Effect of Ni/Co binder on the microstructure and mechanical performance of Fe ₃ C–W high-entropy alloys synthesized via solid-state sintering

Abstract

The development of high-performance Fe-based alloys for structural and wear-resistant applications remains a significant challenge. This study investigates the effect of Ni, Co, and combined NiCo binders on the densification, microstructure, phase evolution, and mechanical properties of Fe ₃ C–10 wt% W alloys produced by powder metallurgy. Powders containing 1.2 wt% carbon were mechanically milled for 10 h at 950 rpm, compacted at 50 MPa, and sintered at 1400°C for 2 h. X-ray diffraction and scanning electron microscopy revealed the formation of Fe–W-rich solid solutions and carbide-containing phases. The addition of Ni- and Co-enhanced diffusion-controlled densification and reduced residual porosity, while the NiCo binder promoted a finer and more homogeneous microstructure with improved interfacial cohesion. The Fe ₃ C–W–NiCo alloy exhibited the best overall performance, achieving a density of 7.7 g·cm ⁻³ , a microhardness of 885 ± 5 HV _0.1 , a flexural strength of 1620 ± 10 N·mm ⁻² , and an impact toughness of 2.0 J·cm ⁻² . These improvements are attributed to the synergistic effects of Ni and Co on diffusion, solid-solution strengthening, and phase stability during sintering.