Study On The Effect Of Nanoparticles On The Properties Of Cu-Sn-graphene Composite Coatings

With the development of electrodeposition tribological coating technology,the preparation of multi-composite wear-resistant and anti-friction coating has become one of the study directions in the field of tribology.Multicomponent composite electrodeposition is co-deposition of various properties on the surface of the substrate,and the influence of each phase and the synergistic mechanism becomes a research difficulty.The choice of composite material is one of the most important parts.Because of the special two-dimensional structure,grapheme has attracted the attention of many researchers and also gradually been applied to the friction parts.However,due to its poor dispersion in aqueous solution and expensive price,the preparation of electrodeposited graphene composite coatings and the study of their tribological mechanism remain to be studied in depth.In this paper,by using the hydrolysis of graphene oxide,the graphene is reduced on the composite coating through cathode in the process of deposition.By using the synergistic advantage of pulsed electrodeposition technology and multi-nanometer composite technology,the Cu-Sn-graphene composite coatings are obtained through the method of nanocomposite electroplating,which also combined with the wear-resistant and anti-friction properties of graphene and the performance of copper and tin alloy co-deposited in the composite material.At the same time,the composite bath with stable performance and uniformity is obtained by dispersing the nano-TiO₂ sol,PTFE suspension and rare earth oxides suspension with suitable surfactants.In order to extend the life of mechanical parts in the harsh conditions and improve its overall performance,the Cu-Sn-graphene composite coatings are modified by TiO₂,PTFE and La₂O₃,which can further improve their strength,corrosion resistance and abrasion resistance.A series of Cu-Sn-graphene,Cu-Sn-graphene-TiO₂,Cu-Sn-graphene-TiO₂-PTFE composite coatings of the coexistence with lubricating phases and strengthen phases are prepared by pulse electrodeposition under the optimum combination of process parameters.The surface morphology,microhardness,tribological properties and corrosion resistance of the coatings are tested by scanning electron microscopy（SEM）,micro-sclerometer,friction-wear tester and electrochemical workstation.The result shows that the performance of Cu-Sn-graphene-TiO₂-PTFE composite coatings is good.The surface of the coating is fine and uniform.The proportion of C element in the coating is between 1.5%and 4.5%,Ti element is between 0.25%and 0.95%,and F elements is between 1.0%and 2.5%.The composite coatings exhibit excellent wear friction and corrosion resistance under the appropriate process parameters and particle concentration,which the micro-hardness is416HV,corrosion potential and corrosion current density is respectively-0.328V and2.168×10-5A/cm²,and the average friction coefficient is about 0.12.The relationship between the surface morphology,microstructure,composition,microhardness,corrosion resistance and tribological properties of each coating are analyzed.The results showed that the addition of nano-graphene not only reduced the coating friction coefficient greatly,but also improved their lubrication ability.But their common defects are that the hardness value is not high,wear and corrosion resistance are also poor.When the TiO₂ particles are added to the bath in the form of nanometer sol,the composite coating hardness and wear resistance is improved.In order to balance the wear and anti-friction properties of the coating,the uniformly distributed PTFE particles are added in the plating bath.Thus,composite coatings consist of Cu-Sn-graphene-TiO₂-PTFE are obtained which further improved the comprehensive properties of the coatings.In order to increase the deposition amount of particles and improve the deposition quality,La₂O₃ is used to strengthen the Cu-Sn-graphene-TiO₂-PTFE composite coatings.The effect of composite coatings is studied by introducing La₂O₃ into the bath.The results showed that the grain density of the coating surface is enhanced and the quality of the coating is obviously improved for the addition of nanometer La₂O₃ particles resulting in an increase of the amount of particles deposited.Meanwhile,at the appropriate concentration,the hardness can reach447HV,corrosion potential and corrosion current density is respectively-0.198V and1.636×10^-5A/cm²,the average friction coefficient is low to 0.1,and wear time increases.