A kind of encapsulated powder for additive manufacturing and its preparation method and use

Abstract

The present invention relates to a rubber-coated powder for additive manufacturing and a preparation method and use thereof, wherein the rubber-coated powder comprises a core and a coating shell; the core is a material powder for 3D printing a molded body, and the particle size of the material powder is greater than 0 μm and less than or equal to 150 μm; the coating shell is glue, and the coating shell thickness of the metal powder is greater than 0 μm and less than or equal to 10 μm, and the coating shell thickness of the ceramic powder is greater than 0 μm and less than or equal to 6 μm; the surface of the rubber-coated powder is dense and has no holes; the fluidity of the rubber-coated powder is less than or equal to 70 s / 50 g for metal and less than or equal to 90 s / 50 g for ceramic. The rubber-coated powder of the present invention is used in additive manufacturing, which enhances the strength of the green body and improves the green body yield; in the printing and powder spreading process, low-power laser curing molding can be used, the requirements for equipment components are greatly reduced, the stability and service life of the 3D printing equipment are improved, and large-scale and industrialized production is easy to achieve.

Description

Technical Field

[0001] The present invention belongs to the technical field of additive manufacturing, and in particular relates to an encapsulated powder for additive manufacturing, a preparation method and use thereof. Background Art

[0002] Additive Manufacturing (AM) uses computers to control 3D data to stack materials layer by layer. It is an efficient net-forming technology based on the discrete-stacking principle. Since the 21st century, additive manufacturing has opened up a new advanced manufacturing technology for the manufacturing industry with its unique advantages, and is regarded by many countries as a new growth point for future industrial development. Additive manufacturing using powder as raw material is one of its important directions and branches. In terms of the energy used, some use high-temperature heat sources, some use low-temperature heat sources, and some use no heat source.

[0003] Currently, technologies that use high-temperature thermal source printing, such as SLM and EBM, do not use glue, and have high requirements for equipment and use environment, high production costs, many unsafe factors in the production process, and easily limited part size. Low-temperature heat source or no heat source process, such as BJ, directly sprays glue onto the powder according to the designed path, and generally continues to lay another layer of powder within a few seconds, and then sprays glue, and repeats this cycle. Due to the short contact time between glue and powder, problems such as low green strength, poor bonding between particles, uneven glue distribution, and large changes in part size are prone to occur. The yield rate is not high and the production efficiency is relatively low. Moreover, it is currently difficult to achieve mass production. Summary of the invention

[0004] In view of the above-mentioned prior art problems, the purpose of the present invention is to provide an encapsulated powder for additive manufacturing and a preparation method and use thereof, so as to solve the problems in the prior art of high equipment requirements, many unsafe factors in the production process, low production efficiency, and difficulty in mass and industrial production.

[0005] On the one hand, the present invention provides a rubber-coated powder for additive manufacturing, the rubber-coated powder comprising a core and a coating shell; the core is a material powder for 3D printing a molded body, and the particle size of the material powder is greater than 0 μm and less than or equal to 150 μm; the coating shell is glue, and the shell thickness of the coating shell is greater than 0 μm and less than or equal to 10 μm; the surface of the rubber-coated powder is dense and has no holes, and the fluidity of the rubber-coated powder is less than or equal to 90s / 50g.

[0006] Furthermore, in the encapsulated powder of the present invention, the material powder is a metal powder, and the fluidity of the encapsulated powder is less than or equal to 70s / 50g.

[0007] Furthermore, in the encapsulated powder of the present invention, the material powder is a ceramic powder, and the shell thickness of the coating shell is less than or equal to 6 μm.

[0008] Furthermore, in the encapsulated powder of the present invention, the glue is a glue material that can be dissolved in water, inorganic solvents and organic solvents at the same time.

[0009] Furthermore, in the encapsulated powder of the present invention, the glue is a mixture of at least two substances selected from the group consisting of a dispersant, a stabilizer, or a lubricant;

[0010] The dispersant is selected from at least one of zinc stearate or polystyrene, the stabilizer is selected from at least one of PVB resin, stearic acid, oleic acid, glycerol or triglyceride, and the lubricant is selected from at least one of stearate or amide.

[0011] Furthermore, in the encapsulated powder of the present invention, the particle morphology of the material powder is spherical, nearly spherical or quasi-spherical.

[0012] In the present invention, when the shell thickness of the coating shell of the metal powder is greater than 10 μm, or when the shell thickness of the coating shell of the ceramic powder is greater than 6 μm, the amount of glue is too much, so that the fluidity of the powder after coating becomes poor, the degumming process becomes difficult, the degumming time is long, and the size of the parts after printing changes greatly, and the accuracy is affected.

