Nanostructures and electrochemical performances of Cr0.4Al0.4N0.2 medium-entropy and Cr0.9N0.1 low–entropy ceramic coatings by DFT calculation

Cr0.4Al0.4N0.2 medium–entropy ceramic (MEC) and Cr0.9N0.1 low–entropy ceramic (LEC) coatings were deposited on Ti6Al4V alloy by cathodic arc ion plating (CAIP) technique. The corrosion mechanism was revealed by the electrochemical impedance spectroscopy (EIS) and density functional theory (DFT) calculation. The results show that the Cr0.4Al0.4N0.2 MEC coating has higher electrochemical corrosion resistance than the Cr0.9N0.1 LEC coating, which is consistent with the DFT calculation. The charge transfer resistance of Cr0.4Al0.4N0.2 MEC coating increases by 589.28% compared with the Cr0.9N0.1 LEC coating, which is contributed to the transfer from the non–band gap energy to the band gap energy.