Hot isostatic pressing method for preparing additive manufacturing substrates by mixing SS-PREP and EIGA Ti6Al4V ELI spherical powders

Abstract

This invention belongs to the field of hot isostatic pressing (HIP) of metal powders and near-net-shape forming in additive manufacturing. It discloses a method for preparing additive manufacturing substrates using a mixture of SS-PREP and EIGA Ti6Al4V ELI spherical powders. The method includes: Step 1: Selecting Ti6Al4V ELI powder prepared by SS-PREP and Ti6Al4V ELI powder prepared by EIGA, and mixing them in a specified ratio under a protective atmosphere; Step 2: Loading the mixed powder into a steel casing in a vacuum vibration powder loading device, and then degassing and sealing it; Step 3: Placing the sealed casing in a hot isostatic pressing device, sintering it under heat and pressure, and then cooling it using a gradient cooling process; Step 4: After cooling, machining to remove the steel casing, obtaining a large-size additive manufacturing substrate. The substrate prepared by this invention exhibits excellent comprehensive mechanical properties, exceeding those of traditional forgings, and meets the application requirements of additive manufacturing.

Description

Technical Field

[0001] This invention belongs to the field of hot isostatic pressing of metal powder and near-net-shape forming of additive manufacturing. In particular, it relates to a hot isostatic pressing method for preparing substrates for additive manufacturing by mixing spherical powders of SS-PREP (ultra-high speed plasma rotating electrode) and EIGA (electrode induction gas atomization) Ti6Al4V ELI (an ultra-low gap element titanium alloy, belonging to α-β type titanium alloy, widely used in aerospace, medical devices and industrial fields). It is especially suitable for preparing large-size Ti6Al4V ELI substrates for industrial-grade metal additive manufacturing. Background Technology

[0002] Metal additive manufacturing technology involves heating metal powder above its melting point, depositing it layer by layer, and rapidly solidifying it into complex-shaped parts. It mainly includes selective laser melting (SLM), laser powder feeding molding, and electron beam selective melting (EBLM). For additive manufacturing of titanium alloy parts, all three technologies require a substrate with high flatness, a coefficient of thermal expansion matching the forming material, and a certain thickness as a base to achieve metallurgical bonding with the part.

[0003] Currently, industrial-grade large-size titanium alloy substrates are typically manufactured using traditional processes such as forging, rolling, and casting. In the forging process, to ensure fatigue resistance and high-temperature stability, the substrate needs to withstand high residual stress and repeated thermal cycling (heating-cooling). However, repeated thermal cycling leads to thermal fatigue, easily causing interfacial stresses to exceed the yield strength of the titanium alloy, resulting in a tendency for microcracks (especially in thin-walled structures), thus shortening the substrate's lifespan. Existing industrial-grade substrates typically only support 20 to 50 printing cycles. The rolling process exhibits anisotropic mechanical properties; specifically, the properties differ significantly between the rolled and unrolled directions, and machining thick plates is difficult. Hot-rolled thick plates are prone to internal stress and require annealing.

[0004] In addition, the traditional methods of forging and rolling are difficult to heat uniformly and control thermal deformation when preparing large-size substrates. This results in a temperature difference of more than 100~150°C between the edge and the center. The substrate edge bends upward due to stress concentration, which affects the accuracy of subsequent printing layers. The typical deformation can reach 0.5~2mm / m. Furthermore, the internal stress difference can also reduce the fatigue life of the printed parts by 20% to 30%.

[0005] In view of this, the present invention is hereby proposed. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and propose a hot isostatic pressing method for preparing additive manufacturing substrates by mixing SS-PREP and EIGATi6Al4V ELI spherical powders. This method achieves multiple objectives of stress control, efficiency improvement and cost reduction through process optimization, providing a more economical and reliable technical solution for the industrial production of titanium alloy substrates.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] On one hand, the present invention provides a hot isostatic pressing method for preparing additive manufacturing substrates by mixing SS-PREP and EIGA Ti6Al4V ELI spherical powders, comprising the following steps:

[0009] Step 1: Mix the Ti6Al4V ELI powder prepared by SS-PREP and the Ti6Al4VELI powder prepared by EIGA under a protective atmosphere according to the set ratio to obtain a mixed powder.

[0010] Step 2: In a vacuum vibration powder loading equipment, the mixed powder is loaded into a sleeve that is compatible with the structure of the Ti6Al4V ELI substrate to be prepared, and then degassed and sealed.

[0011] Step 3: Place the sealed sleeve in a hot isostatic pressing (HIP) machine, maintain the temperature and pressure for sintering and shaping, and then cool it down gradually.

[0012] Step 4: After cooling, the casing is removed by machining to obtain a large-sized Ti6Al4V ELI substrate.

[0013] Furthermore, in step 1, the Ti6Al4V ELI powder prepared by SS-PREP has a particle size of 53~250μm, sphericity >95%, flowability <25s / 50g, hollow powder rate <0.5%, and tap density >2.9g / cm³. 3 The oxygen content is 600~800ppm; the Ti6Al4V ELI powder prepared by EIGA has a particle size of 53~250μm, sphericity >85%, flowability <35s / 50g, hollow powder rate <1%, and tap density >2.8g / cm³. 3 The oxygen content is 800~1300ppm.