[0013] In another aspect, the present invention provides a method for preparing a powder for additive manufacturing, wherein the powder is the encapsulated powder as described in any one of the above items, and the preparation method comprises the following steps:

[0014] S1: Weigh the material powder for 3D printing the molded body, dissolve the glue in a solvent to obtain a glue mixture; take the required amount of the glue mixture according to the amount of glue required by the material powder;

[0015] S2: Turn on the gas protection system and cooling system of the homemade mixer A, add the weighed material powder into the homemade mixer A; spray the glue mixture onto the surface of the material powder, and stir and mix at the same time; after the spraying of the glue mixture is completed, continue stirring for 10 to 40 minutes; then, wait until the material temperature in the homemade mixer A drops below 25°C before discharging the material to obtain wet material powder uniformly coated with the glue;

[0016] During the stirring and mixing process, the stirring speed is 1-20 rpm and the temperature is 30-60°C;

[0017] In the glue mixture, the mixing mass ratio of the solvent to the glue is 999:1 to 19:1;

[0018] During the process of spraying the glue mixture, the spraying pressure is 0.2~0.6MPa;

[0019] When the material powder is metal powder, the mass ratio of the amount of the glue added to the amount of the metal powder added is 1:199-1:33;

[0020] When the material powder is a ceramic powder, the mass ratio of the amount of the glue added to the amount of the ceramic powder added is 1:199~1:19;

[0021] S3: heating and drying the wet material powder at a temperature of 80-130° C. to remove the solvent and obtain a primary encapsulated powder;

[0022] S4: Put the encapsulated powder into a mixer B and disperse it at a speed of 1-10 rpm for 5-10 minutes to obtain any of the encapsulated powders described above.

[0023] In the present invention, the solvent may be preferably selected from one or more of alcohols, benzenes, and lipids. The type of the mixer B is not limited, and any mixer known in the art that has the function of mixing and dispersing powders can be used.

[0024] Furthermore, in the preparation method described in the present invention, the structure of the homemade mixer A includes: an ellipsoidal mixing bin, a nozzle connected to the injection system is provided on the side wall of the mixing bin, and the number of the nozzles is set to 5 to 10, and the nozzles are evenly distributed on the side wall of the mixing bin.

[0025] The encapsulated powder of the present invention requires a complete coating layer without holes, falling off, color difference, cracks, etc., and the fluidity does not exceed 90s / 50g. The amount of glue added is related to factors such as the specific surface area of ​​the powder, the wetting energy of the two, and the desired coating layer thickness. For powders of the same mass, the larger the specific surface area of ​​the powder, the smaller the wetting energy, and the thicker the coating layer, the higher the proportion of glue.

[0026] In another aspect, the present invention provides a use of an encapsulated powder for additive manufacturing, wherein the encapsulated powder is used for additive manufacturing, and the additive manufacturing method comprises the following steps: taking the encapsulated powder described in any one of the above items, adopting a powder spreading or coaxial powder feeding process combined with a heat source scanning printing to obtain a molded body, and sintering and densifying the molded body to obtain the 3D printed molded body product;

[0027] The sintering densification treatment step comprises:

[0028] SS1: Degumming process: at room temperature, the molded green body is placed in a sintering device, and the coating shell is gasified and removed at a temperature of 150-220° C. to obtain a degummed green body;

[0029] SS2: Densification process: The sintering equipment is heated up continuously until the sintering temperature is reached for pressure sintering, and finally the 3D printed molded product is obtained.

[0030] In the present invention, the heat source of the encapsulated powder is not limited, and laser, electron beam, arc, and ordinary resistance heating are all applicable. The heating temperature is relatively low, just slightly higher than the melting temperature of the glue, and the heat resistance requirement of the molding equipment is not high; it can be a powder spreading type or a coaxial powder feeding type, and the two processes can be carried out at the same time, with a large degree of process freedom; multiple powders can also be used at the same time; according to the characteristics and activity of the powder used, vacuum or inert atmosphere protection is selected during molding.

[0031] The sintering and densification technology uses an inert gas protective atmosphere or can be sintered at normal pressure. The low-melting point glue is first removed at a relatively low temperature, and then the temperature is gradually raised to the required sintering temperature for sintering treatment to obtain a product that meets the density requirements.

[0032] Furthermore, in the use described in the present invention, the material powder of the 3D printed molded product is metal powder or ceramic powder; the process parameters of the pressure sintering include: sintering pressure 0.1~10MPa, the protective gas during the sintering process is nitrogen or argon; the sintering temperature curve is: heating to 1000~2000℃ at a heating rate of 1~20℃ / min, keeping temperature for 0.5~3 hours, and then cooling to room temperature at a cooling rate of 1~30℃ / min.

