A method for preparing high-density medium-entropy carbide ceramic composites by pressureless sintering

Abstract

This invention discloses a method for preparing high-density medium-entropy carbide ceramic composite materials by pressureless sintering, comprising the following steps: (1) mixing and ball milling various metal carbide powders and MoSi2 powder in a solvent, drying the slurry after ball milling, and obtaining a mixed powder after grinding and sieving; (2) pre-pressing the mixed powder into a mold, placing it in a sealed bag, vacuum sealing it, and then placing it in a hydraulic environment for cold isostatic pressing to obtain a ceramic green body; (3) embedding and compacting the ceramic green body with metal W powder, placing the ceramic green body in the center of the metal W powder; (4) sintering the embedded ceramic green body at high temperature without pressure under a flowing argon protective atmosphere, and cooling it with the furnace to obtain a medium-entropy carbide ceramic composite material. The method of this invention can achieve complete densification of medium-entropy carbide ceramic composite materials under pressureless sintering, and the obtained medium-entropy carbide ceramic composite materials have high density as well as excellent mechanical properties and ablation resistance.

Description

Technical Field

[0001] This invention relates to a method for preparing high-density, medium-entropy carbide ceramic composite materials by pressureless sintering. Background Technology

[0002] Medium / high entropy carbide ceramics composed of transition metal carbides are core thermal protection candidates for hypersonic vehicles operating under extreme aerodynamic and thermal loads due to their ultra-high melting point, excellent high-temperature thermal stability, strong chemical inertness, high hardness, and wear resistance. However, the strong covalent bonding and extremely low atomic self-diffusion coefficient of transition metal carbides result in insufficient driving force for the sintering densification of medium / high entropy carbide ceramics, posing a significant technical bottleneck in the preparation of high-density bulk materials.

[0003] Currently, the preparation of high-density medium / high entropy carbide ceramics mainly employs pressure-assisted sintering techniques such as hot pressing (HP) and spark plasma sintering (SPS). For example, medium-entropy carbide ceramics (ZrC) can be prepared using HfC, ZrC, and TiC as raw materials. 1 / 3 Hf 1 / 3Ti 1 / 3 At 1950 °C, after holding at 30 MPa for 1 h, the highest density of the sample can reach 97%; high-entropy carbide ceramics (Ti) were prepared. 0.2 Zr 0.2 Nb 0.2 Hf 0.2 Ta 0.2 While a density of 99.1% can be achieved at 1600 °C, the required sintering pressure is as high as 15 GPa. Although the aforementioned pressure-assisted sintering technology can effectively improve the density of materials, the axial loading method imposes strict limitations on the geometry of the sintered blank, making it difficult to manufacture complex irregular structural components required in the aerospace field and failing to meet the application requirements of near-net-shape integrated components.

[0004] To address the limitations of pressure-assisted sintering (PAS) technology in terms of structural design, pressureless sintering is considered a core technological approach for achieving near-net-shape forming of complex carbide ceramics. However, the densification efficiency of existing traditional pressureless sintering processes is relatively low: when preparing (TiZrHfNbTaMo)C high-entropy carbide ceramics, the bulk density is only 84.4% after holding at 2100 ℃ for 1 h; even when the temperature is raised to 2500 ℃, the density only reaches 97%. Insufficient density significantly degrades the mechanical properties and ablation resistance of medium / high-entropy carbide ceramics, failing to meet the service requirements of thermal protection components; while excessively high sintering temperatures not only significantly increase the temperature resistance requirements and equipment costs of sintering equipment, but also significantly increase production energy consumption, restricting the large-scale engineering application of this type of material. Summary of the Invention

[0005] Purpose of the invention: The purpose of this invention is to provide a method for preparing high-density medium-entropy carbide ceramic composite materials by pressureless sintering. The medium-entropy carbide ceramic composite materials prepared by this method not only have high density (up to 100%), but also excellent mechanical properties and ablation resistance.

[0006] Technical solution: The method for preparing high-density, medium-entropy carbide ceramic composite materials by pressureless sintering according to the present invention includes the following steps:

[0007] (1) Mix and ball mill each metal carbide powder and MoSi2 powder in a solvent. After ball milling, dry the slurry, grind and sieve to obtain mixed powder.

