关键词: 黏结剂喷射成形, 氧化铝陶瓷型芯, 氮化硅增强相, 真空浸渗, 孔隙率, 抗弯强度

Abstract: The high efficiency of binder jetting technology (BJAM) and the better high temperature resistance of alumina (Al₂O₃) provided advantages for the fabrication of the turbine blade casting core, however, the lower mechanical performance of BJAM Al₂O₃ ceramic was hard to meet the application standard of cores. To solve the above problems, this study proposed the introduction of silicon nitride (Si₃N₄) and vacuum infiltration of silicon sol to realize the performance improvement of Al₂O₃ ceramic core. Effects of Si₃N₄ contents (0%-20%, wt%) and silica sol on the porosity, dimensional shrinkage, mircostructure, and mechanical performance are systematically investigated. Results show that the optimal generation content of mullite and sialon compounds by the chemical reaction between Si₃N₄ and Al₂O₃ could improve the comprehensive performance of ceramic when the content of Si₃N₄ and sintering parameters are 10% and 1500℃ for 4h, and the relative density and bending strength respectively reached 51.62% and 21.2MPa compared with the 0% Al₂O₃ ceramic, but the dimensional shrinkage of X–, Y–, and Z–axis are increased to 4.55%, 5.36%, and 6.21%. When all Al₂O₃–Si₃N₄ ceramics are initially sintered and vacuum infiltrated with silicon sol after the second sintering, the porosity and bending strength had been further improved by the generation of mullite by the reaction between Al₂O₃and silicon sol, and the corresponding optimal values are 39.77%/34.8MPa (e.g., 0 wt%Si₃N₄–Al₂O₃infiltration sample) and 41.28%/37.9MPa (e.g., 10 wt.%Si₃N₄–Al₂O₃infiltration sample), which indicated that doping Si₃N₄ and vacuum infiltrating silica sol could obviously improve the comprehensive properties of Al₂O₃ ceramics, and laid a theoretical foundation for fast and low–cost preparation of ceramic cores.

Key words: binder jetting forming, alumina ceramic cores, silicon nitride reinforced phase, vacuum infiltration, porosity, bending strength