Method for manufacturing coated structure, and coated 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

[Technical Field]

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

[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. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6058846 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the method disclosed in Patent Document 1, the physical and / or chemical stability and other properties 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 a substrate, and a coated structure. [Means for solving the problem]

[0007] The method for producing a coated structure of the present invention, which has been made to solve the above-mentioned 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 a vacuum while supplying a carbon source and / or a nitrogen source, thereby causing at least one reaction among a carbonization reaction, a carbonitriding reaction, and a nitriding reaction, to form a metal composite coating. 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.

[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, for example, have a metal composite coating on at least one side (e.g., the surface) of the substrate, or may have a metal composite coating on the entire peripheral surface of the substrate, and further includes a substrate 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, which will be described later.

[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 with a multilayer structure in which the outermost layer is made of only carbon or contains 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 can be heated 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 the carbon material of 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, and 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 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 only 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 only 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 only of metal carbide. Examples of the metal carbide contained in the substrate include tungsten carbide, molybdenum carbide, and tantalum carbide.

[0019] The substrate containing a pure metal may be a substrate made only of 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 with a multilayer structure in which the outermost layer is made only of 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 made only of a pure metal. Examples of pure metals contained in the substrate include Ti, V, Fe, Y, Zr, Cr, Ni, Mn, Co, Cu, Zn, and Pb.

[0020] The substrate containing an alloy may be a substrate consisting only of an alloy, a substrate mainly composed of an 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 only of an alloy or mainly composed of an alloy with an alloy content of 50% by mass or more. The substrate containing an alloy is particularly preferably a substrate consisting only of an 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 with the outermost layer consisting solely of a complex metal oxide or 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, etc.

[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 the metal compound-containing material include those containing a compound of at least one metal element selected from Ti, Nb, Mo, Hf, Ta, W, Zr, and Si. Specific examples include peroxo complex metal compounds containing at least one metal element selected from Ti, Nb, Mo, Hf, Ta, W, Zr, and Si (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. Furthermore, the metal compound-containing material may contain a metal element, a metalloid element, or a nonmetal element other than at least one metal element selected from Ti, Nb, Mo, Hf, Ta, W, Zr, and Si. Examples include 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% by mass and not more than 40% by mass, even more preferably 0.1% by mass to 30% by mass, particularly preferably 0.2% by mass to 30% by mass, and particularly preferably 0.3% by mass to 15% by mass. 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 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 necessary, 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 depending on the metal element and the type of carbon-based substrate, and is more preferably more than 0% by mass and less than 35% by mass, even more preferably 0.03% by mass to 25% by mass, particularly preferably 0.06% by mass to 25% by mass, and particularly preferably 0.1% by mass to 15% by 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 element 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 more preferably contains a compound of at least one metal element selected from Nb, Hf, and Ta. Examples of the metal compound-containing material 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, thereby improving film-forming properties and adhesion to the substrate, which is preferable.

[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 contains a metal compound, and more specifically, it may be liquefied by applying shear stress. That is, the metal compound-containing material may be in a liquid, sol, gel, or semi-solid state under normal conditions, and may be applied to a substrate. Furthermore, a solution of the metal compound-containing material used in the method for producing a coated structure of the present invention is more preferable, as it 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 the particles in the metal compound-containing material measured by dynamic light scattering is 3000 nm or less. The metal compound-containing material used in the method for producing a coated structure of the present invention 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, which is preferable from the viewpoints of high dispersibility, excellent uniformity of the components in the liquid, and 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 liquid components. 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= Measurement equipment: UV-Vis-NIR spectrophotometer UH4150 (Hitachi High-Tech Science Corporation) Measurement mode: Wavelength scan Data mode: %T (transparent) Measurement wavelength range: 200nm to 2000nm Scan speed: 600nm / min Sampling interval: 2nm

