JPS63107871A - Manufacture of ceramic product - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] A1 Purpose of the invention (1) Industrial application field The present invention relates to a method for manufacturing ceramic products.

(2) Conventional technology Conventionally, in this type of manufacturing method, a ceramic sintered body such as a ceramic molded body or a temporarily sintered body obtained from the ceramic molded body is sealed in a quartz glass tube or Vyroceram under vacuum. It is known to then perform HIP treatment (hot isostatic pressing treatment).

(3) Problems to be solved by the invention However, according to the above method, when the object to be sintered is relatively large, has a complicated shape, is thin, etc. There is a problem in that it is difficult to encapsulate under vacuum, and if the vacuum encapsulation treatment is not performed reliably, a high-strength ceramic product cannot be obtained by HIP treatment.

In view of the above, the present invention significantly alleviates the restrictions associated with the size, shape, etc. of the sintered body in vacuum encapsulation treatment, improves the process workability, and makes it possible to obtain high-strength ceramic products. It is an object of the present invention to provide the above manufacturing method.

B9 Structure of the Invention (Means for Solving Problems 11) The present invention provides an outer glass-forming powder layer covering the entire ceramic body to be sintered, which has a higher melting point than the glass-forming powder layer, and which has a higher melting point than the glass-forming powder layer. An intermediate inorganic protective layer that prevents the melt of the layer and the glass acid melt obtained from the layer from penetrating into the object to be sintered, and a constituent material of the object to be sintered, and the inorganic protective layer An inner ceramic powder layer, which has a higher melting point than the above-mentioned ceramic powder and prevents the melts of both layers and the glass acid from penetrating into the object to be sintered, is formed by coating, and then sintered under vacuum. The object to be sintered is encapsulated in the glass shell obtained by melting the glass forming powder layer by heat treatment, and then the object to be sintered is heated to H.
It is characterized by being held at the sintering stage in IP processing.

(2) Effect According to the above method, the glass forming powder layer formed by coating is heated and melted under vacuum to obtain glass acid, and at the same time, the object to be sintered is enclosed within the glass shell. Restrictions associated with the form of the sintered body in processing can be greatly relaxed, and since vacuum encapsulation processing is easy, the processing efficiency can be improved.

The inorganic protective layer prevents the melt of the glass-forming powder layer from penetrating into the object to be sintered during heating and melting, and the melt of the glass acid during the sintering stage of the HIP process.

The ceramic powder layer prevents both the melts and the melt of the inorganic protective layer in the sintering step from penetrating into the object to be sintered, and also prevents the oxidation of the object during the heat melting and the sintering step. prevent.

The melt-blocking action of both layers allows the sintering step to be carried out at high temperatures and pressures.

In the sintering step, the glass acid prevents the sintered body from closing its pores due to its high pressure, suppresses the increase in internal pressure of the sintered body, and promotes densification.

The reliability of the vacuum encapsulation process and the action of the ceramic powder layer, the inorganic protective layer and the glass acid make it possible to obtain a ceramic product with high density and therefore high strength, especially excellent high-temperature strength.

(3) Examples The ceramic powders that are the constituent materials of the ceramic sintered body include 5LsN4, SiC, ZrOt, and Al!
A powder such as Os may be used alone, or a plurality of powders selected from these powders may be used in combination.

A ceramic molded body having a predetermined shape is obtained by applying molding methods such as pressure molding and slip casting to ceramic powder.In order to improve the moldability of the ceramic powder, paraffin is added to the powder. Organic binders such as waxes and polyvinyl alcohol binders may also be added. In addition, A is used as a sintering aid that exerts a sintering effect on ceramic powder during the sintering stage of HIP processing.
I! 20 U, Y, O, MgO, etc. are added to the ceramic powder. If necessary, a halide, such as MgFz, which exerts a sintering effect on the ceramic powder during temporary pigeon-holing may be added.
, CaF! , CaC1z, etc. are added to the ceramic powder, thereby improving the strength of the pre-sintered body.

The ceramic molded body or the pre-sintered body obtained from the ceramic molded body is used as a sintered body, and an inner ceramic powder layer, an intermediate inorganic protective layer, and an outer glass-forming powder layer are coated so as to cover the entire body. It is formed.

