Method for manufacturing ceramic articles

Abstract

To provide a ceramic article production method, in ceramic article production by an additional production technique, capable of suppressing the separation of a molded object made into a ceramic article from a base material or its breakage and stably producing a ceramic article.SOLUTION: A ceramic article production method has a process in which powder essentially consisting of laid ceramic is irradiated with an energy beam to sinter or melt and solidify the powder so as to form a solidified part, so that a ceramic article is obtained, and has: a first step in which a first layer comprising a part obtained by mixing a component derived from the base material with a component derived from the powder is formed on the base material; a second step in which a second layer having a relative density lower than that of the ceramic article and thicker than the first layer is formed on the first layer; and a third step in which a structure made into the ceramic article is molded on the second layer.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] This invention relates to a method for producing ceramic articles using a powder mainly composed of ceramics. [Background technology]

[0002] In applications requiring the rapid creation of prototypes or the manufacture of small quantities of parts, a technology that uses an energy beam to bond material powders and directly fabricate desired objects, particularly three-dimensional objects, is becoming widespread.

[0003] Patent Document 1 describes a method for manufacturing articles using a so-called powder bed fusion method. In this method, a powder layer made of material powder is formed on a substrate, and a series of steps are repeatedly performed in which an energy beam is selectively irradiated onto the portion of the powder layer corresponding to the cross-section of the article to sinter the powder. Through the repetition of these steps, the previously sintered portion and the later sintered portion are joined to each other, and finally, the desired article is obtained by removing the unsintered powder and unwanted parts of the sintered portion.

[0004] Additive manufacturing technologies using direct fabrication methods such as powder bed fusion eliminate the need for molds or machining from ingots, allowing for the direct fabrication of three-dimensional objects from powder. This enables the rapid and highly accurate production of three-dimensional objects. Furthermore, because fabrication can be based on three-dimensional shape data created using design tools such as 3D CAD (Computer-Aided Design), design modifications are easy, and it offers the advantage of being able to manufacture complex and intricately shaped three-dimensional objects.

[0005] Regarding additive manufacturing technology, its application to ceramic materials has been discussed and many efforts have been reported, building upon its success in metal fabrication. However, because ceramics have lower thermal conductivity than metals, significant thermal stress occurs during solidification after melting by energy beam irradiation. Therefore, when manufacturing ceramic articles from powders primarily composed of ceramics using additive manufacturing technology, delamination of the fabricated object from the substrate or destruction of the fabricated object can occur.

[0006] Under these circumstances, Patent Document 1 describes a technique for strengthening the bond at the interface between the substrate and the fabricated object by irradiating the first powder layer on the substrate with a sharp-shaped energy beam, thereby melting the first powder layer and the substrate surface. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2019-081358 [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] However, in the technology described in Patent Document 1, depending on the shape of the fabricated object, the thermal stress during the formation of the fabricated object may exceed the bonding force at the joint between the substrate and the fabricated object, resulting in continuous fracture (delamination) at the joint.

[0009] This invention was made to address the aforementioned problems and provides a method for manufacturing ceramic articles that suppresses peeling or fracture of the molded object that becomes a ceramic article from the substrate in additive manufacturing technology, thereby enabling the stable production of ceramic articles. [Means for solving the problem]

[0010] The method for manufacturing a ceramic article according to the present invention is a method for manufacturing a ceramic article, which irradiates a powder mainly composed of a laid ceramic with an energy beam to sinter, melt and solidify the powder, and forms a solidified part to obtain a ceramic article, a first step of forming a first layer including a portion where a component derived from a base material and a component derived from the powder are mixed on the base material, a second step of forming a second layer having a relative density smaller than that of the ceramic article and thicker than the first layer on the first layer, a third step of shaping a structure to be the ceramic article on the second layer, and is characterized by having the above.

Effect of the Invention

[0011] According to the present invention, in the manufacture of a ceramic article by an additive manufacturing technique, there is provided a method for manufacturing a ceramic article that suppresses peeling or breakage of a shaped object to be a ceramic article from a base material and enables stable manufacture of the ceramic article.

Brief Description of the Drawings

[0012] [Figure 1] ​​​​​​​​​​​​​​​​​​

[0013] Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited to these embodiments or specific examples, and can be modified within the scope of the technical idea of the present invention.

[0014] The present invention is preferably used in shaping using a powder bed fusion method (also referred to as a powder bed method) and a directional energy deposition method (so-called cladding method) for building up a shaping material, among additive manufacturing techniques by a direct shaping method. The present invention provides a method for manufacturing a ceramic article by an additive manufacturing technique, which can suppress the detachment or breakage of a shaped object to be a ceramic article from a substrate, and enables the stable manufacture of the ceramic article.

[0015] Hereinafter, the manufacture of a ceramic article by the powder bed fusion method will be described as an example. However, the method for manufacturing a ceramic article according to the present invention is not limited thereto. For example, a ceramic article may be manufactured by the directional energy deposition method. When the directional energy deposition method is used, a layer made of powder is not formed, and material powder is spray-fed from a nozzle to the irradiation position of an energy beam, and the material powder is built up on a layer formed by sintering or melting and solidifying a substrate or powder.

[0016] (Three-dimensional shaping apparatus) First, the three-dimensional shaping apparatus 100 that can be used in one embodiment of the present invention will be described with reference to FIG. 1. The three-dimensional shaping apparatus 100 has a shaping table 101, a substrate 102, a shaping container 103, a vertical movement mechanism 104, a vertical movement mechanism 105, a powder supply container 106, rollers 107, rollers 107, and a movement guide 108. Further, the three-dimensional shaping apparatus 100 further includes a laser light source 109, a scanner 110, and a condenser lens 111.

[0017] The build table 101 is a table for mounting the substrate 102 and also serves as the bottom surface of the build container 103. The build table 101 has pins (not shown) and the substrate 102 is positioned by fitting them into pin holes (not shown) on the substrate 102. Preferably, the substrate 102 is fixed to the build table 101 by screws. The substrate 102 does not necessarily have to be plate-shaped as long as it functions as a support base when forming a three-dimensional object, and the method of positioning and fixing it to the build table is not limited to this example. The build table 101 is supported so as to be movable in the vertical direction by a vertical movement mechanism 104.

[0018] A powder supply container 106, a roller 107, a movement guide 108 for moving the roller 107, a laser light source 109, a scanner 110, and a focusing lens 111 are arranged. The powder supply container 106 is positioned next to the build table 101 and contains the powder 113 for builds, and is a device for adjusting the amount of powder 113 supplied according to the thickness of the powder layer to be deposited in the build container 103. The amount of powder 113 supplied can be adjusted by the upward movement of the vertical movement mechanism 105. The roller 107 is supported by the movement guide 108 so that it can move horizontally, and moves the build powder from the powder supply container 106 to the build container 103, forming a powder layer of a predetermined thickness while leveling the surface. The laser light source 109, scanner 110, and focusing lens 111 constitute an irradiation optical system for locally and selectively irradiating the powder layer with laser light 115.

