Powders for additive manufacturing and additively manufactured bodies

Abstract

To provide powder for additive manufacturing capable of producing an additive manufacturing mold with excellent flowability, mechanical strength, and dimensional accuracy even in a high-temperature environment, and an additive manufacturing mold having the powder for additive manufacturing.SOLUTION: Powder for additive manufacturing comprises a metal powder and a film provided on the surface of particles of the metal powder and containing a compound derived from a coupling agent having a hydrophobic functional group. The powder for additive manufacturing has an average particle diameter of 3.0 μm or more and 30.0 μm or less, and the contact angle of water of 80° or more and 150°or less, the contact angle of water being measured at 25°C by the θ / 2 method after being subjected to a heat treatment at 200°C for 24 hours under an atmospheric atmosphere in a layered state.SELECTED DRAWING: Figure 11

Description

Technical Field

[0001] The present invention relates to powder for additive manufacturing and an additive manufactured object.

Background Art

[0002] In recent years, as a technology for manufacturing three-dimensional solid objects, an additive manufacturing method using metal powder has been spreading. This technology includes a process of calculating the cross-sectional shape when the solid object is thinly sliced in a plane orthogonal to the stacking direction, a process of arranging metal powder in layers to form a powder layer, and a process of solidifying a part of the powder layer based on the shape obtained by the calculation. By repeating the process of forming the powder layer and the process of solidifying a part thereof, a solid object is manufactured.

[0003] As additive manufacturing methods, a fused deposition modeling (FDM) method, a selective laser sintering (SLS) method, a binder jetting method, etc. are known according to the principle of solidification.

[0004] Patent Document 1 discloses, as a modification of the selective laser sintering method, a method for manufacturing an EB sintering type 3D printer-formed product using an electron beam (EB) instead of a laser. This method is a method of manufacturing a metal formed product by stacking surface-treated metal powder for an EB sintering type 3D printer, then performing preheating if desired, and then sintering by EB irradiation. The surface-treated metal powder for an EB sintering type 3D printer is powder obtained by surface-treating the surface of metal powder manufactured by a known method with a coupling agent. By using such surface-treated metal powder, the conductivity during stacking becomes good. Therefore, it can be suitably sintered by EB. Further, it is possible to suppress partial sintering from occurring due to preheating.

Prior Art Documents

Patent Documents

[0005] [Patent Document 1] Japanese Patent Publication No. 2017-25392 [Overview of the project] [Problems that the invention aims to solve]

[0006] However, the surface-treated metal powder described in Patent Document 1 has the problem of reduced fluidity under high temperature and high humidity. When the fluidity of the surface-treated metal powder decreases, for example, when forming a powder layer in a 3D printer, it becomes difficult to improve the packing of the metal powder. This results in a decrease in the mechanical strength and dimensional accuracy of the additively manufactured body. [Means for solving the problem]

[0007] The additive manufacturing powder according to the application example of the present invention is Metal powder and A coating is provided on the particle surface of the metal powder and contains a compound derived from a coupling agent having hydrophobic functional groups, Equipped with, The average particle size is 3.0 μm or more and 30.0 μm or less. After being subjected to a heat treatment in an atmospheric environment at 200°C for 24 hours, the water contact angle measured at 25°C using the θ / 2 method in a layered state was between 80° and 150°. the law of nature, The hydrophobic functional group is a cyclic structure-containing group, a fluoroalkyl group, or a fluoroaryl group. It is characterized by being such.

[0008] The additively fabricated body according to an example of the application of the present invention is A powder for additive manufacturing according to an application example of the present invention, A binder that binds the particles of the additive manufacturing powder together, It is characterized by having the following features. [Brief explanation of the drawing]

[0009] [Figure 1] This is a process diagram illustrating the method for manufacturing additively manufactured objects. [Figure 2] Figure 1 is a diagram illustrating the manufacturing method of the additively manufactured body shown in the figure. [Figure 3] It is a diagram for explaining the method for manufacturing the laminated structure shown in FIG. 1. [Figure 4] It is a diagram for explaining the method for manufacturing the laminated structure shown in FIG. 1. [Figure 5] It is a diagram for explaining the method for manufacturing the laminated structure shown in FIG. 1. [Figure 6] It is a diagram for explaining the method for manufacturing the laminated structure shown in FIG. 1. [Figure 7] It is a diagram for explaining the method for manufacturing the laminated structure shown in FIG. 1. [Figure 8] It is a diagram for explaining the method for manufacturing the laminated structure shown in FIG. 1. [Figure 9] It is a diagram for explaining the method for manufacturing the laminated structure shown in FIG. 1. [Figure 10] It is a diagram for explaining the method for manufacturing the laminated structure shown in FIG. 1. [Figure 11] It is a cross-sectional view schematically showing the powder for laminated manufacturing according to the embodiment. [Figure 12] It is a process diagram for explaining the method for manufacturing the powder for laminated manufacturing. [Figure 13] It is a table schematically showing the state before the coupling agent containing a trialkoxy group reacts with the hydroxyl group generated on the surface of the metal particles after hydrolysis, the state immediately after the coupling agent reacts, and the state after the hydrophobic functional group contained in the film is thermally decomposed. [Figure 14] It is a graph comparing the bending stress of the laminated structure produced using the powder of Example 1 and the bending stress of the laminated structure produced using the powder of Comparative Example 1 among the measurement results of the bending stress shown in Table 2. [Figure 15] It is a graph showing the relationship between the bulk density of the powder of Example 1 and the powder of Comparative Example 1 and the heating time.

MODE FOR CARRYING OUT THE INVENTION

[0010] Hereinafter, preferred embodiments of the powder for laminated manufacturing and the laminated structure of the present invention will be described in detail based on the accompanying drawings.

[0011] 1. Method for manufacturing a laminated structure First, a method for manufacturing a laminated structure will be described.

[0012] FIG. 1 is a process diagram for explaining a method of manufacturing a laminated structure. FIGS. 2 to 10 are diagrams for explaining the method of manufacturing the laminated structure shown in FIG. 1. In each figure of the present application, the X-axis, the Y-axis, and the Z-axis are set as three mutually orthogonal axes. Each axis is represented by an arrow, and the tip side is the "plus side" and the base end side is the "minus side". In the following description, particularly, the plus side of the Z-axis is referred to as "up" and the minus side of the Z-axis is referred to as "down". Also, both directions parallel to the X-axis are referred to as the X-axis direction, both directions parallel to the Y-axis are referred to as the Y-axis direction, and both directions parallel to the Z-axis are referred to as the Z-axis direction.

[0013] The method of manufacturing the laminated structure shown in FIGS. 1 to 10 is a method called the binder jet method, and as shown in FIG. 1, it has a powder layer forming step S102, a binder solution supply step S104, and a repeating step S106.

