1. Metal peeling on the raceway surface
The rolling elements of the bearing and the raceway surfaces of the inner and outer rings are subjected to periodic pulsating loads, resulting in cyclically varying contact stress. When the number of stress cycles reaches a certain value, fatigue spalling occurs on the rolling elements or the working surfaces of the inner and outer ring raceways. This fatigue is exacerbated if the bearing is overloaded. In addition, if the bearing is not installed correctly and the shaft is bent, the phenomenon of raceway peeling will also occur.
Fatigue spalling of the bearing raceway will reduce the running accuracy of the shaft, causing vibration and noise in the mechanism.

2. Bearing burns
Burned bearings have tempered color on their raceways and rolling elements. The causes of burns are generally insufficient lubrication, unsatisfactory quality or deterioration of lubricating oil, and excessively tight bearing assembly.

3. Plastic deformation
The uneven pits appear on the contact surface between the raceway and the roller of the bearing, indicating that the bearing has plastic deformation. The reason is that under the action of a large static load or impact load, the local stress of the working surface exceeds the yield limit of the material, which generally occurs on bearings rotating at low speeds.

4. Bearing race crack
The reason for the cracks in the bearing race may be that the bearing is too tight, the bearing or inner ring is loose, the bearing part is deformed, and the surface of the installed bearing is poorly machined.

5. Cage broken
The reasons are insufficient lubrication, broken rolling elements, skewed races, etc.

6. The metal of the cage adheres to the rolling elements
Possible causes are rolling elements stuck in the cage or insufficient lubrication.