A columnar crystal blade directional solidification manufacturing method and columnar crystal blade

Abstract

The application discloses a columnar crystal blade directional solidification manufacturing method and a columnar crystal blade, and belongs to the field of aero-engines. In the columnar crystal blade directional solidification manufacturing method, a seed crystal with <001> preferred orientation is obtained through rolling or extrusion, seed crystal raw materials are fixed on a bonding wax block to obtain an integrated blade wax mold, one or more integrated wax molds are combined with a casting assembly to form a columnar crystal blade assembly tree, and after a coating, dewaxing and sintering treatment, a directional solidification casting with a crystal beam structure is obtained through a directional solidification process. The method can effectively reduce the risk of occurrence of transverse crystals and wide crystals in the crystal beam, and effectively improve the manufacturing efficiency and the crystal beam qualified rate of the columnar crystal blade.

Description

Technical Field

[0001] This invention belongs to the field of aero-engines, specifically relating to a method for directional solidification manufacturing of columnar crystal blades and columnar crystal blades. Background Technology

[0002] Turbine blades in aero-engines are subjected to high temperatures and centrifugal forces. Under these harsh operating conditions, creep is one of the main failure modes of turbine blades. The typical mechanism of creep is the sliding of grain boundaries under high-temperature stress, leading to metal strain. An effective way to increase the creep resistance of metals is to reduce the number of grain boundaries, which has led to the development of directionally solidified columnar blades. Directionally solidified columnar blades require a certain number of crystal bundles in the blade cross-section. The initial section has a relatively large number of oriented columnar crystals, but during blade growth, due to grain competition, non-preferred oriented grains are continuously consumed, and the grain bundles do not meet the requirements. The large difference in primary orientation between grains easily leads to lateral grain growth during the growth process, resulting in transverse crystal fragmentation, which affects the use of the blade.

[0003] Patent CN107745093B discloses a method for manufacturing a nickel-based single-crystal guide vane, which involves cutting grains from a nickel-based single-crystal high-temperature alloy block. <001> A nickel-based single-crystal guide vane is produced by directional solidification casting using a seed crystal with a specific orientation as the raw material. However, this method only provides a manufacturing method for single-crystal guide vanes, and its manufacturing process is based on existing single-crystal alloy blocks as the raw material. This method cannot be applied to the manufacture of columnar crystal blades with polycrystalline structures.

[0004] Therefore, this paper provides a method for directional solidification manufacturing of columnar crystal blades, which is of positive significance for improving the production efficiency and economy of columnar crystal blades for aero-engines. Summary of the Invention

[0005] The purpose of this invention is to provide a method for directional solidification manufacturing of columnar crystal blades, so as to manufacture columnar crystal blades having a columnar crystal structure. This invention also provides a columnar crystal blade.

[0006] According to one aspect of the present invention, a method for manufacturing columnar crystal blades by directional solidification is provided, the method comprising the following steps:

[0007] Step a): Provide isotropic equiaxed crystal raw materials, and roll or extrude the equiaxed crystal raw materials to obtain materials with... <001> Preferred orientation of seed crystal raw materials;

[0008] Step b): Connect the seed crystal material to the adhesive wax block, and sequentially set the tenon wax model and the blade wax model at the far end of the seed crystal material relative to the adhesive wax block to obtain an integrated wax model;

[0009] Step c): Combine one or more of the integrated wax molds with the casting components to obtain a columnar blade assembly tree;

[0010] Step d): The shell is attached to the surface of the integrated wax mold and dewaxing and sintering are performed, followed by directional solidification to obtain a directional solidified casting.

[0011] Step e): The directional solidification casting is cut and heat-treated to obtain the finished columnar blade.

[0012] This method can effectively reduce the primary orientation difference between grains, reduce the risk of lateral grain growth during directional solidification, and avoid transverse crystal fracture.

[0013] Furthermore, in some embodiments, in step a), the seed crystal raw material is a deformed high-temperature alloy with a face-centered cubic structure.

[0014] Furthermore, in some embodiments, in step b), a portion of the seed crystal material is inserted into the adhesive wax block.

[0015] Furthermore, in some embodiments, in step b), the seed crystal material is connected to the tenon wax mold via a transfer wax mold.

[0016] Furthermore, in some embodiments, the cross-sectional area of ​​the transfer wax mold perpendicular to the directional solidification direction is larger than that of the seed crystal raw material and the tenon wax mold.

[0017] Furthermore, in some embodiments, the tenon wax mold includes an extension root.

[0018] Furthermore, in some embodiments, in step d), the number of shell layers is 5-12, and after dewaxing, it is calcined at 850℃-1000℃, and the pulling speed for directional solidification is 5mm / min-10mm / min.

