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Light Water Reactor Sustainability Research and Development Fracture Resistance of Cast Stainless Steels after Thermal Aging for up to 10000 Hours Cast Stainless Steel Aging (LW-18OR040215)

September 2018

U.S. Depart of Energy

Office of Nuclear Energy

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DISCLAIMER This information was prepared as an account of work sponsored by an agency of the U.S. Government. Neither the U.S. Government nor any agency thereof, nor any of their employees, makes any warranty, expressed or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness, of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. References herein to any specific commercial product, process, or service by trade name, trade mark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the U.S. Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the U.S. Government or any agency thereof.

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Department of Energy/Office of Nuclear Energy

LWR Sustainability R&D Cast Stainless Steels Aging (WP#: LW-18OR040215)

Fracture Resistance of Cast Stainless Steels after Thermal Aging for up to 10000 Hours

Thak Sang Byun (PI) David A. Collins, Emily L. Barkley, Timothy G. Lach

Pacific Northwest National Laboratory Feng Yu

Electric Power Research Institute

Pacific Northwest National Laboratory operated by

Battelle for the

U.S. Department of Energy under contract DE-AC05-76RL01830

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TABLE OF CONTENT LIST OF TABLES AND FIGURES ------------------------------------------------------------------------------ 5

ABSTRACT ------------------------------------------------------------------------------------------------------------ 7

1. INTRODUCTION ----------------------------------------------------------------------------------------------- 8

2. EXPERIMENTAL --------------------------------------------------------------------------------------------- 10

2.1. Test materials ----------------------------------------------------------------------------------------------------------------- 10 2.2. Fracture toughness testing and data analysis ------------------------------------------------------------------------- 12

3. EFFECTS OF THERMAL AGING ON FRACTURE TOUGHNESS ----------------------------- 14

3.1. Selected fracture resistance (J-R) curves -------------------------------------------------------------------------------- 14 3.2. Activation energies and a new definition of aging parameter ---------------------------------------------------- 23 3.3. Fracture toughness versus aging parameter curves ----------------------------------------------------------------- 24

4. SUMMARY AND CONCLUSIONS ----------------------------------------------------------------------- 32

REFERENCES ------------------------------------------------------------------------------------------------------- 33

APPENDIX: TABLES OF FRACTURE TOUGHNESS DATA ------------------------------------------ 35

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LIST OF TABLES AND FIGURES

Table 2-1. Chemical compositions of model and EPRI-provided CASS materials. The amounts are given in wt.% for main alloy elements or in ppm for trace elements, i.e., C, S, O and N. ................................. 10

Table 2-2. δ-ferrite content measured in the as-cast condition (the volume fraction in % was calculated from FN measurements) ........................................................................................................................... 11

Figure 2-1. SEB specimen geometry showing a 15% deep groove on each side. .................................... 12

Figure 3-1. Selected J-R curves for the wrought alloy 304L, which was aged for 10kh at four different temperatures and tested at 330°C. ............................................................................................................. 15

Figure 3-2. Selected J-R curves for the wrought alloy 316L, which was aged for 10kh at four different temperatures and tested at 330°C. ............................................................................................................. 15

Figure 3-3. Selected J-R curves for the cast alloy CF3, which was aged for 10kh at four different temperatures and tested at 330°C. ............................................................................................................. 17

Figure 3-4. Selected J-R curves for the cast alloy CF3M, which was aged for 10kh at four different temperatures and tested at 330°C. ............................................................................................................. 18

Figure 3-5. Selected J-R curves for the cast alloy CF8, which was aged for 10kh at four different temperatures and tested at 330°C. ............................................................................................................. 18

Figure 3-6. Selected J-R curves for the cast alloy CF8M, which was aged for 10kh at four different temperatures and tested at 330°C. ............................................................................................................. 19

Figure 3-7. Selected J-R curves for the cast alloy CF8 (ELB), which was aged for 10kh at two different temperatures and tested at 330°C. ............................................................................................................. 21

Figure 3-8. Selected J-R curves for the cast alloy CF8M (K23), which was aged for 10kh at four different temperatures and tested at 330°C. .............................................................................................. 21

Figure 3-9. Selected J-R curves for the cast alloy CF8 (S43), which was aged for 10kh at four different temperatures and tested at 330°C. ............................................................................................................. 22

Figure 3-10. Selected J-R curves for the cast alloy CF3 (Z21), which was aged for 10kh at four different temperatures and tested at 330°C. ............................................................................................................. 22

Table 3-1. Conversion of aging time and temperature to aging parameter A (Q = 215 kJ/mole) ............ 24

Figure 3-11. Dependence of fracture toughness on the aging parameter for 304L. ................................ 25

Figure 3-12. Dependence of fracture toughness on the aging parameter for 316L. ................................. 25

Figure 3-13. Aging parameter dependence of fracture toughness for CF3. .............................................. 27

Figure 3-14. Aging parameter dependence of fracture toughness for CF3M. .......................................... 27

Figure 3-15. Aging parameter dependence of fracture toughness for CF8. .............................................. 28

Figure 3-16. Aging parameter dependence of fracture toughness for CF8M. .......................................... 28

Figure 3-17. Aging parameter dependence of fracture toughness for CF8 (ELB). .................................. 30

Figure 3-18. Aging parameter dependence of fracture toughness for CF8 (S43). .................................... 30

Figure 3-19. Aging parameter dependence of fracture toughness for CF8M (K23). ............................... 31

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Figure 3-20. Aging parameter dependence of fracture toughness for CF3 (Z21). ................................... 31

Table A1. Crack lengths, aging parameters, and fracture toughness parameters for wrought 304L. ....... 36

Table A2. Crack lengths, aging parameters, and fracture toughness parameters for wrought 316L. ....... 37

Table A3. Crack lengths, aging parameters, and fracture toughness parameters for static cast CF3. ...... 38

Table A4. Crack lengths, aging parameters, and fracture toughness parameters for static cast CF3M. .. 39

Table A5. Crack lengths, aging parameters, and fracture toughness parameters for static cast CF8. ...... 40

Table A6. Crack lengths, aging parameters, and fracture toughness parameters for static cast CF8M. .. 41

Table A7. Crack lengths, aging parameters, and fracture toughness parameters for static cast CF8 (ELB).................................................................................................................................................................... 42

Table A8. Crack lengths, aging parameters, and fracture toughness parameters for centrifugal cast CF8M (K23 & K25). ............................................................................................................................................ 43

Table A9. Crack lengths, aging parameters, and fracture toughness parameters for static cast CF8 (S43 & S52). ...................................................................................................................................................... 44

Table A10. Crack lengths, aging parameters, and fracture toughness parameters for centrifugal cast CF3 (Z21 & Z43). ............................................................................................................................................. 45

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Fracture Resistance of Cast Stainless Steels after Thermal Aging for up to 10000 Hours Thak Sang Byun, David A. Collins, Emily L. Barkley, Timothy G. Lach Pacific Northwest National Laboratory Feng Yu Electric Power Research Institute

ABSTRACT This work package, Cast Stainless Steel Aging, aims to achieve a comprehensive scientific

understanding of the aging and failure phenomena in cast austenitic stainless steels (CASSs) using holistic experimental and modeling methods and to provide a practical and science-based model to predict the degree of thermal degradation of CASS components in extended-term operations. The test materials in the project include four model CASSs (CF3, CF3M, CF8, and CF8M), four EPRI-provided CASSs (CF3, two CF8s, and CF8M), and two reference wrought materials (304L and 316L); the δ-ferrite content of these materials ranges from ~2% for the wrought alloys to 33% for one of the EPRI-provided alloys. These materials have been thermally aged at two light water reactor (LWR)-relevant temperatures (290 and 330°C) and at two accelerated-aging temperatures (360 and 400°C) for up to three years.

In the 2018 fiscal year, the fracture toughness tests and J-R curve calculations were completed for the listed materials aged up to 10,000 hours. This report is to present the results of the static fracture (J-R) testing for the model and EPRI-provided CASS materials after thermal aging up to 10,000 hours. In order to quantify the effects of thermal aging, a new aging parameter (A) was defined so that the effects of aging degradation could be compared against a single variable. This definition is used to scale an aging time at a temperature to the effective aging time at a reference temperature based on the Arrhenius equation, which is a rate theory equation for thermally activated mechanisms. The fracture test results are presented in the forms of fracture resistance (J-R or J-Δa) curves, KJQ versus A curves, and tabulated crack length and fracture toughness data for more than 460 fracture tests. The fracture test results indicate that the fracture toughness tends to increase in early aging; after a short time, however, it decreases with the aging parameter at a rate dependent on the volume fraction of δ-ferrite. Overall, the decrease of static fracture toughness due to thermal aging is less significant than that of the Charpy impact energy, which is usually measured as the reduction of the upper shelf energy and the shift of the ductile-brittle transition temperature. The preliminary conclusion regarding the static fracture behavior of aged CASS materials derived from this research is that the cast stainless steels with δ-ferrite contents less than ~20% will not undergo a significant reduction of static fracture toughness or embrittlement over the extended lifetimes of reactors.

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1. INTRODUCTION

The coolant system of a pressurized water reactor is built to remove thermal energy from the reactor core and transfer that energy to the steam turbine. Therefore, its components are extensively exposed to the damaging environments of high temperature (270–330°C), high pressure (~15.5 MPa), corrosive coolant chemistry, and radiation, and can be subjected to various safety issues in long-term operation [1-3]. The cast iron-chromium-nickel (Fe-Cr-Ni) alloys with mostly 300-series stainless steel compositions and austenite (γ)–ferrite (δ) duplex structures have been used for the majority of the components of the primary coolant system because of their high heat and corrosion resistance [2-7]. In particular, these cast austenitic stainless steel (CASS) materials are most commonly used for the massive primary coolant system components such as coolant piping, valve bodies, pump casings, and piping elbows. Since a large number of CASS components are installed in every nuclear power plant and, since replacing such massive components is prohibitively expensive, any significant degradation in the mechanical properties (cracking resistance in particular) that affects the structural integrity of the CASS components is a serious threat to the performance of entire nuclear power plant [2,3]. In most past researches, however, the CASS materials were thermally aged in selected (i.e. highly accelerated) conditions only, and the material properties measured were also highly limited. In fact, the existing prediction models and criteria for the integrity of CASS components were established based on incomplete datasets including estimated fracture toughness values [8,9]; naturally, these models lack the ability to predict system integrity during the proposed extended-term operations. Therefore, the ongoing research, Cast Stainless Steel Aging, aims to systematically expand the scientific understanding and property database of thermal-aging induced degradation in CASSs, and ultimately to provide a knowledge-based, conclusive prediction for the integrity of CASS components during the service life extended up to and beyond 60 years [2].

The CASS alloys generally have an austenite (γ)–ferrite (δ) duplex structure which results from the casting process; this process consists of alloy melting and either pouring or centrifugally injecting liquid metal into a static or spinning mold [4-7]. Although the commonly used static and centrifugal casting processes enable the fabrication of massive components with proper resistance to environmental attacks, the alloying and microstructural conditions are not highly controllable in actual fabrication, especially in the casting processes of massive components. Therefore, the actual microstructure of a CASS component varies widely with its composition, casting method, and wall thickness (i.e., cooling rate). The most common cast stainless alloy grades include the CF3 and CF8 alloy families with nominally ~19% Cr and ~10% Ni and 3–30% δ-ferrite [8-16]. The minor (δ-ferrite) phase is inevitably formed during the casting process, and is in a non-equilibrium state subject to detrimental changes during exposure to elevated temperature and/or radiation.

The degree of aging degradation in a CASS alloy is determined by the chemistry and processing route of the alloy [8-18] because these determine the amount and distribution of δ-ferrite and small precipitates. The primary fracture mechanism observed in a thermally embrittled duplex stainless steel is cleavage initiation at the aged δ-ferrite followed by propagation through separation of the ferrite-austenite phase boundary. This cracking mechanism could be caused or enhanced by various microstructural changes during thermal aging, such as the formation of a Cr–rich α'-phase through the spinodal decomposition of δ-ferrite, precipitation of G-phase and M23C6 carbide, and additional precipitation and growth of carbides and nitrides at ferrite-austenite phase and grain boundaries [21-31]. In the austenite matrix, on the other hand, thermal aging induces various precipitations but usually causes a more moderate to negligible effect on the properties of the phase [12-15].

This research project has investigated the thermal aging effects in four model CASSs (CF3, CF3M,

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CF8, and CF8M) and four EPRI-provided CASSs (CF3, two CF8s, and CF8M). These materials have been thermally aged at LWR-relevant temperatures (290 and 330°C) as well as at accelerated-aging temperatures (360 and 400°C) to cover a large range of aging parameter and to validate the accelerated aging technique by comparison. To quantify the degradation of CASS materials during thermal aging, the mechanical properties (fracture toughness, tensile strength and ductility, and Charpy impact energy) of eight CASS materials and two wrought stainless steels aged at 290–400°C have been evaluated. Recently, the fracture toughness tests and J-R curve calculations were completed for all ten materials aged up to 10,000 hours. This report is to present the fracture toughness data from that testing campaign as well as to draw a preliminary prediction on the overall static facture behavior of the CASS materials in extended operations.

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2. EXPERIMENTAL

2.1. Test materials The most common CASS materials used in nuclear power plants are CF grades, which normally

have alloy compositions of ~19% Cr and ~10% Ni and austenitic(γ)-ferritic(δ) duplex structures [9-12]. The volume fraction of δ-ferrite formed during the casting process is dependent on the cooling rate, which is usually influenced by the size of the CASS component and casting method (typically static casting or centrifugal casting) as well as the composition of the alloy. Nuclear grade CASS alloys typically contain 3–30% δ-ferrite in an austenite matrix [2]. Since the volume fraction of the retained δ-ferrite is the most influential parameter related to the degree and rate of aging degradation, eight cast stainless steels containing a wide range of δ-ferrite (4–33%) and two reference wrought alloys with < 3% δ-ferrite were tested in this research [32].

