Cr-induced phase instability and hierarchical microstructure development in Co-based superalloys

Zaiser E, Meng W, Zhou X, Mantha L, Pavel MJ, Neumeier S, Long Y, Weaver ML, Gault B, Wu Y, Vogel F (2026)

Publication Type: Journal article

Publication year: 2026

Journal

Journal of Materials Science & Technology Elsevier

Book Volume: 261

Pages Range: 309-321

DOI: 10.1016/j.jmst.2025.10.017

Abstract

Reproducibility of hierarchical γ/γ' microstructures in Co-based superalloys significantly influences their reliability and performance at elevated temperatures. This study investigates the formation and stability of such microstructures in nominally identical Co-9Al-9W-8Cr alloys. Despite nearly identical composition and heat treatment, significant microstructural differences emerged, including the formation of a hierarchical γ/γ' + γ architecture in one variant. Using scanning electron microscopy (SEM), atom probe tomography (APT), wavelength-dispersive spectroscopy (WDS), inductively coupled plasma optical emission spectroscopy (ICP-OES), and Thermo-Calc simulations, we identify subtle local Cr fluctuations and incomplete homogenization as key drivers of phase instability. High Cr levels alter partitioning behavior, promote the formation of the χ-Co3W phase, modify the γ matrix composition, reducing supersaturation and affecting γ particle formation inside γ' precipitates. APT analyses across multiple locations reveal significant nanoscale compositional variability, underlining the need for statistical sampling. Our findings show that hierarchical microstructures can form under narrow local conditions, with γ' size and local chemistry. The results highlight the sensitivity of the Co-Al-W-Cr system and the importance of precise process control to achieve reproducible, stable microstructures for advanced Co-based superalloys.

Authors with CRIS profile

Steffen Neumeier Lehrstuhl für Werkstoffwissenschaften (Allgemeine Werkstoffeigenschaften)

Involved external institutions

South China University of Technology (SCUT) / 华南理工大学 Technische Universität Berlin Max-Planck-Institut für Nachhaltige Materialien / Max Planck Institute for Sustainable Materials (MPIE) University of Science and Technology Beijing (USTB) / 北京科技大学

How to cite

APA:

Zaiser, E., Meng, W., Zhou, X., Mantha, L., Pavel, M.J., Neumeier, S.,... Vogel, F. (2026). Cr-induced phase instability and hierarchical microstructure development in Co-based superalloys. Journal of Materials Science & Technology, 261, 309-321. https://doi.org/10.1016/j.jmst.2025.10.017

MLA:

Zaiser, Erika, et al. "Cr-induced phase instability and hierarchical microstructure development in Co-based superalloys." Journal of Materials Science & Technology 261 (2026): 309-321.

BibTeX: Download