A cemented carbide material for drill bits and a method of manufacturing the same

Abstract

The application discloses a cemented carbide for drill bits and a preparation method thereof. The cemented carbide for drill bits is obtained by sintering raw material powder, and the raw material powder comprises the following components in mass fractions: 30-50 parts of 2-3 mu m first tungsten carbide grains, 40-60 parts of 9-12 mu m second tungsten carbide grains, 10-17 parts of 0.6-1.5 mu m cobalt powder, 1-2.1 parts of a metallographic regulator, wherein the metallographic regulator comprises 90.5-91.2 wt% nickel and 7.8-9.5 wt% carbon nanotubes. The coarse-grained and fine-grained tungsten carbide in the alloy microstructure is reasonably matched, and the metallographic regulator obtained by a specific preparation method is added, wherein the metallographic regulator is uniformly dispersed with more carbon nanotubes with complete structures. The performance is enhanced by the carbon nanotubes, the metallographic structure of the sintering interface of the alloy is changed, and finally the toughness and wear resistance of the alloy material are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to oilfield drill bits, in particular to a hard alloy material for drill bits and a preparation method thereof. BACKGROUND

[0002] The drilling depth of oilfields is generally thousands of meters or even tens of thousands of meters, and the construction period is long. If the alloy teeth appear abnormal conditions such as poor wear resistance, broken teeth and corrosion during drilling, the drilling construction will be stopped, the construction period will be extended, and even the drilling will be scrapped. The alloy teeth used in the three-cone drill bit must have excellent wear resistance, toughness and corrosion resistance at the same time to ensure smooth drilling to the designed depth of the oil well.

[0003] The alloy teeth (hereinafter referred to as oilfield teeth) used in the current three-cone drill bit are generally tungsten-cobalt alloys, mainly composed of tungsten carbide and cobalt, with a cobalt content of about 10% to 17% and a tungsten carbide particle size of about 2.4 to 3.6 μm, which is a coarse-grained alloy. The wear resistance and toughness of tungsten-cobalt alloy are a pair of contradictions. The wear resistance is provided by tungsten carbide, while the toughness is provided by cobalt. Generally, the finer the tungsten carbide grains, the less the cobalt content, the higher the hardness, the better the wear resistance, and the worse the toughness. Conversely.

[0004] The hardness of the conventional ordinary coarse-grained oilfield teeth is generally 85.0 to 87.5, and the wear is fast. The service life is generally short during use, and the drilling depth is low. In order to overcome this problem, the number of teeth on the drill bit is increased, and the diameter of the teeth is increased to reduce the wear rate of single teeth and improve the service life of the drill bit. However, this increases the material cost. SUMMARY

[0005] In order to improve the service life of the drill bit, a hard alloy for drill bits and a preparation method thereof are provided.

[0006] The above first invention purpose of the present application is realized by the following technical scheme:

[0007] A hard alloy for drill bits is obtained by sintering raw material powder, and the raw material powder comprises the following components in mass fraction:

[0008] 30 to 50 parts of first tungsten carbide grains,

[0009] 40 to 60 parts of second tungsten carbide grains,

[0010] 10 to 17 parts of cobalt powder,

[0011] The particle size of the first tungsten carbide grains is 2 to 3 μm, and the particle size of the second tungsten carbide grains is 9 to 12 μm,

[0012] The particle size of the cobalt powder is 0.6 to 1.5 μm;

[0013] Metal phase adjuster 1-2.1 parts, metal phase adjuster particle size is 9-12 microns, metal phase adjuster is obtained by coating carbon nanotubes with nickel.

[0014] The preparation method of the metal phase adjuster is as follows:

[0015] The carbon nanotubes and the dispersion medium are mixed into a mixed solution, the mixed solution is uniformly stirred, then sprayed on a nickel foil, and after drying, another layer of nickel foil is covered, and a composite film is obtained by rolling;

[0016] The metal phase adjuster of the required particle size is obtained by cutting and ball milling the composite film.

