US20170291220A1 - Metal powder for powder metallurgy, compound, granulated powder, sintered body, and heat resistant component - Google Patents

Metal powder for powder metallurgy, compound, granulated powder, sintered body, and heat resistant component Download PDF

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US20170291220A1
US20170291220A1 US15/477,336 US201715477336A US2017291220A1 US 20170291220 A1 US20170291220 A1 US 20170291220A1 US 201715477336 A US201715477336 A US 201715477336A US 2017291220 A1 US2017291220 A1 US 2017291220A1
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mass
powder
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sintered body
metal powder
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Hidefumi Nakamura
Taku Kawasaki
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Seiko Epson Corp
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Seiko Epson Corp
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    • B22F1/0014—
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C1/00—Making non-ferrous alloys
    • C22C1/04—Making non-ferrous alloys by powder metallurgy
    • C22C1/0433—Nickel- or cobalt-based alloys
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/05—Metallic powder characterised by the size or surface area of the particles
    • B22F1/052—Metallic powder characterised by the size or surface area of the particles characterised by a mixture of particles of different sizes or by the particle size distribution
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/14—Treatment of metallic powder
    • B22F1/148—Agglomerating
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C19/00—Alloys based on nickel or cobalt
    • C22C19/03—Alloys based on nickel or cobalt based on nickel
    • C22C19/05—Alloys based on nickel or cobalt based on nickel with chromium
    • C22C19/051—Alloys based on nickel or cobalt based on nickel with chromium and Mo or W
    • C22C19/055—Alloys based on nickel or cobalt based on nickel with chromium and Mo or W with the maximum Cr content being at least 20% but less than 30%
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C19/00—Alloys based on nickel or cobalt
    • C22C19/03—Alloys based on nickel or cobalt based on nickel
    • C22C19/05—Alloys based on nickel or cobalt based on nickel with chromium
    • C22C19/051—Alloys based on nickel or cobalt based on nickel with chromium and Mo or W
    • C22C19/056—Alloys based on nickel or cobalt based on nickel with chromium and Mo or W with the maximum Cr content being at least 10% but less than 20%
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C19/00—Alloys based on nickel or cobalt
    • C22C19/07—Alloys based on nickel or cobalt based on cobalt
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C30/00—Alloys containing less than 50% by weight of each constituent
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F2301/00—Metallic composition of the powder or its coating
    • B22F2301/15—Nickel or cobalt
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F2304/00—Physical aspects of the powder
    • B22F2304/10—Micron size particles, i.e. above 1 micrometer up to 500 micrometer

Definitions

  • the present invention relates to a metal powder for powder metallurgy, a compound, a granulated powder, a sintered body, and a heat resistant component.
  • a composition containing a metal powder and a binder is molded into a desired shape to obtain a molded body, and the obtained molded body is degreased and sintered, whereby a sintered body is produced.
  • an atomic diffusion phenomenon occurs among particles of the metal powder, whereby the molded body is gradually densified, resulting in sintering.
  • JP-A-8-302463 proposes a target for a magneto-optical recording medium obtained by sintering an alloy powder containing a rare earth metal at 15 to 30 at %, with the remainder consisting of a transition metal. It is disclosed that in this target, Ti, V, Y, Nb, Ta, or the like is added at 15 at % or less as an element which improve corrosion resistance. According to this, in the invention described in Patent Document 1, improvement of the mechanical strength of the target is achieved.
  • JP-A-2012-87416 proposes a metal powder for powder metallurgy which contains Zr and Si, with the remainder consisting of at least one element selected from the group consisting of Fe, Co, and Ni, and inevitable elements. According to such a metal powder for powder metallurgy, the sinterability is enhanced, whereby a sintered body having a high density can be easily produced. Such a sintered body is getting widely used in various machine components, structural components, etc. recently.
  • a sintered body is further subjected to an additional treatment such as a hot isostatic pressing treatment (HIP treatment) to increase the density, however, the workload is significantly increased, and also an increase in the cost is inevitable.
  • HIP treatment hot isostatic pressing treatment
  • An advantage of some aspects of the invention is to provide a metal powder for powder metallurgy, a compound, and a granulated powder, each of which is capable of producing a sintered body having a high density, and a sintered body and a heat resistant component, each of which has a high density.
  • a metal powder for powder metallurgy according to an aspect of the invention contains Co as a principal component, Cr in a proportion of 10 mass % or more and 25 mass % or less, Ni in a proportion of 5 mass % or more and 40 mass % or less, at least one of Mo and W in a proportion of 2 mass % or more and 20 mass % or less in total, Si in a proportion of 0.3 mass % or more and 1.5 mass % or less, and C in a proportion of 0.05 mass % or more and 0.8 mass % or less, wherein when one element selected from the group consisting of Ti, V, Y, Zr, Nb, Hf, and Ta is defined as a first element, and one element selected from the group consisting of Ti, V, Y, Zr, Nb, Hf, and Ta, and having a higher group number in the periodic table than that of the first element or having the same group number in the periodic table as that of the first element and a higher period number in the periodic table than that of the first element is
  • the alloy composition is optimized so that the densification during sintering of the metal powder for powder metallurgy can be enhanced.
  • a metal powder for powder metallurgy capable of producing a sintered body having a high density is obtained without performing an additional treatment.
  • Fe is further contained in a proportion of 0.5 mass % or more and 5 mass % or less.
  • X1 a value obtained by dividing the content of the first element by the mass number of the first element
  • X2 a value obtained by dividing the content of the second element by the mass number of the second element
  • the sum of the content of the first element and the content of the second element is 0.05 mass % or more and 0.6 mass % or less.
  • the metal powder for powder metallurgy it is preferred that the metal powder has an average particle diameter of 0.5 ⁇ m or more and 30 ⁇ m or less.
  • a compound according to an aspect of the invention includes the metal powder for powder metallurgy according to the aspect of the invention.
  • a granulated powder according to an aspect of the invention includes the metal powder for powder metallurgy according to the aspect of the invention.
  • a sintered body according to an aspect of the invention contains Co as a principal component, Cr in a proportion of 10 mass % or more and 25 mass % or less, Ni in a proportion of 5 mass % or more and 40 mass % or less, at least one of Mo and W in a proportion of 2 mass % or more and 20 mass % or less in total, Si in a proportion of 0.3 mass % or more and 1.5 mass % or less, and C in a proportion of 0.05 mass % or more and 0.8 mass % or less, wherein when one element selected from the group consisting of Ti, V, Y, Zr, Nb, Hf, and Ta is defined as a first element, and one element selected from the group consisting of Ti, V, Y, Zr, Nb, Hf, and Ta, and having a higher group number in the periodic table than that of the first element or having the same group number in the periodic table as that of the first element and a higher period number in the periodic table than that of the first element is defined as a second element
  • a heat resistant component according to an aspect of the invention includes the sintered body according to the aspect of the invention.
  • FIG. 1 is a side view showing a nozzle vane for a turbocharger (a view when a blade section is viewed in a plan view) to which a first embodiment of a heat resistant component according to the invention is applied.
  • FIG. 2 is a plan view of the nozzle vane shown in FIG. 1 .
  • FIG. 3 is a rear view of the nozzle vane shown in FIG. 1 .
  • FIG. 4 is a perspective view showing a compressor blade to which a second embodiment of a heat resistant component according to the invention is applied.
  • a sintered body having a desired shape can be obtained by molding a composition containing a metal powder for powder metallurgy and a binder into a desired shape, followed by degreasing and sintering.
  • a powder metallurgy technique an advantage that a sintered body with a complicated and fine shape can be produced in a near-net shape (a shape close to a final shape) as compared with the other metallurgy techniques is obtained.
  • the obtained sintered body was further subjected to an additional treatment such as a hot isostatic pressing treatment (HIP treatment) to increase the density in some cases.
  • an additional treatment such as a hot isostatic pressing treatment (HIP treatment) to increase the density in some cases.
  • HIP treatment hot isostatic pressing treatment
  • such an additional treatment requires much time, labor, and cost, and therefore becomes an obstacle to the expansion of the application of the sintered body.
  • the present inventors have made intensive studies to find conditions for obtaining a sintered body having a high density without performing an additional treatment. As a result, they found that the density of a sintered body can be increased by optimizing the composition of an alloy which forms a metal powder, and thus completed the invention.
  • the metal powder for powder metallurgy according to the invention is characterized by containing Co as a principal component, Cr in a proportion of 10 mass % or more and 25 mass % or less, Ni in a proportion of 5 mass % or more and 40 mass % or less, at least one of Mo and W in a proportion of 2 mass % or more and 20 mass % or less in total, Si in a proportion of 0.3 mass % or more and 1.5 mass % or less, C in a proportion of 0.05 mass % or more and 0.8 mass % or less, the below-mentioned first element in a proportion of 0.01 mass % or more and 0.5 mass % or less, and the below-mentioned second element in a proportion of 0.01 mass % or more and 0.5 mass % or less.
  • the densification during sintering can be particularly enhanced.
  • a sintered body having a high density can be produced without performing
  • a sintered body having excellent mechanical properties By increasing the density of a sintered body, a sintered body having excellent mechanical properties is obtained.
  • Such a sintered body can be widely applied also to, for example, machine components, structural components, and the like, to which an external force (load) is applied.
