A lightweight, high-strength, and tough TiB2-TiC-based cermet with a dual "core-ring" structure and its preparation method.

Abstract

This invention relates to a lightweight, high-strength, and high-toughness TiB2-TiC-based cermet composite material with a dual "core-ring" structure and its preparation method. The mass percentage composition is as follows: TiB2: 45%–80%; TiC: 0–30%; Co: 5–13%; Ni: 5–13%; the sum of the mass percentages of each component is 100%. The raw material powder is ball-milled, vacuum-dried, sieved, and pressed into shape. A vacuum reduction-vacuum liquid-phase sintering-solution extraction integrated technology is adopted, and sintering is performed between 1450℃ and 1480℃ to prepare the lightweight, high-strength, and high-toughness TiB2-TiC-based cermet with a dual "core-ring" structure. Its bulk density is 4.96–5.11 g / cm³. 3 The hardness is 89.1–94.4 HRA, the flexural strength is 1576.61–1724.86 MPa, and the fracture toughness is 10.47–11.48 MPa·m. 1 / 2 Compared with existing TiB2-based cermets, the overall mechanical properties are significantly improved. The preparation process of this invention is simple and suitable for industrial production, and it has broad application prospects in precision machining cutting tools, wear-resistant parts, forging machine hammers, composite casting, electrode materials, and other fields.

Description

Technical Field

[0001] This invention belongs to the field of metal-ceramic material preparation, specifically relating to a lightweight, high-strength, and tough TiB2-TiC-based metal-ceramic with a dual "core-ring" structure and its preparation method. It provides a new technology for preparing high-performance TiB2-TiC-based metal-ceramic materials with controllable preparation process, stable performance, and the potential for industrial-scale production. Technical Background

[0002] TiB2 possesses excellent physicochemical properties, including low density, high hardness, high melting point, and high elastic modulus. It also exhibits excellent chemical stability, thermal and electrical conductivity, and resistance to friction and wear. Therefore, it holds broad application prospects in cutting tools, wear-resistant components, aerospace, tank armor protection materials, and cathode conductive materials. However, its high melting point, low self-diffusion coefficient, and difficulty in densification, coupled with its relatively low toughness, and the high temperature (above 2000℃) and long sintering time required for single-phase TiB2 densification, which can lead to abnormal grain growth and severe degradation of mechanical properties, significantly limit the industrial application of TiB2 ceramics. Therefore, employing advanced sintering technologies and finding suitable sintering aids to lower the sintering temperature and shorten the sintering time to obtain high-density TiB2-based ceramic composites that simultaneously improve strength and toughness while maintaining high hardness, is crucial for the industrial application of TiB2 ceramic materials.

[0003] For nearly 30 years, generations of materials scientists have continuously explored ways to improve the strength and toughness of TiB2-based ceramics. Using metals or "metal + ceramic" as sintering aids to prepare TiB2-based cermets is considered one of the most promising methods for achieving low-temperature sintering, shortening sintering time, increasing sintering density, enhancing strength, and improving toughness in TiB2-based ceramic materials. While significant progress has been made in the research of TiB2-based cermets, several shortcomings remain. Based on a comprehensive summary of previous research, the shortcomings in the research of TiB2-based cermets are briefly summarized as follows:

[0004] Most TiB2-based cermets currently developed have a flexural strength below 1000 MPa and a fracture toughness of 5–10 MPa·m. 1 / 2 Insufficient strength and toughness are the biggest problems currently existing in TiB2-based cermets. Therefore, how to further enhance the strength and toughness of TiB2-based cermets to promote their practical application in a wide range of production fields is one of the important research topics urgently needed for this material system.

[0005] In the preparation of TiB2-based cermets using metals or "metal + ceramic" as sintering additives, the focus has been primarily on improving the strength and toughness of TiB2-based cermets by altering the elemental composition and content of the additives, but the effect has been quite limited. No research has specifically focused on improving the wettability of the binder phase to TiB2 ceramic particles, thereby enhancing the interfacial bonding strength between the binder and hard phases, and ultimately improving the strength and toughness of TiB2-based cermets.

[0006] Among the TiB2-based cermets currently being developed, no research reports have been found specifically focusing on the high-temperature reduction of oxides on the surface of ceramic powders in cermets. Complete reduction of ceramic oxides (such as TiO2) under high-temperature and high-vacuum conditions is beneficial for improving the wettability of the metal binder phase on TiB2 ceramic particles, improving the sintering performance of the material system, purifying grain boundaries, and enhancing the interfacial bonding strength between the binder phase and the hard phase.

[0007] Vacuum sintering for the preparation of TiB2-based cermets has unique advantages, especially in the high-temperature, high-vacuum environment of 1100–1300℃. In this temperature range, oxides on the surface of TiB2 and other ceramic powders undergo carbothermic reduction, which helps improve the purity of both the metal and ceramic powders, enhances the wettability of the metal binder to the ceramic particles, improves the microstructure of the cermet, and ultimately improves its overall mechanical properties. However, in the past 30 years, there has been very little research specifically focused on this area.

[0008] In TiC / Ti(C,N)-based cermets, the formation of core-ring structures has been proven to significantly enhance their strength and toughness. However, current literature on TiB2-based cermets does not specifically focus on forming similar core-ring structures and controlling the composition of these structures to strengthen the interfacial bonding between TiB2 ceramic particles and the binder phase, thereby improving the strength and toughness of TiB2-based cermets. Therefore, achieving the strengthening and toughening of cermets through the formation of core-ring structures in TiB2-based cermets has significant research value. Summary of the Invention

