Manufacturing method of tungsten alloy

Abstract

The invention relates to a manufacturing method of a tungsten alloy, which comprises the following steps of: mixing tungsten powder and HfC powder, spreading on a substrate of laser powder bed melting additive manufacturing equipment, melting and solidifying to obtain a deposition layer, completing single-layer forming, repeating the steps on the deposition layer to obtain a W-HfC alloy sample formed by additive manufacturing, and then the W-HfC alloy sample is subjected to heat treatment strengthening, nano HfC particles are separated out from a tungsten matrix, dispersion strengthening is achieved, and the tungsten alloy is obtained. The tungsten alloy prepared through the method is free of crack defects and has high density and compressive strength, and the mechanical property is remarkably improved.

Description

Technical Field

[0001] The present invention belongs to the field of metal additive manufacturing, and relates to a method for manufacturing a tungsten alloy, and specifically to a method for manufacturing the tungsten alloy by utilizing laser powder bed melting additive manufacturing technology and strengthening the tungsten alloy by heat treatment. Background Art

[0002] Tungsten has the characteristics of high melting point (up to 3410℃), high strength at room temperature and high temperature, high thermal conductivity, small thermal expansion coefficient and good radiation resistance. It is often used to manufacture high-temperature structural parts such as rocket nose cones, nozzles, throat liners, and the first wall materials of nuclear fusion reactors. It is widely used in the fields of aerospace and nuclear reactors. Due to the high melting point of tungsten, powder metallurgy is usually used for forming. However, due to its process characteristics, the conventional powder metallurgy method used for tungsten parts is difficult to form parts with complex shapes.

[0003] CN118682132A discloses a sintering model of a high-density and high-strength tungsten alloy and a method for preparing a tungsten alloy using the sintering model. The high-frequency alternating load sintering technology is used to perform densification sintering by means of the coupling effect of the thermal field and the force field in the sintering furnace. A correlation model between sintering parameters such as sintering temperature, sintering time, and alternating frequency during the sintering process is proposed. Using this model, a tungsten alloy with high density and excellent mechanical properties can be sintered. However, this method is difficult to form tungsten alloy parts with complex shapes, and the maximum compressive strength of the tungsten alloy is only 1572MPa, which still needs further optimization.

[0004] Laser powder bed fusion additive manufacturing technology is a 3D printing technology. It is a precision manufacturing technology that has emerged and developed rapidly in recent years. This technology uses laser as a heat source and a digital model as a basis. It melts and solidifies metal powder layer by layer according to the product contour, and accumulates layer by layer to form parts with complex structures. It has been widely used in aerospace, medical, personalized customization and other fields. Laser powder bed fusion additive manufacturing technology can form tungsten parts with complex shapes, which promotes the application of tungsten in various fields.

[0005] However, due to the intrinsic brittleness of tungsten and the characteristics of rapid melting and rapid solidification of laser powder bed melting additive manufacturing technology, there are many crack defects inside the tungsten parts manufactured by laser powder bed melting additive manufacturing, the density of tungsten parts is low, and the mechanical properties of tungsten parts are deteriorated.

[0006] CN118720162A discloses a method for preparing 3D printed tungsten alloy, firstly, Ni, Fe, Co and M are mixed and ball milled to obtain NiFeCoM powder, wherein M contains one or more of Al, V and Nb, and then tungsten powder and NiFeCoM powder are mixed for the first time, mixed for the second time and laser printed to obtain tungsten alloy. The tungsten alloy prepared by this method has uniform composition and no obvious element segregation, but its tensile strength is low, with a maximum of only 1084MPa.

[0007] Therefore, there has been an urgent need to manufacture tungsten alloy parts with fewer defects and better performance. Summary of the invention

[0008] Problem that the invention aims to solve

[0009] The present invention aims to provide a method for manufacturing tungsten alloy, specifically to provide a method for manufacturing tungsten alloy by using laser powder bed fusion additive manufacturing technology and strengthening tungsten alloy by heat treatment. The tungsten alloy manufactured by this method has no crack defects, has high density and compressive strength, and has significantly improved mechanical properties.

[0010] Solutions for solving problems

[0011] In order to solve the above problems, the present invention provides the following technical solutions:

[0012] [1] A method for manufacturing a tungsten alloy, comprising the following steps:

[0013] Step S1: mixing tungsten powder and HfC powder to obtain W-HfC alloy powder;

[0014] Step S2: spreading the W—HfC alloy powder on a substrate of a laser powder bed melting additive manufacturing device, performing melting-solidification to obtain a deposition layer, and completing single-layer forming;

[0015] Step S3: repeating step S2 on the deposited layer to obtain a melt-formed W-HfC alloy sample;

[0016] Step S4: heat-treating and strengthening the W—HfC alloy sample to obtain the tungsten alloy.

