Tungsten-based heavy alloy and preparation method thereof

Abstract

The present invention relates to a tungsten-based heavy alloy and a preparation method thereof. The mass percentages of the components of the tungsten-based heavy alloy are: W-Ni-Fe-Co: (100-x)%; m: x%; wherein 0<x≤0.5, and m is a high-hardness nanoparticle carbide or a high-hardness nanoparticle oxide. Preparation steps: 1. Raw material prefabrication: spherical tungsten powder, national standard fine tungsten powder, spherical nickel powder, spherical iron powder, spherical cobalt powder and m particles are mixed evenly and dried to obtain a mixed powder, wherein, in the W powder with a mass percentage of 93%, the content of spherical tungsten powder is 73-83%, and the content of national standard fine tungsten powder is 10-20%; 2. Efficient forming and printing: the mixed powder of step 1 is subjected to binder jet printing to obtain a blank; 3. Degreasing process; 4. Sintering process; 5. Vacuum heat treatment process. The present invention can obtain a freely formed tungsten-based heavy alloy with excellent mechanical properties.

Description

Technical Field

[0001] The present invention belongs to the technical field of alloy materials, and in particular relates to a tungsten-based heavy alloy and a preparation method thereof. Background Art

[0002] Tungsten-based heavy alloys composed of tungsten, nickel, and iron possess excellent properties such as high strength, plasticity, density, and impact toughness. However, traditional cold isostatic pressing or compression molding processes can only produce alloy materials with specific shapes, making secondary processing difficult and resulting in significant waste of raw materials.

[0003] Selective laser melting and electron beam melting additive manufacturing technologies can be used for free-form forming of tungsten-based heavy alloys, but they require high energy input, are limited in sample size, and contain internal microcracks, resulting in low mechanical elongation of the material.

[0004] Binder jetting technology creates a three-dimensional solid part by spraying a binder layer by layer. However, the tungsten-based heavy alloys produced by this technology suffer from insufficient sintering densification, resulting in room-temperature brittleness. Furthermore, major challenges with mass production include a lengthy process and uneven sintering shrinkage. Summary of the Invention

[0005] The first technical problem to be solved by the present invention is to provide a tungsten-based heavy alloy in view of the current status of the existing technology to improve its mechanical properties.

[0006] The second technical problem to be solved by the present invention is to provide a method for preparing the above-mentioned tungsten-based heavy alloy in an efficient and near-net-shape manner.

[0007] The technical solution adopted by the present invention to solve the first technical problem is: a tungsten-based heavy alloy, characterized in that the mass percentages of the components of the tungsten-based heavy alloy are:

[0008] W-Ni-Fe-Co: (100-x)%;

[0009] m: x%;

[0010] Wherein, 0<x≤0.5, m is high hardness nanoparticle carbide or high hardness nanoparticle oxide.

[0011] m can be HfC, TaC, La2O3, etc. Preferably, m is ZrC or Al2O3.

[0012] Preferably, in W-Ni-Fe-Co, in terms of mass percentage, W is 93%, Ni is 4.55%, Fe is 2.1%, and Co is 0.35%.

[0013] The technical solution adopted by the present invention to solve the second technical problem is: a method for preparing the tungsten-based heavy alloy as described above, characterized by the following steps:

[0014] 1. Raw material preparation: spherical tungsten powder, national standard fine tungsten powder, spherical nickel powder, spherical iron powder, spherical cobalt powder and m particles are mixed evenly and dried to obtain a mixed powder, wherein the mass percentage of W powder is 93%, the mass percentage of spherical tungsten powder is 73-83%, and the mass percentage of national standard fine tungsten powder is 10-20%;

[0015] 2. Efficient forming and printing: The mixed powder in step 1 is subjected to binder jet printing and forming to obtain a blank;

[0016] 3. Degreasing process: The blank is placed in a high-temperature degreasing furnace to remove carbon and oxygen elements to obtain a pre-sintered part;

[0017] 4. Sintering process: The pre-burned part is placed in a sintering furnace and sintered to obtain a sintered part;

[0018] 5. Vacuum heat treatment process: Place the sintered part in a vacuum heat treatment furnace for vacuum heat treatment, and then cool it with the furnace to obtain a tungsten-based heavy alloy sample.

