JP2021055160A - Method for manufacturing molded article - Google Patents

Abstract

To provide a method for manufacturing a molded article, by which a dense molded article in a three-dimensional shape with high hardness can be manufactured.SOLUTION: The method for manufacturing a molded article includes: a step of forming a molded article in a three-dimensional shape by use of a powder material for additive manufacturing, the powder material comprising tungsten carbide and cobalt, by irradiation with laser light or an electron beam; a step of heat-treating the molded article in a reduced pressure environment; and a step of subjecting the heat-treated molded article to a hot isotropic pressing process.SELECTED DRAWING: Figure 3

Description

The present invention relates to a method for producing a modeled object.

In additive manufacturing technology, an object is created based on a numerical representation of a three-dimensional shape (typically 3D CAD data) by adhering a material. Typically, powdered materials (Adaptive Manufacturing materials) are joined or sintered as thin layers having a shape corresponding to the cross section of the model to be modeled, and the thin layers are sequentially stacked to form a desired three-dimensional shape. To model. In this additional manufacturing, in recent years, there has been a demand for improvement of a laminated molding technique in which a cemented carbide powder material such as a WC group is used to directly mold a cemented carbide member without requiring a molding mold (for example, Patent Documents). See 1-4).

International Publication No. 2015/194678 JP-A-2017-113952 Japanese Unexamined Patent Publication No. 2017-114716 JP-A-2017-115194

In the additive manufacturing method, a technique for producing a dense and highly hard model is desired.

Here, the present inventors describe the additive manufacturing method for producing a three-dimensional shaped object by irradiating a laser beam or an electron beam with the components and modeling process of a powder material for additive manufacturing, and the physical properties of the modeled object. We examined the relationship between. As a result, it has been found that by defining the components of the powder material for laminated modeling and the modeling process under specific conditions, it is possible to produce a dense and hard model.
The present invention has been made in view of the above problems, and an object of the present invention is to provide a method for manufacturing a shaped object capable of producing a dense and highly hard three-dimensional shaped object.

The method for producing a modeled object according to one aspect of the present invention includes a step of forming a three-dimensional shaped object by irradiating a laser beam or an electron beam with a powder material for laminated modeling containing tungsten carbide and cobalt. The steps include a step of heat-treating the modeled object in a reduced pressure atmosphere and a step of subjecting the heat-treated modeled object to hot isotropic pressure pressurization.
The modeled object according to one aspect of the present invention is a powder material for laminated modeling used for producing a three-dimensional shaped object by irradiating a laser beam or an electron beam, and comprises tungsten carbide and cobalt. , Titanium carbide, and the content of titanium carbide is 1% by mass or more and 20% by mass or less.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a method for manufacturing a modeled object capable of modeling a three-dimensionally shaped object having a high density and high hardness.

FIG. 1 is a schematic view showing a configuration example of a laminated modeling apparatus for executing the method for manufacturing a modeled object according to the embodiment of the present invention. FIG. 2 is an enlarged SEM image showing a cross section of the three-dimensional modeled object (Comparative Example 2) after the heat treatment. FIG. 3 is an enlarged SEM image showing a cross section of the three-dimensional modeled object (Example 1) after HIP. FIG. 4 is an enlarged SEM image showing a cross section of the three-dimensional modeled object (Example 2) after HIP.

<Definition>
As used herein, the term "powder material" refers to a powdered material used for laminated molding. The powder material may be referred to as a modeling material. The powder material is typically composed of a collection of secondary particles described below, but it goes without saying that mixing of the primary particles described below is allowed. In the present specification, the “primary particle” means the smallest unit that can be identified as a particulate matter from the appearance among the morphological components constituting the powder material. In particular, it refers to one particle (one particulate matter) that constitutes a secondary particle described later.

As used herein, the term "secondary particle" refers to a particulate matter (in the form of a particle) in which primary particles are three-dimensionally bonded and behave as one particle as a unit. The term "bonding" as used herein means that two or more primary particles are directly or indirectly bound to each other. For example, primary particles are bonded to each other by a chemical reaction or simple adsorption to each other. Includes bonds that attract each other, bonds between primary particles that utilize the effect of attracting due to static electricity, and bonds where the surface of the primary particles is melted and integrated.

As used herein, the term "raw material particles" refers to particles constituting a raw material powder for forming a powder material. Secondary particles can be produced by three-dimensionally bonding the raw material particles by an appropriate method. Further, the particles constituting the secondary particles produced in this way are referred to as primary particles. The primary particles may have almost the same form as the raw material particles, or may have a form different from the raw material particles such that two or more raw material particles react or are integrated to the extent that they are morphologically indistinguishable. There may be. Further, the primary particles may have the same composition as the raw material particles, or may have a composition different from that of the raw material particles due to the reaction of two or more kinds of raw material particles.

