The highest fatigue strength for steels

Abstract

Improving the fatigue strength of engineering materials is the most important strategy to ensure the safety of key components. Regrettably, although a large number of high-strength materials have tensile strengths over 3 GPa, their fatigue strengths do not exceed 1 GPa under push-pull loading. Here, we report the highest fatigue strength for steels to date (of 1103 MPa) under push-pull loading with the stress ratio of R =-1 in a GCr15 bearing steel, achieved by precisely controlling the microstructure and defects. First, the plasticity of the inclusions is improved by adding minute rare-earth elements, which efficiently prevents their brittle fracture. Second, a new shearable inclusion/matrix interface structure is formed, further improving their collaborative deformation ability. Third, an excellent synergy between tensile strength and plasticity is achieved by adjusting heat treatment to reduce the fatigue cracking tendency at inclusions. These new findings provide insight into how the fatigue strength of high-strength steels can be improved, through microstructural adjustment and defect control. This strategy can be readily achieved with current industrial technologies and provides a promising and effective procedure to improve the fatigue properties of other high-strength metallic materials.