TC4 titanium alloy graded powder for hot isostatic pressing forming and method and application thereof

Abstract

This invention discloses a graded powder for hot isostatic pressing (HIP) of C4 titanium alloys. The graded powder is composed of a graded mixture of spherical and non-spherical TC4 powders. The graded powder consists of the following components by mass percentage: 60%–95% spherical TC4 powder and 5%–40% non-spherical TC4 powder. The loose density of the graded powder is not less than 92% of the loose density of pure spherical TC4 powder. This method addresses the technical problems of high cost of high-quality spherical powder and the inability of non-spherical powder alone to meet the requirements of HIP processes in existing technologies. This invention also relates to a method for preparing the graded powder for hot isostatic pressing of TC4 titanium alloys, and the application of the graded powder in hot isostatic pressing.

Description

Technical Field

[0001] This invention belongs to the field of powder metallurgy technology, specifically relating to graded powder for hot isostatic pressing of TC4 titanium alloy, a method for preparing graded powder for hot isostatic pressing of TC4 titanium alloy, and the application of graded powder in hot isostatic pressing. Background Technology

[0002] TC4 titanium alloy (Ti-6Al-4V) is widely used in aerospace, military, and shipbuilding industries due to its low density, high specific strength, good biocompatibility, and excellent corrosion resistance. Powder metallurgy hot isostatic pressing (PM-HIP) technology can achieve near-net-shape forming of titanium alloys. Its fine grain and segregation-free characteristics enable the parts to obtain excellent microstructure and properties, avoiding high-energy-consuming processes such as melting, casting, and forging, and significantly improving the utilization rate of titanium alloys.

[0003] However, the core contradiction currently facing TC4 titanium alloy powder metallurgy technology lies in the fact that high-quality spherical powders (such as those prepared by the PREP method and EIGA method) have good flowability, high bulk density and excellent formability, but their high preparation cost severely restricts the promotion and application of PM-HIP technology in the civilian field; while low-cost non-spherical powders (such as those prepared by the HDH method) have significant raw material cost advantages, but their poor powder flowability and low bulk density make it difficult to meet the requirements of hot isostatic pressing process for powder filling and densification effect when used alone.

[0004] While existing technologies have reported on mixing powders of different morphologies or particle sizes—for example, Chinese patent CN202311117507.0 discloses a method for preparing TC4 titanium alloy preforms and their plates, involving HIP forming of TC4 powder—this technical solution does not address the core requirements of the HIP process regarding powder filling properties, flowability, and densification effects. It lacks a systematic gradation strategy aimed at maximizing the utilization of low-cost non-spherical powders while ensuring process reliability. Although existing technologies involve powder mixing, none have employed a high-quality spherical powder as the main component (>60%), supplemented by the introduction of fine-grained (-200 mesh) non-spherical powders to fill the gaps between the spherical powders, thus achieving a synergistic optimization of cost and performance. Furthermore, no technical solution has been found that systematically optimizes the gradation ratio of spherical and non-spherical powders to achieve cost optimization, taking into account the characteristics of the HIP process and ensuring process feasibility. Therefore, developing a TC4 titanium alloy gradation powder that meets the requirements of the HIP process while minimizing raw material costs has significant engineering application value. Summary of the Invention

[0005] The first objective of this invention is to provide graded powder for hot isostatic pressing (HIP) of TC4 titanium alloy, thereby solving the technical problems in the prior art where the cost of high-quality spherical powder is too high and non-spherical powder alone cannot meet the requirements of HIP process.

[0006] The second objective of this invention is to provide a method for preparing graded powder for hot isostatic pressing of TC4 titanium alloy.

[0007] A third objective of this invention is to provide the application of graded powders in hot isostatic pressing.

[0008] The first technical solution adopted in this invention is a graded powder for hot isostatic pressing of TC4 titanium alloy, wherein the graded powder is composed of a graded mixture of spherical TC4 powder and non-spherical TC4 powder. The graded powder is composed of the following components by mass percentage: 60%~95% of spherical TC4 powder and 5%~40% of non-spherical TC4 powder; the loose density of the graded powder is not less than 92% of the loose density of pure spherical TC4 powder.

