How to manufacture the component

Abstract

A method for manufacturing a component, the component including a body and a ceramic coating, the method including at least partially filling a container with a powder material, subjecting the container to a compaction pressure at a temperature and for a duration sufficient to at least partially solidify the powder material to form the body of the component, and forming the ceramic coating by exposing the container to oxidizing, nitriding, and / or carburizing conditions.

Description

[Technical Field]

[0001] The present invention relates to a method for producing a component having a ceramic coating, to an apparatus including a component produced by the method, and to the use of the apparatus, particularly in a tritium breeder blanket. [Background technology]

[0002] Tritium has been proposed as a fuel for nuclear fusion reactors. However, because it is a relatively short-lived isotope (half-life of 12.3 years), existing fusion reactor designs require so-called "breeder" elements to maintain acceptable tritium levels. Many types of breeder materials are known to those skilled in the art, primarily containing lithium as the breeder element. For example, breeder elements include liquid (or molten) lithium, lithium-containing ceramics, lithium-lead eutectic, molten lithium salts, lithium-containing intermetallic compounds, and ternary lithium alloys. Anticipated problems include corrosion of the reactor's structural components, magnetohydrodynamic (MHD) pressure losses when using liquid metal breeders, tritium permeation into these structural components, or a combination of these.

[0003] For this reason, it has been proposed to coat structural components of fusion reactors that come into contact with lithium-containing materials and / or tritium with a ceramic layer (<100 μm thick). The materials used for the coating vary depending on the breeder design, but include alumina, silicon carbide, aluminum nitride, calcium oxide, erbium oxide, yttrium oxide, titanium carbide or titanium nitride, zirconium carbide, and others. Such ceramic coatings provide a physical barrier to tritium permeation between the breeder and the structural components, as well as a resistance barrier to limit MHD pressure loss and corrosion rates. The cladding is also compatible with the breeder material and, to some extent, resilient to physical and property degradation (e.g., neutron irradiation) over its service life.

[0004] Traditionally, ceramic coatings are applied by line-of-sight methods, such as (a) chemical vapor deposition (CVD), plasma vapor deposition (PVD), and magnetron sputtering. Problems with most of these methods include their inability to coat complex surfaces (i.e., large and / or nonplanar), and the coated components cannot be subsequently bonded and / or shaped without affecting the quality of the coating. Another problem is that the brittleness of ceramic coatings makes them vulnerable to localized failure (e.g., cracks, spalling, etc.). More specifically, due to the mismatch in thermal expansion coefficients between the ceramic coating and the more ductile underlying structural material, high stresses are generated within the breeder blanket where steep thermal gradients exist, leading to the formation of cracks. This is also exacerbated by neutron irradiation. Localized failure areas (e.g., cracks) in the cladding can act as "highways" for tritium permeation to the underlying structural components and / or as conductive paths in the case of liquid metal breeders, as well as areas of accelerated corrosion.

[0005] Therefore, improved methods for producing ceramic coatings on components with more complex geometries, and improved coatings that are more robust, particularly against localized failure during operation, are desired. Summary of the Invention

[0006] According to a first aspect of the present invention, there is provided a method of manufacturing a component, the component including a body and a ceramic coating, the method comprising at least partially filling a container with a powder material, subjecting the container to a compaction pressure at a temperature and for a duration sufficient to at least partially solidify the powder material to form the body of the component, and forming the ceramic coating by subjecting the container to oxidizing, nitriding and / or carburizing conditions.

[0007] Optionally, the thickness of the ceramic coating formed by the oxidation, nitriding, and / or carburizing conditions is less than the thickness of the vessel, thereby defining a cladding layer between the body and the ceramic coating. The cladding layer is an intermediate layer disposed between the body of the component and the ceramic coating. The cladding layer constitutes a portion of the vessel that is not converted to ceramic or remains substantially unaffected by the oxidation, nitriding, or carburizing conditions.

[0008] Optionally, the thickness of the container is about 1 mm to 3 mm and the thickness of the ceramic coating is about 5 to 15 μm. In some examples, prior to the oxidation, nitriding and / or carburizing steps, the container may be subjected to acid leaching or pickling to reduce its thickness to 200 to 500 microns.

[0009] The ceramic coating may comprise oxides, nitrides and / or carbides of metallic components present in the composition of the vessel.

[0010] In some examples, the ceramic coating includes a metal oxide, and the method further includes providing one or more elements having a higher affinity for oxygen than the metal of the metal oxide in the vicinity of the ceramic coating by exposing the ceramic coating to a carrier fluid containing the one or more elements, whereby the process replaces the metal oxide in the ceramic coating with oxides of the one or more elements.

[0011] The container may be manufactured by additive manufacturing methods.

[0012] The packing density of the powder material in the container may be less than 70%, which can be achieved, for example, with a powder material having a monomodal size distribution.

[0013] The compaction pressure may be isostatic, with an average isostatic pressure in the range of 50 to 150 MPa, an average temperature in the range of 1000 to 1300°C, and a duration at said temperature and pressure in the range of 3 to 5 hours. These average isostatic pressures, average temperatures, and durations may result in dynamic grain recrystallization of the powder material.

[0014] The powder material may be produced by nitrogen or argon gas atomization.

[0015] The powder material may be a pre-alloyed powder containing an alloy of vanadium, chromium, and at least one of titanium and zirconium. For example, the pre-alloyed powder may contain 4-5 wt% chromium, 4-5 wt% titanium, less than 0.2 wt% yttrium, and 89.8-91.8 wt% vanadium. Alternatively, the powder material may include any one of ODS steel, austenitic stainless steel, or reduced activation ferritic / martensitic steel.

[0016] The container may comprise any one or more of iron, chromium, aluminum, titanium, zirconium, or alloys thereof.

[0017] According to a second aspect of the present invention, there is provided a component comprising a sintered body, a cladding layer surrounding the sintered body, and a ceramic coating surrounding the cladding layer, wherein the ceramic coating comprises a metal oxide, metal nitride and / or metal carbide of a metal present in the cladding layer. The component may be manufactured by a method according to the first aspect of the present invention.

[0018] According to a third aspect of the present invention there is provided an apparatus comprising a component according to the second aspect, wherein, in use, the apparatus comprises a carrier fluid in contact with a ceramic coating, the carrier fluid comprising gaseous molecules comprising one or more of carbon, nitrogen and / or oxygen.

