Preparation method of high-wear-resistance hard alloy for underground mine

Abstract

The invention relates to the technical field of alloys, in particular to a preparation method of a high-wear-resistance hard alloy for geomines. The method comprises the following steps: taking nickel-based corrosion-resistant alloy powder with specific components as a binding phase instead of cobalt, carrying out wet ball-milling mixing, forming, dewaxing and pre-sintering on the binding phase and hard phase powder such as tungsten carbide, and then carrying out vacuum-back pressure pulse treatment on a pre-sintered body by adopting an infiltration solution containing polyacrylic acid, branched polyethyleneimine and dopamine hydrochloride; and carrying out vacuum final sintering and hot isostatic pressing densification treatment to obtain a final product. Through material system innovation and process optimization, the wear resistance, corrosion resistance and toughness of the hard alloy under the underground severe working condition are remarkably improved, and the problems that a traditional cobalt-based alloy binding phase is prone to corrosion, and the service life of a tool is short are effectively solved.

Description

Technical Field

[0001] This invention relates to the field of alloy technology, and in particular to a method for preparing a high wear-resistant cemented carbide for mining applications. Background Technology

[0002] Traditional tungsten carbide-cobalt cemented carbide has long been widely used in mining drilling and tunneling tools due to its high hardness and excellent wear resistance. However, in actual downhole operating environments, tools not only endure severe impacts and abrasive wear but are also exposed to complex slurry media, which often contain chloride ions, sulfide ions, and acidic components, posing a severe challenge to the alloy materials. While cobalt, as the binder phase, possesses good wettability and toughness, its relatively reactive chemical properties make it susceptible to selective corrosion in acidic or chloride-containing environments. This corrosion preferentially occurs in areas rich in the cobalt phase, leading to the gradual loss of the binder phase and the loss of effective support for the hard phase framework, thus significantly reducing the alloy's overall integrity and load-bearing capacity.

[0003] The corrosion failure of the binder phase not only directly weakens the mechanical properties of the alloy but also triggers a series of chain reactions of severe damage. Once the binder phase is corroded, the tungsten carbide grains that were originally coated and fixed by it are more likely to detach under grinding and impact, forming three-body wear and drastically accelerating the tool failure process. Simultaneously, the micropores and cracks formed by corrosion become stress concentration points and channels for the corrosive medium to further penetrate into the material, causing more severe internal corrosion and significantly shortening the tool's service life. Especially under high impact load conditions, this corrosion-induced material degradation significantly increases the risk of brittle fracture and chipping of the tool.

[0004] To address the corrosion resistance issue of the cobalt binder phase, the industry has made several attempts, such as partially or completely replacing cobalt with nickel or nickel-based alloys. However, simple substitution often fails to replicate the excellent wettability and interfacial bonding strength of the cobalt phase, potentially leading to insufficient densification during sintering or the formation of undesirable interfacial structures, thus sacrificing the alloy's crucial toughness and impact resistance. Furthermore, conventional sintering processes have limitations in controlling the densification and optimizing the microstructure of complex alloy compositions, making it difficult to achieve high corrosion resistance while simultaneously ensuring the high wear resistance and toughness required for mining tools. Therefore, developing a novel cemented carbide material and its preparation technology that can synergistically improve wear resistance, corrosion resistance, and toughness under harsh mining conditions has become a critical problem urgently needing to be solved in this field. Summary of the Invention

[0005] In view of this, the purpose of this invention is to propose a method for preparing a high wear-resistant cemented carbide for mining applications, so as to overcome the defects of existing tungsten carbide-cobalt cemented carbide, which are prone to selective corrosion of the binder phase in downhole chlorine-containing media, resulting in a sharp decline in tool wear resistance, easy chipping, and short tool life.

[0006] To achieve the above objectives, the present invention provides a method for preparing a high wear-resistant cemented carbide for mining applications, comprising the following steps:

[0007] (1) Nickel-based corrosion-resistant alloy powder is obtained by melting and atomizing raw materials such as nickel, chromium, molybdenum, tungsten, aluminum, titanium, silicon and boron.

[0008] (2) Add tungsten carbide powder, nickel-based corrosion-resistant alloy powder, vanadium carbide powder, tantalum carbide powder and chromium tricarbide powder to an organic medium and perform wet ball milling to obtain a mixed powder;

[0009] (3) Add the paraffin-n-heptane forming system to the mixed powder and prepare a slurry, then spray dry and granulate to obtain granules;

[0010] (4) The granules are pressed into shape and dewaxed under vacuum to obtain a dewaxed blank;

[0011] (5) The dewaxed green body is pre-sintered to obtain a pre-sintered body;

[0012] (6) Tris(hydroxymethyl)aminomethane is added to deionized water to form a buffer system and the pH is adjusted to 8.8-9.2. Polyacrylic acid, branched polyethyleneimine and dopamine hydrochloride are added in sequence to obtain an infiltration solution. The pre-sintered body is immersed in the infiltration solution and subjected to vacuum-backpressure pulse treatment, and then dried to obtain the infiltration semi-finished product.

[0013] (7) Vacuum sintering and hot isostatic pressing densification treatment are carried out on the infiltrated semi-finished product to obtain a high wear-resistant cemented carbide for mining.

[0014] Preferably, in step (1), the amounts of nickel, chromium, molybdenum, tungsten, aluminum, titanium, silicon, and boron raw materials added are 73.65g-79.25g, 13g-15g, 5.5g-6.5g, 1.5g-2.5g, 0.9g-1.5g, 0.3g-0.7g, 0.4g-0.8g, and 0.15g-0.35g, respectively.

[0015] Preferably, in step (1), during melting, after evacuating to 0.05 Pa, argon gas is introduced to 0.05 MPa for protection and heated to 1550℃ for 10 min. During atomization powder preparation, argon gas at 4 MPa is used for atomization.

[0016] Preferably, in step (1), the median particle size of the nickel-based corrosion-resistant alloy powder is 4.8-5.7 μm.