[0017] [2] The manufacturing method according to [1], wherein

[0018] The mass fraction of HfC in the W-HfC alloy powder is 1.4% to 9.3%, preferably 2.5% to 7%.

[0019] [3] The production method according to [1] or [2], wherein

[0020] The particle size of the HfC powder is in the range of 1 to 10 μm; preferably, the D 50 4~7μm.

[0021] [4] The manufacturing method according to any one of [1] to [3], wherein

[0022] In step S4, the temperature of the heat treatment strengthening is 850-1650°C, preferably 900-1600°C;

[0023] Preferably, the heat treatment strengthening holding time is 4 to 20 hours, preferably 6 to 12 hours.

[0024] [5] The manufacturing method according to any one of [1] to [4], wherein

[0025] The oxygen content of the tungsten powder is 0-0.02 wt %, preferably 0.005 wt %-0.018 wt %.

[0026] [6] The manufacturing method according to any one of [1] to [5], wherein

[0027] In step S1, the tungsten powder and the HfC powder are mixed by ball milling;

[0028] Preferably, the diameter of the grinding balls used in the ball milling is 4 to 10 mm, the ball-to-material ratio of the ball milling is 7:1 to 14:1, the speed of the ball mill used in the ball milling is 300 to 600 r / min, and the ball milling time is 14 to 27 h.

[0029] [7] The manufacturing method according to any one of [1] to [6], wherein

[0030] In step S2, the laser power of the laser powder bed melting additive manufacturing equipment when melting the W—HfC alloy powder is 150 to 500 W, preferably 200 to 450 W, and the scanning speed is 200 to 600 mm / s, preferably 250 to 500 mm / s.

[0031] [8] The manufacturing method according to any one of [1] to [7], wherein

[0032] In step S2, the melting-solidification is performed under the protection of an inert gas;

[0033] In step S4, the heat treatment strengthening is performed under the protection of an inert gas.

[0034] [9] The tungsten alloy manufactured by the manufacturing method described in any one of [1] to [8] has a density of 99% or more, preferably 99.5% or more; and a compressive strength of 1700 MPa or more, preferably 2100 MPa or more.

[0035] Effects of the Invention

[0036] The present invention has the following technical effects:

[0037] The manufacturing method of the tungsten alloy provided by the present invention greatly improves the performance of the final tungsten alloy product through the synergistic strengthening effect of the solid solution strengthening of Hf and C atoms and the dispersion strengthening of nano-scale HfC particles precipitated by heat treatment, which is specifically reflected in: effectively suppressing cracks in the tungsten alloy; improving the density of the tungsten alloy, and the density can reach more than 99%, or even more than 99.5%; improving the compressive strength, and the compressive strength can reach more than 1700MPa, or even more than 2100MPa.

[0038] The manufacturing method of the tungsten alloy provided by the present invention significantly improves the mechanical properties of the tungsten alloy and can promote the application of the tungsten alloy in various fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 Transmission electron micrograph and element analysis of the tungsten alloy product prepared in Example 1 of the present invention;

[0040] Figure 2 This is a metallographic diagram of the tungsten alloy product prepared in Example 1 of the present invention;

[0041] Figure 3 This is a metallographic diagram of the tungsten alloy product prepared in Example 2 of the present invention;

[0042] Figure 4 This is a metallographic diagram of the tungsten alloy product prepared in Example 3 of the present invention;

[0043] Figure 5 This is a metallographic diagram of the tungsten alloy product prepared in Comparative Example 1 of the present invention;

[0044] Figure 6 This is a metallographic diagram of the tungsten alloy product prepared in Comparative Example 2 of the present invention;

[0045] Figure 7 This is a metallographic diagram of the tungsten alloy product prepared in Comparative Example 3 of the present invention;

[0046] Figure 8 This is a metallographic diagram of the tungsten alloy product prepared in Comparative Example 4 of the present invention;

[0047] Fig. 9 This is a metallographic diagram of the tungsten alloy product prepared in Comparative Example 5 of the present invention;

[0048] Fig.10 This is the metallographic diagram of the tungsten alloy product prepared in Comparative Example 6 of the present invention. DETAILED DESCRIPTION

[0049] Various exemplary embodiments, features and aspects of the present invention will be described in detail below. The word "exemplary" used here means "used as an example, embodiment or illustrative". Any embodiment described here as "exemplary" is not necessarily interpreted as being superior or better than other embodiments.

