A method for laser additive manufacturing of crack-free Ni3Al-based superalloys and its preparation

Abstract

The application provides a preparation method of laser additive manufacturing crack-free Ni3Al-based high-temperature alloy, comprising the following steps: (1) uniformly mixing micron-sized Ni3Al-based high-temperature alloy powder and nano Hf ceramic particles, so that the nano Hf ceramic particles are uniformly wrapped on the surface of the micron-sized Ni3Al-based high-temperature alloy powder, to obtain a composite powder; (2) drying the composite powder; (3) layer-by-layer melt forming the composite powder by using a laser directional deposition device, to obtain the laser additive manufacturing crack-free Ni3Al-based high-temperature alloy. The application also provides the laser additive manufacturing crack-free Ni3Al-based high-temperature alloy prepared by the method. The preparation method of the laser additive manufacturing crack-free Ni3Al-based high-temperature alloy can prepare the crack-free Ni3Al-based high-temperature alloy by the laser additive manufacturing method, and is simple in preparation and low in cost.

Description

Technical Field

[0001] This invention relates to the field of high-performance high-temperature alloy technology, and particularly to the field of Ni3Al-based high-temperature alloy technology, specifically to a laser additive manufacturing method for crack-free Ni3Al-based high-temperature alloys and its preparation method. Background Technology

[0002] With the continuous development of the aviation industry, the thrust-to-weight ratio and combustion chamber operating temperature of aero engines are constantly increasing, which puts forward higher requirements for the service performance of materials.

[0003] Traditional nickel-based and cobalt-based superalloys are nearing their service temperature limits and cannot meet the higher material requirements of future advanced aero-engines. Ni3Al-based superalloys, due to their high melting point, high creep resistance, structural thermal stability, and high specific strength, have attracted widespread research from researchers both domestically and internationally. Among them, MX246A is a Ni3Al-based superalloy with excellent wear resistance and high-temperature performance, and has been selected as a key material for high-temperature components of China's next-generation aero-engines.

[0004] Furthermore, with the continuous increase in the thrust-to-weight ratio of aero engines and the gradual reduction of compressor and turbine technologies, operating conditions are becoming increasingly severe, and the structures of key components such as working blades and guide vanes are becoming more complex. Traditional processes such as casting, deformation forming, and machining can no longer meet the precision machining requirements of high-temperature structural materials. Additive manufacturing (AM), which uses a method of gradually adding materials to manufacture solid parts, is a rapid processing method that can meet the near-net-shape forming requirements of complex parts. However, the cracks that are prone to occur during laser additive manufacturing (LAM) greatly limit its application. In particular, Ni3Al-based superalloys have extremely high crack sensitivity during LAM, and are prone to solidification cracks, liquefaction cracks, high-temperature loss-of-plasticity cracks, and strain failure cracks. Currently, common methods to eliminate cracks include hot isostatic pressing (HIP), but HIP cannot eliminate all types of cracks and increases the manufacturing cost of parts.

[0005] Therefore, how to use laser additive manufacturing to prepare a crack-free Ni3Al-based high-temperature alloy has become a technical problem that urgently needs to be overcome by those skilled in the art. Summary of the Invention

[0006] In order to overcome the shortcomings of the prior art, one object of the present invention is to provide a method for preparing crack-free Ni3Al-based superalloys by laser additive manufacturing. The method can prepare crack-free Ni3Al-based superalloys by laser additive manufacturing, and the preparation is simple, low-cost, and suitable for large-scale application.

[0007] Another objective of this invention is to provide a crack-free Ni3Al-based high-temperature alloy for laser additive manufacturing, which is crack-free, easy to prepare, low in cost, and suitable for large-scale application.

[0008] To achieve the above objectives, in a first aspect of the present invention, a method for preparing a crack-free Ni3Al-based superalloy using laser additive manufacturing is provided, characterized by comprising the following steps:

[0009] (1) Mix micron-sized Ni3Al-based high-temperature alloy powder and nano-Hf ceramic particles evenly, so that the nano-Hf ceramic particles are uniformly coated on the surface of micron-sized Ni3Al-based high-temperature alloy powder to obtain composite powder.

