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

Abstract

The high-temperature and low-stress creep (1293K, 160MPa) of the single-crystal Ni-based superalloy LEK 94 is investigated, comparing the tensile creep behavior of miniature creep specimens in [001] and [110] directions. In the early stages of creep, the [001]-direction loading shows higher minimum creep rates, because a greater number of microscopic crystallographic slip systems are activated, the dislocation networks at γ/γ′ interfaces accommodate lattice misfit better, and γ channels are wider. After the creep rate minimum, creep rates increase more strongly as a function of strain for [110] tensile loading. This may be related to the nature of rafting during [110] tensile creep, which results in a more open topology of the γ channels. It may also be related to more frequent γ′ cutting events compared with [100] tensile creep.