Centripetal turbine with end teeth and large-twist blades and selective laser melting forming method of centripetal turbine

Abstract

The invention belongs to the technical field of laser additive manufacturing forming, and discloses a centripetal turbine with end teeth and large twisted blades and a selective laser melting forming method thereof.The centripetal turbine comprises a centripetal turbine disc, the upper end and the lower end of the centripetal turbine disc are provided with a front end tooth structure and a rear end tooth structure, and the front end tooth structure is used for being connected with a gas compressor rotor and transmitting torque; the inner side of the front end tooth structure is provided with an annular boss, the front end threaded hole and the rear end threaded hole are connected with a rotor front pull rod and a rotor rear pull rod respectively so that axial tensioning of the centripetal turbine can be achieved, the rear end threaded hole is communicated with a cavity formed in the centripetal turbine disc, and the axial size of the cavity is not smaller than 1 / 2 of the length of the centripetal turbine disc. The average wall thickness of the centripetal turbine disc in the area where the cavities are located is not larger than 8 mm. The wall face of the cavity is provided with a circle of evenly-distributed vent holes, and the centripetal turbine comprises large-distortion centripetal turbine blades evenly distributed in the circumferential direction. After the blade angle and the blade thickness are changed, the working efficiency of the turbine is improved by 8.5%; after the topological optimization design, the weight of the turbine is reduced by 20%; the centripetal turbine structure is machined through the selective laser melting additive manufacturing technology, the centripetal turbine structure can highly meet the aerodynamic performance calculation result, the turbine working efficiency is improved, the weight of the centripetal turbine structure is reduced, the small-batch production cost at the initial stage of product research and development is reduced, and the centripetal turbine manufacturing period is greatly shortened.

Description

Technical Field

[0001] The present invention belongs to the technical field of laser additive manufacturing, and relates to a centripetal turbine manufactured by laser additive manufacturing, and in particular to a centripetal turbine with end teeth and large twisted blades and a laser selective melting forming method thereof. Background Art

[0002] Selective laser melting technology is an advanced laser additive manufacturing technology developed based on the basic principle of prototype manufacturing technology. This technology uses special software to slice and layer the three-dimensional digital model of the part, obtain the contour data of each section, and then use a high-energy laser beam to selectively melt the metal powder layer by layer according to the contour data. The three-dimensional solid parts are manufactured by layer-by-layer powder laying, melting, solidification and accumulation. Since this technology can directly sinter high-melting-point metals into metal parts, and generate complex and high-strength parts that are difficult to process by traditional cutting methods, it has extremely high application value in the preparation of aerospace devices, aircraft engine parts, etc.

[0003] The centrifugal turbine, also known as the radial turbine, has the advantages of small size, light weight, compact structure, large single-stage power addition, and high efficiency in a small power range. It has been widely used in power equipment such as small aircraft engines, aircraft engine auxiliary power units, and small and medium-power gas turbines. At present, an important application direction of the centrifugal turbine is to be installed on a micro-turbine engine of 5 to 20 cm to provide power for air weapon platforms such as micro-cruise missiles, drones, and target drones. The traditional manufacturing method of producing centrifugal turbines usually uses a casting process to prepare the blank, and then uses a mechanical finishing process to remove the material locally to achieve the final delivery state. The service environment of the centrifugal turbine is usually harsh, and it will be subjected to the combined action of centrifugal force, thermal stress, gas force and other loads during the working process. In order to make the delivered turbine rotor meet the requirements of static strength, fatigue resistance, and creep resistance, the fine-grained casting process is currently usually used to prepare the centrifugal turbine blank. This process is difficult, and defects such as pores, cracks, inclusions, and local grain size not meeting the standard are prone to occur during the casting process, and the casting qualification rate is low. On the other hand, the casting process requires that the geometric shape of the part is as convenient as possible for casting. These include controlling the bend angle, transition angle and section thickness, avoiding large plane areas, and reserving shrinkage margins. The above requirements will limit the design of the centripetal turbine structure, especially the geometric characteristic parameter design of the blades, resulting in the turbine being unable to meet the expected performance indicators of the design. In addition, the casting process requires the manufacture of molds before production, which has complicated steps, high costs for small-batch production of parts, and long preparation cycles, which usually slows down the progress of product development in the early stages.

[0004] Therefore, the laser selective melting additive manufacturing technology with extremely high design freedom has brought great advantages to the optimization design and rapid prototyping of the centripetal turbine structure. By utilizing the manufacturing advantages of laser selective melting additive manufacturing technology, on the one hand, the limitations of the processing technology in the process of centripetal turbine structure optimization are reduced, the blade design freedom is higher, the structural weight is reduced and the turbine performance is improved; on the other hand, the processing cycle of parts can be greatly shortened, effectively reducing product development costs and accelerating the progress of new product development.

