Method for electromagnetic heating assisted laser directional energy deposition of ceramic

Abstract

The invention discloses a method for electromagnetic heating assisted laser directional energy deposition of ceramic, and belongs to the technical field of additive manufacturing. Graphene oxide is added into initial powder to serve as an electromagnetic induction heating inducer, a plurality of heat source points are formed in a ceramic formed part, induction heating serves as an auxiliary heating source, and uniform heat source distribution is provided on the basis of laser heating, so that the defect of non-uniform temperature distribution is effectively overcome, and the quality of the ceramic formed part is improved. And the problems of thermal stress and cracks caused by overlarge temperature gradient are reduced. In addition, the method can optimize a temperature control system in the whole manufacturing process, belongs to real-time temperature field regulation and control in the forming process, can effectively avoid thermal stress concentration, reduces the rejection rate and post-treatment requirements caused by uneven temperature, and compared with an integral in-furnace heat preservation mode, the method has the advantages that the production cost is reduced, and the efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of additive manufacturing, and particularly to a method for electromagnetic heating-assisted laser directed energy deposition of ceramics. Background Art

[0002] As an important high-performance material, advanced ceramics are widely used in high-end manufacturing fields such as aerospace, automotive, machinery, electronics, chemical industry, and medical due to their excellent mechanical properties, high temperature resistance, corrosion resistance, and excellent electrical insulation properties. Especially in applications that require high strength, wear resistance, and resistance to extreme environments, advanced ceramics play an irreplaceable role. With the continuous development of 3D printing technology, laser additive manufacturing (LAM) technologies, such as laser directed energy deposition (LDED), as an important forming method, have shown great potential in the preparation of advanced ceramics due to their advantages of no need for molds, integrative forming, high material utilization rate, and flexible design. However, despite the excellent properties of advanced ceramics, their application in laser additive manufacturing still faces many challenges.

[0003] Currently, laser additive manufacturing technology mainly relies on the single heating method of high-energy laser beams. Although this method can quickly heat ceramic powders, due to the poor thermal conductivity and high melting point of ceramics themselves, the heat distribution still cannot be effectively controlled after the heating and forming method is optimized through processes. As a result, the temperature gradient is too large, leading to problems such as deformation and cracks. Furthermore, it is difficult for the existing technology to solve the problem of thermal stress concentration in the production of complex geometric shape and large-size ceramic parts, seriously affecting the quality and performance of ceramic components. Although induction heating technology has made great progress in metal material processing, in the application of advanced ceramic laser additive manufacturing, induction heating technology is still in the experimental stage. The low electrical conductivity of advanced ceramics greatly reduces the effect of induction heating and it is difficult to provide a sufficiently uniform heating effect during the high-temperature heating process of ceramic materials.

[0004] In the prior art, the main technical solutions for advanced ceramic laser additive manufacturing are as follows:

[0005] The Chinese invention patent with the publication number CN117843349A and the name of "A Laser Directed Energy Deposition Method for Healing Cracks in Ceramic Turbine Blades" discloses a method of adding silicon-containing powder and activator during the laser additive manufacturing of Al2O3-based ceramic turbine blades, so that the silicon-containing powder reacts with oxygen in an aerobic environment to form a silicon-containing liquid phase, and the silicon-containing liquid phase flows to autonomously heal and form cracks, preparing ceramic turbine blades with high fracture toughness and good density. However, due to the characteristics of rapid cooling of the laser, the silicon-containing liquid phase formed during the forming process is difficult to flow effectively, the crack healing effect is limited, and it is difficult to form complex structure ceramic parts.

[0006] The paper "Microstructure and Mechanical Properties of Al2O3 / ZrO2 Directionally Solidified Eutectic Ceramic Prepared by Laser 3D Printing" published by Chinese scholars Zhi Liu, Kan Song, Bo Gao, etc. in the "Journal of Materials Science & Technology", Volume 32, 2016, proposed to preheat the forming substrate by induction heating, but the material of the substrate in this scheme was not published, and its effectiveness needs to be further verified. Moreover, due to the poor thermal conductivity of ceramics, whether the formed part is tightly combined with the substrate is crucial. Poor combination will lead to worse heat dissipation and form high stress concentration. Therefore, only preheating the substrate to regulate the temperature field of ceramic part forming is insufficient, especially in the preparation of complex structure and large-size formed parts, the effect is worse and the production efficiency is low. In addition, due to the poor conductivity of ceramics, this scheme is not suitable for the laser forming of ceramic parts.