[0017] By adopting the above technical scheme, two kinds of tungsten carbide powders with different particle sizes are used as raw materials, the coarse grain and fine grain tungsten carbide in the alloy structure are reasonably matched, the fine grain has high hardness to provide wear resistance, and the coarse grain can resist crack propagation to provide toughness,

[0018] In addition, the carbon nanotubes are first dispersed in the mixed solution, then transferred between the two layers of nickel foil, and then ball milled. The carbon nanotubes are located between the two layers of nickel foil, reducing the possibility of deformation or even breaking of the carbon nanotubes during ball milling due to collision with high-speed rotating abrasives. At the same time, the abrasives are used for grinding to form a strong bond between the carbon nanotubes and the nickel, and then the carbon nanotubes are more complete and uniformly dispersed in the metal phase adjuster after ball milling. The metal phase adjuster is mixed with other raw materials for sintering, the metal of the metal phase adjuster forms a eutectic body with cobalt and forms an alloy with tungsten carbide, and the carbon nanotubes are more complete and brought into the alloy material. Through the performance enhancement and change of the alloy sintering interface brought by the carbon nanotubes, the coarse grain and fine grain tungsten carbide combination interface has high strength and good toughness, thereby amplifying the coarse grain and fine grain tungsten carbide combination effect, finally significantly improving the toughness and wear resistance of the alloy material, and obtaining a material with good comprehensive performance.

[0019] Optionally, the dispersion medium is a mixture of ethanol and polyethylene glycol 400.

[0020] By adopting the above technical scheme, ethanol is a good dispersion system for carbon nanotubes, and polyethylene glycol 400 is used as a surfactant to promote the dispersion of carbon nanotubes, so that the carbon nanotubes are more uniformly distributed on the nickel foil, and the obtained metal phase adjuster has better effect. In addition, polyethylene glycol 400 can adjust the viscosity of the mixed solution, facilitate the adhesion of the mixed solution on the nickel foil, and facilitate production.

[0021] Optionally, the mass ratio of isopropyl alcohol to polyethylene glycol in the dispersion medium is 100:(1.8-2.6).

[0022] By adopting the above technical scheme, the alloy has good toughness and wear resistance.

[0023] Optionally, the cobalt powder is spherical cobalt powder with a purity greater than 99.4wt%.

[0024] By adopting the above technical scheme, the cobalt powder is high-purity spherical cobalt powder with a particle size of 0.6-1.5 microns, as a binder phase, the binding interface metallographic structure after sintering of the cobalt powder and tungsten carbide is more compact, the toughness is better, and the comprehensive performance of the alloy is better.

[0025] Optionally, the first tungsten carbide grains and the second tungsten carbide grains are subjected to high-temperature carbonization treatment, and the high-temperature carbonization treatment temperature is not less than 1750 DEG C and is lower than the melting point of tungsten carbide.

[0026] By adopting the above technical scheme, after high-temperature carbonization treatment at 1750-2100 DEG C, the tungsten carbide has complete crystallization, complete grain boundary, high hardness and good toughness compared with ordinary tungsten carbide, and is not easy to be ground in the ball milling process; and at the sintering temperature of 1430-1500 DEG C of the alloy material, the tungsten carbide grains are not easy to abnormally grow, so that the comprehensive performance of the alloy is better and more stable.

[0027] Optionally, 0.1-0.5 parts of a binder strengthening phase are further included, and the binder strengthening phase is a soluble rare earth salt.

[0028] By adopting the above technical scheme, trace rare metal elements and rare earth elements are added to improve the comprehensive performance of the material.

[0029] Optionally, the binder strengthening phase is a compound of ytterbium salt and yttrium salt.

[0030] By adopting the above technical scheme, the obtained alloy material has better comprehensive performance.

[0031] The above second invention purpose of the application is realized by the following technical scheme:

[0032] A preparation method of a hard alloy for a drill bit, comprising the following steps:

[0033] The raw materials are weighed according to the amount ratio, the first tungsten carbide grains are taken as raw material group A, the second tungsten carbide grains are taken as raw material group B, and the remaining other raw materials are mixed to be taken as raw material group C,

[0034] The raw material group A, part of the raw material group C and grinding medium are added into a ball mill for ball milling to obtain slurry A,

[0035] The raw material group B, the remaining raw material group C and grinding medium are added into a ball mill for ball milling to obtain slurry B,

[0036] After the slurry A and the slurry B are uniformly mixed, slurry C is obtained,

[0037] The slurry C is spray dried to obtain a mixed material,

[0038] After the mixture is pressed and sintered, a sintered blank tooth is obtained.

