Study On The Tribological Properties Of Ti6Al4V Alloy Grafted With Hydrophilic Polymer Membranes

Ti6Al4V alloy has excellent mechanical properties as well as superior corrosion resistance and biocompatibility. However, the poor tribological properties restrict its extensive applications in artificial joints seriously. On the purpose of improving the wettability and wear resistance of titanium, we mimic the surface characteristics of natural cartilage and modify the Ti6A14V alloy. A porous TiO2 film was prepared on the surface of Ti6A14V alloy by anodic oxidation method, and hydrophilic polymer brushes were grafted on its surface. Surface morphology, hardness and roughness of TiO2 film were investigated. Composition and structure of the grafted Ti6A14V alloys were characterized by Fourier-transform infrared spectroscopy with attenuated total reflection (FTIR/ATR), and the wettability was evaluated. Friction and wear properties of UHMWPE sliding against modified alloys were tested by a pin-on-disc tribometer under different lubricants (namely distilled water, saline and bovine serum) and different load.The results showed that, the porous oxide layer of Ti6A14V treated by anodic oxidation was formed when the voltage reached as high as 100V, and the roughness and hardness of TiO2 film increased with the increasing of voltage. Hydrophilic monomers (AA or DMMPPS) could be grafted from Ti6A14V effectively by UV radiation and were supposed to be self-polymerized to form a brush-like layer. The contact angle of modified Ti6A14V alloys changed from 68°to 17-27°, thus the wettability was improved significantly. The friction coefficient of modified titanium alloy was much lower and more stable than the untreated one. At high load (9.8N), the lowest friction coefficient was obtained when UHMWPE was sliding against the samples anodized at 100V and grafted with DMMPPS, and the value was 0.132. The friction coefficient under low load was higher than that at high load. Many deep furrows were found on the UHMWPE sliding against the untreated Ti6Al4V alloy, while the wear track on the surface of UHMWPE against modified one was not obvious.