JPH01249666A - Method for bonding ceramic by thermal spraying - Google Patents

Abstract

PURPOSE:To improve the strength of a bonded body at high temp. by imparting surface roughness at a limited level to the bonding parts, and then applying building-up thermal spraying on the bonded part at the time of bonding the same or different ceramics. CONSTITUTION:When the same or different split ceramics are bonded, the surface roughness of 20-60mu Rmax is imparted to the bonding parts, and then building-up thermal spraying is applied on the bonded part. The same pretreatment as described above is applied to the parts of the same or different ceramics already bonded by an adhesive, etc., then building-up thermal spraying is applied on the bonded part, and the bonded part of the ceramics can be reinforced. In this ceramic bonding method, a groove or a groove having a flat face or a curved face is formed at the bonding parts, and then building-up thermal spraying is preferably applied on the bonded part.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for joining ceramics and a method for reinforcing a joint between two ceramics that have been previously joined.

(Prior Art) In recent years, ceramics have been developed for use in various industries because they have characteristics such as high strength under high temperatures, hardness, resistance to friction, and good corrosion resistance.

However, in general, ceramics have drawbacks that make it difficult to manufacture large, complex-shaped structures due to manufacturing problems, so the development of ceramic bonding technology has become an important issue (Japanese Patent Application Laid-Open No. 60-1970). -16883).

Ceramic bonding techniques generally include organic adhesive methods, inorganic adhesive methods, brazing, metallizing, diffusion bonding methods, pressure bonding methods, laser methods, electric bonding methods, and the like. Among the above bonding methods, organic adhesive methods, brazing, metallizing, etc. do not have strength at high temperatures (for example, 600'C to 700'C or higher).

That is, in these joints, since the joining materials are different materials, the thermal stress between the base material and the joining material becomes large at high temperatures, resulting in a low joining strength. Furthermore, since the bonding material generally uses an active low melting point material that is highly reactive with the base material, the bonded portion lacks strength at high temperatures.

Furthermore, the bonding strength of the inorganic adhesive method is extremely low compared to that of the base material. Diffusion method, crimping method, laser method, electric welding method are
Although the bonding strength at high temperatures is high, the shape of the bonding base material is limited and a large bonding device is required, so it has not been put into practical use.

On the other hand, thermal spraying techniques include gas spraying, plasma spraying, etc., and all of them exist as coating techniques for ceramics, metals, etc. for the purpose of corrosion resistance or wear resistance. However, since the sprayed film thickness is as thin as 1 mm or less, when applied to thick film deposition, unless some solution is taken, the base material and the sprayed bonding layer will separate due to thermal stress, and the sprayed bonding layer will become stressed. cause cracks.

By the way, thermal spray bonding is seen in the case of metal materials, but since metal materials easily deform plastically due to thermal stress, separation between the base material and the thermal spray bonding layer and stress cracking in the thermal spray bond layer can be alleviated and large It's not a problem.

However, since ceramic is a brittle material, it is difficult to deform plastically.
Because thermal capacity mitigation is difficult, ceramic bonding techniques by thermal spraying cannot be achieved by simply applying metal thermal spray overlay techniques.

Therefore, ceramic bonding techniques that can easily obtain high bonding strength at high temperatures have not been generalized.

(Problems to be Solved by the Invention) As described above, there are a limited number of bonding techniques that provide high bonding strength under high temperatures, and even if they exist, the construction method is not easy and the shape of the base material is limited.

Therefore, an object of the present invention is to provide a method for joining ceramics that has high strength at high temperatures and solves many of these problems.

(Means for Solving the Problems) The present invention, as shown in FIG. A groove shape is provided, and the groove part (surface to be thermally sprayed) has a surface roughness of 2.
Perform pre-treatment of 0 to 60 μ using plus I-, etc., if necessary, to reduce the thermal expansion difference between the thermal sprayed bonding layer/base material.
In this method, the base material is preheated to a certain temperature or higher, the atmosphere is adjusted, and the bonding material is deposited by thermal spraying.

