ORNL-TM-1341.txt

 

OAK RIDGE NATIONAL LABORATORY

 
  

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e operated by
Ed UNION CARBIDE CORPORATION
@; for the |

U.S. ATOMIC ENERGY COMMISSION
ORNL- TM- 1341
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B ELEVATED-TEMPERATURE MECHANICAL PROPERTIES OF WELDS
*;‘: IN A Ni=-Mo~-Cr-Fe ALLOY

T

;.h' R. G. Gilliland

g J. T. Venard

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- TO THE AEC AND ITS CONTRACTORS ONLY.

.

NOT APPROVED FOR PUBLIC RELEASE. AVAILABLE l

NOTIGE This document contains information of a preliminary nature
and was prepared primarily for internal use at the Ook Ridge National
Laboratory. It is subject to revision or correction and therefore does

not represent a final report.

 
;_“uwg ._.7__}

e mim e e e e L EGAL NOTICE —————— i e e e
|
|

This report was prepared as an cccount of Government sponsored work. Neither the United States,

nor the Commission, nor any person acting on behalf of the Commissicon:

 

A, Makes any warranty or representotion, expressed or implied, with respect to the accuracy,
completeness, or usefulness of the information contained in this report, or that the use of |

any information, apparatus, method, or process disciosed in this report may not infringe

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privately owned rights; or
B. Assumes any liabilities with respect to the use of, or for damages resulting fram the use of l
any information, apparatus, method, or process disclosed in this report. i
As used in the above, '‘person acting on behalf of the Commission’’ includes any employee or !
contractor of the Commission, or employee of such contractor, to the extent that such employse
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provides access to, any information pursuant tc his employment or contract with the Commission,

or his employment with such contractor.
 

Nt i e G0t By B 8 8 WL et ettt S e R S it

 

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ORNL-TM-1341

Contract No. W-7405-eng-26

METALS AND CERAMICS DIVISION

ELEVATED-TEMPERATURE MECHANICAL PROPERTTES OF WELDS
IN A Ni-Mo-Cr-Fe ALLOY

R. G. Gilliland and J. T. Venard

-

This paper has been submitted
! to the Welding Journal

 JANUARY 1966

OAK RIDGE NATIONAL LABORATORY
- Osk Ridge, Tennessee
: - - operated by
- UNION CARBIDE CORPORATION
| - - for the
- - U.,S, ATOMIC ENERGY COMMISSION

 
 

| £ ..

 

 

 

 

 

 

 
 

. /’p

ELEVATED TEMPERATURE MECHANICAL PROPERTIES OF
WELDS IN A Ni-Mo-Cr-Fe ALLOY¥
R. G. Gillilend and J. T. Venard
Metals and Ceramics Division

Osk Ridge National Laboratory
Oak Ridge, Tennessee

ABSTRACT

A non-agthardenable; high-strength alloy was developed et the

.o

Oak Ridge National Laboratory for use as the primary containment mate-

rial for the Molten Salt Reactor Experiment\(MSRE). The alloy was

molten fluoride salts in thet1100 to 1500°F temperature range,

tailored to give good strength, ductility and corrosion resistance to

work reported here concerns the elevated-temperature mechanical proper-

tles of welds made in thls ‘alloy, known as INOR 8 as represented by

~

. several heats of MSRE-grade material

Tensile tests on transverse weld samples in the as-welded and

annealed conditions show”a_good combinationrof strength and ductility

at temperatures ranging from 70 to 1800°F. Tensile properties of these

- weld samples compare favorably W1th those of the base,metal

reliEV1ng at 1600 F for 2'hr results in a 1owering of the tensile yield -
strength- Creep-rupture tests at llOO 1300 and 1500°F on’ these same

, S type specimens show s1gnificant improvement in strength and ductlllty

at 1300°F folloW1ng & hydrogen atmosphere stress rellef Both as-

- welded and stress-relieved creep-rupture behav1or was as good as the

 

contract with the Union Carblde Corporation.

base metel-behav1orp The;nil-ductility temperature, as determined by

QEJ , *Research sponsored by the U.S. Atomic Energy Commission under

 
 

 

 

o

simulated heat-affected zone thermal cycle tests, was found to be 2300°F.

