas atomised, H1150

99% survival, R = 0.1

490

Gas atomised, sintered

50% survival, R = -1

470

Gas atomised, HT

50% survival, R = -1

630

Not disclosed

500

Gas atomised, sintered

Table 12 Fatigue endurance strength (107 cycles) for sintered 17-4 PH stainless steel

Reports on the fatigue endurance limit are collected in Table 12 [43, 49, 114, 130]. Fatigue strength for the fully reversed cycle (R =Â -1, where RÂ = min stress over max stress) at 50% survival is 517 MPa for sintered mixed elemental powder heat treated to H900. On the other hand, gas atomised powder in the H1150 heat treatment is lower at 423 MPa. Due to scatter, the 99% survival fatigue strength is reduced to 362 MPa. Other reports compare heat treatment against as-sintered,

giving 630 and 470 MPa, respectively. Low cycle fatigue after HIP and heat treatment (H1100) is not as good as wrought, but better than cast material [19]. Over a large number of studies, there is no statistical evidence of mechanical property differences between gas and water atomised powders. However, in a direct comparison, the tensile strength is 1280 MPa for gas atomised and 1136 MPa for water atomised after sintering 1350Â°C for 60 min followed

June 2018 Powder Injection Moulding International

MIM 17-4 PH stainless steel

480°C aging h

Hardness HRC

Corrosion rate g/(m2 h)

Wrought, solution, aged

4.2

Sintered, no solution, aged

2.5

Sintered, no solution, no age

25.4

Sintered, solution, aged

7.1

Preparation*

* Solution treatment 1020°C, 60 min, water quench; aging 480°C

Table 13 Ferric chloride (6% solution) corrosion rates

Corrosion, wear and biocompatibility

by solutionisation and H900 heat treatment [53]. Note, heat treated tensile strength reaches to 1485 MPa with 8-9% elongation using gas atomised powder [44, 56, 64]. Likewise, for ductility, a direct comparison for 1300°C sintering using 14 µm gas and water atomised powders reports 14.5% elongation and 1% elongation, respectively [71]. The sintering cycle apparently needs to be modified to accommodate the powder type and then similar properties are possible.

Standard corrosion testing involves exposure to various environments - ferric chloride, artificial saliva, chloride bleach, salt water, Ringer’s solution, dilute sulphuric acid, copper sulphate solution, nitric acid and salt sprays [2, 51, 95, 131-135]. Extensive corrosion testing of four sintered stainless steels found 17-4 PH to be least resistant to a variety of environments [134]. Wrought material is

Wear loss (mg) 15

6 Pin on disk (HRC 62) dry sliding wear unlubricated 12 kg load, 1400 m, 0.2 m/s

100 98

99 Density (%)

Fig. 21 Wear loss in sliding pin on disc tests for sintered 17-4 PH, illustrating the gains in wear resistance that come with higher sintered density [66]

Powder Injection Moulding International

June 2018

more corrosion resistant than sintered material, partly because pores induce local corrosion (concentration polarisation) in the sintered material. However, when wrought is subjected to a “sintering” cycle it too degrades. The high temperature exposure associated with sintering induces segregation that gives galvanic corrosion. Also, any retained oxygen is a negative factor. Oxygen is avoided by use of gas atomised powder [135]. However, in one test, sintered (1370°, 75 min, hydrogen) master alloy powder resulted in a better corrosion resistance (2% salt water, 60°C, 2 weeks immersion) [70]. Generally, hydrogen sintering provides corrosion resistance. In a novel study, 14 µm gas atomised powder (sintered in hydrogen for 60 min at 1300°C) has a low corrosion rate (1.7 g/(m2 h)) in 6% ferric chloride solution when solutionisation is skipped and aging extended to 180 min at 480°C [27]. As-sintered salt water immersion tests report about 2.2 g/ (m2 h) corrosion rate [88]. Table 13 illustrates the differing corrosion rates [27]. The sintered material (1300°C, 60 min, H2) without solutionisation, but with 120 min aging at 480°C, was the most corrosion resistant. A different study (water atomised, sintered 1340°C, hydrogen, 30 min) reports that sulphuric acid corrosion resistance was best in the H900 condition [136]. Adding to the confusion, one report is for corrosion resistance after sintering without solutionisation or aging [95]. For medical applications, nitric acid passivation reportedly improves corrosion resistance [127]. No indication is given on how frequently this is applied or the corresponding rate of corrosion. Wear tests on sintered 17-4 PH using the pin on disc test show that material loss depends on sintered density, as illustrated in Fig. 21 [66]. The mass loss increases with sliding distance and load. No comparative standards are included, so the relative wear behaviour of sintered versus wrought material is unknown. Biocompatibility is related to corrosion resistance. The corrosion resistance makes 17-4 PH good

Vol. 12 No. 2

Shrinkage (%)

in cytotoxicity [137], but it is not competitive in overall biocompatibility when compared to sintered titanium and cobalt alloys [138].

Dimensional variability depends on several factors and is often dominated by shaping and feedstock factors. Sintering amplifies the effects from variations occurring during shaping. Effectively, some of the sintered size variation is embedded in the part mass variation, emerging in the sintering step [139]. Depending on sensors and controls employed in shaping, up to a ten-fold difference in dimensional variability results between vendors. The nominal capability is termed the coefficient of variation CV. Expressed as a percent, CV is measured using several components:

đ?&#x2018;&#x2020;đ?&#x2018;&#x2020;đ?&#x2018;&#x2020;đ?&#x2018;&#x2020; đ?&#x2018;&#x2C6;đ?&#x2018;&#x2C6;đ?&#x2018;&#x2C6;đ?&#x2018;&#x2C6;

cooling

Dimensional control

đ??śđ??śđ??śđ??śđ?&#x2018;&#x2030;đ?&#x2018;&#x2030;đ?&#x2018;&#x2030;đ?&#x2018;&#x2030; = 100

MIM 17-4 PH stainless steel

(13)

where S is the standard deviation and U is the mean size. Over the industry, the typical value is Âą 0.3% [2, 131]. An assumption is that the mean size is centred to the middle of the tolerance range, which is not always possible. An audit of injection moulded and sintered 17-4 PH dental brackets finds CV ranges from Âą 1.2% to Âą 0.3% [137]. This is the same as seen in another study [57]. Of that variation, 69% is related to sintering time, temperature and heating rate while 31% is due to other factors. Impressive results are reported using solvent debinding with the largest CV (Âą 0.17%) aligned with gravity [29]. Sintered dimensional prediction is a major focus of computer simulations [18, 54, 81, 82, 86]. The models require several input parameters. Most efforts invoke viscous approximations for sintering shrinkage and embed those approximations into finite element analysis. Fig. 22 plots experimental and simulated shrinkage for a 10 Âľm gas atomised

experiment simulation

8 4

heating

0 200

400

600

800

1000

1200

1400

Temperature (Â°C)

Fig. 22 Dilatometry sintering shrinkage for 10 Âľm 17-4 PH stainless steel powder, including both heating and cooling, comparing the computer simulated dimensional change with the experimentally measured behaviour [82] đ?&#x2018;Ąđ?&#x2018;Ąđ?&#x2018;Ąđ?&#x2018;Ą

powder. The sintering starts with 55% density, following a cycle of 10Â°C/Â min to 1010Â°C with 60 min hold, then 2Â°C/Â min to 1365Â°C (no hold), with cooling at 10Â°C/min [82]. The experimental curve is from dilatometry. The simulation prediction is off by 0.6% on final size. Such an error is larger than a typical component size tolerance. Thus, such models help in estimating size change, but not designing tooling. Another approach to predicting final size is via the master sintering curve. This employs a thermal work of sintering concept as captured in an integral of the time (t) and temperature (T, absolute temperature) [39, 54, 89, 111, 140]. The work of sintering Î¸ term is calculated using an apparent activation energy QE as follows: đ?&#x2018;Ąđ?&#x2018;Ąđ?&#x2018;Ąđ?&#x2018;Ą

đ?&#x153;&#x192;đ?&#x153;&#x192;đ?&#x153;&#x192;đ?&#x153;&#x192; = ďż˝ 0

1 đ?&#x2018;&#x201E;đ?&#x2018;&#x201E;đ?&#x2018;&#x201E;đ?&#x2018;&#x201E;đ??¸đ??¸đ??¸đ??¸ đ?&#x2018;&#x2019;đ?&#x2018;&#x2019;đ?&#x2018;&#x2019;đ?&#x2018;&#x2019;đ?&#x2018;&#x2019;đ?&#x2018;&#x2019;đ?&#x2018;&#x2019;đ?&#x2018;&#x2019;đ?&#x2018;&#x2019;đ?&#x2018;&#x2019;đ?&#x2018;&#x2019;đ?&#x2018;&#x2019; ďż˝â&#x2C6;&#x2019; ďż˝ đ?&#x2018;&#x2018;đ?&#x2018;&#x2018;đ?&#x2018;&#x2018;đ?&#x2018;&#x2018;đ?&#x2018;Ąđ?&#x2018;Ąđ?&#x2018;Ąđ?&#x2018;Ą đ?&#x2018;&#x2021;đ?&#x2018;&#x2021;đ?&#x2018;&#x2021;đ?&#x2018;&#x2021; đ?&#x2018;&#x2026;đ?&#x2018;&#x2026;đ?&#x2018;&#x2026;đ?&#x2018;&#x2026; đ?&#x2018;&#x2021;đ?&#x2018;&#x2021;đ?&#x2018;&#x2021;đ?&#x2018;&#x2021;

(14)

again R is the universal gas constant. The heating cycle is tracked to include the thermal contributions on the way to the peak temperature, an important part of densification.

Vol. 12 No. 2 ÂŠ 2018 Inovar Communications Ltd đ?&#x2018;&#x201C;đ?&#x2018;&#x201C;đ?&#x2018;&#x201C;đ?&#x2018;&#x201C;đ?&#x2018;&#x2020;đ?&#x2018;&#x2020;đ?&#x2018;&#x2020;đ?&#x2018;&#x2020; = đ?&#x2018;&#x201C;đ?&#x2018;&#x201C;đ?&#x2018;&#x201C;đ?&#x2018;&#x201C;đ??şđ??şđ??şđ??ş +

đ?&#x153;&#x192;đ?&#x153;&#x192;đ?&#x153;&#x192;đ?&#x153;&#x192; = ďż˝

The only0adjustable parameter is the activation energy, which changes due to phase transformations for 17-4 PH stainless steel. The fractional sinter density fS at any point is calculated from the integral work and starting green density fG,

đ?&#x2018;&#x201C;đ?&#x2018;&#x201C;đ?&#x2018;&#x201C;đ?&#x2018;&#x201C;đ?&#x2018;&#x2020;đ?&#x2018;&#x2020;đ?&#x2018;&#x2020;đ?&#x2018;&#x2020; = đ?&#x2018;&#x201C;đ?&#x2018;&#x201C;đ?&#x2018;&#x201C;đ?&#x2018;&#x201C;đ??şđ??şđ??şđ??ş +

1 â&#x2C6;&#x2019; đ?&#x2018;&#x201C;đ?&#x2018;&#x201C;đ?&#x2018;&#x201C;đ?&#x2018;&#x201C;đ??şđ??şđ??şđ??ş (15) đ?&#x2018;&#x17D;đ?&#x2018;&#x17D;đ?&#x2018;&#x17D;đ?&#x2018;&#x17D; đ?&#x2018;&#x17D; đ?&#x2018;&#x2122;đ?&#x2018;&#x2122;đ?&#x2018;&#x2122;đ?&#x2018;&#x2122;đ?&#x2018;&#x2122;đ?&#x2018;&#x2122;đ?&#x2018;&#x2122;đ?&#x2018;&#x2122;đ?&#x153;&#x192;đ?&#x153;&#x192;đ?&#x153;&#x192;đ?&#x153;&#x192; 1 + đ?&#x2018;&#x2019;đ?&#x2018;&#x2019;đ?&#x2018;&#x2019;đ?&#x2018;&#x2019;đ?&#x2018;&#x2019;đ?&#x2018;&#x2019;đ?&#x2018;&#x2019;đ?&#x2018;&#x2019;đ?&#x2018;&#x2019;đ?&#x2018;&#x2019;đ?&#x2018;&#x2019;đ?&#x2018;&#x2019; đ?&#x2018;&#x2019; ďż˝ đ?&#x2018;?đ?&#x2018;?đ?&#x2018;?đ?&#x2018;?

