Composite Sintered Body and Method for Producing the Same

Abstract

To provide a manufacturing method for a compound sintered compact where sintered compacts made of a Ni-based alloy are joined by a fine joint layer.SOLUTION: In a manufacturing method according to an embodiment, a first temporarily sintered compact 2A composed of powder made of a first Ni-based alloy is prepared along with the preparation of a second temporarily sintered compact 3A composed of powder made of a second Ni-based alloy. Then, the first temporarily sintered compact 2A and the second temporarily sintered compact 3A are made to face each other with a prescribed gap 4 therebetween, and a joint material 6 made of a Ni-based alloy a liquidus curve temperature of which is lower than those of the first Ni-based alloy and the second Ni-base alloy is installed in a space 5, toward which the gap 4 opens, adjacent to the first temporarily sintered compact 2A and the second temporarily sintered compact 3A. After the installation of the joint material 6, the joint material 6 is molten by heating the first temporarily sintered compact 2A and the second temporarily sintered compact 2B to penetrate into the gap 4, then the first temporarily sintered compact 2A and the second temporarily sintered compact 3A are made to be a first compact and a second compact, respectively.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a composite sintered body, a composite sintered body obtained by the manufacturing method, and a bonding material used in the manufacturing method.

Background Art

[0002] Conventionally, a composite sintered body has been manufactured by joining a plurality of sintered bodies to each other by brazing or welding. A sintered body is obtained, for example, by producing a green compact containing a metal powder and a binder by metal powder injection molding, and then degreasing and sintering the green compact.

[0003] However, in the method for manufacturing a composite sintered body as described above, it is necessary to perform a joining step after forming the sintered body. On the other hand, Patent Document 1 discloses a method of performing sintering and joining simultaneously when manufacturing a composite sintered body.

[0004] Specifically, in the method for manufacturing a composite sintered body disclosed in Patent Document 1, after producing a first green compact and a second green compact by metal powder injection molding, the first green compact and the second green compact are adhered to each other with a paste made of a metal powder and an organic binder, and then degreasing and sintering are performed.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, in the method for manufacturing a composite sintered body disclosed in Patent Document 1, since a paste containing metal powder is used, the bonding layer in the composite sintered body after manufacturing is porous like the sintered bodies on both sides thereof. On the other hand, there is a desire to make the bonding layer in the composite sintered body dense, such as in conventional soldering.

[0007] In addition, Patent Document 1 describes, as an example, using a powder made of stainless steel in metal powder injection molding. On the other hand, it is desired to bond sintered bodies made of Ni-based alloys.

[0008] Therefore, an object of the present invention is to provide a method for manufacturing a composite sintered body in which sintered bodies made of Ni-based alloys are joined by a dense bonding layer, and a composite sintered body obtained by the manufacturing method. Another object of the present invention is also to provide a bonding material that can be suitably used for joining sintered bodies made of specific Ni-based alloys.

Means for Solving the Problems

[0009] In order to solve the above problems, a method for manufacturing a composite sintered body according to one aspect of the present invention includes a step of preparing a first green compact composed of a powder made of a first Ni-based alloy, a step of preparing a second green compact composed of a powder made of a second Ni-based alloy, a step of opposing the first green compact and the second green compact with a predetermined gap therebetween, a step of installing a bonding material made of a Ni-based alloy having a liquidus temperature lower than that of the first Ni-based alloy and the second Ni-based alloy in a space where the gap opens and faces the first green compact and the second green compact, and after installing the bonding material, heating the first green compact and the second green compact to melt the bonding material and infiltrate it into the gap, and then making the first green compact and the second green compact into a first sintered body and a second sintered body, respectively.

[0010] Here, the "semi-sintered body" refers to a powder compact obtained by heating an unsintered body (a powder compact in which particles in the powder are bonded, having an open porosity greater than 20%, or a powder compact in which the spaces between particles in the powder are filled with a binder) formed by shaping powder into a predetermined shape, and having an open porosity greater than 2% and less than or equal to 20%. The "sintered body" refers to a powder compact obtained by heating the semi-sintered body, and having an open porosity of 2% or less.

