Method for preparing ceramic parts by fused deposition

Abstract

The present invention discloses a method for preparing ceramic parts by fused deposition, comprising weighing ceramic powder, a low molecular weight polymer, stearic acid, ethylene-vinyl acetate copolymer, polyethylene, polyvinyl butyral and a plasticizer for mixing to obtain a block feed, crushing and sieving to obtain a granular printing feed, adding the feed to the FDM3D printer hopper to prepare a printing blank by fused deposition, the printing blank is subjected to isostatic pressing, a gas pressure melting process, degreasing, debinding, and sintering to obtain a ceramic blank, which is then precisely machined and polished to obtain a ceramic part. The method of the present invention synergizes ceramic fused deposition technology, isostatic pressing technology and gas pressure melting process, significantly improving the blank density and interlayer bonding strength, and making the ceramic part have high mechanical properties and reliability.

Description

Technical Field

[0001] The present invention belongs to the technical field of ceramic parts preparation, and relates to a method for preparing ceramic parts by using fused deposition, and in particular to a method for preparing high-reliability ceramic parts by using fused deposition. Background Art

[0002] Advanced ceramic materials possess excellent properties such as high strength, high hardness, high temperature resistance, good chemical stability, and corrosion resistance, and are widely used in industries such as aerospace, automobiles, and biology. However, ceramic materials are brittle and hard, making them prone to defects during processing. Ceramic 3D printing technology can produce high-strength, high-precision ceramic parts. Compared with traditional ceramic molding processes, this technology not only significantly shortens the production cycle and saves raw materials, but also enables the production of ceramic devices with complex structures. Among them, ceramic fused deposition modeling technology is highly favored due to its advantages such as low working environment requirements, simple operation and preliminary work, and low cost. It mainly uses ceramic powder and organic matter to mix into ceramic feed, and then uses FDM equipment to make the ceramic feed into a printed body. After debinding and sintering, the ceramic device is obtained. However, there are currently several major problems with ceramic fused deposition modeling technology: on the one hand, ceramic fused deposition technology extrudes molten filaments through a nozzle to print ceramic green bodies layer by layer. The bond between the molten layer and the solidified layer is generally weak, which often leads to low interlayer bonding strength of the printed green body, and defects are prone to occur during the subsequent debinding and sintering processes; on the other hand, during the printing process, due to uneven feeding or improper control of printing parameters, holes and microcracks caused by missing feeding will appear inside the green body. The presence of these microcracks and hole defects will seriously affect the interlayer bonding of the printed green body, and ultimately cause a significant reduction in the density, flexural strength and reliability of the ceramic material. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a method for preparing ceramic parts by fused deposition, which can significantly improve the density of the green body and the interlayer bonding strength, and the ceramic parts after sintering have high mechanical properties and reliability.

[0004] In order to solve the above technical problems, the present invention adopts the following technical solutions.

[0005] A method for preparing a ceramic part by fused deposition, comprising the following steps:

[0006] (1) mixing raw ceramic powder, low molecular weight polymer, stearic acid, ethylene-vinyl acetate copolymer, polyethylene, polyvinyl butyral and plasticizer at a mixing temperature of 140° C. to 200° C., and cooling to obtain a bulk feed; wherein the low molecular weight polymer is paraffin wax or polyethylene glycol, and the raw materials are calculated by mass fraction as follows: ceramic powder is 60% to 90%, low molecular weight polymer is 5% to 20%, stearic acid is 0.5% to 3%, ethylene-vinyl acetate copolymer is 1% to 10%, polyethylene is 1% to 10%, polyvinyl butyral is 0% to 5%, and plasticizer is 1% to 5%;

[0007] (2) crushing and sieving the obtained bulk feed to obtain granular printing feed;

[0008] (3) adding the obtained granular printing feed into the FDM 3D printer hopper, importing the printing model, and adopting the screw extrusion printing method to obtain the printing blank by melt deposition;

[0009] (4) isostatically pressing the obtained printed body at a pressure of 100 MPa to 200 MPa;

[0010] (5) The printed body after isostatic pressing is subjected to air pressure melting at a temperature of 120°C to 180°C and an air pressure of 1MPa to 5MPa to eliminate internal defects;

[0011] (6) The printed blank after air pressure melting is degreased, debinded, and sintered to obtain a ceramic blank, which is then precisely processed and polished to obtain a ceramic part.

