Thermal spray particles, method for producing thermal spray particles, and thermal spray coating

Abstract

The present invention provides particles for thermal spray, said particles being generally spherical, while containing iron and aluminum. The amount of aluminum contained in the particles for thermal spray is within the range of from 32% by mass to 48% by mass; and each of the particles for thermal spray has a first region wherein the aluminum concentration is within the range of from 22% by mass to 37% by mass, and a second region wherein the aluminum concentration is within the range of from 40% by mass to 50% by mass.

Description

[Technical Field]

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

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

[0003] For example, Patent Document 1 describes the formation of a coating of an iron-aluminum intermetallic compound on the surface of stainless steel by atmospheric plasma spraying using a thermal spray raw material powder containing iron and aluminum. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. WO2018 / 116856 Summary of the Invention [Problem to be solved by the invention]

[0005] Cited Document 1 describes that the thermal spray coating described in Cited Document 1 can be used as a surface treatment coating for metals that constitute glass transport rolls.

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

[0007] The thermal spray raw material powder in Cited 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. The inventors of the present application have recognized that each particle contained in this thermal spray raw material powder has an aluminum-depleted region. Therefore, it is believed that a thermal spray coating formed using such a thermal spray raw material powder also has an aluminum-depleted region, and as a result, good high-temperature sulfidation resistance cannot be obtained.

[0008] Thus, there is still a need for a technology for forming a thermal spray coating that has good high-temperature sulfidation resistance.

[0009] The present invention has been made in view of the above background, and an object of the present invention is to provide particles for thermal spraying that have better high-temperature sulfidation resistance than conventional particles. Another object of the present invention is to provide a method for producing such particles for thermal spraying. A further object of the present invention is to provide a thermal spray coating that has better high-temperature sulfidation resistance than conventional particles. [Means for solving the problem]

[0010] In the present invention, Particles for thermal spraying, is generally spherical and comprises iron and aluminum; the amount of aluminum contained in the thermal spray particles is in the range of 32% by mass to 48% by mass, The thermal spray particles are a first region having an aluminum concentration in the range of 22% by mass to 37% by mass; a second region having an aluminum concentration in the range of 40% by mass to 50% by mass; The present invention provides particles for thermal spraying, having the following structure:

[0011] In addition, in the present invention, A method for producing particles for thermal spraying, comprising: a method for producing a mixed particle by mixing iron-containing particles to be treated, an aluminum source, an activator containing a halide, and a sintering inhibitor; The mixed particles are heated, and the treated particles are calorified by utilizing the gaps formed between the sintering inhibitors, thereby obtaining a treated mixture containing aluminum-infiltrated particles; A manufacturing method is provided in which the sintering inhibitor is removed from the treated mixture to obtain particles for thermal spraying.

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

[0013] The present invention can provide particles for thermal spraying that have better high-temperature sulfidation resistance than conventional particles. The present invention also can provide a method for producing such particles for thermal spraying. Furthermore, the present invention can provide a thermal spray coating that has better high-temperature sulfidation resistance than conventional particles. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a diagram schematically illustrating a cross section of a particle for thermal spraying according to one embodiment of the present invention. [Figure 2] FIG. 3 is a diagram schematically illustrating a cross section of a particle for thermal spraying according to another embodiment of the present invention. [Figure 3] FIG. 4 is a diagram schematically showing a cross section of a particle for thermal spraying according to yet another embodiment of the present invention. [Figure 4] FIG. 4 is a diagram schematically showing a cross section of a particle for thermal spraying according to yet another embodiment of the present invention. [Figure 5] FIG. 1 is a diagram schematically illustrating an example of a flow of a method for producing particles for thermal spraying according to an embodiment of the present invention. [Figure 6] FIG. 2 is a diagram schematically illustrating a state in which mixed particles are filled in a reaction vessel. [Figure 7] FIG. 1 is a diagram showing (a) a cross section of a particle for thermal spraying (sample 1) obtained in one embodiment of the present invention, and (b) the distribution of aluminum contained in the cross section. [Figure 8] FIG. 2 is a diagram showing (a) a cross section of a particle for thermal spraying (sample 2) obtained in another embodiment of the present invention, and (b) a distribution of aluminum contained in the cross section. [Figure 9] FIG. 2 is a diagram showing (a) a cross section of a particle for thermal spraying (sample 3) obtained in yet another embodiment of the present invention, and (b) the distribution of aluminum contained in the cross section. [Figure 10] FIG. 2 is a diagram showing (a) a cross section of a particle for thermal spraying (sample 4) obtained in yet another embodiment of the present invention, and (b) the distribution of aluminum contained in the cross section. [Figure 11] FIG. 10 is a diagram showing a cross section of a particle for thermal spraying (sample 5) obtained in yet another embodiment of the present invention, and the distribution of each element contained in the cross section. [Figure 12] 1 is a cross-sectional photograph of a thermal spray coating according to one embodiment of the present invention. [Figure 13] 13 is an enlarged cross-sectional photograph of the thermal spray coating shown in FIG. 12. [Figure 14] FIG. 13 is a diagram showing the results of EPMA analysis of a portion of the cross section of the thermal spray coating shown in FIG. [Figure 15] FIG. 2 is an EDX mapping diagram of sulfur (S) after a high-temperature corrosion resistance test of a thermal spray coating according to one embodiment of the present invention. [Figure 16] FIG. 10 is an EDX mapping diagram of sulfur (S) after a high-temperature corrosion resistance test of another thermal sprayed coating according to one embodiment of the present invention. [Figure 17] FIG. 1 is an EDX mapping diagram of sulfur (S) after a high-temperature corrosion resistance test of a thermal spray coating in a comparative example. [Figure 18] 1 is an electron microscope photograph showing a cross section of Sample 21 after testing. DETAILED DESCRIPTION OF THE INVENTION