[0005] However, the centrifugal turbine is different from a single blade structure. Its structure is three-dimensional and has more structural features, such as end teeth, twisted blades, cavities, etc. Without reasonable process and process parameters, it is impossible to manufacture qualified centrifugal turbine products. Summary of the invention

[0006] In order to solve the above problems, the present invention proposes a centripetal turbine with end teeth and large twisted blades and a laser selective melting forming method thereof. The centripetal turbine can be efficiently produced through an additive manufacturing method, and due to the different process methods, blades with larger twisting angles can be used, and the end tooth structure can be pre-formed with the help of the technical advantages of additive manufacturing, thereby reducing the workload of end tooth processing, reducing product production costs and greatly shortening the manufacturing cycle; the present invention provides detailed process and process parameters, so that the centripetal turbine product can be formed by laser selective melting and have qualified quality.

[0007] The technical solution of the present invention is as follows:

[0008] A centrifugal turbine with end teeth and large twisted blades, comprising a centrifugal turbine disk, wherein the centrifugal turbine disk has a narrow and low raised annular belt near the edge of the disk, and the raised annular belt is used to provide a grinding margin for the centrifugal turbine in a dynamic balancing test; the upper and lower ends of the centrifugal turbine disk have a front tooth structure and a rear tooth structure, the front tooth structure is used to connect to the compressor rotor and transmit torque, and the rear tooth structure is used to connect to the rear-stage turbine rotor and transmit torque; the front tooth structure has an annular boss on the inner side, and the inner surface of the annular boss is a front threaded hole; the rear tooth structure has a rear threaded hole on the inner side; the front threaded hole and the rear threaded hole are respectively connected to the front pull rod and the rear pull rod of the rotor to realize the centrifugal The turbine is axially tightened; the rear end threaded hole is connected to the cavity arranged inside the centripetal turbine disk; the axial dimension of the cavity is not less than 1 / 2 of the length of the centripetal turbine disk, and the average wall thickness of the centripetal turbine disk in the area where the cavity is located is not more than 8mm; the wall surface of the cavity is provided with air vents evenly distributed around the circumference, and the air vents provide a circulation path for cold air, and the cold air enters the cavity to cool the turbine disk; the centripetal turbine includes circumferentially evenly distributed large twisted centripetal turbine blades, the ratio of the maximum height of the centripetal turbine blades to the axial length is not more than 0.5, the difference between the inlet geometric angle and the outlet geometric angle of the centripetal turbine blades is not less than 60°, and the radius of the arc of the trailing edge of the centripetal turbine blades is not more than 1.5mm.

[0009] A laser selective melting forming method for a centripetal turbine with end teeth and large twisted blades comprises the following steps:

[0010] S1: Model the aforementioned centrifugal turbine with end teeth and large twisted blades in a 3D modeling software. During the modeling process, the end teeth structures at both ends are designed with allowances. Then, the established centrifugal turbine geometric model is imported into the supporting software of the laser selective melting forming equipment.

[0011] S2: Based on the centripetal turbine geometric model, a centripetal turbine process model is created and optimized, and sufficient supports are set in the centripetal turbine process model to reinforce the parts of the centripetal turbine that are prone to collapse during the printing process;

[0012] S3: Set the working parameters in the supporting software of the laser selective melting forming equipment: select the printing material as GH4251 high temperature alloy, set the printing process parameters, including: ambient atmosphere, layer thickness, laser power, scanning speed, scanning spacing, scraper type, substrate type, substrate thickness; then slice the centripetal turbine process model file in the software, divide it into several two-dimensional layers with each layer thickness being the thickness of the alloy powder layer, and save the slice file;

[0013] S4: Import the model slice file into the laser selective melting equipment, load the alloy powder into the powder cavity of the equipment, install the substrate on the forming platform, adjust the position of the forming substrate and install the scraper, close the equipment door, and provide the equipment with an environmental atmosphere;

[0014] S5: Turn on the laser to print out the centripetal turbine blank;

[0015] S6: Clean the powder on the surface of the centrifugal turbine blank and the substrate, and place the assembly of the substrate and the centrifugal turbine blank into a heat treatment furnace to perform stress relief, hot isostatic pressing, solution treatment and aging treatment in sequence;

[0016] S7: cutting the centripetal turbine blank from the base plate, and removing all supports of the centripetal turbine blank;

[0017] S8: The end teeth and other required areas of the centrifugal turbine blank are machined to achieve the final delivery state.

[0018] Furthermore, in S2, the part model is placed in a direction perpendicular to the central axis of the printing work platform to ensure the quality and consistency of the blade forming of the part; the parts are placed according to the principle of "small on top and large on bottom", that is, the blade inlet is placed downward on the work platform.

[0019] Furthermore, in S2, the auxiliary support setting of the part includes three parts: the first part of the support is set between the inlet side of the centripetal turbine and the working platform, which is used to support the blades and the entire wheel of the centripetal turbine, and an easily removable block support is set at a position that is not easy to remove, and a solid support is set at a locally easy-to-remove position; the second part of the support is set at the middle section of the blade of the centripetal turbine, specifically between adjacent blades, to avoid blade deformation caused by a large change in the position of the blade profile in the centerline direction from the blade inlet to the blade outlet of the large twisted blade, and the middle section of the blade support adopts an easily removable block support structure; the third part of the support is set in the cavity structure, which is used to support the cavity structure from collapsing, and adopts an easily removable block support structure.

