CN112359298A - High-toughness coarse-grain hard alloy and preparation method thereof - Google Patents
High-toughness coarse-grain hard alloy and preparation method thereof Download PDFInfo
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Abstract
The invention relates to a high-toughness coarse-grain hard alloy and a preparation method thereof, belonging to the technical field of special alloy preparation. The high-toughness coarse-grained hard alloy prepared by the invention is prepared by mixing and reacting the self-made toughening filler, the porous silicon carbide fiber and the tungsten source material, and toughening by using the dispersed particles and the self-made toughening filler in a composite way, so that the toughness of the tungsten alloy material is greatly improved, the working application range of the tungsten alloy material is greatly improved, and the alloy material is prepared by the preparation process of raw material preparation, mixture preparation, green compact forming and sintering, and has wide application prospect.
Description
Technical Field
The invention relates to a high-toughness coarse-grain hard alloy and a preparation method thereof, belonging to the technical field of special alloy preparation.
Background
Tungsten (W) is widely used in the fields of national defense and military industry, aerospace and controlled nuclear fusion due to its good physical properties, such as high density, high hardness, high melting point, high thermal conductivity, low sputtering yield, etc. Such as high density alloy cutters made from tungsten material.
However, some problems with tungsten materials limit their application. The tungsten has high ductile-brittle transition temperature (DBTT) (above 400 ℃) and low recrystallization temperature (below 1300 ℃), so that the tungsten material has obvious low-temperature brittleness and high-temperature recrystallization brittleness. When the tungsten material is prepared and processed at the temperature lower than DBTT and bears external load, the tungsten material is easy to break. Therefore, the tungsten material for strengthening and toughening reduces DBTT, stabilizes high-temperature tissue, improves recrystallization temperature and enhances thermal shock cracking resistance, and is an important performance index.
In view of the above-mentioned drawbacks, the present inventors have made active research and innovation to create a high-toughness coarse-grained cemented carbide and a method for manufacturing the same, which have industrial utility value
Disclosure of Invention
In order to solve the technical problems, the invention aims to provide a high-toughness coarse-grain hard alloy which is prepared by sintering a reduction toughening alloy precursor through green compacts and spark plasmas;
the reduction toughening alloy precursor is prepared by reducing the toughening alloy precursor by high-purity hydrogen;
the precursor of the toughened alloy is prepared by heating, stirring and reacting a suspension and then drying;
the suspension consists of the following raw materials in parts by weight:
150-200 parts of ammonium metatungstate;
5-8 parts of hydrochloric acid;
3-5 parts of polyvinylpyrrolidone;
1.5-2.0 parts of porous silicon carbide fiber;
2-3 parts of self-made toughening filler;
1000-1500 parts of deionized water;
the porous silicon carbide fiber is prepared by carrying out mildewing, fermentation, carbonization and hydrofluoric acid soaking on rice hulls and sugarcane juice;
the self-made toughening filler is prepared by sintering nickel chloride, copper chloride, magnesium chloride and expanded graphite after an electroplating reaction.
A preparation method of high-toughness coarse-grain hard alloy comprises the following specific preparation steps:
(1) preparing a toughening precursor:
mixing nickel chloride, copper chloride and magnesium chloride, heating, after the mixed salt is melted, electroplating by taking an aluminum sheet as a positive electrode and taking expanded graphite as a negative electrode, and taking down the electroplated negative electrode to obtain a toughening precursor;
(2) preparing a self-made toughening filler:
carrying out heat preservation sintering treatment on the toughening precursor, naturally cooling to room temperature, taking out a sintering product, repeatedly washing, naturally airing, crushing and sieving to obtain a self-made toughening filler for later use;
(3) preparation of the mildew product:
mixing the rice hulls and the sugarcane juice, putting the mixture into a greenhouse, and naturally mildewing to obtain a mildewed product after the mildewing is finished;
(4) preparing porous silicon carbide fibers:
transferring the mildewed product into a fermentation tank, sealing and fermenting, filtering after fermentation is finished, transferring filter residue into a carbonization furnace, carbonizing, and soaking with hydrofluoric acid to obtain porous silicon carbide fiber;
(5) preparation of the suspension:
weighing ammonium metatungstate, hydrochloric acid, polyvinylpyrrolidone, porous silicon carbide fiber, self-made toughening filler and deionized water, and mixing to obtain a suspension;
(6) preparing a precursor of the toughened alloy:
putting the suspension into a magnetic stirrer, stirring at room temperature for reaction, heating while stirring, preserving heat for full precipitation, and drying to obtain a toughening alloy precursor;
(7) preparing a reduction toughening precursor:
loading the precursor of the toughening alloy into a tubular reduction furnace, and carrying out heat preservation reduction treatment to obtain a reduced toughening alloy precursor;
(8) preparing the high-toughness silicon carbide tungsten alloy:
and (3) putting the reduction toughening alloy precursor into a mould, pressing into a blank, putting the obtained blank into spark plasma sintering equipment, sintering, cooling to room temperature along with a furnace, and taking out to obtain the high-toughness coarse-grain hard alloy.
