A preparation process for additive manufacturing-hot isostatic pressing composite gradient materials

Abstract

This application discloses a fabrication process for additive manufacturing-hot isostatic pressing (HIP) composite gradient materials. First, the target gradient component is digitally discretized and positioned in three dimensions, dividing it into multiple gradient material filling regions and ceramic spacer medium filling regions, and the model is sliced. Then, a powder densification constitutive model is constructed using ANSYS finite element analysis, and multi-step transient analysis is performed on the entire HIP process to accurately predict component shrinkage, densification behavior, and residual stress. Subsequently, based on the sliced ​​data, a coaxial powder feeding additive manufacturing process is used to accurately fill and preform multiple components within a universal, repeatable steel sheath. Finally, the gradient component is obtained through HIP densification and post-processing. This invention uses a universal sheath instead of a customized sheath, and combines digital additive manufacturing to achieve precise and controllable fabrication of complex three-dimensional gradient structures, significantly shortening the production cycle, reducing fabrication costs, and improving the forming accuracy and performance consistency of the gradient component.

Description

Technical Field

[0001] This invention relates to the field of gradient functional materials preparation technology, specifically to a preparation process for additive manufacturing-hot isostatic pressing composite gradient materials. Background Technology

[0002] Hot isostatic pressing (HIP) is an advanced manufacturing technology that integrates powder metallurgy and isostatic pressing. It involves simultaneously applying high temperatures of 70% to 90% of the material's melting point and isotropic ultra-high static pressure of 100 MPa to 200 MPa to encapsulated metal powder within a sealed high-pressure container. This causes the powder particles to achieve consolidation, densification, and metallurgical bonding through creep, atomic diffusion, and plastic flow. This process can produce metal components with densities close to theoretical values ​​and mechanical properties superior to traditional forgings, and is widely used in high-end manufacturing fields such as aerospace, biomedicine, and nuclear power.

[0003] Currently, for the hot isostatic pressing (HIP) fabrication of metal-based graded functional materials, the publicly disclosed mainstream HIP methods all require a customized cladding that matches the component structure. The cladding material is mostly low-carbon steel, stainless steel, or glass, used to isolate high-pressure gases and transmit isostatic pressure. However, this type of technology suffers from the following insurmountable technical drawbacks:

[0004] 1. The design, welding, and airtightness testing of customized sleeves are complex processes, resulting in long production cycles and high manufacturing costs. Especially for complex structural components, sleeve design has become a core technical bottleneck restricting molding accuracy. Moreover, most sleeves are for single use, which further increases production costs.

[0005] 2. After hot isostatic pressing, the cladding needs to be removed by mechanical cutting, chemical pickling, electrolysis and other methods. This not only increases the number of processes, but also easily causes damage and component contamination to the near-surface layer of the component. At the same time, it generates a large amount of waste and wastewater, resulting in high environmental treatment costs.

[0006] 3. Precise control of gradient composition is difficult. Metal / ceramic powders with different compositions have significant differences in density, flowability and sintering characteristics. Traditional manual powder spreading or simple mechanical powder spreading is prone to problems such as interlayer mixing, interface blurring and structural collapse. The repeatability and consistency of gradient structure are poor, making it difficult to prepare complex three-dimensional continuous gradient structures.

[0007] 4. It is impossible to accurately predict the shrinkage differences of different materials during hot isostatic pressing, which can easily lead to problems such as component deformation, dimensional deviations, and residual stress concentration at the interface, resulting in a low finished product qualification rate. This is especially true for small-batch customized components, where the research and development iteration costs are extremely high.

