JPH0328391B2 - - Google Patents

Description

[Detailed Description of the Invention] (a) Technical Field The present invention relates to a bonded composite of ceramics and metal that is applied to heat-resistant, corrosion-resistant structural parts, etc.

(b) Technical background Automotive engine parts, heat resistance for chemical plants,
Various ceramics such as Al ₂ O ₃ , Si ₃ N ₄ , and SiC have been developed as corrosion-resistant structural materials. These ceramics have high melting points and excellent heat resistance and corrosion resistance, but when it comes to mechanical strength, they are inferior to ordinary metals and alloys, and are often restricted in the fields of use. For this reason, it has been proposed that ceramics and metal be used as a composite bonded together.

In the bonding between ceramic and metal, it is a matter of course that the bonding strength is required to be high, but it is particularly important to eliminate the difference in coefficient of thermal expansion.

A possible solution to this problem is to bond the bonding surfaces via an intermediate layer. As the middle layer,
There are soft metal layers (aluminum foil, etc.), foam metal layers, and composite material layers, but . In the second method, the intermediate layer has a thermal expansion coefficient intermediate between that of ceramics and metal, and is used as a buffer layer. However, a second layer with a conventional intermediate layer
A composite with the structure shown in Figure A has insufficient bonding strength and cannot be put to practical use.

(C) Disclosure of the Invention The present invention attempts to analyze the stress of the bonding intermediate layer in the above-mentioned ceramic-metal composite, which has high strength and solves the problem of thermal expansion strain. It is something that can be achieved.

The ceramic-metal composite of the present invention has the configuration shown in FIG. The purpose can be achieved by using a metal or alloy whose coefficient of expansion a is close to that of the ceramic 1, and by using a metal or alloy whose coefficient of thermal expansion a is smaller than that of the ceramic 1 as the second intermediate layer 4 in contact with the metal 2. This is what we discovered.

In the joined body with the configuration shown in Figure 2 A, Al ₂ O ₃ is used for the ceramic 1, stainless steel (SUS405L) is used for the metal 2, and the temperature difference is 975℃ (1000℃→
We investigated the maximum tensile stress that occurs in the intermediate phase when a temperature of 25°C is applied.

First, when we measure the maximum tensile stress in Al ₂ O ₃ without an intermediate layer (Figure 2 b), it is 94 in the direction of the arrow in the figure.
The value is Kg/ ^mm2 . Next, by inserting an intermediate layer as shown in FIG. 2A, the element on which the maximum tensile stress acts changes somewhat, but there is no major deviation. The stress can be reduced by changing the thickness of the intermediate layer, but in practical terms the thickness of this intermediate layer must be made as small as possible.

As a result of various studies, it was found that it was sufficient to apply thermal expansion stress in the radial direction to the interface of the intermediate layer, and the invention of a joined body having the above-mentioned structure was achieved.

Next, the effects will be explained using examples.

Example A comparison was made by bonding Al ₂ O ₃ and stainless steel (SUS405L) using only 1 mm of Nb and Nb-Mo as an intermediate layer.

_Nb was added to the Al ₂ O ₃ with a diameter of 5 mm and a thickness of ₂ mm by changing the Nb/Mo ratio to a thickness of 1 mm (2 sheets).
plates were brought into contact with each other and vacuum sealed in a Pyrex glass enclosure. This bonded pair was bonded using a HIP (hot isostatic pressing machine) at 1300° C. for 30 minutes at 100 MPa. Next, a piece of stainless steel (diameter 5 mm, thickness 2 mm) was sealed in contact with the Mo of this bonded pair,
Bonding was also performed using HIP at 900°C, 100 MPa, and 30 minutes to obtain a bonded body of Al ₂ O ₃ /Nb/Mo/stainless steel.

As a comparative example, Nb and Mo only, one layer sandwiched between 1 mm thickness, Al ₂ O ₃ /Nb / stainless steel, Al ₂ O ₃ /Mo /
A stainless steel joint was created.

The maximum tensile stress of the obtained joined body is shown in FIG. From the figure, compared to the case where the middle layer is one layer, Nb/
It can be seen that the stress decreases when the Mo2 layer is used, and a minimum stress exists. Next, increase the bonding strength by 0.5mm/
Tensile test at min speed showed 0.5 to 0.5 for Nb single layer.
1Kg/ ^mm2 , whereas in the case of two layers of Nb/Mo, it is 2
Kg/mm ² or more.

[Brief explanation of the drawing]

FIG. 1 is a front sectional view of a composite of the present invention, FIG. 2 is a front sectional view of a conventional composite, and FIG. 3 is a diagram showing the results of an example of the present invention. 1: Ceramics, 2: Metal, 3, 4: Intermediate layer.

Claims (1)

[Claims] 1 In a composite body in which a metal and a ceramic are bonded via an intermediate layer, the intermediate layer is composed of two layers, the intermediate layer in contact with the ceramic is a metal or alloy whose coefficient of thermal expansion is close to that of the ceramic, and the intermediate layer in contact with the metal is a metal or alloy whose thermal expansion coefficient is close to that of the ceramic. A metal-ceramic composite, characterized in that the layer is a metal or alloy whose coefficient of thermal expansion is smaller than that of the ceramic.