JPS58167086A - Diffusion joining method - Google Patents

Abstract

PURPOSE:To prevent defects such as joining failure and voids and to reduce the stage for diffusion treatment after joining considerably by placing a member to be joined which has a low m.p. alloy layer on the joint surface and a member to be joined which does not have said layer so as to face each other and joining both member. CONSTITUTION:An alloy layer 4 having a m.p. lower than the m.p. of joining members is provided on one joint surface of said members and the members are joined. Such method is employed because one of the joint surfaces is used as a base material 1 and therefore an element for lowering the melting point in the joint part is diffused and the constituting elements of the base material to be joined are made more vulnerable to diffusion in the joined part. The amt. of the intermetallc compd. to be formed in the joint part is thus decreased considerably, and defects such as joining failure and voids are less produced as compared to joining of the alloy layers to each other.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a diffusion bonding method, and particularly to a bonding method suitable for diffusion bonding of heat-resistant alloys.

Conventionally, welding or brazing has been used as a joining method for heat-resistant alloys.
Soldering has problems such as low joint strength and low melting point of the joint, and it is impossible to say that either of these is sufficient.Therefore, when joining heat-resistant alloys, these problems are Therefore, diffusion bonding is currently mainly used to obtain high-quality joints.

Diffusion bonding methods are classified into two types: in-phase diffusion bonding method and liquid phase diffusion bonding method. In-phase diffusion bonding requires the application of a relatively high unit pressure at the bonding temperature, and in the case of fragile or high-precision parts, the disadvantage is that the high pressurizing force tends to cause deformation noise and limits the range of use. There is. Liquid phase diffusion bonding is a method in which a thin layer with a low melting point (foil, powder, etc.) is inserted between the materials to be bonded, and the materials are then bonded together. However, with the method of inserting foil or powder, when the joint surface has a complex shape or becomes large, the powder in the foil may shift or peel off from the joint surface, resulting in poor joints and poor reliability. The present inventors have developed a method that can perform bonding more reliably by taking advantage of the advantage of liquid phase diffusion bonding, which does not require high pressure compared to solid phase diffusion bonding. As a result of extensive research, it was discovered that good diffusion bonding could be achieved by providing a low melting point alloy layer on one of the bonding surfaces, and the present invention was achieved.The purpose of the present invention is to eliminate defects ( It is an object of the present invention to provide a diffusion bonding method which makes it possible to obtain a smooth joint with extremely few bonding defects (bonding defects, voids, inclusions, etc.), and which uses low pressure and short diffusion processing time.

The purpose of this is to provide an alloy layer with a melting point lower than that of the wire bonding material on one bonding surface and facing the other bonding surface in a method of bonding the bonding surfaces of the members to be bonded in seconds by diffusion bonding. By the diffusion bonding method, which is characterized in that the material is made of a metal material and then subjected to diffusion bonding, four parts are formed in a uniform manner.

The present invention will be described in detail below.The method of the present invention is different from the conventional diffusion bonding method, except that an alloy layer having a lower melting point than that of the member is provided on one of the mating surfaces of the seat-joining members. It can be done in exactly the same way.

In the present invention, an alloy having a lower melting point than that of the member (hereinafter referred to as "low melting point alloy") provided on the joint surface of the member to be joined is
When the base material of the members to be joined is a metal or an alloy, an alloy based on the same metal or alloy as the base material is most preferable.

For example, if the member to be joined is an N1-based alloy, Ni
It is advantageous to further provide the base alloy with a layer of a low melting point alloy containing B, Sl, etc. as a melting point depressing element. Particularly in this case, since B has a fast diffusion rate in the solid, the presence of B is preferable because it improves the homogenization of the joint by diffusion.

In the present invention, the provision of a lower melting point alloy layer on one side of the member to be joined than the Homare joining member prevents the displacement of the powder in the foil from the joining surface that occurs in the conventional method of inserting foil or powder and joining. It is possible to prevent bonding defects due to peeling, etc.

Furthermore, it is dangerous to provide a low melting point alloy layer, the bonding time is short, and the pressure required during bonding is small enough to prevent deformation caused by high pressure during bonding.

When the low melting point alloy layer contains constituent elements of the base material of the members to be joined, the diffusion treatment time is further shortened, which is extremely advantageous.

According to the present invention, a member to be joined with a low melting point alloy layer pipe provided on the joint surface is joined by facing each other (joining of an alloy layer and a base material)
This method promotes homogenization of the joint and shortens the diffusion process time compared to joining parts to be joined with a low melting point alloy layer on the joint surface (joining between alloy layers) or joining by inserting foil. Ru.

This is because one of the bonding surfaces is used as the base material f#:, so the elements that lower the melting point of the bonded portion are diffused, and the constituent elements of the base material O to be bonded are more likely to be diffused into the bonded portion. Moreover, as a result, the amount of intermetallic compounds produced in one joint is extremely small, and the bonding according to the present invention has fewer defects such as poor bonding and voids than bonding between alloy layers, and improves the bonding rate.

