JP7393166B2 - Method for producing thermal spray powder, thermal spray slurry, and thermal barrier coating - Google Patents

Description

The present invention relates to a thermal spraying powder, a thermal spraying slurry containing the same, and a method for producing a thermal barrier coating using the same. More specifically, the present invention relates to a thermal spray powder and a thermal spray slurry for forming a thermal barrier coating that can improve CMAS resistance, and a method for producing a thermal barrier coating using the same.

For materials used under high temperatures, such as gas turbine engine stator blades, moving blades, and combustor wall materials, heat-resistant components are coated with a heat-insulating film to protect them from high temperatures. . Such materials also contain calcia-magnesia-alumina-silicate deposits derived from the ingestion of silica-based minerals (dust, sand, volcanic ash, runway debris, etc.) associated with gas turbine engine air intake. (CMAS) tolerance is required.

CMAS-resistant coatings are often applied by thermal spray methods. Thermal spraying is one of the surface modification techniques that have been put into practical use, along with physical vapor deposition, chemical vapor deposition, and the like. Thermal spraying has the following advantages: there is no limit to the size of the substrate, it can form a uniform sprayed coating even on a wide area of the substrate, the coating can be formed at a high speed, it can be easily applied on-site, and it is relatively easy to apply. Due to its ability to form thick films, its application has expanded to a variety of industries in recent years, making it an extremely important coating technology.

U.S. Pat. No. 5,005,001 describes an article comprising a CMAS-resistant thermal barrier coating (TBC) layer, the TBC composition comprising about 50% to about 90% by weight and about 10% to about 50% by weight of the CMAS-resistant composition. Articles are disclosed, including alumina, silica, etc., as CMAS-resistant compositions.
Patent Document 2 discloses a suspension containing a sintering aid containing a rare earth silicate and one or more oxides suspended in a liquid carrier for the purpose of forming a rare earth silicate airtight layer. SiO ₂ having an outer diameter of about 5 nm to about 3 μm, about 5 nm to about 100 nm, about 30 nm to about 70 nm is disclosed as a sintering aid.

JP2013-540887A Japanese Patent Application Publication No. 2015-172245

However, these conventional techniques have had problems such as insufficient CMAS resistance or a decrease in hardness or Young's modulus due to improved CMAS resistance. The present invention provides a thermal spray powder for forming a thermal spray coating with improved CMAS resistance and excellent mechanical properties such as hardness and Young's modulus, a thermal spray slurry containing the same, and a thermal barrier coating using the same. The purpose is to provide a manufacturing method for.

In order to solve the above problems, the present invention provides a thermal spraying powder for thermal barrier coating, which contains SiO ₂ and an oxide material other than SiO ₂ , and which reduces the amount of SiO ₂ in the thermal spraying powder. Provided is a powder for thermal spraying having a content of 1% by mass to 10% by mass.

By forming a thermal spray film using the thermal spray powder of the present invention, a thermal barrier coating that suppresses the invasion of CMAS, further improves CMAS resistance, and has excellent mechanical properties such as hardness and Young's modulus. can be formed.

FIG. 1 shows a cross-sectional scanning electron microscope (SEM) photograph of a CMAS penetration layer formed in a thermally sprayed coating of a comparative example. (a) is a CMAS interstitial layer formed on a thermally sprayed coating made of YbTaO, (b) is a CMAS interstitial layer formed on a thermally sprayed coating made of 8YSZ, and (c) is a CMAS interstitial layer formed on a thermally sprayed coating made of Yb ₂ SiO ₅ . A cross-sectional micrograph of the CMAS penetration layer is shown.

An embodiment of the present invention will be described in detail. Note that the following embodiment shows an example of the present invention, and the present invention is not limited to this embodiment. Furthermore, various changes or improvements can be made to the embodiments described below, and forms with such changes or improvements are also included in the present invention. It can be done.

One embodiment of the present invention is a thermal spray powder for thermal barrier coating, which includes SiO ₂ powder and an oxide-based powder other than SiO ₂ , wherein the content of SiO ₂ in the thermal spray powder is A thermal spray powder having a content of 1% to 10% by weight is provided.
Further, the content of SiO ₂ is 1% by mass to 10% by mass, preferably 3% by mass to 8% by mass. If the content of SiO ₂ is less than 1% by mass, the effect of improving CMAS resistance will not appear, and if it exceeds 10% by mass, the effect of improving CMAS resistance will be saturated, but the mechanical properties such as hardness and Young's modulus of the sprayed coating will be reduced. The properties tend to deteriorate, reducing its practicality as a heat-shielding coating.

