Abstract
Ti-6Al-4V alloy with TiO2 coating is the most commonly selected material to construct an aortic heart valve. Wear resistance is the main mechanical property to be evaluated for this purpose. In this paper, the wear resistance of TiO2 thin films obtained by anodic oxidation of Ti-6Al-4V is evaluated. Anodic oxidation was performed at 20 V to 70 V with a H2SO4 1 M electrolyte. The samples were thermally treated at 500°C for 1 h, and crystalline phases of TiO2 were obtained. The wear was performed in a ball-on-flat reciprocating machine with a range of loads from 1 gf to 4 gf and times between 60 s and 1200 s, using a diamond sphere as counterface. The counterface oscillates at 0.5 Hz and 4 mm in amplitude. The wear is measured using a profilometer and is calculated as the worn volume. The wear resistance of the coated samples is larger than the substrate, and increases with thickness and with crystalline coating.
Highlights
Ti-6Al-4V alloy coated with a nano-film of TiO2 is a promising material to build prosthetic heart valves with good haemocompatibility properties [1,2,3]
From previous reports [10,11,12,13,14,15] it is known that films obtained by this technique produced using a 1 M H2SO4 electrolyte solution up to an applied voltage of 60 V are amorphous
The results show that the crystalline films (70, 500, 20-500, 40-500 and 60-500) present higher wear resistance than the amorphous films (20, 40, 60)
Summary
Ti-6Al-4V alloy coated with a nano-film of TiO2 is a promising material to build prosthetic heart valves with good haemocompatibility properties [1,2,3]. The thickness of the coating can be controlled through the applied voltage between the anode (the sample) and the cathode [9]. From previous reports [10,11,12,13,14,15] it is known that films obtained by this technique produced using a 1 M H2SO4 electrolyte solution up to an applied voltage of 60 V are amorphous. In order to obtain crystalline coating a heat treatment must be applied. It has been found that a heat treatment of 1 h at 500°C produces good crystalline coating without significant changes in thickness or morphology of the films [14, 15]
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