Tensile and Fatigue Properties of WC-20 wt%Co Cemented Carbides under Microstructural Variations

Abstract

WC-Co cemented carbide has excellent mechanical properties and is widely used in many industrial applications including cold forging dies and cutting tools. The tensile and fatigue properties of WC-20wt%Co cemented carbides with microstructural variations were investigated. Microstructure parameters such as Co binder content, WC particle size, binder mean free path, and contiguity were obtained by linear intercept method using BSE microstructure images. Standard specimens of WC-20wt%Co cemented carbides were prepared for tensile and fatigue testing. Uniaxial tensile stress-strain curves and tensile-compression fatigue S-N curves were obtained. The 22Co-Cr alloy with higher Co content showed the largest binder mean free path and the lowest continuity. The 20Co-dwc alloy with fine WC grains of submicron size showed the lowest binder mean free path due to fine WC grain distribution. The 20Co-dwc alloy with fine WC grains showed the highest tensile strength and fatigue strength, compared to other alloys. The 22Co-Cr alloy with a higher FCC Co phase content, which has excellent plastic deformability, showed higher fatigue properties. The fatigue life of the 22Co-Cr alloy increased with increasing compressive mean stress level. Based on the axial tensile and fatigue properties, a reasonable fatigue life prediction of WC-20wt%Co cemented carbide dies for cold forging can be estimated.