Oxidation Behavior of TiAl3-Al Composite Coating on γ-TiAl Based Alloy at 950 °C

Abstract

TiAl3-Al composite coating on γ-TiAl alloy was prepared by cold spray and subsequent heat-treatment. The Oxidation test, which was carried out at 950 °C in air, indicated that the bare alloy exhibited poor oxidation resistance, significant weight loss was observed after oxidation for 70 h. The oxides formed were the mixture of TiO2 /Al2O3. For the specimen with the TiAl3–Al coating, great improvement in oxidation resistance was observed. Approximate parabolic oxidation kinetics was observed for the oxidation period. The microstructure analysis showed a dense TiAl2 interlayer and a reticular Cr rich phase formed between the composite coating and the substrate. The oxides in the oxidized coating were mainly alumina, with only trace of titanium dioxide and titanium nitrides after oxidation up to 1000 h. A certain amount of TiAl3 phase in the coating remained unoxidized and unconsumed. The EPMA analyses of the coated samples showed that no trend of oxygen or nitride diffusion into the substrate and no oxide formed beneath the TiAl2 interlayer.