NASA

Technical

Memorandum

NASA TM - 108386

/ i/'/"- _ 7

?"-/_t

(NASA-TM-I08386) [HE EFFECT OF

TENSILE STRESS ON HYDROGEN

DIFFUSION IN METAL ALLOYS (NASA)

43 p

N93-16701

Unclas

G3126 0135334

THE EFFECT OF TENSILE STRESS ON HYDROGEN

DIFFUSION IN METAL ALLOYS

By M.D. Danford

Materials and Processes Laboratory

Science and Engineering Directorate

December 1992

Nf SA

National Aeronautics and

Space Adminrstratton

George C. Marshall Space Flight Center

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1. AGENCY USE ONLY (Leave blank) 2. REPORT DATE 3. REPORT TYPE AND DATES COVERED

December 1992 Technical Memorandum

4. TITLE AND SUBTITLE S. FUNDING NUMBERS

The Effect of Tensile Stress on Hydrogen Diffusion in Metal Alloys

6. AUTHOR(S)

M.D. Danford

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESStES)

George C. Marshall Space Flight Center

Marshall Space Flight Center, Alabama 35812

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)

National Aeronautics and Space Administration

Washington, DC 20546

8. PERFORMING ORGANIZATION

REPORT NUMBER

10. SPONSORING / MONITORING

AGENCY REPORT NUMBER

NASA TM - 108386

11. SUPPLEMENTARY NOTES

Prepared by Materials and Processes Laboratory, Science and Engineering Directorate.

12a.DISTRIBUTION/ AVAILABILITYSTATEMENT

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12b. DISTRIBUTION CODE

13. ABSTRACT (Maximum 200words)

The effect of tensile stress on hydrogen diffusion has been determined for Type 303 stainless

steel, A286 CRES, and Waspaloy and IN100 nickel-base alloys. It was found that hydrogen diffusion

coefficients are not significantly affected by stress, while the hydrogen permeabilities are greatly

affected in Type 303 stainless steel and A286 CRES (iron-based alloys), but are affected little in

Waspaloy (nickel-base) and not affected at all in 1N100 (nickel base). These observations might be

taken as an indication that hydrogen permeabilities are affected by stress in iron-based alloys, but only

slightly affected in nickel-based alloys. However, it is too early to make such a generalization based on

the study of only these four alloys.

14. SUBJECTTERMS

Hydrogen diffusion in metals, hydrogen diffusion coefficients and stress,

hydrogen diffusion and permeability with stress, hydrogen trapping and stress

17. SECURITYCLASSIFICATION18. SECURITYCLASSIFICATION19. SECURITYCLASSIFICATION

OFREPORT OFTHISPAGE OFABSTRACT

Unclassifted Unclassifted Unclassifted

NSN7s4o-o_-28o-ssoo

15. NUMBER OF PAGES

44

16. PRICE CODE

NPs

20. LIMITATION OF ABSTRACT

Unlimited

Standard Form 298 (Rev 2-89)

TABLE OF CONTENTS

INTRODUCTION ......................................................................................

EXPERIMENTAL ......................................................................................

RESULTS .............................................................................................

Type 303 StainlessSteel..........................................................................

A286 CRES ....................................................................................

Waspaloy (Nickel-Base Alloy) ....................................................................

INI00 (Nickel-Base Alloy) ........................................................................

DISCUSSION AND CONCLUSIONS ....................................................................

REFERENCES ..............................................................................................................................

Page

1

1

2

2

3

3

3

4

5

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111

PRECEDING P.._G_ _LAHK PlOT FILB,_D
LIST OF ILLUSTRATIONS

Figure

1.

2.

3.

4.

5.

6.

,

8.

9.

10.

11.

12.

13.

14.

15.

16.

17.

18.

19.

20.

21.

Title

Hydrogen Desorption Curves for Type 303SS at Zero Stress ......................................

