The unlubricated sliding of AlSi alloys against steel: Mössbauer spectroscopy and X-ray diffraction of wear debris

The behaviour of iron atoms during the unlubricated sliding of AlSi alloys against a steel countersurface has been investigated. Mössbauer spectroscopy and X-ray diffraction have been used to identify the form of the iron that was present in the mostly aluminium surface layers that were formed by the wearing process. The iron was found to exist mostly as elemental iron, 57–80 at.%, with a significant amount as Fe 2+, 14–29 at.%. The Fe 2+ was probably a finely dispersed amorphous iron oxide which, it is suggested, increases the stability of the surface layers by pinning the grain boundaries.