Improvement of corrosion resistance and biocompatibility of 316L stainless steel for joint replacement application by Ti-doped and Ti-interlayered DLC films

Titanium was incorporated and interlayered into diamond-like carbon (DLC) films deposited on 316L stainless steel using a filtered cathodic vacuum arc. The local bonding structure, corrosion, and biocompatibility of non-doped DLC (ta-C), Ti-interlayered (ta-C/Ti), Ti-doped (ta-C:Ti), and Ti-doped and Ti-interlayered (ta-C:Ti/Ti) DLC films were thoroughly investigated. ta-C:Ti/Ti (0.55 at.%Ti) exhibited not only the highest corrosion resistance performance, including the lowest corrosion rate (7.34 × 10−8 mm yr−1), the highest pitting potential (1672.97 mV), and the highest polarization resistance (5.97 MΩ cm2), owing to the formation of TiO2 on its surface, as confirmed by X-ray photoelectron spectroscopy and near-edge X-ray absorption fine structure spectroscopy, but also the highest amount of hydroxyapatite, an indicator for biocompatibility, on its surface as determined with Fourier transform infrared spectroscopy and scanning electron microscopy. Two barrier layers, namely, outer and inner layers, were observed in ta-C/Ti and ta-C:Ti/Ti, while only one barrier layer was in ta-C and ta-C:Ti, as demonstrated by electrochemical impedance spectroscopy. Therefore, ta-C:Ti/Ti is an alternative promising DLC film for joint replacement biomaterials.