Metal powder for additive manufacturing and additive manufactured body

Abstract

A metal powder for additive manufacturing for molding an additive manufactured body by an additive manufacturing method for forming a stable powder bed capable of obtaining a high-density additive manufactured body having a relative density of 99% or more, the metal powder for additive manufacturing having a-63 [mu] m + 45 [mu] m sieve particle size (mass%) of 9% or more and a particle size (D5) of 9 [mu] m or more. Also disclosed is an additive manufactured body which is molded using an additive manufacturing device using the metal powder for additive manufacturing, and which is characterized in that the relative density of the additive manufactured body is 99.0% or more.

Description

Technical Field

[0001] This invention relates to metal powders for additive manufacturing and additive manufactured bodies. Background Technology

[0002] In the aforementioned technical field, Patent Document 1 discloses an additive manufacturing body with a relative density of 95% or more that can be obtained by forming a powder bed from metal powder with properties specified by average particle size D50 and TD (tap density).

[0003] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 2021-017639 Summary of the Invention

[0004] The problem that the invention aims to solve However, it is believed that open pores will appear at a relative density of 95%, which could lead to leaks and other malfunctions when used as an additive material for fluid handling. Therefore, to obtain additive materials with a high density of 99% or higher, a more stable powder bed needs to be formed.

[0005] The purpose of this invention is to provide a technique for solving the above-mentioned problems.

[0006] Methods for solving problems To achieve the above objectives, the additive manufacturing metal powder of the present invention is an additive manufacturing metal powder used for manufacturing additive bodies by an additive manufacturing method. The particle size (mass%) of the -63μm and +45μm sieves is above 9%, and the particle size D5 is above 9μm.

[0007] To achieve the above objectives, the additively manufactured body of the present invention is an additively manufactured body formed using the aforementioned additive manufacturing metal powder and an additive manufacturing apparatus. The relative density of the aforementioned additively manufactured body is above 99.0%.

[0008] Invention Effects According to the present invention, a stable powder bed can be formed for obtaining high-density additive manufactured articles with a relative density of 99% or more. Attached Figure Description

[0009] [ Figure 1 The graph shows the particle size distribution of the average particle size D50, and the relationship between the particle size D5 corresponding to the particle size distribution and the particle size (mass%) of the -63μm +45μm sieve.

[0010] [ Figure 2 [A graph showing the evaluation results of the powder bed in this embodiment and the comparative example.]

[0011] [ Figure 3 [A graph showing the relationship between the particle size D5 of the additive manufacturing metal powder in this embodiment and the particle size (mass%) of the -63μm +45μm sieve.]

[0012] [ Figure 4 [This is shown with the particle size D5 value on the horizontal axis.] Figure 3 A graph showing the particle size distribution in each region.

[0013] [ Figure 5 [A diagram showing air leakage in the cylinder of the additively manufactured body in this embodiment and comparative example.]

[0014] [ Figure 6A The graph shows the experimental results for the relationship between the particle size (mass%) and particle diameter D5 (μm) of the -63μm and +45μm sieves, the quality and stability of powder bed formation, and the stability of the relative density of the additively manufactured body under various combinations of metals and elements.

[0015] [ Figure 6B The graph shows the experimental results for the relationship between the particle size (mass%) and particle diameter D5 (μm) of the -63μm and +45μm sieves, the quality and stability of powder bed formation, and the stability of the relative density of the additively manufactured body under various combinations of metals and elements.

[0016] [ Figure 7A The graph shows the experimental results for the relationship between the particle size (mass%) and particle diameter D5 (μm) of the -63μm and +45μm sieves, the quality and stability of powder bed formation, and the stability of the relative density of the additively manufactured body under various combinations of metals and elements.

[0017] [ Figure 7B The graph shows the experimental results for the relationship between the particle size (mass%) and particle diameter D5 (μm) of the -63μm and +45μm sieves, the quality and stability of powder bed formation, and the stability of the relative density of the additively manufactured body under various combinations of metals and elements.

[0018] [ Figure 8A The graph shows the experimental results for the relationship between the particle size (mass%) and particle diameter D5 (μm) of the -63μm and +45μm sieves, the quality and stability of powder bed formation, and the stability of the relative density of the additively manufactured body under various combinations of metals and elements.

