The Role of the Atom Probe in the Study of Nickel-Based Superalloys

Nanostructural features of nickel-based superalloys as revealed by Field-Ion Microscopy, Atom Probe (APFIM), and 3D Atom Probe are reviewed. The unique and original information provided by these techniques is discussed on the basis of an extended and almost exhaustive analysis of bibliography over the last 30 years. Atom Probe techniques are shown to be able to measure the composition of tiny γ′ precipitates, a few nanometer in size, to detect ordering or subtle clustering effects within the γ solid solution or γ′ particles. Plane-by-plane analysis of (001) planes of the γ′ phase makes it possible to estimate the degree of order as well as the preferential sites of various addition elements included in superalloys. Due to its ultrahigh depth resolution, the microchemistry of interfaces and grain boundaries can also be characterized on an atomic scale. Most salient results will be reviewed, and the specific role of 3D APFIM will be highlighted with selected examples.