TiAl alloy electron beam selective melting and shot peening strengthening in-situ compounding manufacturing method and device

Abstract

The invention discloses a TiAl alloy electron beam selective melting and shot peening strengthening in-situ compounding manufacturing method and device, and relates to the technical field of additive manufacturing. The method comprises the following steps: establishing a three-dimensional digital model of a to-be-printed part, and performing slicing and layering to obtain layered scanning data; under the vacuum condition, TiAl alloy powder is spread on the preheated base plate according to the set thickness, and a powder bed is formed; according to the layered scanning data, scanning and melting the powder bed through a focused electron beam, completing single-layer scanning and melting, completing scanning and melting layer by layer until the part is printed and cooled, and recovering unmelted TiAl alloy powder; and under the vacuum condition, the surface of the printed part is scanned and heated through a defocusing electron beam, TiAl alloy powder is adopted as shot blasting powder, the surface of the heated part is subjected to microparticle shot blasting strengthening treatment, after the treatment is finished, cooling is conducted, scattered shot blasting powder is recycled, and the finished TiAl alloy part is obtained. By means of the collaborative process design of electron beam selective melting and in-situ high-temperature microparticle shot blasting and device integration, the problems that in TiAl alloy additive manufacturing, cracking is prone to occurring, and the strengthening effect is poor are solved.

Description

Technical Field

[0001] The present application relates to the field of additive manufacturing technology, and in particular to a manufacturing method and device for in-situ composite TiAl alloy electron beam selective melting and shot peening. Background Art

[0002] TiAl alloys are considered promising lightweight, heat-resistant materials due to their low density, high specific strength, and excellent high-temperature oxidation and creep resistance. They are expected to replace nickel-based superalloys in the 600°C-900°C temperature range and become ideal aerospace engine materials. TiAl alloys are mostly formed using casting, forging, and powder metallurgy techniques. However, conventional casting techniques are prone to forming a coarse microstructure and severe compositional segregation, as well as defects such as porosity and inclusions. This prevents the formation of a fine, uniform microstructure, necessitating subsequent mechanical heat treatment for grain refinement. Electron beam melting (EBM) technology, due to its high energy density and vacuum environment, is an ideal choice for forming complex TiAl alloy components. However, this technology still presents challenges: residual stress can easily lead to cracking in the formed parts, and the surface quality of the formed parts is insufficient. Surface roughness and microcracks directly affect fatigue performance. Shot peening is a common method for improving the fatigue performance of metal materials. However, the traditional shot peening process is carried out at room temperature. Due to the brittle nature of TiAl alloys, the material has poor plasticity at low temperatures. The shot peening process easily induces surface microcracks, which in turn reduces fatigue life. Furthermore, it only produces minor plastic deformation on the surface, resulting in a shallow strength layer and small residual compressive stress values, resulting in a weak strengthening effect. Furthermore, existing devices cannot be integrated in situ with additive manufacturing processes, resulting in complex processes and a sharp increase in costs. Based on this, this application proposes a manufacturing method and device for TiAl alloys that combines electron beam selective melting and shot peening in situ. Summary of the Invention

[0003] The main purpose of this application is to provide a manufacturing method and device for in-situ composite electron beam selective melting and shot peening of TiAl alloy, aiming to solve the technical problems of easy cracking and insufficient surface strengthening effect in the existing TiAl alloy additive manufacturing process.

[0004] To achieve the above objectives, the present application proposes a TiAl alloy electron beam selective melting and shot peening in-situ composite manufacturing method, comprising the following steps: S1. Create a three-dimensional digital model of the part to be printed, slice and layer it, and obtain layered scanning data; S2. Under vacuum conditions, spreading TiAl alloy powder to a set thickness on a preheated substrate to form a powder bed; S3. Melting the powder bed by focused electron beam scanning according to the layered scanning data to complete single-layer scanning melting; S4. Repeat steps S2 to S3 to complete scanning and melting layer by layer until the part is printed. After cooling, recover the unmelted TiAl alloy powder. S5. Under vacuum conditions, the printed part surface is heated by scanning with a defocused electron beam, and the TiAl alloy powder is used as shot peening powder to perform microparticle shot peening strengthening treatment on the heated part surface. After completion, the part surface is cooled and the scattered shot peening powder is recovered to obtain a finished TiAl alloy part.

