Laser additive manufacturing spray head, equipment and method for heterostructure parts

Abstract

The invention provides a laser additive manufacturing spray head, equipment and method for heterostructure parts, the spray head comprises a powder premixing mechanism, a gas powder mixing mechanism and a powder distributing mechanism, the upper end of a shell of the powder premixing mechanism is connected with a plurality of raw material powder input pipes, and a stirring screw rod is arranged in the powder premixing mechanism; the gas powder mixing mechanism comprises a gas powder mixing mechanism inlet, a gas spraying nozzle and a mixed powder outlet; the powder distributing mechanism comprises a powder distributing mechanism shell and a laser output channel, powder distributing mechanism channels are arranged on the powder distributing mechanism shell, the interior of the powder distributing mechanism shell is divided into three powder outlet cavities, and a powder outlet channel is arranged in each powder outlet cavity. Different component proportions or different types of powder are mixed in situ in the spray head, and the response time of powder component adjustment is short; a two-stage mixing mode is adopted, and the mixing mode of mechanically premixing composite gas is utilized, so that the uniformity of the mixed powder can be greatly improved.

Description

Technical Field

[0001] The present invention belongs to the field of laser processing equipment, and in particular relates to a nozzle, equipment and method for laser additive manufacturing of heterogeneous structure parts. Background Art

[0002] With the development of science and technology in my country, the mechanical equipment required by fields such as aerospace, marine vessels, and mining machinery needs to operate for long periods of time in extremely harsh environments. The performance requirements for mechanical equipment are becoming increasingly higher, and with them comes an increasing demand for high-performance materials in these fields. Taking mining machinery as an example, the middle trough of the scraper conveyor in the fully mechanized mining face is subjected to long-term friction and wear from coal and gangue. Therefore, the scraper conveyor needs to have extremely high hardness and strength. At the same time, the impact of coal and gangue also requires the scraper conveyor to have excellent plasticity and toughness. Therefore, it is necessary to develop and use high-strength and plasticity-synergistic materials to manufacture corresponding equipment components to cope with these complex working conditions.

[0003] As we all know, most methods of strengthening metals will lead to the loss of their plasticity and toughness, that is, the strength and plasticity of metal materials are inverted or contradictory. In recent years, studies have found that heterostructures can break through the constraints of the inverted relationship between strength and plasticity of traditional alloys, which is manifested as a simultaneous improvement in strength and plasticity. Heterostructures refer to structures with alternating soft and hard phases and gradual changes. The synergistic improvement of the strength and plasticity of heterostructures can be attributed to the contribution of stress-strain distribution, strain delocalization, back stress strengthening and other effects, which is the key to breaking through the strength and plasticity limits of existing metal materials. Therefore, the manufacture of parts with heterostructures is expected to solve the requirements of aerospace, marine ships, mining machinery and other fields for high-strength and plasticity synergy of equipment.

[0004] Since its inception, laser coaxial powder feeding additive manufacturing (APM) technology, with its unique manufacturing concept, has become one of the most anticipated disruptive technologies in the mechanical manufacturing field. Compared to the traditional "casting-forging-machining" method, APM offers advantages such as material conservation, low cost, high manufacturing precision, and a shortened R&D cycle. Most importantly, APM utilizes a layer-by-layer deposition process, enabling the fabrication of component-modified parts that are difficult to achieve with traditional methods. By leveraging the layered nature of APM, the composition of each deposited layer can be varied to achieve the fabrication of heterogeneous components. However, traditional APM technology requires a ball mill to pre-mix the various powders required for fabrication in a uniform ratio. The mixed powders are then fed sequentially into a powder feeder. This necessitates the removal of the existing powder from the feeder and the addition of the newly mixed powders each time the material composition is adjusted, significantly limiting the efficiency of APM technology for fabricating heterogeneous components. Summary of the Invention

