Microstructure and Wear Behavior of In Situ Multi‐Ceramic‐Reinforced Al0.5CoCrFeNi Coating Tuned by Laser Energy Density

ABSTRACT In this work, in situ multi‐ceramic‐phase‐reinforced Ti 0.6 (B 4 C) 0.4 Al0.5CoCrFeNi high‐entropy alloy (HEA) composite coatings were successfully fabricated on 304 steel substrates via laser cladding under varying laser energy densities ( E L ). The influence of E L on the geometric characteristics, phase constitution, microstructure evolution, microhardness, and tribological behavior of the coatings was systematically investigated. All coatings demonstrated strong metallurgical bonding with the substrate, while increasing E L promoted better particle dissolution and defect reduction, but led to significant dilution. The coatings predominantly consisted of FCC matrix with in situ formed TiC and Ti/Cr borides, whose morphologies and distribution transformed markedly with E L . Microhardness decreased significantly with increasing E L due to grain coarsening and the diminished contributions of second‐phase and solid solution strengthening, declining from 1107.6 HV0.2 to 420.0 HV0.2. The wear resistance first improved and then deteriorated with rising E L , achieving optimal performance at E L = 30 J/mm 2 , with a minimum friction coefficient of 0.44 and a wear rate of 9.32 × 10 −7 mm 3 /N·m. Wear mechanisms transitioned from abrasive wear at low E L to fatigue and oxidative/adhesive wear at higher E L . These findings demonstrate that appropriate modulation of laser energy density effectively tailors phase composition and microstructural features and achieves excellent wear performance.