ML20207L320
| ML20207L320 | |
| Person / Time | |
|---|---|
| Issue date: | 03/05/1999 |
| From: | Mayfield M NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES) |
| To: | Monaly K NRC (Affiliation Not Assigned) |
| References | |
| NUDOCS 9903180078 | |
| Download: ML20207L320 (46) | |
Text
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~O March 5,1999 MEMORANDUM TO: Kamal A. Manoly, Acting Chief Mechanical Engineering Branch Division of Engineering, NRR FROM:
Michael E. Mayfield, Chief Electrical, Materials and Mechanical Engineering Branch Division of Engineering Technology, RES
SUBJECT:
TRANSMITTAL OF
SUMMARY
MATERIAL FROM STELLITE FRICTIONAL TESTING MEETING The summary material contained in the attachment is transmitted as requested.
The attachment includes descriptive information about fabrication and testing of Stellite 6 l
specimens, characterization of the oxide film, simulation of valve wedging, and friction testing of specimens at BWR coolant conditions. It contains the results from the oxide film characterization and friction testing, including the concerns raised by the National Institute of Standards and Technology review of this test program and their recommendations. We plan to complete the report on this research in April 1999.
If you have any questions on the attachment, please contact Jerry Jackson (415-6656) of my staff.
Attachment:
As stated
/
/
l 9903190078 990305
[O3 PDR ORO NRRA PDR Distribution:
Branch Reading File
^ -n]
Document Control Desk t b
'(,~..
Public Document Room 1
j Tscarbrough DTerao l
DOCUMENT NAME: G:UJACKsoNVtitmtg To receive a copy of this document, indicate in the box: "C" = Copy without attachment / enclosure "E' = Copy with attachment / enclosure
- N" = No copy OFFICE EMMEB
_IE EMMEM
__l EMMEB l
l l
NAMEt.
J. Jackson ji(/
J.Vor(J V M Mayfield DATE3, 4 3 / l0 V/09/
d3 4 /99
/
/99 OFFICIAL RECORD COPY Hg,S Feie Code: 18-5 1
I l
1 s
Summary and Evaluation of NRC Sponsored Stellite 6 Aging and Friction Testing l
John C. Watkins I
Kevin G. DeWall l
Idaho National Engineering and Environmental Laboratory l
i Jerry E. Jackson USNRC Project Manager NRC Headquarters March 3,1999 l.
Washington, DC i
O
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Background
l The INEEL is performing research related to motor-i operated valves (MOVs) to assist the NRC. The results of l
this project will provide information to:
i Determine how aging can affect the performance of motor-operated gate valves.
Determine the disc-to-seat friction as a gate valve ages and whether the friction reaches a plateau.
Determine the effect periodic gate valve cycling due to in-service testing has on friction.
i GObe corse 2
.j.
Background (continued)
A critical review of the test methods, processes, and l
results was recently performed by the National Institute of
(
l Standards and Technology (NIST). Based on this review, they concluded:
- The technical work described in the reports was 1
)
technically sound and the results had been obtained j
with care.
l
- The quality of data and the trends observed based l
on the test methodology were consistent with good engineering practices.
The Stellite 6 surfaces were carefully prepared and J
l the properties measured carefully.
However, as a basis for regulatory action, the results l7 are not sufficient..."
i.
i t
l l
Outline l
i Description of the techniques used to fabricate and t
then test the Stellite 6 specimens.
Results of the Stellite 6 oxide film characterization Results of the Stellite 6 friction testing l
i Recommendations from NIST i
l I
i GC990006 4
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We prepared the Stellite 6 specimens
)
using typical industry methods.
1 Deposited the Stellite 6 hardfacing onto ANSI 1020 i
carbon steel blanks using a Gas Tungsten Arc Welding (GTAW) process. Used an uncoated weld rod of 0.125 l
j in. and 0.094 in. diameter for the inner and outer friction specimens.
.i i
Deposited the hardfacing in three passes to achieve a l
final thickness of at least 0.20 in. and to minimize iron l
dilution.
}
l
l The Stellite 6 specimens were sized to fit the friction autoclave.
The Stellite 6 surface on the large inner friction specimens
=
j l
was approximately 0.5 in. wide by 3.0 in. long.
i spe ens o 0.2 in. w de 11 in on r the 10 k est specimens.
i Machined the Stellite 6 surface to a final surface finish of 16 microinch or better.