Next, the present invention will be explained in more detail by citing examples, but the present invention does not go beyond the gist and is not limited to the following examples.Example 1 The test materials were: 1N-738LC was used as the Ni-based alloy. N1 to form a low melting point alloy layer on the joint surface of the test materials
-ntB:s*) powder (particle size 7Is~100μm) t-
The method for forming the low melting point alloy layer for Z and fc is to apply the above N1-B powder to the joint surface of IN-738LC as a binder agent (acrylic resin).
The alloy layer was fixed in place by laser irradiation to form an alloy layer tube. The melting point of the nine alloy layers formed is about 105 (1-110), and the alloy layer vlII is about 250 μm-300 μm.

In this way, the low melting point alloy layer is formed only on one joint surface (method of the present invention, see FIG. 1 (3)), and
In the case where a low melting point alloy layer was formed on both bonding surfaces (comparative example, see FIG. 1 (2)), diffusion bonding was performed under the conditions shown in Table 1. As a result, the bonding rate of the bonded portion by the method of the present invention is 99III, and the bonding rate of the bonded portion of the low melting point alloy layers is 65III, so the bonding rate of the bonded portion by the method of the present invention is extremely It has been proven that a high bonding rate can be obtained, and the micrograph of the metallographic structure of these bonded parts is shown in Fig. 2. )) The joints are uniform,
Compared to the joint between alloy layers (see Figure 2(a)).

It is clear that defects such as voids during poor bonding are significantly improved.

Table 1 Example 2 JIS standard BNi-2 brazing filler metal was applied to the welding surfaces of the members to be welded using the same test materials as in Example 1, with the welding temperature, pressure and atmosphere set the same as in Example 1. In the case of inserting and diffusion bonding (comparative example, see Fig. 1 (1)), the parts to be bonded having a low melting point alloy layer (forming method is the same as in Example 1) on the bonding surfaces were diffusion bonded. Case (comparative example, 1st
In the case of diffusion bonding with a low melting point alloy layer (formation method is the same as in Example 1) only on one joint surface (see Figure 1 (3)), and diffusion bonding method according to the present invention (see Figure 1 (3)) The processing time required until the parts became homogeneous was determined. The results are shown in Table 2.

Table 2 From Table 2, it can be seen that the bonding method of the present invention can significantly shorten the diffusion treatment time compared to other methods. In the Examples, it was confirmed that the method of the present invention produces less intermetallic compounds compared to other methods. The low melting point alloy layer was formed on the joint surface by a boriding process. Table 3 shows the boriding conditions. When formed under the conditions shown in Table 3, the melting point of the alloy layer was approximately 1135 t". After spinning, the thickness of the alloy layer is about 20 μm.

Table 3 In this way, the low melting point alloy layer is formed only on one joint surface, and the alloy layer and the base material are diffusion bonded (t6). The bonding rate was determined in the same manner as in Example 1 for nine cases (comparative examples) in which alloy layers were formed and diffusion bonded to each other. As a result, it was found that the bonding rate of the method of the present invention was 98, which was extremely superior to the bonding rate of 85- in the comparative example.

As is clear from FIG. 3, which shows a microscopic photograph of the metal structure of both joints, void-like defects often occur in the diffusion joint between alloy layers (see FIG. 3(a)). Therefore,
The bonding rate is poor at approximately SS*, and intermetallic compounds are often formed.

On the other hand, the diffusion bond between the alloy layer and the base material of the present invention (
Referring to FIG. 3(b)), there is no occurrence of void-like defects, so the bonding ratio is very good at about 98 inches, and the formation of intermetallic compounds is also very small.

Example 4 The same method of forming a low melting point alloy layer as in Example 3 was employed, and the diffusion treatment time in various diffusion bonding methods was determined in the same manner as in Example 2 except for the following. The results are shown in Table 4.

Table 4 From Table 4, it is clear that according to the method of the present invention, the diffusion and escape time can be significantly shortened.

According to the present invention, by joining a workpiece having a low melting point alloy layer on the joint surface and a workpiece without such a layer facing each other, defects such as voids during joint failure can be prevented, and defects necessary after joining can be prevented. The diffusion process can be significantly shortened.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view explaining the outline of various diffusion bonding methods, (1) is foil insert diffusion bonding, (2) is diffusion bonding between alloy layers, and (3) is diffusion bonding between alloy layer and base material. The bonding process (method of the present invention) is shown respectively. Figures 2 and 3 show a comparison of the joints in Example 1 and Example 3, respectively, and Figure 2 (a) and Figure 3 (a)
i is a microscopic photograph of the metallographic structure of the joint according to the comparative example, and FIG. 2 φ) and FIG. 1... Base material, 2... Insert foil, 3... Low melting point alloy layer tube 1 Figure (+) /2)
(3) vl Z times

Claims (1)

[Claims] 1. In a method of joining joining surfaces of members to be joined by diffusion bonding, an alloy layer having a lower melting point than that of the joining surfaces is provided on one joining surface, and the alloy layer is made to face the other joining surface. , a diffusion bonding method characterized by performing diffusion bonding. 2. The diffusion bonding method according to claim 1, wherein the alloy layer contains zero constituent elements of the base material of the members to be bonded. 1% allowance The diffusion bonding method according to claim 1 or 2, characterized in that the member to be joined is a heat-resistant alloy. A method characterized in that the low melting point alloy layer provided on the member to be welded is made of an alloy made by adding a melting point lowering element to the heat resistant alloy.