Very high cycle fatigue behaviors of GH4169 superalloy at room and high temperatures

The fatigue behavior of a Ni-based superalloy of grade GH4169 has been investigated at room temperature and high temperature (RT and HT) up to a very high cycle regime using ultrasonic and electromagnetic fatigue systems. The experiments reveal that mixed-mode cracking occurred in the first crack growth stage at HT. It was followed by a horizontal crack propagation stage regardless of the initial orientation of the crack. Complex pod-like structures occur in the grain after being loaded by a large number of cycles at RT. These structures are induced by the interaction of dislocation movement with gamma '' precipitates. With the help of transmission electron microscopy investigations, it could be shown that shear bands indicate that the sliding movement dominates the superalloy's microstructure variation.