CALPHAD method is used to study and optimize the composition of Ni-based GH3128 alloy and the law of precipitate phase. The results show that the main harmful precipitated phase in GH3128 is phase μ and its principle chemical composition is (NiCr)

3

( WMo)

2

. With the increase of W

Mo and Cr content

the precipitated amount of phase μ increases. But addition of 17%Cr induces the transformation of phase μ into phase σ resulting in the decrease of phase μ precipitation decreases. With C content increased

the amount of carbide precipitation increases

not only can also lead to decrease of precitated amount of γ’ phase

but as C content lower than 0.02%

to prompte phase μ precipitated at 700℃ . As the elements of Al and Ti increase

although the amount of

γ’ phase precipitation increases

the a phase is also precipitated. Therefore

Through GH3128 Ni-based alloy composition optimization (/% : 0.032C

20. l0Cr

8.02W

7.92Mo

0.72A1

0.62Ti

0.30Fe

0.005B

0.06Zr

0.05Ce

0.35Mn

0.43Si)

it can make the alloy at the working temperature above 900℃; without harmful phase and harmful a phase precipitation amount is reduced.