JPH07149578A - Strong brazing joint of silicon carbide ceramic material to metal and method for making the joint - Google Patents

Abstract

PURPOSE:To provide a method for making a strong brazing joint of a silicon carbide ceramic material to metal and obtain a strong joint of a silicon carbide ceramic material to metal. CONSTITUTION:When making a brazing joint of a silicon carbide ceramic material to metal using an active brazing metal, an intermediate layer composed of Si3N4/Ni/Mo/Ni or Si3N4/Ni/W/Ni is placed between the members to be joined, wherein the Si3N4 layer faces to the ceramic material. In this joint, the application of a barrier layer composed of Si3N4 as an intermediate layer touching the silicon carbide ceramic material prevents the formation of a fragile corrosion region by Cu contained in the active brazing metal or Ni diffused from a stress relaxing agent in the silicon carbide ceramic material. Accordingly, the obtained joint of a silicon carbide ceramic material to metal has such a high joint strength and high reliability as not to be available in a conventional brazing joint.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brazed joined body of silicon carbide ceramics and a metal, and a joining method therefor,
Particularly, the present invention relates to a joined body having a large joining strength and a joining method thereof.

[0002]

2. Description of the Related Art Ag-Cu-Ti and Cu-Ti active metal brazes are known as metal brazes used for joining silicon carbide ceramics.

The joining mechanism in brazing of silicon carbide ceramics using an active metal braze is based on the reaction between active metal braze and silicon carbide ceramics and mutual element diffusion.
It is known as a method for enabling high-strength bonding to cause a reaction between the silicon carbide ceramic and the silicon carbide ceramic and form a reaction layer of TiC, Ti ₃ SiC ₂ or the like on the silicon carbide ceramic side bonding interface.

When the silicon carbide ceramics and the metal are brazed together, a large thermal stress is generated due to the difference in the thermal expansion coefficient between the two. As a method for relaxing this thermal stress, a method of interposing a soft metal typified by Cu between the silicon carbide ceramics and the metal, and a low expansion metal typified by Mo or W between the silicon carbide ceramics and the metal. Method, or Nb / Mo, Ni / W
There is known a method of combining a soft metal and a low expansion metal as represented by / Ni and interposing it between the silicon carbide ceramic and the metal. Above all, Ni is used for soft metals.
By using Mo or W as a low expansion metal, Ni / Mo /
It is known that the method of interposing between Ni or Ni / W / Ni three layers and interposing it between the silicon carbide ceramics and the metal has a great effect of alleviating thermal stress, and the resulting joined body has a high heat resistance temperature. There is.

[0005]

Problems to be Solved by the Invention However, Ni / M
When o / Ni or Ni / W / Ni is interposed as a stress relaxation material between the silicon carbide ceramics and the metal, Ti which is the active component contained in the active metal brazing material and Ni used as the stress relaxation material A reaction occurs during the formation of a Ti-Ni-based reaction product in the bonded interface. As a result, the reaction between the active metal braze and the silicon carbide ceramics becomes insufficient, and a reaction layer of TiC, Ti ₃ SiC ₂ or the like cannot be formed sufficiently, and the silicon carbide ceramics in contact with the bonding interface cannot be activated. An erosion region due to Cu contained therein and Ni used as a stress relaxation material is generated. This erosion region is a porous and extremely embrittled region. Due to the presence of this erosion region, Ni / Mo / Ni or Ni / W / Ni is used as a stress relaxation material between the silicon carbide ceramic and the metal. Bonding strength when intervening is up to 8k in 4-point bending test
It was about g / mm ² , which was much smaller than the strength of the members to be used and had a problem of lack of reliability.

[0006]

DISCLOSURE OF THE INVENTION The present invention has been found as a result of an examination for the purpose of solving the above-mentioned problems in the conventional method for joining a silicon carbide ceramic and a metal. That is, when joining the silicon carbide ceramics and the metal, Si ₃ N ₄ / Ni / Mo / Ni or Si ₃ N ₄ / Ni /
It is a joined body of silicon carbide ceramics and a metal provided with an intervening layer made of W / Ni.