[0019] [ Figure 8B The graph shows the experimental results for the relationship between the particle size (mass%) and particle diameter D5 (μm) of the -63μm and +45μm sieves, the quality and stability of powder bed formation, and the stability of the relative density of the additively manufactured body under various combinations of metals and elements.

[0020] [ Figure 9A The graph shows the experimental results for the relationship between the particle size (mass%) and particle diameter D5 (μm) of the -63μm and +45μm sieves, the quality and stability of powder bed formation, and the stability of the relative density of the additively manufactured body under various combinations of metals and elements.

[0021] [ Figure 9B The graph shows the experimental results for the relationship between the particle size (mass%) and particle diameter D5 (μm) of the -63μm and +45μm sieves, the quality and stability of powder bed formation, and the stability of the relative density of the additively manufactured body under various combinations of metals and elements. Detailed Implementation

[0022] Hereinafter, embodiments of the present invention will be described in detail by way of illustration with reference to the accompanying drawings. However, the constituent elements described in the following embodiments are merely illustrative and are not intended to limit the technical scope of the present invention to therein.

[0023] As the additive manufacturing metal powder of this embodiment, copper alloy powder (an alloy powder with copper as the main component element) will be described. Before that, the current status of copper alloy powder for additive manufacturing will be explained.

[0024] <Current Status of Metal Powders for Additive Manufacturing> Patent document 1 discloses that when additive manufacturing is performed by forming a powder bed of metal powder with properties specified by average particle size D50 and TD (tap density), an additive manufactured body with a relative density of 95% or more can be obtained.

[0025] However, the average particle size D50 represents the median of the powder's particle size distribution. Therefore, as... Figure 1 As shown in particle size distribution 110, even powders with the same average particle size D50 value are expected to have wide powder size distributions 111 (where micro and coarse powders are abundant) and narrow powder size distributions 112 (where micro and coarse powders are essentially absent). Therefore, the amount of micro and coarse powders cannot be clearly known based on the average particle size D50 value. Consequently, even if the average particle size D50 is adjusted, the powder bed may become unstable. By making the relative density of the additively manufactured body less than 99%, adverse conditions such as leakage may occur, especially when handling fluids.

[0026] Figure 1 Powder diameter distributions 113 and 114 show powder diameter distributions located between a wide powder diameter distribution 111 and a narrow powder diameter distribution 112, wherein it is assumed that there is a stable powder bed and the relative density of the additively manufactured body is stable at 99% or higher.

[0027] <Metal powder for additive manufacturing according to this embodiment> As a characteristic that specifies the stable generation of powder beds and the stable relative density of additively manufactured bodies at 99% or higher, the inventors of this application focus on the particle size D5 (μm), which represents the size of particles that hinder the formation of powder beds, and the -63μm +45μm sieve particle size (mass%), which shows the amount of coarse powder used to improve flowability and powder bed density to form a stable powder bed. Here, the particle size D5 is a value obtained by laser diffraction, and the -63μm +45μm sieve particle size is a value obtained by the sieving test method specified in JIS Z8815:1994.

[0028] Powder diameter distributions 111–114 with the same average particle size D50 value are mapped onto graph 120, where the horizontal axis represents particle size D5 (μm) and the vertical axis represents the amount of coarse powder used to form a stable powder bed. The particle size is -63μm to +45μm (mass%). Based on the results of the examples and comparative examples, powder diameter distribution 113, which stably generates a powder bed and whose relative density of the additively manufactured body is stable at 99% or higher, particle size threshold 121 (particle size D5 of 9μm), and particle size threshold 122 (-63μm to +45μm (mass%)) are used to distinguish it from other powder diameter distributions 111, 112, and 114.

[0029] For powders with a particle size D5 less than 9 μm and a particle size (mass%) of 9% or more on a -63 μm to +45 μm sieve, the particle size distribution is wide, similar to powder diameter distribution 111. Therefore, in the additive manufacturing apparatus, the metal powder for additive manufacturing segregates during storage and fails to form a stable powder bed before additive manufacturing is completed.

