| Nanocomposite coatings are widely used in surface modification and surface repair of mechanical parts due to their excellent properties.Ni-Co alloy coating has a good protective effect on the base metal because of its excellent wear resistance,high temperature resistance,corrosion resistance and electromagnetic properties.SiC particles have been used as one of the ideal materials to improve the hardness,wear resistance and corrosion resistance of metal coatings due to their low density,high hardness,wear resistance and other excellent properties.Compared with conventional electrodeposition,spray electrodeposition has higher deposition rate and can significantly improve the quality of coating.The application of ultrasonic technology in spray electrodeposition can further improve the comprehensive properties of the coating surface.Therefore,Ni-Co-SiC nano coatings were prepared by ultrasonic spray electrodeposition.Because the nozzle is one of the key parts of jet electrodeposition device,FLUENT software was used to simulate the distribution of flow field around three nozzle structures(cylindrical,conical,cylinder cone cylindrical),and the velocity cloud,pressure cloud and turbulent kinetic energy cloud of flow field around different nozzle structures were obtained,A monitoring line is set at 2 mm on the surface of the specimen to obtain the velocity,pressure and turbulent kinetic energy distribution curve of the fluid at the monitoring line.The results show that the flow field distribution around the cylinder cone cylinder nozzle is the best.Then,three kinds of nozzles with different structures were used to prepare Ni-Co-SiC nano coatings to verify the accuracy of the simulation results.By analyzing the coating thickness and microhardness,it is concluded that the coating thickness and microhardness are the highest when the cylinder cone cylinder nozzle is used.The preparation parameters of Ni-Co-SiC nano coating have great influence on its structure and properties.Therefore,the effects of ultrasonic power,cathode current density and bath flow rate on the structure and properties of Ni-Co-SiC nano coatings were studied.Scanning electron microscope,X-ray diffractometer,friction and wear tester and scratch tester were used to test the surface morphology,phase composition,wear resistance,corrosion resistance and adhesion of the coating.The results show that when the ultrasonic power is 200 W,the cathode current density is 40 A/dm~2 and the bath flow rate is 4.5 L/min,the surface of Ni-Co-SiC nano coating is compact and smooth,the grain is refined,and the content of SiC nano particles in the coating is the highest.After friction and wear,the scratch on the surface of the coating is shallow,and the microstructure does not fall off.After the corrosion of the coating,the surface corrosion is good,and only a small amount of corrosion pits appear on the surface of the coating.Scratch tester test results show that the coating has the highest adhesion and excellent comprehensive performance.Therefore,the optimum process parameters for the preparation of the coating were determined as follows:ultrasonic power 200 W,cathode current density 40 A/dm~2,bath flow 4.5 L/min. |
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