A high specific gravity tungsten alloy powder for additive manufacturing, preparation method and application

Abstract

The present invention provides a high-density tungsten alloy powder for additive manufacturing, which belongs to the technical field of metal-based composite materials and additive manufacturing, and contains W elements and transition metal elements, wherein the mass fraction of the W element is ≥30%, and the mass fraction of the transition metal element is ≤70%; the high-density tungsten alloy powder is a solid spherical alloyed powder, and there is no pore inside the powder, and its microstructure is composed of tungsten grains and a transition metal element bonding phase with tungsten solid solution; the high-density tungsten alloy powder has a bulk density of 50% or more of the theoretical density, a tap density of 60% or more of the theoretical density, a Hall flow rate of ≤14s / 50g, and a particle size distribution of 15 to 53μm. The high-density tungsten alloy powder has higher self-strength, bulk density and tap density, and lower Hall flow rate, which is conducive to improving the performance of additive manufacturing products. The present invention also provides a preparation method and application of a high-density tungsten alloy powder for additive manufacturing.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal-based composite materials and additive manufacturing, and particularly relates to a high-density tungsten alloy powder for additive manufacturing, a preparation method and an application thereof. Background Art

[0002] Refractory metal alloy materials composed of refractory metal elements tungsten (W), molybdenum (Mo), rhenium (Re) and one or more transition metals nickel (Ni), iron (Fe), chromium (Cr), copper (Cu), cobalt (Co), manganese (Mn), and silver (Ag) are typical metal matrix composites (MMCs). The microstructure of this material consists of a transition metal binder phase with refractory metal elements dissolved in it and refractory metal particles. It has both structural and functional characteristics and can provide a higher operating temperature limit than its base metal counterparts. The strength, stiffness, thermal conductivity, wear resistance, creep resistance or dimensional stability can be improved by changing its composition, composition or processing form. It has broad application potential.

[0003] Additive manufacturing (AM) technology is a technology that uses a gradual accumulation of materials to manufacture solid parts. Compared with traditional material removal-cutting processing technology, it is a bottom-up manufacturing method. AM technology can manufacture parts with very complex geometries efficiently and at low cost. It is a supplement to traditional manufacturing technology and even shows a trend of replacing traditional manufacturing technology in some application fields. The AM technology of refractory metal materials mainly includes selective laser melting (SLM), selective electron beam melting (SEBM), binder jet additive manufacturing (BJAM), etc. Different from traditional powder metallurgy technology, these AM technologies have three requirements for raw material powder: first, the powder particle size is usually between 10 and 50 μm, second, there are certain requirements for the sphericity and fluidity of the powder, and third, there are certain requirements for the internal pores and bulk density of the powder. These three factors of powder have a significant impact on the surface morphology, dimensional accuracy, microstructure and performance of parts produced by additive manufacturing technology.

[0004] The common preparation methods of MMCs type refractory metal alloy powders used in AM technology include: gas atomization (GA), plasma atomization (PA), plasma rotating electrode process (PREP), etc. Among them, the gas atomization technology requires that the MMCs type refractory metal alloy powders be melted first, which will lead to the segregation of the binder phase elements and the refractory metal elements. The prepared powder has a wide particle size distribution and has more hollow powders and satellite powders; the plasma atomization powder preparation using wire as raw material has a better effect, but the cost is high and it is not suitable for mass production; the plasma rotating electrode process will also encounter the problems of high cost, low efficiency and segregation of alloy elements.

[0005] In order to solve these problems, patent CN112692294B mixes tungsten powder, nickel powder, iron powder, forming agent and solvent in a protective atmosphere and ball mills them to obtain a slurry with a powder particle size of 1.8-2.5μm, a flow rate of 3.0-3.5L / H and a solid content of 75-85%, and then centrifuges the slurry for granulation and screening to obtain a high-density tungsten alloy powder. The invention controls the obtained slurry to meet the above three indicators, so that the particle size of the obtained high-density tungsten alloy powder is 18-48μm, of which the weight of spherical powder with a particle size of 18-40μm accounts for more than 95%, the Hall flow rate is ≤8s / 50g, the sphericity is more than 98%, the loose density is 30%-40% of the theoretical density, the solidity is more than 98%, and the oxygen content is not higher than 60ppm. Although this method has a simple process and low cost, the powder particles prepared are actually loose particle aggregates of the raw material powders. The loose particle aggregates have low self-bonding strength and are easily broken during transfer or additive manufacturing. In addition, the loose particle aggregates have a low bulk density, which will cause the final product obtained by additive manufacturing to be deformed due to a large dimensional shrinkage rate or to be non-dense due to the presence of residual pores, ultimately affecting the performance and quality of the additively manufactured products.