[0019] The control unit 112 is a computer for controlling the operation of the three-dimensional molding device 100, and it is equipped with a CPU, memory, storage device, I / O ports (input / output section), etc.

[0020] Memory includes random access memory (RAM) and read-only memory (ROM). Storage devices include hard disk drives, disk drives, and magnetic tape drives, and store programs that implement the processing shown in the flowchart described later.

[0021] The I / O ports are connected to external devices and networks, allowing for data input and output necessary for 3D printing to and from an external computer, for example. The data necessary for 3D printing includes shape data of the 3D object to be manufactured, information on the materials used for printing, and shape data of each sintered layer divided into multiple layers in a predetermined direction, i.e., slice data. The slice data may be received from an external computer, or it may be created by the CPU in the control unit 112 based on the shape data of the 3D object and stored in memory.

[0022] The CPU loads the program stored in the storage device into memory and executes it, thereby causing the three-dimensional molding device 100 to perform the processing steps described later.

[0023] The control unit 112 is connected to various parts such as the vertical movement mechanism 104 of the build table 101, the vertical movement mechanism 105 of the bottom surface of the powder supply container 106, the rollers 107, the laser light source 109, the scanner 110, and the focusing lens 111, and controls the operation of these parts to execute the build process.

[0024] Figure 2 shows the process flow in a method for manufacturing a ceramic article according to one embodiment of the present invention. Hereinafter, one embodiment of the present invention will be described in accordance with the flow shown in Figure 2, but the present invention is not limited in any way to the following specific example.

[0025] (Outline of the process) Based on Figures 1 and 2, the overall flow of the manufacturing method for ceramic articles according to one embodiment of the present invention will be explained, followed by a description of the characteristic features of the present invention. Each step of the manufacturing method described below is realized by the CPU loading a program stored in a storage device into memory and executing it.

[0026] First, the three-dimensional shape data of the ceramic object to be fabricated is acquired (step S1). The three-dimensional shape data of the ceramic object is input from 3D CAD or a 3D scanner via the I / O port of the control unit 112 and stored in memory.

[0027] Next, based on the three-dimensional shape data of the ceramic article, the three-dimensional shapes of the first and second layers that support the structure 114 when forming the structure 114, which will become the ceramic article, in the three-dimensional molding apparatus 100 are designed (step S2). In the present invention, the structure 114 corresponds to the ceramic article to be molded, and the first and second layers are parts added to assist in the molding of the structure 114. The first layer includes a part in which components derived from the base material 102 and components derived from the molding powder are mixed. The first layer is formed so that a part of it penetrates the base material 102 and is a structure to prevent the second layer and structure 114, which are formed sequentially on top of the first layer, from peeling off from the base material 102. The second layer is thicker than the first layer and has a lower relative density than the structure 114. The second layer is a structure to relieve the stress generated during the process of forming the structure 114 and to prevent the structure 114 from breaking or peeling off from the base material 102.

[0028] Next, information on amorphous / crystalline and porous / dense properties is added (step S3). Specifically, information is added to the three-dimensional shape data of structure 114, the first layer, and the second layer, indicating which layers have a higher proportion of amorphous or crystalline material, and which layers have a higher proportion of porous or dense material. Crystalline refers to a solid material that has a crystalline structure. Amorphous refers to a solid material that aggregates without forming crystals. Whether a material is crystalline or amorphous can be determined by X-ray diffraction, electron diffraction, etc.

[0029] As will be explained in more detail later, it is preferable to designate the first layer formed on the substrate as a layer with a high proportion of amorphous material, and the other parts as layers with a high proportion of crystalline material. It is also preferable to designate the second layer as a layer with a high proportion of porous material, and the other parts as layers with a high proportion of dense material.

[0030] The above amorphous / crystalline and porous / dense information can be added by inputting it to the control unit 112 via the I / O port. For example, the user can use a mouse to set the parts corresponding to amorphous / crystalline or porous / dense on the three-dimensional shape data of the structure 114 displayed on the display unit connected to the I / O port, with the first and second layers added to it. Alternatively, the user may select a mode in which the parts with a high proportion of amorphous or crystalline material are pre-configured, such as a mode that designates the first layer as having a high proportion of amorphous material and the other parts as having a high proportion of crystalline material. Similarly, the method for adding porous / dense information can also be configured by selecting a pre-configured mode.

[0031] The range designated as having a high proportion of amorphous material or a high proportion of crystalline material can be changed in accordance with the irradiation diameter of the laser beam 115 and the layering pitch. In particular, the range with a high proportion of amorphous material or a high proportion of crystalline material is preferably designated with a size of 100 μmφ or larger in the in-plane direction of the layering direction and the surface parallel to the substrate 102, and more preferably with a size of 200 μmφ or larger.

[0032] Next, the three-dimensional molding apparatus 100 creates slice data for each layer necessary for the three-dimensional molding apparatus to layer-form the three-dimensional object, namely the structure 114, the first layer, and the second layer (step S4).

[0033] Steps S1 to S4 may be created by the CPU of the control unit 112 based on the three-dimensional shape data of the structure 114, the first layer, and the second layer, and stored in RAM, or they may be executed on an external computer and received via an I / O port. Furthermore, if three-dimensional shape data or slice data of the structure 114 with the first and second layers added is available as molding data, each of these steps can be omitted.

[0034] Next, the substrate 102 is positioned and fixed to the three-dimensional molding apparatus 100 (step S5). The fixing of the substrate 102 may be performed before steps S1 to S4.

[0035] Next, as the first step in the present invention, a first layer is fabricated on the substrate 102 (step S6). The three-dimensional molding apparatus 100 forms one layer of powder, then irradiates the powder layer with laser light 115 according to the slice data to form a solidified portion. The formation of the powder layer and the formation of the solidified portion are repeated to fabricate the first layer. Once the fabrication of the first layer is complete, the second step in the present invention is to fabricate a second layer on the first layer in the same manner (step S7). Once the fabrication of the second layer is complete, the third step in the present invention is to fabricate a structure 114, which is the part corresponding to the ceramic article, on the second layer in the same manner (step S8). Once the fabrication of the structure 114 is complete, the substrate 102 is removed from the three-dimensional molding apparatus 100 (step S9), and the ceramic article is obtained after separating the structure 114 from the substrate 102 (step S10).

[0036] To ensure that the amorphous / crystalline and porous / dense properties differ between the first layer, the second layer, and the structure, the laser irradiation conditions for the first, second, and third steps are different. By storing the correspondence between crystalline / amorphous and porous / dense property information and laser irradiation conditions in the control unit 112 in advance, the laser irradiation conditions are adjusted by the control unit 112 according to the added crystalline / amorphous and porous / dense property information.

[0037] Next, steps S6 to S10 described above will be explained in more detail using Figures 3(a) to 3(h). Figures 3(a) to 3(h) are schematic cross-sectional views illustrating steps S6 to S10 shown in Figure 2.