[0008] (2) After the mixed powder is pre-pressed into shape, it is placed in a sealed bag and vacuum sealed. Then it is placed in a hydraulic environment for cold isostatic pressing to obtain a high-density ceramic green body.

[0009] (3) Use metal W powder to embed and compact the ceramic green body. The ceramic green body is placed in the center of the metal W powder, that is, the outer periphery of the ceramic green body is completely covered by metal W powder.

[0010] (4) Under the protective atmosphere of flowing argon, the embedded ceramic green body is subjected to high-temperature pressureless sintering and then cooled in the furnace to obtain a medium-entropy carbide ceramic composite material.

[0011] In step (1), the purity of all metal carbide powders and MoSi2 powders is ≥99.9%, and the particle size is 1~3 μm. The molar ratio of each metal carbide is 1:1:1. The amount of MoSi2 powder added is 15~30 vol.% of the total volume of the metal carbide powders. The solvent is anhydrous ethanol, and the mass ratio of powder to solvent is 1:1. During ball milling, the rotation speed is not less than 300~450 rpm, and the ball milling time is 8~12 h. After ball milling, the slurry is dried in a vacuum drying oven at 80~100 ℃ for 12~24 h, and then sieved through a 200-mesh stainless steel sieve.

[0012] In step (2), the pre-pressing pressure is 10~20 MPa and the holding time is 1~5 min. The cold isostatic pressing pressure is 150~250 MPa and the holding time is 5~10 min.

[0013] In step (3), the purity of the metal W powder is greater than 99.9% and the particle size is 200 mesh.

[0014] In step (4), during the sintering process, the heating rate is 10~20 ℃ / min, the sintering temperature is 2000~2100 ℃, and the holding time is 2~4 h.

[0015] The W powder encapsulating the ceramic green body plays a dual role at 2100 ℃, stabilizing the ceramic matrix structure (W powder encapsulation provides uniform macroscopic constraint, effectively suppressing gravitational deformation and cracking of the ceramic matrix during ultra-high temperature sintering) and active infiltration: on the one hand, it acts as a physical barrier to inhibit the excessive volatilization of internal additives (MoSi2); on the other hand, driven by the transient liquid phase of MoSi2, the W powder efficiently infiltrates into the ceramic matrix along the pores. This invention, through in-situ infiltration of W powder, is equivalent to introducing a discretely distributed tough W phase into the hard, medium-entropy carbide ceramic matrix. This microstructure overcomes the inherent brittleness of carbide ceramics. The W phase, acting as a ductile ligand, triggers frequent crack deflection, bridging, and crack tip passivation mechanisms along the crack propagation path. This enables the medium-entropy carbide ceramic composite to maintain high hardness while possessing good toughness, and also significantly improves its ablation resistance. The medium-entropy carbide ceramic composite ultimately obtained by this invention achieves a relative density of 100%, an open porosity of 0%, a Vickers hardness of 26 GPa, and a fracture toughness of 3.4 MPa·m. 1 / 2 At a heat flux density of 44 MW·m -2 After 120 s of high-energy laser ablation, the linear ablation rate in the central region was only 3.48 μm·s. -1 It not only achieves a balance between high hardness and high toughness, but also has excellent resistance to ablation.

[0016] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: The method of the present invention can achieve complete densification of medium-entropy carbide ceramic composite materials under pressureless sintering. The medium-entropy carbide ceramic composite materials obtained have high density as well as excellent mechanical properties and ablation resistance. Attached Figure Description

[0017] Figure 1 The images show SEM images of the surface of the medium-entropy carbide ceramic composites obtained in Examples 1-4 and the medium-entropy carbide ceramics and medium-entropy carbide ceramic composites obtained in Comparative Examples 1-2.

[0018] Figure 2 The Vickers hardness of the medium-entropy carbide ceramic composites obtained in Examples 1-4 and the medium-entropy carbide ceramics and medium-entropy carbide ceramic composites obtained in Comparative Examples 1-2 is measured.