[0005] Optionally, in the step of spreading the TiAl alloy powder on the preheated substrate with a set thickness under vacuum conditions to form a powder bed, the average particle size of the TiAl alloy powder is 30 μm-105 μm, the powder thickness is 40 μm-60 μm, and the vacuum condition is a vacuum degree of 1.0×10 -3 Pa-1.0×10 -4 Pa.

[0006] Optionally, in the step of spreading the TiAl alloy powder on a preheated substrate with a set thickness under vacuum conditions to form a powder bed, the substrate is preheated to 500°C-600°C by a defocused electron beam, the scanning beam current of the defocused electron beam is 25mA-35mA, and the scanning speed is 8m / s-12m / s.

[0007] Optionally, in the step of melting the powder bed by scanning with a focused electron beam, the beam spot diameter of the focused electron beam is 150 μm-250 μm, the focused beam current is 15 mA-25 mA, the scanning speed is 1 m / s-3 m / s, and the scanning pitch is 50 μm-90 μm.

[0008] Optionally, the step of heating the printed part surface by scanning with a defocused electron beam under vacuum conditions includes: Maintain vacuum at 1.0×10 -3 Pa-1.0×10 -4 Pa, the surface of the printed part is heated to 400℃-600℃ by scanning with a defocused electron beam; wherein the scanning beam current of the defocused electron beam is 25mA-35mA, and the scanning speed is 8m / s-12m / s.

[0009] Optionally, in the step of using the TiAl alloy powder as shot peening powder to perform microparticle shot peening strengthening treatment on the surface of the heated part, the shot peening pressure is controlled to be 0.3MPa-0.8MPa, and the shot peening time is 5min-20min.

[0010] The present application also proposes a TiAl alloy electron beam selective melting and shot peening in-situ composite manufacturing device, which is used to implement the above-mentioned TiAl alloy electron beam selective melting and shot peening in-situ composite manufacturing method, and the manufacturing device comprises: A vacuum forming chamber, wherein a workbench is provided inside the vacuum forming chamber for carrying a substrate; a powder feeding mechanism, the powder feeding mechanism being located in the vacuum forming chamber and connected to the workbench, and being used for spreading metal powder onto the substrate; An electron beam emission and focusing scanner is provided at the top of the vacuum forming chamber, and a scanning range of the electron beam emission and focusing scanner covers the forming area on the workbench; a shot blasting mechanism, the shot blasting mechanism being disposed on the top of the vacuum forming chamber and connected to the powder supply mechanism; a powder recovery mechanism, the powder recovery mechanism being disposed at the bottom of the vacuum forming chamber, the powder recovery mechanism being connected to the workbench, and being used to recover unmelted TiAl alloy powder and scattered shot blasting powder; A controller is integrated outside the vacuum forming chamber and is connected to the powder supply mechanism, the electron beam emission and focusing scanner, the shot blasting mechanism, and the powder recovery mechanism through electrical signals, so as to regulate the parameters of the electron beam and the powder transportation.

[0011] Optionally, the manufacturing device further includes a rotatable Z-axis mechanism, which is connected to the workbench and is used to control the lifting and rotation of the part.

[0012] Optionally, the shot blasting mechanism includes a shot blasting nozzle and a high-pressure gas pipeline, one end of the high-pressure gas pipeline is connected to the external gas, and the other end is connected to the shot blasting nozzle, and the high-pressure gas pipeline is also connected to the powder supply mechanism.

[0013] Optionally, the powder recovery mechanism includes a first negative pressure pipe and a second negative pressure pipe, the first negative pressure pipe is connected to the workbench to recover unmelted TiAl alloy powder; the inlet of the second negative pressure pipe is located around the workbench to recover scattered shot blasting powder.

