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Metals
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Tungsten and Tungsten Alloys
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Tungsten and Tungsten Alloys

A special issue of Metals (ISSN 2075-4701). This special issue belongs to the section "Metal Casting, Forming and Heat Treatment".

Deadline for manuscript submissions: 30 September 2024 | Viewed by 13331

Special Issue Editor

Prof. Dr. Andrey M. Litnovsky

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Guest Editor
1. Senior researcher at the Forschungszentrum Jülich GmbH, Wilhelm-Johnen-Str. D-52425 Jülich, Germany
2. Teaching Professor at the National Research Nuclear University MEPhI, Moscow, Russian Federation, Kashirskoe sh., 31, 115409 Moscow, Russia
Interests: refractory metals; self-passivating alloys; single crystals; metallic mirrors; plasma-facing materials; materials for extreme environments; mechanical alloying; field-assisted sintering technology; materials modeling; materials engineering; surface diagnostics; plasma–surface interactions and plasma diagnostics

Special Issue Information

Dear Colleagues,

Tungsten, one of the most remarkable refractory materials, has attracted the attention of scientists and engineers for the last two centuries. The technological boom we are currently witnessing has significantly advanced our knowledge and understanding of this extraordinary metal. The application range of tungsten has significantly expanded, and now we can see this material applied in automotive and lighting industries, shipbuilding, aerospace, medicine, heavy machinery, mining, and many other areas of our lives.

Besides the ultimate advantages of tungsten (e.g., the highest melting point among all metals, high thermal conductivity at elevated temperatures, heavy mass, relatively low induced activation), there are some properties which until now had limited the potential application of this metal. These properties, such as the intrinsic brittleness of tungsten and its vulnerability to oxidation, were formerly accepted as given by nature. Presently, however, inspired by the unprecedented technological development, modern machinery, highly sophisticated modeling, advanced engineering, and fantastic analytic tools, scientists and engineers “dare” to change these properties as well.

One of the most prominent examples of these developments comes from the area of the controlled fusion, the energy source of the stars—one of the most challenging environments imaginable so far. Here, tungsten has found its place as the material protecting the interior of the power station from the hot fusion plasma. New advanced technology, nano-engineering, and sophisticated alloying have helped to turn the disadvantageous properties of tungsten back and to attain the qualities of this material which it had never possessed before. In this Special Issue devoted to tungsten and tungsten alloys, we will see the results of these challenging, but remarkable and fascinating, transformations of tungsten.

I would like to take this opportunity to welcome you to this Special Issue of Metals devoted to tungsten and tungsten alloys. Please enjoy reading the selected articles devoted to the recent developments in the science, technology, and engineering of tungsten. I am also kindly inviting you to share your own research by contributing with your own manuscript to this Special Issue.

I am looking forward to hearing from you.

Prof. Dr. Andrey M. Litnovsky
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Metals is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Tungsten
  • Tungsten alloys
  • High-entropy alloys
  • Smart materials
  • Corrosion
  • Materials modeling
  • Fusion
  • Plasma–material interaction
  • Field-assisted sintering technology
  • Hot isostatic pressing
  • Mechanical alloying

Published Papers (7 papers)

