Hydrogen shielding film

Abstract

To provide a hydrogen shielding film that can suppress hydrogen embrittlement of a structural material for a long term under a hydrogen environment.SOLUTION: A hydrogen shielding film is constituted of a multilayer film laminated on an outside surface of a structural material comprising a metal and / or an alloy which are susceptible to hydrogen embrittlement. The number of layers constituting the multilayer film is at least two. The number of layers constituting the multilayer film laminated in part of the region of the outside surface of the structural material is different from the number of layers constituting the multilayer film laminated in the other regions of the outside surface of the structural material. In a hydrogen-resistant structural material, the whole outside surface of the structural material is coated on the hydrogen shielding film.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to hydrogen barrier membranes. More particularly, the present disclosure relates to hydrogen barrier membranes for structural materials. [Background technology]

[0002] In recent years, technological development related to hydrogen energy has been progressing with the aim of utilizing hydrogen, which is expected to be a clean energy source to replace fossil fuels. In each stage of hydrogen production, storage, transportation and use, buildings, facilities, machinery, etc. are placed in a hydrogen environment.

[0003] Metallic materials are widely used in buildings, facilities, machinery, etc. It has been known that metal materials are susceptible to fracture due to hydrogen embrittlement. Hydrogen embrittlement is believed to occur when hydrogen penetrates into metal materials. In the development of hydrogen utilization technology, brittle fracture of metal components exposed to hydrogen is a major safety issue. There is a need for technology to suppress hydrogen embrittlement of metallic materials in hydrogen environments.

[0004] Non-Patent Document 1 (E. Serra et al., "Hydrogen Permeation Measurements on Alumina," Journal of American Ceramic Society (2004)) discloses ceramics as a material with hydrogen barrier properties. Non-Patent Document 2 (Tsukahara Sonoko, "Metallic Materials and Hydrogen Viewed as Ultra-High Vacuum Materials," Applied Physics (2000)) describes research into TiN coating of metal parts to suppress hydrogen release from the metal parts in order to improve the degree of vacuum in vacuum equipment.

[0005] Patent Document 1 (JP 2021-139009 A) discloses a hydrogen barrier functional film with a thickness of 0.5 μm to 2 μm, which is made by stacking layers made of alloy nitrogen-containing compounds in a total of 10 to 1000 layers.Furthermore, with regard to rare earth magnets, which are known to be materials that are susceptible to hydrogen embrittlement, Patent Document 2 (JP 2007-116171 A) discloses a method for preventing hydrogen embrittlement of rare earth sintered magnets, in which a metal oxide layer and / or a metal nitride layer is formed on the surface of the rare earth sintered magnet directly or via a metal plating layer. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent Publication No. 2021-139009 [Patent Document 2] Japanese Patent Application Laid-Open No. 2007-116171 [Non-patent literature]

[0007] [Non-Patent Document 1] E. Serra et. al., "Hydrogen Permeation Measurements on Alumina", Journal of American Ceramic Society (2004) [Non-patent document 2] Tsukahara Sonoko, "Metallic materials and hydrogen viewed as ultra-high vacuum materials," Applied Physics (2000) Summary of the Invention [Problem to be solved by the invention]

[0008] In the case of ceramic coatings or metal coatings, tiny cracks or pinholes usually form during film formation. Furthermore, when a metal film is subjected to high-temperature oxidation treatment to form a metal oxide layer, the coating may peel off during the high-temperature treatment. Hydrogen gas can pass through tiny cracks or pinholes formed in the coating. If cracks or pinholes penetrate the coating, hydrogen that has passed through the coating comes into contact with the metal material. The presence of coating peeling increases the likelihood of hydrogen coming into contact with the metal material, which may result in embrittlement. Furthermore, under high-pressure environments, hydrogen permeates the coating more easily and also penetrates more easily into the metal material it comes into contact with, accelerating hydrogen embrittlement.

[0009] No technology has yet been proposed that simply and efficiently prevents hydrogen embrittlement in structural materials exposed to hydrogen for long periods under pressures of several MPa or more, which is required in hydrogen energy-related technologies.The purpose of this disclosure is to provide a hydrogen barrier film that can suppress hydrogen embrittlement in structural materials for long periods in hydrogen environments. [Means for solving the problem]

[0010] The hydrogen barrier film according to the present disclosure is a hydrogen barrier film for covering a structural material made of a hydrogen-embrittled metal and / or alloy. This hydrogen barrier film is composed of a multilayer film laminated on the outer surface of the structural material. The number of layers constituting this multilayer film is two or more. [Effects of the Invention]

[0011] The hydrogen barrier film according to the present disclosure has excellent hydrogen barrier properties. By covering a structural material with this hydrogen barrier film, contact between hydrogen gas and the structural material can be prevented for a long period of time in a high-pressure hydrogen environment. A structural material provided with this hydrogen barrier film has excellent durability in a hydrogen environment. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a cross-sectional view of a hydrogen barrier film according to an embodiment of the present disclosure. [Figure 2] 2A and 2B are conceptual diagrams for explaining the hydrogen barrier film of the present disclosure. [Figure 3] 3A to 3F are conceptual diagrams for explaining a method for manufacturing the hydrogen-shielding film of FIG. [Figure 4] FIG. 4 shows images of cross sections of Example 1 and Comparative Example 2 taken by a scanning electron microscope. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, the present disclosure will be described in detail based on preferred embodiments, with reference to the drawings as appropriate. The present disclosure is not limited to the following embodiments, and additions, deletions, and modifications are possible within the scope of the present disclosure. In this specification, unless otherwise specified, "X to Y" means "X or more and Y or less."

