Delayed surface degradation in W-Ta alloys at 400°C under high-fluence 40 eV He plasma exposure

E. Yildirim; P. M. Mummery; T. W. Morgan; E. Jimenez-Melero

doi:10.1016/j.fusengdes.2023.114061

Delayed surface degradation in W-Ta alloys at 400°C under high-fluence 40 eV He plasma exposure

E. Yildirim^*, P. M. Mummery, T. W. Morgan, E. Jimenez-Melero

^*Corresponding author for this work

Metallurgy and Materials

Research output: Contribution to journal › Article › peer-review

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Abstract

The surface modifications in W-xTa alloys (x = 0, 6, 11 wt.%), as potential material candidates for tokamak components facing the fusion plasma, have been assessed at a temperature of ∼400 °C, by exposing the material surface to 40 eV He for increasing He fluences up to 10²⁷ m⁻² and flux of ∼10²³ m⁻² s⁻¹. Surface wave-like structures appear in all samples at a fluence of ∼10²⁶ m⁻², whereas at the higher fluence of ∼10²⁷ m⁻² the material's surface is characterised by the presence of blisters and ablations. This suggests a new critical fluence for blistering in pure He plasma to be between 10²⁶ and 10²⁷ m⁻². There is also a near-surface layer with a thickness of ∼200 nm that contains He bubbles of 2.20–2.70 nm in average size. Increasing Ta content leads to a small reduction in bubble size, and to clear reductions in the presence of blisters and ablations. Ta alloying can improve the hardness and yield strength and reduce the He diffusivity in the material. This therefore delays bubble formation and surface blistering and ablations that are affected by these mechanical properties. This was exemplified at the highest fluence by a large mitigation of surface material ablation.

Original language	English
Article number	114061
Number of pages	10
Journal	Fusion Engineering and Design
Volume	197
Early online date	16 Nov 2023
DOIs	https://doi.org/10.1016/j.fusengdes.2023.114061
Publication status	Published - Dec 2023

Bibliographical note

Funding Information:
We wish to acknowledge the support of the EPSRC through grant number EP/L01663X/1 and the Henry Royce Institute for EY through the Royce PhD Equipment Access Scheme enabling access to Arc Melting facilities at Royce @Sheffield ; EPSRC Grant Number EP/R00661X/1 . We also acknowledge the support of the Magnum-PSI Facility Team at DIFFER. The Magnum-PSI facility at DIFFER has been funded by the Netherlands Organisation for Scientific Research ( NWO ) and EURATOM . DIFFER is part of the institutes organisation of NWO. 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 opinions expressed herein do not necessarily reflect those of the European Commission.

Keywords

Electron microscopy
Helium bubbles
Image analysis
Linear plasma device
Surface blistering
Tungsten alloys

ASJC Scopus subject areas

Civil and Structural Engineering
Nuclear Energy and Engineering
General Materials Science
Mechanical Engineering

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Cite this

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title = "Delayed surface degradation in W-Ta alloys at 400°C under high-fluence 40 eV He plasma exposure",

abstract = "The surface modifications in W-xTa alloys (x = 0, 6, 11 wt.%), as potential material candidates for tokamak components facing the fusion plasma, have been assessed at a temperature of ∼400 °C, by exposing the material surface to 40 eV He for increasing He fluences up to 1027 m−2 and flux of ∼1023 m−2 s−1. Surface wave-like structures appear in all samples at a fluence of ∼1026 m−2, whereas at the higher fluence of ∼1027 m−2 the material's surface is characterised by the presence of blisters and ablations. This suggests a new critical fluence for blistering in pure He plasma to be between 1026 and 1027 m−2. There is also a near-surface layer with a thickness of ∼200 nm that contains He bubbles of 2.20–2.70 nm in average size. Increasing Ta content leads to a small reduction in bubble size, and to clear reductions in the presence of blisters and ablations. Ta alloying can improve the hardness and yield strength and reduce the He diffusivity in the material. This therefore delays bubble formation and surface blistering and ablations that are affected by these mechanical properties. This was exemplified at the highest fluence by a large mitigation of surface material ablation.",

keywords = "Electron microscopy, Helium bubbles, Image analysis, Linear plasma device, Surface blistering, Tungsten alloys",

author = "E. Yildirim and Mummery, {P. M.} and Morgan, {T. W.} and E. Jimenez-Melero",

