Method for manufacturing an article mainly composed of silicon carbide and raw material powder used therefor

Abstract

To manufacture an article having silicon carbide as a main component by a PBF (powder bed fusion) method with smaller energy.SOLUTION: A method for manufacturing an article having silicon carbide as a main component includes the steps of: forming a layer of a raw-material powder; and irradiating the layer with a laser on the basis of data pertaining to a three-dimensional model, wherein each of these steps is performed a plurality of times. The raw-material powder is a mixed powder of a silicon carbide powder, a metal silicon powder, and a carbon powder. The silicon carbide powder is included in a proportion of 60 at% or more and less than 100 at%. The spatial laser power density of the laser in the step of irradiating the layer with a laser ranges from 11 J / mm3 or more and 50 J / mm3 or less.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a technique for manufacturing an article mainly composed of silicon carbide using a powder bed fusion method.

Background Art

[0002] As a method for manufacturing prototypes or small-lot, multi-variety articles having complex shapes, an additive manufacturing method called 3D printing, which irradiates a laser onto metal or resin powder according to the three-dimensional data of the article to be manufactured, is being utilized. In recent years, there has been a demand for the shaping of articles made of inorganic compounds that are difficult to process, such as SiC and TiAl, not only metals and resins.

[0003] Patent Document 1 proposes a method for producing an article mainly composed of silicon carbide by using a raw material containing silicon carbide particles and molding resin particles such as nylon, polypropylene, and polyethylene terephthalate, and using a powder bed fusion method. Further, Patent Document 2 discloses a method for performing shaping using a powder containing silicon carbide and a metal boride having a melting point lower than the sublimation point of silicon carbide.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the case of a process of forming by heating a mixture of silicon carbide particles and molding resin particles as in Patent Document 1, when irradiating with a laser to sinter the irradiated portion, voids are formed inside the article. Patent Document 2 utilizes a eutectic of silicon carbide and metal boride and can perform forming while suppressing the sublimation of silicon carbide, so that a molded article with relatively high density can be obtained. However, it is necessary to heat up to about 2000 °C or higher, which is the melting point of the metal boride, and high energy is required for forming.

[0006] Under such circumstances, a technique for producing an article mainly composed of silicon carbide by an additive manufacturing method with less energy than conventional methods without using an organic material such as resin is desired.

Means for Solving the Problem

[0007] The first aspect according to the present invention is a method for manufacturing an article mainly composed of silicon carbide, including a step of forming a layer of raw material powder, and a step of irradiating the layer with a laser based on data of a three-dimensional model, each being repeated a plurality of times, wherein the raw material powder is a mixed powder of silicon carbide powder, metal silicon powder, and carbon powder, the silicon carbide powder is contained at a ratio of 60 at% or more and less than 100 at%, and the spatial laser power density of the laser in the step of irradiating the laser is 11 J / mm 3 or more and 50 J / mm 3 or less.

[0008] Further, the second aspect according to the present invention is a raw material powder for manufacturing an article mainly composed of silicon carbide using a powder bed fusion method, wherein the raw material powder is a mixed powder of silicon carbide powder, metal silicon powder, and carbon powder, and the silicon carbide powder is contained at a ratio of 60 at% or more and less than 100 at%.

Advantages of the Invention

[0009] According to the present invention, it becomes possible to produce an article mainly composed of silicon carbide by a powder bed fusion method with less energy than conventional methods without using an organic material such as resin.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0011] As one of the methods for producing an article mainly composed of a high melting point inorganic compound, a process called combustion synthesis is known. Combustion synthesis is a simple and economical method in which energy q is applied to (ignited) a part of the powder composed of the constituent elements of the inorganic compound to cause a chemical reaction, and the reaction heat Q generated during the chemical reaction is propagated into the powder as a combustion wave to promote the combination. For example, a combustion reaction in which a compound AB is formed by the chemical reaction of element A and element B is represented by formula (1). In the present invention, the main component of the article means a component that occupies 75 at% or more of the article. A + B + q → AB + Q ··· (1)

[0012] q represents the input energy, Q represents the reaction heat, is expressed in the unit of [KJ / mol], and q < Q. The reaction phenomenon of formula (1) is a very short-time reaction that occurs within 1 second, and the temperature rises explosively. Note that formula (1) represents the stoichiometric relationship in an omitted form.

