CN107262707B

CN107262707B - Metal powder for powder metallurgy, composite, granulated powder, and sintered body

Info

Publication number: CN107262707B
Application number: CN201710195531.4A
Authority: CN
Inventors: 中村英文; 川崎琢
Original assignee: Seiko Epson Corp
Current assignee: Seiko Epson Corp
Priority date: 2016-04-06
Filing date: 2017-03-28
Publication date: 2021-10-26
Anticipated expiration: 2037-03-28
Also published as: US20170291220A1; JP2017186620A; CN107262707A; JP6372512B2

Abstract

Disclosed are a metal powder for powder metallurgy, a composite, a granulated powder, and a sintered body, which can produce a sintered body having a high density. The metal powder for powder metallurgy contains Co as a main component, 10-25 mass% of Cr, 5-40 mass% of Ni, 2-20 mass% of Mo and W in total, 0.3-1.5 mass% of Si, 0.05-0.8 mass% of C, one element selected from the group consisting of Ti, V, Y, Zr, Nb, Hf and Ta is used as a first element, and one element selected from the group consisting of elements having a larger group than the first element in the periodic table or an element having the same group as the first element and a larger period than the first element is used as a second element, the first element is contained in 0.01-0.5 mass% and the second element is contained in 0.01-0.5 mass%.

Description

Metal powder for powder metallurgy, composite, granulated powder, and sintered body

Technical Field

The present invention relates to a metal powder for powder metallurgy, a composite, a granulated powder, and a sintered body.

Background

In the powder metallurgy method, a composition containing a metal powder and a binder is molded into a desired shape to obtain a molded body, and then the molded body is degreased and sintered to produce a sintered body. In the production process of such a sintered body, a diffusion phenomenon of atoms occurs between particles of the metal powder, whereby the compact is gradually densified, and sintering is achieved.

For example, patent document 1 proposes a target (target) for a magneto-optical recording medium, which is obtained by sintering an alloy powder containing 15 to 30 atomic% of a rare earth metal and the balance being a transition metal. In addition, as an element for improving corrosion resistance, it is disclosed that Ti, V, Nb, Ta, or the like is added in an amount of 15 atomic% or less to the target material. Thus, in the invention described in patent document 1, it is desired to improve the mechanical strength of the target.

On the other hand, in patent document 2, there has been proposed a metal powder for powder metallurgy containing Zr and Si, and the remainder being composed of at least one selected from the group consisting of Fe, Co, and Ni, and an unavoidable element. According to the metal powder for powder metallurgy, the sinterability is improved, and a sintered body having a high density can be easily produced. In recent years, such sintered bodies have been widely used for various machine parts, structural parts, and the like.

However, depending on the use of the sintered body, further densification may be necessary. In this case, the density of the sintered body is increased by further performing additional processing such as Hot Isostatic Pressing (HIP) processing, but the number of working steps is greatly increased and the cost is inevitably increased.

Accordingly, expectations for realizing a metal powder that can produce a high-density sintered body without performing additional processing or the like have been increasing.

[ Prior Art document ]

[ patent document ]

Patent document 1: japanese laid-open patent publication No. 8-302463

Patent document 2: japanese patent laid-open publication No. 2012 and 87416

Disclosure of Invention

The purpose of the present invention is to provide a metal powder for powder metallurgy, a composite, and a granulated powder, which are capable of producing a high-density sintered body, and a high-density sintered body and a heat-resistant member.

The above object is achieved by the present invention described below.

The metal powder for powder metallurgy is characterized in that Co is a main component, Cr is contained at a ratio of 10 to 25 mass%, Ni is contained at a ratio of 5 to 40 mass%, at least one of Mo and W is contained at a ratio of 2 to 20 mass%, Si is contained at a ratio of 0.3 to 1.5 mass%, C is contained at a ratio of 0.05 to 0.8 mass%, one element selected from the group consisting of Ti, V, Y, Zr, Nb, Hf and Ta is a first element, and one element selected from the group, i.e., an element having a larger group in the periodic table than the first element or an element having the same group in the periodic table as the first element and having a larger period in the periodic table than the first element is contained at a ratio of 0.01 to 0.5 mass% as the second element, the second element is contained in a proportion of 0.01 to 0.5 mass%.

This makes it possible to optimize the alloy composition and promote densification of the metal powder for powder metallurgy during sintering. As a result, a metal powder for powder metallurgy which can produce a sintered body having a high density can be obtained without performing additional treatment.

In the metal powder for powder metallurgy of the present invention, Fe is preferably further contained in a proportion of 0.5 to 5 mass%.

This can further improve the mechanical properties of the sintered body to be produced.

In the metal powder for powder metallurgy of the present invention, it is preferable that X1/X2 is 0.3 or more and 3 or less, when a value obtained by removing a content of the first element by a mass number of the first element is X1 and a value obtained by removing a content of the second element by a mass number of the second element is X2.

Thus, the variation in timing of the precipitation of the carbide of the first element or the like and the precipitation of the carbide of the second element or the like can be optimized when the metal powder for powder metallurgy is fired. As a result, the pores remaining in the molded body can be sequentially removed from the inside and discharged, and therefore, the occurrence of pores in the sintered body can be suppressed to the minimum. Therefore, a metal powder for powder metallurgy which can produce a sintered body having a high density and excellent sintered body characteristics can be obtained.

In the metal powder for powder metallurgy according to the present invention, the total content of the first element and the second element is preferably 0.05 mass% or more and 0.6 mass% or less.

This makes it possible to obtain a sintered body which is required to have a high density and is sufficient.

In the metal powder for powder metallurgy of the present invention, the average particle diameter is preferably 0.5 μm or more and 30 μm or less.

This makes it possible to produce a sintered body having a particularly high density and excellent mechanical properties because the number of voids remaining in the sintered body is extremely small.

The composite of the present invention is characterized by comprising the metal powder for powder metallurgy of the present invention.

This results in a composite capable of producing a sintered body having a high density.

The granulated powder of the present invention is characterized by comprising the metal powder for powder metallurgy of the present invention.

This gives a granulated powder which can produce a sintered body having a high density.

The sintered body of the present invention is characterized in that Co is a main component, Cr is contained at a ratio of 10 to 25 mass%, Ni is contained at a ratio of 5 to 40 mass%, at least one of Mo and W is contained at a ratio of 2 to 20 mass%, Si is contained at a ratio of 0.3 to 1.5 mass%, C is contained at a ratio of 0.05 to 0.8 mass%, one element selected from the group consisting of Ti, V, Y, Zr, Nb, Hf and Ta is used as a first element, one element selected from the group, that is, an element having a larger group than the first element in the periodic table or an element having the same group as the first element and having a larger period than the first element in the periodic table is used as a second element, the first element is contained at a ratio of 0.01 to 0.5 mass%, the second element is contained in a proportion of 0.01 to 0.5 mass%.

Thus, a high-density sintered body can be obtained without additional treatment.

The heat-resistant member of the present invention is characterized by comprising the sintered body of the present invention.

Thus, a heat-resistant member having high density and excellent heat resistance can be obtained without additional treatment.

Drawings

Fig. 1 is a side view (a view in a plan view of an airfoil portion) showing a nozzle blade for a turbo charger to which a first embodiment of a heat-resistant member according to the present invention is applied.

FIG. 2 is a top 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 wing to which a second embodiment of the heat-resistant member of the present invention is applied.

Description of the symbols

1 … nozzle blade; 2 … compressor wing; 11 … a shaft portion; 12 … wing portions; 13 … axis; 14 … a central aperture; 15 … flat portion; 16 … edge portions; 17, chamfering; 18 … chamfering; 21 … inner rim; 22 … outer rim; 23 … wing portions; angle θ ….

Detailed Description

The metal powder, composite, granulated powder, sintered body, and heat-resistant member for powder metallurgy according to the present invention will be described in detail below.

[ Metal powder for powder metallurgy ]

First, the metal powder for powder metallurgy of the present invention will be explained.

In powder metallurgy, a composition including a metal powder for powder metallurgy and a binder is formed into a desired shape, and then degreased and fired, whereby a sintered body having a desired shape can be obtained. This powder metallurgy technique has an advantage that a sintered body having a complicated and fine shape can be produced in a near-net shape (a shape close to a final shape) as compared with other metallurgical techniques.

Conventionally, attempts have been made to increase the density of a sintered body to be produced by appropriately changing the composition of a metal powder for powder metallurgy used in powder metallurgy. However, since voids are easily formed in the sintered body, it is necessary to further increase the density of the sintered body in order to obtain mechanical properties equivalent to those of the molten material.

Conventionally, the obtained sintered body may be additionally subjected to Hot Isostatic Pressing (HIP) treatment or the like to increase the density. However, such additional processing involves much trouble and cost, and therefore, it is disadvantageous in terms of expanding the use of the sintered body.

In view of the above-described problems, the present inventors have conducted intensive studies on conditions for obtaining a high-density sintered body without performing additional treatment. As a result, the composition of the alloy constituting the metal powder was optimized to increase the density of the sintered body, and the present invention was completed.

Specifically, the metal powder for powder metallurgy according to the present invention is characterized in that Co is a main component, and contains Cr at a ratio of 10 to 25 mass%, Ni at a ratio of 5 to 40 mass%, at least one of Mo and W at a ratio of 2 to 20 mass%, Si at a ratio of 0.3 to 1.5 mass%, C at a ratio of 0.05 to 0.8 mass%, a first element described later at a ratio of 0.01 to 0.5 mass%, and a second element described later at a ratio of 0.01 to 0.5 mass%. According to this metal powder, the alloy composition can be optimized, and as a result, densification during sintering can be particularly improved. As a result, a high-density sintered body can be produced without additional processing.

Further, by making the sintered body high in density, a sintered body excellent in mechanical properties can be obtained. Such a sintered body can be widely used in applications where an external force (load) is applied, for example, to a machine component, a structural member, or the like.

The first element is an element selected from the group consisting of seven elements of Ti, V, Y, Zr, Nb, Hf and Ta. The second element is an element selected from the group consisting of the seven elements and having a group larger than the first element, or an element selected from the group consisting of the seven elements and having a group identical to the element selected as the first element and having a period larger than the first element.

The alloy composition of the metal powder for powder metallurgy according to the present invention will be described in more detail below. In the following description, the metal powder for powder metallurgy may be simply referred to as "metal powder".

(Cr)

Cr (chromium) is an element that imparts corrosion resistance and oxidation resistance to the sintered body to be produced, and by using a metal powder containing Cr, a sintered body capable of maintaining high mechanical properties for a long period of time can be obtained. Therefore, a structural member that can maintain the function even if exposed to high temperature, for example, can be realized.

The content of Cr in the metal powder is 10 mass% to 25 mass%, preferably 15 mass% to 24 mass%, and more preferably 18 mass% to 23 mass%. If the content of Cr is less than the lower limit, the corrosion resistance of the sintered body to be produced will be insufficient depending on the whole composition, and the heat resistance will be lowered. On the other hand, if the Cr content exceeds the upper limit, the sinterability decreases depending on the entire composition, and it becomes difficult to increase the density of the sintered body. This makes it difficult to improve the corrosion resistance (heat resistance) of the sintered body to be produced.