Reasonable recovery of mechanical properties.follows'a simulated welding

ecycle with a 2300°F mascimum temperature.

INTRODUCTION

In order to fully realize the potential of nuclear regctor systems
utilizing molten fluoride salts as'fuel, the structural materials must
possess adequate combinations of strength, ductility, and corrosion
reSistance at temperatures in the 1100-1500°F temperature'?ange. Thé
non-age-hardenable nickel-moiybdenum-chromium-irofi élloy, designated as
INOR-8 [Ni-17 Mo~7 Cr-5 Fe (wt %) ] is such an'alloy and was the culmina-
tion of a comprehensive alloy development and evaluation program carrigd
out at the Oak Ridge National L:atboraa:l;o:c';;r.J"‘3 It is now commerciélly
available®* and is the primary containment material for the Molten Saxt
Reactor Experiment which achieved criticality on June 1, 1965, at Oak
Ridge, Tennessee. A vital part of the overall welding study on INOR-8
was the determination of the ‘elevated-temperature mechanical properties
of welds. This report summarizes the findings on the mechanical behavior

of'welds‘in some of the actual heats of material used in the MSRE.

'MATERIALS, TESTING PROGEDURE AND EXPERIMENTAL RESULTS

Transverse samples'machined from 1-in.-thick welds, made under

highly restrained conditions were used in the testing. These butt welds

were fabricated in the manner illustrated in Fig. 1 and described in

earlier work.? The transverse tensile specimens used were of the -

 

¥ Designated as Hastelloy N by.Stellite Division of Union Carbide
Corporation.

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DIMENSIONS IN INCHES ' -

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L Y6 MAX

~ JOINT DESIGN AND WELDING SEQUENCE
" Fig. 1 — The INOR-8 high-restraint weldability test specimen,u'sed |

- to provide samples for the mechanical properties study.

 
 

 

 

desigrn shown in Fig. 2. The manual gas tungsten arc-welding process

was used to fabricate the joints; the filler metal used was of the

same nominal composition as the base metal.

The INOR-8 material used

in this study was taken ffom the stock purchased for construction of

the MSRE. The heat numbers and the tests to which each heat of INOR-8

was subjected are tabulated below.

Heat Number Type of Test
5055 (Weld Metal)
5057 _ Creep-stress relieved, hydrogen
5060 Creep-as-welded
5062 Tensile-as-welded
5064 Tensile-stress relieved, argon
5067 Creep-stress relieved, hydrogen
5068 Creep-stress relieved, argon
5069 Creep-as-welded
5070 ' Tensile-stress relieved, hydrogen -
5071 -~ Tensile-as-welded
5072 Creep-stress relieved, hydrogen
5073 Tensile-stress relieved, hydrogen
5074 Tensile-as-~welded; creep—stress
relieved, argon -
5075 Tensile- stress relieved, argon,
Creep-as-welded
5081 Tensile-stress relieved, argon
- 5083 Creep-as-welded
5089 Creep-stress relieved, hydrogen
5090 ~ (Weld Metal)

The chemical analyses of these heats are presented in Table 1. Note

that the filler metal used to fabricate the weld specimens was teken

from heat numbers 5055 and 5090.

Because of material fabrication schedules, it was necessary to do

the welding operations on platé which had the final rolling operation

performed normal to the welding direction.

This schedule caused the

Y

materials' inherent stringer line to be located in the plate-thickness

- direction and parallel to the fusion line.

A typical cross section of

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}' Vzrin *-! 0.252 + 0.005-in. DIAM
| GAGE LENGTH re9e = BTN

AMERICAN STANDARD COARSE THREAD—
CLASS 2FIT

(@) Tra_né#er‘ée Weld Tensile Specimen.

4, in.
3 1/2 m
L—O.250-|n. DIAM /
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| (b) ”;I'-idt.Ddcfility Specim'en.

