Microstructural and Tribological Characteristics of In Situ Induced Chrome Carbide Strengthened CoCrFeMnNi High-Entropy Alloys

Bulk (CoCrFeMnNi)(100-x)C-x (x = 0, 0.2, 0.6, 0.8. 1.0. 1.2 wt.%) high-entropy alloys (HEAs) prepared via a discharge plasma sintering process were found to be composed of a simple FCC solid solution. With increasing C concentration, the grain of the HEAs transformed from columnar to equiaxial and the abundance of precipitated M7C3 and M23C6 phases increased. The valence state of Co, Fe, Mn, and Ni was not found to change with C concentration, but rather remained as a solid solution. The effects of chrome carbide concentration on the HEA microstructural and mechanical properties were investigated in detail. The hardness was nearly 1.5 times greater for HEAs containing 1.2 wt.% C than for HEAs without C. Wear rate, on the other hand, was found to first increase and then decrease with increasing C content. The best wear resistance, corresponding to a wear rate of 1.59 x 10(-4) mm(3) N-1 m(-1), was obtained at a C concentration of 1.2 wt.%. The wear mechanisms of this material were dominated by adhesive wear, oxidative wear, and contact fatigue.