JP7690281B2 - Method for manufacturing silicon carbide-based article and raw material powder used therein - Google Patents

Description

The present invention relates to a technology for manufacturing silicon carbide-based articles using powder bed fusion bonding.

Additive manufacturing, or 3D printing, is becoming increasingly popular as a method for manufacturing prototypes with complex shapes and small quantities of a wide variety of items. In this method, a laser is irradiated onto metal or resin powder to create a shape based on the three-dimensional data of the item to be manufactured. In recent years, there has been a demand for the manufacturing of not only metals and resins, but also inorganic compounds that are difficult to process, such as SiC and TiAl.

Patent Document 1 proposes a method for producing an article whose main component is silicon carbide by powder bed fusion bonding using raw materials containing silicon carbide particles and molding resin particles such as nylon, polypropylene, and polyethylene terephthalate. In addition, Patent Document 2 discloses a method for forming an article using a powder containing silicon carbide and a metal boride having a melting point lower than the sublimation point of silicon carbide.

JP 2017-171577 A JP 2019-64226 A

In the case of a process in which a mixture of silicon carbide particles and molding resin particles is heated to form a shape, as in Patent Document 1, voids are formed inside the article when the irradiated portion is sintered by irradiating it with a laser. Patent Document 2 uses a eutectic of silicon carbide and metal boride, and can form an object while suppressing the sublimation of silicon carbide, resulting in a relatively dense object. However, it is necessary to heat the object to above about 2000°C, which is the melting point of the metal boride, and a large amount of energy is required for forming the object.

For these reasons, there is a need for a technology that uses additive manufacturing to create silicon carbide-based objects without using organic materials such as resins and with less energy than conventional methods.

A first form of the present invention is a method for manufacturing an article whose main component is silicon carbide, comprising: a step of forming a layer of raw material powder; and a step of irradiating the layer with a laser based on three-dimensional model data, each of the steps being repeated multiple times; the raw material powder is a mixed powder of silicon carbide powder, metallic silicon powder, and carbon powder, and contains the silicon carbide powder in a ratio of 60 at% or more and less than 100 at%, and the spatial laser power density of the laser in the laser irradiation step is 11 J/ ^mm3 or more and 50 J/ ^mm3 or less.

The second aspect of the present invention is a raw material powder for manufacturing an article mainly composed of silicon carbide using a powder bed fusion method, characterized in that the raw material powder is a mixed powder of silicon carbide powder, metallic silicon powder, and carbon powder, and contains the silicon carbide powder in a proportion of 60 at% or more and less than 100 at%.

The present invention makes it possible to produce silicon carbide-based articles using powder bed fusion without using organic materials such as resins and with less energy than conventional methods.

FIG. 1 is a schematic diagram of an apparatus according to the present invention. FIG. 1A is a schematic diagram showing laser irradiation in a single stroke, and FIG. 1B is a schematic diagram showing the order of irradiation when the irradiation area is divided into rectangles and laser irradiation is performed discretely. FIG. 13 is a diagram showing the relationship between the height of a structure produced with a different raw material powder composition and the spatial laser power density.

A process called combustion synthesis is known as one of the methods for producing an article whose main component is an inorganic compound with a high melting point. Combustion synthesis is a simple and economical method in which energy q is applied (ignited) to a part of a powder made 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 as a combustion wave within the powder to promote chemical synthesis. For example, the combustion reaction in which a compound AB is produced by a chemical reaction between element A and element B is represented by formula (1). In the present invention, the main component of an article refers to a component that occupies 75 at% or more of the article.
A+B+q→AB+Q...(1)

q is the input energy, Q is the heat of reaction, and is expressed in units of [KJ/mol], with q<Q. The reaction phenomenon in formula (1) is a very short reaction that occurs within one second, and the temperature rises explosively. Note that formula (1) is expressed without including the stoichiometric relationship.

When producing silicon carbide, it is preferable to use the chemical reaction between silicon metal and carbon, with A in formula (1) being silicon metal (Si) and B being carbon (C).

If this type of combustion synthesis process is applied to powder bed fusion, it is expected that it will be possible to create objects with a high ratio of the desired inorganic compounds using less energy. However, as mentioned above, the reaction heat generated in the combustion synthesis process propagates, so the chemical reaction does not remain in the area irradiated by the laser. In addition, the temperature rises explosively, which can cause voids to form in the sintered body, making it difficult to maintain the shape.

