Particles for thermal spraying, method for manufacturing thermal spraying particles, and thermal spray coating

Abstract

The present invention provides thermal spray particles that have better high-temperature sulfurization resistance compared to conventional particles. [Solution] A thermal spray particle, which is substantially spherical and contains iron and aluminum, wherein the amount of aluminum contained in the thermal spray particle is in the range of 32% to 48% by mass, and the thermal spray particle has a first region in which the aluminum concentration is in the range of 22% to 37% by mass, and a second region in which the aluminum concentration is in the range of 40% to 50% by mass.

Description

[Technical Field]

[0001] This invention relates to thermal spray particles, a method for producing thermal spray particles, and a thermal spray coating. [Background technology]

[0002] Thermal spraying technology, which uses a heat source to melt and spray particles such as metals or ceramics to form a coating on the surface of an object, is used in a variety of fields.

[0003] For example, Reference 1 describes using thermal spraying powder containing iron and aluminum to perform atmospheric plasma spraying and form a coating of an iron-aluminum intermetallic compound on the surface of stainless steel. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] International Publication No. WO2018 / 116856 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] Reference 1 states that the thermal spray coating described in Reference 1 can be used as a surface treatment coating for the metal constituting the glass transport rolls.

[0006] However, according to the inventors of the present invention, it has been found that the thermal spray coating obtained by the method described in Reference Document 1 does not have very good resistance to high-temperature sulfidation.

[0007] The thermal spray raw material powder in Reference Document 1 is prepared by firing a mixed powder containing an iron-aluminum intermetallic compound powder and an iron-containing powder at a high temperature. According to the inventors of the present invention, it has been found that each particle contained in this thermal spray raw material powder has aluminum-deficient regions. Therefore, it is thought that aluminum-deficient regions will also occur in the thermal spray coating formed using such thermal spray raw material powder, and as a result, good high-temperature sulfidation resistance cannot be obtained.

[0008] Thus, there is still a need for thermal spray coating technology that possesses good resistance to high-temperature sulfurization.

[0009] This invention has been made in view of the above background, and aims to provide thermal spray particles having better high-temperature sulfurization resistance than conventional particles. Furthermore, this invention aims to provide a method for producing such thermal spray particles. Moreover, this invention aims to provide a thermal spray coating having better high-temperature sulfurization resistance than conventional coatings. [Means for solving the problem]

[0010] In this invention, Particles for thermal spraying, It is roughly spherical and contains iron and aluminum. The amount of aluminum contained in the thermal spray particles is in the range of 32% to 48% by mass. The thermal spray particles are, A first region in which the aluminum concentration is in the range of 22% by mass to 37% by mass, A second region where the aluminum concentration is in the range of 40% to 50% by mass, Particles for thermal spraying are provided, having the following characteristics.

[0011] Furthermore, in this invention, A method for producing particles for thermal spraying, A mixture of iron-containing particles to be treated, an aluminum source, a halogenated activator, and a sintering inhibitor is obtained to obtain mixed particles. Heat the mixed particles, and utilize the gaps between the sintering inhibitors formed by the sintering inhibitors to perform calorization treatment on the particles to be treated, and obtain a treated mixture containing aluminum-permeated particles. A manufacturing method is provided, which removes the sintering inhibitor from the treated mixture to obtain particles for thermal spraying.

[0012] Furthermore, in the present invention, A thermal spray coating containing an aluminum-iron alloy, The mass ratio (Al / Fe) of aluminum to iron contained in one flat particle is in the range of 32 / 68 to 48 / 52. A thermal spray coating is provided, in which acicular or spherical oxides with a maximum dimension in the range of 0.1 μm to 2 μm are mixed in the flat particles.

Advantages of the Invention

[0013] In the present invention, particles for thermal spraying having better high-temperature sulfidation resistance than the prior art can be provided. Also, in the present invention, a manufacturing method for such particles for thermal spraying can be provided. Furthermore, in the present invention, a thermal spray coating having better high-temperature sulfidation resistance than the prior art can be provided.

Brief Description of the Drawings

[0014] [Figure 1] It is a diagram schematically showing a cross-section of particles for thermal spraying according to an embodiment of the present invention. [Figure 2] It is a diagram schematically showing a cross-section of particles for thermal spraying according to another embodiment of the present invention. [Figure 3] It is a diagram schematically showing a cross-section of particles for thermal spraying according to still another embodiment of the present invention. [Figure 4] It is a diagram schematically showing a cross-section of particles for thermal spraying according to still another embodiment of the present invention. [Figure 5] It is a diagram schematically showing an example of the flow of a manufacturing method of particles for thermal spraying according to an embodiment of the present invention. [Figure 6] It is a diagram schematically showing the state where the reaction vessel is filled with mixed particles. [Figure 7] This figure shows a cross-section (a) of a thermal spray particle (sample 1) obtained in one embodiment of the present invention, and the distribution of aluminum contained in the cross-section (b). [Figure 8] This figure shows a cross-section (a) of thermal spray particles (Sample 2) obtained in another embodiment of the present invention, and the distribution of aluminum contained in the cross-section (b). [Figure 9] This figure shows a cross-section (a) of thermal spray particles (Sample 3) obtained in yet another embodiment of the present invention, and the distribution of aluminum contained in the cross-section (b). [Figure 10] This figure shows a cross-section (a) of thermal spray particles (sample 4) obtained in yet another embodiment of the present invention, and the distribution of aluminum contained in the cross-section (b). [Figure 11] This figure shows a cross-section of a thermal spray particle (Sample 5) obtained in yet another embodiment of the present invention, and the distribution of each element contained in the cross-section. [Figure 12] This is a cross-sectional photograph of a thermal spray coating in one embodiment of the present invention. [Figure 13] Figure 12 shows a magnified cross-sectional photograph of the thermal spray coating. [Figure 14] Figure 12 shows the EPMA analysis results of a portion of the cross-section of the thermal spray coating. [Figure 15] This is an EDX mapping diagram of sulfur (S) after a high-temperature corrosion resistance test of a thermal spray coating in one embodiment of the present invention. [Figure 16] This is an EDX mapping diagram of sulfur (S) after a high-temperature corrosion resistance test of another thermal spray coating according to one embodiment of the present invention. [Figure 17] This is an EDX mapping diagram of sulfur (S) after a high-temperature corrosion resistance test of the thermal spray coating in the comparative example. [Figure 18] This is an electron microscope image showing a cross-section of sample 21 after testing. [Modes for carrying out the invention]

[0015] The following describes one embodiment of the present invention.