[0014] [Hydrogen shielding film] The hydrogen barrier film according to the present disclosure is formed by coating the outer surface of a structural material made of a metal material that is susceptible to hydrogen embrittlement. Specifically, this hydrogen barrier film is composed of a multilayer film laminated on the outer surface of the structural material. The number of layers constituting this multilayer film is at least two. In the present disclosure, the number of layers constituting the multilayer film constituting the hydrogen barrier film differs in parts. In other words, in this hydrogen barrier film, the number of layers constituting the multilayer film laminated in a part of the outer surface of the structural material, which covers the entire outer surface of the structural material, is different from the number of layers constituting the multilayer film laminated in another part of the outer surface of the structural material.

[0015] In this specification, the phrase "composed of a multilayer film" means that the hydrogen barrier film of the present disclosure is substantially a multilayer film. Hereinafter, each layer constituting the multilayer film may be referred to as a "film" or a "coating." In addition, in this specification, the term "structural material" means a member for constituting a structure such as a building, device, or machine. The term "metallic material" refers to a metal and / or alloy, and the term "metal" refers to a single metal, and the term "alloy" refers to a substance composed of two or more elements including a metallic element, and is a concept that includes intermetallic compounds. The term "hydrogen-embrittled metallic material" refers to a metal or alloy that is susceptible to embrittlement when in contact with hydrogen.

[0016] According to the hydrogen barrier film of the present disclosure, the multilayer film of two or more layers inhibits hydrogen permeation in a hydrogen environment of several MPa. In a structural material whose entire outer surface is covered with this hydrogen barrier film, contact between hydrogen and the structural material is avoided. This suppresses hydrogen embrittlement in structural materials made of hydrogen-embrittled metals and / or alloys, reducing brittle fracture caused by hydrogen. The hydrogen shielding of the present disclosure can contribute to improving the durability and safety of structural materials in a hydrogen environment.

[0017] 1 shows a cross-sectional view of a hydrogen barrier film 40 according to an embodiment of the present disclosure. The hydrogen barrier film 40 is composed of a multilayer film 40 including a first layer 6 laminated on the outer surface of a structural material 4, a second layer 8 laminated on the outer surface of the first layer, a third layer 10 laminated on the outer surface of the second layer 8, and a fourth layer 12 laminated on the outer surface of the third layer.

[0018] The structural material 4 is made of a metal and / or alloy that is susceptible to hydrogen embrittlement. As shown in the figure, the number of layers in one region of the outer surface of the structural material 4 differs from the number of layers in other regions of the outer surface of the structural material 4, but at least two layers are laminated over the entire outer surface of the structural material 4. That is, the hydrogen shielding film 40 covers the entire outer surface of the structural material 4. In other words, the structural material 4 is shielded from the outside air by the hydrogen shielding film 40, which is composed of the first layer 6, the second layer 8, the third layer 10, and the fourth layer 12. The outer surface of the structural material 4 is not exposed to the outside air (i.e., hydrogen) even in a hydrogen environment. The structural material 4, whose entire outer surface is covered with the hydrogen shielding film 40, has excellent durability in a hydrogen environment. A hydrogen-resistant structural material 2 according to an embodiment of the present disclosure includes the hydrogen shielding film 40 and the structural material 4.

[0019] In Figure 1, the region indicated by the double-headed arrow M is a region where a two-layer film consisting of a first layer 6 and a second layer 8 is laminated on the outer surface of the structural material 4. Figures 2A and 2B show partially enlarged cross-sectional views (conceptual diagrams) for explaining the state of this region M during the process of forming the first and second layers. The configuration and effects of the present disclosure will be explained below using Figures 2A and 2B.

[0020] 2A shows a structural material 4 and a portion of a first layer 6 that covers the outer surface of the structural material 4. As shown in the figure, the first layer 6 contains a plurality of minute cracks 14. It is believed that the cracks 14 in the first layer 6 are generated during the formation of the first layer 6. The cracks 14 may penetrate the first layer 2.

[0021] 2B shows a structural material 4, a first layer 6 covering the outer surface of the structural material 4, and a portion of a second layer 8 covering the outer surface of the first layer 6. As shown in the figure, the second layer 8 also contains a plurality of minute cracks 14. It is believed that the cracks 14 in the second layer 8 are generated during the formation of the second layer 8. In some cases, the cracks 14 penetrate the second layer 8.

[0022] In this specification, the term "crack" refers to a defect or void present in the coating immediately after the coating is formed, and there are no particular limitations on the shape of the crack. The presence of cracks in the coating can be confirmed by observation with an optical microscope or an electron microscope.

