Effect of VC Doping on Diffusion Mechanism at WC/Co Interface

Abstract

Effect of VC addition on diffusion mechanism at the WC/Co interface using a VC doped diffusion couple was investigated. In the diffusion couple with VC doped to WC half, (WC + VC)/Co, the η and η’ phases were formed between WC/Co interface after 1623 K for 14.4 ks treatment. In contrast, the η, η’, W and W₂C phases were observed in the couple with VC doped to Co half, WC/(Co + VC). The phase change on the C-Co-W ternary isothermal phase diagram was inferred from the microstructure of diffusion couple. The (WC + VC)/Co couple showed the phase change through WC-η, η-η’, η’-Co along with these tie-lines on the C-Co-W isothermal phase diagram. The WC/(Co + VC) couple showed more complicated phase change as compared with the (WC + VC)/Co. The phase change was through the (WC + W₂C + η), (W₂C + η), (W + η) coexisting region, and along with tie-lines of η-η’ and η’-Co.