Achieving near-atomic-level surface finish on GCr15 bearing steel via CMP: mechanisms and process optimization

GCr15, a widely utilized high-carbon chromium bearing steel, is extensively employed in manufacturing bearing rings due to its excellent wear resistance and corrosion resistance. In aerospace applications where stringent surface roughness requirements are imposed on bearings, this study presents a novel polishing slurry comprising D-sorbitol, silica sol, H 2 O 2 , disodium EDTA, and benzotriazole (BTA) to achieve near-atomic-level polishing of GCr15 bearing steel within a defined parameter range. Under a 20 μm × 20 μm measurement area, the lowest reported areal surface roughness (Sa) value of 0.204 nm was attained, approaching atomic-scale smoothness. The polishing mechanism was investigated via Energy-Dispersive X-ray Spectroscopy (EDS), X-ray Photoelectron Spectroscopy (XPS) and Inductively Coupled Plasma Mass Spectrometry (ICP-MS), revealing that under alkaline conditions, H 2 O 2 and disodium EDTA oxidize Fe and Cr to form chelate complexes such as [Fe(EDTA)] − and [Cr(EDTA)] - . These complexes synergize with the mechanical removal action of SiO 2 abrasives to realize an ultra-smooth surface. • Developed a novel polishing fluid that achieved an ultra-smooth surface of 0.204 nm on GCr15 steel. • Optimized and validated the optimal fluid formulation through orthogonal experiments and grey relational analysis. • Unveiled a synergistic oxidation-chelation polishing mechanism, offering a new route for efficient ultra-precision machining.