(Ni)

By adding Ni (nickel) together with Cr, pitting corrosion and the rate of corrosion development of the chromium oxide layer formed on the surface of the sintered body can be reduced, and the strength (heat resistance) of the sintered body at high temperatures can be improved. Further, the heat resistance of the sintered body can be achieved from the viewpoint that the austenitization can stabilize the crystal phase in the sintered body even at high temperature.

The Ni content in the metal powder is 5 mass% to 40 mass%, preferably 7 mass% to 37 mass%, and more preferably 9 mass% to 36 mass%. If the Ni content is less than the lower limit, corrosion resistance and heat resistance are reduced. On the other hand, if the Ni content is higher than the upper limit, the Cr and Co contents relatively decrease, and therefore the corrosion resistance and heat resistance also decrease.

(Mo and W)

Mo (molybdenum) and W (tungsten) each enhance the heat resistance of the sintered body produced. Mo and W are combined with C to form carbide, respectively, but it is considered that the carbide improves the high-temperature strength. Further, by using Cr in combination, the mechanical strength and hardness of the sintered body can be improved even at high temperatures. Therefore, the heat resistance of the sintered body can be improved.

The metal powder contains at least one of Mo and W. The content of Mo and W in the metal powder is 2 mass% or more and 20 mass% or less, but is preferably 5 mass% or more and 18 mass% or less, and more preferably 7 mass% or more and 16 mass% or less, based on the total of Mo and W. If the total content of Mo and W is less than the lower limit, there is a possibility that the heat resistance of the sintered body cannot be sufficiently improved. On the other hand, if the total content of Mo and W exceeds the upper limit, a large amount of intermetallic compounds may be formed to embrittle the sintered body.

In addition, in the case where the metal powder contains both Mo and W, the ratio of Mo and W is not particularly limited, but is preferably 10: 90 above 90: less than 10, more preferably 20: 80 above 80: 20 or less.

(Si)

Si (silicon) plays a role in improving corrosion resistance and mechanical properties of the sintered body to be produced. When Si is added, oxides of metal elements such as Co are reduced in the alloy, and silicon oxide in which a part of Si is oxidized is generated. Examples of the silicon oxide include SiO and SiO 2. The silicon oxide can inhibit the metal crystal from growing to be significantly enlarged during the sintering of the metal powder. Therefore, in the alloy to which Si is added, the grain size of the metal crystal is suppressed to be small, and the corrosion resistance and mechanical properties of the sintered body can be further improved. In particular, when Co atoms are replaced with Si atoms as a replacement element, the crystal structure is slightly distorted, and the young's modulus is increased. Therefore, by adding Si, excellent mechanical properties, particularly excellent young's modulus, can be obtained. As a result, a sintered body having higher deformation resistance even at high temperatures can be obtained.

The content of Si in the metal powder is 0.3 mass% or more and 1.5 mass% or less, preferably 0.4 mass% or more and 1.2 mass% or less, and more preferably 0.5 mass% or more and 1 mass% or less. If the content of Si is less than the lower limit, the amount of silicon oxide is too small depending on the sintering conditions, and there is a concern that the metal crystal tends to increase during sintering of the metal powder. On the other hand, if the Si content exceeds the upper limit, the amount of silicon oxide becomes excessive depending on the sintering conditions, and therefore, a region in which silicon oxide is spatially continuously distributed is likely to be generated. In this region, the possibility of the mechanical characteristics being degraded increases.

(C)

C (carbon) can be used in combination with a first element and a second element described later, thereby particularly improving sinterability and increasing the density. Specifically, the first element and the second element are respectively bonded to C to generate carbide. This carbide is dispersed and precipitated, and thus, the effect of preventing the remarkable growth of crystal grains is exerted. The reason why such an effect can be obtained is not clear, but it is considered that, as one of the reasons, dispersed precipitates are an obstacle to remarkable growth of crystal grains, and therefore, fluctuation in crystal grain size can be suppressed. This makes it difficult to form voids in the sintered body, and prevents the crystal grains from being enlarged, thereby obtaining a sintered body having high density and high mechanical properties.

The content of C in the metal powder is 0.05 to 0.8 mass%, preferably 0.2 to 0.6 mass%, and more preferably 0.3 to 0.5 mass%. If the content of C is less than the lower limit, crystal grains tend to grow depending on the whole composition, and the mechanical properties of the sintered body become insufficient. On the other hand, if the content of C exceeds the above upper limit, the content of C becomes too large depending on the entire composition, and the sinterability is rather lowered.

(first element and second element)

The first element and the second element precipitate carbide and oxide (hereinafter, collectively referred to as "carbide and the like"). Further, it is considered that the precipitated carbide and the like inhibit the remarkable growth of crystal grains when the metal powder is sintered. As a result, it becomes difficult to form voids in the sintered body as described above, and at the same time, the increase in the grain size is prevented, and a sintered body having high density and high mechanical properties is obtained.

In addition, as will be described in detail later, precipitated carbides and the like promote the aggregation of silica at grain boundaries, and as a result, it is possible to promote sintering and increase the density while suppressing the increase in the crystal grain size.

The first element and the second element are two elements selected from the group consisting of Ti, V, Y, Zr, Nb, Hf, and Ta seven elements, but preferably include elements (Ti, Y, Zr, Hf) belonging to group 3A or group 4A of the long-period periodic table. By including an element belonging to group 3A or group 4A as at least one of the first element and the second element, oxygen contained in the metal powder in the form of an oxide is removed during sintering, and the sinterability of the metal powder can be particularly improved.

The first element may be one element selected from the group consisting of seven elements of Ti, V, Y, Zr, Nb, Hf and Ta as described above, but is preferably an element belonging to group 3A or group 4A of the long-period periodic table. The elements belonging to group 3A or group 4A in the above group remove oxygen contained in the metal powder in the form of an oxide, and further can particularly improve the sinterability of the metal powder. This can reduce the concentration of oxygen remaining in the grains after sintering. As a result, the oxygen content of the sintered body can be reduced, and the density can be increased. Further, these elements are highly active elements, and therefore, it is considered that rapid atomic diffusion is brought about. Therefore, the atomic diffusion becomes a driving force to efficiently shorten the inter-particle distance of the metal powder, and the neck portion is formed between the particles to promote the densification of the compact. As a result, the density of the sintered body can be further increased.

On the other hand, the second element may be one element selected from the group consisting of Ti, V, Y, Zr, Nb, Hf and Ta as described above and may be an element different from the first element, but it is preferably an element belonging to group 5A of the long period periodic table in the above group. The element belonging to group 5A in the above group efficiently precipitates particularly the carbide and the like, and therefore can efficiently inhibit the remarkable growth of crystal grains during sintering. As a result, the generation of fine crystal grains can be promoted, and the density of the sintered body can be increased and the mechanical properties can be improved.

In the combination of the first element and the second element composed of the above-described elements, the respective effects are exhibited without interfering with each other. Therefore, the metal powder including the first element and the second element is a metal powder capable of producing a sintered body having an extremely high density.

Further, it is more preferable to use a combination of an element in which the first element is an element belonging to group 4A and the second element is Nb.

Further, it is more preferable to use a combination of Zr or Hf as the first element and Nb as the second element.

By adopting such a combination, the above-described effect becomes more remarkable.

Among these elements, Zr is a ferrite-forming element, and therefore can precipitate a body-centered cubic lattice phase. Such a body-centered cubic lattice phase has superior sinterability to other 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 preferably set to 0.03 mass% or more and 0.2 mass% or less, and more preferably 0.05 mass% or more and 0.1 mass% or less. If the content of the first element is less than the lower limit, the effect of adding the first element is weak for some of the entire composition, and therefore, the density of the sintered body to be produced becomes insufficient. On the other hand, if the content of the first element exceeds the upper limit, the first element becomes too large in some entire compositions, so that the proportion of the carbide or the like described above becomes too large, and the densification is adversely impaired.

The content of the second element in the metal powder is set to 0.01 mass% or more and 0.5 mass% or less, but is preferably set to 0.03 mass% or more and 0.2 mass% or less, and more preferably 0.05 mass% or more and 0.1 mass% or less. If the content of the second element is less than the lower limit, the effect of adding the second element is weak for some of the entire composition, and therefore, the density of the sintered body to be produced becomes insufficient. On the other hand, if the content of the second element exceeds the above upper limit, the second element becomes too large in some entire compositions, so that the proportion of the carbide or the like described above becomes too large, and the densification is adversely impaired.

In addition, as described above, when the first element and the second element each precipitate carbide or the like, and the element belonging to group 3A or group 4A is selected as the first element as described above and the element belonging to group 5A is selected as the second element as described above, it is estimated that the timing (timing) at which the carbide or the like of the first element precipitates and the timing at which the carbide or the like of the second element precipitates are shifted from each other in the sintered metal powder. By shifting the timing of precipitation of carbide and the like in this manner, sintering proceeds slowly, and therefore, it is considered that generation of voids is suppressed, and a dense sintered body is obtained. That is, it is considered that the presence of both the carbide of the first element and the carbide of the second element can increase the density and suppress the enlargement of crystal grains.

Further, the ratio of the content of the first element to the content of the second element is preferably set 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.

Specifically, when the value obtained by removing the content E1 (mass%) of the first element by the mass number of the first element is an index X1 and the value obtained by removing the content E2 (mass%) of the second element by the mass number of the second element is an index X2 when the first element is E1 and the second element is E2, 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, and still more preferably 0.75 or more and 1.3 or less. By setting X1/X2 within the above range, the deviation between the timing of precipitation of the carbide of the first element or the like and the timing of precipitation of the carbide of the second element or the like can be optimized when the metal powder is fired. This allows the pores remaining in the molded body to be sequentially cleaned from the inside and discharged, thereby minimizing the occurrence of pores in the sintered body. Therefore, by setting X1/X2 within the above range, a sintered body having high density and excellent mechanical properties can be obtained. Further, since the balance between the number of atoms of the first element and the number of atoms of the second element is optimized, the effect of the first element and the effect of the second element are exerted in a double manner, and a sintered body having a particularly high density can be obtained.

Here, as an example of a specific combination of the first element and the second element, a ratio E1/E2 of the content ratio (mass%) of the first element E1 to the content ratio (mass%) of the second element E2 is also calculated from the range of the ratio X1/X2 described above.

For example, in the case where the first element E1 is Zr and the second element E2 is Nb, the mass number of Zr is 91.2 and the mass number of Nb is 92.9, and thus E1/E2 is preferably 0.29 to 2.95, and more preferably 0.49 to 1.96.

In addition, in the case where the first element E1 is Hf and the second element E2 is Nb, since the mass number of Hf is 178.5 and the mass number of Nb is 92.9, E1/E2 is preferably 0.58 to 5.76, and more preferably 0.96 to 3.84.