[0019] Figure 3 This is a backscattered image of the surface of the medium-entropy carbide ceramic composite material obtained in Example 2;

[0020] Figure 4 Here is a SEM image of the surface of the medium-entropy carbide ceramic composite material obtained in Comparative Example 3;

[0021] Figure 5The images show the macroscopic morphology of the medium-entropy carbide ceramic composite material obtained in Example 2 and the medium-entropy carbide ceramic and medium-entropy carbide ceramic composite material obtained in Comparative Examples 1 and 2 after ablation. Detailed Implementation

[0022] Example 1

[0023] The preparation method of the entropy carbide ceramic composite material in this invention includes the following steps:

[0024] (1) After mixing HfC, TaC and TiC powders in a molar ratio of 1:1:1, mix them with an appropriate amount of MoSi2 powder. The volume ratio of the mixed carbide to MoSi2 is 17:3, and the total weight of the powder is about 30 g.

[0025] (2) The powder was loaded into a tungsten carbide ball mill jar, and 30 g of anhydrous ethanol and 150 g of cemented carbide balls were added. The mixture was then ball milled at 300 rpm for 8 h.

[0026] (3) The ball-milled slurry was dried in a vacuum drying oven at 80 °C for 12 h, and then manually ground and passed through a 200-mesh stainless steel sieve;

[0027] (4) The sieved powder is loaded into the mold, and pre-pressed into a green blank with a diameter of 10 mm by uniaxial compression. The green blank is then placed into a plastic bag, vacuum sealed and tightly fitted. The plastic bag containing the green blank is placed into a cold isostatic pressing chamber filled with hydraulic oil and held under pressure at 250 MPa for 5 min to obtain a high-density molded green blank.

[0028] (5) Place the shaped green body into a graphite crucible, pour in metal W powder to bury and compact it, so that the green body is in the center of the powder and the outer periphery of the shaped green body is completely covered by metal W powder.

[0029] (6) The crucible was placed in a tungsten filament furnace and heated to 2100 ℃ at a rate of 10 ℃ / min under flowing argon gas. After holding at this temperature for 2 h, the crucible was cooled to room temperature with the furnace to obtain a medium-entropy carbide ceramic composite material with the chemical formula (Hf). 1 / 3 Ta 1 / 3 Ti 1 / 3 C-15 vol.% MoSi2-W.

[0030] Example 2

[0031] The preparation method of the entropy carbide ceramic composite material in this invention includes the following steps:

[0032] (1) After mixing HfC, TaC and TiC powders in a molar ratio of 1:1:1, mix them with an appropriate amount of MoSi2 powder. The volume ratio of the mixed carbide to MoSi2 is 4:1, and the total weight of the powder is about 30 g.

[0033] (2) The powder was loaded into a tungsten carbide ball mill jar, and 30 g of anhydrous ethanol and 150 g of cemented carbide balls were added. The mixture was then ball milled at 300 rpm for 8 h.

[0034] (3) The ball-milled slurry was dried in a vacuum drying oven at 80 °C for 12 h, and then manually ground and passed through a 200-mesh stainless steel sieve;

[0035] (4) The sieved powder is loaded into the mold, and pre-pressed into a green blank with a diameter of 10 mm by uniaxial compression. The green blank is then placed into a plastic bag, vacuum sealed and tightly fitted. The plastic bag containing the green blank is placed into a cold isostatic pressing chamber filled with hydraulic oil and held under pressure at 250 MPa for 5 min to obtain a high-density molded green blank.

[0036] (5) Place the shaped green body into a graphite crucible, pour in metal W powder to bury and compact it, so that the green body is in the center of the powder and the outer periphery of the shaped green body is completely covered by metal W powder.

[0037] (6) The crucible was placed in a tungsten filament furnace and heated to 2100 ℃ at a rate of 10 ℃ / min under flowing argon gas. After holding at this temperature for 2 h, the crucible was cooled to room temperature with the furnace to obtain a medium-entropy carbide ceramic composite material with the chemical formula (Hf). 1 / 3 Ta 1 / 3 Ti 1 / 3 C-20 vol.% MoSi2-W.

