A novel FeCrAlWx high entropy alloy coating for enhancing lead-bismuth eutectic corrosion resistance

The use of ferritic/martensitic (F/M) steel as a container material for liquid lead-bismuth eutectic (LBE) presents several challenges owing to the complex and diverse types of LBE corrosion, including dissolution corrosion and oxidation corrosion. This paper proposes a novel strategy to address these challenges, based on the optimization of the design and composition of FeCrAlWx high-entropy alloy (HEA) coating. The objective is to simultaneously enhance the resistance of F/M steel to both dissolution corrosion and oxidation corrosion. Following LBE corrosion, the surface of the coating exhibits oxide layers consisting of an outer oxide layer (OOL, composed of Fe oxides) and an inner oxide layer (IOL, composed of Al2O3 and Cr2O3). Among the tested samples, FeCrAlW0.75 HEA coating exhibits the thinnest OOL and IOL layers when subjected to LBE corrosion over different durations, demonstrating superior resistance against LBE corrosion. The incorporation of W in the coating increases the covalency of the HEA coating, thereby improving the bonding strength. In addition, it decreases the adsorption energy of Pb and Bi on the surface, thereby effectively limiting the mutual diffusion of the coating elements and Pb and Bi and inhibiting dissolution corrosion. Furthermore, the IOL formed by Al and Cr exhibits protective properties and improves the oxidation corrosion resistance of the coating. These effects are further enhanced by the high adsorption capacity of the FeCrAlW0.75 HEA coating to O, which helps accelerate the formation of the IOL. Additionally, the FeCrAlW0.75 HEA coating retains satisfactory mechanical properties after being subjected to LBE corrosion for 2000 h, with the Hv, E, Hv/E, and Hv3/E2 values being 6.92 GPa, 197.2 GPa, 0.0351, and 0.00852, respectively.