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

Abstract 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.