Silica strengthened alumina ceramic cores prepared by 3D printing

Ceramic cores based on alumina and silica are important in the manufacturing of hollow blades. However, obtaining good properties and precision is still challenging. In this research, alumina-based ceramics cores were obtained by 3D printing technology, and the effects of silica contents on the mechanical properties of the as-obtained alumina ceramic cores were evaluated. The results showed significant improvements in flexural strengths of the ceramics from 13.3 MPa to 46.3 MPa at silica contents from 0 wt% to 30 wt% due to formation of mullite phase (Al₆Si₂O₁₃). By contrast, the flexural strengths declined as silica content further increased due to the generation of massive liquid phase. Also, porous structures and cracks were observed by scanning electron microscopy due to the removal of cured photosensitive resin and the mullitization reaction between alumina and silica, respectively. The manufacturing process of hollow blades required ceramic cores with flexural strengths greater than 20 MPa to resist the strike of metal liquid, as well as open porosity above 20 % to provide space for alkali liquor to dissolve the ceramic cores. As a result, 10 wt% silica was determined as the optimal value to yield ceramics with improved properties in terms of flexural strength (35.6 MPa) and open porosity (47.5 %), thereby satisfy the application requirement for the fabrication of ceramic cores.