Microstructure and corrosion properties of CoCrCuFeMnNix high-entropy alloys prepared by powder metallurgy

CoCrCuFeMnNix (x = 0.5, 1.0, 1.5, 2.0 mol, named Ni-0.5, Ni-1.0, Ni-1.5, and Ni-2.0, respectively) high-entropy alloys (HEAs) were prepared by powder metallurgy. The effects of Ni content on its microstructure and corrosion resistance in a 3.5% NaCl solution were studied. The HEAs with low Ni content consisted of FCC1 primary phase, FCC2 secondary phase, and a few sigma phases. While the Ni-2.0 alloy was composed of the FCC phase and a small amount of sigma phase. The results of polarization corrosion in 3.5% NaCl solution show that the increase of Ni content led to the increase of corrosion potential of the alloy and the decrease of corrosion current density and average corrosion rate. Among them, Ni-2.0 alloy had the best corrosion resistance. The electrochemical impedance spectroscopy analysis showed that the increase in Ni content promoted the increase of the polarization resistance of the alloy R-CPE and the thickness of the passive film, thus improving the corrosion resistance of the alloys.