  • the first element is one element selected from the group consisting of the following seven elements: Ti, V, Y, Zr, Nb, Hf, and Ta
  • the second element is one element selected from the group consisting of the above-mentioned seven elements and having a higher group number in the periodic table than that of the first element or one element selected from the group consisting of the above-mentioned seven elements and having the same group number in the periodic table as that of the first element and a higher period number in the periodic table than that of the first element.
  • metal powder for powder metallurgy is sometimes simply referred to as “metal powder”.
  • Cr chromium
  • Cr chromium
  • chromium is an element which imparts corrosion resistance and oxidation resistance to a sintered body to be produced.
  • the metal powder containing Cr By using the metal powder containing Cr, a sintered body capable of maintaining high mechanical properties over a long period of time is obtained. Due to this, for example, a structural component capable of maintaining its function even if it is exposed to a high temperature can be realized.
  • the content of Cr in the metal powder is set to 10 mass % or more and 25 mass % or less, but is set to preferably 15 mass % or more and 24 mass % or less, more preferably 18 mass % or more and 23 mass % or less.
  • the content of Cr is less than the above lower limit, the corrosion resistance of a sintered body to be produced is insufficient depending on the overall composition, and the heat resistance is deteriorated.
  • the content of Cr exceeds the above upper limit, the sinterability is deteriorated depending on the overall composition, and therefore, it becomes difficult to increase the density of the sintered body. Due to this, it becomes difficult to enhance the corrosion resistance (heat resistance) of a sintered body to be produced.
  • Ni decreases the speed of progress of pitting corrosion or erosion of a chromium oxide layer formed on the surface of a sintered body and enhances the strength (heat resistance) under a high temperature of the sintered body when it is added along with Cr. Further, by achieving austenitization, the crystalline phase in the sintered body is stabilized even under a high temperature, and therefore, also from such a viewpoint, the heat resistance of the sintered body can be achieved.
  • the content of Ni in the metal powder is set to 5 mass % or more and 40 mass % or less, but is set to preferably 7 mass % or more and 37 mass % or less, more preferably 9 mass % or more and 36 mass % or less.
  • the content of Ni is less than the above lower limit, the corrosion resistance or heat resistance is deteriorated.
  • the content of Ni exceeds the above upper limit, the content of Cr or Co is relatively decreased, and therefore, the corrosion resistance or heat resistance is deteriorated.
  • Mo (molybdenum) and W (tungsten) each enhance the heat resistance of a sintered body to be produced.
  • Mo and W each form a carbide by binding to C, and it is considered that this carbide enhances the high-temperature strength. Further, by using Mo and W in combination with Cr, the mechanical strength and hardness of the sintered body even at a high temperature can be increased. Therefore, the heat resistance of the sintered body can be enhanced.
  • the metal powder contains at least one of Mo and W.
  • the sum of the contents of Mo and W in the metal powder is set to 2 mass % or more and 20 mass % or less, but is set to preferably 5 mass % or more and 18 mass % or less, more preferably 7 mass % or more and 16 mass % or less.
  • the heat resistance of a sintered body may not be able to be sufficiently enhanced.
  • the sum of the contents of Mo and W exceeds the above upper limit, many intermetallic compounds are formed, and therefore, the sintered body may be embrittled.
  • the ratio of Mo to W is not particularly limited, but is preferably 10:90 or more and 90:10 or less, more preferably 20:80 or more and 80:20 or less by a mass ratio.
  • Si acts to enhance the corrosion resistance and mechanical properties of a sintered body to be produced.
  • Si acts to enhance the corrosion resistance and mechanical properties of a sintered body to be produced.
  • Si silicon
  • an oxide of a metal element such as Co is reduced, part of Si is oxidized to forma silicon oxide.
  • the silicon oxide include SiO and SiO 2 .
  • Such a silicon oxide suppresses a significant increase in the size of a metal crystal when the metal crystal grows during the sintering of the metal powder. Due to this, in an alloy to which Si is added, the particle diameter of the metal crystal is kept small, and thus, the corrosion resistance and mechanical properties of the sintered body can be further enhanced.
  • the content of Si in the metal powder is set to 0.3 mass % or more and 1.5 mass % or less, but is set to preferably 0.4 mass % or more and 1.2 mass % or less, more preferably 0.5 mass % or more and 1 mass % or less.
  • the content of Si is less than the above lower limit, the amount of silicon oxide is too small depending on the firing conditions, and therefore, the size of a metal crystal may be liable to increase during the sintering of the metal powder.
  • the content of Si exceeds the above upper limit, the amount of silicon oxide is too large depending on the firing conditions, and therefore, a region where silicon oxide is continuously distributed in space is liable to be generated. In this region, the possibility of decreasing the mechanical properties is high.
  • C carbon
  • the first element and the second element each form a carbide by binding to C.
  • the dispersed deposit serves as an obstacle to inhibit the significant growth of crystal grains, and therefore, a variation in the size of crystal grains is suppressed. Accordingly, it becomes difficult to generate pores in a sintered body, and also the increase in the size of crystal grains is prevented, and thus, a sintered body having a high density and excellent mechanical properties is obtained.
  • the content of C in the metal powder is set to 0.05 mass % or more and 0.8 mass % or less, but is set to preferably 0.2 mass % or more and 0.6 mass % or less, more preferably 0.3 mass % or more and 0.5 mass % or less.
  • the content of C is less than the above lower limit, crystal grains are liable to grow depending on the overall composition, and therefore, the mechanical properties of the sintered body become insufficient.
  • the content of C exceeds the above upper limit, the amount of C is too large depending on the overall composition, and therefore, the sinterability is deteriorated instead.
  • the first element and the second element each deposit a carbide or an oxide (hereinafter also collectively referred to as “carbide or the like”). It is considered that this deposited carbide or the like inhibits the significant growth of crystal grains when the metal powder is sintered. As a result, as described above, it becomes difficult to generate pores in a sintered body, and also the increase in the size of crystal grains is prevented, and thus, a sintered body having a high density and excellent mechanical properties is obtained.
  • the deposited carbide or the like promotes the accumulation of silicon oxide at a crystal grain boundary, and as a result, the sintering is promoted and the density is increased while preventing the increase in the size of crystal grains.
  • the first element and the second element are two elements selected from the group consisting of Ti, V, Y, Zr, Nb, Hf, and Ta, but preferably include an element belonging to group IIIA or group IVA in the long periodic table (Ti, Y, Zr, or Hf).
  • group IIIA or group IVA in the long periodic table (Ti, Y, Zr, or Hf).
  • the first element is only required to be one element selected from the group consisting of Ti, V, Y, Zr, Nb, Hf, and Ta as described above, but is preferably an element belonging to group IIIA or group IVA in the long periodic table in the above-mentioned group.
  • An element belonging to group IIIA or group IVA in the above-mentioned group removes oxygen contained as an oxide in the metal powder and therefore can particularly enhance the sinterability of the metal powder. According to this, the concentration of oxygen remaining in the crystal grains after sintering can be decreased. As a result, the content of oxygen in the sintered body can be decreased, and the density can be increased. Further, these elements are elements having high activity, and therefore are considered to cause rapid atomic diffusion.
  • this atomic diffusion acts as a driving force, and thereby a distance between particles of the metal powder is efficiently decreased and a neck is formed between the particles, so that the densification of a molded body is promoted. As a result, the density of the sintered body can be further increased.
  • the second element is only required to be one element selected from the group consisting of Ti, V, Y, Zr, Nb, Hf, and Ta and different from the first element as described above, but is preferably an element belonging to group VA in the long periodic table in the above-mentioned group.
  • An element belonging to group VA in the above-mentioned group particularly efficiently deposits the above-mentioned carbide or the like, and therefore, can efficiently inhibit the significant growth of crystal grains during sintering. As a result, the formation of fine crystal grains is promoted, and thus, the density of the sintered body can be increased and also the mechanical properties of the sintered body can be enhanced.
  • the metal powder containing such a first element and a second element enables the production of a sintered body having a particularly high density.
  • Zr is a ferrite forming element, and therefore deposits a body-centered cubic lattice phase.
  • This body-centered cubic lattice phase has more excellent sinterability than the other crystal lattice phases, and therefore contributes to the densification of a sintered body.
  • the content of the first element in the metal powder is set to 0.01 mass % or more and 0.5 mass % or less, but is set to preferably 0.03 mass % or more and 0.2 mass % or less, more preferably 0.05 mass % or more and 0.1 mass % or less.
  • the content of the first element is less than the above lower limit, the effect of the addition of the first element is weakened depending on the overall composition, and therefore, the density of a sintered body to be produced is not sufficiently increased.
  • the content of the first element exceeds the above upper limit, the amount of the first element is too large depending on the overall composition, and therefore, the ratio of the above-mentioned carbide or the like is too high, and the densification is deteriorated instead.
  • the content of the second element in the sintered body is set to 0.01 mass % or more and 0.5 mass % or less, but is set to preferably 0.03 mass % or more and 0.2 mass % or less, more preferably 0.05 mass % or more and 0.1 mass % or less.
  • the content of the second element is less than the above lower limit, the effect of the addition of the second element is weakened depending on the overall composition, and therefore, the density of a sintered body to be produced is not sufficiently increased.
  • the content of the second element exceeds the above upper limit, the amount of the second element is too large depending on the overall composition, and therefore, the ratio of the above-mentioned carbide or the like is too high, and the densification is deteriorated instead.
