High-homogeneity and high-strength W-7Cu composite material and preparation method thereof

Abstract

The invention discloses a high-homogeneity and high-strength W-7Cu composite material and a preparation method thereof, and belongs to the technical field of metal composite material preparation. The high-homogeneity and high-strength W-7Cu composite material is prepared through the technological processes of spray drying, reduction, ball milling, pressing, sintering, infiltration and the like. According to the preparation method, firstly, high-homogeneity tungsten-coated copper composite powder is prepared through spray drying and reduction, the content of copper is 6-9%, and the particle size of the powder is 4-6 microns; further, the reduced tungsten-copper composite powder is subjected to ball milling for 4-6 h, and the tungsten-copper composite powder with the particle size being 1-3 microns is obtained; the tungsten-copper composite powder is pressed, and the density of a pressed blank is larger than or equal to 13.5 g / cm < 3 >; the pressed blank is sintered at the temperature of 1300-1400 DEG C, and the heat preservation time is 2-4 h; and the sintered blank is subjected to heat preservation for 2-4 h at the temperature of 1100-1300 DEG C for infiltration, so that the high-homogeneity and high-strength W-7Cu composite material is obtained, the copper content in the composite material is 6-9%, the density is larger than or equal to 17.3 g / cm < 3 >, the room-temperature tensile strength is larger than or equal to 500 MPa, no obvious copper segregation exists, and the high-homogeneity and high-strength W-7Cu composite material can be applied to the advanced fields of aerospace, the national defense military industry, the nuclear industry and the like.

Description

Technical Field

[0001] The invention relates to the technical field of metal composite material preparation, and in particular to a high-homogeneity and high-strength W-7Cu composite material and a preparation method thereof. Background Art

[0002] Tungsten copper composite materials have the characteristics of high melting point and high thermal conductivity. Due to the large difference in physical properties between the two, they are usually prepared by melt infiltration. The low-copper content composite material prepared by the copper infiltration process retains the high hardness, high strength, low thermal expansion coefficient and excellent wear and corrosion resistance of the skeleton, while also having the advantages of good high temperature strength and mechanical properties. In addition, when the service temperature exceeds the melting point of copper, the copper evaporates and gasifies to take away most of the heat and lower the ambient temperature, thereby ensuring the stability of the throat lining, and is a good rocket engine throat lining material.

[0003] The traditional infiltration method is mainly divided into sintering of tungsten skeleton and infiltration of copper. Usually, the method of sintering tungsten skeleton at high temperature and then infiltrating copper is adopted. Its mechanism is to use the action of capillary force to make liquid copper infiltrate the porous tungsten matrix and fill the pores of the porous tungsten skeleton, so as to obtain a composite material with high density and excellent performance. However, there are also some disadvantages in the preparation of tungsten-copper composite materials using the existing infiltration method. For example, when the tungsten skeleton is in contact infiltration, the copper liquid needs to overcome part of the gravity to do work, which leads to a slow infiltration speed. Compared with contact infiltration, the full infiltration speed is faster, but it is impossible to prepare a composite material with high density.

[0004] The Chinese patent application document with publication number CN116652179A discloses a tungsten-copper alloy composite material and its preparation process, which includes the following steps: S1, tungsten powder treatment: chemical nickel plating of tungsten powder to obtain pre-treated tungsten powder; adding the pre-treated tungsten powder to the electroplating solution for stirring-electroplating, repeating the stirring-electroplating process 10 times, washing the obtained powder with water until it is neutral, and vacuum drying to obtain a composite powder; the electroplating solution includes nano silicon carbide and surfactant; S2, mixing the composite powder with copper powder and pressing into shape; S3, sintering, the sintering atmosphere is hydrogen; S4, multiple hot rolling and annealing. The tungsten powder treatment in this patent is conducive to reducing the thermal expansion coefficient of the material and improving the thermal conductivity of the material. The multiple hot rolling process can improve the degree of densification of the plate structure, and can effectively eliminate defects such as copper phase enrichment areas and holes, so that the copper phase forms a dense network structure inside the alloy. However, the mechanical properties of the material are still poor, so it needs to be further improved. Summary of the invention

[0005] The problem to be solved by the present invention is how to solve the problems of low homogeneity, low density and poor strength of the existing tungsten-copper composite material.

