JPH10310841A - Ceramic coating material, its production and high temperature member using the same material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily form a ceramic coating layer composed of rare earth metal oxide having excellent characteristics on the surface of a metallic material formed body by heating a formed body composed of a mixture of high m.p. metal and rare earth metal to a specified temp., vapor-depositing the rare earth metal on the surface of the metallic formed body and executing oxidation. SOLUTION: A granular mixture of high m.p. metal such as W, Mo, Ta, Nb or the like and rare earth metal of 5 to 30%, by volume is formed into a crucible, wire rod or the like. This formed body is used as a cathode, arc discharge is generated between it and an anode, heating is executed to a temp. lower than the m.p. of the high m.p. metal and more than that of the rare earth metal or the oxide thereof to vapor-deposit the rare earth metal on the surface of the formed body, and oxidation is executed in the air to form a ceramic-coated layer composed of rare earth metal oxide on the surface of the formed body by the high m.p. metal. The ceramic coating metallic material excellent in adhesion and homogeneity and further excellent in corrosion- resistance, arc resistance and thermoelectron releasability by the molten metal can be obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for producing and utilizing a ceramic coating material in which a metal material is coated with a ceramic on the surface thereof, and particularly to a metal coating having excellent corrosion resistance, arc resistance, and thermionic emission characteristics. The present invention relates to a ceramic coating material, a manufacturing method thereof, and a high-temperature member using the same.

[0002]

2. Description of the Related Art Metal oxides, especially oxides of rare earth metals, generally have a low free energy of oxide formation, are chemically stable, and have excellent corrosion resistance to molten metal. It is considered to be suitable as such a material. However, on the other hand, it has disadvantages such as high brittleness and poor thermal shock resistance. Therefore, it has not been conventionally used industrially as a member mainly composed of the oxide itself.

[0003] Therefore, when such an oxide is used, it is applied as a coating of a coating material on the surface of a substrate of a heat-resistant material such as a high melting point metal or graphite by slip coating or plasma spraying. Often done. In particular, plasma spraying is a method in which an oxide powder, which is a coating material, is melted by a high-temperature plasma frame, and is coated by spraying it on the surface of a metal substrate.
It has a tendency to be widely used because it has a characteristic that it can form a film of the type described above, can be coated in the atmosphere, and can be applied to a large-sized member or a member having a complicated shape.

[0004] Further, rare earth metals and oxides of rare earth metals have a small work function and are excellent in thermionic emission characteristics. Therefore, they are used for arc consumable electrodes and the like by being combined with a high melting point metal. It is used for filaments and the like by coating.

As a coating method at that time, physical vapor deposition (PVD) or chemical vapor deposition (CVD) that can coat a fine thin film having a thickness of 1 μm or less on the surface of a fine filament or the like is used. PVD is a method in which a coating material is heated and evaporated, and the vapor is vapor-deposited on the surface of a metal substrate.In CVD, elements constituting the coating material are supplied as a gas and reacted on the surface of the metal substrate. It is a method of coating. Either way,
It has the feature that a thin film coating film with excellent adhesion can be formed.

[0006]

However, the coating obtained by plasma spraying is a porous material and has low adhesion to the substrate, so that it easily peels or cracks due to thermal stress during melting of the metal. have. Further, it is difficult to coat a thin film of 1 μm or less on the surface of a fine product such as a filament. On the other hand, PV
D and CVD have the disadvantages that they require a large amount of time for coating because the film formation rate is slow, and they cannot be applied to large-sized members because they must be performed in a vacuum chamber or reaction vessel. ing.

[0007] In addition, plasma spraying or PVD cannot be applied to a shaded portion such as the inner surface of a pipe. In the case of a CDV in which the coating material is supplied in a gaseous state, it is possible to coat the inner surface of the pipe. However, as the reaction proceeds from the upstream side to the downstream side of the supplied gas, the concentration of the reaction element in the gas gradually decreases. Therefore, it is difficult to form a film having a uniform thickness.

On the other hand, in a composite material in which ceramic particles such as a metal oxide are dispersed in a metal matrix, the metal portion exposed on the surface is selectively corroded, and conversely, the thermionic emission characteristic is obtained at the time of arc discharge. Since an arc spot is formed on the rare earth metal oxide particles having excellent heat resistance, there is a problem that the rare earth metal oxide particles are selectively worn.

