JPS62235272A - Method and structure of joining sintered ceramic to metal - Google Patents

Abstract

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

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a bonding structure and a bonding method between a sintered ceramic and a metal.

[Conventional technology and its problems]

Ceramics have excellent strength, corrosion resistance, wear resistance, etc. at high temperatures, and are therefore attracting attention as high-temperature components for internal combustion engines such as gas turbines and diesel engines. but,
Ceramics have a fundamental drawback of being brittle, and for this reason, a promising method for practical use is to use ceramics only in parts that require severe usage conditions and to use them by bonding them to metals.

Ceramics for internal combustion engines include s S I C + S
tsN4 is the most promising, but these are covalent bonding methods. Brazing properties, ■In-phase diffusion bonding method is known.

However, among these methods, method (2) has the disadvantage of a complicated process and high cost. The method of Saita is currently the most widely researched and developed, but in most of these methods the brazing temperature is over 900°C, which may reduce the strength of the metal side, and in addition, the brazing metal enters a liquid phase during bonding. Therefore, if the joint is on a curved surface, the brazing material will flow and the joint will not be successful.

On the other hand, method (2) requires a simple process and does not require a liquid phase state, so it is possible to lower the bonding temperature by selecting an appropriate intermediate layer. However, even with this method, the thermal expansion coefficient (
The coefficient of thermal expansion (approximately 13 x 10-'/°C) is significantly smaller than that of metal materials such as Ni-based heat-resistant alloys, heat-resistant steel, and heat-resistant cast steel used in internal combustion engines (approximately 13 x 10-'/°C). ,
For this reason, cracks occur in the ceramic due to thermal stress generated during cooling after joining or during operation. As a method for alleviating such thermal stress, a method has also been proposed in which a metal with a coefficient of thermal expansion between the two materials or a soft metal with high plastic deformability is interposed as an intermediate layer between the ceramic and the metal. However, this alone cannot produce sufficient effects.

[Means to solve the problem]

The present inventors have repeatedly investigated these problems, and as a result, they have developed a bonding metal layer and a soft metal layer for thermal stress relaxation as intervening layers between the metal base material and the sintered ceramic. It has been found that by providing a bonding structure and relatively regulating the thicknesses of these members, it is possible to appropriately reduce thermal stress and obtain a bonded structure in a strongly bonded state.

That is, the present invention provides a bonding structure between a metal base material and a sintered ceramic obtained by solid-phase diffusion bonding, which includes a base metal layer between the metal base material and the ceramic, and has a thickness of the bonding metal layer. Its basic feature is that tB and the thickness tB of the soft metal layer satisfy the following relationship: tB/(tB+tg)≦0.5.

In addition, the present invention provides a method for obtaining such a joining structure by interposing a soft metal and a joining metal from the metal base material side between the metal base material to be joined and the sintered ceramic.
In vacuum or in an inert gas atmosphere, the soft metal layer thickness tS after bonding and the bonding metal layer float tB are tB/
Another basic feature is that solid-phase diffusion bonding is performed by applying pressure while heating so as to satisfy CtB +tS )≦0.5.

The present invention will be explained in detail below.

FIG. 1 shows an example of the bonding structure of the present invention, in which a metal layer (1) and a bonding metal layer (2) are provided between a metal base material (4) and a sintered ceramic (3). ing.

In such a joint structure of the present invention, sintered ceramic (4
) can be alleviated by the soft metal layer (1), thereby appropriately suppressing the thermal stress acting on the sintered ceramic 1.

Furthermore, in the present invention, a soft metal layer (1) for relaxing thermal stress is provided.
The thickness tS of the bonding metal layer (2) and the thickness tB of the bonding metal layer (2) are regulated so as to titrate the following equation.

tB/(tB+tS)≦O15 FIG. 2 shows ta/(t
This shows the relationship between the maximum thermal stress σ8 generated in the sintered ceramic (4) and the relationship between 1. /(1,+1
．． ) is 0.5 or less, σ8 shows a small value. In this way, by relatively regulating the thickness of the bonding Meta/+4 (2) and the soft metal layer (1), the thermal stress generated in the sintered ceramic can be appropriately alleviated, and the sintered As a soft metal, it is softer (lower elastic modulus and has less plastic deformability) than the joining metal. A metal with a large diameter) is used, and specifically, an alloy containing lead or copper as a base is used.

The bonding metal is for firmly bonding the sintered ceramic to its lower member, that is, the thermal stress relaxation member, and is made of an active metal. As this joining metal, nickel, nickel alloy, titanium, titanium alloy, etc. are used.

In addition, as sintered ceramic, 81CI 813N4
Materials such as +zro, , ZrB, and PSZ (partially stabilized zirconia) are used.

Next, the joining method of the present invention will be explained.

FIG. 3 shows the joining process according to the method of the present invention, in which there is a
A soft metal (1) and a joining metal (21) are interposed from the metal base material side, and the members are solid phase diffusion bonded to each other by heating and pressurizing in a vacuum or an inert gas atmosphere.

