JP2002348653A - Particles of rare-earths oxide for thermal spraying, thermal sprayed member and corrosion resistant member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide particles of high purity rare-earths oxide for thermal spraying, which can form a thermal sprayed coating with high adhesiveness in spite of employing rare-earths oxide with high melting point. SOLUTION: The particles of rare-earths oxide for thermal spraying have a mean particle diameter of 3-20 μm, dispersion index of 0.4 or less, and an aspect ratio of 2 or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spray coating of high adhesion, smoothness and high purity when a rare earth oxide spray coating is formed on the surface of a base material such as metal or ceramics by plasma spraying or the like. TECHNICAL FIELD The present invention relates to a rare-earth oxide spray particle capable of forming the following, a spray member having a coating made of the spray particle, and a corrosion-resistant member using the spray member.

[0002]

2. Description of the Related Art Conventionally, a coating is formed by spraying a metal oxide onto a metal, ceramics, or the like to impart heat resistance, abrasion resistance, and corrosion resistance. ing. As a method for producing thermal spray particles for forming such a thermal spray coating, (1) a raw material is melted in an electric furnace, cooled and solidified, pulverized with a pulverizer, and then classified to adjust the particle size and melt. (2) a method of obtaining a pulverized powder, (2) a method of obtaining a sintered pulverized powder by sintering a raw material, pulverizing the raw material with a pulverizer, and then classifying the powder to obtain a sintered pulverized powder; A method of obtaining granulated powder by adjusting the particle size by slurrying, granulating using a spray-drying type granulator, firing, and, if necessary, classifying, is mentioned.

Further, the properties required for the above-mentioned particles for thermal spraying are that the material can be supplied stably and quantitatively up to the plasma flame or flame flame at the time of thermal spraying, and at the time of supply and thermal spraying (in the plasma flame or flame flame). It is required that the particle shape does not collapse, and that the particles are completely melted during thermal spraying (in a plasma flame or flame flame).
Each of these characteristics is quantitatively expressed by a powder property value consisting of more than ten items.

Since the above-mentioned spray particles are supplied to the spray gun through a narrow flow path such as a transport tube, it is determined whether or not the supply can be performed stably and quantitatively. During physical properties, it is considerably affected by fluidity. However, the melt-pulverized powder and the sinter-pulverized powder obtained by the methods (1) and (2) have an irregular shape and a wide particle size distribution. In addition to the occurrence, the angle of repose is large and the fluidity is poor, so that there is a problem that clogging or the like occurs in the transfer tube or the spray gun, and the spray cannot be continuously performed.

In order to solve the problems of each of these pulverized powders, granulated powders obtained by the above method (3),
Granulated powders having the characteristic that they have a good flowability due to their spherical or nearly spherical shape have been developed. Since the powder strength of this granulated powder is determined by the particle size distribution of the raw material particles and the conditions of the sintering process, the powder strength tends to vary, and the powder having a low strength is supplied during supply and There has been a problem that it tends to collapse during thermal spraying (in flame flame or plasma flame).

On the other hand, when thermal spraying particles made of a metal oxide are sprayed, it is necessary to completely melt the thermal spraying particles in a flame flame or plasma flame at the time of thermal spraying in order to form a thermal spray coating having excellent adhesion strength. There is. In particular, when a rare earth oxide is used, its melting point is high, so that it is necessary to use thermal spraying particles having a small average particle size to completely melt. However, in the case of granulated powder using a spray-drying type granulator, it is difficult to reduce the average particle diameter to 20 μm or less, while, in the case of melt-pulverized powder or sintered pulverized powder, the average particle diameter is small by pulverization. Although a thermal spray material can be obtained, contamination from a pulverizer or the like has prevented the introduction of impurities of about several tens ppm in ordinary particles.

As described above, the above-mentioned melt-pulverized powder, sintered pulverized powder, and granulated powder each have advantages and disadvantages, and thus cannot be said to be necessarily the most suitable as a rare-earth oxide thermal spray material. In addition, all three types of powder have contamination from the pulverizing step, the granulating step, and the classifying step, and thus have a problem in terms of high purification. That is, in the melt-pulverized powder, sintered pulverized powder, and granulated powder obtained through each of the above steps, impurities such as iron group elements, alkali metal elements, and alkaline earth metal elements are usually mixed in at least 20 ppm. In addition, there is a problem that a thermal spray member having a coating formed by thermal spraying of the thermal spray particles is liable to corrode from an impurity portion, and sufficient durability cannot be obtained.