[0006] The metal alloy powder prepared by patent CN110049836A adopts 90% or more tungsten and 10% or less one or more other elements of nickel, iron, copper, cobalt, and manganese. The obtained metal alloy powder for additive manufacturing process contains a plurality of substantially spherical composite particles, each composite particle containing a plurality of tungsten grains surrounded by a matrix containing the one or more other elements. In various embodiments, the metal alloy powder formed at least partially by spray drying to form agglomerate particles and / or by plasma densification to form composite particles is used as a raw material for forming a three-dimensional metal part in an additive manufacturing process, or the metal alloy powder is used to manufacture a raw material for forming a three-dimensional metal part in an additive manufacturing process. The prepared metal alloy powder has a bulk density ranging from about 35% to about 65% of the theoretical density, a tap density ranging from about 40% to about 75% of the theoretical density, and a Hall flow rate ranging from about 1s / 50g to about 15s / 50g. This method uses agglomerated particles obtained by spray drying to replace wire raw materials for plasma atomization. Although it can reduce the production cost of plasma atomization raw materials, the low yield and high cost problems of the plasma atomization process itself are still not solved. Summary of the invention

[0007] In order to solve the problem that the existing high-density tungsten alloy powder has low self-strength and low loose density that affect the performance of additive manufacturing products, the present invention provides a high-density tungsten alloy powder for additive manufacturing. The high-density tungsten alloy powder has higher self-strength, loose density and tap density, and lower Hall flow rate, is suitable for additive manufacturing, and is beneficial to improving the performance and quality of additive manufacturing products.

[0008] The present invention also provides a preparation method and application of high-density tungsten alloy powder for additive manufacturing.

[0009] The present invention is achieved through the following technical solutions:

[0010] The present invention provides a high-density tungsten alloy powder for additive manufacturing, wherein the high-density tungsten alloy powder contains a W element and a transition metal element, wherein the mass fraction of the W element is ≥30%, and the mass fraction of the transition metal element is ≤70%;

[0011] The transition metal element includes Ni and at least one of Fe, Cu and Co;

[0012] The high specific gravity tungsten alloy powder is a solid spherical alloyed powder, and the solid spherical alloyed powder has no pores inside;

[0013] The microstructure of the high specific gravity tungsten alloy powder consists of tungsten grains and a transition metal element bonding phase in which tungsten is solid-dissolved;

[0014] The bulk density of the high specific gravity tungsten alloy powder is 50% or more of the theoretical density;

[0015] The tap density of the high specific gravity tungsten alloy powder is 60% or more of the theoretical density;

[0016] The Hall flow rate of the high specific gravity tungsten alloy powder is ≤14s / 50g;

[0017] The particle size distribution of the high specific gravity tungsten alloy powder is 15-53 μm.

[0018] Furthermore, the carbon content of the high specific gravity tungsten alloy powder is less than 5 μg / g, and the oxygen content is less than 100 μg / g;

[0019] Furthermore, when the mass fraction of the W element is ≥90%, the Hall flow rate of the high-density tungsten alloy powder is ≤8s / 50g; when the mass fraction of the W element is ≥60%, the Hall flow rate of the high-density tungsten alloy powder is ≤11s / 50g; when the mass fraction of the W element is ≥30%, the Hall flow rate of the high-density tungsten alloy powder is ≤14s / 50g;

[0020] In the microstructure of the high-density tungsten alloy powder, the grain size of the tungsten grains is ≤30 μm.

[0021] Based on the same inventive concept, the present invention also provides a method for preparing a high-density tungsten alloy powder for additive manufacturing, the preparation method comprising:

[0022] Using tungsten powder and transition metal powder as raw materials, mixing the raw materials, an inorganic binder and water to prepare a slurry;

[0023] The slurry is spray-dried to obtain powder particle aggregates;

[0024] calcining the powder particle aggregates, and reducing the calcined product to obtain a reduced product;

[0025] The reduction product is sintered and densified to obtain a high-density tungsten alloy powder for additive manufacturing.

[0026] Furthermore, in the raw material, the mass fraction of the tungsten powder is ≥30%, and the mass fraction of the transition metal powder is ≤70%;

[0027] The transition metal powder includes nickel powder and at least one of iron powder, copper powder and cobalt powder;

[0028] Among the raw materials, the average particle sizes of tungsten powder, nickel powder, cobalt powder, iron powder and copper powder are all 0.5-5 μm, and the purity is all ≥99.9%.

[0029] Furthermore, the inorganic binder includes at least one of water-soluble inorganic salts of W, Fe, Cu and Co, and the addition amount of the inorganic binder is 2.0 to 20.0% of the total weight of the raw materials.

[0030] Preferably, the inorganic binder includes at least one of ammonium metatungstate, ferric nitrate, copper nitrate and cobalt nitrate.

[0031] Furthermore, the powder particle aggregate is calcined, and the calcined product is reduced to obtain a reduced product, which specifically includes:

[0032] calcining the powder particle aggregate at 400-700° C. for 1-6 hours in a calcination atmosphere of nitrogen, argon or vacuum to obtain a calcined product;

[0033] The calcined product is reduced at 400-900° C. for 0.5-2 h in a reducing atmosphere of hydrogen to obtain a reduced product.

