Plasma surface modification of titanium by TiB precipitation for biomedical applications

In order to improve the surface properties of titanium and expand its clinical application, many methods have been applied to modify its surface. In this work, properties of titanium were modified by boride microplasma surface alloying. Plasma surface alloying gives a wide range of layer thickness, which is controlled by the amount of the placed powder and process parameters. Formation of TiB phase precipitation was confirmed by XRD analysis. Additionally, the modified microstructure was observed by optical microscopy. The Vickers microhardness was significantly improved from 180 HV for original titanium substrate to 900 HV in obtained composite layer structure, with a smooth hardness reduction in the cross section profile. Strong heat penetration from microplasma melt-in technique led to substrate dissolution with formation of stable TiB phase dispersed in α-Ti matrix. The electrochemical treatment in phosphoric acid electrolyte resulted in developed surface formation, attractive for tissue fixing and growth. In vitro cytocompatibility of these materials was evaluated and compared with a conventional microcrystalline titanium, where normal human osteoblast (NHOst) cells from Lonza (CC-2538) were cultured on the disks of the materials and cell growth was examined. The results of the in vitro test suggest that TiB phase dispersed in α-Ti matrix displays good cytocompatibility, compared to that of microcrystalline titanium. Additionally, the SEM observation reveals a significant difference in morphological characteristics of the cells on developed and polished material, just after 1 day of cell culture. It can be concluded that, plasma alloying is an effective method to produce TiB phase dispersed in α-Ti matrix with high hardness, good cytocompatibility, which makes them potential candidates for biomedical applications.