Shaping methods

Abstract

This invention provides a novel method for obtaining a desired shape made of oxides, using commonly available oxide particles (powder). [Solution] The present invention is a molding method comprising a coating step of applying a slurry in which oxide particles are dispersed to form a coating layer, and an irradiation step of irradiating the coating layer with a high-energy beam to melt and solidify the oxide particles to obtain a molded object. Instead of the coating layer, a sheet in which oxide particles are held together by a binder may be used (arrangement step). The binder is made of, for example, an organic material (resin), but this organic material disappears (burns away) in the irradiation step. In other words, binder residues and the like hardly affect the composition and structure of the molded object made of stable oxides. The oxide particles are made of, for example, zirconia or alumina.

Description

Technical Field

[0006]

[0001] The present invention relates to a method for obtaining a shaped object made of an oxide, etc.

Background Art

[0002] Different from subtractive manufacturing (cutting, grinding, cutting, etc.) and forming manufacturing (casting, forging, pressing, etc.), additive manufacturing (AM: Additive Manufacturing) that can obtain a desired shaped object without the need for a dedicated mold or a large machine tool has attracted attention.

[0003] Typical examples thereof are the powder bed fusion method (PBF: powder bed fusion) and the directed energy deposition method (DED: Directed Energy Deposition) in which a raw material powder (including a mixed powder) is irradiated with a high-energy beam (a heat source such as a laser or an electron beam) to obtain a shaped object in which the raw material powder is melted and solidified (bonded).

[0004] Most of the raw material powders are highly fluid metal powders composed of substantially spherical particles produced by an atomization method or the like. On the other hand, it is rare for ceramic (especially oxide) powders to be directly used in PBF or the like. This is because high-melting-point ceramic powders are difficult to produce by the atomization method and usually consist of irregularly shaped (acicular, angular, etc.) particles and have low fluidity.

[0005] Under such circumstances, descriptions regarding ceramic powders for additive manufacturing are found in, for example, the following documents.

Prior Art Documents

Patent Documents

[0008] Patent Document 1 proposes a granulated powder consisting of secondary ceramic particles. While the granulated powder improves fluidity, it consists of particles that contain many voids, which causes it to shrink during additive manufacturing, making it prone to significant distortion and cracking in the fabricated object.

[0009] Non-patent documents 1 and 2 relate to spherical secondary particles obtained by freeze-drying a slurry containing ceramic particles by dropping it into liquid nitrogen through an orifice. Such particles are porous, easily crushed, have high manufacturing costs, and low productivity. It is difficult to use powders made from such secondary particles in industrial additive manufacturing.

[0010] This invention has been made in view of these circumstances, and aims to provide a new method for obtaining a molded body made of oxide using oxide particles, which are a typical example of ceramic particles. [Means for solving the problem]

[0011] Through diligent research, the inventors have conceived and realized a method for obtaining fabricated objects by melting and solidifying oxide particles via a coating layer or sheet, a departure from conventional powder bed fusion manufacturing. By further developing this result, the present invention described below has been completed.

[0012] 《Modeling method》 (1) One aspect of the present invention is a molding method comprising, for example, a coating step of applying a slurry in which oxide particles are dispersed to form a coating layer, and an irradiation step of irradiating the coating layer with a high-energy beam to melt and solidify the oxide particles in order to obtain a molded object.

[0013] (2) Another aspect of the present invention is a fabrication method comprising, for example, a placement step of arranging a sheet consisting of oxide particles and a binder that holds the oxide particles together, and an irradiation step of irradiating the sheet with a high-energy beam to melt and solidify the oxide particles and obtain a fabricated product.

[0014] According to the molding method of the present invention, it is possible to obtain a molded object made of oxide in a desired shape using readily available oxide particles (powder), without having to use granulated or other secondary particles.

[0015] 《Sculpture》 The present invention may be understood as a molded object obtained by the molding method described above.