Hydrogen Desorption Curves for Type 303SS at 25 Percent of Yield .........................

Hydrogen Desorption Curves for Type 303SS at 50 Percent of Yield .........................

Hydrogen Desorption Curves for Type 303SS at 75 Percent of Yield .........................

Hydrogen Desorption Curves for Type 303SS at 90 Percent of Yield .........................

Least-Squares Fit of a Second-Degree Polynomial to Percent Uniformity Versus

Percent Yield for Type 303SS ......................................................................................

Hydrogen Desorption Curves for A286 CRES at Zero Stress ......................................

Hydrogen Desorption Curves for A286 CRES at 25 Percent of Yield .........................

Hydrogen Desorption Curves for A286 CRES at 50 Percent of Yield .........................

Hydrogen Desorption Curves for A286 CRES at 75 Percent of Yield .........................

Hydrogen Desorption Curves for A286 CRES at 90 Percent of Yield .........................

Least-Squares Fit of a Second-Degree Polynomial to Percent Uniformity Versus

Percent Yield for A286 CRES ......................................................................................

Hydrogen Desorption Curves for Waspaloy at Zero Stress ...........................................

Hydrogen Desorption Curves for Waspaloy at 25 Percent of Yield ..............................

Hydrogen Desorption Curves for Waspaloy at 50 Percent of Yield ..............................

Hydrogen Desorption Curves for Waspaloy at 75 Percent of Yield ..............................

Hydrogen Desorption Curves for Waspaloy at 90 Percent of Yield .............................

Least-Squares Fit of a Second-Degree Polynomial to Percent Uniformity Versus

Percent Yield of Waspaloy ...........................................................................................

Hydrogen Desorption Curves for IN100 at Zero Stress ................................................

Hydrogen Desorption Curves for IN100 at 25 Percent of Yield ...................................

Hydrogen Desorption Curves for IN100 at 50 Percent of Yield ...................................

Page

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29

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31

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iv
LIST OF ILLUSTRATIONS (Continued)

Figure

22.

23.

Title

Hydrogen Desorption Curves for IN100 at 75 Percent of Yield ...................................

Hydrogen Desorption Curves for IN 100 at 90 Percent of Yield ...................................

Page

34

34
Table

1.

2.

3.

4.

5.

6.

7.

8.

9.

10.

11.

12.

LIST OF TABLES

Title

ChemicalAnalysisof Type303StainlessSteelChips..................................................

ParametersObtainedFrom303SSDesorptionData .....................................................

HydrogenTrappingby 303SSasaFunctionof Stress..................................................

ChemicalAnalysisof A286 CRES ...............................................................................

ParametersObtainedFromA286CRESDesorptionData ...........................................

HydrogenTrappingby A286CRESasaFunctionof Stress........................................

ChemicalAnalysisof Waspaloy...................................................................................

ParametersObtainedFromWaspaloyDesorptionData ...............................................

HydrogenTrappingbyWaspaloyasaFunctionof Stress............................................

ChemicalAnalysisof IN100Alloy ...............................................................................

ParametersObtainedFromIN100DesorptionData .....................................................

HydrogenTrappingby IN100asaFunctionof Stress..................................................

Page

6

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vi
CHEMICAL SYMBOLS

A1 Aluminum

B Boron

Bi Bismuth

C Carbon

Co Cobalt

Cr Chromium

Cu Copper

Fe Iron

Mo Molybdenum

Mn Manganese

Nb Niobium

Ni Nickel

O Oxygen

P Phosphorous

Pb Lead

S Sulfur

Si Silicon

Ta Tantalum

Ti Titanium

V Vanadium

W Tungsten

Zr Zirconium

vii

TECHNICAL MEMORANDUM

THE EFFECT OF TENSILE STRESS ON HYDROGEN DIFFUSION

IN METAL ALLOYS

INTRODUCTION

The present work was undertaken to provide further information regarding the effect of tensile

stress on the hydrogen distribution in metals on charging and also on the effect on other parameters

involved, such as mean hydrogen concentrations and hydrogen diffusion coefficients. Experimentally, it

is desirable to carry out the investigations in the elastic region since detelmination of the hydrogen diffusion coefficient is a sensitive function of the sample radius, and deformation of the sample in the plastic region would prevent accurate determination of this parameter. However, small plastic deformations

did occur at 90-percent yield, but these are not considered great enough to seriously affect the results.