[0038] Example 3

[0039] The preparation method of the entropy carbide ceramic composite material in this invention includes the following steps:

[0040] (1) After mixing HfC, TaC and TiC powders in a molar ratio of 1:1:1, mix them with an appropriate amount of MoSi2 powder. The volume ratio of the mixed carbide to MoSi2 is 3:1, and the total weight of the powder is about 30 g.

[0041] (2) The powder was loaded into a tungsten carbide ball mill jar, and 30 g of anhydrous ethanol and 150 g of cemented carbide balls were added. The mixture was then ball milled at 300 rpm for 8 h.

[0042] (3) The ball-milled slurry was dried in a vacuum drying oven at 80 °C for 12 h, and then manually ground and passed through a 200-mesh stainless steel sieve;

[0043] (4) The sieved powder is loaded into the mold, and pre-pressed into a green blank with a diameter of 10 mm by uniaxial compression. The green blank is then placed into a plastic bag, vacuum sealed and tightly fitted. The plastic bag containing the green blank is placed into a cold isostatic pressing chamber filled with hydraulic oil and held under pressure at 250 MPa for 5 min to obtain a high-density molded green blank.

[0044] (5) Place the shaped green body into a graphite crucible, pour in metal W powder to bury and compact it, so that the green body is in the center of the powder and the outer periphery of the shaped green body is completely covered by metal W powder.

[0045] (6) The crucible was placed in a tungsten filament furnace and heated to 2100 ℃ at a rate of 10 ℃ / min under flowing argon gas. After holding at this temperature for 2 h, the crucible was cooled to room temperature with the furnace to obtain a medium-entropy carbide ceramic composite material with the chemical formula (Hf). 1 / 3 Ta 1 / 3 Ti 1 / 3 C-25 vol.% MoSi2-W.

[0046] Example 4

[0047] The preparation method of the entropy carbide ceramic composite material in this invention includes the following steps:

[0048] (1) After mixing HfC, TaC and TiC powders in a molar ratio of 1:1:1, mix them with an appropriate amount of MoSi2 powder. The volume ratio of the mixed carbide to MoSi2 is 7:3, and the total weight of the powder is about 30 g.

[0049] (2) The powder was loaded into a tungsten carbide ball mill jar, and 30 g of anhydrous ethanol and 150 g of cemented carbide balls were added. The mixture was then ball milled at 300 rpm for 8 h.

[0050] (3) The ball-milled slurry was dried in a vacuum drying oven at 80 °C for 12 h, and then manually ground and passed through a 200-mesh stainless steel sieve;

[0051] (4) The sieved powder is loaded into the mold, and pre-pressed into a green blank with a diameter of 10 mm by uniaxial compression. The green blank is then placed into a plastic bag, vacuum sealed and tightly fitted. The plastic bag containing the green blank is placed into a cold isostatic pressing chamber filled with hydraulic oil and held under pressure at 250 MPa for 5 min to obtain a high-density molded green blank.

[0052] (5) Place the shaped green body into a graphite crucible, pour in metal W powder to bury and compact it, so that the green body is in the center of the powder and the outer periphery of the shaped green body is completely covered by metal W powder.

[0053] (6) The crucible was placed in a tungsten filament furnace and heated to 2100 ℃ at a rate of 10 ℃ / min under flowing argon gas. After holding at this temperature for 2 h, the crucible was cooled to room temperature with the furnace to obtain a medium-entropy carbide ceramic composite material with the chemical formula (Hf). 1 / 3 Ta 1 / 3 Ti 1 / 3 C-30 vol.% MoSi2-W.

[0054] Comparative Example 1

[0055] A method for preparing a medium-entropy carbide ceramic material includes the following steps:

[0056] (1) After mixing HfC, TaC and TiC powders in a molar ratio of 1:1:1, the total weight of the powder is about 30 g;

[0057] (2) The powder was loaded into a tungsten carbide ball mill jar, and 30 g of anhydrous ethanol and 150 g of cemented carbide balls were added. The mixture was then ball milled at 300 rpm for 8 h.