Further, the preparation method comprises the following specific steps:
(1) preparing a toughening precursor:
mixing nickel chloride, copper chloride and magnesium chloride according to the mass ratio of 8:1:1 to obtain mixed salt, heating the mixed salt to 150-160 ℃, putting the mixed salt into an electrolytic bath after the mixed salt is molten, electroplating for 4-5 hours by using an aluminum sheet as a positive electrode and using expanded graphite as a negative electrode, and taking down the electroplated negative electrode to obtain a toughening precursor;
(2) preparing a self-made toughening filler:
putting the obtained toughening precursor into a sintering furnace, heating to 800-850 ℃, carrying out heat preservation sintering treatment for 3-5 h, after sintering, naturally cooling to room temperature, taking out a sintered product, repeatedly washing with absolute ethyl alcohol for 3-5 times, naturally drying, crushing, and sieving with a 200-mesh sieve to obtain a self-made toughening filler for later use;
(3) preparation of the mildew product:
mixing the rice hulls and the sugarcane juice according to the mass ratio of 1:1, putting the mixture into a ceramic pot, moving the ceramic pot into a greenhouse, and naturally mildewing for 7-10 days to obtain a mildewed product after the mildewing is finished;
(4) preparing porous silicon carbide fibers:
transferring the obtained mildewed product into a fermentation tank, sealing the opening of the tank, putting the tank into a constant temperature box, sealing and fermenting for 3-5 days, filtering and separating after the fermentation is finished to obtain filter residue, transferring the filter residue into a carbonization furnace, carbonizing for 1-2 hours, discharging, and soaking for 10-12 hours by using hydrofluoric acid with the mass fraction of 40% to obtain porous silicon carbide fiber;
(5) preparation of the suspension:
weighing 150-200 parts of ammonium metatungstate, 5-8 parts of hydrochloric acid, 3-5 parts of polyvinylpyrrolidone, 1.5-2.0 parts of the porous silicon carbide fiber, 2-3 parts of standby self-made toughening filler and 1000-1500 parts of deionized water, and mixing to obtain a suspension;
(6) preparing a precursor of the toughened alloy:
putting the obtained suspension into a magnetic stirrer, stirring and reacting at the room temperature at the rotating speed of 80-100 r/min for 2 hours, then heating to 70 ℃ while stirring, preserving heat at 70 ℃ for 30-40 min for full precipitation, filtering and separating to obtain precipitates, washing the precipitates for 3-5 times by using absolute ethyl alcohol and deionized water respectively, putting the precipitates into an oven, and drying at 70 ℃ for 3-5 hours to obtain a toughening alloy precursor;
(7) preparing a reduction toughening precursor:
putting the toughened alloy precursor into a tubular reduction furnace, and carrying out reduction treatment for 2-3 h to obtain a reduced toughened alloy precursor;
(8) preparing the high-toughness silicon carbide tungsten alloy:
and (3) putting the reduction toughening alloy precursor into a mould, pressing into a blank, putting the obtained blank into spark plasma sintering equipment for sintering treatment, cooling to room temperature along with a furnace, and taking out to obtain the high-toughness coarse-grain hard alloy.
Further, the conditions of the plating in the step (1) are such that the distance between the two stages is maintained at 40mm and the current density is 1.06A/dm2。
Further, the temperature of the greenhouse in the step (3) is 35-45 ℃, and the relative humidity of air is 60-70%.
Further, the temperature of the sealed fermentation in the step (4) is 30-40 ℃, and the temperature of the carbonization treatment is 1600-1700 ℃.
Further, the reduction treatment conditions in the step (7) are as follows: controlling the paving thickness of the toughening alloy precursor to be 2mm, introducing high-purity hydrogen with the dew point of-50 ℃ and the purity of 99.999 percent into a reducing furnace at the flow rate of 0.5L/min as reducing gas, and carrying out heat preservation reduction treatment at the temperature of 600-800 ℃.
Further, the sintering treatment in the step (8) is carried out under the conditions that the temperature is increased to 700 ℃ at the heating rate of 150 ℃/min, then the temperature is increased to 1200 ℃ at the heating rate of 80 ℃/min, the temperature is kept for 3min under the pressure of 20MPa, finally the temperature is increased to 1600 ℃ at the heating rate of 150 ℃, and the temperature is kept for 1min under the pressure of 50 MPa.
By the scheme, the invention at least has the following advantages:
according to the high-toughness macrocrystalline hard alloy prepared by the invention, the self-made toughening filler, the porous silicon carbide fiber and the tungsten source material are mixed and reacted, and dispersed particles and the self-made toughening filler are used for composite toughening, so that the toughness of the tungsten alloy material is greatly improved, the working application range of the tungsten alloy material is greatly improved, and the application prospect is wide.
