Effect of SiO₂ barrier scale prepared by pre-oxidation on hot corrosion behavior of MoSi₂-based coating on Nb alloy

Using pre-oxidation at 1500 °C for 10 h, a continuous SiO₂ barrier scale was fabricated on MoSi₂-based/NbSi₂ coating of Nb alloy expected to resist hot corrosion with Na₂SO₄ at 1000 °C. No obvious corrosion occurred for 2 h, while the corroded products including Na₂Si₂O₅, Na₂MoO₄ and SiO₂ deposits were generated respectively for 4 h and 8 h. The degradation of SiO₂ scale triggered an evident increase in surface roughness. Due to a slow reaction rate, SiO₂ scale can serve as a barrier isolating from Na₂SO₄ salt to alleviate the degradation of MoSi₂-based coating effectively.