Structure and corrosion resistance of Ti/TiC coatings fabricated by plasma immersion ion implantation and deposition on nickel–titanium

Titanium carbide coatings have a broad range of biomedical applications because of their high hardness, low friction, excellent corrosion resistance, and good biocompatibility. NiTi alloys are also widely used in surgical implants in orthodontics and orthopedics. In order to improve the surface properties, nanostructured titanium carbide coatings are deposited on NiTi by plasma immersion ion implantation and deposition after a titanium interlayer has been fabricated on the NiTi substrate. The structure and corrosion behavior which impact the biological properties are investigated systematically by X-ray diffraction, X-ray photoelectron spectroscopy, field-emission scanning electron microscopy, atomic force microscopy, and electrochemical impedance spectroscopy in simulated body fluids at 37°C. The TiC thin films with a C/Ti ratio of 1.087 have the (220) orientation. The EIS results demonstrate that the Ti/TiC multilayer provides significantly better corrosion resistance and stability compared to the uncoated NiTi substrate. ► A homogeneous and more corrosion resistant TiC ultra thin film is deposited by PIIID. ► The Ti thin film is deposited as an intermediate layer on NiTi on steel by magnetron sputtering. ► The Ti/TiC multilayer constitutes a barrier layer that is more protective than the native passive layer. ► High quality TiC coating led to improved corrosion resistance of NiTi.