JPS5893584A - Joining method for heat resisting alloy - Google Patents

Abstract

PURPOSE:To obtain joined parts having high quality with high efficiency by forming a composite electroless nickel plating layer contg. powder for joining on the surface of a heat resisting alloy to be joined to form a low m.p. alloy layer and subjecting the heat resisting alloy to diffusion bonding. CONSTITUTION:Fine powder for joining is mixed with an electroless nickel plating soln. and while both are agitated, the powder for joining is stuck on the fayed surface by means of nickel plating. After a composite electroless nickel plating layer 2 contg. powder 3 for joining is formed on the surface to be joined, said layer is heated in a vacuum and inert gaseous atmosphere to melt the layer 2 at the temp. lower than the m.p. of the heat resisting alloy, whereby a low m.p. alloy layer is formed. The fayed surfaces having the low m.p. alloy metal are faced to each other and are subjected to diffusion bonding, whereby the joined parts, having high quality are obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a diffusion bonding method, and more particularly to a method for forming a low melting point alloy layer and a bonding method for diffusion bonding of a heat-resistant alloy having a low melting point alloy layer.

Welding of heat-resistant alloys has problems such as the welded part being brittle and prone to cracking, and wax bone joints having low joint strength and a low melting point of the joint. As described above, there are limitations to the application of fusion welding and brazing to heat-resistant alloys. Due to the above-mentioned background, a bondable diffusion bonding method has been applied to obtain high-quality bonded parts.

In the diffusion bonding method, materials to be bonded are bonded through a thin layer with a low melting point. As a method of intervening this thin layer, bonding is usually performed by sandwiching a thin alloy foil or applying alloy powder.

Thin foils inserted into the surfaces of heat-resistant alloys to be joined are easy to manufacture when the material is ductile, but it is difficult to manufacture the foil when the material is brittle such as a high alloy.

Therefore, the material of the foil to be inserted is limited.

In the method of inserting powder such as alloy powder into the surface of the heat-resistant alloy to be joined, the powder is fixed to the joint surface using an organic solvent, etc., which may cause unevenness of the coating film, contamination of impurities, and damage to the coating film.
Defects such as scratches are likely to occur.

In the foil and powder insert methods described above, when the surfaces of the members to be joined have complicated shapes or are large in size, the work becomes complicated and time is wasted.

Furthermore, even if foil or powder is inserted into the surfaces to be bonded, deviations or defects from the bonding surfaces may occur, resulting in defective bonding and the like, impairing reliability.

The purpose of the present invention is to enable the formation of a low melting point alloy layer such as a brittle alloy or intermetallic compound, and to obtain a high-efficiency, high-quality joint even when the joint surface has a complex shape. To provide insert methods and joining methods.

The present invention forms a composite electroless nickel plating layer containing bonding powder on the surface of a heat resistant alloy to be joined, and heats and melts the composite electroless nickel plating layer below the melting point of the heat resistant alloy. This is a diffusion bonding method having a low melting point alloy layer, which is characterized by forming a low melting point alloy layer on the surfaces to be bonded and then diffusion bonding a heat resistant alloy.

According to the insert method and bonding method of the present invention, when diffusion bonding heat-resistant alloys, it is possible to form a low melting point alloy layer containing brittle alloys and intermetallic compounds, simplifying the work, and eliminating defects. Fewer and better joints are obtained.

In the present invention, in the composite electroless nickel plating containing bonding powder, fine bonding powder is mixed into a conventional electroless nickel plating solution, and while stirring, the bonding powder is fixed to the bonding surface by nickel plating. That is, nickel plating acts like a binder, and covers the bonding powder with a nickel plating film, thereby metallically bonding the bonding powder to the bonding surface.

Next, after forming a composite electroless nickel plating layer containing the above-mentioned bonding powder on the joint surfaces to be joined, the composite electroless nickel plating layer is heated in a vacuum and an inert gas atmosphere to form a composite electroless nickel plating layer at a temperature lower than the melting point of the heat-resistant alloy. A low melting point alloy layer can be formed by melting the layer, and adsorbed gas contained in the plating layer can be removed by heating and melting.

As a result, a high quality bonded part can be obtained by making the bonding surfaces having low melting point metals face each other and performing diffusion bonding.

The insert method and bonding method of the present invention have fewer bonding interfaces than conventional methods of inserting foil or powder and performing bonding, so they are effective in obtaining high-quality bonded parts.

