A method for preparing a titanium alloy powder hot isostatic pressing forming complex thin-walled workpiece and application thereof

Abstract

The application belongs to the technical field of powder metallurgy, and particularly relates to a preparation method of titanium alloy powder hot isostatic pressing forming complex thin-wall workpiece and application. The method comprises the following steps: step one: a sleeve is prepared to form a sealed sleeve; step two: the sealed sleeve is subjected to multi-stage gradient heating, and then multi-gradient cooling treatment is performed; step three: the sealed sleeve is subjected to stress relief annealing treatment, and then the sleeve is removed to obtain a preform; step four: the preform is subjected to cleaning and hydrogen removal treatment, and then mechanical processing is performed, and the workpiece after mechanical processing is subjected to stabilization treatment to obtain a thin-wall workpiece. The application can not only systematically reduce the initial residual stress of the workpiece after hot isostatic pressing forming to the lowest level, but also homogenize the stress distribution from the micro level, and maximally weaken the macro residual stress caused by uneven cooling from the root, thereby laying a foundation for the overall stress stability of the workpiece.

Description

Technical Field

[0001] This invention belongs to the field of powder metallurgy technology, specifically relating to a method for preparing complex thin-walled parts by hot isostatic pressing of titanium alloy powder and its application. Background Technology

[0002] As high-end equipment such as aerospace engines and hypersonic vehicles develop towards greater strength, lighter weight, and higher reliability, titanium alloy components are continuously evolving towards larger size, integrated construction, and thinner walls to meet the stringent challenges of extreme thermomechanical coupling environments. Hot isostatic pressing (HIP) technology for titanium alloy powders, with its unique process advantages, has become a key technological path for achieving near-net-shape forming of large, complex, thin-walled components. This technology, through integrated dense forming of alloy powders in a high-temperature, high-pressure environment, combined with precise control of component shape and size using molds and cores, not only significantly improves material properties and structural integrity but also possesses irreplaceable strategic value in reducing weight, shortening manufacturing cycles, lowering costs, and enhancing overall equipment performance. It is of great significance for promoting the innovative development of next-generation high-end transportation equipment.

[0003] When fabricating large, complex, thin-walled parts using hot isostatic pressing (HIP), problems such as abnormal deformation and dimensional deviations after processing are prone to occur due to the inherent structural characteristics and process features of the parts. The main reason is that these parts typically have complex spatial curved surfaces, uneven wall thickness, and weak local stiffness. During the HIP powder densification shrinkage process, they are easily affected by the geometric constraints of the parts, resulting in non-uniform internal stress distribution. In later processing, as the external sheath and the main body material are gradually removed, the original stress equilibrium is disrupted, leading to unpredictable elastic or plastic deformation, especially in high-curvature regions and thin-walled joints. Simultaneously, for large, complex, thin-walled parts, it is difficult to achieve absolute uniformity in the temperature and pressure fields during HIP, further exacerbating the spatial heterogeneity of residual stress. This deformation often exhibits nonlinear and hysteretic characteristics, and conventional straightening processes alone are insufficient to completely eliminate it, easily damaging material properties. Ultimately, this results in critical dimensions such as profile accuracy, positional accuracy, and wall thickness variation exceeding design tolerances, severely impacting the assemblability and service performance of the parts.

[0004] Existing technologies typically focus on optimizing machining parameters, such as using shallower depths of cut, higher rotational speeds, or adding part straightening processes. However, these are all "post-production remedial" measures and cannot fundamentally reduce the initial stress state of the blank. They are costly and have limited effectiveness. To control deformation, more intermediate inspection processes and full-dimensional inspections are often added, relying on more precise and expensive inspection equipment, such as coordinate measuring machines and blue light scanners, leading to an increase in overall manufacturing costs. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and to propose a method for preparing complex thin-walled parts by hot isostatic pressing of titanium alloy powder and its application.

