Damage to rolling bearings due to overheating: severe discoloration of bearing components*). The raceway/rolling element plastic deformation is serious. The temperature changes sharply. Bearing sticks 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 Remedy: – Increase Bearing Clearance – If there is an external heat source, ensure slow heating and cooling, i.e. uniform heating of the entire set of bearings – Avoid lubricant build-up – Improve lubrication 47 Evaluate running characteristics and damage on dismantled bearings.

Contact Mode 77 of Rolling Bearings: Overheated FAG Cylindrical Roller Bearings with Deep Adhesive Indentations on the Rollers on the Raceways. *) 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.

Bearing scratches: For separable cylindrical roller bearings or tapered roller bearings, there is material missing from the rolling elements and raceways that is parallel to the axis and equidistant from the rolling elements. Sometimes there are several sets of marks in the circumferential direction. This trace is usually found only in the circumferential direction of about B/d rather than the entire circumference, see Figure 76. Cause: Misalignment and rubbing against each other when installing a single ferrule and a ferrule with rolling elements. It is especially dangerous when moving components of large mass (when the thick shaft with the bearing inner ring and rolling element assembly is pushed into the outer ring already installed in the bearing housing). Remedy: – Use suitable installation tools – Avoid misalignment – ​​If possible, turn slowly when installing components.