The Oxidational Wear of High-Chromium Ferritic Steel on Austenitic Stainless Steel

Experiments are described in which high-chromium ferritic steel pins were slid, without lubrication, against austenitic stainless steel disks, under loads varying from 7 to 95N and speeds varying from 0.23 to 3.3 ms−1. Although no external heating was supplied, all the worn surfaces were oxidized, as also was the wear debris, indicating that some form of mild wear always occurred under these conditions. Measurements were made, using a special tilt correction facility on the Scanning Electron Microscope, of the thicknesses of the oxide formed both on the pin and the disk surfaces, due to the evolution of frictional heating at the interface. The division of heat at the interface was also deduced from thermocouple measurements. These measurements, combined with the surface model used as the basis for the Oxidational Wear Theory, are shown to give rise to independent estimates of the contact temperature (Tc), the number of contacts beneath the pin at any instant (N), and the radius (a) of each of those contacts, that are consistent with those obtained in earlier published experiments involving the mild wear of low-alloy steels. In these earlier experiments, the validity of the estimates of N, Tc and “a,” depended upon the validity of the choice of Arrhenius Constant used in the Oxidational Wear Theory. The correlation between the two sets of estimates is discussed. Suggestions are made for further work to validate the Oxidational Theory of the mild wear of these industrially-important materials, particularly at elevated temperatures.