Cyclic oxidation behavior of Nb/Mn/Si alloying beta-gamma TiAl alloys

Cyclic oxidation behavior at 750−850 °C was investigated for Ti42Al1.5Mn3Nb0.1B and Ti42Al1.5Mn- 3Nb0.1B0.2C0.2Si alloy by using scanning electron microscopy, electron probe microanalysis, electron backscatter diffraction and X-ray diffraction analysis. The kinetic curves for both alloys roughly follow a parabolic law, with the reduced oxidation rate constant compared to that of Ti42Al5Mn1W alloy at 800 °C. Well-protected oxide films are generated on both alloys at all experimental temperatures, without cracking or spalling of the oxide layer. The addition of Nb inhibits the growth of TiO2 and promotes the selective oxidation of Al to form a dense and protective Al2O3 layer. What is more, the addition of trace Si further promotes the oxidation resistance of the alloy, prompting the alloy to generate a denser alumina layer, which further inhibits the internal diffusion of O and reduces the oxidation mass gain, and this effect is more significant at higher temperatures.