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(Left) Schematic of a tokamak fusion reactor [4]. (Right) Cross section of ITER vacuum vessel and the plasma facing components (courtesy of ITER).
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![Figure 1. (Left) Schematic of a tokamak fusion reactor [4]. (Right)...](publication/337835451/figure/fig1/AS:834189687529472@1575897728075/Left-Schematic-of-a-tokamak-fusion-reactor-4-Right-Cross-section-of-ITER-vacuum_Q320.jpg)
Harnessing nuclear fusion is a challenging task, in particular because of the demands put on the used materials. In tokamaks, future energy sources, the inner-most chambers are to be coated with dense coatings of W, or W-Cr-based alloys. So far, the attempts for such coatings formation by other methods failed due to oxidation, high porosity, insuff...
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... represent an inherently safe and relatively cheap energy technology (considering the abundance of fuel) that produces radioactive waste with relatively short half-life. An illustration of a tokamak vessel is provided in Figure 1. In these reactors, the materials will be subjected to extreme thermo-mechanical or radiation conditions and required to sustain functionality for prolonged periods of time. ...
Context 2
... and its alloys have many favorable properties, such as high melting point (T m = 3422 • C for pure W), thermal conductivity superior to the structural steels, low erosion (i.e., high energy threshold to suffer from sputtering) as well as low tritium retention. Understandably, pure tungsten is therefore intended to be applied in the lower part of the reactor vessel, so called divertor region ( Figure 1 shows such solution for the tokamak ITER), while tungsten alloys are planned for the remaining surfaces of the so called first wall. Unfortunately, the processing of PFCs is complicated by tungsten's inherent brittleness (high ductile-to-brittle transition temperature), poor weldability and machinability, thermal expansion coefficient mismatch with the structural steels, or susceptibility to grain growth and to oxidation above 500 • C. ...
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Citations
... Moreover, free-standing 3D structures can serve as current collectors [56] or heat sinks [57], while doping Cu or W phases into a primary metal matrix can enhance thermal properties [47,48]. Several additive and subtractive manufacturing methods, such as photolithography, plasma etching, wet etching, dry reactive etching, ion beam lithography, machining, physical vapor deposition, chemical vapor deposition, powder metallurgy, laser melting, and combinations of these methods have been used to fabricate these two transition metals or dope these materials into another material [38,48,[58][59][60][61][62][63][64][65]. ...
... Cu has high electrical conductivity and thermal conductivity, making it a suitable candidate for printed electronics [1][2][3][4][5], catalysis [6][7][8][9][10][11][12], sensors [13][14][15], two-phase heat transfer [16], current collectors for batteries [17], solar cells [18][19][20][21][22], photo-detectors [23], and heat sinks [24][25][26]. Likewise, W also has good electrical and thermal conductivities [27], a low coefficient of thermal expansion [27], good chemical and corrosion resistance [27,28], high-temperature stability [27], and hardness, making it suitable for interconnects [29], diffusion barriers [29], solar applications [30][31][32], catalysis [33][34][35][36], armors [37,38], nuclear applications [39], and other high-temperature applications [40,41]. ...
Copper (Cu) and tungsten (W) possess exceptional electrical and thermal conductivity properties, making them suitable candidates for applications such as interconnects and thermal conductivity enhancements. Solution-based additive manufacturing (SBAM) offers unique advantages, including patterning capabilities, cost-effectiveness, and scalability among the various methods for manufacturing Cu and W-based films and structures. In particular, SBAM material jetting techniques , such as inkjet printing (IJP), direct ink writing (DIW), and aerosol jet printing (AJP), present a promising approach for design freedom, low material wastes, and versatility as either stand-alone printers or integrated with powder bed-based metal additive manufacturing (MAM). Thus, this review summarizes recent advancements in solution-processed Cu and W, focusing on IJP, DIW, and AJP techniques. The discussion encompasses general aspects, current status, challenges, and recent research highlights. Furthermore, this paper addresses integrating material jetting techniques with powder bed-based MAM to fabricate functional alloys and multi-material structures. Finally, the factors influencing large-scale fabrication and potential prospects in this area are explored.
... The mean value of gray correlation coefficient (GRC) of different dimensions of each factor is taken as the result of quantitative expression of the correlation degree between the reference series and the comparison series, and the result of ranking them is used as the gray relationship grade (GRG) [23][24][25][26][27]. Step 7: Calculation of the grey-fuzzy relational grade (GFRG) The trigonometric function is selected as a fuzzy system of the degree of dependence function. ...
