Preparation Of Ni-Ti Alloy Porous Material And Study On Its Seawater Corrosion Resistance

Nowadays,with the rapid development of world industry,environmental pollution,resource waste and other problems have become more and more serious.Metal porous materials have the advantages of small specific gravity,high specific strength,weldability and easy processing.However,in actual industrial applications,it is often because Due to the structural and metallic properties of porous metal materials,their seawater corrosion resistance has always been poor.Therefore,the research on the seawater corrosion resistance of porous metal materials is of great significance.In this paper,Ni powder and Ti powder with a purity of more than 99%are used as raw materials,and four mixed powders with a mass ratio of Ni Ti element powders of 6:4—7.5:2.5 are prepared respectively,and Ni-Ti alloy porous materials are prepared by powder metallurgy.X-ray diffraction（XRD）and scanning electron microscopy（SEM）were used to characterize and analyze the surface morphology and structure of the material,and electrochemical methods（open circuit potential,dynamic potential scanning and AC impedance）and seawater immersion corrosion experiments were used to analyze the porous Ni Ti alloy The research work on the anti-corrosion performance of materials in seawater mainly achieved the following results:It was found that the mixed powders with the mass ratio of Ni and Ti element powders of（6:4）,（6.5:3.5）,（7:3）and（7.5:2.5）were prepared at 930℃,960℃,1000℃and 1070℃respectively At this time,the obtained Ni-Ti alloy porous material has the best shape and has uniform and abundant pores,and the corresponding porosities are35.7%,36.2%,39.8%and 40.7%,respectively.XRD analysis results show that the four groups of materials are mainly composed of three intermetallic compounds,Ni Ti,Ni Ti₂and Ni₃Ti,and the positions of the corresponding three strong diffraction peaks are roughly 2θ=46°,44°and 42°.The most content of the three phases is the Ni₃Ti compound.The corrosion behavior and corrosion mechanism of the above four groups of Ni-Ti alloy porous materials in seawater were explored by using immersion corrosion and electrochemical methods.It was found that the mass change rate before and after immersion corrosion was 4.65%in the first 8 days of seawater immersion corrosion.It is due to the formation of the passivation film and ion adsorption in the early stage of corrosion;the sample quality is very close to the original quality after 24 days of immersion and corrosion.This is due to the dissolution of Ni ions and the shedding of the passivation film（Ti O₂and Ni O）.The change is not obvious,and it is still relatively smooth.The open circuit potentials of four groups of Ni-Ti alloy porous materials immersed in seawater for 8 hours were studied,and their relative equilibrium potentials were found to be-0.11V,-0.13V,-0.14V and-0.16V,respectively.Ni Ti（6.5:3.5）alloy The lowest self-corrosion potential of porous materials is-0.2904V,and the other three groups are-0.49718V,-0.81797V and-0.43642V respectively.The corrosion current density of Ni Ti（6.5:3.5）alloy porous material is 1.6944×10^-4A/cm2.The AC impedance test result of Ni Ti（6.5:3.5）alloy porous material shows that its equivalent circuit is a series model of two time constants.