[0012] In the above-mentioned method for preparing ceramic parts by fused deposition, preferably, in step (1), the ceramic powder includes one or more of alumina powder, zirconium oxide powder, silicon nitride powder, silicon carbide powder and yttrium oxide, the polyethylene glycol is polyethylene glycol 1000 and / or polyethylene glycol 2000, and the plasticizer is dibutyl phthalate or dioctyl phthalate; and the mixing time is 2h to 4h.

[0013] In the above-mentioned method for preparing ceramic parts by fused deposition, preferably, in step (2), the particle size of the granular printing feed is less than 5 mm.

[0014] In the above-mentioned method for preparing ceramic parts by fused deposition, preferably, in step (3), the temperature of the screw extrusion is 160°C to 200°C, the temperature of the printer hot bed is 60°C to 100°C, and the printing speed is 10mm / s to 30mm / s.

[0015] In the above-mentioned method for preparing ceramic parts by fused deposition, preferably, in step (4), the holding time of the isostatic pressing is 5 minutes to 30 minutes.

[0016] In the above-mentioned method for preparing ceramic parts by fused deposition, preferably, in step (5), the atmosphere of the gas pressure melting is nitrogen or air, and the holding time of the gas pressure melting is 10 minutes to 30 minutes.

[0017] The above-mentioned method for preparing ceramic parts by fused deposition, preferably, in step (6): the degreasing is carried out in a solvent, when the low molecular weight polymer is paraffin, kerosene is used as the solvent, when the low molecular weight polymer is polyethylene glycol, water is used as the solvent; the degreasing temperature is 40°C to 60°C, and the degreasing time is 10h to 30h; the debinding heating rate is 0.05°C / min to 0.5°C / min, the atmosphere is air or nitrogen, and the debinding temperature is 600°C to 1200°C; the sintering is one of gas pressure sintering, vacuum sintering or normal pressure sintering, the atmosphere of the gas pressure sintering and normal pressure sintering is one or more of nitrogen, air and hydrogen, the sintering heating rate is 0.5°C / min to 5°C / min, the sintering temperature is 1400°C to 2000°C, and the holding time is 2h to 5h.

[0018] In the above-mentioned method for preparing ceramic parts by fused deposition, preferably, in step (6): when the printed body is a solid structure, the printed body is first coated with a rubber film after degreasing, and then isostatic pressing is performed at a pressure of 100MPa to 200MPa and a holding time of 5min to 30min, and then debinding is performed.

[0019] In the present invention, FDM3D printing is also called fused deposition printing, that is, the printing feed is first melted at high temperature in the screw, and then the screw is extruded and gradually deposited on the printing base plate (hot bed) to finally become a printed body.

[0020] Compared with the prior art, the advantages of the present invention are:

[0021] The present invention synergizes the ceramic melt deposition technology, isostatic pressing technology and gas pressure melting process to significantly improve the density and interlayer bonding strength of the printed body. After debinding and sintering, ceramic parts (including ceramic special-shaped parts) with high mechanical properties and high reliability can be obtained. The present invention designs a suitable binder composition according to the process requirements, obtains a ceramic feed suitable for FDM3D printing, and the printed body has relatively excellent mechanical properties. The printed body is isostatically pressed using an isostatic pressing process, which can eliminate the holes and microcracks inside the printed body caused by the lack of feed and improve the body density. During the isostatic pressing process, although the internal microcracks and holes are eliminated, the bonding strength there is still low, and the interlayer bonding of the body itself is weak. In order to improve the interlayer bonding strength, the body is softened by high temperature and pressurized uniformly in all directions by gas pressure, which improves the bonding strength and prevents deformation, and is conducive to suppressing the defects generated during debinding and sintering. For simple ceramic special-shaped parts, secondary isostatic pressing of the green body after solvent degreasing can increase the green body density, reduce sintering defects, and thus improve the mechanical properties of the ceramic parts. DETAILED DESCRIPTION

