Effects of tempering treatment on structural evolution and electrochemical properties of laser cladded NiAlCrZrMo medium–entropy alloy coating by DFT calculation

A NiAlCrZrMo medium–entropy alloy (MEA) coating with solid solution was fabricated by laser cladding, which was evolved to high–entropy alloy (HEA) structure by tempering treatment for the improvement of corrosion resistance. The effects of tempering treatment on the structural evolution and electrochemical properties of obtained MEA coatings were comparatively investigated, and the corrosion mechanism was discussed with the density functional theory (DFT) calculation. The results show that the MEA structure of original MEA coating is evolved to HEA structure of tempered MEA coating by tempering treatment, which is composed of AlNi2Ti and Cr phases. The charge transfer resistance of tempered MEA coating is increased by ∼140 times compared with the original MEA coating, in which the diffusion of electrons is held back by its HEA structure. Moreover, the tempered MEA coating possesses higher electrochemical resistance compared with the original MEA coating, which is attributed to the AlNi2Ti phase of tempered MEA coating decreasing the corrosion tendency by the effect of high–entropy evolution.