[0007] Swiss scholar Fabrizio Verga, The paper published by Makowska, Gugliemo Cellerai, etc.: "Crack-healing, a novel approach for a laser-based powder bed fusion of high-performance ceramic oxides", Additive Manufacturing Letters, Volume 1 in 2021, proposed a method of inducing crack healing to suppress the forming cracks of laser-formed ceramic parts. However, this solution belongs to post-heat treatment repair and has nothing to do with the process of laser additive manufacturing of ceramic parts.

[0008] In summary, there is an urgent need to provide an efficient method for laser additive manufacturing of advanced ceramic parts. Summary of the Invention

[0009] [Technical Problem]

[0010] The technical problem to be solved by the present invention is: an efficient method for laser additive manufacturing of advanced ceramic parts. Using the method of the present invention, the fracture toughness of the obtained ceramic parts reaches up to 7.4 MPa·m 1 / 2 , the highest relative density reaches 99.7%, and high-efficiency forming can be achieved.

[0011] [Technical Solution]

[0012] To solve the above technical problems, the present invention provides the following technical solution:

[0013] In the first aspect, the present invention provides a method for electromagnetic heating-assisted laser-directed energy deposition of ceramics, including the following steps:

[0014] S1. Raw material pretreatment:

[0015] Mix ceramic matrix powder and graphene oxide to obtain a mixture of ceramic matrix powder and graphene oxide;

[0016] S2. Induction heating pretreatment:

[0017] Fix the TC4 titanium alloy substrate in the middle of the induction heating coil, introduce the mixture of ceramic matrix powder and graphene oxide described in step S1 to the surface of the TC4 titanium alloy substrate, and preheat the mixture and the TC4 titanium alloy substrate through the induction heating coil;

[0018] S3. Deposition and forming:

[0019] Under the protection of inert gas, carry out laser-directed energy deposition forming;

[0020] S4. Post-treatment:

[0021] After forming is completed, cool to room temperature.

[0022] In one embodiment, in the step S1, the uniform dispersion of the ceramic matrix powder and graphene oxide is achieved by high-energy ball milling; the high-energy ball milling includes planetary ball milling, vibratory ball milling or plasma ball milling.

[0023] In one embodiment, in the step S1, the power of the high-energy ball milling is 500 - 1500 W. It can be optionally 500 W, 800 W or 1500 W.

[0024] In one embodiment, in the step S1, the mass ratio of the ceramic matrix powder to graphene oxide is 10:(1 - 3).

[0025] In one embodiment, the ceramic matrix powder includes at least one of Al2O3, mullite, ZrO2, GdAlO3, Y3Al5O 12 , high-entropy oxide ceramics.

[0026] In one embodiment, in the step S2, the power of the electromagnetic heater during preheating is 1000 - 2500 W. It can be optionally 1000 W, 2000 W or 2500 W.

[0027] In one embodiment, the step S3 includes: setting the laser processing forming parameters, the laser power density is (1 - 6)×10 6 W / cm 2 , the powder feeding rate is (2.3 - 4.3) g / min, the scanning speed is (500 - 1500) mm / min, the upward lifting height of the laser processing head per pass is (0.3 - 0.5) mm, the lifting speed is (5000 - 8000) mm / min; the inert gas flow rate is (6 - 15) L / min, the air pressure is (0.1 - 0.15) MPa, the powder feeding gas flow rate is (6 - 8) L / min, the air pressure is (0.1 - 0.2) MPa; turn on the water cooler and the laser, and use laser direct energy deposition to form. During the forming process, adjust the electromagnetic heater so that when the height of the formed part increases by (0.3 - 0.5) mm, the power density of the electromagnetic heater increases by (0.35 - 0.6) W / cm 2 .

[0028] In one embodiment, the step S4 includes:

[0029] a) Stop the water cooler, inert gas, powder feeder and laser in sequence;

[0030] b) After the laser processing head is removed from the processing area, keep the electromagnetic heater working continuously for 20 - 80 min;

[0031] c) By controlling the electromagnetic power to decrease, the formed part is cooled at a rate gradient less than 100 °C / min.

[0032] In a second aspect, the present invention also provides a ceramic prepared by using the method described in the first aspect.

[0033] In a third aspect, the present invention also provides the application of the method described in the first aspect in ceramic preparation or ceramic repair.

[0034] In one embodiment, the ceramic includes advanced ceramics.

[0035] It should be understood that within the scope of the present invention, the above technical features of the present invention and the technical features specifically described below (such as in the examples) can be combined with each other to form new or preferred technical solutions. Due to space limitations, they will not be elaborated one by one here.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] (1) By adding graphene oxide as an electromagnetic induction heating inducer to the initial powder in the present invention, multiple heat source points are formed in the ceramic formed part. Induction heating serves as an auxiliary heating source, providing a uniform heat source distribution on the basis of laser heating, thereby effectively improving the drawback of uneven temperature distribution and reducing the thermal stress and crack problems caused by too large a temperature gradient. In addition, this method can also optimize the temperature control system of the entire manufacturing process, which belongs to real-time regulation of the temperature field during the forming process, can effectively avoid thermal stress concentration, reduce the rejection rate and post-treatment requirements caused by uneven temperature. Compared with the overall furnace heat preservation mode, the production cost is reduced and the efficiency is improved.

