Multicomponent cemented carbide and method for producing the same

Abstract

This invention discloses a multi-component composite cemented carbide and its preparation method, relating to the field of alloy technology. The method includes the following steps: alumina powder, molybdenum carbide powder, carbon powder, and 10-30% cobalt powder are premixed in the presence of multidentate ligands; subsequently, tungsten carbide powder and the remaining cobalt powder are added for primary mixing, resulting in a powder. Based on a modified SPS method, the powder is sintered: the powder is subjected to a uniaxial mechanical load of 58-62 MPa, heated to a non-equilibrium peak temperature at a heating rate of 80-120°C and held for 0.5-1 min, then cooled to the equilibrium holding temperature within 5-10 s and held for 4-6 min. After holding, the uniaxial mechanical load is unloaded, and the material is cooled to room temperature under vacuum. The non-equilibrium peak temperature is 1275-1285°C, and the equilibrium holding temperature is 1220-1230°C. The cemented carbide obtained by this method exhibits strong mechanical properties.

Description

Technical Field

[0001] This invention relates to the field of alloy preparation technology, specifically to a multi-component composite cemented carbide and its preparation method. Background Technology

[0002] PDC cutting teeth are the core rock-breaking components of drill bits used in oil drilling and geological exploration. In the structural design of PDC teeth, WC-10Co (tungsten carbide-10% cobalt) cemented carbide serves as the matrix material. Due to its excellent hardness, strength, and good hot-pressing bonding performance with the diamond layer, it has become the most standard and widely used proportion in the industry. This ratio provides sufficient supporting strength while, through the liquid-phase sintering of the cobalt phase, absorbing the impact energy during drilling, thus forming the cornerstone of ensuring the overall structural stability of the cutting teeth.

[0003] Although WC-10Co has balanced performance, its limitations are becoming increasingly apparent in the field of high-performance PDC. To improve the performance of PDC cutting teeth, it is necessary to perform synergistic modification of WC-10Co cemented carbide to toughen and harden it. Summary of the Invention

[0004] To address at least one of the aforementioned problems, this invention proposes a multi-component composite cemented carbide and its preparation method, which can yield cemented carbide with higher strength and better toughness.

[0005] The technical solution of this invention to solve the above problems is as follows: A method for preparing a multi-component composite cemented carbide, wherein, by mass, the multi-component composite cemented carbide comprises 87.5-90 parts of tungsten carbide powder, 10 parts of cobalt powder, 0.2-0.6 parts of alumina powder, 0.5-2 parts of molybdenum carbide powder, and 0.13-0.3 parts of carbon powder, and the method comprises the following steps: Take the formula amount of alumina powder, molybdenum carbide powder, carbon powder and 10-30% of cobalt powder, and premix them in the presence of multidentate ligands; then add tungsten carbide powder and the remaining cobalt powder for primary mixing, and the powder is obtained after primary mixing. Based on the improved SPS method, the powder is sintered and formed as follows: the powder is taken, a uniaxial mechanical load of 58~62MPa is applied, and under vacuum conditions, the temperature is raised to the non-equilibrium peak temperature at a heating rate of 80~120℃ and held for 0.5~1min. Then, the temperature is lowered to the equilibrium holding temperature within 5~10s and held for 4~6min. After the holding period, the uniaxial mechanical load is unloaded and the powder is cooled to room temperature to obtain the final product. The non-equilibrium peak temperature is 1275~1285℃, and the equilibrium holding temperature is 1220~1230℃.

[0006] In this invention, the addition of carbon powder is mainly to compensate for carbon loss during the sintering process; therefore, the amount of carbon powder added should not be excessive.

[0007] Meanwhile, the addition of Al2O3 and Mo2C in this invention effectively improves the performance of cemented carbide, enhancing its strength and hardness. Al2O3, as a reinforcing phase, acts as a pinning agent against grain boundary migration, inhibiting grain coarsening and improving the alloy's hardness and strength, achieving a better match between hardness and fracture toughness. Further introduction of the transition metal carbide Mo2C as a grain boundary regulating phase alters the system's thermodynamic equilibrium, reduces the solid-liquid interfacial energy, and optimizes the problems of excessively large wetting angles and high interfacial energy caused by the inherent physicochemical differences between the oxide ceramic Al2O3 and the metallic binder phase Co. The improved binder phase strength and the enhanced wettability of the heterogeneous interface produce a synergistic effect, resulting in optimal wear resistance and overall mechanical properties of the alloy.

