Dilution induced variation in corrosion resistance properties on Co–Cr–Fe–Ni high-entropy alloy coatings prepared by laser cladding

Co–Cr–Fe–Ni high-entropy alloy (HEA) coatings were prepared by cable-type welding wire laser cladding (CTWW-LC) method and their corrosion behavior and mechanisms within a wide dilution rate range (79.23 %–17.23 %) were systematically studied. The results showed that the passive films of the coatings with high dilution rates were composed only of hydroxides, while those of the coatings with low dilution rates had a composite structure of hydroxides, oxides, and pure metals, significantly enhancing their density and corrosion resistance. In addition, the coatings with high dilution rates had a high density of dislocations due to martensitic phase transformation, which aggravated the local corrosion diffusion; while the coatings with low dilution rates had a single stable face-centered cubic (FCC) phase, with an extremely low dislocation density, effectively suppressing the expansion of corrosion. A sudden transition in corrosion performance was observed as the dilution rate decreased, characterized by variation in corrosion morphology, self-corrosion potential, and passive film thickness. This study first clarified how the dilution rate affects the corrosion mechanism by regulating the composition of the passive film and the dislocation density in a synergistic way, providing a theoretical basis for the process optimization and engineering application of Co–Cr–Fe–Ni HEA coatings.