This sigmoid function accounts for how density reaches saturation at 100%, no matter what additional work is added. For 10 Âľm gas atomised 17-4 PH powder, value of a = 29.93 and b = 1.521 with QE = 350 kJ/mol. Equation 15 is employed to compute shrinkage and final component size. If the phase transformation is ignored, QE = 360 kJ/mol and predicted sintered size is good to within 0.8%. Smaller powders sinter more easily, resulting in a further reduction in activation energy [39] as summarised in Table 14. The model accuracy is improved by using an activation energy of 321Â kJ/Â mol for austenite (below 1200Â°C) and 350 kJ/mol for delta-

â&#x2C6;&#x2019; đ?&#x2018;&#x201C;đ?&#x2018;&#x201C;đ?&#x2018;&#x201C;đ?&#x2018;&#x201C;đ??şđ??şđ??şđ??ş Powder Injection Moulding International June12018 đ?&#x2018;&#x17D;đ?&#x2018;&#x17D;đ?&#x2018;&#x17D;đ?&#x2018;&#x17D; đ?&#x2018;&#x17D; đ?&#x2018;&#x2122;đ?&#x2018;&#x2122;đ?&#x2018;&#x2122;đ?&#x2018;&#x2122;đ?&#x2018;&#x2122;đ?&#x2018;&#x2122;đ?&#x2018;&#x2122;đ?&#x2018;&#x2122;đ?&#x153;&#x192;đ?&#x153;&#x192;đ?&#x153;&#x192;đ?&#x153;&#x192; 1 + đ?&#x2018;&#x2019;đ?&#x2018;&#x2019;đ?&#x2018;&#x2019;đ?&#x2018;&#x2019;đ?&#x2018;&#x2019;đ?&#x2018;&#x2019;đ?&#x2018;&#x2019;đ?&#x2018;&#x2019;đ?&#x2018;&#x2019;đ?&#x2018;&#x2019;đ?&#x2018;&#x2019;đ?&#x2018;&#x2019; đ?&#x2018;&#x2019; ďż˝ đ?&#x2018;?đ?&#x2018;?đ?&#x2018;?đ?&#x2018;?

MIM 17-4 PH stainless steel

Particle size (µm)

Activation energy (kJ/mol)

10.0

360

8.3

358

4.2

308

3.2

278

Table 14 Master sintering curve apparent activation energy versus median particle size

ferrite. This effectively embeds the phase change into the shrinkage behaviour. The two-step treatment reduces the prediction error to less than the measurement error [54, 111].

Conclusions and identified needs Starting around 1990, considerable effort emerged on the sintering of 17-4 PH stainless steel, with much focus on structural property optimisation. Tremendous progress has taken place, delivering an attractive combination of sintered properties suitable for many applications. With regard to properties, the sintering temperature is a dominant factor. It is more important than powder type, particle size, green density, hold time and other parameters, as covered in this article. Sintered properties are sensitive to what phases exist in the sintered material. Likewise, properties vary with the phase morphology, sintered density and post-sintering heat treatment. Hot Isostatic Pressing improves properties, but sintered density is the key factor determining properties. Statistically significant correlations are found between strength and density, strength and hardness and ductility and density. However, impact properties are very suspect. The reason for variability is not clear. This implies that uncontrolled factors are causing property variations. Most likely the final carbon, oxygen and nitrogen levels, as well as phase morphology (for

example delta-ferrite on grain boundaries), pore size and grain size are uncontrolled factors. Often only the starting powder carbon content is reported. Critical study is needed on final C, O, N contents as linked to properties. Further, classic heat treatments are not optimal for sintered 17-4 PH stainless steel. To emphasise this point, note that the highest tensile strength reports are associated with 17-4 PH stainless steel powders treated with intentional additives of boron or carbon. The initial alloy composition and heat treatments used for sintered powders were optimised for cast and wrought products. Sintered products benefit from modified compositions and different heat treatments, as noted in this report. Two areas of uncertainty are impact toughness and corrosion resistance. Further, fracture toughness is missing adequate attention. The measures to date indicate a low resistance to crack propagation. Much progress has taken place over the years since sintered 17-4 PH stainless steel gained attention. When an injection moulded aerospace component with a tensile strength of 1068 MPa was given “part of the year” designation, sintered 17-4 PH jumped to the forefront of metal Powder Injection Moulding. That platform is now an important basis for Additive Manufacturing and other binder-assisted forming approaches, all relying on this strong technology base. Much progress is evident in the many reports to date. With focused attention to some opportunities, many more applications for sintered 17-4 PH are anticipated.

Powder Injection Moulding International

June 2018

Author Professor Randall M. German Former Associate Dean of Engineering San Diego State University 5500 Campanile Drive San Diego California 92182-1326 USA Professor German is the author of more than1000 articles, 18 books, and 24 patents and has been active in PIM for over 20 years. He conducts research and consults with firms on issues of customer development, technology enhancements, new product development and R&D policy. He has three books on PIM and is a Consulting Editor of PIM International.

References [1] D. Peckner, I. M. Bernstein, Handbook of Stainless Steels, McGraw-Hill, New York, NY, 1977. [2] Materials Standards for Metal Injection Molded Parts, MPIF Standard 35, Metal Powder Industries Federation, Princeton, NJ, 2016. [3] R. M. German, “The Production of Stainless Steels by Injection Molding Water Atomized Prealloy Powders,” Journal of Injection Molding Technology, 1997, vol. 1, pp. 171-180. [4] J. R. Davis (ed.), Stainless Steels, ASM International, Materials Park, OH, 1994. [5] H. J. Rack, Physical and Mechanical Properties of Cast 17-4 PH Stainless Steel, Report SAND80-2302, Sandia National Laboratories, Albuquerque, NM, 1981. [6] D. J. Gossens, R. E. Whitfield, A. J. Studer, “Optimising Sintering in Metal Injection Moulding Using In Situ Neutron Diffraction,” Materials Science Forum, 2012, vol. 706, pp. 1737-1742. [7] J. A. Grohowski, PIM Tolerance Control for Different Powder Systems, PM Lab, Penn State University, State College, PA, 20 Oct 1994. [8] Y. Kankawa, K. Saitou, T. Kida, K. Ono, Y. Kaneko, “Injection Molding of SUS316L Powder with Polyacetal,” Journal of the Japan Society of Powder and Powder Metallurgy, 1993, vol. 40, pp. 379-383. [9] H. Abolhasani, N. Muhamad, “A New Starch-Based Binder for Metal Injection Molding,” Journal of Materials Processing Technology, 2010, vol. 210, pp. 961-968. [10] Y. Kankawa, M. Atarashi, Y. Akifusa, Y. Kaneko, A. Fusamoto, H. Ikeda, “Injection

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Molding of SUS316L Powder with Polyacetal Polyethylene Polymer-Alloy Polymer,” Journal of the Japan Society of Powder and Powder Metallurgy, 1996, vol. 43, pp. 840-845. [11] J. Ryuhgoh, K. Kawamoto, T. Osanaga, Y. Nakata, Moldable Composition, Process for Producing Sintered Body Therefrom and Products from Same, U. S. Patent 5,432,224, issued 11 July 1995. [12] M. Achikita, A. Oktsuka, Composition for Injection Molding, U. S. Patent 5,030,677, issued 9 July 1991. [13] T. Shimizu, S. Mochizuki, T. Sano, S. Fuchizawa, “Supercritical CO2 Debinding Method in MIM Process - Debinding Conditions and Process in Supercritical Debinding,” Journal of the Japan Society of Powder and Powder Metallurgy, 1996, vol. 43, pp. 1188-1192. [14] H. H. Angermann, O. O. Van Der Biest, “Low Temperature Debinding Kinetics of Two-Component Model Systems,” International Journal of Powder Metallurgy, 1993, vol. 29, pp. 239-250. [15] K. C. Hsu, C. C. Lin, G. M. Lo, “Effect of Wax Composition on Injection Moulding of 304L Stainless Steel Powder,” Powder Metallurgy, 1994, vol. 37, pp. 272-276. [16] Y. Kankawa, “Effects of Polymer Decomposition Behavior on Thermal Debinding Process in Metal Injection Molding,” Materials and Manufacturing Processes, 1997, vol. 12, pp. 681-690. [17] H. Nakayama, H. Kyogoku, S. Komatsu, “Effect of MIM Process Conditions on Microstructure and Mechanical Properties of Sintered SUS630 Compacts,” Journal of the Japan Society of Powder and Powder Metallurgy, 1997, vol. 44, pp. 1019-1023. [18] S. Ahn, S. J. Park, S. Lee, S. V. Atre, R. M. German, “Effect of Powders and Binders on Material Properties and Molding Parameters in Iron and Stainless Steel Powder Injection Molding Process,” Powder Technology, 2009, vol. 193, pp. 162-169. [19] K. A. Green, “PIM 17-4 PH Actuator Arm for Aerospace Applications,” Advances in Powder Metallurgy and Particulate Materials - 1998, Metal Powder Industries Federation, Princeton, NJ, 1998, pp. 5.119-5.130. [20] J. C. Lasalle, M. Zedalis, “Net-Shape Processing Using an Aqueous-Based MIM Binder,” Journal of Metals (JOM), 1999, vol. 51, no. 7, pp. 38-39. [21] H. I. Bakan, Y. Jumadi, P. F. Messer, H. A. Davies, B. Ellis, “Study of Processing Parameters for MIM Feedstock Based on Composite PEG-PMMA Binder,” Powder Metallurgy, 1998, vol. 41, pp. 289-291. [22] T. Shimizu, Y. Murakosi, T. Sano, “Evaluations of Binder Systems for Supercritical Carbon Dioxide Debinding Process,” Proceedings 1998 PM World