[0011] Note that the open porosity is a value obtained by dividing the total volume of open pores (pores inside the specimen that open on the surface of the specimen; pores inside the specimen that do not open on the surface of the specimen are closed pores) by the apparent volume of the specimen (the volume determined from the dimensions of the specimen). For example, if the density ρ of the volume surrounded by the surface of the specimen and the continuous surface formed by the open pores is measured by, for example, the Archimedes method, the open porosity Vop is calculated by the following formula using the mass m and the apparent volume V of the specimen 。 Vop = ((V - m / ρ) / V) × 100

[0012] Further, a method for manufacturing a composite sintered body from another aspect of the present invention includes a step of preparing a first semi-sintered body composed of powder of a first Ni-based alloy, a step of preparing a second semi-sintered body composed of powder of a second Ni-based alloy, a step of opposing the first semi-sintered body and the second semi-sintered body with a joining material made of a Ni-based alloy having a liquidus temperature lower than that of the first Ni-based alloy and the second Ni-based alloy sandwiched therebetween, and a step of heating the first semi-sintered body and the second semi-sintered body to melt the joining material and then forming the first semi-sintered body and the second semi-sintered body into a first sintered body and a second sintered body, respectively.

[0013] According to the above configuration, a joining layer is formed between the first sintered body and the second sintered body by solidification of the melted joining material. Therefore, a composite sintered body in which sintered bodies made of Ni-based alloy are joined by a dense joining layer can be obtained.

[0014] The composite sintered body obtained by the above manufacturing method is a composite sintered body in which a first sintered body made of a first Ni-based alloy and a second sintered body made of a second Ni-based alloy are joined by a joining layer made of a Ni-based alloy having a composition different from that of the first Ni-based alloy and the second Ni-based alloy, the joining layer is denser than the first sintered body and the second sintered body, and the thickness of the joining layer is 200 μm or more.

[0015] Further, the joining material of the present invention is characterized by being made of a Ni-based alloy containing, by mass percentage, 18.0 to 23.0% of Cr, 1.5 to 6.5% of Mo, 3.5 to 8.5% of Si, 13.0% or less of Fe, 2.5% or less of Nb + Ta, and 1.0% or less of Co.

[0016] The joining material having the above configuration can be suitably used for joining sintered bodies made of a Ni-based alloy containing 18.0 to 25.0% of Cr, 7.0 to 11.0% of Mo, 22.0% or less of Fe, 4.5% or less of Nb + Ta, and 3.0% or less of Co.

Advantages of the Invention

[0017] According to the present invention, there is provided a method for manufacturing a composite sintered body in which sintered bodies made of a Ni-based alloy are joined by a dense joining layer to obtain a composite sintered body.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0019] Figure 1 shows a composite sintered body 1 obtained by the method for manufacturing a composite sintered body according to an embodiment of the present invention. This composite sintered body 1 is obtained by joining a first sintered body 11 and a second sintered body 12 with a joining layer 13.

[0020] The first sintered body 11 is made of a first Ni-based alloy, and the second sintered body 12 is made of a second Ni-based alloy. The first Ni-based alloy and the second Ni-based alloy may have the same composition or different compositions. The joining layer 13 is made of a Ni-based alloy having a composition different from that of the first Ni-based alloy and the second Ni-based alloy.

[0021] In Figure 1, both the first sintered body 11 and the second sintered body 12 are plate-shaped, and they are joined in a state where they are orthogonal to each other. More specifically, an end face of the second sintered body 12 is joined to a part of the main surface of the first sintered body 11 via the joining layer 13.

[0022] However, the shapes of the first sintered body 11 and the second sintered body 12 and the joined portions can be appropriately changed. For example, the first sintered body 11 and the second sintered body 12 may be rod-shaped, and their end faces may be joined by the joining layer 13 in a butted state.

[0023] As shown in Figure 2(b), the manufacturing method of the present embodiment includes a step of preparing a first green compact 2A having a shape similar to that of the first sintered body 11 and a step of preparing a second green compact 3A having a shape similar to that of the second sintered body 12. The first green compact 2A is composed of powder made of a first Ni-based alloy, and the second green compact 3A is composed of powder made of a second Ni-based alloy.

