A cemented carbide for drill tools and a method for producing the same

Abstract

The present application relates to the field of hard alloy material, in particular to a kind of hard alloy for drilling tool and preparation method thereof, made of hard phase and binder phase;The binder phase is composed of microcrystalline wax and hydroxyl functionalized hyperbranched polyethylene, the hard alloy prepared in the application has higher bending strength and hardness, and excellent wear resistance, is high-quality raw material for preparing special-shaped drilling tool.

Description

Technical Field

[0001] This invention relates to the field of cemented carbide materials, specifically to a cemented carbide for drilling tools and its preparation method. Background Technology

[0002] Cemented carbide is an alloy material made by forming and sintering a refractory metal carbide hard phase (WC, TiC) as the main component, with the addition of a metallic binder phase (Co, Ni, Mo, etc.). Cemented carbide possesses high hardness, strength, and excellent wear resistance, corrosion resistance, and many other superior properties. Often referred to as the "teeth of modern industry," it is widely used in defense, aerospace, electronics and communications, metallurgy, cutting tools, drilling tools, and many other fields.

[0003] Traditional cemented carbide production methods, such as pressing and sintering, can only produce products with simple shapes, and subsequent machining costs are high, material utilization is low, and production efficiency is low. These drawbacks have greatly limited the wider application and development of cemented carbide products. The unparalleled advantages of injection molding technology have brought new opportunities for the application and development of irregularly shaped cemented carbide parts with high melting points and difficult machining, such as irregularly shaped drill bits.

[0004] Currently, the mainstream binder for cemented carbide injection molding technology is paraffin-based binder. Paraffin-based binders have advantages such as low melting point, low viscosity, high loading capacity, and wide injection temperature range. However, they are prone to two-phase separation during the mixing process, which can adversely affect the performance of the prepared cemented carbide. Summary of the Invention

[0005] Purpose of the invention: In view of the above-mentioned technical problems, the present invention proposes a cemented carbide for drilling tools and its preparation method.

[0006] The technical solution adopted is as follows:

[0007] A cemented carbide for drilling tools, made of a hard phase and a binder phase;

[0008] The binder phase consists of microcrystalline wax and hydroxyl-functionalized hyperbranched polyethylene.

[0009] Furthermore, the mass ratio of the hard phase to the binder phase is 3-5:1.

[0010] Furthermore, the hard phase is composed of tungsten carbide and cobalt powder.

[0011] Furthermore, the mass ratio of the microcrystalline wax to the hydroxyl-functionalized hyperbranched polyethylene is 1-3:1.

[0012] Furthermore, the hydroxyl-functionalized hyperbranched polyethylene is obtained by reacting hyperbranched polyethylene with mercaptoalkyl alcohol.

[0013] Furthermore, the mercaptoalkyl alcohol has ≥6 carbon atoms.

[0014] Furthermore, the preparation method of the hydroxyl-functionalized hyperbranched polyethylene is as follows:

[0015] Under nitrogen protection, a mixture of free radical initiator, hyperbranched polyethylene, mercaptoalkyl alcohol and toluene is heated to 80-100℃ and kept at this temperature for 12-48 hours. After the mixture is brought back to room temperature, water is added for extraction, the organic phase is separated by vacuum distillation, and purified by column chromatography.

[0016] This invention also provides a method for preparing cemented carbide for drilling tools:

[0017] The hard phase and the binder phase are mixed and then injection molded to obtain a blank. The blank is then degreased and sintered to obtain the cemented carbide.

[0018] Furthermore, the mixing temperature is 180-190℃, and the mixing time is 1-2 hours.

[0019] Furthermore, the sintering temperature is 1400-1500℃, and the sintering time is 2-4 hours.

[0020] It has the following beneficial effects:

[0021] This invention provides a cemented carbide for drilling tools. Traditional cemented carbide injection molding typically uses paraffin-based binders in thermoplastic systems. However, paraffin-based binders have significant drawbacks, such as the tendency for phase separation during mixing, which adversely affects the performance of the final cemented carbide. In this invention, the binder phase consists of microcrystalline wax and hydroxyl-functionalized hyperbranched polyethylene. Compared to paraffin, microcrystalline wax has a higher melting point and viscosity, as well as better toughness and ductility. Using microcrystalline wax as the main binder component can improve the defects of paraffin-based binders, such as easy volatility and phase separation. The unique hyperbranched structure of hydroxyl-functionalized hyperbranched polyethylene can serve as a skeleton component to effectively support the green body during degreasing. The hydroxyl groups can not only form hydrogen bonds or chemical adsorption with hydrogen-containing groups on the surface of the hard phase, improving the wettability between the binder phase and the hard phase and further inhibiting phase separation, but also disperse the hard phase particles through electrostatic repulsion, reducing their agglomeration, thereby improving the uniformity of the green body and laying a good foundation for subsequent sintering. The cemented carbide prepared by this invention has high bending strength and hardness, as well as excellent wear resistance, making it a high-quality raw material for preparing special-shaped drill bits. Attached Figure Description

