A wide-temperature-range wear-resistant self-adaptive lubrication dual-phase high-entropy ceramic material and a preparation method thereof

Abstract

This invention relates to a wide-temperature-range wear-resistant adaptive lubrication dual-phase high-entropy ceramic material and its preparation method. The chemical composition of the dual-phase high-entropy ceramic material is (Hf... 0.2 Mo x Ti y Nb z Ta 0.2 )C-pwt%(Hf 0.2 Mo x Ti y Nb z Ta 0.2 B2, x+y+z=0.6, 0.15≤x≤0.25, 0.20≤y≤0.30, 0.15≤z≤0.20, 20≤p≤75; and the material has a hardness of 20.0~23.5 GPa at room temperature, exhibits excellent tribological properties over a wide temperature range from room temperature to 1100 ℃, and has a wear rate of 10. ‑5 -10 ‑7 mm 3 The friction coefficient is on the order of Nm, and is as low as 0.18. This invention also discloses a method for preparing this dual-phase high-entropy ceramic. Based on entropy regulation combined with dual-phase design, this invention, by controlling the material composition, microstructure, and preparation process, induces the exchange of metal elements and solid solution reactions during high-temperature preparation, resulting in a high-performance carbide-boride dual-phase high-entropy bulk ceramic material. This dual-phase high-entropy ceramic material possesses excellent mechanical properties and wide-temperature-range wear resistance and adaptive lubrication performance, making it suitable for applications under extreme and harsh conditions such as high temperatures.

Description

Technical Field

[0001] This invention relates to the field of high-entropy materials technology, and in particular to a wide-temperature-range wear-resistant adaptive lubrication dual-phase high-entropy ceramic material and its preparation method. Background Technology

[0002] With the rapid development of high-end equipment in fields such as next-generation nuclear reactors, hypersonic aircraft, and rail transportation towards high performance and long service life, the service environment faced by their moving mechanical components is becoming increasingly harsh. Especially in high-temperature environments across a wide temperature range (room temperature to above 1100℃), moving components not only endure severe friction and wear, but also experience the coupled effects of high-temperature oxidation, thermal stress cycling, and other factors, leading to a rapid degradation of material properties and a significantly accelerated failure process. Therefore, developing ceramic-based materials that combine excellent mechanical properties with wide-temperature-range self-lubricating functions has become a research hotspot in this field.

[0003] Traditional lubricating materials (such as lubricating greases and soft metal films) fail rapidly after exceeding their thermal stability limits, failing to meet the requirements for use under extreme operating conditions. While structural ceramics (such as Al₂O₃, SiC, and ZrO₂) possess high melting points, high hardness, and excellent high-temperature strength, they lack inherent lubricating properties. Their coefficient of friction when mated with ceramic components is typically as high as 0.8–1.6, with wear rates exceeding 10⁻⁶. -4 mm 3 Insulation levels above the N•m level make it difficult to meet the demands of long-life, high-reliability applications. Currently, the main strategy for imparting lubrication properties to ceramic materials is to introduce solid lubricants (such as MoS2, Ag, graphite, or fluorides) into the matrix. However, while this method effectively reduces the coefficient of friction, it inevitably sacrifices the material's mechanical properties significantly—the introduction of the lubricating phase significantly reduces the ceramic's hardness, strength, and creep resistance. Furthermore, during wide-temperature thermal cycling, microcracks are easily induced due to thermophysical property mismatch, ultimately leading to premature material failure under extremely harsh conditions. This traditional design paradigm of "sacrificing mechanical properties for lubrication performance" is no longer sufficient to meet the extreme requirements of next-generation equipment for the comprehensive performance of materials.

[0004] High-entropy materials are a novel material system developed in recent years. They are characterized by a unique high-entropy effect, which, through stabilizing solid solution phases and inducing lattice distortion and hysteresis diffusion, endows materials with superior mechanical properties, thermal stability, and functional characteristics that surpass those of their constituent elements. Among them, high-entropy carbide ceramics exhibit excellent tribological properties (wear rate ≤10) at temperatures not exceeding 800 °C. -5 mm 3 (on the order of N•m). However, studies have shown that high-entropy carbide ceramics oxidize severely above 800 °C, leading to a sharp deterioration in wear resistance and a wear rate that rises to 10. -4 ~10 -3 mm3 The N•m range severely limits its application in higher temperature ranges. On the other hand, although high-entropy boride ceramics have better high-temperature oxidation resistance, their hardness and room-temperature tribological properties are often inferior to those of carbide systems.

