Effect of nonuniform sintering on mechanical and thermal properties of silica-based ceramic cores

• Published in: China foundry Vol. 18; no. 5; pp. 457 - 462
• Main Authors: Pan, Zhi-ping, Guo, Jian-zheng, Li, Shuang-ming, Li, Xu-guang
• Format: Journal Article
• Language: English
• Published: Singapore Springer Singapore 01.09.2021; Foundry Journal Agency; State Key Laboratory of Solidification Processing,Northwestern Polytechnical University,Xi'an 710072,China; Wedge Central South Research Institute,Shenzhen 518045,Guangdong,China%Wedge Central South Research Institute,Shenzhen 518045,Guangdong,China; Powder Metallurgy Research Institute,Central South University,Changsha 410083,China%State Key Laboratory of Solidification Processing,Northwestern Polytechnical University,Xi'an 710072,China
• Subjects: Aluminum oxide; Analysis; Engineering; Machines; Manufacturing; Materials Engineering; Mechanical properties; Metallic Materials; Methylene blue; Powders; Processes; Research & Development; Silica; Sintering; Thermal properties; Turbines; China; 1; A; alkali metal content; non-uniform sintering; silica-based ceramic core; mechanical and thermal properties; TG221
• ISSN: 1672-6421; 2365-9459
• DOI: 10.1007/s41230-021-1024-8

During sintering of the silica-based ceramic core of turbine blades, a phenomenon called “nonuniform sintering” occurs that negatively affects the thermal and mechanical properties of the core. Standard samples of silica-based core were prepared by an injection molding method and sintered with alumina backfilling powder with different sodium contents. The effect of sodium content on the nonuniform sintering of silica-based cores and the thermal and mechanical properties was evaluated. Results show that the sintering level and the content of α-cristobalite in the surface layer are significantly higher than that of the sample interior. A considerable number of microcracks are found in the surface layer due to the β to α-phase transition of cristobalite. As the sodium content in the alumina powder decreases, the level of the nonuniform sintering and the amount of crystallized cristobalite in the surface layer decrease, which is beneficial to the thermal expansion and flexural strength at ambient temperature. The flexural strength and thermal deformation at high temperature are improved by reducing the surface cracks, but deteriorated with the decrease of the cristobalite crystallization when the surface cracks are macroscopically invisible.