In addition, in the case where the first element E1 is Ti and the second element E2 is Nb, since the mass number of Ti is 47.9 and the mass number of Nb is 92.9, E1/E2 is preferably 0.15 to 1.55, and more preferably 0.26 to 1.03.

In addition, when the first element E1 is Nb and the second element E2 is Ta, the mass number of Nb is 92.9 and the mass number of Ta is 180.9, and therefore E1/E2 is preferably 0.15 to 1.54, and more preferably 0.26 to 1.03.

In addition, when the first element E1 is Y and the second element E2 is Nb, the mass number of Y is 88.9 and the mass number of Nb is 92.9, and therefore E1/E2 is preferably 0.29 to 2.87, and more preferably 0.48 to 1.91.

In addition, in the case where the first element E1 is V and the second element E2 is Nb, since the mass number of V is 50.9 and the mass number of Nb is 92.9, E1/E2 is preferably 0.16 to 1.64, and more preferably 0.27 to 1.10.

In addition, in the case where the first element E1 is Ti and the second element E2 is Zr, the mass number of Ti is 47.9 and the mass number of Zr is 91.2, and therefore E1/E2 is preferably 0.16 to 1.58, and more preferably 0.26 to 1.05.

In addition, when the first element E1 is Zr and the second element E2 is Ta, the mass number of Zr is 91.2 and the mass number of Ta is 180.9, and therefore E1/E2 is preferably 0.15 to 1.51, and more preferably 0.25 to 1.01.

In addition, when the first element E1 is Zr and the second element E2 is V, the mass number of Zr is 91.2 and the mass number of V is 50.9, and thus E1/E2 is preferably 0.54 to 5.38, and more preferably 0.90 to 3.58.

In addition to the combinations described above, E1/E2 can be calculated in the same manner as described above.

When the total of the content of the first element E1 and the content of the second element E2 is E1+ E2, E1+ E2 is preferably 0.05% by mass or more and 0.6% by mass or less, more preferably 0.10% by mass or more and 0.48% by mass or less, and still more preferably 0.12% by mass or more and 0.24% by mass or less. By setting the total content of the first element and the second element within the above range, an amount for the first element or the second element to act sufficiently when the metal powder is fired can be secured, and densification of the produced sintered body will be necessary and sufficient.

When the ratio of the total of the content of the first element E1 and the content of the second element E2 to the content of Si is (E1+ E2)/Si, (E1+ E2)/Si is preferably 0.03 to 2, more preferably 0.05 to 1, and still more preferably 0.1 to 0.5. By setting (E1+ E2)/Si within the above range, it is possible to sufficiently compensate for the problem of, for example, the decrease in toughness when Si is added, by the addition of the first element and the second element. As a result, a sintered body having excellent mechanical properties such as toughness and corrosion resistance due to Si can be obtained in spite of its high density.

Further, it is considered that by adding an appropriate amount of the first element and the second element, a carbide of the first element or the like and a carbide of the second element or the like become "nuclei" at crystal grain boundaries in the sintered body, and silicon oxide is aggregated. The concentration of oxide in the crystal grains is reduced due to the concentration of silicon oxide at the crystal grain boundaries, thereby achieving the purpose of promoting sintering. As a result, it is considered that densification of the sintered body is further promoted.

In addition, since the precipitated silicon oxide is likely to move to a triple point of the grain boundary in the process of aggregation, crystal growth (pinning effect) at this point can be suppressed. As a result, significant growth of crystal grains can be suppressed, and a sintered body having finer crystal grains can be obtained. Such sintered bodies have particularly high mechanical properties.

When the ratio of the total of the content of the first element E1 and the content of the second element E2 to the content of C is (E1+ E2)/C, (E1+ E2)/C is preferably 0.05 or more and 3 or less, more preferably 0.1 or more and 2 or less, and still more preferably 0.2 or more and 1 or less. By setting (E1+ E2)/C within the above range, the increase in hardness and the decrease in toughness when C is added and the densification by the addition of the first element and the second element can be simultaneously performed. As a result, a metal powder capable of producing a sintered body excellent in mechanical properties such as tensile strength and toughness can be obtained.

In addition, although the metal powder may contain two elements selected from the group consisting of Ti, V, Y, Zr, Nb, Hf and Ta, an element selected from the group, that is, an element different from the two elements may be contained. That is, the metal powder may contain 3 or more elements selected from the above group. This can enhance the above effect even though the combination method is somewhat different.

(other elements)

The metal powder for powder metallurgy of the present invention may contain at least one of Fe, B, Mn, and S, if necessary, in addition to the above elements. In addition, these elements may be inevitably contained.

Fe (iron) imparts high mechanical properties to the sintered body produced.

Although not particularly limited, the content of Fe in the metal powder is preferably 0.5 mass% or more and 5 mass% or less, more preferably 0.8 mass% or more and 3 mass% or less, and further preferably 1 mass% or more and 2.5 mass% or less. By setting the Fe content in the metal powder within the above range, the mechanical properties of the sintered body to be produced can be further improved.

If the Fe content is less than the lower limit, the mechanical properties of the sintered body may not be sufficiently improved depending on the overall composition. On the other hand, if the Fe content exceeds the above upper limit, there is a concern that the corrosion resistance and oxidation resistance of the sintered body may be reduced depending on the composition of the whole body.

B (boron) strengthens the grain boundary and improves the high-temperature strength and ductility of the sintered body.

The content of B in the metal powder is not particularly limited, but is preferably 0.002 to 0.1 mass%, more preferably 0.004 to 0.05 mass%, and still more preferably 0.006 to 0.02 mass%. By setting the content of B within the above range, a sintered body excellent in heat resistance and ductility can be obtained.

If the content of B is less than the lower limit, the heat resistance of the sintered body to be produced may be lowered and the brittleness may be increased depending on the overall composition. On the other hand, if the content of B is higher than the above upper limit, there is a fear that the heat resistance and ductility may be deteriorated conversely.

Like Si, Mn (manganese) imparts corrosion resistance and high mechanical properties to the sintered body produced.

The Mn content in the metal powder is not particularly limited, but is preferably 0.005 mass% or more and 0.3 mass% or less, and more preferably 0.01 mass% or more and 0.1 mass% or less. By setting the Mn content within the above range, a sintered body having high density and excellent mechanical properties can be obtained. In addition, an increase in brittleness at high temperatures (red heat) can be suppressed.

If the Mn content is less than the lower limit, there is a fear that the corrosion resistance and mechanical properties of the produced sintered body cannot be sufficiently improved depending on the overall composition, while if the Mn content is more than the upper limit, there is a fear that the corrosion resistance and mechanical properties are rather lowered.

S (sulfur) improves the machinability of the sintered body produced.

The content of S in the metal powder is not particularly limited, but is preferably 0.5 mass% or less, and more preferably 0.01 mass% or more and 0.3 mass% or less. By setting the S content within the above range, the machinability of the produced sintered body can be further improved without causing a significant decrease in the density of the produced sintered body.

In addition, N, Al, P, Se, Te, Pd, and the like may be added to the metal powder for powder metallurgy of the present invention. In this case, the content of these elements is not particularly limited, but is preferably 0.05% by mass or less, and is preferably less than 0.2% by mass in total. In addition, these elements may be inevitably contained.

The metal powder for powder metallurgy of the present invention may contain impurities. Examples of the impurities include all elements other than the above-mentioned elements, specifically, Li, Be, Na, Mg, K, Ca, Sc, Zn, Ga, Ge, Ag, In, Sn, Sb, Os, Ir, Pt, Au, and Bi. The mixing amounts of these impurities are preferably controlled so that the respective elements are less than the respective contents of the essential elements. The mixing amount of these impurities is preferably set to less than 0.03 mass%, more preferably less than 0.02 mass%. Further, the total amount is preferably less than 0.3% by mass, more preferably less than 0.2% by mass. In addition, as long as the content of these elements is within the above range, the above effects are not hindered, and therefore, they may be intentionally added.

On the other hand, O (oxygen) may be intentionally added or inevitably mixed, but the content thereof is preferably about 0.8% by mass or less, more preferably about 0.5% by mass or less. By suppressing the oxygen content in the metal powder to such a degree, a sintered body having high sinterability, high density, and excellent mechanical properties is obtained. The lower limit is not particularly limited, but is preferably 0.03 mass% or more from the viewpoint of ease of mass production and the like.

Co (cobalt) is a component (main component) having the highest content in the alloy constituting the metal powder for powder metallurgy of the present invention, and has a large influence on the characteristics of the sintered body. The content of Co is not particularly limited, but is preferably 45 mass% or more, and more preferably 50 mass% or more.

The composition ratio of the metal powder for powder metallurgy can be determined by the following method: examples of the method include an iron and steel atomic absorption spectrometry method defined in JIS G1257 (2000), an iron and steel ICP emission spectrometry method defined in JIS G1258 (2007), an iron and steel spark discharge emission spectrometry method defined in JIS G1253 (2002), an iron and steel X-ray fluorescence analysis method defined in JIS G1256 (1997), and a gravimetric, titrimetric, and absorptiometric method defined in JIS G1211 to JIS G1237. Specifically, there may be mentioned: for example, a solid emission spectrum analyzer (spark discharge emission spectrum analyzer, model: SPECTROLA; type: LAVMBO8A) manufactured by SPECTRO corporation, and an ICP apparatus (CIROS120 type) manufactured by Japan science (K.K.).

JIS G1211 to G1237 are as follows.

Method for determining iron and steel-carbon in JIS G1211 (2011)

JIS G1212 (1997) method for determining iron and steel-silicon

JIS G1213 (2001) method for determining iron and steel-manganese

JIS G1214 (1998) method for determining iron and steel-phosphorus

JIS G1215 (2010) method for determining iron and steel-sulfur content

JIS G1216 (1997) method for determining iron and steel-nickel content

JIS G1217 (2005) method for determining iron and steel-chromium

JIS G1218 (1999) method for determining iron and steel-molybdenum

JIS G1219 (1997) method for determining iron and steel-copper

JIS G1220 (1994) method for determining the quantity of iron and steel-tungsten

JIS G1221 (1998) method for quantifying iron and steel-vanadium

JIS G1222 (1999) method for determining iron and steel-cobalt

JIS G1223 (1997) method for determining iron and steel-titanium

JIS G1224 (2001) method for determining iron and steel-aluminum

JIS G1225 (2006) method for determining iron and Steel-arsenic

JIS G1226 (1994) method for determining iron and steel-tin

JIS G1227 (1999) method for determining iron and steel-boron

JIS G1228 (2006) method for determining iron and steel-nitrogen

JIS G1229 (1994) Steel-lead quantitative method

Method for determining zirconium in JIS G1232 (1980) steel

JIS G1233 (1994) steel-selenium quantitative method

Method for quantifying tellurium in JIS G1234 (1981) steel

Method for determining amount of antimony in iron and steel according to JIS G1235 (1981)

Method for quantifying tantalum in JIS G1236 (1992) steel

JIS G1237 (1997) method for determining iron and steel-niobium

In addition, for specifying C (carbon) and S (sulfur), oxygen flow combustion (high-frequency induction furnace combustion) -infrared absorption method specified in JIS G1211 (2011) may be exclusively used. Specifically, the carbon sulfur analyzer manufactured by LECO, CS-200, may be mentioned.

