Fatigue strength optimization of high-strength steels by precisely controlling microstructure and inclusions

With the increasing demand for high-performance metallic materials, the improvement of fatigue strength (FS) has become a crucial issue. This study focuses on the AISI 52100 steel, a material with leading fatigue performance and low-cost raw material, aiming to further improve its FS. It is found that the fatigue damage mechanism of 52100 steels with different tensile strengths has undergone significant changes, and the inclusions, mainly nitride and oxide, are key factors limiting the further improvement of FS. Therefore, the size reduction and modification of inclusions were attempted through the rare earth addition and strict control of harmful elements. Combining targeted microstructure adjustment, the FS of the 52100 steel has been further enhanced to similar to 1.6 GPa, exceeding that of other metallic materials (performed in uniaxial tension with a stress ratio of R = 0.1), and thus establishing it as a standout for its exceptional performance-to-cost ratio. By clarifying the influences of different types of inclusions on fatigue performance and establishing the correlation between micro-hardness (or strength) and FS, an optimization strategy for FS improvement of the 52100 steel was proposed. The FS has been improved by approximately 187 MPa at most by implementing this strategy. These achievements provide feasible technical approaches and theoretical foundations for the anti-fatigue design of metallic materials. (c) 2025 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.