[0017] Preferably, in step (2), the amounts of tungsten carbide powder, nickel-based corrosion-resistant alloy powder, vanadium carbide powder, tantalum carbide powder, dichromium carbide powder, anhydrous ethanol and stearic acid are 887g-893g, 100g, 2g-4g, 3g-5g, 2g-4g, 1.2g and 2g, respectively.

[0018] Preferably, in step (2), the median particle size of tungsten carbide powder is 3.5 μm, the median particle size of vanadium carbide powder is 4.8 μm, the median particle size of tantalum carbide powder is 3.2 μm, and the median particle size of chromium tricarbide powder is 3.5 μm.

[0019] Preferably, in step (2), the ball-to-material ratio of wet ball milling is 6:1, the ball milling speed is 200 rpm, the ball milling time is 18 h, and the temperature of the ball milling tank is controlled below 35°C.

[0020] Preferably, in step (2), after ball milling, the material is filtered through a 200-mesh sieve and then vacuum dried at 60°C for 8 hours.

[0021] Preferably, in step (3), the paraffin-n-heptane forming system is a paraffin-n-heptane solution, which is obtained by heating n-heptane to 80°C and adding paraffin while stirring to dissolve.

[0022] Preferably, in step (3), the spray drying granulation is centrifugal spray drying granulation, with an inlet air temperature of 160°C, an outlet air temperature of 90°C, and an atomizing disc rotation speed of 12000 rpm.

[0023] Preferably, in step (4), the pressing process includes unidirectional pressing and cold isostatic pressing, wherein the unidirectional pressing pressure is 200 MPa and the holding pressure is 30 s, and the cold isostatic pressing pressure is 250 MPa and the holding pressure is 2 min.

[0024] Preferably, in step (4), dewaxing is carried out in a vacuum furnace with a vacuum degree of 0.05 Pa, and the temperature is increased to 450°C at 1°C / min and held for 60 min, then increased to 600°C at 2°C / min and held for 30 min, and then cooled to room temperature with the furnace.

[0025] Preferably, in step (5), the pre-sintering is carried out in a vacuum furnace with a vacuum degree of 0.006Pa-0.015Pa, and the temperature is increased to 980°C at 4°C / min-6°C / min and held for 40min-50min, then increased to 1180°C at 2°C / min-4°C / min and held for 80min-100min, and then decreased to 200°C at 2°C / min-4°C / min and cooled with the furnace.

[0026] Preferably, in step (6), the infiltration solution is prepared from the following components: 4500g-5500g deionized water, 5g-7g tris(hydroxymethyl)aminomethane, 4g-6g polyacrylic acid, 4g-6g branched polyethyleneimine and 8g-12g dopamine hydrochloride; the amount of the pre-sintered body is 1000g.

[0027] Preferably, in step (6), the number average molecular weight of polyacrylic acid is 25,000-35,000; and the number average molecular weight of branched polyethyleneimine is 8,000-12,000.

[0028] Preferably, in step (6), the vacuum-backpressure pulse treatment is as follows: pump to 15kPa-30kPa and hold for 4min-6min, then backpressure to 101kPa and soak for 20min-30min, repeating 2-4 times.

[0029] Preferably, in step (7), the vacuum final sintering is carried out under a vacuum of 0.003Pa-0.008Pa, and the temperature is increased to 600℃ at 2℃ / min-4℃ / min and held for 50min-70min, then increased to 950℃ at 4℃ / min-6℃ / min and held for 40min-50min, then increased to 1410℃ at 2℃ / min-4℃ / min and held for 60min-80min, and then decreased to 1150℃ at 8℃ / min-12℃ / min and cooled to room temperature with the furnace.

[0030] Preferably, in step (7), the hot isostatic pressing densification treatment is carried out in an argon atmosphere, heated to 1320℃-1380℃ and pressurized to 80MPa-120MPa, held for 50min-70min and then cooled out of the furnace.

[0031] The beneficial effects of this invention are:

[0032] This invention fundamentally improves the stability of cemented carbide in corrosive environments by using a specific nickel-based corrosion-resistant alloy system as the binder phase, replacing traditional cobalt metal. During sintering, the various corrosion-resistant elements in this alloy system form a dense passivation film, effectively blocking the corrosive medium from eroding the binder phase, thereby significantly enhancing the overall corrosion resistance of the alloy and enabling the tool to maintain long-term performance stability in harsh mineral slurry environments.

[0033] By optimizing the pre-sintering and final sintering processes, combined with hot isostatic pressing post-treatment, precise control of the material's microstructure was achieved. This process promoted the full densification of the sintered body, significantly reducing internal porosity and other defects, while simultaneously suppressing the abnormal growth of hard phase grains, resulting in a fine-grained and uniform microstructure. This dense and uniform structure allows the material to maintain high hardness while possessing excellent toughness and impact resistance, effectively resisting impact loads and stress concentrations during operation and preventing brittle chipping.

[0034] A unique infiltration deposition process introduces a functional precursor into the material. This precursor decomposes during subsequent heat treatment, effectively replenishing carbon and preventing the formation of harmful decarburized phases. Furthermore, its decomposition products help fill micropores and improve interfacial bonding. This process further optimizes the interfacial properties between the hard and binder phases, enhancing the bonding strength and continuity of the interface, thereby improving the material's strength-toughness balance and load transfer efficiency.

[0035] In summary, this invention, through synergistic innovation in material system design and preparation process, successfully achieves simultaneous improvement in the core properties of cemented carbide, such as wear resistance, corrosion resistance, and toughness. The resulting alloy is particularly suitable for harsh mining environments characterized by high impact, strong abrasion, and corrosive media, providing a reliable material basis for extending the service life of drilling tools and improving operational efficiency. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0037] Example 1:

[0038] Step S1: Preparation of nickel-based corrosion-resistant alloy powder

[0039] 79250 mg of nickel granules (purity ≥99.9%), 13000 mg of chromium granules (purity ≥99.9%), 5500 mg of molybdenum powder (purity ≥99.9%), 1500 mg of tungsten powder (purity ≥99.9%), 900 mg of aluminum granules (purity ≥99.9%), 300 mg of titanium powder (purity ≥99.9%), 400 mg of silicon granules (purity ≥99.9%), and 150 mg of boron powder (purity ≥99.5%) were sequentially added to a vacuum induction melting crucible. The crucible was evacuated to 0.05 Pa and then argon gas was introduced to 0.05 MPa for protection. The temperature was raised to 1550 °C and held for 10 min to allow the alloy to melt completely and be thoroughly stirred. The alloy powder was then atomized with argon gas at 4 MPa in an argon atomization powder making device. The powder was cooled and recovered under an inert atmosphere and then classified by airflow to obtain nickel-based corrosion-resistant alloy powder with a median particle size of 5.7 μm.