[0010] (2) Dry the composite powder;

[0011] (3) The composite powder is melted and solidified layer by layer using a laser directional deposition equipment to obtain a crack-free Ni3Al-based high-temperature alloy for laser additive manufacturing.

[0012] Preferably, in step (1), the particle size of the micron-sized Ni3Al-based high-temperature alloy powder is 53μm~150μm, and the particle size of the nano-Hf ceramic particles is 60nm~100nm.

[0013] Preferably, in step (1), the micron-sized Ni3Al-based superalloy powder is prepared by plasma rotating electrode method, and the purity of the micron-sized Ni3Al-based superalloy powder is 99.99%.

[0014] Preferably, in step (1), the micron-sized Ni3Al-based high-temperature alloy powder is a micron-sized MX246A alloy powder; the nano-Hf ceramic particles are nano-hafnium boride particles, nano-hafnium carbide particles, or nano-hafnium oxide particles.

[0015] Preferably, in step (1), the mass ratio of the micron-sized Ni3Al-based high-temperature alloy powder to the nano-sized Hf ceramic particles is 98~99:1~2.

[0016] Preferably, in step (1), the mixing is carried out using an acoustic resonance mixing device.

[0017] More preferably, in step (1), the frequency of the acoustic resonance mixing device is 40 kHz to 50 kHz, the amplitude of the acoustic resonance mixing device is 1.0 MPa to 3.0 MPa, and the time for uniform mixing is 40 min to 60 min.

[0018] Preferably, in step (2), the drying temperature is 100℃~150℃ and the drying time is 1h~3h.

[0019] Preferably, in step (3), the process parameters of the laser directional deposition equipment are: laser power 1200W, scanning speed 900mm / min, spot diameter 1mm, layer thickness 0.8mm, interlayer cooling time 60s, and laser scanning reverse rotation angle of adjacent layers 45°.

[0020] In a second aspect of the present invention, a crack-free Ni3Al-based superalloy for laser additive manufacturing is provided, characterized in that it is prepared by the above-described method for preparing crack-free Ni3Al-based superalloys for laser additive manufacturing.

[0021] The main beneficial effects of this invention are:

[0022] 1. The method for preparing crack-free Ni3Al-based superalloy by laser additive manufacturing of the present invention includes the following steps: (1) mixing micron-sized Ni3Al-based superalloy powder and nano-sized Hf ceramic particles uniformly, so that the nano-sized Hf ceramic particles are uniformly coated on the surface of the micron-sized Ni3Al-based superalloy powder to obtain composite powder; (2) drying the composite powder; (3) using a laser directional deposition device to perform layer-by-layer melting and solidification of the composite powder to obtain crack-free Ni3Al-based superalloy by laser additive manufacturing. Therefore, crack-free Ni3Al-based superalloy can be prepared by laser additive manufacturing method, and the preparation is simple, low cost, and suitable for large-scale promotion and application.

[0023] 2. The laser additive manufacturing crack-free Ni3Al-based high-temperature alloy of the present invention is prepared by the above-mentioned laser additive manufacturing crack-free Ni3Al-based high-temperature alloy preparation method. Therefore, it is crack-free, simple to prepare, low in cost, and suitable for large-scale promotion and application.

[0024] These and other objects, features and advantages of the present invention will be fully apparent from the following detailed description and drawings, and can be achieved by the means, devices and combinations thereof specifically pointed out in the summary of the invention. Attached Figure Description

[0025] Figure 1These are SEM and EDS images and particle size distribution diagrams of the composite powder prepared in Example 1 of the present invention, wherein (a) is an SEM image of Ni3Al-based powder in Example 1; (b) is an SEM image of a single Ni3Al-based powder particle; (c) is an SEM image of the prepared Ni3Al-based powder / HfB2 composite powder; (d) is a particle size distribution diagram of Ni3Al-based powder; (e) is an SEM image of nano-hafnium boride particles; and (f) is an EDS surface distribution diagram of Hf element.

[0026] Figure 2 This is a photograph of the crack-free Ni3Al-based superalloy prepared by laser additive manufacturing in Example 1 of the present invention.