F:Lg. 2 — Transverse tensile spe01men used for hlgh-restraint

: VINOR 8 weld evaluations., = -

 
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Table 1. Chemical Analysis of the INOR-8 Heats

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Heat Analysis (wt %)®

Number

Mo Cr Pe c Si Al Ti B Co v Mn W P S

5055 16.20 17.86 3.76 0.06 0.61 0.06 0.02 0.005 0.10 0.21 0.69 0.03 0.006 0.008
5057 16.80 7.47 3.50 0.05 0.52 0.0L 0,01 0.005 0.09 0.23 0.58 0,02 0.001 0.006
5060 16.20 6.92 4.03 0.07 0.56 0,01 .0.0l 0.004 0.02 0.26 0.46 0.04 0,001 0.00L
5062 16.17 ‘.7.45 3.78 0.04 0.58 0.00 0.01 0.005 0.08 0.24 0.63 ‘0.08 0.001 1 0.006
5064 16.37 7.90 3.59 0.07 0.69 0.0L 0.01 0.005 0.06 0.29 0.59 0.03 0.00L  0.006
5067 17.07 7.23 4,20 0,06 0.43 0.0L 0,01 0,004 0,09 0.30 0.60 0.06 0.00L 0.006
5068 16.50 6.45 4,11 0.05 0.58 '0.0L 0.0L 0.004 0.09 0.27 0.45 0.07 0.003 0,008

- 5069 16.22 6.42 3,93 0.07 0.56 0.01 0.01L 0.006 0.12  0.23 0,52 0.06 0.003 0.009
>070 16.06 6.62 3.93 6.06 0.60 0.04 0.22 0.64 0.03 0.00L 0.008
5071 16.22 7.21 4,35 0.07 0.63 0.0L 0.01 0.004 0,07 0,20 0.65 0.02 0.001 .0.068
5072 15.50 7.03 4.06 0.06 0.57 0.0L 0.02 0,005 0.09 0,27 0.57 0.04_,'0.001 0.012
5073 16.21  6.77 ©3.90 0.05 0.60 0.01 0.0r 0.006 0:07 0.34 0.50 ‘0.03 0.004 0.008
507 16.17 6.77 3.70 0.07 0.62 0.01 0.0pL 0.007 0;67 0.24 0.51 0. 006

——

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0.001

 
 

 

[

Heat‘

Analysis (vt %)%

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Number | ‘ :
Mo Cr- Fe

Si

Al

Ti

B

Co

 

5075 16.42 6.7 4.08
5081 16.90 7.7 = 3.56
5083 17.03 751 3.80
5089 16.69 6.78 3.8l

5090 16.22 7.59 4.03

0.06
- 0.06
0.05

- 0.05

0.07

0.57

0.60

0.52

1 0.36

0.56

0.03
0.00
0.01
0.01

0.01

- 0.01
- 0.01
0.01

0.01

0.01

10.001

0. 005

- 0.005

0.004

0.005

0.06

0.07

- 0.10

0.14

0.12

0.28

0.27

0.38

0.39

0.04
0.04

0.05

0.05

0.04

© 0.003

0.003

0.001

- 0.011

“0.001

0.005
0.006

. 0.006

0.012

0.008

 

®Balance nickel.

 

 
 

 

 

 

 

the.weld fusion line area is éhown in Fig. 3. Thié fiiew illustrates the
| orientation of the stringer formation with respect to tfie fusion line
‘and its pérpendicular orientation with respect to the welding dire¢tion
and specimen axis.

The transverse weld specimens contained weld metal, hé;t—affected
iones, and base metal and were tested at elevated temperatures in
sténdard tensile tests (0.03 min-') and in creep tests. Elevated-

_ fempérature tensile tests were performed between 600 and 1800°F at

200°F intervalé, and creep testing was dOne at 1100, 1300 and 1500°F.
The specimefis were tested in both the as-welded.and stress-relieved
conditions, with stress relieving béing performed in bbth argon and
-hydrogen atmospheres (2‘hr afi 1600°F). Samples were also machined from
the as-received base metal for the'determinationof elevated-température
hot ductility after being subjected to simulated heat-affected zone
thermal cycles.

