A method for 3D printing of zirconia toughened niobium tungsten alloy

Abstract

A kind of zirconium oxide toughened niobium-tungsten alloy 3D printing method, belong to powder metallurgy field.Niobium-tungsten alloy is Nb-5W-2Mo-1Zr-0.1% to 0.2%O alloy, and the raw material for preparation is pre-alloy powder or element mixed powder with different oxygen content, wherein oxygen content is 1000-2000ppm, and carbon content is less than 30ppm.ZrO2 Nano precipitated phase is generated in situ during 3D printing process, and no carbide is precipitated, so that the ZrO2 toughened niobium-tungsten alloy printing piece is dispersedly distributed.Single crystal nano ZrO2 precipitated phase can be plastic deformed with matrix, absorb energy, delay sample necking, on the basis of guaranteeing dispersion strengthening, can significantly improve the plasticity of the niobium-tungsten alloy.By reducing carbon and increasing oxygen, the precipitation of brittle carbide is inhibited;By adjusting the oxygen content in powder and the process parameters of 3D printing, the size and quantity of ZrO2 precipitated phase in niobium-tungsten alloy printing piece are controlled, and the mechanical properties of niobium-tungsten alloy are controlled.The process of the present application is short, simple in operation, low in cost, and the mechanical properties of printed parts are excellent and controllable.

Description

Technical Field

[0001] This invention belongs to the field of powder metallurgy, specifically a 3D printing method for zirconium oxide-strengthened niobium-tungsten alloy. More particularly, it relates to a novel niobium-tungsten alloy that is strengthened by uniformly introducing oxygen elements into raw material powder, and finally generating dispersed nano-zirconia (ZrO2) in situ through 3D printing. Technical Background

[0002] Niobium and its alloys (including niobium-tungsten alloys, Nb-5W-2Mo-1Zr) possess excellent high-temperature performance and specific strength, as well as good corrosion resistance and weldability, making them widely used in the aerospace field. Traditional machining methods such as casting and forging are difficult and complex, resulting in significant waste. In contrast, 3D printing technology enables near-net-shape forming of high-performance, lightweight niobium alloy structural components with complex shapes, making it a new research hotspot in niobium alloy preparation. Currently, niobium-tungsten alloys are mostly strengthened using carbides (Nb2C, NbC, ZrC, etc.). While the high hardness and non-deformable nature of carbides provide significant strengthening, they also cause a certain loss of plasticity. During 3D printing, the extremely high cooling rate of the molten pool results in a fine grain structure and large residual internal stresses within the matrix. These factors combined lead to 3D-printed carbide-strengthened niobium-tungsten alloy products exhibiting high yield strength and low plasticity, particularly failing to meet standard requirements for plasticity. Therefore, there is an urgent need to develop a new type of niobium-tungsten alloy with a material composition suitable for 3D printing without compromising performance. Summary of the Invention

[0003] To address the issue of poor plasticity in niobium-tungsten alloys prepared by 3D printing, this invention, from a materials design perspective, alters the oxygen and carbon content ratio in the raw material powder, reducing carbon and increasing oxygen. This allows for the in-situ generation of a high-density, plastically deformable nano-ZrO2 reinforcing phase during the 3D printing process, replacing the traditional brittle carbide precipitates. Under applied stress, the nano-single-crystal ZrO2 precipitates deform synergistically with the matrix, absorbing energy and delaying the material's necking process. Simultaneously, it improves the interfacial relationship between the niobium matrix and the precipitates; the semi-coherent interface facilitates the storage and transfer of dislocations at the phase interface, thereby significantly improving the plasticity of 3D-printed niobium-tungsten alloy products without sacrificing material strength.

[0004] The technical problem solved by this invention is achieved by the following technical solution:

[0005] A 3D printing method for zirconium oxide-strengthened niobium-tungsten alloy, characterized in that the niobium-tungsten alloy is an Nb-5W-2Mo-1Zr-0.1%~0.2%O alloy, and the preparation steps are as follows: Step 1) Using pre-alloyed powder or element-mixed powder with different oxygen contents as raw materials, the pre-alloyed powder is prepared by hydrogenation and dehydrogenation powder combined with air jet milling modification; the element-mixed powder is obtained by uniformly mixing pure metal powders of Nb, W, Mo and Zr at room temperature to obtain a 3D printable mixed powder; oxygen is uniformly introduced by adjusting the powder process, thereby controlling the oxygen content of the powder to be 1000~2000ppm;

[0006] Step 2) The raw material powder is 3D printed to form a novel niobium-tungsten alloy printed product with dispersed ZrO2 nano-precipitate phase generated in situ during the printing process, which inhibits the precipitation of carbides.