[0013] When producing silicon carbide, it is preferable to use the chemical reaction between metallic silicon (Si) as A and carbon (C) as B in formula (1).

[0014] If such a combustion synthesis process is applied to the powder bed fusion method, it is expected that a shaped article with a high ratio of a desired inorganic compound can be produced with less energy. However, as described above, since the reaction heat generated in the combustion synthesis process propagates, the chemical reaction does not stay in the portion irradiated with the laser. In addition, since the temperature rises explosively, voids may be generated in the sintered body, and it may be difficult to maintain the shape.

[0015] As a result of investigations to solve the above problems, it has been found that by adding an appropriate amount of silicon carbide generated by the reaction of silicon metal and carbon to the powders of silicon metal and carbon in advance, the propagation of the chemical reaction and the temperature rise can be suppressed within a predetermined region.

[0016] However, the effect expected from the addition of silicon carbide depends on the composition ratio of the silicon metal powder, carbon powder, and silicon carbide powder. When producing silicon carbide, it is preferable to use a powder containing silicon metal, carbon, and silicon carbide as raw material powders, with a silicon carbide content of 80 at% or more. The silicon carbide powder added to the raw material powders suppresses the reactivity between the silicon metal and carbon, and restricts the propagation of the combustion wave accompanying the combustion synthesis. Furthermore, since silicon carbide absorbs heat and suppresses heat transfer to the surroundings, it is considered possible to perform shaping while keeping the explosive temperature rise during shaping within the laser irradiation region. In addition, the atomic ratio of carbon contained in the raw material powders is preferably equal to or higher than the atomic ratio of silicon metal. By setting the atomic ratio of carbon to be equal to or higher than the atomic ratio of silicon metal, the carbon remaining without reacting with the silicon metal can be utilized as C for combining with the silicon metal to be impregnated in the solid phase impregnation process described later.

[0017] The outline of a modeling apparatus 100 that can be suitably used for a powder bed fusion method using raw material powder according to the present invention is shown in FIG. 1. The modeling apparatus 100 is an apparatus that performs modeling using the powder bed fusion method, and has a chamber 101 that can control the internal atmosphere by a gas introduction mechanism 113 and an exhaust mechanism 114. Inside the chamber 101, there are a modeling container 120 for modeling a three-dimensional object and a powder container 121 for storing raw material powder as a modeling material (hereinafter, may be simply described as a modeling material or powder). Furthermore, it has a powder layer forming mechanism 106 for spreading the raw material powder stored in the powder container 121 in the modeling container 120 to form a powder layer 111.

[0018] The exhaust mechanism 114 may be provided with a pressure adjustment mechanism such as a butterfly valve to adjust the pressure, or may be configured to adjust the atmosphere in the chamber by gas supply and the accompanying pressure increase (generally called blow replacement).

[0019] The bottoms of the modeling container 120 and the powder container 122 can be changed in position in the vertical direction by a lifting mechanism 108, respectively. The bottom of the modeling container 120 is configured as a stage 107 on which a base plate 121 is installed. The moving direction and the moving amount of the lifting mechanism 108 are controlled by the control unit 115, and the moving amounts of the bottom of the powder container 122 and the stage 107 are determined according to the layer thickness of the powder layer 111 to be formed. Usually, since the lifting mechanism 108 moves up and down at a height of several tens of μm, it is desirable that the height resolution is 1 μm or less.

