Hot Dip Aluminizing Process for TBM applications - An Overview

Venue: IPR, Bhat, G’nagar, India22-July-2008

Workshop on Steels & Fabrication Technologies 200821-22 July, 2008

Organized by: IPR & IGCAR

Hot Dip Aluminizing Process for TBM

applications- An Overview

Nirav I. Jamnapara, S. Mukherjee, P. M. Raole, E. RajendrakumarINSTITUTE FOR PLASMA RESEARCH

Gandhinagar – 382044, India

N.I. Jamnapara, S. Mukherjee, P. M. Raole, E. RajendrakumarWS&FT ’08, 21-22 July, 2008

22-July-08IPR, Gandhinagar

About LLCB

Solid + Liquid Breeder Concept

Li2TiO3 pebbles as solid breeder & Pb-17Li Eutectic as liquid breeder.

Fig 1: Open view of LLCB TBM



Schematic 450-900 C

2

325 C PbLi in

460 C PbLi out



Environment & Challenges

Liquid Pb-17Li @ 1.2 MPa, 325-460 C, 0.5-1 m/s velocities [1] – Hot Corrosion-erosion

T generation in CB & Pb-Li circuits [1] – Tritium permeation through FMS

Thermal Cycles [1]

MHD effects [1] – Insulation needed



Why coating?

Fig 3: T permeation into coolant from Pb-17Li blanket by Reiter [2] Fig 4: Permeability of several metals by P.S. Korinko [3]

Crsn



Ideal Coating Should…

Protect FMS against corrosion from Pb-17Li (> 10,000 hrs) [5, 6]

Resist Tritium permeation through FMS (PRF > 75 in Pb-17Li conditions) [4]

Maintain thermal compatibility ()

be Electrically insulating (to resist MHD effects)

not affect heat transfer be easy to apply on substrates



Candidate coatings

Type of coatings Thickness Agency / Country Year reported

Fe-Al+Al2O3150-180 m FZK Germany (HDA),

& CEA France (CVD)Feb-Sep ’04

Al2O3100 m JRC, Ispra, Italy (VPS) Feb 2004

Er2O3 1 m IPP, Germany (PVD) Aug 2007

Cr2O3-SiO2)+

CrPO4

80-200 m JAERI, Japan (CDC) Nov 2001



Why Aluminide coating?

Good resistance to T permeation* Good corrosion resistance of FMS against

liquid Pb-Li (480 – 550 C) Thermally compatible Electrically Insulating top layer (Al2O3)

Volume resistivity: 0.01 m

*EU Fusion Technology Program has considered aluminide coatings as ‘reference coating’ (HDA & CVD) as tritium permeation barriers.

Ref # 09: J. Konys et. al., FZK Germany



Comparison

Coating\Properties Max. thickness reported

Corrosion Resistance

Thermal shock resist.

TPR (PRF)

Al2O3 100 m Very good poor 100-1000

Fe-Al+Al2O3 180 m Good Very good 1000

Er2O3 1 m Not reported Not reported 800

(Cr2O3-SiO2)+CrPO4 80-200 m Not reported good 1000



Why Hot Dip Aluminizing?

Aluminizing possible by solid, liquid & gas processing [3]

Better PRFs with H2 as compared to CVD (J. Konys; FZK, Germany, [4])

Ease of processing complex geometries Scalable Adherent alumina by oxidation of surface



Targeted Aluminide Coating

Intermetallic Fe-Al + Al2O3

1-10 m Al2O3

(for resistance to corrosion, MHD and Erosion)

150-180 m Intermetallic Fe-Al(for Tritium Permeation Resistance)

Ref: J. Konys et. al., FZK [4,5]



Targeted MicrostructuresParameters for hot dipping: temperature at 700°C and dipping time of 30 s

Microstructure of hot dipped surface

The alloyed surface layer consists of brittle Fe2Al5, covered by solidified Al

Microstructure after heat treatment

F82H-mod.

Fe2Al5

AlFeAl

-Fe(Al)

F82H-mod.

