Influence of dwell times on the thermomechanical fatigue behavior of a directionally solidified Ni-base superalloy

摘要

In-phase (IP) and out-of-phase (OP) thermomechanical fatigue tests with T=100-750 ℃ and optional dwells of 20min at 750 ℃ were carried out on directionally solidified Ni-base Alloy 247 LC DS. Introducing dwells reduced the lifetime for both phase angles to about one sixth. Specific damage mechanisms were internal carbide and carbide-matrix interface cracks in IP tests and crack propagation along {111}-microtwin planes in OP tests. Introducing dwells intensified both effects, thus contributing to the lifetime reduction. During dwells, the gauge length may exhibit transversal creep because of extensome-ter forces distorting the strain measurement.