System and method for laser additive manufacturing of high-melt-difference two-dimensional gradient wing rudder

Abstract

The application relates to a system and method for laser additive manufacturing of a high-melting-difference two-dimensional gradient wing rudder, and belongs to the technical field of additive manufacturing. The high-melting-difference gradient wing rudder prepared by the method has a windward surface at the front end made of a high-temperature-resistant material, meets the demand of a service temperature greater than 1200 DEG C, and has two sides made of high-strength materials, meeting the performance demands of high bearing; a middle part is made of pure titanium alloy, meeting the demand of lightweight of components. Through optimized laser deposition process parameters and reasonable forming paths, the thermal stress of the gradient interface, the interlayer aggregation of the unmelted particle reinforced phase and the size of the equiaxed primary phase are reduced, so that the overall performance of the two-dimensional gradient wing rudder is improved. The laser additive manufacturing technology is used to add different contents and types of high-melting-point particles (melting point greater than 3000 DEG C) in the titanium alloy base body to enhance the performance of the base body. Compared with sample pieces prepared by other additive manufacturing technologies such as powder metallurgy technology, the two-dimensional gradient wing rudder has relatively high density and tensile strength, and finally obtains a two-dimensional gradient wing rudder without macroscopic defects such as cracking and porosity, and can meet the requirements of the aerospace field on lightweight, multi-performance / multi-function integrated attitude control wing rudders.

Description

Technical Field

[0001] This invention belongs to the field of laser additive manufacturing technology and uses a coaxial powder feeding laser additive manufacturing device. Specifically, it relates to a system and method for laser additive manufacturing of high melting point two-dimensional gradient wing rudders. Background Technology

[0002] High-melting-point materials generally possess high melting points, high strength, high hardness, and low coefficients of thermal expansion, making them suitable for use as the leading edge of wing rudders. Titanium alloys, on the other hand, have low density, high specific strength, high corrosion resistance, good toughness, and weldability, making them suitable for use as the middle and rear aft sections of wing rudders. Novel gradient materials can fully combine the advantages of both materials, exhibiting high temperature resistance, high strength, and lightweight properties, thus meeting the stringent service performance requirements of attitude control wing rudders.

[0003] Materials formed using traditional gradient material preparation techniques such as powder metallurgy often suffer from poor density, uneven distribution of reinforcing phases, and uncontrollable equiaxed primary phases, resulting in low thermal strength and poor toughness in components, severely hindering the capability leap of aircraft. In contrast, laser additive manufacturing technology, with its advantages of high energy density, high production efficiency, and integrated control of microstructure and properties at the two-phase interface, has become an effective means to solve the challenges of gradient material preparation. It possesses enormous market value and broad application prospects in the development of key components in aerospace and other fields.

[0004] Patent CN117123779A discloses a warhead shell and its powder hot isostatic pressing forming method, which realizes the forming of a tungsten alloy and titanium alloy composite warhead shell and ensures a dense metallurgical bond between the tungsten alloy shell head and the titanium alloy shell body. This method has low production efficiency, the microstructure of the tungsten-titanium alloy transition zone is uncontrollable, and it is prone to additive manufacturing process defects.

[0005] Patent CN111112619A discloses a method for ultrasonic-assisted laser additive manufacturing of two-dimensional titanium-based functionally graded materials. This method intervenes in the flow and solidification process of the molten pool by applying bottom ultrasound to promote the uniform distribution of ceramic particles in the titanium-based functionally graded material, break up coarse dendrites, and refine the microstructure. However, this method has low ultrasonic efficiency, a complex forming path, and its process parameters are not suitable for the fabrication of high melting point gradient fins. Therefore, it is necessary to rationally plan the scanning path and process parameters of the gradient region. Summary of the Invention

[0006] The purpose of this invention is to provide a method for laser additive manufacturing of high melting point two-dimensional gradient wing fins. This method has high production efficiency, and the formed high melting point two-dimensional gradient wing fins are free of macroscopic cracks and have high density. It can greatly reduce the thermal stress concentration caused by high energy density and the interlayer aggregation of unmelted particle reinforcing phases, and improve the bonding strength of the gradient interface, which can meet the service performance requirements of high-end equipment in the aerospace field.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A system for laser additive manufacturing of high melting point two-dimensional gradient rudders, the system comprising a protective gas 1, a powder feeder 2, a powder feeding cylinder 3, a CNC worktable 4, an industrial computer 5, a titanium alloy substrate 6, a coaxial powder feeding nozzle 7, a laser 8, and a cooling water circulation system 9.