[0023] 2B , in region M of this hydrogen barrier film 40, no cracks 14 in the second layer 8 are located directly below the cracks 14 in the first layer 6. In other words, this hydrogen barrier film 40 does not include cracks 14 that penetrate from its outer surface toward the structural material 4. With this hydrogen barrier film 40, hydrogen gas that passes through the cracks 14 in the first layer 6 is blocked by the second layer 8. In region M of this hydrogen barrier film 40, contact between the structural material 4 and hydrogen gas is inhibited in a hydrogen environment.

[0024] According to conventionally known film-forming methods and film-forming conditions, it is difficult to completely avoid the formation of cracks 14 during film formation. However, the size (surface area) of the first layer 6 and the second layer 8 is usually sufficiently large compared to the size of the cracks 14 formed during film formation. Therefore, the probability that a crack 14 contained in the second layer 28 will be located directly above a crack 14 contained in the first layer 26 is sufficiently small.

[0025] Similarly, in other regions forming the outer surface of the structural material 4, the third layer 10 laminated on the outer surface of the second layer 8 and the fourth layer 12 laminated on the outer surface of this third layer 10 may each contain multiple cracks. These cracks may penetrate each of the layers forming the multilayer film 40. However, the size of the cracks is considerably small compared to the size (surface area) of the third layer 10 and the fourth layer 12. Therefore, the probability that a crack in the third layer 10 or the fourth layer 12 is located directly above a crack in another layer is sufficiently small. Therefore, the probability that a crack in each layer will form so as to penetrate all of the layers forming the multilayer film 40 is considered to be quite small.

[0026] In this hydrogen barrier film composed of the multilayer film 40, hydrogen gas passing through cracks in the outermost fourth layer 12 is blocked by the inner third layer 10 and does not reach the structural material 4. This hydrogen barrier film 40, composed of at least two multilayer films, effectively prevents hydrogen gas from permeating. Even if multiple microcracks 14 are formed in the layers of the multilayer film during deposition, this hydrogen barrier film 40 can prevent hydrogen gas from permeating the hydrogen barrier film 40 and coming into contact with the structural material 4. This hydrogen barrier film has high hydrogen barrier properties. Even when the structural material 4 coated with this hydrogen barrier film 40 is exposed to a hydrogen environment for a long period of time, morphological changes and performance degradation due to hydrogen embrittlement are suppressed. By covering the entire outer surface of the structural material 4 with this hydrogen barrier film, a hydrogen-resistant structural material 2 with excellent durability in a hydrogen environment can be obtained.

[0027] As described above, the hydrogen barrier film of the present disclosure is composed of a multilayer film. From the viewpoint of effectively blocking the passage of hydrogen gas in a hydrogen environment, the number of layers constituting the multilayer film is at least 2, and may be 3 or more, 4 or more, 5 or more, or 6 or more, and may be 20 or less, 15 or less, or 10 or less. Preferably, the number of layers constituting the multilayer film is selected from the range of 2 to 10.

[0028] In an embodiment in which the number of layers of the multilayer film varies in different regions, the number of layers of the multilayer film laminated in each region of the outer surface of the structural material may be selected from 2 to 20, and preferably selected from 2 to 10. For example, in one embodiment of the present disclosure, the number of layers of the multilayer film may be at least 2 in the entire region of the outer surface of the structural material, and the number of layers of the multilayer film may be 3 or more in a portion of the outer surface of the structural material. In another embodiment, the number of layers of the coating may be at least 2 in the entire region of the outer surface of the structural material, and the number of layers of the multilayer film may be 3 or more in a portion of the outer surface of the structural material, and the number of layers of the multilayer film may be 4 or more in another portion of the outer surface of the structural material.

[0029] As long as the effects of the present disclosure can be obtained, the thickness of the multilayer film is not particularly limited. Similarly, the thickness of each layer constituting the multilayer film is not particularly limited. For example, the thickness of each layer constituting the multilayer film may be 1 nm or more, 2 nm or more, 3 nm or more, or 5 nm or more, and may be 10 μm or less, 9 μm or less, or 8 μm or less. The thicknesses of each layer constituting the multilayer film may be the same or different.

[0030] The average thickness of the entire multilayer film may be 2 nm or more, 3 nm or more, or 5 nm or more, or 20 μm or less, or 18 μm or less. The hydrogen barrier film may be composed of a multilayer film having the same thickness over the entire area of the outer surface of the structural material, or may include a multilayer film having a different thickness in a partial area of the outer surface of the structural material. The thickness of the multilayer film and the thickness of each layer constituting the multilayer film can be determined by observation using an optical microscope or an electron microscope.

[0031] The material of the multilayer film may be any material having hydrogen barrier properties, such as ceramics, metals, and alloys. Examples of metals used as the material of the multilayer film include aluminum (Al), chromium (Cr), titanium (Ti), and zinc (Zn). Two or more metals may be used in combination.

[0032] Examples of alloys include titanium alloys, aluminum alloys, chromium alloys, and zinc alloys. Among these, titanium alloys (Ti alloys) are preferred, and titanium alloys with a titanium content of 60% by mass or more are more preferred. The titanium content of the titanium alloy may be 70% by mass or more, 80% by mass or more, or 90% by mass or more. As long as the effects of the present disclosure are obtained, the titanium alloy may contain other elements that are intentionally added or may contain other elements as unavoidable impurities. Examples of other elements contained in the titanium alloy include nickel (Ni), aluminum (Al), V (vanadium), Mo (molybdenum), iron (Fe), palladium (Pd), platinum (Pt), tin (Sn), niobium (Nb), zinc (Zn), and chromium (Cr). Two or more types of alloys may be used in combination.

