Manufacturing method for laminated structures

Abstract

To provide a method of making a laminate structure that is easy to control a crystal texture in a laminate structure.SOLUTION: A method of making a laminate structure comprises providing a gas flow parallel to a surface of a powder bed, forming a first fusion-solidified layer by emitting an energy beam in a first direction while scanning the same, forming a second fusion-solidified layer by emitting an energy beam in a second direction intersecting with the first direction while scanning the same, adjusting a first deposition thickness of the powder bed and a first quantity of heat input of the energy beam and controlling a lamination thickness of the first fusion-solidified layer and a fusion depth of the first fusion-solidified layer, adjusting a second deposition thickness of the powder bed and a second quantity of heat input of the energy beam and controlling the lamination thickness of the second fusion-solidified layer and the fusion depth of the second fusion-solidified layer, adjusting an angle α1 defined between the first direction and the direction of the gas flow and controlling the first quantity of heat input, adjusting an angle α2 defined between the second direction and the direction of the gas flow and controlling the second quantity of heat input, and controlling a remaining thickness of the first fusion-solidified layer and a remaining thickness of the second fusion-solidified layer in a crystal texture.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a laminated structure.

Background Art

[0002] There is a case where a laminated structure is manufactured using an energy beam like additive manufacturing technology. For example, based on arbitrary CAD (Computer Aided Design) data, metal layers obtained by laser irradiation are sequentially laminated, and a laminated structure of an arbitrary shape can be manufactured as a three-dimensional structure. Additive manufacturing technology is applied to industrial equipment fields including aircraft-related members and medical equipment fields, and is attracting attention as a promising technology. In recent years, in order to impart desired mechanical properties to a laminated structure, it has been proposed to control the crystal structure of the laminated structure. For example, mechanical strength and elastic modulus can be controlled by controlling the crystal structure. In addition, depending on the crystal structure having a preferential crystal orientation, anisotropy such as Young's modulus, yield stress, and fatigue resistance can be imparted to the laminated structure.

[0003] In Patent Documents 1 to 3, it has been proposed to adjust process parameters such as laser scan speed, laser output, pitch width, and scan strategy as methods for controlling the crystal structure.

[0004] In Patent Document 1, in order to achieve a low elastic modulus in a β titanium alloy, it has been proposed to control the crystal orientation by adjusting the scanning direction in the melting process. In Patent Document 2, it has been proposed to form a single crystal-like structure in the lamination direction by combining a scan strategy and laser power, and controlling the irradiation direction and power of laser light and arc discharge. In Patent Document 3, it has been proposed to obtain a single crystal-like structure by guiding a beam from a directional energy source, performing a deposition and fusion process, and remelting and solidifying with another external heat control device.

[0005] On the other hand, Patent Document 4 discloses an additive manufacturing method that removes fumes generated when forming a metal layer by laser irradiation by providing a gas flow near the surface of the powder bed, and also allows switching the direction of the gas flow according to the scanning direction of the laser. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2017-171985 [Patent Document 2] Japanese Patent Publication No. 2018-115090 [Patent Document 3] Patent No. 6216881 [Patent Document 4] Japanese Patent Publication No. 2019-183282 [Overview of the project] [Problems that the invention aims to solve]

[0007] However, as disclosed in Patent Document 4, when a metal layer is formed by irradiating a laser while providing a gas flow near the surface of a powder bed, and then stacking these metal layers to manufacture a laminated structure, it was difficult to control the crystalline structure in the laminated structure simply by adjusting process parameters such as the laser scan speed, laser output, pitch width, and scan strategy, as disclosed in Patent Documents 1 to 3.

[0008] The present invention has been made in view of the above circumstances, and aims to provide a method for manufacturing a laminated structure in which the crystalline structure in the laminated structure can be easily controlled. [Means for solving the problem]

[0009] As a result of diligent research by the inventors of this invention, they found that as the laser scanning direction and the gas flow direction become the same direction (i.e., parallel), in other words, as the angle α between the laser scanning direction and the gas flow direction approaches 0°, the sputter and fumes generated when the raw material powder melts due to laser irradiation flow in the laser scanning direction due to the gas flow, causing laser attenuation in that scanning direction and reducing the amount of heat input to the laser. Furthermore, they found that because the gas flows in the longitudinal direction of the molten pool, heat dissipation from the molten raw material is promoted, thus completing the present invention.

[0010] To solve the above problems, the present invention has the following configuration. [1] A gas flow parallel to the surface is provided along the surface of a powder bed on which raw material powder is deposited. A first molten and solidified layer is formed by irradiating the surface while scanning it with an energy beam in a first direction parallel to the surface. A second molten and solidified layer is formed by irradiating the surface with an energy beam while scanning it in a second direction parallel to the surface and intersecting the first direction. A method for producing a laminated structure having a crystalline structure in which one or more first and second molten solidified layers are each stacked in multiple layers in the thickness direction, When forming the first molten solidified layer, the first deposition thickness of the powder bed and the first heat input of the energy rays irradiated onto the powder bed are adjusted to control the layer thickness of the first molten solidified layer and the melting depth of the first molten solidified layer. When forming the second molten solidification layer, the second deposition thickness of the powder bed and the second heat input of the energy rays irradiated onto the powder bed are adjusted to control the deposition thickness of the second molten solidification layer and the penetration depth of the second molten solidification layer. The first heat input is controlled by adjusting the angle α1 between the first direction and the direction of the gas flow. The second heat input is controlled by adjusting the angle α2 between the second direction and the direction of the gas flow, A method for manufacturing a laminated structure, comprising controlling the remaining thickness of the first molten solidified layer and the remaining thickness of the second molten solidified layer in the crystalline structure. [2] The manufacturing method of the laminated structure according to [1], wherein one of the angle α1 and the angle α2 is adjusted to be 45° or more and 90° or less, and the other is adjusted to be 0° or more and 45° or less. [3] The manufacturing method of the laminated structure according to [1] or [2], further comprising a crystal structure in which only the first melt-solidified layer or the second melt-solidified layer is included, and a plurality of these are laminated in the thickness direction. [4] While scanning an energy beam in a third direction that is parallel to the surface and intersects the first direction and the second direction respectively, irradiate to form a third melt-solidified layer. The manufacturing method of the laminated structure according to any one of [1] to [3], manufacturing a laminated structure further including at least one or more of the third melt-solidified layers, and a crystal structure in which a plurality of these are laminated in the thickness direction.

Advantages of the Invention

[0011] The manufacturing method of the laminated structure of the present invention enables easy control of the crystal structure in the laminated structure.

