Multi-component alloy powder and compact

Abstract

To provide a powder metallurgical compact having high mixing entropy ΔSmix and excellent in balanced of hardness, softening resistance, strength and stretchability.SOLUTION: A compact is obtained from powders. A material of this compact is a multicomponent alloy. The multicomponent alloy contains Co: 5 atomic % or more and 35 atomic % or less, Cr: 5 atomic % or more and 35 atomic % or less, Fe: 5 atomic % or more and 35 atomic % or less, Ni: 5 atomic % or more and 35 atomic % or less, C: 0.47 atomic % or more and 8.74 atomic % or less and unavoidable impurities. The entropy ΔSmix of mixing of the multicomponent alloy is 1.30 R or more. The metallographic structure of the compact contains a matrix and a large number of carbides dispersed in this matrix. A maximum equivalent circle diameter (MD2) of these carbides is 15 μm or less. The Fe content (Pi) in the matrix is 13 mass% or more and 28 mass% or less.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a powder and a compact made of a multi-component alloy having a large entropy of mixing ΔSmix. [Background technology]

[0002] Multi-element alloys with high entropy of mixing ΔSmix are attracting attention. Medium entropy alloys and high entropy alloys are known as such alloys. The entropy ΔSmix of medium entropy alloys is 1.0 times or more the gas constant R. The entropy ΔSmix of high entropy alloys is 1.5 times or more the gas constant R. These multi-element alloys exhibit characteristic mechanical properties.

[0003] JP 2019-532169 A discloses a multi-element alloy containing Co, Cr, Fe, and Ni as main elements. This alloy also contains C or N. This alloy has excellent properties at cryogenic temperatures.

[0004] JP 2019-163535 A discloses a multi-element alloy containing Cr, Fe, and V as main elements. C is added to this alloy. This alloy has excellent corrosion resistance.

[0005] Huang TD, et al.: Science China Technological Sciences, Vol 61 (2018), 117-123 discloses a multi-element alloy containing Co, Cr, Fe and Ni as major elements. C can be added to this alloy. This alloy has excellent wear resistance. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Special publication 2019-532169 [Patent Document 2] JP2019-163535A [Non-patent literature]

[0007] [Non-Patent Document 1] Huang TD,et al.:Science China Technological Sciences,Vol61(2018),117-123 Summary of the Invention [Problem to be solved by the invention]

[0008] The alloy disclosed in JP2019-532169A contains a large amount of Fe. The entropy ΔSmix of this alloy is not high. The hardness of this alloy is insufficient.

[0009] The alloy disclosed in JP 2019-163535 A contains a large amount of V. In this alloy, V precipitates a brittle phase. The elongation of this alloy is insufficient.

[0010] The C-free alloy disclosed in the aforementioned Science China Technological Sciences contains a single-phase solid solution, which has poor softening resistance at high temperatures.

[0011] The alloy containing C disclosed in the aforementioned Science China Technological Sciences contains a network of carbides. The elongation of this alloy is insufficient.

[0012] An object of the present invention is to provide a powder metallurgy compact which is made of an alloy having a high entropy of mixing ΔSmix and which has an excellent balance of hardness, softening resistance, strength and elongation. [Means for solving the problem]

[0013] The powder material according to the present invention is a multi-element alloy. Co: 5 atomic% or more and 35 atomic% or less, Cr: 5 atomic% or more and 35 atomic% or less, Fe: 5 atomic% or more and 35 atomic% or less, Ni: 5 atomic% or more and 35 atomic% or less, C: 0.47 atomic% or more and 8.74 atomic% or less and Inevitable impurities The multi-component alloy has an entropy ΔSmix of 1.30R or more. The metal structure of the powder includes a matrix and a large number of carbides dispersed in the matrix. The maximum circle equivalent diameter (MD1) of these carbides is 5 μm or less. The Fe content (Pi) of the matrix is ​​13 mass% or more and 28 mass% or less.

[0014] In another aspect, the powder metallurgy compact according to the present invention is made of a multi-component alloy. Co: 5 atomic% or more and 35 atomic% or less, Cr: 5 atomic% or more and 35 atomic% or less, Fe: 5 atomic% or more and 35 atomic% or less, Ni: 5 atomic% or more and 35 atomic% or less, C: 0.47 atomic% or more and 8.74 atomic% or less and Inevitable impurities The entropy of mixing ΔSmix of this multi-element alloy is 1.30R or more. The metal structure of this compact includes a matrix and a large number of carbides dispersed in the matrix. The maximum circle equivalent diameter (MD2) of these carbides is 15 μm or less. The Fe content (Pi) of this matrix is ​​13 mass% or more and 28 mass% or less.

