Femtosecond laser surface texturing of diamond-like nanocomposite films to improve tribological properties in lubricated sliding

We report on femtosecond laser ablation and surface micropatterning (texturing) of diamond-like nanocomposite (DLN) films (a-C:H:Si:O films), aimed to improve tribological properties of laser-patterned films under lubricated sliding conditions. Femtosecond laser system generating pulses of 320-fs duration at the wavelength 515 nm is applied. Femtosecond laser ablation of 2.7-μm-thick DLN films is studied to determine optimum irradiation parameters for laser surface texturing with the requirements of the minimal spot size, high ablation rate, surface quality and pattern depth less than the film thickness. Periodic microcrater patterns (with 10 μm diameter, 2.2 μm depth, and different area density of microcraters) have been fabricated on the DLN films over the areas of 6 mm × 10 mm size. Tribological tests of the original and laser-patterned DLN films are performed using a ball-on-flat tribometer under linear reciprocating sliding against 100Cr6 steel balls in the presence of oil lubrication (engine oils of low and high viscosity). The ball-on-flat investigations have demonstrated the reduced friction and wear properties of the laser-textured DLN films, depending on the area density of microcraters and lubrication conditions. The obtained results evidence that femtosecond laser surface texturing is an effective technique to improve lubricated sliding performance of the DLN coatings.