[0008] In addition, existing technologies also disclose methods for preparing metal components by additive manufacturing combined with hot isostatic pressing, but these methods are only applicable to homogeneous metal components and do not involve the preparation of graded functional materials. Furthermore, they still require customized packaging and cannot solve the core pain points in the preparation process of the aforementioned graded materials. Summary of the Invention

[0009] To address the shortcomings of existing hot isostatic pressing (HIP) techniques for preparing gradient materials, such as high cost of customized encapsulation, complex processes, low precision in controlling gradient structures, poor molding consistency, and uncontrollable shrinkage deformation, this invention aims to provide a preparation process for composite gradient materials based on additive manufacturing-HIP. This process utilizes digital discrete modeling, precise finite element shrinkage prediction, coaxial powder feeding additive manufacturing, and a universal, repeatable encapsulation combined with a ceramic spacer medium to achieve low-cost, high-precision, and high-consistency preparation of gradient functional materials.

[0010] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0011] A preparation process for additive manufacturing-hot isostatic pressing composite gradient materials includes the following steps:

[0012] S1, Digital Discretization and Occupancy Modeling: The target gradient component is processed into a three-dimensional digital model. At the digital level, the component is discretized into at least two sets of filling regions of different metal-based gradient materials. The three-dimensional model of the gradient component is placed into the three-dimensional model of a general-purpose casing. The remaining space in the casing, excluding the filling region of the gradient component, is defined as the ceramic occupancy medium filling region. After the partitioning is completed, the three-dimensional model is sliced, and a coaxial powder feeding scanning path is generated according to the preset layer thickness.

[0013] S2, Finite Element Prediction Analysis of Hot Isostatic Pressing Shrinkage: Based on the slice and partition model of step S1, a three-dimensional analysis model containing different gradient materials, ceramic occupier medium and general package is constructed using ANSYS finite element software. Performance parameters of each partition material as a function of temperature are defined, and a custom constitutive model for powder densification adapted to the hot isostatic pressing process is defined. Transient structural analysis with multiple load steps is set up to simulate the complete hot isostatic pressing heating and pressurization, heat preservation and pressurization, and cooling and depressurization cycle process. The overall and directional shrinkage rate of the gradient component, densification evolution law and residual stress distribution data are obtained by solving the problem, thereby optimizing the three-dimensional model and slice parameters of step S1.

[0014] S3, Additive Manufacturing Preform Preparation: Based on optimized slice data and scanning path, a coaxial powder feeding additive manufacturing device is used to precisely deliver the corresponding powder to the corresponding filling area within the universal casing, deliver the corresponding metal-based powder to the gradient material filling area, and deliver ceramic powder to the ceramic occupier medium filling area; vibration densification treatment is assisted during the powder feeding process, and interlayer vibration compaction is performed after the single layer powder feeding is completed to obtain a powder preform with high initial density; after the preform is filled, the universal casing is vacuumed and sealed.

[0015] S4, Hot Isostatic Pressing Densification Treatment: The sealed general-purpose package, together with the internal powder preform, is placed into a hot isostatic pressing furnace. The hot isostatic pressing cycle is performed according to the preset process parameters, so that the powders of different metal-based gradient materials achieve complete densification and metallurgical bonding through plastic flow and atomic diffusion. During the process, the ceramic powder acts as a pressure transmission medium to transmit isostatic pressure, and at the same time, it acts as a space occupier to restrict the high-temperature flow of the metal powder. After cooling, a removable support structure is formed.

[0016] S5, Post-processing: After the hot isostatic pressing cycle, the general-purpose casing and ceramic spacer medium are removed to obtain a near-net-shape gradient functional component, which is then finished to obtain the target product.

[0017] In a preferred embodiment, in step S1, the preset layer thickness of the slicing process is 0.03mm to 10cm, which is adjusted according to the composition gradient accuracy and molding size requirements of the gradient component; the metal-based gradient material filling area includes at least a first metal powder filling area and a second metal powder filling area to achieve a stepped or continuous composition gradient distribution design.

[0018] In a preferred embodiment, in step S2, the powder densification constitutive model is imported through the ANSYS USERMAT subroutine, and either the Abouaf creep model or the Ashby powder yield model is used to describe the relationship between the relative density of the powder and stress, temperature, and holding time. In the multi-load step transient analysis, the large deformation effect and stress hardening options are enabled, the mesh is refined in the gradient material interface region, and the contact behavior between the cladding and the powder preform is defined. In the heat preservation and pressure holding stage, a time substep adapted to creep deformation is set.

