OXIDATION OF TITANIUM NITRIDE IN OXYGEN - BEHAVIOR OF TIN0.83 AND TIN0.79 PLATES

The oxidation of 0.13 mm thick TiN0.83 plates between 850 and 1005°C and 0.38 mm thick TiN0.79 plates between 890 and 1220°C was studied at oxygen pressures in the range 15-600 Torr. The oxidation behavior of the first compound, TiN0.83, was found to be very close to that recently described for the nitride TiN0.91. There was formation of a rutile scale with a layered structure and the kinetics were quasilinear for conversion degrees 0.25<α<0.9. By applying a pseudolinear oxidation model involving a diffusion regime through a scale of variable thickness, it was found that the activation energy of the limiting process, i.e., the diffusion of the reactants through the inner growing layer, was ∼43 kcal/mole. The second compound, TiN0.79, showed a slightly better oxidation resistance. The irregular kinetic curves obtained (mainly above 1000°C) were associated with sintering and grain growth in the oxide starting at the outer surface of the scale and gave indirect information on the pressure dependence of the linear oxidation of nitrides TiN0.83 and TiN0.91. © 1979 Plenum Publishing Corporation.