[0022] Figure 1 The reaction equation for preparing hydroxyl-functionalized hyperbranched polyethylene in Example 1 is shown. Detailed Implementation

[0023] Unless otherwise specified in the examples, the conditions were performed under standard conditions or as recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products. Techniques not mentioned in this invention refer to existing technologies. Unless otherwise specified, the following examples and comparative examples are parallel experiments, using the same processing steps and parameters.

[0024] This invention provides a cemented carbide for drilling tools, which is made of a hard phase and a binder phase;

[0025] The binder phase consists of microcrystalline wax and hydroxyl-functionalized hyperbranched polyethylene.

[0026] Traditional cemented carbide injection molding typically uses paraffin-based binders in thermoplastic systems. However, paraffin-based binders have significant drawbacks, such as the tendency for phase separation during mixing, which negatively impacts the performance of the final cemented carbide. This invention utilizes a binder phase composed of microcrystalline wax and hydroxyl-functionalized hyperbranched polyethylene. Compared to paraffin, microcrystalline wax has a higher melting point and viscosity, as well as better toughness and ductility. Using microcrystalline wax as the main binder component overcomes the volatilization and phase separation issues inherent in paraffin-based binders. The unique hyperbranched structure of hydroxyl-functionalized hyperbranched polyethylene effectively supports the preform during debinding, acting as a skeletal component. The hydroxyl groups not only form hydrogen bonds or undergo chemical adsorption with hydrogen-containing groups on the surface of the hard phase, improving wettability between the binder and hard phases and further inhibiting phase separation, but also disperse hard phase particles through electrostatic repulsion, reducing agglomeration and improving the uniformity of the preform, thus laying a solid foundation for subsequent sintering.

[0027] The mass ratio of the hard phase to the binder phase is 3-5:1.

[0028] The specific mass ratio of the hard phase to the binder phase can be 3:1, 3.1:1, 3.2:1, 3.3:1, 3.4:1, 3.5:1, 3.6:1, 3.7:1, 3.8:1, 3.9:1, 4:1, 4.1:1, 4.2:1, 4.3:1, 4.4:1, 4.5:1, 4.6:1, 4.7:1, 4.8:1, 4.9:1, or 5:1. These ratios are merely examples to aid understanding and are not intended to be limiting.

[0029] The hard phase is composed of tungsten carbide and cobalt powder.

[0030] Tungsten carbide is a ceramic material with extremely high hardness, exhibiting excellent wear resistance and high-temperature stability. Cobalt is a common metallic element with good machinability and ductility. Adding cobalt powder to tungsten carbide powder helps maintain its toughness and machinability. Hard alloys composed of tungsten carbide and cobalt powder can be widely used in the manufacture of cutting tools, drills, abrasives, and wear-resistant parts.

[0031] The mass ratio of tungsten carbide to cobalt powder is 5-15:1, preferably 9:1.

[0032] The mass ratio of the microcrystalline wax to the hydroxyl-functionalized hyperbranched polyethylene is 1-3:1.

[0033] The specific mass ratio of microcrystalline wax to hydroxyl-functionalized hyperbranched polyethylene can be 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1, 2.5:1, 2.6:1, 2.7:1, 2.8:1, 2.9:1, or 3:1. These ratios are merely examples to aid understanding and are not intended to be limiting.

[0034] The hydroxyl-functionalized hyperbranched polyethylene is obtained by reacting hyperbranched polyethylene with mercaptoalkyl alcohol.

[0035] This invention prepares hydroxyl-functionalized hyperbranched polyethylene by a click reaction of hyperbranched polyethylene (Mn=560 g / mol, PDI=1.3) with mercaptoalkyl alcohols via a thiol-olefin reaction. Mercaptoalkyl alcohols specifically refer to a class of non-aromatic organic compounds containing both thiol (-SH) and hydroxyl (-OH) functional groups.