[0005] In response to the technical problem that the above-mentioned laser coaxial powder feeding additive manufacturing equipment cannot efficiently transport powders of different components when used for the processing and manufacturing of heterogeneous structure parts, the present invention proposes a laser additive manufacturing nozzle, equipment and method for heterogeneous structure parts. The nozzle, equipment and method can in-situ mix the powders of multiple components transported by the powder input pipeline according to the material composition designed in the additive process, thereby efficiently processing high-strength and high-plasticity parts with heterogeneous structures.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is: A laser additive manufacturing nozzle for heterogeneous structure parts includes a pre-mixing mechanism, a gas mixing mechanism, and a powder separation mechanism. The pre-mixing mechanism includes a pre-mixing mechanism housing. The upper end of the pre-mixing mechanism housing is connected to multiple raw material powder input pipes, and the lower end is provided with a pre-mixing mechanism outlet. The pre-mixing mechanism is provided with a stirring screw. The gas powder mixing mechanism comprises a gas powder mixing mechanism housing, the gas powder mixing mechanism housing being provided with a gas powder mixing mechanism inlet connected to the pre-mixing powder mechanism outlet, a gas injection nozzle and a mixed powder outlet; The powder separation mechanism includes a powder separation mechanism housing and a laser output channel. The powder separation mechanism housing is provided with a powder separation mechanism channel connected to the mixed powder outlet. The powder separation mechanism housing is divided into three powder outlet chambers, and each powder outlet chamber is connected to a powder outlet channel.

[0007] Preferably, the stirring screw comprises a stirring shaft, on which spiral blades are provided.

[0008] Preferably, a scraper is provided on the outer edge of the spiral blade.

[0009] Preferably, the outer shell of the premixed powder mechanism is conical, and the width of the spiral blades gradually increases from bottom to top.

[0010] Preferably, a gas powder mixing chamber is provided in the outer shell of the gas powder mixing mechanism, and the gas powder mixing chamber includes a contraction section, a straight section and an expansion section. The inner diameter D at the inlet of the contraction section is 50-60 mm, and the inclination angle α of the contraction section is 25°; the diameter d of the straight section is 25-30 mm, the length m of the straight section is 105-115 mm, the inner diameter H at the outlet of the expansion section is 35-45 mm, and the inclination angle β of the expansion section is 10°.

[0011] Preferably, the three powder outlet channels are distributed around the laser output channel.

[0012] Preferably, a first partition and a second partition are provided in the powder separation mechanism channel, dividing the powder separation mechanism channel into three branch channels respectively connected to the powder discharge chambers.

[0013] Preferably, the bottom wall of the powder outlet channel and the bottom wall of the powder outlet chamber are both inclined toward the powder outlet channel.

[0014] Preferably, the powder separation mechanism further includes a cooling liquid channel.

[0015] The present invention also proposes a laser additive manufacturing device for heterogeneous structure parts, which includes a computer, a motion control system and a robotic arm, and the above-mentioned nozzle is installed at the front end of the robotic arm.

[0016] The present invention also provides a laser additive manufacturing method for heterogeneous structure parts, comprising the following steps: The raw material powder required for the first deposition layer is delivered to the nozzle through multiple sets of powder feeders. The raw material powder is evenly mixed inside the nozzle through mechanical stirring and gas injection. The nozzle moves along a preset trajectory while the laser and the mixed powder act to complete the first layer of deposition. The type and ratio of the raw material powder delivered by the powder feeder are changed, and the second layer of deposition is completed after even mixing. The above process is repeated to complete the additive manufacturing process of the entire part.

[0017] Compared with the prior art, the advantages and positive effects of the present invention are: 1. The laser additive manufacturing equipment for heterogeneous structure parts of the present invention adopts an in-situ powder mixing nozzle, and the response time of powder composition adjustment is short. Different component ratios or different types of powders are mixed in situ inside the nozzle, thus having the ability to quickly respond to the powder feeding amount and powder composition adjustment.

[0018] 2. The nozzle adopts a two-stage mixing mode, utilizing mechanical pre-mixing and compound gas mixing to significantly improve the uniformity of the mixed powder and avoid the structural segregation caused by inconsistent powder composition. To meet different material requirements, simply adjust the type of powder input in the input pipeline to mix powders with specific components for different application scenarios, thus providing the advantage of high flexibility.

