Design of

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Design of Creep-Resistant Steels Part 1
Microstructure
Joe Robson Harsha Sree Lalam Marimuthu
Murgananth Thomas Sourmail Nobuhiro Fujita Shingo
Yamasaki David Cole
CSIRO
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0.5 µm
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0.5 µm
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x
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a
time t?t
time t
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b
a
time t?t
time t
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2.25Cr1Mo 600 C
M3C
M2X
M23C6
Time / h
1000 h
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3Cr1.5Mo 600 C
M23C6
Time / h
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0.02500
NF616 600 C
M23C6
M
C
3
0.02000
0.01500
0.01000
Laves
M
X
0.00500
2
0.00000
1e-03
1e00
1e03
Time / h
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Yamasaki Bhadeshia, 2003
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Brun, Robson, Narayan, MacKay Bhadeshia, 1998
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Components of Creep Strength, 2.25Cr1Mo
iron microstructure
550 C
solid solution
600 C
precipitates
Murugananth Bhadeshia, 2001
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elements in solution
Murugananth Bhadeshia, 2001
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Cole Bhadeshia, 1999
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Alloys designed at Cambridge University and made
by Nippon Steel
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Coarsening
diffusion
r
r
2
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flux
a
q
q
concentration
aq
c
r
aq
1
c
r
2
distance
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1/3
Mean radius / m
1/2
Time / s
-3
Number density
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10 m
Time / s
Fujita Bhadeshia, 2000
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Data from Abe, 1999 Fe-9Cr-W alloys
0W 1W 2W 4W
M_23C_6 size / µm
Time at 600 C / h
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Multicomponent coarsening
Venugopalan Kirkaldy, 1978
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Coarsening accelerated by tungsten!
-1
chromium alone
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Effective diffusivity / m s
multicomponent
Tungsten / wt
Bhadeshia, 2000
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M_23 C_6
Mole fraction of phase
Laves phase
Tungsten / wt
Bhadeshia, 2000
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Multiphase coarsening
Laves
concentration
in ferrite
q
q
distance
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Source code Compiled programs Web-based
calculators
www.msm.cam.ac.uk/phase-trans