The reason why CMAS resistance is improved by adding 1% to 10% by mass of SiO ₂ to thermal spray powder materials is not necessarily established, but the addition of SiO ₂ may improve the contact of the coating film with CMAS. One reason is thought to be that the wettability of the surface decreases, making it difficult for CMAS to penetrate from the surface. It is also thought that this is because the amount of deoxidized oxides other than SiO ₂ decreases due to the evaporation of SiO ₂ particles in the sprayed coating. That is, in conventional heat-resistant oxide coatings, when CMAS adheres, CMAS penetrates into the coating film due to deoxidation of the oxide, and a reaction phase of the oxide and CMAS is formed. On the other hand, by adding SiO ₂ , the deoxidation of heat-resistant oxides other than SiO ₂ is reduced, and furthermore, the wettability at the contact surface with CMAS is reduced, so that the invasion of CMAS can be reduced. Therefore, it is expected that CMAS resistance will be improved by adding 1% to 10% by mass of SiO ₂ to various heat-resistant oxides.

The particle size of the SiO ₂ powder in the obtained thermal spray powder is not particularly limited, but may be 0.001 to 2 μm, preferably 0.001 to 0.5 μm, in volume-based average particle size. The smaller the volume-based average particle diameter of the SiO ₂ powder is and the easier it is to volatilize, the lower the amount of deoxidation from oxide particles other than SiO ₂ tends to be, and the more CMAS intrusion tends to be reduced. When the volume-based average particle diameter of the SiO ₂ powder exceeds 2 μm, the SiO ₂ powder tends to be difficult to volatilize. Further, it is preferable that the volume-based average particle size of the SiO ₂ powder is smaller than or about the same as the volume-based average particle size of the oxide-based powder other than SiO ₂ . As the volume-based average particle size of SiO ₂ powder is smaller than the volume-based average particle size of oxide powders other than SiO ₂ , the amount of deoxidation of oxide particles other than SiO ₂ tends to decrease. This is because the intrusion of

As the oxide powder other than SiO ₂ , oxide powders generally used for heat-resistant materials can be used. For example, oxides or composite oxides of rare earth elements such as Yb, Y, Sc, Lu, Dy, Er, and Sm, and metals such as Al, Ti, Ta, and Zr may be used. Specifically, metal oxides such as yttrium oxide (Y ₂ O ₃ ), aluminum oxide (Al ₂ O ₃ ), titanium oxide (TiO ₂ ), zirconium oxide (ZrO ₂ ), hafnium oxide (HfO ₂ ), and yttria (Y ₂ O ₃ ) stabilized zirconia (YSZ), Ytterbia tantalum oxide (YbTaO), Ytterbia (Yb ₂ O ₃ ) stabilized zirconia (YbSZ), Ytterbia silica (Yb ₂ SiO ₅ , Yb ₂ Si ₂ O ₇ ) , hafnia silica (HfSiO), dysprosia (Dy ₂ O ₃ ) stabilized zirconia (DySZ), Erbia (Er ₂ O ₃ ) stabilized zirconia (ErSZ), and SmYbZr ₂ O ₇ . Among the yttria-stabilized zirconias, zirconia stabilized with 8% by mass of yttria (8YSZ) and zirconia stabilized with 20% by mass of yttria (20YSZ) may be used.

The particle size of the oxide powder other than SiO ₂ in the obtained thermal spray powder is not particularly limited, but may be 1 to 5 μm, preferably 1.5 to 3 μm, in volume-based average particle size. If the volume-based average particle diameter of the oxide powder other than SiO ₂ is less than 1 μm, the resulting thermal spray coating tends to have poor durability in environments where heat shielding properties are required; The ability to prevent CMAS intrusion tends to decrease in environments where the heat shielding properties of the coating are required.

