WO2022118958A1 - Thermal spray material, thermal spray method using same, and thermal spray coating film - Google Patents

Abstract

In order to provide a thermal spray material that can maintain stability even when held for a long period of time in an actual use environment when a rare earth silicate is thermally sprayed, a thermal spray material is used which contains: a rare earth silicate; and a Si-based compound selected from a Si oxide, a compound that is combined with oxygen to form a Si oxide, or a combination thereof. Thus, the Si-based compound is oxidized during the formation of a thermal spray coating film and during subsequent high-temperature heating to supplement the volatile content of a SiO2 component.

Description

Thermal spray material, thermal spraying method using it, thermal spray coating

The present invention relates to a thermal spray material capable of improving the heat resistance stability of a thermal spray coating, a thermal spraying method using the same, and a thermal spray coating.

For example, in order to impart durability such as heat resistance to a base material such as a metal part of various industrial machines, a dry coating technique of providing a thermal spray coating on the surface of the part is applied. The thermal spraying method, which is one of the dry coating technologies, melts a granular thermal spray material made of metal, ceramic, cermet, etc. with a heat source such as a combustion flame or electric energy, and accelerates the thermal spray particles to form a surface of the substrate. It is a method of forming a film by spraying and depositing.

Among these methods, an environmental coating made of rare earth silicate is applied as a film of an aircraft / turbine used in a combustion environment or a steam environment in a temperature range of about 1300 ° C to 1400 ° C. For example, Patent Document 1 proposes the use of a composite film containing a rare earth silicate.

However, in the sprayed coating using a rare earth silicate material, the SiO ₂ component in the coating volatilizes when the sprayed coating is formed and when the high temperature environment is maintained thereafter, and the composition changes (thickening of the coating) and the function as a coating is not satisfied. The problem has arisen. This is because SiO ₂ volatilizes when sprayed with a rare earth silicate, the crystal phase separates, and SiO ₂ volatilizes even in an actual use environment, resulting in low stability when used in an actual environment for a long time. Because it will end up.

Japanese Unexamined Patent Publication No. 2008-308374

An object of the present invention is to provide a thermal spraying material that can maintain stability even when it is kept in an actual use environment for a long time when a rare earth silicate is sprayed.

The present invention uses a thermal spraying material containing a rare earth silicate and a compound that combines with Si oxide or oxygen to form a Si oxide, or a Si-based compound selected from a combination thereof, in order to achieve the above object. .. This makes it possible to supplement the volatile content of the SiO ₂ component by oxidizing the Si-based compound during the formation of the thermal spray coating and the subsequent high-temperature heating, and can solve the above-mentioned problems.

The rare earth silicate may be a compound represented by RE ₂ Si ₂ O ₇ or RE ₂ SiO ₅ (RE is a rare earth element). For example, Yb ₂ Si ₂ O ₇ , Yb ₂ SiO ₅ , ErSi ₂ O ₇ , Er ₂ SiO ₅ , Ho ₂ Si ₂ O ₇ , Ho ₂ SiO ₅ , Dy ₂ Si ₂ O ₇ , Dy ₂ SiO _5, Gd ₂ Examples thereof include SiO ₅ , Gd ₂ Si ₂ O ₇ . The rare earth silicate is preferably a rare earth disilicate.

Examples of the Si oxide include SiO ₂ , and examples of the compound that combines with oxygen to form a Si oxide include SiC, SiC, and SiCN. The Si-based compound is preferably an oxide or carbide of Si.

