Enhancing wear resistance of laser-clad AlCoCrFeNi high-entropy alloy via ultrasonic surface rolling extrusion

The AlCoCrFeNi high-entropy alloy (HEA) coating was synthesized by laser cladding and subsequently processed by ultrasonic surface rolling extrusion (USRE) with varying static loads of 100 N, 200 N, and 300 N. This study aimed to explore the effects of static load on the microstructure, mechanical properties, and tribological characteristics of the coatings. The findings indicate that increased static load results in the precipitation of martensitic phases, grain refinement, enhanced microhardness, and an elevated dislocation density. Specifically, after USRE with 300 N static load, the coating's microhardness reaches 753 HV, 1.4 times greater than the un-USRE coating. This enhancement is attributed to the synergistic effect of martensite phase transformation, grain refinement, and dislocation strengthening. The volume wear rate of the coating decreases to 1.31 × 10−4 mm3·N−1·m−1 following USRE at 300 N, demonstrating superior resistance to abrasive wear due to the high microhardness. Besides, the high-density dislocations facilitate rapid migration and diffusion of oxygen elements, thereby enhancing the oxide layer's protective properties and improving the coating's resistance to oxidation wear.