[0019] According to a fourth aspect of the present invention there is provided the use of a component according to the second aspect or an apparatus according to the third aspect in a magnetic confinement plasma chamber.

[0020] According to a fifth aspect of the present invention there is provided a tokamak comprising a tritium breeder blanket, said tritium breeder blanket comprising a component according to the second aspect.

[0021] The tritium breeder blanket may include a carrier fluid in contact with a ceramic coating, the ceramic coating including a metal oxide, and the carrier fluid including one or more elements having a higher affinity for oxygen than the metal of the metal oxide.

[0022] Optionally, the carrier fluid further comprises liquid lithium or lithium-lead eutectic, and the one or more elements are erbium, yttrium, and calcium dissolved in the carrier fluid at a concentration of 5 to 10 wt %.

[0023] In use, the tritium breeder blanket may include a carrier fluid in contact with the ceramic coating, the carrier fluid including one or more carbon-, nitrogen-, and / or oxygen-containing gaseous molecules, the gaseous molecules being one or more of nitrogen, nitric oxide, carbon monoxide, carbon dioxide, water vapor, and oxygen, and the carrier fluid further including one of a helium-hydrogen mixture, liquid lithium, and a lead-lithium eutectic.

[0024] According to a sixth aspect of the present invention there is provided the use of a component produced according to the method of the first aspect in an apparatus, which may be a component part of a hydrogen (e.g. tritium) and / or liquid lithium transport system, such as a magnetic confinement plasma chamber or a pipe.

[0025] According to a seventh aspect of the present invention, there is provided a method for manufacturing a component having a ceramic coating, the method comprising at least partially filling a container with a powder material, exposing the powder material to a compressive pressure at a temperature and for a duration sufficient to at least partially solidify the powder material and form a body of the component, and converting an exterior surface of the container to a ceramic coating, leaving an unconverted layer of the container between the body of the component and the ceramic coating. The ceramic coating provides a protective barrier against hydrogen, particularly tritium, for the body of the component. The unconverted layer allows the ceramic coating to self-heal in the event of a crack or other failure in the ceramic coating. [Brief explanation of the drawings]

[0026] Some embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0027] [Figure 1] FIG. 1 is a schematic diagram of one component having a ceramic coating. [Figure 2] FIG. 10 is a schematic diagram of another component having a ceramic coating. [Figure 3] FIG. [Figure 4] FIG. 1 is a schematic diagram of a component during manufacture. DETAILED DESCRIPTION OF THE INVENTION

[0028] This disclosure proposes a method for fabricating components having a ceramic coating. When used in a tritium breeder blanket, the ceramic coating limits tritium permeation, limits corrosion of underlying structural components, and / or functions as an electrical insulator to reduce MHD pressure losses. This method is particularly advantageous for fabricating ceramic coatings on components with complex geometries that cannot be applied using conventional line-of-sight techniques. Similarly, because this method involves the integrated fabrication of net- or near-net-shape components (which may have complex geometries) and the ceramic coating, assemblies (e.g., complex-shaped) including an arrangement of these net- or near-net-shape components can be made with fewer joints than would be possible using components made with conventional methods limited to simpler geometries.

[0029] Referring to FIG. 1 , a cross-section of a component 100 having a ceramic coating 106 is shown. The component 100 includes a body 102 surrounded by a cladding layer 104. The cladding layer 104 has a ceramic coating 106 on its outer surface. The cladding layer 104 and the body 102 are composed of dissimilar metals or metal alloys and are chemically bonded to each other via a peripheral interface. The ceramic coating 106 on the cladding layer 104 is a ceramic composed of at least one of a nitride, oxide, or carbide. The ceramic may be a nitride, oxide, or carbide of at least one metallic component included in the composition of the cladding layer 104. Alternatively or additionally, the ceramic may include a nitride, oxide, or carbide of another metallic component (i.e., not present in the cladding layer 104).

[0030] In some instances, the component may not include the cladding layer 104. This may occur if the vessel in step 208 is completely converted to the ceramic coating 106, leaving no cladding layer. The requirement that the component 100 include the cladding layer 104 is not essential in this regard.

[0031] The cross-section of Figure 1 is shown as circular in the example of Figure 1. Those skilled in the art will understand that component 100 may have any other regular or irregular cross-section.

[0032] 2, there is shown a cross-section of another component 200 in the form of a hollow tube. The component includes a body 102 having a cladding 104 and a ceramic coating layer 106. The cladding 104 and the ceramic coating layer 106 are disposed on the radially inner and outer surfaces of the body portion 102. While the tube is shown as circular in cross-section, other cross-sections are possible.

[0033] In some examples (not shown), the cladding layer 104 and ceramic coating 106 are disposed on only one of the radially inner or radially outer surfaces of the body portion 102. A component 200 having the cladding and ceramic coating layer disposed on at least the radially inner surface is particularly useful as a pipe or other form of container intended to transport, hold, or otherwise be exposed to lithium or tritium (or other hydrogen isotopes) containing materials.

[0034] Figure 3 illustrates a method for manufacturing the component 100 shown in Figure 1. The results of each step are shown schematically in Figure 4. Those skilled in the art will appreciate that this method can be applied in a similar manner to make the component shown in Figure 2. The primary differences are that the container 402 defines an annular cavity for receiving the powder material 404, and that the oxidation, carburizing, and nitriding conditions in step 308 may be applied to one or both of the radially inner and outer surfaces of the container 402 following step 306.

[0035] In step 302, a container 402 is manufactured.

[0036] In step 304 , a container 402 is at least partially filled with a powder material 404 .

[0037] In step 306, the container 402 is the metal powder 404 contained within the metal container 402 at least partially solidifies (i.e., densifies by sintering) to form the body 102 of the component 100; and subjecting the inwardly facing surface of the metal container 402 to isostatic pressure at a temperature and for a period sufficient to cause the inwardly facing surface of the metal container 402 to bond with the body 102.

[0038] In optional step 307, the container 402 may be subjected to a heat treatment for a period of time, for example, heated to dynamic recrystallization of the body 102 of the component.

[0039] In step 308, the vessel 402 is exposed to one or more of an oxidizing, nitriding, and carburizing environment to form a ceramic coating 106 on at least the outwardly facing surface of the vessel 402. The formed ceramic coating 106 comprises oxides, nitrides, and / or carbides of metallic components present in the vessel 402. The remaining vessel, which is substantially unaffected by the oxidation, nitriding, and carburizing steps, constitutes the cladding layer 104 of Figure 1. The material composition of the vessel in step 302 and the material composition of the cladding layer are substantially the same.

