Effect of temperature on cavitation erosion of 9Cr steel in liquid metal University of Fukui, Japan...
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Transcript of Effect of temperature on cavitation erosion of 9Cr steel in liquid metal University of Fukui, Japan...
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.
• 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.
Fast breeder reactor “Monju”.
2
Previous research
• 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.
• 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.
3
※ Hattori et al. Wear 267 (2009) 2033-2038
Objectives
• Test temperature range is very limited for 75 to 150 ℃ (1.4 - 16° of relative temperature ranges)
• Erosion rate at high temperatures remains uncertain.
• 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.
Problems
Present test region
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”.
• Liquid metal is a low melting-point PbBi alloy which consists of the elements Bi, Pb, Sn, and Cd. Melting temperature is 68 .℃
Material C Si Mn P S Ni Cr Mo V Nb Al HV
9Cr steel 0.09 0.23 0.37 0.02 0.001 0.18 8.82 0.97 0.20 0.07 0.004 180
SUS304 0.05 0.33 1.76 0.036 0.022 8.49 18.2 ― ― ― ― 189
Bi Pb Sn Cd
PbBi-68 50 26.7 13.3 10 PbBi-68
Freezing point [℃] 68
Boiling point [℃] 575
Density 20℃ [g/cm3] 9.38 5
100 mmPbBi
Test apparatus and test conditions
• 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.
Piezo-electric oscillation apparatus (according to ASTM G32)
Test temperature available : 50 - 400℃Vibrational frequency : 20kHzPeak-to-peak displacement amplitude : 40μmCovering gas : Ar
( for the tests at 250 to 400 )℃Test method
6
Specimen
Mantle heater
Cooling coil
Thermocouple
Piezo converter Amplifying horn
Fig. Whole test apparatus
Fig. Cooling coil
8.2 /min℃
5.6
Performance of test apparatus
• Test temperature increased and deceased in a short time.
• Test temperature was controlled with cooling air with a tolerance ±3℃.
Variation in temperature for heatingTemperature decrease for cooling
Variation in temperature during test
7.9
3.5
7
Melting
Mass loss curves in liquid metal
• 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.
9Cr steel SUS304
8
69
515490
250
22 mg/h50
266
267488
553265
Incubation period
Eroded specimen surfaces
In PbBi of 400℃
In deionized water of 25℃
9Cr steel 9Cr steel In water In PbBi
Uneroded regionIn deionized water at 400 9Cr steel after 5 hours℃
Specimen surface of before test
15.6mm
μm
In PbBi at 400 9Cr steel after 2 hours℃
5mm
9
• 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.
Mean depth of erosion rate and temperature
• 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.
( )
6.6 %
3.3 %4.3%
6.1 %
1 – 2 %
10
Prediction method of erosion rate in sodium : Basic idea
※ Hattori et al. Wear 265 (2008) 1649-1654
𝑎=1
( 1𝜌𝐿𝐶𝐿
+ 1𝜌𝑆𝐶𝑆
)√𝜌𝐿
𝑀𝐷𝐸𝑅𝑚𝑎𝑥=𝑘𝑎𝑛ρ: Density, C: Sound velocity, S: Solid, L: Liquid
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• 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 . The lower equation can be obtained.
• We predicted the erosion rate by using this equation.
Liquid
PbBi 120,000
Deionized water 45,000
Sodium 69,000
[ √𝑘𝑔√𝑚𝑠
]
12
Prediction method of erosion rate in sodium: Procedure
• Prediction erosion rate curve in sodium is located halfway from the rates between PbBi and deionized water.
① Select a temperature to obtain the MDERmax in deionized water and in PbBi.
② k and n are obtained.
③ MDERmax in sodium is obtained using the value 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.
𝑴𝑫𝑬𝑹𝒎𝒂𝒙=𝒌𝒂𝒏
①
②
③④
Conclusions1. 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.
13
AcknowledgementThe 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 Education, Culture, Sports, Science and Technology of Japan (MEXT).