Preparation Of Ni Based Composite Coatings By Electrodeposition

Nickel based composite coatings have the advantages of high hardness,good compactness,good corrosion resistance and high wear resistance.They are widely used in aerospace,automotive,electronics and other fields.With the rapid development of society and economy,a single nickel based coating has been unable to meet the needs of high-performance,multi-functional products.The quantum size effect,small size effect,surface effect are the characteristics of nanometer materials which can exhibit special optical,mechanical,electrical,chemical properties and wear and corrosion resistance,high elastic modulus and other advantage.It was known as the twenty-first Century most development materials,which shows attractive prospect.Therefore,how to make the composite coating of nano particles and metal matrix maximize fully fuifilled has become our research focus.In this paper,Ni based composite coatings were prepared by electrodeposition,and Ni-SiC,Ni-Al₂O₃ and Ni-SiC-Al₂O₃ composite coatings were prepared by electrodeposition,the type and concentration of surfactants were studied,the particle concentration and particle size,deposition method,surfactant coating sequence and structure of surfactants on the coating,and the effect of grain size of nano particles composite content in deposit.By scanning electron microscopy,energy spectrum analyzer of microstructure,the prepared coating composition,structure analysis and the content of second phase particles.The hardness of the coating was examined by microhardness tester,and the corrosion resistance of the coating was examined by electrochemical impedance spectroscopy and polarization curves.The properties of Ni-SiC,Ni-Al₂O₃ and Ni-SiC-Al₂O₃ composite coatings were studied.The effect of surfactant concentration and type on Ni-SiC composite coating on Ni-SiC composite coating was studied.And the experimental results shows that the optimum concentration of SDS is 5 g/L,the optimum concentration of PEI is 0.08 g/L,the optimum concentration of CTAB is 0.5 g/L,and the high concentration of PEI will change the morphology of the coating;Compared with the coating prepared by adding anionic surfactant,the size of Ni base in the coating prepared by adding cationic surfactant is tinier,and the agglomeration phenomenon of SiC particles is obviously weakened.The effect of SiC particle concentration and particle size on Ni-SiC composite coating was studied.The results showed that within a certain range,with the increase of SiC particle concentration in the plating solution,the content of SiC particles in the coating increased first and then decreased;Compared with the addition of 500 nmSiC particles,the microstructure of the Ni-SiC composite coating prepared by 40nm SiC particles is more compact and uniform.The Ni-Al₂O₃ composite coating was analyzed and studied.The results showed that compared with the DC electrodeposition method,the Ni-Al₂O₃ composite coating prepared by pulse electrodeposition method had higher content of alumina particles;When the concentration of PEI is 0.1 g/L,the surface morphology of Ni-Al₂O₃composite coating is the best,the content of nano Al₂O₃ particles in coating is the highest,the dispersion effect is the best,and the distribution in the coating is the most uniform.Comparative study of surfactant SDS,the results showed that the effect of PEI on the electrodeposition of Ni-Al₂O₃ composite coatings,dispersion effect,the two kinds of surfactants on Al₂O₃ particles is similar,but the adding PEI to make the Al₂O₃ particle content in the coating more than the addition of SDS.For Ni-SiC-Al₂O₃ composite coating,the optimum dosage of surfactant SDS was7 g/L;In the study area,the best combination of surfactant was 5 g/L SDS and 0.1g/L PEI mixed use;The effect of SDS and PEI surfactant mixture is better than that of single surfactant SDS to improve the coating quality;When the surfactant is preferentially coated with nanoparticles,the particles are dispersed in the coating,and the doping effect is better;Compared with DC electrodeposition,the nano Ni-SiC-Al₂O₃ composite coating prepared by pulse electrodeposition has more advantages in Ni based grain size,Al₂O₃ particle composite content and uniform distribution.By studying the hardness of Ni based composite coating.The results show that when the concentration of SiC particles is 6 g/L,the hardness of Ni-SiC composite coating obtained by pulse electrodeposition is the maximum,which is 398.24 Hv;the hardness of Ni-Al₂O₃ composite coating made by adding cationic surfactant PEI is higher than that of anionic surfactant SDS;Under the same conditions,with the increase of surfactant PEI concentration,the hardness of Ni-SiC and Ni-SiC-Al₂O₃two composite coatings increased obviously.When the concentration was 0.08 g/L,the hardness of two coating was the highest;by compareing the microhardness of two kinds of Ni based composite coatings in a longitudinal way,the microhardness of Ni-SiC-Al₂O₃ composite coating was higher than that of Ni-SiC composite coating.The corrosion resistance of the coating was tested by AC impedance and polarization curves.The results show that the Ni-SiC composite coating has the best particle dispersion effect and the best corrosion resistance in the study area when the addition of 0.08 g/L PEI in the plating bath;The results shows that the Ni-Al₂O₃composite coating prepared by pulse electrodeposition method is compact and homogeneous,with small grain size,high impedance and good corrosion resistance;The Ni-SiC-Al₂O₃ composite coating prepared by composite surfactant PEI and SDS has higher content of second phase ceramic particles,higher impedance and better corrosion resistance;Under the same conditions,the corrosion resistance of Ni-SiC-Al₂O₃ composite coating is better than that of Ni-SiC composite coating.