SYMPOSIA PAPER Published: 08 September 2020

Lubricant-Induced White Etching Cracks: Mechanism and Effects of Surface Finishing


Cylindrical roller thrust bearings (CRTBs) were fatigue tested in various lubricants under rolling-sliding conditions. The bearings exhibited premature damage when the tests were performed in a lubricant containing significant additives (referred to in this paper as “test gear oil”). Bearing life in the test gear oil was less than 5% of bearing life when tested in a mineral oil containing no additives. Investigations on posttest bearings from the test gear oil revealed localized raised areas on the tribosurfaces of the raceways. Upon further examination, subsurface white etching cracks (WECs) were observed beneath the raised surface features. The raised areas resembled hydrogen-induced blisters. Subsequent thermal desorption spectroscopy analysis of the bearing races with the raised features revealed hydrogen evolution from the posttest raceways. In contrast, races exhibited typical point surface origin (PSO)-type damage when the bearings were tested in plain mineral oil. Also, there were no subsurface crack networks or white etching features associated with the PSO spalling damage. Additional tests were performed with embedded abrasive particles that were introduced onto the raceways using a lapping process. Posttest investigations showed neither the raceways nor the rollers contained WECs, and the damage mode had changed even though they were tested in the test gear oil. Although WECs are generated in the subsurface, their formation depends on the surface condition of the raceways, so these results suggest that WEC formation is a surface-driven phenomenon. Based on these insights, possible WEC mitigation and prevention methods are discussed.

Author Information

Paladugu, Mohanchand
The Timken Company World Headquarters, North Canton, OH, US
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Pages: 131–146
DOI: 10.1520/STP162320190112
ISBN-EB: 978-0-8031-7693-5
ISBN-13: 978-0-8031-7692-8