Powder material for additive manufacturing and molded article

Abstract

The objective of the present invention is to provide a means enabling further improvement of the bending strength of a molded article obtained by additive manufacturing.　The present invention provides a powder material for additive manufacturing containing components derived from tungsten carbide, titanium carbide, and cobalt. The composition ratio of titanium is more than 4.1 mass% and 9 mass% or less, and the composition ratio of cobalt is 16-40 mass%, as measured by elemental analysis using X-ray fluorescence analysis (XRF).

Description

Powder materials and molded objects for additive manufacturing

[0001] This invention relates to additive manufacturing powder materials and molded objects.

[0002] Additive manufacturing (also known as additive manufacturing) is a technology that creates objects based on a numerical representation of a three-dimensional shape (typically 3D CAD data) by depositing materials. Typically, powder materials are joined or sintered as thin layers corresponding to the cross-sectional shape of the object to be fabricated, and these thin layers are sequentially stacked to create the desired three-dimensional shape. In recent years, there has been a demand for improvements in additive manufacturing technology that uses cemented carbide powder materials such as WC / Co to directly fabricate cemented carbide components without the need for molds (see, for example, International Publication No. 2015 / 194678, Japanese Patent Publication No. 2017-113952, Japanese Patent Publication No. 2017-114716, and Japanese Patent Publication No. 2017-115194).

[0003] However, our investigations have revealed that even with the techniques described in the above-mentioned literature, there is still room for improvement in order to further enhance the flexural strength of products manufactured by additive manufacturing. Therefore, the present invention aims to provide a means to further improve the flexural strength of products manufactured by additive manufacturing.

[0004] In order to solve the above problems, the inventors conducted diligent research and discovered that the above problems can be solved by controlling the composition ratio of titanium and cobalt in an additive manufacturing powder material containing components derived from tungsten carbide (WC), titanium carbide (TiC), and cobalt (Co) to a predetermined range. Furthermore, they discovered that the above problems can be solved by controlling the composition ratio of titanium and cobalt in a molded object using an additive manufacturing powder material containing components derived from tungsten carbide, titanium carbide, and cobalt to a predetermined range, and thus completed the present invention.

[0005] In other words, one embodiment of the present invention is a powder material for addition manufacturing containing components derived from tungsten carbide, titanium carbide, and cobalt, wherein the composition ratio of titanium is greater than 4.1% by mass and less than or equal to 9% by mass, as measured by elemental analysis by X-ray fluorescence analysis (XRF), and the composition ratio of cobalt is 16 to 40% by mass.

[0006] Furthermore, one embodiment of the present invention is a molded object made using an additive manufacturing powder material containing components derived from tungsten carbide, titanium carbide, and cobalt, wherein the titanium composition ratio, as measured by elemental analysis by X-ray fluorescence analysis (XRF), is greater than 3.8% by mass and 9% by mass or less, and the cobalt composition ratio is 10.5% to 35% by mass.

[0007] Figure 1 is a schematic diagram showing an example of the configuration of an additive manufacturing apparatus. Figure 2 shows the XRD spectra of the fabricated objects (after HIP treatment) from Examples 1, 5, and 7, and Comparative Example 2.

[0008] One embodiment of the present invention is a powder material for addition manufacturing containing components derived from tungsten carbide, titanium carbide, and cobalt, wherein the composition ratio of titanium is greater than 4.1% by mass and less than or equal to 9% by mass, as measured by elemental analysis by X-ray fluorescence analysis (XRF), and the composition ratio of cobalt is 16 to 40% by mass.

[0009] Furthermore, one embodiment of the present invention is a molded object made using an additive manufacturing powder material containing components derived from tungsten carbide, titanium carbide, and cobalt, wherein the titanium composition ratio, as measured by elemental analysis by X-ray fluorescence analysis (XRF), is greater than 3.8% by mass and 9% by mass or less, and the cobalt composition ratio is 10.5% to 35% by mass.

[0010] According to the present invention, the flexural strength of a molded product produced by additive manufacturing can be further improved.

[0011] Preferred embodiments of the present invention will be described below, but the present invention is not limited to these embodiments. Matters other than those specifically mentioned herein that are necessary for carrying out the present invention can be understood as design matters for those skilled in the art based on the prior art. The present invention can be carried out based on the contents disclosed herein and common technical knowledge in the art. In this specification, the notation "X to Y" indicating a numerical range includes X and Y and means "X or more and Y or less". Also, the dimensional ratios in the drawings are exaggerated for explanatory purposes and may differ from the actual ratios.

[0012] <Definitions> In this specification, "powder material" refers to a powdered material used in additive manufacturing. Powder material may also be called a molding material. Powder material is typically composed of aggregates of secondary particles as described below, but it goes without saying that the inclusion of primary particles as described below is permissible. In this specification, "primary particle" means the smallest unit of morphological components constituting the above-mentioned powder material that can be identified as particulate matter from its appearance. In particular, it refers to a single particle (a single particulate matter) that constitutes a secondary particle as described below.

[0013] In this specification, "secondary particle" refers to a particulate matter (a particle in form) in which primary particles are three-dimensionally bonded together and behave as a single particle. Here, "bonding" refers to the direct or indirect bonding of two or more primary particles, and includes, for example, bonding of primary particles by chemical reactions, bonding of primary particles by simple adsorption, bonding of primary particles utilizing the effect of electrostatic attraction, and bonding in which the surfaces of primary particles melt and become one.

[0014] In this specification, "raw material particles" refers to particles that constitute the raw material powder for forming a powder material. Secondary particles can be manufactured by bonding the raw material particles three-dimensionally in an appropriate manner. The particles that constitute the secondary particles thus manufactured are called primary particles. These primary particles may have substantially the same form as the raw material particles, or they may have a different form from the raw material particles, for example, by two or more raw material particles reacting or becoming integrated to the extent that they are morphologically indistinguishable. Furthermore, primary particles may have the same composition as the raw material particles, or they may have a different composition from the raw material particles, for example, by two or more types of raw material particles reacting.

[0015] In this specification, "additive manufacturing (also called additive manufacturing)" broadly encompasses various manufacturing methods that use powder materials in additive manufacturing technology. Additive manufacturing may also be called powder additive manufacturing. Examples of methods for bonding powder materials in additive manufacturing include laser metal deposition (LMD), selective laser melting (SLM), electron beam melting (EBM), and aerosol deposition (AD).

[0016] <Powder Material> One embodiment of the present invention is a powder material for addition manufacturing containing components derived from tungsten carbide, titanium carbide, and cobalt, wherein the composition ratio of titanium is greater than 4.1% by mass and less than or equal to 9% by mass, as measured by elemental analysis by X-ray fluorescence analysis (XRF), and the composition ratio of cobalt is 16 to 40% by mass.

