Powder material for layering molding and method for manufacturing molded article using the powder material

Abstract

The powder material for layered shaping disclosed herein comprises tungsten carbide (WC), cobalt (Co), and carbon additives containing carbon (C) as the main constituent element, and is a powder material with a carbon content A (mass%) value of 6.4 ≤ A ≤ 7.2, wherein the carbon content A is expressed by the following formula: (mass of C derived from WC + mass of C derived from carbon additives) / (mass of WC) × 100.

Description

Technical Field

[0001] This invention relates to powder materials for layered molding. Furthermore, this invention relates to a method for manufacturing molded objects, characterized by using the powder material for layered molding. This application claims priority to Japanese Patent Application No. 2021-059464, filed March 31, 2021, the entire contents of which are incorporated herein by reference. Background Technology

[0002] The so-called three-dimensional modeling technology, which uses three-dimensional shape data (such as three-dimensional CAD data) to create the object to be manufactured, is becoming increasingly popular. One example of this modeling technology is the layering modeling method, which involves laying thin layers of powder material, bonding or sintering them into a shape corresponding to the cross-section of the object to be modeled, and then sequentially stacking these thin layers as a single unit.

[0003] In the past, resin materials have often been used as shaping materials for powders used in this layered shaping process. However, in recent years, powder materials for layered shaping made of metals and ceramics that can be used for layered shaping in processes such as powder bed fusion bonding (PBF) and laser powder surfacing (LMD) have been developed (see Patent Documents 1-4).

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: International Publication No. 2015 / 194678

[0007] Patent Document 2: Japanese Patent Application Publication No. 2017-113952

[0008] Patent Document 3: Japanese Patent Application Publication No. 2017-114716

[0009] Patent Document 4: Japanese Patent Application Publication No. 2017-115194 Summary of the Invention

[0010] One of the research goals for developing powder materials for laminated molding, composed of inorganic materials such as metals and ceramics, is to develop powder materials that can produce molded objects without cracks or notches and with high mechanical strength. As materials that meet this goal, research has been ongoing on powder materials with tungsten carbide (WC) and cobalt (Co) as the main components. Tungsten carbide and cobalt are raw materials for cemented carbide (WC-Co alloy), making them suitable as materials for manufacturing high-hardness molded objects through laminated molding.

[0011] However, for the powder materials developed so far that are mainly composed of tungsten carbide and cobalt, there is still room for improvement in order to further enhance the mechanical strength of the laminated structures.

[0012] In view of the above, the object of the present invention is to provide a tungsten carbide and cobalt-based powder material for layered molding (hereinafter also referred to as "WC / Co-containing powder material") that can form layered molded objects with superior mechanical strength. Another object of the present invention is to provide a method for manufacturing molded objects, characterized by using this powder material for layered molding.

[0013] To achieve the above objectives, the inventors conducted a detailed study on the alloy microstructure of laminated structures composed primarily of powder materials with tungsten carbide and cobalt as the main components. The results showed that the higher the proportion of the η phase present in the structure, the lower the mechanical strength. However, by intentionally increasing the carbon (C) content in the WC / Co-containing powder material used for laminated structures, the formation of the η phase, which is a brittle phase, can be suppressed, thereby improving the mechanical strength of the structure, thus completing this invention.

[0014] The layered molding powder material disclosed herein is a layered molding powder material containing tungsten carbide (WC), cobalt (Co), and carbon additives containing carbon (C) as the main constituent element.

[0015] Furthermore, it refers to WC / Co-containing powder materials where, when the carbon content A (mass%) is set to the value shown in the following formula, the carbon content A (mass%) meets the condition of 6.4 ≤ A ≤ 7.2:

[0016] (mass of C derived from WC + mass of C derived from carbon additives) / (mass of WC) × 100.

[0017] Based on the technical knowledge obtained by the inventors, in powder lamination forming processes such as powder bed fusion bonding (PBF) and laser powder deposition modeling (LMD) using WC / Co powder materials, the carbon content is lower than theoretically expected due to the laser and electron beam irradiation energy during the forming process. This can easily lead to the formation of an η-phase, which acts as a brittle layer, within the microstructure of the formed material. Furthermore, by pre-adding a material containing a predetermined amount of carbon (carbon additive) to the WC / Co powder material, the inventors prevented a decrease in the carbon content during powder lamination forming. As a result, the formation of the η-phase, which acts as a brittle layer, within the microstructure of the formed material was suppressed, and the decrease in mechanical strength caused by the presence of the η-phase in the formed material composed of WC / Co powder materials was also suppressed.

[0018] Therefore, the WC / Co powder material for laminated molding disclosed herein can prevent the decrease of carbon content during laminated molding and suppress the formation of the η phase in the microstructure of the molded material, thereby preventing a decrease in the mechanical strength of the molded material.

