Misorientation-dependent solute enrichment at interfaces and its contribution to defect formation mechanisms during laser additive manufacturing of superalloys

Hariharan, Avinash; Lü, Lin; Risse, Jeroen; Kostka, Aleksander; Gault, Baptiste; Jägle, Eric Aimé; Raabe, Dierk

doi:10.1103/physrevmaterials.3.123602

Cited by 46 publications

(51 citation statements)

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“…The quantitative chemical compositions are listed inTable 2together with the TEM results. Compared to the AM-built Ni-base superalloys, the current 0.5Al alloy seems to have a higher tolerance of Si without having extensive hot cracks[12,26,51]. Since hot cracking only occurs along HAGBs at the end of solidification, where Al-enriched B2/BCC phases are present, a closer examination of these B2/BCC phases is thus needed.Bright and dark field TEM images of the dendritic and interdendritic areas are shown inFig.…”

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Reducing hot tearing by grain boundary segregation engineering in additive manufacturing: example of an AlxCoCrFeNi high-entropy alloy

et al. 2021

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One major hindrance that alloy design for additive manufacturing (AM) faces nowadays is hot tearing. Contrary to the previous works which either try to reduce solidification range or introduce grain refinement, the current work presents a new approach of employing segregation engineering to alter the residual stress states at the interdendritic and grain boundary regions and consequently prevent hot tearing. Here, in situ Al alloying is introduced into an existing hot-cracking susceptible highentropy alloy CoCrFeNi. It is found that within a certain range of compositions, such as Al0.5CoCrFeNi, the hot crack density was drastically decreased. During the solidification of this specific alloy composition, Al is firstly ejected from the primary dendritic face-centred cubic (FCC) phase and segregates into the interdendritic regions. Spinodal decomposition then occurs in these Al-enriched regions to form the ordered B2 NiAl and disordered body-centred cubic (BCC) Cr phases. Due to the higher molar volume and lower homologous temperatures of these B2/BCC phases, the inherent residual strain is accommodated and transformed from a maximum 0.006 tensile strain in CoCrFeNi to a compressive strain of ~0.001 in Al0.5CoCrFeNi. It is believed that this grain boundary segregation engineering method could provide a new pathway to systematically counteract the hot tearing problem in additive manufacturing of metals and alloys, using available thermodynamic and kinetic database information.

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Reducing hot tearing by grain boundary segregation engineering in additive manufacturing: example of an AlxCoCrFeNi high-entropy alloy

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“…[3,4] Solidification cracking issues have also been realized during the recent acceleration of metals additive manufacturing technologies. [5][6][7] The detection of solidification cracks immediately after processing results in costly rework or, in extreme cases, components must be discarded. If solidification cracks go undetected, the resulting service life of the component may be jeopardized.…”

Section: Introductionmentioning

confidence: 99%

New Composition Based Technique for Solidification Cracking Resistance Evaluation

Sutton

Ramírez

2021

Metall Mater Trans A

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Predicting the occurrence of solidification cracking during the solidification of metallic alloys by numerical simulation is a crucial move for avoiding such defects. Several models are widely available, however, the application of such are impacted due to the specific and not accessible parameters required. A simple, composition-based approach to rank solidification cracking susceptibility is presented. The procedure links computational thermodynamic and computational fluid dynamics (CFD) to provide an evaluation tool for solidification cracking. The method is related to the liquid filling phenomena in dendritic arms during solidification, which plays a critical role in solidification cracking phenomena. The dendritic profiles were constructed using the fraction of solid calculated by commercial thermodynamic software packages. The calculated results were compared with experimental solidification cracking data and showed satisfactory accuracy. The method capability to rank the solidification cracking propensity of similar alloys based on composition provides an important new operative tool to aid alloy development in welding and additive manufacturing related areas.

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“…This precipitation implies a ductility reduction that together with residual stresses could lead to crack formation [ 17 ]. Nevertheless, in the LPBF manufactured as-built IN738LC superalloy, it is mostly established that the crack formation is mainly due to solidification cracking mechanism [ 18 , 19 ]. Additionally, some published research works point out the influence of powder particle size distribution on the crack formation in additively manufactured parts [ 20 , 21 ].…”

Section: Introductionmentioning

confidence: 99%

“…Thus, the authors identified the increase in Zr and B microsegregation at grain boundaries, which implies the generation of higher shrinkage strains, as the cause of solidification crack formation. Comparatively, Hariharan et al [ 18 ] identified also by APT that Zr and Si were only enriched at high angle grain boundaries (HAGB) and they stated that these elements enrichment promoted an increase in the solidification range of the superalloy. However, they concluded that as the same Zr and Si concentration was observed in cracked and non-cracked HAGB, Zr and Si enrichment at grain boundaries was not the main reason for solidification cracks formation.…”

Section: Introductionmentioning

confidence: 99%

“…In the research work of Chauvet et al [ 27 ], the authors observed that hot cracks were only formed at high angle grain boundaries, which seems to be related to the grain boundary energy variation. Finally, some authors [ 18 , 26 ] studied the effect of minor elements microsegregation and grains misorientation simultaneously in the formation of solidification cracks. They concluded that minor elements microsegregation was favored in the high angle grain boundaries, leading to an increase of the mushy zone in these localized areas and promoting the formation of solidification cracks.…”

Section: Introductionmentioning

confidence: 99%

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Influence of Minor Alloying Element Additions on the Crack Susceptibility of a Nickel Based Superalloy Manufactured by LPBF

et al. 2021

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Inconel 738LC (IN738LC) is a nickel-based superalloy specially used in the hot section components of turbine engines. One of its main drawbacks relies on the cracking susceptibility when it is manufactured by laser powder bed fusion (LPBF). This paper analyzes the influence of minor alloying element concentration on cracking tendency of IN738LC superalloy manufactured by LPBF. For that objective, samples were manufactured using two powders, which presented different minor alloying elements concentration (Si, Zr and B). It was shown that the samples crack tendency was very different depending on the powder used for their manufacturing. In fact, the measured crack density value was 2.73 mm/mm2 for the samples manufactured with the powder with higher minor alloying elements concentration, while 0.25 mm/mm2 for the others. Additionally, a special emphasis has been put on elemental composition characterization in cracked grain boundaries in order to quantify possible Si or Zr enrichment. It has been also studied the differences of solidification ranges and grain structures between both samples as a consequence of different minor alloying elements concentration in order to analyze their effect on crack susceptibility. In this sense, Scheil-Gulliver simulation results have shown that samples with higher Si and Zr contents presented higher solidification range temperature. This fact, as well as an increase of the presence of high angle grain boundaries (HAGB), leaded to an increment in the crack formation during solidification. Therefore, in this research work, an understanding of the factors affecting crack phenomenon in the LPBF manufactured IN738LC was accomplished.

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Misorientation-dependent solute enrichment at interfaces and its contribution to defect formation mechanisms during laser additive manufacturing of superalloys

Cited by 46 publications

References 83 publications

Reducing hot tearing by grain boundary segregation engineering in additive manufacturing: example of an AlxCoCrFeNi high-entropy alloy

Reducing hot tearing by grain boundary segregation engineering in additive manufacturing: example of an AlxCoCrFeNi high-entropy alloy

New Composition Based Technique for Solidification Cracking Resistance Evaluation

Influence of Minor Alloying Element Additions on the Crack Susceptibility of a Nickel Based Superalloy Manufactured by LPBF

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