Hydrogen Embrittlement of a CoNiCr-Based Superalloy: The Role of the Intermetallic Precipitation Phases β and γ′

Nagel O, Strobel L, Stark A, Fritton M, Höschen C, Felfer P, Gilles R, Neumeier S (2026)

Publication Type: Journal article

Publication year: 2026

Journal

Metallurgical and Materials Transactions A-Physical Metallurgy and Materials Science ASM International

DOI: 10.1007/s11661-026-08130-1

Abstract

Hydrogen embrittlement (HE) presents a critical challenge for the application of superalloys in hydrogen-containing environments, such as future turbine systems. This study investigates the influence of the β phase and γ′ phase on HE sensitivity in the CoNiCr-based superalloy CoWAlloy6. A tailored heat treatment strategy was applied to vary the β and γ′ phase fraction while maintaining all other microstructural aspects constant. Tensile tests after high-pressure hydrogen charging (1000 bar, 300 °C) reveal reduced HE susceptibility for CW6+β/−γ′ (CoWAlloy6 with higher β and lower γ′ content), compared to CW6−β/+γ′ (CoWAlloy6 with lower β and higher γ′ content). Thermal desorption spectroscopy measurements confirm that an increased β and the associated decreased γ′ phase fraction correlates with lower overall hydrogen solubility and slightly reduced diffusion rates. In addition, NanoSIMS mappings demonstrate the highest hydrogen uptake inside β phase precipitates. Consequently, the amount of diffusible hydrogen in the γ/γ′ compound is lower in CW6+β/−γ′, which in turn results in a modest work-hardening behavior. This work-hardening potential is essential for reducing the severity of HE. Furthermore, a slower strain rate during tensile testing increases HE severity, confirming the role of diffusible hydrogen content as a key aspect in the embrittlement mechanism. EBSD analyses of secondary cracks reveal predominantly transgranular cracking, indicating weakened γ/γ′ interfaces in the presence of hydrogen. The findings suggest that tuning the β and γ′ content by small modifications in heat treatment can positively affect the alloy’s resistance to hydrogen embrittlement, primarily by reducing the hydrogen solubility through a lower γ′ fraction and by lowering the amount of diffusible hydrogen in the microstructure through an increased β fraction.

Authors with CRIS profile

Oliver Nagel Lehrstuhl für Werkstoffwissenschaften (Allgemeine Werkstoffeigenschaften) Peter Felfer Professur für Atom Probe Tomography Steffen Neumeier Lehrstuhl für Werkstoffwissenschaften (Allgemeine Werkstoffeigenschaften)

Involved external institutions

Helmholtz-Zentrum Hereon DE Germany (DE) Technische Universität München (TUM) DE Germany (DE)

How to cite

APA:

Nagel, O., Strobel, L., Stark, A., Fritton, M., Höschen, C., Felfer, P.,... Neumeier, S. (2026). Hydrogen Embrittlement of a CoNiCr-Based Superalloy: The Role of the Intermetallic Precipitation Phases β and γ′. Metallurgical and Materials Transactions A-Physical Metallurgy and Materials Science. https://doi.org/10.1007/s11661-026-08130-1

MLA:

Nagel, Oliver, et al. "Hydrogen Embrittlement of a CoNiCr-Based Superalloy: The Role of the Intermetallic Precipitation Phases β and γ′." Metallurgical and Materials Transactions A-Physical Metallurgy and Materials Science (2026).

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