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i Composition of the Stellite 6 Weld Rod i
i I
Element Mfg Specified AWS Small Rod Large Rod Averaqe Value Requirement Composition Composition C.
1i.2..
.. 0.9.1 A.
Mn.
0.05
.1.00. max..
~
.Si _
.1.4
. 2.0. max.
. 1,1..
1,4 Mo
. 0.1
- 1..O max.
Ni 2.0 3.0 rnax 1.8..
2.5..
Fe.
2.1 3.0. max..
. 1,8..
2.4 W.
4.7 3 0-6.0 5 A..
4.8 Cr 29.0..
26.0-32.0_
28.1
. 27.4 Co Balance (60)
Balance (49-70) 61.9 60.6 e
GC990096 9
=
Composition of the Stellite 6 Friction l
Testing Specimens 1
l Element Large Specimen Large Specimen Small Specimen Small Specimen l
- 1
- 2
- 28
- 29 l
Si 1.2..
1.2..
.1.2..
..1.1 l
...W..
..... 5.5..
5.5..
.4 a...
..4,6.._
_Ni
..2.2.
.. 2.2...
.1.7..
1.8.
{
Fe.
2.5..
. 2.5_
_8.9
.._10.3....
Cr 28.3 28.4 25.7
_ 5.2 2
Co.
60 4.
60.4 58.4
. 57 1..
Hardness (HRC) 44.0 44.7 41.8 41.0 i
4 1
i
~
i
l The Stellite 6 specimens were aged at simulated BWR coolant conditions in a corrosion autoclave.
k Temperature 550 F j
I Pressure 1050 psi t
)
~
pH (room temperature) 6.5 to 7.0 l
Oxygen 100 to 200 ppb Conductivity
< 1.0 micro S/cm i
Flow velocity 2.2 to 2.8 ft/sec i
i l
All specimen aging was performed in a 5-gallon l
autoclave except during the last test series, which l
used a 1-gallon autoclave.
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The Stellite 6 specimens were aged over a two year period.
Specimen aning Final test report l
2,10, and 20 days December 1995 40 days November 19.96 i
78 days June 1997 4
The last test series also investigated the effect periodic valve cycling due to in-service testing had on the oxide i
film growth characteristics and on the resulting friction.
4 GG4 00E6 12
l i
l The oxide film on the Stellite 6 i
l specimens was characterized.
i The chemical composition of the oxide film was l
determined using X-ray photoelectron spectroscopy
~
l (XPS).
The thickness of the oxide film was based on the change in chemical composition versus depth.
NIST also investigated the morphology of the oxide L
film using an Atomic Force Microscope (AFM) and X-ray diffraction.
GObg ante 4 e
'3
4 Simulated valve wedging and its effect l
on the oxide film was also investigated.
j j
Specimens in the in-service testing simulation fixture were i
processed in a water bath at room temperature and.
atmospheric pressure instead of at BWR conditions.
4 The simulated valve wedging test sequence consisted of:
i Placing like sized specimens with their Stellite 6 l
surfaces face-to-face.
.i Applying a normal load of 20 ksi.
i Moving the specimens 0.040-in. relative to each other.
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Friction testing was performed in an autoclave at BWR coolant conditions.
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l Results of the Stellite 6 Oxide l
Film Characterization 1
oco.-
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i
1 Characterization Results 1
The composition of the oxide film was determined using Stellite 6 specimens that were aged for 10,20, 25,40, and 78 days.
The composition of the oxide film was similar to that l
observed by other researchers for Stellite 6 specimens exposed to lithiated high temperature water.
Results show that the surface of the oxide film is rich in chromium and lean in cobalt.
~
Characterization Results (continued) 1 NIST noted that there are some differences between specimens from the last test series (25 and 78 day specimens) and specimens from the earlier test series:
l
- The concentration of chromiurn oxide at the l
surface was lower on specimens from the last l
test series.
- The concentration of oxygen at the surface was
~
higher on specimens from the last test series.
L
- The concentration of cobalt, cobalt oxide, and chromium was about the same.
~
.j
XPS depth profile for Stellite 6 after 20 day's
]
exposure to natural aging conditions.
