ORNL-2264.txt

   

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ORNL.2264

AEC RESEARCH AND DEVELOPMENT REPORT - P
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3 445k 0022989 3

      
 
 

INCONEL AS A STRUCTURAL MATERIAL FOR A
HIGH.-TEMPERATURE FUSED.SALT REACTOR

    

J. R. Weir, Jr.
D. A. Douglas
W. D. Manly

  
 

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OAK RIDGE NATIONAL LABORATORY

OPERATED BY

UNION CARBIDE NUCLEAR COMPANY
A Division of Union Carbide and Carbon Corpurufi@‘r\:

uce NG

POST OFFICE BOX X * OAK RIDGE, TENNESSEE

 RESTRICTED.DATA

 

 

 
 

ORNL.-2264

This document consists of 78 pages.

Copy\_,c_-nf 191 copies. Series A.

Contract No. W-7405-eng-26

METALLURGY DIVISION

INCONEL AS A STRUCTURAL MATERIAL FOR A
HIGH-TEMPERATURE FUSED-SALT REACTOR

DATE ISSUED

JUN 41357

 

ATIONAL LAEDRATORY LIBS.

OAK RIDGE NATIONAL LABORATORY

UNION cmmgfl'%fibfia COMPANY 3 yys5& 00229489 3

A Division of Union Carbide and Corben Corporati
Post Office Box X
Oak Ridge, Tennessee

 

 

 

 

 

 

 

 

 

 

 

 
 

 

 

 
 

CONTENTS
SUMMARY . .coocuonnssmmmsisse

Corrosion Resistance........c..ccoeeeennns

B ORI, comoirsmnsrnesmomemmarbefearertrr i ns e s e A i vmun i b prson i st s mesarmmssbensiiepr s b
B b FR DB R oLl s sessmninssssk B ek B LN B B o e o R DR
Effects Produced by Neutron and Gamma Flux ..........

Mechanical Properties of the Alloy in Contact with Various Environments at
High Temperatures...................

MATERIALS AND EQUIPMENT ....cccoommninn
TESTING EQUIPMENT ......ccovvnrvnnenes

RESULTS AND INTERPRETATION ...cccccccmmmsnisnisasins:
Creep-Rupture Tests ..........
Effect of a Biaxial Stress System on the Stress-Rupture Properties ........ccoovevivinnrrnnnne
Effect of Section Thickness on the Creep-Rupture Properties in the Various Media .................
Effect of Welding on the Creep-Rupture Strength...cccccviniecnniance
Variations in Strength Among Various Heats of Inconel. ..o
Tensile Properties of Inconel...............
Some Physical Properties of Inconel..............

Design Data...c.ccccevereereneinscniiinnnnnnanens
DISCUSSION iiccicviiins
CONCLUSIONS AND RECOMMENDATIONS .....ocooorrcecierrecererereienes

ACKNOWLEDGMENTS :....cocemssernssicsansanss

 

MR R = =

43
45
53
56
62
63

67
71

71
 

 
 

INCONEL AS A STRUCTURAL MATERIAL FOR A HIGH-TEMPERATURE FUSED-SALT REACTOR

J. R. Weir, Jr.

SUMMARY

A prototype aircraft reactor test unit is being
constructed in which fused fluoride salt No. 30
{NqF-ZrF4+UF4, 50-46-4 mole %) is used as the
fuel and as the primary-circuit heat transfer fluid,
with sodium and NaK used as the secondary-
circuit heat transfer media. Inconel was selected
as the material to be used for the construction of
this reactor, and an extensive testing program was
initiated to evaluate its high-temperature mechani-
cal properties.

The elevated-temperature creep-rupture properties
were evaluated at 1300, 1500, and 1650°F in
various reactor environments. The tests were
carried out under constant load conditions, since
this type of test produces more realistic design
data. The data were obtained in the inert gas
argon, and the results of creep data obtained in
environments of sodium, fused salt No. 30, and
air are compared with the argon data as a reference
for determining environmental effects.

The fused salt, which is corrosive to Inconel,
was found to reduce the creep strength and to
decrease the rupture life in comparision with tests
conducted in argon. High-purity sodium is inert
to Inconel in an isothermal system, and creep
results in this medium compare well with data
obtained in argon. The results of creep tests in
an air environment indicate that thin-sheet Inconel
is strengthened by this oxidizing environment.
In thicker sections this environment does not
appreciably affect the creep rate but does prolong
the rupture life at lower stress levels. The results
of creep-rupture tests conducted with sheet speci-
mens of various thickness indicate that the dele-
terious effect of the fused salts on the strength
of Inconel becomes more pronounced as the speci-
men thickness is decreased.

Variations in structure resulting from annealing
treatments have an effect on the creep properties.
The data indicate that the fine-grained material
has superior strength at low temperatures and high
stresses and that the coarse-grained material has
better strength at high temperatures and low
stresses.

 

D. A. Douglas

W. D. Manly

Considerable variation in properties may be
expected from different heats of Inconel. Appar-
ently these variations in strength result from
small differences in chemical composition or
fabrication procedures.

Tests in the sodium environment show that the
liquid-metal coolants are inert under isothermal
conditions if there is no contamination from oxygen.
Sodium contaminated with oxygen decarburizes
Inconel, thus decreasing the creep properties and
rupture life.

Air tests reveal that in large sections the data
will correspond very well with the argon data but
that thin sections are significantly strengthened
by the oxidizing environment.

INTRODUCTION

The use of a circulating-fuel type of nuclear
reactor as an energy source in aircraft propulsioen
systems imposes wupon the structural material
metallurgical restrictions which limit the appli-
cability of certain types of alloys. The general
factors which must be considered in the selection
of an alloy for this application are corrosion
resistance, fabricability, nuclear properties, radi-
ation damage, and elevated-temperature strength.
In the following discussion the importance of each
of these topics will be pointed out and it will be
shown that the selection of Inconel as a structural
material was based on these criteria.

Corrosion Resistance

The interaction between the structural material
and the circulating fluids is of major importance,
since all the reactor components in contact with
these fluids must operate without leakage through-
out the proposed 1000-hr operating life. In liquid
media, corrosion phenomena such as dissimilar-
metal transfer and temperature-induced mass
transfer, as well as general solution, occur. The
mode and rate of attack will depend upon such
factors as the temperature, the thermodynamic
activity and the solubility of the various metallic
phases and elemental constituents of the alloy,
and the chemical reactions involving the liquid,
impurties of the liquid, and the elemental con-
stituents of the alloy. The base metal must also
be alloyed such that, in the presence of air moving
at high velocity, the oxide formed will be protective.

Fabricability

The alloy or alloys to be used in the construc-
tion of reactors of this type must be amenable to
welding, brazing, and hot and cold forming.

Welding. — The weldability of an alloy is de-
pendent primarily upon the physical and mechanical
properties of the base metal during and after
welding. During the welding operation stresses
may be induced in the weld zone by volume changes
resulting from the thermal coefficient of expansion,
the allotropic phase transformations, and the
solution and precipitation of gases and minor
phases. The stresses may result in failure of the
weld if the strength of the weld is low at temper-
atures near the melting point or if the weld is
weokened by porosity, low-melting eutectics, or
gross oxidation. Some of the problems asscciated
with welding can be alleviated by carefully se-
lecting the alloying el ements to include deoxidizers
and solid-solution strengtheners and by controlling
the residual elements.

Brazing. — Alloys which are best suited for
hydrogen-furnace brazing must have easily reducible
oxides, form no stable hydrides, contain no alloying
element which will form a brittle intermetallic
compound with the brazing alloy, and be metal-
lurgically stable at the brazing temperature, since
further heat treatment involving any higher temper-
ature is not possible.

Hot and Cold Forming. — Hot-forming operations
such as tube or pipe extrusion and rolling must
be performed at temperatures high encugh to render
the material weak so that prohibitively high-press
capacities and roll pressures will not be involved.
On the other hand, the temperature at which the
material becomes ‘‘hot short'’ must be avoided.
These two factors place a lower and upper temper-
ature limitation on the hot-working range of the
alloy. For both practicality and quality control,
the best alloys are those with a wide temperature
range in which hot work is possible. It is also
desirable to have the metal ductile and soft at
room temperature so that cold rolling and machining
operations may be more easily accomplished.
Although not a major consideration, the castability
of the alloy may be important, since casting is
less expensive ond less time consuming than

forging and machining operations. The use of
casting as a means of forming may be limited
by the sometimes poor corrosion resistance and
ductility of cast structures.

Nuclear Properties

In order to attain high neutron efficiency in the
core of a reactor, the structural material in this
region must have a low neutron cross section,
a requirement which limits the use of elements
such as cobalt, tungsten, and manganese. The
restriction of the use of cobalt is unfortunate
since it is one of the most potent agents used to
obtain strength at high temperatures.

Effects Produced by Neutron and Gamma Flux

Although the data in the field are meager, it is
known that neutron and gamma flux may affect the
creep and tensile properties, the oxidation resist-
ance, and the corrosion resistance of the materials
exposed to this flux.
effects depends, of course, upon the flux density,
the temperature, and the particular material in-
volved.

The importance of these

Mechanical Properties of the Alloy in Contact with
Various Environments at High Temperatures

Some of the more important considerations in the
selection of an alloy for aircraft reactor application
are its strength and ductility at high temperatures
in such environments as air, sodium, NaK, and the
proposed liquid fuel. The advantages to be gained
from the use of high-strength alloys are a decrease
in reactor weight, an increased design margin of
safety, and a longer life expectancy for critically
stressed components.

Commercial high-temperature alloys may be
classified into the two broad categories of second-
phase-hardened ond solid-solution-hardened alloys.
At low temperatures the phose-hardened alloys
have the advantage of being generally stronger
than the solid-solution-hardened alloys, although
As the temperature is increased,
however, they tend to lose their strength because
of the instability of the precipitate and therefore
lose this advantage.

A survey of the commercial high-temperature
alloys, based on the factors discussed above as
the criteria for selection, yielded Inconel as the
most promising reactor material. It then became
the responsibility of the Mechanical Properties
Group to obtain the necessary data needed for the

less ductile.

2 " &}@:
design of a prototype reactor using fused fluoride
No. 30 (NuF-ZrF‘-UFd, 50-46-4 mole %) as the
fuel and as the primary-circuit heat transfer fluid,
with sodium and NaK as the secondary-circuit heat
transfer media.

This report is a summary of the work of the
Mechanical Properties Group in an effort to obtain
the necessary mechanical properties data for
Inconel in the temperature range 1200 to 1650°F.

MATERIALS AND EQUIPMENT

The reactor design is such that formed sheet and
tubular materials are used to a great extent in the
construction. Since it follows that any surface
reaction which might occur between the liquid-
metal coolants and Inconel or between fused
fluorides and Inconel would have a greater effect
on the strength of a thin sheet than on the strength
of a heavier section, it was decided that the testing
of thin sheet and tube materials would produce the
most useful design data.

The basic design of the sheet and tube specimens
used in testing is shown in Fig. 1. The machining
methods used to form these specimens are described

in ORNL-2053.7 The ASTM specification for the

chemical composition of Inconel is reproduced in
Table 1. Also listed are the chemical compositions
of the various materials which have been tested.

TESTING EQUIPMENT

The equipment used for creep-rupture tests and
for tests of the tubular specimens in the various
liquid and goeeous environments is described in

detail in ORNL-2053.2

RESULTS AND INTERPRETATION
Creep-Rupture Tests

For the purpose of obtaining the basic design
data a large quantity of 0.060-in.-thick sheet
Inconel was obtained. The chemical composition
of this heat (designated as heat B) of Inconel is
given in Table 1. Specimens from this heat of
Inconel were creep-rupture tested at 1300, 1500,
and 1650°F (except for tests in sodium, which did

 

lD. A. Douglas and W. D. Manly, A Laboratory for the
High Temperature Creep Testing of Metals and Alloys
in Controlled Environments, ORNL-2053 (Sept. 18, 1956).

21pid., p 9.