[0009] The titanium alloy substrate 6 is fixed on the CNC worktable 4, 5-12 mm directly below the coaxial powder feeding nozzle 7. The protective gas 1 is high-purity argon, used to transport metal powder from the two powder feeding cylinders 3 on the dual-cylinder powder feeder 2 to the coaxial powder feeding nozzle 7, and to protect the molten pool and adjacent areas from oxidation. The laser 8 is connected to the coaxial powder feeding nozzle 7 and the industrial control computer 5. The cooling water circulation system is connected to the laser 8, the coaxial powder feeding nozzle 7, and the industrial control computer 5, and is used to cool the laser 8 and the coaxial powder feeding nozzle 7. When the protective gas 1 and the powder feeding cylinders 3 are turned on, the laser 8 generates a high-energy laser, which is transmitted to the coaxial powder feeding nozzle 7 through an optical fiber. The laser and the powder work together to form a molten pool on the titanium alloy substrate 6 and cool and shape it. According to the optimized scanning path and process parameters, a high melting difference two-dimensional gradient frigate is directly laser deposited to obtain the shaped sample 10.

[0010] A method for laser additive manufacturing of high-melting-point two-dimensional gradient wing rudders, the method comprising the following steps:

[0011] S1: Fix the polished, cleaned and dried titanium alloy substrate 6 horizontally on the CNC worktable 4, preheat it to 100-200°C and place it 5-12 mm directly below the coaxial powder feeding nozzle 7 to ensure that the laser and powder are focused on the upper surface of the titanium alloy substrate 6.

[0012] S2: High-melting-point powder and titanium alloy powder are dried at 100℃~150℃ for 4~6 hours, and then placed into two powder feeding cylinders 3 on the powder feeder 2. During the forming process, the composition ratio of the two materials is adjusted in real time according to the four different functional zones of the gradient wing rudder. Specifically:

[0013] The gradient wing fin is a plate-like integrated structure with a certain thickness in its XZ cross-section and a right-angled trapezoidal cross-section in its XY cross-section, including a right-angled triangle at the front and a square structure at the rear. The gradient wing fin has four functional zones: the forward zone at the windward end, the left side zone, the right side zone, and the middle zone. The left, right, and middle zones are distributed along the thickness direction of the XZ cross-section, and the forward zone at the windward end refers to the right-angled triangle at the front of the gradient wing fin. Optimized direct laser deposition process parameters are set to reduce interlayer aggregation of unmelted particle reinforcing phases and the size of equiaxed primary phases, promoting the melting / dissolution of particles. The process parameters are set as follows:

[0014] The windward end, area a, is made of high-temperature resistant material, with a laser power P of 600-700W and a scanning speed V of 100-120mm / min;

[0015] The b and d areas on both sides of the wing rudder are designed with high-strength materials. The laser power P of the right b area is 550-600W and the scanning speed V is 120-150mm / min. The laser power P of the left d area is 550-600W and the scanning speed V is 120-150mm / min. The parameters of the b and d areas on both sides are the same.

[0016] The middle section (c area) of the wing rudder is made of pure titanium alloy, with a laser power P of 450-500W and a scanning speed V of 150-200mm / min.

[0017] The system employs simultaneous feeding of high-melting-point powder and titanium alloy powder. The dual-cylinder powder feeder can dynamically adjust the feeding rate Q1 of titanium alloy powder and the feeding rate of high-melting-point powder in powder feeder 2. The total powder feeding rate Q = Q1 + Q2 is 2.0 to 2.5 g / min, and the mass fraction ω of high melting point powder conveyed per unit time can be adjusted arbitrarily between 0% and 50%.

