A transition metal non-stoichiometric compound reinforced and toughened high-entropy nitride ceramic and a preparation method thereof

Abstract

This invention discloses a transition metal non-stoichiometric compound-reinforced and toughened high-entropy nitride ceramic and its preparation method. The raw materials for preparing this nitride ceramic include a transition metal non-stoichiometric compound and a transition metal nitride. The chemical formula of the transition metal non-stoichiometric compound in the raw material is MXy, where M is selected from Cr, V, Mo, W, Ti, Nb, Ta, Hf, and Zr metals; and X is selected from C, B, or N nonmetals. The chemical formula of the transition metal nitride in the raw material is TMN. x TM is selected from at least one of Cr, V, Mo, W, Ti, Nb, Ta, Hf, and Zr. The core innovation of this invention lies in using non-stoichiometric compounds as the reinforcing phase of nitride ceramics to construct a "defect-driven" toughening mechanism, which can achieve rapid densification of the material at a lower sintering temperature and effectively improve the fracture toughness of the material.

Description

Technical Field

[0001] This invention relates to the field of composite material technology, specifically to a transition metal non-stoichiometric compound-reinforced and toughened high-entropy nitride ceramic and its preparation method. Background Technology

[0002] High-entropy ceramics have attracted widespread attention due to their unique properties resulting from high configurational entropy, such as high hardness, excellent high-temperature resistance, and corrosion resistance. Among them, high-entropy nitride ceramics combine the advantages of transition metal nitrides, including high hardness, high melting point, and good chemical stability, and have broad application prospects in cutting tools, wear-resistant coatings, and high-temperature structural components. However, high-entropy nitride ceramics generally suffer from high sintering temperatures, high intrinsic brittleness, and insufficient fracture toughness, and still face a series of key challenges in their preparation and application: First, their sintering temperatures typically need to exceed 1800 °C, resulting in high energy consumption and extremely stringent equipment requirements; second, the material's inherent brittleness and insufficient fracture toughness severely restrict its reliable application in structural components; furthermore, the poor controllability of the preparation process, the easy formation of oxide impurities, and the uneven regional properties have not yet been effectively resolved. Finally, current research is mostly focused on the laboratory proof-of-concept stage, and has not yet overcome the technical bottlenecks of high cost and low reproducibility in large-scale preparation, thus hindering its engineering application. Therefore, there is an urgent need to develop a new type of high-entropy nitride ceramic that can be densified at lower temperatures, has both high hardness and high toughness, and possesses good process controllability.

[0003] Zou Yongtao et al. disclosed a high-entropy ceramic material of transition metal nitrides and its preparation method. The key technical point is that n kinds of transition metal nitride powders are mixed with m kinds of transition metal powders, where n≥1, m≥0, and the sum of the types of transition metal elements in the precursor is ≥4. Regarding the raw material specifications, the transition metal nitride powders are selected from ZrN, TiN, NbN, HfN, TaN, CrN, VN, etc., with a powder size of 5~50 μm; the transition metal powders are selected from the corresponding elemental metals. In terms of preparation process, firstly, transition metal nitride powder and transition metal powder are mixed evenly and vacuum dried at 50~150 ℃ for 8~16 h to obtain a precursor; then, the precursor is placed in a mold and pre-pressed at 10~30 ℃ and 2~4 GPa to obtain a pre-pressed sample with a density of 70~90%; finally, high-pressure sintering is carried out in a closed environment at a sintering temperature of 500~3500 ℃, a pressure of 2~28 GPa, a holding time of 5~120 min, a pressurization rate of 1~2 GPa / h, a heating rate of 40~80 ℃ / min, a cooling rate of 80~120 ℃ / min, and a depressurization rate of 0.5~1 GPa / h. This technology, through two pressure treatments, improves the stability of the precursor and reduces the size and distance of particles within the precursor. It achieves, for the first time, the synthesis of high-density, high-purity transition metal nitride high-entropy ceramic materials via solid-state reaction, enabling the synthesis of hexagonal high-entropy nitrides that are impossible to synthesize using traditional pressureless / low-pressure sintering techniques. The technology uses transition metal powder as a reactive sintering agent, utilizing the powder's participation in the reaction during sintering to effectively inhibit nitride decomposition and enhance nitrogen retention. However, this technology has the following problems: First, the sintering pressure is as high as 2~28 GPa, which places extremely stringent requirements on the equipment, making it difficult to achieve large-scale production and engineering promotion; Second, this technology mainly focuses on densification, without specifically addressing the core bottleneck of high-entropy nitride ceramics having high intrinsic brittleness and insufficient fracture toughness; Third, the mechanism of transition metal powder as a sintering agent is mainly to promote solid-state reaction, without involving the use of lattice defects for strengthening and toughening design [Zou Yongtao, Zhang Zuhua, Chen Haiyan, et al. A transition metal nitride high-entropy ceramic material and its preparation method: CN202410530597, Shenzhen Technology University, published on August 15, 2024].

[0004] Liu Yanhui et al. disclosed an aluminum-containing high-entropy carbonitride ceramic and its preparation method. The key technical point is that the aluminum-containing high-entropy carbonitride ceramic consists of a high-entropy carbonitride ceramic matrix and AlN particles dispersed within the matrix, with Al element present in the high-entropy carbonitride ceramic matrix. Regarding raw materials, oxides of transition metal elements (selected from any five of Ti, V, Zr, Nb, Mo, Hf, Ta, and Cr, with an average particle size of 0.2–10 μm), nano-alumina (average particle size of 0.04–0.08 μm), and carbon black (average particle size of 0.1–2 μm) are used, with the atomic percentage of aluminum controlled at 1–4 at.%. In the preparation process, raw materials are weighed and mixed according to the designed ratio, with a ball-to-material ratio of 3~7:1, a rotation speed of 150~300 r / min, and a ball milling time of 24~48 h to obtain a mixed powder. The mixed powder is then subjected to an in-situ carbothermic reduction nitridation reaction in a nitrogen atmosphere, with a nitrogen flow rate of 8~12 sccm / g, a reaction temperature of 1500~1700 ℃, and a holding time of 1~3 h to obtain aluminum-containing high-entropy carbonitride ceramic powder. Finally, densification sintering is performed by spark plasma sintering (SPS) at a heating rate of 80~120 ℃ / min to obtain aluminum-containing high-entropy carbonitride ceramics. Performance and mechanism: This technology allows some Al to enter the high-entropy carbonitride ceramic lattice structure through in-situ reaction, while some Al reacts with N to form AlN particles in situ. The solid solution of Al and the AlN second phase synergistically improve the mechanical properties of the high-entropy ceramic through solid solution strengthening and second phase strengthening, respectively. At the same time, the formation of aluminum oxides during oxidation enhances the oxidation resistance of the high-entropy ceramic. However, this technology has the following problems: First, Al does not belong to transition metals, and its strengthening mechanism is similar to that of traditional second-phase reinforcement, without involving the use of lattice vacancy defects for strengthening and toughening design; Second, the interfacial bonding strength between AlN second phase and matrix is ​​difficult to control precisely; Third, this technology is mainly aimed at carbonitride systems and does not involve the problem of low-temperature densification and fracture toughness synergistic improvement of nitride ceramics [Liu Yanhui, Liu Fangfang, Peng Fang et al. An aluminum-containing high-entropy carbonitride ceramic and its preparation method: CN118239786A, Hunan University, published on June 25, 2024].

[0005] While current methods for preparing high-entropy nitride ceramics have mitigated sintering temperatures to some extent by altering raw material formulations or sintering methods, making the process easier, several key challenges remain. For instance, achieving both strength and toughness is difficult; prolonged high-energy ball milling is energy-intensive, easily introduces impurities, and the absolute toughness is insufficient to completely eliminate the risk of brittle fracture. In-situ reaction sintering with elemental metals and nitride sources simplifies the process and solves the problem of impurity phase precipitation, but data fluctuations are significant, the reaction system is complex and prone to generating byproducts, and high-temperature performance support is lacking. Performance issues also exist: for example, high-pressure sintering can easily generate residual compressive or tensile stresses due to mismatches in the thermal expansion coefficients of the sample and mold, or differences in compressibility between different phases within the sample. If the stress exceeds the material's strength, microcracks will form, significantly reducing mechanical properties. Summary of the Invention

[0006] The technical problem to be solved: The intrinsic brittleness of high-entropy nitride ceramics leads to low fracture toughness and a risk of sudden brittle fracture. Simultaneously, due to strong covalent bonds and low diffusion coefficients, achieving both hardness and toughness is difficult, requiring sintering densification temperatures typically above 1800 °C. Existing low-temperature preparation processes often sacrifice density, sample size, or process stability, resulting in lower density and deterioration of the ceramic's oxidation resistance. Current technologies address the high sintering temperature and low fracture toughness of high-entropy nitride ceramics primarily through strategies such as physically adding reinforcing phases (e.g., SiC whiskers, graphene) or chemically adding sintering aids. However, these methods introduce a series of new problems, including poor dispersion of the reinforcing phase, weak interfacial bonding, persistently high sintering temperatures, introduction of impurity phases, and poor process controllability.

[0007] 2. Technical Solution: A transition metal non-stoichiometric compound-reinforced and toughened high-entropy nitride ceramic, wherein the raw materials for preparing the nitride ceramic include a transition metal non-stoichiometric compound and a transition metal nitride; The chemical formula of the non-stoichiometric compound of the transition metal in the raw material is MXy, where M is selected from Cr, V, Mo, W, Ti, Nb, Ta, Hf, Zr metals; X is selected from C, B or N nonmetals; and y is the value of its stoichiometric ratio, which ranges from 0.3 to 1.8. The chemical formula of the transition metal nitride in the raw material is TMN. x TM is selected from at least one of Cr, V, Mo, W, Ti, Nb, Ta, Hf, and Zr, and x is the numerical value of its stoichiometric ratio; The mass fraction of transition metal nitrides is 79.29 ~ 93.33 wt.%; the balance is non-stoichiometric transition metal compounds.

[0008] Furthermore, when X is selected from C or B, the transition metal non-stoichiometric compound MXy is composed of elemental metal M powder and its corresponding stoichiometric compound MX. z The powder is prepared by mechanical alloying in a certain proportion; when X is selected from N, the transition metal non-stoichiometric compound MXy is prepared by mechanical alloying of elemental metal M powder and urea CH4N2O in a certain proportion.

[0009] Furthermore, the metallic elemental powder M and the stoichiometric compound MX z The powder has a particle size of 0.5~3 μm and a purity of not less than 99.5%; the urea (CH4N2O) has a purity of not less than 99%.

[0010] Preferably, the transition metal non-stoichiometric compound MXy is selected from TiC. 0.4 VC 0.5 、NbC 0.5 WC 0.5 TiB 1.8 and TiN 0.3 At least one of them.

[0011] Preferably, the transition metal nitride is a mixture of nitrides of V, Ti, Nb, Ta, Hf, and Zr, with the mass fractions of V, Ti, Nb, Ta, Hf, and Zr being 7.09~8.34%, 6.75~7.95%, 11.67~13.74%, 21.28~25.05%, 21.01~24.73%, and 11.49~13.52%, respectively.