The present invention has been made in view of such circumstances, and a first object of the present invention is to provide a ceramic coating material in which a coating film does not easily peel or crack, and is hardly worn. It is in.

Another object of the present invention is to provide a method for producing a ceramic coating material capable of forming a coating film of a rare earth metal or a rare earth metal oxide having excellent adhesion and homogeneity in a short time. .

It is a third object of the present invention to provide a high-temperature member which can be widely used from fine products such as filaments to large products by using the ceramic coating material having the above-mentioned excellent characteristics.

[0012]

SUMMARY OF THE INVENTION Since rare earth metal oxides are excellent in thermionic emission properties and molten metal corrosion resistance, the inventors have invented a high melting point metal material containing a rare earth metal or an oxide of a rare earth metal. Was heated to a temperature equal to or higher than the melting point of the rare earth metal or the oxide of the rare earth metal and equal to or lower than the melting point of the high melting point metal, thereby melting and evaporating the rare earth metal. At this time, a reduced-pressure atmosphere is preferable so that vapor of the rare earth metal is easily generated.Also, in order to suppress oxidation of the high melting point metal which is a matrix and reduce a chemically stable rare earth metal oxide to facilitate evaporation. It is preferable to add a reducing gas such as hydrogen. The vapor of the rare earth metal evaporated in this manner is deposited on the surface of the metal material and combined with oxygen in the atmosphere, so that the surface of the metal material can be easily coated with the rare earth metal oxide.

The work function of the rare earth metal or the oxide of the rare earth metal is smaller than that of the refractory metal serving as the matrix. Therefore, by generating an arc on the surface of a metal material composed of a high melting point metal and a rare earth metal or a rare earth metal oxide, a high-temperature arc spot is preferentially formed on the rare earth metal or the rare earth metal oxide. By promoting the evaporation of the rare earth metal, a uniform coating film can be obtained in a shorter time.

The matrix metal constituting the metal material together with the rare earth metal or the rare earth metal oxide includes:
Melting point higher than rare earth metal or rare earth metal oxide,
W, Mo, Ta, Nb which are metal materials having low vapor pressure
And alloys of these metals are preferred.

Rare earth metals excellent in thermionic emission properties and molten metal corrosion resistance include Y, La, Ce, Nd, Sm, and E.
u, Gd, Tb, Dy, Ho, Er, their alloys, or their oxides are preferred. Each of these elements has a small oxide generation free energy and is easily oxidized during the heating step or use during the coating, and therefore, the form of addition to the metal matrix may be a metal state or an oxide state. .

On the other hand, in order to uniformly coat the surface of the metal material with the rare earth metal oxide, the rare earth metal or the oxide of the rare earth metal, which is the vapor generation source, is uniformly dispersed in the matrix of the high melting point metal. Is preferred. From such a viewpoint, it is effective that the rare earth metal or the rare earth metal oxide is dispersed in the matrix metal in the form of a lump, a particle, or a powder.

Further, as a method for effectively generating a rare earth metal vapor, only the surface of the metal material to be coated is heated to a high temperature of 1500 ° C. or more in a short time.
This is effective for suppressing deformation of members and reducing coating costs. As a heating method suitable for such a demand, a plasma, an electron beam, and a laser beam are suitable.

As a method for producing a metal material in which a rare earth metal or a rare earth metal oxide and a high melting point metal matrix are uniformly mixed, a powder sintering process in which both raw material powders are mixed in advance and sintered is effective. Since this powder sintering process can be performed at a relatively low temperature without melting the material, it is also effective from the viewpoint of suppressing the reaction between the dispersed particles and the high melting point metal matrix.

Further, from the viewpoint of the composition processing after sintering and the corrosion resistance of molten metal, it is preferable that the sintered body be densified to near the true density. As a method for obtaining such a dense sintered body, hot pressing or Pressure sintering using HIP or the like is promising.

In consideration of mass production at low cost, the hot press becomes a single product and the HI using the gas pressure is used.
In P sintering, it is necessary to vacuum-enclose the material powder in a metal capsule. However, once the relative density of the sintered body can be reduced to 90% or more by sintering, the pores remaining in the sintered body become closed pores not communicating with the outside. By directly subjecting to HIP processing, it is possible to densify almost to the true density.

The volume of the rare earth metal or the oxide of the rare earth metal to be added to the refractory metal is too small to form a uniform coating layer, while if too large, the strength is reduced. 5% by volume to 50% by volume is preferred.
In order to completely cover the surface of the material, the content is preferably 5% by volume or more, and when used as a high-temperature strength member, the content is preferably 30% by volume or less.

