Accelerated oxidation behavior of NbSi2 coating grown on Nb substrate at 600–900 °C

Highlights: • Study of accelerated isothermal oxidation behavior of NbSi₂ coating grown on Nb substrate in air at 600–900 °C. • Pesting-induced accelerated oxidation was due to the cracking and spalling of NbSi₂ coating at 700 °C. • Oxide fracture-induced accelerated oxidation was due to the cracking of oxide scale at 750 °C. • Accelerated oxidation model of NbSi₂ coating has been established. - Abstract: Isothermal oxidation of NbSi₂ coating formed on Nb substrate was investigated in air at 600–900 °C, which exhibited the complex and accelerated kinetics at intermediate temperatures and failed due to either the cracking of the NbSi₂ coating or the oxide layer formed. This complex oxidation behavior was governed by the balance between the stress generated by the forming of oxide phases and the subsequent stress relaxation processes. Pesting-induced accelerated oxidation at 700 °C was affected by extrinsic factors such as pre-existing defects in NbSi₂ coating. Accelerated oxidation originated from the oxide layer cracking at 750 °C was intrinsic to NbSi₂.