[0017] A powder material according to one embodiment of the present invention contains components derived from tungsten carbide, titanium carbide, and cobalt. In a preferred embodiment, the powder material contains tungsten carbide, titanium carbide, and cobalt as raw material particles. In a preferred embodiment, the raw material particles of tungsten carbide, titanium carbide, and cobalt are bonded together by sintering to form granulated sintered powder. In a preferred embodiment, the powder material can also be understood as having tungsten carbide, titanium carbide, and cobalt as primary particles, with the granulated sintered powder forming secondary particles. It is preferable that the raw material particles of tungsten carbide, titanium carbide, and cobalt are generally uniformly mixed and dispersed to form secondary particles. Needless to say, in such a powder material, it is permissible for the raw material particles of tungsten carbide, titanium carbide, and cobalt to be included in the form of secondary particles (for example, 10% by mass or less).

[0018] In the powder material according to this embodiment, the composition ratio of titanium, as measured by elemental analysis by X-ray fluorescence analysis (XRF), is greater than 4.1% by mass and less than or equal to 9% by mass, and the composition ratio of cobalt is 16 to 40% by mass.

[0019] One of the development goals for additive manufacturing powder materials, consisting of inorganic materials such as metals and ceramics, is the development of powder materials that can produce molded objects with high hardness. As a material that meets this goal, development of powder materials mainly composed of tungsten carbide (WC) and cobalt (Co) is underway. Tungsten carbide and cobalt are raw materials for WC-Co alloy, a cemented carbide, and are suitable as materials for producing high-hardness molded objects by additive manufacturing. Furthermore, the hardness of the molded object can be further improved by including titanium carbide (TiC) in the powder material. In particular, if the molded object has undergone hot isostatic pressing (HIP) treatment, densification of the component occurs, and high hardness can be achieved. However, the flexural strength of the component is still not sufficient.

[0020] In contrast, in the powder material of the present invention, the composition ratio of titanium (Ti) measured by elemental analysis via X-ray fluorescence analysis (XRF) is more than 4.1% by mass and 9% by mass or less. When the composition ratio of Ti in the powder material exceeds 4.1% by mass, sufficient transverse rupture strength can be obtained in the shaped article. TiC, which is a titanium source, has higher hardness than WC and can contribute to increasing the hardness of the shaped article. Furthermore, TiC has an effect of suppressing grain growth of WC particles in WC / Co cemented carbides, and thus can contribute to refining WC particles in the shaped article. In addition, TiC has a non-stoichiometric composition, and against changes in the carbon content in the cemented carbide, Co ３ W ３ Since the existing range of the structure not containing the C phase (η phase) is wide, it can contribute to suppressing the formation of brittle phases in the shaped article. Therefore, when the composition ratio of Ti in the powder material exceeds 4.1% by mass, the above effects of TiC such as increased hardness, refinement of WC particles, and suppression of brittle phase formation can be exhibited. For this reason, it is considered that high transverse rupture strength can be obtained. On the other hand, even when the composition ratio of Ti in the powder material is 9% by mass or less, sufficient transverse rupture strength can be obtained in the shaped article. TiC, which is a titanium source, has lower wettability and solubility to Co than WC. Therefore, when the composition ratio of Ti is 9% by mass or less, it is considered that the bonding between WC or TiC and Co is enhanced, and the transverse rupture strength of the shaped article is improved. The composition ratio of Ti measured by elemental analysis via XRF in the powder material is preferably 4.4 to 9% by mass, more preferably 4.5 to 8.5% by mass, still more preferably 4.6 to 8.2% by mass, even more preferably 5 to 8% by mass, still even more preferably 5.5 to 7.5% by mass, still even more preferably 6 to 7% by mass, still even more preferably 6 to 6.5% by mass, and particularly preferably 6.1 to 6.4% by mass.

[0021] Further, in the powder material of the present invention, the composition ratio of cobalt (Co) measured by elemental analysis via XRF is 16 to 40% by mass. When the composition ratio of Co in the powder material is 16% by mass or more, sufficient transverse rupture strength can be obtained in a shaped article. Co serves as a binder for WC and TiC, which are hard particles. When the composition ratio of Co is 16% by mass or more, WC and TiC as hard particles can be sufficiently retained, so that the hardness and transverse rupture strength of the shaped article can be improved. In addition, since defects (voids and cracks) in a member can be sufficiently filled during the production of the shaped article, local defects (pores) are less likely to occur in the shaped article, and a decrease in transverse rupture strength caused by such local defects (pores) is less likely to occur. Further, in a cemented carbide containing WC and TiC when Co is added, Co against changes in carbon content ３ W ３ It is known that the range of existence of a structure not containing a C phase (η phase) is wide. When the composition ratio of Co is 16% by mass or more, the above effect can be sufficiently obtained, a brittle phase is less likely to be formed, and the transverse rupture strength of the shaped article can be improved. On the other hand, when the composition ratio of Co is 40% by mass or less, the composition ratio of W becomes relatively high, so both the transverse rupture strength and hardness can be improved. The composition ratio of Co measured by elemental analysis via XRF in the powder material is preferably 17 to 38% by mass, more preferably 18 to 37% by mass, still more preferably 20 to 35% by mass, and even more preferably 22 to 30% by mass.

[0022] In the powder material of the present embodiment, the composition ratio of tungsten (W) measured by elemental analysis via XRF is not particularly limited, but is preferably 51 to 74% by mass. When the composition ratio falls within the above range, the hardness and transverse rupture strength of the shaped article can be further improved. The composition ratio of W measured by elemental analysis via XRF in the powder material is more preferably 51 to 71% by mass, and still more preferably 55 to 65% by mass.

[0023] In the powder material of the present embodiment, the composition ratio of carbon (C) measured by elemental analysis using a carbon / sulfur analyzer with a high-frequency induction heating method is not particularly limited, but is, for example, 2 to 10% by mass, and preferably 4 to 8% by mass.

[0024] The composition ratios of Ti, Co, W, and C can be determined by elemental analysis using X-ray fluorescence analysis (XRF) and a carbon-sulfur analyzer with high-frequency induction heating, as described in the examples below. In the powder material of this embodiment, the composition ratios of Ti, Co, W, and C can be controlled by adjusting the blending ratios of, for example, tungsten carbide, titanium carbide, and cobalt used as raw materials, as determined by elemental analysis using X-ray fluorescence analysis (XRF) and a carbon-sulfur analyzer with high-frequency induction heating.

[0025] The powder material in this embodiment may contain optional components other than those derived from tungsten carbide, titanium carbide, and cobalt. Optional components include carbon materials (e.g., particulate solid carbon materials). Examples of such solid carbon materials include graphite, carbon black (acetylene black, Ketjenblack, etc.), activated carbon, carbon fibers (PAN-based carbon fibers, pitch-based carbon fibers, graphite fibers, etc.), and nanocarbons (carbon nanotubes, fullerenes, graphene, diamond nanoparticles, etc.). Optional components may also include binders, dispersants, surfactants, inorganic pigments, organic pigments, etc. The binders, dispersants, surfactants, inorganic pigments, and organic pigments are not particularly limited, and known materials can be appropriately selected. Furthermore, the powder material in this embodiment may contain unavoidable impurities such as Fe, Zr, and Cr.

