| The slurry pump,which was mainly used for the transportation of slurry,is widely used in phosphorus mining operations.Meanwhile,the key components such as the turbine blades and gas valves of the slurry pump incline to failure under the corrosion of large load torque,high pressure erosion and acidic slurry during the process of phosphorus slurry transport.In order to improve the surface performance of phosphorus slurry consumables and their service life in engineering applications,this paper not only design and construct the experiment platform,the basic research of the CNT nano-enhanced nickel-based composite coating of the magnetic field jet section also has been performed.In addition,a detailed characterization and analysis of the prepared nanocomposite coating(including microhardness,friction coefficient,surface morphology,and electrochemical corrosion)were investigated.The main study contents of this paper can be followed:Firstly,preparation method of jet electrodeposition coating under magnetic field was put forward and then the jet electrodeposition platform was constructed.The design of platform mainly includ main drive system,electroplating liquid circulation system,nozzle system,workpiece fixture,water bath heating system and control system.Through the design of the core module of the jet electrodeposition devices,the problems of low efficiency and poor quality of ordinary electrodeposition coating are solved well,and the temperature and injection speed of electroplating fluid are controlled precisely.Secondly,the formula of electroplating liquid and coating preparation process was determined.Ni?Cu-Ni and Cu-Ni/CNTs composite coatings were prepared through electro-codeposition by adding nickel sulfate hexahydrate and carbon nanotube(CNT)in copper sulfate pentahydrate plating solution.The hardness and friction and wear properties of composite coating reinforced by CNT(Cu-Ni/CNTs)were investigated by micro-hardness meter and tribometer;and the surface morphology,element distribution and morphology of wear scar of the coating were characterized by scanning electron microscope(SEM)and energy dispersive spectrometer(EDS).The electrochemical impedance spectroscopy(Nyquist)and Tafel curves of the coatings were measured in3.5%Na Cl solution.The results show that the process parameters of ordinary electrodeposition are p H=4.2±0.1,temperature(52±1)?,and time 45min.Coating performance:Cu-Ni/CNTs coatings have a microhardness of up to 560.59HV in the range of investigation,When the Cu-Ni co-deposition plating solution was added with CNT with the mass percentage of0.08%,the composite coating presented the highest corrosion potential of-436.08 m V due to the physical shielding of CNT,and the lowest self-corrosion rate and corrosion resistance.The coating resistance Rc was(1573?·cm~2).Compared with the pure Ni coating,the corrosion suppression efficiency of Cu-Ni/CNT(0.08%)was 95.86%,the average friction coefficient of the coating was 0.52 which was the lowest,and the wear resistance was also the best.Finally,the parameters of electroplating solution and preparation process of jet electrodeposition Cu-Ni/CNTs composite coating were determined.Formula and preparation process of Cu-Ni/CNTs coating electroplating solution were optimized further thorough designing L~9(3~3)orthogonal test.Three main factors include magnetic field enviroment,current density and CNT concentration(mass percentage).The microhardness,friction coefficient and resistance of electrochemical coating were used as the evaluation indexes to determine the preparation process parameters of CNT nano-reinforced composite Cu-Ni/CNTs coating.The ideal preparation process was radial(vertical)magnetic field environment and current density 40 A/dm~2,as well as CNT mass fraction0.12%.The microhardness of the Cu-Ni/CNTs coating prepared under the ideal preparation process is as high as 593.45 HV,the lowest friction coefficient is 0.35,and the highest electrochemical corrosion resistance of the coating is 1537.8(?·cm~2),which indicates that it has the excellent corrosion property,and the surface of the Cu-Ni/CNT coating is also the most flat.The mechanism concerns:The interaction between vertical magnetic field,electric field and flow field disturbs the electroplating solution and scour the cathode substrate at the same time,thus the sharp grain growth on the cathode substrate is continuously broken,leveled and nucleated.The grain nucleation rate is larger than the growth rate,and the grain is refined and the overall quality of the prepared coating can be improved. |
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