Key Takeaways & Executive Findings
- •• Increasing final sintering temperature and nano-ZrO2 content enhance sintering degree, leading to higher shrinkage, lower porosity, and increased bulk density in SLA-fabricated SiO2-based ceramic cores. • Elevated temperatures promote cristobalite and ZrSiO4 network formation, which inhibits viscous flow and significantly improves high-temperature flexural strength and creep resistance. • Optimal properties are achieved at 1,250 °C with 1.5-2.0 wt.% nano-ZrO2, yielding balanced shrinkage, porosity, density, and mechanical strength for investment casting applications. • The study provides practical guidance for optimizing sintering processes of SLA ceramic cores, enhancing their industrial applicability in superalloy turbine blade manufacturing.
Abstract
As a reliable additive manufacturing technology, the stereolithography (SLA) ceramic core necessitates a tailored sintering process to achieve optimal performance. This study explored the effects of final sintering temperatures (specifically 1,150, 1,250, and 1,300 °C) on the properties of SLA-fabricated SiO2-based ceramic cores reinforced with nano-ZrO2 (at concentrations of 1.0wt.%, 1.5wt.%, and 2.0wt.%). The results demonstrate that increasing the final sintering temperature and the incorporation of nano-ZrO2 enhance the viscous flow of quartz glass, resulting in a higher sintering degree. As the final sintering temperature rises, the ceramic samples exhibit increased shrinkage rate, decreased apparent porosity, and increased bulk density. Higher final sintering temperatures also promote greater cristobalite precipitation, promoting an increase in the amount and precipitation rate of quartz during investment casting. The formation of a cristobalite and ZrSiO4 network at elevated temperatures effectively inhibits the viscous flow of quartz glass, thereby significantly improving high-temperature flexural strength and creep resistance of ceramic cores. When the content of nano-ZrO2 is between 1.5wt.% and 2.0wt.%, the final sintering temperature of 1,250 °C is the best choice. Under these conditions, the shrinkage rate along the Z direction ranges from 3.35% to 3.68%, the porosity lies between 25.57% and 26.03%, the bulk density varies from 1.612 to 1.645 g·cm-3, the room temperature flexural strength is between 26.79 and 27.85 MPa, and the flexural strength at high temperatures is within the range of 30.77 to 33.02 MPa. The deflection at high-temperatures is 3.37-5.31 mm, while the surface roughness of the upper surface is 3.26-4.79 μm, and the surface roughness of the side surface is 4.97-5.79 μm. These findings provide valuable guidance for optimizing the sintering processes of SLA ceramic cores, offering potential for industrial applications.
1. Introduction
Ni-based single-crystal superalloy turbine blades serve as a critical component in modern jet engines, significantly enhancing performance through their exceptional improved high-temperature resistance and superior mechanical properties [1-3]. The capacity to endure higher temperatures directly correlates with an increase in turbine inlet temperatures, thereby boosting the thrust and power output of the engine [4, 5]. In addition to alloy composition and thermal barrier coatings, the fabrication of ceramic cores is essential for producing complex internal cooling channels in these blades.
Stereolithography (SLA) additive manufacturing has emerged as a reliable method for producing ceramic cores with high precision and complex geometries. However, the sintering process is a critical factor that affects the transformation of the ceramic cores from a green body to a ceramic core sample. Sintering is the key step affecting the comprehensive performance and dimensional accuracy of SLA ceramic cores. The evolution of the ceramic microstructure during the sintering process has a significant impact on their anisotropy [36, 37]. Various factors, including the sintering method, heating rate, final sintering temperature, and holding time, all contribute to these differences in microstructure and, consequently, anisotropy.
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Qi-qi Huang, Chao-yue Chen, Yu-hao Yin, Song-zhe Xu, Xia Li, Tao Hu, Shuo Yin, Jiang Wang, Wei-dong Xuan, Zhong-ming Ren (2025). Influence of final sintering temperature on properties of nano-ZrO2 reinforced SiO2-based ceramic cores via stereolithography additive manufacturing. China Foundry. https://doi.org/10.1007/s41230-025-4182-2
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Frequently Asked Questions
What is the optimal final sintering temperature for SLA-fabricated SiO2-based ceramic cores reinforced with nano-ZrO2?
The optimal final sintering temperature is 1,250 °C when the nano-ZrO2 content is between 1.5 wt.% and 2.0 wt.%, as it provides a balanced combination of shrinkage, porosity, density, and mechanical strength.
How does nano-ZrO2 addition affect the properties of SiO2-based ceramic cores?
Nano-ZrO2 addition enhances the viscous flow of quartz glass during sintering, leading to higher sintering degree, increased shrinkage, decreased porosity, and improved high-temperature flexural strength and creep resistance due to the formation of cristobalite and ZrSiO4 networks.
What are the key mechanical properties of the ceramic cores at the optimal sintering conditions?
At 1,250 °C with 1.5-2.0 wt.% nano-ZrO2, the room temperature flexural strength is 26.79-27.85 MPa, high-temperature flexural strength is 30.77-33.02 MPa, and high-temperature deflection is 3.37-5.31 mm.
Why is the sintering process critical for SLA ceramic cores?
Sintering determines the final microstructure, dimensional accuracy, and mechanical properties of the ceramic cores. It affects anisotropy, densification, and the formation of phases like cristobalite, which are crucial for high-temperature performance in investment casting.
What are the potential industrial applications of this research?
The findings provide guidance for optimizing sintering processes of SLA ceramic cores, which are used in the investment casting of Ni-based single-crystal superalloy turbine blades for jet engines, enhancing their performance and reliability.
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