The foregoing is a summary of the present invention, and in order to provide a clear understanding of the technical means of the present invention and to be implemented in accordance with the present specification, the following is a detailed description of the preferred embodiments of the present invention.
Detailed Description
The following examples are given to further illustrate the embodiments of the present invention. The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention.
Firstly, preparation of raw materials
(1) Mixing nickel chloride, copper chloride and magnesium chloride according to a mass ratio of 8:1:1 to obtain mixed salt, heating the mixed salt to 150-160 ℃, putting the mixed salt into an electrolytic cell after the mixed salt is molten, taking an aluminum sheet as a positive electrode and taking the expanded graphite as a negative electrode, keeping the distance between the two stages at 40mm, and keeping the current density at 1.06A/dm2Electroplating for 4-5 h under the condition, and taking down the electroplated cathode to obtain a toughened precursor; firstly, using expanded graphite as a template, and electroplating a mixed metal layer on the surface of the expanded graphite by a metal mixed salt electroplating method to obtain a toughening precursor;
(2) putting the obtained toughening precursor into a sintering furnace, heating to 800-850 ℃, carrying out heat preservation sintering treatment for 3-5 h, after sintering, naturally cooling to room temperature, taking out a sintered product, repeatedly washing with absolute ethyl alcohol for 3-5 times, naturally drying, crushing, and sieving with a 200-mesh sieve to obtain a self-made toughening filler for later use; sintering the electroplated expanded graphite in a sintering furnace, and removing the graphite template through high-temperature sintering to obtain hollow layered mixed metal powder which is the same as the expanded graphite and is used as a self-made toughening filler;
(3) mixing the rice hulls and the sugarcane juice according to the mass ratio of 1:1, putting the mixture into a ceramic pot, moving the ceramic pot into a greenhouse with the temperature of 35-45 ℃ and the relative air humidity of 60-70%, and naturally mildewing for 7-10 days to obtain a mildewed product after the mildewing is finished; firstly, rice hulls and honey are used as raw materials, the rice hulls and the honey are mixed and then placed in a high-temperature and high-humidity environment for sealing and mildewing, and microorganisms are introduced;
(4) transferring the obtained mildewed product into a fermentation tank, sealing the opening of the tank, putting the tank into a constant temperature box, sealing and fermenting for 3-5 days at the temperature of 30-40 ℃, filtering and separating to obtain filter residues after fermentation is finished, transferring the filter residues into a carbonization furnace, heating to 1600-1700 ℃, performing carbonization treatment for 1-2 hours, discharging, and soaking for 10-12 hours by using hydrofluoric acid with the mass fraction of 40% to obtain porous silicon carbide fibers; then, the mildewed product is fermented in a sealed mode, the rice hulls are subjected to micro-corrosion by using microorganisms, so that the rice hulls have the porous characteristic, and then the porous rice hulls are carbonized to obtain silicon carbide materials;
preparation of the mixture
(5) Weighing 150-200 parts of ammonium metatungstate, 5-8 parts of hydrochloric acid, 3-5 parts of polyvinylpyrrolidone, 1.5-2.0 parts of the porous silicon carbide fiber, 2-3 parts of standby self-made toughening filler and 1000-1500 parts of deionized water, and mixing to obtain a suspension; mixing a tungsten raw material, hydrochloric acid, a non-ionic dispersing agent, porous silicon carbide fibers, a self-made toughening filler and water to obtain a suspension;
(6) putting the obtained suspension into a magnetic stirrer, stirring and reacting at the room temperature at the rotating speed of 80-100 r/min for 2 hours, then heating to 70 ℃ while stirring, preserving heat at 70 ℃ for 30-40 min for full precipitation, filtering and separating to obtain precipitates, washing the precipitates for 3-5 times by using absolute ethyl alcohol and deionized water respectively, putting the precipitates into an oven, and drying at 70 ℃ for 3-5 hours to obtain a toughening alloy precursor; in 70 ℃ hydrochloric acid solution, metatungstate ions directly react with acid radical ions to quickly form a fulvic acid precipitate to coat the surfaces of the doped self-made toughening filler and the porous silicon carbide fiber to form a toughening alloy precursor;
(7) loading the toughening alloy precursor into a tubular reduction furnace, controlling the paving thickness of the toughening alloy precursor to be 2mm, introducing high-purity hydrogen with the dew point of-50 ℃ and the purity of 99.999% into the reduction furnace at the flow rate of 0.5L/min as a reduction gas, and carrying out heat preservation reduction treatment for 2-3 h at the temperature of 600-800 ℃ to obtain a reduction toughening alloy precursor; reducing the yellow tungstic acid precipitate by using high-purity hydrogen to form elemental tungsten to coat the surfaces of the doped self-made toughening filler and the porous silicon carbide fiber, thereby obtaining a reduced toughening alloy precursor;
thirdly, forming and sintering
