JP2008038228A - Sintering tray - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tray for sintering in which reactivity to a sintering object is reduced as much as possible. <P>SOLUTION: The tray for sintering is provided with: a base material; and one or more layers of films formed on the base material. The base material is composed of a carbonaceous material, each film is composed of the crystal grains of oxide with the average grain diameter of 1 to 800 nm, the density thereof is 35 to 99%, and there is no through holes passing to the surface of the base material from the surface of each film. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a sintering tray used in a sintering process for producing a sintered body.

  In general, a sintered body such as a powder metallurgy product is manufactured by mixing a main alloy and a binder component, and sintering them after pressure molding. In the sintering step, a pressure-molded molded body (hereinafter, not only such a molded body but also an object to be sintered is referred to as a “sintered object”) is placed on a sintering tray. Is performed.

  However, in this sintering process, the following problems have been pointed out conventionally, and improvement has been desired. That is, in this sintering process, the object to be sintered reacts with the sintering tray, and as a result, the composition of the sintered body is different from that of the desired composition. It is a problem that it does not sufficiently show the characteristics required for the body. This problem is particularly prominent when a carbonaceous material is used as the base material for the sintering tray.

And as a means to solve this problem, attempts to form various coatings on the surface of the base material that constitutes a sintering tray conventionally, and filling the pores of such base material with Al ₂ O ₃ An attempt has been made (Patent Document 1). However, in the attempt to fill this Al ₂ O ₃ , it was difficult to sufficiently prevent the above reaction because Al ₂ O ₃ does not form a continuous film.

On the other hand, as an attempt to form various coatings on the surface of a substrate, for example, a method of forming a composite coating composed of ZrO ₂ and Y ₂ O ₃ has been proposed (Patent Document 2). However, this composite film has a problem that cracks or peeling occurs in the film, and the above reaction cannot be sufficiently prevented due to the cracks or peeling.

Moreover, although proposals have been made to form a film containing a rare earth oxide as such a film (Patent Documents 3 and 4), it has the same problem as the above composite film, It was not. Furthermore, in order to solve these problems, an attempt to form a mixed layer of different types of ceramics on a substrate has been proposed, but there is a problem that the coating is more easily peeled off.
Japanese Patent Application Laid-Open No. 07-089769 Special Table 2000-509102 JP 2003-073794 A JP 2003-0842402 A

  The present invention has been made in view of the above situation, and an object of the present invention is to provide a sintering tray in which the reactivity with respect to the object to be sintered is reduced as much as possible.

  The present inventor has made extensive studies to solve the above-mentioned problems. As a result, the physical properties of the coating rather than improving the material (chemical composition) of the coating formed on the substrate constituting the sintering tray. The present inventors have finally obtained the knowledge that it is more effective to improve the structural structure, and have made further studies based on this knowledge to finally complete the present invention.

  That is, the present invention is a sintering tray comprising a base material and one or more layers of coatings formed on the base material, the base material comprising a carbonaceous material, It is composed of oxide crystal particles having a particle size of 1 nm or more and 800 nm or less, and the density thereof is 35% or more and 99% or less, and there are no through-holes extending from the surface of the coating to the surface of the substrate. This relates to the sintering tray.

Here, it is preferable that the denseness is not uniform in the thickness direction, and the oxide is preferably one or more oxides, and Al ₂ O ₃ , ZrO ₂ , Y It is preferably at least one selected from the group consisting of ₂ O ₃ , TiO ₂ , HfO ₂ , and Cr ₂ O ₃ .

  The total thickness of the coating film is preferably 20 nm or more and 100 μm or less, and the base material is preferably filled with oxide crystal particles in an interface portion in contact with the coating film.

  Further, the coating is preferably formed by an aerosol deposition method using a fine oxide powder as a raw material, and the fine oxide powder preferably has an average particle size of 1 nm or more and 1 μm or less.

  The tray for sintering of the present invention has the configuration as described above, so that the reactivity with respect to the object to be sintered is reduced as much as possible.

