A method for preparing high-density SiC ceramics using 3D printing

Abstract

The application relates to a method for preparing high-density SiC ceramics by using 3D printing and belongs to the field of additive manufacturing. The application aims to solve the problem of high porosity of SiC ceramic test pieces manufactured by using the existing 3D printing technology. The method comprises the following steps: 1, preparing a composite powder; 2, setting printing parameters; 3, degreasing; 4, impregnating; 5, drying; and 6, high-temperature sintering. The application is used for preparing high-density SiC ceramics by using 3D printing.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of additive manufacturing. BACKGROUND

[0002] Silicon carbide (SiC) ceramics are the first choice of high-temperature structural materials in aerospace, nuclear energy and transportation fields due to their low density, high stiffness, high-temperature resistance, superior specific strength, high thermal conductivity and excellent mechanical properties.

[0003] 3D printing technology is a new forming method, which is a technology of constructing objects through layer-by-layer printing based on digital model files and using powder-like metal or plastic and other adhesive materials. Compared with traditional technology, 3D printing technology can not only shorten the manufacturing cycle, but also provide a new way for manufacturing high-shape-complexity ceramic parts. At present, 3D printing technology has been relatively mature in manufacturing metal parts and has been widely applied. However, there are still many challenges in manufacturing ceramic test pieces by using 3D printing technology, such as the problem of high porosity of the test pieces after forming. SUMMARY

[0004] The present application aims to solve the problem of high porosity of SiC ceramic test pieces manufactured by using 3D printing technology, and further provides a method for preparing high-density SiC ceramics using 3D printing.

[0005] A method for preparing high-density SiC ceramics using 3D printing, which is carried out according to the following steps:

[0006] I. Preparation of composite powder:

[0007] Take 57-76 parts by mass of large-particle-size silicon carbide powder, 19-38 parts by mass of small-particle-size silicon carbide powder and 5-10 parts by mass of binder and mix to obtain a composite powder;

[0008] II. Setting of printing parameters:

[0009] Under the conditions of layer thickness of 0.01-1 mm, filling speed of 1000-5000 mm / s, contour speed of 1000-3500 mm / s, filling interval of 0.01-0.4 mm, filling power of 5-25 W, contour power of 2-20 W, preheating temperature of 30-80℃ and processing temperature of 30-90℃, the composite powder is used for selective laser sintering 3D printing to obtain a ceramic preliminary blank;

[0010] The thickness of the ceramic preliminary blank is 0.1-0.5 mm;

[0011] III. Debinding:

[0012] The ceramic green body is subjected to a debinding treatment to obtain a debound ceramic piece;

[0013] Four, impregnation:

[0014] The debound ceramic piece is impregnated in a nano-alumina sol impregnation solution to obtain an impregnated ceramic piece;

[0015] Five, drying:

[0016] The impregnated ceramic piece is dried to remove water to obtain a dried ceramic piece;

[0017] Six, high-temperature sintering:

[0018] The dried ceramic piece is heated to 1200-1400 DEG C, then kept at a temperature of 1200-1400 DEG C, and finally cooled to room temperature, thereby completing the method for preparing high-density SiC ceramics using 3D printing.

[0019] The method has the following advantages:

[0020] One, the method realizes the preparation of high-density SiC ceramics by controlling the printing thickness, i.e., the thickness of the ceramic green body in step two, thereby improving the density of SiC ceramics treated by Al2O3 sol impregnation and ensuring good mechanical properties.

[0021] Two, the method realizes the preparation of high-density SiC ceramics without changing the post-treatment of SiC ceramics, thereby saving the cost of post-treatment and meeting the requirements of economy and environmental protection compared with other post-treatments.

[0022] Three, the method for preparing high-density SiC ceramics can be suitable for generating ceramic products with complex shapes and high dimensional accuracy.

[0023] Four, the method has obvious advantages in further improving the air tightness of nuclear structural parts, and has broad application prospects in automobile manufacturing, high-end manufacturing, precision casting and the like.

[0024] Five, the method has simple process and short production cycle.

