Preparation And Properties Of Ni-Co-SiC Composite Coatings By Electrodeposition

Nickel-based composite coatings play an important role in various fields due to its advantages of high density,good corrosion resistance and high hardness.With the in-depth research on the preparation and properties of composite coatings,electrodeposition of Ni-Co-SiC composite coatings has attracted more attention from researchers,and great progress has been made in the research on the effects of nanoparticle dispersion,co-deposition amount,microstructure and composition of composite coatings on their properties.However,the influencing factors of electrolyte system in the preparation of Ni-Co-SiC composite coatings are complex,and the co-deposition amount and dispersion uniformity of particles are difficult to control.Therefore,the preparation of nickel-based composite coatings with excellent performance is our current research focus.The influencing factors of electrodeposited Ni-Co-SiC composite coatings were investigated in this paper.The morphology and composition of Ni-Co-SiC composite coatings were detected by SEM and EDS.Vickers hardness tester measures the hardness of composite coatings.The corrosion resistance of Ni-Co-SiC composite coatings was studied by analyzing electrochemical impedance spectroscopy and polarization curve.Firstly,the effect of cationic surfactant PEI on Ni-Co-SiC composite coatings was studied.The experimental results show that when PEI concentration is 0.06g/L,SiC particles in the composite coating are more dispersed,SiC content increases,matrix grains are smaller in the composite coating,and the coating surface is compact and flat.Increasing PEI concentration by one order of magnitude changes the morphology of the composite coatings,and the existence of cracks can be observed obviously.Pre-coating makes the surfactant fully adsorbed on nano-SiC particles,effectively dispersing the SiC particles,reducing the grain size of matrix,and improving morphology of the composite coating.Secondly the influence of technological parameters on Ni-Co-SiC composite coatings was investigated.The effect of adding 40 nm SiC on refining matrix grains is better than that of 100 nm SiC,and the prepared Ni-Co-SiC composite coating is smoother.When the current density is 3A/dm~2and the temperature is 50℃,the prepared Ni-Co-SiC composite coatings contains more SiC particles,the average grain size of nickel-cobalt matrix is the smallest,and the composite coating has the best morphology.Finally the hardness and corrosion resistance of composite coatings are the best when PEI concentration is 0.06g/L.Increasing PEI concentration by one order of magnitude does not improve the hardness and corrosion resistance of composite coatings.Compared with uncoated composite coatings,pre-coated composite coatings can effectively improve the hardness of composite coating,hardness value increased by 119.26 Hv,corrosion resistance also improved.The hardness and corrosion resistance of composite coatings prepared by adding 40 nm SiC particles are higher than that prepared by adding 100 nm SiC particles.With the increasing of current density and temperature,the hardness and corrosion resistance of Ni-Co-SiC composite coatings increase first and then decrease.When the current density is3A/dm~2and the plating temperature is 50℃,the Ni-Co-SiC composite coatings has the highest hardness and best corrosion resistance.