[0012] A method for preparing transition metal non-stoichiometric compound-reinforced and toughened high-entropy nitride ceramics includes the following steps: S1, non-stoichiometric compound MX y Powder preparation: In air, according to MX y Weigh out the metal M elemental powder and the corresponding stoichiometric compound MX according to the stoichiometric ratio. z Powder or urea CH4N2O is prepared by mechanical alloying. S2, Preparation of composite powder: The non-stoichiometric compound MX obtained in step S1 is... y The powder is mixed with selected transition metal nitride powder in air in a certain proportion and then ball-milled. S3. Cold pressing: The composite powder obtained in step S2 is cold pressed into a pre-formed shape. S4. Obtain the blank by spark plasma sintering (SPS); S5. The prepared blank is subjected to surface grinding and deburring to obtain a transition metal non-stoichiometric compound-reinforced and toughened high-entropy nitride ceramic.

[0013] Further, in S1, the ball milling time of the mechanical alloying method is 2~60 h, the rotation speed is 350~600 r / min, and the ball-to-material ratio is 2:1~20:1, to prepare nanocrystalline non-stoichiometric compound MX. y pink.

[0014] Furthermore, during ball milling in S2, the ball-to-material mass ratio is 2:1 to 20:1, the ball milling time is 2 to 60 hours, and the rotation speed is 350 to 600 r / min.

[0015] Furthermore, during the cold pressing preforming in S3, the cold pressing mold is made of graphite, the cold pressing load is 30 MPa, and the holding time is 15 s.

[0016] Furthermore, SPS sintering is carried out in S4 at a sintering temperature of 1500~1900 °C, a holding time of 5~60 min, a heating rate of 100 °C / min, a sintering pressure of 40 MPa, and a vacuum degree of 60 Pa. The SPS sintering process and parameters are as follows: After placing the graphite mold with graphite felt, it is placed in the SPS sintering furnace and the pressure is slowly increased to 40 MPa; after evacuating to 60 Pa, sintering is carried out according to the set heating mechanism; the set heating mechanism is as follows: heat from room temperature to 600 ℃ in 5 min, hold at 600 ℃ for 5 min, stop evacuating after holding, and fill with argon gas to -0.05 Pa; then heat at a rate of 100 ℃ / min to a temperature 50 ℃ lower than the final sintering temperature, and then sinter at a rate of 15 ℃ / min for 2 min and 10 ℃ / min for 2 min to the final sintering temperature; hold at the final sintering temperature for 5~60 min, and remove the blank after furnace cooling.

[0017] 3. Beneficial effects: This invention provides a high-entropy nitride ceramic reinforced and toughened with a transition metal non-stoichiometric compound and its preparation method, aiming to solve the technical bottlenecks of existing high-entropy nitride ceramics, such as high sintering temperature, low fracture toughness, and poor controllability of the reinforcing process. This technical solution uses at least one nitride as the matrix phase and at least one transition metal non-stoichiometric compound MXy as the reinforcing phase. The non-stoichiometric compound is prepared by mechanical alloying. Subsequently, the non-stoichiometric compound MXy... y Composite powder was prepared by ball milling the powder with selected nitride powder in air. High-entropy nitride ceramics were then prepared using spark plasma sintering (SPS) technology. The prepared high-entropy nitride ceramics had a bulk density of 11.83–13.81 g / cm³. 3 It has a density of 91.45%–98.65%, a Vickers hardness of 17.5–22.0 GPa, and a fracture toughness of 4.2–6.5 MPa·m. 1 / 2The initial oxidation temperature is 669.4~722.9 ℃, the final oxidation temperature is 839.3~938.7 ℃, and the oxidation weight gain is 12.8~17.52%.

[0018] The core innovation of this invention lies in using non-stoichiometric compounds as the reinforcing phase of nitride ceramics to construct a "defect-driven" toughening mechanism. On the one hand, the presence of vacancies can significantly reduce the diffusion activation energy of atoms or ions in the crystal lattice, accelerating the diffusion process, thereby achieving rapid densification of the material at a lower sintering temperature and effectively reducing energy consumption and production costs during the preparation process. On the other hand, vacancies, as point defects in the crystal lattice, induce cracks to deflect, branch, or detour during propagation, absorbing more fracture energy by extending the crack propagation path and increasing the fracture surface area, thus effectively improving the fracture toughness of the material. Simultaneously, by utilizing the lattice defects (vacancies not caused by stoichiometry) and high reactivity of the reinforcing phase itself, in-situ reaction and coherent / semi-coherent bonding with the matrix are achieved during sintering. This fundamentally solves the problems of uneven dispersion of the reinforcing phase and weakened interfaces, achieving simultaneous improvement in hardness and toughness. Furthermore, the difference in elastic modulus and coefficient of thermal expansion between the introduced reinforcing phase and the matrix can induce various toughening mechanisms such as crack deflection, bypassing, or reinforcing phase bridging when cracks propagate to the interface region, further consuming crack propagation energy. This, combined with the vacancy defects, significantly improves the fracture toughness of high-entropy nitride ceramics. Therefore, the resulting high-entropy nitride ceramics have broad application prospects in extreme environment fields such as aerospace thermal protection, nuclear energy structural components, and high-speed cutting tools. Attached Figure Description

[0019] Figure 1 The XRD patterns are for the high-entropy nitride ceramics corresponding to Examples 1, 2, 3, 4, and 5.

[0020] Figure 2 The bulk density and compactness of the high-entropy nitride ceramics corresponding to Examples 1, 2, 3, 4, and 5 are given.

[0021] Figure 3 The XRD patterns are for the high-entropy nitride ceramics corresponding to Examples 3, 6, and 7.

[0022] Figure 4 The bulk density and compactness of the high-entropy nitride ceramics corresponding to Examples 3, 6, and 7 are given.

[0023] Figure 5 The images show the fracture surface SEM images of the high-entropy nitride ceramics corresponding to Examples 2, 3, and 4.

[0024] Figure 6 The XRD patterns of the high-entropy nitride ceramics corresponding to Examples 8 and 9 are shown.

[0025] Figure 7 The image shows the fracture surface SEM image of the high-entropy nitride ceramic corresponding to Example 8.

[0026] Figure 8 The XRD patterns are for the high-entropy nitride ceramics corresponding to Examples 8 and 10.

[0027] Figure 9 The XRD patterns of the high-entropy nitride ceramics corresponding to Examples 11 and 12 are shown.

[0028] Figure 10 The fracture surface SEM image is shown for the high-entropy nitride ceramic corresponding to Example 12.

[0029] Figure 11 The XRD patterns of the high-entropy nitride ceramics corresponding to Examples 12 and 13 are shown.

[0030] Figure 12 The XRD patterns are for the high-entropy nitride ceramics corresponding to Examples 14 and 15.

[0031] Figure 13 The fracture surface SEM image is shown for the high-entropy nitride ceramic corresponding to Example 14.

[0032] Figure 14 The XRD patterns are for the high-entropy nitride ceramics corresponding to Examples 14 and 16.

[0033] Figure 15 The XRD patterns are for the high-entropy nitride ceramics corresponding to Examples 17 and 18.

[0034] Figure 16 The fracture surface SEM image is shown for the high-entropy nitride ceramic corresponding to Example 18.

[0035] Figure 17 The XRD patterns are for the high-entropy nitride ceramics corresponding to Examples 18 and 19.

[0036] Figure 18 The XRD patterns are for the high-entropy nitride ceramics corresponding to Examples 20 and 21.

[0037] Figure 19 The XRD patterns are for the high-entropy nitride ceramics corresponding to Examples 20 and 22.

[0038] Figure 20 The image shows the fracture surface SEM image of the high-entropy nitride ceramic corresponding to Example 20.

[0039] Figure 21 Example 7 ( Figure 21 a) 10 ( Figure 21 b), 13 Figure 21 c), 16 Figure 21d), 19 ( Figure 21 e), 22 ( Figure 21 f) The TG-DSC curve of the corresponding high-entropy nitride ceramic. Detailed Implementation

[0040] The present invention will now be described in detail with reference to the accompanying drawings.

[0041] As attached Figure 1 To be continued Figure 21 . Example 1

[0042] A method for preparing transition metal non-stoichiometric compound-reinforced and toughened high-entropy nitride ceramics includes the following steps: S1, non-stoichiometric compound TiC 0.4 Powder preparation: 3.48 g of Ti powder and 2.9 g of TiC powder were weighed in air. The powder was prepared by mechanical alloying, with a ball milling time of 60 h, a rotation speed of 450 r / min, and a ball-to-powder ratio of 20:1, to obtain the non-stoichiometric compound TiC. 0.4 pink.

[0043] S2. Preparation of composite powder: Weigh TiC in air. 0.4 1.267 g of powder, 0.781 g of VN powder, 1.285 g of NbN powder, 2.344 g of TaN powder, 1.265 g of ZrN powder, 2.315 g of HfN powder, and 0.744 g of TiN powder were placed in a ball mill jar and ball-milled for 20 h. The mass of the grinding balls was 200 g, the ball-to-powder mass ratio was 20:1, and the ball milling speed was 400 r / min.

[0044] S3. Cold pressing: The composite powder obtained in step S2 is cold pressed into a preform. The cold pressing mold is graphite, the cold pressing load is 30MPa, and the holding time is 15s.

[0045] S4. Densification sintering by spark plasma sintering (SPS): sintering temperature 1500 °C, holding time 10 min, heating rate 100 °C / min, sintering pressure 40 MPa, vacuum degree 60 Pa.

[0046] The specific sintering process and parameters for SPS are as follows: After placing the graphite mold in a graphite felt, it is placed in the SPS sintering furnace. The pressure is slowly increased to 40 MPa, and after vacuuming to 60 Pa, sintering is carried out according to the set heating mechanism. The specific heating mechanism is as follows: the temperature is increased from room temperature to 600 ℃ in 5 min, held at 600 ℃ for 5 min, and after the holding period, the vacuuming is stopped and argon gas is introduced to -0.05 Pa; then the temperature is increased to 1450 ℃ at a rate of 100 ℃ / min, and then sintered at a rate of 15 ℃ / min for 2 min and 10 ℃ / min for 2 min to 1500 ℃ in sequence; the temperature is held at 1500 ℃ for 10 min, and the blank is removed after cooling in the furnace.

[0047] S5. The prepared blank is subjected to surface grinding and deburring to obtain a transition metal non-stoichiometric compound-reinforced and toughened high-entropy nitride ceramic.

[0048] The obtained high-entropy nitride ceramic samples were polished and then subjected to microstructure and performance testing. Figure 1 The XRD patterns of the high-entropy nitride ceramics corresponding to Examples 1, 2, 3, 4, and 5 are shown in the figures. The phases of these examples are high-entropy nitrides and a small amount of oxides. The results show that their bulk density is approximately 13.40 g / cm³, density is approximately 91.45%, Vickers hardness is approximately 18.9 GPa, and fracture toughness is approximately 4.7 MPa·m. 1 / 2 . Example 2

[0049] A method for preparing transition metal non-stoichiometric compound-reinforced and toughened high-entropy nitride ceramics includes the following steps: S1, non-stoichiometric compound TiC 0.4 Powder preparation: 3.48 g of Ti powder and 2.9 g of TiC powder were weighed in air. The powder was prepared by mechanical alloying, with a ball milling time of 60 h, a rotation speed of 450 r / min, and a ball-to-powder ratio of 20:1, to obtain the non-stoichiometric compound TiC. 0.4 pink.

