Titanium interlayer between Ti-O film on CoCrMo implant alloy for improving adhesion: Detailed XPS and TEM analysis of the interface

The stability of interface adhesion of the Ti-O film is an important factor in evaluation of the suitability of Ti-O surface modification of stents. In our previous work, Ti-O films were deposited on Ti pre-coated and virgin CoCrMo substrate by high power pulsed magnetron sputtering. A Ti interlayer that formed on the CoCrMo alloy substrate can improve the film-substrate adhesion. In order to further understand the properties of the Ti-O coating on CoCrMo with Ti interlayer, the elemental composition and chemical state of the Ti-O/Ti film were measured by X-ray photoelectron spectroscopy layer-by-layer. The microstructure and chemistry at the interface were characterized by Transmission Electron Microscopy. The results indicate that there is no delamination even though the substrate endures large deformation. The Ti interlayer significantly improves the Ti-O film adhesion, which may be ascribed to the presence of Co-Ti metal bonding in the TiO/Ti/CoCrMo system as well as strong physical bonding. Thus we find that a Ti interlayer can release shear stress generated in interface deformation and improve the deformation coordination between the Ti-O film and the CoCrMo substrate.