Method for inhibiting cracks in additive manufacturing of Ti2AlNb alloy with high O phase content

Abstract

The invention discloses a method for inhibiting cracks in additive manufacturing of a high-O-phase-content Ti2AlNb alloy. The method comprises the following steps that firstly, supplied materials are detected; 2, slicing the model; 3, preheating the substrate; 4, prefabricating a bottom layer; and 5, alloy preparation is conducted, and the crack-free high-O-phase-content Ti2AlNb alloy component is obtained. By preheating the substrate and the powder layer for multiple times and matching with the powder melting process, powder melting solidification and metallurgical bonding can be remarkably improved, the temperature gradient in the forming process can be effectively regulated and controlled, assistance of other equipment is not needed, thermal stress can be remarkably relieved, and the inhibition effect on generation of cracks in the alloy is achieved; the high-O-phase-content Ti2AlNb alloy component without internal cracks is prepared, the technical problems that the high-O-phase-content Ti2AlNb alloy is poor in additive manufacturing forming quality and the internal crack inhibition process is complex are effectively solved, and the method has wide application prospects in the fields of advanced aviation and weaponry.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal additive manufacturing, and particularly relates to a method for suppressing cracks in additive manufacturing of Ti2AlNb alloy with a high O-phase content. Background Art

[0002] Ti2AlNb alloy is a key material for hot-end components such as high-temperature combustion chambers and nozzles in the aviation industry. Due to the complex and variable shapes of aviation parts, high material performance requirements, and high processing difficulties, it is very difficult to directly form complex-structured Ti2AlNb alloy components by traditional hot processing methods. Additive manufacturing technology sets a forming scheme according to a digital three-dimensional model and stacks layers to form an additive product, providing a new way for the efficient integrated manufacturing of large and complex integral Ti2AlNb alloy components. However, during the additive manufacturing process, it experiences rapid melting and solidification and repeated remelting processes. The Ti2AlNb alloy with a high O-phase content has defects such as a large temperature gradient, high internal thermal stress in the formed part, and easy crack generation, seriously reducing the forming quality and application value of the additive manufacturing components.

[0003] In response to the above problems, exploration and research have been carried out at home and abroad, including methods such as introducing ultrasonic external fields and electron beam peening, or reducing and eliminating stress through subsequent hot isostatic pressing, stress relief annealing, etc. to control cracks. However, the above methods require adding equipment functions or combining other equipment for assistance, which not only increases the complexity of the preparation process but also raises the preparation cost.

[0004] In the invention patent with the publication number CN110977137A, AECC Shenyang Liming Aero-Engine Co., Ltd. proposed a method for controlling welding cracks in inertia friction welding of Ti-2AlNb-based alloy. This method mainly customizes and designs a heating device according to the narrowest gap when the main shaft and tailstock of the inertia friction welding equipment are welded, preheats the welded parts before welding, and slowly cools them after welding, which can effectively control the generation of welding cracks. However, it requires adding equipment functions or combining other equipment for assistance, which not only increases the complexity of the preparation process but also raises the preparation cost.

[0005] In the invention patent with the publication number CN119057079A, Harbin Institute of Technology proposed a laser melting deposition additive manufacturing method for Ti2AlNb alloy. This method mainly uses a layer-by-layer pause printing method. During the pause process, the temperature of the printed alloy drops rapidly, which can effectively reduce the oxidation tendency of the alloy. However, the internal thermal stress of the material is large and the cracking is serious.

[0006] In the invention patent with the publication number CN114318056A, Harbin Institute of Technology (Weihai) and Shenzhen Polytechnic proposed a Ti-2AlNb alloy for additive manufacturing of dual-wire cored wire and its manufacturing method. This method mainly adopts measures such as adjusting the angle of the dual wires and the wire electrode spacing to make the cored wire and the pure Ti wire continuously and uniformly transition into the molten pool at the same wire feeding speed, solving the problem of segregation of deposited elements in the additive parts. However, it is necessary to increase the equipment function or combine with other equipment for assistance, and the material cracking is serious, and the additive manufacturing forming quality is poor.

