Neutron and X-ray diffraction measurements on micro- and nano-sized precipitates embedded in a Ni-based superalloy and after their extraction from the alloy

Abstract

Neutron and X-ray diffraction are eminently suitable techniques to determine lattice misfit in nickel-based superalloys. Due to the different measuring techniques and sensitivities of the probes, sometimes one method is preferable to the other. This paper demonstrates how the use of neutrons allows a better determination of the misfit value in a bulk single-crystal tungsten-rich nickel superalloy with oriented precipitates than the use of X-rays, although the resolution in neutron diffraction is generally inferior to that in X-ray diffraction. It also yields more accurate results when the precipitates are at the nanoscale. The neutron measurements were carried out using a special technique to detect a larger number of reflections in single-crystal samples than observed in standard diffraction geometry. A comparison of the measurements by neutron and X-ray diffraction of precipitates separated from the bulk is also included in the investigation.