A hot isostatic pressing near-net-shape forming method based on 3D printing can

Abstract

The application discloses a hot isostatic pressing near-net forming method based on a 3D printing package, aiming at realizing high-quality and low-cost manufacturing of complex shape titanium alloy parts. First, according to the target component, different oxygen content titanium alloy return material powders are accurately calculated and mixed to obtain mixed raw materials with uniform components; second, a metal package matching the shape of the part is manufactured by using a metal 3D printing technology; then, the mixed powder is filled into the package, and after being vibrated, vacuumized and sealed and welded, hot isostatic pressing sintering is carried out; under the action of high temperature and high pressure, the powder is densified into a near-net forming blank body consistent with the shape of the inner cavity of the package, and finally the finished product can be obtained through a small amount of machining. The method combines the high design freedom of 3D printing with the full densification capability of hot isostatic pressing, realizes low-cost and high-quality near-net forming of complex shape titanium alloy parts, and improves the recycling rate of titanium alloy return materials.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical titanium, specifically relating to a near-net-shape forming method based on 3D printed encapsulation using hot isostatic pressing. Background Technology

[0002] Titanium metal possesses a series of advantages, including low density, high strength, good corrosion resistance, and high biocompatibility, making it a promising material for applications in aerospace, marine, medical, and chemical industries. However, the high production cost of titanium alloys limits their large-scale application, primarily due to the complex hot working process (accounting for approximately 50% of the total cost) and low material utilization (20-50%). Furthermore, obtaining complex-shaped titanium products often requires further processing, resulting in significant waste of titanium material. 3D printing, which can directly print finished-size parts from powder with minimal additional processing, significantly improves material utilization and is therefore widely used in titanium alloy products. Currently, various powder preparation methods and processes in 3D printing generate large amounts of coarse powder particles. These spherical powders have poor compressibility and cannot be sintered using traditional powder metallurgy techniques. During vacuum melting, titanium alloy powder can be sucked away by the vacuum pump, leading to production accidents. With the large-scale application of 3D printing technology in industrial production, the recycling and reuse of waste generated from 3D printing has become a widely concerned issue.

[0003] Hot isostatic pressing (HIP) is commonly used to heat-press coarse powder generated during 3D printing into titanium alloy profiles for reuse. However, the HIP sheath typically requires machining removal after HIP, and it's difficult to fabricate complex shapes. Usually, blanks are created, the sheath is removed through subsequent machining, and then the blanks are extensively machined into titanium alloy parts, resulting in high costs and hindering the recycling of the recovered titanium alloy powder. Achieving low-cost reuse of recovered materials is a key challenge. Furthermore, while 3D printing technology can manufacture complex parts with near-net-shape forming, improving material utilization, its layer-by-layer printing method leads to long overall part fabrication cycles, and the formed parts usually require subsequent HIP processing to achieve full densification. Summary of the Invention

[0004] This invention aims to overcome the shortcomings of existing technologies and provide a near-net-shape hot isostatic pressing (HIP) method based on 3D printed casings. This method primarily addresses the challenges of manufacturing complex-shaped HIP casings, controlling the uniformity of recycled material composition, and overcoming the complex processes and high costs associated with traditional methods. It achieves direct, high-quality conversion of recycled titanium alloy materials into high-value-added, complex parts, thereby reducing overall costs.

[0005] The technical solution of this invention: A near-net-shape forming method based on 3D printed sleeves using thermo-isostatic pressing includes the following steps: S1. Raw material proportioning and mixing: According to the composition requirements of the target part, accurately calculate and weigh titanium alloy recycled powder with different oxygen contents for proportioning, and mix evenly to obtain a mixed powder with uniform composition. S2. Sheath preparation: Based on the three-dimensional digital model of the target part, a titanium alloy sheath matching the outer contour shape is manufactured using metal 3D printing technology; S3. Powder filling and encapsulation: The mixed powder obtained in step S1 is filled into the sleeve prepared in step S2, compacted, and then the sleeve is vacuumed and sealed by welding. S4. Hot isostatic pressing sintering: The sealing sleeve is subjected to hot isostatic pressing, which densifies the powder inside the sleeve and combines it into a whole blank through high temperature and high pressure. S5. Post-processing: The dense blank obtained in step S4 is machined to obtain the final part.

[0006] In step S1, the titanium alloy return material powder is powder that does not meet the specifications for direct use and is generated during atomization powder production or additive manufacturing.

[0007] Step S1 also includes adding micron- or nano-scale second-phase reinforcing particles to the proportioned titanium alloy powder and mixing them.

[0008] In step S2, the 3D printing uses titanium alloy raw materials with the same powder composition as those obtained in step S1.

