Coating structure manufacturing method, and coating structure

Abstract

A coating structure manufacturing method according to the present invention is for manufacturing a coating structure having a metal composite coating on a substrate, the method comprising: a step for applying a metallic compound-containing substance on the substrate or immersing the substrate in the metallic compound-containing substance; and a reaction step for forming the metal composite coating by heating the substrate under reduced pressure or under vacuum in a state of being supplied with a carbon source and / or a nitrogen source, to cause at least one reaction of a carbonizing reaction, a nitrocarburizing reaction, or a nitriding reaction. In a coating structure according to the present invention, the peak area ratio of D band / G band is 0.5-2.0 in a Raman spectrometry performed on a metal-carbon composite coating.

Description

Method for manufacturing coated structure, and coated structure

[0001] The present invention relates to a method for producing a coated structure and a coated structure.

[0002] In metal processing, carburizing, carbonitriding, and nitriding are carried out to harden the surface layer.

[0003] For example, Patent Document 1 discloses a method for hardening the surface of a steel workpiece by contacting the steel workpiece with a hardening gas in which carbon or nitrogen is combined with hydrogen in a treatment furnace under a vacuum atmosphere.

[0004] Patent No. 6058846

[0005] However, in the method disclosed in Patent Document 1, the physical properties, such as the physical and / or chemical stability, of the surface layer formed on the surface of a steel workpiece, i.e., a substrate, by carburizing, carbonitriding, or nitriding depend on the type and material of the substrate.

[0006] In view of the above problems, the present invention provides a method for producing a coated structure, which is capable of forming a physically and chemically stable surface layer independent of the substrate, and which is capable of producing a coated structure having a uniform metal composite coating on the substrate, and a coated structure.

[0007] The method for producing a coated structure of the present invention, which has been made to solve the above problems, is a method for producing a coated structure having a metal composite coating on a substrate, and is characterized by comprising: a step of applying or immersing a metal compound-containing material on the substrate; and a reaction step of heating the substrate under reduced pressure or in vacuum while supplying a carbon source and / or a nitrogen source, thereby causing at least one reaction of carbonization, carbonitriding, or nitriding to form a metal composite coating. The method for producing a coated structure of the present invention is independent of the substrate and can produce a coated structure having a uniform metal composite coating on a substrate, which can form a physically and chemically stable surface layer.

[0008] In the present specification, a "metal composite coating" may be a coating in which a metal element is present in a state bonded to other metal elements, metalloid elements, or nonmetallic elements. Alternatively, the metal element may be present in a mixed or dispersed state, rather than being bonded to other metal elements, metalloid elements, or nonmetallic elements. Examples of the metal compound include metal carbides, metal nitrides, metal carbonitrides, metal oxides, metal sulfides, and metal hydroxides. Metal carbides, metal nitrides, and metal carbonitrides are preferred, and a plurality of compounds may be present.

[0009] Here, the coated structure produced by the method for producing a coated structure of the present invention has a metal composite coating on a substrate, and may be, for example, a structure having a metal composite coating on at least one side (e.g., the surface) of the substrate, or a structure having a metal composite coating on the entire peripheral surface of the substrate, and further includes a structure having a metal composite coating on only a portion of one side of the substrate.

[0010] First, in the step of applying or immersing a substrate in a material containing a metal compound according to the method for producing a coated structure of the present invention, the substrate is applied with or immersed in a material containing a metal compound.

[0011] The substrate used in the method for producing a coated structure of the present invention is characterized by containing at least one material selected from the group consisting of carbon, metal carbide, pure metal, alloy, metal oxide, and composite metal oxide. The substrate used in the method for producing a coated structure of the present invention may be any substrate containing at least one material selected from the group consisting of carbon, metal carbide, pure metal, alloy, metal oxide, and composite metal oxide, as described below.

[0012] The carbon-containing substrate may be a substrate made of only carbon, a substrate containing carbon as the main component with a carbon content of 50% by mass or more, or a substrate having a multilayer structure with the outermost layer made of only carbon or containing carbon as the main component with a carbon content of 50% by mass or more. It is particularly preferable that the carbon-containing substrate is a substrate made of only carbon.

[0013] The size and shape of the carbon-containing substrate are not particularly limited as long as they are heatable in a static furnace used in the steps described below. Specific examples of the carbon substrate include crucibles, furnace materials, electrodes, fibers, filtration devices, filters, protective tubes, heater tubes, burner nozzles, and fire-resistant jigs.

[0014] Examples of carbon materials for the carbon-containing substrate include fullerene, carbon nanotube, carbon nanofiber, graphene, graphene oxide, carbon nanohorn, diamond, hyperdiamond, and carbon fiber.

[0015] The carbon material may be composed of only carbon or other materials containing carbon. Furthermore, the structure of the carbon material may be a uniform structure or a non-uniform structure. The uniform structure may be hollow or porous. The non-uniform structure may be, for example, an island-in-the-sea structure, a multi-layer structure, a hollow structure, or a porous structure.

[0016] Furthermore, the carbon material may be in the form of a powder, a plate, a film, a fiber, or the like, or may be in the form of a molded product thereof, i.e., a mixture, a multilayer body, a pressed powder body, a sintered body, a fiber bundle, a nonwoven body, or a woven material (plain weave, twill weave, satin weave, basket weave).

[0017] The carbon material is particularly preferably a fibrous material, and specific examples thereof include metal fibers (steel fibers, etc.), ceramic fibers (metal oxide fibers, metal carbide fibers, metal nitride fibers, silicon carbide fibers, glass fibers, etc.), and polymer fibers (natural polymer fibers, polysaccharide fibers, cellulose fibers, artificial polymer fibers, resin fibers, carbon fibers, etc.).

[0018] The substrate containing metal carbide may be a substrate consisting solely of metal carbide, a substrate containing metal carbide as the main component with a metal carbide content of 50% by mass or more, or a substrate having a multilayer structure in which the outermost layer is composed solely of metal carbide or a substrate containing metal carbide as the main component with a metal carbide content of 50% by mass or more. The substrate containing metal carbide is particularly preferably a substrate consisting solely of metal carbide. Examples of the metal carbide contained in the substrate include tungsten carbide, molybdenum carbide, tantalum carbide, and the like.

[0019] The substrate containing a pure metal may be a substrate consisting of only a pure metal, a substrate mainly composed of a pure metal with a pure metal content of 50% by mass or more, or a substrate having a multilayer structure in which the outermost layer is composed of only a pure metal or mainly composed of a pure metal with a pure metal content of 50% by mass or more. The substrate containing a pure metal is particularly preferably a substrate consisting of only a pure metal. Examples of pure metals contained in the substrate include pure metals such as Ti, V, Fe, Y, Zr, Cr, Ni, Mn, Co, Cu, Zn, and Pb.

[0020] The substrate containing an alloy may be a substrate consisting solely of the alloy, a substrate mainly composed of the alloy with an alloy content of 50% by mass or more, or a substrate with a multilayer structure in which the outermost layer is composed solely of the alloy or mainly composed of the alloy with an alloy content of 50% by mass or more. The substrate containing an alloy is particularly preferably a substrate consisting solely of the alloy. Examples of alloys contained in the substrate include alloys containing at least one metal element selected from stainless steel (SUS), steel, brass, duralumin, titanium alloys, nickel alloys, aluminum alloys, copper alloys, zinc alloys, etc.

[0021] Specific examples of the substrate material include SUS304 (JIS G4305 (2021)), SUS310S (JIS G4305 (2005)), SUS316 (JIS G4305 (2015)), SUS316L (JIS G4305 (2015) SUS316L), Ti (JIS H 4600 TP340C), and Inconel (SB-168UNSN06600 (2019ED)).

[0022] The substrate containing a metal oxide may be a substrate consisting solely of a metal oxide, a substrate containing a metal oxide as a main component with a metal oxide content of 50% by mass or more, or a substrate having a multilayer structure in which the outermost layer is composed solely of a metal oxide or a substrate containing a metal oxide as a main component with a metal oxide content of 50% by mass or more. The substrate containing a metal oxide is particularly preferably a substrate consisting solely of a metal oxide. Examples of metal oxides contained in the substrate include titanium oxide, alumina, zirconia, magnesia, vanadia, nickel oxide, and silica.

[0023] The substrate containing a complex metal oxide may be a substrate consisting solely of a complex metal oxide, a substrate containing a complex metal oxide as a main component with a complex metal oxide content of 50% by mass or more, or a substrate having a multilayer structure in which the outermost layer is composed solely of a complex metal oxide or a substrate containing a complex metal oxide as a main component with a complex metal oxide content of 50% by mass or more. The substrate containing a complex metal oxide is particularly preferably a substrate consisting solely of a complex metal oxide. Examples of the complex metal oxide contained in the substrate include complex metal oxides containing at least one metal element selected from mullite, a silica-alumina mixture, an alumina-zirconia mixture, and the like.

[0024] The size and shape of the substrate are not particularly limited as long as they are capable of undergoing at least one of the carbonization reaction, carbonitriding reaction, and nitriding reaction described below, and may be plate-shaped, tubular, cubic, etc. Specific examples of the substrate include crucibles, furnace materials, electrodes, fibers, filtration devices, filters, protective tubes, heater tubes, burner nozzles, and fire-resistant jigs.

[0025] Furthermore, the metal compound-containing material used in the method for producing a coated structure of the present invention preferably contains a compound of at least one metal element selected from Ti, Nb, Mo, Hf, Ta, W, Zr, and Si. Examples of such metal compound-containing materials include compounds of at least one metal element selected from Ti, Nb, Mo, Hf, Ta, W, Zr, and Si. Specific examples of such metal compound-containing materials include peroxo complex metal compounds (e.g., peroxohydroxy acid complex metal compounds, peroxocitrate complex metal compounds, and peroxoammonium complex metal compounds) containing at least one metal element selected from Ti, Nb, Mo, Hf, Ta, W, Zr, and Si, metal hydroxides, hydroxy acid complex metal compounds (e.g., ammonium oxalate complex metal compounds), and polyacids, but are not limited to these compounds. The metal compound-containing material may also contain metal elements, semimetal elements, or nonmetal elements other than at least one metal element selected from Ti, Nb, Mo, Hf, Ta, W, Zr, and Si, such as B and P.

[0026] When the metal compound-containing material is a peroxo complex metal compound, even if the substrate does not contain carbon, by heating the substrate coated with the peroxo complex metal compound, the metal element contained in the peroxo complex metal compound reacts with carbon to form a metal carbide. Similarly, when the metal compound-containing material is a hydroxy acid complex metal compound, the metal element contained in the hydroxy acid complex metal compound reacts with carbon to form a metal carbide.

[0027] The content of the metal compound-containing material is preferably adjusted depending on the metal element and the type of carbon-based substrate, and is more preferably more than 0 mass% and not more than 40 mass%, further preferably 0.1 mass% to 30 mass%, particularly preferably 0.2 mass% to 30 mass%, and particularly preferably 0.3 mass% to 15 mass%. Note that when the metal compound-containing material contains multiple metal elements selected from Ti, Nb, Mo, Hf, Ta, W, Zr, and Si, the total value of the mass fractions of the metal elements is preferably within the above-mentioned numerical range.

[0028] Here, the content of the metal compound-containing material may be calculated by diluting the metal compound-containing material appropriately with dilute hydrochloric acid as needed, and measuring the mass fraction in terms of metal using ICP optical emission spectrometry (AG-5110 manufactured by Agilent Technologies) in accordance with JIS K0116:2014.

[0029] The content of the metal compound-containing material is preferably adjusted according to the type of metal element and carbon-based substrate, and is more preferably more than 0 mass% and not more than 35 mass%, even more preferably 0.03 mass% to 25 mass%, particularly preferably 0.06 mass% to 25 mass%, and particularly preferably 0.1 mass% to 15 mass%. When the metal compound-containing material contains multiple metal elements selected from Ti, Nb, Mo, Hf, Ta, W, Zr, and Si, the total mass fraction of each metal is preferably within the above-mentioned range. In this specification, "metal equivalent" refers to Ti equivalent, Nb equivalent, Mo equivalent, Hf equivalent, Ta equivalent, W equivalent, Zr equivalent, and Si equivalent.