[0050] In addition, in order to better illustrate the present invention, numerous specific details are provided in the following specific embodiments. It should be understood by those skilled in the art that the present invention can be implemented without certain specific details. In other examples, methods, means, equipment and steps well known to those skilled in the art are not described in detail in order to highlight the subject matter of the present invention.

[0051] Unless otherwise stated, the units used in this specification are all international standard units, and the numerical values ​​and numerical ranges appearing in the present invention should be understood to include the inevitable systematic errors in industrial production.

[0052] In this specification, the word "may" means both performing a certain process and not performing a certain process.

[0053] In this specification, the references to "some specific / preferred embodiments", "other specific / preferred embodiments", "some embodiments", etc., mean that the specific elements (e.g., features, structures, properties and / or characteristics) related to the embodiments are included in at least one embodiment described herein, and may or may not exist in other embodiments. In addition, it should be understood that the elements may be combined in various embodiments in any suitable manner.

[0054] In this specification, the numerical range expressed using "a numerical value A to a numerical value B" means a range including the endpoints A and B.

[0055] In the present specification, when "normal temperature" or "room temperature" is used, the temperature may be 15°C to 30°C, further 15°C to 25°C, for example, 20°C.

[0056] In this specification, "laser additive manufacturing" is the same as "laser powder bed fusion additive manufacturing".

[0057] Before the emergence of laser powder bed melting additive manufacturing technology, the preparation process of tungsten alloys only involved powder metallurgy, and only second-phase particles such as HfC could be added mechanically. The second-phase particles would not melt and precipitate, nor could they form a supersaturated solid solution with the matrix. After subsequent aging precipitation, the state of the second-phase particles before and after addition remained unchanged. However, with the use of laser powder bed melting additive manufacturing technology, HfC and tungsten will both melt during the preparation process, which allows HfC to form a supersaturated solid solution in the tungsten matrix, and through subsequent aging precipitation, the strength of the tungsten alloy is further improved. Although there are many studies on laser additive manufacturing of tungsten alloys, there is no research on aging precipitation strengthening (dispersion strengthening) of tungsten alloys. The present invention is the first to conduct relevant research on aging precipitation strengthening of tungsten alloys.

[0058] The present invention discovers for the first time that HfC can be dissolved in tungsten at high temperature to form a solid solution. Therefore, by adding micron-sized HfC particles to tungsten and utilizing the characteristics of rapid cooling and solidification of laser powder bed melting additive manufacturing, a local supersaturated solid solution can be formed. Such micron-sized HfC particles will melt during printing, and some of the melted particles will resolidify into HfC particles, some will dissolve into the tungsten lattice to form a supersaturated solid solution, and nano-sized HfC particles will be precipitated in the subsequent heat treatment process, and some will decompose into Hf and C atoms that dissolve into the tungsten lattice to form a solid solution. In this way, the method of the present invention can produce solid solution strengthening of Hf and C atoms and dispersion strengthening of nano-sized HfC particles, thereby achieving composite strengthening of the tungsten matrix.

[0059] Specifically, the method for manufacturing tungsten alloy provided by the present invention comprises the following steps:

[0060] Step S1: mixing tungsten powder and HfC powder to obtain W-HfC alloy powder;

[0061] Step S2: spreading the W—HfC alloy powder on a substrate of a laser powder bed melting additive manufacturing device, performing melting-solidification to obtain a deposition layer, and completing single-layer forming;

[0062] Step S3: repeating step S2 on the deposited layer to obtain a melt-formed W-HfC alloy sample;

[0063] Step S4: heat-treating and strengthening the W—HfC alloy sample to obtain the tungsten alloy.

[0064] In the present invention, the mass fraction of HfC in the W-HfC alloy powder is too low to form a supersaturated solid solution, and too high will cause cracking of the tungsten alloy. In the present invention, the mass fraction of HfC in the W-HfC alloy powder is 1.4% to 9.3%, preferably 2.5% to 7%, for example, 1.5%, 2%, 2.2%, 2.3%, 2.4%, 5%, 7.1%, 7.2%, 7.3%, 7.5%, 8%, 9%, etc. When the mass fraction of HfC in the W-HfC alloy powder is within this range, HfC may form a supersaturated solid solution in the tungsten alloy, and the strength of the tungsten alloy can be further improved by subsequent heat treatment.

[0065] In the present invention, the particle size of the HfC powder is in the range of 1 to 10 μm, such as 2 μm, 4 μm, 6 μm, 8 μm, etc. When the particle size of HfC is less than 1 μm, HfC diffuses relatively quickly in the tungsten molten pool and cannot form a supersaturated solid solution; when the particle size of HfC is greater than 10 μm, it will cause severe splashing during forming, which is not conducive to forming. In addition, if the particle size of HfC is too small or too large, the cost will increase.