(8) And (2) putting the reduction toughening alloy precursor into a mould, pressing into a blank, putting the obtained blank into spark plasma sintering equipment, heating to 700 ℃ at the heating rate of 150 ℃/min, heating to 1200 ℃ at the heating rate of 80 ℃/min, preserving heat for 3min under the pressure of 20MPa, heating to 1600 ℃ at the heating rate of 150 ℃, preserving heat for 1min under the pressure of 50MPa, cooling to room temperature along with the furnace, and taking out to obtain the high-toughness coarse-crystal hard alloy. The sintering densification process has a direct relation with the applied pressure, under 1600 ℃, when the pressure of 20MPa is applied, the displacement is obviously increased along with the increase of the sintering pressure, the powder pressing densification mainly occurs in the stage, along with the elimination of gas and the compression of air holes among powder particles, the gaps among the powder particles are reduced, the subsequent displacement change tends to be stable, at 1600 ℃, along with the increase of the pressure to 50MPa, the displacement of a pressure head is rapidly increased, the rapid densification of a sintered body mainly occurs in the stage, and finally the alloy material is obtained, while the self-made toughening filler is doped and coated in the tungsten alloy, because the hollow layer of the expansion graphite-like structure can slide along the stress transmission direction through the interlayer of the self-made toughening filler and directionally move along the bending direction when the alloy receives the external bending stress, the consumption of the internal energy of the tungsten alloy material is reduced, the bending loss of the tungsten alloy material is reduced, and the hollow structure can avoid the damage of the tungsten alloy structure caused by repeated volume change, so that the toughness of the tungsten alloy material is improved;
in addition, the invention also dopes dispersed porous silicon carbide fibers, the silicon carbide fibers are distributed in the alloy in a disordered manner to form a network structure, and when the alloy material is subjected to external bending stress, the disordered network structure can play a role in dispersing the bending stress, so that the stress damage of the alloy material when the alloy material is subjected to the external stress is relieved, and the toughness of the alloy material is increased;
the self-made toughening filler and the porous silicon carbide fiber of the invention can be used as dispersed particles to inhibit the grain growth of tungsten in the densification process so as to obtain a fine-grained material, so that the proportion of the grain boundary of the tungsten alloy is increased, the concentration of impurity elements in the alloy at the grain boundary is reduced, the brittleness of the material is improved, the retardation effect of the grain boundary on dislocation is enhanced due to grain refinement, so that the toughness of the material is improved, the grain boundary is strengthened by introducing the dispersed particles, and more energy can be absorbed when the material is deformed due to the interaction of the particles and the dislocation, so that the initial property of the material is improved, in addition, when the material is fractured, the tough grain is cut into second-phase particles, so that the fracture toughness of the material is improved, and when the crack is expanded due to the proportion that the grain boundary is refined to improve the proportion of the grain boundary, the grain boundary is deflected, if fine disperse phase exists in the crystal grain, dislocation can be pinned by the particles, and the moving speed of the dislocation to a grain boundary is reduced, so that the initiation speed of microcracks of the material is reduced, more sliding systems can be started to generate deformation, the toughness of tungsten is further improved, the alloy material has excellent toughness, and the application prospect is wide.
Example 1
Mixing nickel chloride, copper chloride and magnesium chloride according to the mass ratio of 8:1:1 to obtain mixed salt, heating the mixed salt to 150 ℃, putting the mixed salt into an electrolytic cell after the mixed salt is melted, taking an aluminum sheet as a positive electrode and taking the expanded graphite as a negative electrode, keeping the distance between the two stages at 40mm, and keeping the current density at 1.06A/dm2Electroplating for 4 hours under the condition of (1), and taking down the electroplated cathode to obtain a toughened precursor; putting the obtained toughening precursor into a sintering furnace, heating to 800 ℃, carrying out heat preservation sintering treatment for 3h, after sintering, naturally cooling to room temperature, taking out a sintered product, repeatedly washing the sintered product for 3 times by using absolute ethyl alcohol, naturally drying, crushing, and sieving by using a 200-mesh sieve to obtain a self-made toughening filler for later use; mixing the rice hulls and the sugarcane juice according to the mass ratio of 1:1, and putting the mixture into a ceramic potThen, the ceramic pot is moved into a greenhouse with the temperature of 35 ℃ and the relative air humidity of 60 percent, and naturally mildews for 7 days to obtain a mildewed product after the mildewing is finished; transferring the obtained mildewed product into a fermentation tank, sealing the opening of the tank, putting the tank into a constant temperature box, sealing and fermenting for 3 days at the temperature of 30 ℃, filtering and separating to obtain filter residue after