JPH0147277B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to objects to be joined of Ni-based, Co-based or Fe-based alloys and a method for joining the same, and in particular, to a material that can significantly reduce joint defects at joints and is suitable for joining joints with complex shapes. This article relates to objects to be joined and methods for joining them. Ni-based, Co-based and Fe-based alloys are often used in high temperature parts such as gas turbines and jet engines. In recent years, efforts have been made to increase the combustion efficiency of these gas turbines and jet engines by increasing the combustion gas temperature. However, from the viewpoint of materials, there has not necessarily been any advance in the development of materials that can withstand use at high temperatures. For this reason, parts used in high-temperature parts are sometimes cooled by introducing air. For example, cooling for blades includes convection cooling, impingement cooling, film cooling, and exudation cooling, and these are used alone or in combination to enhance the cooling effect. Therefore, the cooling holes, which are the flow paths for cooling air, become extremely complicated. Therefore, the blade is divided into a plurality of parts and cast, and then the divided cast products are joined to produce a single blade. Conventionally, methods for joining various alloys include inserting alloy foil or alloy powder into the surfaces to be joined, heating them and diffusing them into the joining surfaces; There is a method of joining these by melting them. However, the former method requires heating at high temperatures and for a long time, and also requires applying a large load to increase the bonding strength. In the latter method, it is necessary to bring the alloy foil or powder into close contact with the joint surface, and for this purpose a large load must be applied. Among both methods, especially the method using alloy powder, it is difficult to place the alloy powder uniformly on the surface to be joined, so a preform is made in advance with alloy powder and acrylic adhesive and placed on the surface to be joined. However, it is not sufficient to form a uniform layer.
Furthermore, a common point between both methods is that when the joint surface has a complex shape, it is difficult to sandwich the alloy foil as an intermediate layer or the preform of alloy powder and acrylic adhesive in a manner corresponding to the joint surface. There is a drawback. The purpose of the present invention is to provide a method for joining alloys that eliminates the above-mentioned drawbacks of the prior art, enables sufficient joining even when the joining surfaces have a complicated shape, and has extremely few joining defects, and a method for joining alloys that can be used in this joining method. The object of the present invention is to provide a suitable material to be joined. The present inventors used Ni ₂ B in the case of Ni-based alloys and Ni 2 B in the case of Co-based alloys as materials to be joined in order to obtain a good joint surface with extremely few joint defects at the joints.
In the case of Co ₂ B and Fe-based alloys, it has been found that forming an intermetallic compound of Fe ₂ B on the surface is extremely effective. The present invention has been made based on the above findings, and provides a material to be joined in which a compound layer of Ni, Co, or Fe and B is formed on the surface of a Ni-based, Co-based, or Fe-based alloy, respectively. This is a method of joining materials to be joined together on which a compound layer is formed, or materials to be joined on which a compound layer is formed and materials to be joined on which an intermetallic compound layer is not formed. In the present invention, the boron treatment for forming boron compounds on Ni-based, Co-based, or Fe-based alloys can be carried out by dipping the alloy in molten salt, by using a vapor phase method using gas, or by burying the alloy in powder. Any method may be used, such as a solid heating method, sputtering method, or vapor deposition method. As a boron compound layer formed on the surface of the alloy
Ni ₂ B, Co ₂ B, and Fe ₂ B are preferable, and the thickness is 4~
It is desirable that the thickness be 100 μm, preferably 30 to 40 μm. If the M ₂ B layer is too thick, an excessive amount of B will be contained in the joint interface, which will have negative effects such as deteriorating the mechanical properties of the joint, and if the M ₂ B layer is too thin, the joint strength will be insufficient. Become. In the joining method of the present invention, alloys having a boron compound layer formed on their surfaces as described above are joined by contact heating while sandwiching the boron compound layer. That is, it is sufficient that the boron compound layer is formed on at least one of the surfaces of the alloy to be joined. In the case of Ni-based alloys, heating during bonding is required for Ni and Ni ₃ B.
In the case of Co-based alloys, the temperature range should be above the eutectic point of Co and Co ₃ B and below the melting point of Co-based alloys.
In the case of a base alloy, the temperature range is preferably higher than the eutectic point of Fe and Fe ₃ B and lower than the melting point of the Fe-based alloy. The heating atmosphere during bonding needs to be a non-oxidizing atmosphere to prevent oxidation of the materials to be bonded, but not only vacuum but also Ar gas has a sufficient effect. Under the above heating conditions, the surface of the materials to be joined melts, and after melting, B has a large affinity for Ni, Co, or Fe, and the mutual wettability is good, resulting in a good joint with few joint defects. . In addition, Ni ₂ B, Co ₂ B, or Fe ₂ B exists over the entire joint surface, and the entire joint surface melts when heated, so that sufficient joining can be achieved without applying any load during joining. Of course, it goes without saying that the bonding can be more effectively achieved by applying a load; in this case, a slight load of 0.3 kg/cm ² or less is sufficient. The details of the present invention will be explained below by showing examples. The material used in the experiment was IN-738LC, a Ni-based alloy, whose chemical composition is shown in Table 1.