[0066] In some embodiments, the HfC powder has a D 10 It is 1 to 4 μm, for example, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, etc.

[0067] In some embodiments, the HfC powder has a D 50 It is 4 to 7 μm, for example, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, etc.

[0068] In some embodiments, the HfC powder has a D 90 It is 7 to 10 μm, for example, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, etc.

[0069] In some embodiments, the tungsten powder is spherical tungsten powder.

[0070] In the present invention, the oxygen content of the tungsten powder cannot be too high, otherwise it will cause tungsten cracking. The embrittlement caused by oxygen in tungsten products is due to the segregation of oxygen on the crystal plane. This segregation reduces the grain boundary strength and leads to intergranular cracking. From a macroscopic point of view, an increase in oxygen content will reduce the tensile strength of tungsten products, resulting in cracking. In some embodiments, the oxygen content (mass fraction) of the tungsten powder does not exceed 0.02%, that is, 0 to 0.02%, for example, it can be in the range of 0.005% to 0.018%, such as 0.008%, 0.01%, 0.015%, etc.

[0071] In the present invention, the particle size of the tungsten powder cannot exceed 53 μm. In the laser additive manufacturing process, if the particle size of tungsten exceeds 53 μm, the laser will not be able to melt through the tungsten powder. In some embodiments, the particle size of the tungsten powder ranges from 8 to 53 μm, such as 10 μm, 15 μm, 20 μm, 30 μm, 40 μm, 50 μm, etc. In the present invention, the tungsten powder is composed of powders of various particle sizes within the particle size range, and the percentage of powders of each particle size is approximately normally distributed.

[0072] In some embodiments, the D of the tungsten powder 10 It is 8 to 25 μm, for example, 9 μm, 12 μm, 15 μm, 20 μm, 22 μm, etc.

[0073] In some embodiments, the D of the tungsten powder 50 It is 10 to 40 μm, for example, 12 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, etc.

[0074] In some embodiments, the D of the tungsten powder 90 It is 15 to 53 μm, for example, 20 μm, 25 μm, 30 μm, 40 μm, 45 μm, 50 μm, etc.

[0075] In the present invention, the better the fluidity of the tungsten powder, the more uniform the mixing with the HfC powder. The uniformity of the mixing directly affects the density and performance of the alloy. Uniform mixing can ensure that the density of the powder particles is uniform during the forming process, thereby improving the density and mechanical properties of the product. In some embodiments, the Hall flow rate of the tungsten powder is (5 to 9) s / 50g, for example, 5.5s / 50g, 6s / 50g, 7s / 50g, 8s / 50g, 8.5s / 50g, etc.

[0076] In some embodiments, in step S1, the tungsten powder and the HfC powder are mixed evenly to obtain W—HfC alloy powder.

[0077] In some embodiments, in step S1, the tungsten powder and the HfC powder are mixed by ball milling (for example, using a ball mill for ball milling). In some specific embodiments, the diameter of the grinding balls used in the ball milling is 4 to 10 mm, for example, 4 mm, 6 mm, 8 mm, 10 mm, etc. In some specific embodiments, the ball-to-material mass ratio is 7:1 to 14:1, for example, 8:1, 10:1, 12:1, 13:1, etc. In some specific embodiments, the ball mill speed used in the ball milling is 300 to 600 r / min, for example, 350 r / min, 400 r / min, 500 r / min, etc. In some specific embodiments, the ball milling time is 14 to 27 h, for example, 16 h, 18 h, 20 h, 22 h, 25 h, etc.

[0078] In some embodiments, in step S2, the W-HfC alloy powder needs to be dried and loaded into the powder supply bin of the laser powder bed melting additive manufacturing equipment, and the substrate is installed on the processing platform of the equipment. In some specific embodiments, the drying is vacuum drying at 50-80°C (e.g., 55°C, 60°C, 65°C, 70°C, etc.) for 3-8h (e.g., 4h, 5h, 6h, etc.).

[0079] In some embodiments, in step S2, the substrate is a stainless steel substrate, a molybdenum substrate or a tungsten substrate.

[0080] In some embodiments, in step S2, before spreading the W—HfC alloy powder, the substrate needs to be preheated to 115° C. to 230° C., such as 120° C., 140° C., 150° C., 160° C., 170° C., 180° C., 200° C., 220° C., etc. Preheating the substrate can reduce the residual stress generated by printing and inhibit cracking.

[0081] In some embodiments, in step S2, the thickness of the powder layer of the W—HfC alloy powder on the substrate is 25-45 μm, for example, 30 μm, 35 μm, 40 μm, etc.

