The thermal spray processes belong to a family of surface engineering possibilities in which powder formed materials are injected into a hot flame, accelerated and hence form a mechanically stable coating usually applied to metallic substrates.
The component surface is not, however, melted as in many welding processes but the surface is subjected only to moderate temperatures. The coating is bonded due to the mechanical keying with the substrate and is then built up in layers.
Quality criteria for thermally sprayed coatings are, low porosity, high bond strength to the substrate, free from cracks and homogeneity of structure.
The purpose of the process is the coating of both metallic, non-metallic, oxides, carbides and hybrides thereof aimed toward targeted modification of surface properties.
Thermally sprayed coatings are used in many areas of industry. The main areas of use are in the reduction of wear, corrosion, protection from hot gases, thermal isolation, friction characteristics and the re-generation of worn components.