The thermal spray powder of the present invention may be a simple mixture of SiO ₂ powder and an oxide powder other than SiO ₂ , or may be a composite particle in which both are combined. Alternatively, the particles may be composite particles in which oxide particles are coated with SiO ₂ particles. By forming composite particles, in particular by forming composite particles in which oxide particles are coated with SiO ₂ particles, it is expected that the amount of deoxidation from the oxide particles will be further reduced, thereby further preventing CMAS intrusion. The composite particles may have an average particle diameter on an average volume basis of 2 to 50 μm. If the volume-based average particle diameter of the composite particles is less than 2 μm, the thermal sprayed coating tends to have poor durability in environments where heat shielding properties are required. CMAS intrusion prevention tends to decline under demanding environments.

The volume-based average particle size of SiO ₂ powder, the volume-based average particle size of oxide powder other than SiO ₂ , and the volume-based average particle size of composite particles can be measured by a laser diffraction method or a gas adsorption method. For example, as a laser diffraction/scattering particle size analyzer, a laser diffraction particle size distribution analyzer Mastersizer 3000 manufactured by Malvern Panalytical can be used.
In order to obtain such mixed forms, composite particles, and coated particles, processes such as mixing SiO ₂ powder and oxide powder other than SiO ₂ in a predetermined ratio, granulation, sintering, crushing, and classification are required. The method may be selected as appropriate depending on the particle form to be used. Specifically, it can be manufactured by a granulation and sintering method, a sintering and pulverizing method, a melting and pulverizing method, and the like.

For example, in the mixing step, a slurry is prepared by dispersing powder particles in a solvent such as a mixed solution of water and alcohol. When granulating, the prepared slurry is granulated into droplets using a granulator such as a spray granulator, and then dried. In order to obtain composite particles, SiO ₂ powder and oxide powder other than SiO ₂ may be mixed in advance at a predetermined ratio and granulated. At this time, by adjusting the particle sizes of the SiO ₂ powder and the oxide powder other than SiO ₂ , composite particles in which the oxide particles are coated with the SiO ₂ particles can be obtained. In sintering, it is desirable to obtain optimal mechanical strength by appropriately controlling the sintering temperature, sintering aid, etc. Thereafter, a powder for thermal spraying adjusted to a predetermined particle size can be obtained by pulverization and classification.

The granulation and sintering method is a method in which raw material particles are granulated into secondary particles and then sintered to firmly bond (sinter) the raw material particles to each other. In this granulation and sintering method, granulation can be carried out using a granulation method such as dry granulation or wet granulation. Specifically, the granulation method includes, for example, rolling granulation method, fluidized bed granulation method, stirring frame granulation method, crushing granulation method, melt granulation method, spray granulation method, and microemulsion granulation method. Laws etc. Among them, a spray granulation method is suitable as a granulation method.

In the sintering and pulverization method, first, a plurality of raw material powders are mixed and compression molded to form a compact. Next, the compact is sintered to form a sintered body. Subsequently, the sintered body is crushed and classified to obtain the desired thermal spray powder. In the melt-pulverization method, first, a plurality of raw material powders are mixed, heated and melted, and then cooled to form a solidified product (ingot). Next, the solidified product is crushed and classified to obtain the desired thermal spray powder.
In order to form coated particles, the raw material particles are divided into core particles with large primary particles and fine particles with small primary particles, and these are blended appropriately. Attach by adhesive force. After that, it can be obtained by increasing the bonding strength between particles in a sintering process.

A thermal spray coating can be formed on various substrates by thermal spraying using various thermal spraying methods using the thermal spray powder produced by the above method. Thermal spraying methods are not particularly limited, but examples include atmospheric plasma spraying (APS), suspension plasma spraying (SPS), low pressure plasma spraying (LPS), and high pressure plasma spraying. pressure plasma spraying), high velocity oxygen flame (HVOP) spraying, warm spray spraying, and high velocity air flame (HVAF) spraying. High-speed flame spraying or the like can be suitably used.

The thermal spraying powder produced by the above method can be supplied to the thermal spraying apparatus in the form of a powder, or may be supplied to the thermal spraying apparatus in the form of a slurry. When the thermal spray material is in the form of a slurry, it can be prepared using a dispersion medium. Examples of the dispersion medium include alcohols such as methanol and ethanol, toluene, hexane, and kerosene. The thermal spray material in slurry form may further contain other additives, such as dispersants, flocculants, viscosity modifiers, etc.