[0019] The present invention utilizes a mismatch between active fine powder and spherical powder within a specific ratio range to promote the FCC phase formed by Ni and Fe to wet the tungsten powder particles during sintering, thereby promoting atomic diffusion. At the same time, the addition of dispersed particles m can activate the spherical powder and promote the sintering mass transfer process. In addition to pinning dislocations and improving the interfacial bonding strength, thereby improving the mechanical properties of the alloy, the carbide dispersed particles can also react with the impurity O to purify the grain boundaries. In addition, the modified powder forms a contact angle with the binder injection molding binder interface, and capillary forces are generated between the powder particles, thereby absorbing the binder into the powder bed, filling the entire pore space with the binder, thereby improving the surface roughness and green strength of the printed part. At the same time, a three-step degreasing, sintering and high vacuum heat treatment at a fixed point and time are adopted to improve the shape and property control capabilities of the printed part.

[0020] Preferably, in step 1, the particle size range of the spherical tungsten powder, spherical nickel powder, spherical iron powder, and spherical cobalt powder is 0-53 μm, d 50 The national standard of fine tungsten powder is FW-2; the average particle size of the m particles is less than 100nm.

[0021] Preferably, in step 1, ball mill mixing is performed at a rotation speed of 100 to 300 rpm. The mixing time is preferably 8 hours. The drying temperature is preferably 80° C., and the drying time is preferably 8 hours.

[0022] Binder jet printing is an existing technology, and its molding method is as follows: the three-dimensional model of the part is layered and the corresponding control code is generated, the mixed powder is spread on the substrate and compacted through the powder feeding system, the binder droplets are sprayed, and after pre-baking for a few seconds, the substrate is lowered, and another layer of mixed powder is spread and compacted, and the binder droplets are sprayed. After pre-baking for a few seconds, the substrate is lowered, and the process is continuously spread in this cycle to form a blank, which is then cleaned and cured at a high temperature of 160°C for 8 hours to obtain a blank.

[0023] Furthermore, the powder bed area of ​​the binder jet printing is 400mm×400mm, the droplet of a single nozzle of the water-based binder is 30pL, and a multi-nozzle combination mode is adopted, and the powder layer thickness is 50~100μm.

[0024] Preferably, in step three, the degreasing process is divided into two steps: the first step: keeping warm at 500-600°C for 1.5-2.5 hours; the second step: keeping warm at 1000°C for 1 hour.

[0025] Preferably, in step 4, the sintering temperature is 1440-1470° C. and the temperature is kept for 2 hours.

[0026] Furthermore, in step 5, the vacuum degree during vacuum heat treatment is 10 -3 Pa, temperature is 1200~1250℃, and holding time is 2~4h.

[0027] Furthermore, in step five, the carbon content of the sample is less than 0.02%.

[0028] Compared with the prior art, the advantages of the present invention are as follows: the present invention utilizes the mismatch of active fine powder and spherical powder within a specific ratio range to promote the wetting of tungsten powder particles by the FCC phase formed by Ni and Fe during sintering, thereby promoting atomic diffusion; at the same time, the addition of dispersed particles m can activate the spherical powder and promote the sintering mass transfer process. In addition, the carbide dispersed particles can not only pin dislocations, improve the interfacial bonding strength, and thus improve the mechanical properties of the alloy, but also react with the impurity O to purify the grain boundaries. In addition, the modified powder forms a contact angle with the binder injection molding binder interface, and capillary forces are generated between the powder particles, thereby absorbing the binder into the powder bed, filling the entire pore space with the binder, thereby improving the surface roughness and green strength of the printed part. At the same time, the use of fixed-point and timed three-step degreasing, sintering and high vacuum heat treatment improves the ability to control the shape and properties of the printed part.