[0040] Optionally, in step 310, the ceramic coating 106 is exposed to a carrier fluid. The carrier fluid is used to transport one or more elements that have a higher affinity for oxygen than the metals in the metal oxides present in the ceramic coating 106. These elements at least partially reduce the metal oxides present in the ceramic coating 106 from step 308 and replace the elements with their oxides.

[0041] 3 may be performed sequentially, simultaneously, or according to any other order of operations. For example, steps 306, 307, and / or 308 may be performed together.

[0042] Further details of the method of FIG. 3 are now provided.

[0043] container

[0044] The container 402 may be manufactured by known additive manufacturing methods or known subtractive methods. Suitable additive manufacturing methods include powder-based processing routes such as direct metal laser sintering (DMLS), selective laser sintering (SLS), direct metal printing (DMP), laser powder bed fusion (LPBF), electron beam melting (EBM), electron beam additive manufacturing (EBAM), laser engineered net shaping (LENS), direct metal deposition (DMD), selective laser melting (SLM), and metal injection molding (MIM).

[0045] 4 is at least partially hollow and has an opening at one end. The container is made of metal. The as-manufactured container is considered to have a net or near-net shape, i.e., a shape that corresponds to the intended shape of the final component.

[0046] The vessel 402 has a composition that includes at least one element capable of forming an oxide, nitride, or carbide in an oxidizing, nitriding, or carburizing environment. Exemplary elements include iron, aluminum, chromium, titanium, and / or zirconium. In some examples, the vessel is an alloy (e.g., FeCrAl, Fe—Ti). In some examples, the weight fraction of each of aluminum, titanium, zirconium, and / or chromium is greater than 5%. Some of the alloys may include erbium and yttrium.

[0047] For components 100, 200 intended as structural components, the thickness of the container following the method of FIG. 3 is preferably less than the lateral dimensions of the container's hollow interior. This ensures that the mechanical strength of the component 100, 200 is determined primarily by the mechanical properties of the material comprising the body 102, rather than the cladding 104 and / or ceramic coating 106, which may generally be weaker. More specifically, the container's thickness is less than a threshold fraction of the lateral dimensions of the container's hollow portion. Specifically, that fraction is less than 0.25, more specifically less than 0.1, and even more specifically less than 0.05. At a sufficiently low fraction, the mechanical properties of the cladding and / or ceramic coating layer are negligible.

[0048] At the same time, the thickness of the container is large enough to ensure that no bursting or loss of powder occurs during isostatic pressing in step 306. Generally speaking, this means that the as-produced container 402 in step 302 is at least 1 to 2 mm (or 1 to 3 mm) thick, unless the overall thickness of the produced component 100, 200 is less than this.

[0049] Thus, in instances where the thickness of the container is preferably minimal (e.g., less than 5% of the lateral dimension of the hollow portion of the container, as discussed above), the container 402 may initially be of a large fractional thickness (>5%) and reduced to the desired appropriate thickness following step 306 (e.g., to 200 to 500 microns by acid leaching or pickling).

[0050] powder material

[0051] The powder material may be gas atomized. Exemplary gases include nitrogen, argon (or other inert gases), etc. The powder material 404 has a powder size distribution that may include multiple peaks at different powder sizes or only a single peak (unimodal). As those skilled in the art know, the powder size distribution affects the packing density of the powder during packing in step 304 and the degree of deformation during the powder solidification process in step 306. Packing density is defined as the volume occupied by the powder material divided by the volume of the hollow portion of the container.

[0052] For powder distributions with multiple peaks (and spaced apart to allow smaller powder particles to reside in the interstices between the larger powder particles), at least partial filling in step 304 means filling the container 402 with powder to a high packing density (greater than 80%, more preferably 90%, and even more preferably greater than 95%). The higher the packing density of the powder material 404, the less solidification is required to achieve its theoretical density. As a result, powder solidification in step 306 requires lower temperatures, lower pressures, and / or shorter times under those conditions.

[0053] For powder distributions with a single peak (or peaks that are not sufficiently spaced to allow smaller powder particles to reside in the interstices between larger powder particles), at least partial filling in step 304 refers to filling the container 404 with powder to a relatively low packing density, e.g., less than about 70%. A powder material 404 with a lower packing density (e.g., less than about 70%) requires greater solidification to achieve its theoretical density. As a result, the powder material 404 undergoes plastic deformation to a greater extent. The stored energy associated with this plastic deformation can result in dynamic recrystallization, improving the microstructure of the component body 102 after powder solidification. For example, grains can be refined and impurities (e.g., in the form of oxides) at prior particle boundaries can be removed (discussed in more detail below).

[0054] A narrow powder size distribution (e.g., a unimodal distribution) can be produced using sieving or other size selection methods known to those skilled in the art. Because the packing density of the powder is lower with a narrower size distribution, more plastic deformation occurs during the solidification step 306.

[0055] The inventors have realized that by reducing the packing density (e.g., to less than 75%, more specifically less than 70%), the plastic deformation induced in step 306 can be large enough to cause dynamic recrystallization in some alloys, particularly austenitic steels and vanadium alloys. In the case of vanadium alloys, this is a surprising result because the phenomenon of dynamic recrystallization is typically observed only in low to moderate stacking fault energy materials (e.g., austenitic steels, nickel-based alloys, copper, etc.).

[0056] Solidification of powder materials

[0057] Step 304 may further include closing the opening of container 402, for example, by providing a fluid-tight seal at the open end of the container, by crimping the open end of the container closed, etc. This step is well known to those skilled in the art and ensures that the powder material is retained within container 402 during solidification.

[0058] Preferably, after step 306, the density of the body 102 is greater than 90%, more preferably greater than 95%, and even more preferably greater than 99% of the theoretical density. The theoretical density of the body 102 is the average density of the individual powder particles in the absence of voids or porosity. This value is well known to those skilled in the art.