Brief Description of the Drawings

[0012] [Figure 1] It is a schematic diagram showing an example of the configuration of a manufacturing apparatus for a laminated structure applicable to the present embodiment. [Figure 2] It is a plan view of a modeling stage included in a manufacturing apparatus for a laminated structure applicable to the present embodiment. [Figure 3] It is a diagram for explaining the minimum angle among the angles formed by the scanning direction of the energy beam and the direction of the gas flow F in the present embodiment. [Figure 4] It is a diagram for explaining an example of the manufacturing method of the laminated structure. [Figure 5] It is a diagram for explaining an example of the manufacturing method of the laminated structure. [Figure 6] It is a diagram for explaining the crystal structure of the laminated structure obtained by the manufacturing method of the laminated structure of the present embodiment. [Figure 7] It is a diagram for explaining the crystal structure of the laminated structure obtained by the manufacturing method of the laminated structure of the present embodiment. [Figure 8] This is a diagram for explaining the crystal structure of the laminated structure obtained by the manufacturing method of the laminated structure of the present embodiment. [Figure 9] This is a diagram of the laminated structures fabricated in Examples 1 and 2. [Figure 10] This is a diagram showing the results of observing the crystal orientation maps (IPF maps) and pole figures of the laminated structures fabricated in Examples 1 and 2. [Figure 11] This is a diagram showing the results of observing the crystal structure of the laminated structures fabricated in Examples 1 and 2. [Figure 12] This is a diagram showing the results of observing the crystal structure of the laminated structure fabricated in Experimental Example 3. [Figure 13] This is a diagram showing the relationship between the deposition thickness of the powder bed and the depth of the melt pool in Example 3. [Figure 14] This is a diagram showing the results of observing the remaining thickness (x-scan thickness) of the x-scan layer and the remaining thickness (y-scan thickness) of the y-scan layer in Experimental Example 4, respectively. [Figure 15] This is a diagram showing the results of observing the remaining thickness (x-scan thickness) of the x-scan layer and the remaining thickness (y-scan thickness) of the y-scan layer in Experimental Example 4, respectively. [Figure 16] This is a diagram of the laminated structure fabricated in Experimental Example 5. [Figure 17] This is a diagram showing the results of observing the crystal structure of the laminated structure fabricated in Example 5.

Mode for Carrying Out the Invention

[0013] [[ID=三十五]] [[ID=三十六]](Definition)[[ID=三十七]] In the specification, crystal planes are indicated as follows: (001): When the axis is considered fixed, {001}: When the x, y, z, etc. axes are not considered fixed, in which case the crystal planes cannot be distinguished by the viewing direction. Crystal orientation is indicated as follows:

[0001] : When the axis is considered fixed, <001> When considering the crystal without fixing axes such as x, y, and z, the orientation of the crystal cannot be distinguished by the viewing direction. (001), etc., represent Miller indices. The "~" symbol indicating a numerical range means that the numbers before and after it are included as the lower and upper limits, respectively.

[0014] <Method for manufacturing laminated structures> The present invention provides a method for manufacturing a laminated structure comprising: providing a gas flow parallel to the surface of a powder bed on which raw material powder is deposited; irradiating the powder bed with energy rays while scanning in a first direction parallel to the surface of the powder bed to form a first molten and solidified layer; irradiating the powder bed with energy rays while scanning in a second direction parallel to the surface of the powder bed and intersecting the first direction to form a second molten and solidified layer; and manufacturing a laminated structure containing one or more first and second molten and solidified layers, with multiple layers of these layers stacked in the thickness direction; When forming the first molten solidification layer, the first deposition thickness of the powder bed and the first heat input of the energy rays irradiated onto the powder bed are adjusted to control the thickness of the first molten solidification layer and the penetration depth of the first molten solidification layer; When forming the second molten solidification layer, the thickness of the second molten solidification layer and the penetration depth of the second molten solidification layer are controlled by adjusting the second deposition thickness of the powder bed and the second heat input of the energy rays irradiated onto the powder bed; The first heat input is controlled by adjusting the angle α1 between the first direction and the direction of gas flow; The second heat input is controlled by adjusting the angle α2 between the second direction and the direction of gas flow; This involves controlling the remaining thickness of the first molten solidified layer and the remaining thickness of the second molten solidified layer in the crystalline structure.

[0015] In this invention, by adjusting the amount of heat input of the energy beam irradiated onto the powder bed in each scanning direction of the energy beam, it is possible to control the thickness of the molten solidified layer formed by the irradiation of the energy beam and the penetration depth of the molten solidified layer. Specifically, by adjusting the first heat input of the energy rays, the thickness of the first molten solidified layer and the penetration depth of the first molten solidified layer can be controlled. Similarly, by adjusting the second heat input of the energy rays, the thickness of the second molten solidified layer and the penetration depth of the second molten solidified layer can be controlled.

[0016] Furthermore, the first and second heat inputs can be controlled by adjusting the minimum angle α1 between the first direction and the gas flow direction, and the minimum angle α2 between the second direction and the gas flow direction, respectively.

[0017] Here, when the direction of gas flow and the scanning direction of energy rays coincide (i.e., when the direction of gas flow and the scanning direction of energy rays are parallel), spatter and fumes generated when the raw material powder melts due to irradiation of the powder bed with energy rays flow in the direction of gas flow, causing attenuation of the energy rays scanning in that direction and reducing the amount of heat. In addition, since gas flows in the longitudinal direction of the molten pool, heat dissipation from the molten raw material is promoted. Therefore, by changing the smallest angle α (α1, α2) between the scanning direction of energy rays and the direction of gas flow, the amount of heat input of the energy rays irradiated onto the powder bed can be adjusted, and as a result, the penetration depth of the molten solidified layer formed by the energy rays scanned in the required direction can be controlled.

[0018] Specifically, by bringing the smallest angle α between the scanning direction of the energy rays and the direction of the gas flow closer to 0°, the reduction in heat input increases, and the penetration depth of the molten solidified layer formed by the energy rays scanned in that direction can be reduced. In contrast, by bringing the minimum angle α between the scanning direction of the energy rays and the direction of the gas flow closer to 90°, the decrease in heat input is reduced, and the penetration depth of the molten solidified layer formed by the energy rays scanned in that direction can be increased. As a result, the remaining thickness of the molten solidified layer to be controlled can be altered in the crystalline structure contained within the laminated structure. Therefore, since the orientation of the crystal orientation can be adjusted by changing the smallest angle α between the energy ray scanning direction and the gas flow direction, the crystalline structure of the laminated structure can be easily controlled.

[0019] Furthermore, the first and second heat inputs may be controlled by a scan strategy, such as the energy ray output, scanning speed, scanning interval, and irradiation position. This invention allows for the control of the amount of heat input from energy rays irradiated onto a powder bed, thereby altering the remaining thickness of the crystalline structure when forming the molten and solidified layer of the target object. As a result, further versatility in controlling the crystalline structure of laminated structures may be provided.

[0020] In this invention, by adjusting the stacking thickness of the powder bed for forming the molten solidified layer that constitutes the crystalline structure, it is possible to control the stacking thickness of the molten solidified layer formed by irradiation with energy rays and the penetration depth of the molten solidified layer.

[0021] Specifically, the thickness of the first molten and solidified layer can be controlled by adjusting the first layer thickness of the powder bed. Similarly, the thickness of the second molten and solidified layer can be controlled by adjusting the second layer thickness of the powder bed. Furthermore, the thickness of the first layer of the powder bed and the thickness of the second layer may be the same or different.

[0022] In this invention, the deposition thickness of the powder bed for the molten solidified layer to be controlled and the deposition thickness of the powder bed for the molten solidified layer adjacent to the molten solidified layer above and below in the thickness direction can be varied relative to each other. Therefore, the remaining thickness in the molten solidified layer can be more precisely varied between the molten solidified layer to be controlled and the molten solidified layers adjacent to it above and below in the thickness direction.

