High and Room Temperature Mechanical Evaluation of SiC Ceramics with Alumina and Rare Earth Oxides Additions

In this work, the mechanical properties of SiC samples with (5 wt%) alumina and (5 wt%) rare earth oxides (REO) additions were investigated at room and high temperatures. The possibility of using REO instead of pure yttria could bring cost reductions to obtain sintered SiC ceramics. The powders were mixed, milled, sieved and hot-pressed at 1800 degrees C in argon atmosphere. Hardness and fracture toughness were evaluated at room temperature. The compressive creep behavior was carried out under stress range from 150 to 300MPa and temperatures of 1300, 1350 and 1400 degrees C. After creep tests, the surface analysis of the samples by XRD and SEM showed indications of oxidation reactions, cavity and cracking. The possible creep mechanisms activated in this system were diffusion, grain boundary sliding and cavitation