Alumina-based ceramic cores prepared by vat photopolymerization and buried combustion method

Abstract

Alumina (Al2O3)-based ceramic cores are extensively employed to form cavities within complex or difficult-to-form casting parts. As a conventional manufacturing process, investment casting requires molds and is labor-intensive. Therefore, it is crucial to develop a direct method for preparing Al2O3-based ceramic cores at a low cost. As an AM process, vat photopolymerization (VPP) can produce high-quality parts with smooth surface finish and fine details. Therefore, extensive attentions have been attracted to processing ceramic materials by VPP. Despite these benefits, the layer-by-layer accumulation strategy of VPP inevitably induces low bonding strength between adjacent layers, and induces cracks in the sintered parts. To mitigate these problems, burying VPP-printed Al2O3 green bodies into silica has been proposed in this investigation. Results show that cracks and deformation problems have been reduced when the buried combustion method is adopted. To create Al2O3-based ceramic cores with desired porosity and flexural strength properties, process parameters have been optimized. A systematic study on how the inclusion of SiO2 particles and variations in sintering temperature impact the microstructure and mechanical properties of Al2O3-based ceramic cores fabricated through VPP printing is presented. Based on experimental results, a 1300 ℃ sintering temperature is selected to produce appropriate shrinkages (4%∼8%), open porosity of over 20%, and flexural strength ranging from 20 to 50 MPa of ceramic cores.