Table 1. Chemical Composition (%) of Various Heats of Inconel

 

0.060-in.-Sheet

 

iy A.S.'I'M | Seacimbes 0.0 20-i.n.-5hee| Tl.-lbfl
Specification Tk R Specimens Specimens

Ni 72 (min) 78 76 76 76
Cr 1417 14.9 15.4 14.8 16.0
Fe 6-10 6.4 7.4 8.1 7.6
Mn 1.0 (max) 0.31 0.23 0.29
G 0.15 (max) 0.04 0.04 0.02 0.04
Cu 0.5 (max) 0.13 0.09 0.13 0.13
Si 0.5 (max) 0.18 0.21 0.09 0.22
S 0.01 (max) 0.007 0.007 0.007 0.007
Al 0.08 0.19 0.15
T 0.16 0.33 0.20
B 0.091 0.094
N, 0.091 0.027

 
UNCLASSIFIED
ORNL-LR-DWG 17942

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TUBE BURST SPECIMEN

Fig. 1. Drawing of Sheet and Tubular Types of Specimen.

 

 

 
not exceed 1500°F) in the environments and con-
ditions listed below:

Specimen Condition Environment
As-received Argon
Fused salt No, 30
Sodium
Air
Annealed at 2050°F for 2 hr Argon

Fused salt Neo. 30

The material designated ‘‘as-received’’ was
tested in the condition in which it was received
from International Nickel Company, Inc. The INCO
sheet fabrication procedure consists of

1. hot working from 18 x 18 in. ingot to 20% over
finish size,

passing through the 1900°F hot zone of the
annealing furnace in 3% min,

. pickling in an HNO,-HF mixture,

20% cold working to size,

passing through the 1900°F hot zone of the

annealing furnace in 4]’2 min,

2.

 

6. pickling in an HNO,-HF mixture,
7. roller leveling.

The microstructure resulting from this treatment
is shown by the photomicrographs of the as-received
material in Figs. 2 and 3. The material in this
condition is fine-grained, having an ASTM grain
size number of 6 to 7. The fine precipitate seen
within the grains at a magnification of 100 dia
(Fig. 2) appears at 500 dia (Fig. 3) as precipitate
originally present in the grain boundaries before
the material was given the mill anneal.

The material designated as ‘‘annealed” was
annealed ot 2050°F for 2 hr before it was tested.
The microstructure of the annealed material is
shown in Fig. 4. This high-temperature anneal
results in the solution of the carbide precipitates
seen in the as-received material and
coarsening to an ASTM grain size number of 1.

Tests in Argon. — The creep-rupture data ob-
tained in an atmosphere of pure argon are used as
a basis for comparison in studying the effect of
other environments on the creep-rupture properties
of Inconel. The argon atmosphere is considered
to have no effect on the properties of a metal at
high temperature, since no interaction between the

in grain

 

 

 

 

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Fig. 2. Photomicrograph of As<Received Inconel. 100X. Electrolytically etched with 10% oxalic acid.
 

UNCLASSIFIE
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Fig. 4, Photomicrograph of Annealed Inconel. 100X. Electrolytically etched with 10% oxalic acid.

 

D

 

 

 

 

 

 
 

metal and argon is possible. However, if the gas
contains a high level of impurities such as O,
Co,, H20, or sz the properties of the metal may
be altered as a result of interaction with these
impurities. The argon used as an environment in
the creep-rupture testing of Inconel was purified
by being scrubbed with liquid sodium. This pro-
cedure for gas purification is described in detail
in ORNL-2053.2

The results of creep-rupture testing of Inconel
(heat B) in the as-received and annealed conditions
tested in argon at 1300, 1500, and 1650°F are
presented as graphs of stress vs time to 0.5, 1, 2,
5, 10% elongation and rupture in Figs. 5 through 10.
At the stress levels for which these design curves
are drawn, the as-received material is seen to have
better creep properties than the annealed material
at all three temperatures in that at approximately
the same stress level the time to the various
elongations is greater. The stiffness exhibited
by the as-received material may be attributed to
residual cold work and to the precipitate which

20,000

10,000

5000

STRESS (psi)

2000

1000

20 50

 

exists in the microstructure, neither of which is
present in the annealed material.

The stress-rupture properties of the as-received
and annealed materials tested ot 1300, 1500, and
1650°F in argon are compared in Fig. 11. The as-
received material is seen to have better rupture
properties at 1300 ond 1500°F, whereas the an-
nealed material exhibits better rupture properties
at 1650°F. Selected representative microstructures
of material taken from stressed and unstressed
portions of as-received and annealed specimens
tested at 1300, 1500, and 1650°F are presented in
Figs. 12 through 29.

The photomicrographs of specimens tested at
1300°F (Figs. 12-17) indicate that transgranular
slip is the principal mode of deformation at this
temperature for both the as-received and the an-
nealed material. A tendency for precipitation to
occur in primary slip planes and in previous grain-
boundary areas left segregated by the short high-
temperature annealing treatment is seen in the
case of the annealed material.

UNCLASSIFIED
ORNL-LR-DWG 19142

RUPTURE

100 200 500 {000 2000 5000 10,000

TIME (hr)

Fig. 5. Design Curve for As-Received Inconel Tested in Argon at 1300°F.

 
STRESS (psil

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

30,000
20,000
10,000
RUPTURE
i
E 5000
2000
1000
1 2 5 10 20 50 100 200 500 1000 2000 5000 10,000
TIME (hr)
Fig. 6. Design Curve for Annealed Inconel Tested in Argon at 1300°F,
UNCLASSIFIED
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20,000
10,000 | [ t
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2000 SN
1000 L | y
1 2 5 10 20 50 100 200 500 1000 2000 5000 10,000

TIME (hr)

Fig. 7. Design Curve for As-Received Inconel Tested in Argon at 1500°F.

 

 
 

UNCLASSIFIED
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1000
| { 2 5 10 20 50 100 200 500 1000 2000 5000 10,000
‘ » TIME (hr)
i Fig. 8. Design Curve for Annealed Inconel Tested in Argon at 1500°F.
UNCLASSIFIED
ORNL-LR-DWG 15366
20,000
10,000 __ S
I- ! 1 i - — — e
N N |
7 %% 115. 29, 5% | J0%| LRUPTURE '
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{ 2 5 10 20 50 100 200 500 1000 2000 5000 10,000
- TIME (hr)

Fig. 9. Design Curve for As-Received Inconel Tested in Argon at 1650°F,

 

 

 
Photomicrographs token from as-received and
annealed specimens tested at 1500 and 1650°F
show (Figs. 19, 20, 22) that considerable grain-
boundary cracking occurs during test, indicating
that at these temperatures the mode of deformation

 

   

UNCLASSIFIED
ORNL-LR-DWG 15616
20,000 | it
|
10000 |— - s
@ 5000 {2% 5% 1'0% RUPTURE
E Hll e P et it bld
= |
“ 05% i
2000
| |
1009 e e L e e e el
! 10 100 1000 10,000
TIME [hr)
Fig. 10. Design Curve for Annealed Inconel Tested

in Argon at 1650°F.

20,000

10,000

5000

STRESS {psi)

2000 [—

1000
10

20 50 100 200

 

is intergranular, that is, by grain-boundary sliding
rather than by transgranular slip. However, in
tests of the as-received and annealed material at
1500°F under stresses which produce rupture in
less than approximately 200 hr, the strain rate is
rapid enough for some transgranular slip to occur,
as is illustrated in Figs. 18 and 21. The photo-
micrograph in Fig. 27 shows that the annealed
material behaves at 1650°F in a manner similar
to that at 1500°F, in that at stresses which produce
rupture in less than approximately 80 hr some
transgranular slip is seen to occur.

At 1500°F a rather slight tendency for carbides
to precipitate from the annealed matrix exists.
This phenomenon is not always reproducible and
usually takes place in tests in excess of 1000-hr
duration. The microstructures of two specimens
tested at 1500°F under a stress of 3500 psi are
compared in Figs. 30 and 31. The specimen in
which the precipitation occurred ruptured in 3300
hr (Fig. 31), whereas the specimen in which no
precipitate occurred ruptured in 1200 hr (Fig. 30).

UNCLASSIFIED
ORNL=LR=DWG 17340

500 1000 2000 5000 10,000

TIME (hr}

Fig. 11. Comparison of the Stress=Rupture Properties of As-Received and Annealed Inconel Tested in Argon at

1300, 1500, and 1650°F.

10

 
 

 

 

 

Fig. 12. Photomicrograph of As-Received Inconel Tested at 1300°F Under 15,000-psi Stress in Argon. The
surface of the stressed specimen is shown on the left. 100X. Electrolytically etched with 10% oxalic acid.

 

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Fig. 13. Photomicrograph of As-Received Inconel Tested at 1300°F Under 12,000-psi Stress in Argon. The
surface of the stressed specimen is shown on the left. 100X. Electrolytically etched with 10% oxalic acid.

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surface of the stressed specimen is shown on the right. 100X. Electrolytically etched with 10% oxalic acid.

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Fig. 15. Photomicrograph of Annealed Inconel Tested ot 1300°F Under 11,500-psi Stress in Argon, The surface
of the stressed specimen is shown on the right. 100X. Electrolytically etched with 10% oxalic acid.

12
 

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Fig. 17. Photomicrograph of Annealed Inconel Tested at 1300°F Under BO0O-psi Stress in Argon. The surface

of the stressed specimen is shown on the right.
 

Fig. 18, Photomicrograph of As«Received Inconel Tested at 1500°F Under 6500-psi Stress in Argon.
surface of the stressed specimen is shown on the left. 100X. Electrolytically etched with 10% oxalic acid.

Fig. 19. Photomicrograph of As-Received Inconel Tested ot 1500°F Under 3500-psi Stress in Argon. The
surface of the stressed specimen is shown on the left. 100X. Electrolytically etched with 10% oxalic acid.

14

 
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Fig. 20. Photomicrograph of As-Received Inconel Tested at 1500 °F Under 2500-psi Stress in Argon,
Electrolytically etched with 10% oxalic acid.

UNCLASSIFIED
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Fig. 21. Photomicrograph of Annealed Inconel Tested ot 1500°F Under 6500-psi Stress in Argon. The surface
of the stressed specimen is shown on the right. 100X. Electrolytically etched with 10% oxalic acid. Reduced 4%.

15

 
 

Fig. 22. Photomicrograph of Annealed Inconel Tested at 1500°F Under 3000-psi !‘p_tnn in Argon. The surface
of the stressed specimen is shown on the right. 100X. Electrolytically etched with 10% oxalic acid.

Fig. 23, Photemicrograph of Annealed Inconel Tested at 1500°F Under 2000=psi Stress in Argon. The surface
of the stressed specimen is shown on the left. 100X. Electrolytically etched with 10% oxalic acid.

16

 
| Fig. 24, Photomicrograph of As<Received Inconel Tested at 1650°F Under 4500-psi Stress in Argon.
surface of the stressed specimen is shown on the left. 100X, Electrolytically etched with 10% oxalic acid.

Fig. 25. Photomicrograph of AssReceived Inconel Tested at 1650°F Under 2500-psi Stress in Argon. The
surface of the stressed specimen is shown on the left, 100X. Electrolytically etched with 10% oxalic acid.

17

 
 

Fig. 26. Photomicrograph of As-Received Inconel Tested at 1650°F Under 1750-psi Stress in Argon. The
surface of the stressed specimen is shown on the right. 100X. Electrolytically etched with 10% oxalic acid.

Fig. 27. Photomicregraph of Annealed Inconel Tested at 1650°F Under 4500-psi Stress in Argon. The surface
of the stressed specimen is shown on the right. 100X. Electrolytically etched with 10% oxalic acid.

18

 
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Fig. 28, Photomicrograph of Annealed Inconel Tested at 1650°F Under 2500-psi Stress in Argon. The surface

of the stressed specimen is shown on the left. 100X. Electrolytically etched with 10% oxalic acid.

UNCLASSIFIED
Y-20381
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Fig. 29. Photomicrograph of Annealed Inconel Tested at 1650°F Under 2000-psi Stress in Argon. The surface
of the stressed specimen is shown on the left. 100X. Electrolytically etched with 10% oxalic acid.