[0040] Step S2: Mixing and wet ball milling

[0041] Weigh out 893g of tungsten carbide powder (median particle size 3.5μm), 100g of nickel-based corrosion-resistant alloy powder, 2000mg of vanadium carbide powder (median particle size 4.8μm), 3000mg of tantalum carbide powder (median particle size 3.2μm), 2000mg of chromium tricarbide powder (median particle size 3.5μm), 1200g of anhydrous ethanol, and 2000mg of stearic acid, and add them to a cemented carbide ball mill jar. Control the ball-to-powder ratio at 6:1, and ball mill at 200rpm for 18h in a planetary ball mill, while using circulating water to control the jar temperature below 35℃. After ball milling, filter through a 200-mesh sieve, recover the ethanol from the filtrate by vacuum rotary evaporation, and then vacuum dry at 60℃ for 8h to obtain a mixed powder.

[0042] Step S3: Add to the forming system and spray granulation

[0043] 1000g of mixed powder was added to a sealed stirred tank. 200g of n-heptane was heated to 80℃ and 15000mg of paraffin was added and stirred to dissolve, forming a paraffin-n-heptane solution. Under argon protection, the solution was slowly added to the mixed powder while hot and stirred at 600rpm for 20min to form a uniform slurry. Then, centrifugal spray drying was used to granulate the slurry with an inlet air temperature of 160℃, an outlet air temperature of 90℃, and an atomizing disc speed of 12000rpm to obtain granules.

[0044] Step S4: Pressing and shaping

[0045] 1015g of granular material was loaded into a cemented carbide mold and unidirectionally pressed at 200MPa for 30s to obtain a compact. The compact was then placed in a rubber sleeve and subjected to cold isostatic pressing at 250MPa for 2min, followed by pressure release to obtain a blank. The blank was placed in a graphite boat in a vacuum furnace, and the vacuum was evacuated to 0.05Pa. The temperature was then increased to 450℃ at 1℃ / min and held for 60min. The temperature was then increased to 600℃ at 2℃ / min and held for 30min. The blank was then cooled to room temperature in the furnace to obtain a dewaxed blank.

[0046] Step S5: Low-carbon rich alloy pre-sintering

[0047] 1000g of dewaxed green body was placed in a vacuum furnace again, and the vacuum was evacuated to 0.015Pa. The temperature was then increased to 980℃ at 4℃ / min and held for 40min. The temperature was then increased to 1180℃ at 2℃ / min and held for 80min. The temperature was then decreased to 200℃ at 2℃ / min and cooled with the furnace to obtain a pre-sintered body.

[0048] Step S6: Infiltration and deposition of polydopamine-branched polyethyleneimine / polyacrylate ionic composite precursor

[0049] Add 4500g of deionized water to a reaction vessel, add 5000mg of tris(hydroxymethyl)aminomethane to prepare a buffer system, and adjust the pH of the solution to 8.8 with 10% hydrochloric acid solution. Add 4000mg of polyacrylic acid (number average molecular weight approximately 30,000) and stir for 15 minutes. Then add 4000mg of branched polyethyleneimine (Shanghai Aladdin Biochemical Technology Co., Ltd., item number P434400, number average molecular weight approximately 10,000) and stir for 15 minutes. Finally, add 8000mg of dopamine hydrochloride and stir for 8 minutes to obtain an infiltration solution. Completely immerse 1000g of the pre-sintered body in this solution and place it in a vacuum tank. Pump the pressure to 30kPa and maintain it for 4 minutes. Then slowly return the pressure to 101kPa and soak for 20 minutes. Repeat this vacuum-return pressure pulse twice. After removal, rinse with deionized water for 8 seconds and vacuum dry at 55℃ for 3 hours to obtain the infiltration semi-finished product.

[0050] Step S7: Final sintering and hot isostatic pressing

[0051] 1000g of the infiltrated semi-finished product was placed in a graphite boat in a vacuum sintering furnace. After being evacuated to 0.008Pa, the temperature was increased to 600℃ at 2℃ / min and held for 50min. Then, the temperature was increased to 950℃ at 4℃ / min and held for 40min. After that, the temperature was increased to 1410℃ at 2℃ / min and held for 60min. Subsequently, the temperature was decreased to 1150℃ at 8℃ / min and cooled to room temperature with the furnace to obtain a sintered body. The sintered body was then subjected to hot isostatic pressing densification treatment: the temperature was increased to 1320℃ under an argon atmosphere and the pressure was increased to 80MPa and held for 50min. After cooling, the body was removed from the furnace to obtain a high wear-resistant cemented carbide for mining applications.

[0052] Example 2:

[0053] Step S1: Preparation of nickel-based corrosion-resistant alloy powder

[0054] 76450 mg of nickel granules (purity ≥99.9%), 14000 mg of chromium granules (purity ≥99.9%), 6000 mg of molybdenum powder (purity ≥99.9%), 2000 mg of tungsten powder (purity ≥99.9%), 1200 mg of aluminum granules (purity ≥99.9%), 500 mg of titanium powder (purity ≥99.9%), 600 mg of silicon granules (purity ≥99.9%), and 250 mg of boron powder (purity ≥99.5%) were sequentially added to a vacuum induction melting crucible. The crucible was evacuated to 0.05 Pa and then argon gas was introduced to 0.05 MPa for protection. The temperature was raised to 1550 °C and held for 10 min to allow the alloy to melt completely and be thoroughly stirred. Subsequently, the alloy powder was obtained by atomization with argon gas at 4 MPa in an argon atomization powder preparation device. The powder was cooled and recovered under an inert atmosphere and then classified by airflow to obtain nickel-based corrosion-resistant alloy powder with a median particle size of 5.2 μm.

