Regulation of Cu Segregation by Y ₂ O ₃ in Laser‐Cladded AlCrFeNiCu High‐Entropy Alloy Coatings: Microstructural Homogenization and Performance Enhancement

Cu segregation is prevalent in AlCrFeNiCu‐based high‐entropy alloy (HEA) coatings and compromises microstructural uniformity and property stability. Y 2 O 3 /AlCrFeNiCu HEA composite coatings were fabricated on 17‐4PH stainless steel substrates by laser cladding (LC), and their microstructure, mechanical properties, and electrochemical behavior were investigated. The results indicate that Cu tends to locally enrich and segregate due to its relatively large mixing enthalpy with the other principal elements. Appropriate Y 2 O 3 addition suppresses local Cu enrichment and interdendritic segregation, promoting microstructural homogenization and grain refinement. It also facilitates the formation of a continuous and compact CrO‐dominated passive film, effectively suppressing Cu‐enrichment‐induced porous corrosion products and localized corrosion defects. An optimal property profile is obtained at a Y 2 O 3 addition of 1.5 wt%, with an average Vickers hardness of 629.9 ± 9.6 HV 0 . 2 , corresponding to an increase of approximately 90.9% compared with the substrate. In 3.5 wt% NaCl solution, the corrosion current density decreases to 7.05 × 10 −6 A·cm −2 , corresponding to a reduction of about 95.2% relative to the substrate. With further increasing Y 2 O 3 content, coating performance deteriorates due to the introduction of defects associated with particle agglomeration. These findings provide a preliminary basis for optimizing Y 2 O 3 addition in AlCrFeNiCu‐based HEA coatings for marine protective applications.