The repeated thermal shock behaviors of a ZrB2–SiC composite heated by electric resistance method

Repeated thermal shocks of ZrB2–20 vol.% SiC (ZrB2–SiC) composite was investigated by the electric resistance method with 330 A and 4 V. It was found that the maximum temperature of the specimen center was obtained in 20 s and the specimen was cooled down to room temperature in 10 s due to a coolant system, and then the specimen was heated again. The thermal shock treatment increased the flexural strength with a peak at 20 cycles. Even though 30 cycles showed the minimum strength, it was still higher than that of the unshocked specimen. The increase in the strength was attributed to the formation of the oxide layer and the compression stress that resulted from volume expansion upon conversion of ZrB2 and SiC, to ZrO2, B2O3 and SiO2.