Microstructural investigations in binderless tungsten carbide with grain growth inhibitors

The microstructure of binderless tungsten carbide, with small additions of Cr3C2 or VC, was investigated using transmission electron microscopy associated with X-ray energy dispersive spectrometry. The distribution of Cr and V elements was determined. In the material sintered with Cr3C2, numerous (Cr,W)2C grains were found, some of them displaying an epitaxy orientation relationship with the basal facet of adjacent WC grains, and Cr segregation was observed in all examined grain boundaries. In the carbide with VC additive, small V-rich carbides were found at triple junctions of WC grains. Unlike Cr, no V segregation was detected in grain boundaries. The grain growth inhibiting effect of Cr3C2 and VC is very likely different. For Cr3C2, it is supposed that both (Cr,W)2C grains and Cr segregation reduce the mobility of grain boundaries. For VC, probably the grain boundary triple junctions are pinned by small V-rich carbide grains.