[0039] By adopting the technical scheme, the tungsten carbide of different particle sizes is ball milled in different processes, the coarse particle tungsten carbide is ball milled for a short time, the fine particle tungsten carbide is ball milled for a long time, the tungsten carbide is separately ball milled in different ball-to-material ratios and ball milling medium amounts, the tungsten carbide is in the best ball milling state, and the toughness and wear resistance of the obtained alloy material are better.

[0040] In summary, the present application has at least the following beneficial effects:

[0041] 1. The coarse grain and fine grain tungsten carbide in the alloy structure are reasonably matched, and a metallographic regulator obtained by a specific preparation method is added, a large number of carbon nanotubes with complete structure are uniformly dispersed in the metallographic regulator, the performance is enhanced and the metallographic structure of the sintering interface of the alloy is changed through the carbon nanotubes, and finally the toughness and wear resistance of the alloy material are improved;

[0042] 2. The tungsten carbide is subjected to high-temperature carbonization treatment at 1750-2100°C, the tungsten carbide has complete crystallization and grain boundary, has high hardness and good toughness compared with ordinary tungsten carbide, and is not easy to be ground in the ball milling process; and at the sintering temperature of 1430-1500°C of the alloy material, the tungsten carbide grains are not easy to abnormally grow, so that the comprehensive performance of the alloy is better and more stable;

[0043] 3. The two kinds of tungsten carbide are separately ball milled, the tungsten carbide is in the best ball milling state, and the toughness and wear resistance of the obtained alloy material are better. DETAILED DESCRIPTION

[0044] Raw materials

[0045] Tungsten carbide grains: The purity is 99.9wt%, and there are two particle size specifications, 2-3μm and 9-12μm. The commercially available products are obtained after secondary screening.

[0046] Cobalt powder: There are two specifications of raw materials; spherical cobalt powder, the purity is 99.9wt%, and the particle size is 0.6-1.5μm. The commercially available products are obtained after secondary screening; polyhedral cobalt powder, the purity is 99.9wt%, and the particle size is 0.6-1.5μm. The commercially available products are obtained after secondary screening.

[0047] Bonding strengthening phase: It is a soluble rare earth salt, specifically ytterbium(III) acetate tetrahydrate and yttrium acetate tetrahydrate.

[0048] Nickel foil: pure nickel foil, the purity is 99.96wt%, the thickness is 0.02mm, and the gram weight is 178g / m 2 , which is customized in Shanghai Laminate Metal Material Technology Co., Ltd.

[0049] Nickel powder: purity of 99.96wt%, particle size of 9-12μm, customized by Shanghai Laminate Metal Material Technology Co., Ltd.

[0050] Carbon nanotube: single-walled carbon nanotube, tube diameter of 10-15nm, tube length of 5-8μm, purity of ≥98wt%, ash content of ≤2%, specific surface area of 150-250, customized by Shandong Carbon Peak New Material Technology Co., Ltd.

[0051] Polyethylene glycol 400, ethanol, polyethylene glycol 800 are commercially available analytical grade products.

[0052] Preparation Example 1

[0053] A metallographic modifier, the main components of which are nickel and carbon nanotubes.

[0054] The specific preparation method is as follows:

[0055] Mix the carbon nanotubes and the dispersion medium in a mass ratio of 27.8:100 to obtain a mixed solution, and the dispersion medium is obtained by mixing ethanol and polyethylene glycol 400 in a mass ratio of 100:1.8;

[0056] Unfold a piece of nickel foil to obtain a first nickel foil, spray the mixed solution onto the first nickel foil, and then spray again after drying. After multiple spraying, the spraying amount of carbon nanotubes reaches 32g / m 2 ;

[0057] Take another piece of nickel foil as a second nickel foil, align and cover the second nickel foil on the carbon nanotube spraying surface, and then press roll the first nickel foil and the second nickel foil under a roll pressure of 0.04MPa. Trim and cut off the misaligned part of the edge to obtain a composite film.

