Microstructure characterizations of NiTi containing non-metallic inclusions and hydrogen: implications to the self-expandable stents

The structural integrity of self-expandable stent is of great importance for the performance of this safety critical device during deployment and life-time service. The presentation firstly reports our recent finding about the dependence between the corrosion susceptibility and the inclusion contents. The comparative microstructural characterizations of the laboratory-made and commercial stents are presented before and after ASTM F2129 assessments to show the effects of inclusions in different area fractions. As the second part of the presentation, our recent finding about the effect of hydrogen is reported to the change of deformation mechanism of superelastic NiTi. The hydrogen concentrations in the commercial stents are measured and used as studying targets. In-situ microstructural characterizations, coupling EBSD with tensile loading, are performed on the samples charged to different hydrogen concentrations to study the hydrogen’s influences to the local operating mechanisms of NiTi. Towards the structural integrity and safety concerns, implications of the results are discussed under the conditions of self-expandable stent application.