For example, when Yb ₂ Si ₂ O ₇ is used as a rare earth silicate in a thermal spray material to form a Yb ₂ Si ₂ O ₇ thermal spray coating, the SiO component volatilizes during the thermal spray coating formation and high temperature heating, resulting in Yb ₂ SiO. ₅ is generated. At this time, if, for example, SiC is included as a compound that combines with oxygen to form a Si oxide in the sprayed material, the SiO ₂ generated by the oxidation of SiC is volatile by the following reaction formula (1). The reaction formula (2) makes it possible to retain the Yb ₂ Si ₂ O ₇ component.
SiC + 2O ₂ → SiO ₂ + CO ₂ ... (1)
Yb ₂ SiO ₅ + SiO ₂ → Yb ₂ Si ₂ O ₇ ... (2)

Further, for example, when Yb ₂ Si ₂ O ₇ is used as a rare earth silicate in the spray material and a Yb ₂ Si ₂ O ₇ bulk sintered body is formed by a hot press method, SiC is contained in the spray material. By heat-treating the Yb ₂ Si ₂ O ₇ bulk sintered body, for example, holding it at 1250 ° C. for 5 hours, cracks formed on the surface of the sintered body due to the volatilization of SiO ₂ can be repaired.

The reaction described above may also include, as the spraying material, a rare earth silicate compound other than Yb ₂ Si ₂ O ₇ and a compound other than SiC or a compound that combines with oxygen to form a Si oxide, or a combination thereof. Since it is generated, cracks generated on the surface of the film due to the volatilization of SiO ₂ can be repaired as in the case of SiC.

The electron micrographs of (a) the sprayed coating using the mixed powder of Example 1 and (b) the sprayed coating using the granulated powder of Example 6 in the state of being sprayed without heat treatment are shown. .. Regarding the sprayed coating of Example 6, (a) an electron microscope secondary electron image photograph after heat treatment and (b) an electron microscope reflected electron image photograph after heat treatment are shown. An electron micrograph of the surface of the sprayed coatings of (a) Example 6 and (b) Example 7 observed without heat treatment and an electron micrograph after heat treatment at 1300 ° C. for 100 hours are shown.

The rare earth silicate and Si-based compound in the thermal spray material can be particles, respectively. Such particles may be composed of granulated particles obtained by granulating finer primary particles, or may be mainly composed of aggregates of primary particles (may include a form of agglomeration). It may be a powder. More preferably, it may be a granule composed of an aggregate of primary particles. Further, the granules may be composed of a composite granule composed of a collection of primary particles of a rare earth silicate and primary particles of a Si-based compound. When the thermal spray coating is formed of such a thermal spray material containing granules made of a composite granule, the amount of volatilization of the Si-based compound due to the thermal effect during film formation can be further suppressed.

The particle size of the rare earth silicate particles and Si-based compounds in the thermal spraying material is not particularly limited. It is preferable that the ratio DvR / DvSi of the volume-based average particle diameter DvSi of the Si-based compound particles to the volume-based average particle diameter DvR of the rare earth silicate particles is 1/10 or more and 4 or less. Within this range, the Si-based compound can more preferably supplement the volatile content of the SiO2 component during the formation of the sprayed coating and the subsequent high-temperature heating, and has the effect of containing a large amount of rare earth disilicate structure. There is.

The average particle size of the sprayed material particles is not particularly limited as long as it is about 10 μm or less, and the lower limit of the average particle size is also not particularly limited. However, the volume-based average particle size of the Si-based compound particles is preferably 0.3 μm or more and 2 μm or less. Further, it is preferable that the average particle size of the rare earth silicate particles based on the volume is 1 μm or more and 3 μm or less. Further, the average particle size on a volume basis in the case of granules is preferably 10 μm or more and 50 μm or less. Within these ranges, the Si-based compound can more preferably supplement the volatile matter of the SiO ₂ component at the time of forming the thermal spray coating and at the time of subsequent high-temperature heating, and can contain a large amount of rare earth disilicate structure. There is an effect.

For particles with an average particle size of approximately 1 μm or more, for example, a laser diffraction / scattering type particle size distribution measuring device (Spectris Co., Ltd., laser diffraction type particle size distribution measuring device master sizer) is used for the average particle size of the sprayed particles. The measured 50% integrated particle size (D50) in the volume-based particle size distribution can be adopted.

