Effect of brake pressure and brake speed on the tribological properties of carbon/carbon composites with different pyrocarbon textures

Effect of brake pressure and brake speed on the tribological properties of carbon/carbon (C/C) composites with a single-layered smooth laminar (SL) pyrocarbon texture and a double-layered rough laminar (RL) and SL pyrocarbon texture was investigated using a friction performance tester. The morphology of the worn surface and wear debris was observed by scanning electron microscopy (SEM) and optical microscopy (OM). The results showed that the average friction coefficient reduced and the braking stability increased when a smooth and completed friction film formed gradually on the worn surface under higher brake pressure or brake speed, whereas the mass wear and linear wear increased under these conditions due to the flake damage of friction film and high oxidation loss. Moreover, the average friction coefficient reached the maximum value under the brake pressure of 0.6 MPa and the brake speed of 15 m/s. C/C composites with the double-layered RL and SL texture had more stable friction and lower wear than those with the single-layered SL texture under the same braking condition owing to the formation of the more completed friction film and the lower oxidation loss.

Research highlights▶ The average friction coefficient decreases and the braking stability increases when a smooth and completed friction film forms under higher brake pressure or brake speed. ▶ The mass wear and linear wear increase under higher brake pressure or brake speed due to the flake damage of friction film and the high temperature oxidation. ▶ C/C composites with the double-layered RL and SL texture have more stable friction and lower wear than those with the single-layered SL texture under the same braking condition.