[0029] In the present invention, the binder jetting manufacturing technology can effectively improve the free forming ability of the material, and the prepared alloy material also has good mechanical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The scanning electron microscope microscopic morphology images of the samples of various embodiments of the present invention are shown in FIG. Figure 1(a), (b), and (c) are scanning electron microscope microscopic images of the samples of Example 1, Example 2, and Example 3, respectively;

[0031] Figure 2 The scanning electron microscope microscopic morphology of each comparative example sample of the present invention is shown in FIG. Figure 2 (a) and (b) are scanning electron microscope microscopic morphologies of the samples of comparative example 1 and comparative example 2, respectively. DETAILED DESCRIPTION

[0032] The present invention will be described in further detail below with reference to the accompanying drawings and embodiments. Example 1:

[0033] The mass percentages of the components of the tungsten-based heavy alloy of this embodiment are:

[0034] 93W-4.55Ni-2.1Fe-0.35Co (i.e., in mass percentage, W is 93%, Ni is 4.55%, Fe is 2.1%, and Co is 0.35%, the same below): 99.8%;

[0035] ZrC: 0.2%.

[0036] The preparation steps are as follows:

[0037] (1) Raw material preparation: Spherical tungsten powder, national standard fine tungsten powder, spherical nickel powder, spherical iron powder, spherical cobalt powder and ZrC particles were weighed in proportion, and then mixed evenly at a speed of 200 r / min using a planetary ball mill under Ar gas protection, and then vacuum dried for 8 hours to obtain a mixed powder; among them, in the W powder with a mass percentage of 93%, spherical tungsten powder accounted for 74.4%, and national standard fine tungsten powder accounted for 18.6%, and the particle size range of spherical tungsten powder, spherical nickel powder, spherical iron powder and spherical cobalt powder was 0~30μm, d 50 The particle size is 5~15μm, and the national standard fine tungsten powder is FW-2; the average particle size of ZrC particles is 50nm;

[0038] (2) Efficient forming and printing: Set the part model control code, spread the mixed powder on the substrate and compact it through the powder feeding system, spray water-based binder droplets (the binder single nozzle droplet is 30pL), and after a few seconds of pre-baking, the substrate is lowered to make the powder layer thickness 50μm. Another layer of powder is spread, and this cycle is continuously spread to form a blank. The powder is cleaned and cured at a high temperature of 160℃ for 8h to obtain the blank;

[0039] (3) Debinding process: The blank obtained in step (2) is placed in a vacuum debinding furnace, first at a debinding temperature of 600°C for 2.5 hours, then heated to 1000°C for 1 hour, and then gradually cooled to obtain a pre-sintered part;

[0040] (4) Sintering process: The pre-burned part obtained in step (3) is placed in a hydrogen sintering furnace, sintered at 1460°C under a hydrogen protective atmosphere, and kept warm for 2 hours to obtain a sintered part;

[0041] (5) Vacuum heat treatment process: Place the sintered parts in a vacuum heat treatment furnace with a vacuum degree of 10 -3 Pa, the treatment temperature is 1250℃, the holding time is 4h, and the tungsten-based heavy alloy sample is obtained by cooling with the furnace. Example 2:

[0042] The mass percentages of the components of the tungsten-based heavy alloy of this embodiment are:

[0043] 93W-4.55Ni-2.1Fe-0.35Co (i.e., in mass percentage, W is 93%, Ni is 4.55%, Fe is 2.1%, and Co is 0.35%, the same below): 99.5%;

[0044] ZrC: 0.5%.

[0045] The preparation steps are as follows:

[0046] (1) Raw material preparation: Spherical tungsten powder, national standard fine tungsten powder, spherical nickel powder, spherical iron powder, spherical cobalt powder and ZrC particles were weighed in proportion, and then mixed evenly at a speed of 250r / min using a planetary ball mill under Ar gas protection, and then vacuum dried for 8h to obtain a mixed powder; among them, in the W powder with a mass percentage of 93%, spherical tungsten powder accounts for 80%, and national standard fine tungsten powder accounts for 13%, and the particle size range of spherical tungsten powder, spherical nickel powder, spherical iron powder and spherical cobalt powder is 0~30μm, d 50 The particle size is 5~15μm, and the national standard fine tungsten powder is FW-2; the average particle size of ZrC particles is 50nm;

[0047] (2) Efficient forming and printing: Set the part model control code, spread the mixed powder on the substrate and compact it through the powder feeding system, spray water-based binder droplets (the binder single nozzle droplet is 30pL), and after a few seconds of pre-baking, the substrate is lowered to make the powder layer thickness 50μm. Another layer of powder is spread, and this cycle is continuously spread to form a blank. The powder is cleaned and cured at a high temperature of 160℃ for 8h to obtain the blank;