[0009] The invention is further characterized in that: The spherical TC4 powder is prepared by mixing spherical TC4 powder obtained by gas atomization and spherical TC4 powder obtained by PREP method. The oxygen content of the resulting spherical TC4 powder is 0.10wt%~0.15wt%. The mass ratio of spherical TC4 powder obtained by the gas atomization method to that obtained by the PREP method is 6-8:2-4.

[0010] The particle size range of spherical TC4 powder is 53μm~250μm.

[0011] The non-spherical TC4 powder was prepared by the hydrogenation-dehydrogenation (HDH) method. The particle size of the non-spherical TC4 powder was less than 200 mesh and the oxygen content was ≤0.25wt%.

[0012] The raw material for non-spherical TC4 powder comes from TC4 recycled waste, which includes one or more of the following: processing scraps, molding residues, and metallurgical waste.

[0013] The second technical solution adopted in this invention is a method for preparing the graded powder for hot isostatic pressing of the above-mentioned TC4 titanium alloy, comprising the following steps: Step (1): Prepare spherical TC4 powder and non-spherical TC4 powder respectively; Step (2): Combine spherical TC4 powder and non-spherical TC4 powder according to the following mass percentages: 60%~95% of spherical TC4 powder and 5%~40% of non-spherical powder. Weigh and mix the ingredients. Step (3): Mix spherical TC4 powder and non-spherical TC4 powder using a V-type mixer or a three-dimensional mixer; Step (4): The mixed graded powder is sieved to remove agglomerates and obtain the finished graded powder.

[0014] The invention is further characterized in that: In step (3), the mixing time is 30 min to 120 min and the mixing speed is 20 r / min to 50 r / min.

[0015] In step (4), the mixed graded powder is subjected to 150-mesh sieve treatment.

[0016] The third technical solution adopted in this invention is the application of the above-mentioned graded powder in hot isostatic pressing. The process parameters for hot isostatic pressing are: temperature of 920℃~980℃, pressure of 100MPa~140MPa, and holding time of 120min~180min.

[0017] The beneficial effects of this invention are: (1) Effective control of raw material costs: While maintaining the excellent process performance of the spherical powder body (≥60%), by adding 5%~40% low-cost HDH non-spherical powder, the raw material cost of graded powder is reduced by 5%~30% compared with pure spherical powder, thus achieving a balance between performance and cost optimization.

[0018] (2) Ensure the feasibility of HIP process: The loose density of graded powder is not less than 92% of that of pure spherical powder, and the flowability meets the requirements of powder filling process, ensuring the uniformity and densification effect of the encapsulation filling.

[0019] (3) The performance of the parts meets the standard requirements: After the graded powder of the present invention is formed by HIP, the density of the parts is ≥99.5% and the mechanical properties meet the requirements of GB / T 45339-2025 "General Technical Specification for Hot Isostatic Pressed Titanium Alloy Parts" (tensile strength ≥895 MPa, yield strength ≥828 MPa, elongation ≥8%).

[0020] (4) Realize the resource utilization of titanium alloy waste: Non-spherical powder uses TC4 recycled waste (chips, scraps, etc.) as raw materials to realize high-value recycling and utilization, with significant environmental and economic benefits.

[0021] (5) Precise control of oxygen content in spherical powder: By pre-mixing atomized powder (oxygen content ≤ 0.15%) with PREP powder (oxygen content ≤ 0.08%), the mechanical properties of single PREP powder that are too low in oxygen content can be avoided, and the cost is reduced compared with pure PREP powder. Attached Figure Description

[0022] Figure 1 This is a process flow diagram of the preparation of graded powder and the preparation of TC4 titanium alloy parts using graded powder in Embodiment 1 of the present invention. Figure 2 The image shows the SEM morphology of the spherical TC4 powder (a mixture of atomized powder and PREP powder) in Example 1. Figure 3 The image shows the SEM morphology of the non-spherical TC4 powder (HDH method) in Example 1. Figure 4 The image shows the microstructure of the graded powder obtained in Example 1. Detailed Implementation

[0023] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0024] This invention provides a graded powder for hot isostatic pressing of TC4 titanium alloy, the graded powder being a graded mixture of spherical TC4 powder and non-spherical TC4 powder; The graded powder is composed of the following components by mass percentage: 60%~95% of spherical TC4 powder and 5%~40% of non-spherical TC4 powder; the loose density of the graded powder is not less than 92% of the loose density of pure spherical TC4 powder.