[0030] Furthermore, the metal compound-containing material used in the method for producing a coated structure of the present invention preferably contains a compound of at least one metal element selected from Nb, Hf, and Ta. Examples of such metal compound-containing materials include those containing a compound of at least one metal element selected from Nb, Hf, and Ta. Specific examples include peroxo complex metal compounds containing at least one metal element selected from Nb, Hf, and Ta (e.g., peroxohydroxy acid complex metal compounds, peroxocitrate complex metal compounds, and peroxoammonium complex metal compounds), metal hydroxides, hydroxy acid complex metal compounds (e.g., ammonium oxalate complex metal compounds), and polyacids, but are not limited to these compounds.

[0031] The metal compound-containing material used in the method for producing a coated structure of the present invention may also contain a resin. If the metal compound-containing material contains a resin, the resin is uniformly compatible with the metal compound and acts to adhere to the substrate, which is preferable in that the film-forming properties and adhesion to the substrate are improved.

[0032] Examples of the resin contained in the metal compound-containing material include polyolefin compounds and polyvinyl compounds.

[0033] The metal compound-containing material used in the method for producing a coated structure of the present invention may also contain a carbon material. If the metal compound-containing material contains a carbon material, the carbon material becomes a carbon component during carbonization, which is preferable in that carbonization is improved.

[0034] Furthermore, the metal compound-containing material used in the method for producing a coated structure of the present invention may be a solution, sol, or gel. The metal compound-containing material is a material containing a metal compound, and more specifically, a material that is liquefied by the application of shear stress. That is, the metal compound-containing material may be a material that is normally in a liquid, sol, gel, or semi-solid state and can be applied to a substrate. Furthermore, a metal compound-containing material used in the method for producing a coated structure of the present invention is preferably a solution, which can be easily applied to a substrate. Furthermore, the gel may have a viscosity of 200 mPa·s or more at 25°C as measured by a rotating cylinder method.

[0035] The metal compound-containing material used in the method for producing a coated structure of the present invention is characterized in that the maximum light transmittance in the wavelength range of 500 nm to 700 nm is 70% T or more, and the particle diameter (D50) of particles in the metal compound-containing material is 3000 nm or less as measured by dynamic light scattering. When the metal compound-containing material used in the method for producing a coated structure of the present invention has a maximum light transmittance in the wavelength range of 500 nm to 700 nm of 70% T or more, and the particle diameter (D50) of particles in the metal compound-containing material is 3000 nm or less as measured by dynamic light scattering, the degree of dispersion is high, the uniformity of the components in the liquid is excellent, and this is preferred from the viewpoint of stability over time.

[0036] The metal compound-containing material used in the method for producing a coated structure of the present invention preferably has a maximum light transmittance of 70%T or more in the wavelength region of 500 nm to 700 nm, resulting in high dispersibility and excellent uniformity of the components in the liquid. The maximum light transmittance in the wavelength region of 500 nm to 700 nm is more preferably 72%T or more, even more preferably 74%T or more, particularly preferably 76%T or more, even particularly preferably 78%T or more, and even particularly preferably 80%T or more. The light transmittance in the wavelength region of 500 nm to 700 nm may be 80%T. Note that, due to measurement error or the like, the measured light transmittance may exceed 100%T. However, since the theoretical upper limit is 100%T, if the measured value exceeds 100%T, it is considered to be 100%T.

[0037] Here, the light transmittance in the wavelength region of 500 nm to 700 nm is measured using a spectrophotometer under the following light transmittance measurement conditions for the metal compound-containing material used in the method for producing a coated structure of the present invention.

[0038] =Light transmittance measurement conditions= Measuring device: Ultraviolet-visible-near-infrared spectrophotometer UH4150 (manufactured by Hitachi High-Tech Science Corporation) Measurement mode: Wavelength scan Data mode: %T (transmittance) Measurement wavelength range: 200 nm to 2000 nm Scan speed: 600 nm / min Sampling interval: 2 nm

[0039] On the other hand, when the metal compound-containing material used in the method for producing a coated structure of the present invention contains a Si compound, the light transmittance in the wavelength region of 500 nm to 700 nm can be determined by placing 3 g of the metal compound-containing material containing a Si compound adjusted to room temperature (25°C) in a measurement cell (light path length 1 cm) and measuring the ultraviolet-visible absorption spectrum (UV-Vis absorption spectrum) in accordance with JIS K 0115, 2004 "General rules for absorptiometric analysis methods" under the following light transmittance measurement conditions (including Si):

[0040] =Light transmittance measurement conditions (including Si)= Measuring device: U-2900 spectrophotometer (manufactured by Hitachi High-Tech Corporation) Measurement mode: wavelength scan Data mode: %T (transmission) Measurement wavelength range: 200 nm to 1000 nm Scan speed: 200 nm / min Sampling interval: 1 nm Cell length: 10 mm Measurement cell: disposable square cell for particle size (manufactured by Otsuka Electronics Co., Ltd.)

[0041] Furthermore, from the viewpoint of stability over time, the particle diameter (D50) of the particles in the metal compound-containing material used in the method for producing a coated structure of the present invention is preferably 3000 nm or less, more preferably 2000 nm or less, and may be 1000 nm or less, 500 nm or less, 400 nm or less, or 300 nm or less. On the other hand, the particle diameter (D50) is preferably 0.1 nm or more, more preferably 0.5 nm or more, even more preferably 0.7 nm or more, and particularly preferably 1 nm or more. Typically, the particle diameter (D50) is 0.6 nm or more and 200 nm or less.

[0042] Here, dynamic light scattering is a method in which a solution such as a suspension is irradiated with light such as laser light, and the light scattering intensity from a group of particles undergoing Brownian motion is measured, and particle size and distribution are determined from the temporal fluctuations of this intensity. Specifically, the particle size distribution is evaluated using a zeta potential, particle size, and molecular weight measurement system (manufactured by Otsuka Electronics Co., Ltd.: ELSZ-2000ZS) in accordance with JIS Z 8828:2019 "Particle Size Analysis - Dynamic Light Scattering." If necessary, the measurement sample is diluted 1000 times with pure water. Just before measurement, the measurement sample is filtered through an 11 μm pore size filter to remove dust and other particles, and then ultrasonicated for 3 minutes in an ultrasonic cleaner (manufactured by AS ONE Corporation: VS-100III). Furthermore, the liquid temperature of the measurement sample was adjusted to 25°C. The particle size (D50) refers to the median diameter (D50), which is the particle size that represents the 50% integrated value of the cumulative distribution curve.

[0043] Furthermore, the metal compound-containing material used in the method for producing a coated structure of the present invention preferably has a pH greater than 7, and the solvent may be water, alcohol, ketone, ester, or the like. Two or more solvents may be mixed, and preferably contains water. A pH greater than 7 is preferable in terms of good solubility. Furthermore, the pH of the metal compound-containing material is more preferably 7.5 or higher, and even more preferably 8.0 or higher. The pH of the metal compound-containing material may be 8.5 or higher, 9.0 or higher, 9.5 or higher, 10.0 or higher, 10.5 or higher, or 11.0 or higher. On the other hand, the pH of the metal compound-containing material is preferably 13.5 or lower, more preferably 13.0 or lower, and even more preferably 12.5 or lower. Furthermore, it is preferable for the metal compound-containing material to contain water as a solvent in terms of reducing environmental impact.

[0044] Here, the pH of the metal compound-containing material used in the method for producing a coated structure of the present invention is measured by immersing an electrode (HORIBA: Standard ToupH electrode 9615S-10D) of a pH meter (HORIBA: Glass electrode type hydrogen ion concentration indicator D-51) in the metal compound-containing material, and confirming that the liquid temperature has stabilized at 25°C.

[0045] In the step of applying or immersing a material containing a metal compound on a substrate according to the method for producing a coated structure of the present invention, the material containing a metal compound is applied to or immersed on the substrate.

[0046] Specific examples of methods for applying the metal compound-containing material onto a substrate include spraying, inkjet coating, dispenser coating, nozzle coating, slit coating, die coating, roll coating, spin coating, blade coating, knife coating, wire bar coating, screen printing, and brush coating.

[0047] The method of immersing a substrate in a material containing a metal compound involves immersing the substrate in a container filled with the material containing a metal compound, thereby impregnating the substrate with the material containing a metal compound. The immersion time in this step is preferably 6 minutes to 1 hour, and more preferably 12 minutes to 54 minutes. The step of immersing a substrate in a material containing a metal compound may be performed at room temperature, or may involve heating and then cooling to room temperature.

[0048] Furthermore, in the immersion step in the method for producing a coated structure of the present invention, if the substrate is immersed in the metal compound-containing material under reduced pressure or in vacuum, the substrate is more likely to be impregnated with the metal compound-containing material, and the immersion time in this step can be shortened, which is preferable.

[0049] Specifically, the container filled with the metal compound-containing material in which the substrate is immersed is placed in a pressure reducing device and placed under reduced pressure or vacuum, which makes it easier for the metal compound-containing material to be impregnated into the substrate.

[0050] The degree of vacuum in the pressure reducing device is preferably 0.05 MPa or less, more preferably 0.04 MPa or less, even more preferably 0.03 MPa or less, and particularly preferably 0.02 MPa or less. The immersion time in the immersion step under reduced pressure or vacuum is preferably 0.1 hour to 0.5 hours, and more preferably 0.2 hour to 0.4 hours.

[0051] Furthermore, when a metal composite coating is formed only on one surface of a substrate, for example, on the surface, only the surface of the substrate is immersed in the metal compound-containing material, whereas when a metal composite coating is formed on the entire peripheral surface of the substrate, the entire peripheral surface of the substrate is immersed in the metal compound-containing material.

[0052] Next, in the reaction step according to the method for producing a coated structure of the present invention, the substrate is heated under reduced pressure or vacuum while a carbon source and / or a nitrogen source is being supplied, thereby causing at least one reaction selected from the group consisting of a carbonization reaction, a carbonitriding reaction, and a nitriding reaction, to form a metal composite coating.

[0053] Here, the carbonization reaction, carbonitriding reaction, or nitriding reaction is a reaction that includes the following multiple processes.

[0054] First, the substrate coated with or immersed in the metal compound-containing material is placed in a vacuum carbonitriding furnace (e.g., Oriental Engineering Co., Ltd., Model: VCQ400) and placed under reduced pressure or vacuum. Next, under reduced pressure or vacuum, it is heated at a preheating temperature for a predetermined preheating time. Subsequently, it is further heated at a soaking temperature for a predetermined soaking time. Thereafter, a carbon source and / or nitrogen source is supplied from the outside, and the substrate is heated at a carburizing temperature, a carbonitriding temperature, or a nitriding temperature for a predetermined carburizing time, a carbonitriding time, or a nitriding time. This causes carbon and / or nitrogen to penetrate from the surface of the metal compound-containing material and the substrate into the interior, and the carbon and / or nitrogen are dissolved in the metal compound-containing material and the substrate. This is a carburizing, carbonitriding, or nitriding treatment. Then, under reduced pressure or vacuum, a diffusion treatment is performed to diffuse carbon and / or nitrogen into the metal compound-containing material and the substrate at a diffusion temperature and for a predetermined diffusion time. In this way, a metal composite coating is formed on the substrate.

[0055] Furthermore, the method for producing a coated structure of the present invention is characterized in that the reaction step is a carbonization reaction, and the carbon source is either one containing an unsaturated hydrocarbon and an inert component, or a saturated hydrocarbon. When the reaction step in the method for producing a coated structure of the present invention is a carbonization reaction, it is preferable that the carbon source supplied into the vacuum carbonitriding furnace is either one containing an unsaturated hydrocarbon and an inert component, or a saturated hydrocarbon, because hydrogen produced by decomposition of the unsaturated hydrocarbon or saturated hydrocarbon removes oxygen from the applied metal compound-containing material and promotes the metal carbide production reaction.

[0056] The unsaturated hydrocarbon may be acetylene, etc. The inert component may be argon, nitrogen, etc.

[0057] Furthermore, the method for producing a coated structure of the present invention is characterized in that the reaction step is a carbonitriding reaction or a nitriding reaction, and the nitrogen source contains ammonia and an inert component. When the reaction step in the method for producing a coated structure of the present invention is a carbonitriding reaction or a nitriding reaction, it is preferable that the nitrogen source supplied into the vacuum carbonitriding furnace contains ammonia and an inert component, in order to promote the reaction for producing a metal carbonitride or a metal nitride. The inert component is as described above.

[0058] Furthermore, in the method for producing a coated structure of the present invention, when the reaction step is a carbonitriding reaction, it is preferable that the carbon source and nitrogen source supplied into the vacuum carbonitriding furnace contain either all of an unsaturated hydrocarbon, a nitriding agent, and an inert component, or all of a saturated hydrocarbon and a nitriding agent, in that this makes it easy to control the carbide-forming reaction or the nitride-forming reaction.

