Heat-resistant tubular member, method for manufacturing the same, high-temperature processing equipment, and heat-resistant substrate

Abstract

To provide various heat resisting tubular members, such as a thermocouple protective tube, that can have superior high-temperature corrosion resistance and mechanical characteristics when used in an environment in which heating and cooling are repeated in a high-temperature corrosive atmosphere, and a method of manufacturing the same.SOLUTION: A heat resisting tubular member is formed of a heat resisting base material consisting of a first alloy base material (20), a second alloy base material (40), and a porous intermediate layer (30) provided between them and containing at least Al, wherein the first alloy base material (20) has Al-containing alloy layers (21, 22) on both principal surfaces respectively, the second alloy base material (40) has Al-containing alloy layers (41, 42) at least on the principal surface on a side of the intermediate layer (30) between both principal surfaces, and the heat resisting base material has a tubular shape having the first alloy base material (20) on an outer side.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a heat-resistant tubular member, a method for manufacturing the same, high-temperature processing equipment, and a heat-resistant base material, and is suitably applied to, for example, thermocouple protection tubes, nozzles, incinerators, boilers, exhaust gas system members, turbines, combustion equipment and the like that are used in environments where heating and cooling are repeated in a high-temperature corrosive atmosphere.

Background Art

[0002] The high-temperature atmosphere to which heat-resistant members are exposed becomes a reducing and carburizing atmosphere due to oxidizing and corrosive components such as oxygen, nitrogen, water vapor, sulfur compounds and chlorine compounds, as well as unburned components. When a heat-resistant material is exposed to these corrosive and carburizing high-temperature atmospheres, high-temperature corrosion, internal corrosion, carburization and the like occur due to the corrosive components in the atmosphere, which may cause wall thinning of the material and reduce the material strength (see Non-Patent Document 1).

[0003] High-temperature oxidation and high-temperature corrosion can be prevented by coating the surface of the heat-resistant material with a protective film having excellent environmental barrier properties. Examples of the protective film include Al₂O₃, Cr₂O₃, SiO₂ and the like, and Al₂O₃ is typically used. A method is adopted in which Al contained in the base material diffuses to the surface layer in an oxidizing atmosphere and reacts with oxygen to form a protective Al₂O₃ film, or a method in which Al in an Al-containing alloy film formed by calorizing treatment, aluminum plating, molten aluminum immersion, CVD, thermal spraying, electron beam vapor deposition or the like is oxidized to form a protective Al₂O₃ film.

[0004] Because heat-resistant ceramic materials possess superior strength and high-temperature corrosion resistance compared to heat-resistant alloy materials, they are often used in thermocouple protection tubes, particularly in harsh, high-temperature environments. However, heat-resistant ceramic materials are brittle, and a problem arises when they catastrophically lose their mechanical properties due to cracking and breakage. Therefore, a double-tube structure of ceramics and alloys is sometimes employed (see Patent Document 1). As thermocouple protection tubes, there are also known types in which a double-walled metal tube is used, with molten aluminum plating applied in between to fuse the two layers of metal (see Patent Document 2).

[0005] When an Al-containing alloy film is formed on the surface of an Al-containing heat-resistant alloy substrate, when exposed to a high-temperature atmosphere, the Al in the substrate and the alloy film forms an Al2O3 film to protect the substrate. However, the Al concentration on the surface of the substrate decreases compared to the interior, forming a so-called Al-deficient layer. In the case of an Al-containing alloy film, along with the Al-deficient layer, a so-called interdiffusion layer is formed due to interdiffusion between the substrate and the film, resulting in a decrease in the Al concentration of the film.

[0006] The formation of the aforementioned Al-deficient layer and interdiffusion layer reduces the ability to form and maintain protective Al2O3. When thermal strain due to heating and cooling causes cracks in the Al2O3 film, and even delamination occurs, the ability to regenerate a new protective Al2O3 film is lost, leading to accelerated high-temperature oxidation of the substrate and a deterioration of its mechanical properties. In other words, improvement in the formation and maintenance of the Al2O3 film and its regeneration ability during delamination is required.

[0007] To ensure the ability to form, maintain, and regenerate a protective Al2O3 film, it is conceivable to increase the Al concentration in both the substrate and the Al-containing alloy film. However, increasing the Al concentration in the substrate weakens its mechanical properties, resulting in poor workability and weldability, thus limiting the Al concentration.

[0008] When Al in an Al-containing alloy coating diffuses into the substrate, it causes changes in the substrate's structure and a decrease in its strength. Furthermore, an increase in the Al concentration in the coating increases thermal stress due to the difference in thermal expansion coefficients between the substrate and the coating, inducing cracks in the coating and leading to accelerated oxidation and delamination. Therefore, there is a limit to the Al concentration in an Al-containing alloy coating.

[0009] To suppress the decrease in Al concentration in Al-containing alloy films, the present inventors have proposed a diffusion barrier coating composed of continuous or single-phase Re-Cr-Ni σ-phases. However, while this diffusion barrier coating exhibits excellent properties for Ni-based alloys, it has the problem of being difficult to adopt for Fe-based alloys due to its high cost. Details of the diffusion barrier coating are described in Patent Documents 3 to 9.

[0010] On the other hand, the high-temperature corrosion resistance of Fe, Cr, and Ni contained in heat-resistant alloys varies depending on the type of gas in the atmosphere. Cr and Fe have corrosion resistance to reactions with sulfur, while Ni has excellent corrosion resistance to chlorine gas corrosion. Therefore, in environments where the combustion gas atmosphere changes spatially and temporally, such as in thermocouple protection tubes, nozzles, boilers, incinerators, and turbines, it can be difficult to achieve both mechanical properties and high-temperature corrosion resistance in heat-resistant alloys. [Prior art documents] [Patent Documents]

[0011] [Patent Document 1] Japanese Utility Model Publication No. Showa 63-187018 [Patent Document 2] Japanese Patent Publication No. 2002-5749 [Patent Document 3] Patent No. 3857689 specification [Patent Document 4] Patent No. 3857690 specification [Patent Document 5] Patent No. 3910588 specification [Patent Document 6] Patent No. 4753720 specification [Patent Document 7] Patent No. 5905336 specification [Patent Document 8] Patent No. 5905354 specification [Patent Document 9] Patent No. 5905355 specification [Non-patent literature]

[0012] [Non-Patent Document 1] "Case Studies of High-Temperature Corrosion Caused by Boiler Combustion Gases and Countermeasures," supervised by Masaharu Nakamori, Techno System Co., Ltd. (published August 11, 2012) [Non-Patent Document 2] Koichi Maruyama (ed.), Eiji Nakajima (author), Materials Science of High-Temperature Strength, Uchida Rokakuho (published November 1, 2002) [Overview of the project] [Problems that the invention aims to solve]

[0013] The problem that this invention aims to solve is to provide various heat-resistant tubular members, such as thermocouple protection tubes, that can obtain excellent high-temperature corrosion resistance and mechanical properties when used in environments where heating and cooling are repeatedly performed in a high-temperature corrosive atmosphere, a method for manufacturing these heat-resistant tubular members, high-temperature processing equipment using these heat-resistant tubular members, and a heat-resistant substrate suitable for use with heat-resistant tubular members. [Means for solving the problem]

[0014] To solve the above problems, this invention provides: It is composed of a first alloy substrate, a second alloy substrate, and a heat-resistant substrate consisting of a porous intermediate layer containing at least Al, provided between the first and second alloy substrates. The first alloy substrate described above has an Al-containing alloy layer on each of its two main surfaces. The second alloy substrate described above has an Al-containing alloy layer on at least the main surface on the intermediate layer side of both main surfaces. The heat-resistant substrate described above is a heat-resistant tubular member having a tubular shape with the first alloy substrate described above on the outside.

[0015] The first and second alloy substrates serve as the outer and inner layer substrates, respectively. Typically, the Al concentration in the Al-containing alloy layer of the first alloy substrate decreases toward the interior of the first alloy substrate, and the Al concentration in the Al-containing alloy layer of the second alloy substrate decreases toward the interior of the second alloy substrate. The Al concentration in these Al-containing alloy layers is, for example, between 15 atomic% and 55 atomic% and typically between 20 atomic% and 50 atomic%, but is not limited to this. The Al-containing alloy layer on the outer surface of the first alloy substrate, which serves as the outer layer substrate, forms a protective Al2O3 film in a high-temperature corrosive atmosphere, thereby protecting both the first and second alloy substrates. Furthermore, the Al supplied from the Al-containing alloy layer on the main surface on the intermediate layer side of the first alloy substrate suppresses the decrease in Al concentration on the outer main surface, i.e., the outer surface side, of the first alloy substrate. Therefore, the formation of an Al-deficient layer is suppressed, and the formation, maintenance, and regeneration of the protective Al2O3 film becomes possible. The second alloy substrate may have an Al-containing alloy layer not only on the main surface on the intermediate layer side, but also on the main surface opposite the intermediate layer, i.e., the inner surface. By having an Al-containing alloy layer on the inner surface of the second alloy substrate in this way, when the heat-resistant tubular member is used at high temperatures, the oxygen inside the heat-resistant tubular member is consumed by the oxidation of this Al-containing alloy layer, thus keeping the oxygen concentration inside the heat-resistant tubular member low. For example, if the heat-resistant tubular member is a thermocouple protection tube sealed at one end, it is possible to reduce oxidative damage to the thermocouple wires (especially the K and N wires) inserted inside the thermocouple protection tube. In this case, it is not necessary to fill the inside of the thermocouple protection tube with oxide ceramics, which has been conventionally done to suppress the entry and exit of air inside the thermocouple protection tube.

[0016] The materials of the first alloy base material and the second alloy base material are not particularly limited, and are selected from, for example, Fe-based alloys, Ni-based alloys, Co-based alloys, refractory metals (alloys of W, Ta, Mo, Nb, etc.), etc. Among these, Fe-based alloys are preferred, and Fe-Cr-based alloys, Fe-Cr-Ni-based alloys and the like are more preferred. The porous intermediate layer containing at least Al typically contains one or more elements contained in the first alloy base material and the second alloy base material in addition to Al. The porosity of this intermediate layer is not particularly limited, but is typically 20% to 90%, more typically 40% to 70%. Since this intermediate layer is porous, even when the heat-resistant tubular member is placed in an environment where heating and cooling are repeated in a high-temperature corrosive atmosphere, the stress generated between the first alloy base material and the second alloy base material can be relaxed, and damage and fracture of the heat-resistant base material can be prevented. In addition, when the inside of the intermediate layer communicates with the air outside the heat-resistant tubular member, air flows in and out of the intermediate layer from the outside of the heat-resistant tubular member due to the so-called pumping action. For this reason, since air is contained in the pores (or voids) of the intermediate layer, when the heat-resistant tubular member is placed in a high-temperature corrosive atmosphere, Al contained in the intermediate layer is oxidized by oxygen in this air, and as a result, protective Al₂O₃ is formed inside these pores. In addition, due to the air contained in the intermediate layer, a protective Al₂O₃ film is also formed on the main surface of the first alloy base material on the intermediate layer side and the main surface of the second alloy base material on the intermediate layer side, and an Al₂O₃ film may also be formed on the main surface of the second alloy base material opposite to the intermediate layer. The protective Al₂O₃ films respectively formed on the main surface of the first alloy base material on the intermediate layer side, the main surface of the second alloy base material on the intermediate layer side, and the main surface of the second alloy base material opposite to the intermediate layer have a low oxygen concentration because oxygen in the intermediate layer is consumed as oxidation progresses, so they are thinner than the protective Al₂O₃ film formed on the outer main surface (outer surface) of the first alloy base material that is directly exposed to the high-temperature corrosive atmosphere. These protective Al₂O₃ films, together with the protective Al₂O₃ film formed on the outer main surface of the first alloy base material, contribute to the protection of the first alloy base material and the second alloy base material.