[0025] The spherical TC4 powder is prepared by mixing spherical TC4 powder obtained by gas atomization and spherical TC4 powder obtained by PREP method. The oxygen content of the resulting spherical TC4 powder is 0.10wt%~0.15wt%. The mass ratio of spherical TC4 powder obtained by the gas atomization method to that obtained by the PREP method is 6-8:4-2.

[0026] The particle size range of spherical TC4 powder is 53μm~250μm.

[0027] The non-spherical TC4 powder was prepared by the hydrogenation-dehydrogenation (HDH) method. The particle size of the non-spherical TC4 powder was less than 200 mesh and the oxygen content was ≤0.25wt%.

[0028] The raw material for non-spherical TC4 powder comes from TC4 recycled waste, which includes one or more of the following: processing scraps, molding residues, and metallurgical waste.

[0029] This invention also provides a method for preparing graded powder for hot isostatic pressing of TC4 titanium alloy, comprising the following steps: Step (1): Prepare spherical TC4 powder and non-spherical TC4 powder respectively; Step (1) specifically involves mixing spherical TC4 powder obtained by gas atomization with spherical TC4 powder obtained by PREP method in a certain proportion to obtain spherical TC4 powder with a particle size of 53μm~250μm and an oxygen content of 0.10~0.15wt%. Non-spherical TC4 powder with a particle size of less than 200 mesh and an oxygen content of ≤0.25 wt% was prepared by hydrogenation-dehydrogenation (HDH). The mass ratio of spherical TC4 powder obtained by the gas atomization method to that obtained by the PREP method is 6-8:2-4.

[0030] Step (2): Combine spherical TC4 powder and non-spherical TC4 powder according to the following mass percentages: 60%~95% of spherical TC4 powder and 5%~40% of non-spherical powder. Weigh and mix the ingredients. Step (3): Mix spherical TC4 powder and non-spherical TC4 powder using a V-type mixer or a three-dimensional mixer; In step (3), the mixing time is 30 min to 120 min and the mixing speed is 20 r / min to 50 r / min.

[0031] Step (4): The mixed graded powder is sieved to remove agglomerates and obtain the finished graded powder.

[0032] In step (4), the mixed graded powder is subjected to 150-mesh sieve treatment.

[0033] The present invention also provides the application of graded powder in hot isostatic pressing (HIP). The process parameters for HIP are: temperature of 920℃~980℃, pressure of 100MPa~140MPa, and holding time of 120min~180min.

[0034] The technical principle involved in the graded powder for hot isostatic pressing of TC4 titanium alloy of this invention is as follows: (1) The "critical packing density" effect of powder gradation: Through extensive experiments, this invention has found that when the loose packing density of the graded powder is less than 92% of that of pure spherical powder, the local density of the HIP molded part will drop sharply to below 99.5%, making it difficult to meet the standard requirements. This 92% threshold is the key critical point to ensure that the powder forms a uniform initial packing state without macroscopic segregation within the casing, and to achieve rapid particle rearrangement and densification under the initial high pressure of HIP. Below this value, the "bridging" effect of non-spherical particles will irreversibly lead to residual pores.

[0035] (2) Synergistic optimization of cost and performance: Spherical powder (≥60%) ensures the excellent flowability and packing uniformity of the graded powder, ensuring the reliability of the encapsulation filling; although the proportion of non-spherical powder is relatively low, its edges and corners generate local stress concentration under HIP stress, which promotes diffusion bonding and mechanical interlocking. By controlling the proportion of non-spherical powder to ≤40%, flowability deterioration can be avoided, while achieving a cost reduction of 5%~30%.

[0036] (3) Dual densification mechanism under HIP process: Under high temperature and high pressure, spherical powder undergoes plastic flow to preferentially fill the pores, while the corners of non-spherical powder promote interfacial diffusion to form metallurgical bond. The synergistic effect of the two makes the part have both high strength and good plasticity.

[0037] (4) Mechanism of synergistic regulation of oxygen content in spherical powder: PREP powder has extremely high sphericity and extremely low oxygen content (≤0.08 wt%), but too low oxygen content will lead to poor mechanical properties of HIP parts; gas atomized powder has a moderate oxygen content (0.10~0.15 wt%) and relatively low cost. By mixing the two in a certain proportion, the oxygen content can be precisely controlled to the optimal range of 0.10~0.15 wt%, which not only ensures the strength-plasticity match, but also avoids the high cost of full PREP powder.

