| About this Abstract |
| Meeting |
10th International Symposium on Superalloy 718 and Derivatives (2023)
|
| Symposium
|
Superalloy 718 and Derivatives
|
| Presentation Title |
High-temperature Properties of Alloy 718 Made by Laser Powder-bed Fusion |
| Author(s) |
David B. Witkin, Tait McLouth, Glenn Bean, Julian Lohser, Robert Hayes |
| On-Site Speaker (Planned) |
David B. Witkin |
| Abstract Scope |
The properties of alloy 718 made by laser powder-bed fusion have been widely reported, and while their room-temperature static properties are often similar to wrought material, elevated temperature properties have proven inferior, especially at slow strain rates. Stress rupture tests performed on LBPF 718 material after Hot isostatic Pressing (HIP) and heat treating in conformance with AMS 5663 have persistently led to brittle notch failures with limited elongation. Creep testing at 650 °C and 690 MPa shows a similar tendency, with samples showing capability of sustaining a load but with limited elongation and abrupt, transgranular failure. Alternative heat treatments performed to enhance high-temperature ductility have shown success in adjusting delta phase population but without benefit for stress rupture. Alternative HIP schedules have also been performed that led to changes in room-temperature and elevated temperature static strength but no benefit in stress rupture behavior. The root cause of this behavior is attributed to the dispersion of NbC that is a consequence of the LPBF process that results in fine-scale segregation of Nb and C during rapid solidification. Deliberately lowering the carbon content of the powder feedstock led to a greater number of smaller Y” particles and smaller size NbC particles resulting in an increase in static strength at room and elevated temperatures but no improvement in stress rupture. The presence of a large number of NbC particles leads to environmental sensitivity of LPBF 718 that is most apparent at elevated temperatures and slow strain rates. |
| Proceedings Inclusion? |
Definite: At-meeting proceedings |