Method for preparing dense and high-hardness carbon-rich high-entropy alloy or carbon-rich high-entropy alloy-high-entropy ceramic composite material

Abstract

The application discloses a preparation method of a dense and high-hardness carbon-rich high-entropy alloy or carbon-rich high-entropy alloy-high-entropy ceramic composite material, and comprises the following steps: using metal oxide powder and a carbon source as raw materials, the raw materials are weighed according to a designed proportion, an organic solvent is added, and the raw materials are fully mixed, then rotary evaporation drying is performed; the dried powder is pressed into a shape by using a mold, and pressureless sintering is performed in a vacuum state after shaping, so that the dense and high-hardness carbon-rich high-entropy alloy is obtained. The metal oxide powder is used as the raw material, and the carbon-rich high-entropy alloy or the carbon-rich high-entropy alloy-high-entropy ceramic composite material is successfully prepared by using a pressureless reaction sintering one-step method, so that the production cost is greatly reduced, and meanwhile, it is expected to successfully prepare a complex-configuration part.

Description

Technical Field

[0001] This invention belongs to the field of alloy and alloy-ceramic composite material preparation technology, specifically relating to a method for preparing a dense and high-hardness carbon-rich high-entropy alloy or a carbon-rich high-entropy alloy-high-entropy ceramic composite material. Background Technology

[0002] High-entropy alloys, as novel high-performance structural materials, have attracted widespread attention since their initial proposal by Taiwanese scholar Yeh Chun-wei in 1995. Their unique multi-element composition endows them with excellent mechanical properties and high-temperature stability [Journal of Alloys and Compounds, 549(2013): 195-199]. Their high hardness, high strength, and wear resistance make them widely used in machine tools, hard tool coatings, and motors; simultaneously, their stable performance under high-temperature conditions and excellent oxidation resistance make them highly sought after for components used in extreme environments (engine blades, jet engines, nuclear fusion) [International Journal of Refractory Metals and Hard Materials, 105(2022): 105836]. Therefore, the applications of high-entropy alloys are very extensive, and their future development is promising.

[0003] Subsequently, researchers conducted a long and in-depth exploration of the preparation methods for high-entropy alloys. Among these, the most commonly used methods include resistance induction melting, vacuum arc melting, mechanical alloying, powder metallurgy, and laser cladding. Patent CN 111206174 A discloses a two-step method using mechanical alloying combined with spark plasma sintering to prepare a (Fe50Mn30Cr10Co10)100-XAlX (x=8-20) high-entropy alloy, achieving a compressive strength of 1916 MPa and a hardness of 614 Hv. Patent CN 108531799 A discloses the use of arc melting to obtain a TiAlNbVMo master alloy button ingot, with a compressive strength of 1000 MPa measured after post-processing. Most existing high-entropy alloy preparation processes use high-purity metal powders as raw materials, which suffers from problems such as high raw material costs, susceptibility to oxidation, and cumbersome process operations. Due to limitations in the preparation process, the resulting alloys fall far short of meeting the demands of complex structural components in engineering applications. At the same time, the material's mechanical properties are also unsatisfactory. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention designs components to use inexpensive metal oxide powders as raw materials, add a certain amount of carbon source, and prepare dense and high-hardness carbon-rich high-entropy alloys or carbon-rich high-entropy alloy-high-entropy ceramic multiphase materials through pressureless reaction sintering, which can significantly reduce the production cost of high-entropy alloys.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0006] On one hand, the present invention provides a method for preparing a dense and high-hardness carbon-rich high-entropy alloy, comprising:

[0007] Metal oxide powder and carbon source are used as raw materials. They are weighed according to the design ratio and mixed thoroughly with organic solvent. Then, they are dried by rotary evaporation. The dried powder is pressed into shape using a mold. After molding, it is sintered without pressure under vacuum to obtain a dense and high-hardness carbon-rich high-entropy alloy.

[0008] Preferably, the metal elements in the metal oxide are Cr, V, W and Mo, the atomic ratio of Cr, V, W, Mo and C is 1:1:1:1:0.53~0.61, and the carbon-rich high-entropy alloy is a BCC phase carbon-rich high-entropy alloy.

