Hard alloy and preparation method thereof

Abstract

The invention provides a hard alloy with high toughness and wear resistance and a preparation method thereof. The hard alloy comprises the following components in percentage by mass: 3 to 5 percent of WC-W2C, 8 to 12 percent of (CoCrNi) 94Al3Ti3 high-entropy alloy and the balance of WC. The preparation method comprises the following steps that WC-W2C powder, (CoCrNi) 94Al3Ti3 high-entropy alloy powder and WC powder are subjected to ball milling and powder mixing according to the mass ratio, then the evenly-mixed powder is put into a mold to be sintered, the powder is cooled to the room temperature after sintering is completed, and then heat treatment and cooling are sequentially conducted. The hard alloy provided by the invention has high hardness, high toughness and excellent tribological properties.

Description

Technical Field

[0001] The present invention provides cemented carbide and a preparation method thereof, and particularly relates to the technical field of WC cemented carbide. Background Art

[0002] WC cemented carbide has high hardness and high wear resistance, and is the main material for machining tools. WC cemented carbide tools are known as "industrial teeth" and play an important role in the development of high-end equipment manufacturing. The performance of WC cemented carbide directly determines the machining accuracy and stability of the tools. Therefore, it is of great significance to develop cemented carbide with high strength, toughness and wear resistance.

[0003] Ultrafine-grained WC-Co cemented carbide is widely used in machining tools. This cemented carbide mainly relies on the synergistic effect of ultrafine-grained WC particles and the bonding phase Co to achieve high strength and toughness. However, there are the following problems: high preparation cost, WC with a particle size <1μm must be used, and the price of fine-grained WC powder is high; high equipment requirements, in order to avoid grain growth of WC, high-precision and high-price sintering equipment must be used for preparation; Co element not only has a high price, but also has certain toxicity; the core technology is protected by foreign patents. At present, there is high-entropy alloy bonded cemented carbide. The cemented carbide used is still ultrafine-grained powder, and the high-entropy alloy used is nano-powder prepared by high-energy ball milling. The preparation process is not only complex, but also still limited to the ultrafine-grained structure. Summary of the Invention

[0004] The present invention solves the technical problems in the prior art that the preparation process of WC-Co cemented carbide is complex, the cost is high, and the equipment requirements are high.

[0005] The present invention is realized as follows. The cemented carbide includes the following components and their mass percentages: WC-W2C 3-5 wt.%, (CoCrNi) 94 Al3Ti3 high-entropy alloy 8-12 wt.%, and the balance is WC.

[0006] As a further preference, the WC-W2C is spherical powder with a particle size of 30-50μm, and the (CoCrNi) 94 Al3Ti3 high-entropy alloy is spherical powder with a particle size of 10-25μm; the WC is spherical powder with a particle size of 20-50μm.

[0007] As a further preference, the cemented carbide includes the following components and their mass percentages: WC 87.5 wt.%, WC-W2C 2.5 wt.%, (CoCrNi) 94 Al3Ti3 high-entropy alloy 10 wt.%.

[0008] Preparation method of cemented carbide, WC-W2C, (CoCrNi)94 The Al3Ti3 high-entropy alloy and WC material are ball-milled and mixed to obtain a mixed powder; then the mixed powder is loaded into a mold and sintered. After sintering, the material is cooled to room temperature with the furnace and then heat-treated and cooled again.

[0009] As a further preference, the ball-milling conditions are as follows: for every 100 g of the mixed powder, 1 - 5 mL of absolute ethanol is added as a grinding medium, the grinding balls are WC balls, the ball-to-material ratio is 1 - 2:1, the ball-milling speed is 100 - 300 r / min, and the ball-milling time is 5 - 15 h.

[0010] As a further preference, the sintering conditions are as follows: the sintering temperature is 1250 - 1350 °C, the heating rate is 60 - 200 °C / min, the sintering pressure is 35 - 45 MPa, the holding time is 5 - 10 min, and the protective gas is argon.

[0011] As a further preference, the heat-treatment conditions are as follows: the temperature is 600 - 800 °C, and the holding time is 3 - 5 hours.

[0012] As a further preference, the (CoCrNi) 94 Al3Ti3 high-entropy alloy is in powder form and is prepared by an atomization method.