Other studies concerning the influence of stress on hydrogen diffusion have been carried out.

Wriedt and OrianP showed that an elastically stressed 75-weight-percent palladium to 25-weight-percent silver alloy in a hydrogen atmosphere increased in hydrogen content under uniaxial tension and

decreased in hydrogen content under uniaxial compression. Bockris et al. 2 studied Armco iron and 4340

steel and found that hydrogen permeation was increased by tensile stress and decreased by compressive

stress, with the hydrogen diffusion coefficient being unaffected by the applied stress.

Results for A286 CRES steel have been reported previously. 3 The present study includes work

on Type 303 stainless steel (303SS) and nickel-base alloys IN100 and Waspaloy. There are, therefore,

two iron-base alloys and two nickel-base alloys, and it is of interest to compare the effect of stress on the

hydrogen diffusion in these different alloys.

This report presents the results obtained by electrochemical methods on all four alloys under

stresses corresponding to 0, 25, 50, 75, and 90 percent of yield. Calculations were made using the standard procedure previously developed and described 4 for data extending to large time (0 to 150,000 s).

EXPERIMENTAL

The EG&G-PARC model 350A corrosion measurement console was employed for the electrochemical measurements of hydrogen desorption.

Samples consisted of tensile specimens of the metal alloys which were 5.08-cm (2-in) long with

a gauge length of 1.905 cm (0.75 in) and a diameter of 0.3175 cm (0.125 in). The specimens were

threaded at both ends with 1/4-20 NC threads. All metal parts, except for the gauge section, were coated

with Micromask stop-off lacquer to prevent electrical contact.

The specimens were mounted on a Korros Data slow strain rate (SSR) machine, enclosed in a

glass cell having a 1-L capacity. The cell was filled with a 0.1N sodium hydroxide (NaOH) solution

which provided a medium for charging of the sample with hydrogen and for conduction of the hydrogen
desorptioncurrent.The SSRmachinewasthendrivento theproperloadlevel, whichwasmaintained

throughoutthecharginganddesorptionstages.Sampleblanks were run at a constant potential of 0.0 V

versus the saturated calomel electrode. The period of measurement was 150,000 s for each sample with

values of the current being recorded every 500 s. After running the blanks, the specimens were then

electrolytically charged with hydrogen for a period of 1 h at a current density of 90 mA/cm 2.

Measurements of the desorption current were initiated immediately on completion of charging,

with current measurements being taken in the same manner as for the blanks. After completion of each

run, data were read to an IBM PC/AT computer for calculation purposes. Currents due only to hydrogen

were obtained by subtraction of the currents for blanks. After data for both the hydrogen-containing

sample and its blank were obtained, the experimental curve Q(t), the coulombs of hydrogen desorbed

after time t, versus time was obtained through integration of the current-time curves. Values of Q(t) were

corrected for cutoff at finite time (150,000 s) by procedures described previously, 4 obtaining values for

Q**HM, the observed concentration t_, the apparent surface concentration Co, and the hydrogen-diffusion

coefficient D. The procedures for obtaining these quantities are described in Reference 4. Theoretical

hydrogen-desorption curves were calculated for both uniform and nonuniform hydrogen distributions

using the computer program PDEONE. 5

Residual hydrogen concentrations (hydrogen remaining after complete desorption of the mobile

hydrogen) were determined using the Leco Model RH2 hydrogen analyzer. Calibration of the hydrogen

analyzer was accomplished using standard samples. The gauge sections of the tensile test specimens

were retained for these analyses after removing the remaining shoulders and threaded sections at each

end with a diamond saw.