For particles having an average particle diameter of less than about 1 μm, a sphere-equivalent diameter calculated based on the specific surface area can be adopted. The specific surface area is, for example, a value calculated by the BET 1-point method from the amount of gas adsorbed such as _N2 measured by the continuous flow method using a specific surface area measuring device (manufactured by Mountech, fully automatic specific surface area measuring device Macsorb). can do. The critical value of the average particle size to which each measurement method is applied is not strictly defined in the above, and may be changed according to the accuracy of the analyzer used.

The content of the Si-based compound in the thermal spraying material is not particularly limited, but is preferably 1% by weight or more and 10% by weight or less. If it is less than 1% by weight, the effect of replenishing the SiO ₂ volatile matter is not sufficient, and if it exceeds 10% by weight, when it is exposed to a high temperature environment after the thermal spray coating is formed, cracks occur on the film surface as the oxidation reaction progresses. Because there is a tendency. It is considered that this is because the effect of the addition of SiC reaches supersaturation, and the formation of SiO ₂ causes volume expansion and cracks. More preferably, it is 5% by weight or more and 10% by weight or less.

The thermal spraying material may be a mixture of rare earth silicate particles and Si-based compound particles. Alternatively, using rare earth silicate particles and Si-based compound particles, composite particles may be produced by a solid-phase sintering method such as an atomizing method, a melt-crushing method, or a sintering-crushing method and a granulation-sintering method. Can be done.

The atomizing method is obtained by melting a mixture of a rare earth silicate powder and a Si-based compound powder, spraying and cooling the mixture, and then classifying the mixture as necessary. In the melt-pulverization method, a mixture of a rare earth silicate powder and a Si-based compound powder is melted, cooled and solidified, then pulverized, and if necessary, classified thereafter. The granulation-sintering method is obtained by preparing a granulation powder from a mixture of a rare earth silicate powder and a Si-based compound powder, sintering the granulation powder, and further crushing and classifying the granulation powder. The sintering-crushing method is obtained by compression-molding a mixture of a rare earth silicate powder and a Si-based compound powder, sintering the mixture, and pulverizing and classifying the obtained sintered body.

Among these, it is preferable to produce a granulated powder by a granulation-sintering method in which a granulated powder is produced from a powder mixed with raw materials and the granulated powder is sintered. The sprayed material produced by the granulation-sintering method is generally produced by another manufacturing method such as the sintering-sintering method, in which the raw material powder is compression-molded and then sintered, and the obtained sintered body is crushed. It has better fluidity than the fired material produced. Moreover, in the case of the granulation-sintering method, since the pulverization step is not included in the manufacturing process, impurities can be further suppressed during pulverization.

The method for spraying the thermal spraying material of the present embodiment may be high-speed flame spraying such as high-speed oxygen fuel (HVOF) spraying, plasma spraying such as atmospheric pressure plasma spraying (APS), or explosive spraying. You may. Alternatively, it may be cold process spraying such as cold spray, warm spray and high speed air fuel (HVAF) spraying.

Among these, high-speed oxygen fuel (HVOF) spraying or plasma spraying is preferably applied. Even when a sprayed material having a relatively large average particle size is used, the sprayed particles can be sufficiently softened and melted and accelerated. As a result, even when a thermal spraying material containing particles having a large average particle size is used, it is possible to form a thermal sprayed coating that is dense and has a high pickers hardness.

