JPS60255679A - Bonded body of ceramic and 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 [Industrial Field of Application] The present invention relates to a joined body of ceramic and metal joined by brazing.

BACKGROUND OF THE INVENTION Ceramics generally have excellent properties such as heat resistance, thermal shock strength, mechanical strength at high temperatures, abrasion resistance, and high insulation properties, so they have been used in various fields in recent years. However, ceramics are rarely used alone, and are usually used together with other materials, such as metals, in mechanical parts, etc., to perform their functions.

Therefore, people have been wondering how to bond ceramics and metals to obtain a bonded body with high strength.

Research is underway to see if it can be done. This is due to the difference in the coefficient of thermal expansion of ceramics and the coefficient of thermal expansion of the metals to be joined.If the joint is made by simple brazing (J), the joined part of the ceramic will be more likely to crack due to residual stress due to thermal strain after joining. Conventionally, as a countermeasure against this problem, a buffer layer made of metal or the like is provided between the ceramic and the metal to buffer the residual stress. A method is used to do this.

However, even when ceramics and metal are joined by brazing through a buffer layer in this way, if the brazing material remains in places other than the joint surface, for example around the joint part, Due to the difference in coefficient of thermal expansion between the brazing filler metal and the ceramic, the brazing filler metal tightens around the ceramic after joining, resulting in residual stress being applied to the ceramic itself, making it susceptible to cracking.

[Objective of the Invention] Therefore, an object of the present invention is to provide a joined body of ceramic and metal with high strength by alleviating the residual stress of the ceramic as much as possible.

[Configuration of the Invention] The configuration of the present invention to achieve the above object is to provide a bonded body of ceramic and metal in which the ceramic and metal are bonded by brazing, and after bonding, the outer periphery of the bonded portion by top brazing is , the gist is a joined body of ceramics and metal, characterized in that it is machined so that the brazing material does not come into contact with at least the bonded surfaces of the ceramics.

Here, the ceramic may be any commonly used ceramic such as silicon nitride, zirconia, alumina, silicon carbide, etc., and the same applies to metals.

Next, the brazing material may be any commonly used material such as silver thread, nickel-based, copper-based, aluminum-based, etc. The brazing can be done by, for example, igniting the metal in a vacuum, and then heating the metal in a vacuum. The bonded surface is once metallized by a vapor deposition method in which steam is deposited on the bonded surface of the ceramic.
Then, there is a method of brazing using the above-mentioned brazing material,
Alternatively, a metal mixture mainly composed of active metals such as titanium and zirconium and metals such as silver, copper, and nickel is applied to the bonding surface of the ceramic, and the bonding surface is metallized by heating in a non-oxidizing atmosphere. , and brazing methods.

In addition, in the joint area, instead of simply brazing the ceramic and metal directly, as described in the prior art section, a loose braze is used to buffer residual stress. An Ii layer may also be provided. The joint portion may be ground by cutting the outer periphery of the joint using, for example, a diamond wheel, but in this case it is necessary to prevent the brazing filler metal from coming into contact with at least the surfaces other than the ceramic joint surface. For example, as shown in Figure 1 (a), the brazing filler metal C covers the outer periphery of the joint part of ceramic a, or as shown in Figure 1 (b), the brazing material C covers the chamfered part d of the joint part of ceramic a. When the brazing filler metal C is bonded, stress in the direction of the arrow e remains inside the ceramic a due to cooling of the brazing filler metal C after bonding.
This is because the ceramic a becomes easily cracked by external shocks such as vibrations. In the figure, f is a metal bonded to ceramic a.

[Effects of the Invention] In the bonded body of the present invention configured as described above, the brazing filler metal that comes into contact with surfaces other than the bonding surfaces of the ceramics is removed, so that the brazing filler metal does not come into contact with the outer periphery or chamfered portion of the bonded portion of the ceramics. Since the ceramic is not tightened inward, residual stress caused by this can be removed, and the strength of the joined body itself can be increased. Therefore, even when the joined body of the present invention is applied to peripheral parts of internal combustion engines used under high temperature and high vibration conditions, such as gas turbine parts and turbocharger parts, it has high strength and durability. Therefore, it can be a highly reliable component.

[Example] Embodiments of the present invention will be described below with reference to the drawings.

In this example, a joined body A was created by brazing ceramics 1 and metal 2 with a brazing filler metal 4 with a copper plate 3 interposed as shown in FIG. The strengths of the bonded body B and the bonded body A, which had only been top-brazed, were measured by an Izot impact test.

