Transcript Diapositive 1 - Royal Institute of Technology

ODS steels – part I :
manufacture, mechanical properties
and oxidation behaviour
Yann de Carlan, Jean Henry, Ana Alamo
Arnaud Monnier
Raphael Couturier, Emmanuel Rigal
Céline Cabet
Commissariat à l’Energie Atomique CEA, FRANCE
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Overview
Why ODS steels?
Manufacture
Observation and analysis
Microstructure control
Mechanical properties (+ radiation stability)
Welding techniques
Oxidation properties
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Why ODS ?
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Why ferritic ODS?
• Radiation resistance at high temperature
M. Inoue, JAEA, MATGENIV, 2007
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Strengthening of alloys: ODS principle
• Increase obstacles to dislocation glide
– Precipitates or other dislocations
– Finer dispersoides and higher number density
Ds  A 
2b
l precitates
lprecipitates
Clement, CEA
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Manufacture
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Overview of the powder metallurgy process
Caning
degassing
Mechanical Alloying
(MA)
Raw material
powder
Elemental or
prealloyed powder
High Isostatic
Pressure
soft steel
can
MA
powder
Y2O3 powder
Attrition Mill
Hot/cold Rolling
Hot Extrusion
Annealing
Intermediate
heat treatment
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Mother tube
Machining
Drilling
Matgen4.2 – February 6, 2009– TR 7
Atomisation of an alloy
R. Lindau, FZK, GETMAT project
P91 steel
SEM of atomized powder
Powder sieving
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Photo attritor + parameters
R. Lindau, FZK, GETMAT project
alloying parameters
- powder to ball ratio
- milling energy (-> rpm, cycling)
- milling time
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Hot extrusion
Y de Carlan, CEA
ODS steel
Hot extrusion
soft steel
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What happens during the process ?
Mechanical
alloying
Consolidation
12h milling – With Ti
200nm
12h milling
no Ti
Before milling
nano clusters
< 10 nm
After milling
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Fe-18Cr-Ti Y2O3 , Y. De Carlan et al., ICRFM13, 2007
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What happens during the process ?
Study by X Ray diffraction : Pre-alloyed powder + 10% of yttria
M. Ratti et al., Boston, MRS 2008
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What happens during the process?
Study by X Ray diffraction : Pre-alloyed powder + 10% of yttria
7000
5000
Monoclinic base centered yttrium oxide peaks according to ICDD database
Body centered cubic yttrium oxide peaks according to ICDD database
4500
6000
Face centered cubic yttrium oxide peaks according to ICDD database
4000
5000
3500
Fe peak
After MA
48h milling with titanium
Nombre de coups
3000
After 1h
MA
After
@950°C
Nombre de coups
4000
2500
48h milling withoutHeat
titanium
treatment 950°C/1h with titanium
3000
2000
Heat treatment 950°C/1h without titanium
1500
2000
1000
1000
500
00
26
26
31
31
36
36
Angle
2.Théta
Angle
2.Théta
41
41
46
46
51
51
M. Ratti et al., Boston, MRS 2008
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Characterization by Tomographic Atom Probe
Consolidation
1100°C
UT -BAT T EL L E
O ak Ridge National Laboratory, U .S . Department of Energy
D. Hoelzer
M.K. Miller, D.T. Hoelzer, E.A. Kenik, K.F. Russell,
Nanometer scale precipitation in ferritic MA/ODS
alloy MA957, Journal of nuclear materials 2004
After mechanical
alloying
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After consolidation
Matgen4.2 – February 6, 2009– TR 14
14
Alternative process routes
M. Inoue, JAEA
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Alternative process routes
OCAS, GETMAT project
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Characterization
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Optical microscopy
• General microstructure
Optical micrographs of the general microstructure of MA957 in the
(a) as- received condition and after annealing at 1300°C for (b) 1 h and (c) 24 h
M.K. Miller et al., JNM 329–333 (2004) 338–341
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SEM, EDX and microprobe
• Grain size and morphology
• Structure homogeneity
SEM picture of MA957 recrystallized grains
obtained after deformation by cold-drawing and
recrystallization heat treatment at 1100°C
Microprobe analysis of asmanufactured Fe-18Cr-Ti-Y2O3 alloy
0.85 W
0.46 Y
0.3 Ti
Y de Carlan, CEA
A. Alamo et al., JNM 329–333 (2004) 333–337, CEA
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TEM
12Y1 ODS steel: bright- and dark-field TEM micrographs
taken near beam direction B ~(1 2 2)
Y2O3 particle sizes
are in the
range of a few
tens of
nanometers in
diameter
I.-S. Kim et al., JNM 280 (2000) 264-274
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Atom Probe
Nanometer scale precipitation in ferritic MA/ODS alloy MA957 after
hot consolidation
M.K. Miller et al., JNM, 2004
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21
Analysis by XRD and SANS
• Nature of crystallized phases
