Thermodynamic evaluation of SiC oxidation in Al2O3–MgAl2O4–SiC–C refractory castables

Abstract The literature suggests that MgAl 2 O 4 can accelerate SiC oxidation in Al 2 O 3 –MgAl 2 O 4 –SiC–C refractory castables. Thus, in this work thermodynamic calculations have been carried out using FactSage ® software in order to explore, search for and understand the role of MgAl 2 O 4 on the SiC oxidation. According to the thermodynamic predictions, at 1500 °C and under a reducing atmosphere, there is no evidence that spinel might directly affect SiC oxidation. The increase of SiC content in an Al 2 O 3 –SiC–C (AL) castable composition was mainly related to the reaction between mullite and carbon. On the other hand, the SiC generation in the Al 2 O 3 –MgAl 2 O 4 –SiC–C (SP) composition was a result of the reaction involving liquid SiO 2 and carbon from the refractory. Therefore, the lower SiC content in the SP castable resulted from the refractory's phase transformations. It was also suggested that the samples thermally treated 15 times at 1500 °C did not reach the equilibrium condition, which explains the differences between experimental and thermodynamic results.