JP6996921B2 - Structure for protective tube of thermocouple for incinerator and its manufacturing method - Google Patents

Description

The present disclosure relates to a structure for a protective tube of a thermocouple for an incinerator having excellent heat resistance and corrosion resistance, and a method for manufacturing the same.

Some high-temperature environments in which a general heat-resistant structure is used may be accompanied by an oxidizing atmosphere. Further, as a harsher environment, there is an environment in which convection is generated in the furnace and the scale is fluttering on the convection. These environments cause the structure to deteriorate due to heat due to high temperature and deterioration due to the oxidizing atmosphere, and also cause severe wear due to wear caused by the collision of the scale on the convection, which is a factor of shortening the life. Will be. Therefore, it is necessary to frequently purchase and replace the relevant parts, which causes a large cost. Conventionally, as a means for improving the heat resistance and corrosion resistance of a base material, it is known to coat the surface of the base material with a material such as ceramics having heat resistance and corrosion resistance. Examples of the method for forming the surface layer containing ceramics include thermal spraying technology and coating technology such as aluminize.

For example, when a powder having a composition different from that of the base material is sprayed onto the surface of the base material from a ceramic nozzle or a plastic nozzle, an intermediate layer having excellent bonding strength with the material of the base material or the material of the film is applied to the surface of the base material. There is a disclosure of a method for manufacturing a composite member of different materials forming the above (see, for example, Patent Document 1).

Further, there is a disclosure of an oxidation-resistant coating structure of a heat-resistant alloy in which an oxidation-resistant film in which oxide fibers and particles are dispersed in an alloy layer containing at least Al or Si is formed on the surface of the base material of the heat-resistant alloy. See, for example, Patent Document 2).

Further, Cr: 10 to 30 wt%, Ti, Nb, V, Zr at least one type: 0.6 wt% or less, C: 0.1 wt% or less, N: 0.05 wt% or less, Si: 2.0 wt% Hereinafter, Mn: 2.0 wt% or less, a stainless steel base material whose balance is iron and unavoidable impurities, an aluminum diffusion layer made of iron-chromium-aluminum, and a 0.3-5.0 μm thick aluminum oxide film. There is a disclosure of a heater material having excellent surface insulating properties (see, for example, Patent Document 3).

Further, in a high-temperature wear-resistant member formed by burying a base material in a mixed powder such as a metal powder or a heat-resistant film-forming powder material and heating it at a high temperature, the hardness of the film layer of the base material is Hv700 or more and the film thickness. There is a disclosure of a wear resistant member for high temperature having a hardness of 0.03 mm or more and a surface aluminum concentration of 10% or more (see, for example, Patent Document 4). Patent Document 4 discloses that alumina is formed in the film layer.

Further, there is disclosure of metal gas carburizing furnace parts and jigs having an Al diffusion permeation layer having an Al concentration of 10 to 50% by weight on the outermost surface, which is further subjected to a calorizing treatment (for example, Patent Document). See 5.).

Japanese Unexamined Patent Publication No. 2009-191345 Japanese Unexamined Patent Publication No. 2008-069403 Japanese Unexamined Patent Publication No. 5-283149 Japanese Unexamined Patent Publication No. 2003-129217 Japanese Unexamined Patent Publication No. 10-168555

Patent Documents 1 to 5 disclose techniques for coating the surface of a base material with a coating film. However, in any of the coating techniques, the adhesion between the base material and the surface layer is an issue. If the adhesion between the base material and the coating layer is not sufficient, cracks are easily generated, the coating layer is peeled off from the base material, and thermal deterioration, corrosion, and wear from the peeled portion occur. In addition, if the base material and the surface layer are incompatible with each other, the film thickness and composition distribution of the surface layer may not be formed as intended, and the surface layer cannot exhibit sufficient functions and sufficiently achieve a long life. It will not be possible.

For example, there is no intermediate layer such as a diffusion layer between the film formed by thermal spraying and the base material, and the adhesion depends on the bonding force of only the anchor effect due to the unevenness of the surface of the base material. In such a bonded state, cracks or the like are easily generated due to the difference in the thermal expansion rate between the base material and the film, leading to peeling.

Further, in the case of the method of performing the aluminate treatment on a metal base material such as iron or nickel, a diffusion layer is formed between the film and the base material, and a strong bond is achieved. However, when the same treatment is applied to chromium and the chromium alloy, a large number of cracks and peelings occur in the formed film, resulting in poor quality.

Therefore, it is a structure having a protective film, and the base material originally has characteristics such as heat resistance, oxidation resistance, and wear resistance while improving the adhesion so as not to cause peeling of the film. At present, it is not easy to obtain a structure that can be improved as much as possible.

Therefore, the purpose of the present disclosure is to have a surface layer that has good adhesion to the base material, suppresses the generation and peeling of cracks, and can exhibit the function according to the design, and has improved oxidation resistance and wear resistance. It is to supply a structure for a protective tube of a thermocouple for an incinerator.

