Effect of temperature on cavitation
erosion of 9Cr steel in liquid metal
University of Fukui, Japan
○ Akihiro Nimura
Shuji Hattori
Hiroki Yada
Research background
• Research on cavitation erosion in
liquid metal is very important to
confirm the safety of the “Monju”.
• But, research on cavitation
erosion on liquid metal has been
hardly done compared with
research in water.
Fast breeder reactor “Monju”.
• Cavitation erosion rate at a temperature of 260℃ in sodium
was 9 times higher than that in water.
• We are afraid that cavitation erosion rate increases at 500℃.
• Cavitation erosion in a fast breeder reactor environment has
hardly been studied.
2
Previous research
• We carried out the
cavitation erosion tests in
three kinds of lead bismuth
( PbBi ) alloy.
• Effect of test temperature
is larger than that of metal
composition on cavitation
erosion.
※ Hattori et al. Wear 267 (2009) 2033-2038
• In the previous research, we clarified that erosion
rates in PbBi at relative temperature of 14° is 10 - 12
times higher than that in deionized water.
3
Problems
• Test temperature range is very
limited for 75 to 150℃ (1.4 16° of relative temperature
ranges)
• Erosion rate at high
temperatures remains uncertain.
Present test region
𝑅𝑒𝑙𝑎𝑡𝑖𝑣𝑒 𝑡𝑒𝑚𝑝𝑒𝑟𝑎𝑡𝑢𝑟𝑒 =
𝑇𝑒𝑠𝑡 𝑡𝑒𝑚𝑝𝑒𝑟𝑎𝑡𝑢𝑟𝑒 −𝐹𝑟𝑒𝑒𝑧𝑖𝑛𝑔 𝑝𝑜𝑖𝑛𝑡
𝐵𝑜𝑖𝑙𝑖𝑛𝑔 𝑝𝑜𝑖𝑛𝑡 −𝐹𝑟𝑒𝑒𝑧𝑖𝑛𝑔 𝑝𝑜𝑖𝑛𝑡
× 100
Objectives
• Cavitation erosion tests were carried out at various temperatures.
• Effect of the test temperature on the cavitation erosion rates is
clarified.
• A method for predicting the erosion rate in sodium is proposed
using the test results of deionized water and PbBi alloy obtained
in this study.
4
Chemical composition and physical properties
of test materials
• Test specimen is 9Cr steel which is proposed to be used for pipes in
the next-generation fast breeder reactor and stainless steel SUS304
which is used for pipes in the present fast breeder reactor “Monju”.
Material
C
Si
Mn
P
9Cr steel 0.09 0.23
0.37
0.02
SUS304
1.76
0.036
0.05 0.33
Cr
Mo
V
Nb
Al
HV
0.001 0.18
8.82
0.97
0.20
0.07
0.004
180
0.022 8.49
18.2
―
―
―
―
189
S
Ni
• Liquid metal is a low melting-point PbBi alloy which consists of the
elements Bi, Pb, Sn, and Cd. Melting temperature is 68℃.
PbBi-68
PbBi
Bi
Pb
Sn
50
26.7 13.3
100 mm
Cd
10
PbBi-68
Freezing point [℃]
68
Boiling point [℃]
575
Density 20℃ [g/cm3]
9.38
5
Test apparatus and
test conditions
Piezo-electric oscillation apparatus
(according to ASTM G32)
Test temperature available : 50 - 400℃
Vibrational frequency
: 20kHz
Peak-to-peak displacement
amplitude : 40μm
Covering gas
: Ar
( for the tests at 250 to 400℃)
Piezo converter
Amplifying
horn
Specimen
Mantle
heater
Test method
• Cavitation erosion tests were carried
out with the vibratory specimen
method specified in ASTM G32.
• Cavitation erosion was evaluated in
terms of mass loss and instantaneous
MDER (Mean Depth of Erosion
Rate) of the test specimen.
Fig. Whole
test apparatus
Thermocouple
Cooling
coil
Fig. Cooling coil
6
Performance of test apparatus
5.6
Melting
7.9
8.2℃/min
3.5
Variation in temperature for heating
Temperature decrease for cooling
• Test temperature increased and
deceased in a short time.
• Test temperature was controlled
with cooling air with a tolerance
±3℃.
Variation in temperature during test
7
Mass loss curves in liquid metal
SUS304
9Cr steel
488
515
490
265
553
250
69
22 mg/h
267
266
50
Incubation period
• For 9Cr steel, incubation period were 1 hour at 100℃, 0.3 hour
at 250℃ and 300℃, and 0.2 hour at 350℃ and 400℃.
