| In order to reduce the friction loss of energy and resource and to prevent the failure of mechanical equipments caused by the wear between moving surfaces,more and more researchers pay their attention to the surface engineering.It is known that Cn-Sn alloy is a common matrix forwear-resistant and antifriction composite coating because of its excellent properties.However,direct current and cyanideplating solutionare still used in most of the present researches on Cn-Sn alloy composite coating.In this paper,wear-resistant and antifriction composite coating Cu-Sn-PTFE and Cu-Sn-Ni-PTFE are deposited by pulse current in pyrophosphate-stannateplating solution and their properties are investigated respectively.In the experiment,plating solutions for Cu-Sn and Cu-Sn-Ni alloy are prepared before the nano-sized PTFE particles dispersed by surfactant and mechanical force are added in.Then the composite coating is electrodeposited according to the experiment plan in which the density,frequency and duty ratio of pulse current and the concentration of PTFE particles in solution are selected as variable parameters for Cu-Sn-PTFE plating.For the Cu-Sn-Ni-PTFE plating,the concentration of nicke ion and PTFE particles in solution are selected as variable parameters.After all coatings are prepared,test and analysis are carried out in order to investigate the properties of coatings,including composition,morphology,hardness,corrosion resistance,deposition rate and tribological properties.Influence of variable parameters in experiment on the properties of coatings is discussed and the coating Cu-Sn-PTFE andCu-Sn-Ni-PTFE which own best properties are obtained respectively.Results show that the composite plating solution and process parameters used in the plating experiment are able to produce composite coating Cu-Sn-PTFE and Cu-Sn-Ni-PTFE which own excellent quality and properties.Composition analysis by EDS shows that the contents of element F in composite coatings vary with the trend of rising then declining in the range of 1%~3% when the concentration of PTFE particles in solution rises.The contents of element Ni in coatings Cu-Sn-Ni-PTFE are in the range of 1.5%~3.5%.Phase analysis by XRD shows that metal elements in the composite coatings exist in forms of Cu-Sn alloy and Cu in Cu-Sn-PTFE and Cu-Sn,Sn-Ni and Cu-Sn-Ni alloy and Cu in Cu-Sn-Ni-PTFE respectively.SEM observation show all the prepared coatings own uniformly smooth surface and fine grain and few defects are found.Coating grain of Cu-Sn-Ni-PTFE will become lager with the rising of the concentration of nicke ion in solution when it is higher than 0.1mol/L.It is current parameters that have major influence on the deposition rate of coating Cu-Sn-PTFE.The deposition rate of Cu-Sn-Ni-PTFE is lower than that of Cu-Sn-PTFE and declines with the rising of the concentration of nicke ion in solution.Using pulse current in electrodeposition can improve the hardness of coating Cu-Sn-PTFE to top of HV383 under proper plating parameters.Because of the existence of element Ni,coating Cu-Sn-Ni-PTFE own higher hardness than Cu-Sn-PTFE and the top hardness is HV421.But too much nicke ion in solution will decrease the hardness of coating Cu-Sn-Ni-PTFE.Tafel curves show that coating Cu-Sn-PTFE own good corrosion resistance and that of coating Cu-Sn-Ni-PTFE is better because the element Ni.Tribological properties results obtained by friction and wear test machine show that particles PTFE in coating make Cu-Sn-PTFE and Cu-Sn-Ni-PTFE own excellent wear-resistant and antifriction property.Coating Cu-Sn-PTFE prepared under proper plating parameters has the lowest friction coefficient of 0.1 and its wear loss in test is very little.Coating Cu-Sn-Ni-PTFE has better wear resistance and larger friction coefficient than Cu-Sn-PTFE because of the element Ni.The observation of SEM on polishing scratch shows that both abrasive wear and adhesive wear happened in friction and wear test on the coatings and PTFE materials serve as lubrication film to reduce friction and wear. |
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