[0007] Therefore, a method for suppressing cracks in the additive manufacturing of Ti2AlNb alloy with a high O-phase content is needed. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to provide a method for suppressing cracks in the additive manufacturing of Ti2AlNb alloy with a high O-phase content in view of the deficiencies of the above-mentioned prior art. This method preheats the substrate and preheats before each layer of powder is melted to regulate the temperature gradient in the forming process of the Ti2AlNb alloy with a high O-phase content to relieve thermal stress. At the same time, combined with the powder melting scanning process, it can avoid cracks caused by internal thermal stress in the Ti2AlNb alloy with a high O-phase content, and prepare a Ti2AlNb alloy component with a high O-phase content and no internal cracks, solving the technical problems of poor forming quality and complex internal crack suppression process in the existing additive manufacturing of Ti2AlNb alloy with a high O-phase content.

[0009] To solve the above technical problems, the technical solution adopted by the present invention is: a method for suppressing cracks in the additive manufacturing of Ti2AlNb alloy with a high O-phase content, characterized in that the method includes the following steps:

[0010] Step 1. Incoming material inspection:

[0011] Inspect the particle size, fluidity, loose bulk density, and oxidation state of the raw materials to obtain Ti2AlNb alloy powder with a high O-phase content that meets the requirements;

[0012] Step 2. Model slicing:

[0013] Establish a three-dimensional CAD model of the Ti2AlNb alloy component with a high O-phase content, and perform layer slicing processing in the forming height direction of the three-dimensional CAD model to obtain slice data;

[0014] Step 3. Substrate preheating:

[0015] Place the Ti2AlNb alloy powder with a high O-phase content that meets the requirements obtained in Step 1 into the powder feeder of the additive manufacturing equipment, and then evacuate to a vacuum degree not lower than 1.2×10 -1Preheat the substrate in the additive manufacturing equipment to 820 °C to 1100 °C and keep it warm for 10 min to 45 min, and finally cool it in the furnace to 350 °C to 600 °C and keep it at a constant temperature to obtain a dried substrate;

[0016] Step Four: Preparing the bottom layer:

[0017] Import the sliced data obtained in Step Two into the additive manufacturing equipment and set the additive manufacturing parameters. Then start the powder feeder, and evenly spread the powder of the high-O-phase-content Ti2AlNb alloy that meets the requirements with a layer thickness of 30 μm to 150 μm on the upper surface of the dried substrate obtained in Step Three. After that, preheat the spread powder to 820 °C to 1200 °C and keep it warm for 3 s to 20 s. Then start the electron beam emitter to heat the spread powder until the powder is completely melted. Finally, cool it in the furnace to 350 °C to 600 °C and keep it at a constant temperature to obtain the prefabricated bottom layer;

[0018] Step Five: Alloy preparation:

[0019] Repeat the spreading, preheating, heat preservation, melting, and constant temperature of the powder in Step Four on the upper surface of the prefabricated bottom layer obtained in Step Four until the prefabricated component is processed by cumulative lamination. Then cool it in the furnace to room temperature, and then separate the prefabricated component from the substrate to obtain a crack-free high-O-phase-content Ti2AlNb alloy component.

[0020] By inspecting the particle size, fluidity, loose bulk density, and oxidation state of the raw materials, and using the powder of the high-O-phase-content Ti2AlNb alloy that meets the requirements for component processing, the present invention is beneficial to ensuring the adaptability of the blank additive manufacturing process and improving the product quality. Without the inspection link for the powder-free raw materials, the product quality risk will be greatly increased and the product qualification rate will be reduced.

