Traditional techniques for the evaluation of a rolling bearing material or lubricant rely on the accelerated life testing of large lots of bearings. The rating of the bearing performance is then established on the basis of statistical estimates of the experimental Weibull parameters.

Optical evaluation of bearing surfaces has long been used to supplement life data. However, optical examination is limited to evaluating the validity of specific test points. Another surface analysis technique, scanning electron microscopy (SEM), can now be used to augment test data because of the high magnifications and depth of field available. SEM examination of tested surfaces at magnifications up to ×1000 can define alterations in surface morphology produced by wear, fatigue, and corrosive failure modes long before signs would be detectable by optical means or failure would be precipitated. These characteristics can be qualitatively evaluated to supplement collected life data, and comparisons can yield relative evaluations of bearing performance. In this manner, meaningful long-range performance projections can be obtained using small test groups.

An example of the application of this technique for the evaluation of a series of synthetic lubricants and mineral oils is presented in this paper.