[0038] First, in step S6 (first step) for forming the first layer, a powder layer 302 having a predetermined thickness is laid on the substrate 320 using a roller 352 with a material powder 301 which is a powder mainly composed of ceramics (Figure 3(a), (b)).

[0039] Furthermore, the base material 320 can be appropriately selected and used from materials such as metals and ceramics that are commonly used in the manufacture of molded objects, taking into consideration the intended use and manufacturing conditions of the molded object.

[0040] Furthermore, the method for forming the powder layer 302 is not particularly limited; the powder layer 302 can be formed while defining the layer thickness using a roller 352 or blade, as shown in Figure 3(a).

[0041] Next, a process of sintering or melting and solidifying the material powder 301 (hereinafter also abbreviated as the melting / solidifying process) (Figure 3(c)) is performed. In the melting / solidifying process, a laser beam 501 emitted from a laser beam source 500 is scanned and irradiated onto a predetermined area on the surface of the powder layer 302 based on slice data generated from the three-dimensional shape data of the first layer. While the laser beam 501 is irradiated onto the material powder 301, the material powder 301 absorbs energy, and this energy is converted into heat, causing the material powder 301 to melt. When the scanning laser beam 501 passes and irradiation ends, the melted material powder 301 is cooled and solidified. As a result, a solidified portion 307 in which the material powder 301 has melted and solidified, and an unformed portion 303 corresponding to the layer that remains in a powder state are formed (Figure 2(c)).

[0042] At this time, the output of the laser beam 501 is adjusted by the control unit 112 so that the heat applied to the material powder 301 reaches the interface between the substrate 320 and the powder layer 302, resulting in a state where the substrate 320 and the solidified portion 307 are joined together. That is, at the interface between the substrate 320 and the powder layer 302, a portion of the substrate 320 and a portion of the powder layer 302 melt and mix together due to irradiation with the laser beam 501, and then solidify. As a result, a portion is formed in which the components derived from the substrate 320 and the components derived from the material powder 301 are mixed. In this way, the substrate 320 and the solidified portion 307 formed from the powder layer 302 laid on the substrate 320 are joined together via the portion in which the components derived from the substrate 320 and the components derived from the material powder 301 are mixed.

[0043] Next, the stage 351 is lowered to a position one layer below the upper edge of the molding container 353 by the thickness of one powder layer, and a new powder layer 302 is formed to cover the solidified portion 307 and the non-molded portion 303 (Figure 2(d)). The process of forming the powder layer 302 and the melting / solidification process are repeated once or multiple times to form a first layer 300 in which the solidified portions 307 formed from each powder layer 302 are integrated.

[0044] As described above, the first layer 300 includes a portion in which components derived from the base material 320 and components derived from the material powder 301 are mixed. This results in the first layer 300 being bonded to the base material 320, making it possible to prevent the three-dimensional object from peeling off from the base material 320 during the process of forming the second layer 304 and the structure 305 on top of the first layer 300.

[0045] Next, in step S7 (second step) for forming the second layer, the laser beam irradiation conditions are adjusted by the control unit 112, and the second layer 304 is formed in the same manner as the first layer 300 (Figure 3(e)). When the laser beam 501 is irradiated onto a predetermined area of ​​the powder layer 302 formed on the first layer 300, a solidified portion that will become part of the new second layer 304 is formed. At this time, the heat supplied to the material powder 301 is made to reach the interface between the previously formed first layer 300 and the subsequently formed second layer 304, thereby bonding the previously formed first layer 300 and the newly formed second layer 304.

[0046] In the second step, the control unit 112 adjusts the irradiation conditions of the laser beam 501 so that the second layer 304 has a lower relative density than the structure 305 that is to be fabricated next. By having the second layer 304 have a lower relative density than the structure 305, the stress generated during the fabrication process of the structure 305 can be relieved, and the failure of the structure 305 and the substrate 320 can be suppressed.

[0047] The relative densities [%] of the first layer 300, the second layer 304, and the structure 305 can be calculated by dividing their respective bulk densities (weight divided by volume) by their theoretical densities. The theoretical densities can be calculated from the crystal structure. The crystal structure can be identified by performing Rietveld analysis after conducting X-ray diffraction measurements.

[0048] Furthermore, the second layer 304 is fabricated to be thicker than the first layer 300. This allows the stress generated during the fabrication process of the structure 305 to be preferentially relieved in the second layer 304 rather than the first layer 300.

[0049] Furthermore, in step S8 (the third step) for fabricating the structure, the irradiation conditions of the laser beam 501 are adjusted again by the control unit 112, and the structure 305 is formed in the same manner as the first layer 300 and the second layer 304 (Figure 3(f)).

[0050] As described above, the solidified parts formed in each powder layer join together, and a three-dimensional object is formed in which the first layer 300, the second layer 304, and the structure 305 are integrated.

[0051] Next, the material powder 301 from the non-formed portion 303 is removed (Figure 3(g)), and if necessary, the structure 305 is subjected to post-processing such as separation from the base material 320 and removal of the first layer 300 and the second layer 304 to obtain the ceramic article 306 (Figure 3(h)). The recovered material powder 301 from the non-formed portion 303 can be reused to form the powder layer 302.

[0052] Any method is acceptable for separating the structure 305 from the base material 320. The base material 320 and the structure 305 may be separated using a wire saw or the like, with the first layer 300 or the second layer 304 as the cutting point, or the base material 320, the first layer 300, and the second layer 304 may be ground with a grinding machine or the like to cut out the structure 305.

[0053] In the first step described above, in order to strengthen the bond between the first layer 300 and the substrate 320, it is preferable that the portion where the components derived from the substrate 320 and the components derived from the material powder 301 are mixed is formed to penetrate deeper into the substrate 320. Specifically, this can be adjusted by the ratio D / L of the width L (see Figure 4, details described later) in the direction perpendicular to the scanning direction and the depth D (see Figure 4, details described later) from the surface of the molten portion formed when the laser beam 501 is scanned once in one direction. In the present invention, D / L is defined as the ratio of the width (L) in the direction perpendicular to the scanning direction and parallel to the surface of the powder layer to the depth (D) of the molten portion when a laser beam is irradiated onto a powder layer of one thickness with a single line scan. The laser beam irradiation when determining the value of D / L is performed under the same laser power and scan speed as during fabrication.

[0054] If D1 / L1 is the D / L obtained under the irradiation conditions of the laser beam 501 in the first step of forming the first layer 300, it is preferable to adjust the irradiation conditions of the laser beam 501 so that D1 / L1 is greater than the D / L when the laser is irradiated to other parts. As a result, the portion of the substrate 320 that melts at the interface between the substrate 320 and the powder layer 302 for forming the first layer 300 becomes deeper. Therefore, when the melted portion solidifies due to cooling, the portion where the components derived from the substrate 320 and the components derived from the material powder 301 are mixed is formed in a state where it penetrates deeper into the substrate 320.

[0055] Specifically, D1 / L1 is preferably greater than 1.0. The specific irradiation conditions for laser beam 501 to adjust the D / L will be described later.

