Influence of γ / γ ′ lattice misfit on creep behaviours of FGH95 Ni based superalloy

Abstract

By means of microstructure observation and X-ray diffraction (XRD) analysis and creep properties measurement, an investigation has been made into the effects of γ/γ′ lattice misfit on creep behaviours of FGH95 Ni based superalloy. The results showed that, compared with the ‘oil cooling’ alloy, the fine γ′ particles with larger size and better cube degree distribute in the alloy quenched in molten salt bath. By XRD analysis, it indicates that the γ/γ′ interface of the ‘molten salt cooling’ alloy possesses bigger lattice misfit, which may hinder the dislocation movement to enhance the creep resistance of the alloy. During creep, the deformation mechanism of the oil cooling alloy is that the dislocations with different orientations slip in the matrix and form dislocation tangles. Moreover, the configuration of the partial dislocations plus stacking fault may be activated in the molten salt cooling alloy, and the deformed dislocations may bypass γ′ phase by Orowan mechanism, shear or climb over γ′ phase.