Method for preparing silicon carbide coating on hard alloy substrate

Abstract

The invention relates to the technical field of preparation of silicon carbide coatings, in particular to a method for preparing a silicon carbide coating on a hard alloy substrate. The method comprises the following steps that firstly, a hard alloy substrate is pretreated, then the pretreated substrate is placed on a clamp in hot filament chemical vapor deposition equipment, then tetramethylsilane and hydrogen are introduced into a reaction cavity, precursor cracking is excited through a hot filament, and the hard alloy substrate is obtained. The compact and uniform silicon carbide coating is obtained on the surface of the hard alloy substrate, and meanwhile the hard alloy substrate with more excellent performance is provided. According to the method, the applicable substrate of the preparation technology of the silicon carbide coating is widened, the application range of the silicon carbide coating is expanded, and the silicon carbide coating prepared on the hard alloy substrate has high purity, good crystal quality and excellent film-substrate adhesion strength; and the wear resistance and the service life of the cutter can be obviously improved when applied to the surface of the hard alloy cutter.

Description

Technical Field

[0001] This invention relates to the field of silicon carbide coating preparation technology, and more specifically, to a method for preparing a silicon carbide coating on a cemented carbide substrate. Background Technology

[0002] In recent years, with the development of the aerospace industry, typical difficult-to-machine materials, represented by titanium alloys, have been widely used, placing higher performance demands on cutting tools required for material machining. Carbide tools are widely used in general cutting processes; however, due to limitations in their wear resistance and thermal stability, they suffer from severe wear, low durability, and difficulty in guaranteeing machining accuracy when applied to typical difficult-to-machine materials. Preparing high-performance coatings on the surface of carbide tools is an effective way to improve tool performance. Silicon carbide possesses extremely high hardness, excellent wear resistance, superior thermal stability, and good thermal conductivity. Preparing silicon carbide coatings can impart these advantageous properties to the substrate material, thus demonstrating great potential as a tool coating for improving the cutting performance of carbide tools.

[0003] Currently, the main methods for preparing silicon carbide coatings include Physical Vapor Deposition (PVD) and Chemical Vapor Deposition (CVD). PVD silicon carbide coatings are formed by the diffusion and deposition of target material components onto the substrate surface through evaporation or sputtering. However, the substrates for current PVD silicon carbide coatings are mainly limited to materials such as silicon and silicon carbide. CVD silicon carbide coatings are formed by the excitation of silicon- and carbon-containing precursors by energy (high temperature, plasma, etc.) to induce a series of chemical reactions, ultimately depositing the silicon carbide coating onto the substrate surface. CVD silicon carbide coatings have many advantages, such as high growth efficiency and good bonding strength, making them the main process for preparing silicon carbide coatings. However, CVD silicon carbide coatings are also mainly applied to substrates such as silicon, silicon carbide, and graphite. Hot filament chemical vapor deposition (HFCVD) offers advantages such as low equipment cost, ease of control, and stable process, making it widely used in tool coating preparation. Therefore, exploring methods for preparing silicon carbide coatings on cemented carbide substrates using HFCVD is of significant value and crucial for expanding the application of silicon carbide coatings in the tool coating field.

[0004] Chinese invention patent CN118326365A discloses a method for preparing silicon carbide coatings by chemical vapor deposition. The method uses an organosilicon source (methyltrichlorosilane, dimethyldichlorosilane, or dimethylsilane), hydrogen, and dilution gas (argon or helium) as gas sources to prepare a highly dense silicon carbide coating on a substrate by chemical vapor deposition. However, the substrates applicable to this method are limited to graphite, carbon, silicon carbide, or ceramics.

[0005] Chinese invention patent CN120192165A discloses a method for preparing CVD silicon carbide coatings. It proposes a method for preparing silicon carbide coatings using chemical vapor deposition technology to solve the problems of poor uniformity and unsatisfactory anti-oxidation effect of existing silicon carbide coatings. However, this method is only used to prepare silicon carbide coatings on the surface of carbon fiber sealing strips.

