The influence of Ti additions on the mechanical and electrochemical behavior of β-Ta5Si3 nanocrystalline coating

Abstract

In this study, the effects of Ti substitutional additions on the mechanical and electrochemical corrosion behavior of β-Ta5Si3 were investigated through both theoretical calculation and experiment. Initially, first-principles calculations, based on density functional theory, were used to guide compositional design, according to the calculation of mechanical parameters (for example, bulk modulus, shear modulus, Young's modulus, the shear modulus/bulk modulus ratio and Poisson's ratio). This analysis showed that optimum mechanical performance may be achieved through Ta atoms in the Ta20Si12 unit cell being replaced by two Ti atoms. Subsequently, both the binary β-Ta5Si3 coating and the optimized Ti-alloyed β-Ta5Si3 coating (i.e., β-(Ta0.902Ti0.098)5Si3) were deposited onto Ti–6Al–4V substrates using a double cathode glow discharge plasma method. Both as-deposited coatings exhibited a tetragonal crystal structure with fine equiaxed grains ∼4nm in diameter. The mechanical properties of the coatings were determined by both nanoindentation and Vickers indentation techniques, and their electrochemical corrosion behavior was examined by potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and Mott-Schottky analysis in naturally aerated 0.9wt.% NaCl solution at 37°C. These investigations showed that the addition of Ti significantly improved the damage resistance of β-Ta5Si3, with little negative impact on its corrosion resistance.