Microstructural stability of long-term aged wrought Ni–Fe-based superalloys

ABSTRACT

The influence of long-term thermal exposure on the microstructure and microhardness of a new Ni–Fe-based superalloy, for advanced ultra-supercritical coal-fired power plants, was studied. Spherical γ′ particles were coarsened with the increase of aging time, while the volume fraction of γ′ was decreased. The amount of M₂₃C₆ carbides was increased with aging time at 750°C, and the coarsening rate of the width of M₂₃C₆ was consistent with that of the LSW model. The microhardness of the alloy was maintained following 935 h of aging time and then was slightly decreased. It was found that the transition from the strongly coupled dislocations model to the Orowan model was dependent on the size and volume fraction of γ′.

KEYWORDS:

• Ni–Fe-based superalloys
• thermal exposure
• coarsening
• microstructure
• microhardness

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the Science Foundation of Huaneng Power International Inc. (ZD-15-HJK02), the Science Foundation of the Xi’an Thermal Power Research Institute Co. Ltd. (ZD-15-TYK07), National Nature Science Foundation of China under Grant Nos. 51301130 and 51401164.