[0034] Furthermore, the reduction product is sintered and densified to obtain a high-density tungsten alloy powder for additive manufacturing, specifically comprising:

[0035] The reduced product is sintered and densified at 1200-1450° C. for 0.5-3 h in a densification atmosphere of hydrogen, argon or vacuum to obtain a high specific gravity tungsten alloy powder for additive manufacturing.

[0036] Based on the same inventive concept, the present invention also provides an application of high specific gravity tungsten alloy powder for additive manufacturing in the preparation of solid parts by additive manufacturing process.

[0037] One or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages:

[0038] 1. The present invention discloses a high-density tungsten alloy powder for additive manufacturing. The high-density tungsten alloy powder is a solid spherical alloyed powder with no pores inside. Its loose density is 50% or more of the theoretical density, its tap density is 60% or more of the theoretical density, its Hall flow rate is ≤14s / 50g, and its particle size distribution is 15-53μm. Compared with the existing high-density tungsten alloy powder, it has higher self-strength, loose density and tap density, and lower Hall flow rate, is suitable for additive manufacturing, and is conducive to improving the performance and quality of additive manufacturing products.

[0039] 2. The present invention discloses a method for preparing high-density tungsten alloy powder for additive manufacturing. The method calcines and reduces powder particle aggregates prepared by spray drying, which can fully remove non-metallic impurity elements such as carbon and oxygen that remain in the raw material powder or are introduced into the powder particle aggregates during the spray drying process. The reduction product is then sintered and densified. The sintering and densification treatment can sinter the loose powder particle aggregates, and the various metal elements in the powder particle aggregates are fully diffused and alloyed to obtain a completely dense and pore-free high-density tungsten alloy powder. The sintered and densified high-density tungsten alloy powder has higher self-strength, loose density and tap density, and lower Hall flow rate, and is suitable for use in additive manufacturing.

[0040] 3. The present invention discloses a method for preparing a high-density tungsten alloy powder for additive manufacturing. In the method, in the slurry spray drying process, inorganic salts of various metal raw materials are used to replace traditional organic binders. On the one hand, the introduction of carbon elements can be reduced, thereby reducing the carbon content in the final alloy powder. On the other hand, inorganic salts of metal raw materials are used as binders. After calcination and reduction, fine raw metal powder can be generated in situ between the powder particles of each metal element in the powder particle aggregates. The powder has higher sintering activity, which is beneficial to the sintering densification process of the powder particle aggregates, so that the final alloy powder has higher loose density and tap density, and lower Hall flow rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0042] Figure 1 The microstructure comparison diagram of 93WNiFeCo powder particle aggregates and 93WNiFeCo alloy powder: the left figure is the microstructure diagram of 93WNiFeCo powder particle aggregates after reduction; the right figure is the microstructure diagram of sintered densified 93WNiFeCo alloy powder.

[0043] Figure 2 This is the microscopic morphology of the 93WNiFeCo powder particle aggregates after spray drying.

[0044] Figure 3 This is the microscopic morphology of the fully dense 93WNiFeCo alloy powder after sintering densification.

[0045] Figure 4 This is the microstructure diagram of the fully dense 93WNiFeCo alloy powder after sintering densification. DETAILED DESCRIPTION

[0046] The present invention will be described in detail below in conjunction with specific implementations and examples, and the advantages and various effects of the present invention will be more clearly presented. It should be understood by those skilled in the art that these specific implementations and examples are used to illustrate the present invention, rather than to limit the present invention.

[0047] Throughout the specification, unless otherwise specifically stated, the terms used herein should be understood as meanings commonly used in the art. Therefore, unless otherwise defined, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art to which the present invention belongs. In the event of a conflict, the present specification takes precedence.

[0048] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0049] The overall idea of ​​the present invention is as follows:

[0050] The applicant found that when the method of patent CN110049836A uses spray drying alone to form agglomerate particles as the raw material for additive manufacturing, the problems are the same as those of patent CN112692294B: the agglomerate particles directly prepared by spray drying have low self-bonding strength and are easily broken and ineffective; or the final product obtained by additive manufacturing is deformed or not dense due to low bulk density, affecting the performance and quality of additive manufacturing products. In addition, in the method of CN110049836A, whether the composite particles formed by plasma densification are used alone or partially as the raw material for additive manufacturing, the problems of low efficiency and high cost of the plasma densification process itself have not been solved.

[0051] Based on the above findings, the present invention provides a high-density tungsten alloy powder for additive manufacturing and a preparation method thereof. The method calcines, reduces and sinters the powder particle aggregates obtained by spray drying. Experimental verification shows that the sintering densification treatment can cause the loose powder particle aggregates to sinter, and the various metal elements in the powder particle aggregates are fully diffused and alloyed to obtain a completely dense and pore-free high-density tungsten alloy powder. The sintered and densified high-density tungsten alloy powder has higher self-strength, loose density and tap density, and lower Hall flow rate, and is more suitable for additive manufacturing.

