Nanostructured tantalum nitride coatings are widely used in biomedical engineering due to the good hardness, wear resistance, and corrosion resistance. In this work, TaN and Ta/TaN nanostructured coatings were deposited on the NiTi alloy by magnetron sputtering for 150 min at a pressure of 3.8 × 10–3 mbar using a power of 143 W. The phase, structure, morphology, and thickness were evaluated by X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscopy (FE-SEM), and atomic force microscopy (AFM), respectively. The nanomechanical properties such as Young's modulus (E) and hardness were determined by nano-indentation and nano-scratch tests. To assess the biological properties of the coatings, the antimicrobial activity was monitored by the disk diffusion antibiogram technique using E.coli as the model gram-negative bacteria and S. aureus as the gram-positive bacteria and the biocompatibility was also studied. A homogeneous, uniform, and crack-free of TaN monolayered and Ta/TaN bilayered coating with a thickness 1050 and 1310 nm, respectively, were produced by magnetron sputtering. As a result of the Ta middle layer in the Ta/TaN coating, the hardness increased by 22% from 6.3 ± 0.5 GPa to 7.6 ± 0.5GPa under a load of 700 µN and 6% from 6.1 ± 0.2 GPa to 6.5 ± 0.3 GPa under a load of 1000 µN. The critical load also increased from 3.7 ± 0.2 to 4.1 ± 0.6 N in the presence of the Ta intermediate layer which improved the adhesion strength of the Ta/TaN bilayer compared to the TaN monolayer. In addition, the Ta intermediate layer increased the flexibility leading to a adhesive wear mechanism for the friction behavior of Ta/TaN. The bacteriostatic ability against gram-negative bacteria and bacteriocidal ability against gram-positive bacteria increase. Our results demonstrate that the nanostructured Ta/TaN bilayer coating provides a better bioactive surface for the growth and proliferation of MG-63 ossicular osteosarcoma cells growth as well.