[0059] The bond formed between the metal container 402 and the body 102 in step 306 may be a diffusion bond. Such a bond is formed when at least one of the metal components of the container 402 is at least partially soluble in at least one of the metal components present in the powder material 404 / body 102, or vice versa, and the container 402 is held at an elevated temperature and isostatic pressure for a sufficient time (e.g., several hours) for significant diffusion of these components to occur. The diffusion bond may contain the metal components of the container 402 (e.g., Zr, Al, Ti, Cr, Y, Er) in solid solution within the body 102, or may contain the metal components in solid solution within the body 102 in the container 402. A dispersion of precipitates may exist in the diffusion bond. The composition and microstructure of the diffusion bond depend on the chemical compositions of the container and powder material, as well as the HIP (hot isostatic pressing) processing conditions (time, temperature, and pressure). The diffusion bond creates a compositional gradient of the metal components present in the container 402 within the body 102. This composition gradient increases monotonically from the fractional amount of that component in the body (i.e., powder material), which may be a trace amount (less than 0.01 wt%), to the fractional amount of that component in the container 40 .

[0060] In some instances, the compaction pressure is applied via hot isostatic pressing. Other methods suitable for achieving consolidation and sintering of powder materials are well known to those skilled in the art.

[0061] In a particular example, the average temperature during step 306 is in the range of 1000 to 1300°C, more specifically 1100 to 1200°C, and even more specifically 1130 to 1170°C, the average isostatic pressing pressure is 50 to 150 MPa, more specifically 75 to 125 MPa, and even more specifically 90 to 110 MPa, and the predetermined period of time (over which the pressure and temperature are applied) is 3 to 5 hours, more specifically 3.5 to 4.5 hours, and even more specifically 4 hours.

[0062] Those skilled in the art will appreciate that the temperature and pressure values ​​used in processing are somewhat interchangeable, for example, processing at relatively high pressure and low temperature may densify metal powders to equivalent theoretical densities compared to processing at relatively low pressure and high temperature.

[0063] In some examples, steps 302 to 306 are replaced by an additive manufacturing process to produce a compositionally graded structure including body 102 (representing the sintered powder from step 206) and "container" layer 402 (shown in FIG. 4) having different compositions. The use of additive manufacturing to produce compositionally graded structures is known per se.

[0064] Heat Treatment

[0065] In optional step 307, the container 402 may be heated for a period of time to recrystallize the component body 102. This recrystallization process can remove prior grain boundaries (PPBs) and achieve a finer grain structure, thereby improving the mechanical properties of the component 100.

[0066] Recrystallization is the process by which "high energy" grains are replaced by a set of new "low energy" grains that nucleate and grow at the expense of the "high energy" grains. The "low energy" grains are generally defect-free, whereas the "high energy" grains contain defects or deformations (i.e., stored plastic energy), which are the driving force for recrystallization.

[0067] The recrystallization that occurs during step 306 is advantageous because it reduces the overall concentration of defects in the body 102 of the component, and further because it removes prior grain boundaries (PPBs).

[0068] PPBs are particularly common in components manufactured by hot isostatic pressing (HIP) and result from incomplete solidification of the powder material. PPBs correspond to the boundaries of powder particles before solidification occurs. Because the powder material often has an oxide coating, the PPBs are correspondingly associated with the oxides, forming weak bonds through the body 102 of the component 100, 200. Additional oxides and / or impurities may also segregate to the PPBs. These weak bonds significantly reduce ductility. Recrystallization advantageously removes these PPBs, thus avoiding the segregation of oxides and / or impurities at those boundaries, thereby improving the mechanical properties (e.g., ductility) of the body 102.

[0069] As will be appreciated by those skilled in the art, the plastic deformation induced in step 306 may change the shape of container 402, which may be modeled using software tools known to those skilled in the art. Thus, container 402 may be manufactured according to a shape that will form a component of a desired shape after plastic deformation in step 306.

[0070] Step 307 can be performed simultaneously with step 306, for example, using well-known hot isostatic pressing (HIP) machines (e.g., AVURE / Quintus technologies) that are capable of uniform rapid cooling (URQ) and heating. Thus, the heat treatment that induces recrystallization can be performed while the powder is solidifying. This reduces manufacturing costs and means, for example, that an additional heat treatment is not required after the ceramic coating is formed in step 310.

[0071] In some instances, the vessel 402 is completely converted to the ceramic coating 106 and no cladding layer 104 remains after step 308 .

[0072] Carrier Fluid

[0073] The carrier fluid may be a liquid or a gas. Exposing the ceramic coating 106 to the carrier fluid means providing these elements in the vicinity of the ceramic coating. Step 310 may include flowing the carrier fluid over some or all of the ceramic coating 106, disposing the ceramic coating 106 in the carrier fluid, etc.

[0074] In one example, the carrier fluid is liquid lithium and the element it transports is calcium dissolved therein. If the metal oxide present in the ceramic coating after step 308 is iron oxide, the iron oxide present in the ceramic coating is replaced with a deposit of calcium oxide during step 308.

[0075] As one skilled in the art will appreciate, exemplary ceramic coatings include aluminum oxide, titanium oxide, zirconia, yttrium oxide, zirconium carbide, titanium nitride, titanium carbide, erbium oxide, aluminum nitride, etc., depending on i) the type of conditions in step 308, ii) whether optional step 310 is performed, and iii) the composition of the vessel 402.

[0076] Manufactured Components

[0077] Preferably, but not necessarily, the thickness of the container after step 310 is greater than the thickness of the ceramic coating 106 that develops on its surface after steps 308 and 310. The difference in thickness defines the cladding layer 104. Typical thickness values ​​for the container, ceramic coating 106, and cladding layer 104 are approximately 1 to 2 mm (or 1 to 3 mm), 5 to 15 μm, and 50 to 100 μm, respectively. However, other thickness values ​​are possible.

[0078] Under some operating conditions, such as when wear is prevalent, the ceramic coating 106 may spall or break, leaving areas of the exterior surface of the component 100 without the ceramic coating 106. These areas are undesirable because they act as sites for accelerated corrosion, potentially causing corrosion of the body 102. By ensuring that the cladding layer 104 is provided around the body 102, a "reservoir" of metal elements (e.g., Al, Ti, Zr, Cr) can be provided to form new ceramic coating 106 without damaging the body 102.

[0079] The process of using a container 402 to contain a metal powder for densification is well known to those skilled in the art. However, the prior art container 402 used to contain the powder is typically completely removed (e.g., by pickling) after solidification in step 306. It does not form part of the manufactured component. Conversely, in the proposed method, at least a portion of the container 402 forms an integral part of the component 100, i.e., the cladding layer 104, and / or is used to form the ceramic coating. Because the container forms part of the manufactured component, a subtractive manufacturing process that is wasteful in terms of material, cost, and time can be avoided.