Hereinafter, the present invention will be described in more detail.
<Sintering tray>
The tray for sintering of the present invention is a tray used when sintering a sintered object, and is in contact with the sintered object by placing the sintered object or the like. Therefore, the name is not limited to the sintering tray as long as it is a member applied to such a use. For example, what is called a tray and a sintering tray, and what is called a sintering setter etc. is also contained.

  In addition, although the composition is not specifically limited as used herein, the sintered object is, for example, a material that is sintered to form a sintered body made of cemented carbide or cermet.

  Such a sintering tray of the present invention comprises a base material and one or more layers of coating formed on the base material.

<Base material>
The base material of the present invention is made of a carbonaceous material. Any carbonaceous material can be used without particular limitation as long as it is a carbonaceous material used for this type of application.

  In addition, a carbonaceous material means the molded object which has carbon as a main component here. For example, an inorganic molded body (graphite tray) mainly composed of graphite is included. Such a molded article may contain a binder component.

<Coating>
The coating film of the present invention is formed on a substrate by one or more layers, and is composed of oxide crystal particles having an average particle diameter of 1 nm or more and 800 nm or less, and the density thereof is 35% or more and 99% or less. It is characterized in that there are no through-holes leading from the surface of the coating to the surface of the substrate.

  Such a coating preferably has a total film thickness of 20 nm or more and 100 μm or less, more preferably an upper limit of 50 μm or less, and a lower limit of 1 μm or more, and further preferably 5 μm or more. When the total film thickness is less than 20 nm, it may be difficult to sufficiently suppress the reactivity with the sintered object. On the other hand, if the total film thickness exceeds 100 μm, self-destruction of the film may occur.

  The total film thickness of the coating means the thickness of the coating when the coating consists of one layer, and the total thickness of the layers when the coating consists of two or more layers.

<Oxide crystal particles>
The coating film of the present invention is composed of oxide crystal particles having an average particle diameter of 1 nm to 800 nm. Thus, by limiting the average particle size of the oxide crystal particles constituting the coating to a specific minute range, the coating of the present invention can be used even when cracks are generated by heating / cooling cycles, etc. The progress can be prevented very effectively. For this reason, it is considered that the main cause of mass transfer through cracks in the coating is the sintered object and the sintering tray (in this case, it may be more accurate to express “substrate”, unless otherwise noted. In the following, it is possible to effectively suppress the reaction between the “sintering tray”.

  In addition, even if such mass transfer does not occur, cracks may move along the grain boundaries of the crystal. As described above, the average particle size is limited to a specific minute range. As a result, the crystal grains are not arranged in a specific orientation, so that a grain boundary that affects mass transfer is not formed in the coating. For this reason, the reaction between the sintering object and the sintering tray can be effectively suppressed.

  More preferably, the upper limit of such average particle diameter is 500 nm or less. When the average particle diameter is less than 1 nm or more than 800 nm, the above-mentioned effective effects cannot be shown.

  Such average particle diameter can be measured as follows. That is, first, using transmission electron microscope (TEM), oxide crystal particles present on an arbitrary line segment of a predetermined length parallel to the substrate surface in the cross section of the coating (cross section parallel to the thickness direction) The value obtained by dividing the predetermined length by the number of crystal grains is defined as the particle diameter of the oxide crystal grains. Then, the same measurement is performed for three line segments as the above arbitrary line segments, and the average value of the particle diameters is defined as the average particle diameter. The predetermined length of the line segment is preferably about 3 μm to 5 μm.

  On the other hand, the oxide constituting such crystal grains may be composed of only one kind, or may be composed by combining two or more kinds. When the coating is composed of two or more layers, the oxide crystal particles constituting each layer may be of the same type or different types. By configuring the coating with oxide crystal particles in this way, the reaction between the object to be sintered and the sintering tray can be effectively suppressed chemically, and in particular, the coating itself and the firing can be prevented. The reaction with the binding tray can be suppressed.

As such an oxide, it can be used without particular limitation conventional oxide (inorganic oxide) to be used as a coating, such as a heat resistant member, as a particularly preferred example, Al ₂ It is preferable to use at least one selected from the group consisting of O ₃ , ZrO ₂ , Y ₂ O ₃ , TiO ₂ , HfO ₂ , and Cr ₂ O ₃ .

