High-velocity flame spray apparatus and method of forming materials

Abstract

A supersonic flame spray apparatus capable of forming a high-energy stream of a particulate feedstock for flame spray applications. The flame spray apparatus includes a converging throat in which a two-stage exothermic reaction is created and maintained comprising a flame front and a steady-state continuous detonation. As fuel gas is injected into the flame front, a steady-state continuous detonation reaction is achieved in a fuel-rich zone. A partriculate feedstock is fed into the converging throat at a low-pressure region of the continuous detonation and then passes through the flame front heating the particles. The heated particles are entrained in the expanding combustion gases which flow in an axial high-velocity collimated particle spray stream through a tubular barrel. In one aspect, the flame spray apparatus includes a two-wire arc assembly positioned spatially along the axial center line of the particle stream exiting the barrel. The wires are melted by an electric arc in an arc zone and the molten metal is atomized by the collimated particle stream emerging from the barrel outlet to form a composite particle stream which contains two dissimilar feedstocks. Spray-formed materials are also provided including substantially fully dense metal-matrix composites which may be formed as coatings or as freestanding near-net shapes.