[0050] S2. Preparation of composite powder: Weigh TiC in air. 0.4 1.267 g of powder, 0.781 g of VN powder, 1.285 g of NbN powder, 2.344 g of TaN powder, 1.265 g of ZrN powder, 2.315 g of HfN powder, and 0.744 g of TiN powder were placed in a ball mill jar and ball-milled for 20 h. The mass of the grinding balls was 200 g, the ball-to-powder mass ratio was 20:1, and the ball milling speed was 400 r / min.

[0051] S3. Cold pressing: The composite powder obtained in step S2 is cold pressed into a preform. The cold pressing mold is graphite, the cold pressing load is 30MPa, and the holding time is 15s.

[0052] S4. Densification sintering by spark plasma sintering (SPS): sintering temperature 1600 °C, holding time 10 min, heating rate 100 °C / min, sintering pressure 40 MPa, vacuum degree 60 Pa.

[0053] The specific sintering process and parameters for SPS are as follows: After placing the graphite mold in a graphite felt, it is placed in the SPS sintering furnace. The pressure is slowly increased to 40 MPa, and after vacuuming to 60 Pa, sintering is carried out according to the set heating mechanism. The specific heating mechanism is as follows: the temperature is increased from room temperature to 600 ℃ in 5 min, held at 600 ℃ for 5 min, and after the holding period, the vacuuming is stopped and argon gas is introduced to -0.05 Pa; then the temperature is increased to 1550 ℃ at a rate of 100 ℃ / min, and then sintered at a rate of 15 ℃ / min for 2 min and 10 ℃ / min for 2 min to 1600 ℃ in sequence; the temperature is held at 1600 ℃ for 10 min, and the blank is removed after cooling in the furnace.

[0054] S5. The prepared blank is subjected to surface grinding and deburring to obtain a transition metal non-stoichiometric compound-reinforced and toughened high-entropy nitride ceramic.

[0055] The obtained high-entropy nitride ceramic samples were polished and then subjected to microstructure and performance testing. Figure 1 The XRD patterns of the high-entropy nitride ceramics corresponding to Examples 1, 2, 3, 4, and 5 are shown in the figures. It can be seen from the figures that the phases of this example are high-entropy nitrides and a small amount of oxides. Figure 5 The image shows the fracture surface SEM image of the corresponding high-entropy nitride ceramic. The results indicate that its bulk density is approximately 13.70 g / cm³, its density is approximately 94.0%, its Vickers hardness is approximately 18.3 GPa, and its fracture toughness is approximately 5.9 MPa·m. 1 / 2 . Example 3

[0056] A method for preparing transition metal non-stoichiometric compound-reinforced and toughened high-entropy nitride ceramics includes the following steps: S1, non-stoichiometric compound TiC 0.4 Powder preparation: 3.48 g of Ti powder and 2.9 g of TiC powder were weighed in air. The powder was prepared by mechanical alloying, with a ball milling time of 60 h, a rotation speed of 450 r / min, and a ball-to-powder ratio of 20:1, to obtain the non-stoichiometric compound TiC. 0.4 pink.

[0057] S2. Preparation of composite powder: Weigh TiC in air. 0.4 1.267 g of powder, 0.781 g of VN powder, 1.285 g of NbN powder, 2.344 g of TaN powder, 1.265 g of ZrN powder, 2.315 g of HfN powder, and 0.744 g of TiN powder were placed in a ball mill jar and ball-milled for 20 h. The mass of the grinding balls was 200 g, the ball-to-powder mass ratio was 20:1, and the ball milling speed was 400 r / min.

[0058] S3. Cold pressing: The composite powder obtained in step S2 is cold pressed into a preform. The cold pressing mold is graphite, the cold pressing load is 30MPa, and the holding time is 15s.

[0059] S4. Densification sintering by spark plasma sintering (SPS): sintering temperature 1700 °C, holding time 10 min, heating rate 100 °C / min, sintering pressure 40 MPa, vacuum degree 60 Pa.

[0060] The specific sintering process and parameters for SPS are as follows: After placing the graphite mold in a graphite felt, it is placed in the SPS sintering furnace. The pressure is slowly increased to 40 MPa, and after vacuuming to 60 Pa, sintering is carried out according to the set heating mechanism. The specific heating mechanism is as follows: the temperature is increased from room temperature to 600 ℃ in 5 min, held at 600 ℃ for 5 min, and after the holding period, the vacuuming is stopped and argon gas is introduced to -0.05 Pa; then the temperature is increased to 1650 ℃ at a rate of 100 ℃ / min, and then sintered at a rate of 15 ℃ / min for 2 min and 10 ℃ / min for 2 min to 1700 ℃ in sequence; the temperature is held at 1700 ℃ for 10 min, and the blank is removed after cooling in the furnace.

[0061] S5. The prepared blank is subjected to surface grinding and deburring to obtain a transition metal non-stoichiometric compound-reinforced and toughened high-entropy nitride ceramic.

[0062] The prepared high-entropy nitride ceramic samples were polished and then subjected to microstructure and property testing. Figure 1 As can be seen in this embodiment, the phases are high-entropy nitrides and a small amount of oxides. Figure 5 The image shows the fracture surface SEM image of the corresponding high-entropy nitride ceramic. The results indicate that its bulk density is approximately 11.83 g / cm³, its density is approximately 94.3%, its Vickers hardness is approximately 18.9 GPa, and its fracture toughness is approximately 6.0 MPa·m. 1 / 2 . Example 4

[0063] A method for preparing transition metal non-stoichiometric compound-reinforced and toughened high-entropy nitride ceramics includes the following steps: S1, non-stoichiometric compound TiC 0.4 Powder preparation: 3.48 g of Ti powder and 2.9 g of TiC powder were weighed in air. The powder was prepared by mechanical alloying, with a ball milling time of 60 h, a rotation speed of 450 r / min, and a ball-to-powder ratio of 20:1, to obtain the non-stoichiometric compound TiC. 0.4 pink.

[0064] S2. Preparation of composite powder: Weigh TiC in air. 0.4 1.267 g of powder, 0.781 g of VN powder, 1.285 g of NbN powder, 2.344 g of TaN powder, 1.265 g of ZrN powder, 2.315 g of HfN powder, and 0.744 g of TiN powder were placed in a ball mill jar and ball-milled for 20 h. The mass of the grinding balls was 200 g, the ball-to-powder mass ratio was 20:1, and the ball milling speed was 400 r / min.

[0065] S3. Cold pressing: The composite powder obtained in step S2 is cold pressed into a preform. The cold pressing mold is graphite, the cold pressing load is 30MPa, and the holding time is 15s.

[0066] S4. Densification sintering by spark plasma sintering (SPS): sintering temperature 1800 °C, holding time 10 min, heating rate 100 °C / min, sintering pressure 40 MPa, vacuum degree 60 Pa.

[0067] The specific sintering process and parameters for SPS are as follows: After placing the graphite mold in a graphite felt, it is placed in the SPS sintering furnace. The pressure is slowly increased to 40 MPa, and after vacuuming to 60 Pa, sintering is carried out according to the set heating mechanism. The specific heating mechanism is as follows: the temperature is increased from room temperature to 600 ℃ in 5 min, held at 600 ℃ for 5 min, and after the holding period, the vacuuming is stopped and argon gas is introduced to -0.05 Pa; then the temperature is increased to 1750 ℃ ​​at a rate of 100 ℃ / min, and then sintered at a rate of 15 ℃ / min for 2 min and 10 ℃ / min for 2 min to 1800 ℃ in sequence; the temperature is held at 1800 ℃ for 10 min, and the blank is removed after cooling in the furnace.

[0068] S5. The prepared blank is subjected to surface grinding and deburring to obtain a transition metal non-stoichiometric compound-reinforced and toughened high-entropy nitride ceramic.

[0069] The obtained high-entropy nitride ceramic samples were polished and then subjected to microstructure and performance testing. Figure 1 The XRD patterns of the high-entropy nitride ceramics corresponding to Examples 1, 2, 3, 4, and 5 are shown in the figures. It can be seen from the figures that the phases of this example are high-entropy nitrides and a small amount of oxides. Figure 5The image shows the fracture surface SEM image of the corresponding high-entropy nitride ceramic. The results indicate that its bulk density is approximately 13.60 g / cm³, its compactness is approximately 94.8%, its Vickers hardness is approximately 19.0 GPa, and its fracture toughness is approximately 6.1 MPa·m. 1 / 2 . Example 5

[0070] A method for preparing transition metal non-stoichiometric compound-reinforced and toughened high-entropy nitride ceramics includes the following steps: S1, non-stoichiometric compound TiC 0.4 Powder preparation: 3.48 g of Ti powder and 2.9 g of TiC powder were weighed in air. The powder was prepared by mechanical alloying, with a ball milling time of 60 h, a rotation speed of 450 r / min, and a ball-to-powder ratio of 20:1, to obtain the non-stoichiometric compound TiC. 0.4 pink.

[0071] S2. Preparation of composite powder: Weigh TiC in air. 0.4 1.267 g of powder, 0.781 g of VN powder, 1.285 g of NbN powder, 2.344 g of TaN powder, 1.265 g of ZrN powder, 2.315 g of HfN powder, and 0.744 g of TiN powder were placed in a ball mill jar and ball-milled for 20 h. The mass of the grinding balls was 200 g, the ball-to-powder mass ratio was 20:1, and the ball milling speed was 400 r / min.

[0072] S3. Cold pressing: The composite powder obtained in step S2 is cold pressed into a preform. The cold pressing mold is graphite, the cold pressing load is 30MPa, and the holding time is 15s.

[0073] S4. Densification sintering by spark plasma sintering (SPS): sintering temperature 1900 °C, holding time 10 min, heating rate 100 °C / min, sintering pressure 40 MPa, vacuum degree 60 Pa.

[0074] The specific sintering process and parameters for SPS are as follows: After placing the graphite mold in a graphite felt, it is placed in the SPS sintering furnace. The pressure is slowly increased to 40 MPa, and after vacuuming to 60 Pa, sintering is carried out according to the set heating mechanism. The specific heating mechanism is as follows: the temperature is increased from room temperature to 600 ℃ in 5 min, held at 600 ℃ for 5 min, and after the holding period, the vacuuming is stopped and argon gas is introduced to -0.05 Pa; then the temperature is increased to 1850 ℃ at a rate of 100 ℃ / min, and then sintered at a rate of 15 ℃ / min for 2 min and 10 ℃ / min for 2 min to 1900 ℃ in sequence; the temperature is held at 1900 ℃ for 10 min, and the blank is removed after cooling in the furnace.

[0075] S5. The prepared blank is subjected to surface grinding and deburring to obtain a transition metal non-stoichiometric compound-reinforced and toughened high-entropy nitride ceramic.

[0076] The obtained high-entropy nitride ceramic samples were polished and then subjected to microstructure and performance testing. Figure 1 The XRD patterns of the high-entropy nitride ceramics corresponding to Examples 1, 2, 3, 4, and 5 are shown in the figures. The phases of these examples are high-entropy nitrides and a small amount of oxides. The results show that their bulk density is approximately 13.55 g / cm³, density is approximately 94.0%, Vickers hardness is approximately 18.8 GPa, and fracture toughness is approximately 5.8 MPa·m. 1 / 2 . Example 6

[0077] A method for preparing transition metal non-stoichiometric compound-reinforced and toughened high-entropy nitride ceramics includes the following steps: S1, non-stoichiometric compound TiC 0.4 Powder preparation: 3.48 g of Ti powder and 2.9 g of TiC powder were weighed in air. The powder was prepared by mechanical alloying, with a ball milling time of 60 h, a rotation speed of 450 r / min, and a ball-to-powder ratio of 20:1, to obtain the non-stoichiometric compound TiC. 0.4 pink.

