Synergistic strengthening and corrosion resistance mechanisms of 1.5% carbon nanotube-reinforced FeCoCrNiMo high-entropy alloy composite coatings

High-entropy alloys (HEAs) exhibit great potential for corrosion- and wear-resistant applications; however, their service reliability is often limited by the instability of passive films in chloride-containing environments. In this work, FeCoCrNiMo HEA coatings and carbon nanotube (CNT)-reinforced composite coatings were fabricated on 316L stainless steel via laser cladding. The influence of CNT addition on microstructure, strengthening mechanisms, and corrosion behavior was systematically investigated. The results show that CNTs promote the dispersed precipitation of M23C6 carbides during rapid solidification, resulting in significant grain refinement and reduced solidification defects, including decreased porosity and refined dendritic spacing. Consequently, the average microhardness increased by 57.6%, while the wear rate decreased to 3.32 × 10 -7 mm 3 ·N -1 ·m -1 . Electrochemical analyses revealed a more positive open-circuit potential, lower corrosion current density, and higher charge-transfer resistance for the HEA/CNT coating, indicating the formation of a denser and more stable passive film. The enhanced performance is attributed to a CNT-induced carbon-modified heterogeneous structure, which provides multiscale synergistic effects including structural densification, diffusion barrier formation, and passive film reinforcement, thereby effectively suppressing corrosive species penetration and improving passive film regeneration.