SYNTHESIS OF COBALT-FREE HIGH-STRENGTH WC-BASED CEMENTED CARBIDES BY SPARK PLASMA SINTERING

Abstract

This paper examines the effect of spark plasma sintering (SPS) temperatures (1250°C and 1300°C) on the structure, phase composition, and microhardness of WC-Fe-Ni, WC-Fe, and WC-Ni carbide systems. It is shown that at 1250°C, the WC-Fe-Ni alloy forms a homogeneous dense structure with uniform distribution of the WC particles, whereas an increase in temperature to 1300°C results in grinding of the WC grains. In contrast, the WC-Fe system exhibits grain coarsening at 1300°C. The WC-Ni alloy is characterized by large, irregular grains, low integrity, and the formation of brittle phases (W₂C, W₃Ni₃C), which leads to embrittlement. Phase analysis confirmed the presence of Fe₃W₃C and FeNi₃, Fe_0,51Ni_0,49, Fe_0,5Ni_0,5 in the WC-Fe-Ni binder system, while undesirable carbide phases predominate in the WC-Ni system. The results demonstrate the critical role of binder composition and sintering temperature in determining the properties. Further optimization of sintering parameters is required to suppress undesirable phases and improve mechanical properties. This work is aimed at obtaining cobalt-free turning cutters based on hard alloys of the WC-(FeNi) and WCFe/Ni systems, synthesized by the SPS method, in order to study their phase composition, morphology, hardness and physical and mechanical properties, as well as to assess the possibility of using nickel-iron binders as an alternative to cobalt in hard alloys for cutting tools. Overall, the obtained results demonstrate that both binder composition and sintering temperature play a critical role in determining the structural integrity and phase stability of WC-based hardmetals.