Abstract: A plasma gun apparatus with precision adjustment of arc voltage, includes a gun body with a bore therethrough, a nozzle anode in the bore, a cathode holder engaged in the bore with threads, and a cathode mounted on the cathode holder. A locking ring is engaged in the bore with threads for locking the cathode holder. An inner wrench is formed of a handle attached to a shaft inserted through a hole in the locking ring and engaged with the cathode holder to rotate the same for axial positioning. A sleeve wrench is disposed coaxially over the shaft and engaged with the locking ring. The handle and the sleeve wrench each has a plurality of angular position markings thereon mutually alignable to provide rotational reference for precision positioning of the cathode holder.

Abstract: A method of and apparatus for producing a dense and tenacious coating with a thermal spray gun including a nozzle member and a gas cap. The gas cap extends from the nozzle and has an inwardly facing cylindrical wall defining a combustion chamber with an open end and an opposite end bounded by the nozzle. An annular flow of a combustible mixture is injected at a pressure of at least two bar above atmospheric pressure from the nozzle coaxially into the combustion chamber. An annular outer flow of pressurized air is injected from the nozzle adjacent to the cylindrical wall. Heat fusible powder entrained in a carrier gas is fed axially from the nozzle into the combustion chamber. An annular inner flow of pressurized air is injected from the nozzle into the combustion chamber coaxially between the combustible mixture and the powder-carrier gas. Upon combusting the annular mixture a supersonic spray stream containing the powder is propelled through the open end to produce a coating.