EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

The structural integrity of Nitinol stents is of great importance for the successful deployment and life-time service in the patients receiving stent implantation. Over years, problems caused by unknown reason keep being reported from industrial quality control and clinical operations, such as unexpected corrosion susceptibility, strut damage and incomplete self-expansion. In order to optimize the reliability and safety of industrial products, fundamental researches are carried out on non-metallic inclusions and hydrogen content in commercial Nitinol stents and materials. The presentation firstly reports on the recent findings about the dependence between the corrosion susceptibility and the inclusions contents The comparative microstructural characterization of the laboratory-made and commercial stents are presented before and after ASTM F2129 assessments to show the effects of inclusions on corrosion susceptibility for different area fractions. As the second part of the presentation, the recent findings about the effect of hydrogen is reported regarding the change of deformation mechanisms of Nitinol. The hydrogen concentration in the commercial stents is measured and used as studying targets. In-situ microstructural characterization, coupling EBSD with tensile loading, is performed on the samples charged to different hydrogen concentrations to investigate the hydrogen effect on the local operating deformation mechanisms of NiTi.