[0008] The present invention has been made in view of such circumstances, and it is possible to form a sprayed coating having high adhesion even with the use of a rare-earth oxide having a high melting point. It is another object of the present invention to provide a thermal spraying member obtained by spraying the thermal spraying particles on the surface of a base material, and a corrosion resistant member using the thermal spraying member.

[0009]

Means for Solving the Problems and Embodiments of the Invention
The present inventors have conducted intensive studies in order to achieve the above object, and as a result, in the rare-earth oxide thermal spraying powder, the average particle diameter, the dispersion index, and the aspect ratio to a predetermined value, further if necessary By controlling the specific surface area, bulk density, crystallites, and the total amount of the iron group, alkali metal and alkaline earth metal elements within a predetermined range, good fluidity, dense and high strength, do not collapse during thermal spraying In addition to finding that there is a possibility of completely dissolving in, the coating formed by spraying the particles for thermal spraying is smoother and more pure than the conventional thermal spray coating, and is found to be excellent in adhesion and corrosion resistance, The present invention has been completed.

That is, the present invention provides: Average particle size is 3-20 μm, dispersion index is 0.4 or less,
1. particles for rare earth oxide spraying, wherein the aspect ratio is 2 or less; ^2. particles for rare earth oxide spraying, wherein the particles have a specific surface area of 0.3 to 1.0 m ² / g; 3. particles for rare earth oxide spraying according to 1 or 2, wherein the bulk density is 30 to 50% of the true density; 1, characterized in that the crystallite is at least 25 nm.
4. particles for rare earth oxide spraying of 2 or 3; 5. The rare earth oxide spray particles according to any one of 1 to 4, wherein the total amount of the iron group element, the alkali metal element, and the alkaline earth metal element is 20 ppm or less. 7. A thermal spray member comprising: a base material; and a film formed by spraying the rare earth oxide thermal spray particles according to any one of 1 to 5 on the surface of the base material. The present invention provides a corrosion-resistant member characterized by using:

Hereinafter, the present invention will be described in more detail. As the rare earth oxide in the present invention, one or more of the group 3A rare earth elements including yttrium (Y) can be used. The rare earth oxide and A
A composite oxide with one or more metals selected from l, Si, Zr, In and the like may be used. The average particle diameter of the particles for spraying rare earth oxides is 3 to 20 μm, especially 7 to 16 μm.
μm is preferred. If the average particle size is less than 3 μm, there is a problem that evaporation and scattering occur in a plasma flame or the like at the time of thermal spraying, resulting in a loss correspondingly. On the other hand, when the average particle size is 20
If it exceeds μm, it is not completely melted and remains in a plasma flame or the like at the time of thermal spraying, and remains unfused, resulting in a decrease in adhesion strength. The average particle size is
It is a value of D50 of the particle size distribution measured by a laser diffraction method.

The rare earth oxide molten particles of the present invention have a sphere or a shape close to a sphere and a narrow particle size distribution. Specifically, the particles have a dispersion index of 0.4 or less and an aspect ratio of 2 or less. Here, the dispersion index is 0.4
If the particle size exceeds 1, the particle size distribution becomes broad, the fluidity deteriorates, and clogging or the like occurs in the nozzle during powder supply. A more preferred dispersion index is 0.3 or less. In addition,
The dispersion index is defined by the following equation. Dispersion index = (D90−D10) / (D90 + D1)
0) In the above formula, D10 is the particle size at 10% by weight, D90
Indicates a particle size at 90% by weight, and both are values measured by a laser diffraction method.

The aspect ratio is expressed by the ratio of the major axis to the minor axis, that is, the major axis / minor axis, and serves as an index indicating whether the shape is close to a sphere. Here, when the aspect ratio exceeds 2, the shape becomes far apart from the sphere, and the fluidity deteriorates. In this case, the lower limit of the aspect ratio is not particularly limited, but a value closer to 1 is preferable.