[0021] In the present invention, by preheating the substrate at 820°C to 1100°C for heat preservation for 10 min to 45 min, the temperature of the substrate is increased in advance, which is beneficial to reducing the temperature gradient and avoiding the generation of thermal stress, and has the effect of suppressing the cracks of the blank. If the initial preheating temperature of the substrate is lower than 820°C or the heat preservation time is less than 10 min, the prefabricated bottom layer and the substrate will not be effectively metallurgically bonded, which is extremely likely to induce cracks in the blank. If the initial preheating temperature of the substrate is higher than 1100°C or the heat preservation time is longer than 45 min, the thermal stress of the substrate is too large and it is prone to distortion, which will accelerate the generation of microcracks in the blank; finally, the substrate is furnace-cooled to 350°C to 600°C and kept at a constant temperature to obtain a dry substrate, which is beneficial to suppressing the cracks of the blank. If the temperature of the dry substrate is higher than 600°C, local caking will occur in the prefabricated bottom layer powder, which is not conducive to the uniform spreading of the powder. If the temperature of the dry substrate is lower than 350°C, it is not conducive to the metallurgical bonding between the substrate and the prefabricated bottom layer, and powder blowing will occur, and a uniform bottom layer cannot be obtained, resulting in various metallurgical defects such as poor fusion and voids, accelerating the formation of cracks in the blank; by performing high-temperature preheating treatment on the substrate and then cooling it to 350°C to 600°C for powder layer laying, it is beneficial to the uniform distribution of the temperature field of the fusion layer and the dispersed distribution of thermal stress, and has the effect of reducing the cracking of the blank.

[0022] In the present invention, by controlling the powder layer thickness to be 30 μm to 150 μm, the penetration depth of the electron beam voltage is made appropriate, ensuring that the powder is completely melted and a good metallurgical bond is formed. At the same time, excessive penetration is avoided, which may cause substrate damage or excessive heat loss, being beneficial to the suppression of billet cracks; by preheating each powder layer at 820 °C to 1100 °C and holding for 3 s to 20 s, the temperature of the Ti2AlNb alloy powder with a high O-phase content can be pre-elevated during the powder spreading process of the next layer. This can avoid a large instantaneous temperature rise and the generation of thermal stress when melting the Ti2AlNb alloy powder with a high O-phase content, improving the dispersion distribution of thermal stress, being beneficial to the suppression of billet cracks. If the preheating temperature of each powder layer is lower than 820 °C or the holding time is less than 3 s, the powder layer cannot be effectively metallurgically bonded, which will induce cracks in the billet. If the preheating temperature of each powder layer is higher than 1100 °C or the holding time is longer than 20 s, the thermal stress of the fusion layer is too large and it is prone to distortion, which will accelerate the generation of microcracks in the billet; after the powder is completely melted, it is furnace-cooled to 350 °C to 600 °C and kept at a constant temperature, which can avoid too large a difference in the melting temperature between the solidified Ti2AlNb alloy with a high O-phase content in the previous layer and the newly laid Ti2AlNb alloy powder layer with a high O-phase content, being beneficial to the uniform spreading of the powder, improving the metallurgical bond between layers, and reducing defects such as pores and poor fusion, being beneficial to the suppression of billet cracks. If the temperature of the previous layer is higher than 600 °C, the newly laid powder will undergo over-melting and local caking, which is not conducive to the uniform spreading of the powder and a uniform powder layer cannot be obtained. If the temperature of the previous layer is lower than 350 °C, it is not conducive to the metallurgical bond between the previous layer and the newly laid powder layer, and various metallurgical defects such as poor fusion and voids will be generated, accelerating the generation of cracks in the billet.

