Refining Crystal Grain of Inconel 718 by δ Process

Abstract

  The Ni-based superalloy Inconel 718 is used for aero-engine disks and is processed by forging and subsequent machine work. This study aimed to achieve uniformly fine crystal grain of Inconel 718 by the δ process, which prevents grain growth by applying a pinning force that intentionally precipitates any δ phase products. We observed the morphology of the δ phase, which changes according to the process of δ-phase precipitation heat treatment, and then prepared δ-processed Inconel 718 (DP718) by a small-size compression test that simulated the precision forging process. It was found that δ-processed specimens had finer and more uniform microstructures than the traditional processed Inconel 718.