19
 

 

Fig. 30. Photomicrograph of Annealed Inconel Tested at 1500°F Under 3500-psi Stress in Argon. The surface
100X. Electrolytically etched with

of the stressed specimen, which ruptured in 1200 hr, is shown on the left.

10% oxalic acid.

Since this precipitation does not occur in all
cases, the design plot for the annealed material
at 1500°F does not include tests in which pre-
cipitation occurred.

At 1650°F the solubility of carbon is high enough
for little carbide to precipitate from the solution-
annealed matrix during testing, and that which
does occur is of large size and therefore not so
effective as a strengthener.

Tests in Fused Salt No. 30. = The testing appa-
ratus used in creep-rupture testing in liquid media
is described in detail in ORNL-2053.? Essentially,
the apparatus consists of a chamber filled with
liquid, into which may be placed the test specimen.
A bellows and pull-rod system allows for a load to
be applied to the specimen by external means.

The mechanism by which the fused salts corrode
Inconel involves the selective leaching of chromium
from the surface of the metal in contact with the
salt. This leaching action is accomplished by the
following reactions between the chromium in the

20

 

Inconel and the UF, and metal fluoride impuri-
ties in the salt:3

Cr + Fer = Cer + Fe
Cr + Nin « Cer + Ni

A summary of the creep-rupture data for as-
received and annealed Inconel in fused salt No.
30 at 1300, 1500, and 1650°F is afforded by Figs.
32 through 37. Stress is plotted vs time to 0.5,
1, 2, 5, 10% elongation and rupture. Photomicro-
graphs of the surfaces of as-received and annealed
specimens tested under various stresses in fused
salt No. 30 are presented in Figs. 38 through 55.

The following might be concluded from a com-
parison of the properties of the as-received and
the annealed materials in fused salt No. 30.

 

3-ujl- Dl R‘dmflfl md C- Fll Wa'flvcr HNP Qmfl Prflgo
Rep. June 10, 1954, ORNL-1729, p 50; ANP Quar. Prog,
Rl’fi- SEPL Ifl; 1954::- DRNL"IHIJ P 60; J'l D. R‘dl’l’lfll‘l,
ANP Quar, Prog. Rep. June 10, 1956, ORNL-2106, p 94;
W. R. Grimes, op. cit,, p 96.
 

Fig. 31. Photomicrograph of Annealed Inconel Tested at 1500°F Under 3500-psi Stress in Argon. The surface
of the stressed specimen, which ruptured in 3300 hr, is shown on the left. 100X. Electrolytically etched with
10% oxalic acid. Reduced 4%.

UNCLASSIFIED
ORNL-LR-DWG 15360
20,000

RUPTURE

10,000

5000

STRESS {(psi)

2000

 

1000
1 2 8 10 20 50 100 200 500 1000 2000 10,000

TIME (hr)

Fig. 32. Design Curve for As-Received Inconel Tested in Fused Salt No. 30 at 1300°F. (Secret with caption)

21
 

 

 

 

 

22

UNCLASSIFIED
ORML-LR-DWG 153

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

20,000 l I l
2% 5% 10 %
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aat
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X \--h""---. \"'--. M\-‘ —— \H"H
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8
@ 5000
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TIME (hr)
Fig. 33. Design Curve for Annealed Inconel Tested in Fused Salt No. 30 at 1300°F. (Secret with caption)
UNCLASSIFIED
BB o : ORNL-LR-DWG 15364
T T T T
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1 |
10,000 :
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1 2 5 10 20 50 100 200 500 1000 2000 5000
TIME (hr)

10,000

Fig. 34. Design Curve for As-Received Inconel Tested in Fused Salt No. 30 at 1500°F. (Secret with caption)

 
1. At 1300°F, under stresses over 6000 psi,
the as-received material exhibits greater creep
and rupture strength. At stresses below 6000 psi
the annealed material exhibits greater creep-rupture
strength.

2. At 1500°F the annealed Inconel is superior
to the as-received material in rupture life and,
after 0.5% elongation, in creep properties.

3. At 1650°F the as-received material exhibits
better creep properties at stresses above roughly
1500 psi and better rupture properties at stresses
above roughly 2500 psi.

A comparison of the rupture properties of as-
received Inconel and of annealed Inconel, tested
in fused salt No. 30 and in argon, is afforded by
Figs. 56 and 57, respectively. At 1300, 1500, and
1650°F the strength of the as-received material is
seen to be more drastically offected by the cor-
rosive action of the salt than is the strength of
the annealed material.

Comparison of the photomicrographs of the
surfaces of as-received and annealed specimens

 

tested in fused salt No. 30 reveals that, in general,
the entire surface of the as-received specimens
has been chemically altered but that the annealed
specimens have been attacked only in isolated
grain-boundary areas on the surface. A reasonable

 

   

 

       

 

 

 

 

UNCLASSIFIED
ORNL-LA-DWG 15617
20,000 T
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= kU 1 .
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2000 efed e
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1000 — ‘
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TIME (hr)
Fig. 36. Design Curve for As-Received Inconel

Tested in Fused Salt No. 30 at 1650°F.

caption)

(Secret with

UNCLASSIFIED
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20,000
10,000
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Fig. 35. Design Curve for Annealed Inconel Tested in Fused Salt No. 30 at 1500°F. (Secret with caption)

23

 
 

 

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ORNL-LR-DWG 139145

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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Fig. 37. Design Curve for Annealed Inconel Tested in Fused Salt No. 30 at 1650°F, (Secret with caption)

 

Fig. 38. Photomicrograph of As-Received Inconel Tested at 1300°F Under 1500-psi Stress in Fused Salt No. 30,

The surface of the stressed specimen is shown on the left.

(Secret with caption)

24

 

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Fig. 39. Photomicrograph of As-Received Inconel Tested at 1300°F Under 11,000-psi Stress in Fused Salt No.
30. The surface of the stressed specimen is shown on the left. 100X, Electrolytically etched with 10% oxalic acid.
(Secret with caption)

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Fig. 40. Photomicrograph of As-Received Inconel Tested at 1300°F Under 6000-psi Stress in Fused Salt No. 30.
The surface of the stressed specimen is shown on the right. 100X. Electrolytically etched with 10% oxalic acid.
(Secret with caption)

25
 

 

Fig. 41. Photomicrograph of Annealed Inconel Tested at 1300°F Under 15,000-psi Stress in Fused Salt No. 30.
The surface of the stressed specimen is shown on the left. 100X. Electrolytically etched with 10% oxalic acid.
(Secret with caption)

 

Fig. 42. Photomicrograph of Annealed Inconel Tested at 1300°F Under 12,000-psi Stress in Fused Salt No. 30.
The surface of the stressed specimen is shown on the left. 100X. Electrolytically etched with 10% oxalic acid.

(Secret with caption)

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Fig. 43. Photomicrograph of Annecled Inconel Tested at 1300°F Under 8000-psi Stress in Fused Salt Ne. 30.

The surface of the stressed specimen is shown on the left. 100X. Electrolytically etched with 10% oxalic acid.

(Secret with caption)

  
 

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Fig. 44. Photomicrograph of As-Received Inconel Tested at 1500°F Under 3500-psi Stress in Fused Salt No. 30.
The surface of the stressed specimen is shown on the left. 100X, Electrolytically etched with 10% oxalic acid.

(Secret with caption)

27
 

 

 

Fig. 45. Photomicrograph of As-Received Inconel Tested ot 1500°F Under 2000-psi Stress in Fused Salt No. 30,
The surface of the stressed specimen is shown on the right. 100X. Electrolytically etched with 10% oxalic acid.
(Secret with caption)

 

 

 

Fig. 46. Photomicrograph of As-Received Inconel Tested at 1500°F Under 1000-psi Stress in Fused Salt No. 30.
The surface of the stressed specimen is shown on the right. 100X. Electrolytically etched with 10% oxalic acid,
(Secret with caption)

28

 

 

 
 

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Fig. 47. Photomicrograph of Annealed Inconel Tested at 1500°F Under 7500-psi Stress in Fused Salt No. 30.
The surface of the stressed specimen is shown on the left, 100X,

Electrolytically etched with 10% oxalic acid.
(Secret with caption)

 

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Fig. 48. Photomicrograph of Annealed Inconel Tested at 1500°F Under 3500-psi Stress in Fused Salt No. 30.

The surface of the stressed specimen is shown on the left. 100X. Electrolytically etched with 10% oxalic acid.
(Secret with caption)

29
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- : L ; T x i
= T - e
2 . ot (= & L
- ¢ L8 I & vl Y y . .
Y s i P f r 0 N
20 ks : # | ¥ aat i
[ =y T b i 5 i & !
5 J il = ! - *
At l | v = L & [ Nl e
- W £ Fo ity 4 N .J
R iy - 5 ‘l - . 5 4 /
o Ve - " 5 -
1 : : ~ i '
. 1 3 r . "y & i . '
£y S ¥ . 2 g . '\';\N e L 4 t . /
DGy ST i i AN, :
e 0% . =N T . FEas
" ¥ e x = K = A e i
i 5 Ty * / 5 i {" . ‘ P “H-"H“ '
o .‘_ e X * ] v . ‘I ; \ s ',
. oS 8 : '
d ‘g : % " ; - "
: > T = maid X /-' -
a A .
e et Y 2 | . x , -I ! / o R
oy . - .y - o .
2 St el W N\ %S, e e
wi-g - _ - o o= W I e v
; E b K2 = : # “
'y L= . . i, o ! " &
i Eh LN 2
g w# - "' -
-
5 ! .
o 100X INCHES
o 1 1

 

 

Fig. 49.
The surface of the stressed specimen is shown on the left.

(Secret with caption)

Photomicrograph of Annealed Inconel Tested at 1500°F Under 2500-psi Stress in Fused Salt No. 30.
100X.

Electrolytically etched with 10% oxalic acid.

 

 

 

 

 

 

100X

 

INCHES

Fig. 50. Photomicrograph of As-Received Inconel Tested

The surface of the stressed specimen is shown on the left.

(Secret with caption)

30

at 1650°F Under 3500-psi Stress in Fused Salt No. 30.
100X. Electrolytically etched with 10% oxalic acid.
Vs A LR i -UNCL'AL]S%I:IIED
3 ; ) o i g LA D , Y-15
-‘.1\"‘— s ‘\1"' } | 1 3 T ' 1 :\":’ <

 

 

 

 

 

 

500
o
S~
>

€00

 

 

Fig. 51. Photomicrograph of As-Received Inconel Tested at 1650°F Under 2000-psi Stress in Fused Salt No. 30.
The surface of the stressed specimen is shown on the right. 100X. Electrolytically etched with 10% oxalic acid.

(Secret with caption)

 
   
  
 

A gy et v UNCLASSIFIED
2 el I ‘o'_- s d
. . A

% e L

:;;f_‘\ 343 7.. ;

N

   

 

 

1
INCHE{S

 

 

 

 

Fig. 52, Photomicrograph of As-Received Inconel Tested at 1650°F Under 1000-psi Stress in Fused Salt No. 30.
The surface of the stressed specimen is shown on the left. 100X. Electrolytically etched with 10% oxalic acid.

