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.