[0052] Specifically, the present invention provides a method for preparing a high specific gravity tungsten alloy powder for additive manufacturing, comprising the following steps:

[0053] S1. Using tungsten powder and transition metal powder as raw materials, mixing the raw materials, an inorganic binder and water to prepare a slurry;

[0054] S2. The slurry is spray dried to obtain powder particle aggregates;

[0055] S3. The powder particle aggregate is calcined, and the calcined product is reduced to obtain a reduced product;

[0056] S4. Sintering and densifying the reduced product to obtain high-density tungsten alloy powder for additive manufacturing.

[0057] In step S1, the mass fraction of the tungsten powder in the raw material is ≥30%, and the mass fraction of the transition metal powder is ≤70%;

[0058] The transition metal powder includes nickel powder and at least one of iron powder, copper powder and cobalt powder;

[0059] Among the raw materials, the average particle sizes of tungsten powder, nickel powder, cobalt powder, iron powder and copper powder are all 0.5-5 μm, and the purity is all ≥99.9%.

[0060] In the present invention, the average particle size of tungsten powder, nickel powder, cobalt powder, iron powder and copper powder is 0.5-5 μm. All raw material powders in this particle size range are industrial products mass-produced in the field of powder metallurgy, and have both good sintering activity and low cost.

[0061] In step S1, the inorganic binder includes at least one of water-soluble inorganic salts of W, Fe, Cu and Co, and the addition amount of the inorganic binder is 2.0-20.0% of the total weight of the raw materials.

[0062] Preferably, the inorganic binder includes at least one of ammonium metatungstate, ferric nitrate, copper nitrate and cobalt nitrate.

[0063] The present invention adopts inorganic salts of various metal raw materials to replace traditional organic binders. On the one hand, it can reduce the introduction of carbon elements and reduce the carbon content in the final alloy powder; on the other hand, by using inorganic salts of metal raw materials as binders, after calcination and reduction, fine raw metal powder can be generated in situ between the powder particles of various metal elements in the powder particle aggregates. The powder has higher sintering activity, which is beneficial to the sintering densification process of the powder particle aggregates, so that the final alloy powder has higher loose density and tap density, and lower Hall flow rate.

[0064] In step S3, the powder particle aggregate is calcined, and the calcined product is reduced to obtain a reduced product, which specifically includes:

[0065] calcining the powder particle aggregate at 400-700° C. for 1-6 hours in a calcination atmosphere of nitrogen, argon or vacuum to obtain a calcined product;

[0066] The calcined product is reduced at 400-900° C. for 0.5-2 h in a reducing atmosphere of hydrogen to obtain a reduced product.

[0067] In the present invention, the powder particle aggregate is calcined at 400-700°C for 1-6h. The advantage is that the inorganic binder such as ammonium metatungstate, ferric nitrate, copper nitrate, and cobalt nitrate can be fully converted into the corresponding metal oxides after sufficient calcination under this condition. The calcination temperature is 400-700°C. If the temperature is too low, the inorganic binder such as ammonium metatungstate, ferric nitrate, copper nitrate, and cobalt nitrate cannot be completely converted into the corresponding metal oxides. When the temperature is too high, the raw material tungsten powder, nickel powder, cobalt powder, iron powder, and copper powder will be oxidized and affect the subsequent reduction effect. The calcined product is reduced at 400-900°C for 0.5-2h. On the one hand, the inorganic binder can be fully reduced to the corresponding metal powder particles after calcination and reduction; on the other hand, the non-metallic impurity elements such as carbon and oxygen remaining in the raw material powder or introduced in the spray drying process can be fully removed. Both effects are conducive to the subsequent sintering and densification of the powder particle aggregate. The reduction temperature is 400-900°C. When the temperature is too low or too high, it will affect the removal of non-metallic impurity elements such as carbon and oxygen in the powder particle aggregates, thereby affecting the subsequent sintering densification effect and the purity of the final powder.

[0068] In step S4, the reduction product is sintered and densified to obtain a high-density tungsten alloy powder for additive manufacturing, which specifically includes:

[0069] The reduced product is sintered and densified at 1200-1450° C. for 0.5-3 h in a densification atmosphere of hydrogen, argon or vacuum to obtain a high specific gravity tungsten alloy powder for additive manufacturing.

[0070] In the present invention, the benefit of sintering and densifying the reduction product at 1200-1450°C for 0.5-3h is that the surface and interior of the powder particle aggregates are completely dense after sufficient sintering, which is beneficial to improving the self-strength of the powder particles and the use effect of the additive manufacturing process. The sintering densification temperature is 1200-1450°C. When the sintering temperature is too low, the powder particle aggregates cannot be sintered densely, the strength of the particles themselves is low, and there are a large number of pores on the surface and inside of the particles; when the sintering temperature is too high, the powder particle aggregates will stick together.

[0071] The following will describe in detail a high specific gravity tungsten alloy powder for additive manufacturing, a preparation method and an application of the present invention in combination with embodiments and experimental data.

