A super coarse grain WC-Co cemented carbide for mining and a method for preparing the same
Patent Information
- Application Number
- CN202611076042.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-07-20
- Publication Date
- 2026-09-25
AI Technical Summary
[0003]现有普遍使用的掘进机用截齿在工作过程中，受到冲击载荷的作用，截齿头处于高应力状态，当遇到坚硬的岩层，高压应力超过硬质合金的强度极限时便会发生脆性断裂，这是目前造成硬质合金截齿头断裂的主要原因；另一方面，如果硬质合金中Co含量不足时也会导致截齿产品的韧性不足，在相同工况下，也会相对更容易发生断裂故障
[0018]本发明通过在WC-Co硬质合金中添加Y2O3、LaB6、ZrC和Si3N4组合添加剂，制备得到平均晶粒度大于11 μm的硬质合金材料，该材料与常规工艺制备的粗晶硬质合金材料相比，在不增加合金成本的前提下，保证了硬质合金材料在具有较高的强度、硬度性能的基础上，断裂韧性高达21.5 MPa.m1/2，有效提高了合金的抗冲击性能，更适合作为核心材料用于采矿掘进机用截齿，可以提高采矿效率和降低成本。
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Abstract
Description
Technical Field
[0001] This invention relates to the field of powder metallurgy technology, and in particular to a mining-grade ultra-coarse-grained WC-Co cemented carbide and its preparation method. Background Technology
[0002] Cemented carbide is an alloy material composed of hard metals such as tungsten and tantalum with carbon. It possesses high hardness, high strength, and high wear resistance, and is widely used in industry, aerospace, and military fields. With continuous technological advancements, the performance requirements for cemented carbide are becoming increasingly stringent, necessitating the research and development of high-performance cemented carbide materials. This is particularly true in mining, where the increasing difficulty of mining operations demands continuous improvement in tunneling machines, especially placing higher requirements and expectations on the performance of cutting teeth used in tunneling machines.
[0003] Existing widely used tunneling machine cutting tools are subjected to impact loads during operation, placing the cutting head in a high-stress state. When encountering hard rock formations, the high-pressure stress exceeds the strength limit of the cemented carbide, leading to brittle fracture. This is currently the main cause of cemented carbide cutting tool fractures. On the other hand, insufficient Co content in the cemented carbide also results in insufficient toughness in the cutting tool, making it more prone to fracture under the same working conditions. However, increasing the Co content in the cemented carbide not only significantly increases material costs, but simply improving strength and hardness does not actually improve its service life. The toughness of the cutting tool also has a crucial impact on its service life. Therefore, how to improve toughness while ensuring high strength in cemented carbide is a current technical challenge in this field.
[0004] Therefore, there is an urgent need to develop new cemented carbide preparation technologies to comprehensively improve the hardness, strength, and toughness of cemented carbide while controlling costs, thereby extending its service life. Summary of the Invention
[0005] This invention aims to at least solve one of the technical problems existing in the prior art. To this end, this invention provides a mining-grade ultra-coarse-grained WC-Co cemented carbide with an average grain size greater than 11 μm. This invention uses high-temperature reduced tungsten carbide powder with a Fisher particle size of 20-40 μm as the main component, and adds an appropriate amount of Co powder and a small amount of additives, specifically ZrC and Si3N4 additives, to prepare an ultra-coarse-grained WC-Co cemented carbide with an average grain size exceeding 11 μm. Compared with coarse-grained cemented carbide materials prepared by conventional processes, without increasing the alloy cost, this invention ensures that the cemented carbide material has certain strength and hardness, while achieving a fracture toughness of 21.5 MPa.m. 1 / 2 This effectively improves the impact resistance of the alloy and extends the service life of the cutting teeth used in tunneling machines.
[0006] This invention provides a mining-grade coarse-grained WC-Co cemented carbide, wherein the raw material components, by mass percentage, include: Co 4%~10%, Y2O3 0%~0.5%, ZrC 0.01%~0.5%, Si3N4 0.01%~0.5%, LaB6 0%~0.5%, and the balance WC.
