Structural-Phase Evolution and Morphology of Cobalt-Free WC Hard Alloys Produced by SPS

This study examines the effect of spark plasma sintering (SPS) temperature on the phase composition, microstructure, densification, and microhardness of cobalt-free WC–Fe and WC–Fe–Ni hard alloys. Increasing the sintering temperature from 1250 °C to 1300 °C improved densification in both alloy systems. Residual porosity decreased from 13.2% to 12.7% in the WC–Fe–Ni alloy and from 13.8% to 12.0% in the WC–Fe alloy, while the density increased from 12.39 g/cm3 to 12.46 g/cm3 and from 12.15 g/cm3 to 12.40 g/cm3, respectively. The WC–Fe -Ni alloy exhibited a more homogeneous microstructure and higher microhardness, increasing from 708 ± 10 HV0.2 to 823 ± 15 HV0.2, whereas the WC–Fe alloy showed an increase from 630 ± 15 HV0.2 to 770 ± 5 HV0.2. X-ray diffraction analyses identified Fe3W3C, FeNi3, and (Fe, Ni) solid-solution phases formed during SPS. The results indicate that both the sintering temperature and binder composition influence densification, phase evolution, and mechanical performance. Among the investigated materials, the WC–Fe–Ni alloy showed better microstructural stability and hardness than the WC–Fe alloy. These findings suggest that Fe–Ni binders are promising candidates for cobalt-free cemented carbides, although additional studies on fracture toughness and wear resistance are required before practical cutting-tool applications can be fully assessed.