• Particles size and distribution
XRD of ODS steels with 0.3%Y2O3 and 10% Ti
major peak of Fe
according to ICDD db
SANS of ODS steels with 0.3%Y2O3 and
10%Ti at RT under magnetic field (2 Teslas)
perpendicular to the incident neutron beam
direction, in a range of scattering vectors
going from 0 to 0.16 nm-1
M. Ratti et al., Boston, MRS, 2008, CEA
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M. Ratti et al., ICRFM13, 2007
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Microstructure control
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Chemical composition: Minor Alloying Elements
Refinement of dispersoids size by Minor Alloying Elements
•
Precipitation of Ti-Y-O (C)
nanoscale clusters
•
Ti is the most effective element to
refine the dispersoid sizes
AP-FIM with 3D mapping MA/ODS12-YWT
Larson D.J. et al., Scripta Mater. 44 (2001) 359-364, ORNL
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Inoue M., JAEA, MATGENIV, 2007
Matgen4.2 – February 6, 2009– TR 24
Chemical composition: Y2O3 content
• Effect of addition of Y2O3 in 13Cr-3W-0.5Ti on
tensile properties at 650°C
• Effect of addition of Y2O3 in 13Cr-3W-0.5Ti on
creep rupture strength at 650°C
Ukai S., JNM 204 (1993) 65-73
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Chemical composition: Minor Alloying Elements
• Effect of addition of Ti in 13Cr-3W-0.5Y2O3 on creep
rupture strength at 650°C
Fig 4 Ukai JNM 1993
Ukai S., JNM 204 (1993) 65-73
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Chemical composition: Excess of oxygen
• Effect of excess O in 13Cr-3W-0.5Ti-0.5Y2O3 on creep
rupture strength at 650°C
Ukai S., JNM 204 (1993) 65-73
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Effect of the grain size
•
Effect of MA957 ODS-alloy microstructure on
– the impact properties
– the tensile properties
MA957
Fine Grains
Recrystallised
DBTT (°C)
- 110
+ 60
USE (J)
7.7
9.2
fine grain
12
Energy ( J)
10
8
6
Fine grains
Recrystallised
4
2
0
-200
-100
0
100
Temperature (°C)
200
A. Alamo et al. , JNM 329–333 (2004) 333–337
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Mechanical properties
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Creep properties (creep rupture time)
A. Alamo et al., JNM 329–333 (2004) 333–337
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Creep of high strength ODS alloys
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Welding
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Basis of welding
• Welding of two metallic pieces
= creation of a metal bond between the atoms of the 2 parts
liquid state welding
solid state welding
• Weld must be as mechanically strong as the base metal
• HT strength is due to the uniform dispersion of nanoscale
oxide particles
 welding operation has to retain the nanostructure
 no reallocation of the dispersoids
 no aggregation of the dispersoids
 no change in the initial microstructure
[email protected]
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Liquid state welding
melting of the base metal
Arc welding:
change in the microstructure
- GTAW (Gas Tungsten Arc Welding)
- GMAW (Gas Metal Arc Welding): MIG (Metal Inert Gas) or MAG (Metal Active Gas)
 Electron beam welding, laser welding
GTAW welder (2)
GTAW
principle
(2)
GTAW
equipment
(1)
GMAW (1)
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(1) CEA/DEN/DANS/DM2S/SEMT/LTA
(2) www.wikipedia.com
GTAW weld in narrow gap (1)
Matgen4.2 – February 6, 2009– TR 34
electron beam equipment (1)
Solid state wedling
Solid state welding
retain the microstructure
• Solid state welding
+ nuclear constraints: large scale, glove box working
– HIP (Hot Isostatic Pressing)
– SPS (Spark Plasma Sintering)
– Friction Stir Welding, Resistance Welding
FSW principle (6)
Resistance welding principle (4)
SPS principle (3)
(3) www.ceramicindustry.com
(4) www.swantec.com
(5) www.plasmo.eu
Resistance welding operation (5)
(6) www.wikipedia.com
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Hot Isostatic Pressure
•
Surface conditioning:
– Degreasing, acid cleaning, mechanical
cleaning, ionic sputtering, coating…
•
Canning:
– in a steel capsule (welded by GTAW)
•
•
•
•
Degassing of the can (P ~ 10-5 mbar)
Closing of the can, gas-tightness
HIP cycling : ~1000 °C/1000 bar/1 h
Removal of the can:
– machining, chemical dissolution
[email protected]
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High Isostatic Pressing
Mockup:
upper plate
[email protected]
Mockup: first wall
Mockup:
cooling plate
Eurofer joint
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Spark Plasma Sintering (SPS)
[email protected], CEA
Université de Bourgogne
SPS principle
INSA Lyon
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Resistance welding
www.cea.fr
Resistance welding device of
CEA/DEN/DANS/DM2S/SEMT/LTA
[email protected]
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Resistance welding – characterization of the weld
 hardness of the weld = hardness of the base metal
 needs for accurate analysis of the dispersoid size and allocation
[email protected]
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Characterization of ODS weld
• How to characterize an ODS weld?
