A ceramic mold with surface microstructures, its structure optimization method and application

Abstract

The present invention discloses a ceramic mold with surface microstructures, its structural optimization method and application, belonging to the technical field of metal casting. This optimization method correlates the longitudinal temperature gradient during directional solidification with the structural parameters of the ceramic mold with surface microstructures, constructs a mathematical model between the longitudinal temperature gradient and the surface microstructure parameters, and adjusts the surface structure shape of the ceramic mold through surface microstructure design and quantitative optimization driven by the mathematical model, effectively improving the heat transfer and heat dissipation paths during the solidification of the casting alloy. By locally adapting to complex geometric requirements and actively regulating the thermal field, effective control of the overall longitudinal temperature gradient is achieved, systematically solving the problems of insufficient temperature gradient, non-uniform microstructure and defects caused by structural limitations of traditional ceramic mold shells, and providing an innovative technical path for the low-cost manufacturing of high-performance single crystal blades.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal casting, and relates to a ceramic mold with a surface microstructure, and a method and application for optimizing its structure. Background Art

[0002] The manufacturing material of gas turbine turbine blades is mainly superalloy to meet the stringent requirements of working in an extremely high-temperature environment. Under high-temperature conditions, the grain boundaries inside traditional polycrystalline materials will act as weakening points, resulting in a significant decrease in the strength and stiffness of the materials, which cannot meet the performance requirements of gas turbine turbine blades. Therefore, single-crystal blades came into being. By eliminating all grain boundaries, single-crystal blades significantly improve the temperature-bearing capacity and creep performance of the alloy and become the main type of current gas turbine turbine blades. The manufacturing of single-crystal blades relies on advanced directional solidification technology, which establishes a temperature gradient with a specific direction inside the mold. During the solidification process, the heat flow is perpendicular to the solidification interface and is exported in a single direction. This special heat conduction method prompts the crystal to grow in the direction opposite to the heat flow, and finally forms a columnar crystal or single-crystal structure with a specific orientation. This preparation process is crucial for the successful manufacturing of superalloy single-crystal blades.

[0003] However, the directional solidification technology also faces a series of challenges in the preparation process of single-crystal blades. Among them, problems such as non-uniform microstructure and coarse grains are particularly prominent. In addition, defects such as stray grains and freckles often appear. The stray grain defect refers to the formation of unexpected grains during the manufacturing process of single-crystal blades due to the complexity of solidification conditions. These unexpected grains destroy the integrity of the single-crystal structure of the blade, thereby affecting its high-temperature performance and reliability. The freckle defect usually appears on the vertical outer surface of the casting, presenting as continuous or intermittent slender chain-like parallel to the gravity direction, and is composed of many fine grains with disordered orientations. These defects not only seriously reduce the high-temperature mechanical properties of the blade but also cannot be eliminated by subsequent heat treatment, thus greatly affecting the qualified rate of turbine blades. Research results show that a high longitudinal temperature gradient can effectively inhibit the formation of the above defects and simultaneously prepare a directionally columnar crystal with a uniform structure and fine grains.

[0004] Further analysis reveals that the reduction of the longitudinal temperature gradient of the blade is mainly related to the material and structural characteristics of the ceramic mold. During the directional solidification process, the main role of the ceramic mold is to provide a stable heat conduction path to control the solidification process of the molten metal. When the superalloy molten metal is injected into the ceramic mold, it will start to cool and solidify. During this process, the material and structural characteristics of the ceramic mold play a decisive role in the heat conduction path and rate. As Figure 1As shown in the figure, during the directional solidification process, after the heat of the molten metal of the blade is conducted to the ceramic mold, since the transverse comprehensive heat transfer coefficient of the traditional ceramic mold with smooth inner and outer walls is less than the longitudinal comprehensive heat transfer coefficient, the heat will quickly conduct along the longitudinal direction of the ceramic mold. This leads to a decrease in the temperature difference between the unfrozen area and the frozen area of the casting, and further reduces the longitudinal temperature gradient at the solidification front during the directional solidification of the blade. This change directly results in the coarsening of the blade grains, the increase in the dendrite spacing, and the non-uniformity of the microstructure. Chinese Patent Application No. CN110252958A discloses a method for preparing a blade mold for suppressing stray crystal defects based on the hollow / porous structure of the flange. By setting the hollow / porous structure at specific positions of the mold, direct control of the temperature gradient during the directional solidification process is achieved. However, due to geometric differences in areas such as the blade body, blade root, and blade tip of the blade, different temperature gradient requirements exist, and the currently disclosed ceramic molds cannot meet the differential heat dissipation requirements of the casting. Summary of the Invention