note = "Funding Information: We wish to acknowledge the support of the EPSRC through grant number EP/L01663X/1 and the Henry Royce Institute for EY through the Royce PhD Equipment Access Scheme enabling access to Arc Melting facilities at Royce @Sheffield ; EPSRC Grant Number EP/R00661X/1 . We also acknowledge the support of the Magnum-PSI Facility Team at DIFFER. The Magnum-PSI facility at DIFFER has been funded by the Netherlands Organisation for Scientific Research ( NWO ) and EURATOM . DIFFER is part of the institutes organisation of NWO. 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 opinions expressed herein do not necessarily reflect those of the European Commission.",

year = "2023",

month = dec,

doi = "10.1016/j.fusengdes.2023.114061",

language = "English",

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AU - Yildirim, E.

AU - Mummery, P. M.

AU - Morgan, T. W.

AU - Jimenez-Melero, E.

N1 - Funding Information: We wish to acknowledge the support of the EPSRC through grant number EP/L01663X/1 and the Henry Royce Institute for EY through the Royce PhD Equipment Access Scheme enabling access to Arc Melting facilities at Royce @Sheffield ; EPSRC Grant Number EP/R00661X/1 . We also acknowledge the support of the Magnum-PSI Facility Team at DIFFER. The Magnum-PSI facility at DIFFER has been funded by the Netherlands Organisation for Scientific Research ( NWO ) and EURATOM . DIFFER is part of the institutes organisation of NWO. 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 opinions expressed herein do not necessarily reflect those of the European Commission.

PY - 2023/12

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N2 - The surface modifications in W-xTa alloys (x = 0, 6, 11 wt.%), as potential material candidates for tokamak components facing the fusion plasma, have been assessed at a temperature of ∼400 °C, by exposing the material surface to 40 eV He for increasing He fluences up to 1027 m−2 and flux of ∼1023 m−2 s−1. Surface wave-like structures appear in all samples at a fluence of ∼1026 m−2, whereas at the higher fluence of ∼1027 m−2 the material's surface is characterised by the presence of blisters and ablations. This suggests a new critical fluence for blistering in pure He plasma to be between 1026 and 1027 m−2. There is also a near-surface layer with a thickness of ∼200 nm that contains He bubbles of 2.20–2.70 nm in average size. Increasing Ta content leads to a small reduction in bubble size, and to clear reductions in the presence of blisters and ablations. Ta alloying can improve the hardness and yield strength and reduce the He diffusivity in the material. This therefore delays bubble formation and surface blistering and ablations that are affected by these mechanical properties. This was exemplified at the highest fluence by a large mitigation of surface material ablation.

AB - The surface modifications in W-xTa alloys (x = 0, 6, 11 wt.%), as potential material candidates for tokamak components facing the fusion plasma, have been assessed at a temperature of ∼400 °C, by exposing the material surface to 40 eV He for increasing He fluences up to 1027 m−2 and flux of ∼1023 m−2 s−1. Surface wave-like structures appear in all samples at a fluence of ∼1026 m−2, whereas at the higher fluence of ∼1027 m−2 the material's surface is characterised by the presence of blisters and ablations. This suggests a new critical fluence for blistering in pure He plasma to be between 1026 and 1027 m−2. There is also a near-surface layer with a thickness of ∼200 nm that contains He bubbles of 2.20–2.70 nm in average size. Increasing Ta content leads to a small reduction in bubble size, and to clear reductions in the presence of blisters and ablations. Ta alloying can improve the hardness and yield strength and reduce the He diffusivity in the material. This therefore delays bubble formation and surface blistering and ablations that are affected by these mechanical properties. This was exemplified at the highest fluence by a large mitigation of surface material ablation.

KW - Electron microscopy

KW - Helium bubbles

KW - Image analysis

KW - Linear plasma device

KW - Surface blistering

KW - Tungsten alloys

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DO - 10.1016/j.fusengdes.2023.114061

M3 - Article

AN - SCOPUS:85177219666

SN - 0920-3796

VL - 197

JO - Fusion Engineering and Design

JF - Fusion Engineering and Design

M1 - 114061

ER -

Delayed surface degradation in W-Ta alloys at 400°C under high-fluence 40 eV He plasma exposure

Abstract

Bibliographical note

Keywords

ASJC Scopus subject areas

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