The recrystallization of nickel-base superalloys

Porter, Angus; Ralph, B.

doi:10.1007/bf02402788

Cited by 111 publications

(30 citation statements)

References 12 publications

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“…and "Is there a problem on local recrystallization in this case?" Relating to these questions, some researchers have confirmed that local recrystallization [5,6] and abnormal precipitation growth were induced by local strain, [7][8][9][10][11] accompanied by the formation of cellular ␥/␥Ј microstructures. Similar abnormal microstructures were found to be nucleated by many types of actual service damage, e.g., fatigue and thermomechanical fatigue.…”

Section: Introductionmentioning

confidence: 96%

“…Thus, repair, recoating, and refurbishment technologies, especially of the hot section components that are subjected to extremely severe conditions, have been inevitable for this decade. [1][2][3][4][5][6][7][8][9][10] The techniques of recoating, welding, and bonding, as well as new material design, are very important, although all of them are on the way of development. Nowadays many techniques have enabled us to repair polycrystalline superalloys and relatively lower temperature section components.…”

Section: Introductionmentioning

confidence: 99%

“…[4] On the contrary, microstructurally controlled Ni-base superalloys, single crystal and directionally solidified alloys, are still the most difficult materials for joining and repair. [1,[5][6][7][8][9][10] A. Outline of Cellular Microstructure…”

Section: Introductionmentioning

confidence: 99%

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Damage repair in CMSX-4 alloy without fatigue life reduction penalty

Okazaki

Ohtera

Harada

2004

Metall Mater Trans A

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The microstructural changes in a single-crystal Ni-base superalloy, CMSX-4, that might occur during the processes of repair and recoating of hot section components for advanced gas turbines were studied. It is shown that the cellular ␥/␥Ј microstructure is formed when the material is subjected to local plastic straining, followed by the reheat treatments during the course of damage recovery. The formation of cellular microstructure in the material led to the remarkably reduced fatigue strength. In order to reduce or prevent the preceding undesirable effect resulting from cellular microstructure, a new method based on applying overlay coating technique was developed. The method is based on an idea that the alloying elements that are depleted in base alloys could be supplemented via the overlay coating. An X alloy, which contains grain boundary strengthening elements, was selected and coated on the CMSX-4 with the cellular microstructure by low-pressure plasma spraying. The fatigue tests on the coated CMSX-4 specimens demonstrated the effectiveness of the method. The observations of the crack initiation site, the fatigue fracture mode, the crack density in the cellular transformed area, and the crack propagation morphologies near the prior interface strongly supported the validity of this approach. The method is expected to build a road to a so-called damage cure (or recovery) coating.

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Section: Introductionmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

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Damage repair in CMSX-4 alloy without fatigue life reduction penalty

Okazaki

Ohtera

Harada

2004

Metall Mater Trans A

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“…M 23 C 6 carbides are supposed to affect the dynamic recrystallization and final grain size distribution. [46][47][48][49] They also act as deep traps of hydrogen in sour and hydrogen containing environments and thus promote hydrogen embrittlement. [21] Therefore, the identification and characterization of this phase help the understanding of the grain size distribution and also the hydrogen embrittlement of alloy 718 in harsh hydrogen containing environments.…”

Section: Introductionmentioning

confidence: 99%

Identification of Mo-Rich M23C6 Carbides in Alloy 718

Aghajani¹,

Tewes²,

Parsa

et al. 2016

Metall Mater Trans A

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In the present study, we systematically identify and characterize a (Nb, Mo)-rich M 23 C 6 type of M 23 C 6 carbide with a lattice parameter of 1.094 nm in alloy 718 for the first time using a combination of selected area electron diffraction pattern and powder X-ray diffraction analysis. The time-temperature-precipitation diagrams of the precipitates in both annealed and strained conditions are obtained by particle analysis using an automated scanning electron microscopy method. (Nb, Mo)-rich M 23 C 6 carbides first precipitate after 24 hours at 1223 K (950°C) annealing, while they form after 10 minutes at 1273 K (1000°C) in the strained condition. This correlates with the excess dislocations produce during deformation.