[0014] Furthermore, in step 1, the atmosphere is 99.999% argon.

[0015] Further, in step 1, the set ratio is a mass ratio of 1:1; during the mixing process, the weight of a single mixing is 100~1000kg, the rotation speed is 15~20r / min, and the time is 2~4h.

[0016] Further, in step 1, the sphericity of the mixed powder is >90%, the flowability is <30s / 50g, the hollow powder ratio is between 0.25% and 0.75%, and the tap density is >2.8g / cm³. 3 The oxygen content is between 700 and 1050 ppm.

[0017] Furthermore, in step 2, the powder loading vacuum degree is <10. -3 Pa, the powder loading temperature is 400~450℃, and after holding at this temperature for 2~3 hours, degassing is performed.

[0018] Furthermore, in step 3, during the heat preservation and pressure holding sintering process, the heating rate is 10℃ / min, the heat preservation temperature is 920~950℃, the pressure holding pressure is 150MPa, and the heat preservation and pressure holding time is 2~4h.

[0019] Furthermore, in step 3, during the gradient cooling process, in the first gradient cooling stage, the temperature is reduced from HIP (hot isostatic pressing) to 900℃ at a cooling rate of 8~10℃ / min; in the second gradient cooling stage, the temperature is reduced from 900℃ to 800℃ at a cooling rate of 5~8℃ / min; in the third gradient cooling stage, the temperature is reduced from 800℃ to 600℃ at a cooling rate of 3~5℃ / min; in the fourth gradient cooling stage, the temperature is reduced from 600℃ to 300℃ at a cooling rate of 1~3℃ / min; and in the fifth gradient cooling stage, the temperature is naturally cooled from 300℃ to room temperature.

[0020] Furthermore, the Ti6Al4V ELI substrate obtained in step 4 has an oxygen content of 800~1300ppm, tensile strength >920MPa, yield strength >850MPa, elongation >12%, reduction of area >40%, fracture toughness >100MPa·mˆ1 / 2, hardness >35HRC, and density >99.99%.

[0021] On the other hand, the present invention provides an application of a Ti6Al4V ELI substrate prepared by the hot isostatic pressing method for preparing additive manufacturing substrates as described above in the additive manufacturing of titanium alloy parts.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1) This invention innovates the raw material system and forming process by mixing Ti6Al4V ELI spherical powders prepared by SS-PREP and EIGA processes in a specific ratio to form a composite raw material system with complementary properties. Through a near-net-shape forming process using hot isostatic pressing, relying on the combined effects of particle proximity and rearrangement mechanisms, plastic deformation mechanisms, and diffusion creep mechanisms, large-size Ti6Al4V ELI substrates are ultimately formed. This solves the problem of traditional processes causing microcracks in the substrate due to repeated thermal cycling, thus shortening the substrate's lifespan, and the difficulty in uniform heating and controlling thermal deformation during the preparation of large-size substrates using traditional processes, leading to warping deformation at the edges due to stress concentration. The method of this invention can effectively improve material utilization, save R&D and production cycles, improve microstructure uniformity, and eliminate the differences in mechanical properties in different directions of the substrate, providing a new technical path that combines reliability and economy for the industrial preparation of high-performance large-size titanium alloy substrates.

[0024] 2) This invention uses a mixture of spherical powders prepared by SS-PREP and EIGA processes in a specific ratio, achieving precise control over powder properties. The hollow powder ratio is adjusted to 0.25%~0.75%, and the oxygen content to 700~1050ppm, thereby leveraging the excellent fracture toughness and plasticity of SS-PREP Ti6Al4V ELI powder-based parts and the excellent strength and hardness of EIGA Ti6Al4V ELI powder-based parts. This overcomes the bottlenecks of insufficient comprehensive performance, low utilization rate, and limited application scenarios in the preparation of 53~250μm coarse-grained Ti6Al4V ELI titanium alloy powders by traditional atomization processes. Furthermore, through the mixed powder hot isostatic pressing process, it is applied to the preparation of large-size substrates in the additive manufacturing field, significantly improving the comprehensive mechanical properties of the substrates and providing a new path for the low-cost and high-efficiency production of high-performance large-size titanium alloy substrates.

[0025] 3) This invention uses powder with a particle size of 53~250μm instead of powder with a particle size of 15~53μm as raw material. Through a dual approach of optimizing raw material costs and innovating process technology, it significantly reduces raw material consumption costs while ensuring high substrate performance, thereby maximizing economic benefits. Specifically, the selection of larger particle size powder can directly reduce raw material costs. At the same time, combined with targeted process optimization, it avoids performance loss caused by particle size differences, ultimately achieving efficient synergy between low-cost raw materials and high-performance substrate preparation.