[0019] Therefore, according to the technology disclosed herein, it is possible to manufacture laminated shapes with excellent mechanical properties made of cemented carbide with WC-Co as a constituent element.

[0020] A preferred embodiment of the powder material disclosed herein is that the carbon content A has the condition 6.6 ≤ A ≤ 6.9.

[0021] The layered molding powder material based on this structure can better suppress the formation of the η phase and maintain better mechanical properties of the molded object.

[0022] In another preferred embodiment of the powder material disclosed herein, the aforementioned carbon additive material comprises at least one solid carbon material selected from the group consisting of graphite, carbon black, activated carbon, carbon fiber, and nano-carbon.

[0023] According to the layered powder material of this structure, since the carbon additive is composed of solid carbon, it is possible to effectively supplement the carbon composition.

[0024] In another preferred embodiment of the powder material disclosed herein, the aforementioned carbon additive material comprises a carbide of at least one metal selected from the group consisting of titanium (Ti), vanadium (V), chromium (Cr), niobium (Nb) and molybdenum (Mo).

[0025] The layered molding powder material based on this structure contains any of the aforementioned metal carbides as a carbon additive, thus enabling the manufacture of molded objects made of alloy materials with excellent mechanical strength due to the presence of dissimilar metal elements other than WC and Co, in addition to supplementing the carbon content.

[0026] In another preferred embodiment of the powder material disclosed herein, the powder material is composed of granulated sintered particles formed by mixing the aforementioned tungsten carbide, cobalt, and carbon additives.

[0027] Powder materials composed of granulated sintered particles formed by mixing the above three components, such as the above-mentioned tungsten carbide particles (which can be called primary particles, the same below), the above-mentioned cobalt particles, and the above-mentioned carbon additive particles formed by mixing granulated sintered particles (which can be called secondary particles, the same below), can effectively supplement the carbon components and more effectively suppress the formation of the η phase.

[0028] The average particle size of the granulated sintered particles is preferably 10 μm or more and 30 μm or less. Here, the particles constituting the granulated sintered particles (primary particles) include particles composed of the tungsten carbide with an average particle size of less than 1 μm, particles composed of cobalt with an average particle size of 2 μm or more and 10 μm or less, and particles constituting the carbon additive material with an average particle size of 1 μm or more and 5 μm or less.

[0029] Granulated and sintered particles with such specified particle size can more effectively suppress the formation of the η phase.

[0030] Furthermore, this disclosure provides a method for manufacturing a shaped object, characterized by using any of the powder materials disclosed herein for lamination shaping. As described above, according to the technology disclosed herein, it is possible to manufacture laminations with excellent mechanical properties made of hard alloys with WC-Co as a constituent element. Attached Figure Description

[0031] Figure 1 This is a simplified diagram of a powder lamination forming apparatus according to one embodiment.

[0032] Figure 2 This is an XRD diagram showing the relationship between the amount of carbon added and the degree of inhibition of the formation of the η phase in the shaped material.

[0033] Figure 3 It is an optical microscope photograph showing a cross section of a cubic shape (sintered body) made using the powder material involved in one embodiment. Detailed Implementation

[0034] The preferred embodiments of the present invention will be described below. It should be noted that, for matters not specifically described in this specification but necessary for the implementation of the present invention, these can be considered as conventional technical means employed by those skilled in the art based on existing technology. The present invention can be implemented based on the content disclosed in this specification and common technical knowledge in the field. Furthermore, unless otherwise specified, the expression "X~Y" indicating a numerical range in the specification means "X or more, Y or less".

[0035] <Definition>

[0036] In this specification, "powder material" refers to a powdered material used for lamination molding. The powder material disclosed herein is a WC / Co powder material, that is, a lamination molding powder material with tungsten carbide and cobalt as the main components (i.e., a lamination molding powder material whose largest component in the whole powder material is WC+Co based on mass).

[0037] In this specification, "primary particle" refers to the smallest unit among the morphological components constituting the above-described powder material that can be visually identified as a granular object. Therefore, when the WC / Co-containing powder material disclosed herein includes secondary particles (e.g., granulated particles), the particles constituting these secondary particles can be referred to as primary particles. Here, "secondary particle" refers to a granular object (having a granular morphology) in which primary particles are combined in a three-dimensional manner to form a single entity, functioning as a single particle. Granulated particles and granulated-sintered particles after granulation are typical examples of "secondary particles" as referred to herein.

[0038] It should be noted that the term "bonding" here refers to the direct or indirect bonding of two or more primary particles. Examples include bonding of primary particles through chemical reactions, bonding of primary particles through simple adsorption, bonding of primary particles through the anchoring effect of adhesive materials entering the uneven surface of primary particles, bonding of primary particles through electrostatic attraction, and bonding of primary particles through surface melting and integration.

