X-Ray Diffraction in Failure Analysis of Rolling Bearings

Abstract

By X-ray diffraction (XRD) measurements, material conditions of rolling bearings are red that point to a variety of load possibilities especially at raceway surfaces. Due to unambiguously distinguishable damage symptoms, according to H. Muro, it is differentiated between the surface and sub-surface failure mode in the literature. Surface distress of different intensity can be generated by particle-contaminated lubricants that result in raceway indentations. These micro-Hertzian contacts may lead to changes in residual stress and line broadening and in the microstructure. Another cause of surface distress is boundary lubrication. Relevant position and nature of the failure mechanisms are characterized. In case of initial material stabilization, the time alterations of the XRD parameters correlate with the statistical parameter of the 10 % bearing life. Contrary to the L10 value for sub-surface fatigue, which leads to spalling only a long time after incipient material softening, in the surface damage mode the L10 life roughly coincides with the beginning of the instability phase. Surface pitting or gray staining turns up frequently with low XRD indication of material aging. Here, scanning electron microscopy and electron microprobe analysis point to corrosion fatigue. The interaction between material and lubricant opens research in the field of tribology.