A superhard, fine-grained core-shell structured TiB2-TiC-W composite ceramic, its preparation method, and its applications.

Abstract

The application belongs to the technical field of ceramics, and discloses a superhard fine-grain core-shell structure TiB2-TiC-W composite ceramic and a preparation method and application thereof; in the fine-grain core-shell structure TiB2-TiC-W ceramic, the core is a TiB2 and TiC matrix, and the shell is a (Ti, W)B2 solid solution and a (Ti, W)C solid solution. The composite ceramic is obtained by ball milling and mixing TiB2 powder, TiC powder, W powder and Al2O3 powder to obtain a mixed powder; under vacuum conditions, the mixed powder is subjected to an axial pressure of 30-35 MPa, and is sintered by discharge plasma at a temperature of 1800-1900 DEG C. The superhard fine-grain core-shell structure TiB2-TiC-W composite ceramic has high hardness, high toughness and high wear resistance, and can be applied in the fields of wear-resistant parts and ceramic cutters.

Description

Technical Field

[0001] This invention belongs to the field of structural ceramics technology, specifically relating to an ultrahard, fine-grained core-shell structure TiB2-TiC-W composite ceramic, its preparation method, and its application. Background Technology

[0002] TiB2 ceramics, a transition metal boride, are high-performance, ultra-hard ceramic materials that possess excellent thermal conductivity, chemical stability, wear resistance, high melting point, and high hardness. They hold great promise for applications in cutting tools, high-temperature coatings, high-temperature structural components, and armor protection materials. However, the sintering performance of pure TiB2 ceramics is poor, and high-density pure TiB2 ceramics are difficult to obtain using traditional sintering methods, limiting their practical applications. To improve the sintering performance of TiB2-based ceramics, the addition of metal sintering aids (Ni, Co, Mo, etc.) and second ceramic phases (B4C, Al2O3, etc.) is a common method. Obtaining almost completely densified ceramics requires relatively stringent process conditions, such as very high sintering temperatures and long sintering times. Low-melting-point metals such as Ni can also cause abnormal grain growth, reducing ceramic properties and failing to achieve complete densification. Further improving the density of TiB2-based ceramics is key to enhancing their hardness, toughness, and wear resistance. Summary of the Invention

[0003] To address the shortcomings of the existing technology, the primary objective of this invention is to provide an ultra-hard, fine-grained core-shell structured TiB2-TiC-W composite ceramic. In this composite ceramic, the core is a TiB2 and TiC matrix, and the shell is a (Ti,W)B2 solid solution and a (Ti,W)C solid solution, exhibiting high hardness, high toughness, and high wear resistance.

[0004] Another objective of this invention is to provide a method for preparing the above-mentioned ultrahard, fine-grained core-shell structured TiB2-TiC-W composite ceramic.

[0005] Another objective of this invention is to provide an application of the above-mentioned ultrahard, fine-grained core-shell structured TiB2-TiC-W composite ceramic.

[0006] The objective of this invention is achieved through the following technical solution: A superhard, fine-grained core-shell structured TiB2-TiC-W composite ceramic has a core of TiB2 and TiC matrix, and a shell of (Ti,W)B2 solid solution and (Ti,W)C solid solution. This composite ceramic is prepared by ball milling TiB2 powder, W powder, TiC powder and Al2O3 powder, drying and sieving to obtain a mixed powder; under vacuum conditions, the mixed powder is subjected to an axial pressure of 35~40MPa and sintered by spark plasma at 1800~1900℃.

[0007] Preferably, the TiB2 powder has a particle size of 1~3μm and a purity of 99wt% or higher; the TiC powder has a particle size of 500nm and a purity of 99wt% or higher; the W powder has a particle size of 0.4~1μm and a purity of 99wt% or higher; and the Al2O3 powder has a particle size of 500nm and a purity of 99wt% or higher.

[0008] Preferably, the mass ratio of TiB2 powder, TiC powder and W powder is (6~8.5):(1.2~3):(0.3~1), and the Al atoms in the Al2O3 powder are 0.1~0.5 at of the total atoms in TiB2, TiC and W.

[0009] Preferably, the sieve has a pore size of 100-200 mesh, and the composite ceramic has a grain size of 1-3 μm.

[0010] Preferably, the TiB2-W-TiC composite ceramic has a density of 99.7% or higher, a hardness of 27.2~29.5 GPa, and a fracture toughness of 4.71~5.67 MPa·m. 1 / 2 .

