Anisotropy of stress rupture properties of a Ni base single crystal superalloy at two temperatures

Abstract

The stress rupture properties of a single crystal superalloy in three orientations were tested under 871 °C/552 MPa and 1010 °C/248 MPa. The [0 0 1] orientation shows the longest life and good elongation at 871 °C, the [1 1 1] orientation exhibits the best elongation, while the life and elongation of [0 1 1] orientation are both poor at this test condition. At 1010 °C, the anisotropy between [0 0 1] and [0 1 1] orientation is evidently reduced, however the [1 1 1] orientation shows the longest life at the same condition. In [0 0 1] orientation, the N type rafts are formed under two test conditions. In [1 1 1] orientation, the γ′ keep cuboidal shape under 871 °C/552 MPa, while rafts with direction varying with local position are formed under 1010 °C/248 MPa. In [0 1 1] orientation, lots of stacking faults appears in γ′ under 871 °C/552 MPa, while many twins are formed under 1010 °C/248 MPa, which are both related to the activation of {1 1 1} 〈1 1 2〉 slip system. The influence of orientation and test condition on the deformation mechanisms and stress rupture properties is discussed.