[0006] The present invention solves the above technical problems through the following technical means:

[0007] The first aspect of the present invention provides a method for preparing a high-homogeneity, high-strength W-7Cu composite material, comprising the following steps:

[0008] S1 Preparation of high homogeneity tungsten-copper composite powder: Sodium tungstate, copper sulfate solution and oxalic acid solution are mixed and reacted, and then a tungsten-copper composite precursor is prepared by spray drying, and then reduced in a hydrogen atmosphere to obtain a tungsten-copper composite powder; wherein the copper content is 6-9%, and the powder morphology is a tungsten-coated copper structure;

[0009] S2 ball milling: ball milling the composite powder obtained in S1;

[0010] S3 pressing: pressing the composite powder obtained in S2 to obtain a green body to be sintered;

[0011] S4 pre-sintering: sintering the green body obtained in S3 under a hydrogen atmosphere to obtain a tungsten skeleton with a low copper content;

[0012] S5 Infiltration: In a hydrogen atmosphere, copper powder is infiltrated into the tungsten skeleton obtained in S4.

[0013] Preferably, in S1, the solution mixing reaction is magnetically stirred at 75°C-80°C for 4-5 hours, and the magnetic speed is 300-400 r / min, and more preferably: 80°C, 4.5 hours, 350 r / min.

[0014] Preferably, in S1, the rotation speed of the spray drying atomizer is 24000-26000 r / min, the air inlet temperature is 180-220°C, and the air outlet temperature is 120-150°C, and more preferably, 25000 r / min, 200°C, 130°C.

[0015] Preferably, in S1, the hydrogen reduction temperature is 800-1200°C, and the time is 0.5-4h, and more preferably: 1000°C, 2h.

[0016] Preferably, in S2, wet milling is performed for 4 to 6 hours, wherein the rotation speed of the ball mill is 150 to 250 r / min in the first half of the time and 250 to 350 r / min in the second half of the time.

[0017] Preferably, in S2, cemented carbide ball milling beads and anhydrous ethanol are added as ball milling media, and the mass ratio of the cemented carbide ball milling beads to the composite powder is 4 to 6:1, and more preferably 5:1.

[0018] Preferably, the diameter of the cemented carbide milling beads is 3 to 5 mm, more preferably 4 mm.

[0019] Preferably, the particle size of the composite powder after ball milling is 1 to 3 μm, and the shape changes from spherical to irregular powder.

[0020] Preferably, in S3, the tungsten-copper composite powder is pressed at a pressure of 600-800 MPa, and the density of the obtained compact is ≥13.5 g / cm 3 .

[0021] Preferably, in S4, the sintering temperature of the tungsten skeleton is 1300-1400°C, the time is 2-4 hours, and the density of the obtained tungsten skeleton is ≥15.2 g / cm 3 .

[0022] Preferably, in S5, the infiltration temperature is 1100-1300°C, the holding time is 2-4h, and the density of the obtained composite material is ≥17.3g / cm 3 .

[0023] Preferably, in S5, the mass of the copper powder used for infiltration is calculated based on the density of the tungsten skeleton; and the particle size of the copper powder used for infiltration is 2 to 5 μm.

[0024] The second aspect of the present invention provides a high-homogeneity, high-strength W-7Cu composite material obtained by the above preparation method.

[0025] The beneficial effects of the present invention are:

[0026] (1) The present invention prepares highly homogeneous tungsten-coated copper alloy powder by spray drying. The powder structure of tungsten-coated copper enables the tungsten-copper composite material prepared in the subsequent sintering process to have better component structure uniformity and density, thereby improving the mechanical strength of the composite material while increasing the thermal stability and wear resistance of the material.

[0027] (2) The present invention obtains irregularly shaped fine and highly homogeneous tungsten-copper composite powders by ball milling. Compared with the spherical powder structure, the irregular powder structure can eliminate the interfacial stress between the spherical powders to a certain extent. At the same time, it can improve the compactness of the powder, reduce the porosity, and thus improve the density and mechanical properties of the composite material.

[0028] (3) The present invention uses copper powder instead of copper sheet for infiltration. The use of copper powder for infiltration can control the copper content in the composite material, and the copper phase of the prepared tungsten-copper composite material is evenly distributed without obvious copper segregation. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a scanning electron microscope image of the cross section of the highly homogeneous tungsten-copper composite powder prepared in Example 1 of the present invention.

[0030] Figure 2 This is a scanning electron microscope image of the composite powder after ball milling in Example 1 of the present invention.

[0031] Figure 3This is a scanning electron microscope image of the W-7Cu composite material of Example 1 of the present invention.

[0032] Figure 4 This is a three-point bending stress-displacement diagram of the W-7Cu composite material of Example 2 of the present invention.

[0033] Figure 5 This is a scanning electron microscope image of the fracture of the W-7Cu composite material of Example 3 of the present invention.