[0019] According to another aspect of the present invention, a columnar crystal blade is provided. This columnar crystal blade is manufactured using the columnar crystal blade directional solidification manufacturing method provided in any of the foregoing embodiments. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the seed crystal raw material preparation in one embodiment;

[0021] Figure 2 This is a schematic diagram of the cross-section of the seed crystal raw material in one embodiment;

[0022] Figure 3 This is a schematic diagram of the projection of the blade cross section onto the cross section of the seed crystal raw material in one embodiment;

[0023] Figure 4This is a schematic diagram of an integrated wax mold structure in one embodiment;

[0024] Figure 5 This is a schematic diagram of a partial structure of a columnar crystal blade group in one embodiment.

[0025] Meaning of the reference numerals in the attached figures:

[0026] 1-Seed crystal raw material;

[0027] 11-grain;

[0028] 21-Projection of the blade root section;

[0029] 3-Integrated wax model;

[0030] 31-Adhesive wax block;

[0031] 32-Transfer wax mold;

[0032] 33-Tenon wax model;

[0033] 34-Leaf wax model;

[0034] 41 - Pouring cup;

[0035] 42-Injection tube;

[0036] 43-Chassis;

[0037] 44-Gating plate.

[0038] The purpose of the above-described drawings is to provide a detailed description of the invention in conjunction with the accompanying drawings, so that those skilled in the art can understand the technical concept of the invention, and not to limit the invention. For the sake of brevity, the above-described drawings only schematically depict the structures related to the technical features of the invention, and do not depict the complete structure and all details strictly according to actual scale. Detailed Implementation

[0039] The present invention will now be described in further detail with reference to specific embodiments and accompanying drawings.

[0040] The term "embodiment" as used herein means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment herein. The phrase appearing in various places in the specification does not necessarily refer to the same embodiment, nor is it limited to mutually exclusive, independent, or alternative embodiments. Those skilled in the art will understand that the embodiments herein can be combined with other embodiments without causing structural conflicts.

[0041] In this description, unless otherwise explicitly specified and limited, the technical terms "installation," "connection," "joining," etc., should be interpreted broadly, for example, referring to movable connections, fixed connections, or integration. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this application based on the specific circumstances.

[0042] In this description, terms such as "upper," "lower," "left," "right," "lateral," "longitudinal," "height," "length," and "width," which indicate orientation or positional relationships, are intended to accurately describe the embodiments and simplify the description, rather than limiting the parts or structures involved to have a specific orientation, or to be installed or operated in a specific orientation, and should not be construed as limiting the embodiments in this document.

[0043] In this description, terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating relative importance or limiting the number, specific order, or primary / secondary relationship of the described technical features. In this description, "multiple" means at least two.

[0044] Turbine blades in aero-engines are subjected to high temperatures and centrifugal forces. Under these harsh operating conditions, creep is one of the main failure modes of turbine blades. Creep is the process by which metals, under high-temperature stress (generally at temperatures exceeding 40% of their melting point), undergo strain over time. The typical mechanism of creep is the sliding of grain boundaries under high-temperature stress, leading to strain in the metal. Currently, reducing grain boundaries and forming microstructures such as grain bundles within the metal matrix is ​​considered one of the effective technical solutions to improve the creep resistance of metals. Directional solidification columnar crystals are grain bundles that grow along the direction of heat flow. The number and orientation of these grain bundles determine their performance. Besides being related to the alloy solidification parameters and temperature field, the number of grain bundles, according to the Walton-Chalmers model's competitive growth mechanism, is determined by the proportion of preferentially oriented grains in the initial stage. During growth, the competitive growth mechanism gives preferentially oriented grains a significant advantage in solidification. The preferred orientation of cubic unit cells in alloys is... <001> .

[0045] The seed crystal method is a technique used in the preparation of single-crystal superalloys to obtain single crystals with consistent orientation. By pre-fabricating single-crystal seed crystals, the metal solidifies and propagates at the seed crystal interface, avoiding random grain growth caused by over-cooling and solidification nucleation, thus obtaining grains with consistent and controllable orientation.

[0046] Currently, some technical solutions provide methods for preparing single-crystal materials using single-crystal seed crystals as raw materials through directional solidification processes; however, effective preparation processes for crystal bundles with polycrystalline structures are still lacking. For crystal bundles, during directional solidification, different grains compete for growth, and non-preferred oriented grains are continuously absorbed. When the primary orientation difference of the polycrystalline seed crystal is significant, lateral grain growth easily occurs during directional solidification, leading to transverse crystal fragmentation in the material and severely affecting the performance of the crystal bundle.