[0009] In step S3, the vacuuming process is a degassing process performed under heating conditions, with a heating temperature of 200~450℃ and a vacuum degree of not less than 1×10⁻⁶. -2 Pa, degassing time is 1~6 hours.

[0010] In step S4, the process parameters for hot isostatic pressing sintering are: sintering temperature 800~1150℃, pressure 80~200MPa, and holding time 1~6 hours.

[0011] In step S2, two types of sleeves, one large and one small, are prepared. The outer contour of the large sleeve matches the outer contour of the target part, while the small sleeve has a regular shape. First, powder filling, encapsulation, and sintering are performed in the small sleeve. Then, the sintered small sleeve is placed in the large sleeve as a preform, and powder filling, encapsulation, and sintering are performed again.

[0012] The inner wall of the sleeve has a regular shape, and the corners are chamfered.

[0013] The beneficial effects of this invention are: 1. Guaranteed Uniformity of Composition: By pre-processing and independently proportioning and mixing powders, the uniformity of the raw materials for molding is fundamentally ensured. This effectively solves the core problem of easy agglomeration when filling mixed powders in complex encapsulations using traditional methods, which is of decisive significance for the preparation of dispersion-reinforced materials or parts where oxygen content control is crucial.

[0014] 2. Breakthrough in manufacturing complex shapes: By using 3D printing technology to manufacture casings, the geometric shape limitations of traditional casings have been completely broken, enabling near-net-shape forming of complex structural parts.

[0015] 3. Optimized process flow and improved efficiency: The simplified process of using 3D printing to encapsulate the shell, then filling the shell with recycled powder, and finally hot isostatic pressing for near-net-shape forming reduces intermediate steps and improves manufacturing efficiency.

[0016] 4. Significantly reduced overall costs: Efficient use of recycled materials, near-net-shape forming to reduce machining allowances, and the use of the same material for the casing and the part body for integrated use reduce manufacturing costs from multiple dimensions. Attached Figure Description

[0017] Figure 1 This is a microscopic view of the HDH-TC4 coarse powder return material.

[0018] Figure 2 This is a schematic diagram of a 3D printed conical sleeve.

[0019] Figure 3 This is a schematic diagram of a double-layered sheath structure. Detailed Implementation

[0020] Example 1: A near-net-shape forming method based on 3D printed casing using thermo-isostatic pressing (HIP) is proposed. Its core lies in optimizing the process sequence to ensure material uniformity, and integrating the "free-form" capability of additive manufacturing with the "full densification" capability of HIP. The specific steps are as follows: Step S1: Precisely proportion and homogenize the raw materials.

[0021] This is a crucial step. Based on the performance requirements of the target part (especially oxygen content requirements), precise calculations and weighing proportions are performed on the recycled titanium alloy powders from various sources with different oxygen contents. If necessary, a fixed amount of second-phase reinforcing particles (such as TiC or TiB2) can be added to the matrix powder. The proportioned powder is then thoroughly mixed in a high-efficiency mixer to ensure uniform composition at both the macroscopic and microscopic scales. This step yields a batch of homogeneous mixed powder, providing a consistent raw material base for all subsequent processes.

[0022] Step S2: 3D printing manufacturing of the package based on the digital model.

[0023] Based on the 3D model of the target part, a manufacturability analysis is performed, and a digital model of the casing that conforms to it or has uniform machining allowance is designed. The casing is then printed using a metal 3D printer with the same titanium alloy raw material as the powder mixed in step S1.

[0024] Step S3: Powder filling and vacuum sealing.

[0025] The uniform powder prepared in step S1 is filled into the casing manufactured in step S2. After compaction, the casing is degassed under vacuum under heating conditions to fully remove adsorbed gas and moisture. After achieving high vacuum, it is then sealed. Because the powder has been pre-mixed uniformly, regardless of where it is filled into the casing, its local composition is consistent with the overall ratio, fundamentally eliminating component segregation during the filling process.

[0026] Step S4: Hot isostatic pressing densification molding.

[0027] The sealing sleeve is subjected to hot isostatic pressing. Under the combined action of high temperature and high pressure, the uniform powder inside the sleeve is densified, forming a fully dense and homogeneous metal blank with the same shape as the inner cavity of the sleeve. Metallurgical bonding may be formed between the sleeve and the blank.

[0028] Step S5: Post-processing to obtain parts.

[0029] According to the design, or by directly precision machining the assembly, the final part is obtained.

[0030] Example 2: First, the usage ratio of titanium alloy recycled coarse powder with different oxygen contents was calculated. These coarse powders were then weighed and mixed in a V-type mixer. Next, the mixed titanium alloy recycled coarse powder was loaded into a 3D-printed titanium alloy sheath shell and compacted.