[0072] The determination methods of the powder particle size, bulk density, tap density, carbon content, oxygen content, and Hall flow rate mentioned in the embodiments and comparative examples of the present invention are as follows:

[0073] (1) Powder particle size distribution: refer to the standard "GB / T 19077-2016 Particle size distribution laser diffraction method", and use a laser particle size distribution analyzer for testing; (2) Bulk density: refer to the standard "GB / T 31057.1-2014 Physical properties of granular materials Part 1: Measurement of bulk density", and use a bulk density meter for testing; (3) Tap density: refer to the standard "GB / T31057.2-2018 Physical properties of granular materials Part 2: Measurement of tap density", and use a tap density meter for testing; (4) Carbon content: refer to the standard "GB / T (5) Oxygen content: referring to the standard "GB / T4324.25-2012 Tungsten Chemical Analysis Method Part 25: Determination of Oxygen Content - Pulse Heating Inert Gas Fusion-Infrared Absorption Method", using an oxygen and nitrogen analyzer for testing; (6) Hall flow rate: referring to the standard "GB / T 1482-2022 Metal Powder Fluidity Determination Standard Funnel Method (Hall Rheometer)", using a Hall Rheometer for testing.

[0074] Example 1

[0075] This embodiment provides a method for preparing a high specific gravity tungsten alloy powder 93WNiFeCo for additive manufacturing, comprising the following steps:

[0076] (1) Raw material preparation: Tungsten powder, nickel powder, iron powder and cobalt powder are used as raw materials, among which the average particle size of tungsten powder is 1.2μm, and the purity is ≥99.95%; the average particle size of nickel powder is 0.9μm, and the purity is ≥99.9%; the average particle size of iron powder is 2.5μm, and the purity is ≥99.9%; the average particle size of cobalt powder is 1.5μm, and the purity is ≥99.9%. The mass fractions of tungsten, nickel, iron and cobalt in 93WNiFeCo alloy powder are 92.8%, 4.5%, 2.0% and 0.7% respectively. When calculating the amount of each raw material powder, the amount of the corresponding metal powder generated after the calcination and reduction of the inorganic binder needs to be deducted.

[0077] (2) Slurry preparation and spray drying: The raw material powder in step (1) is mixed with ammonium metatungstate and water in a certain proportion to form a slurry, wherein the amount of ammonium metatungstate added is 15.0% of the total weight of each metal raw material powder, and the amount of water added is 31.2% of the total weight of each metal raw material powder. The obtained slurry is dried in a centrifugal spray drying tower to obtain 93WNiFeCo powder particle aggregates.

[0078] (3) Calcination and reduction: The 93WNiFeCo powder particle aggregates were calcined in a nitrogen atmosphere at a calcination temperature of 580°C for 4.5 h; the calcined 93WNiFeCo powder particle aggregates were then reduced in a hydrogen atmosphere at a reduction temperature of 750°C for 1 h to obtain reduced 93WNiFeCo powder particle aggregates.

[0079] (4) Sintering densification: The reduced 93WNiFeCo powder particle aggregates were placed in a sintering boat and sintered in a hydrogen atmosphere for densification. The sintering temperature was 1445 °C and the sintering time was 2 h to obtain a fully dense 93WNiFeCo alloy powder for additive manufacturing.

[0080] After testing, the 93WNiFeCo alloy powder used for additive manufacturing in this embodiment is a solid powder. The particle sizes of D10, D50 and D90 of the powder are 18.7μm, 34.3μm and 49.4μm respectively, and the bulk density is 9.48g / cm 3 (Theoretical density is 17.71g / cm 3 , the bulk density is 53.5% of the theoretical density), and the tap density is 11.58 g / cm 3 (Theoretical density is 17.71g / cm 3 , the tap density is 65.4% of the theoretical density), the carbon content is 2 μg / g, the oxygen content is 48 μg / g, and the Hall flow rate is 6.3 s / 50 g.

[0081] Example 2

[0082] This embodiment provides a method for preparing a high-density tungsten alloy powder 60WNiFe for additive manufacturing, comprising the following steps:

[0083] (1) Raw material preparation: Tungsten powder, nickel powder and iron powder are used as raw materials, among which the average particle size of tungsten powder is 2.9μm, and the purity is ≥99.95%; the average particle size of nickel powder is 3.3μm, and the purity is ≥99.9%; the average particle size of iron powder is 1.5μm, and the purity is ≥99.9%. The mass fractions of tungsten, nickel and iron in 60WNiFe alloy powder are 60.0%, 28.0% and 12.0% respectively. When calculating the amount of each raw material powder, the amount of the corresponding metal powder generated after the calcination and reduction of the inorganic binder needs to be deducted.

[0084] (2) Slurry preparation and spray drying: The raw material powder in step (1) is mixed with ferric nitrate and water in a certain proportion to form a slurry, wherein the amount of ferric nitrate added is 5.5% of the total weight of each metal raw material powder, and the amount of water added is 18.4% of the total weight of each metal raw material powder. The obtained slurry is dried in a centrifugal spray drying tower to obtain 60WNiFe powder particle aggregates.

[0085] (3) Calcination and reduction: The 60WNiFe powder particle aggregates were calcined in a nitrogen atmosphere at a calcination temperature of 410°C for 2.5 h; the calcined 60WNiFe powder particle aggregates were then reduced in a hydrogen atmosphere at a reduction temperature of 550°C for 1.5 h to obtain reduced 60WNiFe powder particle aggregates.

