Research On Controllable Friction Aided Jet Electrodeposition Of Film Preparation Technology

The preparation of functional or decorative film for the parts on the surface is a common method to ensure the stability,extend the service life or to meet some special appearance requirements.Because of excellent magnetic performance,NdFeB material has important use in many industries,and the protective coatings are often used to guarantee the stability of parts.With the development of industry,people have higher requirements on the efficiency and quality of the film preparation.Thus,this paper puts forward a new method: controllable friction aided jet electrodeposition(CFAJE),which can prepare high quality coatings with high efficiency.The main work of this research is as follows:(1)Put forward CFAJE technology and did some feasibility study.This new method was raised to solve the follow problem: traditional flexible friction method can't get high quality coatings under high current density.The key to CFAJE is to design a nozzle which could provide controllable friction.In this paper,the flow field of jet electrodeposition was simulated by Fluent software,and the influence of nozzle cavity on the flow field was obtained.At the same time,the friction nozzle was designed and verified.(2)Complete the key design of controllable friction technology.This paper proposed the rolling nozzle design scheme innovatively,which use a friction rod hanging outside the nozzle to replace traditional friction medium and springs were installed in the friction device to control the friction pressure,thus,the nozzle not only has the function of hydrogen resistance,removing tumor and homogenizing electric field distribution,but also can ensure the quality of coating under extreme conditions by controlled friction.(3)The mechanism of CFAJE improving surface quality and deposition efficiency was studied.Single factor test was used to prepare nickel coating on graphite substrate.The optimum rolling parameters were as follows: pressure 5.2N,cathode scanning speed 860mm/min.Controllable friction technology can effectively refine the grains,enhance the update of plating solution on the cathode surface,so under the optimal conditions,the limit current density of this new method could reach to 200A/dm2,which was 1.54 times of conventional jet electrodeposition,1.43 times of the floating friction processing mode,lead great improve of the deposition efficiency.(4)The mechanism of CFAJE improving the bonding strength between coating and substrate was studied.The nickel coating was prepared on the NdFeB substrate by orthogonal test.The optimum conditions were as follows: rolling pressure is3.1N;deposition time is 10min;bath temperature is 50?.The new method can effectively improve the grain growth during the deposition process,relieve inner stress and enhance the "riveting" connection on the interface of the coating and substrate.The comparative experiments show that the controllable friction technique makes the adhesion strength become 1.6 times of the original force.