A method for preparing tungsten-molybdenum composite-based ultrafine hard alloy

Abstract

The application discloses a preparation method of tungsten-molybdenum composite-based ultrafine hard alloy, and belongs to the technical field of hard alloy preparation. The hard alloy components are as follows in percentage by weight: 8-15wt% Co / Ni / Cr, 35-55wt% Mo2C, 0.5-1.5wt% VC / TaC, and the balance is WC; the Mo2C grain size is 0.8-1.2 microns, the WC grain size is 0.4-1.0 microns, and the low-pressure sintering process is adopted. The application solves the problems of low Mo2C replacement amount and poor pure Mo2C alloy performance in the prior art by using 35-65wt% Mo2C to efficiently replace WC, combining with proportion optimization and grain size control. The alloy prepared has a bending strength of 3300-3800 MPa, a fracture toughness of 9.3-11.2, and a hardness (HRA) of greater than or equal to 91.1, is excellent in comprehensive performance, and has a material cost of cutters reduced by more than 30%, can meet the requirements of cutting machining and wear-resistant part preparation in many fields such as semiconductors and new energy, is easy to be industrialized, and has significant application value.

Description

Technical Field

[0001] This invention relates to the field of cemented carbide preparation technology, specifically to a method for preparing tungsten-molybdenum composite-based ultrafine cemented carbide, applicable to the preparation of cutting tools and wear-resistant parts in fields such as semiconductors, new energy, aerospace and military, and machining. Background Technology

[0002] Tungsten, with its high melting point of 3422℃, high hardness, high density, and excellent corrosion resistance, has become a core material in modern industry and high-tech fields. With the rapid development of emerging industries such as semiconductors, new energy, aerospace, military, and nuclear power, market demand for tungsten has continued to rise sharply, leading to continuously increasing prices and tight supply of tungsten products. Consequently, the cost of using WC-based cemented carbide tools, which use tungsten as the main raw material, has also increased dramatically. Therefore, finding suitable elements to partially replace the increasingly scarce tungsten has become an important research direction in the field of cemented carbide preparation.

[0003] Due to its high hardness and low raw material cost, Mo2C has become a preferred material to replace WC. Currently, it is mainly added in small amounts as a grain growth inhibitor in the production of ultrafine cemented carbide. However, Mo2C itself has shortcomings in toughness and high-temperature performance, and cannot directly and completely replace WC. Moreover, in the existing technology, cemented carbide containing Mo2C only adds 5-20% Mo2C, which is too low to achieve effective reduction of tungsten and has no practical cost control significance.

[0004] In existing technologies, Europe, the United States, the Soviet Union, and China have all conducted research on pure Mo2C-Co cemented carbides. Japan has prepared pure Mo2C-Co alloys through hot pressing sintering and applied them to woodworking tools. The United States has used the SPS+HIP sintering method to prepare Mo2C+Ni / Co cemented carbides containing trace amounts of TaC, which improves the red hardness of the alloy and is used in high-temperature cutting tools. However, the Mo2C-based cemented carbides prepared in the above studies either have significantly lower overall mechanical properties than traditional WC-based cemented carbides, or their preparation processes are complex and their applicable scenarios are limited, failing to meet the diverse cutting needs of industrial fields. Therefore, there is an urgent need to develop a cemented carbide preparation method that can efficiently replace WC with Mo2C and has excellent overall performance. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing tungsten-molybdenum composite-based ultrafine cemented carbide, so as to solve the technical problems in the prior art where the Mo2C substitution amount is low and has no practical significance, and the performance of pure Mo2C cemented carbide is too far behind that of WC-based cemented carbide.

[0006] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: A method for preparing a tungsten-molybdenum composite-based ultrafine cemented carbide, wherein the cemented carbide comprises, by weight percentage: 8-15 wt% Co / Ni / Cr, 35-55 wt% Mo2C, 0.5-1.5 wt% VC / TaC, with the balance being WC; the Mo2C has a grain size of 0.8-1.2 μm, and the WC has a grain size of 0.4-1.0 μm; the tungsten-molybdenum composite-based ultrafine cemented carbide is prepared by a low-pressure sintering process.

