A rare earth modified tungsten carbide alloy and a method for producing the same

Abstract

The application discloses a rare earth modified tungsten carbide alloy and a preparation method thereof, and belongs to the technical field of tungsten carbide alloys. The rare earth modified tungsten carbide alloy comprises a hard phase and a matrix, the mass percentage of the hard phase is 80wt.%-90wt.%, the mass percentage of the matrix is 10wt.%-20wt.%, and the hard phase is uniformly distributed in the matrix; the hard phase comprises a rare earth modified tungsten carbide core, the outside of the rare earth modified tungsten carbide core is coated with a nano tungsten carbide shell, the mass percentage of the rare earth modified tungsten carbide core in the hard phase is 85wt.%-95wt.%, and the mass percentage of the nano tungsten carbide shell in the hard phase is 5wt.%-15wt.%. The rare earth modified tungsten carbide alloy and the preparation method thereof can solve the problems of poor hardness and wear resistance of the existing tungsten carbide alloy, and are beneficial to improving the toughness of the tungsten carbide alloy.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of tungsten carbide alloy, and particularly relates to a rare earth modified tungsten carbide alloy and a preparation method thereof. BACKGROUND

[0002] Tungsten carbide-based hard alloy is widely used in cutting tools, mining tools and wear-resistant parts due to its high hardness, wear resistance and thermal stability. In the field of mechanical processing, tungsten carbide tools can significantly improve metal cutting efficiency; in the oil drilling industry, tungsten carbide drill bits can effectively cope with complex formation conditions and prolong service life. With the development of manufacturing industry towards high precision, high efficiency and high reliability, higher requirements are put forward for the comprehensive performance of tungsten carbide alloy. The traditional tungsten carbide alloy still has many technical bottlenecks in practical application, and its toughness and hardness are difficult to achieve an ideal balance. Although the conventional tungsten carbide-cobalt (WC-Co) alloy has high hardness, it is prone to brittle fracture when subjected to impact load or alternating stress, which limits its application in high load and high dynamic stress working conditions.

[0003] The existing patent CN202311052539.7 discloses a tungsten carbide super wear-resistant hard alloy and a preparation method and application thereof. The tungsten carbide super wear-resistant hard alloy comprises 90-97wt% of tungsten carbide powder, 0.1-2.3wt% of limiting agent, 0.1-1.3wt% of cobalt and 0.1-1.5wt% of rare earth metal. The limiting agent added in the tungsten carbide powder is a mixture of chromium and vanadium with a mass ratio of 0.5-1.5:1. The preparation method comprises the following steps: (1) mixing the tungsten carbide powder with the limiting agent and the rare earth metal, and grinding by adding alcohol; (2) vacuum drying after discharging the slurry; (3) sieving by using a special sieve machine to obtain WC alloy powder; (4) placing the WC alloy powder in a mold and pressing into shape by using a cold isostatic pressing machine; (5) placing the pressed blank in a vacuum sintering furnace for sintering; and (6) obtaining the tungsten carbide super wear-resistant hard alloy by natural cooling to room temperature after sintering. The tungsten carbide super wear-resistant hard alloy improves wear resistance and reduces production cost, and is suitable for large-scale industrial production. The above patent controls the growth of alloy crystals and improves the closure degree of alloy crystals by adding limiting agent and rare earth metal into tungsten carbide. However, the hardness and wear resistance of the prepared tungsten carbide alloy are still relatively low, and the toughness of the tungsten carbide alloy is poor. SUMMARY

[0004] The present application aims to provide a rare earth modified tungsten carbide alloy and a preparation method thereof, which solve the problem of poor hardness and wear resistance of the existing tungsten carbide alloy and improve the toughness of the tungsten carbide alloy.

[0005] In order to achieve the above object, the present application provides a rare earth modified tungsten carbide alloy, which comprises a hard phase and a matrix, the mass percentage of the hard phase is 80wt.%-90wt.%, the mass percentage of the matrix is 10wt.%-20wt.%, the hard phase is uniformly distributed in the matrix; the hard phase comprises a rare earth modified tungsten carbide core, the outside of the rare earth modified tungsten carbide core is coated with a nano tungsten carbide shell, the mass percentage of the rare earth modified tungsten carbide core in the hard phase is 85wt.%-95wt.%, and the mass percentage of the nano tungsten carbide shell in the hard phase is 5wt.%-15wt.%.

[0006] Preferably, the rare earth modified tungsten carbide core is spherical, and the particle size of the rare earth modified tungsten carbide core is 20μm-30μm.

[0007] Preferably, the rare earth modified tungsten carbide core comprises the following components in the following mass percentages: 15wt.%-20wt.% of tungsten carbide particles with a particle size of 150nm-200nm, 50wt.%-70wt.% of tungsten carbide particles with a particle size of 1.0μm-1.5μm, 10wt.%-20wt.% of tungsten carbide particles with a particle size of 3μm-5μm, 0.1wt.%-0.5wt.% of rare earth oxides, and 8wt.%-10wt.% of cobalt powder with a particle size of 1.0μm-1.5μm.

[0008] Preferably, the particle size of the rare earth oxides is 0.5μm-1.0μm, and the rare earth oxides are one of cerium oxide and yttrium oxide.

[0009] Preferably, the particle size of the nano tungsten carbide in the nano tungsten carbide shell is 0.2μm-0.4μm, and the nano tungsten carbide shell comprises 90wt.%-95wt.% of nano tungsten carbide, 5wt.%-10wt.% of cobalt, and 1wt.%-2wt.% of water glass.

[0010] Preferably, the matrix comprises 80wt.%-85wt.% of tungsten carbide, 3wt.%-5wt.% of molybdenum carbide, 10wt.%-15wt.% of a binder, and 3wt.%-5wt.% of an additive; the particle size of the tungsten carbide in the matrix is 2μm-3μm, the particle size of the molybdenum carbide is 3μm-5μm, the binder comprises four elements of Fe, Co, Ni, and Cr in a molar ratio of 1:1:1:1, and the additive is a mixture of one or more of titanium, tantalum, and niobium.

