Integrated Materials Plan Progress:Helium Blistering and Refractory Armored Materials
Lance L SneadHigh Average Power Lasers Workshop
December 6, 2002. Naval Research Laboratory
Blistering RAM’sAlexander Federov, DELFT Jake Blanchard, UCSBJohn Hunn, ORNL Craig Blue, ORNLGene Lucas, UCSB Tatsuya Hinoki, ORNLNalin Parikh, UNC Rene Raffray, UCSDNao Hashimoto, ORNL Steve Zinkle, ORNL
Chambers Phase I Goals1. Develop a viable first wall concept for a fusion power plant.2. Produce a viable “point design” for a fusion power plant
UCSDWisconsinSNLORNLLLNLUCSD
Long term material issues are being resolved.
Example- Ion exposures on RHEPP
0 2 4 6 8 10time (? )sec
Surface temperature
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5000 2 4 6 8 10
(time ? )sec
Surface1 micron5 microns10 microns100 microns
3000
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2200
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1600
1200
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200 ( )Chamber Wall Temperature deg C
400 MJ Target 8.25 Graphite wall @ m radius
25 mTorr Xe in chamber
154 MJ Target 6.5 Tungsten wall @ m radius
No gas in chamber
0 2 4 6 8 10 (time ? )sec
Surface temperature
3000
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(time ? )sec
Surface1 micron5 microns10 microns100 microns
Surface1 micron5 microns10 microns100 microns
3000
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1200
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200 ( )Chamber Wall Temperature deg C
400 MJ Target 8.25 Graphite wall @ m radius
25 mTorr Xe in chamber
154 MJ Target 6.5 Tungsten wall @ m radius
No gas in chamber
Exfoliation of W Surface
5.5 x 5.5 mm implant area 10x further magnification
• At the IFE flux of ~ 2x1018 He/m2-s exfoliation will lead to the exfoliation of ~ 2cm/yr of tungsten in the absence of helium diffusion.
• The helium diffusion in tungsten is not well understood though will be a function of implantation temperature, annealing temperature, and microstructure.
1022 He/m2-s 800°C implantation followed by 2000°C anneal
NRA (entire spectrum)
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0 2000 4000 6000 8000 10000 12000 14000 16000
Energy (keV)
Counts 3He(d, p)4He
“peak integration”
12C(d, p)13C
W target1.3 MeV 3He
12 m Mylar
Detector
13 MeV p+, , backscattered D2
3Heprofile
Experiment
Materials : Single Crystal (001) W
Powder Met PolyX W
CVD W
Implantation : Step Implantation/Anneal
Continuous Implantation/Anneal 2000°C
Techniques ; Nuclear Reaction Analysis, TEM, Thermal Desorption, Surface Inspection
Final Results: Mapping kinetics of He diffusion in W as a function of temp. and microstructure
Single Crystal
50 step doses vs. single dose (10 19/m2)
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Energy (keV)
Counts
50 steps annealed between
whole dose then annealed
50°C ImplantSingle Crystal
IFE dose ~ 1017/m2-shotExp. Step = 2x1017/m2
Anneal is 2000°C
• Repetitive dose/anneal exhibits less retained helium compared to a single dose
followed by annealing (272 -vs- 582 counts.)
--> Annealing helium before it forms immobile clusters will extend lifetime
Effect of Stepwise Annealing
Implanted 10 19/m2 at 800 CAs-implanted Analysis
0
5
10
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12500 13000 13500 14000
Energy (keV)
Counts
CVD
Polycrystalline
Single Crystal
Effect of Microstructure
1019/m2 at 800°C
• The tungsten microstructure has a strong influence on trapping of helium. In this case CVD has higher retention than polycrystalline (238-vs-82 counts) while single crystal had no measurable retained helium.
• Annealing to 2000°C did not reduce the retained He
Conclusion and Completion of Work
• There is a stong function of microstructure and implantation temperature on the helium diffusion in W at IFE-relevant helium implantation doses and temperature. By the correct choice of material it may be possible to avoid blistering.
• Future Work
--> Map the retained helium and calculate diffusion coefficients as a function of implantation temperature.
--> Determine microstructural features controlling trapping
--> Use diffusion coefficients to model helium diffusion in IFE heat pulse
--> Automate implantation target to carry out high-dose step-wise implantation/anneal (5x1017/m2 , 2000°C) to 1x1023/m2
--> 1 yr IFE fluence = ~ 1025/m2
SiC Coating Procedure
SiC (Hexoloy SA)
Pretreatment*
Brush or spray powder (W or Mo)
IR processing SiC
*Pretreatment: Ti vapor deposition W or Mo vapor deposition Anneal 72 hours (1300 or 1500ºC)
Vapor deposited Ti
Vapor deposited W or Mo
Anneal
W or Mo powderPlasma Arc
Lamp
coating
Specimen size: 25×15×3 (mm)Lamp size used: 31.75×10 (mm)IR processing: uniform irradiance or scan
Flash
Effect of IR Processing on Surface Roughness
SiC without coating
SiC
W coating
IR processing
10µm
Interface
Optical microscope (OM) images
SEM Images of W Coating Processed at 1828 W/cm2
Scanning electron imageBack scattering (composition) electron image
EDS Mapping of W Coating
SiC
Wcoating
W
C
SiBack scattering (composition) electron image
EDS mappingof W, C, Si
W+C W+Si
Hexoloy SiC + W (no pretreatment)Lamp power: 2350 W/cm2
Scan speed: 9mm/sec
Effect of Vapor Deposited W and Pre-heating on Crack Propagation into SiC
10µm
SiC
W coating
2350W/cm2(3sec)
522W/cm2(20sec)+2350W/cm2(3sec)
VD W+2350W/cm2(3sec)
SEM Images of W coating on SiC
Scanning electron imageBack scattering (composition) electron image
With pre-heating 522W/cm2 (20sec) + 2350W/cm2 (3sec)
SiC
W coating
W+C
SiCSi+W
100
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200
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3 5 7 9 11Scan speed (mm/sec)
Flexural strength (MPa)
Without VDWith VD
Effect of Processing Condition on Flexural Strength of W Coated SiC
W coating side
Four point flexural testSpecimen size: 50x4x3 mmSupport span: 40 mmLoading span: 20 mmCrosshead speed: 10um/sec
Substrate strength
W coating was not peeled off during flexural testStrength of substrate SiC was decreased by IR processingVapor deposition prior to powder coating prevented degradation of strength
Tungsten on Reduced Activation Ferritic
Melt Zone
Tungsten
Base Metal
OM Images on Ferritic Steel
IR processing: 2350W/cm2 (scan: 7mm/sec)Near edge
OM Images on Ferritic Steel
IR processing: 2350W/cm2 (scan: 6mm/sec)
OM Images on Ferritic Steel
IR processing: 2350W/cm2 (Flash: 6sec)
OM Images on Ferritic Steel
IR processing: 2350W/cm2 (Flash: 6sec)
Concuding Remarks and Future Work
• Refractory armored SiC has been produced with strength considerably higher than conventional techniques (CVD, PVD, etc.) Composite armoring to follow.
• Additional development including repeated layering may be required to make transition to 100% W surface.
• Ongoing work includes strength, fatigue, and thermal shock using IR processing facility.
• Initial attempt to armor ferritic steel was of limited success. Additional development work to reduce the melt/recrystallized zone will be carried out.
300,000 Watt Plasma Radiant Processing Facility
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