Sintering and physicochemical properties of compositions in the SiC–Al2O3–La2O3–Cr2O3 system II. Oxidation resistance of pressureless sintered compacts in the SiC–Al2O3–La2O3–Cr2O3 system

Compacts prepared from SiC (70–55 wt%), Al2O3 (10 wt%) and LaCrO3 (20–35 wt%) by pressureless sintering in carbon at 1700°C were studied for their oxidation resistance in air at 1300, 1400 and 1500°C. The oxidation resistance of the material at 1500°C was dependent on the quantity of La2O3–Al2O3–SiO2 melt, which diffused from inside to the surface of the compacts. Instead, chromium compounds were retained in the material and barred the melt diffusion. Nevertheless, at 1300°C, La2O3 of the compacts reacted with SiO2 and gave a dependable protective layer of lanthanum silicates.