[0022] The present invention will be further described below with reference to specific preferred embodiments, but the scope of protection of the present invention is not limited thereby. The materials and instruments used in the following examples are all commercially available, among which ethylene-vinyl acetate copolymer was purchased from Beijing Organic Chemical Plant, polyethylene was purchased from Taiwan Polymer Chemical Co., Ltd.,

[0023] Example 1

[0024] A method for preparing a ceramic part by fused deposition of the present invention comprises the following steps:

[0025] (1) Weigh 1600 g of alumina powder, 220 g of paraffin wax, 48 g of stearic acid, 44 g of ethylene-vinyl acetate copolymer, 112 g of polyethylene, and 28 g of dibutyl phthalate and mix them in an internal mixer at a mixing temperature of 170°C for 3 h. After cooling, a block feed is obtained.

[0026] (2) Use a jaw crusher to crush the cooled block feed, and after screening, obtain granular printing feed with a particle size of 1-5 mm.

[0027] (3) The granular printing feed was added into the FDM3D printer hopper, and the printing model (60×60×10 mm, non-solid structure) was imported. The printing blank was prepared by melt deposition using a screw extrusion method. The extrusion temperature was 160°C, the hot bed temperature was 80°C, and the printing speed was 15 mm / s.

[0028] (4) Use isostatic pressing equipment to isostatically press the formed printed body with a pressure of 150 MPa and a holding time of 20 min.

[0029] (5) The printed body after isostatic pressing is placed in a gas pressure sintering furnace for gas pressure melting process to eliminate internal defects and improve bonding strength. The atmosphere is air atmosphere, the temperature is 150 ° C, the gas pressure is 2 MPa, and the holding time is 20 min.

[0030] (6) Remove the printed body from the gas pressure sintering furnace and place it in kerosene for solvent degreasing to remove the paraffin in the body. The temperature is 40°C and the time is 20 hours. Remove the body from the kerosene, dry it, and then place the ceramic body in a debinding furnace for debinding to remove the polymer binder in the ceramic body. The debinding temperature is 600°C, the heating rate is 0.1°C / min, and the atmosphere is air. Place the debinding body in a sintering furnace for sintering. The sintering method is normal pressure sintering, the temperature is 1600°C, the heating rate is 1°C / min, the holding time is 3 hours, and the sintering atmosphere is air to obtain a ceramic blank. Use a CNC machine tool to perform precision processing and polishing on the ceramic blank to obtain alumina ceramics.

[0031] Example 2

[0032] A method for preparing a ceramic part by fused deposition of the present invention comprises the following steps:

[0033] (1) Weigh 1600 g of alumina powder, 220 g of paraffin wax, 48 g of stearic acid, 44 g of ethylene-vinyl acetate copolymer, 112 g of polyethylene, and 28 g of dibutyl phthalate and mix them in an internal mixer at a mixing temperature of 170°C for 3 h. After cooling, a block feed is obtained.

[0034] (2) Use a jaw crusher to crush the cooled block feed, and after screening, obtain granular printing feed with a particle size of less than 5 mm.

[0035] (3) The granular printing feed was added into the FDM3D printer hopper, and the printing model (60×60×10 mm, solid structure) was imported. The printing blank was prepared by melt deposition using a screw extrusion method. The extrusion temperature was 160°C, the hot bed temperature was 80°C, and the printing speed was 15 mm / s.

[0036] (4) Use isostatic pressing equipment to isostatically press the formed printed body with a pressure of 150 MPa and a holding time of 20 min.

[0037] (5) The printed body after isostatic pressing is placed in a gas pressure sintering furnace for gas pressure melting process to eliminate internal defects and improve bonding strength. The atmosphere is nitrogen atmosphere, the temperature is 150 ° C, the gas pressure is 2 MPa, and the holding time is 20 min.