[0055] Step S2: Mixing and wet ball milling

[0056] 890g of tungsten carbide powder (median particle size 3.5μm), 100g of nickel-based corrosion-resistant alloy powder, 3000mg of vanadium carbide powder (median particle size 4.8μm), 4000mg of tantalum carbide powder (median particle size 3.2μm), 3000mg of chromium tricarbide powder (median particle size 3.5μm), 1200g of anhydrous ethanol, and 2000mg of stearic acid were weighed and added to a cemented carbide ball mill jar. The ball-to-powder ratio was controlled at 6:1. The mixture was ball-milled at 200rpm for 18h in a planetary ball mill, and the jar temperature was controlled below 35℃ using circulating water. After ball milling, the mixture was filtered through a 200-mesh sieve. The filtrate was vacuum rotary evaporated to recover ethanol and then vacuum dried at 60℃ for 8h to obtain a mixed powder.

[0057] Step S3: Add to the forming system and spray granulation

[0058] 1000g of mixed powder was added to a sealed stirred tank. 200g of n-heptane was heated to 80℃ and 15000mg of paraffin was added and stirred to dissolve, forming a paraffin-n-heptane solution. Under argon protection, the solution was slowly added to the mixed powder while hot and stirred at 600rpm for 20min to form a uniform slurry. Then, centrifugal spray drying was used to granulate the slurry with an inlet air temperature of 160℃, an outlet air temperature of 90℃, and an atomizing disc speed of 12000rpm to obtain granules.

[0059] Step S4: Pressing and shaping

[0060] 1015g of granular material was loaded into a cemented carbide mold and unidirectionally pressed at 200MPa for 30s to obtain a compact. The compact was then placed in a rubber sleeve and subjected to cold isostatic pressing at 250MPa for 2min, followed by pressure release to obtain a blank. The blank was placed in a graphite boat in a vacuum furnace, and the vacuum was evacuated to 0.05Pa. The temperature was then increased to 450℃ at 1℃ / min and held for 60min. The temperature was then increased to 600℃ at 2℃ / min and held for 30min. The blank was then cooled to room temperature in the furnace to obtain a dewaxed blank.

[0061] Step S5: Low-carbon rich alloy pre-sintering

[0062] 1000g of dewaxed green body was placed in a vacuum furnace again, and the vacuum was evacuated to 0.01Pa. The temperature was then increased to 980℃ at 5℃ / min and held for 45min. The temperature was then increased to 1180℃ at 3℃ / min and held for 90min. The temperature was then decreased to 200℃ at 3℃ / min and cooled with the furnace to obtain a pre-sintered body.

[0063] Step S6: Infiltration and deposition of polydopamine-branched polyethyleneimine / polyacrylate ionic composite precursor

[0064] Add 5000g of deionized water to a reaction vessel, add 6000mg of tris(hydroxymethyl)aminomethane to prepare a buffer system, and adjust the pH of the solution to 9.0 with 10% hydrochloric acid solution. Add 5000mg of polyacrylic acid (number average molecular weight approximately 30000) and stir for 20min. Then add 5000mg of polyethyleneimine (Shanghai Aladdin Biochemical Technology Co., Ltd., item number P434400, number average molecular weight approximately 10000) and stir for 20min. Finally, add 10000mg of dopamine hydrochloride and stir for 10min to obtain an infiltration solution. Completely immerse 1000g of the pre-sintered body in this solution and place it in a vacuum tank. Pump the pressure to 20kPa and hold for 5min, then slowly return the pressure to 101kPa and soak for 25min. Repeat this vacuum-return pressure pulse 3 times. After removal, rinse with deionized water for 10s and vacuum dry at 60℃ for 4h to obtain the infiltration semi-finished product.

[0065] Step S7: Final sintering and hot isostatic pressing

[0066] 1000g of the infiltrated semi-finished product was placed in a graphite boat in a vacuum sintering furnace. After being evacuated to 0.005Pa, the temperature was increased to 600℃ at 3℃ / min and held for 60min. Then, the temperature was increased to 950℃ at 5℃ / min and held for 45min. After that, the temperature was increased to 1410℃ at 3℃ / min and held for 70min. Then, the temperature was decreased to 1150℃ at 10℃ / min and cooled to room temperature with the furnace to obtain a sintered body. The sintered body was then subjected to hot isostatic pressing densification treatment: the temperature was increased to 1350℃ under an argon atmosphere and the pressure was increased to 100MPa and held for 60min. After cooling, the body was removed from the furnace to obtain a high wear-resistant cemented carbide for mining applications.

[0067] Example 3:

[0068] Step S1: Preparation of nickel-based corrosion-resistant alloy powder

[0069] 73650 mg of nickel granules (purity ≥99.9%), 15000 mg of chromium granules (purity ≥99.9%), 6500 mg of molybdenum powder (purity ≥99.9%), 2500 mg of tungsten powder (purity ≥99.9%), 1500 mg of aluminum granules (purity ≥99.9%), 700 mg of titanium powder (purity ≥99.9%), 800 mg of silicon granules (purity ≥99.9%), and 350 mg of boron powder (purity ≥99.5%) were sequentially added to a vacuum induction melting crucible. The crucible was evacuated to 0.05 Pa and then argon gas was introduced to 0.05 MPa for protection. The temperature was raised to 1550 °C and held for 10 min to allow the alloy to melt completely and be thoroughly stirred. Subsequently, the alloy powder was obtained by atomization with argon gas at 4 MPa in an argon atomization powder making device. The powder was cooled and recovered under an inert atmosphere and then classified by airflow to obtain nickel-based corrosion-resistant alloy powder with a median particle size of 4.8 μm.