[0048] (3) Debinding process: The blank obtained in step (2) is placed in a vacuum debinding furnace, first at a debinding temperature of 600°C for 2 h, then heated to 1000°C for 1 h, and then gradually cooled to obtain a pre-sintered part;

[0049] (4) Sintering process: The pre-burned part obtained in step (3) is placed in a hydrogen sintering furnace, sintered at 1470°C under a hydrogen protective atmosphere, and kept warm for 3 hours to obtain a sintered part;

[0050] (5) Vacuum heat treatment process: Place the sintered parts in a vacuum heat treatment furnace with a vacuum degree of 10 -3 Pa, the treatment temperature is 1250℃, the holding time is 3h, and the tungsten-based heavy alloy sample is obtained by cooling with the furnace. Example 3:

[0051] The mass percentages of the components of the tungsten-based heavy alloy of this embodiment are:

[0052] 93W-4.55Ni-2.1Fe-0.35Co (i.e., in mass percentage, W is 93%, Ni is 4.55%, Fe is 2.1%, and Co is 0.35%, the same below): 99.8%;

[0053] Al2O3: 0.2%.

[0054] The preparation steps are as follows:

[0055] (1) Raw material preparation: Spherical tungsten powder, national standard fine tungsten powder, spherical nickel powder, spherical iron powder, spherical cobalt powder and Al2O3 particles were weighed in proportion, and then mixed evenly at a speed of 300r / min using a planetary ball mill under Ar gas protection, and then vacuum dried for 8h to obtain a mixed powder; among them, in the W powder with a mass percentage of 93%, spherical tungsten powder accounts for 83%, and national standard fine tungsten powder accounts for 10%, and the particle size range of spherical tungsten powder, spherical nickel powder, spherical iron powder and spherical cobalt powder is 0~30μm, d 50 The particle size is 5~15μm, and the national standard fine tungsten powder is FW-2; the average particle size of Al2O3 particles is 20nm;

[0056] (2) Efficient forming and printing: Set the part model control code, spread the mixed powder on the substrate and compact it through the powder feeding system, spray water-based binder droplets (the binder single nozzle droplet is 30pL), and after a few seconds of pre-baking, the substrate is lowered to make the powder layer thickness 80μm. Another layer of powder is spread, and this cycle is continuously spread to form a blank. The powder is cleaned and cured at a high temperature of 160℃ for 8h to obtain the blank;

[0057] (3) Debinding process: The blank obtained in step (2) is placed in a vacuum debinding furnace, first at a debinding temperature of 600°C for 2 h, then heated to 1000°C for 1 h, and then gradually cooled to obtain a pre-sintered part;

[0058] (4) Sintering process: The pre-burned part obtained in step (3) is placed in a hydrogen sintering furnace, sintered at 1470°C under a hydrogen protective atmosphere, and kept warm for 2 hours to obtain a sintered part;

[0059] (5) Vacuum heat treatment process: Place the sintered parts in a vacuum heat treatment furnace with a vacuum degree of 10 -3Pa, the treatment temperature is 1200℃, the holding time is 3h, and the tungsten-based heavy alloy sample is obtained by cooling with the furnace.

[0060] Comparative Example 1:

[0061] The mass percentages of the components of the tungsten-based heavy alloy of this comparative example are:

[0062] 93W-4.55Ni-2.1Fe-0.35Co (in mass percentage, W is 93%, Ni is 4.55%, Fe is 2.1%, Co is 0.35%, the same below)

[0063] The preparation steps are as follows:

[0064] (1) Raw material preparation: Spherical tungsten powder, spherical nickel powder, spherical iron powder and spherical cobalt powder were weighed in proportion, and then mixed evenly at a speed of 100 r / min using a planetary ball mill under Ar gas protection, and then vacuum dried for 8 hours to obtain a mixed powder; wherein, the particle size range of spherical tungsten powder, spherical nickel powder, spherical iron powder and spherical cobalt powder is 0~53μm, d 50 12~20μm;