[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)= Measurement equipment: U-2900 spectrophotometer (Hitachi High-Tech Corporation) Measurement mode: Wavelength scan Data mode: %T (transparent) Measurement wavelength range: 200nm to 1000nm Scan speed: 200nm / min Sampling interval: 1nm Cell length: 10mm 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] Dynamic light scattering is a method for measuring the light scattering intensity from particles undergoing Brownian motion by irradiating a solution such as a suspension with light such as a laser beam. The particle size and distribution are then determined from the temporal fluctuations of this intensity. Specifically, particle size distribution was evaluated using a zeta potential, particle size, and molecular weight measurement system (Otsuka Electronics Co., Ltd.: ELSZ-2000ZS) in accordance with JIS Z 8828:2019 "Particle Size Analysis - Dynamic Light Scattering." If necessary, the sample was diluted 1000 times with pure water. Just before measurement, the sample was filtered through an 11 μm pore filter and ultrasonicated for 3 minutes in an ultrasonic cleaner (AS ONE Corporation: VS-100III) to remove dust and other particles. The liquid temperature of the sample was adjusted to 25°C. The particle size (D50) is the median diameter (D50), which is the particle size at 50% 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 has a pH of more than 7, and the solvent may be water, alcohol, ketone, ester, etc., and two or more solvents may be mixed, and it is preferable that the solvent contains water. The pH of the metal compound-containing material is preferably greater than 7, as this provides 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 that the metal compound-containing material contains 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 be heated and then cooled 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, 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 in 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 from among a carbonization reaction, a carbonitriding reaction, and a nitriding reaction to occur, thereby forming 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., Model VCQ400 manufactured by Oriental Engineering Co., Ltd.) and placed under reduced pressure or vacuum. Next, under reduced pressure or vacuum, the substrate is heated at a preheating temperature for a predetermined preheating time. Subsequently, the substrate is further heated at a soaking temperature for a predetermined soaking time. Thereafter, a carbon source and / or nitrogen source is supplied from 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 results in the penetration of carbon and / or nitrogen from the surface of the metal compound-containing material and the substrate into the interior, and the carbon and / or nitrogen becoming solid-dissolved in the metal compound-containing material and the substrate. Finally, a diffusion treatment is performed under reduced pressure or vacuum at a diffusion temperature for a predetermined diffusion time to diffuse carbon and / or nitrogen into the metal compound-containing material and the substrate. In this manner, 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, in that 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] 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 to 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 because it can supply carbon suitable for forming 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 because 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 because 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 reaction step is performed at a heating temperature of 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 carburizing reaction, carbonitriding reaction, or nitriding reaction of the coating proceeds sufficiently and the coating quality is stabilized. The heating temperature is the carburizing 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 hours or more and 10 hours or less. A heating time of 0.05 hours or more and 10 hours or less is preferable in that carbon and / or nitrogen necessary for forming metal carbide, metal carbonitride, or metal nitride can be supplied sufficiently. 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 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 metal compound-containing substance on a substrate according to the above-described method for producing a coated structure of the present invention and the reaction step are repeated multiple times. By repeating the process of applying or immersing a metal compound-containing material on a substrate and the reaction process multiple times in the method for producing a coated structure of the present invention described above, a metal composite coating is formed multiple times on the substrate, and a metal composite coating that is more physically and chemically stable can be formed.

[0079] Furthermore, if 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 Ti, Nb, Mo, Hf, Ta, W, Zr, and Si, this is preferable in terms of improving the durability of the coated substrate. 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, and are preferably metal carbides, metal nitrides, or metal carbonitrides, and a plurality of 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 it 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 method for manufacturing a coated structure of the present invention described above can be confirmed to contain a metal compound from the peaks of the X-ray diffraction pattern obtained by X-ray diffraction measurement according to the following X-ray diffraction measurement conditions and X-ray diffraction analysis conditions.

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

[0086] =X-ray diffraction analysis conditions= Use the Rigaku data analysis software PDXL2. · Smooth the peak with b-spline to clarify the peak top.

[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, which makes 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, The metal composite coating is characterized in that it is formed by heating a substrate coated with or immersed in a metal compound-containing material under reduced pressure or vacuum while supplying a carbon source and / or a nitrogen source, thereby causing at least one reaction among a carbonization reaction, a carbonitriding reaction, and a nitriding reaction. The coating structure of the present invention has a uniform metal composite coating on a substrate as a physically and chemically stable surface layer independent of the substrate.

[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 D band / G band peak area ratio of the metal-carbon composite coating measured by Raman spectroscopy is 0.5 or more and 2.0 or less. 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, it is possible to form a physically and chemically stable surface layer, and it is also possible to form a coating with a uniform composition, which is preferable.

