Abstract:The oxidation behaviors of high-entropy alloys Al_xCoCrFeNi (x=0.15, 0.4) in supercritical water at 550 and 600 °C were studied, and compared with HR3C steel. All oxide films formed on alloys are composed of spinel type (Fe, Cr)₃O₄ oxides. Compared with the oxide film on HR3C steel, thinner oxide films with smaller size of oxide particles were realized on Al_0.15CoCrFeNi and Al_0.4CoCrFeNi, indicating a superior oxidation resistance of Al_0.15CoCrFeNi and Al_0.4CoCrFeNi to HR3C steel. Electrochemical test results reveal that surface oxide films greatly affect the electrochemical corrosion behavior of the oxidized alloys in 3.5% NaCl solution. The relatively high corrosion resistance of oxidized Al_0.15CoCrFeNi and HR3C is attributed to the formation of thick and multi-layer oxides.

Key words: high-entropy alloy; high temperature oxidation; polarization; electrochemical impedance spectroscopy (EIS)