The Open-Access Journal for the Basic Principles of Diffusion Theory, Experiment and Application Kinetic peculiarities of two-component diffusion saturation of titanium under rarefied nitrogen-oxygen-containing medium

Previously, it was investigated the kinetics of single-component diffusion saturation of titanium by the interstitial elements (nitrogen or oxygen) [1]. It is clear that diffusion saturation of the materials by two and more components allows to change the properties of surface layers more considerably com-pared with single-component saturation. But it requires the theoretical knowledge about the kinetics of formation of diffusion zone, its composition and distribution of the elements. The aim of this work is to investigate analytically the peculiarities of simultaneous two-component (nitrogen and oxygen) diffusion saturation of titanium under rarefied controlled gaseous medium. Kinetics of the compatible diffusion of nitrogen and oxygen in titanium is complicated and many-sided. The two-component (nitrogen and oxygen) diffusion saturation of titanium under rarefied controlled gaseous medium (PN PO2) will be considered. Will be accepted that nitrogen µG1 (PN) and oxygen µG2 (PO2) potentials in gaseous medium (Fig. 1) such that concentrations of nitrogen C S 1 and oxygen CS2 on the titanium surface equilibrium with the medium do not exceed their maximum solubilities, according to the phase diagrams. For T=800 ◦C they are 16 at. % and 33 at.%, respectively [2]. Figure 1: Scheme of mass transfer in system Ti-G(N, O2) It should be noted that very often in the case of two-component diffusion the influence of one component is more significant than the other component. It will be accepted that oxygen (com-ponent 2) diffuses independently, while it affects the chemical potential (µ1(x,τ) = d11C1(x,τ) + d12C2(x,τ), µ2(x,τ) = d22C2(x,τ)) and diffusion ability (D12 = d12L11, D21 = 0, L11 – Onsager kinetic coefficient) of nitrogen (component 1). We have a system of the differential equations for description of the diffusion of these components