[0007] Furthermore, the Co / Ni / Cr is a binder phase in any proportion, used to improve the toughness and density of the cemented carbide and compensate for the lack of toughness of Mo2C; the VC / TaC is a grain growth inhibitor in any proportion, used to prevent abnormal growth of hard phase grains during sintering and ensure the ultrafine grain structure of the cemented carbide.

[0008] Furthermore, the low-pressure sintering process is a conventional low-pressure sintering process in the field of cemented carbide preparation. The process parameters such as sintering temperature, holding time, and sintering pressure can be adjusted according to actual production needs.

[0009] The tungsten-molybdenum composite-based ultrafine cemented carbide prepared by this invention has a bending strength of 3300-3800 MPa, a fracture toughness of 9.3-11.2, and a hardness (HRA) ≥91.1. It has excellent comprehensive mechanical properties, and the cost of the tool material is reduced by more than 30% compared with traditional WC-based cemented carbide.

[0010] The present invention has the following beneficial effects: Achieving efficient replacement of WC with Mo2C: This invention uses 35-65 wt% Mo2C to partially replace WC in cemented carbide, breaking through the limitation of low Mo2C addition in the prior art, effectively reducing the amount of tungsten used, significantly reducing the preparation cost of cemented carbide from the raw material end, and reducing the cost of tool materials by more than 30%. Excellent comprehensive mechanical properties: By optimizing the ratio of the binder phase Co / Ni / Cr and the grain inhibitor VC / TaC, and combining the grain size control of Mo2C and WC, the defects of insufficient toughness and high temperature performance of Mo2C are made up for. The core mechanical properties of the prepared cemented carbide, such as bending strength, fracture toughness and hardness, all meet the requirements of industrial use and are comparable to traditional WC-based cemented carbide. The preparation process is simple: it adopts the conventional low-pressure sintering process in the field of cemented carbide preparation, without the need for complex special equipment. The process parameters can be flexibly adjusted according to production needs, making it easy to achieve large-scale industrial production. Wide range of applications: The cemented carbide prepared by this invention can have its performance focus adjusted according to the formulation examples, and can be adapted to different scenarios such as high-precision light cutting, medium-load cutting, impact load cutting, and high-strength and high-precision complex cutting. At the same time, it can be used to prepare various industrial wear-resistant parts, meeting the needs of semiconductor, new energy, aerospace and military, and machining industries. Attached Figure Description

[0011] Figure 1 The diagram illustrates the specific steps of this invention. Detailed Implementation

[0012] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0013] This invention discloses a method for preparing tungsten-molybdenum composite-based ultrafine cemented carbide. The core of this method is to partially replace WC in the cemented carbide with 35-65 wt% Mo2C. By optimizing the alloy composition ratio, controlling the grain size of Mo2C and WC, and combining it with a low-pressure sintering process, a tungsten-molybdenum composite-based ultrafine cemented carbide with excellent comprehensive mechanical properties is prepared. This method solves the technical problems in the prior art where the Mo2C substitution amount is too low to be practically meaningful and the performance gap between pure Mo2C cemented carbide and WC-based cemented carbide is too large. At the same time, it achieves the technical effect of reducing the cost of tool materials by more than 30%.

[0014] The tungsten-molybdenum composite-based ultrafine cemented carbide of this invention comprises, by weight percentage: 8–15 wt% Co / Ni / Cr, 35–55 wt% Mo2C, 0.5–1.5 wt% VC / TaC, with the balance being WC; wherein the grain size of Mo2C is controlled to be 0.8–1.2 μm, and the grain size of WC is controlled to be 0.4–1.0 μm. VC / TaC, as a grain growth inhibitor, can effectively prevent abnormal grain growth of the hard phase during sintering; Co / Ni / Cr, as a binder phase, can improve the toughness and density of the cemented carbide, forming a synergistic effect with Mo2C and WC, compensating for the shortcomings of Mo2C itself in toughness and high-temperature performance.