[0011] The preparation method of the rare earth modified tungsten carbide alloy comprises the following steps:

[0012] S1, preparing a rare earth modified tungsten carbide core;

[0013] S2, coating the nanometer tungsten carbide shell outside the rare earth modified tungsten carbide core to obtain the hard phase;

[0014] S3, preparing the base material, adding the hard phase into the base material to mix uniformly, pressing and forming, and then sintering to obtain the rare earth modified tungsten carbide alloy blank;

[0015] S4, performing heat treatment on the hard tungsten carbide alloy blank to obtain the hard tungsten carbide alloy, the heat treatment temperature is 1200-1300℃, and the heat treatment time is 4-6 hours.

[0016] Preferably, the S1 comprises the following steps:

[0017] S11, ball-mixing tungsten carbide particles with a particle size of 150-200nm, tungsten carbide particles with a particle size of 1.0-1.5μm, tungsten carbide particles with a particle size of 3-5μm, and cobalt powder according to the mass ratio to obtain tungsten carbide mixed powder;

[0018] S12, weighing rare earth oxides according to the mass ratio, adding the rare earth oxides and the tungsten carbide mixed powder into a copper sulfate aqueous solution with a mass concentration of 15-20%, and stirring uniformly to obtain a mixed solution;

[0019] S13, sending the mixed solution into an atomizing nozzle to perform atomization, spraying the atomized liquid drops into a reaction furnace with a temperature of 1200-1300℃ to perform reaction, and then washing and drying the reaction product to obtain the rare earth modified tungsten carbide core.

[0020] Preferably, the S2 comprises the following steps:

[0021] S21, adding nanometer tungsten carbide according to the mass ratio, mixing the rare earth modified tungsten carbide core with the nanometer tungsten carbide, adding water glass, and performing ball-mixing in an alcohol medium with a ball-to-material ratio of 5:1-8:1, a ball-milling speed of 300-400r / min, and a ball-milling time of 12-24h to obtain a composite powder;

[0022] S22, pre-sintering the composite powder in a heating furnace, the pre-sintering temperature is 300-500℃, and the pre-sintering time is 1-2h;

[0023] S23, heating the heating furnace to 1200-1300℃ and keeping the temperature for 1-2h, then heating the heating furnace to 1400-1500℃, applying a pressure of 5-10MPa, and keeping the temperature for 1-2h to obtain a sintered body;

[0024] S24, crushing the sintered body, ball-milling, and sieving to obtain hard phase particles.

[0025] Preferably, the S3 comprises the following steps:

[0026] S31, Fe, Co, Ni, Cr powders are weighed according to the component ratio, and are uniformly mixed by ball milling to obtain a binder powder;

[0027] S32, the binder powder, tungsten carbide, molybdenum carbide, titanium, tantalum, and niobium powders are mixed and ball milled to obtain a matrix raw material;

[0028] S33, the hard phase is added to the matrix raw material, and after uniform ball milling and mixing, the mixture is pressed and formed, and then sintered in a spark plasma sintering furnace, to obtain a rare earth modified tungsten carbide alloy blank after cooling; the sintering temperature is 1300 DEG C to 1400 DEG C, the sintering time is 20 min to 30 min, and the sintering pressure is 20 MPa to 40 MPa.

[0029] The rare earth modified tungsten carbide alloy and the preparation method thereof have the following advantages and positive effects:

[0030] 1, in the present application, the core of the rare earth modified tungsten carbide is micron grade, and the inside is mixed by tungsten carbide particles of different particle sizes, different tungsten carbide particles form a multi-stage grain distribution, and the initial strengthening is realized through the "crystal boundary hinders dislocation movement" mechanism. The outer nanometer tungsten carbide shell further improves the surface hardness through the nano effect, the nanometer grain size significantly increases the grain boundary density, the dislocation slip path is greatly shortened, and higher stress is required to initiate plastic deformation, further improving the hardness and fracture toughness of the hard phase surface.

[0031] 2, the rare earth oxide is adsorbed on the WC grain boundary during sintering, which reduces the grain boundary energy and inhibits the abnormal growth of the grain. The rare earth oxide is adsorbed on the surface of the nanometer tungsten carbide and the micron tungsten carbide, which reduces the surface energy difference between the tungsten carbide particles of different particle sizes, reduces the agglomeration tendency caused by the surface energy gradient, promotes the uniform dispersion of particles of different sizes, and improves the bonding strength between the core of the rare earth modified tungsten carbide and the nanometer tungsten carbide shell.

[0032] 3, the molybdenum carbide in the matrix as a hard second phase is uniformly distributed in the tungsten carbide and the binder phase of the matrix, which hinders the dislocation movement through the dispersion strengthening mechanism, improves the toughness and hardness of the matrix, and the cobalt in the nanometer tungsten carbide and the molybdenum carbide in the matrix form a metallurgical bond through cobalt liquid phase diffusion, which promotes the atomic diffusion between the molybdenum carbide and the hard phase, forms a W-Mo-C-Co solid solution transition layer, and improves the bonding strength between the matrix and the hard phase, reduces the risk of peeling of the hard phase.

[0033] 4, Co and Ni in the binder phase diffuse into the MoC lattice to form a Co / Ni doped MoC solid solution, which enhances the interface metallurgical bonding. Cr forms a diffusion barrier, which improves the bonding strength of the molybdenum carbide particles and the matrix, and ensures the stability of the matrix binder composition.

[0034] 5、Water glass is decomposed and forms uniform micropore with size not more than 1 micron on the surface of the nanometer tungsten carbide shell, so that when the hard phase is combined with the matrix, the binder phase in the matrix penetrates into the gap by capillary action to form a "metal pinning" structure, and the "mechanical interlocking interface" formed after cooling is beneficial to improve the bonding strength between the hard phase and the matrix.

[0035] The technical solutions of the present application are further described in detail below through examples. DETAILED DESCRIPTION

[0036] In the present application, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs. If there is any inconsistency, the meaning as explained in the present specification or the meaning derived from the content described in the present specification shall prevail. In addition, the terms used herein are only for the purpose of describing the embodiments of the present application and are not intended to limit the present application.

[0037] The embodiments of the present application are described in detail below.