[0033] Generally, SLM: Selective laser melting is a major technical approach in additive manufacturing of metal materials. This technology uses laser as the energy source, and scans the metal powder bed layer by layer according to the path planned in the 3D CAD slice model. The scanned metal powder is melted and solidified to achieve the effect of metallurgical bonding, and finally the metal parts designed by the model are obtained. SLM technology overcomes the troubles caused by traditional technology in manufacturing metal parts with complex shapes. It can directly form metal parts with nearly full density and good mechanical properties. One of the main benefits of EBM is the ability to "stack" separate parts on top of each other. With the reduction of machine downtime and post-processing, productivity can be greatly improved. BJ binder jetting 3D printing process (Binder jetting) mainly uses powder and liquid binder to combine to make solid parts, so it can be regarded as a 3D printing process that integrates SLS 3D printing principles and material jetting principles. Like the SLS 3D printing process, the material needs to be loaded into the powder bin before starting the 3D printing process, but the 3D printing process of the BJ binder jetting process does not involve the generation of heat throughout the entire process, which means that the powder will not be heated like the SLS 3D printing process. At the beginning of 3D printing, a single layer of powder is deposited on the building platform. The 3D print head sweeps over the powder and selectively sprays binder droplets. Here, the binder droplets can be regarded as glue for the powder particles. The droplets selectively fall and contact with the powder, and the particles fuse together to form a solid. After the single-layer 3D printing is completed, the 3D printing platform descends one layer, and this process is repeated until the target model is completed.

[0034] In the present invention, the coating material powder is used, and the scanning printing temperature is slightly higher than the volatilization temperature of the glue. For SLM or EBM, the printing temperature is generally the sintering temperature of the printed material (such as the printing temperature of titanium alloy is about 1000-1600℃, and the printing temperature of alumina is about 1400-2000℃. The high printing temperature has high requirements for equipment, operation and safety. For the BJ printing process, although the printing temperature is room temperature, it is difficult to fully wet and fully coat the glue and powder due to the short contact time between the glue and the powder (a few seconds), resulting in low green strength and low yield.

[0035] Compared with the prior art, the present invention has the following beneficial technical effects:

[0036] The encapsulated powder for additive manufacturing and the preparation method thereof provided by the present invention adopt glue coating treatment, so that the glue and powder particles have sufficient time to infiltrate each other and are evenly distributed on the surface of the powder particles, which greatly enhances the strength of the green body and greatly improves the yield rate of the green body; in the printing and powder spreading process, low-power laser curing and molding can be used, which greatly reduces the requirements for equipment components, improves the stability and service life of the 3D printing equipment, and is easy to realize large-scale and industrialized production, further reducing costs and increasing efficiency.

[0037] In addition, in the use of the encapsulated powder for additive manufacturing of the present invention, the heat source of the encapsulated powder is not limited, and laser, electron beam, arc, and ordinary resistance heating are all applicable. The heating temperature is relatively low, just slightly higher than the melting temperature of the glue, and the heat resistance requirements of the molding equipment are not high; it can be a powder spreading type or a coaxial powder feeding type, and the two processes can be carried out at the same time, with a large degree of process freedom; multiple powders can also be used at the same time; according to the characteristics and activity of the powder used, vacuum or inert atmosphere protection is selected during molding. The present invention effectively overcomes the shortcomings of the prior art and has a high industrial application value. DETAILED DESCRIPTION

[0038] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, the specific implementation methods of the present invention are now described in detail with reference to the accompanying drawings. The described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. If the specific conditions are not specified in the specific implementation methods, they shall be carried out according to the conventional conditions or the conditions recommended by the manufacturer.

[0039] When the following description refers to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present disclosure. Instead, they are merely examples of devices and methods consistent with some aspects of the present disclosure as detailed in the appended claims. The terms used in the present disclosure are only for the purpose of describing specific embodiments and are not intended to limit the present disclosure.

[0040] The structures, proportions, sizes, etc. illustrated in the drawings in this specification are only used to match the contents disclosed in the specification so as to facilitate understanding and reading by persons familiar with the technology. They are not used to limit the conditions under which the present invention can be implemented, and therefore have no substantive technical significance. Any structural modification, change in proportion or adjustment of size shall still fall within the scope of the technical contents disclosed in the present invention without affecting the effects and purposes that can be achieved by the present invention. Specific implementation method 1

[0042] The present invention provides a rubber-coated powder for additive manufacturing, the rubber-coated powder comprising a core and a coating shell; the core is a material powder for 3D printing a molded body, the particle size of the material powder is greater than 0 μm and less than or equal to 150 μm; the coating shell is glue, the shell thickness of the coating shell is greater than 0 μm and less than or equal to 10 μm; the surface of the rubber-coated powder is dense and has no holes, and the fluidity of the rubber-coated powder is less than or equal to 90 s / 50 g.

[0043] In some embodiments, the material powder is metal powder, the shell thickness of the coating shell is less than or equal to 10 μm, and the fluidity of the encapsulated powder is less than or equal to 70 s / 50 g.

