WEAR BY FRICTION BETWEEN DIAMONDS STUDIED BY ELECTRON-MICROSCOPIC TECHNIQUES

This paper deals with an experimental study of possible structural cha nges which occur upon frictional sliding of a diamond stylus on a diam ond flat. Reflection electron energy loss spectroscopy in the scanning transmission electron microscope has been applied to determine the st ructure of a cleaved {111} diamond surface, of a friction track on thi s surface and of the debris produced during frictional sliding. The st ructure of the debris appeared to be graphitic and different from the structure of the surface in the track, which was still diamond. As the surface studied was the cleaved {111} face, which is the hardest surf ace of diamond, it is assumed that the debris mainly consists of mater ial originally belonging to the stylus. So far, no definite conclusion can be drawn about when the transformation of diamond into less dense forms of carbon takes place. The debris acts as a lubricating materia l which is demonstrated by monitoring the friction coefficient upon re moving debris from the stylus. The outcome of this type of research is expected to throw light on the friction and polishing behaviour of di fferent diamond surfaces. With the improving control of the orientatio nal growth of CVD diamond, results will also be relevant to the fricti on and processing of these polycrystalline diamond surfaces.