[0056] Furthermore, it is preferable that the crystalline content of the second layer 304 formed in the second step is greater than that of the first layer 300. Having a high crystalline content in the second layer 304 forms grain boundaries within the second layer 304, and fine cracks are formed along these grain boundaries. This effectively absorbs or relieves the stress generated by the formation of the structure 305.

[0057] The proportion of crystalline material in the first layer 300, the second layer 304, and the structure 305 can be determined as follows.

[0058] By polishing the surface or any cross-section of the first layer 300, the second layer 304, or the structure 305 to a mirror finish and using a scanning electron microscope (SEM-EBSD) to determine the crystalline and amorphous phases, a mapping image can be created. If the Kikuchi pattern is detected by the backscattered electron diffraction (EBSD) detector, it is determined to be the crystalline phase; if not detected, it is determined to be the amorphous phase. Subsequently, the proportion of each phase can be derived by calculating the area of ​​each phase. Note that if the crystalline material has a phase separation structure consisting of two or more phases, the interface between phases (phase boundary) is amorphous where the Kikuchi pattern is not detected. However, when deriving the volume ratio of the crystalline material, the volume of the phase boundary is also included in the volume of the crystalline material. The volume ratio of amorphous to crystalline material can be considered to be the same as the area ratio of amorphous to crystalline material derived using SEM-EBSD.

[0059] The proportion of crystalline material in the solidified portion can be changed by the solidification rate of the molten material, i.e., the cooling rate. Specifically, a faster cooling rate results in a region with a higher proportion of amorphous material, while a slower cooling rate results in a region with a higher proportion of crystalline material.

[0060] The cooling rate of the molten material can be adjusted by changing the D / L value mentioned above by adjusting the irradiation conditions of the laser beam 501.

[0061] Figure 4 shows the shape of the molten region formed by scanning an energy beam once in one direction over a powder layer, in a cross-section perpendicular to the beam scanning direction. As shown in Figure 4(a), when the ratio of depth D to width L, D / L, is greater than 1.0 (sharp shape in the depth direction), as indicated by the arrow at the bottom of the figure, heat in the molten region dissipates easily in all directions, leading to faster cooling and a tendency towards amorphous material. On the other hand, as shown in Figure 4(b), when the D / L is 1.0 or less (shallow and blunt (i.e., smooth) shape), as indicated by the arrow at the bottom of the figure, heat transfer is reduced and cooling is slower, leading to a tendency towards crystalline material. To increase the proportion of crystalline material in the solidified region, it is preferable that the D / L is less than 0.8, and more preferably that the D / L is less than 0.7.

[0062] In other words, D2 / L2 is the D / L obtained from the laser beam irradiation conditions in the second step for forming the second layer 304. In this case, in order for the second layer 304 to have a higher proportion of crystalline material than the first layer 300, the relationship D1 / L1 > D2 / L2 should be satisfied.

[0063] Furthermore, the cooling rate of the molten material can also be adjusted by the amount of heat input per unit area to the surface of the powder layer 302. Therefore, if you want to finely control the ratio of crystalline to amorphous material, it is preferable to adjust the laser beam output and focal position to constant values, then change the scan speed to adjust the amount of heat input per unit area.

[0064] Furthermore, in the third step, it is preferable to shape the structure 305 such that it has a higher proportion of crystalline material than the second layer 304. A higher proportion of crystalline material in the solidified portion results in a higher relative density, and consequently, higher mechanical strength. Therefore, by having a higher proportion of crystalline material in the structure 305 than in the second layer 304, the mechanical strength of the structure 305 can be made higher than that of the second layer 304. As a result, the stress generated by the shaping of the structure 305 is more likely to be absorbed preferentially by the second layer 304 than by the structure 305.

[0065] Specifically, when the D / L ratio obtained under the laser beam irradiation conditions in the third step is denoted as D3 / L3, it is preferable that the relationship D2 / L2 > D3 / L3 is satisfied.

[0066] Furthermore, it is more preferable that the above-mentioned relationship of the proportion of crystalline material between the first layer 300 and the second layer 304, and the above-mentioned relationship of the proportion of crystalline material between the second layer 304 and the structure 305, be satisfied simultaneously. That is, it is more preferable that the D / L ratios in the first, second, and third steps satisfy the relationship D1 / L1 > D2 / L2 > D3 / L3.

[0067] Furthermore, since the structure 305, which becomes a ceramic article and is formed in the third step, requires high mechanical strength and excellent durability, it is preferable that the structure 305 be formed to have a high proportion of crystalline material. Therefore, D3 / L3 is preferably 1.0 or less, more preferably 0.8 or less, and even more preferably 0.7 or less. By setting D3 / L3 to 1.0 or less, 50 volume percent or more of the structure 305 can be made crystalline. Also, by setting D3 / L3 to 0.8 or less, 70 volume percent or more of the structure 305 can be made crystalline.

[0068] As mentioned earlier, it is preferable that the D1 / L1 obtained under the irradiation conditions of the laser beam 501 in the first step of forming the first layer 300 be a larger value than the D / L when the laser is irradiated to other parts. In this case, the heat of the molten part dissipates easily in all directions and cooling is accelerated, so the proportion of amorphous material in the first layer 300 increases. In other words, it is preferable that the first layer 300 is mainly composed of amorphous material. By making D1 / L1 greater than 1.0, it is possible to make 50 volume% or more of the first layer 300 amorphous. More preferably, D1 / L1 is 1.2 or greater, in which case it is possible to make 70 volume% or more of the first layer 300 amorphous.

[0069] On the other hand, because the first layer 300 has a high proportion of amorphous material, it cannot absorb stress by self-destructing, such as by forming fine cracks inside, and there is a possibility that the first layer 300 will peel off from the substrate, so it is necessary to select an optimal layer thickness. A preferred thickness for the first layer 300 is 2000 μm or less.

[0070] The above D / L value can be adjusted by changing at least one of the following three conditions when irradiating with the laser beam 501 during the melting / solidification process. These three conditions are the distance between the surface of the powder layer 302 and the focal point of the laser beam 501, the output power of the laser beam 501, and the scanning speed of the laser beam 501.

[0071] The D / L ratio, which represents the shape of the molten region, can be adjusted by the distance between the surface of the powder layer 302 and the focal point of the laser beam 501. When the laser beam 501 is focused on the surface of the material powder, the intensity profile within the laser beam 501 becomes steeper, and the D / L ratio increases. As a result, the cooling rate increases, and the solidified region becomes an area with a high proportion of amorphous material.

[0072] A method for irradiating with a laser beam in an out-of-focus state will be described. For example, in the case of a device set to be in focus on the surface of the powder layer 302, it is possible to achieve an out-of-focus state on the surface of the powder layer 302 by changing the height of the stage in the vertical direction.

[0073] Alternatively, instead of adjusting the stage height, the energy intensity profile of the beam spot can be made smoother and the out-of-focus state achieved by driving the optical system included in the laser beam source or by changing the optical system arranged in the optical path.