As a result of diligent studies to solve the above problems, the present inventors have found that in a structure for a protective tube of a thermocouple for an incinerator, two or more intermediate layers and ceramics are dispersed as a surface layer on the surface of the base material. The present invention has been completed by finding that the above problems can be solved by providing the existing alloy layer. That is, the structure for the protective tube of the thermocouple for an incinerator according to the present invention has a base material having the shape of the protective tube of the thermocouple for an incinerator and at least two layers bonded to at least the surface side surface of the base material. A structure for a protective tube of a thermocouple for an incinerator having the above intermediate layer and a surface layer bonded to the surface of the intermediate layer , wherein the element A group is Cr as an element contained in the base material. Is an essential element and is at least one element selected from Cr, Fe, W, Nb and Ti, and the element B group is an element contained in either or both of the intermediate layer and the surface layer. , Fe, Ni, Pd, Be, Mg, Al, Si, Ca, Ti, Cr, Zr, Hf, La, Ce, Y and Sc. The surface layer is composed of an alloy containing at least one element A group and at least two elements B group contained in the base material, and contains a total of three or more elements. One of the three or more kinds of elements in total is chromium, and the surface layer has a structure in which ceramics, which is an oxide of one of the elements in the element B group , is dispersed in a phase made of the alloy. It is characterized by having. Here, in the structure for a protective tube of a thermocouple for an incinerator according to the present invention, the surface layer is made of an alloy containing Al, Cr and Fe in the element A group, and the surface layer is the alloy. It is preferable that the phase composed of the elements has a structure in which ceramics, which is an oxide of Al, is dispersed in the element B group. The oxidation resistance and wear resistance of the structure are further improved.

In the structure for a protective tube of a thermocouple for an incinerator according to the present invention, the surface layer side intermediate layer is at least one layer among the intermediate layers, and the surface layer side intermediate layer is a layer having a uniform composition in the film thickness direction. It is preferable that the thickness of each of the surface layer-side intermediate layers is 1 to 200 μm. It is possible to improve the adhesion between the base material side intermediate layer and the surface layer.

In the structure for a protective tube of a thermocouple for an incinerator according to the present invention, the base material side intermediate layer is at least one layer among the intermediate layers, and the base material side intermediate layer is the composition of the base material and the surface layer side. It is preferable that the composition is between the compositions of the intermediate layer and the thickness of each of the base material side intermediate layers is 10 to 200 μm. The adhesion between the surface layer side intermediate layer and the base material can be further improved.

In the structure for a protective tube of a thermocouple for an incinerator according to the present invention, the base material side intermediate layer is at least one layer among the intermediate layers, and the base material side intermediate layer is the composition of the base material and the surface layer side. It is preferably an inclined functional layer that continuously connects the composition of the intermediate layer, and the thickness of each of the base material side intermediate layers is preferably 10 to 200 μm. The adhesion between the surface layer side intermediate layer and the base material can be further improved.

In the structure for a protective tube of a thermocouple for an incinerator according to the present invention, the total thickness of the intermediate layer is preferably 11 to 400 μm. Adhesion between the surface layer and the base material is improved, and peeling and cracking are less likely to occur.

In the structure for a protective tube of a thermocouple for an incinerator according to the present invention, the ceramics dispersed in the surface layer have 40 ceramic particles having a particle size in the range of 1 to 50 μm in a cross section perpendicular to the surface. It is preferable that it occupies% or more. The oxidation resistance and wear resistance of the structure are improved, and a long life can be sufficiently achieved.

In the structure for a protective tube of a thermocouple for an incinerator according to the present invention, the thickness of the surface layer is preferably 10 to 200 μm. The oxidation resistance and wear resistance of the structure are improved, and peeling and cracking in the surface layer are less likely to occur.

In the structure for a protective tube of a thermocouple for an incinerator according to the present invention, the hardness of the structure measured from the surface layer side is preferably 400 Hv or more in Vickers hardness. Wear of the structure can be suppressed.

In the structure for a protective tube of a thermocouple for an incinerator according to the present invention, the intermediate layer contains at least one of Fe, Ni and Pd, and at least one of Fe, Ni and Pd belongs to the element B group. preferable. The surface layer and the base material are firmly bonded to each other, and peeling and cracking are suppressed.

In the structure for a protective tube of a thermocouple for an incinerator according to the present invention, the ceramics dispersed in the surface layer are Be, Mg, Al, Si, Ca, Ti, Cr, Zr, Hf, La, Ce, Y. , Sc, preferably composed of an oxide of at least one element and an unavoidable impurity. The oxidation resistance and wear resistance of the structure are further improved.

The method for manufacturing a protective tube structure for a thermocouple for an incinerator according to the present invention is a method for manufacturing a structure for a protective tube for a thermocouple for an incinerator according to the present invention, which comprises chromium or a chromium alloy and unavoidable impurities. The first step of forming a pretreatment layer containing at least one of the element B group on the surface of the base material by deposition, diffusion or impregnation, and the surface of the pretreatment layer on the surface of the other element B group. The intermediate layer and the surface layer are formed by alloying the base material, the pretreatment layer, and the coating layer with the second step of forming the coating layer by coating with at least one element. The surface layer alloy has at least one element A group derived from the substrate and at least one element B group derived from the pretreatment layer. An alloy containing a total of three or more elements including at least one other element B group derived from the coating layer, and one of the three or more elements in total is chromium, and the surface layer. The ceramics are dispersed in the coating layer, and the ceramics are an oxide of an element derived from the coating layer. Here, in the method for manufacturing a structure for a protective tube of a thermocouple for an incinerator according to the present invention, the first step is a step of forming a pretreatment layer containing Fe of the element B group on the surface of the base material. The second step is a step of forming a coating layer by coating the surface of the pretreatment layer with Al of the element B group, and the alloy of the surface layer is an element derived from the base material. It is an alloy containing Al, Cr and Fe in the group A, and the ceramics are preferably an oxide of Al in the element B group derived from the coating layer.

