An investigation on corrosion resistance of laser-cladded FeCoNiCrCu high-entropy alloy coatings based on different initial powder particle sizes

This study comprehensively investigates the corrosion mechanism of laser-cladded FeCoNiCrCu high-entropy alloy (HEA) coatings fabricated with varying initial powder particle sizes in a 3.5 % NaCl solution. Subsequent to orthogonal experimental optimization, optimal laser cladding parameters were obtained to generate fine coatings with exceptional quality. It's noteworthy that finer initial powder particles possess higher specific surface energy, promoting the formation of coatings with fewer defects. Aside from that, steady increases in corrosion current density and decreases in corrosion potential were observed with coarser initial powder particles, accompanied by lower charge transfer resistance. Corrosion preferentially initiates at surface defects, with more severe defects directly degrading corrosion resistance. The Cu accumulation at these defects generates a less extensively protective passivation film, which hinders the formation of Cr oxides. As evidently demonstrated by XPS analysis, smaller powder particles form protective films with more Cr oxides and fewer Cu oxides in comparison with those formed by larger particles. To sum up, coatings prepared from finer initial powder particle sizes display superior corrosion resistance.