(Secret with caption)

31
Fig. 53. Photomicrograph of Annealed Inconel Tested at 1650°F Under 4000-psi Stress in Fused Salt No. 30.
The surface of the stressed specimen is shown on the left. 100X. Electrolytically etched with 10% oxalic acid.
(Secret with caption)

Fig. 54, Photomicrograph of Annealed Inconel Tested ot 1650°F Under 1500-psi Stress in Fused Salt No. 30.
The surface of the stressed specimen is shown on the right. 100X. Electrolytically etched with 10% oxalic acid.
(Secret with caption)

32

 
 

 

. Fig. 55. Photomicrograph of Annealed Inconel Tested at 1650°F Under 1000-psi Stress in Fused Salt No. 30.
The surface of the stressed specimen is shown on the left. 100X, Electrclytically etched with 10% oxalic acid.
(Secret with caption)

_ UNCLASSIFIED.
ORNL-LR-DWG 17944

 

20,000

10,000

5000

| STRESS (psi)

2000

& 1000 * - : : ' ; y =
4 2 B 10 20 50 {00 200 S00 {ooo 2000 5000 10,000
TIME (hr)

Fig. 56. Comparison of the Stress-Rupture Properties of As-Received Inconel Tested at 1300, 1500, and 1650°F
in Argon and in Fused Salt No, 30, (Secret with caption)

33

 

 
UNCLASSIFIED
ORNL-LR-DWG 1T 942

 

20,000

10,000

5000

STRESS (psi)

 

 

 

1000 =Lty
{ 20 50 100 200 500

 

100 200 500 {000 2000 5000 10,000

TIME (hr)

Fig. 57. Comparison of the Stress-Rupture Properties of Annealed Inconel Tested ot 1300, 1500, and 1650°F

in Argon and in Fused Salt Mo, 30. (Secret with caption)

explanation for the sensitivity of the as-received
Inconel to the corrosive attack is not immediately
obvious, However, a possible explanation lies
in the carbide strengthening mechanism for the
as-received material and the effect of the corrosion
on these carbides. Deletion of the chromium from
the surface of the as-received material causes an
increase in the solubility of the complex chromium
carbides. The carbide is then dissolved in the
matrix, ond the source of strength for the as-
received material is removed. Although the surface
void formation resulting from deletion of the
chromium from the surface extends to a depth of
only a few mils, the depth to which the chromium
is depleted enough to cause solution of the car-
bides is great enough to significantly affect the
strength of the as-received material. Since the
strength of the annealed Inconel does not depend
on the carbide precipitate, it is not so seriously
weakened by the corrosive attack.

Tests in Sodium. — Creep-rupture tests were
carried out in liquid sodium at 1300 and 1500°F,

34

to determine the effect of this environment on the
strength properties of as-received Inconel. The
results of the creep-rupture tests at 1300°F are
summarized in Fig. 58 and at 1500°F in Fig. 59.
The data obtained in sodium may be compared
with the data for argon shown in Figs. 5 and 7.
Although the data points for rupture obtained in
sodium are somewhat scattered, they do indicate
that the strength of Inconel in argon and sedium
is essentially the same.,

Photomicrographs of the specimens tested in
sodium are shown in Figs. 60 through 66. Evi-
dence of the Inconel having decarburized, as a
result of too high an oxide content in the sodium,
is seen in some of the photomicrographs. The
effect of this decarburization on the creep charac-
teristics is to increase the creep rate, increase
the elongation at rupture, and decrease the rupture
life. The magnitude of these effects is, of course,
dependent on the severity of the decarburization.

Based on these data, then, it appears that if the
purity of the sodium or NaK is high, design for
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

— S ——— =
UNCLASSIFIED
ORNL-LR-DWG 17913
I T T
| | | |
: — e S
-n\""bu. I~ | — I
- " -
“:H:‘T‘nhh \""--.._\\ | '-.._____-,.
T~ e T
T I~~~ ~~
I|-.hl.""""'--.\\\““....-...‘“'"""""""|---| ‘--“""‘ . E“I\L\
I \\H‘MH""'& r“ . | ~
e 1 R 0L Pl T ] et | 4
- | = S T Bl i
L I T~ | [ 5% g
| | . | | 0.5% 1% 21:F°| |
I T | | | LI
- L] A LI — l
E | | | 1
i 5000 o | 1]
i
o |
= |
I ] = - — E:
L ‘. . - {
||
® RUPTURE IN ARGON .
2000 | I
‘ l
| | [ ‘ |
1000 '
i 2 5 {0 20 50 {00 200 500 {000 2000 5000 10,000
TIME {hr)
Fig. 58. Design Curve for As-Received Inconel Tested in Sodium at 1300°F. (Compare with Fig. 5 for data

obtained in argon.)

components in contact with these liquids may be
based on creep data obtained in an argon atmosphere.

Tests in Air. = The data in the literature on the
effect of gaseous and liquid environments on the
mechanical properties of materials at low and high
temperatures is somewhat controversial. The effect
of oxide surface films on the mechanical proper-
ties has been studied, and many proposals have
been made concerning the mechanism by which
the film affects the strength of the material.*~7
Much of the experimental work has been carried

 

4M.\ R. Pickus and E. R. Parker, *'Creep as a Surface
Dependent Phencomenon,”" p 26 in Am. Soc. Testing
Materials Special Technical Publication No, 108, 1951.

50. C. Shepard and W. Shalliol, **The Effect of En-
vironment on the Stress-Rupture Properties of Metals
at Elevated Temperatures,” p 34 in Am Soc. Testing
Materials Special Technical Publication No. 108, 1951.

SE. D. Sweetland and E. R. Porker, ''Effect of Surface
Condition on Creep of Some Commercial Metals,"" J.

Appl. Mechanics 20, 30 (1953).

7p, Shahiman, *'Effect of Environment on Creep-
Rupture Properties of Some Commercial Alloys,"" to be
published in Trans. Am. Soc. Metals 49 (1957).

out with single crystals of very pure metals, and
theories based on dislocation models derived from
these experiments are not easily applied to the
creep behavior of polycrystalline alloys at high
temperatures.

The creep-rupture data obtained in an air en-
vironment on as-received 0,060-in.-thick Inconel
sheet at 1300, 1500, and 1650°F are superimposed
on the argon data for comparative purposes in
Figs. 67 through 69. The data obtained at 1300°F
indicate that an cir environment does not signifi-
cantly affect the creep or rupture strength of as-
received 0.060-in.-thick Inconel sheet when tested
at stress levels which produce rupture in less than
1000 hr. However, the specimen tested in air at
10,000 psi exhibited somewhat better creep proper-
ties and longer rupture life than the material tested
in argon.

At 1500°F and at stress levels above 4000 psi
the creep and rupture strength of Inconel tested in
air is similar to that of the Inconel tested in argon.
The data obtained at stresses which produce rupture
in over roughly 1000 hr indicate that the Inconel

35
 

UNCLASSIFIED
ORNL—LR—DWG 17914

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

20,000
10,000
05% 1% | 2% 5% 10% RUPTURE -
R o T ~ \\H._fih “\-.__
SIS NI
= — ~ .
e \h“"-.:h‘"-., ‘h-.,_;\ .\\h
SRS TN
T
- fi"‘m‘“‘m:"‘fiz:
s \b ™ k e
| L
"""--.""'--..,‘: \‘\\
th‘\\fi\
I
2000
1000
1 2 5 10 20 50 100 200 500 1000 2000 5000 10,000
TIME (hr) a

Fig. 59. Design Curve for As-Received Inconel Tested in Sodium at 1500°F, (Compare with Fig. 7 for data
obtained in argon.)

 

Fig. 60. Photomicrograph of As-Received Inconel Tested at 1300°F Under 17,000-psi Stress in Sodium. The
surface of the stressed specimen is shown on the left. 100X. Electrolytically etched with 10% oxalic acid.

36

 
Fig. 61. Photomicrograph of As-Received Inconel Tested at 1300°F Under 15,000-psi Stress in Sodium. The
surface of the stressed specimen is shown on the left. 100X. Electrolytically etched with 10% oxalic acid.

Fig. 62. Photomicrograph of As-Received Inconel Tested at 1300°F Under 8000-psi Stress in Sodium. The
surface of the stressed specimen is shown on the left. 100X. Electrolytically etched with 10% oxalic acid.

37

 

 
 

Fig. 63. Photomicrograph of As-Received Inconel Tested at 1500°F Under 6000-psi Stress in Sodium. The
surface of the stressed specimen is shown on the right. 100X. Electrolytically etched with 10% oxalic acid.

 

Fig. 64. Photomicrograph of As-Received Inconel Tested at 1500°F Under 5000-psi Stress in Sodium. The
surface of the stressed specimen is shown on the left. 100X. Electrolytically etched with 10% oxalic acid.

38

 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Fig. 65. Photomicrograph of As-Received Inconel Tested at 1500°F Under 3500-psi Stress in Sodium, 200X,
Electrolytically etched with 10% oxalic acid.

UNCLASSIFIED
Y-20287

- ¥ ¥
=5 Y o - ! ' !
’ . 8 T & e 1
-'f"- : 4. -' 3 .I ‘-' i \ ) g
¢ - 1f = A . 2
A C N ey SN
b el I .

 

 

 

g g S ,.. e g " : % .
¥ = = 3 "
LTk el DS T A Z :
N _—ag . \
2
o
o

 

T
IDiI:‘rx

€0'0

 

Z20'0

 

¥
INCHEIS

 

 

Fig. 66. Photomicrograph of As-Received Inconel Tested at 1500°F Under 3000-psi Stress in Sodium. The
surface of the stressed specimen is shown on the left, 100X, Electrolytically etched with 10% oxalic acid.

39
UNCLASSIFIED
ORNL—LR—DWG 173915
20,000

10,000

RUPTURE

5000

LEGEND FOR AIR DATA:
RUPTURE
10 7% ELONGATION
5 %
2 %
i %o
0.5%

STRESS (psi)

2000

 

1000
i 2 5 10 20 50 {00 200 500 1000 2000 5000 10,000
TIME (hr)

Fig. 67. Comparison of the Creep-Rupture Properties of As-Received Inconel Obtained in Argon with Those
Obtained in Air at 1300°F,

UNCLASSIFIED
ORNL-LR-DWG 17946
20,000

10,000
RUPTURE

5000

STRESS (psi)

LEGEND FOR AIR DATA:

A RUPTURE

® 10% ELONGATION

B 5% ELONGATION

O 2% ELONGATION
2000 A 1% ELONGATION
o

0.5 % ELONGATION

 

1000

1 2 5 10 20 50 100 200 500 1000 2000 5000 10,000
TIME (hr)

Fig. 68. Comparison of the Creep-Rupture Properties of As-Received Inconel Obtained in Argon with Those
Obtained in Air at 1500°F.

40

 
20,000

10,000

5000

STRESS (psi)

2000

1000
1 2 5 10 20 S0

 

UNCLASSIFIED
ORNL—LR—DWG {7817

LEGEND FOR AIR DATA:
A RUPTURE
10 %% ELONGATION
5%
2 %
i %
05 %%

100 200 500 {00 2000 5000 10,000

TIME (hr)

Fig. 69. Comparison of the Creep-Rupture Properties of As-Received Inconel Obtained in Argon with Those

Obtained in Air at 1650°F.

is strengthened by the air atmosphere. At 1650°F
the air environment is seen to strengthen Inconel
when tested at the lower stress levels.

The exact mechanism by which an air environ-
ment strengthens as-received Inconel is not fully
understood. However, some useful observations
may be made on the gross effects of the air envi-
ronment. The creep curves plotted in Fig. 70 illus-
trate somewhat more graphically the comparative
behavior of as-received Inconel at 1500°F in argon
and air environments. The strengthening in air
is seen to occur only after considerable defor-
mation has taken place. The microstructures of
specimens tested in air and in argon are shown
in Figs. 71 and 72. These photomicrographs indi-
cate that the air environment retards the rate of
propagation of intergranular cracks and allows the
deformation to proceed without rupture for a con-
siderably longer time.

