Grain Boundary Deformation-Induced Intergranular Stress Corrosion Cracking of Ni-16Cr-9Fe in 360°C Water

Alexandreanu, B.; Was, G. S.

doi:10.5006/1.3277600

Cited by 38 publications

(18 citation statements)

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“…Most likely, the grain boundary sliding occurred during the repair of this weld due to high residual stresses and local heating. Because grain boundary sliding is a precursor to intergranular SCC initiation, 54 these observations suggest that the interface may be quite susceptible to SCC. Nevertheless, the picture shown in Fig.…”

Section: Field Alloysmentioning

confidence: 97%

Crack growth rates and metallographic examinations of Alloy 600 and Alloy 82/182 from field components and laboratory materials tested in PWR environments.

Alexandreanu¹,

Chopra²,

Shack³

2008

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In light water reactors, components made of nickel-base alloys are susceptible to environmentally assisted cracking. This report summarizes the crack growth rate results and related metallography for field and laboratory-procured Alloy 600 and its weld alloys tested in pressurized water reactor (PWR) environments. The report also presents crack growth rate (CGR) results for a shielded-metal-arc weld of Alloy 182 in a simulated PWR environment as a function of temperature between 290°C and 350°C. These data were used to determine the activation energy for crack growth in Alloy 182 welds. The tests were performed by measuring the changes in the stress corrosion CGR as the temperatures were varied during the test. The difference in electrochemical potential between the specimen and the Ni/NiO line was maintained constant at each temperature by adjusting the hydrogen overpressure on the water supply tank. The CGR data as a function of temperature yielded activation energies of 252 kJ/mol for a double-J weld and 189 kJ/mol for a deep-groove weld. These values are in good agreement with the data reported in the literature. The data reported here and those in the literature suggest that the average activation energy for Alloy 182 welds is on the order of 220-230 kJ/mol, higher than the 130 kJ/mol commonly used for Alloy 600. The consequences of using a larger value of activation energy for SCC CGR data analysis are discussed.iv This page is intentionally left blank. Foreword vThis report presents crack growth rate (CGR) data and the results of the corresponding fracture surface and metallographic examinations from cyclic loading and primary water stress-corrosion cracking (PWSCC) tests of two nickel-base Alloy 182 (A182) weldments. These weldments are typical of those used in vessel penetrations and piping butt welds in nuclear power plants. The effect of crack orientation with respect to dendrite orientation is the most significant variable investigated in this study. However, this report also compiles data from other laboratories that describe the effects of material composition, loading characteristics, and chemistry of the aqueous environment. The PWSCC growth rates described for the A182 specimens in the report are comparable to the CGR that characterize the performance of Alloy 600 (A600).This report is one of a series of reports documenting the results of CGR testing in vessel head penetration materials. This report focuses on the Alloy 82 (A82) and A182 weld metals. This report also presents results from tests of the A600 base metal. The researchers tested (1) a laboratory-fabricated, shieldedmetal-arc deposit of A182; (2) a weldment sample from the J-groove weld of a control rod drive mechanism nozzle from the Davis-Besse Nuclear Power Plant; and (3) a hot leg nozzle-to-safe end weld from the Virgil C. Summer Nuclear Station.

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Section: Field Alloysmentioning

confidence: 97%

Crack growth rates and metallographic examinations of Alloy 600 and Alloy 82/182 from field components and laboratory materials tested in PWR environments.

Alexandreanu¹,

Chopra²,

Shack³

2008

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“…7,8,23) Figure 8 shows the angular distribution of step angle obtained using ðp s Þ, which is normalized by the sum of step angles, together with the experimental results shown in Fig. 3.…”

Section: Non-crystal Model (Nc Model)mentioning

confidence: 99%

“…Therefore, the angular distribution of step angle can be estimated from evaluating RSS. In the NC model, which was used in previous studies, 7,8,23) the crystal was assumed to slip in an arbitrary direction once the slip plane was specified. The maximum RSS on a slip plane under a tensile stress is given by…”

Section: Non-crystal Model (Nc Model)mentioning

confidence: 99%

“…The angle can be geometrically obtained from ' and p s using Since it is difficult to identify the angle ' by surface observation, a uniform angular distribution of ' was assumed under an angle p s in the previous studies. 7,8,23) Then, for each step angle p s , the average RSS on the slip plane can be estimated by averaging the values for all possible ' values as…”

Section: Non-crystal Model (Nc Model)mentioning

confidence: 99%

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Angular Distribution of Slip Steps by Three-Dimensional Polycrystalline Model for Stainless Steel