[0038] Example 1 like Figure 1 As shown, the preparation method of graded powder for hot isostatic pressing of TC4 titanium alloy is as follows: (1) Preparation of spherical TC4 powder: Gas-atomized TC4 powder with a particle size of 53 μm to 250 μm and an oxygen content of 0.13 wt% was prepared by the gas atomization method (EIGA method); TC4 powder with a particle size of 53 μm to 250 μm and an oxygen content of 0.06 wt% was prepared by the PREP method. The gas-atomized powder and PREP powder were mixed at a mass ratio of 70:30 to obtain mixed spherical powder with an oxygen content of 0.11 wt%.

[0039] (2) Preparation of non-spherical TC4 powder: TC4 processing waste was used as raw material and prepared by hydrogenation dehydrogenation (HDH) after pretreatment. Specific process: TC4 waste was vacuum annealed at 600℃, then placed in a closed reactor and high-purity hydrogen gas was introduced to a pressure of 1.5 MPa. Hydrogenation was carried out at 500℃ for 10 hours, followed by crushing and sieving to obtain hydride powder. The hydride powder was then placed in a vacuum with a degree ≤10 - In a 2Pa environment, dehydrogenation was carried out at 780℃ for 10h, and after cooling, the powder was passed through a 200-mesh sieve to obtain non-spherical TC4 powder with a particle size ≤74μm and an oxygen content ≤0.20 wt%.

[0040] (3) Grading and mixing: Weigh the above spherical TC4 powder and non-spherical TC4 powder at a mass ratio of 80:20, place them in a V-type mixer, and mix them at a speed of 30 r / min for 50 minutes.

[0041] (4) Sieving: The mixed powder is passed through a 150-mesh sieve to remove agglomerates and obtain the finished graded powder.

[0042] The tap density of the graded powder in this embodiment was measured to be 2.96 g / cm³. 3 It has good fluidity and meets the requirements of the HIP powder filling process.

[0043] The graded powder of this embodiment is loaded into a low carbon steel sleeve, degassed, and then placed in a hot isostatic pressing (HIP) equipment for HIP forming. The process parameters are: heating to 950°C at 5°C / min, applying a pressure of 130MPa, holding the temperature and pressure for 150min, and cooling with the furnace after the holding period.

[0044] Testing revealed that the TC4 titanium alloy parts formed by HIP (High-Intensity Interchange) had a density of 99.8%, a tensile strength of 925 MPa, a yield strength of 852 MPa, and an elongation of 11.5%, meeting the requirements of GB / T 45339-2025 standard. Compared with using 100% spherical TC4 powder (ungraded), the raw material cost was reduced by approximately 18%.

[0045] from Figure 2 It can be seen from this that Figure 2 The image shows the SEM morphology of spherical TC4 powder (a mixture of atomized powder and PREP powder). As can be seen from the image, most powder particles exhibit a regular spherical or near-spherical shape with a smooth and dense surface, and a few satellite particles are present. The particle size distribution is concentrated in the range of 53 μm to 250 μm, with no obvious agglomeration or bridging between particles, indicating that the prepared spherical powder has good dispersibility and flowability.

[0046] from Figure 3 It can be seen from this that Figure 3 This is a SEM image of non-spherical TC4 powder (HDH method). As can be seen from the image, the powder particles are irregularly shaped, with obvious angular, flaky, or blocky features and a rough surface. The particle size is less than 200 mesh (≤74μm). This morphology is conducive to generating localized stress concentration during hot isostatic pressing, promoting mechanical interlocking and diffusion bonding between particles.

[0047] from Figure 4 It can be seen from this that Figure 4The image shows the microstructure of the graded powder. As can be seen, the spherical and non-spherical TC4 powders are uniformly mixed, with the non-spherical particles distributed in the gaps between the spherical particles. The spherical particles constitute the main skeletal structure, while the edges of the non-spherical particles fill the gaps between the spherical particles, forming a graded packing structure of "spherical skeleton + non-spherical filling." This structure helps to improve the bulk density and achieves a synergistic effect of plastic flow of spherical powder and interfacial diffusion of non-spherical powder during the HIP process.

