Combined effect of special grain boundaries and grain boundary carbides on IGSCC of Ni–16Cr–9Fe–xC alloys

Alexandreanu, B.; Capell, Brent; Was, Gary S.

doi:10.1016/s0921-5093(00)01705-6

Cited by 112 publications

(52 citation statements)

References 16 publications

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“…Lehockey and Palumbo 7 have shown that a high fraction of special boundaries significantly enhances the resistance to creep of pure nickel at elevated temperatures. Other studies [10][11][12][13][14][15][16][17][18][19] have demonstrated significant improvements in a number of properties, including stress-corrosion cracking, fatigue, weldability, and creep, with an increase in the special boundary fraction. In terms of stress-corrosion cracking, Ni, Ni-16Cr-9Fe-xC, and Alloy 600 have shown significant improvements with increased fractions of special boundaries, 11,13,16,19 and these findings have been attributed to both the intrinsic corrosion resistance, and the resistance to solute segregation and precipitation exhibited by special boundaries.…”

Section: Methodsmentioning

confidence: 99%

The evolution of grain-boundary cracking evaluated through in situ tensile-creep testing of Udimet alloy 188

et al. 2008

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In situ scanning electron microscopy was performed during elevated-temperature (ഛ760°C) tensile-creep deformation of a face-centered-cubic cobalt-based Udimet 188 alloy to characterize the deformation evolution and, in particular, the grain boundary-cracking evolution. In situ electron backscatter diffraction observations combined with in situ secondary electron imaging indicated that general high-angle grain boundaries were more susceptible to cracking than low-angle grain boundaries and coincident site-lattice boundaries. The extent of general high-angle grain-boundary cracking increased with increasing creep time. Grain-boundary cracking was also observed throughout subsurface locations as observed for postdeformed samples. The electron backscattered diffraction orientation mapping performed during in situ tensile-creep deformation proved to be a powerful means for characterizing the surface deformation evolution and in particular for quantifying the types of grain boundaries that preferentially cracked.

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Section: Methodsmentioning

confidence: 99%

The evolution of grain-boundary cracking evaluated through in situ tensile-creep testing of Udimet alloy 188

et al. 2008

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“…Both these parameters are known to influence the SCC behavior of austenitic alloys in high-temperature water environments. [46][47][48][49][50][51][52] The OIM analysis allows a classification of boundaries according to the coincident site lattice model as either coincident site lattice boundaries (CSLBs) or high-angle boundaries (HABs). The CSLBs are formed when the neighboring grains are in specific orientation relationships and have been shown to possess an increased resistance to SCC over HABs.…”

Section: Laboratory-prepared Alloysmentioning

confidence: 99%

“…The CSLBs are formed when the neighboring grains are in specific orientation relationships and have been shown to possess an increased resistance to SCC over HABs. [46][47][48][49][50][51][52] In addition, texture affects the high-temperature deformation behavior of a polycrystalline material and thus is expected to play a role in the SCC behavior as well. Figure 15 shows the grain-boundary character distribution (GBCD) of the weld alloys.…”

Section: Laboratory-prepared Alloysmentioning

confidence: 99%

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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“…Intergranular SCC behavior of austenitic alloys in high-temperature aqueous environments is known to be strongly influenced by the proportions of boundaries in special orientation relationships and the magnitude and location of residual stress. [32][33][34][35] Thus the information provided by the OIM analysis can give insights into the relative susceptibility of specific welds or components.…”

Section: Examination Of Weld Specimens By Orientation Imaging Microscopymentioning

confidence: 99%

Crack Growth Rates of Nickel Alloy Welds in a PWR Environment

Alexandreanu

Chopra

Shack

2006

Volume 1: Codes and Standards

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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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Combined effect of special grain boundaries and grain boundary carbides on IGSCC of Ni–16Cr–9Fe–xC alloys

Cited by 112 publications

References 16 publications

The evolution of grain-boundary cracking evaluated through in situ tensile-creep testing of Udimet alloy 188

The evolution of grain-boundary cracking evaluated through in situ tensile-creep testing of Udimet alloy 188

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 of Nickel Alloy Welds in a PWR Environment

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