[0014] The beneficial effects of this application include: The application utilizes a focused electron beam to scan and melt TiAl alloy powder, and utilizes a defocused electron beam to scan and heat the surface of the printed part, so as to reduce the temperature gradient and residual stress in the forming process, effectively inhibit the cracking of the part, and close the surface cracks through high-temperature micro-particle shot blasting. By utilizing the characteristics of the high-temperature plasticity of the TiAl alloy, the micro-cracks caused by room-temperature shot blasting are avoided, and a deep plastic deformation and residual compressive stress layer are formed at the same time, so that the surface strengthening effect is enhanced, the fatigue strength of the part is improved, and the surface roughness is effectively controlled, and the defects of the TiAl alloy part are reduced. The application utilizes the same TiAl alloy powder as the printing material as the shot blasting medium, and realizes closed-loop utilization through powder recycling, so as to reduce material waste, avoid pollution of the printing powder by heterogeneous powder, and belong to micro-particle shot blasting, so that the surface roughness of the part can be effectively controlled. The application integrates electron beam selective melting forming and high-temperature micro-particle shot blasting strengthening in the same vacuum forming chamber, and utilizes a set of powder supply mechanism and powder recycling mechanism for the high-temperature shot blasting strengthening and the electron beam powder bed melting forming, so as to realize in-situ combination of the part additive forming and shot blasting strengthening, make the part forming and strengthening seamlessly connected, avoid environmental exposure and heat loss, reduce the part transfer steps, and then shorten the production cycle. The application utilizes the synergistic process design and device integration of the electron beam selective melting and the in-situ high-temperature micro-particle shot blasting, improves the performance of the TiAl alloy component, solves the problems of easy cracking, poor surface quality and inapplicability of traditional strengthening technology in the additive manufacturing of the TiAl alloy, and can be applied to the manufacturing of high-end parts in the fields of aerospace and energy equipment. BRIEF DESCRIPTION OF DRAWINGS

[0015] In order to more clearly illustrate the technical solutions of the embodiments of the application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of the drawings shown.

[0016] Figure 1 The flow chart of the manufacturing method of the TiAl alloy electron beam selective melting and shot blasting strengthening in-situ combination described in the embodiments of the application; Figure 2 The schematic diagram of the TiAl alloy electron beam selective melting forming process described in the embodiments of the application; Figure 3 The schematic diagram of the defocused electron beam heating part surface described in the embodiments of the application; Figure 4 The schematic diagram of the shot blasting strengthening part surface described in the embodiments of the application.

[0017] Reference numerals: 1-vacuum forming chamber; 2-workbench; 3-powder supply mechanism; 4-electron beam emission and focusing scanner; 41-first sealing valve; 5-shot blasting mechanism; 51-shot blasting nozzle; 52-high-pressure gas pipeline; 53-control valve; 54-second sealing valve; 6-powder recovery mechanism; 7-rotatable Z-axis mechanism.

[0018] The realization of the objectives, functional features and advantages of this application will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0019] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0020] In view of the technical problems existing in the prior art, the embodiments of the present application provide a TiAl alloy electron beam selective melting and shot peening in-situ composite manufacturing method, such as Figure 1 As shown, the following steps are included: S1. Create a three-dimensional digital model of the part to be printed, slice and layer it, and obtain layered scanning data.

[0021] S2. Under vacuum conditions, TiAl alloy powder is spread on the preheated substrate with a set thickness to form a powder bed.

[0022] In the specific implementation process, the average particle size of the TiAl alloy powder is 30 μm-105 μm, the powder thickness is 40 μm-60 μm, and the vacuum condition is a vacuum degree of 1.0×10 -3 Pa-1.0×10 -4 Pa.

[0023] Specifically, the substrate is preheated to 500° C.-600° C. by a defocused electron beam, the scanning beam current of the defocused electron beam is 25 mA-35 mA, and the scanning speed is 8 m / s-12 m / s.

[0024] S3. According to the layered scanning data, the powder bed is melted by focused electron beam scanning to complete single-layer scanning melting.

[0025] In a specific implementation process, the beam spot diameter of the focused electron beam is 150 μm-250 μm, the focused beam current is 15 mA-25 mA, the scanning speed is 1 m / s-3 m / s, and the scanning interval is 50 μm-90 μm.

[0026] Specifically, when the beam spot diameter is small and the beam current is high, the energy is highly concentrated, forming a deep and narrow molten pool, ensuring complete melting of the powder and reducing unfused defects; when the beam spot diameter is large and the beam current is low, the energy distribution is more uniform, forming a shallow and wide molten pool, which is suitable for thin-walled structures or low heat input requirements; through flexible adjustment of the beam spot diameter and scanning speed, it can adapt to the geometric shapes of different parts (such as complex cavities and thin-walled structures).

[0027] Preferably, the scanning pitch is 70 μm, which can balance the forming efficiency and quality and reduce the single-layer forming time.

[0028] S4. Repeat steps S2 to S3 to complete scanning and melting layer by layer until the part is printed. After cooling, recover the unmelted TiAl alloy powder.

[0029] S5. Under vacuum conditions, the printed part surface is heated by scanning with a defocused electron beam, and the TiAl alloy powder is used as shot peening powder to perform microparticle shot peening strengthening treatment on the heated part surface. After completion, the part surface is cooled and the scattered shot peening powder is recovered to obtain a finished TiAl alloy part.

