Optimization of Fiber Laser Parameters for Reduced Root Mean Square Deviation along the Surface (Sq) for a Surface with a Smaller Coefficient of Friction

This study investigates the optimization of fiber laser parameters to minimize the root mean square deviation (Sq) of ST52 steel surfaces. The goal is to reduce the coefficient of friction. The Taguchi design of experiments (L16 orthogonal array) was used to systematically analyze the effects of laser power, scanning area, and surface pattern geometry. The results show that laser power is the dominant factor (39.78% contribution), followed by scanning area (36.02%) and pattern type (24.20%). The optimum combination was 40 W laser power, 40% scanning area, and square pattern geometry, yielding an Sq value of 31.76 nm. From a physics perspective, this optimization is governed by the interplay of energy absorption, localized melting, and Marangoni convection within the melt pool. These factors directly influence surface re-solidification and asperity formation. Lower Sq values reduce asperity junctions, decreasing real contact area under Hertzian contact conditions, and minimize frictional energy dissipation according to Bowden–Tabor theory. These findings highlight that laser-based surface modification enables precise tailoring of topography. Laser techniques offer advantages over conventional roughening methods in terms of controllability, repeatability, and application-specific functionality. The results provide a framework for designing next-generation steel components with improved tribological and mechanical performance.