Features of obtaining tantalum-containing coatings by magnetron sputtering

Abstract

Tantalum-containing coatings deposited on titanium in vacuum were studied. For deposition of films, a DC magnetron with a balanced magnetic system was used. High purity (99.99 %) tantalum sheet was used as a target. The current density of the glow discharge during the etching of the target was 20.4 A / m 2 . Plasma-forming gases were argon or a mixture of argon and oxygen. Three types of coatings of tantalum on titanium were obtained: the first one was tantalum oxide on titanium, the secondtantalum on titanium, and the third -tantalum on titanium with a tantalum oxide sublayer. The effect of a pre-deposited sublayer of tantalum oxide on the hardness and morphology of the "base-coating" system was studied. It was found that of the greatest practical interest is an oxygen-saturated tantalum coating with the thickness of 800 nm deposited on a tantalum oxide sublayer with the thickness of 75 -80 nm. Nanoindentation of samples with a tantalum-containing coating without a tantalum oxide sublayer revealed an increase in hardness up to 39 GPa and in elastic modulus up to 194 GPa. In case of the deposited tantalum oxide sublayer, the nanoindentation hardness reached 60 GPa, and the elastic modulus was 230 GPa. This superhard two-layer structure had a bimodal hardness distribution and contained a Ta 2 O phase with a cubic crystal lattice. In this case, the proportion of measurements related to superhard inclusions was at least 43 %. The coating had a heterogeneous structure consisting of agglomerates with a size of 0.4 -0.5 µm. The chemical composition of the surface layer was characterized by an oxygen content of 17.46 at.%, titanium -within 2.00 at.%, and tantalum -80.54 at.%. An increase in the proportion of coating agglomerates with a size of 0.2 -0.3 µm was observed from 53.13 to 68.25 % when using a tantalum oxide sublayer. The results make it possible to consider the developed process of obtaining coatings promising for the application of functional layers on titanium medical devices.