CN112430770A - Multi-scale structure non-uniform hard alloy and preparation method thereof - Google Patents

Multi-scale structure non-uniform hard alloy and preparation method thereof Download PDF

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CN112430770A
CN112430770A CN202011334326.XA CN202011334326A CN112430770A CN 112430770 A CN112430770 A CN 112430770A CN 202011334326 A CN202011334326 A CN 202011334326A CN 112430770 A CN112430770 A CN 112430770A
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powder
hard alloy
scale structure
ball milling
fine
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羊求民
唐彦渊
陈丽勇
徐国钻
毛莉
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Jiangxi University of Science and Technology
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Jiangxi University of Science and Technology
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C29/00—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides
    • C22C29/02—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides based on carbides or carbonitrides
    • C22C29/06—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides based on carbides or carbonitrides based on carbides, but not containing other metal compounds
    • C22C29/08—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides based on carbides or carbonitrides based on carbides, but not containing other metal compounds based on tungsten carbide
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/12—Both compacting and sintering
    • B22F3/14—Both compacting and sintering simultaneously
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C1/00—Making non-ferrous alloys
    • C22C1/04—Making non-ferrous alloys by powder metallurgy
    • C22C1/05—Mixtures of metal powder with non-metallic powder
    • C22C1/051—Making hard metals based on borides, carbides, nitrides, oxides or silicides; Preparation of the powder mixture used as the starting material therefor
    • C22C1/053—Making hard metals based on borides, carbides, nitrides, oxides or silicides; Preparation of the powder mixture used as the starting material therefor with in situ formation of hard compounds
    • C22C1/055—Making hard metals based on borides, carbides, nitrides, oxides or silicides; Preparation of the powder mixture used as the starting material therefor with in situ formation of hard compounds using carbon

Abstract

The invention discloses a heterogeneous hard alloy with a multi-scale structure and a preparation method thereof, wherein the preparation method comprises the following steps: preparing fine-grain precursor pre-sintering powder with uniformly distributed carbon, tungsten oxide and cobaltosic oxide; mixing fine-grain precursor pre-sintering powder, coarse WC powder, cobalt powder and paraffin wax, wherein the fine-grain precursor pre-sintering powder is formed by uniformly distributing carbon, tungsten oxide and cobaltosic oxide, and the mixture is subjected to ball milling treatment to obtain a ball-milled mixed material; and (3) performing compression molding on the ball-milled mixed materials, heating the obtained molded body to the sintering temperature in an inert atmosphere, applying pressure, performing pressurization and heat preservation treatment, and cooling to obtain a product, namely the heterogeneous hard alloy with the multi-scale structure. The heterogeneous hard alloy with the multi-scale structure and the preparation method thereof improve the product performances of toughness and the like of the heterogeneous hard alloy, reduce the production cost of superfine WC powder, simplify the production flow and solve the problems of high production cost and easy performance reduction in the prior art.

Description

Multi-scale structure non-uniform hard alloy and preparation method thereof
Technical Field
The invention belongs to the technical field of powder metallurgy, and relates to a heterogeneous hard alloy with a multi-scale structure and a preparation method thereof.
Background
The tungsten-cobalt hard alloy is formed by compounding a high-strength WC hard phase and a high-toughness Co binder phase, has the excellent characteristics of high hardness, wear resistance, heat resistance, corrosion resistance and the like, is widely applied to the core technical fields of national defense, military industry, engineering manufacturing and the like, and has continuously improved requirements on the performance of the tungsten-cobalt hard alloy along with the improvement of scientific technology in recent years.
At present, the main methods for improving the performance of the tungsten-cobalt hard alloy comprise: adjusting the size of WC crystal grains and the microstructure of the alloy. Wherein, the microstructure of the alloy is adjusted by preparing a gradient alloy structure and a double-crystal structure with thick and thin WC grains. Although the advantage of the double-crystal structure with thick and thin WC grains is great, extra-thick and extra-thin WC powder which is specially prepared is needed, the cost is high, the production condition is harsh, the phenomenon that the thick and thin WC powder is aggregated and grown in the sintering process of the hard alloy prepared by the method is difficult to control the grain size, the homogenization of the thick and thin WC in the sintering process is difficult to avoid, and the condition directly influences the multi-grain size distribution of the hard alloy and deteriorates the product performances such as the obdurability and the like of the hard alloy.