[0038] (6) Remove the printed body from the gas pressure sintering furnace and place it in kerosene for solvent degreasing to remove the paraffin in the body. The temperature is 40℃ and the time is 20h. Remove the body from the kerosene, dry it, and then wrap it with a rubber film. Place it in the isostatic press again for isostatic pressing. The pressure is 150MPa and the holding time is 30min. Place the ceramic body in a debinding furnace for debinding to remove the polymer binder in the ceramic body. The debinding temperature is 600℃, the heating rate is 0.1℃ / min, and the atmosphere is air. Place the debinding body in a sintering furnace for sintering to obtain a ceramic blank. The sintering method is normal pressure sintering, the temperature is 1580℃, the heating rate is 1℃ / min, the holding time is 3h, and the sintering atmosphere is air. After precision processing and polishing the ceramic blank using a CNC machine tool, an alumina ceramic is obtained.

[0039] Example 3

[0040] A method for preparing a ceramic part by fused deposition of the present invention comprises the following steps:

[0041] (1) Weigh 1740 g of zirconium oxide powder, 105 g of polyethylene glycol 2000, 40 g of polyethylene glycol 1000, 35 g of stearic acid, 26 g of ethylene-vinyl acetate copolymer, 73 g of polyethylene, and 28 g of dibutyl phthalate and mix them in an internal mixer at a mixing temperature of 180° C. for 3 h. After cooling, a block feed is obtained.

[0042] (2) Use a jaw crusher to crush the cooled block feed, and after screening, obtain granular printing feed with a particle size of less than 5 mm.

[0043] (3) The granular printing feed was added into the FDM3D printer hopper, and the printing model (60×60×10 mm, solid structure) was imported. The printing blank was prepared by melt deposition using a screw extrusion method. The extrusion temperature was 165°C, the hot bed temperature was 80°C, and the printing speed was 12 mm / s.

[0044] (4) The formed printed body is covered with a rubber film and then isostatically pressed using an isostatic pressing device with a pressure of 150 MPa and a holding time of 20 min.

[0045] (5) The printed body after isostatic pressing is placed in a gas pressure sintering furnace for gas pressure melting process to eliminate internal defects and improve bonding strength. The atmosphere is nitrogen atmosphere, the temperature is 150 ° C, the gas pressure is 2 MPa, and the holding time is 20 min.

[0046] (6) The printed body was removed from the gas pressure sintering furnace and placed in deionized water for water degreasing to remove the polyethylene glycol in the body at a temperature of 40°C for 20 h.

[0047] (7) The green body is removed from the deionized water, dried, and then wrapped with a rubber film. It is then placed in an isostatic press for isostatic pressing again at a pressure of 150 MPa and a holding time of 30 min. The ceramic green body is placed in a debinding furnace for debinding to remove the polymer binder in the ceramic green body. The debinding temperature is 600 ° C, the heating rate is 0.1 ° C / min, and the atmosphere is air. The green body after debinding is placed in a sintering furnace for sintering. The sintering method is normal pressure sintering, the temperature is 1500 ° C, the heating rate is 1 ° C / min, the holding time is 3 h, and the sintering atmosphere is air to obtain a ceramic green body. The ceramic green body is precisely processed and polished using a CNC machine tool to obtain zirconia ceramics.

[0048] Example 4

[0049] A method for preparing a ceramic part by fused deposition of the present invention comprises the following steps:

[0050] (1) Weigh 1550 g of ball-milled ceramic powder (1400 g of silicon nitride, 75 g of yttrium oxide, and 75 g of aluminum oxide), 253 g of paraffin wax, 46 g of stearic acid, 23 g of ethylene-vinyl acetate copolymer, 130 g of polyethylene, 23 g of polyvinyl butyral, and 32 g of dioctyl phthalate, and mix them in an internal mixer at a mixing temperature of 180°C for 3 h. After cooling, a block feed is obtained.

[0051] (2) Use a jaw crusher to crush the cooled block feed, and after screening, obtain granular printing feed with a particle size of less than 5 mm.

[0052] (3) The granular printing feed was added into the FDM3D printer hopper, and the printing model (60×60×10 mm, solid structure) was imported. The printing blank was prepared by melt deposition using a screw extrusion method. The extrusion temperature was 165°C, the hot bed temperature was 80°C, and the printing speed was 15 mm / s.