[0030] In the specific implementation process, the vacuum degree is maintained at 1.0×10 -3 Pa-1.0×10 -4 Pa, the surface of the printed part is heated to 400℃-600℃ by scanning with a defocused electron beam; wherein the scanning beam current of the defocused electron beam is 25mA-35mA, and the scanning speed is 8m / s-12m / s.

[0031] The elongation of TiAl alloy increases significantly above 400℃, which can eliminate the risk of microcracks caused by room temperature brittleness. Shot peening at high temperatures of 400℃-600℃ can promote the in-situ release of residual stress and avoid stress superposition during shot peening that may cause cracking of parts.

[0032] Specifically, during the microparticle shot peening treatment, the shot peening pressure is controlled to be 0.3 MPa-0.8 MPa, and the shot peening time is 5 min-20 min.

[0033] When the shot peening pressure is low, the powder impact speed is low, which can form shallow micro-plastic deformation and close surface micro-cracks. When the shot peening pressure is high, the powder accelerates to hit the part surface, the impact energy is increased, and deep plastic deformation can be produced, which significantly increases the residual compressive stress value. In order to balance the shot peening strengthening effect and the surface roughness of the part, this application controls the shot peening pressure to 0.3MPa-0.8MPa, and achieves crack-free surface and deep strengthening of the part with the lowest energy consumption.

[0034] The embodiments of the present application further provide a manufacturing device for in-situ composite TiAl alloy electron beam selective melting and shot peening, which is used to implement the above-mentioned manufacturing method for in-situ composite TiAl alloy electron beam selective melting and shot peening, and the manufacturing device comprises: A vacuum forming chamber 1, wherein a workbench 2 is provided inside the vacuum forming chamber 1 for carrying a substrate; a powder feeding mechanism 3 , located in the vacuum forming chamber 1 and connected to the workbench 2 , for spreading metal powder onto the substrate; An electron beam emission and focusing scanner, which is arranged on the top of the vacuum forming chamber 1 and has a scanning range covering the forming area on the workbench 2; a shot blasting mechanism 5 , the shot blasting mechanism 5 being disposed on the top of the vacuum forming chamber 1 and connected to the powder supply mechanism 3 ; a powder recovery mechanism 6 , the powder recovery mechanism 6 being disposed at the bottom of the vacuum forming chamber 1 and connected to the workbench 2 , and being used to recover unmelted TiAl alloy powder and scattered shot blasting powder; The controller is integrated outside the vacuum forming chamber 1 and is connected to the powder supply mechanism 3, the electron beam emission and focusing scanner, the shot blasting mechanism 5 and the powder recovery mechanism 6 through electrical signals, so as to adjust the parameters of the electron beam and the powder transportation.

[0035] This application maintains 1.0×10 -3 Pa-1.0×10 -4The vacuum degree of the Pa is used to reduce the oxidation of the metal powder and the interference of impurities, ensure the stability of the energy transmission of the electron beam, and avoid the pollution of the molten pool; the powder supply mechanism 3 comprises a mechanical scraper or a powder spreading roller, which can uniformly spread the metal powder on the substrate with a certain thickness and ensure the density of each layer of powder, thereby providing uniform raw material distribution for subsequent melting; the electron beam emission, gathering and scanning device 4 melts and forms the metal powder by emitting and focusing the electron beam, and heats the substrate and the surface of the part by emitting the defocused electron beam, thereby providing a heat source for high-temperature shot peening; the shot peening mechanism 5 is directly connected with the powder supply mechanism 3, directly calls the TiAl alloy powder used for printing as the shot peening medium, ensures the material homogeneity, and eliminates the risk of heterogeneous pollution; the powder recycling mechanism 6 realizes the recycling of the un-melted TiAl alloy powder and the scattered shot peening powder, and the recycled powder is re-supplied to the powder supply mechanism 3 for subsequent scanning, melting and shot peening strengthening, thereby realizing the closed-loop circulation of the homogenous powder. The controller cooperatively controls the parameters of the electron beam and the powder delivery. The device integrates the functions of electron beam melting, heating and shot peening in the vacuum forming chamber 1, reduces the size of the equipment, and the powder recycling mechanism 6 collects the metal powder under negative pressure at the bottom of the vacuum forming chamber 1, and the powder supply mechanism 3 supplies the powder at the top of the vacuum forming chamber 1, thereby realizing the closed-loop circulation of the TiAl alloy powder “printing-shot peening-recycling” and the in-situ combination of the electron beam powder bed melting and high-temperature shot peening strengthening.