[0086] (4) Sintering densification: The reduced 60WNiFe powder particle aggregates were placed in a sintering boat and sintered in a hydrogen atmosphere for densification. The sintering temperature was 1280°C and the sintering time was 1 h to obtain a fully dense 60WNiFe alloy powder for additive manufacturing.

[0087] After testing, the 60WNiFe alloy powder used for additive manufacturing in this embodiment is a solid powder. The D10, D50, and D90 particle sizes of the powder are 20.3 μm, 36.6 μm, and 47.8 μm, respectively, and the bulk density is 6.72 g / cm 3 (Theoretical density is 12.85g / cm 3 , the bulk density is 52.3% of the theoretical density), and the tap density is 8.20 g / cm 3 (Theoretical density is 12.85g / cm 3 , the tap density is 63.8% of the theoretical density), the carbon content is 3 μg / g, the oxygen content is 54 μg / g, and the Hall flow rate is 10.2 s / 50 g.

[0088] Example 3

[0089] The present embodiment provides a method for preparing a high specific gravity tungsten alloy powder 85WNiCu for additive manufacturing, comprising the following steps:

[0090] (1) Raw material preparation: Tungsten powder, nickel powder and copper powder are used as raw materials, among which the average particle size of tungsten powder is 2.0μm, and the purity is ≥99.95%; the average particle size of nickel powder is 1.8μm, and the purity is ≥99.9%; the average particle size of copper powder is 4.5μm, and the purity is ≥99.9%. The mass content of tungsten, nickel and copper in 85WNiCu alloy powder is 85.0%, 10.0% and 5.0% respectively. When calculating the amount of each raw material powder, the amount of the corresponding metal powder generated after the calcination and reduction of the inorganic binder needs to be deducted.

[0091] (2) Slurry preparation and spray drying: The raw material powder in step (1) is mixed with copper nitrate and water in a certain proportion to form a slurry, wherein the amount of copper nitrate added is 8.6% of the total weight of each metal raw material powder, and the amount of water added is 25.4% of the total weight of each metal raw material powder. The obtained slurry is dried in a centrifugal spray drying tower to obtain 85WNiCu powder particle aggregates.

[0092] (3) Calcination and reduction: The 85WNiCu powder particle aggregates were calcined in a nitrogen atmosphere at a calcination temperature of 490°C for 1.5 h; the calcined 85WNiCu powder particle aggregates were then reduced in a hydrogen atmosphere at a reduction temperature of 620°C for 1.0 h to obtain reduced 85WNiCu powder particle aggregates.

[0093] (4) Sintering densification: The reduced 85WNiCu powder particle aggregates were placed in a sintering boat and sintered in a hydrogen atmosphere for densification. The sintering temperature was 1360°C and the sintering time was 1.2 h to obtain a fully dense 85WNiCu alloy powder for additive manufacturing.

[0094] The test shows that the prepared 85WNiCu alloy powder for additive manufacturing is a solid powder. The D10, D50 and D90 particle sizes of the powder are 18.5μm, 35.9μm and 50.2μm respectively, and the bulk density is 8.51g / cm 3 (Theoretical density is 16.44 g / cm 3 , the bulk density is 51.8% of the theoretical density), and the tap density is 10.26 g / cm 3 (Theoretical density is 16.44 g / cm 3 , the tap density is 62.4% of the theoretical density), the carbon content is 4 μg / g, the oxygen content is 43 μg / g, and the Hall flow rate is 8.6 s / 50 g.

[0095] Example 4

[0096] The present embodiment provides a method for preparing a high specific gravity tungsten alloy powder 90WNiCo for additive manufacturing, comprising the following steps:

[0097] (1) Raw material preparation: Tungsten powder, nickel powder and cobalt powder are used as raw materials, among which the average particle size of tungsten powder is 4.3μm, and the purity is ≥99.95%; the average particle size of nickel powder is 2.2μm, and the purity is ≥99.9%; the average particle size of cobalt powder is 2.6μm, and the purity is ≥99.9%. The mass contents of tungsten, nickel and cobalt in 90WNiCo alloy powder are 90.0%, 7.0% and 3.0% respectively. When calculating the amount of each raw material powder, the amount of the corresponding metal powder generated after the calcination and reduction of the inorganic binder needs to be deducted.

[0098] (2) Slurry preparation and spray drying: The raw material powder in step (1) is mixed with cobalt nitrate and water in a certain proportion to form a slurry, wherein the amount of cobalt nitrate added is 4.2% of the total weight of each metal raw material powder, and the amount of water added is 21.3% of the total weight of each metal raw material powder. The obtained slurry is dried in a centrifugal spray drying tower to obtain 90WNiCo powder particle aggregates.

[0099] (3) Calcination and reduction: The 90WNiCo powder particle aggregates were calcined in a nitrogen atmosphere at a calcination temperature of 520°C for 3.0 h; the calcined 90WNiCo powder particle aggregates were then reduced in a hydrogen atmosphere at a reduction temperature of 590°C for 0.5 h to obtain reduced 90WNiCo powder particle aggregates.