[0044] In some embodiments, the material powder is a ceramic powder, the shell thickness of the coating shell is less than or equal to 6 μm, and the fluidity of the encapsulated powder is less than or equal to 90 s / 50 g.

[0045] In some embodiments, the glue is a glue material that can be dissolved in water, inorganic solvents, and organic solvents at the same time.

[0046] In some embodiments, the glue is a mixture of at least two of a dispersant, a stabilizer or a lubricant; the dispersant is selected from at least one of zinc stearate or polystyrene, the stabilizer is selected from at least one of PVB resin, stearic acid, oleic acid, glycerol or triglyceride, and the lubricant is selected from at least one of stearate or amide.

[0047] In some embodiments, the particle morphology of the above material powder is spherical, nearly spherical or quasi-spherical. Specific implementation method 2

[0049] The present invention provides a method for preparing a powder for additive manufacturing, wherein the powder is the encapsulated powder described in any one of the first specific embodiments, and the preparation method comprises the following steps:

[0050] S1: Weigh the material powder for 3D printing the molded body, dissolve the glue in a solvent to obtain a glue mixture; take the required amount of the glue mixture according to the amount of glue required by the material powder;

[0051] S2: Turn on the gas protection system and cooling system of the homemade mixer A, add the weighed material powder to the homemade mixer A; spray the glue mixture onto the surface of the material powder, and stir and mix at the same time; after spraying the glue mixture, continue stirring for 10 to 40 minutes; then, wait until the material temperature in the homemade mixer A drops below 25°C before discharging the material to obtain wet material powder uniformly coated with the glue;

[0052] During the above stirring and mixing process, the stirring speed is 1-20 rpm and the temperature is 30-60°C;

[0053] In the glue mixture, the mixing mass ratio of the solvent to the glue is 999:1 to 19:1;

[0054] During the process of spraying the above glue mixture, the spraying pressure is 0.2~0.6MPa;

[0055] When the material powder is metal powder, the mass ratio of the amount of the glue added to the amount of the metal powder added is 1:199-1:33;

[0056] When the material powder is ceramic powder, the mass ratio of the amount of the glue added to the amount of the ceramic powder added is 1:199~1:19;

[0057] S3: heating and drying the wet material powder at a temperature of 80-130° C. to remove the solvent and obtain a primary encapsulated powder;

[0058] S4: Put the encapsulated powder into a mixer B and disperse it at a speed of 1-10 rpm for 5-10 minutes to obtain the encapsulated powder of any one of the above-mentioned specific implementation methods 1.

[0059] In some embodiments, the structure of the homemade mixer A includes: an ellipsoidal mixing bin, a nozzle connected to the injection system is arranged on the side wall of the mixing bin, the number of the nozzles is 5 to 10, and the nozzles are evenly distributed on the side wall of the mixing bin.

[0060] In some embodiments, the above solvent may preferably be selected from one or more of alcohols, benzenes, and lipids.

[0061] In some embodiments, the mixing mass ratio of the above-mentioned solvent to the glue is 999:1~19:1.

[0062] In some embodiments, the type of the mixer B is not limited, and any mixer known in the art that has the function of mixing and dispersing powders can be used. Specific implementation method three

[0064] The present invention provides a use of a rubber-coated powder for additive manufacturing, wherein the rubber-coated powder is used for additive manufacturing, and the method for additive manufacturing comprises the following steps: taking the rubber-coated powder of any one of the above-mentioned specific embodiments, adopting a powder spreading or coaxial powder feeding process combined with a heat source scanning printing to obtain a molded body, and sintering and densifying the molded body to obtain the above-mentioned 3D printed molded body product;

[0065] The above-mentioned sintering densification treatment steps include:

[0066] SS1: Degumming process: at room temperature, the above-mentioned molded green body is placed in a sintering device, and the above-mentioned coating shell is gasified and removed at a temperature of 150-220°C to obtain a degummed green body;

[0067] SS2: Densification process: The above sintering equipment is heated up continuously until the sintering temperature is reached for pressure sintering, and finally the above 3D printed molded product is obtained.

[0068] In some embodiments, the material powder of the above-mentioned 3D printed molded product is metal powder; the process parameters of the above-mentioned pressure sintering include: sintering pressure 0.1~10MPa, the protective gas during the sintering process is nitrogen or argon; the sintering temperature curve is: heating to 800~1600℃ at a heating rate of 1~20℃ / min, keeping temperature for 0.5~3 hours, and then cooling to room temperature at a cooling rate of 1~30℃ / min.

[0069] In some embodiments, a powder spreading method is adopted, with laser as a heat source, and molding is performed at a temperature about 10-50° C. higher than the curing temperature of the glue and in a protective atmosphere, and after removing excess powder, a green body with a certain strength is obtained.