[0039] Additionally, in this specification, "raw material particles" refers to the particles that constitute the powder used in the raw material stage for forming the powder material disclosed herein.

[0040] In this specification, unless otherwise specified, "average particle size" for powder materials refers to the average particle size of the cumulative 50% of the particle size distribution on a volume basis, as measured by a particle size distribution measuring device based on laser scattering and diffraction (50% volume average particle size). 50 ).

[0041] <Structure of Powder Materials>

[0042] As described above, the powder material disclosed herein is a WC / Co powder material containing tungsten carbide, cobalt, and carbon additives containing carbon as the main constituent element (i.e., a material in which carbon is the largest constituent element by mass).

[0043] As a preferred form of the powder material, examples include powder materials prepared by mixing WC particles, Co particles, and particles constituting carbon additives as raw material particles, but not limited to this form.

[0044] For example, a high-carbon composite WC powder (HighC-WC powder) can also be used, which contains an amount of C exceeding the stoichiometric ratio of WC by pre-adding an excess of carbon to WC particles (powder) as raw material particles. In one form of the powder material disclosed herein, the HighC-WC powder can be said to be a combination of tungsten carbide and carbon additives.

[0045] As the WC powder (which can also be HighC-WC powder) composed of tungsten carbide raw material particles, various commercially available WC powder materials for cemented carbide forming can be used. Tungsten carbide raw material particles with an average particle size of less than 1 μm (e.g., 0.05–0.5 μm, particularly 0.1–0.3 μm) are preferably used. By employing WC powder composed of such small-sized tungsten carbide raw material particles, it is possible to manufacture laminated structures composed of denser WC-Co alloys.

[0046] Furthermore, the Co powder, which is composed of cobalt raw material particles, used to manufacture the powder material disclosed herein, can be any conventional Co powder used for manufacturing powder metallurgy and cemented carbide materials without particular limitation. Preferably, the Co powder has a particle size range of approximately 1 μm or more (e.g., 2 μm or more) and 10 μm or less (e.g., 5 μm or less).

[0047] The powder material disclosed herein is characterized by the addition of a carbon additive material containing carbon (C) as a main constituent element, in a specified amount determined based on the aforementioned carbon content A (mass%).

[0048] Preferred carbon additives include solid carbon materials at room temperature (preferably granular solid carbon materials). Examples of such solid carbon materials include graphite, carbon black (acetylene black, Ketjen black, etc.), activated carbon, carbon fibers (PAN-based carbon fibers, pitch-based carbon fibers, graphite fibers, etc.), and nano-carbon materials (carbon nanotubes, fullerenes, graphene, fine diamond particles, etc.). These solid carbon materials can also be used as a carbon component supply source in the manufacture of the aforementioned HighC-WC powder.

[0049] Alternatively, other preferred forms of carbon additives include carbides of metallic elements that can form hard alloys with WC and Co. These metallic carbides are compounds that function as a carbon supply source due to irradiation energy such as laser or electron beam during lamination and molding with WC and Co. While not particularly limited, examples of such metallic carbides include carbides of any of the following metals: titanium (Ti), vanadium (V), chromium (Cr), niobium (Nb), and molybdenum (Mo).

[0050] As a carbon additive material composed of the above-mentioned solid carbon material or metal carbide, particulate carbon additive materials with an average particle size range of about 0.5 μm or more (e.g., 1 μm or more) and about 10 μm or less (e.g., 5 μm or less) are particularly preferred.

[0051] Alternatively, as described later, any component used in the manufacture of the powder material disclosed herein, such as the binder, may contain a substance that functions as a carbon additive. For example, the carbon content remaining in the final manufactured powder material, which is an organic material that can be used as a binder, is considered as the mass of C derived from the carbon additive (binder, etc.) when determining the carbon content A.

[0052] The powder materials disclosed herein are laminated molding powder materials (including WC / Co powder materials) with tungsten carbide and cobalt as the main components. As long as a good WC-Co alloy can be formed, the content of WC and Co in the powder material as a whole (based on mass) is not particularly limited. For example, it is appropriate for WC to account for more than 60% by mass of the powder material, preferably more than 70% by mass, and particularly preferably more than 75% by mass.

[0053] On the other hand, it is appropriate for Co to account for 10% or more by mass of the total powder material, preferably 15% or more by mass, and particularly preferably 15% or more by mass. From the perspective of not making the WC content too low, 40% or less by mass is appropriate, preferably 30% or less by mass, and particularly preferably 25% or less by mass. For example, when the WC content in the total powder material is 80 to 85% by mass and the Co content is 15 to 20% by mass, a good WC-Co cemented carbide can be obtained, and therefore this is a particularly preferred embodiment.

