Plasma Immersion Ion Implantation of a Fe-Mn-C Based Steel for Biomedical Applications: Effect of Gases and Treatment Times on the Surface Properties

Abstract

Current research on biodegradable iron-based alloys mainly focuses at regulating the material degradation rate, as well as its biological behavior, especially from the point of view of the hemocompatibility and cytocompatibility. In fact, fine-tuning of the surface roughness, morphology and chemical composition can improve the functional response of the material. For that purpose, a surface modification strategy, namely plasma immersion ion implantation (PIII), is proposed to perform the selective modification of surface properties without affecting the bulk ones. In this work, the influence of treatment time (timp = 15, 60 and 120 min.) and implanted species (O, N or C) on the surface properties of a Fe-13Mn-1.2C resorbable alloy was investigated. The findings demonstrated that varying the process gas and the exposition time led to a variety of topographies, surface energies and chemical compositions. XPS analyses and depth profiles clearly showed the impact of the process parameters on the surface features and element distribution, due to implanted species penetration into the alloy. The implanted samples showed a delayed clotting time, thus a better hemocompatibility. In contrast, nitrogen-treated surfaces displayed a more pronounced hemolytic behavior, whereas oxygen and methane did not. PIII implantation appears to be a versatile solution for fine-tuning surface topography, composition and biological properties, making the process promising for the improvement of metallic biodegradable vascular implants.