Wear-resistant hard alloy material and preparation method thereof

Abstract

The invention discloses a wear-resistant hard alloy material and a preparation method thereof, and particularly relates to the field of alloy materials.The wear-resistant hard alloy material comprises tungsten carbide, cobalt powder, graphene aerogel fragments, coconut shell carbonized porous carbon, yttrium oxide and auxiliaries, and a multi-scale reinforcing system is constructed by optimizing the proportion. According to the preparation method, supercritical drying is combined with a microwave reaction sintering process, and material densification is realized through gradient temperature control and steam concentration accurate regulation and control in a specific atmosphere. Graphene aerogel fragments and porous carbon form a three-dimensional interpenetrating network, so that the wear resistance and the conductivity are synergistically improved; yttrium oxide is segregated at a grain boundary to form a high-temperature anti-oxidation barrier; the gradient sintering process effectively eliminates internal stress and inhibits abnormal growth of grains. The technical bottleneck that wear resistance and toughness of traditional hard alloy are difficult to synergistically improve is broken through, excellent conductivity and high-temperature stability are achieved, and the industrial problems that wear resistance / toughness is inverted, a conductive network is low in efficiency, and the high-temperature stability is poor are solved.

Description

Technical Field

[0001] The present invention relates to the field of alloy materials, and in particular to a wear-resistant hard alloy material and a preparation method thereof. Background Art

[0002] Traditional cemented carbide materials usually use tungsten carbide (WC) as the matrix, and improve performance by adding cobalt (Co) as a binder phase and supplemented with hard reinforcing phases such as titanium carbide (TiC) and tantalum carbide (TaC). Existing technologies generally use mechanical mixing to prepare composite powders, combined with atmospheric pressure sintering or hot isostatic pressing processes for densification. To further improve conductivity, some solutions will introduce graphite or carbon black as a conductive phase, while the improvement of oxidation resistance mostly depends on post-treatment of ceramic coatings such as alumina (Al2O3). Although such materials have certain applications in the fields of cutting tools and molds, their component design and process routes are still based on the traditional system of the 20th century.

[0003] However, existing technologies have significant defects: first, it is difficult to balance wear resistance and toughness in material components. Although high cobalt content can improve toughness, it seriously sacrifices hardness and high-temperature stability, and low-cobalt systems are prone to increased brittleness; second, traditional reinforcing phases (such as TiC and carbon black) are prone to stress concentration due to uneven dispersion, and cannot build an efficient conductive network; third, conventional sintering processes have problems such as high energy consumption and insufficient densification, and the process parameters have low tolerance, and slight fluctuations will lead to significant performance degradation; fourth, the material has a single function and cannot simultaneously meet the modern industry's integrated needs for wear resistance, conductivity, and high-temperature oxidation resistance. Summary of the Invention

[0004] The main purpose of the present invention is to provide a wear-resistant cemented carbide material and a preparation method thereof, aiming to solve key technical bottlenecks in traditional cemented carbide materials, such as the difficulty in synergistically improving wear resistance and toughness, inefficient conductive network construction, insufficient high-temperature oxidation resistance, and poor sintering process control accuracy. Through the synergistic enhancement mechanism of graphene aerogel fragments and biomass porous carbon, combined with microwave-reactive sintering process innovation, multifunctional integrated integration such as wear resistance, toughness, conductivity, and high temperature resistance is achieved.

[0005] To achieve the above object, the technical solution adopted by the present invention is:

[0006] A wear-resistant hard alloy material comprises the following components in parts by weight: 80-86 parts of tungsten carbide, 5-10 parts of cobalt powder, 1-3 parts of graphene aerogel fragments, 2-6 parts of carbonized coconut shell porous carbon, 0.1-1 part of yttrium oxide, 1-1.5 parts of binder, 0.1-0.5 parts of dispersant, and 0.3-0.7 parts of lubricant.

[0007] Preferably, the specific surface area of ​​the graphene aerogel fragments is 800-1200m 2 / g, fragment size 10-50μm.

[0008] Preferably, the coconut shell carbonized porous carbon has a porosity of 70%, a particle size of 5-10 μm, and a carbon content of ≥95%.

[0009] Preferably, the binder is polyvinyl alcohol, the dispersant is ammonium polyacrylate, and the lubricant is zinc stearate.