[0015] An embodiment of the present invention will be described below.

[0016] As described above, the particles contained in the thermal spray raw material powder described in Patent Document 1 contain aluminum-deficient regions, which results in aluminum-deficient regions in the resulting thermal spray coating. Therefore, the thermal spray coating in Patent Document 1 cannot be said to have very good high-temperature sulfidation resistance.

[0017] In contrast to this, in one embodiment of the present invention, Particles for thermal spraying, is generally spherical and comprises iron and aluminum; the amount of aluminum contained in the thermal spray particles is in the range of 32% by mass to 48% by mass, The thermal spray particles are a first region having an aluminum concentration in the range of 22% by mass to 37% by mass; a second region having an aluminum concentration in the range of 40% by mass to 50% by mass; The present invention provides particles for thermal spraying, having the following structure:

[0018] A particle for thermal spraying 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, in this particle for thermal spraying, aluminum is present in an amount of 22 mass % or more even in the first region. The first region mainly contains an FeAl phase, and the second region mainly contains a mixed phase of FeAl2 and FeAl.

[0019] Thermal spray particles according to one embodiment of the present invention contain aluminum throughout the entire particle. Therefore, when such thermal spray particles are used to form a thermal spray coating, the occurrence of aluminum-depleted regions is significantly suppressed, and a thermal spray coating with better high-temperature sulfidation resistance than conventional particles can be provided.

[0020] In addition, in one embodiment of the present invention, A method for producing particles for thermal spraying, comprising: a method for producing a mixed particle by mixing iron-containing particles to be treated, an aluminum source, an activator containing a halide, and a sintering inhibitor; The mixed particles are heated, and the treated particles are calorified by utilizing the gaps formed between the sintering inhibitors, thereby obtaining a treated mixture containing aluminum-infiltrated particles; A manufacturing method is provided in which the sintering inhibitor is removed from the treated mixture to obtain particles for thermal spraying.

[0021] In order to produce particles for thermal spraying having the above-described characteristics, in a method according to one embodiment of the present invention, aluminum impregnation is performed on the particles to be treated using a calorification treatment.

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

[0023] Furthermore, when the thermite reaction occurs, the treatment environment becomes extremely hot, and the mixture after treatment (hereinafter referred to as the "treated mixture") takes on a clump-like form in which all particles are firmly adhered to each other.

[0024] Furthermore, once such a lumpy treated mixture is produced, it becomes impossible to separate the sintering inhibitor from the treated mixture, which results in the problem of being unable to recover the calorified thermal spray particles from the treated mixture.

[0025] In contrast, in a method according to one embodiment of the present invention, the calorification treatment is carried out by utilizing the gaps formed between the sintering-preventing agents.

[0026] In this case, even if a thermite reaction occurs in the reaction system, the possibility of the treated particles adhering to the sintering inhibitor and / or other treated particles can be significantly reduced, since the gaps serve to provide a large number of mutually isolated "small compartments" for the reaction.

[0027] As a result, the treated mixture obtained after the calorification treatment is not in the form of aggregated lumps, but rather the particles for thermal spraying and the sintering inhibitor are separated from each other.

[0028] Therefore, in the method according to one embodiment of the present invention, the sintering inhibitor can be relatively easily removed from the treated mixture after the calorification treatment, and the thermal spray particles can be relatively easily separated and recovered.

[0029] In this way, in the method according to one embodiment of the present invention, the particles to be treated can be appropriately calorified, and particles for thermal spraying containing aluminum throughout can be obtained.

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

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

[0032] (Thermal spray particles according to one embodiment of the present invention) Next, particles for thermal spraying according to one embodiment of the present invention will be described in more detail with reference to the drawings.

[0033] FIG. 1 shows a schematic cross section of a particle for thermal spraying according to one embodiment of the present invention (hereinafter referred to as a "first particle").

[0034] The cross section of the first particle shown in Figure 1 is the "maximum cross section." In this application, the "maximum cross section" refers to a cross section passing through the center of the particle. For example, if the particle is spherical, the diameter of the "maximum cross section" has substantially the same dimension as the diameter of the particle.

