Effect of the carbon content on the morphology evolution of the η phase in cemented carbides with the CoNiFeCr high entropy alloy binder

For studying the evolution of the eta phase in cemented carbides with the CoNiFeCr high entropy alloy binder, we prepared low-carbon, medium-carbon, and high-carbon cemented carbides with a 0.2 wt% difference in the C content using SHIP. The results showed that the eta phase morphology was sensitive to the carbon content. When the carbon content was 4.5%, the eta phase was abundant and uniformly dispersed. When the carbon content increased to 4.7%, the eta phase amount decreased and became locally aggregated in large clusters, showing typical segregation. When the carbon content was further increased to 4.9%, the ri phase disappeared. The eta phase clusters exhibited a sharp contrast between inner and outer parts. The inner part showed the presence of the eta phase, WC with small and round grains, and a small amount of binder. The outer part had only WC with large grain and sharp grains, and a large amount of binder. In addition to the inherent eta phase brittleness, the eta phase segregation resulted in a large hardness dispersion and a further toughness decrease.

Automated summary

The carbon content significantly affects the morphology of the eta phase, with an increase in carbon content leading to a decrease in the amount of eta phase and local aggregation, showing typical segregation. In addition, eta phase segregation results in an increase in hardness dispersion and a further decrease in toughness.