Nitrogen Quantification and Tracking During High Temperature Oxidation in Air of Titanium Using 15N Isotopic Labelling

Isotopic labelling was used to track the diffusion of nitrogen during the oxidation of Titanium in air at 700 degrees C. Alternate exposure in 15N2-labelled air and regular air was used. The nitrogen is mainly located at the oxide/ metal interface and forms essentially a nitride phase close to Ti2N. Each nitrogen isotope was quantified by Nuclear Reaction Analysis. Nitrogen quantity doubles between 5 and 20 h, which represents 16% respectively 12.5%, of the total mass gains. The nitrogen is partially renewed by both inward and outward diffusion during the oxidation. A model for nitrides migration is proposed.