[0014] In the above, it is preferable that the specific surface area of the rare earth oxide particles for thermal spraying is 0.3~1.0m ² / g, more preferably 0.3~0.8m ² / g.
Here, when the specific surface area exceeds 1.0 m ² / g, the surface smoothness may be deteriorated and the fluidity may be reduced. The bulk density is preferably 30 to 50% of the true density. If the bulk density is less than 30% of the true density, the particles tend to be weak because the particles are not dense and may collapse during thermal spraying. It should be noted that no matter how dense the particles are, those whose bulk density exceeds 50% of the true density are hardly seen.

By the way, single crystal particles are the most dense,
It is considered that the polycrystalline particles are denser as the diameter of the single crystal particles constituting the particles is larger. The particle size of the single crystal particles constituting such particles is called a crystallite, and in the rare earth oxide thermal spraying particles, the crystallite is preferably 25 nm or more, more preferably 50 nm or more. When the crystallite size is less than 25 nm, the single crystal particles are polycrystalline particles having a small particle size, and thus it is considered that they are often not dense. Note that the crystallite is the Wils of X-ray diffraction.
This is the value obtained from the on method. In this Wilson method,
The single crystal particles have a maximum particle size of 100 nm or less.

Further, considering that the rare earth oxide thermal spray particles impart sufficient corrosion resistance to a thermal spray member having a coating formed by spraying the thermal spray particles, the iron group element (F
e, Ni, Co, etc.), alkali metal elements (Na, K
And the like, and the total amount of alkaline earth metal elements (Mg, Ca, etc.) is preferably at most 20 ppm, more preferably at most 15 ppm, particularly preferably at most 5 ppm. The total amount of each of these metal elements is preferably as small as possible, but the lower limit is usually about 0.1 ppm. The iron group element, alkali metal element and alkaline earth metal element are measured by ICP spectroscopy (inductively coupled high frequency plasma spectroscopy) after acid-decomposition of the rare earth oxide spray particles.

It is preferable to use the following method for producing the rare earth oxide thermal spray particles. First,
A rare earth aqueous solution (aqueous solution of a water-soluble salt such as chloride, nitrate, sulfate, etc.) and an oxalic acid aqueous solution are mixed in an amount of 1.5 to 2.0 mol based on the total amount of the rare earth as oxalate ions, and -5 to 2
By crystallization at a low temperature of 0 ° C., a rare earth oxalate having an average particle size of 3 to 20 μm, which is close to a sphere, is produced. Subsequently, after the obtained rare earth oxalate is dried at −20 to 80 ° C. by a freeze dryer or the like, it is 800 to 1,700 ° C. in air, more preferably 1,200 to 1,600 ° C., and 1 to 6 ° C. By calcining for a period of time, more preferably 2 to 4 hours, particles for spraying rare earth oxides are obtained.

Here, if the total amount of rare earths is too large (the amount of oxalate ions is less than 1.5 mol), the rare earths will not be completely precipitated, resulting in a poor yield. On the other hand, when the total amount of the rare earth elements is too small (the amount of oxalate ions exceeds 2.0 mol), the amount of oxalic acid is too large, which is not economical. That is, by setting the amount of oxalate ions to the above range relative to the total amount of rare earths, good spherical particles can be obtained with good yield. The above manufacturing method does not require a granulating step and / or a pulverizing step, so that contamination of contaminants from auxiliary materials and equipment is small, and as a result, iron group elements (Fe, Ni, Co, etc.), alkali metal elements (N
a, K, etc.) and alkaline earth metal elements (Mg, Ca, etc.) are easy to obtain spherical particles for thermal spraying having a purity of 20 ppm or less.

As described above, the thermal spraying spherical particles according to the present invention have good fluidity and do not become clogged in a transport tube or the like, so that they can be supplied stably and continuously, and are dense and have high strength. Since it is high, it has the feature that it does not collapse in the plasma flame during thermal spraying. Furthermore, since the average particle diameter is small, there is a possibility that the film is completely melted in the plasma flame at the time of thermal spraying, and since it is high purity and almost spherical, the adhesion strength of the coating composed of the thermal spraying particles can be increased. And the surface roughness of the coating is fine (60μ).
m or less) can be controlled.