[0005] Recently, some studies have attempted to leverage the advantages of two-phase construction by building carbide-boride dual-phase high-entropy ceramics. For example, Duszová et al. (Journal of the European Ceramic Society, 2024) reported a (TiZrNbHfTa)C / (TiZrNbHfTa)B2 dual-phase high-entropy ceramic, which exhibits high hardness (HV1 approximately 29.4 GPa) and low wear rate (~10 GPa) at room temperature. -6 mm 3 (On the order of N·m). However, this study mainly focused on room temperature tribological properties and did not address high-temperature tribological behavior and oxidation resistance. Another study (Hassan et al., Journal of the American Ceramic Society, 2024) reported a dual-phase ultra-high temperature ceramic of (Hf,Nb,Ta,Ti,Zr)C-(Hf,Nb,Ta,Ti,Zr)B2, but its research focused on the synergistic hardening effect of mechanical properties and did not evaluate its wide-temperature-range tribological properties.

[0006] In previous studies, our research group developed single-phase (HfMoNbTaTi)C high-entropy carbide ceramics (CN115925423B) and single-phase (HfMoNbTaTi)B2 high-entropy boride ceramics (CN117383943B). The former exhibited a friction coefficient of approximately 0.6 when worn against Al2O3 balls at 900 ℃, but its wear rate remained relatively high. The latter, while achieving self-lubrication at 800–1200 ℃, had relatively low hardness (19.0–21.2 GPa) and struggled to achieve effective lubrication below 800 ℃. This demonstrates that neither single-phase carbide nor single-phase boride high-entropy ceramics can simultaneously achieve high-temperature oxidation resistance, high hardness, wide-temperature-range self-lubrication, and wear resistance.

[0007] In summary, how to overcome the oxidative wear bottleneck in high-entropy ceramics at temperatures above 800 ℃ while maintaining their excellent mechanical properties, and achieve adaptive lubrication over a wide temperature range (room temperature to 1100 ℃), is a pressing technical challenge in the field of high-entropy ceramic tribology. This invention addresses these technical problems. Summary of the Invention

[0008] To address the technical challenge of existing ceramic materials failing to simultaneously achieve high hardness, high-temperature oxidation resistance, and wide-temperature-range self-lubricating properties under harsh operating conditions across a wide temperature range (room temperature to 1100 ℃), this invention provides a dual-phase high-entropy ceramic material with excellent mechanical properties and capable of wide-temperature-range adaptive lubrication, along with its preparation method. Specifically, it aims to solve the common problems of severe oxidation and wear in single-phase high-entropy carbide ceramics above 800 ℃, low hardness in single-phase high-entropy boride ceramics and difficulty in achieving effective lubrication below 800 ℃, and the significant sacrifice of material mechanical properties by traditional solid lubricant addition strategies.

[0009] To address the aforementioned technical problems, this invention provides a wide-temperature-range wear-resistant adaptive lubricating dual-phase high-entropy ceramic material and its preparation method, based on a synergistic design strategy of entropy regulation and dual-phase design.

[0010] The present invention discloses a wide-temperature-range wear-resistant, adaptive lubricating, dual-phase high-entropy ceramic material, the chemical composition of which is (Hf 0.2 Mo x Ti y Nb z Ta 0.2 )C-pwt%(Hf 0.2 Mo x Ti y Nb z Ta 0.2 B2, x+y+z=0.6, 0.15≤x≤0.25, 0.20≤y≤0.30, 0.15≤z≤0.20, 20≤p≤75; and the material has a hardness of 20.0~23.5 GPa at room temperature, exhibits excellent tribological properties over a wide temperature range from room temperature to 1100 ℃, and has a wear rate of 10. -5 -10 -7 mm 3 The coefficient of friction is on the order of Nm and as low as 0.18.

