Improvement in the oxidation resistance of liquid-phase-sintered silicon carbide with aluminum oxide additions

Improvement in oxidation resistance of silicon carbide (SiC) with aluminum oxide (Al2O3) additions was investigated using high purity starting materials. Green compacts of SiC powders with impurity of approximately 200 ppm metal mixed with a high purity Al2O3 powder were pressureless-sintered followed by hot-isostatic pressing to a density of >99.5%. The sinterability and the strength of the SiC were similar to those from the SiC powder with impurity of 1100 ppm metal. With decreasing Al2O3 content and metallic impurity, the oxidation resistance of the SiC increased. SiC with 1.4 mass% Al2O3 content had a parabolic oxidation rate constant of 7.8 × 10−12 kg2 m−4 s−1 for 400 h oxidation at 1300 °C in dry air, which is lower than those reported for other LPS-SiC and comparable to that of CVD-SiC.