Hard alloy for hard rock deep drilling and preparation method thereof

Abstract

The invention belongs to the technical field of hard alloy materials, and particularly relates to a hard alloy for hard rock deep drilling and a preparation method thereof. The difficult problem of recycling high-quality hard alloy is solved, yttrium-containing fine-grained tungsten carbide and nickel-containing coarse-grained tungsten carbide are obtained through different treatment processes and are used together with other raw materials, the hard alloy for hard rock deep drilling is prepared, recycling of the waste hard alloy is achieved, and the utilization rate of the hard alloy is increased. And the fracture toughness of the hard alloy material is improved through modification treatment, and meanwhile good wear resistance is obtained.

Description

Technical Field

[0001] The present invention belongs to the technical field of cemented carbide materials, and particularly relates to a cemented carbide for hard rock deep drilling and a preparation method thereof. Background Art

[0002] With the development of China's economy, deep underground engineering has gradually increased, and drilling technology has been more and more widely used in various fields. As the drilling depth becomes deeper and the rock becomes harder, the bit life has become a key factor restricting production efficiency. Therefore, the development of efficient rock-breaking tools has become the focus of research. In hard rock deep drilling, cemented carbide has become the core material of key tools such as bits and picks due to its high hardness, wear resistance and impact resistance. Since hard rock deep drilling (such as tunnel excavation, mine exploitation, oil drilling, etc.) faces extreme working conditions such as high temperature, high pressure and high abrasiveness, the cemented carbide material needs to balance wear resistance and fracture toughness.

[0003] Chinese Patent (Publication No. CN111041320B) discloses a cemented carbide with a mixed crystal structure and a preparation method thereof. The cemented carbide of this invention is made of 5-20% by mass of mixture A and 80-95% by mass of mixture B; mixture A includes raw materials with the following mass percentages: 89.3-93.7% of tungsten carbide, 6-10% of cobalt, 0.3-0.7% of chromium carbide; among them, the Fisher particle size of tungsten carbide in mixture A is 0.4-0.8 μm; mixture B includes raw materials with the following mass percentages: 90-94% of tungsten carbide, 6-10% of cobalt; among them, the Fisher particle size of tungsten carbide in mixture B is 2.5-4.5 μm. However, this technology lacks the recycling of waste cemented carbide, and at the same time, the fracture toughness and wear resistance of the cemented carbide also need to be improved.

[0004] Therefore, how to recycle waste cemented carbide, optimize the components, and improve the fracture toughness and wear resistance of the cemented carbide has become the key direction to be overcome. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a cemented carbide for hard rock deep drilling and a preparation method thereof; the present invention breaks through the problem of recycling high-quality cemented carbide, obtains fine-grained tungsten carbide containing yttrium and coarse-grained tungsten carbide containing nickel through different treatment processes, and uses them together with other raw materials to prepare a cemented carbide for hard rock deep drilling, which not only realizes the recycling of waste cemented carbide, but also improves the fracture toughness of the cemented carbide material through modification treatment, and at the same time obtains good wear resistance.

[0006] In the first aspect of the present invention, a cemented carbide for hard rock deep drilling is provided. By weight, it includes 10-20 parts of material A and 80-90 parts of material B. The material A includes 88-94 parts of fine-grained tungsten carbide, 6-10 parts of cobalt, and 0.4-0.8 parts of chromium carbide; The material B includes 90-94 parts of coarse-grained tungsten carbide and 6-10 parts of cobalt; The preparation method of the fine-grained tungsten carbide includes: pretreating waste cemented carbide to obtain waste cemented carbide powder; smelting the waste cemented carbide powder with sodium nitrate to obtain a sodium tungstate smelting block; crushing the sodium tungstate smelting block and then leaching to obtain a sodium tungstate solution; purifying the sodium tungstate solution to obtain tungstic acid; using tungstic acid, ammonia water, and yttrium nitrate to prepare a precursor, and then performing carbonization treatment to obtain fine-grained tungsten carbide; The preparation method of the coarse-grained tungsten carbide includes: crushing waste cemented carbide and adding it to a sulfuric acid solution for ball milling, filtering and separating to obtain recycled tungsten carbide powder; coarsening the recycled tungsten carbide powder, and then coating it with nickel chloride and ammonium oxalate, and performing high-temperature hydrogen reduction treatment to obtain coarse-grained tungsten carbide.