[0026] The total composition ratio (by mass) of components derived from tungsten carbide, titanium carbide, and cobalt in the entire powder material is not particularly limited, but it is preferably more than 50% by mass of the entire powder material, more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, and even more preferably 95% by mass or more. Furthermore, there is no particular upper limit to the total composition ratio of components derived from tungsten carbide, titanium carbide, and cobalt in the entire powder material, but for example it is 100% by mass or less, for example 99% by mass or less, and for example 98% by mass or less.

[0027] (Granulated Sintered Powder) The powder material according to this embodiment may be composed of an aggregate of granulated sintered powder having the form of secondary particles as described above. "Granulated sintered powder" refers to particulate matter (a body of particles) in which primary particles are sintered and behave as a single particle. "Sintering" refers to a state in which primary particles are directly bonded to each other. Therefore, sintering may be either solid-phase sintering or liquid-phase sintering. Furthermore, sintering as used herein may include so-called fusion bonding or melt bonding.

[0028] The powder material according to this embodiment may be realized by solidly integrating individual primary particles through sintering in secondary particles (particle aggregates) having forms such as granular particles or fine particle-coated particles in which fine particles are bonded around core particles. As an energy source in additive manufacturing (also called additive manufacturing), laser light, electron beams, arcs, etc., are used. When laser light or electron beams, etc., are irradiated onto the powder material, high energy is released and shock may occur in the powder material. To avoid the granular particles collapsing or primary particles scattering due to this shock, it is preferable that the granular particles be configured as so-called granulated sintered powder, in which individual primary particles are bonded together by sintering. This granulated sintered powder is preferable because it is less prone to collapse and scattering of the powder material even when irradiated with a higher intensity laser light, etc., as an energy source. This is preferable because it can lead to a higher manufacturing speed without impairing the manufacturing accuracy and quality of the manufactured object (for example, the laser scanning speed can be increased, or there is no need to reduce the laser scanning speed).

[0029] The average particle size (50% volume average particle size; D50) of the powder material according to this embodiment (for example, the powder material in the form of granulated sintered powder) is not particularly limited and can be set to a size suitable for the specifications of the additive manufacturing equipment used. For example, the average particle size of the powder material may be a size suitable for supplying the powder material in additive manufacturing. The upper limit of the average particle size of the powder material may exceed, for example, 200 μm, but is typically 200 μm or less. The upper limit of the average particle size of the powder material is preferably 150 μm or less, more preferably 100 μm or less, even more preferably 40 μm or less, and even more preferably 20 μm or less. As the average particle size of the powder material decreases, the filling density of the powder material in the molding area, for example, can be improved. As a result, the density of the three-dimensional object to be molded can be improved. Furthermore, the surface roughness (Ra) of the three-dimensional object to be molded can be reduced, and the dimensional accuracy can be improved. The lower limit of the average particle size of the powder material is not particularly limited as long as it does not affect the fluidity of the powder material. However, considering the handling when forming the powder material and the fluidity of the powder material, the lower limit of the average particle diameter can be 1 μm or more, preferably 5 μm or more, and more preferably 10 μm or more. As the average particle diameter of the powder material increases, the fluidity of the powder material improves. As a result, the supply of the powder material to the molding apparatus can be carried out smoothly, which is preferable because it results in a good finish for the three-dimensional molded object produced. Furthermore, although not particularly limited, from the viewpoint of the finish of the three-dimensional molded object of the powder material according to this embodiment, the 90% volume average particle diameter (D90) of the powder material (for example, the powder material in the form of granulated sintered powder) is preferably 10 to 50 μm, and more preferably 20 to 40 μm. Furthermore, although not particularly limited, from the viewpoint of the finish of the three-dimensional molded object of the powder material according to this embodiment, the 10% volume average particle diameter (D10) of the powder material (for example, the powder material in the form of granulated sintered powder) is preferably 1 to 30 μm, and more preferably 2 to 20 μm. The values ​​D10, D50, and D90 of the powder material (for example, a powder material in the form of granulated sintered powder) can be determined by the method described in the examples below.

[0030] (Granule Strength) The strength of granular particles (hereinafter referred to as granule strength) in the powder material according to the present embodiment (for example, a powder material in the form of granulated sintered powder) is 1 MPa (1.02×10 －１ kgf / mm ２ ) can be specified to exceed. This suitably suppresses the collapse and scattering of the granulated sintered powder caused by the energy for modeling. As a result, the supply of material powder to the modeling area is stabilized, which is preferable because a high-quality modeled object without unevenness can be formed. The granule strength of the powder material is 5 kgf / mm ２ or more, preferably 10 kgf / mm ２ or more, more preferably 20 kgf / mm ２ or more, still more preferably. On the other hand, from the viewpoint of easily and sufficiently melting the powder material, and from the viewpoint of preventing the properties of the spheroidized particles from becoming similar to those of ungranulated single particles as sintering progresses until the structure becomes similar to that of ungranulated single particles, the granule strength is 1000 kgf / mm ２ is preferably less than, more preferably 500 kgf / mm ２ or less, still more preferably 250 kgf / mm ２ or less, even more preferably 100 kgf / mm ２ or less, still even more preferably 80 kgf / mm ２ or less, further more preferably 50 kgf / mm ２ or less, still even more preferably 40 kgf / mm ２ or less, particularly preferably. The granule strength of the powder material can be determined by the method described in the examples below. As mentioned above, 1 kgf / mm ２ = 9.807 MPa.

[0031] The bulk density of the powder material according to the present embodiment (for example, a powder material in the form of granulated sintered powder) is not particularly limited, but is, for example, 0.5 to 5 g / cm ３ , preferably 1 to 5 g / cm ３ , more preferably 2 to 4 g / cm ３Within the above range, the filling density of the powder material in the molding area can be improved. As a result, the density of the three-dimensional object that is molded can be suitably increased. In addition, the handling of the powder material when forming it and the fluidity of the powder material are excellent. The bulk density of the powder material (for example, powder material in the form of granulated sintered powder) can be determined by the method described in the examples below. Note that 1 g / cm³ ３ = 1000 kg / m ３ That is the case.

[0032] In one embodiment of the present invention, the powder material preferably has a peak originating from TiC around 2θ = 41.6° in the XRD (X-ray diffraction) spectrum using CuKα rays. Having such a peak indicates a sufficient presence of the TiC crystalline phase in the powder material, which can lead to the production of a fabricated object with higher hardness. XRD measurement can be performed using the method described in the examples below.

[0033] In a preferred embodiment, in a powder material (for example, a powder material in the form of granulated sintered powder), the raw material particles (typically primary particles) of tungsten carbide, titanium carbide, and cobalt are three-dimensionally bonded to each other to form the granulated sintered powder. This structure has the advantage that the powder material readily absorbs energy from an energy source (heat source) and is easily melted. As a result, it is possible to obtain a highly dense and hard molded object that is similar to a sintered body (bulk body) manufactured using a mold, for example.

