Mechanical properties of titanium oxide film deposited on LTI-carbon by IBED

Abstract

Titanium oxide films were deposited on low temperature isotropic pyrolytic carbon (LTI-carbon) by ion beam enhanced deposition, and its mechanical properties such as ultramicrohardness, adhesion strength and fatigue property were studied. The microhardness of titanium oxide films prepared at different experimental conditions is maintained between 900 and 1000 kg/mm 2, when measured by UMHT-3 ultramicrohardness tester installed in the scan electronic microscope. The adhesion strength measurement results show that the adhesion strength of titanium oxide films on LTI-carbon substrate is approximately 0.314–0.47 GPa. The deposition of Ti interlayer is beneficial to improve the adhesion strength of the film. Subsequently, the film with the highest adhesion strength was coated on mechanical heart valves, and the fatigue and wear resistance of the film was investigated in a simulated heart-valve-working environment. After 675 500 times of opening-and-closing cycles, a circular abrasion trail appeared, whereas titanium oxide was still present in this area. No peel of the film was observed. When the cycles increased to 1 617 000 times, a small part of the film located at the inboard boundary of the wear trail peeled off, however, Ti still could be detected in the wear trail region.