Effects of the Amount of γ' Phase on the Creep Strength of the Dispersion Strengthened Ni-base Superalloys

Abstract

Effect of the amount of γ' phase was studied on the creep strength of an oxide dispersion strengthened nickel-base superalloy TMO-2, and its related alloys in which the γ' content was varied from 35 to 75 %. At middle or low temperature (1 075 to 1 223 K), both the creep resistance and the rupture life increased with increasing the amount of the γ', phase. This is due to the fact that the creep deformation in this temperature range is accompanied by the shear of the γ' particles precipitated in the γ' phase. At high temperature (1 323 K), neither the creep resistance nor the rupture life depended on the amount of the γ' phase. The creep deformation at this temperature is related to the growth of voids or cracks generated at around needle-like carbides precipitated upon creep testing. Creep rupture elongations were very small (14%) in all test condions, and independent of the amount of the γ' phase. At temperatures below 1 233K, DOBES-MILICKA's relation holds among the rupture elongations, rupture lives and the steady state creep rates.