[0011] The present invention discloses a method for preparing a wide-temperature-range wear-resistant, adaptive lubricating, dual-phase high-entropy ceramic material, comprising the following steps: (1) Weigh out 25~80wt% of (Hf) according to mass percentage. 0.2 Mo x Ti y Nb z Ta 0.2 )C high-entropy ceramic powder and 20~75wt% boride mixed powder, wherein the boride mixed powder is composed of HfB2, MoB2, TiB2, NbB2 and TaB2 in the ratio of (Hf) 0.2 Mo x Ti y Nb z Ta 0.2The raw materials are mixed in the stoichiometric ratio of chemical elements of B2; the raw materials are placed in a ball mill and ball-milled, and anhydrous ethanol of 0.35 to 0.55 times the total mass of the raw materials is added to the mixed raw materials. After mixing evenly, the mixture is dried at 40 to 60 °C and sieved to obtain a final mixed powder with a particle size of 0.10 to 5 μm. (2) The final mixed powder obtained in step (1) is loaded into a graphite mold and subjected to discharge plasma sintering under a vacuum of less than 0.3 Pa: first, the temperature is raised to 1700-1850℃ at an average heating rate of 40-80℃ / min, and held at a pressure of 8-15 MPa for 3-8 min; then, the temperature is raised to 1900-2000℃ at an average heating rate of 80-150℃ / min, and held at a pressure of 25-45 MPa for 5-12 min; the material is cooled with the furnace to obtain the dual-phase high-entropy ceramic material.

[0012] Preferably, the (Hf) 0.2 Mo x Ti y Nb z Ta 0.2 High-entropy ceramic powder refers to a mixture of 21.12–21.96% HfO2, 11.26–18.05% MoO3, 8.01–12.50% TiO2, 10.00–13.66% Nb2O5, 22.17–23.05% Ta2O5, and 20.58–20.83% graphite powder by mass percentage. This mixture is then sintered under conditions of vacuum below 0.3 Pa, average heating rate of 30–55 °C / min, sintering temperature of 1675–1800 °C, pressure of 5–10 MPa, and holding time of 15–25 min to obtain high-entropy ceramic material. The resulting powder is then pulverized using high-energy ball milling to obtain HfO2 powder with a particle size of 0.06–2.5 μm. 0.2 Mo x Ti y Nb z Ta 0.2 C high-entropy ceramic powder. The conditions for high-energy ball milling are: ball-to-powder ratio 0.8:1~1.5:1, rotation speed 180~220 r / min, ball milling time 2~6h, grinding jar and grinding balls are made of carbide cemented carbide, and ball milling is carried out under argon atmosphere protection.

[0013] Preferably, the mixture is composed of HfB2, MoB2, TiB2, NbB2, and TaB2 in the order of (Hf... 0.2 Mo x Ti y Nb z Ta 0.2Boride mixed powder, which is a mixture of stoichiometric elements of B2, can be prepared by the following method: 28.38~29.39% HfB2, 12.74~20.84% ​​MoB2, 9.86~15.31% TiB2, 12.18~16.54% NbB2 and 28.74~29.75% TaB2 raw materials are placed in a ball mill, and anhydrous ethanol is added to the mixed raw materials at a ratio of 0.35~0.45 times the total mass. After mixing evenly, the mixture is dried at 40~60 ℃ and sieved to obtain a mixed powder with a particle size of 0.10~5 μm.

[0014] The dual-phase high-entropy ceramic material described in this invention can be used to prepare wear-resistant self-lubricating components with a wide temperature range, especially bearings, turbine blades, nozzles, sealing rings or friction pairs that can operate in a temperature range from room temperature to 1100 °C.

[0015] Compared with the prior art, the present invention has the following advantages: 1. This invention is based on entropy regulation combined with dual-phase design. By regulating the material composition, microstructure and preparation process, it breaks through the traditional design idea of ​​improving the tribological properties of ceramic materials by adding solid lubricants. It effectively avoids the influence of solid lubricants on the overall performance of the material and obtains for the first time a dual-phase high-entropy ceramic material with excellent mechanical properties and wide temperature range wear resistance and adaptive lubrication.

