| Pulsed spray electrodeposition(also called pulsed electrospray plating)technology is a new type of electrodeposition technology with special flow and electric fields.Compared with traditional electroplating,this technology has the advantages of fast deposition rate,high material transfer efficiency and smooth and dense plating.The Ni-W-P alloy coating has better wear resistance,corrosion resistance,high temperature oxidation resistance and higher hardness.It is comparable to the chromium coating in performance and the preparation process is more environmentally friendly than the chromium plating process.It is used in the fields of anticorrosion of automobile steel plates and petroleum equipment,die-casting molds and surface strengthening of high-silicon cast aluminum materials.Si3N4 particles are not only self-lubricating,but also have good thermal stability and corrosion resistance and high hardness.They are deposited as a dispersed phase in the continuous phase Ni-W-P alloy coating,which can make the coating hardness,corrosion resistance and wear resistance has been further improved.At present,the research on the preparation of Ni-W-P alloy coating mainly focuses on traditional electrodeposition,pulse electrodeposition,electroless plating and very little spray electrodeposition.The application of pulse spray electrodeposition technology to the preparation of Ni-W-P-Si3N4 composite coating is not only It is an extension of the Ni-W-P alloy coating preparation process,and can provide a reference for future related research and supplement and improve the pulse spray electrodeposition theory to a certain extent.In this paper,the Ni-W-P-Si3N4 composite coating was prepared on the improved numerical control pulse jet electrodeposition test equipment by pulse jet electrodeposition process,the performance of the coating was tested and characterized,and the main salt concentration,particle concentration and the effect of process parameters on the performance of the coating,I hope to develop economical and environmentally friendly,superior performance composite coating.The specific research contents are as follows:(1)Determination of main salt concentration and Si3N4 particle concentration.A singlefactor experiment was carried out,and pulse spray electrodeposition Ni-W-P-Si3N4 composite coatings were prepared under different NiSO4 concentration,Na2WO4 concentration and Si3N4 concentration,respectively,and the surface morphology,surface hardness,bonding force and wear scar width of the coating layer Measurement and characterization,analyzed the influence of various factors on the coating performance.Finally,through comprehensive evaluation,it was determined that NiSO4 concentration was 70g/L,Na2WO4 concentration was 52g/L,and Si3N4 concentration was 4g/L.(2)Basic test research on process parameters.A single factor experiment was carried out,and pulse spray electrodeposition Ni-W-P-Si3N4 composite coatings were prepared under different bipolar voltage,reciprocating speed,frequency and duty cycle conditions.The surface morphology,surface hardness,deposition speed,The bonding force and wear scar width were measured and characterized,and the individual effects of various factors on the coating performance were analyzed.Finally,through comprehensive evaluation,it was found that the overall performance of the coating was relatively good when the bipolar voltage was 4.5V,the reciprocating speed was 135mm/s,the frequency was 2kHz,and the duty ratio was 80%.(3)Optimization and analysis of process parameters based on JMP software.The fourfactor three-level test on the voltage,reciprocating speed,frequency and duty cycle of the two poles was designed using JMP software.The interaction effects of various process parameters on the response target surface hardness,deposition speed,binding force and wear scar width are analyzed through the response surface map and contour map,the response regression equations of four response targets are obtained.Simultaneously obtained the four response regression equations and solved it by maximizing willingness,and obtained the combination of process parameters when the overall performance of the coating is the best:bipolar voltage 4.71V,reciprocating speed 135.00mm/s,frequency 2.14kHz,duty ratio 81.02%.The properties of the coating at this time are:surface hardness 630.78HV0.1,deposition rate 31.346?m/h,bonding force 42.50N,wear scar width 455.261 ?m.Finally,the pulse spray electrodeposition Ni-W-P-Si3N4 composite coating was prepared under the above optimal process parameters,and the actual performance of the coating was compared with the predicted performance.It was found that the difference between the two was small and the model prediction was more accurate.(4)Research on the corrosion resistance of pulse spray electrodeposition Ni-W-P-Si3N4 composite coating under the optimal process parameters.The polarization curve of pulse spray electrodeposited Ni-W-P-Si3N4 composite coating under different corrosion solution temperature and stirring speed was measured by the potential scanning method,and the selfcoating of the coating in 3.5%NaCl solution was obtained by Tafel extrapolation.Corrosion potential,self-corrosion current density and corrosion rate,it was found that the corrosion resistance of the coating showed a trend of first getting worse and then getting better as the temperature of the corrosion solution and the stirring speed increased.Finally,the corrosion resistance of 45 steel substrate,Ni-W-P alloy coating and Ni-W-P-Si3N4 composite coating were compared,and it was found that the corrosion resistance of both coatings is better than 45 steel. |
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