Low-carbon-boron refractory high-entropy alloy material and preparation method and application thereof

Abstract

The invention relates to the technical field of refractory high-entropy alloy materials, and discloses a low-carbon-boron refractory high-entropy alloy material and a preparation method and application thereof.The low-carbon-boron refractory high-entropy alloy material comprises W, Mo, Nb, Cr, C and B elements, the atomic ratio of W to Mo to Nb to Cr to C to B is a: b: c: d: e: f, a = 20-25, b = 20-25, c = 20-25, d = 20-25, e = 2-6, f = 2-6, and a + b + c + d + e + f = 100. In the technical scheme, a small amount of C and B elements are added on the basis of low-cost W, Mo, Nb and Cr, the hardness and compression strength of the prepared refractory high-entropy alloy are higher than those of hard alloy, and the refractory high-entropy alloy can be used as a holding-up hammer material.

Description

Technical Field

[0001] The present invention relates to the technical field of refractory high entropy alloy materials, and in particular to a low-carbon boron refractory high entropy alloy material and a preparation method and application thereof. Background Art

[0002] The large cavity press device originated from the high-pressure technology developed by Bridgman and others in the early 20th century. It includes two-sided top presses and polyhedral pressure chamber devices. It is a device for synthesizing superhard materials such as diamond. The polyhedral pressure chamber device includes tetrahedral presses, hexahedral / top presses and octahedral presses (also known as spherical segmentation high-pressure devices), among which the tetrahedral pressure chamber is basically no longer used. The hexahedral top press is divided into two types: hinge type and pull rod type. The maximum pressure that the hexahedral and octahedral pressure chambers can reach is about 15 to 30GPa. Among them, the hexahedral top press is the most widely used large cavity press in China. This press has the advantages of strong self-centering, low cost, and easy operation. It is the main equipment for synthesizing superhard materials such as diamond and cubic boron nitride (CBN) in China.

[0003] The key components of the six-sided top press include top hammer, hydraulic cylinder, hinge beam, etc. The carbide top hammer is an important component of the production of artificial diamonds, and it is subjected to high temperature and high pressure alternating loads during the diamond synthesis process. Its life span directly determines the production cost of diamond synthesis. Since the top hammer is installed on the top of the large pad of the six-sided top press piston, when a group of six top hammers are closed by the oil cylinder to form a high-pressure chamber, the pressure in the chamber can reach more than 10GPa and the temperature can reach more than 1500℃, and it is subjected to compressive stress, tensile stress, shear stress and compressive strength and works in a supercritical state.

[0004] The price of cemented carbide top hammer is very high (a single hammer can be up to 20,000 to 30,000 yuan). A device consists of six top hammers. If one is broken and not discovered, it may cause the breakage of other hammers. Therefore, in order to reduce production costs, improve production efficiency, and promote the rapid development of the artificial cultured diamond industry, it is urgent to develop a material with better performance and lower cost to replace cemented carbide top hammers. Summary of the invention

[0005] The present invention is intended to provide a low-carbon boron refractory high-entropy alloy material and a preparation method and application thereof, and aims to develop a material with better performance and lower cost to replace the cemented carbide top hammer.

[0006] To achieve the above-mentioned purpose, the present invention adopts the following technical scheme: a low carbon boron refractory high entropy alloy material, the alloy includes W, Mo, Nb, Cr, C and B elements, the atomic ratio of W, Mo, Nb, Cr, C elements and B element is a:b:c:d:e:f, a=20~25, b=20~25, c=20~25, d=20~25, e=2~6, f=2~6, and a+b+c+d+e+f=100.

[0007] Preferably, as an improvement, the purity of the single substance powders of W, Mo, Nb, Cr, C and B elements is greater than 99.9%.

[0008] Preferably, as an improvement, the particle size of each elemental powder is 45-75 μm.