the fermentation is finished, transferring the filter residue into a carbonization furnace, heating to 1600 ℃, carbonizing for 1h, discharging, and soaking for 10h by using hydrofluoric acid with the mass fraction of 40% to obtain porous silicon carbide fiber; weighing 150 parts of ammonium metatungstate, 5 parts of hydrochloric acid, 3 parts of polyvinylpyrrolidone, 1.5 parts of the porous silicon carbide fiber, 2 parts of standby self-made toughening filler and 1000 parts of deionized water, and mixing to obtain a suspension; putting the obtained suspension into a magnetic stirrer, stirring and reacting at the room temperature at the rotating speed of 80r/min for 2h, then heating to 70 ℃ while stirring, preserving the heat at 70 ℃ for 30min for full precipitation, filtering and separating to obtain precipitates, washing the precipitates for 3 times by using absolute ethyl alcohol and deionized water respectively, putting the precipitates into an oven, and drying at 70 ℃ for 3h to obtain a toughening alloy precursor; loading the toughening alloy precursor into a tubular reduction furnace, controlling the paving thickness of the toughening alloy precursor to be 2mm, introducing high-purity hydrogen with the dew point of-50 ℃ and the purity of 99.999% into the reduction furnace at the flow rate of 0.5L/min as a reduction gas, and carrying out heat preservation reduction treatment for 2h at the temperature of 600 ℃ to obtain a reduction toughening alloy precursor; and (2) putting the reduction toughening alloy precursor into a mould, pressing into a blank, putting the obtained blank into spark plasma sintering equipment, heating to 700 ℃ at the heating rate of 150 ℃/min, heating to 1200 ℃ at the heating rate of 80 ℃/min, preserving heat for 3min under the pressure of 20MPa, heating to 1600 ℃ at the heating rate of 150 ℃, preserving heat for 1min under the pressure of 50MPa, cooling to room temperature along with the furnace, and taking out to obtain the high-toughness coarse-crystal hard alloy.
Example 2
Mixing nickel chloride, copper chloride and magnesium chloride according to the mass ratio of 8:1:1 to obtain mixed salt, heating the mixed salt to 155 ℃, putting the mixed salt into an electrolytic cell after the mixed salt is melted, taking an aluminum sheet as a positive electrode and taking the expanded graphite as a negative electrode, keeping the distance between the two stages at 40mm, and keeping the current density at 1.06A/dm2Electroplating for 4 hours under the condition of (1), and taking down the electroplated cathode to obtain a toughened precursor; putting the obtained toughening precursor into a sintering furnace, heating to 830 ℃, carrying out heat preservation sintering treatment for 4h, naturally cooling to room temperature after sintering is finished, taking out a sintered product, repeatedly washing the sintered product for 4 times by using absolute ethyl alcohol, naturally drying, crushing, and sieving by using a 200-mesh sieve to obtain a self-made toughening filler for later use; mixing the rice hulls and the sugarcane juice according to the mass ratio of 1:1, putting the mixture into a ceramic pot, moving the ceramic pot into a greenhouse with the temperature of 40 ℃ and the relative air humidity of 65%, and naturally molding for 8 days to obtain a molding product after the molding is finished; transferring the obtained mildewed product into a fermentation tank, sealing the opening of the tank, putting the tank into a constant temperature box, sealing and fermenting for 4 days at the temperature of 35 ℃, filtering and separating to obtain filter residue after the fermentation is finished, transferring the filter residue into a carbonization furnace, heating to 1650 ℃, carbonizing for 2 hours, discharging, and soaking for 11 hours by using hydrofluoric acid with the mass fraction of 40% to obtain porous silicon carbide fiber; weighing 180 parts of ammonium metatungstate, 7 parts of hydrochloric acid, 4 parts of polyvinylpyrrolidone, 1.8 parts of the porous silicon carbide fiber, 2 parts of standby self-made toughening filler and 1300 parts of deionized water, and mixing to obtain a suspension; putting the obtained suspension into a magnetic stirrer, stirring and reacting at room temperature at a rotating speed of 90r/min for 2h, then heating to 70 ℃ while stirring, preserving heat at 70 ℃ for 35min for full precipitation, filtering and separating to obtain precipitates, washing with absolute ethyl alcohol and deionized water for 4 times respectively, putting into an oven, and drying at 70 ℃ for 4h to obtain a toughening alloy precursor; loading the toughening alloy precursor into a tubular reduction furnace, controlling the paving thickness of the toughening alloy precursor to be 2mm, introducing high-purity hydrogen with the dew point of-50 ℃ and the purity of 99.999% into the reduction furnace at the flow rate of 0.5L/min as a reduction gas, and carrying out heat preservation reduction treatment for 2h at 700 ℃ to obtain a reduction toughening alloy precursor; loading the reduced toughened alloy precursor into a mold, pressing into a blank, placing the blank into spark plasma sintering equipment, heating to 700 deg.C at a heating rate of 150 deg.C/min, heating to 1200 deg.C at a heating rate of 80 deg.C/min, holding at 20MPa for 3min, heating to 1600 deg.C at a heating rate of 150 deg.C, and holding at 50MPaAnd (4) heating for 1min, cooling to room temperature along with the furnace, and taking out to obtain the high-toughness coarse-grain hard alloy.