[0009] The purpose of this invention is to provide a lightweight, high-strength, and tough TiB2-TiC-based cermet with a dual "core-ring" structure and its preparation method. This cermet uses TiB2 as the hard phase, CoNi as the binder phase, and TiC as a hard phase additive. Utilizing the saturated solubility of TiC in the CoNi binder phase, during vacuum sintering, TiC preferentially dissolves in the CoNi binder phase over TiB2, and precipitates on undissolved TiB2 and TiC particles through a dissolution-precipitation mechanism, forming two "core-ring" structures with TiB2 and TiC as the cores, thereby achieving the strengthening and toughening of the TiB2-based cermet. During the sintering preparation process of the cermet, TG-DSC-QMS (degassing process) analysis of the TiB2-25 wt% TiC-CoNi cermet mixed powder sintering from room temperature to 1480℃ is combined (e.g.,...). Figure 1 and Figure 2 As shown, a reasonable sintering regime curve was established. Fully utilizing vacuum sintering allows water vapor, oxygen, and other gases contained in the pores of the pressed blank to dissolve, diffuse along grain boundaries, or escape through grains during sintering, resulting in pore-free sintered products and thus increasing density. Vacuum facilitates the reduction of oxides in the raw material powder, improving material purity. Vacuum improves the wettability of the binder phase to the hard phase during liquid-phase sintering, promoting shrinkage and improving the alloy's microstructure and mechanical properties. Vacuum also facilitates the removal of gases generated during sintering, promoting shrinkage in the later stages of sintering. Through precise control of the sintering process, adsorbed water and oxygen in the raw material powder are removed during vacuum sintering, and oxides on the surface of the raw material powder are reduced by vacuum carbothermal reduction, thereby purifying the material and cleaning grain boundaries. This results in a better match between the interfacial bonding between the "TiB2 core-(Ti,Co,Ni)(B,C) ring phase-CoNi binder phase" and the "TiC core-(Ti,Co,Ni)C ring phase-CoNi binder phase" in the prepared TiB2-TiC-based cermets, significantly enhancing the interfacial bonding strength and thereby improving the flexural strength and fracture toughness of the TiB2-WC-based cermets. To achieve the above objectives, the specific technical solution provided by this invention is as follows:

[0010] The lightweight, high-strength, and tough TiB2-TiC-based cermet with a dual "core-ring" structure is composed of the following components by mass percentage: TiB2: 45-80%, TiC: 0-30%, Co: 5-15%, Ni: 5-15%, and the sum of the mass percentages of each component is 100%.

[0011] Preferably, the mass percentage composition of a lightweight, high-strength, and tough TiB2-TiC-based cermet is: TiB2: 50-80%, TiC: 5-30%, Co: 8-12%, Ni: 8-12%.

[0012] The raw materials used in the TiB2-TiC based cermet have an average particle size of 1.0–2.0 μm for TiB2, 0.5–1.0 μm for TiC, 2–4 μm for Ni, and 2–4 μm for Co.

[0013] A method for preparing a lightweight, high-strength, and tough TiB2-TiC-based cermet with a dual "core-ring" structure includes the following specific steps:

[0014] (1) Preparation of mixed powder: Weigh TiB2, TiC, Co and Ni powders according to the above mass percentages, mix them by planetary ball mill or drum ball mill, dry them in a vacuum drying oven at 50-60℃, and then remove agglomerates by 80 mesh sieve to obtain uniformly mixed TiB2-TiC based metal ceramic powder.

[0015] (2) Press molding: The mixed powder is pressed into a rectangular blank using a 100MPa mold, and then cold isostatic pressing is used to hold the pressure at 250-300MPa for 150-200s to further increase the density of the pressed blank.

[0016] (3) Vacuum sintering: The green body obtained in step (2) is subjected to vacuum carbothermal reduction and vacuum liquid phase sintering in a vacuum sintering furnace with a vacuum degree of 10. -3 ~10 -1 Pa, the final sintering temperature is 1450~1480℃, and the holding time is 0.5~3h to obtain a lightweight, high-strength and tough TiB2-TiC-based metal ceramic composite material with a typical double "core-ring" structure. The planetary ball mill or drum ball mill described in step (1) is characterized by: using alcohol or kerosene as the ball milling medium when mixing the powders, the ball-to-material ratio is (1~5):1, and the ball milling speed is 150-200r / min. First, the TiB2 and TiC powders are ball milled and mixed for 12h, then Co and Ni metal powders are added and ball milled together for 24h. The mixing is carried out alternately with 1h forward rotation and 1h reverse rotation to obtain a mixed powder slurry.

[0017] The vacuum sintering described in step (3) is characterized by: heating from room temperature to 134°C at a rate of 1-3°C / min and holding for 1 hour to remove adsorbed water vapor from the raw material powder; then heating to 226°C at a rate of 1-3°C / min and holding for 1 hour to remove adsorbed oxygen from the raw material powder under vacuum; then heating to 336°C at a rate of 1-3°C / min and holding for 1 hour to reduce the oxides on the surface of Co and Ni powders by vacuum carbothermal reduction; then heating to 884°C at a rate of 1-3°C / min and holding for 1 hour; and then heating to 950°C at a rate of 1-3°C / min and holding for 1 hour. The temperature was then increased to 1034℃ at a rate of 1-2℃ / min and held for 1 hour; then increased to 1178℃ at a rate of 1-2℃ / min and held for 1 hour, allowing the TiO2 on the surface of the original TiB2 powder to be reduced by vacuum carbothermal reduction; then increased to 1300℃ at a rate of 1-2℃ / min and held for 1 hour; then increased to 1400℃ at a rate of 1-2℃ / min and held for 1 hour; then increased to 1440℃ at a rate of 1-2℃ / min and held for 1 hour; then increased to 1450℃~1480℃ at a rate of 1-2℃ / min and held for 0.5~3 hours. The heating process was then completed, maintaining a high vacuum throughout, and the furnace was cooled to room temperature.