[0017] The heat-resistant tubular member may be open at both ends, or open at one end and closed at the other end, and is selected as necessary. The cross-sectional shape of the heat-resistant tubular member is not particularly limited, and may be, for example, any of a circular tubular shape, an elliptical tubular shape, a rectangular tubular shape, and a modified shape thereof. Further, the heat-resistant tubular member may have the same cross-sectional shape in the central axis direction, or may have different cross-sectional shapes in the central axis direction, and is selected as necessary. That is, the heat-resistant tubular member may be a straight tubular shape or a stepped tubular shape. The heat-resistant tubular member may basically be of any type, and examples thereof include thermocouple protection tubes, nozzles, incinerators, boilers, exhaust gas system members, and the like.

[0018] Further, the present invention relates to a heat-resistant base material composed of a ceramic base material, an alloy base material, and a porous intermediate layer containing at least Al provided between the ceramic base material and the alloy base material, the alloy base material has an Al-containing alloy layer on at least the main surface on the intermediate layer side among both main surfaces thereof, the heat-resistant base material is a heat-resistant tubular member having a tubular shape in which the ceramic base material is on the outer side.

[0019] The ceramic base material is made of, for example, oxide ceramics, nitride ceramics, carbide ceramics, or the like. Preferred examples of the oxide ceramics include alumina (Al2O3) based ceramics and zirconia (ZrO2) based ceramics, preferred examples of the nitride ceramics include silicon nitride (Si3N4) based ceramics, and preferred examples of the carbide ceramics include silicon carbide (SiC) based ceramics. The thickness of the ceramic base material is selected according to the application, function, etc. of the heat-resistant tubular member, and is generally 0.05 mm or more and 5 mm or less. The alloy base material is the same as the first alloy base material and the second alloy base material in the earlier described invention. The Al-containing alloy layer is also the same as in the earlier described invention. The intermediate layer is basically the same as in the earlier described invention, but from the viewpoint of improving the resistance to peeling or the like at the joint between the intermediate layer and the ceramic base material, it is preferable that the intermediate layer contains Ti in addition to Al.

[0020] Furthermore, this invention, It is composed of an alloy substrate, a ceramic substrate, and a heat-resistant substrate consisting of a porous intermediate layer containing at least Al, provided between the alloy substrate and the ceramic substrate. The above alloy substrate has an Al-containing alloy layer on each of its two main surfaces. The above heat-resistant substrate is a heat-resistant tubular member having a tubular shape with the alloy substrate on the outside.

[0021] The alloy substrate, ceramic substrate, intermediate layer, and Al-containing alloy layer are the same as those described above for the invention using a ceramic substrate.

[0022] Furthermore, this invention, This is a heat-resistant tubular member composed of a heat-resistant substrate having a tubular shape, made of an alloy substrate having an Al-containing alloy layer on each of its two main surfaces.

[0023] The alloy substrate and the Al-containing alloy layer are the same as those described in the previous invention.

[0024] Furthermore, this invention, A step of inserting a second alloy substrate, which has a tubular shape, into a first alloy substrate, which has a tubular shape, with a gap between them, A step of inserting a slurry containing at least Al powder into the gap between the first alloy substrate and the second alloy substrate, The process involves inserting the slurry into the gap between the first alloy substrate and the second alloy substrate, then subjecting the first and second alloy substrates to an Al diffusion treatment to form a porous intermediate layer containing at least Al between the first and second alloy substrates, forming an Al-containing alloy layer on both main surfaces of the first alloy substrate, and forming an Al-containing alloy layer on at least the main surface of the second alloy substrate that is on the side with the intermediate layer. This is a method for manufacturing a heat-resistant tubular member having [a specific characteristic].

[0025] Furthermore, this invention, A process of inserting a tubular alloy substrate into a tubular ceramic substrate with a gap between them, A step of inserting a slurry containing at least Al powder into the gap between the ceramic substrate and the alloy substrate, The process involves inserting the slurry into the gap between the ceramic substrate and the alloy substrate, then subjecting the ceramic substrate and the alloy substrate to an Al diffusion treatment to form a porous intermediate layer containing at least Al between the ceramic substrate and the alloy substrate, and forming an Al-containing alloy layer on at least the main surface of the alloy substrate that is on the side with the intermediate layer. This is a method for manufacturing a heat-resistant tubular member having [a specific characteristic].

[0026] Furthermore, this invention, A process of inserting a tubular ceramic substrate into a tubular alloy substrate with a gap between them, A step of inserting a slurry containing at least Al powder into the gap between the alloy substrate and the ceramic substrate, The process involves inserting the slurry into the gap between the alloy substrate and the ceramic substrate, then subjecting the alloy substrate and the ceramic substrate to an Al diffusion treatment to form a porous intermediate layer containing at least Al between the alloy substrate and the ceramic substrate, and forming an Al-containing alloy layer on both main surfaces of the alloy substrate. This is a method for manufacturing a heat-resistant tubular member having [a specific characteristic].

[0027] In the above invention of a method for manufacturing a heat-resistant tubular member, the Al diffusion treatment may be an Al pack treatment using an Al packing agent, or it may simply be heating in an inert gas atmosphere. In these inventions of a method for manufacturing a heat-resistant tubular member, the provisions described above in relation to the invention of the heat-resistant tubular member are valid, as long as they do not contradict the properties of the member.

[0028] Furthermore, this invention, This is a method for manufacturing a heat-resistant tubular member, comprising the step of forming an Al-containing alloy layer on both main surfaces of an alloy substrate having a tubular shape.

[0029] In this invention of a method for manufacturing a heat-resistant tubular member, the formation of the Al-containing alloy layer can be carried out using Al diffusion treatment such as Al pack treatment, plating, thermal spraying, electron beam deposition, etc. In this invention of a method for manufacturing a heat-resistant tubular member, the provisions described above in relation to the invention of the heat-resistant tubular member are valid, as long as they do not contradict its properties.

[0030] Furthermore, this invention, It is composed of a first alloy substrate, a second alloy substrate, and a heat-resistant substrate consisting of a porous intermediate layer containing at least Al, provided between the first and second alloy substrates. The first alloy substrate described above has an Al-containing alloy layer on each of its two main surfaces. The second alloy substrate described above has an Al-containing alloy layer on at least the main surface on the intermediate layer side of both main surfaces. The above heat-resistant substrate is a heat-resistant tubular member having a tubular shape with the first alloy substrate on the outside. It is a high-temperature processing device that has [a certain feature].

[0031] Furthermore, this invention, It is composed of a ceramic substrate, an alloy substrate, and a heat-resistant substrate consisting of a porous intermediate layer containing at least Al, provided between the ceramic substrate and the alloy substrate. The above alloy substrate has an Al-containing alloy layer on at least the main surface on the intermediate layer side of both main surfaces. The above heat-resistant substrate is a heat-resistant tubular member having a tubular shape with the above ceramic substrate on the outside. It is a high-temperature processing device that has [a certain feature].

[0032] Furthermore, this invention, It is composed of an alloy substrate, a ceramic substrate, and a heat-resistant substrate consisting of a porous intermediate layer containing at least Al, provided between the alloy substrate and the ceramic substrate. The above alloy substrate has an Al-containing alloy layer on each of its two main surfaces. The above heat-resistant substrate is a heat-resistant tubular member having a tubular shape with the alloy substrate on the outside. It is a high-temperature processing device that has [a certain feature].

[0033] Furthermore, this invention, A heat-resistant tubular member is composed of a heat-resistant substrate having a tubular shape, made of an alloy substrate having an Al-containing alloy layer on each of its two main surfaces. It is a high-temperature processing device that has [a certain feature].

[0034] High-temperature processing equipment is not particularly limited as long as it processes objects at high temperatures in some way. Here, processing is interpreted in its broadest sense and includes everything from treating exhaust gases, burning fuels or materials to be processed, to measuring the temperature inside incinerators or heat treatment furnaces or the temperature of molten metals. Equipment also includes everything from machines, instruments, and fixtures. Specifically, high-temperature processing equipment includes, but is not limited to, thermocouples housed in protective tubes, incinerators, boilers, exhaust gas system components, turbines, and combustion equipment.

[0035] Furthermore, this invention, It consists of a first alloy substrate, a second alloy substrate, and a porous intermediate layer containing at least Al, provided between the first and second alloy substrates. The first alloy substrate described above has an Al-containing alloy layer on each of its two main surfaces. The second alloy substrate described above is a heat-resistant substrate having an Al-containing alloy layer on at least the main surface on the intermediate layer side of both main surfaces.

[0036] Furthermore, this invention, It consists of a ceramic substrate, an alloy substrate, and a porous intermediate layer containing at least Al, provided between the ceramic substrate and the alloy substrate. The above alloy substrate is a heat-resistant substrate having an Al-containing alloy layer on at least the main surface on the intermediate layer side of both main surfaces.

[0037] Furthermore, this invention, It consists of an alloy substrate, a ceramic substrate, and a porous intermediate layer containing at least Al, provided between the alloy substrate and the ceramic substrate. The above alloy substrate is a heat-resistant substrate having an Al-containing alloy layer on each of its two main surfaces.

[0038] Furthermore, this invention, This heat-resistant substrate is made of an alloy substrate having an Al-containing alloy layer on each of its two main surfaces.

[0039] In these inventions of heat-resistant substrates, the explanations given in relation to the invention of the heat-resistant tubular member described above are valid, as long as they do not contradict their properties. [Effects of the Invention]

[0040] According to this invention, in a heat-resistant tubular member using a heat-resistant substrate consisting of a first alloy substrate, an intermediate layer and a second alloy substrate, or a heat-resistant substrate consisting of a ceramic substrate, an intermediate layer and an alloy substrate, or a heat-resistant substrate consisting of an alloy substrate, an intermediate layer and a ceramic substrate, excellent high-temperature corrosion resistance can be obtained due to the protective Al2O3 film formed by the Al-containing alloy layer or the excellent corrosion resistance and heat resistance of the ceramics, excellent mechanical properties can be obtained due to the second alloy substrate, alloy substrate and ceramic substrate which constitute the outer layer substrate, and stress generated between the outer layer substrate and the inner layer substrate can be relieved by the porous intermediate layer, thereby preventing damage or fracture of the heat-resistant substrate even when used in an environment where heating and cooling are repeatedly performed in a high-temperature corrosive atmosphere. Furthermore, in a heat-resistant tubular member using a heat-resistant substrate consisting of an alloy substrate having an Al-containing alloy layer on each of its main surfaces, excellent high-temperature corrosion resistance can be continuously obtained even when used in an environment where heating and cooling are repeatedly performed in a high-temperature corrosive atmosphere due to the protective Al2O3 film formed by the Al-containing alloy layer. By using such excellent heat-resistant tubular members, various high-performance high-temperature processing equipment can be realized. [Brief explanation of the drawing]

