Effects of the high-temperature treatment of C/C composites on their tribological properties

C/C composites prepared by chemical vapor infiltration (CVI) were subjected to high temperature treatment (HTT) at 2300 degrees C under an Ar atmosphere. C/C-SiC composites were prepared by liquid silicon infiltration (LSI) of the C/C composites before HTT. The C/C composites before (A) and after (B) HTT were mated with the C/C-SiC to form friction pairs to investigate their tribological properties. Results indicated that the average coefficient of friction (COF) and stable COF of the C/C-B are 0.280 and 0.65 while that of the C/C-B are 0.451 and 0.55, respectively. The average linear wear rate of the C/C-A and the C/C-B are 3.7 and 8.9 um/(slide cycle), respectively. SEM reveals that the wear debris of the C/C-A is particulate while that of the C/C-B are the sheets, and the friction surface is more flat for C/C-B than C/C-A. HTT leads to a softening of the carbon, increases the wear rate, but improves the stable COF of the C/C composites. The wear mechanisms of the composites are mainly grain-abrasion, oxidation loss and fatigue wear.