[0016] As mentioned above, the particles contained in the thermal spraying raw material powder described in Reference 1 contain aluminum-deficient regions, and therefore, aluminum-deficient regions also occur in the resulting thermal spray coating. Consequently, the thermal spray coating in Reference 1 cannot be said to have very good resistance to high-temperature sulfidation.

[0017] In contrast, in one embodiment of the present invention, Particles for thermal spraying, It is roughly spherical and contains iron and aluminum. The amount of aluminum contained in the thermal spray particles is in the range of 32% to 48% by mass. The thermal spray particles are, A first region in which the aluminum concentration is in the range of 22% by mass to 37% by mass, A second region where the aluminum concentration is in the range of 40% to 50% by mass, Particles for thermal spraying are provided, having the following characteristics.

[0018] A thermal spray particle according to one embodiment of the present invention has a first region with a low aluminum concentration and a second region with a high aluminum concentration. However, even in the first region of this thermal spray particle, aluminum is present at a concentration of 22% by mass or more. The first region mainly consists of an FeAl phase, and the second region mainly consists of a mixed phase of FeAl2 and FeAl.

[0019] In one embodiment of the present invention, thermal spray particles contain aluminum throughout the entire particle. Therefore, when a thermal spray coating is formed using such thermal spray particles, the occurrence of aluminum-deficient regions is significantly suppressed, and a thermal spray coating with better high-temperature sulfidation resistance than conventional coatings can be provided.

[0020] Furthermore, in one embodiment of the present invention, A method for producing particles for thermal spraying, A mixture of iron-containing particles to be treated, an aluminum source, a halogenated activator, and a sintering inhibitor is obtained to obtain mixed particles. The mixed particles are heated, and the gaps between the sintering inhibitors formed by the sintering inhibitors are used to calorify the particles to be treated, thereby obtaining a treated mixture containing aluminum-impregnated particles. A manufacturing method is provided for obtaining sprayable particles by removing the sintering inhibitor from the treated mixture.

[0021] In order to produce thermal spray particles having the characteristics described above, in the method according to one embodiment of the present invention, the particles to be treated are subjected to aluminum impregnation treatment using calorization.

[0022] However, if calorizing treatment is simply applied to particulate particles, the thermite reaction is likely to occur. This is because aluminum reacts with the trace amounts of oxygen contained in the treated particles.

[0023] Furthermore, when the thermite reaction occurs, the processing environment becomes extremely hot, and the resulting mixture (hereinafter referred to as the "processed mixture") becomes a clumpy mass in which all the particles are firmly bonded together.

[0024] Furthermore, once such a lumpy processed mixture is formed, it becomes impossible to separate the sintering inhibitor from the processed mixture. Consequently, there is a problem in that it becomes impossible to recover the calorified spray particles from the processed mixture.

[0025] In contrast, in the method according to one embodiment of the present invention, calorizing treatment is performed by utilizing the gaps formed between the sintering inhibitors.

[0026] In this case, even if a thermite reaction occurs within the reaction system, the likelihood of the treated particles adhering to the anti-sintering agent and / or other treated particles can be greatly reduced. This is because the aforementioned gaps serve to provide numerous "small compartments" for the reactions that are separated from one another.

[0027] As a result, the treated mixture produced after calorizing is not in a mass-like aggregate form, but rather the spray particles and sintering inhibitor are separated from each other.

[0028] Therefore, in the method according to one embodiment of the present invention, the anti-sintering agent can be removed from the treated mixture relatively easily after the calorizing treatment. In addition, this allows for the relatively easy separation and recovery of the spray particles.

[0029] Thus, in the method according to one embodiment of the present invention, calorification treatment can be properly carried out on the particles to be treated, and thermal spray particles containing aluminum throughout can be obtained.

[0030] Furthermore, in one embodiment of the present invention, A thermal spray coating containing an aluminum-iron alloy, The mass ratio of aluminum to iron (Al / Fe) contained in a single flattened particle is in the range of 32 / 68 to 48 / 52. A thermal spray coating is provided, in which needle-shaped or spherical oxides with a maximum dimension in the range of 0.1 μm to 2 μm are mixed within the flattened particles.

[0031] The thermal spray coating according to one embodiment of the present invention not only has good resistance to high-temperature sulfurization, but also has good strength because fine oxides are present within the flattened particles.

[0032] (Particles for thermal spraying according to one embodiment of the present invention) Next, with reference to the drawings, we will describe in more detail the sprayable particles according to one embodiment of the present invention.

[0033] Figure 1 schematically shows a cross-section of a thermal spray particle (hereinafter referred to as "the first particle") according to one embodiment of the present invention.

[0034] Note that the cross-section of the first particle shown in Figure 1 is the "maximum cross-section." In this application, the "maximum cross-section" means the cross-section passing through the center of the particle. For example, if the particle is spherical, the diameter of the "maximum cross-section" is substantially the same as the diameter of the particle.

[0035] As shown in Figure 1, the first particle 100 has a substantially spherical shape. In this application, "substantially spherical" or "substantially spherical" is not limited to a pure sphere, but includes ellipses in which the dimensional difference in the mutually orthogonal X-axis and Y-axis directions is within ±20%.

[0036] The cross-section (maximum cross-section; the same applies hereafter) of the first particle 100 has two regions with different aluminum concentrations. Hereafter, the region with a relatively low aluminum concentration will be referred to as the "first region 110," and the region with a relatively high aluminum concentration will be referred to as the "second region 120."

[0037] As shown in Figure 1, the first particle 100 has a core portion that constitutes a first region 110 and an outer layer that constitutes a second region 120. The second region 120 is arranged to surround the first region 110.

[0038] In the example shown in Figure 1, the boundary between the first region 110 and the second region 120 is clearly depicted by a line, but it is also common to see cases where the boundary between the two regions is ambiguous.

[0039] The first particle 100 contains iron and aluminum, and the concentration of aluminum contained throughout the cross-section of the first particle 100 is in the range of 32 wt% to 48 wt%. The concentration of aluminum may also be in the range of, for example, 35 wt% to 45 wt%.

[0040] Furthermore, the iron concentration contained throughout the cross-section of the first particle 100 may be, for example, in the range of 52 wt% to 68 wt%. However, if the first particle 100 contains elements described later, the iron concentration will decrease from this range.

[0041] The concentrations of aluminum and iron contained throughout the cross-section of the first particle 100 can be measured by energy-dispersive X-ray (EDX) analysis or electron beam microanalysis (EPMA) analysis.

[0042] The first particle 100 may contain elements other than iron and aluminum (hereinafter referred to as the "third element"). The third element may include, for example, at least one of chromium, nickel, manganese, phosphorus, sulfur, and carbon.