The room- and elevated-temperature tensile tests were run in air
using a standard 12,000-1b capacity hydraulic testing machine at a
crosshead speed of 0.05 in./min or a strain rate of 3.33%/min. Stress-
strain relationships were obtained using load cell-deflectometer out-
puts. Elevafied-temperature tests were performed using a clamshell-

- type furnace, in which specimens were allowed a 1/2-hr equilibration

period to reach the test temperature. Thé results of these tests for

the as-welded and stresé—:elieved conditions are pfesented in Tables

2 and 3 for test temperatures between room temperature and 1800°F.
Thercreep tests were run in air using standard lever arm testing

machines, and stfain data were obtained through dial-gage extensometers

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PHOTO 80871

ROLLING DIRECTION

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Fig. 3 — Typical fusion-line

- weld used to provide specimens for

Etchant: (r0;, HCl, H,0. 100X,

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area' of . the .i-in..- thit’:k:-restrained
the mechanical property study.

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Table 2. Short-Time Tension Tests of Reactor Grade INOR-8 in As-Welded Condition

 

 

 

 

 

Test | Yield Strength | Elongation
Temperature - 0.2% Offset '~ Tensile Strength in 1 l/2’in.
(°F) (psi) (psi) | (%)

Heat | Heat Heat Heat Heat Heat Heat Heat

5062 5071 5074 5062 5071 507 5062 5071

Room 63,100 67,200 66,000 105,700 108,800 91,500 31,5%  27.5%

600 54,000 58,400 52,100 93,900 95,500 84,300  26.5°  27.5°
800 54,300 51,900 52,600 92,100 91,400 82,300 29.0%  29.5

1000 46,400 50,700 47,100 84,100 83,800 179,800 24.0%  26.5%

1200 43,300 49,500 47,600 73,300 73,400 66,800 - 17.5%  17.5%

1400 42,400 46,600 42,100 61,400 58,600 59,600 1.0  8,5%

1600 36,400 37,700 36,400 38,700 38,400 38,200 10.0% 9.5%

a . -

1800 21,100 21,900 20,800 21,800 22,400 21,200 17.5 22.0

0T

 

aFaifi.ed in weld metal;

 

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Table 3. Sh;;rt-'rime'qzension Tests of Reactor Grade INOR-8 in Stress-Relieved Condition
Test = o Yield Strength Elongation
Temperature - 0.2% Offset. | Tensile Strength o in 1 1/2 in.
(°F) o (pst) B (psi) | (%
i A A S .
Room 461,0005 O 56,500 97,’_'300- o 102,500 a0 ' 26.5°
0 45,400 43,400 43,400 90,600 90,400 91,800 25.5 - 25.0° 29.0°
800 48,400 39,900 43,500 85,500 87,200 89,000 26.0 275  28.5°
1000 { 39',500f 40,400 40,000 85,500 85,300 84,000 32.0 33.0° 30.5° "
11200 | l39‘,5o_o.- 39,300 40,000 75,800 7d;4oo 74,500 28.5°  20.5.  28.0
1400 36,800 © 37,000 40,000 62,100 57,800 61,000 14.0°  14.0° 14.5
1600 B 34,5‘06 35,000 35,500 39,‘660 40,300 39,500 17.5% 10.0° 11.0
1800 L 21-_I,'50'0" 121,800 21 200 21,900 22,100 21,700 9.0 19.5  28.5°

 

Stress relieved 2 hr at 1600°F, hydrogen
Averaged values of Heats 5064, 5075, and 5081 stress relieved 2 hr at 1600°F, argon.
®Failed in weld metal.

 

 
 

 

 

12

attached to the specimen grips, A detailed ta‘bulafiion of the average
vaiues of the creepQrupture teét results are giveh in Table 4.

All heat treatments prior to'testing were'cérried out in either an
argon or hydrogen atmosphere. . The specimens were cooled from the annealing
temperature by pulling them from the hot zone into the water-cooled end
of the furnace muffle. Thermocouples, which weré attached to the speci-
mens during the heat treatment, recorded an average cooling rate down to
500°F of épproximately 250°F/min.~The thermal tfeatment uéed, 2 hr at
1600°F, is the standard stress relieving treatment specified for INOR-8
material, | ’

A‘convenient method for measuring overall weldabilifiy is a hot
ductility test, which has been developed by Nippes and Savage of
Rensselaer Poly'techn-ic’Institute.4 This test synthetically reproduces,
in a 1aboratory specimen, the time-temperature cycle experienced'by any
selected point in the heat-fiffected zone of afi arc weld. Sampies were
taken from all the heats tabulated previously (p. 4) and subjected to

this hot ductility test. The results of these tests will be treated in

the following sectién.

