Chromium diboride target material and preparation method thereof

Abstract

The invention provides a chromium diboride target material and a preparation method thereof, and the preparation method comprises the following steps: performing wet ball milling on chromium diboride powder by using a binder to obtain ball-milled powder; performing cold isostatic pressing on the ball-milled powder to obtain a target material green body; and the target material green body is subjected to vacuum sintering, and the chromium diboride target material is obtained. According to the preparation method provided by the invention, the binder is added into the chromium diboride powder for wet ball milling, the strength among particles is enhanced, then a green body with relatively high density is prepared through cold isostatic pressing, then vacuum pressureless sintering is adopted, further densification of the target material is completed, and finally the chromium diboride target material with high density is prepared. And the density especially reaches 98.0% or above.

Description

Technical Field

[0001] The present invention belongs to the technical field of target material preparation, and relates to a chromium diboride target material, and in particular to a chromium diboride target material and a preparation method thereof. Background Art

[0002] With the development of the aerospace and high-end equipment manufacturing industries, the demand for efficient machining of difficult-to-cut materials (such as titanium alloys and composite materials) is growing. These materials typically possess high strength, high hardness, and corrosion resistance. Traditional tool coatings, such as TiN and AlN, struggle to meet the requirements for efficient and precise machining due to their insufficient heat resistance, low hardness, and susceptibility to oxidation and wear under extreme operating conditions. Therefore, the development of new, high-performance tool coatings has become a research hotspot.

[0003] Chromium diboride (CrB2) is a hexagonal compound whose crystal structure consists of boron atoms (B) forming a two-dimensional network within a chromium (Cr) matrix, stacked with the Cr atoms. This structure endows CrB2 with extremely strong directional chemical bonding characteristics, including B-B covalent bonds and Cr-B ionic bonds, resulting in a range of excellent physical and chemical properties, such as a high melting point, high hardness, and outstanding corrosion resistance. These properties enable chromium diboride coatings to maintain stable mechanical and chemical properties even in the highly corrosive environments of high-temperature, high-speed cutting machines, significantly improving tool life and machining efficiency.

[0004] At present, the preparation methods of chromium diboride coatings mainly include chemical vapor deposition (CVD), brushing, plasma spraying and magnetron sputtering. However, the CVD method usually requires a high deposition temperature and may produce harmful by-products; the coating prepared by the brushing method has poor adhesion; and the plasma spraying method has an extremely high melting point of CrB2, which makes it difficult for the molten particles to spread fully, resulting in insufficient coating density and prone to pores and cracks. In contrast, magnetron sputtering technology has become an ideal method for preparing high-melting-point metastable CrB2 coatings due to its advantages such as low deposition temperature, good coating uniformity and strong adhesion. However, the core challenge of this technology lies in how to prepare high-performance CrB2 targets. CrB2 is a hard and brittle material. Its high melting point and high hardness make it difficult to achieve high densification and homogenization in the powder metallurgy process. Cracks or pores are prone to appear during the sintering process, making it difficult to meet the requirements of magnetron sputtering for the target microstructure and composition uniformity.

[0005] CN114934259A discloses a high-strength and tough aluminum-based composite target material for a multi-component mixed coating and a preparation method thereof, wherein an aluminum-based composite target material is prepared, wherein the chromium diboride content is 10-20%, and the remainder is chromium, tungsten and aluminum; CN118639192A discloses a preparation method for a ceramic metal target material for a silicon-based thin film resistor, wherein a ceramic metal target material is prepared, wherein the components include titanium diboride, chromium diboride, silicon, chromium, silicon carbide and carbon.

[0006] Existing ceramic metal targets often use chromium diboride as an additive component, but this hasn't resulted in high-quality, high-purity chromium diboride targets. Consequently, the preparation of chromium diboride targets still faces significant technical bottlenecks. Developing a process for preparing high-purity, high-density chromium diboride targets is key to promoting the application of magnetron sputtering technology in the large-scale production of chromium diboride coatings. Summary of the Invention

[0007] In view of the shortcomings of the existing technology, the purpose of the present invention is to provide a chromium diboride target and a preparation method thereof, design a preparation process, and prepare high-purity, high-density, high-quality chromium diboride target.

