Details

Autor(en) / Beteiligte

• Burlot, Guillaume
• Cormier, Jonathan
• Eyidi, Dominique
• Cadel, Emmanuel
• Villechaise, Patrick

Titel

Precipitate-free zones formation at grain boundaries in γ/γ′ Ni-based superalloys

Ist Teil von

• Journal of materials science, 2024-06, Vol.59 (23), p.10485-10507

Ort / Verlag

New York: Springer US

Erscheinungsjahr

2024

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• Formation and growth of secondary γ′ precipitate-free zones (PFZ) in the vicinity of grain boundaries in five Ni-based superalloys have been investigated for different heat treatment times and temperatures. A special focus has been placed on a high carbon containing version of the AD730™ alloy. While the formation of PFZ is induced by the precipitation of Ti-rich secondary carbides during aging in Nimonic PE16, it has been shown in the present study that PFZ mainly form during close-to-γ′-solvus heat treatments and are associated with the nucleation of intergranular γ′ precipitates in the studied alloys. Since these precipitates have chemical compositions similar to intragranular secondary γ′ particles, depletion of precipitate-forming elements leads to the dissolution of intragranular secondary γ′ precipitates near grain boundaries and finally to the formation of PFZ. PFZ width evolutions have been described using a parabolic model, and their kinetics obey an Arrhenius-type law indicating a diffusion-controlled process. Thanks to chemical composition analyzes in and near the PFZ, it is shown that both titanium and niobium diffusion, in volume and through the grain boundaries, could be controlling the PFZ formation.