Synergistic friction-reducing and anti-wear behaviors of DLC on NCD films via in-situ synthesis by fs laser ablation

In present work, diamond-like carbon (DLC) films are in-situ synthesized on nano-crystalline diamond (NCD) films via femtosecond laser ablation (FLA). Field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM), atomic force microscopy (AFM), micro-Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and nano-indentation are performed to characterize the as-fabricated DLC/NCD composite films. The tribological performance of as-fabricated DLC/NCD composite films is investigated by ball-on-plate reciprocating friction tests with zirconia bio-ceramic (ZBC) balls as counterparts under simulated body fluid (SBF) lubrication. For comparison, as-grown micro-crystalline diamond (MCD) films and NCD films are also tested. The stable friction coefficient of MCD, NCD and DLC/NCD films is 0.163 ± 0.018, 0.082 ± 0.017 and 0.051 ± 0.016, respectively. Besides, all three types of sample exhibit excellent and close wear resistance, while the wear rate of ZBC counterparts for MCD, NCD and DLC/NCD films varies, which is about 6.59 × 10−8, 1.33 × 10−8 and 1.21 × 10−9 mm3/Nm, respectively. The results show that the DLC/NCD composite films can significantly lower the stable friction coefficient and the amount of wear debris, which is attributed to the lubrication effect and improved surface smoothness by DLC top-layers. On the other hand, much higher stable friction coefficient and greatly increased wear debris can be observed for the MCD and NCD films, which is ascribed to their much rougher surfaces.