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Average Results of Elevated- Temperature Creep Tests on

Table 4}
S INCR-8 Transverse Weld Specimens

 

Test

Applied

 

 

 

 

 

 

_ | | Minimum Creep
Temperature Stress - Time to Rupture - Elongation " Rate
(°F) (psi) __ _{br) (%) (hrt)
‘ - As o Stress Relieved® As o Stress Relieved®  As o Stress Relieved
Welded™ Hp Ar Welded™ H» Ar Welded H» Ar
1100 7% oooj:. 1.3 1.7 ‘4.1 13.0 2.6 x10% 1.3 x 1072
1100"f[54 000 197.8 188.3 2.5 8.2 2,3 x 10-% 1,0 x 10~
1100 49, 000 308.4  570.5 2.2 5.3 1.4 X 10-% 3,2 X 1073
1300 45,000 3.7 6.4 5.5 3.9 8.2 54 4.9 X10°3 7.4 X 10-3 7.0 X 10-3
1300 24,000 158.4 337.8 185.4 3.7 8.8 7.4 1.2 X10-% 1.6 X 10-% 2.2 x 1074
1300 20,000 . 472.3 936.7 452.2 4.6 10.8 3.7 3.5 X10°% 6.6 X 1077 4.4 X 10-%
1500 22,0000 12.7  12.1 '16.9  20.9 5.8 x 107 7.0 x 10-3
1500 13,000 1721 117.5 1.4 9.8 4.8 X 107% 4.4 X 104
1500 10,000 446 9 314.5 8.3 8.1 9.8 x 1075 2,0 x 10

 

a'Ds,ta from tests on heats tabulated on p. 4 of this report.

Stress relieved at 1600°F, 2 hr in atmosphere specified.

T

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14
DISCUSSION AND EVALUATION OF RESULTS

Tensile Tests

The average tensile properties of épecimens in.the as-welded
condition'(heats 5062, 507i and 5074), hydrogen stress-relieved con-
dition (heats 5070 and 5073), and argon stfess-relieved condition
(heats 5064, 5075 and 5081) are presented in Figs. 4, 5 and 6. These
figures show ultimate tensile strength, 0.2% offset yield strength and
elongation vs temperature. The scatter bands for wrought metal shown
in the figures were teken from earlier work. ?

A'qualification'on the ccmbarisons between transverse weld éamfle
properties and wrought metal properties shouid be made at this point.
figure 7 illustrates specimen afid stringer orientations which were
encountered in these two classes of specimens.  Note thaf, as previously
mentioned, the material fabrication scheduies resulted in the stringers
of the transverse weld samples being oriented normal to the stress direc-
tion. This stress direction is the y-direction in Fig. 7. The wrought
material investigation5 done previously did not inélude specimens cut
parallel to the y-direction. The fact that these plates were notrthick
enough to yield reasonably large specimens in the y-direction plus the
assumption of symmetry of properties sbout the z-axis led to the omission.

| Only slight variations in ultimate strengths were observed
between the as-welded and stress-relieved tests; although, at the lower
testing temperatures these stgengthsrwere,less than those for'the |
wrought metal, In the case of the yield strengths noticeable differences
existed between the as-welded samples and stress-relieved_samples. As-

welded specimen yield strengths were consistently higher than those of
 

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120 pANV—— ' 1 I
///// 1 e AS WELDED
2 S o STRESS RELIEVED,

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

= 100 P A |

2 Yoo ////%////)p

g Y T,

g ° | /

z U

g 7

z .
4 40 ‘ ! /{Z;}

B SCATTER BAND FOR WROUGHT METAL 47,
o HEAT NO. 5055 , 5075, AND 5081 /////
| 20 ' '4;';
| I : Y4
o L_V\'

RT 600 800 : '_1000 1200 1400 1600 1_800
| - TEST TEMPERATURE (°F) | -
" Fig. 4 — Ultimate tensile strength of MSRE INOR-8 transverse weld -
specimens. Lo T ST

