Microhomogeneous WC-TiC-Co composite powders with enhanced sinterability via a two-step carburization method

Abstract WC-TiC-Co composite powders with fine WC grains and homogeneously distributed Co and inhibitors were prepared via a two-step carburization method. η phase powders were synthesized via the carburization of the crushed mixture of W, Co, C and TiC; WC-TiC-Co composite powders were then fabricated by the carburization of the η phase powders. The effects of TiC on the carburization process and the microstructure of composite powders, sinter and mechanical properties of WC-TiC-Co cemented carbides were investigated. Co2W4C type η phase powders were confirmed via the first carburization at 1150 °C for 2 h, which were further carburized into WC-TiC-Co composite powders at 1100 °C for 1 h under the flowing hydrogen. During the carburization of η phase powders, TiC accelerated the nucleation of WC through a heterogeneous nucleation mechanism, and effectively inhibited the intrinsic grain growth, which both led to fine and non-equilibrium WC grains with a near-sphere shape. Dense WC-(Ti,W)C-Co was confirmed via low-temperature vacuum sintering of the as-synthesized composite powders, owing to the homogeneously dispersed Co and (Ti, W)C grains. This work showed a way to fabricate micro-homogeneous composite powders of cemented carbides via carburization of the η phase powders.