Method for manufacturing additive manufacturing powders and metal sintered bodies

Abstract

To provide powder for laminate molding capable of, suppressing a use amount of a surface preparation agent, being excellent in filling properties when the powder is levelled into a layer state by a coater or the like, and enhancing mechanical strength in a laminate molded body which is laminate molded by a binder jet method and a temporarily sintered body thereof, and a production method of a metal sintered body which can efficiently produce a metal sintered body whose mechanical strength is great and which has great accuracy to a target shape.SOLUTION: There is provided powder for laminate molding which is used for a binder jet type laminate molding method, the powder comprising: metal powder; and a coat which is provided on a particle surface of the metal powder and includes a compound derived from a coupling agent comprising a reactive functional group. When an average particle diameter of the powder is R (μm), and (R / 10)2 / (R / 10)3 is A, carbon concentration of the coat is 0.02A mass% or more and 0.30A mass% or less.SELECTED DRAWING: Figure 12

Description

[Technical Field]

[0001] This invention relates to a method for manufacturing additive manufacturing powders and metal sintered bodies. [Background technology]

[0002] In recent years, additive manufacturing using metal powders has become increasingly popular as a technology for creating three-dimensional objects. Depending on the solidification principle, various methods for creating three-dimensional objects are known, including selective laser sintering (SLS), binder jetting, and fused deposition molding (FDM).

[0003] Among these methods, the binder jet method involves a step of leveling metal powder in layers using a squeegee or the like to form a powder layer, and a step of supplying a binder solution to a part of the powder layer and solidifying it. By repeating these steps, a three-dimensional object can be fabricated. Furthermore, by subjecting the resulting three-dimensional object to a sintering process, a metal sintered body with the shape of the object can be manufactured. This method allows for the efficient production of a metal sintered body with the desired three-dimensional shape without the use of molds or the like.

[0004] To improve the accuracy of three-dimensional object fabrication, it is important to increase the filling density of metal powder in the powder layer. By increasing the filling density, the mechanical strength of the fabricated object is enhanced, and the dimensional accuracy of the resulting metal sintered body is improved.

[0005] As a method for increasing the packing density of metal powder, for example, Patent Document 1 discloses a method of treating heavy metal powder with a silane-based surface treatment agent or a titanate-based surface treatment agent. In the invention described in Patent Document 1, a high-density weight for an automatic winding watch is achieved by curing such surface-treated heavy metal powder with a coating resin together with a lubricant. By increasing the packing density of the heavy metal powder, the amount of coating resin used can be reduced, thereby achieving a high-density weight and improving mechanical strength. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 60-244888 [Overview of the project] [Problems that the invention aims to solve]

[0007] The surface treatment agent described in Patent Document 1 is used in combination with a lubricant to improve the mechanical strength after molding. Therefore, even if metal powder treated with the surface treatment agent described in Patent Document 1 is used to form a powder layer in the binder jet method, it is not possible to sufficiently increase the filling density of the metal powder in the powder layer. Furthermore, while the mechanical strength of the three-dimensional object formed by the binder jet method is increased when a lubricant is used in combination, when the resulting three-dimensional object is subjected to a sintering process, the volume shrinkage rate increases, and the dimensional accuracy decreases.

[0008] Therefore, the challenge is to increase the packing density of metal powder in the powder layer used in the binder jet method, while reducing the amount of surface treatment agent used, and to increase the mechanical strength of the three-dimensional object. [Means for solving the problem]

[0009] The additive manufacturing powder according to the application example of the present invention is A powder for additive manufacturing used in binder jet additive manufacturing, Metal powder and The particles of the aforementioned metal powder are formed by a hydrolysis reaction, A phenyl group, vinyl group, epoxy group, or amino group A coating containing a compound derived from a coupling agent having a reactive functional group, Equipped with, Let the average particle size be R [μm]. (R / 10) 2 (R / 10) 3 Let A be the case where When the reactive functional group is the phenyl group, the carbon concentration of the coating is 0.07A by mass% or more and 0.30A by mass% or less. When the reactive functional group is the vinyl group, the carbon concentration of the coating is 0.02A by mass% or more and 0.10A by mass% or less. When the reactive functional group is the epoxy group, the carbon concentration of the coating is 0.07A by mass% or more and 0.30A by mass% or less. When the reactive functional group is the amino group, the carbon concentration of the coating is 0.07A by mass% or more and 0.14A by mass% or less. With respect to the true density of the metal powder, the bulk density is 41% or more and 48% or less, and the tap density is 55% or more and 65% or less, which is characteristic.

[0010] The method for manufacturing a metal sintered body according to an application example of the present invention includes a step of laying a powder for laminated molding according to an application example of the present invention to form a powder layer, a step of supplying a binder solution containing a binder to the powder layer to bind the particles of the powder for laminated molding with the binder to obtain a binding layer, a step of obtaining a laminated molded body by repeating the step of forming the powder layer and the step of obtaining the binding layer one or more times, and a step of subjecting the laminated molded body to a sintering treatment. It is characterized by having the above steps.