[0005] Aiming at the problems existing in the prior art, the present invention provides a ceramic mold with a surface microstructure, its structure optimization method and application, so as to solve the technical problems that the ceramic mold in the prior art cannot meet the differential heat dissipation requirements of the casting, the microstructure of the casting is non-uniform, and stray crystal defects are easily generated.

[0006] The present invention is realized through the following technical solutions:

[0007] A method for optimizing the structure of a ceramic mold with a surface microstructure, comprising the following steps:

[0008] S1: Establish a basic directional solidification temperature field by using a ceramic mold with a smooth outer surface;

[0009] S2: Obtain the longitudinal temperature gradient when the blade to be cast undergoes directional solidification on a ceramic mold with a surface microstructure, and establish a mathematical model between the longitudinal temperature gradient and the surface microstructure parameters; optimize the basic directional solidification temperature field based on the mathematical model, and obtain the microstructure of the blade to be cast under the optimized basic directional solidification temperature field;

[0010] S3: If the microstructure of the blade to be cast under the optimized basic directional solidification temperature field is non-uniform or defective, adjust the surface microstructure parameters, and repeat S2 until the microstructure of the blade to be cast meets the requirements, and complete the structure optimization of the ceramic mold with a surface microstructure; the surface microstructure parameters include: the structural shape, structural size, and arrangement mode of the surface microstructure.

[0011] Preferably, in S1, the method of establishing the basic directional solidification temperature field by using a ceramic mold with a smooth outer surface is as follows: on the ceramic mold with a smooth outer surface, at least 10 temperature measurement zones are divided according to the shape change characteristics of the casting and the process requirements, and the simulated directional solidification temperature fields of each temperature measurement zone are calculated through numerical simulation; and an actual directional solidification experiment is carried out by using the ceramic mold with a smooth outer surface, the actual temperature data of each temperature measurement zone are measured in real time, and the actual directional solidification temperature field of the directional solidification process is established according to the actual temperature data; the simulated directional solidification temperature field is used to adjust the actual directional solidification temperature field to complete the establishment of the basic directional solidification temperature field.

[0012] Preferably, 15 of the temperature measurement zones are divided according to the shape change characteristics of the casting and the process requirements.

[0013] Preferably, the method of using the simulated directional solidification temperature field to adjust the actual directional solidification temperature field to complete the establishment of the basic directional solidification temperature field is as follows: if the temperature error between the actual directional solidification temperature field and the simulated directional solidification temperature field of any one temperature measurement zone is greater than 10%, the heat transfer parameters are adjusted, and the simulated directional solidification temperature field is adjusted according to the actual directional solidification temperature field so that the temperature errors between the actual directional solidification temperature fields and the simulated directional solidification temperature fields of all temperature measurement zones are not greater than 10%, and the adjustment of the simulated directional solidification temperature field is completed to realize the establishment of the basic directional solidification temperature field.

[0014] Preferably, in S2, the longitudinal temperature gradient is obtained through the thermal conductivity, heat conduction heat transfer coefficient, radiation heat transfer coefficient, specific heat, latent heat of solidification, and the density, solidus temperature, and liquidus temperature of the alloy.

[0015] Preferably, the thermal conductivity includes the thermal conductivity of the ceramic shell and the thermal conductivity of the non-shell medium; the radiation heat transfer coefficient includes the radiation heat transfer coefficient of the ceramic shell and the radiation heat transfer coefficient of the non-shell medium.

[0016] Preferably, the structural shape of the surface microstructure includes a square or a regular hexagon.

