The Unidirectional Crystallization of Metals and Alloys (Turbine Blades)

Kubiak, Krzysztof; Szeliga, Dariusz; Sieniawski, Jan; Onyszko, A.

doi:10.1016/b978-0-444-63303-3.00011-0

Cited by 16 publications

(16 citation statements)

References 55 publications

(50 reference statements)

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“…[30] Nucleation of pores depending on the local stress level in the interdendritic melt may be driven by stress relaxation after pore nucleation [31] that appeared near areas of step-changes in the mold geometry. The signal of positron annihilation from volumetric defects is high and prevents detecting vacancies and dislocations in an as-cast state.…”

Section: Discussionmentioning

confidence: 99%

Influence of Heat Treatment on Defect Structures in Single-Crystalline Blade Roots Studied by X-ray Topography and Positron Annihilation Lifetime Spectroscopy

Krawczyk

Bogdanowicz

Hanc-Kuczkowska

et al. 2018

Metall Mater Trans A

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Single-crystalline superalloy CMSX-4 is studied in the as-cast state and after heat treatment, with material being taken from turbine blade castings. The effect of the heat treatment on the defect structure of the root area near the selector/root connection is emphasized. Multiscale analysis is performed to correlate results obtained by X-ray topography and positron annihilation lifetime spectroscopy (PALS). Electron microscopy observations were also carried out to characterize the inhomogeneity in dendritic structure. The X-ray topography was used to compare defects of the misorientation nature, occurring in as-cast and treated states. The type and concentration of defects before and after heat treatment in different root areas were determined using the PALS method, which enables voids, mono-vacancies, and dislocations to be taken into account. In this way, differences in the concentration of defects caused by heat treatment are rationalized.

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Section: Discussionmentioning

confidence: 99%

Influence of Heat Treatment on Defect Structures in Single-Crystalline Blade Roots Studied by X-ray Topography and Positron Annihilation Lifetime Spectroscopy

Krawczyk

Bogdanowicz

Hanc-Kuczkowska

et al. 2018

Metall Mater Trans A

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“…Kubiak et al [2] described Bridgman and liquid metal cooling (LMC) methods for the directional solidification of single-crystal turbine blades made of nickel superalloy, applied in the aircraft engines and industrial gas turbines. The manufacturing process of these castings consists of pouring liquid metal into the preheated ceramic shell mold and its withdrawal at a specially selected velocity from the heating to the cooling area of the furnace.…”

Section: The Development Of Turbine Aircraft Engines Ismentioning

confidence: 99%

Effect of Processing Parameters and Shape of Blade on the Solidification of Single-Crystal CMSX-4 Ni-Based Superalloy

Szeliga

2018

Metall Mater Trans B

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The effect of mold withdrawal velocity, heater and pouring temperatures and the thickness of blade root on the solidification parameters and shape of the liquidus isotherm as well as microstructure of single-crystal CMSX-4 nickel-based superalloy, manufactured by the Bridgman method, has been analyzed in the article. The temperature gradient G, solidification rate v and location of the liquidus isotherm were determined in relation to the radiation baffle on the basis of temperature measurements conducted in nine test points along the height of castings (140 mm) with different thicknesses of root (27, 15 and 7 mm) and withdrawal velocities of 3 and 5 mm/min. The increase of root thickness, relative to the airfoil, resulted in the rise of inhomogeneity of solidification parameters as well as the primary dendrite arm spacing and unsteady state solidification along the whole blade height. However, in the case of blade with constant thickness, the steady-state solidification was created at the distance of 65 to 130 mm from its base. The increase of mold withdrawal velocity caused the decrease of temperature gradient. However, the solidification rate was different from the mold withdrawal velocity, especially in the root and middle part of the airfoil. The increase of heater temperature resulted in a rise of temperature gradient and reduction of the curvature of the liquidus isotherm, whereas the pouring temperature did not affect the solidification parameters in the blade. Particularly unfavorable conditions of the solidification process could occur in the middle part of the airfoil and root because of the lowest value of G/v and the largest primary dendrite arm spacing.

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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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The Unidirectional Crystallization of Metals and Alloys (Turbine Blades)

Cited by 16 publications

References 55 publications

Influence of Heat Treatment on Defect Structures in Single-Crystalline Blade Roots Studied by X-ray Topography and Positron Annihilation Lifetime Spectroscopy

Influence of Heat Treatment on Defect Structures in Single-Crystalline Blade Roots Studied by X-ray Topography and Positron Annihilation Lifetime Spectroscopy

Effect of Processing Parameters and Shape of Blade on the Solidification of Single-Crystal CMSX-4 Ni-Based Superalloy

On Crystal Mosaicity in Single Crystal Ni-Based Superalloys

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