[0038] A rare earth modified tungsten carbide alloy includes a hard phase and a matrix, the mass percentage of the hard phase is 80wt.%-90wt.% and the mass percentage of the matrix is 10wt.%-20wt.% and the hard phase is uniformly distributed in the matrix. The hard phase includes a rare earth modified tungsten carbide core, the rare earth modified tungsten carbide core is coated with a nanometer tungsten carbide shell outside, the mass percentage of the rare earth modified tungsten carbide core in the hard phase is 85wt.%-95wt.% and the mass percentage of the nanometer tungsten carbide shell in the hard phase is 5wt.%-15wt.%.

[0039] The rare earth modified tungsten carbide core is spherical and the particle size of the rare earth modified tungsten carbide core is 20μm-30μm.

[0040] The rare earth modified tungsten carbide core includes the following components with the following mass percentages: tungsten carbide particles with a particle size of 150nm-200nm are 15wt.%-20wt.%, tungsten carbide particles with a particle size of 1.0μm-1.5μm are 50wt.%-70wt.%, tungsten carbide particles with a particle size of 3μm-5μm are 10wt.%-20wt.%, rare earth oxides are 0.1wt.%-0.5wt.% and cobalt powder with a particle size of 1.0μm-1.5μm is 8wt.%-10wt.%.

[0041] The particle size of the rare earth oxides is 0.5μm-1.0μm and the rare earth oxides are one of cerium oxide and yttrium oxide.

[0042] The nano tungsten carbide has a particle size of 0.2-0.4 μm, and the nano tungsten carbide shell comprises 90-95 wt.% nano tungsten carbide, 5-10 wt.% cobalt and 1-2 wt.% water glass.

[0043] In the present application, the rare earth modified tungsten carbide core is micron grade, and the inside is mixed with tungsten carbide particles of different particle sizes. Different tungsten carbide particles form a multi-stage grain distribution, and the initial strengthening is realized through the "grain boundary hindering dislocation movement" mechanism. The outer nano tungsten carbide shell further improves the surface hardness through the nano effect. The nano-scale grain size significantly increases the grain boundary density, and the dislocation slip path is greatly shortened, requiring higher stress to initiate plastic deformation, further improving the hardness of the hard phase surface.

[0044] There is a difference in the thermal expansion coefficient between the nano tungsten carbide shell and the micron core. The surface effect of nano WC makes its thermal expansion coefficient slightly higher than that of micron WC. During the cooling process, compressive stress is generated in the shell, and tensile stress is generated in the core, forming a residual stress gradient. When the alloy is subjected to external load, the compressive stress at the interface can offset part of the tensile stress, delaying crack initiation. The high toughness cobalt phase of the nano shell acts as a "toughness buffer layer" and can absorb crack propagation energy, thereby improving the impact toughness of the alloy.

[0045] The rare earth oxide is adsorbed on the WC grain boundary during sintering, reducing the grain boundary energy, inhibiting abnormal grain growth, and reducing the brittle phase precipitation at the grain boundary, thereby enhancing the grain boundary bonding and further improving the fracture toughness. In addition, the rare earth oxide is adsorbed on the surface of nano tungsten carbide and micron tungsten carbide, reducing the surface energy difference between different particle size tungsten carbide particles, reducing the agglomeration tendency caused by the surface energy gradient, and promoting the uniform dispersion of particles of different sizes. During sintering, the rare earth oxide reacts with copper sulfate aqueous solution to form a low melting point phase, forming a temporary liquid phase, filling the gap between nano / micron particles, and enhancing the metallurgical bonding between particles through liquid phase diffusion. The rare earth oxide on the surface of the core reacts with the cobalt phase in the nano tungsten carbide shell during the coating process, forming a rare earth-cobalt composite interface layer, improving the bonding strength between the nano tungsten carbide shell and the rare earth modified tungsten carbide core, and promoting the uniform coating of the nano tungsten carbide shell on the rare earth modified tungsten carbide core.

[0046] The excess rare earth oxide is segregated at the interface to form a "pinning effect". When the crack propagates from the shell to the core, the rare earth oxide can act as a second phase to hinder the straight-line propagation of the crack, forcing the crack to deflect or bifurcate, consuming more energy, thereby improving the toughness and wear resistance of the tungsten carbide alloy.

[0047] In the hard phase, the outer layer of nano WC has high hardness and preferentially bears abrasive wear; the inner layer of nano-micron composite tungsten carbide core provides support to avoid overall crushing. When the shell is worn to a certain extent, the multi-stage grain structure of the core continues to play a wear-resistant role, forming a continuous wear-resistant gradient. The micron-nano composite structure of the tungsten carbide core has very good toughness, and the nano-structured shell has high surface hardness, thereby forming a rare earth modified tungsten carbide hard phase with outer hardness and inner toughness, which is beneficial to improve the hardness, toughness and wear resistance of the tungsten carbide alloy.

[0048] The base body comprises 80wt.%-85wt.% of tungsten carbide, 3wt.%-5wt.% of molybdenum carbide, 10wt.%-15wt.% of a binder, and 3wt.%-5wt.% of an additive; the particle size of the tungsten carbide in the base body is 2-3μm, the particle size of the molybdenum carbide is 3-5μm, the binder comprises four elements of Fe, Co, Ni and Cr in a molar ratio of 1:1:1:1, and the additive is a mixture of one or more of titanium, tantalum and niobium.

[0049] The molybdenum carbide has very high hardness, and the molybdenum carbide is uniformly distributed in the tungsten carbide and the binder phase of the base body as a hard second phase, which hinders dislocation movement through a dispersion strengthening mechanism, thereby improving the toughness and hardness of the base body. The thermal expansion coefficient of the carbonized is between the tungsten carbide and the binder phase, which can reduce the interfacial thermal stress mismatch and reduce the generation of microcracks during the cooling process. The molybdenum carbide and the tungsten carbide form a double-hard-phase system in the base body, which alternately bears cutting, reduces the wear damage of a single phase, and is beneficial to improve the wear resistance of the tungsten carbide alloy.

[0050] The cobalt on the surface of the hard phase with a core-shell structure forms a metallurgical bond with the molybdenum carbide in the base body through cobalt liquid phase diffusion, promotes atomic diffusion between the molybdenum carbide and the hard phase, forms a W-Mo-C-Co solid solution transition layer, improves the bonding strength between the base body and the hard phase, and reduces the risk of peeling of the hard phase.