The ceramic powder layer has a single layer structure of the ceramic powder that is the constituent material of the sintered body, and the single layer is made into two layers, and ceramic powder, an organic binder, a sintering aid, etc. are mixed between them. It has a laminated structure with intervening layers, etc. In the single layer structure, the thickness is halo. The thickness is set to 5 to 1, and in the laminated configuration, the thickness is set to 1 to 21, respectively.

The inorganic protective layer is formed using sodium silicates and sodium phosphates as a binder and ceramic powder as a plaster.

Examples of sodium silicates include Na, ClSiOx,
Sodium silicate such as Nag 0 .2 Si Ox is used, and sodium phosphates such as sodium hexametaphosphate, acidic sodium metaphosphate, and sodium tetraphosphate are used.

Ceramic powder used as aggregate is S
iot, MgO, Adz O,, Nag O・Si
O□ ・HtOlAsh S it Ols (mullite), CaO (may be in the form of Ca(OH)t or CaCO5), BaO (may be in the form of Ba(OH)t or BaCO3), etc. are used.Inorganic retention m The melting point of the layer is 1750℃ or higher, and its thickness is 1-2
set to fi.

The glass forming powder layer contains Na, 0-3iO, -xH2O,
Hs BO3, S t Ox , Mg Os Na A
10 t of mixed powder, Sio, -Na, O-B, Ox
It is formed using finely pulverized powder of CaOAltos glass. The melting point of the layer is 1io0 to 1200°C, and the viscosity of the melt should not be less than 10cP. The thickness of the layer is set between 0.2 and 0.5 m.

If necessary, between the inorganic protective layer and the glass-forming powder layer, a layer having a melting point of 1,700 m
A layer of cristobalite-type quartz fine powder of 0.5 °C is provided, and its thickness is set to 0.5 fin or less.

Brushing, dipping, spraying, etc. are employed as the coating method for each layer.

The glass forming powder layer is heated and melted under vacuum to form a glass shell and at the same time encapsulates the object to be sintered within the glass shell, and the layer may also be formed by coating. Restrictions associated with the form of the sintered body in the vacuum encapsulation process can be significantly alleviated. Further, since the vacuum sealing process is easy, its workability is good.

The vacuum encapsulation treatment is performed either simultaneously with the temporary sintering of the ramic molded body, in an independent heating process using the temporary sintered body, or during the heating process when the temporary sintered body is subjected to HIP treatment. be exposed.

Inorganic protective layer! The layer prevents the melt of the glass-forming powder layer during heating and melting, and the melt of the glass acid and underlying layer from penetrating into the sintered body during the sintering stage of the HIP process.

The ceramic powder layer prevents each of the melts and the melt of the inorganic protective layer in the sintering step from penetrating into the object to be sintered, and also prevents the oxidation of the object during the heat melting and the sintering step. Furthermore, since it does not adhere to ceramic products, it facilitates the crushing and removal of glass acid, etc. from the products.

The melt-blocking action of the inorganic protective layer and the ceramic powder layer allows the sintering step to be carried out at high temperatures and pressures.

In the sintering step, the glass acid prevents the sintered body from closing its pores due to its high pressure, suppresses the increase in internal pressure of the sintered body, and promotes densification.

The reliability of the vacuum encapsulation process and the ceramic powder layer,
High density due to the action of the inorganic protective layer and glass acid,
Therefore, a ceramic product with high strength, particularly excellent high-temperature strength, can be obtained.

〔Example! ]

Production of turbine impeller> Ceramic powder 5iiN, 85.5-98% by weight sintering aid powder Y, 03 1-6% by weight AN, 0.
1-8% by weight MgF, powder
0 to 0.5% by weight of the above various powders were mixed in a ball mill for 24 hours so that the blending amounts varied within the above range,
Prepare many types of raw material powders.

Using each raw material powder, 1. A ceramic molded body having the same shape as the turbine impeller 1 shown in FIG. 2 is molded by applying a slip casting method.

Each ceramic molded body is sufficiently dried at 110 to 220°C.

