Gradient Structured Surface Enhancement and Performance Improvement of Laser Powder Bed Fusion 316L via Multi‐Pass Ultrasonic Surface Rolling

The surface integrity and mechanical properties of laser powder bed fusion (L‐PBF) fabricated 316L stainless steel are often compromised by surface roughness and detrimental tensile residual stresses. This study investigates a multi‐pass ultrasonic surface rolling process (USRP) as a post‐treatment to address these issues. Guided by finite element simulations that optimized pass parameters to achieve a deeper compressive stress field, experiments systematically characterized the gradient nanostructure. Results show that USRP transformed surface tensile stresses into compressive ones, with an affected depth of approximately 0.6 mm. Significant grain refinement was achieved in the surface layer, reducing the average grain size from 18.90 to 11.31 μm, alongside a surface hardness increase to 291.52 HV 0.5 and an 80% reduction in surface roughness. Analysis indicates that the high‐strain‐rate deformation promoted dislocation slip and reorganization, triggering dynamic recrystallization driven by the residual stress field. This process established a synergistic enhancement in hardness, residual compressive stress, and wear resistance, providing an effective strategy for improving the performance of additively manufactured components, which is particularly applicable to aerospace, medical devices and other key fields requiring high‐performance additively manufactured components, showcasing broad industrial application prospects and practical value.