[0043] The third element may be present in a total amount ranging from 0.05 wt% to 1 wt%. If the first particle 100 contains the third element, the iron concentration will be the aforementioned range (52 wt% to 68 wt%) minus the concentration of the third element. In other words, the third element exists as a substitute for iron or as an unavoidable impurity.

[0044] The first region 110 of the first particle 100 mainly contains the FeAl phase. The concentration of aluminum in the first region 110 is in the range of 22 wt% to 37 wt%. The concentration of aluminum may also be in the range of, for example, 25 wt% to 35 wt%.

[0045] On the other hand, the second region 120 of the first particle 100 mainly contains a mixed phase of FeAl phase and FeAl2 phase. The concentration of aluminum contained in the second region 120 is in the range of 40 wt% to 50 wt%. The concentration of aluminum may also be in the range of, for example, 42 wt% to 48 wt%.

[0046] Furthermore, the aluminum concentrations in the first region 110 and the second region 120 of the first particle 100 can be measured by EDX analysis or EPMA analysis of selected portions. In addition, the constituent phases contained in the first region 110 and the second region 120 can be identified by X-ray diffraction analysis.

[0047] In the cross-section of the first particle 100, the area occupied by the second region 120 is, for example, 5% or more. This area percentage can be evaluated by using an SEM backscattered electron image of the cross-section and binarizing the contrast of the Al concentration.

[0048] The average particle size of the first particle 100 is in the range of 5 μm to 200 μm. Preferably, the average particle size of the first particle 100 is in the range of 10 μm to 100 μm.

[0049] The average particle size of the thermal spray particles according to one embodiment of the present invention is measured by the method specified in JIS Z 8801, as described later.

[0050] The first particle 100 contains aluminum throughout its entirety. Therefore, when the first particle 100 is used as a spray particle to form a spray coating, the occurrence of aluminum-deficient regions can be significantly suppressed.

[0051] Therefore, the first particle 100 can be used as a thermal spray particle when forming a thermal spray coating with excellent resistance to high-temperature sulfurization.

[0052] (Particles for thermal spraying according to another embodiment of the present invention) Next, with reference to Figure 2, sprayable particles according to another embodiment of the present invention will be described.

[0053] Figure 2 schematically shows a cross-section of a thermal spray particle (hereinafter referred to as the "second particle") according to another embodiment of the present invention. The cross-section shown in Figure 2 is the "maximum cross-section" of the second particle.

[0054] As shown in Figure 2, the second particle 200 has a substantially spherical shape. Furthermore, the cross-section of the second particle 200 has two regions with different aluminum concentrations.

[0055] However, in the case of the second particle 200, unlike the first particle 100 mentioned above, the two regions are arranged in a "mottled" pattern.

[0056] In other words, in the second particle 200, the second region 220, where the aluminum concentration is relatively high, is distributed in an "island-like" manner relative to the "sea" of the first region 210, where the aluminum concentration is relatively low.

[0057] In other words, the entire cross-section of the second particle 200 is composed of a "sea-like" first region 210 and an "island-like" second region 220. In the case of the second particle 200, both the first region 210 and the second region 220 exist even at the outermost surface.

[0058] The second particle 200 contains iron and aluminum, and the concentration of aluminum contained throughout the cross-section of the second particle 200 is in the range of 32 wt% to 48 wt%. The concentration of aluminum may also be in the range of, for example, 35 wt% to 45 wt%.

[0059] Furthermore, the iron concentration contained throughout the cross-section of the second particle 200 may be in the range of, for example, 52 wt% to 68 wt%. However, as mentioned above, the iron concentration will decrease from this range if the second particle 200 contains a third element.

[0060] The first region 210 of the second particle 200 mainly contains the FeAl phase. The concentration of aluminum in the first region 210 is in the range of 22 wt% to 37 wt%. The concentration of aluminum may also be in the range of, for example, 25 wt% to 35 wt%.

[0061] On the other hand, the second region 220 of the second particle 200 mainly contains a mixed phase of FeAl phase and FeAl2 phase. The concentration of aluminum contained in the second region 220 is in the range of 40 wt% to 50 wt%. The concentration of aluminum may also be in the range of, for example, 42 wt% to 48 wt%.

[0062] The average particle size of the second particle 200 is in the range of 5 μm to 200 μm. Preferably, the average particle size of the second particle 200 is in the range of 10 μm to 100 μm.

[0063] In the cross-section of the second particle 200, the proportion of the area occupied by the second region 220 is, for example, 5% or more.

[0064] In the case of the second particle 200, aluminum is contained throughout the entire particle. Therefore, when the second particle 200 is used as a spray particle to form a spray coating, the occurrence of aluminum-deficient regions can be significantly suppressed.

[0065] Therefore, the second particle 200 can be used as a thermal spray particle when forming a thermal spray coating with excellent resistance to high-temperature sulfurization.

[0066] (Particles for thermal spraying according to yet another embodiment of the present invention) Next, with reference to Figure 3, we will describe sprayable particles according to yet another embodiment of the present invention.

[0067] Figure 3 schematically shows a cross-section of a thermal spray particle (hereinafter referred to as the "third particle") according to yet another embodiment of the present invention. The cross-section shown in Figure 3 is the "maximum cross-section" of the third particle.

[0068] As shown in Figure 3, the third particle 300 has the same morphology as the first particle 100 shown in Figure 1. That is, the third particle 300 has a core portion that constitutes a first region 310 with a relatively low aluminum concentration, and an outer layer that constitutes a second region 320 with a relatively high aluminum concentration.

[0069] However, unlike the first particle 100 mentioned above, the third particle 300 has rod-shaped (or spherical) precipitates 330.

[0070] The precipitate 330 is distributed in a roughly ring shape centered on the center of the third particle 300. The radial dimensions of each precipitate 330 are, for example, in the range of 0.1 μm to 2 μm.

[0071] The precipitate 330 consists of aluminum oxide or a composite oxide of aluminum and iron.

[0072] In the case of the third particle 300, aluminum is contained throughout the entire particle. Therefore, when the third particle 300 is used as a spray particle to form a spray coating, the occurrence of aluminum-deficient regions can be significantly suppressed.

[0073] Therefore, the third particle 300 can be used as a thermal spray particle when forming a thermal spray coating with excellent resistance to high-temperature sulfurization.

[0074] Furthermore, in the third particle 300, the precipitate 330 acts in a direction that suppresses dislocation slip, so it is expected that high strength will be obtained.

[0075] (Particles for thermal spraying according to yet another embodiment of the present invention) Next, with reference to Figure 4, we will describe sprayable particles according to yet another embodiment of the present invention.