[0013] The present invention uses large-grained WC powder, uses the newly developed WC-W2C in recent years as a modified phase, and uses the new high-strength, tough and corrosion-resistant (CoCrNi) 94 Al3Ti3 high-entropy alloy as a bonding phase. Based on the multi-scale and multi-dimensional synergistic effects of WC, WC-W2C, and (CoCrNi) 94 Al3Ti3 high-entropy alloy, and by modifying the interface through heat treatment, through the coupling and good combination of a variety of high-performance heterogeneous structures, under the conditions of a simple preparation process and large-sized grains, the integration of high strength, high toughness, and high wear resistance is achieved, breaking the structural limitation of ultrafine grains while maintaining good mechanical and wear resistance properties and reducing production costs. The high-entropy alloy powder prepared by the atomization method is easy to store and can be prepared industrially in batches. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The following further details the specific embodiments of the present invention with reference to the accompanying drawings.

[0015] Figure 1 This is the SEM morphology of the high-strength, tough and wear-resistant cemented carbide material prepared in Example 1 of the present invention.

[0016] Figure 2 This is the EDS surface scan of the high-strength, tough and wear-resistant cemented carbide material prepared in Example 1 of the present invention.

[0017] Figure 3 SEM morphology of the high-strength, tough and wear-resistant cemented carbide material prepared in Example 2 of the present invention. Detailed implementation mode

[0018] The technical solutions of the present invention will be clearly and completely described below in conjunction with the specific embodiments and drawings of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative work belong to the scope of protection of the present invention.

[0019] WC-W2C, (CoCrNi) 94 WC, WC-W2C, and (CoCrNi) 94 Al3Ti3 high-entropy alloy are all purchased from the market. Among them, the (CoCrNi)

[0020] Example 1

[0021] The high-strength, tough and wear-resistant cemented carbide includes the following components and their mass ratios: WC 87.5 wt.%, WC-W2C 2.5 wt.%, (CoCrNi) 94 Al3Ti3 high-entropy alloy 10 wt.%. The preparation steps are as follows:

[0022] (1) Powder mixing: According to 87.5 wt.% WC - 2.5 wt.% (WC-W2C) - 10 wt.% (CoCrNi) 94 Al3Ti3, weigh WC, WC-W2C, and (CoCrNi) 94 Al3Ti3 powders respectively. WC is spherical powder with a particle size of 20 - 50 μm; WC-W2C is spherical powder with a particle size of 30 - 50 μm; (CoCrNi) 94 Al3Ti3 high-entropy alloy is spherical powder with a particle size of 10 - 25 μm. Put all the powders into a ball mill jar for ball milling. Add 3 mL of anhydrous ethanol as the grinding medium for every 100 g of mixed powder. The grinding balls are WC balls. The ball milling speed is 200 r / min, and the ball milling time is 10 h. After ball milling, it is dried. Drying conditions: Place it in a vacuum drying oven for vacuum drying treatment, and the drying temperature is set at 60 °C. After drying, it is stored to obtain a uniformly mixed original powder.

[0023] (2) Sintering: Put the original powder obtained in step (1) into a graphite mold, and then place it in an SPS spark plasma sintering furnace for sintering. The sintering temperature is 1300 °C, the heating rate is 100 °C / min, the sintering pressure is 40 MPa, the holding time is 8 min, the protective gas is argon. After sintering, the material is cooled to room temperature with the furnace.

[0024] (3) Heat treatment: Place the material obtained in step (2) in a heat treatment furnace, hold it at 700 °C for 4 hours, and then air-cool it in the furnace to obtain the product.

[0025] Refer to Figure 1 and Figure 2 , and use a scanning electron microscope to analyze the material microstructure and surface scanning pattern. The cemented carbide prepared in this example has a variety of heterogeneous structures: WC maintains a large grain morphology, the eutectic structure WC-W2C is dispersed in the WC matrix, and (CoCrNi) 94 Al3Ti3 is a strip-shaped bonding phase, and there is a good interface between each phase.

