Phénomènes Diffusionnels et Recristallisation Accompagnant l'Assemblage de Superalliages Base Nickel par Compression à Chaud

Abstract
Diffusion bonding is the prefered technique to join modern nickel based superalloys and produce hybrid aero-engine parts associating a disk type material (processed by powder metallurgy to resist low cycle fatigue at moderate temperature) and a large grain cast or directionally solidified material resisting creep. The microstructure in the vicinity of the joint, especially the γ' phase is affected by diffusion and mechanical properties are influenced by the transition from one structure to the other. The use of a ductile insert (nickel or nickel-chromium) is a solution to perform a sound bond and to manage a transition in microstructures over distances reaching 100 µm, but diffusion phenomena are amplified. Recristallisation related aspects are discussed.