The influence of thermomechanical processing and heat treatment on the fatigue resistance and fractographic characteristics of a high-carbon bearing steel.

Abstract

This study examined the effects of thermomechanical processing and subsequent conventional heat treatment on microstructure and fatigue in AISI 52100 steel. The thermomechanical processing techniques are essentially those described by Sherby and his co-workers at Stanford University. Previous research by that group and at the Naval Postgraduate School has demonstrated that a wide range of ferrite matrix grain sizes and carbide particle distributions can be obtained in this steel. Studies parallel with this are examining the subsequent heat treatment response of these structures and also the fracture toughness attainable. In this study on fatigue, it was found that both the fatigue life at a given cyclic stress and the endurance limit were improved by processing to produce an ultra-fine grained ferrite-carbide microstructure prior to heat treatment. Improvement in fatigue resistance was especially pronounced when the material was heat treated to fine Bainitic, rather than Martensitic microstructures . These improvements are postulated to result from changes in crack propagation mode and improved resistance to fatigue crack propagation.