[0008] To achieve this object, the present invention adopts the following technical solutions:

[0009] In a first aspect, the present invention provides a method for preparing a chromium diboride target, the method comprising the following steps:

[0010] (1) wet-milling chromium diboride powder using a binder to obtain ball-milled powder;

[0011] (2) cold isostatic pressing the ball-milled powder to obtain a target green body;

[0012] (3) vacuum sintering the target green body to obtain the chromium diboride target.

[0013] The melting point of chromium diboride is 2100-2200℃, which has a high melting point, a Vickers hardness of HV2000-2500, and a fracture toughness of 2.5-4.5MPa·K. 1 / 2, showing significant brittleness and hardness. In the preparation process using powder metallurgy, when the temperature is too low, densification cannot be completed. However, when excessively high temperature or pressure is applied, stress inhomogeneity and severe cracking are prone to occur. It is very sensitive to temperature and pressure conditions, and the preparation process is difficult to control. The preparation method provided by the present invention adds a binder to chromium diboride powder for wet ball milling, coats the powder particles with the binder to enhance the strength between the particles, and then combines cold isostatic pressing and vacuum sintering processes, combining pressure forming at low temperature and pressureless sintering at high temperature. Under cold pressure, the powder is initially densified under the action of the binder to produce a green compact with higher density. Vacuum pressureless sintering is then used to complete further densification and homogenization of the target material, ensuring that the target material does not crack, and finally obtaining a high-density chromium diboride target material, thereby overcoming the technical difficulties in the preparation of chromium diboride targets.

[0014] Preferably, the purity of the chromium diboride powder in step (1) is ≥2N5, for example, it can be 2N5, 3N, 3N5, 4N or 5N, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0015] Preferably, the D of the chromium diboride powder in step (1) is 50 The particle size is 0.5-25 μm, for example, 0.5 μm, 1 μm, 5 μm, 10 μm, 15 μm, 20 μm or 25 μm, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0016] Preferably, the binder in step (1) comprises polyvinyl alcohol.

[0017] Preferably, the mass concentration of the binder in step (1) is 3-8%, for example, 3%, 4%, 5%, 6%, 7% or 8%, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0018] Preferably, the rotation speed of the wet ball milling in step (1) is 100-300 rpm, for example, it can be 100 rpm, 150 rpm, 200 rpm, 250 rpm or 300 rpm, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0019] Preferably, the wet ball milling process in step (1) comprises: mixing chromium diboride powder with water for pre-ball milling to obtain chromium diboride slurry, mixing the chromium diboride slurry with a binder for ball milling, and drying after the ball milling.

[0020] In the present invention, a two-stage ball milling method is adopted. By selecting a reasonable gradation of chromium diboride powder, the powder is first mixed with water and ball milled to achieve uniform dispersion of the chromium diboride powder. Then, a binder is added and ball milled to uniformly coat the surface of the chromium diboride powder particles with the binder, thereby achieving uniform bonding between the particles and generating uniform bonding force, which is crucial for stress homogenization in subsequent pressure forming and sintering processes, and ensures that the target material has uniform composition and does not generate cracks during the processing process.