In order to alleviate the thermal stress of the base material/sprayed bonding layer, if necessary after bonding, the bonded portion is heat treated at a constant temperature for a certain period of time and then slowly cooled. Heat treatment and slow cooling induce a mineral change (phase transformation) in the thermally sprayed bonding layer, resulting in a volume change, which is effective in alleviating thermal stress.

When using a high melting point bonding material such as ZrO2 or MgO, a plasma spraying machine is used as the spraying machine. Plasma spraying machines have high flame temperatures and high spraying speeds, so
The melting state of the high melting point +A material can be controlled and a dense and strong thermal sprayed bonding layer can be formed.

The joining material may be metal, ceramic, or cermet, but a material of the same type as the base material is preferred in order to match the physical properties such as thermal expansion coefficient and elastic modulus with the base material.

The thermal sprayed bonding layer can be completely melted or semi-melted depending on the thermal spraying conditions, and thereby can be controlled from a high-strength dense bonding layer to a semi-paper tight bonding layer that is resistant to spalling.

The method of reinforcing ceramics by thermal spraying is basically the same method as above, and is a method of reinforcing a joint that has been previously joined with an adhesive or the like by overlaying by thermal spraying.

The base material to be joined according to the present invention is an oxide ceramic or a non-oxide ceramic.

(Example) FIG. 1 is a conceptual diagram of joining. 1 is a ceramic to be joined, and a groove with a surface roughness LJ was previously formed by blasting. Reference numeral 2 denotes a thermal spraying device, which performs overlay thermal spraying 15 on the groove.

FIG. 2 is a block diagram of the bonding apparatus, and here the case where a plasma spraying machine is used is shown. 1 is a ceramic base material to be joined, and a furnace 1 is capable of preheating, post-joining heat treatment, heat retention, or slow cooling, and allows atmosphere adjustment.
Set it to 0.

When bonding is performed using an atmosphere-controlled furnace, there are two methods: by spraying the parts while they are in the furnace of a thermal spray machine, or by spraying them from outside the furnace. 3 is a plasma spray gun, and the plasma jet flow is controlled by a plasma gas 4 and a control device W5. Furthermore, it is comprised of a powder supply device 6 for supplying the bonded rice to the thermal spray gun.

(Example 1) The base material was Zr0z ceramic, and a groove was provided at the joint. The bonding material is ZrO, which is the same type as the parent phase.

-3Ap,,O,.2SiOz system. Table 1 shows the chemical components of the base material and bonding material.

The plasma spraying conditions were as shown below.

Thermal spraying distance: 10cm Thermal spraying gun movement speed: 50cm/sec Powder supply rate: 55 g/min Plasma spraying gun output: 40Kw Plasma gas: Ar-H2 As a pre-treatment for overlay bonding, the joint surface (surface to be thermally sprayed) gets stuck in the blast to Rmax
: A surface roughness of 5 to 80μ was obtained.The surface roughness was #10 to #30 using blasting material (A/7.03-3iC).
This was controlled by changing the value to 00.

Figure 3 shows the relationship between the adhesive shear strength of the base material/sprayed layer and the surface roughness of the base material when thermally sprayed onto a flat plate, and high strength was obtained when 20μ≦Rmax≦60μ. Joining 4.
Since the particle size of t II is 30 μ, 1 of that size
A base material surface roughness of /2 to 2 is effective.

Also, at this time, as shown in Figure 4, the temperature of the base material was 800°C.
°C or higher was required. Preheating can reduce the temperature difference between the thermally sprayed bonding layer and the base material immediately after thermal spraying, and has the effect of alleviating thermal stress. In particular, materials such as ZrO, which have a large coefficient of thermal expansion (10
X 10-6/'C) material.

