| In recent years,with the rapid development of automobile industry at home and abroad,the design speed of automobile is getting higher and higher,and the performance of friction material which is a key component in the braking system is required more and more strictly.Therefore,to develop a new friction material with good mechanical properties,friction and wear performance and low noise is of great significance for promoting the development of automobile industry and safeguard the personal safety and property safety.At present,among the many brake friction materials used in high grade automotive,the ceramic-based friction material has gained wide attention from Japanese,European and North American auto manufacturers and consumers and has gained rapid development,due to it possess the low density,high temperature resistance,oxidation resistance,long life and other superior comprehensive performance.However,so far,there has been very little research on the ceramic-based friction materials with hybrid fiber reinforcement used in high grade automobiles in China.To provide experimental evidence and theoretical basis for prepare low cost,high performance ceramic-based friction materials,in this paper,ceramic-based friction materials in terms of industrial waste residue fly ash as the main ceramic components,alumina fiber and zirconia fiber as the reinforcement were prepared.From a single alumina or zirconia fiber reinforced ceramic-based friction materials,the influence of alumina and zirconia fiber on the properties of ceramic-based friction materials was studied systematically and carefully,and wear mechanism was also revealed.According to the experimental research and theoretical analysis of single ceramic fiber reinforced ceramic-based friction material,the ceramic-based friction materials with different proportion and different content of alumina/zirconia hybrid fiber reinforced were prepared,and the optimum hybrid fiber ratio and content of ceramic-based friction materials with stable friction coefficient and low wear rate was also obtained.The main results are as follows.1)With the increase of the content of ceramic fiber,the density and porosity of ceramic-based friction materials reinforced by single alumina fiber or zirconia fiber are rising,while the hardness decreased first and then increased.The compressive strength for alumina fiber reinforced ceramic-based friction materials has shown the trend of decreasing first,then increasing and again decreasing.While for zirconia fiber reinforced ceramic-based friction materials,the compressive strength decreasing first,then increasing.2)When the friction temperature is above 250 ?,the friction coefficient of alumina fiber reinforced ceramic-based friction materials has a slight recession phenomenon,while the friction coefficient of zirconia fiber reinforced ceramic-based friction materials has a small increase.Both wear rates increase with the increase of friction temperature.However,the ceramic-based friction materials reinforced by alumina fiber reinforced show better wear resistance in high temperature.When the friction temperature is between 100?250 ? the wear rate of zirconia fiber reinforced ceramic-based friction material decreases with the increase of zirconia fiber content.But opposite in high temperature.The ceramic-based friction materials reinforced by zirconia fiber reinforced have good wear resistance at low temperature.Therefore,the friction and wear properties of ceramic-based friction materials can be improved effectively by mixing alumina fiber and zirconia fiber.3)Keeping the hybrid fiber at 24%,changing the ratio of hybrid fiber has a small influence on the physical properties and hardness of ceramic-based friction material,but it is relatively complex to the compression strength.Alumina/zirconia hybrid fiber are added at a ratio of 1:1 or 3:1,ceramic friction material has high compression strength.Appropriate proportion of hybrid fiber has remarkable effect on the stability of the friction coefficient at high temperature.When Alumina/zirconia hybrid fiber are added at a ratio of 3:1,ceramic friction material has good friction coefficient stability.Besides,the wear rate can be combined with the wear resistance of alumina fiber reinforced and zirconia fiber reinforced at high temperature and low temperature,which has good wear resistance.4)Keep the alumina/zirconia hybrid fiber are added at a ratio of 3:1,the effect of hybrid fiber content on the physical properties and mechanical properties of ceramic base friction materials is similar to single alumina fiber reinforced.However,when the hybrid fiber content is between 16%with 24%,the friction coefficient of ceramic-based friction material is stable and has good thermal stability.The wear rate of ceramic-based friction materials with 8%and 16%hybrid fiber is small,showing good wear resistance.Based on the above analysis,the ceramic-based friction material with 16%hybrid fiber has better comprehensive performance.5)By observing the wear surface morphology,the main wear mechanism of ceramic-based friction material without adding any fiber is abrasive wear and fatigue wear.However,after adding the single alumina fiber,zirconia fiber or alumina/zirconia hybrid fiber,the main wear mechanism of ceramic-based friction material is gradually changed into abrasive wear and adhesion wear. |
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