High-resolution transmission electron microscopy study of WC-Co alloy doped with other metal carbides; VC, Cr₃C₂, and ZrC

The WC/Co interface structures in WC-Co alloys doped with VC, Cr ₃C₂ or ZrC were examined by high-resolution electron microscopy (HRTEM) and X-ray energy dispersive spectroscopy (EDS) with a special interest in the segregation behavior of respective dopants at the WC/Co interfaces. It was confirmed that the addition of VC or Cr₃C ₂ were effective to reduce WC grain size while that of ZrC was not. In case of VC or Cr₃C₂-doped alloys, the morphology of WC grains largely changed comparing with undoped and ZrC-doped alloys. The WC/Co interfaces of the two alloys tend to form micro facets with (0001) and {1010} habits. EDS analysis with a sub-nano scale probe revealed that the dopants strongly segregated at the two habits. In contrast, such morphology change, and also dopant segregation, could not be observed in ZrC-doped alloy. In our study, doped ZrC was not found to solute in Co-phase. Doped ZrC distributed in Co-phase to form other grains mainly consisting of ZrC The interface structures of WC/Co could be considered to be closely related to the inhibition effect to WC grain growth.