Brief Description of the Drawings

[0011] [Figure 1] It is a process diagram for explaining the method for manufacturing a metal sintered body according to an embodiment. [Figure 2] It is a diagram for explaining the method for manufacturing the metal sintered body shown in FIG. 1. [Figure 3] It is a diagram for explaining the method for manufacturing the metal sintered body shown in FIG. 1. [Figure 4] It is a diagram for explaining the method for manufacturing the metal sintered body shown in FIG. 1. [Figure 5] It is a diagram for explaining the method for manufacturing the metal sintered body shown in FIG. 1. [Figure 6] It is a diagram for explaining the method for manufacturing the metal sintered body shown in FIG. 1. [Figure 7] It is a diagram for explaining the method for manufacturing the metal sintered body shown in FIG. 1. [Figure 8] It is a diagram for explaining the method for manufacturing the metal sintered body shown in FIG. 1. [Figure 9]Figure 1 is a diagram illustrating the manufacturing method of the metal sintered body shown in the diagram. [Figure 10] Figure 1 is a diagram illustrating the manufacturing method of the metal sintered body shown in the diagram. [Figure 11] Figure 1 is a diagram illustrating the manufacturing method of the metal sintered body shown in the diagram. [Figure 12] This is a schematic cross-sectional view showing the additive manufacturing powder according to the embodiment. [Figure 13] This is a process diagram illustrating a method for manufacturing additive manufacturing powder according to an embodiment. [Figure 14] This graph shows the relationship between the carbon concentration of the coating and the bulk density of the additive manufacturing powder. [Figure 15] This graph shows the relationship between the carbon concentration of the coating and the tap density of the additive manufacturing powder. [Modes for carrying out the invention]

[0012] Hereinafter, preferred embodiments of the additive manufacturing powder and the method for manufacturing metal sintered bodies of the present invention will be described in detail with reference to the attached drawings.

[0013] 1. Method for manufacturing a metal sintered body First, a method for manufacturing a metal sintered body according to an embodiment will be described.

[0014] Figure 1 is a process diagram illustrating a method for manufacturing a metal sintered body according to an embodiment. Figures 2 to 11 are diagrams illustrating the method for manufacturing the metal sintered body shown in Figure 1. In the figures of this application, three mutually orthogonal axes are defined as the X-axis, Y-axis, and Z-axis. Each axis is represented by an arrow, with the tip side being the "positive side" and the base side being the "negative side". In the following description, the positive side of the Z-axis will be referred to as "up" and the negative side of the Z-axis as "down". Furthermore, both directions parallel to the X-axis will be referred to as the X-axis direction, both directions parallel to the Y-axis as the Y-axis direction, and both directions parallel to the Z-axis as the Z-axis direction.

[0015] The method for manufacturing a metal sintered body shown in Figures 1 to 11 includes a process for obtaining an additively manufactured body using a method called the binder jet method. The method for manufacturing a metal sintered body shown in Figure 1 comprises a powder layer formation step S102, a binder solution supply step S104, a repeating step S106, and a sintering step S108.

[0016] In the powder layer formation step S102, a powder layer 31 is formed by laying down the additive manufacturing powder 1 according to the embodiment described later. In the binder solution supply step S104, a binder solution 4 is supplied to a predetermined area of ​​the powder layer 31 to bind the particles in the powder layer 31 together and obtain a binding layer 41. In the repeating step S106, the powder layer formation step S102 and the binder solution supply step S104 are repeated one or more times to obtain the additive manufactured body 6 shown in Figure 10. In the sintering step S108, the additive manufactured body 6 is subjected to a sintering process to obtain a metal sintered body 10. Each step will be described in order below.

[0017] 1.1. Additive Manufacturing Equipment First, before explaining the powder layer formation process S102, we will describe the additive manufacturing apparatus 2.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] Furthermore, the additive manufacturing powder 1 that did not form the binding layer 41 from the powder layer 31 is recovered and reused as needed.

[0033] 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, the shrinkage rate in the sintering process S108 described later can be reduced, and unintended deformation of the resulting metal sintered body 10 can be suppressed.

[0034] 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.

[0035] 1.5. Sintering Process In the sintering process S108, the additively manufactured body 6 is subjected to a sintering treatment. In the sintering treatment, the additively manufactured body 6 is heated to induce a sintering reaction. This results in the metal sintered body 10 shown in Figure 11.

[0036] 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.

[0037] 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.

[0038] The metal sintered body 10 obtained as described above can be used as a material to constitute all or part of, for example, 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 terminal 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; and decorative items such as metal tableware, jewelry, and eyeglass frames.

[0039] 2. Powder for additive manufacturing Next, the additive manufacturing powder according to the embodiment will be described. Figure 12 is a schematic cross-sectional view showing the additive manufacturing powder according to the embodiment.

[0040] The additive manufacturing powder 1 according to this embodiment is a powder used in a binder jet additive manufacturing method.

[0041] As shown in Figure 12, the additive manufacturing powder 1 is an aggregate of surface-coated particles 13 comprising 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 a reactive functional group. The average particle size of the additive manufacturing powder 1 is R [μm], and (R / 10) 2 (R / 10) 3 When A is used, the carbon concentration of the coating 12 in the additive manufacturing powder 1 is between 0.02A mass% and 0.30A mass%.

[0042] In this additive manufacturing powder 1, the amount of coupling agent used relative to the metal particles 11 is optimized. This avoids insufficient or excessive use of the coupling agent, thereby increasing the packing density of the metal particles 11 in the powder layer 31. As a result, additively manufactured bodies 6 and their pre-sintered bodies produced by the binder jet method can be manufactured with high shape retention and high mechanical strength. In this specification, the aggregate of metal particles 11 is also referred to as "metal powder".

[0043] 2.1. Metal particles The constituent material of the metal particles 11 is not particularly limited and may be any metallic material that is sinterable. Examples include elemental elements such as Fe, Ni, Co, and Ti, or alloys and intermetallic compounds mainly composed of these elements.

