Abstract
Pin-on-disk type wear tests of 0.35 % C steel in contact with itself were conducted in moist air at various contact loads under dry sliding. The friction and wear were measured continuously throughout the tests. After the tests, the relationship between friction and wear and the difference in properties of the wear surfaces were investigated in each wear mode. The phenomenon of zero wear appears in the early period when the tests are conducted at very low loads. The zero wear continues for a long sliding distance and then changes to mild wear. The specific wear rate is constant irrespective of load in the mild and severe wear regimes. The atomic mass percentage of oxygen and coverage of oxidized surface film on the wear surface of disk increases with sliding distance.