[0026] 4) This invention innovatively employs a gradient cooling method after the hot isostatic pressing process, which can reduce the residual stress of the Ti6Al4V ELI substrate by 40%~60%. Compared with traditional forgings, it eliminates the stress-relief annealing process, reduces manufacturing costs and shortens the production cycle. At the same time, the prepared substrate has excellent comprehensive mechanical properties, which are higher than those of forgings, meeting the application requirements of additive manufacturing. Attached Figure Description

[0027] The accompanying drawings are incorporated in and form part of this specification, and together with the description serve to explain the principles of the invention.

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a schematic diagram of the hot isostatic pressing method for preparing additive manufacturing substrates according to the present invention.

[0030] Figure 2 Scanning image of SS-PREP Ti6Al4V ELI powder, the ultra-high speed plasma rotating electrode of this invention;

[0031] Figure 3 This is a scanning electron microscope image of EIGA Ti6Al4V ELI powder atomized by the electrode sensing gas of this invention.

[0032] Figure 4 This is a scanned image of the ultra-high speed plasma rotating electrode SS-PREP and the electrode-induced gas atomized EIGA Ti6Al4VELI powder after mixing according to the present invention.

[0033] Figure 5 The image shows the metallographic structure of the hot isostatic pressing substrate of Ti6Al4V ELI mixed powder in Example 1.

[0034] Figure 6 This is a photograph of the hot isostatic pressing substrate of the 1Ti6Al4V ELI mixed powder of the present invention.

[0035] Figure 7 Metallographic image of the hot isostatic pressing substrate of Ti6Al4V ELI mixed powder in Example 2;

[0036] Figure 8 This is a metallographic image of the hot isostatic pressing substrate of Ti6Al4V ELI mixed powder in Example 3. Detailed Implementation

[0037] Exemplary embodiments will now be described in detail. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Rather, they are merely examples consistent with some aspects of the invention as detailed in the appended claims.

[0038] On the one hand, please refer to Figure 1This invention provides a hot isostatic pressing method for preparing additive manufacturing substrates using a mixture of SS-PREP and EIGA Ti6Al4V ELI spherical powders, comprising the following steps:

[0039] Step 1: Mix Ti6Al4V ELI spherical powder prepared by SS-PREP and Ti6Al4V ELI spherical powder prepared by EIGA at a mass ratio of 1:1 under 99.999% argon protection using a double cone mixer to obtain mixed powder.

[0040] Specifically, such as Figure 2 As shown, the Ti6Al4V ELI spherical powder prepared by the SS-PREP process has a particle size of 53~250μm, sphericity >95%, flowability <25s / 50g, hollow powder rate <0.5%, and tap density >2.9g / cm³. 3 The oxygen content is 600~800 ppm; such as Figure 3 As shown, the Ti6Al4V ELI spherical powder prepared by EIGA has a particle size of 53~250μm, sphericity >85%, flowability <35s / 50g, hollow powder rate <1%, and tap density >2.8g / cm³. 3 The oxygen content is 800~1300ppm.

[0041] The two powders are mixed, with a single mixing weight of 100~1000kg, a rotation speed of 15~20r / min, and a mixing time of 2~4h.

[0042] It should be noted that while spherical metal powders have good flowability, they are prone to segregation. Therefore, selecting appropriate mixing equipment and optimizing mixing parameters (to avoid over-mixing) are crucial. This invention uses a double-cone mixer combined with the above-mentioned mixing method to ensure the uniformity of the final powder, thereby ensuring the consistency of the final product's composition, the uniformity of its microstructure, and the reliability of its mechanical properties, physical properties, and overall quality.

[0043] like Figure 4 As shown, after uniform mixing, the sphericity of the mixed powder is >90%, the flowability is <30s / 50g, the hollow powder ratio is between 0.25% and 0.75%, and the tapped density is >2.8g / cm³. 3 The oxygen content is between 700 and 1050 ppm.

[0044] It should be noted that when using the HIP process to fabricate large-size Ti6Al4V ELI substrates, optimized parameters after uniform mixing of the Ti6Al4V ELI powder can significantly improve process efficiency and product performance. Specifically, suitable sphericity and reasonable flowability ensure that the powder is tightly packed and uniformly distributed within the encapsulation, avoiding stress concentration or deformation during the HIP process due to localized accumulation differences. This also supports near-net-shape forming of complex shapes and reduces subsequent machining costs. Furthermore, a lower hollow powder ratio eliminates internal porosity issues at the source. Combined with high tap density, this significantly reduces the pressure and holding time required for HIP densification (the cycle can be shortened by 15%~20%), allowing the substrate's relative density to exceed 99.9%, with almost no residual porosity. This improves the ultrasonic testing pass rate to ASTM B311 Class A standard (defects <200μm), while maintaining relatively low cost. Strictly controlled oxygen content (700~1050ppm) suppresses α-phase coarsening under high temperature and high pressure (920~950℃ / 150MPa) process window, ensuring the substrate achieves aerospace-grade mechanical properties: tensile strength ≥920MPa, elongation ≥12% (meeting AMS 4928 standard), and fatigue life is improved compared to conventional powders. As can be seen, the synergistic effect of the mixed powder parameters in this invention not only optimizes the economics of the HIP process (yield >98%, material utilization increased by 30%), but also endows the Ti6Al4V ELI substrate with superior reliability.