[0030] For powders with a particle size D5 of 9 μm or larger and a particle size (mass%) of less than 9% on a sieve from -63 μm to +45 μm, the particle size distribution is narrow, similar to powder diameter distribution 112, and the powder exhibits good flowability. However, the excessive uniformity of particle size reduces the density of the powder bed, leading to a decrease in relative density. Furthermore, in the case of powders produced using methods such as atomization, sieving is required under conditions of a very narrow particle size range, resulting in poor productivity.

[0031] For powders with a particle size D5 of less than 9 μm and a particle size (mass%) of less than 9% on a sieve of -63 μm to +45 μm, the particle size distribution is relatively uniform, similar to powder diameter distribution 114. However, because the powder as a whole is micronized, its flowability is impaired, and it cannot inherently form a powder bed.

[0032] Thus, by using metal powder with a particle size (mass%) of -63μm +45μm sieve of 9% or more and a particle size distribution of 9μm or more based on laser diffraction, a powder diameter distribution of 113 can be stably obtained.

[0033] [First Implementation] As an additive manufacturing metal powder according to the first embodiment, copper powder and copper alloy powder (alloy powder with copper as the main component element) will be described.

[0034] The copper powder in this embodiment contains copper and unavoidable impurities. These unavoidable impurities include elements such as P and Al, which are present in amounts of 0.01% by mass or less.

[0035] In addition, the copper alloy powder of this embodiment contains 0.01% by mass to 32.0% by mass of an added element M (at least one element selected from Mg, Al, Si, P, Cr, Fe, Ni, Zn, Zr, Ag and Sn), with the balance being copper and unavoidable impurities.

[0036] Additive element M is added to improve the properties of copper alloy powder (flowability, etc.), its properties during additive manufacturing (laser reflectivity, laser absorptivity, etc.), and the properties of the additively manufactured body (mechanical properties: strength, wear resistance, toughness, etc.; physical properties: conductivity, heat resistance, etc.). In this embodiment, conditions were found that allow for the stable generation of a powder bed of copper alloy powder and a stable relative density of the additively manufactured body of 99% or higher.

[0037] It should be noted that the addition of element M is done within the following ranges, with the total amount of element M ranging from 0.01% to 32.0% by mass. For example, Al is in the range of 0.01% to 3.92% by mass, Si is in the range of 0.03% to 0.97% by mass, P is in the range of 0.01% to 0.14% by mass, Cr is in the range of 0.01% to 1.33% by mass, Fe is in the range of 0.01% to 0.29% by mass, Ni is in the range of 0.06% to 4.08% by mass, Zr is in the range of 0.04% to 0.31% by mass, and Sn is in the range of 0.24% to 5.09% by mass, etc.

[0038] <Method for Manufacturing Copper Alloy Powder> The method for manufacturing the copper alloy powder for additive manufacturing in this embodiment is not particularly limited, but methods such as gas atomization, water atomization, centrifugal atomization, plasma atomization, and plasma rotating electrode atomization, in which powder particles are rapidly solidified from a molten state, are preferred. From the perspective of mass production, gas atomization is particularly preferred. Regarding the manufactured powder, it can be graded according to known grading methods and prescribed grading conditions to obtain copper alloy powder for additive manufacturing with a suitable particle size. An air classifier can be suitable as the grading apparatus for performing the grading. Alternatively, the copper alloy powder can be mechanically ground. For example, ball milling, bead milling, planetary ball milling, grinding milling, and vibratory ball milling can be used.

[0039] <Manufacturing Method of Additively Manufactured Body> Various known metal additive manufacturing techniques can be used in the fabrication of copper alloy additive bodies. For example, in powder bed fusion, the additive body is fabricated by repeatedly performing the following steps: metal powder is flattened and spread on a molding table using a blade or roller to form a powder layer, and then a laser or electron beam is irradiated onto a predetermined location in the formed powder layer to sinter and melt the metal powder. In the molding process of metal additive manufacturing, a large number of process parameters need to be controlled to obtain high-quality additive bodies.

[0040] In laser-based powder bed melting, numerous scanning conditions exist, including laser output power and scanning speed. Therefore, when setting optimal scanning conditions, energy density, as an indicator encompassing key parameters, is used to adjust these parameters. Regarding energy density E [J / mm²]... 3 For example, when the laser output power is set to P [W], the laser scanning speed to v [mm / s], the laser scanning distance to s [mm], and the powder layer thickness to t [mm], the value is determined by E = P / (v × s × t). In the laser-based powder bed melting method, the preferred energy density is 150 J / mm². 3 Above 450J / mm 3 The following are examples: Energy density less than 150 J / mm² 3 In such cases, defects such as incomplete melting and poor fusion occur in the powder layer, resulting in voids in the additively manufactured body.