[0080] vanadium

[0081] The method of FIG. 3 is particularly advantageous for producing components having a body comprising a vanadium alloy, such as a V-Cr-Ti alloy (e.g., V-4Cr-4Ti wt%), a V-Cr-Ti-Y alloy (e.g., V-4Cr-4Ti-0.2Y wt%), or an oxide dispersion strengthened (ODS) vanadium alloy.

[0082] This is because vanadium alloys are traditionally prepared by a complex process involving ingot casting, hot forging, hot or cold rolling, and subsequent heat treatment at temperatures exceeding 700°C. The unavoidable impurities of carbon, oxygen, and nitrogen present in the melt precipitate in the alloy as Ti-CON, providing strengthening up to their melting temperatures (approximately 1000°C). Another challenge with melt processing is that vanadium has high solid solubility limits for oxygen and nitrogen (e.g., 2.7 wt% and 1.7 wt%, respectively, at 1000°C). Because oxygen and nitrogen are difficult to eliminate, some solid solution strengthening is unavoidable, and such high levels (e.g., the 2.7 wt% and 1.7 wt% mentioned above) result in an undesirable decrease in ductility. Small amounts of yttrium (less than 0.2 wt%) can be added to vanadium alloys during melting, which scavenges oxygen and forms Y2O3 precipitates (i.e., oxide dispersion strengthened vanadium alloys; ODS-vanadium alloys), but achieving a uniform distribution of these Y2O3 precipitates throughout the microstructure, which leads to improved mechanical properties, is a challenge.

[0083] Mechanical (MA) alloying of elemental powders (i.e., vanadium, chromium, titanium, yttrium (and possibly TiC particles)) in a ball mill and consolidation by hot extrusion or hot isostatic pressing (HIP) is an alternative processing route, but is energy intensive and has low scalability.

[0084] Returning to the method of Figure 3, the powder material may be a V-Cr-Ti-Y pre-alloyed powder produced by inert gas atomization (e.g., in nitrogen or argon). The composition may be 4-5 wt% Cr, 4-5 wt% Ti, less than 0.2 wt% Y, and V (balance).

[0085] When nitrogen gas is used as an inert gas for atomization, some nitrogen dissolves in solid solution within the powder as interstitials. Some nitrogen may precipitate in the form of nitride precipitates. Because oxygen is present as an impurity in nitrogen gas and it is difficult to completely eliminate oxygen during powder storage, prealloyed powders may have an oxide layer on their surface. The oxide may be chromium oxide, titanium oxide, vanadium oxide, yttrium oxide, or a combination thereof. Prealloyed powders may also contain oxygen dissolved in solid solution (interstitials) within the alloy. In some instances, oxygen may also preferentially bond with alloying elements (Cr, Ti, Y) to form discrete oxide particles (less than 1 μm). In summary, powder materials may contain oxide and nitride particles located within the powder, an oxide layer on the powder surface, and oxygen and nitrogen dissolved in interstitials as solid solution within the powder.

[0086] As previously mentioned, if the packing density of the vanadium powder is sufficiently low (e.g., less than 75%, more specifically less than 70%, which is typical for a narrow powder size distribution), dynamic recrystallization of the vanadium alloy during solidification in step 306 is possible.

[0087] It has also been discovered that the presence of yttrium in the pre-alloyed powder material can further improve the mechanical properties (e.g., ductility, toughness, strength) of the body 102 during dynamic recrystallization. Specifically, yttrium in solid solution in the powder material captures "free" oxygen that is generated when prior oxides present in the powder are reduced at high temperatures during solidification in step 306. The yttrium forms yttrium oxide. During recrystallization, the grain boundaries migrate, carrying the yttrium oxide with them and, in the process, uniformly dispersing the yttrium oxide within the body 102. This uniform distribution of fine yttrium oxide leads to synergistic improvements in mechanical properties.

[0088] Vanadium alloys, particularly V-4Cr-4Ti(wt%) and ODS V-4Cr-4Ti(wt%), are promising candidates as structural components of breeder blankets in tokamaks or spherical tokamaks, as has been mentioned above. The exact composition of the alloy will be guided by the desired final properties, such as creep resistance and oxidation resistance. Thus, in some cases (i.e., to improve creep and oxidation resistance), a relatively high chromium content and a relatively low vanadium content may be desirable, or a V-Cr-Zi alloy may be preferred over a V-Cr-Ti alloy. The advantages of such alloys include: Low induction (neutron and gamma) activation characteristics, High resistance to neutron radiation damage, High strength over the expected operating temperature range of approximately 400°C to 700°C Excellent compatibility with liquid lithium, and The use of the alloy does not directly affect magnetic plasma confinement because the alloy is non-ferromagnetic. Includes:

[0089] magnetic confinement plasma chamber

[0090] The method of Figure 3 is particularly suitable for fabricating structural components of a magnetic confinement plasma chamber, such as a tokamak, preferably a spherical tokamak. The aspect ratio of a spherical tokamak is preferably, but not necessarily, 2.5 or less. The aspect ratio is the ratio of the major radius to the minor radius of the toroidal plasma confinement region of the tokamak. More specifically, the method of Figure 3 is suitable for fabricating structural components of a tritium breeder blanket for a tokamak or spherical tokamak.

[0091] As previously mentioned, the tritium breeder blanket includes lithium-containing elements that can be solid (eg, lithium compounds) or liquid (eg, liquid lithium, lithium-lead eutectic, or molten salts).

[0092] The inventors have realized that the ceramic coating 106 of the component can be formed or repaired in situ in the presence of a carrier fluid (e.g., liquid lithium, Li-Pb eutectic, H-He gas mixture) in the breeder blanket, which corresponds to step 310 in Figure 3.

[0093] Because the oxygen potential in lithium is low (approximately −500 kJ / mol), most oxide coatings in the ceramic coating 106 are unstable and prone to dissolution in the presence of a lithium-containing carrier fluid, which is undesirable. To avoid dissolution of the ceramic coating 106, it has been proposed to add oxide-forming additives (e.g., erbium, yttrium, or calcium) to the carrier fluid. The additives form stable oxides even in the presence of a lithium-containing carrier fluid. Erbium oxide, yttria, and calcium oxide are particularly beneficial because they are stable in liquid lithium at normal operating conditions (i.e., temperatures up to 700° C.), have high electrical resistivity, and are highly resistant to tritium permeation.

