Burnishing Wear Mechanism of Thin Carbon Film during High Speed Sliding Contact
Chang-Dong Yeo (Texas Tech University), Sungae Lee ()
Contact Mechanics
Tue 10:45 - 12:15
Barus-Holley 163
Thin carbon films are widely used for surface protection of micro/nano-devices under dynamic or quasi-static contact. When the systems are performing high speed sliding contact (i.e., rough surface contact without any third body particles in the interface), the carbon coating is usually worn out by burnishing behavior. Considering the sliding contact typically causes frictional heat flux to the surfaces, the burnishing wear mechanism should take account of the effects of both mechanical stress and material temperature rise. In this study, the thermomechanical contact of thin carbon film is systematically investigated through analytical modeling, whose results are compared with the actual burnishing failure of carbon product. During the sliding contact between two rough surfaces, the mechanical stress is determined from the improved contact model, while the material temperature is calculated from the frictional heat flux and theory of transient heat transfer. From the parametric simulations, it was observed that the mechanical contact stress was not high enough to cause material yielding on carbon film, but the temperature significantly increased beyond the critical value to initiate thermal degradation of carbon atoms (i.e., phase change from sp3 rich to sp2 rich structure). Due to this graphitization (or material softening) process, the carbon film could be worn out by much lower contact stress. Therefore, it could be concluded that the burnishing wear mechanism of carbon film cannot be explained by the mechanical stress only but should include the thermal stability of carbon as well.