Thermospray method for production of aluminum porous boiling surfaces

Claim 1

Method for making an aluminum porous boiling surface having an open cell structure top coating on a metal substrate comprising (a) melting an essentially pure aluminum oxide free wire by means of a thermospray gun; (b) entraining said molten aluminum in an inert gas stream to shield from the surrounding atmosphere, and thereby minimize oxide formation, atomize, and transport, such atomized aluminum particles; (c) positioning said thermospray gun so that the nozzle to substrate distance is in the range of about 2 to 4 inches; (d) impinging said inert gas stream containing the aluminum particles on said metal substrate to form bond coating having less than 15 percent porosity and having a thickness of not greater than 4 mils; (e) than increasing the nozzle to substrate distance to a distance in the range of from 4 to 10 inches; and (f) impinging said inert gas stream containing the aluminum particles on said bond coating to form an open cell structure essentially oxide free top coating, having porosity of greater than 18% and having a thickness of at least four times the thickness of the bond coating, thereby producing a porous boiling surface having sufficient open cell porosity required for effective performance as a boiling surface while exhibiting good adhesion and mechanical strength.