Laser surface texturing under transformer oil conditions for improved process quality and tribological behaviors

Among various surface modification technologies, laser surface texturing (LST) to introduce texture has attracted more scholars' attention for controlling the tribological performance. The enhanced processing quality of the textured surface results in reducing the coefficient of friction and improving the wear resistance. In this study, dielectric transformer oil was used to protect the surface of GCr15 bearing steel from undesired gases in the atmosphere during the laser processing. Three types of dimples, including circle, rectangle and hexagon, were ablated to evaluate their influence on friction and wear. It was found that LST with transformer oil greatly improved the surface texture processing quality, where the edges of dimples were effectively designed and burrs-free. Results showed that the depth of dimples was reduced up to 7%. Compared to the samples fabricated in air, the friction coefficient and the wear of improved surface were reduced up to 55% and 73.8%, respectively. This was attributed to the excellent shielding and coolant property of transformer oil. Additionally, the shapes of the dimples, the applied force and the sliding speed significantly affected the friction coefficient, where dimples operate as lubricant and debris stores. This study provides certain feasibility guidance for the tribological modification of GCr15 bearing material with oil method and expands its application on engineering surfaces.