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.