[0019] 3. The nozzle has a simple structure, high reliability, and is not prone to powder clogging. The powder feeding gas and gas mixing gas used in the laser additive manufacturing equipment for heterogeneous structure parts are both argon gas with protective properties, which can prevent high-temperature oxidation of the powder during the powder mixing process and the additive manufacturing process, and the equipment has strong stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a working principle diagram of the laser additive manufacturing equipment for heterogeneous structure parts of the present invention; Figure 2 This is a schematic diagram of the structure of a nozzle for laser additive manufacturing of heterogeneous structure parts of the present invention; Figure 3This is a schematic diagram of the structure of the premixed powder mechanism of the laser additive manufacturing nozzle for heterogeneous structure parts of the present invention; Figure 4 A three-dimensional diagram of the stirring screw of the pre-mixing mechanism of the laser additive manufacturing nozzle for heterogeneous structure parts of the present invention; Figure 5 This is a schematic diagram of the gas-powder mixing mechanism of the nozzle for laser additive manufacturing of heterogeneous structure parts according to the present invention; Figure 6 A horizontal cross-sectional view of the powder separation mechanism of a nozzle for laser additive manufacturing of heterogeneous structure parts according to the present invention; Figure 7 A longitudinal cross-sectional view of the powder separation mechanism of a nozzle for laser additive manufacturing of heterogeneous structure parts according to the present invention; Figure 8 Schematic diagram of the working process of the laser additive manufacturing equipment for heterogeneous structure parts of the present invention; In the above figures: 1. Premixing powder mechanism; 11. Premixing powder mechanism housing; 12. Raw material powder input pipe; 13. Stirring screw; 131. Stirring shaft; 132. Motor; 133. Spiral blade; 134. Scraper; 14. Premixing powder mechanism outlet; 2. Gas powder mixing mechanism; 21. Gas powder mixing mechanism housing; 22. Gas powder mixing mechanism inlet; 23. Gas injection nozzle; 24. Mixed powder outlet; 25. Gas powder mixing chamber; 3. Powder separation mechanism; 31. Powder separation mechanism housing; 32. Laser output channel; 33. Powder separation mechanism channel; 34. First partition; 35. Second partition; 36. Third partition; 37. Fourth partition; 38. Powder discharge chamber; 39. Powder discharge channel; 4. Substrate; 5. CoCrFeMnNi high entropy alloy layer; 6. AlCoCrFeNi high entropy alloy layer. DETAILED DESCRIPTION

[0021] In order to better understand the present invention, the following is a detailed description with reference to the accompanying drawings and embodiments. Example 1

[0022] In this embodiment, a high-plasticity CoCrFeMnNi high-entropy alloy and a high-strength AlCoCrFeNi high-entropy alloy are selected as raw materials for additive manufacturing of heterogeneous structural parts.

[0023] like Figure 1 、 Figure 2As shown, a laser additive manufacturing nozzle for heterogeneous structure parts includes a premixing mechanism 1, a gas mixing mechanism 2, and a powder separation mechanism 3. Three powder feeders are respectively loaded with sufficient amounts of Co-Cr-Fe-Ni mixed powder and two elemental powders, Mn and Al. According to a set procedure, the three powders are first fed into the premixing mechanism 1: the Co-Cr-Fe-Ni mixed powder and the Mn elemental powder. There, they are initially mixed before being fed into the gas mixing mechanism 2. After a second uniform mixing, the powders are fed into the powder separation mechanism 3, where they are evenly divided into three paths. After being transported out of the powder separation mechanism 3, the mixed powders encounter a high-energy laser, completing a layer of deposition. The types of powders fed are adjusted to the Co-Cr-Fe-Ni mixed powder and the Al elemental powder, and the above process is repeated to complete the second layer of deposition.

