A cemented carbide and a method for producing the same

Abstract

This invention discloses a cemented carbide and its preparation method. The cemented carbide comprises a hard phase A, a binder phase B, a cubic phase C, and a metallic element M dissolved in the hard phase and the binder phase, respectively. The content of cubic phase C is 0–3 wt.% of the cemented carbide; the content of binder phase B is 3–15 wt.% of the cemented carbide; the solid solution content of metallic element M in the hard phase is 0.1–5 wt.%; the solid solution content of metallic element M in the binder phase is 0.3–15 wt.%; and the balance is the hard phase. The preparation method includes: element homogenization; pre-alloying of the binder phase; reduction-carbonization; strengthening solid solution; secondary carbonization; secondary carbonization; mixture preparation; forming; and sintering. This invention yields a cemented carbide with high strength and toughness, resistance to high-temperature deformation, resistance to high-temperature oxidation, and good corrosion resistance, which can be applied to cutting tools, mining tools, and wear-resistant parts.

Description

A cemented carbide and its preparation method Technical Field

[0001] This invention belongs to the field of alloy material preparation technology, and relates to a cemented carbide and its preparation method. Background Technology

[0002] Carbide possesses excellent properties such as high hardness, high strength, corrosion resistance, high temperature resistance, and a low coefficient of thermal expansion, making it widely used in cutting and mining tools and wear-resistant parts. In recent years, the continuously rising demand from global mineral and energy exploration and mining, along with the vigorous development of major infrastructure projects, has promoted the widespread use and development of carbide rock drilling products such as carbide ball teeth, coal cutting teeth, and milling teeth. High-strength, high-toughness, high-wear-resistance, and corrosion-resistant new types of carbide drill bits are one of the key development directions for carbide. Secondly, to meet the demands of modern manufacturing for high efficiency and low cost, there is an urgent need for cutting tools that are highly efficient, highly precise, highly reliable, and specialized ("three highs and one specialization"). On the other hand, the mold manufacturing industry requires precision progressive dies with high hardness, high toughness, and excellent resistance to electrochemical corrosion.

[0003] Hard alloys are mainly composed of a hard phase and a binder phase. Controlling the microstructure and properties of both phases is an effective way to improve the overall performance of hard alloys. Controlling the structure and properties of the hard WC phase primarily involves solid solution or doping of WC grains. Currently, there are technical bottlenecks in controlling the structure and properties of the hard WC phase through solid solution or doping because most metallic elements have very low solubility in WC grains. Mo is one of the known metallic elements with solubility in the WC lattice, but studies have shown that the solubility of Ta, Nb, Cr, V, Ti, and Zr in the WC lattice is less than 10⁻³ atomic fractions. Methods for controlling the structure and properties of the metallic binder phase include alloying (solid solution strengthening), precipitation strengthening, and dispersion strengthening. Partially or completely replacing the Co binder through alloying is a hot research topic in the hard alloy industry, especially through the addition of trace elements to improve hard alloy performance. However, while these methods increase the hardness or strength of the alloy, they often inevitably weaken the corresponding strength or hardness. Therefore, developing a synergistic strengthening technology for the hard phase and binder phase of cemented carbide to achieve comprehensive high performance of cemented carbide is one of the current challenges and hot issues. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a cemented carbide and its preparation method, which improves the hardness and bending strength of the cemented carbide, resulting in a cemented carbide with high strength and toughness, resistance to high-temperature deformation, resistance to high-temperature oxidation, and good corrosion resistance. This cemented carbide can be applied to cutting tools, mining tools, and wear-resistant parts, thus solving the problems existing in the prior art.

[0005] The technical solution adopted in this invention is a cemented carbide with high strength, toughness, high temperature resistance, and corrosion resistance, comprising a hard phase A, a binder phase B, a cubic phase C, and a metallic element M dissolved in the hard phase and the binder phase respectively.

[0006] The content of the cubic phase C is 0–3 wt.% of the cemented carbide.

[0007] The content of the binder phase B is 3–15 wt.% of the cemented carbide.

[0008] The solid solution content of metallic element M in the hard phase is 0.1–5 wt.%;

[0009] The solid solution content of metallic element M in the binder phase is 0.3–15 wt.%;

[0010] The balance is a hard phase.

[0011] Furthermore, the hard phase A is a WC phase, the binder phase B is one or more of Fe, Co, and Ni, the cubic phase C is one or more of VC, Cr3C2, TaC, and NbC, and the metallic element M is any one or more of Re, Ru, Tc, Os, and Rh.

[0012] Furthermore, the particle size of the binder phase B metal powder is 0.1–2.0 μm.

[0013] Furthermore, the metal elements M dissolved in the hard phase and the binder phase are either the same element or different elements, and are added to the hard phase and the binder phase respectively without affecting each other.

