Creep Damage Process and Crystal Misorientation Measurement of Ni-based Superalloy  IN738LC with Multiple Round Notches

Ni-base superalloys consisting of binary phases such as cuboidal γ’ (Ni3Al) precipitates orderly dispersed in the γ matrix (Ni-rich matrix) have been generally used for rotor blades in energy power plants. However, fine dispersed γ’ precipitates are coarsened perpendicularly to the applied load direction during high temperature creep loading. As this phenomenon called “Rafting” proceeds, the strengthened micro texture disappears and then, cracks starts to grow rapidly along the boundaries of the layered texture. Thus, it is very important to evaluate the change of the crystallinity of the alloy in detail for explicating the atomic scale damage process. In this study, the change of the micro-texture of the Ni-base superalloy (CM247LC) was observed by using EBSD method. The change in the crystallinity was evaluated using both Kernel Average Misorientation (KAM) and image quality (IQ) values. The KAM value indicates the dislocation density and the IQ value shows the order of atom arrangement in the observed area. As a result, KAM value showed no significant change with increasing the creep damage. On the other hand, the IQ value monotonically shifted to lower values and the average IQ value gradually decreased as the creep loading time increased. Decreasing IQ value without change in KAM value implies that the density of point defects such as vacancies mainly increased under creep loading and ordered Ll2 structure became disordered. Therefore, the creep damage of this alloy is mainly dominated by not the accumulation of dislocations, but the increase in the disorder of atom arrangement in the micro texture caused by the diffusion of component elements.

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The Creep-Damage Model of Salt Rock Based on Fractional Derivative

Energies ◽

10.3390/en11092349 ◽

2018 ◽

Vol 11 (9) ◽

pp. 2349 ◽

Cited By ~ 15

Author(s):

Hongwei Zhou ◽

Di Liu ◽

Gang Lei ◽

Dongjie Xue ◽

Yang Zhao

Keyword(s):

Fractional Derivative ◽

Creep Test ◽

Damage Model ◽

Creep Damage ◽

Uniaxial Stress ◽

Radioactive Waste Disposal ◽

Creep Process ◽

Salt Rock ◽

Damage Process ◽

Creep Damage Model

The use of salt rock for underground radioactive waste disposal facilities requires a comprehensive analysis of the creep-damage process in salt rock. A computer-controlled creep setup was employed to carry out a creep test of salt rock that lasted as long as 359 days under a constant uniaxial stress. The acoustic emission (AE) space-time evolution and energy-releasing characteristics during the creep test were studied in the meantime. A new creep-damage model is proposed on the basis of a fractional derivative by combining the AE statistical regularity. It indicates that the AE data in the non-decay creep process of salt rock can be divided into three stages. Furthermore, the authors propose a new creep-damage model of salt rock based on a fractional derivative. The parameters in the model were determined by the Quasi-Newton method. The fitting analysis suggests that the new creep-damage model provides a precise description of full creep regions in salt rock.

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High Temperature Damage of Ni-Base Superalloy Caused by the Change of Microtexture due to the Strain-Induced Anisotropic Diffusion of Component Elements

Volume 4: Energy Systems Analysis, Thermodynamics and Sustainability; Combustion Science and Engineering; Nanoengineering for Energy, Parts A and B ◽

10.1115/imece2011-62411 ◽

2011 ◽

Cited By ~ 1

Author(s):

Hideo Miura ◽

Ken Suzuki ◽

Yamato Sasaki ◽

Tomohiro Sano ◽

Naokazu Murata

Keyword(s):

