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

Fe-Mn-C alloys show unique mechanical properties making them a promising candidate to fabricate thin biodegradable cardiovascular stents [1]. However, compared with the conventional Co-Cr stents, these alloys have low radio-visibility under X-ray imaging, and this can impede their visualization during the clinical implantation, and the follow-up procedures [2][3]. Currently, tantalum markers have been used in the extremities of biodegradable stents to improve their radio-visibility. However, Ta is corrosion-resistant and its medium- and long-term fate upon degradation raises concern. The present work investigated the use of radiopaque biodegradable coatings to increase the overall visibility of stents while avoiding corrosion-resistance markers. Tungsten, a high-density biodegradable element (19.3 g.cm-3) with high X-ray attenuation coefficient, was selected to improve the radio-visibility of stents [3]. Fe-Mn-C-W coatings were deposited on Fe-Mn-C substrates by magnetron sputtering plasma deposition. To investigate the effect of W on the properties of the coatings, two coatings with different chemical compositions (50 and 80 at.% W) were prepared using two different sputtering powers for tungsten (200W and 400W), and three different deposition temperatures (25°C, 300°C and 600°C). The effect of the chemical composition and deposition temperature on the physicochemical, electrochemical and mechanical properties and radiopacity of the coatings were carefully studied. The coatings fabricated with higher amount of W (400W) showed different microstructures if compared to the 200W, and the presence of an intermetallic phase was revealed. This peak was not observed in XRD of 400W deposited at 600°C. Finally, the results showed that sample 400W deposited at 600°C had a suited corrosion rate and higher radiopacity, and could therefore be a promising candidate.
References:
[1] H. Hermawan, Prog. Biomater., vol. 7, no. 2, pp. 93–110, 2018.
[2] B. D. Cullity, Addision-Wesley Publishing Company, Inc., 2001.
[3] S. Schewe and D. A. Glocker, “Coatings for Radiopacity,” pp. 115–130, 2016.