[0021] Preferably, the pre-milling time is 2-4 h, for example, 2 h, 2.5 h, 3 h, 3.5 h or 4 h, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0022] Preferably, the solid-to-liquid ratio of the chromium diboride powder to water is (0.1-10):1 g / mL, for example, 0.1:1 g / mL, 0.5:1 g / mL, 1:1 g / mL, 3:1 g / mL, 5:1 g / mL, 8:1 g / mL or 10:1 g / mL, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0023] Preferably, the amount of the binder used in the chromium diboride slurry is 0.2-1% by mass, for example, 0.2%, 0.4%, 0.5%, 0.6%, 0.8% or 1%, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0024] Preferably, the ball milling time is 10-20 h, for example, 10 h, 12 h, 14 h, 16 h, 18 h or 20 h, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0025] Preferably, the pressure of the cold isostatic pressing in step (2) is 150-300 MPa, for example, it can be 150 MPa, 180 MPa, 200 MPa, 220 MPa, 250 MPa, 280 MPa or 300 MPa, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0026] Preferably, the cold isostatic pressing time in step (2) is 2-5 min, for example, 2 min, 2.5 min, 3 min, 3.5 min, 4 min, 4.5 min or 5 min, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0027] Preferably, the density of the target green body in step (2) is ≥70%, for example, it can be 70%, 72%, 75%, 78%, 80%, 82% or 85%, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0028] Preferably, the vacuum degree of the vacuum sintering in step (3) is 1×10 -4 -3×10 -3 Pa, for example, can be 1×10 - 4 Pa, 5×10 -4 Pa, 1×10 -3 Pa, 1.5×10 -3 Pa, 2×10 -3 Pa, 2.5×10 -3 Pa or 3×10 -3 Pa, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0029] Preferably, the heating rate of the vacuum sintering in step (3) is 0.5-2°C / min, for example, it can be 0.5°C / min, 0.8°C / min, 1°C / min, 1.2°C / min, 1.5°C / min, 1.8°C / min or 2°C / min, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0030] Preferably, the vacuum sintering temperature in step (3) is 1500-1600°C, for example, it can be 1500°C, 1520°C, 1540°C, 1550°C, 1560°C, 1580°C or 1600°C, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0031] Preferably, the holding time of the vacuum sintering in step (3) is 4-6 hours, for example, it can be 4 hours, 4.5 hours, 5 hours, 5.5 hours or 6 hours, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0032] As a preferred technical solution of the preparation method provided by the present invention, the preparation method comprises the following steps:

[0033] (1) The purity ≥ 2N5, D 50Chromium diboride powder with a particle size of 0.5-25 μm is pre-ball-milled with water at a solid-to-liquid ratio of (0.1-10):1 g / mL at a pre-ball-milling speed of 100-300 rpm for 2-4 hours to obtain a chromium diboride slurry. The chromium diboride slurry is mixed with a binder, polyvinyl alcohol, and ball-milled, wherein the mass concentration of the binder is 3-8%, the mass fraction of the binder in the chromium diboride slurry is 0.2-1%, the ball-milling speed is 100-300 rpm, the ball-milling time is 10-20 hours, and the ball-milled powder is dried after the ball-milling is completed.

[0034] (2) placing the ball-milled powder into a rubber sleeve and performing cold isostatic pressing, wherein the pressure of the cold isostatic pressing is 150-300 MPa and the time of the cold isostatic pressing is 2-5 minutes, to obtain a target green body with a density of ≥70%;

[0035] (3) placing the target green body into a vacuum pressureless sintering device for sintering, wherein the sintering process includes: evacuating the device to a vacuum of 1×10 -4 -3×10 -3 Pa, start heating at a heating rate of 0.5-2°C / min, heat to 1500-1600°C and keep warm for 4-6 hours. After sintering, the chromium diboride target is obtained.

[0036] In a second aspect, the present invention provides a chromium diboride target, which is prepared by the preparation method described in the first aspect.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] The preparation method provided by the present invention comprises adding a binder to chromium diboride powder and performing wet ball milling to enhance the strength between particles. A green compact with high density is then produced by cold isostatic pressing. Vacuum pressureless sintering is then used to further densify the target material, ultimately producing a uniform high-density chromium diboride target material with a density of more than 98.0%. DETAILED DESCRIPTION

[0039] The technical solution of the present invention is further illustrated below through specific implementation methods.

[0040] In order to clearly illustrate the technical solution of the present invention, in the specific implementation manner, the brand of polyvinyl alcohol used is PVA-1788.