[0014] In the powder layer forming step S102, the powder 1 for laminated manufacturing is laid to form a powder layer 31. In the binder solution supply step S104, the binder solution 4 is supplied to a predetermined region of the powder layer 31 to bind the particles in the powder layer 31 to obtain a binding layer 41. In the repeating step S106, by repeating the powder layer forming step S102 and the binder solution supply step S104 one or more times, the laminated structure 6 shown in FIG. 10 is obtained. Hereinafter, each step will be sequentially described.

[0015] 1.1. Laminated manufacturing apparatus First, prior to the description of the powder layer forming step S102, the laminated manufacturing apparatus 2 will be described.

[0016] The additive manufacturing apparatus 2 comprises an apparatus body 21 having a powder storage section 211 and a molding section 212, a powder supply elevator 22 provided in the powder storage section 211, a molding stage 23 provided in the molding section 212, and a coater 24, rollers 25, and liquid supply section 26 that are movably provided on the apparatus body 21.

[0017] The powder storage section 211 is a recess provided in the main body 21 of the apparatus, with an open top. The additive manufacturing powder 1 is stored in this powder storage section 211. An appropriate amount of the additive manufacturing powder 1 stored in the powder storage section 211 is then supplied to the manufacturing section 212 by the coater 24.

[0018] A powder supply elevator 22 is located at the bottom of the powder storage section 211. The powder supply elevator 22 is movable vertically while loaded with additive manufacturing powder 1. By moving the powder supply elevator 22 upward, the additive manufacturing powder 1 placed on the powder supply elevator 22 is pushed up and spills out of the powder storage section 211. This allows the spilled additive manufacturing powder 1 to be moved towards the manufacturing section 212.

[0019] The molding section 212 is a recess provided in the main body 21 of the apparatus, with an open top. A molding stage 23 is located inside the molding section 212. The additive manufacturing powder 1 is laid in layers on the molding stage 23 by a coater 24. The molding stage 23 is also movable vertically while the additive manufacturing powder 1 is laid on it. The amount of additive manufacturing powder 1 laid on the molding stage 23 can be adjusted by setting the height of the molding stage 23 as appropriate.

[0020] The coater 24 and roller 25 are movable in the X-axis direction from the powder storage section 211 to the molding section 212. The coater 24 can even out and lay the additive manufacturing powder 1 in layers by dragging it. The roller 25 compresses the evenly laid additive manufacturing powder 1 from above.

[0021] The liquid supply unit 26 is composed of, for example, an inkjet head or a dispenser, and is movable in the X-axis and Y-axis directions within the molding unit 212. The liquid supply unit 26 can supply a desired amount of binder solution 4 to the desired position. The liquid supply unit 26 may have multiple discharge nozzles on a single head. The binder solution 4 may be discharged simultaneously or with a time delay from the multiple discharge nozzles.

[0022] 1.2. Powder layer formation process Next, the powder layer formation process S102 using the additive manufacturing apparatus 2 described above will be explained. In the powder layer formation process S102, the additive manufacturing powder 1 is laid on the manufacturing stage 23 to form a powder layer 31. Specifically, as shown in Figures 2 and 3, the coater 24 is used to drag the additive manufacturing powder 1 stored in the powder storage section 211 onto the manufacturing stage 23 and level it to a uniform thickness. This results in the powder layer 31 shown in Figure 4. At this time, the thickness of the powder layer 31 can be adjusted by lowering the upper surface of the manufacturing stage 23 below the upper end of the manufacturing section 212 and by adjusting the amount of lowering. The additive manufacturing powder 1 is a powder with excellent packing properties when leveled, as will be described later. Therefore, a powder layer 31 with a high packing rate can be obtained.

[0023] Next, the roller 25 is moved in the X-axis direction while compressing the powder layer 31 in the thickness direction. This increases the filling density of the additive manufacturing powder 1 in the powder layer 31. The compression by the roller 25 may be performed as needed and may be omitted. Alternatively, the powder layer 31 may be compressed by means other than the roller 25, such as a pressing plate.

[0024] 1.3. Binder Solution Supply Process In the binder solution supply step S104, as shown in Figure 5, the liquid supply unit 26 supplies the binder solution 4 to the formation region 60 of the powder layer 31 that corresponds to the additively manufactured body 6 to be fabricated. The binder solution 4 is a liquid containing a binder and a solvent or dispersion medium. In the formation region 60 to which the binder solution 4 is supplied, the particles of the additive manufacturing powder 1 bind together, and a binding layer 41 is obtained as shown in Figure 6. In the binding layer 41, the particles of the additive manufacturing powder 1 are bound together by the binder and have enough shape retention to prevent them from breaking under their own weight.

[0025] Furthermore, the binding layer 41 may be heated simultaneously with or after the supply of the binder solution 4. This promotes the volatilization of the solvent and dispersion medium contained in the binder solution 4, and also promotes the binding of particles by solidification or hardening of the binder. If the binder contains a photocurable resin or an ultraviolet curable resin, light irradiation or ultraviolet irradiation may be performed instead of heating, or in conjunction with heating.

[0026] The heating temperature is not particularly limited, but is preferably between 50°C and 250°C, and more preferably between 70°C and 200°C. This makes it possible to suppress the deformation of the additive manufacturing powder 1 caused by heating when the additive manufacturing powder 1 that did not bind with the binder solution 4 is reused.

[0027] The binder solution 4 is not particularly limited as long as it is a liquid that has components capable of binding the particles of the additive manufacturing powder 1 together. For example, the solvent or dispersion medium contained in the binder solution 4 may be water, alcohols, ketones, carboxylic acid esters, etc., and may also be a mixture containing at least one of these. Furthermore, examples of binders contained in the binder solution 4 include fatty acids, paraffin wax, microwax, polyethylene, polypropylene, polystyrene, acrylic resins, polyamide resins, polyesters, stearic acid, polyvinylpyrrolidone (PVP), polyvinyl alcohol (PVA), polyethylene glycol (PEG), urethane resins, epoxy resins, vinyl resins, unsaturated polyester resins, phenolic resins, etc.

[0028] 1.4. Repeated Process In the repeating step S106, the powder layer formation step S102 and the binder solution supply step S104 are repeated one or more times until the laminate, which is formed by stacking multiple binding layers 41, takes on a predetermined shape. In other words, these steps are performed a total of two or more times. This results in obtaining a three-dimensional additively fabricated body 6, as shown in Figure 10.

[0029] Specifically, first, a new powder layer 31 is formed on top of the binding layer 41 shown in Figure 6, as shown in Figure 7. Next, as shown in Figure 8, a binder solution 4 is supplied to the formation region 60 of the newly formed powder layer 31. This results in the binding layer 41 shown in Figure 9. By repeating these operations, the additively fabricated body 6 shown in Figure 10 is obtained.

[0030] Furthermore, any additive manufacturing powder 1 that did not form the binding layer 41 from the powder layer 31 is recovered and reused as needed.