[0041] Energy density greater than 450 J / mm 3In certain situations, sputtering occurs, making the surface of the powder layer unstable and creating defects such as voids in the additively manufactured body. In electron beam powder bed fusion, when an electron beam is irradiated onto the powder layer, if negative charges accumulate and charge the powder layer, it causes a mist-like phenomenon where the powder flies around, resulting in poor melting. Therefore, to prevent charging, a preheating process is required to temporarily sinter the powder layer. However, if the preheating temperature is too high, sintering occurs, causing necking, making it difficult to remove residual powder from the additively manufactured body after molding. Therefore, in copper alloy powder for additive manufacturing, the preheating temperature is preferably set to 400–800°C. It should be noted that this example illustrates a metal additive manufacturing technology based on powder bed fusion, but it is not limited to this as a general additive manufacturing method for producing additively manufactured bodies using the copper alloy powder for additive manufacturing of the present invention. For example, additive manufacturing methods based on directional energy deposition can also be used.

[0042] <Methods for determining relative density> As methods for determining relative density, the following methods exist: (1) using a 3D powder additive manufacturing machine to produce an additive body, and calculating the relative density (%) by subtracting the porosity of the cross-section of the additive body from 100; (2) using a 3D powder additive manufacturing machine to produce an additive body, determining the density of the produced additive body using the Archimedes method, and calculating the relative density (%) by setting the theoretical density (the density of a molten material with the same composition as the additive body) to 100%. In this embodiment, method (1) is used.

[0043] According to this embodiment, for copper powder or copper alloy powder for additive manufacturing, the amount of coarse powder used to form a stable powder bed with high density without reducing the apparent density as a powder characteristic is specified by (1) using the "-63μm + 45μm sieve particle size (mass%)" obtained in "JIS Z8815: 1994 Sieve Test Method"; and (2) using the "D5 (μm)" specified in the laser diffraction method to specify the particle size of the micro powder that affects the flowability, thereby enabling the stable formation of a powder bed for obtaining an additively manufactured body with high relative density (over 99%).

[0044] [Second Implementation] As an additive manufacturing metal powder according to the second embodiment, nickel alloy powder (an alloy powder with nickel as the main component element) will be described.

[0045] The nickel alloy powder of this embodiment contains 50.88% by mass of added element N (at least one element selected from Al, Si, Ti, Cr, Mn, Fe, Co, Nb and Mo), with the balance being nickel and unavoidable impurities.

[0046] Additive element N is added to improve the properties of nickel alloy powder, its properties during additive manufacturing, and the properties (mechanical and physical properties) of the additively manufactured body. However, in this embodiment, conditions were found that allow for the stable generation of a powder bed and a stable relative density of the additively manufactured body of nickel alloy powder of 99% or higher. Therefore, the range of amounts of each element added, including N, is not limited and can be appropriately selected.

[0047] The manufacturing method of nickel alloy powder, the manufacturing method of additive manufacturing body using nickel alloy powder, and the method for measuring relative density are the same as those of copper alloy powder in the first embodiment, so repeated descriptions are omitted.

[0048] According to this embodiment, for nickel alloy powder for additive manufacturing, the amount of coarse powder used to form a stable powder bed with high density without reducing the apparent density as a powder characteristic is specified by (1) using the "-63μm + 45μm sieve particle size (mass%)" obtained in "JIS Z8815: 1994 Sieve Test Method"; and (2) using the "D5 (μm)" specified in the laser diffraction method to specify the particle size of the micro powder that affects the flowability, thereby enabling the stable formation of a powder bed for obtaining an additively manufactured body with high relative density (over 99%).

[0049] [Other Implementation Methods] The specification for additive manufacturing metal powder or alloy powder used to form a stable powder bed that yields a high-density additive manufactured body with a relative density of 99% or higher is not limited to copper or nickel alloys as described in the first and second embodiments above. The specification of having a particle size of 9% or higher on a -63μm +45μm sieve and a particle size D5 (μm) of 9μm or higher is a broadly applicable limitation independent of the type of metal or alloy.

