Failure mechanisms in motor bearings

Defective bearings of a motor were investigated for possible mechanisms leading to their premature failure during manufacturing. Detailed studies including visual examination, optical microscopy and scanning electron microscopy were performed to determine the root cause(s) for failure. Based on the results of visual examination, microstructure and fracture surface analysis and the process details for the bearing, it was determined that the motor bearing failed mainly due to improper sintering process and the variation in chemical composition of top layer (containing copper, lead and tin) of the bearing that is bonded to steel base material.