Relation of Internal Stress and Fracture Behavior of Symmetrically Graded Al2O3/TiC/Ni

Graded materials in the system Al2O3/TiC/Ni were prepared by an SHS/HIP process. WC/Co particles were added to the outer Al2O3 layer in order to activate the heterophase toughening effects and control the thermal expansion mismatch between the outer and inner layers. The thermal residual stress was changed by changing the thickness of the outer layer and tailoring the gradient of the layer structures. The residual stress introduced by the compositionally graded structures was analysed by FEM calculation and XRD. Flexural strength and indentation toughness measurements indicated that the compressive surface stresses and WC/Co particles can significantly strengthen and toughen the Al2O3 ceramics. 11 refs.