The HVOF thermal spraying method is a type of frame thermal spraying method that uses a combustion flame obtained by mixing fuel and oxygen and burning them at high pressure as a heat source for thermal spraying. By increasing the pressure in the combustion chamber, a high-speed (including supersonic) high-temperature gas flow is ejected from the nozzle even though it is a continuous combustion flame. The HVOF thermal spraying method includes a general coating method for obtaining a thermal spray coating by putting a thermal spray material into this gas flow, heating and accelerating it, and depositing it on a substrate. According to the HVOF spraying method, for example, by melting and accelerating the sprayed material with a jet of a supersonic combustion flame at 2000 ° C to 3000 ° C, the sprayed particles are based at a high speed of 500 m / s to 1000 m / s. It can be deposited by colliding with the material. The fuel used in the high-speed frame spraying may be a gas fuel of a hydrocarbon such as acetylene, ethylene, propane or propylene, or a liquid fuel such as kerosene or ethanol. Further, it is preferable that the temperature of the supersonic combustion flame is higher as the melting point of the thermal spray material is higher, and from this viewpoint, it is preferable to use gas fuel.

The plasma spraying method is a thermal spraying method that uses a plasma flame as a thermal spraying heat source for softening or melting the thermal spraying material. When an arc is generated between the electrodes and the working gas is turned into plasma by the arc, the plasma flow is ejected from the nozzle as a high-temperature and high-speed plasma jet. The plasma spraying method includes a general coating method for obtaining a thermal spray coating by charging a thermal spray material into this plasma jet, heating and accelerating it, and depositing it on a substrate. The plasma spraying method includes atmospheric plasma spraying (APS: atmospheric plasma spraying) performed in the atmosphere, reduced pressure plasma spraying (LPS: low pressure plasma spraying) performed at a pressure lower than atmospheric pressure, and application higher than atmospheric pressure. It may be an embodiment such as high pressure plasma spraying in which plasma spraying is performed in a pressure vessel. According to plasma spraying, for example, by melting and accelerating the thermal spraying material with a plasma jet of about 5000 ° C to 10000 ° C, the thermal spray particles collide with the substrate at a speed of about 300 m / s to 600 m / s. Can be deposited.

The type of the base material for which the thermal spray coating is formed is not particularly limited, and examples thereof include metal materials, simple ceramic materials, composite ceramic materials, and ceramic matrix composites such as SiC / SiC. Specific examples of the base material include aluminum alloys such as Al ₂ O ₃ , zirconium alloys such as ZrO ₂ , iron, steel, copper, copper alloys, nickel, nickel alloys, gold, silver, bismuth, manganese, zinc, and the like. Examples include metal materials such as zinc alloys and cobalt. Examples of steel include various SUS (stainless steel) materials used as corrosion-resistant structural steel. Examples of the aluminum alloy include A1000 series to A7000 series aluminum alloys that are useful as lightweight structural materials and the like. Corrosion-resistant alloys include, for example, Hasteroy (manufactured by Haynes), which is an alloy in which molybdenum, chromium, etc. are added to a nickel group, and Inconel (manufactured by Special Metals), which is an alloy in which iron, chromium, niobium, molybdenum, etc. are added to a nickel group. Examples thereof include sterite (manufactured by Delorosterite Group), which is an alloy containing cobalt as a main component and added chromium, tungsten, etc., and Inver, which is an alloy obtained by adding nickel, manganese, carbon, etc. to iron.

Next, the present invention will be described in more detail with reference to Examples and Comparative Examples.
<Creation of thermal spray material>
As shown in Table 1, in Example 1, Yb ₂ Si ₂ O particles having an average particle diameter (D50) of 32 μm and α-SiC particles having an average particle diameter (D50) of 2.3 μm were used as α-SiC particles for the entire thermal spraying material. The sprayed material was produced by putting them in a bag so that the amount of SiC particles added was 10% by weight and mixing them well.

Similarly, in Examples 2 and 3, Yb ₂ Si _{2 O7} particles and α-SiC particles having an average particle size shown in Table 1 are added, and the amount of α-SiC particles added to the entire thermal spraying material is 10. The sprayed material was produced by putting the particles in a bag so as to have a weight of% by weight and mixing them well.

