Near-net forming method suitable for titanium alloy component in complex shape and application

Abstract

The invention belongs to the technical field of titanium alloy metallurgy forming, and relates to a near-net forming method and application suitable for a titanium alloy component in a complex shape, and the near-net forming method comprises the steps that titanium alloy powder with the particle size being 50-150 microns and the oxygen content being smaller than or equal to 0.2% is selected and put into a steel ladle sleeve after being screened and dried, and the steel ladle sleeve filled with the powder is vacuumized and sealed; the sealed steel ladle sleeve is heated to 50-100 DEG C below the beta transformation temperature of the titanium alloy, die forging treatment is conducted after heat preservation is conducted for 45-60 min, and a preformed body is obtained; and the preformed body is subjected to hot isostatic pressing treatment, a titanium alloy component blank is obtained, and a target titanium alloy component is obtained after a steel ladle sleeve of the titanium alloy component blank is removed. Through the multidirectional forging and hot isostatic pressing composite technology under the constraint of the steel ladle sleeve, the problems that in traditional hot isostatic pressing forming, the powder stacking density is uneven, the design of the ladle sleeve is complex, and the cost is high are solved.

Description

Technical Field

[0001] The invention belongs to the technical field of titanium alloy powder metallurgy forming, and relates to a near-net forming method suitable for titanium alloy components with complex shapes and its application. Background Art

[0002] Titanium alloys are widely used in aerospace, medical devices, and other fields due to their high strength, low density, excellent corrosion resistance, and high-temperature performance. For complex structural parts such as aero-engine blades and integral frames, powder metallurgy technology demonstrates significant advantages such as near-net-shape formation, high material utilization, and uniform microstructure. However, traditional hot isostatic pressing (HIP) technology has the following core issues 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 product. In particular, key areas such as deep cavities and thin ribs are prone to density deviation. (2) Difficulty and high cost in encapsulation design: For complex structures such as deep cavities with a depth-to-width ratio of ≥3:1 and thin ribs with a thickness of ≤1.5mm, high-precision encapsulation is required, and an extremely long heat preservation and pressure holding time (usually 4-6 hours) is required, which significantly increases production costs. (3) Defects of traditional forging preforming: When directly forged without an encapsulation, loose powder is prone to cracking, making it difficult to achieve precise 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 to solve the problems of insufficient shape accuracy, low production efficiency and high production cost in the existing technology. Summary of the Invention

[0005] In response to the problems of poor shape accuracy, low densification efficiency and high cost in the existing technology of complex parts formed by titanium alloy powder, the present invention provides a near-net forming method suitable for complex-shaped titanium alloy components. The method achieves precise preforming of complex-shaped components through multi-directional forging under the constraint of a steel sleeve, and combines hot isostatic pressing for uniform densification, which significantly improves the dimensional accuracy and production efficiency of the components and reduces the production cost. Specifically, it reduces the cost by 25% compared with traditional forging and by 20% compared with direct hot isostatic pressing.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

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

[0008] Step 1: Select titanium alloy powder with a particle size of 50-150 μm and an oxygen content of ≤0.2%, and place it into a ladle after screening and drying. The ladle is then vacuumed and sealed.

[0009] Step 2: Heat the sealed steel ladle to 50-100°C below the β-transformation temperature of the titanium alloy, keep the temperature for 45-60 minutes, and then perform die forging to obtain a preform;

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

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

[0012] Furthermore, in step 1, at a vacuum degree of ≤1×10 -2 Pa, the titanium alloy powder was sieved to remove impurities, and then the vacuum degree was ≤5×10 -3 Dry at 150-200°C for 4-6 hours.

[0013] Furthermore, in step 1, the ladle is subjected to a vibration treatment during the powder filling process, and after the vibration treatment, the density of the titanium alloy powder in the ladle is 60-70%;

[0014] The vacuum degree inside the ladle after vacuuming and sealing is ≤3×10 -3 Pa.

[0015] Furthermore, the shape of the steel ladle is a cylinder, a round cake or a polygonal cake.

[0016] Furthermore, the specific process of the die forging treatment is: at a die temperature of 800-900°C, a simple die forging or a multi-directional die forging method is used to forge the heated and heat-insulated steel sleeve into a preform having the same shape as the target titanium alloy component.