[0076] Figure 4 schematically shows a cross-section of a thermal spray particle (hereinafter referred to as the "fourth particle") according to yet another embodiment of the present invention. The cross-section shown in Figure 4 is the "maximum cross-section" of the fourth particle.

[0077] As shown in Figure 4, the fourth particle 400 has a similar morphology to the second particle 200 shown in Figure 2. That is, the fourth particle 400 has a first region 410, which is a "sea," where the aluminum concentration is relatively low, and a second region 420 (island), where the aluminum concentration is relatively high.

[0078] However, unlike the second particle 200 mentioned above, the fourth particle 400 has rod-shaped (or spherical) precipitates 430.

[0079] The precipitates 430 are distributed in a roughly ring shape, centered on the fourth particle 400. The radial dimensions of each precipitate 430 are, for example, in the range of 0.1 μm to 2 μm.

[0080] The precipitate 430 consists of aluminum oxide or a composite oxide of aluminum and iron.

[0081] In the case of the fourth particle 400, aluminum is contained throughout the entire particle. Therefore, when the fourth particle 400 is used as a spray particle to form a spray coating, the occurrence of aluminum-deficient regions can be significantly suppressed.

[0082] Therefore, the fourth particle 400 can be used as a thermal spray particle when forming a thermal spray coating with excellent resistance to high-temperature sulfurization.

[0083] Furthermore, in the fourth particle 400, the precipitate 430 acts in a direction that suppresses dislocation slip, so it is expected that high strength will be obtained.

[0084] The characteristics of thermal spray particles according to one embodiment of the present invention have been explained above, using the first particle 100 to the fourth particle 400 as examples.

[0085] However, the first particles 100 to the fourth particles 400 are merely examples, and the sprayable particles according to one embodiment of the present invention may have different forms.

[0086] For example, the thermal spray particles according to one embodiment of the present invention may have a form that combines the particle form shown in Figure 1 and the particle form shown in Figure 2.

[0087] In this case, in the core-shell particle morphology shown in Figure 1, the second region may be distributed within the first region, or conversely, the first region may be distributed within the second region.

[0088] Generally, in the particle manufacturing process described later, if the heat treatment temperature is relatively low and / or the heating time is relatively short, there is a higher tendency to obtain the first particle 100 as shown in Figure 1. Conversely, in the particle manufacturing process described later, if the heat treatment temperature is relatively high and / or the heating time is relatively long, there is a tendency to obtain the second particle 200 as shown in Figure 2.

[0089] (Method for producing thermal spray particles according to one embodiment of the present invention) Next, with reference to Figures 5 and 6, a method for producing thermal spray particles according to one embodiment of the present invention will be described.

[0090] Figure 5 schematically shows an example of a flow chart for a method of producing thermal spray particles according to one embodiment of the present invention.

[0091] As shown in Figure 5, a method for producing thermal spray particles according to one embodiment of the present invention (hereinafter referred to as the "first manufacturing method") is: A step (S110) to prepare mixed particles by mixing iron-containing particles to be treated, an aluminum source, an activator containing a halide, and a sintering inhibitor, The process (S120) involves heating the mixed particles and using the gaps between each sintering inhibitor formed by the sintering inhibitor to calorify the particles to be treated, thereby obtaining a treated mixture containing aluminum-impregnated particles. The process of removing the sintering inhibitor from the treated mixture to obtain sprayable particles (S130), It holds.

[0092] The following provides a more detailed explanation of each step.

[0093] (Step S110) First, the mixed particles are prepared.

[0094] The mixed particles include the particles to be treated, an aluminum source, an activator, and a sintering inhibitor. Each of these particles is described below.

[0095] (Particles to be treated) The particles to be treated contain iron as their main component. These particles may be, for example, iron, iron-aluminum alloy, or stainless steel. These particles may also contain manganese, phosphorus, sulfur, and carbon as unavoidable impurities.

[0096] The average particle size of the particles to be treated is selected to be significantly smaller than the average particle size of the sintering inhibitor described later. For example, the average particle size of the particles to be treated may be 0.29 times or less the average particle size of the sintering inhibitor.

[0097] The particle size of the particles to be treated may be, for example, 10 μm to 600 μm.

[0098] In this application, "average particle size" refers to the measurement method specified in JIS Z 8801.

[0099] Specifically, several sieves with different mesh sizes are stacked in order from the smallest to the largest, and the particles to be measured are vibrated at a constant amplitude for a certain period of time to separate the particles. Next, the mass of the particles remaining on each sieve is measured, and the particle size distribution of the particle mass is graphed. The particle size corresponding to 50% of the cumulative value of the obtained particle size distribution is defined as the "average particle size."

[0100] However, the particle size of the treated particles is expressed within the range of minimum and maximum values.

[0101] (Aluminum source) The aluminum source may be aluminum metal particles or aluminum alloy particles.

[0102] The average particle size of the aluminum source is selected to be significantly smaller than the average particle size of the sintering inhibitor. For example, the average particle size of the aluminum source may be 0.29 times or less the average particle size of the sintering inhibitor.

[0103] The average particle size of the aluminum source may be in the range of, for example, 10 μm to 200 μm.

[0104] Furthermore, it is preferable that the average particle size of the aluminum source be smaller than the average particle size of the particles to be treated.

[0105] (Activating agent) The activator plays a role in promoting the calorification process of the particles to be treated by forming a vapor of metal halide.

[0106] The activator includes, for example, at least one of ammonium chloride, iron chloride, aluminum chloride, iron fluoride, and aluminum fluoride. The activator is added, for example, in an amount ranging from 0.1% to 2% by mass relative to the total mixed particles.

[0107] (Sintering inhibitor) The anti-sintering agent may contain at least one of alumina, kaolin, and silicon dioxide.

[0108] The sintering inhibitor may have at least one shape selected from the group consisting of, for example, spherical, triangular pyramidal, triangular prismatic, tetrahedral, conical, and cylindrical shapes.

[0109] Furthermore, the anti-sintering agent has a sufficiently large average particle size compared to the particles being treated and the aluminum source.

[0110] For example, as mentioned above, the average particle size of the sintering inhibitor is selected to be at least 3.4 times the average particle size of the treated particles and the aluminum source.

[0111] For example, if the anti-sintering agent is approximately spherical, the average particle size of the anti-sintering agent may be in the range of 500 μm to 5000 μm.

[0112] (mixed particles) Mixed particles are prepared by mixing the above components.

[0113] The ratio of the total aluminum component in the mixed particles to the iron component in the treated particles (Al / Fe) is, for example, in the range of 32 / 68 to 48 / 52 by mass ratio.

