Critical Assessment 13: Elimination of white etching matter in bearing steels

One form of damage due to rolling contact fatigue is the formation of localised regions of extremely hard material forming within the body of a bearing. These regions have a relatively homogeneous structure and hence etch mildly with respect to the surrounding unaffected matrix. They, therefore, appear white in a darker background when examined using optical microscopy. We assess here the cause of this damage and propose solutions that are backed by evidence that already is available. The issue is important because of the spate of unexpected failures in large wind turbine bearings and of generic importance in determining the life of more well behaved bearing applications.