While in the stationary mode, capillary action at the contact line between roller and race in a steel rolling mill taper bearing caused a concentration of lubricant and moisture to occur. This lead to lines of corrosion pits at roller intervals. During subsequent operation, the individual corrosion pits acted as stress raisers and initiated coarse grain spalling. Due to a bending moment on the rotating element, this in turn initiated bending fatigue normal to the longitudinal axis, which propagated through to the bore of the inner ring. Stain marks were visible in the bore at a spacing corresponding to roller intervals where lubricant had flowed through the cracks from the race.

The contamination of lubrication with powdered stone resulted in progressive wear of the internal surfaces of a bearing. Because of the motion of rollers, the inner race exhibited an unusual cyclic washboard wear pattern. Because of a lack of bearing conformity, wear progressed into severe coarse-grain spalling.

Butterfly-shaped microstructural features in tempered martensite in an otherwise clean steel suggested that overloading led to premature spalling of a coal-crushing plant taper bearing. Extensive rolling contact fatigue occurred because of the overload condition. The crusher was designed to handle soft lignite coals but had been used to crush hard deep-mined anthracite coals.

Incorrect grounding of an electric motor resulted in electric current passing through a 52100 steel ball bearing and caused multiple arcing between the rolling elements. The multiple arcing developed a pattern on the outer race known as ‘fluting’. A section of ball race outer showed the distinct banding (fluting) resulting from spark discharges while the bearing was rotating. The severe distress of the surface resulted in unacceptable levels of vibration. An SEM photograph of the banded regions showed smoothing of the asperities from continued operation is evident. In the craters the residue of partial melting was seen.