As used herein, the term "laminated modeling" broadly includes various modeling methods using powder materials in additional manufacturing techniques. Additive manufacturing may be referred to as powder additive manufacturing. Examples of the method for bonding the powder materials in the laminated molding include a laser powder overlay method (laser metal deposition method; LMD), a selective laser melting method (select laser melting method; SLM), and an electron beam melting method. A beam irradiation method such as (Electric beam melting method; EBM) can be mentioned.
In the present specification, "X to Y" indicating a range means "X or more and Y or less".
The present invention is not limited to the following embodiments. In addition, the dimensional ratios in the drawings are exaggerated for convenience of explanation and may differ from the actual ratios.

<Powder material>
(composition)
The powder material according to the embodiment of the present invention (hereinafter referred to as the present embodiment) can be used as raw material particles.
(1) Cobalt (Co) and
(2) Titanium carbide (TiC) and
(3) Tungsten carbide (WC) and
including.
Each of the raw material particles (1) to (3) above is bonded by sintering to form a granulated sintered powder. It can also be understood that in the powder material according to the present embodiment, each of the raw material particles (1) to (3) above is used as primary particles, and the granulated sintered powder forms a body of secondary particles. The raw material particles (1) to (3) described above form secondary particles in a state of being substantially uniformly mixed and dispersed. Needless to say, in such a powder material, it is permissible (for example, 10% by mass or less) to include each of the raw material particles (1) to (3) in the form of primary particles.

In the powder material according to the present embodiment, the cobalt content is, for example, preferably 5% by mass or more, more preferably 10% by mass or more, and further preferably 15% by mass or more. Further, in the powder material according to the present embodiment, the cobalt content is preferably, for example, 50% by mass or less, more preferably 35% by mass or less, and further preferably 25% by mass or less. If the cobalt content is within the above numerical range, WC and Co can be combined to form a WC-Co-based cemented carbide when laminating is performed using laser light or an electron beam. it can.

In the powder material according to the present embodiment, the content of titanium carbide is, for example, preferably 1% by mass or more, more preferably 5% by mass or more, and further preferably 10% by mass or more. Further, in the powder material according to the present embodiment, the content of titanium carbide is preferably, for example, 30% by mass or less, more preferably 25% by mass or less, and further preferably 20% by mass or less. ..

When the content of titanium carbide is within the above numerical range, carbon (C) is supplied from titanium carbide to tungsten carbide (WC) when laminating molding is performed using laser light or an electron beam. In laminated molding using laser light or electron beam, the powder material is heated to a high temperature in a short time compared to ordinary powder metallurgy, so C of tungsten carbide (WC) is likely to volatilize, and C of WC is C. It tends to be in a shortage state (that is, a W-rich state). However, the titanium carbide supplies C to the tungsten carbide so as to supplement the volatilized C. As a result, the formation of the η phase (fragile phase) can be suppressed in the WC-Co based cemented carbide.

Further, the titanium carbide contained in the powder material reacts with the tungsten carbide to become tungsten titanium carbide (WTC). TiC does not remain in the WC-Co-based cemented carbide after molding (or even if it remains, the amount thereof is small). The hardness of the WC-Co-based cemented carbide can be further increased by containing WTIC.

In the powder material according to the present embodiment, the content of the tungsten carbide is, for example, preferably 75% by mass or more, more preferably 85% by mass or more, and further preferably 90% by mass or more. Further, in the powder material according to the present embodiment, the content of tungsten carbide is more preferably 94% by mass or less, for example. When the content of tungsten carbide is within the above numerical range, WC and Co are combined to form a WC-Co-based cemented carbide when laminating is performed using laser light or an electron beam. Can be done.

(Granulated sintered powder)
The powder material according to the present embodiment may be configured as an aggregate of granulated sintered powder having the form of secondary particles as described above. The "granulated sintered powder" refers to a particulate matter (a body of particles) in which primary particles are sintered and behave like a single particle as a unit. "Sintering" refers to a state in which primary particles are directly bonded to each other. Therefore, the sintering may be either solid phase sintering or liquid phase sintering. Further, the sintering referred to in the present specification may include so-called fusion and melt bonding.