[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 is usually observed. -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, which is called the "G band." On the other hand, as the crystallinity decreases (the number of crystal structure defects increases), -1 ~1400cm -1 A peak appears at 2400 cm, and this peak is called the "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 few defects in the crystalline structure have a peak at 2400 cm -1 ~2800cm -1 A peak is also detected at 2D band, 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 = Device: Invia Qontor (manufactured by Renishaw) ·Light source: 532nm (RL532-08 150mW) Objective lens: 20x Grating: 1800mm / L Irradiation time: 5 to 10 seconds Accumulation count: 1 time Slit width: 65μm Laser power: 1% ·Using Livetrac function 20x20 square map measurement (10μm intervals in both X and Y directions)

[0094] = Raman spectroscopy analysis conditions = The Raman spectra obtained under the Raman spectroscopy measurement conditions described above were 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 -1 Normalization is performed so that the maximum value in the normalized spectrum is 1. Next, using WaveMetrics' Igor Pro ver. 8.04, multipeak fitting 2 is applied to the normalized spectrum, and the initial peak is set by referring to Table 1 in Chapter 8, Section 4 of the Raman Spectroscopic Data Analysis Casebook (Technical Information Association, Inc.). The peak uses a Gaussian or Lorentzian distribution. Fitting is then performed repeatedly to minimize the χ-square, which represents the difference between the measured peak value and the fitted value. If the χ-square converges beyond 1.0, a new peak is set and fitting is repeated until the χ-square 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, and the sum of the peak areas of each band is calculated. The sum of the D band peak areas divided 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 or more and 2.0 or less in Raman spectroscopy, and the standard deviation of the D band / G band peak area ratio is 0.1 or more and 0.35 or less. 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, and therefore a 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 measurement points of the Raman spectrum measured at any 400 measurement points in the sample made of the coating structure of the present invention, according to the above-mentioned Raman spectroscopy analysis conditions.

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

[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 includes the meaning "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 includes the meaning "preferably larger than X" or "preferably smaller than Y." [Effects of the Invention]

[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. [Brief explanation of the drawings]

[0103] [Figure 1] 1 is a graph showing the measurement results of corrosion resistance test 1 for Example 1 and Comparative Example 2. [Figure 2] 1 is a graph showing the measurement results of corrosion resistance test 1 for Example 5 and Comparative Example 5. [Figure 3] 1 is a graph showing the measurement results of corrosion resistance test 1 for Example 6 and Comparative Example 6. [Figure 4] 1 is a graph showing the measurement results of corrosion resistance test 1 for Example 7 and Comparative Example 7. [Figure 5] 1 is a graph showing the measurement results of corrosion resistance test 1 for Example 8 and Comparative Example 8. [Figure 6] 1 is a graph showing the measurement results of corrosion resistance test 1 for Example 9 and Comparative Example 5. [Figure 7] 1 is a graph showing the measurement results of corrosion resistance test 1 for Example 10 and Comparative Example 5. [Figure 8]1 is a graph showing the measurement results of corrosion resistance test 1 for Example 11 and Comparative Example 5. [Figure 9] 1 is a graph showing the measurement results of corrosion resistance test 1 for Example 12 and Comparative Example 5. [Figure 10] 1 is a graph showing the measurement results of corrosion resistance test 1 for Example 13 and Comparative Example 5. [Figure 11] 1 is a graph showing the measurement results of corrosion resistance test 1 for Example 14 and Comparative Example 5. [Figure 12] 1 is a graph showing the measurement results of corrosion resistance test 2 for Example 15 and Comparative Example 9. [Figure 13] 1 is a graph showing the measurement results of corrosion resistance test 2 for Example 16 and Comparative Example 9. [Figure 14] 1 is a graph showing the measurement results of corrosion resistance test 2 for Example 17 and Comparative Example 9. [Figure 15] 10 is a graph showing the measurement results of corrosion resistance test 2 for Example 18 and Comparative Example 9. [Figure 16] 10 is a graph showing the measurement results of corrosion resistance test 2 for Example 19 and Comparative Example 9. [Figure 17] 1 is a graph showing the measurement results of corrosion resistance test 2 for Example 20 and Comparative Example 9. [Figure 18] 1 is a graph showing the measurement results of corrosion resistance test 2 for Example 21 and Comparative Example 9. [Figure 19] 1 is a graph showing the measurement results of corrosion resistance test 2 for Example 22 and Comparative Example 9. [Figure 20] 10 is a graph showing the measurement results of corrosion resistance test 2 for Example 23 and Comparative Example 10. [Figure 21] 10 is a graph showing the measurement results of corrosion resistance test 2 for Example 24 and Comparative Example 10. [Figure 22] 10 is a graph showing the measurement results of corrosion resistance test 2 for Example 25 and Comparative Example 10. [Figure 23] 10 is a graph showing the measurement results of corrosion resistance test 2 for Example 26 and Comparative Example 10. [Figure 24]10 is a graph showing the measurement results of corrosion resistance test 2 for Example 27 and Comparative Example 9. [Figure 25] 1 is a graph showing the measurement results of corrosion resistance test 2 for Example 28 and Comparative Example 11. [Figure 26] 1(a) is a graph showing the measurement results of a heat resistance test of the coated structure according to Example 2, and FIG. 1(b) is a graph showing the measurement results of a heat resistance test of the tubular metal substrate according to Comparative Example 3. [Figure 27] Graph (a) shows the measurement results of a heat resistance test on the coated structure according to Example 3, graph (b) shows the measurement results of a heat resistance test on the coated structure according to Example 4, and graph (c) shows the measurement results of a heat resistance test on the tubular metal substrate according to Comparative Example 4. BEST MODE FOR CARRYING OUT THE INVENTION

