초록 ▼

A method of operation of a plasma torch, an internal burner or the like to produce a hot gas jet stream directed toward a workpiece to be coated by operating the plasma torch or internal burner at high pressure while feeding a powdered material to the stream to be heated by the stream and projected

A method of operation of a plasma torch, an internal burner or the like to produce a hot gas jet stream directed toward a workpiece to be coated by operating the plasma torch or internal burner at high pressure while feeding a powdered material to the stream to be heated by the stream and projected at high velocity onto a workpiece surface. The improvement resides in expansion of the hot gas prior to feeding of the particles into the jet stream thereby limiting the heating of the powdered material by the jet stream to that only sufficient to raise the temperature of the particles of the powdered material to a temperature lower than the melting point of the material, and maintaining the in-transit temperature of the particles to the workpiece below that melting point, while providing a sufficient velocity to the particles striking the workpiece to achieve an impact energy transformation into heat to raise the temperature of the particles to fusion temperature capable of fusing the material onto the workpiece surface as a dense coating.

대표청구항 ▼

In a thermal spray method comprising the steps of: continuously combusting a fuel and oxidant under pressure within a restricting volume of a combustion chamber and expanding the products o combustion of said fuel and oxidant as gas into an extended nozzle having a throat opening to said combustion

In a thermal spray method comprising the steps of: continuously combusting a fuel and oxidant under pressure within a restricting volume of a combustion chamber and expanding the products o combustion of said fuel and oxidant as gas into an extended nozzle having a throat opening to said combustion chamber and producing at least a sonic flow stream of gases from an said extended nozzle to produce and direct a supersonic jet of said gases toward a workpiece surface to be coated; feeding a powdered material to said stream to be heated b said stream and projected onto the workpiece surface; the improvement wherein the step of feeding said powdered material comprises feeding said powdered material into said extended nozzle at a point downstream from said throat and after expansion of the gases to a temperature which limits the heating of said powdered material to that which raises the temperature of particles of said powdered material to that lower than the melting point of said powdered material, and wherein said method further comprises maintaining an in-transit temperature of said particles from said feeding point to said workpiece below said melting point, and providing a sufficient velocity to said particles such that impact energy caused by said particles striking said workpiece is transformed into heat, thereby increasing the temperature of the particles to the fusion temperature of the particles, thereby fusing the powdered material to form a dense coating on the workpiece surface.