Research On The Microstructure And Corrosion Resistance Of Nickel Matrix Composite Films By Magnetron Sputtering

The corrosion of metal materials can be seen everywhere,not only seriously affects the mechanical properties but also reduces the service time,which causing huge losses in daily life and industrial production.In addition,nickel-based composite materials are widely used in the field of corrosion prevention.Especially,Ni-Zr alloys and NiCrZr ternary alloys have the characteristics of corrosion resistance and good stability,have broad application prospects in various marine environments.Magnetron sputtering has become the main way to prepare thin films because of its large coating area,low requirements on the substrate surface and the strong adhesion between film and substrate.Preparing a smooth and dense Ni-Zr and NiCrZr composite films is an effective way to improve the corrosion resistance of stainless steel materials in the marine environment.In order to meet the needs of severe corrosive environment in the marine,Ni-Zr film and NiCrZr ternary composite films were prepared on 316L stainless steel substrate with different processes by magnetron sputtering.The morphology and phase structure were optimized to improve the corrosion resistance property.The main research contents and results of this dissertation are as follows:(1)Pure Ni target and pure Zr target were used as experimental materials.Ni-Zr composite films were prepared by magnetron sputtering with different sputtering rates in 316L matrix.The experimental results show that with the increase of sputtering rate,the film structure changes from an island shape to a flat shape,and the film surface is continuously refined.The film thickness is continuously increased and the surface roughness is continuously reduced with the increase of the deposition rate.In addition,the crystallinity of the film is gradually enhanced,and the phase mainly consists of the crystalline phase and the amorphous phase,and the crystalline phase mainly includes Ni,Ni3Zr and Ni5Zr.The transmission speed of the corrosion current can be effectively reduced because of the adjacent phases of the different crystalline phase and amorphous phase According to the analysis of EIS and potentiodynamic polarization curve,the corrosion resistance of the film with the 200 W Ni target power and the 100 W Zr target power is the best,and the corrosion current density is 14.51 nA·cm-2,which is reduce by 17 times than 316L stainless steel.(2)The substrate temperature affects the morphology,crystal structure,porosity and corrosion resistance property of the Ni-Zr films.Ni-Zr films were prepared at different substrate temperatures by controlling the temperature of the 316L substrate.It is found that,the morphology of the film changes from lamellar to island,and the crystallinity of the film increase with the increases of the substrate temperature.In addition,crystallization tendency of the film become obvious with the increase of the substrate temperature.The microstructure is mainly amorphous phase and three crystalline phases of Ni,Ni3Zr and Ni5Zr.The Ni5Zr peak is weakened,and the Ni3Zr peak is enhanced,that mains Ni5Zr is decomposed into Ni3Zr with the increase of the substrate temperature.The corrosion resistance of Ni-Zr films prepared at different substrate temperatures is different.The corrosion resistance of Ni-Zr films increases with the increase of substrate temperature because of the decrease of the porosity.Therefore,the Ni-Zr film has the best corrosion resistance prepared at the substrate temperature of 300? and the corrosion current is 25.9 nA·cm-2.(3)Zr content affects the morphology,crystal structure,porosity and corrosion resistance of the NiCrZr films.NiCrZr films were prepared with different Zr target power by magnetron sputtering.The results show that,with the increase of Zr target power,the Zr content of the film increases,the microstructure of the film surface is refined,and the surface roughness is reduced from 4.91 to 2.19 nm.The films are mainly composite of amorphous and Cr3Ni2,Cr1.2Ni0.8Zr,Cr2Zr,CrO3,NiCrO4 and ZrO2,the corrosion current of NiCrZr film decreases and the corrosion potential increases compared with the 316L substrate in 3.5wt.%NaCl solution.When the Zr content is 24.73 at%,in 3.5wt.%NaCl solution the NiCrZr thin films exhibits the best corrosion resistance due to the formation of stable passivation layer,and the corrosion current density reaches a minimum value of 13.10 nA·cm-2,which is reduced by 19 times compared with 248.5 nA cm-2 of 316L.