The effect of an air environment on the creep-
rupture properties of annealed 0.060-in.-thick
Inconel sheet is illustrated in Fig. 73. Creep
curves are plotted for tests in air and in argon at
two stress levels, The creep rate for the annealed

UNCLASSIFIED
ORNL-LR-DWG 17918

 

 

 

 

 

  
    

 

 

 

 

 

 

 

 

 

 

 

 

 

 

o6 I . /_ ]
i L
48 - ' —1
| | S
| |
40 —1_ = _..—.l. ]I .I —
g 1 e
= | , |
S 32 e :
= .
=T
o —
g |
ot e * Y
| |'
16 T 1 —
;/flRGGN =
T A
-‘/r 5
a i
0 400 8OO 1200 4600 2000 2400 2800
TIME (hr)
Fig. 70. Comparison of the Creep Behavior of As-

Received Inconel Tested in Air and in Argon at 1500°F
Under 3500-psi Stress.,

4]

 

 
 

 

 

Elec-

Fig. 71. Photemicrograph of As-Received Inconel Tested at 1500°F Under 3500-psi Stress in Air. 100X,

trolytically etched with 10% oxalic acid.
' S ; Lones U™ 00 1 UNCLASSIFIED

-r 1)-_-‘-' = 'h e £ Ty
gy - w ST e B S g
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v SN N o R T TR R R
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A -~ . g ™, "y N
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5 - = _.' . e ~ -
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ey 1r "'1 1—1 . l 2 -"' Ya \ ‘ ) \‘r o " .-
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¥ a A " * ) =i giie &
KEAY 5 e " \v \ %
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" i - W = -
| | o Sy VT Wit P s
- L ] 3 o ¢ o .
LED , Nsag i) L~ - : . Lo, Al
iy = v - v e . ) "
- ¥ -n ’ i I L
. TEL i * | . v e
\‘ . N\ -:';- '-_. - . & 'j L i -t .
- ! 3 - ‘F - % *.r .r, » i "
. & - r " - -
| AR e () LA
i - - - o ., 3 2 : c i
X B i . 1 5 ’ T -
& 4‘ e b f
g - -~ .
'J ¥ { w 5
S i ! .
/ o l 5 - I '
i "\... Io - & 1..
#
J‘ h
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T
INCH%S

 

o ¥
I 100 %

 

Fig. 72. Photomicrograph of As-Received Inconel Tested at 1500°F Under 3500-psi Stress in Argon. 100X,
Electrolytically etched with 10% oxalic acid.

42
 

=

UNCLASSIFIED
ORML -LR-DWG 15923

20 el I N R T b R 1
16
2 !
> 12 vg@;fi* DISCONTINUED
S N AT 3200 tr; 99%
g | - o5t ™ ELONGATION
x g A
o N

3500

 

0 = — = _—
Q 400 BOO 1200 1600 2000 2400 2800
TIME (hr)
Fig. 73. Comparison of Typical Creep Behavior for

Annealed Inconel Tested in Air and Argon at 1500°F at
Two Stress Levels.

Inconel tested in air is lower than that for the
similar tests in argon throughout the entire life of
the test, and the rupture life is considerably longer.

In general, then, the effect of an air environment
is to strengthen as-received Inconel when the strain
rate, that is, the stress, is low enough that the
mode of deformation tends to be intergranular and
has no effect on the strength at low temperatures
or at high strain rates, where the mode of defor-
mation is mainly transgranular. The limited data
on the annealed material indicate that itis strength-
ened by on air environment, but the stress de-
pendency of this strengthening effect has not been
established.

Effect of a Biaxial Stress System on the
Stress-Rupture Properties

Since the static stresses in the components of
the reactor generally arise as a result of fluid
pressure in tubes and spherically shaped shells,
the stresses will not be uniaxial. Therefore the
effect of a biaxial stress system on the high-
temperature strength properties of Inconel is an
important consideration when creep-rupture data
based on uniaxially stressed sheet are used for
design purposes.

Gensamer® has observed that, in tensile tests
at room temperature of various materials under
a biaxial stress system, failure depends on the

properties of the material in the direction of

 

M. Gensamer, Strength of Metals Under Combined
Stresses, American Society for Metals, Clevelond, 1941.

     

 

the larger of the two combined stresses. Although
the mechanism of deformation of metals under
static loads at elevated temperatures differs from
that which occurs in a tensile test at room temper-
ature, the major stress component is still the
controlling factor determining the type and time to
failure.

The stress-rupture properties of 0.060-in.-wall
tubes under a hoop-to-axial-stress ratio of 2:1 are
compared with those of uniaxially stressed 0,060-
in.-sheet Inconel at 1500 and 1650°F in argen and
in fused salt in Figs. 74 and 75. In the tube-burst
tests the data are based on the hoop stress. It is
seen that there is good agreement between the
stress-rupture properties of the 0.060-in.-wall
tubing and the 0.060-in.-thick sheet at both temper-
atures and in both environments. The small differ-
rences which exist may be due to anisotropy in the
tubing or to the two types of specimens having
been taken from different heats of Inconel and
consequently having different chemical composition
and fabrication history.

Although the stress-rupture strength of 0.060-in.-
wall Inconel tubing is very similar to that of 0.060-
in.-thick Inconel sheet specimens, there is a
significant difference in the total deformation at
rupture of the two types of specimens. Table 2
shows the relative values for the per cent elonga-
tion in the direction of the maximum stress for

Table 2. Comparison of the Total Deformation
at Rupture of 0,060«in.=Thick Inconel Sheet
with That of 0,060«in,=Wall Inconel Tubing

 

Per Cent Elongation

 

 

 

Tamparatirs Streast % FusediSalt

(°F) (psi) In hrgon No. 30
Tubing . 'Shest. ‘Tublog “Shast

1500 5000 9.2 28 102 17
4000 52 20 55 13

000 JAF: a0 A7 8

26000 hE A2

1650 000 67 30 68 19
2500 3.6 30 5.3 16

000 38 3 33 15

1500 31 12 2.8 8

 

*Represents the hoop stress in the case of the tube-

burst tests.,

43
 

 

 

STRESS (psi)

20,000

10,000

5000

2000

1000

Fig. 74.

 

UNCLASSIFIED
ORNL—LR—DWG 17919

e
~
C!oeo
4{ Pf‘h £

IT_J\_{@
las e

e.
Sflck‘ ~

2 S {0 20 50 100 200 500 1000 2000 5000 10,000
TIME {hr}

Comparison of Stress-Rupture Properties of Annealed 0.060-in.-Thick Inconel Sheet with Annealed

0.060-in.-Wall Tubes Tested in Argon at 1500 and 1650°F.

STRESS (psil

UNCLASSIFIED
ORANL-LR-DWG 17220

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

20,000

10,000

5000

|
. -.“‘h‘
2000
1000
1 2 5 10 20 50 100 200 500 1000 2000 5000 10,000
TIME (hr)

Fig. 75. Comparison of Stress-Rupture Properties of Annealed 0.060-in.-Thick Inconel Sheet with Annealed

0.060-in.-Wall Tubes Tested in Fused Salt No. 30 at 1500 and 1650°F. (Secret with caption)

44

 

 
specimens tested at several stresses at 1500 and
1650°F in argon and in the fused salt.

The data presented in Table 2 were obtained
from before- and after-test measurements of the
gage length in the case of the sheet specimens and
the diameter in the case of the tubular specimens.
No detectable change in dimension was noted in
the axial direction in the case of the tube speci-
mens; accurate measurements of the
change in the axial dimension were not possible.

however,

The lower total deformation at rupture exhibited
in the tube-burst type of test may be attributed to
the biaxial stress system set up on a closed-end
pressurized tube. Metals that are deformed at
room temperature under various states of biaxial
stress exhibit increasing or decreasing ductility, as
compared with uniaxial tensile ductility, depending
on whether the stress system tends to increase or
decrease the maximum shear stress.? In a biaxial
tensile stress system, such as is found in the tube-
burst test, the maximum shear stress, in the cir-
cumferential direction, is decreased by the action
of the smaller axial stress so that slip in the cir-

 

cumferential direction is restricted. This results
in the lower ductility at rupture.

Photomicrographs taken from several tubes
tested in argon and in fused salt No. 30 (Figs. 76
through 87) indicate that the deformation mecha-
nism is similar to that which occurs in uniaxially

loaded sheet type of specimens.

Effect of Section Thickness on the Creep-Rupture
Properties in the Various Media

The applicability of the data presented in this
report to design is limited in that the data are valid
only when the material is subjected to operating
conditions similar to those under which the ma-
terial is tested. In a design where various shapes
and thicknesses of material are employed in contact
with corrosive media, the effect of section thickness
becomes an important consideration in the intelli-
gent use of the available data.

The effect of section thickness on the creep-
rupture properties of fine-grained Inconel sheet

 

Ibid., p 20.

INCHES

0.02

 

0.03

 

I
100X
1

 

 

Fig. 76. Photomicrograph from Inconel Tube-Burst Specimen Tested in Argon at 1500°F Under 5000-psi Stress.

100X, Electrolytically etched with 10% oxalic acid.

45
 

Fig. 77. Photomicrograph from Inconel Tube-Burst Specimen Tested in Argon
100X. Electrolytically etched with 10% oxalic acid.

Fig. 78. Photomicrograph from Inconel Tube-Burst Specimen Tested in Argon at 1500°F Under 3000-psi Stress.
100X. Electrolytically etched with 10% oxalic acid. Reduced 3%.

46

 
INCHES

0.02

 

 

 

 

Fig. 79. Photomicrograph from Inconel Tube-Burst Specimen Tested in Fused Salt No. 30 at 1500°F Under
5000-psi Stress. 100X. Electrolytically etched with 10% oxalic acid. (Secret with caption)

'UNCLASSIFIED
' ¥-20274

INCHES

0.02

 

0.03

 

o " .
)‘ ' -
i - o
R

S Ly e ’ E

by w,

 

 

 

Fig. 80. Photomicrograph from Inconel Tube-Burst Specimen Tested in Fused Salt No. 30 at 1500°F Under
4000-psi Stress. 100X. Electrolytically etched with 10% oxalic acid. (Secret with caption)

47
 

 

 

 

 

 

 

Fig. 81. Photomicrograph from Inconel Tube-Burst Specimen Tested in Fused Salt No. 30 ot 1500°F Under
3500-psi Stress. 100X, Electrolytically etched with 10%

 

™
A :
-
- , "F-
M
.

48

Fig. 82. Photomicrograph from Inconel Tube-Burst Specimen Tested in Argon at 1650°F Under 3000-psi Stress.
100X. Electrolytically etched with 10% oxalic acid.

oxalic acid. (Secret with caption)

 

 

 

 

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@ e 3 " - . " o llu W
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Y-20283
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Fig. 83. Photomicrograph from Inconel Tube-Burst Specimen Tested in Argon at 1650°F Under 2000-psi Stress.
100X. Electrolytically etched with 10% oxalic acid. Reduced 3%.

 
 

 

 

g mhes . “ i UNCLASSIF IED
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Fig. 84. Photomicrograph from Inconel Tube-Burst Specimen Tested in Argon at 1650°F Under 1500-psi Stress.
100X. Electrolytically etched with 10% oxalic acid.

49
 

T\ P UNCLASSIFIED | T
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Fig. 85. Photomicrograph from Inconel Tube-Burst Specimen Tested in Fused Salt Mo. 30 at 1650°F Under
3000-psi Stress. 100X. Electrolytically etched with 10% oxalic acid. Reduced 3%. (Secret with caption)

FEPAEE S N B SRR i g B DIRE i e AT - UNCLASSIFIED

Tk

:

.:‘-l
3
2

e

 

 

 

 

 

 

 

Fig. 86. Photomicrograph from Inconel Tube-Burst Specimen Tested in Fused Salt No. 30 at 1650°F Under
2000-psi Stress. 100X. Electrolytically etched with 10% oxalic acid. (Secret with caption)

50
 

Figi 314
1750-psi Stress. 100X. Electrolytically etched with 10% oxalic acid. (Secret with caption)

completely immersed in fused salt No. 30 is illus-
trated in Fig. 88. Time is plotted vs section
thickness with 2, 5, and 10% elongation, with
rupture, and with elongation at rupture as parame-
ters. The specimens were tested at 1500°F under
3500-psi stress. Considerable loss in strength and
ductility is exhibited by the thinner sections, al-
though the strength of sections over 0.060-in. thick
is not so sensitive to changes in section thickness.
A more extensive comparison of the creep-rupture
properties of 0.020- and 0.060-in.-thick Inconel
sheet in fused salt No. 30 at 1500°F is presented
in Fig. 89.

