Hot corrosion of SiO2-Ta2O5 binary scale on MoSi2-based ceramics

Highlights: • SiO₂-Ta₂O₅ binary scales were fabricated on MoSi₂-based ceramics by pre-oxidation. • A dense reaction layer can be in situ formed to prevent the further infiltration of Na₂SO₄ salts. • Addition of Ta₂O₅ can improve remarkably the hot corrosion resistance of the MoSi₂-based ceramics. The SiO₂-Ta₂O₅ binary scales with different Ta₂O₅ contents were prepared on MoSi₂-based ceramics by pre-oxidation. Hot corrosion with Na₂SO₄ was carried out at 1000 °C for 8 h. The pre-oxidized SiO₂-Ta₂O₅ scale on ceramics with 10 % Ta₂O₅ has an excellent hot corrosion resistance. Ta₂O₅ reacted preferentially with Na₂SO₄ forming solid sodium tantalates to retard the dissolution of SiO₂. A dense reaction layer can be formed to prevent the further infiltration of Na₂SO₄. Compared to the pure SiO₂ scale without Ta₂O₅, fewer Na₂MoO₄ and no obvious corrosion hole can be observed.