[0020] Furthermore, in S3, first, nickel-based high-temperature alloy material is selected for printing to meet the high temperature resistance requirements of the centripetal turbine with end teeth and large twisted blades. Secondly, the printing process parameters are set: the ambient atmosphere is set to Ar, the layer thickness is set to 0.04mm, and the layer thickness of 0.04mm can ensure the contour and form and position tolerance requirements of the centripetal turbine blades and end tooth structures. The laser power is set to 240W, the scanning speed is 960mm / s, and the scanning spacing is 0.11mm. The scanning speed of 960mm / s and the scanning spacing of 0.11mm can ensure that the internal quality of the printed product meets the requirements and the printing time is within an acceptable range. The scraper type is a rubber scraper, the substrate type is 45# steel, and the substrate thickness is 30-50mm. The part model file is sliced ​​in the software, divided into several two-dimensional layers with each layer being the thickness of the alloy powder layer, and the sliced ​​file is saved.

[0021] Furthermore, in S4, the model slicing file is imported into the laser selective melting equipment, and the alloy powder is loaded into the powder cavity of the equipment. The alloy powder needs to be baked in a vacuum oven at 120±15°C for more than 4 hours before adding. The baking process can eliminate water vapor and impurities that may exist in the powder, improve the fluidity of the powder, and at the same time avoid the reaction of the alloy powder inside the product with water vapor in a high temperature environment during the printing process to produce oxide inclusions. According to the printing material, a 45# steel substrate is selected and installed on the forming platform, the position of the forming substrate is adjusted and the scraper is installed, the equipment door is closed, and high-purity argon gas is introduced into the equipment until the oxygen content is less than 1000ppm.

[0022] Furthermore, in S6, the specific process parameters are as follows:

[0023] (1) Stress relief: Keep at 550±10℃ for 960±10min, and then slowly cool to below 200℃ in the furnace;

[0024] (2) Hot isostatic pressing: keep the temperature and pressure at 1200±10℃ and 140±5MPa for 240±10min, and then slowly cool down to below 200℃ with the furnace;

[0025] (3) Solution treatment: Keep at 1070±10℃ for 240±10min, then fill with inert gas and cool to below 80℃;

[0026] (4) Aging: Keep at 850±5℃ for 960±10min. After the insulation, fill with inert gas and cool to below 80℃.

[0027] The heat treatment using the above process parameters can achieve a tensile strength of not less than 1090 MPa at 750°C for the printed centripetal turbine sample, a specified non-plastic elongation strength of not less than 920 MPa, and an elongation after fracture of not less than 8.5%.

[0028] Furthermore, in S7, after all supports of the radial turbine blank are removed, the surface of the radial turbine blank is sandblasted to ensure that the surface roughness of the turbine blade flow channel is less than Ra3.2.

[0029] The beneficial effects of the present invention are as follows:

[0030] 1. The present invention provides a topologically optimized centripetal turbine structure and a laser selective melting forming method thereof. Compared with the currently commonly used casting forming method of the centripetal turbine, the turbine working efficiency is improved by 8.5% after the blade angle and blade thickness are changed; after the topological optimization design, the turbine weight is reduced by 20%; the turbine blank processing cycle is shortened by more than half; and the blank preparation qualification rate is greatly improved.

[0031] 2. The present invention adopts laser selective melting additive manufacturing technology to process the centripetal turbine structure, which can make the centripetal turbine structure highly consistent with the aerodynamic performance calculation results, improve the working efficiency of the turbine, reduce the weight of the centripetal turbine structure, reduce the small-batch production cost in the early stage of product research and development, and greatly shorten the manufacturing cycle of the centripetal turbine. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solution of the implementation method of the patent of the present invention, the following is a brief introduction to the drawings required for use in the implementation method. It should be understood that the following drawings only show certain embodiments of the patent of the present invention and should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying creative work.

[0033] Figure 1 This is a structural model diagram of a centripetal turbine with end teeth and large twisted blades according to the present invention;

[0034] Figure 2 This is a process model diagram of a centripetal turbine with end teeth and large twisted blades according to the present invention;

[0035] In the figure: 1- radial turbine disk, 2- radial turbine blade, 3- cavity, 4- front end tooth structure, 5- rear end tooth structure, 6- front end threaded hole, 7- rear end threaded hole, 8- vent hole, 9- raised annular belt, 10- auxiliary support between the inlet side of the turbine blade and the working platform, 11- auxiliary support of the middle section of the turbine blade, 12- auxiliary support inside the cavity. DETAILED DESCRIPTION

[0036] This section is an embodiment of the present invention, which is used to explain and illustrate the technical solution of the present invention. In the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other.

[0037] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate directions or positional relationships as given in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or case referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", etc. are used only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implying the number of technical features indicated. Thus, features defined as "first", "second", etc. may explicitly or implicitly include more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0038] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected" and "connected" should be interpreted in a broad sense, for example, it can be a fixed connection, a detachable connection or an integrated connection; it can be a mechanical connection or a point connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood by specific circumstances.

