M50钢是目前应用最广泛的航空发动机轴承钢，热处理过程中析出的复杂析出相对其性能具有关键影响。目前，有关深冷处理对纳米级碳化物的演化行为和特性的影响尚未澄清，深冷处理对轴承中残余应力的影响也有待揭示。本工作依托中国散裂中子源(CSNS)的小角中子散射(SANS)谱仪和通用粉末衍射(GPPD)谱仪，并结合高分辨透射电镜观察及轮廓法测量残余应力等，系统研究了深冷和回火过程中M50轴承钢中纳米级碳化物的演化行为，以及轴承服役过程中的残余应力变化规律。结果表明，深冷处理的M50轴承钢中主要存在椭球状和杆状两类典型的纳米级碳化物，回火处理后，杆状碳化物的数量增加、平均尺寸减小，增强了二次硬化效果。另外，利用球差校正透射电子显微镜在深冷+回火处理的M50钢中观察到只有几个原子厚的片层状碳化物，原子级能谱分析结果显示，片层状碳化物富集C、Cr、Mo、V元素，具有fcc结构，可以看作是几何各向异性碳化物的前驱体。精研和精磨状态航发轴承套圈中的残余应力基本相同，且处于低应力水平；轴承套圈经过服役后切向残余拉应力增加，自研轴承服役后的残余应力状态与进口轴承状态相近。

Aeroengine bearings, often referred to as the “joints” of the critical aeroengine components, are essential to engine performance, operating under extreme conditions of high temperatures, rapid rotation, and heavy mechanical loads. M50 high-carbon, high-alloy steel, renowned for its exceptional high-temperature stability, hardness, wear resistance, and fatigue resistance, has long been the material of choice for aerospace bearings. Although advances in purification, homogenization, and grain refinement have improved the fatigue life of M50 steel, challenges remain. Notably, microstructural heterogeneities within the matrix, such as coarse carbides, can act as crack initiators under cyclic loading, highlighting the need for advanced microstructural control strategies. This study systematically investigates the evolution of nanoscale carbides in M50 bearing steel during a novel treatment process combining quenching, direct cryogenic treatment, and subsequent tempering, as well as the evolution of residual stress under service conditions. The analyses employed the following methods: small angle neutron scattering and general purpose powder diffraction at the China Spallation Neutron Source, complemented by aberration-corrected high-resolution transmission electron microscopy and residual stress profiling using the contour method. The results demonstrate that elliptical and rod-shaped nanoscale carbides are predominant in the cryogenically treated M50 steel. After tempering, the density of rod-shaped nanoscale carbides increases while the average size decreases, enhancing secondary hardening through the strengthening of carbide dispersion. Remarkably, atomically thin lamellar carbides, with a face-centered cubic structure and bulk enrichment in elements C, Cr, Mo, and V, were identified as precursors to geometrically anisotropic carbides. This novel treatment promotes finer, more uniformly distributed nanoscale carbides comparing to the typical tempering after cryogenically treated microstructure, synergistically improving fatigue strength and hardness while ensuring uniform residual stress distribution in bearing rings. The residual stresses in aeroengine bearing rings under precision and fine grinding conditions are comparable and remain at low levels. Under various service conditions, comparisons between domestically developed and imported bearing rings reveal that after service, transverse residual stress shifts from compressive to tensile, with domestically developed bearings exhibiting residual stress states similar to imported bearings.