[0024] like Figure 3 、 Figure 4 As shown, the premixing mechanism 1 includes a premixing mechanism housing 11. To facilitate mixing and collecting the raw materials inside, the premixing mechanism housing 11 is configured in a conical shape with a larger top and a smaller bottom. Multiple raw material powder input pipes 12 are connected to the upper end of the premixing mechanism housing 11. Each raw material powder input pipe 12 is connected to a powder feeder. The powder feeder uses high-purity argon as the conveying gas and delivers a fixed amount of raw material powder into the premixing mechanism 1 according to a preset ratio. In this embodiment, the powder feeder and raw material powder input pipes 12 are arranged in three groups, respectively delivering a Co-Cr-Fe-Ni mixed powder and two single-element powders of Mn and Al. A stirring screw 13 is provided within the premixing mechanism 1. The stirring screw 13 includes a stirring shaft 131 and a motor 132 that drives the stirring shaft 131 to rotate rapidly. The motor 132 is fixed to the upper portion of the premixing mechanism housing 11. A spiral blade 133 is provided on the stirring shaft 131. The width of the spiral blade 133 gradually increases from bottom to top. At the same time, a scraper 134 is provided on the outer edge of the spiral blade 133. During the stirring process, the stirring shaft 131 rotates rapidly under the drive of the motor 132, and the powder inside the premixed powder mechanism 1 is rotated and stirred by the spiral blade 133, while being lifted in the height direction. The scraper 134 located at the edge of the spiral blade 133 can drive the powder to rotate, so that multiple powders can be quickly mixed. The bottom end of the premixed powder mechanism housing 11 is provided with a premixed powder mechanism outlet 14. The mixed powder is discharged from the premixed powder mechanism outlet 14 and then falls into the gas powder mixing mechanism 2 for further mixing.

[0025] like Figure 5As shown, the gas-powder mixing mechanism 2 includes a gas-powder mixing mechanism housing 21. In this embodiment, the gas-powder mixing mechanism housing 21 is configured as a horizontal cylindrical structure, forming a gas-powder mixing chamber within. A gas-powder mixing mechanism inlet 22 is provided at the top of the gas-powder mixing mechanism housing 21, connected to the pre-powder mixing mechanism outlet 14. A gas injection nozzle 23 is provided on the left side, and a mixed powder outlet 24 is provided on the right end. The gas injection nozzle 23 is connected to an argon gas cylinder via a pipeline, and high-purity argon gas is introduced into the gas-powder mixing chamber 25 through the gas injection nozzle 23. High-purity argon gas can prevent oxidation of metal powder during the additive manufacturing process.

[0026] The gas powder mixing chamber is provided with a contraction section, a straight section and an expansion section in sequence from the inlet end to the outlet end, forming a cylindrical chamber that gradually contracts and then gradually expands. Specifically, the inner diameter D at the inlet of the contraction section is 50-60 mm, and the inclination angle α of the contraction section is 25°; the diameter d of the straight section is 25-30 mm, and the length m of the straight section is 105-115 mm; the inner diameter H at the outlet of the expansion section is 35-45 mm, and the inclination angle β of the expansion section is 10°. According to fluid mechanics theory, argon gas can form high-intensity turbulence in the gas powder mixing chamber with the above structure. Driven by the high-intensity gas turbulence, the pre-mixed powder can be quickly and evenly mixed to obtain a uniform and consistent mixed powder. The evenly mixed powder enters the powder separation mechanism 3 through the mixed powder outlet 24.

[0027] like Figure 6 、 Figure 7As shown, the powder separation mechanism 3 includes a powder separation mechanism housing 31 and a laser output channel 32. The laser output channel 32 is located within the powder separation mechanism housing 31 and extends from top to bottom through the powder separation mechanism housing 31. The laser light emitted by the laser enters the laser output channel 32 after being adjusted by the optical mirror system. The powder separation mechanism housing 31 is also provided with a powder separation mechanism channel 33 connected to the mixed powder outlet 24 of the gas powder mixing mechanism 2. The mixed powder evenly mixed by the gas powder mixing mechanism 2 enters the powder separation mechanism 3 through the powder separation mechanism channel 33. The powder separation mechanism channel 33 is provided with a first partition 34 and a second partition 35, which divide the powder separation mechanism channel 33 into three branch channels. The upper portion of the powder dispensing mechanism housing 31 is a hollow structure forming a powder dispensing chamber 38. The interior of the powder dispensing chamber 38 is divided into a first powder dispensing chamber 38, a second powder dispensing chamber 38, and a third powder dispensing chamber 38 by a first partition 34, a second partition 35, a third partition 36, a fourth partition 37, and a laser output channel 32. The three branch channels of the powder dispensing mechanism channel 33 connect to the first, second, and third powder dispensing chambers 38, respectively. Each powder dispensing chamber 38 is connected to a powder dispensing channel 39. The three powder dispensing channels 39 are uniformly distributed around the laser output channel 32, and the powder dispensing channels 39 transport the mixed powder to the outlet of the laser output channel 32. The bottom walls of the powder dispensing channels 39 and the bottom walls of the powder dispensing chamber 38 are both inclined toward the powder dispensing channels 39 to ensure that the powder can be completely transported out of the powder dispensing mechanism 3 under the action of gravity, preventing powder accumulation inside.

