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

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Surface temperature

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Surface1 micron5 microns10 microns100 microns

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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

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Surface temperature

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Surface1 micron5 microns10 microns100 microns

Surface1 micron5 microns10 microns100 microns

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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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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

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Energy (keV)

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CVD

Polycrystalline

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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

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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