Discoloration of cages, rolling elements and raceway rings occurs due to their reacting with lubricant at high temperature.
Poor lubrication
Oil stain due to a reaction with lubricant
High temperature
Improve the lubrication method
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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