[0009] Preferably, the metal elements in the metal oxide are Cr, V, W and Me, wherein Me = Ti, Zr or Hf, and the atomic ratio of Cr, V, W, Me and C is 1:1:1:1:1:0.54-0.82. The carbon-rich high-entropy alloy is composed of BCC phase carbon-rich high-entropy alloy and HCP phase carbon-rich high-entropy alloy.

[0010] Preferably, the metal elements in the metal oxide are Cr, Mo, V, W and Me, wherein Me = Ti, Zr, Hf or Nb, and the atomic ratio of Cr, Mo, V, W, Me and C is 1:1:1:1:1:0.42~0.66. The carbon-rich high-entropy alloy material is composed of BCC phase carbon-rich high-entropy alloy and HCP phase carbon-rich high-entropy alloy.

[0011] Preferably, the pressureless sintering process is as follows: first, the temperature is raised to 700℃ at a rate of 8℃ / min, then the heating rate is adjusted to 5℃ / min, and the temperature is held at 900℃-950℃, 1100℃-1300℃ and 1600℃ for 10-30 minutes respectively, until the temperature reaches 1650℃-1900℃. After holding at this temperature for 1-2 hours, the furnace body is allowed to cool naturally to room temperature.

[0012] Preferably, after the dried powder is initially pressed into shape, it needs to undergo cold isostatic pressing treatment, and then carry out a carbothermic reduction reaction under vacuum.

[0013] Preferably, the carbon source is selected from graphite or carbon black powder.

[0014] A method for preparing a dense and high-hardness carbon-rich high-entropy alloy-high-entropy ceramic multiphase material includes:

[0015] Metal oxide powder and carbon source are used as raw materials. They are weighed according to the design ratio and mixed thoroughly with organic solvent, and then dried by rotary evaporation. The dried powder is pressed into shape using a mold, and then sintered without pressure under vacuum to obtain a dense and high-hardness carbon-rich high-entropy alloy-high-entropy ceramic multiphase material.

[0016] Preferably, the metal elements in the metal oxide are Cr, V, W and Mo, and the atomic ratio of Cr, V, W, Mo and C is 1:1:1:1:0.62~0.82. In this case, the carbon-rich high-entropy alloy-high-entropy ceramic multiphase material is composed of HCP phase carbon-rich high-entropy alloy and FCC phase high-entropy ceramic.

[0017] Preferably, the pressureless sintering process is as follows: first, the temperature is raised to 700℃ at a rate of 8℃ / min, then the heating rate is adjusted to 5℃ / min, and the temperature is held at 950℃, 1100℃, and 1300-1400℃ for 10-30 minutes respectively, until the temperature reaches 1450-1900℃. After holding at this temperature for 1-2 hours, the sample is allowed to cool naturally to room temperature along with the furnace body.

[0018] The technical solution provided by this invention has the following beneficial effects:

[0019] This invention achieves the preparation of carbon-rich high-entropy alloys or carbon-rich high-entropy alloy-high-entropy ceramic multiphase materials by designing components using inexpensive metal oxide powders as raw materials, adding a certain amount of graphite or carbon black, and through carbothermal reduction reaction, thereby significantly reducing the production cost of high-entropy alloys.

[0020] This invention employs a pressureless reaction one-step sintering method to prepare dense carbon-rich high-entropy alloys or carbon-rich high-entropy alloy-high-entropy ceramic multiphase materials, simplifying the problems of cumbersome operation and high energy consumption of the original technology.

[0021] This invention employs pressureless reaction sintering, which does not limit the configuration of sintered parts. Different configurations of parts can be prepared according to requirements in the early stage of sample preparation, avoiding the limitation of part configuration caused by pressure sintering.

[0022] The present invention prepares a dense and high-hardness carbon-rich high-entropy alloy with a hardness of 730-1230Hv3, a flexural strength of 330-550MPa, a compressive strength of 2.0-2.9GPa, and a Young's modulus of 200-310GPa.

[0023] This invention enables the preparation of dense and high-hardness carbon-rich high-entropy alloy-high-entropy ceramic multiphase materials with different phases by controlling the types of metal oxides and the carbon atom content in the raw materials. The hardness can reach 610-1130Hv3, the flexural strength is 200-550MPa, the compressive strength is 1.9-2.9GPa, and the Young's modulus is 200-310GPa.

