Comparative study of the segregation behavior and crystallographic orientation in a nickel-based single-crystal superalloy

Wang, Fu; Ma, Dexin; Bogner, Samuel; Bührig–Polaczek, Andreas

doi:10.1016/j.jallcom.2015.04.237

Cited by 17 publications

(14 citation statements)

References 28 publications

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“…Figure 1 schematically shows the procedure of the DWDS process. [16] During the procedure, the CMSX-4 superalloy was overheated to 1773 K (1500°C) in a crucible and covered with hollow Al 2 O 3 particles (1-3 mm in diameter) acting as a dynamic baffle. Ceramic tubes (1 mm thick, 200 mm high, with a 10 or 5 mm inside diameter), having a single-crystal seed of CMSX-4 superalloy with [001] crystal orientation in the longitudinal direction, were inserted into the melt.…”

Section: Methodsmentioning

confidence: 99%

“…1-Schematic illustration of the DWDS procedure for casting single-crystal Ni-based superalloy components. [16] (a) Before insertion of the tube into the superalloy melt, (b) the tube inserted into the superalloy melt, and (c) the tube withdrawn out of the superalloy melt. (k 1 ), the size of the c¢ phase, the mean areas of the (c + c¢) eutectic pools, and the size and volume of the microporosities.…”

Section: Methodsmentioning

confidence: 99%

“…[11,12] To offset these disadvantages, the downward directional solidification process (DWDS) was developed. [9,13] Our previous studies [14][15][16][17] proved that this process had many more benefits than the conventional Bridgman process, such as the high thermal gradient, the refined microstructures, the reduction in the size and volume of the microporosities, and the necessary avoidance of freckle formation due to density inversion. [18][19][20] This inversion is an unstable density gradient, which is a major factor leading to the emergence of freckles.…”

Section: Introductionmentioning

confidence: 99%

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Influence of the Size Effect on the Microstructures of the DWDS- and Bridgman-Solidified Single-Crystal CMSX-4 Superalloy

Wang

Mao

et al. 2015

Metall Mater Trans B

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To evaluate the potential benefits of utilizing the downward directional solidification process (DWDS) for controlling the homogeneity of microstructures, single-crystal CMSX-4 superalloy bars having different sizes of cross sections have been directionally solidified at a withdrawal rate of 1 mm/min using the DWDS and Bridgman processes. By varying the sizes of the cross sections, the DWDS process demonstrated higher thermal gradients, with smaller microstructural variations. The higher and more uniform thermal gradients not only refined the microstructures but also improved the microstructural homogeneity. In contrast to this, the Bridgman cast bars exhibited large-sized pores and a high volume of microporosity regardless of the cross-sectional size.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Influence of the Size Effect on the Microstructures of the DWDS- and Bridgman-Solidified Single-Crystal CMSX-4 Superalloy

Wang

Mao

et al. 2015

Metall Mater Trans B

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“…In the D&H process, the interdendritic melt becomes top-light due to the downward direction of solidification. Thus, the mushy zone is relatively stable, and the thermosolutal convection and the related freckle defects are essentially eliminated [49,50].…”

Section: Dipping and Heaving Technologymentioning

confidence: 99%

Novel casting processes for single-crystal turbine blades of superalloys

Ma¹

2017

Front. Mech. Eng.

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This paper presents a brief review of the current casting techniques for single-crystal (SC) blades, as well as an analysis of the solidification process in complex turbine blades. A series of novel casting methods based on the Bridgman process were presented to illustrate the development in the production of SC blades from superalloys. The grain continuator and the heat conductor techniques were developed to remove geometry-related grain defects. In these techniques, the heat barrier that hinders lateral SC growth from the blade airfoil into the extremities of the platform is minimized. The parallel heating and cooling system was developed to achieve symmetric thermal conditions for SC solidification in blade clusters, thus considerably decreasing the negative shadow effect and its related defects in the current Bridgman process. The dipping and heaving technique, in which thinshell molds are utilized, was developed to enable the establishment of a high temperature gradient for SC growth and the freckle-free solidification of superalloy castings. Moreover, by applying the targeted cooling and heating technique, a novel concept for the three-dimensional and precise control of SC growth, a proper thermal arrangement may be dynamically established for the microscopic control of SC growth in the critical areas of large industrial gas turbine blades.

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“…Directional solidification technique was developed for the purpose of unidirectional heat extraction by the Bridgman method. In this method, nucleation of very small grains occurs at the bottom of the starter block followed by the formation of the dendritic microstructure in the <001> preferred growth, which coincides with minimum Young's modulus and longest creep and fatigue lives . The reason is attributed to the atomic growth on planes with highest atomic density and lowest energy.…”

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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Comparative study of the segregation behavior and crystallographic orientation in a nickel-based single-crystal superalloy

Cited by 17 publications

References 28 publications

Influence of the Size Effect on the Microstructures of the DWDS- and Bridgman-Solidified Single-Crystal CMSX-4 Superalloy

Influence of the Size Effect on the Microstructures of the DWDS- and Bridgman-Solidified Single-Crystal CMSX-4 Superalloy

Novel casting processes for single-crystal turbine blades of superalloys

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

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