Order-of-magnitude fatigue life extension in bearing steels via microstructure tailoring around inclusions

A novel heat treatment introduces refined bainite sheaves into the martensite matrix of a bearing steel, particularly concentrating them in the vicinity of inclusions by leveraging the stress fields induced by the inclusions themselves. Among these, the bainite sheaves distributed around the inclusions play a decisive role in enhancing fatigue life. Mechanistically, multi-scale characterization and crystal plasticity simulations reveal that this bainite promotes compatible deformation and mitigates strain localization in the adjacent martensite. Such microstructure tailoring enlarges the FGA and increases the fatigue life by 11-fold. This improvement underscores the critical role of local matrix toughness in delaying fatigue damage.