In the method for manufacturing a structure for a protective tube of a thermocouple for an incinerator according to the present invention, it is preferable that the deposition, diffusion or impregnation is performed by at least one of plating, thermal spraying, diffusion bonding or thermal diffusion. It is possible to form a pretreatment layer having good adhesion to the base material.

In the method for manufacturing a structure for a protective tube of a thermocouple for an incinerator according to the present invention, at least one layer of 1 to 100 μm is deposited, diffused or impregnated on the base material in the first step of forming the pretreatment layer. It is preferable to let it. An intermediate layer and a surface layer having a suitable film thickness can be formed.

In the method for manufacturing a protective tube structure for a thermocouple for an incinerator according to the present invention, the materials to be deposited, diffused or impregnated in the first step of forming the pretreatment layer are Fe, Ni, Pd, Fe alloy and Ni. It preferably contains an alloy or Pd alloy, and unavoidable impurities. An intermediate layer that firmly bonds the surface layer and the base material can be formed.

According to the present disclosure, incinerator has a surface layer that has good adhesion to the base material, suppresses the generation and peeling of cracks, and can exhibit the function according to the design, and has improved oxidation resistance and wear resistance. It is possible to supply a structure for a protective tube of a thermocouple for a furnace.

It is a schematic diagram of the structure for the protection tube of the thermocouple for an incinerator which concerns on this embodiment. It is a cross-sectional SEM image after the pretreatment of Example 1. It is a cross-sectional SEM image after forming the surface layer of Example 1. It is a composition distribution graph in the cross section after the surface layer formation of Example 1. It is a cross-sectional SEM image after the pretreatment of Example 2. It is a cross-sectional SEM image after the surface layer formation of Example 2. It is a composition distribution graph in the cross section after the surface layer formation of Example 2.

Hereinafter, the present invention will be described in detail by showing embodiments, but the present invention is not construed as being limited to these descriptions. The embodiments may be modified in various ways as long as the effects of the present invention are exhibited.

(Structure for protective tube of thermocouple for incinerator)
First, a method for manufacturing a structure for a protective tube of a thermocouple for an incinerator according to the present embodiment will be described. As shown in FIG. 1, the structure 1 for a protective tube of a thermocouple for an incinerator according to the present embodiment has a base material 2 having the shape of a protective tube for a thermocouple for an incinerator and at least the surface side of the base material 2. It has at least two or more intermediate layers 3 bonded to a surface and a surface layer 4 bonded to the surface of the intermediate layer 3.

FIG. 1 shows a form in which the intermediate layer 3 of the protective tube structure 1 has two intermediate layers, a base material side intermediate layer 3a and a surface layer side intermediate layer 3b, but the intermediate layer 3 has three or more. It may be in the form of having an intermediate layer of. Further, FIG. 1 shows a form in which the intermediate layer 3 and the surface layer 4 are provided on the surface side of the protective tube-shaped base material 2, but the intermediate layer 3 and the surface layer are formed on both the surface side of the protective tube and the inner surface side of the tube. It may be a form having 4. Further, the intermediate layer 3 and the surface layer 4 may be provided on the end surface of the opening of the protective tube.

In the structure 1 for the protective tube of the thermocouple for the incinerator according to the present embodiment, the base material 2 is composed of chromium or a chromium alloy and unavoidable impurities, and the surface layer 4 is among the elements A group contained in the base material 2. It is composed of an alloy containing a total of 3 or more elements including at least 1 type and at least 2 types of the element B group, one of the total 3 or more types of elements is chromium, and the surface layer 4 is the alloy. It has a structure in which ceramics, which is an oxide of one of the elements of the element B group , is dispersed in a phase consisting of.

The base material 2 is composed of chromium or a chromium alloy and unavoidable impurities. Cr is essential as the metal contained in the chromium alloy, and it is a metal such as Fe, W, Nb, and Ti. The chromium alloy is characterized in that Cr is contained in the largest amount in atomic percentage (at%) among the contained elements. The chrome alloy is used as a heat-resistant alloy, for example, as a protective tube for a thermocouple that measures the temperature inside an incinerator, but it does not have sufficient oxidation resistance and wear resistance and has a short life. The present invention is effective for solving this problem. For example, it is suitable as a protective tube for a thermocouple used in an environment such as an incinerator where a high temperature and oxidizing atmosphere and convection including scale are generated.

The element A group is an element contained in the base material 2, and is at least one element selected from Cr, Fe, W, Nb and Ti. The element B group is, for example, an element derived from the base material 2 or the pretreatment layer and / or the coating layer in the manufacturing process, and is Fe, Ni, Pd, Be, Mg, Al, Si, Ca, Ti, Cr, Zr. , Hf, La, Ce, Y and Sc. Cr, Fe and Ti belong to both the element A group and the element B group, but when these elements are selected, they may be derived from the base material 2 or derived from the pretreatment layer. It may be derived from the coating layer, the base material 2 and the pretreatment layer, the base material 2 and the coating layer, or the pretreatment layer and the coating layer. It may be derived from the base material, the pretreatment layer and the coating layer. The surface layer 4 is composed of an alloy containing a total of three or more elements including at least one of the element A group and at least two of the element B groups (hereinafter, also referred to as alloy X), but the total is three. One of the elements above the species is always Cr.