[0026] Example 2

[0027] The high-strength, tough and wear-resistant cemented carbide includes the following components and their mass ratios: WC 90 wt.%, WC-W2C 2 wt.%, (CoCrNi) 94 Al3Ti3 high-entropy alloy 8 wt.%. The preparation method is as follows:

[0028] (1) Powder mixing: Weigh WC, WC-W2C, (CoCrNi) 94 Al3Ti3 according to 90 wt.% WC - 2 wt.% (WC-W2C) - 8 wt.% (CoCrNi) 94 Al3Ti3 powder. The WC powder is spherical powder with a particle size of 20 - 50 μm; the WC-W2C powder is spherical powder with a particle size of 30 - 50 μm; (CoCrNi) 94 Al3Ti3 high-entropy alloy powder, which is spherical powder with a particle size of 10 - 25 μm. Put all the powders into a ball mill tank for ball milling. Add 1 mL of anhydrous ethanol as the grinding medium for every 100 g of mixed powder. The grinding balls are WC balls, the ball-to-material ratio is 2:1, the ball milling speed is 100 r / min, and the ball milling time is 15 h. After ball milling, dry it. Drying conditions: Carry out vacuum drying treatment in a vacuum drying oven, and set the drying temperature to 60 °C. Store after drying to obtain a uniformly mixed original powder product.

[0029] (2) Sintering: Put the original powder product obtained in step (1) into a graphite mold, and then place it in an SPS spark plasma sintering furnace for sintering. The sintering temperature is 1250 °C, the heating rate is 200 °C / min, the sintering pressure is 35 MPa, the holding time is 10 min, the protective gas is argon. After sintering, the material is cooled to room temperature with the furnace.

[0030] (3) Heat treatment: Place the material obtained in step (2) in a heat treatment furnace, hold it at 600 °C for 3 - 5 hours, and then air-cool it in the furnace to obtain the product.

[0031] Refer toFigure 3 , the microstructure of the material was analyzed by scanning electron microscopy. The cemented carbide prepared in Example 2 had a variety of heterogeneous structures: WC maintained a large grain morphology, and the eutectic structure WC-W2C was dispersed in the WC matrix, (CoCrNi) 94 Al3Ti3 was a long strip bonding phase, and there was a good interface between each phase.

[0032] Example 3

[0033] The high-strength, tough and wear-resistant cemented carbide included the following components and their mass ratios: WC 85wt.%, WC-W2C 3wt.%, (CoCrNi) 94 Al3Ti3 high-entropy alloy 12wt.%, and the preparation method was as follows:

[0034] (1) Powder mixing: Weigh WC powder, WC-W2C powder, (CoCrNi) 94 Al3Ti3 according to 85wt.% WC - 3wt.% (WC-W2C) - 12wt.% (CoCrNi) 94 Al3Ti3 powder. The WC powder was spherical powder with a particle size of 20 - 50μm; the WC-W2C powder was spherical powder with a particle size of 30 - 50μm; (CoCrNi) 94 Al3Ti3 high-entropy alloy powder was spherical powder with a particle size of 10 - 25μm. All three powders were put into a ball mill jar for ball milling. 5mL of anhydrous ethanol was added as the grinding medium for every 100g of mixed powder. The grinding balls were WC balls, the ball-to-material ratio was 1:1, the ball milling speed was 300r / min, and the ball milling time was 5h. After ball milling, it was dried. Drying conditions: Vacuum drying treatment was carried out in a vacuum drying oven, and the drying temperature was set at 60°C. After drying, it was stored to obtain a uniformly mixed original powder product.

[0035] (2) Sintering: The original powder product obtained in step (1) was loaded into a graphite mold, and then placed in a SPS spark plasma sintering furnace for sintering. The sintering temperature was 1350°C, the heating rate was 60°C / min, the sintering pressure was 45MPa, the holding time was 5min, the protective gas was argon, and after sintering, the material was cooled to room temperature with the furnace.

[0036] (3) Heat treatment: The material obtained in step (2) was placed in a heat treatment furnace and held at 800°C for 3 - 5 hours, and then air-cooled with the furnace to obtain the product.