[0023] The above method for suppressing cracks in additive manufacturing of Ti2AlNb alloy with a high O-phase content is characterized in that, in step one, the qualified Ti2AlNb alloy powder with a high O-phase content is spherical or quasi-spherical powder with a particle size of 35 μm to 150 μm, the mass purity is not less than 99.8%, the molar percentage content of the O-phase is more than 50%, and the qualified Ti2AlNb alloy powder with a high O-phase content is non-oxidized, the fluidity is less than 30 s / 50 g, and the loose bulk density is greater than 2.8 g / cm 3The present invention limits the particle size of spherical or quasi-spherical powder to 35μm to 150μm. If the powder particle size is less than 35μm, powder blowing is likely to occur in additive manufacturing, and a uniform powder layer cannot be obtained. If the powder particle size is greater than 150μm, the powder fluidity is poor. Too large or too small powder particle size and non-spherical powder will significantly reduce the adaptability of the powder additive manufacturing process. The powder quality purity is limited to not less than 99.8%, which can ensure the product qualification rate. If the powder contains more impurities, the mechanical properties of the product are extremely poor and cannot be used. The molar percentage content of the O phase is limited to more than 50%, which is conducive to ensuring the high temperature performance of the product. The O phase is a high temperature strengthening phase, and a high O phase content is the necessary organizational basis for Ti2AlNb alloy to serve in a high temperature environment. The non-oxidation of the powder is the basic guarantee of product quality. If the powder is oxidized, the performance of the product is extremely poor and the product cannot be used. The bulk density of the powder raw material is controlled to be greater than 2.8g / cm 3 , fluidity is less than 30s / 50g. Too small bulk density and too large fluidity will significantly reduce the adaptability of the additive manufacturing process, making it impossible to obtain a dense structure, easily causing cracks, and affecting the engineering application value of the product.

[0024] The above-mentioned method for suppressing cracks in additive manufacturing of a Ti2AlNb alloy with a high O-phase content is characterized in that the additive manufacturing equipment in step 3 is a powder bed selective melting electron beam additive manufacturing equipment; the material of the substrate is 314L stainless steel or 316L stainless steel. The present invention limits the material of the substrate to 314L stainless steel or 316L stainless steel, and uses a dissimilar material as the substrate, which is conducive to separating the formed product from the substrate, does not require other equipment assistance, saves costs, and improves production efficiency.

[0025] The above method for suppressing cracks in additive manufacturing of Ti2AlNb alloy with a high O-phase content is characterized in that the parameters of the additive manufacturing in step four are as follows: the voltage is 40 kV to 80 kV, the current is 6 mA to 18 mA, the scanning speed is 1.2 m / s to 7.5 m / s, the scanning spacing is 40 μm to 200 μm, the energy density is 38 J / mm to 46 J / mm, and the layer rotation is 90°. By controlling the electron beam voltage to be 40 kV to 80 kV, the present invention can provide sufficient energy for the electron beam to melt the Ti2AlNb alloy powder with a high O-phase content and precisely control the input of the energy density of 38 J / mm to 46 J / mm, which helps to achieve a fine microstructure; by controlling the electron beam current to be 6 mA to 18 mA, it helps to reduce the heat affected zone, reduce the concentration of thermal stress and the tendency of cracking, and improve the dimensional accuracy and surface quality of the Ti2AlNb alloy component with a high O-phase content; by controlling the scanning speed to be 1.2 m / s to 7.5 m / s, it can shorten the preparation time, improve the production efficiency and help to reduce the heat accumulation in a relatively fast range; by controlling the scanning spacing range to be 40 μm to 200 μm, it is used to prevent the fusion property of the Ti2AlNb alloy powder with a high O-phase content from being reduced due to too large a scanning spacing, and prevent the phenomenon of over-melting caused by too short a scanning spacing, thus affecting the forming quality of the Ti2AlNb alloy with a high O-phase content; by controlling the layer rotation of 90°, it helps to disperse the residual stress generated in the preparation process and reduce the cracks and deformations caused by stress concentration; by controlling the substrate preheating temperature and holding time, the powder layer preheating temperature and holding time, the scanning voltage, the scanning current, the scanning speed, the scanning spacing, the electron beam energy density, and the layer rotation angle, and jointly acting on the Ti2AlNb alloy powder, it can ensure a uniform distribution of the temperature gradient of the prepared Ti2AlNb alloy material, obtain a component with a dense structure and no cracks, and provide a new design basis for suppressing cracks in the additive manufacturing of Ti2AlNb alloy.

