On the influence of heat treatment on microstructure and mechanical behavior of laser powder bed fused Inconel 718

doi:10.1016/j.msea.2020.140555

Materials Science and Engineering: A

Volume 805, 23 February 2021, 140555

https://doi.org/10.1016/j.msea.2020.140555 Get rights and content

Abstract

A range of heat treatments have been developed for wrought Inconel 718 to obtain desired properties. For additively manufactured Inconel 718, the recently developed standard ASTM F3301 provides guidance for heat treatment of powder bed fusion specimens. Although this standard is based on standards developed for wrought Inconel 718, it does not include direct aging. Since direct aging reduces the number of processing steps, it can result in a post processing cost reduction if the desired properties are obtained. In this study, we characterized the microstructure and tensile behavior of Inconel 718 specimens produced by a laser powder bed fusion process. The specimens were heat treated according to two different routines after stress relieving: a full heat treatment versus a one-step direct aging process. Differences in the resulting texture and grain morphology were observed. The ex-situ stress-strain behavior was broadly similar. However, a slight increase in yield strength was observed for the direct aged specimen. In order to understand this behavior, investigations with in-situ synchrotron energy dispersive X-ray diffraction tensile testing revealed differences in the load partitioning among different crystal directions. Importantly, the elastic anisotropy expressed by the magnitude of the diffraction elastic constants showed a dependency on the microstructures.

Section snippets

Background

Additive manufacturing (AM) of age hardenable alloys with a significant number of alloying elements results in inhomogeneous microstructures with varying phase distributions and grain sizes [1]. Although AM processing offers significant increases in the freedom of design, the microstructures resulting from high thermal gradients and rapid cooling differ significantly from conventional methods such as wrought, cast or powder metallurgy [1].

One alloy of interest for laser powder bed fusion

Sample fabrication

Specimens used in this study were built in a M2 Cusing machine (Concept Laser GmbH, Lichtenfels, Germany) using Micro-Melt Inconel 718 AM. powder from Carpenter Powder Products. The powder was spheroidized in an argon gas atomization process and sieved to obtain a 37 μm D₅₀ particle diameter. To prevent oxidation during L-PBF, a constant argon flow was maintained over the powder bed.

The build parameters utilized in this study were: 180 W laser power, 600 mm/s laser speed, 0.105 mm hatch spacing

Phase analysis

Fig. 2 shows the bulk phase analysis for the DA and the FHT specimens. Fig. 2a shows a slower scan over a narrower range of 2-theta angles to investigate the presence of minor phases with detection of δ, NbC and Laves. A slight increase in intensity for the δ phase between the DA and FHT specimens is attributed to a slight increase in volume fraction. The NbC and Laves phases show similar intensities for the DA and the FHT specimens suggesting no change in volume fraction. A complementary wider

Macro mechanical behavior

The macroscopic stress-strain behavior of the two studied heat treatment variants display broadly similar behaviors with key differences arising in the yielding characteristics, the strain hardening behavior, and the ductility. The possible reasons for these differences are explored in the following sections.

Conclusions

While the influence of heat treatments on the overall room-temperature tensile properties was shown not to be major, such heat treatments resulted in a large variation of the final grain morphology and texture. A discussion on the various contributors to strengthening (σ_YS) showed that grain size, precipitation state, strain hardening, and crystal texture all impact the yield strength to different extents. The similar tensile properties for different microstructures could therefore be explained

Data availability statement

The raw data required to reproduce these findings cannot be shared at this time due to technical limitations. The processed data required to reproduce these findings cannot be shared at this time due to time limitations but is available on request from the corresponding author.

CRediT authorship contribution statement

Jakob Schröder: Writing - original draft, Writing - review & editing, Visualization, Formal analysis, Conceptualization. Tatiana Mishurova: Writing - review & editing, Methodology, Software, Formal analysis, Investigation. Tobias Fritsch: Conceptualization, Investigation, Methodology, Formal analysis, Writing - review & editing. Itziar Serrano-Munoz: Conceptualization, Methodology, Formal analysis, Investigation, Writing - review & editing. Alexander Evans: Supervision, Writing - review &

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

The authors want to acknowledge the support of Mr. Romeo Saliwan-Neumann at the microstructural characterization of the specimens.

Judith Schneider acknowledges funding as a guest scientist at the Bundesanstalt für Materialforschung und -prüfung (BAM).