Furthermore, the characteristics of the coating deteriorate over time due to the wear of the rare earth metal oxide coating layer on the surface during the above-mentioned arc treatment and during use. Therefore, by providing a network structure in which the rare-earth metal or rare-earth oxide dispersed in the material has a three-dimensionally connected network, the coating layer can be formed again on the material surface during use and again by heating or arc treatment. Can be.

As described above, by providing a rare earth metal oxide coating layer on the surface of a material in which a rare earth metal or a rare earth metal oxide is dispersed in a high melting point metal, the corrosion resistance of molten metal can be remarkably improved. Components dissolve active metals in vacuum or inert gas atmosphere,
Most suitable for crucibles and other materials.

Similarly, a member coated with a rare-earth metal oxide having excellent thermoelectron emission characteristics is most suitable as a member requiring high thermoelectron emission characteristics, such as an electrode or a filament.

Based on the above findings, according to the first aspect of the present invention, there is provided a ceramic coating material comprising a ceramic material coated on a surface of a metal material mainly composed of a high melting point metal and a rare earth metal or an oxide of a rare earth metal.
By heating the metal material under a reduced pressure atmosphere to a temperature equal to or higher than the melting point of the rare earth metal or the rare earth metal oxide constituting the metal material and equal to or lower than the melting point of the high melting point metal, the surface of the metal material is oxidized by the rare earth metal. Provided is a ceramic coating material characterized by being coated with a substance whose main component is a substance.

According to a second aspect of the present invention, in the ceramic coating material according to the first aspect, a metal material is used as a cathode, and a voltage is applied between the metal material and the other anode to generate an arc discharge on the surface of the metal material. A ceramic coating material is provided, wherein the surface of the metal material is coated with a substance containing a rare earth metal oxide as a main component.

According to a third aspect of the present invention, in the ceramic coating material according to the first or second aspect, the high melting point metal constituting the metal material is W, Mo, Ta, Nb, or an alloy thereof. A ceramic coating material is provided.

According to a fourth aspect of the present invention, in the ceramic coating material according to any one of the first to third aspects, the rare earth metal constituting the metal material is Y, La, C
e, Nd, Sm, Eu, Gd, Tb, Dy, Ho, E
r, their alloys, or their oxides.

According to a fifth aspect of the present invention, in the ceramic coating material according to any one of the first to fourth aspects, the rare earth metal or an oxide thereof is dispersed in the high melting point metal in a granular, lump or powder form. A ceramic coating material is provided.

According to a sixth aspect of the present invention, in the ceramic coating material according to any one of the first to fifth aspects, the content of the rare earth metal or the oxide of the rare earth metal in the metal material is 2 to 50% by volume, Preferably, the ceramic coating material is provided in an amount of 5 to 30% by volume.

According to a seventh aspect of the present invention, in the ceramic coating material according to any one of the first to sixth aspects, the rare earth metal or the rare earth oxide in the metal material has a three-dimensionally connected network structure. The feature is to provide ceramic coating material.

According to the present invention, in a ceramic coating material in which ceramics are coated on the surface of a metal material mainly composed of a high melting point metal and a rare earth metal or an oxide of a rare earth metal, the metal material is subjected to a reduced pressure atmosphere. By heating the metal material to a temperature higher than the melting point of the rare earth metal or rare earth metal oxide constituting the metal material and lower than the melting point of the high melting point metal, the surface of the metal material is mainly composed of a rare earth metal oxide. The present invention provides a method for producing a ceramic coating material, characterized by being coated with:

According to a ninth aspect of the present invention, in the method for producing a ceramic coating material according to the eighth aspect, a method of heating the metal material comprises using a plasma, an electron beam or a laser beam. I will provide a.

According to a tenth aspect of the present invention, in the method for producing a ceramic coating material according to the eighth aspect, the metal material is formed by firing a mixture of a granular or powdery rare earth metal or an oxide thereof and a powder of a high melting point metal. The present invention provides a method for producing a ceramic coating material obtained by sintering.

According to the eleventh aspect of the present invention, in the method for producing a ceramic coating material according to the tenth aspect, when sintering a mixture of a rare earth metal or an oxide thereof and a refractory metal, hot pressing or HIP processing is used. And a method for producing a ceramic coating material.

