Environmental Effects on Low-Cycle Fatigue
Lives of 316L/316LN Austenitic StainlessSteels in High Temperature Water
Yida Xiong
Advisor: Prof. Yutaka Watanabe
Department of Quantum Science and Energy Engineering,
Graduate School of Engineering, Tohoku University
1

Background and objectives

DO (dissolved oxygen)
The low-cycle fatigue (LCF) lives of austenitic stainless steels (SSs) were longer at highDO level (≥ 100 ppb) than that at low DO level. The reason remains unclear. Most of thedata for high-DO water was obtained by using pure high temperature water, while mostof the data for low-DO water was obtained by using borated and lithiated hightemperature water. This would be one reason why the phenomenon occurred.
14
11.07

12

Fen

10

8
6
3.19

4
2

0
1

10

100

1000

10000

DO（ppb）

Reference : Omesh Chopra and Gary L. Stevens, 2018, “Effect of LWR Water
Environments on the Fatigue Life of Reactor Materials,” NUREG/CR-6909, Rev. 1.

Fen = Nair/Nwater, Nair is the fatigue life in airand Nwater is the fatigue life in water. The
greater the Nair, the more deleterious the2environment.

Background and objectives

DH(dissolved hydrogen)1. Currently, around 2.2~3.1 ppm (25 cc/kg to 35 cc/kg) DH is added in the water.
2. Crack growth rate of nickel alloys showed a dependence on DH level.
3. Whether the DH is the main source of the absorbed hydrogen remains unclear.
Conductivity (μS/cm)

1~40

pH

7.2~7.4 (at 285℃)

B (ppm)Depends oncore reactivity

Li (ppm)

0.2~2.2

Dissolved Oxygen (ppm)<0.005

Dissolved Hydrogen (cm3
(STP) H2/kg H2O)

25~35

Reference : P.L. Andresen, J. Hickling, A. Ahluwalia, and J. Wilson, 2008, Effectof Hydrogen on Stress Corrosion Crack Growth Rate of Nickel Alloys in HignTemperature Water

Reference: 日本原子力学会標準 加圧水型原子炉一次系の水化学管理指針

In corrosion fatigue, change of DH level may affect the crack growth rate of 316
LN, leading to different fatigue lives at different DH level.
3

Background and objectives
Objectives:⚫ Investigating the LCF behaviors of 316L/316LN SSs at different DO
levels.
➢
➢

⚫

⚫
⚫

Are the previous studies right?
Why do the LCF lives change at different DO levels?

Investigating the LCF behaviors of 316LN SSs at different DH levels.
➢ Will the change of the DH level affect the LCF behaviors of 316LN
SS?
➢ What is the main source of the hydrogen absorbed into the 316LN
SS.
Will the addition of boric acid and lithium hydroxide affect the LCF lifeof 316L SS in high-DO water?
Recommendations for the optimization of the water chemistry.

4

LCF behaviors of 316LN/316L
different DO levels
Fatigue life & Cyclic stress response

at

1200
< 5 ppb DO water (306, 309 cycles)
50 ppb DO water (894, 607 cycles)
100 ppb DO water (825, 568 cycles)
2 ppm DO water (359, 371 cycles)

1000

316LN

800

600

400

200

Average fatigue life (cycles)

Average fatigue life (cycles)

1200

SS

30 cc DH & < 5 ppb DO water (289/306 cycles)
50 ppb DO water (710/778 cycles)
1 ppm DO water (346/407 cycles)
1 ppm DO water, 5-day pre-soaking (319/321 cycles)
1 ppm DO water (lower conductivity) (367/315 cycles)
1 ppm DO water (lower conductivity), 5-day pre-soaking (380/401 cycles)

1000

316L

800

600

400

200
1

10

100

1000

10000

DO level (ppb)

1

10

100

1000

10000

DO level (ppb)< 5 ppb, 1 ppm and 2 ppm DO water: Fen > 10
50 ppb, 100 ppb DO water: Fen was ~6
The equation used for predicting the Fen in the reference for austenitic stainless steels was
not conservative enough at DO levels of < 5 ppb, 100 ppb and 2 ppm and not accurate at
DO level of 50 ppb.
Reference:
Omesh Chopra and Gary L. Stevens, 2018, “Effect of LWR Water Environments on the Fatigue Life of Reactor Materials,”
NUREG/CR-6909, Rev. 1

5

LCF behaviors of 316LN/316L SS atdifferent DO levels
Fracture surface and Raman spectroscopy (316LN)< 5 ppb DO water

50 ppb DO water

Magnetite

Magnetite

677 cm-1
677 cm-1

547 cm-1

Intensity (a.u)
200

400

600

800

1000

Raman Shift (cm-1)