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“…When DS components are deformed by the improper operations such as severe grit-blating or polisihing and subsequently heated above the static recrystallization temperature, the static recrystallization occurs. [5][6][7][8] The static recrystallization temperature of DS nickel-base superalloy, dominated by the solution behavior of gamma prime (c′), is close to the dissolution temperature of c′ and about 0.8 ∼ 0.9 times the absolute melting temperature. [9][10] In addition, DS components may be dynamically recrystallized because of the rigorous service conditions even if the operation temperature is slightly lower than that of the static recrystallization.…”

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confidence: 99%

Dynamic Recrystallization Behavior of a Directionally Solidified Superalloy

Tao

Zhang

2007

Adv Eng Mater

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Directionally solidified (DS) nickel-base superalloys are widely used for turbine blades in aircraft engines and industrial gas turbines. The surface recrystallization, detrimental to mechanical properties of DS superalloys, is an influencing factor in the engineering failures. [1][2][3][4] For conventional polycrystalline metals, recrystallization is an effective approach to optimizing microstructure and thus to improving mechanical property, such as grain refining and strength improving. Industrially, the static recrystallization temperature is at which the metal with 70 % cold deformation mostly accomplishs its recrystallization course in one hour. The dynamic recrystallization refers to the recrystallization process during the hot working operation which temperature is higher than the static recrystallization one. [4] However, for DS superalloy, aim of recrystallization researches is to provide effective measures to reduce or even supress surface recrystallization of DS components. When DS components are deformed by the improper operations such as severe grit-blating or polisihing and subsequently heated above the static recrystallization temperature, the static recrystallization occurs. [5][6][7][8] The static recrystallization temperature of DS nickel-base superalloy, dominated by the solution behavior of gamma prime (c′), is close to the dissolution temperature of c′ and about 0.8 ∼ 0.9 times the absolute melting temperature. [9][10] In addition, DS components may be dynamically recrystallized because of the rigorous service conditions even if the operation temperature is slightly lower than that of the static recrystallization.Little information has been available in the open literature on the dynamic recrystallization of DS superalloys, especially on the dynamic recrystallization mechanism. [11][12][13][14] This paper investigates the dynamic recrystallization behavior of a DS nickel-base superalloy. The main purpose is to find out the dynamic recrystallization mechanism and thus to provide measures against the dynamic recrystallization of DS components. Experimental Details MaterialThe alloy investigated was produced by directional solidification and the longitudinal axis was in the [001] direction with not more than 10°deviation. The nominal chemical composition in weight percentage was as follows: C 0.14, Cr 9.5, Co 6.0, W 5.3, Mo 3.8, Al 6.0, Ti 1.8, B 0.02, and balance Ni. The DS nickel-base superalloy was treated by solution (1220°C/4 h, air cool) and subsequent aging (870°C/32 h, air cool). In the heattreated state, the superalloy had a uniform fine cuboidal c′ precipitate, typically 0.1 lm ∼ 0.15 lm in size and approximately 0.6 vol. fraction. The static recrystallization temperature of this superalloy is above 1000°C. [15] Testing ProcedureFull size creep specimens with the gage portion of 52 mm in length and 10 mm in diameter were machined from the DS superalloy. Tensile creep tests were carried out using the single lever type creep machine at three temperatures, i.e. 800°C, 850°C and 900°C und...

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The recrystallization of nickel-base superalloys

Cited by 111 publications

References 12 publications

Damage repair in CMSX-4 alloy without fatigue life reduction penalty

Damage repair in CMSX-4 alloy without fatigue life reduction penalty

Identification of Mo-Rich M23C6 Carbides in Alloy 718

Dynamic Recrystallization Behavior of a Directionally Solidified Superalloy

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