[0038] (2) By controlling the content ratio of graphene oxide to the ceramic matrix powder Al2O3, the substrate material, substrate position, ball milling power, electromagnetic heater pretreatment power for electromagnetic heating assisted laser directed energy deposition, and the adjustment of the electromagnetic heater process, the effective forming of the ceramic part is realized. The fracture toughness and density of the obtained ceramic part reach 5.6 MPa·m 1 / 2 and more than 98.9% respectively. Description of the Drawings

[0039] Figure 1 It is a schematic diagram of the equipment for electromagnetic heating assisted laser directed energy deposition of ceramics. Among them, 1 is the power supply of the electromagnetic heater; 2 is the water cooler; 3 is the laser; 4 is the processing head; 5 is the powder feeder; 6 is the thin-walled part; 7 is the induction coil; 8 is the substrate; 9 is the heat insulation support table. Detailed Embodiments

[0040] The present invention will be further described in detail below in conjunction with specific embodiments. The provided embodiments are only for clarifying the present invention and not for limiting the scope of the present invention. The following provided embodiments can be used as a guide for those of ordinary skill in the art to make further improvements and do not constitute any limitation to the present invention in any way.

[0041] In the present invention, the terms "about" or "approximately" should be understood to include all values within the allowable measurement error range.

[0042] In the following experimental methods of the embodiments, unless otherwise specified, they are all conventional methods, carried out according to the techniques or conditions described in the literature in this field or according to the product specifications. The materials, reagents, etc. used in the following embodiments, unless otherwise specified, can all be obtained from commercial channels.

[0043] Embodiment:

[0044] Embodiment 1:

[0045] A system and method for electromagnetic heating-assisted laser directed energy deposition of ceramics, comprising the following steps:

[0046] Step 1: Raw materials and pretreatment for electromagnetic heating additive manufacturing:

[0047] Select Al2O3 and graphene oxide as the materials for ceramic part forming experiments. Among them, the particle size of the Al2O3 powder is 15 - 120 μm, the length of the graphene oxide is 1 - 50 μm, the aspect ratio is 0.01 - 0.05, and the mass ratio of the Al2O3 powder to the graphene oxide is 10:1. The Al2O3 powder and the graphene oxide are mixed evenly by the method of plasma ball milling, and the ball milling power is 500W.

[0048] Step 2: Electromagnetic heater and laser directed energy deposition system and pretreatment:

[0049] First, place the induction coil of the electromagnetic heater on the heat insulation support platform for fixation, place the substrate made of TC4 titanium alloy on the heat insulation support platform. The size of the substrate is 150mm × 150mm × 20mm. Adjust the height of the heat insulation support platform so that the substrate is in the middle of the induction heating coil. Adjust the distance between the bottom of the processing head and the surface of the substrate to 7.2mm. Open the powder feeder, and use inert gas to transport the evenly mixed ceramic and graphene oxide mixture to the surface of the substrate through the powder feeding tube. Turn on the power of the electromagnetic heater, set the initial heating power to 1000W, and use an infrared thermometer to detect the substrate temperature, so that the mixture and the substrate are heated at 300°C for 5 minutes.

[0050] Step 3: Parameter setting and adjustment of the electromagnetic heater and the laser directed energy deposition system:

[0051] Set the laser processing and forming parameters. The laser power density is 1×10 6 W / cm 2 , the powder feeding rate is 3.1 g / min, the scanning speed is 500 mm / min, the height that the processing head lifts upward for each pass is 0.5 mm, and the lifting speed is 5000 mm / min. Further, set the protective gas flow rate to 10 L / min, the air pressure to 0.1 MPa, the powder feeding gas flow rate to 6 L / min, and the air pressure to 0.15 MPa. Turn on the water cooler and the laser, and use the laser directed energy deposition system to form a thin-walled part with a single length of 30 mm and 40 layers. During the forming process, adjust the electromagnetic heater so that for every 0.5 mm increase in height, the power density of the electromagnetic heater increases by 0.6 W / cm 2 .

[0052] Step 4: Post-treatment of the electromagnetic heater and the laser directed energy deposition system:

[0053] After the forming is completed, turn off the water cooler, the laser, the powder feeder, and the inert gas in sequence, lift the processing head to remove it from the processing area to a safe position, and turn off the electromagnetic heater 20 minutes later. During this process, set the parameters of the electromagnetic heater to control the thin-walled part to cool down to room temperature at a speed of less than 60 °C / min.