The stress-rupture properties of annealed tubular
specimens of 0.020-in.-wall thickness tested in
argon are compared in Fig. 90 with those of the
specimens tested in fused salt No. 30. A similar
comparison for 0.060-in.-wall specimens is given
in Fig. 91. The deleterious effect of the salt on
the rupture properties of the tubes of 0.020-in.-
wall thickness is seen to be much greater than on
the tubes of 0.060-in.-wall thickness. Itis intended
that only the relative properties of the material in
the two environments be considered, since the two

   

 

 

. ' UNCLASSIFIED
72 . Y-20271
o el ? n
8 . " * . toa, = g ) =
m
R o
i
0.02
0.03
o
b O
o

 

 

Photomicrograph from Inconel Tube-Burst Specimen Tested in Fused Salt No. 30 at 1650°F Under

UNCLASSIFIED
ORNL—LR—DWG 17921
BODO

 

700 —— T 52% | | 3%
RUPTURE
800

s00Q

400 |—

TIME (hr)

300

 

200

100
6%

 

   

 

0 - . !
0 20 40 60 BO 100 {20
SPECIMEN THICKNESS (inl

140 {2107

Fig. 88,
Rupture Properties of As-Received Inconel Tested in
Fused Salt No. 30 at 1500°F Under 3500-psi Stress.

(Secret with caption)

Effect of Section Thickness on Creep-

51
UNCLASSIFIED
ORNL—LR—DWG 17922

20,000

— (0.020=~in.~THICK SHEET
=== 0.060=in.~THICK SHEET

10,000

5000

STRESS (psi)

2000

 

1000
{ 2 5 10 20 50 100 200 500 1000 2000 5000 10,000

TIME (hr)

Fig. 89. Comparison of Creep-Rupture Properties of 0.020- and 0.060-in. Fine-Grained Inconel Sheet Tested in
Fused Salt. No, 30 at 1500°F, (Secret with caption)

UNCLASSIFIED
ORNL—LR—DWG 17923

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

20,000
|
10,000
Z 5000 N
A IN LIQUID NO, 3N N\l IN ARGON
i
5 X 3
\ ™
\\
2000 \,\
N
\
1000 N
4 2 5 10 20 50 100 200 500 1000 2000 5000 10,000

TIME (hr)

Fig. 90. Comparison of Stress-Rupture Properties of Annealed 0.020-in. Inconel Tube-Burst Specimens Tested
in Argon and in Fused Salt No. 30 at 1500°F. (Secret with caption)

52

 

 
 

20,000

10,000

5000

STRESS (psi)

2000

1000

100 200 500 1000 2000 5000
TIME (hr)

UNCLASSIFIED
ORNL-LR-DWG 17924

 

10,000

Fig. 91. Comparison of Stress-Rupture Properties of Annealed 0.060-in. Inconel Tube-Burst Specimens Tested
in Argon and in Fused Salt No. 30 ot 1500°F. (Secret with caption)

sizes of specimens were not taken from the same
heat of Inconel.

It is believed that a major portion of the strength
decrement observed in the thinner cross sections
may be attributed to the corrosive action of the
salt. However, there is some experimental evi-
dence '0+11 that the strength of a material may vary
with the cross-sectional area when it is tensile
tested in air at room temperature. Although this
phenomenon is not well understood, it is believed
to be attributable to the statistically inhomogene-
ous stress and strain distribution over the small
cross sections that results from the difference in
strength between the grain boundary and the bulk
grain.

Effect of Welding on the Creep-Rupture Strength

Several 0.060-in.-thick-sheet type of creep speci-
mens were machined from inert-gas-welded }&-in.-
sheet stock, and creep-rupture tests were carried
out in fused salt No. 30 and in argon to determine
the joint efficiency of Inconel weldments in the
two media. The results of these tests are summa-

rized in Table 3.

In all tests the failure occurred roughly %‘in.
from the weld in the parent metal, indicating that
the weld metalis somewhat stronger than the parent
metal at these temperatures. The position of the
failures was not considered to be within the weld
heat-affected zone.

Photomicrographs of the specimens tested in
fused salt No. 30 are presented in Figs. 92, 93,
ond 94. The short rupture times exhibited in the
case of the tests at 1300°F in fused salt No. 30
and the test of the annealed specimen at 4000 psi
at 1500°F in fused salt No. 30 are attributed to the
excessive corrosive attack seen in the photomicro-
graphs of these two specimens. |t is believed that
a leak developed in the testing apparatus during
the tests, which admitted oxygen into the salt
and thereby increased the rate of attack. The
photomicrographs indicate that the weld metal is

 

We ' 8. Baiker and C. F. Riisness, ""Effect of Grain
Siz% and Bar Diameter on Creep Rate of Copper at
200°C,"" Am. Inst. Mining Met. Engrs. 156, 117 (1944).

w. T. Pell-Walpole, *""The Effect of Grain Size on
the Tensile Strength of Tin and Tin Alleys,"" [. Inst
Metals 69, 131 (1943).

 
 

INCHES

0.02

 

e

 

 

 

e

~ i
o -
———
s

[
e

=

*

°r
S

- L, =
£
=l

i

4

=

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3 :

Rl
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&

Y-20285

o
L
i
vl
vl
<
-
L
=
=

 

o

. e
el %
degab i N e
LT S

—
=0
—

Photomicrograph Showing Corrosion of Inconel Specimen Tested in Fused Salt No. 30 at 1300°F Under

Fig. 92.
12,000-psi Stress.

100X. Electrolytically

{a) Wrought sheet Inconel above weld area; (b) as-welded Inconel sheet.

etched with 10% oxalic acid. (Secret with caption)
 

 

 

Fig. 93. Photomicrograph of Inconel Sheet Tested in Fused Salt No. 30 at 1500°F Under 3000-psi Stress.
(a) Wrought sheet Inconel above weld areo; (b) as-welded Inconel sheet. 100X. Electrolytically etched with 10%
oxalic acid. (Secret with caption)

 

 
 

as corrosion resistant as the parent metal. These
data and the data of Scott!? indicate that the joint
efficiencies of Inconel weldments in the temper-

ature range 1300 to 1500°F are from 95 to 100%.

 

12p, A, Scott, ‘‘Rupture Properties of Inconel Weld-
ments ot 1400, 1600, ond 1B00°F,'" Welding J. 35,
1615-163s (1956).

Yariations in Strength Among Yarious
Heats of Inconel

Comparison of the creep-rupture properties of
various heats of Inconel has revealed considerable
differences in strength among these heats. A
summary of the creep-rupture characteristics of
heat A tested at 1500°F in argon in the as-received

Table 3. Summary of Creep-Rupture Test Data on Inconel Weldments

 

 

5 T sl Rupture o Rupture Life
wone vt s e © RN b PR
pe ¥ AR (hr) e B Inconel
12,000 1300 Fused salt No, 30 As wel ded 110 21 600
4,000 1500 Fused salt No. 30 Annealed 380 11 700
4,000 1500 Argon Annealed 1400 16 850
3,000 1500 Fused salt No. 30 As welded 820 5 850
3,000 1500 Argon As welded 2900 7 2200

 

 

Fig. 94. Photomicrograph of Annealed Inconel Sheet Tested in Fused Salt No. 30 at 1500°F Under 4000-psi
Stress. The surface of the stressed specimen is shown on the left. 100X. Electrolytically etched with 10% oxalic
acid. (Secret with caption)

56

 
 

and annealed conditions is shown in Figs. 95 and
96. A comparison of the stress-rupture curves with
similar curves for heat B (Figs. 7 and 8) is given
for the two heats in Fig. 97.

The total deformation at rupture for fine- and
coarse-grained material from the two heats is shown
as a per cent elongation vs rupture time graph in
Fig. 98.

The following may be concluded from the above
comparisons:

1. Heat B exhibits rupture strengths 20 to 40%
higher than heat A at 1500°F.

2. A grain-coarsening anneal reduces the rupture
properties as compared with the fine-grained ma-
terial of both heats by the same magnitude at
1500°F.

3. The creep properties of heat B are superior
to those of heat A at 1500°F.

4. Heat B exhibits greater ductility at rupture
than heat A based on a comparison of per cent
elongation at rupture vs rupture time for both heats.

The microstructures of the two heats in the as-
received and annealed conditions are shown in

Figs. 99, 100, 101, and 102. No significant differ-
ence is seen in the amount or type of precipitate in
the as-received material nor in the appearance of
the material which was given the grain-coarsening
anneal.

The strain aging or precipitation phenomenon
noted with heat B also occurs at 1500°F with
annealed heat A, Figures 103 and 104 are photo-
micrographs taken after creep-rupture testing of
annealed material from heat A at 1500°F and 4000-
psi stress. The precipitate seen in Fig. 104 is
similar to that which occurs in material from heat
B (Figs. 30 and 31) at a similar stress and
temperature.

It appears that no microstructural difference
exists to which may be attributed the observed
variation in strength between the two heats of
Inconel. Based on these data and on the quality
control data obtained at the Huntington, West
Virginia, plant of the International Nickel Company,
Inc., it must be concluded that the creep properties
of Inconel are subject to variations from heat to heat.
Heats A and B exhibit the widest spread in creep

UNCLASSIFIED
ORNL-LR-DWG 17925

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

20,000 I 1 T
. m \
XH“' | ‘ |
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2000 \.’ ™S NN
i
1000 | |
1 2 5 10 20 50 100 200 500 1000 2000 5000 10,000

TIME (hr)

Fig. 95. Design Curve for As-Received Inco

nel (Heat A) Tested in Argon at 1500°F.

57

 
STRESS (psi)

58

20,000

10,000

STRESS (psi)

]
o
o
o

2000

1000

10,000

5000

2000

1000

 

UNCLASSIFIED
ORNL=-LR—DWG {7926

 

5 10 20 50 100 200 500 1000 2000 5000 10,000
TIME {hr}

Fig. 96. Design Curve for Annealed Inconel (Heat A) Tested in Argon at 1500°F,

 

20

UNCLASSIFIED
ORNL—LR—DWG 17927

FINE GRAIN; HEAT "a"

FINE GRNN;.

COARSE GRAIN; HEAT “A

COARSE GRAIN, HEAT "B"

50 100 200 500 1000 2000 5000 10,000
TIME (hr)

Fig. 97. Comparison of the Stress-Rupture Properties of Heats A and B in the As-Received and Annealed Con-

ditions.

 

 

 
 

 

UNCLASSIFIED
ORNL-LR=-DWG 19247
100 :

FINE-GRAINED HEAT B

o

COARSE-GRAINED HEAT B

3

FINE-GRAINED HEAT A

ELONGATION (%)
o

COARSE-GRAINED HEAT A

 

10 20 50 100 200 500 1000 2000 5000 10,000
RUPTURE TIME (hr)

Fig. 98. Creep-Rupture Properties of Inconel from Heats A and B Tested in Argon at 1500°F,

 

Fig. 99. Photomicrograph of As-Received Inconel (Heat A). 100X, Electrolytically etched with 10% oxalic acid.

59

 
 

 

Fig. 100, Photomicrograph of Annealed Inconel (Heat A). 100X. Electrolytically etched with 10% oxalic acid.

-
.l . UNCLASSIFIED
o i i“-"‘:q"_
S
-

 

 

 

Fig. 101. Photomicrograph of As-Received Inconel (Heat B). 100X, Electrolytically etched with 10% oxalic acid.
Reduced 3%.

60

 

 

 
© UNCLASSIFIED
Y=12368

i
=1=

 

Fig. 102, Photomicrograph of Annealed Inconel (Heat B). 100X. Electrolytically etched with 10% oxalic acid.

UNCLASSIFIED
Y-20265

Fig. 103. Photomicrograph of Annealed Inconel (Heat A) Tested at 1500°F Under 4000-psi Stress. The surface
of the stressed specimen, which ruptured at 240 hr, is shown on the left. 100X. Electrolytically etched with 10%
oxalic acid.

61

 
 

 

Fig. 104. Photomicrograph of Annealed Inconel (Heat A) Tested at 1500°F Under 4000-psi Stress. The surface
of the stressed specimen, which ruptured in 1300 hr, is shown on the left. 100X. Electrolytically etched with 10%
oxalic acid.

properties of all the heats examined at ORNL and
thus bracket the range in values which can be
expected for 0.060-in.-thick sheet.