[0035] 1, the first particle 100 has a substantially spherical shape. In this application, the term "substantially spherical" or "approximately spherical shape" is not limited to a pure sphere, but also includes an ellipse with a dimensional difference of ±20% or less in the mutually perpendicular X-axis and Y-axis directions.

[0036] The cross section (maximum cross section; the same applies hereinafter) of the first particle 100 has two regions with different aluminum concentrations. Hereinafter, 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] 1, the core of the first particle 100 constitutes a first region 110, and the outer layer constitutes a second region 120. The second region 120 is disposed so as to surround the first region 110.

[0038] In the example shown in FIG. 1, the boundary between the first region 110 and the second region 120 is depicted by a clear line, but it is often the case that the boundary between the two is unclear.

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

[0040] The iron concentration in the entire 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 further contains elements described below, the iron concentration will be lower than this range.

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

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

[0043] The third element may be contained in a total range of 0.05 wt% to 1 wt%. When the first particle 100 contains the third element, the iron concentration is the concentration obtained by subtracting the concentration of the third element from the aforementioned range (52 wt% to 68 wt%). In other words, the third element exists as a substitute element for iron or as an inevitable impurity.

[0044] The first region 110 of the first particle 100 mainly contains an FeAl phase. The concentration of aluminum contained in the first region 110 is in the range of 22 wt% to 37 wt%. The concentration of aluminum may be, for example, in the range of 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 be, for example, in the range of 42 wt% to 48 wt%.

[0046] 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. Furthermore, the constituent phases contained in each of the first region 110 and the second region 120 can be identified by X-ray diffraction analysis.

[0047] The area ratio of the second region 120 in the cross section of the first particle 100 is, for example, 5% or more. Note that this area ratio can be evaluated by binarizing and defining the contrast of Al concentration using an SEM backscattered electron image of the cross section.

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

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

[0050] Aluminum is contained throughout the entire first particle 100. Therefore, when the first particle 100 is used as a particle for thermal spraying to form a thermal spray coating, the occurrence of aluminum depleted regions can be significantly suppressed.

[0051] Therefore, the first particles 100 can be used as particles for thermal spraying when forming a thermal spray coating that has excellent resistance to high-temperature sulfidation.

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

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

[0054] 2, the second particle 200 has a substantially spherical shape. 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 described above, the two regions are arranged in a "patterned" manner.

[0056] That is, in the second particle 200, the second regions 220 having a relatively high aluminum concentration are distributed in an "island-like" manner in the "sea" of the first regions 210 having a relatively low aluminum concentration.

[0057] In other words, the entire cross section of the second particle 200 is made up of the "sea-like" first region 210 and the "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 on the outermost surface.

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

[0059] The iron concentration in the entire cross section of the second particle 200 may be, for example, in the range of 52 wt% to 68 wt%. However, as described above, if the second particle 200 contains a third element, the iron concentration will be lower than this range.

[0060] The first region 210 of the second particle 200 mainly contains an FeAl phase. The concentration of aluminum contained in the first region 210 is in the range of 22 wt% to 37 wt%. The concentration of aluminum may be, for example, in the range of 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 be, for example, in the range of 42 wt% to 48 wt%.

[0062] The average particle size of the second particles 200 is in the range of 5 μm to 200 μm. The average particle size of the second particles 200 is preferably 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 particles 200, aluminum is also contained throughout the particles. Therefore, when the second particles 200 are used as particles for thermal spraying to form a thermal spray coating, the occurrence of aluminum depleted regions can be significantly suppressed.

[0065] Therefore, the second particles 200 can be used as particles for thermal spraying when forming a thermal spray coating that has excellent high-temperature sulfidation resistance.

[0066] (Particles for thermal spraying according to yet another embodiment of the present invention) Next, with reference to FIG. 3, particles for thermal spraying according to still another embodiment of the present invention will be described.

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

[0068] As shown in Fig. 3, the third particle 300 has a morphology similar to that of the first particle 100 shown in Fig. 1. That is, the third particle 300 has a core portion constituting a first region 310 having a relatively low aluminum concentration and an outer layer constituting a second region 320 having a relatively high aluminum concentration.

[0069] However, the third particles 300 differ from the first particles 100 described above in that they have rod-shaped (or spherical) precipitates 330 .

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

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

[0072] In the case of the third particles 300, aluminum is also contained throughout the particles. Therefore, when the third particles 300 are used as particles for thermal spraying to form a thermal spray coating, the occurrence of aluminum depleted regions can be significantly suppressed.

[0073] Therefore, the third particles 300 can be used as particles for thermal spraying when forming a thermal spray coating that has excellent high-temperature sulfidation resistance.

[0074] In addition, in the third particle 300, the precipitates 330 act in a direction that suppresses dislocation slippage, and therefore it is expected that high strength can be obtained.

[0075] (Particles for thermal spraying according to yet another embodiment of the present invention) Next, particles for thermal spraying according to still another embodiment of the present invention will be described with reference to FIG.

