Durability of molybdenum disilicide in molten alkali borosilicate glass

The kinetics and mechanisms of corrosion of MoSi2 materials were investigated in molten alkali borosilicate glass at 1000–1550°C for 0.5–1510 hours. The corrosion behavior of MoSi2 is compared to an alumina-zirconia-chrome-silica refractory (AZCS). The corrosion rates were evaluated by measuring dimensional changes at, above, and below the molten glass line. MoSi2-based materials perfomed at least as well as AZCS above and below the glass line, but were somewhat inferior at the glass line. The kinetics and mechanisms of corrosion of MoSi2 varied with position in the melt. Above the glass line a semi-protective SiO2 layer forms. Below the glass line, a protective Mo-rich layer forms. At the glass line, simultaneous dissolution of SiO2 and vaporization of MoO3 leads to comparatively rapid loss of material. Based on microstructural studies, a phenomenological model is proposed that illustrates the basic mechanisms of corrosion in these three regions.