Structural investigation, corrosion properties and adhesion behavior of magnetron‐sputtered nanocomposite TiC/a:C thin film coatings

Abstract

Due to the continuous rise in living standards, the continued growth of the world population and the development of medical science an ever‐increasing need for materials especially suited for bio‐implant applications. In case of an implant material a wide variety of parameter (adhesion, corrosion, structural, biological and mechanical properties) to must be considered. Thus, a TiC / amorphous C (TiC/a:C) nanocomposite thin film as bio‐coating was developed by simultaneously depositing Ti and C on TiAl6V4 and Titanium wafers (blasted and unblasted) using DC magnetron sputtering system at room temperature to improve the aforementioned properties. Furthermore, in order to achieve the higher osseointegration, the TiC/a:C thin film was coated with ~500‐600 nm thick biogenic HAp coating by electrospraying. The relationship between the structural, mechanical, adhesion and corrosion properties of TiC/a:C nanocomposite thin film was investigated. The film's composition and morphology were studied by Transmission Electron Microscopy (TEM), X‐ray Photoelectron Spectroscopy (XPS) and X‐ray Diffraction (XRD). In all cases, combination of columnar TiC nanostructure and thin amorphous carbon was showed (Fig.1a) . In the case of Ti content above ~ 18 at%, the presence of the fcc TiC nanocrystals were confirmed by electron diffraction (Fig. 1b.) and by XRD (Fig.2) . The mechanical characteristics of the thin film were investigated by nanoindentation technique while the simulated body fluid (SBF) was developed initially to evaluate the surface structural changes of the film. The applied pH was 7.25. The potential changes in the surface structure of the thin film were investigated by Scanning Electron Microscope (SEM) which does not show special structure change in the film's surface after the corrosion test and the calcination at 900 °C (Fig. 3) . The highest hardness ~ 26 GPa and modulus of elasticity ~ 140 GPa was observed in case of the film prepared at ~ 40 at% Ti content which consisted of ~ 20 nm width TiC columns separated by 2‐3 nm thin a:C layers. Overall, the results demonstrated that the best choice for a protective nanocomposite coating would be the TiC/a:C thin film with ~60 at% a:C and ~40 at% Ti contents which is sufficiently corrosion‐resistant, hydrophobic, nontoxic, biocompatible and mechanically stable.