[0014] A method for preparing a cemented carbide includes the following steps:

[0015] Step 1: Element homogenization;

[0016] Based on the solid solution content of metallic element M in the hard phase of 0.1–5 wt.%, the amounts of tungsten (W) salt and metallic element M salt are determined. The tungsten (W) salt and metallic element M salt are added to an organic solvent to dissolve them, obtaining a mixed salt solution with a W concentration of 15–80 g / L (calculated as WO3). The solution is then spray-dried at 80–160 °C under a protective atmosphere to obtain a mixed salt powder. Too much or too little organic solvent will affect the elemental homogenization of tungsten and metallic element M. The specific spray-drying temperature depends on the boiling point of the organic solvent and the required powder particle size.

[0017] Based on the solid solution content of metal element M in the binder phase being 0.3–15 wt.%, the amounts of binder phase B and metal element M salt solution are determined. The metal powder of binder phase B is added to the salt solution of metal element M, stirred, heated to 60–150°C, and the solution is evaporated to obtain binder phase B powder coated with metal element M salt.

[0018] The ratio of tungsten (W) salt to metallic element M is determined based on the solid solution content of metallic element M in the hard phase. The range of the ratio of binder phase B metal powder to the salt solution of metallic element M is determined based on the solid solution content of metallic element M in binder phase B. A solid solution content lower or higher than the corresponding solid solution content will not achieve the optimal solid solution strengthening effect, and metallic element M is relatively expensive, resulting in high costs for large additions.

[0019] Step 2: Pre-alloying of the binder phase; The binder phase B powder coated with the salt of metal element M is subjected to low-temperature reduction at 650-950℃ and high-temperature solid solution at 800-1300℃ to prepare BM pre-alloyed powder.

[0020] Step 3: Reduction-Carbonization; The mixed salt powder prepared in Step 1 is subjected to a gas-phase reaction to prepare (W, M)C. (1-x) For pre-alloyed powders, the value of x ranges from 0.50 to 0.79; the product (W, M)C when x ranges from 0.50 to 0.79. (1-x) This facilitates the solid solution of metallic element M, increasing the proportion of incompletely carburized products in the final product. Based on the carburization mechanism of W, the process of W→(W, M)C is utilized. (1-x) →The reduction-carbonization process of WC, that is, in the reduction-carbonization process, W and (W, M)C coexist. (1-x) The present invention increases the (W, M)C content in the products by controlling the carbonization process. (1-x) The ratio should be adjusted, and the proportion of W and WC in the product should be minimized as much as possible.

[0021] Step 4: Strengthen solid solution; apply (W, M)C (1-x) Pre-alloyed powder is heated to 860–1200 °C under a protective atmosphere and held for 2–16 h to obtain M-reinforced solid solution (W, M)C. (1-x) Powder; if the temperature is too low, the solid solution time is too long, resulting in insufficient solid solution uniformity. If the temperature is too high, (W, M)C (1-x) If the powder grains grow too quickly, the powder will be coarse, which is not conducive to controlling the powder particle size.

[0022] Step 5: Secondary carbon preparation; (W, M)C is added to M-enhanced solid solution according to the stoichiometric ratio of the chemical formula (W, M)C. (1-x) Powdered activated carbon is added and mechanically ball-milled to mix evenly.

[0023] Step Six: Secondary Carbonization; The powder mixed evenly in Step Five is heated and carbonized in a hydrogen atmosphere at a carbonization temperature of 1300-1800℃ for 1-4 hours to obtain WC powder with M solid solution.

[0024] Step 7: Prepare the mixture; Determine the amount of WC powder in solid solution M and pre-alloyed powder BM according to the content of hard phase A and binder phase B, and mix the WC powder in solid solution M with pre-alloyed powder BM, cubic phase C and forming agent evenly to prepare the mixture.

[0025] Step 8: Shaping and sintering, the mixture is shaped and sintered to obtain cemented carbide.

[0026] Furthermore, in step one, the tungsten salt is one or more of WCl6, WCl5, WCl4 or WCl2 in any proportion, preferably WCl6, which is relatively stable and common; the organic solvent is methanol, ethanol or ethylene glycol, preferably ethanol; organic solvents are inexpensive, safe, can dissolve both tungsten and the salt of metal element M, and have low boiling points.

[0027] In step one, the salt of metal element M is one or more of ammonium ruthenium chloride, ammonium osmium chloride, ammonium rhodium chloride, ammonium perrhenate, rhenium trichloride, technetium sulfide, or ammonium pertechnetate, in any proportion. The salt of metal element M needs to have good solubility in organic solvents and a low sublimation temperature. The solvent for the salt solution of metal element M is one or more of water, methanol, ethanol, ethylene glycol, diethylene glycol, propylene glycol, glycerol, diethyl ether, acetone, diethylamine, or diethanolamine, which is inexpensive, safe, can dissolve the salt of metal element M, and has a low boiling point. Ethanol is preferred; organic solvents are inexpensive, safe, and can dissolve both tungsten and the salt of metal element M simultaneously.

