Recent advances and optimization strategies in tribological performance of high entropy alloys

High-entropy alloys (HEAs) are increasingly considered for tribological components because their compositional freedom enables broad tuning of phase constitution, microstructure, and surface reactivity. Yet, many baseline HEAs exhibit inadequate wear resistance and/or high friction unless they are deliberately designed for the targeted contact conditions. This review consolidates recent progress on improving HEA tribological performance through three complementary routes: (i) composition- and microstructure-driven design (phase engineering, refinement, tribo-oxidation control, and self-lubrication design), (ii) second-phase compositing using hard ceramics and solid lubricants to integrate load support with low-shear interfaces, and (iii) advanced processing and surface engineering (additive manufacturing, laser cladding, magnetron sputtering, and post-treatments) that enable non-equilibrium microstructures, gradient architectures, and high-performance coatings. For each route, we summarize dominant wear mechanisms, identify the governing structure-tribology linkages, and highlight the operating windows in which specific strategies are effective. The review concludes with key challenges and research priorities for translating laboratory-scale tribological gains into application-relevant reliability, including predictive design, mechanistic understanding of tribolayer dynamics, and validation under realistic service modes (e.g., fretting, erosion, and rolling contact fatigue).