[0078] S2. Preparation of composite powder: Weigh TiC in air. 0.4 1.267 g of powder, 0.781 g of VN powder, 1.285 g of NbN powder, 2.344 g of TaN powder, 1.265 g of ZrN powder, 2.315 g of HfN powder, and 0.744 g of TiN powder were placed in a ball mill jar and ball-milled for 20 h. The mass of the grinding balls was 200 g, the ball-to-powder mass ratio was 20:1, and the ball milling speed was 400 r / min.

[0079] S3. Cold pressing: The composite powder obtained in step S2 is cold pressed into a preform. The cold pressing mold is graphite, the cold pressing load is 30MPa, and the holding time is 15s.

[0080] S4. Densification sintering by spark plasma sintering (SPS): sintering temperature 1700 °C, holding time 15 min, heating rate 100 °C / min, sintering pressure 40 MPa, vacuum degree 60 Pa.

[0081] The specific sintering process and parameters for SPS are as follows: After placing the graphite mold in a graphite felt, it is placed in the SPS sintering furnace. The pressure is slowly increased to 40 MPa, and after vacuuming to 60 Pa, sintering is carried out according to the set heating mechanism. The specific heating mechanism is as follows: the temperature is increased from room temperature to 600 ℃ in 5 min, held at 600 ℃ for 5 min, and after the holding period, the vacuuming is stopped and argon gas is introduced to -0.05 Pa; then the temperature is increased to 1650 ℃ at a rate of 100 ℃ / min, and then sintered at a rate of 15 ℃ / min for 2 min and 10 ℃ / min for 2 min to 1700 ℃ in sequence; the temperature is held at 1700 ℃ for 15 min, and the blank is removed after cooling in the furnace.

[0082] S5. The prepared blank is subjected to surface grinding and deburring to obtain a transition metal non-stoichiometric compound-reinforced and toughened high-entropy nitride ceramic.

[0083] The obtained high-entropy nitride ceramic samples were polished and then subjected to microstructure and performance testing. Figure 3 The XRD patterns of the high-entropy nitride ceramics corresponding to Examples 3, 6, and 7 show that the phases of these examples are high-entropy nitrides and a small amount of oxides. The results show that their bulk density is approximately 13.80 g / cm³, density is approximately 98.65%, Vickers hardness is approximately 20 GPa, and fracture toughness is approximately 5.8 MPa·m. 1 / 2 . Example 7

[0084] A method for preparing transition metal non-stoichiometric compound-reinforced and toughened high-entropy nitride ceramics includes the following steps: S1, non-stoichiometric compound TiC 0.4 Powder preparation: 3.48 g of Ti powder and 2.9 g of TiC powder were weighed in air. The powder was prepared by mechanical alloying, with a ball milling time of 60 h, a rotation speed of 450 r / min, and a ball-to-powder ratio of 20:1, to obtain the non-stoichiometric compound TiC. 0.4 pink.

[0085] S2. Preparation of composite powder: Weigh TiC in air. 0.4 1.267 g of powder, 0.781 g of VN powder, 1.285 g of NbN powder, 2.344 g of TaN powder, 1.265 g of ZrN powder, 2.315 g of HfN powder, and 0.744 g of TiN powder were placed in a ball mill jar and ball-milled for 20 h. The mass of the grinding balls was 200 g, the ball-to-powder mass ratio was 20:1, and the ball milling speed was 400 r / min.

[0086] S3. Cold pressing: The composite powder obtained in step S2 is cold pressed into a preform. The cold pressing mold is graphite, the cold pressing load is 30MPa, and the holding time is 15s.

[0087] S4. Densification sintering by spark plasma sintering (SPS): sintering temperature 1700 °C, holding time 20 min, heating rate 100 °C / min, sintering pressure 40 MPa, vacuum degree 60 Pa.

[0088] The specific sintering process and parameters for SPS are as follows: After placing the graphite mold in a graphite felt, it is placed in the SPS sintering furnace. The pressure is slowly increased to 40 MPa, and after vacuuming to 60 Pa, sintering is carried out according to the set heating mechanism. The specific heating mechanism is as follows: the temperature is increased from room temperature to 600 ℃ in 5 min, held at 600 ℃ for 5 min, and after the holding period, the vacuuming is stopped and argon gas is introduced to -0.05 Pa; then the temperature is increased to 1650 ℃ at a rate of 100 ℃ / min, and then sintered at a rate of 15 ℃ / min for 2 min and 10 ℃ / min for 2 min to 1700 ℃ in sequence; the temperature is held at 1700 ℃ for 20 min, and the blank is removed after cooling in the furnace.

[0089] S5. The prepared blank is subjected to surface grinding and deburring to obtain a transition metal non-stoichiometric compound-reinforced and toughened high-entropy nitride ceramic.

[0090] The obtained high-entropy nitride ceramic samples were polished and then subjected to microstructure and performance testing. Figure 3 The XRD patterns of the high-entropy nitride ceramics corresponding to Examples 3, 6, and 7 show that the phases of these examples are high-entropy nitrides and a small amount of oxides. The results show that their bulk density is approximately 13.81 g / cm³, density is approximately 98.5%, Vickers hardness is approximately 20.8 GPa, and fracture toughness is approximately 6.0 MPa·m. 1 / 2 The initial oxidation temperature was 677.3 ℃, the final oxidation temperature was 839.3 ℃, and the weight gain due to oxidation was 17.52%. Example 8

[0091] A method for preparing transition metal non-stoichiometric compound-reinforced and toughened high-entropy nitride ceramics includes the following steps: S1, Non-stoichiometric compound VC 0.5 Powder preparation: 4.47 g of V powder and 5.53 g of VC powder were weighed in air. The powder was prepared by mechanical alloying, with a ball milling time of 60 h, a rotation speed of 450 r / min, and a ball-to-powder ratio of 20:1, to obtain the non-stoichiometric compound VC. 0.5 pink.

[0092] S2. Preparation of composite powder: Weigh VC in air. 0.5 0.727 g of powder, 0.829 g of VN powder, 1.365 g of NbN powder, 2.488 g of TaN powder, 1.343 g of ZrN powder, 2.458 g of HfN powder, and 0.790 g of TiN powder were placed in a ball mill jar and ball-milled for 20 h. The mass of the grinding balls was 200 g, the ball-to-powder mass ratio was 20:1, and the ball milling speed was 450 r / min.

[0093] S3. Cold pressing: The composite powder obtained in step S2 is cold pressed into a preform. The cold pressing mold is graphite, the cold pressing load is 30MPa, and the holding time is 15s.

[0094] S4. Densification sintering by spark plasma sintering (SPS): sintering temperature 1700 °C, holding time 10 min, heating rate 100 °C / min, sintering pressure 40 MPa, vacuum degree 60 Pa.

[0095] The specific sintering process and parameters for SPS are as follows: After placing the graphite mold in a graphite felt, it is placed in the SPS sintering furnace. The pressure is slowly increased to 40 MPa, and after vacuuming to 60 Pa, sintering is carried out according to the set heating mechanism. The specific heating mechanism is as follows: the temperature is increased from room temperature to 600 ℃ in 5 min, held at 600 ℃ for 5 min, and after the holding period, the vacuuming is stopped and argon gas is introduced to -0.05 Pa; then the temperature is increased to 1650 ℃ at a rate of 100 ℃ / min, and then sintered at a rate of 15 ℃ / min for 2 min and 10 ℃ / min for 2 min to 1700 ℃ in sequence; the temperature is held at 1700 ℃ for 10 min, and the blank is removed after cooling in the furnace.

[0096] S5. The prepared blank is subjected to surface grinding and deburring to obtain a transition metal non-stoichiometric compound-reinforced and toughened high-entropy nitride ceramic.

[0097] The obtained high-entropy nitride ceramic samples were polished and then subjected to microstructure and performance testing. Figure 6 The XRD patterns of the high-entropy nitride ceramics corresponding to Examples 8 and 9 show that the phases of this example are high-entropy nitrides and a small amount of oxides. Figure 7 The image shows the fracture surface SEM image of the corresponding high-entropy nitride ceramic. The results indicate that its bulk density is approximately 12.88 g / cm³, its density is approximately 95.5%, its Vickers hardness is 18.5 GPa, and its fracture toughness is 5.9 MPa·m. 1 / 2 . Example 9

[0098] A method for preparing transition metal non-stoichiometric compound-reinforced and toughened high-entropy nitride ceramics includes the following steps: S1, Non-stoichiometric compound VC 0.5 Powder preparation: 4.47 g of V powder and 5.53 g of VC powder were weighed in air. The powder was prepared by mechanical alloying, with a ball milling time of 60 h, a rotation speed of 450 r / min, and a ball-to-powder ratio of 20:1, to obtain the non-stoichiometric compound VC. 0.5 pink.

[0099] S2. Preparation of composite powder: Weigh VC in air. 0.5 0.727 g of powder, 0.829 g of VN powder, 1.365 g of NbN powder, 2.488 g of TaN powder, 1.343 g of ZrN powder, 2.458 g of HfN powder, and 0.790 g of TiN powder were placed in a ball mill jar and ball-milled for 20 h. The mass of the grinding balls was 200 g, the ball-to-powder mass ratio was 20:1, and the ball milling speed was 450 r / min.

[0100] S3. Cold pressing: The composite powder obtained in step S2 is cold pressed into a preform. The cold pressing mold is graphite, the cold pressing load is 30MPa, and the holding time is 15s.

[0101] S4. Densification sintering by spark plasma sintering (SPS): sintering temperature 1800 °C, holding time 10 min, heating rate 100 °C / min, sintering pressure 40 MPa, vacuum degree 60 Pa.

[0102] The specific sintering process and parameters for SPS are as follows: After placing the graphite mold in a graphite felt, it is placed in the SPS sintering furnace. The pressure is slowly increased to 40 MPa, and after vacuuming to 60 Pa, sintering is carried out according to the set heating mechanism. The specific heating mechanism is as follows: the temperature is increased from room temperature to 600 ℃ in 5 min, held at 600 ℃ for 5 min, and after the holding period, the vacuuming is stopped and argon gas is introduced to -0.05 Pa; then the temperature is increased to 1750 ℃ ​​at a rate of 100 ℃ / min, and then sintered at a rate of 15 ℃ / min for 2 min and 10 ℃ / min for 2 min to 1800 ℃ in sequence; the temperature is held at 1800 ℃ for 10 min, and the blank is removed after cooling in the furnace.

[0103] S5. The prepared blank is subjected to surface grinding and deburring to obtain a transition metal non-stoichiometric compound-reinforced and toughened high-entropy nitride ceramic.

[0104] The prepared high-entropy nitride ceramic samples were polished and then subjected to microstructure and property testing. Figure 6 and 8As can be seen in this embodiment, the phases are high-entropy nitrides and a small amount of oxides. The results show that its bulk density is approximately 12.85 g / cm³, its density is approximately 95.5%, its Vickers hardness is 18.5 GPa, and its fracture toughness is 5.9 MPa·m. 1 / 2 . Example 10

[0105] A method for preparing transition metal non-stoichiometric compound-reinforced and toughened high-entropy nitride ceramics includes the following steps: S1, Non-stoichiometric compound VC 0.5 Powder preparation: 4.47 g of V powder and 5.53 g of VC powder were weighed in air. The powder was prepared by mechanical alloying, with a ball milling time of 60 h, a rotation speed of 450 r / min, and a ball-to-powder ratio of 20:1, to obtain the non-stoichiometric compound VC. 0.5 pink.