[0017] A ceramic mold with a surface microstructure is optimized by the above structural optimization method; the ceramic mold includes a ceramic mold body, a hollow chamber is arranged inside the ceramic mold body, and a plurality of grooves with geometric configurations are arranged on the outer wall of the ceramic mold body; the shape of the hollow chamber is the same as the shape of the blade to be cast.

[0018] Preferably, the ceramic mold body is prepared by binder jetting.

[0019] The application of the above-mentioned ceramic mold with a surface microstructure in casting blades.

[0020] Compared with the prior art, the present invention has the following beneficial technical effects:

[0021] In the first aspect, the present invention discloses a structural optimization method for a ceramic mold with a surface microstructure. This optimization method relates the longitudinal temperature gradient during directional solidification to the structural parameters of the ceramic mold with a surface microstructure. The surface microstructure parameters include the structural shape, structural size, and arrangement pattern. A mathematical model between the longitudinal temperature gradient and the surface microstructure parameters is constructed. Through surface microstructure design, the thermal field is actively regulated, quantitative optimization is driven by the mathematical model, and local adaptation to complex geometric requirements is achieved, systematically solving the problems of insufficient temperature gradient, non-uniform microstructure, and defects caused by structural limitations in traditional ceramic shells, providing an innovative technical path for the low-cost manufacturing of high-performance single crystal blades.

[0022] Furthermore, on the ceramic mold with a smooth outer surface, at least 10 temperature measurement zones are divided according to the shape change characteristics of the casting and process requirements. The simulated directional solidification temperature field of each temperature measurement zone is obtained through numerical simulation. Here, by measuring the temperature in zones, the influence of local characteristics of the casting (such as thin walls, abrupt cross-sections) on the thermal field can be captured, effectively realizing the optimization of the temperature gradient.

[0023] Furthermore, 15 of the said temperature measurement zones are divided according to the shape change characteristics of the casting and process requirements, which can fully realize the individual monitoring of the temperature gradient in different blade regions and improve the accuracy of optimization.

[0024] Furthermore, the simulated directional solidification temperature field is used to adjust the actual directional solidification temperature field to complete the establishment of the basic directional solidification temperature field. Specifically: if the temperature error between the actual directional solidification temperature field and the simulated directional solidification temperature field in any one temperature measurement zone is greater than 10%, then the heat transfer parameters are adjusted, and the actual directional solidification temperature field is used to adjust the simulated directional solidification temperature field so that the temperature errors between the actual directional solidification temperature fields and the simulated directional solidification temperature fields in all temperature measurement zones are not greater than 10%, completing the adjustment of the simulated directional solidification temperature field and realizing the establishment of the basic directional solidification temperature field. By setting a temperature error threshold of 10%, the consistency between the simulated directional solidification temperature field and the actual directional solidification temperature field can be effectively ensured, ensuring the accuracy of optimization.

[0025] Furthermore, in S2, the longitudinal temperature gradient is obtained through the thermal conductivity, heat conduction heat transfer coefficient, radiation heat transfer coefficient, specific heat, latent heat of solidification, as well as the density, solidus temperature, and liquidus temperature of the alloy, effectively realizing the high-precision prediction of the temperature gradient, the active control of the microstructure, and the dynamic optimization of the process parameters.