RESULTS

Type 303 Stainless Steel

The material used in this investigation had an ultimate tensile strength (UTS) of 589 MPa (85.4

ksi) and a yield strength (YS) of 265 MPa (38.4 ksi). The chemistry of the Type 303SS alloy is

presented in Table 1. Hydrogen desorption curves, experimental and theoretical, are shown in Figures 1

through 5. Results were obtained under stresses of 0, 66.2 MPa (9.6 ksi), 132.3 MPa (19.2 ksi), 198.5

MPa (28.8 ksi), and 238.5 MPa (34.6 ksi). These stress levels represent 0, 25, 50, 75, and 90 percent of

the yield strength, respectively.

Results from the data analyses are presented in Table 2. These indicate that there is no significant

trend in the values of the diffusion coefficients at the various stress levels. Values of Co, the apparent

concentration of hydrogen at the sample surface, t_, the mean mobile hydrogen concentration in the

sample, and the percent uniformity of the initial hydrogen concentration on charging (parameters related

to hydrogen solubility) indicate that the permeability of Type 303SS increases with stress up to about

50 percent of yield and decreases thereafter. The curve relating the variation of percent uniformity with

percent yield is shown in Figure 6, the data points being fitted with a second-degree polynomial.

Hydrogen trapping as a function of stress is shown in Table 3. The percent of trapped or residual

hydrogen is quite high in all cases, the average percent residual hydrogen being 62.3 percent. The reason

for the very high percentage of trapped hydrogen is not known, but may be due to the high weight percent of sulfur (0.25 percent) present in this alloy. Magnified photographs of the metal matrix show that
therearenumerousstringersinterspersedthroughout,whichareprobablyfilled with sulfuror metallic

sulfides.The hydrogenmaybetrappedin theseregionseitherbythesulfur-containingmaterialsor as

molecularhydrogen.

A286 CRES

A286 CRES had a chemistry (Table 4) conforming to AMS 5732, but the UTS of 1,210 MPa

(175.6 ksi) and a YS of 933 MPa (135.3 ksi) indicated that the material had been solution treated, cold

worked, and precipitation heat treated. Hydrogen desorption curves are shown in Figures 7 through 11.

Results were obtained under stresses of 0, 233 MPa (33.9 ksi), 467 MPa (67.7 ksi), 700 MPa (101.6 ksi),

and 840 MPa (121.9 ksi), representing 0, 25, 50, 75, and 90 percent of the YS.

Results from the data analyses are presented in Table 5. Again, no significant trend in values of

the diffusion coefficients is noted. Values of Co, C, and the percent uniformity of the initial hydrogen

concentration on charging indicate that the permeability of A286 CRES increases up to about 60 percent

of the yield strength, decreasing thereafter. The curve relating the variation of percent uniformity with

percent yield is shown in Figure 12. Again, the data points were fitted with a second-degree polynomial.

The hydrogen trapping as a function of stress is shown in Table 5. The average percent of

trapped hydrogen is 7.6 percent, much lower than that for Type 303SS.

Waspaloy

The Waspaloy material had a UTS of 1,392 MPa (202 ksi) and a YS of 1,024 MPa (148.6 ksi).

The chemistry of Waspaloy is shown in Table 7. Hydrogen desorption curves are shown in Figures 13

through 17. Results were obtained under stresses of 0, 256 MPa (37.2 ksi), 512 MPa (74.3 ksi), 768 MPa

(111.4 ksi), and 922 MPa (133.7 ksi), representing 0, 25, 50, 75, and 90 percent of the YS.

Results from the data analyses are presented in Table 8. As with the previous cases, there is no

significant trend in values of the diffusion coefficients. Values of Co and C are generally higher for

specimens under stress, although there is some scatter. Results for the percent uniformity show a much

less pronounced trend with increasing stress than the two iron-based alloys previously discussed. Hence,

the permeability of this alloy is much less affected by stress than are those for A286 CRES and 303SS.