[0054] Example 2:

[0055] A system and method for electromagnetic heating-assisted laser directed energy deposition of ceramics, comprising the following steps:

[0056] Step 1: Raw materials and pretreatment for electromagnetic heating additive manufacturing:

[0057] Select Al2O3 and graphene oxide as the materials for the ceramic part forming experiment. The particle size of the Al2O3 powder is 15 - 120 μm, the length of the graphene oxide is 1 - 50 μm, the aspect ratio is 0.15 - 0.2, and the mass ratio of the Al2O3 powder to the graphene oxide is 10:3. Use the plasma ball milling method to mix the Al2O3 powder and the graphene oxide evenly, and the ball milling power is 1500 W.

[0058] Step 2: Electromagnetic heater and laser directed energy deposition system and pretreatment:

[0059] First, place the induction coil of the electromagnetic heater on the heat-insulating support platform and fix it. Place the substrate made of TC4 titanium alloy on the heat-insulating support platform. The size of the substrate is 150 mm × 150 mm × 20 mm. Adjust the height of the heat-insulating support platform so that the substrate is in the middle of the induction heating coil. Adjust the distance between the bottom of the processing head and the surface of the substrate to 8.3 mm. Open the powder feeder, and use inert gas to transport the evenly mixed ceramic and graphene oxide mixture to the surface of the substrate through the powder feeding pipe. Turn on the power supply of the electromagnetic heater, set the initial heating power to 2000 W, and use an infrared thermometer to detect the temperature of the substrate, so that the mixture and the substrate are heated at 500 °C for 3 min.

[0060] Step 3: Parameter setting and adjustment of the electromagnetic heater and the laser directed energy deposition system:

[0061] Set the laser processing forming parameters. The laser power density is 2×10 6 W / cm 2 , the powder feeding rate is 2.3 g / min, the scanning speed is 900 mm / min, the upward lifting height of the processing head for each pass is 0.3 mm, and the lifting speed is 8000 mm / min. Further, set the protective gas flow rate to 15 L / min, the air pressure to 0.1 MPa, the powder feeding gas flow rate to 8 L / min, and the air pressure to 0.15 MPa. Turn on the water cooler and the laser, and use the laser directed energy deposition system to form a thin-walled part with a single length of 30 mm and 40 layers. During the forming process, adjust the electromagnetic heater so that for every 0.3 mm increase in height, the power density of the electromagnetic heater increases by 0.35 W / cm 2 .

[0062] Step 4: Post-processing of the electromagnetic heater and the laser directed energy deposition system:

[0063] After the forming is completed, turn off the water cooler, the laser, the powder feeder, and the inert gas in sequence. Lift the processing head and remove it from the processing area to a safe position. Delay closing the electromagnetic heater by 50 min. During this process, set the parameters of the electromagnetic heater to control the thin-walled part to cool down to room temperature at a speed less than 80 °C / min.

[0064] Example 3:

[0065] A system and method for electromagnetic heating-assisted laser directed energy deposition of ceramics, including the following steps:

[0066] Step 1: Raw materials and pretreatment for electromagnetic heating additive manufacturing:

[0067] Al2O3 and graphene oxide were selected as the materials for the ceramic part forming experiment. The particle size of the Al2O3 powder was 15 - 120 μm, the length of the graphene oxide was 1 - 50 μm, the aspect ratio was 0.05 - 0.15, and the mass ratio of the Al2O3 powder to the graphene oxide was 10:2. The Al2O3 powder and the graphene oxide were mixed evenly by the method of plasma ball milling, and the ball milling power was 800 W.

[0068] Step 2: Electromagnetic heater, laser directed energy deposition system and pretreatment:

[0069] First, place the induction coil of the electromagnetic heater on the heat insulation support platform and fix it. Place the substrate made of TC4 titanium alloy on the heat insulation support platform. The size of the substrate is 150 mm × 150 mm × 20 mm. Adjust the height of the heat insulation support platform so that the substrate is in the middle of the induction heating coil. Adjust the distance between the bottom of the processing head and the surface of the substrate to 9.5 mm. Open the powder feeder, and use inert gas to transport the evenly mixed ceramic and graphene oxide mixture to the surface of the substrate through the powder feeding tube. Turn on the power supply of the electromagnetic heater, set the initial heating power to 2500 W, and use an infrared thermometer to detect the temperature of the substrate, so that the mixture and the substrate are heated at 600 °C for 1 min.

