New TiC/Co1.5CrFeNi1.5Ti0.5 Cermet with Slow TiC Coarsening During Sintering

New TiC/Co1.5CrFeNi1.5Ti0.5 cermet was developed by exploiting the advantages of the high-entropy alloy (HEA) binder. A much finer grain structure and thus improved hardness–toughness combination were obtained as compared with two traditional binders, Ni and Ni13Mo7. From the coarsening behavior of TiC grains, the coarsening process of TiC in these three binders is diffusion-controlled. The activation energy of TiC + 20%Co1.5CrFeNi1.5Ti0.5 is the highest and that of TiC + 20%Ni is the lowest. The high activation energy of the Co1.5CrFeNi1.5Ti0.5 binder was attributable to its high content of carbon-strong-binding elements, Cr and Ti, and cooperative diffusion and higher packing density of multiple different-sized atoms. Low diffusion coefficient, low surface energy of TiC grains, and low solubility of Ti in the HEA liquid explain the slow coarsening of TiC grains. This study demonstrates that Co1.5CrFeNi1.5Ti0.5 is an excellent HEA binder for TiC cermets.