[0044] 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.

[0045] Examples of Ni-based alloys include Ni-Cr-Fe alloys, Ni-Cr-Mo alloys, and Ni-Fe alloys.

[0046] Examples of Co-based alloys include Co-Cr alloys, Co-Cr-Mo alloys, and Co-Al-W alloys.

[0047] 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.

[0048] 2.2.Coating The coating 12 is formed by reacting a coupling agent having a reactive functional group with the surface of the metal particles 11. Therefore, the coating 12 contains compounds derived from the coupling agent having a reactive functional group and exhibits properties derived from that reactive functional group.

[0049] The coupling agent used to form the coating 12 is a compound having a hydrolyzable group and a reactive functional group. Examples of such coupling agents include silane coupling agents, titanium coupling agents, zirconium coupling agents, and aluminum coupling agents. The following chemical formula is an example of the molecular structure of a silane coupling agent.

[0050] [ka]

[0051] In the above formula, X is a reactive functional group, Y is a spacer, and OR is a hydrolyzable group. R can be, for example, a methyl group or an ethyl group.

[0052] The hydrolyzable group may be an alkoxy group as shown in the above formula, or a halogen group, but an alkoxy group is preferred. The hydrolyzable group produces a silanol upon hydrolysis. This silanol reacts with the hydroxyl group formed on the surface of the metal particle 11, and the coupling agent adheres to the surface of the metal particle 11.

[0053] 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 three, as shown in the formula above. A coupling agent containing multiple hydrolyzable groups reacts with multiple hydroxyl groups formed on the surface of the metal particles 11. As a result, the coating 12 derived from the coupling agent has particularly good adhesion to the metal particles 11. Therefore, the compound derived from the coupling agent contained in the coating 12 refers to the compound obtained when the hydrolyzable group reacts with the hydroxyl group. Furthermore, a coupling agent containing three hydrolyzable groups also has excellent film-forming properties, so a coating 12 with excellent continuity can be obtained. Such a coating 12 contributes particularly to improving the packing properties of the additive manufacturing powder 1.

[0054] A reactive functional group is a functional group that is highly reactive. This high reactivity contributes to increasing the affinity between the coating 12 and the binder. Therefore, the coating 12, by containing compounds derived from coupling agents with reactive functional groups, exhibits a high bonding strength with the binder. As a result, the mechanical strength of the additively manufactured body 6 and its pre-sintered body can be increased, and their shape retention can be improved.

[0055] Examples of reactive functional groups include phenyl groups, vinyl groups, epoxy groups, amino groups, methacrylic groups, and mercapto groups. Of these, the reactive functional group is preferably a phenyl group, vinyl group, epoxy group, or amino group. These groups exhibit a reaction that binds to resins that can act as binders. Therefore, by using a coupling agent having these reactive functional groups, it is possible to obtain a powder 1 for additive manufacturing with sufficiently high packing properties even when the amount used is reduced.

[0056] Examples of coupling agents containing a phenyl group include phenyltrimethoxysilane, phenyltriethoxysilane, dimethoxydiphenylsilane, diethoxydiphenylsilane, 2,2-dimethoxy-1-phenyl-1-aza-2-silacyclopentane, and N-phenyl-3-aminopropyltrimethoxysilane.

[0057] Examples of coupling agents containing a vinyl group include vinyltris(β-methoxyethoxy)silane, vinyltrimethoxysilane, and vinyltriethoxysilane.

[0058] Examples of coupling agents containing epoxy groups include 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, and 3-glycidoxypropylmethyldiethoxysilane.

[0059] Examples of coupling agents containing an amino group include 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropylmethyldimethoxysilane, 3-aminopropylmethyldiethoxysilane, 2-aminoethyl-3-aminopropyltrimethoxysilane, 2-aminoethyl-3-aminopropyltriethoxysilane, and 2-aminoethyl-3-aminopropylmethyldimethoxysilane.

[0060] Examples of coupling agents containing a methacrylic group include 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, and 3-methacryloxypropyltriethoxysilane.

[0061] Examples of coupling agents containing a mercapto group include γ-mercaptopropyltrimethoxysilane and γ-chloropropyltrimethoxysilane.

[0062] 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 necessary film thickness to maintain the coating 12 and obtain the above-mentioned effects.

[0063] The average thickness of the coating 12 is the average of the film thickness measured at 10 or more locations by observing the cross-section of a single particle of additive manufacturing powder 1 with an electron microscope.

[0064] Furthermore, the coating 12 may be a multilayer film consisting of multiple layers, but it is preferable that it be a monolayer film of the aforementioned compound. With a monolayer coating 12, its thickness can be minimized, and because the aforementioned compound is densely present in the coating 12, the above-mentioned effects can be sufficiently obtained even if the average thickness of the coating 12 is thin. As a result, an additively fabricated body can be obtained with particularly high formation accuracy and a particularly high filling rate of metal particles 11.

[0065] Furthermore, a monolayer is a film formed by the self-assembly of a coupling agent. In a monolayer, molecules of the coupling agent that have affinity for the surface of the metal particles 11 are densely arranged, forming a film with a thickness of one molecule with high continuity. For this reason, good effects can be obtained even if the coating 12 is thin.