[0036] Specifically, mercaptoalkyl alcohols can be 2-mercaptoethanol, 3-mercaptopropanol, 4-mercaptobutanol, 5-mercaptopentanol, 6-mercaptohexanol, 7-mercaptoheptanol, 8-mercaptooctanol, 9-mercaptobenol, and 10-mercaptodecanol. The above compounds are merely examples to aid understanding and are not intended to limit the choice of compounds; other branched structures may also be used.

[0037] The mercaptoalkyl alcohol has ≥6 carbon atoms. Long-chain alkyl groups can further improve the wettability between the binder phase and the hard phase, and reduce the tendency for particle aggregation.

[0038] The preparation method of the hydroxyl-functionalized hyperbranched polyethylene is as follows:

[0039] Under nitrogen protection, a mixture of free radical initiator, hyperbranched polyethylene, mercaptoalkyl alcohol and toluene is heated to 80-100℃ and kept at this temperature for 12-48 hours. After the mixture is brought back to room temperature, water is added for extraction, the organic phase is separated by vacuum distillation, and purified by column chromatography.

[0040] Specifically, under nitrogen protection, a free radical initiator, hyperbranched polyethylene, mercaptoalkyl alcohol and toluene are mixed and heated to 80-100℃. After reacting at this temperature for 12-48 hours, the mixture is restored to room temperature. Water is added to extract the remaining mercaptoalkyl alcohol, the organic phase is separated and purified by vacuum distillation, column chromatography (DCM:MeOH=1:1), and finally the eluent is removed by vacuum distillation.

[0041] A method for preparing cemented carbide for drilling tools:

[0042] The hard phase and the binder phase are mixed and then injection molded to obtain a blank. The blank is then degreased and sintered to obtain the cemented carbide.

[0043] Specifically, tungsten carbide and cobalt powder are mixed, ball-milled, and vacuum-dried to obtain a hard phase. The hard phase is added and mixed in a Banbury mixer at 180-190℃. Microcrystalline wax and hydroxyl-functionalized hyperbranched polyethylene are then added and mixed for 1-2 hours. The mixture is then removed, crushed into feedstock, and injection molded to obtain a preform. The injection molding parameters are: injection temperature 120±10℃, injection pressure 50±5MPa, and mold temperature 50±10℃. After demolding, the preform is immersed in n-heptane at 40±5℃ for solvent degreasing for 10 hours. It is then placed in a muffle furnace and heated to 650℃ at a rate of 1℃ / min for hot degreasing for 30 minutes, followed by sintering at 1400-1500℃ at a rate of 5℃ / min for 2-4 hours.

[0044] The mixing temperature is 180-190℃, and the mixing time is 1-2 hours.

[0045] The sintering temperature is 1400-1500℃, and the sintering time is 2-4h.

[0046] Example 1:

[0047] A cemented carbide for drilling tools is made of a hard phase and a binder phase in a mass ratio of 4:1;

[0048] The hard phase consists of tungsten carbide and cobalt powder in a mass ratio of 9:1.

[0049] The binder phase consists of microcrystalline wax and hydroxyl-functionalized hyperbranched polyethylene in a mass ratio of 2:1;

[0050] The preparation method of hydroxyl-functionalized hyperbranched polyethylene is as follows:

[0051] Under nitrogen protection, a mixture of free radical initiator AIBN (0.82 g, 5 mmol), hyperbranched polyethylene (5.6 g, 10 mmol), 6-mercaptohexanol (13.4 g, 100 mmol), and 50 mL of toluene was heated to 85 °C and reacted for 24 h. The mixture was then brought to room temperature, and 50 mL of water was added for extraction. The organic phase was separated and purified by vacuum distillation, followed by column chromatography (DCM:MeOH = 1:1). Finally, the eluent was removed by vacuum distillation. The specific reaction equation is shown in [reference needed]. Figure 1 .