[0007] As a preferred scheme, the steps of the pretreatment include: soaking the waste cemented carbide in a nitric acid solution with a mass concentration of 60-70% for 20-30 min, drying, crushing, ball milling, and sieving.

[0008] As a preferred scheme, the steps of the smelting treatment include: mixing 10-20 parts of waste cemented carbide powder and 50-60 parts of sodium nitrate evenly by weight, smelting at 1000-1200 °C for 100-120 min, and cooling to room temperature.

[0009] As a preferred scheme, the steps of the leaching include: placing the sodium tungstate smelting block in deionized water, wet-milling and leaching at 80-90 °C for 2-3 h, and filtering.

[0010] As a preferred scheme, the steps of the purification treatment include: adding 20-30 parts of magnesium chloride to 100-120 parts of sodium tungstate solution and stirring for 30-40 min, filtering, adding 200-240 parts of hydrochloric acid solution with a mass concentration of 30-40% to the filtrate for acidification precipitation, filtering, and washing the precipitate with water.

[0011] As a preferred scheme, the steps of the preparation of the precursor include: adding 10-14 parts of tungstic acid to 50-60 parts of 4 mol / L ammonia water and stirring for 50-60 min, keeping warm at 30-34 °C for 20-24 h, filtering to remove the precipitate, placing the filtrate at 80-85 °C and stirring for 20-30 min, adding 4-6 mL of yttrium nitrate aqueous solution with a concentration of 0.1 g / mL after crystallization and stirring evenly, and drying.

[0012] As a preferred solution, the steps of the carbonization treatment include: first, calcine the precursor at 580 - 600 °C for 100 - 120 min, cool it, then mix and ball-mill it with carbon black for 4 - 6 h. Then transfer it to a tube furnace, and under an argon atmosphere, heat it to 1200 - 1400 °C at a rate of 5 °C / min for carbonization for 120 - 140 min.

[0013] As a preferred solution, the particle size of the fine-grained tungsten carbide is 0.2 - 0.4 μm.

[0014] The present invention breaks through the problem of recycling high-quality cemented carbide. First, in the pretreatment, degreasing and decontamination are carried out with nitric acid. After crushing, it is melted with sodium nitrate to obtain a sodium tungstate melting block. Then it is crushed, leached, and purified with magnesium chloride, and tungstic acid is recovered by acidification with hydrochloric acid. Then ammonia solution is used to dissolve tungstic acid, and a precursor is obtained by cooperating with yttrium nitrate. Finally, carbon black is added for high-temperature carbonization to obtain fine-grained tungsten carbide containing yttrium element.

[0015] As a preferred solution, the steps of the ball-milling treatment include: by weight, add 20 - 30 parts of crushed waste cemented carbide into 100 - 120 parts of sulfuric acid solution with a mass concentration of 40 - 50%, and ball-mill at a speed of 200 - 300 rpm for 100 - 120 min.

[0016] As a preferred solution, the steps of the roughening treatment include: add 4 - 6 parts of nitric acid into 100 - 120 parts of hydrofluoric acid solution with a mass concentration of 1%, mix evenly, then add 20 - 30 parts of recycled tungsten carbide powder and stir for 30 - 40 min, wash with water, and dry.

[0017] As a preferred solution, the steps of the coating include: mix 20 - 30 parts of the roughened powder and 90 - 100 parts of nickel chloride aqueous solution with a concentration of 0.4 - 0.6 mol / L, adjust the pH to 5.8 - 6.2, add 8 - 10 parts of ammonium oxalate aqueous solution, stir at 50 - 60 °C for 80 - 90 min, filter by suction, and dry.

[0018] As a preferred solution, the conditions of the high-temperature hydrogen reduction treatment include: placed in a hydrogen atmosphere, the temperature is 400 - 450 °C, and the time is 100 - 120 min.