[0020] The thermal spraying member according to the present invention is characterized by comprising a base material and a coating formed by spraying the rare earth oxide spray particles on the surface of the base material. Here, the substrate is not particularly limited, and Al, Fe, Si, Cr, Z
Metals, alloys, ceramics (metal nitride, metal carbide, metal oxide (eg, alumina, aluminum nitride, silicon nitride, silicon carbide, etc.)) containing n, Zr or Ni as main components, glass (quartz glass, etc.), etc. However, when ceramics or glass is used as the base material, the adhesion of the coating film is weakened, so that Si, Al, Fe or N
It is preferable that the base material is a metal or alloy containing i as a main component.

The thickness of the coating on the surface of the substrate is 50 to 500.
μm is preferred, and more preferably 150 to 300 μm
It is. When the thickness of the coating is less than 50 μm, when the thermal sprayed member having the coating is used as a corrosion-resistant member, it may be necessary to replace it with a slight corrosion. On the other hand, if the thickness of the coating is more than 500 μm, there is a possibility that the coating is too thick and peeling easily occurs inside the coating. Further, the surface roughness of the coating is preferably 60 μm or less, more preferably 20 μm or less. If the surface roughness exceeds 60 μm, the plasma contact area becomes large, so that the corrosion resistance may be deteriorated, and particles may be generated due to the progress of corrosion. That is, by setting the surface roughness of the coating to 60 μm or less, good corrosion resistance can be obtained. Therefore,
Corrosion hardly occurs even in a corrosive gas (eg, halogen-based gas plasma) atmosphere, and the sprayed member can be suitably used as a corrosion-resistant member.

The thermal sprayed member of the present invention can be obtained by forming a coating on the surface of the substrate by the plasma spraying or the reduced pressure plasma spraying of the rare earth oxide spraying particles. Here, the plasma gas is not particularly limited, and may be nitrogen / hydrogen, argon / hydrogen, or argon / hydrogen.
Helium, argon / nitrogen, or the like can be used. The thermal spraying conditions and the like are not particularly limited, and may be appropriately set according to the specific materials such as the base material, the particles for rare earth oxide thermal spraying, and the use of the obtained thermal spraying member.

Also in the thermal spraying member of the present invention, the total amount of the iron group element, the alkali metal element and the alkaline earth metal element in the coating is preferably 20 ppm or less. This can be achieved by forming a coating using the following rare earth oxide spray particles. That is, when a coating is formed using particles for thermal spraying containing at least 20 ppm of an iron group element, an alkali metal element, and an alkaline earth metal element, the coating contains only an iron group element mixed in the thermal spraying particles. However, the alkali metal element and the alkaline earth metal element are mixed as they are, but the use of the rare earth oxide spray particles does not cause such a problem.

If the total amount of each of the above metal elements in the coating is 20 ppm or less, contamination is small, so that the thermal sprayed member can be used without problems in an apparatus which requires high purity. Specifically, it can be suitably used as a member for a liquid crystal manufacturing device, a member for a semiconductor manufacturing device, or the like.

[0025]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

Example 1 While stirring 30 L of a yttrium nitrate solution (0.3 mol / L) cooled to 3 ° C. at a rotation speed of 200 rpm, an oxalic acid solution (0.5 mol
1 / L) was added and reacted over about 5 minutes.
The solution was aged for 10 minutes while maintaining the solution at 3 ° C., and the produced yttrium oxalate was collected by filtration, washed with water, frozen at −10 ° C. for 6 hours, and then dried in vacuum at 20 ° C. for 24 hours. Subsequently, the freeze-dried yttrium oxalate was placed in air at 1,500.
C. for 2 hours to obtain 990 g of yttrium oxide. Table 1 shows the results of measurements of the physical properties of the obtained yttrium oxide, such as the particle size and the crystallite. Note that 5.03 g / cm ³ was used as the true density of yttrium oxide. The yttrium oxide particles are plasma-sprayed with argon / hydrogen to form an aluminum alloy substrate (JI
No. SH4000. 6061) Film thickness 21
A coating of 0 μm was formed. Table 2 shows the measurement results of the physical properties of the formed coating. In Table 2, the surface roughness Ra was measured by a method according to JIS B0601. The corrosion resistance of the member was measured using a RIE (reactive ion etching) device in a CF ₄ plasma.
It was measured by performing a time exposure test and calculated as a percentage of the weight of the member after the test with respect to the weight of the member before the test.