[0025] The application relates to a method for preparing high-density SiC ceramics using 3D printing. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 SEM image of the debound ceramic piece prepared in step three of the embodiment;

[0027] Figure 2 SEM image of the SiC ceramic prepared in the comparative experiment one;

[0028] Figure 3 SEM image of SiC ceramic prepared in Example 1. DETAILED DESCRIPTION

[0029] Specific embodiment one: a method for preparing high-density SiC ceramic using 3D printing, which is carried out according to the following steps:

[0030] I. Preparation of composite powder:

[0031] According to the mass fraction, 57-76 parts of large-particle-size silicon carbide powder, 19-38 parts of small-particle-size silicon carbide powder, and 5-10 parts of binder are taken and mixed to obtain a composite powder;

[0032] II. Setting of printing parameters:

[0033] Under the conditions of a layer thickness of 0.01-1 mm, a filling speed of 1000-5000 mm / s, a contour speed of 1000-3500 mm / s, a filling interval of 0.01-0.4 mm, a filling power of 5-25 W, a contour power of 2-20 W, a preheating temperature of 30-80℃, and a processing temperature of 30-90℃, the composite powder is used for selective laser sintering 3D printing to obtain a ceramic blank;

[0034] The thickness of the ceramic blank is 0.1-0.5 mm;

[0035] III. Degreasing:

[0036] The ceramic blank is subjected to a degreasing treatment to obtain a degreased ceramic part;

[0037] IV. Impregnation:

[0038] The degreased ceramic part is impregnated in a nano-alumina sol impregnation solution to obtain an impregnated ceramic part;

[0039] V. Drying:

[0040] The impregnated ceramic part is dried to remove water to obtain a dried ceramic part;

[0041] VI. High-temperature sintering:

[0042] The dried ceramic part is heated to 1200-1400℃, then kept at a temperature of 1200-1400℃, and finally cooled to room temperature, thereby completing the method for preparing high-density SiC ceramic using 3D printing.

[0043] The beneficial effects of the present embodiment are:

[0044] The present embodiment realizes the preparation of high-density SiC ceramics by regulating the printing thickness, i.e. the thickness of the ceramic preliminary blank in step two, improves the density of SiC ceramics treated by Al2O3 sol impregnation, and ensures good mechanical properties.

[0045] The present embodiment realizes the preparation of high-density SiC ceramics without changing the post-treatment of SiC ceramics, and compared with other post-treatments, the present embodiment saves the cost of post-treatment and realizes the requirements of economy and environmental protection.

[0046] The present embodiment provides a preparation method of high-density SiC ceramics, which can be suitable for generating ceramic products with complex shapes and high dimensional accuracy requirements.

[0047] The present embodiment has obvious advantages in further improving the air tightness of nuclear structural components, and has broad application prospects in automobile manufacturing, high-end manufacturing, precision casting and the like.

[0048] The present embodiment has a simple process and a short production cycle.

[0049] Specific embodiment two: The present embodiment is different from specific embodiment one in that the total mass fraction of the large-particle-size silicon carbide powder, the small-particle-size silicon carbide powder and the binder in step one is 100 parts. The others are the same as specific embodiment one.

[0050] Specific embodiment three: The present embodiment is different from specific embodiment one or two in that the particle size of the large-particle-size silicon carbide powder in step one is 80 μm to 100 μm, and the particle size of the small-particle-size silicon carbide powder in step one is 10 μm to 20 μm. The others are the same as specific embodiment one or two.

[0051] Specific embodiment four: The present embodiment is different from specific embodiment one to three in that the binder in step one is epoxy resin. The others are the same as specific embodiment one to three.

[0052] Specific embodiment five: The present embodiment is different from specific embodiment one to four in that the debinding treatment in step three is specifically performed according to the following steps: the ceramic preliminary blank is placed in a vacuum debinding furnace, vacuum is drawn, nitrogen is introduced, and under the conditions of nitrogen atmosphere and a temperature of 650 ℃ to 750 ℃, the temperature is kept for 1 h to 2 h, and after cooling, the debound ceramic part is obtained. The others are the same as specific embodiment one to four.