[0058] (3) The ball-milled slurry was dried in a vacuum drying oven at 80 °C for 12 h, and then manually ground and passed through a 200-mesh stainless steel sieve;

[0059] (4) The sieved powder is loaded into the mold, and pre-pressed into a green blank with a diameter of 10 mm by uniaxial compression. The green blank is then placed into a plastic bag, vacuum sealed and tightly fitted. The plastic bag containing the green blank is placed into a cold isostatic pressing chamber filled with hydraulic oil and held under pressure at 250 MPa for 5 min to obtain a high-density molded green blank.

[0060] (5) Place the shaped green body into a graphite crucible, pour in metal W powder to bury and compact it, so that the green body is in the center of the powder and the outer periphery of the shaped green body is completely covered by metal W powder.

[0061] (6) The crucible was placed in a tungsten filament furnace and heated to 2100 ℃ at a rate of 10 ℃ / min under flowing argon gas. After holding at this temperature for 2 h, the furnace was cooled to room temperature to obtain a medium-entropy carbide ceramic material with the chemical formula (Hf). 1 / 3 Ta 1 / 3 Ti 1 / 3 C.

[0062] Comparative Example 2

[0063] A method for preparing a medium-entropy carbide ceramic composite material includes the following steps:

[0064] (1) After mixing HfC, TaC and TiC powders in a molar ratio of 1:1:1, mix them with an appropriate amount of MoSi2 powder. The volume ratio of the mixed carbide to MoSi2 is 4:1, and the total weight of the powder is about 30 g.

[0065] (2) The powder was loaded into a tungsten carbide ball mill jar, and 30 g of anhydrous ethanol and 150 g of cemented carbide balls were added. The mixture was then ball milled at 300 rpm for 8 h.

[0066] (3) The ball-milled slurry was dried in a vacuum drying oven at 80 °C for 12 h, and then manually ground and passed through a 200-mesh stainless steel sieve;

[0067] (4) The sieved powder is loaded into the mold, and pre-pressed into a green blank with a diameter of 10 mm by uniaxial compression. The green blank is then placed into a plastic bag, vacuum sealed and tightly fitted. The plastic bag containing the green blank is placed into a cold isostatic pressing chamber filled with hydraulic oil and held under pressure at 250 MPa for 5 min to obtain a high-density molded green blank.

[0068] (5) Place the formed green body into a graphite crucible, then place the crucible in a tungsten wire furnace, and heat it to 2100 ℃ at 10 ℃ / min under flowing argon. After holding at this temperature for 2 h, cool it to room temperature with the furnace to obtain a medium-entropy carbide ceramic composite material with the chemical formula (Hf 1 / 3 Ta 1 / 3 Ti 1 / 3 C-20 vol.% MoSi2.

[0069] Comparative Example 3

[0070] A method for preparing a medium-entropy carbide ceramic composite material includes the following steps:

[0071] (1) After mixing HfC, TaC and TiC powders in a molar ratio of 1:1:1, mix them with an appropriate amount of MoSi2 powder. The volume ratio of the mixed carbide to MoSi2 is 4:1, and the total weight of the powder is about 30 g.

[0072] (2) The powder was loaded into a tungsten carbide ball mill jar, and 30 g of anhydrous ethanol and 150 g of cemented carbide balls were added. The mixture was then ball milled at 300 rpm for 8 h.

[0073] (3) The ball-milled slurry was dried in a vacuum drying oven at 80 °C for 12 h, and then manually ground and passed through a 200-mesh stainless steel sieve;

[0074] (4) The sieved powder is loaded into the mold, and pre-pressed into a green blank with a diameter of 10 mm by uniaxial compression. The green blank is then placed into a plastic bag, vacuum sealed and tightly fitted. The plastic bag containing the green blank is placed into a cold isostatic pressing chamber filled with hydraulic oil and held under pressure at 250 MPa for 5 min to obtain a high-density molded green blank.

[0075] (5) Place the shaped green body into a graphite crucible, pour in metal W powder to bury and compact it, so that the green body is in the center of the powder and the outer periphery of the shaped green body is completely covered by metal W powder.

[0076] (6) The crucible was placed in a tungsten wire furnace and heated to 2000 ℃ at a rate of 10 ℃ / min under flowing argon gas. After holding at this temperature for 2 h, the furnace was cooled to room temperature to obtain a medium-entropy carbide ceramic composite material with the chemical formula (Hf). 1 / 3 Ta 1 / 3 Ti 1 / 3C-20 vol.% MoSi2.

