Patent ID: 6986471

Claim:
A plasma spray apparatus for applying a coating to an article, the apparatus comprising: a plasma generator which includes a cathode support member, supporting a cathode thereon, a cup shaped plasma nozzle having an inner surface disposed about the cathode and the inner surface forming a chamber into which a plasma forming gas is introduced for passage through the cup shaped plasma nozzle, the plasma gas forming a vortex flow around the cathode and exiting the cup shaped nozzle through an orifice, and; an electrical D.C. power source with suitable constant current type operating characteristics providing a negative connection to said cathode and a positive connection to said plasma nozzle of said plasma generator, energizing said plasma generator, which causes a plasma arc to be formed between said cathode and said plasma nozzle causing said plasma gas to be heated and to exit said plasma nozzle in a plasma state, and; a source of main gas which has powder particles entrained, and; A main gas nozzle concentrically surrounding the exterior of said plasma nozzle forming a passage between said main gas nozzle and said plasma nozzle through which said main gas containing powder particles is caused to flow, and; an accelerating nozzle positioned directly at an exit of said plasma nozzle and main gas nozzle, having an entry chamber into which said plasma gas and said main gas with powder particles entrained therein flow and combine to establish a gas mixture having a temperature which is the result of the enthalpy of said plasma gas and said main gas, said gas mixture accelerating through the extended bore of said accelerating nozzle to a sonic or supersonic velocity so that upon impact onto the surface of said article a cohesively bonded coating will form and build-up; and a rotating member having means to commutate said plasma gas flow and said main gas flow with powder particles entrained therein and commutating the electrical power required to function the plasma generator, said rotating member rotating about the central axis of said commutating means, said plasma generator and accelerating nozzle assembly attached to said rotating member and oriented perpendicular to an axis of said commutating means and directed radially towards said axis.