According to a twelfth aspect of the present invention, in the method for producing a ceramic coating material according to the tenth aspect, after sintering a mixture of a rare earth metal or its oxide and a high melting point metal at normal pressure, Provided is a method for producing a ceramic coating material, which is characterized by performing HIP processing.

According to a thirteenth aspect of the present invention, there is provided an electrode, a filament, a member for a metal melting device, a member for an evaporating device, and a casting device, which are formed using the ceramic coating material according to any one of the first to seventh aspects. Components and other high temperature components are provided.

[0038]

Embodiments of the present invention will be described below with reference to the drawings.

First Embodiment (FIGS. 1 and 2) FIGS. 1A, 1B and 1C show a basic embodiment of the present invention. First, as shown in FIG.
A material in which rare-earth metal or rare-earth metal oxide particles 2 are dispersed in a high-melting-point metal matrix 1 is heated under a reduced-pressure atmosphere to a temperature higher than the melting point of the rare-earth metal or rare-earth metal oxide and lower than the melting point of the high-melting-point metal. . Then, Figure 1
As shown in (b), a rare earth metal or a rare earth metal oxide having a low melting point and a low vapor pressure is melted and evaporated to generate a rare earth metal vapor 3. As a result, as shown in FIG. 1 (c), the evaporated rare earth metal atoms are deposited on the surface of the material and combined with oxygen in the atmosphere to form a stable oxide coating film 4.
Is formed.

FIG. 2 shows an example of the result obtained by heating a material in which Y ₂ O ₃ is dispersed in a W matrix by using a plasma flame for 30 minutes and then analyzing the W portion on the surface by an Auger electron spectrometer. In the graph shown, the vertical axis represents the Auger peak intensity, and the horizontal axis represents the distance from the surface. As shown in FIG. 2, Y is not detected at all in the W matrix portion before heating, but the thickness of about 1 mm is observed in the W portion after heating.
Y and O were detected over 0 Å. From this, it became clear that the surface of the W matrix portion was covered with an oxide containing Y ₂ O ₃ as a main component.

Second Embodiment (FIG. 3) In this embodiment, Y ₂ O is included in the W matrix shown in FIG.
₃ is dispersed using a plasma flame to 30
A test piece was obtained by heating for 1 minute (Example 1). A test piece was obtained by forcibly generating an arc discharge using the same material as a cathode (Example 2). FIG. 3 is a graph showing the results obtained by analyzing the surface of the W portion of each of these test pieces with an Auger electron spectrometer.

From FIG. 3, it was confirmed that the Y layer was present in all the test pieces. However, the film thickness of the arc-treated test piece (Example 2) was larger than that of the test piece heated only (Example 1). The thickness was remarkably large, indicating that the arc treatment accelerated the growth of the film.

This is because the work function of a rare earth metal or a rare earth oxide is smaller than that of a high melting point metal such as W, and an arc is preferentially generated in a rare earth metal part or a rare earth metal oxide part. FIG. 1 (b)
This is because the rate of melt evaporation of the rare earth metal or rare earth metal oxide shown in (1) increases.

Third Embodiment (FIG. 4) In this embodiment, W, to which 10% by volume of Y ₂ O ₃ is added,
Heat treatment was performed on a composite material of various refractory metals such as Mo, Ta, and Nb using a plasma flame under the same conditions. FIG. 4 is a graph showing the result of measuring the film thickness in this case.

As shown in FIG. 4, although the film thickness varies depending on the matrix metal used, any of the high-melting-point metals is subjected to heat treatment to form an oxide mainly composed of Y ₂ O ₃ on the surface of the test piece. It was confirmed that coating was possible.

Fourth Embodiment In this embodiment, a test piece in which the matrix metal is W and the material of the dispersed particles is variously changed is heated by a similar plasma frame. The results of measuring the film thickness in this case are shown in Table 1 below.

In Table 1, ○ indicates that the coating film was successfully obtained, △ indicates that the coating thickness was small or non-uniform, and x indicates that the coating was good. The figure shows that no formation was observed.

From the above test results, formation of a film of the dispersed rare earth metal oxide was observed in each of the W alloys in which the rare earth metal and the rare earth metal oxide were dispersed. Therefore, formation of a rare earth metal oxide film by such heating is considered to be a property common to rare earth metals or rare earth metal oxides.

Also, a material in which a rare earth metal oxide is dispersed tends to obtain a better film in general than a material in which a rare earth metal is dispersed. It can be said that addition is more preferable.