[0031] Furthermore, the resulting additively manufactured body 6 may be subjected to pre-sintering as needed. This removes at least a portion of the binder contained in the additively manufactured body 6, thereby increasing the proportion of metal particles. As a result, when the additively manufactured body 6 is sintered to obtain a metal sintered body, the shrinkage rate can be reduced, thus suppressing unintended deformation and other issues.

[0032] The temperature for pre-sintering is not particularly limited, as long as it is a temperature at which at least a portion of the binder is volatilized and the metal powder does not undergo sintering, but it is preferably between 100°C and 500°C, and more preferably between 150°C and 300°C. The pre-sintering time is preferably 5 minutes or more, more preferably between 10 minutes and 120 minutes, and even more preferably between 20 minutes and 60 minutes, within the aforementioned temperature range. Examples of the pre-sintering atmosphere include an air atmosphere, an inert atmosphere such as nitrogen or argon, or a reduced-pressure atmosphere obtained by reducing the pressure of these atmospheres.

[0033] 1.5. Method for Manufacturing Metal Sintered Bodies A metal sintered body is obtained by subjecting the additively manufactured body 6 to a sintering process. In the sintering process, the additively manufactured body 6 is heated to induce a sintering reaction.

[0034] The sintering temperature varies depending on the type and particle size of the additive manufacturing powder 1, but as an example, it is preferably 980°C to 1330°C, and more preferably 1050°C to 1260°C. The sintering time is preferably 0.2 hours to 7 hours, and more preferably 1 hour to 6 hours.

[0035] The atmosphere used for the sintering process can be, for example, a reducing atmosphere such as hydrogen, an inert atmosphere such as nitrogen or argon, or a reduced-pressure atmosphere obtained by reducing the pressure of these atmospheres. The pressure of the reduced-pressure atmosphere is not particularly limited as long as it is less than atmospheric pressure (100 kPa), but it is preferably 10 kPa or less, and more preferably 1 kPa or less.

[0036] The metal sintered body obtained as described above can be used as a material to constitute all or part of the following: parts for transportation equipment such as automobile parts, bicycle parts, railway vehicle parts, ship parts, aircraft parts, and space transport vehicle parts; parts for electronic equipment such as personal computer parts, mobile phone terminal parts, tablet terminal parts, and wearable device parts; parts for electrical equipment such as refrigerators, washing machines, and air conditioners; parts for machinery such as machine tools and semiconductor manufacturing equipment; parts for plants such as nuclear power plants, thermal power plants, hydroelectric power plants, oil refineries, and chemical complexes; parts for watches; metal tableware, jewelry, and eyeglass frames.

[0037] 2. Powder for additive manufacturing Next, the additive manufacturing powder according to the embodiment will be described. Figure 11 is a schematic cross-sectional view showing the additive manufacturing powder according to the embodiment.

[0038] The additive manufacturing powder 1 according to this embodiment is a powder used in various additive manufacturing methods, such as the binder jetting method described above.

[0039] As shown in Figure 11, the additive manufacturing powder 1 has multiple surface-coated particles 13, each containing metal particles 11 that make up the metal powder and a coating 12 that covers the surface of the metal particles 11. Because the additive manufacturing powder 1 having such surface-coated particles 13 has high fluidity, it has high packing ability when leveled.

[0040] 2.1. Metal particles The constituent material of the metal particles 11 is not particularly limited and may be any material that is sinterable. Examples include elemental materials such as Fe, Ni, Co, and Ti, or alloys and intermetallic compounds mainly composed of these elements.

[0041] Examples of Fe-based alloys include stainless steels such as austenitic stainless steel, martensitic stainless steel, and precipitation-hardening stainless steel, as well as low-carbon steel, carbon steel, heat-resistant steel, die steel, high-speed tool steel, Fe-Ni alloy, and Fe-Ni-Co alloy.

[0042] Examples of Ni-based alloys include Ni-Cr-Fe alloys, Ni-Cr-Mo alloys, and Ni-Fe alloys.

[0043] Examples of Co-based alloys include Co-Cr alloys, Co-Cr-Mo alloys, and Co-Al-W alloys.

[0044] Examples of Ti-based alloys include alloys of Ti with metallic elements such as Al, V, Nb, Zr, Ta, and Mo, specifically Ti-6Al-4V and Ti-6Al-7Nb.

[0045] 2.2.Coating The coating 12 is formed by reacting a coupling agent having hydrophobic functional groups with the surface of the metal particles 11. Therefore, the coating 12 contains compounds derived from the coupling agent having hydrophobic functional groups and exhibits properties derived from hydrophobic functional groups.

[0046] Examples of hydrophobic functional groups include those containing cyclic structures, fluoroalkyl groups, fluoroaryl groups, nitro groups, acyl groups, and cyano groups. Of these, the hydrophobic functional group is preferably a cyclic structure-containing group, a fluoroalkyl group, or a fluoroaryl group. These also impart particularly high heat resistance to the coating 12. This makes it possible to realize a powder 1 for additive manufacturing that can maintain good fluidity even after high temperatures.

[0047] A cyclic structure-containing group is a functional group that has a cyclic structure. Examples of cyclic structure-containing groups include aromatic hydrocarbon groups, alicyclic hydrocarbon groups, and cyclic ether groups.

[0048] An aromatic hydrocarbon group is a residue obtained by removing hydrogen from an aromatic hydrocarbon, and preferably has 6 to 20 carbon atoms. Examples of aromatic hydrocarbon groups include aryl groups, alkylaryl groups, aminoaryl groups, and aryl halides. Examples of aryl groups include phenyl groups, tolyl groups, xylyl groups, naphthyl groups, and indenyl groups. Examples of alkylaryl groups include benzyl groups, methylbenzyl groups, phenethyl groups, methylphenethyl groups, and phenylbenzyl groups.

[0049] An alicyclic hydrocarbon group is a residue obtained by removing hydrogen from an alicyclic hydrocarbon, and preferably has 3 to 20 carbon atoms. Examples of alicyclic hydrocarbon groups include cycloalkyl groups and cycloalkylalkyl groups. Examples of cycloalkyl groups include cyclopropyl groups, cyclobutyl groups, cyclopentyl groups, and cyclohexyl groups. Examples of cycloalkylalkyl groups include cyclopentylmethyl groups and cyclohexylmethyl groups.

[0050] Examples of cyclic ether groups include epoxy groups, 3,4-epoxycyclohexyl groups, and oxetanyl groups.

[0051] A fluoroalkyl group is an alkyl group having 1 to 16 carbon atoms or a cycloalkyl group having 3 to 16 carbon atoms, substituted with one or more fluorine atoms. In particular, a perfluoroalkyl group is preferred.

[0052] A fluoroaryl group is an aryl group having 6 to 20 carbon atoms that is substituted with one or more fluorine atoms. In particular, a perfluoroaryl group is preferred.

[0053] These hydrophobic functional groups have relatively good heat resistance. Therefore, the coating 12 containing compounds derived from coupling agents with these hydrophobic functional groups is less likely to degrade even in high-temperature environments. As a result, the surface coating particles 13 are less likely to aggregate and less likely to lose fluidity even in high-temperature environments. Consequently, even when reused, the additive manufacturing powder 1 is obtained that can be well layered and produces additively manufactured bodies 6 with high dimensional accuracy.