There are no particular restrictions on the type of base material on which the thermal spray coating is formed. Examples include metal materials such as alloys, simple ceramic materials, composite ceramic materials, ceramic matrix composites, and the like. Specific examples of metal materials include alloys containing iron, nickel, cobalt, and the like. For example, stainless steel, Hastelloy (manufactured by Haynes), which is a nickel-based alloy with molybdenum, chromium, etc. added, Inconel (manufactured by Special Metals), which is a nickel-based alloy with iron, chromium, niobium, molybdenum, etc. added, Examples include Stellite (manufactured by Delor Stellite Group), which is an alloy containing cobalt as a main component with additions of chromium, tungsten, etc., and Invar, which is an alloy of iron with nickel, manganese, carbon, etc. added thereto. Furthermore, examples of ceramic materials include monolithic ceramics such as zirconia and alumina, ceramic matrix composites (CMC), and the like.

EXAMPLES The present invention will be described in more detail below with reference to Examples, but the present invention is not limited to these Examples in any way.
<Adjustment of thermal spray powder material>
_{Examples 1-} Thermal spray powder materials of No. 8 and Comparative Examples 1 to 5 were prepared. The composition and average particle size of the obtained thermal spray powder material are as shown in Table 1. In the present invention, the average particle size means a volume-based particle size, and the average particle size was measured using a laser diffraction particle size distribution analyzer Mastersizer 3000 manufactured by Malvern Panalytical.

<Formation of thermal spray coating>
Using the thermal spray powder materials of Examples 1 to 8 and Comparative Examples 1 to 5 produced by the above method, a thermal spray coating was applied to a porous zirconia base material by atmospheric pressure plasma spraying (APS) or suspension plasma spraying (SPS). Formed. The thermal spraying methods and conditions for APS and SPS are as follows.

(1) APS (Atmospheric Pressure Plasma Spraying)
A plasma spraying device SG-100 manufactured by Praxair Surface Technologies was used. Plasma generation conditions were as follows: argon gas at a pressure of 0.34 MPa and helium gas at a pressure of 0.34 MPa were used as plasma working gases, and plasma was generated at a voltage of 37.0 V and a current of 900 A. The moving speed of the thermal spray gun was 24 m/min, and the thermal spraying distance was 90 mm.
A powder feeder Model 1264 manufactured by Praxair Surface Technologies was used to supply the thermal spray powder material to the plasma spray apparatus. The rate at which the spray powder material was fed to the plasma spray apparatus was 20 g/min.

(2) SPS (Suspension Plasma Spraying)
A plasma spraying device 100HE manufactured by Progressive Surface Co., Ltd. was used. A Liquifeeder HE (trade name) SPS/SPPS feed system manufactured by Progressive Surface Co., Ltd. was used as a supply device for supplying thermal spraying slurry to the plasma spraying apparatus. The thermal spraying conditions are as follows.
Argon gas flow rate: 180NL/min
Nitrogen gas flow rate: 70NL/min
Hydrogen gas flow rate: 70NL/min
Plasma output: 105kW
Spraying distance: 76mm
Traverse speed: 1500mm/s
Spraying angle: 90°
Slurry supply amount: 38mL/min
Number of passes: 50 passes

<Characteristic evaluation of thermal spray coating>
(1) Measurement of hardness and Young's modulus The Vickers hardness of the sprayed coatings of Examples 1 to 8 and Comparative Examples 1 to 5 formed by the above method was measured using a microhardness meter HMV0001 manufactured by Shimadzu Corporation. The results are shown in Table 1. Similarly, Table 1 shows the results of measuring Young's modulus using an ultra-micro indentation hardness tester HM2000 manufactured by H.FISCHER.

(2) CMAS penetration layer thickness evaluation test CMAS test powder was deposited to a thickness of 0.5 mm on the thermal sprayed coatings of Examples 1 to 8 and Comparative Examples 1 to 5 formed by the above method, and Ar atmosphere was applied. Table 1 shows the results of measuring the thickness of the CMAS penetration layer by evaluating the cross section of the sprayed coating by energy dispersive X-ray analysis (EDX) using a scanning electron microscope (SEM). It was shown to. In this evaluation, powder obtained by pulverizing volcanic ash collected from Sakurajima to an average particle size of 50 μm was used as the CMAS test powder. The main components of the CMAS test powder were silicon oxide, carbon, aluminum oxide, iron oxide, calcium oxide, magnesium oxide, etc. As shown in FIGS. 1(a) to 1(c), cross-sectional electron micrographs of the sprayed coating show that a CMAS penetration layer is formed on the surface. In addition, in FIG. 1, (a) shows the sprayed coating formed in Comparative Example 1, (b) shows Comparative Example 2, and FIG. A cross-sectional electron micrograph is shown. It can be seen that a CMAS intrusion structure with coarse grain size and uneven surface is formed on the surface of the sprayed coating.