[0023] Therefore, in the present invention, the orientation of the crystal orientation can also be adjusted by changing the deposition thickness of the powder bed, making it even easier to control the crystalline structure of the laminated structure. Furthermore, for example, by sequentially laminating the molten solidified layers in the thickness direction while changing the deposition thickness of the powder bed for each molten solidified layer, even greater versatility in controlling the crystalline structure of the laminated structure can be provided.

[0024] Furthermore, in the present invention, one of the minimum angle α1 between the first direction and the gas flow direction, and the minimum angle α2 between the second direction and the gas flow direction, may be adjusted to 45° or more and 90° or less, while the other may be adjusted to 0° or more and 45° or less.

[0025] In this way, by adjusting angles α1 and α2 to be different, it is possible to create a difference between the amount of heat input when irradiating with an energy beam while scanning in the first direction and the amount of heat input when irradiating with an energy beam while scanning in the second direction, without changing the energy beam output or scanning speed.

[0026] As a result, the penetration depth of the molten solidified layer formed in the scanning direction with a small heat input becomes smaller than the penetration depth of the molten solidified layer formed in the scanning direction with a large heat input. Consequently, in the crystalline structure of a laminated structure formed by alternating scanning in the first and second directions, the remaining thickness of the molten solidified layer formed in the scanning direction with a small heat input becomes smaller than the remaining thickness of the molten solidified layer formed in the scanning direction with a large heat input.

[0027] In contrast, by adjusting angles α1 and α2 to 45°, it is possible to adjust the amount of heat input when irradiating with an energy beam while scanning in the first direction and the amount of heat input when irradiating with an energy beam while scanning in the second direction to be approximately the same, without changing the energy beam output or scanning speed.

[0028] As a result, the penetration depth of the first molten and solidified layer and the penetration depth of the second molten and solidified layer become approximately the same, and in the crystalline structure of the laminated structure formed by alternately scanning in the first and second directions, the remaining thickness of the first molten and solidified layer and the remaining thickness of the second molten and solidified layer become approximately the same.

[0029] As a result, the remaining thickness of the molten and solidified layer to be controlled in the crystalline structure contained within the laminated structure can be adjusted to any desired thickness. Furthermore, this may provide greater diversity in the methods of controlling the crystalline structure of the laminated structure.

[0030] Furthermore, the method for manufacturing a laminated structure of the present invention yields a laminated structure comprising a first molten and solidified layer and a second molten and solidified layer, with the first and second molten and solidified layers alternately stacked in the thickness direction. However, the laminated structure may further include a crystalline structure comprising only the first molten and solidified layer, with multiple layers of these stacked in the thickness direction, or a crystalline structure comprising only the second molten and solidified layer, with multiple layers of these stacked in the thickness direction.

[0031] Specifically, when forming a laminated structure by alternately scanning in a first direction and scanning in a second direction, during the formation of the first molten solidified layer, the first deposition thickness of the powder bed is increased to control the laminated thickness of the first molten solidified layer; the first heat input of the energy beam irradiated onto the powder bed is increased to control the penetration depth of the first molten solidified layer; during the formation of the second molten solidified layer, the second deposition thickness of the powder bed is decreased to control the laminated thickness of the second molten solidified layer; and the second heat input of the energy beam irradiated onto the powder bed is decreased to control the penetration depth of the second molten solidified layer. As a result, the remaining thickness of the second molten solidified layer becomes thinner, and when the first molten solidified layer is formed by irradiating with energy beams while scanning in the first direction, the second molten solidified layer is overwritten. As a result, a crystalline structure can be obtained that contains only the first molten solidified layer and has multiple layers of the first molten solidified layer stacked in the thickness direction. Similarly, a crystalline structure can be obtained that contains only the second molten solidified layer, and in which multiple layers of the second molten solidified layer are stacked in the thickness direction.

[0032] Furthermore, the manufacturing method for the laminated structure of the present invention may also involve irradiating the surface of the powder bed with energy rays while scanning them in a third direction parallel to the surface of the powder bed and intersecting the first and second directions, in addition to the first and second directions described above, to form a third molten and solidified layer, and manufacturing a laminated structure that further includes a crystalline structure in which multiple layers of the first to third molten and solidified layers are stacked in the thickness direction, with at least one of these third molten and solidified layers. This allows for greater versatility in controlling the crystalline structure of the laminated structure.

[0033] The following describes in detail, with reference to the drawings, a method for manufacturing a laminated structure, which is one embodiment to which the present invention is applied, along with the manufacturing apparatus for the laminated structure used therein. Note that, for the sake of clarity, the drawings used in the following description may show enlarged versions of key features, and the dimensional ratios of each component may not be the same as in reality.

[0034] (Manufacturing equipment for laminated structures) First, the configuration of a laminated structure manufacturing apparatus applicable to the manufacturing method of a laminated structure, which is one embodiment of the present invention, will be described. Figure 1 is a schematic diagram showing an example of the configuration of a laminated structure manufacturing apparatus applicable to this embodiment. Figure 2 is a plan view of the molding stage included in the laminated structure manufacturing apparatus applicable to this embodiment. In this embodiment, the manufacturing method for the laminated structure uses a laser as the energy beam, with the first direction being the x-axis direction as shown in Figures 1 and 2, and the second direction being the y-axis direction as shown in Figures 1 and 2. This will be explained below as an example. Furthermore, in this embodiment, laser scanning along the x-axis is described as "x-scan," and laser scanning along the y-axis is described as "y-scan."

[0035] As shown in Figure 1, the manufacturing apparatus for laminated structures (hereinafter simply referred to as "manufacturing apparatus") 1 comprises a chamber 2, a powder bed 3, an irradiation unit 4, a gas flow generation unit 5, a molding stage 6, and a control unit (not shown).

[0036] Chamber 2 is the enclosure where the layered structure is fabricated. The upper side of Chamber 2 is connected to a shielding gas supply pipe 15. The shielding gas supply pipe 15 introduces shielding gas into Chamber 2.

[0037] The shielding gas is a gas supplied around the raw material powder in the chamber during laser irradiation. An inert gas is preferred as the shielding gas, and argon gas is more preferred. Depending on the type of raw material powder, a gas other than an inert gas, such as oxygen or hydrogen, which reacts with the raw material, may be used as the shielding gas. When a gas other than an inert gas is used as the shielding gas, the raw material powder and the shielding gas react, potentially imparting new properties to the laminated structure.

[0038] The raw material powder is not particularly limited. Examples of raw material powders include powders of various metals such as magnesium, calcium, chromium, copper, iron, manganese, molybdenum, cobalt, nickel, hafnium, niobium, titanium, and aluminum, as well as alloys thereof. Examples of ceramic powders include powders of silicides, oxides, nitrides, carbides, and borides of the above metals. The raw material powder may also be a mixture of raw material powder and ceramic powder.

[0039] The particle size of the raw material powder is not particularly limited. For example, the particle size can be approximately 10 to 200 μm.

[0040] A molding stage 6 is provided inside the chamber 2. The molding stage 6 includes a powder bed 3, a storage section 7, a recovery section 8, and a recoater 9. The recoater 9 moves back and forth along the x-axis direction shown in the figure.

