Étude de la dégradation in-vitro d'alliages Fe-Mn-C pour des applications de stents cardiovasculaires
|Abstract:||Among steels, Fe-Mn-C alloys achieve the best compromise between high ultimate strength (UTS1000 MPa) and good ductility ((%) 40%) with a deformation mode based on both the dislocations glide and twinning induced plasticity effect (TWIP effect). At this combination of mechanical properties it can be add the fact that Fe-Mn-C alloys are low corrosion resistant in rich chloride ions (Cl-) environment. This good combination of mechanical and low corrosion properties makes them potentially useful materials for biodegradable stents applications. In fact their tendency to be low corrosion resistant can be exploited efficiently for biomedical applications by controlling their degradation behavior. However, Fe-Mn-C alloys are initially designed for the automotive industry in order to get lighter body metals which are able to absorb energy in case of impact. So there is no standard or protocol to perform in-vitro degradation tests for this class of alloys for use as biodegradable stents. This thesis was therefore devoted to studying the degradation behavior of some Fe-Mn-C alloys with TWIP effect in pseudo-physiological solutions. When deploying the stent into arteries they undergo severe plastic deformation, and once deployed, degradation occurs in a CO2-rich environment, therefore this study also examined the influence of plastic deformation and CO2 gas pressure effect on the degradation behavior in order to have experimental conditions that are closer to what happens in the artery. The results obtained show that the plastic deformation has no significant effect on the degradation rate, on the other hand the percentage of Mn, the presence of CO2 partial pressure, the presence and quantities of carbonate and phosphate ions in the solution or the presence of albumin have a great influence on the formation of degradation products and therefore the degradation rate of the Fe-Mn-C alloys.|
|Document Type:||Thèse de doctorat|
|Open Access Date:||24 April 2018|
|Collection:||Thèses et mémoires|
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