US-12623283-B2 - Composite sintered body, method of producing the same, and joining material

US12623283B2US 12623283 B2US12623283 B2US 12623283B2US-12623283-B2

Abstract

A first pre-sintered body composed of a powder made of a first Ni-based alloy is prepared, and a second pre-sintered body composed of a powder made of a second Ni-based alloy is prepared. Subsequently, the first and second pre-sintered bodies are positioned to face each other across a predetermined gap, and a joining material made of a Ni-based alloy having a lower liquidus temperature than the first and second Ni-based alloys is placed in a space that adjoins the first and second pre-sintered bodies and to which the gap opens. After the placing of the joining material, the first and second pre-sintered bodies are heated to melt the joining material, fill the gap with the molten joining material, and subsequently turn the first and second pre-sintered bodies into first and second sintered bodies, respectively.

Inventors

Shinya HIBINO
Ryutaro OKADA
Yoshimichi NOMURA
Kazushige FUJIMITSU

Assignees

KAWASAKI JUKOGYO KABUSHIKI KAISHA

Dates

Publication Date: 20260512
Application Date: 20220307
Priority Date: 20210312

Claims (11)

1 . A method for producing a composite sintered body, comprising: preparing a first pre-sintered body composed of a powder made of a first Ni-based alloy; preparing a second pre-sintered body composed of a powder made of a second Ni-based alloy; positioning the first and second pre-sintered bodies such that the first and second pre-sintered bodies face each other across a predetermined gap; placing a joining material in a space that adjoins the first and second pre-sintered bodies and to which the gap opens, the joining material being made of a Ni-based alloy having a lower liquidus temperature than the first and second Ni-based alloys; and after the placing of the joining material, heating the first and second pre-sintered bodies to melt the joining material, fill the gap with the molten joining material, and subsequently turn the first and second pre-sintered bodies into first and second sintered bodies, respectively.
2 . The method according to claim 1 , wherein a first unsintered body is fabricated by shaping the powder made of the first Ni-based alloy into a predetermined shape, a second unsintered body is fabricated by shaping the powder made of the second Ni-based alloy into a predetermined shape, the first and second unsintered bodies are positioned to face each other across the gap, the joining material is placed in a space that adjoins the first and second unsintered bodies and to which the gap opens, and in a state where the joining material is placed in the space, the first and second unsintered bodies are heated at a temperature lower than the liquidus temperature of the joining material to turn the first and second unsintered bodies into the first and second pre-sintered bodies, respectively.
3 . A method for producing a composite sintered body, comprising: preparing a first pre-sintered body composed of a powder made of a first Ni-based alloy; preparing a second pre-sintered body composed of a powder made of a second Ni-based alloy; positioning the first and second pre-sintered bodies such that the first and second pre-sintered bodies face each other, with a joining material interposed between the first and second pre-sintered bodies, the joining material being made of a Ni-based alloy having a lower liquidus temperature than the first and second Ni-based alloys; and heating the first and second pre-sintered bodies to melt the joining material and subsequently turn the first and second pre-sintered bodies into first and second sintered bodies, respectively.
4 . The method according to claim 3 , wherein a first unsintered body is fabricated by shaping the powder made of the first Ni-based alloy into a predetermined shape, a second unsintered body is fabricated by shaping the powder made of the second Ni-based alloy into a predetermined shape, the first and second unsintered bodies are positioned to face each other, with the joining material interposed between the first and second unsintered bodies, and in a state where the joining material is interposed between the first and second unsintered bodies, the first and second unsintered bodies are heated at a temperature lower than the liquidus temperature of the joining material to turn the first and second unsintered bodies into the first and second pre-sintered bodies, respectively.
5 . The method according to claim 2 , wherein the first and second unsintered bodies are fabricated by metal injection molding.
6 . The method according to claim 1 , wherein the first and second Ni-based alloys have the same composition.
7 . The method according to claim 1 , wherein each of the first and second Ni-based alloys contains, in percent by mass, 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.
8 . The method according to claim 1 , wherein the Ni-based alloy constituting the joining material contains, in percent by mass, 18.0 to 23.0% Cr, 1.5 to 6.5% Mo, 3.5 to 8.5% Si, 13.0% or less Fe, 2.5% or less Nb+Ta, and 1.0% or less Co.
9 . The method according to claim 1 , wherein the joining material is a mixture of a first powder made of a third Ni-based alloy having a lower liquidus temperature than the first and second Ni-based alloys and a second powder made of the first or second Ni-based alloy.
