Key Takeaways & Executive Findings
- •• Optimal sintering at 1,200 °C yields ceramic cores with excellent high-temperature performance: flexural strength of 32.15 MPa at 1,500 °C and minimal deflection of 0.15 mm. • The addition of nano-3YSZ and micron Y2O3 promotes the formation of cristobalite and ZrSiO4, enhancing creep resistance and high-temperature strength. • Increasing sintering temperature improves room-temperature flexural strength and shrinkage but reduces open porosity and high-temperature deflection. • Stereolithography 3D printing enables fabrication of complex-shaped ceramic cores without molds, offering a promising route for advanced hollow turbine blades.
Abstract
Ceramic cores are key to forming a cooling structure within the hollow blade cavities. The use of stereolithography (SL) 3D printing technology eliminates the need for moulds, facilitating the preparation of complex-shaped ceramic cores. In this study, silica-based ceramic cores incorporating nano-3YSZ (3mol.% yttria stabilised zirconia) and micron-sized Y2O3 were prepared via SL 3D printing ceramic technology to promote the formation of cristobalite and ZrSiO4, thereby improving the high-temperature properties. The flexural strength at 25 °C and 1,500 °C, deflection at 1,500 °C, shrinkage rate, and porosity of the core samples sintered at different temperatures (1,170 °C, 1,185 °C, 1,200 °C, 1,215 °C, and 1,230 °C) were tested and investigated. The mechanism underlying the high temperature performance of the cores was elucidated through analysis of cross-sectional morphology, element distribution, and phase constitution of the samples. As the sintering temperature increases, the shrinkage and flexural strength at 25 °C of the core rise, while the open porosity and deflection at 1,500 °C decrease. When the sintering temperature reaches 1,200 °C or higher, the 1,500 °C flexural strength can be measured, which increases as the sintering temperature rises. The core exhibits excellent creep resistance when sintered at temperatures of 1,200 °C and above. Considering the comprehensive performance requirements for the core, the sintering temperature of 1,200 °C was selected. At the sintering temperature of 1,200 °C, the core exhibits shrinkage rates of 3.76% (X), 3.38% (Y), and 3.95% (Z), alongside a flexural strength of 9.01 MPa at 25 °C and 32.15 MPa at 1,500 °C, and an open porosity of 26.39%. The deflection of the core at 1,500 °C is 0.15 mm, which helps to maintain the dimensional stability of the ceramic core during casting. XRD results indicate that samples fractured after 25 °C flexural strength test still contain amorphous quartz glass, alongside substantial quantities of yttria stabilized zirconia and Y2O3. Samples fractured after 1,500 °C flexural strength test exhibit significant crystallisation of amorphous quartz glass into cristobalite, with silica and 3YSZ combining to form ZrSiO4. Y2O3 as a network modifier of the glass network destroys the bridging oxygen in the silica-oxygen bond, thereby reducing the energy required for glass crystallisation and promoting the crystallisation reaction of quartz glass to form cristobalite. In addition, nano-3YSZ combines with SiO2 at high temperatures to form ZrSiO4. Since cristobalite and ZrSiO4 are crystals, both of them have strong creep resistance, thus improving the high temperature flexural strength and deformation resistance of the ceramic cores.
1. Introduction
Aero-engines are the core components that provide power source for aerospace, and their future focuses on improving the thrust-to-weight ratio [1]. Therefore, hollow turbine blades that determine the important performance of engines have become a top priority in research and development [2]. The ceramic core is the key to forming a complex cooling structure within the hollow turbine blade cavity [3]. It is usually required that the ceramic core has a low and stable shrinkage [4], a room temperature flexural strength of over 8 MPa [5], and an open porosity of over 20% to remove the core [6]. Since the ceramic core needs to be kept in molten metal at approximately 1,500 °C for 30 min during casting [7], the ceramic core needs to have excellent high-temperature properties, including the smallest possible deflection and appropriate high-temperature flexural strength [8].
At present, the internal cooling structure of hollow blades has developed from single counter flow air cooling to double wall ultra air cooling [9]. For the development of this new type of blades with complex structures, traditional core preparation methods such as gel injection molding, thermal injection molding require to prepare multiple sets of molds in advance [10], resulting in a long development and production cycle [11]. Therefore, an efficient ceramic core preparation method is urgently needed.
In recent years, additive manufacturing technology [12] (also known as 3D printing technology) has developed rapidly and has been applied to the production of various complex shaped parts [13]. 3D printing technology has the advantages of rapid forming, unrestricted moulding shapes, less material waste, and high dimensional accuracy of finished products [14]. At present, the most widely used 3D printing technology for ceramic materials is photopolymerization 3D printing ceramic technology [15], mainly including stereolithography.
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Yue-ting Ma, Rui-long Yu, Ying-wei Zhou, Peng-wei Wang, Ren-xiao Zou, Tian-jiao Gao, Ming Kang (2025). High-temperature performance of silica ceramic cores with additives prepared by stereolithography 3D printing. China Foundry. https://doi.org/10.1007/s41230-025-4184-0
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Frequently Asked Questions
What is the optimal sintering temperature for silica ceramic cores prepared by stereolithography 3D printing?
The optimal sintering temperature is 1,200 °C, as it provides a balance of high flexural strength (32.15 MPa at 1,500 °C), low deflection (0.15 mm), and adequate open porosity (26.39%) for core removal.
How do nano-3YSZ and Y2O3 additives improve the high-temperature performance of ceramic cores?
These additives promote the formation of cristobalite and ZrSiO4 during sintering. Cristobalite and ZrSiO4 are crystalline phases with strong creep resistance, which enhance the high-temperature flexural strength and deformation resistance of the cores.
What are the key advantages of using stereolithography 3D printing for ceramic cores?
Stereolithography 3D printing eliminates the need for molds, enabling rapid fabrication of complex-shaped ceramic cores with high dimensional accuracy and minimal material waste, which is crucial for advanced hollow turbine blades.
How does sintering temperature affect the properties of the ceramic cores?
As sintering temperature increases, shrinkage and room-temperature flexural strength increase, while open porosity and high-temperature deflection decrease. At temperatures above 1,200 °C, the high-temperature flexural strength becomes measurable and increases with temperature.
What is the significance of the deflection at 1,500 °C for ceramic cores?
Low deflection at 1,500 °C is critical for maintaining dimensional stability during casting. The cores sintered at 1,200 °C exhibit a deflection of only 0.15 mm, ensuring the accuracy of the cooling channels in the final blade.
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