Pre-oxidation temperature optimization of ultra-high temperature ceramic components: Flexural strength testing and residual stress analysis

Pre-oxidation is an effective method to eliminate machining damages and to improve mechanical properties. In this paper, ZrB₂-30 vol% SiC ceramic was pre-oxidized at 800-1200 °C. The effect of pre-oxidation temperature on flexural strength was studied. The flexural strength of ZrB₂-SiC ceramic was significantly improved after pre-oxidation treatment, and it was found that the ceramic had the highest flexural strength after pre-oxidation at 1000 °C. Besides, the residual stress state of ZrB₂-SiC ceramic after pre-oxidation treatment was also investigated using indentation and nanoindentation methods. Pre-oxidation can generate different residual stress states in the oxidation layer and ceramic matrix. When the ZrB₂-SiC ceramic was pre-oxidized at 1000 °C, the oxidation layer had the highest residual tensile stress and the ceramic matrix had the corresponding highest compressive stress, which was believed to be helpful for inhibiting crack propagation and improving mechanical properties.