In the powder material according to the present embodiment, for example, in secondary particles (particle aggregates) having the form of granular particles, fine particle-coated particles formed by binding fine particles around core particles, and the like, individual primary particles are baked. It may be realized by being firmly integrated by the conclusion. A laser beam, an electron beam, an arc, or the like is used as an energy source in the laminated molding. When the powder material is irradiated with laser light, an electron beam, or the like, high energy is released and the powder material may be impacted. Due to this impact, the mere granular particles may collapse or the primary particles may scatter. In order to avoid the occurrence of this situation, the granule particles are configured as so-called granulated sintered powder in which individual primary particles are bonded by sintering. This granulated sintered powder is preferable because the powder material is unlikely to disintegrate or scatter even when irradiated with a laser beam having a higher intensity as an energy source. This is preferable because it can lead to an increase in the modeling speed without impairing the modeling accuracy and quality of the modeled object (for example, the laser scanning speed can be increased or the laser scanning speed does not need to be reduced).

(Granule strength)
The strength of the granule particles in the granulated sintered powder (hereinafter referred to as “granule strength”) can be specified to exceed 1 MPa. As a result, it is possible to suitably suppress the granulated sintered powder from collapsing or scattering due to the energy for modeling. As a result, the supply of the material powder to the modeling area is stable, which is preferable because a high-quality modeled object without unevenness can be modeled. The granule strength of the granulated sintered powder ^{is preferably 1 kg / mm 2} or more, more preferably 5 kg / mm ² or more, and 10 kg / mm ² or more (for example, 20 kg / mm ² or more). Is even more preferable. However, if the granule strength is too strong, it becomes difficult to sufficiently melt the powder material, which is not preferable. In addition, the granulated sintered powder having too strong granule strength is sintered until it has a structure similar to that of a single particle that has not been granulated, and has similar properties to the spheroidized particles. It ends up. From this point of view, the granule strength is set to less than ^{1000 kg / mm 2.} The granule strength is ^{preferably 500 kg / mm 2} or less, more preferably 250 kg / mm ² or less, and even more preferably 100 kg / mm ² or less (for example, 80 kg / mm ² or less).

In the powder material (for example, granulated sintered powder) according to the present embodiment, the raw material particles (typically primary particles) of the above (1) to (3) are three-dimensionally bonded to each other. Consists of granulated sintered powder. Due to this structure, the powder material has an advantage that it easily receives energy from an energy source (heat source) and easily dissolves. As a result, it is possible to obtain a highly dense and hard model that is close to a sintered body (bulk body) manufactured by using a mold, for example.

In particular, the powder material according to the present embodiment contains not only tungsten carbide but also cobalt having a melting point lower than that of tungsten carbide. Further, a plurality of primary particles constituting the powder material are three-dimensionally bonded. As a result, in the powder material, the cobalt melts first, and the cobalt melt can wet and spread on the surface of the tungsten carbide. Alternatively, the tungsten carbide can be incorporated in a dispersed state in the matrix formed by melting the tungsten carbide. As a result, the melting of the tungsten carbide is promoted, and a dense molded product can be obtained. Alternatively, it is possible to obtain a densely shaped product in which the tungsten carbide phase is dispersed in the cobalt phase.

(Average particle size)
The average particle size of the powder material (for example, granulated sintered powder) according to the present embodiment is not particularly limited, and can be a size suitable for the specifications of the laminated modeling apparatus to be used. For example, the average particle size of the powder material can be a size suitable for supplying the powder material in the laminated molding. If the upper limit of the average particle size of the powder material is larger, for example, it may exceed 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, still more preferably 40 μm or less. As the average particle size of the powder material becomes smaller, the filling rate of the powder material can be improved, for example, in the modeling area. As a result, the precision of the three-dimensional model to be modeled can be suitably increased. In addition, the surface roughness (Ra) of the three-dimensional model to be modeled can be reduced, and the effect of improving the dimensional accuracy can be obtained.

Further, 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, when the handling when forming the powder material and the fluidity of the powder material are taken into consideration, the lower limit of the average particle size can be set to 1 μm or more, preferably 5 μm or more, and more preferably 10 μm or more. As the average particle size of the powder material increases, the fluidity of the powder material improves. As a result, the powder material can be satisfactorily supplied to the modeling apparatus, and the finished three-dimensional modeled product to be produced is finished, which is preferable.

<Manufacturing method>
(Manufacturing method of powder material)
As long as the powder material in the present embodiment contains the raw material particles (1) to (3) above, the production method thereof is not particularly limited. For example, as a preferable example, a case where a powder material is produced by a granulation sintering method will be described below. However, the method for producing a powder material disclosed herein is not limited to this.