[0058] Cut the composite film into 1cm×1cm fragments, and then gradually ball mill in a ball mill to obtain a metallographic modifier with a particle size of 9-12μm.

[0059] After testing, the nickel content is 90.92wt%, the carbon nanotube content is 9.05wt%, and the rest is unavoidable impurities.

[0060] Preparation Example 2

[0061] A metallographic modifier, which is different from Preparation Example 1 in that the mixed medium of the mixed solution is dichloromethane.

[0062] Preparation Example 3

[0063] A metallographic modifier, which is different from Preparation Example 1 in that the mixed medium of the mixed solution is obtained by mixing ethanol and polyethylene glycol 400 in a mass ratio of 100:0.8.

[0064] Preparation Example 4

[0065] A metallographic regulator, which is different from Preparation Example 1 in that the mixed medium of the mixed solution is obtained by mixing ethanol and polyethylene glycol 400 at a mass ratio of 100:1.3.

[0066] Preparation Example 5

[0067] A metallographic regulator, which is different from Preparation Example 1 in that the mixed medium of the mixed solution is obtained by mixing ethanol and polyethylene glycol 400 at a mass ratio of 100:2.1.

[0068] Preparation Example 6

[0069] A metallographic regulator, which is different from Preparation Example 1 in that the mixed medium of the mixed solution is obtained by mixing ethanol and polyethylene glycol 400 at a mass ratio of 100:2.6.

[0070] Preparation Example 7

[0071] A modified tungsten carbide grain, which is obtained by high-temperature carbonization treatment of 2-3 μm tungsten carbide grains as raw materials.

[0072] 2-3 μm tungsten carbide grains are uniformly mixed with polyethylene glycol 400 at a mass ratio of 100:1.2, and the polyethylene glycol 400 is carbonized at 1750°C in an argon atmosphere, the high-temperature carbonization treatment time is 7 h, after treatment, the temperature is lowered to 1500°C and kept for 3 h, and then natural cooling is carried out under argon protection, to obtain modified tungsten carbide grains.

[0073] Preparation Example 8

[0074] A modified tungsten carbide grain, which is different from Preparation Example 7 in that 9-12 μm tungsten carbide grains are uniformly mixed with polyethylene glycol 400 at a mass ratio of 100:6.4, and then prepared.

[0075] Example 1

[0076] A hard alloy for drill bits, which raw materials include first tungsten carbide grains, second tungsten carbide grains, cobalt powder, a metallographic regulator, and a bonding strengthening phase.

[0077] The first tungsten carbide grains are prepared by Preparation Example 7; the second tungsten carbide grains are prepared by Preparation Example 8; the cobalt powder is spherical cobalt powder; the metallographic regulator is prepared by Preparation Example 1; and the bonding strengthening phase is obtained by mixing ytterbium(III) acetate tetrahydrate and yttrium acetate tetrahydrate at a mass ratio of 4:3.3.

[0078] The specific preparation method is as follows:

[0079] 380 g of the first tungsten carbide grains are taken as raw material group A, 520 g of the second tungsten carbide grains are taken as raw material group B, 160 g of cobalt powder, 4 g of the bonding strengthening phase, and 18 g of the metallographic regulator are mixed as raw material group C;

[0080] The raw material group A, 85.7g of the raw material group C, and the grinding medium were added into a ball mill for ball milling, the grinding medium was added by 0.25L / kg (ground material), the grinding ball was φ5mm, 35r / min, the ball-to-material ratio was 4:1, the ball milling time was 30h, to obtain the slurry A, the raw material group B, 117.3g of the raw material group C, and the grinding medium were added into a ball mill for ball milling, the grinding medium was added by 0.15L / kg (ground material), the grinding ball was φ5mm, 22r / min, the ball-to-material ratio was 2:1, the ball milling time was 30h, to obtain the slurry B, the slurry A and the slurry B were mixed uniformly to obtain the slurry C,

[0081] The slurry C was spray dried to obtain the mixed material with a particle size of 400μm,

[0082] The mixed material was pressed to obtain the blank, and the blank was pressure sintered at a sintering temperature of 1480℃, a pressure sintering pressure of 7.5MPa, and a sintering time of 95min, to obtain the sintered blank.