Example 3
Mixing nickel chloride, copper chloride and magnesium chloride according to the mass ratio of 8:1:1 to obtain mixed salt, heating the mixed salt to 160 ℃, putting the mixed salt into an electrolytic cell after the mixed salt is melted, taking an aluminum sheet as a positive electrode and taking the expanded graphite as a negative electrode, keeping the distance between the two stages at 40mm, and keeping the current density at 1.06A/dm2Electroplating for 5 hours under the condition, and taking down the electroplated cathode to obtain a toughened precursor; putting the obtained toughening precursor into a sintering furnace, heating to 850 ℃, carrying out heat preservation sintering treatment for 5h, naturally cooling to room temperature after sintering, taking out a sintered product, repeatedly washing the sintered product for 5 times by using absolute ethyl alcohol, naturally drying, crushing, and sieving by using a 200-mesh sieve to obtain a self-made toughening filler for later use; mixing the rice hulls and the sugarcane juice according to the mass ratio of 1:1, putting the mixture into a ceramic pot, moving the ceramic pot into a greenhouse with the temperature of 45 ℃ and the relative air humidity of 70%, and naturally mildewing for 10 days to obtain a mildewed product after the mildewing is finished; transferring the obtained mildewed product into a fermentation tank, sealing the opening of the tank, putting the tank into a constant temperature box, sealing and fermenting for 5 days at the temperature of 40 ℃, filtering and separating to obtain filter residue after the fermentation is finished, transferring the filter residue into a carbonization furnace, heating to 1700 ℃, performing carbonization treatment for 2 hours, discharging, and soaking for 12 hours by using hydrofluoric acid with the mass fraction of 40% to obtain porous silicon carbide fiber; weighing 200 parts of ammonium metatungstate, 8 parts of hydrochloric acid, 5 parts of polyvinylpyrrolidone, 2.0 parts of the porous silicon carbide fiber, 3 parts of standby self-made toughening filler and 1500 parts of deionized water, and mixing to obtain a suspension; putting the obtained suspension into a magnetic stirrer, stirring and reacting at the room temperature at the rotating speed of 100r/min for 2h, then heating to 70 ℃ while stirring, preserving the heat at 70 ℃ for 40min for full precipitation, filtering and separating to obtain precipitates, washing the precipitates for 5 times by using absolute ethyl alcohol and deionized water respectively, putting the precipitates into an oven, and drying at 70 ℃ for 5h to obtain a toughening alloy precursor; loading the precursor into a tubular reduction furnace, controlling the thickness of the precursor to be 2mm, using high-purity hydrogen with dew point of-50 ℃ and purity of 99.999% as a reduction gas, and using 0.5L/5L/4L/Introducing the alloy into a reduction furnace at the flow rate of min, and carrying out heat preservation reduction treatment for 3h at the temperature of 800 ℃ to obtain a reduction toughening alloy precursor; and (2) putting the reduction toughening alloy precursor into a mould, pressing into a blank, putting the obtained blank into spark plasma sintering equipment, heating to 700 ℃ at the heating rate of 150 ℃/min, heating to 1200 ℃ at the heating rate of 80 ℃/min, preserving heat for 3min under the pressure of 20MPa, heating to 1600 ℃ at the heating rate of 150 ℃, preserving heat for 1min under the pressure of 50MPa, cooling to room temperature along with the furnace, and taking out to obtain the high-toughness coarse-crystal hard alloy.
Comparative example 1: the preparation method is essentially the same as in inventive example 1, except that the inventive home-made toughening filler was not added;
comparative example 2: the preparation method was substantially the same as in example 1 of the present invention, except that the porous silicon carbide fiber of the present invention was not added;
comparative example 3: a common pure tungsten metal material;
the examples 1 to 3 of the present invention and the comparative examples 1 to 3 were subjected to performance tests, respectively, and the test results are shown in table 1:
the detection method comprises the following steps:
and (3) testing the bending strength: the bending strength of the alloy is measured by a national standard (GB/T6569-2006) method (the size of a test sample bar is 3mm multiplied by 4mm multiplied by 35mm, the span is 30mm, and the loading rate is 0.5 mm/min);
and (3) testing the ductile-brittle transition temperature: and (3) determining the ductile-brittle transition temperature (DBTT) of the alloy by adopting a high-temperature three-point bending resistance test, wherein the high-temperature bending resistance test temperature is as follows: normal temperature, 100 ℃, 150 ℃, 200 ℃, 250 ℃, 300 ℃, sample size of 1mm multiplied by 2mm multiplied by 14mm, span of 7mm, loading rate of 0.1 mm/min;
and (3) density testing: and (3) determining the density of the alloy by adopting an Archimedes drainage method.