... The presence of Nb and Cu causes the cladding layer to form a hard phase, which increases the hardness. The phenomenon of a sharp increase and then a sharp decrease in hardness in the heat affected zone occurs because of the dilution and remelting of the cladding layer [27]. ...
Laser cladding is a new surface treatment technology that is widely used for surface modification of metal parts, and the high quality of the surface geometry of the cladding layer can save a lot of resources for the company. To obtain high quality of the clad layer, the L25 Taguchi experiment of laser cladding process parameters was designed to laser-clad a single 15-5PH layer on the surface of 45# steel; the effect of process parameters on the surface morphology and dilution rate of the coating was determined by ANOVA; the optimal combination of process parameters was obtained by combining gray correlation and fuzzy inference system method. The ANOVA results show that the scanning speed among the laser cladding process parameters plays a key role in obtaining the best superposition of the four geometrical features of the cladding layer simultaneously; With the optimization objectives of larger clad width and height, smaller clad depth, and 30% dilution rate, the optimal combination of process parameters, (P: 600W, V: 500mm/min, F: 1.3r/min), obtained based on the Gray-fuzzy Taguchi Approach, was compared and analyzed to find a significant improvement in the geometric quality characteristics of the optimized clad layer. The analysis of microstructure, physical phase, hardness, wear resistance and corrosion resistance showed that the 15-5PH clad layer was able to effectively enhance the surface properties of the 12Cr13 substrate. The optimization method proposed in this study can solve the problem of parameter optimization in the industrial multi-parameter and multi-response processes.
... Similar safety considerations for W led to the development of self-passivating tungsten alloys by adding various oxide-forming elements that cause a formation of a protective oxide scale when exposed to air. For example, a significant improvement in oxidation has been achieved with the W-Cr-Y and W-Cr-Ti systems due to cold-spraying technology, when their oxidation behavior was improved by the addition of Cr content [56]. All coatings exhibited high hardness levels, good interface quality, and a potential for formation of stable Cr 2 WO x phases. ...
Studies on the erosion products of tungsten plasma-facing components (films, surfaces, and dust) for thermonuclear fusion reactors by spectroscopic methods are considered and compared with those of carbon deposits. The latter includes: carbon–deuterium CDx (x ~ 0.5) smooth films deposited at the vacuum chamber during the erosion of the graphite limiters in the T-10 tokamak and mixed CHx-Me films (Me = W, Fe, etc.) formed by irradiating a tungsten target with an intense H-plasma flux in a QSPA-T plasma accelerator. It is shown that the formerly developed technique for studying CDx films with 15 methods, including spectroscopic methods, such as XPS, TDS, EPR, Raman, and FT-IR, is universal and can be supplemented by a number of new methods for tungsten materials, including in situ analysis of the MAPP type using XPS, SEM, TEM, and probe methods, and nuclear reaction method. In addition, the analysis of the fractality of the CDx films using SAXS + WAXS is compared with the analysis of the fractal structures formed on tungsten and carbon surfaces under the action of high-intensity plasma fluxes. A comparative analysis of spectroscopic studies on carbon and tungsten deposits makes it possible to identify the problems of the safe operation of thermonuclear fusion reactors.
... Metallographic cross-sections of the coatings created by the separate feeding of coarse W and Ta, where 2 mm-thick coatings were produced from the powder, are shown in the microscopic photographs in Figure 1. All of the coatings exhibit little porosity and a growing W volume fraction with an increasing W powder percent, as can be seen from the images [8,9]. Cold spray coatings with varying amounts of tungsten and tantalum, as seen in metallographic cross-sections [8]. ...
In this paper, the improvement of the characteristics of different steels that are subjected to extreme operating conditions, including the steels used in the manufacture of various military components, the AISI 52100, the manufacture of bearings, and other types of parts that are also subjected to severe operating conditions were analyzed regarding cold spraying, which uses different types of powders to increase the performance of the materials. The cold, thermal spraying technology “Cold Spray” is a method of processing particles in a solid state. Thermal spraying, based on the dynamic increase in gas acceleration up to supersonic speeds, leads to the obtainment of high kinetic energies, and the accelerated particles are deposited at values that are below their melting point. Research conducted through cold spray technology has seen a significant improvement in material properties; when processing the particles in a solid state, they adhere to the surface instead of eroding it. Cold spraying has proven to be an effective technique for improving material properties, as confirmed by its integration into different fields and industries, becoming competitive by being the only method for depositing particles below their melting point.