[0039] Embodiment 1:

[0040] A centrifugal turbine with end teeth and large twisted blades, comprising a centrifugal turbine disk 1, wherein the centrifugal turbine disk 1 has a narrow and low-height protruding annular belt 9 near the edge of the disk, and the protruding annular belt 9 is used to provide a grinding margin for the centrifugal turbine in a dynamic balancing test; the upper and lower ends of the centrifugal turbine disk 1 have a front tooth structure 4 and a rear tooth structure 5, the front tooth structure 4 is used to connect with the compressor rotor and transmit torque, and the rear tooth structure 5 is used to connect with the subsequent turbine rotor and transmit torque; the front tooth structure 4 has an annular boss on the inner side, and the inner surface of the annular boss is a front threaded hole 6; the rear tooth structure has a rear threaded hole 7 on the inner side; the front threaded hole 6 and the rear threaded hole 7 are respectively connected to the front pull rod and the rear pull rod of the rotor to realize the centrifugal turbine. The turbine is axially tightened; the rear end threaded hole 7 is connected to the cavity 3 provided inside the centripetal turbine disk 1; the axial dimension of the cavity 3 is not less than 1 / 2 of the length of the centripetal turbine disk 1, and the average wall thickness of the centripetal turbine disk 1 in the area where the cavity 3 is located is not greater than 8 mm; the wall surface of the cavity 3 is provided with vent holes 8 evenly distributed around the circumference, and the vent holes 8 provide a flow path for cold air, and the cold air enters the cavity to cool the turbine disk; the centripetal turbine comprises a circumferentially evenly distributed large twisted centripetal turbine blade 2, the ratio of the maximum height of the centripetal turbine blade 2 to the axial length is not greater than 0.5, the difference between the inlet geometric angle and the outlet geometric angle of the centripetal turbine blade 2 is not less than 60°, and the trailing edge arc radius of the centripetal turbine blade 2 is not greater than 1.5 mm;

[0041] A laser selective melting forming method for a centripetal turbine with end teeth and large twisted blades comprises the following steps:

[0042] S1: Model the aforementioned centrifugal turbine with end teeth and large twisted blades in a 3D modeling software. During the modeling process, the end teeth structures at both ends are designed with allowances. Then, the established centrifugal turbine geometric model is imported into the supporting software of the laser selective melting forming equipment.

[0043] S2: Based on the centripetal turbine geometric model, a centripetal turbine process model is created and optimized, and sufficient supports are set in the centripetal turbine process model to reinforce the parts of the centripetal turbine that are prone to collapse during the printing process;

[0044] S3: Set the working parameters in the supporting software of the laser selective melting forming equipment: select the printing material as GH4251 high temperature alloy, set the printing process parameters, including: ambient atmosphere, layer thickness, laser power, scanning speed, scanning spacing, scraper type, substrate type, substrate thickness; then slice the centripetal turbine process model file in the software, divide it into several two-dimensional layers with each layer thickness being the thickness of the alloy powder layer, and save the slice file;

[0045] S4: Import the model slice file into the laser selective melting equipment, load the alloy powder into the powder cavity of the equipment, install the substrate on the forming platform, adjust the position of the forming substrate and install the scraper, close the equipment door, and provide the equipment with an environmental atmosphere;

[0046] S5: Turn on the laser to print out the centripetal turbine blank;

[0047] S6: Clean the powder on the surface of the centrifugal turbine blank and the substrate, and place the assembly of the substrate and the centrifugal turbine blank into a heat treatment furnace to perform stress relief, hot isostatic pressing, solution treatment and aging treatment in sequence;

[0048] S7: cutting the centripetal turbine blank from the base plate, and removing all supports of the centripetal turbine blank;

[0049] S8: The end teeth and other required areas of the centrifugal turbine blank are machined to achieve the final delivery state.

[0050] In S2, the part model is placed in a direction perpendicular to the central axis of the printing work platform to ensure the quality and consistency of the blade forming of the part; the parts are placed according to the principle of "small on top and large on bottom", that is, the blade inlet is placed downward on the work platform.

[0051] In S2, the auxiliary support setting of the parts includes three parts: the first part of the support is set between the inlet side of the centripetal turbine and the working platform, which is used to support the blades and the entire wheel of the centripetal turbine. An easily removable block support is set at a position that is not easy to remove, and a solid support is set at a locally easy-to-remove position; the second part of the support is set at the middle section of the blade of the centripetal turbine, specifically between adjacent blades, to avoid blade deformation caused by a large change in the position of the blade profile in the centerline direction from the blade inlet to the blade outlet of the large twisted blade, and the middle section of the blade support adopts an easily removable block support structure; the third part of the support is set in the cavity structure, which is used to support the cavity structure from collapsing, and adopts an easily removable block support structure.