[Table] A test piece with a width of 9 mm, a length of 13 mm, and a thickness of 5 mm was used as the material to be joined. As a method to form Ni ₂ B,
A solid-state method was used in which the materials to be joined were buried in powder and heated. That is, 1w/oB−2.5w/oNH ₄ Cl−residue
The material to be joined is buried in a mixed powder of Al ₂ O ₃ at 650 to 950℃.
Heat treatment was performed in an Ar atmosphere for 3.5 hours. After the treatment, the formations on the surface were identified by X-ray diffraction, and the thickness of the formations on the surface was measured from the cross section of the materials to be joined. As a result, the surface formation was clearly Ni ₂ B, and the relationship between the heat treatment temperature and the thickness of the Ni ₂ B layer was as shown in FIG. Next, bonding was performed using these samples. Prior to bonding, the sample surface was lightly polished with water-resistant emery paper No. 1000. The heating condition for bonding is temperature.
Hold at 1200°C for 1 hour. The bonding atmosphere is vacuum (4×10 ^-5 Torr) or Ar gas. After bonding, the sample was cut, buffed, and the length of the unbonded portion was measured using an optical microscope to calculate the bonding rate (%). Table 2 summarizes the results. The reason for the difference between the thickness of the Ni ₂ B layer shown in Figure 1 and the thickness of the Ni ₂ B layer of the bonded samples shown in Table 2 is that the Ni _{2 B} layer is This is because layer B was polished with water-resistant emery paper. Note that the eutectic point between Ni and Ni ₃ B is 1080°C.

[Table] As is clear from Table 2, on the surface of the materials to be joined.
When Ni ₂ B was formed, an extremely good bonding state was obtained. On the other hand, there was no significant difference in the effect of the bonding atmosphere on the bonding rate when samples a and b were compared in vacuum and in Ar gas, but samples f, g, and h bonded in an Ar gas atmosphere had a It shows a bonding rate of 99%. In addition, regarding the influence of load on the joining rate, b
As is known from the comparison between and c or d and e, it can be seen that the bonding rate is improved in cases b and d where a load is applied. However, applying a load of 0.3 Kg/cm ² or more does not improve the bonding rate and also causes deformation of the materials to be joined, so it is not preferable to apply a load of 0.3 Kg/cm ² or more. As described above, according to the present invention, a boron compound M ₂ B such as Ni ₂ B is formed in advance on the surfaces of the materials to be joined, and since these materials to be joined are heated together, a particularly complex shape can be avoided. This method is effective for joining alloys of 1 to 3, and it is possible to obtain a joint with few joint defects.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the relationship between the heat treatment temperature during Ni ₂ B formation and the thickness of the Ni ₂ B layer.

Claims (1)

[Claims] 1. On the surface of a Ni-based, Co-based, or Fe-based alloy, a Ni ₂ B layer, a Co ₂ B layer, each of which is a compound with B,
A bonded object characterized by forming an Fe ₂ B layer. 2. The bonded material according to claim 1, wherein the compound with B is obtained by burying the compound in a mixture of B powder, ammonium chloride powder, and alumina powder and heating the mixture in an inert atmosphere. body. 3 The thickness of the compound layer with B is 4 to 100 μm
The object to be joined according to claim 1 or 2, characterized in that: 4. In a method of joining Ni-based, Co-based, or Fe-based alloys _, a Ni 2 B layer, a Co ₂ B layer, which is a compound of Ni, Co, or F and B, is formed on at least one surface of the alloy to be joined. After forming the _Fe2B layer,
A joining method characterized by bringing the surfaces of both alloys into contact and heating them to join them. 5 The Ni ₂ B layer, Co ₂ B layer, and Fe ₂ B layer have a thickness of 4 to 100μ
5. The joining method according to claim 4, wherein the bonding method is m. 6. The joining method according to claim 4, wherein both alloys are joined in a non-oxidizing atmosphere. 7. The joining method according to claim 4, in which a pressure of 0.3 Kg/cm ² or less is applied during heating of both alloys. 8. The joining method according to claim 4, wherein the heating temperature during joining with the Ni-based alloy is within a temperature range that is higher than the eutectic point of the compound of Ni and B and lower than the melting point of the Ni-based alloy. 9. The joining method according to claim 4, wherein the heating temperature during joining with the Co-based alloy is within a temperature range that is higher than the eutectic point of the compound of Co and B and lower than the melting point of the Co-based alloy. 10. The joining method according to claim 4, wherein the heating temperature during joining with the Fe-based alloy is within a temperature range that is higher than the eutectic point of the compound of Fe and the B and lower than the melting point of the Fe-based alloy.