[0008] In this invention, the focus of premixing is on "microscopic interface chemical modification and surface coating". 1. The multidentate ligand (citric acid) introduced during premixing utilizes the active hydroxyl groups on the Al2O3 surface for in-situ coordination self-assembly, establishing a chemical continuum of "ceramic-organic chelate chain-metal" between the ceramic phase and the metal element. This intrinsically reduces the interfacial tension of the system in the early stages of ball milling, solving the problem of excessively high physical interface energy of ceramic / metal; 2. Through the self-assembly of multidentate organic molecular chains encapsulating the outer layer of Al2O3, a strong steric repulsion energy barrier can be provided, thereby breaking the spontaneous electrostatic aggregation of nanoparticles under the scouring of mechanical fluids; 3. Utilizing the excellent physical extensibility of the small amount (10%~30%) of metallic Co powder in the premixing, under the synergistic effect of the high-energy shear force of ball milling, the diffused Al2O3 and Mo2C particles are embedded and physically coated on the surface or inside of some Co powder particles, thereby obtaining a highly isotropic heterogeneous precursor network composite slurry.

[0009] The primary purpose of master mixing is to achieve "global homogenization of macroscopic components and matrix construction." After premixing and modification, Al2O3 and Mo2C are already in a stable, "encapsulated, non-agglomerated" state. Master mixing at this stage drives these trace functional phases to achieve atomic-level spatial uniformity of distribution along with the binder phase Co at the grain boundaries of the WC matrix, preventing localized macroscopic segregation, inclusions, or phase separation within the matrix. This ensures that WC particles are uniformly macroscopically surrounded by the Co binder phase containing additives and modified precursors, guaranteeing a completely consistent molten liquid phase flow path during subsequent SPS sintering. This fundamentally prevents localized areas from coarsening WC grains due to a lack of additives or forming structural defects due to macroscopic Co loss and aggregation.

[0010] In this invention, an improved SPS (spark plasma sintering) method is used to sinter the above-mentioned main-mixed material. During the sintering process, a non-equilibrium two-step sintering temperature control process is employed. In the first stage, at the non-equilibrium peak temperature, the molten Co binder phase is endowed with extremely high flow activity, forcibly overcoming the capillary resistance of the ceramic heterostructure interface and rapidly filling the micro-pores, thereby ensuring the alloy's extremely high density. According to actual measurements, the complete liquidation temperature of the main-mixed raw material is above 1300℃, approximately 1310~1330℃. This application sets the non-equilibrium peak temperature to 1275~1285℃, considering the following factors: the non-equilibrium peak temperature belongs to the "hypoeutectic region non-equilibrium densification" temperature range. Under this temperature condition, the entire system has not even reached the complete liquidation temperature thermodynamically. At this time, the liquid phase is in an extremely rare and viscous "non-equilibrium primary / eutectic critical state." In this state, combined with the micro-area electric spark thermal effect of the SPS pulsed current, the preform in this state can rapidly complete densification. At the same time, this state does not damage the stability of Al2O3 powder, making the distribution of Al2O3 powder in hard metals more uniform.

[0011] Meanwhile, after the first stage of heat preservation, a rapid cooling of only 5-10 seconds can greatly improve the overall strength and toughness of cemented carbide. From a thermodynamic perspective, there is an active grain boundary transition zone between the non-equilibrium peak temperature and the equilibrium holding temperature. This invention, through an extreme cooling of 5-10 seconds, utilizes the heat pump effect of the ultra-non-equilibrium state to forcibly implement "kinetic locking" in a very short time, causing a sudden and precipitous drop in the cross-interface diffusion capacity of atoms, thereby physically freezing the grain boundaries. If the cooling time is too long, it will leave sufficient thermodynamic relaxation time for the system, allowing W atoms time to cross the interface to complete local "dissolution and exudation," resulting in thermodynamic relaxation of the grain boundaries, coarsening of the microstructure, and weakening the overall performance of the cemented carbide.

