Author Contributions
Funding acquisition, A.L., C.L. and O.G.; investigation, T.K.; methodology, T.K., A.L. and G.M.; project administration, A.L. and G.M.; resources, A.L. and G.M.; supervision, A.L.; writing—original draft, T.K.; writing—review and editing, T.K., A.L., G.M., C.L. and O.G. All authors have read and agreed to the published version of the manuscript.
Funding
This work has been carried out within the framework of the EUROfusion Consortium, funded by the European Union via the Euratom Research and Training Programme (Grant Agreement No 101052200—EUROfusion). However, the views and opinions here expressed are those of the author(s) only and do not necessarily reflect those of the European Union or the European Commission. Neither the European Union nor the European Commission can be held responsible for them.
Data Availability Statement
All raw data are available on request from the author.
Acknowledgments
The authors would like to thank Marcin Rasinski and Leonardo Lealdini for assisting with the SEM and EDS, Ralf Laufs for his expertise in operating the spraying facilities, and the Zentralinstitut für Engineering, Elektronik und Analytik for the ICP OES analysis of the stockfeed powder.
Conflicts of Interest
The authors declare no conflict of interest.
References
- Matthews, G.F.; Beurskens, M.; Brezinsek, S.; Groth, M.; Joffrin, E.; Loving, A.; Kear, M.; Mayoral, M.-L.; Neu, R.; Prior, P.; et al. JET ITER-like wall—Overview and experimental programme. Phys. Scr. 2011, T145, 14001. [Google Scholar] [CrossRef]
- Tokunaga, K.; Yoshida, N.; Noda, N.; Kubota, Y.; Inagaki, S.; Sakamoto, R.; Sogabe, T.; Plöchl, L. Behavior of plasma-sprayed tungsten coatings on CFC and graphite under high heat load. J. Nucl. Mater. 1999, 266–269, 1224–1229. [Google Scholar] [CrossRef]
- Neu, R.; Maier, H.; Gauthier, E.; Greuner, H.; Hirai, T.; Hopf, C.; Likonen, J.; Maddaluno, G.; Matthews, G.F.; Mitteau, R.; et al. Investigation of tungsten coatings on graphite and CFC. Phys. Scr. 2007, T128, 150–156. [Google Scholar] [CrossRef]
- Kang, H.-K. Thermal properties of plasma-sprayed tungsten deposits. J. Nucl. Mater. 2004, 335, 1–4. [Google Scholar] [CrossRef]
- Hirai, T.; Bekris, N.; Coad, J.P.; Grisolia, C.; Linke, J.; Maier, H.; Matthews, G.F.; Philipps, V.; Wessel, E. Failure modes of vacuum plasma spray tungsten coating created on carbon fibre composites under thermal loads. J. Nucl. Mater. 2009, 392, 40–44. [Google Scholar] [CrossRef]
- Liu, X.; Yang, L.; Tamura, S.; Tokunaga, K.; Yoshida, N.; Noda, N.; Xu, Z. Thermal response of plasma sprayed tungsten coating to high heat flux. Fusion Eng. Des. 2004, 70, 341–349. [Google Scholar] [CrossRef]
- Tamura, S.; Liu, X.; Tokunaga, K.; Tsunekawa, Y.; Okumiya, M.; Noda, N.; Yoshida, N. High-temperature properties of joint interface of VPS-tungsten coated CFC. J. Nucl. Mater. 2004, 329–333, 711–716. [Google Scholar] [CrossRef]
- Vaßen, R. (Ed.) Jülich Thermal Spray Center-A New Research and Innovation Infrastructure of Forschungszentrum Jülich; Ceramic Forum International: Baden-Baden, Germany, 2020. [Google Scholar]
- Tejero-Martin, D.; Rezvani Rad, M.; McDonald, A.; Hussain, T. Beyond Traditional Coatings: A Review on Thermal-Sprayed Functional and Smart Coatings. J. Therm. Spray Technol. 2019, 28, 598–644. [Google Scholar] [CrossRef] [Green Version]
- Rasband, W.S. ImageJ; U.S. National Institutes of Health: Bethesda, MD, USA, 2011. Available online: http://imagej.nih.gov/ij (accessed on 29 January 2023).
