Segregation of Dopants at WC/Co and WC/WC Interfaces in Solid-State-Sintered WC-VC-Cr<sub>3</sub>C<sub>2</sub>-Co Cemented Carbides

Abstract

The segregation of V and Cr at WC/Co and WC/WC interfaces in ultrafine-grained WC-0.7VC-1.4Cr3C2-10Co (mass%) cemented carbides produced through solid-state sintering and semi-sintering was investigated. This segregation was compared against that of a liquid-state-sintered specimen to elucidate the mechanism by which WC grain growth is inhibited by V and Cr. The V and Cr were found to segregate at the WC/Co and WC/WC interfaces during solid-state sintering and semi-sintering, but no differences were observed in the V and Cr concentrations at the interfaces among the liquid-state-sintered, solid-state-sintered and semi-sintered specimens. Furthermore, these concentrations were unchanged by quenching of the solid-state-sintered specimen. From these results, it was concluded that (V,W,Cr)Cx segregation layers are stably formed at the WC/Co and WC/WC interfaces at a temperature below the solidus of the Co phase, but almost dissolve in the liquid Co phase once the temperature exceeds its liquidus. Thus, the (V,W,Cr)Cx segregation layers observed at the WC/Co and WC/WC interfaces at room temperature are formed during the cooling that follows the liquid-state sintering. This supports the finding that WC grain growth is inhibited by the adsorption of dopant atoms onto steps/kinks on the WC surface during liquid-state sintering, as well as by the segregation layers formed on the WC surface during solid-state sintering.