The Formation of the Surface Layers of a VT6 Titanium Alloy by Ion Beam Mixing of Carbon Nanofilms

Resumo

Abstract—The influence of ion beam mixing of carbon on the surface morphology, chemical composition, atomic structure, and microhardness of the surface layers of samples of a VT6 titanium alloy is investigated. It is found that conditions for the formation of titanium carbides are created in the transition layer of the film/substrate system during ion beam mixing. The formation of titanium carbides with both stoichiometric and nonstoichiometric ratios of the components occurs. The concentration of titanium carbides increases with the increase in the irradiation dose and reaches 20 at % at a dose of 4 × 10¹⁷ ion/cm². The mixing manifests itself in the mutual penetration of carbon atoms into the target and target atoms, mainly titanium, into the film. However, a thin surface layer with a depth of about 20 nm which is mainly composed of carbon atoms remains. It is shown that, in this layer, carbon atoms are in a disordered state with both sp² and sp³ hybridization of the C–C bonds. The formation of titanium carbides in the transition layer and the disordered structure of carbon on the surface of the film during ion beam mixing determines the hardening of the surface layer, and as a result, an increase in the microhardness of the samples by 100% or more occurs. It is shown that the growth in the microhardness is associated with the layer formed as a result of mixing rather than the influence of irradiation on the titanium alloy substrate.