Thermal shock resistance of porous ZrB₂–SiC ceramic after oxidation

Thermal shock water quenching tests on porous ZrB₂–SiC (ZS) ceramics with 8.7, 17.9 and 27.3% porosity were conducted after these specimens were oxidised in static air at a constant temperature of 1200°C for 30 min. The effect of oxidation on their thermal shock resistance was investigated in detail. The oxidation improved the material’s thermal shock fracture resistance, but reduced their thermal shock damage resistance (TSDR). The thermal shock critical temperature difference (ΔT_c) of the oxidised porous ZS ceramics decreased as the porosity increased, which was the opposite trend to that observed in the case of unoxidised porous ZS ceramics. ZS ceramics with higher porosity had higher TSDR with or without oxidation treatment. Thickness of the oxidation layer, degree of oxide layer coverage and internal oxidation were observed to affect the thermal shock behaviour of the porous ZS ceramics.