[0041] [Figure 1] This is a cross-sectional view showing a heat-resistant tubular member according to the first embodiment of the present invention. [Figure 2] This is a cross-sectional view showing the state of a heat-resistant tubular member according to the first embodiment of this invention after being heated to a high temperature for a short period of time. [Figure 3] This is a cross-sectional view showing the state of a heat-resistant tubular member according to the first embodiment of this invention after being heated to a high temperature for a long period of time. [Figure 4] This is a cross-sectional view showing a heat-resistant tubular member according to a second embodiment of the present invention. [Figure 5] This is a cross-sectional view showing the state of a heat-resistant tubular member according to a second embodiment of the present invention after being heated to a high temperature for a short period of time. [Figure 6] This is a cross-sectional view showing the state of a heat-resistant tubular member according to a second embodiment of this invention after being heated to a high temperature for a long period of time. [Figure 7] This is a cross-sectional view showing a heat-resistant tubular member according to a third embodiment of the present invention. [Figure 8] This is a cross-sectional view showing the state of a heat-resistant tubular member according to the third embodiment of this invention after being heated to a high temperature for a short period of time. [Figure 9] This is a cross-sectional view showing the state of a heat-resistant tubular member according to the third embodiment of this invention after being heated to a high temperature for a long period of time. [Figure 10] This is a cross-sectional view showing a heat-resistant tubular member according to a fourth embodiment of the present invention. [Figure 11] This is a cross-sectional view showing the state of a heat-resistant tubular member according to the fourth embodiment of this invention after being heated to a high temperature for a short period of time. [Figure 12] This is a cross-sectional view showing the state of a heat-resistant tubular member according to the fourth embodiment of this invention after being heated to a high temperature for a long period of time. [Figure 13] This is a cross-sectional view showing a heat-resistant tubular member according to a fifth embodiment of the present invention. [Figure 14] This is a cross-sectional view showing the state of a heat-resistant tubular member according to the fifth embodiment of this invention after being heated to a high temperature for a short period of time. [Figure 15]This is a cross-sectional view showing the state of a heat-resistant tubular member according to the fifth embodiment of this invention after being heated to a high temperature for a long period of time. [Figure 16] This is a cross-sectional view showing a heat-resistant tubular member according to the sixth embodiment of the present invention. [Figure 17] This is a cross-sectional view showing the state of a heat-resistant tubular member according to the sixth embodiment of this invention after being heated to a high temperature for a short period of time. [Figure 18] This is a cross-sectional view showing the state of a heat-resistant tubular member according to the sixth embodiment of this invention after being heated to a high temperature for a long period of time. [Figure 19] This is a cross-sectional view showing a heat-resistant tubular member according to the seventh embodiment of the present invention. [Figure 20] This is a cross-sectional view showing a heat-resistant tubular member according to the eighth embodiment of the present invention. [Figure 21A] This is a cross-sectional view showing an example of use in which a lance is inserted into a heat-resistant tubular member according to the eighth embodiment of this invention. [Figure 21B] This is a cross-sectional view showing an example of use in which a thermocouple protection tube is inserted into a heat-resistant tubular member according to the eighth embodiment of this invention. [Figure 22] This is a cross-sectional view showing a heat-resistant tubular member according to the ninth embodiment of the present invention. [Figure 23] This is a cross-sectional view showing a heat-resistant tubular member according to the tenth embodiment of the present invention. [Figure 24A] This is a photograph serving as a substitute for a drawing, showing the cross-sectional structure of the inner layer substrate and intermediate layer of the sample from Example 1. [Figure 24B] Figure 24A is a schematic diagram showing the measured concentration distribution of each element in the cross-section. [Figure 25A] This is a photograph serving as a substitute for a drawing, showing the cross-sectional structure of the outer layer substrate and intermediate layer of the sample from Example 1. [Figure 25B] Figure 25A is a schematic diagram showing the measurement results of the concentration distribution of each element in the cross-section. [Figure 26A] This is a photograph serving as a substitute for a drawing, showing the cross-sectional structure of the inner layer substrate and intermediate layer after the cyclic oxidation test of the sample from Example 1. [Figure 26B]Figure 26A is a schematic diagram showing the measured concentration distribution of each element in the cross-section. [Figure 27A] This is a photograph serving as a substitute for a drawing, showing the cross-sectional structure of the outer layer substrate and intermediate layer after the cyclic oxidation test of the sample from Example 1. [Figure 27B] Figure 27A is a schematic diagram showing the measurement results of the concentration distribution of each element in the cross-section. [Figure 28A] This is a photograph serving as a substitute for a drawing, showing the cross-sectional structure of the inner layer substrate and intermediate layer of the sample from Example 2. [Figure 28B] Figure 28A is a schematic diagram showing the measured concentration distribution of each element in the cross-section. [Figure 29A] This is a photograph serving as a substitute for a drawing, showing the cross-sectional structure of the inner layer substrate, intermediate layer, and outer layer substrate of the sample from Example 2. [Figure 29B] Figure 29A is a schematic diagram showing the measured concentration distribution of each element in the cross-section. [Figure 30A] This is a photograph serving as a substitute for a drawing, showing the cross-sectional structure of the outer layer substrate and intermediate layer of the sample from Example 2. [Figure 30B] Figure 30A is a schematic diagram showing the measurement results of the concentration distribution of each element in the cross-section shown. [Figure 31A] This is a photograph serving as a substitute for a drawing, showing the cross-sectional structure of the inner layer substrate, intermediate layer, and outer layer substrate after the cyclic oxidation test of the sample from Example 2. [Figure 31B] Figure 31A is a schematic diagram showing the measurement results of the concentration distribution of each element in the cross-section. [Figure 32A] This is a photograph serving as a substitute for a drawing, showing the cross-sectional structure of the inner layer substrate, intermediate layer, and outer layer substrate of the sample from Example 3. [Figure 32B] Figure 32A is a schematic diagram showing the measured concentration distribution of each element in the cross-section. [Figure 33A] This is a photograph serving as a substitute for a drawing, showing the cross-sectional structure of the inner layer substrate, intermediate layer, and outer layer substrate after the cyclic oxidation test of the sample from Example 3. [Figure 33B] Figure 33A is a schematic diagram showing the measured concentration distribution of each element in the cross-section. [Figure 34A]This is a photograph serving as a substitute for a drawing, showing the cross-sectional structure of the inner layer substrate and intermediate layer of the sample from Example 4. [Figure 34B] Figure 34A is a schematic diagram showing the measurement results of the concentration distribution of each element in the cross-section. [Figure 35A] This is a photograph serving as a substitute for a drawing, showing the cross-sectional structure of the inner layer substrate, intermediate layer, and outer layer substrate of the sample from Example 4. [Figure 35B] Figure 35A is a schematic diagram showing the measured concentration distribution of each element in the cross-section. [Figure 36A] This is a photograph serving as a substitute for a drawing, showing the cross-sectional structure of the outer layer substrate and intermediate layer of the sample from Example 4. [Figure 36B] Figure 36A is a schematic diagram showing the measured concentration distribution of each element in the cross-section. [Figure 37A] This is a photograph used as a substitute for a drawing, showing the cross-sectional structure of the sample from Example 5. [Figure 37B] Figure 37A is a schematic diagram showing the measured concentration distribution of each element in the cross-section. [Figure 38A] This is a photograph serving as a substitute for a drawing, showing the cross-sectional structure of the sample from Example 5 after the cyclic oxidation test. [Figure 38B] Figure 38A is a schematic diagram showing the measurement results of the concentration distribution of each element in the cross-section shown. [Figure 39A] This is a photograph used as a substitute for a drawing, showing the cross-sectional structure of the sample from Example 6. [Figure 39B] Figure 39A is a schematic diagram showing the measurement results of the concentration distribution of each element in the cross-section shown. [Figure 40A] This is a photograph serving as a substitute for a drawing, showing the cross-sectional structure of the sample from Example 6 after the cyclic oxidation test. [Figure 40B] Figure 40A is a schematic diagram showing the measurement results of the concentration distribution of each element in the cross-section. [Figure 41A] This is a photograph used as a substitute for a drawing, showing the cross-sectional structure of the sample from Example 7. [Figure 41B] Figure 41A is a schematic diagram showing the measurement results of the concentration distribution of each element in the cross-section. [Figure 42A] This is a photograph serving as a substitute for a drawing, showing the cross-sectional structure of the sample from Example 7 after the cyclic oxidation test. [Figure 42B] Figure 42A is a schematic diagram showing the measured concentration distribution of each element in the cross-section. [Figure 43A] This is a photograph used as a substitute for a drawing, showing a magnified portion of the cross-section shown in Figure 42A. [Figure 43B] Figure 42A is a schematic diagram showing the measured concentration distribution of each element in the cross-section. [Figure 44A] This is a photograph used as a substitute for a drawing, showing the cross-sectional structure of the sample from Example 8. [Figure 44B] Figure 44A is a schematic diagram showing the measured concentration distribution of each element in the cross-section. [Modes for carrying out the invention]

[0042] The following describes embodiments for carrying out the invention (hereinafter simply referred to as "embodiments").

[0043] <First Embodiment> [Heat-resistant tubular member] Figure 1 shows a heat-resistant tubular member according to the first embodiment, particularly a portion of the tube wall. As shown in Figure 1, this heat-resistant tubular member is composed of a heat-resistant substrate having a tubular shape with Al-containing alloy layers 11 and 12 on both main surfaces of the alloy substrate 10. The alloy substrate 10 can be selected as needed from, for example, those already mentioned. Figure 1 schematically shows an example of the Al concentration distribution of the Al-containing alloy layers 11 and 12 with a dashed line. As shown in Figure 1, the Al concentration of the Al-containing alloy layers 11 and 12 decreases monotonically toward the interior of the alloy substrate 10 (in the thickness direction). The Al concentration of the Al-containing alloy layers 11 and 12 is typically 15 atomic% to 55 atomic%, and more typically 20 atomic% to 50 atomic%. The thickness of the Al-containing alloy layers 11 and 12 can be selected as needed, but for example, it is 200 μm to 400 μm. The thickness of the alloy substrate 10 can be appropriately selected depending on the application and function of the heat-resistant tubular member.

[0044] [Method for manufacturing heat-resistant tubular members] This heat-resistant tubular member can be manufactured as follows. First, an alloy substrate 10 having a desired tubular shape is prepared. Next, Al-containing alloy layers 11 and 12 are formed on both main surfaces of the alloy substrate 10, i.e., the outer and inner surfaces of the heat-resistant tubular member, by performing an Al diffusion treatment such as Al packing, plating, thermal spraying, or electron beam deposition. In this way, the heat-resistant tubular member shown in Figure 1 can be manufactured.

[0045] [High-temperature corrosion behavior of heat-resistant tubular members] Figure 2 shows the state of the heat-resistant tubular member shown in Figure 1 after being heated at a high temperature for a short time in the atmosphere. As shown in Figure 2, when heated to a high temperature, the Al-containing alloy layers 11 and 12 on both main surfaces of the alloy substrate 10 diffuse into the interior of the alloy substrate 10, resulting in a decrease in surface concentration and an expansion of the Al concentration distribution inward. The bases of the Al concentration distribution of Al-containing alloy layer 11 and Al-containing alloy layer 12 overlap. Initially, an Al-deficient layer is formed on both main surfaces of the alloy substrate 10. An Al2O3 film 13, which is a protective oxide, is formed on the Al-containing alloy layers 11 and 12 on both main surfaces of the alloy substrate 10 by oxidation of Al. The alloy substrate 10 is protected by this Al2O3 film 13.

