| In order to improve the biological corrosion and wear resistance of Ti6Al4V surface layer,the Ti6Al4V nanotubes were prepared by shot peening and anodic oxidation.The phase of shot peening samples was analyzed by TTR 18kW X-ray diffractometer.The morphology and structure of shot peening surface were observed by JSM-7200F scanning electron microscopy?SEM?.The effect of vacancies on diffusion coefficient was simulated by density functional theory?DFT?based on first principles VASP software.Electron microscopy was used to observe the microstructure and morphology of anodized nanotubes,X-ray photoelectron spectroscopy?XPS?was used to determine the valence composition of elements in different samples of nanotubes,Flex-Axiom atomic force microscopy?AFM?was used to observe and analyze the length of nanotubes,OM image and Raman spectrum were used to analyze the crystallization properties of nanotubes.The corrosion resistance of titanium dioxide nanotubes was measured by electrochemical workstation,and the wear resistance of titanium dioxide nanotubes was tested by MRTR multifunctional friction and wear tester.On this basis,the main research results are as follows:1)The grain size of the matrix surface is refined continuously by shot peening.With the decrease of shot peening diameter,the plastic deformation of the shot peening surface is intensified.The residual compressive stress of Ti6Al4V surface is significantly increased by shot peening.The surface stress of the sample treated by 6mm diameter shot peening reaches 65.3 MPa,which is 5.9 times that of the sample without shot peening?10.17 MPa?.The residual compressive stress produced by shot peening can effectively improve the surface standard molar formation enthalpy,molar entropy and Gibbs free energy.With the increase of surface residual compressive stress,the standard molar formation Gibbs free energy increases from 0.001 to 0.44kJmol-1,the surface standard molar formation enthalpy increases from 28.71 to 64.90kJmol-1,and the surface standard molar entropy increases from 0.001 to 11.78JK-1mol-1.Based on first principles,VASP software simulates the diffusion mechanism of 0 vacancies and 1 vacancy structure on the surface of Ti element.The diffusion coefficient increases from 5.31exp?-55?to 3.10exp?-47?.2)The increase of anodic oxidation potential can promote the growth of titanium dioxide nanotubes.With the increase of anodic oxidation potential from 10 to 70 V,the average external diameter of titanium dioxide nanotubes on the substrate surface increases from 66.3 to 112.7 nm,with the maximum increase of 69.99%.The wall thickness increases from 7.07 to 14.7 nm,with the maximum increase of 107.20%.The tube depth increases from 345.16 to 774.88 nm,with the maximum increase of124.5%.The potential increases from-1.40 V to-0.5 V,with a maximum increase of1.8 times;the self-corrosion current density decreases from 9.65 to 3.55 A.cm-2,with a maximum decrease of 1.72 times;and the carrier density decreases from 1.03×10-24to 5.21×10-2323 cm-3,with a maximum decrease of 0.98 times.Under artificial saliva lubrication,the friction coefficient decreases from 0.46 to 0.30,and the friction coefficient decreases by 34.78%.Under the condition of pure aqueous lubrication of sodium hyaluronate,the friction coefficient decreases from 0.45 to 0.29,with a decrease of 35.55%.This indicates that the anodic oxidation potential can improve the length and diameter of the nanotubes,thereby improving their corrosion resistance and wear resistance.3)By further studying the properties of titanium dioxide nanotubes prepared by combining shot peening with anodic oxidation,it can be obtained that the properties of shot peening samples are improved in varying degrees compared with those of non-shot peening samples,and their outer diameters are increased by 51.2 nm,57.8nm,77.4 nm and 63.8 nm,their wall thickness is increased by 6 nm,7.4 nm,5 nm and3.8 nm,and their tube depths are increased by 241.35 nm,373.8 nm,respectively.The self-corrosion potential increased by 0.6,0.58,0.09 and 0.09V,increasing by 42.86%,49.15%,13.85%and 18%respectively,and the self-corrosion current density decreased by 3.31,2.92,0.56 and 0.42 A.cm-2,with a decrease of 34.30%,35.92%,13.50%and 11.83%respectively,and the polarization resistance increased by 298.24,478.54,211 and 318.22?.cm2,with an increase of 39.71%,respectively.54.60%,10.81%and 14.46%.It can be seen that shot peening can make the length and diameter of the nanotubes grow,so that the corrosion resistance of the nanotubes can be improved.Under artificial saliva lubrication,the friction coefficients were reduced by 0.05,0.03,0.01 and 0.01,and the decreases were 10.87%,7.31%,2.86%and3.33%,respectively.The friction coefficients of the samples were reduced by 0.05,0.04,0.04 and 0.01 respectively under pure aqueous lubrication of sodium hyaluronate,and the decreases were 10.87%,7.31%,2.86%and 3.33%,respectively.Therefore,shot-peening can improve the diameter and length of titanium dioxide nanotubes in varying degrees,thus improving their anti-wear and anti-corrosion performance effectively. |
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