[0041] The storage unit 7 includes raw material powder for supply to the powder bed 3 and a first lifting platform 11 on which the raw material powder is placed. As the first lifting platform 11 rises, the raw material powder accumulates above the upper surface of the molding stage 6. The accumulated raw material powder is moved along the x-axis by the recoater 9 and supplied to the powder bed 3. The surface of the raw material powder M on the powder bed 3 (the surface of the powder bed) is leveled by the recoater 9.

[0042] The recoater 9 and the first lifting platform 11 are electrically connected to a control unit (not shown). Therefore, the recoater 9 and the first lifting platform 11 can supply the raw material powder from the storage unit 7 to the powder bed 3 according to the instructions of the control unit.

[0043] The powder bed 3 comprises raw material powder M, a second lifting platform 12 on which the raw material powder M is placed, and a base plate (not shown) placed on the surface of the second lifting platform 12. The second lifting platform 12 is movable along the z-axis. Therefore, the powder bed 3 of the raw material powder is movable vertically, i.e., along the z-axis, within the chamber 2.

[0044] In the manufacturing apparatus 1, when the second lifting platform 12 descends by Δh in the z-axis direction, a powder layer of raw material powder M with a thickness of Δh is formed on the powder bed 3. The descent distance Δh of the second lifting platform 12 in the z-axis direction corresponds to the deposition thickness Δh of the powder bed for each melted and solidified layer of the laminated structure.

[0045] The second lifting platform 12 is electrically connected to a control unit (not shown). Therefore, the second lifting platform 12 can control the powder bed deposition thickness Δh according to the instructions of the control unit.

[0046] The irradiation unit 4 includes a laser oscillator 13 and an optical system 14. The laser oscillator 13 can be any laser irradiation source and is not particularly limited.

[0047] The optical system 14 reflects the laser from the laser oscillator 13 and irradiates the raw material powder M in the powder bed 3 with the laser while scanning it. The optical system 14 is composed of one or more reflecting mirrors. Both the laser oscillator 13 and the optical system 14 are electrically connected to a control unit (not shown).

[0048] The irradiation unit 4 controls the reflection direction of the laser by the optical system 14 according to instructions from a control unit (not shown). The irradiation unit 4 then controls the reflection direction of the laser by the optical system 14 and irradiates by scanning with the laser.

[0049] The irradiation unit 4 irradiates the raw material powder in the powder bed 3 with a laser to sinter or melt and solidify the raw material powder M at the irradiation position. As a result, a melted and solidified layer of sintered raw material powder, or a melted and solidified layer of melted and solidified raw material powder, can be formed on the powder bed 3.

[0050] The gas flow generation unit 5 applies a gas flow F along the surface near the surface of the powder bed 3. Therefore, in addition to controlling the crystal structure, the gas flow generation unit 5 can also remove sputter, fumes, etc., generated when the molten and solidified layer is irradiated with a laser, using the gas flow F.

[0051] The gas flow generation unit 5 is electrically connected to a control unit (not shown). The control unit is electrically connected to the laser oscillator 13 and the optical system 14. Therefore, the gas flow generation unit 5 can change the direction of the gas flow F with respect to the scanning direction of the energy beam (laser) irradiated to form the molten solidified layer to be controlled for crystal structure. In addition, the gas flow generation unit 5 can adjust the flow rate of the gas flow F according to the instructions of the control unit (not shown).

[0052] The flow velocity of the gas flow F on the surface of the powder bed 3 is preferably 0.1 to 10 m / s, and more preferably 1.0 to 5.0 m / s.

[0053] The composition of the gas flow F is preferably the same as that of the shielding gas. Examples of such compositions include gases containing at least one selected from the group consisting of helium, nitrogen, neon, argon, and xenon. The gas flow may contain one of these gas components alone, or two or more in combination.

[0054] The gas flow generation unit 5 can change the direction of the gas flow F by changing the position and orientation of the gas flow generation unit 5 relative to the molding stage 6.

[0055] Depending on the type of raw material powder, if a gas other than inert gases such as oxygen or hydrogen that react with the raw material is used as a shielding gas, it is also possible to use a gas other than inert gases such as oxygen or hydrogen as a gas flow. In this case, the raw material powder and the gas flow may react, potentially imparting new properties to the laminated structure.

[0056] The control unit, not shown in the diagram, may include, for example, a central processing unit (CPU), memory, and a hard disk drive. The hard disk drive may include CAD applications and CAM (Computer-Aided Manufacturing) applications. In this case, the control unit can create three-dimensional structural data of a laminated structure of a desired shape.

[0057] A control unit (not shown) creates processing condition data based on three-dimensional structural data. Processing condition data can be created for each molten and solidified layer. Based on the processing condition data, the control unit (not shown) controls the irradiation unit 4 (laser oscillator 13 and optical system 14) and can adjust the laser output, scanning speed, scanning interval, and irradiation position.

[0058] The recovery unit 8 has a third lifting platform 16. The third lifting platform 16 is movable along the z-axis direction. In the manufacturing apparatus 1, when the powder bed 3 is formed by the recoater 9, excess raw material powder can be recovered in the recovery unit 8. Also, when recovering the layered structure after the completion of molding, the raw material powder remaining on the molding stage 6 can be moved to the recovery unit 8 by the recoater 9 and recovered.

[0059] (Method of manufacturing a laminated structure) Next, a method for manufacturing a laminated structure, which is one embodiment of the present invention, will be described. The manufacturing method for the laminated structure of this embodiment is a method for manufacturing a laminated structure that includes a crystalline structure in which multiple layers of x-scan and y-scan are stacked in the thickness direction, and the deposition thickness of the powder bed is multiplied by irradiating a laser along the surface of the powder bed on which raw material powder has been deposited (x-scan) to form an x-scan layer (first molten solidified layer), and irradiating a laser along the y-axis direction (second direction) parallel to the surface of the powder bed and perpendicular to the x-axis direction (y-scan), and the deposition thickness of the powder bed is multiplied by irradiating a laser along the surface of the powder bed (x-scan) to form an x-scan layer (first molten solidified layer), and the deposition thickness of the powder bed is multiplied by irradiating a laser along the surface of the powder bed (x-scan) to form an x-scan layer (second molten solidified layer). The deposition thickness (1) and the amount of heat input from the laser irradiating the powder bed (1st heat input) are adjusted to control the deposition thickness and penetration depth of the x-scan layer; when forming the y-scan layer, the deposition thickness (2nd deposition thickness) of the powder bed and the amount of heat input from the laser irradiating the powder bed (2nd heat input) are adjusted to control the deposition thickness and penetration depth of the y-scan layer; the heat input for x-scan is controlled by adjusting the smallest angle αx(α1) between the x-axis direction and the direction of gas flow F; and the heat input for y-scan is controlled by adjusting the smallest angle αy(α2) between the y-axis direction and the direction of gas flow F; thereby controlling the remaining thickness of the x-scan layer and the remaining thickness of the y-scan layer in the crystalline structure.

[0060] The manufacturing method for the laminated structure of this embodiment will be described in detail below, with reference to the drawings, using the manufacturing apparatus 1 described above.