[0065] (2) Efficient forming and printing: Set the part model control code, spread the mixed powder on the substrate and compact it through the powder feeding system, spray water-based binder droplets (the binder single nozzle droplet is 30pL), and after a few seconds of pre-baking, the substrate is lowered to make the powder layer thickness 80μm. Another layer of powder is spread, and this cycle is continuously spread to form a blank. The powder is cleaned and cured at a high temperature of 160℃ for 8h to obtain the blank;

[0066] (3) Debinding process: The blank obtained in step (2) is placed in a vacuum debinding furnace, first at a debinding temperature of 500°C for 1.5 hours, then heated to 1000°C for 1 hour, and then gradually cooled to obtain a pre-sintered part;

[0067] (4) Sintering process: The pre-burned part obtained in step (3) is placed in a hydrogen sintering furnace, sintered at 1460°C under a hydrogen protective atmosphere, and kept warm for 2 hours to obtain a sintered part;

[0068] (5) Vacuum heat treatment process: Place the sintered parts in a vacuum heat treatment furnace with a vacuum degree of 10 -3 Pa, the treatment temperature is 1200℃, the holding time is 2h, and the tungsten-based heavy alloy sample is obtained by cooling with the furnace.

[0069] Comparative Example 2:

[0070] The mass percentages of the components of the tungsten-based heavy alloy of this comparative example are:

[0071] 93W-4.55Ni-2.1Fe-0.35Co (in mass percentage, W is 93%, Ni is 4.55%, Fe is 2.1%, Co is 0.35%, the same below)

[0072] The preparation steps are as follows:

[0073] (1) Raw material preparation: Spherical tungsten powder, national standard fine tungsten powder, spherical nickel powder, spherical iron powder and spherical cobalt powder were weighed in proportion, and then mixed evenly at a speed of 100 r / min using a planetary ball mill under Ar gas protection, and then vacuum dried for 8 hours to obtain a mixed powder; among them, the mass percentage of W powder is 93%, of which spherical tungsten powder accounts for 73%, and national standard fine tungsten powder accounts for 20%. The particle size range of spherical tungsten powder, spherical nickel powder, spherical iron powder and spherical cobalt powder is 0~53μm, d 50 The particle size is 10~15μm; the national standard fine tungsten powder is FW-2;

[0074] (2) Efficient forming and printing: Set the part model control code, spread the mixed powder on the substrate and compact it through the powder feeding system, spray water-based binder droplets (the binder single nozzle droplet is 30pL), and after a few seconds of pre-baking, the substrate is lowered to make the powder layer thickness 100μm, and another layer of powder is spread. This cycle is continuously spread to form a blank, clean the powder, and cure at a high temperature of 160℃ for 8h to obtain the blank;

[0075] (3) Debinding process: The blank obtained in step (2) is placed in a vacuum debinding furnace, first at a debinding temperature of 500°C for 1.5 hours, then heated to 1000°C for 1 hour, and then gradually cooled to obtain a pre-sintered part;

[0076] (4) Sintering process: The pre-burned part obtained in step (3) is placed in a hydrogen sintering furnace, sintered at 1450°C under a hydrogen protective atmosphere, and kept warm for 2 hours to obtain a sintered part;

[0077] (5) Vacuum heat treatment process: Place the sintered parts in a vacuum heat treatment furnace with a vacuum degree of 10 -3 Pa, the treatment temperature is 1200℃, the holding time is 2h, and the tungsten-based heavy alloy sample is obtained by cooling with the furnace.

[0078] The physical and mechanical properties of the tungsten-based heavy alloy samples prepared in Examples 1 to 3 of the present invention and Comparative Examples 1 and 2 were tested, and the results are shown in Table 1 below:

[0079] Table 1 Performance parameters of various embodiments and comparative examples

[0080]

[0081] Result analysis:

[0082] By comparing the performance parameters of Comparative Example 1 and Comparative Example 2, it can be found that the density and room temperature tensile strength of Comparative Example 2 are improved, and the surface roughness of the alloy sample is reduced, indicating that the mismatch between national standard fine tungsten powder and spherical powder within a specific proportion range can promote the FCC phase formed by Ni and Fe during sintering to wet the tungsten powder particles, promote atomic diffusion, and thus improve the sintering performance and structural organization of the alloy.