[0074] Furthermore, the shape of the molten area can be adjusted by the output of the laser beam 501. Increasing the output of the irradiating laser beam 501 increases the D / L ratio and the amount of heat input per unit area. Since the cooling rate is more greatly affected by D / L than the amount of heat input per unit area, a higher output of the laser beam 501 results in a larger D / L ratio, leading to a faster cooling rate and the formation of a solidified area with a higher proportion of amorphous material.

[0075] Furthermore, the cooling rate can be adjusted by the scanning speed of the laser beam 501. When D / L is kept constant, increasing the scanning speed of the laser beam 501 reduces the amount of heat input per unit time, thus increasing the cooling rate and making the solidified portion more likely to become amorphous.

[0076] As described above, solidified portions with a high proportion of crystalline material and solidified portions with a high proportion of amorphous material can be created by changing one of the following: the output of the laser beam 501, the distance between the surface of the powder layer 302 and the focal point of the laser beam 501, or the scan speed. Furthermore, it is also possible to create solidified portions with a high proportion of crystalline material and solidified portions with a high proportion of amorphous material by combining these parameters.

[0077] If the output of the laser beam 501 is too low, the amount of heat input will be insufficient, resulting in unmelted material powder 301. Conversely, if the output of the laser beam 501 is too high, the material powder 301 may melt too much, resulting in a loss of molding accuracy. To create regions with a high proportion of crystalline material and regions with a high proportion of amorphous material while maintaining molding accuracy, it is preferable to change either the scan speed of the laser beam 501 or the distance between the surface of the powder layer 302 and the focal point of the laser beam 501, or both. Furthermore, the scan speed greatly affects the time required to form the molded object, and when adjusting the scan speed to form regions with a high proportion of crystalline material, it is necessary to reduce the scan speed, which may slow down the molding speed. Therefore, from the viewpoint of molding accuracy and molding speed, it is particularly preferable to create regions with a high proportion of crystalline material and regions with a high proportion of amorphous material solely by changing the distance between the surface of the powder layer 302 and the focal point of the laser beam 501.

[0078] The conditions for achieving a preferred D / L for forming a layer with a high proportion of crystalline material and a preferred D / L for forming a layer with a high proportion of amorphous material vary depending on the composition and particle size of the material powder, the configuration of the 3D printing apparatus, etc. Therefore, it is preferable to consider the irradiation conditions of the laser beam 501 in advance for both the case of forming a layer with a high proportion of crystalline material and the case of forming a layer with a high proportion of amorphous material.

[0079] Furthermore, when fabricating a single powder layer that contains both regions with a high proportion of amorphous material and regions with a high proportion of crystalline material, it is preferable to first form the entire region of one of the regions contained within the layer, and then change the irradiation conditions to form the entire region of the other region. In other words, in the melting / solidification process of the material powder 301 that forms the single powder layer, a first scanning step is provided in which conditions are set to form regions with a high proportion of crystalline material. Then, a second scanning step is provided in which the irradiation conditions of the laser beam 501 are set to be different from those of the first scanning step in order to form regions with a high proportion of amorphous material. The order in which the first and second scanning steps are performed does not matter. By performing fabrication in this manner, fabrication can be carried out efficiently without frequently changing the irradiation conditions of the energy beam.

[0080] The second layer 304, which is fabricated in the second step, is preferably porous from the viewpoint of absorbing or mitigating stress generated during the fabrication of the structure 305. The porous nature of the second layer 304 allows for discontinuous fracture progression, limiting the fracture phenomenon to localized damage and effectively suppressing the fracture of the base material 320 and the structure 305.

[0081] On the other hand, the first layer 300 formed in the first step and the structure 305 formed in the third step are preferably dense in order to increase their mechanical strength.

[0082] In the present invention, it is preferable that the relative density of the second layer 304 is less than 85%, and the relative density of the first layer 300 and the structure 305 is 85% or more. Furthermore, it is more preferable that the relative density of the second layer 304 is less than 75%, and even more preferable that it is less than 65%.

[0083] Furthermore, in the present invention, when the second layer 304 is made porous and the first layer 300 and structure 305 are made dense, it is preferable that the porosity of the second layer 304 is 5 volume% or more, and the porosity of the first layer 300 and structure 305 is less than 5 volume%. Here, the porosity is a value measured by the mercury injection method.

[0084] If the porosity of the second layer 304 is 5 volume% or more, fracture in the second layer 304 due to crack extension, etc., becomes discontinuous, and stress can be relieved by localized fracture only. It is more preferable that the porosity of the second layer 304 be 15 volume% or more, and even more preferable that it be 30 volume% or more. Furthermore, it is preferable that the porosity of the second layer 304 be 60 volume% or less. If the porosity of the second layer 304 is 60 volume% or less, sufficient strength can be obtained as a layer supporting the structure 305.

[0085] Porous and dense materials can be differentiated by irradiating the surface of the powder layer 302 with a laser beam 501 while changing at least one of the following four conditions: the distance between the surface of the powder layer 302 and the focal point of the laser beam 501, the scan pitch of the laser beam 501, the output power of the laser beam 501, and the scan speed of the laser beam 501.

[0086] By adjusting the distance between the surface of the powder layer 302 and the focal point of the laser beam 501, and by adjusting the relationship between the width of the molten area perpendicular to the scanning direction of the laser beam 501 and the scan pitch of the laser beam 501, molten and non-molten areas can be created separately. For example, if the width of the molten area perpendicular to the scanning direction of the laser beam 501 is made smaller than the scan pitch of the laser beam 501, molten and non-molten areas will be arranged alternately. The molten areas will then solidify, but the material powder 301 will remain unmelted / unsolidified in the non-molten areas between the molten areas, and later the material powder 301 will be removed, leaving voids in the areas corresponding to the non-molten areas. By forming voids in the layer formed by the solidified areas in this way, a porous layer can be created. Also, for example, if the width of the molten area perpendicular to the scanning direction of the laser beam 501 is made larger than the scan pitch of the laser beam 501, there will be no non-molten areas and only molten areas, so the above voids will not be formed, and a dense layer will be fabricated.

[0087] In the above, the scan pitch of the laser beam 501 may be adjusted so that the molten and non-molten areas are directly arranged alternately.

[0088] Furthermore, by adjusting the output of the laser beam 501, it is possible to create molten and non-molten areas separately. When the output of the laser beam 501 is low and the material powder 301 is not completely melted, the particles constituting the material powder 301 join with other adjacent particles while maintaining their shape. As a result, spaces are created between the particles constituting the material powder 301, creating a porous layer. When the output of the laser beam 501 is sufficiently high and the particles constituting the material powder 301 are completely melted, the particles lose their shape upon melting and solidify together as one unit without leaving any spaces, thus creating a dense layer.

[0089] Furthermore, by adjusting the scanning speed of the laser beam 501, it is possible to create both molten and unmolten areas. For example, when the scanning speed of the laser beam 501 is high, the amount of laser beam 501 irradiated per unit area decreases, and the same effect as when the output of the laser beam 501 is reduced is obtained. In other words, by increasing the scanning speed of the laser beam 501, the melting of the material powder 301 can be made incomplete, resulting in the creation of a porous layer. Conversely, by sufficiently reducing the scanning speed of the laser beam 501, a dense layer can be created.