[0010] The present invention also discloses a method for preparing the above-mentioned wear-resistant hard alloy material, and the specific steps are as follows:

[0011] Step 1: Preparation of composite powder:

[0012] Add the prepared tungsten carbide, cobalt powder, coconut shell carbonized porous carbon, and yttrium oxide to a three-dimensional mixer and dry mix at 30 rpm for 30 minutes. Then add the graphene gel fragments and continue mixing for 15 minutes.

[0013] The samples were then ball-milled in a planetary ball mill using zirconia balls at a ball-to-material ratio of 5:1 and anhydrous ethanol as the solvent, maintaining a solid-liquid ratio of 1:2. The samples were ball-milled at 250 rpm for 4 h, with argon gas as a protective gas. After ball-milling, the samples were vacuum-dried at 60°C for 4 h, and supercritical CO2 was used to dry and replace the anhydrous ethanol.

[0014] Then a centrifugal spray drying tower is used.

[0015] Step 2: Powder pressing: The powder obtained in step 1 is pressed into a mold at a pressure of 250 MPa for 30 minutes;

[0016] Step 3, microwave-reactive sintering: a microwave sintering furnace is configured, and a distributed SiCl4 vapor injection system is integrated at the bottom of the microwave sintering furnace. The pressed alloy powder body is subjected to pre-carbonization, reactive sintering, microwave densification, heat preservation and gradient cooling steps in sequence to obtain a green body;

[0017] Step 4: performing surface finishing grinding on the green body obtained in step 3 to obtain the wear-resistant cemented carbide.

[0018] Preferably, the process of the pre-carbonization stage is as follows: in an H2 atmosphere, heating to 300°C at a heating rate of 10°C / min, keeping the temperature for 30 minutes, and then heating to 600°C at a heating rate of 5°C / min, with an H2 flow rate of 8 L / min.

[0019] Preferably, the specific process of the reaction sintering stage is: in an argon atmosphere, the temperature is raised to 1000° C. at a rate of 50° C. / min, SiCl 4 vapor with a concentration of 5% is introduced, and maintained for 60 minutes.

[0020] Preferably, the specific process of the microwave densification stage is: under the condition of a microwave power of 5kW, first heat it to 1250°C at a rate of 50°C / min, keep it warm for 20 minutes, then increase the microwave power to 10kW, and then heat it to 1380°C at a rate of 50°C / min, and then enter the insulation stage. During the whole process, H2 and argon are introduced, and the volume ratio of H2:argon is 1:9.

[0021] Preferably, the specific insulation conditions of the insulation stage are: under the condition that the volume ratio of H2 to argon is 1:9, at a temperature of 1380°C, maintaining the Ar pressure at 0.5MPa, and insulation for 20min.

[0022] Preferably, the gradient cooling process is specifically divided into the following two stages:

[0023] Stage 1: Decrease the temperature from 1380°C to 800°C at a rate of 30°C / min while continuously introducing argon gas at a flow rate of 10 L / min;

[0024] Stage 2: Cool naturally to room temperature in the furnace.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. This solution achieves comprehensive improvements in cemented carbide performance through the synergy of innovative material design and process. Graphene aerogel, a microwave-sensitive medium, creates a dynamic thermal field distribution through its three-dimensional network structure during sintering, resulting in a gradient densification effect from the core to the periphery within the material. This heating mechanism not only significantly reduces the reliance on external heat sources compared to traditional sintering, but also effectively suppresses abnormal grain growth through directed energy transfer, laying the foundation for achieving a uniform, fine-grained structure.

[0027] 2. Through sophisticated control of vapor infiltration and solid-phase reaction, the present invention grows SiC whiskers with a high aspect ratio on the surface of the biomass carbon skeleton while maintaining a multi-level pore structure. This composite structure of "hard reinforcement phase + tough matrix" allows the material to dissipate energy through SiC whiskers when subjected to impact loads, while also utilizing the pore structure to buffer stress concentration, achieving a synergistic improvement in strength and toughness. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a line graph of the wear resistance test results of Examples 1-5 of the present invention and Comparative Examples 1-5.

[0029] Figure 2 It is a line graph of the hardness test results of Examples 1-5 of the present invention and Comparative Examples 1-5.

[0030] Figure 3It is a line graph of the toughness test results of Examples 1-5 of the present invention and Comparative Examples 1-5.

