Development of Preliminary Heat Treatment Guidelines for Additively Manufactured Alloy 718 Based on AMS Standards: A Microstructural Perspective

• Published in: Journal of Welding and Joining Vol. 43; no. 3; pp. 231 - 241
• Main Authors: Lim, Sieun, Kim, Chan Kyu, Jeong, Seolbin, Kang, Yongjoon, Oh, Dongjin, Song, Sang Woo, Kang, Namhyun, Park, Gitae
• Format: Journal Article
• Language: English
• Published: 대한용접접합학회 30.06.2025
• Subjects: 기계공학
• ISSN: 2466-2232; 2466-2100
• DOI: 10.5781/JWJ.2025.43.3.1

Conventional heat treatment standards for Alloy 718 are primarily based on cast and wrought processes and may not be suitable for Wire Arc Additive Manufacturing (WAAM), which involves rapid solidification and repeated thermal cycling. As such, there is an increasing need to develop tailored post-processing strategies for additively manufactured Alloy 718. This study investigates the homogenization heat treatment response of WAAM-fabricated Alloy 718, with a focus on the dissolution behavior of Laves phases formed due to elemental segregation. In addition, a review of the conventional Aerospace Material Specifications (AMS) heat treatment standards applied to cast and wrought processes is conducted to provide context and contrast with the WAAM process. Specimens were homogenized at 950 °C, 1100 °C, and 1170 °C for 12 hours. In-depth electron microscopy analyses revealed that Laves phases remained at 950 °C, partially dissolved at 1100 °C, and were completely eliminated at 1170 °C. At 1170 °C, a dominant grain orientation was observed, along with significant grain coarsening. These findings suggest that a homogenization temperature above 1100 °C is required to fully dissolve Laves phases in WAAM Alloy 718, and that optimizing the heat treatment time is essential to minimize grain growth. This study provides insights into the heat treatment behavior of WAAM Alloy 718 from the perspective of Laves phase dissolution and offers design considerations for appropriate post-processing strategies.