Degradable porous Fe-35wt.%Mn produced via powder sintering from NH4HCO3 porogen

In this study, a Fe-35Mn (wt.%) alloy was produced by a simple press-and-sinter process from blended elemental powders with ammonium bicarbonate as porogen (space holding). The addition of NH4HCO3 leads to an open-cell porosity of 25-31% in the sintered compacts. The predominant phases in the sintered porous samples are austenitic γ and martensitic ε phases. The presence of these two antiferromagnetic phases assures magnetic resonance imaging (MRI) compatibility. The degradation performance was evaluated by static immersion and electrochemical test. The degradation rate determined by potentiodynamic analysis ranges from ca. 2 to 8 mmpy in both 5% NaCl and simulated body fluid (SBF) solutions, depending on porosity in the samples. Static immersion test performed under conditions close to in vivo degradation confirms the findings from potentiodynamic test. The degradation rate decreases over time and gradually levels off after 7 days of immersion. The observed degradation rate meets the requirements for a biodegradable material. However, the mechanical properties have to be improved in order to maintain mechanical integrity for biomedical applications if the porous Fe-35Mn is used. Nevertheless, the promising degradation properties would provoke further development of biodegradable Fe-Mn alloys in the future.