[0017] Furthermore, the die used in the die forging process needs to be designed with a magnified shrinkage ratio according to the final shape of the target titanium alloy component and using a powder shrinkage mathematical model.

[0018] Furthermore, the specific process of the hot isostatic pressing treatment is: heating the preform to 30-50° C. below the β-transus temperature of the titanium alloy, applying a pressure of 120-180 MPa, and maintaining the temperature and pressure for 1.5-2.5 hours.

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

[0020] Furthermore, in step 4, the steel jacket 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 forming method suitable for complex-shaped titanium alloy components, and based on the near-net forming method, aircraft engine blades, aircraft engine disks, turbine disks and titanium alloy components with deep cavities or thin rib structures are prepared.

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

[0023] (1) High-precision forming of complex shapes: The present invention uses low-carbon steel to process and manufacture the steel ladle sleeve. The steel ladle sleeve is generally a simple shape, usually a cylinder, a round cake or a polygonal cake. 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 sleeve are designed according to the contour shape of the target titanium alloy component; through the coordinated constraint forming of the steel ladle sleeve and the die forging die, the precise preforming of complex structures such as curved surfaces, deep cavities, and thin ribs is successfully achieved, with a dimensional accuracy of ±0.3mm, which significantly reduces the subsequent machining amount and increases the material utilization rate to more than 90%, solving the problems of difficulty in manufacturing complex-shaped sleeves and difficulty in subsequent powder filling.

[0024] (2) Excellent mechanical properties and uniformity: The steel ladle of the present invention can ensure that the titanium alloy powder flows fully in the steel ladle under the constraint of the mold, and the relative density difference of each part is ≤0.5%. The relative density of conventional ladle is only 60~70%. After forging, the volume shrinks and the density increases, and the average relative density reaches 80~90%. In addition, the use of a simple steel ladle can avoid the problem of difficulty in powder filling in conventional complex ladle and difficulty in ensuring the consistency of relative density of various parts of the ladle, thereby ensuring the performance and uniformity of various parts of complex-shaped titanium alloy components. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings are incorporated in and constitute a part of this specification and, together with the description, serve to explain the principles of the invention.

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0027] Figure 1 The figure is a flow chart of the near-net-shape forming method of the present invention applicable to titanium alloy components with complex shapes. DETAILED DESCRIPTION

[0028] Here, exemplary embodiments will be described in detail, and the embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Instead, they are only examples consistent with some aspects of the present invention described in detail in the appended claims.

[0029] The present invention provides a near net-shape forming method suitable for titanium alloy components with complex shapes. Figure 1 As shown, the following steps are included:

[0030] Step 1: Select titanium alloy powder with a particle size of 50~150μm and an oxygen content of ≤0.2%, and put it into the ladle after screening and drying. The ladle is vacuumed and sealed.

[0031] Specifically, first, titanium alloy powders such as TC4, TC11, TC17, and TC21 powders are prepared by gas atomization or plasma rotating electrode method. Then, titanium alloy powders with a particle size range of 50 to 150 μm and an oxygen content of ≤0.2% are selected and heated in a vacuum of ≤1×10 -2 Pa, the titanium alloy powder was sieved through a 100-mesh sieve to remove impurities larger than the selected particle size range, and the sieving process further ensured that the particle size of the titanium alloy powder was within the range of 50-150 μm. Then, under a vacuum degree of ≤5×10 -3 The sieved titanium alloy powder is dried at 400-200°C for 4-6 hours to completely remove the adsorbed water and gas on the surface of the titanium alloy powder and ensure the purity of the titanium alloy powder. Finally, the sieved and dried titanium alloy powder is placed in a steel ladle, and the steel ladle is vacuumed and sealed. For example, the drying temperature can be 150°C, 160°C, 170°C, 180°C, 190°C, 200°C, etc., and the drying time can be 4h, 5h, 6h, etc., which are not listed here one by one.

[0032] Regarding the design of the ladle sleeve, the present invention uses low carbon steel to process and manufacture the ladle sleeve. The ladle sleeve is generally a simple shape, such as a cylinder, a round cake or a polygonal cake. The shape and size of the ladle sleeve are designed according to the contour shape of the target titanium alloy component.