[0007] According to some embodiments of the present invention, the average grain size of WC in the WC-Co cemented carbide is >11 μm.
[0008] According to some embodiments of the present invention, the WC is high-temperature reduced tungsten carbide powder with a Fisher particle size of 20~40 μm.
[0009] According to some embodiments of the present invention, the raw material components, by mass percentage, include: Co 4%~10%, Y2O3 0.1%~0.3%, ZrC 0.1%~0.3%, Si3N4 0.05%~0.3%, LaB6 0.1%~0.3%, and the balance WC.
[0010] A second aspect of the present invention provides a method for preparing a mining-grade coarse-grained WC-Co cemented carbide as described in the first aspect of the present invention, comprising the following steps:
[0011] The raw material components are ball-milled and mixed, and the mixture is then molded, isostatically pressed, and sintered to obtain an ultra-coarse-grained WC-Co cemented carbide.
[0012] According to some embodiments of the present invention, the ball milling conditions are as follows: ball-to-material ratio of (1~4):(2~5), ball milling time of 8~15 h, ball milling speed of 10~60 r / min, and ball milling temperature of 25~80 ℃.
[0013] According to some embodiments of the present invention, the molding conditions are: pressure 5~15 MPa, time 1~10s.
[0014] According to some embodiments of the present invention, the conditions for the isostatic pressing are: pressure 80~160 MPa, time 10~30 min.
[0015] According to some embodiments of the present invention, the sintering conditions are: temperature 1420~1500 ℃, time 20~40 min.
[0016] A third aspect of the present invention provides a cutting tooth for a tunneling machine, the cutting tooth being prepared from the mining ultra-coarse-grained WC-Co cemented carbide described in the first aspect of the present invention as raw material.
[0017] The beneficial effects of this invention are:
[0018] This invention prepares a cemented carbide material with an average grain size greater than 11 μm by adding a combination of additives, including Y₂O₃, LaB₆, ZrC, and Si₃N₄, to WC-Co cemented carbide. Compared with coarse-grained cemented carbide materials prepared by conventional processes, this material, without increasing alloy costs, ensures high strength and hardness while maintaining a fracture toughness as high as 21.5 MPa. 1 / 2 This effectively improves the impact resistance of the alloy, making it more suitable as a core material for cutting teeth in mining tunneling machines, which can improve mining efficiency and reduce costs.
[0019] This invention utilizes ZrC and Si3N4 as novel ceramic modifying and reinforcing phases. Leveraging their excellent high-temperature stability and interfacial strengthening properties, they can specifically address the performance shortcomings of traditional cemented carbides. Without sacrificing the core hardness of the matrix, they simultaneously improve the alloy's toughness, high-temperature mechanical properties, thermal shock resistance, and corrosion resistance, making them core additives for high-performance, long-life, and low-cost modified cemented carbides. This invention reveals that the high-melting-point, highly stable ceramic phases ZrC and Si3N4 exhibit good compatibility with the WC matrix, without harmful phase transformation reactions, and are suitable for conventional cemented carbide powder metallurgy sintering processes. Their fundamental core characteristics determine their differentiated modification advantages, resulting in strong complementarity. Specifically, ZrC can form a high-strength metallurgical bonding interface with both WC and Co phases, filling micropores in the matrix, increasing the alloy's sintering density (up to 99.8%), and eliminating stress concentration defects caused by porosity. Simultaneously, small amounts of Zr and C elements dissolve in the binder phase, enhancing the high-temperature stability of the Co phase, inhibiting high-temperature softening and loss of the binder phase, and significantly improving the alloy's high-temperature mechanical properties. ZrC possesses extremely high chemical stability, does not react with acidic or alkaline media or high-temperature oxygen, and is uniformly distributed in the matrix and grain