MIM 17-4 PH stainless steel

Congress, Granada Spain, published on CD by European Powder Metallurgy Association, Shrewsbury, UK, December 1998. [23] N. Myers, R. M. German, “Binder Selection for PIM Water Atomized 316L,” Advances in Powder Metallurgy and Particulate Materials - 2001, Metal Powder Industries Federation, Princeton, NJ, 2001, pp. 4.27-4.34. [24] Z. Y. Liu, N. H. Loh, S. B. Tor, K. A. Khor, Y. Murakoshi, R. Maeda, “Binder System for Micropowder Injection Molding,” Materials Letters, 2001, vol. 48, pp. 31-38. [25] S. Supriadi, E. R. Baek, C. J. Choi, B. T. Lee, “Binder System for STS 316 Nanopowder Feedstocks in Micro-Metal Injection Molding,” Journal of Materials Processing Technology, 2007, vol. 188, pp. 270-273. [26] R. E. Wiech, Method for Removing Binder from a Green Body, U. S. Patent 4,404,166, 13 September 1983. [27] H. Zhang, R. M. German, “Powder Injection Molding of 17-4 PH Stainless Steel,” Powder Injection Molding Symposium 1992, P. H. Booker, J. Gaspervich and R. M. German (eds.), Metal Powder Industries Federation, Princeton, NJ, 1992, pp. 219-227. [28] R. Ibrahim, M. Azmirruddin, M. Muhamad, R. Awang, S. Muhamad, “Injection Molding of 316L Stainless Steel Powder for Biomedical Application Using Palm Oil Derivatives Binder System,” Advances in Powder Metallurgy and Particulate Materials - 2009, Metal Powder Industries Federation, Princeton, NJ, 2009, pp. 4.52-4.59. [29] M. S. Park, J. K. Kim, S. Ahn, H. J. Sung, “Water Soluble Binder of Cellulose Acetate Butyrate / Poly(ethylene glycol) Blend for Powder Injection Molding,” Journal of Materials Science, 2001, vol. 36, pp. 5531-5536. [30] M. H. Ismail, M. A. Omar, N. Muhamad, A. Jumahat, “Study of Evolution of Pore Structure during Water Leaching using PEG-PMMA Binder System,” Advances in Powder Metallurgy and Particulate Materials - 2005, Metal Powder Industries Federation, Princeton, NJ, 2005, pp. 4.62-4.71. [31] M. Song, M. S. Park, J. K. Kim, I. B. Cho, K. H. Kim, H. J. Sung, S. Ahn, “Water Soluble Binder with High Flexural Modulus for Powder Injection Molding,” Journal of Materials Science, 2005, vol. 40, pp. 1105-1109. [32] Y. L. Fan, K. S. Hwang, “Properties of Metal Injection Molded Products Using Titanate-Containing Binders,” Materials Transactions, 2007, vol. 48, pp. 544-549. [33] Y. C. Kim, S. Lee, S. Ahn, N.J. Kim, “Application of Metal Injection Molding Process to Fabrication of Bulk Parts of TiAl Intermetallic,” Journal of Materials

Science, 2007, vol. 42, pp. 2048-2053. [34] M. Y. Anwar, H. A. Davies, “A Comparative Review of Various PIM Binder Systems,” Advances in Powder Metallurgy and Particulate Materials - 2007, Metal Powder Industries Federation, Princeton, NJ, 2007, pp. 4.8-4.20. [35] C. Lall, The Science of Stainless Steels Produced by Powder Metallurgy and Metal Injection Molding, Metal Powder Industries Federation, Princeton, NJ, 2006. [36] R. Raza, F. Ahmad, M. A. Omar, R. M. German, A. S. Muhsan, “Defect Analysis of 316L SS during the Powder Injection Moulding Process,” Defect and Diffusion Forum, 2012, vol. 329, pp. 35-43. [37] Y. Li, B. Huang, S. Li, “Evolution of Microstructure and Dimension of As Molded Parts During Thermal Removal Process of Wax Based MIM Binder,” Transactions of the Nonferrous Metals Society of China, 2001, vol. 11, pp. 340-344. [38] P. Setasuwon, A. Bunchavimonchet, S. Danchaivijit, “The effects of binder components in wax / oil systems for metal injection molding,” Journal of Materials Processing Technology, 2008, vol. 196, pp. 94-100. [39] D. Y. Park, G. M. Lee, Y. S. Kwon, Y. J. Oh, S. Lee, M. S. Jeong, S. J. Park, “Investigation of powder size effects on sintering of powder injection moulded 17-4 PH stainless steel,” Powder Metallurgy, 2017, vol. 60, pp. 139-148. [40] V. Demers, M. M. Elmajdoubi, P. Bocher, “Moldability of Low Pressure Powder Injection Molding Feedstocks,” Advances in Powder Metallurgy and Particulate Materials - 2017, Metal Powder Industries Federation, Princeton, NJ, 2017, pp. 401-414. [41] M. T. Zaky, “Effect of Solvent Debinding Variables on the Shape Maintenance of Green Molded Bodies,” Journal of Materials Science, 2004, vol. 39, pp. 3397-3402. [42] J. A. Sago, J. W. Newkirk, G. M. Grasel, “The Effects of MIM Processing Control Parameters on Mechanical Properties,” Advances in Powder Metallurgy and Particulate Materials 2003, Part 8, Metal Powder Industries Federation, Princeton, NJ, 2003, pp. 205-216. [43] A. Luo, J. Arrecoechea, R. Wengler, G. A. Gegel, R. Carlson, D. Dufour, “Mechanical Properties of Metal Injection Molded (MIM) 17-4 PH Stainless Steel,” Advances in Powder Metallurgy and Particulate Materials - 2003, Part 8, Metal Powder Industries Federation, Princeton, NJ, 2003, pp. 245-253. [44] D. A. Hauser, The Effects of Atmospheric Nitrogen on the Mechanical Properties of Sintered 17-4 PH Stainless Steel, MS Thesis, Engineering Mechanics Department, Pennsylvania State University, University Park, PA, May 2002.

June 2018 Powder Injection Moulding International

MIM 17-4 PH stainless steel

[45] D. T. Whychell, J. Stevenson, J. Peltier, M. Goldenberg, J. Lasalle, “Thermal Debind Studies on a Water Based Gel System in Stainless Steel 17-4 PH,” Advances in Powder Metallurgy and Particulate Materials - 2002, Metal Powder Industries Federation, Princeton, NJ, 2002, pp. 10.129-10.136. [46] Y. Wu, D. Blaine, B. Marx, C. Schlaefer, R. M. German, “Sintering Densification and Microstructural Evolution of Injection Molding Grade 17-4 PH Stainless Steel Powder,” Metallurgical and Materials Transactions, 2002, vol. 33A, pp. 2185-2194. [47] Y. Wu, R. M. German, D. Blaine, B. Marx, C. Schlaefer, “Effects of Residual Carbon Content on Sintering Shrinkage, Microstructure and Mechanical Properties of Injection Molded 17-4 PH Stainless Steel,” Journal of Materials Science, 2002, vol. 37, pp. 3573-3583. [48] J. Stampfl, H. C. Liu, S. W. Nam, K. Sakamoto, H. Tsuru, S. Kang, A. G. Cooper, A. Nckel, F. B Prinz, “Rapid prototying and manufacturing by gelcasting of metallic and ceramic slurries,” Materials Science and Engineering, 2002, vol. A334, pp. 187-192. [49] M. K. Bulger, A. R. Erickson, “Fatigue Properties of MIM Fe-7% Ni and 17-4 PH,” Powder Injection Molding Symposium 1992, P. H. Booker, J. Gaspervich and R. M. German (eds.), Metal Powder Industries Federation, Princeton, NJ, 1992, pp. 493-508. [50] T. Findik, S. Tasdemir, I. Sahin, “The use of artificial neural network for prediction of grain size in 17-4 PH stainless steel powders,” Scientific Research and Essays, 2010, vol. 5, pp. 1274-1283. [51] R. M. German, D. Kubish, “Evaluation of Injection Molded 17-4 PH Stainless Steel Using Water Atomized Powder,” International Journal of Powder Metallurgy, 1993, vol. 29, pp. 47-62. [52] R. M. Schmees, J. J. Valencia, “Mechanical Properties of Powder Injection Molded Inconel 718,” Advances in Powder Metallurgy and Particulate Materials - 1998, Metal Powder Industries Federation, Princeton, NJ, 1998, pp. 5.107-5.118. [53] H. O. Gulsoy, S. Ozbek, T. Baykara, “Microstructural and Mechanical Properties of Injection Moulded Gas and Water Atomized 17-4 PH Stainless Steel Powder,” Powder Metallurgy, 2007, vol. 50, pp. 120-126. [54] D. C. Blaine, S. J. Park, R. M. German, J. Lasalle, H. Nandi, “Verifying the Master Sintering Curve on an Industrial Furnace,” Advances in Powder Metallurgy and Particulate Materials 2005, Metal Powder Industries Federation, Princeton, NJ, 2005, pp. 1.13-1.19. [55] R. T. Fox, D. Lee, M. K. Bulger, R. M. German, “Evaluation of Injection Molded

Stainless Steel Powders,” Advances in Powder Metallurgy, vol. 3, Metal Powder Industries Federation, Princeton, NJ, 1990, pp. 359-373. [56] K. Murray, A. J. Coleman, T. A. Tingskog, D. T. Whychell, “Effect of Particle Size Distribution on Processing and Properties of MIM 17-4 PH,” Advances in Powder Metallurgy and Particulate Materials - 2010, Metal Powder Industries Federation, Princeton, NJ, 2010, pp. 4.18-4.27. [57] B. Julien, M. Ste-Marie, R. Pelletier, F. Lapointe, S. Turenne, “Parametric Modeling of MIM As-Sintered Properties of Stainless Steel 17-4 PH and 316L Using a Statistical Model,” Advances in Powder Metallurgy and Particulate Materials - 2010, Metal Powder Industries Federation, Princeton, NJ, 2010, pp. 4.1-4.10. [58] K. Murray, A. J. Coleman, T. Tingkskog, D. Whychell, “The Influence of Powder Size on Processing and Properties of MIM 17-4PH,” Proceedings PM 2010 World Congress, Florence Italy October 2010, European Powder Metallurgy Association, Shrewsbury, UK, on CD. [59] H. J. Sung, T. K. Ha, S. Ahn, Y. W. Chang, “Powder Injection Molding of a 17-4 PH Stainless Steel and the Effect of Sintering Temperature on its Microstructure and Mechanical Properties,” Journal of Materials Processing Technology, 2002, vol. 130, pp. 321-327. [60] H. O. Gulsoy, S. Salman, S. Ozbek, F. Findik, “Sintering of a Boron-Doped Injection Moulded 17-4 PH Stainless Steel,” Journal of Materials Science Letters, 2005, vol. 40, pp. 4101-4104. [61] C. W. Chang, P. H. Chen, K. S. Hwang, “Enhanced Mechanical Properties of Injection Molded 17-4 PH Stainless Steel Through Reduction of Silica Particles by Graphite Additions,” Materials Transactions, 2010, vol. 51, pp. 2243-2250. [62] P. Quirmbach, S. Schwartz, U. Dasbach, F. Petzoldt, L. Kramer, “Processing Parameters for a Continuous MIM-Production with an Aqueous Debinded 17-4 PH,” Advances in Powder Metallurgy and Particulate Materials - 2002, Metal Powder Industries Federation, Princeton, NJ, 2002, pp. 10.284-10.294. [63] H. Irrinki, K. Kate, S. Atre, B. Kumar, J. Stitzel, S. Badwe, “Evaluation of Corrosion Properties of 17-4 PH Stainless Steel Processed by Laser-Powder Bed Fusion,” Advances in Powder Metallurgy and Particulate Materials – 2017, Metal Powder Industries Federation, Princeton, NJ, 2017, on CD. [65] K. Murray, A. J. Coleman, T. Tingskog, D. T. Whychell, “Effect of Particle Size Distribution on Processing and Properties of 17-4 PH,” International Journal of