[0114] Furthermore, the amount of treated particles included in the total mixed particles is, for example, in the range of 10% to 30% by mass. Also, the amount of aluminum source included in the total mixed particles is, for example, in the range of 8% to 18% by mass. Furthermore, the amount of sintering inhibitor included in the total mixed particles is, for example, in the range of 50% to 80% by mass.

[0115] (Process S120) Next, the mixed particles prepared in step S110 are heat-treated. For this reason, the mixed particles may be packed into the reaction vessel.

[0116] By heating the reaction vessel, the particles to be treated undergo calorification. That is, aluminum generated from the aluminum source diffuses and penetrates into the particles to be treated, forming aluminum-permeated particles.

[0117] Here, if the aluminum source included in the mixed particles contains highly reactive aluminum, such as aluminum particles, the likelihood of a thermite reaction occurring between the mixed particles increases when the reaction vessel is heated. This is because the aluminum reacts with trace amounts of oxygen contained in the particles being treated, reducing them.

[0118] When such a thermite reaction occurs, the reaction vessel becomes extremely hot, and the resulting mixture, or "treated mixture," takes on a lumpy form in which all the particles are firmly bound together. Furthermore, once such a lumpy treated mixture is formed, a problem may arise in that it becomes impossible to separate the sintering inhibitor from the treated mixture afterward.

[0119] In contrast, the first manufacturing method can significantly suppress the formation of lumpy mixtures.

[0120] This feature will be explained below with reference to Figure 6.

[0121] Figure 6 schematically shows an example of the configuration when the mixed particles are filled into a reaction vessel. As shown in Figure 6, the reaction vessel is filled with the components of the mixed particles: the particles to be treated 352, the aluminum source 354, the activator, and the sintering inhibitor 358.

[0122] Note that the activator is omitted in Figure 6. Also, it is assumed here that each component of the mixed particles is spherical.

[0123] Here, the diameter of the sintering inhibitor 358 (φ S (represented by) the diameter (φ) of the particles to be processed 352. Fe (represented by) and the diameter (φ) of the aluminum source 354 Al If the amount is sufficiently large compared to the amount shown, a void 365 is created between adjacent sintering inhibitors 358. The treated particles 352 and the aluminum source 354 are then placed in the void 365 created by the sintering inhibitor 358.

[0124] When the reaction vessel is heated with the mixed particles arranged in this manner, even if a thermite reaction occurs within the reaction vessel, the likelihood of the treated particles 352 adhering to the sintering inhibitor 358 and / or other treated particles 352 can be greatly reduced. This is because the voids 365 serve to provide numerous reaction "small compartments" for the calorizing process.

[0125] As a result, the treated mixture produced after heat treatment is not in a mass-like aggregate form, but rather the aluminum-impregnated particles and the sintering inhibitor 358 are separated from each other. Therefore, in subsequent processes, it becomes possible to recover the aluminum-impregnated particles, i.e., the particles for thermal spraying, from the treated mixture.

[0126] Table 1 below shows examples of mixed particle fillings that can produce the above effects.

[0127] Here, the particles to be treated 352 are spherical iron particles (density 7.87 g / cm³). 3 ) and aluminum source 354 is made into spherical aluminum particles (density 2.70 g / cm³).3 ) and the activator is spherical ammonium chloride particles (density 1.527 g / cm 3 ), and the sintering inhibitor 358 is assumed to be spherical alumina (density 4.00 g / cm 3 ).

[0128] Also, assuming the average particle diameter φ of the sintering inhibitor 358 is 1000 μm, the average particle diameter φ of the particles to be treated 352 is 38 μm to 75 μm, the average particle diameter φ of the aluminum source 354 is 50 μm, and the average particle diameter of the activator is 10 μm. S and the average particle diameter φ of the particles to be treated 352 is 38 μm to 75 μm, the average particle diameter φ of the aluminum source 354 is 50 μm, and the average particle diameter of the activator is 10 μm. Fe and the average particle diameter φ of the aluminum source 354 is 50 μm, and the average particle diameter of the activator is 10 μm. Al are assumed to be 50 μm and 10 μm respectively.

[0129]

Table 1

[0130] Assuming that the entire void 365 (100%) is filled with the particles to be treated 352, the aluminum source 354, and the activator, as an example, the amount of the particles to be treated 352 is 2.216 kg, the amount of the aluminum source 354 is 1.491 kg, and the amount of the activator is 0.067 kg.

[0131] Similarly, when 85% of the void 365 is filled with the particles to be treated 352, the aluminum source 354, and the activator, the amount of the particles to be treated 352 can be calculated as 1.879 kg, the amount of the aluminum source 354 is 1.253 kg, and the amount of the activator is 0.066 kg.

[0132] In the above calculations, the Al / Fe ratio in the mixed particles is assumed to be 40 / 60 (mass ratio). Also, the amount of the activator is assumed to be 0.5 wt% of the whole.

[0133] Even when the sintering inhibitor 358 is filled in a manner other than the densest packing, the amounts of each component can be calculated in the same way.

[0134] Furthermore, if the sintering inhibitor 358 is spherical, in order to obtain the aforementioned effects, it is preferable that the filling rate of the sintering inhibitor 358 be in the range of 55% to 74% (when closely packed).

[0135] Furthermore, the packing rate of the treated particles 352, aluminum source 354, and activator in the voids 365 created by the sintering inhibitor 358 is preferably in the range of 60% to 100%.

[0136] However, in practice, the sintering inhibitor 358 may be non-spherical, so a suitable range for the filling rate of the sintering inhibitor 358 is assumed to be 50% to 80%.

[0137] Thus, in the first manufacturing method, the voids 365 that form between the sintering inhibitors 358 can be used to perform the calorification treatment on the particles 352 to be treated.

[0138] The treatment atmosphere for calorizing can be any inert atmosphere that does not contain oxygen, such as an argon gas atmosphere.

[0139] The processing temperature is not particularly limited, as long as aluminum diffusion and penetration occur within the particles being processed. The processing temperature may be, for example, in the range of 800°C to 1100°C.

[0140] There are no specific limitations on processing time, but it is typically in the range of 1 to 10 hours.

[0141] As mentioned above, the lower the processing temperature and / or the shorter the processing time, the more likely it is that particles like the first particle 100 described above, in which the second region 120 is layered around the first region 110, will be obtained. Conversely, the higher the processing temperature and / or the longer the processing time, the more likely it is that particles like the second particle 200 described above will be obtained.

[0142] (Step S130) Next, the sintering inhibitor is removed from the powdered treated mixture formed in step S120. The sintering inhibitor may be removed, for example, by sieving the treated mixture using a sieve that allows only particles with a small average particle size to pass through.