  The oxide crystal particles of the present invention constitute a coating film, but it is preferable that a part of the oxide crystal particles penetrates into the interface portion of the substrate in contact with the coating film. This is because the so-called anchor effect is exhibited, and the adhesion between the coating film and the base material is improved, and peeling of the coating film is effectively suppressed. In addition, it is preferable to make the area | region to penetrate into the range of 0.001 micrometer-0.5 micrometer from the base-material surface in general.

  In addition, when the oxide crystal particles penetrate into the interface portion of the base material in this way, it is difficult to clearly determine the interface portion between the coating film and the base material, and it is difficult to measure the total film thickness of the coating film. In such a case, a point at which the area ratio of the coating component is 50% or more by cross-sectional measurement in the thickness direction of the coating using TEM is regarded as the interface between the two.

<Dense>
The film of the present invention has a density of 35% or more and 99% or less. Thus, by setting the density within a specific range, this acts synergistically with the above-described characteristics, so that the reaction between the object to be sintered and the sintering tray can be extremely effectively suppressed.

  When the density is less than 35%, it becomes difficult to sufficiently suppress the reaction between the sintering object and the sintering tray, whereas when it exceeds 99%, the production is difficult and the productivity is extremely poor. It is not preferable.

  Here, the fine density means a value obtained by dividing the density of the coating of the present invention by the theoretical density of the oxide sintered body constituting the coating, expressed as a percentage (%). And the specific measuring method is as follows.

  First, the density of the coating of the present invention is determined as follows. That is, a flat plate made of the same base material as that of the sintering tray of the present invention is prepared, and a constant thickness (for example, 50 μm) is formed on the flat plate under the same conditions as the film forming conditions when the sintering tray is manufactured A film is formed. And the mass change of this flat plate before and after film formation is measured, and the increase is made into the mass of a film. And the numerical value which remove | divided the film mass by the volume of the film (thickness of the surface of the flat plate on which the film is formed multiplied by the thickness of the film) is defined as the density of the film of the present invention.

  Next, the density is calculated by dividing the density of the coating film of the present invention thus obtained by the theoretical density of the oxide sintered body or single crystal constituting the coating film. Literature values shall be adopted as the theoretical density. In addition, when an oxide is comprised with 2 or more types of thing, what was totaled the numerical value obtained by multiplying the theoretical density of the sintered compact of each oxide by the structural ratio is made into a theoretical density.

  Furthermore, it is preferable that such a density is not uniform in the thickness direction of the film. Thus, by making the density non-uniform, peeling of the film is extremely effectively prevented. This is considered to be because a region having a low density is partially formed in the film.

  That is, the peeling of the coating is mainly caused by the dimensional difference between the two due to the difference in the thermal expansion coefficient between the coating and the substrate when the heating / cooling cycle is repeated. It is thought that the strain due to the difference is alleviated by the low density region.

  In particular, the density distribution is such that the density is large on the surface side of the coating and changes stepwise or in an inclined manner from there to the surface side of the base material, and the density decreases on the surface side of the base material. preferable. By setting it as such distribution, reaction between a sintering object and a sintering tray can be suppressed especially effectively, and peeling of a film can also be prevented effectively.

  Such a change in density can be confirmed, for example, as follows. First, the density of the entire coating is measured as described above. Next, after removing a predetermined thickness from the coating surface by polishing with a diamond grindstone, the density of the coating in the remaining portion is measured. Then, by repeating this operation, a change in the density of the coating can be measured. In addition, since this measurement measures a model using a flat plate made of the same base material as described above, the predetermined thickness polished by the grindstone needs to be determined in correlation with the actual thickness of the target film. is there.

<Through hole>
The coating film of the present invention is characterized in that there are no through-holes extending from the surface of the coating film to the surface of the substrate. Thereby, reaction with a sintering target object and the tray for sintering can be suppressed effectively. Such excellent effects are none other than those brought about by the synergistic action of the other characteristics already described above and the present characteristics, but even in a relatively low density of 35%, The reason for providing a state in which no through-holes exist is that the average grain size of oxide crystal particles is limited to a very small range of 1 nm to 800 nm.

