Effect of sliding speed on the tribological behavior of a PAN-pitch carbon-carbon composite

The study reports the effect of sliding speed on the tribological behavior of a two-dimensional polyacrylonitrile fiber-reinforced pitch matrix carbon-carbon composite. When the composite was slid at 800 and 1100 rpm, no transition of any kind was observed. A thin, smooth lubricative film was formed on the worn surfaces, and both friction (0.1-0.2) and wear (0.10 mg cm^-2) were low throughout all tests. At speeds of 1400 rpm and higher, the composite experienced concurrent transitions in friction, wear and surface morphology. The higher the speed, the shorter the sliding distance at which the transitions occurred. In the pre-transitional period, a smooth film was formed and the friction and wear were as low as those observed at lower speeds. When the transition took place, a thick powdery debris layer was quickly generated and the friction and wear rose abruptly (the friction coefficients rose to 0.6-0.7). This powdery debris was subsequently transformed into a smooth, lubricative film, causing the friction to decline to 0.4-0.5. At 800 and 1100 rpm, the temperatures induced in the friction and wear process were roughly 100 °C at all times. When a frictional transition occurred, the temperatures rose abruptly. At 2300 rpm, the temperature rose to as high as 900 °C at the conclusion of 66 m of sliding.