A Study of Sliver in C-Shaped Grain Selectors during Investment Casting of Single-Crystal Superalloy
Abstract
:1. Introduction
2. Experimental Procedure
2.1. Test and Calculation Method
2.1.1. Experimental Method
2.1.2. Experimental Results
2.2. Numeral Simulation
2.2.1. Temperature Field Model
- (1)
- Heat conduction equation can be described as follows [23]:
- (2)
- The heat radiation between the ceramic shell and furnace chamber is in accordance with the Stefan–Boltzmann law, which is described as follows [24]:
2.2.2. Mathematical Model of Stress Field
2.2.3. Simulation Parameters
3. Results and Discussion
3.1. Microscopic Morphology Analysis of Sliver Defects
3.2. Solidification Interval of Superalloy
3.3. Numerical Calculation of Temperature Field
3.4. Numerical Calculation of Stress Field
3.5. Analysis of the Sliver Formation Mechanism
- The sliver formation initiates at the points that undergo an abrupt transformation, especially at the junction of crystal initiation and separation segments, where the temperature gradient is significant, and the solidification rate is slow.
- The sliver forms among primary dendrites, where many eutectic structures with low melting points are easily formed.
- The sliver mainly forms at the end of solidification. At this point, the liquid phase′s volume fraction is minimal, and it is not easy to replenish the solidification shrinkage with the remaining liquid metal. In addition, the stress grows with the progression of solidification, and the accumulated stress reaches its maximum value at the end of solidification.
- The region with the sliver defect experiences significant tensile stress. The casting exhibits volume changes during solidification due to the lengthy solidification interval of the casting superalloy, which could cause the emergence of many eutectic phases with low melting points among the dendrites at the end of solidification. The dendrites are displaced due to the action of tensile stress and cannot be replenished by the liquid phase, which allows for the formation of the sliver.
4. Conclusions
Author Contributions
Funding
Data Availability Statement
Acknowledgments
Conflicts of Interest
References
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Element | Cr | Co | Mo | W | Al | Ta | Ti | C | Hf | Ni |
---|---|---|---|---|---|---|---|---|---|---|
Mass (wt.%) | 8.2 | 9.2 | 0.5 | 9.4 | 5.6 | 3.2 | 0.7 | 0.08 | 1.1 | Bal. |
Probe | SCd1 | SCd2 | SCd3 | SCd4 | SCd5 | SCd6 | SCd7 | SCd8 |
---|---|---|---|---|---|---|---|---|
Diameter (mm) | 2.6 | 3.0 | 3.4 | 3.8 | 4.2 | 5.4 | 6.0 | 6.6 |
Pitch Length (mm) | 8 | |||||||
Selector Height (mm) | 10 | |||||||
Starter Block Size(mm) | 10 (L) × 10 (W) × 30 (H) |
Temperature | Density of Metal | Thermal Conductivity | Enthalpy of Metal |
---|---|---|---|
T (°C) | ρMetal (kg·m−3) | λMetal (W·m−1·°C−1) | EM (kJ·Kg−1) |
25 | 8.164 | 10.3 | −368.7 |
400 | 8.016 | 15.3 | 191.1 |
1000 | 7.766 | 23.8 | 159.4 |
1324 | 7.505 | 32.8 | 450.1 |
1371 | 7.169 | 30.5 | 700.9 |
1550 | 7.016 | 33.4 | 837.3 |
Temperature | Interface Heat-Transfer Coefficients | Interface Heat-Transfer Coefficients |
---|---|---|
T (°C) | hMetal/Mold (W·m−2·°C−1) | hMetal/Chill (W·m−2·°C−1) |
25 | 150 | 80 |
400 | 150 | 600 |
1000 | 190 | 1510 |
1324 | 350 | 2000 |
1371 | 750 | 2250 |
1550 | 750 | 3010 |
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Yang, Q.; Zhu, X.; Wang, F.; Ma, D.; Wu, J. A Study of Sliver in C-Shaped Grain Selectors during Investment Casting of Single-Crystal Superalloy. Metals 2023, 13, 1102. https://doi.org/10.3390/met13061102
Yang Q, Zhu X, Wang F, Ma D, Wu J. A Study of Sliver in C-Shaped Grain Selectors during Investment Casting of Single-Crystal Superalloy. Metals. 2023; 13(6):1102. https://doi.org/10.3390/met13061102
Chicago/Turabian StyleYang, Qiang, Xintao Zhu, Fu Wang, Dexin Ma, and Jiantao Wu. 2023. "A Study of Sliver in C-Shaped Grain Selectors during Investment Casting of Single-Crystal Superalloy" Metals 13, no. 6: 1102. https://doi.org/10.3390/met13061102