As shown in Table 1 below, in Example 4, a solvent and α-SiC particles having an average particle diameter (D50) of 0.351 μm were used for Yb ₂ Si ₂ O ₇ particles having an average particle diameter (D50) of 1.2 μm. Then, water is used as a solvent to mix and slurry so that the amount of α-SiC particles added to the entire sprayed material is 10% by weight, and spray-dried using a spray dryer to form a composite granulated powder. As a result, the spray material was manufactured.

Similarly, in Examples 5 to 7, Yb ₂ Si ₂ O ₇ particles and α-SiC particles having an average particle size shown in Table 1 are added, and the amount of α-SiC particles added to the entire thermal spraying material is 10. A thermal spraying material was produced by forming a composite granulated powder according to the same procedure as in Example 4 by mixing so as to have a weight of% by weight. Further, in Examples 8 and 9, the silicate compound particles were replaced with Y ₂ Si ₂ O ₇ (itrium silicate) and Gd ₂ Si ₂ O ₇ (gadrinium silicate), respectively, and the silicates having the particle diameters shown in Table 1 were substituted. The compound particles and the α-SiC particles are mixed so that the amount of the α-SiC particles added to the entire sprayed material is 10% by weight, and a composite granulated powder is formed according to the same procedure as in Example 4. By doing so, the thermal spraying material was produced.

As shown in Table 1 below, in the comparative example, Yb ₂ Si ₂ O ₇ particles having an average particle diameter (D50) of 32 μm were used as a thermal spray material.

<Formation of thermal spray coating>
Atmospheric pressure plasma using SG-100 (manufactured by Plax Air Co., Ltd.) (equipment) under the conditions shown in Table 2 using the sprayed materials of Examples 1 to 9 and Comparative Examples manufactured as described above. By the thermal spraying method, a thermal spray coating was formed on the Al ₂ O ₃ substrate in Examples 1 to 3 and Comparative Example 1, and on the ZrO ₂ substrate in Examples 4 to 9.

<Measurement of peak intensity ratio>
After the sprayed coatings of Examples ₁ to ₇ and Comparative Examples were held at a high temperature of 1300 ° C. for 5 hours, the peak intensities of the sprayed coatings _were analyzed by X-ray diffraction. The peak intensity ratio to Yb ₂ SiO ₅ was calculated and the results are shown in Table 3. Further, after the sprayed coatings of Examples 4 to 7 and Comparative Examples were held at a high temperature of 1300 ° C. for 50 hours, the peak intensities of the sprayed coatings were analyzed by X-ray diffraction, and the peak intensities of Yb ₂ Si ₂ O ₇ with respect to Yb ₂ SiO ₅ were analyzed. The ratio was calculated and the results are shown in Table 3. Similarly, in Examples 8 and 9, after holding at a high temperature of 1300 ° C. for 5 hours, the peak intensity of the sprayed coating was analyzed by X-ray diffraction, and in Example 8, the peak intensity ratio of YSi ₂ O ₇ to Y ₂ SiO ₅ was determined. In Example 9, the peak intensity ratio of Gd ₂ Si ₂ O ₇ to Gd ₂ SiO ₅ is shown in Table 4. For X-ray diffraction, use Maxima XRD-7000 (device) manufactured by Shimadzu Corporation under the conditions of tube voltage: 40 kV, tube current: 30 mA, scanning speed: 2.000 deg./min, scanning step: 0.0200 deg. I went below.

For the peak intensity and the peak intensity ratio, the peak corresponding to each crystal structure obtained by X-ray diffraction was selected, normalized, and calculated as the intensity peak and the intensity peak ratio. The same method was used for the following examples.