In addition, when N (nitrogen) and O (oxygen) are specified, a method for determining nitrogen in iron and steel specified in JIS G1228 (2006) and a method for determining oxygen in a metal material specified in JIS Z2613 (2006) may be used. Specifically, there may be mentioned: an oxygen/nitrogen analyzer, TC-300/EF-300, manufactured by LECO.

The average particle diameter of the metal powder for powder metallurgy of the present invention is preferably 0.5 μm or more and 30 μm or less, more preferably 1 μm or more and 20 μm or less, and further preferably 2 μm or more and 10 μm or less. By using the metal powder for powder metallurgy having such a particle diameter, the number of voids remaining in the sintered body can be extremely reduced, and therefore, a sintered body having a high density and excellent mechanical properties can be produced.

In the particle size distribution calculated by the mass standard by the laser diffraction method, the average particle size is a particle size at which the cumulative amount obtained from the smaller diameter side is 50%.

When the average particle diameter of the metal powder for powder metallurgy is less than the lower limit, moldability in forming a shape which is difficult to mold may be lowered, and the sintered density may be lowered.

Further, 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 is preferably 200 μm or less, more preferably 150 μm 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 further densification of the sintered body can be achieved.

The maximum particle size is a particle size at which the cumulative amount obtained from the smaller diameter side in the particle size distribution calculated by the laser diffraction method on a mass basis is 99.9%.

When the short diameter of the metal powder particles for powder metallurgy is S [ mu ] m and the long diameter thereof is L [ mu ] m, the average value of the aspect ratio defined by S/L is preferably 0.4 to 1, more preferably 0.7 to 1. Since the metal powder for powder metallurgy having such an aspect ratio is relatively close to a spherical shape, the filling ratio at the time of molding can be increased. As a result, the sintered body can be further densified.

The long diameter is a maximum length obtainable in a projection image of the particle, and the short diameter is a maximum length in a direction perpendicular to the long diameter. The average value of the aspect ratio is obtained as an average value of the aspect ratio values measured for 100 or more particles.

The tap density of the metal powder for powder metallurgy of the present invention is preferably 3.5g/cm³Above, more preferably 4g/cm³The above. The metal powder for powder metallurgy having a high tap densityWhen a molded article is obtained, the filling property between particles becomes particularly high. Thus, a particularly dense sintered body can be obtained in the end.

The specific surface area of the metal powder for powder metallurgy of the present invention is not particularly limited, but is preferably 0.1m²More preferably 0.2 m/g or more²More than g. When the metal powder for powder metallurgy has such a large specific surface area, the surface activity (surface energy) becomes high, and sintering becomes easy even if a smaller amount of energy is applied. Therefore, when the molded body is sintered, a difference in sintering rate is less likely to occur between the inside and the outside of the molded body, and a phenomenon in which the sintering density is decreased due to the remaining pores on the inside can be suppressed.

The metal powder for powder metallurgy of the present invention may be a powder (pre-alloyed powder) composed of only particles having a single composition, or may be a mixed powder (pre-mixed powder) composed of a plurality of particles having different compositions. In the case of the premixed powder, the whole may satisfy the above combination ratio. This can provide the same effects as described above with the premixed powder, and can produce a high-density sintered body.

Specific examples of the premixed powder include: for example, a mixed powder of a powder obtained by subtracting C (carbon) from the above combination ratio and a C powder (carbon powder), and a mixed powder of a powder obtained by subtracting the first element and the second element from the above combination ratio and a powder of the first element and a powder of the second element. Further, the combination of plural kinds of powders of the mixed powder is not particularly limited, and may be any combination.

[ method for producing sintered body ]

Next, a method for producing a sintered body using the metal powder for powder metallurgy of the present invention will be described.

The method of manufacturing a sintered body includes: [A] a composition preparation step of preparing a composition for producing a sintered body, [ B ] a molding step of producing a molded body, [ C ] a degreasing step of performing degreasing treatment, and [ D ] a firing step of firing. Hereinafter, the respective steps will be described in order. .

[A] Composition preparation step

First, the metal powder for powder metallurgy and the binder according to the above embodiment are prepared, and kneaded by a kneader to obtain a kneaded product.

The kneaded product (embodiment of the composite of the present invention) contains metal powder for powder metallurgy, and is uniformly dispersed. That is, the kneaded product contains a metal powder for powder metallurgy and a binder for binding the particles thereof to each other. According to such a kneaded product (composite), a sintered body having a high density can be easily produced.

The metal powder for powder metallurgy of the present invention is produced by various powdering methods such as an atomization method (for example, a water atomization method, a gas atomization method, a high-speed rotating water stream atomization method, and the like), a reduction method, a carbonyl method, a pulverization method, and the like.

Among them, the metal powder for powder metallurgy of the present invention is preferably produced by an atomization method, and more preferably produced by a water atomization method or a high-speed rotating water stream atomization method. The atomization method is a method of producing metal powder by impinging molten metal (molten metal) on a fluid (liquid or gas) sprayed at a high speed to pulverize the molten metal and cool it at the same time. By producing a metal powder for powder metallurgy by such an atomization method, an extremely fine powder can be efficiently produced. Also, the particle shape of the obtained powder becomes close to a spherical shape by the action of surface tension. Thus, a powder having a high filling rate when molded is obtained. That is, a powder capable of producing a sintered body having a high density can be obtained.

When the atomization method is a water atomization method, the pressure of water injected into the molten metal (hereinafter referred to as "atomized water") is not particularly limited, but is preferably set to 75MPa to 120MPa (750 kgf/cm) inclusive²Above 1200kgf/cm²Below), more preferably 90MPa to 120MPa (900 kgf/cm)²Above 1200kgf/cm²Below) about.

The temperature of the atomized water is not particularly limited, but is preferably set to about 1 ℃ to 20 ℃.

Most of the atomized water is sprayed in a conical shape having a vertex on a falling path of the molten metal and an outer diameter gradually decreasing downward. In this case, the vertex angle of the cone formed by the atomized water is preferably about 10 ° to 40 °, more preferably about 15 ° to 35 °. Thus, the metal powder for powder metallurgy having the above composition can be reliably produced.

Further, according to the water atomization method (particularly, the high-speed rotating water atomization method), the molten metal can be cooled extremely rapidly. Thus, a high quality powder in a wide range of alloy compositions is obtained.

The cooling rate in cooling the molten metal by the atomization method is preferably 1 × 10⁴More preferably 1X 10℃/s or higher⁵The temperature is higher than the second temperature. By this rapid cooling, a homogeneous metal powder for powder metallurgy is obtained. As a result, a high-quality sintered body can be obtained.

The metal powder for powder metallurgy thus obtained may be classified as necessary. Examples of the method of classification include dry classification such as screen classification, inertial classification, and centrifugal classification; wet classification such as sedimentation classification, and the like.

On the other hand, examples of the binder include: polyolefins such as polyethylene, polypropylene, ethylene-vinyl acetate copolymers, and the like; acrylic resins such as polymethyl methacrylate and polybutyl methacrylate; styrene resins such as polystyrene; polyesters such as polyvinyl chloride, polyvinylidene chloride, polyamide, polyethylene terephthalate, and polybutylene terephthalate; various resins such as polyether, polyvinyl alcohol, polyvinyl pyrrolidone, and copolymers thereof; various organic binders such as various waxes, paraffins, higher fatty acids (e.g., stearic acid), higher alcohols, higher fatty acid esters, and higher fatty acid amides may be used by mixing one or more of these.

The content of the binder is preferably about 2 to 20 mass%, more preferably about 5 to 10 mass%, of the whole kneaded material. When the content of the binder is within the above range, the molded article can be formed with high moldability, and the density can be increased to particularly improve the stability of the molded article. In addition, by optimizing the difference in size between the molded body and the degreased body, the shrinkage ratio, and the reduction in dimensional accuracy of the finally obtained sintered body can be prevented. Namely, a sintered body having high density and high dimensional accuracy can be obtained.

In addition, a plasticizer may be added to the kneaded product as needed. Examples of the plasticizer include: for example, phthalate esters (e.g., DOP, DEP, DBP), adipate esters, trimellitate esters, sebacate esters, and the like, and one or more of these may be mixed and used.

In addition, various additives such as a lubricant, an antioxidant, a degreasing accelerator, and a surfactant may be added to the kneaded product as needed, in addition to the metal powder for powder metallurgy, the binder, and the plasticizer.

The kneading conditions vary depending on the metal composition or particle size of the metal powder for powder metallurgy to be used, the binder composition, the amount of the binder to be mixed, and other conditions, and examples thereof include a kneading temperature: can be 50 ℃ to 200 ℃ and the mixing time is as follows: the time can be 15 minutes to 210 minutes.

The kneaded mixture may be pelletized (pelletized) as needed. The pellet has a particle diameter of, for example, about 1mm to 15 mm.

In some of the molding methods described below, granulated powder may be produced instead of the kneaded material. These kneaded materials, granulated powders, and the like are examples of compositions to be subjected to a molding step described later.

An embodiment of the granulated powder according to the present invention is obtained by granulating the metal powder for powder metallurgy according to the above-described embodiment, and bonding a plurality of metal particles to each other with a binder. Such granulated powder can easily produce a high-density sintered body.

Examples of the binder for producing the granulated powder include: polyolefins such as polyethylene, polypropylene, ethylene-vinyl acetate copolymers, and the like; acrylic resins such as polymethyl methacrylate and polybutyl methacrylate; styrene resins such as polystyrene; polyesters such as polyvinyl chloride, polyvinylidene chloride, polyamide, polyethylene terephthalate, and polybutylene terephthalate; various resins such as polyether, polyvinyl alcohol, polyvinyl pyrrolidone, and copolymers thereof; various organic binders such as various waxes, paraffins, higher fatty acids (e.g., stearic acid), higher alcohols, higher fatty acid esters, and higher fatty acid amides may be used by mixing one or more of these.

Among them, a binder containing polyvinyl alcohol or polyvinyl pyrrolidone is preferable. Since these binder components have high binding properties, granulated powder can be efficiently formed even in a relatively small amount. Further, since the thermal decomposition property is high, the resin can be decomposed and removed reliably in a short time at the time of degreasing and firing.

The content of the binder is preferably about 0.2 to 10 mass%, more preferably about 0.3 to 5 mass%, and still more preferably about 0.3 to 2 mass% of the entire granulated powder. When the content of the binder is within the above range, granulated powder can be efficiently formed while suppressing significantly large particles from being granulated or a large amount of metal particles that have not been granulated from remaining. Further, since the moldability is improved, the stability of the shape of the molded article can be particularly improved. By setting the content of the binder within the above range, the shrinkage factor, which is the difference in size between the molded body and the degreased body, can be optimized, and the reduction in dimensional accuracy of the finally obtained sintered body can be prevented.

The granulated powder may be added with various additives such as a plasticizer, a lubricant, an antioxidant, a degreasing accelerator, and a surfactant, if necessary.

