Patent ID: 7108893

Claim:
A method of coating a substrate comprising the steps of: a) providing at least a first population of particles and a second population of particles to be sprayed each population having an average nominal diameter of from 106 to 250 microns; b) providing a supersonic nozzle having a throat with a diameter of from 1.5 to 3.5 millimeters and located between a converging region and a diverging region, directing a flow of a gas through the nozzle, maintaining the gas at a selected temperature, and injecting the first and second populations of particles into the nozzle at the same time and entraining the first and second populations of particles in the flow of the gas; c) the temperature of the gas selected to be insufficient to thermally soften the first population of particles in the nozzle and accelerating the first population of particles to a velocity sufficient to result in direct bonding of the first population of particles onto a substrate positioned opposite the nozzle, and the temperature of the gas selected to be sufficient to heat the second population of particles to a temperature at or above their melting temperature in the nozzle thereby melting the second population of particles and accelerating the molten second population of particles to a velocity sufficient to result in adherence of the second population of particles on the substrate; thereby forming a coating on the substrate that is a combination of the first and second populations of particles.