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Research

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13 pages, 8567 KiB  
Article
Innovative Tungsten Coatings for an Application in Modern and Future Fusion Devices
by Tom Keller, Andrey Litnovsky, Georg Mauer, Christian Linsmeier and Olivier Guillon
Metals 2023, 13(3), 531; https://0-doi-org.brum.beds.ac.uk/10.3390/met13030531 - 06 Mar 2023
Cited by 2 | Viewed by 1204
Abstract
Tungsten is foreseen presently as the plasma-facing material for divertors in fusion power plants. In order to achieve durable operation of divertors of current fusion reactors, an efficient way of maintaining the divertor functionality is needed. A system capable of in situ tungsten [...] Read more.
Tungsten is foreseen presently as the plasma-facing material for divertors in fusion power plants. In order to achieve durable operation of divertors of current fusion reactors, an efficient way of maintaining the divertor functionality is needed. A system capable of in situ tungsten coating of the divertor via low-pressure plasma spraying was proposed to maintain the divertor integrity. In this work, tungsten was deposited on NB31 carbon fibre composite substrates using the low-pressure plasma spraying technology to evaluate the feasibility of this technique. The thickness, porosity, composition, adhesion, and microstructure of the coatings were investigated by scanning electron microscopy image analysis and energy dispersive spectroscopy. Based on the initial results, the spray parameters were iteratively improved in a campaign-based study. The coatings exhibited improving properties through an adjusting of the carrier gas flow, the scanning speed, and the spray distance. By lowering the carrier gas flow, the porosity of the coatings was reduced, resulting in coatings of 98% bulk density. Adjusting the carrier gas flow reduced the amount of semi-molten particles in the coatings significantly. A decrease in both scanning speed and spray distance increased the substrate’s temperature, which led to better adhesion and porosity. Full article
(This article belongs to the Special Issue Tungsten and Tungsten Alloys)
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12 pages, 5322 KiB  
Article
Effect of Pressure on Densification and Microstructure of W-Cr-Y-Zr Alloy during SPS Consolidated at 1000 °C
by Huijuan Zhu, Xiaoyue Tan, Qingbo Tu, Yiran Mao, Zelin Shu, Jie Chen, Laima Luo, Andrey Litnovsky, Jan Willem Coenen, Christian Linsmeier and Yucheng Wu
Metals 2022, 12(9), 1437; https://0-doi-org.brum.beds.ac.uk/10.3390/met12091437 - 29 Aug 2022
Viewed by 1219
Abstract
During the spark plasma sintering (SPS) consolidation process, the pressure affects the densification and microstructure evolution of the sintered body. In this paper, the W-Cr-Y-Zr alloy powder was heated to 1000 °C under different applied pressure conditions using spark plasma sintering process, and [...] Read more.
During the spark plasma sintering (SPS) consolidation process, the pressure affects the densification and microstructure evolution of the sintered body. In this paper, the W-Cr-Y-Zr alloy powder was heated to 1000 °C under different applied pressure conditions using spark plasma sintering process, and the effect of pressure on the densification process and microstructure was analyzed. Due to the low sintering temperature, the crystalline size of all the produced W-Cr-Y-Zr alloy is less than 10 nm, which is close to that of the original powders. Cr-rich phase can be detected in the sintered samples due to spinodal decomposition. It is found in this work that the external pressure will increase the contact area between the powder particles, resulting in a higher local pressure at the particle contact, which promotes densification by sliding between the particles under the condition of softening of the particle surface. Additionally, according to the viscous flow theory, the viscous flow activation energy decreases with the increase of pressure. This is because the pressure provides additional driving force to the powder viscous flow process and accelerates the powder shrinkage. Full article
(This article belongs to the Special Issue Tungsten and Tungsten Alloys)
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22 pages, 5880 KiB  
Article
Microstructural Transitions during Powder Metallurgical Processing of Solute Stabilized Nanostructured Tungsten Alloys
by Nicholas Olynik, Bin Cheng, David J. Sprouster, Chad M. Parish and Jason R. Trelewicz
Metals 2022, 12(1), 159; https://0-doi-org.brum.beds.ac.uk/10.3390/met12010159 - 15 Jan 2022
Cited by 5 | Viewed by 2711
Abstract
Exploiting grain boundary engineering in the design of alloys for extreme environments provides a promising pathway for enhancing performance relative to coarse-grained counterparts. Due to its attractive properties as a plasma facing material for fusion devices, tungsten presents an opportunity to exploit this [...] Read more.
