Process for high value utilization of non-spherical fine particle diameter nb521 powder

Abstract

The application discloses a high-value utilization process method of non-spherical fine-particle Nb521 powder, and comprises the following steps: selecting non-spherical Nb521 alloy powder with a particle size of 15-53 mu m and an oxygen content of less than or equal to 500 ppm as raw material; loading the raw material into a cold isostatic pressing sleeve, cold isostatic pressing forming under a pressure of 170-210 MPa, pressure maintaining for 8-15 min, and obtaining a compact; placing the compact in a vacuum sintering furnace, heating at a heating rate of 5-10 DEG C / min to 1650-1900 DEG C, and keeping the temperature for 4-8 h under the condition that the vacuum degree is 6.7*10-3~1.5*10-3 Pa, and cooling to room temperature to obtain a dense Nb521 alloy rod. 4 The application does not need to perform spheroidization pretreatment on the non-spherical powder, directly adopts a powder metallurgy route to prepare the non-spherical fine-particle Nb521 powder generated in an additive manufacturing process into a high-performance rod, simplifies a process flow, reduces production cost, and the utilization rate of fine powder is more than 99%, the obtained rod has a density of more than or equal to 95%, and has excellent comprehensive mechanical properties.

Description

Technical Field

[0001] This invention belongs to the field of powder metallurgy technology, specifically relating to a high-value utilization process for non-spherical fine-grained Nb521 alloy powder. Background Technology

[0002] With the rapid development of aerospace technology, the market demand for high-performance high-temperature materials is becoming increasingly urgent. Among various high-temperature alloy materials, niobium-based alloys, with their excellent high specific strength, excellent corrosion resistance, and oxidation resistance in the 600-1600℃ range, have become one of the important materials for extreme environments such as aerospace, nuclear industry, and high-end equipment. Among them, Nb521 alloy, due to the addition of W and Mo elements with high elastic modulus, significantly improves alloy performance through solid solution strengthening and slowing down the diffusion rate of Nb atoms. Under the protection of high-temperature coatings, its operating temperature can reach 1550℃, making it a preferred material for high-thrust rocket engines.

[0003] When fabricating complex structural parts from Nb521 alloy, additive manufacturing methods are often employed. During powder preparation, plasma atomization produces powders with a wide particle size distribution, resulting in non-spherical and fine-grained powders with poor flowability, which cannot be directly recycled for 3D printing. In existing technologies, these non-spherical, fine-grained powders can only be converted into spherical powders suitable for 3D printing through downgrading or complex and energy-intensive processes such as remelting, hydrogenation crushing, dehydrogenation, and plasma spheroidization. This method suffers from high costs, cumbersome processes, and poor economic efficiency. Furthermore, 3D printing technology is more suitable for manufacturing complex structural parts; it does not offer cost and efficiency advantages for preparing conventional products such as rods.

[0004] Powder metallurgy technology can directly prepare high-value-added rods from non-spherical fine-grained alloy powders through pressing-sintering processes. Leveraging its advantages of fine-grain strengthening and near-net-shape forming, it is expected to significantly improve the utilization rate of fine-grained powders and reduce production costs. However, current technologies lack specific schemes and process parameters for directly preparing dense rods from non-spherical fine-grained Nb521 alloy powders through cold isostatic pressing combined with vacuum sintering. This is particularly challenging for refractory multi-component alloys like Nb521, which contain W, Mo, and Zr with large density differences and high melting points; determining the powder metallurgy process parameters remains a significant technical challenge. Summary of the Invention

[0005] The purpose of this invention is to provide a high-value utilization process for non-spherical fine-particle Nb521 powder, in order to solve the problems of complex spheroidization pretreatment, cumbersome process flow, and high cost required for the recycling and utilization of non-spherical fine-particle Nb521 alloy powder in the prior art.

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

[0007] A high-value utilization process for non-spherical fine-grained Nb521 powder includes the following steps: S1, Raw material preparation: Selecting non-spherical Nb521 alloy powder with a particle size of 15-53µm as raw material, wherein the oxygen content of the Nb521 alloy powder is ≤500ppm; S2, Cold isostatic pressing: Loading the raw material obtained in S1 into a cold isostatic pressing sleeve, performing cold isostatic pressing at a pressure of 170-210MPa for a holding time of 8-15min to obtain an Nb521 alloy compact; S3, Vacuum sintering: Placing the compact obtained in S2 in a vacuum sintering furnace, heating it to 1650-1900℃ at a heating rate of 5-10℃ / min, and maintaining a vacuum degree of 6.7×10⁻³~1.5×10⁻³. 4 After holding at Pa for 4-8 hours and cooling to room temperature, dense Nb521 alloy rods are obtained.