[0034] (Method for Manufacturing Powdered Material) The powdered material in this embodiment contains components derived from tungsten carbide, titanium carbide, and cobalt, and the method for manufacturing it is not particularly limited as long as the composition ratio of titanium and cobalt measured by elemental analysis by X-ray fluorescence analysis is a predetermined value. The powdered material in this embodiment can be prepared, for example, using raw material particles of tungsten carbide, titanium carbide, and cobalt. For example, as a preferred example of the method for manufacturing the powdered material in this embodiment, the case in which the powdered material is manufactured by a granulation sintering method will be described below. However, the method for manufacturing the powdered material disclosed herein is not limited thereto.

[0035] Granulation and sintering is a method of sintering individual raw material particles by granulating a powder containing tungsten carbide, titanium carbide, and cobalt raw material particles into secondary particles and then firing them. Various known granulation methods can be used as appropriate for granulation. For example, dry granulation or wet granulation can be used as the granulation method. Specifically, examples include rolling granulation, fluidized bed granulation, agitation granulation, crushing granulation, melt granulation, spray granulation, and microemulsion granulation. Among these, spray granulation is a particularly suitable granulation method.

[0036] According to the spray granulation method, powder materials can be manufactured, for example, by following the procedure below. First, a powder (hereinafter also referred to as raw material powder) is prepared by blending tungsten carbide, titanium carbide, and cobalt raw material particles in a predetermined mass ratio. If necessary, the surface of each raw material particle is stabilized with a protective agent or the like. Then, the raw material powder is dispersed in a suitable solvent together with spacer particles, for example, a binder and / or organic material as optional components, to prepare a spray solution. The dispersion of the raw material powder in the solvent can be carried out using a mixer, disperser, etc., such as a homogenizer or a blade agitator. Then, the spray solution is sprayed into an airflow using a spray granulator and dried. This makes it possible to obtain secondary particles (granulated secondary particles) in which each raw material particle is three-dimensionally bound together, for example, by a binder.

[0037] The content of tungsten carbide, titanium carbide, and cobalt in the raw material powder is not particularly limited. Preferably, in the raw material powder, the cobalt content is more than 17% by mass and 37% by mass or less, the titanium carbide content is 7.8% by mass or more and less than 10% by mass, and the remainder is tungsten carbide. More preferably, in the raw material powder, the cobalt content is 18 to 35% by mass, the titanium carbide content is 8 to 8.2% by mass, and the remainder is tungsten carbide. Furthermore, in the raw material powder, the tungsten carbide content is preferably less than 73% by mass, and more preferably 70% by mass or less. In a preferred embodiment, in the raw material powder, the cobalt content is 20 to 30% by mass, the titanium carbide content is 8 to 8.2% by mass, and the tungsten carbide content is 60 to 70% by mass. Within the above ranges, the powder material of this embodiment can be obtained more easily.

[0038] Next, the granulated secondary particles are fired to sinter each raw material particle contained within the secondary particles. This allows the raw material particles to be firmly bonded (sintered) together. In this granulation and sintering method, for example, the granulated particles produced by the above granulation method are subjected to a sintering treatment. At this time, the granulated raw material particles are sintered at their contact points with each other, and are sintered while generally maintaining their granular shape. In systems using a binder, the binder disappears during sintering. In systems using spacer particles, these spacer particles also disappear due to firing. This makes it possible to obtain a powder material consisting of particles in the form of secondary particles in which primary particles have been sintered. In this powder material, the primary particles may have approximately the same dimensions and shape as the raw material particles, or the raw material particles may have grown and been bonded by firing.

[0039] In the manufacturing process described above, in systems using a binder, the granulated particles are in a uniformly mixed state with the raw material particles and the binder, and the raw material particles are bound together by the binder to form mixed particles. In systems using both a binder and spacer particles, the raw material particles and spacer particles are in a uniformly mixed state and are bound together by the binder to form mixed particles. When these mixed particles are fired, the binder (and spacer particles) disappear (burn through), and the raw material particles are sintered, forming secondary particles in which primary particles are bound together.

[0040] During sintering, depending on their composition and size, some of the raw material particles may become part of the liquid phase and contribute to bonding with other particles. Therefore, the average particle size of the primary particles may be larger than that of the starting material particles. The size and proportion of these secondary and primary particles can be appropriately designed according to the desired morphology of the secondary particles.

[0041] In one embodiment of the present invention, the average particle size of the primary particles of the TiC powder and Co powder used as starting materials is preferably 0.5 to 5 μm, and more preferably 1 to 3 μm, respectively. In another embodiment of the present invention, the average particle size of the primary particles of the WC powder used as starting material is preferably 0.5 to 5 μm, and more preferably 2 to 4 μm. When the average particle sizes of these primary particles are within the above ranges, the effects of the present invention can be obtained even more significantly. The value of the average particle size of the primary particles can be determined by the method described in the examples below.

[0042] In the above manufacturing process, the concentration of raw material particles in the prepared spray solution is preferably 10 to 40% by mass. When a binder is used, examples of binders to be added include carboxymethylcellulose, polyvinylpyrrolidone, and polyvinyl alcohol. The amount of binder to be added is preferably adjusted to 0.05 to 10% by mass relative to the mass of the raw material particles. The environment in which the particles are fired is not particularly limited, but it may be in the air, in a vacuum, or in an inert gas atmosphere, and it is preferable to sinter at a temperature of 600°C to 1600°C. In particular, when organic materials such as spacer particles and binders are used, sintering may be carried out in an atmosphere containing oxygen in order to remove the organic materials from the granulated particles. If necessary, the manufactured secondary particles may be crushed and classified.

[0043] The additive manufacturing powder material of the present invention can be used in additive manufacturing, and molded objects can be manufactured by additive manufacturing. By using the additive manufacturing powder material of the present invention, molded objects with even greater hardness can be obtained. The additive manufacturing powder material of the present invention can be applied to various additive manufacturing methods (for example, laser metal deposition (LMD), selective laser melting (SLM), electron beam melting (EBM), aerosol deposition (AD), etc.).

[0044] <Formed Product> One embodiment of the present invention is a formed product made using an additive manufacturing powder material containing components derived from tungsten carbide, titanium carbide, and cobalt, wherein the titanium composition ratio, as measured by elemental analysis by X-ray fluorescence analysis (XRF), is greater than 3.8% by mass and 9% by mass or less, and the cobalt composition ratio is 10.5% to 35% by mass.

[0045] The molded object of the present invention contains components derived from tungsten carbide, titanium carbide, and cobalt. In a preferred embodiment, the molded object is manufactured by additive manufacturing using an additive manufacturing powder material containing components derived from tungsten carbide, titanium carbide, and cobalt. In a preferred embodiment, the molded object is manufactured by additive manufacturing using the additive manufacturing powder material of the present invention described above.