[0050] Example 1 The following experiments were conducted on metals containing only unavoidable impurities, or alloys with different main components, and on the relationship between particle size (mass%) at -63μm and +45μm sieves and particle size D5 (μm) under various combinations of metals and elements, and the goodness, stability, and relative density stability of powder bed formation. The experimental results are presented below. Figures 6A to 9B Here, Examples 101-122 and Comparative Examples 101-111 are experimental results of copper powder or copper alloy powder, and Example 201 is experimental results of nickel alloy powder.

[0051] about Figures 6A to 9B The quality of powder bed formation is shown in the diagram (○: good, △: unstable, X: impossible). Figure 2As shown, an evaluation was conducted by forming a powder bed using additive manufacturing metal powder or additive manufacturing alloy powder. Example 110 ( Figure 2 In Comparative Example 101), a uniform powder bed (○) was formed. Figure 2 In Comparative Example 102), powder clumps were partially formed, and the powder bed was unstable (△). Figure 2 In 203), the powder bed could not be fully formed, and it was impossible to shape (X). Figure 7B The thick box indicates the particle size (mass%) or particle size D5 (μm) of the -63μm to +45μm sieve outside the specified range.

[0052] Figures 6A to 9B The relative density of the additive manufacturing shown can be obtained by using a 3D powder additive manufacturing machine to create the additive body and calculating the relative density (%) by subtracting the porosity of the cross-section of the additive body from 100.

[0053] Figure 6A , Figure 6B and Figure 7A , Figure 7B In Examples 101-122, 201, regarding metals containing only unavoidable impurities or alloys with different main components, since the particle size (mass%) of -63μm +45μm sieve is 9% or more and the particle size D5 is 9μm or more under the combination of various metals and elements, a high-density stable powder bed is formed, and additive manufacturing bodies with a relative density of 99% or more are stably shaped.

[0054] on the other hand, Figure 8A , Figure 8B and Figure 9A , Figure 9B In the case of metals containing only unavoidable impurities or alloys with different main components, due to the combination of various metals and elements, the particle size (mass%) of -63μm +45μm sieve is less than 9% and / or the particle size D5 is less than 9μm, thus forming an unstable powder bed with clumps, resulting in metal powders and alloy powders that fail to form additive manufacturing bodies with a relative density of more than 99%.

[0055] Figure 3 To be Figures 6A to 9B The quality of powder bed formation is plotted as a graph with particle size D5 on the horizontal axis and particle size (mass%) of -63μm to +45μm sieves on the vertical axis. For example... Figure 3 As shown, powder groups 311-314 are related to the quality of powder bed formation. Figure 1 Similarly, it exists with a threshold as its boundary. Figure 4 To and Figure 3The powder diameter distribution corresponding to powder groups 311 to 314 with particle size D5 as the horizontal axis.

[0056] Figure 4 In the case of powders with a particle size D5 less than 9 μm and a particle size (mass%) of 9% or more on a -63 μm to +45 μm sieve, the particle size distribution is wide, similar to powder diameter distribution 311. Therefore, in the additive manufacturing apparatus, the metal powder for additive manufacturing segregates during storage and fails to form a stable powder bed until additive manufacturing is completed.

[0057] Figure 4 In the case of powders with a particle size D5 of 9 μm or larger and a particle size (mass%) of less than 9% on a sieve from -63 μm to +45 μm, the particle size distribution is narrow, similar to powder diameter distribution 312, and the powder exhibits good flowability. However, due to the excessive uniformity of particle size, the density of the powder bed decreases, leading to a decrease in relative density. Furthermore, in the case of powders produced using methods such as atomization, sieving within a very narrow particle size range is required, resulting in poor productivity.

[0058] Figure 4 In the case of powders with a particle size D5 of less than 9 μm and a particle size (mass%) of less than 9% on a sieve of -63 μm to +45 μm, the particle size distribution is relatively uniform, similar to that of powder diameter distribution 314. However, because the powder as a whole is micronized, its flowability is impaired, and it cannot inherently form a powder bed.

[0059] In this way, by using a -63μm +45μm sieve, the particle size (mass%) is above 9%, and the particle size D5 (volume distribution) based on laser diffraction is managed to be above 9μm. Figure 4 Metal powder with a medium particle size distribution of 313 can stably produce high-density (relative density of over 99%) additive manufactured bodies.