[0034] Figure 6 This is a scanning electron microscope image of the fracture of the W-7Cu composite material of Example 4 of the present invention.

[0035] Figure 7 This is a surface optical microscope image of the W-7Cu composite material of Comparative Example 1 of the present invention.

[0036] Figure 8 This is a surface optical microscope image of the W-7Cu composite material of Comparative Example 2 of the present invention.

[0037] Fig. 9 This is a surface optical microscope image of the W-7Cu composite material of Comparative Example 3 of the present invention. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] Unless otherwise specified, the test materials and reagents used in the following examples can be obtained from commercial sources.

[0040] If no specific technology or conditions are specified in the examples, they can be carried out according to the technology or conditions described in the literature in the field or according to the product instructions. Unless otherwise specified, the quantitative tests in the following examples are repeated more than three times, and the results are averaged.

[0041] Embodiment 1:

[0042] Embodiment 1:

[0043] A method for preparing a high-homogeneity, high-strength W-7Cu composite material comprises the following steps:

[0044] S1 Preparation of high-homogeneity tungsten-copper composite powder: Sodium tungstate, copper sulfate solution and oxalic acid solution are mixed, and a magnet is added to the mixed solution. The mixture is magnetically stirred at 80°C for 4 hours, and the magnetic speed is 300r / min. After sufficient reaction, a high-homogeneity tungsten-coated copper composite powder precursor is prepared by spray drying (25000r / min, 200°C, 130°C). The composite powder precursor is reduced in a hydrogen atmosphere (1000°C, 2h) to obtain a high-homogeneity tungsten-copper composite powder with a copper content of 7% and a particle size of 4-5μm.

[0045] S2 ball milling: The prepared high homogeneous tungsten-copper composite powder is ball milled. 100g of tungsten-copper composite powder, 500g of carbide ball milling beads, and 50g of anhydrous ethanol are added to the ball milling jar as the ball milling medium. The diameter of the ball milling beads is 4mm. The ball milling speed is 150r / min for the first 2h and 250r / min for the next 2h. The particle size of the composite powder after ball milling is 2-3μm.

[0046] S3 pressing: The ball-milled composite powder was dried for 120 hours and then pressed at a pressure of 600 MPa and a holding time of 2 minutes. The density of the compact was 13.6 g / cm 3 .

[0047] S4 pre-sintering: Liquid phase sintering of the pressed green body, sintering temperature is 1300℃, holding time is 2h, the obtained tungsten skeleton density is 15.2g / cm 3 .

[0048] S5 Infiltration: Sprinkle copper powder (particle size 2-5 μm) evenly under the tungsten skeleton for infiltration. The infiltration temperature is 1100°C and the insulation time is 2 hours.

[0049] The high-homogeneity and high-strength W-7Cu composite material prepared in this example has a density of 17.3 g / cm 3 , Figure 1 This is a scanning electron microscope image of the cross-section of the highly homogeneous tungsten-copper composite powder prepared in this example. The red arrow in the figure points to the tungsten element, and the dark area pointed by the green arrow is the encapsulated copper element. Therefore, the composite powder structure is tungsten-coated copper, and the copper element is completely encapsulated by tungsten, which is an important factor in the subsequent preparation of highly homogeneous and high-strength composite materials.

[0050] Embodiment 2:

[0051] The difference between this embodiment and embodiment 1 is that:

[0052] S1 contains 9% copper and a particle size of 5 to 6 μm;

[0053] The particle size of the composite powder after ball milling in S2 is 1 to 3 μm.

[0054] The compact density obtained in S3 is 13.5 g / cm 3 .

[0055] The density of the tungsten skeleton obtained in S4 is 15.5 g / cm 3 .

[0056] The infiltration temperature in S5 is 1200° C. The rest is the same as in Example 1.

[0057] The W-7Cu composite material prepared in this example has a density of 17.4 g / cm 3 , Figure 2 This is a scanning electron microscope picture of the composite powder obtained after ball milling of the tungsten-copper composite powder prepared in this example. It can be seen from the picture that the shape of the composite powder after ball milling changes from spherical to irregular, fine, and highly homogeneous tungsten-copper composite powder. The irregular powder structure eliminates the interfacial stress between spherical powders to a certain extent. At the same time, it can improve the compaction of the powder, reduce the porosity, and thus improve the density and mechanical properties of the composite material.

[0058] Embodiment 3:

[0059] The difference between this embodiment and embodiment 1 is that:

[0060] S1 contains 6% copper and a particle size of 4-6 μm.

