Corrosion Behaviors of Zirconia Refractory by CaO–SiO2–MgO–CaF2 Slag

In this work the corrosion behaviors of zirconia refractory (partially MgO-stabilized zirconia) was investigated in CaO–SiO₂–MgO–CaF₂ slag with varying CaF₂ content at 1873 K. To figure out the corrosion mechanism, the characteristics of present slag at high temperature were examined in terms of melting temperature and vaporization behaviors. Corrosion experiment and melting temperature measurement were carried out by heating microscope (HM) and the vaporization phenomenon was investigated by thermo gravimetry–differential scanning calorimetry. After experiment, the corroded interfaces of zirconia refractory by slag were analyzed by scanning electron microscope-energy dispersive spectroscopy and electron probe microanalysis. With an addition of CaF₂, three different layers were formed at the interface of slag and zirconia refractory. Furthermore, the corrosion behaviors of zirconia refractory were found to be continuously accelerated with an increase of CaF₂ which facilitated the dissolution of intermediate compound. On the other hand, melting temperature of CaO–SiO₂–MgO–CaF₂ slag showed no continuous decrease with an increase of CaF₂. Also, considerable vaporization of fluoride gas was occurred in high CaF₂ containing slag during HM experiment which might cause a gradual change of slag composition and also environmental pollution. From the results, present study suggested that a proper amount of CaF₂ should be added when it is used for enhancing refining capacity of slag in order not to cause any severe damage of zirconia-based refractory by slag.