[0007] Furthermore, the oxygen content of the pre-alloyed powder is 1000-2000 ppm, and the carbon content is less than 30 ppm; the average particle size of the powder is 20-60 μm, and it exhibits a normal distribution.

[0008] Furthermore, among the four pure metal powders, the Nb powder has an oxygen content of 1000-2000 ppm and a carbon content of less than 30 ppm; the W, Mo, and Zr powders have an oxygen content of less than 200 ppm and a carbon content of less than 30 ppm.

[0009] Furthermore, the average particle size of Nb, Mo, and Zr powders is 20–60 μm, and the average particle size of W powder is 10–25 μm, all exhibiting a normal distribution.

[0010] Furthermore, the mixed powder is obtained by mixing in a 360-degree rotary mixer at room temperature in an argon or nitrogen atmosphere for 4 to 8 hours.

[0011] Furthermore, the interior of the 3D printed product obtained in step 2) consists of nano ZrO2 precipitates of varying density and dispersed distribution, with no or very few carbides precipitated.

[0012] Furthermore, the ZrO2 reinforcing phase inside the 3D printed product obtained in step 2) is a nanoscale single crystal structure, which can undergo synergistic plastic deformation with the matrix when subjected to external force, thereby absorbing energy and delaying material necking.

[0013] Furthermore, the room temperature tensile strength of the 3D printed product obtained in step 2) can reach more than 550 MPa, and the elongation at break is greater than 25%; the tensile strength at 1600℃ can reach more than 80 MPa, and the elongation at break is greater than 30%.

[0014] Furthermore, by changing the oxygen content of the raw material powder and printing process parameters such as laser power and scanning rate, the quantity and size of ZrO2 precipitates inside the 3D printed product can be controlled, thereby controlling the mechanical properties of zirconia-toughened niobium-tungsten alloy products.

[0015] The key technical point of this invention is:

[0016] The innovation of this invention lies in addressing the poor plasticity of niobium-tungsten alloys prepared by 3D printing. Based on material composition design, this invention uniformly introduces oxygen (1000-2000 ppm) into the raw material powder and reduces the carbon content (below 30 ppm), thereby obtaining a novel zirconia-strengthened niobium-tungsten alloy that differs from traditional carbide-strengthened alloys. Under applied stress, the nanocrystalline ZrO2 precipitates deform synergistically with the matrix, absorbing energy and delaying the material's necking process. Simultaneously, it improves the interfacial relationship between the niobium matrix and the precipitates; the semi-coherent interface facilitates the storage and transfer of dislocations at the phase interface, thus significantly improving the plasticity of 3D-printed niobium-tungsten alloy products without sacrificing material strength.

[0017] Patent CN202211695190.4 discloses a method for preparing niobium-tungsten alloy powder for 3D printing, followed by printing verification. This patent passively introduces oxygen (below 1000 ppm) during powder preparation and subsequently attempts to reduce oxygen through treatments such as adding magnesium powder and heat treatment. Furthermore, the alloy composition does not specify the carbon content, nor does it characterize the microstructure of the printed parts.

[0018] The powder raw material preparation method of this invention is also different from that of patent CN202211695190.4. This invention uses low-cost alloy powder or mixed powder of single elements modified by hydrogenation and dehydrogenation combined with air jet milling as raw material, while the raw material powder of patent CN202211695190.4 is prepared by hydrogenation and dehydrogenation followed by plasma spheroidization, which is relatively more expensive.

[0019] Furthermore, this invention also controls the size and quantity of zirconium oxide precipitates in 3D-printed niobium-tungsten alloys by adjusting the oxygen content in the powder and printing parameters such as laser power and scanning rate, thereby achieving control over the mechanical properties of the printed parts. In contrast, patent CN202211695190.4 only verifies the printing of the prepared powder without characterizing the microstructure.

