Formation of topologically closed packed phases within CMSX-4 single crystals produced by additive manufacturing

Pistor, Julian; Körner, Carolin

doi:10.1016/j.mlblux.2019.100003

Cited by 12 publications

(14 citation statements)

References 4 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In 2016 we were the first to demonstrate the single crystal formation by additive manufacturing (AM), using a conventional nickelbase superalloy 13 . Due to the inherent high solidification velocities, combined with steep thermal gradients, the dendrite arm spacing is about two orders of magnitude smaller compared to the classical Bridgman process 14 , 15 . As a result, these single crystals are homogenized within minutes 14 and also the solidification porosity scales with the dendrite arm spacing 16 .…”

Section: Introductionmentioning

confidence: 99%

A novel mechanism to generate metallic single crystals

Pistor

Körner

2021

Sci Rep

Self Cite

View full text Add to dashboard Cite

Generally, the evolution of metallic single crystals is based on crystal growth. The single crystal is either produced by growing a seed single crystal or by sophisticated grain selection processes followed by crystal growth. Here, we describe for the first time a fully new mechanism to generate single crystals based on thermo-mechanically induced texture formation during additive manufacturing. The single crystal develops due to two different mechanisms. The first step is a standard grain selection process due to directional solidification, leading to a pronounced fiber texture. The second and new mechanism bases on successive thermo-mechanically induced plastic deformations and texture formation in FCC crystals under compression. During this second step, the columnar grain structure transforms into a single crystal by rotation of individual grains. Thus, the single crystal forms step by step by merging the originally columnar grain structure. This novel, stress induced mechanism opens up completely new perspectives to fabricate single crystalline components and to accurately adjust the orientation according to the load.

show abstract

Section: Introductionmentioning

confidence: 99%

A novel mechanism to generate metallic single crystals

Pistor

Körner

2021

Sci Rep

Self Cite

View full text Add to dashboard Cite

show abstract

“…In all cases, grain selection from a columnar to a single crystalline microstructure was achieved by a specific well-defined scanning strategy without using a single crystalline substrate. As expected, elemental segregation was strongly reduced due to the high solidification rate inherent to additive manufacturing [ 15 , 26 ]. This leads to a strong reduction of post-processing time (heat treatment) [ 27 ] and also improved performance.…”

Section: Introductionmentioning

confidence: 62%

“…This leads to a strong reduction of post-processing time (heat treatment) [ 27 ] and also improved performance. Investigations of high-temperature phase stability [ 26 ], low cycle fatigue [ 28 ], high-temperature strength as well as creep [ 29 ] showed the beneficial effect of the additive manufacturing processing route in comparison to the conventional casting one. However, there is an important drawback of additively manufactured single crystals.…”

Section: Introductionmentioning

confidence: 99%

A Single Crystal Process Window for Electron Beam Powder Bed Fusion Additive Manufacturing of a CMSX-4 Type Ni-Based Superalloy

2021

View full text Add to dashboard Cite

Using suitable scanning strategies, even single crystals can emerge from powder during additive manufacturing. In this paper, a full microstructure map for additive manufacturing of technical single crystals is presented using the conventional single crystal Ni-based superalloy CMSX-4. The correlation between process parameters, melt pool size and shape, as well as single crystal fraction, is investigated through a high number of experiments supported by numerical simulations. Based on these results, a strategy for the fabrication of high fraction single crystals in powder bed fusion additive manufacturing is deduced.

show abstract

“…The two step aging was achieved in a Gero LHTM 250/300 (Carbolite Gero GmbH & Co. KG, Neuhausen, Germany) under a controlled Argon flow of 1 L h −1 after prior evacuation of the chamber to 1 × 10 −5 mbar. For the first aging, a temperature of 1140

C for 2

was used, whereas the second aging was performed at 870

C for 20 h. This procedure leads to a completely homogeneous microstructure with no residual dendritic segregation and a defined

microstructure [ 5 , 27 , 28 ]. The heat treatment can be seen in detail in Table 2 .…”

Section: Materials and Methodsmentioning

confidence: 99%

New Grain Formation Mechanisms during Powder Bed Fusion

et al. 2021

View full text Add to dashboard Cite

Tailoring the mechanical properties of parts by influencing the solidification conditions is a key topic of powder bed fusion. Depending on the application, single crystalline, columnar, or equiaxed microstructures are desirable. To produce single crystals or equiaxed microstructures, the control of nucleation is of outstanding importance. Either it should be avoided or provoked. There are also applications, such as turbine blades, where both microstructures at different locations are required. Here, we investigate nucleation at the melt-pool border during the remelting of CMSX-4® samples built using powder bed fusion. We studied the difference between remelting as-built and homogenized microstructures. We identified two new mechanisms that led to grain formation at the beginning of solidification. Both mechanisms involved a change in the solidification microstructure from the former remelted and newly forming material. For the as-built samples, a discrepancy between the former and new dendrite arm spacing led to increased interdentritic undercooling at the beginning of solidification. For the heat-treated samples, the collapse of a planar front led to new grains. To identify these mechanisms, we conducted experimental and numerical investigations. The identification of such mechanisms during powder bed fusion is a fundamental prerequisite to controlling the solidification conditions to produce single crystalline and equiaxed microstructures.

show abstract

Formation of topologically closed packed phases within CMSX-4 single crystals produced by additive manufacturing

Cited by 12 publications

References 4 publications

A novel mechanism to generate metallic single crystals

A novel mechanism to generate metallic single crystals

A Single Crystal Process Window for Electron Beam Powder Bed Fusion Additive Manufacturing of a CMSX-4 Type Ni-Based Superalloy

New Grain Formation Mechanisms during Powder Bed Fusion

Contact Info

Product

Resources

About