[0082] In some embodiments, in step S2, the melting-solidification is performed under the protection of an inert gas. For example, the air in the forming chamber of the laser powder bed fusion additive manufacturing equipment can be replaced by an inert gas, so that the oxygen content (volume fraction) in the forming chamber is reduced to less than 0.02%. In some specific embodiments, the inert gas can be one of nitrogen, argon, helium, or a mixture thereof.

[0083] In some embodiments, in step S2, the laser power of the laser powder bed melting additive manufacturing equipment when melting the W—HfC alloy powder is 150-500 W, preferably 200-450 W, for example, 175 W, 250 W, 300 W, 350 W, 400 W, 475 W, etc.

[0084] In some embodiments, in step S2, the scanning speed of the laser powder bed melting additive manufacturing equipment when melting the W—HfC alloy powder is 200-600 mm / s, preferably 250-500 mm / s, for example, 225 mm / s, 300 mm / s, 350 mm / s, 400 mm / s, 450 mm / s, 525 mm / s, 550 mm / s, etc.

[0085] In the present invention, in step S3, the number of times step S2 is repeated is not particularly limited. In actual production, the number of times step S2 is repeated can be adaptively adjusted according to information such as the thickness, height and shape of the target product until a melt-formed W-HfC alloy sample is obtained. For example, if the target alloy sample is a cube of 10mm*10mm*10mm (length*width*height), the number of times step S2 is repeated can be obtained by dividing its height (10mm) by the thickness of the powder layer.

[0086] In some embodiments, in step S3, before repeating step S2 on the deposition layer, the processing platform of the laser powder bed fusion additive manufacturing equipment is first lowered to a height that is the same as the thickness of the powder layer.

[0087] In the present invention, the characteristics of rapid melting and rapid cooling and solidification of laser additive manufacturing are utilized to form a supersaturated solid solution in the tungsten alloy. The supersaturated solid solution can be decomposed through heat treatment to precipitate nano-sized second phase particles, i.e., nano-scale HfC particles, to achieve dispersion strengthening and further improve the mechanical properties of the tungsten alloy.

[0088] In some embodiments, in step S4, the temperature of the heat treatment strengthening is 850-1650°C, preferably 900-1600°C, for example, 875°C, 1000°C, 1100°C, 1200°C, 1300°C, 1500°C, 1625°C, etc.

[0089] In some embodiments, in step S4, the holding time of the heat treatment strengthening is 4 to 20 hours, preferably 6 to 12 hours, for example, 5 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 13 hours, 15 hours, 18 hours, etc.

[0090] In some embodiments, in step S4, the heat treatment strengthening is performed under the protection of an inert gas. In some specific embodiments, the inert gas can be one of nitrogen, argon, helium or a mixed gas thereof.

[0091] In addition, the present invention also provides a tungsten alloy manufactured by the above-mentioned manufacturing method, which can be applied to multiple fields such as aerospace, medical treatment, and nuclear reactors. In some embodiments, the density of the tungsten alloy of the present invention is 99% or more, preferably 99.5% or more, such as 99% to 100% or 99.5% to 100%. In some embodiments, the compressive strength (compressive strength at room temperature) of the tungsten alloy of the present invention is 1700MPa or more, preferably 1900MPa or more, more preferably 2100MPa or more, such as 1800MPa, 2000MPa, 2200MPa, 2500MPa, etc.

[0092] Compared with the traditional alloy element addition and strengthening method, which limits the second phase strengthening effect due to the agglomeration of the second phase particles, the present invention greatly improves the performance of the final tungsten alloy by selecting the HfC material and the synergistic strengthening effect of the solid solution strengthening of Hf and C atoms in the tungsten alloy produced by the above steps and the dispersion strengthening of nano-scale HfC particles.

[0093] In addition, by adopting the HfC-based alloying strategy and heat treatment strengthening manufacturing method of the present invention, the tensile strength of the tungsten alloy is improved by utilizing the synergistic strengthening effect of the solid solution strengthening of Hf and C atoms and the dispersion strengthening of nano-scale HfC particles, and the thermal stress that causes cracks in the laser powder bed melting additive manufacturing process can be resisted. Therefore, the crack suppression effect of the formed tungsten alloy is greatly enhanced.

[0094] Furthermore, through the method of the present invention, the performance of tungsten alloy can be greatly improved by using micron-sized HfC as raw material, further reducing the manufacturing cost.

[0095] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0096] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0097] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

[0098] Example

[0099] The embodiments of the present invention will be described in detail below in conjunction with the examples, but those skilled in the art will appreciate that the following examples are only used to illustrate the present invention and should not be considered to limit the scope of the present invention. If no specific conditions are specified in the examples, they are carried out according to normal conditions or the conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be obtained commercially.