The surface layer 4 has a structure in which ceramics, which is an oxide of one of the elements in the element B group , is dispersed in a phase made of alloy X. The oxidation resistance and wear resistance of the structure are further improved. Among the elements B group, the elements to be ceramicized are, for example, Be, Mg, Al, Si, Ca, Ti, Cr, Zr, Hf, La, Ce, Y, Sc. Even if a certain element is made into ceramics, the phase composed of alloy X contains a total of three or more kinds of elements. That is, the ceramicized element is present in both the ceramic and the alloy phase, which is a matrix. The ceramics may also contain oxides of unavoidable impurities.

A preferable combination of the alloy phase X and the ceramics is, for example, a combination of the alloy phase (Cr, Al, Fe) and the ceramics (Al ₂ O ₃ ).

As for the ceramics dispersed in the surface layer 4, it is preferable that the ceramic particles having a particle size in the range of 1 to 50 μm occupy 40% or more in the area ratio in the cross section perpendicular to the surface. In observation with an electron microscope, it is preferable that 80% or more (however, the ratio of the number of particles) contained in the visual field is in the range of the particle size of 1 to 50 μm. The particle size range is more preferably 1 to 40 μm, still more preferably 1 to 20 μm. If the number of ceramic particles having a particle size of less than 1 μm increases, it may not be possible to sufficiently contribute to the improvement of oxidation resistance and wear resistance. On the other hand, when the number of ceramic particles having a particle size of more than 50 μm increases, the ceramics having an excessively large diameter cause desorption and cracks. The area ratio of the ceramic particles is preferably 40% or more, more preferably 50% or more, still more preferably 60% or more. The oxidation resistance and wear resistance of the structure are improved, and a long life can be sufficiently achieved. If the area occupied by the ceramics is less than 40%, it cannot sufficiently contribute to the improvement of oxidation resistance and wear resistance.

The thickness of the surface layer 4 is preferably 10 to 200 μm, more preferably 10 to 150 μm, and even more preferably 10 to 100 μm. The oxidation resistance and wear resistance of the structure are improved, and peeling and cracking in the surface layer are less likely to occur. If the thickness of the surface layer 4 is less than 10 μm, it cannot sufficiently contribute to the improvement of oxidation resistance and wear resistance, and if it exceeds 200 μm, it causes desorption and cracks of the surface layer 4.

In the structure 1 for a protective tube of a thermocouple for an incinerator according to the present embodiment, the surface layer side intermediate layer 3b is at least one layer among the intermediate layers 3, and the surface layer side intermediate layer 3b has a uniform composition in the film thickness direction. It is preferable that the thickness of the intermediate layer 3b on the surface layer side is 1 to 100 μm. The adhesion between the surface layer and the base material side intermediate layer 3a can be improved. In FIG. 1, the form in which the surface layer side intermediate layer 3b is one layer is shown, but two or more layers may be used. When the surface layer side intermediate layer 3b is one layer, it is a layer having a uniform composition in the film thickness direction, and its thickness is preferably 1 to 200 μm, more preferably 1 to 150 μm, and further preferably 1 to 100 μm. Is. When the surface layer side intermediate layer 3b is two or more layers, each layer is a layer having a uniform composition in the film thickness direction, and the thickness thereof is preferably 1 to 200 μm, more preferably 1 to 150 μm, and further preferably. Is 1 to 100 μm. When the surface layer side intermediate layer 3b is two or more layers, each layer has a different composition from each other, but each layer has a uniform composition in the film thickness direction. The "uniformity" of a layer having a uniform composition means that there is no uneven distribution of the composition in the layer in which the blur exceeds ± 10% in the observation with SEM-EDX.

The intermediate layer 3 preferably contains at least one of Fe, Ni, and Pd, and preferably at least one of Fe, Ni, and Pd belongs to the element B group. The surface layer and the base material are firmly bonded to each other, and peeling and cracking are suppressed.

In the structure 1 for a protective tube of a thermocouple for an incinerator according to the present embodiment, the base material side intermediate layer 3a is at least one layer among the intermediate layers 3, and the base material side intermediate layer 3a is the composition and surface of the base material 2. It has a composition between the compositions of the layer-side intermediate layer 3b. Further, more preferably, the base material side intermediate layer 3a is a functionally graded layer that continuously connects the composition of the base material 2 and the composition of the surface layer side intermediate layer 3b. The thickness of each of the base material side intermediate layers 3a is preferably 10 to 200 μm. The adhesion between the surface layer and the base material can be further improved. In FIG. 1, a form in which the base material side intermediate layer 3a is one layer is shown, but two or more layers may be used. When the base material side intermediate layer 3a is one layer, the base material side intermediate layer 3a has a composition between the composition of the base material 2 and the composition of the surface layer side intermediate layer 3b, or the composition and surface of the base material 2 It is an inclined functional layer that continuously connects the composition of the layer-side intermediate layer 3b. When the base material side intermediate layer 3a is two or more layers, the two or more layers as a whole have a composition between the composition of the base material 2 and the composition of the surface layer side intermediate layer 3b, or the composition of the base material 2. It is an inclined functional layer that continuously connects the composition of the intermediate layer 3b on the surface layer side, and some kind of boundary is found between each of the two or more layers. The thickness of each of the base material side intermediate layers 3a is more preferably 10 to 150 μm, still more preferably 10 to 100 μm.