[0008] Furthermore, in S1, the raw material preparation step includes: mixing spherical Nb521 alloy powder with a particle size of 15-53µm and non-spherical Nb521 alloy powder at a mass ratio of 1:(4-19), then loading them into a ball mill and ball milling them at a speed of 200-300r / min for 5-8h to obtain uniformly mixed Nb521 alloy powder raw material.

[0009] Furthermore, in S1, the raw material preparation step includes: sieving and classifying non-spherical Nb521 alloy powder with a particle size of 15-53µm to obtain graded powders with particle sizes of 15-38µm, 39-53µm, or 15-53µm.

[0010] Furthermore, in S2, the cold isostatic pressing is performed using either direct pressure increase or stepped pressure increase.

[0011] Furthermore, the spherical Nb521 alloy powder accounts for 5-20 wt% of the total mass.

[0012] Furthermore, the density of the dense Nb521 alloy rod is ≥95%.

[0013] Furthermore, the dense Nb521 alloy rod has a room temperature tensile strength ≥400MPa and a Vickers hardness ≥170HV.

[0014] The high-value utilization process of non-spherical fine-particle Nb521 powder provided by this invention has the following beneficial effects: This invention uses non-spherical fine-particle Nb521 alloy powder as the core raw material, eliminating the need for spheroidization pretreatment. It directly uses a powder metallurgy route combining cold isostatic pressing and vacuum sintering to prepare dense rods, significantly simplifying the process and reducing production costs. The fine powder utilization rate reaches over 99%, and the resulting Nb521 alloy rods have a density ≥95%, a Vickers hardness of 188HV, and a room temperature tensile strength of 423MPa, exhibiting excellent comprehensive mechanical properties. At the same time, the powder metallurgy route effectively avoids the compositional segregation problem that easily occurs in traditional casting processes for multi-element alloys like Nb521 containing W and Mo with large density differences. This provides a highly industrializable technical path for the efficient recovery and high-value utilization of non-spherical fine-particle Nb521 powder. Attached Figure Description

[0015] Figure 1 The process flow diagram for preparing rods from non-spherical fine-particle Nb521 powder is provided in the embodiments of the present invention. Detailed Implementation

[0016] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. The following embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0017] This invention provides a process for the high-value utilization of non-spherical fine-particle Nb521 powder, the process flow of which is as follows: Figure 1 As shown, it mainly includes three steps: raw material preparation, cold isostatic pressing, and vacuum sintering.

[0018] The raw materials used in this invention are mainly non-spherical Nb521 fine-particle alloy powders with an oxygen content ≤500ppm and a particle size of 15-53µm, with non-spherical morphology being the predominantly predominantly spherical. Raw material preparation includes two methods: ① Mixed powder method: Spherical and non-spherical powders are prepared in a specific ratio (the mass percentage of spherical powder is controlled at 5-20wt%), and then ball-milled to obtain a more uniform mixed powder; ② Graded powder method: The non-spherical fine powder is sieved and graded to obtain Nb521 powders with three particle size distributions: 15-38µm, 39-53µm, and 15-53µm. The oxygen content of the Nb521 alloy powder must be controlled below 500ppm. If the oxygen content is high, it can easily lead to defects such as cracks and porosity in the alloy rods, thus affecting the mechanical and processing properties of the final Nb521 rods.

[0019] In the cold isostatic pressing (CIP) step, the above-mentioned raw materials are loaded into a cold isostatic pressing chamber, and cold isostatic pressing is performed using either direct pressure increase or stepped pressure increase. The pressing pressure range is controlled between 170-210 MPa, and the holding time is between 8-15 minutes to complete the powder densification molding.

[0020] In the vacuum sintering step, the cold-pressed compact is placed in a vacuum sintering furnace for densification sintering. The sintering temperature is 1650-1900℃, the holding time is 4-8 hours, the heating rate is 5-10℃ / min, and the vacuum degree is controlled between 6.7×10⁻³ and 1.5×10⁻³. 4 Pa, after cooling to room temperature, yields dense Nb521 bars.

[0021] Example 1

[0022] Non-spherical fine-particle powder with a particle size range of 15-53µm was packed into a cold isostatic pressing sleeve with a thickness of 5mm and cold-pressed at a pressure of 170MPa for 10min. Subsequently, the resulting alloy billet was placed in a vacuum sintering furnace, evacuated to 3.0×10⁻³Pa, heated to 1650℃ at a rate of 5℃ / min, held for 6h, and then cooled to room temperature in the furnace to obtain Nb521 alloy rods.

