A near-net-shaping method and application for complex shape titanium alloy components

Abstract

The present application belongs to the technical field of titanium alloy metallurgical forming, and relates to a near-net forming method suitable for complex-shaped titanium alloy components and application, comprising the following steps: selecting titanium alloy powder with a particle size of 50-150 microns and an oxygen content of less than or equal to 0.2%, and after screening and drying treatment, the powder is loaded into a ladle cover; the ladle cover after powder loading is vacuumized and sealed; the sealed ladle cover is heated to 50-100 DEG C below the beta transformation temperature of the titanium alloy, and after 45-60 min of heat preservation, die forging treatment is performed to obtain a preformed body; the preformed body is subjected to hot isostatic pressing treatment to obtain a titanium alloy component blank, and after removing the ladle cover of the titanium alloy component blank, a target titanium alloy component is obtained. Through the multi-directional forging and hot isostatic pressing composite process under the constraint of the ladle cover, the problems of uneven powder accumulation density, complex ladle cover design, high cost and the like in the traditional hot isostatic pressing forming are solved.

Description

Technical Field

[0001] This invention belongs to the field of titanium alloy powder metallurgy forming technology, and relates to a near-net-shape forming method and its application for titanium alloy components with complex shapes. Background Technology

[0002] Titanium alloys, with their high strength, low density, excellent corrosion resistance, and high-temperature performance, are widely used in aerospace, medical devices, and other fields. For complex structural components such as aero-engine blades and integral frames, powder metallurgy technology exhibits significant advantages such as near-net-shape forming, high material utilization, and uniform microstructure. However, traditional hot isostatic pressing (HIP) technology faces the following core problems when directly forming complex parts:

[0003] (1) Uneven initial packing density of powder: This leads to uneven deformation during hot isostatic pressing, which seriously affects the dimensional accuracy and internal quality of the parts, especially the density deviation in key parts such as deep cavities and thin ribs; (2) High difficulty and cost of sleeve design: For complex structures such as deep cavities with a depth-to-width ratio ≥3:1 and thin ribs with a thickness ≤1.5mm, a high-precision sleeve needs to be designed, and an ultra-long heat preservation and pressure holding time is required (usually 4-6 hours), which greatly increases the production cost. (3) Defects of traditional forging preforming: When forging directly without a sleeve, the loose powder is prone to cracking, making it difficult to achieve accurate forming of complex contours, especially unable to meet the high precision requirements of aerospace components.

[0004] Therefore, there is an urgent need for a composite forming process that can achieve precise preforming and efficient densification of complex shapes in order to solve the problems of insufficient shape accuracy, low production efficiency and high production cost in the existing technology. Summary of the Invention

[0005] To address the challenges of poor shape accuracy, low densification efficiency, and high cost in existing titanium alloy powder forming techniques for complex parts, this invention provides a near-net-shape forming method suitable for complex-shaped titanium alloy components. This method achieves precise pre-forming of complex-shaped components through multi-directional forging under steel cladding constraints, combined with hot isostatic pressing for uniform densification. This significantly improves component dimensional accuracy and production efficiency while reducing production costs. Specifically, it reduces costs by 25% compared to traditional forging and by 20% compared to direct hot isostatic pressing.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a near-net-shape forming method suitable for titanium alloy components with complex shapes, comprising the following steps:

[0008] Step 1: Select titanium alloy powder with a particle size of 50~150μm and an oxygen content of ≤0.2%, and after sieving and drying, pack it into a steel liner. Vacuum the steel liner after it is filled and seal it.

[0009] Step 2: Heat the sealed steel cladding to 50~100℃ below the β transformation temperature of titanium alloy, hold for 45~60min, and then perform die forging to obtain a preform.

[0010] Step 3: Perform hot isostatic pressing on the preform to obtain a titanium alloy component blank;

[0011] Step 4: After removing the steel cladding from the titanium alloy component blank, the target titanium alloy component is obtained.