[0020] The technical effects of this invention are as follows:

[0021] (1) After the raw material powder described in this invention is 3D printed, the resulting niobium-tungsten alloy product with zirconium oxide toughening has high density and a relative density of 98-99%.

[0022] (2) After the raw material powder described in this invention is 3D printed, the resulting zirconia-strengthened niobium-tungsten alloy products have excellent mechanical properties. The room temperature tensile strength can reach more than 550 MPa and the fracture elongation is higher than 25%; the tensile strength at 1600℃ can reach more than 80 MPa and the fracture elongation is greater than 30%; its mechanical properties are better than those of traditional cast niobium-tungsten alloy products, and its plasticity is significantly better than that of 3D printed carbide-strengthened niobium-tungsten alloy products.

[0023] (3) The carbon content of the parts formed by 3D printing using the raw material powder described in this invention is less than 30 ppm, and there are no or very few carbides precipitated inside.

[0024] (4) This invention utilizes the characteristics of 3D printing, which involves layer-by-layer melting and rapid cooling, to generate uniformly distributed ZrO2 nanocrystal particles in situ within the niobium-tungsten alloy. This not only improves the strength of the niobium-tungsten alloy, but also drives the ZrO2 nanoparticles and the matrix to undergo synergistic plastic deformation under stress loading, significantly improving the plasticity of the material.

[0025] (5) By controlling the oxygen content in the powder and the printing process parameters, the present invention can adjust the size and quantity of ZrO2 precipitates in the niobium-tungsten alloy forming parts, thereby controlling the mechanical properties of 3D printed niobium-tungsten parts. Attached Figure Description

[0026] The advantages and benefits of the present invention will be better understood by those skilled in the art through the detailed description of preferred embodiments below.

[0027] Figure 1 This is a scanning electron microscope image of the pre-alloyed powder used in Example 1 of the present invention.

[0028] Figure 2 This is a physical image of the 3D-printed zirconia-strengthened niobium-tungsten alloy product from Embodiment 1 of the present invention.

[0029] Figure 3 This is a scanning electron microscope image of the elemental mixed powder used in Embodiment 2 of the present invention.

[0030] Figure 4 Image (a) is a scanning electron microscope image of the printed part after etching in Embodiment 2 of the present invention; Figure 4 (b) is a bright-field image of the printed part obtained by transmission electron microscopy. Figure 4 Image (c) is a high-resolution transmission electron microscope image of a single precipitated phase. Figure 4 In the middle (d), the corresponding Fourier transform result is shown.

[0031] Figure 5 (a) is a scanning electron microscope image of the printed part after etching in Embodiment 3 of the present invention; Figure 5(b) is a dark-field image of the printed part after tensile fracture, obtained by transmission electron microscopy. Figure 5 Image (c) is a high-resolution transmission electron microscope image of a single precipitate after stretching. Figure 5 In the middle (d), the corresponding Fourier transform result is shown.

[0032] Figure 6 These are scanning electron microscope images of the etched parts after printing at different scanning rates in Embodiment 4 of the present invention. Detailed Implementation

[0033] Example 1

[0034] 1. The raw material is a near-spherical pre-alloyed powder with an oxygen content of 1300 ppm and a carbon content of 23 ppm.

[0035] 2. The pre-alloyed powder has an average particle size of 34.8 μm and exhibits a normal distribution, making it suitable for direct use in 3D printing. Scanning electron micrographs of the powder's morphology are shown below. Figure 1 As shown.

[0036] 3. The density of the pre-alloyed powder 3D printed parts can reach 98.7%, the room temperature tensile strength is above 590MPa, and the elongation at break can reach above 28.5%; the tensile strength at 1600℃ can reach above 85MPa, and the elongation at break is greater than 30%; the mechanical properties are superior to those of traditional niobium-tungsten products made by melting and casting and 3D printing.

[0037] 4. A physical image of a 3D-printed niobium-tungsten alloy product reinforced with zirconia is shown below. Figure 2 As shown.

[0038] Example 2

[0039] 1. The raw material powders are near-spherical elemental powders of Nb, W, Mo, and Zr, with the oxygen content of the Nb powder being 1035 ppm. The four elemental powders of Nb, W, Mo, and Zr are mixed in a 360-degree rotary mixer under argon protection at a mass ratio of 92:5:2:1 for 4 hours to obtain a mixed powder.