[0031] Then, the casing is degassed by heating at 250~400℃ and with a vacuum degree of 1×10⁻⁶. -3 The material is degassed for 2-5 hours, followed by sealing welding. Then, the cladding is subjected to hot isostatic pressing (HIP) sintering at 800-1100℃ and 100-150MPa for 2-5 hours to obtain a near-net-shape titanium alloy part. Finally, the titanium alloy part is machined to obtain the target titanium alloy component.

[0032] Standardized internal cavity design of the sheath (key step): A standardization process was implemented during the design of the sheath's internal cavity (e.g., Figure 2 (As shown).

[0033] The inner cavity surface is designed as a smoothly transitioning curved surface, avoiding sharp edges or deep, narrow grooves. All inner corners are chamfered with a radius of radius (R) ≥ 3 mm, and the target value for the inner wall surface roughness (Ra) is less than 6.3 μm. This design ensures that the powder can be uniformly filled into all corners during vibration, without dead zones, and that pressure is uniformly transmitted during the HIP process, avoiding localized insufficient density or stress concentration caused by abrupt shape changes.

[0034] Fabrication process: Based on this standardized internal cavity model, a titanium alloy sheath is manufactured by 3D printing. Subsequent processes, including powder filling, compaction (with special attention to filling the chamfered areas), degassing, sealing, and HIP (parameters: 880℃, 130MPa, 3 hours), are similar to those in the aforementioned embodiments.

[0035] Results: After HIP, the sheath bonded to the internal preform. The implant was obtained after minimal finishing. Micro-CT examination revealed that the implant was free of pores and inclusions, and the material in the chamfered areas was dense and uniform, fully meeting the stringent requirements for internal quality of implants.

[0036] Example 3: First, based on the complex shape and size requirements of the target part, a titanium alloy cladding for hot isostatic pressing (HIP) is precisely fabricated using 3D printing technology. Then, recycled titanium alloy coarse powder is weighed according to a pre-calculated ratio and evenly filled into the 3D-printed cladding. Next, the filled cladding is placed in a vacuum degassing furnace, with the heating temperature set to 300℃ and the vacuum level reaching 1×10⁻⁶. -3 The titanium alloy powder is degassed for 3 hours to remove moisture and impurities. After degassing, the casing is sealed to ensure its airtightness. Then, the sealed casing is placed in a hot isostatic pressing (HIP) chamber at a temperature of 900℃, a pressure of 120MPa, and a holding time of 3 hours. This HIP technique densifies the titanium alloy powder, forming a near-net-shape part. Finally, the casing is removed by machining, and the formed titanium alloy part undergoes dimensional adjustments and surface treatment to obtain a high-performance titanium alloy part. This part possesses excellent dimensional accuracy and mechanical properties, making it suitable for high-precision applications such as aerospace.

[0037] Example 4: This embodiment demonstrates the "nested sintering" method for large, thin-walled casing parts with a height exceeding 600mm, in order to solve the problems of difficult deformation control and uniform sintering heating in one-time molding of large casing parts.

[0038] Design: The overall component is broken down into a large outer contour enclosure (referred to as the "large enclosure") and a small, regularly shaped cylindrical enclosure (referred to as the "small enclosure"). The inner shape of the large enclosure matches the final shape of the casing. The small enclosure is a simple thin-walled cylindrical shape.

[0039] Preparation of small-package preforms: Raw material mixing: Same as in Example 1, prepare and mix the required amount of TC4 return material powder.

[0040] Preparation and filling: 3D print regular small sleeves (Φ200mm×400mm). Fill these small sleeves with the mixed powder, vibrate, degas, and seal.

[0041] Primary HIP: All small packages undergo a HIP treatment (parameters: sintering temperature 900℃, pressure 100MPa, holding time 2.5 hours) to sinter the internal powder into a high-density, regular cylindrical preform.

[0042] Large-package nested sintering: Preparation of large packaging: such as Figure 2 Based on the shape of the part, a conical thin-walled TC4 sleeve with a height of 700mm was 3D printed.

[0043] Nested assembly: such as Figure 3 The dense small-encased preform (which has now become a solid billet) is placed in the central area of ​​the large-encased container. Then, the same TC4 mixture powder is filled into all the voids around the preform and compacted.

[0044] Final HIP: The entire assembly (large casing + internal preforms + interstitial powder) is vacuum-sealed, welded, and then subjected to final HIP treatment (parameters: 930℃, 140MPa, 4 hours). This HIP process densifies the powder in the interstitial spaces and firmly bonds all the preforms into a single, giant preform with a shape consistent with the large casing.

