Role of Stress on Creep Behaviors for Marm247lc Ds Superalloy

Abstract

The role of stress on creep behaviors of MarM247LC directional-solidified (DS) superalloy was investigated at 900˚C under different stresses. With reduced stress from 400MPa to 230MPa, the creep life has increased by a factor of 24, from 54h to 1351h. Apart from that, the deformation mechanism, creep curves and fracture behavior of the alloy also presented strong dependence on stress. It found that the main deformation mechanism was the precipitate shearing by a/2<110> dislocations under 400MPa. In contrast, dislocations bypassing γ' by a glide-climb process dominated the steady-state creep under 230MPa. Moreover, the degradation of γ/γ' microstructure and formation of creep pores have accelerated the onset of tertiary creep and resulted in more ductile fracture modes at low stress regime.

Keywords: Stress, Creep, Deformation mechanism, Fracture behavior