Effect of the binder phase composition and volume fraction on the sintering behavior of extra-coarse WC-based hardmetals

This work investigates the sintering behavior and microstructural evolution of extra-coarse WC hardmetals using conventional Co and FeNiCo (40/40/20) (wt%) binder phases. Four compositions containing 15 and 20 wt% metallic binder were produced by powder metallurgy and consolidated by sinter-HIP at 1475 °C. Dilatometry and DSC analyses showed that replacing Co with FeNiCo significantly reduces sinterability, shifting densification to higher temperatures despite similar calculated liquid-phase fractions. This behavior is attributed to the lower solubility of WC in FeNiCo liquids compared with liquid Co. Microstructural characterization revealed complete densification and the elimination of W₂C after sintering. WC grain growth was strongly affected by binder chemistry. FeNiCo-bonded alloys exhibited more pronounced changes in grain size distribution with increasing binder content and developed more rounded WC morphologies than WC–Co grades. Hardness measurements confirmed a significant softening associated with FeNiCo substitution, mainly due to the intrinsically lower hardness of Ni-rich metallic matrices.