[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 air-dried. Next, the metal substrate coated with the air-dried 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 with the tantalic acid compound-dispersed coating film formed thereon was placed in a vacuum carbonitriding furnace (Model: VCQ400, manufactured by Oriental Engineering Co., Ltd.) and heated under vacuum at a preheating temperature of 850°C for 60 minutes, followed by a soaking time of 1020°C for 60 minutes. Next, with acetylene gas (C2H2) supplied as a carbon source into the vacuum carbonitriding furnace, a carburizing treatment was carried out for 35 minutes at a carburizing temperature of 1020°C to carburize the tantalic acid compound-dispersed coating film and the metal substrate (hereinafter referred to as the "carburizing time"). The acetylene gas (C2H2) pressure was 1066.576 Pa. Then, a diffusion treatment was carried out for 75 minutes at a diffusion temperature of 1020°C to diffuse the carbon that had penetrated into the tantalic acid compound-dispersed coating film and the metal 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] 137.9 g of tantalum hydroxide (manufactured by Mitsui Mining & Smelting Co., Ltd., Ta2O5 concentration 66 mass%) was dissolved in 120 g of 55 mass% hydrofluoric acid aqueous solution, and 849 mL of ion-exchanged water was added to obtain an aqueous tantalum fluoride solution (Ta2O5 concentration 8.2 mass%).

[0110] To 1,000 g of this tantalum fluoride aqueous solution, 27.5 g of hydrogen peroxide solution (H2O2 concentration 35 mass %) was added (H2O2 / Ta molar ratio = 0.76), and the mixture was stirred for 5 minutes to obtain an aqueous tantalum compound solution.

[0111] 1,000 g of this tantalum compound aqueous solution was added to 6.82 L of ammonia water (NH concentration 25% by mass) over a period of less than 10 minutes (NH / Ta molar ratio = 245, NH / HF molar ratio = 30.7) to obtain a reaction solution (pH 11). This reaction solution was a slurry of tantalum acid compound hydrate, in other words, a slurry of 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 then 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 produce Ta2O5, and the Ta2O5 concentration in the tantalum-containing precipitate slurry was calculated from its weight.

[0114] The tantalum-containing precipitate slurry diluted with pure water, 5 mass% dimethylamine as an organic nitrogen compound, and pure water were mixed so that the tantalum concentration in the final mixture was 5 mass% in terms of Ta2O5 and the weight ratio of Ta2O5 / organic nitrogen compound was 1.0, thereby obtaining the tantalum acid compound-containing liquid used in Example 1. The pH of the tantalum acid compound-containing liquid 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 melting furnace using a brush (the amount applied was 0.1439 g). Next, the SUS protective tube to which the tantalic acid compound-containing liquid had been applied was naturally dried. Next, the naturally dried SUS protective tube to which the tantalic acid compound-containing liquid had been applied was placed in an electric furnace and fired at 350°C for 30 minutes. After firing, 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 with the tantalic acid compound-dispersed coating film formed thereon was placed in a vacuum carbonitriding furnace (Oriental Engineering Co., Ltd., Model: VCQ400) and heated under vacuum at a preheating temperature of 850°C for 60 minutes, followed by a soaking time of 1020°C for 60 minutes. Next, with acetylene gas (C2H2) supplied as a carbon source into the vacuum carbonitriding furnace, a carburizing treatment was performed for 35 minutes at a carburizing temperature of 1020°C to carburize the tantalic acid compound-dispersed coating film and the SUS protective tube. The acetylene gas (C2H2) pressure was 1066.576 Pa. Then, a diffusion treatment was performed 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 manner, the tantalum in the tantalic acid compound-dispersed coating film was carbonized, thereby carrying out the carbonization reaction.