As a result of our investigations into solving the above problems, we discovered that by adding an appropriate amount of silicon carbide, which is produced by the reaction between silicon metal and carbon, to the powder of silicon metal and carbon in advance, it is possible to suppress the propagation of the chemical reaction and the temperature rise within a specified range.

However, the expected effect of adding silicon carbide depends on the composition ratio of metal silicon powder, carbon powder, and silicon carbide powder. When producing silicon carbide, it is recommended to use a powder containing metal silicon, carbon, and silicon carbide and having a silicon carbide content of 80 at% or more as the raw material powder. The silicon carbide powder added to the raw material powder suppresses the reactivity between metal silicon and carbon, limiting 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 mold while keeping the explosive temperature rise during molding within the laser irradiation area. In addition, it is preferable that the atomic ratio of carbon contained in the raw material powder is equal to or greater than the atomic ratio of metal silicon. By setting the atomic ratio of carbon to be equal to or greater than the atomic ratio of metal silicon, the carbon that remains unreacted with metal silicon can be used as C to be combined with the metal silicon to be impregnated in the solid-phase impregnation process described later.

Figure 1 shows an overview of a modeling apparatus 100 that can be suitably used in the powder bed fusion method using the raw material powder according to the present invention. The modeling apparatus 100 is an apparatus for 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 is a modeling container 120 for modeling a three-dimensional object, and a powder container 121 for containing raw material powder (hereinafter, sometimes simply referred to as modeling material or powder) which is a modeling material. In addition, there is a powder layer forming mechanism 106 for spreading the raw material powder contained in the powder container 121 over the modeling container 120 to form a powder layer 111.

The exhaust mechanism 114 may be equipped 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 supplying gas and the associated pressure increase (commonly referred to as blow replacement).

The bottoms of the modeling container 120 and the powder container 122 can each be moved vertically by the lifting mechanism 108. The bottom of the modeling container 120 is configured as a stage 107 on which a base plate 121 is placed. The direction and amount of movement of the lifting mechanism 108 are controlled by the control unit 115, and the amount of movement of the bottom of the powder container 122 and the stage 107 is determined according to the thickness of the powder layer 111 to be formed. Typically, the lifting mechanism 108 moves up and down by a height of several tens of μm, so it is desirable for the height resolution to be 1 μm or less.

The base plate 121 is a plate made of a meltable material such as stainless steel, and when the first powder layer placed on the plate is melted and solidified, its surface melts along with the modeling material, forming a structure that fixes the model to the base plate 121. During modeling, the position of the model on the base plate 121 can be maintained without shifting. After modeling is completed, the base plate 121 is mechanically separated from the model. To improve adhesion between the base plate and the model, a Ti film may be formed in advance on the modeling surface of the base plate.

The powder layer forming mechanism 106 has a powder container that contains raw powder, and a supply mechanism that supplies the raw powder from the powder container 122 to the modeling container 120. It also has at least one of a squeegee and a roller to level the powder layer on the base plate 121 to a set thickness. In order to increase the density of the resulting model and promote the chemical reaction of the powder, it is preferable to have both a squeegee and a roller, and to adjust the thickness of the powder layer with the squeegee, and then apply pressure with the roller to increase the density of the powder layer.

The molding apparatus 100 further includes an energy beam source 102 for causing combustion synthesis of the raw material, scanning mirrors 103A and 103B for scanning the energy beam 112 in two axes, and an optical system 104 for focusing the energy beam on the irradiation portion. Since the energy beam 112 is irradiated from outside the chamber 101, the chamber 101 is provided with an introduction window 105 for introducing the energy beam 112 into the chamber 101. 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 molded acquired by the control unit 115 and the characteristics of the molding material. In addition, the positions of the molding container 120 and the optical system 104 are adjusted in advance so that the desired beam diameter is obtained on the surface of the powder layer 111. The beam diameter on the surface of the powder layer 111 is preferably 30 to 100 μm because it affects the molding accuracy.

A galvanometer mirror can be suitably used as the scanning mirrors 103A and 103B. Since the galvanometer mirror operates at high speed while reflecting the energy beam, it is desirable that it is made of a lightweight material with a low linear expansion coefficient.

Lasers are widely used for the energy beam 112. YAG lasers are often used, but CO2 lasers and semiconductor lasers can also be used. The driving method can be pulsed or continuous irradiation. The laser is preferably selected according to the absorption wavelength of the powder; it is sufficient for the laser to have a wavelength that is absorbed by the powder at 50% or more, and it is more preferable for the laser to have a wavelength that is absorbed at 80% or more.