[0019] As a preferred solution, the particle size of the coarse-grained tungsten carbide is 2 - 5 μm.

[0020] In the present invention, waste cemented carbide is first treated to recover tungsten carbide powder, and then surface roughening is carried out using hydrofluoric acid and nitric acid. After roughening, grooves will appear on the surface of the powder and the specific surface area will increase, making it easier for the particles generated by the chemical coprecipitation reaction of nickel chloride and ammonium oxalate to adhere to the surface of the recovered tungsten carbide powder. Subsequently, the reaction is carried out under high-temperature conditions in a hydrogen atmosphere to reduce and form coarse-grained tungsten carbide with a nickel-containing phase on the surface.

[0021] In the second aspect of the present invention, a method for preparing cemented carbide for hard rock deep drilling as described in the first aspect is provided, including the following steps: S1: By weight, 88-94 parts of fine-grained tungsten carbide, 6-10 parts of cobalt, and 0.4-0.8 parts of chromium carbide are mixed, and then 2-4 parts of paraffin and 50-60 parts of absolute ethanol are added for the first ball milling. After drying, material A is obtained; 90-94 parts of coarse-grained tungsten carbide and 6-10 parts of cobalt are mixed, and then 2-4 parts of paraffin and 40-50 parts of absolute ethanol are added for the second ball milling. After drying, material B is obtained. S2: 10-20 parts of material A and 80-90 parts of material B are mixed and then pressed and sintered to obtain cemented carbide for hard rock deep drilling.

[0022] As a preferred scheme, the ball milling time of the first ball milling is 20-30 h, and the ball milling time of the second ball milling is 30-40 h.

[0023] As a preferred scheme, the sintering conditions include: placed under argon protection, the temperature is 1400-1420 °C, and the sintering time is 2-4 h.

[0024] Compared with the prior art, the present invention has the following beneficial effects: (1) The nickel phase on the surface of the coarse-grained tungsten carbide in the present invention provides additional impedance during crack propagation through interface strengthening. The yttrium-doped fine-grained tungsten carbide can refine grains and increase the crack deflection path; the coarse-grained tungsten carbide provides strong resistance to abrasive wear, and the yttrium-containing fine-grained tungsten carbide plays a role in dispersion strengthening. By jointly using coarse-grained tungsten carbide and fine-grained tungsten carbide, and cobalt as the first binder phase and nickel as the second binder phase, the synergistic effect achieves the effect of both toughness and wear resistance.

[0025] (2) The fine-grained tungsten carbide in the present invention contains rare earth element yttrium, which preferentially segregates to the grain boundaries of tungsten carbide during sintering to form stable oxide or carbide second-phase particles. These second-phase particles can pin the grain boundaries, inhibit grain boundary slip and crack propagation along the grain boundaries, thereby increasing the crack propagation resistance and improving the fracture toughness; in addition, during high-temperature wear, yttrium can promote the formation of a dense yttrium-containing oxide film on the wear surface, reduce adhesive wear and oxidative wear, and reduce the volume wear of the cemented carbide.

[0026] (3) The coarse-grained tungsten carbide with a nickel-containing phase on the surface of the present invention can effectively improve the interfacial bonding strength between tungsten carbide and cobalt. During the stress process, the nickel-containing phase on the surface will cause the crack propagation path to deflect at the interface, thereby consuming more energy and delaying the rapid propagation of cracks, thus improving the fracture toughness. At the same time, the nickel-containing phase on the surface can absorb part of the impact energy under cyclic loading, reduce the initiation and propagation of microcracks, and thus improve the wear resistance of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] To more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0028] Figure 1 Performance test report for Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0029] To facilitate the understanding of the present invention, the following examples are listed. Those skilled in the art should understand that the described examples are only for helping to understand the present invention and should not be regarded as specific limitations of the present invention.