01000μm

200

400

600

800

1000μm1000

Raman Shift (cm-1)

2 ppm DO water

100 ppb DO water
Magnetite

590 cm-1
704 cm-1

Intensity (a.u)

0-1318 cm-1 547 cm

NiFe2O4

Intensity (a.u)

318 cm-1

Intensity (a.u)

677 cm-1
318 cm-1

487 cm-1
333 cm-1

0

200

400

600

800

1000

Raman Shift (cm-1)

547 cm-1

200

400

600

800

1000

Raman Shift (cm-1)

1000μmIntensity (a.u)

0Magnetite

677 cm-1
318 cm-1

0200

547 cm-1

400

600

800

Raman Shift (cm-1)

1000μm6

1000

LCF behaviors of 316LN/316L SS atdifferent DO levels
Fracture surface and Raman spectroscopy (316L)
30 cc DH & < 5 ppb DO water

50 ppb DO water
Magnetite

Magnetite

677 cm-1

677 cm-1
318 cm-1

0200

547 cm-1

400

600

800

1000

0

Raman Shift (cm-1)

1000μm1000μm1 ppm DO water-1

579 cm-1

Intensity (a.u)

677 cm-1

0

200

400

600

Raman Shift (cm-1)
0

200

400

600

Raman Shift (cm-1)

800

1000

400

600

800

Raman Shift (cm-1)

704 cm-1

Intensity (a.u)

490 cm547 cm-1

200

547 cm-1

NiFe2O4

Magnetite
318 cm-1

318 cmIntensity (a.u)

Intensity (a.u)

-1

800

1000

7

1000

Hydrogen desorption rate (ppm/s)

LCF behaviors ofdifferent DO levels
TDS analysis

316LN/316L

SS

at

3.0x10-4
As-machined
Air baked< 5 ppb DO water
50 ppb DO water
100 ppb DO water
2 ppm DO water-4

2.5x10-4

2.0x10316LN

1.5x10-4
1.0x10-4

Condition< 5 ppb
DO
water

50 ppbDO
water

100 ppb
DO
water

2 ppm
DO
water

HydrogenContent(wppm)

0.96

0.13

0.17

0.18

5.0x10-5
0.0
0

200

400

600

800

As-machined: 2.23 ppm
Air baked （325 ℃, 3 days）: 0.11 ppm

Temperature (°C)

Hydrogen desorption rate

1.0x10-4

30 cc DH & < 5 ppb DO water
50 ppb DO water
1 ppm DO water

Condition

30 cc DH & <5 ppb DOwater

50 ppb DOwater

1 ppm DOwater

HydrogenContent(wppm)

0.80

0.22

0.20

316L

5.0x10-5

0.0
0

200

400

Temperature (°C)

600

800

8

LCF behaviors of 316LN/316L SS atdifferent DO levels
Crack propagation path characterization(316LN)< 5 ppb DO water
001

{100}
111

{111}
101

35μm

35μm

9

LCF behaviors of 316LN/316L SS atdifferent DO levels
Crack propagation path characterization (316LN)
50 ppb DO water
1

1

001

2

111
101

{100}
{111}
{100}

{111}

2

50μm

50μm

100μm
10

LCF behaviors of 316LN/316L SS atdifferent DO levels
Crack propagation path characterization (316LN)
100 ppb DO water

2

1

001
{100}

{111}
111
101

{100}
{111}
2
300μm

100μm

1

60μm
11

LCF behaviors ofdifferent DO levels

316LN/316L

SS

at

Crack propagation path characterization (316LN)
2 ppm DO water

001
100μm
{100}

111

{111}

101
{100}
{111}

50μm
100μm
No crystallographic feature was observed at DO levels of 50 ppb, 100 ppb,
and 2 ppm, while the crack mainly propagated along {111} planes andsometimes along {100} planes when the DO level was < 5 ppb.

12

LCF behaviors ofdifferent DO levels

316LN/316L

SS

at

Crack propagation path characterization (316L)
30 cc DH & < 5 ppb DO water

50 ppb DO water
001

{100}

{100}

{111}

{111}

111
101

35μm

35μm

13

Chapter 4: LCF behaviors of 316L SS at different DO levels and somediscussion about the effects of addition of boric acid and lithium hydroxide

Crack propagation path characterization (316L)
1 ppm DO water
{100}
{111}

20 μm
Similar to 316LN, crack of specimen tested in low-DO water showed
crystallographic feature while those tested in oxygenated water did not showsuch a feature. Combining with other results, it is considered that themechanisms for 316L were the same with those for 316LN

14

Chapter 2: LCF behaviors of 316LN SS atdifferent DO levels
Crack initiation and propagation< 5 ppb DO water

H

Metallic element

In the < 5 ppb DO water, more hydrogen wasabsorbed into the metal. Therefore, more hydrogeninduced decohesion occurred. As the hydrogenusually was trapped by the dislocation, thereforehydrogen accumulated along slip plane. Since themain slip system of metals with fcc structure is{111}<110>, crack mainly propagated along {111}.

