About this Abstract |
Meeting |
Superalloys 2024
|
Symposium
|
Superalloys 2024
|
Presentation Title |
Inhomogeneous Distribution and Coarsening of γ″ Precipitates in a Ni-based Superalloy and their Effect on Creep |
Author(s) |
Chang-Yu Hung, Stoichko Antonov, Paul D Jablonski, Martin Detrois |
On-Site Speaker (Planned) |
Chang-Yu Hung |
Abstract Scope |
Modifications to INCONEL® alloy 725 (IN725) with higher Nb or Ta and high Ti/Al ratio previously revealed the formation of γ'' precipitates as the sole precipitate strengthening phase which was accompanied with significant increases in elevated temperature strength and resistance to creep deformation. In this study, the γ'' alloys (named M725-Nb and M725-Ta) were chosen to observe the microstructural evolution of γ'' precipitates during creep. Following aging, γ'' was found to be the main precipitate strengthening phase with no detectable γ' in both M725 alloys. After creep, the grip/gage sections of the crept M725-Nb/Ta exhibited preferential coarsening and inhomogeneous distribution of γ'' platelets, and sandwich-like structures, comprising of cubic γ' precipitates with small γ'' discs on each facet. This γ'' variant selection behavior taking place in the grip section with no stress applied was different from the typical stress-induced variant selection reported in previous literature. However, creep tested specimens with prior high temperature exposure to promote varying γ'' characteristics prior to deformation demonstrated a similar creep behavior when compared to aged specimens tested under identical conditions. This suggested that the coarsening and inhomogeneous distribution of γ'' precipitates was not the determinant factor for creep life in bulk M725-Nb/Ta alloys. The failure of bulk M725 was linked with the development of cracks along grain boundaries (GBs), where the emergence of Nb-rich δ and/or Ta-rich h phases at the GB markedly depleted the γ'' strengthening phase in the surrounding GB regions which led to localized weakening. |
Proceedings Inclusion? |
Definite: At-meeting proceedings |