Flame sprayed coatings of material from solid wire or rods

Claim 1

In a flame spray method including steps of: feeding a rod of solid material to be flame sprayed in and through a flame to heat, atomize and project a spray of particles against a workpiece to be coated, the improvement comprising: controlling transit of said particles in molten droplet form over a path of travel of said particles from a tip of said rod to a surface of the workpiece such that initially liquid droplets of said material separated from and projected from the tip of the rod are at least partially solid at a moment of impact against a surface of the workpiece, spacing the workpiece from a point of separation of the liquid droplets from the tip of the rod at a stand-off distance sufficient to cause the liquid droplets to pass through an initial upstream liquid region and a contiguous downstream transition region from liquid to at least partially solid, wherein said flame is a supersonic flame, and said method further comprises continuously combusting under pressure a continuously supplied compressible combustible gas and fuel mixture including oxygen within an internal burner combustion chamber and discharging combustion product gases from a combustion chamber orifice through an expansion nozzle open at its downstream end via a nozzle extension and forming a supersonic jet exiting said nozzle extension, and said step of controlling the transit of the liquid droplets over the path of travel of the particles to be sprayed from the tip end of the rod to said surface of the workpiece comprises feeding said rod axially through said nozzle extension and causing a flow of liquid coolant to exit from an annulus about an outer periphery of the nozzle extension, and at an exit end of said nozzle extension as an annular coolant stream flowing along an outer surface of the supersonic jet downstream of the exit end of the nozzle extension from the tip of said rod towards said workpiece to thereby effect rapid cooling of the liquid droplets to at least partially solid form prior to impact on the workpiece surface, while substantially reducing the stand-off distance between the exit of the nozzle extension and the workpiece.