Smearing, seizure and creep
Three failures with very different causes: sliding without an oil film, a bearing that has melted together, and a ring that turns on its seat.
Smearing
Smearing is minute seizure on the rolling surface. The surface melts in places from frictional heat, and the damaged area becomes very rough. It happens when the oil film disappears and rolling elements stop rotating, then slide on the raceway. In ball bearings it comes from balls sliding or spinning; in roller bearings it tends to start when a roller enters the load zone.
Smearing: countermeasures
- Improve the formation of the oil film.
- Use an extreme-pressure lubricant.
- Prevent sliding, for example by reducing the mounting clearance.
Seizure
Seizure is the more serious end of scuffing and smearing: parts melt and stick together because of heat or rough rolling surfaces, and the bearing can no longer turn. The cause is abnormal heat from poor lubrication, excessive preload or poor contact of rolling elements with the raceway that cooling and lubrication cannot cope with. A seized bearing cannot be used again because the hardness has fallen and the surface is rough.
Seizure: countermeasure
Find the cause, then take the measures that match the result.
Creep
Creep is movement of a bearing ring relative to the shaft or the housing while running. It happens when the interference is too small for the heat or the load.
Creep: countermeasure
Review the fit between inner ring and shaft and between outer ring and housing, and increase the interference.