A method of photocuring an aluminum powder reinforced silicon-based ceramic core for additive manufacturing

Abstract

The application discloses a kind of light-cured additive manufacturing aluminum powder reinforced silicon-based ceramic core method, comprising S1, light-sensitive resin, liquid dispersing agent, photoinitiator and light inhibitor are mixed sufficiently, obtain liquid mixture, ceramic powder and aluminum powder are added to liquid mixture and mixed sufficiently, and light-cured ceramic slurry of uniform dispersion is obtained;S2, light-cured ceramic slurry is printed into shape by light-cured additive manufacturing technology, and gets blank;S3, blank is analyzed by thermogravimetry, and according to the thermogravimetric curve of blank, pyrolysis temperature program is set, and blank is carried out in air atmosphere in box furnace and is debound and sintered.The advantage is: in air atmosphere, aluminum powder is oxidized to generate aluminum oxide reinforced silicon-based ceramic core, at lower sintering temperature, improve the mechanical strength of light-cured silicon-based ceramic core and reduce sintering shrinkage, realize the integrated manufacturing of aluminum powder reinforced silicon-based ceramic core of low shrinkage, low defect, high mechanical property, with the advantages of no mold, high surface precision.

Description

Technical Field

[0001] This invention relates to the field of photocurable additive manufacturing of ceramic materials, and in particular to a method for photocurable additive manufacturing of aluminum powder reinforced ceramic cores. Background Technology

[0002] With the upgrading of thrust ratio in aero-engines, the requirements for turbine inlet temperature have increased. To improve turbine inlet temperature, the internal structure of engine blades is becoming increasingly complex, and the structure of ceramic cores is also becoming more complex. Traditional ceramic core fabrication processes require molds, have long production cycles, high costs, and cannot meet the fabrication needs of complex ceramic core structures.

[0003] Additive manufacturing technology, as an advanced manufacturing technology, has the advantages of fast forming and high precision, and can be used for the forming of ceramic slurries, with a wide range of applications. Currently, the additive manufacturing technologies used for ceramic slurries are mainly stereolithography (SLA) and digital light processing (DLP) technologies, which are based on photopolymerization technology.

[0004] Silicon-based ceramic cores are widely used due to their low coefficient of thermal expansion and ease of core removal. However, the photopolymerization process of silicon-based ceramic cores involves both mass loss and resin decomposition during pyrolysis. This results in more pores and greater volume shrinkage in the pyrolyzed ceramic products, leading to a decline in the mechanical properties of the ceramic components and limiting their applications. Therefore, a method is urgently needed to enhance the mechanical strength of silicon-based ceramic cores and reduce sintering shrinkage. Summary of the Invention

[0005] The purpose of this invention is to provide a method for photopolymer additive manufacturing of aluminum powder reinforced ceramic cores, thereby solving the aforementioned problems existing in the prior art.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A method for photopolymer additive manufacturing of aluminum powder reinforced ceramic cores includes the following steps.

[0008] S1. Preparation of photocurable ceramic core slurry:

[0009] Weigh appropriate amounts of photosensitive resin, liquid dispersant, photoinitiator, and photoinhibitor, and blend them to obtain a uniform liquid mixture. Add aluminum powder and ceramic powder to the liquid mixture and mix thoroughly to finally obtain a uniformly dispersed photocurable ceramic slurry. The ceramic powder has a mass fraction of 75-85 wt%, the photosensitive resin has a mass fraction of 15-25 wt%, the liquid dispersant has a mass fraction of 1-5 wt% of the ceramic powder, the aluminum powder has a mass fraction of 1-10 wt% of the ceramic powder, the photoinitiator has a mass fraction of 0.5-1 wt% of the photosensitive resin, and the photoinhibitor has a mass fraction of 0.01-0.03 wt% of the photosensitive resin.

[0010] S2. Printing preforms using photopolymer additive manufacturing technology:

[0011] The prepared photocurable ceramic slurry is printed into a shape using photocurable additive manufacturing technology to obtain a green body.

[0012] S3. Debinding and sintering the green body to obtain a photocurable aluminum powder reinforced silicon-based ceramic core:

[0013] Thermogravimetric analysis was performed on the green blank, and a pyrolysis temperature program was set according to the thermogravimetric curve of the green blank. Based on the pyrolysis temperature program, the green blank was degreased in an air atmosphere in a box furnace to completely decompose the photosensitive resin. Then, a high-temperature sintering process was carried out in an air atmosphere to finally obtain a photocurable aluminum powder reinforced silicon-based ceramic core.

