Refining Crystal Grain of Inconel 718 by δ Process

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 delta process, which prevents grain growth by applying a pinning force that intentionally precipitates any delta phase products. We observed the morphology of the delta phase, which changes according to the process of delta-phase precipitation heat treatment, and then prepared delta-processed Inconel 718 (DP718) by a small-size compression test that simulated the precision forging process. It was found that delta-processed specimens had finer and more uniform microstructures than the traditional processed Inconel 718.