Processing route effects on NbC-Fe-Ni cermets: Improving mechanical properties via mechanical alloying

Abstract

Niobium carbide (NbC)-based cermets have become a promising alternative to tungsten carbide (WC) due to their superior thermal stability, wear resistance, and lower toxicity, especially for cutting applications. However, the performance of NbC cermets is largely influenced by the choice of binder. The FeNi binder-modified NbC cermets have recently gained recognition as a cost-effective, environmentally friendly, and less toxic alternative to the much-explored NbC-Ni. This study reports the effects of two distinct routes: tumbler mixing (TM) and high-energy ball milling (MA), on the microstructure and mechanical properties of NbC-Fe-Ni cermets. The Fe and Ni powders were mixed using both TM and MA routes before being combined with NbC to fabricate the cermets. The mixture was then sintered via vacuum liquid phase sintering (LPS) at 1440 °C for 1 h. The microstructure characterization (SEM+ EDX) revealed that samples prepared via MA exhibited finer NbC grain sizes compared to those fabricated by TM, with grain growth more limited as Fe content increased. The MA route resulted in a more uniform FeNi binder distribution around the NbC grains, which was confirmed by energy-dispersive X-ray (EDX) analysis and mapping. Mechanical testing revealed that cermets fabricated by MA route exhibited a significant increase in hardness (up to 21 %) and an improvement in fracture toughness (up to 24 %) compared to those produced by TM. The results demonstrated that MA enhanced densification, microstructural homogeneity, and mechanical properties of NbC-Fe-Ni cermets, making it a more favorable route for the fabrication of NbC cutting tools.