[0090] In the second step, the solidified portion may be formed intermittently in the horizontal direction of the base material 320 to form at least a part of the second layer 304.

[0091] Figure 5 is a schematic diagram showing an example of a three-dimensional object formed on a substrate, including a second layer created by intermittently forming solidified portions horizontally on the substrate. In the example shown in Figure 5, the second layer 304, formed on the first layer 300, has intermittently formed inverted pyramid shapes, with spaces between the inverted pyramid shapes. Therefore, similar to when the second layer 304 is porous, the progression of fracture due to stress generated during the fabrication of the structure 305 becomes discontinuous, limiting fracture to localized areas only. This effectively suppresses fracture of the substrate 320 and the structure 305.

[0092] At the interface between the second layer 304 and the structure 305, it is possible to form the solidified portion of the second layer 304 intermittently in the horizontal direction of the base material 320. However, if there are large gaps between the solidified portions, it may not be possible to stably form the structure 305. Therefore, at the interface between the second layer 304 and the structure 305, it is preferable to form the solidified portion of the second layer 304 continuously and uniformly rather than intermittently.

[0093] In the embodiments described above, an example was shown in which a laser beam 501 is used to sinter, melt, and solidify the material powder 301. However, the energy beam used to sinter, melt, and solidify the material powder 301 is not limited to a laser beam. As an energy beam, an appropriate one can be selected and used in consideration of the absorption characteristics of the material powder. As an energy beam, in order to perform high-precision fabrication, it is preferable to use a laser beam or electron beam that can narrow the beam diameter and has high directivity. For example, if the material powder contains oxide powder, a YAG laser or fiber laser in the 1 μm wavelength band, or a CO2 laser in the 10 μm wavelength band can be applied as the laser beam.

[0094] Furthermore, although the embodiments described above show examples using powder bed fusion, when applying directed energy deposition, it is possible to create different ratios of amorphous / crystalline material and porous / dense material by adjusting the cooling rate of the molten section. Specifically, similar to powder bed fusion, at least one of the following can be appropriately adjusted: the energy beam output, the distance between the fabrication surface and the energy beam focal point, the energy beam scan speed, and the energy beam scan pitch.

[0095] The following describes the material powders that can be used in the present invention. The material powder is preferably a powder mainly composed of ceramics. The powder mainly composed of ceramics only needs to contain ceramics as its main component, and may also contain minor components. Examples of minor components include sintering aids, absorbers, and components that can form a eutectic with the main component. Here, ceramics refers to solid inorganic compounds other than metals, and the bonding state of the solid (crystalline or amorphous) is irrelevant. In this specification, inorganic compounds refer to oxides, nitrides, oxynitrides, carbides, or borides containing one or more elements from the group of elements that includes antimony and bismuth, in addition to the elements from groups 1 to 14 of the periodic table excluding hydrogen.

[0096] The material powder may consist of one type of inorganic compound, or it may be a mixture of two or more types of inorganic compounds. A powder mainly composed of ceramics refers to a powder in which 90 mol% or more of the powder is ceramic. If multiple types of ceramics are included, the total amount of each type must be 90 mol% or more.

[0097] Three-dimensional objects primarily composed of ceramics (hereinafter simply referred to as "objects") possess higher mechanical strength than those made of resin or metal.

[0098] The main component of the ceramic powder is preferably an oxide. Oxides have fewer volatile components compared to other inorganic compounds, thus enabling stable melting, and it is easy to differentiate between regions with a high proportion of crystalline material and regions with a high proportion of amorphous material. Typical oxides include aluminum oxide, zirconium oxide, magnesium oxide, silicon oxide, and mixtures and compounds thereof.

[0099] When the material powder is a powder containing aluminum oxide (Al2O3) (hereinafter sometimes referred to as alumina powder), it is preferable that the alumina powder contains, as other components, an oxide of a rare earth element that forms a eutectic composition with aluminum oxide. Specifically, it is particularly preferable that the alumina powder contains at least one selected from gadolinium oxide (Gd2O3), yttrium oxide (Y2O3), terbium oxide (Tb2O3), and praseodymium oxide (Pr2O3). For example, when the alumina powder contains gadolinium oxide that forms a eutectic composition with aluminum oxide, the melting point near the eutectic composition of the Al2O3-Gd2O3 system (having three eutectic points) becomes sufficiently lower than the melting point of aluminum oxide alone. Therefore, the powder can be melted with less heat, and energy diffusion to the periphery of the molten area is suppressed, thus improving the molding accuracy. In addition, when the alumina powder contains gadolinium oxide, the molded object has a phase-separated structure in which two or more phases are intertwined. This suppresses crack propagation and improves the mechanical strength of the fabricated object. Similar effects can be obtained when other rare earth element oxides, such as yttrium oxide, are included.

[0100] When the energy beam is a laser beam, the alumina powder further contains absorbers. Sufficient energy absorption by the absorbers suppresses and localizes the spread of heat within the powder, reducing the thermal impact on non-formed areas and thus improving fabrication accuracy. For example, when using a 1 μm wavelength Nd:YAG laser or fiber laser, the alumina powder contains terbium oxide (Tb4O7) and praseodymium oxide (Pr6O7) as minor components. 11)、Ti2O3, TiO, SiO, ZnO, antimony-doped tin oxide (ATO), indium-doped tin oxide (ITO), MnO, MnO2, Mn2O3, Mn3O4, FeO, Fe2O3, Fe3O4, Cu2O, CuO, Cr2O3, CrO3, NiO, V2O3, VO2, V2O5, V2O4, Co3O4, CoO, transition metal carbides, transition metal nitrides, Si3N4, AlN, borides, silicides, etc., and it is more preferable to contain components showing good energy absorption. The alumina powder may contain both rare earth elements showing good energy absorption with respect to the laser beam, such as terbium oxide (Tb4O7) or praseodymium oxide (Pr6O 11 ), etc., and other rare earth elements.

[0101] From the above viewpoints, particularly suitable alumina powders include Al2O3-Gd2O3, Al2O3-GdAlO3, Al2O3-Tb4O7, Al2O3-Gd2O3-Tb4O7, Al2O3-GdAlO3-Tb4O7, Al2O3-Pr6O 11 , Al2O3-Gd2O3-Pr6O 11 , Al2O3-GdAlO3-Pr6O 11 , Al2O3-Y2O3, Al2O3-YAlO3, Al2O3-Y3Al5O 12 , Al2O3-Y2O3-Tb4O7, Al2O3-YAlO3-Tb4O7, Al2O3-Y3Al5O 12 -Tb4O7, Al2O3-Y2O3-Pr6O 11 , Al2O3-YAlO3-Pr6O 11 , Al2O3-Y3Al5O 12 -Pr6O 11 , Al2O3-ZrO2, Al2O3-ZrO2-Tb4O7, Al2O3-ZrO2-Pr6O 11 , Al2O3-SiO, Al2O3-Gd2O3-SiO, Al2O3-GdAlO3-SiO, Al2O3-Y2O3-SiO, Al2O3-YAlO3-SiO, Al2O3-Y3Al5O 12 -SiO, Al2O3-ZrO2-SiO, SiO2-Tb4O7, SiO2-Pr6O 11, (MgO-Al2O3-SiO2)-Tb4O7, (MgO-Al2O3-SiO2)-Pr6O 11 , (Al2O3-SiO2)-Tb4O7, (Al2O3-SiO2)-Pr6O 11 These are some examples.