[0061] In the manufacturing method of the laminated structure of this embodiment, a laminated structure is obtained by stacking multiple molten and solidified layers formed by irradiating a powder bed of raw material powder with a laser as an energy ray. Based on the CAD data of the laminated structure, the formation of the powder bed, the formation of the molten and solidified layer, and the stacking of the molten and solidified layer are repeated any number of times.

[0062] When using the manufacturing apparatus 1 shown in Figures 1 and 2, the first layer formed by the initial laser irradiation, i.e., the bottom layer of molten and solidified material, comes into contact with the base plate (not shown) on the surface of the second lifting platform 12. Subsequently, layers of molten and solidified material are sequentially stacked on top of the first layer of molten and solidified material.

[0063] Before laser irradiation, it is preferable to supply shielding gas from the shielding gas supply pipe 15 to the chamber 2 and the cavities beneath the first lifting platform 11, the second lifting platform 12, and the third lifting platform 16. This fills the chamber with shielding gas. Therefore, in the presence of a sufficient amount of shielding gas, heat can be supplied to the raw material powder using the laser to form a molten and solidified layer.

[0064] In this embodiment, by using the irradiation unit 4, x-scan and y-scan can be repeatedly and alternately performed to stack multiple molten and solidified layers in the z-axis direction.

[0065] In this case, as shown in Figure 3, the direction of the shielding gas flow F differs between the x-scan and y-scan. Specifically, when αx is the smallest angle between the scanning direction of the energy rays and the direction of the gas flow F in the x-scan, and αy is the smallest angle between the scanning direction of the energy rays and the direction of the gas flow F in the y-scan, the direction of the shielding gas flow is changed according to the scanning direction of the laser so that αx > αy.

[0066] For example, as shown in Figure 4, a laminated structure 10 can be manufactured by forming the 2n-1 molten solidified layer with y-scan and the 2n molten solidified layer with x-scan (n: natural number). In this case, the 2n-1 molten solidified layer is a molten solidified layer formed with y-scan (hereinafter sometimes referred to as the "y-scan layer"), and the 2n molten solidified layer is a molten solidified layer formed with x-scan (hereinafter sometimes referred to as the "x-scan layer").

[0067] In the formation of the 2n-1 layer powder bed, the raw material powder from the storage section 7 is supplied to the surface of the second lifting platform 12 by the recoater 9, and a powder bed with a deposition thickness Δh is formed above the 2n-2 layer of molten solidified material. A laser is irradiated onto this powder bed with a deposition thickness Δh to form the 2n-1 layer of molten solidified material. In the formation of the 2n-1 layer of molten solidified material, the powder layer is sintered or melted and solidified by laser scanning. As a result, the 2n-1 layer of molten solidified material is stacked above the 2n-2 layer of molten solidified material.

[0068] In the formation of the 2n-th layer of powder bed, a powder bed with a deposition thickness Δh is formed above the 2n-1 layer of molten and solidified material. Then, a laser is shone onto the surface of the 2n-1 layer of molten and solidified material, above the powder bed. As a result, the powder layer is sintered or melted and solidified by the laser scanning, forming the 2n-th layer of molten and solidified material, and the 2n-th layer of molten and solidified material is then laminated on top of the 2n-1 layer of molten and solidified material.

[0069] By repeatedly forming a powder bed, forming a molten and solidified layer, and stacking the layers in this manner, a laminated structure can be manufactured by stacking multiple molten and solidified layers. By repeatedly and alternately performing x-scan and y-scan operations, a laminated structure 10 having a crystalline structure in which x-scan layers and y-scan layers are repeatedly stacked can be manufactured. The laminated structure 10 is recovered from inside the chamber 2 while placed on a base plate.

[0070] The following describes a method for manufacturing a laminated structure, using the manufacturing of laminated structure 10 as an example, in which the x-scan layer and the y-scan layer are the targets for control in the crystalline structure.

[0071] Figure 5 shows the case where the direction of gas flow F is perpendicular to the direction of x-scan and parallel to the direction of y-scan. In this case, αx is 90° and αy is 0°.

[0072] In this case, if the laser output and scanning speed are constant, the laser is affected by the gas flow F, and the amount of heat input to the powder bed by the laser during y-scan is attenuated compared to the amount of heat input to the powder bed by the laser during x-scan. As a result, the penetration depth of the molten and solidified layer decreases during y-scan compared to x-scan, and the thickness of the y-scan layer remaining in the crystal structure becomes smaller than the thickness of the x-scan layer.

[0073] Thus, in the manufacturing method of the laminated structure of this embodiment, when x-scan and y-scan are repeatedly and alternately executed, the direction of the gas flow F is changed so that the relationship αx > αy is satisfied, thereby making the penetration depth of the y-scan layer, which is the target of control in the crystalline structure, less than the penetration depth of the x-scan layer. As a result, the remaining thickness of the y-scan layer in the crystalline structure contained in the laminated structure can be changed.

[0074] According to the manufacturing method of the laminated structure of this embodiment, the crystal orientation and orientation of the crystal structure can be adjusted by intentionally changing the direction of the gas flow F, thus allowing for easy control of the crystal structure of the laminated structure. In addition to changing the direction of the gas flow F, the crystal structure of the laminated structure can be changed more precisely by changing the flow rate of the gas flow F.

[0075] When the y-scan layer is the target of crystalline structure control, it is also effective to vary the deposition thickness of the powder bed for the y-scan layer from the deposition thickness of the powder bed for the adjacent x-scan layer.

[0076] By varying the deposition thickness of the powder bed for the y-scan layer and the deposition thickness of the powder bed for the x-scan layer relative to each other, the remaining thickness of the y-scan layer in the crystalline structure of the laminated structure can be precisely altered.

[0077] As a result, the crystal orientation and orientation of the crystal structure can be adjusted by changing the deposition thickness of the powder bed, thus allowing for easy control of the crystal structure of the laminated structure.

[0078] For example, by making the deposition thickness of the x-scan layer and the deposition thickness of the y-scan layer the same, and by making these deposition thicknesses greater than the difference "Sx-Sy" between the penetration depth "Sx" of the molten solidification layer in the x-scan and the penetration depth "Sy" of the molten solidification layer in the y-scan, the y-scan layer can be overwritten and erased with the x-scan layer.

[0079] Furthermore, by making the deposition thickness of the x-scan layer and the y-scan layer the same, and by making these deposition thicknesses smaller than the difference between the penetration depth "Sx" of the molten solidification layer in the x-scan and the penetration depth "Sy" of the molten solidification layer in the y-scan ("Sx-Sy"), the y-scan layer can be intentionally left in the laminated structure.

[0080] The penetration depth "Sx" of the molten solidification layer in x-scan and the penetration depth "Sy" of the molten solidification layer in y-scan can be determined by observing the metal structure of the fabricated object. Specifically, the metal structure, which has been mirror-finished by sanding and buffing, can be etched and observed under a microscope. The scanning direction of the laser (energy beam) of the observed metal structure can be determined from the direction of overlap of the molten pools. In the case of x-scan, the laser irradiation of x-scan is repeated in the y direction, so an overlap of molten pools occurs in the yz plane, and the molten pools overlap in the y direction. In the case of y-scan, the laser irradiation of y-scan is repeated in the x direction, so an overlap of molten pools occurs in the xz plane, and the molten pools overlap in the -x direction.