[0023] The obtained Nb521 bars have dimensions of Φ34.8×H148mm, a density of 95.1%, a tensile strength of 403MPa, and a Vickers hardness of 170HV, demonstrating excellent overall performance.

[0024] Example 2

[0025] Nb521 fine-particle alloy powder with a particle size distribution of 15-53µm, consisting of spherical and non-spherical particles, was prepared in a 1:4 mass ratio and then fed into a ball mill. The powder was ball-milled at 250 r / min for 8 h to obtain uniform Nb521 alloy powder. The alloy powder was then placed into a 5 mm thick cold isostatic pressing sleeve and cold-pressed at 190 MPa for 10 min. Subsequently, the resulting compact was placed in a vacuum sintering furnace, evacuated to 3.0 × 10⁻³ Pa, heated to 1800 °C at 5 °C / min, held for 6 h, and then cooled to room temperature in the furnace to obtain Nb521 alloy rods.

[0026] The obtained Nb521 bars have dimensions of Φ35×H149mm, a density of 96.4%, a tensile strength of 410MPa, and a Vickers hardness of 175HV, demonstrating excellent overall performance.

[0027] Example 3

[0028] Nb521 non-spherical fine-grained alloy powder with a particle size range of 15-53µm was loaded into a cold isostatic pressing sleeve with a thickness of 5mm. It was cold-pressed using a four-stage stepped pressing method, with a maximum cold pressing pressure of 190MPa and a holding pressure of 10min. Subsequently, the obtained compact was placed in a vacuum sintering furnace, evacuated to 3.0×10⁻³Pa, heated to 1800℃ at 5℃ / min, held at that temperature for 6h, and then cooled to room temperature in the furnace to obtain Nb521 alloy rods.

[0029] The Nb521 bars were tested and found to have dimensions of Φ35×H148mm, a density of over 97%, a tensile strength of 423MPa, and a Vickers hardness of 188HV, demonstrating excellent overall performance.

[0030] Example 4

[0031] Non-spherical fine-grained Nb521 alloy powder with a particle size range of 15-53µm was packed into a 5mm thick cold isostatic pressing sleeve and cold-pressed at 210MPa for 15min. The resulting compact was then placed in a vacuum sintering furnace and evacuated to a vacuum level of 1.5×10⁻⁻⁻⁻⁶. 4 Pa was heated to 1900℃ at 5℃ / min, held for 4 hours, and then cooled to room temperature in the furnace to obtain Nb521 alloy bars.

[0032] Testing revealed that the Nb521 bars had a density of over 97.5%, a tensile strength of 430 MPa, and a Vickers hardness of 192 HV.

[0033] Example 5

[0034] Non-spherical fine-grained Nb521 alloy powder with a particle size range of 15-53µm was packed into a cold isostatic pressing sleeve with a thickness of 5mm and cold-pressed at a pressure of 170MPa for 8min. Subsequently, the resulting compact was placed in a vacuum sintering furnace, evacuated to 6.7×10⁻³Pa, heated to 1650℃ at a rate of 5℃ / min, held for 8h, and then cooled to room temperature in the furnace to obtain Nb521 alloy rods.

[0035] The Nb521 bars were tested and found to have a density of 95.7%, a tensile strength of 406 MPa, and a Vickers hardness of 172 HV.

[0036] Comparative Example 1

[0037] Non-spherical fine-particle powder with a particle size range of 15-53µm was packed into a cold isostatic pressing sleeve with a thickness of 5mm and cold-pressed at a pressure of 150MPa for 10min. Subsequently, the resulting compact was placed in a vacuum sintering furnace, evacuated to 3.0×10⁻³Pa, heated to 1600℃ at a rate of 5℃ / min, held for 6h, and then cooled to room temperature in the furnace to obtain Nb521 alloy rods.

[0038] Testing revealed that the obtained Nb521 bars had dimensions of Φ34×H148mm, a density of only 86%, a tensile strength of 395.8MPa, and a Vickers hardness of only 105HV. This was because both the cold isostatic pressing pressure and sintering temperature were below the lower limit of the parameter range specified in this invention, resulting in insufficient compaction of the pressed blank and inadequate sintering driving force, leading to incomplete densification of the bars.

[0039] Comparative Example 2

[0040] Non-spherical fine-grained Nb521 powder was melted and cast into ingots by electron beam, then subjected to hydrogenation crushing, dehydrogenation, and plasma spheroidization to obtain spherical powder, and finally 3D printing was used to prepare rods.