[0016] 2. This invention is the first to achieve this by controlling the entropy of two-phase high-entropy carbide-boride ceramic materials ((Hf)). 0.2 Mo x Ti y Nb z Ta 0.2 )C-pwt%(Hf 0.2 Mo x Ti y Nb z Ta 0.2 By selecting a suitable preparation process, and allowing the metal elements to exchange and undergo solid solution reactions during the high-temperature preparation process, a high-performance carbide-boride dual-phase high-entropy ceramic bulk material was obtained with the phase composition (x+y+z=0.6, 0.15≤x≤0.25, 0.20≤y≤0.30, 0.15≤z≤0.20, 20≤p≤75).

[0017] 3. This invention, based on a synergistic strategy of entropy regulation and dual-phase formation, utilizes the synergistic effect of the high-temperature oxidation resistance of the boride phase and the high hardness and high melting point of the carbide phase to solve the problem of high-entropy carbide ceramic high-temperature oxidation failure. This significantly improves the material's oxidation resistance and wear resistance at temperatures above 800 °C, thereby extending its wide-temperature-range service capability to even higher temperature ranges. By controlling the phase composition and the main components of molybdenum, titanium, and niobium in the dual-phase high-entropy carbide-boride ceramic material, a dual-phase high-entropy ceramic material with excellent mechanical properties and wide-temperature-range wear resistance and adaptive lubrication can be obtained. The prepared material can achieve a hardness of up to 23.5 GPa and a wear rate as low as 10%. -7 mm 3 It has a coefficient of friction on the order of / Nm and can achieve self-lubrication in a wide temperature range of 25 ℃ to 1100 ℃, with a friction coefficient as low as about 0.18 (as shown in Table 1 below), thus achieving the unity of mechanical and tribological properties of ceramic materials.

[0018] Table 1: Average friction coefficient and wear rate of the dual-phase high-entropy ceramic bulk material and Al2O3 ceramic sphere pair of the present invention 4. The preparation process of this invention is simple. By adjusting the formula and process parameters, the microstructure and properties of the material can be controlled. The resulting high-entropy material can be used under extreme and harsh conditions such as wide temperature range. Attached Figure Description

[0019] Figure 1 (Hf) prepared in Example 1 of this invention 0.2 Mo 0.25 Ti 0.2 Nb 0.15 Ta 0.2 C-20wt%(Hf) 0.2 Mo 0.25 Ti 0.2 Nb 0.15 Ta 0.2 X-ray diffraction pattern of B2.

[0020] Figure 2 (Hf) prepared in Example 2 of this invention 0.2 Mo 0.2 Ti 0.2 Nb 0.2 Ta 0.2 C-50wt%(Hf) 0.2 Mo 0.2 Ti 0.2 Nb 0.2 Ta 0.2 Backscattering diagram of the microstructure of B2.

[0021] Figure 3 (Hf) prepared in Example 3 of this invention0.2 Mo 0.15 Ti 0.3 Nb 0.15 Ta 0.2 C-75wt%(Hf) 0.2 Mo 0.15 Ti 0.3 Nb 0.15 Ta 0.2 The coefficient of friction of B2 at 1100℃.

[0022] In the diagram: HEC represents the high-entropy carbide phase, and HEB represents the high-entropy boride phase. Detailed Implementation

[0023] The technical solution of the present invention will be further described in detail below with reference to specific embodiments, but the scope of protection of the present invention is not limited to these embodiments. All equivalent substitutions or improvements made based on the technical concept of the present invention should be included within the scope of protection of the present invention.

[0024] Example 1 This embodiment provides a wide-temperature-range wear-resistant adaptive lubrication dual-phase high-entropy ceramic material with the following chemical composition: (Hf 0.2 Mo 0.25 Ti 0.2 Nb 0.15 Ta 0.2 C-20wt%(Hf) 0.2 Mo 0.25 Ti 0.2 Nb 0.15 Ta 0.2 )B2.