[0026] The present invention has the following advantages compared with the prior art:

[0027] 1. By preheating the substrate and preheating each powder layer before melting, the present invention is used to regulate the temperature gradient in the forming process of the Ti2AlNb alloy with a high O-phase content to relieve the thermal stress. At the same time, combined with the powder melting and scanning process, it can avoid the generation of cracks caused by the internal thermal stress of the Ti2AlNb alloy with a high O-phase content, and prepare a Ti2AlNb alloy component with a high O-phase content and no internal cracks, solving the technical problems of poor forming quality and complex internal crack suppression process in the existing additive manufacturing of Ti2AlNb alloy with a high O-phase content.

[0028] 2. The present invention is based on the powder bed selective melting electron beam additive manufacturing technology. By combining the powder melting scanning process with the regulation of the preheating temperature of the substrate and powder layer, crack control is achieved during the preparation of high-O-phase-content Ti2AlNb alloy components, without the need to combine other equipment to relieve the cracks in the additive manufactured parts, reducing the complexity of the manufacturing process.

[0029] 3. By comprehensively regulating the electron beam additive manufacturing parameters, the present invention effectively improves the melting, solidification and metallurgical bonding of high-O-phase-content Ti2AlNb alloy powder, enhances the forming quality of the alloy by additive manufacturing, facilitates large-scale production, and can be used as an alternative material for high-temperature structural components of advanced aviation and weaponry.

[0030] The technical solution of the present invention will be further described in detail below with reference to the drawings and embodiments. Description of the Drawings

[0031] Figure 1 is the optical micrograph of the crack-free high-O-phase-content Ti2AlNb alloy component prepared in Example 1 of the present invention.

[0032] Figure 2 is the optical micrograph of the high-O-phase-content Ti2AlNb alloy component prepared in Comparative Example 2 of the present invention. Detailed Embodiments

[0033] Example 1

[0034] This example includes the following steps:

[0035] Step 1. Incoming material inspection: Inspect the particle size, fluidity, loose bulk density, and oxidation state of the raw materials to obtain high-O-phase-content Ti2AlNb alloy powder that meets the requirements; the high-O-phase-content Ti2AlNb alloy powder that meets the requirements is spherical powder with a particle size of 35 μm to 150 μm, a mass purity of 99.8%, a molar percentage content of O phase of 50%, a fluidity of 25 s / 50 g, and a loose bulk density of 2.9 g / cm 3 ;

[0036] Step 2. Model slicing: Establish a three-dimensional CAD model of the high-O-phase-content Ti2AlNb alloy component, and perform layer slicing processing in the forming height direction of the three-dimensional CAD model to obtain slice data;

[0037] Step 3. Substrate preheating: Put the high-O-phase-content Ti2AlNb alloy powder that meets the requirements obtained in Step 1 into the powder feeder of the powder bed selective melting electron beam additive manufacturing equipment, and then evacuate to a vacuum degree of 1.2×10 -1Preheat the 314L stainless steel substrate in the additive manufacturing equipment to 820 °C and hold for 45 min, and finally cool it in the furnace to 350 °C and keep it at a constant temperature to obtain a dry substrate;

[0038] Step four, prefabricate the bottom layer: Import the slice data obtained in step two into the additive manufacturing equipment and set the additive manufacturing parameters. Then start the powder feeder to evenly spread the powder of the Ti2AlNb alloy with a high O-phase content that meets the requirements and a layer thickness of 30 μm on the upper surface of the dry substrate obtained in step three. After that, preheat the spread powder to 820 °C and hold for 15 s, and then start the electron beam emitter to heat the spread powder so that the powder is completely melted. Finally, cool it in the furnace to 350 °C and keep it at a constant temperature to obtain a prefabricated bottom layer; The additive manufacturing parameters are: voltage is 40 kV, current is 6 mA, scanning speed is 1.2 m / s, scanning pitch is 40 μm, energy density is 38 J / mm, and the layer rotates 90°;

[0039] Step five, alloy preparation: Repeat the spreading, preheating, holding, melting, and constant temperature of the powder in step four on the upper surface of the prefabricated bottom layer obtained in step four until the prefabricated component is processed by cumulative lamination. Then cool it in the furnace to room temperature, and then separate the prefabricated component from the substrate to obtain a crack-free Ti2AlNb alloy component with a high O-phase content.

