The interest in biodegradable metallic materials for the application as temporary implants has been continuously increasing within the last years. Due to the progressive degradation after providing a temporary support on healing process of a diseased tissue, disadvantages of permanent implants, such as further surgery, prolonged physical irritation and chronic inflammation, lack of adaptation to growth may overcome. Recent studies mainly focus on Mg- and Fe-based alloys. The broad range of mechanical properties and the excellent processibility of Fe-based alloys are in particular of great interest for stent application.
In this work, the influence of microalloying with sulphur (S) on the microstructure, the tensile behavior and the degradation properties of a cast Fe69Mn30C1 alloy is presented. By applying a special casting process implying relatively high cooling rates and pure preparation conditions alloys with a fine-grained microstructure can be obtained. The addition of S promotes the formation of a face-centered cubic MnS, which was verified by a combination of electron backscatter diffraction (EBSD) and energy dispersive X-ray spectroscopy (EDX). This additional phase leads to changes in the mechanical and degradation behavior. So an increase of the yield strength and ultimate tensile strength could be detected. Furthermore, a pronounced TWIP effect was verified in all examined alloys leading to a pronounced work-hardening capacity. By means of electrochemical polarization tests and microstructural investigations, the corrosion behavior of the alloys was examined in a synthetic body fluid (TBS) and a change in the initial corrosion behavior due to the increase of finely distributed MnS with increasing S content could be detected. Altogether, microalloying with S is an effective method to enhance the performance of cast Fe69Mn30C1 alloy for biomedical applications.