[0054] Furthermore, these hydrophobic functional groups also possess good hydrophobicity. Therefore, the coating 12 containing compounds derived from coupling agents having these hydrophobic functional groups provides excellent fluidity to the additive manufacturing powder 1, even in humid environments.

[0055] The average thickness of the coating 12 is not particularly limited, but is preferably 100 nm or less, more preferably 0.5 nm to 50 nm, and even more preferably 1 nm to 10 nm. This ensures the film thickness necessary to maintain the coating 12. The average thickness of the coating 12 is, for example, the average of the film thickness of the coating 12 obtained from five or more points by observing the particle cross-section of the additive manufacturing powder 1 with a transmission electron microscope.

[0056] Furthermore, the coating 12 may be a multilayer film in which multiple layers of the aforementioned compound molecules are stacked, for example, two to ten layers, but it is preferable that it be a monolayer film of the aforementioned compound. With a monolayer coating 12, the thickness can be minimized.

[0057] Furthermore, the monolayer film is a film formed by the self-assembly of the coupling agent. In other words, the coupling agent allows molecules that have an affinity for the surface of the metal particles 11 to be densely arranged on the surface, thereby efficiently forming a film with a thickness of one molecule.

[0058] 2.3.Various characteristics The average particle size of the additive manufacturing powder 1 according to this embodiment is 3.0 μm or more and 30.0 μm or less, preferably 4.0 μm or more and 15.0 μm or less, and more preferably 5.0 μm or more and 10.0 μm or less. By setting the average particle size of the additive manufacturing powder 1 within the above range, an additively manufactured body 6 can be obtained that has good surface roughness and high dimensional accuracy. The average particle size of the additive manufacturing powder 1 can be determined, for example, by measuring the particle size distribution on a volume basis using a laser diffraction method and obtaining the resulting integrated distribution curve. Specifically, the average particle size is defined as the particle diameter D50 when the cumulative value from the small diameter side is 50% in the integrated distribution curve. An example of a measuring device is the Microtrac HRA9320-X100 manufactured by Nikkiso Co., Ltd.

[0059] Furthermore, the additive manufacturing powder 1 according to this embodiment is subjected to a heat treatment in which it is heated at 200°C for 24 hours in an atmospheric environment, and the water contact angle measured in a layered state is 80° to 150°.

[0060] The additive manufacturing powder 1 exhibiting such a water contact angle is highly fluid because, despite its small average particle size, it is resistant to moisture absorption and aggregation even in high-temperature and high-humidity environments. Therefore, even when reused or exposed to high-temperature and high-humidity environments, this additive manufacturing powder 1 maintains excellent packing properties, contributing to improved mechanical strength and dimensional accuracy of the additively manufactured body 6. As a result, an additively manufactured body 6 capable of producing a metal sintered body with excellent mechanical strength and dimensional accuracy can be obtained.

[0061] Furthermore, additive manufacturing powder 1, whose water contact angle is within the aforementioned range, exhibits excellent affinity with the binder solution 4. Therefore, when the binder solution 4 is supplied after the additive manufacturing powder 1 has been laid to form a powder layer 31, the binder solution 4 easily penetrates the formation region 60 of the powder layer 31. As a result, the binder solution 4 can be uniformly permeated into the formation region 60, enabling the manufacture of additively manufactured bodies 6 with high dimensional accuracy.

[0062] The contact angle of water in additive manufacturing powder 1 can be measured using the following procedure. First, the additive manufacturing powder 1 is subjected to a heat treatment by heating it at 200°C for 24 hours in an air atmosphere. Next, double-sided tape is attached to a flat surface. Then, the heat-treated additive manufacturing powder 1 is spread on the double-sided tape. Finally, the spread additive manufacturing powder 1 is lightly pressed down with a plate-shaped member. Next, any excess additive manufacturing powder 1 is blown away with an air blower. This yields a test specimen for contact angle measurement.

[0063] Next, the contact angle of water on the test specimen will be measured using the θ / 2 method with a DropMaster 500 contact angle measuring device manufactured by Kyowa Interface Science Co., Ltd. The measurement conditions will be a temperature of 25°C and a relative humidity of 50% ± 5%. The amount of water dropped will be 3 μL, and the measurement will be taken 5 seconds after the drop is applied.

[0064] The water contact angle measured for the layered additive manufacturing powder 1 is set to 80° to 150°, as described above, but is preferably set to 95° to 145°, and more preferably to 110° to 140°. The water contact angle may exceed the above upper limit, but in that case, the hydrophobicity will be too high, and depending on the composition of the binder solution 4, the permeability of the binder solution 4 may decrease. This may reduce the homogeneity of the additively manufactured body 6.

[0065] Furthermore, when the particle size distribution based on volume is measured by laser diffraction for the additive manufacturing powder 1 and an integrated distribution curve is obtained, the particle size when the cumulative value from the smallest diameter side is 10% in the obtained integrated distribution curve is defined as D10, and the particle size when the cumulative value from the smallest diameter side is 90% is defined as D90. In this case, (D90-D10) / D50 of the additive manufacturing powder 1 is preferably between 1.0 and 2.7, and more preferably between 1.2 and 2.4. (D90-D10) / D50 is an index that indicates the degree of spread of the particle size distribution, and when this index is within the above range, the packing performance of the additive manufacturing powder 1 becomes particularly good.

[0066] Furthermore, when the additive manufacturing powder 1 according to this embodiment is heated at 200°C for 24 hours in air, it is preferable that the decrease in bulk density from before heating is 2.5% or less, more preferably 2.0% or less, and even more preferably 1.0% or less. This ensures that when additive manufacturing powder 1 that was not bonded in the additive manufacturing method described above is reused, the deformation due to heating is sufficiently suppressed. As a result, even when the reused additive manufacturing powder 1 and newly added additive manufacturing powder 1 are mixed, the difference in fluidity between the two can be minimized. Therefore, additive manufacturing powder 1 with a decrease in bulk density within the above range is suitable for reuse. This effect is a result of the hydrophobic functional groups described above providing good heat resistance to the coating 12.

[0067] The bulk density of additive manufacturing powder 1 is measured according to the apparent density measurement method for metal powders specified in JIS Z 2504:2012. The decrease rate from before heating is calculated by measuring the decrease in bulk density from the bulk density measured before heating to the bulk density measured after heating, and then dividing that decrease by the bulk density before heating. Therefore, if the bulk density increases after heating, the decrease rate is zero.

[0068] Similarly, when the additive manufacturing powder 1 according to this embodiment is heated at 200°C for 24 hours in air, the decrease in tap density from before heating is preferably 10.0% or less, more preferably 5.0% or less, and even more preferably 2.5% or less. This ensures that when the additive manufacturing powder 1 that was not bonded in the additive manufacturing method described above is reused, the deformation due to heating is sufficiently suppressed. As a result, even when the reused additive manufacturing powder 1 and the newly added additive manufacturing powder 1 are mixed, the difference in fluidity between the two can be minimized. Therefore, additive manufacturing powder 1 with a tap density decrease within the above range is particularly suitable for reuse.