[0012] During the sintering process, a vacuum is required throughout. In this invention, the vacuum level is required to be no greater than 10 Pa.

[0013] One feature of the present invention is that ethanol is used as a grinding aid in the premixing process and the main mixing process, and the solid-liquid ratio is 1:0.8~1.2.

[0014] Furthermore, the mass ratio of the polydentate ligand in ethanol is 0.2~0.5%.

[0015] One feature of the present invention is that the polydentate ligand is citric acid.

[0016] One feature of this invention is that the particle size of the tungsten carbide powder, cobalt powder, alumina powder, molybdenum carbide powder, and carbon powder is no greater than 10 μm. For the tungsten carbide powder, cobalt powder, molybdenum carbide powder, and carbon powder, slightly larger micron-sized particles, such as 2 μm, can be selected, or nano-sized powders can be selected; for the alumina powder, more common nano-alumina can be selected, which is relatively easy to obtain.

[0017] One feature of the present invention is that both the premixing and the primary mixing are achieved by ball milling, and in the premixing process, the ball-to-material ratio is 5~6:1, the rotation speed is 240~300 r / min, and the ball milling time is 6~10 h; in the primary mixing process, the ball-to-material ratio is 5~8:1, the rotation speed is 200~300 r / min, and the ball milling time is 24~48 h.

[0018] A feature of this invention is that, after the main mixing is completed, the following steps are included: drying and sieving the mixture. Similar to conventional powder metallurgy, before obtaining the powder, the mixture needs to be dried, and the powder with a certain fineness is used as the raw material for the preform. In this invention, the mixture needs to pass through a 200-mesh sieve.

[0019] The beneficial effects of this invention are as follows: The cemented carbide obtained by the method of this invention can achieve a Vickers hardness of up to 1555 HV and a fracture toughness of up to 11.7 MPa·m. 1 / 2 The bending strength can reach up to 2800 MPa. This demonstrates that the cemented carbide of this invention possesses strong mechanical properties. Attached Figure Description

[0020] Figure 1 This is a test image of the tungsten carbide grains in the cemented carbide of Example 1; Figure 2 This is a test image of the tungsten carbide grains in the cemented carbide in Example 2; Figure 3 This is a test image of the tungsten carbide grains in the cemented carbide in Example 3; Figure 4 This is a test image of the tungsten carbide grains in the cemented carbide in Example 4; Figure 5 The image shows the tungsten carbide grain test results of the cemented carbide in Comparative Example 1. Figure 6 The image shows the tungsten carbide grain test results of the cemented carbide in Comparative Example 2. Figure 7 The image shows the tungsten carbide grain test results of the cemented carbide in Comparative Example 3. Figure 8 The image shows the tungsten carbide grain test results of the cemented carbide in Comparative Example 4. Figure 9 The image shows the tungsten carbide grain test results for the cemented carbide in Comparative Example 5. Figure 10 Vickers hardness test diagrams of cemented carbide for each embodiment and comparative example; Figure 11 Fracture toughness test diagrams of cemented carbide in various embodiments and comparative examples; Figure 12 The diagram shows the bending strength test results of cemented carbide in each embodiment and comparative example. Detailed Implementation

[0021] The specific embodiments of the present invention will be clearly and completely described below with reference to examples. Obviously, the described examples are only some embodiments of the present invention, and not all embodiments.

[0022] In the following examples, the tungsten carbide powder used has an average particle size of 2 μm, the cobalt powder used has an average particle size of 9 μm, the molybdenum carbide powder used has a particle size of 1 μm, the carbon powder used has a particle size of 40 nm, and the alumina powder used has a particle size of 30 nm.

[0023] Unless otherwise specified, the operations used in the following embodiments are all conventional operations in the art.

[0024] Unless otherwise specified, the pharmaceutical agents used in the following examples are all conventional commercial products in the art.

[0025] In the following embodiments, the vacuum refers to an environment with a vacuum level of less than 10 Pa.

