PLASMA SPRAY METHOD AND APPARATUS

摘要

PLASMA SPRAY METHOD AND APPARATUS A plasma spray method capable of directing plasticized powders against a substrate for deposition of a protective coating thereon is disclosed. Various structural details of the apparatus described enable the attainment of high particle velocities without melting the particles. The technical concepts employed are directed to normalizing the temperature of the plasma stream at a reduced value prior to the injection of coating particles. A general reduction in temperature and substantial elimination of a thermal spike at the core of the stream are achieved. Coating particles are injected into the plasma stream only after the plasma is first cooled and then accelerated. In detailed embodiments, a nozzle extension assembly having a plasma cooling zone, a plasma acceleration zone, a powder injection zone and a plasma/powder discharge zone is affixed to the downstream end of a conventional plasma generator. F-4451