Table 1 lists the chemistries of the four model and four EPRI-provided CASS alloys, along with the fabrication methods and geometries of the raw materials [6]. The primarily controlled-elements are C and Mo; the CF3 and CF3M have a lower carbon content (< 0.03 wt.%), while the CF3M and CF8M are alloyed with 2–3 wt.% Mo. The four model CASS alloys (CF3, CF3M, CF8, and CF8M) have been produced in the form of small (Ø~10 cm × L~40 cm) ingots to have relatively low δ-ferrite volume fractions (4–16%), while the four EPRI-provided alloys (CF8M(K23), CF8(S43), CF3(Z21), and CF8(ELB)) were taken from simulated or vintage components in EPRI’s storage yard in Charlotte, NC; these materials have higher δ-ferrite contents (11–33%). All chemical composition data was produced by Dirats Laboratories in Westfield, MA.

Table 2-1. Chemical compositions of model and EPRI-provided CASS materials. The amounts are given in wt.% for main alloy elements or in ppm for trace elements, i.e., C, S, O and N.

Grade (Equivalent Wrought Steel or Component) Fe Cr Ni Mn Mo Si Cu Co V P C S O N CF3 (304L) (~10 cm dia. Ingot) Model/Static casting Bal. 19.17 8.11 1.44 0.34 0.99 0.41 0.18 0.07 0.029 262 324 204 1020

CF3M (316L) (~10 cm dia. Ingot) Model/Static casting Bal. 19.28 9.81 1.14 2.30 1.22 0.28 0.15 0.05 0.033 284 253 224 838

CF8 (304) (~10 cm dia. Ingot) Model/Static casting Bal. 18.72 8.91 1.10 0.29 1.27 0.29 0.15 0.05 0.026 665 376 161 606

CF8M (316) (~10 cm dia. Ingot) Model/Static casting Bal. 18.52 10.38 0.65 2.33 1.02 0.33 0.17 0.06 0.031 433 243 207 1020

CF8 (ELB) (20.3 cm thick elbow) Vintage/Static casting Bal. 21.20 8.45 0.61 0.18 1.78 0.16 0.04 0.02 0.017 360 60 53 411

CF8 (S43) (8.6 cm thick piping) Vintage/Static casting Bal. 20.01 8.61 0.57 0.30 1.31 0.07 0.08 0.02 0.031 590 130 36 450

CF8M (K23) (6.9 cm thick piping) Simulated/Centrifugal casting Bal. 20.77 10.16 0.95 2.51 0.85 0.39 0.16 0.07 0.032 590 220 25 1500

CF3 (Z21) (10.4 cm thick piping) Vintage/Centrifugal casting Bal. 20.69 9.57 0.89 0.14 1.10 0.10 0.03 0.04 0.023 220 30 53 572

For this research, these eight CASS materials, reference wrought stainless steels 304L and 316L, and

three weld alloys have been thermally aged in large capacity furnaces set at 290, 330, 360, and 400°C since either 2014 or 2015. Except for the weld alloys, which is part of I-NERI collaboration, the aging time for the materials has reached 30 kh in this fiscal year and the characterization of the 30 kh aged

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materials is underway. This report presents the fracture toughness datasets for the four model alloys and two wrought alloys aged for 0h, 1.5 kh and 10 kh and for the four EPRI-provided alloys after aging for 0 h and 10 kh.

Table 2-2 lists the δ-ferrite content of the CASS alloys in the as-cast condition [32]. The ferrite numbers (FNs) were measured from the Charpy impact or three-point bend bar fracture specimens using a ferrometer (model: Feritscope-FMP30C of Fisher Co.). For each alloy, many (30–50) FNs were measured and statistically analyzed to provide the data in the table; the volume fraction data listed was converted from the FN measurements.

Among the model alloys, the CF3M alloy has the highest volume fraction average of 15.7%, which is followed by CF3 with 12.4%. The CF8 and CF8M contain relatively low δ-ferrite contents, 4.7 and 5.6% respectively. These model alloys were likely produced at rather high cooling rates as the ingots were only ~10 cm diameter. Table 2-2 also shows that the centrifugal cast CF3 (Z21, Z43) and CF8M (K23, K25) pipings have similar δ-ferrite contents (~12%) as those of the model alloys CF3 and CF3M (< 16%). Both of the static cast materials, CF8 (pipings S43, S52) and CF8 (elbow ELB), however, contain much higher δ-ferrite contents (25–33%). In particular, the CF8 (ELB) alloy has the highest δ-ferrite content (33%) as its cooling was the slowest due to its size (~20 cm thick) and its static casting production method. The casting method is believed to be the most influential factor related to the δ-ferrite content; the Mo and C contents are believed to be the next most influential factors. The chemical composition and cooling rate determine the microstructure after casting, especially the volume fractions of the ferrite (δ) and austenite (γ) phases. The δ-ferrite content can vary widely with the thermal history of the casting process since the cooling rate during the ferrite formation region of the phase diagram might determine the total exposure time for ferrite formation.

Table 2-2. δ-ferrite content measured in the as-cast condition (the volume fraction in % was calculated from FN measurements)

Grade FN STDEV (FN) Vol.% STDEV (Vol.%)

CF3 (Model Alloys) 11.4 0.88 12.4 1.02 CF3M (Model Alloys) 14.6 1.53 15.7 1.76 CF8 (Model Alloys) 4.2 1.01 4.7 1.17 CF8M (Model Alloys) 4.9 0.52 5.6 0.60

CF8M Simulated/Centrifugal

K23 10.4 1.69 11.4 1.94 K25* 11.8 1.82 12.9 2.09

CF8 Vintage/Static

S43 24.7 3.13 25.1 3.57 S52* 31.1 3.35 30.6 3.82

CF3 Vintage/Centrifugal

Z21 10.8 2.21 11.8 2.53 Z43* 11.3 2.60 12.3 2.97

CF8 (ELB) Vintage/Static (Elbow) 34.0 3.75 33.0 4.26 *The second rings machined from the same pipings; the fracture toughness data in as-cast condition are

included in this report.

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2.2. Fracture toughness testing and data analysis Single-edge bend bar (SEB) specimens were used for static fracture testing; the geometry of these

specimens is shown in Figure 2-1. The bars have a center notch approximately 3.5mm deep and side grooves approximately 1.5mm deep on each side of the notch. The purpose of these side grooves was to enhance stress triaxiality (or strain constraint) in the three-point bend loading condition and to guide the direction of crack propagation, which can otherwise be very erratic in ductile materials. For precracking and static fracture testing these samples were loaded in a three-point bend mode, with the span of the bend being approximately 40mm.

Figure 2-1. SEB specimen geometry showing a 15% deep groove on each side.

The SEB specimens were precracked in air at room temperature by cyclically loading between 2100N and 100N at 10 Hz. In order to achieve a desired precrack length of 5 mm or half the width of the specimen (initial crack ratio a/w ≈ 0.5), the displacement mean was monitored until it had increased by 70-100 microns; this generally occurred between 30-100k cycles. The maximum load was then decreased to 1100N and an additional 10k cycles were applied to sharpen the crack tip to maximize the localized stresses at the crack tip.

Static fracture testing was performed at a constant displacement rate using a TestResources servo-electric testing system equipped with a high temperature furnace. Each sample was heated in the zero-load condition in air to the desired temperature; the temperature of the sample was monitored directly via a thermocouple fed through the furnace. Once the sample was within ±3°C of the targeted test temperature, a 100N load was applied and the relative displacement was set to 0 mm for initialization. The sample was then tested at a displacement rate of 0.005 mm/sec and a data acquisition rate of 5 Hz. The load was monitored until the maximum load was reached; the testing machine was then programmed to stop the test once the load had dropped below 55% of the peak load. For this set of tests,

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the nominal test temperatures were room temperature (typically 22°C), 200°C, 290°C, 330°C, 360°C, and 400°C.

After testing, the samples were heat tinted to mark the final crack length, then the samples were bent in half until broken completely. The initial and final crack lengths of each sample were measured by examining the fracture surfaces under a low-magnification optical microscope equipped with a digital camera; the length of the crack was measured in pixels and then converted to the value in mm. As the crack fronts were not perfectly straight, initial and final crack lengths were calculated using a weighted average in accordance with the ASTM standard method E1820 [33]. Nine evenly-spaced points were measured across the initial and final crack fronts, two along the side grooves and seven in between. The lengths of the crack at the side grooves were weighted each at ½, then all the lengths were averaged over a factor of 8.

Prior to calculating the J-R curves and fracture toughness values, the raw data was first smoothed to 100±30 load-displacement data points by averaging the raw data points over the appropriate data spans. Once the raw data had been smoothed, the J-R curve and fracture toughness values were calculated using a modified version of the curve normalization method as outlined in the standard method [33]; this was the only available method as no external displacement gauge was used and frictions at specimen-grip contact faces are too high at elevated temperatures to accurately measure unloading compliances. Modifications were made in a few places to accommodate the simplification of the data acquisition; the main modification made in the J-R data calculation regards the use of displacement data either from the built-in displacement device or from the cross-head movement. Further, as the cast and wrought stainless steel specimens were softer than those for which the ASTM method is generally used, and because the subsize SEB specimen design, even with such deep side grooves, limited the degree of constraint at the crack tip, a couple of modifications had to be made in the calculations to compensate for the excessive ductility. First, the true ultimate tensile stress was used to calculate the flow stress as opposed to the engineering ultimate tensile stress. This is a correction to account for the high uniform ductility of stainless steels. Second, the final fracture length used in the calculations often differed somewhat from the optically measured final fracture length. This correction was used because the iterative calculations which determine the final calculated crack length assume a continuous normalized load-displacement curve; in many cases, in order for this condition to be true, the calculated final crack length differed from the actual value.

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3. EFFECTS OF THERMAL AGING ON FRACTURE TOUGHNESS Currently, more than 460 fracture toughness tests have been performed in this research, which

includes the baseline fracture tests for the as-cast and as-wrought stainless steels [32] as well as the fracture tests after aging for 1.5kh and 10kh at four temperatures presented in this report. In this chapter, only selected sets of J-R curves and fracture toughness data are displayed and discussed for elucidating the effects of thermal aging: (i) Figures 3-1 through 3-10 represent selected J-R curves for all 10 materials tested at 330°C, (ii) Figures 3-11 through 3-20 compare the KJQ versus A (aging parameter) curves for each alloy to display the effect of thermal aging on fracture toughness; the data displayed in these figures are for the specimens tested at 22°C, 290°C, and 400°C only. A full list of fracture toughness values for each alloy at each testing and aging condition is given in Appendix A. The tables in the appendix include both the J-integral value and the stress intensity factor (K) value for each specimen, which are determined at the intersections of the J-R curve with the 0.1 mm and 0.2 mm offset lines of its crack blunting line.

3.1. Selected fracture resistance (J-R) curves

The objective of this project is to evaluate the effect of thermal aging on the mechanical properties of the cast and wrought stainless materials, which are measured by uniaxial tensile, Charpy impact fracture, and static fracture testing. The J-R curve is a useful tool for determining the static fracture resistance of a material, which is essentially a measure of the interplay between crack growth and energy absorbed by the material. In this section, examples of J-R curves of aged and non-aged cast stainless steels are displayed. J-R curves of wrought alloys are also displayed in this section as reference datasets.

Though there are several microstructural factors that may determine the toughness of the cast materials, one of the most prominent and easy to quantify is the amount of the δ-ferrite in the material formed during the casting process. The δ-ferrite phase is highly susceptible to spinodal decomposition, G-phase formation, and segregation at its interface with the austenite matrix. As these are all causes of reduced mechanical performance or embrittlement, the susceptibility of a cast material to aging degradation will be strongly intertwined with the amount of δ-ferrite present. Therefore, the amount of initial δ-ferrite, aging condition, and test temperature for each material will be the key parameters discussed in the following two sections.

As shown in Figures 3-1 and 3-2 for the wrought alloys 304L and 316L (chemically equivalent to CF3 and CF3M, respectively), both materials show excellent fracture resistance regardless of the aging conditions. These materials have very low ferrite contents (< ~3%), so any degradation effects within that part of the microstructure are unlikely to have a significant effect on the macro-scale mechanical properties. Statistical variability between specimens would be the factor most responsible for the differences between the curves, whereas only insignificant or slow degradation with thermal aging is observed for these materials. The J-R curves for 316L do show some dependence on the aging conditions, with the pristine and 10kh/290°C materials showing the best performance and the 10kh/400°C showing the worst; the increased presence of molybdenum may have some effect on the 316L since molybdenum is a ferrite-stabilizing element. Regardless, all the materials in Figures 3-1 and 3-2 show excellent properties.

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Figure 3-1. Selected J-R curves for the wrought alloy 304L, which was aged for 10kh at four different

temperatures and tested at 330°C.

Figure 3-2. Selected J-R curves for the wrought alloy 316L, which was aged for 10kh at four different

temperatures and tested at 330°C.