  And the presence or absence of such a through-hole can be confirmed by observing the surface and cross section of a film with a scanning electron microscope (SEM). That is, when the observation magnification is about 10,000 times and the observation visual field is about 50 μm × 50 μm, by observing the surface of the coating at five locations and the cross-section at five locations, when the through-holes are not confirmed, the substrate is removed from the surface of the coating. It is assumed that there are no through-holes that communicate with the surface.

  In addition, since a through-hole here means the hole which influences the above-mentioned mass transfer, the diameter (maximum diameter) of the hole observed on a film surface and a cross section shall be a thing of 300 nm or more.

<Manufacturing method>
The coating film of the present invention can be formed on a substrate by any conventionally known method. However, the coating of the present invention is particularly preferably formed by an aerosol deposition method using a fine oxide powder as a raw material. This is because the coating film of the present invention having the above-described features can be most efficiently produced. Further, when the coating is composed of two or more types of oxides, it can be easily combined. Hereinafter, the case where a film is formed by this aerosol deposition method will be described.

  FIG. 1 is a conceptual diagram of a film forming apparatus for executing the aerosol deposition method used in the present invention. In this film forming apparatus, an aerosol forming chamber 4 as an aerosol generator is installed at the end of a carrier gas cylinder 1 via a gas carrier line 2. Nitrogen, argon, helium, dry air, etc. can be used as the carrier gas passing through the gas carrier line 2.

  The aerosol chamber 4 is filled with an appropriate amount of fine oxide powder as the raw material 3. The aerosolization chamber 4 is placed on a vibration exciter 5 for applying vibration. The aerosol generation chamber 4 is connected to a nozzle 7 by an aerosol transport line 6, and the nozzle 7 faces the substrate 9 in a chamber 13 constituting a film forming chamber.

  The substrate 9 is held by the substrate stage 10. A mask 8 can be provided between the substrate 9 and the nozzle 7. Aerosol particles 12 are ejected from the nozzle 7 toward the substrate 9. The substrate stage 10 can move in the direction indicated by the arrow 14, and accordingly, the base material 9 also moves together with the substrate stage 10. The chamber 13 is connected to the vacuum pump 11, and the vacuum pump 11 can adjust the pressure in the chamber 13.

  In such a film forming apparatus, the vacuum pump 11 is operated to reduce the pressure in the chamber 13 as the film forming chamber and the aerosol forming chamber 4 to about 1 Pa. The carrier gas cylinder 1 is opened, and the gas flow rate is 0.1 slm (flow rate per minute in the standard state (25 ° C.) is 0.1 l) to 15 slm (flow rate per minute in the standard state (25 ° C.) is 15 l). Then, the gas is sent into the aerosol chamber 4 to generate an aerosol in which the fine oxide powder as the raw material 3 and the gas are mixed at an appropriate ratio.

At this time, since the aerosol flows into the chamber 13 through the nozzle 7 having a minute opening, a pressure difference of about 10 ³ Pa is generated between the aerosol forming chamber 4 and the chamber 13. This aerosol is accelerated through the aerosol transport line 6 and sprayed toward the substrate 9 by the nozzle 7.

  The film of the present invention is formed in a sintered state on the base material 9 by the collision of the fine oxide powder while changing the aerosol collision position by driving the substrate stage 10. By moving the nozzle 7 and the base material 9 relative to each other, a film is formed on a necessary portion. Further, if necessary, the film forming position of the substrate 9 can be designated by fixing the mask 8 having an appropriate pattern on the substrate 9.

  In the above, as the fine oxide powder used as a raw material for film formation, it is preferable to use a powder having an average particle diameter of 1 nm or more and 1 μm or less, more preferably, the upper limit is 500 nm or less, and the lower limit is 10 nm or more. More preferably, it is 50 nm or more. When the average particle size is less than 1 nm, the fine density within the above range may not be obtained. On the other hand, when the average particle size exceeds 1 μm, the growth rate of the film may be slow and productivity may be inferior. In general, when a fine oxide powder having a relatively large average particle diameter is used, a relatively low density tends to be obtained.

