Effect of heat treatment on microstructure evolution of Inconel 718 alloy fabricated by selective laser melting

Xing, Li; Shi, Jianjun; Wang, C.H.; Cao, Guanghui; Russell, Alan M.; Zhou, Ziyun; Li, C.P.; Chen, G.F.

doi:10.1016/j.jallcom.2018.06.112

Cited by 163 publications

(48 citation statements)

References 42 publications

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“…The authors proposed that small and granular Laves phase particles improved yield strength by impacting the g″ phase volume fraction, size, and precipitate distribution. However, while subgrain structures appear to be similar in the as-manufactured samples via low magnification micrographs, closer examination shows that the subgrain structures are not cellular, but rather their morphology is dominated by eutectic formations -a primary difference of the DED AM-IN718 materials relative to what has been reported for L-PBF AM-IN718 [4,12,[20][21][22]. This difference provides strong evidence that the process-structure-property relationships for L-PBF AM-IN718 materials likely differ than for the DED material.…”

Section: Motivationmentioning

confidence: 69%

Knowledge of process-structure-property relationships to engineer better heat treatments for laser powder bed fusion additive manufactured Inconel 718

Gallmeyer

Moorthy

Kappes

et al. 2020

Additive Manufacturing

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Dislocation structures, chemical segregation, γ′, γ″, ! precipitates and Laves phase were quantified within the microstructures of Inconel 718 (IN718) produced by laser powder bed fusion additive manufacturing (AM) and subjected to standard, direct aging, and modified multi-step heat treatments. Additionally, heat-treated samples still attached to the build plates vs. those removed were also documented for a standard heat treatment. The effects of the different resulting microstructures on room temperature strengths and elongations to failure is revealed. Knowledge derived from these process-structure-property relationships was used to engineer a super-solvus solution anneal at 1020 ºC for 15 minutes, followed by aging at 720 ºC for 24 hours heat treatment for AM-IN718 that eliminates Laves and δ phases, preserves AM-specific dislocation cells that are shown to be stabilized by MC carbide particles, and precipitates dense γ′ and γ″ nanoparticle populations. This "optimized for AM-IN718 heat treatment" results in superior properties relative to wrought/additively manufactured, then industry standard heat treated IN718: relative increases of 7/10% in yield strength, 2/7% in ultimate strength, and 23/57% in elongation to failure are realized, respectively, regardless of as-built vs. machined surface finishes.

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Section: Motivationmentioning

confidence: 69%

Knowledge of process-structure-property relationships to engineer better heat treatments for laser powder bed fusion additive manufactured Inconel 718

Gallmeyer

Moorthy

Kappes

et al. 2020

Additive Manufacturing

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“…Zhang et al [19] observed a similar microstructure, moreover, carbides were found at the grain boundaries. Li et al [23], Deng et al [12], and Zhang et al [27] observed Laves phase in the interdendritic zone of as-built specimens and no strengthening phases were revealed. Therefore, the microstructure in the as-built condition is highly dependent on the PBF-LB process parameters.…”

Section: Introduction Of Intermetallic Compounds and Metal Matrix Commentioning

confidence: 98%

“…They are characterized by an arc-shaped or "fish-scale" patterns in the vertical plane, corresponding to the melt pool profile influenced by the Gaussian distribution of the laser energy. In the horizontal plane, the scanning tracks are usually observed as continuous lines [18,19,[22][23][24][25]. The microstructure in the as-built condition usually exhibits epitaxial growth of columnar grains including fine columnar or cellular dendrites along the built direction, owing to the high cooling rates of the PBF-LB process (10 6 K/s [19,26]) and the heat dissipation direction, i.e., vertically through the substrate [13,21,27].…”

Section: Introductionmentioning

confidence: 99%

“…cteristics of parts fabricated by PBF-LB are usually observed at lower e characterized by an arc-shaped or "fish-scale" patterns in the vertical plane, elt pool profile influenced by the Gaussian distribution of the laser energy. In he scanning tracks are usually observed as continuous lines [18,19,[22][23][24][25]. The as-built condition usually exhibits epitaxial growth of columnar grains ar or cellular dendrites along the built direction, owing to the high cooling rates (10 6 K/s [19,26]) and the heat dissipation direction, i.e., vertically through the ,28] studied the microstructure of IN718 parts fabricated by PBF-LB in as-built conditions, revealing carbides, Laves phases, and segregations; therefore, heat to homogenize the microstructure.…”

Section: Introduction Of Intermetallic Compounds and Metal Matrix Commentioning

confidence: 99%

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Laser Powder Bed Fusion of Inconel 718: Residual Stress Analysis Before and After Heat Treatment