[0054] Furthermore, the amount of carbon additive material added to the powder material disclosed herein is limited by a specified range of carbon content A (mass%) as shown by the following formula:

[0055] (mass of C derived from WC + mass of C derived from carbon additives) / (mass of WC) × 100.

[0056] The carbon content A is preferably 6.4% by mass or more, particularly preferably 6.6% by mass or more. Furthermore, A is preferably 7.2% by mass or less, particularly preferably 6.9% by mass or less. If the carbon content A is much lower than 6.4% by mass, the insufficient amount of C may not be compensated, and the inhibition effect on the formation of the η phase will decrease, therefore this is not preferred. Conversely, if the carbon content A is much higher than 7.2% by mass, the excessive amount of C may be detrimental to the formation of WC-Co cemented carbides, therefore this is also not preferred.

[0057] Provided that the carbon content A can be set within a specified range and a good WC-Co alloy can be formed, the powder material disclosed herein may contain any other components. For example, binders, dispersants, surfactants, inorganic pigments, organic pigments, etc., can be cited as materials that do not function as carbon additives during lamination (materials that function as carbon additives are included in the scope of carbon additives in this technology).

[0058] <Preparation of Powder Materials>

[0059] The powder materials disclosed herein can be prepared, for example, by mixing raw material particles composed of tungsten carbide (WC), raw material particles composed of cobalt (Co), and raw material particles constituting a carbon additive material containing carbon (C) as the main constituent element (when using HighC-WC powder, raw material particles constituting a carbon additive material may also be omitted) with any other components. The material composed of this mixed powder is a typical example of the WC / Co-containing powder materials disclosed herein.

[0060] However, a more preferred powder material is a powder material composed of granulated sintered particles in which the above-mentioned components are mixed. Typically, it is a powder material composed of granulated sintered particles in the form of secondary particles, which are formed by mixing and granulating the raw material particles (primary particles) of each component and then further sintering them in a three-dimensional manner with gaps between the primary particles. Hereinafter, an example of a granulation sintering method for producing such granulated sintered particles will be described, but it is not limited to this method.

[0061] <Manufacturing of Granulated and Sintered Particles>

[0062] Granulation and sintering is a method in which raw material particles are granulated into secondary particles and then sintered to bond the particles together (sintering). In this granulation and sintering method, granulation can be carried out using methods such as dry granulation or wet granulation. Examples of granulation methods include rotary granulation, fluidized bed granulation, stirred granulation, crushing granulation, melt granulation, spray granulation, and microemulsion granulation. Among these, spray granulation is a preferred method.

[0063] When using spray granulation, powder materials can be manufactured, for example, by following these steps: First, raw material particles corresponding to tungsten carbide, cobalt, and carbon additives are prepared, and their surfaces are stabilized using a protective agent or the like, as needed. Then, the stabilized raw material particles are dispersed in a suitable solvent, for example, with spacer particles made of organic materials such as binders as any component, to prepare a spray liquid. The dispersion of the raw material particles in the solvent can be carried out, for example, using a homogenizer, a blade mixer, or a disperser. Then, droplets are formed from the spray liquid using an ultrasonic sprayer or the like, and these droplets are loaded onto an airflow and passed through a spray drying device (spray dryer), thereby forming granulated particles.

[0064] By introducing the obtained granulated particles into a specified sintering furnace for sintering, a powder material composed of granulated sintered particles in the form of secondary particles bonded together with gaps between primary particles can be obtained. It should be noted that, here, the primary particles can have approximately the same size and shape as the raw material particles, or they can be formed by the growth and bonding of the raw material particles through sintering.

[0065] It should be noted that in the above manufacturing process, when the droplets are dry, the raw material particles and the binder are in a uniformly mixed state, and the raw material particles are bonded together by the binder to form mixed particles. When spacer particles are used, the raw material particles and spacer particles are bonded together by the binder in a uniformly mixed state to form mixed particles. Then, by sintering these mixed particles, the binder (and spacer particles) disappear (burn off), and at the same time, the raw material particles are sintered to form secondary particles with a gap-bonded structure.

[0066] It should be noted that during sintering, depending on their composition and size, a portion of the raw material particles becomes a liquid phase, which facilitates bonding with other particles. Therefore, sometimes the average particle size of the primary particles is larger than that of the initial raw material particles. The average particle size of the secondary particles and primary particles, as well as the size and ratio of the gaps formed between the primary particles, can be designed according to the desired morphology of the secondary particles.