[0036] As an implementable manner of the present application, the manufacturing device further comprises a rotatable Z-axis mechanism 7 connected with the workbench 2 for controlling the lifting and rotation of the part. The rotatable Z-axis mechanism 7 drives the workbench 2 to rotate, which can uniformly spray the shot peening powder to the surface of the part during the shot peening process, thereby facilitating to improve the strengthening effect of the surface of the part.

[0037] As an implementable manner of the present application, the shot peening mechanism 5 comprises a shot peening nozzle 51 and a high-pressure gas pipeline 52, one end of the high-pressure gas pipeline 52 is connected with an external gas, the other end is connected with the shot peening nozzle 51, and the high-pressure gas pipeline 52 is further connected with the powder supply mechanism 3. For the parts with a large surface area, multiple shot peening mechanisms 5 can be arranged, which can simultaneously perform shot peening on the surface of the large part, thereby improving the efficiency of the shot peening strengthening process.

[0038] As an implementable manner of the present application, the powder recycling mechanism 6 comprises a first negative pressure pipeline and a second negative pressure pipeline, the first negative pressure pipeline is connected with the workbench 2 to recycle the un-melted TiAl alloy powder, and the inlet of the second negative pressure pipeline is located around the workbench 2 to recycle the scattered shot peening powder. The powder recycling mechanism 6 can be connected with a multi-stage screen, and the recycled TiAl alloy powder can be transmitted to the powder supply mechanism 3 for reuse after being filtered.

[0039] The above technical solutions of the present application are described in detail below with reference to specific embodiments.

[0040] Example 1 Taking the manufacturing of aircraft engine blades as an example, the following steps are included: Step 1: Model building and data processing Use CAD software to create a three-dimensional digital model of an aircraft engine blade; The three-dimensional digital model was sliced ​​along the Z axis using slicing software, with the thickness of each layer set to 50 μm to generate layered scanning data.

[0041] Step 2: Equipment preparation and substrate preheating The titanium alloy substrate was mounted on the workbench 2 of the vacuum forming chamber 1, the vacuum forming chamber 1 was closed, the vacuum pump was started, and the vacuum degree of the forming chamber was pumped to 1.0×10 -4 Pa; The first sealing valve 41 is opened, and the controller controls the electron beam emission and focusing scanner 4 to emit a defocused electron beam with a scanning beam current of 30 mA and a scanning speed of 10 m / s to uniformly preheat the substrate surface to 550°C.

[0042] Step 3: Layer by layer Maintain the vacuum degree in the vacuum forming chamber 1 at 1.0×10 -4 Pa, close the control valve 53 and the second sealing valve 54, and the powder supply mechanism 3 delivers spherical TiAl alloy powder (composition: Ti 48wt%, Al 48wt%, Cr 2wt%, Nb 2wt%) with an average particle size of 75μm to the workbench 2 through the pipeline. The TiAl alloy powder is evenly spread on the preheated substrate using a scraper to a powder thickness of 50μm with a thickness error of ≤±5μm, forming a powder bed; like Figure 2 As shown, the controller controls the electron beam emission and focusing scanner 4 to emit a focused electron beam and scan the melted powder bed along the layered scanning data. The beam spot diameter of the focused electron beam is 200 μm, the focused beam current is 20 mA, the scanning speed is 2 m / s, and the scanning pitch is 70 μm. After the single-layer scanning melting is completed, the workbench 2 is lowered by 50 μm, and the powder spreading and scanning melting steps are repeated until the blade part is completely formed.

