The Application of Physical Methods of Analysis to the Study of Surface formed during Wear by Organo-Sulphur Compounds

Abstract

A variety of physical analytical techniques, among them Electron Probe Microanalysis, Scanning Electron Microscopy, X-ray Diffraction and Optical Microscopy, have already been used in the past to investigate the formation and role of surface films developed during wear tests using a four-ball machine to test extreme-pressure additives. Although the existence of such films has been confirmed by these techniques, and theories have been put forward in order to explain the reaction mechanisms of these additives, the actual surface composition is still not known precisely. This inability to define the chemical nature of these surface species is due mainly to the fact that the layers formed are extremely thin. To this effect, an investigation of the possibility of applying nuclear microprobes such as Rutherford Backscattering using 2 MeV alpha-particles and Deuteron-proton stripping reactions [(d,p) reactions], alongside the more conventional techniques, has been undertaken so that a total picture of the thickness and chemical composition of the films generated by the action of the sulphur additives could be drawn. The combination of the results from these different techniques has led to the evaluation of the thickness and to a better understanding of the formation of such films.