[0006] In a first aspect, this invention discloses a method for preparing complex thin-walled parts by hot isostatic pressing of titanium alloy powder, such as... Figure 1 As shown, it includes the following steps: Step 1: Prepare the casing, fill the pre-alloyed powder into the casing, vibrate it, and perform vacuum degassing and sealing welding to form a casing-encased blank; Step 2: Place the encased billet in a hot isostatic pressing (HIP) machine and sequentially perform multi-stage gradient heating, heat preservation and pressure holding, and multi-stage gradient cooling. Finally, release the pressure and remove the billet from the furnace. Step 3: After the pressure is released from the furnace, the encased billet undergoes stress-relieving annealing, and then the encasing is removed to obtain the preform. Step 4: The preform is first cleaned and dehydrogenated, then machined, and then stabilized to obtain a thin-walled part.

[0007] Furthermore, in step one, the pre-alloyed powder is prepared by plasma rotating electrode atomization or electrode-induced atomization.

[0008] Specifically, an automated vibration filling system is used to load pre-alloyed powder into a carbon steel sheath; for parts with internal cavity structures, a core needs to be placed in the sheath beforehand, and the sheath is vacuum degassed and sealed after powder filling.

[0009] Furthermore, in step two, such as Figure 3 As shown, the multi-stage gradient heating includes a first stage heating and a second stage heating. The first stage heating involves heating to 720-850℃ at a rate of 5-15℃ / min; the second stage heating involves heating to 920-940℃ at a rate of 3-8℃ / min.

[0010] Specifically, the first stage involves rapid heating to avoid prolonged exposure to low temperatures and reduce the risk of oxidation and contamination; the second stage involves slow heating to ensure uniform heating of the material as it approaches the β phase transformation point, thereby reducing localized stress concentration caused by uneven phase transformation.

[0011] Furthermore, in the heat preservation and pressure holding process of step two, the heat preservation is carried out at the temperature of the second stage of heating, and the pressure holding is to apply an isostatic pressure of 100-140MPa for 2-4 hours.

[0012] Specifically, the heat preservation and pressure holding stage can promote powder densification, while the pressure action can inhibit the formation of pores and defects and reduce internal stress sources.

[0013] Furthermore, in step two, such as Figure 3As shown, the multi-gradient cooling includes a first slow cooling stage, a second slow cooling stage, and a third cooling stage. The first slow cooling stage involves cooling from the temperature after heat preservation and pressure holding to 750-800℃ at a cooling rate of 0.5-2.0℃ / min; the second slow cooling stage involves cooling from 750-800℃ to 500-600℃ at a cooling rate of 1.0-3.0℃ / min; and the third cooling stage involves cooling with the furnace to below 200℃ at a cooling rate of 2-5℃ / min, followed by depressurization and removal from the furnace.

[0014] Specifically, extremely slow cooling (0.5-2.0℃ / min) is used in the high-temperature zone to promote full stress relaxation of the material and eliminate macroscopic residual stress formed during hot isostatic pressing to the greatest extent. In the medium-temperature zone (500-800℃), the cooling rate is appropriately accelerated (1.0-3.0℃ / min), but still kept slow to avoid uneven shrinkage and new thermal stress caused by excessively rapid cooling. In the low-temperature zone (below 500℃), the cooling rate is further increased (2-5℃ / min), at which point the material is basically stable and it is not easy to generate new macroscopic stress. The entire cooling process is carried out under pressure to suppress deformation caused by temperature difference.

[0015] Furthermore, in step three, stress-relief annealing specifically involves heating to 650-700℃ at a rate of 2-5℃ / min under vacuum or argon protection, holding at that temperature for 2-4 hours, and then furnace cooling to below 300℃ at a rate of ≤2℃ / min before unloading from the furnace. The purpose of this is to homogenize the micro-stress that may exist after gradient cooling, creating conditions for subsequent uniform chemical corrosion. Holding at 650-700℃ can promote dislocation rearrangement and stress relaxation, while slow cooling can avoid introducing secondary stress and maintain the shape stability of the billet.

