Preparation And Properties Of Ceramic-Based Friction Material With Mixture Of Fibers Reinforcement

The reports about the brake failure of brake device, such as industrial brake, high-speed rail, wind power equipment etc., leading to the accident economic losses and casualties appeare. One of the major reasons is closely related to the properties of friction material, for example, its menchanical properties, fade heat resistant and wear resistant. The friction material with stable friction performance and high wear resistance, which is a key and core in the brake device, can provide important technical guarantee and indispensable prerequisite for braking safety, and play a significance role in raising the technology level for brake devices. The research about brake friction material plays a key role in improving the technical level of brake divice, and has important practical value. At present, semi-metal and other types of friction material have reports widely. However, the study about hybrid fibers reinforced ceramic-based friction material is still seldom.In this thesis, on the basis of deep analyzing and investigating the development situations and existing problems of friction material, a variety of fibers were considered as reinforcing fiber in the ceramic-based friction material. On the beginning of the reinforcing fiber, the ceramic-base friction material with respect to menchanical properties and friction-wear properties were analyzed and studied thoroughly, combining with experimental investigation and theoretical analsis. And discussed the wear mechanism and optimized the formulations of the ceramic-based friction material to obtain a ceramic-based friction material with friction stablility and high wear resistant. The main studied innovative results are as follows:The ceramic-based friction material composed of ceramic hybrid materials comprising low price and wide source of alumina, clay, and potash feldspar, and steel fiber employed as reinforcing fibers, and the conventional particles, such as SiC, Fe powder, graphite as friction modifiers was prepared firstly. The effects of steel fiber on the fade, recovery and wear resistant properties were studied. The results show that adding the amount of steel fiber into the ceramic-based friction material can improve its toughness, thermal stability and wear resistance, thus steel fiber is considered fit for use as reinforcing fiber in the ceramic-based friction material. However, there is some compatibility problem between steel fiber and ceramic material, leading to the wear surface of the ceramic-based friction material with steel fiber produce microcrack during the friction process, and aggravating the wear. Thus, reinforcing materials compatibility with ceramic material should be appropriate to add when ceramic-based friction material with steel fiber as reinforcing fiber.Nextly, ceramic-based friction material with a mixture of the steel fiber and mullite ceramic fiber or a mixture of the steel fiber and aluminium-silicate ceramic fiber was prepared, and the mechanical and friction-wear properties were investigated and compared. The results show that it should contain a certain amout of steel fiber as so to have thermal conductivity, and the steel fiber and mullite fiber or aluminium-silicate ceramic fiber can have better hybrid effect. The interface binding performance beteween these fiber and ceramic matrix shows good. The steel fiber and mullite fiber or aluminium-silicate ceramic fiber play a complementary coordinate reinforcement role, improving the menchanical properties of the ceramic-based friction material, which can provide technical direction of the development of ceramic-based friction material.The effects of ceramic fiber on the properties of the ceramic-based friction material with mixing the steel fiber and mullite ceramic fiber or mixing the steel fiber and aluminium-silicate ceramic fiber were systematic studied, obtaining the influence rules of the ceramic fiber content on the properties of ceramic-based friction material. The results show that the ceramic fibers subjected to the friction force are easier to fracture with increasing the amount of ceramic fiber, thus making the worn surface become very rough. The rough worn surface increases the resistance of relative sliding motion. This contributes to the high coefficients of friction, and reduces wear resistance at high temperature. The results can provide the important reference for the formulation of ceramic-based friction material.A formulation of a mixture of the steel fiber and mullite ceramic fiber and aluminium-silicate ceramic fiber reinforced ceramic-based friction material with better comprehensive properties was optimizated by golden section method, orthogonal design experiment, grey correlation analysis and fuzzy comprehensive evaluation method, which has a higher fade resistance and wear resistance than mixing the steel fiber and mullite ceramic fiber or mixing the steel fiber and aluminium-silicate ceramic fiber reinforced or singl steel fiber reinforced the ceramic-based friction material. For the ceramic-based friction material with a mixture of the steel fiber and mullite ceramic fiber and aluminium-silicate ceramic fiber reinforcement, the steel fiber is benefit for improving its tribological property.At last, the friction and wear properties of the optimized ceramic-based friction material with the three reinforcing fiber were determined using dynamometer tester, the worn surfaces were observed. The results show that the optimized ceramic-based friction material has relatively excellence braking performance, and the worn surface has no obviously chipping, but it produces more or less a sticky the counter-disc phenomenon. Spalling pits and grooves are the typical worn surface morphology of ceramic-based friction material, revealing the wear mechanism of the ceramic-based friction material, which have important practical value to the improvement, development and application of fiber reinforced ceramic-based friction material.