Plain bearing failure index

9.0 Incompatible Journal or Thrust Collar Material

Incompatible Journal or Thrust Collar Material Index


9.2 Wire-Wool Failure of Journal and Thrust Bearing

Click on photograph to enlarge
	Wire-wool failure of journal bearing
	Wire-wool failure: damage to journal and thrust collar corresponding to the bearing in Photograph 'a' above.
Main Characteristics	Identified by extensive damage to both bearing and the journal and/or thrust collar with wear products from the shaft collected in the bearing housing where they look like wire wool. A black scab is also often present on the damaged surface, hence the alternative name 'black scab failure'.
Cause	This failure occurs when a small particle of hard dirt or swarf gets embedded in the bearing material, but continues to rub against the steel counterface. At high speed the temperature generated by the frictional rub carburises the chromium in the steel in the presence of a hydrocarbon oil, producing hard chromium carbides that embed in the soft bearing material and act as cutting tools on the journal or thrust collar. The process continues by accretion of the embedded carbides and may result in a journal being turned completely through.
Note	Although wire-wool failures have been most frequently encountered with whitte metals bearings, they can also occur with copper bearing alloys.
Possible Confusion with Other Types of Damage
Comment	The best solution is to limit the chromium content of the steel to 1.5% where surface speeds are greater than 25 m/sec.

Services Index
Site Map
Home page