[0024] In the present embodiment, powder made of a first Ni-based alloy is formed into a predetermined shape to produce a first unsintered body 2, and a first green compact 2A is generated during the process of heating the first unsintered body 2 to obtain the first sintered body 11. Similarly, powder made of a second Ni-based alloy is formed into a predetermined shape to produce a second unsintered body 3, and a second green compact 3A is generated during the process of heating the second unsintered body 3 to obtain the second sintered body 12.

[0025] Depending on the shape of the first green compact 2, during the process of heating the first green compact 2 to obtain the first sintered body 11, a part of the first green compact 2 may be deformed due to the influence of gravity, friction during shrinkage accompanying the progress of sintering, restraint between green compacts, between semi-sintered compacts, and between sintered bodies. Similarly, depending on the shape of the second green compact 3, during the process of heating the second green compact 3 to obtain the second sintered body 12, a part of the second green compact 3 may be deformed due to the influence of gravity, friction during shrinkage accompanying the progress of sintering, restraint between green compacts, between semi-sintered compacts, and between sintered bodies.

[0026] Each of the first Ni-based alloy and the second Ni-based alloy contains, as essential components other than Ni, 18.0 to 25.0% of Cr and 7.0 to 11.0% of Mo by mass percentage (the same hereinafter). Each of the first Ni-based alloy and the second Ni-based alloy may contain at least one of Fe of 22.0% or less, Nb + Ta of 4.5% or less, and Co of 3.0% or less as other optional components. The balance other than the above-described components of each of the first Ni-based alloy and the second Ni-based alloy is Ni and inevitable impurities. Regarding Nb and Ta, each of the first Ni-based alloy and the second Ni-based alloy may not contain either Nb or Ta.

[0027] Examples of the Ni-based alloy having the above composition include Hastelloy X and IN625 (IN is an abbreviation of Inconel (registered trademark)).

[0028] The method for producing the first green compact 2 and the second green compact 3 is not particularly limited. For example, it is metal powder injection molding (MIM), press compression molding, or additive manufacturing such as fused deposition modeling (FDM) or binder jetting in additive manufacturing. Each method is a process for finally obtaining a dense metal part by a sintering process.

[0029] In this embodiment, the first green compact 2 and the second green compact 3 are produced by MIM. Specifically, a powder made of the first Ni-based alloy or the second Ni-based alloy is uniformly kneaded with a binder to produce a compound, and this compound is injected into the cavity of a mold. Thereby, a green compact having the same shape as the cavity of the mold is obtained.

[0030] The average particle diameter (median diameter (d50)) of the powder made of the first Ni-based alloy or the second Ni-based alloy is, for example, 10 to 60 μm. The binder is not particularly limited, and for example, it contains at least one of polypropylene (PP), polyethylene (PE), polyacetal (POM), polymethyl methacrylate (PMMA), carnauba wax (CW), paraffin wax (PW), and stearic acid (St).

[0031] After the production of the first green compact 2 and the second green compact 3, as shown in Fig. 2(a), the main surface of the first green compact 2 and the end surface of the second green compact 3 are opposed to each other with a predetermined gap 4 therebetween. The gap 4 is, for example, 1 to 200 μm.

[0032] Next, as shown in Fig. 2(b), a bonding material 6 is installed in a space 5 facing the first green compact 2 and the second green compact 3 and in which the gap 4 opens (in this embodiment, the corner portion formed by the main surface of the first green compact 2 and the main surface of the second green compact 3).

[0033] The bonding material 6 is made of a Ni-based alloy having a liquidus temperature lower than that of the first Ni-based alloy and the second Ni-based alloy. The Ni-based alloy constituting the bonding material 6 contains, for example, 18.0 to 23.0% of Cr, 1.5 to 6.5% of Mo, and 3.5 to 8.5% of Si as essential components other than Ni, and contains, as other optional components, 13.0% or less of Fe, 2.5% or less of Nb + Ta, and 1.0% or less of Co. The balance other than the above-described components of the Ni-based alloy is Ni and inevitable impurities.