[0006] WC-Co cemented carbide is widely used in cutting tools due to its combination of high hardness, high strength, and excellent toughness. With the rapid development of modern industry, higher requirements are placed on the comprehensive performance of cemented carbide materials. There is an urgent need to develop a new generation of high-performance cemented carbide that combines high hardness, high strength, and excellent corrosion resistance, so as to better combine with silicon carbide coatings and improve product quality.

[0007] Therefore, there is an urgent need for a method to prepare silicon carbide coatings on cemented carbide substrates using HFCVD. Summary of the Invention

[0008] The purpose of this invention is to address the shortcomings of existing technologies by providing a method for preparing silicon carbide coatings on cemented carbide substrates using HFCVD, thus expanding the application range of silicon carbide coatings. The silicon carbide coatings prepared on cemented carbide substrates using this method exhibit a dense microstructure, uniform grain size, and high growth rate, while also demonstrating high purity and crystallinity. Furthermore, the silicon carbide coatings prepared by this method show excellent adhesion strength to the cemented carbide substrate. Depositing silicon carbide coatings on the surface of cemented carbide cutting tools using this method can significantly improve the cutting performance of the tools.

[0009] This invention is achieved through the following technical solution: This invention provides a method for preparing a silicon carbide coating on a cemented carbide substrate, the method comprising the following steps: S1: The equipment used in the method is an HFCVD equipment, which includes a reaction chamber, a hot wire, a fixture, and a worktable. The pretreated cemented carbide substrate is placed in the fixture on the worktable inside the reaction chamber of the HFCVD equipment. S2: Using tetramethylsilane and hydrogen as reaction precursors, and adjusting the deposition parameters, a silicon carbide coating is deposited on the surface of cemented carbide.

[0010] Preferably, the pretreatment method described in S1 is as follows: first, the cemented carbide substrate is immersed in Murakami solution for 15 min, then etched in Caro acid solution for 15 s, then ultrasonically vibrated in diamond micron powder suspension for 15 min, and finally cleaned and dried.

[0011] Preferably, the cemented carbide substrate mentioned in S1 can be various cemented carbide tools such as cemented carbide flat plates, cemented carbide turning tools, cemented carbide end mills, and cemented carbide drills.

[0012] Preferably, the worktable in S1 is a copper water-cooled worktable, and the fixture is made of graphite.

[0013] Preferably, for carbide flat plates and carbide turning tools, the graphite clamp is a graphite disk; for carbide end mills and carbide drills, the clamp is a perforated graphite strip.

[0014] Preferably, the HFCVD equipment uses tantalum wire as the hot wire with a diameter of 0.3mm to 0.6mm. The tantalum wire is electrically heated as the excitation source. During the preparation process, multiple tantalum wires are suspended in parallel and at equal intervals above the worktable.

[0015] Preferably, for carbide flat plates and carbide turning tool substrates, the hot wire spacing is 10~30mm and the distance from the hot wire to the substrate surface is 6~15mm; for carbide end mills and carbide drill substrates, the hot wire spacing is 10~45mm and the hot wire is located between 10mm above and 15mm below the tool tip.

[0016] Preferably, before chemical vapor deposition, liquid tetramethylsilane is first prepared into a tetramethylsilane / hydrogen mixture (tetramethylsilane content is 1%~2%). During chemical vapor deposition, two gases are introduced into the reaction chamber, one is hydrogen and the other is the tetramethylsilane / hydrogen mixture.

[0017] Preferably, the deposition parameters described in S2 are: deposition temperature of 675~725℃, hydrogen flow rate of 800~1200 sccm, mixed gas flow rate of 140~400 sccm, silicon source concentration (ratio of tetramethylsilane to hydrogen) of 0.15%~0.25%, and reaction pressure of 1600~2000 Pa.