[0012] Furthermore, in step 1, the vacuum degree is ≤1×10 -2 Under a pressure of Pa, the titanium alloy powder is sieved to remove impurities. Then, under a vacuum degree ≤5×10⁻⁶, the titanium alloy powder is subjected to further sieving. -3 Dry at 150~200℃ for 4~6 hours.

[0013] Furthermore, in step 1, the steel cladding is subjected to vibration treatment during the powder loading process. After vibration treatment, the density of the titanium alloy powder inside the steel cladding is 60-70%.

[0014] The vacuum level inside the steel cladding after vacuuming and sealing is ≤3×10⁻⁶. -3 Pa.

[0015] Furthermore, the steel sheath is in the shape of a cylinder, a disc, or a polygonal disc.

[0016] Furthermore, the specific process of the die forging is as follows: at a die temperature of 800~900℃, the steel cladding after heating and holding is forged into a preform with the same shape as the target titanium alloy component by using simple die forging or multi-directional die forging.

[0017] Furthermore, the mold used in the forging process needs to be scaled up according to the shrinkage rate of the final shape of the target titanium alloy component, and designed using a powder shrinkage mathematical model.

[0018] Furthermore, the specific process of the hot isostatic pressing treatment is as follows: the preform is heated to 30~50°C below the β transformation temperature of the titanium alloy, a pressure of 120~180MPa is applied, and the temperature and pressure are maintained for 1.5~2.5h.

[0019] Furthermore, the density of the titanium alloy component blank is ≥99.99%, the relative density difference between different parts is ≤0.5%, and the dimensional accuracy is within ±0.3mm.

[0020] Further, in step 4, the steel cladding of the titanium alloy component blank is removed by machining.

[0021] On the other hand, the present invention also provides an application of a near-net-shape forming method suitable for complex-shaped titanium alloy components, which is used to prepare aero-engine blades, aero-engine disks, turbine disks, and titanium alloy components with deep cavities or thin rib structures.

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

[0023] (1) High-precision forming of complex shapes: The steel cladding is made of low carbon steel. The steel cladding is generally simple in shape, such as a cylinder, a disc, or a polygonal disc. During the powder filling process, the problem of uneven density caused by the initial accumulation of titanium alloy powder is avoided. The shape and size of the cladding are designed according to the outline shape of the target titanium alloy component. Through the synergistic constraint forming of the steel cladding and the forging die, the precise preforming of complex structures such as curved surfaces, deep cavities, and thin ribs is successfully achieved. The dimensional accuracy reaches ±0.3mm, which significantly reduces the amount of subsequent machining and increases the material utilization rate to more than 90%. This solves the problems of manufacturing difficulties of complex cladding and the difficulty of subsequent powder filling.

[0024] (2) Excellent mechanical properties and uniformity: Under the constraint of the mold, the steel cladding of the present invention can ensure that the titanium alloy powder flows fully in the steel cladding, and the relative density difference of each part is ≤0.5%. The relative density of conventional cladding is only 60~70%. After forging, the volume shrinks and the density increases, and the average relative density reaches 80~90%. Furthermore, the use of a simple steel cladding can avoid the problems of difficult powder packing and difficulty in ensuring the consistency of relative density of each part of the conventional complex cladding, thereby ensuring the performance and uniformity of each part of the complex-shaped titanium alloy component. Attached Figure Description

[0025] 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.

[0026] 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.

[0027] Figure 1 This is a flowchart of the near-net-shape forming method for complex-shaped titanium alloy components according to the present invention. Detailed Implementation

[0028] 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.

[0029] This invention provides a near-net-shape forming method suitable for complex-shaped titanium alloy components, see below. Figure 1 As shown, it includes the following steps:

[0030] Step 1: Select titanium alloy powder with a particle size of 50~150μm and an oxygen content of ≤0.2%. After sieving and drying, pack it into a steel liner. Vacuum the packed steel liner and seal it.