[0045] Step 2: In a vacuum vibration powder loading device, the mixed powder is loaded into a steel sleeve that is compatible with the structure of the substrate to be prepared, and then degassed and sealed.

[0046] Specifically, the vacuum degree of powder filling is <10. -3 Pa, the powder loading temperature is 400~450℃, and after holding at this temperature for 2~3 hours, degassing is performed.

[0047] The vacuum vibration powder loading equipment is a powder loading device that can continuously load powder into a vibrating sleeve in a high vacuum environment. It belongs to the existing technology and will not be described in detail here.

[0048] It should be noted that the core reason for choosing steel sheathing in the HIP process is that its comprehensive performance perfectly matches the stringent requirements of the technology for high-temperature and high-pressure environments, while also considering process reliability and economy. Steel (especially stainless steel) maintains excellent high-temperature strength and creep resistance under HIP conditions, effectively resisting plastic deformation or cracking caused by high-pressure gases. In contrast, lightweight metals (such as titanium and aluminum) or ceramics are prone to softening and collapse or brittle cracking under these conditions. The ductility of steel allows for high-airtightness sealing through welding, completely isolating the pressure medium (argon) from the powder, preventing contamination of the workpiece. Furthermore, its coefficient of thermal expansion (approximately 12~18×10⁻⁶) is also advantageous. -6 / ℃) and common metal powders (such as TC4 titanium alloy: 8.6~9.5×10 -6 The temperature (°C) is close to that of steel, significantly reducing residual stress caused by shrinkage differences during the cooling stage and ensuring the geometric accuracy and internal integrity of the workpiece. In addition, steel can be made into complex-shaped sleeves using mature processing technologies (welding, spinning), supporting near-net-shape forming, and the cost is much lower than that of refractory metals such as tantalum and molybdenum. After HIP, it can be efficiently removed by mechanical peeling combined with conventional pickling, avoiding damage to the workpiece surface.

[0049] Step 3: Place the sealed sleeve in a hot isostatic pressing (HIP) machine, maintain the temperature and pressure for sintering and shaping, and then cool it down gradually.

[0050] Specifically, during the heat preservation and pressure holding sintering process, the heating rate is 10℃ / min, the heat preservation temperature is 920~950℃, the pressure holding pressure is 150MPa, and the heat preservation and pressure holding time is 2~4h.

[0051] It should be noted that this invention employs a heating rate of 10℃ / min to avoid premature sintering and formation of closed pores on the surface of the mixed powder particles due to rapid thermal shock in the HIP process. Simultaneously, it reduces the temperature gradient caused by the low thermal conductivity of titanium alloy (approximately 7 W / m·K), providing a uniform thermal field for subsequent densification. The holding temperature is set in the α+β two-phase region of 920~950℃. This utilizes the high diffusion rate of the β phase (body-centered cubic) to accelerate atomic migration, while the α phase (hexagonal close-packed) pins grain boundaries to suppress grain coarsening, achieving pore closure while obtaining a fine-grained equiaxed microstructure (grains <20μm). Applying a high pressure of 150MPa, far exceeding the yield strength of TC4 at 900℃ (≈20MPa), forces plastic rheological compression to crush interparticle gaps and potential hollow powder, and increases the vacancy chemical potential, thereby increasing the diffusion densification rate by more than 10 times. The system employs a three-stage densification process involving 2-4 hours of heat and pressure treatment: initial particle rearrangement eliminates macropores, mid-stage volume diffusion closes submicron pores, and final stage vacancy diffusion eliminates isolated closed pores, simultaneously promoting the uniform distribution of β-stabilizing elements (V, Fe). This parameter set, through a synergistic mechanism of thermal activation (diffusion), force-driven (plasticity), and time, achieves comprehensive performance with a residual porosity of <0.05% and a tensile strength ≥920MPa while suppressing β-phase coarsening and α-phase embrittlement, providing a highly reliable substrate for aerospace-grade components.

[0052] Furthermore, in the gradient cooling process, in the first gradient cooling stage, the temperature is reduced from the HIP temperature to 900℃ at a cooling rate of 8~10℃ / min. Rapid cooling to 900℃ reduces the high-temperature dwell time, suppresses β-grain coarsening, and avoids oxide layer thickening caused by slow cooling. In the second gradient cooling stage, the temperature is reduced from 900℃ to 800℃ at a cooling rate of 5~8℃ / min. Slowing down the cooling rate reduces the phase transformation driving force, resulting in more uniform α-phase precipitation and reducing stress concentration caused by local volume changes. The third gradient cooling stage... The first cooling stage involves a slow cooling rate of 3-5℃ / min from 800℃ to 600℃ in the α+β two-phase region, promoting phase transformation uniformity and reducing microstructure stress. The second cooling stage involves a slow cooling rate of 1-3℃ / min from 600℃ to 300℃ in the low-temperature region, allowing residual stress to be released through plastic deformation and diffusion mechanisms. The third cooling stage involves natural cooling from 300℃ to room temperature, relying on natural heat dissipation from the environment to ensure overall temperature uniformity and prevent residual tensile stress caused by sudden surface cooling.