[0028] The concentration of the salt solution of metal element M is 5-300 g / L. If the concentration is too high, the salt of metal element M cannot be fully and uniformly coated on the surface of the binder phase B powder particles. If the concentration is too low, the evaporation time of the solution is long and the energy consumption is high.

[0029] Furthermore, in step two, the atmosphere for low-temperature reduction is hydrogen, and the atmosphere for high-temperature solid solution is hydrogen, argon, or nitrogen.

[0030] Furthermore, in step three, the atmosphere for the gas-phase reaction of WM salt is a mixture of CH4 and H2, the molar ratio of WM salt to CH4-H2 mixed gas inlet is 2:1 to 3:1, the temperature of the gas-phase reaction is 620 to 1380°C, and the pressure of the gas-phase reaction is 0.1 to 0.5 MPa; the molar ratio of CH4 to H2 in the CH4-H2 mixed gas is 1:1 to 1:4, and the preferred molar ratio of CH4 to H2 is 1:4.

[0031] Furthermore, in step four, the protective atmosphere is hydrogen, nitrogen, or argon.

[0032] Furthermore, in step seven, the amount of forming agent used is 1.5 to 3% of the total mass of the M solid solution WC powder, BM pre-alloyed powder and cubic phase C powder.

[0033] The beneficial effects of this invention are:

[0034] This invention uses element M to optimize the structure and enhance the performance of the hard phase and binder phase of cemented carbide, and employs different performance enhancement methods based on the structural characteristics of the hard phase and binder phase.

[0035] For the binder phase of cemented carbide, this invention uses a liquid-phase coating method to uniformly coat trace amounts of solid-solution element M onto the surface of the binder phase particles, which is beneficial for solid solution and alloying with the binder phase. The use of low-temperature reduction and high-temperature solid solution processes to prepare BM pre-alloy powder promotes uniform element distribution, fundamentally avoiding compositional segregation. Sufficient alloying of the BM pre-alloy powder helps to lower the alloy sintering temperature and improve the alloy's hardness and strength properties.

[0036] For the hard phase of cemented carbide, this invention utilizes the dissolution of tungsten chloride and the salt of metallic element M in an organic solution to first achieve a uniform molecular-level mixture of W and M elements. Then, a gas-phase reduction carbonization method is used to prepare (W, M)C from the WM salt. (1-x) Pre-alloyed powders, through precise control of temperature, reaction atmosphere, gas flow rate, and reaction pressure, enhance the production of incompletely carbonized products (W, M)C in the gas-phase reaction products. (1-x) The proportion of W and WC in the product is reduced.

[0037] This invention obtains (W, M)C with M-enhanced solid solution through enhanced solid solution treatment. (1-x) The powder is then processed through a precise secondary carbonization and carbonization process to obtain WC powder with M solid solution. (W, M)C is then applied. (1-x) The differences in crystal structure and transformation mechanism between intermediates and WC crystals, utilizing the element M in (W, M)C (1-x) Due to the high solubility of the intermediate, a two-step carbonization process is employed to achieve the solid solution of element M into the WC grains. During the two-step carbonization process, the carbon content, carbonization time, and carbonization temperature are strictly controlled to ensure that element M is dissolved into the WC grains while avoiding abnormal grain growth and reducing production energy consumption. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 is a process flow diagram of an embodiment of the present invention. Detailed Implementation

[0040] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0041] Example 1,

[0042] A cemented carbide, characterized by high strength and toughness, high temperature resistance, and corrosion resistance, comprises a hard phase A, a binder phase B, a cubic phase C, and a metallic element M dissolved in the hard phase and the binder phase, respectively. The content of the binder phase B is 3-15 wt.% of the cemented carbide, the content of the cubic phase C is 0-3 wt.% of the cemented carbide, the solid solution content of metallic element M in the hard phase is 0.1-5 wt.%, the solid solution content of metallic element M in the binder phase is 0.3-15 wt.%, and the balance is the hard phase.

[0043] Among them, the hard phase A is the WC phase, and the binder phase B is one or more of Fe, Co, and Ni. The particle size of the binder phase B metal powder is 0.1 to 2.0 μm. The appropriate particle size of the binder phase B metal powder is conducive to the element homogenization and solid solution of the binder phase B and the metal element M. If the binder phase B powder is too coarse, it is not conducive to the coating and diffusion of the metal element M.

[0044] The metallic element M can be any one or more of Re, Ru, Tc, Os, and Rh. The metallic element M dissolved in the hard phase or binder phase can be the same element or different elements.

[0045] The cubic phase C is one or more of VC, Cr3C2, TaC, and NbC.

