2nd IAEA TM on Divertor, Suzhou, Nov. 13-16, 2017 R.Neu 1

Max-Planck-Institut für Plasmaphysik

1) Max-Planck-Institut für Plasmaphysik, 85748 Garching, Germany

2) Osram GmbH, SP PRE PLM DMET, 86830 Schwabmünchen, Germany

3) Forschungszentrum Jülich GmbH, Institut für Energie- und Klimaforschung – Plasmaphysik, 52425 Jülich, Germany

4) Technische Universität München, 85748 Garching, Germany

Tungsten Fibre-Reinforced Composites

for Advanced Plasma Facing

Components

J. Riesch1, J. Almanstötter2, M. Balden1, J. W. Coenen3, H.

Gietl1,4, T. Höschen1, Y. Mao3, A. v. Müller1,4, L. Raumann3,

R. Neu1,4 and the Wf/W-Team1,3

2nd IAEA TM on Divertor, Suzhou, Nov. 13-16, 2017 R.Neu 2

• Introduction

• W fibres and preforms

• Wf/W-composite

• Wf/Cu-composite

• Conclusions and outlook

Tungsten fibre-reinforced composites for

advanced plasma facing components

2nd IAEA TM on Divertor, Suzhou, Nov. 13-16, 2017 R.Neu 3

Introduction/Motivation

recrystallisation inherent brittleness

softening

Based on

S.J. Zinkle et al.,

FED 51-52

(2000) 55-71]

and

Timmis,

Mat. Ass. Rep.

(2012)

[G. Pintsuk et al.

FED 88 (2013)

1858]

deep cracking of ITER W

monoblock at 20 MW/m2

• Copper (Cu) based alloys (as for example CuCrZr) are foreseen as heat

sink, whereas as armour tungsten (W) based materials will be used.

• combining both materials in PFCs bears the difficulty that their optimum

operating temperatures do not overlap:

• W should be operated above 800°C

in order to be in a ductile state to avoid

brittle cracking under cyclic load,

• CuCrZr should be operated below 300°C to provide enough

mechanical strength.

2nd IAEA TM on Divertor, Suzhou, Nov. 13-16, 2017 R.Neu 4

Introduction/Motivation

• Copper (Cu) based alloys (as for example CuCrZr) are foreseen as heat

sink, whereas as armour tungsten (W) based materials will be used.

• combining both materials in PFCs bears the difficulty that their optimum

operating temperatures do not overlap:

• W should be operated above 800°C

in order to be in a ductile state to avoid

brittle cracking under cyclic load,

• CuCrZr should be operated below 300°C to provide enough

mechanical strength.

A remedy for both issues

– brittleness of W and degrading strength of CuCrZr –

could be the use of W fibres in W and Cu based composites

2nd IAEA TM on Divertor, Suzhou, Nov. 13-16, 2017 R.Neu 5

• Introduction

• W fibres and preforms

• Wf/W-composite

• Wf/Cu-composite

• Conclusions and outlook

Tungsten fibre-reinforced composites for

advanced plasma facing components

2nd IAEA TM on Divertor, Suzhou, Nov. 13-16, 2017 R.Neu 6

Performance of W-fibres

upper clamp +

load cell

laser spots

diode lasers

lower clamp +

manipulator

16 mm

translationstage

CCD +telecentric lens

W wire

epoxy glue

epoxy glue

[Riesch et al., Physica Scripta, 2016, T167, 014006]

W fibres: - are ductile already @ r.t.

- no embrittlement < 2200 K

- yield strength increases with

decreasing fibre diameter

2nd IAEA TM on Divertor, Suzhou, Nov. 13-16, 2017 R.Neu 7

[Riesch et al., Physica Scripta, T170 (2017) 014032]

use thinner W fibres

(higher deformation)

- higher tensile strength

- more flexible

development of W-yarn

W fibres with PVA enwinding

[Coenen et al., ICFRM]

Performance of W-fibres

2nd IAEA TM on Divertor, Suzhou, Nov. 13-16, 2017 R.Neu 8

Preforms for Wf/W

flat W fibre textiles for layered deposition of Wf /W-samples,

optimum parameters defined:

- 150/50 µm warp/weft wire, 600 mm width,

- eventually yarn to reduce height & stiffness of textile ( higher fibre fraction)

0

282

141

µm

230-250 µm

100-150 µm

warp

150 µm

weft 70 µm

2nd IAEA TM on Divertor, Suzhou, Nov. 13-16, 2017 R.Neu 9

Preforms for Wf/Cu tubes

braided cylindrical preform (23

layers)