On the other hand, examples of the granulation treatment include: for example, Spray drying (Spray Dry), tumbling, fluidized bed, and tumbling are suitable.

In the granulation treatment, a solvent for dissolving the binder is used as necessary. Examples of such a solvent include: for example, an inorganic solvent such as water or carbon tetrachloride, or an organic solvent such as a ketone solvent, an alcohol solvent, an ether solvent, a cellosolve solvent, an aliphatic hydrocarbon solvent, an aromatic heterocyclic compound solvent, an amide solvent, a halogen compound solvent, an ester solvent, an amine solvent, a nitrile solvent, a nitro solvent, or an aldehyde solvent, and one or a mixture of two or more selected from these solvents can be used.

The average particle size of the granulated powder is not particularly limited, but is preferably about 10 μm to 200 μm, more preferably about 20 μm to 100 μm, and still more preferably about 25 μm to 60 μm. The granulated powder having such a particle diameter has good fluidity and can reflect the shape of the mold more faithfully.

The average particle size is determined as a particle size at which the cumulative particle size distribution on a mass basis obtained by a laser diffraction method has a cumulative amount of 50% from the small diameter side.

[B] Shaping step

Next, the kneaded product or granulated powder is molded to produce a molded body having the same shape as the target sintered body.

The method for producing the molded article (Molding method) is not particularly limited, and various Molding methods such as powder compacting (compression Molding), Metal powder Injection Molding (MIM), extrusion Molding, and three-dimensional Molding (3D Molding) can be used.

The molding conditions in the case of the powder compacting method vary depending on the composition and particle size of the metal powder for powder metallurgy used, the binder composition, the amount of the binder to be mixed, and other conditions, but the molding pressure is preferably 200MPa to 1000MPa (2 t/cm)²Above 10t/cm²Below) about.

In the case of the metal powder injection molding method, the molding conditions are different depending on the respective conditions, but it is preferable that the molding conditions are differentThe material temperature is above 80 ℃ and below 210 ℃, and the injection pressure is above 50MPa and below 500MPa (0.5 t/cm)²Above 5t/cm²Below) about.

The molding conditions in the case of the extrusion molding method vary depending on the conditions, but it is preferable that the material temperature is about 80 ℃ to 210 ℃ inclusive, and the extrusion pressure is about 50MPa to 500MPa (0.5 t/cm)²Above 5t/cm²Below) about.

The molded body thus obtained is in a state in which the binder is uniformly distributed in the gaps between the plurality of particles of the metal powder.

Specific examples of the three-dimensional forming method include a material extrusion deposition method, a material injection method, an adhesive injection method, and a stereolithography method.

The shape and size of the molded article to be produced are determined by estimating the shrinkage of the molded article in the subsequent degreasing step and firing step.

[C] Degreasing step

Next, the obtained molded body was subjected to degreasing treatment (binder removal treatment) to obtain a degreased body.

Specifically, the binder is decomposed by heating the molded body, and the binder is removed from the molded body, followed by degreasing. Examples of the degreasing treatment include a method of heating the molded article, a method of exposing the molded article to a gas that decomposes the binder, and the like.

In the case of the method of heating the molded article, the heating conditions of the molded article are somewhat different depending on the composition and the amount of the binder, but the temperature is preferably about 100 ℃ to 750 ℃ and 0.1 hour to 20 hours, and more preferably about 150 ℃ to 600 ℃ and 0.5 hour to 15 hours. This makes it possible to sufficiently degrease the molded body without sintering the molded body. As a result, the binder component can be reliably prevented from remaining in a large amount inside the degreased body.

The atmosphere in heating the molded article is not particularly limited, and examples thereof include: a reducing gas atmosphere such as hydrogen; an inert gas atmosphere such as nitrogen or argon; an oxidizing gas atmosphere such as the atmosphere, or a reduced pressure atmosphere obtained by reducing the pressure of these atmospheres.

On the other hand, examples of the gas for decomposing the binder include ozone gas and the like.

In addition, since the degreasing step is performed by dividing into a plurality of steps (steps) having different degreasing conditions, the binder in the molded body can be decomposed and removed more quickly without remaining in the molded body.

Further, the degreased body may be subjected to machining such as cutting, polishing, or cutting as necessary. Since the degreased body has a relatively low hardness and is relatively rich in plasticity, the shape of the degreased body can be prevented from being deformed, and the degreased body can be easily machined. By such machining, a sintered body with high final dimensional accuracy can be easily obtained.

[D] Firing Process

The degreased body obtained in the step [ C ] is fired in a firing furnace to obtain a sintered body.

By this firing, the metal powder for powder metallurgy is diffused at the interface between the particles until sintering. In this case, the degreased body is rapidly sintered by the mechanism described above. As a result, a high-density sintered body which is dense as a whole is obtained.

The firing temperature varies depending on the composition, particle size, and the like of the metal powder for powder metallurgy used for producing the molded article and the degreased body, and may be set to about 980 ℃ to about 1450 ℃. Preferably, the temperature is set to 1050 ℃ to 1350 ℃.

The firing time may be set to 0.2 hours or more and 7 hours or less, but is preferably set to 1 hour or more and 6 hours or less.

In the firing step, the firing temperature or firing atmosphere described later may be changed in the middle.

By setting the firing conditions within such a range, the entire degreased body can be sufficiently sintered while preventing excessive progress of sintering to cause overburning and further thickening of the crystal structure. As a result, a sintered body having a high density and particularly excellent mechanical properties can be obtained.

Further, since the firing temperature is relatively low, the heating temperature of the firing furnace can be easily controlled to be constant, and the temperature of the degreased body can be easily made constant. As a result, a more homogeneous sintered body can be produced.

Further, since the above-described firing temperature is a firing temperature that can be sufficiently realized in a general firing furnace, it is possible to use an inexpensive firing furnace and to suppress the running cost. In other words, when the above-mentioned firing temperature is exceeded, it may be necessary to use an expensive firing furnace using a special heat-resistant material, and the running cost is increased.

The atmosphere during firing is not particularly limited, but when preventing significant oxidation of the metal powder, it is preferable to use a reducing atmosphere such as hydrogen, an inert gas atmosphere such as argon, or a reduced pressure atmosphere obtained by reducing the pressure of these atmospheres.

In place of the series of steps described above, that is, the composition preparation step, the molding step, the degreasing step, and the firing step, the metal powder may be fired by irradiating the metal powder with an energy beam such as a laser beam to produce a sintered body. According to this method, a metal powder is irradiated with an energy beam such as a laser beam to be spread flatly, and the metal powder is sintered in an irradiation region, thereby producing a sintered body having an arbitrary shape based on the shape of the irradiation region (powder sintering and stacking molding method). This enables a more simple production of the sintered body.

The sintered body thus obtained is an example having the composition of the metal powder for powder metallurgy according to the above-described embodiment.

Specifically, the sintered body according to the present embodiment is characterized in that Co is a main component, Cr is contained at a ratio of 10 mass% to 25 mass%, Ni is contained at a ratio of 5 mass% to 40 mass%, at least one of Mo and W is contained at a ratio of 2 mass% to 20 mass% in total, Si is contained at a ratio of 0.3 mass% to 1.5 mass%, C is contained at a ratio of 0.05 mass% to 0.8 mass%, the first element is contained at a ratio of 0.01 mass% to 0.5 mass%, and the second element is contained at a ratio of 0.01 mass% to 0.5 mass%.

Such a sintered body is a sintered body having high density and excellent mechanical properties without additional treatment. That is, a sintered body produced by molding a composition comprising the metal powder for powder metallurgy of the present invention and a binder, and then degreasing and sintering the molded body has a higher relative density than a sintered body obtained by sintering a conventional metal powder. Therefore, according to the present invention, a high-density sintered body which could not be achieved without performing additional processing such as HIP processing in the past can be realized without performing additional processing.

Specifically, according to the present invention, although the composition of the metal powder for powder metallurgy is somewhat different, as an example, it can be expected that the relative density is improved by 2% or more compared to the conventional one.

As a result, the relative density of the obtained sintered body can be expected to be 97% or more (preferably 98% or more, and more preferably 98.5% or more), as an example. A sintered body having a relative density in such a range is a sintered body having a shape infinitely close to a target shape by the powder metallurgy technique, but has excellent mechanical properties comparable to those of a molten material, and therefore can be applied to various machine parts, structural members, and the like without performing any subsequent processing.

The sintered body obtained has sufficiently high density and mechanical properties even without additional treatment, but various additional treatments may be performed in order to further increase the density and improve the mechanical properties.

The additional treatment may be, for example, an additional treatment for increasing the density, such as the HIP treatment described above, or various quenching treatments, various ice-cooling treatments, various tempering treatments, various annealing treatments, or the like.

In the above-described firing step and various additional treatments, the light element in the metal powder (in the sintered body) volatilizes, and the composition of the finally obtained sintered body may be slightly changed from that in the metal powder.

For example, the content of C in the final sintered body may vary within a range of 5% to 100% (preferably, 30% to 100%) of the content of the metal powder for powder metallurgy, depending on the process conditions and the treatment conditions.

Further, O may vary depending on process conditions and treatment conditions, but the content of O in the final sintered body may vary within a range of 1% to 50% (preferably within a range of 3% to 50%) of the content of the metal powder for powder metallurgy.

On the other hand, as described above, the sintered body after production may be subjected to HIP treatment in one ring of additional treatment performed as necessary. However, the sintered body obtained in the present invention has originally been sufficiently densified at the end of the firing step. Therefore, even if the HIP treatment is further performed, it is difficult to achieve a higher density than that.

In the HIP treatment, since the object to be treated (sintered body) needs to be pressurized via the pressure medium, the object to be treated may be contaminated, or the composition and physical properties of the object to be treated may be unexpectedly changed by contamination, or the object to be treated may be discolored by contamination. Further, residual stress is generated or increased in the object to be processed due to pressurization, and there is a possibility that such a defect occurs that deformation or dimensional accuracy is lowered as the residual stress is released over time.

In contrast, according to the present invention, since a sintered body having a sufficiently high density can be produced without performing such a HIP treatment, a sintered body having a high density and a high strength as in the case of performing the HIP treatment can be obtained. Therefore, the sintered body is less likely to cause contamination, discoloration, unexpected changes in composition and physical properties, and less likely to cause defects such as deformation and deterioration in dimensional accuracy. Therefore, according to the present invention, a sintered body having high mechanical strength and dimensional accuracy and excellent durability can be efficiently produced.

Further, since the sintered body produced in the present invention requires almost no additional treatment for the purpose of improving mechanical properties, the composition and crystal structure are easily made uniform over the entire sintered body. Therefore, the sintered body has high structural isotropy and excellent durability against loads from all directions regardless of the shape.

[ Heat-resistant Member ]

< first embodiment >

The heat-resistant member of the present invention can be applied to, for example, a member for a supercharger. The member for a supercharger described later is a first embodiment of the heat-resistant member of the present invention, and includes the sintered body according to the present embodiment. That is, at least a part of a member for a supercharger described later is composed of the sintered body according to the present embodiment. Such a member for a supercharger can be a heat-resistant member having high density and excellent heat resistance without additional treatment.

