Casting Simulation And Experimental Study Of Nitrocarburizing High Carbon Equivalent Alloy Gray Cast Iron Automobile Brake Disc

As one of the kernel components in automobile braking system,brake disc can transform the kinetic energy into heat energy in braking process,it has a crucial impact on the driving safety of automobile.With the improved of the engine power density and speed,the car is gradually showing the trend of high speed and heavy load,the service condition of the brake disc is becoming worse and worse,the braking performance and operating life of traditional gray cast iron can not meet the requirements for efficient braking and long-term service.In this paper,the surface modification of high carbon equivalent alloy gray cast iron brake disc was carried out by nitrocarburizing,the effects of process parameters on the microstructure,mechanical properties,wear resistance,corrosion resistance and fatigue performance of the brake disc were investigated based on the basis of simulation and experimental research.The innovation points of this paper are as follows:1.In view of the frequent occurrence of porosity shrinkage and hole defects in the casting process of brake disc,simulate the gravity casting process of brake disc by using ProCAST and JMatPro,analyze the flow and temperature field during pouring process,the causes of porosity shrinkage and hole are expounded and predict the position of porosity shrinkage at the same time.Improve the pouring system based on simulation results and verify the rationality of the new pouring system on the basis of experiment.2.The surface modification of high carbon equivalent alloy gray cast iron brake disc was first carried out by nitrocarburizing,in order to improve the wear resistance,corrosion resistance and fatigue properties of gray cast iron brake disc.The effect of temperature and holding time on the microstructure of carburized layer was studied through metallographic analysis,XRD,micro hardness analysis and other testing methods to achieve the optimum process parameters.3.Simulate the internal flow field of the push plate nitrocarburizing furnace by Flunet to obtain the trajectories of NH3 and CO2 in the furnace to verify the rationality of the nozzle layout.The cooling process of the brake disc after nitrocarburizing was simulated by Workbench to obtain the change rule of temperature field,in order to reduce the deformation defects after nitrocarburizing.4.Research the effects of nitrocarburizing on the wear resistance,corrosion resistance and fatigue resistance of high carbon equivalent alloy gray cast iron brake disc.The friction and wear experiments,electrochemical corrosion experiments and constant strain amplitude fatigue test of high carbon equivalent alloy gray cast brake disc after nitrocarburzing were carried out by the friction and wear testing machine,electrochemical workstation and universal testing machine to analysis the wear mechanism,corrosion mechanism and fatigue mechanism of the brake disc after nitrocarburzing,the influence of the mechanism on the wear resistance,corrosion resistance and fatigue performance of the brake disc was revealed,in order to provide a reliable application of basic research for the practical application of nitrocarburzing in high carbon equivalent alloy gray cast brake disc.