INFLUENCE OF FEMTOSECOND-LASER-INDUCED PERIODIC SURFACE STRUCTURES ON THE TRIBOLOGICAL PERFORMANCE OF CVD NANO-CRYSTALLINE DIAMOND FILMS

Laser-induced periodic surface structures (LIPSS, ripples) are generated on CVD nano-crystalline diamond (NCD) films by femtosecond laser irradiation in air (pulse duration 200 fs and central wavelength 1040 nm). The experimental conditions (laser fluence and spatial spot overlap) are optimized to obtain a 3 × 3 mm 2 area covered with homogenous LIPSS. Then, the influence of LIPSS on the frictional performance of NCD films is investigated by dry reciprocating ball-on-disc tests, where ZrO 2 ceramic balls are used as counterparts. The results show that the friction behavior is very sensitive to the orientation of nano-structured ripples in LIPSS. The frictional coefficient can be greatly reduced when the sliding direction is parallel to the orientation of the nano-structured ripples, indicating potential benefit of LIPSS on NCD films for frictional applications.