[0046] Figure 3 shows the state of the heat-resistant tubular member shown in Figure 1 after being heated at a high temperature for a long period of time in the atmosphere. As shown in Figure 3, the Al-containing alloy layers 11 and 12 on both main surfaces of the alloy substrate 10 undergo deep diffusion of Al into the interior of the alloy substrate 10 due to prolonged high-temperature heating. As a result, the surface concentration decreases significantly, and the Al concentration distribution spreads further inside the alloy substrate 10. The Al concentration distribution of Al-containing alloy layer 11 and Al-containing alloy layer 12 become integrated, resulting in a nearly uniform Al concentration distribution. The Al-deficient layer formed on both main surfaces of the alloy substrate 10 in the initial stages of heating disappears. In addition, the Al2O3 film 13 formed on the Al-containing alloy layers 11 and 12 of the alloy substrate 10 becomes thicker. Not only is the alloy substrate 10 protected by this Al2O3 film 13, but because the Al concentration distribution in the alloy substrate 10 is uniform, Al is continuously supplied from inside the alloy substrate 10, suppressing the formation of an Al-deficient layer, and the Al2O3 film 13 is continuously formed on both main surfaces of the alloy substrate 10.

[0047] As described above, according to this first embodiment, the heat-resistant tubular member is constructed from a heat-resistant substrate having a tubular shape with Al-containing alloy layers 11 and 12 on both main surfaces of the alloy substrate 10. This makes it possible to realize a heat-resistant tubular member that can continuously obtain excellent high-temperature corrosion resistance and mechanical properties even when used in an environment where heating and cooling are repeatedly performed in a high-temperature corrosive atmosphere.

[0048] <Second Embodiment> [Heat-resistant tubular base material] Figure 4 shows a heat-resistant tubular substrate according to a second embodiment, particularly a part of the tube wall. As shown in Figure 4, this heat-resistant tubular member is composed of a heat-resistant substrate having a tubular shape, consisting of an outer layer substrate 20, an intermediate layer 30, and an inner layer substrate 40. The outer layer substrate 20 and the inner layer substrate 40 are each made of an alloy substrate. The alloy substrate can be selected as needed from, for example, those already listed. The alloy substrates constituting the outer layer substrate 20 and the alloy substrates constituting the inner layer substrate 40 may be the same or different from each other, and can be selected as needed. Al-containing alloy layers 21 and 22 are provided on the main surface of the outer layer substrate 20 opposite to the intermediate layer 30 and on the main surface on the intermediate layer 30 side, respectively. Al-containing alloy layers 41 and 42 are provided on the main surface of the inner layer substrate 40 on the intermediate layer 30 side and on the main surface opposite to the intermediate layer 30, respectively. Figure 4 shows an example of the Al concentration distribution of the Al-containing alloy layers 21, 22, 41, and 42. As shown in Figure 4, the Al concentration in the Al-containing alloy layers 21 and 22 decreases monotonically toward the interior of the outer substrate 20, and similarly, the Al concentration in the Al-containing alloy layers 41 and 42 decreases monotonically toward the interior of the inner substrate 40. The Al concentration and thickness of the Al-containing alloy layers 21, 22, 41, and 42 are the same as those of the Al-containing alloy layers 11 and 12 in the first embodiment. The intermediate layer 30 is porous and contains a number of randomly distributed pores (voids) 31. The intermediate layer 30 contains at least Al and typically further contains one or more elements contained in the alloy substrates constituting the outer substrate 20 and the alloy substrates constituting the inner substrate 40. The thicknesses of the outer substrate 20 and the inner substrate 40 are appropriately selected depending on the application and function of the heat-resistant tubular member.

[0049] [Method for manufacturing heat-resistant tubular members] This heat-resistant tubular member can be manufactured as follows. First, an outer layer substrate 20 and an inner layer substrate 40 made of an alloy substrate having a desired tubular shape are prepared. Next, the outer layer substrate 20 and the inner layer substrate 40 are held with a gap between them, and a powder containing at least Al is applied to this gap by a slurry method or by inserting a ceramic fiber with powder supported in its voids. Next, by performing an Al diffusion treatment such as Al packing, Al-containing alloy layers 21 and 22 are formed on both main surfaces of the outer layer substrate 20, and Al-containing alloy layers 41 and 42 are formed on both main surfaces of the inner layer substrate 40, and an intermediate layer 30 is formed in the gap between the outer layer substrate 20 and the inner layer substrate 40. In this way, a heat-resistant tubular member can be manufactured. The Al packing process is carried out, for example, by burying the outer layer substrate 20 and the inner layer substrate 40 in a mixed powder of Al-containing alloy powder, ammonium chloride (NH4Cl) powder, and alumina (Al2O3) powder, and heating them in an inert gas atmosphere at a temperature of 700°C to 1100°C for 10 minutes to 20 hours. Examples of Al-containing alloy powders that can be used include FeAl, Fe+FeAl, NiAl, and Ni+NiAl.

[0050] [High-temperature corrosion behavior of heat-resistant tubular members] Figure 5 shows the state of the heat-resistant tubular member shown in Figure 4 after being heated at a high temperature for a short time in the atmosphere. As shown in Figure 5, when heated at a high temperature, the Al-containing alloy layers 21 and 22 on both main surfaces of the outer layer substrate 20 diffuse into the interior of the outer layer substrate 20, resulting in a decrease in surface concentration and a widening of the Al concentration distribution deep inside. The bases of the Al concentration distribution of Al-containing alloy layer 21 and Al-containing alloy layer 22 overlap. Initially, an Al-deficient layer is formed on the outer main surface of the outer layer substrate 20. An Al2O3 film 23 is formed on the Al-containing alloy layer 21 on the outer main surface of the outer layer substrate 20, and a similarly thin Al2O3 film 23 is formed on the Al-containing alloy layer 22 on the main surface of the intermediate layer 30. As a result of high-temperature heating, the Al-containing alloy layers 41 and 42 on both main surfaces of the inner layer substrate 40 diffuse deeply into the interior of the alloy substrate 10, causing the surface concentration to decrease and the Al concentration distribution to spread deeper into the interior. The bases of the Al concentration distribution of Al-containing alloy layer 41 and Al-containing alloy layer 42 overlap. Similarly, a thin Al2O3 film 43 is formed on the Al-containing alloy layers 41 and 42 of the inner layer substrate 40. Al2O332 is formed in the pores 31 of the intermediate layer 30.

[0051] Figure 6 shows the state of the heat-resistant tubular member shown in Figure 4 after being heated at a high temperature for a long period of time in the atmosphere. As shown in Figure 6, the Al-containing alloy layers 21 and 22 on both main surfaces of the outer layer substrate 20 undergo deep diffusion of Al into the interior of the outer layer substrate 20 due to prolonged high-temperature heating. As a result, the surface concentration decreases significantly, and the Al concentration distribution spreads further into the interior. The Al concentration distribution of the Al-containing alloy layer 21 and the Al-containing alloy layer 22 become one, resulting in a nearly uniform Al concentration distribution. The Al-deficient layer formed on the outer main surface of the outer layer substrate 20 in the initial stages of heating disappears. The Al2O3 film 23 formed on the surface of the Al-containing alloy layer 21 on the outer main surface of the outer layer substrate 20 becomes thicker. Not only is the outer layer substrate 20 protected by this Al2O3 film 23, but because the Al concentration distribution in the outer layer substrate 20 is uniform, Al is continuously supplied from the interior of the outer layer substrate 20, and the Al2O3 film 23 is continuously formed on both main surfaces of the outer layer substrate 20. Similarly, in the Al-containing alloy layers 41 and 42 on both main surfaces of the inner layer substrate 40, prolonged high-temperature heating causes Al to diffuse deeply into the interior of the inner layer substrate 40. As a result, the surface concentration decreases significantly, and the Al concentration distribution spreads further into the interior of the inner layer substrate 40. The Al concentration distribution of the Al-containing alloy layer 41 and the Al concentration distribution of the Al-containing alloy layer 42 become integrated, resulting in a nearly uniform Al concentration distribution. Not only is the inner layer substrate 40 protected by the Al2O3 film 43 formed on the Al-containing alloy layers 41 and 42 of the inner layer substrate 40, but because the Al concentration distribution in the inner layer substrate 40 is uniform, Al is continuously supplied from inside the inner layer substrate 40, and the Al2O3 film 43 is continuously formed on both main surfaces of the inner layer substrate 40.

[0052] According to this second embodiment, a heat-resistant tubular member is constructed from a heat-resistant substrate having a tubular shape, comprising an outer layer substrate 20 made of an alloy substrate having Al-containing alloy layers 21 and 22 on both main surfaces, a porous intermediate layer 30 containing at least Al, and an inner layer substrate 40 made of an alloy substrate having Al-containing alloy layers 41 and 42 on both main surfaces. This makes it possible to realize a heat-resistant tubular member that can continuously obtain excellent high-temperature corrosion resistance and mechanical properties even when used in an environment where heating and cooling are repeatedly performed in a high-temperature corrosive atmosphere.

[0053] <Third Embodiment> [Heat-resistant tubular member] Figure 7 shows a heat-resistant tubular member according to the third embodiment. As shown in Figure 7, this heat-resistant tubular member differs from the second embodiment in that the Al-containing alloy layer 41 is provided only on the main surface of the inner layer base material 40 on the side of the intermediate layer 30, and the Al-containing alloy layer 42 is not provided on the main surface on the side opposite to the intermediate layer 30. Otherwise, it is the same as the second embodiment.

[0054] [Method for manufacturing heat-resistant tubular members] This heat-resistant tubular member can be manufactured as follows. First, an outer layer substrate 20 and an inner layer substrate 40 made of an alloy substrate having a desired tubular shape are prepared. Next, the outer layer substrate 20 and the inner layer substrate 40 are held with a gap between them, and a powder containing at least Al is applied to this gap by a slurry method or by inserting a ceramic fiber with powder supported in its voids. Next, by performing an Al diffusion treatment such as Al packing, Al-containing alloy layers 21 and 22 are formed on both main surfaces of the outer layer substrate 20, and an Al-containing alloy layer 41 is formed on one main surface of the inner layer substrate 40, while an intermediate layer 30 is formed in the gap between the outer layer substrate 20 and the inner layer substrate 40. In this way, a heat-resistant tubular member can be manufactured.

[0055] [High-temperature corrosion behavior of heat-resistant tubular members] The high-temperature corrosion behavior of this heat-resistant tubular member is basically the same as that of the heat-resistant tubular member according to the second embodiment.

[0056] Specifically, Figure 8 shows the state of the heat-resistant tubular member shown in Figure 7 after being heated at a high temperature for a short time in the atmosphere. As shown in Figure 8, the Al concentration distribution of the Al-containing alloy layers 21 and 22 on both main surfaces of the outer layer substrate 20 overlaps at the base due to high-temperature heating. The Al concentration distribution of the Al-containing alloy layer 41 on the main surface of the inner layer substrate 40 on the intermediate layer 30 side spreads deep inside. An Al2O3 film 23 is formed on the Al-containing alloy layers 21 and 22 of the outer layer substrate 20, and similarly, an Al2O3 film 43 is formed on the Al-containing alloy layer 41 of the inner layer substrate 40. Al2O332 is formed in the pores 31 of the intermediate layer 30.

[0057] Figure 9 shows the state of the heat-resistant tubular member shown in Figure 7 after being heated at a high temperature for a long period of time in the atmosphere. As shown in Figure 9, the Al concentration distribution of the Al-containing alloy layers 21, 22 on both main surfaces of the outer layer substrate 20 becomes a nearly uniform Al concentration distribution due to high-temperature heating. The Al concentration distribution of the Al-containing alloy layer 41 on the main surface of the inner layer substrate 40 on the intermediate layer 30 side spreads deeper into the interior, resulting in a nearly uniform Al concentration distribution. The Al2O3 film 23 formed on the Al-containing alloy layer 21 of the outer layer substrate 20 becomes thicker.