[0053] (4) Use isostatic pressing equipment to perform isostatic pressing on the formed printed body with a pressure of 150 MPa and a holding time of 20 min.

[0054] (5) The printed body after isostatic pressing is placed in a gas pressure sintering furnace for gas pressure melting process to eliminate internal defects and improve bonding strength. The atmosphere is nitrogen atmosphere, the temperature is 150 ° C, the gas pressure is 2 MPa, and the holding time is 20 min.

[0055] (6) Remove the printed body from the gas pressure sintering furnace and place it in kerosene for solvent degreasing to remove the paraffin in the body. The temperature is 40°C and the time is 20 hours. Remove the body from the kerosene, dry it, and then wrap it with a rubber film. Place it in an isostatic press again for isostatic pressing at a pressure of 150 MPa and a holding time of 30 minutes. Place the ceramic body in a debinding furnace for debinding to remove the polymer binder in the ceramic body. The debinding temperature is 1200°C, the heating rate is 0.1°C / min, and the atmosphere is nitrogen. Place the debinding body in a sintering furnace for sintering to obtain a ceramic blank. The sintering method is gas pressure sintering, the temperature is 1800°C, the heating rate is 1°C / min, the holding time is 5 hours, the sintering atmosphere is nitrogen, and the atmosphere pressure is 3 MPa. Silicon nitride ceramics can be obtained by precision machining and polishing the ceramic blank using a CNC machine tool.

[0056] Comparative Example 1

[0057] A method for preparing ceramic parts is basically the same as Example 1, except that step (5) is not performed, that is, the printed blank after isostatic pressing is not placed in a gas pressure sintering furnace for gas pressure melting process.

[0058] Comparative Example 2

[0059] A method for preparing ceramic parts is basically the same as Example 1, except that step (4) is not performed, that is, the isostatic pressing equipment is not used to isostatically press the formed printed body.

[0060] Comparative Example 3

[0061] A method for preparing ceramic parts is basically the same as Example 4, except that: the printed body is not subjected to the isostatic pressing treatment of step (4), the printed body is not treated by the gas pressure melting process of step (5), and the printed body after degreasing in step (6) is not subjected to isostatic pressing using isostatic pressing molding equipment.

[0062] Table 1 Performance test table of ceramic parts of Examples 1-4 and Comparative Examples 1-3

[0063]

[0064] As can be seen from Table 1, the alumina ceramics of Examples 1-2 have a density of at least 99.3%, an interlayer bonding strength of at least 21.7 MPa, a flexural strength of at least 395 MPa, a Vickers hardness of at least 16.5 GPa, and a Weibull modulus of at least 11.6. The zirconia ceramic of Example 3 has a density of 99%, a hardness of 14.2 GPa, and a flexural strength of 922 MPa. The silicon nitride ceramic of Example 4 has a density of 98.5%, a hardness of 14.3 GPa, an interlayer bonding strength of 22.1 MPa, a flexural strength of 892 MPa, and a Weibull modulus of 10.6. The alumina ceramics provided in Examples 1-2 have significantly improved relative density, interlayer bonding strength, flexural strength, and Weibull modulus compared to the alumina ceramics provided in Comparative Examples 1-2. The silicon nitride ceramic provided in Example 4 also shows a significant improvement in relative density, interlayer bonding strength, flexural strength, and Weibull modulus compared to the silicon nitride ceramic provided in Comparative Example 3. Therefore, the method for preparing high-reliability ceramic parts by melt deposition provided in the present invention can produce ceramic parts with excellent mechanical properties and complex shapes. Compared with traditional FDM 3D printing technology, the method provided in the present invention effectively reduces body defects, improves interlayer bonding strength, and improves the mechanical properties and reliability of ceramic parts. Moreover, compared with ceramic parts prepared by traditional methods, the method provided in the present invention has a simple process, is suitable for industrial production, and can save a lot of processing costs.