[0051] The binder formed by the four elements of Fe, Co, Ni and Cr is beneficial to improve the wettability between the molybdenum carbide and the binder phase, and improve the bonding strength between the molybdenum carbide particles and the base body. The atomic radius of Co and Ni in the binder phase is close to that of Mo in the MoC lattice, which enters the MoC lattice through substitutional diffusion, forms a Co / Ni doped MoC solid solution, and enhances the interfacial metallurgical bonding. Cr has similar electron affinity energy with Mo, and Cr is adsorbed on the interface through electrostatic attraction, forming a Cr-Mo atomic chain at the interface, forming a diffusion barrier, inhibiting the depletion of the binder phase caused by excessive diffusion of Co and Ni into the MoC, while improving the bonding strength between the molybdenum carbide particles and the base body, and ensuring the stability of the binder composition of the base body.

[0052] The preparation method of the rare earth modified tungsten carbide alloy comprises the following steps:

[0053] S1, preparing a rare earth modified tungsten carbide core.

[0054] The method comprises the following steps:

[0055] S11, tungsten carbide particles with a particle size of 150-200 nm, tungsten carbide particles with a particle size of 1.0-1.5 μm, tungsten carbide particles with a particle size of 3-5 μm and cobalt powder are weighed according to the mass ratio and ball-mixed to obtain tungsten carbide mixed powder. Zirconium balls are used for ball-milling, the ball-to-material ratio is 6:1, the ball-milling speed is 300-400 r / min, and the ball-milling time is 12-24 h.

[0056] S12, rare earth oxides are weighed according to the mass ratio, and the rare earth oxides and the tungsten carbide mixed powder are added into a copper sulfate aqueous solution with a mass concentration of 15-20%, and stirred uniformly to obtain a mixed solution.

[0057] S13, the mixed solution is sent into an atomizing nozzle for atomization, the atomized liquid droplets are sprayed into a reaction furnace with a temperature of 1200-1300 ℃ for reaction, and the reaction product is washed and dried to obtain the rare earth modified tungsten carbide core.

[0058] S2, a nano tungsten carbide shell is coated on the outside of the rare earth modified tungsten carbide core to obtain a hard phase.

[0059] The method comprises the following steps:

[0060] S21, nano tungsten carbide is added according to the mass ratio, the rare earth modified tungsten carbide core and the nano tungsten carbide are mixed, water glass is added, and ball-mixing is performed in an alcohol medium at a ball-to-material ratio of 5:1-8:1, a ball-milling speed of 300-400 r / min and a ball-milling time of 12-24 h to obtain a composite powder.

[0061] The water glass acts as a dispersant in the ball-milling stage, prevents the nano tungsten carbide from agglomerating through electrostatic repulsion, and is beneficial to improving the uniformity of the dispersion between the nano tungsten carbide and the rare earth modified tungsten carbide core.

[0062] S22, the composite powder is placed into a heating furnace for pre-sintering, the pre-sintering temperature is 300-500 ℃, and the pre-sintering time is 1-2 h.

[0063] The pre-sintering heating rate is no more than 5°C / min. At a lower heating rate, it is conducive to the volatilization of alcohol, and water glass decomposes at 300°C-500°C, releasing carbon dioxide gas, forming uniform micropores no larger than 1 micron on the surface of the nano-tungsten carbide shell. When the hard phase is combined with the matrix, the bonding phase in the matrix penetrates into the gaps through capillary action, forming a "metal pinning" structure. After cooling, a "mechanical interlocking interface" is formed, which is conducive to improving the bonding strength between the hard phase and the matrix. It also increases the actual contact area between the hard phase and the matrix, which is also conducive to improving the bonding strength between the hard phase and the matrix. The porosity of the nano-tungsten carbide shell is below 5%. The Co and Ni in the bonding phase react with the nano-tungsten carbide to form a solid solution strengthening layer, which seals the micropores on the nano-tungsten carbide shell.

[0064] S23. Raise the heating furnace temperature to 1200-1300°C and hold the temperature for 1-2 hours; then raise the heating furnace temperature to 1400-1500°C, apply a pressure of 5-10 MPa, and hold the temperature for 1-2 hours to obtain a sintered body. The entire sintering process is carried out under inert gas protection.

[0065] S24, crushing the sintered body, ball milling, and sieving to obtain hard phase particles with a particle size of 25 μm-35 μm.

[0066] S3. Prepare a matrix raw material, add the hard phase into the matrix raw material and mix them evenly, press and form them, and then sinter them to obtain a rare earth modified tungsten carbide alloy blank.

[0067] The following steps are involved:

[0068] S31. Weigh Fe, Co, Ni, and Cr powders according to the composition ratio and mix them uniformly by ball milling to obtain a binder powder. The ball-to-material ratio of the ball milling is 10:1, the ball milling speed is 300-400 rpm, and the ball milling time is 40-50 hours.

[0069] S32. Mix and ball-mill the binder powder, tungsten carbide, molybdenum carbide, titanium, tantalum, and niobium powders to obtain a matrix material. The ball-to-material ratio during ball milling is 6:1, the milling speed is 300-400 rpm, and the milling time is 12-24 hours. After ball milling, the matrix material is dried in a vacuum drying oven at 60°C for 12-24 hours.

[0070] S33, the hard phase is added to the base material, and after ball milling and uniform mixing, it is pressed and formed. The ball milling ratio of the ball and the material is 6:1, the ball milling speed is 300r / min-400r / min, and the ball milling time is 12h-24h. Sintering is carried out in a spark plasma sintering furnace, and after cooling, a rare earth modified tungsten carbide alloy blank is obtained. The sintering is carried out under the protection of inert gas, the sintering temperature is 1300℃-1400℃, the sintering time is 20min-30min, and the sintering pressure is 20MPa-40MPa.

[0071] During the sintering process, pressure sintering is carried out, so that the molten binder phase can fully extrude into the micropores on the surface of the hard phase, and at the same time, the nano-carbide particles are plastically deformed, the pores of the shell are closed, and the density and the bonding strength of the hard phase and the matrix are improved.