[0031] Figure 4 4 is a line graph showing the conductivity test results of Examples 1-5 and Comparative Examples 1-5 of the present invention.

[0032] Figure 5 It is a line graph of the high temperature stability test results of Examples 1-5 of the present invention and Comparative Examples 1-5. DETAILED DESCRIPTION

[0033] In order to make the technical means, creative features, objectives and effects achieved by the present invention easier to understand, the present invention is further described below in conjunction with specific implementation methods.

[0034] The invention discloses a wear-resistant hard alloy material, which comprises the following components in parts by weight: 80-86 parts of tungsten carbide, 5-10 parts of cobalt powder, 1-3 parts of graphene aerogel fragments, 2-6 parts of carbonized porous carbon from coconut shells, 0.1-1 parts of yttrium oxide, 1-1.5 parts of a binder, 0.1-0.5 parts of a dispersant, and 0.3-0.7 parts of a lubricant. The carbonized porous carbon from coconut shells has a porosity of 70%, a particle size of 5-10 μm, and a carbon content of ≥95%.

[0035] Specifically, the binder is polyvinyl alcohol, the dispersant is ammonium polyacrylate, and the lubricant is zinc stearate.

[0036] It should be noted that graphene gel and its preparation method are already fully disclosed in the prior art. The present invention can prepare graphene gel by conventional preparation methods in the prior art, and then grind and grind the graphene gel to obtain a specific surface area of ​​800-1200m 2 / g, graphene gel fragments with a size of 10-50μm.

[0037] The role of graphene aerogel fragments in this scheme is: as a nano-reinforcement phase: improving fracture toughness through crack deflection and bridging mechanisms; as a lubricating phase: releasing graphene sheets during friction and reducing the friction coefficient.

[0038] The preparation method of coconut shell carbonized porous carbon is as follows: first, the coconut shell is crushed into 1-3 cm particles, washed and dried, and then carbonized at 600 ° C for 2 hours in an inert atmosphere (N2) to obtain a primary carbonized material; then it is mixed with KOH at a mass ratio of 1:3 and impregnated, activated at 800 ° C for 1 hour to generate a hierarchical pore structure, and the pore size distribution is optimized by water vapor expansion; finally, it is neutralized with hydrochloric acid, washed with deionized water, vacuum dried and air flow pulverized to obtain a particle size of 5-10 μm, a porosity of more than 70% and a specific surface area of ​​800-1200 m 2 / g of porous carbon.

[0039] The following is a preparation method of the wear-resistant cemented carbide material disclosed in the present invention in combination with the above-mentioned specific materials. The specific process is as follows:

[0040] Step 1: Preparation of composite powder:

[0041] Add the prepared tungsten carbide, cobalt powder, coconut shell carbonized porous carbon, and yttrium oxide to a three-dimensional mixer and dry mix at 30 rpm for 30 minutes. Then add the graphene gel fragments and continue mixing for 15 minutes.

[0042] Then, a planetary ball mill was used for ball milling: zinc stearate and ammonium polyacrylate were added after dry mixing, and then polyvinyl alcohol solution was added dropwise as a binder. Zirconia balls were used for ball milling, the ball-to-material ratio was 5:1, and anhydrous ethanol was used as the solvent, maintaining a solid-liquid ratio of 1:2. The ball milling was carried out at a speed of 250 rpm for 4 hours, and argon gas was introduced for protection during the process. After the ball milling was completed, vacuum drying was carried out at 60°C for 4 hours, and supercritical CO2 was used to dry and replace the anhydrous ethanol.

[0043] It should be noted that if dry ball milling is used, there is a lack of solvent lubrication, and the tungsten carbide / cobalt particles are easily cold-welded. The frictional heat during dry milling causes the local temperature to be >200°C, the oxidation rate of the cobalt powder increases, and the graphene aerogel fragments are easily crushed during dry milling. Therefore, we added anhydrous ethanol as a solvent for lubrication.

[0044] In this step, if the ethanol is not completely volatilized, it may carbonize to form free carbon during sintering, affecting the fluidity of cobalt. Therefore, vacuum drying is required. In addition, ethanol penetrates into the pores of carbonized porous carbon of coconut shells, and the residue after drying causes a decrease in porosity. Therefore, supercritical CO2 drying (critical point 31°C, 7.4MPa) is used to replace the ethanol, retaining >95% of the pore structure.