[0033] As used herein, the term "ceramics" refers to inorganic compounds such as oxides, carbides, nitrides, borides, and fluorides of metal and nonmetal elements, as well as composite compounds thereof. Metal elements constituting ceramics include aluminum (Al), chromium (Cr), erbium (Er), titanium (Ti), tungsten (W), zirconium (Zr), iron (Fe), zinc (Zn), magnesium (Mg), calcium (Ca), niobium (Nb), lead (Pb), lanthanum (La), cerium (Ce), gallium (Ga), hafnium (Hf), neodymium (Nd), manganese (Mn), tantalum (Ta), antimony (Sb), strontium (Sr), tin (Sn), nickel (Ni), and yttrium (Y). Nonmetal elements constituting ceramics include silicon (Si), boron (B), and the like.

[0034] Examples of ceramics used as materials for the multilayer film include oxide ceramics such as Al2O3, Cr2O3, Er2O3, SiO2, ZrO2, TiO2, ZrSiO4, MgO, and Al2O3·TiO2; nitride ceramics such as BN, TiN, TiAlN, SiN, WN, CrWN, CrN, Cr2N, AlCrN, ZrN, TaN, AlN, Si3N4, HfN, and NbN; carbide ceramics such as TiC, SiC, ZrC, TaC, HfC, and Cr3C2; and fluoride ceramics such as CaF2, YF3, and Y2O3F. Two or more ceramics may be used in combination. Ceramics may also be used in combination with the metals and / or alloys described above.

[0035] The material of the multilayer film may be one or more selected from the group consisting of oxide ceramics, nitride ceramics, carbide ceramics, metals, and alloys. The material of the multilayer film may be one or more selected from the group consisting of Al2O3, Cr2O3, Er2O3, SiO2, BN, TiN, TiAlN, SiN, WN, CrWN, CrN, Cr2N, AlCrN, ZrN, TiC, Al, Cr, Zn, Ti, and Ti alloys. Furthermore, as long as the effects of the present disclosure are obtained, the materials of the layers constituting the multilayer film may be the same or different.

[0036] The method for forming the hydrogen barrier film by laminating a multilayer film on the outer surface of the structural material is not particularly limited, and known techniques such as physical vapor deposition (PVD), chemical vapor deposition (CVD), and thermal spraying can be appropriately selected and used. Examples of physical vapor deposition (PVD) include vacuum deposition, sputtering, and ion plating. Examples of chemical vapor deposition (CVD) include thermal CVD, plasma CVD, and photo CVD. Examples of thermal spraying include flame spraying, high-velocity flame spraying, detonation spraying, electric spraying, and cold spray. Depending on the materials of the multilayer film and the structural material, electrolytic or electroless plating may also be used.

[0037] As an example, a method for manufacturing a hydrogen shielding film using a sputtering apparatus will be described below. The sputtering apparatus is equipped with a vacuum chamber. A workpiece and a target are placed in the vacuum chamber, and a small amount of inert gas (e.g., argon gas) is introduced into the chamber. The inert gas is converted into plasma and collides with the target. This collision causes components of the target to be ejected at the molecular level, which then adhere and deposit on the workpiece placed opposite the target. This adhesion and deposition forms a layer made of the components of the target on the surface of the workpiece. Note that, in the present disclosure, regardless of the manufacturing method, it is sufficient to laminate a multilayer film so as to obtain a hydrogen shielding film that covers the entire outer surface of the structure, and the apparatus and conditions can be selected according to the material of the structure and the multilayer film.

[0038] 3A to 3F show an example of a method for manufacturing a hydrogen barrier film according to one embodiment. In these figures, the top-to-bottom direction is the vertical direction, and the left-to-right direction is the horizontal direction. In these figures, reference numeral 16 denotes a holder for holding a workpiece in a vacuum chamber of a sputtering apparatus.

[0039] As shown in FIG. 3A, in this manufacturing method, first, a structural material 4 made of a hydrogen-embrittled metal material is prepared and placed on a holder 16. A target is disposed in a position facing the structural material 4 in the vacuum chamber. The target contains the constituent components of the multilayer film described above. The target material may be, for example, one or more selected from the group consisting of oxide ceramics, nitride ceramics, carbide ceramics, metals, and alloys. Sputtering is performed using this target to form a first layer 6 that coats the outer surface of the structural material 4 and constitutes a multilayer film 40 (FIG. 3B). Subsequently, sputtering is performed using the same target or a target made of a different material to form a second layer 8 that coats the outer surface of the first layer 6 and constitutes a multilayer film 40 (FIG. 3C).

[0040] 3B and 3C, the first layer 6 and the second layer 8 are formed in the region where the structural material 4 is not in contact with the holding portion 16, but are not formed in the region where the structural material 4 is in contact with the holding portion 16. In other words, the outer surface of this structural material 4 is composed of a region covered with a multilayer film 40 having a two-layer structure consisting of the first layer 6 and the second layer 8, and a region not covered with the multilayer film 40.