[0019] In a preferred embodiment, in step S3, the particle size of both the metal-based powder and the ceramic powder is 0~250μm. The coaxial powder feeding device is equipped with a multi-hopper powder feeding system to simultaneously realize the independent conveying and precise proportioning of powders with different components, adapting to the preparation requirements of continuous gradient components.

[0020] In a preferred embodiment, in step S3, the vibration densification process employs an ultrasonic vibration device or a mechanical vibration device to apply continuous vibration to the general-purpose packaging throughout the powder feeding process; the interlayer vibration compaction is completed by a mechanical arm driven by the vibration compaction disc, which is linked to the powder feeding device, and the compaction pressure is adjusted according to the powder flowability and the preset initial density, so that the initial relative density of the powder preform is ≥65%.

[0021] In a preferred embodiment, in step S4, the hot isostatic pressing process parameters are as follows: the processing temperature is 70% to 90% of the melting point of the metal material to be densified, the processing pressure is 100 MPa to 200 MPa, and the holding time is 1 h to 6 h; the heating, pressurizing and cooling processes all adopt a linear control mode.

[0022] In a preferred embodiment, the ceramic occupant medium is made of high-temperature non-adhesive ceramic powder, which does not undergo metallurgical reaction or interfacial adhesion with the metal-based gradient material under the temperature and pressure conditions of hot isostatic pressing; the ceramic powder can be reused after sieving.

[0023] In a preferred embodiment, the universal casing is made of reusable low-carbon steel or stainless steel rectangular mold, which does not require customized design and processing based on the structure of the gradient component. After hot isostatic pressing and surface treatment, it can be reused for preform preparation.

[0024] In a preferred embodiment, in step S5, the ceramic spacer medium is loosened by vibration, and a steel rod is used simultaneously to further loosen the ceramic spacer medium, allowing the part to be removed directly. The universal sleeve can be recycled multiple times. The finishing process is carried out by CNC milling or grinding to meet the dimensional accuracy and surface roughness requirements of the component.

[0025] In one preferred embodiment, the gradient functional components include hot-end components for aerospace engines, biomedical metal implants, and wear-resistant gradient components for molds and dies, which are suitable for multi-variety, small-batch customized production and rapid research and development iteration of new material systems.

[0026] Due to the application of the above technical solution, the beneficial effects of this application compared with the prior art are as follows:

[0027] 1. Significantly reduced manufacturing costs and production cycle: This invention uses a reusable universal rectangular steel mold to replace the traditional disposable customized sleeve, completely eliminating the complex and costly processes of customized sleeve design, welding, and airtightness testing. It also avoids the subsequent acid washing and removal of the sleeve and the environmental treatment costs. The universal sleeve is reusable, and the ceramic occupant medium can be recycled and reused after screening, further reducing raw material costs. For small-batch customized gradient components, the production cycle can be shortened by more than 60%, and the overall manufacturing cost is reduced by more than 50%.

[0028] 2. Achieving high-precision, high-consistency, and controllable preparation of gradient structures: This invention digitizes the gradient component design and filling process, and achieves precise interlayer / intralayer distribution of powders with different components through coaxial powder feeding additive manufacturing technology. It can prepare arbitrarily complex three-dimensional stepped or continuous gradient structures, breaking through the gradient precision limitations of traditional powder spreading technology. At the same time, the powder feeding process is supplemented with full-process vibration and interlayer compaction, avoiding interlayer mixing of different powders and structural collapse. The molding consistency and repeatability of gradient structures are greatly improved, and the batch-to-batch component deviation can be controlled within 1%.