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

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

[0078] However, the fourth particle 400 differs from the second particle 200 described above in that it has rod-shaped (or spherical) precipitates 430 .

[0079] The precipitates 430 are distributed in a substantially ring shape centered on the center of the fourth particle 400. The size of each precipitate 430 along the radial direction is, for example, in the range of 0.1 μm to 2 μm.

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

[0081] In the case of the fourth particles 400, aluminum is also contained throughout the particles. Therefore, when the fourth particles 400 are used as particles for thermal spraying to form a thermal spray coating, the occurrence of aluminum depleted regions can be significantly suppressed.

[0082] Therefore, the fourth particles 400 can be used as particles for thermal spraying when forming a thermal spray coating that has excellent high-temperature sulfidation resistance.

[0083] In the fourth particle 400, the precipitates 430 act in a direction that suppresses dislocation slippage, and therefore it is expected that high strength can be obtained.

[0084] The features of particles for thermal spraying according to one embodiment of the present invention have been described above using the first particles 100 to the fourth particles 400 as examples.

[0085] However, the first particles 100 to the fourth particles 400 are merely examples, and the particles for thermal spraying according to one embodiment of the present invention may have shapes different from these.

[0086] For example, particles for thermal spraying according to one embodiment of the present invention may have a morphology that combines the particle morphology shown in FIG. 1 and the particle morphology shown in FIG.

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

[0088] Generally, in the particle production process described below, when the heat treatment temperature is relatively low and / or the heating time is relatively short, the first particles 100 shown in Fig. 1 tend to be obtained. In addition, in the particle production process described below, when the heat treatment temperature is relatively high and / or the heating time is relatively long, the second particles 200 tend to be obtained in the form shown in Fig. 2.

[0089] (Method of manufacturing particles for thermal spraying according to one embodiment of the present invention) Next, a method for producing particles for thermal spraying according to one embodiment of the present invention will be described with reference to FIGS.

[0090] FIG. 5 is a schematic diagram showing an example of the flow of a method for producing particles for thermal spraying according to one embodiment of the present invention.

[0091] As shown in FIG. 5, a method for producing particles for thermal spraying according to one embodiment of the present invention (hereinafter referred to as the “first production method”) includes the following steps: A step (S110) of preparing mixed particles by mixing particles to be treated containing iron, an aluminum source, an activator containing a halide, and a sintering inhibitor; a step (S120) of heating the mixed particles and calorifying the treated particles by utilizing the gaps between the sintering inhibitors formed by the sintering inhibitors to obtain a treated mixture containing aluminum-infiltrated particles; a step (S130) of removing the sintering inhibitor from the treated mixture to obtain particles for thermal spraying; It has.

[0092] Each step will be described in more detail below.

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

[0094] The mixed particles include the treated particles, the aluminum source, the activator, and the sintering inhibitor. Each of the particles will be described below.

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

[0096] The average particle size of the treated particles is selected to be significantly smaller than the average particle size of the sintering inhibitor described below. For example, the average particle size of the treated particles 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 the present application, the "average particle size" is measured by the method specified in JIS Z 8801.

[0099] That is, several sieves with different mesh sizes are stacked on top of each other in order of size, starting with the smallest, and the particles to be measured are vibrated at a constant amplitude for a fixed period of time to sieve them. 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 at which the cumulative value of the obtained particle size distribution corresponds to 50% is defined as the "average particle size."

[0100] However, the particle size of the treated particles is expressed as a range between the 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, for example, in the range of 10 μm to 200 μm.

[0104] The average particle size of the aluminum source is preferably smaller than the average particle size of the particles to be treated.

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

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

[0107] (Sintering prevention agent) The sintering inhibitor may include at least one of alumina, kaolin, and silicon oxide.

[0108] The sintering inhibitor may have at least one shape selected from the group consisting of, for example, a sphere, a triangular pyramid, a triangular prism, a tetrahedron, a cone, and a cylinder.

[0109] The sintering inhibitor has a sufficiently large average particle size compared to the particles to be treated and the aluminum source.

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

[0111] For example, when the sintering inhibitor is substantially spherical, the average particle size of the sintering inhibitor may be in the range of 500 μm to 5000 μm.

[0112] (mixed particles) The above components are mixed to prepare mixed particles.

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

[0114] The amount of treated particles contained in the entire mixed particles is, for example, in the range of 10% to 30% by mass. The amount of aluminum source contained in the entire mixed particles is, for example, in the range of 8% to 18% by mass. The amount of sintering inhibitor contained in the entire 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 purpose, the mixed particles may be filled into a reaction vessel.

[0116] The reaction vessel is heated to calorify the particles, that is, aluminum produced from the aluminum source diffuses and penetrates into the particles, forming aluminum-infiltrated particles.

