Sandeep Kumar Yadav, Ayush Verma, Balasubramanian Kandasubramanian, T. Shanmugasundaram
Abstract Since 2004, extensive research reports the phase stability, mechanical, functional, oxidation, corrosion, and wear properties of high-entropy alloys (HEAs). This work presents a comprehensive review of the wear behavior of HEAs, with a particular emphasis on CoCrFeNi-based and AlCoCrFeNi-based systems, as well as other HEAs and HEA-based coatings. The influence of various processing techniques, including vacuum arc melting (VAM), air plasma spraying (APS), spark plasma sintering (SPS), and laser cladding, on microstructural evolution, hardness, and wear-rate is systematically compared and discussed. The role of alloying elements in governing the microstructure, hardness, and wear resistance of CoCrFeNi-based and AlCoCrFeNi-based systems is critically analyzed. High-temperature wear behavior of HEAs is also reviewed, along with alloy design strategies and their application potential. This review shows that although processing-induced variations in hardness influence wear-rates, the dominant wear mechanisms remain largely unchanged across different processing routes. AlCoCrFeNi-based systems exhibit enhanced hardness and reduced wear-rates primarily due to Al addition, while other targeted alloying additions (e.g., Ti, Nb, Mo, C, WC, B, Si, graphene, and solid lubricants) significantly contribute to improved wear resistance.