Modeling of heat transfer, fluid flow and solidification microstructure of nickel-base superalloy fabricated by laser powder bed fusion

Lee, Yousub; Zhang, Wei

doi:10.1016/j.addma.2016.05.003

Cited by 208 publications

(120 citation statements)

References 38 publications

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“…As a consequence, EBM microstructures will tend to homogenize more rapidly compared with cast microstructures. It has been has shown that other AM processes such as laser metal directed energy deposition and selective laser melting of Alloy 718 resulted PDAS values with a similar order of magnitude to EBM, [8,24] which indicates that the segregated microstructures produced in these processes can be homogenized rather rapidly compared with cast products. This difference could facilitate the design of new heat treatment protocols for AM microstructures.…”

Section: B Phase-field Solidification Simulation Results Of Ebm Allomentioning

confidence: 92%

Predicting the Microstructural Evolution of Electron Beam Melting of Alloy 718 with Phase-Field Modeling

Kumara

Deng

Hanning

et al. 2019

Metall Mater Trans A

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Electron beam melting (EBM) is a powder bed additive manufacturing process where a powder material is melted selectively in a layer-by-layer approach using an electron beam. EBM has some unique features during the manufacture of components with high-performance superalloys that are commonly used in gas turbines such as Alloy 718. EBM has a high deposition rate due to its high beam energy and speed, comparatively low residual stresses, and limited problems with oxidation. However, due to the layer-by-layer melting approach and high powder bed temperature, the as-built EBM Alloy 718 exhibits a microstructural gradient starting from the top of the sample. In this study, we conducted modeling to obtain a deeper understanding of microstructural development during EBM and the homogenization that occurs during manufacturing with Alloy 718. A multicomponent phase-field modeling approach was combined with transformation kinetic modeling to predict the microstructural gradient and the results were compared with experimental observations. In particular, we investigated the segregation of elements during solidification and the subsequent ''in situ'' homogenization heat treatment at the elevated powder bed temperature. The predicted elemental composition was then used for thermodynamic modeling to predict the changes in the continuous cooling transformation and time-temperature transformation diagrams for Alloy 718, which helped to explain the observed phase evolution within the microstructure. The results indicate that the proposed approach can be employed as a valuable tool for understanding processes and for process development, including post-heat treatments.

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Section: B Phase-field Solidification Simulation Results Of Ebm Allomentioning

confidence: 92%

Predicting the Microstructural Evolution of Electron Beam Melting of Alloy 718 with Phase-Field Modeling

Kumara

Deng

Hanning

et al. 2019

Metall Mater Trans A

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“…FE modelling has been mainly employed to assess the influence of process parameters [30,38,46] and to evaluate distortions and residual stresses [9,13,16,23,34]. In this sense, thermal modelling, apart from being an input for the mechanical analysis, is fundamental to characterise the melt pool and the microstructure in an AM process [20,25,33,41] and also guides the selection of the printing process parameters in engineering design [26,32,44].…”

Section: Introductionmentioning

confidence: 99%

Numerical modelling and experimental validation in Selective Laser Melting

Chiumenti

Neiva

Salsi

et al. 2017

Additive Manufacturing

113

111

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In this work a finite-element framework for the numerical simulation of the heat transfer analysis of additive manufacturing processes by powder-bed technologies, such as Selective Laser Melting, is presented. These kind of technologies allow for a layer-by-layer metal deposition process to cost-effectively create, directly from a CAD model, complex functional parts such as turbine blades, fuel injectors, heat exchangers, medical implants, among others. The numerical model proposed accounts for different heat dissipation mechanisms through the surrounding environment and is supplemented by a finite-element activation strategy, based on the born-dead elements technique, to follow the growth of the geometry driven by the metal deposition process, in such a way that the same scanning pattern sent to the numerical control system of the AM machine is used. An experimental campaign has been carried out at the Monash Centre for Additive Manufacturing using an EOSINT-M280 machine where it was possible to fabricate different benchmark geometries, as well as to record the temperature measurements at different thermocouple locations. The experiment consisted in the simultaneous printing of two walls with a total deposition volume of 107 cm3 in 992 layers and about 33,500 s build time. A large number of numerical simulations have been carried out to calibrate the thermal FE framework in terms of the thermophysical properties of both solid and powder materials and suitable boundary conditions. Furthermore, the large size of the experiment motivated the investigation of two different model reduction strategies: exclusion of the powder-bed from the computational domain and simplified scanning strategies. All these methods are analysed in terms of accuracy, computational effort and suitable applications.Peer ReviewedPostprint (author's final draft

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“…This results in a high sensitivity of material properties to process parameters. According to source parameters, the material can experience different thermal histories and thus different microstructures [1][2][3][4]. The microstructure of AM parts can be highly anisotropic and can reach a density greater than 99.5% [5,6].…”

Section: Introductionmentioning

confidence: 99%

Fatigue Assessment of Ti–6Al–4V Circular Notched Specimens Produced by Selective Laser Melting

Razavi

Ferro

Berto

2017

Metals

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Additive manufacturing (AM) offers the potential to economically produce customized components with complex geometries in a shorter design-to-manufacture cycle. However, the basic understanding of the fatigue behavior of these materials must be substantially improved at all scale levels before the unique features of this rapidly developing technology can be used in critical load bearing applications. This work aims to assess the fatigue strength of Ti-6Al-4V smooth and circular notched samples produced by selective laser melting (SLM). Scanning Electron Microscopy (SEM) was used to investigate the fracture surface of the broken samples in order to identify crack initiation points and fracture mechanisms. Despite the observed fatigue strength reduction induced by circular notched specimens compared to smooth specimens, notched samples showed a very low notch sensitivity attributed both to hexagonal crystal lattice characteristics of tempered alpha prime grains and to surface defects induced by the SLM process itself.

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Modeling of heat transfer, fluid flow and solidification microstructure of nickel-base superalloy fabricated by laser powder bed fusion

Cited by 208 publications

References 38 publications

Predicting the Microstructural Evolution of Electron Beam Melting of Alloy 718 with Phase-Field Modeling

Predicting the Microstructural Evolution of Electron Beam Melting of Alloy 718 with Phase-Field Modeling

Numerical modelling and experimental validation in Selective Laser Melting

Fatigue Assessment of Ti–6Al–4V Circular Notched Specimens Produced by Selective Laser Melting

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