The effects of nitrogen on the kinetics and mechanisms of oxidation of titanium-tantalum alloys

The oxidation kinetics of Titanium alloys containing nominally 5, 40, and 60 weight percent Ta were measured for 16 hr in nitrogen-20% oxygen. In all three alloys at each temperature tested oxidation rates in the nitrogen-oxygen mixture were significantly lower than those previously measured in argon-20% oxygen or pure oxygen. Using X-ray diffraction and electron microprobe a nitrogen rich layer was identified in the scale near the scale/metal interface. This layer apparently acts as an oxygen-diffusion barrier, as demonstrated by the reduced depth of oxygen penetration in the metal relative to identical specimens oxidized in nitrogen-free atmospheres.