Microstructure, phase evolution, mechanical properties and slag corrosion resistance of ZrO2 reinforced Al2O3–Cr2O3 composites

Abstract

Al2O3–Cr2O3 refractories have excellent slag corrosion resistance and can adapt to the oxidation/reduction atmosphere in the smelting reduction ironmaking furnace. Improving the corrosion resistance of chrome corundum refractories is of great significance for extending the life length of industrial kilns and decreasing carbon emissions. In this work, the influences of ZrO2 content on the phase evolution, microstructure, physicochemical properties, mechanical properties and slag corrosion resistance of the ZrO2 reinforced Al2O3–Cr2O3 composite refractories were investigated. The results show that the ZrO2 reinforced Al2O3–Cr2O3 composites are primarily composed of (Al, Cr)2O3 solid solution and m-ZrO2. The compressive strength, flexural strength and hardness of the composite refractories can be improved by adding 2.5 wt% ZrO2. However, adding more ZrO2 will reduce its mechanical properties. This is due to ZrO2 excessive content will augement the porosity of the composite refractories, and the phase transformation of ZrO2 will also lead to the formation of microcracks during the cooling process. It is worth noting that higher ZrO2 content improves the thermal shock resistance of the composites, which is primarily put down to the microcrack toughening mechanism of ZrO2. The corrosion tests show that the thicknesses of the corrosion and infiltration layers of composite refractories are significantly decreased accompanied by ZrO2 content increase. This is because the formation of high melting point CaZr4O9 reduces the CaO content and slag alkalinity, and inhibits the dissolution of Al2O3 into the slag to a certain extent. Therefore, the slag corrosion/penetration resistance of the of the composites are obviously improved with the increase of ZrO2 addition.