[0050]

[Table 1]

Fifth Embodiment (FIG. 5) In this embodiment, a test piece was prepared in which the addition amount of Y ₂ O ₃ was constant at 20% by volume and the size of Y ₂ O ₃ was changed. FIG.
Is a graph showing the maximum value and the minimum value in the case where the test piece was subjected to a heat treatment and the film thickness of each test piece was measured at five points.

FIG. 5 shows that when the Y ₂ O ₃ particle diameter is small, a film having a substantially uniform thickness can be obtained at any measurement position, but as the Y ₂ O ₃ particle diameter increases, It can be seen that the nonuniformity of the film thickness tends to be remarkable. This is because the region to be coated by heating is limited around the dispersed rare earth metal or rare earth metal oxide.

Therefore, it is preferable that the rare earth metal or rare earth metal oxide particles are dispersed as uniformly and finely as possible in the high melting point metal matrix.
Granular or powdery forms are suitable.

From the results shown in FIG. 5, the size of the dispersed rare earth metal or rare earth metal oxide particles is 500 μm.
It can be said that m or less is preferable.

Sixth Embodiment (FIG. 6) In this embodiment, the surface of a 20 volume% Y ₂ O ₃ -W material was heated for a certain time by various heating methods. FIG. 6 is a graph showing the measurement results of the film thickness after the heating.

FIG. 6 shows that the thickness of the formed film tends to decrease in the order of the plasma frame, the electron beam, the laser beam, the high-frequency heating, and the resistance heating.
This result indicates that a heating method in which the instantaneous temperature of the material surface is high is suitable.

Therefore, it is clear that a plasma flame, an electron beam, and a laser beam are effective as a process for forming a rare earth metal oxide coating layer in a short time.

Seventh Embodiment (FIGS. 7 (a) to 7 (d)) This embodiment is implemented by focusing on the following points. That is, typical methods for producing a material in which a rare earth metal or a rare earth metal oxide is dispersed in a high melting point metal include a melting method and a powder metallurgy method. The former heats and melts at a temperature higher than the melting point of the high-melting-point metal that is the matrix, so that a part of the added rare-earth metal forms a solid solution in the matrix or forms a brittle intermetallic compound phase.

It has been confirmed that a film is hardly formed even when heat treatment is performed on such a material in which a rare-earth metal is dissolved or an intermetallic compound is formed. Also,
In the case of rare earth metal oxides, the specific gravity is remarkably smaller than that of the high melting point metal, so that even if added to a high melting point metal melt, it is separated or decomposed, so that it is impossible to produce a uniform material. Therefore, it is considered that the melting method is not suitable as a method for producing the material of the present invention.

On the other hand, the powder metallurgy method can be manufactured at a heating temperature of about 60% of the melting point without melting the high melting point metal of the matrix, so that the reaction between the rare earth metal or rare earth metal oxide and the high melting point metal is slight, Further, the difference in specific gravity does not cause a significant problem, and it can be said that the material is suitable as a method for producing the present material.

FIGS. 7A to 7D are process diagrams showing a method for producing a composite material of a high melting point metal and a rare earth metal or a rare earth metal oxide by a powder sintering method. First, the powder 5 of the high melting point metal as the raw material and the rare earth metal or rare earth metal oxide powder 6 are uniformly mixed by using a ball mill 7 (FIG. 7A). At this time, the particle size of the refractory metal powder should be 1 μm or more from the viewpoint of sinterability and powder filling property.
μm or less is preferred.

The rare earth metal powder has a thickness of 10 μm in consideration of reaction with the matrix during the sintering process.
More preferably, it is 1 mm or less. On the other hand, rare earth metal oxide particles are brittle and are ground during the mixing process by a ball mill, so the particle size of the raw material powder is relatively large, but the coarse oxide particles in the sintered material have the strength of the material. Is preferably 100 μm or less in order to significantly reduce the

The powder 8 mixed by the ball mill is pressure-formed into a predetermined shape by a press machine 9 (FIG. 7).
(B)). Thereafter, the obtained molded body 10 is heated in a vacuum or an inert gas atmosphere (FIG. 7).
(C)) A material 11 in which rare earth metal or rare earth metal oxide particles are uniformly dispersed in a high melting point metal matrix is obtained (FIG. 7 (d)).

