Abstract
An alloy's processing history, including melting, remelting or the choice of stock material, affects its purity and eventually involves tramp element pickup or retention. In this investigation, variants of a novel Ni-based superalloy were manufactured with different levels of purity. The so-called low purity alloys contained 0.138 wt. % Cu and 0.019 wt. % Si while the Cu and Si levels were below x-ray fluorescence (XRF) detection limits of 0.003 and 0.010 wt. %, respectively, in the high purity ingots. Atom-probe tomography (APT) was carried out and revealed Si partitioning at the following interfaces: grain boundaries, MC carbide/γ, M3B2 boride/γ and M3B2 boride/γ′. Copper was found to primarily segregate to the γ′ precipitates. An average of 2.4 × decrease in creep life and 4.3 × decrease in creep ductility was measured in the low purity alloys, which was attributed to the embrittlement caused by Si segregation to grain boundaries. Furthermore, the positive effect of B on the creep properties was mitigated by the presence of Si. Thermodynamic predictions for the matrix and γ′ precipitate compositions represented the trends observed experimentally although the extent of preferential partitioning lacks accuracy. Monte Carlo simulations were performed to describe the partitioning of Cu and Si atoms to either γ or γ′ phases.
| Original language | English |
|---|---|
| Article number | 100843 |
| Journal | Materialia |
| Volume | 13 |
| DOIs | |
| State | Published - Sep 2020 |
Funding
This work was funded by the Department of Energy, National Energy Technology Laboratory, an agency of the United States Government, through a support contract with Leidos Research Support Team (LRST). Neither the United States Government nor any agency thereof, nor any of their employees, nor LRST, nor any of their employees, makes any warranty, expressed or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. This work was performed in support of the US Department of Energy's Fossil Energy Crosscutting Technology Research Program. The Research was executed through the NETL Research and Innovation Center's Advanced Alloy Development Field Work Proposal. Research performed by Leidos Research Support Team staff was conducted under the RSS contract 89243318CFE000003. MD, PDJ and JAH would like to thank E.R. Argetsinger and J.A. Mendenhall for assistance in melting, C.D. Powell for mechanical testing, R.E. Chinn and C. McKaig for chemistry analysis, M.B. Fortner for metallographic preparation and T.A. Godell for sample machining. APT was conducted at ORNL's Center for Nanophase Materials Sciences (CNMS), which is a U.S. DOE Office of Science User Facility. The authors would like to thank James Burns for performing APT sample preparation and running the APT experiments. This work was performed in support of the US Department of Energy's Fossil Energy Crosscutting Technology Research Program. The Research was executed through the NETL Research and Innovation Center's Advanced Alloy Development Field Work Proposal. Research performed by Leidos Research Support Team staff was conducted under the RSS contract 89243318CFE000003. MD, PDJ and JAH would like to thank E.R. Argetsinger and J.A. Mendenhall for assistance in melting, C.D. Powell for mechanical testing, R.E. Chinn and C. McKaig for chemistry analysis, M.B. Fortner for metallographic preparation and T.A. Godell for sample machining. APT was conducted at ORNL's Center for Nanophase Materials Sciences (CNMS), which is a U.S. DOE Office of Science User Facility. The authors would like to thank James Burns for performing APT sample preparation and running the APT experiments.
| Funders | Funder number |
|---|---|
| DOE Office of Science | |
| LRST | |
| US Department of Energy | 89243318CFE000003 |
| U.S. Department of Energy | |
| National Energy Technology Laboratory |
Keywords
- Ni-based superalloys;Atom-probe tomography;Grain boundaries;Silicon;Copper