TABLE 1 Performance test results
| Detecting items | Bending strength (MPa) | Hardness (HV) | Density (%) |
| Example 1 | 2521 | 547 | 99.6 |
| Example 2 | 2530 | 549 | 99.7 |
| Example 3 | 2548 | 550 | 99.8 |
| Comparative example 1 | 1986 | 498 | 99.2 |
| Comparative example 2 | 2015 | 512 | 99.4 |
| Comparative example 3 | 1064 | 437 | 99.1 |
It can be seen from the detection data in the above table that, the self-made toughening filler of the present invention is not added in the comparative example 1, so that the final bending strength, hardness and density are both significantly reduced, and thus it can be seen that the self-made toughening filler of the present invention indeed improves the bending toughness of the alloy, and also improves the hardness and density of the alloy as a dispersion filler, and the comparative example 2 does not add porous silicon carbide fiber, so that the final bending strength, hardness and density are both significantly reduced, and thus it can be seen that the self-made toughening filler of the present invention indeed improves the bending toughness of the alloy, and also improves the hardness and density of the alloy as a dispersion filler, and compared with the pure tungsten alloy of the comparative example 3, the change of each performance data is more obvious, which indicates that the self-made toughening filler and porous silicon carbide fiber of the present invention have obvious effects.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, it should be noted that, for those skilled in the art, many modifications and variations can be made without departing from the technical principle of the present invention, and these modifications and variations should also be regarded as the protection scope of the present invention.
Claims (8)
1. A high-toughness coarse-grain hard alloy is characterized in that: is prepared by sintering a reduction toughening alloy precursor through green pressing and spark plasma;
the reduction toughening alloy precursor is prepared by reducing the toughening alloy precursor by high-purity hydrogen;
the precursor of the toughened alloy is prepared by heating, stirring and reacting a suspension and then drying;
the suspension consists of the following raw materials in parts by weight:
150-200 parts of ammonium metatungstate;
5-8 parts of hydrochloric acid;
3-5 parts of polyvinylpyrrolidone;
1.5-2.0 parts of porous silicon carbide fiber;
2-3 parts of self-made toughening filler;
1000-1500 parts of deionized water;
the porous silicon carbide fiber is prepared by carrying out mildewing, fermentation, carbonization and hydrofluoric acid soaking on rice hulls and sugarcane juice;
the self-made toughening filler is prepared by sintering nickel chloride, copper chloride, magnesium chloride and expanded graphite after an electroplating reaction.
2. A preparation method of high-toughness coarse-grain hard alloy is characterized by comprising the following specific preparation steps:
(1) preparing a toughening precursor:
mixing nickel chloride, copper chloride and magnesium chloride, heating, after the mixed salt is melted, electroplating by taking an aluminum sheet as a positive electrode and taking expanded graphite as a negative electrode, and taking down the electroplated negative electrode to obtain a toughening precursor;
(2) preparing a self-made toughening filler:
carrying out heat preservation sintering treatment on the toughening precursor, naturally cooling to room temperature, taking out a sintering product, repeatedly washing, naturally airing, crushing and sieving to obtain a self-made toughening filler for later use;
(3) preparation of the mildew product:
mixing the rice hulls and the sugarcane juice, putting the mixture into a greenhouse, and naturally mildewing to obtain a mildewed product after the mildewing is finished;
(4) preparing porous silicon carbide fibers:
transferring the mildewed product into a fermentation tank, sealing and fermenting, filtering after fermentation is finished, transferring filter residue into a carbonization furnace, carbonizing, and soaking with hydrofluoric acid to obtain porous silicon carbide fiber;
(5) preparation of the suspension:
weighing ammonium metatungstate, hydrochloric acid, polyvinylpyrrolidone, porous silicon carbide fiber, self-made toughening filler and deionized water, and mixing to obtain a suspension;
(6) preparing a precursor of the toughened alloy:
putting the suspension into a magnetic stirrer, stirring at room temperature for reaction, heating while stirring, preserving heat for full precipitation, and drying to obtain a toughening alloy precursor;
(7) preparing a reduction toughening precursor:
loading the precursor of the toughening alloy into a tubular reduction furnace, and carrying out heat preservation reduction treatment to obtain a reduced toughening alloy precursor;
(8) preparing the high-toughness silicon carbide tungsten alloy:
and (3) putting the reduction toughening alloy precursor into a mould, pressing into a blank, putting the obtained blank into spark plasma sintering equipment, sintering, cooling to room temperature along with a furnace, and taking out to obtain the high-toughness coarse-grain hard alloy.
