Atomic-scale investigation of grain-boundary microchemistry in the nickel-based superalloy Astroloy with a three-dimensional atom probe

A new three-dimensional (3D) atom probe was used to study grain-boundary segregation and ordering phenomena in a two-phase (γ-γ') Ni-based superalloy, namely Astroloy. The tomographic images show that the grain-boundary serration is due to γ' precipitates which develop along boundaries during cooling. These 3D reconstructions also exhibit segregations of B, C, Mo and Cr at grain boundaries. They also reveal that the degree of order in γ' particles which are located along boundaries is preserved up to the grain boundary.