[0046] Example 2,

[0047] A method for preparing a cemented carbide, as shown in Figure 1, includes the following steps:

[0048] Step 1: Dissolve WCl6 and ammonium ruthenate in an organic solvent (ethanol solution). The molar ratio of WCl6 to ammonium ruthenate is 103.67:1 to obtain a mixed solution with a WCl6 concentration of 20 g / L (calculated as WO3). Spray dry the mixed solution at 60°C under a nitrogen atmosphere to obtain WCl6-(NH4)2RuCl6 salt powder, which is a mixed powder of WCl6 and (NH4)2RuCl6.

[0049] In this embodiment of the invention, the content of the metal element Ru in the hard phase is relatively low. Liquid-phase dissolution followed by spray drying facilitates the achieving molecular-level uniform mixing of trace (low-content) metal elements with W. On the other hand, WCl6 is relatively reactive and readily reacts with water and air at high temperatures; therefore, this embodiment of the invention uses an organic solvent with a low boiling point.

[0050] Co powder with a particle size of 1 μm was added to an ammonium chlororuthenate-ethanol solution with a concentration of 5 g / L. The molar ratio of Co powder to ammonium chlororuthenate was 564.23:1. The solution was heated to 80 °C under stirring to evaporate the solution, and a (NH4)2RuCl6-coated binder phase Co powder was obtained.

[0051] Step 2: The (NH4)2RuCl6-coated binder phase Co powder was subjected to low-temperature reduction and high-temperature solution treatment at 900℃ and 1200℃ to prepare Co-0.3Ru (values ​​are mass fractions) pre-alloyed powder. Both the low-temperature reduction and high-temperature solution treatments were conducted under hydrogen atmosphere. The Ru metal element content in the binder phase was 0.3 wt.%, and the Ru metal element added in Step 1 was completely dissolved.

[0052] Step 3: WCl6-(NH4)2RuCl6 is subjected to a gas-phase reaction under a mixed gas of CH4 and H2 at 900℃ and 0.1 MPa to prepare (W, Ru)C by reduction-carbonization. (1-x) Pre-alloyed powder, x=0.5. The molar ratio of WCl6-(NH4)2RuCl6 gas to CH4-H2 mixed gas is 2:1, and the molar ratio of CH4 to H2 in the CH4-H2 mixed gas is 1:4.

[0053] Step 4: Combine (W, Ru)C (1-x) Pre-alloyed powder was solution-treated at 1200℃ in a hydrogen atmosphere for 5 hours to obtain Ru-reinforced solid solution (W, Ru)C. (1-x) Powder. The hydrogen atmosphere serves two purposes: firstly, it provides a protective atmosphere; secondly, the reduction-carbonization product obtained in step three may contain a small amount of WC, which can be reduced to WC using hydrogen. (1-x) .

[0054] Step 5: Add (W, Ru)C to Ru for solid solution reinforcement according to the stoichiometric ratio of the chemical formula (W, Ru)C. (1-x) Powdered activated carbon is added and mechanically ball-milled to mix evenly.

[0055] Step 5: The amount of activated carbon added equals the carbon content required for the chemical formula (W, Ru)C minus (W, Ru)C. (1-x) The carbon content contained in it. For example: 1 mol of (W, Ru)C requires 1 mol of carbon. The (W, Ru)C obtained in step four... (1-x)Its X value is 0.5, then 1 mol of (W, Ru)C 0.5 The carbon content in the sample is 0.5 mol, so the amount of carbon that needs to be added in step five is 1 mol - 0.5 mol = 0.5 mol.

[0056] Step 6: The powder obtained from the secondary carbonization in Step 5 is heated at 1370℃ for 3 hours under a hydrogen atmosphere to obtain WC powder with Ru solid solution (WC-0.5Ru), and the solid solution content of metal element M in the hard phase is 0.5 wt.%.

[0057] Step 7: Mix 88.97g of Ru solution WC powder, 10.03g of Co-0.3Ru pre-alloyed powder, 0.5g of TaC, 0.5g of NbC powder and 2.5g of paraffin forming agent to prepare a mixture.

[0058] Step 8: After the mixture is pressed and sintered, 88.525WC-10Co-0.475Ru-0.5TaC-0.5NbC cemented carbide is obtained, with the value being the mass fraction wt.%.

[0059] The hardness of the cemented carbide prepared in Example 2 is 1345HV10, and the bending strength is 3034.91MPa.

[0060] Example 3,

[0061] A method for preparing a cemented carbide includes the following steps:

[0062] Step 1: Dissolve WCl6 and ReCl3 (rhenium trichloride) in an ethanol solution at a molar ratio of 78.83:1 to obtain a mixed solution with a WCl6 concentration of 80 g / L (calculated as WO3). Spray dry at 160 °C under an argon atmosphere to obtain WCl6-ReCl3 salt powder.

[0063] Ni powder with a particle size of 0.1 μm was added to an aqueous solution of ammonium perrhenate (NH4ReO4) with a concentration of 300 g / L. The molar ratio of Ni to NH4ReO4 was 32.1:1. The solution was heated to 150 °C under stirring to evaporate the solution and obtain Ni powder coated with NH4ReO4 as the binder phase.

