The influence of lubricant formulation on early thrust and radial bearing damage associated with white etching cracks

In the past, results have shown the influence of oil-additive systems in the life of rolling bearings, also hypotheses have been formulated on the influence of lubricant formulation on the development of early bearing damage associated with white etching cracks. In some earlier work of the authors with different operating conditions, early damage, and white etching cracks had been generated by mechanical stresses. In this study, tests with custom-made lubricants have been performed on thrust as well as radial bearings to clarify some assumptions. The tested oils differ only by the presence of three additives, but only one oil has led systematically to white etching cracks despite the fact that both oils lead to similar mechanical stresses. The results confirm that under mixed lubrication conditions with certain lubricant formulations, early damage, in particular white etching cracks, can be influenced by the oil-additive system likely affecting the bearing steel. Hypotheses are formulated and the influence of different parameters is discussed. This paper, combined with earlier work of the authors, confirms that the understanding and solution to an early bearing damage associated with white etching cracks can only be validated using the appropriate test method.