Rolling contact fatigue in bearings: multiscale overview

For over a century, rolling contact fatigue in bearings has been recognised as a key feature limiting bearing life. The phenomenon is manifested through dark etching regions, 30 and 80 degrees white etching bands as well as white etching areas, the latter often forming intricate defects commonly referred to as butterflies. Their presence depends on testing conditions, such as contact pressure, temperature, number of revolutions and steel cleanliness. Microstructural inspection demonstrates that precipitate shearing, dissolution, cell and nanocrystal formation as well as matrix/inclusion debonding may take place throughout bearing life. Such microstructural features have a negative effect on bearing hardness, strength, ductility and toughness, usually preceding failure. The present review shows how such phenomena are interconnected, highlighting the need for integral characterisation and modelling across the scales. This will aid in the conception of new heat treatments, steel grades and microstructures for enhanced rolling contact fatigue, leading to increased bearing life.