[0053] Specific embodiment six: The present embodiment is different from specific embodiment one to five in that the mass percentage of the nano-alumina sol impregnation liquid in step four is 10% to 20%. The others are the same as specific embodiment one to five.

[0054] Specific embodiment seven: the difference between this embodiment and one of the specific embodiments one to six is that the said impregnation in step four is specifically carried out by the following steps: first, keeping at room temperature and vacuum degree of 0.06 MPa-0.08 MPa for 20 min-25 min, then pressurizing at room temperature and pressure of 0.3 MPa-0.4 MPa for 20 min-25 min. The others are the same as specific embodiments one to six.

[0055] Specific embodiment eight: the difference between this embodiment and one of the specific embodiments one to seven is that the said drying in step five is specifically carried out at temperature of 60℃-80℃ for 6h-8h. The others are the same as specific embodiments one to seven.

[0056] Specific embodiment nine: the difference between this embodiment and one of the specific embodiments one to eight is that the said temperature rising in step six is specifically carried out by the following steps: rising from room temperature to 200℃-300℃ for 0.5h-1h, then rising to 700℃-900℃ for 0.5h-1h, finally rising to 1200℃-1400℃ for 1h-2h. The others are the same as specific embodiments one to eight.

[0057] Specific embodiment ten: the difference between this embodiment and one of the specific embodiments one to nine is that the said keeping at temperature of 1200℃-1400℃ in step six is for 0.5h-1h. The others are the same as specific embodiments one to nine.

[0058] The following examples are used to verify the beneficial effects of the present application:

[0059] Example one:

[0060] A method for preparing high-density SiC ceramic using 3D printing, which is carried out by the following steps:

[0061] I. Preparation of composite powder:

[0062] Take 76 parts of large-particle-size silicon carbide powder, 19 parts of small-particle-size silicon carbide powder and 5 parts of adhesive by mass fraction and mix to obtain a composite powder;

[0063] The particle size of the large-particle-size silicon carbide powder is 80μm-100μm; the particle size of the small-particle-size silicon carbide powder is 10μm-20μm;

[0064] The adhesive is epoxy resin, the manufacturer is Guangdong Nanyang Chemical New Material Co., Ltd., the particle size is 3000#, the average particle size is about 3μm-5μm, and the model is E-12;

[0065] II. Setting of printing parameters:

[0066] The ceramic blank is obtained by using the composite powder for selective laser sintering 3D printing under the conditions that the layered thickness is 0.1 mm, the filling speed is 3500 mm / s, the contour speed is 3000 mm / s, the filling interval is 0.1 mm, the filling power is 14 W, the contour power is 12 W, the preheating temperature is 35℃, and the processing temperature is 40℃.

[0067] The thickness of the ceramic blank is 0.1 mm.

[0068] III. Debinding:

[0069] The ceramic blank is placed in a vacuum debinding furnace, vacuum is drawn, and then nitrogen is introduced. Under the conditions of nitrogen atmosphere and a temperature of 700℃, the ceramic blank is kept for 2 hours, and then cooled to obtain a debound ceramic part.

[0070] IV. Impregnation:

[0071] The debound ceramic part is immersed in a nano-alumina sol impregnation solution. First, it is kept at room temperature and a vacuum degree of 0.08 MPa for 20 minutes, and then it is pressurized at room temperature and a pressure of 0.3 MPa for 20 minutes to obtain an impregnated ceramic part.

[0072] The mass percentage of the nano-alumina sol impregnation solution is 20%, the manufacturer is Dezhou Jinghuo Technology Glass Co., Ltd., and the model is JHAL-20.

[0073] V. Drying:

[0074] The impregnated ceramic part is kept at a temperature of 60℃ for 6 hours to obtain a dried ceramic part.

[0075] VI. High-temperature sintering:

[0076] The dried ceramic part is heated from room temperature to 300℃ for 1 hour, then heated to 850℃ for 55 minutes, and finally heated to 1400℃ for 1.5 hours. Then, it is kept at a temperature of 1400℃ for 0.5 hours, and finally cooled to room temperature to obtain a SiC ceramic.