[0070] Step 3: Parameter setting and adjustment of the electromagnetic heater and the laser directed energy deposition system:

[0071] Set the laser processing forming parameters. The laser power density is 6×10 6 W / cm 2 , the powder feeding rate is 4.3 g / min, the scanning speed is 1500 mm / min, the height that the processing head lifts upward for each pass is 0.4 mm, and the lifting speed is 8000 mm / min. Further, set the protective gas flow rate to 15 L / min, the air pressure to 0.1 MPa, the powder feeding gas flow rate to 8 L / min, and the air pressure to 0.15 MPa. Turn on the water cooler and the laser, and use the laser directed energy deposition system to form a thin-walled part with a single length of 30 mm and 40 layers. During the forming process, adjust the electromagnetic heater so that for every 0.4 mm increase in height, the power density of the electromagnetic heater increases by 0.45 W / cm 2 .

[0072] Step 4: Post-treatment of the electromagnetic heater and the laser directed energy deposition system:

[0073] After the forming is completed, turn off the water cooler, the laser, the powder feeder, and the inert gas in sequence. Lift the processing head and remove it from the processing area to a safe position. Delay closing the electromagnetic heater by 80 min. During this process, set the parameters of the electromagnetic heater to control the thin-walled part to cool down to room temperature at a speed of less than 100 °C / min.

[0074] Comparative example 1: Without graphene oxide

[0075] Compared with Example 1, the graphene oxide in the raw materials was replaced with ZrO2 powder, and the other conditions and parameters remained the same, as follows:

[0076] Step 1: Raw materials and pretreatment for electromagnetic heating additive manufacturing:

[0077] Select Al2O3 and ZrO2 as the materials for ceramic part forming experiments. The particle sizes of both Al2O3 and ZrO2 powders are 15 - 120 μm, and the mass ratio of Al2O3 and ZrO2 powders is 10:1. The Al2O3 and ZrO2 powders are mixed evenly by the method of plasma ball milling, and the ball milling power is 500W.

[0078] Steps 2 - 4 are the same as those in Example 1.

[0079] Result: The forming of the ceramic thin-walled part was interrupted and the forming failed.

[0080] Comparative Example 2: Too little graphene oxide doping

[0081] Compared with Example 1, the content of graphene oxide was reduced, and the other conditions and parameters remained the same, as follows:

[0082] Step 1, Raw materials and pretreatment for electromagnetic heating additive manufacturing:

[0083] Select Al2O3 and graphene oxide as the materials for ceramic part forming experiments. The particle size of the Al2O3 powder is 15 - 120 μm, the length of the graphene oxide is 1 - 50 μm, the aspect ratio is 0.01 - 0.05, and the mass ratio of the Al2O3 powder and graphene oxide is 20:1. The Al2O3 powder and graphene oxide are mixed evenly by the method of plasma ball milling, and the ball milling power is 500W.

[0084] Steps 2 - 4 are the same as those in Example 1.

[0085] Result: Too little graphene oxide doping led to insufficient conductivity, and the forming of the ceramic thin-walled part was interrupted and the forming failed.

[0086] Comparative Example 3: Too much graphene oxide doping

[0087] Compared with Example 1, the content of graphene oxide was increased, and the other conditions and parameters remained the same, as follows:

[0088] Step 1, Raw materials and pretreatment for electromagnetic heating additive manufacturing:

[0089] Select Al2O3 and graphene oxide as the materials for the ceramic part forming experiment. Among them, the particle size of the Al2O3 powder is 15 - 120 μm, the length of the graphene oxide is 1 - 50 μm, the aspect ratio is 0.01 - 0.05, and the mass ratio of the Al2O3 powder to the graphene oxide is 2:1. Use the plasma ball milling method to mix the Al2O3 powder and the graphene oxide evenly, and the ball milling power is 500 W.

[0090] Steps 2 to 4 are the same as those in Example 1.

[0091] Result: The doping amount of graphene is too much, the powder feeding pipeline is blocked, the forming of the ceramic thin-walled part is interrupted, and the forming fails.

[0092] Comparative Example 4: Select an alumina substrate

[0093] Compared with Example 2, in Step 2, the substrate made of TC4 titanium alloy is replaced with an alumina substrate, and the remaining conditions and parameters are the same, as follows:

[0094] Step 1 is the same as that in Example 2.

[0095] Step 2: Electromagnetic heater and laser direct energy deposition system and pretreatment:

[0096] First, place the induction coil of the electromagnetic heater on the heat insulation support table and fix it. Place the substrate made of alumina on the heat insulation support table. The size of the substrate is 150 mm × 150 mm × 20 mm. Adjust the height of the heat insulation support table so that the substrate is in the middle of the induction heating coil. Adjust the distance between the bottom of the processing head and the surface of the substrate to 8.3 mm. Open the powder feeder, and use inert gas to transport the evenly mixed ceramic and graphene oxide mixture to the surface of the substrate through the powder feeding pipe. Turn on the power of the electromagnetic heater, set the initial heating power to 2000 W, use an infrared thermometer to detect the temperature of the substrate, and heat the mixture and the substrate at 500 °C for 3 min.