[0031] Specifically, firstly, titanium alloy powders, such as TC4, TC11, TC17, and TC21 powders, are prepared using gas atomization or plasma rotating electrode methods. Then, titanium alloy powders with a particle size range of 50–150 μm and an oxygen content ≤0.2% are selected and processed under a vacuum degree ≤1×10⁻⁶. -2 Under Pa conditions, titanium alloy powder is sieved through a 100-mesh sieve to remove impurities larger than the selected particle size range. This sieving process further ensures that the particle size of the titanium alloy powder is within the range of 50~150 μm. Then, under a vacuum degree ≤5×10⁻⁶, the powder is further processed. -3 The sieved titanium alloy powder is dried at 150-200℃ for 4-6 hours to thoroughly remove adsorbed water and gas from the powder surface, ensuring its purity. Finally, the sieved and dried titanium alloy powder is packed into a steel sleeve, which is then vacuum-sealed. For example, drying temperatures can be 150℃, 160℃, 170℃, 180℃, 190℃, 200℃, etc., and drying times can be 4h, 5h, 6h, etc., which will not be listed here.

[0032] For the design of the steel cladding, the present invention uses low carbon steel to process and manufacture the steel cladding. The steel cladding is generally a simple shape, such as a cylinder, a disc, or a polygonal disc. The shape and size of the steel cladding are designed according to the outline shape of the target titanium alloy component.

[0033] A vibration-loading process is used to ensure that the initial packing density of titanium alloy powder inside the steel cladding reaches 60%-70% of the theoretical density. Electron beam welding is then used to seal the steel cladding, ensuring an internal vacuum degree ≤3×10⁻⁶. -3 Pa forms a closed forging space. The filled steel sleeve is similar to the blank of a die forging, but it is filled with titanium alloy powder and its size is about 30%-40% larger than the original blank of a normal die forging. This is because the titanium alloy powder has a lower relative density than the original blank of a normal die forging.

[0034] Step 2: Heat the sealed steel cladding to 50~100℃ below the β transformation temperature of titanium alloy, hold for 45~60 minutes, and then perform die forging to obtain a preform.

[0035] Specifically, firstly, the sealed steel cladding is placed in a resistance furnace and heated to 50-100°C below the β-transformation temperature of the titanium alloy, and held for 45-60 minutes to achieve temperature homogenization within the cladding. Different types of titanium alloys have different β-transformation temperatures; for TC4 alloy, it needs to be heated to 900-950°C, while for TC11 alloy, it needs to be heated to 950-1000°C. Then, the steel cladding is quickly transferred to a die forging press, with the die temperature maintained at 800-900°C to ensure temperature matching between the cladding and the die during forging. Simple die forging or multi-directional die forging is used to deform the steel cladding into a preform that is essentially the same shape as the target titanium alloy component. The die shape is designed according to the dimensions of the target titanium alloy component and the hot isostatic pressing deformation characteristics. For example, the holding time can be 45 minutes, 50 minutes, 55 minutes, 60 minutes, etc., and will not be listed here.

[0036] For multi-directional forging, the main pressure and lateral pressure are applied in stages, with the main pressure ≥250MPa and the lateral pressure 25~40MPa.

[0037] The die forging molds are designed and manufactured based on the shrinkage rate amplification of the final shape of the target titanium alloy component and using the Shima-Oyane powder shrinkage mathematical model. Therefore, the preform formed by die forging of a relatively simple steel cladding changes its shape to be basically consistent with the shape of the target titanium alloy component, only slightly larger in size than the final shape.

[0038] Step 3: Perform hot isostatic pressing on the preform to obtain a titanium alloy component blank.

[0039] Specifically, the preform is heated to 30-50°C below the β-transformation temperature of the titanium alloy, and a pressure of 120-180 MPa is applied, holding the temperature and pressure for 1.5-2.5 hours. For TC4 alloy, the temperature needs to be heated to 930-950°C, and for TC11 alloy, it needs to be heated to 960-980°C. Under high temperature and high pressure, the forged steel cladding causes the preform to shrink and deform, further densifying it to obtain a titanium alloy component blank, ultimately achieving 99.99% of the theoretical density and achieving near-net-shape forming. For example, the holding time can be 1.5 hours, 2 hours, 2.5 hours, etc., which will not be listed here.