[0026] Second aspect, the present invention also discloses a ceramic mold with surface microstructures, which is optimized by the above-mentioned structure optimization method. The surface of the ceramic mold is provided with grooves of geometric configurations, and the grooves of geometric configurations are the surface microstructures in the present invention. The ceramic mold optimized by this method can change the heat conduction route, realize the uniformity of heat transfer and heat dissipation during the directional solidification of the casting alloy, improve the temperature gradient of the traditional ceramic mold, meet the differential requirements of different positions of the blade, and further realize the grain refinement and microstructure optimization of the blade, inhibit the generation of heterocrystalline defects, and improve the tissue uniformity and overall performance of the alloy blade; in addition, the grooves on the surface of the optimized ceramic mold also increase the outer wall surface area of the mold, strengthening the radiation heat dissipation. In addition, due to the enhanced fluid disturbance in the grooves for heat transfer, this groove design also strengthens the convective heat transfer. In actual working conditions, the depth, width and distribution density of the grooves can be optimized to targetedly reduce the thermal resistance of specific regions, improve the local cooling rate and temperature gradient, enhance the stability of dendritic directional growth, and reduce the heterocrystalline defect rate. In addition, the chamber shape of the ceramic mold in the present invention is completely consistent with the blade, ensuring uniform melt filling and reducing local undercooling or overheating caused by poor contact between the mold shell and the melt. Through the optimization of the groove structure, the ceramic mold systematically solves the problems of insufficient temperature gradient and solidification defects caused by structural limitations of the traditional mold, providing an innovative solution for the efficient and low-cost manufacturing of single crystal blades of superalloys. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0028] Figure 1 Schematic diagram of the heat conduction route of a traditional ceramic mold with a smooth outer wall;

[0029] Figure 2 Schematic flow chart of the structure optimization method of a ceramic mold with surface microstructures in the present invention;

[0030] Figure 3 Front view (A), right view (B) and top view (C) of the ceramic mold in Embodiment 3 of the present invention;

[0031] Figure 4 Schematic diagram of the heat conduction route of the ceramic mold in Embodiment 3 of the present invention;

[0032] Figure 5 Temperature simulation results on the ceramic mold during casting using the ceramic mold in Embodiment 3 of the present invention;

[0033] Figure 6 The front view (A), right view (B), and top view (C) of the ceramic mold in Embodiment 4 of the present invention;

[0034] Figure 7 The partial enlarged schematic view of the outer wall of the ceramic mold in Embodiment 4 of the present invention;

[0035] Figure 8 The schematic diagram of the heat conduction route of the ceramic mold in Embodiment 4 of the present invention;

[0036] Figure 9 The temperature simulation result on the ceramic mold during pouring using the ceramic mold in Embodiment 4 of the present invention;

[0037] Figure 10 The front view (A), right view (B), and top view (C) of the ceramic mold in Embodiment 5 of the present invention;

[0038] Figure 11 The partial enlarged schematic view of the outer wall of the ceramic mold in Embodiment 5 of the present invention;

[0039] Figure 12 The schematic diagram of the heat conduction route of the ceramic mold in Embodiment 5 of the present invention;

[0040] Figure 13 The temperature simulation result on the ceramic mold during pouring using the ceramic mold in Embodiment 5 of the present invention.

[0041] Wherein, 1, the ceramic mold body; 2, the hollow chamber; 3, the groove. Detailed implementation manners

[0042] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Usually, the components of the embodiments of the present invention described and illustrated herein can be arranged and designed in various different configurations.

[0043] Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed present invention, but merely represents the selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0044] It should be noted that like reference numerals and letters refer to like items in the following figures, and thus, once an item is defined in one figure, it need not be further defined and explained in subsequent figures.

[0045] In the description of the embodiments of the present invention, it should be noted that if terms such as "upper", "lower", "horizontal", "inner", etc. are used to indicate the orientation or positional relationship, it is based on the orientation or positional relationship shown in the figures, or the orientation or positional relationship in which the invention product is usually placed during use. This is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation of the present invention. In addition, terms such as "first", "second", etc. are only used for distinguishing descriptions and cannot be construed as indicating or implying relative importance.

[0046] In addition, if the term "horizontal" appears, it does not mean that the component is required to be absolutely horizontal, but it can be slightly inclined. For example, "horizontal" only means that its direction is more horizontal relative to "vertical", and does not mean that the structure must be completely horizontal, but it can be slightly inclined.

