Multi-Parameter Optimization and Corrosion Behavior of FeCoNiCrAl HEA Coatings via Laser Cladding

In this study, FeCoNiCrAl high-entropy alloy (HEA) coatings were fabricated on Q235 steel surfaces using laser cladding (LC) to enhance corrosion resistance in harsh environments. The laser processing parameters (laser power, defocus distance, and scanning speed) were optimized using response surface methodology (RSM), establishing a mathematical model to guide the process. The optimized coatings demonstrated strong metallurgical bonding to the substrate, with a microstructure comprising Al-Ni-rich B2 phases and Cr-Fe-rich BCC phases. Elemental segregation was effectively mitigated as energy density decreased, leading to significant improvements in corrosion resistance. Electrochemical tests in 3.5 wt.% NaCl and 0.5 mol/L H2SO4 solutions showed that the optimized coating (laser power: 800 W, scanning speed: 450 mm/min, defocus: −15 mm) exhibited exceptionally low corrosion current densities of 1.78 × 10−7 A/cm2 and 1.07 × 10−5 A/cm2, respectively. The passive film on the optimized coating surface consisted of stable oxides, with low oxygen vacancy densities of 1.937 × 1023 cm−3 in NaCl and 4.967 × 1021 cm−3 in H2SO4, significantly enhancing its resistance to localized and uniform corrosion. These results demonstrate the effectiveness of RSM-based optimization in producing HEA coatings with superior corrosion resistance suitable for applications in highly corrosive environments.