Stady Of Preparation And Properties Of Copper Base Powder Metallurgy Friction Materials For Collector Shoe

Collector shoe is an important part of the third rail system of modern electric locomotives.It is of great significance to study the preparation and properties of copper base powder metallurgy friction materials for collector shoe for improving the operating efficiency of the train system and breaking the monopoly position of foreign materials in the collector shoe of high-speed electric locomotives.In this paper,copper base powder metallurgy friction materials with different components were designed and prepared.The mechanical properties,electrical properties and friction and wear properties of the materials were tested by universal testing machine,conductivity testing machine and friction-abrasion testing machine,and the microstructure of the materials was observed by scanning electron microscopy.The research results show that:(1)The copper base powder metallurgy materials with double lubrication of flake graphite and particle graphite were designed and prepared by orthogonal test method.The results show that the tribological properties of the material improve with the increase of graphite content,and the small content of flake graphite affects the distribution of particle graphite and reduces the tribological properties of the material.Particle graphite increases porosity and decreases Brinell hardness and electrical conductivity.Adding Fe,Cr to enhance the composition and similar particle size of flake graphite and particle graphite,the material has better comprehensive properties.(2)The effects of La₂O₃ on the properties of copper base powder metallurgy friction materials were studied.The results show that La₂O₃ can improve the sintering quality and strengthen the mechanical properties of materials by means of dispersion strengthening.The impact strength and Brinell hardness of materials increase with the increase of La₂O₃ content.Adding proper amount of La₂O₃ into copper base powder metallurgy friction material can increase the stability of the material during medium and high speed friction process.(3)The effects of Zn,Ni,Ti,Al and other alloying elements on the properties of copper base powder metallurgy friction materials were studied.The results show that the alloying elements can improve the bonding strength of metal and non- metal particles through solution strengthening and dispersion strengthening,and improve the mechanical properties,electrical properties,friction and wear properties of the materials.The formula consists of 6 wt.%Zn,12 wt.%Fe,3 wt.%Sn,3 wt.%Mo S₂,5 wt.%flake graphite and 0.3 wt.%La₂O₃.The performance indexes of the sample meet the standard requirements of TB/T 1842.1-2002"Pantograph Skateboard powder Metallurgy Skateboard of Electric Locomotive".(4)The microstructure of friction surface and subsurface was observed by scanning electron microscope,and the evolution mechanism of friction film of copper base powder metallurgy friction material during friction process was explored.It is found that the friction and wear properties of materials are mainly affected by the coverage rate of friction film,the forming speed is the main factor for the coverage rate of friction film when the initial braking speed is low,the forming quality is the main factor for the initial braking speed when the initial braking speed is high,and the forming process is less affected by the composition of materials.When the initial braking velocity is high,the strength of the friction film can be significantly increased by the matrix strengthening component,but the thickness of the near-surface plastic deformation layer will be reduced,and th forming of the near-surface plastic deformation layer will be affected.