[0100] Embodiment 1:

[0101] (1) Spherical tungsten powder and HfC powder are placed in a ball mill and mixed evenly to obtain a uniformly mixed W-HfC alloy powder (tungsten alloy powder). The oxygen content (mass fraction) of the spherical tungsten powder is 0.009%; the mass fraction of HfC in the tungsten alloy powder is 2.5%; the particle size of the spherical tungsten powder is 8 to 53 μm (D 10 =12.3μm, D 50 =26.2μm, D 90 =49.6μm), Hall flow rate is 5.6s / 50g; HfC powder particle size is 1-10μm (D 10 =2.1μm, D 50 =5.6μm, D 90 =8.4μm); grinding ball diameter is 4mm; ball-to-material ratio is 7:1; ball mill speed is 300r / min; ball milling time is 14h.

[0102] (2) The prepared W-HfC alloy powder was dried (vacuum dried at 60°C for 4 h) and then loaded into the powder supply bin of the laser additive manufacturing equipment, and a stainless steel substrate was installed on the forming bin processing platform of the equipment.

[0103] (3) Using argon gas to replace the air in the forming chamber of the laser additive manufacturing equipment, the oxygen content (volume fraction) in the forming chamber is reduced to below 0.02%; and the stainless steel substrate is preheated to 150°C.

[0104] (4) The W-HfC alloy powder in the powder supply bin is evenly spread on the substrate, and the tungsten alloy powder is melted and solidified to obtain a deposition layer to complete the single-layer forming. The thickness of the W-HfC alloy powder layer is 25 μm; the laser power for melting the W-HfC alloy powder is 200 W, and the scanning speed is 250 mm / s.

[0105] (5) The processing platform of the laser additive manufacturing equipment is lowered by a powder layer thickness, and step (4) is repeated until a cubic W-HfC alloy sample with a size of 10 mm*10 mm*10 mm (length*width*height) formed by laser powder bed fusion is obtained.

[0106] (6) The W-HfC alloy sample was heat-treated and strengthened in an argon atmosphere at a temperature of 900° C. for a holding time of 6 h to obtain a tungsten alloy product of the present invention. The transmission electron micrograph and element analysis thereof are as follows: Figure 1 As shown, its metallographic diagram is as follows Figure 2 shown.

[0107] Depend on Figure 1 It can be seen that the tungsten alloy of the present invention will precipitate nano-sized HfC particles after heat treatment strengthening, and the method of the present invention further improves the mechanical properties of the tungsten alloy product through dispersion strengthening.

[0108] Embodiment 2:

[0109] (1) Spherical tungsten powder and HfC powder are placed in a ball mill and mixed evenly to obtain a uniformly mixed W-HfC alloy powder (tungsten alloy powder). The oxygen content of the spherical tungsten powder is 0.013%; the mass fraction of HfC in the tungsten alloy powder is 5%; the particle size of the spherical tungsten powder is 8 to 28 μm (D 10 =9.4μm, D 50 =15.6μm, D 90 =25.7μm), Hall flow rate is 6.4s / 50g; HfC powder particle size is 1~10μm (D 10 =2.5μm, D 50 =5.1μm, D 90 =9.1μm); grinding ball diameter is 8mm; ball-to-material ratio is 10:1; ball mill speed is 400r / min; ball milling time is 20h.

[0110] (2) The prepared W-HfC alloy powder was dried (vacuum dried at 60°C for 4 h) and then loaded into the powder supply bin of the laser additive manufacturing equipment, and the molybdenum substrate was installed on the forming bin processing platform of the equipment.

[0111] (3) Using helium to replace the air in the forming chamber of the laser additive manufacturing equipment, the oxygen content (volume fraction) in the forming chamber is reduced to below 0.02%; and the substrate is preheated to 180°C.

[0112] (4) The W-HfC alloy powder in the powder supply bin is evenly spread on the substrate, and the tungsten alloy powder is melted and solidified to obtain a deposition layer to complete the single-layer forming. The thickness of the W-HfC alloy powder layer is 30 μm; the laser power for melting the tungsten alloy powder is 350 W, and the scanning speed is 300 mm / s.

[0113] (5) The processing platform of the laser additive manufacturing equipment is lowered by a powder layer thickness, and step (4) is repeated until a cubic W-HfC alloy sample with a size of 10 mm*10 mm*10 mm (length*width*height) formed by laser powder bed fusion is obtained.