[0018] The TiB2-TiC-based cermet prepared by this invention has a bulk density of 4.96–5.11 g / cm³. 3 The hardness is 89.1–94.4 HRA, the flexural strength is 1576.61–1724.86 MPa, and the fracture toughness is 10.47–11.48 MPa·m. 1 / 2 Compared with TiB2-based cermets reported in existing literature, the overall mechanical properties were significantly improved. The main reason for this is that in TiB2-TiC-based cermets, a large number of two "core-ring" structures were formed: "TiB2 core-(Ti,Co,Ni)(B,C) ring phase" and "TiC core-(Ti,Co,Ni)C ring phase" (e.g., TiB2 core-(Ti,Co,Ni)C ring phase). Figure 4 (As shown in the diagram). The TiB2 core has an HCP structure, the (Ti,Co,Ni)(B,C) ring phase has an HCP structure, the TiC core has an FCC structure, and the (Ti,Co,Ni)C ring phase has an FCC structure. A completely coherent two-phase interface is formed between the TiB2 core and the (Ti,Co,Ni)(B,C) ring phase; a coherent two-phase interface is also formed between the (Ti,Co,Ni)(B,C) ring phase and the CoNi binder phase. A 2–5 nm wide CoNi amorphous metal banded thin layer is formed between the TiC core and the (Ti,Co,Ni)C ring phase, and an amorphous metal thin layer is formed between the (Ti,Co,Ni)C ring phase and the CoNi binder phase, with locally amorphous regions existing in the CoNi binder phase region. The coherent interface and the amorphous metal thin layer significantly improve the interfacial bonding strength, enhancing the flexural strength and fracture toughness of the cermet.

[0019] Compared with the invention patents (Patent No.: ZL202010416184.5, title: A core-shell structure TiB2-based cermet and its preparation method and Patent No.: ZL202010416239.2, title: A core-shell structure reinforced TiB2-TiC-based cermet and its preparation method), there are fundamental differences. Firstly, the chemical composition of the cermets differs. The authorized patents contain three hard phases: TiB2, WC, and TiC, while this invention only contains two hard phases: TiB2 and TiC. Secondly, the authorized invention patents use TiB2 powder with an average particle size of 3.0–3.5 μm, while this invention uses 1.0–2.0 μm. This difference in the particle size of the main hard phase, TiB2, directly affects the overall mechanical properties of the cermet. Secondly, the composition of the ring phase in the core-ring structure differs. Authorized patents show two core-ring structures: a "TiB2 core-(Ti,W)(B,C) ring phase" and a "TiC core-(Ti,W)C ring phase." This invention, however, produces two core-ring structures: a "TiB2 core-(Ti,Co,Ni)(B,C) ring phase" and a "TiC core-(Ti,Co,Ni)C ring phase." Furthermore, when developing the sintering regime curve for TiB2-TiC-based cermets, this invention, based on the TG-DSC-QMS analysis results of the TiB2-TiC-CoNi mixed powder, developed a more scientifically sound sintering regime curve. Through precise sintering process control, the interface bonding of the core-ring structure in the TiB2-TiC-based cermets is more matched, resulting in higher bonding strength. Amorphous metallic thin layers appeared between the TiC core and the (Ti,Co,Ni)C annular phase, and between the (Ti,Co,Ni)C annular phase and the CoNi binder phase, which was not found in the research content of previous authorized invention patents. Finally, the TiB2-TiC based cermet prepared by this invention has a density of (4.96~5.11g / cm³). 3 In terms of comprehensive properties such as hardness (89.1~94.4HRA), flexural strength (1576.61~1724.86MPa), it is comparable to the already granted invention patent (granted patent ZL202010416184.5: density 5.42~5.94g / cm³). 3 Hardness 87.3~89.2HRA, flexural strength 898~1376MPa; Authorized patent ZL202010416239.2: density 5.21~5.75g / cm³ 3 Compared to other materials with a hardness of 86.8–88.9 HRA and a flexural strength of 1042–1421 MPa, it has a greater competitive advantage. Attached Figure Description

[0020] Figure 1 Example 6 of this invention: TG-DSC analysis of TiB2-25%TiC-20%CoNi cermet mixed powder

[0021] Figure 2 Gas emissions during the sintering process of TiB2-25%TiC-20%CoNi cermet in Example 6 of this invention

[0022] Figure 3 XRD phase analysis of TiB2-TiC based cermets in Examples 1-7 of this invention

[0023] Figure 4 TEM transmission electron microscopy analysis of the double "core-ring" structure in TiB2-TiC based cermets of the present invention, Example 6.

[0024] Figure 5 Backscattering morphology of TiB2-TiC based cermets in Examples 1-7 of this invention Detailed Implementation Plan

[0025] Example 1: The TiB2-TiC-based cermet is composed of powders with the following mass percentages and average particle sizes: TiB2: 80%, average particle size 1.25 μm; TiC: 0%, average particle size 0.81 μm; Co: 10%, average particle size 2.5 μm; Ni: 10%, average particle size 2.5 μm. The mass ratio of the binder phase is Co:Ni = 1:1, and the sum of the mass percentages of all components is 100%.

[0026] The specific steps for preparing cermets are as follows:

[0027] (1) Preparation of mixed powder: TiB2, Co, and Ni powders were weighed according to the above-mentioned mass percentages, and mixed using a planetary ball mill with alcohol as the milling medium. The ball-to-powder ratio was 1:1, and the milling speed was 190 r / min. The TiB2, Co, and Ni powders were planetarily ball milled for 24 h to obtain a mixed powder slurry. The mixed powder slurry was dried in a vacuum drying oven at 52℃ for 15 h, and then sieved through an 80-mesh sieve to remove agglomerates, thus obtaining TiB2-CoNi cermet mixed powder.

[0028] (2) Compression molding: First, use molding to press the material into a size of 25×8×5mm under a pressure of 100MPa. 3 The rectangular compact is then subjected to cold isostatic pressing at 270MPa for 150s to further increase its density.

[0029] (3) Vacuum sintering: The green body prepared in step (2) is subjected to vacuum sintering, maintaining a vacuum level of 10 throughout the process. -1 ~10 -3The specific sintering process is as follows: The temperature is increased from room temperature to 134℃ at a rate of 1-3℃ / min and held for 1 hour to remove adsorbed water vapor from the raw material powder; then, the temperature is increased to 226℃ at a rate of 1-3℃ / min and held for 1 hour to vacuum reduce adsorbed oxygen in the raw material powder; then, the temperature is increased to 336℃ at a rate of 1-3℃ / min and held for 1 hour to vacuum carbothermally reduce the oxides on the surface of the Co and Ni powders; then, the temperature is increased to 884℃ at a rate of 1-3℃ / min and held for 1 hour; finally, the temperature is increased to 950℃ at a rate of 1-3℃ / min and held for 1 hour. The temperature was raised to 1034℃ at a rate of 1-2℃ / min and held for 1 hour; then raised to 1118℃ at a rate of 1-2℃ / min and held for 1 hour, allowing the TiO2 on the surface of the original TiB2 powder to be reduced by vacuum carbothermal reduction; then raised to 1300℃ at a rate of 1-2℃ / min and held for 1 hour; then raised to 1400℃ at a rate of 1-2℃ / min and held for 1 hour; then raised to 1440℃ at a rate of 1-2℃ / min and held for 1 hour; finally raised to 1460℃ at a rate of 1-2℃ / min and held for 1 hour. The heating process was then completed, maintaining a high vacuum throughout, and the furnace was cooled to room temperature.

