The GH4169 Galloy forgings have light and dark banded defects during low power inspection

which was observed through micro metallography.The results reveal that theδ-Ni

3

Nb phase is segregated in banding defect with coarse grain size

in addition

it is independent on the segregation of carbide and carbonitride.The JMatPro software was used to simulate the phase transition of GH4169 Galloy during solidification process.The results reveal that the equilibrium distribution coefficient of Nb in the alloy is 0.19

so composition segregation is easily formed

which are responsible for dark and light banded structure formed.The homogenizing treatment of alloy is modified from two-stage into the three-stage of 1 120℃×15 h、1 160℃×30 hand 1 190℃×60 h

so the banded structure is eliminated.