There are two methods for controlling the laser irradiation intensity: one is to control the in-plane laser power density, and the other is to control the spatial laser power density. The in-plane laser power density is the laser irradiation intensity per unit area, and is expressed in units of J/ ^mm2 . On the other hand, the spatial laser power density is the laser irradiation intensity per unit volume, and is expressed in units of J/ ^mm3 . When forming a model by controlling the film thickness as in a 3D printer, it is appropriate to take the spatial laser power density into consideration. The spatial laser power density J is expressed by the following formula.
J=W/(P×V×D)

Here, W is the laser irradiation power, P is the laser irradiation pitch, V is the laser scanning speed, and D is the powder laying thickness. In a typical 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 10,000 mm/sec, and the powder laying thickness D is usually 5 to 500 μm. When molding using the raw material powder of the present invention, the parameters W, P, V, and D can be controlled within the above ranges, and the spatial laser power density J can be adjusted in 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 ³ is the region where molding becomes impossible due to the volatilization of the powder.

During modeling, 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. Once the replacement is complete, the 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 according to the slice pitch of the slice data generated from the three-dimensional shape data of the object to be modeled, i.e., the layering pitch. Then, the energy beam 112 is scanned according to the slice data, and the laser is irradiated onto the powder in a specified area.

When irradiation of one layer of laser light based on the slice data is completed, the lifting mechanism 108 lowers the modeling stage 107 by the layer pitch, and the bottom of the material container 122 is raised according to the layer pitch. Then, the powder layer forming mechanism 106 moves the raw powder from the material container 122 to the modeling container 120, and a new powder layer is formed by spreading the powder on top of the layer scanned with the energy beam, and scanning and irradiation with the energy beam 112 are performed.

As described above, in the area irradiated with the energy beam 112, the surface of the layer previously scanned with the energy beam 112 is also solidified again. If the area in the new powder layer directly below the area irradiated with the energy beam 112 is already solidified, the materials in the beam irradiated area of the new powder layer will mix and solidify at the boundary with the previously melted and solidified area, and they will bond together. By repeating these operations, a model 110 can be formed.

When irradiating the powder layer with a laser, it is preferable to irradiate the laser discretely by dividing the irradiation area into rectangles as shown in FIG. 2(b). The size of one rectangular area is preferably 5 mm×5 mm or less, more preferably 2 mm×2 mm or less. As shown in FIG. 2(a), if the laser is continuously scanned in one stroke, reaction heat accumulates at each turning point, causing variation in the composition of the molded object or the generation of voids. However, if the laser is irradiated discretely as shown in FIG. 2(b), the propagation of the combustion wave can be restricted in the in-plane direction, and the variation in reaction heat within the molded surface can be suppressed. The irradiation area does not need to be rectangular, and may be polygonal or circular. Even if it is not rectangular, it is preferable to set the area per area to 25 mm ² or less, more preferably 5 mm ² or less.

The particle diameter of the particles contained in the raw powder including 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 powder are in this range, suitable particle fluidity for forming a powder layer during molding can be obtained, and it is also possible to mold fine objects. The particle diameter here refers to the Feret diameter (unidirectional diameter) measured using a microscope.

Furthermore, it is preferable that the average particle size of each of the SiC, Si, and C particles is smaller for compositions with higher melting or sublimation points, and that the relationship is C powder < SiC powder < Si powder. By making the particles of C and SiC with higher melting or sublimation points in the raw powder smaller, the C and SiC particles can be covered with molten Si, promoting the reaction and suppressing sublimation. The average particle size here is the average particle size of the various powders contained in the raw powder in which SiC, Si, and C powders are mixed, and it is preferable to measure the Feret diameter (unidirectional diameter) of at least 1,000 particles of each type of powder using a microscope and calculate the average value. When the SiC, Si, and C powders before mixing are available, or when the powders can be separated by type from the mixed powder, the median diameter measured by using a laser diffraction type particle size distribution measuring device for each type is used as the average particle size.

Even if raw powder containing the powder according to the present invention is used, if the intensity of the irradiated laser is too strong, an explosive reaction will occur. Therefore, in order to prevent an explosive reaction, it is advisable to control the power density of the laser irradiated to the raw powder within a predetermined range according to the composition of the raw 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), which has a melting point lower than the decomposition point of SiC of 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 called SixCy, in which part of the crystal structure of Si is replaced with C, is formed. The solidified material bonded by this Si, as well as the shaped object containing SixCy, can be converted into SiC in its entirety by subsequent heat treatment.