[0027] Figure 3 This is an OM image of the crack-free Ni3Al-based superalloy prepared by laser additive manufacturing in Example 1 of the present invention.

[0028] Figure 4 This is an OM image of the crack-free Ni3Al-based superalloy prepared by laser additive manufacturing in Example 2 of the present invention.

[0029] Figure 5 This is an OM image of the crack-free Ni3Al-based superalloy prepared by laser additive manufacturing in Example 3 of the present invention.

[0030] Figure 6 This is an OM image of the MX246A alloy prepared in the comparative example of the present invention. Detailed Implementation

[0031] In order to prepare crack-free Ni3Al-based superalloys using laser additive manufacturing, the inventors discovered through in-depth research that by uniformly mixing nano-Hf ceramic particles and micron-sized Ni3Al-based superalloy powder, the nano-Hf ceramic particles are uniformly coated on the surface of the micron-sized Ni3Al-based superalloy powder. Then, Ni3Al-based superalloys are prepared using laser additive manufacturing. Surprisingly, the prepared Ni3Al-based superalloys are crack-free. Based on this, the present invention was completed.

[0032] This invention first provides a method for preparing crack-free Ni3Al-based superalloys using laser additive manufacturing, comprising the following steps:

[0033] (1) Mix micron-sized Ni3Al-based high-temperature alloy powder and nano-Hf ceramic particles evenly, so that the nano-Hf ceramic particles are uniformly coated on the surface of micron-sized Ni3Al-based high-temperature alloy powder to obtain composite powder.

[0034] (2) Dry the composite powder;

[0035] (3) The composite powder is melted and solidified layer by layer using a laser directional deposition equipment to obtain a crack-free Ni3Al-based high-temperature alloy for laser additive manufacturing.

[0036] The melting point of the nano-Hf ceramic particles is basically between 2400℃ and 3950℃, and their high-temperature stability is much higher than that of the micron-sized Ni3Al-based high-temperature alloy powder (melting point of about 1400℃).

[0037] In step (1), the micron-sized Ni3Al-based superalloy powder and the nano-Hf ceramic particles can have any suitable particle size. Preferably, in step (1), the particle size of the micron-sized Ni3Al-based superalloy powder is 53μm~150μm, and the particle size of the nano-Hf ceramic particles is 60nm~100nm.

[0038] In step (1), the micron-sized Ni3Al-based superalloy powder can be prepared by any suitable method, and the micron-sized Ni3Al-based superalloy powder can have any suitable purity. Preferably, in step (1), the micron-sized Ni3Al-based superalloy powder is prepared by the Plasma Rotating Electrode Process (PREP), and the purity of the micron-sized Ni3Al-based superalloy powder is 99.99%.

[0039] The micron-sized Ni3Al-based superalloy powder can be any suitable specific micron-sized Ni3Al-based superalloy powder. Preferably, in step (1), the micron-sized Ni3Al-based superalloy powder is a micron-sized MX246A alloy powder.

[0040] The nano Hf ceramic particles can be any suitable specific nano Hf ceramic particles. Preferably, in step (1), the nano Hf ceramic particles are nano hafnium boride particles, nano hafnium carbide particles, or nano hafnium oxide particles.

[0041] In step (1), the mass ratio of the micron-sized Ni3Al-based superalloy powder to the nano-sized Hf ceramic particles can be determined as needed. Preferably, in step (1), the mass ratio of the micron-sized Ni3Al-based superalloy powder to the nano-sized Hf ceramic particles is 98~99:1~2.

[0042] In step (1), the mixing can be carried out using any suitable equipment. Preferably, in step (1), the mixing is carried out using an acoustic resonance mixing device.

[0043] In step (1), the frequency and amplitude of the acoustic resonance mixing device and the mixing time can be determined as needed. More preferably, in step (1), the frequency of the acoustic resonance mixing device is 40 kHz to 50 kHz, the amplitude of the acoustic resonance mixing device is 1.0 MPa to 3.0 MPa, and the mixing time is 40 min to 60 min.

[0044] In step (2), the drying temperature and time can be determined as needed. Preferably, in step (2), the drying temperature is 100℃~150℃ and the drying time is 1h~3h.