[0067] In the above manufacturing process, the concentration of the raw material particles in the spray liquid that needs to be adjusted is preferably 10 to 40% by mass. Additionally, examples of added binders include carboxymethyl cellulose (CMC) and polyvinylpyrrolidone (PVP). The added binder is preferably adjusted to a ratio of 0.05 to 10% by mass (e.g., 1 to 5% by mass) relative to the raw material particles. The sintering environment is not particularly limited; sintering can be carried out in the atmosphere, in a vacuum, or in an inert gas atmosphere, preferably at a temperature of 600°C or higher and 1600°C or lower. In particular, when using spacer particles or binders made of organic materials, sintering can also be carried out in an oxygen-containing atmosphere to remove organic materials from the granulated particles. The manufactured secondary particles can be crushed and graded as needed.

[0068] The strength (hereinafter referred to as "particle strength") of the granulated sintered particles constituting the powder material manufactured in this way is preferably 1 kgf / mm². 2 The above is further preferred to be 5 kgf / mm 2 The above is particularly preferred, with 10 kgf / mm² being the most desirable. 2 Above (e.g., 20 kgf / mm) 2 (Above). This effectively suppresses the disintegration or scattering of the granulated sintered powder due to the energy used for shaping. As a result, the supply of powder material to the shaping area is stable, thus enabling the shaping of high-quality, uniform products.

[0069] On the other hand, if the particle strength is too high, it is difficult for the powder material to melt completely, so it is not preferred. From this perspective, a particle strength of less than 500 kgf / mm² is preferable. 2 It is appropriate, preferably 300 kgf / mm 2 The following is a further preferred value: 200 kgf / mm 2 The following is particularly preferred: 100 kgf / mm 2 Below (e.g., 50 kgf / mm) 2 the following).

[0070] <Layered Forming Method>

[0071] The powder materials disclosed herein (including WC / Co powder materials) can be used in the same lamination process as when manufacturing laminated shapes made of conventional WC-Co alloys.

[0072] Typical examples of this layered forming method include laser powder deposition (also known as laser metal deposition; LMD) and powder bed fusion bonding (PBF). Powder bed fusion bonding (PBF) includes selective laser melting (SLM), which uses laser as the irradiation energy, and electron beam melting (EBM), which uses electron beam as the irradiation energy.

[0073] Laser powder cladding is a technique that involves supplying powder material to a desired part of a structure, irradiating it with a laser to melt and solidify the powder material, and then cladding (i.e., creating a shape) at that location. Using this method, for example, when a structure experiences physical degradation such as wear, the material constituting the structure or a reinforcing material is supplied as powder to the deteriorated area, and by melting / solidifying the powder material, cladding can be performed on the deteriorated area.

[0074] Powder bed fusion bonding is based on slice data made according to design drawings. For each cross section (1 slice data), the operation of scanning the powder layer with laser or electron beam to deposit powder material is repeated and the powder layer is melted and solidified into the desired shape, so that it can be stacked to form a three-dimensional structure.

[0075] Reference Figure 1 An example of a method for manufacturing a shape by using the powder layering of the powder materials disclosed herein is described.

[0076] Figure 1This is a simplified diagram of a stacking and forming apparatus for powder stacking and forming. As shown in the figure, the stacking and forming apparatus generally includes: a stacking region 10 serving as a space for stacking and forming; a storage chamber 1212 for pre-storing powder material; a scraper 11 for assisting in supplying powder material to the stacking region 10; and a curing device (such as a laser oscillator, YAG laser, or energy irradiation device, such as a beam irradiator) 13 for curing the powder material.

[0077] Typically, the stacked region 10 has a shaping space enclosed by its outer periphery below the shaping surface, and within this shaping space is a lifting platform 14 that can be raised and lowered. This lifting platform 14 can gradually descend by a predetermined thickness Δt1, and the target object is shaped on this lifting platform 14. A storage chamber 12 is disposed near the stacked region 10, and for example, has a base plate (lifting platform) that can be raised and lowered using a barrel or the like within a storage space enclosed by its outer periphery. By raising the base plate, a predetermined amount of powder material can be supplied (extruded) to the shaping surface.

[0078] In this layering and shaping apparatus, a powder material layer 20 of a specified thickness Δt1 is prepared by supplying a powder material layer 20 to the layering region 10 with the lifting platform 14 lowered only by a specified thickness Δt1 from the shaping surface. At this time, by scanning the shaping surface with the scraper 11, the powder material extruded from the storage chamber 12 can be supplied to the layering region 10, and the surface of the powder material can be planarized to form a homogeneous powder material layer 20. Then, for example, for the formed first powder material layer 20, only in the curing region corresponding to the first layer slice data, the powder material can be melted or sintered into the desired cross-sectional shape by irradiating the curing device 13 with energy such as laser or electron beam, thereby forming the first powder curing layer 21.

