Enhanced hydrogen resistance and corrosion protection of FeNiMnCr-based high-entropy alloy coatings via elemental alloying

The rapid hydrogen permeation and corrosive degradation of structural alloys in hydrogen-rich environments critically hinder their long-term service reliability. In this study, FeNiMnCr-based high-entropy coatings alloyed with Al and V (FeNiMnCrAl and FeNiMnCrV) were fabricated via Co-FCVA to explore their hydrogen barrier and corrosion protection capabilities. Compared to the bare X70 substrate, the FeNiMnCrV coating exhibited the lowest apparent diffusion coefficient (6.843 × 10⁻⁷ cm²·s⁻¹) and the steady-state hydrogen permeation flux (1.287 × 10⁻¹⁰ mol·cm⁻²·s⁻¹), representing an order of magnitude improvement. Corrosion current density decreased from 5.598 × 10⁻⁵ A·cm⁻² (bare-X70) to 6.251 × 10⁻⁶ A·cm⁻² (FeNiMnCrV), confirming superior corrosion resistance. SEM and TEM characterizations revealed a columnar nanocrystalline structure with refined grain boundaries and homogeneous elemental distribution. Furthermore, FeNiMnCrV exhibited higher saturation magnetization and residual compressive stress, which jointly contributed to enhanced hydrogen trapping. These results suggest that V-alloying in high-entropy coatings provides synergistic effects for mitigating hydrogen ingress and corrosion, offering a promising pathway for advanced barrier coatings in harsh environments.