[0094] By controlling the flow rate of the carrier fluid, the concentration of the additives in the carrier fluid, the temperature and / or pressure of the carrier fluid, the oxides in the ceramic coating 106 formed in step 208 can be reduced and replaced with more stable oxides. Exemplary conditions include erbium, yttrium, and / or calcium at concentrations of 5 wt % to 10 wt % at temperatures below 600° C. Ceramic coatings containing these stable oxides would be difficult to achieve by other methods because their high affinity for oxygen makes it impractical to fabricate containers from these elements (i.e., erbium, calcium, or yttrium).

[0095] If the carrier fluid does not contain lithium, it is proposed to add (e.g., dissolve or suspend) gaseous molecules containing carbon, nitrogen, or oxygen (e.g., nitrogen, carbon dioxide, carbon monoxide, water vapor, oxygen, nitric oxide, etc.) to the carrier fluid so that, if the ceramic coating 106 becomes damaged (e.g., by abrasion, erosion, etc.), the cladding layer 104 will spontaneously react with the gaseous molecules to repair the ceramic coating 106. In this regard, the presence of the cladding layer 104 is advantageous in providing a self-repair effect during use. Exemplary carrier fluids include helium-hydrogen mixtures, liquid lithium, lithium-lead eutectic, and molten lithium salts.

[0096] System example

[0097] Solid lithium breeder: Lithium-containing ceramic (Li2TiO3, Li4SiO4 or mixtures thereof)

[0098] In a particular example, the component 100, 200 is used, for example, as a structural component, in a lithium-containing ceramic breeder blanket. The component 100, 200 includes a body 102 formed from steel (preferably an oxide dispersion strengthened (ODS) steel or a reduced activation ferritic / martensitic (RAF / M) steel, such as Eurofer-97 (herein referred to as Eurofer) or F82H steel), a cladding layer 104 including an aluminum-containing alloy, and a ceramic coating including aluminum oxide. Thus, in the method of FIG. 3 , (i) the container 402 and (ii) the powder material 404 are (i) an aluminum-containing alloy (e.g., an FeCrAl alloy) and (ii) an ODS steel or RAF / M steel, respectively. The ceramic coating is formed in step 308 via an oxidation process, or alternatively, is formed using a carrier fluid via step 310. The carrier fluid is a gas mixture of helium and hydrogen that is fed through a bed of lithium ceramic pebbles to transport water vapor. The supply of a helium-hydrogen gas mixture (but without water vapor) to the pebble bed is well known to those skilled in the art and is the basis for tritium extraction. By varying the flow rate of the helium-hydrogen mixture, the concentration of water vapor, the temperature, and / or the pressure, the conditions in the breeder blanket can be controlled so that it is energetically favorable for the cladding layer 104 to oxidize and form aluminum oxide. This ability to form the ceramic layer 106 in situ is advantageous because, should the ceramic coating 106 be compromised (e.g., by wear, erosion, etc.), the coating 106 can be spontaneously replenished by oxidation of the cladding layer 104, thus reducing damage to the underlying components of the system.

[0099] Unless expressly stated to the contrary, steels include one or more of the following phase constituents: austenite, ferrite, martensite, bainite, and precipitates or particles dispersed within these one or more constituents, such as carbides, nitrides, and oxides. Exemplary steels include ferritic / martensitic steels (e.g., Eurofer-97, a cast nanostructured alloy), austenitic stainless steels (e.g., 316L), ferritic steels, or oxide dispersion strengthened (ODS) steels (both ferritic and ferritic / martensitic).

[0100] The composition of Eurofer-97 is less than 0.01 wt% aluminum, less than 0.01 wt% nickel, less than 0.02 wt% titanium, 0.015-0.045 wt% nitrogen, less than 0.01 wt% cobalt, less than 0.01 wt% oxygen, less than 0.05 wt% silicon, 0.15-0.25 wt% vanadium, 8.50-9.50 wt% chromium, 0.20-0.60 wt% manganese, 0.10-0.14 wt% tantalum, 1.0-1.2 wt% tungsten, less than 0.01 wt% copper, 0.090-0.120 wt% carbon, and less than 0.072 wt% other impurities including phosphorus, sulfur, molybdenum, niobium, boron, arsenic, tin, antimony, and zirconium, with the balance being iron.

[0101] The composition of F82H is iron (balance), 0.098 wt% carbon, 7.81 wt% (about 8 wt%) chromium, 1.88 wt% (about 2 wt%) tungsten, 0.44 wt% manganese, 0.19 wt% vanadium, and 0.037 wt% tantalum.

[0102] The ODS steels can be ferritic (9-16 wt% Cr) or martensitic (8-9 wt% Cr) as pre-alloyed powder material 404. Example compositions include 9Cr-0.13C-0.2Ti-2W-0.35Y2O3, 13Cr-0.02C-3W-0.7Ti-0.46Y2O3, 13Cr-0.05C-3W-0.5Ti-0.34Y2O3, and 11Cr-0.09C-3W-0.4Ti-0.66Y2O3 (all compositions in wt%, balance iron).

[0103] These steel composition details apply for the remaining breeder blanket type examples and will not be repeated for the sake of brevity.

[0104] Breeder blanket type - Pb-Li eutectic (14-17at% Li)

[0105] In a particular example, the component 100, 200 is used, for example, as a structural component in a lithium-lead eutectic breeder blanket. The component 100, 200 includes a body 102 formed from steel (preferably an oxide dispersion strengthened (ODS) steel or an RAF / M steel such as Eurofer), a cladding layer 104 including an FeCrAl alloy (e.g., 20-30 wt% Cr, 4-7.5 wt% Al, balance Fe), and a ceramic coating including aluminum oxide. Thus, in the method of FIG. 3, (i) the container 402 and (ii) the powder material 404 are (i) the FeCrAl alloy and (ii) the ODS steel or the RAF / M steel, respectively. The ceramic coating is formed in step 308 via an oxidation process, or alternatively, is formed using a carrier fluid via step 310. The carrier fluid is a lithium-lead eutectic with dissolved oxygen therein. The oxygen concentration in the lithium-lead eutectic and / or the replenishment rate (e.g., flow rate) of the lithium-lead eutectic on the component 100, 200 can be controlled to ensure that sufficient dissolved oxygen is present to form or replenish the aluminum oxide ceramic coating. As discussed above, the ability to form the ceramic layer 106 in situ is advantageous because if the ceramic coating 106 is compromised (e.g., by wear, erosion, etc.), the coating 106 is spontaneously replenished by oxidation of the cladding layer 104, thus reducing damage to the underlying components of the system.