[0117] Here, if the aluminum source contained in the mixed particles contains highly active aluminum, such as aluminum particles, there is a high possibility that a thermite reaction will occur between the mixed particles when the reaction vessel is heated. This is because the aluminum reacts with the trace amount of oxygen contained in the treated particles to reduce the treated particles.

[0118] When such a thermite reaction occurs, the temperature inside the reaction vessel becomes extremely high, and the mixture after treatment, i.e., the "treated mixture," becomes a mass in which all particles are firmly bonded together. Furthermore, once such a mass of treated mixture is produced, it can become difficult to separate the sintering inhibitor from the treated mixture.

[0119] In contrast, in the first production method, the formation of a lumpy mixture can be significantly suppressed.

[0120] This feature will be described below with reference to FIG.

[0121] An example of the form of the mixed particles when they are filled in a reaction vessel is shown in Fig. 6. As shown in Fig. 6, the reaction vessel is filled with the components of the mixed particles, namely, particles to be treated 352, an aluminum source 354, an activator, and a sintering inhibitor 358.

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

[0123] Here, the diameter (φ S ) is the diameter (φ Fe ) and the diameter of the aluminum source 354 (φ Al When the thickness of the sintering-preventing agent 358 is sufficiently larger than the thickness of the sintering-preventing agent 358, gaps 365 are formed between adjacent sintering-preventing agents 358. Furthermore, the particles 352 to be treated and the aluminum source 354 are placed in the gaps 365 formed by the sintering-preventing agent 358.

[0124] When the reaction vessel is heated with the mixed particles arranged in this manner, even if a thermite reaction occurs in the reaction vessel, the possibility that the treated particles 352 will stick 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 "small compartments" for the reaction during the calorification process.

[0125] As a result, the treated mixture produced after the heat treatment is not in the form of clumps, but rather the aluminum-infiltrated particles and the sintering inhibitor 358 are separated from each other. This makes it possible to recover the aluminum-infiltrated particles, i.e., the particles for thermal spraying, from the treated mixture in a subsequent step.

[0126] Table 1 below shows examples of packing mixed particles that can achieve the above effects.

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

[0128] In addition, the average particle size φ of the sintering inhibitor 358 S is assumed to be 1000 μm, and the average particle diameter φ of the particles 352 to be treated is Fe is set to 38 μm to 75 μm, and the average particle diameter φ of the aluminum source 354 is set to 38 μm to 75 μm. Al is assumed to be 50 μm and the average particle size of the active agent is assumed to be 10 μm.

[0129] [Table 1] From Table 1, when 10 kg of sintering prevention agent 358 is packed most densely, 74% of the total space volume is occupied by sintering prevention agent 358. Therefore, voids 365 are 26%.

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

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

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

[0133] When the sintering inhibitor 358 is packed in a manner other than closest packing, the amount of each component can be calculated in a similar manner.

[0134] When sintering prevention agent 358 is spherical, the packing rate of sintering prevention agent 358 is preferably in the range of 55% to 74% (at closest packing) in order to obtain the above-mentioned effect.

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

[0136] However, in reality, it is assumed that the sintering prevention agent 358 may be non-spherical, and therefore the preferred range of the filling rate of the sintering prevention agent 358 is assumed to be 50% to 80%.

[0137] In this way, in the first manufacturing method, the gaps 365 formed between the sintering inhibitors 358 can be utilized to perform the calorification treatment of the particles 352 to be treated.

[0138] The treatment atmosphere for the calorifying treatment may be an inert atmosphere that does not contain oxygen, such as an argon gas atmosphere.

[0139] The treatment temperature is not particularly limited as long as aluminum diffuses and penetrates into the particles to be treated. The treatment temperature may be in the range of 800°C to 1100°C, for example.

[0140] The treatment time is not particularly limited, but is, for example, in the range of 1 hour 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 having second regions 120 arranged in layers around first regions 110, such as the first particle 100, will be obtained. Conversely, the higher the processing temperature and / or the longer the processing time, the more likely it is that particles such as the second particle 200 will be obtained.

[0142] (Step S130) The sintering inhibitor is then 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 described above, the first production method can significantly prevent the reaction system from becoming too hot due to the accumulation of excess heat that can be generated in the thermite reaction.

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

[0145] In the first manufacturing method, aluminum is infiltrated into the entire treated particle by the calorifying treatment, and therefore, the first manufacturing method can form particles for thermal spraying in which aluminum depletion regions are significantly reduced.

[0146] (Application example 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 above-described characteristics can be used to form thermal spray coatings on the surfaces of various types of 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, it is possible to form a thermal spray coating of an Fe—Al alloy in which aluminum depletion regions are significantly suppressed.

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

[0149] Such a thermal sprayed coating of an Fe—Al alloy has significantly reduced aluminum depletion regions and therefore has better high-temperature sulfidation resistance than conventional coatings. For example, a thermal sprayed coating formed using thermal spray particles according to one embodiment of the present invention can be applied to the surface of a metal constituting a glass transport roll that is exposed to a high-temperature sulfidation environment.