[0052] The preparation method of the above-mentioned cemented carbide for drilling tools is as follows:

[0053] Tungsten carbide and cobalt powder were added to a ball mill jar and mixed in a planetary ball mill at 400 rpm for 12 hours using anhydrous ethanol as the milling medium. After mixing, the mixture was vacuum dried to obtain a hard phase. The internal mixer temperature was set to 185℃, and the hard phase was added and mixed for 30 minutes. Then, microcrystalline wax and hydroxyl-functionalized hyperbranched polyethylene were added and mixed for 1.5 hours. The mixture was then removed, crushed into feedstock, and injection molded to obtain a preform. The injection molding parameters were: injection temperature 120±10℃, injection pressure 50±5MPa, and mold temperature 50±10℃. After demolding, the preform was obtained and immersed in n-heptane at 40±5℃ for solvent degreasing for 10 hours. It was then placed in a muffle furnace and heated to 650℃ at a rate of 1℃ / min for hot degreasing for 30 minutes, followed by sintering at 1450℃ at a rate of 5℃ / min for 3 hours.

[0054] Example 2:

[0055] A cemented carbide for drilling tools is made of a hard phase and a binder phase in a mass ratio of 5:1;

[0056] The hard phase consists of tungsten carbide and cobalt powder in a mass ratio of 9:1.

[0057] The binder phase consists of microcrystalline wax and hydroxyl-functionalized hyperbranched polyethylene in a mass ratio of 3:1;

[0058] The preparation method of hydroxyl-functionalized hyperbranched polyethylene is as follows:

[0059] Under nitrogen protection, free radical initiator AIBN (0.82 g, 5 mmol), hyperbranched polyethylene (5.6 g, 10 mmol), 6-mercaptohexanol (13.4 g, 100 mmol) and 50 ml of toluene were mixed and heated to 85 °C. After reacting at this temperature for 24 h, the mixture was brought to room temperature, and 50 ml of water was added for extraction. The organic phase was separated and purified by vacuum distillation, column chromatography (DCM:MeOH = 1:1), and finally the eluent was removed by vacuum distillation.

[0060] The preparation method of the above-mentioned cemented carbide for drilling tools is as follows:

[0061] Tungsten carbide and cobalt powder were added to a ball mill jar and mixed in a planetary ball mill at 400 rpm for 12 hours using anhydrous ethanol as the milling medium. After mixing, the mixture was vacuum dried to obtain a hard phase. The internal mixer temperature was set to 190℃, and the hard phase was added and mixed for 30 minutes. Then, microcrystalline wax and hydroxyl-functionalized hyperbranched polyethylene were added and mixed for 2 hours. The mixture was then removed, crushed into feedstock, and injection molded to obtain a preform. The injection molding parameters were: injection temperature 120±10℃, injection pressure 50±5MPa, and mold temperature 50±10℃. After demolding, the preform was obtained and immersed in n-heptane at 40±5℃ for solvent degreasing for 10 hours. It was then placed in a muffle furnace and heated to 650℃ at a rate of 1℃ / min for hot degreasing for 30 minutes, followed by sintering at 1500℃ at a rate of 5℃ / min for 4 hours.

[0062] Example 3:

[0063] A cemented carbide for drilling tools is made of a hard phase and a binder phase in a mass ratio of 3:1;

[0064] The hard phase consists of tungsten carbide and cobalt powder in a mass ratio of 9:1.

[0065] The binder phase consists of microcrystalline wax and hydroxyl-functionalized hyperbranched polyethylene in a mass ratio of 1:1;

[0066] The preparation method of hydroxyl-functionalized hyperbranched polyethylene is as follows:

[0067] Under nitrogen protection, free radical initiator AIBN (0.82 g, 5 mmol), hyperbranched polyethylene (5.6 g, 10 mmol), 6-mercaptohexanol (13.4 g, 100 mmol) and 50 ml of toluene were mixed and heated to 85 °C. After reacting at this temperature for 24 h, the mixture was brought to room temperature, and 50 ml of water was added for extraction. The organic phase was separated and purified by vacuum distillation, column chromatography (DCM:MeOH = 1:1), and finally the eluent was removed by vacuum distillation.

[0068] The preparation method of the above-mentioned cemented carbide for drilling tools is as follows:

[0069] Tungsten carbide and cobalt powder were added to a ball mill jar and mixed in a planetary ball mill at 400 rpm for 12 hours using anhydrous ethanol as the milling medium. After mixing, the mixture was vacuum dried to obtain a hard phase. The internal mixer temperature was set to 180℃, and the hard phase was added and mixed for 30 minutes. Then, microcrystalline wax and hydroxyl-functionalized hyperbranched polyethylene were added and mixed for 1-2 hours. The mixture was then removed, crushed into feedstock, and injection molded to obtain a preform. The injection molding parameters were: injection temperature 120±10℃, injection pressure 50±5MPa, and mold temperature 50±10℃. After demolding, the preform was obtained and immersed in n-heptane at 40±5℃ for solvent degreasing for 10 hours. It was then placed in a muffle furnace and heated to 650℃ at a rate of 1℃ / min for hot degreasing for 30 minutes, followed by sintering at 1400℃ at a rate of 5℃ / min for 2 hours.