[0029] 3. Precise control of hot isostatic pressing shrinkage deformation to improve product qualification rate: This invention uses a custom powder densification constitutive model to perform multi-step transient finite element analysis on the entire hot isostatic pressing cycle process. It can accurately predict the overall and directional shrinkage rates of materials with different gradients, the densification evolution process and the distribution of residual stress at the interface, and optimize the model and process parameters in advance to avoid problems such as component deformation, dimensional deviation, and interface cracking. The product qualification rate can be increased to over 95%.

[0030] 4. Enhanced design freedom and R&D iteration efficiency: The gradient structure design of this invention is completely digital. Changing the gradient design only requires adjusting the three-dimensional digital model and powder feeding program, without the need to redesign and manufacture the packaging and mold. It is very suitable for customized production of gradient components with multiple varieties and small batches, as well as rapid R&D iteration of new material systems. The R&D cycle can be shortened by more than 70%.

[0031] 5. Improved overall performance of gradient components: This invention combines the precise composition control capability of additive manufacturing with the extreme densification capability of hot isostatic pressing. The density of the prepared gradient components can reach over 99.9%, close to the theoretical density. The gradient interface achieves good metallurgical bonding with no interface defects. The mechanical properties are superior to those of gradient components prepared by traditional forging processes, which can meet the stringent requirements of high-end applications such as aerospace hot-end components and biomedical implants. Attached Figure Description

[0032] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0033] Figure 1 This is a schematic diagram of a preparation process for an additive manufacturing-thermal isostatic pressing composite gradient material according to the present invention. Detailed Implementation

[0034] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0035] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate for the embodiments of this application described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0036] In this application, the terms "upper," "lower," "left," "right," "front," "rear," "top," "bottom," "inner," "outer," "middle," "vertical," "horizontal," "lateral," and "longitudinal" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are primarily for the purpose of better describing the invention and its embodiments, and are not intended to limit the indicated device, element, or component to having a specific orientation, or to be constructed and operated in a specific orientation.

[0037] Furthermore, in addition to indicating direction or positional relationship, some of the aforementioned terms may also have other meanings. For example, the term "above" may also be used in certain situations to indicate a dependency or connection. Those skilled in the art can understand the specific meaning of these terms in this invention based on the specific circumstances.

[0038] Furthermore, the terms "installation," "setup," "equipped with," "connection," "linking," and "socketing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral structure; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium, or an internal connection between two devices, components, or parts. Those skilled in the art can understand the specific meaning of these terms in this invention based on the specific circumstances.

[0039] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0040] Example 1

[0041] Please see Figure 1 This embodiment provides a preparation process based on additive manufacturing-hot isostatic pressing composite gradient material, wherein the additive manufacturing-hot isostatic pressing composite gradient material is a Ti6Al4V / TiNi gradient functional component, and the specific steps are as follows:

[0042] S1, Digital Discretization and Occupancy Modeling: The target Ti6Al4V / TiNi gradient joint implant is digitally modeled into a three-dimensional model. At the digital level, the component is discretized into a Ti6Al4V metal powder filling area (bone stem body, high strength area), a TiNi metal powder filling area (joint contact surface, high damping and wear-resistant area), and a gradient interface area with continuous component transition. The three-dimensional model of the gradient component is placed into a three-dimensional model of a stainless steel universal sleeve with dimensions of 200mm×150mm×100mm. The remaining space in the sleeve, excluding the gradient component filling area, is defined as the alumina ceramic occupancy medium filling area. After partitioning, the three-dimensional model is sliced ​​with a slice thickness of 0.1mm to generate a coaxial powder feeding scanning path.

