Frictional properties of diamond-like carbon, glassy carbon and nitrides with femtosecond-laser-induced nanostructure

This paper reports macro and micro frictional properties of DLC, TiN, CrN films and GC substrate of which surfaces are nanostructured with femtosecond (fs) laser pulses. The friction coefficient μ of the nanostructured surface was measured at a usual load with a ball-on-disk friction test machine. The results have shown that carbon materials of DLC and GC provide lower values of μ than TiN and CrN, and μ of DLC and TiN measured with a hardened steel ball decreases with an increase of the laser pulse energy. On the other hand, μ of nanostructured surfaces of thin films monotonously increases with an increase in laser pulse energy, which was measured with a micro-scratch test at an ultralight load of 1.5 mN utilizing a diamond tip. The friction coefficient of the GC substrate irradiated at a low fluence around the ablation threshold has shown a lower value than that of the non-irradiated surface.

Research Highlights
► The frictional properties of DLC, GC, TiN and CrN nanostructured with femtosecond laser pulses are reported.
► At a usual load, DLC and GC provide fairly lower friction coefficients µ than nitrides.
► At an ultralight load of 1.5 mN, µ of DLC and nitrides monotonously increases with an increase in laser fluence.
► Meanwhile, µ of GC irradiated at a low fluence represents a minimum value of 0.05.