[0070] Step S2: Mixing and wet ball milling

[0071] 887g of tungsten carbide powder (median particle size 3.5μm), 100g of nickel-based corrosion-resistant alloy powder, 4000mg of vanadium carbide powder (median particle size 4.8μm), 5000mg of tantalum carbide powder (median particle size 3.2μm), 4000mg of chromium tricarbide powder (median particle size 3.5μm), 1200g of anhydrous ethanol, and 2000mg of stearic acid were weighed and added to a cemented carbide ball mill jar. The ball-to-powder ratio was controlled at 6:1. The mixture was ball-milled at 200rpm for 18h in a planetary ball mill, and the jar temperature was controlled below 35℃ using circulating water. After ball milling, the mixture was filtered through a 200-mesh sieve. The filtrate was vacuum rotary evaporated to recover ethanol and then vacuum dried at 60℃ for 8h to obtain a mixed powder.

[0072] Step S3: Add to the forming system and spray granulation

[0073] 1000g of mixed powder was added to a sealed stirred tank. 200g of n-heptane was heated to 80℃ and 15000mg of paraffin was added and stirred to dissolve, forming a paraffin-n-heptane solution. Under argon protection, the solution was slowly added to the mixed powder while hot and stirred at 600rpm for 20min to form a uniform slurry. Then, centrifugal spray drying was used to granulate the slurry with an inlet air temperature of 160℃, an outlet air temperature of 90℃, and an atomizing disc speed of 12000rpm to obtain granules.

[0074] Step S4: Pressing and shaping

[0075] 1015g of granular material was loaded into a cemented carbide mold and unidirectionally pressed at 200MPa for 30s to obtain a compact. The compact was then placed in a rubber sleeve and subjected to cold isostatic pressing at 250MPa for 2min, followed by pressure release to obtain a blank. The blank was placed in a graphite boat in a vacuum furnace, and the vacuum was evacuated to 0.05Pa. The temperature was then increased to 450℃ at 1℃ / min and held for 60min. The temperature was then increased to 600℃ at 2℃ / min and held for 30min. The blank was then cooled to room temperature in the furnace to obtain a dewaxed blank.

[0076] Step S5: Low-carbon rich alloy pre-sintering

[0077] 1000g of dewaxed green body was placed in a vacuum furnace again, and the vacuum was evacuated to 0.006Pa. The temperature was then increased to 980℃ at 6℃ / min and held for 50min. The temperature was then increased to 1180℃ at 4℃ / min and held for 100min. The temperature was then decreased to 200℃ at 4℃ / min and cooled with the furnace to obtain a pre-sintered body.

[0078] Step S6: Infiltration and deposition of polydopamine-branched polyethyleneimine / polyacrylate ionic composite precursor

[0079] Add 5500g of deionized water to a reaction vessel, add 7000mg of tris(hydroxymethyl)aminomethane to prepare a buffer system, and adjust the pH of the solution to 9.2 with 10% hydrochloric acid solution. Add 6000mg of polyacrylic acid (number average molecular weight approximately 30000) and stir for 25min. Then add 6000mg of branched polyethyleneimine (Shanghai Aladdin Biochemical Technology Co., Ltd., item number P434400, number average molecular weight approximately 10000) and stir for 25min. Finally, add 12000mg of dopamine hydrochloride and stir for 12min to obtain an infiltration solution. Completely immerse 1000g of the pre-sintered body in this solution and place it in a vacuum tank. Pump the pressure to 15kPa and maintain it for 6min. Then slowly return the pressure to 101kPa and soak for 30min. Repeat this vacuum-return pressure pulse 4 times. After removal, rinse with deionized water for 12s and vacuum dry at 65℃ for 5h to obtain the infiltration semi-finished product.

[0080] Step S7: Final sintering and hot isostatic pressing

[0081] 1000g of the infiltrated semi-finished product was placed in a graphite boat in a vacuum sintering furnace. After being evacuated to 0.003Pa, the temperature was increased to 600℃ at 4℃ / min and held for 70min. Then, the temperature was increased to 950℃ at 6℃ / min and held for 50min. Next, the temperature was increased to 1410℃ at 4℃ / min and held for 80min. Then, the temperature was decreased to 1150℃ at 12℃ / min and cooled to room temperature with the furnace to obtain a sintered body. The sintered body was then subjected to hot isostatic pressing densification treatment: the temperature was increased to 1380℃ under an argon atmosphere and the pressure was increased to 120MPa and held for 70min. After cooling, the body was removed from the furnace to obtain a high wear-resistant cemented carbide for mining applications.

[0082] Comparative Example 1:

[0083] The difference between Comparative Example 1 and Example 2 is that: in step S1, 1200mg of aluminum particles are not added, and nickel is used to make up the same mass to keep the total amount of alloy constant; the other conditions are the same as in Example 2.

[0084] Comparative Example 2:

[0085] The difference between Comparative Example 2 and Example 2 is that: in step S1, 600mg of silicon particles are not added, and nickel is used to make up the same mass to keep the total amount of alloy constant; the other conditions are the same as in Example 2.

[0086] Comparative Example 3:

[0087] The difference between Comparative Example 3 and Example 2 is that 250mg of boron powder is not added in step S1, and nickel is used to make up the same mass to keep the total amount of alloy constant; the other conditions are the same as in Example 2.

[0088] Comparative Example 4:

[0089] The difference between Comparative Example 4 and Example 2 is that the 980°C holding stage for 45 minutes is omitted in step S5. Only the subsequent procedure of raising the temperature to 1180°C at 3°C / min and holding for 90 minutes, followed by lowering the temperature to 200°C at 3°C / min and cooling with the furnace remains unchanged. The other conditions are the same as in Example 2.

[0090] Comparative Example 5:

[0091] The difference between Comparative Example 5 and Example 2 is that in step S6, 5000 mg of polyacrylic acid is not added when preparing the infiltration solution; the other conditions are the same as in Example 2.

[0092] Comparative Example 6:

[0093] The difference between Comparative Example 6 and Example 2 is that in step S6, 5000 mg of branched polyethyleneimine is not added when preparing the infiltration solution; the other conditions are the same as in Example 2.