• Mass loss rate in the maximum rate stage were about 3 times
higher at 100℃, 12 times at 250℃ and 300℃, and 23 times at
350℃ and 400℃ compare with that in deionized water.
• Mass loss rates increased with the temperature.
• Incubation period of SUS304 is similar to that of 9Cr steel.
8
Eroded specimen surfaces
9Cr steel
In water
9Cr steel
In PbBi
5mm
In deionized water
of 25℃
In PbBi of 400℃
μm
15.6mm
Specimen surface of before test
Uneroded region
In deionized water at 400℃ 9Cr steel after 5 hours
In PbBi at 400℃ 9Cr steel after 2 hours
• In deionized water, the test
surface has an uneroded ring
region.
• In PbBi, the test surface is
eroded over the whole surface.
• The difference in surface
profile is due to the difference
in the mobility of vapor
bubbles.
9
Mean depth of erosion rate and temperature
𝑀𝑎𝑠𝑠 𝑙𝑜𝑠𝑠
𝑀𝑒𝑎𝑛 𝐷𝑒𝑝𝑡ℎ 𝑜𝑓 𝐸𝑟𝑜𝑠𝑖𝑜𝑛 𝑅𝑎𝑡𝑒 =
𝑀𝑎𝑡𝑒𝑟𝑖𝑎𝑙𝑠 𝑑𝑒𝑛𝑠𝑖𝑡𝑦 ×𝐸𝑟𝑜𝑑𝑒𝑑 𝑎𝑟𝑒𝑎 ×𝐸𝑥𝑝𝑜𝑠𝑢𝑟𝑒 𝑡𝑖𝑚𝑒 𝑖𝑛𝑡𝑒𝑟𝑣𝑎𝑙
( 𝑀𝐷𝐸𝑅 )
6.1％
6.6％
4.3％
3.3％
1–2%
• MDERmax of 9Cr steel and SUS304 changes similarly.
• In deionized water, each increase of 1℃ increases the erosion rate by 1
to 2 % at near 25℃.
• In PbBi, each increases 1°in relative temperature increased the
erosion rate in PbBi by 3 - 4 % at 10 - 40°and by 6 - 7 % at 40 - 50°.
• The increasing ratio in PbBi was almost 3 times higher.
10
Prediction method of erosion rate in sodium
: Basic idea
𝑎=
1
1
1
+
𝜌𝐿 𝐶𝐿 𝜌𝑆 𝐶𝑆
[
𝜌𝐿
𝑘𝑔
]
𝑚𝑠
ρ: Density, C: Sound velocity, S: Solid, L: Liquid
𝑀𝐷𝐸𝑅𝑚𝑎𝑥 = 𝑘𝑎𝑛
※ Hattori et al. Wear 265 (2008) 1649-1654
Liquid
𝒂
PbBi
120,000
Deionized water
45,000
Sodium
69,000
• MDERmax can be evaluated in various liquids and liquid
metals by using the this parameter.
• MDERmax can be expressed with a power law as a
function of 𝑎. The lower equation can be obtained.
• We predicted the erosion rate by using this equation.
11
Prediction method of erosion rate in sodium
① Select a temperature to obtain
: Procedure
the MDERmax in deionized
water and in PbBi.
② k and n are obtained.
𝑴𝑫𝑬𝑹𝒎𝒂𝒙 = 𝒌𝒂𝒏
②
③ MDERmax in sodium is
obtained using the value 𝒂 of
sodium.
④ Prediction curve of MDERmax
is obtained as a function of
relative temperature.
⑤ Young’s test results in sodium
(green points) agree with the
prediction curve.
③
④
①
• Prediction erosion rate curve in sodium is located halfway
from the rates between PbBi and deionized water.
12
Conclusions
1. Performance test of newly developed apparatus
showed that test temperature increased and deceased
in a short time and test temperature was controlled
with a tolerance of ± 3℃.
2. Each increase of 1°relative temperature increased
the erosion rate in PbBi by 3 - 7 % and the increasing
ratio in PbBi is almost 3 times higher than that in
deionized water
3. Erosion rate in sodium was estimated to be located
halfway from the rates between lead bismuth and
deionized water.
Acknowledgement
The present study includes the FY2010 result of the “Core R&D
program for commercialization of the fast breeder reactor by utilizing
Monju” entrusted to the University of Fukui by the Ministry of
13
Education, Culture, Sports, Science and Technology of Japan (MEXT).