[0058] According to this third embodiment, the same advantages as those of the second embodiment can be obtained.

[0059] <Fourth Embodiment> [Heat-resistant tubular member] Figure 10 shows a heat-resistant tubular member according to the fourth embodiment, particularly a portion of the tube wall. As shown in Figure 10, this heat-resistant tubular member is composed of a heat-resistant substrate having a tubular shape, consisting of an outer layer substrate 50, an intermediate layer 60, and an inner layer substrate 70. The outer layer substrate 50 is made of a ceramic substrate, and the inner layer substrate 70 is made of an alloy substrate. Al-containing alloy layers 71 and 72 are provided on the main surface of the inner layer substrate 70 on the side facing the intermediate layer 60 and on the main surface opposite the intermediate layer 50, respectively. Figure 10 shows the Al concentration distribution of the Al-containing alloy layers 71 and 72. From Figure 10, it can be seen that the Al concentration of the Al-containing alloy layers 71 and 72 decreases monotonically toward the interior of the inner layer substrate 70. The Al concentration and thickness of the Al-containing alloy layers 71 and 72 are the same as those of the Al-containing alloy layers 11 and 12 in the first embodiment. The intermediate layer 60 is porous and contains a large number of holes 61. The intermediate layer 60 contains at least Al, and typically further contains one or more elements contained in the alloy substrate constituting the inner layer substrate 70. To improve the resistance to delamination of the bond between the intermediate layer 60 and the ceramic substrate constituting the outer layer substrate 50, preferably the intermediate layer 60 contains Ti in addition to Al. The thickness of the outer layer substrate 50 and the inner layer substrate 70 is appropriately selected according to the application and function of the heat-resistant tubular member.

[0060] [Method for manufacturing heat-resistant tubular members] This heat-resistant tubular member can be manufactured as follows. First, an outer layer substrate 50 made of a ceramic substrate having a desired tubular shape and an inner layer substrate 70 made of an alloy substrate are prepared. Next, the outer layer substrate 50 and the inner layer substrate 70 are held with a gap between them, and a powder containing at least Al is applied to this gap by a slurry method or by inserting a ceramic fiber with powder supported in its voids. Next, by performing an Al diffusion treatment such as Al packing, Al-containing alloy layers 71 and 72 are formed on both main surfaces of the inner layer substrate 70, and an intermediate layer 60 is formed in the gap between the outer layer substrate 50 and the inner layer substrate 70. In this way, a heat-resistant tubular member can be manufactured.

[0061] [High-temperature corrosion behavior of heat-resistant tubular members] Figure 11 shows the heat-resistant substrate after heating the heat-resistant tubular member shown in Figure 10 at a high temperature for a short time in the atmosphere. As shown in Figure 11, when heated to a high temperature, the Al-containing alloy layers 71 and 72 on both main surfaces of the inner layer substrate 70, which is made of an alloy substrate, diffuse into the interior of the alloy substrate. As a result, the surface concentration decreases and the Al concentration distribution spreads inward, causing the bases of the Al concentration distribution of Al-containing alloy layer 71 and Al-containing alloy layer 72 to overlap. An Al2O3 film 73 is formed on the Al-containing alloy layers 71 and 72 on both main surfaces of the inner layer substrate 70. Al2O362 is formed in the pores 61 of the intermediate layer 60. If cracks or the like are formed in the outer layer substrate 50, which is made of a ceramic substrate, the Al2O362 formed by the Al contained in the intermediate layer 60 and the Al2O3 film 73 formed on the Al-containing alloy layer 71 on the main surface of the inner layer substrate 70 on the intermediate layer 50 side can maintain oxidation resistance. Furthermore, if the Al in the Al-containing alloy layer 71 on the main surface of the inner layer substrate 70 on the side of the intermediate layer 50 is consumed, the Al in the Al-containing alloy layer 72 on the main surface (inner surface) of the inner layer substrate 70 opposite to the intermediate layer 50 is supplied to the main surface of the inner layer substrate 70 on the side of the intermediate layer 50, forming an Al2O3 film 73, thereby maintaining oxidation resistance.

[0062] Figure 12 shows the heat-resistant substrate after heating the heat-resistant tubular member shown in Figure 10 at a high temperature for a long period of time in the atmosphere. As shown in Figure 12, the Al-containing alloy layers 71 and 72 on both main surfaces of the inner layer substrate 70 undergo deep diffusion of Al into the interior of the inner layer substrate 70 due to prolonged high-temperature heating. As a result, the surface concentration decreases significantly, and the Al concentration distribution spreads further into the interior of the inner layer substrate 70. The Al concentration distribution of the Al-containing alloy layer 71 and the Al concentration distribution of the Al-containing alloy layer 72 become one, resulting in a nearly uniform Al concentration distribution.

[0063] According to this fourth embodiment, a heat-resistant tubular member is constructed from a heat-resistant substrate having a tubular shape, comprising an outer layer substrate 50 made of a ceramic substrate with excellent corrosion resistance and heat resistance, a porous intermediate layer 60 containing at least Al, and an inner layer substrate 70 made of an alloy substrate having Al-containing alloy layers 71 and 72 on both main surfaces. This makes it possible to realize a heat-resistant tubular member that can continuously obtain excellent high-temperature corrosion resistance and mechanical properties even when used in environments where heating and cooling are repeatedly performed in a high-temperature corrosive atmosphere. This heat-resistant tubular member is particularly suitable for use in ultra-high temperature or severe high-temperature corrosive environments.

[0064] <Fifth Embodiment> [Heat-resistant base material] Figure 13 shows a heat-resistant tubular member according to the fifth embodiment, particularly a part of the tube wall. As shown in Figure 13, this heat-resistant tubular member differs from the fourth embodiment in that the Al-containing alloy layer 71 is provided only on the main surface of the inner layer base material 70 on the side of the intermediate layer 60, and the Al-containing alloy layer 72 is not provided on the main surface opposite to the intermediate layer 60. Otherwise, it is the same as the fourth embodiment.

[0065] [Method for manufacturing heat-resistant tubular members] This heat-resistant tubular member can be manufactured as follows. First, an outer layer substrate 50 made of a ceramic substrate having a desired tubular shape and an inner layer substrate 70 made of an alloy substrate are prepared. Next, the outer layer substrate 50 and the inner layer substrate 70 are held with a gap between them, and a powder containing at least Al is applied to this gap by a slurry method or by inserting a ceramic fiber with powder supported in its voids. Next, by performing an Al diffusion treatment such as Al packing, Al-containing alloy layers 71 and 72 are formed on both main surfaces of the inner layer substrate 70, and an intermediate layer 60 is formed in the gap between the outer layer substrate 50 and the inner layer substrate 70. In this way, a heat-resistant tubular member can be manufactured.

[0066] [High-temperature corrosion behavior of heat-resistant tubular members] Figure 14 shows the heat-resistant substrate after heating the heat-resistant tubular member shown in Figure 13 at a high temperature for a short time in the atmosphere. As shown in Figure 14, when heated to a high temperature, the Al-containing alloy layer 71 on the main surface of the inner layer substrate 70 on the side of the intermediate layer 60 diffuses into the interior of the inner layer substrate 70, resulting in a decrease in surface concentration and an expansion of the Al concentration distribution deep inside. Al2O373 is formed in the Al-containing alloy layer 71 on the main surface of the inner layer substrate 70 on the side of the intermediate layer 60. Al2O362 is formed in the pores of the intermediate layer 60.

[0067] Figure 15 shows the heat-resistant substrate after heating the heat-resistant tubular member shown in Figure 13 at a high temperature for a long period of time in the atmosphere. As shown in Figure 15, the Al-containing alloy layer 71 on the main surface of the inner layer substrate 70 on the intermediate layer 60 side diffuses deeply into the interior of the inner layer substrate 70 due to prolonged high-temperature heating. As a result, the surface concentration decreases significantly and the Al concentration distribution spreads further into the interior of the inner layer substrate 70, resulting in a nearly uniform Al concentration distribution. An Al2O3 film 73 is formed on the Al-containing alloy layer 71 of the inner layer substrate 70. Thus, the formation of the Al2O3 film 73 on the main surface of the inner layer substrate 70 on the intermediate layer 60 side not only protects the inner layer substrate 70, but also ensures that Al is continuously supplied from inside the inner layer substrate 70 because the Al concentration distribution in the inner layer substrate 70 is uniform. Therefore, the Al2O3 film 73 is continuously formed on the main surface of the inner layer substrate 70 on the intermediate layer 60 side.

[0068] According to this fifth embodiment, the same advantages as those of the fourth embodiment can be obtained.

[0069] <Sixth Embodiment> [Heat-resistant base material] Figure 16 shows a heat-resistant tubular member according to the sixth embodiment, particularly a portion of the tube wall. As shown in Figure 16, this heat-resistant tubular member consists of an outer layer substrate 80, an intermediate layer 90, and an inner layer substrate 100. The outer layer substrate 80 is made of an alloy substrate, and the inner layer substrate 100 is made of a ceramic substrate. Al-containing alloy layers 81 and 82 are provided on the main surface of the outer layer substrate 80 opposite to the intermediate layer 90 and on the main surface on the intermediate layer 90 side, respectively. Figure 16 shows the Al concentration distribution of the Al-containing alloy layers 81 and 82. As shown in Figure 16, the Al concentration of the Al-containing alloy layers 81 and 82 decreases monotonically toward the interior of the outer layer substrate 80. The Al concentration and thickness of the Al-containing alloy layers 81 and 82 are the same as those of the Al-containing alloy layers 11 and 12 in the first embodiment. The intermediate layer 90 is the same as the intermediate layer 30 in the fourth embodiment. The intermediate layer 90 contains holes 91. The thickness of the outer layer substrate 80 and the inner layer substrate 100 is appropriately selected according to the application and function of the heat-resistant tubular member.

[0070] [Method for manufacturing heat-resistant tubular members] This heat-resistant tubular member can be manufactured as follows. First, an outer layer base material 80 made of an alloy base material having a desired tubular shape and an inner layer base material 100 made of a ceramic base material are prepared. Next, the outer layer base material 80 and the inner layer base material 100 are held with a gap between them, and a powder containing at least Al is applied to this gap by a slurry method or by inserting a ceramic fiber with powder supported in its voids. Next, by performing an Al diffusion treatment such as Al packing, Al-containing alloy layers 81 and 82 are formed on both main surfaces of the outer layer base material 80, and an intermediate layer 90 is formed in the gap between the outer layer base material 80 and the inner layer base material 100. In this way, a heat-resistant tubular member can be manufactured.

[0071] [High-temperature corrosion behavior of heat-resistant tubular members] Figure 17 shows the heat-resistant substrate after heating the heat-resistant tubular member shown in Figure 16 at a high temperature for a short time in the atmosphere. As shown in Figure 17, when heated to a high temperature, the Al-containing alloy layers 81 and 82 on both main surfaces of the outer substrate 80 diffuse into the interior of the outer substrate 80, resulting in a decrease in surface concentration and an expansion of the Al concentration distribution inward. The bases of the Al concentration distribution of Al-containing alloy layer 81 and Al-containing alloy layer 82 overlap. An Al-deficient layer is formed on the outer main surface of the outer substrate 80 in the initial stages of heating. An Al2O3 film 83 is formed on the Al-containing alloy layers 81 and 82 on both main surfaces of the outer substrate 80. Al2O3 92 is formed in the pores 91 of the intermediate layer 90.