[0052] In S3, first, nickel-based high-temperature alloy materials are selected for printing to meet the high temperature resistance requirements of the centripetal turbine with end teeth and large twisted blades. Secondly, the printing process parameters are set: the ambient atmosphere is set to Ar, the layer thickness is set to 0.04mm, and the layer thickness of 0.04mm can ensure the contour and form and position tolerance requirements of the centripetal turbine blades and end tooth structures. The laser power is set to 240W, the scanning speed is 960mm / s, and the scanning spacing is 0.11mm. The scanning speed of 960mm / s and the scanning spacing of 0.11mm can ensure that the internal quality of the printed product meets the requirements and the printing time is within an acceptable range. The scraper type is a rubber scraper, the substrate type is 45# steel, and the substrate thickness is 30-50mm. The part model file is sliced ​​in the software, divided into several two-dimensional layers with each layer thickness being the thickness of the alloy powder layer, and the sliced ​​file is saved.

[0053] In S4, the model slice file is imported into the laser selective melting equipment, and the alloy powder is loaded into the powder cavity of the equipment. The alloy powder needs to be baked in a vacuum oven at 120±15℃ for more than 4 hours before adding. The baking process can eliminate the water vapor and impurities that may exist in the powder, improve the powder fluidity, and at the same time avoid the reaction of the alloy powder inside the product with water vapor in a high temperature environment during the printing process to produce oxide inclusions. According to the printing material, a 45# steel substrate is selected and installed on the forming platform, the position of the forming substrate is adjusted and the scraper is installed, the equipment door is closed, and high-purity argon gas is introduced into the equipment until the oxygen content is less than 1000ppm.

[0054] In S6, the specific process parameters are as follows:

[0055] 1. Stress relief: Keep at 550±10℃ for 960±10min, and then slowly cool down to below 200℃ with the furnace;

[0056] 2 Hot isostatic pressing: keep the temperature and pressure at 1200±10℃ and 140±5MPa for 240±10min. After the temperature and pressure are kept, slowly cool down to below 200℃ with the furnace;

[0057] 3 Solution: Keep at 1070±10℃ for 240±10min, then fill with inert gas and cool to below 80℃;

[0058] 4 Aging: Keep warm at 850±5℃ for 960±10min. After the heat preservation, fill with inert gas and cool to below 80℃.

[0059] The heat treatment using the above process parameters can achieve a tensile strength of not less than 1090 MPa at 750°C for the printed centripetal turbine sample, a specified non-plastic elongation strength of not less than 920 MPa, and an elongation after fracture of not less than 8.5%.

[0060] In S7, after all supports of the centrifugal turbine blank are removed, the surface of the centrifugal turbine blank is sandblasted to ensure that the surface roughness of the turbine blade flow channel is less than Ra3.2.

[0061] Embodiment 2:

[0062] Step 1: In the 3D modeling software, the centripetal turbine structure with end teeth and large twisted blades is modeled according to the aerodynamic design results. During the modeling process, it is ensured that the arc radius of the blade trailing edge is not greater than 1.5mm, the axial size of the internal cavity is not less than 1 / 2 of the axial length of the disk, and the average wall thickness of the disk in the cavity area is not greater than 8mm, so as to ensure the working efficiency of the turbine and the weight reduction effect of the overall structure. The end tooth structure at both ends of the turbine structure is designed with a margin, and the end tooth characteristic surface is thickened by 0.5mm in the normal direction to provide a margin for the final processing of the end tooth. The established centripetal turbine geometric model is imported into the supporting software of the laser selective melting forming equipment in the specified format.

[0063] Step 2: Create and optimize the process model of the centripetal turbine with end teeth and large twisted blades. Place the part model in a direction perpendicular to the central axis and the printing work platform to ensure the quality and consistency of the part blade forming. The parts are placed according to the principle of "small on top and large on bottom", that is, the blade inlet is placed on the work platform facing down. The auxiliary support setting of the part includes three parts. The first part of the support is set between the inlet side of the turbine blade and the work platform to support the blade and the entire wheel. Block supports (easy to remove) are set at positions that are not easy to remove, and a small amount of solid supports are set at local easy-to-remove positions; the second part of the support is set at the middle section of the blade, between adjacent blades, to avoid blade deformation caused by the large change in the position of the blade profile in the centerline direction from the blade inlet to the blade outlet. The middle section of the blade support adopts an easily removable block support structure; the third part of the support is set in the cavity structure to support the cavity structure from collapse, and also adopts an easily removable block support structure.

[0064] Step 3: Set the working parameters in the supporting software of the laser selective melting forming equipment. First, select GH4251 high-temperature alloy material for printing to meet the high temperature resistance requirements of the centripetal turbine with end teeth and large twisted blades. Secondly, set the printing process parameters: the ambient atmosphere (ambient gas) is set to Ar, the layer thickness is set to 0.04mm (layer thickness), the laser power is set to 240W, the scanning speed is 960mm / s, the scanning spacing is 0.11mm, the scraper type is a rubber scraper, the substrate type is 45# steel, and the substrate thickness is 30-50mm. Slice the part model file in the software, divide it into several two-dimensional layers with each layer thickness being the thickness of the alloy powder layer, and save the slice file.