Eighth Embodiment (FIGS. 7 (e), (f),
(D)) Depending on the combination of materials, the normal pressure sintering method shown in FIGS. 7A to 7D does not provide a dense sintered body close to the true density, and a large number of sintered bodies are formed inside the sintered body. Pores may remain. In particular, with respect to the molten metal corrosion resistance, there is a high possibility that the molten metal penetrates into the interior through such pores and significantly impairs the corrosion resistance.

Therefore, as a method for producing a sintered body having extremely small residual pores, a hot press or a pressure sintering method using HIP is effective.

In the present embodiment, the method for producing a material by HIP is such that a powder 8 uniformly mixed by a ball mill is filled in a metal capsule (can) 12, degassed by baking, and then vacuumed. Then, the capsule 12 is welded and vacuum sealed (FIG. 7 (e)). Next, the metal capsule 12 is set in the HIP device 13, and is heated and pressed to be densified to a true density (FIG. 7).
(F)).

Thereafter, the surrounding cans are removed by machining to obtain a dense material 11 in which rare earth metal or rare earth metal oxide particles are uniformly dispersed in a high melting point metal matrix (FIG. 7D).

Ninth Embodiment (FIG. 8) In the pressure sintering by HIP described above, a material having a very fine structure and a fine material can be produced, but there is a problem that the production cost is high. On the other hand, as shown in FIG. 8, in the sintered body having a higher relative density after the relative density after normal pressure sintering is 88 to 92%, the residual pores in the sintered body do not communicate with the outside. It becomes a closed pore.

Therefore, in the present embodiment, a complicated vacuum sealing was not performed, and the sintered body of the material was left as it was, and HIP processing was performed. Thereby, it can be densified almost to the true density.

According to the present embodiment, the density of the sintered body can be increased by optimizing the particle diameter of the raw material powder and the sintering conditions, thereby providing a dense material at low cost. It becomes possible.

Tenth Embodiment (FIG. 9) In this embodiment, a Y ₂ O ₃ -W material was manufactured with a different amount of Y ₂ O ₃ added. FIG. 9 shows the results of measuring the thickness of the rare earth metal oxide film after the heat treatment and the bending strength of this composition.

FIG. 9 shows that the addition amount of Y ₂ O ₃ was 2% by volume.
The formation of the film was observed from the extent, and then the thickness of the rare earth metal oxide film increased with the increase in the amount added,
It became clear that the uniformity of the film thickness was also improved.

Thus, from a coating standpoint, Y
It can be said that the addition amount of ₂ O ₃ is preferably 2% by volume or more, and from the viewpoint of uniformity of the film thickness, 5% by volume or more is preferable.

[0074] On the other hand, the bending strength of the material shows a tendency to decrease with the increase of Y ₂ O ₃ amount, decrease in strength becomes remarkable especially Y ₂ O ₃ amount exceeds 50 vol%. Therefore, from the viewpoint of strength characteristics, the amount of Y ₂ O ₃ added is 50% by volume.
The following is appropriate, and considering the use as a high-temperature strength member, the content is preferably 30% by volume or less.

Eleventh Embodiment (FIG. 10) In this embodiment, a voltage is applied between a 10 vol% Y ₂ O ₃ -W alloy material and a counter electrode, and the time of arc current when used as an arc discharge electrode. The change was measured. FIG. 10 shows this result. In the figure, the relative current density was plotted with the current density at the beginning of discharge as a reference (100%).

FIG. 10 shows that the arc current of the material in which Y ₂ O ₃ is uniformly dispersed (Example 3) tends to gradually decrease as the test time increases. This is because Y is excellent in thermionic emission characteristics of the surface due to arc discharge.
_{This is because 2} O ₃ is gradually worn.

On the other hand, in the case of a material having a network structure in which Y ₂ O ₃ is three-dimensionally connected inside the material (Example 4), Y ₂ O ₃ is supplied from the inside, and even during the arc discharge test, the film is formed. Due to the formation, almost no decrease in arc current is observed. Thus, it can be understood that the formation of such a network structure is extremely effective in suppressing aging by optimizing the manufacturing conditions.

Twelfth Embodiment (FIG. 11) In this embodiment, Y ₂ O _{3 is} applied to the W surface by plasma spraying.
And a 10% by volume Y ₂ O ₃ − plasma-heated after sintering.
A test piece of W alloy (Example 1) was prepared. FIG.
These test pieces were placed in molten yttrium at 1600 ° C.
The test in which the test was immersed for 10 hours was repeated 10 times, and then the result of measuring the amount of corrosion was shown.