The curve relating the variation of percent uniformity with percent yield is shown in Figure 18, with all

observed data points again being fitted with a second-degree polynomial.

The hydrogen trapping as a function of stress is shown in Table 9. The average percent trapped

hydrogen is 20.6 percent.

INIO0

The IN100 material obtained from a powder metallurgy isothermal forging, heat treated at

Sintech, Inc., had a UTS of 1,606 MPa (233 ksi) and a YS of 1,160 MPa (168.3 ksi). The chemistry of

this material is shown in Table 10. Hydrogen desorption curves are shown in Figures 19 through 23.

Results were obtained under stresses of 0, 290 MPa (42 ksi), 580 MPa (84 ksi), 870 MPa (126 ksi), and

1,044 MPa (151 ksi). These stress levels represent 0, 25, 50, 75, and 90 percent of the YS, respectively.
Resultsfrom thedataanalysesarepresentedin Table11.Thereis againnosignificanttrendin

thevaluesof thediffusioncoefficients.Theresultsaresomewhatsurprising,sinceit is obviousthat

IN100showsnoeffectsdueto stress.Thevaluesof C appear to actually decrease with increasing stress,

although this is probably attributable mostly to scatter in the experimental results. The percent

uniformity remains 100-percent nonuniform throughout, indicating no increase in permeability. This is

to be compared with the results obtained for A286 CRES, Type 303SS, and Waspaloy. A286 CRES and

Type 303SS, both iron-based alloys, show the most pronounced changes in permeability with stress,

while Waspaloy, a nickel-based alloy, is only slightly affected.

Hydrogen trapping as a function of stress is shown in Table 12. The average percent trapped

hydrogen is 21.5 percent, comparable to the value obtained for Waspaloy (20.6 percent). Thus, the value

of 62.3 percent obtained for Type 303SS is far higher than the values obtained for the other three alloys.

DISCUSSION AND CONCLUSIONS

The results all show no significant trends in values of the hydrogen diffusion coefficients, in

agreement with the results of Bockris et al.2 Distinct increases in the mean mobile hydrogen concentrations were observed at higher stress levels for Type 303SS, A286 CRES, and slightly in Waspaloy, but

not observed for IN 100, where there was no effect due to stress.

Since the values of the diffusion coefficients were nearly the same for all four metal alloys, the

increased hydrogen penetration in type 303SS, A286 CRES, and Waspaloy on charging cannot be

explained using standard diffusion theory along with the observed hydrogen diffusion coefficients,

which were obtained in hydrogen desorption measurements. It is likely that the increased penetration is

due to increased permeability. For a thin membrane, the permeability is given by

DSP

Permeation - (1)

L

Here, D is the hydrogen diffusion coefficient, S is the solubility of hydrogen, P is the exterior hydrogen

pressure, and L is the membrane thickness. Percent uniformities of the hydrogen distributions are

accompanied by factors related to the solubility of hydrogen in the metals, namely the mean mobile

hydrogen concentrations C.

The difference between the permeability of hydrogen in iron-base alloys and that in the nickelbase alloys has not previously been observed. From this limited work, it is too early to make a generalization that all iron-base and nickel-base alloys are affected differently by tensile stress, the iron-base

alloys being much more affected than the nickel-base alloys. However, the observations made in this

work might be an indication that this could be the case.

4
REFERENCES

1. Wriedt, H.A., and Oriani, R.A.: Acta Metall., vol. 18, 1970, p. 753.

2. Bockris, J. O'M., Beck, W., Genshawl, M.A., Subramanyan, P.K., and Williams, F.S.: Acta Metall.,

vol. 19, 1971, p. 1209.