[0045] Step 2: Powder pressing and molding:

[0046] The powder obtained in step 1 was pressed into a mold at a pressure of 250 MPa for 30 minutes;

[0047] When designing the mold, the compression ratio is guaranteed to be 1.8:1, and 10% is reserved as an aerogel compression margin.

[0048] Step 3: Microwave-reaction sintering:

[0049] A microwave sintering furnace is configured, and a distributed SiCl4 vapor injection system is integrated at the bottom of the microwave sintering furnace. The pressed alloy powder body is subjected to pre-carbonization, reaction sintering, microwave densification, heat preservation and gradient cooling steps in sequence to obtain a green body;

[0050] As a preferred embodiment of step 3:

[0051] The specific process of the pre-carbonization stage is as follows: in H2 atmosphere, the temperature is raised to 300℃ at a heating rate of 10℃ / min, kept at this temperature for 30min, and then raised to 600℃ at a heating rate of 5℃ / min. The H2 flow rate is 8L / min.

[0052] During the pre-carbonization process, the temperature rises and the anhydrous ethanol added in step 1 is completely decomposed (this conclusion can be verified by TGA);

[0053] In addition, polyvinyl alcohol is added as a binder during the planetary ball milling process in step 1, and polyvinyl alcohol can react with the subsequently injected SiCl4 vapor to generate SiC impurities. Therefore, in this step, the added polyvinyl alcohol needs to be completely decomposed;

[0054] In this step, polyvinyl alcohol reacts with the added H2, and the reaction formula is as follows:

[0055]

[0056] Product composition: solid residue: amorphous carbon (accounting for 5% to 10% of the original PVA mass); gaseous products: H2O, CH4, CO, CO2, C2H4, etc. Under the reducing H2 atmosphere, the amount of C generated is very small. In addition, during this step, the H2 atmosphere can be regulated, such as adding 5% CH4 (methane) as a carbon trap to react with the residual carbon:

[0057]

[0058] In this way, the residual C is further removed to prevent it from reacting with the subsequently injected SiCl4 vapor to generate SiC impurities. It can be seen that the polyvinyl alcohol added in step 1 is not completely decomposed during the pre-carbonization process in this stage, and no SiC impurities are generated subsequently.

[0059] As a preferred embodiment of step 3:

[0060] The specific process of the reaction sintering stage is as follows: in an argon atmosphere, the temperature is raised to 1000°C at a rate of 50°C / min, SiCl4 vapor with a concentration of 5% is introduced, and the temperature is maintained for 60 minutes.

[0061] The core goal of this stage is to generate SiC whiskers in situ, and the key reaction process is:

[0062]

[0063] During this reaction process, the concentration of SiCl4 vapor is controlled at 5% because if it is excessive, free Si will be generated, and the SiC whisker growth mechanism is the VLS (Vapor-Liquid-Sol id) mechanism. SiC whiskers are interspersed in the aerogel pores to form a three-dimensional reinforced network. In this process, cobalt powder droplets act as catalysts. The mechanism is as follows: SiCl4 vapor decomposes gaseous Si atoms at high temperature, which are adsorbed and melted by cobalt droplets to form a Co-Si-C ternary liquid phase. When the concentration of Si in the Co droplets exceeds the solubility, Si reacts with the surrounding C to precipitate SiC. The liquid Co droplets act as mobile catalysts to guide the SiC whiskers to grow along the crystal direction, such as Figure 1 Shown is an electron microscope image of SiC whiskers.

[0064] It should be noted that the melting point of cobalt is 1495°C. However, in this case, after preliminary ball milling, the average particle size of the cobalt powder is reduced to 50-200nm, its melting point is lowered, and under the action of local thermodynamic fluctuations and stress, the nano-Co particles can form a transient liquid phase, thereby playing a catalytic role.

[0065] In addition, it should be noted that in this process, the flow rate of argon is 5 L / min, the purpose of which is to quickly remove Cl2 and prevent the formation of Co chloride (CoCl2 has a melting point of 737°C, which will destroy the stability of the droplets).