[0016] Furthermore, in step three, the sheath needs to be removed using a chemical dissolution method at a temperature of 30-50℃.

[0017] Specifically, the chemical dissolution method requires the use of a mixed acid solution mainly composed of HNO3 and HCl at a temperature of 30-50℃. The casing and core are dissolved and removed by spraying or immersion, which can avoid the stress impact and deformation introduced by mechanical removal. Furthermore, the chemical dissolution method is a non-contact removal method without the application of external mechanical force. Subsequent ultrasonic cleaning and vacuum environment can fully remove hydrogen that may be introduced during the pickling process, thus avoiding hydrogen embrittlement and microcracks.

[0018] Furthermore, in step four, the preform is first cleaned and dehydrogenated, including: multi-stage ultrasonic cleaning of the titanium alloy billet with deionized water, followed by vacuum drying at 120-150℃ for 2-4 hours, and then vacuum dehydrogenation treatment: in a vacuum furnace, it is kept at 550-650℃ for 4-8 hours to eliminate hydrogen that may be absorbed during pickling.

[0019] Furthermore, in step four, machining is performed on the preform using a CNC machine tool with machining parameters of 80-150 m / min cutting speed, 0.05-0.2 mm depth of cut and 0.02-0.08 mm / z feed rate, supplemented by milling with high-pressure internal coolant of >10 MPa.

[0020] Specifically, the machining process employs a low-stress machining strategy, with the machining path following symmetrical and layered principles. Priority is given to removing excess material from areas of high stress to further control machining deformation based on a low-stress blank. This strategy reduces cutting heat and force through high cutting speed, shallow depth of cut, and small feed rate combined with high-pressure cooling. Simultaneously, the symmetrical layered machining path evenly releases internal potential stress, avoiding deformation caused by localized stress concentration and stress redistribution.

[0021] Furthermore, in step four, the stabilization treatment involves subjecting the machined parts to vibration aging or low-temperature vacuum aging treatment. Specifically, in step four, vibration aging or low-temperature vacuum aging at 400-500℃ for 2-3 hours can release trace amounts of machining stress and stabilize the final dimensions. Performing this treatment after precision machining can promote the microscopic relaxation of residual stress through vibration aging or low-temperature vacuum aging without causing phase transformation or recrystallization, thus avoiding affecting the precision and performance of the parts, ensuring dimensional stability during long-term use, and preventing later deformation due to stress release.

[0022] Secondly, this invention discloses the application of complex thin-walled parts formed by hot isostatic pressing of titanium alloy powder in the manufacture of aerospace engines, and the thin-walled parts are prepared by the method of preparing complex thin-walled parts by hot isostatic pressing of titanium alloy powder.

[0023] Compared with the prior art, the present invention has the following beneficial effects: The titanium alloy parts provided by this invention, through a systematic, multi-stage, low-stress-oriented process design, implement corresponding stress control strategies throughout the entire chain of hot isostatic pressing, stress-relief annealing, chemical decladding, machining, and stabilization processes. This fundamentally suppresses the machining deformation problem caused by residual stress in thin-walled titanium alloy powder metallurgy parts, achieving stress-relaxed and stable part blank preparation, and providing a reliable foundation for high-precision machining. Specifically: 1) The combined control method of multi-stage gradient cooling and stress-relief annealing can not only systematically reduce the initial residual stress of the part after hot isostatic pressing to the lowest level, but also homogenize the stress distribution at the micro level, and maximize the reduction of macroscopic residual stress caused by uneven cooling from the root, laying the foundation for the overall stress stability of the part. 2) The chemical dissolution method is used to replace the traditional machining method to remove the casing and core, which effectively avoids the introduction of new mechanical stress or damage to the parts during the casing and core removal process, ensuring the continuity of the low-stress blank state and realizing stress-free forming of the parts; at the same time, the stress homogenization treatment directly ensures the stress uniformity of the parts after chemical etching, avoids the risk of anisotropic corrosion of the parts caused by stress concentration, and makes the blank size closer to the theoretical design value, providing a high-precision benchmark for subsequent precision machining. 3) Construct a complete process control chain of low-stress forming, stress homogenization, stress-free uncoating, and stable machining. Each process works in synergy and supports each other, ultimately achieving high-precision and low-deformation manufacturing of complex thin-walled titanium alloy parts. This significantly improves product qualification rate and performance consistency, and ensures the dimensional stability of parts during long-term service. It is especially suitable for manufacturing critical components in the aerospace field with extremely high reliability requirements. 4) By precisely controlling key process parameters such as multi-level gradient heating and cooling curves and stress-relief annealing regime, the initial stress state of the billet can be effectively controlled, reducing the over-reliance on the operator's experience in the production process, improving process repeatability and stability, and facilitating the smooth progress of large-scale mass production. Attached Figure Description