In view of the above, it is desirable to provide a novel tungsten-cobalt hard alloy and a preparation method thereof, which can improve the product performances such as toughness of the non-uniform hard alloy, reduce the production cost of the ultrafine WC powder, simplify the production process, increase the application field of the non-uniform hard alloy with multiple grain sizes, and promote the development of the non-uniform hard alloy with multiple grain sizes industry, in order to solve the problems of the existing non-uniform hard alloy with multiple grain sizes and the production conditions.
Disclosure of Invention
In order to achieve the purpose, the invention provides the heterogeneous hard alloy with the multi-scale structure and the preparation method thereof, which improve the product performances such as obdurability and the like of the heterogeneous hard alloy, reduce the production cost of the superfine WC powder, simplify the production flow and solve the problems of high production cost and easy performance reduction in the prior art.
The technical scheme adopted by the invention is that the preparation method of the heterogeneous hard alloy with the multi-scale structure comprises the following steps:
s1, preparing fine-grain precursor pre-sintering powder with uniformly distributed carbon, tungsten oxide and cobaltosic oxide;
s2, uniformly distributing carbon, tungsten oxide and cobaltosic oxide to obtain fine-grain precursor pre-sintering powder, coarse WC powder, cobalt powder and paraffin according to the mass percent of 10-40 wt%: 50wt% -80 wt%: 4wt% -12 wt%: mixing the raw materials in a ratio of 0.5-2 wt%, performing ball milling treatment on the obtained mixture, and drying and grinding the obtained ball milling product to obtain a ball milling mixed material; wherein, the main purpose of the paraffin is a forming agent, which is beneficial to the subsequent compression molding. The purpose of ball milling is to realize uniform mixing of coarse WC and fine grain precursor pre-sintered powder;
s3, performing ball milling and mixing, performing compression molding, heating the obtained molded body to a sintering temperature in an inert atmosphere, then applying pressure, performing pressurization and heat preservation treatment, and cooling to obtain a product, namely the multi-scale structure non-uniform hard alloy. The pressing forming process adopts a simple mould pressing process, the pressing pressure is 200 MPa-400 MPa, and the pressed sample has no cracks and has no phenomena of edge falling and corner falling;
the existing nanometer/superfine WC powder is expensive, so that the superfine/nanometer WC-Co composite powder generated in situ in the sintering process of fine crystal precursor pre-sintering powder with uniformly distributed carbon, tungsten oxide and cobaltosic oxide is used as a fine crystal component, the fine crystal cost is reduced, and the Co generated in situ covers the superfine/nanometer WC crystal particles, so that the grain boundary fusion among the WC crystal particles is hindered, the aggregation and growth among the fine crystals and among the WC crystal particles with different scale structures are effectively inhibited, the homogenization of the WC with different scale structures in the sintering process is avoided, and the preparation of the high-performance multi-scale hard alloy is realized.
Further, in S1, preparing a fine-grained precursor pre-sintered powder with uniformly distributed carbon, tungsten oxide and cobaltosic oxide, includes the following steps:
s11, according to WO in ammonium tungstate solution3The mass ratio of the glucose to the water-soluble cobalt salt is 1-4: 0.2-4: 0.016-0.2, respectively weighing ammonium tungstate solution, glucose and water-soluble cobalt salt; wherein WO in ammonium tungstate solution3The content is 200-300 g/L;
s12, adding the glucose and the water-soluble cobalt salt weighed in the S11 into the weighed ammonium tungstate solution to form a system, and adding water into the system to form WO3The content is 100-150 g/L, and the mixture is fully stirred until the glucose and the water-soluble cobalt salt are completely dissolved and the system is uniformly mixed to obtain a mixed solution;
s13, spray drying the mixed solution obtained in the S12 to obtain precursor powder;
s14, calcining the precursor powder obtained in the step S13 at the temperature of 300-600 ℃ for 0.5-2 h in an inert atmosphere to obtain fine-grain precursor pre-sintering powder with uniformly distributed carbon, tungsten oxide and cobaltosic oxide;
