Next-generation surface design technology due to femtosecond-laser-induced nanostructure formed on hard thin films

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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. As for the macro frictional properties, the friction coefficients of carbon materials of DLC and GC exhibited fairly lower values compared with those of TiN and CrN. The friction coefficient μ of DLC obtained for a hardened steel ball decreased with an increase of the laser power and approached to μ of GC because of the modification from DLC to GC. The friction coefficient μ of the nanostructured surface was measured with a micro-scratch test at an ultralight load of 1.5mN. For this condition, μ of the nano -structured surface of DLC, TiN, and CrN increased, compared with those of the non-irradiated surface. On the other hand, μ of GC irradiated at a low laser energy has shown a minimum value of 0.05 and then increases with an increase of the laser power.