Wear-electrochemical noise behavior of Cr-N coating on M2 HSS in Na ₃PO ₄ solution

Cr-N hard coating was synthesized on M2 HSS surface by magnetron sputtering deposition. Scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and glow discharge optical emission spectroscopy (GDOES) analysis were used to characterize coating microstructure, electronic state of Cr and N elements in the surface and main elements distribution. Corrosion-wear behaviors of M2 substrate and coating sliding against corundum were studied using an electrochemical noise technique in 0.02 mol/L Na ₃PO ₄ solution. Wear behaviors of the M2 steel and Cr-N coating in ambient air were also investigated for comparison. The results show that the Cr-N coating has duplex-layer structure, where Cr and CrN are mainly of coating composition, and wear resistance of the M2 substrate in ambient air is significantly improved by the Cr-N coating. In Na ₃PO ₄ solution, as the depassivation-repassivation and interface pitting accelerate both corrosion and abrasion, the Cr-N coating has no antifriction and antiwear effect on the M2 substrate, and its failure characteristic is completely different from that of in ambient air condition.