Deposition of titanium aluminides

Claim 1

In a method for producing a titanium aluminide coating on a substrate surface, the improvement for varying the atomic ratio of titanium to aluminum in said coating which comprises: (a) supporting the substrate with the surface to be coated in a reactor chamber, (b) providing a flow of hydrogen and gaseous aluminum monochloride and a flow of gaseous titanium trichloride at gas temperatures of between about 800° C. and about 1200° C. over the surface of the substrate, by passing a flow of gaseous aluminum trichloride over a titanium surface at a temperature sufficient to cause the gases to react to produce said flow of gaseous titanium trichloride and aluminum monochloride, (c) providing from no flow to an appreciable flow of hydrogen chloride coincident with the flow of aluminum trichloride in step (b), wherein the flow rate of hydrogen chloride is controlled to provide the atomic ratio between the titanium and aluminum in said coating between about one and three, and (d) maintaining the substrate surface at a temperature below the temperature of said gases sufficient to cause disproportionation of said gases to deposit titanium and aluminum on said substrate surface.