  • each of the first element and the second element deposits a carbide or the like, however, in the case where an element belonging to group IIIA or group IVA is selected as the first element as described above and an element belonging to group VA is selected as the second element as described above, it is presumed that when the metal powder is sintered, the timing when a carbide or the like of the first element is deposited and the timing when a carbide or the like of the second element is deposited differ from each other. It is considered that due to the difference in timing when a carbide or the like is deposited in this manner, sintering gradually proceeds so that the generation of pores is prevented, and thus, a dense sintered body is obtained. That is, it is considered that by the existence of both of the carbide or the like of the first element and the carbide or the like of the second element, the increase in the size of crystal grains can be suppressed while increasing the density of the sintered body.
  • the ratio of the content of the first element to the content of the second element in consideration of the mass number of the element selected as the first element and the mass number of the element selected as the second element.
  • the ratio (X1/X2) of the index X1 to the index X2 is preferably 0.3 or more and 3 or less, more preferably 0.5 or more and 2 or less, further more preferably 0.75 or more and 1.3 or less.
  • the ratio X1/X2 By setting the ratio X1/X2 within the above range, a difference between the timing when a carbide or the like of the first element is deposited and the timing when a carbide or the like of the second element is deposited can be optimized. According to this, pores remaining in a molded body can be eliminated as if they were swept out sequentially from the inside, and therefore, pores generated in a sintered body can be minimized. Therefore, by setting the ratio X1/X2 within the above range, a sintered body having a high density and excellent mechanical properties can be obtained.
  • the balance between the number of atoms of the first element and the number of atoms of the second element is optimized, and therefore, an effect brought about by the first element and an effect brought about by the second element are synergistically exhibited, and thus, a sintered body having a particularly high density can be obtained.
  • the ratio E1/E2 of the content (mass %) of the first element E1 to the content (mass %) of the second element E2 is also calculated.
  • E1/E2 is preferably 0.29 or more and 2.95 or less, more preferably 0.49 or more and 1.96 or less.
  • E1/E2 is preferably 0.58 or more and 5.76 or less, more preferably 0.96 or more and 3.84 or less.
  • E1/E2 is preferably 0.15 or more and 1.55 or less, more preferably 0.26 or more and 1.03 or less.
  • E1/E2 is preferably 0.15 or more and 1.54 or less, more preferably 0.26 or more and 1.03 or less.
  • E1/E2 is preferably 0.29 or more and 2.87 or less, more preferably 0.48 or more and 1.91 or less.
  • E1/E2 is preferably 0.16 or more and 1.64 or less, more preferably 0.27 or more and 1.10 or less.
  • E1/E2 is preferably 0.16 or more and 1.58 or less, more preferably 0.26 or more and 1.05 or less.
  • E1/E2 is preferably 0.15 or more and 1.51 or less, more preferably 0.25 or more and 1.01 or less.
  • E1/E2 is preferably 0.54 or more and 5.38 or less, more preferably 0.90 or more and 3.58 or less.
  • E1/E2 can be calculated in the same manner as described above.
  • E1+E2 is preferably 0.05 mass % or more and 0.6 mass % or less, more preferably 0.10 mass % or more and 0.48 mass % or less, further more preferably 0.12 mass % or more and 0.24 mass % or less.
  • (E1+E2)/Si is preferably 0.03 or more and 2 or less, more preferably 0.05 or more and 1 or less, further more preferably 0.1 or more and 0.5 or less.
  • the carbide or the like of the first element and the carbide or the like of the second element act as “nuclei”, and therefore, silicon oxide is accumulated at a crystal grain boundary in the sintered body.
  • silicon oxide is accumulated at a crystal grain boundary in the sintered body.
  • the deposited silicon oxide easily moves to the triple point of a crystal grain boundary during the accumulation, and therefore, the crystal growth is suppressed at this point (a flux pinning effect). As a result, the significant growth of crystal grains is suppressed, and thus, a sintered body having finer crystals is obtained. Such a sintered body has particularly high mechanical properties.
  • (E1+E2)/C is preferably 0.05 or more and 3 or less, more preferably 0.1 or more and 2 or less, further more preferably 0.2 or more and 1 or less.
  • the metal powder it is only necessary that two elements selected from the group consisting of Ti, V, Y, Zr, Nb, Hf, and Ta are contained, however, an element which is selected from this group and is different from the two elements may be further contained. That is, in the metal powder, three or more elements selected from the above-mentioned group may be contained. According to this, although it varies depending on the elements to be combined, the above-mentioned effect can be further enhanced.
  • the metal powder for powder metallurgy according to the invention may contain, other than the above-mentioned elements, at least one element of Fe, B, Mn, and S as needed. These elements may be inevitably contained therein.
  • Fe (iron) imparts high mechanical properties to a sintered body to be produced.
  • the content of Fe in the metal powder is not particularly limited, but is preferably 0.5 mass % or more and 5 mass % or less, more preferably 0.8 mass % or more and 3 mass % or less, further more preferably 1 mass % or more and 2.5 mass % or less.
  • the content of Fe When the content of Fe is less than the above lower limit, the mechanical properties of a sintered body may not be able to be sufficiently enhanced depending on the overall composition. On the other hand, when the content of Fe exceeds the above upper limit, the corrosion resistance or oxidation resistance of a sintered body may be deteriorated depending on the overall composition.
  • B (boron) strengthens the crystal grain boundary and improves the high-temperature strength and ductility of a sintered body.
  • the content of B in the metal powder is not particularly limited, but is preferably 0.002 mass % or more and 0.1 mass % or less, more preferably 0.004 mass % or more and 0.05 mass % or less, further more preferably 0.006 mass % or more and 0.02 mass % or less.
  • the heat resistance of a sintered body to be produced may be deteriorated or the brittleness thereof may be increased depending on the overall composition.
  • the content of B exceeds the above upper limit, the heat resistance or ductility may be deteriorated instead.
  • Mn manganese
  • the content of Mn in the metal powder is not particularly limited, but is preferably 0.005 mass % or more and 0.3 mass % or less, more preferably 0.01 mass % or more and 0.1 mass % or less.
  • the content of Mn in the metal powder is not particularly limited, but is preferably 0.005 mass % or more and 0.3 mass % or less, more preferably 0.01 mass % or more and 0.1 mass % or less.
  • the corrosion resistance or mechanical properties of a sintered body to be produced may not be sufficiently enhanced depending on the overall composition.
  • the content of Mn exceeds the above upper limit, the corrosion resistance or mechanical properties may be deteriorated instead.
  • S sulfur enhances the machinability of a sintered body to be produced.
  • the content of S in the metal powder is not particularly limited, but is preferably 0.5 mass % or less, more preferably 0.01 mass % or more and 0.3 mass % or less.
  • N, Al, P, Se, Te, Pd, or the like may be added other than the above-mentioned elements.
  • the contents of these elements are not particularly limited, but the content of each of these elements is preferably 0.05 mass % or less, and also even the total content of these elements is preferably less than 0.2 mass %. These elements may be inevitably contained.
  • the metal powder for powder metallurgy according to the invention may contain impurities.
  • the impurities include all elements other than the above-mentioned elements, and specific examples thereof include Li, Be, Na, Mg, K, Ca, Sc, Zn, Ga, Ge, Ag, In, Sn, Sb, Os, Ir, Pt, Au, and Bi.
  • the incorporation amounts of these impurity elements are preferably controlled such that the content of each of the impurity elements is less than the content of each of the above-mentioned essential elements. Further, the incorporation amounts of these impurity elements are preferably set such that the content of each of the impurity elements is less than 0.03 mass %, more preferably less than 0.02 mass %.
  • these impurity elements is set to preferably less than 0.3 mass %, more preferably less than 0.2 mass %. These elements do not inhibit the effect as described above as long as the contents thereof are within the above range, and therefore may be intentionally added to the metal powder.
  • O oxygen
  • the amount thereof is preferably about 0.8 mass % or less, more preferably about 0.5 mass % or less.
  • the lower limit thereof is not particularly set, but is preferably 0.03 mass % or more from the viewpoint of ease of mass production or the like.
  • Co is a component (principal component) whose content is the highest in the alloy forming the metal powder for powder metallurgy according to the invention and has a great influence on the properties of a sintered body.
  • the content of Co is not particularly limited, but is preferably 45 mass % or more, more preferably 50 mass % or more.
  • the compositional ratio of the metal powder for powder metallurgy can be determined by, for example, Iron and steel—Atomic absorption spectrometric method specified in JIS G 1257 (2000), Iron and steel—ICP atomic emission spectrometric method specified in JIS G 1258 (2007), Iron and steel—Method for spark discharge atomic emission spectrometric analysis specified in JIS G 1253 (2002), Iron and steel—Method for X-ray fluorescence spectrometric analysis specified in JIS G 1256 (1997), gravimetric, titrimetric, and absorption spectrometric methods specified in JIS G 1211 to G 1237, or the like.
  • an optical emission spectrometer for solids (spark optical emission spectrometer, model: SPECTROLAB, type: LAVMB08A) manufactured by SPECTRO Analytical Instruments GmbH or an ICP device (model: CIROS-120) manufactured by Rigaku Corporation can be used.
  • JIS G 1211 to G 1237 are as follows.
  • JIS G 1214 Iron and steel—Methods for determination of phosphorus content
  • JIS G 1221 Iron and steel—Methods for determination of vanadium content
  • JIS G 1223 (1997): Iron and steel—Methods for determination of titanium content
  • C (carbon) and S (sulfur) are determined, particularly, an infrared absorption method after combustion in a current of oxygen (after combustion in a high-frequency induction heating furnace) specified in JIS G 1211 (2011) is also used.
