Influence of Al film deposition and following treatment on the high temperature isothermal oxidation behavior of a γ-TiAl-based alloy

The isothermal oxidation behavior of a γ-TiAl-based alloy Ti–48Al–1.3Fe–1.1V–0.3B (at.%) at 1123 K for 360 ks in air, which was treated by a combination process of pure Al film deposition with a thickness of approximately 0.2 and 0.4 μm by IBAD and the following pre-diffusion treatment of 873 K/86.4 ks in vacuum, respectively, was studied. It was found that the Al film was transformed into a layer of TiAl3 through the pre-diffusion process. The isothermal oxidation resistance of the γ-TiAl-based alloy was improved by this kind of treatment especially that with 0.2 μm thickness Al film showed a considerable enhancement effect. The thickness of Al film formed by IBAD is a key factor of this kind of treatment since the microstructure of the TiAl3 layer transformed by the following pre-diffusion treatment strongly depends on it. It is concluded that the existence of a layer of TiAl3 which is rich in Al could favor the formation of Al2O3 and therefore retarded the diffusion rate during oxidation.