Abstract
The size evolution and phase composition of sigma phases were investigated for a 347H stainless steel subject to isothermal aging at 750 °C for up to 10,000 h. Scanning electron microscopy reveals that sigma phases are present before 336 h aging and they continue to grow for all aging times studied. Atom probe tomography shows little variation in the sigma phase composition with aging time up to 10,000 h, and only the C content decreases with aging time. The comparison of C concentration suggests that the sigma phase does not nucleate within the C-depleted matrix or precipitate free grain boundaries, leaving dissolving metastable M23C6 as the only possible nucleation site. Based on the experimental results and thermodynamic simulations, the desirable Nb concentration is discussed to reduce the kinetics of sigma phase growth, and possible design directions are suggested to improve 347H.
| Original language | English |
|---|---|
| Article number | 101485 |
| Journal | Materialia |
| Volume | 24 |
| DOIs | |
| State | Published - Aug 2022 |
Funding
This work was performed in support of the US Department of Energy (DOE) Office of Fossil Energy and Carbon Management through the eXtremeMAT(XMAT) program under Crosscutting Technology High Performance Materials Research Program. APT research was supported by the Center for Nanophase Materials Sciences (CNMS), which is a US Department of Energy, Office of Science User Facility at Oak Ridge National Laboratory. The authors would like to thank Paul Jablonski, Martin Detrois, and Jeff Hawk at National Energy Technology Laboratory (NETL) for making the materials, Caitlin Duggan at the ORNL Materials Science and Technology Division (MSTD) for metalography sample preparation, and James Burns at the ORNL CNMS for assistance in performing APT sample preparation and running the APT experiments. This manuscript has been authored by UT-Battelle, LLC, under contract DE-AC05–00OR22725 with the US Department of Energy (DOE). The US government retains and the publisher, by accepting the article for publication, acknowledges that the US government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for US government purposes. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan ( http://energy.gov/downloads/doe-public-access-plan ). This work was performed in support of the US Department of Energy (DOE) Office of Fossil Energy and Carbon Management through the eXtremeMAT(XMAT) program under Crosscutting Technology High Performance Materials Research Program. APT research was supported by the Center for Nanophase Materials Sciences (CNMS), which is a US Department of Energy, Office of Science User Facility at Oak Ridge National Laboratory. The authors would like to thank Paul Jablonski, Martin Detrois, and Jeff Hawk at National Energy Technology Laboratory (NETL) for making the materials, Caitlin Duggan at the ORNL Materials Science and Technology Division (MSTD) for metalography sample preparation, and James Burns at the ORNL CNMS for assistance in performing APT sample preparation and running the APT experiments.
Keywords
- Aging
- Scanning electron microscopy (SEM)
- Sigma phase
- Stainless steel
- Three-dimensional atom probe (3DAP)