 
 

 

 

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ORNL-DWG €65-6811

 

 

 

 

 

 

 

 

 

40 ,,‘4;///,,!;/ lll A
20 SCATTER BAND FOR WROUGHT METAL 7 2
HEAT NO. 5055, 5075, AND 5081

 

 

- - e AS WELDED -

a o STRESS RELIEVED, H,
§ 80 ' a STRESS RELIEVED, Ar
1 ‘

= 60 |

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=

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Lo
RT 600 800 1000 1200 {1400 1600 1800

TEST TEMPERATURE (°F)

Fig. 5 — Yield strength (0.2%) of MSRE INOR-8 transverse weld
specimens. '

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—A\\ _ — ! I
7 ,/ SCATTER BAND FOR
" B / |
46 ' % i ,A:{//,
oL IAS \fl\IELDED " R fi ;E | i
o STRESS RELIEVED, Hp - |
| | & STRESS RELIEVED, Ar
N~ ol 1 |

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RT 600 800 {000 1200 1400 1600 - 1800
o - TEST TEMPERATURE {°F)

Fig. 6 Ductility'of MBRE INOR 8 transverse weld specimens.

 
 

 

 

 

 

 

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ORNL-DWG 65-10484

SPECIMEN CUT PARALLEL
TO ROLLING DIRECTION

   

 

 

 

 

L[i:c, z
SPECIMEN CUT NORMAL STRINGER

To ROLLING DIRECTION  ORIENTATION
SPECIMEN ORIENTATIONS IN INOR-8 WROUGHT PLATE i ) .

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WELDABILITY
N_—"" TEST PLATE

ROLLING DIRECTION, =2 Dmllgégwgi\l
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STRINGER
ORIENTATION

fin"""
[ oxio

\ TRANSVERSE
WELD SAMPLE

F'ig. 7 — Sketch showing orientetions of stringers and specimens
for wrought metal and transverse weld samples,

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19 -

specimens tested after stress reliev1ng, no difference in annealing atmos-

phere was-observed except at room temperature. Yield strengths for trans-

. verse specimens in all conditions were‘generally higher than the wrought

metal yield strengths.
The total elongation data, presented in Tables 2 and 3 and depicted

graphically in-Fig;'G, show that the overall ductility of welds is less
i .

than that observed in the wrought metal. However, this difference is

;_ probably due to the specimen orientation, as previously explained Stress

reliev1ng produces 8 general improvement of this property at all test

 temperatures, with argon prOV1ding a sllghtly better atmosphere than

hydrogen.
The macrographs of Figs. 8, 9, and 10 illustrate the variations in

fracture location with each heat and with test temperature. The as-welded

tests in heat 5074 of Fig 8'exhibit failures in the base metal, except at

1400 and 1600°C w1th low ductilities (Table 2) &s compared with the weld
metal failures in heat 5062 of Fig. 9. The variation of fracture loca-

tions with temperature for the stress-relieved'heat_5070 (Fig. 10) is .

',typical of specimens tested in this condition.

On the basis of the data presented above on the ultimate and yield

'strengths the assumption of symmetry in strength properties seems Justified.
-”.pThe ductility data however, and in particular the ductility of those spe-
= cimens which fractured predominantly in the base metal,,suggest that the

-strain-at-fracture properties of INOR-B are not symmetrical about the

7 axis., ' ,T'JT;§ U

Metallographic examination was performed on one heat tested in the
as-welded condition (5074) and one heat in the stress-relieved condltion

(5073). The micrographs shown in Fig. 11A and 118 for the 1800°F tests

A

 
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20 ‘

 

 

 

 

  
 

  

 

 

 

  

" INOR-B; ‘HEAT NO. 5074

 

 

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Fig. 8 — Tensile tests in INOR-8 heat 5074 (as welded) showing

location of fracture.
 

 

 

 

 

 

 
 

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Fig, 10 — Tensile tests in INOR-8 heat 5070 (stress relleved 2 hr

at 1600°F in hydrogen) showing location of fracture.