[0066] 2.3. Carbon Concentration As mentioned above, the carbon concentration of the coating 12 is optimized based on the average particle size R of the additive manufacturing powder 1. Specifically, (R / 10) 2 (R / 10) 3 When A is used, the carbon concentration of the coating 12 is between 0.02A mass% and 0.30A mass%. The inventors have conducted thorough research and found that the carbon concentration of the coating 12 is closely related to the concentration of reactive functional groups in the coating 12. Furthermore, it has been found that the carbon concentration of the coating 12 can be a parameter that represents the excess or deficiency of the effect of the coating 12. Therefore, in this embodiment, by optimizing the carbon concentration of the coating 12, a additive manufacturing powder 1 is realized that can avoid deficiency or excessive use of the coupling agent.

[0067] If the carbon concentration of the coating 12 is within the aforementioned range, the amount of coupling agent used will be set appropriately regardless of the type of coupling agent or the average particle size R, thereby increasing the packing density of the metal particles 11 in the powder layer 31. As a result, the occurrence of voids in the additively manufactured body 6 produced by the binder jet method can be suppressed, and the mechanical strength of the additively manufactured body 6 and its pre-sintered body can be increased.

[0068] Furthermore, the carbon concentration of the coating 12 can be further optimized depending on the type of reactive functional group present in the coupling agent.

[0069] When the reactive functional group is a phenyl group, the carbon concentration is preferably 0.07A mass% or more and 0.30A mass% or less, more preferably 0.09A mass% or more and 0.20A mass% or less, and even more preferably 0.10A mass% or more and 0.16A mass% or less. This allows for the optimization of the carbon concentration of the coating 12, taking into account the affinity between the phenyl group and the binder. As a result, the packing of metal particles 11 can be particularly improved in the powder layer 31 formed using the additive manufacturing powder 1 in which the reactive functional group is a phenyl group.

[0070] Furthermore, if the reactive functional group is a phenyl group and the carbon concentration is 0.07 A by mass or more and 0.30 A by mass or less, the binder contained in binder solution 4 preferably includes a vinyl resin, an unsaturated polyester resin, or a phenolic resin.

[0071] Coupling agents containing phenyl groups exhibit high bonding affinity to binders containing the resins described above. Examples of bonding reactions include π-CH reactions with vinyl resins and unsaturated polyester resins, and π-π reactions with phenolic resins. Through these reactions, the coating 12 and the binder can be bonded via compounds derived from the coupling agent. A π-CH reaction refers to a reaction (CH / π interaction) that generates an attractive force between a π-electron system, such as a benzene ring, and a CH bond (a bond between a carbon atom and a hydrogen atom). A π-π reaction refers to a reaction (π / π interaction) that generates an attractive force between two π-electron systems, such as benzene rings.

[0072] When the reactive functional group is a vinyl group, the carbon concentration is preferably 0.02A mass% or more and 0.10A mass% or less, and more preferably 0.04A mass% or more and 0.08A mass% or less. This allows for the optimization of the carbon concentration of the coating 12, taking into account the affinity between the vinyl group and the binder. As a result, the packing of metal particles 11 can be particularly improved in the powder layer 31 formed using the additive manufacturing powder 1 in which the reactive functional group is a vinyl group.

[0073] Furthermore, if the reactive functional group is a vinyl group and the carbon concentration is 0.02 A mass% or more and 0.10 A mass% or less, it is preferable that the binder contained in binder solution 4 contains a vinyl resin or an unsaturated polyester resin.

[0074] Coupling agents containing vinyl groups exhibit high bonding affinity to binders containing resins as described above. An example of a bonding reaction is a graft reaction with respect to the resin. Through this reaction, compounds derived from the coupling agent are grafted as side chains of the binder, thereby bonding the coating 12 to the binder.

[0075] Examples of vinyl resins include polyvinyl alcohol, polyvinyl acetate, polyvinyl butyral, polyvinyl acetal, and polyvinylpyrrolidone, and one or more of these can be used as a mixture.

[0076] Examples of unsaturated polyester resins include polymers of unsaturated polyesters obtained by reacting an acid component containing an α,β-unsaturated dicarboxylic acid with an alcohol. Examples of α,β-unsaturated dicarboxylic acids include maleic acid, fumaric acid, itaconic acid, citraconic acid, aconitic acid, tetrahydrophthalic acid, dihydromuconic acid, or derivatives thereof such as acid anhydrides, and one or a mixture of two or more of these can be used.

[0077] When the reactive functional group is an epoxy group, the carbon concentration is preferably 0.07A mass% or more and 0.30A mass% or less, more preferably 0.09A mass% or more and 0.20A mass% or less, and even more preferably 0.10A mass% or more and 0.16A mass% or less. This allows for the optimization of the carbon concentration of the coating 12, taking into account the affinity between the epoxy group and the binder. As a result, the packing of metal particles 11 can be particularly improved in the powder layer 31 formed using the additive manufacturing powder 1 in which the reactive functional group is an epoxy group.

[0078] Furthermore, if the reactive functional group is an epoxy group and the carbon concentration is 0.07A by mass% or more and 0.30A by mass% or less, the binder contained in binder solution 4 preferably includes a urethane resin, an epoxy resin, an unsaturated polyester resin, or a phenolic resin.

[0079] Coupling agents containing epoxy groups exhibit high bonding affinity to binders containing resins as described above. An example of a bonding reaction is the epoxy ring-opening reaction with respect to the resin. Through this reaction, the coating 12 and the binder can be bonded via compounds derived from the coupling agent.

[0080] The urethane resin is a polymer having urethane bonds and is not particularly limited as long as it is produced by a condensation reaction between a compound having an isocyanate group and a compound having a hydroxyl group. Examples of urethane resins include thermoplastic polyurethane resins (polyurethane thermoplastic elastomers) and thermosetting polyurethane resins.