100 90 l-e-O O Cr -A-CrO Co O coo 80 70 O
3 60
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20 0
~'
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0 500 1000 1500 2000 2500 Etch time (s)
XPS depth profile of the chromium oxide in Stellite 6 specimens exposed to natural aging conditions.
100 90
-e-10 day C 20 day -e-25 day +40 day -U-78 day 80 i
70 i
8 60 o
E 50 i
o
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40 30
_ _m, m
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10
- ^
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0 0
500 1000 1500 2000 2500 3000 Etch time (s)
XPS depth profile of the oxygen in Stellite 6 l
specimens exposed to natural aging conditions.
100
-e-10 day -B-20 day -*-25 day H>-40 day -O-78 day 90 lQi
~
\\
X N
\\
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NN 20 g
10 0
0 500 1000 1500 2000 2500 3000 Etch time (s)
- - =
i XPS depth profile of the cobalt in Stellite 6 specimens exposed to natural aging conditions.
100 90
-e-10 day -e-20 day -&-25 day +40 day -U-78 day 80 i
70 60 o
i E
50 40 W
/
30 1
20 10 o
g
-yc x a
0 500 1000 1500 2000 2500 3000 Etch time (s)
i i
The thickness of the oxide film was based on the chemical composition of the Stellite 6 oxide film.
The thickness was defined as the point where the l
concentration of chromium and chromium oxide was equal.
The thickness measurements were based on single specimens; no repeat testing was performed.
The thickness of the oxide film during the last test series could be influenced by the apparent change in the concentration profile of the chromium oxide:
i i
e c.:eeooes a 1
The growth rate of the Stellite 6 oxide film is parabolic.
2000 l
1500 o
t
@1000 o
i isz b
t l
5%
o Time (d)
~~ u o
r
i l
l l
The oxide film was also analyzed by NIST.
I 10 day and 50 day specimens were analyzed.'
l Used Atomic Force Microscope (AFM) and X-ray diffraction.
The results indicate that the oxide film contains crystalline solids within an amorphous substrate.
i l
Crystalline solids are, in general, very abrasive and can l
result in high friction between moving surfaces.
l i
I GC980096 37
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,,,,~.-w.,--,.m,
l l
We also investigated whether in-service testing affects the oxide film growth characteristics.
Stellite 6 specirnens were aged for 78 days with in-j service test cycles after 25 days and again after 50 i
days.
l Results show that the oxide film thickness was affected j
by the simulated wedging; however, the oxide film i
continues to follow the general thickness trend of the undisturbed aging tests.
i am =
t
-,m,
The oxide film thickness is altered during the simulated wedging, but follows the general thickness trend of the undisturbed aging tests.
l 2000 l
l l
1500 isT l
Aging
^
l 5
m
$1000 isT 500
/
0 10 20 30 40 50 60 70 80 Time (d) t t
i i
l Results of the Oxide Film l
Characterization to Date i
The growth of the Stellite 6 oxide film has not plateaued.
l The surface of the oxide film is rich in chromium and lean j
in cobalt and contains crystalline solids within an l
amorphous substrate.
The thickness of the oxide film was affected by the i
simulated wedging; however, the oxide film continues to follow the general thickness trend of the undisturbed 1
aging tests.
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Five sets of aged specimens underwent friction testing.
l Specimens were aged for 2,10,20,40, and.78 days.
The maximum and nominal friction continues to increase l
on Stellite 6 specimens aging up to 78 days.
l The maximum friction not only increases, but also does not appear to reach a plateau.
The nominal friction does not appear to plateau during the first two strokes, but does during the following three strokes.
W N
The maximum friction continues to increase on Stellite 6 specimens aged for 78 days 0.6 2 day maximum x
i 10 day maximum l
+
20 day maximum o
l 40 day maximum 1
0.5 a
78 day maximum o
l g
O i
E 0.4 a
o a
o g
- C O
X o
A
)
o g
c 0.3
+
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o o
o i
Q)
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+
+
s b
X
+
+
0 O
x x
x x
j x
0 0.2 l
0.1 O
1 2
3 4
5 6
7 8
b 1b Stroke number i
=
y y
,m__.,,m-,,
4
--'w-yw y,,
The nominal friction continues to increase on specimens naturally aged for 78 days.
