Improvement in wear resistance of stainless steel by laser-induced local surface treatment

To improve the wear resistance of small machine parts such as microscale gears, we developed a novel surface treatment process, laser-induced local surface treatment. Disk-shaped austenitic stainless steel (SUS316L) specimens were soaked in Al(NO3)3 solution and subsequently irradiated by a nano-pulse fiber laser beam. The treated surfaces were then observed under a scanning electron microscope and analyzed using an energy dispersive X-ray spectrometer. The effects of defocus amount, tribology behavior, and wear resistance on the characteristics of the treated surface were examined in detail. The surface roughness of the treated specimens with the defocus range of -1 to -2 mm was lower than that of the treated specimen without defocus. The thickness of the treated layer decreased when the defocus amount was increased within the abovementioned range of values. However, when treatment was performed with a defocus amount of -3 mm, no noticeable change was observed on the treated surface; this was attributed to the difference in laser-energy density. The friction coefficient of the laser-treated specimen with the defocus level of -1 mm was much lower than that of the untreated specimen. This implies that the wear resistance of austenitic stainless steel can be improved with the proposed surface treatment method.