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Example J-R curves of the model CASS materials (CF3, CF3M, CF8 and CF8M) are displayed in Figures 3-3 through 3-6, respectively. To understand the detailed fracture resistance behavior of these model alloys, it needs to be considered that the relatively high cooling rate during casting due to the small ingot diameters (typically ~10 cm) resulted in low δ-ferrite contents and fine grain structures. In the cast alloys with low δ-ferrite contents the effect of degradation of the δ-ferrite phase is not expected to be a predominant factor in the macroscopic property changes; changes in these properties might be similarly contributed to some minor effects such as softening in the austenite phase and stress relaxation. Therefore, the dependence of fracture toughness on the aging conditions may not be simply proportional to the main microstructural processes in the δ-ferrite, but rather may be more complex and involve multiple microstructural features and processes.

Figure 3-3 shows the J-R curves for non-aged CF3 (~12% δ-ferrite) tested at 330°C. Relative to its wrought material counterpart (304L), it has considerably lower fracture resistance overall. Even an elevated level of ferrite has an adverse effect on the fracture toughness, regardless of whether or not the material has degraded. When compared to the J-R curve of non-aged CF3, the 290°C and 330°C aged materials actually show better resistance to crack propagation over the whole crack extension range; the J-values of the 360°C and 400°C aged materials become higher in the larger crack range as well. It is obvious that the thermal aging of cast materials sometimes results in thermally induced toughening, albeit the degree of toughening is not significant and it might only improve the properties of the materials with low amounts of δ-ferrite. This could be attributed to several factors regarding the non-equilibrium as-cast status of the material, including possible thermal softening due to diffusion and dislocation movement and the resultant relaxation of internal stresses. It is also possible that the 290°C and 330°C materials had a lower ferrite content than the pristine materials and were therefore less affected by its presence, even possibly to the point that the expected effects of thermal degradation were offset.

Figure 3-4 shows selected curves for CF3M (~16% δ-ferrite), a high-molybdenum version of CF3 and the chemical counterpart of 316L. For this material, there doesn’t appear to be any apparent correlation between aging temperature and fracture resistance. Though the pristine material shows somewhat better fracture resistance at room temperature, the temperature-dependent interplay between strength and ductility can make these properties more unpredictable at elevated temperatures. An embrittled material may be less tough than a pristine material at room temperature, the hardening mechanism associated with that embrittlement can improve that material’s resistance to softening at elevated temperature, giving it superior properties relative to the non-aged material.

Figure 3-5 displays the J-R curves for CF8 (~5% δ-ferrite) tested at 330°C. Its carbon content is higher than that of CF3, but its molybdenum amount is lower. On the whole, its qualitative behavior is similar to that of CF3 and CF3M. Unlike the two previous cast materials, the pristine material shows the best fracture resistance, while the worst is arguably that of the 400°C aged material, though it could be argued the 330°C aged material is worse, depending on what crack length is considered. As with the other materials, the correlation between δ-ferrite content, aging condition, and fracture properties is complex. However, in this case, the ferrite content of these materials is relatively low, whereas for CF3 and CF3M the ferrite content is higher. The CF3 and CF3M contrast with the CF8 in that for the former two materials the pristine versions of the materials show relatively poor behavior compared to their aged versions, whereas the pristine CF8 material performs noticeably better than its aged versions. It is possible that the thermal degradation of the other microstructural features in the material is dominating the mechanical properties. Obviously, aging does have some effect on this material, but it is unclear that if the ferrite content is high enough to be the driving force or if some other factor is dominant.

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Figure 3-6 shows J-R curves for CF8M (~6% δ-ferrite), a high-molybdenum version of CF8. In this plot, the pristine material shows the worst properties while the 400°C aged material generally shows the best and the other three materials are somewhere in between. This behavior is reflected in the behavior of this material at room temperature, with the material aged at 400°C showing the highest toughness and the pristine material showing only slightly better toughness than the material aged at 360°C. Since the material subjected to the most extreme aging conditions actually shows the best properties at both room temperature and elevated temperature, it can be concluded that at a δ-ferrite content of ~6% the ferrite content is low enough that its spinodal decomposition and embrittlement is not the dominant factor related to the overall aging effects, at least for this particular material. It would appear that the effects of aging on the other microstructural features are dominant for this material, and those effects provide a toughening rather than an embrittling effect.

Figure 3-3. Selected J-R curves for the cast alloy CF3, which was aged for 10kh at four different

temperatures and tested at 330°C.

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Figure 3-4. Selected J-R curves for the cast alloy CF3M, which was aged for 10kh at four different

temperatures and tested at 330°C.

Figure 3-5. Selected J-R curves for the cast alloy CF8, which was aged for 10kh at four different

temperatures and tested at 330°C.

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Figure 3-6. Selected J-R curves for the cast alloy CF8M, which was aged for 10kh at four different

temperatures and tested at 330°C.

Figures 3-7 through 3-10 display the selected J-R curves of the EPRI-provided CASS materials (CF8 (ELB), CF8M (K23), CF8 (S43), and CF3 (Z21)). These materials have a wider range of δ-ferrite content than the model alloys, and therefore the effects of aging on fracture resistance are expected to vary more widely. In particular, the static cast alloys with the highest δ-ferrite contents, CF8 (ELB) and CF8 (S43) (~33% and ~25%, respectively), demonstrate more obvious and profound fracture resistance degradation. The centrifugally cast alloys, CF8M (K23) and CF3 (Z21), show less significant and mixed degradation behavior.

Figure 3-7 compares three J-R curves for the CF8 (ELB) material with ~33% δ-ferrite. All three materials perform better at 330°C than at room temperature, even the pristine material. It seems that the degraded ferrite in the 10kh/330°C material is still reasonably ductile when tested at 330°C and hence the 330°C aged material can perform comparably with the pristine material; the 360°C aged material performs significantly more poorly. Although not shown here, the effect of such a high ferrite content is highly apparent at room temperature, with the 10kh/360°C material performing very poorly, the pristine material performing reasonably well, and the 10kh/330°C performing somewhere in between. All three materials show a similar temperature dependence on toughness, where the toughness is low at low (RT) and high (400°C) test temperatures, but relatively high at moderate temperatures (290-330°C). However, the more extreme the aging conditions the material has been subjected to are, the more extreme the reduction in fracture toughness will be relative to the less-aged materials for the same temperature. It appears that with such a high ferrite content the material will become degraded so much that elevating the test temperature cannot improve its fracture toughness.

As can be seen in Figure 3-8, which shows several J-R curves for the alloy CF8M (K23, with ~11%

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δ-ferrite), the degree of thermal aging in this material is generally indicative of its fracture resistance, with the pristine material performing the best and the more heavily-aged materials performing the worst. It seems obvious that these EPRI-provided materials, which might have enough annealing effects during cooling (i.e., stress relaxation and near-equilibrium phases), demonstrate aging degradation in a more orderly manner. That is, the property degradation is proportional to the degree of thermal aging. Further, the fine microstructure with a limited amount of ferrite, which resulted from the centrifugal casting, seems to have muted the detrimental effect of the high Mo content. With such a non-dramatic degradation in toughness, it is probably better to think of the performance of these materials based on how the curves cluster rather than the individual curves themselves. For example, it can be assumed that a relatively low-aged material will perform comparable to the pristine and 290°C aged materials, whereas a more heavily-aged one will perform similar to the other three; this can be inferred based on the two fairly distinct clusters of the J-R curves for those particular materials. Assuming this, these curves are useful for approximating the performance of a material not explicitly characterized here.

The J-R curves for CF8 (S43, δ-ferrite content ~25%) obtained at 330°Care compared in Figure 3-9. For this static cast material, though its δ-ferrite content is the second highest among the ten alloys, the effects of aging are not particularly noticeable except for the 360°C and 400°C aged materials. It is chemically equivalent to ELB and its performance is remarkably similar—the pristine and 330°C aged material perform roughly the same while the 360°C material does not perform as well, though the difference in performance for this material is less extreme and can probably be attributed at least in part to the lower ferrite content relative to ELB. As expected, the 400°C aged material performs the worst. For materials with high ferrite content aged 10kh at 330°C and below, it would seem that at elevated temperatures the performance of the degraded materials is comparable to that of the pristine materials.

Figure 3-10 shows several J-R curves for CF3 (Z21, ~12% δ-ferrite). As with the other low-molybdenum EPRI-provided materials, its performance seems to show that for materials aged at or above 360°C there is a decrease in performance relative to those aged at 330°C, at least for this test temperature (though the 10kh/290°C material was tested at 330°C, its J-R curve proved difficult to construct, but it showed a very high fracture toughness). An interesting observation for this material is that, although it is chemically and ferrite-content-wise very similar to the model alloy CF3, its fracture toughness for the respective aging conditions is much higher than that of the model alloy version. Indeed, the results in Figures 3-3 and 3-10 contrast the influence of different fabrication routes with very close chemistries: the centrifugal cast Z21 (CF3) demonstrates much better fracture resistance than its static cast counterpart or model alloy CF3. Further, when compared to the 304L alloy with similar chemistry but dissimilar ferrite content, the performance is similar for aging at or below 330°C, but whereas the J-R curves of the 304L cluster closely regardless of aging, there is a noticeable drop in performance for materials aged at 360°C and above. It should be noted that the worst-performing Z21 material shown here performs comparatively to the best-performing model alloy CF3 material shown in Figure 3-3. Despite similar chemistries and ferrite contents these two materials display wildly varying properties—obviously whatever microstructural differences that exist between these two materials, most likely the grain size, are highly influential, and it is likely they have a significant influence on the mechanical properties of the other materials as well.

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Figure 3-7. Selected J-R curves for the cast alloy CF8 (ELB), which was aged for 10kh at two different

temperatures and tested at 330°C.

Figure 3-8. Selected J-R curves for the cast alloy CF8M (K23), which was aged for 10kh at four

different temperatures and tested at 330°C.

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Figure 3-9. Selected J-R curves for the cast alloy CF8 (S43), which was aged for 10kh at four different

temperatures and tested at 330°C.

Figure 3-10. Selected J-R curves for the cast alloy CF3 (Z21), which was aged for 10kh at four different

temperatures and tested at 330°C.

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3.2. Activation energies and a new definition of aging parameter Thermal aging of cast stainless steels with duplex structures involves multiple major and minor

mechanisms in the constituent phases [17-31]. It is known that the spinodal decomposition and G-phase formation in δ-ferrite and segregation and precipitation at interfaces and grain boundaries are the main property degradation mechanisms. Other minor processes such as the stress relaxation in the early aging stage and precipitation of carbide and other phases in the austenite and boundaries will also affect the properties. The kinetics of these aging mechanisms will also be vastly different and strongly dependent on aging temperature and alloy composition. Therefore, defining a universal parameter to measure the degree of thermal aging is not a simple task. Traditionally, the degree of thermal aging has been defined as a measure of aging time at a temperature based on the Arrhenius' equation. Arrhenius' equation gives the dependence of the rate constant of a thermally activated reaction on the absolute temperature as well as a pre-exponential factor and other constants of the reaction. A thermal aging parameter that has been used for the aging of cast stainless steels was defined by [10]

𝑃𝑃 = 𝑙𝑙𝑙𝑙𝑙𝑙10 < 𝑡𝑡 × 𝑒𝑒𝑒𝑒𝑒𝑒 [(−𝑄𝑄 /𝑅𝑅) ∗ (1𝑇𝑇−

1673.15

)] >

where t = aging time at temperature T (in K), Q = activation energy (J/mole), R = gas constant (8.3145 J/(K·mole)).

This aging parameter P is the logarithm of the aging time at T scaled to the time at 673.15 K (400°C). Since this aging parameter is defined only for aged status, the data of non-aged materials (t=0) cannot be expressed in the same equation. Also, the aging time scaled to the time of accelerated aging at 400°C is arbitrary and is not directly related to the reactor operation. In this research, therefore, the aging times are scaled to those at a representative coolant temperature of 325 °C and one (1) is added to the scaled times to avoid having the indefinite value for the non-aged materials. Then, the parameter is expressed as

𝐴𝐴 = 𝑙𝑙𝑙𝑙 < 1 + 𝑡𝑡 × 𝑒𝑒𝑒𝑒𝑒𝑒 [(−𝑄𝑄 /𝑅𝑅) ∗ (1𝑇𝑇− 1

598.15)] >.

In this definition of aging parameter, the activation energy (Q) is, again, the most important but highly unknown parameter. The activation energy measured by a specific mechanical property change, such as the increase in hardness or decrease in toughness, may not accurately represent the microstructural processes during aging because those macroscopic properties can be influenced both positively and negatively by the effects of multiple aging processes. Some precipitation mechanisms may soften a phase, which generally helps increase fracture toughness, but may also provide new crack initiation sites, which will lower the toughness value. For instance, some Charpy-impact datasets yielded activation energies in the range of 75–100 kJ/mole, which is well below the average value of ~215 kJ/mole for chromium bulk diffusion [34-36]; this has been assumed to be rate-controlling in the low-temperature decomposition of the ferritic phase [12,37]. The activation energies for diffusion of metallic alloy elements in the ferrite phase are in the 180–250 kJ/mole rage [34-43]. For example, the activation energies for Ni and Fe diffusion are known to be, respectively, lower and higher than that of Cr [40]. This Q-range should approximately represent the spinodal decomposition process to form α′ and α phases in various conditions. It was also shown that the activation energies measured for the spinodal decomposition and G-phase precipitation were very similar, and a value of 243±80 kJ/mole was

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obtained for both mechanisms [44]. Recognizing that these complexities can lead to significant uncertainties when calculating the aging parameter (A), we decided to use the average activation energy measured for the chromium bulk diffusion (215 kJ/mole) in the calculation of aging parameter A as a gage for the degree of thermal aging. Table 3-1 shows the conversion of the aging times at different temperatures to equivalent aging times at 325°C and then to the parameter A.