[0045] In step (2), the drying can be carried out using any suitable equipment, preferably using a vacuum drying oven.

[0046] In step (3), the laser directional deposition equipment can use any suitable process parameters. Preferably, in step (3), the process parameters of the laser directional deposition equipment are: laser power 1200W, scanning speed 900mm / min, spot diameter 1mm, layer thickness 0.8mm, interlayer cooling time 60s, and laser scanning reverse rotation angle of adjacent layers 45°.

[0047] In step (3), the laser directional deposition equipment can use any suitable powder feeder. Preferably, in step (3), the laser directional deposition equipment uses a four-way coaxial powder feeder.

[0048] In step (3), the forming chamber of the laser directional deposition equipment can have any suitable oxygen and water content. Preferably, in step (3), the oxygen and water content in the forming chamber of the laser directional deposition equipment are both controlled below 50 ppm.

[0049] In step (3), during the layer-by-layer melting and solidification process, the substrate may undergo any suitable pretreatment. Preferably, in step (3), during the layer-by-layer melting and solidification process, the substrate is pretreated by polishing, chemical degreasing, alcohol cleaning, and drying.

[0050] In step (3), after the layer-by-layer melting and solidification, any other suitable steps may be included. Preferably, in step (3), after the layer-by-layer melting and solidification, the laser additive manufacturing crack-free Ni3Al-based high-temperature alloy may be separated from the substrate after being cooled for 40 minutes.

[0051] The present invention also provides a laser additive manufacturing method for a crack-free Ni3Al-based superalloy, which is prepared by the above-mentioned method for preparing a crack-free Ni3Al-based superalloy using laser additive manufacturing.

[0052] The laser additive manufacturing process produces a crack-free Ni3Al-based superalloy with no internal solidification cracks, liquefaction cracks, or plasticity loss cracks.

[0053] The microstructure of the laser additive manufacturing crack-free Ni3Al-based superalloy can have any suitable structure. Preferably, the microstructure of the laser additive manufacturing crack-free Ni3Al-based superalloy is a near-equiaxed crystal structure reinforced with nano-Hf ceramic particles.

[0054] The near-equiaxed crystal structure can have any suitable columnar crystal ratio, nano-Hf ceramic particle distribution, and volume fraction of nano-Hf ceramic particles. More preferably, the columnar crystal ratio in the near-equiaxed crystal structure is less than 5%, the nano-Hf ceramic particles are uniformly distributed at the grain boundaries and within the grains, and the volume fraction of nano-Hf ceramic particles is 0.8% to 1.9%.

[0055] The laser additive manufacturing of crack-free Ni3Al-based superalloys can have any suitable grain size, preferably with a grain size ≤50μm.

[0056] To better understand the technical content of this invention, the following embodiments are provided for detailed explanation.

[0057] Example 1

[0058] The mass ratio of micron-sized Ni3Al-based superalloy powder to nano-sized Hf ceramic particles is 99:1, wherein:

[0059] Micron-sized Ni3Al-based superalloy powder: Micron-sized MX246A alloy powder, prepared by plasma rotating electrode method, with a purity of 99.99% and a particle size of 53μm. Please refer to [link / reference]. Figure 1 As shown in (a), (b) and (d).

[0060] Nano-Hf ceramic particles: Nano-hafnium boride particles (nano-HfB2 particles), with a particle size of 80 nm. Please refer to [link / reference]. Figure 1 As shown in (e) and (f).

[0061] (1) Micron-sized MX246A alloy powder and nano-HfB2 particles were placed in a PC container and then mixed in an acoustic resonance powder mixing device (acoustic resonance powder mixer, Jinggong Ruiyi Technology Co., Ltd.). The frequency of the acoustic resonance powder mixing device was 40 kHz, the amplitude was 3.0 MPa, and the mixing time was 50 min. After acoustic resonance powder mixing, a composite powder of MX246A and HfB2 was obtained. The nano-HfB2 particles were uniformly coated on the surface of the MX246A alloy powder. The SEM morphology of the mixed composite powder is as follows: Figure 1 As shown in (c).

[0062] (2) The composite powder obtained in step (1) is placed in a vacuum drying oven and dried. The temperature of the vacuum drying oven is 120°C and the drying time is 1 hour.