[0053] Step 4: After cooling, the casing is removed by machining to obtain a large-sized Ti6Al4V ELI substrate;

[0054] The Ti6Al4V ELI substrate obtained in step 4 has an oxygen content of 800~1300ppm, tensile strength >920MPa, yield strength >850MPa, elongation >12%, reduction of area >40%, fracture toughness >100MPa·mˆ1 / 2, hardness >35HRC, and density >99.99%.

[0055] It should be added that the industrial-grade large-size Ti6Al4V ELI substrate has a length of no less than 1000mm, a width of no less than 800mm, and a thickness of no less than 80mm.

[0056] On the other hand, the present invention provides an application of a large-size Ti6Al4V ELI substrate, prepared by the hot isostatic pressing method for preparing additive manufacturing substrates as described above, in the additive manufacturing of titanium alloy parts. This includes applications such as selective laser melting, laser powder feeding, and electron beam selective melting in the manufacture of titanium alloy parts.

[0057] To further verify the effectiveness of the present invention, the inventors conducted the following specific experiments:

[0058] Example 1

[0059] This embodiment provides a hot isostatic pressing method for preparing additive manufacturing substrates using a mixture of SS-PREP and EIGA Ti6Al4V ELI spherical powders, including the following steps:

[0060] Step 1: Mix Ti6Al4V ELI powder prepared by SS-PREP and Ti6Al4V ELI powder prepared by EIGA at a mass ratio of 1:1 under 99.999% argon protection using a double cone mixer to obtain mixed powder.

[0061] Specifically, the Ti6Al4V ELI powder prepared by the SS-PREP process has a particle size of 53~250μm, a sphericity of 96%, a flowability of 24s / 50g, a hollow powder rate of 0.48%, and a tap density of 2.91g / cm³. 3 The oxygen content is 600 ppm;

[0062] The Ti6Al4V ELI powder prepared by the EIGA process has a particle size of 53~250μm, a sphericity of 86%, a flowability of 34s / 50g, a hollow powder content of 0.98%, and a tap density of 2.81g / cm³. 3 The oxygen content is 1300 ppm;

[0063] The two powders were mixed, with a single mixing weight of 1000 kg, a mixing time of 4 h, and a rotation speed of 20 r / min.

[0064] After thorough mixing, the mixed powder exhibited the following characteristics: sphericity 91%, flowability 29s / 50g, hollow powder content 0.73%, and tap density 2.86g / cm³. 3 Oxygen content 950ppm.

[0065] Step 2: In the vacuum vibration powder loading equipment, the mixed powder is loaded into a rectangular steel sleeve, and then degassed and sealed.

[0066] Specifically, the powder filling vacuum degree is 9×10 -4 Pa, powder loading temperature of 450℃, degassing under the condition of heat preservation for 3 hours.

[0067] Step 3: Place the sealed sleeve in a hot isostatic pressing (HIP) machine, maintain the temperature and pressure for sintering and shaping, and then cool it down gradually.

[0068] Specifically, during the heat preservation and pressure holding sintering process, the heating rate is 10℃ / min, the heat preservation temperature is 950℃, the pressure holding pressure is 150MPa, and the heat preservation and pressure holding time is 4h.

[0069] The gradient cooling process is as follows: Phase 1: Cooling from 950°C to 900°C at a cooling rate of 10°C / min; Phase 2: Cooling from 900°C to 800°C at a cooling rate of 8°C / min; Phase 3: Cooling from 800°C to 600°C at a cooling rate of 5°C / min; Phase 4: Cooling from 600°C to 300°C at a cooling rate of 3°C / min; Phase 5: Natural cooling from 300°C to room temperature.

[0070] Step 4: After cooling, the casing is removed by machining to obtain a large-sized Ti6Al4V ELI substrate, such as... Figure 5 and Figure 6 As shown;

[0071] The Ti6Al4V ELI substrate prepared by the method in this embodiment has a length of 1000 mm, a width of 800 mm, and a thickness of 80 mm; an oxygen content of 1100 ppm; a tensile strength of 938 MPa; a yield strength of 876 MPa; an elongation of 14%; a reduction of area of ​​44%; a fracture toughness of 108 MPa·mˆ1 / 2; a hardness of 35.3 HRC; and a density of 99.997%.

[0072] In this embodiment, the Ti6Al4V ELI substrate has a lifespan of 55 printing cycles.

[0073] Example 2

[0074] This embodiment provides a hot isostatic pressing method for preparing additive manufacturing substrates using a mixture of SS-PREP and EIGA Ti6Al4V ELI spherical powders, including the following steps:

[0075] Step 1: Mix Ti6Al4V ELI powder prepared by SS-PREP and Ti6Al4V ELI powder prepared by EIGA at a mass ratio of 1:1 under 99.999% argon protection using a double cone mixer to obtain mixed powder.