[0018] S3: Turn on the cooling water circulation system 9, laser 8, protective gas 1 and powder feeder 2 in sequence; wherein, the laser power of laser 1 is 200-2000W and the scanning speed is 100-1000mm / min.

[0019] S4: When forming a gradient wing rudder on a titanium alloy substrate preheated to 100℃~150℃, in order to reduce the thermal stress caused by the temperature gradient and prevent the gradient wing rudder sample from cracking, it is divided into five forming zones, and the key points of the forming path are determined according to the zones. For the five forming zones of the gradient wing rudder, the laser head starts forming according to the bidirectional reciprocating scanning path. The five forming zones are: the windward end zone in the longitudinal XY section of the gradient wing rudder, the upper right corner zone, the lower left corner zone, the lower right corner zone, and the lower left corner zone, excluding the windward end zone. Among them, the upper right corner zone is designated as zone A, the lower left corner zone as zone B, the lower right corner zone as zone C, the lower left corner zone as zone D, and the windward end zone as zone E. The key points of the forming path include the upper right vertex O1, center point O2 (O2 is the center point of the square structure at the rear end of the XY cross section), lower left vertex O3, right center point O4, lower center point O5, upper center point O6, left center point O7, and lower left vertex O8 of the windward end in the XY plane of the gradient wing rudder, excluding the windward end.

[0020] The formation is carried out sequentially in the order of A area (O1 scanned to O2), B area (O2 scanned to O3), C area (O4 scanned to O5), left D area (O6 scanned to O7), and E area (O3 scanned to O8). The overlap rate λ between adjacent tracks is 50-60%, and the Z-axis lifting amount of the CNC worktable 4 is 0.1-1.5mm.

[0021] S5: During the experiment, every 10 to 30 layers were formed, the laser line energy density E = P / V was reduced by 0.1 to 1 W / (mm / min) (while keeping the scanning speed V constant) to reduce the temperature gradient between layers and prevent excessive heat input from causing residual thermal stress that could crack the sample. Finally, a high melting difference two-dimensional gradient wing rudder sample was obtained.

[0022] Furthermore, the high-melting-point powder in S2 is a near-spherical high-melting-point W, TiC, or Ta powder with a diameter of 15–53 μm, and the titanium alloy powder in S2 is a spherical Ti6Al4V powder with a diameter of 10–90 μm.

[0023] Furthermore, in the cooling water circulation system 9 of S3, the cooling water flow rate is 0.026 to 0.1 kg / s, and the protective gas 1 pressure is 0.3 to 0.5 MPa.

[0024] Furthermore, the high melting point two-dimensional gradient wing rudder of the shaped sample 10 belongs to a two-dimensional titanium-based functionally graded material. In the XY and XZ planes, it is a one-dimensional gradient transition of material composition, and in space, it belongs to a two-dimensional gradient transition.

[0025] Compared with the prior art, the present invention has the following advantages:

[0026] (1) Compared with traditional gradient material preparation technologies such as powder metallurgy, the present invention has a high material utilization rate, greatly shortens the production cycle, and the sample has relatively high density and tensile strength.

[0027] (2) Divide the sample into five forming areas A to E in the XY plane. The laser head starts forming according to the bidirectional reciprocating scanning path and forms in the order of area A (O1 scans to O2), area B (O2 scans to O3), area C (O4 scans to O5), area D (O6 scans to O7), and area E (O3 scans to O8) to reduce the thermal stress caused by the temperature gradient and prevent the sample from cracking.

[0028] (3) In the XZ plane, the sample is divided into four functional areas according to the different materials: the windward end area a, the two sides of the wing b and d, and the middle part of the wing c. Under the action of the optimized direct laser deposition process parameters, the interlayer aggregation of unmelted particle reinforcement phase and the size of equiaxed primary phase are reduced, and the melting / dissolution degree of particles is ensured to improve the mechanical properties of functionally graded materials. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the apparatus for laser additive manufacturing of high melting point two-dimensional gradient fins according to the present invention.

