Creep-rupture behavior of a directionally solidified nickel-base superalloy

The creep-rupture behavior of the directionally solidified (DS) nickel-base superalloy DZ17G has been investigated over a wide stress range of 60 to 9 50 MPa at high temperature (923 to 1323 K). In this article, the detailed c reep deformation and fracture mechanisms at constant load have been studied . The results show that all creep curves exhibit a short primary and a domi nant accelerated creep stage, which results in higher ductility of DS super alloy DZ17G compared to the conventionally cast alloy. From the creep param eters and transmission electron microscopy (TEM) observations, it is sugges ted that the dominant creep deformation mechanism has a change from gamma p rime particles shearing by matrix dislocations in high stress region to dis location climb process in low stress region. It is found that the fracture mode of DS superalloy DZ17G is transgranular, and it is controlled by the p ropagation rate of deep cracks initiated at both surface and inner microstr ucture discontinuities. The creep rupture data follows the Monkman-Grant re lationship under all the explored test conditions.