High-temperature oxidation behavior of Ti3AlC2 in air

Not only the isothermal oxidation behaviors at 900–1 300 °C for 20 h in air of bulk Ti3AlC2 with 2.8% TiC which was sintered by hot pressing with the additive of silicon, but also the cyclic oxidation behavior at 1 100–1 300 300 °C for 30 cycles, were investigated by using TG, XRD, SEM. The isothermal and cyclic oxidation behaviors generally follow a parabolic rate law. The parabolic rate constants of the former increased from 1.39×10−10 kg2/(m4·s) at 900 °C to 5.56×10−9 kg2/(m4·s) at 1 300 °C. The calculated activation energy is 136.45 kJ/mol. The oxidation products are α-Al2O3 and little TiO2 at 900–1 000 °C, however when the temperature is raised up to 1 200 °C, TiO2 partially reacts to Al2TiO5, and the reaction is completed at 1 300 °C. This demonstrates that Ti3AlC2 has excellent oxidation resistance and good thermal shock because the dense continuous oxide scale consists of mass α-Al2O3 and little TiO2 and/or Al2TiO5. Generally, the oxide scale is grown by the inward diffusion of O2- and the outward diffusion of Ti4+ and Al3+.