[0024] Since carbon, as an interstitial element, can combine with most metal oxides and ultimately exist as a reinforcing phase in the form of carbon compounds, this is universally applicable to the preparation of carbon-containing high-entropy alloys using the carbothermic reduction method. Therefore, this invention is of great significance in terms of method innovation and has broad application prospects. Attached Figure Description

[0025] Figure 1 This invention relates to the preparation process of carbon-rich high-entropy alloys or carbon-rich high-entropy alloy-high-entropy ceramic multiphase materials.

[0026] Figure 2 The XRD diffraction patterns of the carbon-rich high-entropy alloys and the carbon-rich high-entropy alloy-high-entropy ceramic composite materials prepared in Examples 1-4 of this invention are shown.

[0027] Figure 3 The images show SEM images of the polished surfaces of the carbon-rich high-entropy alloy and the carbon-rich high-entropy alloy-high-entropy ceramic composite material obtained in Examples 1 and 2 of this invention.

[0028] Figure 4 The image shows the compressive stress-strain curve of the carbon-rich high-entropy alloy-high-entropy ceramic composite material obtained in Example 1 of this invention.

[0029] Figure 5 XRD diffraction patterns of CrMoVW high-entropy ceramic materials were prepared for comparative examples 1 and 2.

[0030] Figure 6 SEM images of the polished surfaces of CrMoVW high-entropy ceramic materials prepared for comparative examples 1 (Fig. A) and 2 (Fig. B). Detailed Implementation

[0031] To enable those skilled in the art to better understand the technical solutions of the present invention, the preferred embodiments of the present invention are described below in conjunction with specific examples. However, these should not be construed as limiting the present invention and are merely examples.

[0032] Unless otherwise specified, the test methods or experimental methods described in the following examples are conventional methods; unless otherwise specified, the reagents and materials are obtained from conventional commercial sources or prepared by conventional methods.

[0033] The present invention will now be described in further detail with reference to the accompanying drawings.

[0034] Example 1

[0035] like Figure 1 As shown, Cr2O3, MoO3, V2O5, WO3 powders and graphite or carbon black were selected as raw materials. The atomic ratio of Cr, Mo, V, W, and C in the high-entropy alloy was 1:1:1:1:0.53-0.61. A highly dense carbon-rich high-entropy alloy-high-entropy ceramic multiphase material was prepared in one step by carbothermal reduction combined with pressureless sintering. The raw materials contained only Cr, Mo, V, W, C, and O elements; the particle size of the metal oxide powder was ~0.2 μm, and the particle size of the graphite or carbon black powder was ~2 μm. The specific preparation method included the following steps:

[0036] S1. Mixing: Mix high-purity (purity ≥99.9%) Cr2O3, MoO3, V2O5, WO3 and graphite or carbon black in a molar ratio of 0.5:1:0.5:1:7.42~8.54, then add a certain amount of ethanol and mix thoroughly on a roller mixer at a speed of 80-120 r / min for 16-24h.

[0037] S2. Drying: The mixed powder is subjected to rotary evaporation at 50°C and under vacuum. The evaporated powder is then placed in an oven at 60°C for 8 hours to dry, in order to remove excess ethanol.

[0038] S3. Sintering: After drying, the powder is passed through an 80-mesh sieve and then pressed into discs with a diameter of Φ30 using a mold. After initial shaping, it is cold isostatically pressed at 200MPa for 10 minutes, followed by a carbothermic reduction reaction under vacuum. The sintering process involves raising the temperature to 700℃ at a rate of 8℃ / min, then adjusting the heating rate to 5℃ / min, and holding at 950℃, 1100℃, and 1300℃ for 10-30 minutes respectively, until the temperature reaches 1450℃-1800℃, which is then held for 1.5 hours. The process is then complete, and the sample is allowed to cool naturally to room temperature with the furnace. XRD phase analysis and SEM of the polished surface indicate that the material prepared at this stage is a dense BCC phase carbon-rich high-entropy alloy (e.g., ...). Figure 2 and Figure 3 (As shown). Mechanical characterization results show that the material has a Vickers hardness of 730-820 Hv3, a flexural strength of 470-550 MPa, and a compressive strength of 2.3-2.9 GPa (compressive stress-strain curves are shown in Figure 1). Figure 4 As shown in the figure, the Young's modulus is 260-310 GPa.