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

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

[0152] In particular, when thermal spraying is performed using fourth particles 400 including precipitates 430 as shown in Fig. 4, a thermal spray coating is formed in which oxide particles are dispersed within each flat particle. The oxide particles may have an acicular or spherical shape and a maximum dimension ranging from 0.1 µm to 2 µm.

[0153] Such thermally sprayed coatings are believed to exhibit relatively high strength. [Example]

[0154] Examples of the present invention will be described below, in which Examples 1 to 5 and Examples 21 and 22 are Examples, and Examples 11 and 31 are Comparative Examples.

[0155] (Example 1) Particles for thermal spraying were prepared by the following method.

[0156] First, iron particles (13.20% by mass) as particles to be treated, aluminum particles (9.96% by mass) as an aluminum source, ammonium chloride particles (0.5% by mass) as an activator, and spherical alumina particles (76.34% by mass) as a sintering inhibitor were thoroughly mixed to prepare mixed particles.

[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 mixture was packed into a heat-resistant container. The calculated packing ratio of the alumina particles was 74%. The iron particles, aluminum particles, and ammonium chloride particles were packed so that they occupied 85% of the remaining 26% of void space.

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

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

[0161] (Example 2) Calorified iron particles (hereinafter referred to as "particles according to Example 2") were produced in the same manner as in Example 1.

[0162] However, in this Example 2, the content of iron particles contained in the mixed particles was 14.24 mass %, the content of aluminum particles was 9.49 mass %, the content of ammonium chloride particles as an activator was 0.5 mass %, and the content of spherical alumina particles as a sintering inhibitor was 75.77 mass %.

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

[0164] (Example 3) Calorified iron particles (hereinafter referred to as "particles according to Example 3") were produced in the same manner as in Example 1.

[0165] However, in this Example 3, the content of iron particles contained in the mixed particles was 15.71 mass %, the content of aluminum particles was 8.83 mass %, the content of ammonium chloride particles as an activator was 0.5 mass %, and the content of spherical alumina particles as a sintering inhibitor was 74.96 mass %.

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

[0167] (Example 4) Calorified iron particles (hereinafter referred to as "particles according to Example 4") were produced in the same manner as in Example 1.

[0168] However, in this Example 4, the content of iron particles contained in the mixed particles was 16.87 mass %, the content of aluminum particles was 8.31 mass %, the content of ammonium chloride particles as an activator was 0.5 mass %, and the content of spherical alumina particles as a sintering inhibitor was 74.32 mass %.

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

[0170] (Example 5) Particles for thermal spraying (hereinafter referred to as "particles for thermal spraying of Example 5") were produced in the same manner as in Example 3.

[0171] However, in Example 5, the atmosphere inside the heat-resistant container was replaced with argon, 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) Using the same method as in Example 1, an attempt was made to prepare particles for thermal spraying.

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

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

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

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

[0177] [Table 2] Table 3 below shows the packing rate of alumina particles and the packing rate of other components relative to voids in the particles for thermal spraying according to each example.

[0178] [Table 3] In Example 11, the particle size of the alumina particles is almost the same as the particle size of the other components, so the filling rate is omitted. (evaluation) Using the particles for thermal spraying according to each example, the average particle size was measured and the particle morphology was observed.

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

[0180] (analysis) Using the thermal spray particles according to each example, a sample for cross-section observation was prepared by the following method.

[0181] First, a plurality of particles for thermal spraying were embedded in a resin, and the resin was cured. Next, the resin was polished with abrasive paper and a buffing machine to expose the cross section of the particles for thermal spraying.

[0182] The particles for thermal spraying that were observed were those having the "largest cross section." Hereinafter, among the particles for thermal spraying according to Examples 1 to 5, the particles for thermal spraying that were observed will be referred to as "Sample 1" to "Sample 5," respectively.

[0183] The cross sections of the particles for thermal spraying were observed with an SEM for Samples 1 to 4. The cross section of the particle for thermal spraying for Sample 5 was observed with an EPMA. The amounts of iron and aluminum contained in the cross sections of the particles for thermal spraying were also evaluated by EDX analysis.

[0184] 7 shows (a) a cross section of the thermal spray particle obtained in Sample 1 and (b) the distribution of aluminum contained in the cross section. The distribution of iron contained in the cross section was inverted from the distribution of aluminum.

[0185] 7, it was found that the cross section of the particle for thermal spraying in Sample 1 had a form similar to that of the first particle 100. That is, 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 (second region) was measured, and the area ratio of the second region was found to be 78%.

[0187] The iron and aluminum concentrations in the first and second regions were analyzed by EDX. 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 this result, it is estimated that the first region is mainly composed of the FeAl phase, whereas the second region is a mixed phase of the FeAl2 phase and the FeAl phase.

[0189] 8 shows (a) a cross section of the thermal spray particle obtained in Sample 2 and (b) the distribution of aluminum contained in the cross section. The distribution of iron contained in the cross section was inverted from the distribution of aluminum.

