On the evolution of cast microstructures during processing of single crystal Ni-base superalloys using a Bridgman seed technique

Hallensleben, Philipp; Schaar, Helge; Thomé, P.; Jöns, Niels; Jafarizadeh, A.; Steinbach, Ingo; Eggeler, Gunther; Frenzel, Jan

doi:10.1016/j.matdes.2017.05.001

Cited by 45 publications

(37 citation statements)

References 62 publications

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“…Creep research throughout the last few decades has shown that mechanical high-temperature properties strongly depend on microstructure [2,[4][5][6][7]. Therefore, the evolution of the microstructure during processing of SXs is important because processing strongly affects the microstructure [2,[8][9][10][11]. It is also well known that the production of high-quality SX components is no trivial task [6,[12][13][14].…”

Section: Introductionmentioning

confidence: 99%

On Crystal Mosaicity in Single Crystal Ni-Based Superalloys

et al. 2019

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In the present work, we investigate the evolution of mosaicity during seeded Bridgman processing of technical Ni-based single crystal superalloys (SXs). For this purpose, we combine solidification experiments performed at different withdrawal rates between 45 and 720 mm/h with advanced optical microscopy and quantitative image analysis. The results obtained in the present work suggest that crystal mosaicity represents an inherent feature of SXs, which is related to elementary stochastic processes which govern dendritic solidification. In SXs, mosaicity is related to two factors: inherited mosaicity of the seed crystal and dendrite deformation. Individual SXs have unique mosaicity fingerprints. Most crystals differ in this respect, even when they were produced using identical processing conditions. Small differences in the orientation spread of the seed crystals and small stochastic orientation deviations continuously accumulate during dendritic solidification. Direct evidence for dendrite bending in a seeded Bridgman growth process is provided. It was observed that continuous or sudden bending affects the growth directions of dendrites. We provide evidence which shows that some dendrites continuously bend by 1.7° over a solidification distance of 25 mm.

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Section: Introductionmentioning

confidence: 99%

On Crystal Mosaicity in Single Crystal Ni-Based Superalloys

et al. 2019

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“…The presented numerical approach for solidification during casting is validated by experimental results of directionally solidified CMSX-4 Ò applying the vertical Bridgman process. [83] As software tool, the commercial software MICRESS Ò in combination with the databases TCNI8 and MOBNI4 is used. The thermal gradient is taken from previous work, [83] where this value has been determined by a combined numerical and experimental approach.…”

Section: Pdas Modelmentioning

confidence: 99%

“…[83] As software tool, the commercial software MICRESS Ò in combination with the databases TCNI8 and MOBNI4 is used. The thermal gradient is taken from previous work, [83] where this value has been determined by a combined numerical and experimental approach. In the model, the same withdrawal rates are considered as in the case of solidification experiments.…”

Section: Pdas Modelmentioning

confidence: 99%

Development of Single-Crystal Ni-Base Superalloys Based on Multi-criteria Numerical Optimization and Efficient Use of Refractory Elements

Markl

Müller

Ritter

et al. 2018

Metall Mater Trans A

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The development of new Ni-base superalloys with a complex composition consisting of eight or more alloying elements is a challenging task. The experimental state-of-the-art development cycle is based on the adaption of already existing compositions. Although new alloy compositions with potentially improved material properties are expected to be similar to already known superalloys, this procedure impedes efficiently finding these compositions in the large multi-dimensional design-space of all alloying elements. Modern alloy development combines numerical optimization methods with experimental validation to guide the development towards promising compositions. In this work, an improved numerical multi-criteria optimization tool using CALPHAD calculations and semi-empirical models for alloy development is presented. The model improvements to its predecessor are described and the successful application for the development of rhenium-free single-crystal Ni-base superalloys ERBO/13 and ERBO/15 is revisited. The optimization tool is described and the designed alloys are discussed regarding phase stability. Finally, a possible phase stability model extending the optimization tool and improving the alloy composition predictions is presented.

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“…The advancement of various modeling computational methods for foreseeing the material properties prior to experimental testing has helped engineers and designers to drastically reduce the overall cost and material for the production of acute components at extreme conditions . Turbine blades are one of the aforementioned components in both land‐based and aero‐based turbines.…”

Section: Introductionmentioning

confidence: 99%

“…It is reported that the highest rupture life is obtained when misorientation of the [001] single crystal is minimum relative to the longitudinal axis . In addition, the maximum range of 10° misorientation is indicated to be suitable for turbine blade applications . Yang et al.…”

Section: Introductionmentioning

confidence: 99%

Optimizing Grain Selection Design in the Single‐Crystal Solidification of Ni‐Based Superalloys

Sadeghi

Kermanpur

Norouzi‬

2018

Crystal Research and Technology

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An attempt is made to model the design of grain selection during single‐crystal solidification of an Ni‐based superalloy by the Bridgman method. Various geometrical designs of the starter block and spiral grain selector are chosen and their effects on crystal orientation of the single‐crystal part are studied. The competitive grain selection is simulated utilizing the cellular automaton finite element module of the ProCAST software. The simulated results are validated against the experimental observation of grain structure along with the crystal orientation measured by the electron backscatter diffraction (EBSD) and rotational orientation X‐ray diffraction (RO‐XRD) techniques. The results show that in order to obtain the single crystal with a minimum deviation from longitudinal axis, the height and diameter of the starter block as well as the height and the take‐off angle of the spiral should be optimized. It is found that the diameter/height ratio of the starter block should be less than 0.6 to obtain a well‐oriented single crystal prior to entrance of solidification front into the spiral. The height of starter block is found to be more influential than its diameter in selecting the suitable single grain.

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On the evolution of cast microstructures during processing of single crystal Ni-base superalloys using a Bridgman seed technique

Cited by 45 publications

References 62 publications

On Crystal Mosaicity in Single Crystal Ni-Based Superalloys

On Crystal Mosaicity in Single Crystal Ni-Based Superalloys

Development of Single-Crystal Ni-Base Superalloys Based on Multi-criteria Numerical Optimization and Efficient Use of Refractory Elements

Optimizing Grain Selection Design in the Single‐Crystal Solidification of Ni‐Based Superalloys

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