Clarification of the Puzzled Effects of Cold Work on Wear of Metals from the Viewpoint of Wearing Energy Consumption

Although it is known that strain-hardening helps enhance the wear resistance of metallic materials, puzzles or inconsistent phenomena still exist regarding the effect of strain-hardening on the wear resistance. It was reported that strain-hardening showed little or limited benefits to the wear resistance of some carbon steels. Besides, if the strain-hardening works, its benefit to the wear resistance may not be as large as expected. In this study, effects of strain-hardening (cold work) on dry sliding wear of Cu and Mg were investigated. The dry sliding wear tests were performed under different normal loads of 2 N, 5 N, 8 N, and 12 N, respectively, at the room temperature. It was demonstrated that the strain-hardening decreased Young’s moduli of Cu and Mg samples due to deteriorated crystalline integrity, which reduced the benefit of strain-hardening to their wear resistances. The strain-hardening benefited the FCC Cu more than the HCP Mg, and the effectiveness of strain-hardening decreased with the increase in the contact load. Relevant mechanisms are elucidated from the viewpoint of wearing energy consumption.