Investigating the effects of Magnesia addition on properties, phase transformation and microstructure of gelcasted Zirconia bodies

Magnesia Partially Stabilized Zirconia (Mg-PSZ) is the best material for casting nozzles used in steelmaking industry due to high melting point, high mechanical strength, high thermal shock resistance, high toughness, chemical stability and neutrality, which these nozzles should be fabricated using cold isostatic pressing (CIP) method, however wet processing methods such as gelcasting can lead to cheap fabricated bodies with equivalent properties. The aim of this study is to investigate the effects of magnesia on properties, phase transformation and microstructure of Mg-PSZ bodies fabricated by gelcasting method using monoclinic Zirconia and fused Magnesia as raw materials and Agar as gelling agent. Scanning Electron Microscope (SEM), X-Ray Diffraction and Cold Crushing Strength (CCS) tests are used for bodies’ characterization. Based on results, 1680-ZM4 sample with density, monoclinic phase’s volumetric fraction and compressive strength of 4.91 g/cm3, 18.77 % and 363 MPa is chosen as the best composition, respectively, which are in good agreement with zirconia based steel making nozzles. With higher magnesia content, in addition to higher zirconia stability, liquid phase sintering leads to better physical and mechanical properties.