Electron Microscopy of Superalloy Powders

Abstract

Argon or water atomized alloy powders for use in powder-metallurgy parts usually have a particle size in the range 20-200µ. Because of this small size and the accompanying difficulty in specimen preparation, studies of metal powders have usually excluded transmission techniques and knowledge of the microstructure is confined to scanning electron microscopy studies.Fig. 1 shows a scanning electron micrograph of an argon-atomized particle of Haynes alloy 6B. It is clear that the particle is a spherical “microcasting” showing typical dendritic structure. When such particles are mounted and sectioned, the dendritic morphology is still observed (Fig. 2) indicating that there is a solidification structure throughout the particle and not just at the surface.