[0100] (4) Sintering densification: The reduced 90WNiCo powder particle aggregates were placed in a sintering boat and sintered in a hydrogen atmosphere for densification. The sintering temperature was 1420°C and the sintering time was 2.3 h to obtain a fully dense 90WNiCo alloy powder for additive manufacturing.

[0101] After testing, the prepared 90WNiCo alloy powder for additive manufacturing is a solid powder. The D10, D50, and D90 particle sizes of the powder are 16.1μm, 33.4μm, and 48.6μm, respectively, and the bulk density is 9.28g / cm 3 (Theoretical density is 17.29g / cm 3 , the bulk density is 53.7% of the theoretical density), and the tap density is 10.70 g / cm 3 (Theoretical density is 17.29g / cm 3 , the tap density is 61.9% of the theoretical density), the carbon content is 2 μg / g, the oxygen content is 37 μg / g, and the Hall flow rate is 6.9 s / 50 g.

[0102] Comparative Example 1

[0103] Steps (1) to (3) of Comparative Example 1 are exactly the same as those of Example 1. The difference between Comparative Example 1 and Example 1 is that Comparative Example 1 does not perform sintering densification treatment on the reduced 93WNiFeCo powder particle aggregates.

[0104] The test showed that the 93WNiFeCo alloy powder obtained after reduction was a powder particle aggregate. The D10, D50 and D90 particle sizes of the powder were 29.1 μm, 56.8 μm and 79.9 μm respectively, and the bulk density was 4.36 g / cm 3 (Theoretical density is 17.71g / cm 3 , the bulk density is 24.6% of the theoretical density), and the tap density is 5.65g / cm 3 (Theoretical density is 17.71g / cm 3 , the tap density is 31.9% of the theoretical density), the carbon content is 2 μg / g, the oxygen content is 73 μg / g, and the Hall flow rate is 14.4 s / 50 g.

[0105] Comparative Example 2

[0106] In step (2) of comparative example 2, polyethylene glycol is used as an organic binder, and the added amount is 2.0% of the total weight of the metal raw material. The remaining steps are exactly the same as those of example 1.

[0107] After testing, the D10, D50, and D90 particle sizes of the prepared 93WNiFeCo alloy powder for additive manufacturing are 23.1μm, 41.2μm, and 58.9μm, respectively, and the bulk density is 6.94g / cm 3 (Theoretical density is 17.71g / cm 3 , the bulk density is 39.2% of the theoretical density), and the tap density is 8.98g / cm 3 (Theoretical density is 17.71g / cm 3 , the tap density is 50.7% of the theoretical density), the carbon content is 43 μg / g, the oxygen content is 65 μg / g, and the Hall flow rate is 9.3 s / 50 g.

[0108] Table 1 shows the bulk density, tap density, Hall flow rate and particle size distribution data of the 93WNiFeCo powder particle aggregate after reduction in Comparative Example 1 and the 93WNiFeCo alloy powder sintered and densified in Example 1. It can be found that the various indicators of the high specific gravity tungsten alloy powder of Example 1 after spray granulation, calcination, reduction and sintering densification are significantly better than those of the powder particle aggregate after spray granulation, calcination and reduction in Comparative Example 1.

[0109] Table 1 Performance data of 93WNiFeCo powder particle aggregates and 93WNiFeCo alloy powder

[0110]

[0111]

[0112] like Figure 1 The figure shows the microstructure comparison of 93WNiFeCo powder particle aggregates and 93WNiFeCo alloy powder observed by metallographic microscope, wherein the left figure shows the microstructure of 93WNiFeCo powder particle aggregates that have only been spray granulated, calcined, and reduced, and the right figure shows the microstructure of 93WNiFeCo alloy powder that has been sintered and densified. By comparison, it can be found that: the 93WNiFeCo powder particle aggregates that have only been spray granulated, calcined, and reduced in Comparative Example 1 are loose structures, and the various metal raw material powder particles are only partially overlapped, and there are still a lot of gaps. The powder particle aggregates themselves have low strength and are easily broken under external force; while the 93WNiFeCo alloy powder that has been sintered and densified in Example 1 is completely alloyed inside.

[0113] like Figure 2 , 34 are the microscopic morphology of the 93WNiFeCo powder particle aggregates after spray drying, and the microscopic morphology and microstructure of the sintered and densified 93WNiFeCo powder particles (the microscopic morphology was observed by scanning electron microscope, and the microstructure was observed by metallographic microscope). Figure 2 , 3 4 It can be seen that the 93WNiFeCo powder particle aggregates after spray drying are in the form of accumulation of each raw material powder, and there are still a large number of pores on the surface. The surface of the 93WNiFeCo powder particles that have been sintered and densified is completely dense, and the interior of the particles is completely dense and has no pores.

[0114] From Table 1 and Figures 1 to 4 It can be seen that compared with the high-density tungsten alloy powder particle aggregates in Example 1 which are only subjected to spray granulation, calcination and reduction, the high-density tungsten alloy powder in Example 1 which is sintered and densified has higher self-strength, loose density and tap density, and lower Hall flow rate, and is more suitable for additive manufacturing.