Barros

Silva

Gouveia

et al. 2019

Metals

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Residual stresses (RS) of great magnitude are usually present in parts produced by Laser Powder Bed Fusion (PBF-LB), mainly owing to the extreme temperature gradients and high cooling rates involved in the process. Those "hidden" stresses can be detrimental to a part's mechanical properties and fatigue life; therefore, it is crucial to know their magnitude and orientation. The hole-drilling strain-gage method was used to determine the RS magnitude and direction-depth profiles. Cuboid specimens in the as-built state, and after standard solution annealing and ageing heat treatment conditions, were prepared to study the RS evolution throughout the heat treatment stages. Measurements were performed on the top and lateral surfaces. In the as-built specimens, tensile stresses of~400 MPa on the top and above 600 MPa on the lateral surface were obtained. On the lateral surface, RS anisotropy was noticed, with the horizontally aligned stresses being three times lower than the vertically aligned. RS decreased markedly after the first heat treatment. On heat-treated specimens, magnitude oscillations were observed. By microstructure analysis, the presence of carbides was verified, which is a probable root for the oscillations. Furthermore, compressive stresses immediate to the surface were obtained in heat-treated specimens, which is not in agreement with the typical characteristics of parts fabricated by PBF-LB, i.e., tensile stresses at the surface and compressive stresses in the part's core.Diverse metals AM techniques exist, and the most adopted in the industry are Powder Bed Fusion (PBF) and Directed Energy Deposition (DED), as for the classification by the ISO/ASTM 52900 (2015) international standard. These two techniques use a laser or an electron beam as a high energy density source to selectively melt the material and build the parts [3][4][5][6][7]. Actually, different nomenclatures are used for the same process. Laser Powder Bed Fusion (PBF-LB) is also known as Selective Laser Melting (SLM), Direct Metal Laser Sintering (DMLS), and Laser Cusing [7,8,11], depending mostly on the AM systems supplier.Focusing on PBF-LB, a micro-size powder is spread in thin layers of 20 and 50 µm [3], and then a laser beam guided by a galvanometric mirror selectively melts the deposited material according to the CAD model. The parts are built progressively from bottom to top, also known as the building direction (vertical) [7,11]. The use of support structures is common, either to support down-facing surfaces or to prevent part distortion. Part distortion occurs due to the large residual stresses (RS) generated during material solidification layer-by-layer, owing to the extreme temperature gradients and high cooling rates [12].New feedstock materials dedicated to AM systems have been developed; thereby, new opportunities will arise in the near future of AM [13]. Stainless steel; tool steel; and Ni-, Al-, Ti-, Co-Cr-, and Cu-based alloys are just a few of the metallic materials currently available for AM [7,14,15]. Introduction of int...

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“…Selective laser melting (SLM) is one of the most promising additive manufacturing (AM) technologies with the convenience and feasibility of producing high temperature superalloy components, and this has received much attention in various fields, such as aerospace, automobile and biomedical industries . Previous studies have been mainly carried out on the processing parameters, microstructure characteristics of formed parts, welding cracking and effect of post‐process, such as heat treatment (HT) and hot isostatic pressing (HIP). In order to apply the SLM superalloy into the manufacturing of turbine blades and combustors with high reliability, the fatigue behaviour of this kind of materials should be investigated.…”

Section: Introductionmentioning

confidence: 99%

On the fatigue crack growth behaviour of selective laser melting fabricated Inconel 625: Effects of build orientation and stress ratio

Zhang

Ren

et al. 2020

Fatigue Fract Eng Mat Struct

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The building of Inconel 625 material was carried out using the selective laser melting method, and its fatigue crack growth property at ambient temperature was experimentally investigated. Compact‐tension specimens with different building orientations were utilized to determine the stress intensity factor threshold and fatigue crack growth rate curves at different stress ratios (R). The results indicated that the fatigue crack growth properties in the near threshold stress intensity factor and Paris regions were greatly affected by the loading factor, as well as the orientation of the alloy. The mechanism of fatigue crack growth at different stages was observed and discussed using scanning electron microscopy. Finally, based on the framework of the linear elastic fracture, a new and applicable effective driving force factor range was introduced to replace the traditional stress intensity factor range (ΔK) with good accuracy for all of the fatigue crack growth test data, considering both the stress ratio and orientation.

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Effect of heat treatment on microstructure evolution of Inconel 718 alloy fabricated by selective laser melting

Cited by 163 publications

References 42 publications

Knowledge of process-structure-property relationships to engineer better heat treatments for laser powder bed fusion additive manufactured Inconel 718

Knowledge of process-structure-property relationships to engineer better heat treatments for laser powder bed fusion additive manufactured Inconel 718

Laser Powder Bed Fusion of Inconel 718: Residual Stress Analysis Before and After Heat Treatment

On the fatigue crack growth behaviour of selective laser melting fabricated Inconel 625: Effects of build orientation and stress ratio

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