the purpose of step S1 is to obtain fine-grained precursor pre-fired powder with uniformly distributed carbon, tungsten oxide and cobaltosic oxide, so that it is not affected by the ball milling liquid-absolute ethanol during the ball milling process of step S2, and further does not affect the formation of fine-grained components in step S3. In step S1, ammonium tungstate solution, glucose and water-soluble cobalt salt are used as raw materials, the cost is obviously lower than that of the commercially available superfine WC, and the superfine WC-Co component is obtained through mixing, calcining, pressure sintering and in-situ sintering, so that the production cost for preparing the super-hard alloy by directly adopting the commercially available superfine WC can be greatly reduced;
if the precursor powder is not calcined in S14, the precursor powder is directly ball-milled in step S2 and pressure-sintered in step S3, in the ball-milling process in step S2, the precursor powder is water-soluble salt, and is partially dissolved in absolute ethyl alcohol during ball-milling, and is precipitated during drying, so that fine-grained pre-sintered precursor powder with uniformly distributed carbon, tungsten oxide and cobaltosic oxide cannot be obtained, the formation of fine-grained components in the subsequent sintering process of S3 is influenced, glucose, tungsten salt and cobalt salt cannot be taken as a whole, and the reaction among carbon, tungsten oxide and cobalt oxide converted in the subsequent step S3 is also influencedIt is greatly influenced that W which is completely reacted may appear in the final product cemented carbide2C. Multiple carbide (W)xCoyC) And free carbon and other defects, and in the sintering process, because a large amount of gases such as water vapor, ammonia gas and the like are released in the process of converting salt into oxide, pores are easily formed in the sintering process, and qualified products are difficult to obtain;
therefore, the calcining decomposition of S14 in the inert atmosphere is converted into the oxide insoluble in the ball milling liquid, and the change of product properties caused by the dissolution of precursor salt in the wet milling process of the step S2 is avoided. The precursor powder can be calcined in a tube furnace, a box furnace or a rotary furnace and other furnaces which can realize inert atmosphere;
the fine-grained precursor pre-sintering powder with uniformly distributed carbon, tungsten oxide and cobaltosic oxide generated in step S14 has two advantages: one is that the reduction and carbonization ability of the tungsten-cobalt oxide is easier than that of the tungsten oxide, the other is that the wettability of cobalt and WC is good, the cobalt oxide uniformly distributed among the tungsten oxide can be spread on WC crystal grains after being converted into Co in the S3 reaction process, the fusion of grain boundaries among the WC crystal grains with different scale structures can be effectively inhibited, the subsequent distribution of fine crystal components and coarse crystal components is facilitated, the effective control of a multi-scale structure is realized, and the product performance of the hard alloy is regulated and controlled;
the calcination process of step S14 is shown in the following reaction equation (cobalt salts are listed as cobalt acetate):
5(NH4)2O·12WO3·nH2O=12WO3+10NH3↑+(n+5)H2O↑（1）；
C6H12O6=6C+6H2O↑（2）；
3Co(CH3COO)2·4H2O=Co3O4+2CO2↑+4CO↑+3C2H6↑+4H2O↑（3）；
the cobaltosic oxide in the product obtained in the step S14 can not react with the generated carbon monoxide to produce the cobalt oxide, because the calcination process is carried out step by step, and the generated CO is not as good as the generated Co3O4Overflow occurs as a result of the reaction.
Further, in S11, the water-soluble cobalt salt includes: any one of cobalt acetate, cobalt sulfate, cobalt nitrate and cobalt chloride.
Further, in S13, the process conditions of spray drying are specifically: the spray drying adopts a pressure type spray dryer, the inlet temperature is 150-280 ℃, the outlet temperature is 100-150 ℃, and the feeding speed is 200-500 ml/min.
Further, in S2, the particle size of the coarse WC powder is in the range of 3 μm to 300. mu.m.
Further, in S2, the process conditions of the ball milling treatment specifically include: the rotation speed of ball milling is 100 r/min-200 r/min, the ball milling time is 1 h-10 h, and the ball milling medium is absolute ethyl alcohol.
Further, in S3, the sintering temperature is 1410-1470 ℃.
Further, in S3, the pressure is 0.5MPa to 6 MPa.
Furthermore, in S3, the time of the pressure heat preservation treatment is 0.5-4 h.