3. Danford, M.D.: NASA Technical Memorandum TM-103537, May 1991.

4. Danford, M.D.: NASA Technical Paper 2744, July 1987.

5. Sincovec, R.F., and Madsen, N.K.: ACM Trans. Math. Software, vol. 1, 1975, pp. 232-260.
Table1.

Chemical Analysis of Type 303 Stainless Steel Chips.

Element

Cr

Ni

Si

Mn

Mo

Cu

P

Fe

C

S

MSFC Analysis

Weight Percent

18.30

8.82

0.31

1.70

0.18

0.56

0.03

Balance

0.087

0.254

AMS 5640P, Type 1

Weight Percent

17.00- 19.00

8.00- 10.00

1.00 Maximum

2.00 Maximum

0.75 Maximum

0.75 Maximum

0.15 Maximum

Balance

0.15 Maximum

0.15 Minimum

Table 2.

Parameters Obtained from 303SS Desorption Data.

Dxl08 Percent

Percent Yield cm2/s Co* t_t Uniformity

0

25

5O

75

90

6.18

6.86

4.83

2.26

3.62

10.87

22.60

23.89

34.32

24.93

2.27

4.94

4.48

4.76

4.14

0

41.0

35.0

12.0

16.0

* Apparent H concentration at sample surface.

t Mean H concentration.
Table3.

HydrogenTrappingby 303SSasaFunctionof Stress.

Percent

Yield

0

25

5O

75

90

Mobile

Hydrogen

(p/m)

2.27

4.94

4.48

4.76

4.14

Trapped

Hydrogen

(p/m)

7.92

9.93

5.68

5.46

5.60

Total

Hydrogen

(p/m)

10.19

14.87

10.16

10.22

9.74

Percent

Trapped

Hydrogen

77.7

66.8

55.9

53.4

57.5

Table 4.

Chemical Analysis of A286 CRES.

Elements

Cu

V

Si

B

A1

Ti

Mo

Mn

Fe

Ni

Cr

P

C

S

MSFC Analysis

Weight Percent

0.08

0.28

0.25

0.007

0.27

2.24

1.09

0.19

57.33

24.43

13.77

0.014

0.05

0.001

AMS 5732

Weight Percent

0.10-0.50

1.0 Maximum

0.003 - 0.10

0.35 Maximum

1.90 - 2.35

1.00- 1.50

2.0 Maximum

Balance

24.0 - 27.0

13.5- 16.0

0.25 Maximum

0.08 Maximum

0.025 Maximum
Table5.

ParametersObtainedFromA286CRESDesorptionData.

PercentYield

25

5O

75

90

Dxl0 8

cm2/s

4.17

2.17

2.04

2.35

2.47

Co*

(p/m)

31.11

68.96

73.95

51.92

64.58

(p/m)

5.49

8.62

8.97

6.73

8.57

Percent

Uniformity

23

48

88

62

64

* Apparent H concentration at sample surface.

t Mean H concentration.

Table 6.

Hydrogen Trapping by A286 CRES as a Function of Stress.

Percent

Yield

0

25

5O

75

90

Mobile

Hydrogen

(p/m)

5.49

8.62

8.97

6.73

8.57

Trapped

Hydrogen

(p/m)

0.68

0.96

0.40

0.77

0.20

Total

Hydrogen

(p/m)

6.17

9.58

9.37

7.50

8.77

Percent

Trapped

Hydrogen

10.9

10.0

4.3

10.3

2.3

8
Table7.

ChemicalAnalysisof Waspaloy.

Elements

El"

Co

C

Fe

Mo

Ti

AI

Zr

B

Mn

Si

Cu

P

Ni

MSFC Analysis

Weight Percent

18.90

12.80

0.060

0.56

3.80

2.80

1.40

0.063

0.0062

0.03

0.03

Trace

0.005

Balance

ASTM E354

Weight Percent

18.00 - 21.00

12.00- 15.00

0.02 - 0.10

2.0 Maximum

3.5 - 5.0

2.75 - 3.25

1.2- 1.6

0.02 - 0.08

0.003 - 0.010

0.10 Maximum

0.15 Maximum

0.10 Maximum

0.015 Maximum

Balance
Table8.