[0014] Preferably, step S1 specifically involves:

[0015] A liquid mixture is obtained by stirring a photosensitive resin, a liquid dispersant, a photoinitiator, and a photoinhibitor at a first set stirring rate for a first set time; wherein, the first stirring rate is 300-500 r / min, and the first set time is 2-3 h.

[0016] After adding aluminum powder and ceramic powder to a liquid mixture, the mixture is dispersed at a second set dispersion speed for a second set time a certain number of times to obtain a uniformly dispersed photocurable ceramic slurry; wherein the second set dispersion speed is 1000-1500 r / min, the second set time is 30-60 s, and the number of times is 3-6.

[0017] Preferably, the photosensitive resin is any one of propoxylated neopentyl glycol diacrylate, methacrylate, and hexanediol diacrylate.

[0018] Preferably, the liquid dispersant is any one of the polymeric dispersants KOS110, KOS163, SP-710, and BYK111.

[0019] Preferably, the photoinitiator is bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide.

[0020] Preferably, the light inhibitor is a blue light absorber.

[0021] Preferably, the ceramic powder is either spherical fused silica (5-20 μm) or irregular fused silica (5-20 μm).

[0022] Preferably, the aluminum powder is spherical particles with a particle size of 5-20 μm.

[0023] Preferably, the degreasing process involves heating the raw blank to 450-600℃ and holding it at that temperature for 2-3 hours; the atmosphere during the degreasing process is air, the heating rate is 0.1-0.5℃ / min, and the cooling rate is 0.1-0.5℃ / min.

[0024] The sintering process involves heating the degreased ceramic core to 1100-1300℃ and holding it at that temperature for 4-6 hours, then cooling it to room temperature in the furnace to obtain the molded part. The atmosphere for the sintering process is air, with a heating rate of 1-5℃ / min and a cooling rate of 1-5℃ / min.

[0025] Preferably, the photopolymer additive manufacturing technology is one of stereolithography or digital light processing; specifically, a recessed photopolymer printer is used for printing, and the photopolymer ceramic slurry is evenly spread on the printing platform under the action of the printer's scraper, forming a ceramic blank layer by layer.

[0026] The process parameters for photopolymer printing include an exposure power of 20-60 mW / cm². 2 The exposure time is 2-20s, and the curing thickness is 25-200μm.

[0027] The beneficial effects of this invention are: 1. It achieves the oxidation of aluminum powder to form alumina, improving the mechanical strength of silicon-based ceramic cores at lower sintering temperatures and reducing sintering shrinkage. 2. Through precise control of the amount of aluminum powder added and the pyrolysis temperature, the various properties of the silicon-based ceramic cores after pyrolysis are effectively optimized. The final sintered silicon-based ceramic cores achieve a linear shrinkage rate of <2%, a porosity of 25%, a room temperature mechanical strength of 18 MPa, and a high temperature mechanical strength of 20 MPa. 3. Compared with traditional methods, photopolymer additive manufacturing technology has the advantages of fast molding speed, high precision, high efficiency, and moldless manufacturing, enabling the fabrication of complex and fine geometric structures. Attached Figure Description

[0028] Figure 1 This is a process flow diagram of the method in the embodiments of the present invention;

[0029] Figure 2 This is a schematic diagram of the raw blank obtained by printing according to Embodiment 1 of the present invention;

[0030] Figure 3 This is a schematic diagram of the silicon oxide ceramic part obtained in Embodiment 1 of the present invention;

[0031] Figure 4 This is a SEM image of the silicon oxide ceramic part obtained in Embodiment 1 of the present invention. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0033] like Figure 1 As shown in this embodiment, a method for photopolymer additive manufacturing of aluminum powder reinforced ceramic cores is provided, comprising the following steps:

[0034] I. Preparation of photocurable ceramic core slurry:

[0035] Weigh appropriate amounts of photosensitive resin, liquid dispersant, photoinitiator, and photoinhibitor, and blend them to obtain a uniform liquid mixture. Add aluminum powder and ceramic powder to the liquid mixture and mix thoroughly to finally obtain a uniformly dispersed photocurable ceramic slurry. The ceramic powder has a mass fraction of 75-85 wt%, the photosensitive resin has a mass fraction of 15-25 wt%, the liquid dispersant has a mass fraction of 1-5 wt% of the ceramic powder, the aluminum powder has a mass fraction of 1-10 wt% of the ceramic powder, the photoinitiator has a mass fraction of 0.5-1 wt% of the photosensitive resin, and the photoinhibitor has a mass fraction of 0.01-0.03 wt% of the photosensitive resin.