[0076] Specifically, the Ti6Al4V ELI powder prepared by the SS-PREP process has a particle size of 53~250μm, a sphericity of 97%, a flowability of 23s / 50g, a hollow powder rate of 0.25%, and a tap density of 2.92g / cm³. 3 The oxygen content is 600 ppm;

[0077] The Ti6Al4V ELI powder prepared by the EIGA process has a particle size of 53~250μm, a sphericity of 87%, a flowability of 33s / 50g, a hollow powder content of 0.75%, and a tap density of 2.82g / cm³. 3 The oxygen content is 800 ppm;

[0078] The two powders were mixed, with a single mixing weight of 100 kg, a mixing time of 2 h, and a rotation speed of 15 r / min.

[0079] After thorough mixing, the mixed powder exhibits the following characteristics: sphericity 92%, flowability 28s / 50g, hollow powder content 0.50%, and tap density 2.87g / cm³. 3 Oxygen content 700ppm.

[0080] Step 2: In the vacuum vibration powder loading equipment, the mixed powder is loaded into a rectangular steel sleeve, and then degassed and sealed.

[0081] Specifically, the powder filling vacuum degree is 8×10 -4 Pa, powder loading temperature of 400℃, degassing under the condition of heat preservation for 2 hours.

[0082] Step 3: Place the sealed sleeve in a hot isostatic pressing (HIP) machine, maintain the temperature and pressure for sintering and shaping, and then cool it down gradually.

[0083] Specifically, during the heat preservation and pressure holding sintering process, the heating rate is 10℃ / min, the heat preservation temperature is 920℃, the pressure holding pressure is 150MPa, and the heat preservation and pressure holding time is 2h.

[0084] The gradient cooling process is as follows: Phase 1: Cooling from 920°C to 900°C at a cooling rate of 8°C / min; Phase 2: Cooling from 900°C to 800°C at a cooling rate of 5°C / min; Phase 3: Cooling from 800°C to 600°C at a cooling rate of 3°C / min; Phase 4: Cooling from 600°C to 300°C at a cooling rate of 1°C / min; Phase 5: Natural cooling from 300°C to room temperature.

[0085] Step 4: After cooling, the casing is removed by machining to obtain a large-sized Ti6Al4V ELI substrate, such as... Figure 7 As shown;

[0086] Specifically, the Ti6Al4V ELI substrate prepared in this embodiment has a length of 1000 mm, a width of 850 mm, and a thickness of 100 mm. It has an oxygen content of 800 ppm, a tensile strength of 930 MPa, a yield strength of 865 MPa, an elongation of 15%, a reduction of area of ​​46%, a fracture toughness of 110 MPa·m⁻¹ / ², a hardness of 36.6 HRC, and a density of 99.998%.

[0087] In this embodiment, the Ti6Al4V ELI substrate has a lifespan of 60 printing cycles.

[0088] Example 3

[0089] This embodiment provides a hot isostatic pressing method for preparing additive manufacturing substrates using a mixture of SS-PREP and EIGA Ti6Al4V ELI spherical powders, including the following steps:

[0090] Step 1: Mix Ti6Al4V ELI powder prepared by SS-PREP and Ti6Al4V ELI powder prepared by EIGA at a mass ratio of 1:1 under 99.999% argon protection using a double cone mixer to obtain mixed powder.

[0091] Specifically, the Ti6Al4V ELI powder prepared by the SS-PREP process has a particle size of 53~250μm, a sphericity of 98%, a flowability of 22s / 50g, a hollow powder rate of 0.02%, and a tap density of 2.93g / cm³. 3 The oxygen content is 800 ppm;

[0092] The Ti6Al4V ELI powder prepared by the EIGA process has a particle size of 53~250μm, a sphericity of 88%, a flowability of 32s / 50g, a hollow powder content of 0.52%, and a tap density of 2.82g / cm³. 3 The oxygen content is 1300 ppm;

[0093] The two powders were mixed, with a single mixing weight of 500 kg, a mixing time of 3 h, and a rotation speed of 18 r / min.

[0094] After thorough mixing, the mixed powder exhibits the following characteristics: sphericity 93%, flowability 27s / 50g, hollow powder content 0.27%, and tap density 2.88g / cm³. 3 Oxygen content 1050ppm.

[0095] Step 2: In the vacuum vibration powder loading equipment, the mixed powder is loaded into a rectangular steel sleeve, and then degassed and sealed.

[0096] Specifically, the powder filling vacuum degree is 7×10 -4 Pa, powder loading temperature of 425℃, degassing under the condition of heat preservation for 2.5h.

[0097] Step 3: Place the sealed sleeve in a hot isostatic pressing (HIP) machine, maintain the temperature and pressure for sintering and shaping, and then cool it down gradually.

[0098] Specifically, during the heat preservation and pressure holding sintering process, the heating rate is 10℃ / min, the heat preservation temperature is 935℃, the pressure holding pressure is 150MPa, and the heat preservation and pressure holding time is 3h.