boundaries, forming a dense protective network that blocks corrosive media and oxygen from penetrating into the alloy, thus addressing the core pain points of traditional alloys, such as easy corrosion of the Co phase and easy oxidation failure at high temperatures. Meanwhile, β-Si3N4 columnar crystals are interwoven within the alloy. When the alloy is subjected to impact and shear stress, generating microcracks, it can dissipate fracture energy through crack bridging, crack deflection, and crystal phase pull-out, preventing microcrack propagation and fundamentally improving the alloy's fracture toughness, thus solving the industry-wide problem of traditional cemented carbides being "hard and brittle." Furthermore, Si3N4's extremely low coefficient of thermal expansion balances the thermal expansion difference between the WC matrix and the Co binder phase, significantly reducing internal residual stress during sintering cooling and alternating hot and cold operating conditions, reducing microcracks and internal delamination defects, and significantly improving the alloy's resistance to thermal shock fatigue. Si3N4 can lower the alloy's sintering activation energy, promote low-temperature densification sintering, and reduce grain damage and defects caused by high-temperature sintering. Meanwhile, its surface self-lubricating properties can reduce the alloy's friction coefficient, reduce abrasive wear and adhesive wear, and improve wear resistance stability.
[0020] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. Attached Figure Description
[0021] The present invention will be further described below with reference to the accompanying drawings and embodiments, wherein:
[0022] Figure 1 This is a 200x metallographic image of the WC-Co cemented carbide of Example 1 of the present invention;
[0023] Figure 2 This is a 1500x metallographic image of the WC-Co cemented carbide of Example 1 of the present invention;
[0024] Figure 3 This is a 100x metallographic image of the WC-Co cemented carbide of Example 1 of the present invention;
[0025] Figure 4 This is a statistical diagram of the grain distribution of the WC-Co cemented carbide in Example 1 of the present invention. Detailed Implementation
[0026] The following will describe the concept and technical effects of the present invention clearly and completely with reference to embodiments, so as to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention.
[0027] Unless otherwise specified in the examples, the procedures should be performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.
[0028] Example 1
[0029] This embodiment provides a method for preparing ultra-coarse-grained WC-Co cemented carbide for mining, and the specific steps are as follows:
[0030] 1) Raw material preparation: Weigh out 7% Co powder, 0.2% Y2O3 powder, 0.2% ZrC powder, 0.1% Si3N4 powder, 0.2% LaB6 powder, and the balance WC powder (Fairwood particle size 33 μm) by mass percentage.
[0031] 2) Mix all materials and place them in a ball mill for ball milling. The ball milling process is as follows: ball-to-material ratio 7:10, ball milling time 12 h, rotation speed 18 r / min, temperature 26 ℃, and the ball milling media used are φ8 mm, 12 mm high cemented carbide cylindrical ball rods.
[0032] 3) The ball-milled mixture was molded (pressure 10 MPa, holding time 3 s), and then subjected to isostatic pressing (pressure 120 MPa, holding time 20 min). Finally, it was sintered in a sintering furnace at 1460 ℃ (pressurized and held for 30 min) to obtain an ultra-coarse-grained WC-Co cemented carbide.
[0033] Example 2
[0034] This embodiment provides a method for preparing ultra-coarse-grained WC-Co cemented carbide for mining, and the specific steps are as follows:
[0035] 1) Raw material preparation: Weigh out 5% Co powder, 0.2% Y2O3 powder, 0.15% ZrC powder, 0.1% Si3N4 powder, 0.2% LaB6 powder, and the balance WC powder (Fairwood particle size 25 μm) by mass percentage.
[0036] 2) Mix all materials and place them in a ball mill for ball milling. The ball milling process is as follows: ball-to-material ratio 1:2, ball milling time 15 h, rotation speed 30 r / min, temperature 40 ℃, and the ball milling media used are φ4 mm, 12 mm high cemented carbide cylindrical ball rods.
