Ultrafine WC–Ni cemented carbides fabricated by spark plasma sintering

With VC and TaC as WC grain growth inhibitors, ultrafine WC–Ni cemented carbides with different fractions (6–10 wt%) of binder metal nickel were fabricated by utilizing high energy milling together with spark plasma sintering. In the obtained samples, only WC and Ni phases were detected in X-ray diffraction limit. The microstructure of the specimens was examined on fractural, polished, and polished/etched surfaces by scanning electron microscopy, and the results revealed that the average WC grain size of the WC–Ni cemented carbides was about 330 nm, and there were lots of micro-pores in the samples. The relative density of the samples was all higher than 92%. But the measurement of hardness and flexural strength indicated that the existence of micro-pores had no significant influence on the performance of the obtained materials. On the basis of observation on the micro-fracture surface of the samples, it was found that fractures occurred along the binder metal, and the obtained ultrafine WC–Ni cemented carbides showed a very short binder mean free path (about 22 nm), thus resulting in excellent performance in mechanical strength.