[0099] The gradient cooling process is as follows: Phase 1: Cooling from 935°C to 900°C at a cooling rate of 9°C / min; Phase 2: Cooling from 900°C to 800°C at a cooling rate of 6.5°C / min; Phase 3: Cooling from 800°C to 600°C at a cooling rate of 4°C / min; Phase 4: Cooling from 600°C to 300°C at a cooling rate of 2°C / min; Phase 5: Natural cooling from 300°C to room temperature.

[0100] Step 4: After cooling, the casing is removed by machining to obtain a large-sized Ti6Al4V ELI substrate, such as... Figure 8 As shown;

[0101] Specifically, the Ti6Al4V ELI substrate prepared in this embodiment has a length of 1250 mm, a width of 1250 mm, and a thickness of 120 mm. It has an oxygen content of 1300 ppm, a tensile strength of 946 MPa, a yield strength of 887 MPa, an elongation of 14%, a reduction of area of ​​45%, a fracture toughness of 108 MPa·m⁻¹ / ², a hardness of 36.0 HRC, and a density of 99.999%.

[0102] In this embodiment, the Ti6Al4V ELI substrate has a lifespan of 52 printing cycles.

[0103] Comparative Example 1

[0104] The preparation process is as follows:

[0105] Step 1: Use an ultra-high speed plasma rotating electrode to atomize Ti6Al4V ELI powder with a particle size range of 53~250μm prepared by SS-PREP;

[0106] Specifically, the Ti6Al4V ELI powder with a particle size range of 53~250μm prepared by SS-PREP has a sphericity of 96%, a flowability of 21s / 50g, a hollow powder content of 0.45%, and a tap density of 2.91g / cm³. 3 The oxygen content is 500 ppm;

[0107] Step 2: In the vacuum vibration powder loading equipment, SS-PREP powder is loaded into a rectangular steel sleeve, and then degassed and sealed.

[0108] The powder filling vacuum degree is 2×10 -2 Pa, powder loading temperature is 350℃, degassing is performed under the condition of heat preservation for 1 hour;

[0109] Step 3: Place the sealed sleeve in a hot isostatic pressing equipment, maintain temperature and pressure for sintering and shaping, and then cool it with the furnace;

[0110] Specifically, during the heat preservation and pressure holding sintering process, the heating rate is 10℃ / min, the heat preservation temperature is 960℃, the pressure holding pressure is 120MPa, and the heat preservation time is 1h.

[0111] The furnace is cooled to 100°C, and then air-cooled from 100°C to room temperature.

[0112] After cooling, the steel casing is removed by machining to obtain a large-sized Ti6Al4V ELI substrate;

[0113] The Ti6Al4V ELI substrate prepared by this comparative method has a length of 1000 mm, a width of 800 mm, and a thickness of 80 mm; an oxygen content of 700 ppm; a tensile strength of 873 MPa; a yield strength of 796 MPa; an elongation of 15%; a reduction of area of ​​50%; a fracture toughness of 113 MPa·mˆ1 / 2; a hardness of 30.0 HRC; and a density of 99.997%.

[0114] In this comparative example, the Ti6Al4V ELI substrate has a lifespan of 36 printing cycles.

[0115] Comparative Example 2

[0116] The preparation process is as follows:

[0117] Step 1: Select Ti6Al4V ELI powder with a particle size range of 53-250μm prepared by electrode induction gas atomization (EIGA).

[0118] Specifically, the Ti6Al4V ELI powder with a particle size range of 53~250μm prepared by EIGA has a sphericity of 87%, a flowability of 33s / 50g, a hollow powder content of 0.95%, and a tap density of 2.82g / cm³. 3 The oxygen content is 1200 ppm;

[0119] Step 2: In the vacuum vibration powder loading equipment, EIGA powder is loaded into a rectangular steel sleeve, and then degassed and sealed.

[0120] The vacuum degree of powder filling is 3×10 -2 Pa, powder loading temperature of 500℃, degassing under the condition of heat preservation for 1 hour;

[0121] Step 3: Place the sealed sleeve in a hot isostatic pressing equipment, maintain temperature and pressure for sintering and shaping, and then cool it with the furnace;

[0122] Specifically, during the heat preservation and pressure holding sintering process, the heating rate is 10℃ / min, the heat preservation temperature is 880℃, the pressure holding pressure is 120MPa, and the heat preservation time is 1h.

[0123] The furnace is cooled to 100°C, and then air-cooled from 100°C to room temperature.

[0124] After cooling, the steel casing is removed by machining to obtain a large-sized Ti6Al4V ELI substrate;

[0125] The Ti6Al4V ELI substrate prepared by this comparative method has a length of 1000 mm, a width of 1000 mm, and a thickness of 100 mm; an oxygen content of 1450 ppm; a tensile strength of 957 MPa; a yield strength of 889 MPa; an elongation of 8.2%; a reduction of area of ​​32%; a fracture toughness of 86 MPa·mˆ1 / 2; a hardness of 37.0 HRC; and a density of 99.981%.