[0083] The grinding medium was composed of 92wt% of ethanol, 6wt% of water, and 2wt% of polyethylene glycol (PEG800).

[0084] If a test sample was prepared, the mixed material was pressed to obtain the blank, and the blank was sintered to obtain the sample blank.

[0085] Comparative Example 1

[0086] A cemented carbide for drill bit, which is different from Example 1 in that the metallographic adjuster in the raw material is replaced by cobalt powder with equal mass.

[0087] Comparative Example 2

[0088] A cemented carbide for drill bit, which is different from Example 1 in that 18g of the metallographic adjuster in the raw material is replaced by 1.61g of carbon fiber tube and 16.39g of nickel powder.

[0089] Comparative Example 3

[0090] A cemented carbide for drill bit, which is different from Example 1 in that the tungsten carbide grains are single first tungsten carbide grains.

[0091] The difference of the preparation method is as follows:

[0092] 900g of the first tungsten carbide grains were taken as the raw material group A, 160g of cobalt powder, 4g of the bonding strengthening phase, and 18g of the metallographic adjuster were mixed as the raw material group C;

[0093] The raw material group A, the raw material group C, and the grinding medium were added into a ball mill for ball milling, the grinding medium was added by 0.25L / kg (ground material), the grinding ball was φ5mm, 35r / min, the ball-to-material ratio was 4:1, the ball milling time was 30h, to obtain the slurry A,

[0094] Spray drying the slurry A to obtain a mixture of 400 μm,

[0095] Pressing the mixture to obtain a blank, and pressure sintering the blank, the sintering temperature being 1480℃, the pressure sintering pressure being 7.5 MPa, and the sintering time being 95 min, to obtain a sintered blank.

[0096] The grinding medium is 92wt% of ethanol, 6wt% of water, and 2wt% of polyethylene glycol (polyethylene glycol 800).

[0097] Comparative Example 4

[0098] A cemented carbide for drill bits, which is different from Example 1 in that the second tungsten carbide grains are tungsten carbide grains of a single type.

[0099] The difference between the preparation methods is as follows:

[0100] 900g of the second tungsten carbide grains are taken as raw material group B, 160g of cobalt powder, 4g of the bonding strengthening phase, and 18g of the metallographic regulator are mixed as raw material group C;

[0101] The raw material group B, the raw material group C, and the grinding medium are added to a ball mill for ball milling, the grinding medium is added at an amount of 0.15L / kg (ground material), the grinding ball is φ5mm, the rotation speed is 22r / min, the ball-to-material ratio is 2:1, and the ball milling time is 30h to obtain a slurry B,

[0102] Spray drying the slurry B to obtain a mixture of 400 μm,

[0103] Pressing the mixture to obtain a blank, and pressure sintering the blank, the sintering temperature being 1480℃, the pressure sintering pressure being 7.5 MPa, and the sintering time being 95 min, to obtain a sintered blank.

[0104] The grinding medium is 92wt% of ethanol, 6wt% of water, and 2wt% of polyethylene glycol (polyethylene glycol 800).

[0105] Example 2

[0106] A cemented carbide for drill bits, which is different from Example 1 in that the metallographic regulator is prepared by Preparation Example 2.

[0107] Example 3

[0108] A cemented carbide for drill bits, which is different from Example 1 in that the metallographic regulator is prepared by Preparation Example 3.

[0109] Example 4

[0110] A cemented carbide for drill bits, which is different from Example 1 in that the metallographic regulator is prepared by Preparation Example 4.

[0111] Example 5

[0112] A hard metal for drill bits, which differs from Example 1 in that the metallographic modifier is prepared from Preparation Example 5.

[0113] Example 6

[0114] A hard metal for drill bits, which differs from Example 1 in that the metallographic modifier is prepared from Preparation Example 6.

[0115] Example 7

[0116] A hard metal for drill bits, which differs from Example 1 in that the cobalt powder in the raw materials is a polyhedral cobalt powder.

[0117] Example 8

[0118] A hard metal for drill bits, which differs from Example 1 in that the first tungsten carbide grains are 2-3 μm tungsten carbide grains that have not been subjected to high-temperature carbonization, and the second tungsten carbide grains are 9-12 μm tungsten carbide grains that have not been subjected to high-temperature carbonization.

