The nitrogen effect on the oxidation behaviour of Ti6242S titanium-based alloy: contribution of atom probe tomography

^a CIRIMAT laboratory, University of Toulouse, CNRS, INPT, UPS, ENSIACET 4 allée Emile Monso, BP-44362, 31030 Toulouse Cedex 4, FRANCE
^b Aix-Marseille Université, CNRS, IM2NP, Faculté de Saint-Jérôme, Case 142, 13397 Marseille Cedex 20, FRANCE
^c Airbus Operations SAS, 316 Route de Bayonne, 31060 Toulouse Cedex 09, FRANCE

^* Daniel.Monceau@ensiacet.fr

Abstract

At high temperatures under oxidizing environments, titanium-based alloys form an oxide scale and dissolve large amount of oxygen in their metallic matrix. Oxygen dissolution is a cause of embrittlement. Nitrogen is a secondary oxidant, which also dissolves in titanium during oxidation in air. Oxidation experiments of Ti-6Al-2Sn-4Zr-2Mo-0.1Si titanium-based alloy at 650 °C for 1000 h in synthetic air (20%O₂- 80%N₂) and in a mixture of 20%O₂-80%Ar, showed that nitrogen reduces both oxide scale growth and oxygen dissolution. Atom probe tomography revealed that nitrogen effect is due to the formation of an interfacial layer of nitride Ti₂N but also to the formation of a nitrogen rich a-Ti-based solid solution, which both act as difiusion barriers for oxygen because of their low oxygen solubility.