Table 3-1. Conversion of aging time and temperature to aging parameter A (Q = 215 kJ/mole)

Aging Temp. (°C) Aging Time (h) Aging Time at 325°C (h) Aging Time at 325°C (year) A - 0 0 0.00 0.00

290 1500 102 0.01 4.64 330 1500 2147 0.25 7.67 360 1500 16366 1.87 9.70 400 1500 185319 21.16 12.13 290 10000 681 0.08 6.53 330 10000 14310 1.63 9.57 360 10000 109108 12.46 11.60 400 10000 1235458 141.03 14.03

3.3. Fracture toughness versus aging parameter curves Effects of thermal aging on fracture toughness (KJQ) in two reference wrought alloys are presented in

Figures 3-11 and 3-12, in which KJQ is given as a function of A (aging parameter). As listed in Table 3-1, the range of these plots covers practically more than 80 years of reactor operation. Also note that the KJQ data presented in this section, i.e., from the tests at 22°C, 290°C, and 400°C, is less than a half of the total amount of data provided in Appendix-A, with the intended purpose here being better clarity in expression and comparison. In these first two plots, all room temperature data seems to fall within the experimental scattering range. Small aging degradations are observed in the data obtained at 290°C and 400°C, but only in the relatively high-A region. For any A, fracture toughness decreases with test temperature. Despite both of these thermally induced decreases, the wrought alloys 304L and 316L retained high fracture toughness well over 400 MPa√m in any tested condition.

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Figure 3-11. Dependence of fracture toughness on the aging parameter for 304L.

Figure 3-12. Dependence of fracture toughness on the aging parameter for 316L.

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Figures 3-13 to 3-16 present the KJQ versus A curves for the four model CASS materials. In Figure 3-13 it is obvious that initial aging ductilizes the cast materials; the non-aged CF3 alloy has a lower fracture toughness than the alloy with the lowest degree of aging (290°C/1.5kh, A = 4.64) at all three test temperatures. The effect of test temperature is more obvious in the lower A region than in the high A region, where no significant test temperature effect is observed. For each test temperature, the initial increase of KJQ is followed by a rapid decrease until A = 11.6, from which KJQ tends to increase. This slight increase of fracture toughness in the highest A region is likely due to over aging or completion of major aging processes. It is notable that, even if the total decrease of KJQ between 4.64 and 11.6 is significant (the room temperature dataset shows a more than 50% reduction), the minimum KJQ values are still respectfully high for such highly aged materials; over the aging and testing ranges no sign of embrittlement was observed. Figure 3-14 shows that the dependence of fracture toughness on A for CF3M is similar to that of CF3, except for the highest KJQ at 22°C and A = 0, and the more obvious test temperature dependence in the high A region. As these two static cast materials contain similar amounts of δ-ferrite, ~12% and ~16%, respectively, their overall ranges of KJQ values are also similar.

The model CASS alloys CF8 and CF8M contain small amounts of δ-ferrite, ~5% and ~6% respectively, and accordingly, the dependence of fracture toughness on A appears to be insignificant in these alloys, as seen in Figures 3-15 and 3-16. Further, the dependence of fracture toughness on test temperature is generally dependent on the aging parameter region, but this dependence is not obvious in these datasets overall. The CF8 alloy, with the lowest ferrite content among the model CASS materials as well as a lower molybdenum content, demonstrates relatively high fracture toughness over the whole A range; it never decreases below ~250 MPa√m. Meanwhile, the fracture toughness data of the CF8M alloy is in similar range, but a few lower values near 200 MPa√m are found at a high A of ~12.

As listed in Table 3-1, the 80 years of CASS component operation at 325°C is within the range of aging parameter A covered in the research, although the highest As are for the 400°C or highly accelerated aging treatment. It can be stated, therefore, that the minimum fracture toughness among the data given in these plots, ~200 MPa√m, will be the worst case expected in the extended plant lifetime. In summary, the four model CASS alloys demonstrated high fracture toughness after no or a low degree of thermal aging, and thermal degradation afterwards was not profound. This can probably be attributed to the cooling rates in the casting process being relatively high as their ingot diameters were relatively small (< ~10cm). This resulted in relatively low δ-ferrite amounts (<16%), and may have led to the formation of fine microstructures, both of which lead to relatively high fracture toughness and resistance to aging embrittlement.

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Figure 3-13. Aging parameter dependence of fracture toughness for CF3.

Figure 3-14. Aging parameter dependence of fracture toughness for CF3M.

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Figure 3-15. Aging parameter dependence of fracture toughness for CF8.

Figure 3-16. Aging parameter dependence of fracture toughness for CF8M.

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Figures 3-17 and 3-18 display the KJQ versus A curves for the two static cast materials of the four EPRI-provided materials. Both of these elbow (ELB) and piping (S43) materials have CF8 compositions; their δ-ferrite volume fractions are 33% and 25%, respectively, which were highest among all the materials tested in the research. Because of this, the degradation of fracture resistance and toughness is steepest with these alloys. The CF8 (ELB) alloy shows a steep decrease of KJQ with increasing A at all test temperatures; in particular, its KJQ at room temperature was mostly lower than at elevated temperatures, and it decreased with A to slightly above 100 MPa√m, below which the alloy would lose capability as a structural material. This poor behavior at room temperature might be because the ELB alloy has a relatively low strength due to a coarse microstructure formed during slow cooling in the casting process, and because the unique linear slip, which usually is a preferred deformation mechanism under high stress and can result in high ductility and toughness, was not activated in fracture testing. (Note that, because of the limited amount of materials, the CF8 (ELB) alloy was aged in selected conditions only and therefore the number of KJQ values reported here is also limited. The plots in Figure 3-17 might fail to show the possible initial increase of fracture toughness.)

The A-dependence of KJQ for the alloy CF8 (S43) shown in Figure 3-18 resembles that of the model alloys displayed in Figures 3-13, 3-14, and 3-16; there is a clear initial increase of KJQ, followed by a steep decrease, then by a saturation or slight increase at high A values. A few differences are observed as well; the fracture toughness overall is higher in CF8 (S43) than in the model alloys, and the decrease of KJQ is steeper in the A-range of 4–12. Comparing the KJQ versus A plots presented in this report, it is evident that the rate of decrease of fracture toughness in the A-range is dependent on the δ-ferrite content of the alloy.

Figures 3-19 and 3-20 show the effects of aging on the fracture toughness of CF8M (K23) and CF3 (Z21) alloys. Both piping materials were produced through centrifugal casting and have similar amounts of δ-ferrite, 11% and 12% respectively. These δ-ferrite amounts are close to those of static cast model alloys CF3 and CF3M. While the aging effect on KJQ in the CF8M (K23) is close to that of the model alloys, the same effect in CF3 (Z21) seems quite different from that of the static cast model alloys. This might be because the centrifugal cast has produced a finer microstructure in this alloy which can lead to a high fracture toughness. The overall level of KJQ in the Z21 material is highest among the tested cast alloys; the fracture toughness before aging is in the range of 500–800 MPa√m, which is a similar fracture toughness range as that of the wrought alloys, and while some steep decreases are found as the aging parameter increases, the KJQ values remained near or above 300 MPa√m at the highest degree of thermal aging.

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Figure 3-17. Aging parameter dependence of fracture toughness for CF8 (ELB).

Figure 3-18. Aging parameter dependence of fracture toughness for CF8 (S43).

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Figure 3-19. Aging parameter dependence of fracture toughness for CF8M (K23).

Figure 3-20. Aging parameter dependence of fracture toughness for CF3 (Z21).

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4. SUMMARY AND CONCLUSIONS Fracture toughness has been considered as a key parameter that can directly gage thermal

degradation of many large CASS components in nuclear power plants, and retaining high fracture toughness is critical to the structural integrity of the components and entire reactor coolant system. The CASS portfolio in the project includes four model CASSs (CF3, CF3M, CF8, and CF8M) and four EPRI-provided CASSs (CF3, two CF8s, and CF8M). These materials have been thermally aged at 290, 330, 360 and 400°C for more than three years as of today. Two wrought stainless steels, 304L and 316L, have also been aged along with the cast stainless steels to obtain reference degradation data with nearly pure austenitic alloys.

As a main activity of the work scope for the fiscal year, we have carried out a testing and evaluation campaign aimed at building a large fracture toughness database for a variety of CASS materials after thermal aging. It was expected that the campaign outcomes would lead to a useful conclusion regarding the static fracture of CASS components in design or extended term operations. Since the start of the project, more than 460 static fracture toughness (J-R) tests have been completed for the eight CASS and two wrought materials aged up to 10 kh, the results of which are presented in this report. Listed below are the main observations of the campaign:

(1) A new aging parameter (A) was defined to present the aging degradation of the mechanical properties against one common variable, which was based on the Arrhenius equation for scaling the aging times between different aging temperatures. For a conversion of aging time (t) and temperature (T) to an aging time at 325 °C, the parameter is given as

𝐴𝐴 = 𝑙𝑙𝑙𝑙 < 1 + 𝑡𝑡 × exp [(−𝑄𝑄 /𝑅𝑅) ∗ (1𝑇𝑇−

1598.15

)] >.

(2) Fracture test results indicate that the fracture toughness tends to increase in early aging; after a short time, however, it decreases with aging parameter at a rate dependent mostly on the volume fraction of δ-ferrite.

(3) Except for a few cases such as the static cast CF8 (ELB) with the highest δ-ferrite content (33%) and the CF3 (Z21) with extraordinary initial fracture toughness, the decrease of fracture toughness with A appears to stop at a high A of 12 or 14, and in some cases the recovery of fracture toughness due to overaging-induced ductilization is obvious.

(4) The reduction of static fracture toughness due to thermal aging is less significant than that of the Charpy impact energy, which is usually measured as the reduction of the upper shelf energy and the shift of the ductile-brittle transition temperature (see M2LW-17OR0402152).

(5) A preliminary conclusion derived for the static fracture behavior of aged CASS materials is that the cast stainless steels with δ-ferrite contents less than ~20% will not undergo a significant reduction of static fracture toughness or embrittlement over the extended lifetimes of reactors.

(6) In FY 2019, addition of the data for materials aged at 30kh as well as further analysis of current data is expected to help develop more refined criteria relating the microstructural properties and aging conditions of the materials to their mechanical properties.

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[29] K.H. Lo, C.H. Shek, J.K.L. Lai, Mater Sci Eng. R 65, 39 (2009).

[30] P. Hedström, S. Baghsheikhi, P. Liu, J. Odqvist, Mater. Sci. Eng. A 534, 552 (2012).

[31] C. Pareige, S. Novy, S. Saillet, P. Pareige, J. Nucl. Mater. 411, 90 (2011).

[32] T.S. Byun, T.G. Lach, D.A. Collins, E.L. Barkley, F. Yu, Mechanical and Microstructural Characteristics of Cast Stainless Steels after Thermal Aging for 10000 Hours, M2LW-17OR0402152 (PNNL-26656), August 2017.

[33] ASTM E1820 – 08: Standard Test Method for Measurement of Fracture Toughness. [34] A.F. Smith, R. Hales, The Diffusion of Chromium in a Duplex Alloy Steel, Metal Science, 10

(1976) 418-423. [35] A.W. Brown, G.M Leak, Diffusion in BCC Iron Base Alloys, Metall. Transact. 1 (1970) 2767-

2773. [36] P.I. Williams, R.G. Faulkner, Chemical volume diffusion coefficients for stainless steel corrosion

studies, J. Mater. Sci. 22 (1987) 3537-3542. [37] Z.B. Wang, N.R. Tao, W.P. Tong, J. Lu and K. Lu, Acta Mater. 51 (2003) 4319. [38] Z.B. Wang, N.R. Tao, W.P. Tong, J. Lu and K. Lu, Defect Diffusion Forum 249 (2006) 147-154. [39] A.W. Brown, G.M. Leak, Solute Diffusion in Alpha and Gamma-Iron, Metall. Transact.1 (1970)

1695-1700. [40] R.A. Perkins, R.A. Padgett, Jr., N. K. Tunali, Tracer Diffusion of 59Fe and 51Cr in Fe-17 Wt Pct

Cr-12 Wt Pct Ni Austenitic Alloy, Metall. Transact. 4 (1973) 2535-2540. [41] A.F. Smith, The Diffusion of Chromium in Type 316 Stainless steel, Metal Science, 9 (1975), 375-

378. [42] A. F. Smith & G. B. Gibbs, Volume and Grain-Boundary Diffusion in 20Cr/25 Ni/Nb Stainless

Steel, Metal Science, 3 (1969) 93-94. [43] C.C. Hsieh, W. Wu, Precipitation of σ Phase Using General Diffusion Equation with Comparison

to Vitek Diffusion Model in Dissimilar Stainless Steels, J. of Metallurgy, 2012, doi:10.1155/2012/154617.

[44] O.K. Chopra and W. L. Shack, Degradation of LWR Core Materials due to Neutron Irradiation (NUREG/CR-7027, 2010).

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APPENDIX: TABLES OF FRACTURE TOUGHNESS DATA

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Table A1. Crack lengths, aging parameters, and fracture toughness parameters for wrought 304L.