[0119] Example 9

[0120] A hard metal for drill bits, which differs from Example 1 in that the binder strengthening phase is replaced by cobalt powder in equal mass.

[0121] Example 10

[0122] A hard metal for drill bits, which differs from Example 1 in that the binder strengthening phase is ytterbium(III) acetate tetrahydrate.

[0123] Example 11

[0124] A hard metal for drill bits, which differs from Example 1 in that the binder strengthening phase is yttrium acetate tetrahydrate.

[0125] Example 12

[0126] A hard metal for drill bits, which differs from Example 1 in that the preparation method is different, and is as follows:

[0127] 380 g of the first tungsten carbide grains are taken as raw material group A, and 520 g of the second tungsten carbide grains are taken as raw material group B. 160 g of cobalt powder, 4 g of the binder strengthening phase, and 18 g of the metallographic modifier are mixed as raw material group C;

[0128] The raw material group A, the raw material group B, the raw material group C, and the grinding medium are added to a ball mill for ball milling. The amount of the grinding medium is 0.25 L / kg (ground material), the grinding ball φ is 5 mm, the rotation speed is 35 r / min, the ball-to-material ratio is 3:1, and the ball milling time is 30 h, to obtain slurry C. The slurry C is spray dried to obtain a mixture of 400 μm,

[0129] The mixture is pressed into a blank, and the blank is pressure sintered at a sintering temperature of 1480℃, a pressure sintering pressure of 7.5MPa, and a sintering time of 95min, to obtain a sintered blank.

[0130] The grinding medium is 92wt% of ethanol, 6wt% of water, and 2wt% of polyethylene glycol (polyethylene glycol 800).

[0131] Example 13

[0132] A cemented carbide for drill bits, which differs from Example 1 in that the amounts of raw materials are different, specifically:

[0133] The raw material group A is 300g of first tungsten carbide grains;

[0134] The raw material group B is 400g of second tungsten carbide grains;

[0135] The raw material group C is 100g of cobalt powder, 1g of a bonding strengthening phase, and 10g of a metallographic regulator;

[0136] The raw material group A is ball milled with 53.6g of the raw material group C to obtain slurry A;

[0137] The raw material group B is ball milled with 71.4g of the raw material group C to obtain slurry B.

[0138] Example 14

[0139] A cemented carbide for drill bits, which differs from Example 1 in that the amounts of raw materials are different, specifically:

[0140] The raw material group A is 500g of first tungsten carbide grains;

[0141] The raw material group B is 600g of second tungsten carbide grains;

[0142] The raw material group C is 170g of cobalt powder, 5g of a bonding strengthening phase, and 20g of a metallographic regulator;

[0143] The raw material group A is ball milled with 98.6g of the raw material group C to obtain slurry A;

[0144] The raw material group B is ball milled with 118.4g of the raw material group C to obtain slurry B.

[0145] The alloy materials of Examples 1-14 and Comparative Examples 1-4 are detected, and the detection content is fracture toughness, wear resistance, and bending strength.

[0146] Fracture toughness: detected according to GB / T 23806-2009, and the detection result is expressed by fracture toughness MPa / m 2 .

[0147] Wear resistance: The detection was carried out according to GB / T 34501-2017, and the detection result was expressed by volume wear loss. The smaller the volume wear loss, the better the wear resistance.

[0148] Bending strength: The detection was carried out according to GB / T 3851-2015, and the detection result was expressed by bending strength. The detection result is shown in the following table.

[0149] Table 1. Detection results of examples 1-12 and comparative examples 1-4

[0150]

[0151]

[0152] From table 1, it can be seen that, compared with comparative example 1 and comparative examples 1-4, example 1 uses the metallographic modifier prepared in preparation example 1 and tungsten carbide grains with two particle sizes. Compared with example 1, comparative example 1 does not add the metallographic modifier; compared with example 1, comparative example 2 replaces the metallographic modifier with nickel powder and carbon nanotubes; compared with example 1, comparative example 3 only uses tungsten carbide grains with fine particle size; and compared with example 1, comparative example 4 only uses tungsten carbide grains with coarse particle size.

