Effects Of Fluorite And Black Talc On The Properties Of Friction Materials And Mechanism Analysis

The rapid development of the automobile sector has provided new market opportunities for the brake pad industry.The performance improvement of brake pads has also become the top priority of the research nowadays.Researchers have been paying close attention to the non-asbestos organic（NAO）friction materials because of their easy fabrication and outstanding performance.At present,the high hardness of friction-increasing fillers often causes excessive wear,and the third-body particles that do not exist in the brake pads and discs produced during the friction process will cause environmental pollution.In addition,an unstable friction coefficient and the hot recession might result in the emergency brake failure,posing a greater risk of driving.Non-metallic minerals show great advantages in friction materials with their unique morphology,good thermal stability,and low cost.In this paper,fluorite and black talc were selected as friction performance modifiers to prepare high-performance friction materials.The effects of fluorite and black on the friction performance of the prepared samples were investigated.And the corresponding mechanism was evaluated.This work will provide a theoretical guidance for the application of nonmetallic minerals in the field of friction materials.The effects of different purities and contents of fluorite on the physical and mechanical properties and friction performance of friction materials were investigated,using the suitable hardness and distinctive microscopic morphology.The study showed that the friction material with 97%fluorite purity and 20 wt.%content exhibited optimal performance.The friction coefficient is increased by 20%and the fade rate is 6.59%.And the total wear rate was only 0.23×10^-7 cm³/（N·m）.The addition of fluorite improves the coefficient of friction while also demonstrating strong wear resistance.The influence of black talc on the comprehensive performance of brake pads was investigated.The introduction of black talc can help to stabilize the friction coefficient and prevent hot recession.When the content of black talc is 10 wt.%,the friction material has the best stability of the friction coefficient.An orthogonal test with two levels of three factors（coke powder,artificial graphite,and black talc）was designed to investigate the effects of friction-reducing fillers on the friction performance.The study showed that the synergistic effect among black talc,coke powder and artificial graphite increased at higher temperature,which can effectively reduce the wear,and the total wear rate decreased from 2.49×10^-7 cm³/（N·m）to 1.84×10^-7 cm³/（N·m）.The samples including6 wt.%coke powder,9 wt.%artificial graphite,and 7 wt.%black talc showed the best stability of friction coefficient.The effect mechanism of fluorite and black talc on the performance friction materials was explored by FT-IR,TG-DTG,3D non-contact profile scanner,and SEM.A weak bond exhibited between fluorite and phenolic resin hinders the degradation of phenolic resin and improves its stability.Fluorite can increase the plowing effect and improve the friction coefficient,while its lamellar structure of the surface has a certain effect on the reduction of the wear.The friction materials with Black talc produced a large number of secondary contact plateaus,constantly establishing the contact surface and reducing its change,effectively improving the stability of the friction coefficient.In summary,the wear of friction materials is caused by a combination of abrasive wear,adhesive wear,and fatigue wear,and all components in the formulation jointly affect the final performance of friction materials.