Homogenization kinetics of a nickel-based superalloy produced by powder bed fusion laser sintering

Zhang, Fan; Levine, Lyle E.; Allen, Andrew J.; Campbell, Carelyn E.; Lass, Eric A.; Sudha, C.; Stoudt, Mark R.; Williams, Maureen E.; Idell, Yaakov

doi:10.1016/j.scriptamat.2016.12.037

Cited by 73 publications

(44 citation statements)

References 34 publications

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“…Such microstructural changes were presumed to occur due to the combination of nucleation and grain growth in the IN718 cast structures [26,36]. However, for the additive manufactured nickel alloys, Zhang et al [37] described the homogenization kinetics based on the growth of the primary dendrites associated with rapid solidification of individual melt pool. They [37] further related the streaking patterns in homogenized structures to the elemental segregation in the fine columnar dendrites.…”

Section: Microstructure Evolution In Homogenized and Hip-treated Specmentioning

confidence: 99%

Structure, Texture and Phases in 3D Printed IN718 Alloy Subjected to Homogenization and HIP Treatments

Mostafa

Rubio

Braïlovski

et al. 2017

Metals

188

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3D printing results in anisotropy in the microstructure and mechanical properties. The focus of this study is to investigate the structure, texture and phase evolution of the as-printed and heat treated IN718 superalloy. Cylindrical specimens, printed by powder-bed additive manufacturing technique, were subjected to two post-treatments: homogenization (1100 • C, 1 h, furnace cooling) and hot isostatic pressing (HIP) (1160 • C, 100 MPa, 4 h, furnace cooling). The Selective laser melting (SLM) printed microstructure exhibited a columnar architecture, parallel to the building direction, due to the heat flow towards negative z-direction. Whereas, a unique structural morphology was observed in the x-y plane due to different cooling rates resulting from laser beam overlapping. Post-processing treatments reorganized the columnar structure of a strong {002} texture into fine columnar and/or equiaxed grains of random orientations. Equiaxed structure of about 150 µm average grain size, was achieved after homogenization and HIP treatments. Both δ-phase and MC-type brittle carbides, having rough morphologies, were formed at the grain boundaries. Delta-phase formed due to γ -phase dissolution in the γ matrix, while MC-type carbides nucleates grew by diffusion of solute atoms. The presence of (Nb 0.78 Ti 0.22 )C carbide phase, with an fcc structure having a lattice parameter a = 4.43 Å, was revealed using Energy dispersive spectrometer (EDS) and X-ray diffractometer (XRD) analysis. The solidification behavior of IN718 alloy was described to elucidate the evolution of different phases during selective laser melting and post-processing heat treatments of IN718.

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Section: Microstructure Evolution In Homogenized and Hip-treated Specmentioning

confidence: 99%

Structure, Texture and Phases in 3D Printed IN718 Alloy Subjected to Homogenization and HIP Treatments

Mostafa

Rubio

Braïlovski

et al. 2017

Metals

188

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“…Additional studies are in progress to determine the relationship between heat treatment and the dissolution of d in an AM IN625 microstructure. Zhang et al [21] recently demonstrated that annealing for 30 to 60 minutes at 1423 K (1150°C) effectively homogenizes the solidification microstructure of AM IN625. Whether this protocol is sufficient when d is present is not yet clear.…”

Section: Further Thermal Processing and D-phase Removalmentioning

confidence: 99%

“…Recently, Zhang et al [21] investigated the microstructure of IN625 produced using laser powder-bed fusion (L-PBF). They observed a finer cellular/dendritic solidification microstructure than that observed in either EBM or L-DMD, with a primary dendrite spacing of about 1 lm.…”

Section: Introductionmentioning

confidence: 99%

Formation of the Ni3Nb δ-Phase in Stress-Relieved Inconel 625 Produced via Laser Powder-Bed Fusion Additive Manufacturing

Lass

Stoudt

Williams

et al. 2017

Metall Mater Trans A

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152

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The microstructural evolution of laser powder-bed additively manufactured Inconel 625 during a post-build stress-relief anneal of 1 hour at 1143 K (870°C) is investigated. It is found that this industry-recommended heat treatment promotes the formation of a significant fraction of the orthorhombic D0 a Ni 3 Nb d-phase. This phase is known to have a deleterious influence on fracture toughness, ductility, and other mechanical properties in conventional, wrought Inconel 625; and is generally considered detrimental to materials' performance in service. The d-phase platelets are found to precipitate within the inter-dendritic regions of the as-built solidification microstructure. These regions are enriched in solute elements, particularly Nb and Mo, due to the micro-segregation that occurs during solidification. The precipitation of d-phase at 1073 K (800°C) is found to require up to 4 hours. This indicates a potential alternative stress-relief processing window that mitigates d-phase formation in this alloy. Ultimately, a homogenization heat treatment is recommended for additively manufactured Inconel 625 because the increased susceptibility to d-phase precipitation increases the possibility for significant degradation of materials' properties in service.

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“…Heat treatment is often necessary following additive manufacturing to relieve residual stress [1,2], and to homogenize the microstructure [3,4]. Recent work shows that common heat treatments promote precipitation of secondary phases [5], which degrade mechanical properties (such as indentation hardness) in IN625 [6]. Heat treatment schedules for wrought IN625 were designed to avoid these same precipitates [7]; however, there are substantial microstructural differences between wrought and L-PBF material [8], with significant microsegregation of as-solidified material of particular interest here.…”

Section: Introductionmentioning

confidence: 99%

Application of finite element, phase-field, and CALPHAD-based methods to additive manufacturing of Ni-based superalloys

et al. 2017

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Numerical simulations are used in this work to investigate aspects of microstructure and microseg-regation during rapid solidification of a Ni-based superalloy in a laser powder bed fusion additive manufacturing process. Thermal modeling by finite element analysis simulates the laser melt pool, with surface temperatures in agreement with in situ thermographic measurements on Inconel 625. Geometric and thermal features of the simulated melt pools are extracted and used in subsequent mesoscale simulations. Solidification in the melt pool is simulated on two length scales. For the multicomponent alloy Inconel 625, microsegregation between dendrite arms is calculated using the Scheil-Gulliver solidification model and DICTRA software. Phase-field simulations, using Ni–Nb as a binary analogue to Inconel 625, produced microstructures with primary cellular/dendritic arm spacings in agreement with measured spacings in experimentally observed microstructures and a lesser extent of microsegregation than predicted by DICTRA simulations. The composition profiles are used to compare thermodynamic driving forces for nucleation against experimentally observed precipitates identified by electron and X-ray diffraction analyses. Our analysis lists the precipitates that may form from FCC phase of enriched interdendritic compositions and compares these against experimentally observed phases from 1 h heat treatments at two temperatures: stress relief at 1143 K (870 °C) or homogenization at 1423 K (1150 °C).

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Homogenization kinetics of a nickel-based superalloy produced by powder bed fusion laser sintering

Cited by 73 publications

References 34 publications

Structure, Texture and Phases in 3D Printed IN718 Alloy Subjected to Homogenization and HIP Treatments

Structure, Texture and Phases in 3D Printed IN718 Alloy Subjected to Homogenization and HIP Treatments

Formation of the Ni3Nb δ-Phase in Stress-Relieved Inconel 625 Produced via Laser Powder-Bed Fusion Additive Manufacturing

Application of finite element, phase-field, and CALPHAD-based methods to additive manufacturing of Ni-based superalloys

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