JPH0653621B2 - How to join ceramics - Google Patents

Description

Detailed Description of the Invention A. OBJECT OF THE INVENTION (1) Field of Industrial Application The present invention relates to a method for joining ceramic bodies, and more particularly to a method for joining first and second ceramic bodies obtained through molding and sintering steps.

(2) Conventional Technology Conventionally, as this type of joining method, a method has been known in which a metallic joining material existing between joining surfaces of both ceramic bodies is melted to join them (Japanese Patent Laid-Open No. 60-260479). reference).

(3) Problems to be Solved by the Invention However, the above method aims at the wettability of the bonding material to the bonding surface of both ceramic bodies and the bonding by the chemical reaction between both bonding surfaces and the bonding material. Since the bonding effect of the bonding material on the surface is expected, there is a problem that the bonding strength is insufficient under severe conditions such as high temperature.

In view of the above, the present invention obtains not only the bonding effect of the bonding material on the bonding surfaces of both ceramic bodies but also the anchoring effect of the bonding material to the inside rather than both bonding surfaces, thereby significantly increasing the bonding strength of both ceramic bodies. It is an object of the present invention to provide the above-mentioned joining method that can be improved and stabilized.

B. Structure of the Invention (1) Means for Solving the Problems In the present invention, when joining the first and second ceramic bodies obtained through a molding and sintering process, the first and second ceramic bodies are Elutable particles that can be dissolved by an acid, which were compounded prior to their molding, were dissolved while applying ultrasonic vibration to the acid, and both ceramic bodies were provided with a large number of continuous pores opening at their joint surfaces. Forming step; pressurizing both ceramic bodies by interposing a metallic bonding material between the both bonding surfaces of the first and second ceramic bodies, and melting the metallic bonding material; And a step of impregnating the continuous pores of the ceramic body with pressure.

(2) Action During the elution of elutable particles, the acid is circulated and ultrasonic vibration is applied to the acid, so that the soluble salts generated from the elutable particles are prevented from depositing in the continuous pores and the elution reaction is promoted. As a result, continuous pores can be formed quickly and reliably.

Since the melted bonding material wets the bonding surfaces of both ceramic bodies, the bonding effect of the bonding material on both bonding surfaces can be obtained. Moreover, since the molten bonding material is pressure-impregnated into the continuous pores of both ceramic bodies, the anchoring effect of the bonding material can be reliably obtained.

By adopting such a means, it is possible to greatly improve the bonding strength of both ceramic bodies.

In addition, since the particles that can be eluted are mixed in advance and the particles that can be eluted are eluted, it is easy to stabilize the porosity of both ceramic bodies, and thus the anchor effect by pressure impregnation of the bonding material, by the amount of the particles mixed. It is possible to stabilize the bonding strength of both ceramic bodies.

(3) Example FIG. 1 (a) shows a turbine impeller 1 as a first ceramic body, and FIG. 1 (b) shows a rotary shaft 2 as a second ceramic body joined to the turbine impeller 1. Show.

The turbine impeller 1 includes an impeller body 4 having a small-diameter shaft portion 3.
And a joining cylinder portion 5 integrated with the impeller body 4 so as to cover the entire outer surface of the small diameter shaft portion 3.

The rotating shaft 2 includes a shaft body 7 having a square tube portion 6 having a rectangular cross section.
And a joining cylinder portion 8 integrated with the shaft body 7 so as to cover the entire inner surface of the square cylinder portion 6.

The turbine impeller 1 and the rotating shaft 2 are manufactured through the steps of raw material preparation, molding and sintering.

The raw material is the impeller body 4 and the shaft body 7, and the joint tube portions 5, 5.
8, the raw material of the impeller main body 4 and the shaft main body 7 is a ceramic powder, a sintering aid exhibiting a sintering action at the sintering temperature of the powder, and the like.
The raw material of 8 has a three-dimensional network structure having a large number of continuous pores that open to the inside and the outside as the joint surface of the cylinders 5 and 8 in addition to the above, and therefore can be eluted by an acid. Particles are used.

As the ceramic powder, Si ₃ N ₄ , SiC, ZrO is used.
₂ , single powders of TiC, TiN, and the like, and mixed powders selected from these powders are applicable.

As a sintering aid, Al ₂ O ₃ , Y ₂ O ₃ , MgO, S
Single powders such as iO ₂ and mixed powders selected from these are applicable.