[0030] The sources of some components in the examples and comparative examples are as follows: Sodium nitrate, CAS No. 7631-99-4, purchased from Sinopharm Chemical Reagent Co., Ltd.; Magnesium chloride, CAS No. 7786-30-3, purchased from Shanghai Macklin Biochemical Co., Ltd.; Ammonia water, CAS No. 1336-21-6, purchased from Sinopharm Chemical Reagent Co., Ltd.; Yttrium nitrate, CAS No. 13494-98-9, purchased from Shanghai Macklin Biochemical Co., Ltd.; Hydrofluoric acid solution, product number H291695, mass concentration fraction 1%, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; Nickel chloride, CAS No. 7718-54-9, purchased from Shanghai Macklin Biochemical Co., Ltd.; Ammonium oxalate, CAS No. 6009-70-7, purchased from Shanghai Macklin Biochemical Co., Ltd.; Commercially available tungsten carbide I, product number T111338, particle size 0.4 μm, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; Commercially available tungsten carbide II, product number T299279, particle size 2 μm, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; Cobalt, product number C123401, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; Chromium carbide, CAS No. 12012-35-0, was purchased from Shanghai Macklin Biochemical Co., Ltd.

[0031] Example 1 This example provides a method for preparing cemented carbide for deep hard rock drilling, including the following steps: S1: By weight, 94 parts of fine-grained tungsten carbide (grain size of 0.4 μm), 10 parts of cobalt, and 0.8 part of chromium carbide are mixed, and then 4 parts of paraffin and 60 parts of absolute ethanol are added for the first ball milling (ball milling time is 30 h), and after drying, material A is obtained; 94 parts of coarse-grained tungsten carbide (grain size of 2 μm) and 6 parts of cobalt are mixed, and then 4 parts of paraffin and 50 parts of absolute ethanol are added for the second ball milling (ball milling time is 40 h), and after drying, material B is obtained; S2: 20 parts of material A and 80 parts of material B are mixed and then pressed and sintered (under argon protection, at a temperature of 1420 °C, and the sintering time is 2 h) to obtain cemented carbide for deep hard rock drilling. The performance of the cemented carbide in Example 1 is tested, and the results of the third-party test report are as Figure 1 shown. The density of the cemented carbide in Example 1 is 14.22 g / cm 3 , the Rockwell hardness is 86.1 HRA, and the fracture toughness is 19.2 MPa·m 1 / 2 .

[0032] Preparation of the fine-grained tungsten carbide: The waste cemented carbide is soaked in a nitric acid solution with a mass concentration of 70% for 20 min, dried, crushed, ball milled, and sieved to obtain waste cemented carbide powder; by weight, 20 parts of waste cemented carbide powder and 60 parts of sodium nitrate are mixed evenly, melted at 1200 °C for 100 min, and cooled to room temperature to obtain a sodium tungstate melting block; the sodium tungstate melting block is placed in deionized water and wet milled and leached at 90 °C for 2 h, and the sodium tungstate solution is filtered; 30 parts of magnesium chloride are added to 120 parts of the sodium tungstate solution and stirred for 40 min, filtered, and 240 parts of a hydrochloric acid solution with a mass concentration of 40% are added to the filtrate for acid precipitation, filtered, and the precipitate is washed with water to obtain tungstic acid; 14 parts of tungstic acid are added to 60 parts of 4 mol / L ammonia water and stirred for 60 min, kept warm at 34 °C for 20 h, the precipitate is filtered off, the filtrate is stirred at 85 °C for 20 min, after crystallization appears, 6 mL of an aqueous solution of yttrium nitrate with a concentration of 0.1 g / mL is added and stirred evenly, and then dried to obtain a precursor; first, the precursor is calcined at 600 °C for 100 min, cooled, mixed and ball milled with carbon black for 6 h, and then transferred to a tubular atmosphere furnace. Under an argon atmosphere, it is heated to 1400 °C at a rate of 5 °C / min and carbonized for 120 min to obtain fine-grained tungsten carbide.

