S. Tarancón1 | E. Tejado1 | M. Richou2 | J.Y. Pastor1

Presenting author: Elena Tejado, Ph.D.

1 Dpto. Ciencia de Materiales-CIME, Universidad Politécnica de Madrid, Spain

EVALUATION OF THE TENSILE AND ELASTIC PROPERTIES OF W/CU COATINGS FOR ITS APPLICATION TO THE FGM DEMO DIVERTOR CONCEPT

1. Cold-spray graded coatings demonstrated valid for the joint of W to Cu infuture DEMO divertor mockups

2. Tensile tests on single-coatings: revealed elastic behaviour up to fracture andhigh strength values; decohesion of W particles (intergranular fracture between Wgrains) with plastic deformation of the surrounding Cu matrix

3. New method has been followed to measure E through RFA on coating-substratesystems and these results are in agreement with both nE and Young modulusobtained from the σ-ε curves.

FindingsITER based conceptual design of EU-DEMO divertorenvisages W monoblocks as plasma-facing material joinedto a CuCrZr cooling tube with a thick Cu-OHFC interlayer.

Since divertor configuration will define the power exhaustcapabilities of the reactor, additional concepts have beendeveloped within the EUROfusion WPDIV project. TheFunctionally Graded Material (FGM) concept is one of theproposed alternatives.

Solution: replacement with a W to Cu compositionally graded thin film to reduce stresses at the interfaces

2 CEA, IRFM, F-13108 Saint-Paul-Lez-Durance, France

20-25 SEPTEMBER 2020 VIRTUAL EDITION31ST SYMPOSIUM ON FUSION TECHNOLOGY

Problem: armour-to-pipe W to Cu joint (non miscible, large CTE and E mismatch, need for a flexible technique to join tubes…)

40 µm

0 %W

40 µm

25 %W

40 µm

50 %W

40 µm

75 %W

ITER W armoured monoblock geometry at the inner and outer vertical targets

100 %W

100 %Cu

Particle size: 5-50 µm N2 atmosphere Pressure: 10-50 Bar T: 1000 °C

Φ < 4 %

Cold-Spray W/Cu coatings

Fractographic SE+EDX map of the tensile samples, W particles are in green, the Cu matrix in red

Real Strain obtained through DIC (Digital Image Correlation)

Loading rate 10 μm/minCoatings thickness: 260 μm

Linear elastic up to fracture ↑σs→ ↑vol%W except for:

Cu-75W: considerably lower vol%W than expected (≈ 48% lower)

Fracture surfaces: Strong adhesion Cu-W Ductile dimples of Cu matrix

while W particles remain intact

0 %W

20 µm 20 µm

25 %W

20 µm

50 %W

20 µm

75 %W

2 Tensile properties

Acknowledgements• This work has been carried out within the framework of the EUROfusion Consortium

and has received funding from the Euratom research and training programme 2014–2018 and 2019–2020 under grant agreement No 633053. The views and opinionsexpressed herein do not necessarily reflect those of the European Commission.

• The authors would also like to acknowledge the Ministerio de Economía yCompetitividad of Spain (MAT2015-70780-C4-4-P), the Comunidad de Madrid(S2018/NMT-4411 ADITIMAT-CM) and, especially, the Universidad Politécnica deMadrid in the line of action for encouraging research from young doctors (projectM190020074EMTG, COAT4FUSION) for funding this research.

L. Chandra and T. W. Clyne; Use of an ultrasonic resonance technique to measure

the in-plane Young’s Modulus of thin diamond films deposited by a DC plasma JET. J. Mat.

Letts. June 1992

ANEX: Measurement of ERFA of W/Cu coatings on the substrate:

1 Overview 3 Elastic properties

Real stress-strain curves of W/Cu coatings after tensile testing of the isolated coatings and DIC analysis (left) and the Ultimate tensile strength (right) as a function of W content. Tests performed at room temperature

Elastic modulus (otp left) and hardness (bottom right) as a function of W content of W/Cu coatings

Up to 50 %Cu: H with Cu Indentation size effect Lower standard error of

Vickers Hardness (as compared to Instrumented Indentation (75 mN and 0.5 N), where each phase is tested independently

3 different techniques to measure Young Modulus: Agreement among

obtained values, although nE>EIET>ETRAC

Macroscopic values of E can be obtained via RFA in coatings over substrate systems

Coatingsmanufacturingconditions

Functionally Graded Material (FGM) monoblock concept