Microstructure evolution of a new directionally solidified Ni-based
superalloy after long-term aging at 950 °C upto 1 000 h
superalloy after long-term aging at 950 °C upto 1 000 h
(1. Key Laboratory for Anisotropy and Texture of Materials, Northeastern University, Shenyang 110819, China;
2. Department of High-temperature Materials, Central Iron and Steel Research Institute, Beijing 100081, China)
2. Department of High-temperature Materials, Central Iron and Steel Research Institute, Beijing 100081, China)
Abstract: The microstructure evolution of a new directionally solidified (DS) Ni-based superalloy used for gas turbine blades after long-term aging at 950 °C was investigated. The results show that the γ ′ phase becomes more regular in dendritic arm and interdendritic area, while both the mass fraction and the size of γ ′ phase increase gradually with increasing aging time. During long-term aging, the MC carbide dissolves on the edge to provide the carbon for the formation of M23C6 carbide by the precipitation of Cr at the grain boundary. The rose-shaped γ ′/γ eutectic partly dissolves into γ matrix and the aging promotes it transform into raft-shape γ ′. The microstructure is generally stable and no needle-like topologically close-packed phase (TCP) can be found after aging for 1 000 h.
Key words: Ni-based superalloy; long-term aging; microstructures evolution; carbides; γ ′ phase