[0063] (3) Modeling and slicing of the target part

[0064] First, a three-dimensional solid geometric model of the target part is created using Solidworks software on a computer. Then, the three-dimensional solid geometric model is imported into the computer of the laser directional deposition equipment. Slicing software is used to slice the three-dimensional solid geometric model. At the same time, the laser scanning path planning for the printing process is performed and the position of the target part on the machine tool is determined. The printing program is generated, and the process parameters are as follows: laser power (P) is 1200W, laser scanning speed is 900mm / min, spot diameter is 1mm, layer thickness is 0.8mm, the laser scanning reverse rotation angle between adjacent layers is 45°, and a four-way coaxial powder feeder is used for powder feeding.

[0065] (4) Laser-directed deposition process

[0066] The substrate is polished to make its surface smooth, and oil stains are removed by chemical cleaning, followed by cleaning with alcohol and drying to reduce the formation of pores in the deposited layer. The laser directional deposition equipment (Zhongke Yucheng LDM400) mainly includes: an inert gas processing chamber, a regulated power supply, a water chiller, a powder feeder, a gas circulation and purification system, gas cylinders, and a whole machine control box monitoring system. Before forming, the substrate is placed in the forming chamber, the composite powder is poured into the powder cylinder, a vacuum is drawn and protective argon gas is introduced, and the water content and oxygen content are reduced to below 50ppm before the LAM experiment is performed. The forming process is as follows: the powder feeder blows the composite powder onto the substrate under the blowing of argon gas, while the laser is turned on and moves according to the predetermined path in the program. After the first layer is deposited, the interlayer is cooled for 60s and then the next layer is deposited until the alloy is formed. Before the actual printing, a no-load test was performed on the edge of the substrate to ensure that the powder cartridge could dispense powder normally. Then, two 15mm cubes were printed on the substrate to preheat it (the residual temperature of the substrate after this treatment can reach 200~300℃). Then, the actual printing was performed. After forming, the substrate was cooled for 40 minutes. The substrate was then removed, and the MX246A / HfB2 composite alloy was separated from the substrate using wire cutting to obtain the MX246A / HfB2 composite alloy. Figure 2 As shown.

[0067] The MX246A / HfB2 composite alloy was ground and polished using 400-grit, 800-grit, 1200-grit, and 2000-grit SiC sandpaper, respectively. After polishing, it was etched using CuSO4, H2O, and HCl etching solutions. The microstructure was then observed under a metallographic microscope. Figure 3 As shown, it can be seen that there are no cracks inside the alloy structure. After adding nano HfB2 powder, the structure was significantly refined. The alloy structure exhibits a distinct near-equiaxed crystal morphology, and the columnar crystals have obviously disappeared.

[0068] Example 2

[0069] The mass ratio of micron-sized Ni3Al-based superalloy powder to nano-sized Hf ceramic particles is 98:2, wherein:

[0070] Micron-sized Ni3Al-based high-temperature alloy powder: Micron-sized IC-218 alloy powder, prepared by plasma rotating electrode method, with a purity of 99.99% and a particle size of 150μm.

[0071] Nano Hf ceramic particles: Nano hafnium carbide particles (nano HfC particles) with a particle size of 60 nm.

[0072] (1) Micron-sized IC-218 alloy powder and nano HfC particles are placed in a PC container and then put into an acoustic resonance mixing device (acoustic resonance mixing instrument, Jinggong Ruiyi Technology Co., Ltd.) for mixing. The frequency of the acoustic resonance mixing device is 45 kHz, the amplitude is 2 MPa, and the mixing time is 40 min. After acoustic resonance mixing, IC-218 and HfC composite powder is obtained, and nano HfC particles are uniformly coated on the surface of IC-218 alloy powder.

[0073] (2) The composite powder obtained in step (1) is placed in a vacuum drying oven and dried. The temperature of the vacuum drying oven is 150°C and the drying time is 2 hours.