After pretreatment and preheating were performed under the above conditions, bonding was performed, and then the materials were slowly cooled at 10'C/min from the preheating temperature. Slow cooling has an anti-spalling effect on joined bodies with large thermal expansion.

The obtained joined body was cut into a shape of 40 x 4 x 3 rflm, and the four-point bending strength was measured.

Figure 5 shows the relationship between the groove angle and the bonding strength. If the groove angle is less than 60°, the thermal sprayed bonding layer will not become dense and will not be bonded. For a good bond, 120a or more is required. And so.

~9- In addition, good joint strength was also obtained in the joined body shown in FIG. 6 in which the groove portion was made flat. The conditions for good adhesion between the sprayed bonding layer and the base material or the density of the sprayed bonding layer are such that the spray frame is at an angle of at least 60° to the sprayed surface of the base material.
This is because the above is necessary, and the closer to the vertical, the better.

Therefore, in the case of a simple groove shape as shown in FIG. 5, 60° or more is required, and 120° or more is preferable.

Further, the groove shape shown in FIG. 6 required a shape in which the spray frame was 60'' or more with respect to the sprayed surface of the base material. 15 is a sprayed layer.

Figure 7 shows a joint with a groove angle of 120° heated at 1000°C.
The results show the bonding strength up to this point, and the bonding strength is 15kg/mm'' at room temperature and 12k at 1000°C.
g/body 2.

(Example 2) In the case of joining ceramics such as ZrO□ which are not high melting point materials, it is possible to join by propane gas spraying or the like without applying plasma spraying. As shown in Table 2, if the base material is Ajl! The zOs/TiO□-based ceramic was used, and the bonding material was the same as the base material.

Table 2 (wt%) Copan gas spray bonding conditions were as shown below.

Spraying distance: 10cm Spraying gun movement speed: 50cm/sec Powder supply rate: 25g/minGas
: Propane-oxygen base material surface roughness :
3oμ Bevel angle: 120'Aj2203 Since TiO□ has a small coefficient of thermal expansion, it was possible to bond at room temperature without requiring preheating. Moreover, slow cooling, heat retention, and heat treatment were not necessary. As a result of evaluating the joint strength of the joined body in the same manner as in (Example 1), it was found that the four-point bending strength at room temperature was "?"
: 3.5kg/mm2.1000'C hot 3.0
kg/mm” and base material strength 4.5kg/m
m''.

(Example 3) Since it is difficult to thermally spray non-oxide ceramics with current technology, when joining non-oxide ceramic base materials, it is not possible to use a material similar to the base material as the joining material. By thermal spray bonding, it became possible to use a material that is close to the same material as the base material.

Here, as shown in Table 3, the base material is reactive sintered Si3N4, and the bonding material is AI! , 203 3A
i! z O3/2S 102 Aj! It was made into an Si-based composite material.

Table 3 (wt%) The plasma spray bonding conditions were as shown below.

Spraying distance: 10cm Spraying gun movement speed: 5 Q cm/sec Powder supply rate: 30 g/min Plasma spraying gun output: 40Kw Plasma gas: Nz-H□ Base material surface roughness
: 30μ Bevel angle: 120°Jointing is A for thermal sprayed materials! , Si reacts with N2 to form AEN
, Si3N4 to form a thermally sprayed bonding layer.

Also, after thermal spray bonding, unreacted AI! In order to completely nitride the Si, the bonded body after thermal spraying was heat treated at 1000'C or higher and slowly cooled.

The sprayed bonding layer that has undergone the above preheating, heat treatment, and slow cooling has few pores and is strongly bonded, with a room temperature bonding strength of 1.5K.
g/mm2, and the hot bonding strength was 6.8 kg/+++o+2.

The bonded body without preheating or heat treatment has a room temperature bonding strength of 4.
．． 1 kg/mm2, but there was no bonding strength at 1000'C hot. This is due to the N
2 and unreacted, 6-f2. This is because it does not have the strength of St.