[0153] In the detection results, the fracture toughness and bending strength of example 1 are significantly greater than those of comparative examples 1-4, and the volume wear loss of example 1 is significantly smaller than that of comparative examples 1-4. However, the detection results of comparative examples 1-2 are not significantly better than those of comparative examples 3-4, and in some properties, they are even weaker than comparative examples 3-4.

[0154] This is achieved by the combined use of the metallographic modifier and tungsten carbide grains with two particle sizes in example 1. In example 1, two different particle sizes of tungsten carbide powder are used as raw materials, so that the coarse and fine tungsten carbide grains are reasonably matched in the alloy structure, the fine grains provide wear resistance due to high hardness, and the coarse grains provide toughness by resisting crack propagation. In the preparation process of the metallographic modifier in example 1, the two layers of nickel foil protect the carbon nanotubes, reducing the possibility of deformation or even breakage of the carbon nanotubes due to collision with the high-speed rotating grinding material during ball milling. The grinding of the grinding material forms a strong bond between the carbon nanotubes and nickel, and then the carbon nanotubes are more complete and uniformly dispersed in the metallographic modifier after ball milling. Subsequently, in the sintering process, the metals of the metallographic modifier and cobalt form a eutectic body and form an alloy with tungsten carbide, bringing the carbon nanotubes into the alloy material more completely. Through the performance enhancement and change of the alloy sintering interface brought by the carbon nanotubes, the coarse and fine tungsten carbide grain combination interface has high strength and good toughness, thereby amplifying the combination effect of coarse and fine tungsten carbide grains, and finally significantly improving the toughness and wear resistance of the alloy material, and obtaining a material with good comprehensive performance.

[0155] From comparative example 1 and example 2, it can be seen that the fracture toughness and bending strength of example 1 are greater than those of example 2, and the volume wear amount of example 1 is less than that of example 2, which is because the dispersion uniformity of carbon nanotubes in the mixed solution and the distribution on the nickel foil during the preparation process of the metallographic modifier used in example 1 are better than those of the metallographic modifier used in example 2, so the mixture of ethanol and polyethylene glycol 400 is preferably selected as the dispersion liquid of the metallographic modifier.

[0156] In combination with examples 3-6, the fracture toughness and bending strength of examples 1, 5-6 are greater than those of examples 3-4, and the volume wear amount of examples 1, 5-6 is less than that of examples 3-4; the fracture toughness and bending strength of example 5 are greater than those of example 6, and the volume wear amount of example 5 is less than that of example 6, so the mass ratio of nickel ethanol and polyethylene glycol 400 in the dispersion liquid in the application is 100:(1.8-2.6).

[0157] Comparative example 1 and example 7, the fracture toughness and bending strength of example 1 are greater than those of example 7, and the volume wear amount of example 1 is less than that of example 7, so it can be known that cobalt is used as a binder phase of an alloy material, and high-purity spherical cobalt powder is selected in the application, and the combined interface metallographic structure after sintering of the cobalt and tungsten carbide is more dense, the toughness is better, and the comprehensive performance of the alloy is better.

[0158] Comparative example 1 and example 8, the fracture toughness and bending strength of example 1 are greater than those of example 8, and the volume wear amount of example 1 is less than that of example 8, which is because the tungsten carbide after high-temperature carbonization treatment has complete crystal and complete grain boundary, and the hardness is high, and the toughness is good, and it is not easy to be ground during the ball milling process, and the tungsten carbide grains are not easy to abnormally grow at the sintering temperature of the alloy material of 1430-1500℃, so the alloy has better and more stable comprehensive performance.

[0159] Adding trace amounts of rare metal elements, rare earth elements, etc. to improve the comprehensive performance of the material. It can be verified from the comparison of example 1 and example 9 that the fracture toughness and bending strength of example 1 are greater than those of example 9, and the volume wear amount of example 1 is less than that of example 9.

[0160] In combination with examples 10-11, the fracture toughness and bending strength of example 1 are greater than those of examples 10-11, and the volume wear amount of example 1 is less than that of examples 10-11, so it can be known that the complex of ytterbium salt and yttrium salt is used as a binder strengthening phase in the application, and the comprehensive performance of the obtained alloy material is better.

