Dynamic corrosion of Al2O3–ZrO2–SiO2 and Cr2O3-containing refractories by molten frits. Part II: Microstructural study

In this work results on dynamic corrosion studies of fused cast Al2O3–SiO2–ZrO2 and isostatically pressed and sintered Cr2O3-based refractories by two crystalline (transparent) frits are described. Experiments have been performed using the “Merry Go Round” test at ≅1500 °C. tructural and mineralogical analyses of selected areas from the corroded regions of the studied refractories were performed by reflected light optical microscopy and scanning electron microscopy with analysis by X-ray dispersive energy. icant differences between the corrosion mechanisms acting in the two types of materials were found. In the fused cast Al2O3–SiO2–ZrO2 specimens corrosion took place by the dissolution of alumina and zirconia in the frit and in the glass formed by the reaction between the frit and the refractory. In the Cr2O3-based materials the corrosion process was controlled by the capillar penetration of the molten frit through the open pores. The reaction between the ZnO from the frits and Cr2O3 led to the formation of spinel (ZnCr2O4), a high-melting point bonding phase that retarded the frit penetration. Results are discussed using the relevant phase equilibrium diagrams.