Determination of Γ’site Occupancies in Nickel Superalloys Using Atom Probe Tomography and X-ray Diffraction (preprint)

Rene88 samples were investigated using atom probe tomography and x-ray diffraction using a monochromated synchrotron beam with different energy values to determine the preferred site occupancy of various alloying elements within the ordered γ’ precipitates. Samples were solutionized and cooled at 24 degree C/min with subsequent aging at 760 degrees C. The synchrotron-based x-ray diffraction results indicate that niobium prefers to reside on the aluminum sublattice site of the γ’ phase. Additionally, the experimental results also indicate that chromium prefers the nickel sublattice sites while cobalt is likely to occupy both the aluminum and nickel sublattice sites. The x-ray results on the chromium occupancy disagree with atom probe results from the same alloy that indicate that chromium prefers the aluminum sublattice sites. Modeling studies indicate cobalt has no strong site preference.