5000 μm high strength W

fibres (∅: 50 µm)

• tubular fabrics of multi-layered W fibres for Wf /Cu-tubes by braiding (~m)

• optimisation of wire thickness (50 µm), braiding angle (77°) and layer

number (23) successfully completed

• yarns can further optimize performance (easily to be infiltrated)

2nd IAEA TM on Divertor, Suzhou, Nov. 13-16, 2017 R.Neu 10

• Introduction

• W fibres and preforms

• Wf/W-composite

• Wf/Cu-composite

• Conclusions and outlook

Tungsten fibre-reinforced composites for

advanced plasma facing components

2nd IAEA TM on Divertor, Suzhou, Nov. 13-16, 2017 R.Neu 11

Wf/W – state of the art

Principle

Synthesis

Chemical

Vapour

Deposition

(CVD-Wf/W using WF6)

powder metallurgy (PM-Wf/W)

presentation by Y. Mao

Matrix

Fibre:

drawn

W-wire Interface

2nd IAEA TM on Divertor, Suzhou, Nov. 13-16, 2017 R.Neu 12

Artificial

notch First fibre layer

half cut

Mechanical Properties of Wf / W

• Multi-fibre composite (150 µm)

W-CVD layered deposition

Polished

ca. 3 mm x 2 mm x 10 mm

• as fabricated and

embrittled (2000 K, 30 min) Wf / W

2 mm

• stepwise 3-point bending +

in-situ surface observation in SEM (ESI)

2nd IAEA TM on Divertor, Suzhou, Nov. 13-16, 2017 R.Neu 13

2 mm

• stepwise 3-point bending +

in-situ surface observation in SEM (ESI)

Mechanical Properties of Wf / W

• Multi-fibre composite (150 µm)

W-CVD layered deposition

Polished

ca. 3 mm x 2 mm x 10 mm

• as fabricated and

embrittled (2000 K, 30 min) Wf / W

ductile fibre

strength 2900 MPa,

fracture strain 2%

brittle fibre

strength 900 MPa,

fracture strain 0.2 %

matrix failure

= bulk material failure

Lo

ad

[N

]

Displacement [µm]

rising load

bearing capacity

no catastrophic

failure

2nd IAEA TM on Divertor, Suzhou, Nov. 13-16, 2017 R.Neu 14

Cyclic tensile testing of WfW in as-fabricated condition

Fibre orientation

2nd IAEA TM on Divertor, Suzhou, Nov. 13-16, 2017 R.Neu 15

10.000

Cycles 10.000 Cycles

without further damage

115 Overload Cycles

without catastrophic failure

10.000 Cycles @ 60% 10.000 Cycles @ 70% 10.000 Cycles @ 80% 10.000 Cycles @ 90% 10.000 Cycles @ 100%

𝒍

𝒍

𝒍

𝒍

𝒍

𝟐𝒍

𝒍

𝒍

𝒍 ≈ 𝒄𝒐𝒏𝒔𝒕

damage tolerance

H. Gietl

FED 2017

Cyclic tensile testing of WfW in as-fabricated condition

2nd IAEA TM on Divertor, Suzhou, Nov. 13-16, 2017 R.Neu 16

Preliminary FEM analysis of thermal behaviour of Wf /W-composite

therm. conductivity

fibres

100% 50% 10%

fibre volume

fraction:

13%

(Ø0.25mm)

Tmax

surface

2146 219

5

227

0

Tmax fibres 1959 201

1

209

5

fibre volume

fraction:

33% (Ø0.4

mm)

Tmax

surface

2146 229

0

258

9

Tmax fibres 2033 218

3

249

1

debonding length (mm) 0 2 10

fibre volume fraction: 13% (Ø0.25mm)

Tmax surface 2146 2149 2161

Tmax fibres 1959 1961 1974

Maximum temperatures (°C) for different thermal conductivities /

debonding lengths of W fibres

FEM (Abaqus) simulations,

actively cooled component,

20 MW/m² loading

model

fibre

layers

2nd IAEA TM on Divertor, Suzhou, Nov. 13-16, 2017 R.Neu 17

Upscaling of CVD process for Wf/W production

rotatable supply and CVD target

W(CO)6 ‚shower‘

60 mm

Wf/W sample Wf preform

2nd IAEA TM on Divertor, Suzhou, Nov. 13-16, 2017 R.Neu 18

• Introduction

• W fibres and preforms

• Wf/W-composite

• Wf/Cu-composite

• Conclusions and outlook

Tungsten fibre-reinforced composites for

advanced plasma facing components

2nd IAEA TM on Divertor, Suzhou, Nov. 13-16, 2017 R.Neu 19

(hoop)

at 300°C

(W/(m·K))

265

274

283

318

calculated stress-strain behaviour

W fibre-reinforced Cu composites

(a) transversal

(b) axial microsections

of a Wf/Cu heat sink pipe

Manufacturing of W fibre-reinforced Cu composite by means of liquid Cu

melt infiltration in a carbon-free environment!

