Effects of Ru on elemental partitioning and precipitation of topologically close-packed phases in Ni-based superalloys

Two Ni-based superalloys (one Ru-free and one containing 1 at.% Ru) were comparatively studied by Atom Probe Tomography and complimentary techniques. Ru addition impedes precipitation of the a phase at 950 degrees C. Ru partitions nearly equally to the gamma and sigma phase. Neither reverse elemental partitioning nor destabilization of the gamma' phase is detected when adding Ru. We propose an increase in the gamma/sigma lattice misfit caused by Ru as a major reason for impeded nucleation of the a phase. (C) 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.