[0015] The multi-component alloy may contain one or more elements selected from the group consisting of V, Mo, Nb, W, Ti, Zr, Al and Mn. Preferably, the total content of these elements is 20 atomic % or less.

[0016] The multi-component alloy may contain Si. Preferably, the total content of Si is 20 atomic % or less. Effect of the Invention

[0017] In the molded article according to the present invention, the entropy of mixing ΔSmix of the alloy is large. Moreover, this molded article has an excellent balance of hardness, softening resistance, strength, and elongation. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Hereinafter, the present invention will be described in detail based on preferred embodiments with reference to the drawings as appropriate.

[0019] The powder according to the present invention is an aggregate of a large number of particles. The material of these particles is a multi-element alloy. This multi-element alloy is: Co: 5 atomic% or more and 35 atomic% or less, Cr: 5 atomic% or more and 35 atomic% or less, Fe: 5 atomic% or more and 35 atomic% or less, Ni: 5 atomic% or more and 35 atomic% or less, and C: 0.47 atomic% or more and 8.74 atomic% or less The powder is then sintered to obtain a molded body, which will be described later in detail.

[0020] This multi-element alloy contains multiple elements as a base. In this embodiment, Co, Cr, Fe, and Ni are the base elements. The atomic content (at%) of each base element is sufficiently large. Therefore, the metal structure of this multi-element alloy is clearly different from the metal structure of an alloy based on only a single element. The entropy of mixing ΔSmix of this alloy is sufficiently large.

[0021] The entropy of mixing ΔS mix can be calculated by the following formula:

number

[0022] The closer the atomic content of Co, Cr, Fe, and Ni in this alloy is to equal amounts, the larger the entropy of mixing ΔSmix of this alloy. In an alloy with a large entropy ΔSmix, the mixed state is stable. In an alloy with a large entropy ΔSmix, a complex and fine metal structure can be obtained. This metal structure has excellent relaxation diffusion. In an alloy with a large entropy ΔSmix, the lattice distortion caused by the difference in atomic radii is large. Since the large lattice distortion increases the deformation resistance, this alloy has high hardness. From these viewpoints, the entropy of mixing ΔSmix is ​​preferably 1.30R or more, more preferably 1.40R or more, and particularly preferably 1.50R or more. Here, R represents the gas constant. A specific value of the gas constant R is 8.314 J·K. -1 mol -1 It is.

[0023] The respective contents of Co, Cr, Fe and Ni are adjusted to be in the range of 5 atomic % or more and 35 atomic % or less so as to obtain a large entropy ΔSmix. The contents are more preferably 10 atomic % or more, and particularly preferably 15 atomic % or more. The contents are more preferably 30 atomic % or less, and particularly preferably 25 atomic % or less.

[0024] Among Co, Cr, Fe, and Ni, the difference (Pmax-Pmin) between the atomic content Pmax of the element with the maximum atomic content and the atomic content Pmin of the element with the minimum atomic content is preferably 15 atomic % or less, more preferably 10 atomic % or less, and particularly preferably 5 atomic % or less.

[0025] C is a very important element in the multi-component alloy according to the present invention. According to the findings of the inventors, in the alloy according to the present invention, C combines with Cr to form carbides. This alloy has a matrix and a large number of carbides. These carbides are dispersed in the matrix. These carbides can contribute to the high hardness and wear resistance of the compact.

[0026] From the viewpoint of sufficient carbide precipitation, the C content is preferably 0.47 atomic % or more, more preferably 1.39 atomic % or more, and particularly preferably 2.30 atomic % or more. Excessive C leads to excess carbide. Excessive carbide inhibits the extensibility of the molded body. From the viewpoint of extensibility, the C content is preferably 8.74 atomic % or less, more preferably 6.67 atomic % or less, and particularly preferably 4.53 atomic % or less.

[0027] The preferred crystal structure of the matrix is ​​FCC (face-centered cubic). The inventors have found that in FCC-type alloys with a large entropy of mixing ΔSmix, carbides can contribute to high hardness and wear resistance.

[0028] Examples of unavoidable impurities include P, S, Sn, O, and N. The P content is preferably 0.05% by mass or less, and more preferably 0.02% by mass or less. The S content is preferably 0.010% by mass or less, and more preferably 0.002% by mass or less. The Sn content is preferably 0.05% by mass or less, and more preferably 0.02% by mass or less. The O content is preferably 0.10% by mass or less, and more preferably 0.05% by mass or less. The N content is preferably 0.10% by mass or less, and more preferably 0.01% by mass or less.