[0033] The vibration filling process is used to make the initial bulk density of the titanium alloy powder in the steel ladle reach 60%-70% of the theoretical density. The steel ladle is sealed by electron beam welding to ensure that the vacuum degree inside the steel ladle is ≤3×10 -3 Pa, forming a closed forging space. The filled ladle is similar to the blank of the die forging, but it is filled with titanium alloy powder. Its size is about 30%-40% smaller than the original blank of the normal die forging. This is because the relative density of titanium alloy powder is lower than that of the original blank of the normal die forging.

[0034] Step 2: Heat the sealed steel ladle to 50-100°C below the β-transformation temperature of the titanium alloy, keep the temperature for 45-60 minutes, and then perform die forging to obtain a preform.

[0035] Specifically, the sealed steel ladle is first placed in a resistance furnace and heated to 50-100°C below the titanium alloy's β-transus temperature. The temperature is then held for 45-60 minutes to achieve temperature uniformity within the ladle. Different titanium alloys have different β-transus temperatures; TC4 alloys require heating to 900-950°C, while TC11 alloys require heating to 950-1000°C. The ladle is then quickly transferred to a die forging press, with the die temperature maintained at 800-900°C to ensure temperature matching between the ladle and die during the forging process. Simple die forging or multi-directional die forging is used to deform the ladle into a preform that essentially matches the target titanium alloy component. The die shape is designed based on the target titanium alloy component's dimensions and the deformation behavior of hot isostatic pressing. For example, the holding time can be 45 minutes, 50 minutes, 55 minutes, 60 minutes, and so on. These are not listed here.

[0036] For multi-directional die forging, the main pressure and lateral pressure are applied step by step, the main pressure is ≥250MPa, and the lateral pressure is 25~40MPa.

[0037] The die forging dies are designed and manufactured using the Shima-Oyane powder shrinkage model, with the shrinkage ratio magnified based on the desired final shape of the titanium alloy component. As a result, the preform formed by die forging the relatively simple ladle is essentially identical to the desired titanium alloy component, with only slightly larger dimensions than the final shape.

[0038] Step 3: The preform is subjected to hot isostatic pressing to obtain a titanium alloy component blank.

[0039] Specifically, the preform is heated to 30~50℃ below the β-transform temperature of the titanium alloy, a pressure of 120~180MPa is applied, and the temperature is maintained for 1.5~2.5h. For TC4 alloy, it needs to be heated to 930-950℃, and for TC11 alloy, it needs to be heated to 960-980℃. The steel ladle after die forging is placed under high temperature and high pressure to cause the shape of the preform after die forging to shrink and deform, further densify, and obtain a titanium alloy component blank, ultimately reaching 99.99% of the theoretical density and achieving the purpose of near-net forming. For example, the holding time can be 1.5h, 2h, 2.5h, etc., which are not listed here one by one.

[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 jacket of the titanium alloy component blank, the target titanium alloy component is obtained.

[0042] Specifically, the low-carbon steel sheath of the titanium alloy component blank is removed by mechanical stripping to obtain a target titanium alloy component with a complex shape that is near net shape, and only simple processing is required on the parts of the target titanium alloy component that need to be matched.

[0043] The target titanium alloy components obtained above include aircraft engine blades, integral frames or turbine disks and other components with deep cavities and thin rib structures.

[0044] In order to verify the beneficial effects of the preparation method of the present invention, the following examples are provided to further illustrate the effects. Example 1

[0045] This embodiment provides a near-net-shape forming method for a titanium alloy blade for an aero-engine, 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 -2 Then, the vacuum degree is ≤5×10 -3 Pa, 180 ° C under vacuum drying for 5 h; finally, the dried TC4 alloy powder was loaded into a 08Al steel ladle. The 08Al steel ladle was designed according to the blade three-dimensional model and divided into two parts: the blade body cavity and the tenon cavity. After vibration filling, the initial density of the TC4 alloy powder was 68%. Electron beam welding was used to seal the ladle, and the vacuum degree in the ladle reached 5×10 -4 Pa.

[0047] Step 2: The sealed ladle is heated to 930°C, held at this temperature for 50 minutes, and then moved to a simple die forging press at a die temperature of 850°C. The die is designed to reflect the blade and tenon shape before hot isostatic pressing. Under die control and a forging pressure of 5,000 to 10,000 tons, the blade aerodynamic surface and tenon are formed. The forging time is controlled within 5 minutes, and the temperature is maintained at 920 to 940°C to obtain a preform.

