Effect of impregnant on tribological behavior of silicon carbide and carbon-graphite pairs

Silicon carbide in homogeneous contact is commonly used in lubricated conditions. Sometimes in pin-on-disc configuration, it is used in dry friction. In this study, we developed experiments with a ring-on-ring configuration under dry friction in order to fit with new mechanical seal applications. A SiC/SiC pair and a SiC/Carbon-Graphite (CG) pair are used as references. A comparison of tribological behavior is proposed for 3 pairs realized with a SiC ring and a CG ring impregnated with antimony, phenolic resin and PTFE. The choice of the impregnant takes in account their accommodation mechanisms in the contact and their thermal diffusion properties. Tribological tests were run at 3 different temperatures (ambient, 120°C and 300°C), 3 speeds (0.5, 1 and 2 m/s) and different contact pressure (0.5, 0,75 and 1 MPa) with an environmental tribometer. During tests, the thermal gradient is recorded via an IR camera. Results are presented in term of friction coefficients and wear. Characterization of the tribofilm is obtained by using MEB, EDX and Raman spectroscopy. This vibrational spectroscopy is also used to investigate the evolution of mechanical stress at the surface of the 2 rings and for every pairs. We propose a mechanism of creation of the third body and the effect of the environment on it. The material flow in and out of the contact is detailed and the energy balance is discussed.