[0069] The tap density of additive manufacturing powder 1 is measured using a powder property evaluation device, Powder Tester® PT-X, manufactured by Hosokawa Micron Corporation. The rate of decrease from before heating is calculated by measuring the decrease in tap density from the tap density measured before heating to the tap density measured after heating, and then dividing that decrease by the tap density before heating. Therefore, if the tap density increases after heating, the rate of decrease is zero.

[0070] Furthermore, the additive manufacturing powder 1 according to this embodiment preferably has a moisture content of 150 ppm or less by mass ratio, more preferably 10 ppm to 120 ppm, and even more preferably 30 ppm to 100 ppm, as measured by the Karl Fischer method. When the moisture content of the additive manufacturing powder 1 is within the above range, the additive manufacturing powder 1 becomes particularly resistant to aggregation. Therefore, the fluidity and packing properties of the additive manufacturing powder 1 can be particularly improved. In addition, rusting of the metal particles 11 due to moisture can be suppressed, resulting in a metal sintered body with excellent mechanical strength and appearance.

[0071] For measuring moisture content using the Karl Fischer method, for example, a moisture measuring device such as the CA-310 manufactured by Nitto Seikou Analytech Co., Ltd. is used.

[0072] Furthermore, when the additive manufacturing powder 1 according to this embodiment is used in additive manufacturing with a water-soluble resin as a binder, the resulting additively manufactured body has a bending stress of 15 N / cm². 2 Preferably, the pressure is 0.15 MPa or higher, and 20 N / cm². 2 It is more preferable that the pressure is 0.20 MPa or higher. Such additive manufacturing powder 1 makes it possible to manufacture additively manufactured bodies with sufficiently high bending stress. This makes it possible to increase the mechanical strength of the metal sintered body obtained by sintering the additively manufactured body. Furthermore, if the mechanical strength of the metal sintered body is sufficiently high and no further improvement is needed, the amount of binder used during manufacturing can be reduced. This makes it possible to reduce the amount of shrinkage of the additively manufactured body during degreasing and sintering. As a result, the dimensional accuracy of the metal sintered body obtained by sintering the additively manufactured body can be improved.

[0073] 2.4 Effects of the Embodiment As described above, the additive manufacturing powder 1 according to this embodiment comprises metal powder particles (metal particles 11) and a coating 12 provided on the surface of the metal particles 11. The coating 12 contains a compound derived from a coupling agent having hydrophobic functional groups.

[0074] The average particle size of the additive manufacturing powder 1 is between 3.0 μm and 30.0 μm. Furthermore, after the additive manufacturing powder 1 is subjected to a heat treatment in an atmospheric environment at 200°C for 24 hours, the water contact angle measured at 25°C using the θ / 2 method in a layered state is between 80° and 150°.

[0075] Despite having a small average particle size, this additive manufacturing powder 1 is resistant to moisture absorption and aggregation even in high-temperature and high-humidity environments, resulting in high fluidity. Therefore, even when reused or exposed to high-temperature and high-humidity environments, this additive manufacturing powder 1 maintains excellent packing properties, contributing to improved mechanical strength and dimensional accuracy of the additively manufactured body 6. Furthermore, additive manufacturing powder 1 with a water contact angle within the aforementioned range exhibits excellent affinity with the binder solution 4. This allows the binder solution 4 to easily penetrate the formation region 60 of the powder layer 31, enabling the manufacture of an additively manufactured body 6 with high dimensional accuracy. Thus, such an additively manufactured body 6 can be used to produce a metal sintered body with excellent mechanical strength and dimensional accuracy.

[0076] Furthermore, as mentioned above, the hydrophobic functional group is preferably a cyclic structure-containing group, a fluoroalkyl group, or a fluoroaryl group. These hydrophobic functional groups impart not only hydrophobicity but also heat resistance to the coating 12. This makes it possible to realize a powder 1 for additive manufacturing that can maintain good fluidity even after high temperatures.

[0077] Furthermore, as mentioned above, it is preferable that when the additive manufacturing powder 1 is heated at 200°C for 24 hours in an atmospheric environment, the decrease in bulk density is 2.5% or less compared to before heating. This ensures that when additive manufacturing powder 1 that was not bonded during the additive manufacturing process is reused, the degradation due to heating is sufficiently suppressed. As a result, even when the reused additive manufacturing powder 1 and newly added additive manufacturing powder 1 are mixed, the difference in fluidity between the two can be minimized.

[0078] Furthermore, as mentioned above, it is preferable that the coating 12 is a monolayer made of the aforementioned compound. A monolayer coating 12 allows for minimizing its thickness.

[0079] Furthermore, as mentioned above, it is preferable that the moisture content of the additive manufacturing powder 1, as measured by the Karl Fischer method, is 150 ppm or less by mass. This makes the additive manufacturing powder 1 particularly resistant to aggregation. As a result, the fluidity and packing properties of the additive manufacturing powder 1 can be particularly improved.

[0080] Furthermore, as mentioned above, when additive manufacturing powder 1 is used in additive manufacturing with a water-soluble resin as a binder, the resulting additively manufactured body has a bending stress of 15 N / cm². 2 It is preferable that the bending stress is 0.15 MPa or higher. This makes it possible to manufacture additively manufactured bodies with sufficiently high bending stress and to reduce the amount of binder used during manufacturing.

[0081] Furthermore, as described above, the additively manufactured body 6 according to the embodiment comprises additive manufacturing powder 1 and a binder that binds the particles of the additive manufacturing powder 1 together. Such an additively manufactured body 6 benefits from the high fluidity and packing properties of the additive manufacturing powder 1, resulting in high dimensional accuracy and high mechanical strength. Therefore, by sintering such an additively manufactured body 6, a metal sintered body with high dimensional accuracy and mechanical strength can be obtained.

[0082] 3. Method for manufacturing powder for additive manufacturing Next, we will explain the method for producing powder for additive manufacturing. Figure 12 is a process diagram illustrating the manufacturing method of additive manufacturing powder.

[0083] The method for producing additive manufacturing powder shown in Figure 12 comprises a preparation step S202, a coupling agent reaction step S204, and a heating step S206.

[0084] 3.1. Preparation process In preparation step S202, a metal powder containing metal particles 11 is prepared. The metal particles 11 may be manufactured by any method, but it is preferable that the powder be manufactured by an atomization method such as water atomization, gas atomization, or rotary water atomization, and is especially preferable that it be manufactured by water atomization or rotary water atomization. The surface of metal particles 11 manufactured by these methods is easily covered with hydroxyl groups derived from water. This improves the adhesion of the coating 12, and even if the coating 12 is thin, the fluidity of the surface coating particles 13 can be sufficiently increased. As a result, an additively fabricated body 6 can be realized in which the occupancy rate of metal particles 11 is high compared to the coating 12, and the shrinkage rate during sintering is small.