- Renyi, A. (Ed.) On Measures of Entropy and Information, 1st ed.; Berkeley Symposium on Mathematical Statistics and Porbability: Berkeley, CA, USA, 1961. [Google Scholar]
- Russ, J.C.; Dehoff, R.T. Practical Stereology; Springer: Boston, MA, USA, 2000; ISBN 978-1-4613-5453-6. [Google Scholar]
- Guignard, A.; Mauer, G.; Vaßen, R.; Stöver, D. Deposition and Characteristics of Submicrometer-Structured Thermal Barrier Coatings by Suspension Plasma Spraying. J. Therm. Spray Technol. 2012, 21, 416–424. [Google Scholar] [CrossRef]
- Kovářík, O.; Haušild, P.; Siegl, J.; Chráska, T.; Matějíček, J.; Pala, Z.; Boulos, M. The influence of substrate temperature on properties of APS and VPS W coatings. Surf. Coat. Technol. 2015, 268, 7–14. [Google Scholar] [CrossRef]
- Matějíček, J.; Vilémová, M.; Nevrlá, B.; Kocmanová, L.; Veverka, J.; Halasová, M.; Hadraba, H. The influence of substrate temperature and spraying distance on the properties of plasma sprayed tungsten and steel coatings deposited in a shrouding chamber. Surf. Coat. Technol. 2017, 318, 217–223. [Google Scholar] [CrossRef]
- Fukuda, M.; Hasegawa, A.; Nogami, S. Thermal properties of pure tungsten and its alloys for fusion applications. Fusion Eng. Des. 2018, 132, 1–6. [Google Scholar] [CrossRef]
- Bolt, H.; Barabash, V.; Krauss, W.; Linke, J.; Neu, R.; Suzuki, S.; Yoshida, N.; Team, A.U. Materials for the plasma-facing components of fusion reactors. J. Nucl. Mater. 2004, 329–333, 66–73. [Google Scholar] [CrossRef] [Green Version]
- Boire-Lavigne, S.; Moreau, C.; Saint-Jacques, R.G. The relationship between the microstructure and thermal diffusivity of plasma-sprayed tungsten coatings. J. Therm. Spray Technol. 1995, 4, 261–267. [Google Scholar] [CrossRef]
- Fauchais, P. Understanding plasma spraying. J. Phys. D Appl. Phys. 2004, 37, R86–R108. [Google Scholar] [CrossRef]
- Greuner, H.; Bolt, H.; Böswirth, B.; Lindig, S.; Kühnlein, W.; Huber, T.; Sato, K.; Suzuki, S. Vacuum plasma-sprayed tungsten on EUROFER and 316L: Results of characterisation and thermal loading tests. Fusion Eng. Des. 2005, 75–79, 333–338. [Google Scholar] [CrossRef]
- Niu, Y.; Zheng, X.; Ji, H.; Qi, L.; Ding, C.; Chen, J.; Luo, G. Microstructure and thermal property of tungsten coatings prepared by vacuum plasma spraying technology. Fusion Eng. Des. 2010, 85, 1521–1526. [Google Scholar] [CrossRef]
- Shaw, L.L.; Goberman, D.; Ren, R.; Gell, M.; Jiang, S.; Wang, Y.; Xiao, T.; Strutt, P.R. The dependency of microstructure and properties of nanostructured coatings on plasma spray conditions. Surf. Coat. Technol. 2000, 130, 1–8. [Google Scholar] [CrossRef]
- Paradis, P.-F.; Ishikawa, T.; Yoda, S. Viscosity of liquid undercooled tungsten. J. Appl. Phys. 2005, 97, 106101. [Google Scholar] [CrossRef]
- Gottstein, G. Physical Foundations of Materials Science; Springer: Berlin/Heidelberg, Germany, 2004; ISBN 978-3-642-07271-0. [Google Scholar]
- Smirnov, R.D.; Krasheninnikov, S.I.; Pigarov, A.Y.; Rognlien, T.D. Tungsten dust impact on ITER-like plasma edge. Phys. Plasmas 2015, 22, 12506. [Google Scholar] [CrossRef]
- Dutta, B.N.; Dayal, B. Lattice Constants and Thermal Expansion of Palladium and Tungsten up to 878 °C by X-ray Method. Phys. Stat. Sol. (B) 1963, 3, 2253–2259. [Google Scholar] [CrossRef]
- Pintsuk, G.; Compan, J.; Linke, J.; Majerus, P.; Peacock, A.; Pitzer, D.; Rödig, M. Mechanical and thermo-physical characterization of the carbon fibre composite NB31. Phys. Scr. 2007, T128, 66–71. [Google Scholar] [CrossRef]
Figure 1.
