An investigation on the properties of injection-molded pure iron potentially for biodegradable stent application

Abstract

Metal injection molding (MIM) is a near-net-shape manufacturing process suitable for the production of small-size and complex-shape components. As a cost-effective and flexible manufacturing method, it may have distinct advantages over other methods when it comes to the manufacturing of implantable medical devices. However, up till now, the potential for MIM to be employed in the commercial-scale manufacturing of implantable medical devices has been insufficiently exploited. In the present research, an attempt was made to produce porous pure iron, as a metallic degradable biomaterial potentially for stent application, via the MIM route. The effects of iron powder loading and sintering temperature on the porosity, microstructure, mechanical properties, surface properties and in vitro degradation behavior of MIM iron were investigated. The results obtained were compared to those of cast iron. It was found that the amount of porosity retained in the as-sintered specimens had a major effect on their surface and mechanical properties. MIM iron exhibited strengths between those of magnesium alloys and 316 L stainless steel and very high ductility — a specially required property of stent materials. Its degradation rates in Hank's solution were superior to the degradation rate of cast iron. Interestingly, the material made from the feedstock containing 66% of iron powder, above the critical powder loading, showed the highest elongation and a good in vitro degradation rate. In conclusion, MIM is a promising method to be developed as a new route to produce thin-wall tubes for biodegradable stents.