[0106] S2. Preparation of composite powder: Weigh VC in air. 0.5 0.727 g of powder, 0.829 g of VN powder, 1.365 g of NbN powder, 2.488 g of TaN powder, 1.343 g of ZrN powder, 2.458 g of HfN powder, and 0.790 g of TiN powder were placed in a ball mill jar and ball-milled for 20 h. The mass of the grinding balls was 200 g, the ball-to-powder mass ratio was 20:1, and the ball milling speed was 450 r / min.

[0107] S3. Cold pressing: The composite powder obtained in step S2 is cold pressed into a preform. The cold pressing mold is graphite, the cold pressing load is 30MPa, and the holding time is 15s.

[0108] S4. Densification sintering by spark plasma sintering (SPS): sintering temperature 1700 °C, holding time 20 min, heating rate 100 °C / min, sintering pressure 40 MPa, vacuum degree 60 Pa.

[0109] The specific sintering process and parameters for SPS are as follows: After placing the graphite mold in a graphite felt, it is placed in the SPS sintering furnace. The pressure is slowly increased to 40 MPa, and after vacuuming to 60 Pa, sintering is carried out according to the set heating mechanism. The specific heating mechanism is as follows: the temperature is increased from room temperature to 600 ℃ in 5 min, held at 600 ℃ for 5 min, and after the holding period, the vacuuming is stopped and argon gas is introduced to -0.05 Pa; then the temperature is increased to 1650 ℃ at a rate of 100 ℃ / min, and then sintered at a rate of 15 ℃ / min for 2 min and 10 ℃ / min for 2 min to 1700 ℃ in sequence; the temperature is held at 1700 ℃ for 20 min, and the blank is removed after cooling in the furnace.

[0110] S5. The prepared blank is subjected to surface grinding and deburring to obtain a transition metal non-stoichiometric compound-reinforced and toughened high-entropy nitride ceramic.

[0111] The prepared high-entropy nitride ceramic samples were polished and then subjected to microstructure and property testing. Figure 8 As can be seen in this embodiment, the phases are high-entropy nitrides and a small amount of oxides. The results show that its bulk density is approximately 12.92 g / cm³, its density is approximately 96.5%, its Vickers hardness is 21.8 GPa, and its fracture toughness is 6.1 MPa·m. 1 / 2 The initial oxidation temperature was 669.4℃, the final oxidation temperature was 938.7℃, and the weight gain due to oxidation was 16.8%. Example 11

[0112] A method for preparing transition metal non-stoichiometric compound-reinforced and toughened high-entropy nitride ceramics includes the following steps: S1, Non-stoichiometric compound NbC 0.5 Powder preparation: 4.47 g of Nb powder and 5.53 g of NbC powder were weighed in air. The powder was prepared by mechanical alloying, with a ball milling time of 60 h, a rotation speed of 450 r / min, and a ball-to-powder ratio of 20:1, to obtain the non-stoichiometric compound NbC. 0.5 pink.

[0113] S2. Preparation of composite powder: Weigh NbC in air. 0.5 1.199 g of powder, 0.787 g of VN powder, 1.295 g of NbN powder, 2.363 g of TaN powder, 1.275 g of ZrN powder, 2.333 g of HfN powder, and 0.750 g of TiN powder were placed in a ball mill jar and ball-milled for 20 h. The mass of the grinding balls was 200 g, the ball-to-powder mass ratio was 20:1, and the ball milling speed was 400 r / min.

[0114] S3. Cold pressing: The composite powder obtained in step S2 is cold pressed into a preform. The cold pressing mold is graphite, the cold pressing load is 30MPa, and the holding time is 15s.

[0115] S4. Densification sintering by spark plasma sintering (SPS): sintering temperature 1700 °C, holding time 10 min, heating rate 100 °C / min, sintering pressure 40 MPa, vacuum degree 60 Pa.

[0116] The specific sintering process and parameters for SPS are as follows: After placing the graphite mold in a graphite felt, it is placed in the SPS sintering furnace. The pressure is slowly increased to 40 MPa, and after vacuuming to 60 Pa, sintering is carried out according to the set heating mechanism. The specific heating mechanism is as follows: the temperature is increased from room temperature to 600 ℃ in 5 min, held at 600 ℃ for 5 min, and after the holding period, the vacuuming is stopped and argon gas is introduced to -0.05 Pa; then the temperature is increased to 1650 ℃ at a rate of 100 ℃ / min, and then sintered at a rate of 15 ℃ / min for 2 min and 10 ℃ / min for 2 min to 1700 ℃ in sequence; the temperature is held at 1700 ℃ for 10 min, and the blank is removed after cooling in the furnace.

[0117] S5. The prepared blank is subjected to surface grinding and deburring to obtain a transition metal non-stoichiometric compound-reinforced and toughened high-entropy nitride ceramic.

[0118] The prepared high-entropy nitride ceramic samples were polished and then subjected to microstructure and performance testing. Figure 9 The XRD patterns of the high-entropy nitride ceramics corresponding to Examples 11 and 12 show that the phases in this example are high-entropy nitrides and a small amount of oxides. Their bulk density is approximately 13.10 g / cm³, density is approximately 95.0%, Vickers hardness is 20.5 GPa, and fracture toughness is 5.0 MPa·m. 1 / 2 . Example 12

[0119] A method for preparing transition metal non-stoichiometric compound-reinforced and toughened high-entropy nitride ceramics includes the following steps: S1, Non-stoichiometric compound NbC 0.5 Powder preparation: 4.47 g of Nb powder and 5.53 g of NbC powder were weighed in air. The powder was prepared by mechanical alloying, with a ball milling time of 60 h, a rotation speed of 450 r / min, and a ball-to-powder ratio of 20:1, to obtain the non-stoichiometric compound NbC. 0.5 pink.

[0120] S2. Preparation of composite powder: Weigh NbC in air. 0.5 1.199 g of powder, 0.787 g of VN powder, 1.295 g of NbN powder, 2.363 g of TaN powder, 1.275 g of ZrN powder, 2.333 g of HfN powder, and 0.750 g of TiN powder were placed in a ball mill jar and ball-milled for 20 h. The mass of the grinding balls was 200 g, the ball-to-powder mass ratio was 20:1, and the ball milling speed was 400 r / min.

[0121] S3. Cold pressing: The composite powder obtained in step S2 is cold pressed into a preform. The cold pressing mold is graphite, the cold pressing load is 30MPa, and the holding time is 15s.

[0122] S4. Densification sintering by spark plasma sintering (SPS): sintering temperature 1800 °C, holding time 10 min, heating rate 100 °C / min, sintering pressure 40 MPa, vacuum degree 60 Pa.

[0123] The specific sintering process and parameters for SPS are as follows: After placing the graphite mold in a graphite felt, it is placed in the SPS sintering furnace. The pressure is slowly increased to 40 MPa, and after vacuuming to 60 Pa, sintering is carried out according to the set heating mechanism. The specific heating mechanism is as follows: the temperature is increased from room temperature to 600 ℃ in 5 min, held at 600 ℃ for 5 min, and after the holding period, the vacuuming is stopped and argon gas is introduced to -0.05 Pa; then the temperature is increased to 1750 ℃ ​​at a rate of 100 ℃ / min, and then sintered at a rate of 15 ℃ / min for 2 min and 10 ℃ / min for 2 min to 1800 ℃ in sequence; the temperature is held at 1800 ℃ for 10 min, and the blank is removed after cooling in the furnace.

[0124] S5. The prepared blank is subjected to surface grinding and deburring to obtain a transition metal non-stoichiometric compound-reinforced and toughened high-entropy nitride ceramic.

[0125] The obtained high-entropy nitride ceramic samples were polished and then subjected to microstructure and performance testing. Figure 9 The XRD patterns of the high-entropy nitride ceramics corresponding to Examples 11 and 12 show that the phases of this example are high-entropy nitrides and a small amount of oxides. Figure 10 The image shows the fracture surface SEM image of the corresponding high-entropy nitride ceramic. Its bulk density is approximately 13.15 g / cm³, density is approximately 95.8%, Vickers hardness is 21.5 GPa, and fracture toughness is 6.1 MPa·m. 1 / 2 . Example 13

[0126] A method for preparing transition metal non-stoichiometric compound-reinforced and toughened high-entropy nitride ceramics includes the following steps: S1, Non-stoichiometric compound NbC 0.5 Powder preparation: 4.47 g of Nb powder and 5.53 g of NbC powder were weighed in air. The powder was prepared by mechanical alloying, with a ball milling time of 60 h, a rotation speed of 450 r / min, and a ball-to-powder ratio of 20:1, to obtain the non-stoichiometric compound NbC. 0.5 pink.

[0127] S2. Preparation of composite powder: Weigh NbC in air.0.5 1.199 g of powder, 0.787 g of VN powder, 1.295 g of NbN powder, 2.363 g of TaN powder, 1.275 g of ZrN powder, 2.333 g of HfN powder, and 0.750 g of TiN powder were placed in a ball mill jar and ball-milled for 20 h. The mass of the grinding balls was 200 g, the ball-to-powder mass ratio was 20:1, and the ball milling speed was 400 r / min.

[0128] S3. Cold pressing: The composite powder obtained in step S2 is cold pressed into a preform. The cold pressing mold is graphite, the cold pressing load is 30MPa, and the holding time is 15s.

[0129] S4. Densification sintering by spark plasma sintering (SPS): sintering temperature 1800 °C, holding time 20 min, heating rate 100 °C / min, sintering pressure 40 MPa, vacuum degree 60 Pa.

[0130] The specific sintering process and parameters for SPS are as follows: After placing the graphite mold in a graphite felt, it is placed in the SPS sintering furnace. The pressure is slowly increased to 40 MPa, and after vacuuming to 60 Pa, sintering is carried out according to the set heating mechanism. The specific heating mechanism is as follows: the temperature is increased from room temperature to 600 ℃ in 5 min, held at 600 ℃ for 5 min, and after the holding period, the vacuuming is stopped and argon gas is introduced to -0.05 Pa; then the temperature is increased to 1750 ℃ ​​at a rate of 100 ℃ / min, and then sintered at a rate of 15 ℃ / min for 2 min and 10 ℃ / min for 2 min to 1800 ℃ in sequence; the temperature is held at 1800 ℃ for 20 min, and the blank is removed after cooling in the furnace.

[0131] S5. The prepared blank is subjected to surface grinding and deburring to obtain a transition metal non-stoichiometric compound-reinforced and toughened high-entropy nitride ceramic.

