Investigation of solidification microstructure of single crystal CMSX-4 superalloy – experimental measurements and modelling predictions

Matache, Gheorghe; Stefanescu, Doru M.; Puşcaşu, Cristian; Alexandrescu, Elvira; Bührig–Polaczek, Andreas

doi:10.1179/1743133615y.0000000021

Cited by 12 publications

(6 citation statements)

References 27 publications

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“…In both the experiments and simulations, typical elongated columnar grains along the casting height were detected, independently of the process carried out. The number of these grains decreased while their transverse size increased with increasing distance from the chill plate, due to the mechanism of competitive dendrite growth, similar to the other presented investigations [3,4,5,12,16,22,33,34]. However, in the outer area of casting, the grain boundaries were inclined mainly towards the plate axis in both the simulation and experiments for the standard process without IRBs (Figure 12a–d and Figure 13a,b).…”

Section: Resultssupporting

confidence: 90%

“…The conventional Bridgman process has been still the most commonly used for the production of turbine blades with columnar or single crystal structure [5,8,9,13,22]. In general, in the castings produced using this process, the temperature gradient and the shape of liquidus isotherm are mainly controlled by well-known grain continuator technique [23,24,25], withdrawal rate deceleration of the mold [21,22,23,24,26,27] or using a radiation baffle placed between the heating and cooling area of the furnace [8,11]. It was found that the temperature gradient at the solidification front is the largest when the radiation baffle is perfectly adjusted to the shape of mold [11].…”

Section: Introductionmentioning

confidence: 99%

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Application of Inner Radiation Baffles in the Bridgman Process for Flattening the Temperature Profile and Controlling the Columnar Grain Structure of Directionally Solidified Ni-Based Superalloys

et al. 2019

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The technique of flattening the temperature profile and controlling the formation of both the dendritic microstructure and grain structure in the directional solidification of nickel-based superalloy casting, using the novel inner radiation baffles (IRBs) in the Bridgman process, is presented in this paper. These baffles matched to the shape of mold and were placed horizontally along its height at various distances from the casting base. The plate castings of CMSX-4 superalloy were fabricated without and with the use of IRBs, withdrawing the mold at the rate of 6 mm/min from the heating to the cooling area of the industrial Bridgman furnace. Thermal analysis of the directional solidification of castings was carried out using the ProCAST software for a process where the various designs of the radiation baffle were applied. The results of the solidification conditions, the shape of liquidus and solidus isotherms, and grain structure obtained for the IRBs were compared with those reached for the standard ring-shaped (AERB) or perfectly adjusted (PARB) radiation baffles. The use of IRB resulted in flattening of the temperature distribution and decrease of the curvature of liquidus and solidus isotherms, as well as an increase of temperature gradient and cooling rate, compared with the process where AERB was only used. Consequently, primary dendrite arm spacing (PDAS) reached similar values across the width of casting and equaled to approximately 370 μm, reducing its average value by 26%, compared with the standard process. The change in predicted axial temperature gradient in casting was not found when thermophysical properties of molybdenum IRBs were used. The increase in graphite IRBs number in mold from seven to 14 caused the reduction of inhomogeneity of axial temperature gradient along the casting height.

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Section: Resultssupporting

confidence: 90%

Section: Introductionmentioning

confidence: 99%

Application of Inner Radiation Baffles in the Bridgman Process for Flattening the Temperature Profile and Controlling the Columnar Grain Structure of Directionally Solidified Ni-Based Superalloys

et al. 2019

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“…Careful control of solidification and heat treatment conditions is required to understand how dendritic and interdendritic regions form, and how the well-known γ/γ' microstructure evolves [11,[15][16][17][18][19][20]. In the present work, we focus on the evolution of the cast microstructure.…”

Section: Introductionmentioning

confidence: 99%

“…In the present work, we focus on the evolution of the cast microstructure. While there is a good understanding on how large-scale (cast microstructure: dendritic and interdendritic regions, cast microporosity [21], segregation [15,[17][18][19], and defects such as freckles [22][23][24], stray grains [25,26] and slivers [27]) and small-scale heterogeneities (γ' volume fractions, γ' sizes, γ channel widths, [15,28-30]) affect performance and how they can be controlled, there is one aspect which has received insufficient attention. With other single crystals, SXs share the phenomenon of mosaicity, which was first described by C.G.…”

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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“…Furthermore, to complement the experimental study, simulation work was also conducted to study the microstructure of the as-cast alloys [16][17][18][19][20]. For instance, solidification grain structure and texture evolution of Ni-based superalloy CMSX-4 have been studied by directional solidification experiments and Pro-CAST simulation, and a good agreement between these results has been achieved by adjusting the input parameters used in ProCAST simulation [16,17]. However, the parameters used in these simulations, such as maximum nucleation density, are only adjusted manually to fit the experimental results, which may not represent the specific condition of the sample.…”

Section: Introductionmentioning

confidence: 99%

In-situ studies and simulation of equiaxed solidification in Al–20Cu alloy

Luo

Yang

Chen

et al. 2021

Materials Science and Technology

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The equiaxed solidification of Al–20Cu alloy under different cooling rates was investigated using in-situ synchrotron X-ray radiography. The results showed that mean grain size increases rapidly at the early stage of solidification, then reaches the final grain size gradually. And the change of final mean grain size with cooling rate follows d = 4132.3 × R−0.86. In addition, the evolution of grain size in Al–20Cu alloy was also simulated by ProCAST software. The experimental and simulation results indicated that, in the range of the cooling rate (5.0–7.5 K min−1), the major factor influencing the final grain size is the maximum nucleation density, while the nucleation undercooling has an insignificant effect on the final grain size.

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Investigation of solidification microstructure of single crystal CMSX-4 superalloy – experimental measurements and modelling predictions

Cited by 12 publications

References 27 publications

Application of Inner Radiation Baffles in the Bridgman Process for Flattening the Temperature Profile and Controlling the Columnar Grain Structure of Directionally Solidified Ni-Based Superalloys

Application of Inner Radiation Baffles in the Bridgman Process for Flattening the Temperature Profile and Controlling the Columnar Grain Structure of Directionally Solidified Ni-Based Superalloys

On Crystal Mosaicity in Single Crystal Ni-Based Superalloys

In-situ studies and simulation of equiaxed solidification in Al–20Cu alloy

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