Dependence of microcrack number density on microstructural parameters during plastic deformation of WC-Co composite

Previous studies have shown that WC-Co material can plastically deform during indentation test, and microcracking is one of the dominant mechanisms for the plastic deformation. Microcracks follow several paths of microstructure: transgranular cracks within WC grains, intergranular cracks along grain boundary and cracks at WC/Co interface. In this study, six commercial grades of WC-Co material were tested using the Hertzian indentation technique at the same indentation load with the same size of an indenter. The microcrack number density of each grade was measured and its correlation with microstructural parameters was analyzed. Materials with high cobalt content, large grain size, large mean free path and low contiguity form more microcracks in the course of plastic deformation. The microcrack number density is also correlated with mechanical properties. High microcrack number density corresponds to low hardness and high toughness. The mechanism of how the microcracking affects the fracture toughness is also discussed.