中国有色金属学报(英文版)
Transactions of Nonferrous Metals Society of China
Vol. 31 No. 1 January 2021 |
(State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072, China)
Abstract:Oxidation and hot corrosion behaviors at 900 °C of Nb-Si based ultrahigh temperature alloys were investigated. Both oxidation and hot corrosion kinetics curves of the alloy involve an initial parabolic stage and a later rapid linear stage. In the initial oxidation stage (1-50 h), a thin and continuous scale is formed on the alloy surface, while severe pest degradation phenomenon is observed in the linear oxidation stage. Compared with oxidation of the alloy in static air, a linear hot corrosion stage happens earlier and catastrophic scale disintegration occurs after hot corrosion for 20-100 h, demonstrating that molten salts (Na2SO4 and NaCl) could significantly accelerate the oxidation process of the alloy. STEM results indicate that the corroded scale consists mainly of TiO2, Nb2O5, TiNb2O7, amorphous silicate and NaNbO3.
Key words: Nb-Si based alloys; molten salts; oxidation; hot corrosion; silicate