[0020] The base plate 121 is a plate made of a meltable material such as stainless steel. When melting and solidifying the first layer of powder layer disposed on the plate, its surface is melted together with the modeling material, and a structure for fixing the modeled object to the base plate 121 is formed. And during the modeling, the position of the modeled object on the base plate 121 can be held so as not to shift. After the modeling is completed, the base plate 121 is mechanically separated from the modeled object. In order to improve the adhesion between the base plate and the modeled object, a Ti film may be pre-deposited on the modeling surface of the base plate.

[0021] The powder layer forming mechanism 106 has a powder storage part for storing raw material powder and a supply mechanism for supplying the raw material powder from the powder container 122 to the modeling container 120. Further, in order to level the powder layer on the base plate 121 to a set thickness, it has at least one of a squeegee and a roller. In order to increase the density of the resulting modeled object and promote the chemical reaction of the powder, it is preferable to have both a squeegee and a roller, and after adjusting the thickness of the powder layer with the squeegee, pressurize it with the roller to increase the density of the powder layer.

[0022] The modeling apparatus 100 further includes an energy beam source 102 for causing combustion synthesis in the raw material, scanning mirrors 103A and 103B for two-axis scanning of the energy beam 112, and an optical system 104 for condensing the energy beam on the irradiation part. Since the energy beam 112 is irradiated from the outside of the chamber 101, the chamber 101 is provided with an introduction window 105 for introducing the energy beam 112 inside. The power density and scanning position of the energy beam are controlled by the control unit 115 according to the data of the three-dimensional model of the object to be modeled acquired by the control unit 115 and the characteristics of the modeling material. Also, the positions of the modeling container 120 and the optical system 104 are adjusted in advance so that a desired beam diameter is obtained on the surface of the powder layer 111. The beam diameter on the surface of the powder layer 111 preferably ranges from 30 to 100 μm because it affects the modeling accuracy.

[0023] As the scanning mirrors 103A and 103B, galvanometer mirrors can be preferably used. Since galvanometer mirrors operate at high speed while reflecting the energy beam, it is desirable that they be made of a lightweight material with a low coefficient of linear expansion.

[0024] Lasers are widely used as the energy beam 112. Although YAG lasers are often used, CO2 lasers or semiconductor lasers may also be used. The driving method may be a pulse type or a continuous irradiation type. The laser is preferably selected according to the absorption wavelength of the powder, and it is sufficient to have a wavelength with an absorption of 50% or more by the powder, and more preferably a wavelength with an absorption of 80% or more.

[0025] As methods for controlling the irradiation intensity of the laser, there are a method for controlling the in-plane laser power density and a method for controlling the spatial laser power density. The in-plane laser power density is the laser irradiation intensity per unit area, and the unit is J / mm 2 which is expressed as. On the other hand, the spatial laser power density is the laser irradiation intensity per unit volume, and is expressed as J / mm 3 When forming a shaped object by controlling the film thickness as in a 3D printer, it is appropriate to consider the spatial laser power density. The spatial laser power density J is expressed by the following formula. J = W / (P×V×D)

[0026] Here, W is the laser irradiation power, P is the laser irradiation pitch, V is the laser scanning speed, and D is the powder coating thickness. In a general device, the outputtable laser power W is 10 to 1000 W, the laser irradiation pitch P is usually 5 to 500 μm, the laser scanning speed is usually 10 to 10000 mm / sec, and the powder coating thickness D is usually 5 to 500 μm. When forming using the raw material powder of the present invention, the parameters of W, P, V, and D are controlled within the above ranges, and the spatial laser power density J may be adjusted within the range of 11 to 50 J / mm 3 The lower limit of 10 J / mm 3 is the energy required to sufficiently melt the powder, and the upper limit of 30 J / mm 3This is the area where shaping becomes impossible due to the volatilization of the powder.

