JPH06144958A - Production of heat resistant member - Google Patents

Abstract

PURPOSE:To easily, inexpensively and efficiently produce a heat resistant member high in the protective effect of a base body, free from crack, peeling, breaking or the like and excellent in durability by subjecting the surface of the base body consisting of a porous material to spray coating with the slurry of a firerproofing inorganic powder from the upper side, thereafter firing it. CONSTITUTION:The base body 1 consisting of the porous material (e.g. alumina) is placed on the vibrating panel 2A of s vibration generator 2 generating vertical vibration, and subjected to spray coating with the slurry (containing fine grain, medium grain and coarse grain having 1-100mum particle diameter) containing 50-80wt.% fireproofing inorganic material (e.g. partially stabilized zirconia) powder in a tank 3 from the upper side through an air supply pipe 4 and a spray gun 3A while imparting vertical vibration (100-500mum amplitude, 50-200Hz period). The thickness of the coating layer is preferably 50-200mum. The firing after forming the coating layer is executed by the conventional method and the firing condition is properly determined in accordance with the kind or size of the base body or inorganic material powder.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a heat-resistant member, and more particularly, to the surface of a substrate made of a porous material, a slurry of a refractory inorganic powder is spray-coated from above and then sintered by firing. The present invention relates to a method for producing a heat resistant member having improved durability and the like by forming a fire resistant coating layer made of layers.

[0002]

2. Description of the Related Art Conventionally, 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. There is.

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 the surface of a substrate made of a porous material is spray-coated from above with a slurry of a refractory inorganic powder and then fired to form a fire-resistant coating made of a sintered layer. In the method of forming a layer, the effect of protecting the substrate by the coating layer can be reliably obtained, and there is no problem of peeling or cracking of the coating layer.
An object of the present invention is to provide a method for manufacturing a heat-resistant member which is inexpensive, lightweight and excellent in durability.

[0011]

A method for producing a heat-resistant member of the present invention comprises spray coating a slurry of a refractory inorganic powder onto a surface of a substrate made of a porous material from above,
In the method for forming a fireproof coating layer composed of a sintered layer by firing thereafter, a slurry of refractory inorganic powder having a particle size distribution is used as the slurry, and the substrate is vertically vibrated during spray coating. By doing so, the particle size of the refractory inorganic powder becomes finer on the surface of the coating layer, and by sintering this coating layer, the surface side is dense and the bonding interface side with the substrate is porous, and the porosity is It is characterized in that a coating layer is formed which is gradually reduced from the bonding surface with the substrate toward the surface.

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

FIG. 1 is a side view showing an embodiment of a method for manufacturing a heat-resistant member of the present invention, and FIG. 2 is an enlarged sectional view showing an embodiment of a heat-resistant member manufactured by the method of manufacturing a heat-resistant member of the present invention. It is a figure.

As shown in the figure, in the method of manufacturing the heat-resistant member of this embodiment, the substrate 1 made of a porous material is placed on the vibrating plate 2A of the vibration generator 2 for generating vertical vibrations
While applying vertical vibration, the slurry in the tank 3 is spray-coated from above. In addition, 4 is an air supply pipe for slurry spraying, 3 A is a spray gun, and V is a valve.

The slurry used for this spray coating is a slurry of a refractory inorganic powder having a particle size distribution, and in the spray coating of such a slurry, the substrate 1 is vibrated in the vertical direction so that Since the refractory inorganic powder with a large particle size sediments quickly, while the refractory inorganic powder with a small particle size has a low sedimentation rate, the coating layer formed has a finer particle size on the surface side. Will be things.

Therefore, by firing the substrate on which such a coating layer is formed, as shown in FIG. 2, the surface side 5A is dense due to the fine particles of the refractory inorganic powder, and the bonding interface side with the substrate 1 is formed. 5B is porous, and the coating layer 5 has a porosity that gradually decreases from the bonding surface with the substrate 1 toward the surface.
Is obtained.

In the present invention, the magnitude and period of the vertical vibration applied to the substrate are not particularly limited, but in the usual case, the amplitude is 100 to 500 μm, particularly 200 to 30.
0 μm, cycle 50 to 200 Hz, especially 80 to 150 Hz
It is preferable to apply the vertical vibration.

The particle size of the refractory inorganic powder having a particle size distribution forming the slurry is not particularly limited, but in general, it includes fine particles, medium particles and coarse particles having a particle size of 1 to 100 μm. Those are preferable. According to the method of the present invention, a refractory inorganic powder having a particle diameter of 20 to 100 μm and a central particle diameter of 60 μm is used as a coating layer as a coating layer, and a lower layer on the bonding interface side with a substrate is used as an upper layer on the surface side. ,
A refractory inorganic powder having a particle diameter of 1 to 40 μm and a central particle diameter of 10 μm is dispersed, and a refractory inorganic powder having a particle diameter of 10 to 70 μm and a central particle diameter of 40 μm is dispersed in an intermediate layer between the lower layer and the upper layer. Then, it is preferable to form a coating layer on the surface of the substrate having a relative density of 30 to 70% such that the relative density after firing is in the following range.

Upper layer: 50 to 98% Intermediate layer: 40 to 80% Lower layer: 30 to 70% The thickness of this coating layer is preferably 50 to 200 μm.

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, (stabilizer: calcia, yttria, ceria) and the like. Such a slurry of the refractory inorganic powder is a water slurry containing the refractory inorganic powder in a concentration of 50 to 80% by weight, methyl cellulose as a binder in an amount of 0.5 to 3.0% by weight, and a wax as a slurry stabilizing agent. A system emulsion having a viscosity of about 500 to 1500 mPa · s (millipascal second) by adding 0.5 to 3.0% by weight of a system emulsion is used.

