Static water vapor corrosion behavior of MoSi₂/Mullite composite coating on Nb based alloy at 1500 °C

Water vapor corrosion behavior of MoSi₂/Mullite composite coating on Nb based alloy at 1500 °C were investigated compared with its static dry-oxygen oxidation behavior. The oxidation parabolic rate of samples in water vapor environment was − 0.39 mg/(cm² h^1/2), ~ 4 times higher than that in dry oxygen. Water vapor accelerated the penetration of O₂ and resulted in second Mo (sp) and MoO₂ (s), causing stronger volatilization of gaseous species out of the aluminosilicate scale than that in dry oxygen. Moreover, the crystallization of SiO₂ in the scale was inhibited which accelerated the corrosion degradation of coating in water vapor environment at 1500 °C.