The granulation sintering method is a method of sintering individual raw material particles by granulating a powder containing each of the raw material particles (1) to (3) in the form of secondary particles and then firing the powder. In granulation, various known granulation methods can be appropriately used. For example, as a granulation method, a granulation method such as dry granulation or wet granulation can be used. Specific examples thereof include a rolling granulation method, a fluidized bed granulation method, a stirring frame granulation method, a crushing granulation method, a melt granulation method, a spray granulation method, and a microemulsion granulation method. Among them, a spray granulation method is mentioned as a preferable granulation method.

According to the spray granulation method, for example, a modeling material can be produced by the following procedure. That is, first, a powder (hereinafter, also referred to as a compounded powder) in which each of the raw material particles (1) to (3) is blended in a predetermined mass ratio is prepared. If necessary, stabilize the surface with a protective agent or the like. Then, the stabilized compounded powder is dispersed in an appropriate solvent together with, for example, a binder and spacer particles made of an organic material or the like contained as necessary to prepare a spray liquid. Dispersion of the raw material particles in the solvent can be carried out using, for example, a homogenizer, a mixer such as a blade stirrer, a disperser, or the like. As a result, each of the raw material particles (1) to (3) described above is sprayed into an air stream using a spray granulator and dried. As a result, it is possible to obtain secondary particles in which the raw material particles (1) to (3) are three-dimensionally bonded by a binder.

Next, by firing the granulated secondary particles, the raw material particles (1) to (3) contained in the secondary particles are sintered. As a result, the raw material particles can be firmly bonded (sintered) to each other. In this granulation 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 the contact points with each other, and the granulated raw material particles are sintered while maintaining the granulated shape. The binder disappears during sintering. In a system using spacer particles, the spacer particles also disappear by firing. Thereby, a powder material composed of particles in the form of secondary particles in which the primary particles are sintered can be obtained. In this powder material, the primary particles may have substantially the same dimensions and shape as the raw material particles, or the raw material particles may be grown and bonded by firing.

In the above manufacturing process, in the state of the granulated particles, the raw material particles and the binder are in a uniform mixed state, and the raw material particles are bound by the binder to form the mixed particles. In a system using spacer particles, the raw material particles and the spacer particles are bound together by a binder in a uniform mixed state to form mixed particles. Then, when the mixed particles are fired, the binder (and spacer particles) disappear (burn out), and the raw material particles are sintered, so that the secondary particles in the form in which the primary particles are bonded are formed. It is formed.

At the time of sintering, depending on the composition and size of the raw material particles, a part of the raw material particles may become a 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 raw material particles of the starting material. The size and ratio of the average particle diameters of these secondary particles and primary particles can be appropriately designed according to the desired morphology of the secondary particles.

In the above manufacturing process, the concentration of the raw material particles of the spray liquid to be adjusted is preferably 10 to 40% by mass. Examples of the binder to be added include carpoxymethylcellulose, polyvinylpimouth lidone, polyvinylpimouth lidone and the like. The binder to be added is preferably adjusted at a ratio of 0.05 to 10% by mass with respect to the mass of the raw material particles. The environment for firing is not particularly limited, but may be in the air, vacuum, or an inert gas atmosphere, and sintering is preferably performed at a temperature of 600 ° C. or higher and 1600 ° C. or lower. In particular, when spacer particles made of an organic material or the like, a binder or the like are used, sintering may be performed in an atmosphere in which oxygen is present for the purpose of removing the organic material in the granulated particles. If necessary, the produced secondary particles may be crushed and classified.

(Manufacturing method of 3D model)
The powder material obtained as described above can be applied to various laminated moldings (for example, LMD, SLM, EBM, etc.). As an example of a method for manufacturing a three-dimensional model, powder layered manufacturing will be described by taking the case where the select laser melting method (SLM) is adopted as an example. The method for manufacturing a three-dimensional model disclosed herein includes the following steps.
(A) Step of supplying powder material (for example, granulated sintered powder) to the laminated area of the laminated molding apparatus (B) Flattening the supplied powder material with a wiper or the like so as to be uniformly and thinly deposited on the laminated area. Step of forming a thin layer by forming (C) A step of solidifying the powder material by giving a means for joining and sintering the powder material to the formed thin layer of the powder material (for example, irradiating a laser beam). (D) A step (E) of supplying a new powder material on the solidified powder material and laminating the steps (B) to (D) after the above step (A) to obtain a three-dimensional model. ) Step of heat-treating the obtained three-dimensional model in a reduced pressure atmosphere (F) Hot isotropic pressing (HIP: Hot Isostatic Pressing) is performed on the three-dimensional model that has been heat-treated in a reduced pressure atmosphere. Step to be applied The "solidification" in the step (D) includes directly bonding the secondary particles constituting the powder material by melting and solidifying to fix the shape into a predetermined cross-sectional shape.