As shown in the results of Table 3, the Yb ₂ Si ₂ O ₇ / Yb ₂ SiO ₅ intensity ratios after holding at 1300 ° C. for 5 hours and 50 hours were higher in Examples 1 to 7 than in Comparative Examples. It can be seen that in 1 to 7, more Yb ₂ Si ₂ O ₇ was formed by the repair reaction than in the comparative example. Further, after holding at 1300 ° C. for 5 hours, the Yb ₂ Si ₂ O ₇ of the thermal spray coating when the thermal spray material composed of the composite granulated powder of Yb ₂ Si ₂ O ₇ particles and SiC particles of Examples 4 to 7 was used. The / Yb ₂ SiO ₅ intensity ratio is the Yb ₂ Si ₂ O ₇ / Yb ₂ SiO of the thermal spray coating when a thermal spray material composed of a mixed powder of Yb ₂ Si ₂ O ₇ particles and SiC particles of Examples 1 to 3 is used. It can be seen that the intensity ratio tends to be higher than ₅ . This is because the use of composite granulated powder as a raw material has less SiC volatilization, more SiC is left in the sprayed coating, and Yb ₂ Si ₂ O ₇ is produced by the repair reaction. It shows that more were formed. Further, the longer the temperature is kept at high temperature (1300 ° C., 50 hours), the higher the strength ratio of Yb ₂ Si ₂ O ₇ / Yb ₂ SiO ₅ becomes, and the ratio of Yb ₂ Si ₂ O ₇ increases due to the repair reaction. You can see that.

Further, as shown in Table 4, the peak intensity ratio of YSi ₂ O ₇ to Y ₂ SiO ₅ of Example 8 and the peak intensity ratio of Gd ₂ Si ₂ O ₇ to Gd ₂ SiO ₅ of Example 9 are also compared. It was confirmed that the same effect was obtained even if the silicate compound particles were replaced, which was higher than the Yb ₂ Si ₂ O ₇ / Yb ₂ SiO ₅ intensity ratio of the example.

As shown in Table 3, it was obtained by Example 1 in which 10% by weight of α-SiC having the same particle size of 2.3 μm was added and a mixed powder was used, and Example 6 in which granules made of a composite granulated powder were used. Comparing the peak intensity ratio of Yb ₂ Si ₂ O ₇ to Yb ₂ SiO ₅ of the sprayed coating, Example 6 using granules made of composite granulated powder was more than Example 1 using mixed powder. , Yb ₂ Si ₂ O ₇ has a high peak intensity ratio to Yb ₂ SiO ₅ , and the sprayed film formed using the composite granulated powder has more Yb ₂ Si ₂ O ₇ components than the simply mixed one, and is repaired. It can be seen that the effect is great.

<Observation of scanning electron micrograph>
Next, the operation-type electron micrographs of the sprayed coatings of Examples 1 and 6 in the state of being sprayed without heat treatment are shown in FIGS. 1 (a) and 1 (b), respectively. The electron micrograph was taken using a scanning electron microscope SU-70 manufactured by Hitachi High-Tech, and the surface of the sprayed coating sample was observed. The sprayed coating formed by using the granulated powder of Example 6 shown in (b) has more SiC crystals than the sprayed coating formed by using the mixed powder of Example 1 shown in (a). It can be seen that there are many particles. It is considered that this is because the mixed powder has a larger amount of SiC volatilized during the thermal spraying film formation than the granulated powder, and the amount of SiC formed as crystal grains in the thermal sprayed film is smaller.

Next, with respect to the sprayed coating of Example 6, an electron microscope secondary electron image photograph after heat treatment at 1300 ° C. for 5 hours and an electron microscope backscattered electron image photograph of the same region of the secondary electron image photograph are taken. It is shown in (a) and (b) of FIG. 2, respectively. In the electron microscope secondary electron image photograph (a), it can be seen that black SiC particles are deposited on the YbxSiyOz substrate, which is a gray region, and in the electron microscope reflected electron image photograph (b), the black SiC particles are observed. A new gray area appears around it, which is formed by the oxidation of SiC to form SiO ₂ , and the repair reaction between SiO ₂ and Yb ₂ SiO ₅ (bright area) causes the gray area of Yb ₂ Si ₂ O ₇ . Is considered to have been formed.