[0040] 2. The oxygen content of the above-obtained mixed powder is approximately 1050 ppm, and the carbon content is 20 ppm.

[0041] 3. The average particle size of the obtained mixed powder is 43.8 μm, and it exhibits a normal distribution, making it suitable for direct use in 3D printing. Scanning electron microscope (SEM) images of the mixed powder are shown below. Figure 3 As shown.

[0042] 4. Selective Laser Melting: The substrate material is niobium-tungsten alloy. The substrate is preheated to 200℃, the laser power is 370W, the scanning rate is 600mm / s, and the processing layer thickness is 40μm. The formed part is sandblasted, then ultrasonically cleaned for 10 minutes, and then dried to obtain a novel zirconia-strengthened niobium-tungsten alloy 3D printed part.

[0043] 5. The part was tested and found to have a density of 99.1%, a room temperature tensile strength of 563 MPa, and an elongation at break of 32.7%; at 1600℃, the tensile strength was 83 MPa and the elongation at break was 39.2%.

[0044] 6. Scanning and transmission electron microscope images of the printed parts are shown below. Figure 4 As shown in (a) and 4(b), nearly spherical nanoprecipitates are diffusely distributed within the niobium matrix. High-resolution transmission electron microscopy images of individual precipitates are shown below. Figure 4 As shown in (c), perform a Fourier transform on it ( Figure 4 (d)), labeled as t-ZrO2.

[0045] Example 3

[0046] 1. The raw material powders are near-spherical elemental powders of Nb, W, Mo, and Zr, with the oxygen content of the Nb powder being 1860 ppm. The four elemental powders of Nb, W, Mo, and Zr are mixed in a nitrogen-protected 360-degree rotary mixer at a mass ratio of 92:5:2:1 for 8 hours to obtain a mixed powder.

[0047] 2. The oxygen content of the above-obtained mixed powder is approximately 1850 ppm, and the carbon content is 16 ppm.

[0048] 3. The average particle size of the mixed powder obtained above is 32.6 μm and it exhibits a normal distribution, so it can be directly used for 3D printing.

[0049] 4. Selective Laser Melting: The substrate material is niobium-tungsten alloy. The substrate is preheated to 200℃, the laser power is 350W, the scanning rate is 800mm / s, and the processing layer thickness is 30μm. The formed part is sandblasted, then ultrasonically cleaned for 10 minutes, and then dried to obtain a novel zirconia-strengthened niobium-tungsten alloy 3D printed part.

[0050] 5. The part was tested and found to have a density of 98.9%, a room temperature tensile strength of 657 MPa, and an elongation at break of 25.3%; at 1600℃, the tensile strength was 92 MPa and the elongation at break was 31.6%.

[0051] 6. Scanning electron microscope images of the printed parts, such as... Figure 5 As shown in (a). Compared to Figure 4(a) The higher oxygen content in the raw material powder results in a higher density of nano-ZrO2 precipitates distributed within the printed part matrix. Therefore, the printed niobium-tungsten alloy parts have higher strength but slightly lower plasticity.

[0052] 7. Dark-field images of the tissue after fracture in a tensile test, obtained using a transmission electron microscope, are shown below. Figure 5 As shown in (b), the shape of the near-spherical ZrO2 precipitates changed significantly, indicating that they underwent severe plastic deformation. A high-resolution transmission electron microscope image of a single precipitate is shown below. Figure 5 As shown in (c), the spots obtained through Fourier transform ( Figure 5 (d) was calibrated, and under stress-induced phase transformation, t-ZrO2 was converted to m-ZrO2.

[0053] Example 4

[0054] 1. The raw material powders are near-spherical elemental powders of Nb, W, Mo, and Zr, with the oxygen content of the Nb powder being 1520 ppm. The four elemental powders of Nb, W, Mo, and Zr are mixed in a 360-degree rotary mixer under argon protection at a mass ratio of 92:5:2:1 for 5 hours to obtain a mixed powder.

[0055] 2. The oxygen content of the above-obtained mixed powder is approximately 1500 ppm, and the carbon content is 19 ppm.

[0056] 3. The average particle size of the mixed powder obtained above is 34.3 μm and it exhibits a normal distribution, so it can be directly used for 3D printing.