[0046] In the fabricated object of the present invention, the composition ratio of titanium (Ti), as measured by elemental analysis using XRF, is greater than 3.8% by mass and less than or equal to 9% by mass. A Ti composition ratio greater than 3.8% by mass in the fabricated object provides sufficient flexural strength. TiC, the titanium source, has higher hardness compared to WC and can contribute to increasing the hardness of the fabricated object. Furthermore, TiC has a grain growth suppression effect on WC particles in WC / Co cemented carbide, thus contributing to the refinement of WC particles in the fabricated object. Additionally, TiC has a non-stoichiometric composition, and its composition is not affected by changes in the carbon content in the cemented carbide. ３ W ３ Because the microstructure does not contain the C phase (η phase), it can contribute to suppressing the formation of brittle phases in the fabricated object. Therefore, when the Ti composition ratio in the fabricated object exceeds 3.8 mass%, the effects of increased hardness, densification, and suppression of brittle phase formation by TiC as described above can be achieved. As a result, it is thought that high flexural strength can be obtained. On the other hand, even when the Ti composition ratio in the fabricated object is 9 mass% or less, sufficient flexural strength can be obtained in the fabricated object. TiC, which is a titanium source, has lower wettability and solubility in Co compared to WC. Therefore, when the Ti composition ratio is 9 mass% or less, the bonding between WC or TiC and Co increases, and it is thought that the flexural strength of the fabricated object improves. The composition ratio of Ti measured by elemental analysis using XRF in the fabricated object is preferably 4.1 to 9 mass%, more preferably 4.5 to 8.8 mass%, even more preferably 4.9 to 8.6 mass%, even more preferably 5 to 8 mass%, even more preferably 5.5 to 7.5 mass%, and even more preferably 6 to 7 mass%.

[0047] Furthermore, in the fabricated object of the present invention, the composition ratio of cobalt (Co), as measured by elemental analysis using XRF, is 10.5 to 35 mass%. When the composition ratio of Co in the fabricated object is 10.5 mass% or more, sufficient flexural strength can be obtained in the fabricated object. Co plays the role of a binder for the hard particles WC and TiC. When the composition ratio of Co is 10.5 mass% or more, the hard particles WC and TiC can be sufficiently held, so the hardness and flexural strength of the fabricated object can be improved. In addition, since defects (voids and cracks) in the material can be sufficiently filled during the manufacturing of the fabricated object, local defects (pores) are less likely to occur in the fabricated object, and a decrease in flexural strength due to such local defects (pores) is less likely to occur. Furthermore, when Co is added, in cemented carbide containing WC and TiC, Co acts in response to changes in carbon content. ３ W ３ Although it is known that a wide range of structures without the C phase (η phase) exist, the above effects can be sufficiently obtained when the Co composition ratio is 10.5 mass% or more, making it difficult for brittle phases to form and potentially improving the flexural strength of the fabricated object. On the other hand, when the Co composition ratio is 35 mass% or less, the W composition ratio becomes relatively high, which can improve both flexural strength and hardness. The Co composition ratio measured by elemental analysis by XRF in the fabricated object is preferably 11 to 34 mass%, more preferably 14 to 34 mass%, and even more preferably 14 to 32 mass%.

[0048] In the fabricated object of this embodiment, the composition ratio of tungsten (W) measured by elemental analysis by XRF is not particularly limited, but is preferably 51 to 77 mass%. Within this range, the hardness and flexural strength of the fabricated object can be further improved. The composition ratio of W measured by elemental analysis by XRF in the fabricated object is more preferably 52 to 75.5 mass%, even more preferably 52 to 75 mass%, and even more preferably 55 to 70 mass%.

[0049] In the fabricated object of this embodiment, the composition ratio of carbon (C) measured by elemental analysis using a carbon-sulfur analyzer with high-frequency induction heating is not particularly limited, but is, for example, 2 to 10% by mass, and preferably 4 to 8% by mass.

[0050] The composition ratios of Ti, Co, W, and C can be determined by elemental analysis using X-ray fluorescence analysis (XRF) and a carbon-sulfur analyzer with high-frequency induction heating, as described in the examples below. In the fabricated object of this embodiment, the composition ratios of Ti, Co, W, and C can be controlled, for example, by using tungsten carbide, titanium carbide, and cobalt as raw materials in an additive manufacturing powder material containing components derived from tungsten carbide, titanium carbide, and cobalt, and adjusting their blending ratios.

[0051] The fabricated object in this embodiment may contain optional components other than those derived from tungsten carbide, titanium carbide, and cobalt. These optional components are similar to those found in the powder material described above. Furthermore, the fabricated object in this embodiment may contain unavoidable impurities such as Fe, Zr, and Cr.

[0052] The total composition ratio (by mass) of components derived from tungsten carbide, titanium carbide, and cobalt in the molded object is not particularly limited, but it is preferably more than 50% by mass of the total composition ratio of components derived from tungsten carbide, titanium carbide, and cobalt, more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, and even more preferably 95% by mass or more. Furthermore, there is no particular upper limit to the total composition ratio of components derived from tungsten carbide, titanium carbide, and cobalt in the molded object, but for example it is 100% by mass or less, for example 99% by mass or less, and for example 98% by mass or less.

[0053] (Method for Manufacturing Molded Objects) Molded objects of the present invention can be manufactured by additive manufacturing using additive manufacturing powder materials. The additive manufacturing powder materials are not particularly limited as long as they contain components derived from tungsten carbide, titanium carbide, and cobalt, and provide the above-mentioned predetermined titanium and cobalt composition ratio in the molded object. In a preferred embodiment, the additive manufacturing powder materials of the present invention described above are used as the additive manufacturing powder materials. Using the additive manufacturing powder materials of the present invention described above as the additive manufacturing powder materials is preferable because it is easy to obtain molded objects that provide the above-mentioned predetermined titanium and cobalt composition ratio. Examples of additive manufacturing methods include laser metal deposition (LMD), selective laser melting (SLM), electron beam melting (EBM), and aerosol deposition (AD).

[0054] As an example of a method for manufacturing three-dimensional objects, additive manufacturing will be explained using the Select Laser Melting (SLM) method as an example. A method for manufacturing a three-dimensional object using SLM includes the following steps: (A) supplying powder material (e.g., granulated sintered powder) to the layering area of ​​an additive manufacturing apparatus; (B) flattening the supplied powder material with a wiper or the like to form a thin layer so that it is uniformly and thinly deposited in the layering area; (C) solidifying the formed thin layer of powder material by applying means to bond and sinter the powder material (e.g., by irradiating it with laser light); (D) supplying new powder material on top of the solidified powder material and repeating steps (B) to (D) after step (A) to build up the layer and obtain a three-dimensional object; (E) heat-treating the obtained three-dimensional object in a reduced-pressure atmosphere; (F) applying hot isostatic pressing (HIP) to the three-dimensional object that has been heat-treated in a reduced-pressure atmosphere.

[0055] Furthermore, the "solidification" step (D) includes directly bonding the secondary particles constituting the powder material together through melting and solidification, thereby fixing their shape to a predetermined cross-sectional shape.

[0056] Laser metal deposition (LMD) is a technique that involves providing powdered material to a desired location on a structure and then irradiating it with laser light to melt and solidify the powdered material, thereby creating a build-up layer on that location. By using this technique, for example, when physical deterioration such as wear occurs in a structure, the material that makes up the structure or reinforcing material can be supplied as powdered material to the deteriorated area, and the powdered material can be melted and solidified to create a build-up layer on the deteriorated area.

[0057] Selective laser melting (SLM) is a technique for creating three-dimensional structures by repeatedly scanning a powder layer, which is made of powdered material deposited based on slice data created from a design drawing, with a laser beam to melt and solidify the powder layer into the desired shape, for each cross-section (one slice data).