[0018] The cemented carbide substrate comprises the following components by mass percentage: Co 5.8-6.3%, Ce 1.5-2.5%, Mo2C 0.5-0.9%, VC 1.6-1.9%, TaC 0.8-1.3%, Mo 1.0-2.0%, with the balance being tungsten carbide.

[0019] Preferably, the sum of the mass percentages of Mo2C, VC and TaC is 3.0-4.0%.

[0020] This invention improves the bending strength of cemented carbide substrates by adding three carbides in specific proportions and amounts to the cemented carbide formulation. Analysis shows that the three carbides achieve a synergistic effect in the system. VC has low solubility in WC and can rapidly segregate at WC grain boundaries, effectively preventing grain coarsening at high sintering temperatures. TaC inhibits grain growth and improves the alloy's creep resistance, while Mo2C also refines grains. The simultaneous use of these three components enhances grain refinement and further improves toughness and high-temperature performance, collectively increasing bending strength.

[0021] Preferably, the ratio of the sum of the mass percentages of Mo2C, VC, and TaC to the mass percentage of Ce to the mass percentage of Mo is (3.2-3.5): (2.2-2.5): (1.5-1.8).

[0022] Under the above conditions, the hardness and toughness of the cemented carbide substrate are superior. Analysis shows that carbides can improve grain refinement, Ce can improve grain boundary strength and promote sintering densification; the addition of Mo needs to be matched with the content of carbides and Ce; only at a specific ratio can the optimal grain boundary structure and phase interface be formed, thereby improving hardness and fracture toughness.

[0023] Preferably, the cemented carbide substrate comprises the following components by mass percentage: Co 6.0%, Ce 2.3%, Mo2C 0.6%, VC 1.8%, TaC 1.0%, Mo 1.6%, with the balance being tungsten carbide.

[0024] The method for preparing the cemented carbide substrate includes the following steps: (1) The components of the cemented carbide substrate were wet-milled. The ball milling medium was anhydrous ethanol, the ball-to-material ratio was 6:1, the ball milling speed was 100 r / min, and the ball milling time was 36 h. After the ball milling was completed, the slurry was placed in a vacuum drying oven and heated and vacuum dried at 70°C for 6 h to obtain the mixture.

[0025] (2) The mixture was pressed into shape by a 25t single-column hydraulic press and sintered in a sintering furnace at a temperature of 1450℃ for 90 minutes and a pressure of 3.0 MPa to obtain a cemented carbide substrate.

[0026] Compared with the prior art, the present invention has the following superior effects: 1. Using this invention, a silicon carbide coating was successfully prepared on a cemented carbide substrate, which broadened the applicable substrates for silicon carbide coating preparation technology and expanded the application range of silicon carbide coating.

[0027] 2. The silicon carbide coating prepared on a cemented carbide substrate using the present invention has a dense microstructure, uniform grain size and high growth rate, as well as high purity and crystal quality. In addition, it also has high film-substrate adhesion strength, high hardness, good wear resistance and high application value.

[0028] 3. The silicon carbide coating prepared on the cemented carbide substrate using the present invention, when applied to the surface of cemented carbide cutting tools, not only significantly improves the hardness and wear resistance of the tools, but also enhances the thermal stability and thermal conductivity of the tools, thereby improving the tool life when cutting difficult-to-machine materials.

[0029] 4. The silicon carbide coating prepared on the cemented carbide substrate using the present invention is completed by hot-wire chemical vapor deposition equipment. Compared with other silicon carbide coating preparation methods, the equipment cost is low, it is easy to control, and the growth process is simple and stable, which is conducive to the widespread application of silicon carbide coatings on cemented carbide substrates.