The laser metal deposition method (LMD) is a technique in which a powder material is provided to a desired part of a structure, and the powder material is melted and solidified by irradiating the desired part with a laser beam to build up the part. Is. By using this technology, for example, when physical deterioration such as wear occurs in a structure, a material or a reinforcing material constituting the structure is supplied as a powder material to the deteriorated part, and the powder thereof. By melting and solidifying the material, it is possible to build up the deteriorated part and the like.

The SELECT laser melting method (SLM) is an operation in which a laser beam is scanned through a powder layer on which a powder material is deposited based on slice data created from a design drawing, and the powder layer is melted and solidified into a desired shape. This is a technique for forming a three-dimensional structure by repeatedly laminating each cross section (1 slice data). In addition, the electric beam melting method (EBM) is three-dimensional by selectively melting and solidifying the powder layer using an electron beam based on slice data created from 3D CAD data and laminating them. It is a technology to create a simple structure. Each technique includes a step of supplying a powder material, which is a raw material of a structure, to a predetermined modeling position.

FIG. 1 is a schematic view showing a configuration example of a laminated modeling apparatus 100 for executing a method for manufacturing a modeled object according to an embodiment of the present invention. As shown in FIG. 1, the laminated modeling apparatus 100 includes a modeling area 10 which is a space where laminated modeling is performed, a stock 12 for storing powder material, and a wiper which assists the supply of powder material to the modeling area 10. 11 and solidification means (energy supply means such as a laser oscillator) 13 for solidifying the powder material are provided.

The modeling area 10 has a modeling space surrounded by an outer circumference below the modeling surface, and is provided with an elevating table 14 that can be raised and lowered in the modeling space. The elevating table 14 can be moved downward by a predetermined thickness Δt1, and a target model is formed on the elevating table 14. The stock 12 is arranged near the modeling area 10, and is provided with, for example, a bottom plate (elevating table) that can be raised and lowered by a cylinder or the like in a storage space surrounded by an outer circumference. The stock 12 supplies (extrudes) a predetermined amount of powder material to the molding surface by raising the bottom plate.

The laminated modeling apparatus 100 can execute the above steps (A) to (D). For example, the laminated modeling apparatus 100 prepares a layer of the powder material 20 having a predetermined thickness Δt1 by supplying the powder material 20 to the modeling area 10 in a state where the elevating table 14 is lowered by a predetermined thickness Δt1 from the modeling surface.
Next, the laminated modeling apparatus 100 supplies the powder material extruded from the stock 12 onto the modeling area 10 by scanning the wiper 11 on the modeling surface, and flattens the upper surface of the powder material to make a homogeneous powder. Form a layer of material 20.
Next, the laminated molding apparatus 100 applies energy to the formed first layer of the powder material 20 only in the solidified region corresponding to the slice data of the first layer via the solidifying means 13. The powder material is melted or sintered into a desired cross-sectional shape to form the first powder solidified layer 21.

Next, the laminated modeling apparatus 100 lowers the elevating table 14 by a predetermined thickness Δt1, supplies the powder material again, and smoothes it with the wiper 11 to form the second layer powder material 20. Then, the laminated molding apparatus 100 gives a heat source through the solidifying means 13 only to the solidified region corresponding to the slice data of the powder material 20 of the second layer to solidify the powder material and solidify the powder of the second layer. The layer 21 is formed. At this time, the powder solidified layer 21 of the second layer and the powder solidified layer 21 of the first layer, which is the lower layer, are integrated to form a laminated body up to the second layer.

Subsequently, the laminated modeling apparatus 100 lowers the elevating table 14 by a predetermined thickness Δt1 to form a new layer of the powder material 20, and gives a heat source via the solidifying means 13 to form the powder solidified layer 21 at a required location. .. By repeating this step, the laminated modeling apparatus 100 can manufacture a target three-dimensional modeled object.
As a means for solidifying the powder material, a method of melt-solidifying (including sintering) the powder material by applying heat with a laser beam or an electron beam is selected. For example, a carbon dioxide laser or a YAG laser can be preferably used.

