A composite treatment method for improving the tribological properties of GCr15 by combining ultrasonic shot peening and surface texturing

GCr15 bearing steel suffers from severe wear failure under high-speed, heavy-load and thin-oil lubrication conditions, limiting the service reliability of transmission components in aerospace, weaponry and engineering machinery. Surface texturing and shot peening have been widely adopted to improve the tribological performance of metallic materials. Nevertheless, single surface texturing inevitably causes interfacial discontinuity and stress concentration, restricting its wear-resistance improvement. Similarly, conventional shot peening effectively enhances surface hardness and wear resistance via plastic deformation, yet it fails to regulate interfacial lubrication and friction behavior. To address these limitations, this work investigates a composite treatment combining ultrasonic shot peening (USP) and surface micro-texturing, with particular attention to the effects of process parameters and treatment sequence on friction and wear performance. The results reveal that the sequence of “USP followed by texturing” degrades the pre-fabricated strengthening layer. Laser thermal effects may further increase surface roughness, induce grain coarsening, and relax residual compressive stress, ultimately leading to unsatisfactory tribological performance. In comparison, the reverse sequence (“texturing followed by USP”) preserves the lubrication regulation ability of surface textures. The subsequent projectile impact flattens texture edge bulges and further strengthens surface mechanical properties, yielding refined grains (1.13 μm), high microhardness (833 HV), large residual compressive stress (−693 MPa) and improved oleophilicity (53.9°). In addition, the recommended process parameters for the tribological performance is the composite treatment of LST (texture area density of 8%) followed by USP (ultrasonic power of 2 kW). Under the appropriate composite treatment, the untreated specimen exhibited a 94.1% shorter stable low-friction duration than the treated specimen (105 s versus 1788 s), and the wear rate was reduced by 39.5%. This proposed composite process provides a feasible theoretical and technical reference for improving the surface tribological performance of bearing steel under extreme working conditions.