Example 2 In the same manner as in Example 1 except that erbium nitrate was used instead of yttrium nitrate, 1,680 g of erbium oxide was obtained. Table 1 shows the results of measurements of the physical properties of the obtained erbium oxide, such as the particle size and the crystallite. 8.64 g / cm ³ was used as the true density of erbium oxide. The erbium oxide particles were plasma-sprayed with argon / hydrogen to form a 250 μm-thick film on a silicon substrate as a base material. Table 2 shows the measured values of the physical properties and corrosion resistance of the formed coating.

Comparative Example 1 A slurry was prepared by dispersing 5 kg of yttrium oxide having an average particle diameter of 1.2 μm in 15 liters of pure water in which 15 g of PVA (polyvinyl alcohol) was dissolved, and a slurry was prepared using a fluid nozzle spray granulator. This slurry was spray-dried to produce a granulated powder. Further, the granulated powder was fired at 1600 ° C. for 2 hours to obtain thermal spray particles.
Table 1 shows the results of measuring the physical properties of yttrium oxide obtained by the above-described granulation step, such as the particle size and crystallite. Further, the particles for thermal spraying of yttrium oxide were plasma-sprayed with argon / hydrogen to form a coating on the aluminum alloy substrate as a substrate to a thickness of 250 μm. Table 2 shows the measurement results of the physical properties and corrosion resistance of the formed coating.

[0029]

[Table 1]

[0030]

[Table 2]

As shown in Table 1, the rare-earth oxide spray particles obtained in Examples 1 and 2 have an average particle diameter of 20 μm.
Or less, and the dispersion index is as small as 0.3 or less, and Ca
It can be seen that there are few impurities such as O, Fe ₂ O ₃ , Na ₂ O, etc., high purity, high bulk density and high density. On the other hand, the rare-earth oxide spray particles obtained in Comparative Example 1 have a large dispersion index of 0.5, contain impurities such as Fe ₂ O ₃ and Na ₂ O, and have a low bulk density. .

Further, as shown in Table 2, in Example 1,
The coating composed of particles for spraying rare earth oxides is CaO,
Fe ₂ O _3, Na ₂ O or the like impurities less, applications where high purity is required, for example, it can be seen that suitable member and a member for a semiconductor manufacturing apparatus for a liquid crystal manufacturing apparatus. Moreover,
It can also be seen that the surface roughness is fine and suitable as a corrosion-resistant member for a corrosive gas atmosphere (for example, a halogen-based gas plasma). On the other hand, in the coating made of the thermal spray particles of Comparative Example 1, the iron group element, the alkali metal element, and the alkaline earth metal element mixed in the thermal spray particles were directly mixed, and It can be seen that the roughness is as coarse as 73 μm.

[0033]

As described above, the spherical particles for spraying rare earth oxides of the present invention have an average particle diameter of 3 to 20 μm, a dispersion index of 0.4 or less, and an aspect ratio of 2 or less.
Since it can be supplied stably and continuously and may be completely melted in the plasma flame at the time of thermal spraying, the adhesion strength between the coating made of the thermal spraying particles and the material to be sprayed can be increased.

Continued on the front page (72) Inventor Toshihiko Tsukaya 2-1-5 Kitafu, Takefu-shi, Fukui Shin-Etsu Chemical Co., Ltd. Magnetic Materials Research Laboratory F-term (reference) 4K031 AA08 AB02 AB09 CB02 CB17 CB18 CB42 CB52 DA04

Claims (7)

[Claims] 1. Rare earth oxide spray particles having an average particle size of 3 to 20 μm, a dispersion index of 0.4 or less, and an aspect ratio of 2 or less. 2. The rare earth oxide thermal spray particles according to claim 1, wherein the specific surface area is 0.3 to 1.0 m ² / g. 3. The rare earth oxide spray particles according to claim 1, wherein the bulk density is 30 to 50% of the true density. 4. The rare earth oxide thermal spray particles according to claim 1, wherein the crystallite has a crystallite size of 25 nm or more. 5. The rare earth oxide thermal spray particles according to claim 1, wherein the total amount of the iron group element, the alkali metal element, and the alkaline earth metal element is 20 ppm or less. . 6. A base material and a surface of the base material according to claim 1.
And a coating formed by spraying the particles for spraying rare earth oxides according to any one of the above. 7. A corrosion resistant member using the thermal sprayed member according to claim 6.