[0074] (3) Modeling and slicing of the target part

[0075] First, a three-dimensional solid geometric model of the target part is created using Solidworks software on a computer. Then, the three-dimensional solid geometric model is imported into the computer of the laser directional deposition equipment. Slicing software is used to slice the three-dimensional solid geometric model. At the same time, the laser scanning path planning for the printing process is performed and the position of the target part on the machine tool is determined. The printing program is generated, and the process parameters are as follows: laser power (P) is 1200W, laser scanning speed is 900mm / min, spot diameter is 1mm, layer thickness is 0.8mm, the laser scanning reverse rotation angle between adjacent layers is 45°, and a four-way coaxial powder feeder is used for powder feeding.

[0076] (4) Laser-directed deposition process

[0077] The substrate is polished to make its surface smooth, and oil stains are removed by chemical cleaning, followed by cleaning with alcohol and drying to reduce the formation of pores in the deposited layer. The laser directional deposition equipment (Zhongke Yucheng LDM400) mainly includes: an inert gas processing chamber, a regulated power supply, a water chiller, a powder feeder, a gas circulation and purification system, gas cylinders, and a whole machine control box monitoring system. Before forming, the substrate is placed in the forming chamber, the composite powder is poured into the powder cylinder, a vacuum is drawn and protective argon gas is introduced, and the water content and oxygen content are reduced to below 50ppm before the LAM experiment is performed. The forming process is as follows: the powder feeder blows the composite powder onto the substrate under the blowing of argon gas, while the laser is turned on and moves according to the predetermined path in the program. After the first layer is deposited, the interlayer is cooled for 60s and then the next layer is deposited until the alloy is formed. Before the actual printing, the substrate edge is run empty to ensure that the powder can dispense powder normally. Then, two cubes with a side length of 15mm are printed on the substrate to preheat the substrate (the residual temperature of the substrate after this treatment can reach 200~300℃). Then, the actual printing is performed. After the forming is completed, it is cooled for 40 minutes. The substrate is then removed and the IC-218 / HfC composite alloy is separated from the substrate by wire cutting to obtain the IC-218 / HfC composite alloy.

[0078] The IC-218 / HfC composite alloy was ground and polished using 400-grit, 800-grit, 1200-grit, and 2000-grit SiC sandpaper, respectively. After polishing, it was etched using CuSO4, H2O, and HCl etching solutions. The microstructure was then observed under a metallographic microscope. Figure 4 As shown, there are no cracks inside the alloy structure. After adding nano HfC particles, the structure was significantly refined. The growth trend of columnar dendrites in the alloy was suppressed, and the main morphology was near-equiaxed.

[0079] Example 3

[0080] The mass ratio of micron-sized Ni3Al-based superalloy powder to nano-sized Hf ceramic particles is 98.5:1.5, wherein:

[0081] Micron-sized Ni3Al-based high-temperature alloy powder: Micron-sized MX246A alloy powder, prepared by plasma rotating electrode method, with a purity of 99.99% and a particle size of 100μm.

[0082] Nano Hf ceramic particles: Nano hafnium oxide particles (nano HfO2 particles) with a particle size of 100 nm.

[0083] (1) Micron-sized MX246A alloy powder and nano HfO2 particles were placed in a PC container and then put into an acoustic resonance mixing device (acoustic resonance mixing instrument, Jinggong Ruiyi Technology Co., Ltd.) for mixing. The frequency of the acoustic resonance mixing device was 50 kHz, the amplitude was 1 MPa, and the mixing time was 60 min. After acoustic resonance mixing, a composite powder of MX246A and HfO2 was obtained, and the nano HfO2 particles were uniformly coated on the surface of the MX246A alloy powder.

[0084] (2) The composite powder obtained in step (1) is placed in a vacuum drying oven and dried. The temperature of the vacuum drying oven is 100℃ and the drying time is 3h.

[0085] (3) Modeling and slicing of the target part

[0086] First, a three-dimensional solid geometric model of the target part is created using Solidworks software on a computer. Then, the three-dimensional solid geometric model is imported into the computer of the laser directional deposition equipment. Slicing software is used to slice the three-dimensional solid geometric model. At the same time, the laser scanning path planning for the printing process is performed and the position of the target part on the machine tool is determined. The printing program is generated, and the process parameters are as follows: laser power (P) is 1200W, laser scanning speed is 900mm / min, spot diameter is 1mm, layer thickness is 0.8mm, the laser scanning reverse rotation angle between adjacent layers is 45°, and a four-way coaxial powder feeder is used for powder feeding.

