Electron beam selective melting forming method of complex structure ti-al alloy vortex

Abstract

The application provides an electron beam selective melting forming method of a complex structure TiAl alloy vortex flow device, and specifically comprises the following steps: first, blank model making; second, part placement and support addition; third, forming process; fourth, post-processing process; after the forming is completed, the vortex flow device part is taken out from the forming cavity of the forming equipment. First, the part is subjected to powder cleaning, and residual electron beam selective melting TiAl alloy powder is recycled and reused through a PRS system; second, the part is subjected to heat treatment to optimize the performance of the part; the mounting edge of the part is machined; finally, the internal cavity, blade and other internals of the part are subjected to a grit flow process, and the external surface of the part is subjected to a sandblasting process. The application has the following advantages: through a complete set of process development, mainly including internal and contour forming processes and support setting, the electron beam selective melting forming preparation of the complex structure TiAl alloy vortex flow device part is realized.

Description

Technical Field

[0001] This invention relates to the field of metal additive manufacturing technology, and in particular to an electron beam selective melting forming method for a complex structure TiAl alloy eddy current generator. Background Technology

[0002] The vortex generator has a rotating structure with evenly distributed counter-rotating double-stage blades inside the cavity. The component is located at the head of the combustion chamber. The functions of the vortex generator in an aero-engine are: first, to create a low-pressure recirculation zone at the head of the combustion chamber to stabilize the flame; and second, to generate vortex air in the combustion chamber, thereby achieving complete combustion of the fuel by mixing it with the air.

[0003] Traditional vortex generators are made of high-temperature alloys. To improve the overall performance of aero engines, reducing component weight is a crucial and feasible approach. If TiAl alloy is used instead of high-temperature alloy, the component weight can be reduced by more than 50%, resulting in significant weight reduction benefits.

[0004] TiAl alloys (TiAl intermetallic compounds) are newly developed lightweight alloys both domestically and internationally. These alloys have a low density (3.9-4.2 g / cm³). 3 It features high strength, high modulus, good creep resistance and resistance to high-temperature gas corrosion, and can be used at temperatures up to 750℃ for extended periods. It can be used as a material for parts such as turbine blades and vortex generators, partially replacing nickel-based high-temperature alloy structural materials, significantly reducing structural weight and improving engine performance. It has broad application prospects in the aviation and aerospace fields, especially in hypersonic aircraft.

[0005] Due to the poor machinability of TiAl alloys, traditional forming processes struggle to produce TiAl alloy parts with good metallurgical quality and overall performance. In precision casting, factors such as the violent reaction between the TiAl alloy melt and the mold surface causing contamination, excessive growth of the α phase in the single-phase region, and Nb segregation leading to the retention of brittle phases (B2 phase) all worsen the room-temperature plasticity of TiAl alloys. In isothermal forging, the β phase, which is beneficial for high-temperature deformation, cannot be retained at room temperature, and the resulting B2 phase severely deteriorates room-temperature plasticity. In powder metallurgy, controlling the oxygen content is difficult; an oxygen content exceeding 1000 ppm significantly reduces room-temperature plasticity. These persistent limitations in traditional TiAl alloy forming technologies restrict the large-scale application of TiAl alloys.

[0006] Electron beam selective melting (EBM) has become a research hotspot due to its unique advantages in TiAl alloy forming. EBM uses a high-energy-density, fast-moving electron beam as a heat source, maintaining the forming temperature above 900℃ through preheating. This effectively prevents TiAl alloys from rapidly cooling below the ductile-brittle transition temperature. Furthermore, the micro-area metallurgical process effectively reduces grain size and suppresses microsegregation. Simultaneously, the absence of molds in the preparation process effectively avoids mold contamination, thereby improving the room-temperature plasticity of TiAl alloys and providing possibilities for forming high-performance TiAl alloy parts. Summary of the Invention

[0007] This invention employs electron beam selective melting forming technology to prepare TiAl alloy eddy current generator parts. This method overcomes the shortcomings of traditional manufacturing processes and has certain advantages for forming difficult-to-machine alloys and complex structural parts using traditional processes. This invention fully considers the forming process of TiAl eddy current generator parts, ensuring internal density and surface finish of the contours. It also incorporates support design for part forming, facilitating subsequent removal while ensuring part forming quality.