[0036] In this embodiment, the photosensitive resin, liquid dispersant, photoinitiator and photoinhibitor are stirred at a first set stirring rate for a first set time to obtain a liquid mixture; wherein, the first stirring rate is 300-500 r / min and the first set time is 2-3 h.

[0037] After adding aluminum powder and ceramic powder to a liquid mixture, the mixture is dispersed at a second set dispersion speed for a second set time a certain number of times to obtain a uniformly dispersed photocurable ceramic slurry; wherein the second set dispersion speed is 1000-1500 r / min, the second set time is 30-60 s, and the number of times is 3-6.

[0038] In this embodiment, the photosensitive resin is any one of propoxylated neopentyl glycol diacrylate, methacrylate, and hexanediol diacrylate. The photosensitive resin is used for photocuring and printing the raw preform.

[0039] In this embodiment, the liquid dispersant is any one of the polymeric dispersants KOS110, KOS163, SP-710, and BYK111. The liquid dispersant is used to disperse aluminum powder in the photocuring system.

[0040] In this embodiment, the photoinitiator is bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide. The photoinitiator is used to initiate the photocuring reaction of the slurry.

[0041] In this embodiment, the light inhibitor is a blue light absorber. The light inhibitor is used to block the transmission of ultraviolet and blue light.

[0042] In this embodiment, the ceramic powder is either spherical fused silica (5-20 μm) or irregular fused silica (5-20 μm).

[0043] In this embodiment, the aluminum powder is spherical particles with a particle size of 5-20 μm. The aluminum powder undergoes a solid-liquid reaction at around 600℃. As the temperature rises, the aluminum powder melts and oxidizes to form aluminum oxide. During this process, volume expansion and mass increase occur, which can effectively reduce sintering shrinkage and casting shrinkage.

[0044] Alumina ceramic powder is a commonly used mineralizer in silicon-based ceramic cores. The melting temperature of aluminum powder is within the sintering temperature range. Alumina powder oxidizes to form alumina without other impurities, and it does not significantly inhibit the formation of the cristobalite phase during sintering. Therefore, choosing aluminum powder as an additive, compared to the traditional use of alumina powder, can reduce the sintering temperature and sintering shrinkage rate of silicon-based ceramic cores. With alumina ceramic powder, the sintering temperature is above 1200℃, where the alumina powder melts and bonds under the sintering driving force. However, adding aluminum powder can effectively enhance the strength of silicon-based ceramic cores even below 1200℃.

[0045] In this embodiment, the ceramic core prepared by the above method has an open porosity of 25-35% and a photocured bending strength of 10-20 MPa.

[0046] II. Printing preforms using photopolymer additive manufacturing technology:

[0047] The prepared photocurable ceramic slurry is printed into a green body using photocurable additive manufacturing technology. A recessed photocurable printer is used for printing; the ceramic slurry is evenly spread on the printing platform under the action of a doctor blade, forming layer by layer to ultimately obtain the ceramic green body.

[0048] The photopolymer additive manufacturing technology is one of stereolithography and digital light processing; the process parameters for photopolymer printing include an exposure power of 20-60 mW / cm². 2The exposure time is 2-20s, and the curing thickness is 25-200μm.

[0049] 3. Debinding and sintering the green body to obtain a photocurable aluminum powder reinforced silicon-based ceramic core:

[0050] Thermogravimetric analysis was performed on the green blank, and a pyrolysis temperature program was set according to the thermogravimetric curve of the green blank. Based on the pyrolysis temperature program, the green blank was degreased in an air atmosphere in a box furnace to completely decompose the photosensitive resin. Then, a high-temperature sintering process was carried out in an air atmosphere to finally obtain a photocurable aluminum powder reinforced silicon-based ceramic core.

[0051] The degreasing process involves heating the raw blank to 450-600℃ and holding it at that temperature for 2-3 hours. The atmosphere used in the degreasing process is air, with a heating rate of 0.1-0.5℃ / min and a cooling rate of 0.1-0.5℃ / min.

[0052] The sintering process involves heating the degreased ceramic core to 1100-1300℃ and holding it at that temperature for 4-6 hours, then cooling it to room temperature in the furnace to obtain the molded part. The atmosphere for the sintering process is air, with a heating rate of 1-5℃ / min and a cooling rate of 1-5℃ / min.

[0053] In this embodiment, the final ceramic slurry has a viscosity of 20,000-100,000 CP. The ceramic slurry exhibits shear-thinning properties and does not flow when stationary.

