Improving the oxidation resistance of Ti3SiC2 by forming a Ti3Si0.9Al0.1C2 solid solution

The oxidation behavior of the Ti3Si0.9Al0.1C2 solid solution in air was investigated at 1000-1350DGC. The parabolic rate constants of Ti3Si0.9Al0.1C2 were decreased by 2-4 orders of magnitude compared with those of Ti3SiC2 at 1000-1300DGC. At 1000-1100DGC, the oxide scales displayed a continuous *a-Al2O3 inner layer and a discontinuous TiO2 (rutile) outer layer. At 1200-1300DGC, the continuous inner layer was still *a-Al2O3, but the outer layer was a mixture of TiO2 (rutile) and Al2TiO5. The oxide layers were dense, adherent and resistant to thermal cycling. However, the oxidation resistance of Ti3Si0.9Al0.1C2 deteriorated at 1350DGC because of the depletion of *a-Al2O3. This depletion was caused by the extensive reaction between TiO2 (rutile) and *a-Al2O3 to form Al2TiO5. The high activity and diffusion of Al and the low solubility of oxygen in the solid solution were the key factors for the formation of a continuous *a-Al2O3 layer during high-temperature oxidation.