Enhanced Pb-Bi corrosion resistance of FeCrMnAlV coating with V-engineered high-density grain boundaries induced by compact FeCr₂O₄/Al₂O₃ bilayer oxide barrier

Overcoming Pb-Bi eutectic alloy (LBE) corrosion to structural materials remains critical for lead-cooled fast reactor deployment. High entropy alloys (HEAs) coatings are promising but require to further enhance the compactness of protective oxide layer. Herein, this work introduces a novel strategy: fabricating the FeCrMnAlV HEAs coating with V-engineered high-density grain boundaries (H-GBs) via laser cladding to improve oxide layer compactness. Electron backscatter diffraction (EBSD) confirms that the V-addition combined with laser-induced undercooling achieves exceptional grain refinement with averaged grain size of 2.6 μm and high grain boundaries density of 1.5 × 10³ mm²/mm³. Transmission electron microscopy with energy-dispersive X-ray spectroscopy (TEM-EDS) mapping unequivocally reveals V segregation at grain boundaries (27.8 at%), which inhibits grain growth. LBE corrosion tests demonstrates a remarkably low corrosion oxidation rate constant (K_p) of 0.0231 μm²/h for the V-engineered HEAs coating, which is 2–3 orders of magnitude lower than conventional primary structural materials. It can be concluded that the enhanced corrosion resistance of FeCrMnAlV HEAs coating is mainly due to the formation of compact FeCr₂O₄/Al₂O₃ bilayer oxide barrier, facilitated by the V-engineered H-GBs network. This work provides a new strategy towards to V-engineered H-GBs in HEAs coatings for enhancing LBE corrosion resistance.