As shown in FIG. 11, in the test piece coated with Y ₂ O ₃ by plasma spraying, the Y ₂ O ₃ coating layer was peeled off by a single immersion test, and as a result, a reduction due to corrosion of about 12 μm was obtained. Meat was observed. on the other hand,
It was confirmed that the corrosion depth of the test piece subjected to the heat treatment by the plasma flame was about 2 μm, which was reduced to about 1/6 compared to the test piece not subjected to the heat treatment.

Therefore, it is understood that the surface coating with the rare earth metal oxide of this embodiment is extremely effective for improving the corrosion resistance of the metal member to molten metal.

Thirteenth Embodiment (FIG. 12) In the present embodiment, a test piece (conventional example 5) in which the W surface is coated with Y ₂ O ₃ by CVD, and after sintering, a heating treatment is performed by a plasma flame and then an arcing treatment is performed. Y
20% by volume having a network structure of the ₂ O ₃ Y ₂ O ₃
A -W alloy test piece (Example 6) was prepared. FIG.
The results of comparing the arc discharge characteristics of these samples are shown.

In this embodiment, the test piece was used as a cathode, and a constant voltage was applied between the test piece and the counter electrode. FIG. 12 shows a change with time of the arc current density measured at the start of the test.
The vertical axis in FIG. 12 plots the relative current density with respect to the current value measured at the start of the test (100%) in a 20% by volume Y ₂ O ₃ -W alloy test piece. . The figure also shows the amount of wear of the test piece due to arc discharge.

As shown in FIG. 12, in the initial stage of the arc discharge test, there is no remarkable difference between the arc current density and the wear amount. However, the arc current density of the CDV coating material showed a tendency to gradually decrease from about one hour after the test.
In addition, the amount of wear of the test piece also tended to increase.

As described above, the reason why the arc current decreases as the test time becomes longer is that Y ₂ O ₃ coated on the surface gradually wears out and W is exposed on the surface. In addition, once an arc spot is formed on a substance having a large work function such as W, arc concentration occurs on the convex portion, and wear increases rapidly.

On the other hand, it was confirmed that the 20% by volume Y ₂ O ₃ -W alloy test piece coated with Y ₂ O _{3 according} to the present embodiment shows a stable arc current density throughout and has a remarkably small amount of wear. Was. This is because the Y ₂ O ₃ coating layer on the surface is worn away by the arc, and at the same time, Y or Y ₂ O ₃ is supplied to the surface from the inside, so that the surface is always covered with Y ₂ O ₃ .

[0086]

As described in detail above, according to the ceramic coating material of the present invention, the coating film has excellent characteristics such as not easily peeling or cracking and being hardly worn. It will be.

According to the method for producing a ceramic coating material of the present invention, a coating film of a rare earth metal or a rare earth metal oxide having excellent adhesion and homogeneity can be formed in a short time.

Further, according to the high temperature member according to the present invention, the ceramic coating material having the above-mentioned excellent characteristics can be widely applied to fine products such as filaments to large products.

[Brief description of the drawings]

FIGS. 1 (a), 1 (b) and 1 (c) are views for explaining a first embodiment of the present invention, and are schematic views showing the principle of a method of coating a rare earth metal oxide on the surface of a high melting point metal.

FIG. 2 is a diagram illustrating a first embodiment of the present invention, in which Y ₂ O
₃ in coated Y ₂ O ₃ -W alloys, characteristic diagram showing element distributions along the depth direction of the surface W unit.

FIG. 3 is a diagram for explaining a second embodiment of the present invention, and is a characteristic diagram comparing the thickness of a coating layer in a case where a heating process is performed and in a case where an arc process is performed after a heating process.

FIG. 4 is a diagram illustrating a third embodiment of the present invention, and is a characteristic diagram showing an influence of a matrix metal on a thickness of a coating layer.

FIG. 5 is a diagram for explaining a fifth embodiment of the present invention, and is a characteristic diagram showing the influence of the size of Y ₂ O ₃ dispersed particles on the thickness of a coating layer.

FIG. 6 is a view for explaining a sixth embodiment of the present invention, and is a characteristic diagram showing an influence of a heating method on a thickness of a coating layer.

FIGS. 7 (a) to 7 (f) are views showing a seventh and an eighth embodiment of the present invention, and are schematic views of a manufacturing process of a coating material.