[0059] Examples of the nitriding agent include ammonia, nitrogen, etc. Examples of the saturated hydrocarbon include methane, propane, butane, etc. The unsaturated hydrocarbon and the inert component are as described above.

[0060] A carburizing temperature of 800°C or higher and 1150°C or lower is preferable because the carburizing reaction of the coating proceeds sufficiently and the coating quality is stable. A carburizing temperature of 850°C or higher and 1100°C or lower is more preferable, and a carburizing temperature of 900°C or higher and 1050°C or lower is even more preferable.

[0061] A carburization time of 3 minutes to 2 hours is preferable in that it can supply carbon suitable for generating metal carbides, a carburization time of 6 minutes to 1 hour is more preferable, and a carburization time of 6 minutes to 15 minutes is even more preferable.

[0062] A carbonitriding temperature of 700°C or higher and 1050°C or lower is preferable because the carbonitriding reaction of the coating proceeds sufficiently and the coating quality is stable. A carbonitriding temperature of 750°C or higher and 1000°C or lower is more preferable, and a temperature of 800°C or higher and 900°C or lower is even more preferable.

[0063] A carbonitriding time of 3 minutes to 2 hours is preferable in that it allows a sufficient supply of carbon and nitrogen necessary for producing metal carbonitrides, a carbonitriding time of 18 minutes to 1 hour is more preferable, and a carbonitriding time of 18 minutes to 30 minutes is even more preferable.

[0064] A nitriding temperature of 500°C or higher and 1000°C or lower is preferable because the nitriding reaction of the coating proceeds sufficiently and the coating quality is stabilized. The nitriding temperature is more preferably 500°C or higher and 900°C or lower, and even more preferably 750°C or higher and 850°C or lower.

[0065] A nitriding time of 3 minutes to 2 hours is preferable in that it allows a sufficient supply of nitrogen necessary for producing metal nitrides, a nitriding time of 6 minutes to 1 hour is more preferable, and a nitriding time of 6 minutes to 15 minutes is even more preferable.

[0066] The method for producing a coated structure of the present invention is characterized in that the heating temperature in the reaction step is 500° C. or higher and 1150° C. or lower. A heating temperature of 500° C. or higher and 1150° C. or lower is preferable in that the carburization reaction, carbonitriding reaction, or nitriding reaction of the coating proceeds sufficiently, and the coating quality is stabilized. The heating temperature is the carburization temperature, carbonitriding temperature, or nitriding temperature described above.

[0067] The method for producing a coated structure of the present invention is characterized in that the heating time is 0.05 to 10 hours. A heating time of 0.05 to 10 hours is preferable in that it allows a sufficient supply of carbon and / or nitrogen necessary for producing metal carbide, metal carbonitride, or metal nitride. The heating time is the carburizing time, carbonitriding time, or nitriding time.

[0068] The degree of vacuum in the vacuum carbonitriding furnace is preferably 1330 Pa or less, and more preferably 133 Pa or less.

[0069] By the method for producing a coated structure of the present invention described above, a coated structure having a metal composite coating formed on a substrate can be produced.

[0070] Furthermore, the method for producing a coated structure of the present invention may further include a drying step between the step of applying or immersing the metal compound-containing material on the substrate and the reaction step in the method for producing a coated structure of the present invention described above.

[0071] The substrate coated with or immersed in the metal compound-containing material is placed in a static furnace and dried at a drying temperature of 100° C. for 1 hour, which is preferred in that excess impurities such as moisture can be removed.

[0072] The drying temperature in the drying step is more preferably 110°C or higher and 400°C or lower, even more preferably 120°C or higher and 300°C or lower, and particularly preferably 130°C or higher and 200°C or lower.

[0073] The drying time in the drying step is preferably 0.2 hours or more and 3 hours or less, more preferably 0.3 hours or more and 2 hours or less, and even more preferably 0.4 hours or more and 1 hour or less.

[0074] The method for producing a coated structure of the present invention may further include a baking step under vacuum between the drying step and the reaction step in the method for producing a coated structure of the present invention described above.

[0075] The substrate coated with or immersed in the dried metal compound-containing material is preferably fired at a firing temperature of 750° C. for 1 hour, since this allows oxygen to be removed from the metal compound.

[0076] The firing temperature is preferably 750° C. or higher and 1000° C. or lower in terms of efficient oxygen removal, more preferably 800° C. or higher and 950° C. or lower, and even more preferably 850° C. or higher and 900° C. or lower.

[0077] A firing time of 1 hour or more and 3 hours or less is preferred in terms of efficient oxygen removal, and a firing time of 0.5 hours or more and 1.5 hours or less is more preferred.

[0078] Furthermore, the method for producing a coated structure of the present invention is characterized in that the step of applying or immersing a substrate in a metal compound-containing material and the reaction step according to the method for producing a coated structure of the present invention described above are repeated multiple times. By repeating the step of applying or immersing a substrate in a metal compound-containing material and the reaction step multiple times according to the method for producing a coated structure of the present invention described above, a metal composite coating is formed on the substrate multiple times, and a metal composite coating that is more physically and chemically stable can be formed.

[0079] Furthermore, the metal composite coating formed by the method for producing a coated structure of the present invention preferably contains a compound of at least one metal element selected from Ti, Nb, Mo, Hf, Ta, W, Zr, and Si, in order to improve the durability of the coated substrate. Examples of compounds contained in the metal composite coating include metal carbides, metal nitrides, metal carbonitrides, metal oxides, metal sulfides, and metal hydroxides of at least one metal element selected from Ti, Nb, Mo, Hf, Ta, W, Zr, and Si. Metal carbides, metal nitrides, and metal carbonitrides are preferred, and multiple compounds may be present.

[0080] Furthermore, it is more preferable that the metal composite coating formed by the method for producing a coated structure of the present invention contains a compound of at least one metal element selected from Nb, Hf, and Ta, since this further improves the durability of the coated substrate.

[0081] Furthermore, if the metal composite coating formed by the method for producing a coated structure of the present invention contains at least one metal carbide selected from Ti carbide, Nb carbide, Mo carbide, Hf carbide, Ta carbide, W carbide, Zr carbide, and Si carbide, it is particularly preferable in that the coated structure in which the metal composite coating is formed on the substrate is physically and chemically stable.

[0082] Here, the physical stability of the coating structure of the present invention means, for example, physical stability in a heat resistance test, indicating thermal stability at higher temperatures. In addition, there are cases where the physical stability can be further improved in hardness tests, instrumented indentation tests, or scratch tests.

[0083] Furthermore, the coating structure of the present invention being chemically stable means that the coating structure is chemically stable against, for example, hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, hydrofluoric acid, sodium chloride, acetic acid, oxalic acid, ammonia water, sodium hydroxide, potassium hydroxide, water vapor, hydrogen sulfide gas, ammonia gas, hydrogen gas, fluorine gas, chlorine gas, nitrogen oxide gas (NOx), or sulfur oxide gas (SOx).

[0084] The metal composite coating formed on the substrate manufactured by the above-described method for manufacturing a coated structure of the present invention is measured under the following X-ray diffraction measurement conditions and X-ray diffraction analysis conditions. From the peaks in the obtained X-ray diffraction pattern, it can be confirmed that the metal composite coating contains a metal compound.

[0085] = X-ray diffraction measurement conditions = Apparatus: MiniFlex II (manufactured by Rigaku Corporation) Measurement range (2θ): 5 to 90° Sampling width: 0.02° Scan speed: 2.0° / min X-ray: CuKα ray Voltage: 30 kV Current: 15 mA Divergence slit: 1.25° Scattering slit: 1.25° Receiving slit: 0.3 mm

[0086] = X-ray diffraction analysis conditions = · Data analysis software PDXL2 manufactured by Rigaku Corporation is used · Peaks are smoothed using b-spline to clarify peak tops.

[0087] Furthermore, if the thickness of the metal composite coating formed on the substrate manufactured by the method for manufacturing a coated structure of the present invention is 500 nm or less, this is preferable because cracks in the film and peeling of the film itself are less likely to occur. The thickness of the metal composite coating may be 300 nm or less, or may be 100 nm or less. This is because if cracks occur in the metal composite coating, the substrate is oxidized and is more likely to be released as oxides, making it easier for elements in the substrate to decrease. On the other hand, if the thickness of the metal composite coating is 1 nm or more, this is preferable because the substrate can be sufficiently protected. The thickness of the metal composite coating may be 10 nm or more.

[0088] The coated structure of the present invention is a coated structure having a metal composite coating on a substrate, wherein the metal composite coating is formed by heating the substrate, to which a metal compound-containing material has been applied or immersed, under reduced pressure or in vacuum while supplying a carbon source and / or a nitrogen source, thereby causing at least one reaction selected from the group consisting of a carbonization reaction, a carbonitriding reaction, and a nitriding reaction. The coated structure of the present invention is independent of the substrate and has a uniform metal composite coating on the substrate as a physically and chemically stable surface layer.

[0089] The coated structure of the present invention is a coated structure having a metal-carbon composite coating on a substrate, characterized in that the metal-carbon composite coating has a D band / G band peak area ratio of 0.5 or more and 2.0 or less in Raman spectroscopy. The coated structure of the present invention has a metal-carbon composite coating on a substrate, and when the metal-carbon composite coating has a D band / G band peak area ratio of 0.5 or more and 2.0 or less in Raman spectroscopy, it is preferable in that a physically and chemically stable surface layer can be formed and a coating with a uniform composition can be formed.

[0090] In the coating structure of the present invention, the D band / G band peak area ratio is more preferably 0.8 to 2.0, even more preferably 0.8 to 1.5, and particularly preferably 1.1 to 1.3.

[0091] Here, Raman spectroscopy is a spectroscopic method for evaluating the chemical structure and bonding state of carbon materials. In the Raman spectrum of carbon materials, the peak at 1300 cm －１ ~1400cm －１ , and 1550 cm －１ ~1650cm －１ Highly crystalline graphite has a peak at 1550 cm －１ ~1650cm －１ A single peak is observed at 1300 cm, and this peak is called the "G band." On the other hand, as the crystallinity decreases (the number of crystal structure defects increases), －１ ~1400cm －１A peak appears at 2400 cm, and this peak is called "D band". The D band / G band peak area ratio is an index of the amount of defects in the crystalline structure of the carbon material. The smaller the D band / G band peak area ratio, the fewer the amount of defects in the crystalline structure of the carbon material. In this way, carbon materials with fewer defects in the crystalline structure have a peak at 2400 cm －１ ~2800cm －１ A peak is also detected at this position, and this peak is called the “2D band.” The D band / G band peak intensity ratio is sometimes called the R value.

[0092] The metal-carbon composite coating formed on the substrate can be confirmed to be a metal carbide from the peak (half width) of the Raman spectrum obtained by measuring the metal-carbon composite coating under the following Raman spectroscopy measurement conditions.

[0093] = Raman spectroscopy measurement conditions = Apparatus: Invia Qontor (manufactured by Renishaw Ltd.) Light source: 532 nm (RL532-08 150 mW) Objective lens: 20x magnification Grating: 1800 mm / L Irradiation time: 5 to 10 seconds Number of accumulations: 1 Slit width: 65 μm Laser power: 1% Livetrac function used 20 x 20 square map measurement (10 μm intervals in both X and Y directions)

[0094] = Raman spectroscopy analysis conditions = According to the above-mentioned Raman spectroscopy measurement conditions, the Raman spectrum obtained was subjected to baseline correction (intelligence polynomial: degree 6) and averaged spectrum processing in WiRE5.5 manufactured by Renishaw Ltd., and the peak at 1550 cm －１ ~1650cm －１Normalization is performed so that the maximum value at χ-squared is 1. Next, using WaveMetrics' Igor Pro ver. 8.04, multipeak fitting 2 is applied to the normalized spectrum, and the initial peak value is set with reference to the description in Table 1 of Chapter 8, Section 4 of the Raman Spectroscopic Data Analysis Case Studies (Technical Information Association, Inc.). The peak adopts a Gaussian or Lorentzian distribution. Then, fitting is repeatedly performed so that the χ-squared, which represents the difference between the measured value of the peak and the fitted value, is made as small as possible. If the χ-squared converges beyond 1.0, a new peak is set and fitting is repeated until the χ-squared becomes less than 1.0.