[0072] S4, the hard tungsten carbide alloy blank is heat treated to obtain a hard tungsten carbide alloy, and the heat treatment temperature is 1200℃-1300℃ and the heat treatment time is 4-6 hours. Heat treatment causes titanium carbide, niobium carbide and tantalum carbide in the tungsten carbide alloy matrix to precipitate, thereby improving the hardness, wear resistance and heat resistance of the tungsten carbide alloy matrix.

[0073] Example 1

[0074] A rare earth modified tungsten carbide alloy includes a hard phase and a matrix, the mass percentage of the hard phase is 82wt.%, the mass percentage of the matrix is 18wt.%, and the hard phase is uniformly distributed in the matrix. The hard phase includes a rare earth modified tungsten carbide core, and the outside of the rare earth modified tungsten carbide core is coated with a nano-tungsten carbide shell. The mass percentage of the rare earth modified tungsten carbide core in the hard phase is 90wt.%, and the mass percentage of the nano-tungsten carbide shell in the hard phase is 10wt.%.

[0075] The rare earth modified tungsten carbide core includes the following components by mass percentage: 16wt.% of tungsten carbide particles with a particle size of 150nm-200nm, 63.9wt.% of tungsten carbide particles with a particle size of 1.0μm-1.5μm, 12wt.% of tungsten carbide particles with a particle size of 3μm-5μm, 0.1wt.% of rare earth oxides, and 8wt.% of cobalt powder with a particle size of 1.0μm-1.5μm.

[0076] The particle size of the rare earth oxide is 0.5μm-1.0μm, and the rare earth oxide is cerium oxide.

[0077] The particle size of the nano-tungsten carbide in the nano-tungsten carbide shell is 0.2μm-0.4μm, and the nano-tungsten carbide shell includes 93wt.% of nano-tungsten carbide, 6wt.% of cobalt, and 1wt.% of water glass.

[0078] The base body comprises 82wt.% tungsten carbide, 3wt.% molybdenum carbide, 12wt.% binder and 3wt.% additive; the particle size of tungsten carbide in the base body is 2-3μm, the particle size of molybdenum carbide is 3-5μm, the binder comprises four elements of Fe, Co, Ni and Cr in a molar ratio of 1:1:1:1, and the additive is titanium.

[0079] The preparation method of the rare earth modified tungsten carbide alloy comprises the following steps:

[0080] S1, preparing a rare earth modified tungsten carbide core.

[0081] The preparation method comprises the following steps:

[0082] S11, ball-mixing tungsten carbide particles with a particle size of 150-200nm, tungsten carbide particles with a particle size of 1.0-1.5μm, tungsten carbide particles with a particle size of 3-5μm and cobalt powder according to the mass ratio to obtain tungsten carbide mixed powder; zirconium balls are used for ball-milling, the ball-to-material ratio is 6:1, the ball-milling speed is 300r / min, and the ball-milling time is 20h.

[0083] S12, weighing rare earth oxides according to the mass ratio, and adding the rare earth oxides and the tungsten carbide mixed powder into a copper sulfate aqueous solution with a mass concentration of 20% to obtain a mixed solution after stirring uniformly.

[0084] S13, sending the mixed solution into an atomizing nozzle to be atomized, spraying the atomized liquid drops into a reaction furnace with a temperature of 1200℃ to react, and obtaining the rare earth modified tungsten carbide core after washing and drying the reactants.

[0085] S2, coating a nano tungsten carbide shell on the outside of the rare earth modified tungsten carbide core to obtain a hard phase.

[0086] The preparation method comprises the following steps:

[0087] S21, adding nano tungsten carbide according to the mass ratio, mixing the rare earth modified tungsten carbide core with the nano tungsten carbide, and adding water glass to perform ball-mixing in an alcohol medium with a ball-to-material ratio of 6:1, a ball-milling speed of 300r / min and a ball-milling time of 20h to obtain a composite powder.

[0088] S22, pre-sintering the composite powder in a heating furnace at a temperature of 400℃ for 2h.

[0089] S23, heating the heating furnace to 1200℃ and keeping the temperature for 1h, then heating the heating furnace to 1500℃, applying a pressure of 8MPa and keeping the temperature for 2h to obtain a sintered body; the whole sintering process is performed under the protection of inert gas.

[0090] S24, crushing the sintered body, ball milling, and sieving to obtain hard phase particles with a particle size of 25-35 μm.

[0091] S3, preparing a base material, adding the hard phase to the base material and mixing uniformly, pressing and forming, and sintering to obtain a rare earth modified tungsten carbide alloy blank.

[0092] comprising the following steps:

[0093] S31, weighing Fe, Co, Ni, and Cr powders according to the component proportions, and mixing uniformly by ball milling to obtain a binder powder. The ball-to-material ratio for ball milling is 10:1, the ball milling speed is 400 r / min, and the ball milling time is 50 h.

[0094] S32, mixing and ball milling the binder powder, tungsten carbide powder, molybdenum carbide powder, titanium powder, tantalum powder, and niobium powder to obtain a base material. The ball-to-material ratio for ball milling is 6:1, the ball milling speed is 300 r / min, and the ball milling time is 20 h. After ball milling, the base material is dried under the following conditions: drying in a vacuum drying oven at 60°C for 12 h.

[0095] S33, adding the hard phase to the base material, ball milling and mixing uniformly, and pressing and forming. The ball-to-material ratio for ball milling is 6:1, the ball milling speed is 300 r / min, and the ball milling time is 20 h. Sintering is performed in a spark plasma sintering furnace, and a rare earth modified tungsten carbide alloy blank is obtained after cooling. The sintering is performed under inert gas protection, the sintering temperature is 1300°C, the sintering time is 20 min, and the sintering pressure is 25 MPa.

[0096] S4, heat treating the hard tungsten carbide alloy blank to obtain a hard tungsten carbide alloy, the heat treatment temperature is 1200°C, and the heat treatment time is 4 h.

[0097] Example 2

[0098] A rare earth modified tungsten carbide alloy comprises a hard phase and a base material, the mass percentage of the hard phase is 84 wt.%, the mass percentage of the base material is 16 wt.%, and the hard phase is uniformly distributed in the base material. The hard phase comprises a rare earth modified tungsten carbide core, the outside of the rare earth modified tungsten carbide core is coated with a nano tungsten carbide shell, the mass percentage of the rare earth modified tungsten carbide core in the hard phase is 90 wt.%, and the mass percentage of the nano tungsten carbide shell in the hard phase is 10 wt.%.