[0161] In addition, the preparation method of the alloy in the application is also optimized. In Example 1, the milling processes of tungsten carbide with different particle sizes are not the same. The milling time of coarse-grained tungsten carbide is short, while the milling time of fine-grained tungsten carbide is required to be long. Different ball-to-material ratios and ball milling medium amounts are used for separate ball milling of the two kinds of tungsten carbide, so that the tungsten carbide can reach the best ball milling state. The fracture toughness and bending strength of Example 1 are greater than those of Example 12, and the volume wear amount of Example 1 is less than that of Example 12. The comprehensive performance of the alloy material obtained in Example 1 is better.

[0162] In combination with Comparative Examples 1-4 and Examples 13-14, the fracture toughness and bending strength of Examples 13-14 are significantly greater than those of Comparative Examples 1-4, and the volume wear amount of Examples 13-14 is significantly less than that of Comparative Examples 1-4. Therefore, in the application, the amount of alloy raw materials is controlled to be 30-50 parts of first tungsten carbide grains, 40-60 parts of second tungsten carbide grains, 10-17 parts of cobalt powder, 2.4-4.2 parts of metallographic adjuster, and 0.1-0.5 parts of bonding strengthening phase, so that the hard alloy for drill bits with excellent fracture toughness and wear resistance comprehensive performance can be obtained, and the service life of the drill bit is improved.

[0163] The specific embodiments are only an explanation of the application, and are not a limitation of the application. Those skilled in the art can make modifications to the embodiments without creative contribution after reading the specification, as long as the modifications are within the scope of the application.

Claims

1. A cemented carbide for drill bits, characterized in that, Sintered from raw material powder, the raw material powder comprises the following components in mass fraction: 30-50 parts of first tungsten carbide grains, 40-60 parts of second tungsten carbide grains, 10-17 parts of cobalt powder, The particle size of the first tungsten carbide grains is 2-3 μm, the particle size of the second tungsten carbide grains is 9-12 μm, The particle size of the cobalt powder is 0.6-1.5 μm; 1-2.1 parts of metallographic regulator, the particle size of the metallographic regulator is 9-12 μm, the metallographic regulator is obtained by coating carbon nanotubes with nickel, The preparation method of the metallographic regulator is as follows: Mixing carbon nanotubes and a dispersion medium into a mixed solution, spraying the mixed solution on a nickel foil after uniform stirring, covering another layer of nickel foil after drying, and obtaining a composite film through rolling; Cutting and ball-milling the composite film to obtain the metallographic regulator with the required particle size.

2. A cemented carbide for drill bits according to claim 1, characterized in that, The dispersion medium is a mixture of ethanol and polyethylene glycol 400.

3. A cemented carbide for drill bits according to claim 2, characterized in that, The mass ratio of the dispersion medium of ethanol and polyethylene glycol 400 is 100: (1.8-2.6).

4. The cemented carbide for a drill bit according to claim 1, wherein The cobalt powder is high-purity spherical cobalt powder with a purity of greater than 99.4 wt%.

5. The cemented carbide for a drill bit according to claim 1, wherein Both the first tungsten carbide grains and the second tungsten carbide grains are subjected to high-temperature carbonization treatment, and the high-temperature carbonization treatment temperature is not less than 1750℃, which is lower than the melting point of tungsten carbide.

6. The cemented carbide for a drill bit according to claim 1, wherein Further comprising 0.1-0.5 parts of a bonding strengthening phase, the bonding strengthening phase being a soluble rare earth salt.

7. A cemented carbide for drill bits according to claim 6, characterized in that, The bonding strengthening phase is a combination of ytterbium salt and yttrium salt.

8. A method of making a cemented carbide for drill bits as defined in any one of claims 1 to 7, characterized in that, The method comprises the following steps: According to the amount of the raw materials, the first tungsten carbide grains are taken as raw material group A, the second tungsten carbide grains are taken as raw material group B, and the remaining other raw materials are mixed as raw material group C, Part of the raw material group C and grinding medium are added into a ball mill to obtain slurry A, The remaining raw material group C and grinding medium are added into a ball mill to obtain slurry B, The slurry A and the slurry B are mixed uniformly to obtain slurry C, The slurry C is spray-dried to obtain a mixture, The mixture is pressed and sintered to obtain a sintered blank.

Images