Tribological Behavior And Structure Evolution Of Cu Sliding Against GCr15with Increasing Sliding Distance

During sliding friction, the metal material often show the very bright side. The material surface often be strengthened in response to plastic deformation. For many metals and alloys (especially ductile metals), grain refinement of material located at nearby area of contact surface is an important strengthening mechanism that induced by wear deformation. In this paper, the tribological properties of pure copper and the deformation of sub-surface located at the nearby contact surface were investigated using the ball-plate contact mode of the Swiss company CSEM THT07-135high temperature friction and wear testing machine. The pure copper was plate, and GCrl5was ball. The experimental load and sliding speed was2N,2cm/s respectively. A series dry sliding friction experiments was done under different sliding distance condition. The tribological properties and the sub-surface deformation of pure copper be analysed by scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy under the condition of low load and low speed of sliding friction. The main research results are as follows:(1) Under the condition of low speed and low load of sliding friction, with the increase of sliding distance, the friction and wear behaviors of pure copper could be divided into three stages, which had different friction and wear mechanisms. During running-in stage, dual furrow, adhesion effect and the serious plastic deformation in the surface of pure copper resulted in that the friction coefficient was unstable greatly, but the wear rate was very small. During unstable friction stage, with the increase of dislocation density, surface plastic deformation was weakened, and the wear was mainly caused by fatigue fracture and delamination. During stable friction stage, with the accumulation of defect, such as dislocation and grain boundary in near surface material, and the release of deformation storage, oxydic wear became the main form.(2) Under the condition of low speed and low load of sliding friction, layered structure occurred in the sub-surface of pure copper, which were decided by equivalent strain gradient induced by plastic deformation and shear localization, and with the increase of sliding distance, the thickness of layered structure increased. Layered structure was turned around gradually along sliding direction, or parallel to the sliding direction. At last, the grain of pure copper was refined and nanometer frictional layer formed.(3) Under the condition of low speed and low load of sliding friction, with the increase of sliding distance, the formed stable nanometer frictional layer, the lubrication action of copper oxide and the reduction of transfer amount of copper in the dual ball all all had important effect to improve the wear-resisting ability of material.