[0030] The TiB2-0%TiC-based cermet prepared in this embodiment has a bulk density of 4.97 g / cm³. 3 It has a hardness of 94.4 HRA, a flexural strength of 1576.61 MPa, and a fracture toughness of 10.47 MPa·m. 1 / 2 Its XRD phase composition is as follows: Figure 3 As shown, it contains two phases: TiB2 and CoNi binder phases; the back dispersion morphology is as follows. Figure 5 As shown in (a), the black particles are TiB2 ceramic particles, and the white particles are CoNi binder phase.

[0031] Example 2: The TiB2-TiC-based cermet is composed of powders with the following mass percentages and average particle sizes: TiB2: 75%, average particle size 1.32 μm; TiC: 5%, average particle size 0.75 μm; Co: 10%, average particle size 2.0 μm; Ni: 10%, average particle size 3.0 μm. The sum of the mass percentages of each component is 100%.

[0032] The specific steps for preparing cermets are as follows:

[0033] (1) Preparation of mixed powder: TiB2, TiC, Co, and Ni powders were weighed according to the above mass percentages and mixed using a planetary ball mill with alcohol as the milling medium. The ball-to-powder ratio was 2:1, and the milling speed was 160 r / min. TiB2 and TiC powders were first planetarily ball-milled for 12 h, and then Co and Ni powders were added and ball-milled for another 24 h to obtain a mixed powder slurry. The mixed powder slurry was dried in a vacuum drying oven at 54℃ for 15 h, and then sieved through an 80-mesh sieve to remove agglomerates, thus obtaining TiB2-TiC-based cermet mixed powder.

[0034] (2) Compression molding: First, use molding to press the material into 25×8×6mm size under a pressure of 100MPa. 3 The rectangular compact is then subjected to cold isostatic pressing at 250 MPa for 180 seconds to further increase its density.

[0035] (3) Vacuum sintering: The green body prepared in step (2) is subjected to vacuum sintering, maintaining a vacuum level of 10 throughout the process. -1 ~10 -3 The specific sintering process is as follows: The temperature is increased from room temperature to 134℃ at a rate of 1-3℃ / min and held for 1 hour to remove adsorbed water vapor from the raw material powder; then, the temperature is increased to 226℃ at a rate of 1-3℃ / min and held for 1 hour to vacuum reduce adsorbed oxygen in the raw material powder; then, the temperature is increased to 336℃ at a rate of 1-3℃ / min and held for 1 hour to vacuum carbothermally reduce the oxides on the surface of the Co and Ni powders; then, the temperature is increased to 884℃ at a rate of 1-3℃ / min and held for 1 hour; finally, the temperature is increased to 950℃ at a rate of 1-3℃ / min and held for 1 hour. The temperature was raised to 1034℃ at a rate of 1-2℃ / min and held for 1 hour; then raised to 1118℃ at a rate of 1-2℃ / min and held for 1 hour, allowing the TiO2 on the surface of the original TiB2 powder to be reduced by vacuum carbothermal reduction; then raised to 1300℃ at a rate of 1-2℃ / min and held for 1 hour; then raised to 1400℃ at a rate of 1-2℃ / min and held for 1 hour; then raised to 1440℃ at a rate of 1-2℃ / min and held for 1 hour; finally raised to 1470℃ at a rate of 1-2℃ / min and held for 1 hour. The heating process was then completed, maintaining a high vacuum throughout, and the furnace was cooled to room temperature.

[0036] The TiB2-5%TiC-based cermet prepared in this embodiment has a bulk density of 4.96 g / cm³. 3 It has a hardness of 92.7 HRA, a flexural strength of 1506.48 MPa, and a fracture toughness of 10.53 MPa·m. 1 / 2 Its XRD phase composition is as follows: Figure 3 As shown, it contains three phases: TiB2, TiC, and CoNi binder phases; the back dispersion morphology is as follows. Figure 5As shown in (b), a core-ring structure of TiB2 core-(Ti,Co,Ni)(B,C) ring phase was formed in the cermet, and a small amount of TiC ceramic particles were observed at the same time.

[0037] Example 3: The TiB2-TiC-based cermet is composed of powders with the following mass percentages and average particle sizes: TiB2: 70%, average particle size 1.45 μm; TiC: 10%, average particle size 0.62 μm; Co: 11%, average particle size 2.5 μm; Ni: 9%, average particle size 3.0 μm. The sum of the mass percentages of each component is 100%.

[0038] The specific steps for preparing cermets are as follows:

[0039] (1) Preparation of mixed powder: TiB2, TiC, Co, and Ni powders were weighed according to the above mass percentages and mixed using a planetary ball mill with alcohol as the milling medium. The ball-to-powder ratio was 3:1, and the milling speed was 170 r / min. TiB2 and TiC powders were first planetarily ball-milled for 12 h, and then Co and Ni powders were added and milled for another 24 h to obtain a mixed powder slurry. The mixed powder slurry was dried in a vacuum drying oven at 55℃ for 12 h, and then sieved through an 80-mesh sieve to remove agglomerates, thus obtaining TiB2-TiC-based cermet mixed powder.

[0040] (2) Compression molding: First, use molding to press the material into 25×8×7mm size under a pressure of 100MPa. 3 The rectangular compact is then subjected to cold isostatic pressing at 270MPa for 170s to further increase its density.

