Effect of carbon content on the microstructure and properties of WC-CoCrFeNi cemented carbides

Five groups of WC-15 wt% CoCrFeNi cemented carbides with varying carbon contents were prepared by pressure sintering method using 6 μm WC powder as raw material. The results indicated that all the samples exhibited a uniform microstructure and an exceptional relative density exceeding 98.5 %. The WC grains displayed diverse morphologies, including the distinctive serrated-like morphology. It was attributed to the inhomogeneous segregation of Cr atoms on different crystal faces, leading to inconsistent growth rates of WC on different facets. Furthermore, the segregation of Cr atoms exerted a remarkable grain-refining effect on the WC grains, with the average WC grain size in all samples reaching 0.8–0.9 μm, which is 1/8 of the original size of WC. As the proportion of the triangular (0001) basal face-represented facets of the WC grains decreased, the hardness of the as-prepared cemented carbides exhibited a decreasing trend and reached a maximum value of 17.73 GPa at a carbon content of 6.30 wt%. In contrast, the fracture toughness and bending strength showed an ascending trend and reached the maximum values of 2213 MPa and 8.24 MPa m 1/2 at a carbon content of 6.40 wt%, respectively.