[0033] Preparation of the coarse-grained tungsten carbide: By weight, 30 parts of waste cemented carbide are crushed and added to 120 parts of a sulfuric acid solution with a mass concentration of 50%. Ball milling is carried out at a speed of 300 rpm for 120 min, followed by filtration and separation to obtain recycled tungsten carbide powder. 6 parts of nitric acid are added to 120 parts of a hydrofluoric acid solution with a mass concentration of 1% and mixed evenly. Then, 30 parts of the recycled tungsten carbide powder are added and stirred for 40 min, followed by washing with water and drying. 30 parts of the coarsened powder and 100 parts of a 0.6 mol / L nickel chloride aqueous solution are mixed, the pH is adjusted to 6.2, 10 parts of an ammonium oxalate aqueous solution are added, and stirring is carried out at 60 °C for 80 min. Suction filtration and drying are carried out, and after high-temperature hydrogen reduction treatment (placed in a hydrogen atmosphere, temperature of 450 °C, time of 100 min), coarse-grained tungsten carbide is obtained.

[0034] Example 2 This example provides a method for preparing cemented carbide for deep hard rock drilling, including the following steps: S1: By weight, 88 parts of fine-grained tungsten carbide (particle size of 0.4 μm), 6 parts of cobalt, and 0.4 parts of chromium carbide are mixed, and then 2 parts of paraffin and 50 parts of absolute ethanol are added for the first ball milling (ball milling time is 20 h). After drying, material A is obtained. 90 parts of coarse-grained tungsten carbide (particle size of 5 μm) and 10 parts of cobalt are mixed, and then 2 parts of paraffin and 40 parts of absolute ethanol are added for the second ball milling (ball milling time is 30 h). After drying, material B is obtained. S2: 10 parts of material A and 90 parts of material B are mixed and then pressed and sintered (placed under argon protection, temperature of 1400 °C, sintering time is 4 h) to obtain cemented carbide for deep hard rock drilling.

[0035] Preparation of the fine-grained tungsten carbide: Immerse the waste cemented carbide in a nitric acid solution with a mass concentration of 60% for 20 min, dry it, and then perform crushing, ball milling, and sieving to obtain waste cemented carbide powder; by weight, mix 10 parts of the waste cemented carbide powder and 50 parts of sodium nitrate evenly, melt at 1000 °C for 120 min, and cool to room temperature to obtain a sodium tungstate melting block; place the sodium tungstate melting block in deionized water, wet mill and leach at 80 °C for 3 h, and filter to obtain a sodium tungstate solution; add 20 parts of magnesium chloride to 100 parts of the sodium tungstate solution, stir for 30 min, filter, add 200 parts of a hydrochloric acid solution with a mass concentration of 30% to the filtrate for acid precipitation, filter, wash the precipitate with water to obtain tungstic acid; add 10 parts of tungstic acid to 50 parts of 4 mol / L ammonia water, stir for 50 min, keep warm at 30 °C for 24 h, filter to remove the precipitate, place the filtrate at 80 °C and stir for 30 min, after crystallization appears, add 4 mL of an aqueous solution of yttrium nitrate with a concentration of 0.1 g / mL, stir evenly, and dry to obtain a precursor; first calcine the precursor at 580 °C for 120 min, cool it, mix it with carbon black and perform ball milling for 4 h, then transfer it to a tube-type atmosphere furnace, and under an argon atmosphere, heat it to 1200 °C at a rate of 5 °C / min and carbonize for 140 min to obtain fine-grained tungsten carbide.

[0036] Preparation of the coarse-grained tungsten carbide: By weight, crush 20 parts of the waste cemented carbide and add it to 100 parts of a sulfuric acid solution with a mass concentration of 40%, ball mill at a speed of 200 rpm for 120 min, filter and separate to obtain recycled tungsten carbide powder; add 4 parts of nitric acid to 100 parts of a hydrofluoric acid solution with a mass concentration of 1%, mix evenly, then add 20 parts of the recycled tungsten carbide powder, stir for 30 min, wash with water, and dry; mix 20 parts of the coarsened powder and 90 parts of a 0.4 mol / L nickel chloride aqueous solution, adjust the pH to 5.8, add 8 parts of an ammonium oxalate aqueous solution, stir at 50 °C for 90 min, filter by suction, dry, and perform high-temperature hydrogen reduction treatment (place it under a hydrogen atmosphere, the temperature is 400 °C, and the time is 120 min) to obtain coarse-grained tungsten carbide.