[0048] Example 2 The difference between this embodiment and Embodiment 1 is that the mass ratio of spherical TC4 powder to non-spherical TC4 powder is 90:10 (90% spherical powder and 10% non-spherical powder).

[0049] The tap density of the graded powder in this embodiment was measured to be 3.01 g / cm³. 3 It exhibits excellent flowability. After HIP molding, the resulting part has a density of 99.9%, a tensile strength of 938 MPa, a yield strength of 860 MPa, and an elongation of 12.0%. Compared to using 100% spherical TC4 powder, the raw material cost is reduced by approximately 8%.

[0050] Example 3 The difference between this embodiment and Embodiment 1 is that the mass ratio of spherical TC4 powder to non-spherical TC4 powder is 65:35 (65% spherical TC4 powder and 35% non-spherical TC4 powder).

[0051] The tap density of the graded powder in this embodiment was measured to be 2.86 g / cm³. 3 The flowability still meets the powder filling requirements. After HIP molding, the part has a density of 99.6%, a tensile strength of 910 MPa, a yield strength of 838 MPa, and an elongation of 9.8%. Compared with using 100% spherical TC4 powder, the raw material cost is reduced by approximately 28%.

[0052] Example 4 The difference between this embodiment and Embodiment 1 is that the mass ratio of spherical TC4 powder to non-spherical TC4 powder is 60:40 (60% spherical powder and 40% non-spherical powder).

[0053] Testing revealed that the tap density of the graded powder in this embodiment was 2.83 g / cm³, close to the 92% threshold of the loose density of pure spherical powder, and its flowability basically met the requirements of the powder filling process. After HIP molding, the part had a density of 99.5%, a tensile strength of 905 MPa, a yield strength of 832 MPa, and an elongation of 9.0%. Compared to using 100% spherical TC4 powder, the raw material cost was reduced by approximately 32%. This embodiment demonstrates that when the proportion of spherical powder is reduced to 60%, the graded powder can still meet the basic requirements of the HIP process, and the part performance reaches the lower limit of the GB / T 45339-2025 standard.

[0054] Example 5 The difference between this embodiment and Embodiment 1 is that the mass ratio of spherical TC4 powder to non-spherical TC4 powder is 70:30 (70% spherical powder and 30% non-spherical powder).

[0055] Testing revealed that the tap density of the graded powder in this embodiment was 2.90 g / cm³, exhibiting good flowability. After HIP molding, the part achieved a density of 99.7%, a tensile strength of 918 MPa, a yield strength of 845 MPa, and an elongation of 10.2%. Compared to using 100% spherical TC4 powder, the raw material cost was reduced by approximately 23%. This embodiment achieves a good balance between cost and performance, making it suitable for cost-sensitive applications requiring high mechanical properties.

[0056] Example 6 The difference between this embodiment and Embodiment 1 is that the mass ratio of spherical TC4 powder to non-spherical TC4 powder is 95:5 (95% spherical powder and 5% non-spherical powder).

[0057] Testing revealed that the tap density of the graded powder in this embodiment is 3.03 g / cm³, exhibiting excellent flowability. After HIP molding, the resulting part has a density of 99.9%, a tensile strength of 942 MPa, a yield strength of 865 MPa, and an elongation of 12.3%. Compared to using 100% spherical TC4 powder, the raw material cost is reduced by approximately 5%. This embodiment is suitable for applications with extremely high performance requirements and low cost sensitivity, as the performance of the graded powder is close to that of pure spherical powder.

[0058] Comparative Example 1 The difference from Example 1 is that the mass ratio of spherical TC4 powder to non-spherical TC4 powder is 50:50 (50% spherical powder and 50% non-spherical powder).

[0059] The tap density of the graded powder in this embodiment was measured to be 2.79 g / cm³. 3(The content of non-spherical powder is already lower than that of pure spherical powder), resulting in significantly poorer flowability and slight bridging during powder loading. The density of the HIP-formed part is 98.9%, the tensile strength is 873 MPa, the yield strength is 802 MPa, and the elongation is 7.2%, which does not meet the requirements of GB / T 45339-2025 standard. This comparative example illustrates that when the mass fraction of spherical powder is below 60%, excessive non-spherical powder leads to a decrease in bulk density, deterioration of flowability, and performance failure of the HIP part.