  • a carbon-sulfur analyzer, CS-200 manufactured by LECO Corporation can be used.
  • N (nitrogen) and O (oxygen) are determined, particularly, a method for determination of nitrogen content in iron and steel specified in JIS G 1228 (2006) and a method for determination of oxygen content in metallic materials specified in JIS Z 2613 (2006) are also used.
  • an oxygen-nitrogen analyzer TC-300/EF-300 manufactured by LECO Corporation can be used.
  • the average particle diameter of the metal powder for powder metallurgy according to the invention is preferably 0.5 ⁇ m or more and 30 ⁇ m or less, more preferably 1 ⁇ m or more and 20 ⁇ m or less, further more preferably 2 ⁇ m or more and 10 ⁇ m or less.
  • the average particle diameter is obtained as a particle diameter when the cumulative amount from the small diameter side reaches 50% in a cumulative particle size distribution on a mass basis obtained by laser diffractometry.
  • the average particle diameter of the metal powder for powder metallurgy is less than the above lower limit, the moldability is deteriorated in the case where the shape which is difficult to mold is molded, and therefore, the sintered density may be decreased.
  • the average particle diameter of the metal powder exceeds the above upper limit, gaps between the particles become larger during molding, and therefore, the sintered density may be decreased also in this case.
  • the particle size distribution of the metal powder for powder metallurgy is preferably as narrow as possible. Specifically, when the average particle diameter of the metal powder for powder metallurgy is within the above range, the maximum particle diameter of the metal powder is preferably 200 ⁇ m or less, more preferably 150 ⁇ m or less. By controlling the maximum particle diameter of the metal powder for powder metallurgy within the above range, the particle size distribution of the metal powder for powder metallurgy can be made narrower, and thus, the density of the sintered body can be further increased.
  • the “maximum particle diameter” refers to a particle diameter when the cumulative amount from the small diameter side reaches 99.9% in a cumulative particle size distribution on a mass basis obtained by laser diffractometry.
  • the average of the aspect ratio defined by S/L is preferably about 0.4 or more and 1 or less, more preferably about 0.7 or more and 1 or less.
  • the metal powder for powder metallurgy having such an aspect ratio has a shape relatively close to a spherical shape, and therefore, the packing factor when the metal powder is molded is increased. As a result, the density of the sintered body can be further increased.
  • the “major axis” is the maximum length in the projected image of the particle
  • the “minor axis” is the maximum length in the direction perpendicular to the major axis.
  • the average of the aspect ratio is obtained as the average of the measured aspect ratios of 100 or more particles.
  • the tap density of the metal powder for powder metallurgy according to the invention is preferably 3.5 g/cm 3 or more, more preferably 4 g/cm 3 or more. According to the metal powder for powder metallurgy having such a high tap density, when a molded body is obtained, the interparticle packing efficiency is particularly increased. Therefore, a particularly dense sintered body can be obtained in the end.
  • the specific surface area of the metal powder for powder metallurgy according to the invention is not particularly limited, but is preferably 0.1 m 2 /g or more, more preferably 0.2 m 2 /g or more. According to the metal powder for powder metallurgy having such a large specific surface area, a surface activity (surface energy) is increased so that it is possible to easily sinter the metal powder even if less energy is applied. Therefore, when a molded body is sintered, a difference in sintering rate hardly occurs between the inner side and the outer side of the molded body, and thus, the decrease in the sintered density due to the pores remaining inside the molded body can be suppressed.
  • the metal powder for powder metallurgy according to the invention may be a powder (pre-alloy powder) composed only of particles having a single composition, but may also be a mixed powder (pre-mix powder) obtained by mixing a plurality of types of particles having mutually different compositions.
  • pre-mix powder it is only necessary to satisfy the compositional ratio as described above as a whole. According to this, the pre-mix powder brings about the same effect as described above and enables the production of a sintered body having a high density.
  • the pre-mix powder examples include a mixed powder of a C powder (carbon powder) and a powder in which C (carbon) is reduced from the above-mentioned compositional ratio, and a mixed powder of a first element powder, a second element powder, and a powder in which the first element and the second element are reduced from the above-mentioned compositional ratio.
  • the combination of a plurality of types of powders in the mixed powder is not particularly limited, and any combination may be adopted.
  • the method for producing a sintered body includes (A) a composition preparation step in which a composition for producing a sintered body is prepared, (B) a molding step in which a molded body is produced, (C) a degreasing step in which a degreasing treatment is performed, and (D) a firing step in which firing is performed.
  • A a composition preparation step in which a composition for producing a sintered body is prepared
  • B a molding step in which a molded body is produced
  • C a degreasing step in which a degreasing treatment is performed
  • D a firing step in which firing is performed.
  • the metal powder for powder metallurgy according to the above-mentioned embodiment and a binder are prepared, and these materials are kneaded using a kneader, whereby a kneaded material is obtained.
  • This kneaded material (an embodiment of the compound according to the invention) contains the metal powder for powder metallurgy, and this powder is uniformly dispersed therein. That is, the kneaded material contains the metal powder for powder metallurgy and the binder which binds the particles of the powder to one another.
  • a kneaded material compound
  • a sintered body having a high density can be easily produced.
  • the metal powder for powder metallurgy according to the invention is produced by, for example, any of a variety of powdering methods such as an atomization method (such as a water atomization method, a gas atomization method, or a spinning water atomization method), a reducing method, a carbonyl method, and a pulverization method.
  • an atomization method such as a water atomization method, a gas atomization method, or a spinning water atomization method
  • a reducing method such as a carbonyl method, and a pulverization method.
  • the metal powder for powder metallurgy according to the invention is preferably a metal powder produced by an atomization method, more preferably a metal powder produced by a water atomization method or a spinning water atomization method.
  • the atomization method is a method in which a molten metal (metal melt) is caused to collide with a fluid (liquid or gas) sprayed at a high speed to atomize the metal melt into a fine powder and also to cool the fine powder, whereby a metal powder is produced.
  • a molten metal metal melt
  • a fluid liquid or gas
  • the shape of the particle of the obtained powder is closer to a spherical shape by the action of surface tension. Due to this, a metal powder having a high packing factor when molding is obtained. That is, a powder capable of producing a sintered body having a high density can be obtained.
  • the pressure of water (hereinafter referred to as “atomization water”) to be sprayed to the molten metal is not particularly limited, but is set to preferably about 75 MPa or more and 120 MPa or less (750 kgf/cm 2 or more and 1200 kgf/cm 2 or less), more preferably about 90 MPa or more and 120 MPa or less (900 kgf/cm 2 or more and 1200 kgf/cm 2 or less).
  • the temperature of the atomization water is also not particularly limited, but is preferably set to about 1° C. or higher and 20° C. or lower.
  • the atomization water is often sprayed in a cone shape such that it has a vertex on the falling path of the metal melt and the outer diameter gradually decreases downward.
  • the vertex angle of the cone formed by the atomization water is preferably about 10° or more and 40° or less, more preferably about 15° or more and 35° or less. According to this, a metal powder for powder metallurgy having a composition as described above can be reliably produced.
  • the metal melt can be cooled particularly quickly. Due to this, a powder having high quality can be obtained in a wide alloy composition range.
  • the cooling rate when cooling the metal melt in the atomization method is preferably 1 ⁇ 10 4 ° C./s or more, more preferably 1 ⁇ 10 5 ° C./s or more.
  • the thus obtained metal powder for powder metallurgy may be classified as needed.
  • classification method include dry classification such as sieving classification, inertial classification, and centrifugal classification, and wet classification such as sedimentation classification.
  • binder examples include polyolefins such as polyethylene, polypropylene, and ethylene-vinyl acetate copolymers, acrylic resins such as polymethyl methacrylate and polybutyl methacrylate, styrenic resins such as polystyrene, polyesters such as polyvinyl chloride, polyvinylidene chloride, polyamide, polyethylene terephthalate, and polybutylene terephthalate, various resins such as polyether, polyvinyl alcohol, polyvinylpyrrolidone, and copolymers thereof, and various organic binders such as various waxes, paraffins, higher fatty acids (such as stearic acid), higher alcohols, higher fatty acid esters, and higher fatty acid amides. These can be used alone or by mixing two or more types thereof.
  • polyolefins such as polyethylene, polypropylene, and ethylene-vinyl acetate copolymers
  • acrylic resins such as polymethyl methacryl
  • the content of the binder is preferably about 2 mass % or more and 20 mass % or less, more preferably about 5 mass % or more and 10 mass % or less with respect to the total amount of the kneaded material.
  • a molded body can be formed with good moldability, and also the density is increased, and thus, the stability of the shape of the molded body and the like can be particularly enhanced.
  • a difference in size between the molded body and the degreased body, that is, so-called a shrinkage ratio is optimized, whereby a decrease in the dimensional accuracy of the finally obtained sintered body can be prevented. That is, a sintered body having a high density and high dimensional accuracy can be obtained.
  • a plasticizer may be added as needed.
  • the plasticizer include phthalate esters (such as DOP, DEP, and DBP), adipate esters, trimellitate esters, and sebacate esters. These can be used alone or by mixing two or more types thereof.
  • any of a variety of additives such as a lubricant, an antioxidant, a degreasing accelerator, and a surfactant can be added as needed.
  • the kneading conditions vary depending on the respective conditions such as the metal composition or the particle diameter of the metal powder for powder metallurgy to be used, the composition of the binder, and the blending amount thereof.
