Synergistic B/Si Microalloying Induced Wear Resistance Improvement in FeCoNiCrCu High‐Entropy Alloy Coatings Prepared by Annular Oscillating Laser Deposition

ABSTRACT To address the insufficient wear resistance of high‐entropy alloy (HEA) coatings under extreme conditions, FeCoNiCrCu and FeCoNiCrCuB 0.03 Si 0.03 microalloyed coatings were fabricated via annular oscillating laser deposition. This work systematically investigated the effects of synergistic B/Si addition on their phase composition, microstructure, and dry sliding wear, and elucidated the underlying mechanisms. Trace B/Si addition retains the face‐centered cubic (FCC) matrix as the primary phase but breaks the original single‐phase structure, inducing in situ precipitation of a high‐hardness Cr 2 B phase with body‐centered tetragonal (BCT) structure. It also significantly refines grains and transforms Cu from continuous intergranular segregation to a dispersed distribution. The modified coating's average microhardness rises from 208 to 291 HV 0.2 (40% increase). At 40 N load, its friction coefficient drops by 19.4% and wear rate by 71.5%, with stable low‐wear performance across 20–40 N. Mechanism analysis shows that B/Si microalloying enhances plastic deformation resistance via interstitial (B) and substitutional (Si) solid solution strengthening, grain refinement, and Cr 2 B second‐phase strengthening. This work provides theoretical insights and practical guidance for designing wear‐resistant HEA coatings.