[0028] The powder separation mechanism 3 also includes a coolant channel, which surrounds the outside of the powder outlet channel 39. By supplying coolant into the coolant channel, the temperature of the powder separation mechanism 3 is controlled, thereby preventing high-temperature oxidation of the powder and extending the service life of the nozzle.

[0029] This embodiment also provides a laser additive manufacturing device for heterogeneous structure parts, including a computer, a motion control system and a robotic arm, with the above-mentioned nozzle installed at the front end of the robotic arm.

[0030] The laser additive manufacturing equipment for heterogeneous structure parts described in this embodiment uses an in-situ powder mixing nozzle, which has a short response time for adjusting powder composition. Different component ratios or different types of powders are mixed in situ within the nozzle, thus providing a fast response capability for adjusting powder feed quantity and powder composition. If the type and quality of powder fed are adjusted at the powder feeder end, the powder flow needs to pass through a longer powder feed pipeline to reach the coaxial powder feed nozzle, which requires a longer response time. The lack of powder mixing also results in uneven powder delivery.

[0031] The nozzle adopts a two-stage mixing mode, utilizing mechanical premixing and compound gas mixing, significantly improving the uniformity of the mixed powder and avoiding the phenomenon of structural segregation caused by inconsistent powder composition. To meet different material requirements, simply adjust the type of powder input into the input pipeline to mix powders with specific compositions for different application scenarios, thus offering the advantage of high flexibility. The nozzle has a simple structure, high reliability, and is not prone to powder clogging.

[0032] The powder feeding gas and gas mixing gas used in the laser additive manufacturing equipment for heterogeneous structure parts are both argon with protective properties, which can avoid high-temperature oxidation of powder during the powder mixing process and the additive manufacturing process, and the equipment has strong stability. Example 2

[0033] A laser additive manufacturing method for heterogeneous structure parts, such as Figure 1 and Figure 8 As shown, the process includes the following steps: First, additive manufacturing of a CoCrFeMnNi high-entropy alloy layer 5 is performed on a substrate 4. A powder feeder containing a Co-Cr-Fe-Ni mixed powder and a single Mn powder is driven by high-purity argon gas according to a preset program and transported to a pre-mixing mechanism 1, ensuring that the five elements Cr, Fe, Co, Ni, and Mn are delivered to the nozzle in an equiatomic ratio. Mechanical stirring and mixing are performed in the pre-mixing mechanism 1. Afterwards, the powder is thoroughly mixed by a gas mixing mechanism 2 to produce a uniform mixed powder. The mixed powder is then divided into three equal portions by a powder separation mechanism 3 and output through three powder outlet channels 39. Simultaneously, a laser interacts with the substrate 4, locally melting the surface of the substrate 4 to form a molten pool. The CoCrFeMnNi powder enters the molten pool, where it melts, solidifies, and metallurgically bonds with the substrate 4. Driven by a robotic arm, the nozzle moves along a predetermined path to complete the deposition of the first layer of the highly plastic CoCrFeMnNi high-entropy alloy layer 5. Subsequently, according to the preset program, the powder feeder containing the Mn single substance powder stops feeding powder, while the powder feeder containing the Al single substance powder and the Co-Cr-Fe-Ni mixed powder feeder convey the powder at a certain flow rate to ensure that the five elements Cr, Fe, Co, Ni, and Al are conveyed into the nozzle in an equiatomic ratio. The Co-Cr-Fe-Ni mixed powder and the Al single substance powder also undergo the above-mentioned mechanical premixing, gas mixing, and powder separation processes. The evenly mixed AlCoCrFeNi powder is conveyed out of the mixed powder nozzle and then interacts with the laser. Driven by the preset program, the nozzle moves according to a predetermined trajectory to complete the deposition of the second layer of high-strength AlCoCrFeNi high entropy alloy layer 6. In this embodiment, the two high entropy alloy deposition layers of CoCrFeMnNi and AlCoCrFeNi are deposited alternately according to a preset shape, and finally the processing and manufacturing of heterogeneous structure parts are completed.