[0058] Furthermore, electron beam melting (EBM) is a technique that uses an electron beam to selectively melt and solidify the powder layers based on slice data created from 3D CAD data, and then stacks these layers to create a three-dimensional structure.

[0059] In each of these technologies, the process includes supplying powder material, which is the raw material for the structure, to a predetermined molding position.

[0060] Figure 1 is a schematic diagram showing an example of the configuration of an additive manufacturing apparatus 100 for manufacturing a molded object according to one embodiment of the present invention. As shown in Figure 1, the additive manufacturing apparatus 100 comprises a molding area 10 which is a space in which additive manufacturing is performed, a stock 12 for storing powder material, a wiper 11 for assisting in the supply of powder material to the molding area 10, and a solidification means (energy supply means such as a laser oscillator) 13 for solidifying the powder material.

[0061] The build area 10 has a build space enclosed by its outer perimeter located below the build surface, and is equipped with a liftable table 14 that can be raised and lowered within this build space. The liftable table 14 can be moved downward by a predetermined thickness Δt1, and the desired object is built on the liftable table 14. The stock 12 is located next to the build area 10 and, for example, has a storage space enclosed by its outer perimeter, and is equipped with a bottom plate (liftable table) that can be raised and lowered by a cylinder or the like. The stock 12 supplies (extrudes) a predetermined amount of powder material to the build surface by raising the bottom plate.

[0062] The additive manufacturing apparatus 100 can perform the above steps (A) to (D). For example, the additive manufacturing apparatus 100 prepares a layer of powder material 20 of predetermined thickness Δt1 by supplying powder material 20 to the molding area 10 with the lifting table 14 lowered by a predetermined thickness Δt1 from the molding surface.

[0063] Next, the additive manufacturing apparatus 100 supplies the powder material extruded from the stock 12 onto the molding area 10 by scanning the wiper 11 over the molding surface, and flattens the upper surface of the powder material to form a homogeneous layer of powder material 20.

[0064] Next, the additive manufacturing apparatus 100 applies energy to the formed first layer of powder material 20 only to the solidification region corresponding to the slice data of the first layer via the solidification means 13, thereby melting or sintering the powder material into a desired cross-sectional shape and forming the first layer of powder solidified material 21.

[0065] Next, the additive manufacturing apparatus 100 lowers the lifting table 14 by a predetermined thickness Δt1, supplies the powder material again, and forms the second layer of powder material 20 by leveling it with the wiper 11. Then, the additive manufacturing apparatus 100 applies energy via the solidification means 13 only to the solidification region corresponding to the slice data of the second layer of powder material 20 to solidify the powder material and form the second layer of solidified powder 21. At this time, the second layer of solidified powder 21 and the lower layer, the first layer of solidified powder 21, are integrated to form a laminate up to the second layer.

[0066] Next, the additive manufacturing apparatus 100 lowers the lifting table 14 by a predetermined thickness Δt1 to form a new layer of powder material 20, and applies energy via the solidification means 13 to form a powder solidification layer 21 at the required location. By repeating this process, the additive manufacturing apparatus 100 can manufacture the desired three-dimensional object.

[0067] Furthermore, as a means of solidifying the powder material, a method of melting and solidifying the powder material (including sintering) by applying heat with laser light or an electron beam may be selected. As the laser, for example, a carbon dioxide laser or a YAG laser can be suitably used.

[0068] In a preferred embodiment, the process proceeds from step (D) to step (E). In step (E), the fabricated three-dimensional object is subjected to heat treatment. The temperature of the heat treatment in (E) is, for example, 1200°C to 1500°C. The pressure of the heat treatment in (E) is, for example, 1 Pa to 100 Pa. Through the heat treatment in (E), the three-dimensional object is sintered and densified.

[0069] In a preferred embodiment, after step (E) above, the process proceeds to step (F). Hot isostatic pressing (HIP) in (F) is a technique for pressurizing an object at high temperature and high pressure. In this embodiment, the object is a three-dimensional molded object after the heat treatment in (E) above. For example, the three-dimensional molded object after heat treatment is air-cooled to a temperature close to room temperature and then subjected to HIP.

[0070] The heating temperature for HIP is, for example, 1200°C to 1400°C, preferably 1300°C to 1400°C. The pressurizing pressure for HIP is a value sufficiently higher than the heat treatment pressure in (E) above, for example, 50 MPa to 180 MPa. The processing time for HIP is, for example, 1 hour to 5 hours. HIP is performed with the three-dimensional object placed in an inert gas atmosphere such as argon (Ar).

[0071] In the three-dimensional molded object after the heat treatment described in (E) above, micropores may remain in the WC-Co cemented carbide. By performing further HIP after the heat treatment described in (E) above, the micropores can be reduced. As a result, the three-dimensional molded object can be further densified and its strength can be increased.

[0072] As described above, a method for manufacturing a molded object according to one embodiment of the present invention includes the steps of: forming a three-dimensional molded object by irradiating it with laser light or an electron beam using an additive manufacturing powder material; subjecting the molded object to heat treatment in a reduced-pressure atmosphere; and subjecting the heat-treated molded object to hot isostatic pressing. According to this, the three-dimensional molded object, which has been sintered and densified by heat treatment, is further densified by HIP, which reduces micropores. This makes it possible to manufacture a three-dimensional molded object that is dense and has high hardness. A reduced-pressure atmosphere refers to a pressure lower than atmospheric pressure, for example, a vacuum or a pressure close to a vacuum.

[0073] The fabricated object according to one embodiment of the present invention is not particularly limited, but it is preferable that, in the fabricated object after obtaining a three-dimensional fabricated object by additive manufacturing and then performing the heat treatment (E) and the HIP treatment (F) described above, the titanium composition ratio measured by elemental analysis by X-ray fluorescence analysis (XRF) is greater than 3.8 mass% and 9 mass% or less, and the cobalt composition ratio is 10.5 to 35 mass%. For these preferred forms, it is even more preferable that the values ​​in the fabricated object after obtaining a three-dimensional fabricated object by additive manufacturing and then performing the heat treatment (E) and the HIP treatment (F) described above are in the above-described form. Similarly, for the preferred form of the tungsten composition ratio, it is even more preferable that the values ​​in the fabricated object after obtaining a three-dimensional fabricated object by additive manufacturing and then performing the heat treatment (E) and the HIP treatment (F) described above are in the above-described form.

[0074] The fabricated object according to one embodiment of the present invention is not particularly limited, but preferably has a cross-sectional porosity of 0.16% or less, more preferably 0.15% or less, even more preferably 0.14% or less, even more preferably 0.13% or less, and particularly preferably 0.1% or less. The effects of the present invention can be more significantly obtained when the cross-sectional porosity is within the above range. The lower limit of the cross-sectional porosity is not particularly limited, but for example, it is 0.01% or more. In particular, it is preferable that the cross-sectional porosity of the fabricated object after the heat treatment (E) and HIP treatment (F) described above, which are performed after obtaining a three-dimensional fabricated object by additive manufacturing, is within the above range. In a preferred embodiment, the fabricated object has a cross-sectional porosity of 0.1% or less after HIP treatment. The value of the cross-sectional porosity can be determined by the method described in the examples below.