[0066] As a preferred embodiment of step 3:

[0067] The specific process of the microwave densification stage is as follows: under the condition of microwave power of 5kW, the temperature is first increased to 1250℃ at a rate of 50℃ / min, and after holding for 20 minutes, the microwave power is increased to 10kW, and the temperature is then increased to 1380℃ at a rate of 50℃ / min, followed by a holding stage. During the whole process, H2 and argon are introduced, and the volume ratio of H2:argon is 1:9;

[0068] In this process, the microwave absorption properties of graphene aerogel are utilized to achieve densification from the inside out. Graphene preferentially absorbs microwaves due to its high dielectric loss (tanδ=0.3), forming a local high-temperature zone. The internal high temperature (50-80°C higher than the external) drives the pores to close from the inside out, and surface tension is used to eliminate closed pores. At the same time, the microwave electromagnetic field reduces the friction between particles, and the WC particles slide to fill the pores, achieving near-full densification through the generated whiskers.

[0069] As a preferred embodiment of step 3:

[0070] The specific holding conditions in the holding stage are: under the condition of H2 to Ar volume ratio of 1:9, at a temperature of 1380°C, maintaining the Ar pressure at 0.5 MPa, and holding for 20 min;

[0071] The goal of this stage is to crush the residual pores by isostatic pressing (0.5 MPaAr), optimize the Co phase distribution, and inhibit the abnormal growth of WC grains.

[0072] As a preferred embodiment of step 3:

[0073] The gradient cooling process is specifically divided into the following two stages:

[0074] Stage 1: Decrease the temperature from 1380°C to 800°C at a rate of 30°C / min while continuously introducing argon gas at a flow rate of 10 L / min;

[0075] Stage 2: Cool naturally to room temperature with the furnace;

[0076] Through two-stage cooling, stress is released and thermal stress cracking caused by rapid cooling is avoided.

[0077] Step 4: performing surface finishing grinding on the green body obtained in step 3 to obtain the wear-resistant cemented carbide.

[0078] Based on the material ratios and preparation steps of the cemented carbide described above, the present invention is further disclosed below in conjunction with specific embodiments: wherein, embodiments 1-5 are for preparing wear-resistant cemented carbide using different material ratios;

[0079] Example 1

[0080] This embodiment uses the following components in parts by weight: 82 parts of tungsten carbide, 8 parts of cobalt powder, 2 parts of graphene aerogel fragments, 4 parts of carbonized coconut shell porous carbon, 0.5 parts of yttrium oxide, 1.2 parts of polyvinyl alcohol, 0.3 parts of ammonium polyacrylate, and 0.5 parts of zinc stearate, and then prepares wear-resistant cemented carbide according to the above process.

[0081] Example 2

[0082] This embodiment uses the following components in parts by weight: 85 parts of tungsten carbide, 6 parts of cobalt powder, 3 parts of graphene aerogel fragments, 2 parts of carbonized coconut shell porous carbon, 0.8 parts of yttrium oxide, 1.5 parts of polyvinyl alcohol, 0.5 parts of ammonium polyacrylate, and 0.7 parts of zinc stearate, and then prepares wear-resistant cemented carbide according to the above process.

[0083] Example 3

[0084] This embodiment uses the following components in parts by weight: 80 parts of tungsten carbide, 10 parts of cobalt powder, 1 part of graphene aerogel fragments, 6 parts of carbonized coconut shell porous carbon, 0.1 part of yttrium oxide, 1 part of polyvinyl alcohol, 0.1 part of ammonium polyacrylate, and 0.3 part of zinc stearate, and then prepares wear-resistant cemented carbide according to the above process.

[0085] Example 4

[0086] This embodiment uses the following components in parts by weight: 84 parts of tungsten carbide, 7 parts of cobalt powder, 2.5 parts of graphene aerogel fragments, 3 parts of carbonized coconut shell porous carbon, 0.6 parts of yttrium oxide, 1.3 parts of polyvinyl alcohol, 0.4 parts of ammonium polyacrylate, and 0.6 parts of zinc stearate, and then prepares wear-resistant cemented carbide according to the above process.

[0087] Example 5

[0088] This embodiment uses the following components in parts by weight: 86 parts of tungsten carbide, 5 parts of cobalt powder, 1.5 parts of graphene aerogel fragments, 5 parts of carbonized coconut shell porous carbon, 1 part of yttrium oxide, 1.4 parts of polyvinyl alcohol, 0.2 parts of ammonium polyacrylate, and 0.4 parts of zinc stearate, and then prepares wear-resistant cemented carbide according to the above process.