[0097] Steps 3 to 4 are the same as those in Example 2.

[0098] Result: After replacing the substrate made of TC4 titanium alloy with an alumina substrate, the size of the formed part is insufficient, the forming of the ceramic thin-walled part is interrupted, and the forming fails.

[0099] Comparative Example 5: Substrate position adjustment

[0100] Compared with Example 3, in Step 2, the height of the heat insulation support table is not adjusted, so that the TC4 titanium alloy substrate is not in the middle of the induction heating coil, and the remaining conditions and parameters are the same, as follows:

[0101] Step 2: Electromagnetic heater and laser direct energy deposition system and pretreatment:

[0102] First, place the induction coil of the electromagnetic heater on the heat-insulating support platform and fix it. Place the TC4 titanium alloy substrate on the heat-insulating support platform. The size of the substrate is 150 mm × 150 mm × 20 mm. Adjust the distance between the bottom of the processing head and the surface of the substrate to 8.3 mm. Turn on the powder feeder, and use an inert gas to transport the evenly mixed ceramic and graphene oxide mixture to the surface of the substrate through the powder delivery tube. Turn on the power supply of the electromagnetic heater, set the initial heating power to 2000 W, and use an infrared thermometer to detect the temperature of the substrate, so that the mixture and the substrate are heated at 500 °C for 3 minutes.

[0103] Result: The substrate was not placed in the middle of the induction coil, the performance was insufficient, the forming of the ceramic thin-walled part was interrupted, and the forming failed.

[0104] Comparative Example 6: Increase the ball milling power

[0105] Compared with Example 2, in Step 1, the ball milling power was increased to 2500 W, and the other conditions and parameters were the same, as follows:

[0106] Step 1: Raw materials and pretreatment for electromagnetic heating additive manufacturing:

[0107] Select Al2O3 and graphene oxide as the materials for the ceramic part forming experiment. Among them, the particle size of the Al2O3 powder is 15 - 120 μm, the length of the graphene oxide is 1 - 50 μm, the aspect ratio is 0.15 - 0.2, and the mass ratio of the Al2O3 powder to the graphene oxide is 10:3. Use the plasma ball milling method to mix the Al2O3 powder and the graphene oxide evenly, and the ball milling power is 2500 W.

[0108] Steps 2 - 4 are the same as in Example 2.

[0109] Result: The ball milling power was too large, the aspect ratio of the graphene oxide decreased significantly, the graphene oxide was damaged, the powder delivery tube was blocked, the forming of the ceramic thin-walled part was interrupted, and the forming failed.

[0110] Comparative Example 7: Decrease the ball milling power

[0111] Compared with Example 1, in Step 1, the ball milling power was decreased to 350 W, and the other conditions and parameters were the same, as follows:

[0112] Step 1: Raw materials and pretreatment for electromagnetic heating additive manufacturing:

[0113] Select Al2O3 and graphene oxide as the materials for the ceramic part forming experiment. Among them, the particle size of the Al2O3 powder is 15 - 120 μm, the length of the graphene oxide is 1 - 50 μm, the aspect ratio is 0.01 - 0.05, and the mass ratio of the Al2O3 powder to the graphene oxide is 10:1. Use the plasma ball milling method to mix the Al2O3 powder and the graphene oxide evenly, and the ball milling power is 350 W.

[0114] Steps 2 to 4 are the same as in Example 1.

[0115] Result: The ball milling power is too small, the mixing of Al2O3 powder and graphene oxide is uneven, the forming of the ceramic thin-walled part is interrupted, and the forming fails.

[0116] Comparative Example 8: Without electromagnetic heater pretreatment

[0117] Compared with Example 1, there is no electromagnetic heater pretreatment step in Step 2, and the remaining conditions and parameters are the same, as follows:

[0118] Step 2: Electromagnetic heater and laser directed energy deposition system and pretreatment:

[0119] First, place the induction coil of the electromagnetic heater on the heat-insulating support platform and fix it. Place the substrate made of TC4 titanium alloy on the heat-insulating support platform. The substrate size is 150 mm × 150 × 20 mm. Adjust the height of the heat-insulating support platform so that the substrate is in the middle of the induction heating coil. Adjust the distance between the bottom of the processing head and the surface of the substrate to 7.2 mm. Open the powder feeder, and use inert gas to transport the evenly mixed ceramic and graphene oxide mixture to the surface of the substrate through the powder feeding tube.