[0117] Then, 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 manufacturing method similar to that of Example 2 was carried out, 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, and a coated structure according to Example 3 was obtained (the amount of coating 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 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, (ii) the carburizing treatment was carried out twice, and (iii) the carburizing treatment time per carburizing treatment was 110 minutes.

[0120] Specifically, the first carbonization reaction was carried out as described above, and the second carbonization reaction was carried out on the metal-based substrate 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 × width × thickness: 20 mm × 20 mm × 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 × width × thickness: 20 mm × 20 mm × 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 dimensions: 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 × width × thickness: 20 mm × 20 mm × 1.0 mm) and (ii) the carburization temperature was 1070°C, to obtain a coated structure according to Example 1 (the amount of coating 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 × width × thickness: 20 mm × 20 mm × 1.0 mm), (ii) a 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 carburizing temperature was 1070°C, and (iv) the carburizing treatment time was 57 minutes (carburizing time was 18 minutes, 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 obtain an aqueous solution of niobium fluoride (Nb2O5=8.84 mass %).

[0128] 200 mL of this niobium fluoride aqueous solution was added to 1 L of ammonia water (NH concentration 25 mass %) over a period of less than 1 minute (NH / NbO molar ratio = 177.9, NH / HF molar ratio = 12.2) to obtain a reaction solution (pH 11). This reaction solution was a slurry of niobium acid compound hydrate, in other words, a slurry of niobium-containing precipitates.

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

[0130] The niobium-containing precipitate from which the fluoride ions had been removed was then 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 produce Nb2O5, and the Nb2O5 concentration in the niobium-containing precipitate slurry was calculated from its weight.

[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%, thereby adjusting the Nb2O5 solid concentration to 24.0 mass%. This 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 × width × thickness: 20 mm × 20 mm × 1.0 mm), (ii) a 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 (carburization time was 18 minutes, 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 Corporation, TiO2 concentration 33.3 mass%, sulfuric acid concentration 51.1 mass%) was added to 66.7 g of ion-exchanged water and allowed to stand at 90°C or higher for 1 hour to dissolve, thereby obtaining an aqueous titanyl sulfate solution (titanium concentration (TiO2 equivalent) 11 mass%, sulfuric acid 17 mass%, pH 1 or less).

[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 materials, 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, to obtain 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 fired at 1,000°C for 4 hours to produce TiO2, and the TiO2 concentration in the titanium-containing precipitate was calculated from its mass, which was found to be 11.0 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 1 mol of Ti in the titanium-containing precipitate) and shaken with a paint shaker for 24 hours 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 mass % aqueous sulfuric acid solution, and 25 g of ion-exchanged water and 2.5 g (0.026 mol) of 35 mass % aqueous hydrogen peroxide solution were added (H2O2 / ZrO2 molar ratio = 2.6), to obtain an aqueous zirconium sulfate solution containing 4.3 mass % zirconium in terms of ZrO2.

[0142] Next, the entire amount of the zirconium sulfate aqueous solution was added to 100 g (1.47 mol) of ammonia water (NH3 concentration 25 mass%) in less than 1 minute (NH3 / ZrO2 molar ratio = 147, NH3 / SO4 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 fired at 1,000°C for 4 hours to produce ZrO2, and the ZrO2 concentration in the zirconium-containing precipitate slurry from which the sulfur content had been removed was calculated from the weight of the ZrO2.

[0145] The sulfur-removed zirconium-containing precipitate slurry diluted with pure water was mixed with 13.7 g (0.023 mol) of 15 mass% tetramethylammonium hydroxide (TMAH) and 28.5 g of ion-exchanged water (TMAH / ZrO molar ratio = 2.2) so that the final mixture had a zirconium concentration of 4.5 mass% in terms of ZrO and a tetramethylammonium hydroxide (TMAH) concentration of 7.2 mass%, and the mixture was stirred and held at room temperature (25°C) for 1 hour to obtain the zirconate compound-containing solution used in Example 11. The pH of the zirconate compound-containing solution 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 × width × thickness: 20 mm × 20 mm × 1.0 mm), (ii) a 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 (98% purity, powder, manufactured by Kojundo Kagaku Kenkyusho Co., Ltd.), 105.1 g of 55% by mass hydrofluoric acid and 796.9 g of pure water were added, heated to 80 ° C in a water bath, and stirred for 24 hours to dissolve the compound, obtaining a hydrofluoric acid solution of the hafnium compound. 60 g of this hafnium compound hydrofluoric acid solution was added to 2.2 g of 35% by mass hydrogen peroxide water to obtain a hafnium complex aqueous solution (H2O2 / Hf molar ratio = 1.0). After stirring for 5 minutes, this solution was gradually added to 377.2 g of 25% by mass ammonia water (NH3 / Hf molar ratio = 250). After stirring for 5 minutes, a neutralized reaction solution containing hafnium hydroxide was obtained as a precipitate.