[0041] (3) Vacuum sintering: The green body prepared in step (2) is subjected to vacuum sintering, maintaining a vacuum level of 10 throughout the process. -1 ~10 -3The specific sintering process is as follows: The temperature is increased from room temperature to 134℃ at a rate of 1-3℃ / min and held for 1 hour to remove adsorbed water vapor from the raw material powder; then, the temperature is increased to 226℃ at a rate of 1-3℃ / min and held for 1 hour to vacuum reduce adsorbed oxygen in the raw material powder; then, the temperature is increased to 336℃ at a rate of 1-3℃ / min and held for 1 hour to vacuum carbothermic reduction of oxides on the surface of Co and Ni powders; then, the temperature is increased to 884℃ at a rate of 1-3℃ / min and held for 1 hour; finally, the temperature is increased to 950℃ at a rate of 1-3℃ / min and held. The temperature was increased to 1034℃ at a rate of 1-2℃ / min and held for 1 hour; then increased to 1118℃ at a rate of 1-2℃ / min and held for 1 hour, allowing the TiO2 on the surface of the original TiB2 powder to be reduced by vacuum carbothermal reduction; then increased to 1300℃ at a rate of 1-2℃ / min and held for 1 hour; then increased to 1400℃ at a rate of 1-2℃ / min and held for 1 hour; then increased to 1440℃ at a rate of 1-2℃ / min and held for 1 hour; finally increased to 1475℃ at a rate of 1-2℃ / min and held for 1.5 hours. The heating process was then completed, maintaining a high vacuum throughout, and the furnace was cooled to room temperature.

[0042] The TiB2-10%TiC-based cermet prepared in this embodiment has a bulk density of 5.0 g / cm³. 3 It has a hardness of 93.0 HRA, a flexural strength of 1586.64 MPa, and a fracture toughness of 10.96 MPa·m. 1 / 2 Its XRD phase composition is as follows: Figure 3 As shown, it contains three phases: TiB2, TiC, and CoNi binder phases; the back dispersion morphology is as follows. Figure 5 As shown in (c), two "core-ring" structures were formed in the cermet: a TiB2 core-(Ti,Co,Ni)(B,C) ring phase and a TiC core-(Ti,Co,Ni)C ring phase.

[0043] Example 4: The TiB2-TiC-based cermet is composed of powders with the following mass percentages and average particle sizes: TiB2: 65%, average particle size 1.52 μm; TiC: 15%, average particle size 0.82 μm; Co: 12%, average particle size 3.0 μm; Ni: 8%, average particle size 2.4 μm. The sum of the mass percentages of each component is 100%.

[0044] The specific steps for preparing cermets are as follows:

[0045] (1) Preparation of mixed powder: TiB2, TiC, Co, and Ni powders were weighed according to the above mass percentages and mixed using a planetary ball mill with alcohol as the milling medium. The ball-to-powder ratio was 4:1, and the milling speed was 180 r / min. TiB2 and TiC powders were first planetarily ball-milled for 12 h, and then Co and Ni powders were added and ball-milled for another 24 h to obtain a mixed powder slurry. The mixed powder slurry was dried in a vacuum drying oven at 56℃ for 12 h, and then sieved through an 80-mesh sieve to remove agglomerates, thus obtaining TiB2-TiC-based cermet mixed powder.

[0046] (2) Compression molding: First, use molding to press the material into 25×8×6mm size under a pressure of 100MPa. 3 The rectangular compact is then subjected to cold isostatic pressing at 280MPa for 180s to further increase its density.

[0047] (3) Vacuum sintering: The green body prepared in step (2) is subjected to vacuum sintering, maintaining a vacuum level of 10 throughout the process. -1 ~10 -3 The specific sintering process is as follows: The temperature is increased from room temperature to 134℃ at a rate of 1-3℃ / min and held for 1 hour to remove adsorbed water vapor from the raw material powder; then, the temperature is increased to 226℃ at a rate of 1-3℃ / min and held for 1 hour to vacuum reduce adsorbed oxygen in the raw material powder; then, the temperature is increased to 336℃ at a rate of 1-3℃ / min and held for 1 hour to vacuum carbothermic reduction of oxides on the surface of Co and Ni powders; then, the temperature is increased to 884℃ at a rate of 1-3℃ / min and held for 1 hour; finally, the temperature is increased to 950℃ at a rate of 1-3℃ / min and held. The temperature was increased to 1034℃ at a rate of 1-2℃ / min and held for 1 hour; then increased to 1118℃ at a rate of 1-2℃ / min and held for 1 hour, allowing the TiO2 on the surface of the original TiB2 powder to be reduced by vacuum carbothermal reduction; then increased to 1300℃ at a rate of 1-2℃ / min and held for 1 hour; then increased to 1400℃ at a rate of 1-2℃ / min and held for 1 hour; then increased to 1440℃ at a rate of 1-2℃ / min and held for 1 hour; finally increased to 1475℃ at a rate of 1-2℃ / min and held for 1.5 hours. The heating process was then completed, maintaining a high vacuum throughout, and the furnace was cooled to room temperature.

[0048] The TiB2-15%TiC-based cermet prepared in this embodiment has a bulk density of 5.04 g / cm³. 3 It has a hardness of 91.5 HRA, a flexural strength of 1615.04 MPa, and a fracture toughness of 11.18 MPa·m. 1 / 2 Phase composition as follows Figure 3 As shown, the back divergence morphology is as follows Figure 5As shown in (d), two core-ring structures were formed in the cermet: the TiB2 core-(Ti,Co,Ni)(B,C) ring phase and the TiC core-(Ti,Co,Ni)C ring phase. The number of core-ring structures in the TiC core-(Ti,Co,Ni)C ring phase gradually increased.

[0049] Example 5: The TiB2-TiC-based cermet is composed of powders with the following mass percentages and average particle sizes: TiB2: 60%, average particle size 1.65 μm; TiC: 20%, average particle size 0.55 μm; Co: 12%, average particle size 3.5 μm; Ni: 8%, average particle size 2.5 μm. The sum of the mass percentages of each component is 100%.

[0050] The specific steps for preparing cermets are as follows:

[0051] (1) Preparation of mixed powder: TiB2, TiC, Co, and Ni powders were weighed according to the above mass percentages and mixed using a planetary ball mill with alcohol as the milling medium. The ball-to-powder ratio was 2.5:1, and the milling speed was 190 r / min. TiB2 and TiC powders were first planetarily ball-milled for 12 h, and then Co and Ni powders were added and milled for another 24 h to obtain a mixed powder slurry. The mixed powder slurry was dried in a vacuum drying oven at 58℃ for 12 h, and then sieved through an 80-mesh sieve to remove agglomerates, thus obtaining TiB2-TiC-based cermet mixed powder.