If the object you create contains voids, it is a good idea to impregnate it to improve its strength.

For SiC objects, solid-phase impregnation, liquid-phase impregnation, and gas-phase impregnation are known, but solid-phase impregnation and liquid-phase impregnation are preferred because they can increase the strength of objects relatively easily. Solid-phase impregnation is particularly preferred because it can increase strength in a short period of time.

When performing solid-phase impregnation on a SiC shaped object, it is advisable to first support C in the voids of the shaped object, and then pour in molten Si to convert the voids into SiC.

The procedure for solid-phase impregnation is as follows: first, the molded object is immersed in liquid resin and degassed in a vacuum, allowing the liquid resin to be impregnated into the voids. After removing unnecessary liquid resin from the surface of the molded object, the resin is heated to harden and then heated until carbonized, causing C to be supported in the voids. Next, the molded object is brought into contact with molten Si in a vacuum, allowing the Si to be impregnated into the voids, and the voids can be converted to SiC by heating at 1450-1700°C. After the voids have been converted to SiC, excess Si adheres to the surface of the molded object, but this can be removed by post-processing such as polishing or etching.

The resin used to support C in the voids of the molded object does not contain any metal components. If the resin contains metal components, they will react with the Si in the molded object and produce excess compounds. Also, the higher the carbon residue rate of the resin, the higher the SiC rate in the voids can be. The carbon residue rate of the resin is preferably 50% or more, more preferably 60% or more, and phenolic resin is particularly preferred.

In order to allow the resin to penetrate into the voids, the viscosity of the resin is preferably 1000 mPa·s or less, and more preferably 500 mPa·s or less.

When performing liquid phase impregnation on a SiC model, commercially available SiC polymer (polycarbosilane) can be used as the SiC impregnation material. The model is immersed in the SiC polymer liquid, and vacuum degassing is performed to introduce the SiC polymer liquid into the voids of the model. After removing excess liquid from the surface of the model, the SiC polymer is inorganicized by heat treatment at 800 to 1300°C in an inert gas. Since the SiC polymer is a SiC ceramic precursor that contains organic matter, approximately 30 wt. % is lost through volatilization during heat treatment. Therefore, the porosity of the model can be reduced by repeating the impregnation and heat treatment process multiple times. The SiC obtained by heat treating the SiC polymer at 800 to 1300°C has an amorphous structure, but it can be crystallized and hardened by subsequent heat treatment at around 1600°C.

Examples and comparative examples of the present invention are described below. However, the type, composition, particle shape, form, laser power, and other details of the powder described below should be changed as appropriate depending on the configuration of the device to which the invention is applied and various conditions, and are not intended to limit the invention to the scope of the disclosure in this specification.

The raw material powder used was a mixture of SiC powder, Si powder, and C powder. 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 size 45.0 μm
Manufactured by High Purity Chemical Laboratory Co., Ltd. (Product name: SIE19PB)
Powder C: average particle size 5.0 μm
Manufactured by High Purity Chemical Laboratory Co., Ltd. (Product name: CCE03PB)

Raw material powders were prepared with different mixture ratios of SiC, Si, and C powders, and each raw material powder was irradiated with a laser under multiple laser irradiation conditions (spatial laser power density) to create shapes.

The required amounts of SiC, Si, and C powders were weighed out and mixed in a ball mill.

The mixed powder was placed in a material container 122, and the chamber was evacuated, followed by a process of introducing Ar gas several times to replace the atmosphere in the chamber with a _N2 atmosphere. The raw powder in the powder container 122 was spread to a uniform thickness on a stainless steel base plate 121 placed on a stage 107 by a powder layer forming mechanism 106. The height of the stage 107 was adjusted so that the powder thickness was 50 μm.

Next, the powder was irradiated with a laser to perform modeling. A Nd:YAG laser with a wavelength of 1060 nm was used as the laser. The laser power was set to 100 W, the irradiation pitch was set to 40 μm, and the spatial laser power density was changed in the range of 11 to 75 J/mm ³ by adjusting the scanning speed, and modeling was performed according to a three-dimensional model that was a rectangular parallelepiped of 4 mm x 4 mm x 250 μm. After the first layer of laser irradiation was completed, powder was spread and laser irradiation was performed in the same manner as the first layer, and this process was repeated until the model reached the desired height.

As a comparative example, a raw material powder made of SiC powder was irradiated with a laser at a spatial laser power density in the range of 11 to 50 J/ ^mm3 , and a molding was performed in the same manner as in the example.

