Heat-Treatment Control of δ Phase in HIPed L-PBF Alloy 718: Microstructural Baseline for Creep and Dwell-Fatigue Assessment
Rana ELSAYED, Johan MOVERARE, Emil ERIKSSON
Abstract. Alloy 718 is a nickel-based superalloy widely used in fatigue-critical hot-section gas turbine applications because of its high strength at temperatures up to 650 °C, mainly due to γ″ precipitation hardening. While casting and wrought routes are commonly used, additive manufacturing offers on-demand production of complex parts with shorter lead times and reduced waste. However, the high-temperature integrity of laser powder bed fusion (L-PBF) Alloy 718 remains under-characterized, and this material often shows reduced creep ductility, higher dwell-fatigue crack-growth rates, and greater notch sensitivity than wrought or cast alloys. This study investigates the mechanisms behind these limitations and evaluates post-processing strategies to improve microstructural stability and damage tolerance. Microstructural evolution is examined across multiple processing states, and creep and elevated temperature fatigue crack-growth tests are in progress on smooth and notched specimens, with L-PBF material benchmarked against cast and wrought alloys. Preliminary results show similar microstructures in the HIPed and post-HIP conditions, with carbides concentrated near grain boundaries. The standard heat-treated condition shows extensive δ-phase precipitation, while the other heat treatment does not, resulting in a microstructure closer to the post-HIP condition.
Keywords
Alloy 718, Nickel-Based Superalloy, Laser Powder Bed Fusion, Hot Isostatic Pressing, Heat Treatment, Delta Phase, Vickers Hardness, Creep
Published online 11/8/2026, 5 pages
Copyright © 2026 by the author(s)
Published under license by Materials Research Forum LLC., Millersville PA, USA
Citation: Rana ELSAYED, Johan MOVERARE, Emil ERIKSSON, Heat-Treatment Control of δ Phase in HIPed L-PBF Alloy 718: Microstructural Baseline for Creep and Dwell-Fatigue Assessment, Materials Research Proceedings, Vol. 73, pp 51-55, 2026
DOI: https://doi.org/10.21741/9781644904459-11
The article was published as article 11 of the book Mechanics of Advanced Materials and Structures
Content from this work may be used under the terms of the Creative Commons Attribution 3.0 license. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
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