[0041] Next, the structural material 4 coated with the first layer 6 and the second layer 8 is turned upside down and placed on the holder 16 so that the area not coated with the multilayer film 40 faces up (FIG. 3D). In other embodiments, it is not necessary to turn the structural material 4 upside down, but it is sufficient to change the position where it comes into contact with the holder 16 and move it so that the area not coated with the multilayer film 40 is exposed.

[0042] After the structural material 4 coated with the first layer 6 and the second layer 8 is turned upside down, sputtering is performed using the same target or a target of a different material to coat the outer surface of the second layer 8 and part of the outer surface of the structural material 4, forming a third layer 10 constituting the multilayer film 40 (FIG. 3E). Subsequently, sputtering is performed using the same target or a target of a different material to coat the outer surface of the third layer 10, forming a fourth layer 12 constituting the multilayer film 40 (FIG. 3F).

[0043] 3E and 3F , the third layer 10 and the fourth layer 12 are formed in the region where the second layer 8 is not in contact with the retainer 16, but are not formed in the region where the second layer 8 is in contact with the retainer 16. According to this manufacturing method, the regions of the structural material 4 that are not covered with the first layer 6 and the second layer 8 are covered with the third layer 10 and the fourth layer 12. As a result, a hydrogen barrier film composed of a multilayer film 40 of two or more layers is obtained, which is laminated on the outer surface of the structural material 4 and covers the entire outer surface. In other words, the outer surface of the structural material 4 is composed of a region covered with the multilayer film 40 having a four-layer structure consisting of the first layer 6, the second layer 8, the third layer 10, and the fourth layer 12, and a region covered with the multilayer film 40 having a two-layer structure consisting of the third layer 10 and the fourth layer 12. In other words, this hydrogen barrier film is composed of a four-layer multilayer film 40 laminated on a portion of the outer surface of the structural material 4, and a two-layer multilayer film 40 laminated on another portion of the outer surface of the structural material 4.

[0044] The manufacturing method of the hydrogen barrier film in this embodiment includes placing the structural material 4 on the holder 16 (FIG. 3A), forming the first layer 6 and the second layer 8 on the outer surface of the structural material 4 (except for the portion in contact with the holder 16) by sputtering (FIGS. 3B and 34C), moving the structural material 4 coated with the first layer 6 and the second layer 8 so that the outer surface of the second layer 8 contacts the holder 16 (FIG. 3D), and forming the third layer 10 and the fourth layer 12 on the outer surface of the second layer 8 (except for the portion in contact with the holder 16) by sputtering (FIGS. 3E and 34F). A cross-sectional view of the hydrogen barrier film composed of the multilayer film 40 laminated on the outer surface of the structural material 4 by this manufacturing method is shown in FIG.

[0045] As shown in FIG. 1 , a multilayer film 40 covers the entire outer surface of the structural material 4. This multilayer film 40 includes a first layer 6, a second layer 8, a third layer 10, and a fourth layer 12, each of which is made of a material having hydrogen gas barrier properties. As described above, this hydrogen barrier film does not contain any cracks that penetrate from the fourth layer 12 to the first layer 6. The first layer 6, the second layer 8, the third layer 10, and the fourth layer 12 each inhibit the permeation of hydrogen gas. This hydrogen barrier film has excellent hydrogen barrier properties.

[0046] The hydrogen barrier performance of the hydrogen shielding film of the present disclosure can be confirmed by a hydrogen exposure test using a rare-earth magnet, which is highly susceptible to hydrogen embrittlement, as a structural material. Specifically, a rare-earth magnet coated with the hydrogen shielding film is used as a test specimen and exposed to high-pressure (e.g., 1 MPa to 100 MPa) hydrogen gas, and morphological changes are observed after a long period of time (e.g., 1,000 hours or more). Rare-earth magnets without a hydrogen shielding film are pulverized due to hydrogen embrittlement in a hydrogen environment at room temperature and atmospheric pressure. In contrast, rare-earth magnets coated with the hydrogen shielding film of the present disclosure show no change in appearance even after being exposed to 4 MPa hydrogen gas at room temperature for 1,000 hours. This result indicates that the hydrogen shielding film of the present disclosure prevents contact between hydrogen gas and the structural material, preventing hydrogen embrittlement of the structural material. Note that instead of observing the morphology after hydrogen exposure, the hydrogen barrier performance of the hydrogen shielding film may be evaluated by measuring magnetic properties such as coercivity.

[0047] Preferably, the hydrogen barrier film of the present disclosure has a durability in a hydrogen atmosphere of 200 hours or more as determined by the following evaluation test. In this evaluation test, a test specimen is prepared by coating the entire outer surface of a neodymium magnet, which is a rare earth magnet, with a hydrogen barrier film. This test specimen is stored in a hydrogen gas environment (pressure of 4 MPa, room temperature), and the test specimen is observed with the naked eye for changes over time. The storage time during which no change in the appearance of the test specimen is observed is determined as the "durability in a hydrogen atmosphere." From the perspective of improving hydrogen barrier properties, the durability of the hydrogen barrier film in a hydrogen atmosphere may be 300 hours or more, 500 hours or more, 700 hours or more, 900 hours or more, or 1000 hours or more.

