Influence of surface burnishing process with single strain path and reciprocating strain path on copper wear behavior

Abstract

A single strain path (SSP) and reciprocating strain path (RSP) burnishing processes are implemented on copper surfaces using a multi-ball surface burnishing tool. Dry wear tests are performed on both machined samples to investigate the effect of different strain paths on the wear behavior. A backscattered scanning electron microscope and nanoindentation are operated to characterize the microstructure and mechanical properties between samples machined via different strain paths. Molecular dynamics models are developed to explore the mechanism that enhances wear resistance through the gradient grain structure in the surface layers machined by SSP and RSP. The wear test results show that the wear scar volumes of the SSP treated samples are about 70% of the original samples, while the RSP treated samples are about 60%, indicating that the RSP further enhances the wear resistance of copper. Compared to SSP machining, RSP machining activates the Bauschinger effect in the copper to produce the gradient structure with a larger thickness (500 μm–700 μm) and greater hardness (1.72 GPa–1.82 GPa). Consequently, RSP machining further improves the resistance to crack initiation and expansion, resistance to plastic deformation, total strain capacity, and elastic recovery in the wear process, which is why samples machined with RSP have better wear resistance.