[0011] The preparation method of the ultrahard, fine-grained core-shell structured TiB2-TiC-W composite ceramic includes the following specific steps: S1. Add TiB2 powder, TiC powder, W powder and Al2O3 powder to ethanol and Si3N4 balls for ball milling and mixing, dry and sieve to obtain mixed powder; S2. The mixed powder is loaded into a graphite mold, and under vacuum conditions, an axial pressure of 30~35MPa is applied. The temperature is raised to 1800~1900℃ and then sintered by spark plasma to obtain an ultra-hard TiB2-TiC-W composite ceramic with a fine-grained core-shell structure.

[0012] Preferably, the heating rate in step S2 is 80~120℃ / min, and the discharge plasma sintering time is 10~15min.

[0013] The application of the ultrahard, fine-grained core-shell structured TiB2-TiC-W composite ceramic in the field of wear-resistant parts or cutting tools.

[0014] Compared with the prior art, the present invention has the following beneficial effects: 1. The ultrahard, fine-grained core-shell structured TiB2-TiC-W composite ceramic of this invention has a core of TiB2 and TiC matrix, and a shell of (Ti,W)B2 solid solution and (Ti,W)C solid solution. The grain size of the composite ceramic remains essentially unchanged compared to the original powder. The solid solution in the shell structure and the introduction of Al elements refine the grain size, resulting in higher density, hardness, and fracture toughness compared to traditional TiB2-based ceramics.

[0015] 2. The ultra-hard, fine-grained core-shell structured TiB2-TiC-W composite ceramic of the present invention has better wear resistance than traditional low-melting-point sintering aids, enhances the cutting performance of TiB2 tools, and can be applied in the field of cutting tools and wear-resistant parts, for cutting stone, steel, non-ferrous metals, aluminum alloys, high-temperature alloys, etc. Attached Figure Description

[0016] Figure 1 SEM images and EDS images of the ultrahard, fine-grained core-shell structured TiB2-TiC-W composite ceramic of Example 1. Figure 2 TiB2-silicon carbide whiskers (SiC) for Comparative Example 1 w SEM images of the microstructure of the W-C composite ceramic; Figure 3 The image shows the microstructure of the TiB2-TiC-Ni composite ceramic in Comparative Example 2 using SEM. Detailed Implementation

[0017] The present invention will be further described in detail below with reference to embodiments, but the embodiments of the present invention are not limited thereto. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in this technical field.

[0018] Example 1

[0019] 1. Mix 84 wt% TiB2 powder (particle size 1.5 μm), 12 wt% TiC powder (particle size 500 nm), 4 wt% W powder (particle size 400 nm) and Al2O3 (the Al atoms in the Al2O3 powder are 0.2 at% of the total atoms in TiB2, TiC and W) in a nylon ball mill jar, add ethanol and Si3N4 balls as the ball milling medium, the ball-to-particle mass ratio is 4:1, the ball milling time is 24 h, the rotation speed is 300 r / min, after ball milling, rotary evaporation drying, and passing through a 100 mesh sieve to obtain mixed powder; 2. The mixed powder was placed in a graphite mold and placed under vacuum conditions. An axial pressure of 35 MPa was applied, and the temperature was raised to 1850 °C at a rate of 100 °C / min. The mixture was then subjected to spark plasma sintering and held at that temperature for 10 min to obtain an ultra-hard TiB2-TiC-W composite ceramic with a fine-grained core-shell structure.

[0020] The relative density of the ceramic was measured using Archimedes' displacement method. Hardness and fracture toughness were measured using a Vickers hardness tester (HVS-302C / LCD, Shanghai Taiming Optical Instrument Co., Ltd.). Hardness was achieved by applying a load of 1.96 N for 10 seconds, and toughness by applying a load of 98 N for 10 seconds. The ultrahard, fine-grained core-shell structure TiB2-TiC-W composite ceramic of this embodiment has a density of 99.8%, a hardness of 28.99 GPa, and a fracture toughness of 4.71 MPa·m. 1 / 2 . Figure 1 The images show SEM images and EDS diagrams of the ultrahard, fine-grained core-shell structured TiB2-TiC-W composite ceramic from Example 1. Figure 1 It can be seen that the black phase wrapped by the gray phase is the TiB2 matrix, and the gray phase is the (Ti,W)B2 solid solution formed by the diffusion of W element, which wraps the TiB2 matrix in a ring shape. From the enrichment distribution of C and W, it can also be seen that a small amount of TiC as the matrix and white (Ti,W)C solid solution as the shell is formed, forming a "core-shell" structure. The shell-shaped solid solution and the introduction of trace Al element play a role in refining the grain size. The grain size of this composite ceramic is 1.56±0.32μm, which is almost no growth compared with the original TiB2 powder (1~3μm).