[0106] Breeder blanket type - liquid lithium

[0107] In a particular example, the components 100, 200 are used in a liquid lithium breeder blanket, for example as structural components.

[0108] The component 100, 200 may include a body 102 formed from a vanadium alloy (e.g., containing 4-5 wt% Cr, 4-5 wt% Ti, balance V), and a cladding layer 104 comprising an FeCrAl alloy (e.g., 20-30 wt% Cr, 4-7.5 wt% Al, balance Fe) or an Fe-containing alloy (e.g., substantially pure iron). The ceramic coating 106 is initially iron oxide and / or aluminum oxide (e.g., formed during the oxidation treatment of step 308). However, during operation in the breeder blanket, the ceramic coating 106 includes Er2O3, YO3, and / or CaO. In particular, these oxides are generated in situ by reducing the iron oxide and / or aluminum oxide present in the ceramic coating 106 formed in step 308. This can be accomplished by dissolving 5-10 wt% erbium, yttrium, and / or calcium in liquid lithium at a temperature of 500-600°C. Thus, the oxide coating can be replenished in situ during operation, which is advantageous.

[0109] Alternatively, the component 100, 200 may include a body 102 formed from a vanadium alloy (e.g., 4-5 wt% Cr, 4-5 wt% Ti, balance V with less than 1 wt%, more preferably less than 0.2 wt%, yttrium as a pre-alloyed powder), and a cladding layer 104 comprising an FeCrAl alloy (e.g., 20-30 wt% Cr, 4-7.5 wt% Al, balance Fe) or a Ti-containing alloy (e.g., substantially pure titanium, 5-10 wt% Fe-Ti). Yttrium is effective in removing oxygen from solid solution within the vanadium alloy, thereby improving its ductility. This scavenging property of yttrium is discussed above. Accordingly, the powder material 404 may include less than 1 wt% yttrium in the form of a pre-alloyed powder. The ceramic coating 106 includes titanium and / or aluminum nitride (e.g., formed using a carrier fluid during the nitriding process of step 308 or alternatively via step 310). The carrier fluid is liquid lithium with dissolved nitrogen therein. The nitrogen concentration in the liquid lithium and the flow rate of the liquid lithium over the components 100, 200 can be controlled to ensure that sufficient dissolved nitrogen is present to form or replenish the titanium and / or aluminum nitride ceramic coating. As discussed above, the ability to form the ceramic layer 106 in situ is advantageous because if the ceramic coating 106 becomes compromised (e.g., by wear, erosion, etc.), the coating 106 will spontaneously replenish through oxidation of the cladding layer 104. Thus, damage to the underlying components of the system is reduced.

[0110] Alternatively, the component 100, 200 may include a body 102 formed from steel (preferably Eurofer or ODS steel) and a cladding layer 104 comprising an FeCrAl alloy (e.g., 20-30 wt% Cr, 4-7.5 wt% Al, balance Fe) or a Ti-containing alloy (e.g., substantially pure titanium, 5-10 wt% Fe-Ti). The ceramic coating 106 includes titanium and / or aluminum nitride (e.g., formed during the nitriding process of step 308 or alternatively via step 310 using a carrier fluid). The carrier fluid is liquid lithium having dissolved nitrogen therein. The nitrogen concentration in the liquid lithium and the flow rate of the liquid lithium over the component 100, 200 can be controlled to ensure there is sufficient dissolved nitrogen present to form or replenish the titanium and / or aluminum nitride ceramic coating. As discussed above, the ability to form the ceramic layer 106 in situ is advantageous because if the ceramic coating 106 becomes compromised (e.g., by wear, erosion, etc.), the coating 106 will spontaneously replenish through oxidation of the cladding layer 104, thus reducing damage to the underlying components of the system.

[0111] Alternatively, the component 100, 200 may include a body 102 formed from steel (preferably Eurofer or ODS steel) and a cladding layer 104 comprising an FeCrAl alloy (e.g., 20-30 wt% Cr, 4-7.5 wt% Al, balance Fe) or an Fe-containing alloy (e.g., substantially pure iron). The ceramic coating 106 is initially iron oxide and / or aluminum oxide (e.g., formed during the oxidation treatment of step 308). However, during operation in the breeder blanket, the ceramic coating 106 includes Er2O3, YO3, and / or CaO. In particular, these oxides are generated in situ by reducing the iron oxide and / or aluminum oxide present in the ceramic coating 106 formed in step 308. This can be achieved by dissolving 5-10 wt% erbium, yttrium, and / or calcium in liquid lithium at temperatures between 500 and 600°C. Thus, the oxide coating can be replenished in situ during operation, which is advantageous.

[0112] Breeder blanket type - molten lithium salts (e.g., FLiBe)

[0113] In a particular example, the component 100, 200 is used, for example, as a structural component in a molten lithium salt breeder blanket. The component 100, 200 includes a body 102 formed from steel (preferably an oxide dispersion strengthened (ODS) steel or Eurofer steel), a cladding layer 104 including an FeCrAl alloy (e.g., 20-30 wt% Cr, 4-7.5 wt% Al, balance Fe), and a ceramic coating including aluminum oxide. Thus, in the method of FIG. 3, (i) vessel 402 and (ii) powder material 404 are (i) an FeCrAl alloy and (ii) steel (e.g., an ODS steel or Eurofer steel), respectively. The ceramic coating can be formed in step 308 via an oxidation process.

[0114] An example system is summarized in Table 1 below. [Table 1]

[0115] Thus, more generally, the component cladding 106 includes any one or more of Fe, Cr, Al, Ti, and optionally Zr, with the weight fractions of Al and Ti being high enough to allow for the formation of the ceramic coating 106 (e.g., AlN, Al2O3, TiN) in step 308. The powder material 404 that makes up the component body 102 after solidification is steel, a vanadium alloy, or a conventional nickel-based alloy.