H

Publication:
50, 100 ppb DO water

1. Yida Xiong, Yutaka Watanabe, Yuki Shibayama, Nicolas
Mary, Effects of 100 ppb dissolved oxygen on low-cycle
fatigue behaviors of 316LN austenitic stainless steel inborated and lithiated high temperature water and mechanism
behind these effects, Corrosion Science (2020).
https://doi.org/10.1016/j.corsci.2020.108567

15

Chapter 2: LCF behaviors of 316LN SS atdifferent DO levels⚫ With regard to the mechanism of the decrease in LCF life
at DO level of 2 ppm
Crack initiation
Oxide film rupture

Oxide film formation
Cathodic reaction:
O2+4e-+2H2O=4OH-

O2
O2

O2
O2

316LN

O2

O2
O2

O2

O2
O2

Locations with low stressconcentration

Strain applied

O2

O2
O2

Oxide film

O2
O2

316LN

Crack initiation

O2

O2
O2

O2

O2
O2

O2

Oxide film

Rapid Oxide filmreformation due tohighcorrosionrate, leading toLess cracks.

Locations with highstress concentration

More dissolution
bycorrosion
attack caused byhigher corrosion
potential

16

Chapter 2: LCF behaviors of 316LN SS atdifferent DO levels
Crack propagation

More cations produced by metal
dissolution to maintain charge
neutrality

Cathodic reaction:
O2+4e-+2H2O=4OHMainly occurred on
inner surface or
crack mouth (higher potential)
O2
O2
Higher potential gradient

O2

O2

O2

O2 O
2
O2 O2 O2

More anions from bulk water (causedby higher potential gradient)

O2

Oxide film
More metal dissolution(caused by higher crack tip
potential than that in 50 ppb
and 100 ppb DO water)

316LN

Anion

REFERENCE:
1. Yida Xiong, Yutaka Watanabe, Yuki
Shibayama, Nicolas Mary, Xiangyu
Zhong, Low-cycle fatigue behaviors of
316LN austenitic stainless steel inborated and lithiated high temperaturewater with different levels of dissolved
oxygen, Corrosion Science 176 (2020).
DOI:
https://doi.org/10.1016/j.corsci.2020.10904
8.

Anion

Anion

cationcationBare metal

cationAnodic reaction: metal dissolusion(lower potential)
17

LCF behaviors of 316LN SS at different DH
levelsFatigue life & Cyclic stress response
350
0 cc DH water
30 cc DH water
50 cc DH water
ASME Code Design Curve

0.70%

0.60%

300

Stress (MPa)Strain amplitude

0.80%

250
200

273 cycles

150
0 cc DH water
30 cc DH water
50 cc DH water

100

0.50%
50

349 cycles

0
0.40%

0
250

300

350

Fatigue life (cycles)

400

100

200

300

400

Fatigue life (cycles)

Given the typical scatter of the LCF life in simulated PWR primary water, it isconsidered that the change of DH level had no effect on the LCF life of 316LN SS.
The cyclic stress response at different DH level also did not show a big difference.
18

LCF behaviors of 316LN SS at different DH
levelsFracture surface
0 cc DH water

1000μm

30 cc DH water

1000μm

50 cc DH water

1000μmFracture surfaces of specimens tested at different DH level did not show a big
difference. On these surfaces, striation, second crack and tertiary crack wereobserved.

19

Hydrogen Desorption Rate (ppm/s)

LCF behaviors of 316LN SS at different DH
levels
TDS analysis (180th cycle)
3.00E-04-4
3×10

Even no DH was added,
0.96 wppm hydrogen was
detected
insidethematerial.
Hydrogen content increasedslightly with increasing DH.

As-machined: 2.23 ppm
Air baked: 0.11 ppm

As-machined
Air baked
0 cc DH water-4
2.00E-04
2×10

30 cc DH water
50 cc DH water-4
1.00E-04
1×10

00.00E+00
0

100

200

300

400

500

600

700

800

Hydrogenabsorbed
mainly came from thehydrogen produced bycorrosion reaction.

