An effective and innovative application of rare-earth plasma nitriding on high entropy alloy CoCrCuFeNi

[Display omitted] •New plasma nitriding method developed for steels and HEAs with FCC structures.•Increase plasma nitriding efficiency of HEAs (FCC) by addition of La element.•La element overcome sluggish diffusion and Cr trapping of N during nitriding in HEAs.•The addition of La increased the effective hardening layer thickness by 32%.•The addition of La reduces the impact of plowing forces and wear rate by 79%. The addition of rare-earth (RE) element (La) can improve the surface performance of high entropy alloy (HEA) nitrided at 520 °C for 12 h by overcoming the nature of sluggish diffusion. The effective hardening layer thickness increased by 32 % compared to common plasma nitriding. Additionally, there was a 13 % increase in the H/E ratio and a 49 % increase in the H3/E2 ratio after the addition of La. The surface hardness of the RE nitrided layer increased from 1395 HV0.05 to 1666 HV0.05, while the wear rate decreased from 5.57 × 10-7 g·N−1·m−1 to 1.15 × 10-7 g·N−1·m−1. These results demonstrate a significant improvement in the wear resistance of the HEA This study provides new insights into plasma nitriding techniques for high entropy alloys.