[0027] During shaping, the base plate 121 is placed on the stage 107, and the inside of the chamber 101 is replaced with an inert gas such as nitrogen or argon. When the replacement is completed, a powder layer 111 is formed on the base plate 121 by the powder layer forming mechanism 106. The powder layer 111 is formed with a thickness corresponding to the slice pitch of the slice data generated from the three-dimensional shape data of the object to be shaped, that is, the lamination pitch. Then, the energy beam 112 is scanned according to the slice data, and the powder in a predetermined area is irradiated with a laser.

[0028] When the irradiation of the laser for one layer based on the slice data is completed, the shaping stage 107 is lowered by the lamination pitch by the elevating mechanism 108, and the bottom of the material container 122 is raised according to the lamination pitch. Then, the raw material powder in the material container 122 is moved to the shaping container 120 by the powder layer forming mechanism 106, the powder is spread over the layer where the energy beam has been scanned, a new powder layer is formed, and the scanning and irradiation of the energy beam 112 are performed.

[0029] As described above, in the area where the energy beam 112 is irradiated, the surface of the layer where the energy beam 112 has been scanned previously is also solidified again. When the area directly below the area where the energy beam 112 is irradiated in the new powder layer is an already solidified area, the beam irradiation area of the new powder layer solidifies with the material mixed at the boundary with the previously melted and solidified area and binds to each other. By repeating these operations, the shaped object 110 can be formed.

[0030] When irradiating the powder layer with a laser, as shown in Fig. 2(b), it is preferable to divide the irradiation area into rectangles and perform discrete irradiation. The size of one area divided into rectangles is preferably 5 mm × 5 mm or less, more preferably 2 mm × 2 mm or less. As shown in Fig. 2(a), when the laser is continuously scanned in one stroke, reaction heat accumulates at each turning point, resulting in variations in the composition of the shaped object or the generation of voids. However, if discrete irradiation is performed as shown in Fig. 2(b), the propagation of the combustion wave can be restricted in the in-plane direction, and variations in reaction heat within the shaping plane can be suppressed. The irradiation area does not have to be rectangular and may be polygonal or circular. Even when it is not rectangular, per area, it is preferably 2 25 mm or less, more preferably 2 5 mm or less.

[0031] The particle diameter of the particles contained in the raw material powder containing the powder according to the present invention is preferably 0.5 μm or more and 100 μm or less, more preferably 1 μm or more and 70 μm or less. If the particles contained in the raw material powder are within this range, particle fluidity suitable for forming a powder layer during shaping can be obtained, and it becomes possible to shape a fine shaped object. The particle diameter referred to here means the Feret diameter (fixed direction diameter) measured using a microscope.

[0032] Furthermore, the average particle diameter of each of the SiC, Si, and C particles is preferably made smaller for a composition with a higher melting point or sublimation point, and preferably in the relationship of C powder < SiC powder < Si powder. By making the particles of C and SiC with a high melting point or sublimation point in the raw material powder smaller, the molten Si can cover the C and SiC particles, promoting the reaction and suppressing sublimation. The average particle diameter referred to here is such that for the raw material powder in which the powders of SiC, Si, and C are mixed, the Feret diameter (fixed direction diameter) is measured for at least 1000 particles of each type of powder using a microscope, and the average value is obtained. When the powders of SiC, Si, and C before mixing are available, or when the powders can be separated by type from the mixed powder, the median diameter measured using a laser diffraction particle size distribution measuring device for each type is taken as the average particle diameter.

[0033] Even when using the raw material powder containing the powder according to the present invention, if the intensity of the irradiated laser is too high, an explosive reaction will occur. Therefore, in order to prevent an explosive reaction from occurring, it is advisable to control the power density of the laser irradiated on the raw material powder within a predetermined range according to the composition of the raw material powder. Specifically, it is preferable to irradiate the laser to such an extent that Si and C do not completely combine, and Si (melting point 1414 °C) with a melting point lower than the decomposition point of SiC (2545 °C) melts and functions as a binder that physically binds other powders. Furthermore, it is also preferable to irradiate the laser to such an extent that an intermediate product SixCy in which a part of the crystal structure of Si is replaced by C is formed. The solidified product bonded by this Si and the shaped article containing SixCy can be entirely converted to SiC by heat treatment later.