10 . The method according to claim 9 , wherein a mixing ratio of the first powder to the second powder is from 40%:60% to 80%:20% in percent by mass.
11 . The method according to claim 9 , wherein the third Ni-based alloy contains, in percent by mass, 16.0 to 22.0% Cr and 8.0 to 12.0% Si.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This is a U.S. National Phase Application of PCT/JP2022/009780 filed on Mar. 7, 2022, which designates the United States and claims priority to Japanese Patent Application No. 2021-040241, filed on Mar. 12, 2021, the entire contents of which are incorporated herein by reference. TECHNICAL FIELD The present invention relates to a composite sintered body production method, a composite sintered body obtained by the production method, and a joining material used in the production method. BACKGROUND ART It is conventional practice to produce a composite sintered body by joining sintered bodies together by brazing or welding. Each of the sintered bodies is obtained, for example, by fabricating an unsintered body containing a metal powder and a binder through metal injection molding and then by debindering and sintering the unsintered body. However, in the composite sintered body production method as described above, a joining step needs to be performed after fabrication of the sintered bodies. To address this issue, Patent Literature 1 discloses a method in which sintering and joining are simultaneously performed to produce a composite sintered body. Specifically, in the composite sintered body production method disclosed in Patent Literature 1, a first unsintered body and a second unsintered body are fabricated by metal injection molding and, after that, the first and second unsintered bodies are bonded by a paste composed of a metal powder and an organic binder and then are debindered and sintered. CITATION LIST Patent Literature PTL 1: Japanese Laid-Open Patent Application Publication No. 2004-285466 SUMMARY OF INVENTION Technical Problem However, in the composite sintered body production method disclosed in Patent Literature 1, the joining layer in the composite sintered body produced is porous like the sintered bodies located on both sides of the joining layer because of the use of the paste containing a metal powder. In this regard, the joining layer in the composite sintered body is desired to be dense as in the case of conventional brazing. Patent Literature 1 describes examples where a powder made of stainless steel is used in metal injection molding. However, there is a demand for joining of sintered bodies each of which is made of a Ni-based alloy. An object of the present invention is therefore to provide: a composite sintered body production method for obtaining a composite sintered body including sintered bodies each of which is made of a Ni-based alloy and which are joined together by a dense joining layer; and a composite sintered body obtained by the production method. Another object of the present invention is to provide a joining material suitable for use in joining of sintered bodies each of which is made of a specific Ni-based alloy. Solution to Problem To solve the above problems, a method for producing a composite sintered body according to one aspect of the present invention includes: preparing a first pre-sintered body composed of a powder made of a first Ni-based alloy; preparing a second pre-sintered body composed of a powder made of a second Ni-based alloy: positioning the first and second pre-sintered bodies such that the first and second pre-sintered bodies face each other across a predetermined gap; placing a joining material in a space that adjoins the first and second pre-sintered bodies and to which the gap opens, the joining material being made of a Ni-based alloy having a lower liquidus temperature than the first and second Ni-based alloys; and after the placing of the joining material, heating the first and second pre-sintered bodies to melt the joining material, fill the gap with the molten joining material, and subsequently turn the first and second pre-sintered bodies into first and second sintered bodies, respectively. The “pre-sintered body” refers to a powder compact that is obtained by heating an unsintered body formed by shaping a powder into a predetermined shape and that has an open porosity of more than 2% to 20% (the unsintered body is a powder compact in which the particles of the powder are bonded together and which has an open porosity of more than 20% or a powder compact in which the spaces between the particles of the powder are filled with a binder). The “sintered body” refers to a powder compact that is obtained by heating the pre-sintered body and that has an open porosity of 2% or less. The open porosity of a specimen is a value determined by dividing the total volume of open pores (pores inside the specimen that open on the specimen surface (pores inside the specimen that do not open on the specimen surface are closed pores) by the apparent volume of the specimen (volume determined from the dimensions of the specimen). For example, assuming that the density p of a volume surrounded by the surface of the specimen and a continuous surface defined by the open pores is measured, for example, by Archimedes' method, the o