ID Initial Crack Length (mm)

Final Crack Length (mm)

Q (kJ/mole)

Aging Time (h)

Aging Temp. (°C)

Test Temp. (°C)

t(325°C) A JQ-0.1mm (kN/m)

JQ-0.2mm (kN/m)

KJQ-0.1mm (MPa√m)

KJQ-0.2mm (MPa√m)

304L-as received 4.79 7.81 215 0 22 0 0 2129 2277 663 685 304L-as received 4.19 7.86 215 0 200 0 0 2510 2555 719 726 304L-as received 4.55 7.99 215 0 290 0 0 1996 2040 624 631 304L-as received 4.60 7.77 215 0 330 0 0 1454 1469 533 536 304L-as received 4.54 7.85 215 0 360 0 0 1989 1985 623 623 304L-as received 4.47 7.78 215 0 400 0 0 1674 1701 572 577 304L-290°C-1.5kh 5.34 7.88 215 1500 290 22 102 4.64 1849 1959 617 636 304L-290°C-1.5kh 5.02 7.81 215 1500 290 200 102 4.64 1773 1798 605 609 304L-290°C-1.5kh 4.83 7.86 215 1500 290 290 102 4.64 1586 1608 557 561 304L-290°C-1.5kh 4.83 7.92 215 1500 290 330 102 4.64 1623 1675 563 572 304L-290°C-1.5kh 4.75 7.84 215 1500 290 360 102 4.64 1366 1409 517 525 304L-290°C-1.5kh 4.32 7.57 215 1500 290 400 102 4.64 1638 1648 566 567 304L-330°C-1.5kh 5.16 7.82 215 1500 330 22 2147 7.67 1819 1980 612 639 304L-330°C-1.5kh 4.85 7.77 215 1500 330 200 2147 7.67 1857 1874 619 622 304L-330°C-1.5kh 4.65 7.75 215 1500 330 290 2147 7.67 1456 1515 533 544 304L-330°C-1.5kh 4.70 7.83 215 1500 330 330 2147 7.67 1547 1541 550 549 304L-330°C-1.5kh 4.66 7.87 215 1500 330 360 2147 7.67 1734 1755 582 586 304L-330°C-1.5kh 4.58 7.74 215 1500 330 400 2147 7.67 1513 1540 544 548 304L-360°C-1.5kh 5.09 7.61 215 1500 360 22 16366 9.70 1865 1917 620 629 304L-360°C-1.5kh 4.43 7.87 215 1500 360 200 16366 9.70 2343 2396 695 703 304L-360°C-1.5kh 4.51 7.81 215 1500 360 290 16366 9.70 1761 1804 587 594 304L-360°C-1.5kh 4.36 7.71 215 1500 360 330 16366 9.70 1567 1584 553 556 304L-360°C-1.5kh 4.71 7.94 215 1500 360 360 16366 9.70 1504 1602 542 559 304L-360°C-1.5kh 4.47 7.83 215 1500 360 400 16366 9.70 1253 1340 495 512 304L-400°C-1.5kh 4.97 7.74 215 1500 400 22 185319 12.13 2183 2278 671 685 304L-400°C-1.5kh 4.48 7.47 215 1500 400 200 185319 12.13 1387 1474 535 551 304L-400°C-1.5kh 4.65 7.81 215 1500 400 290 185319 12.13 1329 1382 510 520 304L-400°C-1.5kh 4.71 7.86 215 1500 400 330 185319 12.13 1468 1516 535 544 304L-400°C-1.5kh 4.67 7.90 215 1500 400 360 185319 12.13 1300 1390 504 521 304L-400°C-1.5kh 4.66 7.80 215 1500 400 400 185319 12.13 1043 1118 464 480 304L-290°C-10kh 4.94 7.55 215 10000 290 22 681 6.53 2068 2137 636 646 304L-290°C-10kh 5.22 8.04 215 10000 290 200 681 6.53 1627 1700 579 592 304L-290°C-10kh 5.17 8.08 215 10000 290 290 681 6.53 1654 1680 568 573 304L-290°C-10kh 5.23 8.00 215 10000 290 330 681 6.53 1383 1430 520 529 304L-290°C-10kh 4.70 7.98 215 10000 290 360 681 6.53 1600 1628 559 564 304L-290°C-10kh 4.66 7.87 215 10000 290 400 681 6.53 1498 1554 541 551 304L-330°C-10kh 5.53 7.56 215 10000 330 22 14310 9.57 2356 2397 678 684 304L-330°C-10kh 5.12 7.92 215 10000 330 200 14310 9.57 1701 1779 592 606 304L-330°C-10kh 4.94 8.05 215 10000 330 290 14310 9.57 1706 1707 577 577 304L-330°C-10kh 4.82 7.84 215 10000 330 330 14310 9.57 1486 1482 539 538 304L-330°C-10kh 4.79 7.99 215 10000 330 360 14310 9.57 1631 1689 564 574 304L-330°C-10kh 4.85 7.95 215 10000 330 400 14310 9.57 1395 1461 522 534 304L-360°C-10kh 4.60 7.49 215 10000 360 22 109108 11.60 1928 2040 614 631 304L-360°C-10kh 5.35 8.08 215 10000 360 200 109108 11.60 1576 1632 570 580 304L-360°C-10kh 4.96 7.84 215 10000 360 290 109108 11.60 1489 1523 539 545 304L-360°C-10kh 4.74 7.83 215 10000 360 330 109108 11.60 1349 1399 513 523 304L-360°C-10kh 4.85 7.87 215 10000 360 360 109108 11.60 1396 1442 522 531 304L-360°C-10kh 4.72 7.77 215 10000 360 400 109108 11.60 1251 1289 494 502 304L-400°C-10kh 4.89 7.67 215 10000 400 22 1235458 14.03 1950 2076 634 654 304L-400°C-10kh 5.29 7.92 215 10000 400 200 1235458 14.03 1473 1501 551 556 304L-400°C-10kh 4.97 7.84 215 10000 400 290 1235458 14.03 1219 1275 488 499 304L-400°C-10kh 5.08 8.01 215 10000 400 330 1235458 14.03 1487 1513 539 544 304L-400°C-10kh 4.67 7.88 215 10000 400 360 1235458 14.03 1215 1289 487 502 304L-400°C-10kh 4.29 7.47 215 10000 400 400 1235458 14.03 1102 1157 464 475

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Table A2. Crack lengths, aging parameters, and fracture toughness parameters for wrought 316L.

ID Initial Crack Length (mm)

Final Crack Length (mm)

Q (kJ/mole)

Aging Time (h)

Aging Temp. (°C)

Test Temp. (°C)

t(325°C) A JQ-0.1mm (kN/m)

JQ-0.2mm (kN/m)

KJQ-0.1mm (MPa√m)

KJQ-0.2mm (MPa√m)

316L-as received 4.75 7.76 215 0 22 0 0 2199 2249 673 681 316L-as received 4.93 7.99 215 0 200 0 0 1557 1579 567 571 316L-as received 5.28 7.98 215 0 290 0 0 1281 1291 500 502 316L-as received 4.95 7.91 215 0 330 0 0 1084 1143 460 473 316L-as received 4.59 7.77 215 0 360 0 0 1160 1163 476 477 316L-as received 4.61 7.67 215 0 400 0 0 1042 1114 451 467 316L-290°C-1.5kh 4.88 7.71 215 1500 290 22 102 4.64 1589 1728 572 597 316L-290°C-1.5kh 4.93 7.60 215 1500 290 200 102 4.64 1303 1339 518 526 316L-290°C-1.5kh 4.87 7.89 215 1500 290 290 102 4.64 1340 1403 512 524 316L-290°C-1.5kh 4.85 7.83 215 1500 290 330 102 4.64 1250 1282 494 500 316L-290°C-1.5kh 4.68 7.76 215 1500 290 360 102 4.64 1005 1080 443 459 316L-290°C-1.5kh 4.67 7.71 215 1500 290 400 102 4.64 1230 1286 490 501 316L-330°C-1.5kh 4.41 7.42 215 1500 330 22 2147 7.67 1949 2045 634 649 316L-330°C-1.5kh 4.70 7.66 215 1500 330 200 2147 7.67 1397 1436 537 544 316L-330°C-1.5kh 4.56 7.73 215 1500 330 290 2147 7.67 1372 1410 518 525 316L-330°C-1.5kh 4.57 7.76 215 1500 330 330 2147 7.67 1132 1204 470 485 316L-330°C-1.5kh 4.18 7.68 215 1500 330 360 2147 7.67 1082 1146 460 473 316L-330°C-1.5kh 4.39 7.69 215 1500 330 400 2147 7.67 1169 1189 478 482 316L-360°C-1.5kh 4.44 7.43 215 1500 360 22 16366 9.70 2060 2151 652 666 316L-360°C-1.5kh 4.79 7.84 215 1500 360 200 16366 9.70 2011 2011 644 644 316L-360°C-1.5kh 4.59 7.71 215 1500 360 290 16366 9.70 1157 1230 475 490 316L-360°C-1.5kh 4.47 7.75 215 1500 360 330 16366 9.70 1320 1364 508 516 316L-360°C-1.5kh 4.39 7.57 215 1500 360 360 16366 9.70 943 956 429 432 316L-360°C-1.5kh 4.03 7.37 215 1500 360 400 16366 9.70 1208 1254 486 495 316L-400°C-1.5kh 4.95 7.64 215 1500 400 22 185319 12.13 1638 1698 581 592 316L-400°C-1.5kh 4.90 7.67 215 1500 400 200 185319 12.13 1251 1289 508 516 316L-400°C-1.5kh 4.74 7.83 215 1500 400 290 185319 12.13 1236 1281 491 500 316L-400°C-1.5kh 4.60 7.79 215 1500 400 330 185319 12.13 940 1031 429 449 316L-400°C-1.5kh 4.65 7.76 215 1500 400 360 185319 12.13 1137 1174 471 479 316L-400°C-1.5kh 4.61 7.79 215 1500 400 400 185319 12.13 862 927 410 425 316L-290°C-10kh 4.65 7.50 215 10000 290 22 681 6.53 1456 1562 548 567 316L-290°C-10kh 4.96 7.66 215 10000 290 200 681 6.53 1242 1281 506 514 316L-290°C-10kh 4.30 7.57 215 10000 290 290 681 6.53 1514 1524 544 546 316L-290°C-10kh 4.62 7.74 215 10000 290 330 681 6.53 1206 1253 485 495 316L-290°C-10kh 4.44 7.68 215 10000 290 360 681 6.53 1399 1393 523 522 316L-290°C-10kh 4.18 7.44 215 10000 290 400 681 6.53 1275 1335 499 511 316L-330°C-10kh 4.53 7.31 215 10000 330 22 14310 9.57 1512 1578 558 570 316L-330°C-10kh 4.88 7.56 215 10000 330 200 14310 9.57 1239 1272 505 512 316L-330°C-10kh 4.70 7.73 215 10000 330 290 14310 9.57 1342 1375 512 518 316L-330°C-10kh 4.97 7.94 215 10000 330 330 14310 9.57 1063 1090 456 461 316L-330°C-10kh 4.52 7.73 215 10000 330 360 14310 9.57 1335 1370 511 517 316L-330°C-10kh 4.47 7.64 215 10000 330 400 14310 9.57 989 1072 439 458 316L-360°C-10kh 4.76 7.51 215 10000 360 22 109108 11.60 1760 1813 602 611 316L-360°C-10kh 4.85 7.74 215 10000 360 200 109108 11.60 1499 1554 556 566 316L-360°C-10kh 4.83 7.77 215 10000 360 290 109108 11.60 1122 1162 468 476 316L-360°C-10kh 4.61 7.82 215 10000 360 330 109108 11.60 977 1053 437 454 316L-360°C-10kh 4.54 7.60 215 10000 360 360 109108 11.60 1113 1128 466 469 316L-360°C-10kh 4.36 7.52 215 10000 360 400 109108 11.60 965 1009 434 444 316L-400°C-10kh 4.44 7.31 215 10000 400 22 1235458 14.03 1625 1694 579 591 316L-400°C-10kh 4.61 7.57 215 10000 400 200 1235458 14.03 1459 1476 548 552 316L-400°C-10kh 4.66 7.73 215 10000 400 290 1235458 14.03 1107 1183 465 481 316L-400°C-10kh 4.58 7.73 215 10000 400 330 1235458 14.03 915 984 423 438 316L-400°C-10kh 4.31 7.55 215 10000 400 360 1235458 14.03 1096 1141 463 472 316L-400°C-10kh 4.53 7.69 215 10000 400 400 1235458 14.03 1005 1049 443 453

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Table A3. Crack lengths, aging parameters, and fracture toughness parameters for static cast CF3.