The main purposes of pressure sintering are two, wherein the temperature is selected to be 1410-1470 ℃ and the pressure is selected to be 0.5-6 MPa, the first purpose is to promote the added fine-grain precursor pre-sintering powder with uniformly distributed carbon, tungsten oxide and cobaltosic oxide to be fully and completely carbonized, the second purpose is to promote cobalt to form a liquid phase, pores are filled in the sintering process, and the pressure is applied for a period of time at the sintering temperature after the cobalt liquid phase appears, so that the performance of the hard alloy is further improved. If not pressurized, the sample density is low due to shrinkage of the fine crystalline component during the in-situ reaction;
in S3, fine crystal precursor pre-sintered powder, Co3O4The gradual transition process to Co starts from 500 ℃; WO3Gradually converted into W, compound carbide (W)xCoyC）、W2The process of C and WC starts from 700 ℃; carbon converted from glucose is removed of oxygen element in the system, and carbon and oxygen are converted into carbon dioxide by reaction and discharged along with the inert atmosphere; in the sintering process, the phase of the fine crystalline structure undergoes in-situ reaction along with the temperature rise;
heating to 800 deg.C, fine crystal components are mainly W and W2C as main component and a small amount of multiple carbide (W)xCoyC) (ii) a When the temperature is continuously increased to 900 ℃, W in the fine grain components is continuously reduced, the WC content is rapidly increased, and the compound carbide (W)xCoyC) The content is slightly reduced; when the temperature is continuously increased to 950 ℃, almost all phases in the fine crystal components are converted into nano/superfine WC-Co composite powder;
in the process of continuously heating to 1200 ℃, the cobalt powder in the S2 is gradually spread on the WC surface to form a cobalt layer, so that the grain boundary fusion among WC grains is hindered, the aggregation and growth among fine grains and among WC grains with different scale structures are effectively inhibited, the homogenization of WC with different scale structures in the sintering process is avoided, and the preparation of the high-performance multi-scale hard alloy is realized;
the invention also aims to provide the heterogeneous hard alloy with the multi-scale structure, which is prepared according to the preparation method.
The invention has the beneficial effects that:
the method adopts ammonium tungstate solution, glucose and water-soluble cobalt salt as raw materials to prepare fine-grain precursor pre-sintering powder with uniformly distributed carbon, tungsten oxide and cobaltosic oxide; the fine grain precursor pre-sintering powder, the ultra-coarse WC powder, the cobalt powder and the paraffin are mixed and then are pressed and sintered to prepare the hard alloy with the coexistence of the coarse WC powder, the preparation cost is reduced because expensive WC fine grains are not directly added, in-situ carbothermic reaction is carried out on the fine grain precursor pre-sintering powder with uniformly distributed carbon, tungsten oxide and cobaltosic oxide in the process of pressing and sintering to convert the fine grain precursor pre-sintering powder into nano/ultra-fine WC-Co composite powder, the bonding strength between the WC fine grains and the cobalt binding phase is still kept, in-situ generated Co covers the ultra-fine/nano WC grains, the grain boundary fusion between the WC grains is hindered, the aggregation and growth between the fine grains and between the WC grains with different scale structures are effectively inhibited, the homogenization of the WC with different scale structures in the sintering process is avoided, and the toughness of the prepared multi-scale structure non-uniform hard alloy is good, the method has wide application prospect in the field of ground and mine tools such as rock drilling tools, oil drilling teeth, coal cutter teeth, pavement cold milling machine teeth, shield cutters and the like.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a microscopic morphology test chart of the precursor powder prepared in example 3 of the present invention.
Fig. 2 is a microscopic morphology test chart of fine crystalline precursor pre-sintered powder with uniformly distributed carbon, tungsten oxide and cobaltosic oxide prepared in example 3 of the present invention.
FIG. 3 is a micro-topography test chart of the multi-scale structure non-uniform cemented carbide manufactured in example 3 of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The ammonium tungstate used in the embodiment of the invention has a market price of 110-130 yuan/Kg, glucose has a market price of 6 yuan/Kg, and cobalt salt has a market price of 60-80 yuan/Kg.
The granularity of the commercial fine WC powder adopted in the comparative example is 0.2-0.8 mu m, and the commercial price is 280-350 yuan/Kg.
Example 1
A preparation method of a heterogeneous hard alloy with a multi-scale structure comprises the following steps:
(1) preparing fine-grain precursor pre-sintering powder:
(1.1) according to the ammonium tungstate solutionWO of Zhong3The mass ratio of the glucose to the water-soluble cobalt salt is 1: 0.2: 0.016, respectively weighing ammonium tungstate solution, glucose and water-soluble cobalt salt.