[0008] The purpose of this invention is to provide an electron beam selective melting forming method suitable for complex structure TiAl alloy eddy current generators. It fully considers the forming process of TiAl eddy current generator parts, ensures the internal density of the parts and the surface finish of the contours, and also carries out the support design for part forming, which facilitates the subsequent removal while ensuring the forming of the parts.

[0009] This invention provides a method for selective electron beam melting and forming of complex structure TiAl alloy eddy current generators, specifically including: I. Development of the rough model According to the design requirements, the upper and lower surfaces of the mounting edge need to be assembled with other parts, and the surface roughness requirement is Ra1.6. Normal printing using laser selective melting cannot guarantee this surface roughness. A certain allowance is reserved on the upper and lower surfaces of the mounting edge, and the surface roughness will be improved later by machining the allowance of the mounting edge.

[0010] II. Parts Placement and Support Addition When the converging section outlet of the eddy current generator part is placed vertically downwards, a large area of ​​unsupported surface exists inside the cavity, with a significant height difference. Supports are required, and their insertion depth into the part is considerable, making support removal and surface grinding relatively difficult. When the converging section outlet of the eddy current generator part is placed vertically upwards, its internal blades form an angle of 45°-65° with the horizontal direction. An angle greater than 45° allows for self-forming. In this case, supports are needed at the edges of the inner and outer ring channels, the inner and outer ring blades, and the outer ring blades. However, the support height is small, and subsequent removal is simple, making this placement method feasible. In electron beam selective melting technology for forming TiAl alloys, to prevent "powder blowing" during the forming process, preheating scanning is required. Before melting each layer of powder, a high-current, defocused electron beam rapidly scans the powder layer, ensuring the powder layer does not collapse, causing slight sintering of the powder to obtain sufficient impact resistance before selective melting. At this stage, the slightly sintered powder provides some support, but to ensure stable part forming, a certain amount of support is needed to work in conjunction with the slightly sintered powder to complete part fabrication. Thin-walled contour supports with a thickness of 0.2-0.5 mm are used at the part mounting edge. These contour supports are inclined to the substrate, avoiding direct contact with the part's outer surface if vertically positioned. Multiple layers of thin-walled contour supports are generated from the inside out on the lower surface of the mounting edge. The contact point between the contour supports and the lower surface of the vortex generator mounting edge is serrated, inserting 0.1 mm into the part, facilitating removal while ensuring a secure connection. To further facilitate removal of the contour supports at the mounting edge, the thin-walled contour supports are designed with a hollow structure, further reducing their strength. Thin-walled contour supports with a thickness of 0.2-0.5 mm are also used on the outer annular surface of the vortex generator inlet, and these supports are vertically connected to the substrate. Multiple thin-walled contour supports are generated from the inside out on the outer annular surface. The contact point between the contour supports and the lower surface of the eddy current generator mounting edge is serrated, with an insertion depth of 0.1mm, facilitating removal while ensuring a secure connection. At the suspended position of the eddy current generator blade tip, a cross-shaped plate support with a thickness of 0.2-0.5mm is added to ensure stable support growth perpendicular to the substrate and prevent warping.

[0011] III. Molding Process During the part forming process, the scanning path first scans the core, then the outer contour; contour supports and line supports are scanned only from the core. This scanning method ensures the forming accuracy and efficiency of the part, while also making the supports easier to remove, thus improving manufacturing efficiency. In the height direction of the eddy current part, due to the difference in the perimeter of the contour cross-section at different heights, different beam counts are selected. The combination of a small outer beam and a large sub-outer beam ensures contour smoothness while also improving surface density.

[0012] This invention provides a laser selective melting forming scheme for complex TiAl alloy eddy current generators. With appropriate placement, support settings, and process parameter control, it ensures the surface finish and internal density of the parts, while facilitating the removal of supports.

[0013] IV. Post-processing technology After forming, the eddy current generator part is removed from the forming cavity of the forming equipment. First, the part is cleaned of powder, and the residual electron beam selective melting TiAl alloy powder is recycled and reused through the PRS system. Second, the part is heat-treated to optimize its performance. The mounting edge of the part is machined. Finally, abrasive flow process is carried out on the internal parts such as the cavity and blades of the part, and sandblasting process is carried out on the outer surface of the part.