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Powder Metallurgy, 2011, vol. 47, no. 4, pp. 21-28. [65] Y. Li, L. Li, K. A. Khalil, “Effect of Powder Loading on Metal Injection Molding Stainless Steels,” Journal of Materials Processing Technology, 2007, vol. 183, pp. 432-439. [66] K. A. Khalil, S. W. Kim, “Relationship between Binder Content and Mechanical Properties of 17-4 PH Stainless Steel Fabricated by PIM Process and Sintering,” Metals and Materials International, 2006, vol. 12, pp. 1010-106. [67] B. N. Mukund, B. Hausnerova, T. S. Shivashankar, “Development of 17-4 PH stainless steel bimodal powder injection molding feedstock with the help of interparticle spacing / lubricating liquid concept,” Powder Technology, 2015, vol. 283, pp. 24-31. [68] R. M. German, Powder Metallurgy and Particulate Materials Processing, Metal Powder Industries Federation, Princeton, NJ, 2005. [69] C. Terrisse, L. Nyborg, P. Bracconi, “Surface Reaction during Vacuum Sintering of 316L Stainless Steel Powder,” Proceedings 1998 PM World Congress, Granada Spain, European Powder Metallurgy Association, Shrewsbury, UK, December 1998, on CD. [70] S. Banerjee, C. J. Joens, “A Comparison of Techniques for Processing Powder Metal Injection Molded 17-4 PH Materials,” Advanced in Powder Metallurgy and Particulate Materials - 2008, Metal Powder Industries Federation, Princeton, NJ, 2008, on CD. [71] P. K. Minuth, P. Kunert, D. Meinhardt, G. Veltl, L. Kramer, T. Hartwid, “Mechanical Properties of MIM Parts Produced from Mixtures of Stainless Steel 17-4 PH,” Competitive Advantages by Near-Net-Shape Manufacturing, H. D. Kunze (ed.), DGM Informationsgellschaft, Frankfurt, Frankfurt, Germany, 1997, pp. 303-308. [72] G. Kalin, E. Akdag, S. Ozbey, H. O. Gulsoy, “Electrochemical Behavior of Injection Molded Gas and Water Atomized 17-4PH Stainless Steel Powder,” Advances in Powder Metallurgy and Particulate Materials, Metal Powder Industries Federation, Princeton, NJ, 2017, pp. 364-373. [73] R. M. German, “The Sintering of 304L Stainless Steel Powder,” Metallurgical Transactions, 1976, vol. 7A, pp. 1879-1885. [74] T. Shimizu, K. Matsuzaki, T. Sano, “Rapid Prototyping of Metallic Parts by Green Machining,” Journal of the Japan Society for Powder and Powder Metallurgy, 2006, vol. 53, pp. 791-796. [75] E. Klar, P. K. Samal, Powder Metallurgy Stainless Steels, ASM International, Materials Park, OH, 2007.

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[76] S. Krug, S. Zachmann, “Influence of Sintering Conditions and Furnace Technology on Chemical and Mechanical Properties of Injection Moulded 316L,” Powder Injection Moulding International, 2009, vol. 3, no. 4, pp. 66-71. [77] A. Bose, D. Agrawal, R. J. Dowding, “Preliminary Investigations into Microwave Processing of Powder Injection Molded 17-4 PH Stainless Steel,” Advances in Powder Metallurgy and Particulate Materials - 2004, Part 4, Metal Powder Industries Federation, Princeton, NJ, 2004, pp. 53-60. [78] R. M. German, Sintering Theory and Practice, John Wiley and Sons, New York, NY, 1996. [79] C. K. Tai, C. H. Liang, “Study of Powder Characteristics on Mechanical Properties of Metal Injection Molding (MIM) Product,” Advances in Powder Metallurgy and Particulate Materials 2007, Metal Powder Industries Federation, Princeton, NJ, 2007, pp. 4.28-4.37. [80] J. Kazior, A. Szewczyk-Nykiel, T. Pieczonka, M. Hebda, M. Nykiel, “Properties of Precipitation Hardening 17-4 PH Stainless Steel Manufactured by Powder Metallurgy Technology,” Advanced Materials Research, 2013, vol. 811, pp. 87-92. [81] S. H. Chung, Y. S. Kwon, P. Suri, N. Erhardt, D. C. Blaine, C. Schlaefer, R. M. German, “Sintering Simulation of Powder Injection Molded 17-4 PH Stainless Steel,” Proceedings Sintering 2003, R. G. Cornwall, R. M. German, and G. L. Messing (eds.), Materials Research Institute, Pennsylvania State University, University Park, PA, 2003, on CD. [82] Y. S. Kwon, Y. Wu, P. Suri, R. M. German, “Simulation of the Sintering Densification and Shrinkage Behavior of Powder Injection Molded 17-4 PH Stainless Steel,” Metallurgical and Materials Transactions, 2004, vol. 35A, pp. 257-263. [83] A. Simchi, A. Rota, P. Imgrund, “An investigation on the sintering behavior of 316L and 17-4PH stainless steel powders for graded composites,” Materials Science and Engineering, 2006, vol. A424, pp. 282-289. [84] D. C. Blaine, Y. Wu, C. E. Schlaefer, B. Marx, R. M. German, “Sintering Shrinkage and Microstructure Evolution during Densification of a Martensitic Stainless Steel,” Proceedings Sintering 2003, R. G. Cornwall, R. M. German, and G. L. Messing (eds), Materials Research Institute, Pennsylvania State University, University Park, PA, 2003, on CD. [85] D. Blaine, S. H. Chung, S. J. Park, P. Suri, R. M. German, “Finite Element Simulation of Sintering Shrinkage and Distortion in Large PIM Parts,” P/M Science and Technology Briefs, 2004, vol. 6, no. 2, pp. 13-18.

MIM 17-4 PH stainless steel

[86] D. C. Blaine, R. M. German, “Sintering Simulation for PIM Stainless Steel,” Advances in Powder Metallurgy and Particulate Materials - 2002, Metal Powder Industries Federation, Princeton, NJ, 2002, pp. 10.255-10.266. [87] P. G. E. Jerrard, L. Hao, K. E. Evans. “Experimental investigation into selective laser melting of austenitic and martensitic stainless steel powder mixtures.” Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture, 2009, vol. 223, pp. 1409-1416. [88] Y. Li, K. A. Khalil, B. Huang, Metal Injection Molding of 17-4 PH Stainless Steel, National Key Laboratory for Powder Metallurgy, Central South University, Changsha, China, 2005. [89] D. C. Blaine, S. J. Park, R. M. German, “Master Sintering Curve for a Two-Phase Material,” Proceedings of the 4th International Conference on Science, Technology and Applications of Sintering, D. Bouvard (ed.), Institut National Polytechnique de Grenoble, Grenoble, France, 2005, pp. 264-267. [90] R. M. German, “Coordination number changes during powder densification,” Powder Technology, 2014, vol. 243, pp. 368-376. [91] X. Xu, W. Yi, R. M. German, “Densification and Strength Evolution in Solid-State Sintering Part I, Experimental Investigation,” Journal of Materials Science, 2002, vol. 37, pp. 567-575. [92] H. J. Sung, T. K. Ha, S. Ahn, Y. W. Chang, “An Investigation on Elongation - Porosity Relation in Sintered 17-4 PH Stainless Steel,” Materials Science Forum, 2007, vol. 534, pp. 645-648. [93] H. Miura, T. Baba, “Sintering High Strength Injection Molded Stainless Steel Compacts,” Recent Progress in Iron Powder Metallurgy, R. Watanabe and K. Ogura (eds.), School of Engineering, Tohoku University, Sendai, Japan, 1999, pp. 47-57. [94] P. H. Chen, K. S. Hwang, “Mechanical Properties of Powder Injection Moulded 17-4 PH Sintered in Dissociated Ammonia,” Proceedings PM 2010 World Congress, Florence Italy October 2010, European Powder Metallurgy Association, Shrewsbury, UK, on CD. [95] T. Baba, H. Miura, T. Honda, Y. Tokuyama, “High Performance Properties of Injection Molded 17-4 PH Stainless Steel,” Advances in Powder Metallurgy and Particulate Materials - 1995, Metal Powder Industries Federation, Princeton, NJ, 1995, pp. 6.271-6.278. [96] R. M. German, Powder Metallurgy of Iron and Steel, Wiley, Hoboken, NJ, 1998. [97] T. Baba, H. Miura, T. Honda, Y. Tokuyama, “Properties of 17-4 PH Stainless Steels Produced by Metal

Injection Molding Process,” Journal of the Japan Society of Powder and Powder Metallurgy, 1995, vol. 42, pp. 1119-1123. [98] R. M. F. Jones, “The Effect of Processing Variables on the Properties of 316L Powder Compacts,” Progress in Powder Metallurgy, 1974, vol. 30, pp. 25-50. [99] K. Kamada, M. Nakamura, H. Horie, “Development of High Strength P/M SUS 630 Stainless Steels Utilized by the Liquid Phase Sintering,” Proceedings of the 2000 Powder Metallurgy World Congress, Part 2, K. Kosuge and H. Nagai (eds.), Japan Society of Powder and Powder Metallurgy, Kyoto, Japan, 2000, pp. 1021-1024. [100] K. Kamada, M. Nakamura, H. Horie, “Effect of Addition of Boron and Silicon on Mechanical Properties of P/M SUS630 Stainless Steel,” Journal of the Japan Society of Powder and Powder Metallurgy, 2001, vol. 48, pp. 810-815. [101] H. O. Gulsoy, S. Salman, S. Ozbek, “Effect of FeB Additions on Sintering Characteristics of Injection Moulded 17-4 PH Stainless Steel Powder,” Journal of Materials Science, 2004, vol. 39, pp. 4835-4840. [102] H. O. Gulsoy, S. Ozbek, S. Salman, “Sintering and Mechanical Properties of Injection Molded 17-4 PH Stainless Steel Powder with FeB Additions,” Fourth International Powder Metallurgy Conference, Turkish Powder Metallurgy Association, Sakarya University, Sakarya, Turkey, 2005, pp. 415-428. [103] H. O. Gulsoy, S. Salman, “Microstructure and Mechanical Properties of Injection Molded 17-4 PH Stainless Steel Powder with Nickel Boride Additions,” Journal of Materials Science, 2005, vol. 40, pp. 3415-3421. [104] A. Szewczyk-Nykiel, The Effect of the Addition of Boron on the Densification, Microstructure, and Properties of Sintered 17-4 PH Stainless Steel, Institute of Materials Engineering, Cracow University of Technology, Cracow, Poland, 2014. [105] H. O. Gulsoy, “Influence of Nickel Boride Additions on Sintering Behaviors of Injection Moulded 17-4 PH Stainless Steel Powder,” Scripta Materialia, 2005, vol. 52, pp. 187-192. [106] B. Suharno, D. Ferdian, H. R. Saputro, L. P. Suharno, E. R. Baek, S. Supriadi, “Vacuum Sintering Process in Metal Injection Molding for 17-4 PH Stainless Steel as Material for Orthodontic Bracket,” Solid State Phenomena, 2017, vol. 266, pp. 231-237. [107] G. A. Shoales, R. M. German, “Combined Effects of Time and Temperature on Strength Evolution Using Integral Work-of-Sintering Concepts,” Metallurgical and Materials Transactions, 1999, vol. 30A, pp. 465-470.