[0016] "others" In this specification, "x~y" includes the lower limit x and upper limit y unless otherwise specified. Any numerical value included in the various numerical values ​​or ranges described herein may be used to create new lower or upper limits, such as a range "a~b". In this specification, "x~yμm" means xμm~yμm. The same applies to other unit systems. [Brief explanation of the drawing]

[0017] [Figure 1] This is a slurry in which oxide particles are dispersed. [Figure 2] This is a coating layer formed by applying that slurry onto a film. [Figure 3] This is a sheet obtained by peeling the coating layer from the film. [Figure 4] This is a fabricated object (sample 1) obtained by irradiating a small piece cut from the sheet with a laser. [Figure 5] These are SEM images of the fabricated object and Zr distribution images obtained using EDX. [Figure 6] It is a coating layer obtained by applying the slurry to a base plate. [Figure 7] It is a shaped object (Sample 2) obtained by irradiating a section (square region) of the coating layer with a laser. [Figure 8] It is a SEM image of the shaped object and a distribution image of Zr by EDX.

Embodiments for Carrying Out the Invention

[0018] One or more components arbitrarily selected from this specification can be added to the components of the present invention. The content described in this specification is not limited to "methods" (such as shaping methods and manufacturing methods), but also appropriately applies to "objects" (such as shaped objects). Components related to methods can become components related to objects.

[0019] 《Oxide Particles》 The oxide particles (powder) are appropriately selected in terms of component composition, particle shape, particle size, blending, etc. The oxide powder may be composed of single-species oxide particles or a plurality of species of oxide particles (mixed particles).

[0020] The oxide particles are composed of, for example, oxides of Al, Ti, Zr, Si, or Y, etc. The oxide does not matter in terms of the oxidation number of the (semi) metal element. Representative examples are alumina, titania, zirconia, silica, yttria, etc. These oxides are stable ceramics even at high temperatures and are easily available. By using particles (powder) composed of such oxides, a desired shaped object composed of oxides can be efficiently produced at a relatively low cost. Also, shaping is possible not only in an inert atmosphere but also in an oxygen-containing atmosphere (such as an air atmosphere).

[0021] The oxide particles are preferably of a size suitable for the thickness of the coating layer or sheet (regardless of the shape, it is referred to as "particle size"). For example, oxide powder (particles) having a particle size of about 0.1 to 20 μm, 0.3 to 15 μm, or 0.5 to 10 μm may be used.

[0022] Unless otherwise specified, the particle size is specified by the maximum length of the particle, and the particle size distribution is specified by the sieving method of the powder (reference: JIS Z 8801, Z8815, etc.). Particle size distribution: The powder with a particle size of less than x μm (-x μm or <x μm) consists of particles with a size (maximum particle size less than x μm) that pass through a sieve with a mesh size: x (μm). Particle size distribution: The powder with a particle size of more than y μm (+y μm or ≫y μm) consists of particles with a size (minimum particle size more than y μm) that do not pass through a sieve with a mesh size: y (μm). Particle size distribution: The powder with a particle size of y to x (y <x / μm) consists of particles that do not pass through a sieve with a mesh size: y (μm) and pass through a sieve with a mesh size: x (μm). Appropriately, the particle size distribution may be specified alternatively or complementarily using the laser diffraction / scattering method (JIS Z8825, etc.), the dynamic light scattering method, etc.

[0023] 《Coating layer / Coating process》 The coating layer is obtained by applying a slurry in which oxide particles are dispersed (coating process). The applied slurry (layer) may be dried appropriately. The coating and drying may be performed substantially simultaneously or stepwise. The drying may be heating drying or vacuum drying. The heating temperature, vacuum degree, etc. during drying may be such that they promote the evaporation or disappearance of the dispersion medium, etc. contained in the slurry. Rapid drying may cause cracks, bubbles, etc. in the coating layer. In the case of heating drying, for example, the temperature (ambient temperature, substrate temperature, etc.) may be set to about 50 to 350 °C, 100 to 300 °C.

[0024] The formation of the coating layer may be performed on the surface of the substrate or base, or on the previously formed coating layer or shaped article. By repeating the latter operation, a laminated shaped article can be obtained. The number of laminations may be selected in consideration of the size (height) of the shaped article, the thickness of the coating layer, the particle size of the oxide particles, etc.

[0025] The slurry can be any mixture in which oxide particles (powder) are uniformly dispersed. In addition to the main dispersion medium (water, aqueous solution, organic solution such as alcohol, etc.), the slurry may also contain, for example, a binder to bind the oxide particles (e.g., polyurethane, water-soluble ethylene, polyacrylic, methylcellulose, etc.), a surfactant to improve the dispersibility of the oxide particles, and a thickener to improve the coatability. The binder may be the same or different type as the one used in the production of the sheet described later.

[0026] The oxide particles should ideally be present in the entire slurry in an amount of, for example, 20-80% by volume, 30-70% by volume, or 40-60% by volume.