[0037] Comparative Example 1

[0038] Taking 90wt.% WC - 10wt.% (CoCrNi) 94 Al3Ti3 as Comparative Example 1, the preparation method was:

[0039] (1) Powder mixing: According to 90 wt.% WC - 10 wt.% (CoCrNi) 94 Al3Ti3, weigh WC spherical powder and (CoCrNi) 94 Al3Ti3 spherical powder respectively. The WC spherical powder has a particle size of 20 - 50 μm; (CoCrNi) 94 The Al3Ti3 high - entropy alloy spherical powder has a particle size of 10 - 25 μm. Put both powders into a ball - milling jar for ball - milling. Add 3 mL of absolute ethanol per 100 g of the mixed powder as the grinding medium. The grinding balls are WC balls, the ball - to - powder ratio is 1.5:1, the ball - milling speed is 200 r / min, and the ball - milling time is 10 h. After ball - milling, dry it. Drying conditions: Carry out vacuum drying treatment in a vacuum drying oven, and set the drying temperature at 60 °C. Preserve after drying to obtain a uniformly mixed original powder product.

[0040] (2) Sintering: Load the original powder product obtained in step (1) into a graphite mold, and then place it in a SPS spark plasma sintering furnace for sintering. The sintering temperature is 1300 °C, the heating rate is 100 °C / min, the sintering pressure is 40 MPa, the holding time is 8 min, the protective gas is argon. After sintering, the material is cooled to room temperature with the furnace.

[0041] (3) Heat treatment: Place the material obtained in step (2) in a heat treatment furnace, hold it at 700 °C for 4 hours, and then air - cool it with the furnace to obtain the product.

[0042] Comparative Example 2

[0043] Take 97.5 wt.% WC - 2.5 wt.% (WC - W2C) as Comparative Example 1, and the preparation method is as follows:

[0044] (1) Powder mixing: According to 97.5 wt.% WC - 2.5 wt.% (WC - W2C), weigh WC and WC - W2C powders respectively. The WC powder is spherical powder with a particle size of 20 - 50 μm; the WC - W2C powder is spherical powder with a particle size of 30 - 50 μm. Put both powders into a ball - milling jar for ball - milling. Add 3 mL of absolute ethanol per 100 g of the mixed powder as the grinding medium. The grinding balls are WC balls, the ball - to - powder ratio is 1.5:1, the ball - milling speed is 200 r / min, and the ball - milling time is 10 h. After ball - milling, dry it. Drying conditions: Carry out vacuum drying treatment in a vacuum drying oven, and set the drying temperature at 60 °C. Preserve after drying to obtain a uniformly mixed original powder product.

[0045] (2) Sintering: The raw powder product obtained in step (1) is loaded into a graphite mold and then placed in an SPS spark plasma sintering furnace for sintering. The sintering temperature is 1300 °C, the heating rate is 100 °C / min, the sintering pressure is 40 MPa, the holding time is 8 min, the protective gas is argon. After sintering, the material is cooled to room temperature with the furnace.

[0046] (3) Heat treatment: The material obtained in step (2) is placed in a heat treatment furnace and heat-treated at 700 °C for 4 hours, and then air-cooled with the furnace to obtain the product.

[0047] Performance testing

[0048] (1) Vickers hardness

[0049] The Vickers hardness (HV30) of the sintered sample was measured on a FALCON-600 Vickers hardness tester. In the hardness test, the load was set to 294 N and the holding time was set to 15 s. The calculation formula is as shown in Formula Ⅰ below.

[0050]

[0051] In Formula Ⅰ, represents the Vickers hardness (HV30), represents the applied load (N), and represents the average value of the diagonal and length of the indentation (mm).

[0052] (2) Fracture toughness

[0053] The fracture toughness of the sintered sample was calculated by the indentation method. The calculation formula is as shown in Formula Ⅱ.

[0054]

[0055] In Formula Ⅱ, K IC represents the fracture toughness (MPa·m 1 / 2 ), ∑l i represents the sum of crack lengths (mm).

[0056] (3) Tribological properties

[0057] The friction and wear experiment was carried out on a friction testing machine (HT-1000). The wear resistance of the alloy was tested using an HT-1000 pin-on-disc friction and wear testing machine. The material for the test was an Al2O3 ceramic ball with a diameter of 6 mm, the sliding rate was 0.27 m / s, the load was 15 N, and the test time was 60 min. The wear rate was calculated according to the formula W = V / (SF), where W is the wear rate, V is the wear volume measured by a surface profiler, S is the sliding distance, and F is the load.

