Friction Characteristics Of Fluorinated Dlc Films

The fluorinated diamond-like carbon (F-DLC) films were prepared by radio frequency reactive magnetron sputtering with pure graphite as a target, trifluoromethane (CHF3) and argon (Ar) as source gas under different radio-frequency powers and source gas ratio. Surface morphology, hardness, bonding configuration and frictional properties were investigated by atomic force microscopy (AFM), nanoindenter, Raman spectra, FTIR spectra as well as a ball-on-disk test rig. The result shows that the F-DLC films are distributed compactly and homogeneously, it exhibits good friction-reducing behaviors, with the minimum of friction coefficient about 0.40. AFM and Nanoindenter indicate that friction coefficient depends closely on the roughness and hardness but not a simple connection. Both the decrease of roughness and increase of hardness may lead to a lower friction coefficient. Radio-frequency power and the flow ratio of source gas influence the deposition rates , which correlates with the fraction of aromatic ring (corresponding to the sp2) and the frictional behaviors. Combined with the FTIR spectra, it was revealed that the ways of F combination was significant factor which affects the friction coefficient. The weaking of–CF2 asymmetric stretch vibration intensity and formation of CFH in C=C chains may result in a lower friction coefficient of F-DLC films.