Examples of such a member for a supercharger include: such as nozzle vanes for a turbo charger, turbine wheels for a turbo charger, wastegate valves, turbine housings, and the like. These supercharger components are required to have wear resistance because they are exposed to high temperatures for a long period of time and slide with other components as the case may be. As described above, the sintered body of the present invention has excellent heat resistance and mechanical properties due to its high density. Therefore, a member for a supercharger that maintains excellent durability for a long period of time is obtained.

Hereinafter, a nozzle vane for a turbocharger (hereinafter, also simply referred to as "nozzle vane") will be described as an example of the member for a turbocharger. The nozzle blade is used for a variable capacitance type turbo charger, and is a valve body for controlling boost pressure by adjusting the opening degree of a nozzle.

Fig. 1 is a side view (a view when looking down on an airfoil) showing a nozzle blade for a turbo charger to which a first embodiment of a heat-resistant member according to the present invention is applied, fig. 2 is a plan view of the nozzle blade shown in fig. 1, and fig. 3 is a back view of the nozzle blade shown in fig. 1.

The nozzle vane 1 shown in fig. 1 has a shaft portion 11 and an airfoil portion 12.

The cross-sectional shape of the main portion of the shaft portion 11 is circular with the axis 13 as the center axis. The shaft portion 11 is rotatably supported by a nozzle holder (not shown) on the side of the wing portion 12 (left side in fig. 1), and is fixed to a nozzle plate (not shown) on the side opposite to the wing portion 12 (right side in fig. 1). This allows the wing 12 to be rotated about the axis 13 and the angle to be changed, thereby adjusting the nozzle opening.

A center hole 14 is formed in one end surface (right end surface in fig. 1) of the shaft portion 11. The center hole 14 is formed in a circular shape in cross section, with its center coinciding with the axis 13.

A pair of flat portions 15 (double-sided cut portions) facing each other are provided on the outer peripheral surface of one end side (right side in fig. 1) of the shaft portion 11 via an axis 13 (see fig. 3).

Such respective flat portions 15 are used in a state of being abutted to an abutting face formed on an unillustrated steering plate. The rotation angle of the shaft portion 11 about the axis 13 is restricted, and the rotation angle of the nozzle vane 1 about the axis 13 can be adjusted with high accuracy. Each flat portion 15 is formed to be inclined at an angle θ to the projecting direction (airfoil) of the wing portion 12 (see fig. 3).

On the other hand, the shaft portion 11 is provided with a wing portion 12 on the other end side (left end portion in fig. 1). That is, the wing portion 12 is provided to protrude from one end portion of the shaft portion 11.

A flange portion 16 protruding outward of the shaft portion 11 is formed on the other end side of the shaft portion 11.

As shown in fig. 1, the wing portion 12 has a strip shape extending in a direction perpendicular to the axis 13 of the shaft portion 11 in a plan view. The wing portion 12 projects from the shaft portion 11 to a length that is longer on one end side (lower side in fig. 1) than on the other end side (upper side in fig. 1).

The wing portion 12 is chamfered 17 and 18 at the edge portions at both ends in the width direction (the left-right direction in fig. 1) in plan view.

As shown in fig. 2 and 3, the wing portion 12 is slightly curved in the thickness direction thereof. In addition, the thickness of the wing portion 12 decreases toward each end in the extending direction (projecting direction).

The nozzle vane 1 as described above is formed of the embodiment of the sintered body of the present invention. The sintered body of the present invention has high density, and therefore the nozzle vane 1 has excellent heat resistance, mechanical properties, and wear resistance. Moreover, the nozzle vane 1 can be formed into a nozzle vane with high dimensional accuracy even if the shape is complicated. As a result, a supercharger having excellent durability for a long period of time can be realized.

< second embodiment >

The heat-resistant member of the present invention can be applied to, for example, a compressor wing as a component for a jet engine or a component for a power generation pulley. This compressor wing is configured using the second embodiment of the heat-resistant member of the present invention, that is, an embodiment in which at least a part thereof is the sintered body of the present invention.

Fig. 4 is a perspective view showing a compressor wing to which a second embodiment of the heat-resistant member of the present invention is applied. The compressor wing 2 shown in fig. 4 includes an inner rim 21 and an outer rim 22 which are concentrically arranged with each other, and wing portions 23 which are provided between these rims and arranged along the circumferential direction of the inner rim 21. The inner rim 21 and the outer rim 22 are formed in a ring shape, respectively. The wing portion 23 is formed in a flat plate shape including a curved surface. Then, the wing ends (end surfaces) of the wing portions 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 in which a part of the compressor wing 2 is cut away.

The compressor blade 2 is one of components constituting a jet engine or a gas turbine for power generation, and receives gas from the wing portion 23 to rotate a turbine shaft provided further inside the inner rim 21. Thus, the compressor can compress gas in a jet engine or a gas turbine for power generation.

The inner rim 21, the outer rim 22, and the wing 23 may be separate members, but in the compressor wing 2 shown in fig. 4, the inner rim 21, the outer rim 22, and the wing 23 are integrated. Therefore, the relative position accuracy of each part is high, and the performance of the compressor wing is excellent. Thus, by configuring the compressor wing 2 using the embodiment of the sintered body of the present invention, the compressor wing 2 excellent in dimensional accuracy can be obtained.

In general, in a compressor wing, it is necessary to make the shape of the wing portion a three-dimensional shape including a curved surface which is thinner in order to improve aerodynamic performance.

In response to such a problem, the compressor wing 2 having high dimensional accuracy can be realized even if the wing section 23 having a thin and complicated three-dimensional shape is included by forming the entire compressor wing 2 from a sintered body manufactured by a powder metallurgy method.

The sintered body according to the present embodiment also contributes to improvement of mechanical properties of the compressor wing 2 due to high density and excellent heat resistance. That is, since the compressor wing is a member constituting an air flow passage in general, sufficient fatigue strength, wear resistance, and the like are required for vibration even at high temperatures.

In response to such a problem, the compressor wing 2 is made of the sintered body of the present embodiment, and therefore has a high density, excellent heat resistance, and sufficient wear resistance. Thus, the compressor wing 2 excellent in long-term durability can be obtained.

Further, since the compressor wing 2 is manufactured by various molding methods, post-processing after firing is hardly required or the amount of processing can be suppressed to a small amount in manufacturing the compressor wing 2. Further, as described above, since densification is desired, additional treatment such as HIP treatment is not required. Therefore, the production cost can be reduced, and the occurrence of defects due to the post-processing traces can be minimized.

The metal powder for powder metallurgy, the composite, the granulated powder, the sintered body, and the heat-resistant member of the present invention have been described above according to preferred embodiments, but the present invention is not limited thereto.

For example, the sintered body of the present invention can be applied to parts for transportation equipment such as parts for automobiles, parts for bicycles, parts for railway vehicles, parts for ships, parts for aircrafts, and parts for space transporters (e.g., rockets); electronic device parts such as personal computer parts and mobile phone terminal parts; parts for electrical equipment such as refrigerators, washing machines, and cooling/heating machines; machine parts such as machine tools and semiconductor manufacturing apparatuses; parts for plant equipment such as nuclear power plants, thermal power plants, hydroelectric power plants, oil refineries, and chemical complex plants; ornaments such as parts for clocks, tableware, jewelry and eyeglass frames; medical instruments such as surgical instruments, artificial bones, artificial teeth, artificial tooth roots, and parts for dentition correction; in addition to this, all structural elements.

The heat-resistant member of the present invention can be applied to various power generation-related members such as a nuclear power member and a gas turbine member, in addition to the above-described supercharger member, jet engine member and power generation sheave member; various engine parts such as parts for automobile engines and parts for rocket engines; such as parts for boilers, parts for heat exchangers, parts for exhaust gas treatment equipment, parts for heating furnaces, parts for fuel cells, heat-resistant bolts, heat-resistant springs, heat-resistant valves, and the like; in addition to this, all heat-resistant components.

[ examples ] A method for producing a compound

Next, an embodiment of the present invention will be explained.

1. Production of sintered body (Zr-Nb series)

(sample No.1)

[1] First, metal powders having compositions shown in table 1, which were produced by a water atomization method, were prepared. Table 4 shows the average particle size of the prepared metal powder.

The compositions of the powders shown in table 1 were identified and quantified by inductively coupled high-frequency plasma emission spectrometry (ICP analysis). In addition, an ICP apparatus (CIROS120 type) manufactured by japan ltd. For identification and quantification of C, a carbon/sulfur analyzer (CS-200) manufactured by LECO was used. For the identification and quantification of O, an oxygen/nitrogen analyzer (TC-300/EF-300) manufactured by LECO was used.

[2] Next, a mixture of metal powder, polypropylene, and wax (organic binder) was mixed in a mass ratio of 9: the mixed raw materials were weighed and mixed in the manner of 1.

[3] Subsequently, the mixed raw materials were kneaded in a kneader to obtain a composite.

[4] Next, the composite was molded by an injection molding machine under the molding conditions shown below to prepare a molded article.

< Molding Condition >

Material temperature: 150 ℃ C

Injection pressure: 11MPa (110 kgf/cm)²)

[5] Next, the obtained molded body was subjected to a heat treatment (degreasing treatment) under the below-described degreasing conditions, to obtain a degreased body.

< degreasing Condition >

Degreasing temperature: 500 deg.C

Degreasing time: 1 hour (holding time at degreasing temperature)

Degreasing atmosphere: nitrogen atmosphere environment

[6] Next, the obtained degreased body was fired under the firing conditions shown below. Thus, a sintered body was obtained. The sintered body had a cylindrical shape with a diameter of 10mm and a thickness of 5 mm.

< firing Condition >

Firing temperature: 1250 deg.C

Firing time: 3 hours (holding time at firing temperature)

Firing atmosphere: argon atmosphere environment

(sample No.2 to 30)

Sintered bodies were obtained in the same manner as in the method for producing the sintered body of sample No.1, except that the composition of the metal powder for powder metallurgy was changed as shown in table 1. The sintered body of sample No.30 was subjected to HIP treatment under the following conditions after firing. The sintered bodies of

samples

16 and 17 were obtained using metal powder produced by the gas atomization method. In addition, "gas" is indicated in the remarks column of table 1.

< HIP treatment conditions >

Heating temperature: 1100 deg.C

Heating time: 2 hours

Pressure force: 100MPa

TABLE 1

In table 1, of the metal powders for powder metallurgy of each sample No., those corresponding to the present invention are shown as "examples", and those not conforming to the present invention are shown as "comparative examples".

In addition, each of the metal powders for powder metallurgy contains a trace amount of impurities, but the description in table 1 is omitted. In addition, the metal powders according to the examples described in table 1 all had an O (oxygen) content of 0.5 mass% or less.

(sample No.31)

[1] First, as in the case of sample No.1, metal powders having compositions shown in table 2 were prepared by the water mist method. Table 5 shows the average particle size of the prepared metal powder.