The stainless steel used for the base plate has a high thermal conductivity, so if the heat of the irradiated laser is low, it will dissipate. If the energy of the irradiated laser is low, the adhesion between the model and the base plate will be low. Therefore, before starting the modeling of the rectangular parallelepiped model, three layers were modeled with a spatial laser power density of 100 J/ ^mm3 to model the base for the modeling of the rectangular parallelepiped model.

The height of the created object was measured without separating it from the plate. Figure 3 shows the relationship between the height of the object created with the composition of the raw material powder and the spatial laser power density.

The feasibility of the modeling was evaluated based on the deviation between the height of the obtained model and the height of the cube model (250 μm). The mixing ratio of the raw material powders 1 to 9 used for modeling, the spatial laser power density of the irradiated laser, and the evaluation results are all shown in Table 1. The evaluation criteria are as follows. "-" in the table indicates that it was not considered.
A: Height is 200 μm or more. B: Height is 170 μm or more and less than 200 μm. C: Height is less than 170 μm. D: Modeling is not possible.

In the model rated A, the amount of reduction per layer due to laser irradiation was kept to a level where the powder melted and the density increased. In the model rated B, the amount of reduction was greater than in the model rated A, but the explosive temperature rise due to combustion synthesis was suppressed and the raw material powder was prevented from scattering from the printing area, making it possible to create the desired model by adjusting the slice data and printing conditions. In the model rated 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 printing area. As a result, the printing accuracy was extremely low not only in the height direction but also in the printing surface direction. In the model rated D, the powder did not melt and printing was not possible.

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

SiC has no melting point and decomposes at 2545°C, while the decomposition point of C powder, which is an element powder constituting SiC, is 3642°C, and the melting point of Si powder is 1414°C. Powders 1 to 9 were irradiated with a laser under conditions that caused combustion synthesis of Si and C and raised the temperature to a temperature at which the Si powder melted. The composition of the molded objects produced by irradiating powders 1 to 6 with a laser at a spatial laser power density of 11.1 [J/mm ³ ] was confirmed by X-ray diffraction. It was confirmed that each molded object contained a portion in which the SiC powder was bonded with Si and a portion of the diamond lattice of Si was replaced with C atoms, that is, Si _0.98 C _0.02 .

Using the mixture ratio of the raw material powders Powders 1 to 6, four rectangular objects each of 4 mm x 3 mm x 40 mm were fabricated on a stainless steel base plate at a spatial laser power density of 15 [J/mm ³ ].

For two of the four objects on the base plate, a sufficient amount of liquid phenolic resin (PR-50607B, manufactured by Sumitomo Bakelite) was first dripped onto the objects, and then degassed in a vacuum. After wiping off excess phenolic resin from the surface of the objects, the objects were heated to 160°C on a hot plate to thermally harden the phenolic resin.

Then, a diamond wire saw was used to separate the model from the base plate. When the cut surface of the model impregnated with phenolic resin was observed under a microscope, it was confirmed that the phenolic resin had sufficiently permeated the gaps. Furthermore, no chipping occurred in the model when it was separated from the base plate.

On the other hand, some of the molded objects that were not impregnated with phenolic resin had small chips on the edges when they were separated from the base plate. The molded objects that were not impregnated with phenolic resin were not subjected to any further processes because they were used to compare their strength with the molded objects after impregnation.

The molded object impregnated with phenolic resin was immersed in liquid phenolic resin, vacuum degassed, and impregnated again, after which the phenolic resin was carbonized by heat treatment at 800°C for 30 minutes.

After carbonization of the phenolic resin, the volume and weight of the molded object were measured, and the porosity was measured. The amount of Si required for SiC impregnation was calculated from the measured porosity. Alumina balls with a diameter of 2 mm were laid out as setters on the bottom surface of the crucible to prevent the molded object from sticking to the crucible, and then the molded object was placed in the crucible, and an amount of Si pieces approximately 20% more than the calculated amount of Si required was placed on top of the molded object, and heat treatment was performed. The heat treatment was performed at 1500°C for 1 hour in an Ar atmosphere with a pressure of 2600 Pa. Since excess Si was attached to the surface of the molded object, it was ground and polished to form a rectangular shape of 4 mm x 3 mm x 40 mm. When the surface of the molded object after impregnation was observed under a microscope, the cracks and holes were significantly reduced.