[0081] The epoxy resin is not particularly limited as long as it is a compound having two or more epoxy groups in one molecule, but examples include bisphenol A type epoxy resin, bisphenol F type epoxy resin, alicyclic epoxy resin, etc., and one or a mixture of two or more of these can be used.

[0082] Examples of phenolic resins include novolac-type phenolic resins and resol-type phenolic resins. Modified phenolic resins such as alkylphenol-modified phenolic resins, polyvinyl butyral-modified phenolic resins, and rubber-modified phenolic resins may also be used.

[0083] When the reactive functional group is an amino group, the carbon concentration is preferably 0.03A mass% or more and 0.14A mass% or less, more preferably 0.05A mass% or more and 0.12A mass% or less, and even more preferably 0.06A mass% or more and 0.11A mass% or less. This allows for the optimization of the carbon concentration of the coating 12, taking into account the affinity between the amino group and the binder. As a result, the packing of metal particles 11 can be particularly improved in the powder layer 31 formed using the additive manufacturing powder 1 in which the reactive functional group is an amino group.

[0084] Furthermore, if the reactive functional group is an amino group and the carbon concentration is 0.03A by mass% or more and 0.14A by mass% or less, the binder contained in binder solution 4 preferably contains a urethane resin, an epoxy resin, or a phenolic resin.

[0085] Coupling agents containing amino groups exhibit high bonding affinity to binders containing resins as described above. Examples of bonding reactions include ureidation reactions with urethane resins, epoxy ring-opening reactions with epoxy resins, and hydrogen bonding with phenolic resins. Through these reactions, the coating 12 and the binder can be bonded via compounds derived from the coupling agent.

[0086] The carbon concentration of coating 12 can be determined as follows: First, the carbon concentration of the additive manufacturing powder 1 is measured using a method compliant with the oxygen-stream combustion (high-frequency induction heating furnace combustion) - infrared absorption method specified in JIS G 1211:2011. In this method, the additive manufacturing powder 1 is heated in an oxygen stream, and the generated CO2 or CO is detected and the CO2 concentration or CO concentration is measured. Next, the carbon concentration is calculated from the obtained CO2 concentration and CO concentration. Then, the carbon concentration of the metal particles 11 is subtracted from the calculation result. The carbon concentration after subtraction is taken as the carbon concentration of the coating 12. The carbon concentration of the metal particles 11 is a measured value obtained by applying ozone treatment or oxygen plasma treatment to the additive manufacturing powder 1 to remove the coating 12, and then measuring the treated particles in the same manner as above. Whether or not the coating 12 has been removed is determined by performing elemental analysis of the treated particles by X-ray photoelectron spectroscopy to see if the amount of carbon on the particle surface is approximately zero (0.01 mass% or less). An example of a measuring device that conforms to the above JIS standard is the LECO CS-200 carbon-sulfur analyzer.

[0087] 2.4. Powder properties The average particle size R [μm] of the additive manufacturing powder 1 is preferably 3.0 μm or more and 30.0 μm or less, more preferably 4.0 μm or more and 15.0 μm or less, and even more preferably 5.0 μm or more and 10.0 μm or less.

[0088] By setting the average particle size of the additive manufacturing powder 1 within the aforementioned range, the packing efficiency of the powder layer 31 can be particularly improved. This results in an additively manufactured body 6 or a pre-sintered body thereof with high shape accuracy and a high packing rate of metal particles 11. As a result, a metal sintered body 10 with high accuracy to the target shape and particularly high mechanical strength can be obtained. Furthermore, a metal sintered body 10 with low surface roughness and excellent surface smoothness can be obtained.

[0089] The average particle size R of the additive manufacturing powder 1 is the particle size at which the cumulative particle size distribution from the smallest diameter reaches 50%, as obtained by a laser diffraction particle size distribution analyzer.

[0090] Furthermore, in the additive manufacturing powder 1 according to this embodiment, it is preferable that the bulk density is 41% to 48% of the true density of the metal powder, and the tap density is 55% to 65%. Such additive manufacturing powder 1 exhibits particularly high packing performance when the powder layer 31 is formed. The bulk density is thought to mainly contribute to the packing performance of the additive manufacturing powder 1 before it is subjected to the powder layer formation process S102 described above. The tap density is thought to mainly contribute to the packing performance when it is leveled by the coater 24 in the powder layer formation process S102. By optimizing both of these, it is possible to obtain a powder layer 31 with particularly high packing performance, and to manufacture additively manufactured bodies 6 and their pre-sintered bodies with high formation accuracy and mechanical strength.

[0091] Furthermore, the ratio of the bulk density of the additive manufacturing powder 1 to the true density of the metal powder is preferably 41% to 48%, as described above, more preferably 42% to 47%, and even more preferably 43% to 46%.

[0092] Furthermore, the ratio of the tap density of the additive manufacturing powder 1 to the true density of the metal powder is preferably 55% to 65%, as described above, more preferably 57% to 64%, and even more preferably 58% to 63%.

[0093] While the ratio of bulk density and the ratio of tap density may exceed the aforementioned upper limits, it is preferable to keep them below these limits, as they may become overly sensitive to the effects of temperature and humidity.