Examples of particles that can be eluted include Al ₂ O ₃ , Na ₂ O, and SiO.
Those produced through the steps of mixing, melting, cooling and solidifying, and finely pulverizing ₂ , MgO, K ₂ O, B ₂ O ₃ , CaO and, if necessary, CaCl ₂ are applicable.

In preparing the raw materials, the various constituent substances are mixed for a predetermined time using a mixer such as a ball mill to uniformly disperse them.

When a molded body is obtained using the raw material, a pressure molding method,
An injection molding method, a slip casting method using water as a dispersion medium, or the like is used.

The conditions for subjecting the molded body to the sintering treatment are 1200 to 1800 ° C. and 0.5 ° C. in an inert gas atmosphere such as N ₂ gas.
~ 24 hours.

By the sintering treatment, the turbine impeller 1 and the rotating shaft 2 having a dense structure can be obtained. The degree of densification of the turbine impeller 1 and the rotary shaft 2 is mainly controlled by the compounding amount of the sintering aid and the temperature and time in the sintering process.

Further, since the elutable particles also function as a sintering aid, the compounding amount of the particles in both joining cylinders 5 and 8 is also a factor involved in the densification.

As the acid used for eluting the elutable particles from both the joining cylinders 5 and 8, a single acid such as nitric acid or hydrochloric acid, a mixed acid thereof, the single acid or a small amount of hydrofluoric acid in the mixed acid is used. Those added are used.

The particles that can be eluted by each acid are changed to soluble salts and are eluted from both joint cylinders 5 and 8 to form both joint cylinders 5 and 8 into a three-dimensional network structure having a large number of continuous pores. At that time, the acid is circulated and ultrasonic vibration is applied to the acid, thereby avoiding the deposition of soluble salts in the continuous pores, and promoting the elution reaction to form the continuous pores quickly and reliably. You can

In this case, the strength of the two joining cylinders 5 and 8 mainly depends on the size (diameter) of the continuous pores and the porosity.

FIG. 2 shows the relationship between the porosity and the bending strength of the two joining cylinders 5 and 8. Considering the joining strengths thereof, the porosity is 1
0-30% is suitable, and the size of continuous pores is 1-
10 μm is suitable. By setting the size and the porosity of the continuous pores in this way, there is a crystal growth of the ceramic powder due to the densification in the sintering process, so that both the joining cylinder parts 5 and 8 have a necessary strength. You can

Since the size and porosity of the continuous pores depend on the particle size and blending amount of the elutable particles, the particle size and blending amount are determined so that the appropriate range can be obtained.

When the turbine impeller 1 and the rotating shaft 2 are integrated, both the joining cylinder parts 5 and 8 after the elution treatment are fitted and the outer surface of the joining cylinder part 5 and the inner surface of the joining cylinder part 8, and thus both the joining surfaces. A metallic bonding material is interposed therebetween. Then, in an atmosphere such as an atmosphere or a vacuum, the square tube portion 6 is pressed from its outer periphery and the bonding material is melted, and the bonding material wets the bonding surfaces of both the bonding tube portions 5 and 8. Is to be impregnated under pressure into the continuous pores of both joint cylinders 5, 8. It is more effective to melt the bonding material under vacuum because it can prevent the bonding material from being oxidized and thus increase the bonding strength.

Further, the bonding material may be held in advance in at least one of the bonding cylinder portions 5 and 8 by using a means such as vapor deposition.

By the above method, it is possible to surely obtain the joining effect on both joining surfaces based on the wettability of the joining material and the anchor effect by the pressure impregnation of the joining material.
8, therefore, the joint strength between the turbine impeller 1 and the rotating shaft 2 can be significantly improved.

In addition, since the elutable particles that have been mixed in advance are eluted, it is easy to stabilize the porosity of both joining cylinders 5, 8 and hence the anchoring effect by pressure impregnation of the joining material depending on the amount of the particles. Therefore, the joint strength between the turbine impeller 1 and the rotary shaft 2 can be stabilized.

As the metallic bonding material, Ni-containing 5 to 8 wt% Cu
A Cu-based brazing material, a Ni-Cr-based brazing material containing 14% by weight Cr, 4% by weight Si, and 3.4% by weight B, and thus a known brazing material is used.

[Example I]

(a) Preparation of raw materials for impeller body and shaft body Ceramic powder Si ₃ N ₄ 89% by weight with an average particle size of 0.5 μm and maximum particle size of 5 μm Sintering aid powder Y ₂ O ₃ 5% by weight Al ₂ O ₃ 6 Mix by weight in a ball mill for 24 hours.