[0025] (I) (Hf) 0.2 Mo 0.25 Ti 0.2 Nb 0.15 Ta 0.2 Preparation of high-entropy ceramic powder The following raw materials were weighed according to mass percentage (g / g): 21.12% HfO2, 18.05% MoO3, 8.01% TiO2, 10.00% Nb2O5, 22.17% Ta2O5, and 20.65% graphite powder. The raw materials were mixed evenly in a ball mill, then loaded into a graphite mold and subjected to spark plasma sintering under a vacuum of less than 0.3 Pa. The sintering process was as follows: average heating rate 30℃ / min, sintering temperature 1675℃, pressure 10 MPa, and holding time 25 min. After furnace cooling, a high-entropy ceramic bulk was obtained.

[0026] The obtained agglomerates were subjected to high-energy ball milling. The milling conditions were: ball-to-material ratio of 0.8:1, rotation speed of 180 r / min, and milling time of 6 h. The grinding jar and grinding balls were made of carbide cemented carbide, and argon gas was introduced for protection before the start of milling. After milling, (Hf) particles with a particle size of 0.06~2.5 μm were obtained. 0.2 Mo 0.25 Ti 0.2 Nb 0.15 Ta 0.2 C high-entropy ceramic powder.

[0027] (2) (Hf 0.2 Mo 0.25 Ti 0.2 Nb 0.15 Ta 0.2 Preparation of B2 raw material mixed powder Weigh the following raw materials according to their mass percentages (g / g): 28.38% HfB2, 20.84% ​​MoB2, 9.86% TiB2, 12.18% NbB2, and 28.74% TaB2. Place the above raw materials in a ball mill, add anhydrous ethanol at 0.35 times the total mass of the raw materials, mix thoroughly, dry at 40 °C, and sieve to obtain HfB2 particles with a particle size of 0.10~5 μm. 0.2 Mo 0.25 Ti 0.2 Nb 0.15 Ta 0.2 B2 mixed powder.

[0028] (III) Preparation of Two-Phase High-Entropy Ceramic Bulk Weigh 80% of the (Hf) obtained in step (I) according to the mass percentage (g / g). 0.2 Mo 0.25 Ti 0.2 Nb 0.15 Ta 0.2 )C high-entropy ceramic powder and 20% of (Hf) prepared in step (II) 0.2 Mo 0.25 Ti 0.2 Nb 0.15 Ta 0.2 B2 Mixed Powder. Place all raw materials in a ball mill, add anhydrous ethanol at 0.35 times the total mass of the raw materials, mix evenly, dry at 40 ℃, and sieve to obtain mixed powder with a particle size of 0.10~5 μm.

[0029] The above-mentioned mixed powder was loaded into a graphite mold and subjected to two-step discharge plasma sintering under a vacuum of less than 0.3 Pa: Step 1: Raise the temperature to 1700 ℃ at an average heating rate of 40 ℃ / min, apply a pressure of 15 MPa, and hold for 8 min; Step 2: Continue to raise the temperature to 1900 ℃ at an average heating rate of 80 ℃ / min, apply a pressure of 45 MPa, and hold for 12 min.

[0030] After cooling in the furnace, a two-phase high-entropy ceramic bulk material is obtained.

[0031] (iv) Performance Characterization The obtained material was subjected to phase analysis using X-ray diffraction, and the results are as follows: Figure 1 As shown. From Figure 1 It can be seen that the material consists of a high-entropy carbide phase (HEC) and a high-entropy boride phase (HEB), indicating that a two-phase high-entropy ceramic has been successfully prepared.

[0032] The density of the material was measured using Archimedes' principle, and the relative density was calculated to be 98.0%. The room temperature hardness was tested using a Vickers microhardness tester (load 5 kg, loading duration 10 s), and the result was 23.5 GPa.