[0064] Step 2: Ni-9Re (values ​​are mass fractions) pre-alloyed powders were prepared by low-temperature reduction and high-temperature solid solution treatment of Ni powder coated with NH4ReO4 at 650℃ and 800℃, respectively. The atmosphere for both low-temperature reduction and high-temperature solid solution treatment was hydrogen.

[0065] Step 3: WCl6-ReCl3 is subjected to a gas-phase reaction under CH4-H2 mixed gas conditions at 1380℃ and 0.2 MPa to prepare (W, Re)C by reduction-carbonization.(1-x) Pre-alloyed powder, x=0.79. The molar ratio of WCl6-ReCl3 to CH4-H2 mixed gas is 2.5:1, and the molar ratio of CH4 to H2 in the CH4-H2 mixed gas is 1:2.

[0066] Step 4: (W, Re)C (1-x) Pre-alloyed powder was solution-treated at 860℃ for 16 hours under an argon atmosphere to obtain Re-reinforced solid solution (W, Re)C. (1-x) powder.

[0067] Step 5: Add (W, Re)C to the Re-enhanced solid solution according to the stoichiometric ratio of the chemical formula (W, Re)C. (1-x) Add activated carbon to the powder and mix thoroughly by mechanical ball milling.

[0068] Step 6: The powder after secondary carbonization in Step 5 is heated at 1300℃ for 4 hours under a hydrogen atmosphere to obtain WC powder with Re solid solution (WC-1.2Re).

[0069] Step 7: Mix 96.7g of Re solid solution WC powder, 3.3g of Ni-9Re pre-alloyed powder and 3g of paraffin forming agent to prepare a mixture.

[0070] Step 8: After the mixture is pressed into shape, it is sintered to obtain 95.54WC-3Ni-1.46Re cemented carbide, with the value being the mass fraction wt.%.

[0071] The hardness of the cemented carbide prepared in Example 3 is 1284HV10, and the bending strength is 2249.48MPa.

[0072] Example 4,

[0073] A method for preparing a cemented carbide includes the following steps:

[0074] Step 1: Dissolve WCl6 and ReCl3 (rhenium trichloride) in an ethanol solution at a molar ratio of 1020:1 to obtain a mixed solution with a WCl6 concentration of 80 g / L (calculated as WO3). Spray dry at 160 °C under an argon atmosphere to obtain WCl6-ReCl3 salt powder.

[0075] Co-Ni mixed powder with a particle size of 2 μm (Co:Ni molar ratio 1:1) was added to an aqueous solution of ammonium perrhenate (NH4ReO4) with a concentration of 100 g / L. The molar ratio of Co-Ni to NH4ReO4 was 17.87:1. The solution was heated to 150 °C under stirring to evaporate the solution and obtain Co-Ni powder coated with NH4ReO4 as the binder phase.

[0076] Step 2: The NH4ReO4-coated binder phase Co-Ni powder was reduced at low temperature (650℃) and dissolved at high temperature (800℃) to prepare 42.5Co-42.5Ni-15Re (values ​​are mass fractions, the same below) pre-alloyed powder. The atmosphere for both low-temperature reduction and high-temperature solution was hydrogen.

[0077] Step 3: WCl6-ReCl3 is subjected to a gas-phase reaction under CH4-H2 mixed gas conditions at 1380℃ and 0.2 MPa to prepare (W, Re)C by reduction-carbonization. (1-x) Pre-alloyed powder, x=0.65. The molar ratio of WCl6-ReCl3 to CH4-H2 mixed gas is 2.5:1, and the molar ratio of CH4 to H2 in the CH4-H2 mixed gas is 1:2.

[0078] Step 4: (W, Re)C (1-x) Pre-alloyed powder was solution-treated at 860℃ under argon atmosphere for 8 hours to obtain Re-reinforced solid solution (W, Re)C. (1-x) powder.

[0079] Step 5: Add (W, Re)C to the Re-enhanced solid solution according to the stoichiometric ratio of the chemical formula (W, Re)C. (1-x) Add activated carbon to the powder and mix thoroughly by mechanical ball milling.

[0080] Step 6: The powder after secondary carbonization in Step 5 is heated at 1300℃ for 4 hours under a hydrogen atmosphere to obtain WC powder with Re solid solution (WC-0.1Re).

[0081] Step 7: Mix 85.24g of Re solid solution WC powder, 11.76g of 42.5Co-42.5Ni-15Re pre-alloyed powder, 1.5g of TaC, 1.5g of NbC powder and 3g of paraffin forming agent to prepare a mixture.

[0082] Step 8: After the mixture is pressed and shaped, it is sintered to obtain 85.15WC-5Co-5Ni-1.85Re-1.5TaC-1.5NbC cemented carbide, with the value being the mass fraction wt.%.

[0083] The hardness of the cemented carbide prepared in Example 4 is 1306HV10, and the bending strength is 3055.42MPa.

