Oxidation behavior of high-entropy alloys AlxCoCrFeNi (x=0.15, 0.4) in supercritical water and comparison with HR3C steel

The oxidation behaviors of high-entropy alloys AlxCoCrFeNi (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 Al0.15CoCrFeNi and Al0.4CoCrFeNi, indicating a superior oxidation resistance of Al0.15CoCrFeNi and Al0.4CoCrFeNi 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 Al0.15CoCrFeNi and HR3C is attributed to the formation of thick and multi-layer oxides.