References (101)

C. Slama et al.
Structural characterization of the aged Inconel 718
J. Alloys Compd.
(2000)
J. Belan
GCP and TCP phases presented in nickel-base superalloys
Mater. Today-Proc.
(2016)
G.A. Rao et al.
Effect of standard heat treatment on the microstructure and mechanical properties of hot isostatically pressed superalloy inconel 718
Mater. Sci. Eng., A
(2003)
C.L. Qiu et al.
Influence of hot isostatic pressing temperature on microstructure and tensile properties of a nickel-based superalloy powder
Mater. Sci. Eng., A
(2013)
C.L. Qiu et al.
Influence of heat treatment on microstructure and tensile behavior of a hot isostatically pressed nickel-based superalloy
J. Alloys Compd.
(2013)
M. Anderson et al.
Delta Phase precipitation in Inconel 718 and associated mechanical properties
Mater. Sci. Eng., A
(2017)
K.N. Amato et al.
Microstructures and mechanical behavior of Inconel 718 fabricated by selective laser melting
Acta Mater.
(2012)
A. Devaux et al.
Gamma double prime precipitation kinetic in Alloy 718
Mater. Sci. Eng., A
(2008)
S. Azadian et al.
Delta phase precipitation in Inconel 718
Mater. Char.
(2004)
H. Yuan et al.
Effect of the delta phase on the hot deformation behavior of Inconel 718
Mater. Sci. Eng., A
(2005)

D.Y. Cai et al.

Dissolution kinetics of delta phase and its influence on the notch sensitivity of Inconel 718

Mater. Char.

(2007)

P.J.P. Kanetas et al.

Influence of the delta phase in the microstructure of the inconel 718 subjected to "Delta-processing" heat treatment and hot deformed

Procedia Mater. Sci.

(2015)

L.T. Chang et al.

Effect of heat treatment on microstructure and mechanical properties of the hot-isostatic-pressed Inconel 718 powder compact

J. Alloys Compd.

(2014)

Q.B. Jia et al.

Selective laser melting additive manufacturing of Inconel 718 superalloy parts: densification, microstructure and properties

J. Alloys Compd.

(2014)

D.Y. Zhang et al.

Effect of standard heat treatment on the microstructure and mechanical properties of selective laser melting manufactured Inconel 718 superalloy

Mater. Sci. Eng., A

(2015)

T. Trosch et al.

Microstructure and mechanical properties of selective laser melted Inconel 718 compared to forging and casting

Mater. Lett.

(2016)

D.H. Smith et al.

Microstructure and mechanical behavior of direct metal laser sintered Inconel alloy 718

Mater. Char.

(2016)

J.P. Choi et al.

Densification and microstructural investigation of Inconel 718 parts fabricated by selective laser melting

Powder Technol.

(2017)

W.M. Tucho et al.

Microstructure and hardness studies of Inconel 718 manufactured by selective laser melting before and after solution heat treatment

Mater. Sci. Eng., A

(2017)

T. DebRoy et al.

Additive manufacturing of metallic components - process, structure and properties

Prog. Mater. Sci.

(2018)

J. Schneider et al.

Effect of heat treatment variations on the mechanical properties of Inconel 718 selective laser melted specimens

Addit. Manuf.

(2018)

F.C. Liu et al.

Microstructure and residual stress of laser rapid formed Inconel 718 nickel-base superalloy

Optic Laser. Technol.

(2011)

J. Cao et al.

Effect of overlap rate on recrystallization behaviors of Laser Solid Formed Inconel 718 superalloy

Optic Laser. Technol.

(2013)

E. Chlebus et al.

Effect of heat treatment on the microstructure and mechanical properties of Inconel 718 processed by selective laser melting

Mater. Sci. Eng., A

(2015)

H.Y. Wan et al.

Effect of scanning strategy on mechanical properties of selective laser melted Inconel 718

Mater. Sci. Eng., A

(2019)

D.Y. Deng et al.

Microstructure and mechanical properties of Inconel 718 produced by selective laser melting: sample orientation dependence and effects of post heat treatments

Mater. Sci. Eng., A

(2018)

L. Zhou et al.

Microstructure, precipitates and mechanical properties of powder bed fused inconel 718 before and after heat treatment

J. Mater. Sci. Technol.

(2019)

X.M. Zhao et al.

Study on microstructure and mechanical properties of laser rapid forming Inconel 718

Mater. Sci. Eng., A

(2008)

A. Yadollahi et al.

Effects of building orientation and heat treatment on fatigue behavior of selective laser melted 17-4 PH stainless steel

Int. J. Fatig.

(2017)

W. Tillmann et al.

Hot isostatic pressing of IN718 components manufactured by selective laser melting

Addit. Manuf.