[0084] Example 5,

[0085] A method for preparing a cemented carbide includes the following steps:

[0086] Step 1: Dissolve WCl6 and ReCl3 (rhenium trichloride) in an ethanol solution at a molar ratio of 18.03:1 to obtain a mixed solution with a WCl6 concentration of 80 g / L (calculated as WO3). Spray dry at 160 °C under an argon atmosphere to obtain WCl6-ReCl3 salt powder.

[0087] Co-Ni mixed powder with a particle size of 2 μm (Co:Ni molar ratio 1:1) was added to an aqueous solution of ammonium perrhenate (NH4ReO4) with a concentration of 100 g / L. The molar ratio of Co-Ni to NH4ReO4 was 17.87:1. The solution was heated to 150 °C under stirring to evaporate the solution and obtain Co-Ni powder coated with NH4ReO4 as the binder phase.

[0088] Step 2: The NH4ReO4-coated binder phase Co-Ni powder was reduced at low temperature (650℃) and dissolved at high temperature (800℃) to prepare 42.5Co-42.5Ni-15Re (values ​​are mass fractions, the same below) pre-alloyed powder. The atmosphere for both low-temperature reduction and high-temperature solution was hydrogen.

[0089] Step 3: WCl6-ReCl3 is subjected to a gas-phase reaction under CH4-H2 mixed gas conditions at 1380℃ and 0.2 MPa to prepare (W, Re)C by reduction-carbonization. (1-x) Pre-alloyed powder, x=0.65. The molar ratio of WCl6-ReCl3 to CH4-H2 mixed gas is 2.5:1, and the molar ratio of CH4 to H2 in the CH4-H2 mixed gas is 1:2.

[0090] Step 4: (W, Re)C (1-x) Pre-alloyed powder was solution-treated at 860℃ under argon atmosphere for 8 hours to obtain Re-reinforced solid solution (W, Re)C. (1-x) powder.

[0091] Step 5: Add (W, Re)C to the Re-enhanced solid solution according to the stoichiometric ratio of the chemical formula (W, Re)C. (1-x) Add activated carbon to the powder and mix thoroughly by mechanical ball milling.

[0092] Step 6: The powder after secondary carbonization in Step 5 is heated at 1300℃ for 4 hours under a hydrogen atmosphere to obtain WC powder with Re solid solution (WC-5Re).

[0093] Step 7: Mix 88.24g of Re solid solution WC powder, 11.76g of 42.5Co-42.5Ni-15Re pre-alloyed powder and 1.5g of paraffin forming agent to prepare a mixture.

[0094] Step 8: After the mixture is pressed into shape, it is sintered to obtain 83.83WC-5Co-5Ni-6.17Re cemented carbide, with the value being the mass fraction wt.%.

[0095] The hardness of the cemented carbide prepared in Example 5 is 1337HV10, and the bending strength is 2984.37MPa.

[0096] Comparative Example 1

[0097] Step 1: Dissolve WCl6 in an ethanol solution and spray dry to obtain WCl6 powder. Add 1μm Co powder to the ethanol solution and heat to 80℃ under stirring to evaporate the solution, obtaining the binder phase Co powder.

[0098] Step 2: Co powder was prepared by reducing the binder phase Co powder at low temperature (900℃) and dissolving it at high temperature (1200℃), with hydrogen atmosphere used for both the low-temperature reduction and high-temperature dissolution.

[0099] Step 3: WCl6 is subjected to a gas-phase reaction under CH4-H2 mixed gas conditions, at a temperature of 900℃ and a pressure of 0.1 MPa to prepare WC by reduction-carbonization. (1-x) Powder. The molar ratio of WCl6 to CH4-H2 mixed gas in the inlet gas is 2:1, and the molar ratio of CH4 to H2 in the CH4-H2 mixed gas is 1:4.

[0100] Step 4: Put the WC (1-x) The powder was dissolved in hydrogen atmosphere at 1200℃ for 5 hours to obtain WC. (1-x) powder.

[0101] Step 5: Add WC to WC according to the stoichiometric ratio of the chemical formula. (1-x) The powder was added to activated carbon and mechanically ball-milled until uniform.

[0102] Step 6: The powder obtained from the secondary carbonization in Step 5 is heated at 1370℃ for 3 hours under a hydrogen atmosphere to obtain WC powder.

[0103] Step 7: Mix 88.525g of WC powder obtained in Step 6, 10g of Co powder obtained in Step 2, 0.475g of Ru powder, 0.5g of TaC, 0.5g of NbC powder and 2.5g of paraffin forming agent to prepare a mixture.

[0104] Step 8: After the mixture is pressed and shaped, it is sintered to obtain 88.525WC-10Co-0.475Ru-0.5TaC-0.5NbC cemented carbide.