[0149] Next, this neutralized reaction solution was decanted using a centrifuge, and a precipitate (containing hafnium hydroxide) was collected. The collected precipitate was mixed with 200 g of 25 mass % ammonia water to form a slurry, and then decanted again to collect the precipitate. This decantation and collection 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. Pure water was added to the mixed solution until the total weight became 77.7 g so that the final hafnium concentration was 6 mass % in terms of HfO2, and this mixed solution was stirred for 6 hours to obtain the hafnium acid compound-containing solution used in Example 12. The pH of the hafnium acid compound-containing solution 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 × 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), (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% by mass aqueous sulfuric acid solution, and ion-exchanged water was added to obtain a tungsten sulfate aqueous solution containing 100 g / L of tungsten in terms of WO3. 200 mL of this tungsten sulfate aqueous solution was added to 1 L of ammonia water (NH3 concentration 25% by mass) over a period of less than 1 minute (NH3 / WO3 molar ratio = 170.47, NH3 / SO4 2- A reaction solution (pH 11) was obtained (molar ratio = 13.11). This reaction solution 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 produce WO3, and the WO3 concentration in the sulfur-removed tungsten-containing precipitate slurry was calculated from its weight.

[0156] The sulfur-removed tungsten-containing precipitate slurry diluted with pure water was then mixed with 2% by mass of methylamine and pure water so that the tungsten concentration in the final mixture was 10% by mass in terms of WO. The mixture was stirred and held at room temperature (25°C) for 1 hour to obtain the tungsten compound-containing liquid used in Example 13. The pH of the tungsten 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 × width × thickness: 20 mm × 20 mm × 1.0 mm), (ii) a 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% by mass aqueous sulfuric acid solution, and ion-exchanged water was added to obtain a molybdenum sulfate aqueous solution containing 100 g / L of molybdenum in terms of MoO3. 200 mL of this molybdenum sulfate aqueous solution was added to 1 L of ammonia water (NH3 concentration 25% by mass) over a period of less than 1 minute (NH3 / MoO3 molar ratio = 105.66, NH3 / SO4 2- A reaction solution (pH 11) was obtained (molar ratio=65.56). This reaction solution was a slurry of a molybdic acid compound hydrate, in other words, a slurry of a molybdenum-containing precipitate.

[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 had been removed was diluted with pure water to obtain a molybdenum-containing precipitate slurry from which the sulfur had been removed. A portion of the molybdenum-containing precipitate slurry from which the sulfur had been removed was dried at 110°C for 24 hours and then calcined at 1,000°C for 4 hours to produce MoO3, and the MoO3 concentration in the molybdenum-containing precipitate slurry from which the sulfur had been removed was calculated from the weight of the MoO3.

[0162] The molybdenum-containing precipitate slurry diluted with pure water and from which the sulfur content had been removed was mixed with 2% by mass of methylamine and pure water so that the final mixture had a molybdenum concentration of 10% by mass in terms of MoO, 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 The coated structure of 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 × width × thickness: 20 mm × 20 mm × 1.0 mm), (ii) a 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 coating 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) a 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 zirconium oxide 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 hafnic acid compound-containing liquid used in Example 19 was obtained in the same manner as the hafnic acid 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 liquid 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 × width × thickness: 20 mm × 20 mm × 1.0 mm), (ii) a 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 × width × thickness: 20 mm × 20 mm × 1.0 mm), (ii) the silicate 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] In a 100 mL beaker, 11.0 g of tetraethoxysilane (TEOS, manufactured by Tokyo Ohka Kogyo Co., Ltd.), a silicon-containing raw material, was added with 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 at room temperature (25°C) for 20 hours 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 to obtain the silicic acid compound-containing liquid used in Example 22.

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

[0181] Example 24 In Example 24, a coating 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 × width × thickness: 20 mm × 20 mm × 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 × width × thickness: 20 mm × 20 mm × 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 × width × thickness: 20 mm × 20 mm × 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.

