Constitutive Equation for WC-Co Functionally Graded Cemented Carbides and Application

Functionally graded cemented carbides (FGCCs) have an excellent combination of high hardness and high toughness. But the appearance of residual stresses, resulting from cobalt gradient and mismatch between mechanical properties and material constituents, influences the lifetime of FGCCs. To get the thermal stress field distribution, a constitutive equation for WC-Co FGCCs was developed by redefinition of elastic constraint factor and introduction of plastic constraint factor. The constitutive model was applied to thermal stress analysis of WC-Co composites. The distribution of thermal stresses in WC-Co specimen was obtained by the finite element numerical method. Simultaneously, the surface compressive stress of FGCCs alloy was measured by X-ray diffraction (sinψ)2. Numerical results show the thermal stresses of WC-Co composites mainly concentrate in the cobalt gradient zone and the maximum value of principal compressive stress is 380 MPa in the surface zone. This result is in good agreement with X-ray diffraction measurement.