[0105] Compared to Example 2, Comparative Example 1 did not pre-prepare Ru-solution WC powder and Co-Ru pre-alloy powder; Ru raw material powder was directly added in step seven, and the other steps were the same as in Example 2. A cemented carbide with the same composition as in Example 2, consisting of 88.525WC-10Co-0.475Ru-0.5TaC-0.5NbC, was obtained. The cemented carbide obtained in Comparative Example 1 had a 22% lower hardness (1049HV10 vs. 1345HV10) and a 15% lower bending strength (2579.67MPa vs. 3034.91MPa) than the cemented carbide obtained in Example 2.

[0106] Comparative Example 2

[0107] Step 1: Dissolve WCl6 and ammonium ruthenium chloride in an ethanol solution, and spray dry to obtain WCl6-(NH4)2RuCl6 salt powder. Add 1μm Co powder and ammonium ruthenium chloride to the ethanol solution, heat to 80℃ under stirring to evaporate the solution, and obtain (NH4)2RuCl6-coated binder phase Co powder.

[0108] Step 2: Co-0.3Ru pre-alloyed powder was prepared by low-temperature reduction and high-temperature solid solution of (NH4)2RuCl6-coated binder phase Co powder at 900℃ and 1200℃ respectively. The atmosphere for both low-temperature reduction and high-temperature solid solution was hydrogen.

[0109] Step 3: WCl6-(NH4)2RuCl6 is subjected to a gas-phase reaction under CH4-H2 mixed gas conditions at 1200℃ and 0.6 MPa to prepare WC-Ru powder by reduction-carbonization. The molar ratio of WCl6-(NH4)2RuCl6 to the CH4-H2 mixed gas is 1:2, and the molar ratio of CH4 to H2 in the CH4-H2 mixed gas is also 1:2.

[0110] This step differs from step three of Example 2 in terms of temperature, pressure, air intake, and atmosphere during reduction-carbonization. The comparison illustrates that the temperature, pressure, air intake, and reduction-carbonization atmosphere in step three can affect the formation of carbonization products.

[0111] Step 4: Dissolve WC-Ru powder in a hydrogen atmosphere at 1200℃ for 5 hours to obtain WC-Ru powder.

[0112] Step 5: Mix WC-Ru powder, Co-0.3Ru pre-alloyed powder, TaC, NbC powder and paraffin forming agent to prepare a mixture.

[0113] Step 6: After the mixture is pressed and shaped, it is sintered to obtain WC-10Co-0.475Ru-0.5TaC-0.5NbC cemented carbide.

[0114] Compared to Example 2, Comparative Example 2 directly reduced and carbonized WCl6-(NH4)2RuCl6 into WC-Ru powder in step three. The solid solution strengthening conditions in step four were the same, without the secondary carbonization and secondary carbonization steps found in Example 2. The hardness of the cemented carbide obtained in Comparative Example 2 was 17% lower than that of the cemented carbide obtained in Example 2 (1116HV10 vs. 1345HV10), and its bending strength was 3% lower (2943.86MPa vs. 3034.91MPa).

[0115] Existing methods for controlling the structure and properties of hard WC phases through solid solution or doping face technical bottlenecks because most metal elements have very low solubility in WC grains. Mo is one of the known metal elements with solubility in the WC lattice, but studies have shown that the solubility of elements such as Ta, Nb, Cr, V, Ti, and Zr in the WC lattice is less than 10⁻³ atomic fractions. To address the problem of low solubility of metal element M in WC grains, embodiments of this invention employ the following measures to achieve solid solution of trace / low-content metal elements into WC grains:

[0116] (1) By dissolving tungsten chloride and metal element M salt in an organic solution, W and trace / low content M elements are first uniformly mixed at the molecular level.

[0117] (2) WM salt was prepared into (W, M)C by gas-phase reduction-carbonation method. (1-x) Pre-alloyed powders, through precise control of reaction temperature, pressure, gas flow rate, and reduction-carbonization atmosphere, improve the incomplete carbonization of (W, M)C in the gas-phase reaction products. (1-x) The proportion of W and WC in the product is reduced.

[0118] (3) Obtaining (W, M)C with M-enhanced solid solution through enhanced solid solution. (1-x) The powder is then processed through a precise secondary carbonization and carbonization process to obtain WC powder with M solid solution. (W, M)C is then applied. (1-x) The differences in crystal structure and transformation mechanism between intermediates and WC crystals, utilizing the element M in (W, M)C (1-x) Due to the high solubility of the intermediate, a two-step carbonization process is employed to achieve the solid solution of element M into the WC grains. During the two-step carbonization process, the carbon content, carbonization time, and carbonization temperature are strictly controlled to ensure that element M is dissolved into the WC grains while avoiding abnormal grain growth and reducing production energy consumption.

[0119] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the scope of protection of the present invention.