[0030] 5. This invention also provides a novel cemented carbide substrate, which, through the adjustment of components and proportions, exhibits excellent hardness and mechanical properties, significantly superior to commercially available products. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the HFCVD equipment used in the method for preparing silicon carbide on a cemented carbide substrate according to the present invention; wherein, 1 is the reaction chamber, 2 is the hot wire, 3 is the pretreated cemented carbide substrate, 4 is the fixture, and 5 is the water-cooled worktable. Figure 2 This is a surface morphology diagram of the silicon carbide coating prepared on a cemented carbide substrate in Example 1; Figure 3 This is a cross-sectional morphology diagram of the silicon carbide coating prepared on a cemented carbide substrate in Example 1; Figure 4 The image shows the Raman spectrum of the silicon carbide coating prepared on a cemented carbide substrate in Example 1. Detailed Implementation

[0032] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0033] like Figure 1As shown, a method for preparing a silicon carbide coating on a cemented carbide substrate uses an HFCVD apparatus, including a reaction chamber 1, a hot wire 2, a fixture 4, and a water-cooled worktable 5. The reaction chamber 1 is provided with two air inlets and outlets for introducing the precursor and discharging waste gas. The heated hot wire 2 serves as the excitation source for the precursor. The graphite fixture 4 is placed on the water-cooled worktable 5, and the cemented carbide substrate 3 is placed on the fixture 4. During the preparation process, multiple hot wires 2 are arranged in parallel and at equal intervals above the water-cooled worktable 5.

[0034] This invention provides a method for preparing a silicon carbide coating on a cemented carbide substrate, the specific steps of which are as follows: First, the cemented carbide substrate is pretreated by immersing it in Murakami solution for 15 minutes, then etching it in Caro acid solution for 15 seconds, followed by ultrasonic oscillation in diamond micron powder suspension for 15 minutes, and finally cleaning and drying.

[0035] Next, the pretreated cemented carbide substrate is placed on a graphite fixture on the worktable inside the reaction chamber of the HFCVD equipment. During the deposition process, multiple tantalum wires are arranged in parallel and at equal intervals above the worktable, maintaining a certain distance between the hot wires and the substrate surface / tip. Subsequently, hydrogen and a tetramethylsilane / hydrogen mixture are simultaneously introduced into the reaction chamber, and the deposition parameters are adjusted. The precursor is decomposed by activating the hot wires, and a silicon carbide coating is deposited on the surface of the cemented carbide substrate.

[0036] The present invention will now be described in further detail with reference to specific embodiments.

[0037] The specific product information used in the following examples is as follows: Murakami solution: KOH, K3[Fe(CN)6] and H2O in a mass ratio of 1:1:10.

[0038] Caro acid solution: HCl:H2O2 in a mass ratio of 3:7.

[0039] Example 1: This embodiment provides a method for preparing a silicon carbide coating on a cemented carbide substrate, including the following steps: (1) The cemented carbide substrate is a cemented carbide flat sheet with dimensions of 20mm×6.5mm×5.25mm. First, the selected cemented carbide substrate is pretreated by immersing the cemented carbide flat sheet in Murakami solution for 15min, then etching it in Caro acid solution for 15s, then ultrasonically vibrating it in diamond micron powder suspension for 15min, and finally cleaning and drying it.

[0040] (2) Next, the pretreated cemented carbide substrate is placed on the graphite fixture on the worktable inside the reaction chamber of the HFCVD equipment. The graphite fixture is a circular graphite disk with a diameter of 100 mm and a thickness of 8 mm. The hot wire is a tantalum wire with a diameter of 0.6 mm. During the deposition process, four hot wires are arranged in parallel and at equal intervals above the substrate, with a spacing of 15 mm between the hot wires and a distance of 10 mm from the hot wire to the substrate surface. Then, hydrogen and a tetramethylsilane / hydrogen mixture (the volume fraction of tetramethylsilane in the mixture is 2%) are simultaneously introduced into the reaction chamber. The reaction is generated by the hot wire to deposit a silicon carbide coating on the surface of the cemented carbide substrate. The deposition parameters are: deposition temperature 700℃, hydrogen flow rate 1000 sccm, silicon source concentration 0.2%, reaction pressure 1800 Pa, and deposition time 6 h, to obtain a silicon carbide coating prepared on the cemented carbide substrate.