[0116] Conventionally, corrosion-resistant nickel-based alloys (e.g., Hastelloy®) are used as structural components in tokamaks, e.g., for lithium molten salt, FLiBe-type breeder blankets. However, under neutron irradiation, nickel-based alloys develop high activation levels, which are undesirable from a nuclear waste management perspective. The proposed method of developing a protective barrier coating 106 on the body 102 of the structural component allows the use of lower activation structural alloys (e.g., Eurofer 97, ODS steels, vanadium alloys) in corrosive environments where they were previously unsuitable.

[0117] Other applications of the components 100, 200 include replacing refractory metals (e.g., tungsten) with ceramic-coated non-refractory metals (e.g., steel) in tokamak divertors, heat exchanger elements especially for gas-cooled reactors, tritium permeation barriers in molten salt fission reactors (e.g., fluoride salt-cooled high-temperature reactors), high-performance structural components in Gen-IV reactors (using 4-5 wt% Cr, 4-5 wt% Ti, less than 0.2 wt% Y, and V (balance)), and even hydrogen storage technologies, as the ceramic coating 106 is effective in protecting the body 102 against hydrogen embrittlement.

[0118] While the present invention has been described in terms of the preferred embodiments set forth above, it should be understood that these embodiments are merely exemplary and that the claims are not limited to those embodiments, and features from different embodiments may be combined as appropriate to form other working embodiments.

Claims

1. 1. A method of manufacturing a component, comprising: the component includes a body and a ceramic coating; The method comprises: at least partially filling a container with a powder material; subjecting the container to a compressive pressure at a temperature and for a duration sufficient to at least partially solidify the powder material and form the body of the component; exposing said container to oxidizing, nitriding and / or carburizing conditions, thereby forming said ceramic coating; A method comprising:

2. The method of claim 1 , wherein the thickness of the ceramic coating is less than the thickness of the container.

3. The method of claim 1 or claim 2, further comprising a cladding layer between the body and the ceramic coating.

4. 4. The method of claim 1, wherein the thickness of the container is about 1 mm to 3 mm and the thickness of the ceramic coating is about 5 to 15 μm.

5. 5. The method of claim 1, wherein the step of exposing the vessel to oxidizing, nitriding and / or carburizing conditions comprises exposing the vessel to carburizing conditions such that the ceramic coating comprises carbides of metallic components present in the composition of the vessel.

6. 5. The method of claim 1, wherein the ceramic coating comprises oxides, nitrides and / or carbides of metallic components present in the composition of the vessel.

7. the ceramic coating comprises a metal oxide; The method further includes providing one or more elements having a higher affinity for oxygen than the metal of the metal oxide in the vicinity of the ceramic coating by exposing the ceramic coating to a carrier fluid containing the one or more elements; 5. The method of claim 1, wherein said step replaces the metal oxide in the ceramic coating with an oxide of said one or more elements.

8. 8. The method of claim 1, wherein the container is manufactured by additive manufacturing.

9. 9. The method of claim 1, wherein the packing density of the powder material in the container is less than 70%.

10. 10. The method of claim 9, wherein the size distribution of the powder material is unimodal.

11. 11. The method of any one of claims 1 to 10, wherein the compaction pressure is isostatic, the average isostatic pressure being in the range of 50 to 150 MPa, the average temperature being in the range of 1000 to 1300°C, and the time period at said temperature and pressure being in the range of 3 to 5 hours.

12. 12. The method of claim 11 when dependent on any one of claims 9 to 10, wherein the average isostatic pressure, average temperature and duration result in dynamic grain recrystallization of the powder material.

13. 13. The method according to claims 10 to 12, wherein the powder material is produced by nitrogen gas or argon gas atomization.

14. 14. The method of claims 10 to 13, wherein the powder material is a pre-alloyed powder comprising an alloy of vanadium, chromium and at least one of titanium or zirconium.

15. 15. The method of any one of claims 1 to 14, wherein the powder material comprises any one of an ODS steel, an austenitic stainless steel, or a reduced activation ferritic / martensitic steel.

16. 16. The method of any one of claims 1 to 15, wherein the container comprises any one or more of iron, chromium, aluminum, titanium, zirconium, or alloys thereof.

17. 1. A component comprising a sintered body, a cladding layer surrounding the sintered body, and a ceramic coating surrounding the cladding layer, The component, wherein the ceramic coating comprises a metal oxide, a metal nitride, and / or a metal carbide of a metal present in the cladding layer.

18. 18. An apparatus including the component of claim 17, In use, the apparatus includes a carrier fluid in contact with the ceramic coating, the carrier fluid including gaseous molecules containing one or more of carbon, nitrogen and / or oxygen.

19. 19. Use of a component according to claim 17 or a device according to claim 18 in a magnetic confinement plasma chamber.

20. 20. A tokamak comprising a tritium breeder blanket, said tritium breeder blanket comprising the component of claim 17.

21. 21. The tokamak of claim 20, wherein the tritium breeder blanket includes a carrier fluid in contact with the ceramic coating, the ceramic coating including a metal oxide, and the carrier fluid including one or more elements having a higher affinity for oxygen than a metal of the metal oxide.

22. 22. The tokamak of claim 21 , wherein the carrier fluid further comprises liquid lithium or lithium-lead eutectic, and the one or more elements are erbium, yttrium, and calcium dissolved in the carrier fluid at a concentration of 5 to 10 wt %.

23. 23. The tokamak of claim 22, wherein, in use, the tritium breeder blanket comprises a carrier fluid in contact with the ceramic coating, the carrier fluid comprising gaseous molecules comprising one or more of carbon, nitrogen and / or oxygen.

24. 24. The tokamak of claim 23, wherein the gaseous molecules are any one or more of nitrogen, nitrogen oxides, carbon monoxide, carbon dioxide, water vapor, and oxygen, and the carrier fluid further comprises any one of a helium-hydrogen mixture, liquid lithium, and a lead-lithium eutectic.

25. 10. Use of a component manufactured by the method of claim 1 in an apparatus, said component comprising a sintered body and a ceramic coating.

26. 26. The use according to claim 25, wherein the device is a magnetic confinement plasma chamber.

27. 26. The use according to claim 25, wherein the device is a system for transporting hydrogen.

28. 1. A method for manufacturing a component having a ceramic coating, comprising: at least partially filling a container with a powder material; subjecting the powder material to a compaction pressure at a temperature and for a time sufficient to at least partially solidify the powder material and form a body of the component; converting an exterior surface of the container to a ceramic coating, leaving an unconverted layer of the container between the body of the component and the ceramic coating; A method comprising:

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