Enhancing the High-Temperature Strength of a Co-Base Superalloy by Optimizing the γ/γ′ Microstructure
Abstract
:1. Introduction
2. Materials and Methods
3. Results
3.1. Microstructural Characterization
3.1.1. Electron Microscopy
3.1.2. Small-Angle Neutron Scattering
3.2. Mechanical Properties
4. Discussion
5. Conclusions
- A two-step aging heat treatment at 900 °C/4 h + 750 °C/16 h leads to the highest strength.
- The total γ′ volume fraction is above 70%, as determined by SANS, which is exceptionally high for a wrought alloy.
- An optimum γ′ precipitate size in the range of about 30–40 nm is found to reach the maximum strength, which can be explained by the model for weak and strong pair-coupling of dislocations.
Author Contributions
Funding
Acknowledgments
Conflicts of Interest
References
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Element | Co | Ni | Cr | Al | W | Ti | Ta | Si | Zr | Hf | B | C |
---|---|---|---|---|---|---|---|---|---|---|---|---|
CoWAlloy2 | 40.8 | 32.0 | 12.0 | 9.0 | 5.0 | 0.3 | 0.2 | 0.4 | 0.01 | 0.1 | 0.08 | 0.08 |
Co | Ni | Cr | Al | W | Ti | Ta | Si | Hf | B | C | |
---|---|---|---|---|---|---|---|---|---|---|---|
γ matrix | 49.0 | 21.3 | 20.9 | 3.6 | 4.4 | 0.04 | 0.03 | 0.64 | 0.02 | 0.013 | 0.008 |
±0.6 | ±0.2 | ±0.6 | ±0.1 | ±0.1 | ±0.01 | ±0.01 | ±0.05 | ±0.01 | ±0.01 | ±0.01 | |
secondary γ′ | 32.8 | 39.4 | 5.4 | 14.5 | 6.1 | 0.50 | 0.37 | 0.35 | 0.14 | 0.025 | 0.006 |
±0.5 | ±0.7 | ±0.2 | ±0.4 | ±0.4 | ±0.02 | ±0.08 | ±0.02 | ±0.03 | ±0.01 | ±0.01 | |
γ matrix | 48.5 | 22.0 | 20.0 | 4.1 | 4.5 | 0.07 | 0.03 | 0.61 | 0.02 | 0.016 | 0.007 |
±2.4 | ±2.9 | ±2.5 | ±1.5 | ±0.4 | ±0.08 | ±0.03 | ±0.09 | ±0.01 | ±0.01 | ±0.01 | |
tertiary γ′ | 34.9 | 38.2 | 5.4 | 12.5 | 7.4 | 0.44 | 0.19 | 0.38 | 0.06 | 0.011 | 0.008 |
±1.4 | ±1.4 | ±1.0 | ±0.7 | ±0.5 | ±0.06 | ±0.04 | ±0.06 | ±0.02 | ±0.01 | ±0.01 |
Heat Treatment | 800 °C | 900 °C | 800 °C/4 h +725 °C/16 h | 900 °C/4 h +750 °C/16 h | ||||||
---|---|---|---|---|---|---|---|---|---|---|
Time/h | 2 | 4 | 8 | 16 | 2 | 4 | 8 | 16 | ||
Mean radius sec. γ′/nm | 10.3 ±2.0 | 12.8 ±2.6 | 14.6 ±4.5 | 19.6 ±4.0 | 21.4 ±7.2 | 26.4 ±6.5 | 34.2 ±8.8 | 45.2 ±13.5 | 19.4 ±6.4 | 36.1 ±7.0 |
Condition | Secondary γ′ | Tertiary γ′ | Total γ′ | ||||
---|---|---|---|---|---|---|---|
r/nm | σ/nm | f/% | r/nm | σ/nm | f/% | f/% | |
as-RX | - | - | - | 4.7 | 0.3 | 51 | 51 |
800 °C/1 h | 7.0 | 0.3 | 41 | 3.7 | 0.5 | 33 | 74 |
800 °C/2 h | 9.2 | 0.3 | 56 | 4.5 | 0.2 | 17 | 73 |
900 °C/1 h | 18.3 | 0.3 | 39 | 7.2 | 0.4 | 12 | 51 |
900 °C/2 h | 23.5 | 0.3 | 42 | 9.7 | 0.3 | 9 | 51 |
800 °C/4 h + 725 °C/16 h | 12.2 | 0.3 | 49 | 5.6 | 0.2 | 21 | 70 |
900 °C/4 h + 750 °C/16 h | 39.8 | 0.3 | 41 | 8.0 | 0.3 | 35 | 76 |
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Hausmann, D.; Solís, C.; Freund, L.P.; Volz, N.; Heinemann, A.; Göken, M.; Gilles, R.; Neumeier, S. Enhancing the High-Temperature Strength of a Co-Base Superalloy by Optimizing the γ/γ′ Microstructure. Metals 2020, 10, 321. https://doi.org/10.3390/met10030321
Hausmann D, Solís C, Freund LP, Volz N, Heinemann A, Göken M, Gilles R, Neumeier S. Enhancing the High-Temperature Strength of a Co-Base Superalloy by Optimizing the γ/γ′ Microstructure. Metals. 2020; 10(3):321. https://doi.org/10.3390/met10030321
Chicago/Turabian StyleHausmann, D., C. Solís, L.P. Freund, N. Volz, A. Heinemann, M. Göken, R. Gilles, and S. Neumeier. 2020. "Enhancing the High-Temperature Strength of a Co-Base Superalloy by Optimizing the γ/γ′ Microstructure" Metals 10, no. 3: 321. https://doi.org/10.3390/met10030321
APA StyleHausmann, D., Solís, C., Freund, L. P., Volz, N., Heinemann, A., Göken, M., Gilles, R., & Neumeier, S. (2020). Enhancing the High-Temperature Strength of a Co-Base Superalloy by Optimizing the γ/γ′ Microstructure. Metals, 10(3), 321. https://doi.org/10.3390/met10030321