[0143] As mentioned above, the first manufacturing method can significantly suppress the temperature increase of the reaction system due to the accumulation of excess heat that may occur in the thermite reaction.

[0144] Therefore, in the first manufacturing method, the sintering inhibitor and the spray particles can be separated relatively easily.

[0145] In the first manufacturing method, aluminum is permeated throughout the entire particle to be treated by the calorizing process. Therefore, in the first manufacturing method, it is possible to form sprayable particles in which the aluminum-deficient region is significantly reduced.

[0146] (Example of application of thermal spray particles according to one embodiment of the present invention) The thermal spray particles according to one embodiment of the present invention, having the characteristics described above, can be used when forming thermal spray coatings on the surfaces of various objects to be treated.

[0147] The thermal spray particles according to one embodiment of the present invention contain aluminum throughout the entire particle. Therefore, when a thermal spray coating is formed using the thermal spray particles according to one embodiment of the present invention, a thermal spray coating of Fe-Al alloy can be formed in which the aluminum-deficient region is significantly suppressed.

[0148] For example, in a thermal spray coating, the mass ratio (Al / Fe) of aluminum to iron contained in a single flat particle may be in the range of 32 / 68 to 48 / 52.

[0149] Such Fe-Al alloy thermal spray coatings have significantly suppressed aluminum-deficient regions, resulting in better high-temperature sulfidation resistance compared to conventional coatings. For example, a thermal spray coating formed using thermal spray particles according to one embodiment of the present invention can be applied to the surface of metal constituting glass conveying rolls that are exposed to high-temperature sulfidation environments.

[0150] Furthermore, when forming a thermal spray coating using thermal spray particles according to one embodiment of the present invention, the type of thermal spray is not particularly limited.

[0151] For example, spray particles according to one embodiment of the present invention can be applied to various spraying methods, such as plasma spraying, explosive spraying, and high-velocity flame (HVOF) spraying.

[0152] In particular, when thermal spraying is performed using a fourth particle 400 containing precipitates 430 as shown in Figure 4 above, a thermal spray coating is formed in which oxide particles are dispersed within each flattened particle. The oxide particles may have a needle-like or spherical shape and their maximum dimensions may be in the range of 0.1 μm to 2 μm.

[0153] Such thermal spray coatings are expected to exhibit relatively high strength. [Examples]

[0154] Examples of the present invention will be described below. In the following description, Examples 1 to 5 and Examples 21 to 22 are examples, while Examples 11 and 31 are comparative examples.

[0155] (Example 1) The following method was used to prepare the particles for thermal spraying.

[0156] First, a mixed particle was prepared by thoroughly mixing iron particles (13.20% by mass) as the particles to be treated, aluminum particles (9.96% by mass) as the aluminum source, ammonium chloride particles (0.5% by mass) as the activator, and spherical alumina particles (76.34% by mass) as the anti-sintering agent.

[0157] The iron particles had a particle size of 10 μm to 75 μm, the aluminum particles had an average particle size of 50 μm, the activator had a particle size of 10 μm, and the alumina particles had a particle size of 1000 μm.

[0158] This mixed particle was packed into a heat-resistant container. Calculations showed that the alumina particles filled 74% of the container. Iron particles, aluminum particles, and ammonium chloride particles were then packed to occupy 85% of the remaining 26% of the void.

[0159] Next, the atmosphere inside the heat-resistant container was replaced with an argon atmosphere, and then the heat-resistant container was heated to 1000°C. After being held at 1000°C for 10 hours, the heat-resistant container was furnace-cooled.

[0160] Subsequently, the treated mixture was removed from the heat-resistant container and passed through a #32 mesh sieve to remove the alumina powder. This yielded spherical particles (hereinafter referred to as "particles according to Example 1").

[0161] (Example 2) Using the same method as in Example 1, calorified iron particles (hereinafter referred to as "particles related to Example 2") were prepared.

[0162] However, in this Example 2, the iron particle content in the mixed particles was set to 14.24% by mass, the aluminum particle content to 9.49% by mass, the ammonium chloride particle content as an activator to 0.5% by mass, and the spherical alumina particle content as an anti-sintering agent to 75.77% by mass.

[0163] Other conditions, such as the packing density of alumina particles, are the same as in Example 1.

[0164] (Example 3) Using the same method as in Example 1, calorified iron particles (hereinafter referred to as "particles related to Example 3") were prepared.

[0165] However, in this Example 3, the iron particle content in the mixed particles was set to 15.71% by mass, the aluminum particle content to 8.83% by mass, the ammonium chloride particle content as an activator to 0.5% by mass, and the spherical alumina particle content as an anti-sintering agent to 74.96% by mass.

[0166] Other conditions, such as the packing density of alumina particles, are the same as in Example 1.

[0167] (Example 4) Using the same method as in Example 1, calorified iron particles (hereinafter referred to as "particles related to Example 4") were prepared.

[0168] However, in this Example 4, the iron particle content in the mixed particles was set to 16.87% by mass, the aluminum particle content to 8.31% by mass, the ammonium chloride particle content as an activator to 0.5% by mass, and the spherical alumina particle content as an anti-sintering agent to 74.32% by mass.

[0169] Other conditions, such as the packing density of alumina particles, are the same as in Example 1.

[0170] (Example 5) Sprayable particles (hereinafter referred to as "sprayable particles according to Example 5") were prepared using the same method as in Example 3.

[0171] However, in this example 5, the atmosphere inside the heat-resistant container was replaced with an argon atmosphere, and then the heat-resistant container was heated to 1100°C. After being held at 1100°C for 10 hours, the heat-resistant container was furnace-cooled.

[0172] (Example 11) We attempted to produce sprayable particles using the same method as in Example 1.

[0173] However, in this example 11, the average particle size of the iron particles in the mixed particles was set to 50 μm, the average particle size of the aluminum particles to 50 μm, and the average particle size of the alumina particles to 60 μm. In addition, the content of iron particles in the mixed particles was set to 56.00 mass%, the content of aluminum particles to 24.00 mass%, the content of ammonium chloride particles as an activator to 0.50 mass%, and the content of alumina particles to 19.50 mass%.

[0174] The heating temperature was set to 1000°C, and the heating time was set to 10 hours.

[0175] The treated mixture obtained after heat treatment was lumpy, and it was difficult to separate and remove the alumina particles.

[0176] Table 2 below summarizes the content and particle size of each component in the mixed particles used in each example.

[0177] [Table 2] Furthermore, Table 3 below summarizes the packing density of alumina particles and the packing density of other components in the voids for each example of thermal spray particles.