[0047] Generally, the orientation of grains in polycrystalline materials is randomly distributed, resulting in overall isotropic properties. However, after deformation, the grains in polycrystalline materials exhibit a clear regularity in orientation distribution. Rolling and extrusion deformation processes can produce textured materials. For example, literature indicates that electrical silicon steel sheets utilize this process to obtain anisotropic materials, thereby achieving anisotropic electrical properties; extruded MGH754 alloy extruded bars are mainly used for... <001> orientation.

[0048] Based on this, one embodiment of the present invention provides a method for directional solidification manufacturing of columnar crystal blades, which uses rolled or extruded metal as raw material to perform directional solidification of crystal bundles to reduce the risk of transverse crystal formation and improve the quality and performance of columnar crystal blades.

[0049] The method includes the following steps:

[0050] First, seed crystals are prepared.

[0051] For single-crystal directional solidification, a suitable shape of material can be directly cut from the single-crystal alloy as a seed crystal, ensuring the overall orientation consistency of the seed crystal (only a single grain). However, the seed crystals used in polycrystalline bundle directional solidification cannot be directly cut from the single-crystal alloy.

[0052] For isotropic equiaxed crystal raw materials, multi-pass rolling or extrusion can create internal structures within the raw material. <001> The preferred orientation texture deviates from the original disordered state of the polycrystalline structure.

[0053] In a preferred embodiment, such as Figure 1 As shown, the polycrystalline seed crystal raw material 1 undergoes multiple passes of unidirectional rolling or extrusion deformation processing to achieve the desired properties. <001> Preferred-oriented grains 11 deviate from disorder in the microstructure and are preferentially distributed, such as... Figure 2 As shown.

[0054] Specifically, the texture state in the seed crystal raw material can be obtained by cutting a sample from the raw material, polishing it, and then performing backscattered electron diffraction (EBSD) analysis.

[0055] In a preferred embodiment, the seed crystal raw material 1 is a high-temperature alloy with a face-centered cubic structure. <001> The orientation grows preferentially during solidification, aligning with the growth direction required by the crystal bundle. This allows control over the angle of the crystal bundle, preventing excessive deviation in orientation during growth and the formation of transversely fractured crystals.

[0056] The seed crystal material 1 used in the crystal bundle directional solidification is a polycrystalline material, which can control the number of columnar crystals in the crystal bundle during the excitation growth stage and avoid defects such as wide crystals in the blades in the future.

[0057] Based on the desired size of the columnar crystal blades, a seed crystal raw material of appropriate size is cut for subsequent directional solidification processing, such as... Figure 3 As shown, seed crystal raw material 1 <001> The cross section with the preferred orientation is not less than the projection of the blade root section 21.

[0058] The next step is the manufacturing of the integrated wax mold for the blades.

[0059] like Figure 4 As shown, the seed crystal raw material 1 and the integrated wax mold 3 are pressed together.

[0060] The integrated wax model 3 includes an adhesive wax block 31, a transfer wax model 32, a tenon wax model 33, and a blade wax model 34.

[0061] The adhesive wax block 31 is connected to the seed crystal material 1 for subsequent connection with the base of the casting component. In a preferred embodiment, in order to achieve better connection, the seed crystal material 1 is inserted into the adhesive wax block 31 to a certain depth. Specifically, a groove can be pre-made when the adhesive wax block 31 is formed and the seed crystal material 1 can be inserted into the groove, or a part of the seed crystal material 1 can be directly pressed into the adhesive wax block 31.

[0062] The tenon wax mold 33 is used to form the tenon portion of the columnar crystal blade. In a preferred embodiment, the tenon wax mold 33 includes an extension root, and the root of the tenon wax mold 33 has an inner cavity with the same shape as the cross-sectional projection 21 of the blade root. The blade wax mold 34 is used to form the blade portion of the columnar crystal blade. The blade wax mold 34 is connected to the inner cavity of the tenon wax mold 33, and together they define the outer contour shape of the columnar crystal blade. The tenon wax mold 33 and the adhesive wax block 31 are disposed opposite to each other at the other end of the seed crystal raw material 1 (i.e., the end away from the adhesive wax block 31), and the blade wax mold 34 is connected to the tenon wax mold 33.

[0063] In a preferred embodiment, the seed crystal material 1 is connected to the bottom of the tenon wax mold 33 via a transfer wax mold 32. The cross-sectional area of ​​the transfer wax mold 32 (the cross-section perpendicular to the growth direction of the columnar crystals during directional solidification) is larger than the cross-sectional area of ​​the seed crystal material 1 and the cross-sectional area of ​​the tenon wax mold 33.