In the method for manufacturing a three-dimensional model according to the present embodiment, after the step (D), the process proceeds to the step (E). In the step (E) above, the modeled three-dimensional model is heat-treated. The temperature of the heat treatment in (E) is, for example, 1200 ° C. or higher and 1500 ° C. or lower. The heat treatment pressure of the above (E) is, for example, 1 Pa or more and 100 Pa or less. By the heat treatment of (E) above, the three-dimensional model is sintered and densified.

Next, the process proceeds to the above step (F). The hot isotropic pressure pressurization (HIP) of the above (F) is a technique for pressurizing an object at high temperature and high pressure. In the present embodiment, the object is a three-dimensional model after undergoing the heat treatment of (E) above. For example, the three-dimensional model after heat treatment is air-cooled to a temperature close to room temperature and then subjected to HIP.

The heating temperature of the HIP is, for example, 1200 ° C. or higher and 1400 ° C. or lower, preferably 1300 ° C. or higher and 1400 ° C. or lower. The pressurizing pressure of the HIP is a value sufficiently higher than the pressure of the heat treatment of the above (E), and is, for example, 50 MPa or more and 180 MPa or less. The processing time of HIP is, for example, 1 hour or more and 5 hours or less. The HIP is performed in a state where the three-dimensional model is placed in an atmosphere of an inert gas such as argon (Ar).

In the three-dimensional model after the heat treatment of (E), micropores remain in the WC-Co-based cemented carbide, and the strength tends to decrease. In the present embodiment, the micropores are reduced by performing HIP after the heat treatment of (E) above. As a result, the three-dimensional model is further refined and its strength is increased.

<Effect of embodiment>
As described above, the method for manufacturing a modeled object according to the embodiment of the present invention uses a powder material for laminated modeling containing tungsten carbide and cobalt, and irradiates a laser beam or an electron beam to form a three-dimensional shape. It includes a step of forming an object, a step of heat-treating the shaped object in a reduced pressure atmosphere, and a step of subjecting the heat-treated shaped object to hot isotropic pressure processing. According to this, the micropores of the three-dimensional model that has been sintered and densified by heat treatment are reduced by HIP, and the three-dimensional model is further densified. As a result, it is possible to manufacture a three-dimensionally shaped object that is dense and has high hardness. The reduced pressure atmosphere is a pressure lower than the atmospheric pressure, and means, for example, a vacuum or a pressure close to a vacuum.

The powder material according to the embodiment of the present invention is a powder material for laminated molding used for producing a three-dimensional shaped product by irradiating a laser beam or an electron beam, and comprises tungsten carbide and cobalt. , Titanium carbide, and the content of titanium carbide is 1% by mass or more and 20% by mass or less. According to this, the titanium carbide (TiC) reacts with the tungsten carbide (WC) to become the tungsten titanium carbide (WTC) when the laminated molding is performed using the laser light or the electron beam. Since WTIC is a part of the composition of the WC-Co-based cemented carbide, a WC-Co-based cemented carbide having higher hardness can be obtained. Further, carbon (C) is supplied from the titanium carbide to the tungsten carbide when laminating modeling is performed using a laser beam or an electron beam. As a result, a WC-Co-based cemented carbide in which the formation of the η phase (fragile phase) is suppressed can be obtained.

In this embodiment, the powder material does not have to contain titanium carbide. In the method for producing a modeled object according to the present embodiment, even when the powder material does not contain titanium carbide, the HIP of the above (F) is performed after the heat treatment of the above (E) to obtain a dense and high hardness. It is possible to manufacture a three-dimensional shaped object.

The present invention will be described in more detail with reference to the following examples and comparative examples. However, the technical scope of the present invention is not limited to the following examples.
<Example 1>
(Manufacturing method of powder material)
As raw material powders, tungsten carbide (WC) powder having an average particle size of 0.76 μm, cobalt (Co) powder having an average particle size of 1.30 μm, and titanium carbide (TiC) powder having an average particle size of 0.6 μm. Prepared.
Each of the prepared raw material powders was blended in the ratio shown in Table 1 described later to obtain a blended powder (in the form of primary particles). The obtained compounded powder was wet-mixed and then granulated by a spray dryer. The obtained granulated powder was sintered to prepare a granulated sintered powder (in the form of secondary particles). The obtained granulated sintered powder was classified with a sieve having an opening of 25 μm. The average particle size, bulk density, and granule strength of each of the obtained granules after classification were measured. Table 1 shows the average particle size, bulk density, granule strength, and chemical composition of each granule after classification.

