Fe–Cu/graphite composites are promising friction materials for wet clutch applications in electrified powertrains, where stable frictional behavior and wear resistance under automatic transmission fluid (ATF) lubrication are critical. In this study, composites containing 1 and 3 wt% graphite were prepared by mechanical alloying (MA) and by a post‑mixing powder metallurgy route (PM). The processing route strongly influenced graphite morphology, grain characteristics, and tribological behavior under ATF lubrication. In the MA route, co‑milling fragmented graphite through a cushioning effect, resulting in matrix softening and unstable friction. By contrast, the PM route preserved graphite morphology, promoted grain refinement, and yielded a hard, stable matrix, exhibiting lower and more stable friction coefficients with superior wear resistance. These findings highlight that graphite functionality is dictated by its structural state and distribution rather than its amount, providing practical guidelines for designing Fe–Cu-based friction materials for EV/HEV clutch applications.
Lee et al. (Fri,) studied this question.