[0026] Example 1: A method for preparing a multi-component composite cemented carbide, wherein the multi-component composite cemented carbide comprises 88 parts by weight of tungsten carbide powder, 10 parts by weight of cobalt powder, 0.5 parts by weight of alumina powder, 1.5 parts by weight of molybdenum carbide powder, and 0.23 parts by weight of carbon powder, and the preparation method is as follows: Take 0.5 parts of alumina powder, 1.5 parts of molybdenum carbide powder, 2 parts of cobalt powder and 0.23 parts of carbon powder and put them into a ball mill. Add 4.2 parts of ethanol solution containing 0.3 wt% citric acid as grinding aid and premix. The ball-to-material ratio is 5:1 and the ball mill speed is 300 r / min. After ball milling, a premixed slurry is obtained.

[0027] The above-mentioned premixed slurry, 88 parts of tungsten carbide powder, 8 parts of cobalt powder and 96 parts of ethanol were mixed and put into a ball mill for main mixing. The ball-to-material ratio was 6:1, the rotation speed was 280 r / min and the ball milling time was 24 h. After the ball milling was completed, it was dried at 80℃ and then sieved through a 200 mesh sieve. The sieved material was collected and powder was obtained.

[0028] Based on the improved SPS method, the powder is sintered and formed as follows: a uniaxial mechanical load of 60 MPa is applied, and under vacuum conditions, the temperature is raised to 1280℃ at a heating rate of 100℃ / min and held for 30s. After the holding period, the system is cooled to 1230℃ in 10s and held for 5min. After the holding period, the load is unloaded and the mixture is cooled to room temperature under vacuum conditions to obtain the final product.

[0029] Example 2: A method for preparing a multi-component composite cemented carbide, wherein the multi-component composite cemented carbide comprises 89 parts by weight of tungsten carbide powder, 10 parts by weight of cobalt powder, 0.5 parts by weight of alumina powder, 0.5 parts by weight of molybdenum carbide powder, and 0.13 parts by weight of carbon powder, and the preparation method is as follows: Take 0.5 parts of alumina powder, 0.5 parts of molybdenum carbide powder, 2 parts of cobalt powder and 0.23 parts of carbon powder and put them into a ball mill. Add 3.3 parts of ethanol solution containing 0.4 wt% citric acid as grinding aid and premix. The ball-to-material ratio is 5:1 and the ball mill speed is 250 r / min. After ball milling, a premixed slurry is obtained.

[0030] The above-mentioned premixed slurry, 89 parts of tungsten carbide powder, 8 parts of cobalt powder and 97 parts of ethanol were mixed and put into a ball mill for primary mixing. The ball-to-material ratio was 6:1, the rotation speed was 220 r / min and the ball milling time was 40 h. After the ball milling was completed, it was dried at 80℃ and then sieved through a 200 mesh sieve. The sieved material was collected and powder was obtained.

[0031] Based on the improved SPS method, the powder is sintered and formed: a uniaxial mechanical load of 60 MPa is applied, and under vacuum conditions, the temperature is raised to 1285℃ at a heating rate of 100℃ / min and held for 30s. After the holding period, the system is cooled to 1220℃ in 10s and held for 5min. After the holding period, the load is unloaded and the mixture is cooled to room temperature under vacuum conditions to obtain the final product.

[0032] Example 3: A method for preparing a multi-component composite cemented carbide, wherein the multi-component composite cemented carbide comprises 88.5 parts by weight of tungsten carbide powder, 10 parts by weight of cobalt powder, 0.5 parts by weight of alumina powder, 1.0 part by weight of molybdenum carbide powder, and 0.18 parts by weight of carbon powder, and the preparation method is as follows: Take 0.5 parts of alumina powder, 1.0 parts of molybdenum carbide powder, 2 parts of cobalt powder and 0.18 parts of carbon powder and put them into a ball mill. Add 3.5 parts of ethanol solution containing 0.2 wt% citric acid as grinding aid and premix. The ball-to-material ratio is 5:1 and the ball mill speed is 280 r / min. After ball milling, a premixed slurry is obtained.

[0033] The premixed slurry, 88.5 parts of tungsten carbide powder, 8 parts of cobalt powder, and 97 parts of ethanol were mixed and fed into a ball mill for primary mixing. The ball-to-material ratio was 6:1, the rotation speed was 260 r / min, and the ball milling time was 30 h. After ball milling, the mixture was dried at 80 °C until dry, and then sieved using a 200 mesh sieve. The sieved material was collected to obtain powder.

