Preparation And Properties Of Nano Oxide Thin Films On 316L Stainless Steel Surface By R.F. Reaction Magnetron Sputtering

As the heart stents material 316L stainless steel has been widely used because of its excellent mechanics, corrosion resistance. But it has some disadvantages. It has poor biocompatibility and hemocompatibility, and it is easy to be corroded in body after a long time, then Ni2+, Cr3+ and Cr6+ released by 316L stainless steel will engender adverse impact on the human body. TiO2 and Al2O3, which have excellent biocompatibility and hemocompatibility and strong corrosion resistance, can improve 316L stainless steel’s biocompatibility and hemocompatibility and prevent the releasing of Ni2+, Cr3+ and Cr6+, by coated on 316L stainless steel using RF magnetron sputtering.By changing the substrate temperature, total pressure, oxygen partial pressure, target power and deposition time, and using rf magnetron reaction sputtering, TiO2 thin films were coated on 316L stainless steel substrates. Thin films’morphology, phase, corrosion resistance were been studied, by using FESEM, XRD and electrochemical workstation. After the research discoveried that crystallinity and corrosion resistance increased with the temperature, especially P=0.2Pa, T=300℃ had a higher degree of crystallinity. In low Ptotat (0.2Pa-0.2 Pa) Although TiO2 rutile type was existed, but with the increase of Ptotat crystallinity decreased, and the corrosion resistance were similar and all very resistant to corrosion, corrosion current reached 10 magnitude mostly, less than 316L stainless steel’s 7.221×10-7 A, and the corrosion potential were higher than 316L stainless steel substrates’.The optimum process for preparation of TiO2 thin films is Ptotat=0.2Pa, PO2=0.01Pa, T=300℃, tTi=3min, tTiO2=60min, P=400W. In this condition, the films have much better degree of crystallinity, also have the best corrosion resistance, with the corrosion current and corrosion potential respectively 5.995×10-8 A and -0.226V. Under the optimum process, heart stents were simulated service test (coating after open, twist open again), and films on them were still Smooth and compact, no crack and fall off was found. So heart stents coated by this condition meet the quality requirements of drug-coated stent surface, and can improve drug loadings and the adhesion strength of the stents and drug coating.In order to improve the drug loading capability of 316L stainless steel heart stents,Al2O3 films were prepared by the reaction rf magnetron sputtering.Al2O3 films which were perpred in certain scope of process, were studied by using FESEM, XRD and electrochemical curve. Discovery that Al2O3 film grain size is larger, and the space between the grain is obviously beneficial to drug immersion, the corrosion current 9.218×10-8 A was better than stainless steel corrosion resistance, which corrosion current is 7.22110-7A. More conducive to the preparation of the ideal coated drug loadings stents.