[0040] After testing, the crack-free Ti2AlNb alloy component prepared in this example has no unmelted powder, good interlayer bonding, no pores, cracks, or holes inside, and has good additive manufacturing forming quality.

[0041] Figure 1 is the optical micrograph of the crack-free Ti2AlNb alloy component prepared in this example. As Figure 1 shown, the crack-free Ti2AlNb alloy component prepared in this example has no unmelted powder, good interlayer bonding, no pores, cracks, or holes inside, and has good additive manufacturing forming quality.

[0042] Comparative example 1

[0043] The difference between this comparative example and Example 1 is that: the preheating temperature of the substrate in step three is 800 °C.

[0044] After testing, the Ti2AlNb alloy component with a high O-phase content prepared in this comparative example has obvious microcracks and holes inside, and the additive manufacturing forming quality is poor.

[0045] Comparative example 2

[0046] The difference between this comparative example and Example 1 is that: in step four, preheating to 820 °C and holding for 15 s are not carried out.

[0047] After detection, obvious microcracks, pores, and poor fusion defects exist inside the high-O-phase-content Ti2AlNb alloy prepared in this comparative example, and the additive manufacturing forming quality is poor.

[0048] Figure 2 This is the optical micrograph of the high-O-phase-content Ti2AlNb alloy component prepared in this comparative example. As Figure 2 shown, obvious microcracks, pores, and poor fusion defects exist inside the high-O-phase-content Ti2AlNb alloy component prepared in this comparative example, and the additive manufacturing forming quality is poor.

[0049] By comparing Comparative Example 1 and Comparative Example 2 with Example 1, it can be seen that in Example 1, through preheating the substrate and preheating the powder layer multiple times, combined with the powder melting scanning process, the powder melting and solidification and metallurgical bonding can be significantly improved, the temperature gradient during the forming process can be effectively regulated, without increasing the equipment function or combining with other equipment for assistance, the thermal stress can be significantly relieved, and the inhibition of crack generation inside the high-O-phase-content Ti2AlNb alloy can be achieved.

[0050] Example 2

[0051] This example includes the following steps:

[0052] Step 1. Incoming material inspection: Inspect the particle size, fluidity, loose bulk density, and oxidation state of the raw materials to obtain high-O-phase-content Ti2AlNb alloy powder that meets the requirements; the high-O-phase-content Ti2AlNb alloy powder that meets the requirements is spherical-like powder with a particle size of 35 μm to 150 μm, and the mass purity is 99.8%, the molar percentage content of the O phase is 60%, the fluidity is 22 s / 50 g, and the loose bulk density is 3.0 g / cm 3 ;

[0053] Step 2. Model slicing: Establish a three-dimensional CAD model of the high-O-phase-content Ti2AlNb alloy component, and perform layer slicing processing in the forming height direction of the three-dimensional CAD model to obtain slice data;

[0054] Step 3. Substrate preheating: Put the high-O-phase-content Ti2AlNb alloy powder that meets the requirements obtained in Step 1 into the powder feeder of the powder bed selective melting electron beam additive manufacturing equipment, then evacuate to a vacuum degree of 1.2×10 -1 Pa, then preheat the 316L stainless steel substrate in the additive manufacturing equipment to 950 °C and keep it warm for 25 min, and finally cool it in the furnace to 450 °C and keep it at a constant temperature to obtain a dry substrate;

