Surface characterization and preparation of Ta coating on Ti6Al4V alloy

In this study, high quality Ta coating was made on both plate and porous Ti6Al4V alloy substrates by atmospheric pressure chemical vapor deposition (APCVD) in order to further improve the corrosion resistance and biocompatibility of Ti alloys for medical application. XRD analyses showed that the coatings were mainly composed of Ta with the substrate temperature (T-s) of 1000 degrees C, 950 degrees C and 900 degrees C. The morphology, microstructure and elements composition were characterized by optical microscope, scanning electron microscopy (SEM), atomic force microscopy (AFM) and energy-dispersive spectroscopy (EDS). It was found that the coating surface became much more smooth and uniform at low H-2 gas flow rate of 120 mL/min, and the root-mean-square (RMS) roughness was decreased with the increase of T-s,. The wettability of Ta coating was investigated by measuring contact angel of water and alpha-bromonaphthalene (alpha-BrNp). The Ta coating with Ts of 950 degrees C showed the lowest of gamma(s), gamma(d)(s) and gamma(d)(s)/gamma(p)(s)), indicating a better hemocompatibility of the Ta coating than that of substrate. The corrosion behavior of the coating was studied by electrochemical test in 0.9% NaCl solution at 37 degrees C. The Ta coating exhibited higher corrosion potential (E-corr) and lower corrosion current density indicating an improved corrosion resistance compared with the Ti6Al4V substrate. Ta coating was fabricated not only on the plate substrate, but also on a porous Ti6Al4V substrate. The above results made it possible to develop a novel class of Ta-coated Ti alloy implants with wide clinical applications. (C) 2015 Elsevier B.V. All rights reserved.