EVALUATING SOL-GEL CERAMIC THIN-FILMS FOR METAL IMPLANT APPLICATIONS .2. ADHESION AND FATIGUE PROPERTIES OF ZIRCONIA FILMS ON TI-6AL-4V

The degree to which ceramic coatings or thin films applied to bone-int erfacing metallic implants can improve the overall performance of thes e implants with respect to implant fixation, wear, or corrosion relies especially on the response of these films to loading. In this study, the adhesion and fatigue properties of sol-gel zirconia films that cou ld be reproducibly deposited onto polished Ti-6Al-4V substrates was in vestigated. For zirconia films on the order of 100 nm thick, a shear l ag-based strain approach indicated a shear adhesion strength of approx imately 275 MPa. Small variations in film thickness and substrate surf ace preparation had little effect on this adhesion, which was believed to be due to alkoxide molecule interactions with free hydroxyl groups on the substrate surface as well as some limited interfacial diffusio n following the 500 degrees C anneal. Subsequent fatigue testing of th ese films in air using novel tapered rotating beam fatigue samples dem onstrated their excellent fatigue characteristics, with films survivin g up to 10(7) cycles, the endurance limit of the Ti-6Al-4V (similar to 635 MPa). Overall, the exceptional mechanical properties of this ZrO2 /Ti-6Al-4V system along with the inherent advantages of sol-gel proces sing support continued studies to utilize this technology for implant surface modification. (C) 1996 John Wiley & Sons, Inc.