[0052] (2) Compression molding: First, use molding to press the material into 25×8×7mm size under a pressure of 100MPa. 3 The rectangular compact is then subjected to cold isostatic pressing at 290MPa for 170s to further increase its density.

[0053] (3) Vacuum sintering: The green body prepared in step (2) is subjected to vacuum sintering, maintaining a vacuum level of 10 throughout the process. -1 ~10 -3The specific sintering process is as follows: The temperature is increased from room temperature to 134℃ at a rate of 1-3℃ / min and held for 1 hour to remove adsorbed water vapor from the raw material powder; then, the temperature is increased to 226℃ at a rate of 1-3℃ / min and held for 1 hour to vacuum reduce adsorbed oxygen in the raw material powder; then, the temperature is increased to 336℃ at a rate of 1-3℃ / min and held for 1 hour to vacuum carbothermally reduce the oxides on the surface of the Co and Ni powders; then, the temperature is increased to 884℃ at a rate of 1-3℃ / min and held for 1 hour; finally, the temperature is increased to 950℃ at a rate of 1-3℃ / min and held for 1 hour. The temperature was raised to 1034℃ at a rate of 1-2℃ / min and held for 1 hour; then raised to 1118℃ at a rate of 1-2℃ / min and held for 1 hour, allowing the TiO2 on the surface of the original TiB2 powder to be reduced by vacuum carbothermal reduction; then raised to 1300℃ at a rate of 1-2℃ / min and held for 1 hour; then raised to 1400℃ at a rate of 1-2℃ / min and held for 1 hour; then raised to 1440℃ at a rate of 1-2℃ / min and held for 1 hour; finally raised to 1480℃ at a rate of 1-2℃ / min and held for 1 hour. The heating process was then completed, maintaining a high vacuum throughout, and the furnace was cooled to room temperature.

[0054] The TiB2-20%TiC-based cermet prepared in this embodiment has a bulk density of 5.08 g / cm³. 3 It has a hardness of 90.7 HRA, a flexural strength of 1643.45 MPa, and a fracture toughness of 11.48 MPa·m. 1 / 2 .

[0055] Example 6: The TiB2-TiC-based cermet is composed of powders with the following mass percentages and average particle sizes: TiB2: 55%, average particle size 1.15 μm; TiC: 25%, average particle size 0.65 μm; Co: 10%, average particle size 2.5 μm; Ni: 10%, average particle size 2.5 μm. The sum of the mass percentages of each component is 100%.

[0056] The specific steps for preparing cermets are as follows:

[0057] (1) Preparation of mixed powder: TiB2, TiC, Co, and Ni powders were weighed according to the above mass percentages and mixed using a planetary ball mill with alcohol as the milling medium. The ball-to-powder ratio was 1.5:1, and the milling speed was 200 r / min. TiB2 and TiC powders were first planetarily ball-milled for 12 h, and then Co and Ni powders were added and milled for another 24 h to obtain a mixed powder slurry. The mixed powder slurry was dried in a vacuum drying oven at 55℃ for 12 h, and then sieved through an 80-mesh sieve to remove agglomerates, thus obtaining TiB2-TiC-based cermet mixed powder.

[0058] (2) Compression molding: First, use molding to press the material into 25×8×7mm size under a pressure of 100MPa. 3The rectangular compact is then subjected to cold isostatic pressing at 300MPa for 180s to further increase its density.

[0059] (3) Vacuum sintering: The green body prepared in step (2) is subjected to vacuum sintering, maintaining a vacuum level of 10 throughout the process. -1 ~10 -3 The specific sintering process is as follows: The temperature is increased from room temperature to 134℃ at a rate of 1-3℃ / min and held for 1 hour to remove adsorbed water vapor from the raw material powder; then, the temperature is increased to 226℃ at a rate of 1-3℃ / min and held for 1 hour to vacuum reduce adsorbed oxygen in the raw material powder; then, the temperature is increased to 336℃ at a rate of 1-3℃ / min and held for 1 hour to vacuum carbothermally reduce the oxides on the surface of the Co and Ni powders; then, the temperature is increased to 884℃ at a rate of 1-3℃ / min and held for 1 hour; finally, the temperature is increased to 950℃ at a rate of 1-3℃ / min and held for 1 hour. The temperature was raised to 1034℃ at a rate of 1-2℃ / min and held for 1 hour; then raised to 1118℃ at a rate of 1-2℃ / min and held for 1 hour, allowing the TiO2 on the surface of the original TiB2 powder to be reduced by vacuum carbothermal reduction; then raised to 1300℃ at a rate of 1-2℃ / min and held for 1 hour; then raised to 1400℃ at a rate of 1-2℃ / min and held for 1 hour; then raised to 1440℃ at a rate of 1-2℃ / min and held for 1 hour; finally raised to 1480℃ at a rate of 1-2℃ / min and held for 1 hour. The heating process was then completed, maintaining a high vacuum throughout, and the furnace was cooled to room temperature.

[0060] The TiB2-25%TiC-based cermet prepared in this embodiment has a bulk density of 5.11 g / cm³. 3 It has a hardness of 90.2 HRA, a flexural strength of 1724.86 MPa, and a fracture toughness of 11.35 MPa·m. 1 / 2 Phase composition as follows Figure 3 As shown, the TEM transmission analysis morphology of the metal ceramic is as follows: Figure 4 As shown, two core-ring structures are clearly visible: the TiB2 core-(Ti,Co,Ni)(B,C) ring phase and the TiC core-(Ti,Co,Ni)C ring phase. A completely coherent two-phase interface is formed between the TiB2 core and the (Ti,Co,Ni)(B,C) ring phase; a coherent two-phase interface is also present between the (Ti,Co,Ni)(B,C) ring phase and the CoNi binder phase. An approximately 5 nm wide CoNi amorphous metal band-shaped thin layer is formed between the TiC core and the (Ti,Co,Ni)C ring phase, and an amorphous metal thin layer is generated between the (Ti,Co,Ni)C ring phase and the CoNi binder phase, with locally amorphous regions existing within the CoNi binder phase region.