[0030] Figure 2 This is a design drawing of the five forming zones in the XY plane of the two-dimensional gradient wing rudder of the present invention.

[0031] Figure 3 This is a schematic diagram of the laser scanning path within the five forming zones of the present invention.

[0032] Figure 4 This is a schematic diagram of the laser scanning path between layers in this invention.

[0033] Figure 5 This is a schematic diagram of the four functional areas within the XZ plane of the two-dimensional gradient wing rudder of the present invention.

[0034] Figure 6 This is a high-melting-point two-dimensional gradient wing and rudder diagram of the final shaped sample prepared according to the present invention.

[0035] Figure 1 In the middle: 1. Protective gas; 2. Powder feeder; 3. Powder feeding cylinder; 4. CNC worktable; 5. Industrial computer; 6. Titanium alloy substrate; 7. Coaxial powder feeding nozzle; 8. Laser; 9. Cooling water circulation system; 10. Molded sample. Detailed Implementation

[0036] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0037] A method for laser additive manufacturing of high-melting-point two-dimensional gradient wing rudders, the method being direct laser deposition technology, specifically including the following steps:

[0038] (1) Fix the polished, cleaned and dried titanium alloy substrate 6 on the CNC worktable 4. The dimensions of the titanium alloy substrate 6 are length × width × height = 130 × 130 × 9 mm. 3 After preheating to 120℃, the powder is placed 9mm directly below the coaxial powder feeding nozzle 7. Near-spherical high-melting-point W powder (15–53μm) and spherical Ti6Al4V powder (10–90μm) are dried at 120℃ for 5 hours and then placed into two powder feeding cylinders 3 on the powder feeder 2. During the forming process, the composition ratio of the two materials is adjusted in real time according to the different functional zones of the gradient wing fin.

[0039] (2) In sequence, turn on the cooling water circulation system 9 with a flow rate of 0.05 kg / s, the laser 8, the protective gas 1 with a pressure of 0.3 MPa, and the powder feeder 2 with a total powder feeding rate of 2.0 g / min;

[0040] (3) Make the coaxial powder feeding nozzles follow the direction of the powder feeding nozzles. Figure 3 , Figure 4scanning according to the scanning path. The scanning path is specifically as follows: different forming zones adopt a "zigzag" scanning mode, and the inter-layer scanning mode adopts a bidirectional reciprocating mode.

[0041] (4) For the five forming zones of the gradient wing rudder, the laser head starts forming according to the bidirectional reciprocating scanning path, and performs forming in sequence in the order of Zone A (scanning from O1 to O2), Zone B (scanning from O2 to O3), Zone C (scanning from O4 to O5), Zone D (scanning from O6 to O7), and Zone E (scanning from O3 to O8). The overlapping rate λ between adjacent passes is 50%, and the lifting amount of the Z-axis of the CNC machine tool is 1.2 mm; for the four functional zones a to d of the gradient wing rudder, the windward end Zone a adopts 30wt.% W / Ti6Al4V composite material, with a laser power P of 600W and a scanning speed V of 100 mm / min; Zone b of the wing rudder adopts 10wt.% W / Ti6Al4V composite material, with a laser power P of 550W and a scanning speed V of 120 mm / min; Zone d of the wing rudder adopts 10wt.% W / Ti6Al4V composite material, with a laser power P of 550W and a scanning speed V of 120 mm / min; the middle part Zone c of the wing rudder adopts pure Ti6Al4V, with a laser power P of 500W and a scanning speed V of 150 mm / min.

[0042] (5) During the experiment, in order to reduce the temperature gradient between layers and prevent residual thermal stress caused by excessive heat input from cracking the sample, every 15 layers are deposited, the laser linear energy density E=P / V is reduced by 0.1 W / (mm / min) (ensuring that the scanning speed V remains unchanged), and finally the formed sample 10, the two-dimensional gradient wing rudder of high melting point difference tungsten-titanium alloy, is obtained.

[0043] (6) After all the functional zones are formed, the laser 8 is first turned off, and then the powder feeder 2 and the shielding gas 1 (high-purity argon) are turned off.

