Understanding Microstructural Transitions Occurring Under Rolling Contact Fatigue

Rolling contact fatigue is accompanied by complex microstructural transitions occurring at a variety of scales; its understanding may lead to enhancing bearing life. However, a challenge faced by the metallurgist is the spread of scales at which contact fatigue spans. Alterations in precipitate morphology and cellular structures forming down to the scale of a few nanometres are common. This demands the use of a wide range of characterisation techniques. In addition to this, a quantitative description of the microstructural transitions remains a challenge. By employing high resolution experimental techniques, such as three dimensional atom probe, and by postulating new dislocation-based models for describing plasticity, the present work aims at providing a clearer view of the nature of white etching areas and dark etching regions. Observations down to the atomic scale indicate that carbon and silicon shun each other on the formation of nanometric cellular structures in white etching areas. Modelling indicates that dislocations may provide a vehicle for carbon transport in dark etching region formation. This provides a more integral picture of the transitions occurring throughout rolling contact fatigue in bearings.