Research On The Ni-TiN Nanocomposite Coating Prepared By Ultrasonic-Electrodeposition

Composite electrodeposition technology is a method to obtain composite coatings by adding insoluble micrometer- or nanometer-sized solid particles(such as TiN,AIN,SiC, Al₂O₃ and so on) to the electrolyte to co-deposit the particles and metal matrix with electrodeposition.In recent years,nanocomposite coatings have become the focus of widespread research owing to favorable properties such as optical non-linearity,magnetism and mechanical performance such as high hardness,wear resistance and corrosion resistance. At present,the research of nanocomposite coatings is still in the exploratory stage,and the codeposition theory of nanoparticles and the matrix grains is not perfect.The study on such as the preparation of nanocomposite coatings technology,the evenly dispersed issue of nanoparticles in the bath and coating,and the role of mechanisms of nanoparticles in coatings is weak relatively.This will restrict the further study and application of nanocomposite coatings seriously.In this thesis,the technological preparation and the main performance of Ni-TiN nanocomposite coatings are studied by combining theoretical analysis with experimental verification,the forecast models for TiN particles content and microhardness of Ni-TiN nanocomposite coatings are established by using the BP neural network.Firstly,based on the preparation of Ni-TiN nanocomposite coatings mechanism,the Ni-TiN nanocomposite coatings are prepared by ultrasonic electrodepostion,then the effects of ultrasonic power,current density,duty cycle,TiN nanoparticles concentration and surfactants on the surface morphologies,microhardness and TiN particles in coatings are studied. The technological parameters of Ni-TiN nanocomposite coatings prepared by ultrasonic electrodeposition are optimized with the orthogonal test.The constituent,surface morphologies and surface roughness of Ni-TiN nanocomposite coatings are characterized.The results show that the technological parameters of Ni-TiN nanocomposite coatings prepared by ultrasonic electrodeposition have great effects on the microhardness and TiN particles of coatings.The order from large to small is:TiN nanoparticles concentration＞Ultrasonic power＞Current density＞Duty cycle＞Surfactants concentration.And the optimal parameters are as follows: Temperature 50℃,pH 4.5,Time 50min,TiN nanoparticles concentration 4g/l,Current density 5A/dm²,Duty cycle 40%,Surfactants concentration 80mg/l,ultrasonic power 200W. By using XPS,TEM,EPMA and AFM,the Ni,Ti and N elements are investigated systematically on the surface of Ni-TiN nanocomposite coatings prepared by ultrasonic electrodeposition method,The Ni crystal and nano TiN particles are measured as approximately 55 nm and 35 nm.Moreover,the surface of Ni-TiN nanocomposite coatings is evener,the fluctuation is smaller and the exterior protuberance is also small,and the roughness of the coating are Rms =19.242 nm,Ra =15.719 nm and Rmax=125.53 nm.And they are smaller than that of Ni-TiN nanocomposite coatings prepared by mechanical stirring electrodeposition obviously.Secondly,the effect mechanism of the ultrasonic in media is outlined.The effects of different stirring ways on the surface morphologies,microstructure,the TiN particles content and the abrasion of Ni-TiN nanocomposite coatings are studied.The role of ultrasonic is discussed in the Ni-TiN nanocomposite coatings prepared by the electrodeposition method. Then the Ni-TiN nanocomposite coatings are characterized.The results show that the ultrasonic has obvious stirring scattered role,strengthen and promoting role and refining the nickel grains and particles TiN role.The XRD shows that the average sizes of nickel gains and TiN particles are 119.3nm and 56.7nm,separately,in the Ni-TiN nanocomposite coatings prepared by mechanical stirring electrodeposition.While the average sizes of nickel grains and TiN particles are 74.6nm and 34.8nm,separately,in the Ni-TiN nanocomposite coatings prepared by ultrasonic electrodeposition.The XPS indicates that there are nickel and Ti element in the Ni-TiN nanocomposite coatings surface.The AFM shows that the surface roughness of the nickel coating prepared by electrodeposited method are Rms = 48.213nm, Ra = 39.567nm and Rmax = 339.28nm.The surface roughness of the Ni-TiN nanocomposite coatingprepared by mechanical stirring electrodeposited method is Rms=27.427nm, Ra=21.857nm and Rmax=174.74nm.And the surface roughness of the Ni-TiN nanocomposite coating prepared by ultrasonic electrodeposited method is Rms=19.242nm, Ra=15.719nm and Rmax=125.53nm.This shows that the mixing nanoparticles by the ultrasonic dispersed more than that by mechanical agitation to achieve the degree of dramatic.In order to study the main performance of the coatings,the Ni-TiN nanocomposite coatings and nickel coatings are prepared by mechanical stirring electrodeposition and ultrasonic electrodeposition.The microhardness,binding force,porosity,the anti-corrosive and wear resistant performances are studied by using Vickers microhardness microscope,scratch tester, corrosive test,NSS and wear testing machine.On this basis,the corrosion resistance and wear resistance mechanism of Ni-TiN nanocomposite coatings are discussed.The result indicates that the Ni-TiN nanocomposite coatings not only have the high microhardness,anti-corrosive and the wear resistant performances,but also have lower porosity and the friction coefficient. The microhardness of the coatings is about 2 times for nickel coating;the porosity approximately 1/3 for about nickel coating,and the abrasion is about 1/4 for nickel coating. But the binding force is close to that of nickel coating between 60～70N.The order of the specimen average corrosion rate is:45 steel＞Nickel coating prepared by mechanical stirring electrodeposition＞Nickel coating prepared by ultrasonic electrodeposition＞Ni-TiN nanocomposite coating by mechanical stirring electrodeposition＞Ni-TiN nanocomposite coating prepared by ultrasonic electrodeposition.Finally,the forecast models of the TiN particles content and microhardness of the Ni-TiN nanocomposite coatings are established by using the BP neural network.The results indicate that the prediction error of the BP network models is small relatively,and the largest relative error is 5.43%.The fitting effect of the BP network forecast model is explained perfectly,the rate of accuracy is high.The establishment of the BP network forecast models has provided a new way for processing the tentative data.