NARROW BEAM ARC SPRAY DEVICE AND METHOD

摘要

A narrow beam arc spray head device (12) includes a convergent-divergent nozzle; a number of wires (26) the paths of which intersect at a point in the nozzle (38); means for supplying an electrical current to the wires so that an arc is formed between the wires causing a portion of at least one of the wires to melt; a primary axial gas stream impinging upon the wire path intersection to cause the molten metal to be carried axially away from the area of the intersection; and a secondary gas stream forming a generally conical sheath around the axial gas stream in the divergent portion of the nozzle; whereby the primary gas stream and the secondary gas stream emerge from the nozzle (38) as substantially coaxial gas streams thus tending to concentrate the flow of the molten metal carried by the coaxial streams. A method of coating a surface with a material includes the steps of melting the material in a nozzle (38); propelling the molten material through such nozzle in an axial direction; and, forming a gas sheath around the propelled molten material that is coaxial with the axial direction of the propelled molten material substantially the complete distance to the surface.