Influence of Grain Boundary Character on Creep Void Formation in Alloy 617

Lillo, T.M.; Cole, James I.; Frary, Megan; Schlegel, Scott

doi:10.1007/s11661-009-0051-7

Cited by 56 publications

(16 citation statements)

References 23 publications

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“…Recent work by Lillo et al suggested that significant creep cavitation did not occur in Alloy 617 until greater than 10% creep strain during creep deformation at 900°C and 1000°C (15). In the present work, cavities were not observed in any of the creep-fatigue specimens tested at 950°C with hold times as long as 1800 sec.…”

Section: Al Oxidesupporting

confidence: 43%

The Role of Environment on High Temperature Creep-Fatigue Behavior of Alloy 617

Carroll

Cabet

Wright

2010

ASME 2010 Pressure Vessels and Piping Conference: Volume 6, Parts a and B

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Alloy 617 is the leading candidate material for an intermediate heat exchanger (IHX) application of the Very High Temperature Nuclear Reactor (VHTR), expected to have an outlet temperature as high as 950°C. Acceptance of Alloy 617 in Section III of the ASME Code for nuclear construction requires a detailed understanding of the creep-fatigue behavior. Initial creep-fatigue work on Alloy 617 suggests a more dominant role of environment with increasing temperature and/or hold times evidenced through changes in creep-fatigue crack growth mechanism/s and failure life. Furthermore, previous work on corrosion of nickel base alloys in impure helium has suggested that this environment is far from inert with respect to Alloy 617. Continuous cycle fatigue and creepfatigue testing of Alloy 617 was conducted at 950°C and 0.3% and 0.6% total strain in air to simulate damage modes expected in a VHTR application. Continuous cycle and creep-fatigue specimens exhibited intergranular cracking, but did not show evidence of grain boundary cavitation. Despite the absence of grain boundary cavitation to accelerate crack propagation, the addition of a hold time at peak tensile strain was detrimental to cycle life. This suggests that creep-fatigue interaction may occur by a different mechanism or that the environment may be partially responsible for accelerating failure. INTRODUCTIONThe Next Generation Nuclear Plant (NGNP) being developed in the US is a Very High Temperature Nuclear Reactor (VHTR) with a gas as the primary coolant. Conceptual design requires an outlet temperature of greater than 850°C to efficiently generate hydrogen, with a maximum expected temperature of 950°C. A critical component in the VHTR system is the Intermediate Heat Exchanger (IHX), which will operate at the reactor outlet temperature of up to 950°C.

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Section: Al Oxidesupporting

confidence: 43%

The Role of Environment on High Temperature Creep-Fatigue Behavior of Alloy 617

Carroll

Cabet

Wright

2010

ASME 2010 Pressure Vessels and Piping Conference: Volume 6, Parts a and B

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“…During the constant load uniaxial creep testing at 900°C and 1000°C, creep cavitation did not occur in Alloy 617 until greater than ~10% creep strain [6]. Very limited cavity formation is observed in this alloy and a critical amount of creep deformation is required before creep cavities nucleate.…”

Section: Vib Creepmentioning

confidence: 87%

“…[6] Specimens had a 4.2 mm diameter and 16.6 mm gage length resulting in a gage length to diameter ratio of 4.0. The creep temperature was controlled to within ±3°C of the target creep temperature.…”

Section: Ivc Creep Testingmentioning

confidence: 99%

“…[9] Creep cavitation and wedge cracks were observed predominately near the surface and occurred within the decarburized region. The fatigue specimen tested in a helium environment, (~10 -4 /sec), exhibited a crack propagation mode that switched to intergranular [6]. The addition of a 60 sec tensile hold also resulted in the cracking initiating transgranularly and propagating by a mixed mode [9].…”

Section: Via Fatigue and Creep Fatiguementioning

confidence: 99%

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Characterization of elevated temperature properties of heat exchanger and steam generator alloys

Wright

Carroll

Cabet

et al. 2012

Nuclear Engineering and Design

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“…It has been further shown that voids form along the grain boundaries of high resolved tensile and shear stress, frequently accompanied by a high population of carbides (Lillo et al, 2009). It is easily imagined that a large fraction of the grain boundaries in a multiaxially loaded system satisfies these criteria for carbide redistribution and void formation.…”

Section: Discussionmentioning

confidence: 99%

Predicting Creep in Alloy 617 Pressurized Tubes Using Uniaxial Bar Test Data

Croteau¹,

Bateman²,

Bhetwal

et al. 2014

IJURCA

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This work has undergone a double-blind review by a minimum of two faculty members from institutions of higher learning from around the world. The faculty reviewers have expertise in disciplines closely related to those represented by this work. If possible, the work was also reviewed by undergraduates in collaboration with the faculty reviewers. AbstractAlloy 617, a nickel-based alloy, is a leading candidate for application in next-generation nuclear plants (NGNPs). Creep, a thermally activated, time-dependent deformation process impacts the lifetime and failure of heat exchangers used at the very high operating temperatures and pressures of such plants. Current methods of testing creep are generally limited to bar specimens in uniaxial tension. In an attempt to correlate uniaxial to multiaxial creep behavior a method to test creep in a pressurized tube was developed. Test specimens were pressurized with argon up to 3.5 MPa, and heated to 950°C. Creep rates were measured as strain rates by tracking diametric changes with time. Parallel experimental and modeling efforts were used to characterize creep behavior in the pressurized tubes. The aim of this research was to use the existing body of knowledge concerning creep in Alloy 617 to develop a model to accurately predict creep in tubular components. Towards this end, a constitutive model was developed and computer simulations undertaken which were ultimately verified experimentally.

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Influence of Grain Boundary Character on Creep Void Formation in Alloy 617

Cited by 56 publications

References 23 publications

The Role of Environment on High Temperature Creep-Fatigue Behavior of Alloy 617

The Role of Environment on High Temperature Creep-Fatigue Behavior of Alloy 617

Characterization of elevated temperature properties of heat exchanger and steam generator alloys

Predicting Creep in Alloy 617 Pressurized Tubes Using Uniaxial Bar Test Data

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