[0099] The rare earth modified tungsten carbide core comprises the following components by mass percentage: 18 wt.% of tungsten carbide particles with a particle size of 150 nm-200 nm, 57.6 wt.% of tungsten carbide particles with a particle size of 1.0 μm-1.5 μm, 15 wt.% of tungsten carbide particles with a particle size of 3 μm-5 μm, 0.4 wt.% of rare earth oxides, and 9 wt.% of cobalt powder with a particle size of 1.0 μm-1.5 μm.

[0100] The particle size of the rare earth oxides is 0.5 μm-1.0 μm, and the rare earth oxides are cerium oxides.

[0101] The particle size of the nanometer tungsten carbide in the nanometer tungsten carbide shell is 0.2 μm-0.4 μm, and the nanometer tungsten carbide shell comprises 90 wt.% of nanometer tungsten carbide, 8 wt.% of cobalt, and 2 wt.% of water glass.

[0102] The matrix comprises 80 wt.% of tungsten carbide, 4 wt.% of molybdenum carbide, 13 wt.% of a binder, and 3 wt.% of an additive; the particle size of the tungsten carbide in the matrix is 2 μm-3 μm, the particle size of the molybdenum carbide is 3 μm-5 μm, the binder comprises four elements of Fe, Co, Ni, and Cr in a molar ratio of 1:1:1:1, and the additive is titanium.

[0103] The method for preparing the rare earth modified tungsten carbide alloy comprises the following steps:

[0104] S1, preparing a rare earth modified tungsten carbide core.

[0105] comprises the following steps:

[0106] S11, weighing and mixing tungsten carbide particles with a particle size of 150 nm-200 nm, tungsten carbide particles with a particle size of 1.0 μm-1.5 μm, tungsten carbide particles with a particle size of 3 μm-5 μm, and cobalt powder according to the mass ratio to obtain a tungsten carbide mixed powder; zirconium balls are used for ball milling, the ball-to-material ratio is 6:1, the ball milling speed is 300 r / min, and the ball milling time is 20 h.

[0107] S12, weighing rare earth oxides according to the mass ratio, and adding the rare earth oxides and the tungsten carbide mixed powder into a copper sulfate aqueous solution with a mass concentration of 20% to obtain a mixed solution after stirring uniformly.

[0108] S13, sending the mixed solution into an atomizing nozzle to perform atomization, spraying the atomized liquid drops into a reaction furnace with a temperature of 1300 ℃ to perform a reaction, and obtaining the rare earth modified tungsten carbide core after washing and drying the reaction product.

[0109] S2, coating a nanometer tungsten carbide shell on the outside of the rare earth modified tungsten carbide core to obtain a hard phase.

[0110] comprises the following steps:

[0111] S21, nano tungsten carbide is added according to the mass ratio, the rare earth modified tungsten carbide core is mixed with the nano tungsten carbide, water glass is added, and ball milling is carried out in an alcohol medium at a ball-to-material ratio of 6:1, a ball milling speed of 300 r / min, and a ball milling time of 20 h to obtain a composite powder.

[0112] S22, the composite powder is placed in a heating furnace for pre-sintering, the pre-sintering temperature is 500 DEG C, and the pre-sintering time is 2 h.

[0113] S23, the heating furnace is heated to 1300 DEG C and kept for 2 h, then the heating furnace is heated to 1500 DEG C, a pressure of 10 MPa is applied, and kept for 2 h to obtain a sintered body. The whole sintering process is carried out under inert gas protection.

[0114] S24, the sintered body is crushed, ball milled and sieved to obtain hard phase particles with a particle size of 25-35 μm.

[0115] S3, the base material is prepared, the hard phase is added to the base material and uniformly mixed, and then sintered after being pressed into a shape to obtain a rare earth modified tungsten carbide alloy blank.

[0116] comprising the following steps:

[0117] S31, Fe, Co, Ni and Cr powders are weighed according to the component ratio, and uniformly mixed by ball milling to obtain a binder powder. The ball-to-material ratio of ball milling is 10:1, the ball milling speed is 400 r / min, and the ball milling time is 50 h.

[0118] S32, the binder powder, tungsten carbide, molybdenum carbide, titanium, tantalum and niobium powders are mixed and ball milled to obtain a base material. The ball-to-material ratio of ball milling is 6:1, the ball milling speed is 300 r / min, and the ball milling time is 20 h. After ball milling, the base material is dried in a vacuum drying oven at 60 DEG C for 24 h.

[0119] S33, the hard phase is added to the base material, uniformly mixed by ball milling, and then pressed into a shape. The ball-to-material ratio of ball milling is 6:1, the ball milling speed is 300 r / min, and the ball milling time is 20 h. Sintering is carried out in a spark plasma sintering furnace, and a rare earth modified tungsten carbide alloy blank is obtained after cooling. The sintering is carried out under inert gas protection, the sintering temperature is 1400 DEG C, the sintering time is 30 min, and the sintering pressure is 30 MPa.

[0120] S4, the hard tungsten carbide alloy blank is heat treated to obtain a hard tungsten carbide alloy, the heat treatment temperature is 1200 DEG C, and the heat treatment time is 5 hours.

[0121] Example 3

[0122] A rare earth modified tungsten carbide alloy, comprising a hard phase and a matrix, the mass percentage of the hard phase being 89wt.%, the mass percentage of the matrix being 11wt.%, the hard phase being uniformly distributed in the matrix. The hard phase comprises a rare earth modified tungsten carbide core, the rare earth modified tungsten carbide core being coated with a nano tungsten carbide shell outside, the mass percentage of the rare earth modified tungsten carbide core in the hard phase being 94wt.%, the mass percentage of the nano tungsten carbide shell in the hard phase being 6wt.%.

[0123] The rare earth modified tungsten carbide core comprises the following components by mass percentage: 15wt.% of tungsten carbide particles with a particle size of 150nm-200nm, 61.8wt.% of tungsten carbide particles with a particle size of 1.0μm-1.5μm, 15wt.% of tungsten carbide particles with a particle size of 3μm-5μm, 0.2wt.% of rare earth oxides, and 8wt.% of cobalt powder with a particle size of 1.0μm-1.5μm.

