Abstract
The effect of Ni and Cr additions on microstructure, lattice misfit, oxidation, and creep properties are investigated for six W- and Mo-free cobalt-based superalloys with compositions Co-xNi-5Al-yCr-3V–2Ti-1.5Nb-1.5Ta-0.08B (at.%), where x = 10, 20, or 30 and y = 4 or 8. In all alloys, the γ + γ′ microstructure is stable for up to 1000 h upon aging at 850 °C. As Ni increases from 10 to 30 at.%, the γ′ area fraction increases from 32 to 49% in the three low-Cr alloys, while remaining constant (45%) for the high-Cr alloys. All alloys show positive γ/γ′ lattice misfits of 0.8 ± 0.2%, consistent with γ’ rafting observed after creep. Both Cr and Ni additions increase oxidation resistance, more so for 8% Cr than for 30% Ni, as expected from the high stability of chromium oxide. Increasing Cr from 4 to 8 at.% slightly increases creep resistance at 850 °C and increasing Ni from 10 to 30% has a similar effect.
Original language | English (US) |
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Article number | 143401 |
Journal | Materials Science and Engineering: A |
Volume | 849 |
DOIs | |
State | Published - Aug 1 2022 |
Funding
This study was supported by the U.S. Department of Commerce , National Institute of Standards and Technology , as part of the Center for Hierarchical Materials Design ( CHiMaD ) at Northwestern University via award 70NANB14H012. This work made use of the MatCI Facility which receives support from the MRSEC Program ( NSF DMR- 1720139) of the Materials Research Center at Northwestern University; and the IMSERC X-RAY and the EPIC facility of Northwestern University's NUANCE Center, which received support from the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource ( NSF ECCS-1542205). Synchrotron x-ray diffraction was performed at the DuPont-Northwestern-Dow Collaborative Access Team (DND-CAT) located at Sector 5 of the Advanced Photon Source (APS). DND-CAT is supported by Northwestern University , The Dow Chemical Company , and DuPont de Nemours, Inc. The Advanced Photon Source is a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357.
ASJC Scopus subject areas
- General Materials Science
- Condensed Matter Physics
- Mechanics of Materials
- Mechanical Engineering