About this Abstract |
| Meeting |
11th International Symposium on Superalloy 718 and Derivatives 2026: Legacy, Innovations, and Future Directions
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| Symposium
|
Superalloy 718 and Derivatives 2026: Legacy, Innovations, and Future Directions
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| Presentation Title |
Comparison of Creep Behaviors Between Alloy 718 and Ta-718 |
| Author(s) |
Satoru Kobayashi, Takumi Tsuya |
| On-Site Speaker (Planned) |
Satoru Kobayashi |
| Abstract Scope |
Alloy 718 is an important class of Nb-bearing Ni-based superalloys for high-temperature applications, such as compressor disks/blades and turbine disks in gas turbine systems. However, its service temperature is limited to below 650 °C due to the thermal instability and degradation of the γ” precipitates. To understand and improve the creep properties of 718-type superalloys, we investigated and compared the creep behaviors of alloy 718 and alloy Ta-718, which are strengthened by γ”-Ni3Nb and γ”-Ni3Ta precipitates, respectively.
Creep tests were conducted at 700 °C under applied stresses of 400 and 500 MPa for both alloys in the aged condition. While the minimum creep rates were comparable between the two alloys, creep acceleration was significantly suppressed in the Ta-718 specimens compared with the 718 specimens under the conditions studied, leading to prolonged creep life or delayed rupture in the Ta-718 specimens. Microstructural observations before and after creep testing revealed that the γ” precipitates in the Ta-718 specimens remained noticeably finer than those in the 718 specimens throughout creep exposure. In addition, planar defects and shearing of γ” precipitates were observed more frequently in the 718 specimens than in the Ta-718 specimens. These differences in creep behavior are discussed in terms of the critical resolved shear stress for γ” precipitate shearing. |
| Proceedings Inclusion? |
Definite: At-meeting proceedings |