[0034] In this embodiment, the bonding material 6 is a mixture of two types of powders (first powder and second powder) with different compositions from each other. However, the bonding material 6 may be a single type of powder with a single composition. Alternatively, the bonding material 6 does not necessarily have to be a powder, and may be in a paste form or a film form. When the bonding material 6 is a mixture of the first powder and the second powder, the liquidus temperature of the bonding material 6 refers to the temperature when all the powders are melted.

[0035] The first powder is composed of a third Ni-based alloy having a lower liquidus temperature than the first Ni-based alloy and the second Ni-based alloy, and the second powder is composed of the first Ni-based alloy or the second Ni-based alloy. The third Ni-based alloy contains, for example, 16.0 to 22.0% of Cr and 8.0 to 12.0% of Si in mass percentage. Examples of such Ni-based alloys include AMS4782.

[0036] The Si in the third Ni-based alloy can lower the liquidus temperature of the bonding material 6, which is a mixture of the second powder composed of the first Ni-based alloy or the second Ni-based alloy and the first powder composed of the third Ni-based alloy, below the liquidus temperature of the first Ni-based alloy or the second Ni-based alloy.

[0037] For example, the mixing ratio of the first powder and the second powder is 40%:60% to 80%:20% in mass percentage. For example, when the material of the first powder is AMS4782 (liquidus temperature: 1135 °C), the material of the second powder is IN625 (liquidus temperature: 1360 °C), and the mixing ratio of the first powder and the second powder is 60%:40%, the liquidus temperature of the bonding material 6 is 1226 °C.

[0038] After the bonding material 6 is installed in the space 5, as shown in FIG. 3, over a certain period of time (for example, 10 to 20 hours), the first green compact 2 and the second green compact 3 are heated to a predetermined temperature (for example, 400 to 600 °C) to remove the binder (debinding) from the first green compact 2 and the second green compact 3.

[0039] In this embodiment, degreasing is performed under a nitrogen atmosphere. However, degreasing may be performed under an argon atmosphere. In this embodiment, degreasing, pre-sintering, and sintering described later are performed in the same furnace.

[0040] Thereafter, while the joining material 6 is installed in the space 5, the first green compact 2 and the second green compact 3 are heated at a pre-sintering temperature T1 lower than the liquidus temperature T2 of the joining material 6 (pre-sintering), so that the first green compact 2 and the second green compact 3 are respectively made into a first pre-sintered body 2A and a second pre-sintered body 3A. That is, by performing pre-sintering, the first pre-sintered body 2A and the second pre-sintered body 3A face each other with a gap 4 therebetween, and the joining material 6 is installed in the space 5 facing the first pre-sintered body 2A and the second pre-sintered body 3A and where the gap 4 opens.

[0041] The pre-sintering temperature T1 is desirably less than a temperature T1a (= T2 - 50) that is 50°C lower than the liquidus temperature T2 of the joining material 6 (T1 < T1a). Alternatively, the pre-sintering temperature T1 may be less than the solidus temperature T2a of the joining material 6 (T1 < T2a).

[0042] In this embodiment, pre-sintering is performed in a vacuum environment. However, pre-sintering may be performed under a nitrogen atmosphere or an argon atmosphere.

[0043] Thereafter, the first pre-sintered body 2A and the second pre-sintered body 2B are heated at a sintering temperature T3 higher than the liquidus temperature T2 of the joining material 6 (sintering). As shown in FIG. 2(c), after melting the joining material 6 and infiltrating it into the gap 4, the first pre-sintered body 2A and the second pre-sintered body 3A are respectively made into a first sintered body 11 and a second sintered body 12.

[0044] The sintering temperature T3 is a temperature lower than the liquidus temperature of the first Ni-based alloy and the liquidus temperature of the second Ni-based alloy. The sintering temperature T3 desirably exceeds a temperature T3a (= T2 + 15) that is 15°C higher than the liquidus temperature T2 of the joining material 6 (T3a < T3). Also, the sintering temperature T3 desirably is less than the solidus temperature of the first Ni-based alloy and the solidus temperature of the second Ni-based alloy.

