Al-Pt MOCVD coatings for the protection of Ti6242 alloy against oxidation at elevated temperature

摘要

Results on isothermal oxidation at 873 K for 90 h of Al-Pt coatings on Ti6242 coupons are reported. These coatings were obtained by low temperature, low pressure metalorganic chemical vapor deposition using MC3(MeCp)Pt(VI) and dimethylethylamine alane. Three coating architectures were investigated, namely pure Al, Pt and Al sequential sublayers, and co-deposited Al and Pt. Oxidation kinetics revealed a strong transient oxidation regime followed by a diffusion driven parabolic one. Such coatings allow to decrease oxidation kinetics more than one order of magnitude compared with those of the bare Ti6242. Scanning electron microscopy, second ion mass spectrometry, X-ray diffraction and transmission electron microscopy revealed that these coatings present a rough surface morphology. They are dense, they develop scales composed of gamma-Al2O3 and delta-Al2O3 and they prevent titanium diffusion from the alloy to the surface.