[0095] Each peak obtained by the above procedure is classified into a D band and a G band based on the peak position, the sum of the peak areas of each band is calculated, and the value obtained by dividing the sum of the D band peak areas by the sum of the G band peak areas is defined as the D band / G band peak area ratio.

[0096] The coated structure of the present invention is a coated structure having a metal-carbon composite coating on a substrate, characterized in that the metal-carbon composite coating has a D band / G band peak area ratio of 0.5 to 2.0 in Raman spectroscopy and a standard deviation of the D band / G band peak area ratio of 0.1 to 0.35. The coated structure of the present invention has a metal-carbon composite coating on a substrate, and when the metal-carbon composite coating has a D band / G band peak area ratio of 0.5 to 2.0 in Raman spectroscopy and a standard deviation of the D band / G band peak area ratio of 0.1 to 0.35, it is preferable in that a physically and chemically stable surface layer can be formed and a coating having a uniform composition can be formed.

[0097] In the coating structure of the present invention, the D band / G band peak area ratio is more preferably 0.8 to 2.0, even more preferably 0.8 to 1.5, and particularly preferably 1.1 to 1.3. Note that the D band / G band peak area ratio is as described above, so detailed description thereof will be omitted.

[0098] Furthermore, in the coating structure of the present invention, the standard deviation of the D band / G band peak area ratio is more preferably 0.2 or more and 0.33 or less, and even more preferably 0.23 or more and 0.30 or less.

[0099] Furthermore, the standard deviation of the D band / G band peak area ratio can be calculated based on the above-mentioned D band / G band peak area ratio. Specifically, the standard deviation can be calculated from the D band / G band peak area ratios calculated for the 400 locations of the Raman spectrum measured at any 400 measurement locations in a sample made of the coating structure of the present invention, according to the above-mentioned Raman spectroscopy analysis conditions.

[0100] Furthermore, in the coating structure of the present invention, if the thickness of the metal-carbon composite coating formed on the substrate is 300 nm or less, it is preferable in that cracks in the coating and peeling of the coating itself are unlikely to occur.

[0101] In this specification, when "X to Y" (X and Y are any numbers) is expressed, unless otherwise specified, it means "X or more and Y or less", and also means "preferably larger than X" or "preferably smaller than Y". Furthermore, when "X or more" (X is any number) or "Y or less" (Y is any number), it also means "preferably larger than X" or "preferably smaller than Y".

[0102] The method for producing a coated structure of the present invention is independent of the substrate and can form a physically and chemically stable surface layer, thereby producing a coated structure having a uniform metal composite coating on a substrate.

[0103] 1 is a graph showing the measurement results of corrosion resistance test 1 for Example 1 and Comparative Example 2. FIG. 2 is a graph showing the measurement results of corrosion resistance test 1 for Example 5 and Comparative Example 5. FIG. 3 is a graph showing the measurement results of corrosion resistance test 1 for Example 6 and Comparative Example 6. FIG. 4 is a graph showing the measurement results of corrosion resistance test 1 for Example 7 and Comparative Example 7. FIG. 5 is a graph showing the measurement results of corrosion resistance test 1 for Example 8 and Comparative Example 8. FIG. 6 is a graph showing the measurement results of corrosion resistance test 1 for Example 9 and Comparative Example 5. FIG. 7 is a graph showing the measurement results of corrosion resistance test 1 for Example 10 and Comparative Example 5. FIG. 8 is a graph showing the measurement results of corrosion resistance test 1 for Example 11 and Comparative Example 5. FIG. 9 is a graph showing the measurement results of corrosion resistance test 1 for Example 12 and Comparative Example 5. FIG. 10 is a graph showing the measurement results of corrosion resistance test 1 for Example 13 and Comparative Example 5. FIG. 11 is a graph showing the measurement results of corrosion resistance test 1 for Example 14 and Comparative Example 5. FIG. 11 is a graph showing the measurement results of corrosion resistance test 2 for Example 15 and Comparative Example 9. 1 is a graph showing the measurement results of corrosion resistance test 2 for Example 16 and Comparative Example 9. FIG. 2 is a graph showing the measurement results of corrosion resistance test 2 for Example 17 and Comparative Example 9. FIG. 3 is a graph showing the measurement results of corrosion resistance test 2 for Example 18 and Comparative Example 9. FIG. 4 is a graph showing the measurement results of corrosion resistance test 2 for Example 19 and Comparative Example 9. FIG. 5 is a graph showing the measurement results of corrosion resistance test 2 for Example 20 and Comparative Example 9. FIG. 6 is a graph showing the measurement results of corrosion resistance test 2 for Example 21 and Comparative Example 9. FIG. 7 is a graph showing the measurement results of corrosion resistance test 2 for Example 22 and Comparative Example 9. FIG. 8 is a graph showing the measurement results of corrosion resistance test 2 for Example 23 and Comparative Example 10. FIG. 9 is a graph showing the measurement results of corrosion resistance test 2 for Example 24 and Comparative Example 10. FIG. 10 is a graph showing the measurement results of corrosion resistance test 2 for Example 25 and Comparative Example 10. FIG. 11 is a graph showing the measurement results of corrosion resistance test 2 for Example 26 and Comparative Example 10. FIG. 12 is a graph showing the measurement results of corrosion resistance test 2 for Example 27 and Comparative Example 9. 10A and 10B are graphs showing the measurement results of a corrosion resistance test 2 for Example 28 and Comparative Example 11. (a) is a graph showing the measurement results of a heat resistance test for the coated structure for Example 2, and (b) is a graph showing the measurement results of a heat resistance test for the tubular metal-based substrate for Comparative Example 3.1A is a graph showing the measurement results of a heat resistance test of the coated structure according to Example 3, FIG. 1B is a graph showing the measurement results of a heat resistance test of the coated structure according to Example 4, and FIG. 1C is a graph showing the measurement results of a heat resistance test of the tubular metal substrate according to Comparative Example 4.

[0104] The coated structure according to the embodiment of the present invention will be further described below with reference to the following examples. However, the present invention is not limited to these examples. The JIS standards for the metal substrate materials used in each example are as described above.

[0105] Example 1 A tantalic acid compound-containing liquid was applied to the entire surface of a metal substrate (SUS304) (length x width x thickness: 30 mm x 35 mm x 1.5 mm) using a brush (the amount applied was 0.015 g). Next, the metal substrate coated with the tantalic acid compound-containing liquid was naturally dried. Next, the naturally dried metal substrate coated with the tantalic acid compound-containing liquid was placed in an electric furnace and fired at 350°C for 30 minutes. After firing, the substrate was air-cooled to room temperature. During this process, a tantalic acid compound-dispersed coating film was formed on the metal substrate.

[0106] After air cooling, the metal substrate on which the tantalic acid compound dispersed coating film was formed was placed in a vacuum carbonitriding furnace (manufactured by Oriental Engineering Co., Ltd., model: VCQ400) and heated in a vacuum at a preheating temperature of 850°C for 60 minutes, and then heated at a soaking temperature of 1020°C for 60 minutes. Next, acetylene gas (C ２ H ２ ) was supplied into the vacuum carbonitriding furnace, and the carburizing treatment was carried out for 35 minutes (hereinafter referred to as "carburizing time") at a carburizing temperature of 1020°C to carburize the tantalate compound dispersed coating film and the metal-based substrate. ２ H ２The gas pressure of the tantalum oxide compound dispersed coating film was 1066.576 Pa. Then, a diffusion treatment was carried out in a vacuum at a diffusion temperature of 1020°C for 75 minutes to diffuse the carbon that had penetrated into the tantalic acid compound dispersed coating film and the metal-based substrate (hereinafter referred to as the "diffusion time"). Here, the total time of the "carburizing time" and the "diffusion time" is referred to as the "carburizing treatment time" in Table 1. In this way, the tantalum in the tantalic acid compound dispersed coating film was subjected to a carbonization reaction.

[0107] Then, the coated structure according to Example 1 was obtained.

[0108] The tantalic acid compound-containing liquid used in Example 1 was obtained as follows.

[0109] 137.9g ​​of tantalum hydroxide (Ta) manufactured by Mitsui Mining & Smelting Co., Ltd. ２ O ５ A tantalum fluoride aqueous solution (Ta fluoride concentration 66 mass%) was dissolved in 120 g of a 55 mass% hydrofluoric acid aqueous solution, and 849 mL of ion-exchanged water was added to the solution. ２ O ５ A concentration of 8.2% by weight was obtained.

[0110] 1,000 g of this tantalum fluoride aqueous solution was mixed with 27.5 g of hydrogen peroxide (H ２ O ２ Concentration 35% by mass) was added (H ２ O ２ The mixture was stirred for 5 minutes (molar ratio of tantalum to tantalum = 0.76), to obtain an aqueous solution of a tantalum compound.

[0111] 1,000 g of this tantalum compound aqueous solution was added to ammonia water (NH ３ (NH ３ / Ta molar ratio = 245, NH ３ A reaction solution (pH 11) was obtained (mole ratio of HCl / HF=30.7). This reaction solution was a slurry of a tantalic acid compound hydrate, in other words, a slurry of a tantalum-containing precipitate.

[0112] The reaction solution was then decanted using a centrifuge and washed until the amount of liberated fluoride ions was 100 mg / L or less, yielding a tantalum-containing precipitate from which the fluoride ions had been removed, using aqueous ammonia as the washing liquid.

[0113] The tantalum-containing precipitate from which the fluoride ions had been removed was diluted with pure water to obtain a tantalum-containing precipitate slurry. A portion of this tantalum-containing precipitate slurry was dried at 110°C for 24 hours and then fired at 1,000°C for 4 hours to obtain Ta. ２ O ５ and from the weight thereof, the Ta contained in the tantalum-containing precipitation slurry is calculated. ２ O ５ The concentration was calculated.

[0114] Then, the tantalum-containing precipitate slurry diluted with pure water, 5 mass % of dimethylamine as an organic nitrogen compound, and pure water were mixed together to form a final mixture with a tantalum concentration of Ta ２ O ５ 5 mass% in terms of Ta ２ O ５ The tantalic acid compound-containing solution used in Example 1 was obtained by mixing the tantalic acid compound-containing solution and the organic nitrogen compound so that the weight ratio of the tantalic acid compound to the organic nitrogen compound was 1.0. The pH of the tantalic acid compound-containing solution used in Example 1 was 12.0.

[0115] Example 2 In Example 2, a tantalic acid compound-containing liquid was applied to the surface of a SUS protective tube (SUS304) (tube diameter x length x thickness: φ25 mm x 300 mm x 1.0 mm) for a thermocouple temperature sensor [K type] in a molten metal furnace using a brush (the amount applied was 0.1439 g). Next, the SUS protective tube coated with the tantalic acid compound-containing liquid was naturally dried. Next, the naturally dried SUS protective tube coated with the tantalic acid compound-containing liquid was placed in an electric furnace and baked at 350°C for 30 minutes. After baking, it was air-cooled to room temperature. During this process, a tantalic acid compound-dispersed coating film was formed on the surface of the SUS protective tube.

[0116] After air cooling, the SUS protective tube on which the tantalic acid compound dispersed coating film was formed was placed in a vacuum carbonitriding furnace (manufactured by Oriental Engineering Co., Ltd., model: VCQ400) and heated in a vacuum at a preheating temperature of 850°C for 60 minutes, and then heated at a soaking temperature of 1020°C for 60 minutes. Next, acetylene gas (C ２ H ２) was supplied into the vacuum carbonitriding furnace, and a carburizing treatment was carried out for 35 minutes at a carburizing temperature of 1020°C to carburize the tantalate compound dispersed coating film and the SUS protective tube. ２ H ２ The gas pressure of the gas mixture was 1066.576 Pa. Then, a diffusion treatment was carried out for 75 minutes under vacuum at a diffusion temperature of 1020°C to diffuse the carbon that had penetrated into the tantalic acid compound dispersed coating film and the SUS protective tube. In this way, the tantalum in the tantalic acid compound dispersed coating film was subjected to a carbonization reaction, thereby carrying out a carbonization reaction.

[0117] Thus, a coated structure according to Example 2 was obtained. The tantalic acid compound-containing liquid used in Example 2 was obtained in the same manner as the tantalic acid compound-containing liquid used in Example 1.