[0027] The method of applying the slurry is not limited, but a uniform coating or paint layer can be formed using methods such as the doctor blade method, spray method, or spin coating method.

[0028] The thickness of the coating layer is adjusted as needed, but is typically around 5-500 μm, 10-250 μm, or 20-125 μm.

[0029] Sheet / Placement Process The sheet is formed by holding oxide particles with a binder. The binder is mainly made of resin, for example. The type and properties of the resin (thermoplastic, thermosetting, crystalline, amorphous, etc.) are not limited, but it is preferable that it disappears (including burning out) in the subsequent irradiation process. Examples of such resins include polyurethane, epoxy, water-soluble ethylene, polyacrylic, and methylcellulose. In addition to the binder (resin), the sheet may also contain dispersants, release agents, and defoaming agents. Since the oxide particles remain stable even after irradiation with a high-energy beam, the residue (organic matter, etc.) of the binder (similar to the slurry mentioned above) after the irradiation process usually has little effect on the composition and structure of the fabricated object.

[0030] The sheet may be formed by coating (applying, drying, etc.) the slurry described above, or by molding a mixture (kneaded) of oxide powder and binder by injection, compression, etc. The size of the oxide particles contained in the sheet and the thickness of the sheet may be adjusted as appropriate, but can be considered in the same way as the coating layer described above.

[0031] Similar to the coating layer, the sheet may be placed on the surface of the substrate or base, or on top of the previous sheet or printed object. Repeating the latter process yields a layered object. The number of layers should be selected considering the size (height) of the object, the thickness of the sheet, the particle size of the oxide particles, etc.

[0032] The placement process may involve simply placing the sheet in a predetermined position, securing it with tape or jigs, or using a pressure difference (reduced pressure atmosphere) to make the sheet adhere tightly to the object to be molded (base, base, molded object, etc.).

[0033] High-energy beam / irradiation process The fabricated object is obtained by melting and solidifying oxide particles contained within a coating layer or sheet that has been irradiated with a high-energy beam (irradiation process).

[0034] High-energy beams are, for example, lasers or electron beams with high energy density (fluence). Lasers are selected and adjusted as appropriate, depending on their type (amplification medium, excitation source, optical resonator, etc.), output, energy density, irradiation area, overlap rate, etc. Lasers can be continuous-wave lasers or pulsed lasers. One example of a laser is a fiber laser (a type of solid-state laser) that uses an optical fiber (for example, a double-clad fiber doped with rare earth elements in the core) as the amplification medium. The irradiation process may be performed using a high-energy beam source located in a powder bed fusion (PBF) or directed energy deposition (DED), etc.

[0035] Depending on the beam irradiation range and trajectory, the desired shape (or area) is formed across the entire or localized area of ​​the coating layer or sheet. By repeating the coating or placement process and the irradiation process, three-dimensional additive manufacturing is also possible. In addition, the coating process and placement process may be mixed or coexist during additive manufacturing.

[0036] 《Application》 The form, function, and application of the fabricated object are not restricted. According to the fabrication method of the present invention, for example, an oxide film with excellent corrosion resistance, heat resistance, insulation, and non-magnetic properties can be formed on the surface of a substrate, or molds (die casting, forging, sliding), bearings, machining tools (cutting tools, excavators), gas turbine blades, etc., made of oxides can be fabricated. [Examples]

[0037] The appearance and structure of fabricated objects (samples) using oxide powder were evaluated. The present invention will be described in more detail based on such specific examples.

[0038] [First Embodiment] Sample preparation (1) Slurry Zirconia (ZrO2) powder (zirconium oxide powder manufactured by High Purity Chemical Laboratory Co., Ltd.: ZRO02PB) was prepared. This powder consisted of irregularly shaped particles (non-spherical particles), and its average particle size was approximately 1 μm.

[0039] The powder and dispersion medium (Selander DB-20, manufactured by Hi-Chem) were manually stirred for about 5 minutes to obtain a homogeneous slurry. The slurry, which was placed in a container, is shown in Figure 1. Alternatively, a commercially available mixing machine or defoaming device may be used for stirring.

[0040] The amount of powder was set to 50% by mass of the total slurry (powder + dispersion medium). The dispersion medium contained a binder whose main component was a polyurethane resin, as well as a thickener and a defoaming agent.