(b) Preparation of Raw Material for Both Jointed Cylinders First, elutable particles are manufactured using the following method.

Al ₂ O ₃ 5.9 wt%, _Na 2 O11.4 wt%, SiO ₂ 2
5.2 wt%, MgO 13.0 wt%, K ₂ O 4.0 wt%, B ₂
A mixture consisting of 38.0 wt% O ₃ and 2.5 wt% CaO is thoroughly mixed in a ball mill, the mixture is heated to 1400 ° C. to be melted, and then the melt is cooled and solidified. The solidified material is subjected to fine pulverization treatment to obtain elutable particles having an average particle size of 0.5 μm and a maximum particle size of 5 μm. The particle size distribution of the elutable particles is matched to that of the ceramic powder.

Ceramic powder having an average particle size of 0.5 μm and a maximum particle size of 5 μm Si ₃ N ₄ 81% by weight Sintering aid powder Y ₂ O ₃ 2% by weight Al ₂ O ₃ 3% by weight Elutable particles 14% by weight in a ball mill 24 Mix for hours.

A slip casting method is applied using the raw material of (a) and water as a dispersion medium to obtain a molded body corresponding to the impeller body 1.

Using the raw material (b) and water as a dispersion medium, a slip casting method is applied to obtain a molded body corresponding to the joining cylinder portion 5, and at the same time, the molded body and the molded body are integrated to form a turbine impeller 1 The final molded body corresponding to is manufactured.

A final molded body corresponding to the rotary shaft 2 is manufactured by the same method.

Both final molded bodies are installed in a sintering furnace, the temperature in the furnace is raised to 1600 ° C. while N ₂ gas is passed through the furnace, and this temperature is maintained for 2 hours.

By this sintering treatment, the turbine impeller 1 and the rotating shaft 2
To get

The density in the turbine impeller 1 and the rotary shaft 2 is 95% or more of the theoretical density, which is very dense, and the bending strength at room temperature is 85 to 90 kgf / m in a three-point bending test.
m ² . When the fracture surface was observed with a scanning electron microscope, the grain size of the ceramic powder was 3 with the growth of the crystal.
It is a hexagonal columnar crystal having a size of ˜4 μm, and no abnormal crystal growth is observed.

The joining cylinder portion 5 of the turbine impeller 1 is subjected to the elution treatment described below.

25% nitric acid is heated to 50 ° C., the nitric acid is circulated and ultrasonic vibration is applied to the nitric acid, and the joining cylinder 5 is immersed in nitric acid under this condition for 30 minutes to elute the elutable particles.

By the same method, the joining cylinder portion 8 of the rotary shaft 2 is subjected to the elution treatment.

The weight reduction rate of both the joining cylinders 5 and 8 was 15.0%, which means that almost all of the elutable particles were eluted.

By observing the fracture surface of both joint cylinder parts 5, 8, both joint cylinder parts 5, 8
The size of the pores in 8 is about 2 μm, and the porosity is 16
%, And it is confirmed that most of the pores are continuous. Since the porosity after sintering was apparently 0%, there is about 1% of closed porosity.

As shown in FIG. 3, the Ni-Cu-based brazing filler metal is interposed between the joint tubular portions 5 and 8 and the outer surface of the joint tubular portion 5 and the inner surface of the joint tubular portion 8, and thus both the joint surfaces. Let
Both 1 and 2 are installed in the press 9. Then, under vacuum, the upper and lower punches 10 and 11 press the square tube portion 6 under pressure 2.
The Ni-Cu brazing material is heated to 1200 ° C. and melted while being pressurized with 00 kgf / mm ^{2, and} the Ni-Cu brazing material wets the joint surfaces of both joint cylinders 5 and 8.
The i-Cu-based brazing material is pressure-impregnated into the continuous pores of both joint cylinders 5 and 8.

After the joining work, the square tubular portion 6 of the rotary shaft 2 is subjected to finishing work to obtain a joined body of the turbine impeller 1 and the rotary shaft 2 shown in FIG.

In this joined body, as shown in FIG. 5, the joining surfaces of the joining tubular portions 5 and 8 are joined by the Ni—Cu brazing filler metal B, and between the ceramic materials C mainly composed of Si ₃ N ₄ . The continuous pores P are filled with the Ni—Cu brazing filler metal B, and the anchor effect occurs. The state of impregnation of the Ni—Cu brazing filler metal B was observed with an optical microscope and a scanning electron microscope, and it was confirmed that there were no impregnated defects.