[0081] In this way, by introducing further changes to the crystal orientation and crystal direction of the crystal structure in each layer constituting the laminated structure, it is possible to provide even greater precision in controlling the crystal structure.

[0082] Furthermore, by changing the deposition thickness △h of the powder bed, it is possible to impart different crystalline structures within a single laminated structure, thereby creating anisotropy in its mechanical properties.

[0083] For example, as shown in Figure 6, by repeatedly performing additive manufacturing with a layer thickness of △h20μm to form crystalline structure A, and then repeatedly performing additive manufacturing with a layer thickness of △h60μm to form crystalline structure B, a laminated structure with a change in crystalline structure in the Z direction can be manufactured.

[0084] Furthermore, the crystalline structure can be controlled not only in the stacking direction (Z direction) but also within the XY plane of the molten and solidified layer. For example, if a molten and solidified layer is formed by irradiating a laser at an arbitrary location while the deposition thickness △h of the powder bed (powder layer) is small, and a powder bed is placed on top of it, the remaining thickness can be locally increased by irradiating the upper part of the powder bed above the portion of the thin powder bed that has not been irradiated with the laser. In this way, it is also possible to control the crystalline structure within the plane of the molten and solidified layer.

[0085] For example, as shown in Figure 7, in additive manufacturing with a layer thickness Δh of 20 μm, the left and right manufacturing regions in the figure may be irradiated with a laser each time a layer is added to form a crystalline structure A, while the central manufacturing region in the figure may not be irradiated with a laser in the first and second layering processes, but irradiated with a laser in the third layering process to form a crystalline structure B with a layer thickness Δh of 60 μm.

[0086] As described above, the manufacturing method for laminated structures of this embodiment allows for easy control of the crystalline structure contained in any three-dimensional laminated structure and enables control of any crystal orientation. Such laminated structures have advantageous effects on a wide range of product groups in various industrial fields. For example, it provides advantages such as obtaining a crystalline structure that exhibits desired mechanical properties and satisfying various requirements for properties of the laminated structure.

[0087] For example, if the deposition thickness △h of the powder bed (powder layer) is reduced, the y-scan layer is more likely to disappear from the laminated structure. Therefore, even if x-scan and y-scan are performed alternately, the y-scan layer can be intentionally removed from the laminated structure, and a laminated structure with the same crystalline structure as when only x-scan is performed can be manufactured.

[0088] In contrast, when the deposition thickness △h of the powder bed (powder layer) is increased, the y-scan layer is more likely to remain in the laminated structure. Therefore, a crystalline structure in which both x-scan and y-scan layers are mixed is more likely to appear.

[0089] For example, in a stainless steel laminated structure, if a y-scan layer is alternately laminated as the 2n-1 layer and an x-scan layer as the 2n layer with a predetermined laminate thickness or greater, along the laminate direction, i.e., the z-axis direction, <001> A single-crystal-like structure is observed.

[0090] On the other hand, in a stainless steel laminated structure, when a y-scan layer is alternately laminated as the 2n-1 layer and an x-scan layer as the 2n layer with a thickness less than a predetermined laminate thickness, two types of layers are formed along the laminate direction, i.e., the z-axis direction. <001> and <011> A lamellar crystal structure composed of these elements is expressed.

[0091] In this embodiment, the deposition thickness △h of the powder bed for each molten and solidified layer of the laminated structure was changed by changing the downward distance △h of the second lifting platform 12 in the z-axis direction. In addition, the deposition thickness △h of the powder bed may be changed by forming a powder bed again without irradiating the powder bed with a deposition thickness △h after the powder bed with a deposition thickness △h has been formed on the upper side of the molten and solidified layer. For example, as shown in Figure 8, with a laminate thickness △h of 20 μm, the laminate thickness △h may be made 60 μm by not irradiating with a laser in the first and second lamination processes, and irradiating with a laser in the third lamination process.

[0092] (Other embodiments) Although one embodiment has been described above, the present invention is not limited to the contents of this disclosure and can be implemented with appropriate modifications without changing the gist of the invention. The disclosed embodiment can be implemented in various other forms, and various omissions, substitutions, and modifications are possible without departing from the gist of the invention.

[0093] For example, in the embodiment described above, the molten solidified layer whose crystalline structure is to be controlled may be multiple molten solidified layers or a single molten solidified layer. When multiple molten solidified layers are to be controlled, all of these molten solidified layers may be formed with energy lines in the same scanning direction, or they may be formed with energy lines in different scanning directions.

[0094] Furthermore, although the above-described embodiment explained the case where the laser scanning direction is in two directions, the x-direction and the y-direction, as an example, the present invention is not limited to this. The laser scanning direction may be in three or more directions. Specifically, if the laser scanning direction is in three directions, the smallest angle between the first and second directions, the smallest angle between the second and third directions, and the smallest angle between the third and first directions may each be set to 60°. Furthermore, if the laser scanning direction is four directions, the smallest angle between the first and second directions, the smallest angle between the second and third directions, the smallest angle between the third and fourth directions, and the smallest angle between the fourth and first directions may each be 45°.

[0095] Furthermore, the present invention includes the following embodiments (1) to (5), where the first to fifth molten solidified layers are designated A, B, C, C, D, and E, respectively. (1) A fabrication method in which layers A and B are alternately layered throughout the entire laminated structure. Bottom layer: ABABABAB···ABABABAB: Top layer (2) A fabrication method in which layers A to E are repeatedly layered throughout the entire laminated structure. Bottom layer: ABCDE...ABCDE: Top layer (3) A fabrication method in which layers A, B, and C are repeatedly layered throughout the entire laminated structure. Bottom layer: ABCABCABC...ABCABCABC: Top layer (4) A fabrication method in which continuous A layers and continuous B layers are alternately stacked throughout the entire laminated structure. Bottom layer: AAABBBAAA···BBBAAABBB: Top layer (5) A fabrication method in which continuous A layer, continuous B layer, and continuous C layer are repeatedly stacked throughout the entire laminated structure. Bottom layer side: AABBCC...AABBCC: Top layer side

[0096] In the embodiment described above, the case in which the direction of gas flow F is perpendicular to the direction of x-scan and the direction of gas flow F is parallel to the direction of y-scan (i.e., αx = 90°, αy = 0°) was explained as an example, but the invention is not limited to this. For example, αx may be between 45° and 90°, and αy may be between 0° and 45°.

[0097] For example, in the above embodiment in which the 2n-1 molten and solidified layer is formed by y-scan and the 2n molten and solidified layer is formed by x-scan to manufacture the laminated structure 10, it is possible to modify the system by adopting the following constituent elements (α) and (β).

[0098] Constituent requirement (α): When forming the 2n-1 y-scan layer, change the direction of the gas flow F so that αy is between 0° and 45°. Configuration requirement (β): When forming the 2nth x-scan layer, change the direction of the gas flow F so that αx is between 45° and 90°.