[0070] The present invention is further described in detail below in conjunction with specific embodiments. Example 1

[0071] The present invention discloses a rubber-coated powder for additive manufacturing, the rubber-coated powder comprises a core and a coating shell; the core is a material powder for 3D printing a molded body, the particle size of the metal powder is greater than 0 μm and less than or equal to 150 μm; the coating shell is glue, and the shell thickness of the coating shell is greater than 0 μm and less than or equal to 10 μm (metal); the surface of the rubber-coated powder is dense and has no holes, and the fluidity of the rubber-coated powder is less than or equal to 70 s / 50 g. The particle morphology of the material powder is spherical or quasi-spherical.

[0072] The glue is a mixture of at least two substances selected from the group consisting of a dispersant, a stabilizer or a lubricant; the dispersant is selected from at least one of zinc stearate or polystyrene, the stabilizer is selected from at least one of PVB resin, stearic acid, oleic acid, glycerol or triglyceride, and the lubricant is selected from at least one of stearate or amide. Example 2

[0073] The present invention discloses an encapsulated powder for additive manufacturing, the encapsulated powder comprising a core and a coating shell; the core is a material powder for 3D printing a molded body, the particle size of the ceramic powder is greater than 0 μm and less than or equal to 150 μm; the coating shell is glue, the shell thickness of the coating shell is greater than 0 μm and less than or equal to 6 μm; the surface of the encapsulated powder is dense and has no holes, and the fluidity of the encapsulated powder is less than or equal to 90 s / 50 g. The particle morphology of the material powder is spherical, quasi-spherical or nearly spherical.

[0074] The glue is a mixture of at least two substances selected from the group consisting of a dispersant, a stabilizer or a lubricant; the dispersant is selected from at least one of zinc stearate or polystyrene, the stabilizer is selected from at least one of PVB resin, stearic acid, oleic acid, glycerol or triglyceride, and the lubricant is selected from at least one of stearate or amide. Example 3

[0075] A method for preparing powder for additive manufacturing of the present invention comprises the following steps:

[0076] S1: Weigh the material powder for 3D printing the molded body, dissolve the glue in the solvent to obtain a glue mixture; according to the amount of glue required by the material powder, take the required amount of the glue mixture;

[0077] S2: Turn on the gas protection system and cooling system of the homemade mixer A, add the weighed material powder into the homemade mixer A; spray the glue mixture onto the surface of the material powder, and stir and mix at the same time; after the glue mixture is sprayed, continue stirring for 10 to 40 minutes; then, wait until the material temperature in the homemade mixer A drops below 25°C before discharging the material to obtain wet material powder uniformly coated with glue;

[0078] During the stirring and mixing process, the stirring speed is 1~20rpm and the temperature is 30~60℃;

[0079] In the glue mixture, the mass ratio of solvent to glue is 999:1~19:1;

[0080] During the process of spraying the glue mixture, the spraying pressure is 0.2~0.6MPa;

[0081] When the material powder is metal powder, the mass ratio of the amount of glue added to the amount of metal powder added is 1:199~1:33;

[0082] When the material powder is ceramic powder, the mass ratio of the amount of glue added to the amount of ceramic powder added is 1:199~1:19;

[0083] S3: heating and drying the wet material powder at a temperature of 80-130° C. to remove the solvent and obtain a primary encapsulated powder;

[0084] S4: Put the encapsulated powder into the mixer B and disperse it at a speed of 1-10 rpm for 5-10 minutes to obtain the encapsulated powder of Example 1 and Example 2. Example 4

[0085] The structure of the homemade mixer A used in Example 2 includes: an ellipsoidal mixing bin, on the side wall of which are disposed nozzles connected to the injection system, the number of the nozzles being 5 to 10, and the nozzles being evenly distributed on the side wall of the mixing bin.

[0086] In the preparation methods of the above-mentioned Examples 3 and 4, the glue and the material powder particles have sufficient time to infiltrate each other and are evenly distributed on the surface of the powder particles. The obtained encapsulated powder is used in additive manufacturing, which greatly enhances the strength of the green body and improves the yield rate of the green body. During the printing and powder spreading process, the encapsulated powder can be cured and formed by low-power laser, which reduces the requirements for equipment components, improves the stability and service life of the 3D printing equipment, and can realize large-scale, industrialized production. Example 5

[0087] A use of a rubber-coated powder for additive manufacturing, wherein the rubber-coated powder is used for additive manufacturing, and the additive manufacturing method comprises the following steps: taking the rubber-coated powder of Example 1 and Example 2, adopting a powder spreading or coaxial powder feeding process combined with a heat source scanning printing to obtain a molded body, and sintering and densifying the molded body to obtain a 3D printed molded body product;

[0088] The sintering densification process steps include:

[0089] SS1: Degumming process: at room temperature, the molded green body is placed in a sintering device, and the coating shell is gasified and removed at a temperature of 150-220°C to obtain a degummed green body;

[0090] SS2: Densification process: The sintering equipment is heated up until the sintering temperature is reached for pressure sintering or hot isostatic pressing to finally obtain a 3D printed molded product.

