Oxidation Behavior of TiAl3-Al Composite Coating on g-TiAl Based Alloy At 950 °C

TiAl3-Al composite coating on r-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 hte bare alloy exhibited poor oxidation resistance, significant weight loss was observed after oxidation for 70h. the oxides formed were the mixture of TiO2/Al2O3. for the speciment with the coating , great improvement in oxidation resistance was observed. approximated 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 1000h.  A certain amount of TiAl3 phase in the coating remained unoxidized and unconsumed. the EPMA analysis of the coated samples showed that no trend of oxygen or nitride diffusion into the substrate and no oxide formed  beneath the TiAl2 interlayer.