(2017)

S. Leuders et al.

On the mechanical behavior of titanium alloy TiAl6V4 manufactured by selective laser melting: fatigue resistance and crack growth performance

Int. J. Fatig.

(2013)

S. Tammas-Williams et al.

Porosity regrowth during heat treatment of hot isostatically pressed additively manufactured titanium components

Scripta Mater.

(2016)

K. Kunze et al.

Texture, anisotropy in microstructure and mechanical properties of IN738LC alloy processed by selective laser melting (SLM)

Mater. Sci. Eng., A

(2015)

C. Genzel et al.

The materials science synchrotron beamline EDDI for energy-dispersive diffraction analysis

Nucl. Instrum. Methods Phys. Res., Sect. A

(2007)

F. Bachmann et al.

Grain detection from 2d and 3d EBSD data-Specification of the MTEX algorithm

Ultramicroscopy

(2011)

S. Tammas-Williams et al.

XCT analysis of the influence of melt strategies on defect population in Ti-6Al-4V components manufactured by Selective Electron Beam Melting

Mater. Char.

(2015)

T. Mishurova et al.

New aspects about the search for the most relevant parameters optimizing SLM materials

Addit. Manuf.

(2019)

J.N. Wagner et al.

Microstructure and temperature dependence of intergranular strains on diffractometric macroscopic residual stress analysis

Mater. Sci. Eng., A

(2014)

C.H. Pei et al.

Assessment of mechanical properties and fatigue performance of a selective laser melted nickel-base superalloy Inconel 718

Mater. Sci. Eng., A

(2019)

M.D. Sangid et al.

Role of heat treatment and build orientation in the microstructure sensitive deformation characteristics of IN718 produced via SLM additive manufacturing

Addit. Manuf.

(2018)

M.E. Aydinöz et al.

On the microstructural and mechanical properties of post-treated additively manufactured Inconel 718 superalloy under quasi-static and cyclic loading

Mater. Sci. Eng., A

(2016)

M. Ni et al.

Anisotropic tensile behavior of in situ precipitation strengthened Inconel 718 fabricated by additive manufacturing

Mater. Sci. Eng., A

(2017)

H.Y. Wan et al.

Effect of scanning strategy on grain structure and crystallographic texture of Inconel 718 processed by selective laser melting

J. Mater. Sci. Technol.

(2018)

R. Jiang et al.

Varied heat treatments and properties of laser powder bed printed Inconel 718

Mater. Sci. Eng., A

(2019)

Z.Q. Wang et al.

Diffraction and single-crystal elastic constants of Inconel 625 at room and elevated temperatures determined by neutron diffraction

Mater. Sci. Eng., A

(2016)

P.E. Aba-Perea et al.

Determination of the high temperature elastic properties and diffraction elastic constants of Ni-base superalloys

Mater. Des.

(2016)

T.M. Holden et al.

Intergranular strains in Inconel-600 and the impact on interpreting stress fields in bent steam-generator tubing

Mater. Sci. Eng., A

(1998)

I. Gibson et al.

Additive Manufacturing Technologies: Rapid Prototyping to Direct Digital Manufacturing

(2010)

J.F. Radavich

The physical metallurgy of cast and wrought alloy 718, Superalloy 718

Metall. Appl., Proc. Int. Symp. Metall. Appl. Superalloy

(1989)

D.F. Paulonis et al.

Precipitation in nickel-base alloy 718

ASM Trans. Q.

(1969)

Cited by (32)