[0043] Step 4: Recover unmelted powder Close the first sealing valve 41 to allow the blade part to cool naturally to below 50°C in a vacuum environment; The controller activates the powder recovery mechanism 6 to recover the unmelted TiAl alloy powder through the first negative pressure pipe (negative pressure value: -0.1 MPa), and after filtering through a multi-stage sieve (pore size: coarse sieve 100 μm, fine sieve 20 μm), returns it to the powder supply mechanism 3; Step 5: In-situ high temperature shot peening After the blade parts have been polished and machined, they are re-fixed on the workbench 2, the control valve 53 and the second sealing valve 54 are closed, and the vacuum is drawn to 1.0×10 -4 Pa; like Figure 3 As shown, the first sealing valve 41 is opened, and the controller controls the electron beam emission and focusing scanner 4 to emit a defocused electron beam with a scanning beam current of 30 mA and a scanning speed of 10 m / s, so as to quickly scan and heat the surface of the blade part, raising the surface temperature to 500°C; like Figure 4 As shown, the shot peening mechanism 5 is turned on, the control valve 53 and the second sealing valve 54 are opened, the powder supply mechanism 3 only provides shot peening powder to the shot peening mechanism 5, and high-pressure gas enters the high-pressure gas pipeline 52 from the outside, and the gas pressure is controlled to be 0.5 MPa to accelerate the shot peening powder and spray it out through the shot peening nozzle 51. The shot peening powder is sprayed onto the surface of the blade part. At the same time, the workbench 2 is rotated by the rotatable Z-axis mechanism 7 (rotation speed 5 rpm) to achieve uniform shot peening strengthening of the part surface particles at high temperature. The shot peening time is set to 15 minutes.

[0044] Step 6: Shot blasting powder recovery After shot peening is completed, the control valve 53, the first sealing valve 41 and the second sealing valve 54 are closed, and the controller starts the powder recovery mechanism 6. The scattered shot peening powder is collected through the second negative pressure pipe (negative pressure value: -0.08MPa), filtered through a multi-stage sieve (pore size: coarse sieve 100μm, fine sieve 20μm), and then returned to the powder supply mechanism 3. The blade parts are naturally cooled to below 50°C and taken out to obtain the strengthened aircraft engine blades.

[0045] Example 2 Taking the manufacture of high-temperature connection brackets for spacecraft as an example, the following steps are included: Step 1: Model building and data processing Use CAD software to design a three-dimensional digital model of a spacecraft high-temperature connection bracket; The three-dimensional digital model was sliced ​​along the Z axis using slicing software, with the thickness of each layer set to 50 μm to generate layered scanning data.

[0046] Step 2: Equipment preparation and substrate preheating Choose a molybdenum alloy substrate (with a thermal expansion coefficient matching that of TiAl alloy) and spray a boron nitride coating on the surface to reduce the risk of adhesion; The molybdenum alloy substrate was mounted on the workbench 2 of the vacuum forming chamber 1, the vacuum forming chamber 1 was closed, the vacuum pump was started, and the vacuum degree of the forming chamber was pumped to 1.0×10 -4 Pa; The first sealing valve 41 is opened, and the controller controls the electron beam emission and focusing scanner 4 to emit a defocused electron beam with a scanning beam current of 30 mA and a scanning speed of 10 m / s to uniformly preheat the substrate surface to 550°C.

[0047] Step 3: Layer by layer Maintain the vacuum degree in the vacuum forming chamber 1 at 1.0×10 -4 Pa, close the control valve 53 and the second sealing valve 54, and the powder supply mechanism 3 delivers spherical TiAl alloy powder (composition: Ti 50.5wt%, Al 47wt%, W 2wt%, Nb 0.5wt%) with an average particle size of 45μm to the workbench 2 through the pipeline. The TiAl alloy powder is evenly spread on the preheated substrate using a scraper to a powder thickness of 50μm with a thickness error of ≤±5μm, forming a powder bed; The controller controls the electron beam emission and focusing scanner 4 to emit a focused electron beam and scan the melted powder bed along the layered scanning data. The beam spot diameter of the focused electron beam is 180 μm, the focused beam current is 25 mA, the scanning speed is 1 m / s, and the scanning pitch is 60 μm. After the single-layer scanning melting is completed, the workbench 2 is lowered by 50 μm, and the powder spreading and scanning melting steps are repeated until the connecting bracket parts are completely formed.

[0048] Step 4: Recover unmelted powder Close the first sealing valve 41 to allow the connecting bracket parts to cool naturally to below 50° C. in a vacuum environment; The controller activates the powder recovery mechanism 6 to recover the unmelted TiAl alloy powder through the first negative pressure pipe (negative pressure value: -0.1 MPa), and after filtering through a multi-stage sieve (pore size: coarse sieve 100 μm, fine sieve 20 μm), returns it to the powder supply mechanism 3; Step 5: In-situ high temperature shot peening After polishing and machining, the connecting bracket parts are fixed to the workbench 2 again, the control valve 53 and the second sealing valve 54 are closed, and the vacuum is pumped to 1.0×10 -4 Pa; Open the first sealing valve 41, and the controller controls the electron beam emission and focusing scanner 4 to emit a defocused electron beam with a scanning beam current of 30 mA and a scanning speed of 10 m / s, to rapidly scan and heat the surface of the connecting bracket parts, raising the surface temperature to 600°C. Turning on the shot blasting mechanism 5, opening the control valve 53 and the second sealing valve 54, the powder supply mechanism 3 only provides shot blasting powder for the shot blasting mechanism 5, high-pressure gas enters the high-pressure gas pipeline 52 from the outside, and the gas pressure is controlled to be 0.8 MPa to accelerate the shot blasting powder and spray it out through the shot blasting nozzle 51, and the shot blasting powder is sprayed to the surface of the connecting bracket part, at the same time, the workbench 2 is rotated (rotation speed 5 rpm) through the rotatable Z-axis mechanism 7 to realize uniform shot blasting strengthening of the surface microparticles of the part at high temperature, and the shot blasting time is set to 8 min.