[0009] Preferably, as an improvement, a method for preparing a low-carbon boron refractory high entropy alloy material comprises the following steps:

[0010] (1) weighing and mixing the single substance powders of W, Mo, Nb, Cr, C and B according to the atomic ratio of 20-25:20-25:20-25:20-25:20-25:2-6:2-6;

[0011] (2) Mix the weighed powders;

[0012] (3) Powder ball milling;

[0013] (4) After sintering, cooling is performed to obtain a low-carbon boron refractory high-entropy alloy material.

[0014] Preferably, as an improvement, in step (2), the powder mixing operation is performed in a V-shaped powder mixer, and the mixing time is 6-10 hours.

[0015] Preferably, as an improvement, in step (3), the ball mill and the grinding balls are both made of cemented carbide materials, the average diameter of the grinding balls is 6-15 mm, and the ball-to-material mass ratio is 10:1-15:1.

[0016] Preferably, as an improvement, in step (3), the rotation speed of the ball mill is 100-400 r / min, and the ball milling time is 30-50 h.

[0017] Preferably, as an improvement, in step (4), the sintering method is hot isostatic pressing, the sintering pressure is 25-60 MPa, the sintering temperature is 1400-1600° C., and the holding time is 30-90 min.

[0018] Preferably, as an improvement, a low-carbon boron refractory high-entropy alloy material is used in the preparation of a cemented carbide top hammer.

[0019] The principle and beneficial effect of this technical solution are: high entropy alloys have many excellent properties such as high strength, high hardness, high wear resistance, high fracture toughness, excellent low temperature performance and structural stability, good corrosion resistance and oxidation resistance due to the high entropy effect in thermodynamics, slow diffusion effect in kinetics, lattice distortion effect in structure and cocktail effect in performance, and are called "the king of future materials". Refractory high entropy alloys are composed of a variety of refractory elements, and their high temperature mechanical properties are excellent. They are very suitable for working in harsh high temperature environments and have great potential in the manufacture of hot end components. In this technical solution, a small amount of C and B elements are added to the low-cost W, Mo, Nb, Cr. The hardness and compressive strength of the prepared refractory high entropy alloy are higher than those of cemented carbide, and can be used as an alternative to the top hammer material. During the technical research and development period, the determination of the composition of alloy elements is one of the difficulties of this technical solution. This solution uses W, Mo, Nb, and Cr as matrix elements, and the cost is relatively low. In addition, the combination of C and B elements can achieve the enhancement of element performance. In addition, this technical solution creatively uses the B element, and through research it is found that the absolute value of the negative mixing enthalpy of the B element with Mo and Nb is large, which causes the element to aggregate to form borides, thereby improving the strength of the alloy, with unexpected technical effects.

[0020] 1. The technical solution of the present invention uses a new type of refractory high entropy alloy material instead of cemented carbide as an anvil, thereby improving the hardness and compression strength. At the same time, compared with Ta and Hf refractory elements, W, Mo, Nb, and Cr as matrix elements have relatively low costs.

[0021] 2. This technical solution uses C (carbon) and B (boron) as added elements. The absolute value of the negative mixing enthalpy of B with Mo and Nb is large, which causes the elements to segregate to form borides. The formation of borides can strengthen the alloy through the Orowan mechanism, thereby improving the strength of the alloy. The interstitial element C significantly improves the yield strength and ultimate strength of the matrix through solid solution strengthening. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of the microstructure of the alloy of Example 1 of the present invention. DETAILED DESCRIPTION

[0023] The following is further described in detail through specific implementations, but the implementation of the present invention is not limited thereto. Unless otherwise specified, the technical means used in the following implementations are conventional means well known to those skilled in the art; the experimental methods used are all conventional methods; the materials, reagents, etc. used can all be obtained from commercial channels.

[0024] Program Overview:

[0025] A low-carbon boron refractory high-entropy alloy material, the alloy comprising W, Mo, Nb, Cr, C and B elements, the atomic ratio of W, Mo, Nb, Cr, C elements and B element is a:b:c:d:e:f, a=20-25, b=20-25, c=20-25, d=20-25, e=2-6, f=2-6, and a+b+c+d+e+f=100.

