Micro-arc Oxidation Films On Titanium, Zirconium, Tantalum And Their Bio-tribological Behaviors

Titanium, zirconium and tantalum are all bio-inert materials with poor wear resistance. Titanium and zirconium treated by micro-arc oxidation (MAO) could be improved the biocompatibility and wear resistance. But nowadays the research of tantalum treated by micro-arc oxidation has not been reported. The amounts of titanium MAO films' research on bio-tribological properties are relatively small, while zirconium and tantalum MAO films' bio-tribological properties are rarely reported. In this research porous MAO films contained Ca and P firstly were prepared in situ on titanium, zirconium and tantalum. Then the morphology, structure and composition of MAO films were investigated. The tribological behaviors of the films were mainly investigated by using ball-on-disc reciprocating friction and wear tests in 25% calf bovine synovia lubrication.The results showed that titanium, zirconium and tantalum MAO films were rough and porous. With the anode voltage increased, the films' thickness and pore diameter increased. Zirconium MAO films' pore size and thickness had bigger size compared to titanium and tantalum MAO films. The nano-hardness of the films were higher than the matrix materials, however their elastic modulus were lower than the matrix materials.Titanium MAO films were mainly composed of anatase TiO2 at the 300V voltage. As the voltage increased, the anatase TiO2 gradually transformed into rutile TiO2.Zirconium MAO films were mainly composed of c-ZrO2, t-ZrO2 and a small amounts of m-ZrO2.Tantalum MAO films were mainly composed of Ta2O5, TaO, and CaTa2O6.The tribological tests of the MAO films sliding against Si3N4 ceramic ball in 25% calf bovine synovia lubrication showed that the friction coefficient of the three materials' MAO films were higher than the matrix materials. Except MAO films of titanium treated at 450V, the other films' wear rates were lower than the matrix materials', which exhibited good anti-wear property.A comparison of the biological friction and wear properties of the three metals' MAO films indicated that the friction coefficient of titanium sliding against Si3N4 ball were higher than that of tantalum MAO films, but lower than that of and zirconium MAO films. The wear rates of zirconium MAO films were much more higher. Marks ploughed and scratched on the titanium and tantalum MAO films' surface were more obvious, while the peeling pits' amounts and size of zirconium MAO films were much more and bigger. These illustrated that zirconium ceramic films were more brittle than the other two films and the wear mechanism was fatigue peeling wear. The abrasive wear mechanism of these three metals' MAO films both had micro-cutting and fatigue peeling.