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The degradation behavior of alumina (10–20 wt%) carbon refractories was investigated during high temperature (1 550 °C) contact with a ternary casting mould meniscus slag containing 50% MnO, 25% SiO2, and 25% Al2O3 and a binary slag containing 40% MnO and 60% SiO2. Using the sessile drop approach, the transient progress of corrosion reactions was investigated as a function of time and refractory composition. An in-depth characterization and analysis of reacted assemblies was carried out using optical and scanning electron microscopy (SEM). Optical micrographs showed a significant penetration of both slags within the refractory substrate, with very little slag remaining behind after 15 min of contact. The depth of penetration of ternary slag was found to increase with carbon concentration in the refractory. An all-round corrosion was observed with extensive refractory degradation over a period of time. Corrosion was determined to a great extent by dissolution reactions in the interfacial region; alumina dissolution from the refractory resulted in the formation of needle-like corundum crystallites which transformed to a cohesive network of faceted corundum crystals on extended contact. A number of reaction products containing Mn and Si were also observed.

We report an investigation on the corrosion behavior of ZrO2–graphite insert in submerged entry nozzles (SEN) during its high temperature interaction with the mould flux focused specifically on the role of glaze coating. A detailed metallographic examination of the representative samples collected at different stages of its usage was carried out to examine the transient progress of corrosion. The interaction between the glaze material and the base refractory at the typical preheating temperature of SEN initiated the degradation of the partially stabilized ZrO2 grains due to the formation of reaction products. Clear evidence is presented to show that the reaction product and the original layer of glaze coating survived after 90 min of casting. Early stages of corrosion involved the progressive congruent dissolution of reaction products and the residual glaze phase into the mould flux. Due to the absence of the glaze layer in the later stages of operation (480 min), corrosion was caused by the fragmentation of the aggregate phase and structural damage. This work highlights the importance of compositional control and coating thickness of the glaze material on the ZrO2–graphite refractory insert.

The degradation behavior of Zirconia – 20% carbon refractory was investigated during high temperature (1550 °C) contact with a casting mould meniscus slag containing 50% MnO, 25% SiO2, and 25% Al2O3. Using the sessile drop approach, the transient progress of corrosion reactions was investigated as a function of time; in-depth characterization and analysis of reacted assemblies was carried out using optical and scanning electron microscopy. Optical micrographs showed a significant penetration of slag within the refractory substrate, with very little slag remaining behind after 15 min of contact. In situ carbothermic reduction of zirconia and the presence of reducible oxides in the slag significantly depleted carbon from the substrate further aiding the penetration of slag. Interaction between slag and zirconia resulted in the depletion of phase-stabilizing Y2O3 from zirconia granules resulting in their fragmentation and subsequent diffusion in slag rich regions. An aggressive all-round corrosion was observed with extensive refractory degradation over a period of time; a number of reaction products such as Mn5Si3 were also observed. These experimental investigations were supplemented with thermodynamic investigations using FactSage.