[0091] The process parameters of pressure sintering or hot isostatic pressing sintering include: sintering pressure 0.1~10MPa, the protective gas during the sintering process is nitrogen or argon; the sintering temperature curve is: heating to 1000~2000℃ at a heating rate of 1~20℃ / min, keeping time 0.5~3 hours, and then cooling to room temperature at a cooling rate of 1~30℃ / min.

[0092] The green body strength during the preparation process of this embodiment 5 is high, and the green body yield rate exceeds 95%; during the printing and powder laying process, low-power laser curing molding is used, which greatly reduces the requirements for equipment components and improves the stability and service life of the 3D printing equipment. Example 6

[0093] The present invention discloses an encapsulated powder for additive manufacturing, comprising a core and a coating shell; the core is a material powder for 3D printing a molded body, the material powder is a titanium alloy powder, and the particle size of the material powder is 85-150 μm; the coating shell is glue, and the shell thickness of the coating shell is 10 μm; the surface of the encapsulated powder is dense and has no holes, and the fluidity of the encapsulated powder is 60s / 50g; the particle morphology of the material powder is nearly spherical.

[0094] The preparation method of the encapsulated powder of this embodiment 6 comprises the following steps:

[0095] S1: Weigh the material powder for 3D printing the molded body, dissolve the glue in the solvent to obtain a glue mixture; according to the amount of glue required by the material powder, take the required amount of the glue mixture;

[0096] S2: Turn on the gas protection system and cooling system of the homemade mixer A, add the weighed material powder into the homemade mixer A; spray the glue mixture onto the surface of the material powder, and stir and mix at the same time; after the glue mixture is sprayed, continue stirring for 10 to 40 minutes; then, wait until the material temperature in the homemade mixer A drops below 25°C before discharging the material to obtain wet material powder uniformly coated with glue;

[0097] The glue is a mixture of stearate and triglyceride in a mass ratio of 20:1 to 1:1;

[0098] During the stirring and mixing process, the stirring speed is 1~20rpm and the temperature is 30~60℃;

[0099] The solvent is selected from one or more of alcohols, benzenes, and lipids; in the glue mixture, the mixing mass ratio of the solvent to the glue is 999:1~19:1;

[0100] During the process of spraying the glue mixture, the spraying pressure is 0.2~0.6MPa;

[0101] The addition ratio of glue and titanium alloy powder is 2%:98%.

[0102] The additive manufacturing method using the encapsulated powder of Example 6 is: using a powder spreading method, using laser as a heat source, the power of the laser is 500~1500W, the temperature of the laser as a heat source is slightly higher than the glue temperature, and molding is performed at a temperature of about 10~50°C higher than the glue curing temperature and in a protective atmosphere, and after removing excess powder, a green body with a certain strength is obtained.

[0103] The molding process uses powder-laying printing equipment, and the specific steps are as follows:

[0104] 1) Turn on the protective gas system;

[0105] 2) Load the above encapsulated powder into the powder feeding system of the powder spreading printing equipment;

[0106] 3) The powder feeding system transports the powder to the molding cavity;

[0107] 4) The powder spreading system spreads the powder evenly on the printing substrate;

[0108] 5) The thermal source scanning and printing system scans and prints the powder layer according to the input model software information;

[0109] Note: The scanning energy should be set so that the scanning area is slightly higher than the glue temperature by 10-50℃. If it is too high, the glue will evaporate / burn seriously, affecting the strength and quality of the green body. If it is too low, the glue will not melt fully, the scanning area will not be firmly bonded, and the production process cannot be continued or the printed part will break.

[0110] 6) The substrate device moves downward;

[0111] 7) Repeat steps 3-6 until the molding is completed and a green body of the desired shape and size is obtained.

[0112] The formed green body is subjected to sintering and densification treatment, the steps comprising:

[0113] SS1: Degumming process: at room temperature, the molded green body is placed in a sintering device, and the coating shell is gasified and removed at a temperature of 150-220°C to obtain a degummed green body;

[0114] SS2: Densification process: The sintering equipment is heated up until the sintering temperature is reached for pressure sintering or hot isostatic pressing to finally obtain a 3D printed molded product.

[0115] The process parameters of pressure sintering or hot isostatic pressing sintering include: sintering pressure 0.1~10MPa, the protective gas during the sintering process is nitrogen or argon; the sintering temperature curve is: heating to 1000~2000℃ at a heating rate of 1~20℃ / min, keeping warm for 1~2 hours, and then cooling to room temperature at a cooling rate of 1~30℃ / min; cooling to room temperature, taking out of the furnace, and obtaining the desired 3D printed molded product.