[0118] (Example 3) In Example 3, a coating structure according to Example 3 was obtained by carrying out a manufacturing method similar to that of Example 2, except that the substrate was a SUS protective tube (SUS316) (tube diameter x length x thickness: φ21.7 mm x 300 mm x 2.8 mm) for a thermocouple temperature sensor [K type] in a molten metal furnace (the coating amount was 0.125 g).

[0119] Example 4 In Example 4, a coated structure according to Example 4 was obtained (the amount of coating was 0.125 g) by carrying out the same manufacturing method as in Example 2, except that (i) the substrate was a stainless steel protective tube (SUS316) (tube diameter x length x thickness: φ21.7 mm x 300 mm x 2.8 mm) for a thermocouple temperature sensor [K type] in a molten metal furnace, (ii) the carburizing treatment was carried out twice, and (iii) the carburizing treatment time per carburizing treatment was 110 minutes.

[0120] Specifically, a first carbonization reaction was carried out as described above, and a second carbonization reaction was carried out on the metal-based substrate obtained after the first carbonization reaction in the same manner as the first carbonization reaction, thereby forming a second tantalate compound-dispersed coating film on the metal-based substrate after the first carbonization reaction. That is, in Example 4, the carburization treatment was carried out twice.

[0121] Example 5 In Example 5, a coating structure according to Example 5 was obtained (the coating amount was 0.016 g) by carrying out the same manufacturing method as in Example 1, except that (i) the substrate was a metal substrate (SUS304) (length x width x thickness: 20 mm x 20 mm x 1.0 mm) and (ii) the carburization temperature was 1070°C.

[0122] Example 6 In Example 6, a coating structure according to Example 6 was obtained (the coating amount was 0.016 g) by carrying out the same manufacturing method as in Example 1, except that (i) the substrate was a metal substrate (SUS310S) (length x width x thickness: 20 mm x 20 mm x 1.0 mm) and (ii) the carburization temperature was 1070°C.

[0123] Example 7 In Example 7, a coating structure according to Example 7 was obtained (the coating amount was 0.016 g) by carrying out the same manufacturing method as in Example 1, except that (i) the substrate was a metal substrate (Inconel: registered trademark) (length x width x thickness: 20 mm x 20 mm x 1.0 mm) and (ii) the carburization temperature was 1070°C.

[0124] Example 8 In Example 8, the same manufacturing method as in Example 1 was carried out, except that (i) the substrate was a metal substrate (made of titanium) (length x width x thickness: 20 mm x 20 mm x 1.0 mm) and (ii) the carburization temperature was 1070°C, to obtain a coated structure according to Example 1 (the coating amount was 0.016 g).

[0125] Example 9 In Example 9, a coated structure according to Example 9 was obtained by carrying out the same manufacturing method as in Example 1, except that (i) the substrate was a metal substrate (SUS304) (length x width x thickness: 20 mm x 20 mm x 1.0 mm), (ii) the niobate compound-containing liquid was applied to the entire surface of the substrate using a brush (the amount applied was 0.0135 g), (iii) the carburization temperature was 1070°C, and (iv) the carburization treatment time was 57 minutes (the carburization time was 18 minutes, and the diffusion time was 39 minutes).

[0126] The niobic acid compound-containing liquid used in Example 9 was obtained as follows.

[0127] 100 g of niobium pentoxide was dissolved in 200 g of a 55 mass % aqueous solution of hydrofluoric acid, and 830 mL of ion-exchanged water was added to prepare a niobium fluoride aqueous solution (Nb ２ O ５ = 8.84% by mass).

[0128] 200 mL of this niobium fluoride aqueous solution was added to ammonia water (NH ３ (NH ３ / Nb ２ O ５ Molar ratio = 177.9, NH ３ / HF molar ratio=12.2), a reaction liquid (pH 11) was obtained. This reaction liquid was a slurry of a niobic acid compound hydrate, in other words, a slurry of a niobium-containing precipitate.

[0129] The reaction solution was then decanted using a centrifuge and washed until the amount of liberated fluoride ions was 100 mg / L or less, to obtain a niobium-containing precipitate from which the fluoride ions had been removed. At this time, aqueous ammonia was used as the washing liquid.

[0130] Furthermore, the niobium-containing precipitate from which the fluoride ions had been removed was diluted with pure water to obtain a slurry. A portion of this niobium-containing precipitate slurry was dried at 110°C for 24 hours and then calcined at 1000°C for 4 hours to obtain Nb ２ O ５ and determining the Nb content of the niobium-containing precipitation slurry from the weight of the resulting slurry. ２ O ５ The concentration was calculated.

[0131] Then, pure water was added to the niobium-containing precipitate slurry diluted with pure water, and a 50 mass % aqueous dimethylamine solution was added as an organic nitrogen compound so that the dimethylamine concentration was 7.2 mass %. ２ O ５ The solid content of the slurry was adjusted to 24.0% by mass. The slurry was stirred for 48 hours to obtain the niobic acid compound-containing liquid used in Example 9. The pH of the niobic acid compound-containing liquid used in Example 9 was 11.0.

[0132] Example 10 In Example 10, a coated structure according to Example 10 was obtained by carrying out the same manufacturing method as in Example 1, except that (i) the substrate was a metal substrate (SUS304) (length x width x thickness: 20 mm x 20 mm x 1.0 mm), (ii) the titanate compound-containing liquid was applied to the entire surface of the substrate using a brush (the amount applied was 0.01 g), (iii) the carburization temperature was 1070°C, and (iv) the carburization treatment time was 57 minutes (the carburization time was 18 minutes, and the diffusion time was 39 minutes).

[0133] The titanic acid compound-containing liquid used in Example 10 was obtained as follows.

[0134] 33.3 g of titanyl sulfate (manufactured by Teika Co., Ltd., TiO ２ A titanyl sulfate solution (titanium concentration (TiO equivalent) 11 mass%, sulfuric acid concentration 17 mass%, pH 1 or less) was obtained by adding 66.7 g of ion-exchanged water to the titanyl sulfate solution (titanium concentration (TiO equivalent) 11 mass%, sulfuric acid concentration 17 mass%, pH 1 or less) containing 11.3% by mass of titanium dioxide and 17.3% by mass of sulfuric acid.

[0135] 100 g of this titanyl sulfate aqueous solution was added to 100 g of 50% by mass dimethylamine (6.4 moles of amine per mole of sulfuric acid in the titanyl sulfate aqueous solution) over a period of less than 1 minute. The mixture was then stirred for 15 minutes to obtain a neutralized reaction solution (pH 12). This neutralized reaction solution was a slurry of titanium-containing material, in other words, a slurry of titanium-containing precipitates.

[0136] Next, the neutralized reaction solution was decanted using a centrifuge and washed until the sulfuric acid concentration in the supernatant was 100 mg / L or less, thereby obtaining a titanium-containing precipitate from which sulfuric acid had been removed. At this time, ammonia water was used as the washing liquid.

[0137] A portion of this titanium-containing precipitate was calcined at 1,000°C for 4 hours to obtain TiO ２ and from the mass thereof, TiO contained in the titanium-containing precipitate is calculated. ２ The concentration was calculated. ２ The concentration was 11.0% by mass.

[0138] Then, 45 g of this titanium-containing precipitate was mixed with 5 g of tetramethylammonium hydroxide pentahydrate (TMAH concentration 50% by mass) (0.443 mol per mol of Ti in the titanium-containing precipitate), and the mixture was shaken and mixed for 24 hours using a paint shaker to obtain the titanic acid compound-containing liquid used in Example 10.

[0139] Example 11 In Example 11, a coated structure according to Example 11 was obtained by carrying out the same manufacturing method as in Example 1, except that (i) the substrate was a metal substrate (SUS304) (length × width × thickness: 20 mm × 20 mm × 1.0 mm), (ii) the zirconium oxide compound-containing liquid was applied to the entire surface of the substrate using a brush (the amount applied was 0.02 g), (iii) the carburization temperature was 1070°C, and (iv) the carburization treatment time was 57 minutes (the carburization time was 18 minutes, and the diffusion time was 39 minutes).

[0140] The zirconate compound-containing liquid used in Example 11 was obtained as follows.

[0141] 3.01 g (0.01 mol) of zirconium sulfate monohydrate was dissolved in 2.50 g (0.014 mol) of 55% by mass aqueous sulfuric acid solution, and 25 g of ion-exchanged water and 2.5 g (0.026 mol) of 35% by mass aqueous hydrogen peroxide solution were added to obtain a solution (H ２ O ２ / ZrO ２ Molar ratio = 2.6), zirconium to ZrO ２ An aqueous solution of zirconium sulfate containing 4.3% by mass in terms of zirconium sulfate was obtained.

[0142] Next, the entire amount of the zirconium sulfate aqueous solution was added to ammonia water (NH ３ (NH ３ / ZrO ２ Molar ratio = 147, NH ３ / SO ４ ２－ A reaction solution was obtained by a reverse neutralization reaction (molar ratio = 43). This reaction solution was a slurry of a zirconate compound hydrate, in other words, a slurry of a zirconium-containing precipitate.

[0143] The reaction solution was decanted using a centrifuge and washed until the conductivity reached 500 μS / cm or less, yielding a zirconium-containing precipitate from which the sulfur content had been removed. In this case, aqueous ammonia was used as the washing liquid.

[0144] Furthermore, the zirconium-containing precipitate from which the sulfur content had been removed was diluted with pure water to obtain a zirconium-containing precipitate slurry from which the sulfur content had been removed. A portion of the zirconium-containing precipitate slurry from which the sulfur content had been removed was dried at 110°C for 24 hours and then calcined at 1,000°C for 4 hours to obtain ZrO ２ and ZrO contained in the zirconium-containing precipitation slurry from which sulfur content has been removed from the weight thereof. ２ The concentration was calculated.

[0145] The zirconium-containing precipitate slurry, diluted with pure water and from which the sulfur content had been removed, was mixed with 13.7 g (0.023 mol) of 15 mass % tetramethylammonium hydroxide (TMAH) and 28.5 g of ion-exchanged water so that the zirconium concentration in the final mixture would be 4.5 mass % in terms of ZrO2 and the tetramethylammonium hydroxide (TMAH) concentration would be 7.2 mass % (TMAH / ZrO ２ (molar ratio of 2.2) This mixture was stirred and held at room temperature (25°C) for 1 hour to obtain the zirconate compound-containing liquid used in Example 11. The pH of the zirconate compound-containing liquid used in Example 11 was 13.7.

[0146] Example 12 In Example 12, a coated structure according to Example 12 was obtained by carrying out the same manufacturing method as in Example 1, except that (i) the substrate was a metal substrate (SUS304) (length x width x thickness: 20 mm x 20 mm x 1.0 mm), (ii) the hafnium oxide compound-containing liquid was applied to the entire surface of the substrate using a brush (the amount applied was 0.014 g), (iii) the carburization temperature was 1070°C, and (iv) the carburization treatment time was 57 minutes (the carburization time was 18 minutes, and the diffusion time was 39 minutes).

[0147] The hafnium oxide compound-containing liquid used in Example 12 was obtained as follows.

[0148] To 76.0 g of hafnium oxide (purity 98%, powder, manufactured by Kojundo Kagaku Kenkyusho Co., Ltd.), 105.1 g of 55 mass % hydrofluoric acid and 796.9 g of pure water were added, and the mixture was heated to 80°C in a water bath and stirred for 24 hours to dissolve the compound, thereby obtaining a hafnium compound hydrofluoric acid solution. 2.2 g of 35 mass % hydrogen peroxide water was added to 60 g of this hafnium compound hydrofluoric acid solution to obtain a hafnium complex aqueous solution (H ２ O ２ / Hf molar ratio = 1.0), and after stirring for 5 minutes, the mixture was gradually added to 377.2 g of 25% by mass ammonia water (NH ３ ( / Hf molar ratio=250) Thereafter, stirring was carried out for 5 minutes to obtain a neutralized reaction liquid containing hafnium hydroxide as a precipitate.

[0149] Next, this neutralization reaction solution was decanted using a centrifuge, and a precipitate (containing hafnium hydroxide) was recovered. The recovered precipitate was mixed with 200 g of 25 mass % ammonia water to form a slurry, and then decanted again to recover the precipitate. This decantation and recovery process of the precipitate (containing hafnium hydroxide) was repeated three times.

[0150] Then, 31.1 g of 25 mass % TMAH was added to the recovered precipitate (containing hafnium hydroxide) to obtain a mixed solution. ２ Pure water was added to the mixture until the total weight of the mixture became 77.7 g, so that the concentration was 6 mass % in terms of the total weight of the hafnium oxide compound, and the mixture was stirred for 6 hours to obtain the hafnium oxide compound-containing liquid used in Example 12. The pH of the hafnium oxide compound-containing liquid used in Example 12 was 14.8.