[0014] Advantages of this invention: Through the development of a complete set of processes, including the forming processes of the interior and contours, as well as the support settings, the electron beam selective melting forming of complex structure TiAl alloy eddy current generator parts was achieved. Attached Figure Description

[0015] Figure 1 Schematic diagram of eddy current generator components; Figure 2 Schematic diagram of adding margin for eddy current generator parts; Figure 3 Add a front view to the vortex support; Figure 4 Add bottom view to vortex support; Figure 5 : Schematic diagram of the eddy current generator component profile parameter setting area. Detailed Implementation

[0016] The present invention will be further explained below with reference to specific implementation schemes, but it is not limited to the present invention. The structures, proportions, sizes, etc. shown in the accompanying drawings are only used to complement the content disclosed in the specification, so as to enable those skilled in the art to understand and read, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modification of the structure, change of the proportion relationship or adjustment of the size, without affecting the effect and purpose that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0017] like Figure 1 As shown, the vortex generator has a rotating structure. The parts have an inner ring channel and an outer ring channel. The inside of the channel is an inner ring blade and an outer ring blade. The middle of the part is the mounting edge, and the bottom of the part is the converging section outlet.

[0018] Step 1: Use modeling software to create a 3D model of the eddy current generator. Extrude the upper and lower surfaces of the mounting edge by 1mm each, resulting in a 2mm thicker mounting edge. Figure 2 As shown.

[0019] Step 2: Import the part's digital model into the model processing software and add support.

[0020] The part was manufactured using electron beam selective melting technology. The part placement and overall support addition scheme are as follows: Figures 3-4 As shown, the converging section outlet of the vortex generator component is placed vertically upwards. Supports are added to the mounting edge, outer edge of the inlet, inner ring blade edge, and outer ring blade edge of the vortex generator. At the mounting edge, a thin-walled profile support with a thickness of 0.3mm is used. The profile support is inclined to the base plate to avoid direct contact with the outer surface of the component if placed vertically. Four layers of thin-walled profile supports are offset from the inside to the outside on the lower surface of the mounting edge. The contact point between the profile support and the lower surface of the vortex generator mounting edge is serrated, inserting 0.1mm into the component, facilitating removal while ensuring a secure connection. To further facilitate removal of the profile support at the mounting edge, the thin-walled profile support is designed as a hollow structure, further weakening its strength. A thin-walled profile support with a thickness of 0.3mm is also used on the outer annular surface of the vortex generator inlet, and this support is vertically connected to the base plate. Multiple thin-walled contour supports are generated from the inside out on the outer annular surface. The contact point between the contour supports and the lower surface of the eddy current generator mounting edge is serrated, with an insertion depth of 0.1mm, which facilitates removal while ensuring a firm connection. At the suspended position of the eddy current generator blade tip, a cross-shaped plate support with a thickness of 0.3mm is added to ensure that the support grows stably perpendicular to the substrate and will not warp.

[0021] Step 3: Use software to slice and fill the eddy current model after adding supports, set specific process parameters, and generate a .cli format processing file.

[0022] The substrate was preheated to 1050℃ for 30 minutes. The powder layer thickness was 0.5mm. After powder deposition, preheating was performed using the following process: electron beam current 8mA, scanning speed 2m / s, 10 scans. After preheating, melting and shaping began using the following process: electron beam current 6mA, scanning speed 0.8m / s, 2 melts. After melting, energy compensation was performed again using the preheating process before continuing powder deposition for the next layer.

[0023] During the part forming process, the scanning path first scans the core, then the outer contour; contour supports and line supports are scanned only from the core. This scanning method ensures the forming accuracy and efficiency of the part, while also making the supports easier to remove, thus improving manufacturing efficiency. In the height direction of the eddy current part, due to the difference in the perimeter of the contour cross-section at different heights, different beam counts are selected. The combination of a small outer beam and a large sub-outer beam ensures contour smoothness while also improving surface density. Specific areas include... Figure 5 As shown in Table 1: Step 4: Import the processing file described in Step 3 into the electron beam selective melting forming equipment to form the part.

[0024] Step 5: Remove powder and support from the parts. The remaining electron beam selective melting TiAl alloy powder is recycled and reused through the PRS system until the powder is completely cleaned.