[0049] Step 6, shot blasting powder recovery After shot blasting, the control valve 53, the first sealing valve 41 and the second sealing valve 54 are closed, the controller starts the powder recovery mechanism 6, collects the scattered shot blasting powder through the second negative pressure pipeline (negative pressure value: -0.08 MPa), filters through the multi-stage screen (pore size: coarse screen 100 μm, fine screen 20 μm), and returns to the powder supply mechanism 3, and the connecting bracket part is naturally cooled to below 50℃, and then taken out, thereby obtaining the strengthened high-temperature connecting bracket of the spacecraft.

[0050] In summary, the application utilizes focused electron beam scanning to melt TiAl alloy powder, and defocused electron beam scanning to heat the surface of the printed part, thereby reducing the temperature gradient and residual stress in the forming process, effectively inhibiting part cracking, and closing the surface cracks through high-temperature microparticle shot blasting. By utilizing the characteristics of high-temperature plasticity of TiAl alloy, the micro-cracks caused by room-temperature shot blasting are avoided, and at the same time, a deep plastic deformation and residual compressive stress layer is formed, thereby enhancing the surface strengthening effect, improving the fatigue strength of the part, effectively controlling the surface roughness, and reducing the defects of the TiAl alloy part. The application uses the same TiAl alloy powder as the printing material as the shot blasting medium, and realizes closed-loop utilization through powder recovery, thereby reducing material waste, avoiding pollution of the printing powder by heterogeneous powder, and the powder size is micron level, which belongs to microparticle shot blasting and can effectively control the surface roughness of the part. The application integrates electron beam selective melting forming and high-temperature microparticle shot blasting strengthening in the same vacuum forming chamber, and the high-temperature shot blasting strengthening and the electron beam powder bed melting forming share a set of powder supply mechanism and powder recovery mechanism, thereby realizing in-situ combination of part additive forming and shot blasting strengthening, seamlessly connecting part forming and strengthening, avoiding environmental exposure and heat loss, reducing part transfer steps, and further shortening the production cycle. Through the synergistic process design and device integration of electron beam selective melting and in-situ high-temperature microparticle shot blasting, the performance of the TiAl alloy component is improved, and the problems of easy cracking, poor surface quality and unsuitable traditional strengthening technology in TiAl alloy additive manufacturing are solved, and the application can be applied to the manufacturing of high-end parts in the fields of aerospace, energy equipment, etc.

[0051] The above description is merely an optional embodiment of the present application and does not limit the patent scope of the present application. All equivalent structural transformations made using the contents of the present application specification and drawings under the inventive concept of the present application, or direct / indirect application in other related technical fields are included in the patent protection scope of the present application.

Claims

1. A TiAl alloy electron beam selective melting and shot peening in-situ composite manufacturing method, characterized in that: The following steps are involved: S1. Create a three-dimensional digital model of the part to be printed, slice and layer it, and obtain layered scanning data; S2. Under vacuum conditions, spreading TiAl alloy powder to a set thickness on a preheated substrate to form a powder bed; S3. Melting the powder bed by focused electron beam scanning according to the layered scanning data to complete single-layer scanning melting; S4. Repeat steps S2 to S3 to complete scanning and melting layer by layer until the part is printed. After cooling, recover the unmelted TiAl alloy powder. S5. Under vacuum conditions, the printed part surface is heated by scanning with a defocused electron beam, and the TiAl alloy powder is used as shot peening powder to perform microparticle shot peening strengthening treatment on the heated part surface. After completion, the part surface is cooled and the scattered shot peening powder is recovered to obtain a finished TiAl alloy part.