[0037] 3) The ball-milled mixture is molded, isostatically pressed, and then sintered in a sintering furnace at 1430 ℃ to obtain an ultra-coarse-grained WC-Co cemented carbide.
[0038] Example 3
[0039] This embodiment provides a method for preparing ultra-coarse-grained WC-Co cemented carbide for mining, and the specific steps are as follows:
[0040] 1) Raw material preparation: Weigh out 5% Co powder, 0.1% Y2O3 powder, 0.2% ZrC powder, 0.3% Si3N4 powder, 0.3% LaB6 powder, and the balance WC powder (Fairwood particle size 36 μm) by mass percentage.
[0041] 2) Mix all materials and place them in a ball mill for ball milling. The ball milling process is as follows: ball-to-material ratio 4:5, ball milling time 10 h, rotation speed 50 r / min, temperature 60 ℃, and the ball milling media used are φ6 mm, 12 mm high cemented carbide cylindrical ball rods.
[0042] 3) The ball-milled mixture is molded, isostatically pressed, and then sintered in a sintering furnace at 1490 ℃ to obtain an ultra-coarse-grained WC-Co cemented carbide.
[0043] Comparative Example 1
[0044] This comparative example provides a method for preparing WC-Co cemented carbide. This comparative example is basically the same as Example 1, except that ZrC powder and Si3N4 powder were not used as raw materials in this comparative example; other preparation methods and process parameters are the same as in Example 1.
[0045] WC-Co cemented carbide was finally obtained.
[0046] Comparative Example 2
[0047] This comparative example provides a method for preparing WC-Co cemented carbide. This comparative example is basically the same as Example 1, except that ZrC powder was not used as the raw material in this comparative example; other preparation methods and process parameters are the same as in Example 1.
[0048] WC-Co cemented carbide was finally obtained.
[0049] Comparative Example 3
[0050] This comparative example provides a method for preparing WC-Co cemented carbide. This comparative example is basically the same as Example 1, except that Si3N4 powder was not used as the raw material in this comparative example; other preparation methods and process parameters are the same as in Example 1.
[0051] WC-Co cemented carbide was finally obtained.
[0052] Comparative Example 4
[0053] This comparative example provides a method for preparing WC-Co cemented carbide. This comparative example is basically the same as Example 1, except that the raw materials used in this comparative example do not include Y2O3 powder, ZrC powder, Si3N4 powder and LaB6 powder; other preparation methods and process parameters are the same as in Example 1.
[0054] WC-Co cemented carbide was finally obtained.
[0055] Performance testing:
[0056] 1. The metallographic image of the WC-Co cemented carbide in Example 1 is shown below. Figure 1 , 2 As shown in Figure 3, where Figure 1 This is a metallographic image magnified 200 times. Figure 2 This is a metallographic image magnified 1500 times. Figure 3 This is a metallographic image magnified 100 times. The average grain size (WC) was tested according to the national standard GB / T3488.1-2014, and the grain distribution diagram is shown below. Figure 4 As shown.
[0057] 2. The WC-Co cemented carbide prepared in each embodiment and comparative example was subjected to performance tests. The average grain size of WC was tested according to the national standard GB / T3488.1-2014, the density was tested according to GB / T3850-2015, the magnetic force was tested according to GB / T3488-2018, the cobalt magnetic force was tested according to GB / T3488-2018, the hardness was tested according to GB / T3489-2018, the bending strength was tested according to GB / T6569-2006, and the fracture toughness was tested according to GB / T21389-2008.
[0058] The test results are shown in Table 1 below:
[0059] 3. The WC-Co cemented carbide prepared in each embodiment and comparative example was used to make cutting teeth for tunneling machines and tested in mining operations. The service life of the cemented carbide in each embodiment and comparative example per 100 meters of tunneling during the mining process in a certain mine (quartz content > 30%) is shown in Table 2 below:
[0060] The performance test results above show that the average grain size of WC in the WC-Co cemented carbide of the present invention is greater than 11 μm, resulting in an ultra-coarse-grained WC-Co cemented carbide. Furthermore, the WC-Co cemented carbide of the present invention achieves a significant improvement in bending strength and fracture toughness while maintaining high density and hardness. The cutting teeth for tunneling machines prepared with the cemented carbide of the present invention maintain a low tooth breakage rate in mining operations, ensuring the service life of the cutting teeth using this cemented carbide in mining, thereby saving mining costs and improving economic efficiency.