[0186] Example 27 In Example 27, a coated structure according to Example 27 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 (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 × width × thickness dimensions: 20 mm × 20 mm × 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.

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

[0189] (Comparative Example 1) Comparative Example 1 is a carbon-based substrate, specifically a graphite extrusion 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) Comparative Example 2 is a metal substrate, specifically the metal 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) 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 melt 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) 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) 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, 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) 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 in a vertical mixer for 5 minutes to obtain a mixed powder.

[0203] This mixed powder was filled into a carbon container (2 kg / bottle), fed into a resistance-heated hydrogen furnace at a rate of two bottles every three hours, and fired at a temperature of 1,700°C for 14 hours to perform primary carbonization, thereby obtaining primary carbide.

[0204] This primary carbide was filled into a carbon crucible (100 kg / bottle), placed in a high-frequency induction heating vacuum furnace, and fired at 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 coarse pulverization, the coarsely pulverized secondary carbide was finely pulverized using a jet mill, an airflow pulverizer, with the feed rate set at 10 kg / hr and the air velocity set at 2.5 m / min.

[0207] The finely pulverized secondary carbide was then classified using a vibrating sieve, and the undersize particles (fine particle side) 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, 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, 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 diluted appropriately with dilute hydrochloric acid, and the mass fraction in terms of metal was measured using an ICP optical emission analyzer (Agilent Technologies: AG-5110) in accordance with JIS K0116:2014.

[0210] Dynamic Light Scattering 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 (manufactured by Otsuka Electronics Co., Ltd.: ELSZ-2000) 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 2 μm pore size filter and subjected to ultrasonic treatment at 28 kHz for 3 minutes in an ultrasonic cleaner (manufactured by AS ONE Corporation: VS-100III). The particle size (D50) refers to the median diameter (D50), which is the particle size that represents the 50% cumulative value of the cumulative 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 range 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 of Examples 1 to 29, the carbon-based substrate of Comparative Example 1, the metal-based substrates of Comparative Examples 2, 5 to 12, the tubular metal-based substrates of Comparative Examples 3 and 4, and the tantalum carbide powder of Reference Example 1 under the three test conditions shown below. The "remaining wall thickness" shown in Tables 4 to 6 was calculated by taking the weight before the corrosion resistance test as 100% and measuring the weight after the corrosion resistance test, i.e., the weight after the immersion time had elapsed, and using the formula "(weight after corrosion resistance test) ÷ (weight before corrosion resistance test) × 100." The "remaining wall thickness" shown in Figs. 1 to 25 was calculated by taking the weight before the corrosion resistance test as 100% and measuring the weight every hour of immersion time, and 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% by mass hydrochloric acid, heated using a hot stirrer so that the temperature of the hydrochloric acid reached 60°C, covered with a perforated plate, 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 were removed from the hydrochloric acid, washed with pure water, and then wiped off with the pure water used for washing. 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 weighed 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 container containing a certain amount of water, which had been a petri dish with a lid immersed in 15 mL of 35% by mass hydrochloric acid. A small amount of nitrogen was introduced into the glass container, and while the container was evacuated, the hydrochloric acid was heated for 1 hour using a hot stirrer, using the water in the glass container as a heat medium, until the temperature of the hydrochloric acid reached 60°C. After that, 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 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 with a lid was heated using water in the sealed glass container as a heat medium, thereby allowing the entire petri dish with a lid to be heated uniformly.

[0215] <Corrosion resistance test 3> The weights of the coated structure of Example 29 and the metal-based substrate of 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 is 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 and washed with pure water, and then the pure water used for washing was wiped off, and the weight after corrosion resistance test 3 (hereinafter referred to as weight after test 3) was measured.

[0218] Furthermore, in corrosion resistance test 3 using 35 mass % sodium hydroxide or 25 mass % ammonia water (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 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-mentioned Raman spectroscopy measurement conditions showed a peak 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, 1300cm -1 ~1400cm -1 The peak observed in the diamond structure (sp 3 The D band / G band peak area ratio calculated according to the Raman spectroscopy analysis conditions described above is derived from the sp 2 Structure and sp 3 The larger the D band / G band peak area ratio, the more sp structure there is in the carbon material. 3 This indicates a high proportion of the structure. 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 has been formed.

