Corrosion mechanism of reactive MgO-bonded Cr₂O₃-bearing castables in CaO-Al₂O₃-Fe₂O₃-SiO_{2-based steel-making slag}

To assess the feasibility of the reactive MgO (RM) binder in preparing Cr2O3-bearing castables, the degradation behavior of RM-bonded Cr2O3-bearing castables in CaO-Al2O3-Fe2O3-SiO2-based steel-making slag was investigated at 1600 degrees C via refractory cup testing. The corrosion resistance and infiltration resistance of RM-bonded castables were compared with hydratable alumina (HA)-bonded and calcium aluminate cement (CAC)-bonded castables with respect to the differences in phase composition and microstructure. Al2O3 grains in RM-bonded castable were preferentially attacked by the slag compared with Mg(Al, Cr)(2)O-4 spinel-based matrix. The formation of spinel-based and CaO6Al(2)O(3)-based solid solutions with volume expansion from slag/castable interactions suppressed slag infiltration into RM-bonded castable matrix. Both experimental observations and thermodynamic calculations indicated that the in situ formed Mg(Al, Cr)(2)O-4 spinel in RM-bonded castables was the predominant reason leading to the superior slag corrosion resistance and infiltration resistance compared with HA-bonded and CAC-bonded Cr2O3-bearing castables.