Kamaya¹,

Fukuya²,

Kitamura

2009

Journal of Nuclear Science and Technology

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Localized deformation plays an important role in the initiation of irradiation-assisted stress corrosion cracking, and it can be characterized by the spacing and inclination of slip steps observed on the surface. In order to examine the contribution of mechanical factors (stress) to slipping, the angular distribution of slip steps was evaluated by using a three-dimensional polycrystalline model generated by Voronoi tessellation. An elastic finite element analysis was performed to derive the resolved shear stress (RSS) acting on each slip system. Random crystallographic orientations assigned to each grain caused the microstructural inhomogeneity of local stress due to anisotropic elastic properties. The angular distribution obtained was compared with the experimental results observed in irradiated and deformed stainless steel. It was shown that mechanical factors dominate the slipping behavior of the irradiated stainless steel and that not only RSS but also normal stress acting on the slip plane affects the crystallographic slip. The angular distribution was also evaluated from the maximum Schmid factor of individual grains, in which the inhomogeneous local stress was not taken into account. The angular distributions obtained using RSS and the Schmid factor were almost the same. This suggests that the inhomogeneity of local stress negligibly affects the angular distribution of slip steps, although the change in the local stress in the polycrystalline material is significant.

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“…We hypothesize that a boundary with a weak Taylor factor mismatch -as would be the case for two neighboring grains sharing a similar orientation -would be less susceptible to deformation, thus less susceptible to cracking. 44 The following experiment was conducted to test this hypothesis. To determine whether the cracking behavior of a grain boundary is influenced by the relative orientation of the adjacent grains, OIM maps were acquired on the cross sections, along the crack path of two specimens, CT31-W02 TS (deep-groove weld) and CT933-TS (double-J weld), from the SCC regions.…”

Section: Effect Of Grain Boundary Type and Relative Grain Orientationmentioning

confidence: 99%

Crack growth rates of nickel alloy welds in a PWR environment.

Alexandreanu¹,

Chopra²,

Shack³

2006

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In light water reactors (LWRs), vessel internal components made of nickel-base alloys are susceptible to environmentally assisted cracking. A better understanding of the causes and mechanisms of this cracking may permit less conservative estimates of damage accumulation and requirements on inspection intervals. A program is being conducted at Argonne National Laboratory to evaluate the resistance of Ni alloys and their welds to environmentally assisted cracking in simulated LWR coolant environments. This report presents crack growth rate (CGR) results for Alloy 182 shielded-metal-arc weld metal in a simulated pressurized water reactor (PWR) environment at 320°C. Crack growth tests were conducted on 1-T compact tension specimens with different weld orientations from both double-J and deep-groove welds. The results indicate little or no environmental enhancement of fatigue CGRs of Alloy 182 weld metal in the PWR environment. The CGRs of Alloy 182 in the PWR environment are a factor of ≈5 higher than those of Alloy 600 in air under the same loading conditions. The stress corrosion cracking for the Alloy 182 weld is close to the average behavior of Alloy 600 in the PWR environment. The weld orientation was found to have a profound effect on the magnitude of crack growth: cracking was found to propagate faster along the dendrites than across them. The existing CGR data for Ni-alloy weld metals have been compiled and evaluated to establish the effects of key material, loading, and environmental parameters on CGRs in PWR environments. The results from the present study are compared with the existing CGR data for Ni-alloy welds to determine the relative susceptibility of the specific Ni-alloy weld to environmentally enhanced cracking. iv Intentionally Left BlankForeword v This report presents crack growth rate data and the results of the corresponding fracture surface and metallographic examinations from cyclic loading and primary water stress-corrosion cracking (PWSCC) tests of two nickel-base Alloy 182 (A182) weldments, which are typical of those used in vessel penetrations and piping butt welds in nuclear power plants. The effect of crack orientation with respect to dendrite orientation is the most significant variable investigated in this study. However, this report also includes a review of data from several laboratories, which describes the effects of material composition, loading characteristics, and chemistry of the aqueous environment. The main conclusion is that the PWSCC growth rates described for A182 specimens in this report are comparable to the crack growth rates that characterize the performance of Alloy 600 (A600).This report is the first in a series documenting the results of crack growth rate testing in vessel head penetration materials, focusing on the weld metals, A182 and A152, and including results of some tests of the base metals, A600 and (eventually) A690. The results presented in this report were obtained in tests of a laboratory-fabricated, shielded metal arc welding deposit of A182. ...

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Grain Boundary Deformation-Induced Intergranular Stress Corrosion Cracking of Ni-16Cr-9Fe in 360°C Water

Cited by 38 publications

References 1 publication

Crack growth rates and metallographic examinations of Alloy 600 and Alloy 82/182 from field components and laboratory materials tested in PWR environments.

Crack growth rates and metallographic examinations of Alloy 600 and Alloy 82/182 from field components and laboratory materials tested in PWR environments.

Angular Distribution of Slip Steps by Three-Dimensional Polycrystalline Model for Stainless Steel

Crack growth rates of nickel alloy welds in a PWR environment.

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