Abstract: A powder injection apparatus for a plasma spray gun includes a block having channelling therein for liquid coolant. A powder port extends through the block in proximity to the channelling so as to be cooled by coolant flowing therein. The port has a powder inlet receptive of spray powder in a carrier gas, and has a powder outlet end formed as a tubular protrusion extending from the block. A pair of extensions extend from the block proximate the protrusion on diametrically opposite sides thereof. Each extension has at least one orifice therein disposed so as to direct gas onto the protrusion. A pair of additional gas exit openings direct gas to the face of the gun.

Abstract: Manufacture of glass mold plungers utilizes a thermal spray gun having combustion chamber with an open channel for propelling combustion products into the ambient atmosphere at supersonic velocity. The method comprises injecting into the chamber a combustible mixture of combustion gas and oxygen at a pressure in the chamber of at least two atmospheres above ambient atmospheric pressure, feeding into the chamber a powder comprising self-fluxing alloy particles, and combusting the combustible mixture in the chamber means whereby a supersonic spray stream containing the powder is propelled through the open channel. The spray stream is directed toward a glass mold plunger substrate such as to produce a coating thereon which is ground and polished. The coating may be fused prior to grinding.