The effects of non-friction time and atmosphere in friction/non-friction areas on the wear of metals

▶ Finding of the logarithmical increase of wear of metals as a function of non-friction time. ▶ Finding of the different roles of the atmosphere of friction area and non-friction area. ▶ Finding of the atmosphere of friction area to increase severe wear. ▶ Finding of the atmosphere of non-friction area to induce mild wear. In repeated sliding wear tests of the pin-on-disk type, all of the wear track of the disk is not simultaneously in sliding contact with the pin. Accordingly, except for the actual duration of the contact, the disk is not sliding against the pin. We call this period the “non-friction time”. The present paper demonstrates that metals exhibit higher wear with increased non-friction time in severe wear mode. The mechanisms will be discussed with regard to the role of atmosphere in friction/non-friction areas. The effects of atmosphere around the friction area and the non-friction area are presented; oxygen atmosphere in the friction area increases severe wear, on the other hand, oxygen atmosphere in the non-friction area is influential for mild wear.