  • the kneading temperature can be set to about 50° C. or higher and 200° C. or lower, and the kneading time can be set to about 15 minutes or more and 210 minutes or less.
  • the kneaded material is formed into a pellet (small particle) as needed.
  • the particle diameter of the pellet is set to, for example, about 1 mm or more and 15 mm or less.
  • a granulated powder may be produced.
  • the kneaded material, the granulated powder, and the like are examples of the composition to be subjected to the molding step described below.
  • the embodiment of the granulated powder according to the invention contains the metal powder for powder metallurgy according to the above-mentioned embodiment, and is a granulated powder obtained by binding a plurality of metal particles to one another with the binder by subjecting the metal powder for powder metallurgy to a granulation treatment.
  • a sintered body having a high density can be easily produced.
  • binder to be used for producing the granulated powder examples include polyolefins such as polyethylene, polypropylene, and ethylene-vinyl acetate copolymers, acrylic resins such as polymethyl methacrylate and polybutyl methacrylate, styrenic resins such as polystyrene, polyesters such as polyvinyl chloride, polyvinylidene chloride, polyamide, polyethylene terephthalate, and polybutylene terephthalate, various resins such as polyether, polyvinyl alcohol, polyvinylpyrrolidone, and copolymers thereof, and various organic binders such as various waxes, paraffins, higher fatty acids (such as stearic acid), higher alcohols, higher fatty acid esters, and higher fatty acid amides. These can be used alone or by mixing two or more types thereof.
  • a binder containing a polyvinyl alcohol or polyvinylpyrrolidone is preferred.
  • These binder components have a high binding ability, and therefore can efficiently form the granulated powder even in a relatively small amount. Further, the thermal decomposability thereof is also high, and therefore, the binder can be reliably decomposed and removed in a short time during degreasing and firing.
  • the content of the binder is preferably about 0.2 mass % or more and 10 mass % or less, more preferably about 0.3 mass % or more and 5 mass % or less, further more preferably about 0.3 mass % or more and 2 mass % or less with respect to the total amount of the granulated powder.
  • a difference in size between the molded body and the degreased body, that is, so-called a shrinkage ratio is optimized, whereby a decrease in the dimensional accuracy of the finally obtained sintered body can be prevented.
  • any of a variety of additives such as a plasticizer, a lubricant, an antioxidant, a degreasing accelerator, and a surfactant may be added as needed.
  • Examples of the granulation treatment include a spray drying method, a tumbling granulation method, a fluidized bed granulation method, and a tumbling fluidized bed granulation method.
  • a solvent which dissolves the binder is used as needed.
  • the solvent include inorganic solvents such as water and carbon tetrachloride, and organic solvents such as ketone-based solvents, alcohol-based solvents, ether-based solvents, cellosolve-based solvents, aliphatic hydrocarbon-based solvents, aromatic hydrocarbon-based solvents, aromatic heterocyclic compound-based solvents, amide-based solvents, halogen compound-based solvents, ester-based solvents, amine-based solvents, nitrile-based solvents, nitro-based solvents, and aldehyde-based solvents, and one type or a mixture of two or more types selected from these solvents is used.
  • the average particle diameter of the granulated powder is not particularly limited, but is preferably about 10 ⁇ m or more and 200 ⁇ m or less, more preferably about 20 ⁇ m or more and 100 ⁇ m or less, further more preferably about 25 ⁇ m or more and 60 ⁇ m or less.
  • the granulated powder having such a particle diameter has favorable fluidity, and can more faithfully reflect the shape of a molding die.
  • the average particle diameter is obtained as a particle diameter when the cumulative amount from the small diameter side reaches 50% in a cumulative particle size distribution on a mass basis obtained by laser diffractometry.
  • the kneaded material or the granulated powder is molded, whereby a molded body having the same shape as that of a target sintered body is produced.
  • the method for producing a molded body is not particularly limited, and for example, any of a variety of molding methods such as a powder compaction molding (compression molding) method, a metal injection molding (MIM) method, an extrusion molding method, and a three-dimensional molding method (3D shaping method) can be used.
  • molding methods such as a powder compaction molding (compression molding) method, a metal injection molding (MIM) method, an extrusion molding method, and a three-dimensional molding method (3D shaping method) can be used.
  • the molding conditions in the case of a powder compaction molding method among these methods are preferably such that the molding pressure is about 200 MPa or more and 1000 MPa or less (2 t/cm 2 or more and 10 t/cm 2 or less), which vary depending on the respective conditions such as the composition and the particle diameter of the metal powder for powder metallurgy to be used, the composition of the binder, and the blending amount thereof.
  • the molding conditions in the case of a metal injection molding method are preferably such that the material temperature is about 80° C. or higher and 210° C. or lower, and the injection pressure is about 50 MPa or more and 500 MPa or less (0.5 t/cm 2 or more and 5 t/cm 2 or less), which vary depending on the respective conditions.
  • the molding conditions in the case of an extrusion molding method are preferably such that the material temperature is about 80° C. or higher and 210° C. or lower, and the extrusion pressure is about 50 MPa or more and 500 MPa or less (0.5 t/cm 2 or more and 5 t/cm 2 or less), which vary depending on the respective conditions.
  • the thus obtained molded body is in a state where the binder is uniformly distributed in gaps between the particles of the metal powder.
  • the three-dimensional molding method include a material extrusion deposition method, a material jetting method, a binder jetting method, and a stereolithography method.
  • the shape and size of the molded body to be produced are determined in anticipation of shrinkage of the molded body in the subsequent degreasing step and firing step.
  • the thus obtained molded body is subjected to a degreasing treatment (binder removal treatment), whereby a degreased body is obtained.
  • the binder is decomposed by heating the molded body, whereby the binder is removed from the molded body.
  • the degreasing treatment is performed.
  • the degreasing treatment include a method of heating the molded body and a method of exposing the molded body to a gas capable of decomposing the binder.
  • the conditions for heating the molded body are preferably such that the temperature is about 100° C. or higher and 750° C. or lower and the time is about 0.1 hours or more and 20 hours or less, and more preferably such that the temperature is about 150° C. or higher and 600° C. or lower and the time is about 0.5 hours or more and 15 hours or less, which slightly vary depending on the composition and the blending amount of the binder.
  • the degreasing of the molded body can be performed necessarily and sufficiently without sintering the molded body. As a result, it is possible to reliably prevent the binder component from remaining inside the degreased body in a large amount.
  • the atmosphere when the molded body is heated is not particularly limited, and an atmosphere of a reducing gas such as hydrogen, an atmosphere of an inert gas such as nitrogen or argon, an atmosphere of an oxidative gas such as air, a reduced pressure atmosphere obtained by reducing the pressure of such an atmosphere, or the like can be used.
  • a reducing gas such as hydrogen
  • an atmosphere of an inert gas such as nitrogen or argon
  • an atmosphere of an oxidative gas such as air
  • a reduced pressure atmosphere obtained by reducing the pressure of such an atmosphere, or the like can be used.
  • Examples of the gas capable of decomposing the binder include ozone gas.
  • this degreasing step into a plurality of steps in which the degreasing conditions are different, and performing the plurality of steps, the binder in the molded body can be more rapidly decomposed and removed so that the binder does not remain in the molded body.
  • the degreased body may be subjected to a machining process such as grinding, polishing, or cutting.
  • the degreased body has a relatively low hardness and relatively high plasticity, and therefore, the machining process can be easily performed while preventing the degreased body from losing its shape. According to such a machining process, a sintered body having high dimensional accuracy can be easily obtained in the end.
  • the degreased body obtained in the above step (C) is fired in a firing furnace, whereby a sintered body is obtained.
  • the firing temperature varies depending on the composition, the particle diameter, and the like of the metal powder for powder metallurgy used in the production of the molded body and the degreased body, but is set to, for example, about 980° C. or higher and 1450° C. or lower, and preferably set to about 1050° C. or higher and 1350° C. or lower.
  • the firing time is set to 0.2 hours or more and 7 hours or less, but is preferably set to about 1 hour or more and 6 hours or less.
  • the firing temperature or the below-described firing atmosphere may be changed in the middle of the step.
  • the firing temperature is a relatively low temperature, it is easy to control the heating temperature in the firing furnace constant, and therefore, also the temperature of the degreased body is likely to be constant. As a result, a more homogeneous sintered body can be produced.
  • the firing temperature as described above is a firing temperature which can be sufficiently realized using a common firing furnace, and therefore, an inexpensive firing furnace can be used, and also the running cost can be kept low. In other words, in the case where the temperature exceeds the above-mentioned firing temperature, it is necessary to employ an expensive firing furnace using a special heat resistant material, and also the running cost may be increased.
  • the atmosphere when performing firing is not particularly limited, however, in consideration of prevention of significant oxidation of the metal powder, an atmosphere of a reducing gas such as hydrogen, an atmosphere of an inert gas such as argon, a reduced pressure atmosphere obtained by reducing the pressure of such an atmosphere, or the like is preferably used.
  • the sintered body may be produced by irradiating the metal powder with an energy beam such as a laser to effect sintering in place of the above-mentioned series of steps, that is, in place of the composition preparation step, the molding step, the degreasing step, and the firing step.
  • the metal powder which is spread flat is irradiated with an energy beam such as a laser, and the metal powder in the irradiated region is sintered, whereby a sintered body having an arbitrary shape corresponding to the shape of the irradiated region is produced (a selective laser sintering method). According to this, a sintered body can be more easily produced.
