Abstract
The oxidation behavior of the TiAl-8Nb alloy has been investigated by the thermogravimetric method. Isothermal experiments were carried out in the temperature range of 1173 to 1473 K in air as atmosphere. The activation energy of the reaction was calculated from the results of the isothermal experiments. The results show that the reaction rate is controlled during the initial stages by the chemical reaction, while, at the later stages, the diffusion process is likely to be the rate-controlling step. Further, the rate-determining diffusion step is likely to be the self-diffusion of Ti in alloy. The microstructure and composition distribution of the oxide layer were analyzed by scanning electronic microscopy (SEM) and electron dispersion spectroscopy (EDS). A mechanism for oxidation of the TiAl-8Nb alloy in the experimental temperature range is proposed based on the experimental results.
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