为了满足镍钨合金的表面强化需求，本工作以固溶态NiW750合金为对象，构筑了“梯度纳米结构-高密度纳米析出”强化表层，研究了超声喷丸(USP)参数(振幅、时间、丸粒数量及直径)和时效处理对表层硬化及其组织演变的影响。结果表明，USP在表层引入梯度位错、梯度纳米晶和梯度纳米孪晶三类晶体缺陷，形成深度> 450 μm的梯度硬化层，表面(喷丸强化区)硬度较固溶态提高约1倍。可通过USP参数调控硬化层深度和硬度，但强化效果存在饱和上限。时效后，合金最表面(距离喷丸表层深度约0 μm)、梯度硬化层和心部的硬度相对喷丸态合金分别提高166.39、59.25和115.30 HV；三类晶体缺陷数量减少，但其协同促进了更高密度、更细小的纳米Ni₄W相的析出。晶体缺陷减少与纳米相析出存在竞争关系，决定了材料不同深度区域的硬度增量。

To meet the surface strengthening requirements of high-strength, high-toughness, medium-heavy Ni–W alloys for warheads, the NiW750 alloy was investigated. The alloy was prepared through vacuum melting, homogenization, forging, and solution treatment. A composite-strengthened surface layer, characterized by gradient nanostructures and high-density nanoprecipitates, was then constructed in the NiW750 alloy through a combined ultrasonic shot peening (USP) and aging treatment. The effects of different USP parameters (amplitude, time, shot quantity, and diameter) and the aging process on the alloy’s surface hardening behavior were investigated, and the microstructure evolution and hardening mechanisms were analyzed. The results indicate that USP introduced three types of crystal defects into the alloy’s surface layer: gradient dislocations, gradient nanograins, and gradient nanotwins, which collectively formed a gradient-hardening layer. This process approximately doubled the surface hardness compared to the solid-solution state, with the hardened layer exceeding 450 μm. Although the depth and hardness of the hardened layer could be regulated within a certain range by adjusting USP parameters, the strengthening effect exhibited a saturation limit. Following aging treatment, the gradient structure, composed of these three types of crystal defects, was retained in the surface layer, and the hardness continued to exhibit a gradient distribution from the surface inward. Hardness at different depths further improved by varying increments: the hardness of the outermost surface, the gradient-hardened layer, and the core increased by 166.39, 59.25, and 115.30 HV, respectively. During aging, the crystal defects introduced by USP promoted the nucleation of the Ni₄W phase, leading to the formation of finer and higher-density nano-dispersed precipitates. Concurrently, the density of these three types of crystal defects decreased during aging. The competition between aging-induced nanoprecipitation and the attenuation of these crystal defects determined the hardness increments at different depths.