0.6 I
2 day nominal x
10 day nominal
+
20 day nominal o
40 day nominal i
0.5 a
78 day nominal o
i 8 0.4 i.
'5 O
o E 0.3
=
s
{
l E
2 o
a
+
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o o
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t e
+
+
x
+
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o A
O 0.2 O.1
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0 1
2 3
4 5
6 7
8 b
10 l
Stroke number
The maximum friction not only increases as the Stellite 6 specimens age, but also does not appear to reach a plateau.
0.50-Maximum 1
0.45 I
)
o 0.40 g
5 i
o l
E 0.35
'b se
$O 0.30 Stroke 1 o
Stroke 2 0.25 a Stroke 3 Stroke 4 i
+
Stroke 5 o
0.200 10 20 30 40 50 60 70 80 Time (d)
- - =
r
The nominal friction does not appear to plateau during the first two strokes, but does in the following three strokes.
0.40 Nominal i
l i
0.35 Eg 5
E
/
E 0.30
^
.9
.9 g
4 8
0.25 o Stroke 1 L
o Stroke 2 l
+
i A Stroke 3 Stroke 4
+
Stroke 5 0.20 0
10 20 30 40 50 60 70 80 Time (d) 4 4
g e
NIST Concerns with the Friction Testing Concerned with simulating the actual operation of a valve. As tested, the full surface is initially in contact and the hard corrosion products are trapped between i
l the surfaces.
During an actual valve closure, the moving suifaces l
may come into contact and push the corrosion products out of the way without being trapped.
p i
GQie 0006 37
To investigate these concerns, selected Stellite 6 specimens were friction tested at NIST.
10 day and 50 day specimens were tested.
The testing was performed at ambient temperature and l
i pressure.
l The friction testing apparatus consisted of either A 13 ksi normal load on either a 0.5-in. or 0.125-in.
l diameter steel ball sliding on the Stellite 6 surface.
a A 13 ksi normal load on.a flat 1.8 mm steel surface sliding on the Stellite 6 surface.
i Results of Friction Testing at NIST The friction in a configuration that pushes the corrosion products out of the way (friction under a ball) was 0.15 to 0.17.
The friction in a configuration that traps the corrosion products (friction under a flat surface) was 0.30 to 0.35.
The flat configuration was comparable to the results l
of friction testing similar specimens in the autoclave, i
0.35 to 0.40.
i i
MM M 4
Specimens subjected to in-service testing were also friction tested.
I l
The in-service testing initially reduced the. maximum and nominal friction.
l After the initial stro'Ke, the effect of the simulated valve wedging was either negligible or varied from stroke to stroke.
l
- l l
I l
I i
In-service testing initially reduced the i
maximum fr. tion.
ic I
0.6 l
o 78 day maximum w/o IST x 78 day maximum w/ IST 1
i i
i i
0.5 a
a 3
o o 0.4
-l 5
x
.l E
x g
x O
b i
E 0.3 o
a
.9
- =
O O
O 0.2 4
0.1
^
l 0
1 2
3 4
5 6
7 8
b iD O
Stroke number GCG80006 48 a
The nominal fr. t.ic ion was init. lly ia I
reduced by in-service testing.
0.6 o 78 day nominal w/o IST l
x 78 day nominal w/ IST l
0.5 1
i o 0.4
.;s o
.O X
g o
a E 0.3 a
d
,g e
e o
0 x
x 6
o a
o O 0.2 l
0.1 I
U O
1 2
3 4
8 b
M Stroke number c.c - a j
e
.... - ~, -
Results of Friction Testing to Date The friction for naturally aged specimens has not l
l plateaued as the specimens age.
l The friction during the first stroke was always the highest l
and decreased substantially during additional stroking.
We are also aware of testing by others that has shown not i
only this decreasing friction trend with additional stroking, i
but a constant friction trend as well.
2 For the single specimen tested, the friction was l
5-10% lower following in-service testing.
l j- ;
4
. ~.....
.~...
. f
i l
Recommendations from NIST Additional work be performed to understand if there are l
any mechanical and load sensitive properties of the j
oxide film.
Additionai friction testing start from a non-contacting l
position similar to the operation of a valve.
l Further studies be performed with more samples to l
i l
verify the results.
i i
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l The opinion presented here today are those l
of the authors and not necessarily endorsed
[.
by our sponsor, the USNRC.
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