[0045] In this embodiment, the first half of the sintering (at least the period during which the bonding material 6 melts and penetrates into the gap 4) is performed in a vacuum environment, and the second half of the sintering is performed in an argon atmosphere. However, the entire period of the sintering may be performed in a vacuum environment or an argon atmosphere.

[0046] When the first Ni-based alloy and the second Ni-based alloy are Hastelloy X, even if the sintering temperature T3 is lower than the solidus temperature of Hastelloy X, if the sintering is performed in a vacuum environment, the Ni-based alloy is likely to evaporate. On the other hand, if the sintering is performed in an argon atmosphere, evaporation of such a Ni-based alloy can be suppressed.

[0047] Thereafter, the first sintered body 11 and the second sintered body 12 are cooled. Thereby, as shown in FIG. 1, the composite sintered body 1 in which the first sintered body 11 and the second sintered body 12 are joined by the joining layer 13 can be obtained. After the production of the composite sintered body 1, HIP treatment and solution treatment may be performed on the composite sintered body 1 at a temperature lower than the liquidus temperature T2 or the solidus temperature T2a of the bonding material 6.

[0048] The joining layer 13 is formed by solidification of the bonding material 6. Solidification of the bonding material 6 is performed by diffusion of specific components in the molten bonding material 6 into the first sintered body 11 and the second sintered body 12, or by cooling the first sintered body 11 and the second sintered body 12.

[0049] FIG. 4 shows a cross section of the composite sintered body 1 obtained by the manufacturing method of this embodiment. The joining layer 13 is denser than the first sintered body 11 and the second sintered body 12, and its thickness is 200 μm or more (even if the gap 4 between the first green compact 2 and the second green compact 3 during the manufacturing process is 1 μm, due to melting of the bonding material 6 and diffusion of components).

[0050] Note that the thickness of the joining layer 13 is in a range where the concentration of a component (for example, Si) contained only in the joining layer 13 is high when component analysis is performed in a direction perpendicular to the joining layer 13 with respect to the cross section of the composite sintered body 1.

[0051] As described above, in the method for manufacturing the composite sintered body of the present embodiment, the joining layer 13 is formed between the first sintered body 11 and the second sintered body 12 by the solidification of the molten joining material 6. Therefore, the composite sintered body 1 in which the sintered bodies 11 and 12 made of Ni-based alloy are joined by the dense joining layer 13 can be obtained.

[0052] Further, in the present embodiment, since the joining material 6 is a mixture of the second powder made of the first Ni-based alloy or the second Ni-based alloy and the first powder made of the third Ni-based alloy, the composition of the joining layer 13 can be made closer to the composition of the first sintered body 11 or the second sintered body 12.

[0053] (Modification example) The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present invention.

[0054] For example, in the above-described embodiment, the first green compact 2 and the second green compact 3 are heated with the joining material 6 placed in the space 5 facing the first green compact 2 and the second green compact 3 to obtain the first semi-sintered body 2A and the second semi-sintered body 3A. However, after the production of the first green compact 2, it can be heated alone to obtain the first semi-sintered body 2A, and after the production of the second green compact 3, it can be heated alone to obtain the second semi-sintered body 3A. Then, the joining material 6 can be placed in the space 5 facing the first semi-sintered body 2A and the second semi-sintered body 3A, and the first semi-sintered body 2A and the second semi-sintered body 3A can be heated. However, with the method as in the above-described embodiment, the first semi-sintered body 2A and the second semi-sintered body 3A can be prepared simultaneously, and semi-sintering, melting of the joining material, and final sintering can be performed continuously.

[0055] Also, in the above-described embodiment, the first green compact 2 and the second green compact 3 are opposed to each other with the gap 4 therebetween, and the joining material 6 is placed in the space 5 facing the first green compact 2 and the second green compact 3 and where the gap 4 opens. However, the first green compact 2 and the second green compact 3 may be opposed to each other with the joining material 6 sandwiched therebetween, and in that state, the first green compact 2 and the second green compact 3 may be heated.

