Investigations on the microstructure and crack formation of IN738LC samples processed by selective laser melting using Gaussian and doughnut profiles

Cloots, Michael; Uggowitzer, Peter J.; Wegener, Konrad

doi:10.1016/j.matdes.2015.10.027

Cited by 328 publications

(123 citation statements)

References 22 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…hatching space (Figure 6c). These results are in agreement with the values found in the literature: the best melt pool depth-to-layer thickness ratio is reported as ~2.5 and the best melt pool width-tohatching space ratio is reported as ~2.8 [21]. Despite the poor sphericity of water-atomized powders and contrary to the results obtained in the literature [22,23], we were able to optimize the printing parameters and manufacture specimens with a density higher than 99.5%.…”

Section: Three-point Bending Tests (Trs-transverse Rupture Strength)supporting

confidence: 92%

Laser Powder Bed Fusion of Water-Atomized Iron-Based Powders: Process Optimization

Letenneur

Braïlovski

Kreitcberg

et al. 2017

JMMP

View full text Add to dashboard Cite

Abstract:The laser powder bed fusion (L-PBF) technology was adapted for use with non-spherical economical water-atomized iron powders. A simplified numerical and experimental modeling approach was applied to determine-in a first approximation-the operation window for the selected powder in terms of laser power, scanning speed, hatching space, and layer thickness. The operation window, delimited by a build rate ranging from 4 to 25 cm 3 /h, and a volumetric energy density ranging from 50 to 190 J/mm 3 , was subsequently optimized to improve the density, the mechanical properties, and the surface roughness of the manufactured specimens. Standard L-PBF-built specimens were subjected to microstructural (porosity, grain size) and metrological (accuracy, shrinkage, minimum wall thickness, surface roughness) analyses and mechanical testing (three-point bending and tensile tests). The results of the microstructural, metrological and mechanical characterizations of the L-PBF-built specimens subjected to stress relieve annealing and hot isostatic pressing were then compared with those obtained with conventional pressing-sintering technology. Finally, by using an energy density of 70 J/mm 3 and a build rate of 9 cm 3 /h, it was possible to manufacture 99.8%-dense specimens with an ultimate strength of 330 MPa and an elongation to failure of 30%, despite the relatively poor circularity of the powder used.

show abstract

Section: Three-point Bending Tests (Trs-transverse Rupture Strength)supporting

confidence: 92%

Laser Powder Bed Fusion of Water-Atomized Iron-Based Powders: Process Optimization

Letenneur

Braïlovski

Kreitcberg

et al. 2017

JMMP

View full text Add to dashboard Cite

show abstract

“…Our observations imply that a bulk-criterion may not allow to appropriately depict near-atomic-scale processes. It is also known that Zr promotes hot cracking in nickel-based superalloys produced by casting [42][43][44][45] and AM processes [5]. Although Zr is added in the bulk composition of the investigated alloy (0.02 -0.025 at.%), APT revealed no segregation of Zr at the grain boundary.…”

Section: Hot Cracking Caused By Grain Boundary-segregation Induced LImentioning

confidence: 82%

“…By contrast, Zr was found to partition to the γ' phase for both columnar cracked and equiax crack-free samples, as shown in Supplementary Figure 1. However, in a different nickel-based superalloy, Zr was found to segregate at the grain boundary [5]. Besides, significant interactions between Zr and B were recently reported during casting [44].…”

Section: Hot Cracking Caused By Grain Boundary-segregation Induced LImentioning

confidence: 95%

“…However, it is very challenging to produce safety-critical components by AM with zero-crack tolerance, yet the digitalisation inherent to AM promises large gains in manufacturing and repair efficiency [2]. The AM community currently invests great efforts to 3D print well-known superalloys compositions considered as non-weldable such as IN738 [3][4][5], CMSX-4 [6], CM247LC [7] among others [8,9]. These alloy grades, which have been classified as non-weldable due to their Ti and Al contents [2] usually imply formation of large volume fractions of γ'-precipitates and were observed to undergo severe cracking when welded or AM built.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Atomic-scale grain boundary engineering to overcome hot-cracking in additively-manufactured superalloys

et al. 2019

View full text Add to dashboard Cite

There are still debates regarding the mechanisms that lead to hot cracking in parts build by additive manufacturing (AM) of non-weldable nickel-based superalloys. This lack of in-depth understanding of the root causes of hot cracking is an impediment to designing engineering parts for safety-critical applications. Here, we deploy a near-atomic-scale approach to investigate the details of the compositional decoration of grain boundaries in the coarse-grained, columnar microstructure in parts built from a non-weldable nickel-based superalloy by selective electron-beam melting. The progressive enrichment in Cr, Mo and B at grain boundaries over the course of the AM-typical successive solidification and remelting events, accompanied by solid-state diffusion, causes grain boundary segregation induced liquation. This observation is consistent with thermodynamic calculations. We demonstrate that by adjusting build parameters to obtain a fine-grained equiaxed or a columnar microstructure with grain width smaller than 100 μm enables to avoid cracking, despite strong grain boundary segregation. We find that the spread of critical solutes to a higher total interfacial area, combined with lower thermal stresses, helps to suppress interfacial liquation.

show abstract

“…So far, the Ni-base superalloys applied to SLM are mainly the weldable ones, i.e., IN718 [113,[160][161][162][163][164][165][166][167], IN625 [79,80,168,169], Hastelloy X [170][171][172][173][174], Nimonic 263 [110], which have low additions of both Ti and Al and are less susceptible to strain age cracking. Expansion to the less-weldable Ni-base superalloys has also been attempted, such as IN939 [175], IN100 [176], IN738LC [177][178][179][180][181], CM247LC [114,[182][183][184] and Rene 142 [81]. These researches have shown the great potential for manufacturing complex-geometry critical and functional components for high temperature application via SLM.…”

Section: Materials Manufactured With Slmmentioning

confidence: 99%

Additively Manufactured Inconel 718 : Microstructures and Mechanical Properties

Deng

2018

Linköping Studies in Science and Technology. Licentiate Thesis

View full text Add to dashboard Cite

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...

show abstract

Investigations on the microstructure and crack formation of IN738LC samples processed by selective laser melting using Gaussian and doughnut profiles

Cited by 328 publications

References 22 publications

Laser Powder Bed Fusion of Water-Atomized Iron-Based Powders: Process Optimization

Laser Powder Bed Fusion of Water-Atomized Iron-Based Powders: Process Optimization

Atomic-scale grain boundary engineering to overcome hot-cracking in additively-manufactured superalloys

Additively Manufactured Inconel 718 : Microstructures and Mechanical Properties

Contact Info

Product

Resources

About