[0120] Step 1, Steps 3 to 4 are the same as in Example 1.

[0121] Result: The forming of the ceramic thin-walled part is interrupted, and the forming fails.

[0122] Comparative Example 9: Reducing the pre-adjusted initial power of the electromagnetic heater

[0123] Compared with Example 1, the pre-adjusted initial power of the electromagnetic heater in Step 2 is too small, which is 500 W, and the remaining conditions and parameters are the same, as follows:

[0124] Step 2: Electromagnetic heater and laser directed energy deposition system and pretreatment:

[0125] First, place the induction coil of the electromagnetic heater on the heat-insulating support platform and fix it. Place the substrate made of TC4 titanium alloy on the heat-insulating support platform. The substrate size is 150 mm × 150 × 20 mm. Adjust the height of the heat-insulating support platform so that the substrate is in the middle of the induction heating coil. Adjust the distance between the bottom of the processing head and the surface of the substrate to 7.2 mm. Open the powder feeder, and use inert gas to transport the evenly mixed ceramic and graphene oxide mixture to the surface of the substrate through the powder feeding tube. Turn on the power of the electromagnetic heater and set the initial heating power to 500 W.

[0126] Step 1, Steps 3 to 4 are the same as in Example 1.

[0127] Result: The pre-adjusted initial power of the electromagnetic heater is too small, the forming of the ceramic thin-walled part is interrupted, and the forming fails.

[0128] Comparative Example 10: Increasing the pre-adjusted initial power of the electromagnetic heater

[0129] Compared with Example 3, the pre-adjusted initial power of the electromagnetic heater is too large, which is 4000W. The remaining conditions and parameters are the same, as follows:

[0130] Step 2: Electromagnetic heater, laser direct energy deposition system and pretreatment:

[0131] First, place the induction coil of the electromagnetic heater on the heat-insulating support platform and fix it. Place the substrate made of TC4 titanium alloy on the heat-insulating support platform. The size of the substrate is 150mm×150×20mm. Adjust the height of the heat-insulating support platform so that the substrate is in the middle of the induction heating coil. Adjust the distance between the bottom of the processing head and the surface of the substrate to 9.5mm. Open the powder feeder, and use inert gas to transport the evenly mixed ceramic and graphene oxide mixture to the surface of the substrate through the powder feeding pipe. Turn on the power supply of the electromagnetic heater and set the initial heating power to 4000W.

[0132] Step 1, Steps 3 to 4 are the same as in Example 3.

[0133] Result: The forming of the ceramic thin-walled part is interrupted and the forming fails.

[0134] Comparative Example 11: Process adjustment of the electromagnetic heater without delay

[0135] Compared with Example 1, the electromagnetic heater is not turned off with a delay after the forming in Step 4. The remaining conditions and parameters are the same, as follows:

[0136] Steps 1 to 3 are the same as in Example 1.

[0137] Step 4: Post-treatment of the electromagnetic heater and the laser direct energy deposition system

[0138] After the forming is completed, turn off the water cooler, laser, powder feeder, and inert gas in sequence. Lift the processing head and remove it from the processing area to a safe position, and then turn off the electromagnetic heater.

[0139] Result: The process adjustment of the electromagnetic heater is inappropriate, and the formed ceramic thin-walled part cracks.

[0140] Comparative Example 12: Process adjustment of the electromagnetic heater with too short delay time

[0141] Compared with Example 1, the time for turning off the electromagnetic heater with a delay after the forming in Step 4 is too short, which is 5 minutes. The remaining conditions and parameters are the same, as follows:

[0142] Steps 1 to 3 are the same as in Example 1.

[0143] Step 4: Post-processing of the electromagnetic heater and the laser directed energy deposition system:

[0144] After forming, turn off the water cooler, laser, powder feeder, and inert gas in sequence. Raise the processing head and remove it from the processing area to a safe position. Turn off the electromagnetic heater 5 minutes later. During this process, set the parameters of the electromagnetic heater to control the thin-walled part to cool down to room temperature at a rate of less than 60 °C / min.

[0145] Result: The formed ceramic thin-walled part cracked.

