Temperature Dependence of Residual Tensile Stresses and Its Influences on Crack Propagation Behaviour

To study the mechanical properties at high temperature of pre-stressed ceramics which were prepared by using higher expansion coefficient materials as coating and lower expansion coefficient materials as substrate,zirconia and alumina were chosen as the coating and the substrate, respectively, to fabricate ZrO2-Al2O3（marked as ZcAs） pre-stressed ceramics with sandwich structure. Meanwhile, Al2O3-ZrO2 pre-stressed ceramics（marked as AcZs, which has the similar section ratio between substrate and coating to ZcAs）, ZrO2 ceramics and Al2O3ceramics were set as the reference samples. Combining the results of bending strength at different temperatures with the results of Vickers indentation, the existence form of residual stress and its influence on crack propagation behavior were clarified as well as the temperature dependence of residual stress. Results show that the residual tensile stress exists in the surface layer of ZcAs, while the compressive stress exists in the substrate. On the contrary,the compressive st