Research On Preparation And Properties Of Cu-matrix Self-lubricating Composites Reinforced By Al And SiC Particles

Cu-matrix self-lubricating composites,which always are used as brake pads and grounding devices,have good properties of electrical conductivity,thermal conductivity and wear resistance.It is very important to save the production cost and improve the service performance of the composites.Cu-matrix self-lubricating composites of different content of Al and β-SiC were prepared by cold pressing-sintering-repressing technology.The effect of Al and SiC content on microstructures,mechanical properties,physical properties,tribological properties and corrosion resistance of Cu/Gr（graphite）and（Cu-9.5wt%Al）/Gr composites were studied.The a-Cu solid solution can be formed firstly because of addition of aluminum,and then the hard and brittle γ2 phase will be formed when Al content reaches 7.6 wt%.When Al content is 9.5 wt%,a large number of γ2 phase is precipitated,and forms network structure.A great deal of agglomeration which is result from addition ofβ-SiC particles happens at the grain boundaries.The higher the content of SiC,the more obvious agglomeration.The composites can have higher macrohardness,matrix microhardness,bending strength and compressive strength due to the increase of aluminum.However the electrical conductivity and plastic gradually get worse.The relative density is highest when the aluminum content is 5.7 wt%.On the other hand,that SiC particles are added in the composites results in the degradation of macrohardness,relative density,electrical conductivity,bending strength,compressive strength and plastic.But when the SiC content is 4wt%,the microhardness of the matrix reaches a maximum value of about 210.9HV.Under the condition of dry friction,the friction coefficient decreases with the increase of Al content,meanwhile the wear rate increases first and then decreases.It has good wear resistance when the content of aluminum is 9.5 wt%.With the growth of SiC content.the friction coefficient grows gradually,but the wear rate increases first and then decreases.And the wear resistance is better when the SiC content is Owt%or 6 wt%.Under the condition of wet friction,the friction coefficient declines at the early stage and then increases because of the growth of Al content,while the wear rate reduces persistently.The composites also have the best abrasion resistance when the aluminum content is 9.5 wt%.As the rise of SiC content,the friction coefficient begins to grow after reduction,but the wear rate decreases all the way.And the abrasion resistance is better when the content of SiC reaches 6 wt%.The friction coefficient and wear rate of wet grinding are both higher than that of dry grinding.The composites have the best corrosion resistance in 5%H₂SO₄ solution with the Al content of 9.5 wt%.The β-SiC particles are harmful to the corrosion resistance of the composites.