Thermal shock behaviour of mullite-bonded porous silicon carbide ceramics with yttria addition

Abstract

Thermal shock resistance of mullite (3Al2O3 · 2SiO2)-bonded porous silicon carbide (SiC) ceramics with 3.0 wt% yttria (Y2O3) addition was evaluated by a water-quenching technique. The thermal shock damage was investigated as a function of the quenching temperature, quenching cycles and specimen thickness. The residual flexural strength of the quenched specimens decreases with increasing quenching temperature and specimen thickness due to the larger thermal stress caused by thermal shock. However, quenching cycles at the temperature difference of 1200 °C have no effect on the residual strength since the same thermal stress was produced in repeated thermal shock processes. The good thermal shock damage resistance of the specimens is contributed mainly by the low strength and moderate elastic modulus. Moreover, the pores prevent the continuous propagation of cracks and alleviate further damage.