The heat treatment required 1000'C or more. The wall time was controlled by the amount of the thermally sprayed bonding layer, and here 11) 1 or more was required.

(Example 4) When joining large-sized base materials, thermal spray overlay joining was performed while the joint portion was placed in the tlj of the temperature-controlled furnace 10, as shown in FIG. The components of the bonding base material 1 and the bonding material 1' were the Zr0z series shown in (Example 1), and the bonding conditions were also the same. As a result, 300 x 50 x shown in Figure 8
A bonding strength of 9.5 kg/n+m2 was obtained with a 50 mm bonded body. 15 is a thermal spray bonding layer, 16 is a window for thermal spraying, and 3 is a thermal spraying machine.

(Example 5) As shown in Fig. 9, the joined body 1 is joined in advance by the inorganic adhesive method.
．． A method of reinforcing 1' by thermal spraying was shown. The base material and bonding material were the same as in (Example 2). After setting a surface roughness of Rmax 30μ on the joint by blasting, the joint was reinforced by thermal spray overlay 15 under the conditions shown in Example 3. As a result, the bonding strength of the bonded body was significantly improved compared to the current inorganic adhesive method.

As mentioned above, by using a ceramic bonding method using thermal spraying, we were able to achieve a bonding method that has high strength at high temperatures. The present invention has made it possible to manufacture large ceramic structures, such as single ceramic tubes, by bonding.
There is hope for manufacturing ceramic piping for high-temperature fluid transport, ceramic heat exchangers, and ceramic engines as shown in Figures 10a, b, and c. Additionally, the technology can be applied to strengthen joints that lack heat resistance, and is expected to reduce equipment maintenance costs.

(Effects of the Invention) The present invention can obtain a ceramic bond having high strength at high temperatures by W-film overlay thermal spraying.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of the present invention, Figure 2 is a detailed diagram of the invention, Figure 3 is a diagram of surface roughness and adhesive shear strength, and Figure 4 is a diagram of base material preheating temperature and adhesive shear strength. , Fig. 5 is a diagram of the groove angle and joint strength, Fig. 6 is an explanatory diagram of the groove joint, Fig. 7 is a diagram of the test temperature and joint strength, and Fig. 8 is a diagram of the example of the present invention. A schematic diagram, FIG. 9 is an explanatory diagram of another embodiment of the present invention, and FIGS. 10 a, b, and c are detailed explanatory diagrams of the present invention. Agent Patent Attorney Tatsuo Chanoki (21/C) ■ Breast pregnancy (2nd grade 78N) Daabuse surname (2nd atmosphere game eJ) Double attack push (1v (β)) tribute (a) (watch) (C)

Claims (1)

[Claims] 1. A ceramic characterized by forming a surface roughness of Rmax 20 to 60μ on the joint part and thermally overlaying the joint part when joining divided ceramics of the same or different components. joining method. 2 Rmax 20 to 60 at the joint between ceramics of the same or different components that have been joined in advance with an adhesive, etc.
A method for joining ceramics, which is characterized by forming a surface roughness of μ, and applying overlay thermal spraying to the joint to reinforce the joint. 3. Ceramic joining according to claim 1 or 2, characterized in that a groove shape having a flat surface or a curved surface is formed in a groove portion or a groove portion in the joint portion, and then overlay thermal spraying is applied to the joint portion. Method. 4. The ceramic joining method according to claim 1 or 2, wherein the joining base material is preheated and then overlay thermal spraying is applied. 5. The ceramic joining method according to claim 1 or 2, characterized in that the overlay thermal spraying is carried out while the joining base material is placed in a furnace where the atmosphere can be adjusted to O_2, H_2, N_2, reduced pressure, etc. 6. The method for joining ceramics according to claim 1 or 2, characterized in that after the thermal spray joining, the joined portion is subjected to heat treatment, heat retention, or gradual cooling.