High-temperature and low-stress creep anisotropy of single-crystal superalloys

The high-temperature and low-stress creep (1293 K, 160 MPa) of the single-crystal Ni-based superalloy LEK 94 is investigated, comparing the tensile creep behavior of miniature creep specimens in [0 0 1] and [1 1 0] directions. In the early stages of creep, the [0 0 1]-direction loading shows higher minimum creep rates, because a greater number of microscopic crystallographic slip systems are activated, the dislocation networks at gamma/gamma' interfaces accommodate lattice misfit better, and gamma channels are wider. After the creep rate minimum, creep rates increase more strongly as a function of strain for [1 1 0] tensile loading. This may be related to the nature of rafting during [1 1 0] tensile creep, which results in a more open topology of the gamma channels. It may also be related to more frequent gamma' cutting events compared with [1 0 0] tensile creep. (c) 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.