[0070] Comparative Example 1:

[0071] It is basically the same as Example 1, except that low-density polyethylene is used instead of hydroxyl-functionalized hyperbranched polyethylene.

[0072] Comparative Example 2:

[0073] The composition is basically the same as in Example 1, except that the binder phase has the following composition:

[0074] Paraffin 63 wt.%, polyethylene glycol 12 wt.%, low-density polyethylene 24 wt.%, stearic acid 1 wt.

[0075] Performance testing:

[0076] The cemented carbide samples from Examples 1-3 and Comparative Examples 1-2 of the present invention were prepared as specimens.

[0077] According to GB / T 232-2010 "Metallic Materials - Bending Test Method", a WDW-5E microcomputer-controlled electronic universal testing machine was used to conduct three-point bending tests on the specimens, with a span of 20 mm and a compression speed of 0.1 mm·min. -1 .

[0078] The HRA hardness of the samples was measured using an HR-150A Rockwell hardness tester (with a load of 60 kg and a diamond cone indenter with a 120° apex angle). During the operation, the sample surface was ground and polished to keep it flat. Five different areas on the sample surface were selected for testing, and the average value was taken as the final hardness test result.

[0079] Wear resistance was measured on an automatic grinding and polishing machine with a pressure of 60 N, a diamond grinding disc diameter of 30 cm, a grit size of 125 μm, a rotation speed of 250 r / min, and a grinding time of 30 min. The sample dimensions were 5.25 mm × 6.5 mm × 21 mm. The sample surface was first surface-ground, and three samples were symmetrically fixed at once using a specific fixture. The mass was measured using an AL204 analytical balance with a measurement accuracy of 0.0001 g. Simultaneously, the density of the samples was accurately measured to calculate the wear volume, and the average value was taken.

[0080] The test results are shown in Table 1 below:

[0081]

[0082] As shown in Table 1 above, the cemented carbide prepared by the present invention has high bending strength and hardness, and excellent wear resistance.

[0083] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A cemented carbide for drill tools, characterized in that, made of hard phase, metal binder phase and binder; the binder is made of microcrystalline wax and hydroxyl functionalized hyperbranched polyethylene.

2. The cemented carbide for a drill according to claim 1, wherein The mass ratio of the sum of the mass of the hard phase and the metal binder phase to the mass of the binder is 3-5:

1.

3. The cemented carbide for a drill according to claim 1, wherein The hard phase is tungsten carbide and the metal binder phase is cobalt powder.

4. The cemented carbide for a drill according to claim 1, wherein The mass ratio of the microcrystalline wax to the hydroxyl functionalized hyperbranched polyethylene is 1-3:

1.

5. The cemented carbide for a drill according to claim 1, wherein The hydroxyl functionalized hyperbranched polyethylene is obtained by reacting hyperbranched polyethylene and mercaptoalkyl alcohol.

6. The cemented carbide for a drill according to claim 5, wherein The mercaptoalkyl alcohol has a carbon atom number of ≥6.

7. The cemented carbide for a drill according to claim 5, wherein The preparation method of the hydroxyl functionalized hyperbranched polyethylene is as follows: Under nitrogen protection, the free radical initiator, hyperbranched polyethylene, mercaptoalkyl alcohol and toluene are mixed and heated to 80-100℃, and after 12-48h of incubation, the reaction is restored to room temperature, water is added for extraction, the organic phase is separated and distilled under reduced pressure, and column chromatography purification is performed.

8. A method of producing a cemented carbide for a drilling tool as claimed in any one of claims 1 to 7, characterized in that, The hard phase, the metal binder phase and the binder are mixed and injection molded to obtain a blank, and the blank is debound and sintered to obtain the hard alloy.

9. The method of producing a cemented carbide for a drill according to claim 8, wherein The mixing temperature is 180-190℃ and the mixing time is 1-2h.

10. The method of producing a cemented carbide for a drill according to claim 8, wherein The sintering temperature is 1400-1500℃ and the sintering time is 2-4h.

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