[0083] Comparing Comparative Example 2 with the various examples reveals improved room-temperature tensile strength and reduced surface roughness in the alloy samples, demonstrating that the addition of ZrC or Al₂O₃ particles activates the spherical powder and promotes mass transfer during sintering. Furthermore, the modified powder forms a contact angle with the binder during injection molding, generating capillary forces between the powder particles. This draws the binder into the powder bed, filling the entire pore space with the binder and improving the surface roughness and green strength of the printed parts.

[0084] Compared with Examples 1 and 3, the carbide dispersed particles (such as ZrC particles) can not only pin dislocations and improve the interface bonding strength, thereby improving the mechanical properties of the alloy, but also react with the impurity O to purify the grain boundaries.

[0085] And contrast Figure 1 and Figure 2 visible, Figure 2 There are a lot of micropores and defects (such as Figure 2 The dotted circle in (a) of the figure shows the part with the broken circle), resulting in poor mechanical strength and plasticity. After mismatching the national standard fine tungsten powder within a specific ratio range with the spherical powder, the density is greatly improved, the pores disappear, and the tungsten phase is evenly distributed (such as Figure 2 (b)), the performance is improved; Figure 1 As shown, by further adopting the process of strengthening and optimizing carbide or oxide dispersed particles, it was found that the tungsten phase grains were refined, and the bonding phase formed by Ni and Fe evenly covered the tungsten phase grains, thereby further improving the performance.

Claims

1. A method for preparing a tungsten-based heavy alloy, characterized in that: The mass percentages of the components of the tungsten-based heavy alloy are: W-Ni-Fe-Co: (100-x)%; m: x%; Wherein, 0<x≤0.5, m is high hardness nanoparticle carbide or high hardness nanoparticle oxide, and in W-Ni-Fe-Co, W is 93%, Ni is 4.55%, Fe is 2.1%, and Co is 0.35% by mass percentage; The steps of the preparation method of the tungsten-based heavy alloy are as follows:

1. Raw material preparation: spherical tungsten powder, national standard fine tungsten powder, spherical nickel powder, spherical iron powder, spherical cobalt powder and m particles are mixed evenly and dried to obtain a mixed powder, wherein the mass percentage of W powder is 93%, the mass percentage of spherical tungsten powder is 73-83%, and the mass percentage of national standard fine tungsten powder is 10-20%; 2. Efficient forming and printing: The mixed powder in step 1 is subjected to binder jet printing and forming to obtain a blank; 3. Degreasing process: The blank is placed in a high-temperature degreasing furnace to remove carbon and oxygen elements to obtain a pre-sintered part; 4. Sintering process: The pre-burned part is placed in a sintering furnace and sintered to obtain a sintered part; 5. Vacuum heat treatment process: The sintered parts are placed in a vacuum heat treatment furnace for vacuum heat treatment, and then cooled with the furnace to obtain tungsten-based heavy alloy; In step 1, the particle size range of spherical tungsten powder, spherical nickel powder, spherical iron powder and spherical cobalt powder is 0~53μm, d 50 The national standard of fine tungsten powder is FW-2; the average particle size of the m particles is less than 100nm.

2. The method for preparing a tungsten-based heavy alloy according to claim 1, wherein: m is ZrC or Al2O3.

3. The method for preparing a tungsten-based heavy alloy according to claim 1 or 2, characterized in that: In step 1, ball milling is performed at a rotation speed of 100 to 300 rpm.

4. The method for preparing a tungsten-based heavy alloy according to claim 1 or 2, characterized in that: In step 2, the binder droplet from a single nozzle is 30 pL, and the powder layer thickness is 50-100 μm.

5. The method for preparing a tungsten-based heavy alloy according to claim 1 or 2, characterized in that: In step three, the degreasing process is divided into two steps: the first step: keeping warm at 500~600℃ for 1.5~2.5h, and the second step: keeping warm at 1000℃ for 1h.

6. The method for preparing a tungsten-based heavy alloy according to claim 1 or 2, characterized in that: In step 4, the sintering temperature is 1440~1470℃, and the temperature is kept for 2h.

7. The method for preparing a tungsten-based heavy alloy according to claim 1 or 2, characterized in that: In step 5, the vacuum degree during vacuum heat treatment is 10 -3 Pa, temperature is 1200~1250℃, and holding time is 2~4h.

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