Study On Ni/PTFE Composite Electroplating

Ni coatings have many advantages, such as excellent corrosion resistance,excellent abrasion resistance, uniform coating thickness and so on. And they have beenwidely used in aviation industry, automobile industry, electronics industry, chemicalindustry and so on. However, the friction resistance of Ni coatings is high. PTFE ispolymerized by tetrafluoroethylene monomers, which makes its performance steady.Not only is it highly chemically resistant, but also it has heat resistance, cold resistanceand very low friction coefficient. Through adding the PTFE particles into theelectroplating solution, the particles will be co-deposited into the Ni coating with the Nideposition, and the fabricated composite coating is with outstanding antifriction effect.In this paper, Ni/PTFE composite coating is successfully fabricated by adding thePTFE emulsion and FC-134cationic surfactant to the Ni electroplating solution. SEMand AFM are applied to observe the surface topography of the composite coating. Thesurface is uniform and smooth, and the roughness Rais23.434nm. The EDS resultsindicate that the PTFE particles are successfully composited into the coating with thePTFE particles content up to41.25%(mass fraction). The F element of the coatingevenly distributes, which indicates the PTFE particles evenly distributes in the coating.In the respect of tribological properties, Ni/PTFE composite coating’s frictioncoefficient is0.218, which is only about34%of that of the Ni coating, but the hardnessis smaller and the abrasion loss is larger because of the recombination of the soft PTFEparticles.The effects of PTFE emulsion concentration, FC-134concentration, currentdensity and temperature on the properties of the composite coating are studied by singlefactor experiments. PTFE emulsion concentration has the most influence on thecomposite coating’s properties. Current density and temperature have little influence,and FC-134concentration has no influence within a certain range we used. On the basis,orthogonal experiment was adopted to ascertain the best electroplating condition, withcomprehensive consideration of friction coefficient, hardness and abrasion loss. Thebest electroplating condition is: the PTFE emulsion concentration is30.0mL/L, thecurrent density is9.0A/dm2, and the temperature is45.0℃.The electrochemical behavior of composite electroplating is studied byelectrochemical experiments, and we found composite electroplating experiences a nucleation process, and the addition of PTFE emulsion and FC-134enlarges thecathodic polarization. The reaction resistance of composite electroplating,426.3·cm2,is much larger than that of Ni electroplating,26.56·cm2, which indicates that thereaction of composite electroplating is much harder than Ni electroplating. In order toexplore the wear mechanisms of Ni coating and composite coating, both themorphologies of the wear tracks were analysed. And we found the wear mechanism ofNi coating mainly is adhesive wear, together with abrasive wear, while that ofcomposite coating is only abrasive wear.