Influence of crystallographic orientation on the early stages of oxidation of polycrystalline titanium nitride

Oxide islands are observed on polycrystalline titanium nitride surface after annealing at 1000 °C for 10 h under secondary vacuum (PO ₂ about 10 ^-6 mbars). EBSD orientation mapping revealed that the growth of these islands is affected by the orientation of the underlying substrate grain. Based on the size and population density of the islands, the following order was established for the reactivity at the early stages oxidation: TiN (1 0 0) > TiN (1 1 0) > TiN (1 1 1). Several possible explanations are proposed to understand the relative stability of TiN (1 1 1) surface. The results are not completely understood and further works are necessary to determine the oxidation rates as a function of the crystallographic orientation.