High-entropy ceramics for tribology applications: Recent advances and future directions

As an emerging class of multifunctional materials, high-entropy ceramics (HECs) exhibit a unique combination of properties that have not yet been fully elucidated, enabled by their distinctive high-entropy design concept. These materials provide valuable scientific insights and significant research potential in the field of tribology. This review critically assesses the tribological performance of HECs across six major categories: carbides, borides, silicides, oxides, nitrides, and MAX phases. Comparative studies among different systems reveal that carbides and nitrides have received far more investigation than silicides and borides, reflecting an unbalanced research landscape. While HECs generally exhibit enhanced wear resistance and adaptive lubrication compared with conventional ceramics, the field currently suffers from a lack of standardized tribological data, insufficient mechanistic understanding of the high-entropy effect, and high synthesis costs. Future efforts should prioritize data-driven rational design, multiscale mechanistic modeling, and cost-effective manufacturing strategies to accelerate the transition of HECs from laboratory to industrial applications.