Damage to rolling bearings caused by overheating: severe discoloration of bearing components*). The raceway/rolling body has serious plastic deformation. The temperature changes drastically. The bearing has stuck several times, see Fig. 77. The hardness is lower than 58HRC. Reason: usually no longer detect failed bearings due to overheating. Possible reasons: The working clearance of the bearing is too small, especially the bearing at high speed. Insufficient lubrication. Radial preload caused by external heat source. Excessive lubricant. The operation is blocked due to the fracture of the cage. Remedial measures: Increase the bearing clearance. If there is an external heat source, ensure slow heating and cooling, that is, heat the entire set of bearings evenly, avoid accumulation of lubricant, improve lubrication 47, evaluate the running characteristics and damage of the removed bearing. Rolling contact mode 77: The rollers of the overheated cylindrical roller bearing have deep glued impressions on the raceways. *) Description of discoloration: When the bearing shows a tempered color, it is related to overheating. The brown and blue appearance is related to the temperature and the length of overheating time. This phenomenon is very similar to the phenomenon of coloring due to high lubricating oil temperature (see section 3.3.1.1). Therefore, it is not possible to judge whether the operating temperature is too high from the discoloration alone. From the discoloration area, it can be judged whether the discoloration is caused by tempering or grease: the latter usually only appears in the load-bearing area of u200bu200brolling elements and rings, while the former usually covers a large area on the bearing surface. However, the only way to determine whether there is high temperature operation is hardness testing.