[0116] In this Example 6, the glue and the material powder particles have sufficient time to infiltrate each other and are evenly distributed on the surface of the powder particles. The obtained titanium alloy encapsulated powder is used to form green bodies in additive manufacturing, and the green body yield rate exceeds 95%. During the printing and powder laying process, low-power laser curing is used, which greatly reduces the requirements for equipment components and improves the stability and service life of the 3D printing equipment. Example 7

[0117] The only difference between this embodiment 7 and embodiment 6 is that the material powder is alumina ceramic powder, and the particle size of the material powder is 0~75μm; the coating shell is glue, and the shell thickness of the coating shell is 1~6μm; the surface of the coated powder is dense and has no holes, and the fluidity of the coated powder is less than or equal to 90s / 50g; the particle morphology of the material powder is nearly spherical.

[0118] The addition ratio of glue and alumina ceramic powder is 1:199~1:19.

[0119] The glue is a mixture of stearate, glycerol and amide in a mass ratio of (25~10):(10~2):(5~0).

[0120] The additive manufacturing method using the encapsulated powder of this embodiment 7 is different from that of embodiment 6 only in that the process parameters of pressure sintering or hot isostatic pressing sintering include: sintering pressure 0.1~10MPa, the protective gas during the sintering process is nitrogen or argon; the sintering temperature curve is: heating to 1400~2000℃ at a heating rate of 1~20℃ / min, keeping temperature for 1~3 hours, and then cooling to room temperature at a cooling rate of 1~50℃ / min; cooling to room temperature, taking out of the furnace, and obtaining the desired 3D printed product.

[0121] In this Example 7, the glue and the material powder particles have sufficient time to infiltrate each other and are evenly distributed on the surface of the powder particles. The obtained alumina encapsulated powder is used to form green bodies in additive manufacturing, and the green body yield rate exceeds 95%. During the printing and powder laying process, low-power laser curing is used, which greatly reduces the requirements for equipment components and improves the stability and service life of the 3D printing equipment.

[0122] Comparative Example 1:

[0123] The difference between Comparative Example 1 and Example 1 is that the shell thickness of the coating shell in Comparative Example 1 is 10.3 μm.

[0124] In this comparative example 1, the additive manufacturing method of Example 5 is used to prepare a 3D printed product. In this comparative example 1, due to the excessive amount of glue, the fluidity of the powder after coating becomes poor, degumming is difficult, the degumming time is long, and the size of the parts after printing changes greatly, which affects the accuracy.

[0125] Comparative Example 2:

[0126] The difference between Comparative Example 2 and Example 1 is that the shell thickness of the coating shell in Comparative Example 1 is 10.5 μm.

[0127] In this comparative example 2, the additive manufacturing method of Example 5 is used to prepare a 3D printed product. In this comparative example 2, due to the excessive amount of glue, the fluidity of the powder after coating becomes poor, degumming is difficult, the degumming time is long, and the size of the parts after printing changes greatly, which affects the accuracy.

[0128] Comparative Example 3:

[0129] The difference between Comparative Example 3 and Example 1 is that the shell thickness of the coating shell in Comparative Example 1 is 11 μm.

[0130] In this comparative example 3, the additive manufacturing method of Example 5 is used to prepare a 3D printed product. In this comparative example 2, due to the excessive amount of glue, the fluidity of the powder after coating becomes poor, the resistance in the powder spreading or feeding process is large, the degumming is difficult, the degumming time is long, and the size of the parts after printing changes greatly, which affects the accuracy.

[0131] Comparative Example 4:

[0132] The difference between Comparative Example 4 and Example 2 is that the shell thickness of the coating shell in Comparative Example 2 is 6.2 μm.

[0133] In this comparative example 4, the additive manufacturing method of Example 5 is used to prepare a 3D printed product. In this comparative example 4, due to the excessive amount of glue, the fluidity of the powder after coating becomes poor, degumming is difficult, the degumming time is long, the size of the parts after printing changes greatly, and the accuracy is affected.

[0134] In the encapsulated powders in the above-mentioned embodiments 1 to 7, the glue and the powder particles have sufficient time to infiltrate each other and are evenly distributed on the surface of the powder particles, thereby enhancing the strength of the green body and achieving a green body yield rate of more than 95%. In the printing and spreading process, low-power laser curing can be used, which reduces the requirements for equipment components, improves the stability and service life of 3D printing equipment, and is easy to achieve large-scale, industrialized production, further reducing costs and increasing efficiency. On the other hand, the encapsulated powders in the above-mentioned embodiments 1 to 7 are used for additive manufacturing. During the product preparation and molding process, the heating temperature of the encapsulated powder heat source is relatively low, just slightly higher than the melting temperature of the glue, and the process has a large degree of freedom. It effectively overcomes the shortcomings of the prior art and has a high industrial application value.