In the present invention, the baking after the coating layer is formed can be carried out by a conventional method, and the baking conditions are appropriately determined depending on the type and size of the base material and the refractory inorganic powder.

[0022]

The settling speed of particles settled in a slurry having a predetermined viscosity is proportional to the particle size, and coarse particles having a larger particle size settle faster, and fine particles having a smaller particle size have a lower settling speed.

In the present invention, utilizing this principle,
When spray-coating a viscous slurry from above the substrate, the substrate is vibrated vertically to accelerate the sedimentation rate of the refractory inorganic powder, and the lower layer (bonding interface side with the substrate) has a larger particle size. The powder is subjected to coating treatment so that the refractory inorganic powder having a larger particle size is distributed in the upper layer (surface side).

However, if the powder has a small particle size,
Since it is possible to form a dense layer and a powder having a large particle size can form a layer having a large porosity, by firing such a coating layer, the surface side is dense, It is possible to form a coating layer in which the side of the joint interface with the substrate is porous and the porosity gradually decreases from the joint interface with the substrate toward the surface.

In the heat-resistant member manufactured in this way,
Of the coating layer formed on the substrate, the vicinity of the bonding interface with the substrate is made to have a density close to that of the substrate, so that the difference in the density between the substrate and the coating layer and the thermal and mechanical It is possible to prevent stress concentration. Therefore, by making the density of the coating layer have a gradient, the stress can be evenly dispersed. Also, regarding the surface of the coating layer,
By forming the dense layer, it is possible to prevent the components of the material to be fired from diffusing and prevent the deterioration of the substrate due to the reaction between the diffusing components and the substrate.

[0026]

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

Example 1 A heat resistant member was manufactured by the method shown in FIG. As the refractory inorganic powder, partially stabilized zirconia (stabilization rate: 80%) powder having a particle size of 1 to 100 μm was used.
0.5% by weight of methyl cellulose as a binder and 2.0% by weight of a wax emulsion as a slurry stabilizing agent were added to a weight% aqueous slurry and mixed by stirring to prepare a slurry for spraying (viscosity 700 mPa · s). .

As shown in FIG. 1, this slurry is sprayed onto a substrate 1 made of a porous molded body containing alumina as a main component and having a density of 55%, which is placed on a vibration oscillator (vibrator) 2. The slurry was sprayed for 30 seconds at a slurry spray rate of 10 ml / sec so that the coating film thickness would be 150 μm.
At this time, simultaneously with the start of spraying, the substrate 1 has a vibration frequency
A vertical vibration of 0 Hz and an amplitude of 250 μm was applied, and the vibration was continued for 120 seconds after the end of spraying.

After spraying, the substrate was naturally dried and then 1650
Calcination was carried out for 2 hours.

The obtained sintered body (100 mm × 100 mm
Bending strength (average of 10 sheets) is 230k
It was gf / cm ² .

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

Further, a thermal cycle life test was carried out by holding this sintered body at a temperature rising / falling rate of 250 ° C./hr 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 with an electron microscope, the density was high on the surface side, and the number of pores gradually increased toward the bonding interface side with the substrate, and in the layer thickness direction. It was confirmed that the density was inclined.

Comparative Example 1 In Example 1, a slurry containing a partially stabilized zirconia (stabilization rate 80%) having a particle size of 1 to 50 μm and an average particle size of 10 μm was added without vibrating the substrate (slurry concentration 60%, A slurry was produced in the same manner except that a slurry having a viscosity of 600 mPa · s) was sprayed to form a coating layer having a thickness of 150 μm on the surface of the substrate.

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. ) This sintered body was subjected to an iron ball drop test and a thermal cycle life test under the same conditions as in Example 1, and as a result, the iron ball dropped and was damaged. 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.

[0036]

As described in detail above, according to the method for producing a heat-resistant member of the present invention, the heat-resistant member has a high effect of protecting the substrate and is free from the problems of cracking, peeling, breakage, and the like. Can be manufactured easily and efficiently at low cost.

The heat-resistant member manufactured according to the present invention as described above is particularly effective as a jig for baking electronic materials such as a setter, and provides a baking jig which is lightweight, low in cost and excellent in durability. By doing so, it is possible to reduce the cost of the electronic material.

[Brief description of drawings]

FIG. 1 is a side view showing an embodiment of a method for manufacturing a heat resistant member of the present invention.

FIG. 2 is an enlarged cross-sectional view showing an embodiment of a heat resistant member manufactured by the method for manufacturing a heat resistant member according to the present invention.

[Explanation of symbols]

 1 Base 2 Vibration Generator 2A Vibration Plate 3 Tank 5 Coating Layer 10 Heat-Resistant Member

Claims (1)

[Claims] 1. A method for forming a refractory coating layer composed of a sintered layer by spray-coating a slurry of a refractory inorganic powder on the surface of a substrate made of a porous material from above, and then firing the slurry to obtain a fire-resistant coating layer. Using a slurry of a refractory inorganic powder having a particle size distribution, and spray coating, by vibrating the substrate in the vertical direction, the particle size of the refractory inorganic powder becomes finer toward the surface of the coating layer, By sintering the coating layer, the surface side is dense and the bonding interface side with the substrate is porous, and the coating layer is formed so that the porosity gradually decreases from the bonding surface with the substrate to the surface. And a method of manufacturing a heat resistant member.