[0079] Next, the lifting platform 14 is lowered only by a predetermined thickness Δt1, and powder material is supplied again. The scraper 11 is used to flatten it, thereby forming a second powder material layer 20. Then, only in the curing area corresponding to the second layer slice data of this powder material layer 20, energy is irradiated by the curing device 13 to cure the powder material, forming a second powder cured layer 21. At this time, the second powder cured layer 21 is integrated with the first powder cured layer 21 below it, forming a laminate up to the second layer. Next, the lifting platform 14 is lowered only by a predetermined thickness Δt1 to form a new powder material layer 20. Energy is irradiated by the curing device 13 to form a powder cured layer 21 only at the desired locations. In this way, by repeating this process, the laminated forming apparatus can manufacture a target three-dimensional shape based on slice data made according to a pre-prepared design drawing (3D CAD data).

[0080] As described above, based on the powder material disclosed herein, the formation of the η phase (Co3W3C) can be suppressed by the above-described layering molding process, and three-dimensional hard alloy structures with WC-Co as the main component, characterized by fewer cracks and notches and high hardness, can be manufactured.

[0081] The following describes embodiments related to the manufacture of the powder materials and shapes disclosed herein, but it is not intended to limit the technology to the technology shown in the following embodiments.

[0082] <Experimental Example>

[0083] As raw material powder, prepare an average particle size (D) 50 Tungsten carbide (WC) powder with an average particle size of approximately 0.2 μm and an average particle size (D) 50 Cobalt (Co) powder with a particle size of approximately 5 μm was used. Then, a mixture was prepared with 17% by mass of Co powder, 1% by mass of binder (CMC), and the remainder being WC powder. The resulting mixture was wet-mixed and then granulated using a spray dryer. The granulated particles were sintered to produce a powder material composed of granulated and sintered particles (secondary particles). This powder material was used as sample A in this experimental example. As mentioned above, sample A does not contain carbon additives.

[0084] Next, for the mixed powder with the same composition as sample A, graphite particles (D) were added. 50 (Approximately 4μm), vanadium carbide (VC) particles (D) 50 Materials consisting of one or two of the following (approximately 4 μm in diameter) were used as carbon additives. Six different mixtures were prepared in varying proportions to create six powder materials composed of granulated sintered particles with varying carbon contents. Starting with the lowest carbon content, these were designated as Sample A, Sample B, Sample C, Sample D, Sample E, Sample F, and Sample G (A < B < C < D < E < F < G).

[0085] Next, the powder materials of samples A to G were used for the experiment, and simple cubic-shaped stacked objects were made using a commercially available stacking device (product name: ProX DMP200, 3Dsystems product).

[0086] That is, a flattened powder material is irradiated with a laser, causing it to melt layer by layer. By repeating this process, a cubic shape is created. In this experimental example, the power was 300W, the scanning speed was 300mm / s, the spacing was 0.1mm, and the layer thickness was 30μm.

[0087] After layering and shaping, the resulting shape is subjected to sintering treatment (heat treatment). That is, sintering is carried out (continuously) at 1380°C in a reduced pressure atmosphere (10 Pa) for 2 hours.

[0088] Next, XRD (X-ray diffraction) measurements were performed on the sintered bodies of the obtained shapes. Then, based on the XRD patterns, the intensities of the peaks (40.1°) representing the Co3W3C (η phase) between samples A and G were compared. The results are as follows... Figure 2 As shown.

[0089] Comparison of the peak heights near 40.1° (representing the η-layer) of each sample in the figure clearly confirms the formation of the η-phase in the microstructures of the molds made from samples A, B, C, and D, which are powder materials with relatively low carbon content. On the other hand, no peaks representing the formation of the η-phase were identified in the microstructures of the molds made from samples E, F, and G, which are powder materials with relatively high carbon content.

[0090] The results indicate that by adding a specified amount of carbon additives, it is possible to suppress the formation of the η phase as a brittle layer in the microstructure of WC-Co alloys.

[0091] <Manufacturing Example>

[0092] (Sample 1)

[0093] As raw material powder, prepare an average particle size (D) 50 Tungsten carbide (WC) powder with an average particle size of approximately 0.2 μm and an average particle size (D) 50 Cobalt (Co) powder with an average particle size of approximately 5 μm was used as a carbon additive to prepare an average particle size (D). 50 Graphite (C) powder with a particle size of approximately 4 μm was prepared. CMC was then used as a binder.

[0094] Then, the powder material was mixed with 17% by mass of Co powder, 1% by mass of CMC, 0.56% by mass of graphite powder, and the balance being WC powder. The resulting mixed powder was wet-mixed and then granulated using a spray dryer. The resulting granulated particles were sintered to manufacture a powder material composed of granulated and sintered particles (secondary particles). This powder material is used as Sample 1 in this manufacturing example.

