Materials for Thermal Spray

Thermal spray is capable of processing materials with jet temperatures ranging from 500 to 15 * 103 K, which enables virtually any material, or combination of materials, to be processed. Because only small volume powder particles are heated in a given time and because, on solidification, only small volumes, typically 5 to 100 /'m in diameter, are being cooled, segregation is not a limiting factor. On the other hand, residual stress can have detrimental effects on the properties and performance of sprayed coatings, its significance varying from process to process and material to material. Also, because materials are deposited in relatively thin (12 to 50 /'m. or 0.0005 to 0.002 in.) layers, many unique combinations of materials can be produced.

Three characteristic types of deposit can be sprayed: (a) Monolithic materials, such as metals, alloys, intermetallics, ceramics, and polymers; (b) composite particles such as cermets (WC/Co, Cr3C2/NiCr, NiCrAlY/Al2O3, etc.), reinforced metals, and reinforced polymers; and (c) layered or graded materials. Some examples of these, and their particular advantages and associated technical challenges, are described below.

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