[0041] The cemented carbide substrate comprises the following components by mass percentage: Co 6.0%, Ce 2.3%, Mo2C 0.6%, VC 1.8%, TaC 1.0%, Mo 1.6%, with the balance being tungsten carbide.

[0042] The method for preparing the cemented carbide substrate includes the following steps: (1) The components of the cemented carbide substrate were wet-milled. The ball milling medium was anhydrous ethanol, the ball-to-material ratio was 6:1, the ball milling speed was 100 r / min, and the ball milling time was 36 h. After the ball milling was completed, the slurry was placed in a vacuum drying oven and heated and vacuum dried at 70°C for 6 h to obtain the mixture.

[0043] (2) The mixture was pressed into shape by a 25t single-column hydraulic press and sintered in a sintering furnace at a temperature of 1450℃ for 90 minutes and a pressure of 3.0 MPa to obtain a cemented carbide substrate.

[0044] Figure 2 and Figure 3 The images show the surface morphology and cross-sectional morphology of the silicon carbide coating prepared on a cemented carbide substrate using the method of the present invention. It can be observed that a uniform and dense silicon carbide coating is deposited on the surface of the cemented carbide substrate. The coating has uniform grain size and a thickness of about 8.5 μm. Figure 4 To obtain the Raman spectrum of the silicon carbide coating prepared on the cemented carbide substrate using the method of this invention, at 796 cm⁻¹ -1 Typical silicon carbide characteristic peaks can be observed nearby, exhibiting high intensity and a sharp peak shape, indicating that the silicon carbide coating has high purity and good crystallinity. Furthermore, a Rockwell indentation test was performed on the prepared silicon carbide coating surface. Under a load of 1000 N, the coating did not peel off; only fine cracks appeared around the indentation, indicating that the silicon carbide coating prepared on the cemented carbide substrate has good adhesion strength.

[0045] Example 2: This embodiment provides a method for preparing a silicon carbide coating on a cemented carbide substrate, including the following steps: (1) The cemented carbide substrate is a cemented carbide turning tool (YG6) with dimensions of 16mm×16mm×4.5mm. First, the selected cemented carbide substrate is pretreated by immersing the cemented carbide turning tool in Murakami solution for 15min, then etching it in Caro acid solution for 15s, then ultrasonically vibrating it in diamond micron powder suspension for 15min, and finally cleaning and drying it.

[0046] (2) Next, the pretreated cemented carbide substrate is placed on the graphite fixture on the worktable inside the reaction chamber of the HFCVD equipment. The graphite fixture is a circular graphite disk with a diameter of 100 mm and a thickness of 8 mm. The hot wire is a tantalum wire with a diameter of 0.6 mm. During the deposition process, four hot wires are arranged in parallel and at equal intervals above the substrate, with a spacing of 15 mm between the hot wires and a distance of 10 mm from the hot wire to the substrate surface. Then, hydrogen and a tetramethylsilane / hydrogen mixture (2% tetramethylsilane content in the mixture) are simultaneously introduced into the reaction chamber. The reaction is generated by the hot wire to deposit a silicon carbide coating on the surface of the cemented carbide substrate. The deposition parameters are: deposition temperature 700℃, hydrogen flow rate 1000 sccm, silicon source concentration 0.2%, reaction pressure 1800 Pa, and deposition time 6 h.

[0047] The silicon carbide coating prepared in this example exhibits a dense and uniform morphology with a thickness of approximately 8.5 μm, along with high purity and good crystallinity. In titanium alloy turning experiments, under the same cutting parameters, the silicon carbide-coated turning tool prepared in this example showed better wear resistance and a significantly improved tool life compared to the uncoated carbide turning tool.