[0024] 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.

[0025] 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.

[0026] Figure 1 This is a flowchart of the preparation method of complex thin-walled parts by hot isostatic pressing of titanium alloy powder according to the present invention; Figure 2 Metallographic micrograph of TA15 cylindrical part A prepared in Example 1; Figure 3 This is a schematic diagram of the multi-level gradient heating and cooling curves in this invention. The vertical axis, Temperature / ℃, represents temperature in degrees Celsius; the horizontal axis, Time / min, represents time in minutes. Figure 4 This is a schematic diagram of the traditional hot isostatic pressing (HIP) heating and cooling curve. The vertical axis, Temperature / ℃, represents temperature in degrees Celsius; the horizontal axis, Time / min, represents time in minutes. Detailed Implementation

[0027] 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.

[0028] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0029] The method for preparing complex thin-walled parts by hot isostatic pressing of titanium alloy powder provided by this invention achieves residual stress suppression or elimination through the synergistic effect of multiple processes, as detailed below: First, the forming process adopts a combination of gradient heating and gradient cooling stress-relief annealing, which minimizes the initial residual stress of the hot isostatic pressed parts and homogenizes the stress distribution at the microscopic level, thus solving the root cause of the deformation problem.

[0030] Secondly, a chemical dissolution method was designed to replace the traditional mechanical processing for removing the casing and core, thus avoiding the introduction of new mechanical stress in the process of removing the casing and core.

[0031] Finally, stress homogenization treatment is added. Vibration aging treatment or low-temperature vacuum aging treatment is performed on the finished parts to release trace machining stress and ensure the final dimensional accuracy. Example 1