[0094] Comparative Example 7:

[0095] The difference between Comparative Example 7 and Example 2 is that the infiltration deposition of the polydopamine-branched polyethyleneimine / polyacrylic acid ionic composite precursor in step S6 is not performed, and in step S7, 1000g of the infiltrated semi-finished product is replaced with 1000g of the pre-sintered body for final sintering and subsequent hot isostatic pressing densification treatment; the other conditions are the same as in Example 2.

[0096] Performance testing:

[0097] Sample preparation: High wear-resistant cemented carbide sintered body samples for mining were prepared according to the examples and comparative examples. For metallographic and grain size testing, 10mm×10mm×5mm blocks were cut from the sample and embedded. The blocks were wet-ground with silicon carbide sandpaper with grits of 240, 400, 800, and 1200, and then polished to a mirror finish with 3μm and 1μm diamond polishing agents. For hardness, Barcol toughness, wear, and salt spray testing, 20mm×20mm×3mm plates were cut from the sample and the test surfaces were polished to a final polish of 1μm. All samples were ultrasonically cleaned in anhydrous ethanol for 5 min, rinsed with deionized water for 30 s, and then vacuum dried at 60℃ for 2 h for later use to ensure that the test surface condition was consistent and repeatable.

[0098] Metallographic defect testing: Metallographic defects were assessed according to GB / T 3488.4-2022. One sample each (10mm×10mm×5mm) from the example and comparative examples were taken. After mounting and mirror polishing, an etching solution with a formula of 10g potassium ferricyanide, 10g potassium hydroxide, and 100mL deionized water was used to etch the sample at 25℃ for 30s, followed by rinsing with deionized water for 10s and drying. Five fields of view were randomly selected and photographed under a metallographic microscope at 200x and 500x magnification. The porosity, non-combined carbon defects, and decarburized phases were classified and recorded according to the standard. The results are shown in Table 1.

[0099] Grain size: Grain size was measured according to GB / T 3488.2-2018. One sample each of Example 1 and Comparative Example 1 (10mm×10mm×5mm) was taken. After obtaining clear grain boundaries according to the sample preparation and etching method of metallographic defect testing, no less than 10 cross-sections with a total length of 10mm were arranged at 500x magnification using the line cut method. The number of intersections between the cross-sections and grain boundaries was counted and the average grain size was calculated. The results are shown in Table 1.

[0100] Density: The density was determined by the hydrostatic weighing method according to GB / T 3850-2015. Five samples (10mm×10mm×5mm) were taken from both the example and comparative examples. The mass m1 in air was weighed using an analytical balance (accuracy 0.1mg). The sample was then immersed in deionized water at 20℃ and the mass m2 in the water was weighed. The density ρ was calculated as ρ = m1 / (m1-m2) × ρ 水 (ρ) 水 Take 0.9982 g / cm 3 The results are shown in Table 1.

[0101] Rockwell hardness: Rockwell hardness was determined according to GB / T 3849.1-2015 (A scale). Five samples each of the example and comparative examples (20mm×20mm×3mm) were taken. A diamond cone indenter was used. The initial test force was 98.07N, the total test force was 588.4N, the holding time was 4s, and the indentation spacing was not less than 3mm. Five points were tested on the polished surface of each sample and the average was taken to obtain the average hardness of each sample. The results are shown in Table 1.

[0102] Barcol toughness: Barcol toughness test was conducted according to GB / T 33819-2017. Five samples (20mm×20mm×3mm) from both Example 1 and Comparative Example 1 were taken. A load of 294.2N was applied to the polished surface using a Vickers indenter and held for 10s. Five indentations were made on each sample. The crack length at the four apex of each indentation was measured under a 500x metallographic microscope, and the total crack length L was calculated. The Barcol toughness W = P / L (P is taken as 294.2N) was calculated, and the average value of W was used as the toughness index. The results are shown in Table 1.

[0103] Sliding wear: The sliding wear test of the test ring and test block was carried out according to GB / T 12444-2006. Five samples (20mm×20mm×3mm) of the example and the comparative example were taken as test blocks and fitted with GCr15 steel test rings (outer diameter 40mm, width 10mm, hardness 60HRC). Under dry friction conditions, a normal load of 200N and a linear velocity of 0.50m / s were applied for a friction time of 30min. Before and after the test, the mass of the test block was weighed with an analytical balance and the wear volume ΔV was converted. The wear rate k = ΔV / (load × sliding distance) was calculated and the average friction coefficient was recorded simultaneously. The results are shown in Table 1.

[0104] Salt spray corrosion: Neutral salt spray test was conducted according to GB / T 10125-2021. Five samples (20mm×20mm×3mm) from both the example and comparative examples were taken and placed in the salt spray chamber at a 20° angle. The spray solution was 50g / L sodium chloride, pH 6.8, chamber temperature 35℃, and continuous spraying was performed for 240h. After the test, the samples were rinsed with deionized water for 30s and vacuum dried at 60℃ for 2h. The mass loss per unit area (mg / cm²) was recorded. 2 And take photos to record the density of corrosion spots (number / cm²). 2 The results are shown in Table 1.

[0105] Table 1 Performance Test Results

[0106] project Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Comparative Example 7 Porosity grade (level) A04B00 A02B00 A02B00 A04B00 A06B02 A06B00 A06B02 A06B02 A06B02 A10B06 Non-combined carbon defect level (grade) C02 C00 C02 C02 C00 C00 C04 C02 C02 C00 Decarburization phase grade (level) E00 E00 E00 E00 E04 E02 E06 E04 E04 E08 Grain size (μm) 1.25 1.15 1.1 1.18 1.3 1.22 1.28 1.2 1.23 1.45 <![CDATA[Density (g / cm 3 ).]]> 14.49 14.53 14.52 14.47 14.42 14.43 14.41 14.44 14.45 14.35 Rockwell hardness (HRA) 90.4 91.2 91.4 90.9 90.6 90.0 91.5 90.8 90.5 89.8 Barcol toughness (N / mm) 12.8 13.4 12.0 12.3 11.5 13.6 10.6 11.6 11.1 10.2 <![CDATA[Wear rate (×10 -6 mm 3 / N·m)]]> 1.95 1.50 1.62 1.72 2.45 2.60 2.05 2.15 2.30 3.85 Average coefficient of friction 0.330 0.295 0.312 0.306 0.365 0.284 0.338 0.326 0.336 0.412 <![CDATA[Mass loss due to salt spray (mg / cm 2 )]]> 0.13 0.09 0.11 0.14 0.18 0.08 0.24 0.20 0.21 0.32 <![CDATA[Salt spray corrosion spot density (number / cm 2 ).]]> 14 9 11 16 24 19 36 28 30 62

