High velocity electric-arc spray apparatus and method of forming materials

A method for forming a matrix metal composite utilizing a transferred-arc-plasma torch assembly which forms a transferred-arc column and plasma jet comprising the steps of

• feeding a metal wire having a central axis into said transferred-arc column at an angle such that no portion of said metal wire is closer to the transferred-arc-plasma torch assembly than the leading edge of said metal wire as said leading edge intersects a plasma flow;
• creating an electrical potential difference between said metal wire leading edge and said transferred-arc-plasma torch assembly;
• and
• feeding a powder downstream of said metal wire in the plasma jet path;
• feeding said powder at an angle of substantially 90.degree. with respect to said plasma jet downstream of said central axis of said metal wire, a distance at least as great as the radius of said wire;
• forming molten droplets of metal at the tip of said metal wire;
• conveying said molten droplets in said plasma stream;
• and
• embedding said powder into said molten droplets.

A method of coating a concave surface utilizing an apparatus including a rotating member having a wire conduit formed therein, said rotating member rotating about said wire conduit, transferred-arc-plasma torch assembly means for forming a transferred-arc column mounted on said rotating member, wire feeding means for feeding a conductive wire of coating material through said wire conduit and into said transferred-arc column at an angle such that no portion of said conductive wire is closer to the transferred-arc-plasma torch assembly means than the leading edge of said conductive wire, power source means coupled to said conductive wire and said transferred-arc-plasma torch assembly means for energizing said transferred-arc-plasma torch assembly means and said conductive wire to create an electrical potential difference therebetween forming said transferred-arc column, comprising tire steps of:

• positioning said rotating member within said concave surface with said wire located generally in tire axis of said concave surface;
• feeding said conductive wire into said transferred-arc column generating a stream of particles of said coating material directed radially toward said concave surface;
• rotating said rotating member about said wire conduit generating said stream of particles radially across said concave surface and forming a generally even coating of said coating material on said concave surface;
• and
• reciprocally moving said rotating member between a first direction along the axis of said concave surface and a second opposite direction along tile axis of said concave surface coating said concave surface with said coating material.

A method of coating an internal surface of a generally cylindrical bore utilizing an apparatus including a rotating member having a wire conduit therein, said rotating member rotating about said wire conduit, a transferred-arc plasma torch assembly mounted on said rotating member, wire feed means for feeding a conductive wire of coating material through said wire conduit into said transfer-are column, a power source coupled to said conductive wire and said transferred-arc-plasma torch assembly energizing said transferred-arc-plasma torch assembly and said conductive wire to create an electrical potential difference therebetween forming a transferred column, comprising the following steps:

• positioning said rotating member within said bore with said conductive wire located generally along the axis of said bore;
• feeding said conductive wire into said transferred-arc column generating a stream of particles of said coating material directed radially toward said internal surface of said generally cylindrical bore;
• rotating said rotating member about said wire conduit directing said stream of coating particles radially across said internal surface and forming a generally uniform coating on said internal surface;
• and
• moving said rotating member generally along the axis of said bore uniformly coating the internal surface of said bore with said coating material.