Improvement of TiN coating on comprehensive performance of NiTi alloy braided vascular stent

Abstract

In order to improve the wear and corrosion resistance of Ni–Ti alloy-based braided stent, High-temperature nitriding technology was used to prepare the TiN coating with different process parameters. Based on the systematic evaluation of nano-mechanical properties, tribological properties, electrochemical corrosion properties, nickel ion release properties and cytotoxicity, the feasibility of the application of the TiN coating in braided peripheral vascular stents was explored. The results showed that TiN coating included the TiN layer of about 1μm and nitrided layer of 50μm under the process parameters of 800 °C and 1h. The nano hardness and elastic modulus for TiN film were 20.50GPa and 281.66GPa, respectively. TiN coating can not only significantly reduce the friction coefficient in dry sliding and lubrication state, but also greatly reduce the wear rate such as by three orders of magnitude in dry sliding condition. TiN film reduced the icorr value with a reduction amount of 75.1%, with the value of 8.41 × 10−8 and 2.09×10−8A/cm2 for NiTi and TiN, respectively. After 28 days of soak experiment in phosphate buffer solution, the total nickel ion release amount of sample TiN#4 and bare NiTi were 0.094 and 1.452ng/m, which was reduced by 93.5%. The relative cell proliferation rate results showed that TiN samples all exceeded 90%, which mean that the cytotoxicity grade was 0. Based on the above results, TiN showed good nano-mechanical, tribological, electrochemical corrosion, nickel ion release and cytotoxity properties, and was expected to be used as a protective layer on the surface of Ni–Ti alloy stent.