Microstructural Stability of a Single Crystal Superalloy DD8 during Thermal Exposure

Microstructural stability of a nickel base single crystal alloy DD8 has been investigated. Standard heat treated specimen showed good microstructural stability at 950℃. While under the as-cast condition, a kind of rod-like phase precipitated in the interdendritic region of as-cast specimen during thermal exposure. The phase, which has bcc structure, was enriched with Cr. Thermo-calc also predicted precipitation of a bcc phase at around 950℃. The Cr-rich bcc phase was considered as α-Cr and formed due to the segregation of Cr under the as-cast condition.