HV 320

270

240

Heat treatment at 1040°C/0.5 h + 750°C/1 h and an applied pressure of >250 bar (HIPing) reduces porosity and transforms the brittle Fe2Al5-phase into the more ductile phases FeAl and -Fe(Al)Ref: J. Konys et. al., FZK [4,5]



HDA Setup - proposed Al2O3 - crucible

Sample

Al-melt

Furnace

Coating conditions [4,5]

Temperature: 700 – 750 °CMelt: Al or Al-Si (7-11% Si)Sample dimensions: 50 mm (l) x 30 mm (w) x 5 mm

Melting chamber

Holding chamber with protective environment



HDA PROCESS

Steel sample (sheet or

tube)Grinding Cleaning in

acetoneCoating, aq. flux-solution Pre-drying :

100°C

Glove-box (Ar-5%H2)

Hot-dip-aluminizing, 700°CCleaning in water

HIP-process (advanced process)

Heat Treatment (Standard process)

Coated sample

Ref: Voltrag, et. al. FZK [4,5]



Challenges

Wettability of sample in Al melt Melt Composition (alloying, viz. Si) Surface Activation (fluxes etc.)

Case composition – tailored (Fe-Al) Post treatment (HIPing), dipping time, batch composition No porosities (HIPing), Case depth

Adherent Al2O3 layer on top Plasma oxidation process

Qualify for validation (performance related)



Plans for development

Development of homogenous aluminized coating after HDA

Generation of desired compositional profile by heat treatment & plasma oxidation

Hot Isostatic Pressing of aluminized samples (To be worked out in collaboration with other national insitutes)

Hot Dip aluminizing700 – 750 C

Plasma Oxidation & H/T 1050 C

HIPing1050 C, 250 Bar

1 hrValidation



Validation:

Pb-17Li Loop testing H2 / T permeation:- Initially the sample will be tested for

Hydrogen permeation- Susequently the sample will be

validated for Tritium permeation in Pb-Li environment

Ref: Schematic of Permeation testing facility at ENEA, Italy



Present status

Design & generation of specs for furnace Fabrication & installation of furnace Preliminary trials for HDA – wettability &

uniformity Heat treatment optimization Characterization Hot Isostatic Pressing Validation



Thank You



References:1) Design Description Document for Indian Lead Lithium cooled ceramic breeder

(LLCB) Blanket

2) G. W. Hollenberg et. al., Tritium / Hydrogen Barrier Development, June 1994, 3rd Intl. Symposium on Fusion Nuclear Technologies, LA, California

3) P.S. Korinko et. al., ‘Dev. of aluminide coatings for Hydrogen isotope permeation resistance’, Tritium 2001, Tsukaba, Japan, 11-16 Nov, 2001

4) J. Konys et. al., ITER TBM Project Meeting, UCLA, Feb 23-25, 2004.

5) J. Konys et. al., J. Nucl. Mat. 367-370 (2007) 1144-1149

6) H. Glasbrenner et. al., J. Nucl. Mat. 307-311 (2002) 1360-1363

BACK



Corrosion data

1

10

100

1.000

10.000

Me

tal

los

sR

[µm

/a]

700 750 800 850 900 950 1.000

Temperature T [K]

450 500 550 600 650 700

T [°C]

Correlation by Sannier et al.ML = 8·10 ·d [µm/a]9 0.875 -0.125·exp{-25690/1.98T}·v h

~20 µm/a

~151 µm/a

typical Picolo flow rate

experimental rangefor LAF steels in Picolo

80 - 100 µm/a

0.05 m/s

0.005 m/s

0.22 m/s

~553 µm/a

Eurofer 97 in Picolo at 550°Cextrapolation by first 3000 h

~ 500 µm/a

BACK

Ref: W. Krauss et. al., Intl. workshop on breeder blankets, RussiaJune, 2006



T (°C) VPS HDA CVD

300 450 3100 3100

350 400 2800 2100

400 380 1500 1600

450 380 2400 1300

pH2= 1 bar, steel: F82H-mod., Ref: J. Konys et. al. [4]

Results of permeation testing in H2–gas in different facilitiesat ENEA Brasimone, Italy (PERI, CORELLI)

Permeation Reduction Factors (PRF)

cancelled

BACK



WHY HIPPING?Microstructure after heat treatment

Heat treatment at 1040°C/0.5 h + 750°C/1 hincorporates the solidified Al and transforms the brittle Fe2Al5-phase into the more ductile

phases FeAl and -Fe(Al)

FeAl

-Fe(Al)

F82H-mod.

HV 320

270

240

Microstructure after HIP

FeAl

-Fe(Al)

F82H-mod.

HV 320

270

240

Heat treatment at 1040°C/0.5 h + 750°C/1 h and an applied pressure of >250 bar (HIPing) reduces porosity and transforms the brittle Fe2Al5-phase into the more ductile phases FeAl and -Fe(Al)BACK

Ref: J. Konys et. al. [4]

Hot Dip Aluminizing Process for TBM applications - An Overview

Documents

liquid pbli

cb pbli circuits

li eutectic

li blanket

li conditions

solid breeder pb

t permeation

resist tritium permeation