FIG. 6 shows the relationship between the temperature and the bending strength at the joints composed of both joint cylinders 5, 8 and the Ni—Cu brazing filler metal B. From FIG. 6, the turbine impeller 1 and the rotary shaft 2 are It is clear that they are integrated by a high-strength joint part that forms part of them at room temperature and high temperature.

Also, when the joined body was rapidly heated to a temperature difference of 700 ° C., immediately dropped in water, and this operation was repeated, a repeated thermal shock resistance test was conducted.
It was confirmed that cracks were generated during the rotation, but no abnormalities such as cracks were generated in the joint portion.

Therefore, it is clear that the joint strength between the turbine impeller 1 and the rotating shaft 2 is significantly improved.

Example II

(a) Preparation of raw materials for impeller body and shaft body Ceramic powder Si ₃ N ₄ 90% by weight with an average particle size of 0.4 μm and maximum particle size of 5 μm Sintering aid powder Y ₂ O ₃ 5% by weight Al ₂ O ₃ 5 Mix by weight in a ball mill for 24 hours.

(b) Preparation of raw materials for both joint cylinders In the case of Example I, there is a report that the Al ₂ O ₃ , MgO components, etc. of the elutable particles form a solid solution with Si ₃ N ₄ which is a ceramic powder. And halide as a new component to change the compounding amount and suppress abnormal crystal growth,
In the examples, CaCl ₂ is used, and elutable particles are manufactured using the following method.

Al ₂ O ₃ 8.6 wt%, _Na 2 O10.3 wt%, SiO ₂ 2
4.2 wt%, MgO 15.0 wt%, K ₂ O 2.1 wt%, B ₂
A mixture consisting of 39.16% by weight of O _3, 0.6% by weight of CaO and 0.04% by weight of CaCl _{2 is} thoroughly mixed in a ball mill, and the mixture is heated to 1200 ° C. to be melted, and then the melt is cooled and solidified. . The solidified product is subjected to fine pulverization treatment to obtain elutable particles having an average particle size of 1 μm and a maximum particle size of 5 μm.

Also, since it is feared that the particles that can be dissolved out will react with the sintering aid and that some of the sintering aids will be eluted by the above-mentioned elution treatment, the sintering aid is excluded and the average particle size of the ceramic powder is 0.4 93% by weight of Si ₃ N _{4 having} a maximum particle size of 5 μm and 7% by weight of elutable particles are mixed in a ball mill for 24 hours.

A slip casting method is applied using the raw material of (a) and water as a dispersion medium to obtain a molded body corresponding to the impeller body 4.

Using the raw material (b) and water as a dispersion medium, a slip casting method is applied to obtain a molded body corresponding to the joining cylinder portion 5, and at the same time, the molded body and the molded body are integrated to form a turbine impeller 1 The final molded body corresponding to is manufactured.

A final molded body corresponding to the rotary shaft 2 is manufactured by the same method.

Both final molded bodies are installed in a sintering furnace, the temperature in the furnace is raised to 1600 ° C. while N ₂ gas is passed through the furnace, and this temperature is maintained for 2 hours.

By this sintering treatment, the turbine impeller 1 and the rotating shaft 2
To get

The densities of the turbine impeller 1 and the rotating shaft 2 are
It is 95 to 97% of the theoretical density and is very dense, and the bending strength at room temperature is about 80 kgf in the three-point bending test.
/ Mm ² . When the fracture surface was observed using a scanning electron microscope, the ceramic powder became hexagonal columnar crystals with a grain size of 3 to 4 μm along with the crystal growth, and no abnormal crystal growth was observed.

The joining cylinder portion 5 of the turbine impeller 1 is subjected to the elution treatment described below.

A mixed acid consisting of 25% nitric acid and 0.1% hydrofluoric acid is heated to 50 ° C., the mixed acid is circulated and ultrasonic vibration is applied to the mixed acid. Immerse to elute the elutable particles.

By the same method, the joining cylinder portion 8 of the rotary shaft 2 is subjected to the elution treatment.

The weight reduction rate of both joining cylinders 5 and 8 is 5.8%, which is smaller than the compounding amount of the elutable particles, but this is because Al ₂ O ₃ , MgO, etc. are among the components of the elutable particles as Si ₃ N ₄ . It is believed that this is due to solid solution and nitridation of SiO ₂ .

By observing the fracture surface of both joint cylinder parts 5, 8, both joint cylinder parts 5, 8
The size of continuous pores in Example 8 was about 3 μm at the maximum, and the porosity was 15%, and it was confirmed that all the pores were continuous without closed pores.