[0056] The first green compact 2 and the second green compact 3 are heated to become the first semi-sintered compact 2A and the second semi-sintered compact 3A respectively, whereby the first semi-sintered compact 2A and the second semi-sintered compact 3A will face each other with the bonding material 6 sandwiched therebetween. Thereafter, when the first semi-sintered compact 2A and the second semi-sintered compact 3A are heated, after the bonding material 6 melts, the first semi-sintered compact 2A and the second semi-sintered compact 3A become the first sintered compact 11 and the second sintered compact 12 respectively.

[0057] Alternatively, after the production of the first green compact 2, it may be heated alone to form the first semi-sintered compact 2A, and after the production of the second green compact 3, it may be heated alone to form the second semi-sintered compact 3A. Thereafter, the first semi-sintered compact 2A and the second semi-sintered compact 3A may be opposed to each other with the bonding material 6 sandwiched therebetween, and in this state, the first semi-sintered compact 2A and the second semi-sintered compact 3A may be heated.

[0058] (Summary) A method for manufacturing a composite sintered body according to one aspect of the present invention includes a step of preparing a first semi-sintered compact composed of powder made of a first Ni-based alloy, a step of preparing a second semi-sintered compact composed of powder made of a second Ni-based alloy, a step of opposing the first semi-sintered compact and the second semi-sintered compact with a predetermined gap therebetween, a step of installing a bonding material made of a Ni-based alloy having a liquidus temperature lower than that of the first Ni-based alloy and the second Ni-based alloy in a space where the gap opens and faces the first semi-sintered compact and the second semi-sintered compact, and a step of heating the first semi-sintered compact and the second semi-sintered compact after the installation of the bonding material to melt the bonding material and infiltrate it into the gap, and then making the first semi-sintered compact and the second semi-sintered compact into a first sintered compact and a second sintered compact respectively.

[0059] According to the above configuration, a bonding layer is formed between the first sintered compact and the second sintered compact as the molten bonding material solidifies. Therefore, a composite sintered body in which sintered bodies made of Ni-based alloys are joined by a dense bonding layer can be obtained.

[0060] The powder made of the first Ni-based alloy is formed into a predetermined shape to produce a first green compact, and the powder made of the second Ni-based alloy is formed into a predetermined shape to produce a second green compact. The first green compact and the second green compact are opposed to each other with the gap therebetween, and the bonding material is placed in the space where the gap opens and faces the first green compact and the second green compact. In this state, the first green compact and the second green compact may be heated at a temperature lower than the liquidus temperature of the bonding material, so that the first green compact and the second green compact are respectively used as a first semi-sintered body and a second semi-sintered body. According to this configuration, the first semi-sintered body and the second semi-sintered body can be prepared simultaneously, and semi-sintering, melting of the bonding material, and full sintering can be continuously performed.

[0061] Moreover, a method for manufacturing a composite sintered body from another aspect of the present invention includes a step of preparing a first semi-sintered body composed of a powder made of a first Ni-based alloy, a step of preparing a second semi-sintered body composed of a powder made of a second Ni-based alloy, and a step of opposing the first semi-sintered body and the second semi-sintered body to each other with a bonding material made of a Ni-based alloy having a liquidus temperature lower than those of the first Ni-based alloy and the second Ni-based alloy sandwiched therebetween, and a step of heating the first semi-sintered body and the second semi-sintered body to melt the bonding material and then using the first semi-sintered body and the second semi-sintered body as a first sintered body and a second sintered body, respectively.

[0062] According to the above configuration, a bonding layer is formed between the first sintered body and the second sintered body as the molten bonding material solidifies. Therefore, a composite sintered body in which sintered bodies made of Ni-based alloys are joined by a dense bonding layer can be obtained.

