Any material that passes through a melting phase when heated. This includes metals, metal alloys, carbides, ceramics & some plastics Materials that go from solid to a gaseous phase when heated, e.g. wood, cannot be sprayed.
CloseSpraying is a line-of-sight process so it cannot penetrate into inaccessible internal areas as plating can. However, sprayed coatings can be applied to much greater thicknesses of up to several millimeters, and avoid the use of dangerous and environmentally threatening chemical plating solutions with all the associated problems of safe disposal.
CloseNo. Parts being sprayed do not generally rise above a temperature of 150° C. If the article being sprayed has a large mass, i.e. heat sink, then its temperature will remain much lower than this.
However, special hardfacing sprayed coatings known as self-fluxing alloys are sprayed and then furnace heat treated at elevated temperatures to diffusion bond the coating to the substrate.
CloseSurfaces must be clean, dry and free of oil and grease. Blasting with appropriate grits is undertaken to provide a mechanical key for the coating and this allied to modern powder and wire formulations results in very high bond strength coatings applied to ferrous and ferrous alloy substrates.
CloseNo, some porosity is present at various levels depending on the type of thermal spray process involved. Porosity can be beneficial as the pores hold oil or lubricants and this aids in-service lubricity whilst reducing friction. However, coating metallography reveals that certain metal and carbide coatings exhibit negligible porosity.
CloseRestoring the worn dimensions of machine element parts by flame spraying is certainly a widespread traditional practice but is now a small sector of the overall market for thermally sprayed coatings.
CloseAlmost too numerous to list here. Anywhere an engineering surface property is required such as wear and abrasion resistance, electrical conductivity or insulation, abradability and cavitation resistance can be met by the correct choice of thermally sprayed coatings.
CloseNo. The molten or 'plasticised' sprayed particles freeze immediately upon impact with the substrate and do not require further time to develop their properties.
CloseThis depends on user requirements and the desired surface finish. Some coatings can be ground and polished to a very high 'mirror' finish or simply machined or brushed. Very often no finishing is necessary as the surface texture of the as-sprayed coating is beneficial in service providing, for example, extra grip or reducing friction.
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