Here, as the ceramic 1, a ceramic material containing 86% silicon nitride is sintered into a rod shape with a diameter of 15 inches, and as the metal 2, a chromium-molybdenum steel with a diameter of 15 inches is used like the ceramic 1. LI Is'-8
A metal rod made of CM435) was used. Each joint surface was chamfered, and 0.2 [μm l, 0.2 Cμm l] of zirconium, chromium, and copper were applied to the joint surface of ceramic 1 to facilitate brazing.
, O,'5 [μIll] and metallized. Thereafter, brazing was performed in a hydrogen furnace at 900['C] using a eutectic brazing filler metal 4 containing 72% silver and 28% copper to obtain the above-mentioned joined body A. In addition, during the bonding holiday, the area around the bonded part of the bonded body created as described above, that is, the area where the ceramic 1, metal 2, copper plate 3, and brazing material 4 were laminated, was polished to a surface roughness of 0.5-s by using a diamond wheel. It was cut down as shown below. As the copper plate 3 interposing the ceramic 1 and the metal 2, a copper plate having a thickness of 2 [I] was used.

Five bonded bodies A and five bonded bodies B were created as described above, and these bonded bodies were made into ceramics 1 by fixing metal 2.
As a result of performing an isot impact test using a point 10 [mm] from the joint surface of
CIll], the minimum Izotsu impact value was 3°3 [ko-cn+], whereas in the case of joined body B, which was machined, the average was 7.3 [ko-cm], the minimum. An Izod impact value of 6.4 [kO·c, m 2 ] was obtained.

From this, it was found that when ceramics and metal are joined by brazing, the strength of the joined body itself increases if the area around the joint is machined.

This is because when simply brazing, a lump of wax forms on the chamfered part of the joint surface, and as the brazing filler metal cools, stress tightening the ceramic joint from the surrounding area is generated. This is thought to be due to the fact that the strength becomes weaker as a result.

Next, using the same ceramics 1, metal 2, copper plate 3, and brazing material 4 as described above, the brazing material 4 covers all the chamfered portions of the ceramics 1 and metal 2 so that the soldering material 7 is An attempt was made to make five joined bodies C with increased bonding strength and conduct an Izot impact test, but in this case, as many as three cracks 8 were generated in the ceramic 1 simply due to cooling after joining.

Therefore, in order to achieve high strength in the bonded body of ceramic and metal, it is necessary to braze with a small amount of brazing material so as not to create a large amount of solder during brazing. It was found that machining should be done to avoid contact with parts other than the joint surface.

[Application Example] Next, as an application example of the present invention, a case where the present invention is applied to a turbine shaft formed by joining a ceramic phase and a metal shaft will be described.

First, in the turbine shaft 1o shown in FIG. 5, a ceramic shaft 12 and a metal shaft 13 are respectively formed so that the machined part 11 of the joint part becomes a gas seal part, and a copper plate 1o is formed as in the previous embodiment.
In the turbine shaft 20 shown in FIGS. 6 and 7, the joint portion 21 is located closer to the compressor (not shown) than the bearing 22 of the turbine shaft 20. However, a ceramic shaft 24 with good heat resistance and wear resistance is attached to the bearing 22 with respect to the metal shaft 23.
A turbine shaft joined and formed in the same manner as the turbine shaft 1o described above is shown. In addition to the copper plate, a thin plate made of a ceramic material constituting the ceramic shaft may be used as the plate interposing the ceramic shaft and the metal shaft.

When the joint between the ceramic shaft and the metal shaft of the turbine shaft is machined in this way, it is possible to not only create a strong and durable turbine shaft with less residual stress due to thermal distortion in the joint, but also It has a beautiful appearance, and the machined portion can be used as a gas seal, such as the turbine shaft 10 described above. When manufacturing this turbine shaft, each ceramic shaft and metal shaft may be finished in advance into a final shape, and finally they may be joined together and the joined portions may be machined.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram of the effects of the present invention, Figures 2 to 4
The figures show an embodiment of the present invention, FIG. 2 is a cross-sectional view showing the joined body A before cutting, FIG. 3 is a cross-sectional view showing the joined body B after cutting, and FIG. 4 shows the soldering material 4. FIGS. 5 to 7 are cross-sectional views showing the joined body C in the case of frequent use, and are half-sectional front views showing the joint portion of the turbine shaft, which are examples of application of the present invention to a turbine shaft. 1, a...ceramics 2, f...metal 3...copper plate 4, C...brazing material agent, patent attorney Tsutomu Adachi and one other person Figure 1 (a) (b) Figure 2 3 Figure β8 Figure 4 Figure 5 Figure 6

Claims (1)

[Scope of Claims] 1. In a ceramic-metal bonded body in which ceramics and metal are bonded by brazing, after bonding, the outer periphery of the brazed bonded portion is coated with at least a surface other than the bonded surface of the ceramic. A bonded body of ceramics and metal, characterized by being machined so that the materials do not come into contact with each other. 2. The ceramic-metal bonded body according to claim 1, wherein the bonded portion is provided with a stress buffer layer for buffering residual stress after bonding.