Study On Wear And Corrosion Resistance Of Ti-6Al-4V Surface By Ultrasonic Cold Forging And Micro Arc Oxidation Technology

At present,the most often used biomedical metal materials are stainless steel,titanium,cobalt base alloy,etc.Ti6A14V was used in this research mainly in that it has good performance,such as good biocompatibility,stable physical and chemical properties,easy to shape etc.Titanium alloy become a kind of widely adopted biological material in artificial joints,fracture fixation,spinal orthopedic fields,such as spinal implants and soft tissue repair,because of its advantages.But its wear resistance and corrosion resistance in the physiological environment and load conditions are poor.In order to improve the wear resistance and corrosion resistance of titanium alloy,ultrasonic cold forging technology(UCFT)was used to prepare the nano layer on the titanium surface,then the UCFT-MAO coating was prepared by micro arc oxidation(MAO)technology(MAO).The roughness of the(UCFT)surface is 36.982nm,measured by atomic force microscope(AFM);the micro structure of UCFT samples at different depths was observed by transmission electron microscope(TEM).And Op,m distance from the surface,the grain boundaries are obvious,while the dislocation phenomenon is less;20?m from the surface,the grain,grain boundary and dislocation exist at the same time;With a distance of 40?m from the surface,only a large number of dislocations and a small amount of grain boundaries exist.Scanning electron microscopy(SEM)was used to investigate a porous structure of MAO honeycomb surface samples.And the porous structure of UCFT-MAO honeycomb surface is more compact than the MAO sample;X ray diffraction(XRD)results show that UCFT pretreatment has little effect on the composition of the coating;Hardness results show that the maximum hardness value of UCFT-MAO,518HV0.05,followed by the MAO samples,the hardness is 487HV0.05;The UCFT-MAO coating is more compact and the hardness is improved,which is favorable to the improvement of wear resistance and corrosion resistance.The wear test was used to check the wear resistance of titanium alloy by friction coefficient and wear rate,and the electrochemical corrosion tests were used to check the corrosion resistance of the samples by measuring the potentiodynamic polarization curves(PDP)and electrochemical impedance spectroscopy(EIS).The results showed that the friction coefficient of MAO coating and the matrix was decreased by ultrasonic cold forging,the wear amount of matrix was 19mg,the amount of wear of UCFT sample was 15mg,and the wear amount of UCFT-MAO was only 6mg.Ultrasonic cold forging as the pretreatment technology of micro arc oxidation coating,the wear resistance of micro arc oxidation coating was remarkably improved.Meanwhile,the UCFT-MAO sample has the lowest corrosion current density and the highest electrochemical impedance value.Ultrasonic cold forging is a new cold processing technology.Its application in titanium alloy is rare.This paper studies the effect of pretreatment on the wear resistance and corrosion resistance of titanium alloy.