Improving the radiopacity of Fe–Mn biodegradable metals by magnetron-sputtered W–Fe–Mn–C coatings: Application for thinner stents
Samira Ravanbakhsh, Carlo Paternoster, G. Barucca, P. Mengucci, Sofia Gambaro, Théophraste Lescot, Pascale Chevallier, Marc‐André Fortin, Diego Mantovani
Abstract
In this exploratory work, micrometric radiopaque W-Fe-Mn-C coatings were produced by magnetron sputtering plasma deposition, for the first time, with the aim to make very thin Fe-Mn stents trackable by fluoroscopy. The power of Fe-13Mn-1.2C target was kept constant at 400 W while that of W target varied from 100 to 400 W producing three different coatings referred to as P100, P200, P400. The effect of the increased W power on coatings thickness, roughness, structure, corrosion behavior and radiopacity was investigated. The coatings showed a power-dependent thickness and W concentration, different roughness values while a similar and uniform columnar structure. An amorphous phase was detected for both P100 and P200 coatings while -Fe, bcc-W and W 3 C phases found for P400. Moreover, P200 and P400 showed a significantly higher corrosion rate (CR) compared to P100. The presence of W, W 3 C as well as the Fe amount variation determined two different microgalvanic corrosion mechanisms significantly changing the CR of coatings, 0.26 0.02, 59.68 1.21 and 59.06 1.16 m/year for P100, P200 and P400, respectively. Sample P200 with its most uniform morphology, lowest roughness (RMS = 3.9 0.4 nm) and good radiopacity (~6%) appeared the most suitable radiopaque biodegradable coating investigated in this study.