[0058] According to the first two methods of performance testing, the mechanical properties of the alloys obtained in Example 1, Example 2 and Example 3 were tested. The results are shown in Table 1.

[0059] Table 1 Test Results of Mechanical Properties of Examples 1 - 3

[0060] Vickers hardness (HV30) <![CDATA[Fracture toughness (MPa·m 1 / 2 )]]> Example 1 1550 11.5 Example 2 1470 11.1 Example 3 1560 10.7

[0061] For the alloys obtained in Example 1, Example 2, Example 3, Comparative Example 1 and Comparative Example, tribological property tests were carried out according to the tribological property test method of performance tests, and the results are shown in Table 2.

[0062] Table 2 Test Results of Tribological Properties

[0063] <![CDATA[Wear rate (×10 -7 mm 3 / Nm)]]> Example 1 2.12 Example 2 3.49 Example 3 1.15 Comparative Example 1 20.7 Comparative Example 2 37.4

[0064] As can be seen from Table 1 and Table 2, the cemented carbides obtained in Examples 1, 2 and 3, based on the advantageous coupling of various heterogeneous structures, maintained a hardness higher than 1450 HV and a fracture toughness higher than 13 MPa·m 1 / 2 under the condition of large grain size. At the same time, the wear rates of Examples 1, 2 and 3 with the addition of (CoCrNi) 94 Al3Ti3 and WC - W2C were lower than 3.5×10 -7 mm 3 / Nm, showing excellent wear resistance. While for Comparative Example 1 and Comparative Example 2, the wear rates with the addition of only (CoCrNi) 94 Al3Ti3 or WC - W2C were higher than 20×10 - 7 mm 3 / Nm. This is due to the synergistic effect of the high - entropy alloy bonding phase and WC - W2C, resulting in good wear - resistant results.

[0065] The cemented carbide provided by the present invention can be used for cutting tools, and can also be used for cutting tools, and can also be used for metallurgical dies (stamping dies, stretching dies, cold - heading dies), rock - drilling bits, oil drilling, wear - resistant valves, etc. Because of its good wear resistance, the components made have a longer working life.

[0066] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims

1. Cemented carbide, characterized in that, The cemented carbide comprises the following components and their mass percentages: WC-W2C 3-5 wt.%, (CoCrNi) 94 Al3Ti3 high-entropy alloy 8-12 wt.%, and the balance is WC.

2. The cemented carbide according to claim 1, characterized in that, The WC-W2C is spherical powder with a particle size of 30 to 50 μm, and the (CoCrNi) 94 Al3Ti3 high-entropy alloy is spherical powder with a particle size of 10 to 25 μm; the WC is spherical powder with a particle size of 20 to 50 μm.

3. The cemented carbide according to claim 2, wherein, The cemented carbide comprises the following components and their mass percentages: WC 87.5 wt.%, WC-W2C 2.5 wt.%, (CoCrNi) 94 Al3Ti3 high-entropy alloy 10 wt.%.

4. The method for preparing cemented carbide according to claim 1, characterized in that, Mix WC-W2C, (CoCrNi) 94 Al3Ti3 high-entropy alloy and WC materials by mass ratio through ball milling to obtain a mixed powder; then load the mixed powder into a mold for sintering. After sintering, let the material cool to room temperature in the furnace, and then perform heat treatment and cool it again.

5. The preparation method according to claim 4, wherein, The ball milling conditions are as follows: 1 - 5 mL of absolute ethanol is added as the grinding medium per 100 g of the mixed powder. The grinding balls are WC balls, the ball-to-powder ratio is 1 - 2:1, the ball milling rotation speed is 100 - 300 r / min, and the ball milling time is 5 - 15 h.

6. The preparation method according to claim 4, wherein The sintering conditions are as follows: the sintering temperature is 1250 - 1350 °C, the heating rate is 60 - 200 °C / min, the sintering pressure is 35 - 45 MPa, the holding time is 5 - 10 min, and the protective gas is argon.

7. The preparation method according to claim 4, characterized in that, The heat treatment conditions are as follows: the temperature is 600 - 800 °C, and the holding time is 3 - 5 hours.

8. The preparation method according to claim 4, characterized in that, The said (CoCrNi) 94 The Al3Ti3 high-entropy alloy is in powder form and is obtained by atomization method.

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