Abstract
In order to improve the corrosion and wear resistance of biomedical Ti-6Al-4V implants, a Ta2N nanoceramic coating was synthesized on a Ti-6Al-4V substrate by the double glow discharge plasma process. The Ta2N coating, composed of fine nanocrystals, with an average grain size of 12.8 nm, improved the surface hardness of Ti-6Al-4V and showed good contact damage tolerance and good adhesion strength to the substrate. The corrosion resistance of the Ta2N coating in Ringer’s physiological solution at 37 °C was evaluated by different electrochemical techniques: potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), potentiostatic polarization and capacitance measurements (Mott-Schottky approach). The evolution of the surface composition of the passive films at different applied potentials was determined by X-ray photoelectron spectroscopy (XPS). The results indicated that the Ta2N coating showed higher corrosion resistance than both commercially pure Ta and uncoated Ti-6Al-4V in this solution, because of the formed oxide film on the Ta2N coating having a smaller carrier density (Nd) and diffusivity (Do) of point defects. The composition of the surface passive film formed on the Ta2N coating changed with the applied potential. At low applied potentials, the oxidation of the Ta2N coating led to the formation of tantalum oxynitride (TaOxNy) but, subsequently, the tantalum oxynitride (TaOxNy) could be chemically converted to Ta2O5 at higher applied potentials.
Highlights
Due to the increased numbers of elderly people in today’s society as a percentage of the population and the growth of accidents, there is ever-increasing demand for artificial joint replacements to surgically substitute for diseased or lost bones to restore form and function [1]
It can be found that the elastic recovery values increase from 28% for uncoated Ti-6Al-4V to 55% for uncoated Ti-6Al-4V to 55% for the Ta2N coating, suggesting better elastic resistance for the the Ta2 N coating, suggesting better elastic resistance for the Ti-6Al-4V substrate coated with Ta2 N
A Ta2 N nanoceramic coating was fabricated onto Ti-6Al-4V substrate in an Ar and N2 gas mixture using a double glow discharge plasma process
Summary
Due to the increased numbers of elderly people in today’s society as a percentage of the population and the growth of accidents, there is ever-increasing demand for artificial joint replacements to surgically substitute for diseased or lost bones to restore form and function [1]. Metallic materials have been extensively used as hard tissue replacements for artificial bone and joint implants. Compared to more conventional stainless steels and cobalt-based alloys, titanium and its alloys have greater advantages for applications in orthopedic implants, because of their lower modulus, lower density, superior biocompatibility and better corrosion resistance [2]. Among various types of Ti alloys, Ti-6Al-4V is the first, and the most commonly used, implant material, for orthopedic prosthesis applications.
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