Atomistic simulations of diffusion in γ′ -strengthened Co-based superalloys and its connection to selective alumina formation in early-stage oxidation

Qin L, Kubacka D, Spiecker E, Drautz R, Rogal J (2023)

Publication Type: Journal article

Publication year: 2023

Journal

Physical Review Materials American Physical Society

Book Volume: 7

Article Number: 013403

Journal Issue: 1

DOI: 10.1103/PhysRevMaterials.7.013403

Abstract

The suppressed diffusion of Al in γ′ precipitates of Co-based superalloys is suspected to be one of the reasons for the selective formation of alumina during the early-stage oxidation above 900°C. In order to scrutinize this assumption, the diffusion properties of Al, Co, and W in a prototype structure of the γ′ phase, L12-Co3(Al,W), are investigated in a combined density functional theory (DFT) and kinetic Monte Carlo (KMC) study. A particular challenge in simulating diffusion in this ordered phase is the representation and evaluation of numerous migration pathways on the L12 sublattices. With specified diffusion models for the L12 structure and random solid solution (γ phase), our KMC results reveal that Al diffusivity in the γ phase with the same stoichiometric composition is more than two orders of magnitude higher than in the L12 ordered γ′ phase at 900°C. Furthermore, in our rapid thermal exposure experiments for a model Co-based superalloy, the formation of alumina nuclei is observed preferentially in the γ channels while the Al content is comparable in both channels and precipitates before oxidation. Combining these insights from experiment and simulation, the sluggish diffusion of Al in γ′ appears to be a key factor in the selective formation of alumina observed in these systems.

Authors with CRIS profile

Dorota Kubacka Lehrstuhl für Werkstoffwissenschaften (Mikro- und Nanostrukturforschung) Erdmann Spiecker Lehrstuhl für Werkstoffwissenschaften (Mikro- und Nanostrukturforschung)

Involved external institutions

Ruhr-Universität Bochum (RUB) DE Germany (DE) New York University (NYU) US United States (USA) (US)

How to cite

APA:

Qin, L., Kubacka, D., Spiecker, E., Drautz, R., & Rogal, J. (2023). Atomistic simulations of diffusion in γ′ -strengthened Co-based superalloys and its connection to selective alumina formation in early-stage oxidation. Physical Review Materials, 7(1). https://dx.doi.org/10.1103/PhysRevMaterials.7.013403

MLA:

Qin, Lin, et al. "Atomistic simulations of diffusion in γ′ -strengthened Co-based superalloys and its connection to selective alumina formation in early-stage oxidation." Physical Review Materials 7.1 (2023).

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