Abstract
The oxidation resistance and degradation process were investigated in air at 1173K for up to 1.44 Ms for the TiAl alloy, which has been pre-sulfidized at 1173K in a H2-H2S gas mixture to form a TiAl3 (+TiAl2) layer with 20 micron thickness on the alloy surface. And the reaction diffusion process of the TiAl3-TiAl2-TiAl system was computer-simulated.
The TiAl3 layer with very good oxidation resitance changed quickly into a TiAl2 at 80ks, which agreed well with the calculated one. The TiAl2 layer transformed slowly to a TiAl, indicating good oxidation resitance for up to 810ks, while with further oxidation it degraded singnificantly at 1.44 Ms, in contrast to the calculated time of 4 Ms. This is due to a locallized oxidation along alloy grain boundaries, and the degradation mechanism was proposed.