[0099] It is believed that the remaining thickness of the x-scan and y-scan layers in the crystalline structure of the laminated structure can be changed depending on the constituent elements (α) and (β). Furthermore, this may provide greater diversity in the manner in which the crystalline structure of the laminated structure can be controlled. Constituent elements (α) and (β) can be used in combination when manufacturing a single laminated structure. When constituent elements (α) and (β) are used, it is thought that the effects of each constituent element are superimposed. In this case, constituent elements (α) and (β) may be used continuously to form adjacent x-scan and y-scan layers; or constituent elements (α) and (β) may be used intermittently to form discrete x-scan and y-scan layers that are not adjacent to each other and are separated by multiple molten and solidified layers.

[0100] Although not shown in the figures, in other embodiments, the 2n-1 layer may be formed by scanning the laser along the x-axis direction, and the 2n layer may be formed by scanning the laser along the y-axis direction. In this case, the 2n-1 layer becomes the x-scan layer, and the 2n layer becomes the y-scan layer.

[0101] Furthermore, in both x-scan and y-scan, the scanning mode can be either reciprocal or unidirectional.

[0102] In the embodiment described above, the scanning direction of the laser was fixed and the direction of the gas flow F was changed, but this is not limited to this. For example, the direction of the gas flow F may be fixed and the scanning direction of the laser may be changed. [Examples]

[0103] The effects of the present invention will be explained below with reference to experimental examples, but the present invention is not limited in any way by the following description.

[0104] <Example of experiment> The following powder composition was used as the raw material. Composition: 18Cr-14Ni-2.5Mo-0.03C-65.47Fe (mass%). The raw material powder used for gas spraying had a particle size of 53 μm or less.

[0105] The manufacturing conditions for the laminated structure are as follows: Equipment used: EOS M290 (manufactured by EOS Corporation); Laser scanning: x-scan and y-scan were performed alternately. In both x-scan and y-scan, the laser scanning was performed in a back-and-forth motion (see Figure 9). Lamination thickness: 20 μm or 60 μm; Output: 250W; X-scan and Y-scan scanning speed: 800 mm / s; X-scan and Y-scan scanning interval: 0.08 mm.

[0106] The gas flow conditions for the gas flow generation unit 5 are as follows: Gas type for gas flow: Argon gas; Gas flow direction: During the y-scan operation, argon gas was flowed along the y-axis. The y-scan layer is the molten and solidified layer being controlled. Gas flow velocity: The flow velocity on the surface of the powder bed 3 within the build stage 6 was measured using a vane-type anemometer testo 440 dP (manufactured by Testo) (see Figure 2). Measurements were taken at three locations P1, P2, and P3 below, on a plane that passes through the center of the powder bed 3 in the x-axis direction and along the y-axis direction. P1: Located closest to the gas flow generation unit 5 in the y-axis direction, and approximately 8 mm away from the surface of the powder bed 3 in the z-axis direction. P2: Located in the y-axis direction, it is the next closest to the gas flow generation unit 5 after P1, and approximately 8 mm away from the surface of the powder bed 3 in the z-axis direction. P3: Located furthest from the gas flow generation unit 5 in the y-axis direction, and approximately 8 mm away from the surface of the powder bed 3 in the z-axis direction. The gas flow velocity at P1 was 1.9 m / s. The gas flow velocity at P2 was 1.7 m / s. The gas flow velocity at P3 was 1.7 m / s.

[0107] The method for evaluating the crystalline structure of a laminated structure is as follows: Scanning electron microscopy (FE-SEM) and backscattered electron diffraction (EBSD) were used. The laminated structure was cut in the xy and yz planes, polished with emery paper up to #4000, and then polished to a mirror finish using colloidal silica. Subsequently, it was etched with an etching solution consisting of 21% HF, 29% HNO3, and 50% H2O. After that, the crystal orientation of the xy and yz cross-sections was observed and analyzed. For the FE-SEM, we used the JIB-4610F (manufactured by JEOL). For EBSD (Evidence-Based Stimulation), we used NordlysMax3 (manufactured by Oxford Instruments).

[0108] <Experimental Example 1> Under the above conditions, the layer thickness was set to 20 μm. Figure 10 shows the crystal orientation map and pole diagram. As shown in Figure 10(a), with respect to the z axis (layering direction), <011> The crystal orientation appears, and at equal intervals <001> A specific lamellar tissue that expresses this substance was identified.

[0109] <Experimental Example 2> Under the above conditions, the layer thickness was set to 60 μm. Figure 10 shows the crystal orientation map and pole diagram. As shown in Figure 10(b), with respect to the z axis (layering direction), <001> A single-crystal-like structure was confirmed.

[0110] <Crystal structure of the layered structures in Experimental Examples 1 and 2> Figure 11 shows the results of observing the crystalline structure of the layered structures fabricated in Experimental Examples 1 and 2. The arrows in Figure 11 indicate the temperature gradient associated with dissolution. Generally, cellular structures (solidified structures) are said to grow in a direction close to this temperature gradient, and the elongation direction of this cellular structure is crystallographic. <100> It is parallel to the direction.

[0111] As shown in the upper part of Figure 11: (a), in Experimental Example 1, which was fabricated with a layer thickness of 20 μm, as indicated by the arrows in the yz plane, the cell structure grew along two directions (±45°) from the construction direction of the melt pool in the x-scan, and in that direction <100> The crystal orientation map <011> It corresponds to the direction. Also, in the center of the melt pool, the cell structure grows along the layering direction. <001> It corresponds to the direction. On the other hand, it was confirmed that the crystal orientation of the x-scan was dominant in the y-scan. This is thought to be because, compared to the layer formed in the x-scan, the y-scan layer was reduced, causing the x-scan layer to overwrite the y-scan layer, resulting in a crystal orientation biased towards the x-scan layer. In Experimental Example 1, it is thought that the y-scan was overwritten by the x-scan, resulting in a decrease or disappearance of the y-scan layer thickness. As a result, it is presumed that a lamellar crystalline structure was formed in the laminated structure.

[0112] As shown in the lower part of Figure 11: (b), in Experimental Example 2, which was fabricated with a layer thickness of 60 μm, elongated cell structures grew from the bottom of the melt pool along the layering direction, and from the upper wall of the melt pool in a direction perpendicular to the fabrication direction. As a result, the layered structure grew along the fabrication direction. <001> A single-crystal-like structure was formed. In Experimental Example 2, the layer thickness was significantly thicker compared to Experimental Example 1, suggesting that y-scans remained and a single-crystal-like structure emerged rather than a lamellar crystal structure.

[0113] <Experimental Example 3> The melting depth of the x-scan layer and the y-scan layer were measured when the layer thickness was changed to 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, and 80 μm. The fabrication conditions for the laminated structures were the same as in Experimental Examples 1 and 2, except that the laminate thickness was changed as described above.

[0114] Figure 12 shows the results of observing the crystalline structure of the laminated structure fabricated in Experimental Example 3. Figure 13 shows the relationship between the powder bed deposition thickness and the molten pool depth in Example 3. As shown in Figures 12 and 13, the energy attenuation in the y-scan was greater than that of the laser scanning perpendicular to the gas flow (x-scan), resulting in a smaller melting depth in the y-scan layer than in the x-scan layer. At this time, the difference between the melting depth "Sx" in the x-scan and the melting depth "Sy" in the y-scan, "Sx-Sy," was as shown in Table 1 below. As shown in Table 1, the average value of "Sx-Sy" was 28.5 μm.

