Thermal shock resistance of a ZrB₂-SiC-graphite composite in low oxygen partial pressure environment

The heating rate and size effect on thermal shock resistance of a ZrB ₂-SiC-graphite (ZSG) composite was studied by measuring the retention of the flexural strength after rapid resistance heating in a low oxygen partial pressure environment. The residual strength values for the specimen heated in a low oxygen partial pressure of 200 Pa decreased gradually as the temperature increased under high heating rate of 200 °C/s, 300 °C/s and 500 °C/s, and then increased suddenly when the temperature reached 1800 °C. The residual strength values for the specimen with heating rate of 200 °C/s were obviously greater than others and approximate that of the original specimen. At a temperature above 1800 °C, the residual strength decreased again with increasing temperature under different heating rate. Furthermore, the size effect on thermal shock at different temperature was investigated. The experimental results revealed that thermal shock resistance of the ZSG composite was sensitive to the heating rate and size effect. The microstructure of the ZSG composite in different conditions were also presented and analyzed.