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Effect of two mould temperatures on solidification microstructures of DD9 single crystal turbine blade |
Yanpeng XUE, Xiaoguang WANG, Jinqian ZHAO, Zhenxue SHI, Shizhong LIU, Jiarong LI( ) |
Science and Technology on Advanced High Temperature Structural Materials Laboratory, AECC Beijing Institute of Aeronautical Materials, Beijing 100095, China |
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Abstract In order to investigate the solidification microstructures in typical section dimensions of a third generation single crystal superalloy DD9 turbine blade with 1500℃ and 1540℃ mould temperatures during directional solidification process, Optical microscopy (OM) and scanning electron microscopy(SEM) were used to analyse the solidification structure of typical sections of the blade. The results show that with increasing mould temperatures, the dendrite patterns have a tendency of becoming more refined, and the secondary dendritic arms tend to be highly developed. With the same mould temperature, the dendrite patterns in the blade aerofoil section are more refined than those in the tenon section. Also with increasing mould temperatures, the γ' precipitates of the interdendritic regions and the dendritic cores tend to be refined, the γ' precipitation size dispersion decreases, and the size distributions of the γ' precipitates follow the normal distribution law. Compared with the interdendritic regions, almost 61% reduction of the γ' precipitation average sizes is measured in the dendritic core. With the same mould temperature, the γ' precipitation sizes in the aerofoil section are more refined than those in the tenon section. Compared with the decreasing sectional areas, the increasing mould temperatures bring down the γ' precipitation sizes obviously. The sizes and contents of the γ-γ' eutectics decrease with increasing mould temperatures. The morphologies of γ-γ' eutectics show both sunflower-like shape and plate-like shape.
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Received: 27 January 2022
Published: 18 July 2022
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Corresponding Authors:
Jiarong LI
E-mail: jrlil26@126.com
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Cr | Co | Mo | W | Ta | Re | Nb | Al | Hf | C | Y | Ni | 3.5 | 7 | 2 | 6.5 | 7.5 | 4.5 | 0.5 | 5.6 | 0.1 | 0.008 | 0.001 | Bal |
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Nominal composition of DD9 alloy(mass fraction/%)[1]
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Schematic diagram of typical sectional positions at the single crystal superalloy turbine blade in a Bridgman furnace
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Dendrite morphologies of the blade typical sectional positions at two mould temperatures (a)aerofoil section; (b)tenon section; (1)1500 ℃; (2)1540 ℃
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Mould temperature/℃ | Section | PDAS/μm | 1500 | Aerofoil | 0.377 | 1540 | Aerofoil | 0.354 | 1500 | Tenon | 0.397 | 1540 | Tenon | 0.361 |
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PDAS of blade typical sectional positions at two mould temperatures
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Microstructures of γ′ precipitates in the dendritic cores of the blade typical sectional positions at two mould temperatures (a)aerofoil section; (b)tenon section; (1)1500 ℃; (2)1540 ℃
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Microstructures of γ′ precipitates in the interdendritic regions of the blade typical sectional positions at two mould temperatures (a)aerofoil section; (b)tenon section; (1)1500 ℃; (2)1540 ℃
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Size distributions of γ′ precipitates in the blade typical sectional positions at two mould temperatures (a)dendritic cores; (b)interdendritic regions; (1)aerofoil section; (2)tenon section
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Mould temperature/℃ | Section | dmean/μm | Dendritic core | Interdendritic region | 1500 | Aerofoil | 0.273 | 0.762 | 1540 | Aerofoil | 0.246 | 0.592 | 1500 | Tenon | 0.310 | 0.803 | 1540 | Tenon | 0.262 | 0.662 |
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γ′ precipitation average sizes of the blade typical sectional positions at two mould temperatures
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γ′ precipitation sizes of the blade typical sectional positions at two mould temperatures (a)dendritic cores; (b)interdendritic regions
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Dendrite | Section | Mould temperature changed/℃ | γ′ precipitation average size changed/μm | Dendritic core | Aerofoil section | 1500→1540 | 0.273→0.246 | | Tenon section | 1500→1540 | 0.310→0.262 | Interdendritic region | Aerofoil section | 1500→1540 | 0.762→0.592 | | Tenon section | 1500→1540 | 0.803→0.662 |
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Mould temperature changed vs γ′ precipitation average size changed
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Dendrite | Mould temperature/℃ | Sectional area changed/mm2 | γ′ precipitation average size changed/μm | Dendritic core | 1500 | Tenon section: 830→aerofoil section: 180 | 0.310→0.273 | | 1540 | Tenon section: 830→aerofoil section: 180 | 0.262→0.246 | Interdendritic region | 1500 | Tenon section: 830→aerofoil section: 180 | 0.803→0.762 | | 1540 | Tenon section: 830→aerofoil section: 180 | 0.662→0.592 |
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Sectional area changed vs γ′ precipitation average size changed
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Microstructures of γ-γ′ eutectics of the blade typical sectional positions at two mould temperatures (a)aerofoil section; (b)tenon section; (1)1500 ℃; (2)1540 ℃
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Numerical simulation of mushy zones in the aerofoil and tenon section of DD9 single crystal blade
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