[0094] The true density of the metal powder is the true density of the constituent material of the metal particles 11. The bulk density of the additive manufacturing powder 1 is measured according to the apparent density measurement method for metal powder specified in JIS Z 2504:2012. The tap density of the additive manufacturing powder 1 is measured using a powder property evaluation device, Powder Tester® PT-X, manufactured by Hosokawa Micron Corporation.

[0095] 2.5. Effects of the Embodiment As described above, the additive manufacturing powder 1 according to the embodiment is a powder used in a binder jet additive manufacturing method, and comprises a metal powder and a coating 12 provided on the particle surface of the metal powder (the surface of the metal particles 11) and containing a compound derived from a coupling agent having a reactive functional group. The average particle size of the additive manufacturing powder 1 is R [μm], and (R / 10) 2 (R / 10) 3 When A is used, as mentioned above, the carbon concentration of the coating 12 is between 0.02A mass% and 0.30A mass%.

[0096] In the additive manufacturing powder 1 having this configuration, the amount of coupling agent used relative to the metal particles 11 is optimized. This avoids insufficient or excessive use of the coupling agent, thereby increasing the packing density of the metal particles 11 in the powder layer 31. As a result, the mechanical strength of the additively manufactured body 6 produced by the binder jet method can be increased. In other words, it is possible to manufacture an additively manufactured body 6 that has high shape retention and is resistant to deformation and cracking. Furthermore, the pre-sintered body obtained by pre-sintering such an additively manufactured body 6 also has high mechanical strength and shape retention. As a result, the metal sintered body obtained by final sintering has high accuracy in relation to the desired shape and high mechanical strength.

[0097] Also, when the laminated compact 6 is calcined at 200°C for 30 minutes in an air atmosphere, the flexural strength of the obtained calcined compact is preferably 0.4 MPa (40 N / cm 2 ), and more preferably 0.5 MPa (50 N / cm 2 ).

[0098] If the flexural strength of the calcined compact is within the above range, the shape retention of the calcined compact can be sufficiently enhanced. That is, a calcined compact with few occurrences of deformation, cracking, etc. can be obtained. By sintering such a calcined compact, a metal sintered compact 10 with high accuracy with respect to the target shape and high mechanical strength can be obtained.

[0099] Moreover, the method for manufacturing a metal sintered compact according to the embodiment includes a powder layer forming step S102, a binder solution supplying step S104, a repeating step S106, and a sintering step S108.

[0100] In the powder layer forming step S102, a powder layer 31 is formed by laying the powder 1 for laminated shaping. In the binder solution supplying step S104, a binder solution 4 containing a binder is supplied to the powder layer 31 to bind the particles of the powder 1 for laminated shaping with the binder, thereby obtaining a binding layer 41. In the repeating step S106, the powder layer forming step S102 and the binder solution supplying step S104 are repeated one or more times to obtain a laminated compact 6. In the sintering step S108, the laminated compact 6 is sintered to obtain a metal sintered compact 10.

[0101] As described above, the powder 1 for laminated shaping is a powder that is excellent in filling property when leveled in layers by a coater or the like while suppressing the amount of the coupling agent as a surface treatment agent used. For this reason, a laminated compact formed by laminated shaping by the binder jet method is excellent in shape retention and has density. Therefore, when such a laminated compact is calcined, a calcined compact having good mechanical strength and shape retention can be obtained. For this reason, according to the method for manufacturing a metal sintered compact according to the present embodiment, a metal sintered compact 10 with high accuracy with respect to the target shape and high mechanical strength can be efficiently manufactured.

[0102] 3. Method for manufacturing powder for additive manufacturing Next, a method for producing additive manufacturing powder according to an embodiment will be described.

[0103] Figure 13 is a process diagram illustrating a method for manufacturing additive manufacturing powder according to an embodiment. The method for producing additive manufacturing powder shown in Figure 13 comprises a preparation step S202, a coupling agent reaction step S204, and a film formation step S206.

[0104] 3.1. Preparation process In preparation step S202, metal particles 11 are prepared. The metal particles 11 may be manufactured by any method, but it is preferable that they be powders manufactured by atomization methods such as water atomization, gas atomization, or rotary water atomization, and it is preferable that they be powders manufactured by water atomization or rotary water atomization. In metal particles 11 manufactured by these methods, the surface is easily covered with hydroxyl groups derived from water. Therefore, the adhesion of the coating 12 to the metal particles 11 can be increased, and even if the coating 12 is thin, the packing of surface coating particles 13 can be sufficiently increased. As a result, it is possible to realize additively fabricated bodies 6 and pre-sintered bodies with a higher occupancy rate of metal particles 11 compared to the coating 12 and a smaller shrinkage rate during sintering.

[0105] Furthermore, the metal powder may be subjected to known pretreatments that generate hydroxyl groups on the surface of the metal particles 11, if necessary. Examples of pretreatments include ozone treatment, oxygen plasma treatment, corona treatment, arc treatment, and ultraviolet irradiation treatment.

[0106] 3.2. Coupling agent reaction process In the coupling agent reaction step S204, a coupling agent having a reactive functional group is reacted with the metal powder. This causes the coupling agent to adhere to the surface of the metal particles 11.

[0107] Examples of such operations include: placing both metal particles 11 and a coupling agent into a chamber and then heating the chamber; placing metal particles 11 into a chamber and then spraying the coupling agent into the chamber while stirring the metal particles 11; and 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.

[0108] The amount of coupling agent added is not particularly limited, but is preferably 0.01% to 1.00% by mass relative to the metal particles 11, and more preferably 0.05% to 0.50% by mass. The coupling agent is supplied into the chamber by methods such as standing or spraying.

