Damage to rolling bearings due to overheating: severe discoloration of bearing components*). The raceway/rolling element plastic deformation is serious. The temperature changes sharply. The FAG bearing has been stuck several times, see Figure 77. The hardness is lower than 58HRC. Reason: Failure of bearings due to overheating is usually no longer detected. Possible causes: – The working clearance of the bearing is too small, especially at high speeds – Insufficient lubrication – Radial preload due to external heat sources – Excessive lubricant – Impeded operation due to cage fracture.

Remedial measures: – Increase bearing clearance – If there is an external heat source, ensure slow heating and cooling, i.e. uniform heating of the entire bearing set – Avoid lubricant build-up – Improve lubrication Contact Mode 77: Overheated cylindrical roller bearing with deep adhesive indentations on the raceways of the rollers. *) Explanation of discoloration: When the bearing takes on a tempered color, it is related to overheating. The appearance of brown and blue is related to the temperature and duration of overheating. This phenomenon is very similar to the coloration of the lubricating oil due to its high temperature (see chapter 3.3.1.1). Therefore, it is not possible to judge whether the operating temperature is too high only from the discoloration. It can be judged from the discoloration area whether it is caused by tempering or by grease: the latter usually only occurs in the load-bearing area of ​​the rolling elements and rings, and the former usually covers a large area of ​​the bearing surface. However, the only identifying measure for the presence or absence of high temperature operation is hardness testing.