Tribological Behavior Study Of Different Types Of Carbon Materials In Copper-based Powder Metallurgy Materials

Based on the technique request of high-speed train braking pad for homemade,copper-based powder metallurgy materials with different content of flake graphite,graphene,mesocarbon microbeads,chemical vapor deposition(CVD)carbon powder were prepared in this paper.The mechanical properties of the fabricated materials were tested by universal mechanical testing machine.The microstructures of friction surface and sub-surface were analyzed via scanning eletron microscope(SEM).The micro-zone compositons of materials were analyzed by energy disperse spectroscopy(EDS).The research results show:(1)With the increasing content of carbon material,the Brinell hardness,density,and compressive strength of copper-based composites decease correspondingly,and the open porosities increase.Copper-based powder metallurgy material with 1 wt% graphene has the highest hardness,density,and compressive strength.(2)With the increasing braking speed,the friction coefficients of copper-based composites decrease,and the wear rates increase.Copper-based powder metallurgy material with 5wt% CVD carbon powder has the highest friction coefficients,and the material with 5wt% flake graphitehas the lowest wear rate.(3)The friction surfaces of copper-based powder metallurgy materials with flake graphite have the whole friction films and obvious plough.The friction sub-surfaces appear the integrated mechanical mixing layers and the plastic disturbing layers,and the thicknesses of plastic disturbing layers are direct proportion to the contents of flake graphite.(4)The friction surface of copper-based powder metallurgy materials with1-4wt% graphene have the friction films.The friction sub-surfaces of the materialwith 1 wt% graphene has not obvious plastic disturbing layers,and the friction surfaces of the materials 2-4 wt% graphene have the cracks and flaking.The friction sub-surfaces of the material with 5 wt% graphene appear the half-baked integrated mechanical mixing layers and plastic disturbing layers.(5)The friction surfaces of copper-based powder metallurgy materials with1-5 wt% MCMB have the friction films,plough and different degrees of cracks.The friction sub-surfaces appear the integrated mechanical mixing layers and plastic disturbing layers.Because of the growth cracks of plastic disturbing layers and weak interfacial of the matrix,The friction surface of the materiasls with 3-5wt% MCMB appear sheet-like peeling.(6)The friction surfaces of copper-based powder metallurgy materials with1-5 wt% CVD carbon powder have the friction films.The friction sub-surfaces appear integrated mechanical mixing layers and plastic disturbing layers.Due to bad interface bonding between CVD carbon powder and copper matrix and the porous nature of CVD carbon powder,the friction surface of the matrerials of3wt%,4wt%,5wt% CVD carbon powder appear the cracks perpendicular to the plough,flaky surface and obvious plough.(7)The wear mechanisms of flake graphite-copper-based powder metallurgy material are abrasive wear and delamination wear.The wear mechanisms of 1wt% graphene-copper-based powder metallurgy material are abrasive wear.The wear mechanisms of 2-4 wt% graphene are abrasive wear and delamination wear,and the wear mechanisms of 5 wt% graphene are adhesion wear.The wear mechanisms of mesocarbon microbeads-copper-based powder metallurgy material are abrasive wear and delamination wear.The wear mechanisms of 1-2 wt% CVD carbon powder-copper-based powder metallurgy material are abrasive wear.The wear mechanisms of 3-4 wt%CVD carbon are abrasive wear and delamination wear.