[0132] The obtained high-entropy nitride ceramic samples were polished and then subjected to microstructure and performance testing. Figure 11 The XRD patterns of the high-entropy nitride ceramics corresponding to Examples 12 and 13 show that the phases of these examples are high-entropy nitrides and a small amount of oxides. The results show that their bulk density is approximately 13.19 g / cm³, density is approximately 96.0%, Vickers hardness is 22.0 GPa, and fracture toughness is 6.1 MPa·m. 1 / 2 The initial oxidation temperature was 669.4 ℃, the final oxidation temperature was 938.7 ℃, and the weight gain due to oxidation was 12.8%. Example 14

[0133] A method for preparing transition metal non-stoichiometric compound-reinforced and toughened high-entropy nitride ceramics includes the following steps: S1, non-stoichiometric compound WC 0.5 Powder preparation: 4.49 g of W powder and 5.51 g of WC powder were weighed in air. The powder was prepared by mechanical alloying, with a ball milling time of 60 h, a rotation speed of 450 r / min, and a ball-to-powder ratio of 20:1, to obtain the non-stoichiometric compound WC. 0.5 pink.

[0134] S2, Preparation of composite powder: Weigh WC in air. 0.5 2.073 g of powder, 0.709 g of VN powder, 1.167 g of NbN powder, 2.128 g of TaN powder, 1.149 g of ZrN powder, 2.101 g of HfN powder, and 0.675 g of TiN powder were placed in a ball mill jar and ball-milled for 20 h. The mass of the grinding balls was 200 g, the ball-to-powder mass ratio was 20:1, and the ball milling speed was 400 r / min.

[0135] S3. Cold pressing: The composite powder obtained in step S2 is cold pressed into a preform. The cold pressing mold is graphite, the cold pressing load is 30MPa, and the holding time is 15s.

[0136] S4. Densification sintering by spark plasma sintering (SPS): sintering temperature 1700 °C, holding time 10 min, heating rate 100 °C / min, sintering pressure 40 MPa, vacuum degree 60 Pa.

[0137] The specific sintering process and parameters for SPS are as follows: After placing the graphite mold in a graphite felt, it is placed in the SPS sintering furnace. The pressure is slowly increased to 40 MPa, and after vacuuming to 60 Pa, sintering is carried out according to the set heating mechanism. The specific heating mechanism is as follows: the temperature is increased from room temperature to 600 ℃ in 5 min, held at 600 ℃ for 5 min, and after the holding period, the vacuuming is stopped and argon gas is introduced to -0.05 Pa; then the temperature is increased to 1650 ℃ at a rate of 100 ℃ / min, and then sintered at a rate of 15 ℃ / min for 2 min and 10 ℃ / min for 2 min to 1700 ℃ in sequence; the temperature is held at 1700 ℃ for 10 min, and the blank is removed after cooling in the furnace.

[0138] S5. The prepared blank is subjected to surface grinding and deburring to obtain a transition metal non-stoichiometric compound-reinforced and toughened high-entropy nitride ceramic.

[0139] The obtained high-entropy nitride ceramic samples were polished and then subjected to microstructure and performance testing. Figure 12 The XRD patterns of the high-entropy nitride ceramics corresponding to Examples 14 and 15 show that the phase of this example is a high-entropy nitride. Figure 13The image shows the fracture surface SEM image of the corresponding high-entropy nitride ceramic. The results indicate a bulk density of approximately 13.20 g / cm³, a density of approximately 96.0%, a Vickers hardness of 19.2 GPa, and a fracture toughness of 6.3 MPa·m. 1 / 2 . Example 15

[0140] A method for preparing transition metal non-stoichiometric compound-reinforced and toughened high-entropy nitride ceramics includes the following steps: S1, non-stoichiometric compound WC 0.5 Powder preparation: 4.49 g of W powder and 5.51 g of WC powder were weighed in air. The powder was prepared by mechanical alloying, with a ball milling time of 60 h, a rotation speed of 450 r / min, and a ball-to-powder ratio of 20:1, to obtain the non-stoichiometric compound WC. 0.5 pink.

[0141] S2, Preparation of composite powder: Weigh WC in air. 0.5 2.073 g of powder, 0.709 g of VN powder, 1.167 g of NbN powder, 2.128 g of TaN powder, 1.149 g of ZrN powder, 2.101 g of HfN powder, and 0.675 g of TiN powder were placed in a ball mill jar and ball-milled for 20 h. The mass of the grinding balls was 200 g, the ball-to-powder mass ratio was 20:1, and the ball milling speed was 400 r / min.

[0142] S3. Cold pressing: The composite powder obtained in step S2 is cold pressed into a preform. The cold pressing mold is graphite, the cold pressing load is 30MPa, and the holding time is 15s.

[0143] S4. Densification sintering by spark plasma sintering (SPS): sintering temperature 1800 °C, holding time 10 min, heating rate 100 °C / min, sintering pressure 40 MPa, vacuum degree 60 Pa.

[0144] The specific sintering process and parameters for SPS are as follows: After placing the graphite mold in a graphite felt, it is placed in the SPS sintering furnace. The pressure is slowly increased to 40 MPa, and after vacuuming to 60 Pa, sintering is carried out according to the set heating mechanism. The specific heating mechanism is as follows: the temperature is increased from room temperature to 600 ℃ in 5 min, held at 600 ℃ for 5 min, and after the holding period, the vacuuming is stopped and argon gas is introduced to -0.05 Pa; then the temperature is increased to 1750 ℃ ​​at a rate of 100 ℃ / min, and then sintered at a rate of 15 ℃ / min for 2 min and 10 ℃ / min for 2 min to 1800 ℃ in sequence; the temperature is held at 1800 ℃ for 10 min, and the blank is removed after cooling in the furnace.

[0145] S5. The prepared blank is subjected to surface grinding and deburring to obtain a transition metal non-stoichiometric compound-reinforced and toughened high-entropy nitride ceramic.

[0146] The prepared high-entropy nitride ceramic samples were polished and then subjected to microstructure and property testing. Figure 12 The XRD patterns of the high-entropy nitride ceramics corresponding to Examples 14 and 15 show that the phase in these examples is a high-entropy nitride. The results indicate that the bulk density is approximately 13.15 g / cm³, the compactness is approximately 95.5%, the Vickers hardness is 18.5 GPa, and the fracture toughness is 5.8 MPa·m. 1 / 2 . Example 16

[0147] A method for preparing transition metal non-stoichiometric compound-reinforced and toughened high-entropy nitride ceramics includes the following steps: S1, non-stoichiometric compound WC 0.5 Powder preparation: 4.49 g of W powder and 5.51 g of WC powder were weighed in air. The powder was prepared by mechanical alloying, with a ball milling time of 60 h, a rotation speed of 450 r / min, and a ball-to-powder ratio of 20:1, to obtain the non-stoichiometric compound WC. 0.5 pink.

[0148] S2, Preparation of composite powder: Weigh WC in air. 0.5 2.073 g of powder, 0.709 g of VN powder, 1.167 g of NbN powder, 2.128 g of TaN powder, 1.149 g of ZrN powder, 2.101 g of HfN powder, and 0.675 g of TiN powder were placed in a ball mill jar and ball-milled for 20 h. The mass of the grinding balls was 200 g, the ball-to-powder mass ratio was 20:1, and the ball milling speed was 400 r / min.

[0149] S3. Cold pressing: The composite powder obtained in step S2 is cold pressed into a preform. The cold pressing mold is graphite, the cold pressing load is 30MPa, and the holding time is 15s.

[0150] S4. Densification sintering by spark plasma sintering (SPS): sintering temperature 1700 °C, holding time 20 min, heating rate 100 °C / min, sintering pressure 40 MPa, vacuum degree 60 Pa.

[0151] The specific sintering process and parameters for SPS are as follows: After placing the graphite mold in a graphite felt, it is placed in the SPS sintering furnace. The pressure is slowly increased to 40 MPa, and after vacuuming to 60 Pa, sintering is carried out according to the set heating mechanism. The specific heating mechanism is as follows: the temperature is increased from room temperature to 600 ℃ in 5 min, held at 600 ℃ for 5 min, and after the holding period, the vacuuming is stopped and argon gas is introduced to -0.05 Pa; then the temperature is increased to 1650 ℃ at a rate of 100 ℃ / min, and then sintered at a rate of 15 ℃ / min for 2 min and 10 ℃ / min for 2 min to 1700 ℃ in sequence; the temperature is held at 1700 ℃ for 20 min, and the blank is removed after cooling in the furnace.

[0152] S5. The prepared blank is subjected to surface grinding and deburring to obtain a transition metal non-stoichiometric compound-reinforced and toughened high-entropy nitride ceramic.

[0153] The obtained high-entropy nitride ceramic samples were polished and then subjected to microstructure and performance testing. Figure 14 The XRD patterns of the high-entropy nitride ceramics corresponding to Examples 14 and 16 show that the phases of these examples are high-entropy nitrides and a small amount of oxides. The results show that their bulk density is approximately 13.23 g / cm³, density is approximately 96.3%, Vickers hardness is 19.5 GPa, and fracture toughness is 6.5 MPa·m. 1 / 2 The initial oxidation temperature was 722.9 ℃, the final oxidation temperature was 856.5 ℃, and the weight gain due to oxidation was 16.77%. Example 17

[0154] A method for preparing transition metal non-stoichiometric compound-reinforced and toughened high-entropy nitride ceramics includes the following steps: S1, non-stoichiometric compound TiB 1.8 Powder preparation: 0.71 g of Ti powder and 9.29 g of TiB2 powder were weighed in air. The powder was prepared by mechanical alloying, with a ball milling time of 60 h, a rotation speed of 450 r / min, and a ball-to-powder ratio of 20:1, to obtain the non-stoichiometric compound TiB2. 1.8 pink.

[0155] S2. Preparation of composite powder: Weigh TiB in air. 1.8 0.848 g of powder, 0.818 g of VN powder, 1.347 g of NbN powder, 2.456 g of TaN powder, 1.326 g of ZrN powder, 2.426 g of HfN powder, and 0.780 g of TiN powder were placed in a ball mill jar and ball-milled for 20 h. The mass of the grinding balls was 200 g, the ball-to-powder mass ratio was 20:1, and the ball milling speed was 400 r / min.

[0156] S3. Cold pressing: The composite powder obtained in step S2 is cold pressed into a preform. The cold pressing mold is graphite, the cold pressing load is 30MPa, and the holding time is 15s.

[0157] S4. Densification sintering by spark plasma sintering (SPS): sintering temperature 1700 °C, holding time 10 min, heating rate 100 °C / min, sintering pressure 40 MPa, vacuum degree 60 Pa.

[0158] The specific sintering process and parameters for SPS are as follows: After placing the graphite mold in a graphite felt, it is placed in the SPS sintering furnace. The pressure is slowly increased to 40 MPa, and after vacuuming to 60 Pa, sintering is carried out according to the set heating mechanism. The specific heating mechanism is as follows: the temperature is increased from room temperature to 600 ℃ in 5 min, held at 600 ℃ for 5 min, and after the holding period, the vacuuming is stopped and argon gas is introduced to -0.05 Pa; then the temperature is increased to 1650 ℃ at a rate of 100 ℃ / min, and then sintered at a rate of 15 ℃ / min for 2 min and 10 ℃ / min for 2 min to 1700 ℃ in sequence; the temperature is held at 1700 ℃ for 10 min, and the blank is removed after cooling in the furnace.

[0159] S5. The prepared blank is subjected to surface grinding and deburring to obtain a transition metal non-stoichiometric compound-reinforced and toughened high-entropy nitride ceramic.