  • the thus obtained sintered body has the composition of the metal powder for powder metallurgy according to the above-mentioned embodiment.
  • the sintered body according to this embodiment is characterized by containing Co as a principal component, Cr in a proportion of 10 mass % or more and 25 mass % or less, Ni in a proportion of 5 mass % or more and 40 mass % or less, at least one of Mo and W in a proportion of 2 mass % or more and 20 mass % or less in total, Si in a proportion of 0.3 mass % or more and 1.5 mass % or less, C in a proportion of 0.05 mass % or more and 0.8 mass % or less, the above-mentioned first element in a proportion of 0.01 mass % or more and 0.5 mass % or less, and the above-mentioned second element in a proportion of 0.01 mass % or more and 0.5 mass % or less.
  • the thus obtained sintered body has a high density and excellent mechanical properties without performing an additional treatment. That is, a sintered body produced by molding a composition containing the metal powder for powder metallurgy according to the invention and a binder, followed by degreasing and sintering has a higher relative density than a sintered body obtained by sintering a metal powder in the related art. Therefore, according to the invention, a sintered body having a high density which could not be obtained unless an additional treatment such as an HIP treatment is performed can be realized without performing an additional treatment.
  • the relative density can be expected to be increased by 2% or more as compared with the related art, which slightly varies depending on the composition of the metal powder for powder metallurgy.
  • the relative density of the obtained sintered body can be expected to be, for example, 97% or more (preferably 98% or more, more preferably 98.5% or more).
  • the sintered body having a relative density within such a range has excellent mechanical properties comparable to those of ingot materials although it has a shape as close as possible to a desired shape by using a powder metallurgy technique, and therefore, the sintered body can be applied to a variety of machine components, structural components, and the like with virtually no post-processing.
  • the thus obtained sintered body has a sufficiently high density and excellent mechanical properties even without performing an additional treatment, however, in order to further increase the density and enhance the mechanical properties, a variety of additional treatments may be performed.
  • an additional treatment of increasing the density such as the HIP treatment described above may be performed, and also a variety of quenching treatments, a variety of sub-zero treatments, a variety of tempering treatments, a variety of annealing treatments, and the like may be performed. These additional treatments may be performed alone or two or more treatments thereof may be performed in combination.
  • the content of C in the final sintered body may change within the range of 5% or more and 100% or less (preferably within the range of 30% or more and 100% or less) of the content of C in the metal powder for powder metallurgy, which varies depending on the conditions for the step or the conditions for the treatment.
  • the content of 0 in the final sintered body may change within the range of 1% or more and 50% or less (preferably within the range of 3% or more and 50% or less) of the content of 0 in the metal powder for powder metallurgy, which varies depending on the conditions for the step or the conditions for the treatment.
  • the produced sintered body may be subjected to an HIP treatment as part of the additional treatments to be performed as needed.
  • the density of the sintered body obtained according to the invention has already been sufficiently increased at the end of the firing step. Therefore, even if the HIP treatment is further performed, further densification hardly proceeds.
  • the material to be treated may be contaminated, the composition or the physical properties of the material to be treated may unintentionally change due to the contamination, or the color of the material to be treated may change due to the contamination.
  • residual stress is generated or increased in the material to be treated, and a problem such as a change in the shape or a decrease in the dimensional accuracy may occur as the residual stress is released over time.
  • a sintered body having a sufficiently high density can be produced without performing such an HIP treatment, and therefore, a sintered body having an increased density and also an increased strength can be obtained in the same manner as in the case of performing an HIP treatment.
  • Such a sintered body is less contaminated or discolored, and an unintended change in the composition or physical properties, or the like occurs less, and also a problem such as a change in the shape or a decrease in the dimensional accuracy occurs less. Therefore, according to the invention, a sintered body having high mechanical strength and dimensional accuracy, and excellent durability can be efficiently produced.
  • the sintered body produced according to the invention requires almost no additional treatments for enhancing the mechanical properties, and therefore, the composition and the crystal structure tend to become uniform in the entire sintered body. Due to this, the sintered body has high structural anisotropy and therefore has excellent durability against a load from every direction regardless of its shape.
  • the heat resistant component according to the invention can be applied to, for example, a supercharger component.
  • the supercharger component described below is a first embodiment of the heat resistant component according to the invention, and contains the sintered body according to this embodiment. That is, at least part of the supercharger component described below is constituted by the sintered body according to this embodiment.
  • Such a supercharger component serves as a heat resistant component having a high density and excellent heat resistance without performing an additional treatment.
  • Examples of such a supercharger component include a nozzle vane for a turbocharger, a turbine wheel for a turbocharger, a waste gate valve, and a turbine housing. Any of these supercharger components is exposed to a high temperature over a long period of time, and also slides between other components in some cases, and therefore is required to have abrasion resistance. As described above, the sintered body according to the invention has a high density, and therefore has excellent heat resistance and mechanical properties. Due to this, a supercharger component having excellent long-term durability is obtained.
  • a nozzle vane for a turbocharger (hereinafter also referred to in short as “nozzle vane”).
  • the nozzle vane is used for a variable displacement turbocharger and is a valve body for controlling a supercharging pressure by adjusting the nozzle opening degree.
  • FIG. 1 is a side view showing a nozzle vane for a turbocharger (a view when a blade section is viewed in a plan view) to which the first embodiment of the heat resistant component according to the invention is applied.
  • FIG. 2 is a plan view of the nozzle vane shown in FIG. 1
  • FIG. 3 is a rear view of the nozzle vane shown in FIG. 1 .
  • a nozzle vane 1 shown in FIG. 1 includes a shaft section 11 and a blade section 12 .
  • the shaft section 11 is configured such that the transverse cross-sectional shape of the main section is a circle with an axial line 13 as the central axis.
  • This shaft section 11 is configured such that a portion on the blade section 12 side (the left side in FIG. 1 ) is rotatably supported by a nozzle mount (not shown), and a portion on the opposite side to the blade section 12 (the right side in FIG. 1 ) is fixed to a nozzle plate (not shown). According to this, the blade section 12 is rotated around the axial line 13 and its angle can be changed, and the nozzle opening degree can be adjusted.
  • a center hole 14 is formed on one end face (an end face on the right side in FIG. 1 ) of the shaft section 11 .
  • This center hole 14 is formed such that the transverse cross-sectional shape thereof is a circle and the center thereof coincides with the axial line 13 .
  • the outer peripheral surface on one end side (the right side in FIG. 1 ) of the shaft section 11 is provided with a pair of flat sections 15 (a two-side cut section) facing each other through the axial line 13 (see FIG. 3 ).
  • Each of such flat sections 15 is used in a state of being in contact with a contact face formed on a lever plate (not shown).
  • a rotation angle around the axial line 13 of the shaft section 11 is regulated, so that a rotation angle around the axial line 13 of the nozzle vane 1 can be highly accurately adjusted.
  • each flat section 15 is formed so as to be inclined at an angle ⁇ with respect to the protruding direction (blade surface) of the blade section 12 (see FIG. 3 ).
  • the blade section 12 is provided on the other end side (an end portion on the left side in FIG. 1 ) of the shaft section 11 . That is, the blade section 12 is provided so as to protrude from the one end portion of the shaft section 11 .
  • a flange section 16 protruding outside the shaft section 11 is formed.
  • Such a blade section 12 has a strip shape extending in a direction perpendicular to the axial line 13 of the shaft section 11 as shown in FIG. 1 in a plan view. Further, the length of the protrusion of the blade section 12 from the shaft section 11 on one end side (the lower side in FIG. 1 ) is longer than the other end side (the upper side in FIG. 1 ).
  • chamfers 17 and 18 are formed in edge portions in both end portions in the width direction (the lateral direction in FIG. 1 ) in a plan view of the blade section 12 .
  • the blade section 12 is slightly curved in the thickness direction.
  • the thickness of the blade section 12 gradually decreases toward each end in the extending direction (protruding direction).
  • the nozzle vane 1 as described above is constituted by an embodiment of the sintered body according to the invention.
  • the sintered body according to the invention has a high density, and therefore, the nozzle vane 1 has excellent heat resistance and mechanical properties, and thus has excellent abrasion resistance. Further, even if the nozzle vane 1 has a complicated shape, it has high dimensional accuracy. As a result, a supercharger having excellent long-term durability can be realized.
  • the heat resistant component according to the invention can be applied to, for example, a compressor blade, which is a jet engine component or a power generation turbine component.
  • a compressor blade is a second embodiment of the heat resistant component according to the invention, and at least part of the component is constituted by an embodiment of the sintered body according to the invention.
  • FIG. 4 is a perspective view showing a compressor blade to which the second embodiment of the heat resistant component according to the invention is applied.
  • a compressor blade 2 shown in FIG. 4 includes an inner rim 21 and an outer rim 22 which are mutually concentrically provided, and blade sections 23 which are provided therebetween and arranged in the circumferential direction of the inner rim 21 .
  • the inner rim 21 and the outer rim 22 each have an annular shape.
  • the blade section 23 has a plate shape including a curved surface.
  • the blade tips (end faces) of each blade section 23 are bonded to the outer peripheral surface of the inner rim 21 and the inner peripheral surface of the outer rim 22 .
  • FIG. 4 is a view illustrating a cut-out portion of the compressor blade 2 .
  • Such a compressor blade 2 is one of the components constituting a jet engine or a power generation gas turbine, and by receiving a gas by the blade sections 23 , a turbine shaft provided on the inner side of the inner rim 21 is rotated. According to this, a compressor can compress the gas in the jet engine or the power generation gas turbine.
