| Graphene and carbon nanotubes are added to metal-based composite materials as solid lubricants due to their excellent physical and chemical properties,which can effectively improve the mechanical properties and tribological properties of the materials.In this dissertation,high-performance graphene/carbon nanotubes and their hybrid structure-reinforced nickel-based composites are prepared by powder metallurgy.XRD,SEM,TEM,and Raman were used to characterize the morphology and structure of the composite.Microhardness testers,3D profilometers,and friction,wear testers were used to test the mechanical properties,friction and wear behavior of the composites.The content,friction pair,load,and friction environment affect the mechanical and tribological properties of the composite material.The morphology,structure,and tribological chemical reaction of the wear surface is analyzed.The strengthening effect and friction and wear mechanism of the composite material is discussed.The main research contents and results are as follows:?1?The powder metallurgy method was used to prepare the nickel-plated carbon nanotube-reinforced nickel-based composites by cold pressing and high-temperature sintering.The effects of the content of nickel-plated carbon nanotubes on the mechanical and tribological properties of the composites were studied.The results demonstrate that as the carbon nanotube content increases from 0 wt.%to 3 wt.%,The hardness of the composite material decreases from 90 HV to 57.56 HV,and the friction coefficient shows a trend of first decrease and then increase.When the content is 2wt.%,The friction coefficient is as low as 0.270,and the wear rate is 1.028×10-3mm3/N·m.Carbon nanotubes form a friction transfer film on the worn surface,which has excellent self-lubricating properties,and the friction coefficient of the composite material is reduced to 35.5%of pure nickel.?2?The powder metallurgy method was used to prepare the nickel-plated graphene-reinforced nickel-based composites by cold pressing and high-temperature sintering processes.The effects of the content of nickel-plated graphene on the mechanical and tribological properties of the composites were studied.The results show that the hardness of the composite is highest when the graphene content is 3 wt.%,Which is 145.2 HV.As the graphene content increases from 0 wt.%to 5 wt.%,The friction coefficient of the composite material first decreases and then increases.When the graphene content is 4 wt.%,The minimum friction coefficient of the composite material is 0.219.The wear rate is 5.70×10-4 mm3/N·m.Obviously,graphene has better self-lubricating properties than carbon nanotubes,but the threshold of graphene content is higher.?3?The powder metallurgy method was used to prepare the graphene-carbon nanotube hybrid structure-reinforced nickel-based composite material through cold pressing and high temperature sintering.Influence law.The results show that one-dimensional carbon nanotubes and two-dimensional graphene have a synergistic lubrication effect.Compared to a single carbon nanostructure reinforced nickel-based composite,when the content of graphene and carbon nanotubes is 1?3,at the same time,the composite material has both a low coefficient of friction?0.219?and a low wear rate(4.55×10-4 mm3/N·m).The 4 wt.%Gr-Ni composite has a hardness of 96.54HV,which is higher than that of graphene-carbon nanotube hybrid structure reinforced nickel-based composites.?4?The graphene-carbon nanotube hybrid structure reinforced nickel-aluminum matrix composites were prepared by means of powder metallurgy,cold pressing,high temperature sintering,repressing and reburning,and the tribological behavior of the composites in dry friction and seawater environment was studied.The results are shown that the hardness of the nickel-aluminum-alloy material and the carbon nano-hybrid structure nickel-based composite material after re-pressing and re-firing have increased by 4.99%and 49.80%,respectively.The composite material has good environmental adaptability and shows excellent friction and wear performance in both dry and seawater environments.In particular,when using Si3N4 ceramic balls as friction counterparts in a seawater environment,the friction coefficient and wear rate of composite materials corresponding to 4 N loads are as low as 0.181 and 5.1×10-5mm3/N·m,respectively.The carbon-based lubricating film formed by externally added graphene and carbon nanotubes and the water lubricating film formed by seawater during the friction process has played a synergistic lubrication effect to a certain extent.The wear mechanism of composite materials mainly manifests as fatigue wear and corrosion wear. |
PDF Full Text Request