Study on crack-healing and its effect on strength of TiC-Al₂O₃ ceramics

TiC-Al₂O₃ composite ceramics was facboricated by hot press and sinter process. Crack was introduced at the surface of the prepared ceramics specimen by a vickers hardness tester. Crack-healing under various heat treatment processes and its effect on mechanical properties of TiC-Al₂O₃ composite ceramics were investigated by SEM and XRD. The results show that the average bending strength of the smooth ceramics specimens is 600 MPa, and the average bending strength of the specimens after introducing cracks reduces to 200 MPa. After heat treatment at 800°C, 1000°C and 1200°C for 4 hours, bending strength of the ceramics specimens with cracks increases to about 500 MPa, 352 MPa, and 259 MPa, respectively. The proper healing temperature is 800°C in the present investigation. The XRD analysis shows that TiC(s)+O₂(g)→TiO₂(s)+CO(g) occurs during heat treatment process. It is the TiO₂ that fills in cracks to improve bending strength of the ceramics.