[0109] 3.3. Film formation process In the coating formation 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.

[0110] The heating temperature for 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.

[0111] Although the additive manufacturing powder and the method for manufacturing a metal sintered body of the present invention have been described above based on the illustrated embodiments, the present invention is not limited thereto. For example, the additive manufacturing powder of the present invention may have any components added to the above embodiments. Furthermore, the method for manufacturing a metal sintered body of the present invention may have any purpose-specific steps added to the above embodiments. [Examples]

[0112] Next, specific embodiments of the present invention will be described. 4. Manufacturing of powder for additive manufacturing 4.1. Sample No. 1 First, a powder (metal powder) of precipitation-hardening stainless steel 17-4PH, manufactured by the water atomization method, was prepared. This resulting metal powder was then used as the additive manufacturing powder for Sample No. 1.

[0113] 4.2. Sample No. 2 First, powder (metal 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. Afterward, the metal powder coated with the solution was dried. This resulted in obtaining a powder for additive manufacturing, with a coating formed on the particle surface of the metal powder. The amount of coupling agent used was equivalent to 0.1% by mass of the metal powder. The true density of the metal powder was 7.78 g / cm³. 3 That was the case.

[0114] Table 1 shows the reactive and hydrolyzable functional groups of the coupling agent. Furthermore, the carbon concentration in the coating is shown in both the form of a multiple of the value of A and the form of a numerical value calculated from the value of A.

[0115] 4.3. Samples No. 3-15 The additive manufacturing powder was obtained in the same manner as for Sample No. 2, except that the manufacturing conditions for the additive manufacturing powder were changed as shown in Table 1. The symbols in the "Substance Name" column in Table 1 correspond to the following substance names.

[0116] a-1: Phenyltrimethoxysilane a-2: Phenyltriethoxysilane a-3: Dimethoxydiphenylsilane x-1: Methyltrimethoxysilane

[0117] 4.4. Samples No. 16-24 The additive manufacturing powder was obtained in the same manner as for Sample No. 2, except that the manufacturing conditions for the additive manufacturing powder were changed as shown in Table 2. The symbols in the "Substance Name" column in Table 2 correspond to the following substance names.

[0118] b-1: Vinyltrimethoxysilane b-2: Vinyltriethoxysilane x-1: Methyltrimethoxysilane

[0119] 4.5. Samples No. 25-36 The additive manufacturing powder was obtained in the same manner as for Sample No. 2, except that the manufacturing conditions for the additive manufacturing powder were changed as shown in Table 3. The symbols in the "Substance Name" column in Table 3 correspond to the following substance names.

[0120] c-1:3-Glycidoxypropyltrimethoxysilane c-2:3-Glycidoxypropyltriethoxysilane x-1: Methyltrimethoxysilane

[0121] 4.6. Sample No. 37-45 The additive manufacturing powder was obtained in the same manner as for Sample No. 2, except that the manufacturing conditions for the additive manufacturing powder were changed as shown in Table 4. The symbols in the "Substance Name" column of Table 4 correspond to the following substance names.

[0122] d-1:3-aminopropyltrimethoxysilane d-2:3-aminopropyltriethoxysilane x-1: Methyltrimethoxysilane

[0123] In Tables 1 to 4, additive manufacturing powders corresponding to the present invention are labeled "Examples," while additive manufacturing powders not corresponding to the present invention are labeled "Comparative Examples."

[0124] 5. Evaluation of additive manufacturing powders and pre-sintered bodies 5.1. Bulk density of powder for additive manufacturing For each sample No. of additive manufacturing powder, the bulk density was measured according to the apparent density measurement method for metal powders specified in JIS Z 2504:2012. The ratio of the measured bulk density to the true density of the metal powder was then calculated. The measurement and calculation results are shown in Tables 1 to 4.

[0125] 5.2. Tap density of additive manufacturing powder For each sample No. of additive manufacturing powder, the tap density was measured using a powder property evaluation device, Powder Tester® PT-X, manufactured by Hosokawa Micron Corporation. The number of taps was 125. The ratio of the measured tap density to the true density of the metal powder was then calculated. The measurement results and calculation results are shown in Tables 1 to 4.

[0126] 5.3. Preparation and evaluation of pre-sintered bodies 5.3.1. Preparation of a temporary sintered body Using the additive manufacturing powders of each sample number, additively manufactured rectangular parallelepiped bodies were fabricated using the binder jet method. The dimensions of the fabricated additively manufactured bodies were 33 mm in length, 12 mm in width, and 6.6 mm in thickness. The binder solution used contained the binders shown in Tables 1 to 4.

[0127] Next, the fabricated additively manufactured body was pre-sintered. The pre-sintering temperature was 200°C, the pre-sintering time was 30 minutes, and the atmosphere was air.

[0128] 5.3.2. Evaluation of the sintered body Next, the bending load was measured on the fabricated pre-sintered body using a three-point bending test fixture. Then, the bending stress σ of the pre-sintered body was calculated using the following formula.

[0129]

number

[0130] Next, the bending stress calculated for the pre-sintered body of sample No. 1 was set to 1, and the relative bending stress for each sample No. 1 pre-sintered body was calculated. Then, the calculated relative values ​​were evaluated against the following evaluation criteria.