[0107] Data Analysis: Table 1 shows that the high wear-resistant cemented carbide for mining applications prepared in this invention exhibits low porosity and carbon defect levels, effectively suppressing decarburization. This indicates that the combination of low-carbon alloying pre-sintering and final sintering with hot isostatic pressing can complete the main pyrolysis and carbon diffusion of the organic precursor before liquid phase formation, further closing residual micropores in subsequent processes. Simultaneously, components such as vanadium carbide, tantalum carbide, and chromium tricarbide inhibit grain growth, keeping the grain size within a fine-grained range. This results in considerable Barcol toughness while maintaining high Rockwell hardness, manifested as a low wear rate and low coefficient of friction. The chromium, molybdenum, and tungsten elements in the binder phase of the nickel-based corrosion-resistant alloy enhance passivation behavior in chlorine-containing media, keeping corrosion spots and mass loss under salt spray conditions at a low level, making it suitable for impact-abrasive-corrosion coupled conditions.

[0108] As can be seen from the data in Example 2 and Comparative Example 1 in Table 1, when aluminum particles are missing from the nickel-based corrosion-resistant alloy powder, the porosity level increases, salt spray mass loss and corrosion spot density increase, and the wear rate also shows unfavorable changes. The main reason may be that after aluminum participates in microalloying, it can improve the interface state of the binder phase during sintering and reduce the risk of binder phase segregation and pore connectivity; after its absence, the residual micropores are more likely to become channels for corrosive media and abrasive particles to enter, causing the coupling performance of wear resistance and corrosion resistance to be damaged simultaneously.

[0109] As can be seen from the data in Example 2 and Comparative Example 2 in Table 1, the removal of silicon particles significantly increased the decarburized phase level. Simultaneously, the porosity level and salt spray corrosion-related indicators worsened, and the wear rate and average friction coefficient also increased. It is speculated that the absence of silicon particles reduced the purification and wetting effect during alloy melting and sintering, making localized carbon depletion more likely and inducing decarburization. Furthermore, the continuous wetting of the binder phase against the tungsten carbide skeleton was affected, leading to a decrease in crack propagation resistance. This resulted in a synergistic effect between abrasive wear and corrosion spots, making it difficult to achieve optimal overall performance.

[0110] As can be seen from the data in Table 1 for Example 2 and Comparative Example 3, the Barcol toughness increased without the addition of boron powder, but the porosity grade and wear rate were unfavorable. The density of salt spray corrosion spots increased, and an anomaly of relatively low mass loss was observed. It is speculated that boron powder is beneficial for sintering densification and interface continuity in microalloying. The absence of boron powder increases the number of local weak bonding areas, making it easier to generate chipping initiation points and form more corrosion spots under abrasive action. On the other hand, the absence of boron powder may reduce the tendency of certain brittle phases to form, so that the uniform weight loss does not necessarily increase synchronously, thus resulting in more spots but lower weight loss.

[0111] As can be seen from the data in Example 2 and Comparative Example 4 in Table 1, after the low-temperature holding stage in the pre-sintering was removed, the level of non-combined carbon defects and the level of decarburized phase both deteriorated significantly, the Barcol toughness decreased, and the wear resistance and corrosion resistance indicators deteriorated simultaneously. An anomaly was observed where the Rockwell hardness was high but the overall performance was reduced. This may be because the low-temperature holding stage is used to allow the organic precursor to complete the main pyrolysis and carbon diffusion before the liquid phase appears. When this stage is removed, the decomposition of organic matter and the wetting and shrinkage process of the liquid phase are coupled, leading to uneven carbon distribution and inducing the decarburized phase. Simultaneously, the pooling of the binder phase causes interface discontinuity, making crack propagation easier.

[0112] As can be seen from the data in Example 2 and Comparative Example 5 in Table 1, when polyacrylic acid is lacking in the infiltration deposition system, the porosity level and decarburization phase level increase, the wear rate increases, and the density of salt spray corrosion spots also increases. It is speculated that polyacrylic acid and branched polyethyleneimine together constitute an ion-composite precursor to stabilize the polydopamine deposition layer and improve the infiltration uniformity; after the absence of polyacrylic acid, the continuity of the deposition layer and the infiltration depth decrease, the carbon replenishment and pore prefilling effects weaken, resulting in local decarburization and residual micropores that are difficult to be fully closed by hot isostatic pressing after final sintering, thus damaging both wear resistance and corrosion resistance.

[0113] As can be seen from the data in Example 2 and Comparative Example 6 in Table 1, when branched polyethyleneimine is absent in the infiltration deposition system, the Barcol toughness and wear resistance decrease, the salt spray mass loss and corrosion spot density increase, and the decarburization phase level remains at a high level. The main reason may be that branched polyethyleneimine participates in the formation of ion-composite precursors and promotes the continuous coverage of polydopamine deposition layer on the pore walls; its absence reduces the infiltration deposition efficiency and the interface transition is insufficient, making it easier for corrosion media to form communication paths between pores and phase boundaries, crack propagation tends to be more direct, and the synergistic strengthening effect is significantly weakened.

[0114] As can be seen from the data in Table 1 for Example 2 and Comparative Example 7, when the ion-composite precursor deposition of polydopamine, branched polyethyleneimine, and polyacrylic acid was not performed, the porosity level, decarburization phase level, and corrosion spot density all deteriorated significantly. The wear rate and average friction coefficient increased significantly, while the density and Barcol toughness decreased, demonstrating a substantial degradation in overall performance. It is speculated that this step simultaneously plays a triple role in regulating carbon diffusion, forming a pore wall deposition layer, and ensuring interface continuity, making subsequent hot isostatic pressing easier to close pores and block the penetration channels of corrosive media. Without this step, relying solely on conventional sintering and hot isostatic pressing makes it difficult to achieve both wear resistance and corrosion resistance.