[0044] (7) The finally obtained formed sample 10, the two-dimensional gradient wing rudder of high melting point difference tungsten-titanium alloy, has a thickness of 9 mm, the thickness of zones b, c and d are all 3 mm, the length of the upper bottom edge is 70 mm, the length of the lower bottom edge is 100 mm, and the height is 50 mm. It belongs to a two-dimensional titanium-based functionally graded material, which has a one-dimensional gradient transition of material composition in the XY and XZ planes, and belongs to a two-dimensional gradient transition in space.

[0045] After testing, the bonding strength of the obtained formed sample 10 at the gradient interface can reach 821.2 MPa, while the tensile strength of the pure Ti6Al4V sample is about 950 MPa, that is, the interface strength coefficient of the high melting point difference tungsten-titanium alloy two-dimensional gradient wing rudder prepared by the present invention (UTS of the gradient sample / UTS of the pure Ti6Al4V sample ≥ 0.7) can meet the requirements of the aerospace field for lightweight, multi-performance / multifunctional integrated attitude control wing rudders.

[0046] The above embodiments are merely illustrative of the implementation methods of the present invention, but the scope of protection of the present invention should not be limited thereto. It should be noted that for those skilled in the art, any modifications or alterations made without departing from the concept of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for laser additive manufacturing of high-melting-point two-dimensional gradient wing rudders, characterized in that, The method is based on a system for laser additive manufacturing of high melting point two-dimensional gradient rudders. The system includes a protective gas (1), a powder feeder (2), a powder feeding cylinder (3), a CNC worktable (4), an industrial computer (5), a titanium alloy substrate (6), a coaxial powder feeding nozzle (7), a laser (8), and a cooling water circulation system (9). The titanium alloy substrate (6) is fixed on the CNC worktable (4) and located directly below the coaxial powder feeding nozzle (7). The protective gas (1) is high-purity argon gas, used to transport metal powder from the two powder feeding cylinders (3) on the dual-cylinder powder feeder (2) to the coaxial powder feeding nozzle (7) and to protect the molten pool and adjacent areas. To prevent oxidation; the laser (8) is connected to the coaxial powder feeding nozzle (7) and the industrial control computer (5); the cooling water circulation system is connected to the laser (8), the coaxial powder feeding nozzle (7) and the industrial control computer (5) to cool the laser (8) and the coaxial powder feeding nozzle (7); the protective gas (1) and the powder feeding cylinder (3) are opened, and the laser (8) generates a high-energy laser that is transmitted to the coaxial powder feeding nozzle (7) through the optical fiber. The laser and the powder work together to form a molten pool on the titanium alloy substrate (6) and cool and form it. According to the optimized scanning path and process parameters, a high melting difference two-dimensional gradient rudder is directly laser deposited to obtain a formed sample (10). The method includes the following steps: S1: Fix the titanium alloy substrate (6) horizontally on the CNC worktable (4), preheat it to 100-200°C and place it 5-12 mm directly below the coaxial powder feeding nozzle (7) to ensure that the laser and powder are focused on the upper surface of the titanium alloy substrate (6). S2: After drying the high melting point powder and titanium alloy powder, they are placed into two powder feeding cylinders (3) on the powder feeder (2). During the forming process, the composition ratio in the two powder feeding cylinders (3) is adjusted in real time according to the four different functional areas of the gradient wing rudder. The process parameters of direct laser deposition are set for different functional areas to reduce the interlayer aggregation of unmelted particle reinforcing phase and the size of equiaxed primary phase, and to promote the melting / dissolution degree of particles. Specifically: The four different functional areas are specifically divided as follows: the gradient wing rudder is a plate-shaped integrated structure with thickness in its XZ cross section and a right trapezoidal cross section in its XY cross section, including a right-angled triangle at the front end and a square structure at the rear end; the four functional areas of the gradient wing rudder are the front windward area, the left side of the wing rudder, the right side of the wing rudder, and the middle area of ​​the wing rudder, wherein the left side of the wing rudder, the right side