  • the inner rim 21 , the outer rim 22 , and the blade section 23 may be mutually different members, however, in the compressor blade 2 shown in FIG. 4 , the inner rim 21 , the outer rim 22 , and the blade section 23 are integrally formed. Due to this, the relative positional accuracy of the respective members is high, and excellent performance as the compressor blade is exhibited. Then, by constituting the entire compressor blade 2 by an embodiment of the sintered body according to the invention, the compressor blade 2 having excellent dimensional accuracy is obtained.
  • the compressor blade is required to have a three-dimensional shape such that the shape of the blade section is thinner and also includes a curved surface by the necessity to improve the aerodynamic performance.
  • the entire compressor blade 2 is constituted by a sintered body produced by a powder metallurgy method, and therefore, even if the blade sections 23 each having a thin and complicated three-dimensional shape are included, the compressor blade 2 having high dimensional accuracy can be realized.
  • the sintered body according to this embodiment has a high density and excellent heat resistance, and therefore, also contributes to the improvement of the mechanical properties of the compressor blade 2 . That is, the compressor blade is generally a component forming an air flow channel, and therefore is required to have sufficient fatigue strength against vibration, abrasion resistance, and the like even under a high temperature.
  • the compressor blade 2 is constituted by the sintered body according to this embodiment, and therefore has a high density and excellent heat resistance, and also has sufficient abrasion resistance. Therefore, the compressor blade 2 having excellent long-term durability is obtained.
  • the production is performed using any of a variety of molding methods, and therefore, in the production of the compressor blade 2 , almost no post-processing after sintering is needed, or the processing amount is reduced.
  • the density is increased, and therefore, an additional treatment such as an HIP treatment is also not needed. Due to this, the production cost is reduced, and also the occurrence of a defect caused by a post-processing mark can be minimized.
  • the metal powder for powder metallurgy, the compound, the granulated powder, the sintered body, and the heat resistant component according to the invention have been described with reference to preferred embodiments, however, the invention is not limited thereto.
  • the sintered body according to the invention may be used for components for transport machinery such as components for automobiles, components for bicycles, components for railroad cars, components for ships, components for airplanes, and components for space transport machinery (such as rockets), components for electronic devices such as components for personal computers and components for mobile phone terminals, components for electrical devices such as refrigerators, washing machines, and cooling and heating machines, components for machines such as machine tools and semiconductor production devices, components for plants such as atomic power plants, thermal power plants, hydroelectric power plants, oil refinery plants, and chemical complexes, components for timepieces, ornaments such as metallic tableware, jewels, and frames for glasses, medical devices such as surgical instruments, artificial bones, artificial teeth, artificial dental roots, and components for orthodontics, and all other sorts of structural components.
  • transport machinery such as components for automobiles, components for bicycles, components for railroad cars, components for ships, components for airplanes, and components for space transport machinery (such as rockets)
  • components for electronic devices such as components for personal computers and components for mobile phone terminals
  • components for electrical devices such as
  • the heat resistant component according to the invention can be applied to, for example, a variety of components associated with power generation such as components for atomic power plants and components for gas turbines, components for a variety of engines such as components for automobile engines and components for rocket engines, components for boilers, components for heat exchangers, components for exhaust gas treatment facilities, components for heating furnaces, components for fuel cells, and all sorts of heat resistant components such as heat resistant bolts, heat resistance springs, and heat resistant valves, other than the above-mentioned supercharger component, jet engine component, and power generation turbine component.
  • components associated with power generation such as components for atomic power plants and components for gas turbines
  • components for a variety of engines such as components for automobile engines and components for rocket engines, components for boilers, components for heat exchangers, components for exhaust gas treatment facilities, components for heating furnaces, components for fuel cells, and all sorts of heat resistant components such as heat resistant bolts, heat resistance springs, and heat resistant valves, other than the above-mentioned supercharger component, jet engine component, and
  • the composition of the powder shown in Table 1 was identified and quantitatively determined by inductively coupled high-frequency plasma optical emission spectrometry (ICP analysis method).
  • ICP analysis method an ICP device (model: CIROS-120) manufactured by Rigaku Corporation was used. Further, in the identification and quantitative determination of C, a carbon-sulfur analyzer (CS-200) manufactured by LECO Corporation was used. Further, in the identification and quantitative determination of O, an oxygen-nitrogen analyzer (TC-300/EF-300) manufactured by LECO Corporation was used.
  • this mixed raw material was kneaded using a kneader, whereby a compound was obtained.
  • this compound was molded using an injection molding machine under the following molding conditions, whereby a molded body was produced.
  • the obtained degreased body was fired under the following firing conditions, whereby a sintered body was obtained.
  • the shape of the sintered body was determined to be a cylinder with a diameter of 10 mm and a thickness of 5 mm.
  • Sintered bodies were obtained in the same manner as the method for producing the sintered body of sample No. 1 except that the composition and the like of the metal powder for powder metallurgy were changed as shown in Table 1, respectively.
  • the sintered body of sample No. 30 was obtained by performing an HIP treatment under the following conditions after firing. Further, the sintered bodies of sample Nos. 16 and 17 were obtained using the metal powder produced by a gas atomization method, respectively, and “Gas” is given in the column of Remarks in Table 1.
  • Each metal powder for powder metallurgy contained very small amounts of impurities, but the description thereof in Table 1 is omitted.
  • the content of O (oxygen) in each of the metal powders according to Example shown in Table 1 was 0.5 mass % or less.
  • a metal powder having a composition shown in Table 2 was produced by a water atomization method in the same manner as in the case of sample No. 1.
  • the average particle diameter of the prepared metal powder is shown in Table 5.
  • the metal powder was granulated by a spray drying method.
  • the binder used at this time was polyvinyl alcohol, which was used in an amount of 1 part by mass with respect to 100 parts by mass of the metal powder. Further, a solvent (ion exchanged water) was used in an amount of 50 parts by mass with respect to 1 part by mass of polyvinyl alcohol. In this manner, a granulated powder having an average particle diameter of 50 ⁇ m was obtained.
  • this granulated powder was subjected to powder compaction molding under the following molding conditions.
  • a press molding machine was used.
  • the shape of the molded body to be produced was determined to be a cube with a side length of 20 mm.
  • Sintered bodies were obtained in the same manner as in the case of sample No. 31 except that the composition and the like of the metal powder for powder metallurgy were changed as shown in Table 2, respectively.
  • the sintered body of sample No. 45 was obtained by performing an HIP treatment under the following conditions after firing. Further, the sintered bodies of sample Nos. 38 and 39 were obtained using the metal powder produced by a gas atomization method, respectively, and “Gas” is given in the column of Remarks in Table 2.
  • Each metal powder for powder metallurgy contained very small amounts of impurities, but the description thereof in Table 2 is omitted.
  • the content of O (oxygen) in each of the metal powders according to Example shown in Table 2 was 0.5 mass % or less.
  • pre-mix powder having a composition shown in Table 3 produced by a water atomization method was prepared.
  • the “pre-mix powder” as used herein refers to a mixed powder of a C powder and a powder in which the C (carbon) component was reduced from the compositional ratio shown in Table 3. Further, the average particle diameter of the prepared metal powder (the powder in which the C (carbon) component was reduced) is shown in Table 6.
  • this mixed raw material was kneaded using a kneader, whereby a compound was obtained.
  • this compound was molded using an injection molding machine under the following molding conditions, whereby a molded body was produced.
  • the obtained degreased body was fired under the following firing conditions, whereby a sintered body was obtained.
  • the shape of the sintered body was determined to be a cylinder with a diameter of 10 mm and a thickness of 5 mm.
  • Sintered bodies were obtained in the same manner as in the case of sample No. 46 except that the composition and the like of the metal powder for powder metallurgy were changed as shown in Table 3, respectively.
  • the sintered body of sample No. 60 was obtained by performing an HIP treatment under the following conditions after firing.
  • Each metal powder for powder metallurgy contained very small amounts of impurities, but the description thereof in Table 3 is omitted.
  • the content of O (oxygen) in each of the metal powders according to Example shown in Table 3 was 0.5 mass % or less.
  • the sintered density was measured in accordance with the method for measuring the density of sintered metal materials specified in JIS Z 2501 (2000), and also the relative density of each sintered body was calculated with reference to the true density of the metal powder for powder metallurgy used for producing each sintered body.
  • the Vickers hardness was measured in accordance with the Vickers hardness test method specified in JIS Z 2244 (2009).
  • the measured hardness was evaluated according to the following evaluation criteria.
  • the hardness of each sample for which “*1” is given in the column of Remarks in each table was evaluated by collating the relative value when the hardness of the sample for which “Standard for *1” is given in the column of Remarks in each table is taken as 100 with the following evaluation criteria.
  • the hardness of each sample for which “*2” is given in the column of Remarks in Table 1 was evaluated by collating the relative value when the hardness of the sample for which “Standard for *2” is given in the column of Remarks in Table 1 is taken as 100, the relative value when the hardness of the sample for which “Standard for 3” is given in the column of Remarks in Table 1 is taken as 100, and the relative value when the hardness of the sample for which “Standard for *4” is given in the column of Remarks in Table 1 is taken as 100, with the following evaluation criteria, respectively.
  • A The relatively value of the Vickers hardness is 110 or more.
  • the relatively value of the Vickers hardness is 105 or more and less than 110.
  • the relatively value of the Vickers hardness is 100 or more and less than 105.
