The oxidation of an equimolar FeCoNiAl medium-entropy alloy at 900 °C in various oxygen pressures

Abstract

The oxidation of an equimolar FeCoNiAl medium-entropy alloy was studied at 900 °C in various O2-containing atmospheres over the oxygen pressure range of 10–105 Pa. The alloy oxidized parabolically, having its oxidation rates steadily increasing with oxygen pressure. Duplex scales formed on the oxidized substrate, consisting of an outer CoFe2O4 layer and an inner α-Al2O3 layer. The position of the Pt-marker was located at the outer- and inner-layer boundary, demonstrating that the outward cation diffusion controlled the formation of CoFe2O4, while the growth of Al2O3 was contributed by the inward oxygen diffusion.