[0114] (6) The W-HfC alloy sample was heat-treated and strengthened in a helium atmosphere at a heat treatment temperature of 1200° C. for a holding time of 10 h to obtain the tungsten alloy product of the present invention. The metallographic image is shown in FIG. Figure 3 shown.

[0115] Embodiment 3:

[0116] (1) Spherical tungsten powder and HfC powder are placed in a ball mill and mixed evenly to obtain a uniformly mixed W-HfC alloy powder (tungsten alloy powder). The oxygen content of the spherical tungsten powder is 0.015%; the mass fraction of HfC in the tungsten alloy powder is 7%; the particle size of the spherical tungsten powder is 15 to 53 μm (D 10 =17.8μm, D 50 =28.2μm, D 90 =47.4μm), Hall flow rate is 8.3s / 50g; HfC powder particle size is 1-10μm (D 10 =3.1μm, D 50 =6.2μm, D 90 =9.2μm); grinding ball diameter is 10mm; ball-to-material ratio is 14:1; ball mill speed is 600r / min; ball milling time is 27h.

[0117] (2) The prepared W-HfC alloy powder is dried (vacuum dried at 60°C for 4 h) and then loaded into the powder supply bin of the laser additive manufacturing equipment, and a tungsten substrate is installed on the forming bin processing platform of the equipment.

[0118] (3) Using a mixed gas of argon and helium (wherein the volume fractions of argon and helium are 50% and 50%) to replace the air in the forming chamber of the laser additive manufacturing equipment, the oxygen content (volume fraction) in the forming chamber is reduced to below 0.02%; and the substrate is preheated to 220°C.

[0119] (4) The W-HfC alloy powder in the powder supply bin is evenly spread on the substrate, and the tungsten alloy powder is melted and solidified to obtain a deposition layer to complete the single-layer forming. The thickness of the W-HfC alloy powder layer is 35 μm; the laser power for melting the tungsten alloy powder is 450 W, and the scanning speed is 500 mm / s.

[0120] (5) The processing platform of the laser additive manufacturing equipment is lowered by a powder layer thickness, and step (4) is repeated until a cubic W-HfC alloy sample with a size of 10 mm*10 mm*10 mm (length*width*height) formed by laser powder bed fusion is obtained.

[0121] (6) The W-HfC alloy sample was heat-treated and strengthened in a mixed atmosphere of argon and helium (wherein the volume fractions of argon and helium were 50% and 50%) at a heat treatment temperature of 1600° C. for a holding time of 12 h to obtain a tungsten alloy product of the present invention, whose metallographic diagram is shown in FIG. Figure 4 shown.

[0122] Comparative Example 1:

[0123] In this comparative example, only the HfC content is changed to 1%, and the remaining steps and parameters are the same as those in Example 2. The metallographic image of the product is shown in FIG. Figure 5 shown.

[0124] Comparative Example 2:

[0125] In this comparative example, only the HfC content is changed to 10%, and the remaining steps and parameters are the same as those in Example 2. The metallographic image of the product is shown in FIG. Figure 6 shown.

[0126] Comparative Example 3:

[0127] In this comparative example, only the heat treatment temperature is changed to 800°C, and the remaining steps and parameters are the same as those in Example 2. The metallographic diagram of the product is shown in FIG. Figure 7 shown.

[0128] Comparative Example 4:

[0129] In this comparative example, only the heat treatment temperature is changed to 1700°C, and the remaining steps and parameters are the same as those in Example 2. The metallographic image of the product is shown in FIG. Figure 8 shown.

[0130] Comparative Example 5:

[0131] In this comparative example, the particle size of HfC is only changed to less than 1 μm, specifically 50 to 200 nm (D 10 =60nm, D 50 =145nm, D 90 =180nm), the remaining steps and parameters are the same as those in Example 2, and the metallographic image of the product is shown in Fig. 9 shown.

[0132] Comparative Example 6:

[0133] In this comparative example, the particle size of HfC is changed to be larger than 10 μm, specifically 15 to 30 μm (D 10 =18.3μm, D 50 =26.3μm, D 90 =28.6μm), the remaining steps and parameters are the same as those in Example 2, and the metallographic image of the product is shown in Fig.10 shown.

[0134] The density of the products prepared in Examples 1-3 and Comparative Examples 1-6 was tested by the Archimedes drainage method. The room temperature compressive strength of the products prepared in Examples 1-3 and Comparative Examples 1-6 was tested according to GB / T7314-2017 “Room Temperature Compression Test of Metallic Materials”. The results are shown in Table 1.