Tensile Properties of Inconel

The results of tensile tests performed at a strain
rate of 0.016 in./min at temperatures ranging from
room temperature to 2200°F on as-received and
annealed Inconel are shown in Fig. 105. Stress is
plotted vs temperature with the ultimate strength
and the 0.2% offset yield stress as parameters.

The modulus of elasticity values for hot-rolled
Inconel at temperatures up to 1800°F are tabulated
graphically in Fig. 106. The as-received material
is seen to exhibit higher yield and tensile strengths
at temperatures up to roughly 1700°F, although
both as-received and annealed materials lose
strength rapidly as the temperature increases above
1000°F. The higher yield and ultimate strengths
of the as-received material may be attributed to the
residual cold work and to the carbide precipitate
which exists in the microstructure. The modulus
of elasticity decreases with temperature above
1500°F but not so rapidly as do the other tensile
properties.

62

 

. UNCLASSIFIED
{-xlc-a} ORNL-LR-DWG 16278
"
10g [—===s====

 

\_  TENSILE STRENGTH OF
) \ AS-RECEIVED INCONEL
90 \

TENSILE STRENGTH OF \t
" ANNEALED INCONEL \

: 1
\ \
- 1
! i
0.2% YIELD POINT OF ‘-,
AS—-RECEIVED INCONEL ‘-l-
4“ -".‘..‘-"'"'-—- “

 

2

 

=
o

 

@
Q

 

STRESS [ psi)
8

 

 

 

0.2% YIELD POINT OF N .l‘L
ANNEALED INCONEL i

20 —

 

--..____‘______- | '\.fi\

"*x"‘-"-:--

e

 

 

 

 

 

 

 

 

 

 

0 400 800 1200 1600 2000 2400 2800
TEMPERATURE (°F)

Fig. 105, Tensile Properties of As-Received and
Annealed Inconel Tested at a Strain Rate of 0.016
in./min.

 

 

 
 

 

(x10%)
40

UNCLASSIFIED
ORNL—LR—-DWG 17928

 

 

38

 

36

 

w
o

 

(o]
ra

|
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M
@

na
o

 

 

ny
£

 

MODULUS OF ELASTICITY (psi)
m
r

 

20

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

fo l
o 100 200 300 400 500 600

700 800 900

000 100 1200 {300 1400 1500 1600 1700 {BOO 1900

TEMPERATURE (°F)

Fig. 106. Modulus of Elasticity of As-Received Inconel.

Some Physical Properties of Inconel

Although a discussion of the physical properties
of Inconel is beyond the intended scope of this
' report, it was deemed advisable to include data
on the thermal conductivity and the coefficient of
thermal expansion because they are so important
in the calculation and evaluation of thermal
stresses.

The mean and instantaneous linear coefficients
of thermal expansion for Inconel at temperatures
up to 1800°F, which were obtained from the
International Nickel Company, Inc., are presented
in Table 4. The data on the variation of thermal
conductivity of Inconel with temperature for temper-
atures up to 1500°F are given on the following

page:

63
Temperature Conductivity
(°F) [Btu/#2ssec/(OF/in.)]
300 0.032
400 0.033
500 0.034
600 0.035
700 0.036
800 0.037
900 0.038
1000 0.039
1100 0.040
1200 0.041
1300 0.042
1400 0.043
1500 0.044

Table 4. Expansion Coefficients of Inconel

 

 

 

Temperature Mean Instantaneous
Ringe Coefficient Coefficient
(°F) in/in/°F(x10~%)  in./in./°F(x10~5)
100 - 200 8.0 8.2
100 — 400 8.1 8.6
100 - 600 8.2 8.8
100 - 800 8.3 8.9
100 — 1000 8.5 9.8
100 — 1200 8.9 10.5
100 - 1400 9.2 10.8
100 — 1600 9.4 10.8
100 — 1800 9.6 10.8

 

Design Data

The design data for as-received and annealed
0.060-in.-thick Inconel sheet tested in argon and
in fused salt No. 30 at 1300, 1500, and 1650°F
have been replotted in two more convenient forms
for use in design.

In Figs. 107 through 118 the data are plotted in
the form of isochronous curves. Stress is plotted

vs strain with 100, 500, 1000, and 2000 hr as time

UNCLASSIFIED
ORNL—LR—DWG 14894

 

18,000

 

16,000

 

 

14,000

12,000 |

 

10000 [—

8000

STRESS (psi)

6000

4000 |

 

2000

 

 

o — et
21 o2 o8 " 1 2 5 10 20 50 100
TOTAL STRAIN (%)

Fig. 107. lIsochronous Design Charts for As-Received
Inconel Tested at 1300°F in Argon.

UNCLASSIFIED
ORNL—LR—DWG 14883

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

18,000 T
| ‘ [ |
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14,000 —ll : ’ HH—t— - = :r/
|
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12000 [+t o
= || Lo | :
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7 | 100 hr || LM
::‘E’ 8000 4 A
w | > g | . 500|h| | | |
L [ 200 hr (111
2Ghd _'“/r’,.-fl-f%:“*moo hr T
=11l | Troconr L
4000 |— % e et by
' | |
I | |
2000 | | t | ‘ .
0 | R ‘ i ! ‘ J £
01 02 05 4 2 5 g 20 50 100
TOTAL STRAIN (%)
Fig. 108. |Isochronous Design Chart for Annealed

Inconel Tested at 1300°F in Argon.

parameters. These curves are used in the following
manner, |f in design a limiting strain in 1000 hr
at 1500°F is the criterion for failure, the stress
which will produce this strain may be picked from
the proper chart.

To facilitate interpolation between the testing
temperatures, stress is plotted vs temperature, at

 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

UNCLASSIFIED
18,000 ORNL—LR—DWG 14893
. 16,000 [— || 4 AT I
|
14,000 | | !"’-":‘ || {.,.';.1;
) 12,000 h [ }‘T/ J_ A H
= | '
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gaogo | l!|/ JT _,4:-1'!!'\ ‘
Z | ,H"y ‘L".-'a " RuPTURES
6000 Pl l/‘f:’""‘ "_...T- al BT ‘
/f’:,,gt?“' 1000 hr | T
v s N LT 1]}
4000 H {' i af*."l" i"' i ; i ]
2000 7 ST | 1 !||“|_
0 I|) I | I _||||| | ’_Iill
of 02 05 1 2 5 10 20 50 100

TOTAL STRAIN (%)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Fig. 109. Isochronous Design Chart for As-Received
Inconel Tested at 1300°F in Fused Salt No. 30. (Secret
- with caption)
UNCL ASSIFIED
s 18,000 ] | DHHL-LF!-{:M]G Maalz
16,000 |
14,000 H
12,000 L
&
~ 10,000 HNEAI
T
E 8000 |- RUPTURE |
- T
6000 L
|
4000 !
2000 i 2 T‘
o lII ! by 1 ! L1l :
04 02 05 4 2 5 0 20 50 400
TOTAL STRAIN (%)
‘Fig. 110, Isochronous Design Charts for Annealed

Inconel Tested at 1300°F in Fused Salt No. 30. (Secret
with caption)

 

UNCLASSIFIED
ORNL-LR—DWG {4888

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

9000
8000
| J
7000 /
/
6000 /
100 hr"m-.Pr-H {
= A /
£ 5000 ] »
0 ‘4?}," A __,..-/' i
g 4000 - T %
» ¥ | _LaTT /T~ruPTURE
3000 g LU ]
.-"""l S =1 ' f |
~ L3N {
2000 e s
- =T | [NI[=1000 hr Il
\N‘EG{ED I ‘
1000 || i he | I[
S L | il
0ot 02 05 { 2 § 0 20 50 100

TOTAL STRAIN (%)

Fig. 111. Isochronous Design Charts for As-Received
Inconel Tested at 1500°F in Argon.

UNCLASSIFIED
ORNL-LR-DWG 14BB6

 

9000

BOOO

 

 

 

 

 

7000

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

STRESS (psi)
n
g

3000 -

 

 

 

 

 

 

 

 

 

 

 

2000

 

 

 

 

 

 

1000

Q.

Fig. 1 12.

 

 

|

 

 

 

 

 

 

 

 

 

 

 

 

 

05 |1 2 5 10 20 50 100

TOTAL STRAIN (%)

i 02

Isochronous Design Charts for Annealed

Inconel Tested at 1500°F in Argon.

65

 

 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

     
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

UNCLASSIFIED
UNCLASSIFIED
_/OGHLLE=EWG 18808 ORNL—LR—DWG 14891
9000 I | | [T ‘ i |II 9000 | ‘ H H T .|‘|
WL AL :
8O0O M| = |74 | 8000
|| 7|
L L] 2
7000 e At i 7000 B
i i |
| a1 L LU i
6000 : ! / =+t 6000
—~ | /! /1 Z
= i = & 5000
2 5000 . : 4 ! = ="
2 | 100 hy | fRUPTURE » L
o 4000 1l /'
E 4000 l/' I | ]l | f’ & f.p- 00 hr ;’
« 500 hr—~1 i !
5000 Ll | PP 3000 g
| / 1000 hr. # ; ) _/'"’ ,pr | .
|| L Tl 11111 2000 1= L _,_.I_a;'f “-RUPTURE
e t t —y T + TT] il i
o A5 I Tt |
T | oo
1000 e =11 SF : - ‘ I .--"""-— 2000 lhr I
O L 11l
‘ ‘ \ \ ‘ ‘ | o1 02 05 1 2 5 0. 20 50 100
0
01 02 05 1 2 5 0 20 50 100 TOTAL STRAIN ()
TOTAL STRAIN (%)

Fig. 113. lsochronous Design Charts for As-Received Fig. 115. lIsochronous Design Charts for As-Received
Inconel Tested at 1500°F in Fused Salt No. 30. (Secret Inconel Tested at 1650°F in Argon. -
with caption)

UNCLASSIFIED UNCLASSIFIED 2
ORNL-LR-DWG 14887 ORNL-LR-DWG 14884
8000 11 BOOO 1 - | ! 5 T
7000 7000 |—+
/9‘! 1 |

6000 = 6000
= '_,.-"/:‘f =
2 5000 / 2 5000 | -

u
& 7 2
4000 1 4000 ' i
- _;..'f! RUPTUTE‘ e /? |
/ | . |
| 3000 ' 3000 : - A T
f ll | 00T ! é,fi’ RUPTURE
: 2000 : W
2000 ‘ 1 :199,_ .—___::,/
LT =g
1000 i 1000 e s = +£oo hr
' ‘ =T {2000 hr ‘
0 L1 ' | i 0 | FEEiL
o 10 20 50 100 64 02 05 {1 2 5 10 20 50 100
TOTAL STRAIN (%) TOTAL STRAIN (%)
Fig. 114, Isochronous Design Charts for Annealed Fig. 116. Isochronous Design Charts for Annealed

Inconel Tested at 1500°F in Fused Salt No. 30. (Secret Inconel Tested at 1650°F in Argon.
with caption)

 
constant time, with 0.5, 1, 2, 5, and 10% elonga-
tion and rupture as parameters in Figs. 119 through

130.