After forming the thermal spray coatings of Examples 6 and 7, an electron micrograph of the surface observed without heat treatment by the same method as described above and an electron micrograph after heat treatment at 1300 ° C. for 100 hours are shown in FIG. 3, respectively. rice field. (A) is the thermal spray coating of Example 6, and (b) is the thermal spray coating of Example 7, respectively, and an electron micrograph of the state in which the thermal spray coating is still formed is shown on the left side, and the same is shown on the right side. An electron micrograph of the test piece observed after heat treatment at 1300 ° C. for 100 hours is shown. In both (a) and (b), cracks were seen in the circled area in the photograph (left side) with the sprayed coating still formed, but in the photograph after heat treatment (right side), almost no cracks were found. You can see that there is. It can be seen that the cracks of both films have been repaired by oxidation by heat treatment for 100 hours. In both Examples 6 and 7, it was confirmed that the addition of SiC particles having a relatively large particle size effectively suppressed the volatilization of SiC and left the SiC particles in the film.

The sprayed coating of Example 6 is heat-treated for a long time by comparing the X-ray diffraction pattern over time with respect to the sprayed coating and the coating after heat treatment at 1300 ° C. for 5, 50 hours and 100 hours. It was confirmed that the peak of Yb ₂ Si ₂ O ₇ decreased and the peak of Yb ₂ Si ₂ O 7 increased due to the progress of the oxidation reaction due to the above, and the composition of the single layer film of Yb ₂ Si ₂ O ₇ was almost approached. .. X-ray diffraction was performed using Maxima XRD-7000 manufactured by Shimadzu Corporation. It was confirmed that the longer the heat treatment time, the more the composition restoration progressed due to the oxidation reaction caused by the long heat treatment.

For the spray coatings of Examples 4 to 7, the electron micrographs of the surfaces observed without heat treatment and the electron micrographs observed after steam oxidation treatment at 1300 ° C. for 100 hours were compared by the same method as described above. However, when the 1.4 to 2.9 μm SiC particles of Examples 5 to 7 were used, it was confirmed that almost no cracks were observed after the water vapor oxidation (electron micrographs are omitted). It was confirmed that even in steam oxidation, the addition of SiC particles having a relatively large particle size suppresses the volatilization of SiC and leaves the SiC particles in the film, thereby effectively repairing cracks.

Claims (12)

1. A thermal spraying material containing a rare earth silicate and a compound that combines with Si oxide or oxygen to form a Si oxide, or a Si-based compound selected from a combination thereof.
2. The thermal spraying material according to claim 1, wherein the rare earth silicate and the Si-based compound are particles, respectively.
3. The thermal spraying material according to claim 2, wherein the particles constitute granules.
4. 2. The thermal spraying material according to 3.
5. The thermal spraying material according to any one of claims 2 to 4, wherein the volume-based average particle diameter of the Si-based compound particles is 0.3 μm or more and 2 μm or less.
6. The thermal spraying material according to any one of claims 2 to 5, wherein the volume-based average particle diameter of the rare earth silicate particles is 1 μm or more and 3 μm or less.
7. The thermal spraying material according to claim 3, wherein the average particle size of the granules based on the volume is 10 μm or more and 50 μm or less.
8. The thermal spraying material according to any one of claims 1 to 7, wherein the content of the Si-based compound in the thermal spraying material is 1% by weight or more and 10% by weight or less.
9. The thermal spraying material according to any one of claims 1 to 8, wherein the rare earth silicate is a rare earth disilicate, and the Si-based compound is an oxide or carbide of Si.
10. A method for forming a thermal spray coating using the thermal spray material according to any one of claims 1 to 9.
11. The method according to claim 10, wherein a thermal spray coating is formed by a plasma spraying method.
12. A thermal spray coating formed by the thermal spray material according to any one of claims 1 to 9.

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