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

[0049] Step 4: After removing the steel jacket of the blade blank, a titanium alloy blade for an aero-engine is obtained.

[0050] CT scans revealed no internal pores larger than 5μm. The blade's density at a thickness of 1.8mm was 99.7%, while the tenon's dimensional accuracy was ±0.25mm, resulting in a density of 99.94%. Density differences between different regions were ≤0.2%, and the material utilization rate reached 92%. Mechanical properties testing revealed tensile strength of 1080MPa, yield strength of 900MPa, elongation of 14%, and fatigue strength of 600MPa. The uniformity of the structure across all parts fully met the requirements for aircraft engine blades. Example 2

[0051] This embodiment provides a near-net-shape forming method for a titanium alloy integral engine disc, comprising 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 -2 Then, the vacuum degree is ≤5×10 -3 Pa, 150 ° C for 6 h; finally, the dried TC11 alloy powder was placed in a Q235 low-carbon steel ladle. The steel ladle was designed to be cylindrical according to the turbine disk structure. After vibration filling, the initial density of the TC11 alloy powder was 70%. The powder was sealed by electron beam welding to make the vacuum degree in the ladle reach 8×10 -4 Pa.

[0053] Step 2: The sealed steel ladle is heated to 950°C, held at this temperature for 60 minutes, and then moved to a multi-directional forging press with a die temperature of 900°C. A main pressure of 250 MPa is first applied, resulting in a 30% deformation. Lateral pressures of 25 to 40 MPa are then applied three times to form the turbine disk rim and hub. Temperature fluctuations are controlled within ±8°C to obtain a preform.

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

[0055] Step 4: After removing the steel jacket of the turbine disk blank, a turbine disk for an aircraft engine is obtained.

[0056] CT scans revealed 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 properties testing revealed tensile strength of 1150 MPa, yield strength of 960 MPa, elongation of 13%, and fatigue strength of 700 MPa. The uniformity of the structure across all parts fully met the requirements for aircraft engine discs.

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

[0058] The foregoing description is intended only to provide specific embodiments of the present invention, which will enable those skilled in the art to understand and implement the present 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 present invention.

[0059] It should be understood that the present invention is not limited to the above description and that various modifications and changes may be made without departing from the scope thereof. 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: The steps include: Step 1: Select titanium alloy powder with a particle size of 50-150 μm and an oxygen content of ≤0.2%, and place it into a ladle after screening and drying. The ladle is then vacuumed and sealed. Step 2: Heat the sealed steel ladle to 50-100°C below the β-transformation temperature of the titanium alloy, keep the temperature for 45-60 minutes, and then perform die forging to obtain a preform; Step 3: hot isostatic pressing the preform to obtain a titanium alloy component blank; Step 4: After removing the steel jacket of 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 Pa, the titanium alloy powder was sieved to remove impurities, and then the vacuum degree was ≤5×10 -3 Dry at 150-200°C 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 ladle is vibrated during the powder filling process, and after the vibration treatment, the density of the titanium alloy powder in the ladle is 60-70%; The vacuum degree inside the ladle after vacuuming and sealing is ≤3×10 -3 Pa.

4. The near-net-shape forming method for complex-shaped titanium alloy components according to claim 1, characterized in that: The shape of the steel ladle is a cylinder, a round cake or a polygonal cake.

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 die forging treatment is: at a die temperature of 800-900°C, a simple die forging or a multi-directional die forging method is used to forge the heated and heat-insulated steel sleeve into a preform having the same shape as the target titanium alloy component.

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

7. 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 treatment is: heating the preform to 30-50° C. below the β-transus temperature of the titanium alloy, applying a pressure of 120-180 MPa, and maintaining the temperature and pressure for 1.5-2.5 hours.

8. 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 of each part is ≤0.5%, and the dimensional accuracy is within ±0.3mm.

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

10. An application of a near-net-shape forming method for complex-shaped titanium alloy components, characterized in that: Aero-engine blades, aero-engine disks, turbine disks, and titanium alloy components containing deep cavities or thin rib structures are manufactured based on the near-net forming method described in any one of claims 1 to 9.

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