Wear of graphite and PAN-pitch carbon-carbon composites

The present paper reports low-energy wear behavior of two-dimensional (2D) and three-dimensional (3D) PAN-pitch based carbon-carbon composites as well as a commercial bulk graphite. Results indicate that, under the same conditions, the 2D composite at all times has a larger weight loss than those of the 3D composite and the bulk graphite. In the first few minutes of wear, weight loss of the 2D is an order of magnitude higher than those of the other two materials. With time, the wear rate of the 2D keeps decreasing and eventually approaches to a level comparable to the other two materials. Scanning electron microscopy shows that formation of a debris film is critical to the wear behavior of all three materials. Once a smooth, adherent and uniform debris film has been developed on the sliding surfaces, the wear rates dropped at the same time due to a lubricative effect. The much larger wear in the wear-in period, for the 2D composite, might be explained by the quick formation of powdery debris which presumably escapes from the sliding surfaces more easily.