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Mechanism of Grain Boundary Widening of Typical Nickel-Based Superalloys Under Near Service Conditions
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Affiliation:

School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, China

Clc Number:

TG132.3+3

Fund Project:

The National Natural Science Foundation of China (General Program, Key Program, Major Research Plan)

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    Abstract:

    This research focused on two candidate materials (alloy A and alloy B) for superheater and reheater in high-parameter advanced ultra-supercritical power plants. It systematically analyzed the phenomenon of local grain boundary widening, the kinetics, and the mechanism of grain boundary widening of two kinds of Ni-based superalloys during long-term aging. The results show that the main precipitates of two alloys in the widening grain boundary region are M23C6 carbide and grain boundary γ′ phase during high-temperature and long-term aging. The evolution of grain boundary widening of two alloys with aging time follows the JMAK equation. The formation process of grain boundary widening consists of three stages. In the first stage, the M23C6 carbides near the grain boundaries are treated by meltback, inducing the coarsening of M23C6 carbides at grain boundary and the grain boundary migration. In the second stage, new M23C6 carbides are precipitated after grain boundary migrating, which makes M23C6 carbides in the grain boundary area arrange in multiple layers, and the width of grain boundary increase. In the third stage, the γ′ phase will precipitate at the M23C6/γ interface with the decreased coarsening rate of carbides, and the short-circuit diffusion of grain boundary makes the γ′ phase grow and the width of grain boundary further increase.

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[Ma Danrui, Guo Jing, Zhang Maicang. Mechanism of Grain Boundary Widening of Typical Nickel-Based Superalloys Under Near Service Conditions[J]. Rare Metal Materials and Engineering,2025,54(4):964~974.]
DOI:10.12442/j. issn.1002-185X.20230799

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History
  • Received:December 08,2023
  • Revised:January 10,2024
  • Adopted:January 26,2024
  • Online: April 23,2025
  • Published: April 21,2025