[0034] The above description is merely a preferred embodiment of the present invention and does not constitute any other form of limitation to the present invention. Any person skilled in the art may utilize the technical contents disclosed above to change or modify them into equivalent embodiments with equivalent changes for application in other fields. However, any simple modification, equivalent change, and modification of the above embodiments made in accordance with the technical essence of the present invention without departing from the technical solution of the present invention shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A laser additive manufacturing nozzle for heterogeneous structure parts, characterized by: It includes a premixing powder mechanism, a gas mixing powder mechanism and a powder separation mechanism. The premixing powder mechanism includes a premixing powder mechanism shell. The upper end of the premixing powder mechanism shell is connected to multiple raw material powder input pipes, and the lower end is provided with a premixing powder mechanism outlet. A stirring screw is provided in the premixing powder mechanism; The gas powder mixing mechanism comprises a gas powder mixing mechanism housing, the gas powder mixing mechanism housing being provided with a gas powder mixing mechanism inlet connected to the pre-mixing powder mechanism outlet, a gas injection nozzle and a mixed powder outlet; The powder separation mechanism includes a powder separation mechanism housing and a laser output channel. The powder separation mechanism housing is provided with a powder separation mechanism channel connected to the mixed powder outlet. The powder separation mechanism housing is divided into three powder outlet chambers, and each powder outlet chamber is connected to a powder outlet channel.

2. The laser additive manufacturing nozzle for heterogeneous structure parts according to claim 1, characterized in that: The stirring screw comprises a stirring shaft, on which a spiral blade is arranged.

3. The laser additive manufacturing nozzle for heterogeneous structure parts according to claim 2, characterized in that: A scraper is provided on the outer edge of the spiral blade.

4. The laser additive manufacturing nozzle for heterogeneous structure parts according to claim 2, characterized in that: The outer shell of the premixed powder mechanism is conical, and the width of the spiral blades gradually increases from bottom to top.

5. The laser additive manufacturing nozzle for heterogeneous structure parts according to claim 1, characterized in that: A gas powder mixing chamber is provided in the shell of the gas powder mixing mechanism, and the gas powder mixing chamber includes a contraction section, a straight section and an expansion section. The inner diameter D at the inlet of the contraction section is 50-60 mm, and the inclination angle α of the contraction section is 25°; the diameter d of the straight section is 25-30 mm, the length m of the straight section is 105-115 mm, the inner diameter H at the outlet of the expansion section is 35-45 mm, and the inclination angle β of the expansion section is 10°.

6. The laser additive manufacturing nozzle for heterogeneous structure parts according to claim 1, characterized in that: A first partition and a second partition are provided in the powder separation mechanism channel, dividing the powder separation mechanism channel into three branch channels respectively connected to the powder discharge chambers.

7. The laser additive manufacturing nozzle for heterogeneous structure parts according to claim 6, characterized in that: The bottom wall of the powder outlet channel and the bottom wall of the powder outlet chamber are both inclined toward the powder outlet channel.

8. The laser additive manufacturing nozzle for heterogeneous structure parts according to claim 1, characterized in that: The powder separation mechanism further includes a cooling liquid channel.

9. A laser additive manufacturing device for heterogeneous structure parts, characterized by: The invention comprises a computer, a motion control system and a mechanical arm, wherein the front end of the mechanical arm is provided with the nozzle according to any one of claims 1 to 8.

10. A laser additive manufacturing method for heterogeneous structure parts, characterized in that: The steps include: The raw material powder required for the first deposition layer is delivered to the nozzle through multiple sets of powder feeders. The raw material powder is evenly mixed inside the nozzle through mechanical stirring and gas injection. The nozzle moves along a preset trajectory while the laser and the mixed powder act to complete the first layer of deposition. The type and ratio of the raw material powder delivered by the powder feeder are changed, and the second layer of deposition is completed after even mixing. The above process is repeated to complete the additive manufacturing process of the entire part.

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