[0077] from Figure 1 As can be seen from (a) to (d), the addition of MoSi2 and the W powder embedding treatment improve the medium entropy carbide ceramic (Hf) 1 / 3Ta 1 / 3 Ti 1 / 3 C achieved a high degree of densification; in Examples 1-4, the density reached 100% due to the infiltration of W powder into the exterior of the ceramic green body. Figure 1 (a) is a surface morphology diagram of the composite material obtained in Example 1 with an addition amount of 15 vol.% of MoSi2 powder. It can be seen that (Hf 1 / 3 Ta 1 / 3 Ti 1 / 3 The surface of the C-15 vol.% MoSi2-W sample is relatively dense, with a small number of defects such as pores and pits, indicating a high degree of densification. Figure 1 (b) is a surface morphology diagram of the composite material obtained in Example 2 with an addition amount of 20 vol.% of MoSi2 powder. It can be seen that (Hf 1 / 3 Ta 1 / 3 Ti 1 / 3 The C-20 vol.% MoSi2-W sample has a dense surface without defects such as pores or cracks, and its degree of densification is extremely high. Figure 1 (c) is a surface morphology diagram of the composite material obtained in Example 3 with a MoSi2 powder addition amount of 25 vol.%. It can be seen that (Hf 1 / 3 Ta 1 / 3 Ti 1 / 3 The C-25 vol.% MoSi2-W sample has a dense surface with only a few shallow pits, indicating a high degree of densification. Figure 1 (d) is a surface morphology diagram of the composite material obtained in Example 4 with an addition amount of 30 vol.% of MoSi2 powder. It can be seen that (Hf 1 / 3 Ta 1 / 3 Ti 1 / 3 The C-30 vol.% MoSi2-W sample had a relatively dense surface, but the number of pores and pits began to increase. This is because excessive MoSi2 formed more liquid phase during sintering, and the loss of these liquid phases would increase the internal defects of the material. Figure 1 (e) is the medium-entropy carbide ceramic sample without MoSi2 in Comparative Example 1. It can be seen that there are many pores on the sample surface, which is caused by the inability of gas inside the bulk to escape during the sintering process. This has a significant impact on the density, which is only 93%. This shows that without sintering aids, densification cannot be achieved by relying solely on externally embedded W powder. Figure 1(f) shows the surface of the sample in Comparative Example 2 with 20 vol.% MoSi2 powder added but without W powder embedding treatment. Local surface densification can be seen, but there are many large pores due to excessive liquid phase loss, and the sample density is only 90%. This indicates that without external W powder embedding treatment, liquid phase loss will actually reduce the density of the ceramic.

[0078] from Figure 2 As can be seen, the hardness of the materials in Examples 1-4 is significantly higher than that in Comparative Examples 1 and 2, that is, the addition of MoSi2 and the W powder embedding treatment significantly improved the hardness (Hf). 1 / 3 Ta 1 / 3 Ti 1 / 3 The mechanical properties of C were analyzed. When the addition amount was 20 vol.%, the Vickers hardness reached 26 GPa. The Vickers hardness of Comparative Example 1 and Comparative Example 2 under the same load was only 14 GPa and 18 GPa, respectively. The fracture toughness of Comparative Example 1 and Comparative Example 2 could not be accurately measured due to severe indentation breakage, indicating that the materials of Comparative Example 1 and Comparative Example 2 are relatively brittle.

[0079] Figure 3 In (a) and (b), we can see that the material contains three phases: light gray, dark black (dark gray), and white, which are respectively (Hf 1 / 3 Ta 1 / 3 Ti 1 / 3 The medium-entropy carbide ceramic composite material consists of a C matrix phase, a Mo-Si phase, and a W metallic phase. The formation of this three-phase structure is determined by the preparation process of this invention. This structure endows the medium-entropy carbide ceramic composite material with excellent properties, namely 100% density and zero open porosity, a Vickers hardness of 26 GPa, and a hardness of 3.4 MPa·m. 1 / 2 Fracture toughness.