[0178] [Table 3] In Example 11, the particle size of the alumina particles is approximately the same as that of the other components, so the packing density is omitted. (evaluation) Using the thermal spray particles from each example, the average particle size was measured and the particle morphology was observed.

[0179] (Average particle size) The average particle size of the thermal spray particles for each example was determined from the particle size distribution obtained using a particle size analyzer (LA-950V2; manufactured by Horiba, Ltd.).

[0180] (analysis) Using the thermal spray particles for each example, samples for cross-sectional observation were prepared by the following method.

[0181] First, multiple thermal spray particles were embedded in the resin, and the resin was allowed to harden. Next, the resin was polished using sandpaper and a buffing device to expose the cross-sections of the thermal spray particles.

[0182] The objects of observation were thermal spray particles having the "maximum cross-section". Hereinafter, in the thermal spray particles related to Examples 1 to 5, the thermal spray particles to be observed will be referred to as "Sample 1" to "Sample 5", respectively.

[0183] In samples 1 through 4, the cross-sections of the thermal spray particles were observed using a scanning electron microscope (SEM). In sample 5, the cross-section of the thermal spray particles was observed using an electrochemical microscope (EPMA). Furthermore, the amounts of iron and aluminum contained in the cross-sections of the thermal spray particles were evaluated by EDX analysis.

[0184] Figure 7 shows the cross-section of the thermal spray particles obtained in Sample 1 (a) and the distribution of aluminum contained in the cross-section (b). The distribution of iron contained in the cross-section was the inverse of the distribution of aluminum.

[0185] Figure 7 shows that in Sample 1, the cross-section of the thermal spray particles had a morphology similar to that of the first particle 100 mentioned above. In other words, the cross-section had a two-layer structure consisting of a core with a low aluminum concentration and an outer layer with a high aluminum concentration.

[0186] The area ratio of the region with a high aluminum concentration (the second region) was measured, and the area ratio of the second region was found to be 78%.

[0187] Furthermore, the concentrations of iron and aluminum were analyzed in the first and second regions using EDX. The results showed that the iron concentration in the first region was 63.3%, and the iron concentration in the second region was 31.3%. The aluminum concentration in the first region was 31.4%, and the aluminum concentration in the second region was 49.4%.

[0188] From these results, it can be inferred that the first region is mainly composed of the FeAl phase, while the second region is a mixed phase of FeAl2 phase and FeAl phase.

[0189] Figure 8 shows a cross-section of the thermal spray particles obtained in Sample 2 (a) and the distribution of aluminum contained in the cross-section (b). The distribution of iron contained in the cross-section was the inverse of the distribution of aluminum.

[0190] Figure 8 shows that in Sample 2, the cross-section of the sprayable particle has a morphology similar to that of the first particle 100 mentioned above. In other words, the cross-section has a two-layer structure consisting of a core with a low aluminum concentration and an outer layer with a high aluminum concentration.

[0191] The area ratio of the region with a high aluminum concentration (the second region) was measured, and the area ratio of the second region was found to be 53%.

[0192] Furthermore, the concentrations of iron and aluminum were analyzed in the first and second regions using EDX. The results showed that the iron concentration in the first region was 63.5%, and the iron concentration in the second region was 50.4%. The aluminum concentration in the first region was 30.5%, and the aluminum concentration in the second region was 47.4%.

[0193] From these results, it can be inferred that the first region is mainly composed of the FeAl phase, while the second region is a mixed phase of FeAl2 phase and FeAl phase.

[0194] Figure 9 shows a cross-section of the thermal spray particles obtained in Sample 3 (a) and the distribution of aluminum contained in the cross-section (b). The distribution of iron contained in the cross-section was the inverse of the distribution of aluminum.

[0195] Figure 9 shows that in Sample 3, regions with low and high aluminum concentrations are dispersed in the cross-section of the thermal spray particles.

[0196] The area percentage of the region with a high aluminum concentration (the second region) was measured, and the area percentage of the second region was found to be 19%.

[0197] Furthermore, the concentrations of iron and aluminum were analyzed in the first and second regions using EDX. The results showed that the iron concentration in the first region was 61.8%, and the iron concentration in the second region was 48.3%. The aluminum concentration in the first region was 31.4%, and the aluminum concentration in the second region was 44.9%.

[0198] From these results, it can be inferred that the first region is mainly composed of the FeAl phase, while the second region is a mixed phase of FeAl2 phase and FeAl phase.

[0199] Figure 10 shows the cross-section (backscattered electron image and secondary electron image) of the thermal spray particles obtained in Sample 4, and the distribution of aluminum, iron, and oxygen contained in the cross-section.

[0200] Figure 10 shows that, similar to sample 3, sample 4 also exhibits a dispersion of low and high aluminum concentration regions in the cross-section of the thermal spray particles.

[0201] The area percentage of the region with a high aluminum concentration (the second region) was measured, and the area percentage of the second region was found to be 9%.

[0202] Furthermore, the concentrations of iron and aluminum were analyzed in the first and second regions using EDX. The results showed that the iron concentration in the first region was 66.5%, and the iron concentration in the second region was 52.7%. The aluminum concentration in the first region was 31.4%, and the aluminum concentration in the second region was 40.7%.

[0203] From these results, it can be inferred that the first region is mainly composed of the FeAl phase, while the second region is a mixed phase of FeAl2 phase and FeAl phase.

[0204] Figure 11 shows the cross-section (backscattered electron image and secondary electron image) of the thermal spray particles obtained in Sample 5, and the distribution of aluminum, iron, and oxygen contained in the cross-section.

[0205] Figure 11 shows that in sample 5, regions with low and high aluminum concentrations were dispersed in the cross-section of the thermal spray particles. However, in sample 5, it was found that aluminum oxide was precipitated and dispersed in a ring shape relative to the center of the particles.

[0206] The area percentage of the region with a high aluminum concentration excluding oxides (the second region) was measured, and the area percentage of the second region was found to be 10%.

[0207] Furthermore, the concentrations of iron and aluminum were analyzed in the first and second regions using EDX. The results showed that the iron concentration in the first region was 65.9%, and the iron concentration in the second region was 53.4%. The aluminum concentration in the first region was 33.1%, and the aluminum concentration in the second region was 46.6%.

[0208] From these results, it can be inferred that the first region is mainly composed of the FeAl phase, while the second region is a mixed phase of FeAl2 phase and FeAl phase.

[0209] Next, energy-dispersive X-ray (EDX) analysis was performed on the cross-sections obtained from each sample to evaluate the concentrations of aluminum and iron contained throughout the entire particle cross-section.