... Moreover, relatively complicated manufacturing routes to produce tungsten in required dimensions are necessary. Thermal spray or cold spray offer an alternative manufacturing technology to cover relatively large and geometrically complex shapes by W [5], with the potential to produce multiphase, multilayered or graded coatings to tackle the discussed issues [6]. During high-temperature thermal spraying, oxidation represents a major problem, vacuum systems [7,8] or systems using gas shrouding [9,10] are therefore used. ...
... Nevertheless, it can be concluded that oxygen was preferably concentrated close to the particle surface. Moreover, the grain boundaries exposed by the inter-granular fracture also showed increased oxygen concentration (5). The oxygen can move to the grain boundaries during solidification and grain growth. ...
Fracture toughness and fatigue crack growth rates of free-standing thick W deposits produced in a protective atmosphere using radio frequency inductively-coupled plasma process were investigated. Stress-strain behavior of the deposits was studied using four-point bending and their fracture toughness was estimated from three-point bending following the ASTM E1820 standard. The fatigue crack growth rates were measured in symmetrical bending using a resonance approach. The results were compared with commercially available bulk tungsten prepared by powder metallurgy that served as a reference. The results showed that the deposits had significantly lower stress-strain properties: the elastic modulus and tensile strength ranged from 30% to 50% of the reference bulk values. The crack growth rate tests together with fractographic analysis suggested that a static failure by inter-granular decohesion predetermines the fatigue properties of the deposits and causes high slopes of the corresponding fatigue crack growth rate curves. Contrary to this, the reference sheet failed trans-granularly. The inter-granular failure mode of the deposits was caused by grain boundary embrittlement, a phenomenon probably related to oxides. The lowest obtained oxygen concentration in deposit was nearly by two orders of magnitude higher, than in reference sheet. The distribution of oxygen was studied by TEM and the amorphous and crystalline oxide phases were identified at splat interfaces. The presence of oxygen in the deposits produced by the inherently non-oxidizing RF technology calls for control of oxygen content in the feedstock powder. The performed characterization provided baseline data of mechanical and fatigue properties of RF plasma sprayed tungsten.
... However, its basic principles (that is, deposition in a solid state condition of the materials) distinguish the method from its high thermal input counterparts and provide the deposits with unique properties [4][5][6][7]. These range from deposition of pure metals without oxidation or phase changes [8][9][10][11], to negligible porosity levels, superior adhesion, excellent machinability, or, given the compressive stresses, to the potential to deposit extremely thick coatings (limitless, in fact). In particular, the latter two allow application of cold spray in restoration/refurbishment of damaged or worn components (aeronautics, automotive), thereby leading to substantial financial savings in these sectors [12,13]. ...
A methodology that allows joint determination of fundamental engineering properties of materials/components vital to their efficient design and a safe service lifetime operation is presented. Using a combination of recently developed techniques, a simultaneous assessment of mechanical properties, fatigue crack growth rates, as well as fracture toughness is described. All these are performed using unified-geometry samples that are simple and easy to produce. The mechanical properties are measured in tensile and compressive modes, while the combination of developed bending test methods (quasi-static four-point bending and fatigue bending) enables to cover the fatigue loading from very low loads corresponding to crack propagation threshold values up to the high loads corresponding to a static fracture of the fracture toughness test. To validate and complement the bending data, additional resonant ultrasonic measurements of the corresponding properties are carried out. The methodology is partially suitable for testing of cold sprayed deposits. Therefore, Al, Cu, Ni and Ti deposits are tested and compared to cold-rolled sheet reference samples. The results are quantified in the form of NASGRO equation, widely used in software for prediction of fatigue lives. Together, the obtained set of data may be readily used for modeling of the performance of cold sprayed parts. Finally, fractographic analysis of the failed specimens is presented to describe the mechanisms leading to failure. At low loads, the reference sheets and the cold sprayed deposits exhibit similar behavior, where the cracks grow in a trans-crystalline mode without any significant interaction with deposit particle boundaries. Contrary to this, the behavior changes at higher loads: the particle interfaces in the cold sprayed deposits become the weak point and the cracks grow at high rates by inter-particle decohesion, while the sheet materials generally fail by striation mechanism at much lower rates.
