Bearing Failure RCA: Flaking

 

When a rolling bearing is damaged during machine operation, the entire machine or equipment can seize or malfunction. Since bearings that fail prematurely or unexpectedly cause trouble, it is important to be able to identify and predict failure beforehand, so that preventive measures can be adopted.

Damage Condition

Flaking occurs when small pieces of bearing material are split off from the smooth surface of the raceway or rolling elements due to rolling fatigue, thereby creating regions having rough and coarse texture.

Possible Causes

  • Excessive load
  • Poor mounting (misalignment)
  • Moment load
  • Entry of foreign debris, water penetration
  • Poor lubrication, improper lubricant
  • Unsuitable bearing clearance
  • Improper precision for shaft or housing, unevenness in housing rigidity, large shaft bending
  • Progression from rust, corrosion pits, Smearing, dents (brinelling)

Countermeasures

  • Reconfirm the bearing application and check the load conditions
  • Improve the mounting method
  • Improve the sealing mechanism, prevent rusting during non-running
  • Use a lubricant with a proper viscosity, improve the lubrication method
  • Check the precision of shaft and housing
  • Check the bearing internal clearance

 

Flaking 1

Part: Inner ring of an angular contact ball bearing
Symptom: Flaking around half of the circumference of the raceway surface
Cause: Poor lubrication due to entry of cutting coolant into bearing

 

Flaking 2

Part: Inner ring of an angular contact ball bearing
Symptom: Flaking diagonally along raceway
Cause: Poor alignment between shaft and housing during mounting

 

Flaking 3

Part: Inner ring of deep groove ball bearing
Symptom: Flaking of raceway at ball pitch
Cause: Dents due to shock load during mounting

 

Flaking 4

Part: Inner ring of an angular contact ball bearing
Symptom: Flaking of raceway at ball pitch
Cause: Dents due to shock load while stationary

 

Flaking 5

Part: Outer ring of damage “Flaking 4”
Symptom: Flaking of raceway surface at ball pitch
Cause: Dents due to shock load while stationary

 

Flaking 6

Part: Balls of damage “Flaking 4”
Symptom: Flaking of ball surface
Cause: Dents due to shock load while stationary

 

Flaking 7

Part: Inner ring of a spherical roller bearing
Symptom: Flaking of only one raceway over its entire circumference
Cause: Excessive axial load

 

Flaking 8

Part: Outer ring of damage “Flaking 7”
Symptom: Flaking of only one raceway over its entire circumference
Cause: Excessive axial load

 

Flaking 9

Part: Inner ring of a spherical roller bearing
Symptom: Flaking of only one row of raceway
Cause: Poor lubrication

 

Flaking 10

Part: Rollers of a cylindrical roller bearing
Symptom: Premature Flaking occurs axially on the rolling surfaces
Cause: Scratches caused during improper mounting


Source: NSK