Chemical reaction in the wear of MgO single crystals on steel was studied. When MgO single crystals were worn on the steel (S15C) disk at the sliding speed of 50 m/s and at the contact load of 200 g, an element and a state analysis of surface layers produced on the wear surface were carried out using the electron probe X-ray micro analyser.
Oxidation of iron and diffusion of Fe into MgO single crystals were confirmed. The results of state analysis indicated that the oxide of iron was FeO and there was a diffusion process in MgO-FeO system in the wear interface. The interfacial material detected on the wear surface was magnesio-wustite. This wear may be also explained by a mechanism in which the surface layer was delaminated by fatigue caused after many cycles of repeated loading.