[2] Next, the metal powder is granulated by a spraying method. The binder used in this case was polyvinyl alcohol, and was used in an amount of 1 part by mass per 100 parts by mass of the metal powder. Further, 50 parts by mass of a solvent (ion-exchanged water) was used with respect to 1 part by mass of polyvinyl alcohol. Thus, a granulated powder having an average particle size of 50 μm was obtained.

[3] Then, the granulated powder was subjected to powder compaction under the following compaction conditions. In addition, this molding uses a molding press. The shape of the molded article was a cube with an angle of 20 mm.

< Molding conditions >

Material temperature: 90 deg.C

Molding pressure: 600Mpa (6 t/cm)²)

[4] Next, the obtained molded body was subjected to a heat treatment (degreasing treatment) under the following degreasing conditions, to obtain a degreased body.

< degreasing Condition >

Degreasing temperature: 450 deg.C

Degreasing time: 2 hours (holding time at degreasing temperature)

Degreasing atmosphere: nitrogen atmosphere environment

[5] Next, the obtained degreased body was fired under the firing conditions shown below. Thus, a sintered body was obtained.

< firing conditions >

Firing temperature: 1250 deg.C

Firing time: 3 hours (holding time at firing temperature)

Firing atmosphere: argon atmosphere environment

(sample No.32 to 45)

Sintered bodies were obtained in the same manner as in sampling No.20, except that the composition of the metal powder for powder metallurgy was changed as shown in table 2. The sintered body of sample No.45 was subjected to HIP treatment under the following conditions after firing. The sintered bodies of samples No.38 and 39 were obtained by using metal powders produced by the gas atomization method. In addition, "gas" is indicated in the remarks column of table 2.

< HIP treatment conditions >

Heating temperature: 1100 deg.C

Heating time: 2 hours

Pressure force: 100MPa

TABLE 2

In table 2, of the metal powders for powder metallurgy of each sample No., those corresponding to the present invention are shown as "examples", and those not conforming to the present invention are shown as "comparative examples".

In addition, each of the powder metallurgy metal powders contains a trace amount of impurities, but the description in table 2 is omitted. In addition, the metal powders according to the examples described in table 2 all had an O (oxygen) content of 0.5 mass% or less.

(sample No.46)

[1] First, premixed powders having the compositions shown in table 3, which were produced by the water mist method, were prepared. The term "premixed powder" as used herein means a powder obtained by subtracting the C (carbon) component from the composition ratio shown in table 3 and a powder obtained by mixing the C powder with the powder. Table 6 shows the average particle size of the prepared metal powder (powder obtained by subtracting component C).

[2] Next, a mixture of the premixed powder, polypropylene, and wax (organic binder) was mixed in a mass ratio of 9: the mixed raw materials were weighed and mixed in the manner of 1.

[3] Next, the mixed raw materials were kneaded in a kneader to obtain a composite.

< Molding conditions >

Material temperature: 150 ℃ C

Injection pressure: 11MPa (110 kgf/cm)²)

< degreasing Condition >

Degreasing temperature: 500 deg.C

Degreasing time: 1 hour (holding time at degreasing temperature)

Degreasing atmosphere: nitrogen atmosphere environment

< firing Condition >

Firing temperature: 1250 deg.C

Firing time: 3 hours (holding time at firing temperature)

Firing atmosphere: argon atmosphere environment

(sample No.47 to 60)

Sintered bodies were obtained in the same manner as in the method for producing the sintered body of sample No.46, except that the composition of the metal powder for powder metallurgy was changed as shown in table 3. The sintered body of sample No.60 was subjected to HIP treatment under the following conditions after firing.

< HIP treatment conditions >

Heating temperature: 1100 deg.C

Heating time: 2 hours

Pressure force: 100MPa

TABLE 3

In table 3, of the metal powders for powder metallurgy of each sample No., those corresponding to the present invention are shown as "examples", and those not conforming to the present invention are shown as "comparative examples".

In addition, each of the powder metallurgy metal powders contains a trace amount of impurities, but the description in table 3 is omitted. In addition, the metal powders according to the examples described in table 3 all had an O (oxygen) content of 0.5 mass% or less.

2. Evaluation of sintered body (Zr-Nb based)

2.1 evaluation of relative Density

Sintered densities of sintered bodies produced using the metal powders of the respective sample nos. shown in tables 1 to 3 were measured according to the method for measuring the density of a sintered metal material prescribed in JIS Z2501 (2000), and relative densities of the respective sintered bodies were calculated with reference to the true densities of the metal powders for powder metallurgy used for producing the respective sintered bodies.

The calculation results are shown in tables 4 to 6.

2.2 evaluation of hardness

Vickers hardness was measured on sintered bodies produced using the metal powders of the respective sample nos. shown in tables 1 to 3 according to the test method of vickers hardness test specified in JIS Z2244 (2009).

The measured hardness was evaluated according to the following evaluation criteria. In the evaluation, the hardness of the sample indicated by "1" in the remark column of each table was evaluated by checking the relative value of 100 against the following evaluation criterion, the hardness of the sample indicated by "reference in the respective tables" indicated by "1". Similarly, regarding the hardness of the sample described in the remark column of table 1 as "2" the relative value when the hardness of the sample described in table 1 as the reference of "2" is 100 is checked against the following evaluation criteria to evaluate, regarding the hardness of the sample described in "3" the relative value when the hardness of the sample described in table 1 as the reference of "3" is 100 is checked against the following evaluation criteria to evaluate, regarding the hardness of the sample described in table 1 as the reference of "4" the relative value when the hardness of the sample described in table 1 as the reference of "4" is 100 is checked against the following evaluation criteria to evaluate.

< evaluation criteria for Vickers hardness >

A: relative value of Vickers hardness of 110 or more

B: relative value of Vickers hardness of 105 or more and less than 110

C: relative value of Vickers hardness of 100 or more and less than 105

D: relative value of Vickers hardness less than 100

The evaluation results are shown in tables 4 to 6.

2.3 evaluation of tensile Strength, 0.2% proof stress and elongation

The sintered bodies produced using the metal powders of the respective sample nos. shown in tables 1 to 3 were measured for tensile strength, 0.2% proof stress and elongation according to the metal material tensile test method specified in JIS Z2241 (2011).

Then, these measured physical property values were evaluated in accordance with the following evaluation criteria. In the evaluation, the physical property values of the samples indicated in the remarks columns of the tables as "1" were evaluated by checking the relative values of the samples indicated in the tables as "reference for" 1 "with the reference 100, against the evaluation criteria below. Similarly, the physical property value of the sample denoted by "[ 2] in the remark column of table 1 is evaluated by checking a relative value when the physical property value of the sample denoted by" [2] in table 1 is 100 against the following evaluation criteria, the physical property value of the sample denoted by "[ 3] is evaluated by checking a relative value when the physical property value of the sample denoted by" [3] in table 1 is 100 against the following evaluation criteria, and the physical property value of the sample denoted by "[ 4] is evaluated by checking a relative value when the physical property value of the sample denoted by" [4] in table 1 is 100 against the following evaluation criteria.

< evaluation criteria for tensile Strength >

A: the relative value of the tensile strength of the sintered body is 109 or more

B: the relative value of the tensile strength of the sintered body is 106 or more and less than 109

C: the relative value of the tensile strength of the sintered body is 103 or more and less than 106

D: the relative value of the tensile strength of the sintered body is 100 or more and less than 103

E: the relative value of the tensile strength of the sintered body is 97 or more and less than 100

F: the relative value of the tensile strength of the sintered body is less than 97

< evaluation criteria for 0.2% proof stress >

A: the relative value of 0.2% proof stress of the sintered body is 109 or more

B: the relative value of 0.2% proof stress of the sintered body is 106 or more and less than 109

C: the relative value of 0.2% proof stress of the sintered body is 103 or more and less than 106

D: the relative value of 0.2% proof stress of the sintered body is 100 or more and less than 103

E: the relative value of 0.2% proof stress of the sintered body is 97 or more and less than 100

F: the relative value of 0.2% proof stress of the sintered body is less than 97

< evaluation criteria for stretching >

A: the relative value of the tensile strength of the sintered body is 115 or more

B: the relative value of the tensile strength of the sintered body is 110 to 115

C: the relative value of the tensile strength of the sintered body is 105 or more and less than 110

D: the relative value of the tensile strength of the sintered body is 100 or more and less than 105

E: the relative value of the tensile strength of the sintered body is 95 or more and less than 100

F: the relative value of the tensile strength of the sintered body is less than 95

The evaluation results are shown in tables 4 to 6.

TABLE 4

TABLE 5

TABLE 6

As is clear from tables 4 to 6, the sintered bodies corresponding to the examples had higher relative densities than those corresponding to the comparative examples (except for the sintered bodies subjected to HIP treatment). In addition, there are significant differences in tensile strength, 0.2% proof stress, and tensile properties.

On the other hand, the comparison of the physical property values between the sintered body corresponding to the examples and the sintered body subjected to the HIP treatment revealed that the physical property values were similar to each other.

3. Production of sintered body (Hf-Nb series)

(sample No.61 to 74)

Sintered bodies were obtained in the same manner as in the method for producing the sintered body of sample No.1, except that the composition of the metal powder for powder metallurgy was changed as shown in Table 7.

TABLE 7

In table 7, of the metal powders for powder metallurgy of each sample No. the samples corresponding to the present invention are shown as "examples", and the samples not conforming to the present invention are shown as "comparative examples".

In addition, each of the powder metallurgy metal powders contains a trace amount of impurities, but the description in table 7 is omitted. In addition, the metal powders according to the examples described in table 7 all had an O (oxygen) content of 0.5 mass% or less.

(sample No.75 to 81)

Sintered bodies were obtained in the same manner as in sampling No.46, except that the composition of the metal powder for powder metallurgy was changed as shown in table 8.

TABLE 8

In table 8, of the metal powders for powder metallurgy of each sample No. the samples corresponding to the present invention are shown as "examples", and the samples not conforming to the present invention are shown as "comparative examples".

In addition, each of the powder metallurgy metal powders contains a trace amount of impurities, but the description in table 8 is omitted. In addition, the metal powders according to the examples described in table 8 all had an O (oxygen) content of 0.5 mass% or less.

4. Evaluation of sintered body (Hf-Nb based)

4.1 evaluation of relative Density

Sintered densities of sintered bodies produced using the metal powders of the respective sample nos. shown in tables 7 and 8 were measured according to the method for measuring the density of a sintered metal material prescribed in JIS Z2501 (2000), and relative densities of the respective sintered bodies were calculated with reference to the true densities of technical powders for powder metallurgy used for producing the respective sintered bodies.

The calculation results are shown in tables 9 and 10.

4.2 evaluation of hardness

Vickers hardness was measured on sintered bodies produced using the metal powder of each sample No. shown in tables 7 and 8 according to the method of vickers hardness test specified in JIS Z2244 (2009).

The measured hardness was evaluated according to the evaluation criteria described in 2.2.

