Creep fracture mechanisms in single crystal superalloys

Ai, Songyuan; Lupínc, V.; Maldini, M.

doi:10.1016/0956-716x(92)90287-o

Cited by 46 publications

(9 citation statements)

References 7 publications

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“…This porosity is represented by small, faceted pores of a few micrometers in size, see Figure 1c. Because of their crystallographic shape, such pores are called as “negative crystals.” [ 9 ] The growth of these pores in single‐crystal superalloys was reported in many papers, [ 10–13 ] and it was shown that they form by condensation of vacancies emitted by the edge parts of dislocations climbing along the γ/γ’ interfaces. [ 13 ] It is proposed to call the types of pores mentioned earlier, respectively, as solidification (S), homogenization (H), and deformation (D) pores.…”

Section: Introductionmentioning

confidence: 99%

Refinement and Experimental Validation of a Vacancy Model of Pore Annihilation in Single‐Crystal Nickel‐Base Superalloys during Hot Isostatic Pressing

et al. 2021

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Initially, as-cast and homogenized single crystals of nickel-base superalloy CMSX-4 are subjected to hot isostatic pressing at 1288 C. Two series of experiments are conducted: under the same pressure of 103 MPa but with different durations, between 0.5 and 6 h, and under different pressures, between 15 and 150 MPa, but for the same time of 0.5 h. The porosity annihilation is investigated metallographically and by high-resolution synchrotron X-ray tomography. The obtained experimental results are compared with the predictions of the vacancy model proposed recently in the group. Herein, the model is further refined by coupling with X-ray tomography. The model describes the evolution of the pore arrays enclosed in the 3D synchrotron tomograms during hot isostatic pressing and properly predicts the time and stress dependences of the pore annihilation kinetics. The validated model and the obtained experimental results are used for selecting the optimal technological parameters such as applied pressure and processing time.

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Section: Introductionmentioning

confidence: 99%

Refinement and Experimental Validation of a Vacancy Model of Pore Annihilation in Single‐Crystal Nickel‐Base Superalloys during Hot Isostatic Pressing

et al. 2021

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“…They annihilate with two c channel dislocations of opposite signs on the other side of the c¢ raft. [26][27][28][29] (5) Creep rupture of Ni-based single-crystal superalloys seems to initiate by the formation of microcracks at pre-existing cast voids [30] and proceed by subsequent microcrack growth. [30][31][32] These damage accumulation processes may well affect tertiary creep of Ni-base single-crystal superalloys.…”

Section: Introductionmentioning

confidence: 99%

Miniature Specimen Assessment of Creep of the Single-Crystal Superalloy LEK 94 in the 1000 °C Temperature Range

Mälzer

Hayes²,

Mack

et al. 2007

Metall Mater Trans A

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The creep behavior of the Ni-base superalloy LEK 94 in the 1000°C range has been investigated. Miniature tensile specimens were employed, which can be taken out of a thin walled blade or used when only limited amounts of material are available. We show that this miniature test technique yields reasonable creep data, including stress exponents n and apparent activation energies Q app . The n values are close to 5 and the Q app values are close to 500 kJ/mole, independent of the crystallographic direction. Creep rates are fastest for samples oriented in the [110] direction, followed by [001] samples. The lowest creep rates are observed for the [111] direction. This difference is related to a difference in resolved shear stresses and in the number of activated crystallographic slip systems. As a striking new result, it was observed that the onset of tertiary creep occurs earlier and rupture strains are significantly smaller in the case of [110] specimens as compared to [100] specimens, while the [111] specimens show an intermediate behavior. These effects are related to the alignment of cast porosity along the axis of primary dendrites. When cast micropores align perpendicular to the axis of the applied tensile stress, the onset of fast tertiary creep occurs early and small rupture strains are observed.

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“…There are different opinions about the presence of pores at single crystal superalloys during creep tests. It was thought no new pores formed during creep test [8]. Komenda et al [10] found that the number of pores in CMSX-4 increased with creep strain during creep at 950 • C, and that a marginal increase in pores content could be detected in spite of a large amount of creep deformation at 750 • C. They attributed the increase of void amount at high temperature to the diffusion-assisted growth of pre-existing micropores which sizes are less than the resolution of microscope.…”

Section: Role Of Subgrain Boundaries In Bonding Zone Of Tlp Joint Durmentioning

confidence: 99%

“…While the creep fracture mechanism of single crystal superalloys has been investigated [7][8][9], very little attention has been paid to creep fracture mechanism of TLP joint of single crystal superalloy. The purpose of the present paper is to investigate the creep fracture process of TLP joint and find out the reason for the peculiar fracture mechanism.…”

Section: Introductionmentioning

confidence: 99%