In addition, as such a fine oxide powder, it is particularly preferable to use two or more kinds of powders having different average particle diameters. This is because the density can be suitably controlled. Incidentally, the average particle size of the fine oxide powder as used herein means a particle size of cumulative mass 50% by mass (typically represented by D _50).

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these.

<Raw material>
As a base material made of a carbonaceous material, a graphite tray having a predetermined shape (outer dimensions: length 230 mm × width 265 mm × height 5 mm) mainly composed of graphite was used. And the sintering tray of this invention and the sintering tray of a comparative example were manufactured by forming a film on this base material using the raw material described in the following Table 1 and Table 2. The film formation conditions are as described below.

In Table 1 and Table 2, the first layer to the third layer represent each layer of the coating, and the compounds described therein are the raw materials. Note that the first layer is formed on the base material, and the second layer and the third layer are described, the second layer is formed on the first layer, and the second layer is formed on the second layer. It shows that the third layer is formed. Moreover, a numerical value shows the average particle diameter (nm) and mixing | blending ratio (mass%) of a raw material (the numerical value in parenthesis is a mixing | blending ratio). That is, when a numerical value is described in a combination of two or more, it indicates that a plurality of raw material powders have been used. For example, in Example 1, two kinds of Y ₂ O ₃ powders having different average particle diameters as raw material fine oxide powders (80 mass% with an average particle diameter of 800 nm and 20 mass% with an average particle diameter of 55 nm) are used. Indicates that

<Film formation conditions>
A film was formed in a sintered state on the substrate by the aerosol deposition method described above using the film forming apparatus of FIG. Specific conditions of the film forming conditions of the examples of the present invention are as follows.

  That is, the raw materials described in Table 1 and Table 2 were filled in the aerosolization chamber 4, respectively. Helium was used as the carrier gas, and the flow rate was adjusted in the range of 0.1 slm to 15 slm. Moreover, the pressure was adjusted with the vacuum pump 11 so that the pressure of the aerosol-generating chamber 4 became 10-20 kPa, and the pressure of the chamber 13 became 5-3000 Pa.

Further, the substrate 9 is set to the substrate stage 10, the aperture size of the nozzle 7 is adjusted in the range of 2-4 mm ^2, the distance between the nozzle 7 and the substrate 9 is adjusted in the range of 4 to 15 mm. Furthermore, the moving speed of the substrate stage 10 was adjusted in the range of 0.1 to 3 mm / s.

  Thus, the film described in Table 3 and Table 4 below was formed on the substrate. When reducing the average particle size of the oxide constituting the coating, the gas flow rate should be increased within the range of the above conditions, and when reducing the density, the particle size of the raw material powder is adjusted within the range of the above conditions. Just do it. That is, powders having different average particle diameters may be mixed so that the entire raw material powder has a large particle diameter. In addition, what is necessary is just to change the said conditions suitably in the middle, when changing a density in each layer. Moreover, the film formation conditions of the comparative example are adjusted beyond the above range.

  In Tables 3 and 4, the first to third layers correspond to the first to third layers in Tables 1 and 2, respectively. The numerical value in parentheses in the material section indicates the composition ratio (% by mass). An average particle diameter (nm) shows the average particle diameter of the oxide crystal particle which comprises the film measured by the method demonstrated above. The numerical value in the term of the density indicates the density (%) and the film thickness (μm) (the value in parentheses is the film thickness). That is, when the numerical value is described in a combination of two or more kinds in the term of the density, it indicates that the density is different in the thickness direction of the film (that is, the density is not uniform). For example, Example 6 shows that a region with a density of 42% is formed on the substrate surface side by 20 μm and a region with a density of 83% is formed by 65 μm on the coating surface side (described on the left side in each layer). Is formed on the substrate side). The density was determined by the method described above.

  The presence or absence of the through hole was also confirmed by the above method, and the results are shown in Tables 3 and 4. In addition, when the cross section of the thickness direction of the film was observed by TEM for the example, it was confirmed that the oxide crystal particles had entered the substrate side at the interface between the substrate and the film.