The molded object without solid-phase impregnation and the molded object with solid-phase impregnation were each subjected to a four-point bending test evaluation using an Instron universal testing machine (4507 type, load cell 1KN). The evaluation conditions were as follows:
Atmosphere: Air Crosshead movement speed: 0.5 mm/min
Distance between supports: L = 30
Jig material: SiC

When the four-point bending test evaluation values of objects that had been subjected to solid-phase impregnation and objects that had not been subjected to solid-phase impregnation were compared for objects created under the same molding conditions, it was confirmed that in both cases the bending strength of the objects was four times or more stronger due to solid-phase impregnation.

After the four-point bending test evaluation, the composition of the solid-phase impregnated molded objects was confirmed using X-ray diffraction. All molded objects contained 75 at% or more SiC and 25 at% or less Si.

These results confirm that by adding an appropriate amount of silicon carbide powder to raw powder containing metallic silicon powder and carbon powder, and controlling the spatial laser power density irradiated according to the mixing ratio of the raw powder, it is possible to suppress the explosive reaction heat caused by combustion synthesis and to create shapes.

Specifically, it is preferable that the raw material powder contains silicon carbide powder at a ratio of 60 at% or more and less than 100 at% and that a laser having a spatial laser power density of 11 J/ ^mm3 or more and 50 J/ ^mm3 or less is irradiated.More preferably, the raw material powder contains silicon carbide powder at a ratio of 75 at% or more and 95 at% or less and that a laser having a spatial laser power density of 15 J/ ^mm3 or more and 35 J/ ^mm3 or less is irradiated.

By performing shaping within this range, it is possible to provide the heat necessary to induce reactions between elements or compounds while suppressing the explosive reaction heat caused by combustion synthesis, thereby producing a shaped object whose main component is silicon carbide.

Once the molding was complete, the molded object was separated from the base plate and heat-treated in an Ar atmosphere at 1500°C for 1 hour. X-ray diffraction of the heat-treated object confirmed that this heat treatment caused the Si to melt and react with the C powder remaining in the molded object, converting it to SiC. The heat treatment temperature of 1500°C is sufficiently lower than the decomposition temperature of SiC and C, so the SiC and C did not decompose, and a dense object was obtained.

Reference Signs List 100 Modeling device 107 Modeling stage 110 Modeled object 111 Powder layer 112 Energy beam

Claims (11)

1. A method for producing a silicon carbide based article, comprising:
forming a layer of raw material powder;
irradiating the layer with a laser based on data of a three-dimensional model;
multiple times,
the raw material powder is a mixed powder of silicon carbide powder, metallic silicon powder, and carbon powder, and contains the silicon carbide powder in a ratio of 60 at% or more and less than 100 at%,
A method for manufacturing an article, characterized in that the average particle size of the silicon carbide powder is smaller than the average particle size of the silicon metallic powder, and the average particle size of the carbon powder is smaller than the average particle size of the silicon carbide powder. The method for manufacturing an article according to claim 1, characterized in that the raw material powder contains the silicon carbide powder in a ratio of 75 at% or more and 95 at% or less. 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 greater than the atomic ratio of metallic silicon. 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 area to be irradiated with the laser is divided into a plurality of areas, and the laser is irradiated discretely. The method for manufacturing an article according to claim 4, characterized in that the spatial laser power density of the laser in the laser irradiation step is 11 J/ ^mm3 or more and 50 J/ ^mm3 or less, and the multiple regions are rectangular regions each having a size of 5 mm x 5 mm or less. a step of impregnating a shaped object obtained by carrying out the step of forming a layer of the raw material powder and the step of irradiating with the laser a plurality of times with a liquid resin;
a step of heating the shaped object impregnated with the liquid resin to carbonize the resin;
impregnating the shaped object obtained by carbonizing the resin with molten metallic silicon;
heating the shaped article impregnated with the metallic silicon to convert the metallic silicon into silicon carbide;
The method of claim 1 , further comprising: The method for manufacturing an article according to claim 6, characterized in that the resin is a phenolic resin. The method for manufacturing an article according to claim 6 or 7, characterized in that it includes a step of post-treating the surface of the resulting shaped object after the step of converting the silicon metal into silicon carbide. 9. The method for manufacturing an article according to claim 1, wherein the particle diameter 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 claim 1 , wherein the raw material powder contains the metallic silicon powder in a ratio of 2.5% to 20 at %. 11. The method for manufacturing an article according to claim 1 , wherein the raw material powder contains the carbon powder in an amount of 2.5% to 20 at %.

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