Wherein WO in ammonium tungstate solution3The content is 200 g/L; the water-soluble cobalt salt is cobalt acetate.
(1.2) adding the glucose and the water-soluble cobalt salt weighed in the step (1.1) into the ammonium tungstate solution weighed in the step (1.1) to form a system, and adding water into the system to form WO3The content is 100g/L, the mixture is fully stirred until the glucose and the water-soluble cobalt salt are completely dissolved, and the system is uniformly mixed to obtain mixed liquid.
And (1.3) spray-drying the mixed solution obtained in (1.2) to obtain precursor powder. The spray drying adopts a pressure type spray dryer, the inlet temperature is 150 ℃, the outlet temperature is 100 ℃, and the feeding speed is 200 ml/min.
And (1.4) calcining the precursor powder obtained in the step (1.3) for 0.5h at the temperature of 300 ℃ in an inert gas atmosphere to obtain fine-grain precursor pre-sintering powder with uniformly distributed carbon, tungsten oxide and cobaltosic oxide.
(2) And (3) pre-sintering powder of the fine crystal precursor obtained in the step (1.4), coarse WC powder, cobalt powder and paraffin according to the mass percent of 10 wt%: 80 wt%: 9.5 wt%: mixing the components in a proportion of 0.5wt%, then carrying out ball milling treatment, drying and grinding the obtained ball milling product to obtain a mixed material.
Wherein the grain size of the ultra-coarse WC powder is 3 μm; the rotation speed of ball milling is 100r/min, the ball milling time is 1h, and the ball milling medium is absolute ethyl alcohol.
(3) Pressing and forming the mixed material obtained in the step (2) to obtain a molded body; heating the modeling body to 1410 ℃ under the argon atmosphere to reach the sintering temperature, then applying pressure, carrying out pressurization and heat preservation treatment for 0.5h under the condition that the pressure is 0.5MPa, and cooling to obtain a sintering product, namely the multi-scale structure non-uniform hard alloy.
The hardness of the multi-scale structure non-uniform hard alloy prepared by the embodiment is 89.4HRA, and the bending strength is 2800 MPa.
Example 2
A preparation method of a heterogeneous hard alloy with a multi-scale structure comprises the following steps:
removing WO from the ammonium tungstate solution in (1.1)3The mass ratio of the glucose to the water-soluble cobalt salt is 4: 4: 0.2; WO in ammonium tungstate solution3The content is 300 g/L; the water-soluble cobalt salt is cobalt sulfate.
(1.2) addition of Water to the System WO3The content was 150 g/L.
(1.3) the inlet temperature of the spray-drying was 280 ℃, the outlet temperature was 150 ℃ and the feed rate was 500 ml/min.
(1.4) calcining the precursor powder for 2h at the temperature of 600 ℃.
(2) The medium fine crystal precursor pre-sintering powder, the coarse WC powder, the cobalt powder and the paraffin are 40wt% in percentage by mass: 50 wt%: 8 wt%: 2wt% of the above-mentioned components. Wherein the particle size of the ultra-coarse WC powder is 300 μm; the rotation speed of ball milling is 200r/min, and the ball milling time is 10 h.
(3) The medium sintering temperature is 1470 ℃, and the pressure and the heat preservation are carried out for 4 hours under the pressure of 6 MPa.
The rest is the same as in example 1.
The hardness of the multi-scale structure non-uniform hard alloy prepared by the embodiment is 89HRA, and the bending strength is 2500 MPa.
Example 3
A preparation method of a heterogeneous hard alloy with a multi-scale structure comprises the following steps:
removing WO from the ammonium tungstate solution in (1.1)3The mass ratio of the glucose to the water-soluble cobalt salt is 2.5: 2.1: 0.108; WO in ammonium tungstate solution3The content is 250 g/L; the water-soluble cobalt salt is cobalt nitrate.
(1.2) addition of Water to the System WO3The content was 125 g/L.
(1.3) the inlet temperature of spray drying was 215 ℃, the outlet temperature was 125 ℃, and the feed rate was 350 ml/min.
(1.4) calcining the precursor powder for 1.25h at the temperature of 450 ℃.
(2) The medium fine crystal precursor pre-sintering powder, the coarse WC powder, the cobalt powder and the paraffin are 25wt% in percentage by mass: 65 wt%: 9 wt%: mixing at a ratio of 1 wt%. Wherein the particle size of the ultra-coarse WC powder is 150 μm; the rotation speed of the ball milling is 150r/min, and the ball milling time is 5.5 h.