ID Initial Crack Length (mm)

Final Crack Length (mm)

Q (kJ/mole)

Aging Time (h)

Aging Temp. (°C)

Test Temp. (°C)

t(325°C) A JQ-0.1mm (kN/m)

JQ-0.2mm (kN/m)

KJQ-0.1mm (MPa√m)

KJQ-0.2mm (MPa√m)

CF3-as received 5.15 7.37 215 0 -175 0 0 420 512 302 333 CF3-as received 4.47 6.43 215 0 -100 0 0 505 533 331 340 CF3-as received 5.15 8.19 215 0 22 0 0 513 623 316 349 CF3-as received 5.00 7.23 215 0 22 0 0 585 624 338 349 CF3-as received 5.08 7.50 215 0 100 0 0 326 371 259 277 CF3-as received 4.45 6.96 215 0 200 0 0 350 414 261 284 CF3-as received 4.94 7.18 215 0 290 0 0 454 467 298 302 CF3-as received 5.19 7.44 215 0 330 0 0 243 297 218 241 CF3-as received 5.24 7.49 215 0 360 0 0 237 272 215 231 CF3-as received 5.34 7.72 215 0 400 0 0 237 251 215 221 CF3-290°C-1.5kh 5.05 7.96 215 1500 290 22 102 4.64 641 921 364 436 CF3-290°C-1.5kh 5.39 7.95 215 1500 290 200 102 4.64 510 602 324 352 CF3-290°C-1.5kh 5.58 8.03 215 1500 290 290 102 4.64 374 589 270 339 CF3-290°C-1.5kh 5.58 8.16 215 1500 290 330 102 4.64 282 331 235 254 CF3-290°C-1.5kh 5.17 7.87 215 1500 290 360 102 4.64 361 423 266 287 CF3-290°C-1.5kh 5.10 7.90 215 1500 290 400 102 4.64 408 467 282 302 CF3-330°C-1.5kh 5.28 7.75 215 1500 330 22 2147 7.67 251 343 227 266 CF3-330°C-1.5kh 5.47 7.83 215 1500 330 200 2147 7.67 229 278 217 239 CF3-330°C-1.5kh 5.51 8.07 215 1500 330 290 2147 7.67 311 394 246 277 CF3-330°C-1.5kh 5.35 7.81 215 1500 330 330 2147 7.67 267 310 228 246 CF3-330°C-1.5kh 4.93 7.60 215 1500 330 360 2147 7.67 301 353 242 263 CF3-330°C-1.5kh 4.84 7.62 215 1500 330 400 2147 7.67 134 215 162 205 CF3-360°C-1.5kh 5.72 7.84 215 1500 360 22 16366 9.70 970 1054 No data CF3-360°C-1.5kh 5.62 7.95 215 1500 360 200 16366 9.70 580 632 346 361 CF3-360°C-1.5kh 5.36 8.08 215 1500 360 290 16366 9.70 447 693 No data CF3-360°C-1.5kh 5.50 8.08 215 1500 360 330 16366 9.70 264 336 227 256 CF3-360°C-1.5kh 5.03 7.96 215 1500 360 360 16366 9.70 162 233 178 213 CF3-360°C-1.5kh 4.43 7.41 215 1500 360 400 16366 9.70 206 264 201 227 CF3-400°C-1.5kh 5.61 7.66 215 1500 400 22 185319 12.13 347 418 267 294 CF3-400°C-1.5kh 5.65 7.90 215 1500 400 200 185319 12.13 310 363 253 274 CF3-400°C-1.5kh 5.66 8.16 215 1500 400 290 185319 12.13 191 262 193 226 CF3-400°C-1.5kh 4.98 7.56 215 1500 400 330 185319 12.13 243 355 218 263 CF3-400°C-1.5kh 4.88 7.77 215 1500 400 360 185319 12.13 149 193 171 194 CF3-400°C-1.5kh 4.65 7.25 215 1500 400 400 185319 12.13 227 273 211 231 CF3-290°C-10kh 4.77 7.70 215 10000 290 22 681 6.53 618 684 357 376 CF3-290°C-10kh 5.31 7.75 215 10000 290 200 681 6.53 539 571 333 343 CF3-290°C-10kh 5.20 8.10 215 10000 290 290 681 6.53 328 404 253 281 CF3-290°C-10kh 4.69 7.90 215 10000 290 330 681 6.53 517 567 318 333 CF3-290°C-10kh 4.76 7.80 215 10000 290 360 681 6.53 370 420 269 286 CF3-290°C-10kh 4.52 7.75 215 10000 290 400 681 6.53 454 465 298 301 CF3-330°C-10kh 4.86 7.49 215 10000 330 22 14310 9.57 188 247 197 226 CF3-330°C-10kh 4.82 7.17 215 10000 330 200 14310 9.57 428 451 297 305 CF3-330°C-10kh 4.73 7.79 215 10000 330 290 14310 9.57 278 346 233 260 CF3-330°C-10kh 4.79 7.81 215 10000 330 330 14310 9.57 245 291 219 238 CF3-330°C-10kh 5.15 8.07 215 10000 330 360 14310 9.57 256 310 224 246 CF3-330°C-10kh 4.63 7.83 215 10000 330 400 14310 9.57 214 259 204 225 CF3-360°C-10kh 5.65 7.89 215 10000 360 22 109108 11.60 142 168 171 186 CF3-360°C-10kh 5.19 7.71 215 10000 360 200 109108 11.60 253 291 228 245 CF3-360°C-10kh 5.25 7.86 215 10000 360 290 109108 11.60 212 262 204 226 CF3-360°C-10kh 4.69 7.55 215 10000 360 330 109108 11.60 199 251 197 222 CF3-360°C-10kh 4.81 7.79 215 10000 360 360 109108 11.60 259 314 225 248 CF3-360°C-10kh 4.45 7.18 215 10000 360 400 109108 11.60 213 225 204 210 CF3-400°C-10kh 5.40 7.61 215 10000 400 22 1235458 14.03 218 303 212 250 CF3-400°C-10kh 5.28 7.92 215 10000 400 200 1235458 14.03 197 259 202 231 CF3-400°C-10kh 5.28 8.13 215 10000 400 290 1235458 14.03 238 283 216 235 CF3-400°C-10kh 5.07 7.98 215 10000 400 330 1235458 14.03 176 212 185 203 CF3-400°C-10kh 4.87 7.71 215 10000 400 360 1235458 14.03 166 268 180 229

Note: ‘No data’ indicates a failed testing or improper crack growth (ex. excessive blunting)

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Table A4. Crack lengths, aging parameters, and fracture toughness parameters for static cast CF3M.

ID Initial Crack Length (mm)

Final Crack Length (mm)

Q (kJ/mole)

Aging Time (h)

Aging Temp. (°C)

Test Temp. (°C)

t(325°C) A JQ-0.1mm (kN/m)

JQ-0.2mm (kN/m)

KJQ-0.1mm (MPa√m)

KJQ-0.2mm (MPa√m)

CF3M-as received 5.31 6.77 215 0 -175 0 0 246 308 231 259 CF3M-as received 4.98 7.35 215 0 -100 0 0 376 415 286 300 CF3M-as received 5.44 7.66 215 0 22 0 0 543 828 335 413 CF3M-as received 5.08 7.39 215 0 100 0 0 473 573 312 344 CF3M-as received 5.34 7.71 215 0 200 0 0 360 395 273 286 CF3M-as received 5.20 7.51 215 0 290 0 0 192 267 194 229 CF3M-as received 5.06 7.60 215 0 330 0 0 217 268 206 229 CF3M-as received 5.26 7.78 215 0 360 0 0 227 255 211 223 CF3M-as received 5.01 7.61 215 0 400 0 0 255 310 223 246 CF3M-290°C-1.5kh 4.97 7.81 215 1500 290 22 102 4.64 527 733 330 389 CF3M-290°C-1.5kh 5.20 7.79 215 1500 290 200 102 4.64 431 475 298 313 CF3M-290°C-1.5kh 5.35 8.30 215 1500 290 290 102 4.64 379 487 272 308 CF3M-290°C-1.5kh 5.15 8.29 215 1500 290 330 102 4.64 248 323 220 251 CF3M-290°C-1.5kh 4.96 7.90 215 1500 290 360 102 4.64 507 575 315 335 CF3M-290°C-1.5kh 5.16 7.99 215 1500 290 400 102 4.64 218 294 207 239 CF3M-330°C-1.5kh 4.80 7.58 215 1500 330 22 2147 7.67 455 538 306 333 CF3M-330°C-1.5kh 5.41 7.94 215 1500 330 200 2147 7.67 235 332 220 262 CF3M-330°C-1.5kh 5.09 7.78 215 1500 330 290 2147 7.67 315 380 248 273 CF3M-330°C-1.5kh 5.42 8.03 215 1500 330 330 2147 7.67 221 261 208 226 CF3M-330°C-1.5kh 5.20 8.12 215 1500 330 360 2147 7.67 306 372 244 270 CF3M-330°C-1.5kh 5.31 7.84 215 1500 330 400 2147 7.67 186 215 191 205 CF3M-360°C-1.5kh 4.35 7.21 215 1500 360 22 16366 9.70 581 783 No data CF3M-360°C-1.5kh 5.73 8.05 215 1500 360 200 16366 9.70 191 272 198 237 CF3M-360°C-1.5kh 5.60 8.19 215 1500 360 290 16366 9.70 274 319 231 249 CF3M-360°C-1.5kh 5.07 8.10 215 1500 360 330 16366 9.70 206 249 201 220 CF3M-360°C-1.5kh 5.25 7.98 215 1500 360 360 16366 9.70 213 295 204 240 CF3M-360°C-1.5kh 4.95 7.93 215 1500 360 400 16366 9.70 167 212 181 204 CF3M-400°C-1.5kh 5.47 8.11 215 1500 400 22 185319 12.13 308 370 252 276 CF3M-400°C-1.5kh 5.63 8.08 215 1500 400 200 185319 12.13 135 179 167 192 CF3M-400°C-1.5kh 5.33 8.11 215 1500 400 290 185319 12.13 240 288 217 237 CF3M-400°C-1.5kh 4.69 7.70 215 1500 400 330 185319 12.13 220 278 207 233 CF3M-400°C-1.5kh 5.15 7.89 215 1500 400 360 185319 12.13 266 324 228 252 CF3M-400°C-1.5kh 5.07 7.85 215 1500 400 400 185319 12.13 151 173 172 184 CF3M-290°C-10kh 4.90 7.57 215 10000 290 22 681 6.53 486 603 317 353 CF3M-290°C-10kh 5.08 7.86 215 10000 290 200 681 6.53 287 358 243 272 CF3M-290°C-10kh 5.51 8.43 215 10000 290 290 681 6.53 427 535 289 323 CF3M-290°C-10kh 5.19 8.07 215 10000 290 330 681 6.53 202 281 198 234 CF3M-290°C-10kh 4.85 7.99 215 10000 290 360 681 6.53 346 408 260 282 CF3M-290°C-10kh 4.72 7.92 215 10000 290 400 681 6.53 246 354 219 263 CF3M-330°C-10kh 4.82 7.67 215 10000 330 22 14310 9.57 486 588 317 348 CF3M-330°C-10kh 4.93 7.53 215 10000 330 200 14310 9.57 176 337 191 264 CF3M-330°C-10kh 4.79 7.86 215 10000 330 290 14310 9.57 378 411 272 283 CF3M-330°C-10kh 5.11 7.93 215 10000 330 330 14310 9.57 302 398 243 279 CF3M-330°C-10kh 4.19 7.51 215 10000 330 360 14310 9.57 404 482 281 307 CF3M-330°C-10kh 4.48 7.77 215 10000 330 400 14310 9.57 129 232 159 213 CF3M-360°C-10kh 4.80 7.58 215 10000 360 22 109108 11.60 454 570 306 343 CF3M-360°C-10kh 5.04 7.77 215 10000 360 200 109108 11.60 222 270 214 236 CF3M-360°C-10kh 5.00 7.81 215 10000 360 290 109108 11.60 258 313 225 247 CF3M-360°C-10kh 5.12 7.96 215 10000 360 330 109108 11.60 173 217 184 206 CF3M-360°C-10kh 4.73 7.91 215 10000 360 360 109108 11.60 240 275 217 232 CF3M-360°C-10kh 4.80 7.58 215 10000 360 400 109108 11.60 251 334 221 255 CF3M-400°C-10kh 4.61 7.44 215 10000 400 22 1235458 14.03 488 578 317 345 CF3M-400°C-10kh 5.31 8.06 215 10000 400 200 1235458 14.03 369 459 276 308 CF3M-400°C-10kh 4.91 8.15 215 10000 400 290 1235458 14.03 335 389 256 276 CF3M-400°C-10kh 4.81 8.00 215 10000 400 330 1235458 14.03 221 348 208 261 CF3M-400°C-10kh 4.67 7.95 215 10000 400 360 1235458 14.03 294 365 240 267 CF3M-400°C-10kh 4.34 7.58 215 10000 400 400 1235458 14.03 238 302 216 243

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Table A5. Crack lengths, aging parameters, and fracture toughness parameters for static cast CF8.

