Effect of SiC content on mechanical properties and thermal shock resistance of BN-ZrO2-SiC composites

BN-ZrO2-SiC composites with different SiC contents have been fabricated by hot pressing to evaluate their mechanical properties and thermal shock resistance. The flexural strength increases first and then decreases with increasing SiC content. Composite incorporated with 15 vol% SiC exhibits the highest flexural strength of 306 MPa. The optimal thermal shock resistance is achieved with 20 vol% SiC and the critical temperature difference is about 700 °C. The residual flexural strength of composites heated in air decrease gradually when temperature difference is below 800 °C, and increase slightly with temperature difference ranging from 1000 °C up to 1200 °C. The increment in the thermal shock resistance is attributed to surface oxide layer at high temperature, compared with that heated in nitrogen atmosphere. The addition of SiC is favorable for forming the continuous and dense glass layer on the surface of composite, which is a benefit to improve the thermal shock resistance.