[0085] 3.2. Coupling agent reaction process In the coupling agent reaction step S204, a coupling agent having hydrophobic functional groups is reacted with the metal powder. This causes the coupling agent to adhere to the surface of the metal particles 11.

[0086] Examples of such operations include the following three:

[0087] The first operation involves introducing both the metal particles 11 and the coupling agent into the chamber, followed by heating the inside of the chamber.

[0088] A second operation involves introducing the metal particles 11 into the chamber, and then spraying a coupling agent into the chamber while stirring the metal particles 11.

[0089] A third procedure involves adding water, a coupling agent, and an alkaline solution such as ammonia or sodium hydroxide to a primary alcohol such as methanol, ethanol, or isopropyl alcohol, stirring, filtering, and then drying.

[0090] Examples of coupling agents include silane coupling agents, titanium coupling agents, and zirconium coupling agents. The following chemical formula is an example of the molecular structure of a silane coupling agent.

[0091] [ka]

[0092] In the above formula, X is a functional group, Y is a spacer, and OR is a hydrolyzable group. R is, for example, a methyl group or an ethyl group.

[0093] Examples of spacers include alkylene groups, arylene groups, aralkylene groups, alkylene ether groups, and the like.

[0094] Hydrolyzable groups include, for example, alkoxy groups, halogen atoms, cyano groups, acetoxy groups, and isocyanate groups. In the case of alkoxy groups, hydrolysis produces silanol. This silanol reacts with the hydroxyl groups formed on the surface of the metal particles 11, and the coupling agent adheres to the surface of the metal particles 11.

[0095] Such hydrolyzable groups only need to be present in the coupling agent at least one, but it is preferable that two or more be present, and more preferably that three hydrolyzable groups be present as shown in the formula above. For example, a coupling agent in which the hydrolyzable group is an alkoxy group preferably contains a dialkoxy group, and more preferably contains a trialkoxy group. A coupling agent containing a trialkoxy group (a coupling agent containing three hydrolyzable groups) reacts with the three hydroxyl groups formed on the surface of the metal particles 11. As a result, the coating 12 derived from the coupling agent has good adhesion to the metal particles 11. Furthermore, a coupling agent containing a trialkoxy group also has excellent film-forming properties, so a coating 12 with excellent continuity can be obtained. Such a coating 12 contributes to further improving the fluidity of the additive manufacturing powder 1.

[0096] Furthermore, in coupling agents containing trialkoxy groups, even if the hydrophobic functional groups decompose thermally after the film 12 is formed, the remainder can continue to cover the surface of the metal particles 11. Specifically, when the hydrophobic functional groups decompose thermally, hydroxyl groups bonded to Si atoms are produced in their place. These hydroxyl groups are fewer in number than the hydroxyl groups initially formed on the surface of the metal particles 11.

[0097] Figure 13 is a schematic table showing the state before the coupling agent CA containing trialkoxy groups reacts with the hydroxyl groups formed on the surface of the metal particles 11 after hydrolysis, the state immediately after the coupling agent CA reacts, and the state after the hydrophobic functional groups contained in the coating 12 have been thermally decomposed.

[0098] As shown in Figure 13, the coupling agent CA containing trialkoxy groups reacts with the three hydroxyl groups formed on the surface of the metal particles 11, and adheres to them via hydrogen bonding. Subsequently, in the heating step S206 described later, a dehydration condensation reaction occurs due to heating, forming covalent bonds and resulting in the formation of a coating 12. Furthermore, if the hydrophobic functional groups decompose due to heating, hydroxyl groups are formed after the hydrophobic functional groups. As a result, the number of hydroxyl groups formed on the coating 12 can be reduced compared to the hydroxyl groups initially formed on the surface of the metal particles 11. Therefore, even if the hydrophobic functional groups decompose due to the formation of the coating 12, moisture resistance (hydrophobicity) can be maintained.

[0099] As mentioned above, examples of hydrophobic functional groups found in coupling agents include cyclic structure-containing groups, fluoroalkyl groups, and fluoroaryl groups.

[0100] Among these, coupling agents containing cyclic structures include, as mentioned above, coupling agents containing aromatic hydrocarbon groups and coupling agents containing cyclic ether groups.

[0101] Examples of coupling agents containing aromatic hydrocarbon groups include, Phenyltrimethoxysilane represented by the following formula (A-1),

[0102] [ka]

[0103] Phenyltriethoxysilane represented by the following formula (A-2),

[0104] [ka]

[0105] Dimethoxydiphenylsilane represented by the following formula (A-3),

[0106] [ka]

[0107] 2,2-dimethoxy-1-phenyl-1-aza-2-silacyclopentane, represented by the following formula (A-4),

[0108] [ka]

[0109] 3-phenoxypropyltrichlorosilane represented by the following formula (A-11),

[0110] [ka]

[0111] Phenyltriacetoxysilane represented by the following formula (A-12),

[0112] [ka]

[0113] Triethoxy(p-tolyl)silane represented by the following formula (A-13),

[0114] [ka]

[0115] p-aminophenyltrimethoxysilane represented by the following formula (A-14),

[0116] [ka]

[0117] m-aminophenyltrimethoxysilane represented by the following formula (A-15),

[0118] [ka]

[0119] ((chloromethyl)phenylethyl)trimethoxysilane, represented by the following formula (A-16),

[0120] [ka]

[0121] These are some examples.

[0122] Examples of coupling agents having a cyclic ether group include, 3-Glycidoxypropylmethyldimethoxysilane, represented by the following formula (A-5),

[0123] [ka]

[0124] 3-glycidoxypropyltrimethoxysilane represented by the following formula (A-6),

[0125] [ka]

[0126] 3-Glycidoxypropylmethyldiethoxysilane, represented by the following formula (A-7),

[0127] [ka]

[0128] 3-glycidoxypropyltriethoxysilane, represented by the following formula (A-8),

[0129] [ka]

[0130] These are some examples.

[0131] Examples of coupling agents containing fluoroalkyl groups include, Trimethoxy(3,3,3-trifluoropropyl)silane represented by the following formula (B-1),

[0132] [ka]

[0133] Trimethoxy(1H,1H,2H,2H-tridecafluoro-n-octyl)silane represented by the following formula (B-2),

[0134] [ka]

[0135] Trimethoxy(1H,1H,2H,2H-nonafluorohexyl)silane represented by the following formula (B-3),

[0136] [ka]

[0137] These are some examples.

[0138] Examples of coupling agents containing a fluoroaryl group include, Trimethoxy(11-pentafluorophenoxyundecyl)silane represented by the following formula (C-1),

[0139] [ka]

[0140] Pentafluorophenyldimethylchlorosilane represented by the following formula (C-2),

[0141] [ka]

[0142] These are some examples.

