Thermal Shock Fatigue of Al₂O₃ Ceramics

Abstract

The effects of a single thermal shock and its repetition on the initiation and growth of cracks were studied experimentally by using notched Al₂O₃ ceramics specimens. Various temperature differences were given by rapid cooling in water after heating at different temperatures in a furnace. The results obtained are summarized as follows;
1) The boiling point of water, instead of water temperature, seems to be appropriate as the low side temperature to determine the critical temperature difference for the initiation of a crack by a single thermal shock as well as for the increase of the crack density under the repetition of thermal shock of small temperature difference.
2) For the increase in the number of surface cracks including branched ones, the temperature of cooling water seems to be appropriate as the low side temperature under the repeated thermal shock conditions.
3) The threshold temperature difference to increase the crack density under the repetition of thermal shocks agreed with the critical temperature difference for crack initiation by a single thermal shock.