[0077] In this embodiment, a three-dimensional model is created using modeling software, and the model thickness is 0.3 mm, i.e., the thickness of the ceramic blank is 0.1 mm. The three-dimensional model is output as a Standard Tessellation Language (STL) format file and imported into a computer.

[0078] In this embodiment, the composite powder is placed in the working cylinder of a selective laser cladding sintering machine. After preheating, the powder is flattened using a roller, and then the sintering process begins to obtain a ceramic blank.

[0079] Example 2: The difference between this example and example 1 is that in step 2, the ceramic green body is obtained by selective laser sintering 3D printing using the composite powder under the conditions of a layer thickness of 0.1 mm, a filling speed of 2500 mm / s, a contour speed of 2000 mm / s, a filling interval of 0.1 mm, a filling power of 12 W, a contour power of 10 W, a preheating temperature of 35℃, and a processing temperature of 40℃. The other steps are the same as in example 1.

[0080] Example 3: The difference between this example and example 1 is that in step 2, the thickness of the ceramic green body is 0.3 mm; in step 4, the ceramic part after debinding is immersed in a nano-alumina sol impregnation solution, first at room temperature and a vacuum degree of 0.08 MPa for 25 min, then at room temperature and a pressure of 0.3 MPa for 25 min, to obtain the impregnated ceramic part. The other steps are the same as in example 1.

[0081] Example 4: The difference between this example and example 1 is that in step 2, the thickness of the ceramic green body is 0.3 mm; in step 4, the ceramic part after debinding is immersed in a nano-alumina sol impregnation solution, first at room temperature and a vacuum degree of 0.06 MPa for 20 min, then at room temperature and a pressure of 0.4 MPa for 20 min, to obtain the impregnated ceramic part. The other steps are the same as in example 1.

[0082] Example 5: The difference between this example and example 1 is that in step 2, the thickness of the ceramic green body is 0.4 mm; in step 6, the dried ceramic part is heated from room temperature to 300℃ for 30 min, then heated to 900℃ for 1 h, and finally heated to 1300℃ for 2 h, then kept at a temperature of 1300℃ for 0.5 h, and finally cooled to room temperature. The other steps are the same as in example 1.

[0083] Example 6: The difference between this example and example 1 is that in step 2, the thickness of the ceramic green body is 0.5 mm. The other steps are the same as in example 1.

[0084] Comparative Experiment 1: The difference between this comparative experiment and example 1 is that in step 1, 19 parts of large particle size silicon carbide powder, 76 parts of small particle size silicon carbide powder, and 5 parts of binder are mixed to obtain a composite powder; in step 2, the thickness of the ceramic green body is 0.6 mm. The other steps are the same as in example 1.

[0085] Comparative Experiment 2: The difference between this comparative experiment and example 1 is that in step 2, the thickness of the ceramic green body is 0.7 mm. The other steps are the same as in example 1.

[0086] Comparative Experiment 3: The difference between this comparative experiment and Example 1 is that the thickness of the ceramic green body in step 2 is 0.9 mm. The others are the same as Example 1.

[0087] Comparative Experiment 4: The difference between this comparative experiment and Example 1 is that the thickness of the ceramic green body in step 2 is 1 mm. The others are the same as Example 1.

[0088] The density and porosity of the SiC ceramics prepared in Examples 1-6 and Comparative Experiments 1-4 were calculated. The density and porosity were calculated by the Archimedes drainage method. Five samples were used for each parameter, and the average value was taken to obtain the density. The average compressive strength was tested according to the standard GB / T 8489-2006 "Fine Ceramic Compressive Strength Test Method". Five samples were tested for each parameter, and then the average value was taken to obtain the average compressive strength. The parameters of each step are shown in the following table:

[0089] Table 1

[0090]

[0091]

[0092] Comparing Example 1 with Comparative Experiment 2, when the thickness of the ceramic green body increases from 0.1 mm to 0.7 mm, the density decreases from 92.32% to 77.25%, and the average compressive strength decreases from 1.01 MPa to 0.71 MPa. This is because the sol can fully penetrate into the SiC sample, reducing its open porosity and enhancing the density and compressive performance. Example 1 and Example 2 show that under the same printing thickness, the higher the density, the stronger the compressive performance of SiC ceramic. The above table fully demonstrates that this method can prepare high-density SiC ceramic.

