On Crystal Mosaicity in Single Crystal Ni-Based Superalloys

Hallensleben, Philipp; Scholz, F.; Thomé, P.; Schaar, Helge; Steinbach, Ingo; Eggeler, Gunther; Frenzel, Jan

doi:10.3390/cryst9030149

Cited by 42 publications

(42 citation statements)

References 67 publications

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“…Otherwise, the force directing effect may increase the α angle. Similar “deflections” processes are described in [30] as “re-emerging”. The authors suggest that the “re-emerging” process may reduce the degree of mosaicity because the short dendrites in the thin-walled areas bend less than the long dendrites in the thick-walled areas due to geometrical constraints [30].…”

Section: Resultsmentioning

confidence: 54%

“…Similar “deflections” processes are described in [30] as “re-emerging”. The authors suggest that the “re-emerging” process may reduce the degree of mosaicity because the short dendrites in the thin-walled areas bend less than the long dendrites in the thick-walled areas due to geometrical constraints [30]. The description of mosaicity creation in the thin-walled area should include not only the length of dendrites, but also the angle between the stems of dendrites and a mould wall.…”

Section: Resultsmentioning

confidence: 54%

“…At the points 1 and 3, the asymmetry of the diffusion area manages to form, whereas at point 2, the asymmetry of the diffusion area does not manage to form, due to the high angle (close to 90°) between the secondary dendrite arms and the mould wall. The reasons of the “morphological bending” proposed in [30,31] may be similar to the reasons of the [001] crystallographic direction deviation in thin-walled areas. The critical angle may exist between dendrites and a mould wall.…”

Section: Resultsmentioning

confidence: 71%

“…The growth direction of the PA was always taken as parallel to the [001] crystallographic direction, as it is often assumed [28,29]. Recent studies [30] show that the difference in the direction of dendrite growth correlates with difference in crystal orientation, which confirms the above assumption. Since the TE is parallel to the TE * , the angle between the PA and the trailing edge TE may be denoted as the α* angle (Figure 5).…”

Section: Resultsmentioning

confidence: 73%

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Primary Crystal Orientation of the Thin-Walled Area of Single-Crystalline Turbine Blade Airfoils

et al. 2019

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The thin-walled airfoil areas of as-cast single-crystalline turbine blades made of CMSX-4 superalloy were studied. The blades were produced by the industrial Bridgman technique at withdrawal rates of 2, 3 and 4 mm/min. The angle between the [001] crystallographic direction and blade axis, related to the primary orientation, was defined by the Ω-scan X-ray diffraction method at points on the camber line located near the tip of an airfoil and at points of a line located in parallel and near the trailing edge. Additionally, primary crystal orientation was determined by Laue diffraction at the selected points of an airfoil. The influence of mould wall inclination on the primary crystal orientation of the thin-walled areas is discussed. The effect of change in the [001] crystallographic direction, named as “force directing”, was considered with regard to the arrangement of primary dendrite arms in relation to the trailing edge and the camber line. It was stated that when the distance between the mould walls is less than the critical value of about 1.5 mm the “force directing” increases as the distance between the walls of the mould decreases. The effect may be controlled by selecting an appropriate secondary orientation using a seed crystal in the blade production process. The model of dendrite interaction with the mould walls, including bending and “deflection”, was proposed.

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Section: Resultsmentioning

confidence: 54%

Section: Resultsmentioning

confidence: 54%

Section: Resultsmentioning

confidence: 71%

Section: Resultsmentioning

confidence: 73%

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Primary Crystal Orientation of the Thin-Walled Area of Single-Crystalline Turbine Blade Airfoils

et al. 2019

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“…Recently, research on the dendritic array formation in the SX casts has been found to be extremely important [28]. Since the mechanisms of the dendrite growth from the selector to the root of the blade are related to the enlargement of the crystallization front cross-section, they have some features similar to the dendritic growth in the platforms [29].…”

Section: Introductionmentioning

confidence: 99%

Variation of Crystal Orientation and Dendrite Array Generated in the Root of SX Turbine Blades

et al. 2019

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The variation of the crystal orientation and the dendrite array generated in the root of the single-crystalline (SX) turbine blades made of CMSX-4 superalloy were studied. The blades with an axial orientation of the [001] type were solidified by the industrial Bridgman technique using a spiral selector at a withdrawal rate of 3 mm/min. The analysis of the crystal orientation and dendrite arrangement was carried out using scanning electron microscopy, X-ray diffraction topography, and Laue diffraction. It was found that the lateral growth of such secondary dendrite arms, which are defined as “leading” and grow in the root at first, is related to the rotation of their crystal lattice, which is the reason for creation of the low-angle boundary (LAB) type defects. The primary crystal orientation of the selector extension (SE) area determines the areas and directions of the lateral growth of the leading arms. Additionally, it was found that in the SE areas of the root, near the connection with the selector, the spatial distribution of the [001]γ′ crystallographic direction has a complex wave-like character and may be related to the shape of the crystallization front.

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Evolution of local misorientations in the γ/γ’‐microstructure of single crystal superalloys during creep studied with the rotation vector baseline (RVB) EBSD method

Gamanov,

Dlouhy,

Bürger

et al. 2023

Microscopy Res & Technique

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The present work uses the rotation vector baseline electron back scatter orientation imaging method (RVB‐EBSD) to study the evolution of small misorientations between the γ‐ and γ′‐phase in Ni‐base single crystal superalloys (SXs) during creep. For this purpose, two material states of the SX ERBO1 (CMSX4 type) were characterized after creep deformation at 850°C and 600 MPa to final strains of 1% and 2%. Obtaining reliable phase boundary misorientation (PBM), kernel average misorientation (KAM) and orientation spread (OS) data represents a challenge for electron backscatter diffraction (EBSD), not only because the method operates at its limits of lateral and angular resolution, but also because it is difficult to differentiate between the two phases merely based on Kikuchi diffraction. The two phases differ in chemical composition which gives rise to different EBSD background intensities. These can be exploited to differentiate between the two phases. In the present work, crystallographic and chemical information are combined to demonstrate that orientation imaging can be used to document the formation of dislocation networks at γ/γ′‐interfaces and the filling of γ‐channels by dislocations. These findings are in good agreement with reference results from diffraction contrast scanning transmission electron microscopy. It is also shown that misorientations evolve between small groups of equally oriented γ/γ′‐neighborhoods, on a size scale above characteristic γ/γ′‐dimensions (>0.5 μm) and below distances associated with dendritic mosaicity (<200 μm). The methodological aspects as well as the new material specific results are discussed in the light of previous work published in the literature.Research Highlights Microstructure evolution during [001] tensile creep of Ni‐based single‐crystalline alloy. Application of RVB‐EBSD technique, focused on angular misorientations between γ/γ′ phases, with accuracy of 0.01°. Separation of γ/γ′ phases using experimental post‐processing of raw EBSD data.

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On Crystal Mosaicity in Single Crystal Ni-Based Superalloys

Cited by 42 publications

References 67 publications

Primary Crystal Orientation of the Thin-Walled Area of Single-Crystalline Turbine Blade Airfoils

Primary Crystal Orientation of the Thin-Walled Area of Single-Crystalline Turbine Blade Airfoils

Variation of Crystal Orientation and Dendrite Array Generated in the Root of SX Turbine Blades

Evolution of local misorientations in the γ/γ’‐microstructure of single crystal superalloys during creep studied with the rotation vector baseline (RVB) EBSD method

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