[0061] Figure 1 and Figure 2 This embodiment presents the comprehensive thermal analysis curves using TG-DSC-QMS. A Netzsch STA449F5 simultaneous thermal analyzer was employed to determine the endothermic, thermogravimetric, and venting behaviors of the TiB2-25%TiC-20%CoNi cermet during the heating process from room temperature to 1480°C. High-purity Ar protection was used during the measurement, with a heating rate of 10°C / min and a gas flow rate of 20 ml / min. Based on the comprehensive thermal analysis results, the sintering regime curves for the TiB2-TiC-based cermets prepared according to this invention were comprehensively set, taking into full account the temperatures corresponding to each endothermic peak, the thermogravimetric changes of the sintering system, the removal temperature of adsorbed water in the mixed powder, the reduction temperature of oxide impurities in the mixed powder, the melting temperatures of Co and Ni in the sintering system, and the dissolution temperatures of TiC and TiB2 ceramic particles in liquid metal. Sufficiently long holding times were set at each corresponding temperature point to ensure the full progress of each reaction. The establishment of these sintering regime curves lays a solid foundation for the preparation of high-performance TiB2-TiC-based cermet materials.

[0062] Example 7: The TiB2-TiC-based cermet is composed of powders with the following mass percentages and average particle sizes: TiB2: 50%, average particle size 1.45 μm; TiC: 30%, average particle size 0.75 μm; Co: 10%, average particle size 3 μm; Ni: 10%, average particle size 3.5 μm. The sum of the mass percentages of each component is 100%.

[0063] The specific steps for preparing cermets are as follows:

[0064] (1) Preparation of mixed powder: TiB2, TiC, Co, and Ni powders were weighed according to the above mass percentages and mixed using a planetary ball mill with alcohol as the milling medium. The ball-to-powder ratio was 4:1, and the milling speed was 170 r / min. TiB2 and TiC powders were first planetarily ball-milled for 12 h, and then Co and Ni powders were added and the milling continued for 24 h to obtain a mixed powder slurry. The mixed powder slurry was dried in a vacuum drying oven at 53℃ for 15 h, and then sieved through an 80-mesh sieve to remove agglomerates, thus obtaining TiB2-TiC-based cermet mixed powder.

[0065] (2) Compression molding: First, use molding to press the material into 25×8×6mm size under a pressure of 100MPa. 3 The rectangular compact is then subjected to cold isostatic pressing at 280MPa for 200s to further increase its density.

[0066] (3) Vacuum sintering: The green body prepared in step (2) is subjected to vacuum sintering, maintaining a vacuum level of 10 throughout the process. -1 ~10 -3The specific sintering process is as follows: The temperature is increased from room temperature to 134℃ at a rate of 1-3℃ / min and held for 1 hour to remove adsorbed water vapor from the raw material powder; then, the temperature is increased to 226℃ at a rate of 1-3℃ / min and held for 1 hour to vacuum reduce adsorbed oxygen in the raw material powder; then, the temperature is increased to 336℃ at a rate of 1-3℃ / min and held for 1 hour to vacuum carbothermally reduce the oxides on the surface of the Co and Ni powders; then, the temperature is increased to 884℃ at a rate of 1-3℃ / min and held for 1 hour; finally, the temperature is increased to 950℃ at a rate of 1-3℃ / min and held for 1 hour. The temperature was raised to 1034℃ at a rate of 1-2℃ / min and held for 1 hour; then raised to 1118℃ at a rate of 1-2℃ / min and held for 1 hour, allowing the TiO2 on the surface of the original TiB2 powder to be reduced by vacuum carbothermal reduction; then raised to 1300℃ at a rate of 1-2℃ / min and held for 1 hour; then raised to 1400℃ at a rate of 1-2℃ / min and held for 1 hour; then raised to 1440℃ at a rate of 1-2℃ / min and held for 1 hour; finally raised to 1480℃ at a rate of 1-2℃ / min and held for 1 hour. The heating process was then completed, maintaining a high vacuum throughout, and the furnace was cooled to room temperature.

[0067] The TiB2-30%TiC-based cermet prepared in this embodiment has a bulk density of 5.09 g / cm³. 3 It has a hardness of 89.1 HRA, a flexural strength of 1527.36 MPa, and a fracture toughness of 11.11 MPa·m. 1 / 2 Its phase composition is as follows: Figure 3 As shown, the back divergence morphology is as follows Figure 5 As shown in (g), a large number of two "core-ring" structures, namely TiB2 core-(Ti,Co,Ni)(B,C) ring phase and TiC core-(Ti,Co,Ni)C ring phase, were observed in the cermet.

Claims

1. A lightweight, high-strength, and tough TiB2-TiC-based cermet with a dual "core-ring" structure, characterized in that: The composition is as follows: TiB2: 50-80%, TiC: 5-30%, Co: 8-12%, Ni: 8-12%, with the sum of the mass percentages of each component being 100%. The average particle size of TiB2 powder is 1.0-2.0 μm, the average particle size of TiC powder is 0.5-1.0 μm, the average particle size of Ni powder is 2-4 μm, and the average particle size of Co powder is 2-4 μm. The TiB2 powder is prepared by chemical vapor deposition, and its surface is coated with a layer of carbon of 2-5 nm. The preparation process of the cermet is as follows: mixing, pressing, ... Vacuum reduction and vacuum liquid-phase sintering; vacuum reduction involves: heating to 336℃ at 1-3℃ / min and holding for 1 hour to carbothermally reduce the oxides on the surface of Co and Ni powders; then heating to 884℃ at 1-3℃ / min and holding for 1 hour; then heating to 950℃ at 1-3℃ / min and holding for 1 hour; then heating to 1034℃ at 1-2℃ / min and holding for 1 hour; then heating to 1178℃ at 1-2℃ / min and holding for 1 hour to carbothermally reduce the TiO2 on the surface of the original TiB2 powder; resulting in the formation of a cermet. Two core-ring structures were identified: a "TiB2 core with a (Ti,Co,Ni)(B,C) ring phase" and a "TiC core with a (Ti,Co,Ni)C ring phase." The TiB2 core and the (Ti,Co,Ni)(B,C) ring phase both exhibit an HCP structure, while the TiC core and the (Ti,Co,Ni)C ring phase both have an FCC structure. A completely coherent two-phase interface is formed between the TiB2 core and the (Ti,Co,Ni)(B,C) ring phase. A coherent two-phase interface exists between the annular phase and the CoNi binder phase; a 2–5 nm wide CoNi nonmetallic ribbon-like thin layer is formed between the TiC core and the (Ti,Co,Ni)C annular phase, and an amorphous metallic thin layer is generated between the (Ti,Co,Ni)C annular phase and the CoNi binder phase, with amorphous metallic regions also present in the CoNi binder phase; the coherent interface and the amorphous metallic thin layer greatly improve the interfacial bonding strength, enhancing the flexural strength and fracture toughness of the cermet; the bulk density of the cermet is 4.96–5.11 g / cm³. 3 Its hardness ranges from 89.1 to 94.4 HRA, its flexural strength from 1506.48 to 1724.86 MPa, and its fracture toughness from 10.47 to 11.48 MPa·m. 1 / 2 .