[0007]

The present invention is applied to the joining surface of the silicon carbide ceramic and the metal, from the silicon carbide ceramic side to Si ₃ N ₄ / Ni /
The feature is that an intervening layer made of Mo / Ni or Si ₃ N ₄ / Ni / W / Ni is provided.

This structure is as shown in FIG.
Is silicon carbide ceramics, and 6 is a metal. A layer 2 made of Si ₃ N _4, layers 3 and 5 made of Ni, and a layer 4 made of Mo or W are interposed between the silicon carbide ceramics 1 and the metal 6. In addition, 7 and 8 are active metal wax,
9, 10 and 11 represent metal brazes.

In the above-mentioned joined body of the present invention, Si
_The layer 2 made of ₃ N ₄ is composed of Cu contained in the active metal braze in the silicon carbide ceramic and Ni as the stress relaxation material which has diffused.
The role of the barrier layer is to prevent the formation of the eroded region by the. Further, the layer 2 made of Si ₃ N ₄ has a difference in coefficient of thermal expansion with silicon carbide ceramics of 8 × 10 ^-7 / ° C.
It is considered that the occurrence of thermal stress in the silicon carbide ceramic due to the existence of the layer 2 itself is small. Further, in this layer 2, an erosion region due to Cu contained in the active metal brazing material or Ni of the stress relaxation material that has diffused does not occur. Therefore, even if a reaction occurs between Ti, which is the active component contained in the active metal braze, and Ni, which is the stress relaxation material, and the Ti concentration contained in the active metal braze is substantially reduced,
The bonding strength is high.

As described above, according to the present invention, it is possible to obtain a highly reliable bonded body of silicon carbide ceramics and metal, which has a large bonding strength and which cannot be obtained by the conventional brazing and bonding method. Hereinafter, the present invention will be described with reference to examples.

[0011]

【Example】

Example 1 Width 10 mm, Length 10 mm, Thickness 10 mm
10 mm wide and 10 m long with silicon carbide ceramics
m, thickness is 1 mm between 5 mm thick stainless steel
Of Si ₃ N ₄ , Ni and Mo from the silicon carbide ceramics side in combination with Si ₃ N ₄ / Ni / Mo / Ni were interposed and joined using silver-based active metal braze or copper-based active metal braze . The joining was performed in vacuum by holding at 870 ° C. for 10 minutes when using a silver-based active metal braze, and at 1090 ° C. for 10 minutes when using a copper-based active metal braze. The coefficient of thermal expansion of silicon carbide ceramics is 4
× 10 ^-6 / ° C, similarly 13 × 10 ^-6 / ° C for stainless steel
Is. In these cases, defects such as cracks did not occur in the ceramics and any of the intervening layers, and a good bonded body was obtained.

[0012]

[Comparative Example 1] Width 10 mm, length 10 mm, thickness 10 mm
10 mm wide and 10 m long with silicon carbide ceramics
m, thickness is 1 mm between 5 mm thick stainless steel
Ni and Mo from the silicon carbide ceramics side to Ni
/ Mo / Ni in combination, and silver-based active metal brazing or copper-based active metal brazing was used for joining. Bonding is performed in a vacuum, and 87 when silver-based active metal brazing is used.
10 minutes at 0 ° C, 1 when using a copper-based active metal braze
The test was carried out by holding each at 090 ° C. for 10 minutes. The coefficient of thermal expansion of silicon carbide ceramics is 4 × 10 ^-6 / ° C, and similarly, that of stainless steel is 13 × 10 ^-6 / ° C. When the silver-based active metal brazing material was used, a bonded body was obtained, but when the copper-based active metal brazing material was used, peeling failure occurred at the silicon carbide-ceramic bonding interface and the bonding could not be achieved. . As a result of detailed observation and analysis of the peeling fracture portion, a thick erosion region due to Cu and Ni was formed at the bonding interface of the silicon carbide ceramics when the copper-based active metal brazing was used.