The total thickness of the intermediate layer 3 is preferably 11 to 400 μm. It is more preferably 11 to 300 μm, still more preferably 11 to 200 μm. Adhesion between the surface layer and the base material is improved, and peeling and cracking in the intermediate layer are less likely to occur. If the total thickness of the intermediate layer 3 is less than 11 μm, the intermediate layer cannot fully function as an intermediate layer, and the occurrence of cracks and the like cannot be sufficiently suppressed. If the total thickness of the intermediate layer 3 exceeds 400 μm, the product diameter (hereinafter, also referred to as the diameter) of the protective tube structure increases too much, which hinders the handling as a structure.

In the structure 1 for a protective tube of a thermocouple for an incinerator according to the present embodiment, the hardness of the structure 1 measured from the surface layer 4 side is preferably 400 Hv or more in Vickers hardness. More preferably, it is 500 Hv or more. Wear of the structure can be suppressed. The measurement conditions are that the Vickers hardness is measured according to JIS Z 2244 with a load of 2.5 kg from the surface of the structure 1 on which the surface layer 4 is formed. If the Vickers hardness is less than 400 Hv, it may not be possible to sufficiently contribute to the improvement of wear resistance.

In the structure for a protective tube of a thermocouple for an incinerator according to the present invention, the intermediate layer contains at least one of Fe, Ni and Pd, and at least one of Fe, Ni and Pd belongs to the element B group. preferable. The surface layer and the base material are firmly bonded to each other, and peeling and cracking are suppressed.

The combination of the specific composition of the base material 2, the intermediate layer 3 and the surface layer 4 will be illustrated. The material of the base material 2 is chromium or a chromium alloy. The base material side intermediate layer 3a has a composition or an inclined composition between the base material 2 and the intermediate layer 3b, and Cr "many" from the base material 2 toward the surface layer side intermediate layer 3b in the base material side intermediate layer 3a. The composition changes from "" to Cr "small". Further, in the base material side intermediate layer 3a, the composition changes from Al "small" to Al "many" from the base material 2 toward the surface layer side intermediate layer 3b. Further, in the base material side intermediate layer 3a, the composition changes from Fe "small" to Fe "many" from the base material 2 toward the surface layer side intermediate layer 3b. The surface layer side intermediate layer 3b is a uniform composition layer and contains Fe, Cr, and Al. The abundance ratio (at%) of Fe is higher in the surface layer side intermediate layer 3b than in the base material side intermediate layer 3a. The abundance ratio (at%) of Cr is lower in the surface layer side intermediate layer 3b than in the base material side intermediate layer 3a. The abundance ratio (at%) of Al is higher in the surface layer side intermediate layer 3b than in the base material side intermediate layer 3a. However, the abundance ratio (at%) of Al is higher in the surface layer 4 than in the surface layer side intermediate layer 3b. The alloy X of the surface layer 4 is an Al—Fe—Cr alloy, and the ceramics are alumina particles. Alumina particles are present only in the surface layer 4.

(Manufacturing method of structure for protective tube of thermocouple for incinerator)
Next, a method for manufacturing a structure for a protective tube of a thermocouple for an incinerator according to the present embodiment will be described. The method for manufacturing a structure for a protective tube of a thermocouple for an incinerator according to the present embodiment is to deposit, diffuse or impregnate at least one of the elements B group on the surface of a base material made of chromium or a chromium alloy and unavoidable impurities. A first step of forming a pretreatment layer containing seeds, and a second step of forming a coating layer by coating the surface of the pretreatment layer with an element which is at least one other element in the element B group. It has a third step of forming the intermediate layer and the surface layer by alloying the base material, the pretreatment layer, and the coating layer. In the third step, the alloy of the surface layer is derived from at least one element A group derived from the substrate, at least one element B group derived from the pretreatment layer, and the coating layer. It is an alloy containing a total of 3 or more elements including at least one other element in the element B group, and one of the total 3 or more elements is chromium, and ceramics are dispersed in the surface layer. The ceramics are oxides of elements derived from the coating layer.

(First step)
In the first step, a pretreatment layer is formed on the surface of a base material composed of chromium or a chromium alloy and unavoidable impurities. The pretreatment layer is formed on the surface of the substrate by deposition, diffusion or impregnation. Here, the deposition, diffusion or impregnation is preferably carried out by at least one of plating, thermal spraying, diffusion bonding or thermal diffusion. It is possible to form a pretreatment layer having good adhesion to the base material. Specifically, the pretreatment layer formed by deposition includes, for example, a film formed on the surface of the base material 2 by a plating method or a thermal spraying method. The pretreatment layer formed by diffusion includes, for example, a bonding layer formed on the surface of the base material 2 by diffusion bonding or thermal diffusion. The pretreatment layer contains at least one of the element B group. The element B group is, for example, at least one of Fe, Ni, Pd, Be, Mg, Al, Si, Ca, Ti, Cr, Zr, Hf, La, Ce, Y, and Sc. The pretreatment layer is formed by including at least one of the elements B group in a plating solution, a sprayed powder, a foil, a powder or a melt.