[0043] S2, Finite Element Prediction Analysis of Hot Isostatic Pressure Shrinkage: Based on the slicing and partitioning model in step S1, a three-dimensional analysis model is established in ANSYS SpaceClaim. The geometry is divided into four bodies: Ti6Al4V, TiNi, alumina ceramic, and stainless steel cladding, and corresponding material properties are assigned. In Engineering Data, the elastic modulus, Poisson's ratio, coefficient of thermal expansion, thermal conductivity, and specific heat capacity of each material as a function of temperature are defined. The Abouaf creep densification constitutive model is imported through the USERMAT subroutine to describe the relationship between the relative density of the powder and stress, temperature, and time. SOLID186 high-order elements are used for mesh generation, and the mesh is refined in the Ti6Al4V / TiNi gradient interface region. The stainless steel cladding is set as an elastic body and a contact pair is established with the powder preform. In Transient The Structural system is configured with three load steps: Load step 1 is a heating and pressurization phase, where the temperature is linearly increased from room temperature to 920℃ and the pressure is linearly increased from 0 to 150MPa within 2 hours; Load step 2 is a heat preservation and pressure holding phase, where the temperature is maintained at 920℃ and 150MPa for 3 hours, with sufficient creep time substeps; Load step 3 is a cooling and pressurization phase, where the temperature is linearly reduced to room temperature and the pressure is reduced to normal pressure within 3 hours; The large deformation effect and stress hardening options are enabled in the solution settings; After the solution is completed, the overall shrinkage rate of the gradient component is 17.2%, and the shrinkage rates in the X / Y / Z directions are 16.8%, 17.1%, and 17.5%, respectively. The maximum residual stress at the interface is 285MPa, which is lower than the material yield strength. Based on this, the 3D model in step S1 is optimized for size compensation, and the slicing parameters are corrected.

[0044] S3, Additive Manufacturing Preform Preparation: Based on optimized slicing data and scanning path, a coaxial powder feeding additive manufacturing device with dual hoppers was used. Ti6Al4V powder and TiNi powder were respectively fed into corresponding areas within a general-purpose stainless steel casing, while alumina ceramic powder was fed into the remaining areas. The powder particle size was 15μm~53μm. During powder feeding, continuous vibration at 20kHz was applied by an ultrasonic vibration device outside the casing. After single-layer powder feeding, interlayer extrusion was performed by a vibratory compaction disc driven by a linked robotic arm. The compaction pressure was set to 0.5MPa, so that the initial relative density of the powder preform reached 68%. After the preform filling was completed, the general-purpose casing was evacuated at 400℃ for 2 hours to achieve a vacuum degree of 1×10⁻⁶. -3 After Pa, sealing welding is performed.

[0045] S4, Hot Isostatic Pressing Densification Treatment: The sealed general-purpose casing, together with the preform, is placed into a hot isostatic pressing furnace, and a hot isostatic pressing cycle is performed according to the process parameters optimized in step S2: the temperature is raised to 920℃, a pressure of 150MPa is applied, and the temperature and pressure are maintained for 3 hours, followed by linear cooling and depressurization to room temperature and atmospheric pressure; during the process, the alumina ceramic powder uniformly transmits the isostatic pressure, while restricting the high-temperature flow of Ti6Al4V and TiNi powders, and preventing interfacial adhesion with the metal powder.

[0046] S5, Post-processing: After hot isostatic pressing, the alumina ceramic spacer medium is loosened by vibration, and a steel rod is used simultaneously to further loosen the alumina ceramic spacer medium, allowing the part to be removed directly. The stainless steel universal sleeve can be recycled multiple times to obtain a near-net-shape Ti6Al4V / TiNi gradient joint implant. Finally, it is precision machined by CNC to meet the requirements of dimensional accuracy and surface roughness.

[0047] The Ti6Al4V / TiNi gradient component prepared in this embodiment has a density of 99.95%, and the gradient interface achieves complete metallurgical bonding without defects such as pores, cracks, or interface mixing. The batch-to-batch dimensional deviation is ≤0.05mm, and the comprehensive mechanical properties meet the requirements for use in medical implants. The general-purpose stainless steel sheath can be reused after surface treatment. The overall preparation cost is reduced by 58% compared with the traditional customized sheath process, and the production cycle is shortened by 65%.