Furthermore, by using the method of the present invention when the joining surfaces to be joined have a complex shape such as an uneven shape or are large in size, it is possible to form a low melting point alloy layer only on the surfaces to be joined, and the conventional insert method can be used. A high-efficiency, high-quality joint can be obtained by preventing defects such as displacement, peeling, and chipping of the insert material.

In the composite solder-free nickel plating layer containing bonding powder as the insert method of the present invention, it is preferable that the bonding powder contains one or more types of metal powder, alloy powder, and intermetallic compound powder whose melting point is lower than the melting point of the heat-resistant alloy. .

The base metal to which the insert material and joining method of the present invention is applied may be any of Fe-based, 1jJi-based, CO-based, and Cr-based alloys, and is particularly effective for Ni-based alloys.

In the insert method of the present invention, a composite electroless nickel plating layer containing a bonding powder may be formed on the bonding surface for bonding.

Examples of the present invention will be described below.

Table 1 shows the chemical composition of the test materials, and Table 2 shows the composition and particle size of the bonding powder. The electroless nickel plating solution is commercially available N1-
One coat of B alloy CB≦1.0%) plating solution was used. The bonding powder is JIS standard Nl-2 powder (approximately 10 μm) and NiB.
Powder (B: 10%, approximately 10 μm) was used.

Formation of a composite electroless nickel plating layer containing bonding powder is performed by mixing a bonding powder into an electroless nickel plating solution and stirring it while degreasing and pickling a test piece (1
010).

FIG. 1 shows a cross section of a composite electroless nickel plating layer containing bonding powder, and FIG. 2 shows the surface condition of the composite electroless nickel plating layer containing bonding powder (BNi-2 powder). As a result, a strong composite electroless nickel plating solution with a thickness of about 20 μm to about 40 μm was formed on the joint surfaces of the Ni-based heat-resistant alloys to be joined without peeling, misalignment, or defects such as missing rings.

Next, the Ni-based heat-resistant alloy having the composite electroless nickel plating layer is heated in vacuum (lx10-'Torr), and the Ni
It was melted at a temperature lower than the melting point (1250°C) of the base heat-resistant alloy to form a stronger and flatter low melting point alloy layer.

*1) Temperature difference = melting point of heat-resistant alloy - melting point of composite electroless nickel plating layer Table 3 shows the melting point and temperature difference of the composite electroless nickel plating layer. The melting point of the composite electroless nickel plating layer containing nNi-2 powder is 1105°C, and the temperature difference from the melting point of the heat-resistant alloy is 155°C. Further, the melting point of the composite non-dissolving nickel plating layer containing NiB powder is 1130°C, and the temperature difference from the melting point of the heat-resistant alloy is 130:'C.

A bonding experiment was conducted on an N1 base heat-resistant alloy having a low melting point alloy layer. Table 4 shows the joining conditions, and FIG. 3 shows the metal structure of the NI-based heat-resistant alloy joint. As a result of joining under the conditions shown in Table 4, a good Ni-based heat-resistant alloy joint was obtained without defects such as voids and poor joining. Further, by performing a diffusion treatment (1100° C. x 15 hours), the B concentration in the bonded portion could be made almost the same as that in the base material.

According to the present invention, during diffusion bonding of heat-resistant alloys, the composite electroless nickel plating treatment and heat treatment on the bonding surfaces make it possible to form an alloy layer with a temperature lower than the melting point of the heat-resistant alloys, and it is also possible to bond joints with complex shapes. Since it is possible to obtain a joint with a high quality, it has the effect of improving efficiency and quality.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional diagram of a composite electroless nickel plating layer containing bonding powder, Figure 2 is a surface photograph of a composite electroless nickel plating layer containing bonding powder, and Figure 3 is a diffusion bonded portion of a heat-resistant alloy. This is a cross-sectional micrograph. Tsukermeggi layer, 3...powder for the stand. $1 b

Claims (1)

[Claims] 1. In diffusion bonding of heat-resistant alloys, a composite electroless nickel plating layer containing bonding powder is formed on the surface of the heat-resistant alloy to be joined, and the composite electroless nickel plating layer is heated and melted. A method for joining heat-resistant alloys, which comprises forming an alloy layer with a low temperature on the surfaces of the heat-resistant alloys to be joined, and then diffusion-bonding the heat-resistant alloys. 2. Claim 1 is characterized in that a composite electroless nickel plating layer containing one or more types of metal powder, alloy powder, and metal surface compound powder whose melting point is lower than the melting point of the heat-resistant alloy is formed as the bonding powder. A method for joining heat-resistant alloys.