ID Initial Crack Length (mm)

Final Crack Length (mm)

Q (kJ/mole)

Aging Time (h)

Aging Temp. (°C)

Test Temp. (°C)

t(325°C) A JQ-0.1mm (kN/m)

JQ-0.2mm (kN/m)

KJQ-0.1mm (MPa√m)

KJQ-0.2mm (MPa√m)

CF8-as received 5.27 7.33 215 0 -175 0 0 184 213 200 215 CF8-as received 5.04 7.33 215 0 -100 0 0 399 462 294 317 CF8-as received 5.29 7.56 215 0 22 0 0 421 563 295 341 CF8-as received 5.03 7.41 215 0 100 0 0 597 651 351 366 CF8-as received 4.75 7.35 215 0 200 0 0 468 545 311 335 CF8-as received 4.90 7.29 215 0 290 0 0 403 470 281 303 CF8-as received 5.14 8.01 215 0 330 0 0 497 596 312 341 CF8-as received 5.24 7.49 215 0 360 0 0 472 536 303 324 CF8-as received 5.15 7.73 215 0 400 0 0 569 620 334 348 CF8-290°C-1.5kh 4.87 7.69 215 1500 290 22 102 4.64 888 982 428 450 CF8-290°C-1.5kh 5.27 7.91 215 1500 290 200 102 4.64 494 609 319 355 CF8-290°C-1.5kh 5.07 8.13 215 1500 290 290 102 4.64 607 662 344 360 CF8-290°C-1.5kh 5.08 8.18 215 1500 290 330 102 4.64 368 528 268 321 CF8-290°C-1.5kh 4.79 8.12 215 1500 290 360 102 4.64 497 623 312 349 CF8-290°C-1.5kh 4.66 7.81 215 1500 290 400 102 4.64 448 566 296 333 CF8-330°C-1.5kh 4.69 7.56 215 1500 330 22 2147 7.67 579 630 345 360 CF8-330°C-1.5kh 4.88 7.70 215 1500 330 200 2147 7.67 520 598 328 351 CF8-330°C-1.5kh 4.69 7.87 215 1500 330 290 2147 7.67 357 444 264 294 CF8-330°C-1.5kh 4.60 7.89 215 1500 330 330 2147 7.67 475 503 305 313 CF8-330°C-1.5kh 4.54 7.45 215 1500 330 360 2147 7.67 437 466 292 302 CF8-330°C-1.5kh 4.62 7.96 215 1500 330 400 2147 7.67 333 433 255 291 CF8-360°C-1.5kh 4.48 7.63 215 1500 360 22 16366 9.70 659 696 369 379 CF8-360°C-1.5kh 5.18 8.07 215 1500 360 200 16366 9.70 476 634 313 361 CF8-360°C-1.5kh 5.05 8.05 215 1500 360 290 16366 9.70 476 523 305 319 CF8-360°C-1.5kh 4.50 8.13 215 1500 360 330 16366 9.70 534 614 323 346 CF8-360°C-1.5kh 3.97 7.54 215 1500 360 360 16366 9.70 603 647 343 355 CF8-360°C-1.5kh 4.11 7.87 215 1500 360 400 16366 9.70 365 403 267 280 CF8-400°C-1.5kh 5.26 8.12 215 1500 400 22 185319 12.13 733 974 389 448 CF8-400°C-1.5kh 5.02 8.09 215 1500 400 200 185319 12.13 481 562 315 340 CF8-400°C-1.5kh 5.22 8.24 215 1500 400 290 185319 12.13 499 582 312 337 CF8-400°C-1.5kh 5.03 8.37 215 1500 400 330 185319 12.13 253 417 222 285 CF8-400°C-1.5kh 4.29 7.87 215 1500 400 360 185319 12.13 585 624 338 349 CF8-400°C-1.5kh 3.78 7.86 215 1500 400 400 185319 12.13 346 432 260 290 CF8-290°C-10kh 4.76 7.65 215 10000 290 22 681 6.53 615 723 356 386 CF8-290°C-10kh 4.83 7.82 215 10000 290 200 681 6.53 550 680 337 374 CF8-290°C-10kh 4.80 7.96 215 10000 290 290 681 6.53 700 749 370 382 CF8-290°C-10kh 4.43 7.89 215 10000 290 330 681 6.53 400 502 280 313 CF8-290°C-10kh 4.53 7.73 215 10000 290 360 681 6.53 501 543 313 326 CF8-290°C-10kh 4.40 7.79 215 10000 290 400 681 6.53 538 549 324 327 CF8-330°C-10kh 4.86 7.94 215 10000 330 22 14310 9.57 416 642 293 364 CF8-330°C-10kh 4.82 7.76 215 10000 330 200 14310 9.57 228 330 217 261 CF8-330°C-10kh 4.74 7.91 215 10000 330 290 14310 9.57 453 489 297 309 CF8-330°C-10kh 4.69 7.77 215 10000 330 330 14310 9.57 334 378 255 272 CF8-330°C-10kh 4.74 7.98 215 10000 330 360 14310 9.57 260 310 225 246 CF8-330°C-10kh 4.75 7.92 215 10000 330 400 14310 9.57 314 405 248 281 CF8-360°C-10kh 4.93 7.68 215 10000 360 22 109108 11.60 896 906 430 432 CF8-360°C-10kh 4.86 7.79 215 10000 360 200 109108 11.60 636 727 362 387 CF8-360°C-10kh 4.76 8.17 215 10000 360 290 109108 11.60 510 606 316 344 CF8-360°C-10kh 4.80 8.28 215 10000 360 330 109108 11.60 639 703 353 371 CF8-360°C-10kh 4.77 7.98 215 10000 360 360 109108 11.60 470 615 303 346 CF8-360°C-10kh 4.59 7.95 215 10000 360 400 109108 11.60 259 339 225 257 CF8-400°C-10kh 4.62 7.78 215 10000 400 22 1235458 14.03 453 561 305 340 CF8-400°C-10kh 4.71 7.59 215 10000 400 200 1235458 14.03 241 303 223 250 CF8-400°C-10kh 4.76 7.81 215 10000 400 290 1235458 14.03 323 376 251 271 CF8-400°C-10kh 4.77 7.86 215 10000 400 330 1235458 14.03 297 357 241 264 CF8-400°C-10kh 4.60 8.00 215 10000 400 360 1235458 14.03 243 288 218 237 CF8-400°C-10kh 4.41 7.71 215 10000 400 400 1235458 14.03 307 342 245 259

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Table A6. Crack lengths, aging parameters, and fracture toughness parameters for static cast CF8M.

ID Initial Crack Length (mm)

Final Crack Length (mm)

Q (kJ/mole)

Aging Time (h)

Aging Temp. (°C)

Test Temp. (°C)

t(325°C) A JQ-0.1mm (kN/m)

JQ-0.2mm (kN/m)

KJQ-0.1mm (MPa√m)

KJQ-0.2mm (MPa√m)

CF8M-as received 4.85 7.03 215 0 -175 0 0 490 566 326 351 CF8M-as received 4.98 7.46 215 0 -100 0 0 975 988 460 463 CF8M-as received 4.71 7.82 215 0 22 0 0 769 875 398 425 CF8M-as received 4.98 7.92 215 0 100 0 0 471 527 311 330 CF8M-as received 5.15 7.63 215 0 200 0 0 282 385 241 282 CF8M-as received 5.20 7.86 215 0 290 0 0 408 475 282 305 CF8M-as received 5.17 7.98 215 0 330 0 0 384 453 274 298 CF8M-as received 5.21 7.64 215 0 360 0 0 409 499 283 312 CF8M-as received 5.53 7.82 215 0 400 0 0 595 721 341 375 CF8M-290°C-1.5kh 3.79 7.36 215 1500 290 22 102 4.64 979 1014 449 457 CF8M-290°C-1.5kh 5.40 7.75 215 1500 290 200 102 4.64 807 877 408 425 CF8M-290°C-1.5kh 4.22 7.60 215 1500 290 290 102 4.64 431 503 290 314 CF8M-290°C-1.5kh 5.17 7.80 215 1500 290 330 102 4.64 448 498 296 312 CF8M-290°C-1.5kh 5.21 215 1500 290 360 102 4.64 473 505 304 314 CF8M-290°C-1.5kh 4.82 8.11 215 1500 290 400 102 4.64 380 469 272 303 CF8M-330°C-1.5kh 5.21 7.86 215 1500 330 22 2147 7.67 361 424 273 296 CF8M-330°C-1.5kh 5.57 7.94 215 1500 330 200 2147 7.67 377 408 279 290 CF8M-330°C-1.5kh 4.75 7.83 215 1500 330 290 2147 7.67 562 599 331 342 CF8M-330°C-1.5kh 5.25 8.16 215 1500 330 330 2147 7.67 549 648 327 356 CF8M-330°C-1.5kh 5.18 215 1500 330 360 2147 7.67 458 542 299 325 CF8M-330°C-1.5kh 5.51 7.93 215 1500 330 400 2147 7.67 467 538 302 324 CF8M-360°C-1.5kh 5.17 7.43 215 1500 360 22 16366 9.70 316 373 255 277 CF8M-360°C-1.5kh 5.59 8.17 215 1500 360 200 16366 9.70 203 279 205 240 CF8M-360°C-1.5kh 5.06 7.92 215 1500 360 290 16366 9.70 352 422 262 287 CF8M-360°C-1.5kh 5.06 7.78 215 1500 360 330 16366 9.70 176 236 185 214 CF8M-360°C-1.5kh 4.91 215 1500 360 360 16366 9.70 194 277 195 233 CF8M-360°C-1.5kh 4.88 7.86 215 1500 360 400 16366 9.70 194 249 194 220 CF8M-400°C-1.5kh 5.20 7.65 215 1500 400 22 185319 12.13 392 459 284 308 CF8M-400°C-1.5kh 5.31 7.99 215 1500 400 200 185319 12.13 273 346 237 267 CF8M-400°C-1.5kh 5.68 7.76 215 1500 400 290 185319 12.13 518 547 318 327 CF8M-400°C-1.5kh 4.96 7.98 215 1500 400 330 185319 12.13 268 315 229 248 CF8M-400°C-1.5kh 5.30 215 1500 400 360 185319 12.13 466 536 302 323 CF8M-400°C-1.5kh 5.19 8.09 215 1500 400 400 185319 12.13 424 499 288 312 CF8M-290°C-10kh 5.02 6.93 215 10000 290 22 681 6.53 612 667 355 371 CF8M-290°C-10kh 5.31 7.75 215 10000 290 200 681 6.53 649 684 366 376 CF8M-290°C-10kh 5.15 7.60 215 10000 290 290 681 6.53 453 529 298 322 CF8M-290°C-10kh 4.68 7.80 215 10000 290 330 681 6.53 462 561 301 331 CF8M-290°C-10kh 4.57 8.08 215 10000 290 360 681 6.53 439 476 293 305 CF8M-290°C-10kh 4.38 8.11 215 10000 290 400 681 6.53 514 609 317 345 CF8M-330°C-10kh 4.92 7.86 215 10000 330 22 14310 9.57 610 649 355 366 CF8M-330°C-10kh 4.57 7.94 215 10000 330 200 14310 9.57 844 886 417 427 CF8M-330°C-10kh 4.45 7.83 215 10000 330 290 14310 9.57 186 201 190 198 CF8M-330°C-10kh 4.79 7.56 215 10000 330 330 14310 9.57 505 584 314 338 CF8M-330°C-10kh 4.67 8.11 215 10000 330 360 14310 9.57 423 506 288 314 CF8M-330°C-10kh 4.74 7.93 215 10000 330 400 14310 9.57 316 411 248 283 CF8M-360°C-10kh 4.91 7.43 215 10000 360 22 109108 11.60 513 585 325 347 CF8M-360°C-10kh 5.31 8.17 215 10000 360 200 109108 11.60 424 454 296 306 CF8M-360°C-10kh 5.39 7.92 215 10000 360 290 109108 11.60 398 491 279 310 CF8M-360°C-10kh 5.33 7.78 215 10000 360 330 109108 11.60 470 524 303 320 CF8M-360°C-10kh 5.34 7.84 215 10000 360 360 109108 11.60 206 283 201 235 CF8M-360°C-10kh 4.80 7.86 215 10000 360 400 109108 11.60 290 310 238 246 CF8M-400°C-10kh 5.53 7.65 215 10000 400 22 1235458 14.03 690 745 377 392 CF8M-400°C-10kh 5.29 7.99 215 10000 400 200 1235458 14.03 465 576 310 345 CF8M-400°C-10kh 5.23 7.76 215 10000 400 290 1235458 14.03 362 434 266 291 CF8M-400°C-10kh 5.35 7.98 215 10000 400 330 1235458 14.03 549 641 328 354 CF8M-400°C-10kh 5.43 7.90 215 10000 400 360 1235458 14.03 475 585 305 338 CF8M-400°C-10kh 5.23 8.09 215 10000 400 400 1235458 14.03 333 463 255 301

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42

Table A7. Crack lengths, aging parameters, and fracture toughness parameters for static cast CF8 (ELB).

ID Initial Crack Length (mm)

Final Crack Length (mm)

Q (kJ/mole)

Aging Time (h)

Aging Temp. (°C)

Test Temp. (°C)

t(325°C) A JQ-0.1mm (kN/m)

JQ-0.2mm (kN/m)

KJQ-0.1mm (MPa√m)

KJQ-0.2mm (MPa√m)

CF8(ELB)-as received 6.20 7.29 215 0 22 0 0 298 373 248 277 CF8(ELB)-as received 4.82 7.69 215 0 22 0 0 261 337 232 264 CF8(ELB)-as received 5.82 8.09 215 0 200 0 0 693 794 378 405 CF8(ELB)-as received 5.18 7.89 215 0 290 0 0 619 802 348 396 CF8(ELB)-as received 5.03 7.78 215 0 330 0 0 763 817 386 400 CF8(ELB)-as received 5.74 7.91 215 0 360 0 0 177 215 186 205 CF8(ELB)-as received 4.87 7.90 215 0 400 0 0 283 358 235 265 CF8(ELB)-330°C-10kh 5.80 7.84 215 10000 330 22 14310 9.57 69 95 119 140 CF8(ELB)-330°C-10kh 5.96 8.04 215 10000 330 200 14310 9.57 376 469 278 311 CF8(ELB)-330°C-10kh 5.93 8.30 215 10000 330 290 14310 9.57 544 591 326 340 CF8(ELB)-330°C-10kh 5.89 8.33 215 10000 330 330 14310 9.57 431 536 290 323 CF8(ELB)-330°C-10kh 6.01 8.37 215 10000 330 360 14310 9.57 146 192 169 194 CF8(ELB)-330°C-10kh 6.42 8.26 215 10000 330 400 14310 9.57 126 171 157 183 CF8(ELB)-360°C-10kh 6.09 8.01 215 10000 360 22 109108 11.60 55 70 107 120 CF8(ELB)-360°C-10kh 5.95 8.15 215 10000 360 200 109108 11.60 72 95 122 140 CF8(ELB)-360°C-10kh 6.07 8.27 215 10000 360 290 109108 11.60 288 356 237 264 CF8(ELB)-360°C-10kh 6.13 8.32 215 10000 360 330 109108 11.60 151 215 172 205 CF8(ELB)-360°C-10kh 6.54 8.93 215 10000 360 360 109108 11.60 64 91 112 133 CF8(ELB)-360°C-10kh 6.21 8.40 215 10000 360 400 109108 11.60 108 121 145 154

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Table A8. Crack lengths, aging parameters, and fracture toughness parameters for centrifugal cast CF8M (K23 & K25).