[0039] Example 2

[0040] like Figure 1As shown, Cr2O3, V2O5, WO3, MoO3, and graphite or carbon black were selected as raw materials. The atomic ratio of Cr, V, W, Me, and carbon in the high-entropy alloy was 1:1:1:1:0.62-0.82. A highly dense carbon-rich high-entropy alloy-high-entropy ceramic multiphase material was prepared in one step by carbothermal reduction combined with pressureless sintering. The raw materials contained only Cr, V, W, Mo, C, and O elements. The particle size of the metal oxide powder was ~0.2 μm, and the particle size of the graphite or carbon black powder was ~2 μm. The specific preparation method included the following steps:

[0041] S1. Mixing: Mix high-purity (purity ≥99.9%) Cr2O3, V2O5, WO3, MoO3 and graphite or carbon black in a molar ratio of 0.5:0.5:1:1:8.68~11.48, then add a certain amount of ethanol and mix thoroughly in a mixer at a speed of 80-120 r / min for 16-24h.

[0042] S2. Drying: The mixed powder is subjected to rotary evaporation at 50°C and under vacuum to remove ethanol. Then it is placed in an oven at 60°C for 8 hours to remove excess ethanol.

[0043] S3. Sintering: After drying, the powder is passed through an 80-mesh sieve and pressed into discs with a diameter of Φ30 using a mold. After initial shaping, it is cold isostatically pressed at 200 MPa for 10 minutes. Then, a carbothermic reduction reaction is carried out under vacuum, with the temperature increased to 700℃ at a rate of 8℃ / min. The heating rate is then adjusted to 5℃ / min, and the temperature is held at 950℃, 1100℃, and 1400℃ for 10 minutes each, until the temperature reaches 1750℃-1900℃. After holding at this temperature for 1.5 hours, the sample is allowed to cool naturally to room temperature with the furnace. XRD phase analysis and SEM of the polished surface show that the material prepared at this stage is a dense HCP phase carbon-rich high-entropy alloy and an FCC phase high-entropy ceramic composite material (e.g., ...). Figure 2 and Figure 3 (As shown). Mechanical characterization results show that the material has a Vickers hardness of 833-1023 Hv3, a flexural strength of 200-380 MPa, a compressive strength of 2.1-2.5 GPa, and a Young's modulus of 200-270 GPa.

[0044] Example 3

[0045] like Figure 1As shown, Cr2O3, V2O5, WO3, and Me (Me = TiO2, ZrO2, or HfO2), along with graphite or carbon black, are selected as raw materials. The atomic ratio of Cr, V, W, Me, and carbon in the high-entropy alloy is 1:1:1:1:0.54-0.82. A highly dense carbon-rich high-entropy alloy-high-entropy ceramic multiphase material is prepared in one step using carbothermal reduction combined with pressureless sintering. The raw materials contain only Cr, V, W, Me, C, and O elements; the metal oxide powder has a particle size of ~0.2 μm, and the graphite or carbon black powder has a particle size of ~2 μm. The specific preparation method includes the following steps:

[0046] S1. Mixing: Mix high-purity (purity ≥99.9%) Cr2O3, V2O5, WO3, Me and graphite or carbon black in a molar ratio of 0.5:1:0.5:1:7.02~10.52, then add a certain amount of ethanol and mix thoroughly in a mixer at a speed of 80-120 r / min for 16-24h.

[0047] S2. Drying: The mixed powder is subjected to rotary evaporation at 50°C and under vacuum to remove ethanol. Then it is placed in an oven at 60°C for 8 hours to remove excess ethanol.

