Tribological properties of 65Mn steel with USRP micro-textures

To address the early failure of 65Mn steel agricultural machinery components caused by low surface hardness and insufficient wear resistance, this study proposes a surface micro-texturing method based on ultrasonic surface rolling processing (USRP). The objective is to elucidate the intrinsic correlations among micro-texture topography, microstructure, and tribological performance. By controlling the processing step-over distance during USRP, micro-textures with defined depth and width were fabricated on 65Mn steel substrates. The influence of step-over distance on surface hardness, plasticity index, and tribological characteristics was systematically evaluated via nanoindentation and dry sliding tribological tests. The results demonstrate that USRP micro-texturing significantly enhances both the surface mechanical properties and the tribological performance of 65Mn steel. At the best-performing step-over distance within the investigated range (120 μm), hardness increased by approximately 58%, and the average coefficient of friction decreased from approximately 0.51 for the polished sample to 0.43, corresponding to an approximately 16% reduction. The wear rates of the substrate and the GCr15 counterface ball decreased by approximately 46% and 54%, respectively. These results identify a mechanism-based balance between surface strengthening and micro-texture-controlled contact behavior under a controlled laboratory sliding condition, rather than a direct quantitative prediction of field service life in soil/sand abrasive environments.