Effects of Grain Sizes on Small Fatigue Crack Growth of GH4169 Ni-base Alloy

The effects of heat treatment on the microstructure, tensile properties of the GH4169 Ni-base superalloy and the effects of grain sizes on the behavior of fatigue crack growth were studied by optical microscopy, scanning electron microscopy, tensile and fatigue testers. The results show that the mechanical properties of the tested alloy were improved after solution treatment followed by double aging treatment. With the increase of the solution temperature, the grain sizes of the alloy increased the strength decreased and the fatigue life was prolonged. The stages of small crack took up about 80% of fatigue life. The effects of grain sizes on small fatigue crack growth were not obvious. However the long crack growth rate decreased with the increase of the grain size.