Research On The Performance And Interfacial Bonding Of Nano-diamond/Ni Composite Coatings By Brush-Plating

Ni-base plating coating and n-diamond/Ni composite coating are prepared respectivelyon Q235#steel matrix by using ultra-high energy mechanical and chemical techniques(HEMC).Again, the technical parameter are optimized by single factor and orthogonal designexperiments. The performance, the morphology and the composition of the interface areanalyzed. And the relationship between the nucleation and growth of nano-crystal and thecharacteristics of brush plating are introduced, the strengthening mechanism ofnano-diamond/Ni coating are also discussed.The results shows that: the dispersed evenly nano-diamond composite-coating areprepared by ultrasonic oscillation，mixing methods，also adding the op-10all together. Theoptimal parameters of the single factor and orthogonal experiments of the brush plating:voltage10V, bath temperature35~40℃, relatively speed11m/min, the content ofnano-diamond in plating5~30g/L, the coating thickness in control50μm around.The test results about frictional wear and hardness illustrated that the performance ofn-diamond/Ni coating is superior to that of rapid Ni-base coating such as higher hardness,higher wear-resistance, high-temperature properties. The wearing loss of the compositecoating is only1/3times than Ni-coating. When the nano-diamond density in the solution is30g/L, the microhardness of n-diamond/Ni composite coating has maximum value. And at200℃, the microhardness can reach687HV. During the coating tests of Bonding strength, nofalling off, cracking, peeling and so on, so the bonding strength is well.Through the analysis of the surface and interface，the cross-section organizations ofcoating has a "beam nodose organization" and "chain ring organization"; the hardness and thed-1/2essentially has a linear relationship, which fit the “Hall-Petch”. The deposition of nickelions is studied by cyclic voltammetry on nickel-plating bath. Then the mechanism ofinterfacial bonding of the coating is introduced and the interface structure, composition andconditions of combination are discussed by metallographic microscope, scanning electronmicroscope (SEM) energy dispersive spectrometry (EDS). Finally, the possibility of theformation of nano-crystalline are presented and the relationship between the nucleation andgrowth of nano-crystal and the characteristics of brush plating are analyzed; the strengtheningmechanism of nano-diamond/Ni coating are discussed, mainly involving fine-crystal, dispersion strengthening, dislocation strengthening.