Abstract
The life cycle of any drive train is given by the reliability of its individual components, e.g., bearings, gears, and their connections. Lubrication as a part prevents wear caused by uncontrolled mixed friction. However, lubricants may interfere in the load capacity of the steel due to chemical and physical processes. White etching crack (WEC) failures are one of the most prominent failure mechanisms supposed to be related to this topic. In order to understand its initiation and progression we carried out a series of tests in the FE8 test rig proven to reproduce WECs by lubrication chemistry. These tests were stopped at an early stage.All lubricant compositions leading to WECs showed pores in the subsurface starting in a depth of about 80 μm as an early state phenomenon, while oils not leading to WECs did not show any changes in a comparable test time. Modifications of the microstructure like new grain boundaries were found next to the pore sites by the use of SEM SE/BSE imaging and EBSD mappings. The present investigations give valuable insight into the formation mechanisms of WECs and on the role of different lubricants in the failure process.
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