<Reactivity test>
Using each of the sintering trays obtained above, a test for confirming the reactivity between the object to be sintered and each of the sintering trays was performed. Specific test conditions are as follows.

First, the following four kinds of objects to be sintered (shape: ISO standard SNMN120408) were used.
Sintering object A: Powder mixed molded body of 10% by mass Co and the balance WC (K20)
Sintered object B: Powder mixed molded body (K40) of 20% by mass Co and the balance WC
Sintered object C: Powder mixed compact of 30% by mass Co and the balance WC D: 20% by mass WC, 5% by mass Mo ₂ C, 10% by mass Co, 5% by mass Ni and the remainder Ti (C , N) powder mixed compact (P30)
And each sintering object was mounted in each said tray for each sintering, and after sintering by heating to 1500 degreeC, it cooled to room temperature. By repeating this operation (putting the object to be sintered on the sintering tray, cooling it after heating and sintering, and then removing the object to be removed from the sintering tray once) The number of times of sintering until the product and the sintering tray (film) were welded was determined. The results are shown in Table 5 and Table 6 below. It shows that the reactivity between a sintering target object and the tray for sintering is suppressed, so that there are many frequency | counts. The upper limit of the number of times of sintering was 300 times, and those not welded at that time were described as “300 or more”.

  In addition, it was also observed whether or not cracks occurred in the coating on the sintering tray when the sintering was performed for the first time, and the results are also shown in Tables 5 and 6 (in the presence or absence of cracks).

In Table 6, Comparative Example 5 shows a sintering tray in which a film was not formed on the substrate, and Comparative Example 6 was a film (ZrO ₂ 20 mass%, Y ₂ O ₃ 80 mass%) on the substrate. The example formed by the thermal spraying method is shown, and Comparative Example 7 shows the case where a coating (Y ₂ O ₃ 60% by mass, Al ₂ O ₃ 40%) is formed on the base material by the coating method. In addition, when the through holes were confirmed in the same manner as described above for Comparative Example 6 and Comparative Example 7, a plurality of through holes were confirmed.

  As is clear from Tables 5 and 6, the sintering tray of the example of the present invention has no cracks during the first sintering, compared to the sintering tray of the comparative example. The reactivity was extremely suppressed.

  Although the embodiments and examples of the present invention have been described as described above, it is also planned from the beginning to appropriately combine the configurations of the above-described embodiments and examples.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a conceptual diagram of the film-forming apparatus for performing the aerosol deposition method used by this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Transfer gas cylinder, 2 Gas transfer line, 3 Raw material, 4 Aerosolization chamber, 5 Vibrator, 6 Aerosol transfer line, 7 Nozzle, 8 Mask, 9 Base material, 10 Substrate stage, 11 Vacuum pump, 12 Aerosol grain, 13 Chamber, 14 arrows.

Claims (8)

A sintering tray comprising a substrate and one or more layers of coatings formed on the substrate,
The base material is made of a carbonaceous material,
The coating is composed of oxide crystal particles having an average particle diameter of 1 nm or more and 800 nm or less, and the density thereof is 35% or more and 99% or less, and penetrates from the surface of the coating to the surface of the substrate. A sintering tray characterized by the absence of holes.   The sintering tray according to claim 1, wherein the denseness is not uniform in the thickness direction of the coating.   The sintering tray according to claim 1 or 2, wherein the oxide is one or more oxides. The oxide claim 1, wherein the at least one selected from _{Al 2 O 3, ZrO 2,} Y 2 O 3, TiO 2, the group consisting of HfO _2, and Cr ₂ O ₃ The sintering tray according to any one of the above.   The sintering tray according to any one of claims 1 to 4, wherein the coating has a total film thickness of 20 nm or more and 100 µm or less.   The sintering tray according to any one of claims 1 to 5, wherein crystal grains of the oxide are infiltrated in an interface portion in contact with the coating film.   The sintering tray according to claim 1, wherein the coating is formed by an aerosol deposition method using fine oxide powder as a raw material.   The sintering tray according to claim 7, wherein the fine oxide powder has an average particle size of 1 nm to 1 μm.

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