[0029] According to another preferred embodiment, the multi-component alloy contains one or more elements selected from the group consisting of V, Mo, Nb, W, Ti, Zr, Al and Mn. The total content of V, Mo, Nb, W, Ti, Zr, Al and Mn is 20 atomic % or less. That is, the multi-component alloy is Co: 5 atomic% or more and 35 atomic% or less, Cr: 5 atomic% or more and 35 atomic% or less, Fe: 5 atomic% or more and 35 atomic% or less, Ni: 5 atomic% or more and 35 atomic% or less, Cu: 0.10 atomic% or more and 7.00 atomic% or less and One or more elements selected from the group consisting of V, Mo, Nb, W, Ti, Zr, Al, and Mn: 20 atomic % or less Preferably, the remainder is unavoidable impurities.

[0030] In a multi-element alloy containing V, Mo, Nb, W, Ti, Zr, Al or Mn, fine compounds containing any of these elements are precipitated in the matrix. Since these fine compounds pin the crystal grains, a compact made of this multi-element alloy has excellent softening resistance. From the viewpoint of softening resistance, it is preferable that the atomic content of V, Mo, Nb, W, Ti, Zr, Al and Mn is large. From the viewpoint of suppressing the formation of a brittle phase and achieving excellent hot workability, it is preferable that the atomic content of these elements is small.

[0031] From the viewpoint of softening resistance and hot workability, the total content of V, Mo, Nb, W, Ti, Zr and Al is more preferably 1 atomic % or more and 16 atomic % or less, and particularly preferably 3 atomic % or more and 9 atomic % or less. The Mn content is more preferably 10 atomic % or less, and particularly preferably 1.00 atomic % or less.

[0032] According to yet another preferred embodiment, the multi-component alloy contains Si. The content of Si is 10 atomic % or less. That is, the multi-component alloy is Co: 5 atomic% or more and 35 atomic% or less, Cr: 5 atomic% or more and 35 atomic% or less, Fe: 5 atomic% or more and 35 atomic% or less, Ni: 5 atomic% or more and 35 atomic% or less, Cu: 0.10 atomic% or more and 7.00 atomic% or less and Si: 10 atomic% or less Preferably, the remainder is unavoidable impurities.

[0033] In a multi-element alloy containing Si, fine compounds containing Si are precipitated in the matrix. Since these fine compounds pin the crystal grains, a compact made of this multi-element alloy has excellent softening resistance. From the viewpoint of softening resistance, it is preferable that the atomic content of Si is large. From the viewpoint of suppressing the formation of a brittle phase and achieving excellent hot workability, it is preferable that this atomic content is small.

[0034] From the viewpoint of softening resistance and hot workability, the Si content is more preferably from 0.5 atomic % to 8 atomic %, and particularly preferably from 1.0 atomic % to 5 atomic %.

[0035] The multi-component alloy contains one or more elements selected from the group consisting of V, Mo, Nb, W, Ti, Zr, Al, and Mn, and may further contain Si. That is, the multi-component alloy is Co: 5 atomic% or more and 35 atomic% or less, Cr: 5 atomic% or more and 35 atomic% or less, Fe: 5 atomic% or more and 35 atomic% or less, Ni: 5 atomic% or more and 35 atomic% or less, Cu: 0.10 atomic% or more and 7.00 atomic% or less One or more elements selected from the group consisting of V, Mo, Nb, W, Ti, Zr, Al, and Mn: 20 atomic % or less and Si: 10 atomic% or less The balance is preferably unavoidable impurities. The total content of V, Mo, Nb, W, Ti, Zr, Al, Mn and Si is preferably 20 atomic % or less.

[0036] The matrix mainly contains Co, Cr, Fe, and Ni. According to the findings of the present inventors, high hardness of the compact can be achieved by optimizing the amount of Fe contained in the matrix. It is presumed that the reason for this is the cocktail effect in an alloy with a large entropy of mixing ΔSmix. From the viewpoint of hardness, the Fe content (Pi) in the matrix is ​​preferably 13 mass% or more and 28 mass% or less. This content is more preferably 15 mass% or more, and particularly preferably 17 mass% or more. This content is more preferably 24 mass% or less, and particularly preferably 20 mass% or less.

[0037] The size of the carbide correlates with the extensibility of the molded body. From the viewpoint of extensibility, the maximum diameter (MD2) of the carbide in the molded body is preferably 15 μm or less, more preferably 13 μm or less, and particularly preferably 10 μm or less. The maximum diameter (MD2) is preferably 1.0 μm or more.