[0089] Comparative Example 1

[0090] The materials and proportions used in this comparative example to prepare the wear-resistant cemented carbide are exactly the same as those in Example 1, with the only difference being that in the preparation method, during the reaction sintering stage in step 3, the concentration of the SiCl4 vapor introduced is adjusted from 5% to 7%.

[0091] Comparative Example 2

[0092] The materials and proportions used in this comparative example to prepare the wear-resistant cemented carbide are exactly the same as those in Example 1, with the only difference being that in the preparation method, during the reaction sintering stage in step 3, the concentration of the SiCl4 vapor introduced is adjusted from 5% to 3%.

[0093] Comparative Example 3 is to prepare cemented carbide by deleting the graphene aerogel fragments from the formula materials based on Example 1; the remaining material proportions and preparation methods are the same as those in Example 1.

[0094] Comparative Example 4 replaces the coconut shell carbonized porous carbon with traditional black carbon on the basis of Example 1, and the remaining material proportions and preparation methods are the same as those in Example 1.

[0095] Comparative Example 5 is based on Example 6, except that the microwave-reactive sintering is replaced by the traditional resistance sintering process, and the remaining material proportions and preparation methods are the same as those of Example 1.

[0096] The wear-resistant cemented carbide samples prepared in Examples 1-5 and Comparative Examples 1-5 were tested for performance as follows:

[0097] 1. Wear resistance test

[0098] According to the ASTMG99-17 standard, the CETRUMT-3 friction and wear tester was used to conduct the pin-disc wear test. #800 grit SiC sandpaper (particle size 21.8μm) was selected for the grinding pair, a 50N normal load (equivalent contact stress 1.2GPa) was applied, the sliding speed was set to 0.2m / s (turntable diameter 40mm, rotation speed 200rpm), and the total sliding distance was 1000m. The test was carried out in a constant temperature and humidity environment (25±2℃, RH45±5%), and the sample mass loss was measured every 200m using a precision balance (accuracy 0.1mg), and the formula W was used to calculate the mass loss of the sample. v =Δm / (ρ·L) to calculate the volume wear rate, where the material density ρ = 14.8g / cm3 and L is the total sliding distance. Specific test results are shown in Table 1 and Figure 1 .

[0099] 2. Hardness test

[0100] According to ASTM E18-22 standard, Wilson 574 Rockwell hardness tester (A scale) was used for testing. The test used a 120° diamond cone indenter and was loaded in two stages: an initial load of 10 kgf was applied for 15 seconds, and then a main load of 60 kgf was applied for 15 seconds. The sample was finely processed with 1 μm diamond polishing liquid. Five test areas were selected for each sample (spacing ≥ 3 times the indentation diameter). After eliminating the maximum and minimum values, the average of the three points was taken as the final hardness value to ensure data reliability. Specific test results are shown in Table 1 and Figure 2 .

[0101] 3. Toughness test

[0102] Following ISO5754:2017, the unnotched specimen test was completed on an Instron Ceast 450J pendulum impact tester. The specimen size was 10×10×55mm, with a span of 40mm, and was impacted using a 150J energy pendulum (pre-swing angle 150°). k =A k / S is used to calculate the impact energy per unit area, where A_k is the absorbed energy value and S is the cross-sectional area of ​​the specimen. A PhantomVEO710 high-speed camera (10 fps) was used to record the crack growth morphology and analyze the fracture mechanism. Specific test results are shown in Tables 1 and Figure 3 .

[0103] 4. Conductivity test

[0104] According to the ASTM F390-11 standard, the resistivity was measured using a Lucas Labs Signatone Pro 4 four-probe tester. The probe spacing was 1.0 mm, a 100 mA DC test current was applied, and the sample was placed on a constant temperature platform at 25 ± 0.5 ° C. A 9-point matrix measurement (3 × 3 distribution) was performed on each sample. After excluding the edge effect data, the volume resistivity was calculated using the formula ρ = (πt / ln2)·(V / I), where t is the sample thickness. Before the test, a standard silicon wafer (0.01Ω·cm) was used to calibrate the system to ensure a measurement accuracy of ±1%. Specific test results are shown in Tables 1 and Figure 4 .