[0047] In the description of the embodiments of the present invention, it should also be noted that unless otherwise clearly specified and limited, if terms such as "set", "installed", "connected", "connected to" are used, they should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0048] The present invention will be further described in detail below with reference to the accompanying drawings:

[0049] Embodiment 1

[0050] As Figure 2 shown, the present invention discloses an optimization method for a ceramic mold structure with a surface microstructure, including the following steps:

[0051] S1: Establish a basic directional solidification temperature field using a ceramic mold with a smooth outer surface;

[0052] S2: Obtain the longitudinal temperature gradient when the blade to be cast undergoes directional solidification on a ceramic mold with a surface microstructure, and establish a mathematical model between the longitudinal temperature gradient and the surface microstructure parameters; optimize the basic directional solidification temperature field based on the mathematical model, and obtain the microstructure of the blade to be cast under the optimized basic directional solidification temperature field;

[0053] S3: If there are non-uniformities or defects in the microstructure of the blade to be cast under the optimized basic directional solidification temperature field, adjust the surface microstructure parameters and repeat step S2 until the microstructure of the blade to be cast meets the requirements, thus completing the structural optimization of the ceramic mold with a surface microstructure.

[0054] The surface microstructure in the present invention refers to the grooved geometric configuration provided on the outer wall of the ceramic mold. Through the optimization of this microstructure, specific optimizations include the optimization of the structural shape, structural size, and arrangement method, so as to optimize the heat transfer path and improve the longitudinal temperature gradient.

[0055] For the above optimization method, in step S1, to establish the basic directional solidification temperature field by using a ceramic mold with a smooth outer surface, specifically: on the ceramic mold with a smooth outer surface, at least 10 temperature measurement zones are divided according to the shape change characteristics of the casting and the process requirements, and the simulated directional solidification temperature fields of each temperature measurement zone are calculated through numerical simulation; and an actual directional solidification experiment is carried out by using the ceramic mold with a smooth outer surface, the actual temperature data of each temperature measurement zone are measured in real time by using the infrared temperature measurement method, and the actual directional solidification temperature field of the directional solidification process is established according to the actual temperature data; the ceramic mold with a smooth outer surface mentioned in the present invention refers to the traditional ceramic mold, whose outer wall is not provided with any microstructure and is a smooth outer wall. Preferably, at least 15 temperature measurement zones can also be set, so that the optimization result is more accurate.

[0056] Furthermore, the simulated directional solidification temperature field is used to adjust the actual directional solidification temperature field to complete the establishment of the basic directional solidification temperature field. Specifically, this process is as follows: if the temperature error between the actual directional solidification temperature field of any temperature measurement zone and the simulated directional solidification temperature field is greater than 10%, adjust the heat transfer parameters, and adjust the simulated directional solidification temperature field according to the actual directional solidification temperature field, so that the temperature errors between the actual directional solidification temperature fields of all temperature measurement zones and the simulated directional solidification temperature field are not greater than 10%, that is, make the simulated temperature field approach the actual temperature field by increasing or decreasing the heat transfer parameters, complete the adjustment of the simulated directional solidification temperature field, and realize the establishment of the basic directional solidification temperature field.

[0057] In step S2, the variables of the mathematical model include the heat conduction coefficient, heat conduction and heat transfer coefficient, radiation heat transfer coefficient, specific heat, latent heat of solidification, alloy density, and solid / liquidus temperature of the alloy. Further, the heat conduction coefficient includes the heat conduction coefficient of the ceramic shell and the heat conduction coefficient of the non-shell medium; the radiation heat transfer coefficient includes the radiation heat transfer coefficient of the ceramic shell and the radiation heat transfer coefficient of the non-shell medium.

[0058] The surface microstructure parameters include: the structural shape, structural size, and arrangement pattern of the surface microstructure. The structural shape of the surface microstructure includes a square or a regular hexagon, or other regular geometric shapes. The arrangement pattern can be a square close-packed arrangement or a triangular close-packed arrangement. The square close-packed arrangement refers to a structural form in which each row and each column are aligned, such as the arrangement form in Figures 3 to 4 ; the triangular close-packed arrangement means that each groove in a row is located between the two closest grooves in the row above it and also between the two closest grooves in the row below it, such as the arrangement forms in Figures 6 to 8 and Figures 10 to 12 .