[0065] The above description is only a preferred embodiment of the present invention and does not constitute any formal limitation to the present invention. Although the present invention has been disclosed as above in terms of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art can, without departing from the spirit and technical solution of the present invention, use the methods and technical contents disclosed above to make many possible changes and modifications to the technical solution of the present invention, or modify it into an equivalent embodiment of equivalent changes. Therefore, any simple modification, equivalent replacement, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention, still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for preparing ceramic parts by fused deposition, characterized in that: The following steps are involved: (1) mixing raw ceramic powder, low molecular weight polymer, stearic acid, ethylene-vinyl acetate copolymer, polyethylene, polyvinyl butyral and plasticizer at a mixing temperature of 140° C. to 200° C., and cooling to obtain a bulk feed; wherein the low molecular weight polymer is paraffin wax or polyethylene glycol, and the raw materials are calculated by mass fraction as follows: ceramic powder is 60% to 90%, low molecular weight polymer is 5% to 20%, stearic acid is 0.5% to 3%, ethylene-vinyl acetate copolymer is 1% to 10%, polyethylene is 1% to 10%, polyvinyl butyral is 0% to 5%, and plasticizer is 1% to 5%; (2) crushing and sieving the obtained bulk feed to obtain granular printing feed; (3) adding the obtained granular printing feed into the FDM 3D printer hopper, importing the printing model, and adopting the screw extrusion printing method to obtain the printing blank by melt deposition; (4) isostatically pressing the obtained printed body at a pressure of 100 MPa to 200 MPa; (5) The printed body after isostatic pressing is subjected to air pressure melting at a temperature of 120°C to 180°C and an air pressure of 1MPa to 5MPa to eliminate internal defects; (6) The printed blank after air pressure melting is degreased, debinded, and sintered to obtain a ceramic blank, which is then precisely processed and polished to obtain a ceramic part.

2. The method for preparing ceramic parts by fused deposition according to claim 1, characterized in that: In step (1), the ceramic powder includes one or more of alumina powder, zirconium oxide powder, silicon nitride powder, silicon carbide powder and yttrium oxide, the polyethylene glycol is polyethylene glycol 1000 and / or polyethylene glycol 2000, and the plasticizer is dibutyl phthalate or dioctyl phthalate; and the mixing time is 2 hours to 4 hours.

3. The method for preparing ceramic parts by fused deposition according to claim 1, characterized in that: In step (2), the particle size of the granular printing feed is less than 5 mm.

4. The method for preparing ceramic parts by fused deposition according to claim 1, characterized in that: In step (3), the temperature of the screw extruder is 160°C to 200°C, the temperature of the printer hot bed is 60°C to 100°C, and the printing speed is 10mm / s to 30mm / s.

5. The method for preparing ceramic parts by fused deposition according to any one of claims 1 to 4, characterized in that: In step (4), the holding time of the isostatic pressing is 5 minutes to 30 minutes.

6. The method for preparing ceramic parts by fused deposition according to any one of claims 1 to 4, characterized in that: In step (5), the atmosphere of the gas pressure melting is nitrogen or air, and the holding time of the gas pressure melting is 10 minutes to 30 minutes.

7. The method for preparing ceramic parts by fused deposition according to any one of claims 1 to 4, characterized in that: In step (6): the degreasing is carried out in a solvent, when the low molecular weight polymer is paraffin, kerosene is used as the solvent, and when the low molecular weight polymer is polyethylene glycol, water is used as the solvent; the degreasing temperature is 40°C to 60°C, and the degreasing time is 10h to 30h; the debinding heating rate is 0.05°C / min to 0.5°C / min, the atmosphere is air or nitrogen, and the debinding temperature is 600°C to 1200°C; the sintering is one of gas pressure sintering, vacuum sintering or normal pressure sintering, the atmosphere of the gas pressure sintering and normal pressure sintering is one or more of nitrogen, air and hydrogen, the sintering heating rate is 0.5°C / min to 5°C / min, the sintering temperature is 1400°C to 2000°C, and the holding time is 2h to 5h.

8. The method for preparing ceramic parts by fused deposition according to any one of claims 1 to 4, characterized in that: In step (6): when the printed body is a solid structure, after the degreasing, the printed body is first coated with a rubber film, and then isostatically pressed at a pressure of 100 MPa to 200 MPa and a holding time of 5 min to 30 min, and then the binder is removed.

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