[0054] Example 1

[0055] In this embodiment, the specific steps of the method for photopolymer additive manufacturing of aluminum powder reinforced silicon-based ceramic cores are as follows:

[0056] (1) First, 70g of photosensitive resin (TMPTA), 3g of dispersant (SP-710), 0.35g of photoinitiator (BAPO), and 0.007g of photoinhibitor (blue light absorber) were added to a container and stirred at 500r / min for 3h to obtain a homogeneous liquid mixture. 300g of 5μm irregular fused silica powder and 3g of aluminum powder were added to the liquid mixture and centrifuged at 1500r / min for 30s in a homogenizer. The mixture was centrifuged and dispersed a total of 5 times to obtain a uniformly dispersed photocurable ceramic slurry.

[0057] (2) The ceramic slurry obtained in step (1) is printed into a green body using a photopolymerization molding equipment, with the exposure intensity set to 35 mW / cm². 2 The exposure time was 2 seconds, the curing thickness was 100 μm, and the printed preform was as follows: Figure 2 As shown.

[0058] (3) Thermogravimetric analysis was performed on the photocured preform. Based on the pyrolysis temperature program, the ceramic preform obtained in step (2) was placed in a box furnace for pyrolysis in air. Temperature program: The heating rate was controlled at 0.2℃ / min, and the preform was held at 450℃ and 600℃ for two hours respectively. Then, the temperature was increased from 600℃ to 1200℃ at a heating rate of 1℃ / min and held at 1200℃ for 5 hours. Then, the preform was cooled from 1200℃ to room temperature at a rate of 2℃ / min. The images and SEM morphology of the pyrolyzed parts are shown below. Figure 3 and Figure 4 As shown;

[0059] (4) The silicon oxide ceramic parts obtained in step (3) were tested and characterized to measure their properties: the porosity can reach 26%, the room temperature mechanical strength can reach 12 MPa, and the high temperature mechanical strength can reach 15 MPa.

[0060] Example 2

[0061] In this embodiment, the specific steps of the method for photopolymer additive manufacturing of aluminum powder reinforced silicon-based ceramic cores are as follows:

[0062] Except for the following steps, all other preparation steps are the same as in Example 1: In step (2), 300g of 10μm irregular fused silica and 3g of aluminum powder are added to the liquid mixture, and the mixture is centrifuged at 1500r / min for 30s in a homogenizer, and centrifuged and dispersed a total of 5 times to obtain a uniformly dispersed photocurable slurry. Compared with Example 1, the shrinkage rate of the obtained silicon-based ceramic core is reduced, and the mechanical strength is decreased.

[0063] Example 3

[0064] In this embodiment, the specific steps of the method for photopolymer additive manufacturing of aluminum powder reinforced silicon-based ceramic cores are as follows: Except for the following steps, the other preparation steps are the same as in Example 1: In step (2), 300g of 5μm irregular fused silica and 6g of aluminum powder are added to the liquid mixture, and centrifuged and mixed in a homogenizer at 1500r / min for 30s, and centrifuged and dispersed a total of 5 times to obtain a uniformly dispersed photopolymer slurry. The heating rate is controlled at 0.2℃ / min, and the temperature is maintained at 450℃ and 600℃ for two hours respectively. Then, the temperature is increased from 600℃ to 1150℃ at a heating rate of 1℃ / min, and maintained at 1150℃ for 5 hours. Then, the temperature is cooled from 1150℃ to room temperature at a rate of 2℃ / min. Compared with Examples 1 and 2, the obtained silicon-based ceramic core has a linear shrinkage rate of <2%, a porosity of 28%, a room temperature mechanical strength of 18MPa, and a high temperature mechanical strength of 20MPa.

[0065] In this embodiment, the effects of aluminum powder addition and pyrolysis temperature on silicon-based ceramic cores are studied using the controlled variable method. The effects of the same aluminum powder addition at different sintering temperatures, and the effect of the same sintering temperature at the same aluminum powder addition, are compared (refer to the three embodiments above). It can be seen that:

[0066] Without aluminum powder, the silicon-based ceramic core exhibits the highest mechanical strength and sintering shrinkage, while having the lowest porosity. Adding aluminum powder decreases both mechanical strength and shrinkage, while increasing porosity. With increasing aluminum powder content, at the same sintering temperature, mechanical strength and sintering shrinkage gradually decrease due to the increased porosity caused by the melting of more aluminum powder. With the same amount of aluminum powder, as the sintering temperature increases, mechanical strength initially increases and then decreases, while shrinkage gradually increases. To balance mechanical strength and shrinkage, 1150℃ was chosen as the sintering temperature.