[0061] In Comparative Examples 1-3, due to the absence of ZrC and Si3N4 powder additives, and the absence of either ZrC or Si3N4 powder additives, the average WC grain size of the resulting WC-Co cemented carbide was less than 10 μm, and its hardness, bending strength, and fracture toughness were significantly reduced. In particular, Comparative Example 4, which used only conventional WC-Co cemented carbide preparation methods without the additive combination described in this application, exhibited the smallest average WC grain size and the worst hardness, bending strength, and fracture toughness.
[0062] According to the core principles of WC-Co cemented carbide, the coarser the grains, the better the toughness and bending impact resistance. Coarse WC grains lengthen the crack propagation path, resulting in significant crack deflection and bridging effects, and consuming more fracture energy. The thicker Co layer between coarse grains and the excellent plasticity of metallic cobalt allow the stress at the crack tip to be plastically relaxed by the Co phase, inhibiting rapid crack penetration. Compared with traditional cemented carbides, cemented carbides with larger WC grain sizes have better toughness, better thermal fatigue resistance, and higher wear resistance, and are widely used in harsh working conditions such as coal mining, engineering tunneling, tunnel boring machines, oil drilling, road milling, stamping dies, and steel rolling.
[0063] The embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof can be combined with each other unless otherwise specified.
Claims
1. A mining-grade ultra-coarse-grained WC-Co cemented carbide, characterized in that, By mass percentage, the raw material components include: Co 4%~10%, Y2O3 0%~0.5%, ZrC 0.01%~0.5%, Si3N4 0.01%~0.5%, LaB6 0%~0.5%, and the balance WC.
2. The mining-grade ultra-coarse-grained WC-Co cemented carbide according to claim 1, characterized in that, The average grain size of WC in the WC-Co cemented carbide is >11 μm.
3. The mining-grade ultra-coarse-grained WC-Co cemented carbide according to claim 1, characterized in that, The WC is high-temperature reduced tungsten carbide powder with a Fisher particle size of 20~40 μm.
4. The mining-grade ultra-coarse-grained WC-Co cemented carbide according to claim 1, characterized in that, By mass percentage, the raw material components include: Co 4%~10%, Y2O3 0.1%~0.3%, ZrC 0.1%~0.3%, Si3N4 0.05%~0.3%, LaB6 0.1%~0.3%, and the balance WC.
5. A method for preparing a mining-grade ultra-coarse-grained WC-Co cemented carbide as described in any one of claims 1 to 4, characterized in that, Includes the following steps: The raw material components are ball-milled and mixed, and the mixture is then molded, isostatically pressed, and sintered to obtain an ultra-coarse-grained WC-Co cemented carbide.
6. The preparation method according to claim 5, characterized in that, The ball milling conditions are as follows: ball-to-material ratio of (1~4):(2~5), milling time of 8~15 h, milling speed of 10~60 r / min, and milling temperature of 25~80 ℃.
7. The preparation method according to claim 5, characterized in that, The molding conditions are: pressure 5~15MPa, time 1~10 s.
8. The preparation method according to claim 5, characterized in that, The conditions for the isostatic pressure test are: pressure 80~160MPa, time 10~30 min.
9. The preparation method according to claim 5, characterized in that, The sintering conditions are: temperature 1420~1500℃, time 20~40 min.
10. A cutting tooth for a tunneling machine, characterized in that, The cutting teeth are prepared from the mining ultra-coarse-grained WC-Co cemented carbide as described in any one of claims 1 to 4.