[0124] The particle size of the rare earth oxides is 0.5μm-1.0μm, and the rare earth oxides are yttrium oxides.

[0125] The particle size of the nano tungsten carbide in the nano tungsten carbide shell is 0.2μm-0.4μm, and the nano tungsten carbide shell comprises 92wt.% of nano tungsten carbide, 6wt.% of cobalt, and 2wt.% of water glass.

[0126] The matrix comprises 82wt.% of tungsten carbide, 3wt.% of molybdenum carbide, 10wt.% of a binder, and 5wt.% of an additive; the particle size of the tungsten carbide in the matrix is 2μm-3μm, the particle size of the molybdenum carbide is 3μm-5μm, the binder comprises four elements of Fe, Co, Ni, and Cr in a molar ratio of 1:1:1:1, and the additive is titanium.

[0127] A preparation method of a rare earth modified tungsten carbide alloy, comprising the following steps:

[0128] S1, preparing a rare earth modified tungsten carbide core.

[0129] comprising the following steps:

[0130] S11, weighing and mixing tungsten carbide particles with a particle size of 150nm-200nm, tungsten carbide particles with a particle size of 1.0μm-1.5μm, tungsten carbide particles with a particle size of 3μm-5μm, and cobalt powder according to the mass ratio to obtain a tungsten carbide mixed powder. Zirconium balls are used for ball milling, the ball-to-material ratio is 6:1, the ball milling speed is 300r / min, and the ball milling time is 20h.

[0131] S12, weighing rare earth oxides according to the mass ratio, and adding the rare earth oxides and the tungsten carbide mixed powder into a copper sulfate aqueous solution with a mass concentration of 15% to obtain a mixed solution after stirring uniformly.

[0132] S13, the mixed solution is sent into an atomizing nozzle for atomization, and the atomized liquid droplets are sprayed into a reaction furnace at a temperature of 1300 DEG C for reaction, and after washing and drying, the rare earth modified tungsten carbide core is obtained.

[0133] S2, a nano tungsten carbide shell is coated on the outside of the rare earth modified tungsten carbide core to obtain a hard phase.

[0134] The method comprises the following steps:

[0135] S21, nano tungsten carbide is added according to a mass ratio, the rare earth modified tungsten carbide core is mixed with the nano tungsten carbide, water glass is added, and ball milling is carried out in an alcohol medium at a ball-to-material ratio of 6:1, a ball milling speed of 300 r / min, and a ball milling time of 20 h to obtain a composite powder.

[0136] S22, the composite powder is placed into a heating furnace for pre-sintering at a temperature of 300 DEG C for 2 h.

[0137] S23, the heating furnace is heated to 1300 DEG C and kept for 2 h, then the heating furnace is heated to 1500 DEG C, a pressure of 10 MPa is applied, and the temperature is kept for 2 h to obtain a sintered body. The whole sintering process is carried out under inert gas protection.

[0138] S24, the sintered body is crushed, ball milled, and sieved to obtain hard phase particles with a particle size of 25-35 mu m.

[0139] S3, a matrix raw material is prepared, the hard phase is added into the matrix raw material and uniformly mixed, and then sintering is carried out after compression molding to obtain a rare earth modified tungsten carbide alloy blank.

[0140] The method comprises the following steps:

[0141] S31, Fe, Co, Ni, and Cr powders are weighed according to a component ratio, and uniformly mixed by ball milling to obtain a binder powder. The ball-to-material ratio of ball milling is 10:1, the ball milling speed is 400 r / min, and the ball milling time is 50 h.

[0142] S32, the binder powder, tungsten carbide, molybdenum carbide, titanium, tantalum, and niobium powders are mixed and ball milled to obtain a matrix raw material. The ball-to-material ratio of ball milling is 6:1, the ball milling speed is 300 r / min, and the ball milling time is 20 h. After ball milling, the matrix raw material is dried in a vacuum drying box at 60 DEG C for 24 h.

[0143] S33, the hard phase is added to the base material, and after ball milling and uniform mixing, it is pressed and formed. The ball milling ratio of the ball to the material is 6:1, the ball milling speed is 300 r / min, and the ball milling time is 20 h. Sintering is performed in a spark plasma sintering furnace, and after cooling, a rare earth modified tungsten carbide alloy blank is obtained. The sintering is performed under inert gas protection, the sintering temperature is 1400℃, the sintering time is 30 min, and the sintering pressure is 30 MPa.

[0144] S4, the hard tungsten carbide alloy blank is subjected to heat treatment to obtain a hard tungsten carbide alloy, the heat treatment temperature is 1200℃, and the heat treatment time is 5 hours.

[0145] Comparative Example 1

[0146] The difference between this comparative example and Example 2 is that in this comparative example, the hard phase only includes the rare earth modified tungsten carbide core, and the outside of the core is not wrapped with a nano tungsten carbide shell.

[0147] The preparation process of the nano tungsten carbide shell is omitted in the preparation method.

[0148] Comparative Example 2

[0149] The difference between this comparative example and Example 2 is that in this comparative example, the rare earth modified tungsten carbide core only includes tungsten carbide particles with a particle size of 3μm-5μm.

[0150] Comparative Example 3

[0151] The difference between this comparative example and Example 2 is that in this comparative example, the rare earth modified tungsten carbide core only includes tungsten carbide particles with a particle size of 150nm-200nm.

[0152] Comparative Example 4

[0153] The difference between this comparative example and Example 2 is that in this comparative example, the nano tungsten carbide shell does not contain water glass, and the mass percentage of cobalt is 10wt.%.

[0154] Comparative Example 5

[0155] The difference between this comparative example and Example 2 is that in this comparative example, the base material does not contain molybdenum carbide, and the mass percentage of tungsten carbide in the base material is 84wt.%.

[0156] The Rockwell hardness, fracture toughness, bending strength and wear volume of the tungsten carbide alloys prepared in Examples 1-3 and Comparative Examples 1-5 were detected, the fracture toughness was detected according to the standard ISO28079-2009, the hardness was detected according to GBT3849.1-2015, the bending strength was detected according to GBT3851-2015, and the wear volume was detected according to Q / 62071126-8F0524-2014. The properties of the tungsten carbide alloys prepared in Examples 1-3 and Comparative Examples 1-5 are shown in Table 1.