[0087] (4) Laser-directed deposition process

[0088] The substrate is polished to make its surface smooth, and oil stains are removed by chemical cleaning, followed by cleaning with alcohol and drying to reduce the formation of pores in the deposited layer. The laser directional deposition equipment (Zhongke Yucheng LDM400) mainly includes: an inert gas processing chamber, a regulated power supply, a water chiller, a powder feeder, a gas circulation and purification system, gas cylinders, and a whole machine control box monitoring system. Before forming, the substrate is placed in the forming chamber, the composite powder is poured into the powder cylinder, a vacuum is drawn and protective argon gas is introduced, and the water content and oxygen content are reduced to below 50ppm before the LAM experiment is performed. The forming process is as follows: the powder feeder blows the composite powder onto the substrate under the blowing of argon gas, while the laser is turned on and moves according to the predetermined path in the program. After the first layer is deposited, the interlayer is cooled for 60s and then the next layer is deposited until the alloy is formed. Before the actual printing, the substrate edge is run empty to ensure that the powder can dispense powder normally. Then, two cubes with a side length of 15mm are printed on the substrate to preheat the substrate (the residual temperature of the substrate after this treatment can reach 200~300℃). Then, the actual printing is performed. After the forming is completed, it is cooled for 40 minutes. The substrate is then removed and the MX246A / HfO2 composite alloy is separated from the substrate by wire cutting to obtain the MX246A / HfO2 composite alloy.

[0089] The MX246A / HfO2 composite alloy was ground and polished using 400-grit, 800-grit, 1200-grit, and 2000-grit SiC sandpaper, respectively. After polishing, it was etched using CuSO4, H2O, and HCl etching solutions. The microstructure was then observed under a metallographic microscope. Figure 5 As shown, it can be seen that there are no cracks inside the alloy structure. After adding nano HfO2 particles, the structure was significantly refined. The alloy structure exhibits a distinct near-equiaxed crystal morphology, and the columnar crystals have disappeared significantly.

[0090] Comparative Example

[0091] The difference between this comparative example and Example 1 is that micron-sized MX246A alloy powder was directly subjected to laser-directed deposition experiments. The OM morphology of the MX246A alloy without the addition of nano-sized HfB2 powder is as follows. Figure 6 As shown, the deposited layers are composed of γ and γ′ eutectic structures, the deposited layers are mainly columnar dendrites, and there are many cracks inside the alloy.

[0092] Therefore, using this invention, during laser-directed deposition (LDD), when the laser power is high or the scanning speed is slow, grains tend to grow along the molten pool boundary, forming columnar crystals. When nano-Hf ceramic particles are added, their high melting point and good high-temperature stability allow them to form stable solid nuclei, acting as heterogeneous nucleation sites to alter the molten pool temperature gradient and solidification rate, thereby increasing the solidification rate. This promotes the transformation of columnar crystals to equiaxed crystals. Simultaneously, adding nano-Hf ceramic particles reduces the undercooling required at the interface front, thus refining the grains, dispersing thermal stress in the molten pool, and reducing the tendency for cracking during the LAM process of Ni3Al-based superalloys.

[0093] Therefore, this invention significantly improves the nucleation rate by introducing nano-Hf ceramic particles as a heterogeneous nucleating agent, promotes the transformation of columnar crystals to equiaxed crystals, refines the grain structure, and effectively disperses local stress, thereby suppressing crack generation during laser additive manufacturing. This invention features a simple and low-cost process, suitable for preparing high-performance, crack-free, complex-structured high-temperature alloy parts.

[0094] Compared with the prior art, the present invention has the following beneficial effects:

[0095] 1) This invention discloses a method for laser additive manufacturing of crack-free Ni3Al-based superalloys and its preparation method. Based on the acoustic resonance powder mixing equipment, it can ensure that nano-Hf ceramic particles can be fully and uniformly wrapped on the surface of micron-sized Ni3Al-based superalloy powder, preventing particle agglomeration and avoiding problems such as stress concentration and early failure caused by particle agglomeration.