[0105] 5. High temperature stability test

[0106] According to ISO4499-4:2016, oxidation experiments were performed using a Netzsch STA449F3 simultaneous thermal analyzer. After ultrasonic cleaning with acetone and vacuum drying, the sample was heated to 800°C at a rate of 10°C / min in a dry air atmosphere (flow rate 50 mL / min) and kept at this temperature for 120 minutes. The mass change was recorded by TG curve, and the oxidation weight gain per unit surface area was calculated as ΔW = (m end -m start ) / S, and the phase change process was analyzed by combining the DSC curve. After the test, XRD was used to identify the composition of the surface oxidation products. The specific test results are shown in Table 1 and Figure 5 .

[0107] Table 1: Performance test results of samples prepared in Examples 1 to 5.

[0108]

[0109] Result analysis:

[0110] 1. Wear resistance analysis

[0111] The wear rates of Examples 1-5 (1.78-3.02) were significantly lower than those of the Comparative Examples (3.45-6.23), with Examples 2 (1.78) and 5 (1.95) performing best. The wear resistance of Comparative Example 3 (5.12) plummeted due to the absence of graphene aerogel, confirming the reinforcing effect of graphene. Comparative Examples 1-2 (3.84-4.56) showed that a 3% deviation in SiCl4 vapor concentration resulted in a 40% to 60% decrease in wear resistance, demonstrating the sensitivity of the sintering process. Comparative Example 4 (6.23) exhibited the highest wear rate due to the replacement of porous carbon with conventional black carbon, validating the lubricating and friction-reducing properties of porous carbon.

[0112] 2. Hardness analysis

[0113] HRA hardness is negatively correlated with cobalt content. Examples 2 (93.5) and 5 (94.1) achieve the highest hardness by reducing the cobalt content (6% and 5%). Comparative Example 4 (85.4) has the lowest hardness due to the inability of traditional carbon black to form a reinforcing phase, while Comparative Example 3 (87.6) lacks the dispersion strengthening effect of graphene, resulting in a significant drop in hardness. Example 3 (90.5) has the lowest hardness due to its high cobalt content (10%), but achieves the best toughness.

[0114] 3. Toughness Analysis

[0115] The impact energy is positively correlated with the cobalt content. Example 3 (19.5 J / cm 2 ) obtains the highest toughness by 10% cobalt content, but Comparative Example 3 (8.5 J / cm 2 ) Due to the lack of graphene's stress dispersion, the toughness dropped by 45%. Comparative Example 5 (10.6 J / cm 2 ) Using conventional sintering results in a 32% decrease in toughness, indicating that microwave sintering improves structural integrity. Example 2 (14.2 J / cm 2 ) Maintaining reasonable toughness in a low-cobalt system through 3% graphene content.

[0116] 4. Conductivity Analysis

[0117] Resistivity is related to the integrity of the conductive network. Example 5 (0.61 μΩ·m) achieves an optimal conductive path through 1.5% graphene + 5% porous carbon. Comparative Example 3 (3.12 μΩ·m) experiences a 411% increase in resistivity due to the complete absence of graphene. In Comparative Example 4 (2.85 μΩ·m), conventional black carbon exhibits inferior conductivity compared to porous carbon. Example 3 (1.15 μΩ·m) exhibits a decrease in conductivity due to the inclusion of only 1% graphene, demonstrating the critical effect of component ratio.

[0118] 5. High temperature stability analysis

[0119] Example 5 (0.72 mg / cm 2 ) The best performance was achieved by forming a dense oxide layer with 1% yttrium oxide, and the comparative example 3 (5.24 mg / cm 2 ) The oxidation weight gain is the highest due to the lack of thermal barrier effect of graphene. 2 ) The oxidation weight gain of conventional sintering is Example 1 (1.05 mg / cm 2 ) is 2.4 times that of the control, which proves that microwave sintering promotes densification. 2 ) shows that the SiCl 4 concentration deviation leads to surface defects that increase the oxidation rate.

[0120] In summary, this scheme achieved wear resistance (wear rate ≤ 3.02×10 - 6 mm 3 / N·m), hardness (HRA≥90.5), toughness (impact energy≥13.8J / cm 2 ), electrical conductivity (resistivity ≤ 1.15 μΩ·m) and high temperature stability (oxidation weight gain at 800℃ ≤ 1.82 mg / cm 2 ) is improved in a balanced way, and the comprehensive performance is improved by 40% to 300% compared with the traditional process.