[0190] 8 shows that in Sample 2, the cross section of the particle for thermal spraying had a form similar to that of the above-described first particle 100. That is, 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.

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

[0192] The iron and aluminum concentrations in the first and second regions were analyzed by EDX. 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 this result, it is estimated that the first region is mainly composed of the FeAl phase, whereas the second region is a mixed phase of the FeAl2 phase and the FeAl phase.

[0194] 9 shows (a) a cross section of the thermal spray particle obtained in Sample 3 and (b) the distribution of aluminum contained in the cross section. The distribution of iron contained in the cross section was inverted from the distribution of aluminum.

[0195] From FIG. 9, it can be seen that in Sample 3, regions with low and high aluminum concentrations are dispersed in the cross section of the particle for thermal spraying.

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

[0197] The iron and aluminum concentrations in the first and second regions were analyzed by EDX. 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 this result, it is estimated that the first region is mainly composed of the FeAl phase, whereas the second region is a mixed phase of the FeAl2 phase and the FeAl phase.

[0199] FIG. 10 shows a cross section (backscattered electron image and secondary electron image) of the particle for thermal spraying obtained in Sample 4, and the distribution of aluminum, iron, and oxygen contained in the cross section.

[0200] From FIG. 10, it can be seen that in Sample 4, as in Sample 3, regions with low and high aluminum concentrations are dispersed in the cross section of the particle for thermal spraying.

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

[0202] The iron and aluminum concentrations in the first and second regions were analyzed by EDX. 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 this result, it is estimated that the first region is mainly composed of the FeAl phase, whereas the second region is a mixed phase of the FeAl2 phase and the FeAl phase.

[0204] FIG. 11 shows a cross section (backscattered electron image and secondary electron image) of the particle for thermal spraying obtained in Sample 5, and the distribution of aluminum, iron, and oxygen contained in the cross section.

[0205] From Figure 11, it was confirmed that regions with low and high aluminum concentrations were dispersed in the cross section of the thermal spray particle in Sample 5. However, it was also found that in Sample 5, aluminum oxide was precipitated and dispersed in a ring shape around the center of the particle.

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

[0207] The iron and aluminum concentrations in the first and second regions were analyzed by EDX. 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 this result, it is estimated that the first region is mainly composed of the FeAl phase, whereas the second region is a mixed phase of the FeAl2 phase and the FeAl phase.

[0209] Energy dispersive X-ray (EDX) analysis was then performed on the cross-section obtained for each sample to assess the aluminum and iron concentrations across the particle cross-section.

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

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

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

[0213] The particles for thermal spraying used were the particles for thermal spraying according to Example 5 above, which were classified using sieves with nominal openings of 20 μm and 45 μm to have particle sizes ranging from a minimum of 20 μm to a maximum of 45 μm. Used.

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

[0215] The spraying conditions are as follows: Spraying distance: 350mm Barrel length: 152.4mm 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: 20μm~45μm.

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

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

[0218] 12 and 13 show cross sections of Sample 21. FIG. 13 is an enlarged cross section of FIG.

[0219] FIG. 14 shows the results of EPMA analysis of a part of the cross section of Sample 21.

[0220] From FIG. 14, it can be seen that in Sample 21, oxides containing aluminum are present between adjacent flat particles and inside each flat particle.

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

[0222] Such a thermal spray coating is believed to have significant strength compared to conventional coatings.

[0223] (Example 22) A thermal spray coating was formed on the surface of a stainless steel substrate by the same method as in Example 21. However, in Example 22, the thermal spray particles according to the above-mentioned Example 3 were used. Also, in Example 22, detonation spraying was used as the thermal spraying method instead of HVOF spraying.

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

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

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

[0227] (High temperature corrosion resistance test) Samples 21, 22, and 31 were subjected to the following high-temperature corrosion resistance test.

[0228] Each sample was exposed to an N2+SO2 (1000 ppm) atmosphere at 700°C for 100 hours, after which the surface of the thermal sprayed coating was analyzed.

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

[0230] 17, the presence of sulfur components was 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 had better high-temperature sulfidation resistance than Sample 31.

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

[0233] After the test, EDX mapping of sulfur (S) components was carried out on the surface of Sample 21. Almost no sulfur components were detected on the surface of Sample 21 after the test.

[0234] Therefore, next, the S component was analyzed at each thickness position in the cross section of the thermal spray coating of Sample 21.

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

[0236] [Table 5] Table 5 shows that for sample 21, no sulfur component was detected at any depth position from X to Z in the thermal spray coating after the test.

