| Carbon ceramic composite friction material is a new type of material used to make brake materials for rail vehicles.It is made up of carbon fiber,silicon carbide and silicon.By adjusting the content of various components and using the difference of its performance,the friction coefficient and wear resistance of the material are required.In this paper,carbon fiber needle felt is used as a preform to produce carbon ceramic composite friction material by chemical vapor infiltration and melt infiltration.The friction coefficient and wear amount under different conditions were obtained by the friction test,the friction test under the constant friction test and the different dry and wet conditions.The change of the surface morphology of the friction surface and the evolution of the third body were observed.The conclusions are as follows:1.Based on the friction test under different pressure and different pressure,it is found that the friction performance of the sample containing silicon carbon and carbon billet of 1.49 g/m3 is the best,the friction coefficient is less affected by the friction speed and the friction pressure in the friction process,but the friction coefficient attenuates seriously under the wet condition..In wet condition,the specimen with a density of 1.49 g/m3 has a better tribological performance.2.Based on friction tests,the effects of carbon and carbon density on the friction and wear properties of desilicon and non silicon samples were compared and analyzed.It is found that with the increase of carbon and carbon density from 1.37g/m3 to 1.59 g/m3,the friction coefficient of the desilication sample increases gradually,and the friction coefficient of the non desilication sample decreases first and then gradually increases.The wear amount of the desilication and the non desilication samples increases first and then decreases.When the carbon and carbon density is 1.49 g/m3,the wear amount of the desilication and the non desilication samples is the most Big.3.When braking under dry condition,the friction coefficient increases gradually with the increase of the initial speed of braking,and the friction coefficient increases sharply in the later braking process,and the friction coefficient has a typical "tail end" phenomenon in the late braking process.The friction system of the sample which has not gone to the density of silicon carbon and carbon blank is 1.49g/m3.With the increase of initial braking speed,the fluctuation amplitude is larger than that of the desilication sample,and the maximum fluctuation range is 0.5.When braking under wet condition,the sample with the density of 1.49g/m3 carbon carbon and carbon billet,with the increase of the initial velocity of the brake,the friction coefficient fluctuates sharply,and the attenuation phenomenon appears.The friction coefficient of the specimen without the density of the silicon carbon and carbon blank is 1.49g/m3,and the coefficient of friction attenuates to almost zero.4.Based observing and analyzing the changes of the surface morphology of the friction surface before and after the friction test,the results show that silicon as a carrier is beneficial to the formation of a continuous third body,and it is not easy to fall off.The friction surface is smooth and smooth and no furrow is found.The third body formed by carbon fiber as a carrier is easy to follow the direction of the carbon fiber framework.Lump fall off,forming a large number of falling pits,with the increase of friction time,carbon fiber shedding is crushed and compacted on the silicon surface to form a layer of lubricating layer,which is conducive to the stability of the friction coefficient.5.The main wear form of the carbon ceramic composite friction material is abrasive wear.With the increase of time,the wear form of the friction material is changed from a single abrasive wear to the wear mechanism of abrasive wear and fatigue wear. |
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