Friction and Surface Deformation During Sliding on a Single Crystal of Copper

Abstract

The effects of crystal orientation and temperature on sliding friction and surface deformation were studied by examination of indentations and wear tracks formed by styli on a single crystal of copper. Copper, diamond and sapphire indenters and sliders were used. Experiments were conducted at room temperature in air and in hydrogen at temperatures up to 800 C. The distribution of dislocation etch pits in the damaged regions was studied microscopically. Friction changed by 50 to over 500%, and track width changed by 15 to 35% as the direction of sliding on a given face in air was varied. These anisotropies are interpreted in terms of topography, work-hardening, and air oxide films. At higher temperatures diamond and sapphire sliders gave lower friction and larger track width than at room temperature. Friction obtained with copper sliders increased markedly with temperature. Surface deformation at intermediate temperatures resulted in recrystallization, and at higher temperatures polygonization resulted.