[0075] The fabricated object according to one embodiment of the present invention is not particularly limited, but it is preferable that the XRD (X-ray diffraction) spectrum using CuKα rays has peaks originating from (Ti,W)C around 2θ = 36.0° and around 41.7°. Such a fabricated object has superior hardness because the (Ti,W)C crystalline phase is sufficiently present in the alloy structure. Furthermore, Co is present at both around 2θ = 40° and around 42.5°. ３ W ３ It is preferable that the peak originating from the C phase (η phase) is not shown. In such a fabricated object, the brittle phase is Co ３ W ３ The formation of the C phase (η phase) is sufficiently suppressed, resulting in superior hardness and flexural strength. In particular, it is preferable that the XRD spectrum of the fabricated object after obtaining a three-dimensional object by additive manufacturing and then performing the heat treatment (E) and the HIP treatment (F) described above has the above characteristics. XRD measurement can be performed by the method described in the examples below.

[0076] The fabricated object according to one embodiment of the present invention is not particularly limited, but preferably has a flexural strength of 1 GPa or more, more preferably 1.1 GPa or more, even more preferably 1.2 GPa or more, and even more preferably 1.3 GPa or more. Within the above range, excellent strength can be obtained in powder metallurgy products of any shape, such as complex shapes. The upper limit of the flexural strength is not particularly limited, but for example, it is 5 GPa or less. In particular, it is preferable that the flexural strength of the fabricated object after obtaining a three-dimensional fabricated object by additive manufacturing and then performing the heat treatment (E) and the HIP treatment (F) above (flexural strength after HIP treatment) is within the above range. The value of the flexural strength can be determined by the method described in the examples below.

[0077] The present invention encompasses the following aspects and forms: 1. A powder material for additive manufacturing containing components derived from tungsten carbide, titanium carbide, and cobalt, wherein the titanium composition ratio, as measured by elemental analysis by X-ray fluorescence analysis (XRF), is greater than 4.1% by mass and 9% by mass or less, and the cobalt composition ratio is 16 to 40% by mass; 2. The powder material according to 1. above, wherein the tungsten composition ratio, as measured by elemental analysis by X-ray fluorescence analysis (XRF), is 51 to 74% by mass; 3. A molded object using the powder material for additive manufacturing containing components derived from tungsten carbide, titanium carbide, and cobalt, wherein the titanium composition ratio, as measured by elemental analysis by X-ray fluorescence analysis (XRF), is greater than 3.8% by mass and 9% by mass or less, and the cobalt composition ratio is 10.5 to 35% by mass; 4. The molded object according to 3. above, wherein the flexural strength after HIP treatment is 1 GPa or more; 5. The fabricated object described in 3. or 4. above, wherein the cross-sectional porosity after HIP treatment is 0.1% or less.

[0078] The present invention will be described in more detail using the following examples and comparative examples. However, the technical scope of the present invention is not limited to the following examples.

[0079] (Preparation of powder materials) <Comparative Examples 1-4, Examples 1-8> As raw material powders, tungsten carbide (WC) powder with an average primary particle diameter of 1.5 μm, cobalt (Co) powder with an average primary particle diameter of 1.5 μm, and titanium carbide (TiC) powder with an average primary particle diameter of 3 μm were prepared.

[0080] Then, in each comparative example and example, Co powder, TiC powder, and WC powder were blended so that the composition ratio (mass%) of W, Ti, Co, and C in the final powder material was as shown in Table 1 below, to obtain a blended powder (primary particle form). Polyvinyl alcohol was added as a binder to the obtained blended powder and wet-mixed, and then granulated by spray granulation using a spray dryer. The obtained granulated powder was sintered to produce granulated sintered powder (secondary particle form). The obtained granulated sintered powder was classified using a sieve with a mesh size of 25 μm to obtain powder material.

[0081] The powder particle size (D10, D50, D90), bulk density, granule strength, chemical composition, and crystalline phase of the powder materials obtained in Comparative Examples 1-4 and Examples 1-8 were measured. The results are shown in Table 1 below.

[0082] For the "average particle diameter" of primary particles, the particle diameter at 50% of the cumulative value in the volume-based particle size distribution measured by a particle size distribution analyzer based on laser diffraction and scattering (50% volume average particle diameter; D50) was adopted.

[0083] (Powder particle size) For secondary particles D10, D50, and D90, the particle diameter at 10% of the cumulative value from the smallest particle size side in the volume-based particle size distribution measured by a particle size distribution analyzer based on laser diffraction and scattering was adopted, respectively.

[0084] (Bulk Density) For bulk density, we adopted values ​​measured in accordance with the apparent density measurement method for metal powders specified in JIS Z2504:2020. Specifically, bulk density was calculated by measuring the mass of the powder when it naturally filled a container of a predetermined capacity with powder that flowed out of a 2.5 mm diameter orifice. For measuring bulk density, we used values ​​measured with a JIS bulk density meter for metal powders (manufactured by Tsutsui Rikagakukikai Co., Ltd.).

[0085] (Granule Strength) For granule strength, the value of the fracture strength of the granule particles, measured using an electromagnetic load compression tester, was adopted. Specifically, for any 10 or more granulated sintered powders constituting the powder material, the arithmetic mean of the fracture strength measured using a microcompression tester (Shimadzu Corporation, MCT-500) was adopted as the granule strength. When the critical load obtained in the compression test for the granulated sintered powder is L [N] and the average particle diameter is d [mm], the fracture strength σ [MPa] of the granulated sintered powder is given by the formula: σ = (2.8 × L / π) / d ２ It is calculated as follows.

[0086] (Chemical Composition) The powder materials (granulated sintered powder) obtained in Comparative Examples 1 to 4 and Examples 1 to 8 were quantitatively analyzed for W, Co, Ti, and unavoidable impurities (here, Fe, Zr, Cr) using a commercially available wavelength-dispersive X-ray fluorescence analyzer (XRF-1800: Shimadzu Corporation) based on the X-ray fluorescence analysis method. In addition, C (carbon) was quantitatively analyzed using a commercially available high-frequency induction heating carbon and sulfur analyzer (EMIA-321V2: Horiba, Ltd.).

[0087] (Crystalline Phase) XRD (X-ray diffraction) measurements using CuKα rays were performed on the powder materials obtained in each example and comparative example. For the XRD measurements, an X-ray diffraction analyzer (RIGAKU Corporation, Ultima IV) was used, with CuKα rays (voltage 20kV, current 10mA) as the X-ray source, and the scanning range was 2θ = 10° to 70°, scan speed: 10° / min, sampling width: 0.01°, divergence slit: 1°, divergence longitudinal limiting slit: 10mm, scattering slit: 1 / 6°, light receiving slit: 0.15mm, and offset angle: 0°. A peak originating from TiC around 2θ = 41.6° was observed, and if the above peak was observed it was indicated as "Present", and if it was not observed it was indicated as "Absent", as shown in Table 1. All of the powder materials obtained in each example and comparative example showed a peak originating from TiC in the XRD measurements, confirming that they are powder materials containing components originating from TiC.