[A. v. Müller FED 124 (2017) 455]

Property Estimation

(Digimat Calculations):

relating micro & macro properties

by averaging quantities over

representative volume element (RVE)

[A. v. Müller ICFRM 2017]

2nd IAEA TM on Divertor, Suzhou, Nov. 13-16, 2017 R.Neu 20

Performance of Wf/Cu composites

100 µm

fracture surface of a W fibre-reinforced Cu pipe specimen:

Cu infiltrated W fibre braiding; axial tensile test at room temperature

necking of W fibres plainly visible

ductile failure of both Cu matrix & W fibrous reinforcements

(already at room temperature)

2nd IAEA TM on Divertor, Suzhou, Nov. 13-16, 2017 R.Neu 21

Performance of mock-ups with Wf/Cu heatsink

HHF testing (GLADIS) of W fibre-reinforced Cu heat sink pipe

successful HHF testing up to 25 MW/m2

indicates good material performance

HHF testing (GLADIS) of monoblock-type mock-up

with W fibre-reinforced Cu heat sink pipe

W fibre-reinforced Cu

pipe before HHF testing

W fibre-reinforced Cu pipe

during HHF testing

W fibre-reinforced Cu pipe

after HHF testing

brazed joint between W monoblocks and

W fibre-reinforced Cu heat sink pipe

successful HHF testing up to 300 load cycles

at 20 MW/m2 without indication of failure

Monoblock-type PFC mock-up

with W fibre-reinforced Cu heat

sink pipe

2nd IAEA TM on Divertor, Suzhou, Nov. 13-16, 2017 R.Neu 22

• Introduction

• W fibres and preforms

• Wf/W-composite

• Wf/Cu-composite

• Conclusions and outlook

Tungsten fibre-reinforced composites for

advanced plasma facing components

2nd IAEA TM on Divertor, Suzhou, Nov. 13-16, 2017 R.Neu 23

Conclusions

• industrial textile processing of W fibres to cylindrical braiding and

flat textiles has been demonstrated

• large scale composites have been produced by layered chemical

vapour deposition (Wf/W ) and infiltration (Wf/Cu)

• Wf/W composites show high toughness and damage tolerance in

cyclic loading even at room temperature

(K-doped fibres resistive against embrittlement up to 1900 C)

• liquid Cu melt infiltration of W fibre preforms is feasible in industrial

environment

• property estimation indicates clearly the potential of Wf/Cu as

advanced heat sink material for DEMO PFCs

• mock-up with Wf/Cu heatsink successful tested @ 20 MW/m²

W fibre reinforcement strongly increases operational temperatures

of W and Cu (& reduced stresses when used in combination!)

2nd IAEA TM on Divertor, Suzhou, Nov. 13-16, 2017 R.Neu 24

Conclusions

recrystallisation inherent brittleness

ductile fibres &

bridging/pull-out if embrittled K doped

fibres

Wf/CuCrZr

softening

2nd IAEA TM on Divertor, Suzhou, Nov. 13-16, 2017 R.Neu 25

Outlook / Development Plan

design & fabrication of wall mock-up (Wf/W)

proof of concept

HHF testing under relevant test conditions (Wf/Cu)

validation

fusion environment interaction / irradiation studies

component validation in relevant environment

application in ASDEX Upgrade

(manipulator & wall tile)

prototype demonstration in relevant environment

Technology

Readiness

Level (TRL) Idea

Application

PFC in

DEMO

After [Riesch et al., Physica Scripta, 2016, T167, 014006]

Current

status

2nd IAEA TM on Divertor, Suzhou, Nov. 13-16, 2017 R.Neu 26

Tungsten manufactured by means of laser beam melting

A.v.Müller, 6th Int. Conf. on Additive

Technologies iCAT 2016, Nürnberg

Small samples produced by

from pure tungsten

Reduce cracks by improved process using higher temperature of W substrate!

2nd IAEA TM on Divertor, Suzhou, Nov. 13-16, 2017 R.Neu 27

Tungsten manufactured by means of laser beam melting

A.v.Müller, 6th Int. Conf. on Additive Technologies iCAT 2016, Nürnberg