It must be remembered that these data are subject

to modification by any of the previously discussed

UNCLASSIFIED
QORNL-LR-DWGL 14890

 

S 9
o
Q

8 8

STRESS (psi)

3000 [—

2000 [—

1000 |-

 

0y DR

  

(TTTT |

 

 

  

| -'-‘-.— lDGIIDhr

-\EOOOh_r '
a9 1 2 5 1o 20 50 100
TOTAL STRAIN (%)

 

 

 

Fig. 117. lIsochronous Design Chorts for As-Received

Inconel Tested at 1650°F in Fused Salt No. 30, (Secret

with caption)

 

 

UNCLASSIFIED
QRNL—LR—DWG 14885

 

 

 

 

 

 

 

 

 

  

 

9000 || Rl [ ‘u
8000 L - ru
L
7000 L— —|—|— iht
| | | ]
L LT
6000 T T
L2 5000 o L
@ [ | |
& || i L
E 4000 =i ——'— 11 |-
= I ' | L1111
3000 — il 4] i L
i -'[jrh“{HUETul?E 1
2000 = i i |. ! . _ :. .I _|. ! ,_._i_.T
1000 ——+ | 11172000he } L1
\ . L]
] 5 | 1] |[T3o0r , ‘ L]
ef D2 05 Y 2 5 0 20 50 100
TOTAL STRAIN (%)
Fig. 118, Isochronous Design Charts for Annealed

Incenel Tested ot 1650°F in Fused Salt No. 30.
with caption)

 

(Secret

effects such as section size, biaxial stress, en-
vironment, and previous mechanical and thermal
treatment.

DISCUSSION

In the evaluation of the data presented from tests

conducted in the sodium and in the fused-salt en-
vironments, it must be recognized that certain errors

STRESS (psi)

20,000

 

UNCLASSIFIED
ORNL—LR=—DWG 17929

 

 

 

 

 

 

 

 

| |
10,000 NG —_—
e e
——
5000 | —_— e
o |
2000 et —
2% |
1% |
5% ELONGATION
05% 1
1300 1400 1500 {800 100 1800
TEMPERATURE (°F)
Fig. 119. Temperature Dependence of the Creep-

Rupture Strength of As-Received Inconel Tested in Argon
'FOI' 500 l'll'i

STRESS (psi)

 

UNCLASSIFIED
ORNL—LR—DWG 17930

 

 

 

1300

Figy

120.

{500
TEMPERATURE (°F)

1400 1600

Temperature Dependence of the Creep-

Rupture Strength of Annealed Inconel Tested in Argon

for 500 hr.

67
 

UNCLASSIFIED
ORNL-LR-DWG 17931

 

20,000
| AOTELONGATION
10,000 [ 5% ELONGATION
/
_RUPTURE
= 0
fi 5000 /-
o3
oy
l
o
=
w
2000
2%, ELONGATION
~ 1%, ELONGATION
1000
0.5 % ELONGATION
800 .
1300 1400 1500 1600 1700 1800 1900

TEMPERATURE (°F)

Fig. 121. Temperature Dependence of the Creep-
Rupture Strength of As-Received Inconel Tested in
Fused Salt No. 30 for 500 hr. (Secret with caption)

UNCLASSIFIED
ORML=LR=DWG 17932

RUPTURE J
s }:éflifi, ELONGATION |

 

20,000

 

 

 

 
   

 

 

 

 

 

 

 

 

 

 

 

 

 

5000
E
=
wn
w
w
1
-
o
2000
0.5% ELONGATION
e et _—:\‘i
e I 1  Talalels v
e ———— ' — t J
500 ke | |
1300 1400 1500 1600 1700 1800

TEMPERATURE (F)

Fig. 122. Temperature Dependence of the Creep-
Rupture Strength of Annealed Inconel Tested in Fused
Salt No. 30. (Secret with caption)

UNCLASSIFIED
ORNL=-LR-DWG 17933

20,000

10,000

5000

 

X RUPTURE
3 |
= 0% ELONGATION
Q 2% ELONGATION 5% ELONGATION
o 5
i NGATION
2660 % ELO
1000
500
1300 1400 1500 1600 1700 1800

TEMPERATURE (°F)

Fig. 123. Temperature Dependence of the Creep-
Rupture Strength of As-Received Inconel Tested in

Argon for 1000 hr, -

UNCLASSIFIED
ORNL-LR-DWG 17934
20,000

10,000

5000
~RUPTUR

10 % ELONGATION

STRESS (psi)

5% ELONGATION

2000 —

2 e ELONGATION

) E_I.:QNFEJETJQN

1000

 

500
1300 1400 1500 1600 1700 1800
TEMPERATURE (°F)

Fig. 124. Temperoture Dependence of the Creep-
Rupture Strength of Annecled Inconel Tested in Argon

for 1000 hr. v

 
 

UNCLASSIFIED
ORNL=-LR-DWG 175935

20,000

10,000

5000

STRESS (psil

2000

5% ELONGATION

1000 —0 2% ELONGATION

1% ELONGATION

 

500
1300 1400 1500 1600 gele] 1800
TEMPERATURE (°F)

Fig. 125. Temperature Dependence of the Creep-
Rupture Strength of As-Received Inconel Tested in
Fused Salt No. 30 for 1000 hr. (Secret with caption)

UNGLASSIFIED
2. 660 ORNL-LR-DWG 17938

10,000

5000

STRESS (psi)

\"\.
2000

.
™ 5% ELONGATION

™ 2% ELONGATION
1% ELONGATION

1000

 

500
1300 1400 1500 1600 1700 1800

TEMPERATURE (°F)

Fig. 126. Temperature Dependence of the Creep-
Rupture Strength of Annealed Inconel Tested in Fused
Salt No. 30 for 1000 hr. (Secret with caption)

UNCLASSIFIED
ORNL-LR-DWG 17937

20,000

 

10,000
—~ 5000
v
=
@
w
o
=
w
2000
RUPTURE
% ELONGATION
5% ELONGATION
1000
500
1300 1900 1500 1600 {700 1800

TEMPERATURE (°F)

Fig. 127. Temperature Dependence of the Creep-
Rupture Strength of As-Received Inconel Tested in
Argon for 2000 hr.

UNGLASSIFIED
DRNL-LR-DOWG 17938
20,000

10,000
RUPTURE —

} —
{0% ELONGATION —

5000

N

STRESS (psi)

2000
5% ELONGATION

= 2% ELONGATION

1000
1% ELONGATION

 

S00
1300 1400 1500 1600 1700 1800
TEMPERATURE (°F)

Fig. 128. Temperature Dependence of the Creep-
Rupture Strength of Annealed Inconel Tested in Argen
for 2000 hy.

69

 

 

 
exist in the reported strain values because of in-
herent inaccuracies inthe methdd of strain measure-
ment. Conventional types of strain-sensing sys-
tems cannot be used because of the high temper-

UNGLASSIFIED
ORNL-LR-DWG 17929

 

  
    
  

 

 

 

20,000
10,000 ——— e — —
SRUPRIRE=— | - - —— |
—10% ELONGATION =
~ 5000 |- A —————— -
@ I —5% ELONGATION
= . .
o
Lt
: |
€
uy
2000 - - — - |
: N ‘
1000 I
NS . [
- ——————— '\?,"}""'Z%ELDNG&TION
- - T N % E:flHfinfiafi_l
500 | | ' - J
1300 1400 1500 1600 {700 8GO
TEMPERATURE (°F)
Fig. 129. Temperature Dependence of the Creep-

Rupture Strength of As-Received Inconel Tested in
Fused Salt No. 30 for 2000 hr. (Secret with caption)

UNCLASSIFIED
ORNL-LR-DWG 17940

 

26,000 |

 

 

 

|
fooon o1 L { L =
I RUPTURE - .
— 0% ELONGATION
2
oy
w
Lt
* 4
-
wn
{000
=T — Ll = s : L i)
500 I.— S S I P — | S
1300 1400 1500 1600 1700 1800
TEMPERATURE (°F)
Fig. 130. Temperature Dependence of the Creep-

Rupture Strength of Annealed Inconel Tested in Fused
Salt No. 30 for 2000 hr., (Secret with caption)

70

Lo ealam

atures and the existence of corrosive vapors in the
test chamber. Consequently, the movement re-
sulting from deformation of the test specimen is
monitored outside the test chamber roughly 18 in.
from the gage length of the specimen. Thus the
dial goge records, in addition to the movement
due to deformation in the gage length of the speci-
men, the movement resulting from deformation in
the pull rods and the shoulder of the specimen.
The result of this error is that the dial gage indi-
cates shorter time intervals to the lower strains
than are actually occurring in the gage length of
However, the magnitude of this
is constant, and as the strain values in-
crease, the percenfage error decreases rUpEdIy and
therefore the recorded strains above 1% are actu-
ally quite accurate. Since, for design purposes,
it is desirable to obtain accurate low-strain data,
an attempt is being made to devise a more accu-
rate method for measuring creep under these con-
ditions. A recent technique has involved the use
of a variable permeance transducer, the coils of
which are ‘‘canned’’ in a corrosion resistant ma-
terial, actuated by rods fastened directly to the
ends of the gage length of the specimen. One
such test has been conducted with encouraging
It is therefore believed that in future
testing programs the accuracy of the data obtained
in liquid environment will be comparable to that
obtained in gaseous environments,

The data presented in this report represent the
results of an extensive investigation of the high-
temperature properties of Inconel under static load
conditions. It is known that certain parts of the
reactor will be subjected to transient stresses
imposed either thermally or mechanically. In recog-
nition that these data are inadequate for all design
purposes and that they should be supplemented by
tests in which cyclic stresses or strains are im-
posed on the material, a program has been initiated
to obtain the type of design data which will more
closely approach actual service conditions.

It was pointed out in the introduction to this
report that one of the factors considered in the
selection of a material for reactor use is its sto-
bility under radiation. Although no data have been
presented, the importance of this effect has not
been overlooked. This portion of the testing
program is being conducted by the Mechanical
Properties Group of the Sclid State Division., A
coordinated testing program between the above
named group and the Mechanical Properties Group

the specimen.
error

results.
 

of the Metallurgy Division is in progress in an
effort to establish the magnitude of the effect of
radiation on the creep-rupture properties of Inconel
in the temperature range of reactor operation.

CONCLUSIONS AND RECOMMENDATIONS

In the range of temperatures and stresses in-
vestigated, the factors which were found to have
a pronounced effect on the creep-rupture properties
of Inconel are summarized as follows:

1. The effect of groin size or annealing treatment
prior to test depends on the testing temperature
and environment. At 1300°F the fine-grained
material is stronger than the coarse-grained ma-
terial in all environments. At 1500°F the fine-
grained Inconel is stronger than the coarse-grained
material in argon and in sodium but weaker in the
fused salt. At 1650°F the fine-grained Inconel is
weaker than the coarse-grained Inconel in all
environments,

2. The corrosion induced by the fused salt
causes 0 reduction in the creep and rupture proper-
ties of Inconel at all temperatures. This reductien
in strength becomes more marked as the temper-
ature is increased.

3. The effectiveness of the fused salt in de-
creasing the strength of Inconel increases rapidly
as the section thickness is decreased below
0.060 in,

4. Large variations in creep-rupture strength
were observed between different heats of Inconel.
Although the reasons for these variations have
not been definitely established, it appears that
they moy be attributed to minor compositional
differences induced by melting practice or to vari-
ations in fabrication history.

5. Oxidizing environments were found to reduce
the creep rate and to increase the rupture life of
thinner sections. This effect on sections greater
than 0.060 in. thick is to increase the rupture
elongation and time only.

Sodium was found to have no significant effect
on the creep-rupture properties if the purity of the
sodium is high. It is shown that Inconel may be
decarburized by sodium if the oxide content of the
sodium is high, It has also been observed that
Inconel may be carburized by sodium contaminated
with carbon. Since it is anticipated that high-
purity sodium and NaK will be used in reactors, it
is believed that creep data obtained in the argon
environment may be used in the design of structures
in contact with sodium or NaK.

Although a biaxial stress system consisting of
simple hoop and axial stresses does not decrease
the rupture life of the Inconel, the total elongation
at failure in the direction of the maximum stress
may be substantially reduced.

Application of the information contained in this
report for specific design situations will need to
be tempered with considerable caution in certain
cases because of the presence of dynamic or complex
stress conditions induced by thermal fluctuations.

ACKNOWLEDGMENTS

The authors would like to acknowledge the con-
tributions of J. D. Hudson, B. McNabb, C. W. Walker,
J.T. East,C. K. Thomas, V. G. Lane, K. W. Boling,
E. Bolling, E. B. Patton, and F. L. Beeler of the
Mechanical Properties Group in performing the
tests and the metallographic work of N. M. Atchely
of the Metallography Group.