Paper 24: Dry Wear of Steel as Revealed by Electron Microscopy and X-Ray Diffraction

Abstract

Low-alloy, medium-carbon steel (AISI 4340) pins have been worn against discs of the same material at various loads under unlubricated (‘dry’) sliding conditions. Shadowed carbon replicas have been obtained from the surfaces of selected pins and discs. Transmission electron microscopy of these replicas revealed several interesting features, the most interesting being the presence of reproducible crack systems occurring in those parts of the surface at which the wear is taking place. These cracks are very similar to those obtained in fatigue failures. X-ray diffraction patterns were also obtained from these specimens, and from the corresponding wear debris. These indicated that oxidation had occurred at temperatures considerably in excess of the measured ambient temperatures. The various topographic and crystallographic features revealed by the electron microscopy and X-ray diffraction techniques are discussed in relation to a possible mechanism of ‘dry’ wear