Friction reduction of steel by laser-induced periodic surface nanostructures with atomic layer deposited TiO2 coating

We report on the reduction of friction of steel treated by femtosecond laser pulses and subsequent atomic layer deposition. Uniform laser-induced periodic surface structures (LIPSS) are produced on the surfaces of stainless steel samples by an 800-nm femtosecond laser. These nano-textured surfaces are then deposited with TiO2 coating by means of atomic layer deposition (ALD). Friction tests show that the average friction coefficients of the treated samples have been greatly reduced. The improvement of tribological properties is attributed to the intact ripple structures reduce the contact area between friction pairs and act as reservoirs for wear particles. Moreover, the TiO2 coating further reduces adhesion and plastic deformation, which is beneficial to improving tribological properties. It is suggested that the synergistic effect of LIPSS and ALD TiO2 coating had a more marked potential for improving tribological properties.