ID Initial Crack Length (mm)

Final Crack Length (mm)

Q (kJ/mole)

Aging Time (h)

Aging Temp. (°C)

Test Temp. (°C)

t(325°C) A JQ-0.1mm (kN/m)

JQ-0.2mm (kN/m)

KJQ-0.1mm (MPa√m)

KJQ-0.2mm (MPa√m)

CF8M(K23)-as received 4.84 8.51 215 0 22 0 0.00 388 629 283 360 CF8M(K23)-as received 5.01 8.32 215 0 22 0 0.00 416 513 293 325 CF8M(K23)-as received 5.17 7.60 215 0 200 0 0.00 640 738 363 390 CF8M(K23)-as received 5.34 8.13 215 0 290 0 0.00 934 962 427 433 CF8M(K23)-as received 5.41 8.44 215 0 330 0 0.00 468 629 302 350 CF8M(K23)-as received 5.15 7.95 215 0 360 0 0.00 565 623 332 349 CF8M(K23)-as received 4.74 7.95 215 0 400 0 0.00 228 310 211 246 CF8M(K25)-as received 5.04 7.60 215 0 22 0 0.00 1369 1448 531 547 CF8M(K25)-as received 5.33 7.78 215 0 200 0 0.00 869 982 423 450 CF8M(K25)-as received 5.41 7.73 215 0 290 0 0.00 882 917 415 423 CF8M(K25)-as received 5.37 7.87 215 0 330 0 0.00 828 886 402 416 CF8M(K25)-as received 5.72 7.96 215 0 360 0 0.00 1109 1203 466 485 CF8M(K25)-as received 4.73 7.63 215 0 400 0 0.00 586 669 338 362 CF8M(K23)-290°C-10kh 5.69 8.20 215 10000 290 22 681 6.53 1128 1328 No data CF8M(K23)-290°C-10kh 5.71 8.32 215 10000 290 200 681 6.53 469 579 311 346 CF8M(K23)-290°C-10kh 5.52 8.45 215 10000 290 290 681 6.53 667 687 361 366 CF8M(K23)-290°C-10kh 5.64 8.28 215 10000 290 330 681 6.53 527 585 321 338 CF8M(K23)-290°C-10kh 5.69 8.40 215 10000 290 360 681 6.53 564 677 332 364 CF8M(K23)-290°C-10kh 5.52 8.45 215 10000 290 400 681 6.53 459 490 299 309 CF8M(K23)-330°C-10kh 5.70 8.10 215 10000 330 22 14310 9.57 209 248 208 226 CF8M(K23)-330°C-10kh 5.69 8.33 215 10000 330 200 14310 9.57 137 228 168 217 CF8M(K23)-330°C-10kh 5.77 8.23 215 10000 330 290 14310 9.57 479 526 306 321 CF8M(K23)-330°C-10kh 5.71 8.36 215 10000 330 330 14310 9.57 312 350 247 262 CF8M(K23)-330°C-10kh 5.71 8.42 215 10000 330 360 14310 9.57 200 249 198 221 CF8M(K23)-330°C-10kh 5.64 8.62 215 10000 330 400 14310 9.57 296 348 240 261 CF8M(K23)-360°C-10kh 5.73 7.86 215 10000 360 22 109108 11.60 164 187 184 196 CF8M(K23)-360°C-10kh 5.42 7.88 215 10000 360 200 109108 11.60 229 333 217 262 CF8M(K23)-360°C-10kh 5.73 8.14 215 10000 360 290 109108 11.60 194 281 195 234 CF8M(K23)-360°C-10kh 5.69 8.17 215 10000 360 330 109108 11.60 212 279 203 233 CF8M(K23)-360°C-10kh 5.61 8.32 215 10000 360 360 109108 11.60 309 438 246 292 CF8M(K23)-360°C-10kh 5.66 8.17 215 10000 360 400 109108 11.60 380 506 272 314 CF8M(K23)-400°C-10kh 5.19 7.85 215 10000 400 22 1235458 14.03 163 215 183 211 CF8M(K23)-400°C-10kh 5.81 8.17 215 10000 400 200 1235458 14.03 314 364 255 274 CF8M(K23)-400°C-10kh 5.69 8.22 215 10000 400 290 1235458 14.03 278 344 233 259 CF8M(K23)-400°C-10kh 5.74 8.01 215 10000 400 330 1235458 14.03 339 415 257 285 CF8M(K23)-400°C-10kh 5.68 8.15 215 10000 400 360 1235458 14.03 228 250 211 221 CF8M(K23)-400°C-10kh 5.71 8.23 215 10000 400 400 1235458 14.03 270 329 230 254

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Table A9. Crack lengths, aging parameters, and fracture toughness parameters for static cast CF8 (S43 & S52).

ID Initial Crack Length (mm)

Final Crack Length (mm)

Q (kJ/mole) Aging Time (h)

Aging Temp. (°C)

Test Temp. (°C)

t(325°C) A JQ-0.1mm (kN/m)

JQ-0.2mm (kN/m)

KJQ-0.1mm (MPa√m)

KJQ-0.2mm (MPa√m)

CF8(S43)-as received 4.96 7.85 215 0 22 0 0.00 861 978 421 449 CF8(S43)-as received 5.55 8.20 215 0 200 0 0.00 592 642 349 364 CF8(S43)-as received 5.02 7.99 215 0 290 0 0.00 672 734 362 379 CF8(S43)-as received 4.74 7.87 215 0 330 0 0.00 589 631 339 351 CF8(S43)-as received 4.86 8.25 215 0 360 0 0.00 207 282 201 235 CF8(S43)-as received 4.76 8.08 215 0 400 0 0.00 280 333 234 255 CF8(S52)-as received 4.94 7.51 215 0 22 0 0.00 763 917 397 435 CF8(S52)-as received 5.59 8.08 215 0 200 0 0.00 633 745 361 392 CF8(S52)-as received 5.31 8.12 215 0 290 0 0.00 457 518 299 318 CF8(S52)-as received 5.04 7.95 215 0 330 0 0.00 405 506 281 314 CF8(S52)-as received 4.99 7.94 215 0 360 0 0.00 355 491 263 310 CF8(S52)-as received 5.00 7.82 215 0 400 0 0.00 533 567 323 333 CF8(S43)-290°C-10kh 5.61 8.09 215 10000 290 22 681 6.53 521 628 328 360 CF8(S43)-290°C-10kh 5.32 7.89 215 10000 290 200 681 6.53 987 1015 451 458 CF8(S43)-290°C-10kh 5.49 8.26 215 10000 290 290 681 6.53 989 1037 440 450 CF8(S43)-290°C-10kh 5.22 8.14 215 10000 290 330 681 6.53 613 689 346 367 CF8(S43)-290°C-10kh 5.44 8.07 215 10000 290 360 681 6.53 434 535 291 323 CF8(S43)-290°C-10kh 5.29 8.25 215 10000 290 400 681 6.53 534 587 323 339 CF8(S43)-330°C-10kh 5.57 7.95 215 10000 330 22 14310 9.57 205 259 205 231 CF8(S43)-330°C-10kh 5.42 8.12 215 10000 330 200 14310 9.57 519 699 327 380 CF8(S43)-330°C-10kh 5.55 8.26 215 10000 330 290 14310 9.57 319 370 249 269 CF8(S43)-330°C-10kh 5.79 8.35 215 10000 330 330 14310 9.57 477 579 305 336 CF8(S43)-330°C-10kh 5.53 8.36 215 10000 330 360 14310 9.57 236 295 215 240 CF8(S43)-330°C-10kh 5.52 8.22 215 10000 330 400 14310 9.57 152 213 172 204 CF8(S43)-360°C-10kh 5.45 7.87 215 10000 360 22 109108 11.60 151 176 176 190 CF8(S43)-360°C-10kh 5.65 8.17 215 10000 360 200 109108 11.60 254 301 229 249 CF8(S43)-360°C-10kh 5.57 8.04 215 10000 360 290 109108 11.60 419 509 286 315 CF8(S43)-360°C-10kh 5.45 8.20 215 10000 360 330 109108 11.60 306 389 245 276 CF8(S43)-360°C-10kh 5.56 8.31 215 10000 360 360 109108 11.60 212 291 203 238 CF8(S43)-360°C-10kh 5.61 8.33 215 10000 360 400 109108 11.60 215 276 205 232 CF8(S43)-400°C-10kh 5.51 7.67 215 10000 400 22 1235458 14.03 122 150 159 176 CF8(S43)-400°C-10kh 5.58 8.00 215 10000 400 200 1235458 14.03 300 330 249 261 CF8(S43)-400°C-10kh 5.66 8.16 215 10000 400 290 1235458 14.03 277 330 232 254 CF8(S43)-400°C-10kh 5.67 8.25 215 10000 400 330 1235458 14.03 169 201 182 198 CF8(S43)-400°C-10kh 5.55 8.16 215 10000 400 360 1235458 14.03 216 307 205 245 CF8(S43)-400°C-10kh 5.49 8.24 215 10000 400 400 1235458 14.03 234 266 214 228

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Table A10. Crack lengths, aging parameters, and fracture toughness parameters for centrifugal cast CF3 (Z21 & Z43).

ID Initial Crack Length (mm)

Final Crack Length (mm)

Q (kJ/mole) Aging Time (h)

Aging Temp. (°C)

Test Temp. (°C)

t(325°C) A JQ-0.1mm (kN/m)

JQ-0.2mm (kN/m)

KJQ-0.1mm (MPa√m)

KJQ-0.2mm (MPa√m)

CF3(Z21)-as received 4.71 7.79 215 0 22 0 0.00 2671 2857 742 768 CF3(Z21)-as received 5.41 8.16 215 0 200 0 0.00 1920 1940 629 633 CF3(Z21)-as received 5.18 8.21 215 0 290 0 0.00 1896 1934 609 615 CF3(Z21)-as received 4.84 8.02 215 0 330 0 0.00 1360 1451 515 532 CF3(Z21)-as received 4.78 8.12 215 0 360 0 0.00 1829 1873 598 605 CF3(Z21)-as received 4.73 7.97 215 0 400 0 0.00 1358 1416 515 526 CF3(Z43)-as received 4.67 7.70 215 0 22 0 0.00 2220 2309 677 690 CF3(Z43)-as received 4.73 8.08 215 0 200 0 0.00 2351 2386 696 701 CF3(Z43)-as received 215 0 290 0 0.00 No data CF3(Z43)-as received 4.92 8.03 215 0 330 0 0.00 1585 1684 556 573 CF3(Z43)-as received 215 0 360 0 0.00 No data CF3(Z43)-as received 4.60 8.02 215 0 400 0 0.00 1559 1851 552 601 CF3(Z21)-290°C-10kh 5.24 8.09 215 10000 290 22 681 6.53 2265 2397 683 703 CF3(Z21)-290°C-10kh 5.36 8.08 215 10000 290 200 681 6.53 1674 1685 588 589 CF3(Z21)-290°C-10kh 215 10000 290 290 681 6.53 No data CF3(Z21)-290°C-10kh 215 10000 290 330 681 6.53 No data CF3(Z21)-290°C-10kh 5.22 8.51 215 10000 290 360 681 6.53 1850 1873 601 605 CF3(Z21)-290°C-10kh 5.44 8.23 215 10000 290 400 681 6.53 1092 1122 462 468 CF3(Z21)-330°C-10kh 5.03 7.97 215 10000 330 22 14310 9.57 2093 2102 657 658 CF3(Z21)-330°C-10kh 5.12 8.04 215 10000 330 200 14310 9.57 1649 1726 583 597 CF3(Z21)-330°C-10kh 5.19 8.28 215 10000 330 290 14310 9.57 1451 1586 532 557 CF3(Z21)-330°C-10kh 5.35 8.27 215 10000 330 330 14310 9.57 1319 1436 508 530 CF3(Z21)-330°C-10kh 5.31 8.02 215 10000 330 360 14310 9.57 1053 1087 453 461 CF3(Z21)-330°C-10kh 5.18 8.18 215 10000 330 400 14310 9.57 879 949 414 430 CF3(Z21)-360°C-10kh 5.23 7.87 215 10000 360 22 109108 11.60 1435 1480 544 552 CF3(Z21)-360°C-10kh 5.42 8.02 215 10000 360 200 109108 11.60 1464 1520 549 560 CF3(Z21)-360°C-10kh 4.99 8.19 215 10000 360 290 109108 11.60 871 968 412 435 CF3(Z21)-360°C-10kh 5.11 8.03 215 10000 360 330 109108 11.60 979 1043 437 451 CF3(Z21)-360°C-10kh 5.23 7.98 215 10000 360 360 109108 11.60 731 759 378 385 CF3(Z21)-360°C-10kh 5.06 8.22 215 10000 360 400 109108 11.60 733 849 379 407 CF3(Z21)-400°C-10kh 5.20 7.87 215 10000 400 22 1235458 14.03 371 412 277 292 CF3(Z21)-400°C-10kh 5.45 8.04 215 10000 400 200 1235458 14.03 738 814 390 410 CF3(Z21)-400°C-10kh 5.13 8.13 215 10000 400 290 1235458 14.03 860 929 410 426 CF3(Z21)-400°C-10kh 5.30 8.08 215 10000 400 330 1235458 14.03 438 521 292 319 CF3(Z21)-400°C-10kh 5.37 8.08 215 10000 400 360 1235458 14.03 319 421 249 287 CF3(Z21)-400°C-10kh 5.08 8.19 215 10000 400 400 1235458 14.03 548 587 327 339

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