(3) The medium sintering temperature is 1440 ℃, and the pressure and the heat preservation are carried out for 2.25h under the pressure of 3.25 MPa.
The rest is the same as in example 1.
The hardness of the multi-scale structure non-uniform hard alloy prepared by the embodiment is 87.5HRA, and the bending strength is 3050 MPa.
Example 4
A preparation method of a heterogeneous hard alloy with a multi-scale structure comprises the following steps:
removing WO from the ammonium tungstate solution in (1.1)3The mass ratio of the glucose to the water-soluble cobalt salt is 1.8: 1.2: 0.062; WO in ammonium tungstate solution3The content is 225 g/L; the water-soluble cobalt salt is cobalt chloride.
(1.2) addition of Water to the System WO3The content was 110 g/L.
(1.3) the inlet temperature of the spray-drying was 180 ℃, the outlet temperature was 110 ℃ and the feed rate was 275 ml/min.
(1.4) calcining the precursor powder for 0.9h at the temperature of 375 ℃.
(2) The medium fine crystal precursor pre-sintering powder, the coarse WC powder, the cobalt powder and the paraffin are 20wt% in percentage by mass: 75 wt%: 4 wt%: mixing at a ratio of 1 wt%. Wherein the particle size of the ultra-coarse WC powder is 75 μm; the rotating speed of ball milling is 125r/min, and the ball milling time is 3 h.
(3) The medium sintering temperature is 1425 ℃, and the pressure and the heat preservation are carried out for 1.4h under the pressure of 1.9 MPa.
The rest is the same as in example 1.
The hardness of the multi-scale structure non-uniform hard alloy prepared by the embodiment is 88.0HRA, and the bending strength is 3110 MPa.
Example 5
A preparation method of a heterogeneous hard alloy with a multi-scale structure comprises the following steps:
in addition to (1.1)WO in ammonium tungstate solution3The mass ratio of the glucose to the water-soluble cobalt salt is 3.3: 3: 0.15; WO in ammonium tungstate solution3The content was 280 g/L.
(1.2) addition of Water to the System WO3The content was 138 g/L.
(1.3) the inlet temperature of the spray-drying was 250 ℃, the outlet temperature was 140 ℃ and the feed rate was 450 ml/min.
And (1.4) calcining the precursor powder for 1.8h at the temperature of 550 ℃.
(2) The medium fine crystal precursor pre-sintering powder, the coarse WC powder, the cobalt powder and the paraffin are 21wt% in percentage by mass: 65.2 wt%: 12 wt%: 1.8wt% of the above-mentioned components. Wherein the particle size of the ultra-coarse WC powder is 250 μm; the rotation speed of ball milling is 180r/min, and the ball milling time is 9 h.
(3) The medium sintering temperature is 1460 ℃, and the pressure and the heat preservation are carried out for 3.5h under the pressure of 5.5 MPa.
The rest is the same as in example 1.
The hardness of the multi-scale structure non-uniform hard alloy prepared by the embodiment is 87.6HRA, and the bending strength is 3020 MPa.
Example 6
A preparation method of a heterogeneous hard alloy with a multi-scale structure comprises the following steps:
removing WO from the ammonium tungstate solution in (1.1)3The mass ratio of the glucose to the water-soluble cobalt salt is 1.2: 3.8: 0.04.
the rest is the same as in example 3.
The hardness of the multi-scale structure non-uniform hard alloy prepared by the embodiment is 89.5HRA, and the bending strength is 2980 MPa.
Example 7
A preparation method of a heterogeneous hard alloy with a multi-scale structure comprises the following steps:
removing the fine-grain precursor pre-sintering powder, the coarse WC powder, the cobalt powder and the paraffin in the step (2) by mass percent of 38 wt%: 55.5 wt%: 5 wt%: 1.5wt% of the above-mentioned components.
The rest is the same as in example 3.
The hardness of the multi-scale structure non-uniform hard alloy prepared by the embodiment is 89.8HRA, and the bending strength is 3020 MPa.
