Wear Behavior of Cu–Zn Alloy by Ultrasonic Nanocrystalline Surface Modification

The ultrasonic nanocrystalline surface modification (UNSM) was applied to disk specimens made of Cu–Zn alloy in order to investigate the UNSM effects under five various conditions on wear of deformation twinning. In this paper, ball-on-disk test was conducted, and the results of UNSM-treated specimens showed that surface layer dislocation density and multi-directional twins were abruptly increased, and the grain size was altered into nano scale. UNSM delivers force onto the workpiece surface 20,000 times per second with 1,000 to 4,000 contact counts per square millimeter. The UNSM technology creates nanocrystalline and deformation twinning on the workpiece surface. One of the main concepts of this study is that defined phenomena of the UNSM technology, and the results revealed that nanocrystalline and deformation twinning depth might be controlled by means of impact energy of UNSM technology. EBSD and TEM analyses showed that deformation layer was increased up to 268 μm, and initial twin density was 0.001 × 10⁶ cm⁻² and increased up to 0.343 × 10⁶ cm⁻². Wear volume loss was also decreased from 703 × 10³ mm³ to 387 × 10³ mm³. Wear behavior according to deformation depth was observed under three different combinations. This is related to deformation depth which was created by UNSM technology.