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

[0238] 100 Thermal spray particles (first particles) 110 First Area 120 Second Area 200 Thermal spray particles (secondary particles) 210 First Area 220 Second Area 300 Thermal spray particles (third particles) 310 First Region 320 Second Realm 330 Precipitate 352 Treated particles 354 Aluminum Source 358 Anti-sintering agents 365 void 400 Thermal spray particles (fourth particle) 410 First Region 420 Second Area 430 Precipitate

Claims

1. Particles for thermal spraying, is generally spherical and comprises iron and aluminum; the amount of aluminum contained in the thermal spray particles is in the range of 32 mass% to 48 mass%; The thermal spray particles are a first region having an aluminum concentration in the range of 22% by mass to 37% by mass; a second region having an aluminum concentration in the range of 40% by mass to 50% by mass; a precipitate composed of an oxide of aluminum or a composite oxide of aluminum and iron; the precipitates have an acicular or spherical morphology and a maximum dimension in the range of 0.1 μm to 2 μm; Aluminum is contained throughout the thermal spray particles. Particles for thermal spraying.

2. the first region includes an FeAl phase; The second region is composed of an FeAl phase and an FeAl ２ The thermal spray particle of claim 1 , comprising a phase.

3. The particle for thermal spraying has a core portion and an outer layer covering the core portion, The particle for thermal spraying according to claim 1 or 2, wherein the first region forms the core portion, and the second region forms the outer layer.

4. 4. The particle for thermal spraying according to claim 3, wherein the second region occupies 5% or more of a cross section passing through the center of the particle for thermal spraying.

5. The particle for thermal spraying according to claim 1 or 2, wherein the first region and the second region are arranged in a mottled pattern.

6. 6. The particle for thermal spraying according to claim 5, wherein the second region occupies 5% or more of a cross section passing through the center of the particle for thermal spraying.

7. 7. The particles for thermal spraying according to claim 1, wherein the particles for thermal spraying have an average particle size in the range of 10 μm to 100 μm.

8. A particle for thermal spraying described in any one of claims 1 to 7, wherein the precipitates are distributed in an approximately ring shape centered on the center of the particle for thermal spraying.

9. A method for producing particles for thermal spraying, comprising: a method for producing a mixed particle by mixing iron-containing particles to be treated, an aluminum source, an activator containing a halide, and a sintering inhibitor; heating the mixed particles and using the gaps formed by the sintering inhibitors between adjacent particles as small reaction compartments for calorification treatment to calorify the treated particles, thereby obtaining a treated mixture containing aluminum-infiltrated particles; the average particle size of the treated particles is smaller than the average particle size of the sintering inhibitor; the average particle size of the aluminum source is smaller than the average particle size of the sintering inhibitor; The method further comprises removing the sintering inhibitor from the treated mixture to obtain particles for thermal spraying.

10. The mixed particles are filled into a reaction vessel, The manufacturing method according to claim 9, wherein a filling rate of the sintering inhibitor relative to the volume of the reaction vessel is in the range of 50% to 80%.

11. The method according to claim 9 or 10, wherein the sintering inhibitor has at least one shape selected from the group consisting of a sphere, a triangular pyramid, a triangular prism, a tetrahedron, a cone, and a cylinder.

12. The method according to any one of claims 9 to 11, wherein the sintering inhibitor comprises at least one of alumina, kaolin, and silicon oxide.

13. The method according to claim 9 , wherein the average particle size of the treated particles is 0.29 times or less the average particle size of the sintering inhibitor.

14. The method according to claim 9 , wherein the average particle size of the aluminum source is 0.29 times or less the average particle size of the sintering inhibitor.

15. The method according to any one of claims 9 to 14, wherein the average particle size of the particles to be treated is in the range of 10 µm to 200 µm.

16. The method according to any one of claims 9 to 15, wherein the sintering inhibitor has an average particle size in the range of 500 µm to 5000 µm.

17. 17. The manufacturing method according to claim 9, wherein a ratio (Al / Fe) of the aluminum component contained in the mixed particles to the iron component contained in the treated particles is in a range of 32 / 68 to 48 / 52 in mass ratio.

18. The method according to any one of claims 9 to 17, wherein the amount of the particles to be treated is in the range of 10% by mass to 30% by mass with respect to the total amount of the mixed particles.

19. The method according to any one of claims 9 to 18, wherein the amount of the aluminum source is in the range of 8 mass % to 18 mass % with respect to the total amount of the mixed particles.

20. The method according to any one of claims 9 to 19, wherein the amount of the activator is in the range of 0.1% by mass to 2% by mass based on the total amount of the mixed particles.

21. The method according to any one of claims 9 to 20, wherein the amount of the sintering inhibitor is in the range of 50% by mass to 80% by mass with respect to the total amount of the mixed particles.

22. 22. The method according to claim 9, wherein the activator comprises at least one selected from the group consisting of ammonium chloride, iron chloride, aluminum chloride, iron fluoride, and aluminum fluoride.

23. A thermal spray coating containing an aluminum-iron alloy formed from the thermal spray particles according to any one of claims 1 to 8, The mass ratio of aluminum to iron (Al / Fe) contained in each flat particle is in the range of 32 / 68 to 48 / 52, A thermal spray coating in which needle-shaped or spherical oxide particles having a maximum dimension in the range of 0.1 μm to 2 μm are mixed within the flat particles.

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