Mechanistic exploration of the exceptional corrosion resistance of the newly designed FeCoCrNiMoxNbx high-entropy alloys

Corrosion would lead to the failure of materials during service, causing huge economic losses and catastrophic accidents, particularly in chemical industries. In this work, a series of novel high-entropy alloys (HEAs) (FeCoCrNiMo_xNb_x) with exceptional corrosion resistance were designed. The phase composition, corrosion resistance, and passive film properties were determined through micro-characterization and electrochemical tests. First-principles calculations were further performed to unveil the corrosion resistance mechanism at the atomic level, especially the influence of elements on the corrosion resistance. It is found that the appropriate increase in the contents of Mo/Nb elements leads to the increased Laves phase in the HEAs and enhances the corrosion resistance of the HEAs. However, the excessive addition of Mo/Nb elements will cause more severe microgalvanic corrosion between FCC and Laves phases, resulting in a decrease in corrosion resistance. Theoretical calculations demonstrate that the Laves phase is more resistant to the attack of corrosive species. Additionally, the presences of Mo, Nb, and Cr elements in the HEAs facilitate the adsorption of H₂O/O on the HEAs surface, which promotes the formation of a protective passive film, and then provides better protection for the HEAs.