[0065] Step 4: Import the model slice file into the laser selective melting equipment, load the alloy powder into the powder cavity of the equipment, and bake the alloy powder in a vacuum oven at 120±15℃ for more than 4 hours before adding. Select a 45# steel substrate according to the printing material and install it on the forming platform. Adjust the position of the forming substrate and install the scraper. Close the equipment door and introduce high-purity argon into the equipment until the oxygen content is less than 1000ppm.

[0066] Step 5: Turn on the laser. The laser selectively scans the powder along the slicing path. After each layer is printed, the forming plane drops by one powder layer thickness, and the powder cavity rises by 1.5 to 3 times the powder layer thickness to ensure sufficient powder supply. Repeat the above process to complete the printing of each layer, and finally print out a centripetal turbine blank with end teeth and large twisted blades.

[0067] Step 6: After printing is completed, use a compressed air gun to clean the powder on the surface of the blank and the substrate, and place the substrate and the blank in a heat treatment furnace for stress relief, hot isostatic pressing, solution treatment and aging treatment in sequence. The process of each heat treatment link is as follows:

[0068] (1) Stress relief: Keep at 550±10℃ for 960±10min, and then slowly cool to below 200℃ in the furnace;

[0069] (2) Hot isostatic pressing: keep the temperature and pressure at 1200±10℃ and 140±5MPa for 240±10min, and then slowly cool down to below 200℃ with the furnace;

[0070] (3) Solution treatment: Keep at 1070±10℃ for 240±10min, then fill with inert gas and cool to below 80℃;

[0071] (4) Aging: Keep at 850±5℃ for 960±10min, then cool to below 80℃ with inert gas;

[0072] Step 7: Cut the heat-treated blank from the substrate using wire-cutting electrospark cutting, remove all supports, and then perform surface sandblasting to ensure that the surface roughness of the turbine blade flow channel is less than Ra3.2.

[0073] Step 8: After the sandblasting is completed, the end teeth and other required areas of the centrifugal turbine blank are machined to achieve the final delivery state.

[0074] Embodiment 3:

[0075] Figure 1 This is a schematic diagram of the structure of the centripetal turbine with end teeth and large twisted blades according to the present invention. Figure 1As shown, the centripetal turbine structure is an integrated disc and blade design, with end tooth structures at both ends of the turbine for connecting with the remaining rotors. The centripetal turbine has large twisted blades evenly distributed circumferentially, and a cavity is designed inside the disc.

[0076] Furthermore, the ratio of the maximum blade height to the axial length of the centripetal turbine is 0.49, the difference between the blade inlet geometric angle and the outlet geometric angle is 65°, the blade trailing edge arc radius is 1.3mm, the wheel has a cavity structure inside, the ratio of the axial dimension of the cavity area to the axial length of the wheel is 0.54, and the average wall of the wheel in the cavity area is about 7.5mm. The design of the centripetal turbine structure achieves the removal of redundant materials, reduces the structural weight and reduces the blade thickness while ensuring that the blade shape conforms to the aerodynamic design results, effectively achieving the goal of lightweight design and improving the turbine working efficiency.

[0077] The centripetal turbine with end teeth and large twisted blades is manufactured by a laser selective melting forming method. The laser selective melting forming method can realize the rapid forming of large twisted blades and preform the end tooth structure to reduce the workload of end tooth processing. The method specifically includes the following steps:

[0078] Step 1: In the 3D modeling software, a centripetal turbine structure with end teeth and large twisted blades is modeled according to the aerodynamic design results. The arc radius of the trailing edge of the turbine blade is designed to be 1.3mm, the axial dimension of the internal cavity is not less than 1 / 2 of the axial length of the disk, and the average wall thickness of the disk in the cavity area is 7.5mm, so as to ensure the working efficiency of the turbine and the weight reduction effect of the overall structure. The end tooth structure at both ends of the turbine structure is designed with a margin, and the thickness is increased by 0.5mm along the normal direction of the end tooth feature surface to provide a margin for the final processing of the end tooth. The established centripetal turbine geometric model is imported into the supporting software of the laser selective melting forming equipment in the specified format.

[0079] Step 2: Create and optimize the process model of a centripetal turbine with end teeth and large twisted blades. Place the part model in a direction perpendicular to the central axis and the printing work platform to ensure the quality and consistency of the part blade forming. The parts are placed according to the principle of "small on top and large on bottom", that is, the blade inlet is placed on the work platform facing down. The auxiliary support setting of the part includes three parts. The first part of the support is set between the inlet side of the turbine blade and the work platform to support the blade and the entire wheel. Block supports are set in positions that are not easy to remove, and a small amount of solid supports are set in local positions that are easy to remove; the second part of the support is set in the middle section of the blade to avoid blade deformation caused by the large change in the position of the blade profile in the centerline direction from the blade inlet to the blade outlet of the large twisted blade. The middle section of the blade support adopts an easily removable block support structure; the third part of the support is set in the cavity structure, and also adopts an easily removable block support structure.

