CASTOLIN EUTECTIC
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PROFILE
THERMAL SPRAY COATINGS TECHNOLOGY Improving Efficiency in the Shipping Industry For many years thermal spraying a layer of protective material has been successfully used as a coating method to improve or repair a part's surface properties.
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he protective material sprayed in the form of wire, powder or ceramic rods are melted in a gas flame, electric arc or a plasma jet. The melt is atomized into a gas or air stream and then sprayed towards the object to be coated.
Schematic of the thermal spray process to produce coatings
corrosion protection on ocean-going shipping containers and also as tribological coatings on metallic sliding surfaces that are common in all engines. HVOF coatings are employed on critical valve and wear parts and are increasing being used as a replacement for hard chrome on parts such as hydraulic shafts, pumps and seals.
The EuTronic Arc Wire Spraying Process Explained
Metals, ceramics, carbides and plastics are examples of coating materials that can be applied by thermal spraying. Depending on the type of sprayed material the coating can be used as: • Protection against wear, corrosion and heat • As an electric conductive or insulating coating • Repairing and rebuilding of worn parts • Friction increasing or friction-reducing coating There exists a broad range of thermal spray technologies that have been developed by Castolin Eutectic and other pioneers over the years, based on optimisation of feedstock, heat source, particle acceleration and densification method, as illustrated in the table below: Overview of thermal spray processes
As the electrically conductive wires are fed towards each other, a short circuit is established between the wires creating an arc with a temperature of around 5,000°C. This heat causes the wire tips to melt. Compressed air is used to atomize the molten tips and propel the droplets towards the substrate at velocities exceeding 200 meters per second. This is the most cost effective thermal spraying process when large objects shall be sprayed, particularly together with Castolin Eutectic special densification which gives excellent protection in corrosive environments. The characteristics of the arc wire spray coating are that it has a rough surface and two to six per cent porosity. Normally these can be disadvantages but they can act intelligently when used as tribological coatings at an interface between reciprocating parts, such as pistons rings and cylinders. The wide range of alloy chemistries possible and unique structure mean that such coatings can bed down to make a perfect seal, provide improved wear and corrosion resistance over standard alloys and the porous structure can retain lubricants, improving sliding further.
Arc Wire spray process and modern EuTronic ARC spray systems for large surface area coating
The High Density HVOF Process HVOF (High-Velocity Oxy-Fuel) Spraying is a relatively new process giving the densest, hardest coatings with very high bond strength. It can also spray very hard Tungsten Carbide coatings with a hardness of over 1,300 HV. Therefore it is often used to protect against extreme wear and also as a hard chromium replacement and for hydraulic shafts, ball valves, seatings and seals. The key to achieving this coating quality requires a sophisticated spray unit, agglomerated fine powders and
optimised spray parameters. The CJK5 is the latest Castolin Eutectic development of kerosene fuelled high pressure HVOF spray systems and offers the highest quality plus a robust, easy to use and inexpensive package. During HVOF spraying, the ignited kerosen/oxygen mixture produces a hot gas stream (reaching velocity up to 2000 m/s) into which powder is injected. This creates high impact energy particles and the highest quality coating. n
Arc Wire spray process and modern EuTronic ARC spray systems for large surface area coating
Examples of Leading Thermal Spraying Technologies in Shipping In shipping, most thermal spraying technologies are used but Plasma, HVOF and arc wire spraying applications are growing. Today, EuTronic Arc wire spray systems are used for large scale Fully automated CJK5 HVOF spraying system and spraying of ball valves in the workshop
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