[0151] Example 13 In Example 13, a coated structure according to Example 13 was obtained by carrying out the same manufacturing method as in Example 1, except that (i) the substrate was a metal substrate (SUS304) (length x width x thickness: 20 mm x 20 mm x 1.0 mm), (ii) the tungstic acid compound-containing liquid was applied to the entire surface of the substrate using a brush (the amount applied was 0.0165 g), (iii) the carburization temperature was 1070°C, and (iv) the carburization treatment time was 57 minutes (the carburization time was 18 minutes, and the diffusion time was 39 minutes).

[0152] The tungstic acid compound-containing liquid used in Example 13 was obtained as follows.

[0153] 100 g of tungsten trioxide was dissolved in 200 g of a 55 mass % aqueous sulfuric acid solution, and ion-exchanged water was added to convert tungsten to WO ３ An aqueous solution of tungsten sulfate containing 100 g / L of tungsten sulfate was obtained. 200 mL of this aqueous solution of tungsten sulfate was added to ammonia water (NH ３ (NH ３ / WO molar ratio = 170.47, NH ３ / SO ４ ２－ The reaction mixture was a slurry of a tungstic acid compound hydrate, in other words, a slurry of a tungsten-containing precipitate.

[0154] The reaction solution was then decanted using a centrifuge and washed until the conductivity reached 500 μS / cm or less, yielding a tungsten-containing precipitate from which the sulfur content had been removed. In this case, aqueous ammonia was used as the washing liquid.

[0155] Furthermore, the sulfur-removed tungsten-containing precipitate was diluted with pure water to obtain a sulfur-removed tungsten-containing precipitate slurry. A portion of the sulfur-removed tungsten-containing precipitate slurry was dried at 110°C for 24 hours and then calcined at 1,000°C for 4 hours to obtain WO ３ and WO contained in the tungsten-containing precipitation slurry from which sulfur has been removed from the weight of the resulting slurry. ３ The concentration was calculated.

[0156] The tungsten-containing precipitate slurry, from which the sulfur content has been removed and diluted with pure water, is then mixed to form a mixture having a tungsten concentration of WO ３ 2% by mass of methylamine was mixed with pure water so that the total concentration was 10% by mass, and the mixture was stirred and held at room temperature (25°C) for 1 hour to obtain the tungstic acid compound-containing liquid used in Example 13. The pH of the tungstic acid compound-containing liquid used in Example 13 was 8.2.

[0157] Example 14 In Example 14, a coated structure according to Example 14 was obtained by carrying out the same manufacturing method as in Example 1, except that (i) the substrate was a metal substrate (SUS304) (length x width x thickness: 20 mm x 20 mm x 1.0 mm), (ii) the molybdic acid compound-containing liquid was applied to the entire surface of the substrate using a brush (the amount applied was 0.017 g), (iii) the carburizing temperature was 1070°C, and (iv) the carburizing treatment time was 57 minutes (the carburizing time was 18 minutes, and the diffusion time was 39 minutes).

[0158] The molybdic acid compound-containing liquid used in Example 14 was obtained as follows.

[0159] 100 g of molybdenum trioxide was dissolved in 200 g of a 55 mass % aqueous sulfuric acid solution, and ion-exchanged water was added to convert the molybdenum to MoO ３ An aqueous solution of molybdenum sulfate containing 100 g / L of molybdenum sulfate was obtained. 200 mL of this aqueous solution of molybdenum sulfate was added to ammonia water (NH ３ (NH ３ / MoO ３ Molar ratio = 105.66, NH ３ / SO ４ ２－ The reaction mixture was a molybdic acid compound hydrate slurry, in other words, a molybdenum-containing precipitate slurry.

[0160] The reaction solution was then decanted using a centrifuge and washed until the conductivity reached 500 μS / cm or less, yielding a molybdenum-containing precipitate from which sulfur had been removed. In this case, aqueous ammonia was used as the washing liquid.

[0161] Furthermore, the molybdenum-containing precipitate from which the sulfur content had been removed was diluted with pure water to obtain a molybdenum-containing precipitate slurry from which the sulfur content had been removed. A portion of the molybdenum-containing precipitate slurry from which the sulfur content had been removed was dried at 110°C for 24 hours and then calcined at 1,000°C for 4 hours to obtain MoO ３ and MoO contained in the molybdenum-containing precipitation slurry from which sulfur content has been removed from the weight of the resulting slurry. ３ The concentration was calculated.

[0162] The molybdenum-containing precipitate slurry, from which the sulfur content has been removed and diluted with pure water, is then mixed with a molybdenum solution until the molybdenum concentration of the final mixture reaches MoO ３ 2% by mass of methylamine was mixed with pure water so that the total concentration was 10% by mass, and the mixture was stirred and held at room temperature (25°C) for 1 hour to obtain the molybdic acid compound-containing liquid used in Example 14. The pH of the molybdic acid compound-containing liquid used in Example 14 was 9.7.

[0163] Example 15 A coated structure according to Example 15 was obtained by carrying out the same manufacturing method as in Example 6.

[0164] Example 16 In Example 16, a coated structure according to Example 16 was obtained by carrying out the same manufacturing method as in Example 1, except that (i) the substrate was a metal substrate (SUS310S) (length x width x thickness: 20 mm x 20 mm x 1.0 mm), (ii) the niobate compound-containing liquid was applied to the entire surface of the substrate using a brush (the amount applied was 0.0135 g), and (iii) the carburization temperature was 1070°C.

[0165] The niobic acid compound-containing liquid used in Example 16 was obtained in the same manner as the niobic acid compound-containing liquid used in Example 9.

[0166] Example 17 In Example 17, a coated structure according to Example 17 was obtained by carrying out the same manufacturing method as in Example 1, except that (i) the substrate was a metal substrate (SUS310S) (length x width x thickness: 20 mm x 20 mm x 1.0 mm), (ii) the titanate compound-containing liquid was applied to the entire surface of the substrate using a brush (the amount applied was 0.01 g), and (iii) the carburization temperature was 1070°C.

[0167] The titanic acid compound-containing liquid used in Example 17 was obtained in the same manner as the titanic acid compound-containing liquid used in Example 10.

[0168] Example 18 In Example 18, a coated structure according to Example 18 was obtained by carrying out the same manufacturing method as in Example 1, except that (i) the substrate was a metal substrate (SUS310S) (length × width × thickness: 20 mm × 20 mm × 1.0 mm), (ii) the zirconate compound-containing liquid was applied to the entire surface of the substrate using a brush (the amount applied was 0.02 g), and (iii) the carburization temperature was 1070°C.

[0169] The zirconate compound-containing liquid used in Example 18 was obtained in the same manner as the zirconate compound-containing liquid used in Example 11.

[0170] Example 19 In Example 19, a coated structure according to Example 19 was obtained by carrying out the same manufacturing method as in Example 1, except that (i) the substrate was a metal substrate (SUS310S) (length x width x thickness: 20 mm x 20 mm x 1.0 mm), (ii) the hafnium acid compound-containing liquid was applied to the entire surface of the substrate using a brush (the amount applied was 0.0139 g), and (iii) the carburization temperature was 1070°C.

[0171] The hafnium oxide compound-containing liquid used in Example 19 was obtained in the same manner as the hafnium oxide compound-containing liquid used in Example 12.

[0172] Example 20 In Example 20, a coated structure according to Example 20 was obtained by carrying out the same manufacturing method as in Example 1, except that (i) the substrate was a metal substrate (SUS310S) (length×width×thickness: 20 mm×20 mm×1.0 mm), (ii) the tungstic acid compound-containing liquid was applied to the entire surface of the substrate using a brush (the amount applied was 0.0165 g), and (iii) the carburization temperature was 1070° C.

[0173] The tungstic acid compound-containing solution used in Example 20 was obtained in the same manner as the tungstic acid compound used in Example 13.

[0174] Example 21 In Example 21, a coated structure according to Example 21 was obtained by carrying out the same manufacturing method as in Example 1, except that (i) the substrate was a metal substrate (SUS310S) (length x width x thickness: 20 mm x 20 mm x 1.0 mm), (ii) the molybdic acid compound-containing liquid was applied to the entire surface of the substrate using a brush (the amount applied was 0.0173 g), and (iii) the carburization temperature was 1070°C.

[0175] The molybdic acid compound-containing liquid used in Example 21 was obtained in the same manner as the molybdic acid compound-containing liquid used in Example 14.

[0176] Example 22 In Example 22, a coated structure according to Example 22 was obtained by carrying out the same manufacturing method as in Example 1, except that (i) the substrate was a metal substrate (SUS310S) (length x width x thickness: 20 mm x 20 mm x 1.0 mm), (ii) the silicic acid compound-containing liquid was applied to the entire surface of the substrate using a brush (the amount applied was 0.0169 g), and (iii) the carburization temperature was 1070°C.

[0177] The silicic acid compound-containing liquid used in Example 22 was obtained as follows.

[0178] To a 100 mL beaker, 11.0 g of tetraethoxysilane (TEOS, manufactured by Tokyo Ohka Kogyo Co., Ltd.), a silicon-containing raw material, was added 0.1 g of acetic acid (manufactured by Hayashi Pure Chemical Industries, Ltd.), an acidic aqueous solution, 15 g of industrial ethanol (Solmix AP-7 (a mixed alcohol solvent containing 85.5 mass % ethanol, 9.6 mass % 1-propanol, 4.9 mass % 2-propanol, and 0.2 mass % or less water), manufactured by Toyo Petrochemical Co., Ltd.), and 8 g of pure water. The mixture was mixed for 20 hours at room temperature (25°C) while stirring with a stirrer tip, yielding 6 g of a dried silicon compound as a transparent precipitate.

[0179] Next, 2.6 g of 40% by mass methylamine (manufactured by Mitsubishi Gas Chemical Company, Inc.) and 8.9 g of pure water were added to 6 g of the obtained dried silicon compound, and the mixture was mixed at room temperature (25°C) for 10 hours while stirring with a stirrer tip, thereby obtaining the silicic acid compound-containing liquid used in Example 22.

[0180] Example 23 The coated structure according to Example 23 was obtained by carrying out the same manufacturing method as in Example 5.

[0181] Example 24 In Example 24, a coated structure according to Example 24 was obtained by carrying out the same manufacturing method as in Example 1, except that (i) the substrate was a metal substrate (SUS304) (length x width x thickness: 20 mm x 20 mm x 1.0 mm), (ii) a mixed liquid of a tantalic acid compound-containing liquid and a titanic acid compound-containing liquid was applied to the entire surface of the substrate using a brush (the amount applied was 0.013 g), and (iii) the carburization temperature was 1070°C.

[0182] The mixed liquid of tantalic acid compound-containing liquid and titanic acid compound-containing liquid used in Example 24 was prepared by mixing a tantalic acid compound-containing liquid obtained in the same manner as the tantalic acid compound-containing liquid used in Example 1 and a titanic acid compound-containing liquid obtained in the same manner as the titanic acid compound-containing liquid used in Example 10, each adjusted to 50 mass % by mass.

[0183] Example 25 In Example 25, a coated structure according to Example 25 was obtained by carrying out the same manufacturing method as in Example 1, except that (i) the substrate was a metal substrate (SUS304) (length x width x thickness: 20 mm x 20 mm x 1.0 mm), (ii) a mixed liquid of a tantalic acid compound-containing liquid and a tungsten oxide-containing liquid was applied to the entire surface of the substrate using a brush (the amount applied was 0.016 g), and (iii) the carburization temperature was 1070°C.

[0184] The mixed liquid of the tantalic acid compound-containing liquid and the tungstic acid compound-containing liquid used in Example 25 was prepared by mixing a tantalic acid compound-containing liquid obtained in the same manner as the tantalic acid compound-containing liquid used in Example 1 and a tungstic acid compound-containing liquid obtained in the same manner as the tungstic acid compound-containing liquid used in Example 13, each adjusted to 50 mass % by mass.

[0185] Example 26 In Example 26, a coated structure according to Example 26 was obtained (the amount of coating was 0.016 g) by carrying out the same manufacturing method as in Example 1, except that (i) the substrate was a metal substrate (SUS304) (length x width x thickness: 20 mm x 20 mm x 1.0 mm), (ii) the carburizing temperature was 1070°C, (iii) the carburizing treatment was carried out twice, and (iv) the carburizing treatment time per carburizing treatment was 110 minutes.