[0080] Step 3: Set the working parameters in the supporting software of the laser selective melting forming equipment. First, select the nickel-based high-temperature alloy material for printing to meet the high temperature resistance requirements of the centripetal turbine with end teeth and large twisted blades. Secondly, set the printing process parameters: the ambient atmosphere is set to Ar, the layer thickness is set to 0.04mm, the laser power is set to 240W, the scanning speed is 960mm / s, the scanning spacing is 0.11mm, the scraper type is a rubber scraper, the substrate type is 45# steel, and the substrate thickness is 30-50mm. Slice the part model file in the software, divide it into several two-dimensional layers with each layer thickness being the thickness of the powder layer, and save the slice file.

[0081] Step 4: Import the model slice file into the laser selective melting equipment, load the alloy powder into the powder cavity of the equipment, and bake the alloy powder in a vacuum oven at 120±15℃ for more than 4 hours before adding. Select a 45# steel substrate according to the printing material and install it on the forming platform. Adjust the position of the forming substrate and install the scraper. Close the equipment door and introduce high-purity argon into the equipment until the oxygen content is less than 1000ppm.

[0082] Step 5: Turn on the laser. The laser selectively scans the powder along the slicing path. After each layer is printed, the forming plane drops by one powder layer thickness, and the powder cavity rises by 1.5 to 3 times the powder layer thickness to ensure sufficient powder supply. Repeat the above process to complete the printing of each layer, and finally print out a centripetal turbine blank with end teeth and large twisted blades.

[0083] Step 6: After printing is completed, use a compressed air gun to clean the powder on the surface of the blank and the substrate, and place the substrate and the blank in a heat treatment furnace for stress relief, hot isostatic pressing, solution treatment and aging treatment in sequence. The process of each heat treatment link is as follows:

[0084] (1) Stress relief: Keep at 550±10℃ for 960±10min, and then slowly cool to below 200℃ in the furnace;

[0085] (2) Hot isostatic pressing: keep the temperature and pressure at 1200±10℃ and 140±5MPa for 240±10min, and then slowly cool down to below 200℃ with the furnace;

[0086] (3) Solution treatment: Keep at 1070±10℃ for 240±10min, then fill with inert gas and cool to below 80℃;

[0087] (4) Aging: Keep at 850±5℃ for 960±10min, then cool to below 80℃ with inert gas;

[0088] Step 7: Cut the heat-treated blank from the substrate using wire-cutting electrospark cutting, remove all supports, and then perform surface sandblasting to ensure that the surface roughness of the turbine blade flow channel is less than Ra3.2.

[0089] Step 8: After the sandblasting is completed, the end teeth and other required areas of the centrifugal turbine blank are machined to achieve the final delivery state.

[0090] The above is only a specific embodiment of the present invention, and the present invention is described in detail. The unexplained part is a conventional technology. However, the protection scope of the present invention is not limited to this. Any changes or substitutions that can be easily thought of by any technician familiar with the technical field within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. The protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A centripetal turbine with end teeth and large twisted blades, characterized in that: The centrifugal turbine disk (1) comprises a protruding annular belt (9) with a narrow width and a low height near the edge of the disk, and the protruding annular belt (9) is used to provide a grinding margin for the centrifugal turbine in a dynamic balancing test; the upper and lower ends of the centrifugal turbine disk (1) have a front tooth structure (4) and a rear tooth structure (5), the front tooth structure (4) is used to connect with the compressor rotor and transmit torque, and the rear tooth structure (5) is used to connect with the turbine rotor of the next stage and transmit torque; the front tooth structure (4) has a circular annular boss on the inner side, and the inner surface of the circular annular boss is a front threaded hole (6); the rear tooth structure has a rear threaded hole (7) on the inner side; the front threaded hole (6) and the rear threaded hole (7) are respectively connected to the front pull rod and the rear pull rod of the rotor to achieve axial tightening of the centrifugal turbine; The rear end threaded hole (7) is connected to a cavity (3) provided inside the centrifugal turbine disk (1); the axial dimension of the cavity (3) is not less than 1 / 2 of the length of the centrifugal turbine disk (1), and the average wall thickness of the centrifugal turbine disk (1) in the area where the cavity (3) is located is not greater than 8 mm; the wall surface of the cavity (3) is provided with vent holes (8) uniformly distributed around the circumference, the vent holes (8) provide a flow path for cold air, and the cold air enters the cavity to cool the turbine disk; the centrifugal turbine comprises circumferentially uniformly distributed large twisted centrifugal turbine blades (2), the ratio of the maximum height of the centrifugal turbine blades (2) to the axial length is not greater than 0.5, the difference between the inlet geometric angle and the outlet geometric angle of the centrifugal turbine blades (2) is not less than 60°, and the trailing edge arc radius of the centrifugal turbine blades (2) is not greater than 1.5 mm.