[0059] In step S3, specifically, aiming to optimize the microstructure of the alloy blade to be cast and eliminate defects such as stray grains and freckles, the basic directional solidification temperature field obtained in step S1 is optimized according to the mathematical model established in step S3, and the microstructure of the blade to be cast under the optimized basic directional solidification temperature field is obtained; it is judged whether there are non-uniform or defective conditions in the microstructure of the blade to be cast under the optimized basic directional solidification temperature field. If so, the surface microstructure parameters of the ceramic mold with a surface microstructure are changed, and then step S2 is repeated until the grain size, orientation, and structure meet the requirements and there are no defects such as stray grains. When the grain size, orientation, and structure meet the requirements and there are no defects such as stray grains, the modified surface microstructure parameters are saved, that is, the structure optimization of the ceramic mold with a surface microstructure is completed.

[0060] Embodiment 2

[0061] The present invention also discloses a ceramic mold with a surface microstructure, as shown in Figure 3 . It includes a ceramic mold body 1. An inner hollow chamber 2 is provided inside the ceramic mold body 1, and a plurality of grooves 3 with geometric configurations are provided on the outer wall of the ceramic mold body 1; the shape of the hollow chamber 2 is the same as the shape of the blade to be cast; the structural shape, structural size, and arrangement pattern of the grooves 3 with geometric configurations are optimized and determined according to the method in Embodiment 1 of the present invention. Of course, in this embodiment, the shape of the groove 3 is a square, which is only an example for explaining the technical solution of the present invention. The shape of the groove 3 can also be other shapes, which can be optimized and determined according to actual working conditions.

[0062] The ceramic mold body 1 is made by binder jetting, and the groove 3 is integrally provided with the ceramic mold body 1.

[0063] The wall thickness of the ceramic mold body 1 is uniform, and the wall thickness at the thickest part of the ceramic mold body 1 is the minimum thickness to ensure the mechanical properties of the ceramic mold, that is, the minimum thickness of the ceramic mold when the ceramic mold does not break or crack during the alloy casting process.

[0064] In addition, a selector base is provided at the bottom of the ceramic mold body 1 for crystal selection and supporting the integral ceramic mold. The selector base is also integrally provided with the ceramic mold body 1.

[0065] The method of the present invention uses a binder jet additive manufacturing process to manufacture a ceramic mold with a surface microstructure. On the premise that the mechanical strength of the ceramic mold meets the requirements of alloy casting, the design of the surface microstructure of the ceramic mold is realized, breaking through the design shackles that the traditional ceramic mold with a smooth outer wall cannot improve the temperature gradient at the directional solidification front of the casting, and carrying out a structural design on the ceramic mold to avoid problems such as high operation difficulty caused by indirectly increasing the longitudinal temperature gradient; the ceramic mold with a surface microstructure in the present invention can be processed by additive manufacturing technology, solving the problem that it is difficult to prepare complex microstructures by traditional processes, effectively shortening the production cycle and improving the production efficiency. Moreover, the ceramic mold with a surface microstructure in the present invention can also effectively reduce the volume and weight of the ceramic mold, save ceramic powder, and reduce costs.

[0066] The ceramic mold with a surface microstructure prepared based on the above method includes a ceramic mold body 1. A hollow chamber 2 is provided inside the ceramic mold body 1, and a plurality of grooves 3 with geometric configurations are provided on the outer wall of the ceramic mold body 1. Among them, the hollow chamber 2 is the internal working part, and the hollow chamber 2 is used to form the outer shape of the alloy blade, and its shape should be consistent with the structure of the alloy blade. The grooves 3 are used to control the uniformity of the alloy directional solidification temperature field and increase the longitudinal temperature gradient at the alloy solidification front. The thickness of the ceramic mold body 1, the depth of the grooves 3, and the thickness of the bottom of the grooves 3 from the inner wall of the hollow chamber 2 are all carefully designed to maintain the strength of the ceramic mold body 1 and prevent it from breaking under the action of the directional solidification pressure.

[0067] At the same time, the present invention also discloses a casting blade, which is obtained by casting with the above-mentioned ceramic mold with a surface microstructure. Due to the optimization of the surface microstructure of the ceramic mold, the microstructure of the casting blade has good uniformity and no tissue defects.

