Thermodynamic and Experimental Investigations of High-Temperature Refractory Corrosion by Molten Slags

Corrosion mechanisms between MgO refractory substrates and FeNi slags were investigated. The FeNi slags taken into consideration represent a simple synthetically mixed slag with specific oxides and a real slag from a ferroalloy producer. The MgO refractory substrates with the specimens of FeNi slag were heated in a hot-stage microscope at 10 K/min from room temperature to three different temperatures 1573 K, 1723 K, and 1923 K (1300 °C, 1450 °C, and 1650 °C). The experiments were carried out under a controlled gas atmosphere that simulates the relevant process conditions. The corrosion mechanisms of each system were followed by scanning electron microscope analyses. The results obtained showed that slag corrosion dominates, with a pronounced partial dissolution of refractory fines forming Mg-silicates of type forsterite. It was also observed that iron oxide present in the slag diffused into the coarse refractory grains forming magnesiowustite. Finally, the results obtained were compared with those predicted by FACTSAGE software to understand the corrosion mechanisms and draw implications for improving the refractory performance and lifetime.