[0048] Example 2

[0049] This embodiment provides a preparation process based on additive manufacturing-hot isostatic pressing (HIP) composite gradient material, wherein the additive manufacturing-hot isostatic pressing composite gradient material is an Inconel 718 / 316L stainless steel gradient functional component, used in aero-engine combustion chamber components. The specific steps are as follows:

[0050] S1, Digital Discretization and Occupancy Modeling: The target gradient combustion chamber component is processed into a three-dimensional digital model and discretized into an Inconel 718 high-temperature alloy powder filling area (hot end area), a 316L stainless steel powder filling area (cold end area), and a 5-layer stepped gradient transition area; the component model is placed into a low-carbon steel general-purpose cladding model with dimensions of 300mm×200mm×150mm, and the remaining space is defined as a zirconia ceramic occupancy medium filling area; the slice layer thickness is set to 0.5mm, and a coaxial powder feeding scanning path is generated.

[0051] S2, Finite Element Prediction Analysis of Hot Isostatic Pressing Shrinkage: An ANSYS finite element analysis model was established based on a partitioned model. The Ashby powder yield model was imported through the USERMAT subroutine, and the high-temperature performance parameters of each material were defined. In the mesh generation, the mesh was refined in the five gradient interface regions. The hot isostatic pressing process load steps were set as follows: the temperature and pressure were increased to 1150℃ and the pressure was increased to 180MPa within 3 hours; the temperature and pressure were maintained at 1150℃ and 180MPa for 4 hours; and the temperature and pressure were reduced to room temperature and normal pressure within 4 hours. The solution showed that the overall shrinkage rate of the component was 16.5%, the deviation of the shrinkage rate in each direction was ≤0.8%, and the residual stress at the interface was within the safe range. The model size compensation and parameter optimization were completed in this way.

[0052] S3, Additive Manufacturing Preform Preparation: Based on optimized slice data, a multi-hopper coaxial powder feeding device was used to accurately fill the powder. The particle sizes of Inconel 718, 316L, and zirconia powders were all 53μm~150μm. Throughout the powder feeding process, a mechanical vibration device applied continuous vibration of 50Hz to the casing. After single-layer powder feeding, the preform was compacted by a vibrating disc with a compaction pressure of 0.8MPa, achieving an initial relative density of 72%. After filling, the preform was degassed under vacuum at 450℃ for 3 hours, achieving a vacuum degree of 5×10⁻⁶. -4 After Pa, seal.

[0053] S4, Hot Isostatic Pressing Densification Treatment: Perform hot isostatic pressing cycles according to the optimized process parameters, and hold at 1150℃ and 180MPa for 4 hours to complete powder densification and metallurgical bonding.

[0054] S5, Post-processing: The zirconia ceramic spacer is loosened by vibration, and a steel rod is used to further loosen the zirconia ceramic spacer. The part is then directly removed. The low-carbon steel universal sleeve can be recycled multiple times. The target gradient combustion chamber component is obtained by CNC precision machining.

[0055] The Inconel 718 / 316L gradient component prepared in this embodiment has a density of 99.92%, good bonding at the stepped gradient interface, no interlayer mixing or defects, and its high-temperature mechanical properties meet the requirements for use in hot-end components of aero-engines. The finished product qualification rate is 96%, and the R&D iteration cycle is shortened by 72% compared with traditional processes.

[0056] Example 3

[0057] This embodiment provides a preparation process for additive manufacturing-hot isostatic pressing (HIP) composite gradient materials, wherein the additive manufacturing-hot isostatic pressing composite gradient material is a WC / high-speed steel gradient tooling. The specific steps are as follows:

[0058] S1, Digital Discretization and Occupancy Modeling: The target gradient mold is processed into a three-dimensional digital model and discretized into a WC-reinforced metal ceramic powder filling area (wear-resistant working surface), a high-speed steel powder filling area (strong and tough matrix), and a continuous gradient transition area; the component model is placed into a stainless steel universal sleeve model, and the remaining space is defined as a boron nitride ceramic occupancy medium filling area; the slice layer thickness is set to 0.05mm, and a coaxial powder feeding scanning path is generated.