High Temperature ◽

Anisotropic Diffusion ◽

Axial Strain ◽

Creep Damage ◽

Face Centered Cubic ◽

Directional Coarsening ◽

Damage Process ◽

Temperature Damage ◽

Face Centered ◽

Base Superalloy

In order to assure the reliability of advanced gas turbine systems, it is very important to evaluate the damage of high temperature materials such as Ni-base superalloys under creep and fatigue conditions quantitatively. Since the micro texture of the gamma-prime (γ′) phase was found to vary during the creep damage process, it is possible, therefore, to evaluate the creep damage of this material quantitatively by measuring the change of the micro texture. The mechanism of the directional coarsening of γ′ phasesof Ni-base superalloy under uni-axial strain at high temperatures, which is called rafting, was analyzed by using molecular dynamics (MD) analysis. The stress-induced anisotropic diffusion of Al atoms perpendicular to the finely dispersed γ/γ′ interface in the superalloy was observed clearly in a Ni(001)/Ni3Al(001) interface structure. The stress-induced anisotropic diffusion was validated by experiment using the stacked thin films structures which consisted of the (001) face-centered cubic (FCC) interface. The reduction of the diffusion of Al atoms perpendicular to the interface is thus, effective for improving the creep and fatigue resistance of the alloy. It was also found by MD analysis that the dopant elements in the superalloy also affected the strain-induced diffusion of Al atoms. Both palladium and tantalum were effective elements which restrain Al atoms from moving around the interface under the applied stress, while titanium and tungsten accelerated the strain-induced anisotropic diffusion, and thus, the rafting phenomenon.

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OS0804 EBSD Observation and Strain Evaluation on Creep Damage Process of SUS304HTB Steel

The Proceedings of the Materials and Mechanics Conference ◽

10.1299/jsmemm.2012._os0804-1_ ◽

2012 ◽

Vol 2012 (0) ◽

pp. _OS0804-1_-_OS0804-3_

Author(s):

Yoshiki MIZUTANI ◽

Kazunari FUJIYAMA ◽

Hirohisa KIMACHI

Keyword(s):

Creep Damage ◽

Damage Process

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OS1438 EBSD Observation of Creep Damage Process in Ni-Cr-Co-Fe Alloy

The Proceedings of the Materials and Mechanics Conference ◽

10.1299/jsmemm.2009.350 ◽

2009 ◽

Vol 2009 (0) ◽

pp. 350-351

Author(s):

Kazuto HIJIKURO ◽

Kazunari FUJIYAMA ◽

Hikaru NAKASEKO ◽

Ryuichi ISHII ◽

Takehisa HINO

Keyword(s):

Creep Damage ◽

Damage Process

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A Study of High Temperature Damage Processes Using Microradiography

MRS Proceedings ◽

10.1557/proc-142-195 ◽

1988 ◽

Vol 142 ◽

Author(s):

J. E. Benci ◽

D. P. Pope

Keyword(s):

Image Analysis ◽

Alloy Steel ◽

Hydrostatic Stress ◽

Equivalent Stress ◽

Creep Damage ◽

Tensile Tests ◽

Crack Plane ◽

Image Analysis System ◽

Low Alloy Steel ◽

Damage Process

AbstractSynchrotron radiation and microradiographic techniques were used to study the development of creep damage in notched tensile samples. The creep damage in these samples was recorded using microradiography. The density and distribution of creep damage was measured from the microradiographs using an image analysis system. The results from the image analysis can be compared to damage predictions from finite element models of the damage process to determine the quality of these models.Notched tensile samples of copper, iron and a low alloy steel were subjected to slow strain rate tensile tests at 500°C or 700°C. The tests were interrupted after various fractions of the creep lives had been expended. 1 mm thick longitudinal sections were then removed from the center of each sample for microradiography using electro-discharge machining.Creep damage in the copper alloy was concentrated in a fairly narrow band around the plane of minimum cross-section in the samples. This is in stark contrast to the results from iron and the low alloy steel. The creep damage in these materials developed at fairly sharp angles to the notch or crack plane. These results show that the damage process in iron and this steel is controlled by the equivalent stress while the formation of damage in copper is controlled by the maximum principal or hydrostatic stress.