[0160] The obtained high-entropy nitride ceramic samples were polished and then subjected to microstructure and performance testing. Figure 15 The XRD patterns of the high-entropy nitride ceramics corresponding to Examples 17 and 18 show that the phases of these examples are high-entropy nitride TaB and a small amount of oxides. The results show that the bulk density is approximately 12.50 g / cm³, the compactness is approximately 93%, the Vickers hardness is 17.5 GPa, and the fracture toughness is 5.2 MPa·m. 1 / 2 . Example 18

[0161] A method for preparing transition metal non-stoichiometric compound-reinforced and toughened high-entropy nitride ceramics includes the following steps: S1, non-stoichiometric compound TiB 1.8 Powder preparation: 0.71 g of Ti powder and 9.29 g of TiB2 powder were weighed in air. The powder was prepared by mechanical alloying, with a ball milling time of 60 h, a rotation speed of 450 r / min, and a ball-to-powder ratio of 20:1, to obtain the non-stoichiometric compound TiB2. 1.8 pink.

[0162] S2. Preparation of composite powder: Weigh TiB in air. 1.80.848 g of powder, 0.818 g of VN powder, 1.347 g of NbN powder, 2.456 g of TaN powder, 1.326 g of ZrN powder, 2.426 g of HfN powder, and 0.780 g of TiN powder were placed in a ball mill jar and ball-milled for 20 h. The mass of the grinding balls was 200 g, the ball-to-powder mass ratio was 20:1, and the ball milling speed was 400 r / min.

[0163] S3. Cold pressing: The composite powder obtained in step S2 is cold pressed into a preform. The cold pressing mold is graphite, the cold pressing load is 30MPa, and the holding time is 15s.

[0164] S4. Densification sintering by spark plasma sintering (SPS): sintering temperature 1800 °C, holding time 10 min, heating rate 100 °C / min, sintering pressure 40 MPa, vacuum degree 60 Pa.

[0165] The specific sintering process and parameters for SPS are as follows: After placing the graphite mold in a graphite felt, it is placed in the SPS sintering furnace. The pressure is slowly increased to 40 MPa, and after vacuuming to 60 Pa, sintering is carried out according to the set heating mechanism. The specific heating mechanism is as follows: the temperature is increased from room temperature to 600 ℃ in 5 min, held at 600 ℃ for 5 min, and after the holding period, the vacuuming is stopped and argon gas is introduced to -0.05 Pa; then the temperature is increased to 1750 ℃ ​​at a rate of 100 ℃ / min, and then sintered at a rate of 15 ℃ / min for 2 min and 10 ℃ / min for 2 min to 1800 ℃ in sequence; the temperature is held at 1800 ℃ for 10 min, and the blank is removed after cooling in the furnace.

[0166] S5. The prepared blank is subjected to surface grinding and deburring to obtain a transition metal non-stoichiometric compound-reinforced and toughened high-entropy nitride ceramic.

[0167] The obtained high-entropy nitride ceramic samples were polished and then subjected to microstructure and performance testing. Figure 15 The XRD patterns of the high-entropy nitride ceramics corresponding to Examples 17 and 18 show that the phases of this example are high-entropy nitride TaB and a small amount of oxides. Figure 16 The image shows the fracture surface SEM image of the corresponding high-entropy nitride ceramic. The results indicate a bulk density of approximately 12.60 g / cm³, a compactness of approximately 94%, a Vickers hardness of 18.1 GPa, and a fracture toughness of 5.9 MPa·m. 1 / 2 . Example 19

[0168] A method for preparing transition metal non-stoichiometric compound-reinforced and toughened high-entropy nitride ceramics includes the following steps: S1, non-stoichiometric compound TiB 1.8 Powder preparation: 0.71 g of Ti powder and 9.29 g of TiB2 powder were weighed in air. The powder was prepared by mechanical alloying, with a ball milling time of 60 h, a rotation speed of 450 r / min, and a ball-to-powder ratio of 20:1, to obtain the non-stoichiometric compound TiB2. 1.8 pink.

[0169] S2. Preparation of composite powder: Weigh TiB in air. 1.8 0.848 g of powder, 0.818 g of VN powder, 1.347 g of NbN powder, 2.456 g of TaN powder, 1.326 g of ZrN powder, 2.426 g of HfN powder, and 0.780 g of TiN powder were placed in a ball mill jar and ball-milled for 20 h. The mass of the grinding balls was 200 g, the ball-to-powder mass ratio was 20:1, and the ball milling speed was 400 r / min.

[0170] S3. Cold pressing: The composite powder obtained in step S2 is cold pressed into a preform. The cold pressing mold is graphite, the cold pressing load is 30MPa, and the holding time is 15s.

[0171] S4. Densification sintering by spark plasma sintering (SPS): sintering temperature 1800 °C, holding time 20 min, heating rate 100 °C / min, sintering pressure 40 MPa, vacuum degree 60 Pa.

[0172] The specific sintering process and parameters for SPS are as follows: After placing the graphite mold in a graphite felt, it is placed in the SPS sintering furnace. The pressure is slowly increased to 40 MPa, and after vacuuming to 60 Pa, sintering is carried out according to the set heating mechanism. The specific heating mechanism is as follows: the temperature is increased from room temperature to 600 ℃ in 5 min, held at 600 ℃ for 5 min, and after the holding period, the vacuuming is stopped and argon gas is introduced to -0.05 Pa; then the temperature is increased to 1750 ℃ ​​at a rate of 100 ℃ / min, and then sintered at a rate of 15 ℃ / min for 2 min and 10 ℃ / min for 2 min to 1800 ℃ in sequence; the temperature is held at 1800 ℃ for 20 min, and the blank is removed after cooling in the furnace.

[0173] S5. The prepared blank is subjected to surface grinding and deburring to obtain a transition metal non-stoichiometric compound-reinforced and toughened high-entropy nitride ceramic.

[0174] The obtained high-entropy nitride ceramic samples were polished and then subjected to microstructure and performance testing. Figure 17The XRD patterns of the high-entropy nitride ceramics corresponding to Examples 17 and 19 show that the phases of these examples are high-entropy nitride TaB and a small amount of oxides. The results show that the bulk density is approximately 12.70 g / cm³, the density is approximately 95.0%, the Vickers hardness is 20.9 GPa, and the fracture toughness is 6.3 MPa·m. 1 / 2 . Example 20

[0175] A method for preparing transition metal non-stoichiometric compound-reinforced and toughened high-entropy nitride ceramics includes the following steps: S1, non-stoichiometric compound TiN 0.3 Powder preparation: 1.73 g of Ti powder and 8.27 g of CH4N2O were weighed in air. The powder was prepared by mechanical alloying, with a ball milling time of 60 h, a rotation speed of 450 r / min, and a ball-to-powder ratio of 20:1, to obtain the non-stoichiometric compound TiN. 0.3 pink.

[0176] S2. Preparation of composite powder: Weigh TiN in air. 0.3 0.669 g of powder, 0.834 g of VN powder, 1.374 g of NbN powder, 2.505 g of TaN powder, 1.352 g of ZrN powder, 2.473 g of HfN powder, and 0.795 g of TiN powder were placed in a ball mill jar and ball-milled for 20 h. The mass of the grinding balls was 200 g, the ball-to-powder mass ratio was 20:1, and the ball milling speed was 400 r / min.

[0177] S3. Cold pressing: The composite powder obtained in step S2 is cold pressed into a preform. The cold pressing mold is graphite, the cold pressing load is 30MPa, and the holding time is 15s.

[0178] S4. Densification sintering by spark plasma sintering (SPS): sintering temperature 1700 °C, holding time 10 min, heating rate 100 °C / min, sintering pressure 40 MPa, vacuum degree 60 Pa.

[0179] The specific sintering process and parameters for SPS are as follows: After placing the graphite mold in a graphite felt, it is placed in the SPS sintering furnace. The pressure is slowly increased to 40 MPa, and after vacuuming to 60 Pa, sintering is carried out according to the set heating mechanism. The specific heating mechanism is as follows: the temperature is increased from room temperature to 600 ℃ in 5 min, held at 600 ℃ for 5 min, and after the holding period, the vacuuming is stopped and argon gas is introduced to -0.05 Pa; then the temperature is increased to 1650 ℃ at a rate of 100 ℃ / min, and then sintered at a rate of 15 ℃ / min for 2 min and 10 ℃ / min for 2 min to 1700 ℃ in sequence; the temperature is held at 1700 ℃ for 10 min, and the blank is removed after cooling in the furnace.

[0180] S5. The prepared blank is subjected to surface grinding and deburring to obtain a transition metal non-stoichiometric compound-reinforced and toughened high-entropy nitride ceramic.

[0181] The obtained high-entropy nitride ceramic samples were polished and then subjected to microstructure and performance testing. Figure 20 The XRD patterns of the high-entropy nitride ceramics corresponding to Examples 20 and 21 are shown in the figures. It can be seen from the figures that the phases of this example are high-entropy nitrides and a small amount of oxides. Figure 20 The image shows the fracture surface SEM image of the corresponding high-entropy nitride ceramic. The results indicate that its bulk density is approximately 13.20 g / cm³, its density is approximately 96.0%, its Vickers hardness is 19.2 GPa, and its fracture toughness is 5.5 MPa·m. 1 / 2 . Example 21

[0182] A method for preparing transition metal non-stoichiometric compound-reinforced and toughened high-entropy nitride ceramics includes the following steps: S1, non-stoichiometric compound TiN 0.3 Powder preparation: 1.73 g of Ti powder and 8.27 g of CH4N2O were weighed in air. The powder was prepared by mechanical alloying, with a ball milling time of 60 h, a rotation speed of 450 r / min, and a ball-to-powder ratio of 20:1, to obtain the non-stoichiometric compound TiN. 0.3 pink.

[0183] S2. Preparation of composite powder: Weigh TiN in air. 0.3 0.669 g of powder, 0.834 g of VN powder, 1.374 g of NbN powder, 2.505 g of TaN powder, 1.352 g of ZrN powder, 2.473 g of HfN powder, and 0.795 g of TiN powder were placed in a ball mill jar and ball-milled for 20 h. The mass of the grinding balls was 200 g, the ball-to-powder mass ratio was 20:1, and the ball milling speed was 400 r / min.

[0184] S3. Cold pressing: The composite powder obtained in step S2 is cold pressed into a preform. The cold pressing mold is graphite, the cold pressing load is 30MPa, and the holding time is 15s.

[0185] S4. Densification sintering by spark plasma sintering (SPS): sintering temperature 1800 °C, holding time 10 min, heating rate 100 °C / min, sintering pressure 40 MPa, vacuum degree 60 Pa.

[0186] The specific sintering process and parameters for SPS are as follows: After placing the graphite mold in a graphite felt, it is placed in the SPS sintering furnace. The pressure is slowly increased to 40 MPa, and after vacuuming to 60 Pa, sintering is carried out according to the set heating mechanism. The specific heating mechanism is as follows: the temperature is increased from room temperature to 600 ℃ in 5 min, held at 600 ℃ for 5 min, and after the holding period, the vacuuming is stopped and argon gas is introduced to -0.05 Pa; then the temperature is increased to 1750 ℃ ​​at a rate of 100 ℃ / min, and then sintered at a rate of 15 ℃ / min for 2 min and 10 ℃ / min for 2 min to 1800 ℃ in sequence; the temperature is held at 1800 ℃ for 10 min, and the blank is removed after cooling in the furnace.

[0187] S5. The prepared blank is subjected to surface grinding and deburring to obtain a transition metal non-stoichiometric compound-reinforced and toughened high-entropy nitride ceramic.

