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

Abstract

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 cm 2 ), owing to the formation of TiO 2 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 . • ta-C:Ti and ta-C:Ti/Ti notably increased sp 2 bonding fractions. • All DLC films notably improved 316L corrosion resistance in PBS + 1 g L −1 of HA. • Ti interlayer enhanced pitting corrosion resistance while Ti dopant increased R p . • ta-C:Ti/Ti exhibited the most corrosion resistance and biocompatibility due to TiO 2 . • TiO 2 manifested as a barrier layer and a preferred site for HAp formation.