Study On The Effect Of TiO₂ Nanoparticles On The Properties Of Cu-Sn Self-lubrication Composite Coating

For its eminent mechanical properties,corrosion resistance and low friction coefficient,electroplating copper-tin alloy coating was widely used in all sorts of friction parts,though it has soft texture and weak carrying capacity.To strengthen the coating hardness and tribological properties,this paper reinforce the pulsed electrodeposited Cu-Sn plating by compositing nano-TiO₂ particles,and successfully prepared Cu-Sn-TiO₂ composite coating with certain carrying capacity,corrosion resistance and low friction wear properties.After analyzing the theory of Cu-Sn alloy co-deposition and the nanomaterials strengthening mechanism,the experiment has formulated pyrophosphate-stannate system bath,dispersed nano-TiO₂ powder dispersion with about 50nm's diameter,and prepared TiO₂sol with average diameter at 300nm.Through optimization,the experiment prepared Cu-Sn coatings with different frequency,duty ratio and current density,and Cu-Sn-Ti O₂ enhanced by TiO₂ power and sol.Contrasted the performance of the coating of different process.The experiment observed the coating surface by SEM and analyzed its micro-structure and organization by EDS and XRD.The micro-hardness and corrosion resistance of coating were tested by micro-hardness tester and electrochemical workstation.After measured the tribological properties of the coating finally on pin-disc friction and wear testing machine,experiment observed the surface of grinding crack morphology by SEM and analyzed the wear mechanism of coating.The composite coating in exquisite organization and no obvious defects.With high internal crystallization rate,Cu-Sn plating,which main ingredients are Cu₈₁Sn₂₂,Cu_40.5Sn₁₁and part of Cu elemental,contained Cu about 94 wt.%.The main ingredients of Cu-Sn-TiO₂composite coating are Cu₈₁Sn₂₂,Cu₁₀Sn₃ and Ti O₂,and the organization tend to amorphous.The Cu-Sn coating can reach Maximum hardness at 448HV in 5000Hz.The reunite particles in nano-TiO₂ powder dispersion made the hardness of coating in low price.But the sol enhanced Cu-Sn-TiO₂ composite coating obtained a high hardness and maximum value reached 487 HV.Coating with pulsed frequency at 5000Hz and duty ratio at 70%own maximum corrosion potential and minimum corrosion current.The addition of nano-TiO₂reduces the corrosion resistance of coating overall,however,coating has eminent corrosion resistance when adding 11.7mL/L powder dispersion or 80mL/L sol dispersion.The friction coefficient of Cu-Sn coating,which has poor wear resistance,can keep under 0.3 in normal working condition.Anti-friction performance of coating enhanced by adding nano-TiO₂ particles.The nano-powder can reduce the friction coefficient to about 0.2.And the nano-TiO₂ sol particles can not only make the minimum friction coefficient at 0.093,but also enhance coatings'wear resistance.The main wear form of coatings is adhesive wear.Affected by TiO₂ nano-particles,composite coating also appeared different levels of abrasive wear.