[0033] The atmospheric tribological properties of the materials were evaluated using a high-temperature reciprocating friction testing machine (GF-I). The paired balls were Al₂O₃ ceramic. The load was 5 N, the rotational speed was 300 r / min, the amplitude was 5 mm, the testing time was 30 min, and the testing temperatures were 25 ℃, 400 ℃, 800 ℃, and 1100 ℃. The results showed that the average friction coefficients at 25 ℃, 400 ℃, 800 ℃, and 1100 ℃ were 0.45, 0.68, 0.35, and 0.30, respectively; and the wear rates were 5.2 × 10⁻⁶. -7 mm 3 / Nm, 9.0×10 -7 mm 3 / Nm, 3.8×10 -5 mm 3 / Nm and 7.8×10 -5 mm 3 / Nm. This material exhibits excellent self-lubricating properties and wear resistance over a wide temperature range.

[0034] Example 2 This embodiment provides a wide-temperature-range wear-resistant adaptive lubrication dual-phase high-entropy ceramic material with the following chemical composition: (Hf 0.2 Mo 0.2 Ti 0.2 Nb 0.2 Ta 0.2 C-50wt%(Hf) 0.2 Mo 0.2 Ti 0.2 Nb 0.2 Ta 0.2 )B2.

[0035] (I) (Hf)0.2 Mo 0.2 Ti 0.2 Nb 0.2 Ta 0.2 Preparation of high-entropy ceramic powder The following raw materials were weighed according to mass percentage (g / g): 21.15% HfO2, 14.30% MoO3, 8.04% TiO2, 13.66% Nb2O5, 22.27% Ta2O5, and 20.58% graphite powder. After uniform mixing, the mixture was subjected to spark plasma sintering under the following conditions: vacuum degree below 0.3 Pa, average heating rate 40 ℃ / min, sintering temperature 1725 ℃, pressure 8 MPa, and holding time 20 min. The resulting bulk material was then pulverized by high-energy ball milling (ball-to-material ratio 1:1, rotation speed 200 r / min, ball milling time 4 h, argon protection) to obtain HfO2 particles with a particle size of 0.06~2.5 μm. 0.2 Mo 0.2 Ti 0.2 Nb 0.2 Ta 0.2 C high-entropy ceramic powder.

[0036] (2) (Hf 0.2 Mo 0.2 Ti 0.2 Nb 0.2 Ta 0.2 Preparation of B2 raw material mixed powder Weigh the following raw materials by mass percentage (g / g): 28.40% HfB2, 16.69% MoB2, 9.87% TiB2, 16.26% NbB2, and 28.78% TaB2. Place them in a ball mill, add anhydrous ethanol at 0.40 times the total mass of the raw materials, mix thoroughly, dry at 50 °C, and sieve to obtain HfB2 particles with a particle size of 0.10~5 μm. 0.2 Mo 0.2 Ti 0.2 Nb 0.2 Ta 0.2 B2 mixed powder.

[0037] (III) Preparation of Two-Phase High-Entropy Ceramic Bulk Weigh 50% of the (Hf) obtained in step (I) according to the mass percentage (g / g). 0.2 Mo 0.2 Ti 0.2 Nb 0.2 Ta 0.2 )C high-entropy ceramic powder and 50% of the (Hf) obtained in step (II) 0.2 Mo 0.2 Ti 0.2 Nb 0.2 Ta0.2 B2 mixed powder. Place it in a ball mill, add anhydrous ethanol at 0.45 times the total mass of the raw materials, mix evenly, dry at 50 ℃ and sieve to obtain mixed powder with a particle size of 0.10~5 μm.

[0038] The above-mentioned mixed powder was loaded into a graphite mold and subjected to two-step discharge plasma sintering under a vacuum of less than 0.3 Pa: Step 1: Raise the temperature to 1800 ℃ at an average heating rate of 60 ℃ / min, apply a pressure of 10 MPa, and hold for 6 min; Step 2: Continue to raise the temperature to 1950 ℃ at an average heating rate of 120 ℃ / min, apply a pressure of 35 MPa, and hold for 8 min.

[0039] After cooling in the furnace, a two-phase high-entropy ceramic bulk material is obtained.

[0040] (iv) Performance Characterization The microstructure of the obtained material was observed using backscattered electron microscopy, and the results are as follows: Figure 2 As shown. From Figure 2 The carbide phase (HEC, light gray) and the boride phase (HEB, dark gray) can be clearly distinguished. The two phases are evenly distributed and have good interfacial bonding.