[0034] Based on the improved SPS method, the powder is sintered and formed as follows: a uniaxial mechanical load of 60 MPa is applied, and under vacuum conditions, the temperature is raised to 1280℃ at a heating rate of 100℃ / min and held for 55s. After the holding period, the system is cooled to 1220℃ in 10s and held for 5min. After the holding period, the load is unloaded and the mixture is cooled to room temperature under vacuum conditions to obtain the final product.

[0035] Example 4: A method for preparing a multi-component composite cemented carbide, wherein the multi-component composite cemented carbide comprises 87.5 parts by weight of tungsten carbide powder, 10 parts by weight of cobalt powder, 0.5 parts by weight of alumina powder, 2.0 parts by weight of molybdenum carbide powder, and 0.3 parts by weight of carbon powder, and the preparation method is as follows: Take 0.5 parts of alumina powder, 2 parts of molybdenum carbide powder, 2 parts of cobalt powder and 0.3 parts of carbon powder and put them into a ball mill. Add 5 parts of ethanol solution containing 0.2 wt% citric acid as grinding aid and premix. The ball-to-material ratio is 5:1 and the ball mill speed is 280 r / min. After ball milling, a premixed slurry is obtained.

[0036] The premixed slurry, 87.5 parts of tungsten carbide powder, 8 parts of cobalt powder, and 95 parts of ethanol were mixed and fed into a ball mill for primary mixing. The ball-to-material ratio was 6:1, the rotation speed was 260 r / min, and the ball milling time was 30 h. After ball milling, the mixture was dried at 80 °C until dry, and then sieved using a 200 mesh sieve. The sieved material was collected to obtain powder.

[0037] Based on the improved SPS method, the powder is sintered and formed as follows: a uniaxial mechanical load of 60 MPa is applied, and under vacuum conditions, the temperature is raised to 1280℃ at a heating rate of 100℃ / min and held for 55s. After the holding period, the system is cooled to 1220℃ in 10s and held for 5min. After the holding period, the load is unloaded and the mixture is cooled to room temperature under vacuum conditions to obtain the final product.

[0038] Comparative Example 1: Compared with Example 1, the difference is that no molybdenum carbide powder was added, but all other aspects are the same.

[0039] Comparative Example 2: Compared with Example 1, the difference is that molybdenum carbide powder and alumina powder were not added, but all other aspects are the same.

[0040] Comparative Example 3: Compared with Example 1, the difference is that 1280℃ was changed to 1320℃, and the rest are the same.

[0041] Comparative Example 4: Compared with Example 1, the difference is that the heat preservation time was extended from 30s to 120s, and all other aspects are the same.

[0042] Comparative Example 5: Compared with Example 1, the difference is that the cooling time was extended from 10s to 60s, and all other aspects are the same.

[0043] To further illustrate the performance of the cemented carbide obtained in the embodiments of the present invention, the following tests are given.

[0044] 1. Tungsten carbide grain size testing The method for measuring and statistically analyzing the tungsten carbide (WC) grain size in this invention is as follows: Hard alloys prepared in Examples 1-4 and Comparative Examples 1-3 are subjected to wire cutting, stepped mechanical grinding, and metallographic mirror polishing to eliminate the surface damage layer. Subsequently, a field emission scanning electron microscope (FESEM) with backscattered electron (BSE) imaging mode is used for microscopic morphology observation. The difference in atomic number contrast is used to accurately identify the bright white WC hard phase, the dark gray Co binder phase, and the black nano-Al2O3 particles. The acquired high-resolution images are imported into ImageJ professional image analysis software, and the grain size is quantitatively measured based on pixel calibration using the straight line intercept method or the equivalent circle diameter method. During the test, 3-5 independent fields of view are randomly switched in different regions of the sample, and the total number of independent WC grains counted and measured is no less than 200. Finally, the average grain size (d) is calculated. WC Based on this, a statistical histogram of the normal distribution of relative particle size frequency was drawn.

[0045] The final test results are as follows Figures 1-9 As shown, where, Figures 1-4 The figures shown are the test results of the cemented carbide in Examples 1-4, respectively. Figures 5-9 The following are the test results of cemented carbide samples 1 through 5, respectively.