... Alternatively, this issue can be eliminated by spraying in inert atmosphere [22] or vacuum [9,13]; however, such setup demands using deposition chamber with limited volume, is rather expensive and applicable only for torches with moderate power and thus limited material throughput. Application of cold spraying on tungsten powders, bringing the promise of high density and oxide-free coatings, is in its early stages [23]. Various post-treatment techniques have been applied to improve the thermal conductivity of plasma sprayed W-based coatings, such as annealing [12], laser remelting [24] or HIPping [25]. ...
Tungsten is currently the main candidate plasma-facing material for future fusion reactors. For large part of the inner surface, the first wall, it is foreseen to be joined to steel-based structural components. Tungsten-steel composites and graded layers can serve as joining interlayers to reduce the stress concentration at the interface, originating from the different thermal and mechanical properties of tungsten and steel and temperature excursions. Plasma spraying is among the prospective technologies to fabricate such layers.
In this work, tungsten-steel composites and functionally graded materials (FGMs) were prepared using high power hybrid water-argon plasma spraying system. Argon shrouding was applied to reduce the extent of in-flight oxidation of the molten particles. First, steel and tungsten coatings were prepared at a variety of process parameters and subjected to comprehensive characterization. Based on this, optimized parameters were selected for preparation of the composites and FGMs, and their structure, composition and thermal properties were characterized. Finally, hot isostatic pressing (HIP) was explored as a technique to improve the density and thermal conductivity of the coatings.
... When the powder feedstock is designed correctly, cold sprayed cermets can produce coatings with a hardness that can approach or exceed that of hard-chrome coatings and, if properly designed, can exceed the wear and toughness of electrodeposited chromium [18]. Cold spray is capable of depositing a wide range of materials, from metals, such as titanium and aluminum alloys, and cermets to refractories, such as tungsten and tantalum, and high entropy alloys [19][20][21][22][23][24][25]. During deposition, particles are entrained in a gas stream, accelerated to supersonic velocities with a converging-diverging nozzle, and directed at a substrate where the particles plastically deform, adhere, and build up layers. ...
Toxic metal reduction is at the forefront of many design considerations today; additive manufacturing has the ability to combine materials in ways other traditional processes cannot and has the potential to offer unique solutions to reduce hazardous materials needed in manufacturing. Tungsten carbide (WC) has been used as a substitute in wear applications where toxic processes are traditionally utilized, but it can be difficult to deposit high-quality, hard and durable coatings. Additionally, there is a need to apply WC coatings on surfaces not feasible with the current processes. Cold spray, a solid-state directed powder deposition process, is effective at depositing carbides, though powders must be thoughtfully designed to achieve desired mechanical properties. In this study, WC was investigated as a hard chrome alternative for wear applications. Various blend ratios and preparation methods were evaluated as feedstock powder and then sprayed. Feedstock characteristics were compared to cold spray performance. Cold spray consolidations were evaluated for coating porosity and hardness. It was found that when powder make-up and composition were optimized, a high-hardness and low-porosity material was made that will contribute to the reduction in dependency of Cr in wear-facing components.
... Plasma sprayed tungsten-steel composites and graded layers were investigated e.g. in [7,8,9], plasma sprayed tungsten-copper in [10]. Most recently, first results on tungsten-chromium composites prepared by RF-ICP spraying [11] and cold spraying [12] were presented. ...
Cold spray (CS) is a rapid additive manufacturing method for deposition of metallic materials at rates significantly exceeding the laser-based methods, while retaining high deposit quality and low process cost. The mechanisms of the high-rate, extensive deformation of the materials in the CS process were recently intensively studied on macro- and meso-levels. In this paper, we introduce positron annihilation spectroscopy as a viable and reliable analytical method to study lattice defects created in the cold sprayed materials on the atomic-scale level. For the first demonstration, four different base metals were selected (Al, Cu, Ni, and Ti). A high density of dislocations was observed in all four deposits. In addition, deposits of fcc metals (Al, Cu, and Ni) also contain a considerable concentration of vacancy clusters. The results show that the extremely fast deformation in cold spray deposition process prevents recovery of vacancies which tend to agglomerate into clusters.