[0034] When the fabricated shaped article contains voids, impregnation may be performed to improve the strength.

[0035] In the case of a SiC shaped article, solid-phase impregnation, liquid-phase impregnation, and gas-phase impregnation are known. Among them, solid-phase impregnation and liquid-phase impregnation are preferable because the strength of the shaped article can be increased relatively simply. In particular, solid-phase impregnation can improve the strength in a short time and is preferable.

[0036] When performing solid-phase impregnation on a SiC shaped article, after supporting C in the voids of the shaped article, it is advisable to flow a melt of Si into the voids to convert the voids into SiC.

[0037] The procedure for solid-phase impregnation is as follows: First, immerse the shaped article in a liquid resin and degas it in a vacuum to impregnate the liquid resin into the voids. After removing the unnecessary liquid resin on the surface of the shaped article, heat the resin to cure it, and then heat it until carbonization to support C in the voids. Subsequently, bring the obtained shaped article into contact with molten Si in a vacuum to impregnate Si into the voids, and heat it at 1450 to 1700 °C to convert the voids into SiC. After the voids are converted into SiC, excess Si adheres to the surface of the shaped article, but it can be removed by post-treatment such as polishing or etching.

[0038] For the resin for supporting C in the voids of the shaped article, a resin that does not contain a metal component is used. If it contains a metal component, it will react with Si in the shaped article to form an extra compound. Also, the higher the char yield of the resin, the higher the SiC ratio in the voids can be increased. The char yield of the resin is preferably 50% or more, more preferably 60% or more, and a phenolic resin is particularly preferred.

[0039] Also, in order to infiltrate the resin into the voids, the viscosity of the resin is preferably 1000 mPa·s or less, and more preferably 500 mPa·s or less.

[0040] When performing liquid phase impregnation on a SiC shaped article, commercially available SiC polymer (polycarbosilane) can be used as the impregnation material for SiC. The fabricated shaped article is immersed in the SiC polymer solution, and vacuum degassing is performed to introduce the SiC polymer solution into the voids of the shaped article. After removing the excess liquid from the surface of the shaped article, heat treatment is performed at 800 - 1300 °C in an inert gas to inorganify the SiC polymer. Since the SiC polymer is a SiC ceramic precursor containing organic substances, about 30 wt.% is lost by volatilization during the heat treatment. Therefore, the porosity of the shaped article can be reduced by repeating the impregnation and heat treatment steps multiple times. The SiC obtained by heat-treating the SiC polymer at 800 - 1300 °C has an amorphous structure, but it can be crystallized and its hardness can be improved by performing heat treatment at about 1600 °C later.

Example

[0041] Examples and comparative examples according to the present invention will be described. However, the types, compositions, particle shapes, shapes, laser powers, etc. of the powders described below should be appropriately changed according to the configuration and various conditions of the apparatus to which the invention is applied, and are not intended to limit the invention to the scope of the disclosure in this specification.

[0042] As the raw material powder, a mixed powder of SiC powder, Si powder, and C powder was used. The details of each powder are as follows. SiC: Average particle diameter 15.0 μm Manufactured by Shinano Electric Refining Co., Ltd. (Product name: SSC-A15) Si powder: Average particle diameter 45.0 μm Manufactured by High Purity Chemical Research Institute, Inc. (Product name: SIE19PB) C powder: Average particle diameter 5.0 μm Manufactured by High Purity Chemical Research Institute, Inc. (Product name: CCE03PB)

[0043] Raw material powders with different mixing ratios of SiC, Si, and C powders were prepared, and each raw material powder was irradiated with a laser under a plurality of laser irradiation conditions (spatial laser power density) for shaping.