[0067] By adopting the above-disclosed technical solution of this invention, the following beneficial effects are obtained:

[0068] This invention provides a method for photopolymer additive manufacturing of aluminum powder-reinforced silicon-based ceramic cores. Compared with traditional methods, this method achieves aluminum powder oxidation to alumina, improving the mechanical strength of the silicon-based ceramic core at a lower sintering temperature and reducing sintering shrinkage. By precisely controlling the amount of aluminum powder added and the pyrolysis temperature, the various properties of the silicon-based ceramic core after pyrolysis are effectively optimized. The final sintered silicon-based ceramic core exhibits a linear shrinkage rate of <2%, a porosity of 25%, a room temperature mechanical strength of 18 MPa, and a high-temperature mechanical strength of 20 MPa. Compared with traditional methods, photopolymer additive manufacturing technology offers advantages such as fast forming speed, high precision, high efficiency, and moldless manufacturing, enabling the fabrication of complex and intricate geometric structures.

[0069] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for photopolymer additive manufacturing of aluminum powder reinforced ceramic cores, characterized in that: Includes the following steps, S1. Preparation of photocurable ceramic core slurry: Weigh appropriate amounts of photosensitive resin, liquid dispersant, photoinitiator, and photoinhibitor, and blend them to obtain a homogeneous liquid mixture. Add aluminum powder and ceramic powder to the liquid mixture and mix thoroughly to finally obtain a uniformly dispersed photocurable ceramic slurry. The ceramic powder comprises 75-85 wt% of the total mass, the photosensitive resin comprises 15-25 wt% of the total mass, the liquid dispersant comprises 1-5 wt% of the total mass of the ceramic powder, the aluminum powder comprises 1-10 wt% of the total mass of the ceramic powder, the photoinitiator comprises 0.5-1 wt% of the total mass of the photosensitive resin, and the photoinhibitor comprises 0.01-0.03 wt% of the total mass of the photosensitive resin. S2. Printing preforms using photopolymer additive manufacturing technology: The prepared photocurable ceramic slurry is printed into a green body using photocurable additive manufacturing technology. S3. Debinding and sintering the green body to obtain a photocurable aluminum powder reinforced silicon-based ceramic core: Thermogravimetric analysis was performed on the green blank, and the pyrolysis temperature program was set according to the thermogravimetric curve of the green blank. Based on the pyrolysis temperature program, the green blank was degreased in an air atmosphere in a box furnace to completely decompose the photosensitive resin. Then, a high-temperature sintering process was carried out in an air atmosphere to finally obtain a photocurable aluminum powder reinforced silicon-based ceramic core. The light inhibitor is a blue light absorber; The degreasing process involves heating the raw blank to 450-600℃ and holding it at that temperature for 2-3 hours. The atmosphere used in the degreasing process is air, with a heating rate of 0.1-0.5℃ / min and a cooling rate of 0.1-0.5℃ / min. The sintering process involves heating the degreased ceramic core to 1100-1300℃ and holding it at that temperature for 4-6 hours, then cooling it to room temperature in the furnace to obtain the molded part. The atmosphere for the sintering process is air, with a heating rate of 1-5℃ / min and a cooling rate of 1-5℃ / min. The ceramic powder is either spherical fused silica (5-20 μm) or irregular fused silica (5-20 μm); The aluminum powder is in the form of spherical particles with a particle size of 5-20 μm; The photopolymer additive manufacturing technology is one of stereolithography and digital light processing technology; specifically, it uses a recessed photopolymer printer for printing. The photopolymer ceramic slurry is evenly spread on the printing platform under the action of the printer's scraper, and is formed layer by layer to obtain a ceramic blank. The process parameters for photopolymer printing include an exposure power of 20-60 mW / cm². 2 The exposure time is 2-20s, and the curing thickness is 25-200μm.

2. The method for photopolymer additive manufacturing of aluminum powder reinforced ceramic cores according to claim 1, characterized in that: Step S1 specifically involves: A liquid mixture is obtained by stirring a photosensitive resin, a liquid dispersant, a photoinitiator, and a photoinhibitor at a first set stirring rate for a first set time; wherein, the first set stirring rate is 300-500 r / min, and the first set time is 2-3 h. After adding aluminum powder and ceramic powder to a liquid mixture, the mixture is dispersed at a second set dispersion speed for a second set time a certain number of times to obtain a uniformly dispersed photocurable ceramic slurry. The second set dispersion speed is 1000-1500 r / min, the second set time is 30-60 s, and the number of dispersions is 3-6 times. The photosensitive resin is any one of propoxylated neopentyl glycol diacrylate, methacrylate, and hexanediol diacrylate. The liquid dispersant is any one of the polymeric dispersants KOS110, KOS163, SP-710, and BYK111. The photoinitiator is bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide.

Images