2. The method for preparing a lightweight, high-strength, and tough TiB2-TiC-based cermet with a dual "core-ring" structure as described in claim 1, characterized in that... Includes the following steps: (1) Preparation of mixed powder: The composition is TiB2: 50-80%, TiC: 5-30%, Co: 8-12%, Ni: 8-12%, and the sum of the mass percentages of each component is 100%. The TiB2, TiC, Co, and Ni powders are weighed according to the above mass percentages, mixed by planetary ball mill or drum ball mill, dried in a vacuum drying oven at 50-60℃, and then sieved through an 80-mesh screen to remove agglomerates to obtain TiB2-TiC-based metal ceramic mixed powder. (2) Press molding: The mixed powder is pressed under a pressure of 250-300MPa for 150-200s to obtain a green body by cold isostatic pressing. (3) Vacuum sintering: The green body from step (2) is vacuum sintered at a vacuum degree of 10. -3 ~10 -1 TiB2-TiC-based cermets with a dual "core-ring" structure were obtained by sintering at 1450–1480℃ and holding for 0.5–3 h, with a bulk density of 4.96–5.11 g / cm³. 3 Its hardness ranges from 89.1 to 94.4 HRA, its flexural strength from 1506.48 to 1724.86 MPa, and its fracture toughness from 10.47 to 11.48 MPa·m. 1 / 2 .

3. The method for preparing a lightweight, high-strength, and tough TiB2-TiC-based cermet with a dual "core-ring" structure as described in claim 2, characterized in that: In step (1), the mixed powder is prepared by using alcohol or kerosene as the ball milling medium, with a ball-to-material ratio of (1-4):1 and a ball milling speed of 150-200 r / min. First, TiB2 and TiC powders are ball milled together for 12 hours, then Co and Ni powders are added and ball milled together for 24 hours, alternating between forward and reverse rotation for 1 hour.

4. The method for preparing a lightweight, high-strength, and tough TiB2-TiC-based cermet with a dual "core-ring" structure as described in claim 2, characterized in that: The vacuum sintering described in step (3) includes an integrated technology for removing adsorbed water vapor and oxygen, vacuum carbothermal reduction, and vacuum liquid-phase sintering and dissolution. The heating steps are as follows: heating from room temperature to 134°C at a rate of 1-3°C / min and holding for 1 hour to remove adsorbed water vapor from the raw material powder; then heating to 226°C at a rate of 1-3°C / min and holding for 1 hour to vacuum reduce the adsorbed oxygen in the raw material powder; then heating to 336°C at a rate of 1-3°C / min and holding for 1 hour to vacuum carbothermize the oxides on the surface of Co and Ni powders; then heating to 884°C at a rate of 1-3°C / min and holding for 1 hour; then heating to 984°C at a rate of 1-3°C / min... The temperature was raised to 50℃ and held for 1 hour; then the temperature was increased to 1034℃ at a rate of 1-2℃ / min and held for 1 hour; then the temperature was increased to 1178℃ at a rate of 1-2℃ / min and held for 1 hour, so that the TiO2 contained on the surface of the original TiB2 powder was reduced by vacuum carbothermal reduction; then the temperature was increased to 1300℃ at a rate of 1-2℃ / min and held for 1 hour; then the temperature was increased to 1400℃ at a rate of 1-2℃ / min and held for 1 hour; then the temperature was increased to 1440℃ at a rate of 1-2℃ / min and held for 1 hour; then the temperature was increased to 1450℃~1480℃ at a rate of 1-2℃ / min and held for 0.5~3 hours; after the heating was completed, a high vacuum was maintained throughout the process, and the furnace was cooled to room temperature.

5. The method for preparing a lightweight, high-strength, and tough TiB2-TiC-based cermet with a dual "core-ring" structure as described in claim 2, characterized in that: The TiB2-TiC-based cermet with a dual "core-ring" structure generates two core-ring structures: a "TiB2 core-(Ti,Co,Ni)(B,C) ring phase" and a "TiC core-(Ti,Co,Ni)C ring phase". The TiB2 core and the (Ti,Co,Ni)(B,C) ring phase both have an HCP structure, while the TiC core and the (Ti,Co,Ni)C ring phase both have an FCC structure. A ring is formed between the TiB2 core and the (Ti,Co,Ni)(B,C) ring phase. A fully coherent two-phase interface exists; a coherent two-phase interface exists between the (Ti,Co,Ni)(B,C) annular phase and the CoNi binder phase; a CoNi nonmetallic ribbon-like thin layer with a width of 2-5 nm is formed between the TiC core and the (Ti,Co,Ni)C annular phase, and an amorphous metallic thin layer is generated between the (Ti,Co,Ni)C annular phase and the CoNi binder phase, and an amorphous metallic region exists in the CoNi binder phase; the coherent interface and the amorphous metallic thin layer greatly improve the bonding strength of the interface and enhance the bending strength and fracture toughness of the cermet.

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