[0015] This invention employs a low-pressure sintering process to prepare the aforementioned tungsten-molybdenum composite-based ultrafine cemented carbide. The low-pressure sintering environment effectively reduces internal porosity and increases the density of the alloy, further optimizing its core mechanical properties such as bending strength, fracture toughness, and hardness. The prepared cemented carbide exhibits a bending strength of 3300–3800 MPa, a fracture toughness of 9.3–11.2, and a hardness (HRA) ≥91.1, meeting the cutting and wear-resistant part manufacturing requirements of various scenarios in semiconductor, new energy, aerospace, military, and machining industries.

[0016] All embodiments of this invention employ a unified basic preparation process: first, the components are ball-milled and mixed according to the specified ratio to ensure uniformity; then, the mixed powder is granulated and pressed into shape; finally, a low-pressure sintering process is used for sintering to obtain a tungsten-molybdenum composite-based ultrafine cemented carbide. The component ratios, grain size parameters, and performance test results of each embodiment are shown in the table below. Furthermore, the cemented carbides prepared in each embodiment achieve a technical effect of reducing tool material costs by more than 30% compared to traditional WC-based cemented carbides. Example 1 The tungsten-molybdenum composite-based ultrafine cemented carbide provided in this embodiment has the following composition: 8 wt% Co / Ni / Cr, 37 wt% Mo2C, 0.7 wt% VC / TaC, with the balance being WC. The Mo2C grain size is 1.2 μm, and the WC grain size is 1.0 μm. The cemented carbide prepared using the above-described unified basic preparation process exhibits a bending strength of 3500 MPa, a fracture toughness of 9.3, and a hardness (HRA) of 92.1. This represents the optimal hardness among all embodiments, demonstrating outstanding high-precision characteristics and making it suitable for high-precision light-cutting machining applications in fields such as precision instruments and semiconductor components.

[0017] Example 2 The tungsten-molybdenum composite-based ultrafine cemented carbide provided in this embodiment has the following composition: 10 wt% Co / Ni / Cr, 45 wt% Mo2C, 0.7 wt% VC / TaC, with the balance being WC. The Mo2C grain size is 1.2 μm, and the WC grain size is 0.8 μm. The cemented carbide prepared using the above-described unified basic preparation process exhibits a bending strength of 3700 MPa, a fracture toughness of 10.5, and a hardness (HRA) ≥91.3. It combines high toughness and high hardness, demonstrating excellent performance balance, and can be widely applied to medium-load cutting processes in general machining fields. It can also be used in the preparation of various industrial wear-resistant parts.

[0018] Example 3 The tungsten-molybdenum composite-based ultrafine cemented carbide provided in this embodiment has the following composition: 10 wt% Co / Ni / Cr, 55 wt% Mo2C, 0.7 wt% VC / TaC, with the balance being WC. The Mo2C grain size is 1.0 μm, and the WC grain size is 0.7 μm. The cemented carbide prepared using the above-described unified basic preparation process exhibits a bending strength of 3300 MPa and a fracture toughness of 10.9, representing the optimal toughness among all embodiments. It also demonstrates outstanding impact resistance and is suitable for cutting scenarios involving impact loads in fields such as engineering machinery and mining equipment.

