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<p>This study investigates ultrasonic surface rolling process (USRP) of high strength carburized 18CrNiMo7-6 steel to optimize process parameters and improve surface integrity, microstructure, and fatigue performance. A multi-stage indentation-depth model based on Hertzian contact theory and elastoplastic was developed and experimentally validated, achieving an accuracy of R<sup>2</sup> = 0.933 with relative errors below 14%. Sensitivity analysis indicates that roller radius contributes 53.4% and ultrasonic vibration amplitude contributes 26.2% to indentation-depth variation. USRP improves surface morphology through peak shaving and valley filling, reducing <i>Ra</i> by more than 30% and lowering the stress concentration factor <i>K</i><sub>st</sub> from 1.52 to 1.07–1.13. Severe plastic deformation promotes dynamic recrystallization; under the optimal parameters (0.33&#xa0;mm roller radius, 800 N, 8&#xa0;μm, 4 passes), the near-surface grain size decreases by 45.2% relative to the carburized sample, with increases in geometrically necessary dislocation (GND) density and low-angle grain boundary (LAB) fraction of 73.9% and 45.5%, respectively. Fatigue tests demonstrate a 250 to 300 times improvement in fatigue life compared with untreated samples. Overall, the proposed model and the established parameter–microstructure–performance correlations provide practical guidance for USRP parameter optimization in high-strength alloy components.</p>

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Ultrasonic Surface Rolling of 18CrNiMo7-6 Steel: Indentation-Depth Modeling, Surface Integrity, Microstructure, and Fatigue Performance

  • 期刊论文

  • 发表日期：

    2026年2月11日

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  • LanRong Liu,
  • DaoYuan Lv,
  • Kuo Hu,
  • HaoNan Kang,
  • GuangTao Xu,
  • ZengTao Chen,
  • ZhenYe Zhao,
  • YongTao Ma

摘要

This study investigates ultrasonic surface rolling process (USRP) of high strength carburized 18CrNiMo7-6 steel to optimize process parameters and improve surface integrity, microstructure, and fatigue performance. A multi-stage indentation-depth model based on Hertzian contact theory and elastoplastic was developed and experimentally validated, achieving an accuracy of R2 = 0.933 with relative errors below 14%. Sensitivity analysis indicates that roller radius contributes 53.4% and ultrasonic vibration amplitude contributes 26.2% to indentation-depth variation. USRP improves surface morphology through peak shaving and valley filling, reducing Ra by more than 30% and lowering the stress concentration factor Kst from 1.52 to 1.07–1.13. Severe plastic deformation promotes dynamic recrystallization; under the optimal parameters (0.33 mm roller radius, 800 N, 8 μm, 4 passes), the near-surface grain size decreases by 45.2% relative to the carburized sample, with increases in geometrically necessary dislocation (GND) density and low-angle grain boundary (LAB) fraction of 73.9% and 45.5%, respectively. Fatigue tests demonstrate a 250 to 300 times improvement in fatigue life compared with untreated samples. Overall, the proposed model and the established parameter–microstructure–performance correlations provide practical guidance for USRP parameter optimization in high-strength alloy components.