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 preferably 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 .