[0068] Example 3

[0069] In this embodiment, a gas turbine blade is selected as the part for precision casting. According to the method for optimizing the structure of a ceramic mold with a surface microstructure described in the present invention, as Figure 3 shown, a plurality of grooves 3 with a size of 2 mm × 2 mm squares are designed on the surface of the ceramic mold body 1. The depth of the grooves 3 is 5 mm, and the arrangement method is square close-packed. The thickness of the bottom of the grooves 3 from the inner wall of the ceramic mold body 1 is 5 mm, that is, the overall thickness of the ceramic mold body 1 is 10 mm. The heat preservation temperature of the ceramic mold is 1500 °C, and the pulling rate is 3 mm / min.

[0070] The heat conduction path of this embodiment is as Figure 4 shown. It can be seen from Figure 4 that compared with the traditional ceramic mold with a smooth outer wall, this heat conduction path is longer, which reduces the heat conduction rate in the longitudinal direction to a certain extent, increases the longitudinal temperature gradient, that is, increases the longitudinal temperature gradient of the mold shell.

[0071] In addition, Figure 5 Figure Figure 5 shows the temperature simulation results on the ceramic mold during pouring using the ceramic mold in Embodiment 3 of the present invention. It can be seen from

[0072] Embodiment 4

[0073] In this embodiment, a gas turbine blade is selected as the precision casting part. According to a ceramic mold structure optimization method with surface microstructures of the present invention, as Figures 6 to 7 shown, a plurality of 2 mm × 2 mm square grooves 3 are designed on the surface of the ceramic mold body 1. The depth of the groove 3 is 5 mm, and the arrangement is triangular close-packed. The thickness of the bottom of the groove 3 from the inner wall of the ceramic mold body 1 is 5 mm, that is, the overall thickness of the ceramic mold body 1 is 10 mm. The heat preservation temperature of the ceramic mold is 1500 °C, and the drawing rate is 3 mm / min.

[0074] The heat conduction path of this embodiment is as Figure 8 shown. It can be seen from Figure 8 that the heat conduction path of this embodiment case is longer than that of the square close-packed in Embodiment 1, and further reduces the heat conduction in the longitudinal direction to a greater extent, increasing the longitudinal temperature gradient, that is, increasing the longitudinal temperature gradient of the mold shell.

[0075] In addition, Figure 9 Figure Figure 9 shows the temperature simulation results on the ceramic mold during pouring using the ceramic mold with surface microstructures in this embodiment. It can be seen from

[0076] Embodiment 5

[0077] In this embodiment, a gas turbine blade is selected as the precision casting part. According to a ceramic mold structure optimization method with surface microstructures of the present invention, as Figures 10 to 11As shown in the figure, a plurality of regular hexagonal grooves 3 with a spacing of 1 mm are designed on the surface of the ceramic mold body 1. The depth of the groove 3 is 5 mm, the side length of the regular hexagonal groove 3 is 2 mm, and the arrangement method is triangular close packing. The thickness of the bottom of the groove 3 from the inner wall of the ceramic mold body 1 is 5 mm, that is, the overall thickness of the ceramic mold body 1 is 10 mm. The heat preservation temperature of the ceramic mold is 1500 °C, and the drawing rate is 3 mm / min.

[0078] The heat conduction path of this embodiment is as Figure 12 shown, and it can be seen from Figure 12 that the heat conduction path of this embodiment is more complex than that of Embodiment 1 and Embodiment 2. Furthermore, it can reduce the heat conduction in the longitudinal direction to a greater extent, resulting in a significant increase in the longitudinal temperature gradient, that is, the longitudinal temperature gradient of the mold shell is increased.