of the wing rudder, and the middle area of ​​the wing rudder are distributed along the thickness direction of the XZ cross section, and the front windward area refers to the right-angled triangle part at the front end of the gradient wing rudder; The process parameters for the four different functional areas are as follows: The windward end, area a, is made of high-temperature resistant material, with a laser power P of 600-700W and a scanning speed V of 100-120mm / min; The b and d areas on both sides of the wing rudder are designed with high-strength materials. The laser power P of the right b area is 550-600W and the scanning speed V is 120-150mm / min. The laser power P of the left d area is 550-600W and the scanning speed V is 120-150mm / min. The parameters of the b and d areas on both sides are the same. The middle section (c area) of the wing rudder is made of pure titanium alloy, with a laser power P of 450-500W and a scanning speed V of 150-200mm / min. The composition ratio in the two powder feeding cylinders (3) is as follows: high melting point powder and titanium alloy powder are fed synchronously. The double-cylinder powder feeder (2) can dynamically adjust the powder feeding rate of titanium alloy powder in the powder feeder (2). and high melting point powder feeding rate Total powder delivery rate The flow rate is 2.0–2.5 g / min, representing the mass fraction of high-melting-point powder transported per unit time. It can be adjusted arbitrarily between 0% and 50%; The high-melting-point powders are near-spherical high-melting-point W, TiC, and Ta powders with a diameter of 15–53 μm, and the titanium alloy powders are spherical Ti6Al4V powders with a diameter of 10–90 μm. S3: Turn on the cooling water circulation system (9), laser (8), protective gas (1) and powder feeder (2) in sequence; S4: When forming a gradient wing rudder on a titanium alloy substrate, the gradient wing rudder is divided into five forming areas according to its structure, and the key points of the forming path are determined according to the division. For the five forming areas of the gradient wing rudder, the laser head starts forming according to the bidirectional reciprocating scanning path. The five forming zones are specifically: the windward end zone in the longitudinal XY section of the gradient wing rudder, the upper right corner zone, the lower left corner zone, the lower right corner zone, and the upper left corner zone, excluding the windward end zone. Among them, the upper right corner zone is designated as zone A, the lower left corner zone as zone B, the lower right corner zone as zone C, the upper left corner zone as zone D, and the windward end zone as zone E. The key points of the forming path include the upper right vertex O1, center point O2, lower left vertex O3, right center point O4, lower center point O5, upper center point O6, left center point O7, and lower left vertex O8 of the windward end in the XY plane of the gradient wing rudder, excluding the windward end. The scanning path is as follows: scans O1 along a zigzag pattern to O2 in A area, scans O2 along a zigzag pattern to O3 in B area, scans O4 along a zigzag pattern to O5 in C area, scans O6 along a zigzag pattern to O7 in D area, and scans O3 to O8 in E area in sequence. The overlap rate λ between adjacent tracks is 50-60%, and the Z-axis lifting amount of the CNC worktable (4) is 0.1-1.5mm. S5: During the forming process, for every 10 to 30 layers formed, the laser line energy density E=P / V is reduced by 0.1 to 1W / (mm / min). The scanning speed V is kept constant to reduce the temperature gradient between layers, and finally the formed sample (10) high melting difference two-dimensional gradient wing is obtained.

2. The method for laser additive manufacturing of a high-melting-point two-dimensional gradient wing rudder according to claim 1, characterized in that, In step S2, the drying temperature is 100℃~150℃ and the drying time is 4~6h.

3. The method for laser additive manufacturing of a high-melting-point two-dimensional gradient wing rudder according to claim 1, characterized in that, In step S3, the cooling water circulation system (9) has a cooling water flow rate of 0.026 to 0.1 kg / s and a protective gas (1) pressure of 0.3 to 0.5 MPa.

4. The method for laser additive manufacturing of a high-gap two-dimensional gradient wing rudder according to claim 1, characterized in that, The formed sample (10) is a high melting point two-dimensional gradient wing rudder belonging to two-dimensional titanium-based functionally graded materials. In the XY and XZ planes, it is a one-dimensional gradient transition of material composition, and in space, it is a two-dimensional gradient transition.

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