Tailoring the microstructure and mechanical properties of IN718 alloy via a novel scanning strategy implemented in laser powder bed fusion
2023, Materials Science and Engineering: A
The microsegregation of the brittle Laves phase at the interdendritic boundaries during additive manufacturing of IN718 leads to microvoid formation under tensile loads, thus, the mechanical properties are negatively affected. Recent advances have shown that extensive control over microstructural evolution is possible by modifying the additive manufacturing processes. Herein, it is aimed to tailor the final microstructure, managing the morphology of Laves phase, via implementing a novel scanning method, called time-homogenization (TH), in the laser powder bed fusion processing. Direct aging, solutionizing + direct aging, and homogenization + solutionizing + direct aging heat treatments were applied to increase the microstructural stability of additively manufactured IN718 at elevated temperatures. The modified microstructural features, microhardness, room and elevated temperature (550 °C and 650 °C) tensile properties of as-built and heat-treated specimens were systematically investigated considering the precipitation strengthening mechanism. Compared to the samples built by the standard scanning strategy (SP), fine and granular Laves phases were observed in TH specimens while SP specimens have coarse and chain-like Laves phases. Moreover, TH specimens after direct aging heat treatment exhibited an excellent combination of strength and ductility at room and elevated temperature.
Additive manufacturing of nickel-based superalloys: A state-of-the-art review on process-structure-defect-property relationship
2023, Progress in Materials Science
Fusion-based additive manufacturing (AM) has significantly grown to fabricate Nickel-based superalloys with design freedom across multiple length scales. Several phenomena such as feedstock/energy source/melt pool interactions, solidification and phase transformations occur during fusion-based AM processes of Nickel-based superalloys, which determine the ultimate microstructure and mechanical performance of the built parts. In this review, we elaborate a comprehensive discussion on AM Nickel-based superalloys and influential factors including feedstock characteristics (powder morphology, chemistry, contamination, flowability, recycling) and AM processing (parameters, and powder spreading/wall/balling/spattering effects) on their microstructure (micro-segregation, phases formations and grain structures), defect generation (sub-surface/internal defects, microcracks, surface roughness, and residual stress). Furthermore, the mechanical properties of AM Nickel-based superalloys such as tensile, creep and fatigue at room/elevated temperatures are analyzed in accordance with the initial, and post processing effects. Additionally, the commonly utilized modeling approaches in literature to predict the microstructure and mechanical behavior of these alloys are highlighted. Finally, the current challenges and mitigation approaches for future research are identified considering the gaps in the AM Nickel-based superalloys.
Influence of heat-treatment and cryo-treatment on high temperature wear performance of LPBF Inconel 718
2023, Wear
The present study discusses the high temperature tribological performance of Laser Powder Bed Fused (LPBF) Inconel 718 (In718) using a pin-on-disk tribometer. Inconel being an age hardenable alloy with γ′ and γ′′ phases can be manipulated to with-stand elevated environments and thus, the tribology can be improved. This study involves homogenization heat treatment at 1100 °C treatment with and without a two-step aging process (720 °C for 8 h and 620 °C for 10 h). Fine dendritic structure is identified in microscopy after homogenization with the dissolution of δ phase. The microhardness of the sample is influenced by the presence of γ′ and γ′′ phases as the hardness increased by 53.2% and 56.2% respectively after homogenization and cryo-treatment. Tribology of LPBF In718 is evaluated at room temperature (RT), 100, 200, 300, 400, 500 and 600 °C and the worn surfaces were characterized. Wear rate decreased steadily with temperature and became negligible at 600 °C which is caused by the formation of protective NiFe₂O₄ and other oxidative film formation. The transient formation and abrupt rupture and peeling away of the oxide film causes fluctuation in friction coefficient even at elevated temperature giving a non-uniform frictional behavior.
Ultrasonic surface post-processing of hot isostatic pressed and heat treated superalloy parts manufactured by laser powder bed fusion
2022, Additive Manufacturing Letters
Inconel 718 alloy parts were fabricated by the laser powder bed fusion (L-PBF) technique using a multidirectional stripe scanning strategy. Subsequently, the L-PBF-built parts were hot isostatic pressed (HIP), homogenized, and aged. Ultrasonic surface mechanical treatment was applied to modify the surface texture and microstructural layer of the L-PBF-built and heat-treated Inconel 718 alloy parts. Ultrasonic impact treatment (UIT) was implemented using a forcedly rotated multi-pin impact head. The surface texture, roughness, waviness, porosity, microstructure, phase composition, hardness, and residual stresses of the L-PBF-built and thermo-mechanical post-processed specimens were studied and compared. The results revealed that the UIT post-processing leads to work hardening, induces compressive residual stresses, and ∼20% increase in the surface microhardness in the near-surface layer of the heat-treated L-PBF-built 718 alloy parts. The surface roughness and waviness were significantly reduced after UIT, providing a flattened surface microrelief formation.
Laser powder bed fusion of high-strength and corrosion-resistant Inconel alloy 725
2022, Materials Characterization
Citation Excerpt :
Hence, the variation in mechanical properties between the different metal alloys may be explained by their precipitation-hardenability, per the strength-ductility paradigm. We importantly note that many studies have shown that newly designed heat treatments that shift away from industry standards can provide optimised mechanical performance combinations in L-PBF IN718 [57,76] and L-PBF IN625 [71,77,78]. This points to opportunities to enhance the mechanical properties of our L-PBF IN725 by tailoring the heat treatment, and we believe this is an important area for future work.
The development of additive manufacturing, or three-dimensional (3D) printing, technologies has produced breakthroughs in the design and manufacturing of products by enhancing design freedom and minimising manufacturing steps. In addition, the complex, unique microstructures imparted by the additive processes offer prospects of unprecedented advances to produce high-performance metal alloys for high-temperature and corrosive environments. Here, we present the first additive manufacturing of Inconel alloy 725, an advanced nickel-base superalloy that is the widely accepted gold standard material of choice for oil and gas, chemical, and marine applications. We explore the printability of Inconel alloy 725 and identify a wide processing space to build material with a crack- and near-pore-free microstructure. The conventionally heat-treated Inconel alloy 725 has an equiaxed, near-fully recrystallised microstructure containing copious twin boundaries and nano-precipitates. It also displays promising tensile properties and corrosion resistance compared to its wrought counterpart. Our work opens the door toward additive manufacturing of Inconel alloy 725 components with optimised microstructure and topology geometry for applications in harsh environments.
Multiscale plasticity behavior and fatigue performance of laser melting multi-layer nickel-based superalloys upon heat treatments
2022, International Journal of Plasticity
The present work focuses on heat treatment effects on cyclic plasticity behavior, multiscale strengthening mechanisms and low cycle fatigue performance of laser melting nickel-based superalloys. Microscopic indentation analysis, mesoscopic DIC analysis and macroscopic material testing were conducted to identify multiscale mechanical properties. A DIC-aided indentation method was developed to identify the constitutive parameters of the laser melting material by introducing the reference material. The dendritic–cellular microstructures in the remelting zone (RZ) significantly decrease the effects of the grain size and morphology. Heat treatments can improve the strength but decrease the ductility of RZ and do not affect the macroscopic stress–strain responses of the multilayered material. Moreover, the strengthening mechanisms in the laser melting material were verified to reveal size- and plasticity-dependent effects. The strengthening contributed by grain boundaries and twin boundaries yields little effect on the strength at micro scales and the influences increase with plastic deformations. Furthermore, the aging treatment increases the fatigue life of RZ by factor 2 and, however, decreases the low cycle fatigue performance of the multilayered material, meaning that the under-matched material can be stronger than the base material in certain configurations. The stabilized fatigue load of the laser melting material has strong correlations with the mismatching and loading levels. The present study provides a deep insight into the strengthening mechanisms and cyclic plasticity behaviors of laser-manufactured materials.