ParametersObtainedFromWaspaloyDesorptionData.

PercentYield

0

25

50

75

90

Dxl08

cm2/s

5.18

5.40

5.79

3.92

5.02

Co _

(p/m)

26.13

31.19

21.30

32.35

33.73

(p/m)

5.08

6.17

4.35

5.58

6.47

Percent

Uniformity

0

9.7

14.2

11.9

17.4

* Apparent H concentration at sample surface.

t Mean H concentration.

Table 9.

Hydrogen Trapping by Waspaloy as a Function of Stress.

Percent

Yield

0

25

5O

75

90

Mobile

Hydrogen

(p/m)

5.08

6.17

4.35

5.58

6.47

Trapped

Hydrogen

(p/m)

2.41

1.26

1.29

1.53

0.66

Total

Hydrogen

(p/m)

7.49

7.43

5.64

7.11

7.13

Percent

Trapped

Hydrogen

32.2

17.0

22.9

21.5

9.3

10
Table 10.

ChemicalAnalysisof IN100alloy.

Elements

Ni

Co

Ti

Cr

A1

Mo

Bi

Pb

Cu

Zr

W

Nb+Ta

Si

Mn

Fe

V

B

P

C

S

O

MSFCAnalysis

WeightPercent

18.74

4.38

12.39

4.80

3.15

<0.001

<0.003

0.03

0.06

0.01

0.048

0.03

<0.001

0.15

0.64

0.014

0.001

0.0711

0.OO07

0.0168

PWA 1074

WeightPercent

Balance

18.0- 19.0

4.15-4.50

11.90- 12.90

4.80- 5.15

2.80- 3.60

0.00005Maximum

0.0002Maximum

0.07Maximum

0.04- 0.08

0.05Maximum

0.04Maximum

0.10Maximum

0.02Maximum

0.30Maximum

0.58- 0.98

0.016- 0.024

0.01Maximum

0.05- 0.09

0.01Maximum

0.010Maximum

11
Table 11.

ParametersObtainedFromIN100DesorptionData.

PercentYield

0

25

5O

75

90

Dxl0 8

cm2/s

1.00

1.45

5.84

2.47

6.41

Co*

(p/m)

55.80

46.97

25.50

36.21

13.10

_t

(p/m)

6.09

5.65

5.19

5.19

2.78

Percent

Uniformity

0

0

0

0

0

* Apparent H concentration at sample surface.

* Mean H concentration.

Table 12.

Hydrogen Trapping by IN100 as a Function of Stress.

Percent

Yield

0

25

50

75

90

Mobile

Hydrogen

(p/m)

6.09

5.65

5.19

5.19

2.78

Trapped

Hydrogen

(p/m)

2.93

0.43

1.57

0.34

1.70

Total

Hydrogen

(p/m)

9.02

6.08

6.76

5.53

4.40

Percent

Trapped

Hydrogen

32.5

7.1

23.2

6.1

38.6

12
oo

o

0

e_

&

0

0 0 • C_

oxl

0

0

0

I I I I

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35
APPROVAL

THE EFFECT OF TENSILE STRESS ON HYDROGEN

DIFFUSION IN METAL ALLOYS

By M. D. Danford

The information in this report has been reviewed for

technical content. Review of any information concerning

Department of Defense or nuclear energy activities or programs

has been made by the MSFC Security Classification Officer. This

report, in its entirety, has been determined to be unclassified.

_ose_h W. Montano

Chief

Corrosion Research Branch

_ Paul M.' Munafo Chief

Metallic Materials Division

Director

Materials & Processes Laboratory

'_ U. S, GOVERNMENT PRINTING OFFICE 1992 733--060/ 80003