In order to form the pretreatment layer, it is preferable that the material to be deposited, diffused or impregnated contains Fe, Ni, Pd, Fe alloy, Ni alloy or Pd alloy, and unavoidable impurities. An intermediate layer that firmly bonds the surface layer and the base material can be formed.

It is preferable to deposit, diffuse or impregnate the substrate 2 with at least one layer having a thickness of 1 to 100 μm as a pretreatment layer. An intermediate layer and a surface layer having a suitable film thickness can be formed. Two or more pretreatment layers may be formed by sequentially performing deposition, diffusion and impregnation in combination. The total number of pretreatment layers is preferably 1 to 100 μm, more preferably 1 to 75 μm, and even more preferably 1 to 50 μm, even if there are two or more layers. If the pretreatment layer is less than 1 μm, there is no sufficient effect in improving the adhesion, and if it exceeds 100 μm, the diameter increase becomes too large, which hinders handling as a structure.

(Second step)
A coating layer is formed by coating the surface of the pretreatment layer with an element which is at least one other element in the element B group. The element B group is, for example, at least one of Fe, Ni, Pd, Be, Mg, Al, Si, Ca, Ti, Cr, Zr, Hf, La, Ce, Y, and Sc, but is a pretreatment layer. It is selected so that it does not overlap with the elements contained in. For example, among the elements B group, Be, Mg, Al, Si, Ca, Ti, Cr, Zr, Hf, La, Ce, Y, Sc are preferable, and Al, Cr, Ti are more preferable. These elements tend to form ceramics that precipitate in the alloy when alloyed, and tend to contribute to the improvement of durability.

The coating layer is formed by an aluminaization method, a chromaize method, or a titanize method. The thickness of the coating layer is preferably 1 to 100 μm, more preferably 1 to 75 μm, and even more preferably 1 to 50 μm. If the coating layer is less than 1 μm, there is no sufficient effect on the formation of the surface layer, and if it exceeds 100 μm, the diameter increase becomes too large, which hinders handling as a structure. Two or more covering layers may be formed in a range where the total thickness is 1 to 100 μm.

(Third step)
Next, the intermediate layer 3 and the surface layer 4 are formed by alloying the base material 1, the pretreatment layer, and the coating layer. Specifically, it is heated and cooled in an oxidizing atmosphere. The alloy of the surface layer 4 is at least one of the element A group derived from the substrate, at least one of the element B group derived from the pretreatment layer, and the other element B group derived from the coating layer. It is an alloy containing a total of three or more elements including at least one of the above, and one of the three or more elements in total is chromium. Ceramics are dispersed in the surface layer 2, and the ceramics are oxides of elements derived from the coating layer. Cr is always contained in the alloy of the surface layer 4, and the element B group derived from the pretreatment layer is, for example, one kind of the element B group derived from the pretreatment layer when the pretreatment layer is made of metal. When the pretreatment layer is made of an alloy, the number of element B groups derived from the pretreatment layer is two or more. At least one other element B group derived from the coating layer is, for example, when the coating layer is made of metal, the element B group derived from the coating layer is one kind, and when the coating layer is made of an alloy. There are two or more elements B group derived from the coating layer. However, it is preferable that the elements contained in the pretreatment layer and the elements contained in the coating layer do not overlap.

The intermediate layer 3 and the surface layer 4 are not formed separately, but by alloying the base material 1, the pretreatment layer, and the coating layer, the surface layer 4 in which the ceramics are dispersed is formed, and at the same time, the intermediate layer 4 is formed. Layer precipitates. Then, the elements contained in the base material 1, the elements contained in the pretreatment layer, and the elements contained in the coating layer are diffused to be distributed in the intermediate layer 3 and the surface layer 4 at a predetermined ratio. ..

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not construed as being limited to the examples.

(Example 1)
A protective tube (also referred to as a base material) having a hollow tube shape with an outer diameter of 35 mm, an inner diameter of 8 mm, and a length of 200 mm and made of 66Cr-34Fe alloy was prepared. The Vickers hardness of the surface of the protective tube was 380 Hv. The outer peripheral surface of the protective tube was mirror-polished and ultrasonically cleaned in acetone. Next, the protective tube is wrapped with Fe foil, heated at 800 ° C. for 1 hour under pressure using a discharge plasma sintering machine, and the outer peripheral surface of the protective tube is impregnated with Fe to form a pretreatment layer. Formed. FIG. 2 shows a cross-sectional SEM image after the pretreatment. The pretreatment layer consisted of a coating film and an Fe diffusion layer, and the total thickness thereof was 30 μm. By observation with SEM-EDX, it was confirmed that the pretreatment layer contained Cr derived from the substrate and impregnated Fe. The composition was 2 at% for Cr and 98 at% for Fe in atomic percentage. In addition, diffusion of Fe into the substrate was also confirmed (Fe diffusion layer). Next, an Al layer having a thickness of 50 μm was formed as a coating layer on the surface of the pretreatment layer. The coating layer was formed by the calorizing method. Next, a protective tube of Cr alloy as a base material, a pretreatment layer containing iron, and an aluminum coating layer were alloyed. It was heated and cooled in an oxidizing atmosphere. By alloying, the base material side intermediate layer 3a, the surface layer side intermediate layer 3b, and the surface layer 4 were formed. FIG. 3 shows a cross-sectional SEM image after forming the surface layer, FIG. 4 shows a composition distribution graph in the cross section after forming the surface layer, and Table 1 shows the composition of each layer. Further, in the surface layer 4, ceramic particles and an alloy phase were observed. Table 2 shows the composition of the ceramic particles and the alloy phase.