[0186] Example 27 In Example 27, a coated structure according to Example 27 was obtained (the amount of coating was 0.016 g) by the same manufacturing method as in Example 1, except that (i) the substrate was a metal substrate (SUS310S) (length x width x thickness: 20 mm x 20 mm x 1.0 mm), (ii) the carburizing temperature was 1070°C, (iii) the carburizing treatment was performed twice, and (iv) the carburizing treatment time per carburizing treatment was 110 minutes.

[0187] Example 28 In Example 28, a coated structure according to Example 28 was obtained (the amount of coating was 0.016 g) by carrying out the same manufacturing method as in Example 1, except that (i) the substrate was a metal substrate (Inconel: registered trademark) (length x width x thickness: 20 mm x 20 mm x 1.0 mm), (ii) the carburizing temperature was 1070°C, (iii) the carburizing treatment was carried out twice, and (iv) the carburizing treatment time per carburizing treatment was 110 minutes.

[0188] Example 29 The coated structure according to Example 29 was obtained by carrying out the same manufacturing method as in Example 5.

[0189] Comparative Example 1 Comparative Example 1 was a carbon-based substrate, specifically an extruded graphite material (length x width x thickness: 50 mm x 50 mm x 3 mm). Note that no coating film, such as a tantalic acid compound dispersed coating film, was formed on the substrate of Comparative Example 1.

[0190] Comparative Example 2 is a metal-based substrate, specifically the metal-based substrate (SUS304) (length x width x thickness: 30 mm x 35 mm x 1.5 mm) used in Example 1. Note that no coating film such as a tantalic acid compound dispersed coating film was formed on the substrate of Comparative Example 2.

[0191] Comparative Example 3 is a tubular metallic substrate, specifically a SUS protective tube (tube diameter x length x thickness: φ25 mm x 300 mm x 1.0 mm) for a thermocouple sensor [K type] in the molten metal furnace used in Example 2. Note that no coating film such as a tantalic acid compound dispersed coating film was formed on the substrate of Comparative Example 3.

[0192] Comparative Example 4 Comparative Example 4 is a tubular metallic substrate, specifically a SUS protective tube (SUS316) (tube diameter x length x thickness: φ21.7 mm x 300 mm x 2.8 mm) for a thermocouple temperature sensor [K type] in the molten metal furnace used in Examples 3 and 4. Note that no coating film such as a tantalic acid compound dispersed coating film was formed on the substrate of Comparative Example 4.

[0193] Comparative Example 5 is a metal-based substrate, specifically the metal-based substrate (SUS304) (length x width x thickness: 20 mm x 20 mm x 1.0 mm) used in Examples 5, 9 to 14, 22, and 23. Note that no coating film such as a tantalic acid compound dispersed coating film was formed on the substrate of Comparative Example 5.

[0194] Comparative Example 6 is a metal-based substrate, specifically the metal-based substrate (SUS304) (length x width x thickness: 20 mm x 20 mm x 1.0 mm) used in Examples 6, and 15 to 21. Note that no coating film such as a tantalic acid compound dispersed coating film was formed on the substrate of Comparative Example 6.

[0195] Comparative Example 7 Comparative Example 7 is a metal-based substrate, specifically the metal-based substrate (Inconel: registered trademark) (length x width x thickness: 20 mm x 20 mm x 1.0 mm) used in Example 7. Note that no coating film such as a tantalic acid compound dispersed coating film was formed on the substrate of Comparative Example 7.

[0196] Comparative Example 8 is a metal-based substrate, specifically the metal-based substrate (made of titanium) (length x width x thickness: 20 mm x 20 mm x 1.0 mm) used in Example 8. Note that no coating film such as a tantalic acid compound dispersed coating film was formed on the substrate of Comparative Example 8.

[0197] Comparative Example 9 Comparative Example 9 was obtained in the same manner as Comparative Example 6.

[0198] Comparative Example 10 Comparative Example 10 was obtained in the same manner as Comparative Example 5.

[0199] Comparative Example 11 Comparative Example 11 was obtained in the same manner as Comparative Example 7.

[0200] Comparative Example 12 Comparative Example 12 was obtained in the same manner as Comparative Example 5.

[0201] Reference Example 1 Reference Example 1 was a tantalum carbide powder produced as follows.

[0202] 120 kg of tantalum oxide manufactured by Mitsui Mining & Smelting Co., Ltd. and 22 kg of carbon black were weighed on a platform balance and mixed by stirring for 5 minutes in a vertical mixer to obtain a mixed powder.

[0203] This mixed powder was filled into a carbon container (2 kg / bottle), and fed into a resistance heating hydrogen furnace at a rate of two bottles every three hours. Primary carbonization was carried out by firing at a temperature of 1,700°C for 14 hours, and a primary carbide was obtained.

[0204] This primary carbide was filled into a carbon crucible (100 kg / bottle), which was then placed in a high-frequency induction heating vacuum furnace and fired at a temperature of 1,800° C. for 5 hours to obtain a secondary carbide.

[0205] The secondary carbide was cooled to room temperature in the high-frequency induction heating vacuum furnace, removed from the carbon crucible, and coarsely crushed into lumps with a diameter of 2 cm or less using a jaw crusher.

[0206] After the coarse pulverization, the coarsely pulverized secondary carbide was finely pulverized using a jet mill, which is an airflow pulverizer. The jet mill used for fine pulverization was set to a feed rate of 10 kg / hr and a wind speed of 2.5 m / min.

[0207] The finely pulverized secondary carbide was then classified using a vibrating sieve, and the undersize particles (fine particles) were collected to obtain tantalum carbide powder according to Reference Example 1.

[0208] The following physical property values ​​were measured and evaluation tests were carried out for the coated structures according to Examples 1 to 29, the carbon-based substrate according to Comparative Example 1, the metal-based substrates according to Comparative Examples 2 and 5 to 12, the tubular metal-based substrates according to Comparative Examples 3 and 4, and the tantalum carbide powder according to Reference Example 1. The methods for measuring the physical property values ​​and the test methods for the evaluation tests are described below. The physical property values ​​of the coated structures according to Examples 1 to 29, the carbon-based substrate according to Comparative Example 1, the metal-based substrates according to Comparative Examples 2 and 5 to 12, the tubular metal-based substrates according to Comparative Examples 3 and 4, and the tantalum carbide powder according to Reference Example 1 are shown in Tables 1 to 3, and the evaluation test results are shown in Tables 4 to 6.

[0209] <Elemental Analysis> If necessary, the sample was appropriately diluted with dilute hydrochloric acid, and the mass fraction in terms of metal was measured using an ICP optical emission analyzer (AG-5110 manufactured by Agilent Technologies) in accordance with JIS K0116:2014.

[0210] <Dynamic Light Scattering Method> The particle size distribution of the metal compound-containing materials used in Examples 1 to 29 was evaluated using a zeta potential, particle size, and molecular weight measurement system (ELSZ-2000, manufactured by Otsuka Electronics Co., Ltd.) in accordance with JIS Z 8828:2019 "Particle Size Analysis - Dynamic Light Scattering Method." In addition, to remove dust and other particles from the solution to be measured immediately before measurement, the materials were filtered through a filter with a 2 μm pore size and subjected to ultrasonic treatment at 28 kHz for 3 minutes in an ultrasonic cleaner (VS-100III, manufactured by AS ONE Corporation). The particle size (D50) refers to the median diameter (D50), which is the particle size that represents the 50% integrated value of the integrated distribution curve.

[0211] <Light Transmittance Measurement> 4 ml of the metal compound-containing material used in Examples 1 to 29 was placed in a quartz cell with an optical path length of 5.0 mm, and the light transmittance of the metal compound-containing material used in Examples 1 to 29 in the wavelength region of 500 nm to 700 nm was measured using a spectrophotometer according to the light transmittance measurement conditions described above or the light transmittance measurement conditions (including Si).

[0212] <Corrosion Resistance Test> Corrosion resistance tests were conducted on the coated structures according to Examples 1 to 29, the carbon-based substrate according to Comparative Example 1, the metal-based substrates according to Comparative Examples 2, 5 to 12, the tubular metal-based substrates according to Comparative Examples 3 and 4, and the tantalum carbide powder according to Reference Example 1 under the three test conditions shown below. The "remaining wall thickness" shown in Tables 4 to 6 was calculated by setting the weight before the corrosion resistance test to 100% and measuring the weight after the corrosion resistance test, i.e., the weight after the immersion time had elapsed, using the formula "(weight after corrosion resistance test) ÷ (weight before corrosion resistance test) × 100." The "remaining wall thickness" shown in Figures 1 to 25 was calculated by setting the weight before the corrosion resistance test to 100% and measuring the weight every hour of immersion time, using the formula "(weight every hour) ÷ (weight before corrosion resistance test) × 100."

[0213] <Corrosion Resistance Test 1> The weights of the coated structures according to Examples 1 and 5 to 14 and the metal-based substrates according to Comparative Examples 2 and 5 to 8 before corrosion resistance test 1 (hereinafter referred to as "weight before test 1") were measured. The coated structures according to Examples 1 and 5 to 14 and the metal-based substrates according to Comparative Examples 2 and 5 to 8 were each immersed in 15 mL of 35 mass % hydrochloric acid, heated using a hot stirrer so that the temperature of the hydrochloric acid reached 60°C, covered with a perforated plate or the like, and heated for 1 hour. Thereafter, every hour, the coated structures according to Examples 1 and 5 to 14 and the metal-based substrates according to Comparative Examples 2 and 5 to 8 that had been immersed in hydrochloric acid were removed, washed with pure water, and the pure water used for washing was wiped off, and the weights after corrosion resistance test 1 (hereinafter referred to as "weight after test 1") were measured. The coated structures according to Examples 1 and 5 to 14 and the metal-based substrates according to Comparative Examples 2 and 5 to 8 whose weights had been measured were then immersed in fresh hydrochloric acid, heated for 1 hour, and their weights were measured. This process was repeated a maximum of 11 times.

[0214] <Corrosion Resistance Test 2> The weights of the coated structures according to Examples 15 to 28 and the metal-based substrates according to Comparative Examples 9 to 11 before corrosion resistance test 2 (hereinafter referred to as "weight before test 2") were measured. Each of the coated structures according to Examples 15 to 28 and the metal-based substrates according to Comparative Examples 9 to 11 was placed in a glass sealed container containing a certain amount of water, with a lidded petri dish immersed in 15 mL of 35% by mass hydrochloric acid. A small amount of nitrogen was introduced into the glass sealed container, and while evacuating the air, the hydrochloric acid was heated for 1 hour using a hot stirrer, using the water in the glass sealed container as a heat medium, until the temperature of the hydrochloric acid reached 60°C. Thereafter, every hour, the coated structures according to Examples 15 to 28 and the metal-based substrates according to Comparative Examples 9 to 11 that had been immersed in hydrochloric acid were removed, washed with pure water, and then the pure water used for washing was wiped off. The weights of each of the coated structures according to Examples 15 to 28 and the metal-based substrates according to Comparative Examples 9 to 11 after corrosion resistance test 2 (hereinafter referred to as "weight after test 2") were measured. The coated structures according to Examples 15 to 28 and the metal-based substrates according to Comparative Examples 9 to 11 whose weights had been measured were then immersed in fresh hydrochloric acid, heated for 1 hour, and their weights were measured; this process was repeated a maximum of 24 times. In corrosion resistance test 2, the coated structures according to Examples 15 to 28 and the metal-based substrates according to Comparative Examples 9 to 11 were placed in a petri dish with a lid immersed in 15 mL of 35% by mass hydrochloric acid, and the petri dish was heated using water in the sealed glass container as a heat medium, thereby allowing the entire petri dish with a lid to be uniformly heated.

[0215] <Corrosion Resistance Test 3> The weights of the coated structure according to Example 29 and the metal-based substrate according to Comparative Example 12 before corrosion resistance test 3 (hereinafter referred to as "weight before test 3") were measured. In corrosion resistance test 3, corrosion resistance to 35 mass% hydrochloric acid, 50 mass% sulfuric acid, 35 mass% sodium hydroxide, and 25 mass% ammonia water was measured.

[0216] First, the corrosion resistance test 3 using 35 mass % hydrochloric acid was the same as the corrosion resistance test 1, and therefore a detailed description thereof will be omitted.

