Bearing Grease Degradation Related to Water and Roller Bluing
The Federal Railroad Administration sponsored a team from Transportation Technology Center, Inc. to conduct two investigations to improve the safety of roller bearing operations on railcars. The team conducted the research between September 2018 and April 2022 in collaboration with Burlington Northern Santa Fe Railway, Timken Company, and Amsted Rail Company, Inc. to provide insight into the internal state of bearings that have degraded due to grease degradation from water ingress. The tests conducted in the investigation of water ingress-related bearing grease degradation indicated a difference between bearings with “Water-Etch” and “Non-Verified” failure modes based on ferrous debris levels in the grease. This difference is due to wear of the bearing material deposited in the grease. The tests conducted in the investigation of lube stain in bearings showed lube stain does not affect any tested metallurgical material properties other than surface discoloration. The team recommends that further grease samples should be taken to allow statistical inference of other variables other than ferrous wear, including contamination, consistency, and moisture levels.