目的 通过调控离子渗氮层的结构和性能，获得具有良好韧性和疏松度的离子渗氮层，同时提高化合物层和有效硬化层的厚度。方法 在温度520 ℃下对4Cr5Mo2V钢进行离子渗氮（Plasma Nitriding, PN）前，采用不同工艺条件进行3次喷丸处理（Triple Shot Peening, TSP）。通过调整喷丸处理的实验参数，探索它们对渗氮层结构和性能的影响规律。使用光学显微镜、扫描电子显微镜、光学轮廓仪、X射线衍射仪、显微硬度计对渗层的截面显微组织、物相、硬度、韧性、疏松度进行测试分析。结果 与PN处理相比，经TSP3+PN处理后，试样的粗糙度为1.12 μm，化合物层和有效硬化层的厚度分别增加了13.9%和5.4%，韧性和疏松度较好；经TSP2+PN处理后，试样的粗糙度为1.21 μm，ε-Fe2-3N相的含量降低，γ‘-Fe4N相的含量显著提高，化合物层和有效硬化层的厚度分别增加了37.5%和10.7%，韧性和疏松度最佳；经TSP1+PN处理后，试样表面破裂严重，粗糙度为1.46 μm，化合物层和有效硬化层的厚度仅分别增加了1.1%和1.8%，化合物层破损。结论 经预喷丸处理后，表面位错密度提高，晶粒细化，促进了氮原子的扩散，能够提高渗氮层的厚度、硬度和韧性，但喷丸强度过高，则粗糙度过大，会降低喷丸强化作用，渗氮效果不佳。选择TSP2工艺进行预喷丸处理，生成的离子渗氮层γ‘-Fe4N相明显增多，其硬度、韧性和厚度更高。

During the hot stamping process, the primary failure modes of hot stamping dies are high-temperature wear and stress corrosion. Importantly, these failures usually result in significant economic losses. In order to enhance the service performance, the industrial sector often adopts plasma nitriding for surface treatment. Although a nitriding layer without a compound layer exhibits higher toughness, averting brittle spalling, its lower surface hardness can undermine the wear resistance of the material. Thus, there is a need to develop a method that can not only increase the thickness and hardness of the compound layer, but also prevent the early failure of the die caused by brittle fracture. The work aims to regulate the structure and properties of the plasma nitriding layer, achieve a plasma nitriding layer with favorable toughness and porosity, and increase the thickness of the compound layer and the effective hardened layer. Prior to plasma nitriding (PN) of 4Cr5Mo2V steel at 520 ℃ for 10 h, shot peening treatment (SP) under different process conditions was carried out. The effect of shot peening on the structure and properties of nitriding layer was investigated by adjusting the experimental parameters. The microstructure, phase constituents, microhardness gradient, effective thickness, porosity, surface hardness and surface morphology of plasma nitrided 4Cr5Mo2V steel coupled with TSP processing were tested and analyzed by optical microscopy, scanning electron microscope (SEM), X-ray diffraction (XRD), optical profilometer and microhardness tester. The results showed that under different SP treatment conditions, a large number of dislocations, as well as dislocation cells and nanocrystals composed of high-density dislocations were observed in 4Cr5Mo2V steel. In the plasma nitriding layer, ε-Fe2-3N phase was a hard and brittle phase, while γ′-Fe4N phase had good toughness and a certain hardness. XRD analysis revealed that, compared with the PN sample, the surface of the PN samples after SP treatment had the different contents of γ‘-Fe4N and ε-Fe2-3N phase, indicating that shot peening could evidently regulate the phase structure of the nitriding layer. Optical microscopy results showed that, compared with PN treatment, after TSP3 (0.4 mm+0.11 mm+0.11 mm)+PN treatment, the roughness of the sample was 1.12 μm, and the thickness of the compound layer and the effective hardened layer increased by 13.9% and 5.4%, respectively. After TSP2 (0.4 mm+0.19 mm+0.11 mm)+PN treatment, the roughness was 1.21 μm, the content of the ε-Fe2-3N phase decreased, the γ′ phase increased significantly, and the thickness of compound layer and effective hardened layer increased by 37.5% and 10.7%, respectively, with the best toughness and porosity. After TSP1 (0.4 mm+0.28 mm+0.11 mm)+PN treatment, the roughness was 1.46 μm and the thickness of compound layer and effective hardened layer increased by only 1.1% and 1.8%, respectively, with severe damage on the surface. This could be attributed to an increase in dislocation density, crystal refinement, and high strain of carbides and slip bands. However, when the shot peening intensity increases, the sample roughness also increases, which will inhibit the effect of shot peening and affect the efficiency of plasma nitriding. The plasma nitriding layer of 4Cr5Mo2V steel after TSP2 treatment has the best quality, and the surface hardness and thickness are the greatest with values of 980HV0.3 and 310 μm.