[0044] The SiC, Si, and C powders were weighed in the required amounts respectively and mixed by a ball mill.

[0045] The mixed powder was placed in the material container 122, and the chamber was evacuated and then Ar gas was introduced multiple times to replace the atmosphere in the chamber with an N 2 atmosphere. The raw material powder in the powder container 122 was spread evenly on the stainless-steel base plate 121 placed on the stage 107 by the powder layer forming mechanism 106 to have a uniform thickness. The height of the stage 107 was adjusted so that the thickness of the powder was 50 μm.

[0046] Subsequently, the powder was irradiated with a laser for shaping. As the laser, a Nd:YAG laser with a wavelength of 1060 nm was used. The laser power was 100 W, the irradiation pitch was 40 μm, and the spatial laser power density was changed in the range of 11~75 J / mm 3 to perform shaping according to a three-dimensional model in the shape of a 4 mm × 4 mm × 250 μm rectangular parallelepiped. When the laser irradiation of the first layer was completed, powder laying and laser irradiation were performed in the same manner as in the first layer, and this process was repeated until the shaped object reached the desired height.

[0047] Also, as a comparative example, a raw material powder composed of SiC powder was irradiated with a spatial laser power density of 11~50 J / mm3 The laser was irradiated within the range of

[0048] Since the stainless steel used for the base plate has a high thermal conductivity, if the irradiation heat of the laser to be irradiated is low, it will dissipate. If the energy of the laser to be irradiated is low, the adhesion between the shaped object and the base plate will be low. Therefore, before starting the shaping of the rectangular parallelepiped model, the spatial laser power density was 100 J / mm 3 and the shaping was performed in three layers to form a base for the shaping of the rectangular parallelepiped model.

[0049] The height of the fabricated shaped object was measured without separating it from the plate. Fig. 3 shows the relationship between the height of the shaped object fabricated with the composition of the raw material powder and the spatial laser power density.

[0050] The feasibility of the shaped object was evaluated from the deviation amount between the height of the obtained shaped object and the height (250 μm) of the cubic model. The mixing ratios of the raw material powders of powders 1 to 9 used for shaping, the spatial laser power density of the irradiated laser, and the evaluation results are summarized in Table 1. The evaluation criteria are as follows. "―" in the table represents not examined. A: The height is 200 μm or more B: The height is 170 μm or more and less than 200 μm C: The height is less than 170 μm D: Shaping cannot be performed

[0051] For the shaped object evaluated as A, the reduction amount per layer due to laser irradiation is suppressed to a level where the powder melts and the density increases. For the shaped object evaluated as B, although the reduction amount is larger than that of A, the explosive temperature rise due to combustion synthesis is suppressed, and the scattering of the raw material powder from the shaping area is suppressed. By adjusting the slice data and shaping conditions, it is possible to fabricate the target shaped object. For evaluation C, the explosive temperature rise due to combustion synthesis could not be suppressed, the raw material powder volatilized, and not enough powder remained in the shaping area. Therefore, not only the shaping accuracy in the height direction but also the shaping accuracy in the shaping surface direction was extremely low. For evaluation D, the powder did not melt and shaping could not be performed.

[0052] In Table 1, each powder contains metallic silicon powder and carbon powder in the same atomic ratio, but a deviation of about ±10% from the target atomic ratio is allowed.

[0053]

Table 1

[0054] SiC has no melting point and decomposes at 2545 °C. On the other hand, the decomposition point of C powder, which is an elemental powder constituting SiC, is 3642 °C, and the melting point of Si powder is 1414 °C. For Powders 1 to 9, combustion synthesis of Si and C occurred, and a laser was irradiated under conditions where the temperature was raised to a temperature at which Si powder was melted. For the shaped objects produced by irradiating Powders 1 to 6 with a laser at a spatial laser power density of 11.1 [J / mm 3 , the composition was confirmed by X-ray diffraction. In all the shaped objects, it was confirmed that there were portions where SiC powder was bonded with Si and portions of SiC where some of the diamond lattice of Si was substituted with C atoms. 0.98 C 0.02 atoms.