[0143] The amount of coupling agent added is not particularly limited, but is preferably 0.01% by mass or more and 1.00% by mass or less relative to the metal particles 11, and more preferably 0.05% by mass or more and 0.50% by mass or less.

[0144] Furthermore, the coupling agent is supplied by methods such as being left to stand in the chamber or being sprayed into the chamber.

[0145] 3.3.Heating process In heating step S206, the metal particles 11 to which the coupling agent is attached are heated. This forms a coating 12 on the surface of the metal particles 11, yielding the additive manufacturing powder 1. Heating also removes any unreacted coupling agent.

[0146] The heating temperature of the metal particles 11 to which the coupling agent is attached is not particularly limited, but is preferably 50°C to 300°C, and more preferably 100°C to 250°C. The heating time is preferably 10 minutes to 24 hours, and more preferably 30 minutes to 10 hours. Examples of the atmosphere for the heat treatment include an air atmosphere and an inert gas atmosphere.

[0147] The additive manufacturing powder and additively manufactured body of the present invention have been described above based on the illustrated embodiments. However, the present invention is not limited thereto, and for example, the additive manufacturing powder and additively manufactured body of the present invention may have any components added to the above embodiments. [Examples]

[0148] Next, specific embodiments of the present invention will be described. 4. Manufacturing of powder for additive manufacturing 4.1. Example 1 First, a powder of precipitation-hardening stainless steel 17-4PH, manufactured by the water atomization method, was prepared. Then, 100g of the prepared metal powder was pre-treated. Next, a solution was prepared by mixing a coupling agent with water, and this solution was sprayed onto the metal powder heated to 200°C. After that, the metal powder to which the solution had been sprayed was allowed to dry. The amount of coupling agent used was 0.1% by mass of the metal powder. In this way, a powder for additive manufacturing was obtained.

[0149] Subsequently, the obtained additive manufacturing powder was laid in layers to create a test specimen, and the water contact angle of this specimen was measured. The measured values ​​were then classified into one of the following categories, A to D, based on the following classification criteria.

[0150] A: The contact angle is 110° or greater. B: The contact angle is between 95° and 110°. C: Contact angle is 80° or more and less than 95° D: Contact angle is less than 80°

[0151] The classification results are shown in Table 1 as "contact angle of water before heat treatment". Pure water was used, and the measurement temperature was 25°C.

[0152] Next, the additive manufacturing powder was subjected to a heat treatment by heating it at 200°C for 24 hours in an air atmosphere. Then, the heat-treated additive manufacturing powder was laid in layers to create a test specimen, and the water contact angle of this specimen was measured again. The measured values ​​were then classified into one of the categories A to D based on the classification criteria described above. The classification results are shown in Table 1 as "Water Contact Angle After Heat Treatment".

[0153] Furthermore, the moisture content of the obtained additive manufacturing powder was measured. In addition, the particle sizes D10, D50, and D90 were determined for the obtained additive manufacturing powder. The particle size D50 was 7 μm. Then, (D90-D10) / D50 was calculated. The measured moisture content and the calculated (D90-D10) / D50 are shown in Table 1.

[0154] 4.2. Examples 2-6 A powder for additive manufacturing was obtained in the same manner as in Example 1, except that the manufacturing conditions for the additive manufacturing powder were changed as shown in Table 1. The particle size D50 of the metal powder used was 3 to 15 μm.

[0155] 4.3. Comparative Examples 1-7 A powder for additive manufacturing was obtained in the same manner as in Example 1, except that the manufacturing conditions for the additive manufacturing powder were changed as shown in Table 1. The particle size D50 of the metal powder used was 3 to 15 μm. The symbols in the chemical formulas shown in Table 1 correspond to the following compounds.

[0156] D-1: Methyltrimethoxysilane D-2: Propyltrimethoxysilane D-3: Decyltrimethoxysilane D-4: Octadecyltrimethoxysilane D-5: Vinyltrimethoxysilane D-6: Aminotrimethoxysilane

[0157] [Table 1]

[0158] 5. Evaluation of additive manufacturing powders and additively manufactured bodies 5.1.Fillability 50 g of powder from each example and comparative example was placed in a 50 mL screw-cap bottle. The height from the bottom to the top of the powder was measured with the screw-cap bottle standing upright, and the packing efficiency was evaluated accordingly. This packing efficiency evaluation was performed according to the following evaluation criteria.

[0159] A: The height is 25 mm or less. B: The height is greater than 25mm but less than or equal to 30mm. C: The height is more than 30mm

[0160] Next, the powders of each example and comparative example were subjected to a heat treatment by heating at 200°C for 24 hours under an atmospheric environment. The packing properties of the powders after the heat treatment were then evaluated again. The evaluation results are shown in Table 2.

[0161] 5.2. Tapping properties 50g of the powder from each example and comparative example was placed in a 50mL screw-cap vial. The screw-cap vial was then tapped against a table 10 times. After that, with the screw-cap vial standing upright, the height from the bottom to the top of the powder was measured to evaluate the tapping properties. The evaluation of tapping properties was carried out according to the following evaluation criteria.

[0162] A: The height is 19 mm or less. B: The height is greater than 19mm but less than or equal to 25mm. C: The height is greater than 25 mm. The evaluation results are shown in Table 2.

[0163] 5.3. Cohesiveness 50 g of powder from each example and comparative example was placed in a 50 mL screw-cap vial. The vial was then rotated 10 times around an axis passing through the center of the bottom of the vial. After that, the aggregation state of the powder was observed from outside the screw-cap vial, and the aggregation properties were evaluated accordingly. This evaluation of aggregation properties was performed according to the following evaluation criteria.

[0164] A: Aggregation present C: No aggregation

[0165] Next, the powders of each example and comparative example were subjected to a heat treatment by heating at 200°C for 24 hours in an air atmosphere. The cohesiveness of the powders after the heat treatment was then evaluated again. The evaluation results are shown in Table 2.

[0166] 5.4. Changes in bulk density and tap density due to heat treatment The bulk density of each example and comparative example powder was measured according to the apparent density measurement method for metal powders specified in JIS Z 2504:2012. Next, each example and comparative example powder was subjected to a heat treatment by heating at 200°C for 24 hours in an air atmosphere. Then, the bulk density and tap density of the powder after the heat treatment were measured again. The measured values ​​were then evaluated against the evaluation criteria described above. The evaluation results are shown in Table 2. Note that the reduction rate in the evaluation criteria below is the value obtained by dividing the change in bulk density or tap density before and after the heat treatment by the bulk density or tap density before the heat treatment.

[0167] <Evaluation criteria for changes in bulk density due to heat treatment> A: The rate of decrease due to heat treatment is 1.0% or less. B: The rate of decrease due to heat treatment is greater than 1.0% and less than or equal to 2.5%. C: The rate of decrease due to heat treatment is more than 2.5%.