Comparative example 1
A preparation method of a heterogeneous hard alloy with a multi-scale structure comprises the following steps:
(1) the method comprises the following steps of (1) mixing commercially available fine WC powder, coarse WC powder, cobalt powder and paraffin according to the mass percent of 25 wt%: 65 wt%: 9 wt%: 1wt% of the raw materials, then carrying out ball milling treatment, drying and grinding the obtained ball milling product to obtain a mixed material.
Wherein the particle size of the ultra-coarse WC powder is 150 μm; the rotation speed of ball milling is 150r/min, the ball milling time is 5.5h, and the ball milling medium is absolute ethyl alcohol.
(2) Pressing and forming the mixed material obtained in the step (1) to obtain a molded body; heating the modeling body to 1440 ℃ under argon atmosphere to reach sintering temperature, then applying pressure, carrying out pressurization and heat preservation treatment for 2.25h under the condition that the pressure is 3.25MPa, and cooling to obtain the multi-scale structure non-uniform hard alloy.
The hardness of the multi-scale structure non-uniform hard alloy prepared by the comparative example is 85HRA, and the bending strength is 2200 MPa.
Comparative example 2
A preparation method of a heterogeneous hard alloy with a multi-scale structure comprises the following steps:
(1) the method comprises the following steps of (1) mixing commercially available fine WC powder, coarse WC powder, cobalt powder and paraffin according to the mass percent of 25 wt%: 65 wt%: 9 wt%: 1wt% of the raw materials, then carrying out ball milling treatment, drying and grinding the obtained ball milling product to obtain a mixed material.
Wherein the particle size of the ultra-coarse WC powder is 150 μm; the rotation speed of ball milling is 150r/min, the ball milling time is 5.5h, and the ball milling medium is absolute ethyl alcohol.
(2) Pressing and forming the mixed material obtained in the step (1) to obtain a molded body; and (3) heating the modeling body to 1440 ℃ under argon atmosphere to reach the sintering temperature, then preserving heat for 2.25 hours, and cooling to obtain the heterogeneous hard alloy with the multi-scale structure.
The hardness of the multi-scale structure non-uniform hard alloy prepared by the comparative example is 84.5HRA, and the bending strength is 1950 MPa.
Comparative example 3
A preparation method of a heterogeneous hard alloy with a multi-scale structure comprises the following steps:
(1) the adding quality of the medium fine WC powder and the coarse WC powder is the same as that of the comparative example 2, and no cobalt powder and paraffin are added;
the rest is the same as comparative example 2.
The hardness of the multi-scale structure non-uniform hard alloy prepared by the comparative example is 90HRA, and the bending strength is 1000 MPa.
Experimental example 1
In example 3
In the step (1.3), the shape of the precursor powder obtained by spray drying is spherical, the surface is smooth, the holes are few, the sphere particle size of the precursor powder is large, the maximum size can reach about 5 μm, and the minimum size can also reach about 0.5 μm, as shown in fig. 1.
In the step (1.4), the calcined fine grain precursor pre-sintered powder with uniformly distributed carbon, tungsten oxide and cobaltosic oxide is still spherical, but the surface of each spherical powder becomes rough and porous and shows a gradual decomposition trend, as shown in fig. 2, the surface of each spherical powder is formed by assembling a plurality of fine structures, the average grain size of each fine structure is about 0.5 mu m, and the grain size of some fine sheet structures is about 50 nm. This is in accordance with this step consisting of (NH)4)2O·12WO3·nH2The O precursor powder is relevant to the process of continuously generating ammonia gas, water vapor, carbon dioxide, carbon monoxide and ethane gas by calcining, when the precursor powder generates gas in the calcining process, the precursor spherical powder is gradually decomposed into intermediate products of carbon, tungsten and cobalt, and finally fine-grain precursor pre-sintering powder with uniformly distributed carbon, tungsten oxide and cobaltosic oxide is formed, and the precursor powder does not contain other intermediate products and impurities, and the mixed liquid obtained in the step (1.2) is the mixture of molecules and atomic levels, and the precursor powder obtained after the mixture and the spray drying in the step (1.3) has better distribution uniformity.
The microstructure of the multi-scale structure non-uniform hard alloy obtained by pressure sintering in the step (3) is composed of coarse WC, fine WC and cobalt, as shown in figure 3, the coarse WC and the fine WC are uniformly distributed, the grain boundary is clear, the mutual fusion phenomenon is hardly caused, the scale of the fine grain component is kept good, the proportion is large, and the performance of the multi-scale structure non-uniform hard alloy obtained in the way is excellent.
