Optimization of Geometric Parameters in Moon Texturing to Enhance the Tribological Performance of AISI 5115 Steel

Surface texturing can significantly enhance the tribological performance of materials. In this study, a novel moon-shaped surface texture was designed and optimized via computational fluid dynamics (CFD) simulations. The optimal geometric parameters were identified as R 1 = 100 μm, R 2 / R 1 = 1.5, and the contact point at the center of the R 1 circle. Compared with conventional textures (circular, elliptical, square, triangular), the moon texture exhibited superior hydrodynamic lubrication performance due to its “wide inlet, narrow outlet” geometry, which enhances oil film pressure. The optimized textures were fabricated on AISI 5115 steel using femtosecond laser processing. Pin-on-disk friction tests demonstrated that the optimal moon-shaped texture (depth = 10 μm) reduced friction by up to 52% and wear by up to 83.9% at rotational speeds of 100, 400, and 700 rpm relative to an untextured surface. The superior tribological performance arises from a synergistic mechanism: the crescent-shaped cavity enhances hydrodynamic pressure while effectively trapping wear debris, preventing three-body abrasion. These results confirm the significant potential of the moon-shaped texture for improving the tribological performance of AISI 5115 steel in engineering applications.