Claims

1. A cemented carbide, characterized in that, The cemented carbide comprises a hard phase A, a binder phase B, a cubic phase C, and a metallic element M dissolved in the hard phase and the binder phase, respectively. The content of the cubic phase C is 0–3 wt.% of the cemented carbide; the content of the binder phase B is 3–15 wt.% of the cemented carbide; the solid solution content of metallic element M in the hard phase is 0.1–5 wt.%; the solid solution content of metallic element M in the binder phase is 0.3–15 wt.%; and the balance is the hard phase. The cemented carbide is prepared according to the following steps: Step 1: Element homogenization; based on the solid solution content of metallic element M in the hard phase being 0.01–5 wt.%, the amount of tungsten salt and metallic element M salt is determined. The tungsten salt and metallic element M salt are added to an organic solvent and dissolved to obtain a mixed salt solution with a W concentration of 20–80 g / L (calculated as WO3). The solution is spray-dried at 80–160 °C under a protective atmosphere to obtain a mixed salt powder. Based on the solid solution content of metallic element M in the binder phase being 0.3–15 wt.%, the amount of tungsten salt and metallic element M salt is determined. wt.%, determine the amount of binder phase B and the salt solution of metal element M, add the metal powder of binder phase B to the salt solution of metal element M, stir, heat to 60-150℃, evaporate the solution, and obtain the binder phase B powder coated with the salt of metal element M; Step 2: pre-alloying of binder phase. The binder phase B powder coated with the salt of metallic element M is subjected to low-temperature reduction at 650–950℃ and high-temperature solid solution at 800–1300℃ to prepare BM pre-alloyed powder; Step 3: Reduction-Carbonization; The mixed salt powder prepared in Step 1 is subjected to gas-phase reaction to prepare (W, M)C (1-x) Pre-alloyed powder, x ranges from 0.50 to 0.79; Step 4: Strengthening solution; (W, M)C (1-x) Pre-alloyed powder is heated to 860–1200 °C under a protective atmosphere and held for 2–16 h to obtain M-reinforced solid solution (W, M)C. (1-x) Powder; Step 5: Secondary carbon preparation; Add (W, M)C to M-enhanced solid solution according to the stoichiometric ratio of chemical formula (W, M)C. (1-x) Powdered activated carbon is added and mechanically ball-milled to mix evenly; Step 6: Secondary carbonization; The powder mixed evenly in Step 5 is heated and carbonized in a hydrogen atmosphere at a carbonization temperature of 1300-1800℃ for 1-4 hours to obtain WC powder with M solid solution; Step 7: The amount of WC powder with M solid solution and BM pre-alloy powder is determined according to the content of hard phase A and binder phase B. The WC powder with M solid solution is mixed evenly with BM pre-alloy powder, cubic phase C and forming agent to prepare a mixture; Step 8: Forming and sintering; The mixture is formed and sintered to obtain cemented carbide; The hard phase A is WC phase, the binder phase B is one or more of Fe, Co, and Ni, the cubic phase C is one or more of VC, Cr3C2, TaC, and NbC, and the metal element M is one of Re and Ru.

2. The cemented carbide according to claim 1, characterized in that, The particle size of the binder phase B metal powder is 0.1–2.0 μm.

3. The cemented carbide according to claim 1, characterized in that, In step one, the tungsten salt is one or more of WCl6, WCl5, WCl4, or WCl2 mixed in any proportion; the organic solvent is methanol, ethanol, or ethylene glycol; the salt of metal element M is one or more of ammonium ruthenium chloride, ammonium osmium chloride, ammonium rhodium chloride, ammonium perrhenate, rhenium trichloride, technetium sulfide, or ammonium pertechnetate mixed in any proportion; the solvent for the salt solution of metal element M is one or more of water, methanol, ethanol, ethylene glycol, diethylene glycol, propylene glycol, glycerol, diethyl ether, acetone, diethylamine, or diethanolamine mixed in one or more proportions; the concentration of the salt solution of metal element M is 5–300 g / L.

4. The cemented carbide according to claim 1, characterized in that, In step two, the atmosphere for low-temperature reduction is hydrogen, and the atmosphere for high-temperature solid solution is hydrogen, argon, or nitrogen.

5. The cemented carbide according to claim 1, characterized in that, In step three, the atmosphere for the gas-phase reaction of WM salt is a mixture of CH4 and H2, the molar ratio of WM salt to CH4-H2 mixed gas is 2:1 to 3:1, the temperature of the gas-phase reaction is 620 to 1380°C, and the pressure of the gas-phase reaction is 0.1 to 0.5 MPa; the molar ratio of CH4 to H2 in the CH4-H2 mixed gas is 1:1 to 1:

4.

6. The cemented carbide according to claim 1, characterized in that, In step four, the protective atmosphere is hydrogen, nitrogen, or argon.

7. The cemented carbide according to claim 1, characterized in that, In step seven, the amount of forming agent used is 1.5 to 3% of the total mass of the M solid solution WC powder, BM pre-alloyed powder and cubic phase C powder.

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