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

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.