Kinetic spray coating method and apparatus

A method for applying to an article a coating of particles including particles having a particle size in excess of 50 microns, the coating being formed of a cohesive layer of the particles in solid state on the surface of the article, the method comprising:

• mixing, into a gas, particles of a powder of at least one first material selected from the group consisting of a metal, alloy, mechanical mixture of a metal and an alloy, and a mixture of at least one of a polymer, a ceramic and a semiconductor with at least one of a metal, alloy and a mixture of a metal and an alloy;
• accelerating the mixed gas and particles into a supersonic jet while maintaining the temperature of the gas and particles sufficiently low to prevent thermal softening of the first material, said particles having a velocity of from about 300 to about 1,200 m/sec;
• and
• directing the jet of gas and particles in a solid state against an article of a second material selected from the group consisting of a metal, alloy, semiconductor, ceramic and plastic, and a mixture of any combination thereof, thereby coating the article with a desired thickness of the particles;
• wherein said particles have particle sizes of up to about 106 microns and said particles are first mixed with air and injected through a powder feeder injection tube into a flow of said gas consisting of heated air from a main air flow passage, the main air flow passage having a cross-sectional area ratio relative to the injection tube of at least 80/1.