JPH06144959A - Heat resistant member and production thereof - Google Patents

Abstract

PURPOSE:To obtain a inexpensive, lightweight and durable heat resistant member by forming a fireproofing coating layer on the surface of a base body consisting of a porous material. CONSTITUTION:The fireproofing coating layer 3 which is dense at the surface side, and porous at the side of the joining interface to the base body and whose porosity is gradually decreased from the joining interface to the surface is formed on the surface of the base body 2 consisting of the porous material. The surface of the base body is spray-coated plural times with the slurry of the fireproofing inorganic material powder so as to be smaller in particle size in proportion as the layer is upper and is fired. As a result, the concentration of thermal and mechanical stress caused by the difference of density and thermal expansion between the base body and the coating layer is prevented by making the density in the vicinity of the joining interface to the base body approximate to the density of the base body. The stress is uniformly distributed by giving inclination to the density of the coating layer. The surface of the coating layer is made dense to prevent the diffusion of the components of the material to be fired, the deterioration of base body caused by the reaction of the diffusion components with the base body is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-resistant member and a method for producing the same, and more particularly to a heat-resistant member formed by forming a low-reactivity fireproof coating layer on the surface of a substrate made of a porous material,
The present invention relates to a heat resistant member having improved peeling resistance between a substrate and a coating layer and a method for producing the same.

[0002]

2. Description of the Related Art Fire-retardant materials such as alumina, magnesia, mullite, spinel and cordierite have been widely used as firing jig materials used in the production of electronic materials such as capacitors, varistors, thermistors and piezoelectric elements. .

By the way, in recent years, low melting point oxides such as lead and bismuth have come to be used as a part of the composition for electronic materials such as capacitors for the purpose of cost reduction and improvement of characteristics. .

For the firing of electronic materials containing these low-melting-point oxides, a firing jig made of a material that reacts with the electronic material element as little as possible, for example, zirconia or magnesia is used.

However, these materials such as zirconia and magnesia are expensive, and a firing jig made of zirconia or magnesia is costly, heavy and difficult to handle, and has a large heat capacity. It is disadvantageous in terms of firing cost.

For this reason, recently, a firing jig in which a zirconia coating layer is formed on the surface of a lightweight substrate made of an inexpensive porous material such as alumina has come to be used.

Conventionally, such a firing jig is disclosed in Japanese Patent Laid-Open No. 2-69381.

[0008]

However, Japanese Unexamined Patent Publication (Kokai) No. 2-6.
The firing jig disclosed in Japanese Patent No. 9381 has a high-density and high-strength coating layer provided on the surface of the substrate in order to supplement the strength of the substrate, and the density of the substrate and the density of the coating layer are large. Since they are different, the difference in the coefficient of thermal expansion between the two is large. Therefore, stress is easily applied to the bonding interface between the base and the coating layer,
It has the drawback of being very vulnerable to mechanical shock. In addition, since the base and the coating layer have different volumetric shrinkage rates during sintering, there is also a drawback that the coating layer easily peels off. Further, not only thermal properties such as thermal conductivity and thermal expansion coefficient between the substrate and the coating layer but also the Young's modulus have a large difference, so that the coating layer is apt to crack, and the components of the element to be fired are cracked from the crack. Since it diffuses into the substrate and the substrate reacts with this diffusion component, there is also a drawback that the life of the firing jig is short.

As a solution to such a problem, Japanese Patent Publication No. 3-177383 discloses a refractory material in which the porosity of the coating layer is increased to prevent peeling or cracking between the substrate and the coating layer. ing. However, in this refractory, since the coating layer has a large porosity, the components of the element to be fired diffuse into the substrate through the voids, and are unsuitable as a firing jig.

The present invention solves the above-mentioned conventional problems, and is a heat-resistant member having a low-reactivity fireproof coating layer formed on the surface of a substrate made of a porous material, and the effect of protecting the substrate by the coating layer. It is an object of the present invention to provide a heat-resistant member that is inexpensive, lightweight, and has excellent durability, and a method for producing the same, which can reliably obtain the above-mentioned properties, and which is free from the problem of peeling or cracking of the coating layer.

[0011]

A heat-resistant member according to claim 1,
In a heat-resistant member having a refractory coating layer formed on the surface of a substrate made of a porous material, the coating layer has a dense surface side, a bonding interface side with the substrate is porous, and a porosity of It is characterized in that it gradually decreases from the bonding interface to the surface.

