Exploring eutectic high-entropy alloys (EHEAs) for wide-temperature tribological applications is primarily limited by their insufficient intrinsic lubrication and severe wear under thermo-mechanical coupling. In this study, to address this issue, we incorporated hard phases and graphite into the AlCoCrFeNi2.1 alloy through spark plasma sintering. Unlike conventional ex-situ methods, precursor SiC decomposition induces a thermodynamically driven in-situ reaction, leading to the formation of dispersed carbonitride/silicide phases, alongside free graphite precipitation at a critical SiC content of 0.75 at.%. The resulting SiC0.75 composite demonstrates outstanding tribological stability from 25 °C to 900 °C, featuring a low coefficient of friction of 0.28-0.36 and a maximum wear rate nearly two orders of magnitude lower than the unmodified EHEA. Mechanistically, at room and intermediate temperatures, in-situ graphite readily spreads to form a continuous lubricating tribofilm, while dispersed hard phases resist abrasive microcutting. At higher temperatures, where oxidation dominates, the selective outward diffusion of aluminum fosters a dense, adherent Al 2 O 3 -rich glaze layer, effectively suppressing severe oxidative wear. This study offers a practical precursor-controlled synthesis strategy for self-lubricating EHEAs and clarifies their wide-temperature tribological mechanisms.
Chen et al. (Fri,) studied this question.