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

To address the insufficient wear resistance of high-entropy alloy (HEA) coatings under extreme conditions, FeCoNiCrCu and FeCoNiCrCuB0.03Si0.03 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 Cr2B phase with body-centered tetragonal (BCT) structure. It also significantly refines grains and transforms Cu from continuous intergranular segregation to dispersed distribution. The modified coating’s average microhardness rises from 208 to 291 HV0.2 (40% increase). At 20 N load, its friction coefficient drops by 24.5% and wear rate by 71.8%, 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 Cr2B second-phase strengthening. Additionally, it lowers coating surface energy and promotes stable B2O3/SiO2 oxide films, shifting the wear mechanism from severe adhesive-fatigue to mild abrasive-oxidative wear. This work provides theoretical insights and practical guidance for designing wear-resistant HEA coatings.