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Ceramic core is a critical component in the super-alloy turbine blade casting. In our previous work, a novel multi-phase MgAl2O4/MgO porous ceramic was prepared for this purpose. The most important property was that it crumbled completely after hydrothermal treatment in just pure water, due to the hydration of MgO. In this work, the hydration process of the MgO embedded in the inert matrix was investigated in detail. The collapse behaved as an interior destruction without any bulk expansion of the sample. The hydration percentage was the only factor related to the water-collapsibility. The morphology of hydration product indicated that the reaction advanced in particular direction. Based on the finite element analysis for the expansion effect on the porous structure, the interior-collapsing mechanism was proposed. During the hydration process, the MgO grains exerted pressure to the surrounding matrix and induced the collapse in the adjacent structure. This process took place throughout the matrix. Finally, the sample crumbled completely to the powders. No bulk dilatation was detected before the powdering, indicating that the collapse process would not exert pressure outward. Thus the alloy blade would not be damaged during the removal of the ceramic core. It was also predicted that the decrease in the MgO grain size was beneficial to the water-collapsibility.


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Interior-collapsing mechanism by hydrothermal process of the MgAl2O4/MgO porous ceramic

Show Author's information Yao YAOYue ZHANG( )
Key Laboratory of Aerospace Materials and Performance (Ministry of Education), School of Materials Science and Engineering, Beihang University, Beijing 100191, China

Abstract

Ceramic core is a critical component in the super-alloy turbine blade casting. In our previous work, a novel multi-phase MgAl2O4/MgO porous ceramic was prepared for this purpose. The most important property was that it crumbled completely after hydrothermal treatment in just pure water, due to the hydration of MgO. In this work, the hydration process of the MgO embedded in the inert matrix was investigated in detail. The collapse behaved as an interior destruction without any bulk expansion of the sample. The hydration percentage was the only factor related to the water-collapsibility. The morphology of hydration product indicated that the reaction advanced in particular direction. Based on the finite element analysis for the expansion effect on the porous structure, the interior-collapsing mechanism was proposed. During the hydration process, the MgO grains exerted pressure to the surrounding matrix and induced the collapse in the adjacent structure. This process took place throughout the matrix. Finally, the sample crumbled completely to the powders. No bulk dilatation was detected before the powdering, indicating that the collapse process would not exert pressure outward. Thus the alloy blade would not be damaged during the removal of the ceramic core. It was also predicted that the decrease in the MgO grain size was beneficial to the water-collapsibility.

Keywords:

ceramic cores, porous structure, MgO, hydration, interior-collapsing mechanism
Received: 19 December 2021 Revised: 17 January 2022 Accepted: 24 January 2022 Published: 20 April 2022 Issue date: May 2022
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Publication history

Received: 19 December 2021
Revised: 17 January 2022
Accepted: 24 January 2022
Published: 20 April 2022
Issue date: May 2022

Copyright

© The Author(s) 2022.

Acknowledgements

The authors gratefully acknowledge the financial support from the National Key R&D Program of China (Grant No. 2017YFB0310400) and the National Natural Science Foundation of China (Grant No. 51672014).

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