3. The preparation method of the high-toughness coarse-grained hard alloy according to claim 2, characterized by comprising the following specific preparation steps:
(1) preparing a toughening precursor:
mixing nickel chloride, copper chloride and magnesium chloride according to the mass ratio of 8:1:1 to obtain mixed salt, heating the mixed salt to 150-160 ℃, putting the mixed salt into an electrolytic bath after the mixed salt is molten, electroplating for 4-5 hours by using an aluminum sheet as a positive electrode and using expanded graphite as a negative electrode, and taking down the electroplated negative electrode to obtain a toughening precursor;
(2) preparing a self-made toughening filler:
putting the obtained toughening precursor into a sintering furnace, heating to 800-850 ℃, carrying out heat preservation sintering treatment for 3-5 h, after sintering, naturally cooling to room temperature, taking out a sintered product, repeatedly washing with absolute ethyl alcohol for 3-5 times, naturally drying, crushing, and sieving with a 200-mesh sieve to obtain a self-made toughening filler for later use;
(3) preparation of the mildew product:
mixing the rice hulls and the sugarcane juice according to the mass ratio of 1:1, putting the mixture into a ceramic pot, moving the ceramic pot into a greenhouse, and naturally mildewing for 7-10 days to obtain a mildewed product after the mildewing is finished;
(4) preparing porous silicon carbide fibers:
transferring the obtained mildewed product into a fermentation tank, sealing the opening of the tank, putting the tank into a constant temperature box, sealing and fermenting for 3-5 days, filtering and separating after the fermentation is finished to obtain filter residue, transferring the filter residue into a carbonization furnace, carbonizing for 1-2 hours, discharging, and soaking for 10-12 hours by using hydrofluoric acid with the mass fraction of 40% to obtain porous silicon carbide fiber;
(5) preparation of the suspension:
weighing 150-200 parts of ammonium metatungstate, 5-8 parts of hydrochloric acid, 3-5 parts of polyvinylpyrrolidone, 1.5-2.0 parts of the porous silicon carbide fiber, 2-3 parts of standby self-made toughening filler and 1000-1500 parts of deionized water, and mixing to obtain a suspension;
(6) preparing a precursor of the toughened alloy:
putting the obtained suspension into a magnetic stirrer, stirring and reacting at the room temperature at the rotating speed of 80-100 r/min for 2 hours, then heating to 70 ℃ while stirring, preserving heat at 70 ℃ for 30-40 min for full precipitation, filtering and separating to obtain precipitates, washing the precipitates for 3-5 times by using absolute ethyl alcohol and deionized water respectively, putting the precipitates into an oven, and drying at 70 ℃ for 3-5 hours to obtain a toughening alloy precursor;
(7) preparing a reduction toughening precursor:
putting the toughened alloy precursor into a tubular reduction furnace, and carrying out reduction treatment for 2-3 h to obtain a reduced toughened alloy precursor;
(8) preparing the high-toughness silicon carbide tungsten alloy:
and (3) putting the reduction toughening alloy precursor into a mould, pressing into a blank, putting the obtained blank into spark plasma sintering equipment for sintering treatment, cooling to room temperature along with a furnace, and taking out to obtain the high-toughness coarse-grain hard alloy.
4. The method for producing a high toughness macrocrystalline cemented carbide as claimed in claim 2 or 3, wherein: the electroplating conditions in the step (1) are that the distance between two stages is kept to be 40mm, and the current density is kept to be 1.06A/dm2。
5. The method for producing a high toughness macrocrystalline cemented carbide as claimed in claim 2 or 3, wherein: in the step (3), the temperature of the greenhouse is 35-45 ℃, and the relative humidity of air is 60-70%.
6. The method for producing a high toughness macrocrystalline cemented carbide as claimed in claim 2 or 3, wherein: the temperature of the sealed fermentation in the step (4) is 30-40 ℃, and the temperature of the carbonization treatment is 1600-1700 ℃.
7. The method for producing a high toughness macrocrystalline cemented carbide as claimed in claim 2 or 3, wherein: the reduction treatment conditions in the step (7) are as follows: controlling the paving thickness of the toughening alloy precursor to be 2mm, introducing high-purity hydrogen with the dew point of-50 ℃ and the purity of 99.999 percent into a reducing furnace at the flow rate of 0.5L/min as reducing gas, and carrying out heat preservation reduction treatment at the temperature of 600-800 ℃.
8. The method for producing a high toughness macrocrystalline cemented carbide as claimed in claim 2 or 3, wherein: the conditions of the sintering treatment in the step (8) are that the temperature is increased to 700 ℃ at the heating rate of 150 ℃/min, then the temperature is increased to 1200 ℃ at the heating rate of 80 ℃/min, the temperature is kept for 3min under the pressure of 20MPa, and finally the temperature is increased to 1600 ℃ at the heating rate of 150 ℃, and the temperature is kept for 1min under the pressure of 50 MPa.
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| CN115896576A (en) * | 2022-12-23 | 2023-04-04 | 江苏盖特钨业科技有限公司 | High-strength tungsten alloy and preparation method thereof |
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