Critical crack size of healing possibility of SiC ceramics

Crack-healing behavior of SiC ceramics with additive SiO2 has been studied as functions of heat-treatment temperature and crack size. Results showed that heat treatment in air could significantly increase the strength. The heat-treatment temperature has a profound influence on the extent of crack healing and the degree of strength recovery. The optimum heat-treatment temperature had 1 h at an atmospheric level of 1373 K. After heat treatment at the optimum temperature in air, the crack morphology almost entirely disappeared and the strength recovered to the value of the smooth specimens at room temperature for the investigated crack sizes up to 450 μm. The long crack up to 1000 μm with width 1.4 μm could completely heal the surface crack.