[0093] Figure 1 The SEM image of the ceramic part after debinding prepared in Example 1 Step 3; as can be seen from the figure, the particles are scattered between the particles and are not tightly combined, and there are many pores. At this time, the sample has low density and low strength.

[0094] Figure 2 The SEM image of the SiC ceramic prepared in Comparative Experiment 1; as can be seen from the figure, the sample has a certain density and strength compared to the debound sample, but still does not meet the requirements of high-density SiC ceramic.

[0095] Figure 3 The SEM image of the SiC ceramic prepared in Example 1; as can be seen from the figure, the SiC particles in the figure are tightly combined, with few voids, and most of them are closed pores. At this time, the SiC ceramic is high-density SiC ceramic.

Claims

1. A method for preparing high density SiC ceramics using 3D printing, characterized in that It is carried out in the following steps: I. Preparation of composite powder: Take 57-76 parts by mass of large particle size silicon carbide powder, 19-38 parts by mass of small particle size silicon carbide powder and 5-10 parts by mass of binder and mix to obtain a composite powder; And the total mass fraction of large particle size silicon carbide powder, small particle size silicon carbide powder and binder is 100 parts; The particle size of the large particle size silicon carbide powder is 80-100 μm; the particle size of the small particle size silicon carbide powder is 10-20 μm; II. Print parameter setting: Under the conditions of layer thickness of 0.01-0.1 mm, filling speed of 1000-5000 mm / s, contour speed of 1000-3500 mm / s, filling interval of 0.01-0.4 mm, filling power of 5-25 W, contour power of 2-20 W, preheating temperature of 30-80℃ and processing temperature of 30-90℃, the composite powder is used for selective laser sintering 3D printing to obtain a ceramic blank; The thickness of the ceramic blank is 0.1-0.5 mm; III. Degreasing: The ceramic blank is subjected to degreasing treatment to obtain a degreased ceramic part; IV. Impregnation: The degreased ceramic part is impregnated in a nano-alumina sol impregnation solution to obtain an impregnated ceramic part; The impregnation is carried out in the following steps: first, keep at room temperature and vacuum degree of 0.06-0.08 MPa for 20-25 min, then pressurize at room temperature and pressure of 0.3-0.4 MPa for 20-25 min; V. Drying: The impregnated ceramic part is dried to remove moisture to obtain a dried ceramic part; VI. High temperature sintering: The dried ceramic part is heated to 1200-1400℃, then kept at a temperature of 1200-1400℃, and finally cooled to room temperature to complete the method for preparing high density SiC ceramic using 3D printing.

2. The method of claim 1, wherein the method of preparing high density SiC ceramics using 3D printing is characterized by The binder in step I is an epoxy resin.

3. The method of claim 1, wherein the method of fabricating high density SiC ceramics using 3D printing is characterized by The degreasing treatment in step III is carried out in the following steps: the ceramic blank is placed in a vacuum degreasing furnace, vacuum is drawn, nitrogen is introduced, and the ceramic blank is kept at a temperature of 650-750℃ for 1-2 h in a nitrogen atmosphere to obtain a degreased ceramic part.

4. The method of claim 1, wherein the method of fabricating high density SiC ceramics using 3D printing is characterized by The mass percentage of the nano-alumina sol impregnation solution in step IV is 10-20%.

5. The method of claim 1, wherein The drying in step V is carried out at a temperature of 60-80℃ for 6-8 h.

6. The method of claim 1, wherein The heating in step VI is carried out in the following steps: heating from room temperature to 200-300℃ for 0.5-1 h, then heating to 700-900℃ for 0.5-1 h, and finally heating to 1200-1400℃ for 1-2 h.

7. The method of claim 1, wherein In step VI, the temperature is kept at 1200-1400℃ for 0.5-1 h.

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