Exploiting grain boundary engineering in the design of alloys for extreme environments provides a promising pathway for enhancing performance relative to coarse-grained counterparts. Due to its attractive properties as a plasma facing material for fusion devices, tungsten presents an opportunity to exploit this approach in addressing the significant materials challenges imposed by the fusion environment. Here, we employ a ternary alloy design approach for stabilizing W against recrystallization and grain growth while simultaneously enhancing its manufacturability through powder metallurgical processing. Mechanical alloying and grain refinement in W-10 at.% Ti-(10,20) at.% Cr alloys are accomplished through high-energy ball milling with transitions in the microstructure mapped as a function of milling time. We demonstrate the multi-modal nature of the resulting nanocrystalline grain structure and its stability up to 1300 °C with the coarser grain size population correlated to transitions in crystallographic texture that result from the preferred slip systems in BCC W. Field-assisted sintering is employed to consolidate the alloy powders into bulk samples, which, due to the deliberately designed compositional features, are shown to retain ultrafine grain structures despite the presence of minor carbides formed during sintering due to carbon impurities in the ball-milled powders. Full article
(This article belongs to the Special Issue Tungsten and Tungsten Alloys)
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15 pages, 9136 KiB  
Article
Brazing Tungsten/Tantalum/RAFM Steel Joint for DEMO by Fully Reduced Activation Brazing Alloy 48Ti-48Zr-4Be
by Diana Bachurina, Alexey Suchkov, Julia Gurova, Vladislav Kliucharev, Vladimir Vorkel, Maxim Savelyev, Pavel Somov and Oleg Sevryukov
Metals 2021, 11(9), 1417; https://0-doi-org.brum.beds.ac.uk/10.3390/met11091417 - 07 Sep 2021
Cited by 5 | Viewed by 1975
Abstract
To create a DEMO reactor, it is necessary to develop high-quality technology to join tungsten with reduced-activation ferritic-martensitic (RAFM) steel (Rusfer, Eurofer, CLF-1, etc.). Difficulties arise in their direct connection due to the large difference in the coefficient of thermal expansion (CTE). To [...] Read more.
To create a DEMO reactor, it is necessary to develop high-quality technology to join tungsten with reduced-activation ferritic-martensitic (RAFM) steel (Rusfer, Eurofer, CLF-1, etc.). Difficulties arise in their direct connection due to the large difference in the coefficient of thermal expansion (CTE). To suppress the difference of CTE, intermediate interlayers are usually used, such as vanadium or tantalum, and brazing is a prospective technology to conduct the joining. The vast majority of works represent copper- or nickel-based brazing alloys, but their applicability is under significant discussion due to their activation properties. That is why, in this work, fully reduced activation 48Ti-48Zr-4Be wt.% brazing alloy was used. The following joint was made: Rusfer steel/48Ti-48Zr-4Be/Ta/48Ti-48Zr-4Be/W. The brazing was successfully carried out under a mode providing thermal heat treatment of Rusfer. Through EDS and EBSD analysis, the microstructure of the joint was determined. Shear strength of the as-joined composition was measured as 127 ± 20 MPa. The joint endured 200 thermocycles in the temperature range between 300–600 °C, but the fillet regions degraded. Full article
(This article belongs to the Special Issue Tungsten and Tungsten Alloys)
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16 pages, 21226 KiB  
Article
Improving the W Coating Uniformity by a COMSOL Model-Based CVD Parameter Study for Denser Wf/W Composites
by Leonard Raumann, Jan Willem Coenen, Johann Riesch, Yiran Mao, Daniel Schwalenberg, Hanns Gietl, Christian Linsmeier and Olivier Guillon
Metals 2021, 11(7), 1089; https://0-doi-org.brum.beds.ac.uk/10.3390/met11071089 - 08 Jul 2021
Cited by 7 | Viewed by 3154
Abstract
Tungsten (W) has the unique combination of excellent thermal properties, low sputter yield, low hydrogen retention, and acceptable activation. Therefore, W is presently the main candidate for the first wall and armor material for future fusion devices. However, its intrinsic brittleness and its [...] Read more.
Tungsten (W) has the unique combination of excellent thermal properties, low sputter yield, low hydrogen retention, and acceptable activation. Therefore, W is presently the main candidate for the first wall and armor material for future fusion devices. However, its intrinsic brittleness and its embrittlement during operation bears the risk of a sudden and catastrophic component failure. As a countermeasure, tungsten fiber-reinforced tungsten (Wf/W) composites exhibiting extrinsic toughening are being developed. A possible Wf/W production route is chemical vapor deposition (CVD) by reducing WF6 with H2 on heated W fabrics. The challenge here is that the growing CVD-W can seal gaseous domains leading to strength reducing pores. In previous work, CVD models for Wf/W synthesis were developed with COMSOL Multiphysics and validated experimentally. In the present article, these models were applied to conduct a parameter study to optimize the coating uniformity, the relative density, the WF6 demand, and the process time. A low temperature and a low total pressure increase the process time, but in return lead to very uniform W layers at the micro and macro scales and thus to an optimized relative density of the Wf/W composite. High H2 and low WF6 gas flow rates lead to a slightly shorter process time and an improved coating uniformity as long as WF6 is not depleted, which can be avoided by applying the presented reactor model. Full article
