Microstructure, high-temperature oxidation and molten salt corrosion behaviour of CoCrFeNiAl0.1-RE HEA

In this study, CoCrFeNiAl0.1-RE HEA was melted using a magnetic levitation melting furnace, resulting in a single-phase FCC solid solution structure with a coarse irregular equiaxed grain morphology in the period. The oxidation experiment results showed that the samples' oxidation kinetics followed the parabolic rate law, and the oxidation product species increased with increasing temperature. High temperatures primarily revealed Cr2O3, (Cr, Fe)2O3, and other spinel phases such as NiFe2O4, CoCr2O4, and CoFe2O4. Under the oxide film, Al-rich striped raised phases were observed. According to the elemental divisions, the oxide film will be damaged to expose the FCC matrix in molten salt corrosion, and the film can be divided into four layers: peeling layer, newly oxidised-corroded outer layer, transition layer, and matrix. As molten salt is destroyed, cavities and channels appear in the film, allowing molten salt and oxygen to infiltrate and accelerate the oxidation and corrosion of the sample.