Deposition Of Nano Ti-O Films On Cobalt Alloy And The Preliminary Research On Their Fatigue Properties And Corrosion Resistance

Cobalt alloys are widely used in coronary stent for its high strength and good anti-fatigue property. However, both bare stent and drug eluting stent have the risk of restenosis or late thrombosis. Ti-O film which has good biocompatibility and corrosion resistance of stents is considered to deposited on coronary stent to solve this problem. The implanted stent will serve for a long time, Ti-O film should be tightly adhered on the metal stent before clinical application. Based on the service behavior of the implanted nano Ti-O film coated Co alloy stent, the bending fatigue behaviour and crrosion resistance of the film/alloy system were studied.Ti-O films were deposited on CoCrMo substrate by high-power pulse magnetron sputtering (HPPMS), and the phase structure and composition were investigated by using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) respectively. The bending fatigue proterty was investigate by a method proposed by ourselves. The corrosion resistance of film/alloy system which undergone cyclic load were investigaed by Electrochemical polarization test.The main contents and results of this paper are as follows.(1)Rutile TiO2films were deposited on CoCrMo substrate successfully.(2)One simple experiment method is proposed to test bending fatigue life of film/alloy system according to cantilever beam vibration theory and pure bending theory. Sensor and data acquisition system are not needed by this method, and the fatigue life of films undertaking different stress can be test at the same time. Compared with the exsisting method and technology, this mehod can save more time and cost.(3)The fatigue experiments showed there were no cracks or cracks propagation on the surface of Ti-O film under10million cyclic load with a strain amplitude200Mpa. The films prepared in this paper can meet the clinical requirements. The smooth and dense films has more bending fatigue resistance; The thickness of films has no significant effect on the bending fatigue behavior. (4) The electrochemical experiments showed that after several million cycles of loading, the corrosion behavior of the Ti-O films decreased relatively compare with the sample withou loading, but it is still higher than that of bare metal samples; the large thickness of the sample performance better than the small one; the more smooth and dense of the film has the better corrosion performance。The results of this paper help to the application of Ti-O films coated cobalt-based alloy stent.