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 

Discoloration of cages, rolling elements and raceway rings occurs due to their reacting with lubricant at high temperature.

Possible Causes

Countermeasures

Discoloration 1

Part: Inner ring of an angular contact ball bearing
Symptom: Bluish or purplish Discoloration on raceway surface
Cause: Heat generation due to poor lubrication

Discoloration 2

Part: Inner ring of a 4-point contact ball bearing
Symptom: Bluish or purplish Discoloration on raceway surface
Cause: Heat generation due to poor lubrication

Source: NSK