Each ceramic molded body was placed in a vacuum furnace, and the furnace pressure was set to 0.
Maintain the temperature at 8 Torr, and add 30m1/N2 gas into the furnace.
The material is circulated at a flow rate of +*in, and a pre-sintered body is obtained by performing a pre-sintering process using each step shown in the line a of the third figure.

That is, the first temperature increase step (line al
), a first constant temperature step at 650°C for 60 minutes (line a2),
Second temperature increase step (line as) at a temperature increase rate of 20°C ZIlin,
A second constant temperature step (line a4) at 1200°C for 120 minutes,
a first cooling step (line as) with a cooling rate of 15° C. 10+In;
A third constant temperature step at 600 °C for 15 min (line a,) and a second cooling step with a cooling rate of 10 °C/min (line a,
1) is used.

Each pre-sintered body is subjected to the coating treatment described below to form a ceramic powder layer 2, an inorganic preservation layer 11Jif3, and a base layer N4.
and glass forming powder 715 is formed.

(a) Formation of ceramic powder layer 2 St, N4 powder is sufficiently dispersed in water to form a slurry, and this slurry is made into a pre-sintered body to a thickness of 0.5 to 1 m so as to cover the entire body. Brush it on.

Next, the powder layer is made into a slurry and brushed to a thickness of 0.5 W in the same amount as the raw material powder in each pre-sintered body so as to cover the entire powder layer. Furthermore, the above-mentioned Si is applied to the raw material powder layer so as to cover the entire layer.
Brush a slurry of N4 to a thickness of 0°5 to 1fi.

(b) Formation of inorganic protection N3 After the surface of the ceramic powder layer 2 is dried, 2 parts by weight of sodium hexametaphosphate, 0.5 parts by weight of acidic sodium metaphosphate, 1 part by weight of Ca(OH)2 powder, and 32 parts by weight of water. The temporary sintered body is dipped in a suspension in which the remaining part is MgO powder with a particle size of 48 mesh or less to obtain a calendar with a thickness of 1 crane or more. This layer hardens in about 30 seconds.

(C) Formation of glass-forming powder layer 5 No. 8 above! Quality protection H! After step 3 has hardened, brush a slurry of fine quartz powder with a diameter of 10 μm or less to a thickness of about 0.2 mm to cover the entire surface of the N3 base J! form 14. After the surface of the base layer 4 has dried, the layer 4
510t-Nag OB to cover the whole of it.
t Os CaOA'j! 10. Spray a slurry of finely pulverized powder obtained from a glass-based glass to a thickness of about 0.5 W to form a glass-forming powder layer 5.

After sufficiently drying each of Nos. 112 to 5 at 210°C, heat-melting treatment is performed under the same conditions as the above-mentioned pre-sintering treatment to obtain glass acid from the glass-forming powder layer 5, and at the same time, calcining inside the glass shell. Vacuum seal the solid. During this heating and melting process, 1iil! of N2 gas was introduced! i is for each of the above N2 to 5
This is effective in preventing water and air trapped in the pores of the pre-sintered body from blowing out (bumping-off) during the formation of the pre-sintered body.

HIP each pre-sintered body using each process shown in the diagram in Figure 3.
A turbine impeller 1 is obtained by the treatment.

That is, the first temperature increase step (with a temperature increase rate of 20°C/lasn
line b+), the first constant temperature step (k
iAbt), a second temperature increase step at a temperature increase rate of 15°C/min (
mb, ), second constant temperature step (line, ) for 60 minutes at 1450'C, heating rate 10'l? /+win third temperature raising step (line bS), sintering stage, pressure 1000 kg
/cd and a third constant temperature step for 90 minutes at 1750°C (
line bh), and a furnace cooling step to room temperature (line b'r). This HIP treatment makes the substrate N4 glassy and increases the thickness of the glass acid.

After HIP treatment, each turbine impeller 1 has an air pressure of 6, /c
Sandblasting is performed at +d to crush and remove the glass acid. The thickness of the glass acid is 0.1 to 0.3 mm including the glass layer formed by the base layer 4, and most of it is attached to the inorganic protective layer 3, and some of it has penetrated into the ceramic powder N2. However, there was no penetration into the turbine impeller 1, so the surface quality of the turbine impeller 1 was good, and each blade was not bent.