[0032] This embodiment provides a method for preparing complex thin-walled parts by hot isostatic pressing of titanium alloy powder, used to prepare TA15 cylindrical parts A, including the following steps: Step 1: Prepare the casing, fill the casing with TA15 pre-alloyed powder, vibrate it, and perform vacuum degassing and sealing to form a casing-encased blank; Specifically, the TA15 pre-alloyed powder is prepared by a plasma rotating electrode atomization method, and a core is provided inside the package. Step 2: Place the encased billet in a hot isostatic pressing (HIP) machine and sequentially perform multi-stage gradient heating, heat preservation and pressure holding, and multi-stage gradient cooling. Finally, release the pressure and remove the billet from the furnace. Specifically, the encased billet is placed in a hot isostatic pressing (HIP) apparatus and subjected to a multi-stage gradient heating controlled by a program. The first stage of heating is: heating to 790℃ at a rate of 10℃ / min; the second stage of heating and holding is: continuing to heat to 930℃ at a rate of 8℃ / min and performing hot isostatic pressing and holding, applying a pressure of 120MPa, and holding for 2 hours. After the hot isostatic pressing and heat preservation are completed, under the condition of maintaining pressure, a multi-stage gradient cooling controlled by a program is performed. The first slow cooling stage: cooling from 930℃ to 800℃ at a cooling rate of 2℃ / min; the second slow cooling stage: cooling from 800℃ to 500℃ at a cooling rate of 2.0℃ / min; the third cooling stage: cooling with the furnace to below 200℃ at a rate of 3℃ / min to release pressure and exit the furnace. Step 3: After the pressure is released from the furnace, the encased billet undergoes stress-relieving annealing, and then the encasing is removed to obtain the preform. Specifically, the hot isostatically pressed clad billet is placed in a vacuum furnace and heated to 650°C at a rate of 5°C / min, held for 2 hours, and then cooled to below 300°C at a rate of 1.5°C / min before being removed from the furnace. Then, the carbon steel cladding and core of the part are removed by chemical dissolution. A mixed acid solution of HNO3 and HCl is used for dissolution, and the carbon steel cladding and core are removed by immersion in the solution at 30°C. Step 4: The preform is first cleaned and dehydrogenated, then machined, and finally stabilized to obtain a thin-walled part (TA15 cylindrical part A). Specifically, after removing the casing and core, the preform is subjected to multi-stage ultrasonic cleaning with deionized water, followed by vacuum drying at 150℃ for 4 hours. Subsequently, a vacuum dehydrogenation treatment is performed: the preform is held at 650℃ for 6 hours in a vacuum furnace to eliminate hydrogen that may have been absorbed during pickling. The obtained titanium alloy billet is then precision machined using a high cutting speed of 150 m / min, a depth of cut of 0.2 mm, and a feed rate of 0.08 mm / z, supplemented by a high-pressure internal coolant of 15 MPa. The precision-machined part is then subjected to low-temperature vacuum aging treatment at 500℃ for 3 hours to release trace machining stress and obtain the final dimensions.

[0033] The metallographic image of the TA15 cylindrical part A prepared in this embodiment is as follows. Figure 2 As shown, the TA15 cylindrical part A is free of pores, cracks, and other metallurgical defects, with fine internal grains and good structural uniformity. The maximum outer diameter of the TA15 part is 150 mm, the minimum wall thickness is 0.8 mm, and it contains 9 curved cooling channels. Compared with the traditional process of hot isostatic pressing with furnace cooling + machining encapsulation + direct machining, the TA15 cylindrical part A prepared by this method has a reduced average profile error from ±0.15 mm to within ±0.05 mm, a 50% improvement in channel size consistency, and eliminates the need for cumbersome cold straightening, increasing the pass rate from approximately 60% to 95%. Example 2