[0041] Testing revealed that this process took more than three times longer than the present invention, and the resulting bar stock exhibited slight component segregation, with a density of only 90%, a tensile strength of 410 MPa, and a Vickers hardness of 165 HV. Furthermore, the low bulk density (2.976 g / cm³) and flowability (7.58 s / 50g) of the powder made feeding difficult during smelting and casting, resulting in poor component uniformity and consequently reducing ingot quality. Simultaneously, non-spherical fine powder that cannot be directly utilized is still generated during 3D printing.

[0042] Table 1 Summary of effect data for each embodiment and comparative example

[0043] serial number Raw material type CIP pressure / MPa Sintering temperature / °C Density / % Tensile strength / MPa Vickers hardness / HV Example 1 Non-spherical powder (15-53µm) 170 1650 95.1 403 170 Example 2 Mixed powder (ball:non = 1:4) 190 1800 96.4 410 175 Example 3 Non-spherical powder (stepped pressurization) 190 1800 ≥97 423 188 Example 4 Non-spherical powder (15-53µm) 210 1900 ≥97.5 430 192 Example 5 Non-spherical powder (15-53µm) 170 1650 95.7 406 172 Comparative Example 1 Non-spherical powder (15-53µm) 150 1600 86 395.8 105 Comparative Example 2 Traditional spheroidization + 3D printing — — 90 410 165

[0044] As shown in Table 1, Nb521 alloy bars with a density ≥95%, tensile strength ≥400MPa, and Vickers hardness ≥170HV can be obtained in Examples 1-3 of the present invention within the parameter range of cold isostatic pressing pressure 170-190MPa and sintering temperature 1650-1800℃. Among them, Example 3, which adopts a stepped pressurization method, obtained the best comprehensive performance (density ≥97%, tensile strength 423MPa, Vickers hardness 188HV).

[0045] In Comparative Example 1, the cold isostatic pressing pressure (150 MPa) and sintering temperature (1600 °C) were both lower than the lower limit of the parameter range defined in this invention. The resulting bar material had a density of only 86% and a Vickers hardness of only 105 HV, which were far lower than those in the embodiments of this invention. This shows that the parameter range defined in this invention is necessary to obtain high-density, high-performance Nb521 bars.

[0046] Comparative Example 2, employing the traditional spheroidization + 3D printing route, takes more than three times longer than the present invention. Furthermore, the rod material exhibits compositional segregation, with a density of only 90% and a Vickers hardness of only 165 HV. Additionally, non-spherical fine powder waste is still generated during the 3D printing process. The comparison demonstrates that the powder metallurgy route of the present invention is superior to the traditional plasma spheroidization + 3D printing route in terms of process efficiency, cost, and product performance.

Claims

1. A process for high-value utilization of non-spherical fine-particle Nb521 powder, characterized in that, Includes the following steps: S1. Raw material preparation: Select non-spherical Nb521 alloy powder with a particle size of 15-53µm as raw material, wherein the oxygen content of the Nb521 alloy powder is ≤500ppm; S2. Cold isostatic pressing: Load the raw material obtained in S1 into a cold isostatic pressing sleeve, and perform cold isostatic pressing at a pressure of 170-210MPa for a holding time of 8-15min to obtain an Nb521 alloy compact; S3. Vacuum sintering: Place the compact obtained in S2 in a vacuum sintering furnace, and heat it to 1650-1900℃ at a heating rate of 5-10℃ / min, under a vacuum degree of 6.7×10⁻³~1.5×10⁻ 4 After holding at Pa for 4-8 hours and cooling to room temperature, dense Nb521 alloy rods are obtained.

2. The process method according to claim 1, characterized in that, In S1, the raw material preparation step includes: mixing spherical Nb521 alloy powder with a particle size of 15-53µm and non-spherical Nb521 alloy powder at a mass ratio of 1:(4-19), then loading them into a ball mill and ball milling them at a speed of 200-300r / min for 5-8h to obtain uniformly mixed Nb521 alloy powder raw material.

3. The process method according to claim 1, characterized in that, In S1, the raw material preparation step includes: sieving and classifying non-spherical Nb521 alloy powder with a particle size of 15-53µm to obtain graded powder with a particle size of 15-38µm, 39-53µm or 15-53µm.

4. The process method according to claim 1, characterized in that, In S2, the cold isostatic pressing is carried out using either direct pressure increase or stepped pressure increase.

5. The process method according to claim 2, characterized in that, The spherical Nb521 alloy powder accounts for 5-20 wt% of the total mass.

6. The process method according to claim 1, characterized in that, The density of the dense Nb521 alloy rod is ≥95%.

7. The process method according to claim 1, characterized in that, The dense Nb521 alloy bar has a room temperature tensile strength ≥400MPa and a Vickers hardness ≥170HV.

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