[0041] Example 1

[0042] This embodiment provides a method for preparing a chromium diboride target, the method comprising the following steps:

[0043] (1) The purity of 2N5, D 50Chromium diboride powder with a particle size of 10 μm and pure water were pre-mixed by ball milling in a ball mill at a solid-liquid ratio of 1:1 g / mL at a speed of 200 rpm for 3 h to obtain a mixed slurry;

[0044] (2) After premixing, a 5% PVA (polyvinyl alcohol) solution was added, with the mass fraction of PVA in the mixed slurry being 0.6%. The mixture was ball milled at a speed of 200 rpm for 15 h. After the ball milling was completed, the mixture was dried to obtain a ball-milled powder.

[0045] (3) placing the ball-milled powder into a rubber sleeve and performing cold isostatic pressing at a pressure of 200 MPa and a holding time of 4 min to obtain a target green body with a density of 80%;

[0046] (4) Place the target green body into a vacuum pressureless sintering furnace and evacuate to 1×10 -3 Pa, start heating, control the heating rate to be 1℃ / min, to 1550℃ and keep warm for 5h, and carry out mechanical processing after sintering to obtain chromium diboride target.

[0047] Example 2

[0048] This embodiment provides a method for preparing a chromium diboride target, the method comprising the following steps:

[0049] (1) The purity of 2N5, D 50 Chromium diboride powder with a particle size of 2 μm and pure water were pre-mixed by ball milling in a ball mill at a solid-liquid ratio of 1:1 g / mL at a speed of 200 rpm for 2 h to obtain a mixed slurry.

[0050] (2) After premixing, a PVA (polyvinyl alcohol) solution with a mass concentration of 8% was added, and the mass fraction of PVA in the mixed slurry was 0.2%. The mixture was ball-milled at a speed of 200 rpm for 10 h. After the ball-milling was completed, the mixture was dried to obtain a ball-milled powder.

[0051] (3) placing the ball-milled powder into a rubber sleeve and performing cold isostatic pressing at a pressure of 150 MPa and a holding time of 5 min to obtain a target green body with a density of 70%;

[0052] (4) Place the target green body into a vacuum pressureless sintering furnace and evacuate to 3×10 -3 Pa, start heating, control the heating rate to 2℃ / min, heat to 1600℃ and keep it for 4h, and perform mechanical processing after sintering to obtain chromium diboride target.

[0053] Example 3

[0054] This embodiment provides a method for preparing a chromium diboride target, the method comprising the following steps:

[0055] (1) The purity of 2N5, D 50 Chromium diboride powder with a particle size of 25 μm and pure water were pre-mixed by ball milling in a ball mill at a solid-liquid ratio of 1:1 g / mL at a speed of 200 rpm for 4 h to obtain a mixed slurry.

[0056] (2) After premixing, a 3% PVA (polyvinyl alcohol) solution was added, with the mass fraction of PVA in the mixed slurry being 1%. The mixture was ball milled at a speed of 200 rpm for 20 h. After the ball milling was completed, the mixture was dried to obtain a ball-milled powder.

[0057] (3) The ball-milled powder is placed in a rubber sleeve and subjected to cold isostatic pressing. The cold isostatic pressing pressure is 300 MPa and the holding time is 2 min to obtain a target green body. The density of the target green body is 85%;

[0058] (4) Place the target green body into a vacuum pressureless sintering furnace and evacuate to 3×10 -3 Pa, start heating, control the heating rate to 0.5℃ / min, heat to 1500℃ and keep it for 6h, and perform mechanical processing after sintering to obtain chromium diboride target.

[0059] Example 4

[0060] This embodiment provides a method for preparing a chromium diboride target. Compared with Example 1, the D of the chromium diboride powder selected in step (1) is 50 The particle size is 40 μm, and the rest is the same as in Example 1.

[0061] Example 5

[0062] This embodiment provides a method for preparing a chromium diboride target. Compared with Example 1, the ball milling premixing in step (1) is not performed, and the rest is the same as Example 1.

[0063] Example 6

[0064] This embodiment provides a method for preparing a chromium diboride target. Compared with Example 1, in step (2), the pressure of the cold isostatic pressing is set to 120 MPa, and the rest is the same as Example 1.