[0046] As shown in the figure, when the amount of molybdenum carbide is 1.5 parts, the grain size of tungsten carbide in cemented carbide is the smallest. Referring to Comparative Examples 1 and 2, when molybdenum carbide and alumina are not present, the grain size of tungsten carbide increases rapidly. Referring to Comparative Examples 3 to 5, it can be seen that the grain size of tungsten carbide also increases when the sintering process parameters are changed.

[0047] 2. Vickers hardness test The Vickers hardness test method for multi-component composite cemented carbide in this invention is as follows: Following the Vickers hardness test standard for cemented carbide (GB / T 7997-2014), a Vickers hardness tester is used to test the surface of the metallographically polished sample. During the test, a test force of 30 kgf (294.2 N) is selected, and the holding time is 10 to 15 s. A standard diamond square pyramid indenter is used to indent a clear square indentation on the sample surface. The lengths of the two diagonals of the indentation are accurately read using the high-magnification optical measurement system equipped with the hardness tester. The arithmetic mean of these indentations is taken and converted to obtain the Vickers hardness value (HV30) for that test point. To eliminate the influence of microscopic anisotropy and local component inhomogeneity in the alloy matrix, at least five independent sites are randomly selected on each sample surface for indentation testing. Finally, the arithmetic mean and standard deviation of the data from each test point are taken as the final Vickers hardness index of the sample.

[0048] The final results are shown in Table 2 and Figure 10 As shown.

[0049] Table 2 Vickers Hardness Test Results According to Table 2 and Figure 10 It can be seen that the cemented carbide prepared in the embodiments of the present invention has a high Vickers hardness, reaching a maximum of over 1555 HV and a minimum of over 1522 HV. Referring to Comparative Examples 1 and 2, molybdenum carbide and alumina can greatly improve the Vickers hardness of cemented carbide; referring to Comparative Examples 3 to 5, it can be seen that appropriate process parameters have a significant impact on the Vickers hardness of cemented carbide.

[0050] 3. Fracture toughness test The specific method for testing the fracture toughness of multi-component composite cemented carbide in this invention is as follows: Following the standard for testing fracture toughness of cemented carbide (GB / T 36166-2018 / ISO 28079), the Palmqvist indentation method is used to measure the fracture toughness on the surface of a metallographically polished sample. During the test, a Vickers hardness tester applies a test load of 30 kgf (294.2 N) for 10-15 s, indenting a standard conical indentation on the sample surface while simultaneously inducing symmetrical linear cracks to extend outward from the four vertices. A high-magnification optical microscope is used to accurately measure the diagonal length of the indentation and the total length of the four cracks extending from the tip of the indentation. The critical fracture toughness value is then calculated using the Palmqvist fracture toughness classical empirical formula (Shetty formula). At least five independent test points are randomly selected on the surface of each sample, and the arithmetic mean and standard deviation of the data at each point are taken as the final fracture toughness index of the multi-component composite cemented carbide.

[0051] The final test results are shown in Table 3 and Figure 11 As shown.

[0052] Table 3. Fracture toughness test results From Table 3 and Figure 11 It can be seen that the cemented carbide prepared in the embodiments of the present invention has high fracture toughness, up to 11.72 MPa·m. 1 / 2 Referring to Comparative Examples 1 and 2, it can be seen that molybdenum carbide and alumina can greatly improve the toughness of cemented carbide; referring to Comparative Examples 3 to 5, it can be seen that appropriate process parameters have a significant impact on the toughness of cemented carbide.

[0053] 4. Bending strength test The specific method for testing the bending strength of multi-component composite cemented carbide in this invention is as follows: Following the standard for determining the bending strength of cemented carbide (GB / T 3851-2015), a rectangular specimen processed to standard dimensions is tested using an electronic universal testing machine and the three-point bending method. Before testing, the specimen surface is finely ground to eliminate edge burrs and surface defects. The specimen is then placed stably on two parallel support cylinders with a fixed span (e.g., 14.5 mm) on the testing machine. A vertical load is continuously applied at a constant loading rate (e.g., 50 N / s or 0.5 mm / min) at the center of the specimen span by the loading cylinders until the specimen fractures. The maximum load (F) at the moment of fracture is recorded. The actual width (b) and height (h) of the specimen at the fracture surface are accurately measured using vernier calipers, and combined with the support span (L), the bending strength is determined using the classical bending strength formula. The bending strength value is obtained by conversion; each sample is tested in parallel for no less than 3 to 5 specimens, and the arithmetic mean and standard deviation of the valid test data are taken as the final bending strength index of the alloy sample.

