Corrosion and Thermal Stability of CrMnFeNi High Entropy Alloy in Molten FLiBe Salt

The corrosion behavior of the FCC Cr₁₈Mn₂₇Fe27.5Ni27.5 high entropy alloy (HEA) after exposure to molten FLiBe salt at 700 °C for 1000 hours, has been investigated. Results show that the HEA lost a higher mass compared to the reference 316 H stainless steel due to the dissolution of Mn into the molten salt. The loss of Mn from the alloy appeared to discourage the dissolution of Cr in the molten fluoride salts which is widely recognized as the mechanism of corrosion degradation. Thermal exposure at 700 °C for 1000 hours also led to the precipitation of an additional BCC phase Cr₆₇Fe₁₃Mn18.5Ni1.5, which was confirmed by CALPHAD predictions.