SMALL-ANGLE NEUTRON-SCATTERING STUDIES ON ORIENTED SINGLE-CRYSTAL SUPERALLOYS

A single-crystal nickel-base superalloy SC16, recently developed for b lade applications in land-based gas turbines, was investigated using t he SANS instrument (V4) at the BERII reactor in HMI Berlin. The two-di mensional scattering patterns were measured as a function of the cryst allographic orientation and analysed by comparing with iso-intensity p rofiles simulated on the base of a microstructural model of the SC16. Sizes, interparticle distances, volume fraction and morphology of prec ipitates were determined. Depending on the heat treatment conditions d ifferent scattering patterns were observed corresponding to different morphologies of gamma' precipitates. Additionally some samples showed streaks in the two-dimensional scattering patterns, indicating the pre sence of precipitates other than gamma'. This was also confirmed by TE M, SEM and X-ray diffraction studies. (C) 1998 Elsevier Science B.V. A ll rights reserved.