[0034] This embodiment provides a method for preparing complex thin-walled parts by hot isostatic pressing of titanium alloy powder, used to prepare TC4 cylindrical parts B, including the following steps: Step 1: Prepare the casing and core, fill the casing with TC4 pre-alloyed powder, vibrate and vacuum degas and seal to form a casing blank; Specifically, the TC4 pre-alloyed powder is prepared by a plasma rotating electrode atomization method, and a core is provided inside the casing; Step 2: Place the encased billet in a hot isostatic pressing equipment for multi-stage gradient heating, heat preservation and pressure holding, and then perform multi-stage gradient cooling treatment before depressurizing and removing it from the furnace. Specifically, the sealing sleeve is placed in a hot isostatic pressing (HIP) apparatus and subjected to a multi-stage gradient heating controlled by a program. The first stage of heating is: heating to 850°C at a rate of 15°C / min; the second stage of heating and holding is: continuing to heat to 940°C at a rate of 5°C / min and performing hot isostatic pressing and holding, applying a pressure of 140 MPa, and holding for 3 hours. After hot isostatic pressing and heat preservation, under the condition of maintaining pressure, a multi-stage gradient cooling controlled by a program is executed. The first slow cooling stage: cooling from 940℃ to 780℃ at a cooling rate of 0.5℃ / min; the second slow cooling stage: cooling from 780℃ to 550℃ at a cooling rate of 1℃ / min; the third cooling stage: cooling with the furnace to below 200℃ at a rate of 2℃ / min to release pressure and exit the furnace. Step 3: After the pressure is released from the furnace, the encased billet is subjected to stress-relieving annealing, and then the encasing and core are removed to obtain the preform; Specifically, the hot isostatically pressed clad billet is placed in a vacuum furnace and heated to 680°C at a rate of 3°C / min, held for 3 hours, and then cooled to below 300°C at a rate of 2°C / min before being removed from the furnace. Then, the carbon steel cladding and core of the part are removed by chemical dissolution. A mixed acid solution of HNO3 and HCl is used for dissolution at 50°C by spraying to remove the carbon steel cladding and core. Step 4: The preform is first cleaned and dehydrogenated, then machined, and finally stabilized to obtain a thin-walled part (TC4 cylindrical part B). Specifically, after removing the casing and core, the preform is subjected to multi-stage ultrasonic cleaning with deionized water, followed by vacuum drying at 150℃ for 3 hours. Subsequently, a vacuum dehydrogenation treatment is performed: the preform is held at 600℃ for 6 hours in a vacuum furnace to eliminate hydrogen that may have been absorbed during pickling. The obtained titanium alloy billet is then precision machined using a high cutting speed of 80 m / min, a depth of cut of 0.1 mm, and a feed rate of 0.05 mm / z, supplemented by a high-pressure internal coolant of 18 MPa. The precision-machined part is then subjected to low-temperature vacuum aging treatment at 400℃ for 2 hours to release minor machining stress and obtain the final dimensions.

[0035] The TC4 cylindrical part B prepared in this embodiment has a maximum outer dimension of 320mm, a length of 950mm, a minimum wall thickness of 1.2mm, and contains an arc-shaped fixing groove. Compared with the traditional process of hot isostatic pressing with furnace cooling + machining encapsulation + direct machining, the titanium alloy shell part B prepared by this method has a flatness error of less than ±0.15mm on the front and rear end faces, which is reduced to within ±0.03mm. The roundness consistency is improved by 60%, and no cumbersome cold straightening is required. The pass rate is increased from about 70% to 90%. Example 3

[0036] This embodiment provides a method for preparing complex thin-walled parts by hot isostatic pressing of titanium alloy powder, used to prepare TC21 cylindrical parts C, including the following steps: Step 1: Prepare the casing and core, fill the casing with TC21 pre-alloy powder, vibrate and vacuum degas and seal to form a casing blank; Specifically, the TC21 pre-alloyed powder is prepared by a plasma rotating electrode atomization method, and a core is provided inside the casing; Step 2: Place the encased billet in a hot isostatic pressing equipment for multi-stage gradient heating, heat preservation and pressure holding, and then perform multi-stage gradient cooling treatment before depressurizing and removing it from the furnace. Specifically, the sealing sleeve is placed in a hot isostatic pressing (HIP) apparatus and subjected to a multi-stage gradient heating controlled by a program. The first stage of heating is: heating to 720°C at a rate of 5°C / min; the second stage of heating and holding is: continuing to heat to 920°C at a rate of 3°C / min and performing hot isostatic pressing and holding, applying a pressure of 100MPa, and holding for 4 hours. After hot isostatic pressing and heat preservation, under the condition of maintaining pressure, a multi-stage gradient cooling controlled by a program is executed. The first slow cooling stage: cooling from 920℃ to 750℃ at a cooling rate of 1℃ / min; the second slow cooling stage: cooling from 750℃ to 600℃ at a cooling rate of 3.0℃ / min; the third cooling stage: cooling from 600℃ to below 200℃ at a rate of 5℃ / min to release pressure and exit the furnace. Step 3: After the pressure is released from the furnace, the encased billet undergoes stress-relieving annealing, and then the encasing is removed to obtain the preform. Specifically, the hot isostatically pressed clad billet is placed in a vacuum furnace and heated to 700°C at a rate of 2°C / min, held for 4 hours, and then cooled to below 300°C at a rate of 1.8°C / min before being removed from the furnace. Then, the carbon steel cladding and core of the part are removed by chemical dissolution. A mixed acid solution of HNO3 and HCl is used for dissolution, and the carbon steel cladding and core are removed by immersion at 50°C. Step 4: The preform is first cleaned and dehydrogenated, then machined, and finally stabilized to obtain a thin-walled part (TC21 cylindrical part C). Specifically, after removing the casing and core, the preform is subjected to multi-stage ultrasonic cleaning with deionized water, followed by vacuum drying at 120℃ for 2 hours. Subsequently, a vacuum dehydrogenation treatment is performed: the preform is held at 650℃ for 4 hours in a vacuum furnace to eliminate hydrogen that may have been absorbed during pickling. The obtained titanium alloy billet is then precision machined using a high cutting speed of 120 m / min, a depth of cut of 0.05 mm, and a feed rate of 0.02 mm / z, supplemented by a 20 MPa high-pressure internal coolant. The precision-machined part is then subjected to a low-temperature vacuum aging treatment at 450℃ for 2.5 hours to release minor machining stress and obtain the final dimensions.