The Vickers hardness of the surface layer 4 was 693 Hv, which was higher than the surface hardness of the base material. The particle size of the ceramic particles in the surface layer 4 was almost the same, and although there were particles smaller than 1 μm and particles larger than 20 μm, the number of them was small, and most of the particles were distributed in the size of 1 to 20 μm. Was. That is, among the particles that can be recognized in the image observation observed with a scanning electron microscope at a magnification of 1000 times, the ceramic particles having a particle size in the range of 1 to 20 μm account for 40% or more in area ratio in the cross section perpendicular to the surface. Occupied. The alloy X of the surface layer 4 was an Al—Fe—Cr alloy, and the ceramics were alumina particles. Alumina particles were present only in the surface layer 4. In the surface layer 4, the ratio of ceramics was 48.71%. For the measurement, particle size measurement software (Quick Grain manufactured by Innotek Co., Ltd.) was used, and the grain to be measured and the portion not to be measured were divided into light and dark by binarization, and the bright part was measured. The area ratio of the ceramics was calculated using only ceramic particles having a particle size of 1 to 20 μm. Fine particles with a particle size of less than 1 μm were excluded because they have a small effect on the area and are difficult to measure. The base material side intermediate layer 3a had a composition between the base material 2 and the surface layer side intermediate layer 3b. The base material side intermediate layer 3a contained Cr, Al, and Fe. The surface layer side intermediate layer 3b was a uniform composition layer. The blur was within ± 10% in the layer.

(Example 2)
The same protective tube as in Example 1 was prepared. Next, using an Fe plating solution, an Fe film having a thickness of 15 μm was formed as a pretreatment layer by an electrolytic plating method. FIG. 5 shows a cross-sectional SEM image after the pretreatment. By observation with SEM-EDX, it was confirmed that the pretreatment layer contained only Fe of the plating film. Next, an Al layer having a thickness of 50 μm was formed as a coating layer on the surface of the pretreatment layer. The coating layer was formed by the calorizing method. Next, a protective tube of Cr alloy as a base material, a pretreatment layer containing iron, and an aluminum coating layer were alloyed. It was heated and cooled in an oxidizing atmosphere. By alloying, the base material side intermediate layer 3a, the surface layer side intermediate layer 3b, and the surface layer 4 were formed. FIG. 6 shows a cross-sectional SEM image after forming the surface layer, FIG. 7 shows a composition distribution graph in the cross section after forming the surface layer, and Table 3 shows the composition of each layer. Further, in the surface layer 4, ceramic particles and an alloy phase were observed. The composition of the ceramic particles and the alloy phase is shown in Table 4.

The Vickers hardness of the surface layer 4 was 645 Hv, which was higher than the surface hardness of the base material. The particle size of the ceramic particles in the surface layer 4 was almost the same, and although there were particles smaller than 1 μm and particles larger than 20 μm, the number of them was small, and most of the particles were distributed in the size of 1 to 20 μm. Was. That is, among the particles that can be recognized in the image observation observed with a scanning electron microscope at a magnification of 1000 times, the ceramic particles having a particle size in the range of 1 to 20 μm account for 40% or more in area ratio in the cross section perpendicular to the surface. Occupied. The alloy X of the surface layer 4 was an Al—Fe—Cr alloy, and the ceramics were alumina particles. Alumina particles were present only in the surface layer 4. In the surface layer 4, the ratio of ceramics was 50.58%. For the measurement, the particle size measurement software was used, and the grain to be measured and the portion not to be measured were divided into light and dark by binarization, and the bright part was measured. The area ratio of the ceramics was calculated using only ceramic particles having a particle size of 1 to 20 μm. Fine particles with a particle size of less than 1 μm were excluded because they have a small effect on the area and are difficult to measure. The base material side intermediate layer 3a has an inclined composition, and the composition changes from Cr “many” to Cr “low” from the base material 2 toward the surface layer side intermediate layer 3b in the base material side intermediate layer 3a. Further, in the base material side intermediate layer 3a, the composition changed from Al "small" to Al "many" from the base material 2 toward the surface layer side intermediate layer 3b. Further, in the base material side intermediate layer 3a, the composition changed from Fe "small" to Fe "many" from the base material 2 toward the surface layer side intermediate layer 3b. The base material side intermediate layer 3a contained Cr, Al, and Fe. The surface layer side intermediate layer 3b was a uniform composition layer. The blur was within ± 10% in the layer.