[0217] Next, in corrosion resistance test 3 using 50 mass % sulfuric acid, the coated structure according to Example 29 and the metal-based substrate according to Comparative Example 12 were each placed in a 100 mL beaker, and about 30 g of 50 mass % sulfuric acid was added. After immersion in the sulfuric acid for 5 hours with the sulfuric acid temperature adjusted to 25° C., the coated structure according to Example 29 and the metal-based substrate according to Comparative Example 12 were taken out, washed with pure water, and then wiped off the pure water used for washing. The weights after corrosion resistance test 3 (hereinafter referred to as weights after test 3) were measured.

[0218] Furthermore, in corrosion resistance test 3 using 35 mass % sodium hydroxide or 25 mass % aqueous ammonia (hereinafter referred to as basic solution), the coated structure according to Example 29 was placed in a 100 mL beaker, and about 30 g of the basic solution was added. After immersion in the basic solution for 72 hours with the basic solution temperature at 25° C., the coated structure according to Example 29 was taken out, washed with pure water, and then wiped off the pure water used for washing. The weight after each corrosion resistance test 3 (hereinafter referred to as weight after test 3) was measured.

[0219] <Heat Resistance Test> The coated structures of Examples 2 to 4 and the tubular metal substrates of Comparative Examples 3 and 4 were subjected to the following heat resistance test to evaluate their heat resistance. The samples used for the heat resistance test were as follows. The substrate for the coated structure of Example 2 was a SUS protective tube (SUS304) (tube diameter x length x thickness: φ25 mm x 300 mm x 1 mm) for a thermocouple temperature sensor [K type] in a molten metal furnace. The substrate for the coated structures of Examples 3 and 4 was a SUS protective tube (SUS316) (tube diameter x length x thickness: φ21.7 mm x 300 mm x 2.8 mm) for a thermocouple temperature sensor [K type] in a molten metal furnace. These substrates, on which a tantalum-carbon composite coating was formed, were used as samples for the heat resistance test (SUS). On the other hand, the tubular metal-based substrate according to Comparative Example 3 was the SUS protective tube according to Example 2 on which no tantalum-carbon composite coating or the like was formed, and the tubular metal-based substrate according to Comparative Example 4 was the SUS protective tube according to Examples 3 and 4 on which no tantalum-carbon composite coating or the like was formed.

[0220] The weight of the heat resistance test sample obtained in this way before the heat resistance test (hereinafter referred to as "pre-test weight") was measured. Next, the heat resistance test sample was immersed in molten metal maintained at 1200°C, and the endurance time was defined as the first time that the sensor displayed an abnormal temperature exceeding ±200°C for 5 consecutive minutes (1 plot / mm, 5 points).

[0221] <Raman Spectroscopy> For the coated structures according to Examples 1 and 8, the carbon-based substrate according to Comparative Example 1, and the tantalum carbide powder according to Reference Example 1, Raman spectra measured under the above-described Raman spectroscopy measurement conditions showed peaks at 1300 cm －１ ~1400cm －１ , and 1550 cm －１ ~1650cm －１ A peak was observed at 1550 cm －１ ~1650cm －１ The single peak observed in the graphite structure is called the "G band" and is a highly crystalline graphite structure (sp ２ On the other hand, 1300 cm －１ ~1400cm －１ The peak observed in the D band is called the "D band" and corresponds to the diamond structure (sp ３ The D band / G band peak area ratio calculated according to the above-mentioned Raman spectroscopy analysis conditions is derived from the sp ２ Structure and sp ３ The larger the D band / G band peak area ratio, the more sp ３ This indicates that the abundance ratio of the structure is high. In addition, the standard deviation of the D band / G band peak area ratio is an index of the uniformity of the coating composition. The smaller the standard deviation of the D band / G band peak area ratio, the more uniform the coating composition of the formed film.

[0222]

[0223]

[0224]

[0225]

[0226]

[0227]

[0228] In the coating structures according to Examples 1 to 29, a metal compound-containing material was applied to or immersed in a substrate, and the substrate was heated under reduced pressure or in a vacuum while a carbon source and / or a nitrogen source was supplied, thereby causing at least one reaction among a carbonization reaction, a carbonitriding reaction, and a nitriding reaction, thereby forming a uniform metal composite coating on the substrate.

[0229] 1, the coated structure according to Example 1 was not corroded and suffered little weight loss even when boiled in 35% by mass hydrochloric acid, demonstrating corrosion resistance. On the other hand, the metal substrate according to Comparative Example 2 was corroded by 35% by mass hydrochloric acid and suffered significant weight loss.

[0230] 2 to 5, the coated structures according to Examples 5 to 8 were able to maintain a high residual thickness and had corrosion resistance regardless of the type of substrate. In particular, the coated structures according to Examples 7 and 8 maintained a high residual thickness and had remarkable corrosion resistance. On the other hand, the metallic substrates according to Comparative Examples 5 to 8 showed a decrease in the residual thickness.

[0231] As shown in Figures 6 to 11, the coating structures according to Examples 9 to 14 were able to maintain a residual thickness and had corrosion resistance, regardless of the type of metal compound contained in the metal composite coating formed on the substrate.

[0232] As shown in FIGS. 12 to 25, the coated structures according to Examples 15 to 28 were able to maintain the remaining wall thickness and had corrosion resistance even when the heating method for 35 mass % hydrochloric acid was changed.

[0233] The coated structure of Example 29 was able to maintain a residual thickness even in 50% by mass sulfuric acid, 35% by mass sodium hydroxide, and 25% by mass aqueous ammonia, which are basic solutions, in addition to 35% by mass hydrochloric acid, and thus had corrosion resistance.

[0234] 26(a), the coated structure according to Example 2 had a durability of 154 minutes in the heat resistance test, indicating that the metal composite coating formed on the substrate improved the heat resistance of the substrate. On the other hand, as shown in FIG. 26(b), the tubular metal substrate according to Comparative Example 3 had a durability of 102 minutes in the heat resistance test.

[0235] As shown in Figure 27(a), the coated structure according to Example 3 had a durability time of 1,729 minutes in the heat resistance test, indicating that the metal composite coating formed on the substrate dramatically improved the heat resistance of the substrate. Also, as shown in Figure 27(b), the coated structure according to Example 4 had a durability time of 2,650 minutes in the heat resistance test, indicating that the metal composite coating formed on the substrate dramatically improved the heat resistance of the substrate. Meanwhile, as shown in Figure 27(c), the tubular metal substrate according to Comparative Example 4 had a durability time of 232 minutes in the heat resistance test.

[0236] Furthermore, the durability time of the heat resistance test for the coated structure of Example 2 shown in Figure 26(a) is shorter than the durability time of the heat resistance test for the tubular metal substrate of Comparative Example 4 shown in Figure 27(c), but this is due to the difference in the materials of the substrates used in Example 2 and Comparative Example 4.

[0237] In the coating structures of Examples 1 and 8, the metal-carbon composite coatings formed on the substrates had D band / G band peak area ratios of 0.5 or more and 2.0 or less in Raman spectroscopy, which enabled the formation of physically and chemically stable surface layers and coatings of uniform composition, resulting in excellent corrosion resistance of the substrates.Furthermore, in the coating structures of Examples 1 and 6 to 9, the metal-carbon composite coatings formed on the substrates had standard deviations of D band / G band peak area ratios of 0.1 or more and 0.35 or less in Raman spectroscopy, which enabled the formation of physically and chemically stable surface layers and coatings of uniform composition, resulting in excellent corrosion resistance of the substrates.

[0238] The inventions disclosed in this specification include, in addition to the configurations of each invention and embodiment, those specified by changing these partial configurations to other configurations disclosed in this specification, to the extent applicable, or those specified by adding other configurations disclosed in this specification to these configurations, or those specified as higher-level concepts specified by deleting these partial configurations to the extent that partial effects can be obtained.

[0239] The method for producing a coated structure according to the present invention is suitable as a method for producing a coated structure because it can form a uniform metal composite coating on a substrate, which can form a physically and chemically stable surface layer, regardless of the substrate. Specifically, the method for producing a coated structure according to the present invention involves heating the substrate under reduced pressure or vacuum while supplying a carbon source and / or a nitrogen source, thereby causing at least one of a carbonization reaction, a carbonitriding reaction, and a nitriding reaction, thereby forming a metal composite coating at a low temperature, thereby reducing energy costs. Furthermore, the method for producing a coated structure according to the present invention improves heat resistance and reactivity resistance, extending the life of the substrate, thereby reducing waste and reducing energy costs for waste disposal. Furthermore, the coated structure according to the present invention is suitable as a coated structure because it can form a metal composite coating at a low temperature by heating the substrate under reduced pressure or vacuum while supplying a carbon source and / or a nitrogen source, thereby causing at least one of a carbonization reaction, a carbonitriding reaction, and a nitriding reaction. Specifically, the coated structure according to the present invention has a uniform metal composite coating on a substrate, which improves heat resistance and reactivity resistance and extends the life of the substrate, thereby reducing waste and energy costs for waste disposal. These points lead to the sustainable management and efficient benefits of natural resources, as well as the achievement of decarbonization (carbon neutrality).

Claims

1. A method for producing a coated structure having a metal composite coating on a substrate, comprising: a step of applying or immersing a material containing a metal compound onto the substrate; and a reaction step of heating the substrate under reduced pressure or in vacuum while supplying a carbon source and / or a nitrogen source, thereby causing at least one of a carbonization reaction, a carbonitriding reaction, and a nitriding reaction to form a metal composite coating.

2. The method for producing a coated structure according to claim 1, further comprising a drying step of drying the substrate to which the metal compound-containing material has been applied or which has been immersed.

3. The method for producing a coated structure according to claim 1, characterized in that the step of applying or immersing the metal compound-containing material on the substrate and the reaction step are repeated multiple times.

4. A method for producing a coated structure described in any one of claims 1 to 3, characterized in that the substrate contains at least one material selected from the group consisting of carbon, metal carbides, pure metals, alloys, metal oxides, and composite metal oxides.

5. A method for manufacturing a coated structure described in any one of claims 1 to 3, characterized in that the metal composite coating contains a compound of at least one metal element selected from the group consisting of Ti, Nb, Mo, Hf, Ta, W, Zr, and Si.

6. A method for producing a coated structure according to any one of claims 1 to 3, characterized in that the metal composite coating contains a compound of at least one metal element selected from the group consisting of Nb, Hf and Ta.

7. A method for producing a coated structure described in any one of claims 1 to 3, characterized in that the metal composite coating contains at least one metal carbide selected from the group consisting of Ti carbide, Nb carbide, Mo carbide, Hf carbide, Ta carbide, W carbide, Zr carbide, and Si carbide.

8. A method for producing a coated structure described in any one of claims 1 to 3, characterized in that the metal compound-containing material has a maximum light transmittance of 70%T or more in the wavelength region of 500 nm to 700 nm, and the particle diameter (D50) of the particles in the metal compound-containing material measured by dynamic light scattering is 3000 nm or less.

9. A method for producing a coated structure described in any one of claims 1 to 3, characterized in that the reaction process is a carbonization reaction, and the carbon source is either one containing an unsaturated hydrocarbon and an inert component, or a saturated hydrocarbon.

10. A method for producing a coated structure described in any one of claims 1 to 3, characterized in that the reaction process is a carbonitriding reaction or a nitriding reaction, and the nitrogen source contains ammonia and an inert component.

11. A method for producing a coated structure according to any one of claims 1 to 3, characterized in that the reaction step is performed at a heating temperature of 500°C or higher and 1150°C or lower.

12. The method for producing a coated structure according to claim 11, characterized in that the reaction step is performed with a heating time of 0.05 hours or more and 10 hours or less.

13. A coated structure having a metal composite coating on a substrate, the metal composite coating being formed by heating a substrate coated with or immersed in a metal compound-containing substance under reduced pressure or in vacuum while supplying a carbon source and / or a nitrogen source, thereby causing at least one of a carbonization reaction, a carbonitriding reaction, and a nitriding reaction.

14. A coated structure having a metal-carbon composite coating on a substrate, characterized in that the metal-carbon composite coating has a D band / G band peak area ratio of 0.5 or more and 2.0 or less in Raman spectroscopy.

15. A coated structure having a metal-carbon composite coating on a substrate, wherein a D band / G band peak area ratio in Raman spectroscopy of the metal-carbon composite coating is 0.5 or more and 2.0 or less, and a standard deviation of the D band / G band peak area ratio is 0.1 or more and 0.35 or less.