[0048] Thus, the hydrogen barrier film of the present disclosure can impart excellent durability to structural materials in hydrogen environments. This hydrogen barrier film prevents hydrogen gas from reaching the structural material even when placed in a hydrogen environment for a long period of time. By being coated with this hydrogen barrier film, hydrogen embrittlement of metal materials that are prone to hydrogen embrittlement is suppressed. Structural materials equipped with this hydrogen barrier film can be used for long periods of time in high-pressure hydrogen environments.

[0049] [Structural material] The material of the structural material may be any metal or alloy that is susceptible to hydrogen embrittlement, and may be selected appropriately from metal materials used for components that constitute structures such as buildings, devices, and machines.

[0050] Typical metal materials used in structural materials include steel and / or non-ferrous metals. For example, high-strength steel with a tensile strength exceeding 1,000 MPa and titanium and titanium alloys are known to be susceptible to hydrogen embrittlement. The hydrogen barrier film of the present disclosure is particularly effective in structural materials made from these steel and / or non-ferrous metals that are known to be susceptible to hydrogen embrittlement.

[0051] Here, steel materials are materials primarily composed of iron (Fe) and are classified into pure iron with a carbon content of less than 0.02% by mass, steel with a carbon content of 0.02% to less than 2.1% by mass, and cast iron with a carbon content of 2.1% to less than 6.7% by mass. For example, according to classifications such as the Japanese Industrial Standards (JIS), rolled steel, rolled steel plates and strips, steel pipes, wire rods, steel for machine structures, steel for tools, steel for special applications, cast steel, and cast iron may be used as structural materials. Furthermore, steel materials may contain elements other than iron and carbon. Examples of such elements include, but are not limited to, silicon (Si), manganese (Mn), chromium (Cr), molybdenum (Mo), copper (Cu), nickel (Ni), boron (B), phosphorus (P), sulfur (S), and oxygen (O).

[0052] Non-ferrous metal materials are materials whose main component is a metal element other than iron. Examples of non-ferrous metal materials used for structural materials include, but are not limited to, aluminum (Al) and its alloys, copper (Cu) and its alloys, titanium (Ti) and its alloys, zinc (Zn) and its alloys, and magnesium (Mg) and its alloys.

[0053] Note that in this specification, the term "structural material" does not include ferromagnetic materials containing rare earth elements. In other words, the structural material in this disclosure is a metal and / or alloy (excluding ferromagnetic materials containing rare earth elements) that is susceptible to hydrogen embrittlement. Here, rare earth elements refer to the lanthanoid group from lanthanum (atomic number 57) to lutetium (atomic number 71), scandium (atomic number 21), and yttrium (atomic number 39). Intermetallic compounds of these rare earth elements with iron-group elements such as iron and cobalt are known as ferromagnetic materials. In other words, the structural material in this disclosure may be a metal and / or alloy, excluding intermetallic compounds of rare earth elements and iron-group elements.

[0054] As long as the effects of the present disclosure can be obtained, the outer shape, size, etc. of the structural material are not particularly limited. A structural material of an appropriate shape can be selected and used depending on the application.

[0055] [Hydrogen-resistant structural material] The hydrogen-resistant structural material according to the present disclosure includes the aforementioned structural material and hydrogen barrier film. As shown in FIG. 1, in the hydrogen-resistant structural material (2), the entire outer surface of the structural material (4) is covered with a hydrogen barrier film (40). As shown, the hydrogen barrier film (40) is composed of two or more multilayer films laminated on the outer surface of the structural material (4). The number of layers constituting the multilayer film laminated on a portion of the outer surface of the structural material (4) is different from the number of layers constituting the multilayer film laminated on other portions of the outer surface of the structural material (4). As described above, the structural material (4) is made of a metal or alloy that is susceptible to hydrogen embrittlement. Typically, the structural material (4) is made of a steel material or a non-ferrous metal material.

[0056] In the hydrogen-resistant structural material according to the present disclosure, the structural material is shielded from the outside air by a hydrogen barrier film consisting of two or more multilayer films. In this hydrogen-resistant structural material, the outer surface of the structural material is not exposed to the outside air. Furthermore, as described above, this hydrogen-resistant structural material does not contain cracks penetrating the hydrogen barrier film from its outer surface toward the structural material. Even if some layers of the multilayer film contain cracks, the other layers of the multilayer film block the passage of hydrogen gas, preventing contact between the hydrogen gas and the structural material. As a result, this hydrogen-resistant structural material is prevented from undergoing morphological changes and performance degradation due to hydrogen embrittlement, even when exposed to a hydrogen environment for a long period of time. This hydrogen-resistant structural material exhibits excellent durability in a hydrogen environment, particularly a high-pressure hydrogen environment.