[0055] Step 4. Preparing the bottom layer: Import the slice data obtained in Step 2 into an additive manufacturing device and set the additive manufacturing parameters. Then start the powder feeder to evenly spread the powder of the Ti2AlNb alloy with a high O-phase content that meets the requirements and a layer thickness of 70 μm on the upper surface of the dried substrate obtained in Step 3. After that, preheat the spread powder to 950 °C and keep it warm for 12 s. Then start the electron beam emitter to heat the spread powder until the powder is completely melted. Finally, cool it in the furnace to 450 °C and keep it at a constant temperature to obtain the prefabricated bottom layer. The additive manufacturing parameters in Step 4 are as follows: voltage is 60 kV, current is 12 mA, scanning speed is 5.5 m / s, scanning pitch is 100 μm, energy density is 42 J / mm, and the layer rotates 90° between layers.

[0056] Step 5. Alloy preparation: Repeat the spreading, preheating, heat preservation, melting, and constant temperature of the powder in Step 4 on the upper surface of the prefabricated bottom layer obtained in Step 4 until the prefabricated component is processed by cumulative lamination. Then cool it in the furnace to room temperature, and then separate the prefabricated component from the substrate to obtain a crack-free Ti2AlNb alloy component with a high O-phase content.

[0057] After testing, the Ti2AlNb alloy component with a high O-phase content prepared in this example has no unmelted powder, good interlayer bonding, no pores, cracks, or holes inside, and has good additive manufacturing forming quality.

[0058] Example 3

[0059] This example includes the following steps:

[0060] Step 1. Incoming material inspection: Inspect the particle size, fluidity, loose bulk density, and oxidation state of the raw materials to obtain the Ti2AlNb alloy powder with a high O-phase content that meets the requirements. The Ti2AlNb alloy powder with a high O-phase content that meets the requirements is spherical powder with a particle size of 35 μm to 150 μm, a mass purity of 99.8%, a molar percentage content of O-phase of 70%, a fluidity of 18 s / 50 g, and a loose bulk density of 3.2 g / cm 3 ;

[0061] Step 2. Model slicing: Establish a three-dimensional CAD model of the Ti2AlNb alloy component with a high O-phase content, and perform layer slicing processing in the forming height direction of the three-dimensional CAD model to obtain slice data.

[0062] Step 3. Substrate preheating: Put the Ti2AlNb alloy powder with a high O-phase content that meets the requirements obtained in Step 1 into the powder feeder of the electron beam additive manufacturing device for powder bed selective melting. Then evacuate to a vacuum degree of 1.2×10 -1 Pa. Then preheat the 314L stainless steel substrate in the additive manufacturing device to 1100 °C and keep it warm for 10 min. Finally, cool it in the furnace to 600 °C and keep it at a constant temperature to obtain a dried substrate.

[0063] Step 4. Preparing the bottom layer: Import the slice data obtained in Step 2 into the additive manufacturing equipment and set the additive manufacturing parameters. Then start the powder feeder to evenly spread the powder of the Ti2AlNb alloy with a high O-phase content that meets the requirements and a layer thickness of 150 μm on the upper surface of the dried substrate obtained in Step 3. After that, preheat the spread powder to 1100 °C and keep it warm for 3 s. Then start the electron beam emitter to heat the spread powder until the powder is completely melted. Finally, cool it in the furnace to 600 °C and keep it at a constant temperature to obtain the prefabricated bottom layer; the additive manufacturing parameters are: voltage is 80 kV, current is 18 mA, scanning speed is 7.5 m / s, scanning pitch is 200 μm, energy density is 46 J / mm, and the layer rotates 90° between layers.

[0064] Step 5. Alloy preparation: Repeat the spreading, preheating, heat preservation, melting, and constant temperature of the powder in Step 4 on the upper surface of the prefabricated bottom layer obtained in Step 4 until the prefabricated component is processed by cumulative stacking. Then cool it in the furnace to room temperature, and then separate the prefabricated component from the substrate to obtain a crack-free Ti2AlNb alloy component with a high O-phase content.

