Study on the isothermal oxidation behavior in air of Ti_3AlC_2 sintered by hot pressing

摘要

The isothermal oxidation behavior at 900-1300 deg C for 20 h in air of bulk Ti_3AlC_z with 2.8 wt percent TiC sintered by means of hot pressing was investigated in the work. The isothermal oxidation behavior generally followed a parabolic rate law. The parabolic rate constants increased from 1.39 X 10~(-10) kg~2 centre dot m~(-4) cnetre dot s~(-1) at 900 deg C: to 5.56 X 10~(-9) kg~2 centre dot m~(-4) cnetre dot s~(-1) at 1300 deg C. The calculated activation energy was 136.45 kJ/mol. It was demonstrated that Ti_3AlC_2 had excellent oxidation resistance due to the continuous, dense and adhesive protect scales consisted of a mass of alpha-Al_2O_3 and a little of TiO_2 and/or Al_2TiO_5. In principle, the oxide scale was grown by the inward diffusion of O~(2+) and the outward diffusion of Ti~(4+) and Al~(3+). The rapid outward diffusion of cations usually resulted in the formation of cracks, gaps, and holes.