Effect of Heat Treatments on the Crack‐Healing and Static Fatigue Behavior of Silicon Carbide Sintered with Sc2O3 and AlN

Crack-healing behavior of silicon carbide ceramics sintered with AlN and Sc2O3 has been studied as a function of heat-treatment temperature and applied stress. Results showed that heat treatment in air could significantly increase the indentation strength whether a stress is applied or not. After heat treatment with no applied stress at 1300°C for 1 h in air, the indentation strength of the specimen with an indentation crack of ∼100 μm (≈2c) recovered its strength fully at room temperature. In addition, a simple heat treatment at 1200°C for 5 h under an applied stress of 200 MPa in air resulted in a complete recovery of the unindented strength at the healing temperature. However, higher applied stress led to fracture of the specimens during heat treatment. The static fatigue limit of the specimens crack healed at 1200°C for 5 h under 200 MPa was ∼450 MPa at the healing temperature. The ratio of the static fatigue limit of the crack-healed specimen to the unindented strength was ∼80%.

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