[0026] A method for preparing a low-carbon boron refractory high entropy alloy material comprises the following steps:

[0027] (1) weighing and mixing the single-substance powders of W, Mo, Nb, Cr, C and B with a purity greater than 99.9% according to a proportion, and the powder particle size is 45 to 75 μm;

[0028] (2) Place the weighed powder in a V-shaped powder mixer for mixing for 6-10 hours;

[0029] (3) The mixed powder is subjected to high-energy ball milling. The ball mill and the grinding balls are made of cemented carbide (YG6 or YG8), the average diameter of the grinding balls is 6-15 mm, the ball-to-material mass ratio is 10:1-15:1, the ball mill speed is controlled at 100-400 r / min, and the ball milling time is 30-50 h;

[0030] (4) placing the ball-milled powder in a bag for hot isostatic pressing sintering at a sintering pressure of 25-60 MPa, keeping the temperature at 1400-1600° C. for 30-90 min, and then cooling the powder to room temperature to obtain a low-carbon boron refractory high-entropy alloy material.

[0031] Example 1

[0032] W 25 Mo 20 Nb 25 Cr 20 The preparation method of C5B5 refractory high entropy alloy material comprises the following steps:

[0033] (1) The single-element powders of W, Mo, Nb, Cr, C and B with a purity greater than 99.9% are weighed and mixed in proportion, and the powder particle size is 45 to 75 μm; the atomic ratio of W, Mo, Nb, Cr, C and B is 25:20:25:20:5:5.

[0034] (2) The weighed powder is placed in a V-shaped powder mixer for mixing for 8 hours;

[0035] (3) The mixed powder is subjected to high-energy ball milling. The ball mill and the grinding balls are made of cemented carbide. The average diameter of the grinding balls is 10 mm. The ball-to-material mass ratio is 13:1. The speed of the ball mill is controlled at 120 r / min and the ball milling time is 30 h.

[0036] (4) The ball-milled powder is placed in a bag for hot isostatic pressing sintering at a sintering pressure of 25 MPa, kept at 1500°C for 60 min, and then cooled to room temperature with the furnace to obtain a low-carbon boron refractory high-entropy alloy material.

[0037] Example 2

[0038] The difference between this embodiment and embodiment 1 is that in this embodiment, the atomic ratio of W, Mo, Nb, Cr, C and B is 20:25:20:25:2:6.

[0039] Example 2

[0040] The difference between this embodiment and embodiment 1 is that in this embodiment, the atomic ratio of W, Mo, Nb, Cr, C and B is 20:25:20:25:6:2.

[0041] Comparative Example 1

[0042] Cemented carbide anvil (YL28, commercially available).

[0043] Comparative Example 2

[0044] The difference between this comparative example and Example 1 is that in this comparative example, the atomic ratios of W, Mo, Nb, Cr, C and B are added in equal proportions.

[0045] Comparative Example 3

[0046] The difference between this comparative example and Example 1 is that no B element is added in this comparative example.

[0047] Comparative Example 4

[0048] The difference between this comparative example and Example 1 is that no C element is added in this comparative example.

[0049] Comparative Example 5

[0050] The difference between this comparative example and Example 1 is that no Mo element is added in this comparative example.

[0051] Comparative Example 6

[0052] The difference between this comparative example and Example 1 is that in this comparative example, Hf is used to replace the W element which is not added.

[0053] Experimental Example 1

[0054] The performance of the embodiments and comparative examples was characterized, and the test indicators included hardness, room temperature compressive strength, and 1200°C compressive strength. The specific test methods are as follows:

[0055] Specific methods:

[0056] Characterization: The microstructure was observed using a Phenom-XL scanning electron microscope (SEM). Figure 1 shown.