As shown in FIG. 3, both the joining cylinder parts 5 and 8 are fitted together, and the Ni-Cr brazing filler metal is interposed between the outer surface of the joining cylinder part 5 and the inner surface of the joining cylinder part 8, and thus both joining surfaces. , 1 and 2 are installed in the press 9. Then, in an inert gas atmosphere of N ₂ , Ar or the like, the upper and lower punches 1
0, 11 presses the rectangular tube portion 6 with a pressure of 150 kgf / mm ^2, and heats the Ni-Cr brazing material to 1200 ° C to melt it. The joint surfaces are wetted, and the Ni-Cr brazing material is pressure-impregnated into the continuous pores of both joint cylinders 5, 8.

After the joining work, the square tubular portion 6 of the rotary shaft 2 is subjected to finishing work to obtain a joined body of the turbine impeller 1 and the rotary shaft 2 shown in FIG.

In this joined body, as shown in FIG. 5, the joining surfaces of the joining tubular portions 5 and 8 are joined by the Ni—Cr brazing filler metal B, and the continuity between the ceramic materials C mainly composed of Si ₃ N ₄ is continuous. The pores P are filled with the Ni—Cr brazing filler metal B, and the anchor effect occurs.

The bending strength at room temperature of the joint portion composed of both joint cylinders 5 and 8 and the Ni-Cr brazing filler metal B was 90 kgf / mm ² in the three-point bending test, and the bending strength of the ceramic material C was 85 to 9
It is almost equivalent to 0 kgf / mm ^2, and at room temperature to 500 ° C, there is almost no deterioration in the strength of the joint, and the bending strength is 80 to
It is known to hold 100 kgf / mm ² . Therefore, it is apparent that the joining strength between the turbine impeller 1 and the rotary shaft 2 is significantly improved as in the case of the embodiment I.

The present invention is not limited to joining the turbine impeller and the rotary shaft, but is also applicable to joining various ceramic bodies, for example, joining plate-shaped ceramic bodies to each other.

C. EFFECTS OF THE INVENTION According to the present invention, the bonding effect based on the wettability of the bonding material to the bonding surfaces of the first and second ceramic bodies and the anchor effect by the pressure impregnation of the bonding material into the continuous pores of both ceramic bodies are obtained. The anchor effect is stabilized, and the bonding strength of both ceramic bodies can be significantly improved and stabilized.

In addition, continuous pores are formed in both ceramic bodies quickly and reliably by adopting a means such as mixing of elutable particles, elution of the particles with an acid, and circulation of the acid as well as application of ultrasonic vibration thereto. be able to.

[Brief description of drawings]

FIG. 1 (a) is a vertical sectional front view of a turbine impeller, FIG. 1 (b) is a vertical sectional front view of a main portion of a rotating shaft, and FIG. 2 is a porosity and bending of a joining cylinder portion of a turbine impeller and a rotating shaft. Graph showing the relationship with the strength, FIG. 3 is a vertical sectional front view showing the impregnation work of the bonding material, FIG. 4 is a vertical sectional front view of the main part of the bonded body, and FIG.
FIG. 6 is an enlarged view of the portion indicated by the arrow V in FIG. 6, and FIG. 6 is a graph showing the relationship between bending strength and temperature at the joint between the turbine impeller and the rotating shaft. DESCRIPTION OF SYMBOLS 1 ... Turbine impeller as a 1st ceramic body, 2 ... Rotating shaft as a 2nd ceramic body, B ... Ni-Cu type | system | group brazing | wax material as a metallic joining material, Ni-
Cr-based brazing material, C ... Ceramic material, P ... Continuous pores

Claims (1)

[Claims] 1. When joining first and second ceramic bodies (1, 2) obtained through a forming and sintering process, the forming of the first and second ceramic bodies (1, 2) from the first and second ceramic bodies (1, 2) The eluable particles that have been mixed prior to the step of eluting with an acid are eluted while the acid is passed through and ultrasonic vibration is applied to the acid.
A step of forming a large number of continuous pores (P) opening on the joint surfaces of the (1, 2); and a metallic joint between the joint surfaces of the first and second ceramic bodies (1, 2). Both ceramic bodies (1, 2) are pressed with the material (B) interposed, and the metallic bonding material (B) is melted, and the bonding material (B) is applied to the both ceramic bodies (1, 2). A step of impregnating continuous pores (P) under pressure;