[0019] Example 4 The tungsten-molybdenum composite-based ultrafine cemented carbide provided in this embodiment has the following composition: 13wt% Co / Ni / Cr, 55wt% Mo2C, 1.2wt% VC / TaC, with the balance being WC. The Mo2C grain size is 0.8μm, and the WC grain size is 0.4μm. The cemented carbide prepared using the above-mentioned unified basic preparation process exhibits a bending strength of 3800MPa, a fracture toughness of 11.2, and a hardness (HRA) ≥91.7. This represents the optimal solution in terms of overall mechanical properties among all embodiments. Furthermore, the Mo2C substitution ratio reaches 55wt%, resulting in a more significant cost reduction. It is suitable for high-strength, high-precision, and complex cutting processes in aerospace, military, and high-end equipment manufacturing fields.

[0020] Summary table of parameters and performance tests for each embodiment

[0021] The tungsten-molybdenum composite-based ultrafine cemented carbides prepared in all the above embodiments achieved efficient partial substitution of WC by Mo2C through reasonable control of the Mo2C substitution ratio, component ratio and grain size parameters, combined with low-pressure sintering process. Under the premise of ensuring that the core mechanical properties meet the requirements of industrial use, the tool material cost is reduced by more than 30% compared with traditional WC-based cemented carbides, which has significant economic value and industrial application prospects.

[0022] It should be noted that in this invention, Co / Ni / Cr can be used in any proportion as a binder phase, and VC / TaC can also be used in any proportion as a grain growth inhibitor, both of which can achieve the technical effects of this invention; moreover, the low-pressure sintering process described in this invention is a conventional low-pressure sintering process in the field of cemented carbide preparation, and its sintering temperature, holding time, sintering pressure and other process parameters can be conventionally adjusted according to actual production needs without any creative effort.

[0023] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a tungsten-molybdenum composite-based ultrafine cemented carbide, characterized in that, The composition of the cemented carbide by weight percentage is: 8-15 wt% Co / Ni / Cr, 35-55 wt% Mo2C, 0.5-1.5 wt% VC / TaC, with the balance being WC; the tungsten-molybdenum composite-based ultrafine cemented carbide is prepared by low-pressure sintering process.

2. The method for preparing tungsten-molybdenum composite-based ultrafine cemented carbide according to claim 1, characterized in that, The Mo2C has a grain size of 0.8–1.2 μm, and the WC has a grain size of 0.4–1.0 μm.

3. The method for preparing tungsten-molybdenum composite-based ultrafine cemented carbide according to claim 1, characterized in that, The composition of the cemented carbide by weight percentage is: 8 wt% Co / Ni / Cr, 37 wt% Mo2C, 0.7 wt% VC / TaC, with the balance being WC; the grain size of the Mo2C is 1.2 μm, and the grain size of the WC is 1.0 μm.

4. The method for preparing tungsten-molybdenum composite-based ultrafine cemented carbide according to claim 1, characterized in that, The composition of the cemented carbide by weight percentage is: 10wt% Co / Ni / Cr, 45wt% Mo2C, 0.7wt% VC / TaC, with the balance being WC; the grain size of the Mo2C is 1.2μm, and the grain size of the WC is 0.8μm.

5. The method for preparing tungsten-molybdenum composite-based ultrafine cemented carbide according to claim 1, characterized in that, The composition of the cemented carbide by weight percentage is: 10wt% Co / Ni / Cr, 55wt% Mo2C, 0.7wt% VC / TaC, with the balance being WC; the grain size of the Mo2C is 1.0μm, and the grain size of the WC is 0.7μm.

6. The method for preparing tungsten-molybdenum composite-based ultrafine cemented carbide according to claim 1, characterized in that, The composition of the cemented carbide by weight percentage is: 13wt% Co / Ni / Cr, 55wt% Mo2C, 1.2wt% VC / TaC, with the balance being WC; the grain size of the Mo2C is 0.8μm, and the grain size of the WC is 0.4μm.

7. The method for preparing tungsten-molybdenum composite-based ultrafine cemented carbide according to any one of claims 1-6, characterized in that, The prepared tungsten-molybdenum composite-based ultrafine cemented carbide has a bending strength of 3300–3800 MPa, a fracture toughness of 9.3–11.2, and a hardness HRA≥91.1.

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