[0188] The prepared high-entropy nitride ceramic samples were polished and then subjected to microstructure and property testing. Figure 18 As can be seen from the data, the phases of this embodiment are high-entropy nitrides and a small amount of oxides. The results show that its bulk density is approximately 13.18 g / cm³, its density is approximately 95.8%, its Vickers hardness is 19.0 GPa, and its fracture toughness is 5.6 MPa·m. 1 / 2 . Example 22

[0189] A method for preparing transition metal non-stoichiometric compound-reinforced and toughened high-entropy nitride ceramics includes the following steps: S1, non-stoichiometric compound TiN 0.3 Powder preparation: 1.73 g of Ti powder and 8.27 g of CH4N2O were weighed in air. The powder was prepared by mechanical alloying, with a ball milling time of 60 h, a rotation speed of 450 r / min, and a ball-to-powder ratio of 20:1, to obtain the non-stoichiometric compound TiN. 0.3 pink.

[0190] S2. Preparation of composite powder: Weigh TiN in air. 0.30.669 g of powder, 0.834 g of VN powder, 1.374 g of NbN powder, 2.505 g of TaN powder, 1.352 g of ZrN powder, 2.473 g of HfN powder, and 0.795 g of TiN powder were placed in a ball mill jar and ball-milled for 20 h. The mass of the grinding balls was 200 g, the ball-to-powder mass ratio was 20:1, and the ball milling speed was 400 r / min.

[0191] S3. Cold pressing: The composite powder obtained in step S2 is cold pressed into a preform. The cold pressing mold is graphite, the cold pressing load is 30MPa, and the holding time is 15s.

[0192] S4. Densification sintering by spark plasma sintering (SPS): sintering temperature 1700 °C, holding time 20 min, heating rate 100 °C / min, sintering pressure 40 MPa, vacuum degree 60 Pa.

[0193] The specific sintering process and parameters for SPS are as follows: After placing the graphite mold in a graphite felt, it is placed in the SPS sintering furnace. The pressure is slowly increased to 40 MPa, and after vacuuming to 60 Pa, sintering is carried out according to the set heating mechanism. The specific heating mechanism is as follows: the temperature is increased from room temperature to 600 ℃ in 5 min, held at 600 ℃ for 5 min, and after the holding period, the vacuuming is stopped and argon gas is introduced to -0.05 Pa; then the temperature is increased to 1650 ℃ at a rate of 100 ℃ / min, and then sintered at a rate of 15 ℃ / min for 2 min and 10 ℃ / min for 2 min to 1700 ℃ in sequence; the temperature is held at 1700 ℃ for 20 min, and the blank is removed after cooling in the furnace.

[0194] S5. The prepared blank is subjected to surface grinding and deburring to obtain a transition metal non-stoichiometric compound-reinforced and toughened high-entropy nitride ceramic.

[0195] The prepared high-entropy nitride ceramic samples were polished and then subjected to microstructure and property testing. Figure 19 The XRD patterns of the high-entropy nitride ceramics corresponding to Examples 20 and 22 are shown in the figures. The phases of these examples are high-entropy nitrides and a small amount of oxides. The results show that the bulk density is approximately 13.23 g / cm³, the compactness is approximately 96.3%, the Vickers hardness is 19.9 GPa, and the fracture toughness is 5.7 MPa·m. 1 / 2 .

[0196] In TiC 0.4 In the -TMNs system, density and mechanical properties reach their optimal values ​​at 1800 °C with increasing sintering temperature; excessively high temperatures lead to grain coarsening and performance degradation. In VC... 0.5In the -TMNs system, full densification can be achieved at 1700 °C; NbC 0.5 The optimal sintering temperature for the -TMNs system is 1800 °C, resulting in significant improvements in both hardness and toughness; WC 0.5 -TMNs system performs better at 1700 °C; TiB 1.8 -TMNs systems require a relatively long holding time at 1800 °C to achieve sufficient densification; TiN 0.3 The TMNs system performs optimally at 1700 °C; excessively high temperatures may cause nitrogen loss.

[0197] Regarding heat preservation time, TiC 0.4 - Extending the heat treatment time in the TMNs system helps improve density and hardness, but has little impact on toughness; VC 0.5 -TMNs and TiB 1.8 The -TMNs system is sensitive to the holding time; appropriately extending the holding time can significantly improve its mechanical properties. The NbC0.5-TMNs system densifies rapidly, and extending the holding time provides limited performance improvement. WC 0.5 -TMNs and TiN 0.3 The performance of the TMNs system shows a steady upward trend.

[0198] A longitudinal comparison of examples 1-22 shows that the effects of adding different non-stoichiometric compounds on reducing the sintering temperature of high-entropy nitride ceramics to form a single-phase solid solution vary slightly. For example, adding TiB... 1.8 Even with sintering temperatures increased to 1900 °C, high-entropy nitride ceramics failed to completely form a single-phase solid solution. This is due to the presence of TiB... 1.8 In TMN-based high-entropy ceramics, Ta combines with B to form TaB, and the appearance of lamellar hexagonal boron nitride hinders the formation of its single-phase solid solution. However, from an overall perspective, non-stoichiometric compounds, acting as reinforcing phases, utilize their own lattice defects and high reactivity to induce grain boundary segregation, lattice distortion, and in-situ reinforcing phase pinning during sintering through a "defect-driven" mechanism, forming coherent / semi-coherent interfaces with the matrix. This synergistically improves hardness and toughness while lowering the densification temperature. Simultaneously, the combined process of mechanical alloying and spark plasma sintering ensures the nanoscale uniform dispersion of the reinforcing phase in the matrix, avoiding the agglomeration and interface weakening problems of traditional reinforcing phases. This contributes to lowering the sintering temperature for the formation of single-phase solid solutions in high-entropy ceramics.

[0199] Although the present invention has been disclosed above with reference to preferred embodiments, these are not intended to limit the invention. Any person skilled in the art can make various changes or modifications without departing from the spirit and scope of the invention. Therefore, the scope of protection of the present invention should be defined by the scope of the claims of this application.

Claims

1. A transition metal non-stoichiometric compound-reinforced and toughened high-entropy nitride ceramic, characterized in that, The raw materials for preparing this nitride ceramic include non-stoichiometric transition metal compounds and transition metal nitrides; The chemical formula of the non-stoichiometric compound of the transition metal in the raw material is MXy, where M is selected from Cr, V, Mo, W, Ti, Nb, Ta, Hf, Zr metals; X is selected from C, B or N nonmetals; and y is the value of its stoichiometric ratio, which ranges from 0.3 to 1.

8. The chemical formula of the transition metal nitride in the raw material is TMN. x TM is selected from at least one of Cr, V, Mo, W, Ti, Nb, Ta, Hf, and Zr, and x is the numerical value of its stoichiometric ratio; The mass fraction of transition metal nitrides is 79.29 ~ 93.33 wt.%; the balance is non-stoichiometric transition metal compounds.

2. The transition metal non-stoichiometric compound-reinforced and toughened high-entropy nitride ceramic according to claim 1, characterized in that, When X is selected from C or B, the transition metal non-stoichiometric compound MXy is composed of elemental metal M powder and its corresponding stoichiometric compound MX. z The powder is prepared by mechanical alloying in a certain proportion; when X is selected from N, the transition metal non-stoichiometric compound MXy is prepared by mechanical alloying of elemental metal M powder and urea CH4N2O in a certain proportion.

3. The transition metal non-stoichiometric compound-reinforced and toughened high-entropy nitride ceramic according to claim 2, characterized in that, Metallic powder M, stoichiometric compound MX z The powder has a particle size of 0.5~3 μm and a purity of not less than 99.5%; the urea (CH4N2O) has a purity of not less than 99%.

4. The transition metal non-stoichiometric compound-reinforced and toughened high-entropy nitride ceramic according to claim 1, characterized in that, Transition metal non-stoichiometric compound MXy is selected from TiC 0.4 VC 0.5 、NbC 0.5 WC 0.5 TiB 1.8 and TiN 0.3 At least one of them.

5. A transition metal non-stoichiometric compound-reinforced and toughened high-entropy nitride ceramic according to claim 1 or 4, characterized in that, The transition metal nitrides are a mixture of nitrides of V, Ti, Nb, Ta, Hf, and Zr, with mass fractions of V, Ti, Nb, Ta, Hf, and Zr nitrides of 7.09–8.34%, 6.75–7.95%, 11.67–13.74%, 21.28–25.05%, 21.01–24.73%, and 11.49–13.52%, respectively.

6. The method for preparing transition metal non-stoichiometric compound-reinforced and toughened high-entropy nitride ceramics according to any one of claims 1-5, characterized in that, Includes the following steps: S1, non-stoichiometric compound MX y Powder preparation: In air, according to MX y Weigh out the metal M elemental powder and the corresponding stoichiometric compound MX according to the stoichiometric ratio. z Powder or urea CH4N2O is prepared by mechanical alloying. S2, Preparation of composite powder: The non-stoichiometric compound MX obtained in step S1 is... y The powder is mixed with selected transition metal nitride powder in air in a certain proportion and then ball-milled. S3. Cold pressing: The composite powder obtained in step S2 is cold pressed into a pre-formed shape. S4. Obtain the blank by spark plasma sintering (SPS); S5. The prepared blank is subjected to surface grinding and deburring to obtain a transition metal non-stoichiometric compound-reinforced and toughened high-entropy nitride ceramic.

7. The method for preparing transition metal non-stoichiometric compound-reinforced and toughened high-entropy nitride ceramics according to claim 6, characterized in that, In S1, the ball milling time of the mechanical alloying method is 2-60 h, the rotation speed is 350-600 r / min, and the ball-to-material ratio is 2:1-20:1, to prepare nanocrystalline non-stoichiometric compound MX. y pink.

8. The method for preparing transition metal non-stoichiometric compound-reinforced and toughened high-entropy nitride ceramics according to claim 6, characterized in that, When mixing materials in S2 ball mill, the ball-to-material mass ratio is 2:1 to 20:1, the ball milling time is 2 to 60 hours, and the rotation speed is 350 to 600 r / min.

9. The method for preparing transition metal non-stoichiometric compound-reinforced and toughened high-entropy nitride ceramics according to claim 6, characterized in that, During cold pressing preforming in S3, the cold pressing mold is made of graphite, the cold pressing load is 30 MPa, and the holding time is 15s.

10. The method for preparing transition metal non-stoichiometric compound-reinforced and toughened high-entropy nitride ceramics according to claim 6, characterized in that, SPS sintering in S4 is carried out at a sintering temperature of 1500~1900 °C, a holding time of 5~60 min, a heating rate of 100 °C / min, a sintering pressure of 40 MPa, and a vacuum degree of 60 Pa. The SPS sintering process and parameters are as follows: After placing the graphite mold with graphite felt, it is placed in the SPS sintering furnace and the pressure is slowly increased to 40 MPa; after evacuating to 60 Pa, sintering is carried out according to the set heating mechanism; the set heating mechanism is as follows: heat from room temperature to 600 ℃ in 5 min, hold at 600 ℃ for 5 min, stop evacuation after holding, and fill with argon gas to -0.05 Pa; then heat at a rate of 100 ℃ / min to a temperature 50 ℃ lower than the final sintering temperature, and then sinter at a rate of 15 ℃ / min for 2 min and 10 ℃ / min for 2 min to the final sintering temperature; hold at the final sintering temperature for 5~60 min, and remove the blank after furnace cooling.

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