[0057] The hydrogen-resistant structural material according to the present disclosure is suitable for use as a substitute for metal components used in hydrogen environments. For example, in the hydrogen energy field, it can be used as components for buildings, facilities, devices, and the like used in the production, storage, transportation, and use of hydrogen. Specific examples include various components such as compressors and coolers exposed to hydrogen in hydrogen production plants, piping and valves connecting various devices, hydrogen storage containers, components constituting hydrogen transport equipment (e.g., vehicles, ships, etc.), and various components for fuel cells and fuel cell vehicles used for hydrogen utilization. The uses of the hydrogen-resistant structural material according to the present disclosure are not limited to these, and it can be used for various applications not described in this specification. [Example]

[0058] The effects of the present disclosure will be clarified below by examples, but the present disclosure should not be interpreted as being limited based on the description of these examples.

[0059] (Evaluation method: Hydrogen exposure test) A hydrogen exposure test was conducted using neodymium magnets, which are susceptible to hydrogen embrittlement, to evaluate the hydrogen shielding properties of the hydrogen shielding films of the examples and comparative examples. Specifically, a neodymium magnet whose entire outer surface was coated with a hydrogen shielding film was used as a test specimen, which was then stored in a hydrogen gas environment (pressure of 4 MPa, room temperature) for up to 1,000 hours, and the test specimen was observed with the naked eye for any changes in appearance. The observation results are shown in Table 1 below. In Table 1, "○" indicates that the test specimen was not damaged or had no change in appearance, while "×" indicates that damage to the test specimen was observed. The storage time during which no change in appearance was observed for the test specimen was determined as the "durability time in a hydrogen atmosphere."

[0060] (Production of test specimen: Formation of hydrogen barrier film) [Example 1] A specimen having the hydrogen shielding film of Example 1 was prepared according to the manufacturing process shown in FIGS. 3A-3F. First, a neodymium magnet was prepared in place of the structural material (4). This neodymium magnet was placed in the holder (16) of a sputtering device, and CrN was sputtered to obtain a first layer (6) having a thickness of 2 to 3 μm. Visual inspection confirmed that the first layer (6) had been formed on the entire surface of the main body (4) except for the contact area between the main body (4) and the holder (16). Subsequently, CrN was sputtered to obtain a second layer (8) having a thickness of 2 to 3 μm. Visual inspection confirmed that the second layer (8) had been formed on the entire surface of the main body (4) except for the contact area between the main body (4) and the holder (16).

[0061] Next, the main body 4 on which the first layer 6 and the second layer 8 were formed was removed from the sputtering apparatus and placed back on the holder 16 so that the areas where the first layer 6 and the second layer 8 were formed were in contact with the holder 16. Then, CrN was sputtered in the same manner as for the first layer 6 and the second layer 8, forming a third layer 10 and a fourth layer 12, each with a thickness of 2 to 3 μm, to obtain a specimen having the hydrogen barrier film 40 of Example 1. A scanning electron microscope (SEM) image of the cross section of this hydrogen barrier film 40 is shown in FIG. 4. The photograph shown in the "Contrast Enhancement" column in FIG. 4 was obtained by image processing of raw data to clearly show cracks. As shown in FIG. 4, in Example 1, cracks were visible near the main body, but they did not reach the surface of the hydrogen barrier film, and it was confirmed that no cracks penetrated the hydrogen barrier film.

[0062] [Example 2] A specimen having a hydrogen barrier film of Example 2 was obtained in the same manner as Example 1, except that Ti (pure titanium) was sputtered instead of Cr2N of Example 1.

[0063] [Comparative Example 1] The neodymium magnet prepared in Example 1 was used as a specimen for Comparative Example 1. The specimen for Comparative Example 1 was not provided with a hydrogen-shielding film.

[0064] Comparative Example 2 A specimen with a hydrogen barrier film of Comparative Example 2 was obtained by coating the entire surface of the neodymium magnet prepared in Example 1 with a single layer of CrN film. A scanning electron microscope (SEM) image of the cross section of the hydrogen barrier film of Comparative Example 2 is shown in Figure 4. The photograph shown in the "Contrast Enhancement" column in Figure 4 was obtained by processing the raw data to clearly show cracks. As shown in Figure 4, it was confirmed that cracks penetrated the hydrogen barrier film in Comparative Example 2.

[0065] [Table 1]

[0066] As shown in Table 1, Comparative Example 1, which had no hydrogen barrier film, and Comparative Example 2, which had a single hydrogen barrier film, were damaged and pulverized within 168 hours. In contrast, Examples 1 and 2, which had a multilayer hydrogen barrier film consisting of two or more layers, showed no change in appearance even after 1,000 hours of storage. These results demonstrate that by covering the outer surface of a structural material made of a hydrogen-embrittled metal or alloy with the hydrogen barrier film of the present disclosure, hydrogen embrittlement of the structural material can be suppressed for a long period of time, even in a hydrogen environment of several MPa.

[0067] [Disclosure items] Each of the following sections discloses a preferred embodiment.

[0068] [Item 1] It is composed of a multilayer film laminated on the outer surface of a structural material made of a hydrogen-embrittled metal and / or alloy, and the number of layers constituting this multilayer film is two or more, A hydrogen barrier film in which the number of layers constituting the multilayer film laminated on a portion of the outer surface of the structural material is different from the number of layers constituting the multilayer film laminated on another portion of the outer surface of the structural material.