[0048] Example 3: This embodiment provides a method for preparing a silicon carbide coating on a cemented carbide substrate, including the following steps: (1) The cemented carbide substrate is a cemented carbide flat sheet (YG6) with an external dimension of 16mm×16mm×4.5mm. First, the selected cemented carbide substrate is pretreated by immersing the cemented carbide flat sheet in Murakami solution for 15min, then etching it in Caro acid solution for 15s, then ultrasonically vibrating it in diamond micro powder suspension for 15min, and finally cleaning and drying it.

[0049] (2) Next, the pretreated cemented carbide substrate is placed on the graphite fixture on the worktable inside the reaction chamber of the HFCVD equipment. The graphite fixture is a circular graphite disk with a diameter of 80 mm and a thickness of 5 mm. The hot wire is a tantalum wire with a diameter of 0.5 mm. During the deposition process, three hot wires are arranged in parallel and at equal intervals above the substrate, with a spacing of 18 mm between the hot wires and a distance of 12 mm from the hot wire to the substrate surface. Then, hydrogen and a tetramethylsilane / hydrogen mixture (1% tetramethylsilane in the mixture) are simultaneously introduced into the reaction chamber. The reaction is generated by the hot wire to deposit a silicon carbide coating on the surface of the cemented carbide substrate. The deposition parameters are: deposition temperature 675℃, hydrogen flow rate 800 sccm, silicon source concentration 0.15%, reaction pressure 1600 Pa, and deposition time 5 h.

[0050] The silicon carbide coating prepared in this example exhibits a dense morphology with uniform grain size and a thickness of approximately 6.5 μm. The coating also demonstrates high purity, good crystal quality, and excellent film-substrate adhesion strength.

[0051] Example 4: This embodiment provides a method for preparing a silicon carbide coating on a cemented carbide substrate, including the following steps: (1) The cemented carbide substrate is a cemented carbide flat sheet (YG6) with an external dimension of 16mm×10mm×5.5mm. First, the selected cemented carbide substrate is pretreated by immersing the cemented carbide flat sheet in Murakami solution for 15min, then etching it in Caro acid solution for 15s, then ultrasonically vibrating it in diamond micron powder suspension for 15min, and finally cleaning and drying it.

[0052] (2) Next, the pretreated cemented carbide substrate is placed on the graphite fixture on the worktable inside the reaction chamber of the HFCVD equipment. The graphite fixture is a circular graphite disk with a diameter of 80 mm and a thickness of 5 mm. The hot wire is a tantalum wire with a diameter of 0.5 mm. During the deposition process, three hot wires are arranged in parallel and at equal intervals above the substrate, with a spacing of 18 mm between the hot wires and a distance of 8 mm from the hot wire to the substrate surface. Then, hydrogen and a tetramethylsilane / hydrogen mixture (1% tetramethylsilane content in the mixture) are simultaneously introduced into the reaction chamber. The reaction is generated by the hot wire to deposit a silicon carbide coating on the surface of the cemented carbide substrate. The deposition parameters are: deposition temperature 725℃, hydrogen flow rate 1200 sccm, silicon source concentration 0.25%, reaction pressure 2000 Pa, and deposition time 5 h.

[0053] The silicon carbide coating prepared in this example exhibits a dense morphology with uniform grain size and a thickness of approximately 7.0 μm. The coating also demonstrates high purity, good crystal quality, and excellent film-substrate adhesion strength.

[0054] Example 5: This embodiment provides a method for preparing a silicon carbide coating on a cemented carbide substrate, including the following steps: (1) The cemented carbide substrate is a cemented carbide end mill (YG6) with dimensions of (φ4mm×50mm). First, the selected cemented carbide substrate is pretreated by immersing the cemented carbide end mill in Murakami solution for 15min, then etching it in Caro acid solution for 15s, then ultrasonically vibrating it in diamond micron powder suspension for 15min, and finally cleaning and drying it.