[0059] S2, Finite Element Prediction Analysis of Hot Isostatic Pressing Shrinkage: An ANSYS finite element model was established, and an adapted densified constitutive model was imported. Hot isostatic pressing process parameters were set: temperature 1050℃, pressure 160MPa, and heat and pressure holding for 2 hours. The shrinkage rate and residual stress data were obtained through simulation and solution, and the model was optimized and dimensional compensation was completed.

[0060] S3, Additive Manufacturing Preform Preparation: A coaxial powder feeding device is used to accurately fill WC / high-speed steel powder and boron nitride ceramic powder with a powder particle size of 10μm~75μm; ultrasonic vibration is applied throughout the powder feeding process, and single-layer vibration compaction is performed to achieve an initial relative density of 70% for the preform; it is then sealed after vacuum degassing.

[0061] S4, hot isostatic pressing densification treatment: heat and pressure held at 1050℃ and 160MPa for 2 hours to complete densification and metallurgical bonding.

[0062] S5, Post-processing: The boron nitride ceramic spacer is loosened by vibration, and a steel rod is used simultaneously to further loosen the boron nitride ceramic spacer, allowing the part to be removed directly. The stainless steel universal sleeve can be recycled multiple times, and the gradient mold is obtained by grinding and finishing.

[0063] The WC / high-speed steel gradient tooling prepared in this embodiment has a working surface hardness of HRC65 or higher, good matrix impact toughness, no cracking or peeling at the gradient interface, and a service life that is more than 3 times longer than that of traditional homogeneous tooling.

[0064] Finally, it should be noted that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A preparation process for additive manufacturing-hot isostatic pressing composite gradient materials, characterized in that, Includes the following steps: S1, Digital Discretization and Occupancy Modeling: The target gradient component is processed into a three-dimensional digital model. At the digital level, the component is discretized into at least two sets of filling regions of different metal-based gradient materials. The three-dimensional model of the gradient component is placed into the three-dimensional model of a reusable low-carbon steel or stainless steel rectangular universal sleeve. The remaining space inside the sleeve, excluding the gradient component filling region, is defined as the ceramic occupancy medium filling region. After partitioning, the 3D model is sliced, and a coaxial powder feeding scanning path is generated according to the preset layer thickness. S2, Finite Element Prediction Analysis of Hot Isostatic Pressing Shrinkage: Based on the slice and partition model of step S1, a three-dimensional analysis model containing different gradient materials, ceramic occupier medium, and general-purpose casing is constructed using ANSYS finite element software. Performance parameters of each partition material as a function of temperature are defined, and a custom powder densification constitutive model adapted to the hot isostatic pressing process is defined. Differentiated modeling is performed for the shrinkage differences of different gradient materials to obtain the directional shrinkage rate of each region, and non-uniform size compensation is performed on the three-dimensional model accordingly. Transient structural analysis with multiple load steps is set up to simulate the complete hot isostatic pressing heating and pressurization, heat preservation and pressurization, and cooling and depressurization cycle process. The overall and directional shrinkage rates, densification evolution law, and residual stress distribution data of the gradient components are obtained by solving the problem, thereby optimizing the three-dimensional model and slice parameters of step S1. S3, Additive Manufacturing Preform Preparation: Based on optimized slice data and scanning paths, a coaxial powder feeding additive manufacturing device with multiple hoppers is used to simultaneously achieve independent conveying and precise deposition of gradient material powder and ceramic occupier medium powder in the same layer. Corresponding metal-based powder is conveyed in the gradient material filling area, and ceramic powder is conveyed in the ceramic occupier medium filling area. Vibration densification treatment is assisted during the powder feeding process. Interlayer vibration compaction and extrusion are linked synchronously with the powder feeding process. After the powder is conveyed in all areas of a single layer, overall vibration compaction and extrusion are performed immediately to obtain a powder preform with high initial density. After the preform is filled, the general-purpose casing is vacuumed and sealed. S4, Hot Isostatic Pressing Densification Treatment: The sealed general-purpose package, together with the internal powder preform, is placed into a hot isostatic pressing furnace. The hot isostatic pressing cycle is performed according to the preset process parameters, so that the powders of different metal-based gradient materials achieve complete densification and metallurgical bonding through plastic flow and atomic diffusion. During the process, the ceramic powder acts as a pressure transmission medium to transmit isostatic pressure, and at the same time, it acts as a space occupier to restrict the high-temperature flow of the metal powder. After cooling, a removable support structure is formed. S5, Post-processing: After the hot isostatic pressing cycle, the general-purpose casing and ceramic spacer medium are removed to obtain a near-net-shape gradient functional component, which is then finished to obtain the target product.

