Effect of surface oxidation on thermal shock resistance of ZrB2–SiC–G composite

The thermal shock resistance of a ZrB2–SiC composite containing flaky graphite was investigated in two different atmospheres – air and vacuum by measuring the retention of the flexural strength after water quenching for the temperature difference ranging from 200 up to 1900 °C. The residual strength values for the samples heated in vacuum gradually decreased with increasing temperature difference. When the temperature difference was above 1200 °C, the individual sample failed upon quenching. In contrast to the samples heated in vacuum, the residual strength values for the samples heated in air increased gradually as the temperature difference increased from 1200 up to 1700 °C; and the residual strength values again decreased for the temperature difference ranging from 1700 up to 1900 °C. These results indicated that the surface oxidation played the positive role in the thermal shock resistance of the ZrB2–SiC–G composite.