Abstract: An environmental coating is applied to the surface of a titanium-base alloy substrate to protect the surface from oxidation, corrosion, erosion, and other damage. The coating is a mixture of a metal and a ceramic, each selected to contribute to the protective function. The proportions of the metal and the ceramic in the coating are selected such that the coefficient of thermal expansion of the coating is about the same as the coefficient of thermal expansion of the substrate.

Abstract: An article having a protective coating thereon includes a substrate having a substrate composition and a substrate surface, and a protective coating contacting and overlying at least a portion of the substrate surface. The substrate is preferably a Ti--Nb aluminide, an .alpha.2-titanium aluiminide, or a .gamma.-titanium aluminide. The protective coating includes a metallic layer contacting the substrate surface and having a composition, in atomic percent, of from about 5 to about 40 percent chromium, from about 44 to about 59 percent aluminum, balance titanium plus incidental impurities. The protective coating may further include a ceramic layer contacting and overlying the metallic layer, with the metallic layer lying between the ceramic layer and the substrate.