Shangwu Fan

Microstructure and frictional properties of 3D needled C/SiC brake materials modified with graphite

The 3D needled C/SiC brake materials modified with graphite were prepared by a combined process of the chemical vapor infiltration, slurry infiltration and liquid silicon infiltration process. The microstructure and frictional properties of the brake materials were investigated. The density and open porosity of the materials as-received were about (2.1±0.1) g/cm3 and (5±1)%, respectively. The brake materials were composed of 59% C, 39% SiC, and 2% Si (mass fraction). The content of Si in the C/SiC brake materials modified with graphite was far less than that in the C/SiC brake materials without being modified with graphite, and the Si was dispersed. The braking curve of the 3D needled C/SiC modified with graphite was smooth, which can ensure the smooth and comfortable braking. The frictional properties under wet condition of the 3D needled C/SiC modified with graphite showed no fading. And the linear wear rate of the C/SiC modified with graphite was lower than that of the C/SiC unmodified.

Effect of Braking Speed on Frictional Properties of Short Fiber C/C-SiC Brake Materials and Grey Cast Iron

Short fiber C/C-SiC brake materials were prepared by dipping the fibers in resin, chopping, warm pressing, and pyrolyzing, followed by a liquid silicon infiltration process. The effect of braking speed (initial braking speed) on the frictional properties of a pair of short fiber C/C-SiC brake materials and grey cast iron (HT250) (C/C-SiC-HT250) was investigated. The results indicated that the average friction coefficient of the C/C-SiC-HT250 increased to the maximum value at 10 m/s and then decreased with an increase in braking speed. The wear rate of the C/C-SiC increased with increasing braking speed when it was lower than 10 m/s and decreased when it was higher than 10 m/s. The wear was the result of the brittle fracture of asperities when the braking speed was lower than 10 m/s and induced granular debris. The wear for the tough cutting by C/C-SiC asperities or hard phase when the braking speed was higher than 10 m/s and resulted in ribbon debris. When the braking speed was higher than 20 m/s, the texture of the friction surface of the HT250 changed, which would affect the tribological properties.