The evaluation results are shown in tables 9 and 10.

4.3 evaluation of tensile Strength, 0.2% proof stress and elongation

The sintered bodies produced using the metal powders of the respective sample nos. shown in tables 7 and 8 were measured for tensile strength, 0.2% proof stress and elongation according to the metal material tensile test method specified in JIS Z2241 (2011).

The measured physical property values were evaluated according to the evaluation criteria described in 2.3.

The evaluation results are shown in tables 9 and 10.

TABLE 9

Watch 10

As is clear from tables 9 and 10, the sintered bodies corresponding to the examples had higher relative densities than the sintered bodies corresponding to the comparative examples. Further, significant differences were found in the properties such as tensile strength, 0.2% proof stress and elongation.

5. Production of sintered body (Ti-Nb series)

(sample No.82 to 91)

Sintered bodies were obtained in the same manner as in the method for producing the sintered body of sample No.1, except that the composition of the metal powder for powder metallurgy was changed as shown in table 11.

TABLE 11

In table 11, of the metal powders for powder metallurgy of each sample No. are samples corresponding to the present invention and samples not conforming to the present invention, respectively, as "examples" and "comparative examples".

In addition, each of the powder metallurgy metal powders contains a trace amount of impurities, but the description in table 11 is omitted. In addition, the metal powders according to the examples described in table 11 all had an O (oxygen) content of 0.5 mass% or less.

6. Evaluation of sintered body (Ti-Nb series)

6.1 evaluation of relative Density

Sintered densities of sintered bodies produced using the metal powders of the respective sample nos. shown in table 11 were measured according to the method for measuring the density of a sintered metal material specified in JIS Z2501 (2000), and relative densities of the respective sintered bodies were calculated with reference to the true densities of technical powders for powder metallurgy used for producing the respective sintered bodies.

The calculation results are shown in table 12.

6.2 evaluation of hardness

Vickers hardness was measured on sintered bodies produced using the metal powder of each sample No. shown in table 11 according to the method of vickers hardness test specified in JIS Z2244 (2009).

The evaluation results are shown in table 12.

6.3 evaluation of tensile Strength, 0.2% proof stress and elongation

The sintered bodies produced using the metal powders of the respective sample nos. shown in table 11 were measured for tensile strength, 0.2% proof stress and elongation according to the metal material tensile test method specified in JIS Z2241 (2011).

The evaluation results are shown in table 12.

TABLE 12

As is clear from table 12, the sintered bodies corresponding to the examples had higher relative densities than the sintered bodies corresponding to the comparative examples. Further, significant differences were found in the properties such as tensile strength, 0.2% proof stress and elongation.

7. Production of sintered body (Nb-Ta series)

(sample No.92 to 101)

Sintered bodies were obtained in the same manner as in the method for producing the sintered body of sample No.1, except that the composition of the metal powder for powder metallurgy was changed as shown in table 13.

Watch 13

In table 13, of the metal powders for powder metallurgy of each sample No. the samples corresponding to the present invention are shown as "examples", and the samples not conforming to the present invention are shown as "comparative examples".

In addition, each of the powder metallurgy metal powders contains a trace amount of impurities, but the description of table 13 is omitted. In addition, the metal powders according to the examples described in table 13 all had an O (oxygen) content of 0.5 mass% or less.

8. Evaluation of sintered body (Nb-Ta type)

8.1 evaluation of relative Density

Sintered densities of sintered bodies produced using the metal powders of the respective sample nos. shown in table 13 were measured according to the method for measuring the density of a sintered metal material specified in JIS Z2501 (2000), and relative densities of the respective sintered bodies were calculated with reference to the true densities of the metal powders for powder metallurgy used for producing the respective sintered bodies.

The calculation results are shown in table 14.

8.2 evaluation of hardness

Vickers hardness was measured according to the test method of vickers hardness test specified in JIS Z2244 (2009) for sintered bodies produced using the metal powder of each sample No. shown in table 13.

The evaluation results are shown in table 14.

8.3 evaluation of tensile Strength, 0.2% proof stress and elongation

The sintered bodies produced using the metal powders of the respective sample nos. shown in table 13 were measured for tensile strength, 0.2% proof stress and elongation according to the metal material tensile test method specified in JIS Z2241 (2011).

The evaluation results are shown in table 14.

TABLE 14

As is clear from table 14, the sintered bodies corresponding to the examples had higher relative densities than the sintered bodies corresponding to the comparative examples. Further, significant differences were found in the properties such as tensile strength, 0.2% proof stress and elongation.

9. Production of sintered body (Y-Nb series)

(sample No.102 to 112)

Sintered bodies were obtained in the same manner as in the method for producing the sintered body of sample No.1, except that the composition of the metal powder for powder metallurgy was changed as shown in table 15.

Watch 15

In table 15, of the metal powders for powder metallurgy of each sample No. the samples corresponding to the present invention are shown as "examples", and the samples not conforming to the present invention are shown as "comparative examples".

In addition, each of the powder metallurgy metal powders contains a trace amount of impurities, but the description in table 15 is omitted. In addition, the metal powders according to the examples described in table 15 all had an O (oxygen) content of 0.5 mass% or less.

10. Evaluation of sintered body (Y-Nb series)

10.1 evaluation of relative Density

Sintered densities of sintered bodies produced using the metal powders of respective sample nos. shown in table 15 were measured according to the method for measuring the density of a sintered metal material specified in JIS Z2501 (2000), and relative densities of the respective sintered bodies were calculated with reference to the true densities of the metal powders for powder metallurgy used for producing the respective sintered bodies.

The calculation results are shown in table 16.

10.2 evaluation of hardness

Vickers hardness was measured according to the test method of vickers hardness test specified in JIS Z2244 (2009) for sintered bodies produced using the metal powder of each sample No. shown in table 15.

The evaluation results are shown in Table 16.

10.3 evaluation of tensile Strength, 0.2% proof stress and elongation

The sintered bodies produced using the metal powders of the respective sample nos. shown in table 15 were measured for tensile strength, 0.2% proof stress and elongation according to the metal material tensile test method specified in JIS Z2241 (2011).

The evaluation results are shown in Table 16.

TABLE 16

As is clear from table 16, the sintered bodies corresponding to the examples had higher relative densities than the sintered bodies corresponding to the comparative examples. In addition, significant differences were observed in properties such as tensile strength, 0.2% proof stress, tensile and fatigue strength.

11. Production of sintered body (V-Nb series)

(sample No.113 to 122)

Sintered bodies were obtained in the same manner as in the method for producing the sintered body of sample No.1, except that the composition of the metal powder for powder metallurgy was changed as shown in table 17.

TABLE 17

In table 17, of the metal powders for powder metallurgy of each sample No. are samples corresponding to the present invention and samples not conforming to the present invention and comparative examples.

In addition, each of the powder metallurgy metal powders contains a trace amount of impurities, but the description in table 17 is omitted. In addition, the metal powders according to the examples described in table 17 all had an O (oxygen) content of 0.5 mass% or less.

12. Evaluation of sintered body (V-Nb series)

12.1 evaluation of relative Density

Sintered densities of sintered bodies produced using the metal powders of respective sampling nos. shown in table 17 were measured according to the method for measuring the density of a sintered metal material specified in JIS Z2501 (2000), and relative densities of the sintered bodies were calculated with reference to the true densities of the metal powders for powder metallurgy used for producing the sintered bodies.

The calculation results are shown in table 18.

12.2 evaluation of hardness

Vickers hardness was measured according to the test method of vickers hardness test specified in JIS Z2244 (2009) for sintered bodies produced using the metal powder of each sample No. shown in table 17.

The evaluation results are shown in Table 18.

12.3 evaluation of tensile Strength, 0.2% proof stress and elongation

The sintered bodies produced using the metal powders of the respective sample nos. shown in table 17 were measured for tensile strength, 0.2% proof stress and elongation according to the metal material tensile test method specified in JIS Z2241 (2011).

The evaluation results are shown in Table 18.

Watch 18

As is clear from table 18, the sintered bodies corresponding to the examples had higher relative densities than the sintered bodies corresponding to the comparative examples. Further, significant differences were found in the properties such as tensile strength, 0.2% proof stress and elongation.

In addition, in addition to the examples described in tables 1 to 18, as a combination example of the first element and the second element, the sintered body was produced using the metal powders of Ti-Zr based, Zr-Ta based, and Zr-V based in the same manner as described above, and exhibited the same tendency as described above with respect to the relative density, hardness, tensile strength, proof stress, and elongation.

Claims

1. A metal powder for powder metallurgy, characterized in that,

co is a main component of the catalyst and is a main component,

contains 10 to 25 mass% of Cr,

ni is contained in a proportion of 5 to 40 mass%,

contains at least one of Mo and W in a total amount of 2 to 20 mass%,

si is contained in a proportion of 0.3 to 1.5 mass%,

c is contained in an amount of 0.05 to 0.8 mass%,

one element selected from the group consisting of Ti, V, Y, Zr, Nb and Hf is referred to as a first element, an element selected from the group consisting of V, Zr, Nb, Hf and Ta, which has a group larger than the first element in the periodic table, is referred to as a second element, or an element having the same group as the first element and having a period larger than the first element in the periodic table, is referred to as a second element,

the first element is contained in a proportion of 0.01 to 0.5 mass%,

the second element is contained in a proportion of 0.01 to 0.5 mass%.

2. The metal powder for powder metallurgy according to claim 1,

further, Fe is contained in a proportion of 0.5 to 5 mass%.

3. The metal powder for powder metallurgy according to claim 1 or 2,

when a value obtained by removing the content of the first element by the atomic weight of the first element is X1 and a value obtained by removing the content of the second element by the atomic weight of the second element is X2, X1/X2 is 0.3 or more and 3 or less.

4. The metal powder for powder metallurgy according to claim 1 or 2,

the total content of the first element and the second element is 0.05 mass% to 0.6 mass%.

5. The metal powder for powder metallurgy according to claim 1 or 2,

the average particle diameter is 0.5 to 30 μm.

6. A composite, comprising:

the metal powder for powder metallurgy according to any one of claims 1 to 5.

7. A granulated powder, comprising:

the metal powder for powder metallurgy according to any one of claims 1 to 5.

8. A sintered body characterized in that a sintered body,

co is a main component of the catalyst and is a main component,

contains 10 to 25 mass% of Cr,

ni is contained in a proportion of 5 to 40 mass%,

contains at least one of Mo and W in a total amount of 2 to 20 mass%,

si is contained in a proportion of 0.3 to 1.5 mass%,

c is contained in an amount of 0.05 to 0.8 mass%,

one element selected from the group consisting of Ti, V, Y, Zr, Nb, Hf and Ta is used as a first element, an element selected from the group, which is an element having a group larger than the first element in the periodic table or an element having the same group as the first element and having a period larger than the first element in the periodic table, is used as a second element,

the first element is contained in a proportion of 0.01 to 0.5 mass%,

the second element is contained in a proportion of 0.01 to 0.5 mass%.

9. A heat-resistant member, characterized by comprising:

the sintered body of claim 8.