[0055] At the mixing ratio of the raw material powders of Powders 1 to 6, four strip-shaped shaped objects with dimensions of 4 mm × 3 mm × 40 mm were produced on a stainless-steel base plate at a spatial laser power density of 15 [J / mm 3 .

[0056] For two out of the four shaped objects on the base plate, first, a sufficient amount of liquid phenolic resin (PR-50607B manufactured by Sumitomo Bakelite) was dropped onto the shaped objects, and then degassing was performed in a vacuum. After wiping off the excess phenolic resin on the surface of the shaped objects, heating was carried out on a hot plate at 160 °C to thermally cure the phenolic resin.

[0057] After that, the shaped object was separated from the base plate using a diamond wire saw. When the cut surface of the shaped object impregnated with the phenolic resin was observed under a microscope, it was confirmed that the phenolic resin had sufficiently penetrated into the voids. Also, when separating the shaped object from the base plate, no chipping occurred on the shaped object.

[0058] On the other hand, among the shaped objects not impregnated with the phenolic resin, some had small chips at the ends when separated from the base plate. Since the shaped objects not impregnated with the phenolic resin were used for strength comparison with the impregnated shaped objects, the subsequent processes were not carried out.

[0059] The shaped object impregnated with the phenolic resin was immersed in liquid phenolic resin, degassed under vacuum and impregnated again, and then heat-treated at 800 °C for 30 minutes to carbonize the phenolic resin.

[0060] After carbonization of the phenolic resin, the volume and weight of the shaped object were measured, and the porosity was measured. From the measured porosity results, the amount of Si required for SiC impregnation was calculated. φ2 mm alumina balls were arranged side by side as a setter on the bottom surface in the crucible so that the shaped object would not stick to the crucible. After that, the shaped object was placed in the crucible, and Si pieces in an amount about 20% more than the calculated required amount of Si were placed on it, and heat treatment was carried out. The heat treatment was carried out at 1500 °C for 1 hour in an Ar atmosphere with a pressure of 2600 Pa. Since excess Si adhered to the surface of the shaped object, it was shaped into a strip shape of 4 mm × 3 mm × 40 mm by grinding and polishing. When the surface of the impregnated shaped object was observed using a microscope, cracks and holes were significantly reduced.

[0061] For each of the shaped objects without solid-phase impregnation and the shaped objects with solid-phase impregnation, a four-point bending test evaluation was carried out using an Instron universal testing machine (Model 4507, load cell 1KN). The evaluation conditions are as follows. Atmosphere: In air Crosshead movement speed: 0.5 mm / min Distance between supports: L = 30 Jig material: SiC

[0062] For shaped articles with the same shaping conditions, when comparing the values of the four-point bending test evaluation between the shaped article subjected to solid-phase impregnation and the shaped article not subjected to solid-phase impregnation, in all cases, it was confirmed that the bending strength of the shaped article became more than four times stronger by performing solid-phase impregnation.

[0063] After performing the four-point bending test evaluation, when confirming the composition of the shaped article subjected to solid-phase impregnation using the X-ray diffraction method, in all shaped articles, SiC was contained at 75 at% or more, and Si was contained in the range of 25 at% or less.

[0064] From the above results, by adding an appropriate amount of silicon carbide powder to the raw material powder containing metal silicon powder and carbon powder and controlling the spatial laser power density irradiated according to the mixing ratio of the raw material powder, it was confirmed that it is possible to suppress the explosive reaction heat by combustion synthesis and enable shaping.