[0048] S3. Sintering: After drying, the powder is passed through an 80-mesh sieve and then pressed into discs with a diameter of Φ30 using a mold. After initial shaping, it is cold isostatically pressed at 200 MPa for 10 minutes. Subsequently, a carbothermic reduction reaction is carried out under vacuum, with the temperature increased to 700℃ at a rate of 8℃ / min. The heating rate is then adjusted to 5℃ / min, and the temperature is held at 950℃, 1100℃, and 1400℃ for 10 minutes each, until the temperature reaches 1750℃-1900℃. After holding at this temperature for 1.5 hours, the sample is allowed to cool naturally to room temperature with the furnace. XRD phase analysis shows that the material prepared at this stage is a dense BCC phase carbon-rich high-entropy alloy and an HCP phase carbon-rich high-entropy alloy (e.g., ...). Figure 2 (As shown). Mechanical characterization results show that the material has a Vickers hardness of 610-1130 Hv3, a flexural strength of 250-400 MPa, a compressive strength of 1.9-2.5 GPa, and a Young's modulus of 260-290 GPa.

[0049] Example 4

[0050] like Figure 1As shown, Cr2O3, MoO3, V2O5, WO3, Me (Me = TiO2, ZrO2, HfO2 or Nb2O5) powders and graphite or carbon black are selected as raw materials. The atomic ratio of Cr, Mo, V, W, Me, and C in the materials is 1:1:1:1:1:0.42-0.66. A highly dense carbon-rich high-entropy alloy is prepared in one step by carbothermal reduction combined with pressureless sintering. The raw materials contain only Cr, Mo, V, W, Me, C, and O elements. The particle size of the metal oxide powder is ~0.2μm, and the particle size of the graphite or carbon black powder is ~2μm. The specific preparation method includes the following steps:

[0051] S1. Mixing: Mix high-purity (purity ≥99.9%) metal oxide powders Cr2O3, MoO3, V2O5, WO3, Me and graphite or carbon black in a molar ratio of 0.5:1:0.5:1:1 or 0.5:7.0~10.0, add a certain amount of ethanol, and mix thoroughly in a mixer at a speed of 80-120 r / min for 16-24h.

[0052] S2. Drying: The mixed powder is subjected to rotary evaporation at 50°C and under vacuum to remove ethanol. Then it is placed in an oven at 60°C for 8 hours to remove excess ethanol.

[0053] S3. Sintering: After the dried powder is passed through an 80-mesh sieve, it is pressed into discs with a diameter of Φ30 using a mold. After preliminary shaping, it is cold isostatically pressed at 200MPa for 10 minutes. Then, a carbothermic reduction reaction is carried out under vacuum, with the temperature increased to 700℃ at a rate of 8℃ / min. The heating rate is then adjusted to 5℃ / min, and the temperature is held at 900℃-950℃, 1100℃-1300℃, and 1600℃ for 10-30 minutes respectively, until the temperature reaches 1650℃-1900℃. After holding at this temperature for 1-2 hours, the furnace is allowed to cool naturally to room temperature. XRD phase analysis shows that the material prepared at this stage is a dense, carbon-rich, high-entropy alloy of BCC and HCP phases (e.g., ...). Figure 2 (As shown). Mechanical characterization results show that the material has a Vickers hardness of 820-1230 Hv3, a flexural strength of 330-490 MPa, a compressive strength of 2.0-2.6 GPa, and a Young's modulus of 200-270 GPa.

[0054] Comparative Example 1

[0055] The preparation steps of the high-entropy alloy material are the same as in Example 1, except that high-purity Cr2O3, MoO3, V2O5, WO3, and graphite or carbon black are mixed in a molar ratio of 0.5:1:0.5:1:11.48, and the atomic ratio of Cr, Mo, V, W, and C in the material is 1:1:1:1:1:0.82. XRD diffraction of the sintered sample shows that the FCC phase is the main phase (e.g., ...). Figure 5 and Figure 6 (As shown) and the relative density is only 92%, the hardness is improved but the brittleness is high. The main phase is a high-entropy ceramic phase and there is no high-entropy alloy phase. The mechanical characterization results show that the Vickers hardness of the material is 1312Hv3, the bending strength is 230MPa, the compressive strength is 2.5GPa, and the Young's modulus is 276GPa.