[0102] The alumina powder preferably contains a composition that can form a eutectic in a ratio that constitutes the eutectic composition. The eutectic composition is the composition at the eutectic point shown in the phase diagram, but because the shaping process using an energy beam generates very rapid heating and cooling states, a eutectic structure with a phase separation structure is formed even if the composition deviates slightly from the eutectic point. Therefore, it is more appropriate to define the eutectic composition in this invention as the composition range in which the eutectic structure is formed, and this range includes a deviation of ±10 mol% from the eutectic composition as shown in the phase diagram.

[0103] In the case of powders containing ceramics other than aluminum oxide, it is preferable, similar to alumina powder, that the eutectic composition is contained in a ratio that forms a eutectic composition.

[0104] The fact that components X and Y can form a eutectic is sometimes expressed as "components X and Y are in a eutectic relationship." A eutectic is a mixture of two or more crystals that crystallize simultaneously from a liquid containing two or more components. "Components X and Y can form a eutectic" is synonymous with "components X and Y have a eutectic state." When a eutectic state exists, a eutectic point (also called a eutectic point) exists. The eutectic point is the temperature at which the eutectic occurs, and in a phase diagram where temperature is on the vertical axis and the component composition ratio is on the horizontal axis, it corresponds to the minimum value of the liquidus curve. The composition corresponding to the eutectic point is called the eutectic composition (or eutectic composition). Therefore, the eutectic point of components X and Y is lower than the melting points of components X and Y individually.

[0105] In this specification, materials are sometimes represented using chemical formulas, such as Al2O3 and Tb4O7 mentioned above. However, as long as the spirit of the present invention is satisfied, the elemental composition ratio of the actual material does not need to strictly match the ratio in the chemical formula. That is, the valence of the metal elements constituting a material may differ slightly from the valence assumed from the chemical formula, and a deviation from the stoichiometric ratio within ±30% is acceptable. For example, in the case of SiO described as an absorber in this specification, even if the elemental composition ratio of the actual absorber is Si:O = 1:1.30, the actual absorber is included in SiO as an absorber described in this specification.

[0106] The crystalline material formed does not need to be a single phase, but preferably has a phase separation structure consisting of two or more phases. Having a phase separation structure consisting of two or more phases suppresses crack propagation and additionally improves the mechanical strength of the formed object. Examples of ceramic powders that form a phase separation structure consisting of two or more phases include a eutectic mixture of aluminum oxide and zirconium oxide, and a mixture of aluminum oxide and rare earth oxides.

[0107] Furthermore, the material powder in this invention may contain a small amount of resin, metal, etc. (10 parts by weight or less per 100 parts by weight of inorganic compound powder) in addition to the inorganic compound powder, in order to adjust the fluidity of the powder and the performance of the final molded product. [Examples]

[0108] The method for manufacturing ceramic articles according to the present invention will be described in detail below with reference to examples, but the present invention is not limited in any way by the following examples.

[0109] <Example 1> α-Al2O3 powder, Gd2O3 powder, Tb2O 3.5 Prepare a powder (Tb4O7 powder) with a molar ratio of Al2O3:Gd2O3:Tb2O 3.5Each powder was weighed in a ratio of 77.4:20.8:1.8. The weighed powders were ground and mixed in a wet ball mill with ethanol solvent for 24 hours, and then the ethanol was removed to obtain the mixed powder (material powder). An alumina plate was used as the substrate for forming the molded object.

[0110] Next, the object of Example 1 was formed by following a process that was basically the same as the process shown in Figure 2 above. For the formation of the object, a 3D Systems ProX DMP 100 (product name) equipped with a 50W Nd:YAG laser (beam diameter 65μm) was used.

[0111] First, the first layer was formed on the substrate. First, a 20 μm thick powder layer of the mixed powder was formed on the substrate using a roller. Next, a laser beam was irradiated onto the powder layer, melting and solidifying the material powder in a 40 mm x 40 mm square area.

[0112] The laser output was set to 20W, the scan speed to 100mm / s, and the scan pitch to 100μm. The scan direction was set parallel to one side of the square. The distance between the surface of the powder layer and the laser focal point was set by adjusting the stage height to -1.5mm from the focus position.

[0113] Next, a 20 μm thick powder layer was formed using a roller to cover the solidified area. A laser was shone onto the powder layer perpendicular to the scanning direction, forming a 40 mm x 40 mm square area in the same position as the first layer. This process was repeated to fabricate the first layer, which was 200 μm thick.

[0114] Next, a second layer was formed on top of the first layer. The laser output was set to 20W, the scan speed to 100mm / s, the scan pitch to 100μm, and the stage height to -3.0mm. A 40mm x 40mm square area, similar to the first layer, was fabricated until it reached a thickness of 5.0mm.

[0115] Next, a structure was formed on the second layer. The laser output was set to 30W, the scan speed to 140mm / s, the scan pitch to 100μm, and the stage height to -5.0mm. A 40mm x 40mm square area, similar to the first layer, was fabricated until it reached a thickness of 10mm. The D1 / L1 ratio was 1.29, D2 / L2 was 0.66, and D3 / L3 was 0.33. Furthermore, the crystalline content of the first layer was 25%, the crystalline content of the second layer was 85%, and the crystalline content of the structure was 98%.

[0116] Furthermore, the porosity of the second layer was 32%, indicating it was porous. The relative density of the second layer was 65.3%, which was lower than the relative density of the structure (92.3%).

[0117] Visual inspection confirmed that there were no defects such as cracks in the substrate or structure, and that there was no delamination of the structure from the substrate.

[0118] The crystalline content of the structure was high at 98%, allowing us to obtain ceramic articles with high mechanical strength without fracture or other damage.

[0119] <Examples 2-4> Examples 2 to 4 were carried out in the same manner as Example 1, except that the laser beam irradiation conditions for fabricating the first layer, the second layer, and the structure were changed as shown in Table 1. Table 2 shows the D / L ratio and crystalline ratio of the first layer, the second layer, and the structure in Examples 2 to 4, as well as the porosity of the second layer. In all of Examples 2 to 4, ceramic articles were obtained without peeling or breakage from the substrate.

[0120] <Example 5> Example 5 was carried out in the same manner as Example 1, except that the second layer was a layer in which an inverted pyramidal shape was intermittently formed as shown in Figure 5. The angle between the edges of the inverted pyramidal shape and the substrate was set to 45°, and the thickness of the second layer was set to 1000 μm.