[0063] In a method for manufacturing a composite sintered body from another aspect, powder made of the first Ni-based alloy is formed into a predetermined shape to produce a first green compact, and powder made of the second Ni-based alloy is formed into a predetermined shape to produce a second green compact. The first green compact and the second green compact are opposed to each other with the bonding material sandwiched therebetween, and in this state, the first green compact and the second green compact are heated at a temperature lower than the liquidus temperature of the bonding material, so that the first green compact and the second green compact may be used as a first semi-sintered body and a second semi-sintered body, respectively. According to this configuration, the first semi-sintered body and the second semi-sintered body can be prepared simultaneously, and the semi-sintering process and the full-sintering process can be performed continuously.

[0064] For example, the first green compact and the second green compact may be produced by metal powder injection molding.

[0065] For example, the first Ni-based alloy and the second Ni-based alloy may have the same composition.

[0066] For example, each of the first Ni-based alloy and the second Ni-based alloy may contain, by mass percentage, 18.0 to 25.0% of Cr, 7.0 to 11.0% of Mo, 22.0% or less of Fe, 4.5% or less of Nb+Ta, and 3.0% or less of Co.

[0067] For example, the Ni-based alloy constituting the bonding material may contain, by mass percentage, 18.0 to 23.0% of Cr, 1.5 to 6.5% of Mo, 3.5 to 8.5% of Si, 13.0% or less of Fe, 2.5% or less of Nb+Ta, and 1.0% or less of Co.

[0068] The bonding material may be a mixture of first powder made of a third Ni-based alloy having a lower liquidus temperature than the first Ni-based alloy and the second Ni-based alloy, and second powder made of the first Ni-based alloy or the second Ni-based alloy. According to this configuration, the composition of the bonding layer can be made closer to the composition of the first sintered body or the second sintered body.

[0069] For example, the mixing ratio of the first powder and the second powder may be 40%:60% to 80%:20% by mass percentage.

[0070] The third Ni-based alloy may contain 16.0 to 22.0% of Cr and 8.0 to 12.0% of Si by mass percentage. According to this configuration, the Si in the third Ni-based alloy can lower the liquidus temperature of the bonding material, which is a mixture of the second powder made of the first Ni-based alloy or the second Ni-based alloy and the first powder made of the third Ni-based alloy, below the liquidus temperature of the first Ni-based alloy or the second Ni-based alloy.

[0071] The composite sintered body obtained by the above manufacturing method is a composite sintered body in which a first sintered body made of a first Ni-based alloy and a second sintered body made of a second Ni-based alloy are joined by a bonding layer made of a Ni-based alloy having a composition different from that of the first Ni-based alloy and the second Ni-based alloy. The bonding layer is denser than the first sintered body and the second sintered body, and the thickness of the bonding layer is 200 μm or more.

[0072] Further, the bonding material of the present invention is characterized by being made of a Ni-based alloy containing 18.0 to 23.0% of Cr, 1.5 to 6.5% of Mo, 3.5 to 8.5% of Si, 13.0% or less of Fe, 2.5% or less of Nb + Ta, and 1.0% or less of Co by mass percentage.

[0073] The bonding material having the above configuration can be suitably used for joining sintered bodies made of a Ni-based alloy containing 18.0 to 25.0% of Cr, 7.0 to 11.0% of Mo, 22.0% or less of Fe, 4.5% or less of Nb + Ta, and 3.0% or less of Co.

Explanation of Symbols

[0074] 1 Composite sintered body 11 First sintered body 12 Second sintered body 13 Bonding layer 2 First unsintered body 2A First presintered body 3 Second unsintered body 3A Second Sintered Body 4 Gap 5 Space

Claims

1. A step of preparing a first green compact composed of powder made of a first Ni-based alloy; A step of preparing a second green compact composed of powder made of a second Ni-based alloy; A step of opposing the first green compact and the second green compact with a predetermined gap therebetween; A step of installing a bonding material made of a Ni-based alloy having a liquidus temperature lower than that of the first Ni-based alloy and the second Ni-based alloy in a space where the gap opens and that faces the first green compact and the second green compact; After installing the bonding material, heating the first green compact and the second green compact to melt the bonding material and infiltrate it into the gap, and then forming the first green compact and the second green compact into a first sintered body and a second sintered body, respectively; A method for manufacturing a composite sintered body, including the above steps.

