Study On The Wear-corrosion Behavior Of Medical Titanium Alloy Under Low Dissolved Oxygen Condition

Titanium has a strong oxygen affinity and can spontaneously form a dense passive film.Therefore,titanium alloys have excellent corrosion resistance.And it is often used as biomedical implant materials.During service,tribocorrosion are one of the most common forms of failure.Moreover,the lower concentration of dissolved oxygen in the body fluid environment can affect the regeneration process of its passive film,thereby affected the tribocorrosion performance of titanium alloys and the release concentration of metal elements.The article uses two titanium alloys for research,namely Ti-6Al-4V and Ti-13Nb-13 Zr alloys.Among them,Ti-6Al-4V is currently the most widely used medical titanium alloy implant material,but the Al and V elements in it pose certain hazards to the human body.As the third-generation medical titanium alloy,Ti-13Nb-13 Zr contains both Nb and Zr,which are harmless to the human body and are considered the most promising alloy to replace Ti-6Al-4V.Due to the current unclear nature of titanium alloy passive film under low dissolved oxygen concentration.Therefore,by controlling the dissolved oxygen concentration in 1 M HCl,the tribocorrosion performance of titanium alloys under different dissolved oxygen concentration and the structure of regenerated passive film were studied.The main research content are as follows:(1)The tribocorrosion performance of titanium alloys under different dissolved oxygen concentration and the amount of dissolved elements were analyzed and monitored by electrochemical methods,laser confocal microscopy,SEM,and ICP-OES.The results indicate that the protective performance of the original passive film of Ti-6Al-4V alloy under low dissolved oxygen concentration decreases.In addition,the solubility of Al and V increases sharply under low dissolved oxygen concentration.After the wear stopped,a large amount of Al and V still dissolve out,which means that the protective performance of the regenerated passive film formed under low dissolved oxygen conditions was severely reduced.(2)In order to the inferior protective performance of Ti-6Al-4V regenerated passive film under low dissolved oxygen concentration,the structure and performance of the regenerated passive film were studied using methods such as EPMA,XPS and HRTEM.The results indicate that mechanical wear causes a large number of dislocations inside the sample,which provides a fast channel for the dissolution of metal elements and the inward diffusion of oxygen atoms,leading to the dissolution of internal metal elements and the occurrence of internal oxidation of the sample after exposure air.In addition,the weighted vacancy formation energy of Al and V is much smaller than that of Ti through first-principles calculations.(3)Using the same method,analyze the tribocorrosion performance and elemental dissolution of Ti-13Nb-13 Zr under different dissolved oxygen concentration.The results indicate that Ti-13Nb-13 Zr alloy under different dissolved oxygen concentration exhibits more stable corrosion resistance,but its wear resistance is inferior.In addition,during the tribocorrosion process,the dissolution of alloy elements is relatively small,and the regenerated passive film still has excellent protective performance.