[0065] Specifically, the raw material powder contains silicon carbide powder at a ratio of 60 at% or more and less than 100 at%, and it is preferable to irradiate a laser with a spatial laser power density of 11 J / mm 3 or more and 50 J / mm 3 or less. Furthermore, it is preferable to irradiate a laser with a spatial laser power density of 15 J / mm 3 or more and 35 J / mm 3 or less when the silicon carbide powder is contained at a ratio of 75 at% or more and 95 at% or less.

[0066] By performing shaping within such a range, it is possible to provide the heat necessary to cause a reaction between elements or compounds, suppress the explosive reaction heat by combustion synthesis, and manufacture a shaped article mainly composed of silicon carbide.

[0067] Once the shaping was completed, the shaped object was detached from the base plate and heat-treated at a temperature of 1500 °C for 1 hour in an Ar atmosphere. By X-ray diffracting the article after the heat treatment, it was confirmed that Si became a melt and reacted with the C powder remaining in the shaped object, being converted to SiC. Since the heat treatment temperature of 1500 °C is sufficiently lower than the decomposition temperatures of SiC and C, SiC and C did not decompose, and a dense article could be obtained.

Explanation of Signs

[0068] 100 Shaping apparatus 107 Shaping stage 110 Shaped object 111 Powder layer 112 Energy beam

Claims

1. A method for manufacturing an article mainly composed of silicon carbide, comprising: a step of forming a layer of raw material powder; a step of irradiating the layer with a laser based on data of a three-dimensional model; which is included multiple times respectively; wherein the raw material powder is a mixed powder of silicon carbide powder, metal silicon powder and carbon powder, and contains the silicon carbide powder at a ratio of 60 at% or more and less than 100 at%, the average particle size of the silicon carbide powder is smaller than the average particle size of the metal silicon powder, and the average particle size of the carbon powder is smaller than the average particle size of the silicon carbide powder, characterized in that it is a method for manufacturing an article.

2. The method for manufacturing an article according to claim 1, wherein the raw material powder contains the silicon carbide powder at a ratio of 75 at% or more and 95 at% or less.

3. The method for manufacturing an article according to claim 1 or 2, characterized in that the atomic ratio of the carbon powder contained in the raw material powder is equal to or more than the atomic ratio of the metal silicon.

4. The method for manufacturing an article according to any one of claims 1 to 3, characterized in that in the step of irradiating the laser, the irradiation region for irradiating the laser is divided into a plurality of regions, and the laser is irradiated discretely.

5. The spatial laser power density of the laser in the step of irradiating the laser is 11 J / mm ３ or more and 50 J / mm ３ or less, and the plurality of regions are rectangular regions each having an area of 5 mm × 5 mm or less. The method for manufacturing an article according to claim 4, characterized in that

6. a step of impregnating a shaped article obtained by performing the step of forming a layer of the raw material powder and the step of irradiating the laser multiple times with a liquid resin; a step of heating the shaped article impregnated with the liquid resin to carbonize the resin; a step of impregnating the shaped article with carbonized resin with molten metal silicon; a step of heating the shaped article impregnated with the metal silicon to convert the metal silicon into silicon carbide; further comprising, characterized in that it is a method for manufacturing an article according to any one of claims 1 to 5.

7. The method for manufacturing an article according to claim 6, wherein the resin is a phenolic resin.

8. The method for manufacturing an article according to claim 6 or 7, characterized by having a step of post-treating the surface of the obtained shaped article after the step of converting the metal silicon into silicon carbide.

9. The method for manufacturing an article according to any one of claims 1 to 8, characterized in that the particle size of the particles contained in the raw material powder is 0.5 μm or more and 100 μm or less.

10. The method for manufacturing an article according to any one of claims 1 to 9, characterized in that the raw material powder contains the metal silicon powder at a ratio of 2.5% or more and 20 at% or less.

11. The method for manufacturing an article according to any one of Claims 1 to 10, characterized in that the raw material powder contains the carbon powder in a proportion of 2.5% or more and 20 at% or less.

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