FIG. 8 is a diagram for explaining a ninth embodiment of the present invention;
FIG. 4 is a characteristic diagram showing a comparison of the relative density of the sintered body before and after the treatment.

FIG. 9 is a diagram for explaining a tenth embodiment of the present invention, and is a characteristic diagram showing the effect of the addition amount of Y ₂ O ₃ on the thickness and the bending strength of the coating layer.

FIG. 10 is a view for explaining an eleventh embodiment of the present invention. FIG. 10 is a characteristic diagram showing a change over time of an arc current density when coating is performed using a material having a continuous structure of Y ₂ O _{3 according} to the present invention. .

FIG. 11 is a diagram for explaining a twelfth embodiment of the present invention, and is a characteristic diagram showing a change with time of an arc current density in a material coated with Y ₂ O _{3 according} to the present invention.

FIG. 12 is a view for explaining a thirteenth embodiment of the present invention, and is a characteristic diagram showing a change with time of an arc current density and a wear amount of a material coated with Y ₂ O _{3 according} to the present invention.

[Explanation of symbols]

 1 matrix metal 2 dispersed particles 3 metal vapor 4 ceramic coating layer

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C23C 4/06 C23C 4/06 30/00 30/00 A

Claims (13)

[Claims] 1. A ceramic coating material in which a ceramic material is coated on a surface of a metal material containing a high melting point metal and a rare earth metal or an oxide of a rare earth metal as a main component, the metal material is placed under a reduced pressure atmosphere. By heating to a melting point of the rare earth metal or the rare earth metal oxide constituting the above and not more than the melting point of the high melting point metal, the surface of the metal material is coated with a substance mainly composed of the rare earth metal oxide. A ceramic coating material, characterized in that: 2. The ceramic coating material according to claim 1, wherein the metal material is used as a cathode, and a voltage is applied between the metal material and the other anode to cause an arc discharge on the metal material surface, thereby forming a surface of the metal material. Is coated with a substance containing a rare earth metal oxide as a main component. 3. The ceramic coating material according to claim 1, wherein the high melting point metal constituting the metal material is W, Mo, Ta, Nb, or an alloy thereof. 4. The ceramic coating material according to claim 1, wherein the rare earth metal constituting the metal material is Y, La, Ce, Nd, Sm, E
A ceramic coating material, which is u, Gd, Tb, Dy, Ho, Er, an alloy thereof, or an oxide thereof. 5. The ceramic coating material according to claim 1, wherein the rare earth metal or the oxide thereof is in the form of a particle, a lump or a powder, and is dispersed in the refractory metal. Characteristic ceramic coating material. 6. The ceramic coating material according to claim 1, wherein the content of the rare earth metal or the oxide of the rare earth metal in the metal material is 2 to 5.
Ceramic coating material characterized by being 0% by volume, preferably 5 to 30% by volume. 7. The ceramic coating material according to claim 1, wherein the rare earth metal or the rare earth oxide in the metal material has a three-dimensionally connected network structure. . 8. A ceramic coating material in which a ceramic material is coated on a surface of a metal material mainly composed of a high melting point metal and a rare earth metal or an oxide of a rare earth metal, the metal material is placed under a reduced pressure atmosphere. By heating to a melting point of the rare earth metal or the rare earth metal oxide constituting the above and the melting point of the high melting point metal or less, it is possible to coat the surface of the metal material with a substance mainly composed of the rare earth metal oxide. A method for producing a ceramic coating material. 9. The method for manufacturing a ceramic coating material according to claim 8, wherein the method for heating the metal material uses plasma, an electron beam, or a laser beam. 10. The method for producing a ceramic coating material according to claim 8, wherein the metal material is obtained by sintering a mixture of a granular or powdered rare earth metal or an oxide thereof and a powder of a high melting point metal. A method for producing a ceramic coating material. 11. The method for producing a ceramic coating material according to claim 10, wherein when a mixture of a rare earth metal or an oxide thereof and a refractory metal is sintered, hot pressing or HIP processing is used. Manufacturing method of coating material. 12. The method for producing a ceramic coating material according to claim 10, wherein a mixture of a rare earth metal or an oxide thereof and a refractory metal is sintered at normal pressure, and then subjected to HIP as a post-treatment. A method for producing a ceramic coating material, comprising: 13. An electrode, a filament, a member for a metal melting device, a member for an evaporator, a member for a casting device, and other high-temperature members, wherein the member is formed using the ceramic coating material according to any one of claims 1 to 7. .