Influence of Electrical Current on Bearing Flaking Life

A peculiar type of flaking occasionally occurs on bearings that are used in automotive electrical instruments. This flaking, which is called brittle flaking, is accompanied by a unique microstructure change consisting of a white structure below the surface of the bearing raceway. Brittle flaking prevention is necessary because it occurs after such a short time in some applications. The cause of brittle flaking is considered to be hydrogen embrittlement.

This paper presents the data from several tests in which direct current was passed through the bearings. The result was that the brittle flaking occurred on the bearing after a short time. Additionally, there was an increase in the amount of hydrogen retained in the bearing steel. By increasing the direct electrical current, the brittle flaking occurred in less time. Greases with various additives were tested in order to establish countermeasures for brittle flaking. A metal powder was found to be effective for preventing brittle flaking.