The "average particle size" of the primary particles is the particle size at an integrated value of 50% in the volume-based particle size distribution measured by a particle size distribution measuring device based on the laser diffraction / scattering method (50% volume average particle size; D50). )It was adopted. For powder having an average particle diameter of less than 1 μm (tungsten carbide powder), a value calculated as the diameter of spherical particles (corresponding diameter to a sphere) calculated from the specific surface area was adopted. The average particle size (Dave) of the primary particles can be obtained based on the formula: Dave = 6 / (ρSm) when the specific surface area of the raw material powder is Sm and the density is ρ. The specific surface area, for example, a specific surface area measuring apparatus (Micromeritics Inc., FlowSorbII 2300) using, from the gas adsorption amount of _{N 2} or the like which is measured by the continuous flow method, be a value calculated by the BET method it can. This specific surface area measurement can be performed according to the "method for measuring the specific surface area of powder (solid) by gas adsorption" specified in JIS Z8830: 2013 (ISO9277: 2010).

The "average particle size" of the secondary particles is the particle size at an integrated value of 50% in the volume-based particle size distribution measured by a particle size distribution measuring device based on the laser diffraction / scattering method (50% volume average particle size; D50). )It was adopted.
For the bulk density, a value measured according to the metal powder-apparent density measuring method specified in JIS Z2504: 2012 was adopted. Specifically, the bulk density was calculated by measuring the mass of the powder when a container having a predetermined capacity was filled in a naturally filled state with the powder that naturally flows out from an orifice having a diameter of 2.5 mm. For the measurement of bulk density, the value measured using a JIS bulk specific gravity measuring instrument for metal powder (manufactured by Tsutsui Rikagaku Kikai Co., Ltd.) was adopted.

For the granule strength, the value of the breaking strength of the granule particles measured using an electromagnetic force loading type compression tester was adopted. Specifically, the arithmetic average value of the fracture strength measured using a microcompression test device (manufactured by Shimadzu Corporation, MCT-500) for any 10 or more granulated sintered powders constituting the powder material. , Adopted as granule strength. Regarding the granulated sintered powder, when the critical load obtained in the compression test is L [N] and the average particle size is d [mm], the fracture strength σ [MPa] of the granulated sintered powder is Formula: Calculated by σ = 2.8 × L / π / d2.

(How to model a three-dimensional model)
Using the above powder material, a laminated modeling device (product name: ProX DMP200, manufactured by 3D System) irradiates the powder material laid flat with laser light, melts it layer by layer, and repeats this process to create three dimensions. Manufactured a model. At this time, the output was 300 W, the scanning speed was 300 mm / s, the pitch width was 0.1 mm, and the stacking thickness was 30 μm. After modeling, the relative density (%), Rockwell hardness (HRA), and anti-folding force (MPa) of the three-dimensional model were measured. This measured value was designated as Comparative Example 1. The relative density is an index indicating which state is between the densest state and the sparser state. The bending force is a physical property value indicating the strength against bending. The bending force may be called bending strength.

Next, the three-dimensional model was heat-treated. The conditions of the heat treatment are a reduced pressure atmosphere (10 Pa), a heating temperature of 1500 ° C., and a heating time of 2 hours (continuous). After the heat treatment, the relative density (%) of the three-dimensional model, the Rockwell hardness (HRA), and the bending force (MPa) were measured. This measured value was designated as Comparative Example 2.
Next, the three-dimensional model after the heat treatment was subjected to hot isotropic pressure pressurization (HIP). The conditions of HIP are an argon (Ar) gas pressurized atmosphere (100 MPa), a heating temperature of 1380 ° C., and a heating time of 4 hours (continuous). After HIP, the relative density (%) of the three-dimensional model, the Rockwell hardness (HRA), and the bending force (MPa) were measured. This measured value was used as the evaluation result of Example 1.
(Evaluation)
Table 2 shows the evaluation results of Example 1 and Comparative Examples 1 and 2.

As shown in Table 2, it was confirmed that the Rockwell hardness was lowered when the three-dimensional modeled object after modeling was heat-treated. Further, it was confirmed that when HIP was applied to the three-dimensional model after the heat treatment, the Rockwell hardness was increased. It was confirmed that the three-dimensional modeled product after HIP (Example 1) had higher Rockwell hardness than that after modeling and heat treatment.
FIG. 2 is a SEM (Scanning Electron Microscope) image showing an enlarged cross section of a three-dimensional model (Comparative Example 2) after heat treatment. FIG. 3 is an enlarged SEM image showing a cross section of the three-dimensional modeled object (Example 1) after HIP.

