Effect of densification cycles on continuous friction behavior of carbon–carbon composites

This paper studies the continuous friction behavior of carbon–carbon composites (C/C) fabricated by the coal tar pitch densification process. In the densification process, different numbers of densification cycle are adopted to investigate the influence on physical properties, mechanical properties, microstructure and friction behavior. Experimental results indicate that open porosity decreases with the number of densification cycle. Both bulk density and flexural strength increase with the number of densification cycle. Apparent reduction in wear rate and average friction coefficient can be detected even if the lower densification cycle is adopted. As the number of densification cycle increases, C/C specimens exhibit the lower wear rate and smoother friction coefficient curves. Morphological observations show that the number of open pores for these materials decreases and they exhibit a denser morphology as the number of densification cycle increases. Furthermore, as the number of densification cycle increases, a smooth, adherent lubricating film is formed on the sliding surface. Therefore, the variation in average friction coefficient of specimens becomes smoother; in the meantime, the wear rate becomes lower.