Preparation And Simulation Research Of Spray Electrodeposited Ni-TiN Nano-plating

Nano-composite coatings now have a very important position in terms of materials,machinery and chemicals.Since the nano-composite coating has the dual performance of the matrix metal and nano-particles,the Ni-TiN nano-composite coating has more excellent surface properties than the pure nickel coating.Compared with ordinary electrodeposition,spray electrodeposition has the advantages of fast deposition speed and good quality of the prepared coating.In this paper,the four preparation parameters of spray electrodeposition: nozzle outlet diameter,nozzle contraction angle,pole spacing and spray pressure are explored in depth.First,Ni-TiN nanocomposite coatings were prepared on the surface of Q235 steel by spray electrodeposition using different process parameters,and the optimal spray parameter range was obtained by comparing the microhardness and wear of the Ni-TiN nanocomposite coatings(nozzle exit diameter 4 ～ 8)mm,nozzle contraction angle 30 ° ～ 60 °,spray pressure 4 ～ 8 MPa,pole spacing 10 ～ 20 mm).Then,according to the orthogonal experiment table with microhardness as the index,four sets of preparation parameters with higher microhardness were obtained,and the flow field around the nozzle during the spraying electrodeposition process of the four sets of preparation parameters was simulated using Fluent software.The results showed that the preparation parameters of the spray electrodeposition test specimen No.5were the best(nozzle outlet diameter 6 mm,nozzle contraction angle 45 °,pole spacing 10 mm,spray pressure 8 MPa).Because the simulation software cannot fully consider the uncertain factors in the human experiment.Therefore,it is necessary to use the scanning electron microscope(SEM),X-ray diffractometer(XRD),friction and wear testing machine,coating thickness gauge,etc.to test the coatings prepared by these four sets of preparation parameters to verify the accuracy of the simulation results.The SEM results show that the size of nickel grains and TiN particles produced by the preparation parameters of specimen No.5 are the smallest,which are 78.8 nm and 46.9 nm,respectively.It can be seen that the surface of the coating prepared by the preparation parameters ofspecimen No.5 is flat and smooth.The surface of the coating has a dense structure and the surface pores of the coating are significantly less than those prepared by the other three preparation parameters.XRD results show that the diffraction peaks of nickel grains and TiN particles of specimen No.5 are the shortest and slowest.This shows that the grains on the surface of the coating are fine,the particles are deposited uniformly and the coating is thick.The friction and wear test results show that the friction coefficient of the Ni-TiN nano-composite coating deposited on the preparation parameters of specimen No.5 is the smallest,with an average value of 0.403.That is to say,the hard particles on the surface of the nano-composite coating deposited on the preparation parameters of specimen No.5 are small and evenly distributed.The results of the electrochemical corrosion experiment show that the average value of the self-corrosion potential of the coating prepared by the spray electrodeposition parameter of specimen No.5 is-0.1039 V,which is more positive than the other three types,and the corrosion phenomenon has the smallest tendency to occur and is the most difficult to be corroded.At the same time,the self-corrosion current density of the coating prepared by spray electrodeposition parameters of specimen No.5 is smaller than that of the other three types,and the speed of self-corrosion of the coating is the slowest.According to the test results of the coating adhesion and coating thickness,the average thickness of the coating produced by the No.5 test piece spray electrodeposition parameter is the largest and the coating adhesion is the largest,which is 201.4 nm and 41.88 N respectively.Therefore,the coating of test piece No.5 is the least likely to be peeled off.The above experimental results show that the Ni-TiN nanocomposite coating deposited by the spray electrodeposition parameters of specimen No.5 has the best performance,which is consistent with the simulation results.