[0057] 4. Selective Laser Melting: The substrate material was niobium-tungsten alloy. The substrate was preheated to 200℃, the processing layer thickness was 30μm, and the laser power was 360W. Printing was performed using scanning rates of 600mm / s, 800mm / s, and 1000mm / s. The formed parts were then sandblasted, ultrasonically cleaned for 10 minutes, and dried to obtain a novel 3D-printed zirconia-strengthened niobium-tungsten alloy part.

[0058] 5. The parts were tested and found to have a density of over 98.2%, a room temperature tensile strength of over 590 MPa, and an elongation at break of over 26%; at 1600℃, the tensile strength can reach over 80 MPa and the elongation at break can reach over 32%.

[0059] 6. Scanning electron microscope images of the printed parts obtained at different scanning rates are shown below. Figure 6 As shown, with increasing scan rate, the cooling rate of the molten pool during printing is faster, and some oxygen atoms remain dissolved in the niobium matrix without time to precipitate. Therefore, the number and size of nano-ZrO2 precipitates in the matrix decrease with increasing scan rate (see...). Figure 6The mechanical properties of the printed parts show that as the scanning rate increases, the strength decreases slightly and the plasticity increases slightly.

Claims

1. A 3D printing method for zirconium oxide-strengthened niobium-tungsten alloy, characterized in that, The niobium-tungsten alloy is an Nb-5W-2Mo-1Zr-0.1%~0.2%O alloy, and the preparation steps are as follows: Step 1) Use pre-alloyed powder or element-mixed powder with different oxygen contents as raw material powder. The pre-alloyed powder is prepared by hydrogenation and dehydrogenation powder combined with air jet milling modification. The element-mixed powder is obtained by uniformly mixing four pure metal powders, Nb, W, Mo and Zr, at room temperature to obtain a mixed powder that can be 3D printed. By adjusting the powder process, oxygen is uniformly introduced, thereby controlling the oxygen content of the raw material powder to be 1000-2000 ppm and the carbon content to be less than 30 ppm. Step 2) The raw material powder is 3D printed to form a ZrO2 nano-precipitate phase in situ during the printing process, which inhibits the precipitation of carbides, so that no carbides or very few carbides are precipitated, thereby obtaining a ZrO2-strengthened niobium-tungsten alloy printed product with dispersed distribution. The ZrO2 reinforcing phase inside the obtained niobium-tungsten alloy printed product is a nanoscale single crystal structure. Under external force loading, it can undergo synergistic plastic deformation with the matrix, thereby absorbing energy and delaying the necking of the niobium-tungsten alloy printed product. The resulting niobium-tungsten alloy printed products have a room temperature tensile strength of over 550 MPa and a fracture elongation of over 25%; at 1600℃, the tensile strength can reach over 80 MPa and the fracture elongation is over 30%.

2. The 3D printing method for niobium-tungsten alloy according to claim 1, characterized in that, The pre-alloyed powder has an oxygen content of 1000–2000 ppm and a carbon content of less than 30 ppm; the average particle size of the pre-alloyed powder is 20–60 μm and exhibits a normal distribution.

3. The 3D printing method for niobium-tungsten alloy according to claim 1, characterized in that, Of the four pure metal powders Nb, W, Mo, and Zr, the oxygen content of Nb powder is 1000–2000 ppm and the carbon content is less than 30 ppm; the oxygen content of W, Mo, and Zr powders is less than 200 ppm and the carbon content is less than 30 ppm.

4. The 3D printing method for niobium-tungsten alloy according to claim 1, characterized in that, Among the four pure metal powders Nb, W, Mo, and Zr, the average particle size of Nb, Mo, and Zr powders is 20–60 μm, and the average particle size of W powder is 10–25 μm. The average particle size of the four pure metal powders all exhibits a normal distribution.

5. The 3D printing method for niobium-tungsten alloy according to claim 1, characterized in that, The elemental mixed powder is obtained by mixing in a 360-degree rotary mixer at room temperature in an argon or nitrogen atmosphere for 4 to 8 hours.

6. The 3D printing method for niobium-tungsten alloy according to claim 1, characterized in that, By changing the oxygen content of the raw material powder, the laser power, and the scanning rate printing process parameters, the quantity and size of the ZrO2 precipitate phase inside the niobium-tungsten alloy printed product can be controlled, thereby regulating the mechanical properties of the zirconia-strengthened niobium-tungsten alloy product.

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