[0065] Example 7

[0066] This embodiment provides a method for preparing a chromium diboride target. Compared with Example 1, in step (2), the pressure of the cold isostatic pressing is set to 320 MPa, and the rest is the same as Example 1.

[0067] Example 8

[0068] This embodiment provides a method for preparing a chromium diboride target. Compared with Example 1, in step (3), the sintering temperature is set to 1400° C., and the rest is the same as Example 1.

[0069] Example 9

[0070] This embodiment provides a method for preparing a chromium diboride target. Compared with Example 1, in step (3), the sintering temperature is set to 1700° C., and the rest is the same as Example 1.

[0071] Example 10

[0072] This embodiment provides a method for preparing a chromium diboride target. Compared with Example 1, in step (3), the heating rate is set to 3°C / min, and the rest is the same as Example 1.

[0073] Comparative Example 1

[0074] This comparative example provides a method for preparing a chromium diboride target. Compared with Example 1, PVA is not added in step (2), and the rest is the same as Example 1.

[0075] Comparative Example 2

[0076] This comparative example provides a method for preparing a chromium diboride target. Compared with Example 1, the ball milling of steps (1) and (2) is not performed. That is, equal amounts of water and a binder are added to the chromium diboride powder and mixed, and then steps (3) and (4) are directly performed. The rest are the same as in Example 1.

[0077] Comparative Example 3

[0078] This comparative example provides a method for preparing a chromium diboride target. Compared with Example 1, the cold isostatic pressing in step (3) is not performed, and the rest is the same as Example 1.

[0079] Comparative Example 4

[0080] This comparative example provides a method for preparing a chromium diboride target. Compared with Example 1, in step (4), no vacuuming is performed, and the rest is the same as Example 1.

[0081] The chromium diboride targets prepared in the examples and comparative examples were sampled at both ends and the midpoint along the length direction to test their density. The three sampling points were marked as A, B, and C, respectively. The density data of the three sampling points illustrate the density and homogenization of the target. The results are listed in Table 1.

[0082] Table 1

[0083]

[0084]

[0085] “ / ” in the table means no data.

[0086] As can be seen from Table 1:

[0087] The preparation method provided by the present invention prepares a chromium diboride target material with uniform composition and high density through a combination of ball milling, cold isostatic pressing and vacuum sintering processes. The density of the target material can especially reach above 98.0%.

[0088] Compared with the results of Example 1, the particle size used in Example 4 is relatively large, resulting in increased porosity, making it difficult to achieve complete densification during the process, and the density is reduced; in Example 5, no ball milling pre-mixing is performed, which easily causes particle agglomeration, is not conducive to densification, and the density is significantly reduced; in Example 6, the cold isostatic pressing pressure is relatively low, the pressure is insufficient, and the density is reduced; in Example 7, when the cold isostatic pressing pressure is too high, the cold pressing pressure is too high, resulting in cracking of the target material, and the target material cannot be used; in Example 8, when the sintering temperature is too low, complete densification cannot be achieved, and the density is reduced; in Example 9, even if the sintering temperature is further increased, the density cannot be further improved, but it is easy to cause the target material to crack; in Example 10, when the heating rate is too high, the target material is subjected to uneven thermal stress, resulting in cracking of the target material.

[0089] In Comparative Example 1, no binder was added, the cold isostatic pressing process could not form the target, and the target material could not be prepared; in Comparative Example 2, the ball milling mixing process was not performed, resulting in uneven powder mixing, color spots after sintering, and the target material could not meet the use requirements; in Comparative Example 3, cold isostatic pressing was not performed, and direct sintering caused the target material to shrink severely and exhibit serious dimensional deformation, making it unusable; in Comparative Example 4, vacuum was not applied and the target material was sintered in normal pressure air, resulting in a target material density of only about 50%, making it completely unusable.