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MIM 17-4 PH stainless steel

[108] S. V. Atre, G. A. Shoales, A. Lal, K. K. Comstock, D. M. Errick, R. M. German, “Strength Evolution During the Thermal Debinding of PIM Components,” Powder Injection Molding Technologies, R. M. German, H. Wiesner, and R. G. Cornwall (eds.), Innovative Material Solutions, State College, PA, 1998, pp. 217-226. [109] X. Xu, P. Lu, R. M. German, “Densification and Strength Evolution in Solid-State Sintering: Part II, Strength Model,” Journal of Materials Science, 2002, vol. 37, pp. 117-126. [110] R. Schroeder, G. Hammes, C. Binder, A. N. Klein, “Plasma Debinding and Sintering of Metal INjection Moulded 17-4 PH Stainless Steel,” Materials Research, 2011, vol. 14, pp. 564-568. [111] I. D. Jung, S. Ha, S. J. Park, D. C. Blaine, R. Bollina, R. M. German, “Two-Phase Master Sintering Curve for 17-4 PH Stainless Steel,” Metallurgical and Materials Transactions, 2016, vol. 47A, pp. 5548-5556. [112] J. J. Valencia, T. J. McCabe, H. Dong, “Microstructure and Mechanical Properties of Powder Injection Molded 17-4 PH Stainless Steel for Aircraft Engine Components,” Advances in Powder Metallurgy and Particulate Materials - 1995, Metal Powder Industries Federation, Princeton, NJ, 1995, pp. 6.205-6.214. [113] J. L. LaGoy, M. K. Bulger, “Effect of HIP on the Microstructure and Impact Strength of MIM 17-4 PH Stainless Steel,” Advances in Powder Metallurgy and Particulate Materials - 2009, Metal Powder Industries Federation, Princeton, NJ, 2009, pp. 4.70-4.80. [114] MatWeb Material Property Data, www.matweb.com. [115] M. Gross, “MIM helps Raytheon improve product performance and lower manufacturing costs,” Powder Injection Moulding International, 2014, vol. 8, no. 1, pp. 13-15. [116] H. Nakayama, H. Kyogoku, S. Komatsu, “Effect of Heat Treatment Conditions on Microstructure and Mechanical Properties of Sintered SUS630 Compacts by MIM Process,” Journal of the Japan Society of Powder and Powder Metallurgy, 1998, vol. 45, pp. 882-886. [117] H. O. Gulsoy, R. M. German, “Sintered Foams from Precipitation Hardened Stainless Steel Powder,” Powder Metallurgy, 2008, vol. 51, pp. 350-353. [118] R. M. German, “Sintering Trajectories: Description on How Density, Surface Area, and Grain Size Change,” Journal of Metals (JOM), 2016, vo. 68, pp. 878-884. [119] J. L. Johnson, Assessment of the Properties of AMT Stainless Steels and Tool Steels, Technical Report #2003-05, AMTellect, State College, Pennsylvania, 2003.

[120] P. Suri, B. P. Smarslok, R. M. German, “Impact Properties of Sintered and Wrought 17-4 PH Stainless Steel,” Powder Metallurgy, 2006, vol. 49, pp. 40-47. [121] J. A. Sago, M. W. Broadley, J. K. Eckert, R. J. White, “The Influence of Microstructure on the Mechanical Properties of 17-4 PH Stainless Steel,” Advances in Powder Metallurgy and Particulate Materials - 2007, Metal Powder Industries Federation, Princeton, NJ, 2007, pp. 4.99-4.109. [122] S. Cheruvathur, E. A. Lass, C. E. Campbell, “Additive Manufacturing of 17-4 PH Stainless Steel: Post Processing Heat Treatment to Achieve Uniform Reproducible Microstructure,” Journal of Metals (JOM), 2015, vol. 68, no. 3, pp. 930-942. [123] A. Ziewiec, A. Zielinska-Lipiec, E. Tasak, “Microstructure of Welded Joints of X5CrNiCuNb16-4 (17-4 PH) Martensitic Stainless Steel After Heat Treatment,” Archives of Metallurgy and Materials, 2014, vol. 59, pp. 965-970. [124] H. Miura, T. Baba, “High Performance Injection Molded Stainless Steels,” Processing and Fabrication of Advanced Materials VI, vol. 2, K. A. Khor, T. S. Srivatsan, J. J. Moore (eds.), Institute of Materials, London, UK, 1998, pp. 1377-1387. [125] A. Gratton, “Comparison of Mechanical, Metallurgical Properties of 17-4 PH Stainless Steel between Direct Metal Laser Sintering (DMLS) and Traditional Manufacturing Methods,” Proceedings of the National Conference on Undergraduate Research, Weber State University, Ogden, UT, 2012. [126] C. J. Joens, “Laminar Gas Flow Enhances Debind and Sinter of PIM Parts,” Industrial Heating, 2004, June, pp. 37-39. [127] J. L. Johnson, “Corrosion Resistant Medical Instruments Produced by Metal Injection Molding,” Medical Device Materials, S. Shrivastave (ed.), ASM International, Materials Park, OH, 2004, pp. 408-413. [128] H. J. Rack, D. Kalish, “The Strength, Fracture Toughness, and Low Cycle Fatigue Behavior of 17-4 PH Stainless Steel,” Metallurgical Transactions, 1974, vol. 5, pp. 1595-1605. [129] R. M. German, Particulate Composites, Springer, Basel Switzerland, 2016, pp. 127-130. [130] S. A. Slaby, O. Kraft, C. Eberl, “Fatigue Properties of Conventionally Manufactured and Micro Powder Injection Moulded 17-4 PH Microcomponents,” Fatigue and Fracture of Engineering Materials and Structures, 2016, vol. 39, pp. 780-789. [131] R. M. German, Metal Injection Molding A Comprehensive MIM Design

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Guide, Metal Powder Industries Federation, Princeton, NJ, 2011. [132] P. K. Samal, N. Nandivada, I. Hauer, “Properties of 17-4 PH Stainless Steel Produced via Press and Sinter Route,” Advances in Powder Metallurgy and Particulate Materials - 2008, Metal Powder Industries Federation, Princeton, NJ, 2008, Part 7, pp. 109-120. [133] S. Bannerjee, “Structure - Property Relationship of Metal Injection Molded 17-4 PH Orthodontic Parts,” Powder Injection Molding Symposium 1992, P. H. Booker, J. Gaspervich and R. M. German (eds.), Metal Powder Industries Federation, Princeton, NJ, 1992, pp. 181-192. [134] H. Wohlfromm, M. Blomacher, P. J. Uggowitzer, R. Magdowski, M. O. Speidel, “Corrosion Resistance of MIM Stainless Steels,” Advanced in Powder Metallurgy and Particulate Materials – 1999, vol. 2, Metal Powder Industries Federation, Princeton, NJ, 1999, pp. 6.27-6.38. [135] I. Costa, C. V. Franco, C. T. Kunioshi, J. L. Rossi, “Corrosion Resistance of Injection Molded 17-4PH Steel in Sodium Chloride Solution,” Corrosion, 2006, vol. 62, pp. 357-365. [136] A. Szewczyk-Nykiel, J. Kazior, “Effect of Aging Temperature on Corrosion Behavior of Sintered 17-4 PH Stainless Steel in Dilute Sulfuric Acid Solution,” Journal of Materials Engineering and Performance, 2017, vol. 26, pp. 3450-3456. [137] K. T. Oh, S. U. Choo, K. M. Kim, K. N. Kim, “A stainless steel bracket for orthodontic application,” European Journal of Orthodontics, 2005, vol. 27, pp. 237-244. [138] J. A. Sago, M. W. Broadley, J. K. Eckert, H. Chen, “Manufacturing of Implantable Biomedical Devices by Metal Injection Molding,” Advances in Powder Metallurgy and Particulate Materials 2010, Metal Powder Industries Federation, Princeton, NJ, 2010, pp. 4.89-4.99. [139] R. M. German, “Green Body Homogeneity Effects on Sintered Tolerances,” Powder Metallurgy, 2004, vol. 47, pp. 157-160. [140] D. C. Blaine, S. J. Park, P. Suri, R. M. German, “Application of Work of Sintering Concepts in Powder Metallurgy,” Metallurgical and Materials Transactions, 2006, vol. 37A, pp. 2827-2835.

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MIM 17-4 PH stainless steel

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Shanghai Future High-tech

Shanghai Future High-tech: Research & development as a route to continued MIM growth China’s emergence as a leading player in the world of Metal Injection Moulding demonstrates how a globally competitive industry can be built over a relatively short period of time with diligence, entrepreneurial skill and a receptive end-user market. Dr Georg Schlieper recently visited Shanghai Future High-tech Co., Ltd., one of China’s leading MIM manufacturers, and reports exclusively for PIM International about the importance of research partnerships, the company’s achievements to-date and its future ambitions.

Shanghai Future High-tech Co. Ltd. (SHF) was established in 1999, moving to its current headquarters on an industrial park close to a harbour area in the northern precincts of Shanghai in 2004. The capital for the new enterprise was organised by Yu Li-Gang, one of the founders of the business, and in less than twenty years the company has become one of the world’s largest producers of MIM and CIM parts in China. Today, SHF has three manufacturing sites; its headquarters in Shanghai, another site 20 km north of its headquarters (Fig. 1) and a factory in Shenzhen, near Hong Kong. The company is committed to further strong growth, with ambitions to become one of the world’s largest MIM manufacturers. With a workforce of more than 2,200, it is already among the leading international MIM companies and, over the past three years, has produced more than 500 million parts annually. Between 300 and 400 new MIM parts are launched every year by SHF.

The management team emphasises that the success of the company is determined by its workforce. It stipulates high ethical values that guide the conduct of all employees, foremost among them the commitment to delivering high-quality products to customers at reasonable

prices that satisfy customer requirements and reward staff, shareholders and society. The management team is also aware of the fact that the success of the company depends on the success of its customers; the entire staff is therefore encouraged to feel

Fig. 1 Shanghai Future’s new operation in Northern Shanghai

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Shanghai Future High-tech

Fig. 2 MIM parts for computers and consumer electronics manufactured by SHF

a sense of responsibility for the performance of the company and continuously improve its processes. Employees are also encouraged to maintain an open and innovative state of mind at all times and strive for even better solutions to problems. The management stated that it appreciates the talents and skills of its employees and is confident that they will use them to create better relationships with their customers for mutual benefit.

A focus on MIM research Rick Zhong, Chairman and Co-founder of SHF, and Joey Deng, Director of Shanghai Future’s Central Research Institute, spoke at length with Georg Schlieper during a plant visit for PIM International. The two engineers studied metal powder technology at Central South University (CSU) in Changsha, Hunan Province. In the beginning it was Zhong who brought his technical knowledge to the company.

In 2016, the company established its own research institute, of which Deng is the Director. The institute is involved in the long-term development of new materials, energy efficient processes and cost efficient MIM and CIM production technology. “We put a strong emphasis on

“By doing research for a certain application,” added Zhong, “we learn more and more about the real problems that have to be solved and we try to develop solutions on the basis of MIM technology. We already hold approximately thirty patents relating to Metal Injection Moulding technology.”

“The institute is involved in the long-term development of new materials, energy efficient processes and cost efficient MIM and CIM production technology.” research and, in this respect, we are pioneers in China”, explained Deng. “When we develop new designs of technical components or sub-assembles for MIM technology that are not yet commercialised, this is beneficial for the entire MIM industry.”

