Superalloy substrate plasma sprayed with protective coating - followed by hot isostatic pressing which consolidates the coating

摘要

A coating of MCrAlY, where M is Ni,Co or Fe, is applied by plasma spraying onto a superalloy substrate. The coating contains pores, voids, and other defects, some reaching surface of the coating, which is then sealed. Hot isostatic pressing is then used to close the defects in coating thereby considerably improving the protective quality of coating, and the seal prevents the atmos. used in pressing from entering the pores etc. Seal is pref. a metal envelope esp. a metal which improves the protective quality of coating, the hot isostatic pressing pref. also causes diffusion of metal into coating. Metal is pref. Cr or Al and/or is an electroplated metal, sealing may alternatively be achieved by cold working the surface of the coating. The sealing envelope may also be a metal foil, esp. of Al. The final protective coating, is free from surface and internal defects, and has a resistance to oxidn. and corrosion at least equal to that of a similar compsn. obtd. by vacuum metallisation.