[0072] Figure 18 shows the heat-resistant substrate after heating the heat-resistant tubular member shown in Figure 16 at a high temperature for a long period of time in the atmosphere. As shown in Figure 18, the Al-containing alloy layers 81 and 82 on both main surfaces of the outer substrate 80 undergo deep diffusion of Al into the interior of the outer substrate 80 due to prolonged high-temperature heating. As a result, the surface concentration decreases significantly, and the Al concentration distribution spreads further into the interior of the outer substrate 80. The Al concentration distribution of the Al-containing alloy layer 81 and the Al-containing alloy layer 82 become integrated to form a nearly uniform Al concentration distribution. The Al-deficient layer formed on the outer main surface of the outer substrate 80 in the initial stages of heating disappears. The Al2O3 film 83 formed on the Al-containing alloy layer 81 of the outer substrate 80 becomes thicker. Not only is the outer substrate 80 protected by the Al2O3 film 83, but because the Al concentration distribution in the outer substrate 80 is uniform, Al is continuously supplied from the interior of the outer substrate 80, and a continuously thick Al2O3 film 83 is formed on the outer main surface of the outer substrate 80.

[0073] According to this sixth embodiment, the heat-resistant tubular member is constructed from a heat-resistant substrate having a tubular shape, comprising an outer layer substrate 50 made of an alloy substrate having Al-containing alloy layers 51 and 52 on both main surfaces, a porous intermediate layer 60 containing at least Al, and an inner layer substrate 70 made of a ceramic substrate. This makes it possible to realize a heat-resistant tubular member that can continuously obtain excellent high-temperature corrosion resistance and mechanical properties even when used in an environment where heating and cooling are repeatedly performed in a high-temperature corrosive atmosphere.

[0074] <Seventh Embodiment> [Heat-resistant tubular member] Figure 19 shows a heat-resistant tubular member 200 according to the seventh embodiment. As shown in Figure 19, this heat-resistant tubular member 200 is a stepped tube made of a heat-resistant base material 210 similar to the heat-resistant tubular member according to any of the first to sixth embodiments. Both ends of this heat-resistant tubular member 200 are open. This heat-resistant tubular member 200 can be used, for example, as a nozzle.

[0075] According to this seventh embodiment, the same advantages as those of any of the first to sixth embodiments can be obtained.

[0076] <Eighth Embodiment> [Heat-resistant tubular member] Figure 20 shows a heat-resistant tubular member 300 according to the eighth embodiment. As shown in Figure 20, this heat-resistant tubular member 300 is a sealed tube at one end (lower end) and is made of a heat-resistant base material 310 similar to the heat-resistant tubular member according to any of the first to sixth embodiments. The other end (upper end) of this heat-resistant tubular member 300 is open.

[0077] Figure 21A shows an example of the use of the heat-resistant tubular member 300. As shown in Figure 21A, in this example, a lance (thin tube) 400 is inserted from the open other end of the heat-resistant tubular member 300, and water, gas, or other fluid supplied from the other end of the lance 400 is supplied from one end into the interior of the heat-resistant tubular member 300 as indicated by the arrow, to perform internal cooling, heat exchange, gas reaction, etc.

[0078] Figure 21B shows another example of the use of the heat-resistant tubular member 300. As shown in Figure 21B, in this example, a one-end sealed thermocouple protection tube 500 is inserted from the open other end of the heat-resistant tubular member 300. A lid 510 is attached to the other end of the thermocouple protection tube 500, and the thermocouple wire 520 is attached through this lid 510. The heat-resistant tubular member 300 is passed through a through-hole provided in the wall of a combustion furnace such as an incinerator and is exposed to the combustion gas atmosphere inside the furnace. The temperature inside the combustion furnace is then measured by the thermocouple wire 520. It is desirable that the open other end of the heat-resistant tubular member 300 is outside the furnace.

[0079] According to this eighth embodiment, the same advantages as those of the first to sixth embodiments can be obtained in applications such as those shown in Figures 21A and 21B.

[0080] <Ninth Embodiment> [Heat-resistant tubular member] Figure 22 shows a heat-resistant tubular member according to the ninth embodiment. As shown in Figure 22, this heat-resistant tubular member is composed of a heat-resistant substrate consisting of an outer layer substrate 600, an intermediate layer 700, and an inner layer substrate 800. However, the open end (upper end) of the inner layer substrate 800 is further outward (upper) than the open end (upper end) of the outer layer substrate 600. In addition, the intermediate layer 700 is not provided across the entire area between the outer layer substrate 600 and the inner layer substrate 800, but is not provided on a portion of the open end side of the outer layer substrate 600. The outer layer substrate 600, intermediate layer 700, and inner layer substrate 800 are the same as the heat-resistant substrates of the heat-resistant tubular member according to any embodiment of the second to sixth embodiments. In operating environments such as incinerators and boilers, one sealed end of the outer layer substrate 600 is exposed to the combustion gas atmosphere, but it is desirable that the other open end of the outer layer substrate 600 is outside the furnace. When the open end of the outer layer substrate 600 is outside the furnace, the atmosphere inside the intermediate layer 700 and the inner layer substrate 800 is connected to the atmosphere outside the furnace, allowing for the exchange of air and other elements.

[0081] According to this ninth embodiment, the same advantages as those of the second to sixth embodiments can be obtained.

[0082] <Tenth Embodiment> [Heat-resistant tubular member] Figure 23 shows a heat-resistant tubular member according to the tenth embodiment. As shown in Figure 23, this heat-resistant tubular member is composed of a heat-resistant substrate consisting of an outer layer substrate 600, an intermediate layer 700, and an inner layer substrate 800, similar to the ninth embodiment, but differs from the ninth embodiment in that both ends (upper and lower ends) of the outer layer substrate 600 are open.

[0083] According to this tenth embodiment, the same advantages as those of the second to sixth embodiments can be obtained.

[0084] Examples will be described.

[0085] (Example 1) Example 1 corresponds to the third embodiment.

[0086] Fe-21Cr substrate (composition in mass%) was used as the outer layer substrate 20, and Fe-25Cr-20Ni substrate was used as the inner layer substrate 40. These substrates were placed facing each other with a gap between them, and a slurry containing Al powder and FeAl powder was inserted into the gap as a material for forming the intermediate layer. Then, these substrates were embedded in a mixed powder of FeAl powder, NH4Cl powder and Al2O3 powder (10 mass% FeAl powder + 1 mass% NH4Cl powder + 89 mass% Al2O3 powder), and heated at 1050°C for 1 hour in an Ar + 3 vol% H2 atmosphere to perform Al packing.

[0087] A portion of the substrate that had undergone Al-pack treatment was cut, and its cross-sectional structure was observed and the concentration distribution of each element was measured using a SEM-EDX (Scanning Electron Microscope-Energy Dispersive Spectrometer). Figures 24A and 24B show the cross-sectional SEM image of the Fe-25Cr-20Ni substrate portion, which served as the inner layer substrate 40, and the measurement results of the concentration distribution of each element measured using EDX (concentration distribution along the analytical line LG2 in the image shown in Figure 24A), respectively. Figures 25A and 25B show the cross-sectional SEM image of the Fe-21Cr substrate portion, which served as the outer layer substrate 20, and the measurement results of the concentration distribution of each element measured using EDX (concentration distribution along the analytical line LG1 in the image shown in Figure 25A), respectively. From Figures 24A, 24B, 25A, and 25B, a 52.6 atomic % Al-containing alloy layer is observed on one main surface of the Fe-25Cr-20Ni substrate used as the inner layer substrate 40, a 50.3 atomic % Al-containing alloy layer is observed on the outer surface of the Fe-21Cr substrate used as the outer layer substrate 20, a 50.4 atomic % Al-containing alloy layer is observed on the opposite surface, and a porous intermediate layer containing Al, Fe, Cr, Ni, etc. is observed between the two substrates.

[0088] The prepared samples were subjected to 10 cycles of oxidation in air, consisting of holding at 1200°C for 60 minutes and holding at room temperature for 15 minutes. Figures 26A and 26B show cross-sectional SEM images of the Fe-25Cr-20Ni substrate portion as the inner layer substrate 40 after cycle oxidation, and the concentration distribution of each element measured using EDX (concentration distribution along the analytical line LG6 in the image shown in Figure 26A), respectively. Figures 27A and 27B show cross-sectional SEM images of the Fe-21Cr substrate portion as the outer layer substrate 20, and the concentration distribution of each element measured using EDX (concentration distribution along the analytical line LG5 in the image shown in Figure 27A), respectively. From Figures 27A and 27B, it can be observed that the Al concentration distributions of the Al-containing alloy layers formed on both main surfaces of the Fe-21Cr substrate as the outer layer substrate 20 have merged, resulting in a smoothed Al concentration distribution. The Al-containing alloy layer on the outer surface of the Fe-21Cr substrate contains 12.2 atomic% Al, while the Al-containing alloy layer on the opposite side contains 22.0 atomic% Al.

[0089] (Example 2) Example 2 corresponds to the third embodiment.

[0090] Fe-18Cr-8Ni substrate was used as the outer layer substrate 20, and Fe-27Cr substrate was used as the inner layer substrate 40. These substrates were placed facing each other with a gap between them, and a slurry containing Al powder and FeAl powder was inserted into the gap as a material for forming the intermediate layer. Then, these substrates were embedded in a mixed powder of FeAl powder, NH4Cl powder, and Al2O3 powder (10 mass% FeAl powder + 1 mass% NH4Cl powder + 89 mass% Al2O3 powder), and heated at 1050°C for 4 hours in an Ar + 3 vol% H2 atmosphere to perform Al packing.

[0091] A portion of the substrate that had undergone Al-pack treatment was cut, and its cross-sectional structure was observed and the concentration distribution of each element was measured using an SEM-EDX apparatus. Figures 28A and 28B show the cross-sectional SEM image of the Fe-27Cr substrate portion as the inner layer substrate 40 and the measurement results of the concentration distribution of each element measured using EDX (concentration distribution along the analytical line LG2 in the image shown in Figure 28A), respectively. Figures 29A and 29B show the cross-sectional SEM image of the portion between the Fe-18Cr-8Ni substrate as the outer layer substrate 20 and the Fe-27Cr substrate as the inner layer substrate 40 and the measurement results of the concentration distribution of each element measured using EDX (concentration distribution along the analytical line LG4 in the image shown in Figure 29A), respectively. Figures 30A and 30B show the cross-sectional SEM image of the Fe-18Cr-8Ni substrate portion as the outer layer substrate 20 and the measurement results of the concentration distribution of each element measured using EDX (concentration distribution along the analytical line LG1 in the image shown in Figure 30A), respectively. From Figures 28A, 28B, 29A, 29B, 30A, and 30B, a 29.7 atomic% Al-containing alloy layer is observed on one main surface of the Fe-27Cr substrate, which serves as the inner layer substrate 40. A 54.3 atomic% Al-containing alloy layer is observed on the outer surface of the Fe-18Cr-8Ni substrate, which serves as the outer layer substrate 20. A 33.5 atomic% Al-containing alloy layer is observed on the opposite surface. Between the two substrates, a porous intermediate layer containing Al (14.8-44.5 atomic%), Fe (12.6-43.4 atomic%), Cr (10.5-32.4 atomic%), Ni (0.0-7.6 atomic%), etc., is observed.