View all citing articles on Scopus

On the influence of heat treatment on microstructure and mechanical behavior of laser powder bed fused Inconel 718

Abstract

Section snippets

Background

Sample fabrication

Phase analysis

Macro mechanical behavior

Conclusions

Data availability statement

CRediT authorship contribution statement

Declaration of competing interest

Acknowledgements

J. Alloys Compd.

Mater. Today-Proc.

Mater. Sci. Eng., A

Mater. Sci. Eng., A

J. Alloys Compd.

Mater. Sci. Eng., A

Acta Mater.

Mater. Sci. Eng., A

Mater. Char.

Mater. Sci. Eng., A

Mater. Char.

Procedia Mater. Sci.

J. Alloys Compd.

J. Alloys Compd.

Mater. Sci. Eng., A

Mater. Lett.

Mater. Char.

Powder Technol.

Mater. Sci. Eng., A

Prog. Mater. Sci.

Addit. Manuf.

Optic Laser. Technol.

Optic Laser. Technol.

Mater. Sci. Eng., A

Mater. Sci. Eng., A

Mater. Sci. Eng., A

J. Mater. Sci. Technol.

Mater. Sci. Eng., A

Int. J. Fatig.

Addit. Manuf.

Int. J. Fatig.

Scripta Mater.

Mater. Sci. Eng., A

Nucl. Instrum. Methods Phys. Res., Sect. A

Ultramicroscopy

Mater. Char.

Addit. Manuf.

Mater. Sci. Eng., A

Mater. Sci. Eng., A

Addit. Manuf.

Mater. Sci. Eng., A

Mater. Sci. Eng., A

J. Mater. Sci. Technol.

Mater. Sci. Eng., A

Mater. Sci. Eng., A

Mater. Des.

Mater. Sci. Eng., A

Additive Manufacturing Technologies: Rapid Prototyping to Direct Digital Manufacturing

The physical metallurgy of cast and wrought alloy 718, Superalloy 718

Metall. Appl., Proc. Int. Symp. Metall. Appl. Superalloy

Precipitation in nickel-base alloy 718

ASM Trans. Q.