[0060] Example 2 Using the copper alloy powders from Example 110 and Comparative Example 102, cylinders with a maximum thickness of 2 mm and a minimum thickness of 1 mm were fabricated, and leak checks were performed based on 0.2 MPa compressed air. Figure 5 The results of a leak inspection based on 0.2 MPa compressed air are shown.

[0061] like Figure 5 As shown, a cylinder 501 with a maximum thickness of 2 mm and a minimum thickness of 1 mm was fabricated. Compressed air at 0.2 MPa was applied to the cylinder 501 to check for air leakage in water. The cylinder 502, obtained by additive manufacturing using the copper alloy powder of Example 110, showed no air leakage. On the other hand, the cylinder 503, obtained by additive manufacturing using the copper alloy powder of Comparative Example 102, showed air leakage. The relative density of cylinder 503 was on the order of 98%, resulting in open pores; therefore, air leakage was considered to have occurred.

[0062] This application claims priority based on Japanese Application Special Hoc 2023-188963, filed on November 3, 2023, and incorporates all the disclosures therein.

Claims

1. Additive manufacturing metal powder, which is a copper-based additive manufacturing metal powder used to shape additive bodies by forming a powder bed additive manufacturing method, wherein... The added element comprises at least one of the following: Al: 0.01% to 3.92% by mass; Si: 0.01% to 0.97% by mass; P: 0.01% to 0.14% by mass; Cr: 0.01% to 1.33% by mass; Fe: 0.01% to 0.29% by mass; Ni: 0.06% to 4.08% by mass; Zr: 0.04% to 0.31% by mass; Sn: 0.24% to 5.09% by mass; Mg: 0.01% to 0.21% by mass; and Zn: 0.01% to 32.0% by mass, with the balance being copper and unavoidable impurities. The additive manufacturing metal powder has a particle size (mass%) of -63μm +45μm sieve of 9% or more and a particle size D5 of 9μm or more.

2. Additive manufacturing metal powder, which is a nickel-based additive manufacturing metal powder used to shape additive bodies by forming a powder bed additive manufacturing method, wherein... The added element N, comprising 50.88% by mass, contains at least one element selected from Al, Si, Ti, Cr, Mn, Fe, Co, Nb, and Mo, with the balance being nickel and unavoidable impurities. The additive manufacturing metal powder has a particle size (mass%) of -63μm +45μm sieve of 9% or more and a particle size D5 of 9μm or more.

3. The metal powder for additive manufacturing as described in claim 1 or 2, wherein, The -63μm +45μm sieve particle size (mass%) is a value obtained by the sieving test method specified in JIS Z8815:1994, and the particle size D5 is a value obtained by laser diffraction.

4. An additively manufactured body, which is an additively manufactured body obtained by additive manufacturing using the metal powder for additive manufacturing according to claim 1 through an additive manufacturing method of forming a powder bed, wherein, The added element comprises at least one of the following: Al: 0.01% to 3.92% by mass; Si: 0.01% to 0.97% by mass; P: 0.01% to 0.14% by mass; Cr: 0.01% to 1.33% by mass; Fe: 0.01% to 0.29% by mass; Ni: 0.06% to 4.08% by mass; Zr: 0.04% to 0.31% by mass; Sn: 0.24% to 0.97% by mass; Mg: 0.01% to 0.21% by mass; and Zn: 0.01% to 32.0% by mass, with the balance being copper and unavoidable impurities. The cross-sectional area ratio of the additively manufactured body, obtained by subtracting the porosity of the cross-section of the additively manufactured body from 100, is 99.0% or more.

5. An additively manufactured body, which is an additively manufactured body obtained by additive manufacturing using the metal powder for additive manufacturing according to claim 2 through an additive manufacturing method of forming a powder bed, wherein, The added element N, comprising 50.88% by mass, contains at least one element selected from Al, Si, Ti, Cr, Mn, Fe, Co, Nb, and Mo, with the balance being nickel and unavoidable impurities. The cross-sectional area ratio of the additively manufactured body, obtained by subtracting the porosity of the cross-section of the additively manufactured body from 100, is 99.0% or more.

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