[0057] Hardness: HV-1000A microhardness tester was used, the load was set to 1 kg, the loading time was 10 s, 9 evenly distributed points were randomly selected on the test surface for testing, and the average value was taken as the test result. The results are shown in Table 1.

[0058] Room temperature compression strength: E45-105 electronic universal testing machine was used for room temperature compression test, with a strain rate of 10 -3 / s, deformation 40%, the results are shown in Table 1.

[0059] 1200℃ compression strength: Gleeble-3500 thermal simulation test machine was used for high temperature compression test. The thermocouple was platinum-rhodium thermocouple. The heating rate was 10℃ / s, the temperature was kept for 5min, and the vacuum degree was 10 -3 Pa, strain rate 10 -3 / s, deformation 50%. The dimensions of the room temperature and high temperature compression specimens are The experiment was repeated three times for each group, and the results are shown in Table 1: From the results in Table 1, it can be seen that the hardness, room temperature compressive strength and 1200°C compressive strength of the alloy materials prepared in Examples 1-3 of the present invention are significantly higher than the YL28 cemented carbide top hammer commercially available in the prior art, and the mechanical properties are excellent. In addition, combined with Comparative Examples 2-6, it can be seen that the element composition of the cemented carbide of the present invention, that is, the addition ratio, has a key influence on the mechanical properties. Adding or reducing or replacing the key elements in equal proportions will lead to the deterioration of the mechanical properties of the alloy material.

[0060] Table 1

[0061]

[0062] The above is only an embodiment of the present invention, and the common knowledge such as the known specific technical solutions and / or characteristics in the solution is not described in detail here. It should be pointed out that for those skilled in the art, without departing from the technical solution of the present invention, several modifications and improvements can be made, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A low carbon boron refractory high entropy alloy material, characterized in that: The alloy includes W, Mo, Nb, Cr, C and B elements, and the atomic ratio of W, Mo, Nb, Cr, C and B elements is a:b:c:d:e:f, a=20~25, b=20~25, c=20~25, d=20~25, e=2~6, f=2~6, and a+b+c+d+e+f=100.

2. A low carbon boron refractory high entropy alloy material according to claim 1, characterized in that: The purity of the single substance powders of W, Mo, Nb, Cr, C and B elements is greater than 99.9%.

3. A low carbon boron refractory high entropy alloy material according to claim 1, characterized in that: The particle size of each elemental powder is 45 to 75 μm.

4. A method for preparing a low-carbon boron refractory high entropy alloy material according to any one of claims 1 to 3, characterized in that: The steps include: (1) weighing and mixing the single substance powders of W, Mo, Nb, Cr, C and B according to the atomic ratio of 20-25:20-25:20-25:20-25:20-25:2-6:2-6; (2) Mix the weighed powders; (3) Powder ball milling; (4) After sintering, cooling is performed to obtain a low-carbon boron refractory high-entropy alloy material.

5. The method for preparing a low-carbon boron refractory high entropy alloy material according to claim 4, characterized in that: In step (2), the powder mixing operation is completed in a V-shaped powder mixer, and the mixing time is 6-10 hours.

6. The method for preparing a low-carbon boron refractory high entropy alloy material according to claim 5, characterized in that: In step (3), the ball mill and the grinding balls are both made of cemented carbide materials, the average diameter of the grinding balls is 6-15 mm, and the ball-to-material mass ratio is 10:1-15:

1.

7. The method for preparing a low-carbon boron refractory high entropy alloy material according to claim 6, characterized in that: In step (3), the rotation speed of the ball mill is 100-400 r / min, and the ball milling time is 30-50 h.

8. The method for preparing a low-carbon boron refractory high entropy alloy material according to claim 7, characterized in that: In step (4), the sintering method is hot isostatic pressing, the sintering pressure is 25-60 MPa, the sintering temperature is 1400-1600° C., and the insulation time is 30-90 min.

9. Use of a low-carbon boron refractory high entropy alloy material according to any one of claims 1 to 3 in the preparation of a cemented carbide top hammer.

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