[0092] The prepared samples were subjected to 14 cycles of oxidation in air, consisting of holding at 1200°C for 60 minutes and holding at room temperature for 15 minutes. Figures 31A and 31B show cross-sectional SEM images of the Fe-27Cr substrate as the inner layer substrate 40 and the Fe-18Cr-8Ni substrate as the intermediate and outer layer substrates 20 after cycle oxidation, as well as the concentration distribution of each element measured using EDX (concentration distribution along the analytical line LG1 in the image shown in Figure 31A), respectively. From Figures 31A and 31B, it can be observed that the Al concentration distributions of the Al-containing alloy layers formed on both main surfaces of the Fe-18Cr-8Ni substrate as the outer layer substrate 20 have merged, resulting in a smoothed Al concentration distribution. The Al-containing alloy layer on the outer surface of the Fe-18Cr-8Ni substrate contains 18.0 atoms of Al, the Al-containing alloy layer on the main surface of the intermediate layer contains 11.1 atoms of Al, and the Al-containing alloy layer on the main surface of the intermediate layer of the Fe-27Cr substrate contains 12.6 atoms of Al.

[0093] (Example 3) Example 3 corresponds to the third embodiment.

[0094] Fe-21Cr substrate was used as the outer layer substrate 20, and Fe-25Cr-20Ni substrate was used as the inner layer substrate 40. These substrates were placed facing each other with a gap between them, and a slurry containing Al powder and FeAl powder was inserted into the gap as a material for forming the intermediate layer. Then, these substrates were embedded in a mixed powder of FeAl powder, NH4Cl powder, and Al2O3 powder (10 mass% FeAl powder + 1 mass% NH4Cl powder + 89 mass% Al2O3 powder), and heated at 1100°C for 8 hours in an Ar + 3 vol% H2 atmosphere to perform Al packing.

[0095] A portion of the substrate that had undergone Al-pack treatment was cut, and its cross-sectional structure was observed and the concentration distribution of each element was measured using an SEM-EDX apparatus. Figures 32A and 32B show cross-sectional SEM images of the Fe-25Cr-20Ni substrate as the inner layer substrate 40 and the Fe-21Cr substrate as the intermediate and outer layer substrate 20, respectively, as well as the measurement results of the concentration distribution of each element measured using EDX (concentration distribution along the analysis line in the image shown in Figure 32A). From Figures 32A and 32B, a 49 atomic% Al-containing alloy layer is observed on one main surface of the Fe-25Cr-20Ni substrate used as the inner layer substrate 40, a 34.5 atomic% Al-containing alloy layer is observed on the outer surface of the Fe-21Cr substrate used as the outer layer substrate 20, and a 40.7 atomic% Al-containing alloy layer is observed on the opposite surface. Between the two substrates, a porous intermediate layer containing Al (6.9-28.6 atomic%), Fe (23.0-78.3 atomic%), Cr (4.2-18.7 atomic%), Ni (0.0-2.3 atomic%), etc., is observed.

[0096] The prepared samples were subjected to 67 cycles of oxidation in air, consisting of holding at 1100°C for 60 minutes and holding at room temperature for 15 minutes. Figures 33A and 33B show cross-sectional SEM images of the Fe-25Cr-20Ni substrate (inner layer substrate 40) and the Fe-21Cr substrate (intermediate layer and outer layer substrate 20) after cycle oxidation, as well as the concentration distribution of each element measured using EDX (concentration distribution along the analytical line in the image shown in Figure 33A), respectively. From Figures 33A and 33B, it can be observed that the Al concentration distributions of the Al-containing alloy layers formed on both main surfaces of the Fe-21Cr substrate (outer layer substrate 20) merged, resulting in a smoothed Al concentration distribution. The Al concentration of the Al-containing alloy layer after merging is 32.5 atomic percent.

[0097] (Example 4) Example 4 corresponds to the third embodiment.

[0098] Fe-21Cr substrate was used as the outer layer substrate 20, and Fe-27Cr substrate was used as the inner layer substrate 40. These substrates were placed facing each other with a gap between them, and a slurry containing Al powder and FeAl powder was inserted into the gap as a material for forming the intermediate layer. Then, these substrates were embedded in a mixed powder of FeAl powder, NH4Cl powder, and Al2O3 powder (10 mass% FeAl powder + 1 mass% NH4Cl powder + 89 mass% Al2O3 powder), and heated at 1050°C for 4 hours in an Ar + 3 vol% H2 atmosphere to perform Al packing.

[0099] A portion of the substrate that had undergone Al-pack treatment was cut, and its cross-sectional structure was observed and the concentration distribution of each element was measured using an SEM-EDX apparatus. Figures 34A and 33B show the cross-sectional SEM images of the Fe-27Cr substrate portion as the inner layer substrate 40 and the measurement results of the concentration distribution of each element measured using EDX (concentration distribution along the analytical line LG2 in the image shown in Figure 34A), respectively. Figures 35A and 35B show the cross-sectional SEM images of the portion between the Fe-21Cr substrate as the outer layer substrate 20 and the Fe-27Cr substrate as the inner layer substrate 40 and the measurement results of the concentration distribution of each element measured using EDX (concentration distribution along the analytical line LG4 in the image shown in Figure 35A), respectively. Figures 36A and 36B show the cross-sectional SEM images of the Fe-21Cr substrate portion as the outer layer substrate 20 and the measurement results of the concentration distribution of each element measured using EDX (concentration distribution along the analytical line LG1 in the image shown in Figure 36A), respectively. From Figures 34A, 34B, 35A, 35B, 36A, and 36B, a 29.3 atomic% Al-containing alloy layer is observed on one main surface of the Fe-27Cr substrate, which serves as the inner layer substrate 40. A 54.3 atomic% Al-containing alloy layer is observed on the outer surface of the Fe-21Cr substrate, which serves as the outer layer substrate 20. A 33.5 atomic% Al-containing alloy layer is observed on the opposite surface. Between the two substrates, a porous intermediate layer containing Al (14.8-44.5 atomic%), Fe (12.6-43.3 atomic%), Cr (10.5-25.3 atomic%), Si (0.0-8.2 atomic%), etc., is observed.

[0100] (Example 5) Example 5 corresponds to the first embodiment.

[0101] Fe-18Cr-8Ni substrate was used as the alloy substrate. This Fe-18Cr-8Ni substrate was embedded in a mixed powder of FeAl powder, NH4Cl powder, and Al2O3 powder (10 mass% FeAl powder + 1 mass% NH4Cl powder + 89 mass% Al2O3 powder), and heated at 1050°C for 8 hours in an Ar + 3 vol% H2 atmosphere to perform Al pack treatment.

[0102] A portion of the substrate that had undergone Al-pack treatment was cut, and its cross-sectional structure was observed and the concentration distribution of each element was measured using an SEM-EDX apparatus. Figures 37A and 37B show the cross-sectional SEM image of the Fe-18Cr-8Ni substrate and the measurement results of the concentration distribution of each element measured using EDX (concentration distribution along the analytical line LG6 in the image shown in Figure 37A), respectively. From Figures 37A and 37B, Al-containing alloy layers are observed on both main surfaces of the Fe-18Cr-8Ni substrate. The Al-containing alloy layer on the outer surface of the Fe-18Cr-8Ni substrate contains 42.9 atomic % Al, and the Al-containing alloy layer on the opposite surface contains 33.7 atomic % Al.

[0103] The prepared samples were subjected to 10 cycles of oxidation in air, consisting of holding at 1200°C for 60 minutes and holding at room temperature for 15 minutes. Figures 38A and 38B show the cross-sectional SEM images of the Fe-18Cr-8Ni substrate and the concentration distribution of each element measured using EDX (concentration distribution along the analytical line LG5 in the image shown in Figure 38A), respectively. From Figures 38A and 38B, it can be observed that the Al concentration distributions of the Al-containing alloy layers formed on both main surfaces of the Fe-18Cr-8Ni substrate merged, resulting in a smoothed Al concentration distribution. The Al-containing alloy layer on the outer surface of the Fe-18Cr-8Ni substrate contains 10.3 atomic % Al, while the Al-containing alloy layer on the opposite surface contains 9.7 atomic % Al.

[0104] (Example 6) Example 6 corresponds to the first embodiment.

[0105] Fe-21Cr substrate was used as the alloy substrate. This Fe-21Cr substrate was embedded in a mixed powder of FeAl powder, NH4Cl powder, and Al2O3 powder (10% by mass FeAl powder + 1% by mass NH4Cl powder + 89% by mass Al2O3 powder), and heated at 1050°C for 8 hours in an Ar + 3 vol% H2 atmosphere to perform Al pack treatment.

[0106] A portion of the substrate that had undergone Al-pack treatment was cut, and its cross-sectional structure was observed and the concentration distribution of each element was measured using an SEM-EDX apparatus. Figures 39A and 39B show the cross-sectional SEM image of the Fe-21Cr substrate and the measurement results of the concentration distribution of each element measured using EDX (concentration distribution along the analytical line LG3 in the image shown in Figure 39A), respectively. From Figures 39A and 39B, Al-containing alloy layers are observed on both main surfaces of the Fe-21Cr substrate. The Al-containing alloy layer on the outer surface of the Fe-21Cr substrate contains 25.9 atomic % Al, and the Al-containing alloy layer on the opposite surface contains 26.7 atomic % Al.

[0107] The prepared samples were subjected to 10 cycles of oxidation in air, consisting of holding at 1200°C for 60 minutes and holding at room temperature for 15 minutes. Figures 40A and 40B show the cross-sectional SEM images of the Fe-21Cr substrate and the concentration distribution of each element measured using EDX (concentration distribution along the analytical line LG4 in the image shown in Figure 40A), respectively. From Figures 40A and 40B, it can be observed that the Al concentration distributions of the Al-containing alloy layers formed on both main surfaces of the Fe-21Cr substrate merged, resulting in a smoothed Al concentration distribution. The Al-containing alloy layer on the outer surface of the Fe-21Cr substrate contains 11.8 atomic % Al, and the Al-containing alloy layer on the opposite surface contains 11.6 atomic % Al.

[0108] (Example 7) Example 7 corresponds to the first embodiment.

[0109] Fe-21Cr substrate was used as the alloy substrate. This Fe-21Cr substrate was embedded in a mixed powder of Fe powder, FeAl powder, NH4Cl powder, and Al2O3 powder (5% by mass Fe powder + 5% by mass FeAl powder + 1% by mass NH4Cl powder + 89% by mass Al2O3 powder), heated at 1100°C for 8 hours in an Ar + 3 vol% H2 atmosphere, and subjected to Al pack treatment.

[0110] A portion of the substrate that had undergone Al-pack treatment was cut, and its cross-sectional structure was observed and the concentration distribution of each element was measured using an SEM-EDX apparatus. Figures 41A and 41B show the cross-sectional SEM image of the Fe-21Cr substrate and the measurement results of the concentration distribution of each element measured using EDX (concentration distribution along the analytical line LG3 in the image shown in Figure 41A), respectively. From Figures 41A and 41B, Al-containing alloy layers are observed on both main surfaces of the Fe-21Cr substrate. The Al-containing alloy layer on the outer surface of the Fe-21Cr substrate contains 28.6 atoms of Al, and the Al-containing alloy layer on the opposite surface contains 20.5 atoms of Al.