2. The preparation process of additive manufacturing-hot isostatic pressing composite gradient materials according to claim 1, characterized in that, In step S1, the preset layer thickness of the slicing process is 0.03mm~10cm, which is adapted and adjusted according to the composition gradient accuracy and molding size requirements of the gradient component; the metal-based gradient material filling area includes at least a first metal powder filling area and a second metal powder filling area to realize a stepped or continuous composition gradient distribution design.

3. The preparation process of additive manufacturing-hot isostatic pressing composite gradient materials according to claim 1, characterized in that, In step S2, the powder densification constitutive model is imported through the ANSYS USERMAT subroutine, and the Abouaf creep model or Ashby powder yield model is used to describe the relationship between the relative density of the powder and stress, temperature, and holding time. In the multi-load step transient analysis, the large deformation effect and stress hardening options are enabled, the mesh is refined in the gradient material interface region, and the contact behavior between the cladding and the powder preform is defined. In the heat preservation and pressure holding stage, a time substep adapted to creep deformation is set.

4. The preparation process of additive manufacturing-hot isostatic pressing composite gradient materials according to claim 1, characterized in that, In step S3, the particle size of both the metal-based powder and the ceramic powder is 0~250μm. The multi-bin coaxial powder feeding device simultaneously realizes the independent conveying and precise proportioning of powders with different components, adapting to the preparation requirements of continuous gradient components.

5. The preparation process of additive manufacturing-hot isostatic pressing composite gradient materials according to claim 1, characterized in that, In step S3, the vibration densification process employs an ultrasonic vibration device or a mechanical vibration device to apply continuous vibration to the general-purpose packaging throughout the powder feeding process. The interlayer vibration compaction is completed by a mechanical arm driven by a powder feeding device to compact the disc. The compaction pressure is adjusted according to the powder flowability and the preset initial density so that the initial relative density of the powder preform is ≥65%.

6. The preparation process of additive manufacturing-hot isostatic pressing composite gradient materials according to claim 1, characterized in that, In step S4, the hot isostatic pressing process parameters are as follows: the processing temperature is 70% to 90% of the melting point of the metal material to be densified, the processing pressure is 100 MPa to 200 MPa, and the holding time is 1 h to 6 h; the heating, pressurizing and cooling, and depressurizing processes all adopt a linear control mode.

7. The preparation process of additive manufacturing-hot isostatic pressing composite gradient materials according to claim 1, characterized in that, The ceramic occupant medium uses high-temperature non-adhesive ceramic powder, which does not undergo metallurgical reaction or interfacial bonding with the metal-based gradient material under the temperature and pressure conditions of hot isostatic pressing; the ceramic powder can be reused after sieving.

8. The preparation process of additive manufacturing-hot isostatic pressing composite gradient materials according to claim 1, characterized in that, The universal sheath, after hot isostatic pressing and surface treatment, can be repeatedly used for preform preparation.

9. The preparation process of additive manufacturing-hot isostatic pressing composite gradient materials according to claim 1, characterized in that, In step S5, the ceramic spacer medium is loosened by vibration, and a steel rod is used simultaneously to further loosen the ceramic spacer medium, allowing the part to be removed directly. The universal sleeve can be recycled multiple times. The finishing process is carried out by CNC milling or grinding to meet the dimensional accuracy and surface roughness requirements of the component.

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