The high temperature sliding wear of stainless steel in a CO 2 atmosphere—The effect of adding low concentrations of O 2

Abstract

Sudden transitions in the friction and wear behaviour of stainless steel have recently been identified as a function of the sliding distance during high temperature sliding wear in CO 2. This work has studied the effect of making controlled additions of O 2 to CO 2 on such behaviour. The predominant effect is a significant fall in the number of cycles at which a severe-to-mild wear transition takes place, this being explained in terms of an increased rate of substrate hardening due to oxide inclusion into the subsurface layer. It is postulated that the enhanced rate of hardening is due to an acceleration in the linear oxidation rate of freshly revealed metal surface with increasing O 2 concentration. The present data are fitted to such a hypothesis on the basis of a previous model for the cycles to a transition; development of the previous model allows the fitting of the data with only one unknown parameter, the dissociation rate of CO 2. The best-fit value for this parameter is in reasonable agreement with that derived from existing linear oxidation data.