Mating Material-Dependence of Tribological Behavior of Fluorinated Amorphous Carbon-Based Films

In order to understand the influence of fluorine incorporation on the tribological behavior of amorphous carbon films, fluorinated amorphous carbon-based (a-C:H:F) films containing different F contents were synthesized by plasma-enhanced chemical vapor deposition system, using C₂H₂ and CF₄ as precursor. Their microstructure, chemical composition and mechanical properties were examined by various techniques, i.e. X-ray photoelectron spectrometer, scanning electron microscopy, Raman and nanoindenter. Tribological properties of films were tested against different mating materials by reciprocating sliding tribometer with a ball-on-disk contact geometry. Results indicate that friction behavior of a-C:H:F films depended on the adhesion of counterpart material to C and chemical affinity of F with counterpart material. In sliding against mating materials with strong adhesion to carbon (Ti, WC and Si₃N₄), the a-C:H:F films with relatively low F contents showed similar friction behavior to that of a-C:H film. In sliding against inert ZrO₂ and Al₂O₃ counterparts, the a-C:H:F films showed increasing friction coefficient. Friction coefficient of a-C:H:F films against GCr15 balls increased as the increase in F content, but wear rates decreased. High F content within films resulted in marked fluctuation of friction coefficient of films against Cu, and significantly increased the friction coefficient of films against Al. Noticeably, highly fluorinated films exhibited a combination of high friction and low wear. It is found that tribochemical reactions between F and mating materials reasonably explained the friction behavior of different systems.