Preparation And Properties Investigation Of SiC/TiN Particle Reinforced Ni-Mo Nanocomposite Coating By Pulse Electrodeposition

As one of the surface modification methods,electrodeposition technology,combined with dispersion strengthening and electrocrystallization theory,can significantly improve the surface protection characteristics of the coating by adding nanoparticles in the electrodeposition process.Pulse electrodeposition can make full use of the current relaxation effect to prepare nanocomposite coatings with better comprehensive properties,and related research issues have become the research hotspot of composite electrodeposition.In this paper,Ni based composite coating was studied.By combining the synergistic advantages of pulsed electrodeposition technology and multi-element nanocomposit,Si C/Ti N particle-reinforced Ni-Mo nanocomposite coating was prepared on the surface of 6061aluminum alloy.The effects of particle concentration,average current density,duty cycle and pulse frequency on the microstructure,wear and corrosion properties of nanocomposite coatings have been studied.The coating formation process and grain refinement mechanism of nanoparticle-enhanced coatings are discussed,and the relationship between the structure of composite coatings and corrosion resistance and wear resistance is studied.The main research contents and conclusions are as follows:The effects of pulse parameters on the morphology,structure and properties of Ni-Mo-Si C-Ti N nanocomposite coatings were studied.The optimum process parameters were obtained at current density of 8 A·dm^-2,duty cycle of 20%and pulse frequency of 1000 Hz.The coating has typical FCC structure and(111)preferred orientation.With the decrease of duty cycle and the increase of pulse frequency,the Ni-Mo-Si C-Ti N coating prepared under the optimal parameters has the smallest grain size and the highest nanoparticle content.The results of tribological and electrochemical tests show that the addition of nanoparticles can significantly improve the wear resistance and corrosion resistance of the coating.Under the optimal process parameters,the wear rate of Ni-Mo-Si C-Ti N nanocomposite coating is the lowest(4.812×10^-4mm³/N.m),about 2/5 of that of Ni-Mo coating.Compared with Ni-Mo coating,the corrosion current density of Ni-Mo-Si C-Ti N nanocomposite coating is reduced by 53.24%.By reducing the duty cycle and increasing the pulse frequency,the nucleation rate of nickel and the incorporation of nano particles can be promoted,thus affecting the performance of the coating.The effect of nanoparticle content on the morphology and structure of the coating was further analyzed under the optimal electrical parameters.The results show that the coating is smooth and compact with the highest particle content when the electrolyte concentration is 20g/L.The existence of nanoparticles in the coating significantly reduces the grain size of the coating,the grain size of the coating is 11.85 nm at 20 g/L.Tafel polarization test and wear test show that the addition of two kinds of hard particles can significantly improve the performance of the coating,and the corrosion current density is reduced by 74%,reaching 1.84?A/cm².The wear rate decreases from 10.196×10^-4 mm³/N.m to 2.65×10^-4 mm³/N.m.The duplex hard-particles in the coating play a bearing and hindering role in the friction and corrosion process,the good bonding ability between the nanoparticles and the matrix makes the coating have higher load transfer effect.The deposition of particles in the gaps and pores of the coating prevents the entry of corrosive media and plays an effective mitigation effect,thereby significantly improving the wear and corrosion resistance of the coating.