[0069] [Item 2] Item 2. The hydrogen barrier film according to item 1, wherein the number of layers constituting the multilayer film is selected from the range of 2 to 10.

[0070] [Item 3] 3. The hydrogen barrier film according to item 1 or 2, wherein the thickness of each layer constituting the multilayer film is 1 nm or more and 10 μm or less.

[0071] [Item 4] 4. The hydrogen barrier film according to any one of items 1 to 3, wherein the materials of the layers constituting the multilayer film are one or more selected from the group consisting of Al2O3, Cr2O3, Er2O3, SiO2, BN, TiN, TiAlN, SiN, WN, CrWN, CrN, Cr2N, AlCrN, ZrN, TiC, Al, Cr, Zn, Ti, and Ti alloys.

[0072] [Item 5] 5. The hydrogen barrier film according to item 4, wherein the Ti alloy has a titanium content of 60 mass % or more.

[0073] [Item 6] 6. The hydrogen barrier film according to any one of items 1 to 5, wherein the thickness of each layer constituting the multilayer film is 1 nm or more and 10 μm or less.

[0074] [Item 7] 7. The hydrogen barrier film according to any one of items 1 to 6, wherein the multilayer film includes layers made of different materials.

[0075] [Item 8] 8. The hydrogen barrier film according to any one of items 1 to 7, wherein the multilayer film does not contain any cracks penetrating from its outer surface toward the structure.

[0076] [Item 9] 9. The hydrogen barrier film according to any one of items 1 to 8, which has a durability of 200 hours or more in a hydrogen atmosphere as determined by the following evaluation test. (Evaluation test) The entire outer surface of a neodymium magnet is coated with the above-mentioned hydrogen-shielding film to form a test specimen. This test specimen is then stored in a hydrogen gas environment (pressure 4 MPa, room temperature), and the test specimen is observed with the naked eye for changes over time. The storage time during which no change in the appearance of the test specimen is observed is determined as the "durability time in a hydrogen atmosphere."

[0077] [Item 10] A hydrogen-resistant structural material, the entire outer surface of which is covered with the hydrogen barrier film according to any one of items 1 to 9.

[0078] [Item 11] Item 11. A hydrogen-resistant structural material according to item 10, wherein the structural material is made of a steel material and / or a non-ferrous metal material. [Industrial Applicability]

[0079] The hydrogen barrier film and the hydrogen-resistant structural material provided with this hydrogen barrier film described above can be used in a variety of applications requiring durability in a hydrogen environment. [Explanation of symbols]

[0080] 2...Water resistant structural material 4...Structural material 6...First layer 8...Second layer 10...Third layer 12...Fourth layer 40 Hydrogen barrier film 14. Crack 16...Holding part

Claims

1. The multilayer film is laminated on the outer surface of a structural material made of a hydrogen-embrittled metal and / or alloy, and the number of layers constituting the multilayer film is at least two; A hydrogen barrier film in which the number of layers constituting the multilayer film laminated on a portion of the outer surface of the structural material is different from the number of layers constituting the multilayer film laminated on another portion of the outer surface of the structural material.

2. 2. The hydrogen barrier film according to claim 1, wherein the number of layers constituting the multilayer film is selected from the range of 2 to 10.

3. 2. The hydrogen barrier film according to claim 1, wherein the materials of the layers constituting the multilayer film are one or more selected from the group consisting of oxide ceramics, nitride ceramics, carbide ceramics, metals and alloys.

4. The material of the layers constituting the multilayer film is Al ２ O ３ , Cr ２ O ３ , Er ２ O ３ , SiO ２ , BN, TiN, TiAlN, SiN, WN, CrWN, CrN, Cr ２ 2. The hydrogen barrier film according to claim 1, wherein the hydrogen barrier film is one or more selected from the group consisting of N, AlCrN, ZrN, TiC, Al, Cr, Zn, Ti, and Ti alloys.

5. 5. The hydrogen barrier film according to claim 4, wherein the Ti alloy has a titanium content of 60 mass % or more.

6. 2. The hydrogen barrier film according to claim 1, wherein each layer of said multilayer film has a thickness of 1 nm to 10 μm.

7. The hydrogen barrier film according to claim 1 , wherein the multilayer film includes layers made of different materials.

8. 2. The hydrogen barrier membrane according to claim 1, wherein the multilayer membrane does not contain cracks penetrating from its outer surface toward the structural material.

9. 2. The hydrogen barrier film according to claim 1, which has a durability of 200 hours or more in a hydrogen atmosphere as determined by the following evaluation test. (Evaluation test) A neodymium magnet whose entire outer surface is coated with the above-mentioned hydrogen-shielding film is used as a test specimen, which is then stored in a hydrogen gas environment (pressure of 4 MPa, room temperature) and the test specimen is observed with the naked eye for changes over time. The storage time during which no change in the appearance of the test specimen is observed is determined as the "durability time in a hydrogen atmosphere."

10. A hydrogen-resistant structural material, the entire outer surface of which is covered with the hydrogen barrier film according to claim 1.

11. 11. The hydrogen-resistant structural material according to claim 10, wherein the structural material is made of a steel material and / or a non-ferrous metal material.

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