High-Entropy Alloy Coatings by Laser Cladding: Processing Strategies, Service Performance, and Unresolved Mechanisms

Abstract

Laser cladding (LC) has emerged as a pivotal technology for fabricating high-entropy alloy (HEA) coatings, offering superior wear resistance, corrosion protection, and thermal stability. This review examines HEA coatings fabricated by LC against the background of two decades of HEA development, focusing on preparation strategies, microstructure regulation, service performance, and unresolved mechanisms. The review traces the evolution from the discovery of HEAs by Cantor and Yeh in 2004 to contemporary advances in 2025. We analyze four preparation strategies: direct deposition, in situ ceramic phase synthesis through doping, multilayer gradient structures, and high-entropy amorphous coatings. The review evaluates how elemental additions (Cr, Mo, Al, Ti, Nb, Si) enhance performance through passivation film formation, solid solution strengthening, and precipitation hardening. Furthermore, we identify three fundamental challenges constraining industrial application: unclear three-dimensional structural features of short-range order, unpredictable “cocktail effects” in multicomponent systems, and poorly understood stress generation mechanisms during processing. Finally, we propose future research emphasizing in situ characterization, cross-scale modeling, and intelligent process optimization to bridge the gap between promising service performance and unresolved underlying mechanisms, ultimately enabling reliable design of next-generation protective coatings for extreme environments.