[0121] In Example 5, too, ceramic articles were obtained without peeling from the substrate or damage to the structure.

[0122] <Example 6> Example 6 was carried out in the same manner as Example 5, except that the thickness of the second layer was set to 5000 μm, the laser output of the second layer was set to 30 W, the scan speed to 140 mm / s, the scan pitch to 100 μm, and the stage height to -4.5 mm. The D1 / L1 ratio was 1.29, D2 / L2 was 0.40, and D3 / L3 was 0.33. The crystalline content of the first layer was 24%, the crystalline content of the second layer was 92%, and the crystalline content of the structure was 97%. The relative density of the second layer was 83.1%, which was lower than the relative density of the structure (92.3%). In Example 6, too, ceramic articles were obtained without peeling from the substrate or damage to the structure.

[0123] <Comparative Example 1> Comparative Example 1 was carried out in the same manner as in Example 1, except that the first layer was fabricated with the laser output set to 30W, the scan speed to 140mm / s, the scan pitch to 100μm, and the stage height to -5.0mm. When the structure reached a thickness of 3000μm, the first layer delaminated from the substrate, and it was not possible to continue fabricating the structure any further.

[0124] <Comparative Example 2> Comparative Example 2 was performed in the same manner as in Example 1, except that the structure was fabricated with the laser output set to 20W, the scan speed to 100mm / s, the scan pitch to 100μm, and the stage height to -1.5mm. Fabrication was stopped when cracks occurred in the structure after it reached a thickness of 2100μm.

[0125] <Comparative Example 3> Comparative Example 3 was carried out in the same manner as in Example 1, but without forming the first and second layers. When the structure reached a thickness of 1000 μm, it peeled off from the substrate, and further fabrication could not be continued.

[0126] <Comparative Example 4> A structure was fabricated on the first layer without forming a second layer. Comparative Example 4 was carried out in the same manner as in Example 1. The structure began to delaminate from the first layer after it had been fabricated to a thickness of 3000 μm, and further fabrication could not be continued.

[0127] <Comparative Example 5> The thickness of the first layer was set to 2500 μm, and the second layer was not formed. Comparative Example 5 was carried out in the same manner as in Example 1. When the structure was fabricated to a thickness of 1000 μm, the structure delaminated from the first layer, and numerous cracks also appeared in the first layer.

[0128] <Comparative Example 6> Comparative Example 6 was carried out in the same manner as in Example 1, except that the second layer and the structure were fabricated without forming the first layer. When the structure reached a thickness of 500 μm, the second layer peeled off from the substrate, and further fabrication could not be continued.

[0129] [Table 1]

[0130] [Table 2] [Explanation of Symbols]

[0131] 100 3D printing equipment 101 Modeling Table 102 Base material 103 Molding container 104 Vertical movement mechanism 105 Vertical movement mechanism 106 Powder supply container 107 Rollers 108 Travel Guide 109 Laser light source 113 Powder for molding 114 Structure 115 Laser light 300 First Layer 301 Material powder 302 Powder layer 303 Non-printing part 304 Second Layer 305 Structure 306 Ceramic articles 320 Base material 351 Stages 352 Rollers 353 Molding container 501 Laser Beam

Claims

1. A method for manufacturing a ceramic article in which a solidified portion is formed by irradiating a powder mainly composed of ceramics laid on a substrate with an energy beam to sinter, melt and solidify the powder, A first step is to form a first layer on the substrate, which is composed of the solidified portion including a portion in which the component derived from the substrate and the component derived from the powder are mixed, A second step of forming a second layer on the first layer, which is composed of the solidified portion and has a lower relative density than the ceramic article and is thicker than the first layer, A third step involves forming a structure on the second layer that will become the ceramic article composed of the solidified portion, It has, A method for manufacturing a ceramic article, characterized in that the proportion of crystalline material in the second layer is greater than the proportion of crystalline material in the first layer.

2. The method for manufacturing a ceramic article according to claim 1, wherein the thickness of the first layer is 2,000 μm or less.

3. A method for manufacturing a ceramic article according to claim 1 or 2, wherein the irradiation conditions of the energy beam are different in the first step, the second step, and the third step.

4. When the energy beam is scanned once in one direction, the ratio of the width L in the direction perpendicular to the scanning direction to the depth D from the surface of the solidified portion is defined as D / L. A method for manufacturing a ceramic article according to any one of claims 1 to 3, wherein when the D / L obtained under the irradiation conditions of the energy beam in the first step is D1 / L1, and the D / L obtained under the irradiation conditions of the energy beam in the second step is D2 / L2, the relationship D1 / L1 > D2 / L2 is satisfied.

5. When the energy beam is scanned once in one direction, the ratio of the width L in the direction perpendicular to the scanning direction to the depth D from the surface of the solidified portion is defined as D / L. A method for manufacturing a ceramic article according to any one of claims 1 to 4, wherein when the D / L obtained under the energy beam irradiation conditions in the second step is D2 / L2, and the D / L obtained under the energy beam irradiation conditions in the third step is D3 / L3, the relationship D2 / L2 > D3 / L3 is satisfied.

6. When the energy beam is scanned once in one direction, the ratio of the width L in the direction perpendicular to the scanning direction to the depth D from the surface of the solidified portion is defined as D / L. A method for manufacturing a ceramic article according to any one of claims 1 to 5, wherein when the D / L obtained under the irradiation conditions of the energy beam in the first step is defined as D1 / L1, D1 / L1 is greater than 1.

0.

7. When the energy beam is scanned once in one direction, the ratio of the width L in the direction perpendicular to the scanning direction to the depth D from the surface of the solidified portion is defined as D / L. A method for manufacturing a ceramic article according to any one of claims 1 to 6, wherein when the D / L obtained under the irradiation conditions of the energy beam is defined as D3 / L3, D3 / L3 is 0.8 or less.

8. A method for manufacturing a ceramic article according to any one of claims 1 to 7, wherein the distance between the surface of the laid powder and the focal point of the energy beam in the first step, the second step, and the third step is closest in the first step and furthest in the third step.

9. A method for manufacturing a ceramic article according to any one of claims 1 to 8, wherein the proportion of amorphous material in the first layer is 50 volume% or more.

10. A method for manufacturing a ceramic article according to any one of claims 1 to 9, wherein the proportion of crystalline material in the structure is greater than the proportion of crystalline material in the second layer.

11. A method for manufacturing a ceramic article according to any one of claims 1 to 10, wherein the porosity of the first layer is less than 5 volume percent.

12. A method for manufacturing a ceramic article according to any one of claims 1 to 11, wherein the porosity of the second layer is 5% by volume or more.

13. A method for manufacturing a ceramic article according to any one of claims 1 to 11, wherein the porosity of the second layer is 15% by volume or more.

14. A method for manufacturing a ceramic article according to any one of claims 1 to 13, wherein in the second step, the solidified portion is formed intermittently in the horizontal direction of the substrate to form at least a part of the second layer.

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