[0079] In addition, Figure 13 Figure Figure 13 is the temperature simulation result on the ceramic mold during casting using the ceramic mold in Embodiment 5 of the present invention. It can be seen from

[0080] that for the gas turbine blade prepared using the ceramic mold with surface microstructures in this embodiment, the microstructure of the blade is more uniform, and the solidification front tends to be horizontal. The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A structural optimization method for a ceramic mold with surface microstructures, characterized in that, It includes the following steps: S1: Establish a basic directional solidification temperature field by using a ceramic mold with a smooth outer surface; S2: Obtain the longitudinal temperature gradient when the blade to be cast undergoes directional solidification on a ceramic mold with surface microstructures, and establish a mathematical model between the longitudinal temperature gradient and the surface microstructure parameters; Optimize the basic directional solidification temperature field based on the mathematical model, and obtain the microstructure of the blade to be cast under the optimized basic directional solidification temperature field; S3: If there are non-uniformities or defects in the microstructure of the blade to be cast under the optimized basic directional solidification temperature field, adjust the surface microstructure parameters, and repeat S2 until the microstructure of the blade to be cast meets the requirements, thus completing the structural optimization of the ceramic mold with surface microstructures; the surface microstructure parameters include the structural shape, structural size, and arrangement pattern.

2. The structural optimization method of a ceramic mold with surface microstructures according to claim 1, characterized in that, In S1, the establishment of the basic directional solidification temperature field by using a ceramic mold with a smooth outer surface is specifically as follows: on the ceramic mold with a smooth outer surface, at least 10 temperature measurement zones are divided according to the shape change characteristics of the casting and the process requirements, and the simulated directional solidification temperature fields of each temperature measurement zone are obtained through numerical simulation; and an actual directional solidification experiment is carried out by using the ceramic mold with a smooth outer surface to obtain the actual temperature data of each temperature measurement zone, and the actual directional solidification temperature field of the directional solidification process is established based on the actual temperature data; Adjust the actual directional solidification temperature field by using the simulated directional solidification temperature field to complete the establishment of the basic directional solidification temperature field.

3. The structural optimization method of a ceramic mold with a surface microstructure according to claim 2, characterized in that, Fifteen of the temperature measurement zones are divided according to the shape change characteristics of the casting and the process requirements.

4. The structural optimization method of a ceramic mold with a surface microstructure according to claim 2, characterized in that, The adjustment of the actual directional solidification temperature field by using the simulated directional solidification temperature field to complete the establishment of the basic directional solidification temperature field is specifically as follows: if the temperature error between the actual directional solidification temperature field of any temperature measurement zone and the simulated directional solidification temperature field is greater than 10%, adjust the heat transfer parameters, and adjust the simulated directional solidification temperature field by using the actual directional solidification temperature field to make the temperature errors between the actual directional solidification temperature fields of all temperature measurement zones and the simulated directional solidification temperature field not greater than 10%, thus completing the adjustment of the simulated directional solidification temperature field and realizing the establishment of the basic directional solidification temperature field.

5. The structural optimization method of a ceramic mold with a surface microstructure according to claim 1, characterized in that In S2, the longitudinal temperature gradient is obtained through the thermal conductivity, heat transfer coefficient of heat conduction, radiation heat transfer coefficient, specific heat, latent heat of solidification, and the density, solidus temperature, and liquidus temperature of the alloy.

6. The structural optimization method of a ceramic mold with a surface microstructure according to claim 5, characterized in that, The thermal conductivity includes the thermal conductivity of the ceramic shell and the thermal conductivity of the non-shell medium; the radiation heat transfer coefficient includes the radiation heat transfer coefficient of the ceramic shell and the radiation heat transfer coefficient of the non-shell medium.

7. The structural optimization method of a ceramic mold with a surface microstructure according to claim 1, characterized in that, The structural shape of the surface microstructure includes a square or a regular hexagon.

8. A ceramic mold with a surface microstructure, characterized in that Optimized by the structural optimization method according to any one of claims 1 to 7; the ceramic mold includes a ceramic mold body (1), a hollow chamber (2) is provided inside the ceramic mold body (1), and a plurality of grooves (3) with geometric configurations are provided on the outer wall of the ceramic mold body (1); the shape of the hollow chamber (2) is consistent with the shape of the blade to be cast.

9. A ceramic mold with a surface microstructure according to claim 8, characterized in that, The ceramic mold body (1) is obtained by binder jetting.

10. Application of a ceramic mold with a surface microstructure according to any one of claims 8 to 9 in casting a blade.

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