Effect of Nitrogen on the Kinetics of Oxide Scale Growth and of Oxygen Dissolution in the Ti6242S Titanium-Based Alloy

Titanium-based alloys are increasingly used in aircraft industry due to their good mechanical properties and low density. To reach better efficiencies, the engine design is constantly evolving and the temperature of the combustion chamber is always increasing. Then, surrounding parts are exposed to higher working temperatures and consequently have to cope with more severe oxidation phenomena. For Ti-based alloys, this leads to the formation of an external oxide scale and a large oxygen dissolution in the metal, which may be detrimental for ductility. As nitrogen is the major element of the atmosphere, it seems relevant to study its effect on the oxidation behavior of Ti-6Al-2Sn-4Zr-2Mo-0.1Si titanium-based alloy used for these applications. Thermogravimetric analyses were carried out at 650 A degrees C for 100 h in synthetic air (20%O-2-80%N-2) and in a mixture of 20%O-2-80%Ar. Results showed that nitrogen decreases the oxidation kinetics by slowing down the oxide scale growth but also by limiting the oxygen dissolution in the alloy.