[0065] After testing, the Ti2AlNb alloy component with a high O-phase content prepared in this embodiment has no unmelted powder, good interlayer bonding, no pores, cracks, or holes inside, and has good additive manufacturing forming quality.

[0066] The above is only a preferred embodiment of the present invention and does not impose any limitation on the present invention. Any simple modification, change, and equivalent change made to the above embodiments according to the technical essence of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for suppressing cracks in additive manufacturing of Ti2AlNb alloy with high O-phase content, characterized in that, The method comprises the following steps: Step 1, incoming material inspection: Inspect the particle size, fluidity, loose bulk density, and oxidation state of the raw materials to obtain high-O-phase-content Ti2AlNb alloy powder that meets the requirements; Step 2, model slicing: Establish a three-dimensional CAD model of the high-O-phase-content Ti2AlNb alloy component, and perform layer slicing processing in the forming height direction of the three-dimensional CAD model to obtain slice data; Step 3. Substrate preheating: Place the Ti2AlNb alloy powder with a high O-phase content obtained in Step 1 that meets the requirements into the powder feeder of the additive manufacturing equipment, and then evacuate to a vacuum degree not lower than 1.2×10 -1 Pa. Then preheat the substrate in the additive manufacturing equipment to 820°C to 1100°C and hold for 10 min to 45 min, and finally cool in the furnace to 350°C to 600°C and keep it at a constant temperature to obtain a dry substrate; Step 4, prefabricating the bottom layer: Import the slice data obtained in Step 2 into the additive manufacturing equipment and set the additive manufacturing parameters, then start the powder feeder, evenly spread the powder of the high-O-phase-content Ti2AlNb alloy that meets the requirements with a layer thickness of 30μm - 150μm on the upper surface of the dried substrate obtained in Step 3. After that, preheat the spread powder at 820°C - 1200°C and keep it warm for 3s - 20s, then start the electron beam emitter to heat the spread powder until the powder is completely melted, and finally cool it in the furnace to 350°C - 600°C and keep it at a constant temperature to obtain the prefabricated bottom layer; Step 5, alloy preparation: Repeat the spreading, preheating, heat preservation, melting, and constant temperature of the powder in Step 4 on the upper surface of the prefabricated bottom layer obtained in Step 4 until the prefabricated component is processed by cumulative stacking, then cool it in the furnace to room temperature, and then separate the prefabricated component from the substrate to obtain a crack-free high-O-phase-content Ti2AlNb alloy component.

2. A method for suppressing cracks in additive manufacturing of Ti2AlNb alloy with a high O-phase content according to claim 1, characterized in that, The high-O-phase-content Ti2AlNb alloy powder meeting the requirements in Step 1 is spherical or quasi-spherical powder with a particle size of 35 μm to 150 μm, a mass purity of not less than 99.8%, a molar percentage content of the O phase of more than 50%. The high-O-phase-content Ti2AlNb alloy powder meeting the requirements is free of oxidation, has a fluidity of less than 30 s / 50 g, and a tapped density of greater than 2.8 g / cm 3 .

3. A method for suppressing cracks in additive manufacturing of Ti2AlNb alloy with a high O-phase content according to claim 1, characterized in that The additive manufacturing equipment described in Step 3 is a powder bed selective melting electron beam additive manufacturing equipment; the substrate is made of 314L stainless steel or 316L stainless steel.

4. A method for suppressing cracks in additive manufacturing of Ti2AlNb alloy with high O-phase content according to claim 1, characterized in that, The parameters of the additive manufacturing described in Step 4 are: voltage is 40kV - 80kV, current is 6mA - 18mA, scanning speed is 1.2m / s - 7.5m / s, scanning pitch is 40μm - 200μm, energy density is 38J / mm - 46J / mm, and the layer rotates 90° between layers.

Images