A plasma spray gun nozzle with fins for cooling. The fins are designed in the region radially outward of the point where the arc strikes the nozzle to have a base width and a slot width and slot depth having advantageous dimensions. Coolant is forced through the slots at a rate to achieve optimum heat transfer. Accordingly, the design for the nozzle used in its desired manner provide a plasma flame spray gun which will operate for an appreciably longer time than could prior art plasma flame spray guns before a gun failure is likely to occur.