[0210] Table 4 below summarizes the analysis results obtained for each sample.

[0211] [Table 4] Thus, it was found that samples 1 to 5 contained aluminum in the range of 32% to 48% by mass.

[0212] (Example 21) Using thermal spray particles according to one embodiment of the present invention, a thermal spray coating was actually formed and its properties were evaluated.

[0213] For the thermal spraying particles, the thermal spraying particles described in Example 5 above were classified using sieves with nominal mesh sizes of 20 μm and 45 μm, resulting in a particle size range of a minimum of 20 μm and a maximum of 45 μm. I used it.

[0214] Using these classified spray particles, a sprayed coating was formed on the surface of a stainless steel (SUS304) substrate by the HVOF spraying method.

[0215] The thermal spraying conditions are as follows: Thermal spray distance: 350 mm Barrel length: 152.4 mm Oxygen flow rate; 46.7m 3 / h(1650SCFH) Fuel flow rate; 22.7L / h (6.0GPH) Combustion ratio: 0.99 Particle size for thermal spraying: 20 μm to 45 μm.

[0216] The target thickness of the thermal spray coating was 200 μm.

[0217] The resulting substrate with the thermal spray coating will be referred to as "Sample 21".

[0218] Figures 12 and 13 show cross-sections of sample 21. Figure 13 is an enlarged cross-section of Figure 12.

[0219] Figure 14 also shows the EPMA analysis results of a portion of the cross-section of sample 21.

[0220] Figure 14 shows that in sample 21, aluminum-containing oxides are present between adjacent flattened particles and within each flattened particle.

[0221] Of these, the oxides between the flattened particles are thought to have been formed by the oxidation of the particles during thermal spraying. On the other hand, the oxides inside each individual flattened particle are thought to correspond to the oxide precipitates contained in the thermal spray particles used to prepare Sample 21 (see the ring-shaped precipitates in Figure 11).

[0222] This type of thermal spray coating is thought to have significantly greater strength compared to conventional coatings.

[0223] (Example 22) A thermal spray coating was formed on the surface of a stainless steel substrate using the same method as in Example 21. However, in Example 22, the thermal spray particles described in Example 3 were used. In addition, in Example 22, explosive thermal spraying was used instead of HVOF thermal spraying as the thermal spraying method.

[0224] The resulting substrate with the thermal spray coating will be referred to as "Sample 22".

[0225] (Example 31) A thermal spray coating was formed on the surface of a stainless steel substrate using the same method as in Example 21. However, in Example 31, particles described in Patent Document 1 were used as the thermal spraying material. In addition, plasma spraying was used instead of HVOF thermal spraying as the thermal spraying method.

[0226] The resulting substrate with the thermal spray coating is referred to as "Sample 31".

[0227] (High-temperature corrosion resistance test) The following high-temperature corrosion resistance tests were conducted using samples 21, 22, and 31.

[0228] Each sample was exposed to a 700°C N2+SO2 (1000 ppm) atmosphere for 100 hours, and then the surface of the thermal spray coating was analyzed.

[0229] Figures 15 to 17 show the EDX mapping results of the sulfur (S) component obtained for each sample. Figure 15 shows the results for sample 21, Figure 16 shows the results for sample 22, and Figure 17 shows the results for sample 31.

[0230] As is clear from Figure 17, sulfur components were observed on the surface of sample 31. On the other hand, no sulfur components were detected on the surface of samples 21 and 22.

[0231] Thus, it was confirmed that samples 21 and 22 exhibited better high-temperature sulfurization resistance compared to sample 31.

[0232] Using Sample 21, a high-temperature corrosion resistance test was conducted under more severe conditions. Specifically, the test environment was changed to a 700°C N2+SO2 (3000 ppm) atmosphere, and the sample was exposed for 400 hours.

[0233] EDX mapping for sulfur (S) components was performed on the surface of sample 21 after testing. Almost no sulfur components were detected on the surface of sample 21 after testing.

[0234] Next, the S component was analyzed at each thickness position in the cross-section of the thermal spray coating of sample 21.

[0235] Figure 18 shows a cross-section of sample 21 after testing. EDX analysis was performed on the thermal spray coating at the height levels indicated by the labels X, Y, and Z in Figure 18. The results are shown in Table 5.

[0236] [Table 5] Table 5 shows that in Sample 21, no sulfur components were detected at any of the X to Z depth positions of the thermal spray coating after testing.

[0237] This application claims priority based on Japanese Patent Application No. 2020-202261, filed on 4 December 2020, and the entire contents of the said Japanese application are incorporated herein by reference. [Explanation of Symbols]

[0238] 100 Particles for thermal spraying (first particle) 110 First Domain 120 Second Domain 200 Particles for thermal spraying (second particle) 210 First Domain 220 Second Domain 300 Thermal spray particles (third particle) 310 First Domain 320 Second Domain 330 Precipitate 352 Particles to be treated 354 Aluminum source 358 Sintering inhibitor 365 void 400 Thermal spray particles (fourth particle) 410 First Domain 420 Second Domain 430 Precipitate

Claims

1. A thermal spray coating containing an aluminum-iron alloy, The mass ratio of aluminum to iron (Al / Fe) contained in a single flattened particle is in the range of 32 / 68 to 48 / 52. A thermal spray coating wherein needle-shaped or spherical oxides with a maximum dimension in the range of 0.1 μm to 2 μm are mixed within the flattened particles.

2. The flattened particles are, A first region in which the aluminum concentration is in the range of 22% by mass to 37% by mass, A second region in which the aluminum concentration is in the range of 40% to 50% by mass, The thermal spray coating according to claim 1, having the following characteristics.

3. The first region includes the FeAl phase, The second region is the FeAl phase and FeAl ２ A thermal spray coating according to claim 2, comprising a phase.

4. The flattened particle has a core portion and an outer layer covering the core portion. The thermal spray coating according to claim 2 or 3, wherein the first region forms the core portion and the second region forms the outer layer.

5. The thermal spray coating according to claim 4, wherein the proportion of the second region in a cross-section passing through the center of the flattened particle is 5% or more.

6. The thermal spray coating according to claim 2 or 3, wherein the first region and the second region are arranged in a mottled pattern.

7. The thermal spray coating according to claim 6, wherein the proportion of the second region in a cross-section passing through the center of the flattened particle is 5% or more.

8. The thermal spray coating according to any one of claims 1 to 7, wherein the flattened particles have an average particle size in the range of 10 μm to 100 μm.

9. The thermal spray coating according to any one of claims 1 to 8, wherein the oxide is distributed in a substantially ring shape centered on the center of the flattened particle.

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