[0096] 2) The addition of nano-Hf ceramic particles can act as a non-uniform heterogeneous nucleating agent, which can improve the nucleation rate of Ni3Al-based superalloys during LAM. Therefore, adding nano-Hf ceramic particles to Ni3Al-based superalloys can refine the grains. The refinement of the structure can effectively disperse local strain and make the stress distribution more uniform, thereby reducing the occurrence rate of hot cracks.

[0097] 3) Using nano-Hf ceramic particles as the core of heterogeneous nucleation significantly reduces the energy barrier required for nucleation, which is conducive to promoting the transformation of columnar crystals to equiaxed crystals. This gives Ni3Al-based superalloys higher plasticity, toughness and crack resistance.

[0098] In summary, the method for preparing crack-free Ni3Al-based superalloys by laser additive manufacturing of the present invention can prepare crack-free Ni3Al-based superalloys by laser additive manufacturing, and the preparation is simple, low-cost, and suitable for large-scale application.

[0099] Therefore, it is evident that the objective of this invention has been fully and effectively achieved. The function and structural principles of this invention have been demonstrated and explained in the embodiments. Any modifications can be made to the implementation methods without departing from these principles. Therefore, this invention includes all modified embodiments based on the spirit and scope of the claims.

Claims

1. A method for preparing a crack-free Ni3Al-based superalloy using laser additive manufacturing, characterized in that, Includes the following steps: (1) Micron-sized Ni3Al-based high-temperature alloy powder and nano-Hf ceramic particles are mixed evenly, so that the nano-Hf ceramic particles are uniformly coated on the surface of the micron-sized Ni3Al-based high-temperature alloy powder to obtain composite powder. The nano-Hf ceramic particles are nano-hafnium boride particles, nano-hafnium carbide particles or nano-hafnium oxide particles. The mass ratio of the micron-sized Ni3Al-based high-temperature alloy powder to the nano-Hf ceramic particles is 98~99:1~2. The mixing is carried out using an acoustic resonance powder mixing device. The frequency of the acoustic resonance powder mixing device is 40kHz~50kHz, the amplitude of the acoustic resonance powder mixing device is 1.0MPa~3.0MPa, and the mixing time is 40min~60min. (2) Dry the composite powder; (3) The composite powder is melted and solidified layer by layer using a laser directional deposition equipment to obtain a crack-free Ni3Al-based high-temperature alloy for laser additive manufacturing.

2. The method for preparing crack-free Ni3Al-based superalloys by laser additive manufacturing as described in claim 1, characterized in that, In step (1), the particle size of the micron-sized Ni3Al-based high-temperature alloy powder is 53μm~150μm, and the particle size of the nano Hf ceramic particles is 60nm~100nm.

3. The method for preparing crack-free Ni3Al-based superalloys by laser additive manufacturing as described in claim 1, characterized in that, In step (1), the micron-sized Ni3Al-based superalloy powder is prepared by plasma rotating electrode method, and the purity of the micron-sized Ni3Al-based superalloy powder is 99.99%.

4. The method for preparing crack-free Ni3Al-based superalloys by laser additive manufacturing as described in claim 1, characterized in that, In step (1), the micron-sized Ni3Al-based high-temperature alloy powder is a micron-sized MX246A alloy powder.

5. The method for preparing crack-free Ni3Al-based superalloys by laser additive manufacturing as described in claim 1, characterized in that, In step (2), the drying temperature is 100℃~150℃ and the drying time is 1h~3h.

6. The method for preparing crack-free Ni3Al-based superalloys by laser additive manufacturing as described in claim 1, characterized in that, In step (3), the process parameters of the laser directional deposition equipment are: laser power 1200W, scanning speed 900mm / min, spot diameter 1mm, layer thickness 0.8mm, interlayer cooling time 60s, and laser scanning reverse rotation angle of adjacent layers 45°.

7. A laser additive manufacturing method for a crack-free Ni3Al-based superalloy, characterized in that, It is prepared by the laser additive manufacturing method for crack-free Ni3Al-based superalloys as described in any one of claims 1 to 6.

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