[0111] The prepared samples were subjected to 120 cycles of oxidation in air, consisting of holding at 1200°C for 60 minutes and holding at room temperature for 15 minutes. Figures 42A and 42B show the cross-sectional SEM images of the Fe-21Cr substrate and the concentration distribution of each element measured using EDX (concentration distribution along the analytical line LG1 in the image shown in Figure 42A), respectively. Figures 43A and 43B show the cross-sectional SEM images of a magnified portion of the cross-sectional structure shown in Figure 42A and the concentration distribution of each element measured using EDX (concentration distribution along the analytical line LG2 in the image shown in Figure 43A), respectively. From Figures 42A, 42B, 43A, and 43B, it can be observed that the Al concentration distributions of the Al-containing alloy layers formed on both main surfaces of the Fe-21Cr substrate merged, resulting in a smoothed Al concentration distribution. The Al-containing alloy layer on the outer surface of the Fe-21Cr substrate contains 12.1 atoms of Al, and the Al-containing alloy layer on the opposite surface contains 12 atoms of Al.

[0112] (Example 8) Example 8 corresponds to the first embodiment.

[0113] Fe-21Cr substrate was used as the alloy substrate. This Fe-21Cr substrate was embedded in a mixed powder of Fe powder, FeAl powder, NH4Cl powder, and Al2O3 powder (5% by mass Fe powder + 5% by mass FeAl powder + 1% by mass NH4Cl powder + 89% by mass Al2O3 powder), heated at 1100°C for 8 hours in an Ar + 3 vol% H2 atmosphere, and subjected to Al pack treatment.

[0114] A portion of the substrate that had undergone Al-pack treatment was cut, and its cross-sectional structure was observed and the concentration distribution of each element was measured using a SEM-EDX apparatus. Figures 44A and 44B show the cross-sectional SEM image of the Fe-21Cr substrate and the measurement results of the concentration distribution of each element measured using EDX (concentration distribution along the analysis line in the image shown in Figure 44A), respectively. From Figures 44A and 44B, Al-containing alloy layers are observed on both main surfaces of the Fe-21Cr substrate. The Al-containing alloy layer on the outer surface of the Fe-21Cr substrate is 20.9 atomic % Al, and the Al-containing alloy layer on the opposite surface is 19.1 atomic % Al.

[0115] The prepared samples were subjected to cyclic oxidation in air, with holding at 1200°C for 60 minutes and holding at room temperature for 15 minutes. After 120 cycles, the Fe-21Cr substrate was oxidized for the first time.

[0116] Furthermore, verification was also performed on embodiments corresponding to the fourth and sixth embodiments, but there was no change whatsoever in the ceramic substrate constituting the outer or inner layer substrate, and the changes occurring in the alloy substrate were the same as in Examples 1 to 4.

[0117] Although embodiments and examples of this invention have been described in detail above, this invention is not limited to the embodiments and examples described above, and various modifications based on the technical idea of ​​this invention are possible. [Explanation of symbols]

[0118] 10…Alloy substrate, 11, 12…Al-containing alloy layer, 13…Al2O3 coating, 20…Outer layer substrate, 21, 22…Al-containing alloy layer, 23…Al2O3 coating, 30…Intermediate layer, 31…Pores, 32…Al2O3, 40…Inner layer substrate, 41, 42…Al-containing alloy layer, 43…Al2O3 coating, 50…Outer layer substrate, 60…Intermediate layer, 61…Pores, 62…Al 2O3, 70...Inner layer substrate, 71, 72...Al-containing alloy layer, 73...Al2O3 coating, 80...Outer layer substrate, 81, 82...Al-containing alloy layer, 83...Al2O3 coating, 90...Intermediate layer, 91...Hole, 92...Al2O3, 100...Inner layer substrate, 200, 300...Heat-resistant tubular member, 400...Lance, 500...Protective tube, 510...Lid, 520...Thermocouple wire

Claims

1. It is composed of a first alloy substrate, a second alloy substrate, and a heat-resistant substrate consisting of a porous intermediate layer containing at least Al, provided between the first and second alloy substrates. The first alloy substrate described above has an Al-containing alloy layer on each of its two main surfaces. The second alloy substrate described above has an Al-containing alloy layer on at least the main surface on the intermediate layer side of both main surfaces. The Al concentration in the Al-containing alloy layer of the first alloy substrate decreases toward the interior of the first alloy substrate, and the Al concentration in the Al-containing alloy layer of the second alloy substrate decreases toward the interior of the second alloy substrate. The Al concentration in the above Al-containing alloy layer is between 15 atomic percent and 55 atomic percent. The heat-resistant substrate is a heat-resistant tubular member having a tubular shape with the first alloy substrate on the outside.

2. A heat-resistant substrate comprising a ceramic substrate, an alloy substrate, and a porous intermediate layer containing at least Al provided between the ceramic substrate and the alloy substrate, The above alloy substrate has an Al-containing alloy layer on at least the main surface on the intermediate layer side of both main surfaces. The Al concentration in the Al-containing alloy layer of the above alloy substrate decreases toward the interior of the alloy substrate. The Al concentration in the above Al-containing alloy layer is between 15 atomic percent and 55 atomic percent. The above heat-resistant substrate is a heat-resistant tubular member having a tubular shape with the above ceramic substrate on the outside.

3. A heat-resistant substrate comprising an alloy substrate, a ceramic substrate, and a porous intermediate layer containing at least Al provided between the alloy substrate and the ceramic substrate, The above alloy substrate has an Al-containing alloy layer on each of its two main surfaces. The Al concentration in the Al-containing alloy layer of the above alloy substrate decreases toward the interior of the alloy substrate. The Al concentration in the above Al-containing alloy layer is between 15 atomic percent and 55 atomic percent. The above heat-resistant substrate is a heat-resistant tubular member having a tubular shape with the alloy substrate on the outside.

4. A step of inserting a second alloy substrate having a tubular shape into the interior of a first alloy substrate having a tubular shape, with a gap between them, A step of inserting a slurry containing at least Al powder into the gap between the first alloy substrate and the second alloy substrate, The process involves inserting the slurry into the gap between the first alloy substrate and the second alloy substrate, then subjecting the first and second alloy substrates to an Al diffusion treatment to form a porous intermediate layer containing at least Al between the first and second alloy substrates, forming an Al-containing alloy layer on both main surfaces of the first alloy substrate where the Al concentration decreases toward the interior of the first alloy substrate and the Al concentration is between 15 atomic% and 55 atomic%, and forming an Al-containing alloy layer on at least the main surface of the second alloy substrate on the side with the intermediate layer where the Al concentration decreases toward the interior of the second alloy substrate and the Al concentration is between 15 atomic% and 55 atomic%, and A method for manufacturing a heat-resistant tubular member having the following characteristics.

5. A step of inserting a tubular alloy substrate into a tubular ceramic substrate with a gap between them, A step of inserting a slurry containing at least Al powder into the gap between the ceramic substrate and the alloy substrate, The process involves inserting the slurry into the gap between the ceramic substrate and the alloy substrate, then subjecting the ceramic substrate and the alloy substrate to an Al diffusion treatment to form a porous intermediate layer containing at least Al between the ceramic substrate and the alloy substrate, and forming an Al-containing alloy layer on at least the main surface of the alloy substrate on the side of the intermediate layer, where the Al concentration decreases toward the interior of the alloy substrate and the Al concentration is 15 atomic% or more and 55 atomic% or less. A method for manufacturing a heat-resistant tubular member having the following characteristics.

6. A step of inserting a tubular ceramic substrate into a tubular alloy substrate with a gap between them, A step of inserting a slurry containing at least Al powder into the gap between the alloy substrate and the ceramic substrate, The process involves inserting the slurry into the gap between the alloy substrate and the ceramic substrate, then subjecting the alloy substrate and the ceramic substrate to an Al diffusion treatment to form a porous intermediate layer containing at least Al between the alloy substrate and the ceramic substrate, and forming an Al-containing alloy layer on both main surfaces of the alloy substrate, wherein the Al concentration decreases toward the interior of the alloy substrate, and the Al concentration is between 15 atomic% and 55 atomic%. A method for manufacturing a heat-resistant tubular member having the following characteristics.

7. A heat-resistant substrate comprising a first alloy substrate, a second alloy substrate, and a porous intermediate layer containing at least Al provided between the first alloy substrate and the second alloy substrate, The first alloy substrate described above has an Al-containing alloy layer on each of its two main surfaces. The second alloy substrate described above has an Al-containing alloy layer on at least the main surface on the intermediate layer side of both main surfaces. The Al concentration in the Al-containing alloy layer of the first alloy substrate decreases toward the interior of the first alloy substrate, and the Al concentration in the Al-containing alloy layer of the second alloy substrate decreases toward the interior of the second alloy substrate. The Al concentration in the above Al-containing alloy layer is between 15 atomic percent and 55 atomic percent. The above heat-resistant substrate is a heat-resistant tubular member having a tubular shape with the first alloy substrate on the outside. High-temperature processing equipment having the following features.

8. A heat-resistant substrate comprising a ceramic substrate, an alloy substrate, and a porous intermediate layer containing at least Al provided between the ceramic substrate and the alloy substrate, The above alloy substrate has an Al-containing alloy layer on at least the main surface on the intermediate layer side of both main surfaces. The Al concentration in the Al-containing alloy layer of the above alloy substrate decreases toward the interior of the alloy substrate. The Al concentration in the above Al-containing alloy layer is between 15 atomic percent and 55 atomic percent. The above heat-resistant substrate is a heat-resistant tubular member having a tubular shape with the above ceramic substrate on the outside. High-temperature processing equipment having the following features.

9. A heat-resistant substrate comprising an alloy substrate, a ceramic substrate, and a porous intermediate layer containing at least Al provided between the alloy substrate and the ceramic substrate, The above alloy substrate has an Al-containing alloy layer on each of its two main surfaces. The Al concentration in the Al-containing alloy layer of the above alloy substrate decreases toward the interior of the alloy substrate. The Al concentration in the above Al-containing alloy layer is between 15 atomic percent and 55 atomic percent. The above heat-resistant substrate is a heat-resistant tubular member having a tubular shape with the alloy substrate on the outside. High-temperature processing equipment having the following features.

10. A material comprising a first alloy substrate, a second alloy substrate, and a porous intermediate layer containing at least Al, provided between the first alloy substrate and the second alloy substrate. The first alloy substrate described above has an Al-containing alloy layer on each of its two main surfaces. The second alloy substrate described above has an Al-containing alloy layer on at least the main surface on the intermediate layer side of both main surfaces. The Al concentration in the Al-containing alloy layer of the first alloy substrate decreases toward the interior of the first alloy substrate, and the Al concentration in the Al-containing alloy layer of the second alloy substrate decreases toward the interior of the second alloy substrate. The above Al-containing alloy layer has an Al concentration of 15 atomic% or more and 55 atomic% or less, which is a heat-resistant substrate.

11. Comprising a ceramic substrate, an alloy substrate, and a porous intermediate layer containing at least Al provided between the ceramic substrate and the alloy substrate, The above alloy substrate has an Al-containing alloy layer on at least the main surface on the intermediate layer side of both main surfaces. The Al concentration in the Al-containing alloy layer of the above alloy substrate decreases toward the interior of the alloy substrate. The above Al-containing alloy layer has an Al concentration of 15 atomic% or more and 55 atomic% or less, which is a heat-resistant substrate.

12. Comprising an alloy substrate, a ceramic substrate, and a porous intermediate layer containing at least Al provided between the alloy substrate and the ceramic substrate, The above alloy substrate has an Al-containing alloy layer on each of its two main surfaces. The Al concentration in the Al-containing alloy layer of the above alloy substrate decreases toward the interior of the alloy substrate. The above Al-containing alloy layer has an Al concentration of 15 atomic% or more and 55 atomic% or less, which is a heat-resistant substrate.

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