[0037] The TC21 cylindrical part C prepared in this embodiment has a maximum outer dimension of φ220mm and a minimum wall thickness of 1.5mm. It contains a non-uniform transition gradient structure and reinforcing ribs. Compared with the traditional process of hot isostatic pressing with furnace cooling + machining encapsulation + direct machining, the TC21 cylindrical part C prepared by this method has a reduced average contour error from ±0.2mm to within ±0.05mm, a 50% improvement in coaxiality dimensional consistency, and eliminates the need for cumbersome cold straightening. The pass rate has increased from about 60% to 92%. Comparative Example 1

[0038] This comparative example provides the fabrication process of TC4 part D, specifically including the following steps: Step 1: Prepare the casing and core, and fill, vibrate, and vacuum degasse and seal the TC4 pre-alloyed powder prepared by plasma rotating electrode atomization method. Step 2: Place the sealing sleeve in a hot isostatic pressing (HIP) apparatus, such as... Figure 4 As shown, the temperature was controlled by the program: the temperature was increased to 930℃ at a rate of 12℃ / min for hot isostatic pressing, and a pressure of 140MPa was applied for holding at the temperature and pressure for 3 hours. Step 3: Cool the furnace to below 200°C, then remove it from the furnace and depressurize. Step 4: Perform precision machining on the obtained titanium alloy billet, using a high cutting speed of 100 m / min, a cutting depth of 0.1 mm, and a feed rate of 0.05 mm / z to complete the part machining.

[0039] The material provided in this comparative example is TC4 alloy. The maximum outer dimension of the shell is φ320mm, the length is 950mm, the minimum wall thickness is 1.2mm, and it contains an arc-shaped fixing structure. The titanium alloy shell part D, which is prepared by hot isostatic pressing with furnace cooling + machining package + direct machining, has an average flatness error of ±1.5mm on the front and rear end faces, a diameter error of ±1.2mm on φ320mm, and slight deformation. Its average contour error is ±2.5mm, which does not meet the tolerance requirement of ±0.2mm.

[0040] To further verify the technical effects of the present invention, the following tests and analyses were conducted: 1. Microstructure observation: Metallographic analysis was performed on the TA15 cylindrical part A finally prepared in Example 1, such as... Figure 2 As shown; 2. Mechanical property testing: In accordance with GB / T228 "Metallic materials - Tensile testing at room temperature" and GBT4161-2007 "Metallic materials - Plane strain fracture toughness KIC test method", the tensile and impact properties of the titanium alloy parts prepared in Examples 1-3 were tested respectively. The specific test results are shown in Table 1.

