| Nanocomposite coatings have attracted more and more attention due to their excellent wear resistance,high hardness,high temperature oxidation resistance and corrosion resistance.At present,the preparation methods of nanocomposite coatings mainly include composite electrodeposition,composite chemical deposition and so on.The composite electrodeposition method is widely used in chemical,petroleum,aviation,aerospace and other fields due to its simple operation,simple preparation,excellent coating performance and low cost.The magnetic field-jet electrodeposition technology is a new technology based on the composite electrodeposition method to deposit coatings on metal substrates,which combines magnetic field and jet electrodeposition,not only can improve the liquid phase mass transfer ability in the deposition process and change the crystal organization of the coating,but also can promote the dispersion of nanoparticles in the plating solution,thus improving the composite electrodeposition efficiency and the quality of nanocomposite coatings.SiC nanoparticles have the characteristics of high hardness,small particle size,high activity and high specific surface area,which make them very suitable as reinforcing phase particles to improve the comprehensive properties of metal matrix nanocomposite coatings.At present,in the research of magnetic field-jet electrodeposition process,most scholars mainly use orthogonal experiment to study the influence of one or several factors on the deposition process.There are few studies on the influence of the interaction of magnetic field-jet electrodeposition related factors on the experimental results,and the response surface method is used to optimize the magnetic field-jet electrodeposition process parameters.Therefore,Ni-W-SiC nanocomposite coating was taken as the research object,and the process parameters and main properties of Ni-W-SiC nanocomposite coating by magnetic field-jet electrodeposition were studied by theoretical analysis,numerical simulation,multi-response surface method and experimental verification.Firstly,through the basic theoretical analysis of magnetic field-jet electrodeposition,it was revealed that the main mechanism of magnetic field-jet electrodeposition different from traditional composite electrodeposition was that the liquid phase mass transfer mode changes from diffusion to forced convection.The high-speed flow of the plating solution effectively reduces the thickness of the diffusion layer and increases the limiting current density of the cathode,thereby increasing the deposition rate of nanoparticles and metal ions on the cathode surface.Then,through the analysis of the structure and characteristics of the flow field and electric field of the magnetic field-jet electrodeposition,it was found that the electric field was limited by the distribution of the jet field,and the electric field only exists in the jet area of the plating solution,which makes the magnetic field-jet electrodeposition have unique regional selectivity.Secondly,COMSOL software was used to simulate the processing area of magnetic field-jet electrodeposition Ni-W-SiC nanocomposite coatings under different injection parameters.The influence of flow field and electric field distribution on the actual processing was analyzed,and the numerical simulation results were compared with the experimental results.Then,the microhardness,surface roughness and deposition rate of Ni-W-SiC nanocomposite coatings prepared by magnetic field-jet electrodeposition were modeled and predicted by JMP software,and the effects of process parameters on the microhardness,surface roughness and deposition rate of Ni-W-SiC nanocomposite coatings were discussed.The multivariate response prediction model established by JMP software was used to optimize the optimal process parameters of magnetic field-jet electrodeposition Ni-W-SiC nanocomposite coating.The optimal process parameters were as follows:current density was68.91 A/dm~2,SiC nanoparticle concentration was 8.27 g/L,magnetic field strength was 0.22 T,and jet flow was 200.2 L/h.Finally,MJED coating,JED coating and Ni-W coating were prepared by magnetic field-jet electrodeposition process and jet electrodeposition process.The surface morphology,microstructure,microhardness,wear resistance and corrosion resistance of the three coatings were tested.The Ni-W coating prepared by the jet electrodeposition process had coarser grains and lower microhardness.The surface asperities undergo large plastic deformation after being subjected to force,and quickly break and peel off.In the JED coating prepared by jet electrodeposition,SiC nanoparticles were embedded in the nanocomposite coating,which inhibits the continuous growth of grains,makes the surface of the coating smoother,reduces the surface roughness of the JED coating,and improves the microhardness of the coating.However,the agglomeration of SiC nanoparticles in the coating was serious,forming large groups,resulting in microcracks and pits in the JED coating.However,the MJED coating prepared by magnetic field-jet electrodeposition had a flatter surface,a fine and dense microstructure,and a higher microhardness.In addition,the amount of SiC nanoparticles in the MJED coating was larger and the grain size was smaller.The average particle sizes of Ni-W solid solution and SiC were 43.3 nm and 37.7 nm,respectively.In addition,the MJED coating had excellent wear resistance and corrosion resistance. |
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