[0037] Example 3 This example provides a method for preparing cemented carbide for deep hard rock drilling, including the following steps: S1: By weight, mix 90 parts of fine-grained tungsten carbide (particle size is 0.2 μm), 8 parts of cobalt, and 0.6 parts of chromium carbide, then add 3 parts of paraffin wax and 55 parts of absolute ethanol for the first ball milling (the ball milling time is 25 h), and dry to obtain material A; mix 92 parts of coarse-grained tungsten carbide (particle size is 3 μm) and 8 parts of cobalt, then add 3 parts of paraffin wax and 45 parts of absolute ethanol for the second ball milling (the ball milling time is 35 h), and dry to obtain material B; S2: Mix 15 parts of material A and 85 parts of material B, then carry out pressing and sintering (under argon protection, at a temperature of 1410 °C and a sintering time of 3 h) to obtain cemented carbide for deep hard rock drilling.

[0038] Preparation of the fine-grained tungsten carbide: Immerse waste cemented carbide in a nitric acid solution with a mass concentration of 65% for 25 min, dry it, then crush, ball-mill, and sieve it to obtain waste cemented carbide powder; By weight, mix 15 parts of waste cemented carbide powder and 55 parts of sodium nitrate evenly, melt it at 1100 °C for 110 min, and cool it to room temperature to obtain a sodium tungstate melting block; Place the sodium tungstate melting block in deionized water, wet-mill and leach it at 85 °C for 2 h, and filter to obtain a sodium tungstate solution; Add 25 parts of magnesium chloride to 110 parts of the sodium tungstate solution, stir for 35 min, filter, add 220 parts of a hydrochloric acid solution with a mass concentration of 35% to the filtrate for acidification and precipitation, filter, wash the precipitate with water to obtain tungstic acid; Add 12 parts of tungstic acid to 55 parts of 4 mol / L ammonia water, stir for 58 min, keep it warm at 32 °C for 22 h, filter to remove the precipitate, place the filtrate at 82 °C and stir for 25 min, after crystallization appears, add 5 mL of an aqueous solution of yttrium nitrate with a concentration of 0.1 g / mL and stir evenly, then dry it to obtain a precursor; First, calcine the precursor at 590 °C for 110 min, cool it, mix it with carbon black and ball-mill for 5 h, then transfer it to a tubular atmosphere furnace, under an argon atmosphere, heat it up to 1300 °C at a rate of 5 °C / min and carbonize it for 130 min to obtain fine-grained tungsten carbide.

[0039] Preparation of the coarse-grained tungsten carbide: By weight, crush 25 parts of waste cemented carbide and add it to 110 parts of a sulfuric acid solution with a mass concentration of 45%, ball-mill it at a speed of 250 rpm for 110 min, filter and separate to obtain recycled tungsten carbide powder; Add 5 parts of nitric acid to 110 parts of a hydrofluoric acid solution with a mass concentration of 1%, mix evenly, then add 25 parts of the recycled tungsten carbide powder and stir for 35 min, wash it with water and dry it; Mix 25 parts of the coarsened powder and 95 parts of a 0.5 mol / L nickel chloride aqueous solution, adjust the pH to 5.9, add 9 parts of an ammonium oxalate aqueous solution, stir at 55 °C for 85 min, filter with suction, dry it, and carry out high-temperature hydrogen reduction treatment (under a hydrogen atmosphere, at a temperature of 430 °C and a time of 110 min) to obtain coarse-grained tungsten carbide.

[0040] Comparative Example 1 The difference between this comparative example and Example 1 is that commercially available tungsten carbide Ⅰ is used to replace the fine-grained tungsten carbide, and commercially available tungsten carbide Ⅱ is used to replace the coarse-grained tungsten carbide.

[0041] Comparative Example 2 The difference between this comparative example and Example 1 is that commercially available tungsten carbide Ⅰ is used to replace the fine-grained tungsten carbide.

[0042] Comparative Example 3 The difference between this comparative example and Example 1 is that commercially available tungsten carbide II is used to replace the coarse-grained tungsten carbide.

