Microstructure evolution of a new directionally solidified Ni-based superalloy after long-term aging at 950 °C upto 1 000 h

The microstructure evolution of a new directionally solidified (DS) Ni-based superalloy used for gas turbine blades after long-term aging at 950 degrees C was investigated. The results show that the gamma' phase becomes more regular in dendritic arm and interdendritic area, while both the mass fraction and the size of gamma' 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 M(23)C(6) carbide by the precipitation of Cr at the grain boundary. The rose-shaped gamma'/gamma eutectic partly dissolves into. matrix and the aging promotes it transform into raft-shape gamma'. The microstructure is generally stable and no needle-like topologically close-packed phase (TCP) can be found after aging for 1 000 h.