As shown in Table 1, when comparing Example 1 with Comparative Example 1, it is found that 5% by mass of SiO ₂ is contained in the APS sprayed coating of Comparative Example 1, which is made only of YbTaO by granulation and sintering. It can be seen that in Example 1, although the hardness and Young's modulus are slightly reduced, the thickness of the CMAS interstitial layer is significantly reduced from 8.2 μm to 3.5 μm. Similarly, when comparing Examples 2, 3, 4, and 5 with Comparative Example 2, it is found that in Examples 2, 3, and 4, compared to the APS sprayed coating of Comparative Example 2 consisting only of 8YSZ by granulation and sintering. , 1% by mass, 5% by mass, 8% by mass and 10% by mass of SiO ₂ , respectively, caused the hardness and Young's modulus to decrease slightly with increasing SiO ₂ content, but the CMAS interstitial layer It can be seen that the thickness decreases from 5.6 μm to 3.4 μm, 2.2 μm, 1.8 μm, and 1.4 μm, respectively, as the SiO ₂ content increases. On the other hand, when Comparative Example 3 and Example 5 are compared, Comparative Example 3 has a too high SiO ₂ content of 20% by mass, so the thickness of the CMAS interstitial layer is equivalent to 1.4 μm in Example 5. However, it can be seen that the hardness and Young's modulus are significantly reduced. Next, comparing Comparative Example 4 and Example 6, it is found that 5% by mass of SiO ₂ is contained in the APS sprayed coating of Comparative Example 4, which is made of only Yb ₂ SiO ₅ by granulation and sintering. It can be seen that Example 6 has almost the same hardness and Young's modulus as Comparative Example 4, but the thickness of the CMAS penetration layer is significantly reduced from 1.4 μm to 0.5 μm. Furthermore, when Comparative Example 5 and Example 7 are compared, it is found that 5% by mass of SiO ₂ is contained in the SPS sprayed coating of Comparative Example 5, which is made only of 8YSZ by sintering and pulverization, so that in Example 7, the hardness and It can be seen that although the Young's modulus slightly decreases, the thickness of the CMAS interstitial layer decreases significantly from 1.4 μm to 0.5 μm. On the other hand, in Example 8, which had the same composition as Example 7 but had a particle form of 8YSZ coated with SiO ₂ fine particles to form an SPS sprayed coating, the hardness was lower than that of Example 7. Although the Young's modulus decreased slightly, the thickness of the CMAS interstitial layer decreased further to 1.2 μm.

Claims (8)

A thermal spray powder for thermal barrier coating,
Contains SiO ₂ particles and oxide particles other than SiO ₂ ,
The content of the SiO ₂ particles in the thermal spray powder is 1% by mass to 10% by mass,
A powder for thermal spraying, wherein the oxide particles other than SiO ₂ are ytterbia silica . The thermal spray powder according to claim 1, wherein the volume-based average particle size of the SiO ₂ is smaller than the volume-based average particle size of the oxide particles other than SiO ₂ . The thermal spray powder according to claim 2, wherein the volume-based average particle size of the oxide particles other than SiO ₂ is 1 to 5 μm, and the average particle size of the SiO ₂ particles is 0.001 to 2 μm. The thermal spray powder according to any one of claims 1 to 3, wherein the oxide particles other than SiO ₂ and the SiO ₂ particles are composited to form composite particles. 5. The thermal spray powder according to claim 4, wherein the composite particles have surfaces of oxide particles other than the SiO ₂ coated with the SiO ₂ particles. The thermal spray powder according to claim 4 or 5, wherein the composite particles have a volume-based average particle diameter of 2 to 50 μm. A thermal spraying slurry comprising the thermal spraying powder according to any one of claims 1 to 6 and a dispersion medium in which the thermal spraying powder is dispersed. A method for producing a thermal barrier coating, which comprises forming the thermal spraying powder according to any one of claims 1 to 6 or the thermal spraying slurry according to claim 7 on a substrate by plasma spraying.