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More fundamental and applied research is undertaken in close cooperation with the University of Science and Technology Beijing in the form of Bachelor’s and Master’s theses, the topics of which are proposed by Shanghai Future. Introducing MIM technology to students at the

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Shanghai Future High-tech

university is regarded as a key activity for drawing interest to MIM and developing a sound source of qualified engineers. Between twenty and thirty university graduates are employed every year by SHF, whilst machine operators are trained in-house. In addition to the Central Research Institute, Shanghai Future maintains an Engineering Centre for product development in close cooperation with its customers. This department is strongly focused on customer requirements and customer designs, which are reviewed for feasibility for production using MIM technology and modified using FMEA (Failure Mode and Effects Analysis) where appropriate.

Products and markets “The first seven years were very difficult for Shanghai Future,” stated Zhong. “Our first products were tungsten heavy metal alloy parts for fishing rods.” Later, SHF produced watchcases from tungsten carbide until, finally, the first orders for parts for the 3C industry (Computers, Communication and Consumer Electronics) were received. Among the latter were parts for telecommunications base stations and CPU socket caps. “These parts gave us the chance to develop our technology to the point where we were able to start mass production,” added Deng. In 2005, the first automotive parts were produced by Shanghai Future. Figs. 2–6 show examples of MIM products made by SHF. Among the mobile phone components produced are carriers for SIM and SD cards and camera frames. Roughly 70% of Shanghai Future’s business is with the 3C industry. Second are automotive components (Fig. 3), followed by parts for medical applications (Fig. 4), locks (Fig. 5), tools and other applications. Parts for handguns and military equipment, an important market for the MIM industry elsewhere and especially in North America, play virtually no role in China. Approximately 40% of SHF’s production is exported.

Fig. 3 MIM parts for automotive applications manufactured by SHF

Fig. 4 MIM parts for medical applications manufactured by SHF

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Shanghai Future High-tech

Shanghai Future is capable of producing parts with a mirror-like surface finish (Fig. 6). This is only possible with virtually pore-free materials that are absolutely free from non-metallic contamination. By strictly controlling raw materials and using a special sintering process, SHF can produce such parts without a Hot Isostatic Pressing (HIP) treatment after sintering. Today, the majority of MIM parts produced at SHF are in 17-4PH, 316L, 440C and 304L stainless steels. For a special application where the high strength of 17-4PH is required in combination with the non-magnetic properties of 316L, the company has developed a special sintering process that causes 17-4PH, a material which is normally ferromagnetic, to be non-magnetic. Besides stainless steels, the company also produces parts from nickel-base superalloys, low-alloy steels, high-speed steels, copper, bronze, cobalt-based alloys, titanium and zirconia ceramic. Although most parts produced by SHF are very small, often weighing only fractions of a gram, the company also produces some large parts weighing up to 400 g. One third of the parts the company produces weigh around 1 g and below, with the smallest weighing only 20 mg.

Fig. 5 A MIM mechanical part for a lock application

Fig. 6 One of a number of parts with a mirror-like surface finish

Production and inspection equipment

Fig. 7 Approximetaley 300 injection moulding machines are installed at SHF

Although most raw materials used at SHF come from domestic suppliers, some imported feedstocks are also processed. Facilities for feedstock preparation, both for catalytic and solvent debinding systems, are available at all manufacturing sites. Some of the equipment used in feedstock preparation has been developed in-house. A high feedstock quality is ensured by pycnometer density and flow rate measurements. Approximately three hundred injection moulding presses (Fig. 7) are installed at SHF’s facilities, along with almost one hundred debinding and sintering furnaces, seven of which are continuous furnaces (Figs. 8-9).

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Shanghai Future High-tech

Fig. 8 A continuous sintering furnace installed at SHF

According to SHF, its continuous sintering furnaces run twenty-four hours a day, seven days a week. Secondary operations include the resizing of critical tolerances, tapping, sand blasting, surface finishing, heat treatment and more. The majority of surface treatment is applied in-house, but certain processes are outsourced. The CNC machining of MIM parts The company has developed specific expertise in the CNC machining of MIM parts. “The combination of MIM processing and finish machining is often beneficial for serving a wider range of MIM applications,” explained Deng. More than one hundred CNC machining centres (Fig. 10), as well as a variety of high-precision grinding and milling machines, are used in the finishing of MIM parts. These are mainly used for automotive parts. Deng added, “Much of our leading position in the MIM industry is due to the fact that we are able to offer complete solutions. We even assemble groups of components for our customers.”

Tool design and manufacture Experienced tool designers translate customer requirements into the part design language of MIM technology and thus develop optimal solutions for the benefit of the customers. Manufacturing and repair of injection moulding tools is performed in tool shops equipped with modern CNC machining centres, EDM and high-precision

hot runner tools are standard in order to avoid the recycling of sprues and runners. Process automation Process automation is a key topic at Shanghai Future. A particularly impressive example of automated MIM production is a fully automatic production line consisting of four injection moulding presses that feed

“The capacity of the tool shops is approximately sixty tool sets per month. Multi-cavity tools with up to thirty-two cavities are in use and hot runner tools are standard...” grinding machinery (Fig. 11). The capacity of the tool shops is approximately sixty tool sets per month. Multi-cavity tools, with up to thirty-two cavities, are in use and

a continuous debinding and sintering furnace. Pick-and-place robotic arms remove green parts from the moulds and place them on trays for debinding and sintering (Fig. 12). A special

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Shanghai Future High-tech

department is currently designing and installing devices and lines for fully automatic manufacturing. Secondary operations and quality inspection systems, too, are often automated. These include an automatic laser welding line and automatic dimensional and shape inspection with in-line cameras. Quality inspection Much emphasis is placed on quality inspection. The metallographic laboratory is equipped with all standard inspection devices such as hardness testers, metal microscopes, Archimedes density measurement, etc. MIM parts are inspected for internal defects by eddy current and X-ray inspection. SHF’s quality management system is certified according to the industry standards ISO 9001, 14001, 13485, TS16949 and OHSAS18001.

Fig. 9 MIM batch furnaces at SHF

Future expectations The Chinese MIM and CIM industry is led by a group of around ten large companies. Deng estimates the industry at more than two hundred companies in total, a large portion of which operate just a few injection moulding machines. Most Chinese MIM companies are located in the Shanghai and Shenzhen areas and the main driving force of the fast-growing industry is the consumer electronics market, which offers a huge demand for MIM parts. Other markets for MIM parts are also being steadily developed. Along with the fast-growing MIM industry, China has developed an extensive supply chain industry. “Raw materials, debinding ovens for catalytic and solvent binder systems and sintering furnaces, both batch and continuous types, are available in high quality from domestic suppliers, so Chinese manufacturers rely no longer on imported equipment,” stated Zhong.

Fig. 10 CNC machining centres for MIM parts at SHF

Mitigating the risks of the 3C industry The management is aware of the risks of a strong dependence on a single market segment, such as SHF’s dependence on the 3C industry. The

Fig. 11 A view of the tool shop at SHF

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Shanghai Future High-tech

Fig. 12 An automated MIM production line consisting of four injection moulding presses that feed a continuous debinding and sintering furnace

marketing strategy is therefore directed at strengthening growth in other markets, such as automotive and medical applications, reducing the supply of 3C components to 50% of its overall part production. Further growth in traditional MIM markets is expected to be supported by declining raw material costs. “There are many powder suppliers in China who have developed lower cost processes for powder production and the quality is very good,” stated Zhong. “This will lead to a significant improvement in our competitiveness in comparison with the investment casting industry and we will increase our share of this huge market.” Shanghai Future’s Central Research Institute continuously extends the company’s range of materials and develops process technologies for MIM parts that meet customer requirements in various applications. Deng foresees a high growth potential in MIM parts for the automotive industry.

In order to access new markets, SHF believes young engineers, who will become potential users of MIM components, must be educated on the benefits that MIM has to offer because, in many disciplines, engineers still have little to no knowledge of the technology. Zhong feels that his company’s resources for this task are limited and more support should be supplied by the industry’s associations. “One way to generate new business is growth in existing markets,” he explained. “But technical changes are so fast that even entirely new market segments may emerge during the years to come.”

Contact Rick Zhong Chairman Shanghai Future High-tech Co., Ltd. No. 4318, Yixian Road, Baoshan District, Shanghai China Tel: +86 021 56442850 Email: rick@future-sh.com.cn www.future-sh.com.cn

Author Dr Georg Schlieper Harscheidweg 89 D-45149 Essen Germany Tel: +49 201 71 20 98 Email: info@gammatec.com www.gammatec.com

June 2018 Powder Injection Moulding International

World PM2018

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Shenzhen Shindy Technology

Shenzhen Shindy Technology: Rapid product development and high-volume production drive innovation Shenzhen Shindy Technology Co., Ltd. is one of a new generation of young, capable and fast-growing Chinese MIM producers. Within a decade, the company has joined the top-tier of global MIM producers and has ambitious plans for further expansion. Dr Georg Schlieper visited the company and reports exclusively for PIM International on the growth of MIM in Shenzhen, the current status of MIM technology at ShindyTech and the challenges of very high volume production.

The city of Shenzhen is located in Guangdong Province, close to the Pearl River Delta and the Special Administrative Region of Hong Kong in Southern China. Before 1980, Shenzhen was a small town of 30,000 inhabitants. At that time, the central government established a Special Economic Zone on the border with Hong Kong in order to promote investment in the region. This started an extraordinary economic boom that was unusual even by Chinese standards. Hong Kong investors have been instrumental in transforming Shenzhen within a few decades into one of the country’s most modern and prosperous cities. Today, the cityscape is dominated by high-rise steel and glass buildings, spacious green areas and wide streets built to cope with the rapidly growing road traffic in a city where the population has risen to more than 10 million. A modern subway system makes travel within the city easy, allowing access to its numerous world-class attractions.

ShindyTech’s history Shenzhen is a centre for the production of mobile phones and other consumer electronic products. In particular, this industry demands small metal parts of complex shape, best produced by Metal Injection

Moulding. Consequently, many MIM operations have been - and continue to be - established here. Today, at least eighteen MIM factories are located in the Shenzhen area. Shenzhen Shindy Technology Co., Ltd. (ShindyTech) was founded in 2009 on a technology park on

Fig. 1 Parts produced in high volumes for the smartphone sector include connectors (top left), camera frames (top right) and fingerprint sensor housings (bottom). Note that these images are not to scale.

