Improvement of wear resistance for carbon steel under unlubricated sliding and variable loading conditions

► Unlubricated wear tests of steel were conducted under increased loading. ► The load was stepwise changed from low to high levels. ► Low wear rate was kept at loads much higher than critical load for constant loading. ► Thus a considerable improvement in wear resistance has been attained. ► This is due to formation of oxidized, work-hardened, flat surfaces at the low load.