In Situ Investigation with Neutrons on the Evolution of Gamma' Precipitates at High Temperatures in a Single Crystal Ni-Base Superalloy

Abstract

Single crystal Ni-base superalloys based on the g / g`m system are widely used in gas turbine applications. To understand the formation of precipitates, including size distribution and growth, we performed in situ small-angle neutron scattering (SANS) measurements at elevated temperatures and - together with TEM as well as SEM imaging - studied changes in the precipitates in short and long time scale. In the early stages, a bimodal precipitate size distribution is observed, which (depending on the annealing temperature) changes to a cuboidal or nearly spherical morphology with nearly unimodal size distribution.