[0038] In measuring the maximum diameter (MD2), a backscattered electron image of the polished surface of the molded body is taken using a scanning electron microscope. The equivalent circle diameter D2 of each carbide present in the image obtained by taking the image is calculated. The maximum diameter (MD2) is the maximum value of the equivalent circle diameters D2 of all the carbides present in the image. In other words, the maximum diameter (MD2) is the maximum value of the equivalent circle diameters D2 of the carbides in the molded body. The equivalent circle diameter D2 is the diameter of a perfect circle having the same area as the area S of the carbide. The equivalent circle diameter D2 can be calculated by the following formula. D2 = (4 × S / π) 0.5

[0039] The maximum diameter (MD1) of the carbide in the powder is preferably 5 μm or less. A compact having a maximum diameter (MD2) of 15 μm or less can be obtained from a powder having a maximum diameter (MD1) of 5 μm or less. From this viewpoint, the maximum diameter (MD1) is more preferably 4 μm or less, and particularly preferably 3 μm or less. The maximum diameter (MD1) is preferably 0.1 μm or more. The maximum diameter (MD1) is the circle-equivalent diameter D1 of the carbide in the powder. maximum The maximum diameter (MD1) is measured by observing the cross section of a powder particle in the same manner as for measuring the maximum diameter (MD2).

[0040] The present invention is also directed to a molded body. This molded body can be manufactured by a powder metallurgy method. In other words, the molded body according to the present invention is a powder metallurgy molded body. The powder to be subjected to the powder metallurgy method is preferably obtained by an atomization method. Gas atomization method, disk atomization method, water atomization method, single roll quenching method, twin roll quenching method, and centrifugal atomization method are adopted. Preferred atomization methods are gas atomization method and disk atomization method. The powder obtained by atomization may be subjected to mechanical milling or the like. Spherical carbides can be obtained by rapid solidification in atomization. The effect of pinning the crystal grains of this spherical carbide is large. The molded body containing this spherical carbide is excellent in softening resistance. Rapid solidification in atomization further contributes to the refinement of the carbide. The molded body containing fine carbide is excellent in elongation.

[0041] A typical method for solidifying the powder is sintering. In this sintering, the powder is subjected to a pressure treatment. A typical pressure treatment is hot isostatic pressing. The sintered body obtained by sintering is subjected to plastic processing such as hot forging to obtain the molded body according to the present invention. Carbide grows by sintering and hot processing. The maximum diameter (MD2) of the carbide in the molded body is larger than the maximum diameter (MD1) of the carbide in the powder. EXAMPLES

[0042] The effects of the present invention will be clarified by the following examples, but the present invention should not be construed as being limited based on the description of these examples.

[0043] [Example 1] A metal having the composition shown in Table 1 was melted to obtain a molten metal. The molten metal was melted in an inert gas atmosphere and subjected to nitrogen gas atomization to obtain a powder. The powder was subjected to classification to adjust the particle size to 300 μm or less. The powder was filled into a capsule and the capsule was sealed. The powder was subjected to hot isostatic pressing (HIP) at 1170°C to obtain a sintered body. The sintered body was heated to 1100°C. The compact was forged and air-cooled to obtain the powder metallurgy compact of Example 1.

[0044] [Examples 2-15 and Comparative Examples 1-14] Powder metallurgy compacts of Examples 2-15 and Comparative Examples 1-14 were obtained in the same manner as in Example 1, except that the compositions were as shown in Tables 1 and 2 below.

[0045] [Comparative Examples 15 and 16] The compacts were obtained by arc melting.

[0046] [Maximum diameter of carbide (MD1)] The maximum value (MD1) of the equivalent circle diameter D1 of the carbide was measured using the above-mentioned method for the powder before being sintered. The results are shown in Tables 1 and 2 below.

[0047] [Maximum diameter of carbide (MD2)] A test piece was cut out from the molded body. The size of this test piece was 10 mm x 10 mm x 10 mm. This test piece was observed with a scanning electron microscope (SEM) to obtain a backscattered electron image at 4000 times magnification. From this electron image, the maximum circle equivalent diameter (MD2) of the carbide was calculated by image processing. The results are shown in Tables 1 and 2 below. The shape of the carbide in Comparative Examples 15 and 16 was reticulate, and it was impossible to measure the diameter.

[0048] [Fe content in matrix (Pi)] A test piece was cut out from the molded body. The size of this test piece was 10 mm x 10 mm x 14 mm. This test piece was observed with a scanning electron microscope (SEM) to obtain a backscattered electron image at 4000 times magnification. EDS analysis was performed on the matrix of this electron image to calculate the Fe content (Pi). The results are shown in Tables 1 and 2 below.