[0088] (Preparation of the fabricated object) Using the powder materials obtained in Comparative Examples 1 to 4 and Examples 1 to 8 described above, a three-dimensional fabricated object (10 mm long x 30 mm wide x 10 mm thick) was manufactured by irradiating the flattened powder material with laser light using an additive manufacturing apparatus (product name: ProX DMP200, manufactured by 3DSsystem Inc.), melting it layer by layer, and repeating this process. At this time, the output was 300 W, the scanning speed was 300 mm / s, the pitch width was 0.1 mm, and the layer thickness was 30 μm.

[0089] Next, the resulting three-dimensional object was subjected to heat treatment. The heat treatment conditions were a reduced pressure atmosphere (10 Pa), a heating temperature of 1400°C, and a heating time of 2 hours (continuous).

[0090] Next, the three-dimensional molded objects after heat treatment were subjected to hot isostatic pressing (HIP). The HIP conditions were a pressurized argon (Ar) gas atmosphere (100 MPa), a heating temperature of 1380°C, and a heating time of 4 hours (continuous). This yielded the molded objects of Comparative Examples 1-4 and Examples 1-8, respectively.

[0091] The chemical composition, cross-sectional porosity, crystalline phase, and flexural strength of the fabricated objects of Comparative Examples 1-4 and Examples 1-8 were measured. The results are shown in Table 2 below.

[0092] (Chemical composition) The chemical composition of the molded object was measured using the same method as the measurement of the chemical composition of the powder material described above.

[0093] (Cross-sectional porosity) The molded object was cut perpendicular to its longitudinal direction (horizontal direction) so that the vertical and height-direction surfaces were exposed. The cross-section was then mirror-polished, and the area ratio of pores in the cross-section (= pore area ÷ total area × 100) was calculated by image analysis of the cross-sectional observation image and defined as the cross-sectional porosity. Pore areas in the image were extracted by performing binarization on the cross-sectional image at a magnification of 100x. The cross-sectional observation image was acquired using a microscope VHX-5000 (manufactured by Keyence Corporation), and the observation conditions were coaxial reflected light mode (bright-field observation) and a shutter speed of "0.11 ms" in manual mode. The image analysis software used was the analysis function installed in the microscope VHX-5000 (manufactured by Keyence Corporation), and the threshold for binarization was set to "-20".

[0094] (Crystalline phase) For the observation of the crystalline phase, the cross-section of the fabricated object was mirror-polished, and XRD measurements were performed on this cross-section using the same method as the XRD measurements of the powder material described above. In the XRD spectrum, peaks originating from (Ti,W)C were observed around 2θ = 36.0° and 41.7°. If either of these peaks was observed, the (Ti,W)C peak was considered "present," and if it was not observed, it was considered "absent." In addition, Co was observed around 2θ = 40° or 42.5°. ３ W ３ If a peak originating from the C phase (η phase) is observed, Co ３ W ３ If the C (η phase) peak was observed, it was marked as "present," and if not observed, it was marked as "absent." In this case, Co around 2θ = 40° and 42.5° ３ W ３ If the height of the peak originating from the C phase (η phase) is less than 1% of the height of the peak originating from WC around 2θ = 35.5°, then Co ３ W ３ Peaks originating from the C phase (η phase) were marked as "absent," and if the height of at least one of the peaks around 2θ = 40° and 42.5° was 1% or more, it was marked as "present." In addition, the height of the peak originating from WC around 2θ = 35.5° was considered in relation to Co.３ W ３ Determine the ratio of the peak heights originating from the C phase (η phase) (the height of the larger of the two peaks around 2θ = 40° and 42.5°), and Co ３ W ３ The ratio was given as C / WC (η phase ratio) (%).

[0095] Figure 2 shows the XRD spectra of the HIP-treated objects fabricated in Examples 1, 5, 7, and Comparative Example 2. In all of the objects fabricated in Examples 1, 5, 7, and Comparative Example 2, a peak originating from (Ti,W)C was observed in the XRD spectrum. Furthermore, the objects fabricated in Examples 1, 5, and 7 showed Co ３ W ３ No peaks originating from the C phase (η phase) were observed, but the fabricated object in Comparative Example 2 showed Co around 2θ = 40° and 42.5°. ３ W ３ A peak originating from the C phase (η phase) was observed.

[0096] (Flexural Strength) Flexural strength is a physical property that indicates the strength against bending. Flexural strength may also be called bending strength. Flexural strength was measured under the following conditions: After grinding the molded object, it was polished with #800 abrasive paper to create a test specimen with dimensions of 24 mm in length, 8 mm in width (w), and 4 mm in thickness (t). The flexural strength was measured using this test specimen. The flexural strength was measured using an Instron universal material testing machine (model 5585) under normal temperature and pressure conditions with a support distance of 20 mm and a crosshead speed of 0.5 mm / min. The flexural strength σ (GPa) was calculated using the following formula: σ = 10 －３ × (3 × P × l) / (2 × w × t) ２ P: Maximum load (N) at which the test specimen broke; l: Distance between supports (mm); w: Width of the test specimen (mm); t: Thickness of the test specimen (mm).

[0097]

[0098] As shown in Tables 1 and 2, it was found that the molded objects produced using the powder materials of Examples 1 to 8, in which the titanium composition ratio measured by XRF was greater than 4.1 mass% and 9 mass% or less, and the cobalt composition ratio was 16 to 40 mass%, all had higher flexural strength than the molded objects produced using the powder materials of Comparative Examples 1 to 4, which did not have the above composition ratios.

[0099] This application is based on Japanese Patent Application No. 2025-056913, filed on 28 March 2025, the disclosures of which are incorporated herein by reference in their entirety.

[0100] 10. Molding area 11. Wiper 12. Stock 13. Solidification means 14. Lifting table 20. Powder material 21. Powder solidification layer 100. Additive manufacturing apparatus

Claims

1. A powder material for addition manufacturing containing components derived from tungsten carbide, titanium carbide, and cobalt, wherein the titanium composition ratio, as measured by elemental analysis by X-ray fluorescence (XRF), is greater than 4.1% by mass and less than or equal to 9% by mass, and the cobalt composition ratio is 16 to 40% by mass.

2. The powder material according to claim 1, wherein the composition ratio of tungsten, as measured by elemental analysis by X-ray fluorescence (XRF), is 51 to 74% by mass.

3. A molded object made using an additive manufacturing powder material containing components derived from tungsten carbide, titanium carbide, and cobalt, wherein the titanium composition ratio, as measured by elemental analysis by X-ray fluorescence (XRF), is greater than 3.8% by mass and less than or equal to 9% by mass, and the cobalt composition ratio is between 10.5% and 35% by mass.

4. The fabricated product according to claim 3, wherein the flexural strength after HIP treatment is 1 GPa or more.

5. The fabricated object according to claim 3 or 4, wherein the cross-sectional porosity after HIP treatment is 0.1% or less.

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