Segregation layers of grain growth inhibitors at WC/WC interfaces in VC-doped submicron-grained WC-Co cemented carbides

The WC/WC interface in VC-doped submicron-grained WC-Co cemented carbides was investigated using high-resolution transmission electron microscopy (HRTEM) and energy-dispersive X-ray microanalysis (XMA) spectroscopy. Both V and Co were segregated at WC(0001)/WC(0001) or WC(0001)/WC(randomly oriented plane) interfaces and were slightly segregated at WC(101¯0)/WC(101¯0) or WC(101¯0)/WC(randomly oriented plane) interfaces. The V concentrations at these interfaces were 6-14 at.% and 2-6 at.%, respectively, and the Co concentrations were 7-20 at.% and 4-28 at.%, respectively. The V concentration depended on the WC crystallographic orientation, whereas the Co concentration had a small correlation. On the basis of this result and the previous results for the WC/Co interface, it is concluded that the segregation of V at WC/WC interfaces occurs by the same mechanism as that at WC/Co interfaces. In particular, rather than equilibrium segregation occurring during the heating and holding stages of sintering, segregation onto the WC surface proceeds during the cooling stage of the sintering process.