An investigation on hot corrosion behavior of Al0.4MnCrCoFeNi high entropy alloy in different molten salts at 750 °C

Abstract

The hot corrosion behavior of Al0.4MnCrCoFeNi high entropy alloy in different molten salts at 750 °C was investigated. The high entropy alloy was synthesized by vacuum melting and casting. The hot corrosion tests were performed in 75%Na2SO4 + 25%NaCl, 75%Na2SO4 + 20%NaCl + 5%V2O5, 75%Na2SO4 + 5%NaCl + 10%V2O5, and 60%Na2SO4 + 40%V2O5 mixture salts. Microstructural characterizations were carried out using a field emission scanning electron microscope equipped with an X-ray energy dispersive (EDS) analyzer. X-ray diffraction method with CuKα radiation was also used for phase analysis of corrosion products. The results indicated that Al0.4MnCrCoFeNi alloy had relatively good resistance to hot corrosion in 75%Na2SO4 + 25%NaCl molten salt compared to the other salts due to the formation of a protective layer consisting of Mn, Cr, and Al oxides. The addition of V2O5 to the mixture salt promoted the dissolution of the oxide layer in the molten salt and hence decreased the resistance of the alloy to hot corrosion. The mechanisms of hot corrosion were oxidation-sulfidation and fluxing. The least resistance to hot corrosion was observed in 60%Na2SO4 + 40%V2O5 mixture salt because the oxide scale was destroyed seriously, resulting in accelerated propagation of hot corrosion.