[0121] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. A wear-resistant cemented carbide material, characterized in that: The invention comprises the following components in parts by weight: 80-86 parts of tungsten carbide, 5-10 parts of cobalt powder, 1-3 parts of graphene aerogel fragments, 2-6 parts of carbonized porous carbon from coconut shell, 0.1-1 part of yttrium oxide, 1-1.5 parts of binder, 0.1-0.5 parts of dispersant and 0.3-0.7 parts of lubricant.

2. The wear-resistant hard alloy material according to claim 1, characterized in that: The specific surface area of ​​the graphene aerogel fragments is 800-1200m 2 / g, fragment size 10-50μm.

3. The wear-resistant hard alloy material according to claim 1, characterized in that: The coconut shell carbonized porous carbon has a porosity of 70%, a particle size of 5-10 μm, and a carbon content of ≥95%.

4. The wear-resistant hard alloy material according to claim 1, characterized in that: The binder is specifically polyvinyl alcohol, the dispersant is specifically ammonium polyacrylate, and the lubricant is specifically zinc stearate.

5. A method for preparing the wear-resistant hard alloy material according to any one of claims 1 to 4, characterized in that: The specific steps are as follows: Step 1: Preparation of composite powder: Add the prepared tungsten carbide, cobalt powder, coconut shell carbonized porous carbon, and yttrium oxide to a three-dimensional mixer and dry mix at 30 rpm for 30 minutes. Then add the graphene gel fragments and continue mixing for 15 minutes. The samples were then ball-milled in a planetary ball mill using zirconia balls at a ball-to-material ratio of 5:1 and anhydrous ethanol as the solvent, maintaining a solid-liquid ratio of 1:

2. The samples were ball-milled at 250 rpm for 4 h, with argon gas as a protective gas. After ball-milling, the samples were vacuum-dried at 60°C for 4 h, and supercritical CO2 was used to dry and replace the anhydrous ethanol. Then a centrifugal spray drying tower is used. Step 2: Powder pressing: The powder obtained in step 1 is pressed into a mold at a pressure of 250 MPa for 30 minutes; Step 3, microwave-reactive sintering: a microwave sintering furnace is configured, and a distributed SiCl4 vapor injection system is integrated at the bottom of the microwave sintering furnace. The pressed alloy powder body is subjected to pre-carbonization, reactive sintering, microwave densification, heat preservation and gradient cooling steps in sequence to obtain a green body; Step 4: performing surface finishing grinding on the green body obtained in step 3 to obtain the wear-resistant cemented carbide.

6. The preparation method according to claim 5, characterized in that The process of the pre-carbonization stage is specifically as follows: in an H2 atmosphere, the temperature is raised to 300°C at a heating rate of 10°C / min, kept at that temperature for 30 minutes, and then raised to 600°C at a heating rate of 5°C / min, with an H2 flow rate of 8 L / min.

7. The preparation method according to claim 5, characterized in that The specific process of the reaction sintering stage is: in an argon atmosphere, the temperature is raised to 1000° C. at a rate of 50° C. / min, SiCl 4 vapor with a concentration of 5% is introduced, and the temperature is maintained for 60 minutes.

8. The preparation method according to claim 5, characterized in that The specific process of the microwave densification stage is as follows: under the condition of a microwave power of 5 kW, the temperature is first increased to 1250°C at a rate of 50°C / min, and after keeping warm for 20 minutes, the microwave power is increased to 10 kW, and then the temperature is increased to 1380°C at a rate of 50°C / min, and then the temperature enters the holding stage. During the whole process, H2 and argon are introduced, and the volume ratio of H2:argon is 1:

9.

9. The preparation method according to claim 5, characterized in that The specific insulation conditions of the insulation stage are: under the condition that the volume ratio of H2 to argon is 1:9, at a temperature of 1380°C, maintaining the Ar pressure at 0.5 MPa, and insulation for 20 minutes.

10. The preparation method according to claim 5, characterized in that The gradient cooling process is specifically divided into the following two stages: Stage 1: Decrease the temperature from 1380°C to 800°C at a rate of 30°C / min while continuously introducing argon gas at a flow rate of 10 L / min; Stage 2: Cool naturally to room temperature in the furnace.

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