[0135] Table 1 Density and room temperature compressive strength of products of Examples 1-3 and Comparative Examples 1-6

[0136]

[0137] By comparison, the tungsten alloys prepared in Examples 1-3 have no cracks (see Figure 2 , Figure 3 , Figure 4 ), the density reaches more than 99%, and the compressive strength reaches up to 2156MPa. Comparative Example 1 Due to the low HfC content, the crack suppression effect is limited, and the tungsten alloy product has more cracks (see Figure 5 ), the density is only 97.6%, and the compressive strength is only 1149MPa. Comparative Example 2 Due to the high HfC content, splashing occurs during printing, and the tungsten alloy has more cracks (see Figure 6 ), the density is only 98.4%, and the compressive strength is only 1254MPa. Although the tungsten alloys obtained in Comparative Examples 3 and 4 have no crack defects (see Figure 7 , Figure 8 ), the density reached 99.4% and 99.3% respectively, but due to the heat treatment temperature being too low or too high, the nano-scale HfC particles did not precipitate or coarsened after precipitation, resulting in lower mechanical properties than Example 2, with compressive strengths of only 1485MPa and 1516MPa. Although the tungsten alloy obtained in Comparative Example 5 has fewer crack defects (see Fig. 9 ), the density reaches 99.2%, but because the HfC particle size is too small, it cannot form a supersaturated solid solution locally, cannot be further precipitated by heat treatment, and is more easily decomposed, resulting in its compressive strength being lower than that of Example 2, and the compressive strength is only 1457MPa. Comparative Example 6 Due to the large HfC particle size, splashing occurs during printing, and the tungsten alloy product has more crack defects (see Fig.10 ), the density is only 98.2%, and the compressive strength is only 1233MPa. It can be seen that the tungsten alloy manufacturing method provided by the present invention can effectively inhibit cracks, significantly improve the density and mechanical properties of tungsten alloy, and has obvious technical advantages.

[0138] It should be noted that, although the technical solution of the present invention is introduced with specific examples, those skilled in the art will appreciate that the present invention should not be limited thereto.

[0139] The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The selection of terms used herein is intended to best explain the principles of the embodiments, practical applications, or technical improvements in the market, or to enable other persons of ordinary skill in the art to understand the embodiments disclosed herein.

Claims

1. A method for manufacturing a tungsten alloy, comprising the following steps: Step S1: mixing tungsten powder and HfC powder to obtain W-HfC alloy powder; Step S2: spreading the W—HfC alloy powder on a substrate of a laser powder bed melting additive manufacturing device, performing melting-solidification to obtain a deposition layer, and completing single-layer forming; Step S3: repeating step S2 on the deposited layer to obtain a melt-formed W-HfC alloy sample; Step S4: heat-treating and strengthening the W—HfC alloy sample to obtain the tungsten alloy.

2. The manufacturing method according to claim 1, characterized in that: The mass fraction of HfC in the W-HfC alloy powder is 1.4% to 9.3%, preferably 2.5% to 7%.

3. The manufacturing method according to claim 1 or 2, characterized in that: The particle size of the HfC powder is in the range of 1 to 10 μm. Preferably, the D 50 4~7μm.

4. The manufacturing method according to any one of claims 1 to 3, characterized in that: In step S4, the temperature of the heat treatment strengthening is 850-1650°C, preferably 900-1600°C; Preferably, the heat treatment strengthening holding time is 4 to 20 hours, preferably 6 to 12 hours.

5. The manufacturing method according to any one of claims 1 to 4, characterized in that: The oxygen content of the tungsten powder is 0-0.02 wt %, preferably 0.005 wt %-0.018 wt %.

6. The manufacturing method according to any one of claims 1 to 5, characterized in that: In step S1, the tungsten powder and the HfC powder are mixed by ball milling; Preferably, the diameter of the grinding balls used in the ball milling is 4 to 10 mm, the ball-to-material ratio of the ball milling is 7:1 to 14:1, the speed of the ball mill used in the ball milling is 300 to 600 r / min, and the ball milling time is 14 to 27 h.

7. The manufacturing method according to any one of claims 1 to 6, characterized in that: In step S2, the laser power of the laser powder bed melting additive manufacturing equipment when melting the W—HfC alloy powder is 150 to 500 W, preferably 200 to 450 W, and the scanning speed is 200 to 600 mm / s, preferably 250 to 500 mm / s.

8. The manufacturing method according to any one of claims 1 to 7, characterized in that: In step S2, the melting-solidification is performed under the protection of an inert gas; In step S4, the heat treatment strengthening is performed under the protection of an inert gas.

9. the tungstenalloy obtained by the manufacture method described in any one of claims 1-8 is manufactured, the density of the tungstenalloy being more than 99%, preferably more than 99.5%; The compressive strength of the tungstenalloy being more than 1700MPa, preferably more than 2100MPa.

Images