Effect of Al(OH)3 on the properties of silica-based ceramic cores prepared by laser powder bed fusion combined with vacuum infiltration

Abstract

Silica-based ceramic cores, with low coefficients of thermal expansion, low sintering temperatures, and excellent acid and alkali leaching capabilities, are essential materials for the production of hollow blades. However, their mechanical properties are suboptimal, and they present various processing challenges. In this study, silica-based ceramic cores were prepared using a combination of vacuum infiltration (VI) and laser powder bed fusion (LPBF) techniques. Al(OH)₃ was employed as a mineralizer to enhance the post-sintering mechanical properties and improve the efficiency of the vacuum infiltration process, thereby enhancing the overall performance of the silica-based ceramic cores. The VI process facilitated the penetration of nano-SiO₂ into the samples, increasing their density and promoting the formation of cristobalite during sintering at 1225°C. Additionally, the Al(OH)₃ powder, through pyrolysis into Al₂O₃ during sintering, reduced microcracks, inhibited excessive cristobalite transformation, and improved the VI process, resulting in enhanced room-temperature flexural strength. By optimizing the Al(OH)₃ content and the VI process, significant improvements in the microstructure and properties of the silica-based ceramic cores were achieved. After three rounds of vacuum infiltration and the addition of 4 wt% Al(OH)₃, the samples exhibited a high-temperature creep of 0.17 mm, with flexural strengths of 15.23 MPa at room temperature and 23.55 MPa at high temperature.