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Shenzhen Shindy Technology

Fig. 2 The 194 CNC machining centres at ShindyTech, used for the finishing of MIM parts, give a sense of the scale of MIM operations in China

Fig. 3 Dr Q (Yau-Hung Chiou) with the author (Courtesy Georg Schlieper)

the outskirts of Shenzhen by two young Chinese investors. From the beginning, the company’s business model specifically focused on the production of MIM components. During the first three years, the technological and managerial foundations were laid for the surge in business that was soon to come. By 2011, the company’s quality and environmental management systems were certified according to ISO 9001 and 14001 and in the same year a sales office was opened in Hong Kong. It was in 2012 that the

mass production of components commenced at ShindyTech. The first orders for smartphone components were received through one of the major manufacturing partners for the market leading smartphone brands, which remains to this day one of ShindyTech’s most important customers. Fig. 1 shows a selection of mobile phone parts produced by ShindyTech, all made from 316L stainless steel. The part on the left belongs to a connector and features a polished surface and two PVD coated through

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June 2018

holes. Also shown are a frame for a smartphone camera and the frame of a fingerprint identification sensor. The latter two parts are also polished and PVD coated. With the commencement of mass production, the original premises soon became too small for the expanding company and ShindyTech moved to its present location at Silicon Valley Power Low-Carbon Industrial Park in the Guanlan District of Shenzhen. In order to increase its capabilities for materials research and technical innovation, ShindyTech began cooperation on MIM technology development with the Powder Metallurgy Research Institute of Central South University (CSU) in Changsha, Hunan Province, in 2013. This cooperation includes support from CSU to develop the range of MIM materials. As part of the arrangement, a scholarship is provided to the university by ShindyTech. One research project, launched in 2015, addresses the production of high-precision complex shape miniature ceramic parts and is supported by the Innovation of Science and Technology Committee of Shenzhen City. By 2014, the company’s machining capacities had been expanded to a total of 194 CNC machining centres (Fig. 2). An in-house tool shop was opened in 2015, allowing the company a high degree of self-sufficiency in the manufacture of injection moulding tools, substantially reducing the time to market for new products. In 2016, the company received a government grant from a high-tech fund, allowing it to invest in additional production equipment. Today, the area around ShindyTech’s factory has changed dramatically as a result of Shenzhen’s rapid growth. Many new factories and residential areas have been built, leaving little room for further expansion at the company’s current site. The decision was therefore taken to build a new 35,000 m² factory approximately 20 km from the present site. This new plant is expected to open in 2019.

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Shenzhen Shindy Technology

Fig. 4 MIM CPU cooling fans developed by Shindy’s R&D team. The larger part has a diameter of 56 mm and the blades have a wall thickness of 0.2 mm and a height of 5 mm

Dr Q, the MIM expert behind ShindyTech’s success MIM technology was brought to ShindyTech by Yau-Hung Chiou, a Taiwanese consultant who is widely known by friends and colleagues as Dr Q (Fig. 3). A graduate of the National Taiwan University of Science and Technology (NTUST), he received his PhD degree under Prof S T Lin, himself a former student of MIM technology under Prof Randall M German in the United States. On leaving university in 1996, Dr Q worked in various MIM-related fields of activity. Since 2014, he has served as a full-time Technical Advisor on MIM technology for more than ten companies in Taiwan and China. Among his major activities are the promotion of MIM technology, training in MIM technology, the planning of new plants and MIM process troubleshooting. Since 2017, Dr Q has also been an Associate Professor at Dongguan

University of Technology, not far from Shenzhen. His other positions include Supervisor of the MIM and Materials Science Team of the Association of CAE Moulding

acid as, he stated, this method does not produce environmentally harmful nitric oxides. Dr Q installed the equipment for preparation and granulation of MIM feedstock at

“MIM technology was brought to ShindyTech by Yau-Hung Chiou, a Taiwanese consultant who is widely known by friends and colleagues as Dr Q.” Technology (ACMT) and President of the Chinese Alliance of the MIM Industry (PIMA). The MIM process applied by Dr Q is based predominantly on the polyoxymethylene (POM) binder system developed by BASF; however, instead of debinding in concentrated nitric acid, as most MIM producers do, he advises his clients to debind in oxalic

ShindyTech, consisting of a kneader with an integrated pelletiser. Dr Q leads ShindyTech’s R&D department and the high standard of ShindyTech’s MIM technology is evidenced by the CPU cooling fans shown in Fig. 4. The larger part has a diameter of 56 mm and the blades have a wall thickness of only 0.2 mm and a height of 5 mm.

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Shenzhen Shindy Technology

MIM operations at ShindyTech

Fig. 5 Injection moulding machines manufactured by JSW are fitted with automated part removal systems

Fig. 6 A line of SinterZone batch debinding systems installed at ShindyTech

Fig. 7 A line of HIPER vacuum sintering furnaces

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ShindyTech employs a staff of approximately four hundred across five departments: Sales, R&D, Operations, Quality and HR & Administration. In the company’s financial year 2017, annual sales were approximately USD $45 million, with a yearly growth rate of about 20%. The management’s ethical and strategic targets for the company are focused on four principles in particular: honesty, professionalism, service and ‘win-win’ business. Above all, the company states that it has a commitment to honesty in dealing with customers and suppliers. The seriousness and ambition with which the company’s goals are viewed is visible at all levels of the company, evidenced by the professional approach taken by its employees in their contact with external companies as well as in their internal interactions. The company seeks to gain lasting customer loyalty through on-time deliveries and comprehensive customer service, and has a business attitude oriented towards generating mutual benefits for itself and its customers. The financial goals of the management team for the future are ambitious; the company wants to grow further and, ultimately, become one of the leading MIM manufacturers in China. ShindyTech’s tool shop is equipped with six CNC, six EDM, three wire EDM and six grinding machines. The tool shop is capable of producing thirty tool sets per month; with the support of outside toolmakers, the total capacity can be increased to fifty tools per month. As ShindyTech’s customers – mainly in the consumer electronics industry – expect that new designs are realised very quickly, the tool shop is optimised and its staff trained for extremely short lead times. For so-called ‘soft tools’, which are not hardened and are used only for prototype production,

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the lead time can be as short as one to two weeks. Hardened multi-cavity tools for mass production can be provided within two to four weeks. Danny Young, Overseas Marketing Manager, states that a fast response to customer requirements is essential for the success of ShindyTech’s business and that toolmaking is one of ShindyTech’s strongest points. Twenty injection moulding machines are used for the manufacture of the green MIM parts (Fig. 5). Pick-and-place robots are installed at some machines, but often skilled young workers remove burrs and ejection marks by hand directly at the machine before placing the green parts on ceramic trays for transfer to the debinding section. Debinding is carried out in eight catalytic debinding units (Fig. 6). Sintering is performed in twelve batch-type furnaces suitable for atmospheric and vacuum sintering. Where necessary, functionally critical tolerances of parts that cannot be met directly by MIM processing are achieved by a sizing step. Fig. 7 shows a view of the sintering shop. The installation of nearly 200 CNC machines for the finish machining of MIM parts indicates that most MIM products are not ready for shipment when they leave the sintering

Shenzhen Shindy Technology

Fig. 8 Manual inspection of MIM parts at ShindyTech (Courtesy Georg Schlieper)

Today, about 70% of ShindyTech’s feedstocks are based on BASF’s Catamold binder. The materials produced are 75% 17-4PH, 20% 316L with the balance being low-alloy steels and BASF’s P.A.N.A.C.E.A, a nickel-free austenitic stainless steel. Quality control in the MIM industry, particularly for a company such as ShindyTech that produces a wide variety of extremely high volumes of miniature parts, can be a challenging

“Automated test methods such as in-line cameras or eddy current testing are often inapplicable here, as they are not sensitive enough to detect very small defects.” furnace and that a number of secondary operations are performed before the manufacturing process is complete. Besides CNC machining, surface treatment such as polishing or PVD coating is often applied for aesthetic reasons. For consumer products in particular, where parts are visible, an aesthetically pleasing appearance is of prime importance.

process. Automated test methods such as in-line cameras or eddy current testing are often inapplicable here as they are not sensitive enough to detect very small defects. In such cases, the human eye is still the most reliable test method. Final inspection is therefore often carried out manually, by young workers with well-trained eyes (Fig. 8).

Products and markets As previously mentioned, ShindyTech’s business relies to a great extent on the consumer electronics market. To break away from its reliance on these products, ShindyTech is actively promoting entry into other markets for MIM parts, especially consumer products, medical devices, automotive and industrial applications. A selection of MIM parts, including a number of consumer products for which ShindyTech has begun to enter the market, can be seen in Figs. 9-13. Examples are also shown of parts produced for the automotive, medical and industrial sectors.

Expectations for the future ShindyTech has entered into strategic alliances with several companies in China and abroad in order to obtain technical support, extend its production capacities and support sales growth. Among these are Vincent Vacuum Technology in Taiwan and Dingding Alloy Material in China. The strength of the Chinese consumer electronics industry has provided the basis for unprecedented

June 2018 Powder Injection Moulding International

Shenzhen Shindy Technology

Fig. 9 An automotive interior component

Fig. 10 MIM watch case

Fig. 12 Earphone hinge shaft

Fig. 11 A selection of MIM parts that includes 3C, medical and consumer components

Fig. 13 Eyewear hinge

success in the MIM industry in China in recent years. However, this has resulted in a strong dependency on one market, which many now recognise as a risk to the future of the industry; this market could cease to grow, shrink gradually or even suddenly collapse if new technologies or changes in consumer habits reduce the need for MIM parts. ShindyTech is therefore striving to extend its customer base to other markets such as consumer products, medical and automotive applications. Initial success has already been achieved in this respect. The expansion of the company’s portfolio to include ceramics, cemented carbides and tungsten heavy metals is part of this future strategy.

Contact

According to Dr Q, the expected downward trend of raw material prices for Metal Injection Moulding has already begun. He predicts that prices for stainless steel powders will drop by at least 20% over the next three years. Falling raw material prices will further enhance the competitiveness of the Chinese MIM industry over investment casting and CNC machining, leading to further growth. The young and ambitious team at Shenzhen Shindy Technology appears to be well positioned to secure its share of the growing MIM industry, supported in large part by solid capabilities in toolmaking and extensive experience in the high-volume manufacturing of complex miniature parts.

Powder Injection Moulding International

June 2018

Dr Q Shenzhen Shindy Technology Co., Ltd. Bldg A10, Silicon Valley Power Low-Carbon Industrial Park Guanlan Street, Zhangge Community, Shenzhen China Tel: +86 755 81734586 Email: drq_chiou@shindytech.com

Author Dr Georg Schlieper Harscheidweg 89 D-45149 Essen Germany Tel: +49 201 71 20 98 Email: info@gammatec.com www.gammatec.com

Vol. 12 No. 2

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Vol. 12 No. 2

Cost-effective Hot Isostatic Pressing

Cost-effective Hot Isostatic Pressing: A cost calculation study for MIM parts Hot Isostatic Pressing (HIP) has become an important post-processing option for the Metal Injection Moulding industry. Whilst the majority of MIM components do not require HIPing in order to meet performance specifications, high-performance applications in the automotive and aerospace sector rely on HIP to remove residual porosity. The use of HIP is also common for aesthetic applications, where reduced porosity delivers improved polishability. Magnus Ahlfors and colleagues from Quintus Technologies AB present cost calculations for the HIP of a MIM turbocharger impeller, along with the pros and cons of purchasing a HIP system.

Hot Isostatic Pressing has been used for several decades in different industries for a wide variety of applications and has, over the years, become an important finishing process for Metal Injection Moulding. The HIP process eliminates the remaining residual porosity in sintered MIM components, resulting in superior material properties such as improved fatigue, ductility and fracture toughness. HIP is also used to obtain high-quality machined and polished surfaces for MIM parts, since there is no residual porosity that can be revealed in the surface by the subtractive process. In many MIM applications, HIPing plays an important role in achieving the required properties and material performance. The cost of a HIP cycle may vary depending on the specific quantity of parts to be processed, the type of components to be processed and how the process is achieved, either through a HIP service provider or an in-house operation. This article will

Vol. 12 No. 2 ÂŠ 2018 Inovar Communications Ltd

investigate and explain the variables that affect the cost of a HIP operation, together with a study on the cost of HIPing for a typical production case of a MIM component. The different ways of having the HIP process performed, by HIP service provider or in-house operation, will also be discussed.

HIP operation cost variables From an end-user perspective, it is the total cost per HIPed component that is of most interest. This cost is determined by the cost of running the HIP cycle and, of course, how many parts are processed per batch.