[0055] (2) Next, the pretreated cemented carbide substrate is placed on the graphite fixture on the worktable inside the reaction chamber of the HFCVD equipment. The graphite fixture is a perforated graphite strip with dimensions of 20mm×20mm×200mm. The hot wire is a tantalum wire with a diameter of 0.3mm. During the deposition process, a total of six hot wires are arranged in parallel and at equal intervals below the tip of the milling cutter, with a spacing of 30mm between the hot wires and a distance of 6mm from the hot wire to the tip of the substrate. Then, hydrogen and a tetramethylsilane / hydrogen mixture (2% tetramethylsilane content in the mixture) are simultaneously introduced into the reaction chamber. The reaction is generated by the hot wire to deposit a silicon carbide coating on the surface of the cemented carbide substrate. The deposition parameters are: deposition temperature 700℃, hydrogen flow rate 1000sccm, silicon source concentration 0.2%, reaction pressure 1800Pa, and deposition time 6h.

[0056] The silicon carbide coating prepared in this example exhibits a dense morphology with uniform grain size and a thickness of approximately 8.0 μm. The coating also demonstrates high purity and good crystallinity. In titanium alloy milling experiments, under the same cutting parameters, the silicon carbide-coated end mill prepared in this example showed a significantly improved tool life compared to the uncoated carbide end mill.

[0057] Comparative Example 1: The difference between this comparative example and Example 1 lies in the deposition parameters. The deposition parameters are: temperature 700℃, hydrogen flow rate 1000 sccm, silicon source concentration 0.35%, reaction pressure 1800 Pa, and deposition time 6 h. Based on the results of Example 1 and Comparative Example 1, the coating prepared in Comparative Example 1 has low density, numerous defects, and significantly reduced purity and crystallinity.

[0058] Comparative Example 2 The difference between this comparative example and Example 1 is that Mo2C, VC, and TaC are replaced with Mo2C.

[0059] The cemented carbide substrate comprises the following components by mass percentage: Co 6.0%, Ce 2.3%, Mo2C 3.4%, Mo 1.6%, with the balance being tungsten carbide.

[0060] Comparative Example 3 The difference between this comparative example and Example 1 is that the proportions of Mo2C, VC, and TaC are different.

[0061] The cemented carbide substrate comprises the following components by mass percentage: Co 6.0%, Ce 2.3%, Mo2C 1.8%, VC 1.0%, TaC 0.6%, Mo 1.6%, with the balance being tungsten carbide.

[0062] Comparative Example 4 The difference between this comparative example and Example 1 is that the total amount of Mo2C, VC, and TaC added is different.

[0063] The cemented carbide substrate comprises the following components by mass percentage: Co 6.0%, Ce 2.3%, Mo2C 1.5%, VC 2.0%, TaC 1.5%, Mo 1.6%, with the balance being tungsten carbide.

[0064] Comparative Example 5 The difference between this comparative example and Example 1 is that the cemented carbide substrate comprises the following components by mass percentage: Co 6.0%, Ce 2.0%, Mo2C 0.5%, VC 1.5%, TaC 1.0%, Mo 2.3%, with the balance being tungsten carbide.

[0065] Comparative Example 6 The difference between this comparative example and Example 1 is that the cemented carbide substrate is a commercially available cemented carbide flat sheet (YG6).

[0066] Comparative Example 7 This comparative example is the product with a Mo2C addition of 5.0% from the article "The Influence of Mo2C Addition on the Microstructure and Properties of YG6 Fine-Grained Cemented Carbide".

[0067] The performance of the cemented carbide flat sheets from Examples 1 and Comparative Examples 2-7 was tested. Specifically, the hardness was determined using a Rockwell hardness tester; the bending strength was determined using an electronic universal testing machine; and the fracture toughness of the alloy was measured using the indentation method. The results are shown in Table 1.

[0068] Table 1 Test Results As shown in Table 1, the hard alloy substrate prepared in Example 1 exhibits excellent hardness and mechanical properties, significantly superior to commercially available products and products of the prior art (Note: Data in Comparative Example 7 are provided in the article). Comparative Examples 2-4 show that adding three carbides—Mo2C, VC, and TaC—in specific proportions significantly improves flexural strength compared to adding only Mo2C. Furthermore, in Comparative Example 4, changing the total amount of each carbide actually worsens the mechanical properties compared to Comparative Example 2. This is because there is an optimal window for adding the three carbides; too little results in coarse grains and poor performance, while too much introduces brittleness, reducing both strength and toughness.