[0041] (2) Coating (sheet manufacturing) The slurry described above was applied to a film (base) made of plate glass using the doctor blade method (coating process). Figure 2 shows the state after coating.

[0042] The resulting layered slurry was dried by holding it in an atmospheric environment (room temperature) for 24 hours (drying step). This yielded a solidified coating layer on the film. Figure 3 shows the coating layer (sheet) peeled from the film. This sheet measured approximately 75 mm × 90 mm × 100 ± 20 μm in thickness.

[0043] (3) Placement Small pieces (10mm x 10mm) cut from the sheet were placed on an iron base plate (substrate) (placement process). At this time, the outer circumference of the small pieces was secured to the base plate with aluminum tape.

[0044] (4) Irradiation (shaping) Each small piece was irradiated with laser light using a PBF (Print-Blower) system (2Create, manufactured by 2oneLab). The irradiation conditions were as follows: laser wavelength: 1070 nm, beam diameter (focus diameter): 40 μm, power output: 200 W, scanning speed: 1000 mm / sec, hatch spacing: 20 μm, layer thickness: 25 μm (equivalent to the feed amount in the thickness direction during fabrication), and atmosphere: Ar gas atmosphere (room temperature). The resulting film-like fabricated object (sample 1) is shown in Figure 4.

[0045] "evaluation" The fabricated object was observed and analyzed using a scanning electron microscope with energy-dispersive X-ray analysis (SEM-EDX). The obtained SEM and EDX images are shown in Figure 5.

[0046] As is clear from Figure 5, no residual or missing zirconia particles were observed, and it was confirmed that a homogeneous coating made of molten and solidified ZrO2 was fabricated with almost no cracking. Furthermore, impurities other than Zr and O (such as C) were hardly observed in the fabricated object.

[0047] [Second Example] Sample preparation (1) Coating A coating layer was formed by directly applying a slurry onto an iron base plate (coating process). The slurry preparation and coating (application and drying) were carried out in the same manner as in the first example. In this example, the application and drying process was repeated twice to achieve a target coating layer thickness of approximately 50 μm. The appearance of the resulting coating layer is shown in Figure 6.

[0048] (2) Irradiation (formation) Using the PBF apparatus described above, a section (square area: 10 mm × 10 mm) created in a part of the coating layer was irradiated with laser light. The irradiation conditions were: laser wavelength: 1070 nm, beam diameter (focusing diameter): 40 μm, output: 200 W, scanning speed: 1000 mm / sec, hatch spacing: 10 μm, layer thickness: 50 μm (equivalent to the feed amount in the thickness direction during fabrication), and atmosphere: room temperature Ar atmosphere. The resulting film-like fabricated object (sample 2) is shown in Figure 7.

[0049] "evaluation" Similar to sample 1, the fabricated object was observed and analyzed using SEM-EDX. The obtained SEM and EDX images are shown in Figure 8.

[0050] As is clear from Figure 8, a good coating consisting of molten and solidified ZrO2 was obtained, similar to sample 1 (Figure 5). The spots seen in the SEM image are sputter generated during the fabrication process. Furthermore, since sample 2 is thicker than sample 1, no cracks were observed at all. In sample 2 as well, impurities other than Zr and O (such as C) were hardly observed in the fabricated object.

[0051] From the above, it has been confirmed that, according to the molding method of the present invention, a good molded product made of oxide is obtained using oxide powder consisting of primary particles.

Claims

1. A coating process in which a slurry containing dispersed oxide particles is applied to form a coating layer, An irradiation step to obtain a fabricated object by irradiating the coating layer with a high-energy beam to melt and solidify the oxide particles, A molding method comprising the following features.

2. The molding method according to claim 1, wherein the coating layer is obtained by drying the slurry after applying it.

3. A placement step involves arranging a sheet consisting of oxide particles and a binder that holds the oxide particles together. An irradiation step to obtain a fabricated object by irradiating the sheet with a high-energy beam to melt and solidify the oxide particles, A molding method comprising the following features.

4. The molding method according to claim 3, wherein the sheet is obtained by applying a slurry containing the oxide particles and the binder and then drying it.

5. The molding method according to claim 3 or 4, wherein the binder is made of an organic material.

6. The molding method according to any one of claims 1 to 4, wherein the oxide particles consist of one or more oxides of Al, Ti, Zr, Si, or Y.

7. The molding method according to any one of claims 1 to 4, wherein the oxide particles have a particle size of 20 μm or less.

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