Characterisation of gradient interfaces in thin film multilayers used to protect orthopaedic implants

Titanium-titanium nitride multilayers were firstly used to enhance the corrosion protection and mechanical properties of coatings and, for this reason, they are good candidates for protective coatings for orthopaedic implants. These properties are strongly dependent on the thin film deposition method and on the shape of the interface between the titanium and the titanium nitride layers. In this work we use a set of multilayers with a titanium to titanium nitride thickness ratio in the range from 0.25 to 4. The films were deposited by magnetron sputtering and ion beam assisted deposition, and the deposition parameters were changed to obtain an interface in gradient (or not as the case may be). The film composition, the periodic structure of the multilayers and the interface type were characterised by means of Rutherford backscattering. nuclear reaction analysis and cross sectional transmission electron microscopy and the crystal phases and textures were studied with X-ray diffraction. To compare the coatings, the corrosion protection power, obtained by means of cyclic voltammetry, and the coating micro-hardness measured with a Vickers indentor, were used. (C) 1999 Elsevier Science S.A. All rights reserved.