Temperature (℃)

Condition

0 cc DH water

30 cc DH water

50 cc DH water

Hydrogen Content(wppm)

0.96

0.99

1.11
20

Chapter 3: LCF behaviors of 316LN SS atdifferent DH levels
Oxide film characterization
30 cc DH water

0 cc DH water

50 cc DH water
Oxide particles formedat different DH level had
similar shape.
Fe3O4 was confirmed by
Raman Spectroscopy.

0

500
1000
-1
Raman Shift (cm )547 cm-1

0677 cm-1

318 cm-1

547 cm-1

Intensity (a.u)

Intensity (a.u)

318 cm-1

677 cm-1

Intensity (a.u)

547 cm-1

500
1000
-1
Raman Shift (cm )

Fe3O4

0

677 cm-1

318 cm-1

Change of DH level
had no significant
effect on the oxide
morphology.

500
1000
-1
Raman Shift (cm )21

Chapter 3: LCF behaviors of 316LN SS atdifferent DH levels
Oxide film characterization
90
80
70
60
50
40
30
20
10
0

Oxide layer (~50 min)

0100

30 cc DH water
Atomic percent (%)

Atomic percent (%)

0 cc DH water

O
Fe
Cr
Ni

200
300
Sputtering time (min)

400

90
80
70
60
50
40
30
20
10
0

Oxide layer (~50 min)

0

100

O
Fe
Cr
Ni

200
300
Sputtering time (min)400

Atomic percent (%)

50 cc DH water
90
80
70
60
50
40
30
20
10
0

Oxide layer (~50 min)

0

100

200
300
Sputtering time (min)Oxide films formed at different
DH levels had similar XPS
depth profile.

O
Fe
Cr
Ni

400

22

Chapter 3: LCF behaviors of 316LN SS atdifferent DH levels
Oxide film0characterizationmin
10 min
10000

Intensity (a.u)

12000

3+
Cr
Cr2O
3

0 cc DH water
30 cc DH water
50 cc DH water

Cr0

8000

Cr(OH)3

6000

4000
2000

Cr3+

0 cc DH water
30 cc DH water
50 cc DH water

8000
6000
4000
2000

0

Cr(OH)3

0
567

577
587
Binding energy (eV)

597

607

567

577
587
597
Binding energy (eV)607

40 min

12000

Cr0

10000

Intensity (a.u)

Cr0

10000

Intensity (a.u)

12000

Cr(OH)3

8000

0 cc DH water
30 cc DH water
50 cc DH water

6000
4000
2000

Cr3+

0
567

577
587
Binding energy (eV)

597

607

Oxide films formed at different
DH levels showed similar Cr
2p spectrums. Combining withthe depth profiles, it isconsidered the change of DH
level had no significant effecton the oxide film composition.
23

Chapter 5: Conclusions⚫ Key results:➢ LCF behaviors of 316L/316LN at different DO levels••

The LCF lives of 316L/316LN at different DO levels were different from the dataobtained by previous studies. The LCF lives of 316L/316LN in < 5 ppb DO water
was shorter than the LCF lives in middle DO water (50 ppb or 100 ppb for 316LN
and 50 ppb for 316L) but closed to the LCF lives at high DO levels (2 ppm for
316LN, 1 ppm for 316L). The discrepancy between this study and previous studies
was probably caused by the materials used.
When the DO added was above 5 ppb (50 ppb, 100 ppb and 2 ppm for 316LN; 50
ppb, 1 ppm for 316L), the hydrogen absorption was inhibited, which caused theincrease in the LCF lives at these DO levels. However, when the DO added was 2
ppm DO for 316LN or 1 ppm for 316L, even though the hydrogen absorption was
inhibited, the crack tip potential, potential gradient between the crack mouth andcrack tip were higher, which caused the decrease in the LCF lives at these DO level.

➢ LCF behaviors of 316LN at different DH levels••

Change of DH level did not have significant effects on the LCF life, corrosion
behaviors of 316LN SS.
The amount of hydrogen absorbed into the 316LN slightly increased with increasing
DH level. The main source of the hydrogen absorbed into the 316LN is thehydrogen produced by corrosion reaction, instead of the dissolved hydrogen added24
intentionally.

Chapter 5: Conclusions⚫ Recommendations:➢ Recommendations for the optimization of the water chemistry.
•

The hydrogen absorbed into the material and the crack tip potential & potential
gradient between the crack mouth and the crack tip are considered the factors
determining the LCF lives of 316L/316LN SSs. Therefore, adding little DO(50 or
100 ppb in the present case) into the water is beneficial to the 316L/LN SS fromthe point of view of the LCF, because the adding of the DO can inhibit thehydrogen absorption. However, adding too much DO(2 ppm DO in the presentcase) will be deleterious to this material as it can increase the potential
mentioned.

25