Impact of Ultrasonic Surface Rolling Processes on Microstructures and Fatigue Properties of 300M Steel Laser-Cladding-Repaired Components

Laser cladding repair (LCR) is the primary method used for rectifying surface scratches on axial components. However, it often results in an uneven residual stress distribution and a substantial postcladding surface roughness, deteriorating the mechanical properties of the repaired components and rendering them unsuitable for direct use. To enhance the overall mechanical performance of LCR samples obtained after LCR, an ultrasonic surface rolling process (USRP)-based approach is employed. Herein, the microstructure, surface roughness, hardness, residual stress, and fatigue performance of the samples after USRP reinforcement are investigated. Furthermore, the effect of the number of USRP passes is analyzed. Results reveal that after USRP, the sample surfaces exhibit a more refined strengthening layer. The surface roughness decreases by 55.4% and 61.6% in the cladded and base material zones, respectively, while the surface hardness increases by 6.8% and 18.7%, respectively. The residual stress on the surface transitions from tensile to compressive stress. In addition, the residual compressive stress becomes more uniform and pronounced with increasing number of rolling passes. Furthermore, a 13.2-fold increase in fatigue life is observed. The number of USRP passes considerably influences the strengthening effects on the repaired samples with optimal surface and fatigue performances achieved after six passes.