1 Structure for protective tube of thermocouple for incinerator 2 Base material 3 Intermediate layer 3a Base material side intermediate layer 3b Surface layer side intermediate layer 4 Surface layer

Claims (16)

A base material having the shape of a protective tube for a thermocouple for an incinerator, at least two or more intermediate layers bonded to at least the surface side surface of the base material, and a surface bonded to the surface of the intermediate layer. A structure for a protective tube of a thermocouple for an incinerator having a layer.
The element A group contains Cr as an essential element contained in the base material, and is at least one element selected from Cr, Fe, W, Nb and Ti.
The element B group includes Fe, Ni, Pd, Be, Mg, Al, Si, Ca, Ti, Cr, Zr, Hf, La, as elements contained in either one or both of the intermediate layer and the surface layer. At least two species selected from Ce, Y and Sc.
The base material is composed of chromium or a chromium alloy and unavoidable impurities.
The surface layer is composed of an alloy containing a total of three or more elements including at least one element A group and at least two elements B group contained in the base material, and the total three or more elements. One of them is chromium, and the surface layer is characterized by having a structure in which ceramics, which is an oxide of one element of the element B group , is dispersed in a phase made of the alloy. Structure for protective pipe of thermocouple for incinerator. The surface layer is made of an alloy containing Al, Cr and Fe in the element A group, and the surface layer is a phase made of the alloy in which ceramics which is an oxide of Al in the element B group are dispersed. The structure for a protective tube of a thermocouple for an incinerator according to claim 1, wherein the structure has a ceramic structure. Of the intermediate layers, the surface layer side intermediate layer is at least one layer, the surface layer side intermediate layer is a layer having a uniform composition in the film thickness direction, and each thickness of the surface layer side intermediate layer is 1 to 1. The structure for a protective tube of a thermocouple for an incinerator according to claim 1 or 2 , which is 200 μm. Of the intermediate layers, the base material side intermediate layer is at least one layer, the base material side intermediate layer has a composition between the composition of the base material and the composition of the surface layer side intermediate layer, and the base material is The structure for a protective tube of a thermocouple for an incinerator according to claim 3 , wherein each thickness of the side intermediate layer is 10 to 200 μm. Of the intermediate layers, the base material side intermediate layer is at least one layer, and the base material side intermediate layer is an inclined functional layer that continuously connects the composition of the base material and the composition of the surface layer side intermediate layer. The structure for a protective tube of a thermocouple for an incinerator according to claim 3 , wherein each thickness of the base material side intermediate layer is 10 to 200 μm. The structure for a protective tube of a thermocouple for an incinerator according to any one of claims 1 to 5 , wherein the total thickness of the intermediate layer is 11 to 400 μm. Claims 1 to 6 of the ceramics dispersed in the surface layer are characterized in that ceramic particles having a particle size in the range of 1 to 50 μm occupy 40% or more in area ratio in a cross section perpendicular to the surface. The structure for a protective tube of a thermocouple for an incinerator according to any one of the above. The structure for a protective tube of a thermocouple for an incinerator according to any one of claims 1 to 7 , wherein the surface layer has a thickness of 10 to 200 μm. The structure for a protective tube of a thermocouple for an incinerator according to any one of claims 1 to 8 , wherein the hardness of the structure measured from the surface layer side is 400 Hv or more in Vickers hardness. The intermediate layer according to any one of claims 1 to 9 , wherein the intermediate layer contains at least one of Fe, Ni, and Pd, and at least one of Fe, Ni, and Pd belongs to the element B group. Structure for protective tube of thermocouple for incinerator. The ceramics dispersed in the surface layer are composed of oxides of at least one element of Be, Mg, Al, Si, Ca, Ti, Cr, Zr, Hf, La, Ce, Y and Sc and unavoidable impurities. The structure for a protective tube of a thermocouple for an incinerator according to any one of claims 1, 3 to 10, characterized in that. The method for manufacturing a structure for a protective tube of a thermocouple for an incinerator according to any one of claims 1 to 11 .
The first step of forming a pretreatment layer containing at least one of the element B group by deposition, diffusion or impregnation on the surface of a base material composed of chromium or a chromium alloy and unavoidable impurities.
A second step of forming a coating layer by coating the surface of the pretreatment layer with an element which is at least one other element in the element B group.
It has a third step of forming the intermediate layer and the surface layer by alloying the base material, the pretreatment layer, and the coating layer.
The alloy of the surface layer is composed of at least one element A group derived from the substrate, at least one element B group derived from the pretreatment layer, and an element B group derived from the coating layer. It is an alloy containing a total of 3 or more elements including at least one of them, and one of the total 3 or more elements is chromium.
Ceramics are dispersed in the surface layer,
A method for manufacturing a structure for a protective tube of a thermocouple for an incinerator, wherein the ceramic is an oxide of an element derived from the coating layer. The first step is a step of forming a pretreatment layer containing Fe in the element B group on the surface of the base material.
The second step is a step of forming a coating layer by coating the surface of the pretreatment layer with Al of the element B group.
The alloy of the surface layer is an alloy containing Al, Cr and Fe in the element A group derived from the base material.
The method for manufacturing a structure for a protective tube of a thermocouple for an incinerator according to claim 12, wherein the ceramic is an oxide of Al among the element B group derived from the coating layer. The structure for a protective tube of a thermocouple for an incinerator according to claim 12 or 13 , wherein the deposition, diffusion or impregnation is performed by at least one of plating, thermal spraying, diffusion bonding or thermal diffusion. Production method. The first step of forming the pretreatment layer, according to any one of claims 12 to 14 , wherein at least one layer of 1 to 100 μm is deposited, diffused or impregnated on the substrate. A method for manufacturing a structure for a protective tube of a thermocouple for an incinerator. 13. The method for manufacturing a structure for a protective tube of a thermocouple for an incinerator according to any one of 14 to 15 .

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