[0126] In this comparative example, the Ti6Al4V ELI substrate has a lifespan of 31 printing cycles.

[0127] To verify the performance of the Ti6Al4V ELI substrates prepared in Examples 1-3 and Comparative Examples 1-2, the following standards were used: oxygen content ("Determination of Oxygen, Nitrogen and Hydrogen Content in Titanium and Titanium Alloys" GB / T 4698.7-2019); tensile strength / yield strength / elongation after fracture / reduction of area ("Metallic Materials - Tensile Testing at Room Temperature" GB / T 228.1-2021); fracture toughness ("Metallic Materials - Plane Strain Fracture Toughness Test" GB / T 4161-2022); hardness ("Britton Hardness: Brinell Hardness Test for Metallic Materials" GB / T230.1-2018); and density ("Metallographic Method: Quantitative Analysis of Porosity" ASTM E2109-23). ​​The test results are shown in Table 1.

[0128] Table 1. Performance test results of Ti6Al4V ELI substrates prepared in each embodiment and comparative example.

[0129]

[0130] As can be seen from the data in Table 1, the Ti6Al4V ELI substrate prepared by the method of the present invention has excellent comprehensive performance, and gives full play to the excellent fracture toughness and plasticity of SS-PREP Ti6Al4V ELI powder and the excellent strength and hardness of EIGA Ti6Al4V ELI powder.

[0131] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention.

[0132] It should be understood that the present invention is not limited to the content already described above, and various modifications and changes can be made without departing from its scope. The scope of the present invention is limited only by the appended claims.

Claims

1. A hot isostatic pressing method for preparing additive manufacturing substrates using a mixture of SS-PREP and EIGA Ti6Al4V ELI spherical powders, characterized in that, Includes the following steps: Step 1: Mix Ti6Al4V ELI powder prepared by SS-PREP and Ti6Al4V ELI powder prepared by EIGA in a mass ratio of 1:1 under a protective atmosphere to obtain a mixed powder. The Ti6Al4V ELI powder prepared by SS-PREP has a particle size of 53~250μm, sphericity >95%, flowability <25s / 50g, hollow powder content <0.5%, and tap density >2.9g / cm³. 3 The oxygen content is 600~800ppm; the Ti6Al4V ELI powder prepared by EIGA has a particle size of 53~250μm, sphericity >85%, flowability <35s / 50g, hollow powder rate <1%, and tap density >2.8g / cm³. 3 The oxygen content is 800~1300 ppm; Two powders were mixed using a double-cone mixer. The mixing method was as follows: a single mixing weight of 100-1000 kg, a rotation speed of 15-20 r / min, and a mixing time of 2-4 h. The mixed powder had the following characteristics: sphericity > 90%, flowability < 30 s / 50 g, hollow powder content between 0.25% and 0.75%, and tap density > 2.8 g / cm³. 3 Oxygen content is between 950 and 1050 ppm; Step 2: In a vacuum vibration powder loading equipment, the mixed powder is loaded into a sleeve that is compatible with the structure of the Ti6Al4V ELI substrate to be prepared, and then degassed and sealed. Step 3: Place the sealed sleeve in a hot isostatic pressing (HIP) machine, maintain the temperature and pressure for sintering and shaping, and then cool it down gradually. During the heat preservation and pressure holding sintering process, the heating rate is 10℃ / min, the heat preservation temperature is 920~950℃, the pressure holding pressure is 150MPa, and the heat preservation and pressure holding time is 2~4h. In the gradient cooling process, the temperature is reduced from HIP temperature to 900℃ at a cooling rate of 8~10℃ / min in the first gradient cooling stage; from 900℃ to 800℃ at a cooling rate of 5~8℃ / min in the second gradient cooling stage; from 800℃ to 600℃ at a cooling rate of 3~5℃ / min in the third gradient cooling stage; from 600℃ to 300℃ at a cooling rate of 1~3℃ / min in the fourth gradient cooling stage; and from 300℃ to room temperature by natural cooling in the fifth gradient cooling stage. Step 4: After cooling, the casing is removed by machining to obtain a large-sized Ti6Al4V ELI substrate.

2. The hot isostatic pressing method according to claim 1, characterized in that, In step 1, the atmosphere is 99.999% argon.

3. The hot isostatic pressing method according to claim 1, characterized in that, In step 2, the powder loading vacuum degree is <10. - 3 Pa, the powder loading temperature is 400~450℃, and after holding at this temperature for 2~3 hours, degassing is performed.

4. The hot isostatic pressing method according to claim 1, characterized in that, The Ti6Al4V ELI substrate obtained in step 4 has an oxygen content of 800~1300ppm, tensile strength >920MPa, yield strength >850MPa, elongation >12%, reduction of area >40%, fracture toughness >100MPa·mˆ1 / 2, hardness >35HRC, and density >99.99%.

5. The application of a Ti6Al4V ELI substrate prepared by the hot isostatic pressing method according to any one of claims 1 to 4 in additive manufacturing of titanium alloy parts.

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