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Fig. 11 — Short-time tensile test failures of INCR-8 material

tested at 1800°F in air. A, Heat 5074, as welded; B. Heat 5073, stress
relieved 2 hr at 1600°F in hydrogen. Etchant: Cr0s;, HC1, H,O0. 100x.

 
 

 

 

-24
are representative of the base metal failures of all the tensile tests.
All failures, whether in the base metal or weld metal, were generally
intergranular, As noted by'McCoy,6 mest of the small base metel cracks-
appear to fiave been initiated by'cracks'in the'precipitates; Here, as in
McCoy's work, the intergranular cracks are predominantly normal te the
applied stress with their lengths comparable to the grain diametef. As can

be seen in Fig. 11, the cracks are parallel to and exist primarily in the

‘stringer line.

Creep-Rupture Tests

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Cfeep-rupture Qata'for specimens in the as-welded and argon or

| hydrogen stress-relieved conditions are presented graphically in Figs.
12-15. Average values of rupture time vs applied stress at 1100, 1300
and 1500°F are presented in Fig. 12. These studies indicate that as-
welded specimens possess stress-rupture strengths!equivalent to those of

the base metal at all test temperatures, Stress relieving, using a hydro-

gen atmosphere, created a significant improvement in the creep properties of‘

samples tested at 1300°F. A factor of two improvement was noted in both the
time-to-rupture and the total strain propexties when this treatment vas em-
ployed (see Table 4). The creep-rupture tests on stress-relieved samplesr
at 1100 and 1500°F showed little or no improfiement over as-welded proper-‘
ties.- The curves of Fig. 13 illustrate the stress-temperature relationships
necessary to cause rupture in 10, 100 and §OO hr for thesexcomposite speci-
mene. ‘The improvement over the as-welded strength at 1300°F by stress
relieving in hydrogen at 1600°F for 2 hr is vividly shown in this figure. -
The minimum creep fate for tests on ae-fielded and stress-relieved

specimens, shown in Figs. 14 and 15, respectively, was generaliy observed.

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- Fig. 12. Average creep—rupture data for transverse weld specimens‘

r;:of MSRE INOR-8 in the as-welded and argon and hydrogen stress-relieved .

conditlon.

 
 

 

 

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Fig. 13 — Creep-rupture data for transverse weld specimens of
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Fig. 14 — Mlnimum creep-ra.te data for as-welded transverse weld

- specimens in MSRE INOR-8 heats 5060, 5069, 5075 and 5083.

 
 

 

28

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Fig. 15 — Minimum creep-rate data for stress-relieved transverse
weld specimens in MSRE INOR-8. Heats 5057, 5067, 5072 and 5083, annealed
in hydrogen, and heats 5068 and 5074, annealed in argon, were held for

2 hr at 1600°F. ‘

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to be‘slightlyrloWEr than that found for wrought metal at all test tem-

29

i

peratures and stresses.. One exception to this general cbservation was
noted for stress-relieved specimens tested at 1100°F.

‘Metallographic examiuation of several creep-rupture specimens

revealed that stress relieving had the general effect of shifting the

hrupture,location from the basegmetal to the weld metal., The fracture of

the as-welded,specimen in Fig. 16 shows & typical intergranular failure
in base metal, with associated graianoundary cracking normal to the

applied stress. The appearance of the base metal cracks is very similar

" to those discussed above for the short time ten51le tests. The weld |

- metal failure of Fig. 16 is typical of creep test fractures observed in

.stress-relieved specimens.i"Some'fractures of specimens in this condition

-were'observed to occur aloug the weld fusion line,

I-Iot Ductility Tests
Hot ductility experiments using synthetic heat-affected zone speci-
‘mens revealed the eleveted-temperature nil-ductility p01nt for this mater-
ial to be 2300°F as shown 1n Fig 17 The area of‘the heat-affected zone

whlch would experience this maximum peak temperature corresponds to & plane

calculated to be O, 032 in. from the weld fusion line. 'The curves of this

figure indicate that reasonable recovery of the mechanical properties after

heating to the nil- ductility temperature was exhibited, although some dam-

- age'occurred as afresult:of;the,welding thermal cycle,  Since no attempt

| was'made'to identify'each»sample‘with a hesat humber,\the obsexved behavior

”is considered to'be"t&piCal'of-MSRE reactor grade INOR-8.