The heat-resistant member according to claim 2 is the heat-resistant member according to claim 1, wherein the refractory coating layer has a particle diameter of 1 to 100 μm.
It is a coating layer having a thickness of 50 to 200 μm, which is made of the refractory inorganic powder.

A heat-resistant member according to claim 3 is the heat-resistant member according to claim 1 or 2, wherein the substrate has a relative density of 30 to 70%, and the relative density of the upper layer on the front surface side of the fireproof coating layer is 50 to 70%. The relative density of the lower layer is 98%, the relative density of the lower layer on the bonding interface side with the substrate is 30 to 70%, and the relative density of the intermediate layer between the upper layer and the lower layer is 40 to 80%.

According to a fourth aspect of the present invention, there is provided a method for producing a heat-resistant member, wherein the surface of a substrate made of a porous material is spray-coated with a slurry of a refractory inorganic powder and then fired to form a fire-resistant coating layer made of a sintered layer. The method of forming a coating layer comprising a laminate of a plurality of layers by performing the spray coating a plurality of times, and then performing the firing, wherein the inorganic powder of each layer of the laminate is formed. The grain size is made smaller toward the upper layer, so that the surface side of the refractory coating layer made of the above-mentioned sintered layer is dense, the joint interface side with the substrate is porous, and the porosity is the same as that of the substrate. The coating layer is characterized in that the coating layer is gradually reduced from the interface toward the surface.

The present invention will be described in detail below with reference to the drawings.

FIG. 1 is a schematic cross-sectional view showing an embodiment of the heat-resistant member of the present invention, FIG. 2 is an enlarged view of an essential part of FIG. 1, and FIG.
The drawings are cross-sectional views showing an embodiment of the method for manufacturing a heat-resistant member of the present invention.

As shown in FIGS. 1 and 2, in the heat resistant member 1 of the present invention, the refractory coating layer 3 is formed on the surface of the substrate 2 made of a porous material.
The refractory coating layer 3 has a dense surface side, a joint interface side with the base 2 is porous, and a porosity from the joint interface with the base 2 to the surface. It is gradually decreasing toward.

In the present embodiment, in particular, the refractory coating layer 3 has an upper layer 3A on the front side and the substrate 2 in terms of its density.
Lower layer 3C on the side of the bonding interface with and intermediate layer 3B between them
And three layers, and the substrate and each layer preferably have the following relative densities.

Base: 30 to 70% Upper layer: 50 to 98% Intermediate layer: 40 to 80% Lower layer: 30 to 70% The particle size of the refractory inorganic powder constituting the refractory coating layer 3 is 1 Is preferably in the range of
The fireproof coating layer 3 preferably has a thickness of 50 to 200 μm.

Next, an embodiment of a method for manufacturing a heat-resistant member of the present invention, which is suitable for manufacturing such a heat-resistant member of the present invention, will be described with reference to FIG.

In FIG. 3, 2 is a substrate, 10 is a conveyor, 11 is a first tank, 12 is a second tank, and 13 is a third tank.
Tanks, 11A, 12A, 13A are spray nozzles, 1
4, 14A, 14B and 14C are air supply pipes for spraying, and V ₁ , V ₂ and V ₃ are valves.

In this embodiment, the substrate 2 is the conveyor 10
Causes the first to move while moving from left to right in the drawing.
Each slurry is sprayed from the tank 11, the second tank 12, and the third tank 13.

The slurry in the first tank 11 is a coarse-grained slurry of refractory inorganic powder having a large particle size.
As the slurry in the third tank 13, a fine-grained slurry of refractory inorganic powder having a small particle size is used.
As the second slurry, medium-sized slurry of refractory inorganic powder having an intermediate particle size between the slurry in the first tank 11 and the slurry in the third tank 13 is stored.

Specifically, the particle size of the refractory inorganic powder which constitutes the slurry of each tank is set as follows.

First tank: particle size 20 to 100 μm, central particle size 60 μm Second tank: particle size 10 to 70 μm, central particle size 40 μm
m Third tank: particle size 1 to 40 μm, central particle size 10 μm
m By using such a slurry, the coating layer formed has a particle diameter of 20 to 100 μm (central particle diameter of 60 μm).
In the lower layer (layer on the joint interface side with the substrate) composed of coarse particles of m), the one having a small particle size in the above particle size distribution contributes to maintaining the bonding strength with the substrate, The larger ones contribute to forming voids to increase the porosity and to form a less dense layer.