[0043] Comparative Example 4 The difference between this comparative example and Example 1 is that recycled tungsten carbide powder is used to replace the coarse-grained tungsten carbide.

[0044] The properties of the cemented carbides provided in the above examples and comparative examples were tested, and the test methods are as follows: (1) Density test: The test was carried out with reference to the requirements of "GB / T 3850-2015 Dense sintered metallic materials and hardmetals - Determination of density".

[0045] (2) Rockwell hardness test: The test was carried out with reference to the requirements of "GB / T 3849.1-2015 Hardmetals - Rockwell hardness test (scale A) - Part 1: Test method".

[0046] (3) Fracture toughness test: The test was carried out with reference to the requirements of "JB / T 12616-2016 Detection method for fracture toughness of cemented carbide tool substrate materials".

[0047] (4) Wear resistance test: The test was carried out with reference to the requirements of "GB / T 34501-2017 Hardmetals - Wear test methods".

[0048] The above performance test data are shown in Table 1.

[0049] Table 1 Performance test results <![CDATA[Density (g / cm 3 ).]]> Rockwell hardness (HRA) <![CDATA[Fracture toughness (MPa·m 1 / 2 )]]> <![CDATA[Volume wear amount (cm 3 )]]> Example 1 14.22 86.1 19.20 2.7 Example 2 14.25 86.6 19.34 2.5 Example 3 14.19 87.3 19.26 2.8 Comparative Example 1 14.43 89.9 14.82 7.8 Comparative Example 2 14.35 89.1 17.78 4.5 Comparative Example 3 14.28 88.5 16.93 5.3 Comparative Example 4 14.31 87.8 15.96 6.1 As can be seen from the above, the present invention breaks through the problem of recycling high-quality cemented carbides, obtains fine-grained yttrium-containing tungsten carbide and coarse-grained nickel-containing tungsten carbide through different treatment processes, and is used in combination with other raw materials to prepare cemented carbides for deep hard rock drilling (Examples 1 to 3). It not only realizes the recycling of waste cemented carbides, but also improves the fracture toughness of the cemented carbide material through modification treatment, and at the same time obtains good wear resistance.

[0050] Compared with Example 1, when commercially available tungsten carbide I is used to replace fine-grained tungsten carbide and commercially available tungsten carbide II is used to replace coarse-grained tungsten carbide, the fracture toughness decreases and the wear resistance deteriorates due to the lack of the functions of fine-grained tungsten carbide and coarse-grained tungsten carbide (Comparative Example 1); compared with Example 1, when commercially available tungsten carbide I is used to replace fine-grained tungsten carbide, the fracture toughness decreases and the wear resistance deteriorates due to the lack of the function of rare earth element yttrium in fine-grained tungsten carbide (Comparative Example 2); compared with Example 1, when commercially available tungsten carbide II is used to replace coarse-grained tungsten carbide, the fracture toughness decreases and the wear resistance deteriorates due to the lack of the surface nickel phase in coarse-grained tungsten carbide (Comparative Example 3); compared with Example 1, when recycled tungsten carbide powder is used to replace coarse-grained tungsten carbide, the fracture toughness decreases and the wear resistance deteriorates due to the impurities in the recycled tungsten carbide powder and the lack of the surface nickel phase (Comparative Example 4).

Claims

1. A cemented carbide for deep hard rock drilling, characterized in that: In parts by weight, it includes 10-20 parts of material A and 80-90 parts of material B; The material A comprises 88-94 parts of fine-grained tungsten carbide, 6-10 parts of cobalt and 0.4-0.8 parts of chromium carbide; The B material includes 90-94 parts of coarse-grained tungsten carbide and 6-10 parts of cobalt; The preparation method of fine-grained tungsten carbide comprises: pre-treating waste cemented carbide to obtain waste cemented carbide powder; smelting the waste cemented carbide powder and sodium nitrate to obtain a sodium tungstate smelting block; crushing the sodium tungstate smelting block and leaching it to obtain a sodium tungstate solution; purifying the sodium tungstate solution to obtain tungstic acid; using tungstic acid, ammonia water and yttrium nitrate to prepare a precursor, and then carbonizing it to obtain fine-grained tungsten carbide; The preparation method of coarse-grained tungsten carbide comprises: crushing waste cemented carbide, adding sulfuric acid solution to perform ball milling, filtering and separating to obtain recycled tungsten carbide powder; roughening the recycled tungsten carbide powder, then coating it with nickel chloride and ammonium oxalate, and performing high-temperature hydrogen reduction to obtain coarse-grained tungsten carbide.