[0115] Table 2 shows the bulk density, tap density, Hall flow rate, and particle size distribution data of the 93WNiFeCo alloy powders prepared by spray granulation, calcination, reduction, and sintering densification using an organic binder in Comparative Example 2 and an inorganic binder in Example 1. It can be found that under the same sintering densification process conditions, the 93WNiFeCo alloy powders for additive manufacturing prepared by using an inorganic binder have higher bulk density and tap density, and lower Hall flow rate.

[0116] Table 2 Performance data of 93WNiFeCo alloy powder prepared with organic binder and inorganic binder

[0117]

[0118]

[0119] Finally, it should be noted that the terms "comprises," "includes," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements that are inherent to such process, method, article, or apparatus.

[0120] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0121] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A high specific gravity tungsten alloy powder for additive manufacturing, characterized in that: The high specific gravity tungsten alloy powder contains W element and transition metal element, wherein the mass fraction of W element is ≥30%, and the mass fraction of transition metal element is ≤70%; The transition metal element includes Ni and at least one of Fe, Cu and Co; The high specific gravity tungsten alloy powder is a solid spherical alloyed powder, and the solid spherical alloyed powder has no pores inside; The microstructure of the high specific gravity tungsten alloy powder consists of tungsten grains and a transition metal element bonding phase in which tungsten is solid-dissolved; The bulk density of the high specific gravity tungsten alloy powder is 50% or more of the theoretical density; The tap density of the high specific gravity tungsten alloy powder is 60% or more of the theoretical density; The Hall flow rate of the high specific gravity tungsten alloy powder is ≤14s / 50g; The particle size distribution of the high specific gravity tungsten alloy powder is 15-53 μm.

2. The high-density tungsten alloy powder for additive manufacturing according to claim 1, characterized in that: The carbon content of the high-density tungsten alloy powder is less than 5 μg / g, and the oxygen content is less than 100 μg / g; 3. The high-density tungsten alloy powder for additive manufacturing according to claim 1, characterized in that: When the mass fraction of W element is ≥90%, the Hall flow rate of the high specific gravity tungsten alloy powder is ≤8s / 50g; when the mass fraction of W element is ≥60%, the Hall flow rate of the high specific gravity tungsten alloy powder is ≤11s / 50g; when the mass fraction of W element is ≥30%, the Hall flow rate of the high specific gravity tungsten alloy powder is ≤14s / 50g; In the microstructure of the high-density tungsten alloy powder, the grain size of the tungsten grains is ≤30 μm.

4. A method for preparing a high-density tungsten alloy powder for additive manufacturing as claimed in any one of claims 1 to 3, characterized in that: The preparation method comprises: Using tungsten powder and transition metal powder as raw materials, mixing the raw materials, an inorganic binder and water to prepare a slurry; The slurry is spray-dried to obtain powder particle aggregates; calcining the powder particle aggregates, and reducing the calcined product to obtain a reduced product; Sintering and densifying the reduction product to obtain a high-density tungsten alloy powder for additive manufacturing; the mass fraction of the tungsten powder is ≥30%, and the mass fraction of the transition metal powder is ≤70%; The transition metal powder includes nickel powder and at least one of iron powder, copper powder and cobalt powder; Among the raw materials, the average particle size of tungsten powder, nickel powder, cobalt powder, iron powder and copper powder is 0.5-5 μm, and the purity is ≥99.9%; The inorganic binder includes at least one of water-soluble inorganic salts of W, Fe, Cu and Co. The addition amount of the inorganic binder is 2.0-20.0% of the total weight of the raw materials.

5. The method for preparing a high-density tungsten alloy powder for additive manufacturing according to claim 4, characterized in that: The inorganic binder includes at least one of ammonium metatungstate, ferric nitrate, copper nitrate and cobalt nitrate.

6. The method for preparing a high-density tungsten alloy powder for additive manufacturing according to claim 4, characterized in that: The step of calcining the powder particle aggregate and reducing the calcined product to obtain a reduced product specifically comprises: calcining the powder particle aggregate at 400-700° C. for 1-6 hours in a calcination atmosphere of nitrogen, argon or vacuum to obtain a calcined product; The calcined product is reduced at 400-900° C. for 0.5-2 h in a reducing atmosphere of hydrogen to obtain a reduced product.

7. The method for preparing a high-density tungsten alloy powder for additive manufacturing according to claim 4, characterized in that: The reducing product is sintered and densified to obtain a high-density tungsten alloy powder for additive manufacturing, specifically comprising: The reduced product is sintered and densified at 1200-1450° C. for 0.5-3 h in a densification atmosphere of hydrogen, argon or vacuum to obtain a high specific gravity tungsten alloy powder for additive manufacturing.

8. Use of a high specific gravity tungsten alloy powder for additive manufacturing as claimed in any one of claims 1 to 3 in the preparation of solid parts by additive manufacturing process.

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