[0222] [Table 1]

[0223] [Table 2]

[0224] [Table 3]

[0225] [Table 4]

[0226] [Table 5]

[0227] [Table 6]

[0228] In the coating structures of 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 of 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] As shown in Fig. 26(a), the coated structure according to Example 2 had a durability of 154 minutes in the heat resistance test, which indicates 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 of Example 3 had a durability 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 of Example 4 had a durability 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 of Comparative Example 4 had a durability 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 by Raman spectroscopy, which indicated that a physically and chemically stable surface layer could be formed and a coating with a uniform composition could be formed, resulting in excellent corrosion resistance of the substrate. 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 by Raman spectroscopy, which indicated that a physically and chemically stable surface layer could be formed and a coating with a uniform composition could be formed, resulting in excellent corrosion resistance of the substrate.

[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. [Industrial Applicability]

[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 physically and chemically stable surface layer on a substrate, regardless of the substrate, and therefore can form a uniform metal composite coating on 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 metal compound-containing material on the substrate; a reaction step of heating the substrate under reduced pressure or vacuum while supplying a carbon source and / or a nitrogen source, thereby causing the metal element in the metal compound-containing material to undergo at least one of a carbonization reaction, a carbonitriding reaction, and a nitriding reaction, thereby forming a metal composite coating; and A method for producing a coated structure, wherein 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.

2. A method for producing a coated structure having a metal composite coating on a substrate, comprising: a step of applying or immersing a metal compound-containing material on the substrate; a reaction step of heating the substrate under reduced pressure or vacuum while supplying a carbon source and / or a nitrogen source, thereby causing the metal element in the metal compound-containing material to undergo at least one of a carbonization reaction, a carbonitriding reaction, and a nitriding reaction, thereby forming a metal composite coating; and The metal compound-containing material has a maximum light transmittance of 70%T or more in a wavelength region of 500 nm to 700 nm, and the metal composite coating is Ti, Nb, Mo, Hf, Ta, W, Zr, and Si. A method for producing a coated structure, characterized in that it contains a compound of at least one metal element selected from the group consisting of Si, Nb, Mo, Hf, Ta, W, Zr, and Si.

3. A method for producing a coated structure having a metal composite coating on a substrate, comprising: a step of applying or immersing a metal compound-containing material on the substrate; a reaction step of heating the substrate under reduced pressure or vacuum while supplying a carbon source and / or a nitrogen source, thereby causing the metal element in the metal compound-containing material to undergo at least one of a carbonization reaction, a carbonitriding reaction, and a nitriding reaction, thereby forming a metal composite coating; and A method for producing a coated structure, characterized in that the metal compound-containing material has particles in the metal compound-containing material with a particle diameter (D50) of 3000 nm or less as measured by a dynamic light scattering method, and the metal composite coating contains a compound of at least one metal element selected from Ti, Nb, Mo, Hf, Ta, W, Zr, and Si.

4. 4. The method for producing a coated structure according to claim 1, further comprising a drying step of drying the substrate coated with or immersed in the metal compound-containing material.

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

6. 4. The method for producing a coated structure according to claim 1, wherein the substrate contains at least one material selected from the group consisting of carbon, metal carbide, pure metal, alloy, metal oxide, and composite metal oxide.

7. 4. The method for producing a coated structure according to claim 1, wherein the metal composite coating contains a compound of at least one metal element selected from the group consisting of Nb, Hf, and Ta.

8. 4. The method for manufacturing a coated structure according to claim 1, wherein 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.

9. 2. The method for producing a coated structure according to claim 1, wherein the metal compound-containing material has a maximum light transmittance of 70%T or more in a wavelength region of 500 nm to 700 nm, and the particle diameter (D50) of the particles in the metal compound-containing material measured by a dynamic light scattering method is 3000 nm or less.

10. 4. The method for producing a coated structure according to claim 1, wherein 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.

11. 4. The method for producing a coated structure according to claim 1, wherein the reaction step is a carbonitriding reaction or a nitriding reaction, and the nitrogen source contains ammonia and an inert component.

12. 4. The method for producing a coated structure according to claim 1, wherein the reaction step is performed at a heating temperature of 500° C. or higher and 1150° C. or lower.

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

14. the metal composite coating is a metal-carbon composite coating, 4. The method for producing a coated structure according to claim 1, wherein the metal-carbon composite coating has a D band / G band peak area ratio in Raman spectroscopy of 0.5 or more and 2.0 or less.

15. the metal composite coating is a metal-carbon composite coating, 4. The method for producing a coated structure according to claim 1, wherein 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, and the standard deviation of the D band / G band peak area ratio is 0.1 or more and 0.35 or less.

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