[0049] [Rockwell hardness (HRB)] The hardness H1 of the compact was measured. The compact was heated to 870°C, held for 1 hour, and then slowly cooled. The hardness H2 of the compact was measured. The hardness H1 and H2 were measured using the Rockwell Hardness Scale B. Furthermore, the difference in hardness (H1-H2) was calculated. These results are shown in Tables 1 and 2 below.

[0050] [Tensile test] A JIS No. 14A φ5 test piece (φ5 × GL25 mm) was cut out from the molded body. This test piece was subjected to a tensile test at room temperature to measure the tensile strength and elongation. The results are shown in Tables 1 and 2 below.

[0051] [Specific wear rate] A test piece was cut out from the molded body. The size of the test piece was 19 mm x 41 mm x 6 mm. The test piece was set in an Ohkoshi type abrasion tester, and the specific abrasion rate was measured. The measurement conditions were as follows: Mating material: SCM420 Wear speed: 2.38m / sec Wear distance: 200m Final load: 20.6N Lubrication: None Temperature: room temperature The wear scar width obtained in the test was measured, and the wear volume was calculated. The specific wear amount was calculated by dividing the wear volume by the product of the wear distance and the final load. The results are shown in Tables 1 and 2 below.

[0052] [Table 1]

[0053] [Table 2]

[0054] The powder according to Comparative Example 1 does not contain C. The compact obtained from this powder is inferior in hardness, softening resistance, tensile strength and wear resistance. The powder according to Comparative Example 2 contains excessive C. The compact obtained from this powder is inferior in extensibility. In the powder according to Comparative Example 3, the content of Fe in the matrix is ​​too small. The compact obtained from this powder is inferior in extensibility. The powder according to Comparative Example 4 contains excessive Fe. The compact obtained from this powder is inferior in hardness and tensile strength. The powder according to Comparative Examples 5-13 contains excessive additive elements. The compacts obtained from these powders are inferior in extensibility. The powder according to Comparative Example 14 contains coarse carbides. The compact obtained from this powder is inferior in extensibility. The powder according to Comparative Example 15 contains too small a content of C. The compact obtained from this powder is inferior in hardness. In the powder according to Comparative Example 16, carbides precipitated in a net shape. The compact obtained from this powder is inferior in balance between strength and extensibility.

[0055] The compacts obtained from the powders according to the respective Examples achieved a Rockwell hardness of 100 HRB or more, a difference (H1-H2) of 10 HRB or less, a tensile strength of 750 MPa or more, and an elongation of 5% or more.

[0056] These evaluation results clearly show the superiority of the present invention. [Industrial Applicability]

[0057] The multi-component alloys described above are suitable for a variety of applications where toughness is required.

Claims

1. The material is a multi-element alloy, The multi-component alloy is Co: 5 at% or more and 35 at% or less, Cr: 5 at% or more and 35 at% or less, Fe: 5 at% or more and 35 at% or less, Ni: 5 at% or more and 35 at% or less, and C: 1.39 atomic% or more and 8.74 atomic% or less and the remainder being unavoidable impurities, The entropy of mixing ΔS of the multi-component alloy is 1.30R or more; The metal structure includes a matrix and a large number of carbides dispersed in the matrix, The maximum equivalent circle diameter (MD1) of these carbides is 5.0 μm or less, The powder has an Fe content (Pi) in the matrix of 13 mass % or more and 24 mass % or less.

2. The multi-component alloy is One or more elements selected from the group consisting of V, Mo, Nb, W, Ti, Zr, Al, and Mn: 20 atomic % or less 2. The powder of claim 1 further comprising:

3. The multi-component alloy is Si: 10 atomic% or less 3. The powder according to claim 1 or 2, further comprising:

4. The material is a multi-element alloy, The multi-component alloy is Co: 5 at% or more and 35 at% or less, Cr: 5 at% or more and 35 at% or less, Fe: 5 at% or more and 35 at% or less, Ni: 5 at% or more and 35 at% or less, and C: 1.39 atomic% or more and 8.74 atomic% or less and the remainder being unavoidable impurities, The entropy of mixing ΔS of the multi-component alloy is 1.30R or more; The metal structure includes a matrix and a large number of carbides dispersed in the matrix, The maximum equivalent circle diameter (MD2) of these carbides is 15.0 μm or less, The powder metallurgy compact has an Fe content (Pi) in the matrix of 13 mass % or more and 24 mass % or less.

5. The multi-component alloy is One or more elements selected from the group consisting of V, Mo, Nb, W, Ti, Zr, Al, and Mn: 20 atomic % or less The powder metallurgical compact according to claim 4, further comprising:

6. The multi-component alloy is Si: 10 atomic% or less 6. The powder metallurgical compact according to claim 4 or 5, further comprising:

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