4 to 6 show the relative density of each turbine impeller 1,
Figure 4 shows 2% by weight Yt C1+, 3% by weight AI! zo
When the blending amount of M g F z is changed in z, FIG. 5 shows the case when the blending amount of AltOl is changed in 4 wt. .0.
This applies to cases where the blended amount of Y2O is changed.

In each figure, the line (, 1%) indicates the turbine impeller 1 obtained by the present invention, and the lines d and -d indicate the turbine impeller 1 obtained by sintering at 1600 to 1800°C under writing pressure after preliminary sintering. In addition, lines e and -e correspond to other comparative examples obtained by performing HIP treatment without providing the above-mentioned layer after preliminary sintering.

In FIG. 4, MgFz is used to increase the strength of the pre-sintered body, and in the case of line C1 in the present invention, MgF can be almost completely volatilized and removed during the HIP process. Even if the blending amount of , increases, the relative density of the turbine impeller l hardly changes, and is extremely high at approximately 99%.

In the case of line d1 in the comparative example, as M g F t increases, its volatilization is not sufficiently removed, resulting in a decrease in relative density.

In the case of line eI in other comparative examples, since no glass acid is provided, the pores of the pre-sintered body are closed by the high pressure during HIP treatment, and in this state the volume of the pre-sintered body is reduced, so the pre-sintering Densification stops as the internal pressure of the body increases, and M g F z
The volatilization removal of is prevented, resulting in a lower relative density than in the case of line d.

Fifth. In FIG. 6, in the case of line C2°C1 in the present invention, the relative density is very high even if the amount of sintering aids such as A 1 z Os and Yz Ox is small, and the value depends on the amount of sintering aids. There is almost no difference even if the amount increases.

Sintering aids are a factor in reducing the strength of ceramic products, so
It is better to have as little as possible, so the present invention
, , d, or ex, is an excellent method for obtaining a ceramic product with higher strength than C3.

Furthermore, as a comparative example, only a glass-forming powder layer was provided on the pre-sintered body and HIP treatment was performed under the same conditions as above. It has been found that the relative density of the turbine impeller is as low as about 85% due to the infiltration of the glass shell.

[Example ■]

Manufacturing of turbine impeller> Ceramic powder Si3N4 95.0% by weight Sintering aid powder YzOs 1.0% by weight A11
02 2.0% by weight organic binder polyvinyl alcohol emulsion 2.0% by weight is mixed in a ball mill for 24 hours to prepare a raw material powder.

The above raw material powder is dispersed in water, and a slip casting method is applied to form a ceramic molded body similar to that in Example (2).

The ceramic molded body is dried to harden the organic binder.

The ceramic molded body is subjected to the coating treatment described below to form a ceramic powder layer, an inorganic protective layer, an underlayer, and a glass-forming powder layer.

(Al Formation of ceramic powder layer St, N, powder is sufficiently dispersed in water to make a slurry, and this slurry is applied to a ceramic molded body to a thickness of 0.5 mm to cover the entire body. Paint.

(b) Formation of an inorganic protective layer After the surface of the ceramic powder layer is dried,
For 100 parts by weight of MgO powder of µm or less, 3 parts by weight of sodium hexametaphosphate, 1 part by weight of sodium tetraphosphate, 1 part by weight of Ca(Off) powder, pJ
az O・5iOz・Hgo 1 part by weight and water 2
The ceramic molded body is dipped in a suspension containing 5 to 32 parts by weight to obtain a layer having a thickness of 1 to 2N. This layer hardens in about 30 seconds.

(Formation of C1 Glass Forming Powder Layer After the inorganic protective layer has hardened, a slurry of fine quartz powder with a diameter of 108 m or less is applied to the layer so as to cover it entirely, taking into consideration its penetration into the ceramic molded body. thickness 0.5
Brush it on below fi to form a base layer. After the surface of the base layer is dry, Nat O-3ioz ・xH
*0 3 parts by weight, H, BO 6 parts by weight, 5ift
89 parts by weight, 2 parts by weight of MgO, a small amount of N a A 1
A glass-forming powder layer is formed by spraying a slurry of 0 t on the base layer to a thickness of about 0.2 to 0.5 mm so as to cover the entire base layer.

