Wear Resistance of N-Doped CoCrFeNiMn High Entropy Alloy Coating on the Ti-6Al-4V Alloy

N-doped CoCrFeNiMn high entropy alloy coating (N-HEA) was prepared on Ti-6Al-4V alloy by high-velocity oxygen fuel (HVOF) spraying coupled with double glow plasma nitriding. The results show that the CoCrFeNiMn high entropy alloy coating (HEA) is mainly composed of single CoCrFeNiMn face-centered cube (fcc) phase with a little MnCr2O4 spinel phase, and the thickness is approximately 200 mu m. After plasma nitriding, the surface morphology of the coating is reconstructed, changing from the molten and semi-melted coral-like structure to cauliflower-like structure, while the surface roughness and the thickness have no significant change. The phase composition of the N-HEA coating has no obvious change, and the N mainly exists as interstitial atoms in solid solution. The microhardness of the HEA coating is highly significantly higher than Ti-6Al-4V alloy, and it is further increased by 45% after plasma nitriding. The friction coefficient of N-HEA coating is as low as 0.38, and the wear rate is 1.283 x 10-4 mm-3N-1 min-1, which is 53 and 72% lower than those of the HEA coating and the Ti-6Al-4V alloy, respectively. Both the wear mechanism of the N-HEA and HEA samples against GCr15 steel ball are mainly adhesive wear, while more Fe elements are transferred from the GCr15 steel ball onto the surface of the N-HEA sample.