(This article belongs to the Special Issue Tungsten and Tungsten Alloys)
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11 pages, 4799 KiB  
Article
Characteristics of Microstructure Evolution during FAST Joining of the Tungsten Foil Laminate
by Xiaoyue Tan, Wujie Wang, Xiang Chen, Yiran Mao, Andrey Litnovsky, Felix Klein, Pawel Bittner, Jan Willem Coenen, Christian Linsmeier, Jiaqin Liu, Laima Luo and Yucheng Wu
Metals 2021, 11(6), 886; https://0-doi-org.brum.beds.ac.uk/10.3390/met11060886 - 28 May 2021
Cited by 4 | Viewed by 1984
Abstract
The tungsten (W) foil laminate is an advanced material concept developed as a solution for the low temperature brittleness of W. However, the deformed W foils inevitably undergo microstructure deterioration (crystallization) during the joining process at a high temperature. In this work, joining [...] Read more.
The tungsten (W) foil laminate is an advanced material concept developed as a solution for the low temperature brittleness of W. However, the deformed W foils inevitably undergo microstructure deterioration (crystallization) during the joining process at a high temperature. In this work, joining of the W foil laminate was carried out in a field-assisted sintering technology (FAST) apparatus. The joining temperature was optimized by varying the temperature from 600 to 1400 °C. The critical current for mitigating the microstructure deterioration of the deformed W foil was evaluated by changing the sample size. It is found that the optimal joining temperature is 1200 °C and the critical current density is below 418 A/cm2. According to an optimized FAST joining process, the W foil laminate with a low microstructure deterioration and good interfacial bonding can be obtained. After analyzing these current profiles, it was evident that the high current density (sharp peak current) is the reason for the significant microstructure deterioration. An effective approach of using an artificial operation mode was proposed to avoid the sharp peak current. This study provides the fundamental knowledge of FAST principal parameters for producing advanced materials. Full article
(This article belongs to the Special Issue Tungsten and Tungsten Alloys)
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18 pages, 2179 KiB  
Review
Advanced Self-Passivating Alloys for an Application under Extreme Conditions
by Andrey Litnovsky, Felix Klein, Xiaoyue Tan, Janina Ertmer, Jan W. Coenen, Christian Linsmeier, Jesus Gonzalez-Julian, Martin Bram, Ivan Povstugar, Thomas Morgan, Yury M. Gasparyan, Alexey Suchkov, Diana Bachurina, Duc Nguyen-Manh, Mark Gilbert, Damian Sobieraj, Jan S. Wróbel, Elena Tejado, Jiri Matejicek, Henning Zoz, Hans Ulrich Benz, Pawel Bittner and Anicha Reubanadd Show full author list remove Hide full author list
Metals 2021, 11(8), 1255; https://0-doi-org.brum.beds.ac.uk/10.3390/met11081255 - 09 Aug 2021
Cited by 12 | Viewed by 2587
Abstract
Self-passivating Metal Alloys with Reduced Thermo-oxidation (SMART) are under development for the primary application as plasma-facing materials for the first wall in a fusion DEMOnstration power plant (DEMO). SMART materials must combine suppressed oxidation in case of an accident and an acceptable plasma [...] Read more.
Self-passivating Metal Alloys with Reduced Thermo-oxidation (SMART) are under development for the primary application as plasma-facing materials for the first wall in a fusion DEMOnstration power plant (DEMO). SMART materials must combine suppressed oxidation in case of an accident and an acceptable plasma performance during the regular operation of the future power plant. Modern SMART materials contain chromium as a passivating element, yttrium as an active element and a tungsten base matrix. An overview of the research and development program on SMART materials is presented and all major areas of the structured R&D are explained. Attaining desired performance under accident and regular plasma conditions are vital elements of an R&D program addressing the viability of the entire concept. An impressive more than 104-fold suppression of oxidation, accompanied with more than 40-fold suppression of sublimation of tungsten oxide, was attained during an experimentally reproduced accident event with a duration of 10 days. The sputtering resistance under DEMO-relevant plasma conditions of SMART materials and pure tungsten was identical for conditions corresponding to nearly 20 days of continuous DEMO operation. Fundamental understanding of physics processes undergone in the SMART material is gained via fundamental studies comprising dedicated modeling and experiments. The important role of yttrium, stabilizing the SMART alloy microstructure and improving self-passivating behavior, is under investigation. Activities toward industrial up-scale have begun, comprising the first mechanical alloying with an industrial partner and the sintering of a bulk SMART alloy sample with dimensions of 100 mm × 100 mm × 7 mm using an industrial facility. These achievements open the way to further expansion of the SMART technology toward its application in fusion and potentially in other renewable energy sources such as concentrated solar power stations. Full article
(This article belongs to the Special Issue Tungsten and Tungsten Alloys)
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