[0054] The final results are shown in Table 4 and Figure 12 As shown.

[0055] Table 4 Bending Strength Test Results As shown in Table 4, the cemented carbide prepared in the embodiments of the present invention has high bending strength, with a maximum of 2843 MPa and a minimum of 2372 MPa. Referring to Comparative Examples 1 and 2, it can be seen that molybdenum carbide and alumina can greatly improve the bending strength of cemented carbide; referring to Comparative Examples 3 to 5, it can be seen that suitable process parameters have a significant impact on the bending strength of cemented carbide.

[0056] In summary, the cemented carbide prepared in the embodiments of the present invention has a smaller tungsten carbide grain size, indicating that with appropriate processes and formulations, tungsten carbide (WC) grain coarsening can be prevented and the WC grain size can be reduced. This significantly improves the mechanical properties of the cemented carbide.

[0057] The present invention has been disclosed above with preferred embodiments. However, those skilled in the art should understand that these embodiments are only for describing the present invention and should not be construed as limiting the scope of the present invention. Further improvements can be made without departing from the principles of the present invention, and these improvements should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a multi-component composite cemented carbide, characterized in that, The formulation of the multi-component composite cemented carbide, by weight, comprises 87.5-90 parts of tungsten carbide powder, 10 parts of cobalt powder, 0.2-0.6 parts of alumina powder, 0.5-2 parts of molybdenum carbide powder, and 0.13-0.3 parts of carbon powder. The method includes the following steps: Alumina powder, molybdenum carbide powder, carbon powder, and 10-30% of cobalt powder are taken according to the formula amount and premixed in the presence of a multidentate ligand; then, tungsten carbide powder and the remaining cobalt powder are added for primary mixing, and the powder is obtained after primary mixing; the multidentate ligand is citric acid. Based on the improved SPS method, the powder is sintered and formed as follows: the powder is taken, a uniaxial mechanical load of 58~62MPa is applied, and under vacuum conditions, the temperature is raised to the non-equilibrium peak temperature at a heating rate of 80~120℃ and held for 0.5~1min. Then, the temperature is lowered to the equilibrium holding temperature within 5~10s and held for 4~6min. After the holding period, the uniaxial mechanical load is unloaded and the powder is cooled to room temperature to obtain the final product. The non-equilibrium peak temperature is 1275~1285℃, and the equilibrium holding temperature is 1220~1230℃.

2. The method for preparing the multi-component composite cemented carbide according to claim 1, characterized in that, In both the premixing and main mixing processes, ethanol is used as a grinding aid, and the solid-liquid ratio is 1:0.8~1.

2.

3. The method for preparing multi-component composite cemented carbide according to claim 2, characterized in that, The mass ratio of the polydentate ligand in ethanol is 0.2~0.5%.

4. The method for preparing multi-component composite cemented carbide according to claim 1, characterized in that, The particle size of the tungsten carbide powder, cobalt powder, alumina powder, molybdenum carbide powder, and carbon powder is no greater than 10 μm.

5. The method for preparing multi-component composite cemented carbide according to claim 1, characterized in that, Both the premixing and primary mixing are achieved by ball milling. During the premixing process, the ball-to-material ratio is 5~6:1, the rotation speed is 240~300 r / min, and the ball milling time is 6~10 h. During the primary mixing process, the ball-to-material ratio is 5~8:1, the rotation speed is 200~300 r / min, and the ball milling time is 24~48 h.

6. The method for preparing multi-component composite cemented carbide according to claim 1, characterized in that, After the main mixing is completed, the following steps are also included: drying and sieving the mixture.

7. A multi-component composite cemented carbide, prepared by the method described in any one of claims 1 to 6.

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