[0060] Table 1. Comparison of relevant performance of Examples 1-6 and Comparative Example 1

[0061] As can be seen from the data in Table 1, the performance of the parts obtained in Examples 1-6 meets the standard requirements: after HIP forming using the graded powder of the present invention, the density of the parts is ≥99.5%, and the mechanical properties meet the requirements of GB / T 45339-2025 "General Technical Specification for Hot Isostatic Pressed Titanium Alloy Parts" (tensile strength ≥895 MPa, yield strength ≥828 MPa, elongation ≥8%).

Claims

1. A graded powder for hot isostatic pressing of TC4 titanium alloy, characterized in that, The graded powder is composed of a graded mixture of spherical TC4 powder and non-spherical TC4 powder; The graded powder is composed of the following components by mass percentage: the mass fraction of spherical TC4 powder is 60%~95%, and the mass fraction of non-spherical TC4 powder is 5%~40%; the loose density of the graded powder is not less than 92% of the loose density of pure spherical TC4 powder.

2. The graded powder for hot isostatic pressing of TC4 titanium alloy according to claim 1, characterized in that, The spherical TC4 powder is obtained by mixing spherical TC4 powder obtained by gas atomization and spherical TC4 powder obtained by PREP method. The oxygen content of the spherical TC4 powder obtained after mixing is 0.10wt%~0.15wt%. The mass ratio of spherical TC4 powder obtained by the gas atomization method to that obtained by the PREP method is 6-8:2-4.

3. The graded powder for hot isostatic pressing of TC4 titanium alloy according to claim 1, characterized in that, The particle size range of the spherical TC4 powder is 53μm~250μm.

4. The graded powder for hot isostatic pressing of TC4 titanium alloy according to claim 1, characterized in that, The non-spherical TC4 powder is prepared by hydrogenation-dehydrogenation method. The particle size of the non-spherical TC4 powder is less than 200 mesh and the oxygen content is ≤0.25wt%.

5. The graded powder for hot isostatic pressing of TC4 titanium alloy according to claim 4, characterized in that, The raw material for the non-spherical TC4 powder comes from TC4 recycled waste, which includes one or more of the following: processing scraps, molding residues, and metallurgical waste.

6. The method for preparing graded powder for hot isostatic pressing of TC4 titanium alloy according to any one of claims 1 to 5, characterized in that, Includes the following steps: Step (1): Prepare spherical TC4 powder and non-spherical TC4 powder respectively; Step (2): Combine spherical TC4 powder and non-spherical TC4 powder according to the following mass percentages: 60%~95% of spherical TC4 powder and 5%~40% of non-spherical powder. Weigh and mix the ingredients. Step (3): Mix spherical TC4 powder and non-spherical TC4 powder using a V-type mixer or a three-dimensional mixer; Step (4): The mixed graded powder is sieved to remove agglomerates and obtain the finished graded powder.

7. The method for preparing graded powder for hot isostatic pressing of TC4 titanium alloy according to claim 6, characterized in that, Step (1) specifically involves mixing spherical TC4 powder obtained by gas atomization with spherical TC4 powder obtained by PREP method in a certain proportion to obtain spherical TC4 powder with a particle size of 53μm~250μm and an oxygen content of 0.10~0.15wt%. Non-spherical TC4 powder with a particle size of less than 200 mesh and an oxygen content of ≤0.25 wt% was prepared by hydrogenation-dehydrogenation method. The mass ratio of spherical TC4 powder obtained by the gas atomization method to that obtained by the PREP method is 6-8:2-4.

8. The method for preparing graded powder for hot isostatic pressing of TC4 titanium alloy according to claim 6, characterized in that, In step (3), the mixing time is 30 min to 120 min and the mixing speed is 20 r / min to 50 r / min.

9. The method for preparing graded powder for hot isostatic pressing of TC4 titanium alloy according to claim 6, characterized in that, In step (4), the mixed graded powder is subjected to 150-mesh sieve treatment.

10. The application of the graded powder according to any one of claims 1-5 in hot isostatic pressing, characterized in that, The process parameters for hot isostatic pressing are: temperature 920℃~980℃, pressure 100MPa~140MPa, and holding time 120min~180min.

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