[0021] Example 2

[0022] 1. 75 wt% TiB2 powder (particle size 1.5 μm), 20 wt% TiC powder (particle size 500 nm), 5 wt% W powder (particle size 400 nm) and Al2O3 (the Al atoms in the Al2O3 powder are 0.3 at% of the total atoms in TiB2, TiC and W) were mixed and placed in a nylon ball mill jar. Ethanol and Si3N4 balls were added as the ball milling media. The ball-to-particle mass ratio was 4:1. The ball milling time was 24 h and the rotation speed was 300 r / min. After ball milling, rotary evaporation and drying, the mixture was passed through a 100-mesh sieve to obtain the mixed powder. 2. The mixed powder was placed in a graphite mold and placed under vacuum. An axial pressure of 35 MPa was applied, and the temperature was raised to 1800 °C at a rate of 100 °C / min. The mixture was then subjected to spark plasma sintering and held at that temperature for 10 min to obtain an ultra-hard TiB2-TiC-W composite ceramic with a fine-grained core-shell structure.

[0023] The ultrahard, fine-grained core-shell structured TiB2-TiC-W composite ceramic of this embodiment has a density of 99.8%, a hardness of 27.9 GPa, and a fracture toughness of 5.32 MPa·m. 1 / 2 The grain size is 1.5±0.3μm.

[0024] Example 3

[0025] 1. Mix 65wt% TiB2 powder (particle size 1.5μm), 30wt% TiC powder (particle size 500nm), 5wt% W powder (particle size 400nm) and Al2O3 (the Al atoms in the Al2O3 powder are 0.3at% of the total atoms in TiB2, TiC and W) in a nylon ball mill jar, add ethanol and Si3N4 balls as the ball milling media, the ball-to-particle mass ratio is 4:1, the ball milling time is 24h, the rotation speed is 300r / min, after ball milling, rotary evaporation drying, and passing through a 100-mesh sieve to obtain mixed powder; 2. The mixed powder was placed in a graphite mold and placed under vacuum. An axial pressure of 35 MPa was applied, and the temperature was raised to 1800 °C at a rate of 100 °C / min. The mixture was then subjected to spark plasma sintering and held at that temperature for 10 min to obtain an ultra-hard TiB2-TiC-W composite ceramic with a fine-grained core-shell structure.

[0026] The ultrahard, fine-grained core-shell structured TiB2-TiC-W composite ceramic of this embodiment has a density of 99.8%, a hardness of 27.2 GPa, and a fracture toughness of 5.67 MPa·m. 1 / 2 The grain size is 1.45±0.41μm.

[0027] Comparative Example 1 1. Mix 84 wt% TiB2 powder (particle size 1.5 μm) and 12 wt% silicon carbide whiskers (SiC). w Long rod-shaped powder (length to diameter ratio 5:1, width 500nm) and 4wt% W powder (particle size 400nm) were mixed and placed in a nylon ball mill jar. Ethanol and Si3N4 balls were added as the ball milling media. The ball-to-material mass ratio was 4:1. The ball milling time was 24h and the rotation speed was 300r / min. After ball milling, rotary evaporation and drying, the mixture was passed through a 100-mesh sieve to obtain the mixed powder. 2. The mixed powder was placed in a graphite mold and placed under vacuum. An axial pressure of 35 MPa was applied, and the temperature was increased to 1850 °C at a rate of 100 °C / min. The mixture was then subjected to spark plasma sintering and held at that temperature for 10 min to obtain TiB2-SiC. w -W composite ceramics.

[0028] Figure 2 TiB2-SiC for Comparative Example 1 w SEM images of the microstructure of -W composite ceramics. Figure 2 It can be seen that the added SiC w The TiB2-SiC has undergone high-temperature extrusion deformation, resulting in irregular grains that have changed from rod-shaped grains to irregular grains with a grain size of 2.13 ± 0.82 μm. w The density of the -W composite ceramic is 99.1%, SiC w The introduction of [a substance] reduced its hardness to 25.34 GPa, and it also transformed into dot-like SiC.w It did not provide any toughening effect, and its fracture toughness was only 3.67 MPa·m. 1 / 2 .

[0029] Comparative Example 2 1. Mix 84 wt% TiB2 powder (particle size 1.5 μm), 12 wt% TiC powder (particle size 500 nm) and 4 wt% Ni powder (particle size 500 nm) in a nylon ball mill jar, add ethanol and Si3N4 balls as the ball milling media, the ball-to-particle mass ratio is 4:1, the ball milling time is 24 h, the rotation speed is 300 r / min, after ball milling, rotary evaporation drying, and passing through a 100 mesh sieve to obtain mixed powder; 2. The mixed powder was placed in a graphite mold and placed under vacuum. An axial pressure of 35 MPa was applied, and the temperature was raised to 1800 °C at a rate of 100 °C / min. The mixture was then subjected to spark plasma sintering and held at that temperature for 10 min to obtain TiB2-TiC-Ni composite ceramic.