[0045] Advantages: This method breaks down the one-time filling and sintering of ultra-large spaces into two steps: "first preparing regular small dense bodies, and then filling the remaining voids." This reduces the deformation risk of ultra-large enclosures in a single HIP process, solves the problem of difficult heat and pressure conduction in the central part of large sintered parts, and improves the uniformity and reliability of large-volume powder filling, making it particularly suitable for the manufacture of ultra-large and complex parts.

[0046] Example 5: Raw material proportioning and mixing: Atomized TA15 titanium alloy recycled coarse powder (oxygen content 0.11 wt.%) was used as the matrix. To improve wear resistance, titanium carbide particles with an average particle size of 0.8 μm were added as a second-phase reinforcement, at an addition amount of 3.0 wt.% of the total mass of the matrix powder. The TA15 powder and TiC powder were placed together in a planetary ball mill and mixed at a low speed (200 rpm) for 5 hours under argon protection to avoid excessive cold welding and ensure that the TiC particles were uniformly dispersed on the surface of the titanium alloy powder.

[0047] Sleeve fabrication and subsequent processes: Based on the 3D model of the wear-resistant liner part, a TA15 titanium alloy sleeve matching the outer contour was 3D printed. Subsequent processes included powder filling, compaction, and degassing (300℃, 1×10⁻⁶). -2 The sealing and HIP processes (parameters: 950℃, 150MPa, 4 hours) are similar to those in Example 1.

[0048] Results: In the obtained part, TiC particles were uniformly dispersed in the TA15 matrix. Testing showed that the room temperature hardness of this part was approximately 40% higher than that of the unreinforced TA15 material, and its wear resistance was improved by more than 50%, fully meeting the requirements of the operating conditions.

Claims

1. A near-net-shape forming method based on 3D printed casing using thermo-isostatic pressing, characterized in that, Includes the following steps: S1. Raw material proportioning and mixing: According to the composition requirements of the target titanium alloy parts, calculate and weigh titanium alloy recycled powder with different oxygen contents, and mix them evenly to obtain a mixed powder with uniform composition. S2. Sheath preparation: Based on the three-dimensional digital model of the target part, a titanium alloy sheath matching the outer contour shape is manufactured using metal 3D printing technology; S3. Powder filling and encapsulation: The mixed powder obtained in step S1 is filled into the sleeve prepared in step S2, compacted, and then the sleeve is vacuumed and sealed by welding. S4. Hot Isostatic Pressing Sintering: The sealing sleeve is placed in a hot isostatic pressing equipment and sintered and densified under high temperature and isostatic pressure, so that the powder inside the sleeve is combined with the sleeve to form a dense green body. S5. Post-processing: The dense blank obtained in step S4 is machined to obtain the final titanium alloy part.

2. The near-net-shape forming method based on 3D printed casing using thermo-isostatic pressing according to claim 1, characterized in that: In step S1, the titanium alloy return material powder is powder that does not meet the specifications for direct use and is generated during atomization powder production or additive manufacturing.

3. The near-net-shape forming method based on 3D printed casing using thermo-isostatic pressing according to claim 1 or 2, characterized in that, Step S1 further includes adding micron- or nano-scale second-phase reinforcing particles to the proportioned titanium alloy powder and mixing them.

4. The near-net-shape forming method based on 3D printed casing using thermo-isostatic pressing according to claim 1, characterized in that... In step S2, the 3D printing uses titanium alloy raw materials with the same powder composition as those obtained in step S1.

5. The near-net-shape forming method based on 3D printed casing using thermo-isostatic pressing according to claim 1, characterized in that: In step S3, the vacuuming process is a degassing process performed under heating conditions, with a heating temperature of 200-450℃ and a vacuum degree of not less than 1×10⁻⁶. -2 Pa, degassing time is 1~6 hours.

6. The near-net-shape forming method based on 3D printed casing using thermo-isostatic pressing according to claim 1, characterized in that: In step S4, the process parameters for hot isostatic pressing sintering are: sintering temperature 800~1150℃, pressure 80~200MPa, and holding time 1~6 hours.

7. The near-net-shape forming method based on 3D printed casing using thermo-isostatic pressing according to claim 1, characterized in that: In step S2, two types of sleeves, one large and one small, are prepared. The outer contour of the large sleeve matches the outer contour of the target part, while the small sleeve has a regular shape. First, powder filling, encapsulation, and sintering are performed in the small sleeve. Then, the sintered small sleeve is placed in the large sleeve as a preform, and powder filling, encapsulation, and sintering are performed again.

8. The near-net-shape forming method based on 3D printed casing using thermo-isostatic pressing according to claim 1, characterized in that: The inner wall of the sleeve has a regular shape, and all corners are chamfered.

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