Abstract: An improved combustion head for use with flame spray apparatus constructed according to the principles described in U.S. Pat. No. 4,416,421 is provided with a recess in the floor of the counterbore receiving hot pressurized combustion gases from the combustion chamber. The recess is of depth sufficient to redistribute the heat of the combustion gases to prevent local hot spots in the counterbore and to avoid cracking and erosion in the combustion head by reducing thermal fatigue which occurs in cyclic use of the flame spray apparatus. The improved combustion head is also provided with radially spaced longitudinal channels extending inwardly from the periphery thereof, along which channels cooling water is passed to cool the improved combustion head.

Abstract: Apparatus and method are disclosed for introducing powder into a stream of plasma generated in a plasma torch such as a plasma transferred arc torch.The nozzle of the torch has a central base through which the stream of plasma flows, the bore being conically flared immediately adjacent the exit end of the nozzle. Powder is fed through feed bores in the nozzle to the conically flared portion of the central bore and is directed in the form of streams of powder toward the plasma streams at angles to the longitudinal axis of the central bore of between about 45.degree. and about 50.degree., preferably 50.degree., with a velocity component in the direction of travel of the plasma stream. The streams of powder are fed sufficiently close to the plasma stream as to avoid spreading of the streams of powder before they reach the plasma stream, but not so close to the plasma stream as would cause plugging of the feed bores in the nozzle.