Fig. 1 The Quintus QIH 15L HIP unit is one of the systems used in the cost calculations

June 2018 Powder Injection Moulding International

Cost-effective Hot Isostatic Pressing

HIP system characteristics • Size • Make • Furnace type

HIP cycle characteristics • Parameters • Material • Payload weight

Local price for utilities kWh, Nm3, man hours = $

Consumption • Electricity • Gas • Wear parts • Maintenance • Labour

Total operations cost / HIP cycle

Fig. 2 Variables for HIP operation cost

The cost of the HIP cycle depends on the consumption of electricity, process gas and labour hours needed per cycle, together with the price of these at the specific site where the HIP unit operates. The consumption of wear parts and regular maintenance of the equipment is also divided into a cost per cycle. The consumption of these resources, in turn, depends on the HIP unit used, the HIP cycle parameters and the material being processed, commonly called the load. A schematic overview of the variables that affect the HIP cycle cost is presented in Fig. 2. The size of HIP system used has a significant influence on the operational costs, whereas a large HIP system will consume more electricity and gas than a smaller one. On the other hand, of course, more parts can be processed in one cycle.

For the HIP cycle parameters, temperature has a direct influence on the consumption of electricity, since the furnace heating elements account for the majority of the electricity consumption. A higher temperature means that more energy is needed to heat up the system, comprising the load and the furnace internals, as well as a higher heat loss during the hold time. A higher pressure increases the density of the gas, with consequent higher thermal conductivity. This gives rise to higher heat loss, with corresponding higher power consumption. A longer hold time leads to more total heat loss and thus higher electricity consumption. The process gas, typically argon, is normally reused in a HIP operation; at the end of the HIP cycle, the highly

41 mm / 1.61”

44 mm / 1.74” Fig. 3 Schematic picture and size of the impeller used for the analysis

Powder Injection Moulding International

June 2018

pressurised gas in the HIP vessel is reclaimed to a gas storage tank. In this way the gas can be reused for the next HIP cycle; typically, up to 95% of the process gas can be reclaimed per cycle. Because the process gas is reclaimed at the end of the cycle, the temperature, pressure and cycle time have little influence on gas consumption. The load, or material which is being processed in the HIP, also has some influence on the consumption of gas and, where a heavier load and/ or materials with high specific heat capacity (Cp) are being processed, there will be an increase in the energy needed to reach the set temperature, and thus an increase in power consumption.

MIM cost calculation case study To demonstrate the total operation cost to HIP a typical MIM part, a cost calculation study has been made for an IN718 (UNS N07718) turbocharger impeller load. The size of the impeller is shown in Fig. 3. Two different HIP sizes with two different annual part production volumes have been evaluated to show the effect of HIP size on operation cost per HIPed part. Operation cost calculation The first step in the calculation is to analyse how many parts can fit each of the two HIP units per cycle. The

Vol. 12 No. 2

data for the calculation of how many impellers can be processed per cycle for the two HIP sizes is presented in Table 1. The smaller HIP unit, QIH15L, can fit nine impellers per load level and, based on the height of the furnace, can take ten load levels, resulting in 90 impellers total per cycle. The larger unit, QIH48, can in the same way take 46 impellers per level with 22 levels, which gives 1012 impellers per cycle. To calculate the consumption of electricity and gas per cycle, the total load weight, including the load baskets, is used together with the specific heat capacity of the material and the cycle parameters as the basis for this evaluation. Typical HIP parameters for IN718 (UNS N07718), according to ASTM F3055 − 14a, have been used. The input data and results for this calculation are shown in Table 2, together with typical man hour estimates for maintenance and HIP operation per cycle. Loading and unloading the parts accounts for the majority of the time spent, along with monitoring of the process and the average weekly, monthly and annual maintenance time. The values for the gas consumption of 6 and 13 Nm3 respectively are based on 90% of the process gas being reclaimed, which is possible in these systems. The relatively short cycle times of 7.6 and 8.2 hours to process IN718 according to ASTM F3055 − 14a is based on the use of URC® rapid cooling which the QIH15L and QIH48 are equipped with as standard. The typical costs for the utilities are presented in Table 3. The prices presented are an industry average for the US and Canada and can vary depending on geographical location and type of site. An estimated cost for wear parts and maintenance is also included in Table 3 as an average cost per cycle. Summarising all of the above results in the operation cost for the HIP process for the two different HIP sizes, presented in Table 4. As can be seen, the cost per part for the larger HIP system is dramatically lower than for the

Cost-effective Hot Isostatic Pressing

QIH15L

QIH48

Height (mm (inch))

500 (19.7)

1200 (47.2)

Inner diameter (mm (inch))

186 (7.3)

375 (14.8)

Height (mm (inch))

41 (1.6)

Apparent diameter (mm (inch))

44 (1.7)

Weight (g (lbs))

200 (0.44)

Impellers per cycle

9 x 10 = 90

46 x 22 = 1012

18 (40)

202 (445)

Furnace hot zone size

Turbocharger impeller size

Pay load weight per cycle (kg (lbs))

Table 1 The in data used for the calculation of how many impellers can be processed per cycle

QIH15L

QIH48

34 (75)

332 (732)

435 (0.104)

Temperature (°C (°F))

1185 (2165)

Pressure (MPa (psi))

150 (21750)

7.6 (with rapid cooling)

8.2 (with rapid cooling)

Electricity consumption (kWh)

128

520

Gas consumption (Nm3 (Scf))

6 (212) (with gas reclaimed)

13 (459) (with gas reclaimed)

1.1

1.6

Total load weight/cycle (kg (lbs)) Specific heat capacity (J/kg°C (BTU/lb-°F)) HIP parameters

Hold time (h) Total cycle time (h)

Labour (h)

Table 2 HIP cycle consumptions

QIH15L

QIH48

0.05

0.7 (0.02)

Cost labour ($/h)

Wear parts and maintenance ($/cycle)

Price electricity ($/kWh) Price Argon ($/Nm ($/Scf)) 3

Table 3 Cost of consumables and utilities in US$

QIH15L

QIH48

Operation cost per cycle ($)

158

Operation cost per part ($)

1.05

0.16

Table 4 Operation costs in US$

June 2018 Powder Injection Moulding International

Cost-effective Hot Isostatic Pressing

QIH15L

QIH48

Total cycle time (h)

7.6

8.2

Number of cycles per week

Working weeks per year

Working days per week

Working hours per day

90 (10% downtime for preventive maintenance, service etc.)

Number of cycles per year

648

604

Number of parts per year

58,320

611,248

Uptime (%)

Table 5 Annual volume HIP capacity

smaller system. This is because the number of parts that can be placed in the furnace increases more than the operation cost for the cycle with increasing HIP size. Typically, if a larger HIP unit can be completely filled with parts, the cost per part will be lower than if the same number of parts was processed in a smaller HIP with a corresponding larger number of cycles. A larger HIP unit will of course mean a more significant investment, so the annual volume of parts to be processed determines which HIP size is most suitable for the production case. Productivity analysis To show the typical annual volumes these two HIP units are able to process based on the same case as above, a productivity analysis has been made. This shows how many cycles per year it is possible to run with each HIP unit and, as a result, how many parts per year can be processed. Based on the total load weight, specific heat capacity of the material and the HIP parameters stated above, a total cycle time can be calculated. Based on assumptions and estimates of typical full shift HIP production conditions, this gives the total number of cycles possible to run per year. Consequently, the number of parts that can be processed per year can be calculated. These assumptions and results are shown in Table 5.

The two different HIP systems have the annual capacity to process 58,320 turbine impellers for the QIH15L and 611,248 for the QIH48.

Routes for sourcing HIP cycles Typically, two different routes are used to facilitate HIP. Either the service can be bought from a HIP service provider, or a company can own and operate a HIP system in-house for internal HIP needs. Traditionally, it has been more common to use one or more of the few large HIP service providers available. However, some companies are moving towards bringing the HIP process in-house. One reason for this trend is the strong development and improvement of HIP units in recent years. The HIP units of today are small, flexible and cost-effective. They are also as easy to operate and maintain as a CNC machine, Additive Manufacturing machine or heat treatment furnace. For relatively small annual part volumes, the HIP service provider is usually a good alternative, since they can normally consolidate lots together in one HIP cycle, making it a very cost-effective route. Another benefit of using a service provider is that no real knowledge about HIPing is needed in-house, since the service provider already has the necessary

Powder Injection Moulding International

June 2018

know-how to process the parts. Some companies also prefer to outsource operations to conserve capital. For larger annual part volumes, in-house HIP processing can be a good alternative. If the volumes are high enough to justify a HIP investment, the cost per processed part will be significantly lower than the standard service provider rate. Doing the HIP processing in-house can improve control over the whole process, including adjustment of cycle parameters and other processing conditions and improvement in terms of logistics and delivery time. A much greater opportunity for process development is possible since the HIP parameters can be optimised as opposed to buying standard HIP cycles from a service provider. This makes it possible to tailor the process to achieve specific material properties for components. The lead times can be reduced drastically due to reduced loading, shipping and wait time to and from an external site. To have the process in-house also gives a very high degree of flexibility. One of the important recent developments within HIP equipment is rapid cooling. Rapid cooling HIP furnaces can shorten the total HIP cycle time significantly by reducing the cooling time. This facilitates a very high throughput capacity with relatively small HIP units. The achievable cooling rates in these HIP furnaces are up to 4000°C/min (7200 °F/min), which also makes it possible to combine the HIP cycle with conventional heat treatment where high cooling rates are required to generate a specific microstructure and mechanical properties. By combining the HIP and heat treatment steps into one cycle in the HIP, the manufacturer will reduce the number of process steps, the total cycle, time at elevated temperature and the total equipment needed, which is positive. This type of equipment and processing is not currently available at most service providers. More information about rapid cooling HIP furnaces URC®/URQ® and combined HIP and heat treatment can be found in [1,2].

Vol. 12 No. 2

Cost-effective Hot Isostatic Pressing

Conclusions As has been demonstrated, both HIPing routes offer benefits. Whichever alternative is best is primarily dependent on the annual volume of parts to be HIPed, together with the manufacturer’s business philosophy. The main operational costs affecting HIPing are the consumption of electricity, gas, wear parts and operator man hours. In this study of a typical production case of a MIM IN718 (UNS 07718) turbocharger impeller it was shown that the operation HIP cost per impeller is $0.16/ pc in a QIH48, a 375 mm (14.8 inches) diameter HIP unit. It was also shown that the capacity of a smaller modern HIP system is very good, where a 375 mm (14.8 inches) diameter HIP unit can process as many as 611,248 turbocharger impellers per year under normal production conditions. The choice of HIP route is largely determined by the annual volume of parts per year. A high enough volume of parts may justify an in-house HIP investment which comes with benefits such as lower costs, shorter lead times, flexibility and control over the process.

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Authors Magnus Ahlfors, Johan Hjärne and James Shipley Quintus Technologies AB Quintusvägen 2 SE-721 66 Västerås Sweden Tel: +4621 327 000 magnus.ahlfors@quintusteam.com www.quintustechnologies.com

References [1] A Weddeling and W Theisen, Energy and time saving processing: A combination of hot isostatic pressing and heat treatment, Metal Powder Report, May 2016 [2] B Ruttert et al, Rejuvenation of creep resistance of a Ni-base single-crystal superalloy by Hot Isostatic Pressing, Materials & Design, Volume 134, 15 November 2017

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