Schematic of the plasma spray process.
Figure 2.
From left to right: sample 1, 2, and 3.
Figure 3.
SEM images of the cross sections of the coatings, in which the porosity and microstructure are clearly visible. (a) Inter splat voids observed in sample 1; (b) Cross section of sample 7 with reduced porosity.
Figure 4.
Image of the cross sections, with clearly visible grain structures close to the substrate observed in sample 4.
Figure 5.
(
a) CoNiCrAl inclusions close to the CFC substrate of sample 7. Tungsten appears as light grey, inclusions as dark grey; (
b) EDS map spectrum of
Figure 5b. The dominant tungsten peak is accompanied by several Co, Ni, Cr, and Al peaks.
Figure 6.
(a) EDS map of a single particle. Tungsten is colored light blue; oxygen is colored red; (b) SEM image of a cross section of the oxidized interface area; the white matter is tungsten oxide at the tungsten–CFC interface.
Figure 7.
Comparison of the plasma jet (a) before and (b) after adjustments of the carrier gas flow.
Figure 8.
(a) Overspray particles observed on the surface of sample 3; (b) overspray particles, marked by black circles, seen in the cross section of sample 3.
Figure 9.
Infiltration of a coating into the substrate’s surface, here observed in sample 7.
Figure 10.
Delamination close to the edge of sample 1 (a) and in the vicinity of surface cracks in sample 6 (b).
Table 1.
Spray parameters varied for the coating of samples.
Campaign # * | Sample # * | Nozzle Diameter [mm] | Carrier Gas Flow [slpm **] | Scanning Speed [mm/s] | Spray Distance [mm] |
---|
1 | 1 | 7 | 1.2 | 440 | 300 |
1 | 2 | 8 | 1.2 | 440 | 300 |
1 | 3 | 7 | 1.2 | 220 | 300 |
2 | 4 | 8 | 0.9 | 440 | 300 |
2 | 5 | 8 | 0.9 | 220 | 300 |
3 | 6 | 8 | 0.9 | 220 | 275 |
3 | 7 | 8 | 0.9 | 220 | 250 |
Table 2.
Spray parameters.
Parameter | Value |
---|
Plasma gas ratio | 3.48 (sl Ar)/(sl H) |
Plasma gas flow rate | 51.5 slpm |
Powder feed rate | 215 g/min |
Process pressure | 60 mbar |
Path offset | 4 mm |
Torch power | 50 kW |
Table 3.
Overspray volume fraction of the samples.
Campaign # * | Sample # * | | Overspray [Vol-%] |
---|
1 | 1 | Bright side | 7.4 |
Dark side | 10.6 |
2 | Bright side | 1.6 |
Dark side | 6.2 |
3 | Bright side | 4.7 |
Dark side | 10.4 |
2 | 4 | - | 2.3 |
5 | - | 2.2 |
3 | 6 | - | 1.0 |
7 | - | 1.5 |
Table 4.
Volumetric porosities.
Sample # * | Porosity [vol-%] |
---|
1 | 10.3 |
2 | 9.9 |
3 | 8.6 |
4 | 4.9 |
5 | 5.2 |
6 | 3.6 |
7 | 3.5 |
Table 5.
Impurity content of the powder feedstock.
Element | Weight Percent |
---|
Si | 0.1602 |
Pb | 0.0071 |
As | 0.0033 |
Fe | 0.0062 |
Ni | 0.0099 |
Mo | 0.0034 |
Cd | 0.0021 |
O | 0.135 |
Table 6.
Average thickness of the coatings.
Sample # * | Thickness [µm] |
---|
1 | 133 |
2 | 117 |
3 | 102 |
4 | 101 |
5 | 112 |
6 | 114 |
7 | 122 |
| Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content. |
© 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).