Study On The Preparation Of Ni-based Composite Coating With Nano-SiO₂ As Dispersion Phase And Its Properties

In this thesis,dispersible SiO₂ nanoparticles were used to prepare Ni-P/nano-SiO₂ composite coatings without any surfactants in plating bath by the technology of electroless.The process of Ni-P/nano-SiO₂ electroless plating is discussed and optimized.And we also investigated the effect of process of electroless plating on mechanical property and tribological performance.Ni-P-SiO₂-ZrO₂ composite coatings were prepared by electroless.Effect of proportions of SiO₂ and ZrO₂,on tribological performance of the composite coatings was discussed.Ni-P-SiO₂-ZrO₂ composite coating with super-hydrophobic performance was also prepared,and the tribological behavior of the composite coating was studied.The microstructure,morphology,composition,mechanical property of Ni-R Ni-P/ nano-SiO₂ composite coatings and Ni-P-SiO₂-ZrO₂ composite coatings by electroless plating are studied with the help of modern analytical instrument,such as X-ray diffraction(XRD),scan electron microscope(SEM),photo electron spectroscopy(EDS), and so on.The friction and wear properties of Ni-P coatings,Ni-P/nano-SiO₂.composite coating and Ni-P-SiO₂-ZrO₂ composite coatings were studied on the UMT-2 multifunctional micro-tribometer,and wear mechanism was discussed preliminary.The results show that process parameters directly,affect the tribological properties of Ni-P/nano-SiO₂,composite coating.The wear-resistant property was improved by adding appropriate amount of nano-SiO₂ in solution.Ni-P alloy coating and Ni-P/nano-SiO₂ composite coating have much better wear resistance than hardened and tempered 45#steel.Specially,Ni-P/nano-SiO₂ composite coating has lower friction coefficient than Ni-P alloy coating.The best heat treatment temperature of amorphous Ni-P coating and Ni-P/nano-SiO₂ composite coating are 400℃,Ni-P coating and Ni-P/nano-SiO₂ composite coating have highest microhardness and lowest friction coefficient,respectively.Wear mechanisms of Ni-P alloy coating are mainly adhesive wear,abrasive wear,while Ni-P/nano-SiO₂ composite coating could improve wear resistance properties greatly.When the mass percentage of nano-SiO₂ and micron- ZrO₂ is 1:1,Ni-P-SiO₂-ZrO₂ composite coating with super-hydrophobic performance was obtained.And the composite coating showed excellent tribological properties under water lubrication.