| Due to their advantages of high specific strength,high formability,and good biocompatibility,titanium and its alloys are widely used in the aerospace industry,shipbuilding,petrochemical industry,automobile manufacturing,and biomedicine.Among of them,TC4 alloy which exceeds 50%of the total amount of titanium alloy is one of the widely used engineering materials.However,because of the low hardness,poor oxidation resistance and wear resistance,the applications of TC4 alloy are restricted.In this paper,the surface treatment of TC4 alloy by micro-arc oxidation（MAO）is used to study the influence rules of oxidation time and oxidation voltage on the properties of the oxide film.Subsequently,in order to improve and enhance the properties of the oxide film layer of TC4 surface,the annealing treatment and the sealing treatment are carried out.First,the oxide film,which is distributed with micron-level micropores on the TC4alloy surface subjected the MAO tratment,is mainly composed of anatase structured titanium dioxide（Anatase-Ti O2,A-Ti O2）andα-Ti.The addition of Na OH in electrolyte increased the pore size and thickness of TC4 surface oxide film,reduced surface defects and smoothness,and improved the comprehensive properties of films.When the voltage is 280V,the hardness,roughness,bonding strength,corrosion resistance and wear resistance of the sample increase with the oxidation time increasing.When the oxidation time is 20 min,the hardness,the roughness,the bonding force,the wear rate,the self-corrosion current density and the polarization resistance of the MAO-TC4 alloy film are 449.82 HV0.2,0.69μm,74.25 N,1.06×10-3g/cm2,0.54×10-6A/cm2,and 97.56 kΩ·cm2,respectively,and the corrosion resistance and wear resistance of MAO-TC4 alloy are the best.When the oxidation time is 20min,the hardness,the roughness and the bonding strength of MAO-TC4 alloy film increases with the increase of working voltage.When the working voltage increases,the corrosion resistance and the wear resistance of the MAO-TC4 alloy film first increase and then decrease.When the voltage is 280V,the film of MAO-TC4 alloy obtain the best corrosion resistance and wear resistance properties,and the self-corrosion current density,the polarization resistance,and the wear rate is 0.52×10-6A/cm2,94.68 kΩ·cm2,and 1.07×10-3g/cm2,respectively.Secondly,the MAO-TC4 alloy treated at 280V for 20 min is annealed at the different temperatures,and it is found that the oxide film is mainly composed of A-Ti O2,rutile titanium dioxide（Rutile-Ti O2,R-Ti O2）andα-Ti.The hole size,the hardness and the roughness of the oxide film on the surface of MAO-TC4 alloy increase with the annealing temperatures increasing,but the bonding force,corrosion resistance and wear resistance show a trend of first increasing and then decreasing with the annealing temperature increase.When the annealing temperature is 650℃,the best corrosion resistance and wear resistance of MAO-TC4 alloy obtain,and the bonding force,the self-corrosion current density,the polarization resistance is 76.45 N,0.13×10-6A/cm2,and 147.97 kΩ·cm2,respectively.Finally,the MAO-TC4 alloy treated at 280V for 20 min is sealed under the different times.The hardness,the roughness and the bonding force of the film increase with the increase of the sealing time,but the corrosion resistance and wear resistance of the film present the first increases and then decreases with the increase of the sealing time.When the sealing time is 10 min,the corrosion resistance and wear resistance of the MAO-TC4 alloy is best,and the wear rate,the self-corrosion current density and the polarization resistance is0.35×10-3g/cm2,0.44×10-6A/cm2,and 77.06 kΩ·cm2,respectively.In conclusion,the corrosion resistance and wear resistance of the film of TC4 alloy treated by 280V and 20 min micro arc oxidation in Na OH electrolyte are improved.The corrosion resistance of MAO-TC4 alloy annealed at 650°C is significantly improved compared with that of the sample un-annealed.And the wear resistance of MAO-TC4 alloy sealing treated for 10 min is significantly improved compared with that of the sample un-sealed. |
PDF Full Text Request