[0095] (Samples 2-7)

[0096] The raw material powder is further prepared to achieve an average particle size (D). 50 Vanadium carbide (VC) powder with a thickness of approximately 4 μm was mixed with 17% by mass of Co powder, 1% by mass of CMC, 1% by mass of VC, 0.28% by mass of graphite powder, and the remainder being WC powder. Otherwise, the powder material of sample 2 was manufactured using the same process as sample 1.

[0097] In addition, the powder material was mixed in such a way that 17% by mass of the powder material was Co powder, 1% by mass of CMC, 0.84% ​​by mass of graphite powder, and the balance was WC powder. Otherwise, the powder material of sample 3 was manufactured using the same process as sample 1.

[0098] In addition, the powder material was mixed in such a way that 17% by mass of the powder material was Co powder, 1% by mass of CMC, 3% by mass of VC, 0.14% by mass of graphite powder, and the balance was WC powder. Otherwise, the powder material of sample 4 was manufactured using the same process as sample 1.

[0099] In addition, the powder material was mixed in such a way that 17% by mass of the powder material was Co powder, 1% by mass of CMC, 0.28% by mass of graphite powder, and the balance was WC powder. Otherwise, the powder material of sample 5 was manufactured using the same process as sample 1.

[0100] In addition, the powder material was mixed in such a way that 17% by mass of the powder material was Co powder, 1% by mass of CMC, 0.14% by mass of graphite powder, and the balance was WC powder. Otherwise, the powder material of sample 6 was manufactured using the same process as sample 1.

[0101] In addition, the powder material was mixed with 17% by mass of Co powder, 1% by mass of CMC, and the remainder of WC powder. Otherwise, the powder material of sample 7 was manufactured using the same process as sample 1. That is, no substances equivalent to carbon additives were added to the powder material of sample 7.

[0102] For the powder materials (granulated sintered particles) of samples 1–7, the volumetric particle size distribution was determined using a commercially available particle size distribution measuring device based on laser diffraction / scattering. D3 and D are shown in the corresponding columns of Table 1. 10 D 50 D 90 and D 97 The value of .

[0103] The average particle size (D) was confirmed in all samples. 50 The particle size ranges from 15 to 20 μm, with most particles ranging from 8 to 40 μm.

[0104] For the powder materials (granulated sintered particles) of samples 1 to 7, quantitative analysis of W, Co, V and unavoidable impurity components (Fe and Zr in this case) was performed using a commercially available wavelength dispersive X-ray fluorescence analyzer based on fluorescence X-ray analysis (XRF-1800: product of Shimadzu Corporation).

[0105] In addition, the total carbon content (C content) was measured using a commercially available carbon and sulfur analysis device (EMIA: product of Horiba Manufacturing Co., Ltd.). Then, based on the quantitative value of W, the C content derived from WC was stoichiometrically calculated, and the C content derived from WC was obtained by subtracting this C content from the total C content as the C content derived from the carbon additive.

[0106] The content (mass%) of each element obtained in this way is shown in the corresponding column of Table 1. In addition, the corresponding column of Table 1 records the carbon content A (mass%) of each sample calculated according to the above formula.

[0107] In addition, for the powder materials (granulated sintered particles) of samples 1 to 7, the particle strength was determined using a compression testing machine with electromagnetic force loading. Specifically, more than 10 granulated sintered particles constituting each sample of powder material were randomly sampled, and the arithmetic mean of the fracture strength measured using a commercially available micro compression testing device (MCT-500: a product of Shimadzu Corporation) was taken as the particle strength (kgf / mm²). 2 It should be noted that for granulated sintered particles, when the critical load obtained in the compression test is set as L [N] and the average particle size is set as d [mm], the fracture strength σ [MPa] of the granulated sintered particles can be calculated using the formula: σ = 2.8 × L / π / d². The particle strength (kgf / mm²) of each sample is also shown. 2 As shown in the corresponding column of Table 1.

[0108] Next, the powder materials from samples 1 to 7 were used in the experiments, and simple cubic stacked shapes were created using a commercially available stacking device (product name: ProX DMP200, 3DSystem). That is, similar to the experimental example, the flattened powder material was irradiated with a laser, causing it to melt layer by layer. This process was repeated to create cubic shapes. In this experimental example, the power was 300W, the scanning speed was 300mm / s, the spacing was 0.1mm, and the stacking thickness of each layer was 30μm.

[0109] After layering and shaping, the resulting shape is subjected to sintering treatment (heat treatment). That is, sintering is carried out (continuously) at 1380°C in a reduced pressure atmosphere (10 Pa) for 2 hours.

[0110] Next, XRD (X-ray diffraction) measurements were performed on the sintered bodies of the obtained molds. In the XRD measurements, the intensity of the peak representing Co3W3C (η phase) (40.1°) and the intensity of the peak representing WC (35.6°) were measured. Based on these peak ratios (Co3W3C / WC), the presence and extent of η phase formation in the laminated molds (sintered bodies) of each sample were evaluated. The results are shown in the corresponding columns of Table 1.

