Anisotropy of high cycle fatigue behavior of a Ni-base single crystal superalloy

The rotary bending high cycle fatigue properties of a single crystal superalloy in three orientations were tested at 700 degrees C in ambient atmosphere. The [011] orientation shows the highest fatigue strength. Moreover, the fatigue strength with < 111 > orientation is obviously higher than that with < 001 > orientation. There are two types of fracture modes, one is cleavage fracture for the [001] orientation, the other is the mixed fracture of cleavage and tearing for the [011] orientation. The < 011 > orientation shows more pronounced crystal lattice rotation than the < 111 > orientation. Nevertheless, lattice rotation does not occur in the crystals with [001] orientation. Fatigue steps of the [001] and [111] orientated crystals propagate along different {111} glide planes, which means that the slip in < 111 > orientation moves more easily than in < 011 > orientation. The typical deformation mode of [001], [011] or [111] orientation is respectively slip bands running through gamma and gamma' phases, dislocation pairs shearing gamma' particles, or superlattice stacking faults besides high-density dislocation shearing gamma' particles. (C) 2013 Elsevier B.V. All rights reserved.