Characterization and friction wear study of Single-layer diamond films with different microstructures on silicon carbide substrates

Ceramic bearings may crack and wear at high speeds. To address this issue, this study prepared high-performance diamond films on ceramics, aiming to reduce wear and extend the bearing lifespan. By utilizing Hot Filament Chemical Vapor Deposition (HFCVD) technology and adjusting the substrate temperature and methane concentration, the content of the sp² phase in the diamond films was precisely controlled, leading to the fabrication of micron- and nanometer-scale diamond-graphite composite films (MCD/G and NCD/G). The tribological properties of these films were tested with silicon nitride ceramic balls under dry friction conditions. During the tests, loads of 15 N, 25 N, and 35 N were applied, respectively, with a friction distance of 10 millimeters, a test duration of 60 min, and a reciprocating frequency of 3 Hz. The friction coefficient varied with load changes and the transformation from sp³ to sp² on the diamond surface. As the load increased, MCD films exhibited scratches and grain shedding, while NCD films showed increasing wear and the formation of transfer films. MCD/G films, due to their high graphite content, exhibited low wear and friction. Conversely, NCD/G films displayed plastic deformation and ripple-like wear marks due to their low diamond purity. Notably, the wear rate of the diamond films decreased as the load increased. Compared to the uncoated substrate, the prepared films reduced wear by approximately 99.98% (MCD), 99.69% (NCD), 99.90% (MCD/G), and 99.86% (NCD/G).