[0115] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity.

Claims

1. A method for preparing a high wear-resistant cemented carbide for mining applications, characterized in that, Includes the following steps: (1) Nickel-based corrosion-resistant alloy powder is obtained by melting and atomizing raw materials such as nickel, chromium, molybdenum, tungsten, aluminum, titanium, silicon and boron. (2) Add tungsten carbide powder, nickel-based corrosion-resistant alloy powder, vanadium carbide powder, tantalum carbide powder and chromium tricarbide powder to an organic medium and perform wet ball milling to obtain a mixed powder; (3) Add the paraffin-n-heptane forming system to the mixed powder and prepare a slurry, then spray dry and granulate to obtain granules; (4) The granules are pressed into shape and dewaxed under vacuum to obtain a dewaxed blank; (5) The dewaxed green body is pre-sintered to obtain a pre-sintered body; (6) Tris(hydroxymethyl)aminomethane is added to deionized water to form a buffer system and the pH is adjusted to 8.8-9.

2. Polyacrylic acid, branched polyethyleneimine and dopamine hydrochloride are added in sequence to obtain an infiltration solution. The pre-sintered body is immersed in the infiltration solution and subjected to vacuum-backpressure pulse treatment, and then dried to obtain the infiltration semi-finished product. (7) Vacuum sintering and hot isostatic pressing densification treatment are carried out on the infiltrated semi-finished product to obtain a high wear-resistant cemented carbide for mining. In step (1), the amounts of nickel, chromium, molybdenum, tungsten, aluminum, titanium, silicon, and boron raw materials added are 73.65g-79.25g, 13g-15g, 5.5g-6.5g, 1.5g-2.5g, 0.9g-1.5g, 0.3g-0.7g, 0.4g-0.8g, and 0.15g-0.35g, respectively; in step (2), tungsten carbide powder, nickel-based corrosion-resistant alloy powder, vanadium carbide powder, tantalum carbide powder, and chromium tricarbide powder are added. The amounts of anhydrous ethanol and stearic acid are 887g-893g, 100g, 2g-4g, 3g-5g, 2g-4g, 1.2kg and 2g, respectively; in step (6), the infiltration solution is prepared from the following components: 4500g-5500g deionized water, 5g-7g tris(hydroxymethyl)aminomethane, 4g-6g polyacrylic acid, 4g-6g branched polyethyleneimine and 8g-12g dopamine hydrochloride; the amount of pre-sintered body is 1000g.

2. The method for preparing high wear-resistant cemented carbide for mining applications according to claim 1, characterized in that, In step (1), during melting, the vacuum is drawn to 0.05 Pa and then argon gas is introduced to 0.05 MPa for protection and the temperature is raised to 1550℃ and held for 10 min. During atomization powder preparation, argon gas at 4 MPa is used for atomization.

3. The method for preparing high wear-resistant cemented carbide for mining applications according to claim 1, characterized in that, In step (2), the ball-to-material ratio of wet ball milling is 6:1, the ball milling speed is 200 rpm, the ball milling time is 18 h, and the temperature of the ball milling tank is controlled below 35℃.

4. The method for preparing high wear-resistant cemented carbide for mining applications according to claim 1, characterized in that, In step (3), the paraffin-n-heptane forming system is a paraffin-n-heptane solution, which is obtained by heating n-heptane to 80°C and adding paraffin while stirring to dissolve.

5. The method for preparing high wear-resistant cemented carbide for mining applications according to claim 1, characterized in that, In step (4), the pressing process includes unidirectional pressing and cold isostatic pressing, wherein the unidirectional pressing pressure is 200 MPa and the holding pressure is 30 s, and the cold isostatic pressing pressure is 250 MPa and the holding pressure is 2 min.

6. The method for preparing high wear-resistant cemented carbide for mining applications according to claim 1, characterized in that, In step (4), dewaxing is carried out in a vacuum furnace with a vacuum degree of 0.05 Pa, and the temperature is increased to 450°C at 1°C / min and held for 60 min, then increased to 600°C at 2°C / min and held for 30 min, and then cooled to room temperature with the furnace.

7. The method for preparing a high wear-resistant cemented carbide for mining applications according to claim 1, characterized in that, In step (5), the pre-sintering is carried out in a vacuum furnace with a vacuum degree of 0.006Pa-0.015Pa, and the temperature is increased to 980℃ at 4℃ / min-6℃ / min and held for 40min-50min, then increased to 1180℃ at 2℃ / min-4℃ / min and held for 80min-100min, and then decreased to 200℃ at 2℃ / min-4℃ / min and cooled with the furnace.

8. The method for preparing high wear-resistant cemented carbide for mining applications according to claim 1, characterized in that, In step (6), the number average molecular weight of polyacrylic acid is 25,000-35,000; the number average molecular weight of branched polyethyleneimine is 8,000-12,000.

9. The method for preparing a high wear-resistant cemented carbide for mining applications according to claim 1, characterized in that, In step (6), the vacuum-backpressure pulse treatment is as follows: pump to 15kPa-30kPa and hold for 4min-6min, then backpressure to 101kPa and soak for 20min-30min, repeat 2-4 times.

10. The method for preparing a high wear-resistant cemented carbide for mining applications according to claim 1, characterized in that, In step (7), the vacuum final sintering is carried out under a vacuum of 0.003Pa-0.008Pa, and the temperature is increased to 600℃ at 2℃ / min-4℃ / min and held for 50min-70min, then increased to 950℃ at 4℃ / min-6℃ / min and held for 40min-50min, then increased to 1410℃ at 2℃ / min-4℃ / min and held for 60min-80min, and then decreased to 1150℃ at 8℃ / min-12℃ / min and cooled to room temperature in the furnace; the hot isostatic pressing densification treatment is carried out in an argon atmosphere, and the temperature is increased to 1320℃-1380℃ and pressurized to 80MPa-120MPa and held for 50min-70min before being cooled out of the furnace.