[0013]

Example 2 Width 10 mm, length 10 mm, thickness 18 mm
10 mm wide and 10 m long with silicon carbide ceramics
m, thickness is 1 mm between stainless steel of 2 mm thickness
Of Si ₃ N ₄ , Ni and Mo from the silicon carbide ceramics side in combination with Si ₃ N ₄ / Ni / Mo / Ni is interposed, and silicon carbide ceramics / Si ₃ N ₄ / Ni
/ Mo / Ni / Stainless Steel / Ni / Mo / Ni / Si
_{The 3} N ₄ / silicon carbide ceramic structure was joined using a silver-based active metal braze or a copper-based active metal braze. The details are shown in FIG. The joining was performed in vacuum by holding at 870 ° C. for 10 minutes when using a silver-based active metal braze, and at 1090 ° C. for 10 minutes when using a copper-based active metal braze. The coefficient of thermal expansion of silicon carbide ceramics is 4 × 10 ^-6 / ° C. Similarly, stainless steel is 13 ×
It is 10 ^-6 / ° C. The reason why the structure shown in FIG. 2 is bonded is that the symmetry of the load stress in the bending strength evaluation test of the bonded body is taken into consideration. After joining, a bending test piece having a width of 4 mm, a thickness of 3 mm and a length of 46 mm was cut out from the joined body and subjected to a 4-point bending strength test with a span of 30 mm. As a result, the strength of the joined body was determined by using a silver-based active metal braze. The average value was 16 kg / mm ² (average value), and the value when the copper-based active metal braze was used was 18 kg / mm ² (average value).

[0014]

[Comparative Example 2] Width 10 mm, length 10 mm, thickness 18 mm
10 mm wide and 10 m long with silicon carbide ceramics
m, thickness is 1 mm between stainless steel of 2 mm thickness
Ni and Mo from the silicon carbide ceramics side to Ni
/ Mo / Ni in combination with silicon carbide ceramics / Ni / Mo / Ni / stainless steel / N
Those having a structure of i / Mo / Ni / silicon carbide ceramics were joined using a silver-based active metal braze. Bonding was performed in vacuum by holding at 870 ° C. for 10 minutes. The coefficient of thermal expansion of silicon carbide ceramics is 4 × 10 ^-6 / ° C, and similarly, that of stainless steel is 13 × 10 ^-6 / ° C. After joining, a bending test piece having a width of 4 mm, a thickness of 3 mm, and a length of 44 mm was cut out from the joined body and subjected to a 4-point bending strength test with a span of 30 mm. As a result, the strength of the joined body was 8 kg / mm ² (maximum). It was 5 kg / mm ² (average value).

[0015]

EFFECTS OF THE INVENTION It is possible to provide a highly reliable bonded body of silicon carbide ceramics and metal, which has a high bonding strength, which cannot be obtained by the conventional brazing and bonding method.

Bonding can be performed by heating once, and no particular pressurization is required, so that the number of steps can be reduced and expensive equipment is not required.

[Brief description of drawings]

FIG. 1 is a structural diagram of a high-strength brazed joined body of a silicon carbide ceramic and a metal according to the present invention.

FIG. 2 is a structural diagram of a high-strength brazed joined body of silicon carbide ceramics and metal in Example 2.

[Explanation of symbols]

1, 12, 13 Silicon Carbide Ceramics 2, 14, 15 Layers _{3 of} Si ₃ N _{4 3, 5} , 16, 17, 18, 19 Layers of Ni 4 Layers of Mo or W 6, 22 Metals 7, 8 , 23, 24, 25, 26 Active metal brazes 9, 10, 11, 27, 28, 29, 30, 31, 32
Layer composed of metal braze 20, 21 Mo

[Procedure amendment]

[Submission date] October 25, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Brief description of the drawing

[Correction method] Delete

Claims (2)

[Claims] 1. When brazing and joining a silicon carbide ceramic and a metal using an active metal braze, Si ₃ N ₄ / Ni / Mo / Ni or Si ₃ N ₄ / Ni is provided between the members to be joined from the ceramic side. / W / Ni intervening layer made of silicon carbide ceramics and metal brazed joint 2. Si ₃ N ₄ / Ni / Mo / Ni or Si ₃ N ₄ / Ni from the ceramics side between the members to be joined when brazing and joining the silicon carbide ceramics and the metal by using the active metal braze. Method for brazing silicon carbide ceramics to metal, characterized by having an intervening layer composed of / W / Ni