The Impact Of Pretreatment Process On Structure And Functions Of TC4Alloy Electroplating Copper Coating

TC4alloy has good mechanical properties and shows excellent corrosion resistance in avariety of media, which have been widely used in sea oil well pipes. Wherein the connectionbetween pipe and coupling are connected by screw thread, but the poor wear resistance andlow thermal conductivity of titanium alloy make gluing phenomenon happens in makeup andbreakout operation, which caused huge economic losses. The copper plating on titanium alloysurface is an effective anti-galling process; however, plating on titanium surface is ratherdifficult. Therefore, the copper plating pretreatment process on TC4titanium alloy surface isstudied in this paper to improve its anti-galling properties.Firstly, the directly copper plating, pre-nickel copper plating, activating copper platingand activating pre-nickel copper plating processes were employed in this paper. The coatingsurface and cross section morphology were observed by scanning electron microscopy andsurface roughness measuring instrument, the coating surface roughness was also measured. Itis found that, the coating without activation is rough, and cracked from substrate. The coatingis dense and smooth after activating copper plating and activating pre-nickel copper plating.Analysis showed that, the activation result in the formation of a slate-gray conversion coatingand the closure effect, which inhibited oxygen permeation and diffusion during coatingformation process, the coating is well-distributed and dense. Ni plating is formed after pre-activation of the Cu/Ni/Ti multilayer structure between the Ti/Ni metallurgical bondinglayer is easily formed, reducing the stress of the coating and substrate binding, increasing thestability of the interface. A Cu/Ni/Ti multilayer structure formed after the activating of pre-plating Ni, the metallurgical bonding is easy to form between Ti/Ni films which reduced thestress between coating and substrate, and increased the stability of interface.Secondly, the division and tensile method were used to measure the bonding strength, theresults indicate that, the copper coating after activation and activating pre-nickel copperplating processes combined with the substrate well, the tensile fracture morphology and composition were analyzed; It is found from the friction wear tests that, the wear mode ofTC4titanium alloy is changed after copper plating; the electrochemical corrosion showed that,the self corrosion potential of the copper coating obtained by activating pre-nickel platingprocess is the most positive, the corrosion current is the minimum and shows the bestcorrosion resistance.Finally, the TC4titanium alloy coupling physical was pre-plated by the activating pre-nickel plating process, then copper plating process. After make-and-break test10times, thecoupling copper layer is substantially non-shredded, the coating showed a few spots off, theresults showed that: the copper coating obtained by activating pre-nickel copper platingprocess can inhibit the gluing between tubes and couplings, and shows good gluing resistance.