[0168] <Evaluation criteria for changes in tap density due to heat treatment> A: The rate of decrease due to heat treatment is 2.5% or less. B: The rate of decrease due to heat treatment is greater than 2.5% and less than or equal to 5.0%. C: The rate of decrease due to heat treatment is greater than 5.0%.

[0169] 5.5. Bending stress of additively manufactured objects Using the powders from each example and comparative example, additively fabricated rectangular parallelepiped bodies were created by the binder jet method. The dimensions of the fabricated additively fabricated bodies were 40 mm in length, 20 mm in width, and 6.6 mm in thickness. A polyvinyl alcohol aqueous solution was used as the binder solution.

[0170] Next, the bending load was measured on the fabricated additively manufactured object using a three-point bending test jig. Then, the bending stress σ of the additively manufactured object was calculated using the following formula.

[0171]

number

[0172] In the above formula, F is the bending load, L is the distance between the supports of the three-point bending test fixture, b is the width of the additively manufactured object, and h is the thickness of the additively manufactured object.

[0173] Furthermore, in the fabrication of the additively manufactured bodies, additively manufactured bodies were created with binder amounts of 70% and 100% by mass of metal powder, and the bending stress σ was calculated for each additively manufactured body. The calculation results are shown in Table 2.

[0174] 5.6. Dimensional accuracy of additively manufactured objects Using the powders from each example and comparative example, additively manufactured rectangular parallelepiped bodies were fabricated by the binder jet method. Next, the dimensions of the additively manufactured bodies were measured. The deviation from the target dimension was calculated, and the ratio of the deviation to the target dimension was defined as the dimensional accuracy. In addition, additively manufactured bodies were fabricated with binder amounts of 70%, 85%, and 100% by mass of the metal powder, and the dimensional accuracy was calculated for each additively manufactured body. The calculation results are shown in Table 2. In dimensional accuracy, a negative value indicates that the dimension was smaller than the target value, and a positive value indicates that the dimension was larger than the target value.

[0175] [Table 2]

[0176] As shown in Table 2, the additive manufacturing powders of each example exhibited better tapping properties compared to the additive manufacturing powders of each comparative example, and also showed good packing and cohesive properties both before and after heat treatment. Furthermore, the additive manufacturing powders of each example showed small changes in bulk density and tap density before and after heat treatment.

[0177] From the above, it is presumed that the additive manufacturing powder according to the present invention can improve the packing properties when leveled in layers. The reason why such an effect can be obtained is that, even after heat treatment, the additive manufacturing powders of each embodiment maintain good hydrophobicity, with the water contact angle remaining within a predetermined range.

[0178] Furthermore, it was found that by using the additive manufacturing powders of each embodiment, it is possible to produce additively manufactured bodies with high bending stress and high dimensional accuracy. In particular, with the additive manufacturing powders of each embodiment, the decrease in bending stress and dimensional accuracy was less even when the amount of binder used was reduced compared to the additive manufacturing powders of each comparative example.

[0179] Here, Figure 14 shows a graph comparing the bending stress of the additively manufactured body made using the powder of Example 1 and the bending stress of the additively manufactured body made using the powder of Comparative Example 1, based on the bending stress measurement results shown in Table 2.

[0180] As shown in Figure 14, the bending stress of the additively manufactured body made using the additive manufacturing powder of Example 1 was higher than that of the additively manufactured body made using the additive manufacturing powder of Comparative Example 1, even when the amount of binder used was reduced by 70%. Therefore, it can be said that with the additive manufacturing powders of each example, it is possible to reduce the amount of binder used while maintaining the bending stress of the additively manufactured body.

[0181] Furthermore, the additive manufacturing powders in each embodiment had a low moisture content. In addition, the (D90-D10) / D50 value, which represents the degree of particle size distribution spread, was kept low in the additive manufacturing powders in each embodiment. These characteristics are also presumed to contribute to the good mechanical strength and dimensional accuracy of the additively manufactured bodies.

[0182] Furthermore, the change in the bulk density of the powder was measured when the aforementioned heat treatment time was varied. The measurement results are shown in Figure 15. Figure 15 is a graph showing the relationship between the bulk density of the powder from Example 1 and Comparative Example 1 and the heat treatment time, with the heat treatment time (heating time) on the horizontal axis and bulk density on the vertical axis.

[0183] As shown in Figure 15, in the powder of Example 1, the decrease in bulk density was suppressed even with a long heat treatment time, and in fact, the bulk density increased. Therefore, it can be seen that the powder of Example 1 does not easily lose fluidity even when the powder is repeatedly reused after being placed in a high-temperature environment. On the other hand, in the powder of Comparative Example 1, the bulk density decreased in accordance with the heating time, indicating that the fluidity tends to decrease when placed in a high-temperature environment. Furthermore, the powders of the other examples and the other comparative examples showed similar trends to the powders of Example 1 and Comparative Example 1.

[0184] From this, it is recognized that the additive manufacturing powder of the present invention maintains good fluidity and packing properties even when placed in a high-temperature environment, making it suitable for reuse. [Explanation of symbols]

[0185] 1…Additive manufacturing powder, 2…Additive manufacturing apparatus, 4…Binder solution, 6…Additive manufactured body, 11…Metal particles, 12…Coating, 13…Surface coating particles, 21…Apparatus body, 22…Powder supply elevator, 23…Building stage, 24…Coater, 25…Rotor, 26…Liquid supply unit, 31…Powder layer, 41…Binding layer, 60…Formation area, 211…Powder storage unit, 212…Building unit, CA…Coupling agent, S102…Powder layer formation process, S104…Binder solution supply process, S106…Repeat process, S202…Preparation process, S204…Coupling agent reaction process, S206…Heating process

Claims

1. Metal powder and A coating is provided on the particle surface of the metal powder and contains a compound derived from a coupling agent having hydrophobic functional groups, Equipped with, The average particle size is 3.0 μm or more and 30.0 μm or less. After being subjected to a heat treatment in an atmospheric environment at 200°C for 24 hours, the water contact angle measured at 25°C using the θ / 2 method in a layered state was between 80° and 150°. The aforementioned hydrophobic functional group is characterized by being a cyclic structure-containing group, a fluoroalkyl group, or a fluoroaryl group.

2. The additive manufacturing powder according to claim 1, wherein when heated at 200°C for 24 hours in an atmospheric environment, the rate of decrease in bulk density is 2.5% or less compared to before heating.

3. The additive manufacturing powder according to claim 1 or 2, wherein the coating is a monomolecular film of the compound.

4. The additive manufacturing powder according to any one of claims 1 to 3, wherein the moisture content measured by the Karl Fischer method is 150 ppm or less by mass.

5. The additive manufacturing powder according to any one of claims 1 to 4, wherein when additive manufacturing is performed using a water-soluble resin as a binder, the bending stress of the resulting additively manufactured body is 15 N / cm² (0.15 MPa) or more.

6. A powder for additive manufacturing according to any one of claims 1 to 5, A binder that binds the particles of the additive manufacturing powder together, A laminated body characterized by having the following features.

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