[0090] In summary, the preparation method provided by the present invention adds a binder to the chromium diboride powder for wet ball milling to enhance the strength between the particles, then forms a green body with high density by cold isostatic pressing, and then uses vacuum pressureless sintering to further densify the target material, ultimately producing a uniform high-density chromium diboride target material, with a density of particularly above 98.0%.

[0091] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a chromium diboride target, characterized in that: The preparation method comprises the following steps: (1) wet-milling chromium diboride powder using a binder to obtain ball-milled powder; (2) cold isostatic pressing the ball-milled powder to obtain a target green body; (3) vacuum sintering the target green body to obtain the chromium diboride target.

2. The preparation method according to claim 1, characterized in that The purity of the chromium diboride powder in step (1) is ≥2N5; Preferably, the D of the chromium diboride powder in step (1) is 50 The particle size is 0.5-25μm.

3. The preparation method according to claim 1 or 2, characterized in that The binder in step (1) comprises polyvinyl alcohol; Preferably, the mass concentration of the binder in step (1) is 3-8%.

4. The preparation method according to any one of claims 1 to 3, characterized in that The rotation speed of the wet ball milling in step (1) is 100-300 rpm; Preferably, the wet ball milling process in step (1) comprises: mixing chromium diboride powder with water and performing pre-ball milling to obtain chromium diboride slurry, mixing the chromium diboride slurry with a binder and performing ball milling, and drying after the ball milling is completed; Preferably, the pre-milling time is 2-4 hours; Preferably, the solid-to-liquid ratio of the chromium diboride powder to water is (0.1-10):1 g / mL; Preferably, the amount of the binder used is 0.2-1% by mass of the chromium diboride slurry; Preferably, the ball milling time is 10-20 hours.

5. The preparation method according to any one of claims 1 to 4, characterized in that The pressure of the cold isostatic pressing in step (2) is 150-300 MPa; Preferably, the cold isostatic pressing time in step (2) is 2-5 minutes.

6. The preparation method according to any one of claims 1 to 5, characterized in that The density of the target green body in step (2) is ≥70%.

7. The preparation method according to any one of claims 1 to 6, characterized in that The vacuum degree of the vacuum sintering in step (3) is 1×10 -4 -3×10 -3 Pa; Preferably, the heating rate of the vacuum sintering in step (3) is 0.5-2°C / min.

8. The preparation method according to any one of claims 1 to 7, characterized in that The temperature of the vacuum sintering in step (3) is 1500-1600° C. Preferably, the holding time of the vacuum sintering in step (3) is 4-6 hours.

9. The preparation method according to any one of claims 1 to 8, characterized in that The preparation method comprises the following steps: (1) The purity ≥ 2N5, D 50 Chromium diboride powder with a particle size of 0.5-25 μm is pre-ball-milled with water at a solid-to-liquid ratio of (0.1-10):1 g / mL at a pre-ball-milling speed of 100-300 rpm for 2-4 hours to obtain a chromium diboride slurry. The chromium diboride slurry is mixed with a binder, polyvinyl alcohol, and ball-milled, wherein the mass concentration of the binder is 3-8%, the mass fraction of the binder in the chromium diboride slurry is 0.2-1%, the ball-milling speed is 100-300 rpm, the ball-milling time is 10-20 hours, and the ball-milled powder is dried after the ball-milling is completed. (2) placing the ball-milled powder into a rubber sleeve and performing cold isostatic pressing, wherein the pressure of the cold isostatic pressing is 150-300 MPa and the time of the cold isostatic pressing is 2-5 minutes, to obtain a target green body with a density of ≥70%; (3) placing the target green body into a vacuum pressureless sintering device for sintering, wherein the sintering process includes: evacuating the device to a vacuum of 1×10 -4 -3×10 -3 Pa, start heating at a heating rate of 0.5-2°C / min, heat to 1500-1600°C and keep warm for 4-6 hours. After sintering, the chromium diboride target is obtained.

10. A chromium diboride target, characterized in that: The chromium diboride target is prepared by the preparation method according to any one of claims 1 to 9.

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