• Usual methods to characterize a weld
– SEM, EDS analysis, hardness profile
– Do not allow observing nanoscale dispersoids
• Methods to characterize an ODS
– TEM, nano-indentation, SANS
– Do not allow checking for the weld homogeneity
– + technically difficult to perform
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Oxidation properties
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Example of commercial ODS
chromia-forming
from
Fe
MA 956
INCO
PM 2000
ODM 751
Cr
Al
Ti
base
20
4,5
0,5
0,5
Plansee
base
20
5,5
0,5
0,5
Dour Metal
base
16,5
4,5
0,6
1,5
0,5
MA 957
INCO
base
14
1
0,3
0,25
MA758
INCO
base
30
0,3
0,5
0,05
0,6
MA754
INCO
base
20
0,3
0,5
0,05
0,6
Plansee
base
20
0,3
0,5
INCO
base
20
6
2
3,5
Zr 0,15
PM 3030
Plansee
base
17
6
2
3,5
Ta 2 Si 0,95
MA757E
INCO
base
16,8
4
HDA-8077
Cabot
base
15,7
4,2
MA6000 (g')
INCO
base
15
4,5
2
MA753 (g')
INCO
base
20
1
2,2
PM 1000
MA760
0,5
Ni
alumina-forming
Mo
W
others
Y2O3
0,6
0,5
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C
2
2
Ta 2 Zr 0,15
0,05
0,95
1,1
0,06
0,7
0,06
Y :1,6
0,05
1,1
0,05
1,3
Matgen4.2 – February 6, 2009– TR 43
Y is a RE !!!
• RE = Reactive Element
effective when added as
–
–
–
–
metal or alloy
oxide dispersoids (ODS)
ionic implantation
surface coating
Fe-24Cr
800°C, air
• Improve the oxidation and
corrosion properties
 longer service life
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Improvement of the oxidation properties
• Surface oxide thickness
• Mass gain
• Spallation
alumina scale
spalls out
protection is lost
12Cr-2W ODS (0.24 Y2O3)
FMS 12Cr-2W
Oxidation in dry air at 650°C for 2000hrs
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Influence on the scale formation
Chromia forming
Alumina forming
• Decrease of the critical
Cr% for chromia formation
Fe-Cr
Co-Cr
Ni-Cr
no Y
20%Cr 25%Cr 35%Cr
Y2O3
10-13% Cr
• Promote -Al2O3 (no
transitory θ-Al2O3)
• Decreases the duration of transitory oxidation
(reduces the base metal oxidation)
12Cr steel oxidized at 1300°C in dry air for 50h
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Influence on the scale growth
Chromia forming
Alumina forming
O2
Cr
O2
O
• Possible change in the
oxidation kinetics (from
parabolic to
subparabolic)
• Supress outward
diffusion of metal cation
• Decrease the oxidation
rate (parabolic constant)
no Y
Y2O3
Wagner theory
 ox  k p .t
  Ea 
k p  D  D.exp

 RT 
O2
O
ox
ox2
t
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t
Influence on the scale microstructure and adhesion
Chromia forming
Alumina forming
• Increase adhesion
 spallation resistance
• Increase the scale
compacity and decrease
the oxide grain size
• Supress the pores at the
alloy/scale interface
FeCrAl oxidized at
1300°C for 100h
2µm
Al2O3 dispersion
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Tb4O7 dispersion
Matgen4.2 – February 6, 2009– TR 48
Which is the optimum RE quantity?
• No practical rule
• It depends on
– Chemical nature of the RE
– Size and distribution
– Chemical interaction
with Ti, C, N
– Fabrication technique
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Temperature range for ODS use
Fe-Cr-Al
Ni-Cr
Ni-Cr-Al
FeCr
800°C
950°C
evaporation
oxidation rate
spallation
1200°C1300°C
spallation
breakaway oxidation
breakaway oxidation
Fe-12Cr
evaporation
PM2000 tested in air at 1200°C for
1825 h, cycling at RT every 48h
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Conclusion
• Gen IV systems are highly demanding toward structural
materials:
high temperature, extended service life, high neutron
dose, corrosive environment…
 ODS steels and alloys could met these high level
requirements especially for
– SFR cladding
– VHTR heat exchanger or GT-MHR turbine
– GFR cladding
• Oxide dispersion strengthening
– Nanoscale particles = obstacle to dislocation glide
– Superior HT strength
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Conclusion cont.
• ODS can be produced via powder metallurgy processes
– Fabrication route and parameters impact microstructure and
properties of the final ODS product
• ODS can be characterized by
– Microscopy, SEM, microprobe analysis  global microstructure
– TEM, AP-FIM, DRX, SANS  dispersoids
• ODS welding
– Solid state welding processes are to be used (resistance welding)
• ODS oxidation properties
– Y is a Reactive Element that improves HT oxidation properties
– Chromia-forming alloy: lower oxidation rate
– Alumina forming alloys: improved spallation resistance
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