JP3153872B2 - Metal-nitride ceramic bonding structure - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal having a joint having a sufficient joint strength even at an operating temperature of 500.degree.
The present invention relates to a bonding structure of a nitride ceramic.

[0002]

2. Description of the Related Art Conventionally, engines and other components used at high temperatures, such as turbine engines and turbochargers, have been made of ceramics and metals in order to improve energy efficiency and heat resistance. The integrated joined body is used with the former being on the high temperature side.

[0003] In order to obtain the joined body, various joining methods and structures have been studied and disclosed.

For example, an active metal (Ti, Zr, Ta) having a thickness of 1 to 30 μm is provided on one or both sides of a brazing material (copper brazing, silver brazing, nickel brazing, etc.) between a nitride ceramic member and a metal member. , Nb, etc.) with a bonding structure comprising an active metal layer-a brazing layer (-active metal layer) with a bonding sheet material sandwiched therebetween and subjected to heat treatment at 950 ° C. in a vacuum atmosphere. Known (JP-A-60-81)
071).

Further, ductile metals such as copper and copper alloys and Ti,
There is also disclosed a bonding structure having a group IVa nitride layer-a ductile metal layer (-group IVa nitride layer) bonded using a group IVa nitride such as Zr (Japanese Patent Application Laid-Open No. 60-77178).
issue).

[0006] When the metal-ceramic joint is used in a cycle between room temperature and high temperature, the linear expansion coefficients of the members to be joined (metal and ceramic) are different (for example, iron is 10 to 15 × 10 ⁻⁶ / ° C., 2.5 to 4 × 10 ⁻⁶ / ° C. for silicon nitride), and the difference causes residual thermal stress, which ultimately leads to breakage of the joined body.

[0007] Therefore, as a method which is one step ahead of the above two conventional methods, as one of the joining members, a metal having a large plastic deformation ability, in other words, a metal having a stress buffering ability is interposed to reduce the residual thermal stress at the joint. Structures, specifically those with a brazing layer-nickel layer (or copper layer) -silver brazing layer, have also been developed.

[0008]

However, in the conventional bonded body in which the stress buffer layers are arranged, the bonding strength at room temperature (25 to 35 kg / mm ² ) can be almost satisfied. In some cases, the strength is significantly reduced due to softening, and may not be usable. For example, in the above-described application, the temperature of the joint may be 500 depending on the place where the joint is used.
° C, and the bonding strength at that time sharply decreased to about 15 kg / mm ² , which had a defect of lacking safety.

As a solution to this problem, a method of increasing the thickness of the nitride-based ceramic applied to the high-temperature side to enhance the heat insulating property and lowering the temperature of the joint can be considered. Due to the relationship with the equipment, there is not enough space, and this method cannot be adopted in most cases.

The inventors of the present invention have studied the bonding members and arrangements having sufficient stress buffering capacity, no cracks, and high bonding strength at a high temperature of 500 ° C. The inventors have found that the invention described in detail above achieves the above object and completed the invention.

[0011]

That is, the present invention SUMMARY OF THE INVENTION may, wax layer junction from the metal side of the metal and the nitride-based ceramic, niobium layer are composed of wax layers, at the same time wax
At and / or near the interface between the layer and the nitride ceramic
The gist of the present invention is a metal-nitride ceramic bonding structure in which niobium nitride is present .

Hereinafter, the present invention will be described in detail. Wax layer and b
C) By interposing a layer made of metallic niobium between layers
Niobium has a greater plastic deformability than nickel or copper.
And the coefficient of linear expansion is smaller than tungsten or molybdenum
Although not so, at around room temperature, it sufficiently absorbs the residual thermal stress generated between the metal and the nitride-based ceramics, and at a high temperature, the softening thereof does not lower the bonding strength. Also, no crack is generated in the joint even when the room temperature-high temperature cycle is used.

Although the thickness of the niobium layer is not particularly limited, it is 10 to 500 μm, especially 25 to 50 μm.
μm is preferred because it exhibits high bonding strength.

According to the present invention, in addition to the niobium layer, an interface between the brazing layer and the nitride-based ceramics and / or the vicinity thereof may be provided .
Even higher by the presence of niobium nitride
Develops strong bonding strength.

Here, niobium nitride cannot be specified at this stage, but may be one or two of niobium alone, a compound of niobium and nitrogen, a compound of niobium and nitrogen, a compound of a brazing material component, and the like.
It seems that more than one species were mixed. In particular, as described below, the existence state when concentrated in the wax layer is unknown.

The niobium nitride is dispersed as a distinct layer at the interface or in the brazing layer, and most of the niobium nitride is concentrated along the interface and in the vicinity of the interface, preferably at a position in contact with the interface. It is essential for the present invention that they exist or that both forms coexist.

When the niobium nitride is a layer, the thickness of the layer cannot be unconditionally determined in relation to the following relative count value of EPMA. A layer thickness of about 1 μm when viewed is sufficient. The niobium nitride layer contains a considerable amount of a compound not containing niobium.

The term "concentration of niobium nitride in the vicinity of the interface" means a state in which the niobium nitride is unevenly distributed on the interface side in the brazing layer. In addition, the concentration at the portion in contact with the interface has the highest concentration, and sharply decreases as the distance from the interface increases (that is, approaches the niobium layer). On the other hand, the concentration is desirably the same at any position corresponding to the bonding surface of the nitride ceramics. It is not preferable that the niobium nitride is simply dispersed at a high concentration in the entire brazing layer, since the bonding strength is rather lowered.