The particle size is 1 to 40 μm (center particle size 10
μm) in the upper layer (surface layer) composed of fine particles,
The fine particles form a dense and dense layer.

However, in the intermediate layer (layer between the upper layer and the lower layer) composed of medium particles having a particle size of 10 to 70 μm (center particle size 40 μm), a layer having an intermediate density between the upper layer and the lower layer is formed. As a result, it is possible to form the heat resistant member of the present invention in which the porosity (density) is inclined in the layer thickness direction as a whole.

In the present invention, the firing after forming the coating layer can be carried out by a conventional method, and the firing conditions are appropriately determined depending on the substrate, the kind and size of the refractory inorganic powder, and the like.

In the present invention, examples of the constituent material of the substrate include alumina, magnesia, spinel, mullite, cordierite and the like. Examples of the refractory inorganic powder include zirconia, preferably partially stabilized zirconia, (calcium, yttria, ceria as a stabilizer) and the like. As a slurry of such refractory inorganic powder, the refractory inorganic powder is 50 to 80% by weight.
0.5 to 3.0% by weight of methyl cellulose as a binder and 0.5 to 3.0% by weight of a wax-based emulsion as a slurry stabilizing agent in a water slurry containing a concentration.
A material having a viscosity of about 500 to 1500 mPa · s (millipascal second) is added and used.

The illustrated embodiment is an embodiment of the present invention, and the present invention is not limited to the illustrated embodiment as long as the gist thereof is not exceeded.

For example, the heat-resistant member of the present invention is not limited to one in which the density (or porosity) of the coating layer changes stepwise in the layer thickness direction, but may change continuously.

Further, in the heat-resistant member of the present invention, the coating treatment is not limited to three times and may be performed twice or four times or more.

[0033]

In the heat-resistant member of the present invention, in the coating layer formed on the substrate, the vicinity of the bonding interface with the substrate has a density close to that of the substrate, so that the density difference between the substrate and the coating layer
It is possible to prevent the concentration of thermal and mechanical stress due to the difference in thermal expansion. Therefore, by making the density of the coating layer have a gradient, the stress can be evenly dispersed.
Further, by forming a dense layer on the surface of the coating layer, it is possible to prevent the components of the material to be burned from diffusing and prevent the deterioration of the substrate due to the reaction between the diffusing components and the substrate.

According to the method for manufacturing a heat resistant member of the present invention, such a heat resistant member can be manufactured easily and efficiently.

That is, if the powder has a small particle size, a dense layer can be formed, and if the powder has a large particle size,
A layer with high porosity can be formed. For this reason,
The spray coating is performed in multiple steps, and the slurry is spray-coated so that the particle size of the refractory inorganic powder becomes smaller toward the upper layer, so that the surface side is dense and the bonding interface side with the substrate is porous. In addition, it is possible to form a coating layer in which the porosity gradually decreases from the bonding interface with the substrate toward the surface.

[0036]

EXAMPLES The present invention will be described more specifically with reference to Examples and Comparative Examples below.

Example 1 A heat-resistant member of the present invention was manufactured by the method shown in FIG. As the refractory inorganic powder, partially stabilized zirconia (stabilization rate 80%, stabilizer calcia) powder was used, and powder particles of slurry (water slurry) supplied to each of the first tank, second tank, and third tank. The diameter, concentration and viscosity were as follows. In each of the slurries, 1.0% by weight of methyl cellulose as a binder and 1.0% by weight of a wax emulsion as a slurry stabilizing agent were added and mixed with stirring.

First tank: particle diameter 30 to 100 μm, concentration 60%, viscosity 700 mPa · s Second tank: particle diameter 10 to 40 μm, concentration 60%, viscosity 1000 mPa · s Third tank: particle diameter 1 to 30 μm, concentration 60%, viscosity 1500 mPa · s, conveyor feed speed is 3.0 cm / sec,
Slurry spraying amount is 4.0m evenly from each nozzle
1 / sec.

As the substrate, a porous molded body containing alumina as a main component and having a density of 55% was used.

