Phase Composition and Biocompatibility of Coatings Produced on Ti–6Al–5V Titanium Alloy via Diffusion Saturation with Oxygen, Nitrogen, and Carbon

Abstract

Ti–6Al–5V titanium alloy was subjected to surface saturation with carbon, nitrogen, and oxygen in order to study the effect of surface modification on its wear resistance and biocompatibility. The alloy was saturated with carbon and nitrogen in low-pressure atmospheres. Oxygenation was carried out by heating the alloy in a solid carburizing agent. The structure and phase state of the grown layers were studied by optical microscopy and X-ray diffraction. General trends in the saturation of the titanium alloy with nonmetals are the formation of a diffusion layer and an increase in the amount of phases based on the α-Ti solid solution, followed by the formation of intermediate phases, such as carbides, nitrides, and oxides differing in stoichiometry, on the surface of the continuous layer. After saturation, the alloy was covered with thin carbide, nitride, and oxide surface layers and had diffusion layers under them. The hardness of the nitrogenated and oxygenated surfaces was 950–1000 HV, and that of the surfaces saturated with carbon was 570 HV. The wear resistance of the alloy was lowest in the as-prepared state and highest after oxygenation. Biocompatibility was assessed from the proliferation of osteoblast-like cells of the MG-63 line. The best biocompatibility was demonstrated by the oxygenated samples, and the biocompatibility of the nitrogenated samples was better than that of the carburized samples. The untreated alloy showed the lowest biocompatibility.