Alloy 718 is a Ni-based superalloy with excellent high-temperature mechanical properties, corrosion resistance, and excellent weldability. It is highly relevant for additive manufacturing (AM) of high-performance components with complex geometries in defense and aerospace applications. AM of Alloy 718 via electron powder bed fusion leads to complex microstructures that are reasonably well characterized for simple geometries, such as cubes, and generally constitute a combination of <InlineEquation ID="IEq1"> <EquationSource Format="TEX">$\delta $</EquationSource> <EquationSource Format="MATHML"><math> <mi>δ</mi> </math></EquationSource> </InlineEquation>, carbides, <InlineEquation ID="IEq2"> <EquationSource Format="TEX">${\gamma }^{\prime}$</EquationSource> <EquationSource Format="MATHML"><math> <msup> <mrow> <mi>γ</mi> </mrow> <mo>′</mo> </msup> </math></EquationSource> </InlineEquation>, <InlineEquation ID="IEq3"> <EquationSource Format="TEX">${\gamma }^{{\prime}{\prime}}$</EquationSource> <EquationSource Format="MATHML"><math> <msup> <mrow> <mi>γ</mi> </mrow> <mrow> <mo>′</mo> <mo>′</mo> </mrow> </msup> </math></EquationSource> </InlineEquation>, and sometimes Laves phases. However, there has been little consideration on the impact of complex build geometries and build layout on the microstructure evolution of Alloy 718. Hence, the current study considers how complex build geometries and their layout on the build plate impact as-built Alloy 718 microstructures. We apply a combination of near infrared (NIR) imaging, materials characterization, and computational analyses to achieve systematic correlations. NIR reveals changing thermal signatures within individual builds due to changes in geometry and how said builds were positioned on the build plate. The change in NIR signature is associated with changes in preheat temperature that led to site-specific ageing. Our results demonstrate that the build geometry, their position on the build plate, and the resulting thermal signatures needs to be considered to obtain more homogeneous AM microstructures. Graphical abstract

Correlating Part Geometry to Microstructures in Electron Powder Bed Fusion Additive Manufacturing of Alloy 718

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发表日期：

2026年1月3日

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Michael P. Haines,
Ally Bradley,
Sudarsanam Suresh Babu,
Nima Haghdadi,
Sophie Primig

摘要

Alloy 718 is a Ni-based superalloy with excellent high-temperature mechanical properties, corrosion resistance, and excellent weldability. It is highly relevant for additive manufacturing (AM) of high-performance components with complex geometries in defense and aerospace applications. AM of Alloy 718 via electron powder bed fusion leads to complex microstructures that are reasonably well characterized for simple geometries, such as cubes, and generally constitute a combination of $\delta $ $δ$ , carbides, ${\gamma }^{\prime}$ $γ^{'}$ , ${\gamma }^{{\prime}{\prime}}$ $γ^{''}$ , and sometimes Laves phases. However, there has been little consideration on the impact of complex build geometries and build layout on the microstructure evolution of Alloy 718. Hence, the current study considers how complex build geometries and their layout on the build plate impact as-built Alloy 718 microstructures. We apply a combination of near infrared (NIR) imaging, materials characterization, and computational analyses to achieve systematic correlations. NIR reveals changing thermal signatures within individual builds due to changes in geometry and how said builds were positioned on the build plate. The change in NIR signature is associated with changes in preheat temperature that led to site-specific ageing. Our results demonstrate that the build geometry, their position on the build plate, and the resulting thermal signatures needs to be considered to obtain more homogeneous AM microstructures.

Graphical abstract