[0041] The material was tested and found to have a relative density of 99.0% and a room temperature hardness of 22.0 GPa. Tribological performance testing conditions were the same as in Example 1. The results showed that the average coefficients of friction at 25 ℃, 400 ℃, 800 ℃, and 1100 ℃ were 0.49, 0.60, 0.31, and 0.25, respectively; and the wear rates were 6.0 × 10⁻⁶. -7 mm 3 / Nm, 1.1×10 -6 mm 3 / Nm, 2.2×10 -5 mm 3 / Nm and 4.6×10 -5 mm 3 / Nm.

[0042] Example 3 This embodiment provides a wide-temperature-range wear-resistant adaptive lubrication dual-phase high-entropy ceramic material with the following chemical composition: (Hf 0.2 Mo 0.15 Ti 0.3 Nb 0.15 Ta 0.2 C-75wt%(Hf) 0.2 Mo 0.15 Ti 0.3 Nb 0.15 Ta 0.2)B2.

[0043] (I) (Hf) 0.2 Mo 0.15 Ti 0.3 Nb 0.15 Ta 0.2 Preparation of high-entropy ceramic powder The following raw materials were weighed according to mass percentage (g / g): 21.96% HfO2, 11.26% MoO3, 12.50% TiO2, 10.40% Nb2O5, 23.05% Ta2O5, and 20.83% graphite powder. After uniform mixing, the mixture was subjected to spark plasma sintering under the following conditions: vacuum degree below 0.3 Pa, average heating rate 55 ℃ / min, sintering temperature 1800 ℃, pressure 5 MPa, and holding time 15 min. The resulting bulk material was then pulverized by high-energy ball milling (ball-to-material ratio 1.5:1, rotation speed 220 r / min, ball milling time 2 h, argon protection) to obtain HfO2 particles with a particle size of 0.06~2.5 μm. 0.2 Mo 0.15 Ti 0.3 Nb 0.15 Ta 0.2 C high-entropy ceramic powder.

[0044] (2) (Hf 0.2 Mo 0.15 Ti 0.3 Nb 0.15 Ta 0.2 Preparation of B2 raw material mixed powder Weigh the following raw materials by mass percentage (g / g): 29.39% HfB2, 12.94% MoB2, 15.31% TiB2, 12.61% NbB2, and 29.75% TaB2. Place them in a ball mill, add anhydrous ethanol at 0.45 times the total mass of the raw materials, mix thoroughly, dry at 60 °C, and sieve to obtain HfB2 particles with a particle size of 0.10~5 μm. 0.2 Mo 0.15 Ti 0.3 Nb 0.15 Ta 0.2 B2 mixed powder.

[0045] (III) Preparation of Two-Phase High-Entropy Ceramic Bulk Weigh 25% of the (Hf) obtained in step (I) according to the mass percentage (g / g). 0.2 Mo 0.15 Ti 0.3 Nb 0.15 Ta 0.2 )C high-entropy ceramic powder and 75% of the (Hf) obtained in step (II) 0.2 Mo 0.15Ti 0.3 Nb 0.15 Ta 0.2 B2 mixed powder. Place it in a ball mill, add anhydrous ethanol at 0.55 times the total mass of the raw materials, mix evenly, dry at 60 ℃ and sieve to obtain mixed powder with a particle size of 0.10~5 μm.

[0046] The above-mentioned mixed powder was loaded into a graphite mold and subjected to two-step discharge plasma sintering under a vacuum of less than 0.3 Pa: Step 1: Raise the temperature to 1850 ℃ at an average heating rate of 80 ℃ / min, apply a pressure of 8 MPa, and hold for 3 min; Step 2: Continue to raise the temperature to 2000 ℃ at an average heating rate of 150 ℃ / min, apply a pressure of 25 MPa, and hold for 5 min.

[0047] After cooling in the furnace, a two-phase high-entropy ceramic bulk material is obtained.