  • the relatively value of the Vickers hardness is less than 100.
  • the measured physical property values were evaluated according to the following evaluation criteria.
  • the physical property values of each sample for which “*1” is given in the column of Remarks in each table were evaluated by collating the relative values when the physical property values of the sample for which “Standard for *1” is given in the column of Remarks in each table are each taken as 100 with the following evaluation criteria.
  • the physical property values of each sample for which “*2” is given in the column of Remarks in Table 1 were evaluated by collating the relative values when the physical property values of the sample for which “Standard for *2” is given in the column of Remarks in Table 1 are each taken as 100, the relative values when the physical property values of the sample for which “Standard for 3” is given in the column of Remarks in Table 1 are each taken as 100, and the relative values when the physical property values of the sample for which “Standard for *4” is given in the column of Remarks in Table 1 are each taken as 100, with the following evaluation criteria, respectively.
  • the relatively value of the tensile strength of the sintered body is 109 or more.
  • the relatively value of the tensile strength of the sintered body is 106 or more and less than 109.
  • the relatively value of the tensile strength of the sintered body is 103 or more and less than 106.
  • the relatively value of the tensile strength of the sintered body is 100 or more and less than 103.
  • the relatively value of the tensile strength of the sintered body is 97 or more and less than 100.
  • the relatively value of the tensile strength of the sintered body is less than 97.
  • A The relatively value of the 0.2% proof stress of the sintered body is 109 or more.
  • the relatively value of the 0.2% proof stress of the sintered body is 106 or more and less than 109.
  • the relatively value of the 0.2% proof stress of the sintered body is 103 or more and less than 106.
  • the relatively value of the 0.2% proof stress of the sintered body is 100 or more and less than 103.
  • the relatively value of the 0.2% proof stress of the sintered body is 97 or more and less than 100.
  • A The relatively value of the elongation of the sintered body is 115 or more.
  • the relatively value of the elongation of the sintered body is 110 or more and less than 115.
  • the relatively value of the elongation of the sintered body is 105 or more and less than 110.
  • the relatively value of the elongation of the sintered body is 100 or more and less than 105.
  • the relatively value of the elongation of the sintered body is 95 or more and less than 100.
  • the relatively value of the elongation of the sintered body is less than 95.
  • Example 8.96 99.3 A B B A No. 14 Example 3.15 99.3 A A A A No. 15
  • Example 10.68 99.3 A A A A No. 17 Example 15.89 99.2 A A A A No. 18 Comp. Ex. 3.58 97.2 C D D D No. 19 Comp. Ex. 4.25 97.4 C D D D No. 20 Comp. Ex. 3.56 96.5 D E E D No. 21 Comp. Ex. 5.02 95.8 D E E D No. 22 Comp. Ex. 4.35 95.4 D E E E No. 23 Comp. Ex. 3.44 96.2 D D D C No. 24 Comp. Ex.
  • the sintered bodies corresponding to Example each have a higher relative density than the sintered bodies corresponding to Comparative Example (excluding the sintered bodies having undergone the HIP treatment). Further, it was also confirmed that there is a significant difference in properties such as tensile strength, 0.2% proof stress, and elongation between the sintered bodies corresponding to Example and the sintered bodies corresponding to Comparative Example (excluding the sintered bodies having undergone the HIP treatment).
  • Sintered bodies were obtained in the same manner as the method for producing the sintered body of sample No. 1 except that the composition and the like of the metal powder for powder metallurgy were changed as shown in Table 7, respectively.
  • Each metal powder for powder metallurgy contained very small amounts of impurities, but the description thereof in Table 7 is omitted.
  • the content of O (oxygen) in each of the metal powders according to Example shown in Table 7 was 0.5 mass % or less.
  • Sintered bodies were obtained in the same manner as in the case of sample No. 46 except that the composition and the like of the metal powder for powder metallurgy were changed as shown in Table 8, respectively.
  • Each metal powder for powder metallurgy contained very small amounts of impurities, but the description thereof in Table 8 is omitted.
  • the content of O (oxygen) in each of the metal powders according to Example shown in Table 8 was 0.5 mass % or less.
  • the sintered density was measured in accordance with the method for measuring the density of sintered metal materials specified in JIS Z 2501 (2000), and also the relative density of each sintered body was calculated with reference to the true density of the metal powder for powder metallurgy used for producing each sintered body.
  • the measured hardness was evaluated according to the evaluation criteria described in 2.2.
  • the sintered bodies corresponding to Example each have a higher relative density than the sintered bodies corresponding to Comparative Example. It was also confirmed that there is a significant difference in properties such as tensile strength, 0.2% proof stress, and elongation between the sintered bodies corresponding to Example and the sintered bodies corresponding to Comparative Example.
  • Sintered bodies were obtained in the same manner as the method for producing the sintered body of sample No. 1 except that the composition and the like of the metal powder for powder metallurgy were changed as shown in Table 11, respectively.
  • Pre-alloy *1 No. 88 Comp. Ex.
  • Each metal powder for powder metallurgy contained very small amounts of impurities, but the description thereof in Table 11 is omitted.
  • the content of O (oxygen) in each of the metal powders according to Example shown in Table 11 was 0.5 mass % or less.
  • the sintered density was measured in accordance with the method for measuring the density of sintered metal materials specified in JIS Z 2501 (2000), and also the relative density of each sintered body was calculated with reference to the true density of the metal powder for powder metallurgy used for producing each sintered body.
  • the Vickers hardness was measured in accordance with the Vickers hardness test method specified in JIS Z 2244 (2009).
  • the measured hardness was evaluated according to the evaluation criteria described in 2.2.
  • the sintered bodies corresponding to Example each have a higher relative density than the sintered bodies corresponding to Comparative Example. It was also confirmed that there is a significant difference in properties such as tensile strength, 0.2% proof stress, and elongation between the sintered bodies corresponding to Example and the sintered bodies corresponding to Comparative Example.
  • Sintered bodies were obtained in the same manner as the method for producing the sintered body of sample No. 1 except that the composition and the like of the metal powder for powder metallurgy were changed as shown in Table 13, respectively.
  • Each metal powder for powder metallurgy contained very small amounts of impurities, but the description thereof in Table 13 is omitted.
  • the content of O (oxygen) in each of the metal powders according to Example shown in Table 13 was 0.5 mass % or less.
  • the sintered density was measured in accordance with the method for measuring the density of sintered metal materials specified in JIS Z 2501 (2000), and also the relative density of each sintered body was calculated with reference to the true density of the metal powder for powder metallurgy used for producing each sintered body.
  • the measured hardness was evaluated according to the evaluation criteria described in 2.2.
  • the sintered bodies corresponding to Example each have a higher relative density than the sintered bodies corresponding to Comparative Example. It was also confirmed that there is a significant difference in properties such as tensile strength, 0.2% proof stress, and elongation between the sintered bodies corresponding to Example and the sintered bodies corresponding to Comparative Example.
  • Sintered bodies were obtained in the same manner as the method for producing the sintered body of sample No. 1 except that the composition and the like of the metal powder for powder metallurgy were changed as shown in Table 15, respectively.
  • Each metal powder for powder metallurgy contained very small amounts of impurities, but the description thereof in Table 15 is omitted.
  • the content of O (oxygen) in each of the metal powders according to Example shown in Table 15 was 0.5 mass % or less.
  • the sintered density was measured in accordance with the method for measuring the density of sintered metal materials specified in JIS Z 2501 (2000), and also the relative density of each sintered body was calculated with reference to the true density of the metal powder for powder metallurgy used for producing each sintered body.
  • the Vickers hardness was measured in accordance with the Vickers hardness test method specified in JIS Z 2244 (2009).
  • the measured hardness was evaluated according to the evaluation criteria described in 2.2.
  • the sintered bodies corresponding to Example each have a higher relative density than the sintered bodies corresponding to Comparative Example. It was also confirmed that there is a significant difference in properties such as tensile strength, 0.2% proof stress, and elongation between the sintered bodies corresponding to Example and the sintered bodies corresponding to Comparative Example.
  • Sintered bodies were obtained in the same manner as the method for producing the sintered body of sample No. 1 except that the composition and the like of the metal powder for powder metallurgy were changed as shown in Table 17, respectively.
  • Pre-alloy *1 No. 119 Comp. Ex. Ex.
  • Each metal powder for powder metallurgy contained very small amounts of impurities, but the description thereof in Table 17 is omitted.
  • the content of O (oxygen) in each of the metal powders according to Example shown in Table 17 was 0.5 mass % or less.
  • the sintered density was measured in accordance with the method for measuring the density of sintered metal materials specified in JIS Z 2501 (2000), and also the relative density of each sintered body was calculated with reference to the true density of the metal powder for powder metallurgy used for producing each sintered body.
  • the measured hardness was evaluated according to the evaluation criteria described in 2.2.
  • the sintered bodies corresponding to Example each have a higher relative density than the sintered bodies corresponding to Comparative Example. It was also confirmed that there is a significant difference in properties such as tensile strength, 0.2% proof stress, and elongation between the sintered bodies corresponding to Example and the sintered bodies corresponding to Comparative Example.
  • Sintered bodies were produced in the same manner as described above also for Ti—Zr based, Zr—Ta based, and Zr—V based metal powders as examples of the combination of the first element with the second element other than the examples shown in Tables 1 to 18, and each of these sintered bodies showed the same tendency as described above with respect to the relative density, hardness, tensile strength, proof stress, and elongation.

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