Abstract: A method of staggering reversal of thermal spray inside a cylinder bore of an internal combustion engine. The method includes the steps of thermally spraying a surface of the cylinder bore by moving a thermal spray gun along a length of the surface. The method also includes the steps of reversing a direction of travel of the thermal spray gun inside the cylinder bore at different points along the length of the surface to provide a multi-layered coating on the surface.

Abstract: A plasma transferred wire arc thermal spray apparatus and method producing an extended-arc and supersonic plasma jet stream for applying a dense metallic coating on a substrate, such as a concave internal surface of a bore. The apparatus includes a plasma generating torch assembling having a cathode and an anode nozzle surrounding the cathode and a wire feeder which continuously feeds the tip of a wire feedstock opposite a constricted nozzle orifice and wherein the wire feedstock is maintained at the same positive electrical potential as the nozzle. Plasma gas is directed into the nozzle, preferably generating a vortex flow around the cathode and exiting the restricted nozzle orifice. The improved apparatus includes a pilot power supply and a high voltage or high frequency power supply which initiates the electric arc and the constricted plasma arc and a separate main power supply which extends the constricted plasma arc to the wire tip.

Abstract: A method of eliminating unevenness in pass-reversal thermal spraying of a substrate surface by: uniformly thermally spraying a substrate surface by moving a wire fed arc spray gun along the length of the substrate surface at constant spray parameters while using a first wire feed rate and a first current level for the gun's power supply; (b) when said spray gun approaches an end zone of the pass length requiring reversal of spray gun movement, reducing the wire feed rate and current by up to about 25% until the spray gun has completed such reversal and has exited from said end zone in the opposite direction; (c) while still continuing thermal spraying, restoring the wire feed rage and current to said first levels; and (d) repeating steps (b) and (c) as the spray gun approaches other or repeated end zones of the substrate length during repeated passes.