[0048] (iv) Performance Characterization Figure 3 This is a curve showing the change in the coefficient of friction of the material prepared in this embodiment over time when it is rubbed against Al2O3 ceramic balls at 1100 °C. From... Figure 3 It can be seen that at a high temperature of 1100 ℃, the coefficient of friction quickly enters a stable state with an average value of about 0.18 and small fluctuation range, indicating that the material has excellent high-temperature self-lubricating properties and frictional stability.

[0049] The material was tested and found to have a relative density of 99.5% and a room temperature hardness of 20.0 GPa. Tribological performance testing conditions were the same as in Example 1. The results showed that the average coefficients of friction at 25 ℃, 400 ℃, 800 ℃, and 1100 ℃ were 0.54, 0.56, 0.24, and 0.18, respectively; and the wear rates were 6.8 × 10⁻⁶. -7 mm 3 / Nm, 1.7×10 -6 mm 3 / Nm, 1.1×10 -5 mm 3 / Nm and 2.5×10 -5 mm 3 / Nm.

[0050] Examples 1-3 above demonstrate that by controlling the phase composition (carbide phase mass fraction 25-80%, boride phase mass fraction 20-75%) and main component (x=0.15-0.25, y=0.20-0.30, z=0.15-0.20) of the dual-phase high-entropy carbide-boride ceramic, combined with a two-step spark plasma sintering process, a relative density of 98.0-99.5%, a room temperature hardness of 20.0-23.5 GPa, a wide temperature range (room temperature to 1100 ℃) friction coefficient of 0.18-0.68, and a wear rate as low as 10 can be obtained. -7 mm 3 A dual-phase high-entropy ceramic material on the order of / Nm. This material achieves a balance between mechanical properties and wide-temperature-range self-lubricating properties, meeting the application requirements of moving parts under extremely harsh conditions.

[0051] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A wide-temperature-range wear-resistant, adaptive lubrication, dual-phase high-entropy ceramic material, characterized in that: The chemical composition of the dual-phase high-entropy ceramic material is (Hf) 0.2 Mo x Ti y Nb z Ta 0.2 )C-pwt%(Hf 0.2 Mo x Ti y Nb z Ta 0.2 )B2, x+y+z=0.6, 0.15≤x≤0.25, 0.20≤y≤0.30, 0.15≤z≤0.20, 20≤p≤75.

2. A method for preparing the wide-temperature-range wear-resistant adaptive lubrication dual-phase high-entropy ceramic material as described in claim 1, characterized in that, Includes the following steps: (1) Weigh out 25~80wt% of (Hf) according to mass percentage. 0.2 Mo x Ti y Nb z Ta 0.2 )C high-entropy ceramic powder and 20~75wt% boride mixed powder, wherein the boride mixed powder is composed of HfB2, MoB2, TiB2, NbB2 and TaB2 in the ratio of (Hf) 0.2 Mo x Ti y Nb z Ta 0.2 The raw materials are mixed in the stoichiometric ratio of chemical elements of B2; the raw materials are placed in a ball mill and ball-milled, and anhydrous ethanol of 0.35 to 0.55 times the total mass of the raw materials is added to the mixed raw materials. After mixing evenly, the mixture is dried at 40 to 60 °C and sieved to obtain a final mixed powder with a particle size of 0.10 to 5 μm. (2) The final mixed powder obtained in step (1) is loaded into a graphite mold and subjected to discharge plasma sintering under a vacuum of less than 0.3 Pa: first, the temperature is raised to 1700-1850 ℃ at an average heating rate of 40-80 ℃ / min, and held at a pressure of 8-15 MPa for 3-8 min; then, the temperature is raised to 1900-2000 ℃ at an average heating rate of 80-150 ℃ / min, and held at a pressure of 25-45 MPa for 5-12 min; the material is cooled with the furnace to obtain the dual-phase high-entropy ceramic material.

3. The application of the dual-phase high-entropy ceramic material as described in claim 1 in the preparation of wear-resistant self-lubricating components with a wide temperature range.

4. The application according to claim 3, characterized in that: The components are bearings, turbine blades, nozzles, sealing rings, or friction pair components that operate in a temperature range from room temperature to 1100 °C.

Images