Dimensionally stable subsonic plasma arc spray gun with long wearing electrodes

摘要

An improved plasma arc spray gun performs with higher deposition efficiency and longer lasting anodes and cathodes than prior spray guns. The spray gun of the invention includes a housing made of a glass fiber reinforced TORLON material that remains dimensionally stable under all operating conditions. The anode of a relatively low velocity subsonic spray gun has an interior with five sections, two of which have cylindrical inner surfaces and three of which have frusto-conical surfaces. The cathode tip is carefully located within the anode interior such that the electrical arc between the anode and cathode attaches to the anode at a circular line at a junction of a cylindrical surface and a frusto-conical surface. Relatively high velocity subsonic versions of the plasma arc spray gun utilize anodes with three interior sections and streamlined passages for vortex stabilized flow of the primary gas. The primary gas flows in a vortex such that the point of attachment of the arc to the anode travels continuously along the circular line to reduce anode wear. The improved gas dynamics cools the cathode tip and thereby increases its service life.