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Microstructure and mechanical properties of nano-carbon reinforced Cu-based powder metallurgy friction materials produced by hot isostatic pressing

Abstract Cu-based powder metallurgy friction material is technically one of the most important powder metallurgy friction materials due to its high conductivity, high strength, good thermal properties and wear endurance. In this paper, nano-carbon reinforced Cu-based powder metallurgy friction materials were prepared by hot isostatic pressing (HIP). Microstructure and mechanical properties of nano-carbon reinforced Cu-based powder metallurgy friction materials with different nano-carbon content were systematically investigated. The microstructures of the nanocomposites were examined by optical microscopy (OM), X-ray diffraction (XRD), back scattered electron imaging (BSE), scanning electron microscope (SEM) equipped with an energy dispersive spectrometer (EDS). Mechanical properties were determined from micro-hardness, shear strength and compressive strength. The fracture and strengthening mechanisms of nano-carbon reinforced Cu-based powder metallurgy friction materials are explored on the basis of the microstructure and composition of the nanocomposites along with the formation and function of the interface. The nano-carbon mainly enhances the nanocomposites by load transfer and obstruction of dislocation. The synergistic effect of multi-walled carbon nanotubes (MWCNTs)and graphene improves the dispersion but hinders the densification process. The interfaces between carbon and copper are the main source of cracks, and the nanocomposites are mainly composed of brittle fracture.