2. The method for manufacturing a composite sintered body according to claim 1, wherein the powder made of the first Ni-based alloy is formed into a predetermined shape to produce a first green body, and the powder made of the second Ni-based alloy is formed into a predetermined shape to produce a second green body. The first green body and the second green body are opposed to each other with the gap therebetween, and the bonding material is installed in a space where the gap opens and that faces the first green body and the second green body. In this state, the first green body and the second green body are heated to a temperature lower than the liquidus temperature of the bonding material to form the first green body and the second green body into a first green compact and a second green compact, respectively.

3. A step of preparing a first green compact composed of powder made of a first Ni-based alloy; A step of preparing a second green compact composed of powder made of a second Ni-based alloy; A step of opposing the first green compact and the second green compact with a bonding material made of a Ni-based alloy having a liquidus temperature lower than that of the first Ni-based alloy and the second Ni-based alloy sandwiched therebetween; A step of heating the first green compact and the second green compact to melt the bonding material, and then forming the first green compact and the second green compact into a first sintered body and a second sintered body, respectively; A method for manufacturing a composite sintered body, including the above steps.

4. The powder made of the first Ni-based alloy is formed into a predetermined shape to produce a first green compact, and the powder made of the second Ni-based alloy is formed into a predetermined shape to produce a second green compact. The first green compact and the second green compact are opposed to each other with the bonding material sandwiched therebetween, and in this state, the first green compact and the second green compact are heated at a temperature lower than the liquidus temperature of the bonding material, whereby the first green compact and the second green compact are respectively made into a first semi-sintered compact and a second semi-sintered compact. The method for manufacturing a composite sintered body according to claim 3.

5. The method for manufacturing a composite sintered body according to claim 2 or 4, wherein the first green compact and the second green compact are produced by metal powder injection molding.

6. The method for manufacturing a composite sintered body according to any one of claims 1 to 3, wherein the first Ni-based alloy and the second Ni-based alloy have the same composition.

7. Each of the first Ni-based alloy and the second Ni-based alloy contains, by mass percentage, 18.0 to 25.0% of Cr, 7.0 to 11.0% of Mo, 22.0% or less of Fe, 4.5% or less of Nb + Ta, and 3.0% or less of Co. The method for manufacturing a composite sintered body according to any one of claims 1 to 6.

8. The Ni-based alloy constituting the bonding material contains, by mass percentage, 18.0 to 23.0% of Cr, 1.5 to 6.5% of Mo, 3.5 to 8.5% of Si, 13.0% or less of Fe, 2.5% or less of Nb + Ta, and 1.0% or less of Co. The method for manufacturing a composite sintered body according to any one of claims 1 to 7.

9. The bonding material is a mixture of a first powder made of a third Ni-based alloy having a lower liquidus temperature than the first Ni-based alloy and the second Ni-based alloy, and a second powder made of the first Ni-based alloy or the second Ni-based alloy. The method for manufacturing a composite sintered body according to any one of claims 1 to 8.

10. The mixing ratio of the first powder and the second powder is 40%:60% to 80%:20% by mass percentage. The method for manufacturing a composite sintered body according to claim 9.

11. The third Ni-based alloy contains, by mass percentage, 16.0 to 22.0% of Cr and 8.0 to 12.0% of Si. The method for manufacturing a composite sintered body according to claim 9 or 10.

12. A composite sintered body in which a first sintered body made of a first Ni-based alloy and a second sintered body made of a second Ni-based alloy are joined by a joining layer made of a Ni-based alloy having a composition different from that of the first Ni-based alloy and the second Ni-based alloy, each of the first Ni-based alloy and the second Ni-based alloy contains, by mass percentage, 18.0 to 25.0% Cr, 7.0 to 11.0% Mo, 22.0% or less Fe, 4.5% or less Nb+Ta, and 3.0% or less Co, The composite sintered body, wherein the joining layer is denser than the first sintered body and the second sintered body, and the thickness of the joining layer is 200 μm or more.

Images