[0041] Table 1. Mechanical properties and dimensional profile test results of the titanium alloy parts prepared in Examples 1-3: Table 1:

[0042] As can be seen from the mechanical property test results in Table 1, the parts AC all have excellent strength-plasticity matching, which reflects a good performance matching of high strength, high plasticity and high toughness. Compared with Comparative Example 1, the present invention can significantly improve dimensional accuracy while ensuring that the mechanical properties remain unchanged.

[0043] 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.

[0044] 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 method for preparing complex thin-walled parts by hot isostatic pressing of titanium alloy powder, characterized in that, Includes the following steps: Step 1: Prepare the casing, fill the pre-alloyed powder into the casing, vibrate it, and perform vacuum degassing and sealing welding to form a casing-encased blank; Step 2: Place the encased billet in a hot isostatic pressing (HIP) machine and sequentially perform multi-stage gradient heating, heat preservation and pressure holding, and multi-stage gradient cooling. Finally, release the pressure and remove the billet from the furnace. Step 3: After the pressure is released from the furnace, the encased billet undergoes stress-relieving annealing, and then the encasing is removed to obtain the preform. Step 4: The preform is first cleaned and dehydrogenated, then machined, and then stabilized to obtain a thin-walled part; In step two, the multi-stage gradient heating includes a first stage heating and a second stage heating. The first stage heating is to heat to 720-850℃ at a rate of 5-15℃ / min; the second stage heating is to continue heating to 920-940℃ at a rate of 3-8℃ / min. In step two, the multi-gradient cooling includes a first slow cooling stage, a second slow cooling stage, and a third cooling stage. The first slow cooling stage involves cooling from the temperature after heat preservation and pressure holding to 750-800℃ at a cooling rate of 0.5-2.0℃ / min; the second slow cooling stage involves cooling from 750-800℃ to 500-600℃ at a cooling rate of 1.0-3.0℃ / min; and the third cooling stage involves cooling along with the furnace to below 200℃ at a cooling rate of 2-5℃ / min, followed by depressurization and removal from the furnace. In step three, the stress-relief annealing process specifically involves heating to 650-700℃ at a rate of 2-5℃ / min under vacuum or argon protection, holding at that temperature for 2-4 hours, and then furnace cooling to below 300℃ at a rate of ≤2℃ / min before removing from the furnace.

2. The method for preparing complex thin-walled parts by hot isostatic pressing of titanium alloy powder according to claim 1, characterized in that, In step one, the pre-alloyed powder is prepared by plasma rotating electrode atomization or electrode-induced atomization.

3. The method for preparing complex thin-walled parts by hot isostatic pressing of titanium alloy powder according to claim 1, characterized in that, In the second step of heat preservation and pressure holding, heat preservation is carried out at the temperature of the second stage of heating, and pressure holding is carried out by applying an isostatic pressure of 100-140MPa for 2-4 hours.

4. The method for preparing complex thin-walled parts by hot isostatic pressing of titanium alloy powder according to claim 1, characterized in that, In step three, the casing needs to be removed at a temperature of 30-50℃ using a chemical dissolution method.

5. The method for preparing complex thin-walled parts by hot isostatic pressing of titanium alloy powder according to claim 1, characterized in that, In step four, the machining is performed on the preform using a CNC machine tool. The machining parameters are: cutting speed of 80-150 m / min, depth of cut of 0.05-0.2 mm, and feed rate of 0.02-0.08 mm / z.

6. The method for preparing complex thin-walled parts by hot isostatic pressing of titanium alloy powder according to claim 1, characterized in that, In step four, stabilization treatment involves vibration aging or low-temperature vacuum aging treatment of the machined parts.

7. An application of complex thin-walled parts formed by hot isostatic pressing of titanium alloy powder in the manufacture of aerospace engines, characterized in that, The thin-walled part is prepared by the method for preparing complex thin-walled parts by hot isostatic pressing of titanium alloy powder as described in any one of claims 1-6.

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