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Thermal Spray Coating Processes |
Thermal spraying is an industrial coating process in which heated or molten materials are sprayed onto surfaces to create protective layers. This versatile technique applies metal, ceramic, or polymer materials at high speed to improve wear resistance, corrosion protection, and thermal insulation of components.
Thermal spray systems are widely used in the aerospace, mechanical engineering, marine, and automotive industries. They are also used in electronics, the biomedical sector, and various other applications.
Thermal spraying typically uses an electric arc or high-temperature combustion as the energy source to create coatings from accumulated powdered material.
It is distinguished by its ability to deposit coatings of metals (such as stainless steel), ceramics, and polymers in layers of defined thickness onto substrate materials for technical applications.
Almost any material can be applied, as long as it melts or plasticizes during spraying. On the substrate surface, the particles form "specks" or "platelets" that interlock and accumulate to form the coating.
The deposit does not fuse with the substrate and does not need to form a solid solution to bond with the surface to be coated, which is a key feature of thermal spraying.
The bond between a thermally sprayed coating and the substrate is primarily mechanical, not metallurgical or molten. Adhesion to the substrate depends on the condition of the substrate surface, which must be clean and roughened by shot blasting or machining before spraying.
Types of Thermal Spraying
The atmospheric plasma spray (APS) process can apply the widest variety of coating materials, by far, of any thermal spray process. APS performs where other processes cannot with an unlimited coating applications on metallic substrates.
VPS is a relatively new technique in which heat-softened or molten particles are rapidly transported to a substrate, where they flatten and solidify. VPS coatings generally exhibit higher densities than those possible with other thermal spray processes.
High velocity oxy-fuel spraying involves a continuous gas combustion under high pressure in a combustion chamber. The spray material, in powder form, is fed into the central axis of the chamber.
Wire Flame Spraying is a widely used process with a very high quality standard for the sprayed layer. Wire flame spraying is suitable for components exposed to corrosion and high mechanical loads.
The Arc Spray process uses a pair of electrically conductive wires, which are melted by an electric arc. The molten material is then atomized by compressed air and sprayed onto a substrate surface.
Plasma Spraying is a rapid solidification process in which finely powdered material is injected into a plasma jet, melting almost instantly and propelled at high velocity by a strong magnetohydrodynamic force against a suitable surface, creating a well-adhering coating.
Thermal spraying processes have been widely used for years in all major sectors of mechanical engineering for the protection and recycling of components. Recent developments in equipment and processes have improved the quality and expanded the application range of thermal spray coatings.
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