Feasibility of in situ controlled heat treatment (ISHT) of Inconel 718 during electron beam melting additive manufacturing

Sames, William J.; Unocic, Kinga A.; Helmreich, Grant W.; Kirka, Michael M.; Medina, Frank; Dehoff, Ryan R.; Babu, S. S.

doi:10.1016/j.addma.2016.09.001

Cited by 55 publications

(44 citation statements)

References 32 publications

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“…In the upper part of the build, the solidification becomes predominantly equiaxed with a random orientation of the grains. This evolution has been pointed out by Kirka et al [19] in the case of the electron beam-melting of IN718. It is also confirmed using the G/R diagram of solidification for IN718 [20] and the model developed by Renderos et al [21].…”

Section: Interpretationssupporting

confidence: 55%

Microstructure characterization of recycled IN718 powder and resulting laser clad material

Renderos

Torregaray

Gutiérrez-Orrantia

et al. 2017

Materials Characterization

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A B S T R A C TThe possibility to reuse the metal powder wasted in Laser Material Deposition (LMD) process has been evaluated and a simple procedure developed. LMD uses metal powder which is fed through a nozzle into the focal point of a laser, where it melts the powder and the substrate material. During the process, a high ratio of particles hits against an unmelted area and directly bounces off the deposited area. The efficiency ratio of deposition can drop to 40% depending on the configuration and spot size. This work deals with the design of a procedure to recollect and reuse the wasted powder of a nickel based superalloy IN718. After usage, powder is recollected, undesired fractions are magnetically segregated and aggregates are removed by sieving. The particles are mixed again and ready for reuse. In order to study the effectiveness of the process, no new powder has been added to the recovered fraction, and this procedure has been repeated five times. Experimental tests show that deposited material present similar properties than those obtained with new powder grains. But, after 3 reuses, the porosity content increases consequently and the rupture strain decreases strongly. The implementation of this process allows the improvement of the final efficiency, reducing costs and decreasing the hazardous powder amount.

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Section: Interpretationssupporting

confidence: 55%

Microstructure characterization of recycled IN718 powder and resulting laser clad material

Renderos

Torregaray

Gutiérrez-Orrantia

et al. 2017

Materials Characterization

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“…An in situ controlled heat treatment was attempted, by scanning the top surface of the build after the process was finished, to homogenize and age the microstructure, but resulted in cracks and poor tensile performance [188]. Efforts have also been put in identifying process-microstructure relationship, showing that besides the higher density and better surface finish, the controlled tailoring of grain structures and crystallographic textures can be achieved by adjusting the scan strategies [62,76,78,189,190].…”

Section: Ebm In718mentioning

confidence: 99%

Additively Manufactured Inconel 718 : Microstructures and Mechanical Properties

Deng

2018

Linköping Studies in Science and Technology. Licentiate Thesis

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Linköping 2018Cover image: A fracture surface of EBM IN718 after tensile test at room temperature.During the course of research underlying this thesis, Dunyong Deng was enrolled in Agora Materiae, a multidiciplinary doctoral program at Linköping University, Sweden. Printed by LiU-Tryck 2018 © Dunyong Deng AbstractAdditive manufacturing (AM), also known as 3D printing, has gained significant interest in aerospace, energy, automotive and medical industries due to its capabilities of manufacturing components that are either prohibitively costly or impossible to manufacture by conventional processes. Among the various additive manufacturing processes for metallic components, electron beam melting (EBM) and selective laser melting (SLM) are two of the most widely used powder bed based processes, and have shown great potential for manufacturing high-end critical components, such as turbine blades and customized medical implants. The futures of the EBM and SLM are doubtlessly promising, but to fully realize their potentials there are still many challenges to overcome.Inconel 718 (IN718) is a nickel-base superalloy and has impressive combination of good mechanical properties and low cost. Though IN718 is being mostly used as a turbine disk material now, the initial introduction of IN718 was to overcome the poor weldability of superalloys in 1960s, since sluggish precipitation of strengthening phases γ ′ /γ ′′ enables good resistance to strain-age cracking during welding or post weld heat treatment. Given the similarity between AM and welding processes, IN718 has been widely applied to the metallic AM field to facilitate the understandings of process-microstructure-property relationships.The work presented in this licentiate thesis aims to better understand microstructures and mechanical properties EBM and SLM IN718, which have not been systematically investigated. Microstructures of EBM and SLM IN718 have been characterized with scanning electron microscopy (SEM), transmission electron microscopy (TEM) and correlated with the process conditions. Monotonic mechanical properties (e.g., Vickers microhardness and tensile properties) have also been measured and rationalized with regards to the microstructure evolutions before and after heat treatments.For EBM IN718, the results show the microstructure is not homogeneous but dependant on the location in the components, and the anisotropic mechanical properties are probably attributed to alignment of porosities rather than texture.iii Post heat treatment can slightly increase the mechanical strength compared to the as-manufactured condition but does not alter the anisotropy. SLM IN718 shows significantly different microstructure and mechanical properties to EBM IN718. The as-manufactured SLM IN718 has very fine dendritic microstructure and Laves phases in the interdendrites, and is "work-hardened" by the residual strains and dislocations present in the material. Mechanical properties are different between horizontally and vertically built samples, and heat treatment can m...

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“…It is important to note that both the Laves phase and the hardening phases γ and γ" consume niobium for their formation. The dissolution temperature of the Laves phase is between 982 and 1093 • C [43], while γ and γ" precipitates form during the cooling phase at about 900 • C [44]. As already detailed above, it can be concluded that during the build, the temperatures within the strut deviated significantly from the bulk, eventually leading to the different appearance of the microstructure within the struts.…”

Section: Microstructurementioning

confidence: 72%

Damage Tolerance Evaluation of E-PBF-Manufactured Inconel 718 Strut Geometries by Advanced Characterization Techniques

et al. 2020

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By means of electron beam powder bed fusion (E-PBF), highly complex lightweight structures can be manufactured within short process times. Due to the increasing complexity of producible components and the entangled interplay of damage mechanisms, common bulk material properties such as ultimate tensile or fatigue strength are not sufficient to guarantee safe and reliable use in demanding applications. Within this work, the damage tolerance of E-PBF-manufactured Ni-based alloy Inconel 718 (IN 718) strut geometries under uniaxial cyclic loading was investigated supported by several advanced measurement techniques. Based on thermal and electrical measurements, the failure of single struts could reliably be detected, revealing that continuous monitoring is applicable for such complex geometries. Process-induced surface roughness was found to be the main reason for early failure during cyclic loading. Thus, adequate post-processing steps have to be established for complex geometries to significantly improve damage tolerance and, eventually, in-service properties.

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Feasibility of in situ controlled heat treatment (ISHT) of Inconel 718 during electron beam melting additive manufacturing

Cited by 55 publications

References 32 publications

Microstructure characterization of recycled IN718 powder and resulting laser clad material

Microstructure characterization of recycled IN718 powder and resulting laser clad material

Additively Manufactured Inconel 718 : Microstructures and Mechanical Properties

Damage Tolerance Evaluation of E-PBF-Manufactured Inconel 718 Strut Geometries by Advanced Characterization Techniques

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