目的 对18CrNiMo7-6渗碳钢进行不同丸粒条件下的混合射流喷丸研究。方法 基于Hertz理论分析，构建一次喷丸工艺的残余应力场解析预测模型，并进行试验验证，在此基础上获取达到残余应力场近饱和的喷丸试验参数;选择不同的丸粒类型、压力等试验参数来探究二次微细喷丸处理渗碳钢对其残余应力、表面质量的影响规律。结果 在一次喷丸(First-shot peening)处理获得饱和残余应力场的条件下，采用?0.1 mm的铸钢丸和?0.05 mm的强化钢丸/玻璃丸进行二次喷丸(Secondary-shot peening)时，随着喷丸强度的提高，铸钢丸喷丸处理出现了过喷，并发生残余应力消退(消残)现象，在最高强度下残余应力最大值所在深度降低了约50 μm，总影响深度降低了约120 μm，表面粗糙度Ra随之增大，由0.78 μm升至1.78 μm;微细强化钢丸未对已有残余应力场造成过大的影响，表面粗糙度先减小后增大，最低为0.81 μm;微细玻璃丸对试样的残余应力场、表面粗糙度的影响不大。铸钢丸在压力2 MPa、喷嘴移速16 mm/s，或微细强化钢丸在6 MPa、4 mm/s时，其喷丸效果更好。结论 二次喷丸工艺中，在适宜的喷丸强度下使用微细丸粒不仅能增强原有的残余应力场，还可以显著提高一次喷丸处理后的表面质量。

High surface integrity plays a key role in determining the performance of basic components such as gears. As a high-quality gear steel, 18CrNiMo7-6 carburized steel has become a focus of engineering and academic research for surface treatment to improve fatigue performance. Composite water jet shot peening (WJSP) improves the fatigue strength of metal components by introducing near-surface plastic strain and residual compressive stress, and can be used for metal surface strengthening. In this study, first shot peening and secondary fine shot peening of hybrid water jet were performed on 18CrNiMo7-6 carburized steel for surface strengthening. Through theoretical analysis of the shot peening residual stress field, a predictive model for the residual stress distribution after shot peening was established and experimentally validated. The results showed that the model maintained good predictions within an acceptable error range. The primary shot peening parameters were based on the comprehensive results of predictive model and experimental validation of the residual stress field from primary shot peening. Primary shot peening trials were conducted with 0.2 mm and 0.5 mm steel wire cut shots, with each shot peening trial conducted twice in forward and reverse directions along the shot peening trajectory to obtain near-saturated residual stress field parameters. Subsequently, based on the good residual stress gradient field results from primary shot peening, secondary fine shot peening was performed on the carburized steel by reducing the shot peening intensity, selecting different shot types, pressures, and other experimental parameters. Surface integrity, including residual stress, surface morphology, and roughness under different processing conditions, was characterized through white light interferometry and X-ray diffraction stress measurement, exploring the relationship between different processing parameters and surface integrity. The results indicated that water jet shot peening could achieve near-saturation state in one pass, with little impact on the overall residual stress field from increasing the number of shot peening passes. Under conditions where the primary shot peening achieved a saturated residual stress field, secondary shot peening using ?0.1 mm cast steel shots reduced Ra value from 1.007 μm in FSP to 0.78 μm at the lowest intensity shot peening. With the increasing shot peening intensity, over-peening and stress relaxation occurred, reducing the maximum residual stress depth from 120 μm in FSP to 70 μm, total affected depth from 340 μm to 220 μm, and increasing surface roughness to a maximum of 1.78 μm. The use of ?0.05 mm strengthened steel shots and glass shots had no significant impact on the existing residual stress field. With the increasing shot peening intensity, micro-strengthened steel shots initially decreased and then increased the surface roughness, with Ra value reaching a minimum of 0.81 μm at medium-low intensity. Fine glass shots had minimal impact on residual stress field and surface roughness. The best shot peening effect was achieved with cast steel shots at 2 MPa-16 mm/s (pressure, nozzle traverse speed) or micro-strengthened steel shots at 6 MPa-4 mm/s. Therefore, in secondary shot peening processes, using fine shots for medium-low intensity shot peening can significantly improve surface quality after primary shot peening treatment, with slight enhancement in surface residual stress without disrupting the original residual stress field.