[0131] A: The relative value of the bending stress is greater than 1.20. B: The relative value of the bending stress is greater than 1.15 and less than or equal to 1.20. C: The relative value of the bending stress is greater than 1.10 and less than or equal to 1.15. D: The relative value of the bending stress is greater than 1.05 and less than or equal to 1.10. E: The relative value of the bending stress is greater than 1.00 and less than or equal to 1.05. F: The relative value of the bending stress is 1.00 or less. The evaluation results are shown in Tables 1 to 4.

[0132] 5.3. Evaluation Results Tables 1 through 4 show the evaluation results for additive manufacturing powders and pre-sintered bodies.

[0133] [Table 1]

[0134] [Table 2]

[0135] [Table 3]

[0136] [Table 4]

[0137] As shown in Tables 1 to 4, the additive manufacturing powders corresponding to the examples were found to have sufficiently high ratios of bulk density to true density and tap density to true density. This confirms that the additive manufacturing powders corresponding to the examples exhibit good packing properties when leveled by a coater or the like, contributing to the formation of a dense powder layer.

[0138] Furthermore, as shown in Tables 1 to 4, by using additive manufacturing powders corresponding to the examples, it was possible to increase the strength of the pre-sintered bodies of additively manufactured objects produced by the binder jet method. In addition, no deformation or cracking was observed in these pre-sintered bodies.

[0139] Next, the obtained pre-sintered body was sintered in a sintering furnace. The sintering conditions were 1300°C for 3 hours in an argon atmosphere. This yielded a metal sintered body. The metal sintered body produced using the additive manufacturing powder corresponding to the example exhibited high dimensional accuracy with respect to the desired shape and high mechanical strength. These results confirm that the present invention achieves the aforementioned effects.

[0140] The calculated bending stress is the stress at fracture and therefore corresponds to the bending strength of the pre-sintered body. All pre-sintered bodies manufactured using additive manufacturing powders corresponding to the examples had a bending strength of 0.4 MPa or higher. In particular, pre-sintered bodies that received an evaluation result of B or higher according to the above evaluation criteria had a bending strength of 0.6 MPa or higher.

[0141] Furthermore, when the mechanical strength of the additively manufactured bodies before pre-sintering was evaluated, the additively manufactured bodies produced using the additive manufacturing powder corresponding to the example showed a similar trend to the evaluation results of the pre-sintered bodies described above. From these results, it is considered that the packing properties of the metal powder in the additively manufactured bodies contribute to the mechanical strength and shape retention of the pre-sintered bodies.

[0142] Figure 14 is a graph showing the relationship between the carbon concentration of the coating and the bulk density of the additive manufacturing powder. Figure 15 is a graph showing the relationship between the carbon concentration of the coating and the tap density of the additive manufacturing powder. The data used in Figures 14 and 15 are from samples No. 1 to 10.

[0143] As shown in Figures 14 and 15, it was found that the bulk density and tap density could be increased by optimizing the carbon concentration of the coating. Furthermore, it was confirmed that the strength of the pre-sintered body could be increased by using additive manufacturing powder with high bulk density and tap density. [Explanation of symbols]

[0144] 1…Additive manufacturing powder, 2…Additive manufacturing apparatus, 4…Binder solution, 6…Additive manufactured body, 10…Metal sintered body, 11…Metal particles, 12…Coating, 13…Surface coating particles, 21…Apparatus body, 22…Powder supply elevator, 23…Building stage, 24…Coater, 25…Roller, 26…Liquid supply unit, 31…Powder layer, 41…Binding layer, 60…Formation area, 211…Powder storage unit, 212…Building unit, S102…Powder layer formation process, S104…Binder solution supply process, S106…Repeat process, S108…Sintering process, S202…Preparation process, S204…Coupling agent reaction process, S206…Coating form process

Claims

1. A powder for additive manufacturing used in binder jet additive manufacturing, Metal powder and A coating comprising a compound derived from a coupling agent having a reactive functional group of one of the following: a phenyl group, a vinyl group, an epoxy group, or an amino group, which is formed on the particle surface of the metal powder by a hydrolysis reaction, Equipped with, Let the average particle size be R [μm]. (R / 10) 2 / (R / 10) 3 Let A be the case, When the reactive functional group is the phenyl group, the carbon concentration of the coating is 0.07 A mass% or more and 0.30 A mass% or less. When the reactive functional group is the vinyl group, the carbon concentration of the coating is 0.02 A mass% or more and 0.10 A mass% or less. When the reactive functional group is the epoxy group, the carbon concentration of the coating is 0.07 A mass% or more and 0.30 A mass% or less. When the reactive functional group is the amino group, the carbon concentration of the coating is 0.07 A mass% or more and 0.14 A mass% or less. With respect to the true density of the aforementioned metal powder, The bulk density is between 41% and 48%. The tap density is between 55% and 65%. A powder for additive manufacturing characterized by the following features.

2. A step of laying the additive manufacturing powder described in Claim 1 to form a powder layer, A step of supplying a binder solution containing a binder to the powder layer, binding the particles of the additive manufacturing powder together with the binder, and obtaining a binding layer. A step of obtaining an additively fabricated body by repeating the step of forming the powder layer and the step of obtaining the binding layer one or more times, The process involves subjecting the aforementioned additively manufactured body to a sintering process to obtain a metal sintered body, A method for manufacturing a metal sintered body, characterized by having the following features.

3. When the aforementioned additively fabricated body is pre-sintered in an air atmosphere at a temperature of 200°C for 30 minutes, the bending strength of the resulting pre-sintered body is 0.4 MPa (40 N / cm²). 2 The method for manufacturing a metal sintered body according to claim 2, wherein the method is as described above.

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