[0025] Step 6: The parts undergo heat treatment. The heat treatment process is as follows: 1310-1340℃ / 4h, air cooling + 900-930℃ / 8h, furnace cooling.

[0026] Step 7: Machining the mounting edges of the part. Roughing: spindle speed 300 r / min, feed 0.1 mm / r, depth of cut 0.3 mm; Finishing: spindle speed 300 r / min, feed 0.1 mm / r, depth of cut 0.1 mm.

[0027] Step 8: Perform abrasive flow machining on the part, with the following parameters: abrasive volume 500 inches. 3 Pressure 6 MPa, cycle 4 times.

[0028] Step 9: Perform sandblasting on the outer surface of the part to further improve the surface finish.

[0029] Matters not covered in this invention are common knowledge.

[0030] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for selective electron beam melting and forming of a complex structure TiAl alloy eddy current generator, characterized in that: Specifically, it includes: I. Development of the rough model According to the design requirements, the upper and lower surfaces of the mounting edge need to be assembled with other parts, and the surface roughness requirement is Ra1.

6. Normal printing using laser selective melting cannot guarantee this surface roughness. A certain amount of allowance is reserved on the upper and lower surfaces of the mounting edge, and the surface roughness will be improved later by machining the allowance of the mounting edge. II. Parts Placement and Support Addition When the converging section outlet of the eddy current generator part is placed vertically downwards, there is a large area of ​​unsupported surface inside the cavity with a significant height difference, requiring additional support. Furthermore, the support penetrates deeply into the part, making its removal and surface grinding relatively difficult. When the converging section outlet of the eddy current generator part is placed vertically upwards, its internal blades form an angle of 45° to 65° with the horizontal direction. An angle greater than 45° allows for self-forming. In this case, supports are needed at the edges of the inner and outer ring channels, the inner and outer ring blades. Since selective electron beam melting (SEBLM) for TiAl alloy forming requires preheating scanning before melting each powder layer, a high-current, defocused electron beam is used to rapidly scan the powder layer to achieve slight sintering and sufficient impact resistance before selective melting. To ensure stable part forming, a certain amount of support is used in conjunction with the slightly sintered powder to complete the part preparation. III. Molding Process During the part forming process, the part scanning path is to first scan the core and then scan the outer contour; contour support and line support only scan the core; in the height direction of the eddy current part, due to the difference in the perimeter of the contour section in different height directions, different beam number settings are selected. The outer small beam + the second outer large beam ensure the contour smoothness while improving the density of the surface area. IV. Post-processing technology After forming, the eddy current generator part is removed from the forming cavity of the forming equipment. First, the part is cleaned of powder, and the residual electron beam selective melting TiAl alloy powder is recycled and reused through the PRS system. Second, the part is heat-treated to optimize its performance. The mounting edge of the part is machined. Finally, abrasive flow process is carried out on the cavity, blades and other internal parts of the part, and sandblasting process is carried out on the outer surface of the part.

2. The electron beam selective melting forming method for complex structure TiAl alloy eddy current generators according to claim 1, characterized in that: In step two, part placement and support addition, to ensure stable part forming, a certain amount of support is set up in conjunction with slightly sintered powder to complete part preparation. At the part mounting edge, thin-walled contour supports with a thickness of 0.2-0.5 mm are used. The contour supports are inclined and connected to the substrate to avoid direct contact with the outer surface of the part if set vertically. Multiple layers of thin-walled contour supports are generated from the inside out on the lower surface of the mounting edge. The contact point between the contour supports and the lower surface of the eddy current generator mounting edge is serrated, inserting 0.1 mm into the part. The thin-walled contour supports... The structure is designed to be hollow, further weakening its strength; thin-walled contour supports with a thickness of 0.2-0.5mm are also used on the outer annular surface of the vortex inlet, and these supports are vertically connected to the base plate; multiple layers of thin-walled contour supports are generated from the inside to the outside on the outer annular surface, and the contact point between the contour supports and the lower surface of the vortex mounting edge is serrated, with the inserted parts inserted 0.1mm, which facilitates removal while ensuring a firm connection; at the suspended position of the vortex blade head, a cross-shaped plate support with a thickness of 0.2-0.5mm is added.

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