Thus, a coating layer having a thickness of 150 μm was formed on the substrate, which was naturally dried and then 1650
Calcination was carried out for 2 hours.

The obtained sintered body (100 mm × 100 mm
X5mm thickness) bending strength (average of 10 sheets) is 200k
It was gf / cm ² .

Further, when the obtained sintered body was placed horizontally on a surface plate and 50 g of iron balls were dropped from 20 cm above the surface, no damage was found on all 10 sheets.

Further, a thermal cycle life test of this sintered body was carried out at a temperature rising / falling rate of 250 ° C./hr and held at 1450 ° C. for 2 hours. Even after 60 thermal cycle tests, 10 sheets were cracked. No peeling or cracking was observed.

When the cross-sectional structure of the coating layer portion of this sintered body was observed by an electron microscope, it was confirmed that the density was high on the surface side, low on the bonding interface side with the substrate, and inclined in the layer thickness direction. Was done. Comparative Example 1 In Example 1, the particle size is 1 to 50 μm, and the average particle size is 1.
Slurry containing 0 μm partially stabilized zirconia (stabilization rate 80%) (slurry concentration 60%, slurry viscosity 1300
15 mPa · s) and sprayed on the substrate surface
A sintered body was manufactured in the same manner except that a coating layer having a thickness of 0 μm was formed.

The bending strength of the obtained sintered body is 500 kgf.
Was / cm ² . In this sintered body, the stress generated due to the difference in sintering contraction between the substrate and the coating layer is introduced into the bonding interface to provide high strength, but this strength is unnecessarily large and not practical. (Practical strength is 100-200
kgf / cm ² is sufficient. When an iron ball drop test and a thermal cycle life test were performed on this sintered body under the same conditions as in Example 1, the iron ball was damaged by being dropped. Further, in the heat cycle life test, cracks were generated in the heat cycle test 20 times, and peeling was observed in the heat cycle test 25 times.

[0046]

As described above in detail, according to the heat-resistant member of the present invention, the effect of protecting the substrate is high, and furthermore, cracking, peeling,
Provided is a heat-resistant member having excellent durability and free from problems such as breakage.

Such a heat-resistant member of the present invention is extremely effective especially for a jig for firing electronic materials such as a setter,
It is possible to reduce the cost of electronic materials by providing a firing jig that is lightweight, low cost, and excellent in durability.

According to the method for producing a heat-resistant member of the present invention, such a highly durable heat-resistant member can be produced easily and efficiently at low cost.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing an embodiment of a heat resistant member of the present invention.

FIG. 2 is an enlarged view of a main part of FIG.

FIG. 3 is a cross-sectional view showing an embodiment of a method for manufacturing a heat resistant member of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Heat resistant member 2 Substrate 3 Fireproof coating layer 10 Conveyor 11 First tank 12 Second tank 13 Third tank

Claims (4)

[Claims] 1. A heat-resistant member comprising a substrate made of a porous material and a refractory coating layer formed on the surface of the substrate, wherein the coating layer has a dense surface side and a joint interface side with the substrate is porous. A heat-resistant member having a porosity gradually decreasing from a bonding interface with a substrate toward the surface. 2. The heat-resistant member according to claim 1, wherein the fire-resistant coating layer is a coating layer made of a fire-resistant inorganic powder having a particle size of 1 to 100 μm and a thickness of 50 to 200 μm. 3. The heat resistant member according to claim 1, wherein the base has a relative density of 30 to 70%, and the relative density of an upper layer on the surface side of the fire resistant coating layer is 50 to 98%. The heat-resistant member, wherein the lower layer on the bonding interface side has a relative density of 30 to 70%, and the intermediate layer between the upper layer and the lower layer has a relative density of 40 to 80%. 4. A method for forming a fire-resistant coating layer made of a sintered layer by spray-coating a slurry of a fire-resistant inorganic powder on the surface of a substrate made of a porous material, and then firing the slurry. In this method, a coating layer composed of a laminate of a plurality of layers is formed by performing a plurality of times, and then the firing is performed, so that the particle size of the inorganic powder in each layer of the laminate is smaller in the upper layer. As a result, the surface side of the refractory coating layer made of the sintered layer is dense, the joint interface side with the substrate becomes porous, and the porosity gradually increases from the joint interface with the substrate toward the surface. A method for manufacturing a heat-resistant member, comprising forming a reduced coating layer.