[0111] In the "Presence of η Phase" column of Table 1, for samples with an XRD peak ratio (%) of 0%, the presence of η phase was not confirmed, so it was recorded as "None". For samples with an XRD peak ratio (%) of not 0 but less than 1%, the presence of η phase was confirmed, but its presence rate was extremely low, so it was recorded as "Almost None".

[0112] On the other hand, for samples with an XRD peak ratio (%) of 1% or more but less than 3%, although the presence of the η phase is slightly confirmed, its presence ratio has no substantial impact on mechanical strength, and is therefore recorded as "slightly". For samples with an XRD peak ratio (%) of 3% or more, the presence of the η phase is confirmed, and compared with samples without the η phase, its presence ratio has a substantial impact on mechanical strength, and is therefore recorded as "present".

[0113] The cubic shape (sintered body) of sample 1 was cut along a direction perpendicular to the stacking direction, and its cross-section was observed with an optical microscope. Figure 3 It is a microscope photograph showing the cross-section of the shaped object (sintered body) of sample 1.

[0114] [Table 1]

[0115]

[0116] Table 1, which shows the results of this manufacturing example, and Figure 3 It can be seen that in the sintered bodies (sintered bodies) manufactured by laminating samples 1 to 6, in which carbon additives (here, graphite, VC, CMC) are added in a manner where the amount of C exceeds the stoichiometric ratio of WC relative to the WC / Co powder material, specifically in samples 1 to 6 where the carbon content A (mass%) is 6.4 ≤ A ≤ 7.2, the η phase is completely absent in the WC-Co alloy microstructure, or even if it is formed, its extent is extremely small. Therefore, as... Figure 3 As shown, it is possible to manufacture shapes composed of WC-Co alloy microstructures with dense structures of unidentified cracks and notches.

[0117] In the molded material made from the powder material of sample 7 with a stoichiometric composition ratio of carbon content A approximately equal to WC, a large amount of η phase was formed in the structure, and no improvement in mechanical strength was confirmed.

[0118] Although detailed data are not shown, the mechanical properties (hardness, etc.) of sintered bodies made from powder materials of samples 1, 2, and 5, in particular, with carbon additives such as graphite added in a manner where the carbon content A (mass%) is 6.6 ≤ A ≤ 6.9, are superior to those of sintered bodies made from powder materials of the other samples. This indicates that by using a more appropriate amount of carbon additives (in other words, a more suitable amount of C), the formation of the η phase in the WC-Co alloy microstructure can be effectively suppressed.

[0119] Explanation of reference numerals in the attached figures

[0120] 10 Shaping Area

[0121] 11 Scraper

[0122] 12 Storage Room

[0123] 13 Curing device

[0124] 14 Lifting Platform

[0125] 20 Powder Material Layers

[0126] 21 Powder Curing Layer

Claims

1. A powder material for layered shaping, comprising: Tungsten carbide WC particles, Cobalt Co particles, and The particles that constitute carbon-based additive materials with carbon (C) as the main constituent element are referred to as primary particles. The layered shaping powder material is composed of granulated sintered particles, which are formed by bonding the primary particles in a three-dimensional manner with gaps between them. The particle strength of the granulated sintered particles is 5 kgf / mm². 2 Above and below 500 kgf / mm 2 , Here, the carbon content A, as shown by the following formula, satisfies the condition 6.4 ≤ A ≤ 7.2: (Mass of C derived from WC + Mass of C derived from carbon additives) / (Mass of WC) × 100 The unit of the carbon content A is mass.

2. The powder material according to claim 1, wherein, The carbon content A has the condition that 6.6 ≤ A ≤ 6.

9. The unit of the carbon content A is mass.

3. The powder material according to claim 1 or 2, wherein, The carbon additive material comprises at least one solid carbon material selected from the group consisting of graphite, carbon black, activated carbon, carbon fiber, and nano-carbon.

4. The powder material according to claim 1 or 2, wherein, The carbon additive material comprises a carbide of at least one metal selected from the group consisting of titanium (Ti), vanadium (V), chromium (Cr), niobium (Nb), and molybdenum (Mo).

5. The powder material according to claim 1 or 2, wherein, The average particle size of the granulated sintered particles is greater than 10 μm and less than 30 μm. Here, the particles constituting the granulated sintered particles include: Particles composed of the tungsten carbide with an average particle size of less than 1 μm; Particles composed of said cobalt with an average particle size of 2 μm or more and 10 μm or less; and The carbon additive material consists of particles with an average particle size of 1 μm or more and 5 μm or less.

6. A method for manufacturing a shaped object, characterized in that, Layering and shaping are performed using the powder material according to any one of claims 1 to 5.

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