It is noted that, in the present application, relational terms such as first, second, and third, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.
All the embodiments in the present specification are described in a related manner, and the same and similar parts among the embodiments may be referred to each other, and each embodiment focuses on the differences from the other embodiments.
The above description is only for the preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention shall fall within the protection scope of the present invention.

Claims (10)

1. The preparation method of the heterogeneous hard alloy with the multi-scale structure is characterized by comprising the following steps:
s1, preparing fine-grain precursor pre-sintering powder with uniformly distributed carbon, tungsten oxide and cobaltosic oxide;
s2, uniformly distributing carbon, tungsten oxide and cobaltosic oxide to obtain fine-grain precursor pre-sintering powder, coarse WC powder, cobalt powder and paraffin according to the mass percent of 10-40 wt%: 50wt% -80 wt%: 4wt% -12 wt%: mixing the raw materials in a ratio of 0.5-2 wt%, performing ball milling treatment on the obtained mixture, and drying and grinding the obtained ball milling product to obtain a ball milling mixed material;
s3, performing ball milling and mixing, performing compression molding, heating the obtained molded body to a sintering temperature in an inert atmosphere, then applying pressure, performing pressurization and heat preservation treatment, and cooling to obtain a product, namely the multi-scale structure non-uniform hard alloy.
2. The method for preparing the multi-scale structure non-uniform hard alloy according to the claim 1, wherein in S1, the step of preparing the fine crystal precursor pre-sintering powder with the carbon, the tungsten oxide and the cobaltosic oxide uniformly distributed comprises the following steps:
s11, according to WO in ammonium tungstate solution3The mass ratio of the glucose to the water-soluble cobalt salt is 1-4: 0.2-4: 0.016-0.2, respectively weighing ammonium tungstate solution, glucose and water-soluble cobalt salt; wherein WO in ammonium tungstate solution3The content is 200-300 g/L;
s12, adding the glucose and the water-soluble cobalt salt weighed in the S11 into the weighed ammonium tungstate solution to form a system, and adding water into the system to form WO3The content is 100-150 g/L, and the mixture is fully stirred until the glucose and the water-soluble cobalt salt are completely dissolved and the system is uniformly mixed to obtain a mixed solution;
s13, spray drying the mixed solution obtained in the S12 to obtain precursor powder;
and S14, calcining the precursor powder obtained in the step S13 at the temperature of 300-600 ℃ for 0.5-2 h in an inert atmosphere to obtain the fine-grain precursor pre-sintering powder with uniformly distributed carbon, tungsten oxide and cobaltosic oxide.
3. The method as claimed in claim 2, wherein in S11, the water-soluble cobalt salt comprises: any one of cobalt acetate, cobalt sulfate, cobalt nitrate and cobalt chloride.
4. The method for preparing the heterogeneous hard alloy with the multi-scale structure according to claim 2, wherein in S13, the spray drying process conditions are as follows: the spray drying adopts a pressure type spray dryer, the inlet temperature is 150-280 ℃, the outlet temperature is 100-150 ℃, and the feeding speed is 200-500 ml/min.
5. The method according to claim 1, wherein in S2, the grain size of the WC powder is in the range of 3-300 μm.
6. The method for preparing the heterogeneous hard alloy with the multi-scale structure according to claim 1, wherein in S2, the process conditions of the ball milling treatment are as follows: the rotation speed of ball milling is 100 r/min-200 r/min, the ball milling time is 1 h-10 h, and the ball milling medium is absolute ethyl alcohol.
7. The method for preparing the heterogeneous hard alloy with the multi-scale structure according to claim 1, wherein in S3, the sintering temperature is 1410-1470 ℃.
8. The method for preparing the heterogeneous hard alloy with the multi-scale structure according to claim 1, wherein in S3, the pressure is 0.5-6 MPa.
9. The method for preparing the heterogeneous hard alloy with the multi-scale structure according to claim 1, wherein in S3, the time of the pressure and heat preservation treatment is 0.5-4 h.
10. The heterogeneous hard alloy with the multi-scale structure is characterized by being prepared according to the preparation method of any one of claims 1 to 9.
CN202011334326.XA 2020-11-24 2020-11-24 Multi-scale structure non-uniform hard alloy and preparation method thereof Pending CN112430770A (en)

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