2. The hard alloy for hard rock deep drilling according to claim 1, characterized in that: The smelting treatment step comprises: mixing 10-20 parts of waste cemented carbide powder and 50-60 parts of sodium nitrate uniformly by weight, smelting at 1000-1200° C. for 100-120 minutes, and cooling to room temperature.

3. The hard alloy for hard rock deep drilling according to claim 1, characterized in that: The purification treatment step includes: adding 20-30 parts of magnesium chloride to 100-120 parts of sodium tungstate solution, stirring for 30-40 minutes, filtering, adding 200-240 parts of hydrochloric acid solution with a mass concentration of 30-40% to the filtrate for acidification and precipitation, filtering, and washing the precipitate with water.

4. The hard alloy for hard rock deep drilling according to claim 1, characterized in that: The preparation steps of the precursor include: adding 10-14 parts of tungstic acid to 50-60 parts of 4 mol / L ammonia water, stirring for 50-60 minutes, keeping warm at 30-34° C. for 20-24 hours, filtering to remove precipitates, stirring the filtrate at 80-85° C. for 20-30 minutes, adding 4-6 mL of 0.1 g / mL yttrium nitrate aqueous solution after crystallization, stirring evenly, and drying.

5. The hard alloy for hard rock deep drilling according to claim 1, characterized in that: The carbonization treatment steps include: first calcining the precursor at 580-600°C for 100-120 minutes, mixing and ball milling with carbon black for 4-6 hours after cooling, and then transferring to a tubular atmosphere furnace, heating to 1200-1400°C at a rate of 5°C / min in an argon atmosphere and carbonizing for 120-140 minutes.

6. The hard alloy for hard rock deep drilling according to claim 1, characterized in that: The particle size of the fine-grained tungsten carbide is 0.2-0.4 μm.

7. The hard alloy for hard rock deep drilling according to claim 1, characterized in that: The roughening treatment step includes: adding 4-6 parts of nitric acid to 100-120 parts of 1% hydrofluoric acid solution by mass concentration and mixing evenly, then adding 20-30 parts of recovered tungsten carbide powder and stirring for 30-40 minutes, washing with water, and drying.

8. The hard alloy for hard rock deep drilling according to claim 1, characterized in that: The coating step comprises: mixing 20-30 parts of the roughened powder with 90-100 parts of a 0.4-0.6 mol / L nickel chloride aqueous solution, adjusting the pH to 5.8-6.2, adding 8-10 parts of an ammonium oxalate aqueous solution, stirring at 50-60° C. for 80-90 minutes, filtering, and drying.

9. The hard alloy for hard rock deep drilling according to claim 1, characterized in that: The coarse-grained tungsten carbide has a particle size of 2-5 μm.

10. A method for preparing a cemented carbide for deep hard rock drilling according to any one of claims 1 to 9, characterized in that: The following steps are involved: S1: In parts by weight, 88-94 parts of fine-grained tungsten carbide, 6-10 parts of cobalt and 0.4-0.8 parts of chromium carbide are mixed, and then 2-4 parts of paraffin wax and 50-60 parts of anhydrous ethanol are added for the first ball milling, and then dried to obtain material A; 90-94 parts of coarse-grained tungsten carbide and 6-10 parts of cobalt are mixed, and then 2-4 parts of paraffin wax and 40-50 parts of anhydrous ethanol are added for the second ball milling, and then dried to obtain material B; S2: 10-20 parts of material A and 80-90 parts of material B are mixed, pressed and sintered to obtain cemented carbide for hard rock deep drilling.

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