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The Creep-Damage Model of Salt Rock Based on Fractional Derivative

10.20944/preprints201807.0584.v1 ◽

2018 ◽

Author(s):

Hongwei Zhou ◽

Di Liu ◽

Gang Lei ◽

Dongjie Xue ◽

Yang Zhao

Keyword(s):

Fractional Derivative ◽

Creep Test ◽

Damage Model ◽

Creep Damage ◽

Uniaxial Stress ◽

Radioactive Waste Disposal ◽

Creep Process ◽

Salt Rock ◽

Damage Process ◽

Creep Damage Model

The use of salt rock for underground radioactive waste disposal facilities requires a comprehensive analysis of creep-damage process in salt rock. A computer-controlled creep setup is employed to carry out a creep test of salt rock lasted as long as 359 days under a constant uniaxial stress. The AE space-time evolution and energy releasing characteristics during creep test are studied in the meantime. A new creep-damage model is proposed on the basis of fractional derivative by combining the AE statistical regularity. It indicates that the AE data in non-decay creep process of salt rock can be divided into three stages. Furthermore, the parameters of new creep-damage model are determined by Quasi-Newton method. The fitting analysis suggests that the creep-damage model based on fractional derivative in this paper provides a precise description of full creep regions in salt rock.

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Evaluation of Microstructures and Creep Damages in HAZ of P91 Steel Weldment

Volume 6: Materials and Fabrication ◽

10.1115/pvp2007-26495 ◽

2007 ◽

Author(s):

Masaaki Tabuchi ◽

Hiromichi Hongo ◽

Yongkui Li ◽

Takashi Watanabe ◽

Yukio Takahashi

Keyword(s):

Damage Mechanics ◽

Early Stage ◽

Rupture Life ◽

Creep Damage ◽

Specimen Thickness ◽

Creep Tests ◽

Steel Weldment ◽

Type Iv ◽

Damage Process ◽

Term Creep

The present paper aims to clarify the Type IV creep damage process of Mod.9Cr-1Mo (Gr.91) steel weldment. Long-term creep tests for base metal and simulated fine-grained HAZ and welded joints were conducted at 550, 600 and 650 °C. Furthermore, creep tests of thick welded joint specimens were interrupted at 0.2, 0.5, 0.7, 0.8, 0.9 of rupture life, and damage distributions were measured quantitatively. It was found that creep voids initiated at the early stage of life inside the specimen thickness, and grew into cracks at the later stage of life. Experimental creep damage distributions were compared with computed ones using FEM and damage mechanics analysis. The effect of multiaxial stress condition on creep damage evolution is discussed.

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Creep Damage Process of Ni-Base Superalloy Caused by Stress-Induced Anisotropic Atomic Diffusion

Journal of Solid Mechanics and Materials Engineering ◽

10.1299/jmmp.3.487 ◽

2009 ◽

Vol 3 (3) ◽

pp. 487-497 ◽

Cited By ~ 2

Author(s):

Ken SUZUKI ◽

Hiroyuki ITO ◽

Tatsuya INOUE ◽

Hideo MIURA

Keyword(s):

Creep Damage ◽

Atomic Diffusion ◽

Damage Process ◽

Base Superalloy

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Formulation of Cross-Hardening in Creep and its Effect on the Creep Damage Process of Copper

Journal of Engineering Materials and Technology ◽

10.1115/1.3225856 ◽

1986 ◽

Vol 108 (2) ◽

pp. 167-173 ◽

Cited By ~ 15

Author(s):

S. Murakami ◽

Y. Sanomura ◽

K. Saitoh

Keyword(s):

Creep Damage ◽

Principal Stress Rotation ◽

Stress Rotation ◽

Polycrystalline Metals ◽

Proposed Model ◽

Slip Planes ◽

Damage Process ◽

Cross Hardening ◽

Active Slip ◽

Anisotropic Creep

The present paper is concerned with the modelling of creep and creep damage in polycrystalline metals and the experimental evaluation of the proposed model. By ascribing the reduction of creep rates caused by the principal stress rotation (i.e., cross-hardening) to the intersection mechanism of dislocations on active slip planes in crystal grains, a constitutive equation of creep describing the cross-hardening is first formulated. Then, in view of the metallurgical observations on the nucleation and the growth of grain boundary cavities in the creep damage process, an evolution equation of anisotropic creep damage is expressed as a function of the stress, a second rank damage tensor and the creep rate of the material. Finally, the validity of the proposed theory is discussed by performing systematic creep damage tests of thin-walled copper tubes under nonsteady multiaxial states of stress at 250°C.

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