Effect Of External Copper And Iron Third Bodies On Friction Performance

Copper-based powder metallurgy friction materials are used in high-speed trains due to their stable friction properties.To improve the performance of friction materials,it is necessary to grasp the relationship between material composition and friction performance.The friction coefficient is a comprehensive reflection of the material composition,surface structure and the state of the third body.To clarify the relationship between a certain composition and the friction coefficient will face interference from other factors.Therefore,revealing the degree of influence of the third body composition on the friction coefficient is instructive for improving the performance of friction materials.In order to clarify the influence of the third body components of copper and iron on the friction performance,this article aims at the copper-based friction material,using the inertial scale test bench and infrared thermal imager,with the help of the external third body method,the copper and iron third body The powder is added to the friction interface.By comparing the changes of material surface morphology,friction coefficient and brake disc temperature,the influence mechanism of external copper and iron third body on friction performance is analyzed.The main conclusions are as follows:(1)The addition of external copper third body increases the fluctuation range of the friction coefficient,which increases with the increase of pressure and braking times.The pressure increased from 0.25 MPa to 0.5 MPa,the fluctuation range of the friction coefficient of a single brake increased from 0.02 to 0.08,and the fluctuation range of the fifth brake increased from 0.07 to 0.1.The increase in pressure and braking times increases the compactness of the copper third body and makes the surface smoother.(2)The addition of the third body of external source iron increases the fluctuation range of the friction coefficient,which increases with the increase of pressure and braking times.The pressure increased from 0.25 MPa to 0.5MPa,the fluctuation range of the friction coefficient of a single brake increased from 0.04 to 0.15,and the fluctuation range of the fifth brake increased from 0.07 to 0.18.The increase of the pressure and the number of braking increases the filling degree of the spalling pits by the iron third body and the strength of the dense iron third body.(3)The fluctuation range of the friction coefficient of the external copper third body(0.1)is lower than that of the iron third body(0.2).At a speed of 20km/h,the iron third body has a stronger ability to fill spalling pits;at a speed of 160km/h,the copper third body plays a role of lubrication,and the fallen iron third body plays a role of abrasive particles.(4)Both the external source copper and the iron third body effectively reduce the difference in the radial average temperature of the brake disc.The maximum radial average temperature difference of the brake disc with the copper third body is 40?,and the maximum temperature difference with the iron third body is 72?.The third body of copper and iron enhances the heat generation capacity of the friction interface,and the strengthening effect of the third body of iron is stronger.(5)The hardness of the dense iron third body shed from the friction interface is greater than the hardness of the dense copper third body.The denser the shape of the iron third body,the greater the hardness,while the copper third body is the opposite.The increase in pressure reduces the hardness value of the third body of dense copper from 157.78 HV to 103.94 HV,and the hardness value of the third body of dense iron increases from 304.02 HV to 508.07 HV.The third body of dense copper reduces the friction coefficient and becomes dense.The iron third body increases the friction coefficient.