As shown in Fig.flS,rno gross grain boundaryiliquatiou has occurred;

—

however, nhmerous indiVidual,precipitate fiarticles are present which retard

 
 

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Fig. 17 = Results of hoit‘--'ducrtility tests on MSRE'reactbf-grade
INOR-8. The nil-ductility temperature for the material was found to be
2300°F. - SR S I R

 
 

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Fig. 18 — Micrograph of the structure of MSRE INOR-8 which has
experienced & welding thermal cycle with & peak temperature of 2300°F
(NDT). Etchent: H3PO,, Ho0. 1000X.
 

 

 

33

the motion of the grain'boundaries and cause them to be quite irregular.

| These boundaries etch rapidly_and.appear quite,broad; indicating that,
possibly, an impurity 1ayer'ispresent. Earlier studies have shown that
by very rapid cooling from very high temperatureS'(2500°F),,the-pre-
cipitate or stringer particles appear to be converted to an 1ntergranular
lamellar product Gross - formation of this product throughout the heat-
affected zone of INOR-8 welds could cause permanent damage, resultlng in
almost certain failure under high restraint. The hot ductility tests
-conducted here do not.indicate that this condition is a‘serious problem

for the material investigated.
- CONCLUSIONS

It appears from this.study that the room- and elevated—temperature

mechanical properties of welds in INOR-8 compare favorably With the

base metal propertlesf' Tensile testing of these transverse specimens
.showed_that this material possessed a good combination of strength and
.ductility.' Stress relieving.producedthe general effect of'lowering
the.0.2% offset yield;strength.. The.creep studies of_as#Welded samples
'indicated that they possessed'stress?rupture properties equivalent to
rthose of base metal at all test temperatures. Stressrelieving, uSing-

a hydrogen atmosphere, caused a significant improvement in the creep

jmproperties of samples tested at 1300°F Heat-affected zone hot ductility

'1pexperiments establlshed the nil-ductility temperature for this material

o _to be 2300°F, with reasonable mechanical property recovery after

o ;experiencing th1s temperature.‘l

 

 
 

 

 

 

34
ACKNOWLEDGMENTS

The authors gratefully’acknowledge these people in connection with
thé preparation of specimensfandrthe performance of tests: C. W. Dollins,
L. C. Williems, H. R. Tinch, E. B. Patton, C. W. Walker, and V. G. Lane.
~The efforts of the Metals and Ceramics Division Reports Office and the

ORNL Graphic Arts Department in document preparation is also appreciated.

C

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35
REFERENCES
1. Manly, W. D. et al., "Metallurgical Problems in Molten

Fluoride Systems," Progr. Nuclear Energy, Tech. and Engr. Series IVQ

 

Vol 2, Pergamon Press (1960).

 

2. Roche, T. K., The Influence of Composition Upon the 1500°F

 

Creep-Rupture.Strength and Microstrueture of Molybdenum-Chromium-Iron-

' Nickel-Base Alloys, ORNL-2524 (June 24, 1958).

 

73. Gillilend, R. G. and Slaughter, G. M., "Influence of Minor
Alloying Additions in INOR-S Welds," to be published in the WELDING
JOURNAL, |

4. Nippes,'E F. et al., "An Investigation of the Hot Ductility

of High Temperature Alloye,“ WELDING JOURNAL, 34 (4), 183 to 185 (1955)

5. Venard, J. T., Tens1le and Creep Properties of INOR-S for
the Molten-Salt Reactor Experlment ORNL,-TM-1017 (February 1965).
6. McCoy, H. E., Influence of Several MEtallurgical Variables

on the Tensile Properties of Hastelloy N, ORNL-3661 (August 1964).

 
 

 

 

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1-2.,

3.

6.

9.
10.
S 11,
12.
13.
1.
15,
16.
17.

18. -

19.
20.
21.
22.
23.

25,
26.
_7.
28.
29,
. 30.
31.
32,
33,

35,

V 360

37.
- 38,

39.

41.
42,
43,

45,
46,

Mwwcnggfiymfizqz

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38

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