In such a heating and pressurizing process, the soft metal (15) and the joining metal (2') undergo creep deformation (
therefore, soft metals (
1') and the joining metal (2') have a thickness that takes into account the creep deformation described above, and for joining ζζ, the joining metal layer thickness tB and the soft metal layer thickness tS after joining are , tB/(tB+tB, ) < 0.5 while heating and compressing.

Specific methods of solid-phase diffusion bonding as described above include: ■ Laminating each member and solid-phase diffusion bonding at the same time; ■ Using sintered ceramic for some or all of the intervening members (joining metal and soft metal). A method of solid-phase diffusion bonding this intermediate bonded body to the metal base material after solid-phase diffusion bonding to the metal base material.
It is also possible to form the film on a sintered ceramic or the like in advance using a known method such as VD, and then solid-phase diffusion bond the film to another member.

In addition, as a main aspect of the above-mentioned method (2), for example, a method in which only the joining metal is joined, a method in which the joining metal and the soft metal are joined, etc. can be considered. In such an intermediate joint (sintered ceramic and insert material), if there is any unjoined insert material, it is necessary to join it to the metal base material while interposing them between it and the metal base material. I am forced to do it. That is, if there is any remaining insert material, the above-mentioned intermediate joined body is placed on the metal base material with the remaining insert material in between, and the members are heated and pressurized in a vacuum or an inert gas atmosphere to form solid phase diffusion bonding between each member.

In such bonding, the solid-phase diffusion bonding surface always forms a metal-to-metal bond, so that an appropriate bonding state can be obtained even at a relatively low heating temperature, thereby making it possible to prevent over-aging of the base material.

In addition, each insert material is not limited to a plate, but granules or powder can also be used.

In FIG. 3, (5) is a high-frequency induction coil, and each member is heated by this high-frequency induction coil (5) and compressed and pressurized by a load applying device (not shown) to be solid phase diffusion bonded. Apparatuses for performing such pressurized and heat treatment can be of any suitable configuration, including those equipped with a high-frequency induction coil (5) and a load loading device as shown in A device such as a press, so-called HIP, etc. can also be used.

Note that solid-phase diffusion bonding is performed, for example, under the following conditions.

Atmosphere: Vacuum (approximately IX 10-” torr) or inert gas atmosphere Bonding temperature: 700 to 1000°C Bonding pressure: 1 to 10 Kg/ll+/ [Example] A bonded body with the structure and materials shown in Fig. 5 was bonded. , was manufactured using equipment equipped with a high-frequency induction coil for heating and a load-bearing device as shown in FIG.

The bonding conditions are as follows.

Bonding temperature 950℃ Bonding compressive stress 1.5f/wr” Bonding time 2
0 rnin atmosphere i,o X 10 tor
rThe tensile strength of this joined body at room temperature is 4f: JK4f
It was /-.

〔Effect of the invention〕

According to the present invention described above, the occurrence of thermal stress during cooling after joining and during use is appropriately reduced, and the maximum thermal stress generated in the ceramic is suppressed by about 5 to 20 Kyf/-1, resulting in a sound joint structure. In addition, it is possible to obtain a bonded structure that has higher tensile strength than conventional bonded structures, is less likely to cause peeling or cracking of the sintered ceramic, and has excellent bonding strength. Further, according to the method of the present invention, such a joining structure can be appropriately and easily obtained.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an example of the joining structure of the present invention. In Figure 2, the thickness of the soft metal layer is Ls. When the thickness of the bonding metal layer is tB, ta/(tB
+tS) and the maximum thermal stress σS generated in the sintered ceramic. FIGS. 3(A) and 3(B) are explanatory diagrams showing the bonding process according to the method of the present invention. FIG. 4 shows the relationship between the bonding time and the amount of creep deformation of the insert material in solid phase diffusion bonding. FIG. 5 is an explanatory diagram showing the structure and material of the joined body obtained in the example. In the figure, (1) is a soft metal layer;
(2) is a bonding metal layer; (2) is a bonding metal layer; (3) is a bonding metal layer;
) is a sintered ceramic, and (4) is a metal base material. Patent applicant: Nippon Kokan Co., Ltd. Inventor: Yama 1) Kaikai Takeshi
Hide Sekiguchi Jitsuki
Hiroshi Okamoto
Higashi Sho ball quantity
Sho Kitamura 3rd Figure Materials ℃ Funaigu Pressure 9u 2nd Figure te / (te + tS) Figure 4 1 o-B r4 ゛

Claims (2)

[Claims] (1) In the bonding structure between a metal base material and sintered ceramic obtained by solid-phase diffusion bonding, a soft metal layer for thermal stress relaxation is bonded between the metal base material and the sintered ceramic from the metal base material side. A bonding structure between a sintered ceramic and a metal, characterized in that a thickness t_B of the bonding metal layer and a thickness t_S of the soft metal layer satisfy the following formula. t_B/(t_B+t_S)≦0.5 (2) Between the metal base material to be joined and the sintered ceramic,
A soft metal and a bonding metal are interposed from the metal base material side, and the bonding metal layer t_B and the soft metal layer thickness t_S after bonding are such that t_B/(t_B+t_S)≦0 in a vacuum or an inert gas atmosphere. .5 A method for joining sintered ceramic and metal, characterized by solid phase diffusion joining by applying pressure while heating.