[0146] Table 1 shows the comparison of the performance parameters of the ceramic thin-walled part samples prepared in Examples 1-3 and Comparative Examples 1-12

[0147] Table 1 Performance parameters of the ceramic thin-walled part samples prepared in Examples 1-3 and Comparative Examples 1-12

[0148]

[0149]

[0150] As can be seen from Table 1, by using the method of the present invention and selecting the materials and forming processes of the present invention, the ceramic formed parts prepared have high fracture toughness and good densification (reflected in Examples 1-3); while by using the method of the present invention and selecting materials other than those of the present invention, such as using Al2O3 / ZrO2, the ceramic formed parts prepared fail to form, and the fracture toughness of the samples is low and the density is poor (reflected in Comparative Example 1); and by using the method of the present invention and selecting the materials of the present invention but selecting process parameters outside the scope of the present invention, the ceramic formed parts prepared fail to form, and the performance of the thin-walled samples is low (reflected in Comparative Examples 2-3); and by using the method of the present invention and selecting the materials of the present invention but selecting a substrate material other than titanium alloy of the present invention, such as an Al2O3 substrate, the ceramic formed parts prepared fail to form, and the performance of the samples is poor (reflected in Comparative Example 4); and by using the method of the present invention and selecting the materials of the present invention and selecting the titanium alloy substrate of the present invention, but the substrate is not placed in the middle of the induction coil in the height direction, the ceramic formed parts prepared fail to form, and the performance of the samples is poor (reflected in Comparative Example 5); and by using the method of the present invention and selecting the materials of the present invention, but not performing plasma ball milling or the nodularizing process on the raw materials according to the present invention is inappropriate, the ceramic formed parts prepared fail to form, and the performance of the samples is poor (reflected in Comparative Examples 6-7); and by using the method of the present invention and selecting the materials of the present invention, but not performing electromagnetic heating pretreatment on the raw materials according to the present invention or the initial power is inappropriate, the ceramic formed parts prepared fail to form, and the performance of the samples is poor (reflected in Comparative Examples 8-10); and by using the method of the present invention and selecting the materials of the present invention and selecting the titanium alloy substrate of the present invention, but not delaying the closing of the electromagnetic heater or the delay time is too short, the ceramic thin-walled parts crack, and the performance of the samples is poor (reflected in Comparative Examples 11-12).

[0151] Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person familiar with this technology can make various modifications and decorations without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention should be defined by the claims.

Claims

1. A method for electromagnetic heating assisted laser directed energy deposition of ceramics, characterized in that, It includes the following steps: S1. Raw material pretreatment: Mix ceramic matrix powder and graphene oxide to obtain a mixture of ceramic matrix powder and graphene oxide; S2. Induction heating pretreatment: Fix the TC4 titanium alloy substrate in the middle of the induction heating coil, introduce the mixture of ceramic matrix powder and graphene oxide described in step S1 to the surface of the TC4 titanium alloy substrate, and preheat the mixture and the TC4 titanium alloy substrate through the induction heating coil; S3. Deposition forming: Under the protection of inert gas, carry out laser directed energy deposition forming; S4. Post-treatment: After forming, cool to room temperature.

2. The method according to claim 1, wherein In step S1, the uniform dispersion of ceramic matrix powder and graphene oxide is realized by high-energy ball milling; the high-energy ball milling includes planetary ball milling, vibration ball milling or plasma ball milling.

3. The method according to claim 2, wherein The power of the high-energy ball milling is 500 - 1500W.

4. The method according to claim 1, characterized in that, The mass ratio of the ceramic matrix powder to graphene oxide in step S1 is 10:(1 - 3).

5. The method according to claim 1, characterized in that, The ceramic matrix powder includes at least one of Al2O3, mullite, ZrO2, GdAlO3, Y3Al5O 12 , and high-entropy oxide ceramics.

6. The method according to claim 1, characterized in that, The power of the induction heating coil for preheating in step S2 is 1000 - 2500W.

7. The method according to claim 1, wherein The step S3 includes: setting laser processing and forming parameters, where the laser power density is (1 - 6)×10 6 W / cm 2 , the powder feeding rate is (2.3 - 4.3) g / min, the scanning speed is (500 - 1500) mm / min, the upward lifting height of the laser processing head for each pass is (0.3 - 0.5) mm, and the lifting speed is (5000 - 8000) mm / min; the inert gas flow rate is (6 - 15) L / min, the air pressure is (0.1 - 0.15) MPa, the powder feeding gas flow rate is (6 - 8) L / min, and the air pressure is (0.1 - 0.2) MPa; turn on the water cooler and the laser, and use laser directed energy deposition to form. During the forming process, adjust the electromagnetic heater so that when the height of the formed part increases by (0.3 - 0.5) mm, the power density of the electromagnetic heater increases by (0.35 - 0.6) W / cm 2 .

8. The method according to claim 7, wherein Step S4 includes: a) Stop the water cooler, inert gas, powder feeder and laser in sequence; b) After the laser processing head moves out of the processing area, keep the electromagnetic heater working continuously for 20 - 80 min; c) Through electromagnetic power decreasing control, make the formed part cool down at a rate gradient less than 100°C / min.

9. A ceramic prepared by the method according to any one of claims 1 - 8.

10. The application of the method according to any one of claims 1 - 8 in ceramic preparation or ceramic surface repair.

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