2. The TiAl alloy electron beam selective melting and shot peening in-situ composite manufacturing method according to claim 1, characterized in that: In the step of spreading TiAl alloy powder on a preheated substrate with a set thickness under vacuum conditions to form a powder bed, the average particle size of the TiAl alloy powder is 30 μm-105 μm, the powder thickness is 40 μm-60 μm, and the vacuum condition is a vacuum degree of 1.0×10 -3 Pa-1.0×10 -4 Pa.

3. The TiAl alloy electron beam selective melting and shot peening in-situ composite manufacturing method according to claim 1, characterized in that: In the step of spreading TiAl alloy powder on a preheated substrate with a set thickness under vacuum conditions to form a powder bed, the substrate is preheated to 500°C-600°C by a defocused electron beam, the scanning beam current of the defocused electron beam is 25mA-35mA, and the scanning speed is 8m / s-12m / s.

4. The TiAl alloy electron beam selective melting and shot peening in-situ composite manufacturing method according to claim 1, characterized in that: In the step of melting the powder bed by scanning with a focused electron beam, the beam spot diameter of the focused electron beam is 150 μm-250 μm, the focused beam current is 15 mA-25 mA, the scanning speed is 1 m / s-3 m / s, and the scanning pitch is 50 μm-90 μm.

5. The TiAl alloy electron beam selective melting and shot peening in-situ composite manufacturing method according to claim 1, characterized in that: The step of scanning and heating the printed part surface by a defocused electron beam under vacuum conditions comprises: Maintain vacuum at 1.0×10 -3 Pa-1.0×10 -4 Pa, the surface of the printed part is heated to 400℃-600℃ by scanning with a defocused electron beam; wherein the scanning beam current of the defocused electron beam is 25mA-35mA, and the scanning speed is 8m / s-12m / s.

6. The TiAl alloy electron beam selective melting and shot peening in-situ composite manufacturing method according to claim 1, characterized in that: In the step of using the TiAl alloy powder as shot peening powder to perform microparticle shot peening strengthening treatment on the surface of the heated part, the shot peening pressure is controlled to be 0.3MPa-0.8MPa, and the shot peening time is 5min-20min.

7. A manufacturing device for TiAl alloy electron beam selective melting and shot peening in-situ composite, characterized in that: A manufacturing method for implementing the in-situ composite method of TiAl alloy electron beam selective melting and shot peening according to any one of claims 1 to 6, wherein the manufacturing device comprises: A vacuum forming chamber, wherein a workbench is provided inside the vacuum forming chamber for carrying a substrate; a powder feeding mechanism, the powder feeding mechanism being located in the vacuum forming chamber and connected to the workbench, and being used for spreading metal powder onto the substrate; An electron beam emission and focusing scanner is provided at the top of the vacuum forming chamber, and a scanning range of the electron beam emission and focusing scanner covers the forming area on the workbench; a shot blasting mechanism, the shot blasting mechanism being disposed on the top of the vacuum forming chamber and connected to the powder supply mechanism; a powder recovery mechanism, the powder recovery mechanism being disposed at the bottom of the vacuum forming chamber, the powder recovery mechanism being connected to the workbench, and being used to recover unmelted TiAl alloy powder and scattered shot blasting powder; A controller is integrated outside the vacuum forming chamber and is connected to the powder supply mechanism, the electron beam emission and focusing scanner, the shot blasting mechanism, and the powder recovery mechanism through electrical signals, so as to regulate the parameters of the electron beam and the powder transportation.

8. The manufacturing device for in-situ composite TiAl alloy electron beam selective melting and shot peening according to claim 7, characterized in that: The manufacturing device further comprises a rotatable Z-axis mechanism, which is connected to the workbench and is used to control the lifting and rotation of the parts.

9. The manufacturing device for in-situ composite TiAl alloy electron beam selective melting and shot peening according to claim 7, characterized in that: The shot blasting mechanism includes a shot blasting nozzle and a high-pressure gas pipeline. One end of the high-pressure gas pipeline is connected to the external air, and the other end is connected to the shot blasting nozzle. The high-pressure gas pipeline is also connected to the powder supply mechanism.

10. The TiAl alloy electron beam selective melting and shot peening in-situ composite manufacturing device according to claim 7, characterized in that: The powder recovery mechanism includes a first negative pressure pipe and a second negative pressure pipe. The first negative pressure pipe is connected to the workbench to recover unmelted TiAl alloy powder; the inlet of the second negative pressure pipe is located around the workbench and is used to recover scattered shot blasting powder.

Images