[0064] Next, we will create a wax model tree.

[0065] like Figure 5 As shown, multiple integrated wax molds 3 are assembled with casting components to obtain a columnar crystal blade tree.

[0066] The casting components include a pouring cup 41, a central pouring pipe 42, a base plate 43, and a runner plate 44. The adhesive wax block 31 is fixedly connected to the base plate 43, and the inner cavity of the blade wax model 34 is connected to the runner plate 44 from the top.

[0067] Then, the shell is made and cast.

[0068] A shell is applied to the surface of the wax model. After the shell is applied, the wax is removed and the model is sintered at high temperature until it is solid.

[0069] In a preferred embodiment, 5 to 12 layers of mortar are brushed onto the surface of the wax mold during the shell-coating process. After dewaxing, the mold shell is sintered at 850°C-1000°C.

[0070] The sintered modules are used for casting and directional solidification, with the directional solidification pulling speed being 5mm / min-10mm / min.

[0071] Finally, after directional solidification, the mold shell is removed, and the resulting columnar crystal blades are cut and heat-treated to obtain the finished columnar crystal blades.

[0072] In another embodiment of the present invention, a columnar crystal blade is provided, manufactured using the columnar crystal blade directional solidification manufacturing method provided in the above embodiments. This columnar crystal blade can be used in high-temperature service scenarios such as the manufacturing of low-pressure turbines for aero-engines.

[0073] The columnar blade directional solidification manufacturing method provided in the above embodiments uses polycrystalline seed crystals with preferred orientation as raw materials, increases the number of crystal bundles in the directional solidification process, improves the consistency of the primary orientation of the crystal bundles, reduces the risk of transverse crystal breakage during directional solidification, effectively improves the finished quality of columnar blades, and optimizes the production efficiency and manufacturing cost of columnar blades.

[0074] The purpose of the above embodiments is to provide a further detailed description of the present invention in conjunction with the accompanying drawings, so that those skilled in the art can understand the technical concept of the present invention. Within the scope of the present invention, optimization or equivalent substitution of the method steps involved, as well as combination of implementation methods in different embodiments without causing structural and principle conflicts, all fall within the protection scope of the present invention.

Claims

1. A method for manufacturing columnar crystal blades by directional solidification, characterized in that, Includes the following steps: Step a): Provide isotropic equiaxed crystal raw materials, and roll or extrude the equiaxed crystal raw materials to obtain materials with... <001> Preferred orientation of seed crystal raw materials; Step b): Connect the seed crystal material to the adhesive wax block, and sequentially set the tenon wax model and the blade wax model at the far end of the seed crystal material relative to the adhesive wax block to obtain an integrated wax model; Step c): Combine one or more of the integrated wax molds with the casting components to obtain a columnar blade assembly tree; Step d): A shell is attached to the surface of the integrated wax mold and dewaxing and sintering are performed, followed by directional solidification to obtain a directional solidified casting; Step e): The directional solidification casting is cut and heat-treated to obtain the finished columnar blade.

2. The method for manufacturing columnar crystal blades by directional solidification according to claim 1, characterized in that, In step a), the seed crystal raw material is a deformed high-temperature alloy with a face-centered cubic structure.

3. The method for manufacturing columnar crystal blades by directional solidification according to claim 1, characterized in that, In step b), a portion of the seed crystal material is inserted into the adhesive wax block.

4. The method for manufacturing columnar crystal blades by directional solidification according to claim 1 or 3, characterized in that, In step b), the seed crystal raw material is connected to the tenon wax mold via a transfer wax mold.

5. The method for manufacturing columnar crystal blades by directional solidification according to claim 4, characterized in that, The cross-sectional area of ​​the transfer wax mold perpendicular to the directional solidification direction is larger than that of the seed crystal raw material and the tenon wax mold.

6. The method for manufacturing columnar crystal blades by directional solidification according to claim 1 or 3, characterized in that, The tenon wax mold includes an extension root.

7. The method for manufacturing columnar crystal blades by directional solidification according to claim 1, characterized in that, In step c), the casting assembly includes a pouring cup, an inlet pipe, a base plate, and a runner plate.

8. The method for directional solidification manufacturing of columnar crystal blades according to claim 1, characterized in that, In step d), the number of shell layers is 5-12, and after dewaxing, it is calcined at 850℃-1000℃, with a pulling speed of 5mm / min-10mm / min for directional solidification.

9. A columnar crystal blade, characterized in that, The columnar blade is manufactured by the columnar blade directional solidification manufacturing method as described in any one of claims 1 to 8.

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