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.

Abstract: An arc spray gun has a generally frusto-conical head member of electrically insulating material, with the small end facing forwardly in the direction of spray. Wire is fed through a pair of electrically conductive tubular wire guides containing pressure contact means that extend through the head member and converge to contact the wire ends for arc formation and melting of the metal. A gas jet nozzle provides compressed gas for atomization and spraying of the molten metal. A first gas cap is disposed coaxially on the head with rear and forward gas seals so as to define an annular gas chamber. A secondary gas is supplied to the annular chamber, and the first gas cap has a pair of diametrically opposite orifices therein for directing the secondary gas from the chamber to modify the molten metal spray in a fan shape. The orifice may have elongated cross sections to produce a rough coating surface if desired.