Optical and Other Properties Changes of M-50 Bearing Steel Surfaces for Different Lubricants and Additives Prior to Scuffing

Abstract

An ester lubricant base oil containing one or more standard additives to protect against wear, corrosion, and oxidation was used in an experimental ball/plate elastohydrodynamic contact under load and speed conditions such as to induce scuffing failure in short times. Both the ball and the plate were of identically treated M-50 steel. After various periods of operating time, the wear track on the plate was examined (a) with an interference microscope of ± 30 A depth resolution and (b) sometimes also with a scanning ellipsometer, and (c) a scanning Auger spectrometer. The optically deduced surface profiles varied with wavelength, indicating the presence of surface coatings, which were confirmed by the other instrumentations. As scuffing was approached, a thin (∼40 A) oxide layer and a carbide layer formed in the wear track, in particular, when tricresylphosphate antiwear additive was present in the lubricant. The rates of the formation of these layers and their reactivity toward dilute alcoholic HCl depend...