2. A laser selective melting forming method for a centripetal turbine with end teeth and large twisted blades, characterized in that: The following steps are involved: S1: Model the centrifugal turbine with end teeth and large twisted blades in the 3D modeling software. During the modeling process, the end teeth structure at both ends is designed with allowances. Then, the established centrifugal turbine geometric model is imported into the supporting software of the laser selective melting forming equipment. S2: Based on the centripetal turbine geometric model, a centripetal turbine process model is created and optimized, and sufficient supports are set in the centripetal turbine process model to reinforce the parts of the centripetal turbine that are prone to collapse during the printing process; S3: Setting working parameters in the supporting software of the laser selective melting forming equipment: selecting the printing material, setting the printing process parameters, including: ambient atmosphere, layer thickness, laser power, scanning speed, scanning spacing, scraper type, substrate type, substrate thickness; then slicing the centripetal turbine process model file in the software, dividing it into several two-dimensional layers with each layer thickness being the thickness of the alloy powder layer, and saving the slice file; S4: Import the model slice file into the laser selective melting equipment, load the alloy powder into the powder cavity of the equipment, install the substrate on the forming platform, adjust the position of the forming substrate and install the scraper, close the equipment door, and provide the equipment with an environmental atmosphere; S5: Turn on the laser to print out the centripetal turbine blank; S6: Clean the powder on the surface of the centrifugal turbine blank and the substrate, and place the assembly of the substrate and the centrifugal turbine blank into a heat treatment furnace to perform stress relief, hot isostatic pressing, solution treatment and aging treatment in sequence; S7: cutting the centripetal turbine blank from the base plate, and removing all supports of the centripetal turbine blank; S8: The end teeth and other required areas of the centrifugal turbine blank are machined to achieve the final delivery state.

3. The laser selective melting forming method of a centripetal turbine with end teeth and large twisted blades according to claim 2 is characterized in that: In S2, the part model is placed in a direction perpendicular to the central axis of the printing work platform to ensure the quality and consistency of the blade forming of the part; the parts are placed according to the principle of "small on top and large on bottom", that is, the blade inlet is placed downward on the work platform.

4. The laser selective melting forming method of a centripetal turbine with end teeth and large twisted blades according to claim 2 is characterized in that: The auxiliary support setting of the parts includes three parts: the first part of the support is set between the inlet side of the centripetal turbine and the working platform, which is used to support the blades and the entire wheel of the centripetal turbine. An easily removable block support is set at a position that is not easy to remove, and a solid support is set at a locally easy-to-remove position; the second part of the support is set at the middle section of the blade of the centripetal turbine, specifically between adjacent blades, to avoid blade deformation caused by a large change in the position of the blade profile in the centerline direction from the blade inlet to the blade outlet of the large twisted blade. The middle section of the blade support adopts an easily removable block support structure; the third part of the support is set in the cavity structure, which is used to support the cavity structure from collapsing, and adopts an easily removable block support structure.

5. The laser selective melting forming method of a centripetal turbine with end teeth and large twisted blades according to claim 2 is characterized in that: In S3, first, nickel-based high-temperature alloy material is selected for printing to meet the high-temperature resistance requirements of the centripetal turbine with end teeth and large twisted blades. Secondly, the printing process parameters are set: the ambient atmosphere is set to Ar, the layer thickness is set to 0.04mm, the laser power is set to 240W, the scanning speed is 960mm / s, the scanning spacing is 0.11mm, the scraper type is a rubber scraper, the substrate type is 45# steel, and the substrate thickness is 30-50mm. The part model file is sliced ​​in the software and divided into several two-dimensional layers, each layer is the thickness of the alloy powder layer, and the sliced ​​file is saved.

6. The laser selective melting forming method of a centripetal turbine with end teeth and large twisted blades according to claim 2 is characterized in that: In S4, the model slicing file is imported into the laser selective melting equipment, and the alloy powder is loaded into the powder cavity of the equipment. The alloy powder needs to be baked in a vacuum oven at 120±15℃ for more than 4 hours before adding. A 45# steel substrate is selected according to the printing material and installed on the forming platform. The position of the forming substrate is adjusted and the scraper is installed. The equipment door is closed, and high-purity argon gas is introduced into the equipment until the oxygen content is less than 1000ppm.

7. The laser selective melting forming method of a centripetal turbine with end teeth and large twisted blades according to claim 2 is characterized in that: In S6, the specific process parameters are as follows: (1) Stress relief: Keep at 550±10℃ for 960±10min, and then slowly cool to below 200℃ in the furnace; (2) Hot isostatic pressing: keep the temperature and pressure at 1200±10℃ and 140±5MPa for 240±10min, and then slowly cool down to below 200℃ with the furnace; (3) Solution treatment: Keep at 1070±10℃ for 240±10min, then fill with inert gas and cool to below 80℃; (4) Aging: Keep at 850±5℃ for 960±10min. After the insulation, fill with inert gas and cool to below 80℃.

8. The laser selective melting forming method of a centripetal turbine with end teeth and large twisted blades according to claim 2 is characterized in that: In S7, after all supports of the centrifugal turbine blank are removed, the surface of the centrifugal turbine blank is sandblasted to ensure that the surface roughness of the turbine blade flow channel is less than Ra3.2.

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