Enhanced high-temperature tribological performance of fluorinated tetrahedral amorphous carbon (ta-C:F) coatings in sliding applications

Abstract

This study investigated the dry sliding behaviour of fluorinated tetrahedral amorphous carbon (ta-C:F) coatings against uncoated 52100 steel at temperatures ranging from 25 °C to 300 °C. The ta-C:F coatings demonstrated significant reductions in both the coefficient of friction(COF) during the running-in stage and at steady state, particularly within the temperature range of 25 °C to 200 °C, surpassing the performance of well-established a-C:H coatings. SEM analyses revealed the formation of transfer layers on the contact surface of 52100 steel when tested against ta-C:F coatings at temperatures up to 200 °C, while none were detected at temperatures ≥250 °C. Raman spectroscopy indicated a transition from sp3 to sp2 carbon structures in the carbonaceous transfer layers with increasing temperature, and XPS scans confirmed an increase in fluorine (F) concentration within these layers, correlating with reduced COF. The comparative analysis at 120 °C emphasized the intrinsic advantages of ta-C:F coatings in high-temperature applications, demonstrating a nearly 50% lower COF (0.08) when compared to traditional boundary-lubricated steel-to-steel sliding contacts. These findings have significant implications for enhancing the efficiency and durability of various mechanical systems, particularly in industries like automotive and manufacturing.