[0080] Figure 4 The SEM image and corresponding EDS spectrum of Comparative Example 3 surface reveal numerous pores and a loose structure within the ceramic, with no detected W element. This indicates that when the sintering temperature is too low, the added MoSi2 cannot form a liquid phase to assist sintering, nor can it transport external W powder into the green body, thus failing to achieve a highly dense structure and the formation of an internal W metallic phase.

[0081] Figure 5 Example 2, Comparative Example 1, and Comparative Example 2 were compared at a heat flux density of 44 MW·m. -2 Macroscopic morphology image after high-energy laser ablation for 120 seconds. From Figure 5 As can be seen, in Example 2, the block remained intact without cracks after ablation, the center of the ablation pit was relatively flat, and the linear ablation rate was only 3.48 μm·s. -1Comparative Example 1, after ablation under the same conditions, showed that the block cracked due to extreme thermal stress, indicating that the material has poor resistance to laser ablation. Comparative Example 2, after ablation under the same conditions, showed severe depression at the center of the ablation pit and cracks appearing at the edge of the block, with a linear ablation rate of 7.21 μm·s. -1 This indicates that its resistance to laser ablation is poor.

Claims

1. A method for preparing high-density, medium-entropy carbide ceramic composite materials by pressureless sintering, characterized in that, Includes the following steps: (1) Mix and ball mill each metal carbide powder and MoSi2 powder in a solvent. After ball milling, dry the slurry, grind and sieve to obtain mixed powder. (2) After the mixed powder is pre-pressed into shape, it is placed in a sealed bag and vacuum sealed. Then it is placed in a hydraulic environment for cold isostatic pressing to obtain ceramic green body; (3) The ceramic green body is embedded and compacted with metal W powder, and the ceramic green body is placed in the center of the metal W powder; (4) Under the protective atmosphere of flowing argon, the embedded ceramic green body is subjected to high-temperature pressureless sintering and then cooled in the furnace to obtain a medium-entropy carbide ceramic composite material.

2. The method for preparing high-density, medium-entropy carbide ceramic composite materials by pressureless sintering according to claim 1, characterized in that: In step (1), all metal carbide powders and MoSi2 powders have a purity of ≥99.9% and a particle size of 1~3μm.

3. The method for preparing high-density, medium-entropy carbide ceramic composite materials by pressureless sintering according to claim 2, characterized in that: The metal carbides are mixed in equimolar amounts; the amount of MoSi2 powder added is 15~30 vol.% of the total volume of the metal carbide powder.

4. The method for preparing high-density, medium-entropy carbide ceramic composite materials by pressureless sintering according to claim 1, characterized in that: In step (1), the solvent is anhydrous ethanol, and the powder and solvent are mixed in equal mass.

5. The method for preparing high-density, medium-entropy carbide ceramic composite materials by pressureless sintering according to claim 1, characterized in that: In step (1), during the ball milling process, the rotation speed is not less than 300~450 rpm, and the ball milling time is 8~12h.

6. The method for preparing high-density, medium-entropy carbide ceramic composite materials by pressureless sintering according to claim 1, characterized in that: In step (1), the ball-milled slurry is dried in a vacuum drying oven at 80~100℃ for 12~24h and then sieved through a 200-mesh stainless steel sieve.

7. The method for preparing high-density, medium-entropy carbide ceramic composite materials by pressureless sintering according to claim 1, characterized in that: In step (2), the pre-compression pressure is 10~20MPa and the holding time is 1~5min.

8. The method for preparing high-density, medium-entropy carbide ceramic composite materials by pressureless sintering according to claim 1, characterized in that: In step (2), the pressure of cold isostatic pressing is 150~250MPa, and the holding time is 5~10min.

9. The method for preparing high-density, medium-entropy carbide ceramic composite materials by pressureless sintering according to claim 1, characterized in that: In step (3), the purity of the metal W powder is greater than 99.9% and the particle size is 200 mesh.

10. The method for preparing high-density, medium-entropy carbide ceramic composite materials by pressureless sintering according to claim 1, characterized in that: In step (4), during the sintering process, the heating rate is 10~20℃ / min, the sintering temperature is 2000~2100℃, and the holding time is 2~4h.

Images