Microstructure, mechanical properties, and blood compatibility of zirconium nitride deposited on nickel–titanium shape memory alloy

ZrN is deposited on electropolished NiTi shape memory alloy to enhance the surface properties. The microstructure, mechanical properties, and blood compatibility are evaluated by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), nanoindentation, hemolysis analysis, and blood platelet adhesion test. The ZrN film has a fine fibrous structure composed of the desirable stable ZrN phase together with a small amount of a second ZrO2 phase. The hardness and modulus values increase initially with larger nanoindentation depths and after reaching maximum values, gradually decrease finally attaining stable values of about 3.4 GPa and 68 GPa, respectively which reflect the composite hardness and modulus values of the system. Our study reveals that the ZrN film may degrade the surface wettability, but the hemolysis resistance and thromboresistance can be improved thereby making the surface treated materials more suitable in biomedical implants.