[0069] Comparative Example 5 shows that the sum of the amounts of Mo2C, VC, and TaC, and the ratio between Ce and Mo, have a significant impact on the hardness and fracture toughness of cemented carbide.

[0070] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A method for preparing a silicon carbide coating on a cemented carbide substrate, characterized in that, The method includes the following steps: S1: The equipment used in the method is an HFCVD equipment, which includes a reaction chamber, a hot wire, a fixture, and a worktable. The pretreated cemented carbide substrate is placed in the fixture on the worktable inside the reaction chamber of the HFCVD equipment. S2: Using tetramethylsilane and hydrogen as reaction precursors, and adjusting the deposition parameters, a silicon carbide coating is deposited on the surface of cemented carbide.

2. The method for preparing a silicon carbide coating on a cemented carbide substrate according to claim 1, characterized in that, The pretreatment method is as follows: first, the cemented carbide substrate is immersed in Murakami solution, then etched in Caro acid solution, then ultrasonically vibrated in diamond micro powder suspension, and finally cleaned and dried.

3. The method for preparing a silicon carbide coating on a cemented carbide substrate according to claim 1, characterized in that, The carbide substrate is selected from any one of carbide flat plates, carbide turning tools, carbide end mills, and carbide drills.

4. The method for preparing a silicon carbide coating on a cemented carbide substrate according to claim 1, characterized in that, The worktable is a copper water-cooled worktable, and the fixture is made of graphite.

5. The graphite clamp according to claim 3, characterized in that, When the cemented carbide substrate is a cemented carbide flat sheet or a cemented carbide turning tool, the graphite fixture is a graphite disk; when the cemented carbide substrate is a cemented carbide end mill or a cemented carbide drill bit, the fixture is a perforated graphite strip.

6. The method for preparing a silicon carbide coating on a cemented carbide substrate according to claim 1, characterized in that, The HFCVD equipment uses tantalum wire as the hot wire, with a diameter of 0.3mm to 0.6mm. The tantalum wire is electrically heated as the excitation source. During the preparation process, multiple tantalum wires are suspended in parallel and at equal intervals above the worktable.

7. The hot wire according to claim 3, characterized in that, When the carbide substrate is a carbide flat sheet or a carbide turning tool substrate, the hot wire spacing is 10~30mm, and the distance from the hot wire to the substrate surface is 6~15mm; when the carbide substrate is a carbide end mill or a carbide drill substrate, the hot wire spacing is 10~45mm, and the hot wire is located between 10mm above and 15mm below the tool tip.

8. The method for preparing a silicon carbide coating on a cemented carbide substrate according to claim 1, characterized in that, Before chemical vapor deposition, liquid tetramethylsilane is first converted into a tetramethylsilane / hydrogen mixture. During chemical vapor deposition, two gases are introduced into the reaction chamber: one is hydrogen, and the other is the tetramethylsilane / hydrogen mixture.

9. A method for preparing a silicon carbide coating on a cemented carbide substrate according to claim 1, characterized in that, The deposition parameters are: deposition temperature 675~725℃, hydrogen flow rate 800~1200sccm, mixed gas flow rate 140~400sccm, silicon source concentration 0.15%~0.25%, and reaction pressure 1600~2000Pa.

10. A method for preparing a silicon carbide coating on a cemented carbide substrate according to claim 1, characterized in that, The cemented carbide substrate comprises the following components by mass percentage: Co 5.8-6.3%, Ce 1.5-2.5%, Mo2C 0.5-0.9%, VC 1.6-1.9%, TaC 0.8-1.3%, Mo 1.0-2.0%, with the balance being tungsten carbide.

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