[0040] The relative density difference of each part of the obtained titanium alloy component blank is ≤0.5%, the dimensional accuracy is within ±0.3mm, and the material utilization rate is ≥90%.

[0041] Step 4: After removing the steel cladding from the titanium alloy component blank, the target titanium alloy component is obtained.

[0042] Specifically, by mechanically peeling away the low-carbon steel cladding of the titanium alloy component blank, a near-net-shape target titanium alloy component with a complex shape is obtained, and only the parts of the target titanium alloy component that need to be fitted are simply processed.

[0043] The target titanium alloy components obtained above include components with deep cavities and thin ribs, such as aero-engine blades, integral frames, or turbine disks.

[0044] To verify the beneficial effects of the preparation method of the present invention, the following examples are provided for further explanation. Example 1

[0045] This embodiment provides a near-net-shape forming method for titanium alloy blades used in aero engines, comprising the following steps:

[0046] Step 1: First, select TC4 alloy powder with a particle size of 50~150μm and an oxygen content of 0.15%, and heat it under a vacuum degree ≤1×10 -2 Sieving was performed at Pa. Then, the vacuum degree was ≤5×10 -3 Vacuum drying was performed at 180℃ and Pa for 5 hours. Finally, the dried TC4 alloy powder was packed into a 08Al steel cladding. The 08Al steel cladding, designed according to the three-dimensional model of the blade, consisted of a blade cavity and a tenon cavity. After vibration packing, the initial density of the TC4 alloy powder was 68%. Electron beam welding was used to seal the cladding, achieving a vacuum level of 5 × 10⁻⁶ Pa within the steel cladding. -4 Pa.

[0047] Step 2: Heat the sealed steel bladder to 930℃, hold for 50 minutes, and then transfer it to a simple die forging press. The die temperature is 850℃. The die is designed with the blade and tenon shapes before hot isostatic shrinkage. Under the control of the die and the forging pressure of 5000~10000 tons, the aerodynamic curved surface of the blade and the tenon are formed. The forging time is controlled within 5 minutes, and the temperature is maintained at 920~940℃ to obtain the preform.

[0048] Step 3: The preform is subjected to hot isostatic pressing (HIP) with the following parameters: temperature 950℃, pressure 160MPa, and holding at the temperature and pressure for 2 hours to obtain the blade blank.

[0049] Step 4: After removing the steel cladding from the blade blank, titanium alloy blades for aero-engines are obtained.

[0050] CT scans revealed no pores larger than 5μm inside the blade. The density at a thickness of 1.8mm was 99.7%, the tenon dimensional accuracy was ±0.25mm, the density was 99.94%, the density difference between different areas was ≤0.2%, and the material utilization rate reached 92%. Mechanical property tests showed a tensile strength of 1080MPa, a yield strength of 900MPa, an elongation of 14%, and a fatigue strength of 600MPa. The microstructure was uniform throughout, fully meeting the requirements for aero-engine blades. Example 2

[0051] This embodiment provides a near-net-shape forming method for an integral titanium alloy engine disk, including the following steps:

[0052] Step 1: First, select TC11 alloy powder with a particle size of 75~150μm and an oxygen content of 0.05%, and heat it under a vacuum degree ≤1×10⁻⁶. -2 Sieving was performed at Pa. Then, the vacuum degree was ≤5×10 -3 Vacuum drying was performed at 150℃ and Pa for 6 hours. Finally, the dried TC11 alloy powder was packed into a Q235 low-carbon steel sheath. The sheath was cylindrical, designed according to the turbine disk structure. After vibration packing, the initial density of the TC11 alloy powder was 70%. Electron beam welding was used to seal the sheath, achieving a vacuum level of 8 × 10⁻⁶ Pa within the sheath. -4 Pa.

[0053] Step 2: Heat the sealed steel cladding to 950℃ and hold for 60 minutes before transferring it to a multi-directional forging press with a die temperature of 900℃. First, apply a principal pressure of 250MPa with a deformation of 30%. Then, apply lateral pressure of 25~40MPa in three stages to form the turbine disk rim and hub. Temperature fluctuations are controlled within ±8℃ to obtain the preform.

