States, describes and classifies the characteristics, changes in appearance and possible causes of failure of rolling bearings, occurring in service. It will assist in the understanding of the various forms of change in appearance and the failure that has occurred.

This document classifies different modes of failure occurring in service for rolling bearings made of standard bearing steels. For each failure mode, it defines and describes the characteristics, appearance and possible root causes of failure. It will assist in the identification of failure modes based on appearance.

For the purposes of this document, the following terms are explained:

• failure of a rolling bearing: the result of a damage that prevents the bearing meeting the intended design performance or marks the end of service life;

• in service: as soon as the bearing has left the manufacturer’s factory;

• visible features: those that are possible to observe directly or with magnifiers or optical microscopes, also those from pictures, but only with the use of non-destructive methods.

Consideration is restricted to characteristic forms of change in appearance and failure that have well-defined appearance and which can be attributed to particular causes with a high degree of certainty. The features of particular interest for explaining changes and failures are described. The various forms are illustrated with photographs and the most frequent causes are indicated.

If the root cause cannot be reliably assessed by the examination and characterization of visual features against the information in this document, then additional investigations are to be considered. These methods are summarized in A.3 and may involve, for example, the use of invasive methods possibly including taking of cross sections, metallurgical structural analysis by visual and electronic microscopes, chemical and spectrographic analysis. These specialized methods are outside the scope of this document.

The failure mode terms shown in the subclause titles are recommended for general use. Where appropriate, alternative expressions or synonyms used to describe the submodes are given and explained in A.4.

Examples of rolling bearing failures are given in A.2, together with a description of the causes of failure and proposed corrective actions.