As described above, since niobium nitride is composed of complex components, in the present invention, niobium is measured for the determination of niobium nitride. That is, the cross section of the joint is EPM
By using A (electron beam micropart analyzer), only niobium was subjected to line analysis.

The line analysis by EPMA can be carried out by the relative count value of the niobium present at the interface and / or in the vicinity thereof, when the value (count value) measured with the niobium foil is 100. The count relative value in that case is not particularly limited, but is preferably 30 or less (a count relative value of zero is outside the scope of the present invention ).

As described above, the niobium nitride present at the interface and / or in the vicinity thereof is concentrated at the interface when the joint is viewed in cross section, so that the relative count value is measured as one peak. Is done.

Next, the member to be joined, the brazing material and the like will be described. The metal member is not limited to various metals and alloys for general structures. The nitride ceramic member is a sintered body of silicon nitride, sialon, aluminum nitride, or the like.

Any material such as silver brazing, copper brazing or nickel brazing can be used as long as the material of the brazing layer has a solidus point of about 750 ° C. or higher. Further, the brazing layer on the metal member side and the brazing layer on the nitride ceramics need not be made of the same material. The brazing layer on the nitride ceramics side is preferably an active brazing containing titanium. The thickness of the two brazing layers may be in accordance with a conventional method, but is preferably as thin as possible (about 30 μm or less).

[0024](Preparation of sample)  The structure of the joining portion is a brazing layer-niobium layer-brazing layer,
Niobium at the interface (near) between the layer and the nitride ceramic
Nitride, each arrangedIfA joint of
An experiment was conducted on the bonding strength of the steel.

Metal and nitride ceramics of the materials shown in Table 1 were cut into 3 × 4 × 18 mm to obtain members to be joined. Metal is stainless steel according to JIS standard SUS-30
4. Carbon steel for general structural use S-45C, special steel SNCM
-439, and three types of nitride-based ceramics are three types of sintered bodies of Sialon, silicon nitride, and aluminum nitride (all of which are manufactured by Nippon Ceratech Co., Ltd.).

As a material of each layer of the bonding portion, a wax: TKC-710 manufactured by Tanaka Kikinzoku Kogyo Co., Ltd. (trade name: active wax for ceramics: 70.6 wt% silver-27.4 wt% copper-2.
0 wt% titanium), 50 μm-thick foil niobium: Various thicknesses (purity 99.9%) manufactured by Nilaco Co., Ltd. were cut into a size of 3 × 4 mm.

After assembling the above-mentioned various members into an array of metal-row-niobium-row-nitride ceramics using a jig, heat treatment is performed in a vacuum at different temperatures (800 ° C. or higher) and holding times for various times. A conjugate was made.

When the heat treatment conditions are set to a high temperature and a long holding time, part of the niobium diffuses into the molten wax, and the niobium that has reached the vicinity of the interface reacts with nitrogen or the like of the nitride ceramic to form niobium nitride. It was formed and deposited according to the conditions to form niobium nitride as a layer, to be unevenly distributed in the brazing, or to reveal both of them.

The joined body obtained as described above is divided into 3 minutes, and a part thereof is subjected to room-temperature strength and strength at the time of heating at 500 ° C. (in each case, a four-point bending test in which the joint is in the middle: JISR
1601) and the results are shown in Table 1.

[0030]

[Table 1]

The other part was cut to inspect the joint, and the cut surface was measured for the thickness of the niobium layer and the niobium nitride layer clearly deposited at the interface, and the relative count value by EPMA. The results are shown in the same table.

The remaining joined body was heated between room temperature and 500 ° C. for 25 minutes.
After 00 cycles, the joints were visually observed while applying finger pressure to check for cracks. As a result, no crack was observed in any of the joined bodies according to the present invention.

In addition, the bonded body was prepared and measured in the same manner as in the embodiment except that the niobium of the above embodiment was replaced with a nickel foil of a conventional method, and the heat treatment conditions of holding at 850 ° C. for 7 minutes in vacuum were used. Is also shown in the same table as Comparative Example 9 .

[0034]

According to the present invention, a metal (object to be bonded) -a brazing layer-
Nickel layer or copper layer-brazing layer-nitride ceramic
(Joint), a niobium layer is arranged in place of the nickel layer or the copper layer, and at the same time , the interface between the brazing layer and the nitride ceramic and / or its vicinity (particularly, the interface in the brazing layer) Side), the bonding strength when the bonded body is heated to 500 ° C. is reduced by the niobium nitride.
It can be higher than when you don't place things
You.

Further, considering that the joint does not crack even if the room temperature-high temperature is excessively repeated and has a sufficient stress buffering ability, it is most suitable for use in various high-temperature engine parts. It will fully contribute to the development in this area.

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) C04B 37/02 B23K 1/19

Claims (1)

(57) [Claims] 1. A joining portion between a metal and a nitride ceramic is composed of a brazing layer, a niobium layer, and a brazing layer from the metal side, and at the same time, an interface between the brazing layer and the nitride ceramic is formed.
And / or a metal-nitride-based ceramics joint structure in which niobium nitride exists in the vicinity thereof.