Car Semi-metallic Friction Material Friction And Wear Properties And Mechanism

With the development of modern automotive industry and the enhancement of consciousness on environment protection, there have been great developments on automotive friction materials on such aspects as materials and fabricating process abroad. And many new non-asbestos friction materials appear. As China's entrance into WTO, its friction materials must face with rigorous challenge and must accelerate the step on developing automotive friction materials especially on non-asbestos materials. As semi-metallic friction material shows great overall properties* it becomes one of the most important non-asbestos friction materials being popularized in China. As research on friction materials focuses on the optimization of formulation and the design of fabricating process, and theories on the friction and wear characteristics of friction materials has not been studied deeply, the design of formulation and fabricating process is somewhat blind and often bases on real experience. Nowadays, theories on metal friction and wear are often borrowed to explain the phenomenon in friction materials.The friction and wear properties of semi-metallic friction materials with different fibers and lubricants at different temperatures are studied in this paper. And the friction and wear mechanism is discussed from the wear debris by SEM and EDX methods. The study is expected to supply useful data for material design. The results show that adding copper or purple copper fibers can greatly improve the friction and wear properties: more stable coefficient of friction and lower wear rate than those of steel fibers and adding purple copper shows the best overall properties; The. coefficient of friction of friction materials with MoS2 is higher than that of graphite, but the wear rate is higher, From the morphology analysis of wear debris, it is believed that at low temperature, material wear is controlled by abrasive and adhesive wear, so the debris is very small except some very large particles; At mid temperature, the formation of oxidized film stabilize the friction; At higher temperature, the degradation of organic materials and friction film and maybe the fatigue wear of surface are the main reasons to material wear. So the wear debris, is more larger than that at low temperature and there are many thin flakes in it; The wear of fibers play the key role to material wear. The friction film formed by copper fibers on the friction surfaces can accumulate iron so there is much iron in the wear debris. Purple copper fibersshow the most apparent in this aspect and fillers such as CaF2 and BaSO4 are not easy to drop out of the materials due to the good plastic property of purple copper; FeCr2O4 and Sb2S3 are not easy to wear and drop out of the material; The fillers in friction materials with graphite are more easy to drop out of materials than those of MoS2.