Effects of stress and temperature on creep behavior of a new third-generation powder metallurgy superalloy FGH100L

In this paper, a new third generation powder metallurgy nickel-based superalloy, designated as FGH100L, was prepared by Spray Forming, followed by Hot Isostatic Pressing, Isothermal Forging and Heat Treatment. The effects of stress and temperature on the creep properties of the alloy were studied by analyzing the creep mechanism and fracture characteristics. The results show that the creep life of the alloy decreases significantly with the increase of stress and temperature. The creep fracture indicates mixed intergranular and transgranular fracture characteristics for all the tested specimens. However, at low stress or low temperature conditions, the intergranular fracture is more prominent in the fracture source region and almost no shear lip region can be observed in the final rupture region. With the increase of stress and temperature, the transgranular fracture becomes more prominent, and the shear lip region is enlarged. The misorientation within the grain decreases with the increase of stress and temperature, indicating that the higher the stress and the temperature, the lower the local strain the alloy can bear. Under the creep condition of high temperature and high stress, the misorientation is much larger around the original grain boundary than in the interior of the original grain, indicating that the internal strain of the alloy is mainly concentrated near the original grain boundary under this condition.
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