[0030] Figure 3 The image shows a SEM image of the microstructure of the TiB2-TiC-Ni composite ceramic in Comparative Example 1. Figure 3 It can be seen that the composite ceramic still exhibits obvious pores, lacks a solid solution shell structure, and has a relatively large grain size of 4.15±1.23 μm. The TiB2-TiC-Ni composite ceramic has a density of 97.3%, a hardness of 23.13 GPa, and a fracture toughness of 3.17 MPa·m. 1 / 2 .

[0031] In summary, the TiB2-TiC-W composite ceramics with ultra-hard core-shell structures in Examples 1-3 exhibit significantly higher hardness and fracture toughness than the TiB2-SiC composite ceramic in Comparative Example 1. w The TiB2-TiC-Ni composite ceramic and the TiB2-TiC-Ni composite ceramic of Comparative Example 2 achieved almost complete densification. When the TiC content was 12~30wt% and the W content was 3~10wt%, a core-shell structure could be formed, forming two solid solutions, (Ti,W)B2 and (Ti,W)C, which respectively encapsulated the TiB2 and TiC matrix, thus maintaining their excellent performance. When the sintering time was increased from 10 min to 15 min, the content of the shell solid solution increased significantly.

[0032] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations and simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A TiB2-TiC-W composite ceramic with an ultrahard, fine-grained core-shell structure, characterized in that, The fine-grained core-shell structure of the TiB2-TiC-W composite ceramic consists of a TiB2 and TiC matrix as the core and a (Ti,W)B2 solid solution and a (Ti,W)C solid solution as the shell. This composite ceramic is prepared by ball milling TiB2 powder, TiC powder, W powder and Al2O3 powder, drying and sieving to obtain a mixed powder. Under vacuum conditions, the mixed powder is subjected to an axial pressure of 35~40MPa and sintered by spark plasma at 1800~1900℃.

2. The ultra-hard, fine-grained core-shell structured TiB2-TiC-W composite ceramic according to claim 1, characterized in that, The TiB2 powder has a particle size of 1~3μm and a purity of ≥99wt%; the TiC powder has a particle size of 500nm and a purity of ≥99wt%; the W powder has a particle size of 0.4~1μm and a purity of ≥99wt%; and the Al2O3 powder has a particle size of 500nm and a purity of ≥99wt%.

3. The ultra-hard, fine-grained core-shell structured TiB2-TiC-W composite ceramic according to claim 1, characterized in that, The mass ratio of TiB2 powder, TiC powder and W powder is (6~8.5):(1.2~3):(0.3~1), and the Al atoms in the Al2O3 powder are 0.1~0.5 at of the total atoms in TiB2, TiC and W.

4. The ultra-hard, fine-grained core-shell structured TiB2-TiC-W composite ceramic according to claim 1, characterized in that, The sieve has a pore size of 100-200 mesh, and the composite ceramic has a grain size of 1-3 μm.

5. The ultra-hard, fine-grained core-shell structured TiB2-TiC-W composite ceramic according to claim 1, characterized in that, The TiB2-W-TiC composite ceramic has a density of over 99.7%, a hardness of 27.2~29.5 GPa, and a fracture toughness of 4.71~5.67 MPa·m. 1 / 2 .

6. The method for preparing the ultrahard, fine-grained core-shell structured TiB2-TiC-W composite ceramic according to any one of claims 1 to 5, characterized in that, The specific steps include the following: S1. Add TiB2 powder, TiC powder, W powder and Al2O3 powder to ethanol and Si3N4 balls for ball milling and mixing, dry and sieve to obtain mixed powder; S2. The mixed powder is loaded into a graphite mold, and under vacuum conditions, an axial pressure of 30~35MPa is applied. The temperature is raised to 1800~1900℃ and then sintered by spark plasma to obtain an ultra-hard TiB2-TiC-W composite ceramic with a fine-grained core-shell structure.

7. The method for preparing the ultrahard, fine-grained core-shell structured TiB2-TiC-W composite ceramic according to claim 6, characterized in that, The heating rate in step S2 is 80~120℃ / min, and the discharge plasma sintering time is 10~15min.

8. The application of the ultrahard, fine-grained core-shell structured TiB2-TiC-W composite ceramic as described in any one of claims 1 to 5 in the field of wear-resistant parts or cutting tools.

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