In FIGS. 2 and 3, the white part is tungsten carbide (WC) and the black part is cobalt (Co). The gray part is tungsten titanium carbide (WTC). As can be seen by comparing FIGS. 2 and 3, the tungsten carbide is present in a fibrous form in the three-dimensional model after heat treatment, whereas the tungsten carbide is present in granular form in the three-dimensional model after HIP. doing. In the three-dimensional model after HIP, tungsten titanium carbide is uniformly distributed and the overall hardness is high.

<Example 2>
(Manufacturing method of powder material)
As raw material powders, a tungsten carbide (WC) powder having an average particle size of 0.76 μm and a cobalt (Co) powder having an average particle size of 6.72 μm were prepared. In Example 2, the only difference from Example 1 is that the powder material does not contain titanium carbide (TiC). Each of the prepared raw material powders was blended in a proportion of 17% by mass of cobalt and 83% by mass of tungsten carbide to obtain a blended powder (in the form of primary particles).
Subsequent steps are the same as in Example 1. That is, the obtained compounded powder was wet-mixed and then granulated by a spray dryer. The obtained granulated powder was sintered to prepare a granulated sintered powder (in the form of secondary particles). The obtained granulated sintered powder was classified with a sieve having an opening of 25 μm.

(How to model a three-dimensional model)
Using the above powder material, the powder material laid flat was irradiated with laser light by a laminated molding apparatus to be melted layer by layer, and this process was repeated to manufacture a three-dimensional modeled product. At this time, the output was 300 W, the scanning speed was 300 mm / s, the pitch width was 0.1 mm, and the stacking thickness was 30 μm. After modeling, the relative density (%), Rockwell hardness (HRA), and anti-folding force (MPa) of the three-dimensional model were measured. This measured value was designated as Comparative Example 3.
Next, the three-dimensional model was heat-treated. The conditions of the heat treatment are a reduced pressure atmosphere (10 Pa), a heating temperature of 1500 ° C., and a heating time of 2 hours (continuous). After the heat treatment, the relative density (%) of the three-dimensional model, the Rockwell hardness (HRA), and the bending force (MPa) were measured. This measured value was designated as Comparative Example 4.

Next, the three-dimensional model after the heat treatment was subjected to hot isotropic pressure pressurization (HIP). The conditions of HIP are that the heating temperature is 1380 ° C. and the heating time is 4 hours (continuous) in a pressurized atmosphere of argon (Ar) gas (100 MPa). After HIP, the relative density (%) of the three-dimensional model, the Rockwell hardness (HRA), and the bending force (MPa) were measured. This measured value was used as the evaluation result of Example 2.
(Evaluation)
Table 3 shows the evaluation results of Example 2 and Comparative Examples 3 and 4.

As shown in Table 3, even when the raw material powder contains tungsten carbide (WC) powder and cobalt (Co) powder and does not contain titanium carbide (TiC), HIP is applied to the three-dimensional model after heat treatment. It was confirmed that when applied, the Rockwell hardness increased. It was confirmed that the three-dimensional modeled product after HIP (Example 2) had higher Rockwell hardness than that after modeling and heat treatment.
FIG. 4 is an enlarged SEM image showing a cross section of the three-dimensional modeled object (Example 2) after HIP. In FIG. 4, the white part is tungsten carbide (WC) and the black part is cobalt (Co). In Example 2, the amount of tungsten carbide is large and uniformly distributed, and the overall hardness is high.

10 Modeling area 11 Wiper 12 Stock 13 Solidification means 14 Lifting table 20 Powder material 21 Powder solidification layer

Claims (6)

A process of forming a three-dimensional model by irradiating a laser beam or an electron beam with a powder material for laminated modeling containing tungsten carbide and cobalt.
A step of heat-treating the modeled object in a reduced pressure atmosphere,
A method for producing a modeled object, which comprises a step of subjecting the heat-treated object to hot isotropic pressure processing. The method for producing a model according to claim 1, wherein the powder material contains titanium carbide. The method for producing a modeled product according to claim 2, wherein the content of the titanium carbide in the powder material is 1% by mass or more and 20% by mass or less. The method for producing a modeled object according to any one of claims 1 to 3, wherein the heating temperature of the hot isotropic pressure processing is 1200 ° C. or higher and 1400 ° C. or lower. The method for producing a modeled object according to any one of claims 1 to 4, wherein the pressurizing pressure of the hot isotropic pressurization process is 50 MPa or more and 180 MPa or less. The method for producing a modeled object according to any one of claims 1 to 5, wherein the processing time of the hot isotropic pressure processing is 1 hour or more and 5 hours or less.

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