[0061] The particle size of the composite powder after ball milling in S2 is 1 to 3 μm.

[0062] The pressing pressure in S3 is 700 MPa, and the density of the obtained compact is 13.8 g / cm 3 .

[0063] The density of the tungsten skeleton obtained in S4 is 15.7 g / cm 3 .

[0064] In S5, the infiltration temperature is 1300°C and the holding time is 3 hours. The rest is the same as in Example 1.

[0065] The W-7Cu composite material prepared in this example has a density of 17.3 g / cm 3 , Figure 3 This is a scanning electron microscope image of the W-7Cu composite material prepared in this example. It can be seen from the image that the composite material has fewer pores, fine tungsten grains, and no obvious copper segregation, indicating that the composite material has high density and high strength.

[0066] Embodiment 4:

[0067] The difference between this embodiment and embodiment 1 is that:

[0068] The copper content in S1 is 6.5%;

[0069] In S2, the ball milling speed was 200 r / min for the first 2.5 h and 300 r / min for the last 2.5 h.

[0070] The pressing pressure in S3 is 700 MPa, and the density of the obtained compact is 13.8 g / cm 3 .

[0071] The density of the tungsten skeleton obtained in S4 is 15.8 g / cm 3 .

[0072] The holding time in S5 is 3 hours. The rest is the same as in Example 1.

[0073] The W-7Cu composite material prepared in this example has a density of 17.4 g / cm 3 , Figure 4 This is the three-point bending stress-displacement diagram of the W-7Cu composite material prepared in this example. It can be seen that the composite material has good bending resistance and the bending strength reaches 539MPa.

[0074] Embodiment 5:

[0075] The difference between this embodiment and embodiment 1 is that:

[0076] The copper content of S1 is 7.5%, and the particle size is 4-6 μm;

[0077] In S2, the ball milling speed was 250 r / min for the first 3 h and 350 r / min for the next 3 h. The particle size of the composite powder after ball milling was 1-3 μm.

[0078] The pressing pressure in S3 is 800 MPa, and the density of the obtained compact is 14.0 g / cm 3 .

[0079] The density of the tungsten skeleton obtained in S4 is 15.9 g / cm 3 .

[0080] In S5, the infiltration temperature is 1200°C and the holding time is 4 hours. The rest is the same as in Example 1.

[0081] The W-7Cu composite material prepared in this example has a density of 17.5 g / cm 3 , Figure 5 This is the fracture morphology of the W-7Cu composite material prepared in this example. It can be seen from the figure that the fracture is a brittle fracture, so the composite material is a brittle material. The flexural strength of the composite material in this example reaches 512MPa.

[0082] Embodiment 6:

[0083] The difference between this embodiment and embodiment 1 is that:

[0084] The copper content of S1 is 8.5%, and the particle size is 4-6 μm;

[0085] In S2, the ball milling speed was 250 r / min for the first 3 h and 350 r / min for the next 3 h. The particle size of the composite powder after ball milling was 1-2 μm.

[0086] The pressing pressure in S3 is 800 MPa, and the density of the obtained compact is 14.0 g / cm 3 .

[0087] The density of the tungsten skeleton obtained in S4 is 16.0 g / cm 3 .

[0088] In S5, the infiltration temperature is 1400°C and the holding time is 4 hours. The rest is the same as in Example 1.

[0089] The W-7Cu composite material prepared in this example has a density of 17.5 g / cm 3 , Figure 6 This is the fracture morphology of the W-7Cu composite material prepared in this example. From the fracture in the figure, it can be seen that the composite material has a high density, no obvious holes, and no obvious copper segregation, which means that the copper element is evenly distributed in the composite material, and the overall uniformity of the material is high, which improves the reliability and consistency of the material. The flexural strength of the composite material in this example reaches 543MPa.

[0090] The performance test data of Examples 1 to 6 are shown in the following table:

[0091] <![CDATA[Density / g·cm -3 > Bending strength / MPa Hardness / HV Example 1 17.3 524 352.8 Example 2 17.4 564 374.9 Example 3 17.3 521 369.2 Example 4 17.4 539 374.6 Example 5 17.5 512 383.5 Example 6 17.5 543 388.3

[0092] Comparative Example 1:

[0093] The difference between this comparative example and Example 1 is:

[0094] No S2 step.

[0095] The compact density obtained in S3 is 10.5 g / cm 3 .

[0096] The density of the tungsten skeleton obtained in S4 is 12.3 g / cm 3 The rest is the same as in Example 1.