[0054] Step 3: The preform is subjected to hot isostatic pressing (HIP) with the following parameters: temperature 1000℃, pressure 180MPa, and holding time 1.5h to obtain the turbine disk blank.

[0055] Step 4: After removing the steel cladding from the turbine disk blank, the turbine disk for aero-engines is obtained.

[0056] CT scans revealed that the turbine disk for aero-engines has a dimensional accuracy of ±0.25mm, a density of 99.92%, a density difference of ≤0.3% between different regions, and a material utilization rate of 91%. Mechanical property tests showed a tensile strength of 1150MPa, a yield strength of 960MPa, an elongation of 13%, and a fatigue strength of 700MPa. The microstructure is uniform across all parts, fully meeting the requirements for aero-engine disk components.

[0057] The experimental data from the above embodiments demonstrate that the present invention has significant technical advantages and engineering application value in the forming of complex-shaped titanium alloy components.

[0058] 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.

[0059] 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 near-net-shape forming method suitable for complex-shaped titanium alloy components, characterized in that, Includes the following steps: Step 1: Select titanium alloy powder with a particle size of 50~150μm and an oxygen content of ≤0.2%, and after sieving and drying, pack it into a steel sleeve. Vacuum the steel sleeve after it is filled and seal it. The shape of the steel sleeve is a cylinder, a disc, or a polygonal disc. Step 2: Heat the sealed steel cladding to 50-100°C below the β-transformation temperature of the titanium alloy, hold for 45-60 minutes, and then perform die forging to obtain a preformed body. The specific process of the die forging is as follows: at a die temperature of 800-900°C, use simple die forging or multi-directional die forging to forge the heated and held steel cladding into a preformed body with the same shape as the target titanium alloy component. Step 3: Perform hot isostatic pressing on the preform to obtain a titanium alloy component blank; Step 4: After removing the steel cladding from the titanium alloy component blank, the target titanium alloy component is obtained.

2. The near-net-shape forming method for complex-shaped titanium alloy components according to claim 1, characterized in that, In step 1, the vacuum degree is ≤1×10 -2 Under a pressure of Pa, the titanium alloy powder is sieved to remove impurities. Then, under a vacuum degree ≤5×10⁻⁶, the titanium alloy powder is subjected to further sieving. -3 Dry at 150~200℃ for 4~6 hours.

3. The near-net-shape forming method for complex-shaped titanium alloy components according to claim 1, characterized in that, In step 1, the steel cladding is vibrated during the powder loading process. After vibration treatment, the density of the titanium alloy powder inside the steel cladding is 60-70%. The vacuum level inside the steel cladding after vacuuming and sealing is ≤3×10⁻⁶. -3 Pa.

4. The near-net-shape forming method for complex-shaped titanium alloy components according to claim 1, characterized in that, The mold used in the forging process needs to be designed using a powder shrinkage mathematical model based on the final shape of the target titanium alloy component.

5. The near-net-shape forming method for complex-shaped titanium alloy components according to claim 1, characterized in that, The specific process of the hot isostatic pressing is as follows: the preform is heated to 30~50°C below the β transformation temperature of the titanium alloy, a pressure of 120~180MPa is applied, and the temperature and pressure are maintained for 1.5~2.5h.

6. The near-net-shape forming method for complex-shaped titanium alloy components according to claim 1, characterized in that, The density of the titanium alloy component blank is ≥99.99%, the relative density difference between different parts is ≤0.5%, and the dimensional accuracy is within ±0.3mm.

7. The near-net-shape forming method for complex-shaped titanium alloy components according to claim 1, characterized in that, In step 4, the steel cladding of the titanium alloy component blank is removed by machining.

8. An application of a near-net-shape forming method suitable for complex-shaped titanium alloy components, characterized in that, Aero-engine blades, aero-engine disks, turbine disks, and titanium alloy components with deep cavities or thin rib structures are prepared based on the near-net-shape forming method according to any one of claims 1 to 7.

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