Mechanical and Microstructural Characterization of Additively Manufactured Inconel 718

Additive manufacturing of Inconel 718 via laser powder bed fusion produces a unique microstructure defined by columnar dendritic grains, pronounced ‹100› crystallographic textures and microsegregated Nb-rich phases. Rapid solidification engenders high dislocation densities, residual stresses and the formation of brittle Laves and δ-phase precipitates in interdendritic regions. Tailored post-processing—including homogenisation, solution-heat treatment, ageing and hot isostatic pressing—is essential to dissolve detrimental phases, promote uniform precipitation of strengthening γ′ and γ″ phases, and refine grain structure. Mechanical testing reveals a delicate balance between room-temperature strength, elevated-temperature creep resistance and ductility, with grain-boundary pinning by δ-phase and carbide networks governing high-temperature performance. Emerging research integrates in-situ process monitoring and microstructural mapping to establish processing–structure–property relationships, thereby accelerating qualification of AM Inconel 718 for aerospace, energy and nuclear applications.

Research from Nature Portfolio

Recent studies have mapped the influence of homogenisation and solution-treatment durations on the high-temperature behaviour of laser-powder-bed-fused Inconel 718. By varying homogenisation times at ~1080 °C and solution treatments at ~980 °C, these investigations delineate how the balance of precipitation hardening and substructural recovery affects strength and elongation at 650 °C. Shorter homogenisation promotes fine γ″ precipitates and maintains dislocation tangles, yielding peak strength and moderate ductility, whereas prolonged treatment encourages coarse MC carbide growth and reduced ductility. Solution-time adjustments were shown to enhance grain-boundary strength via δ-phase pinning, with fracture mechanisms transitioning from ductile dimpling to mixed-mode failure. A comprehensive processing map now guides optimisation of thermal regimes to tailor mechanical properties for service demands.

Mechanical and Microstructural Characterization of Additively Manufactured Inconel 718 publication trend

The graph below shows the total number of articles in mechanical and microstructural characterization of additively manufactured inconel 718 across all publications each year (not limited to Nature Index journals).

Technical terms

Laser powder bed fusion (LPBF): A layer-wise additive process in which a laser selectively melts metal powder to build complex components.

Hot isostatic pressing (HIP): A post-processing technique applying high pressure and temperature to eliminate internal porosity and homogenise microstructure.

δ-phase: A Ni₃Nb intermetallic precipitate that forms at grain boundaries, affecting grain growth, creep and fatigue behaviour.

Laves phase: A brittle, Nb-rich intermetallic that precipitates in interdendritic regions; often dissolved by solution treatments.

Recrystallization: The nucleation and growth of new, strain-free grains within a deformed or highly dislocated matrix during heat treatment.

Epitaxial growth: Successive grain growth across deposited layers following the same crystallographic orientation under directional solidification.

References

1. Heat-treated Nickel Alloys Produced Using Laser Powder Bed Fusion-based Additive Manufacturing Methods: A Review. Chinese Journal of Mechanical Engineering Additive Manufacturing Frontiers (2023).
2. Texture and Microstructural Features at Different Length Scales in Inconel 718 Produced by Selective Laser Melting. Materials (2019).
3. Effect of homogenization and solution treatments time on the elevated-temperature mechanical behavior of Inconel 718 fabricated by laser powder bed fusion. Scientific Reports (2021).
4. Impact of high temperature stress relieving on final properties of Inconel 718 processed by laser powder bed fusion. Materials Science and Engineering A (2021).
5. Recrystallization and grain growth kinetics of IN718 manufactured by laser powder bed fusion. Journal of Materials Research and Technology (2022).