[0135] The present invention is described by the above specific embodiments, and those skilled in the art should understand that various changes and equivalent substitutions can be made to the present invention without departing from the scope of the present invention. The parts not described in detail in the present specification are well-known technologies to those skilled in the art. In addition, various modifications can be made to the present invention for specific situations or specific circumstances without departing from the scope of the present use. Therefore, the present invention is not limited to the specific embodiments disclosed, but should include all implementation methods falling within the scope of the claims of the present invention.

Claims

1. A method for preparing powder for additive manufacturing, characterized in that: The preparation method comprises the following steps: S1: Weighing material powder for 3D printing a molded body, dissolving glue in a solvent to obtain a glue mixture; taking a required amount of the glue mixture according to the amount of glue required by the material powder; the particle morphology of the material powder is spherical or quasi-spherical; S2: Turn on the gas protection system and cooling system of the homemade mixer A, add the weighed material powder into the homemade mixer A; spray the glue mixture onto the surface of the material powder, and stir and mix at the same time; after the spraying of the glue mixture is completed, continue stirring for 10 to 40 minutes; then, wait until the material temperature in the homemade mixer A drops below 25°C before discharging the material to obtain wet material powder uniformly coated with the glue; The structure of the self-made mixer A includes: an ellipsoidal mixing bin, a nozzle connected to the injection system is arranged on the side wall of the mixing bin, and the number of the nozzles is 5 to 10, and the nozzles are evenly distributed on the side wall of the mixing bin; During the stirring and mixing process, the stirring speed is 1-20 rpm and the temperature is 30-60°C; In the glue mixture, the mixing mass ratio of the solvent to the glue is 999:1 to 19:1; During the process of spraying the glue mixture, the spraying pressure is 0.2~0.6MPa; When the material powder is metal powder, the mass ratio of the amount of the glue added to the amount of the metal powder added is 1:199-1:33; When the material powder is a ceramic powder, the mass ratio of the amount of the glue added to the amount of the ceramic powder added is 1:199~1:19; S3: heating and drying the wet material powder at a temperature of 80-130° C. to remove the solvent and obtain a primary encapsulated powder; S4: putting the encapsulated powder into a mixer B, and dispersing it at a speed of 1-10 rpm for 5-10 minutes to obtain an encapsulated powder; The encapsulated powder comprises a core and a coating shell; the core is a material powder for 3D printing a molded body, and the particle size of the material powder is greater than 0 μm and less than or equal to 150 μm; the coating shell is glue, and the surface of the encapsulated powder is dense and has no holes; When the material powder is a metal powder, the shell thickness of the coating shell is greater than 0 μm and less than or equal to 10 μm; the fluidity of the encapsulated powder is less than or equal to 70 s / 50 g; The material powder is ceramic powder, the shell thickness of the coating shell is less than or equal to 6 μm, and the fluidity of the encapsulated powder is less than or equal to 90 s / 50 g.

2. The preparation method according to claim 1, characterized in that: The glue is a glue material that can be dissolved in both inorganic solvents and organic solvents.

3. The preparation method according to claim 2, characterized in that: The glue is a mixture of at least two substances selected from the group consisting of a dispersant, a stabilizer, or a lubricant; The dispersant is selected from at least one of zinc stearate or polystyrene, the stabilizer is selected from at least one of PVB resin, stearic acid, oleic acid, glycerol or triglyceride, and the lubricant is selected from at least one of stearate or amide.

4. A use of encapsulated powder for additive manufacturing, characterized in that: The encapsulated powder is used for additive manufacturing, and the additive manufacturing method comprises the following steps: taking the encapsulated powder according to any one of claims 1 to 3, adopting a powder spreading or coaxial powder feeding process combined with a heat source scanning printing to obtain a molded body, and sintering and densifying the molded body to obtain the 3D printed molded body product; The sintering densification treatment step comprises: SS1: Degumming process: at room temperature, the molded green body is placed in a sintering device, and the coating shell is gasified and removed at a temperature of 150-220° C. to obtain a degummed green body; SS2: Densification process: The sintering equipment is heated up continuously until the sintering temperature is reached for pressure sintering, and finally the 3D printed molded product is obtained.

5. The use according to claim 4, characterized in that The material powder of the 3D printed molded product is metal powder or ceramic powder; The process parameters of the pressure sintering include: a sintering pressure of 0.1~10MPa, a protective gas of nitrogen or argon during the sintering process; a sintering temperature curve: heating to 1000~2000°C at a heating rate of 1~20°C / min, keeping the temperature for 0.5~3 hours, and then cooling to room temperature at a cooling rate of 1~30°C / min.