[0115] [Table 1]

[0116] In Figure 13, the asterisk "*" indicates that the p-value, statistically analyzed using the Student's t-test described below, is less than 0.05. A p-value less than 0.05 indicates that the differences in the data connected by lines are statistically significant. All the data differences shown in Figure 13 have p-values ​​less than 0.05, confirming their statistical significance.

[0117] Here, "Student's t-test" consists of p-value-based significance determination and confidence intervals for the difference in population means. P-value-based significance determination was performed by investigating whether the population means of the two populations (two groups) were equal based on the means and standard deviations of the two populations. Specifically, 10 samples each of melting depth Sx and Sy were measured, and a t-test (two-tailed test) was performed on two samples with equal variances using the "T.TEST" function in "Microsoft Excel for Microsoft 365".

[0118] <Experimental Example 4> The remaining thickness of the x-scan layer (x-scan thickness) and the remaining thickness of the y-scan layer (y-scan thickness) were measured when the layer thickness was changed to 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, and 80 μm. The fabrication conditions for the laminated structures were the same as in Experimental Examples 1 and 2, except that the laminate thickness was changed as described above.

[0119] As shown in Figures 14 and 15, the energy attenuation in the y-scan was greater than that of the laser scanning perpendicular to the gas flow (x-scan), resulting in a smaller thickness for the y-scan layer than for the x-scan layer. Furthermore, all of the data differences in Figure 15 had p-values ​​less than 0.05, confirming their statistical significance.

[0120] In addition, at a laminate thickness of 20 μm, the y-scan was overwritten by the x-scan, and a crystalline structure with a crystal orientation biased towards the x-scan was observed. As a result, one type of crystalline structure remained in the laminated structure and appeared along the lamination direction.

[0121] At a laminate thickness of 30 μm, the y-scan was not overwritten by the x-scan, and a crystalline structure with biased crystal orientation towards both the x-scan and y-scan was observed. As a result, two types of crystalline structures remained in the laminated structure and appeared along the lamination direction.

[0122] At layer thicknesses of 40 μm or more, the y-scan was not overwritten by the x-scan, and a crystalline structure with biased crystal orientation towards both the x-scan and y-scan was observed. Furthermore, it was confirmed that adjacent molten pools were in contact with the y-scan crystalline structure. The number of contact points increased as the layer thickness increased.

[0123] <Experimental Example 5> The layer thickness of the powder bed was repeatedly changed to 20 μm, 60 μm, and 20 μm. It is believed that the layered structure shown in Figure 16 is produced. As shown in Figure 16, when the layer thickness is 20 μm, the y-scan layer is overwritten by the x-scan layer and disappears from the layered structure. On the other hand, when the layer thickness is 60 μm, the y-scan layer remains in the layered structure. As a result, a layered structure in which the y-scan layer is partially absent is obtained. As shown in Figure 17, two types of crystalline structures appeared along the layering direction.

[0124] From the results of the above experimental examples, by controlling the minimum angle α between the scanning direction of the laser (energy beam) and the direction of the gas flow F, and by controlling the deposition thickness of the powder bed, at least in the stacking direction <001> and <011> Lamellar tissue consisting of <001> We confirmed that a single-crystal-like structure can be formed. Thus, even if the laser scanning direction is fixed to xy (90°), it is advantageous that the crystal orientation can be changed in the stacking direction by controlling the smallest angle α between the laser scanning direction and the gas flow F direction, and by controlling the powder bed deposition thickness. For example, even if the orientation of the part relative to the stacking direction is changed, a part with any desired crystal orientation can be obtained, and it is expected that properties such as mechanical strength and elastic modulus can be broadly controlled by controlling the crystal orientation.

[0125] Generally, any raw material powder can be melted by adjusting the output of the heat source (energy ray), the scan speed, and the process parameters of the scan strategy. The above experimental example shows the results for stainless steel alloys, but similar effects can be obtained with any raw material that can be melted by a laser. [Explanation of Symbols]

[0126] 1...Laminated structure manufacturing apparatus, 2...Chamber, 3...Powder bed, 4...Irradiation unit, 5...Gas flow generation unit, 6...Building stage, 7...Storage unit, 8...Recovery unit, 9...Recoater, 10...Laminated structure, 11...First lifting platform, 12...Second lifting platform, 13...Laser oscillator, 14...Optical system, 15...Shielding gas supply pipe, 16...Third lifting platform, M...Raw material powder.

Claims

1. A gas flow parallel to the surface is provided along the surface of the powder bed on which the raw material powder is deposited. A first molten and solidified layer is formed by irradiating the surface with an energy beam while scanning it in a first direction parallel to the surface. A second molten and solidified layer is formed on the first molten and solidified layer by irradiating it with an energy beam while scanning it in a second direction parallel to the surface and intersecting the first direction. A method for producing a laminated structure having a crystalline structure in which one or more first and second molten solidified layers are each stacked in multiple layers in the thickness direction, When forming the first molten solidified layer, the first deposition thickness of the powder bed and the first heat input of the energy rays irradiated onto the powder bed are adjusted to control the deposition thickness of the first molten solidified layer and the melting depth of the first molten solidified layer. When forming the second molten solidification layer, the second deposition thickness of the powder bed and the second heat input of the energy rays irradiated onto the powder bed are adjusted to control the deposition thickness of the second molten solidification layer and the melting depth of the second molten solidification layer. The process includes at least one of the following steps: adjusting the angle α1 between the first direction and the gas flow direction according to the first deposition thickness of the powder bed, so that spatter and fumes generated when the raw material powder melts due to irradiation with energy rays are flowed in the scanning direction of the energy rays by the gas flow, and reducing the first heat input by utilizing the attenuation of energy rays that occurs in the scanning direction; and adjusting the angle α2 between the second direction and the gas flow direction according to the second deposition thickness of the powder bed, so that spatter and fumes generated when the raw material powder melts due to irradiation with energy rays are flowed in the scanning direction of the energy rays by the gas flow, and reducing the second heat input by utilizing the attenuation of energy rays that occurs in the scanning direction. A difference is created between the first heat input and the second heat input. The remaining thickness of the first molten solidified layer and the remaining thickness of the second molten solidified layer in the crystalline structure are controlled as follows: A method for manufacturing a laminated structure, comprising controlling the crystal orientation in the crystalline structure of the laminated structure.

2. The method for manufacturing a laminated structure according to claim 1, wherein one of the angles α1 and α2 is adjusted to 45° or more and 90° or less, and the other is adjusted to 0° or more and 45° or less.

3. A method for manufacturing a laminated structure according to claim 1, further comprising a crystalline structure in which multiple layers of the first molten solidified layer or the second molten solidified layer are stacked in the thickness direction.

4. A third molten and solidified layer is formed by irradiating the surface with energy rays while scanning in a third direction parallel to the surface and intersecting the first and second directions, respectively. A method for manufacturing a laminated structure according to claim 1, comprising manufacturing a laminated structure that further includes a crystalline structure comprising at least one third molten solidified layer, wherein multiple layers of these layers are stacked in the thickness direction.

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