Oxide Film Generation In Titanium Implant Cutting And Its Corrosion Resistance

The Oxide Film of titanium and titanium alloys implant play a key role on their corrosion resistance. In a conventional way, implants are machined firstly and then treated by surface engineering to obtain titanium oxide film. Those methods require lots of equipments and the processes are complicated, time consuming and the cost is high. This paper presents a new approach that cutting heat in cutting process is employed to get titanium surface oxide in oxygen-enriched atmosphere for surface modification.Pure titanium TA2is employed as implant material in this paper. Gibbs free energy is calculated at different temperatures of the titanium oxide. Thermodynamic analysis shows that titanium react with oxygen under normal temperature and pressure. The higher the temperature the more favorable oxidation reaction.Turning is used to machine titanium bar. The thickness of sample is measured with AES.Then the changes of color are observed after processing, and the elements of the surface are analyzed by EDS (Energy-dispersive X-ray Spectroscopy). The results show that the thickness of the Oxide Film increased230nm; by analyzing the color of samples, the surface oxidation in oxygen-enriched atmosphere is much higher than in natural atmosphere, and the surface color is much more multiple. Oxygen element is detected by EDS in line scan mode. Oxide film is obtained by machining.The corrosion resistance of the sample is investigated in simulated body fluid by static immersion test. The main type of the corrosion is pitting and there is partial erosion too. TThe degree of corrosion damage of samples gradually increased with the corrosion cycles. And the corrosion resistance of oxygen-enriched atmosphere is better than that in natural state.The corrosion resistance is assessed by measuring Tafel curve and anodic liner polarization curve in electrochemical corrosion test. Corrosion potential moves to the right side on the axis as cutting speed increases. It shows that the corrosion resistance enhanced. At the same speed, corrosion potential of sample of oxygen-enriched atmosphere is higher than that obtained in natural state. It indicates that the corrosion resistance of sample of oxygen-enriched atmosphere is better than the natural state. According to the corrosion current density, corrosion rate of samples in oxygen-enriched state and high-speed cutting is minimum. Corrosion rate of samples in natural state and low-speed cutting is the maximum.In summary, the desired thickness of the oxide film is obtained by using cutting heat during cutting process, combined with oxygen-enriched atmosphere; the results of saliva corrosion and electrochemical corrosion demonstrated that the corrosion resistance of the sample in the oxygen-rich atmosphere can be greatly improved.This project is supported by National Natural Science Fund (grant number51175306) and Program for New Century Excellent Talents (grant number NCET-11-0310)...