[0157] Table 1 Properties of tungsten carbide alloys prepared in Examples 1-3 and Comparative Examples 1-5

[0158] ;

[0159] As shown in Table 1, the tungsten carbide alloy in which the nano tungsten carbide shell is wrapped outside the rare earth modified tungsten carbide core can effectively improve the hardness, fracture toughness, bending strength and wear resistance of the tungsten carbide alloy; the micro-nano composite structure of the rare earth modified tungsten carbide core, the addition of molybdenum carbide in the matrix, and the addition of water in the nano tungsten carbide shell are all conducive to improving the hardness, fracture toughness and bending strength of the tungsten carbide alloy, and the wear volume is small, which is conducive to improving the wear resistance of the tungsten carbide alloy.

[0160] Therefore, the rare earth modified tungsten carbide alloy and the preparation method thereof can solve the problems of poor hardness and wear resistance of the existing tungsten carbide alloy, and are conducive to improving the toughness of the tungsten carbide alloy.

[0161] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application but not to limit it, although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can still be modified or replaced by equivalents, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present application.

Claims

1. A rare earth modified tungsten carbide alloy, characterized in that: The invention comprises a hard phase and a matrix, wherein the mass percentage of the hard phase is 80wt.%-90wt.%, the mass percentage of the matrix is ​​10wt.%-20wt.%, and the hard phase is uniformly distributed in the matrix; the hard phase comprises a rare earth modified tungsten carbide core, the outer surface of the rare earth modified tungsten carbide core is coated with a nano tungsten carbide shell, the mass percentage of the rare earth modified tungsten carbide core in the hard phase is 85wt.%-95wt.%, and the mass percentage of the nano tungsten carbide shell in the hard phase is 5wt.%-15wt.%; The rare earth modified tungsten carbide core includes the following components in mass percentage: 15wt.%-20wt.% of tungsten carbide particles with a particle size of 150nm-200nm, 50wt.%-70wt.% of tungsten carbide particles with a particle size of 1.0μm-1.5μm, 10wt.%-20wt.% of tungsten carbide particles with a particle size of 3μm-5μm, 0.1wt.%-0.5wt.% of rare earth oxide, and 8wt.%-10wt.% of cobalt powder with a particle size of 1.0μm-1.5μm.

2. A rare earth modified tungsten carbide alloy according to claim 1, characterized in that: The rare earth modified tungsten carbide core is spherical, and the particle size of the rare earth modified tungsten carbide core is 20 μm-30 μm.

3. A rare earth modified tungsten carbide alloy according to claim 2, characterized in that: The particle size of the rare earth oxide is 0.5 μm-1.0 μm, and the rare earth oxide is one of cerium oxide and yttrium oxide.

4. The method for preparing a rare earth modified tungsten carbide alloy according to claim 3, wherein: The following steps are involved: S1. preparing a rare earth modified tungsten carbide core; S2, coating the outer surface of the rare earth modified tungsten carbide core with a nano-tungsten carbide shell to obtain a hard phase; S3, preparing a matrix raw material, adding the hard phase to the matrix raw material and mixing them evenly, pressing and then sintering to obtain a rare earth modified tungsten carbide alloy blank; S4. Heat-treating the hard tungsten carbide alloy blank to obtain hard tungsten carbide alloy, wherein the heat-treating temperature is 1200° C.-1300° C., and the heat-treating time is 4 hours-6 hours.

5. The method for preparing a rare earth modified tungsten carbide alloy according to claim 4, characterized in that: Said S1 comprises the following steps: S11, weighing tungsten carbide particles with a particle size of 150 nm to 200 nm, tungsten carbide particles with a particle size of 1.0 μm to 1.5 μm, tungsten carbide particles with a particle size of 3 μm to 5 μm, and cobalt powder according to a mass ratio, ball-milling and mixing to obtain a tungsten carbide mixed powder; S12, weighing rare earth oxide according to the mass ratio, adding the rare earth oxide and tungsten carbide mixed powder to a copper sulfate aqueous solution with a mass concentration of 15%-20%, stirring evenly to obtain a mixed solution; S13, sending the mixed liquid into an atomizing nozzle for atomization, spraying the atomized liquid droplets into a reactor with a temperature of 1200° C.-1300° C. for reaction, washing and drying the reactants to obtain a rare earth modified tungsten carbide core.

6. The method for preparing a rare earth modified tungsten carbide alloy according to claim 5, wherein: The S2 comprises the following steps: S21. Add nano-tungsten carbide according to the mass ratio, mix the rare earth modified tungsten carbide core and the nano-tungsten carbide, add water glass, and ball mill the mixture in an alcohol medium at a ball-to-material ratio of 5:1-8:1 at a ball milling speed of 300 rpm to 400 rpm for 12 h to 24 h to obtain a composite powder; S22, placing the composite powder into a heating furnace for pre-sintering at a temperature of 300° C. to 500° C. for a time of 1 h to 2 h; S23, heating the heating furnace to 1200-1300° C. and keeping the temperature for 1-2 hours; then heating the heating furnace to 1400-1500° C., applying a pressure of 5 MPa-10 MPa, and keeping the temperature for 1-2 hours to obtain a sintered body; S24, crushing the sintered body, ball milling, and sieving to obtain hard phase particles.

7. The method for preparing a rare earth modified tungsten carbide alloy according to claim 6, characterized in that: The S3 includes the following steps: S31, weighing Fe, Co, Ni, and Cr powders according to the component ratio, and mixing them uniformly by ball milling to obtain a binder powder; S32, mixing and ball-milling the binder powder, tungsten carbide, molybdenum carbide, titanium, tantalum, and niobium powder to obtain a matrix raw material; S33. Add the hard phase to the matrix raw material, mix evenly by ball milling, press into shape, sinter in a spark plasma sintering furnace, and obtain a rare earth modified tungsten carbide alloy blank after cooling; the sintering temperature is 1300°C-1400°C, the sintering time is 20min-30min, and the sintering pressure is 20MPa-40MPa.