[0097] The W-7Cu composite material prepared in this comparative example was tested and its density was 15.1 g / cm 3 , its metallographic structure is as follows Figure 7 As shown, there are many holes and defects in the composite material.

[0098] Comparative Example 2:

[0099] The difference between this comparative example and Example 1 is:

[0100] The ball milling time in S2 is 2 h, and the particle size of the composite powder after ball milling is 3-5 μm.

[0101] The pressing pressure in S3 is 500 MPa, and the density of the obtained compact is 13.3 g / cm 3 .

[0102] The density of the tungsten skeleton obtained in S4 is 14.6 g / cm 3 The rest is the same as in Example 1.

[0103] The W-7Cu composite material obtained in this comparative example was tested and its density was 16.7 g / cm 3 , its metallographic structure is as follows Figure 8 As shown, there are a small number of holes in the composite material, but no obvious defects.

[0104] Comparative Example 3:

[0105] The difference between this comparative example and Example 1 is:

[0106] The particle size of the composite powder after ball milling in S2 is 1 to 3 μm.

[0107] The compact density obtained in S3 is 13.8 g / cm 3 .

[0108] The sintering temperature in S4 is 1200℃, the holding time is 1h, and the density of the obtained tungsten skeleton is 14.8g / cm 3 .

[0109] In S5, the infiltration temperature is 1000°C and the holding time is 1 hour. The rest is the same as in Example 1.

[0110] The W-7Cu composite material obtained in this comparative example has a density of 16.4 g / cm3 and a metallographic structure as shown in FIG. Fig. 9 As shown in the figure, it can be seen that there are a small number of defects in the composite material.

[0111] In summary, step S2 is an indispensable step of the present invention and has a significant impact on the microstructure and properties of the composite material. Secondly, the change of sintering temperature in step S4 has a greater impact on the properties of the composite material.

[0112] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a high-homogeneity, high-strength W-7Cu composite material, characterized in that: The following steps are involved: S1: After sodium tungstate, copper sulfate solution and oxalic acid solution are mixed and reacted, a tungsten-copper composite precursor is prepared by spray drying, and then reduced in a hydrogen atmosphere to obtain a tungsten-copper composite powder; wherein the copper content is 6-9%, and the powder morphology is a tungsten-coated copper structure; S2: ball milling the composite powder obtained in S1; S3: pressing the composite powder obtained in S2 to obtain a green body to be sintered; S4: sintering the green body obtained in S3 under a hydrogen atmosphere to obtain a tungsten skeleton with a low copper content; S5: In a hydrogen atmosphere, the tungsten skeleton obtained in S4 is infiltrated with copper powder.

2. The preparation method according to claim 1, characterized in that: In S1, the solution mixing reaction is magnetically stirred at 75°C-80°C for 4-5 hours, and the magnetic speed is 300-400r / min; the spray drying atomizer speed is 24000-26000r / min, the inlet air temperature is 180-220°C, and the outlet air temperature is 120-150°C; the hydrogen reduction temperature is 800-1200°C, and the time is 0.5-4h.

3. The preparation method according to claim 1, characterized in that: In S2, wet milling is performed for 4 to 6 hours, wherein the rotation speed of the ball mill is 150 to 250 r / min in the first half and 250 to 350 r / min in the second half.

4. The preparation method according to claim 1, characterized in that: In S2, cemented carbide ball milling beads and anhydrous ethanol are added as ball milling media, the mass ratio of the cemented carbide ball milling beads to the composite powder is 4-6:1; and the diameter of the cemented carbide ball milling beads is 3-5 mm.

5. The preparation method according to claim 1, characterized in that: The particle size of the composite powder after ball milling is 1 to 3 μm.

6. The preparation method according to claim 1, characterized in that: In S3, the tungsten-copper composite powder is pressed at a pressure of 600-800 MPa, and the density of the obtained compact is ≥13.5 g / cm 3 .

7. The preparation method according to claim 1, characterized in that: In S4, the sintering temperature of the tungsten skeleton is 1300-1400℃, the time is 2-4h, and the density of the obtained tungsten skeleton is ≥15.2g / cm 3 .

8. The preparation method according to claim 1, characterized in that: In S5, the infiltration temperature is 1100-1300℃, the holding time is 2-4h, and the density of the obtained composite material is ≥17.3g / cm 3 .

9. The preparation method according to claim 1, characterized in that: In S5, the mass of the copper powder used for infiltration is calculated based on the density of the tungsten skeleton; the particle size of the copper powder used for infiltration is 2 to 5 μm.

10. The high-homogeneity and high-strength W-7Cu composite material prepared by the preparation method according to any one of claims 1 to 9.

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