Each layer is thoroughly dried by heating in two stages, at 110°C and 210°C.

The ceramic molded body is placed in a vacuum furnace, and the ceramic molded body is pre-sintered and the glass forming powder is heated and melted under the conditions described below.

That is, the furnace pressure was maintained at 0.8 Torr, and N was
A first constant temperature step at 650° C. for 45 minutes after raising the temperature by circulating two gases at a flow rate of 30 ml/ll1in;
After a second constant temperature step at 200° C. for 90 minutes, a temporary sintered body is obtained from the ceramic molded body, a glass shell is obtained from the glass forming powder layer, and at the same time, the temporary sintered body is vacuum sealed in the glass shell.

The temporary sintered body is subjected to HIP treatment to obtain a turbine impeller.

In the HIP process, the conditions for the sintering stage are a pressure of 10
00 kg/d, temperature 1700° C. and holding time 120 minutes.

After the HIP treatment, the turbine impeller was cooled to room temperature, and the glass shell was crushed and removed in the same manner as in Example I. The thickness of the glass shell was about 0.5 u+, and most of it was attached to the inorganic protective layer. Some of it penetrated into the ceramic powder layer, but it did not penetrate into the turbine impeller.

Note that the present invention is applicable not only to turbine impellers but also to the manufacture of various ceramic products, especially those requiring high-temperature strength.

C9 Effects of the Invention According to the present invention, by employing means such as forming a glass-forming powder layer by coating and forming a glass shell by heating and melting the glass-forming powder layer under vacuum, the sintering target in the vacuum encapsulation process is reduced. Restrictions associated with body shape can be significantly alleviated. Further, since the vacuum encapsulation process is easy, the workability of the process can be improved, and the productivity of ceramic products can be improved.

Furthermore, the ceramic powder layer acts to prevent oxidation of the sintered object, the ceramic powder layer and the inorganic protective layer prevent the melt of the glass forming powder layer from entering the sintered object, and the glass shell prevents the sintered object from oxidizing. Due to the densification promoting effect, a high-strength ceramic product can be obtained through the sintering stage of HIP treatment.

[Brief explanation of the drawing]

1st. Fig. 2 shows the turbine impeller, Fig. 1 is a plan view, Fig. 2 is a sectional view taken along the line ■-■ in Fig. 1, and Fig. 3 shows the relationship between time and temperature in preliminary sintering treatment and HIP treatment. The graph shown in Figure 4 is Aj! A graph showing the relationship between the blending amount of M g F t and the relative density of the turbine impeller when the blending amounts of zOa and Y2O are held constant. Figure 5 shows A1 when the blending amount of Y2O is constant. .03
Figure 6 is a graph showing the relationship between the blending amount of YtOs and the relative density of the turbine impeller when the blending amount of AlzOx is kept constant. . 1...Turbine impeller as a ceramic product, 2.
...Ceramic powder layer, 3...Inorganic protective layer, 4...
・Underlayer, 5...Glass forming powder layer patent applicant: Agent for Honda Motor Co., Ltd.
Patent Attorney Ken Ochiai Figure 1 Figure 2 Figure 3 Time (h,)

Claims (1)

[Claims] an outer glass-forming powder layer covering the entire ceramic body to be sintered, the melting point of which is higher than that of the glass-forming powder layer;
an intermediate inorganic protective layer that prevents the melt of the layer and the melt of the glass shell obtained from the layer from penetrating into the object to be sintered; and a constituent material of the object to be sintered; An inner ceramic powder layer having a higher melting point than that of the layer and preventing the melts of both layers and the glass shell from penetrating into the object to be sintered is formed by coating, and then sintered under vacuum. The object to be sintered is encapsulated in the glass shell obtained by melting the glass forming powder layer through a heat treatment, and then the object to be sintered is held at the sintering stage in the HIP process. Method of manufacturing ceramic products.