[0056] Comparative Example 2

[0057] The preparation steps of the high-entropy alloy material are the same as in Example 1, except that high-purity chromium trioxide, molybdenum oxide, vanadium pentoxide, tungsten oxide, and carbon are mixed in a molar ratio of 0.5:1:0.5:1:11.6-14.0, and the atomic ratio of chromium, molybdenum, vanadium, tungsten, and carbon in the material is 1:1:1:1:1:0.83-1.0. The sintered sample shows an FCC phase (e.g., ...) according to XRD diffraction. Figure 5 and Figure 6 As shown in the figure, the hardness is improved, but the brittleness is high. The main phase is ceramic phase with no alloy phase. The relative density is only 58.5~86.7%, and the mechanical properties cannot be characterized.

[0058] This invention employs a one-step carbothermal reduction method and pressureless sintering preparation conditions, which not only has a simple process and strong controllability, but also enables the preparation of complex components. In addition, the high-entropy alloy is formed by introducing interstitial element carbon, which significantly improves the hardness of the alloy material through solid solution strengthening while maintaining the alloy's plasticity.

[0059] The above are merely preferred embodiments of the present invention. It should be noted that the above preferred embodiments should not be considered as limitations on the present invention, and the scope of protection of the present invention should be determined by the scope defined in the claims. For those skilled in the art, several improvements and modifications can be made without departing from the spirit and scope of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a dense and high-hardness carbon-rich high-entropy alloy, characterized in that, include: Metal oxide powder and carbon source are used as raw materials. They are weighed according to the designed ratio and added to an organic solvent for thorough mixing, followed by rotary evaporation and drying. The metal elements in the metal oxide are Cr, V, W and Me, where Me = Ti, Zr or Hf, and the atomic ratio of Cr, V, W, Me and C is 1:1:1:1:0.54-0.

82. Alternatively, the metal elements in the metal oxide are Cr, Mo, V, W and Me, where Me = Ti, Zr, Hf or Nb, and the atomic ratio of Cr, Mo, V, W, Me and C is 1:1:1:1:1:0.42~0.

66. The dried powder is pressed into shape using a mold, and then pressureless sintering is performed under vacuum. The pressureless sintering process is as follows: first, the temperature is raised to 700℃ at a rate of 8℃ / min, then the heating rate is adjusted to 5℃ / min, and the temperature is held at 900℃-950℃, 1100℃-1300℃ and 1600℃ for 10-30 min respectively, until the temperature reaches 1650℃-1900℃. After holding at this temperature for 1-2 h, the furnace body is allowed to cool naturally to room temperature, resulting in a dense and high-hardness carbon-rich high-entropy alloy. The carbon-rich high-entropy alloy is composed of BCC phase carbon-rich high-entropy alloy and HCP phase carbon-rich high-entropy alloy.

2. The method for preparing a dense and high-hardness carbon-rich high-entropy alloy according to claim 1, characterized in that, After the dried powder is initially pressed into shape, it undergoes cold isostatic pressing and then carbothermic reduction reaction under vacuum conditions.

3. The method for preparing a dense and high-hardness carbon-rich high-entropy alloy according to claim 1, characterized in that, The carbon source is selected from graphite or carbon black powder.

4. A method for preparing a dense and high-hardness carbon-rich high-entropy alloy-high-entropy ceramic multiphase material, characterized in that, include: Metal oxide powder and carbon source are used as raw materials. They are weighed according to the designed ratio and added to organic solvent for thorough mixing, and then dried by rotary evaporation. The metal elements in the metal oxide are Cr, V, W and Mo, and the atomic ratio of Cr, V, W, Mo and C is 1:1:1:1:0.62~0.

82. The dried powder is pressed into shape using a mold, and then pressureless sintering is performed under vacuum. The pressureless sintering steps are as follows: first, the temperature is raised to 700℃ at 8℃ / min, then the heating rate is adjusted to 5℃ / min, and the temperature is held at 950℃, 1100℃, and 1300-1400℃ for 10-30 min respectively, until the temperature reaches 1450-1900℃. After holding at this temperature for 1-2 h, the sample is allowed to cool naturally to room temperature with the furnace body, resulting in a dense and high-hardness carbon-rich high-entropy alloy-high-entropy ceramic multiphase material. The carbon-rich high-entropy alloy-high-entropy ceramic multiphase material is composed of HCP phase carbon-rich high-entropy alloy and FCC phase high-entropy ceramic.

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