2-10 [mu] m superfine tungsten carbide metal ceramic spherical powder and preparation method thereof

Abstract

The invention provides 2-10 [mu] m superfine tungsten carbide metal ceramic spherical powder and a preparation method thereof.The preparation method comprises the following steps that 1, hard phase powder, metal binding phase powder, a binding agent and a wet grinding medium are added into a ball milling tank to be subjected to ball milling and even mixing, and mixed powder slurry is obtained; wherein the hard phase powder is tungsten carbide, the metal binding phase powder is metal cobalt and metal chromium, and the binding agent is a cellulose derivative; (2) carrying out spray drying granulation on the mixed powder slurry by using a spray dryer to obtain pre-sintered composite powder; and (3) the pre-sintered composite powder is placed in a tubular furnace to be sintered, and the superfine tungsten carbide metal ceramic spherical powder is obtained. Wherein the particle size of the tungsten carbide metal ceramic spherical powder is 2-10 [mu] m. According to the preparation method disclosed by the invention, the tungsten carbide metal ceramic spherical powder with regular morphology, uniform components, high yield and ultrafine particle size (2-10 microns) can be obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of ceramic materials, and in particular to a 2-10 μm ultrafine tungsten carbide metal ceramic spherical powder and a preparation method thereof. Background Art

[0002] Cermets refer to a type of powder metallurgy material that is formed by mixing some high-melting-point, high-hardness metal carbide powders (such as WC, TiC, etc.) with a binder phase (Co, Ni, etc.), pressing and forming, and then sintering. It not only maintains the high strength, high hardness, wear resistance, high temperature resistance, oxidation resistance, and chemical stability of ceramics, but also has good metal toughness and plasticity. For example, tungsten carbide-cobalt (WC-Co)-based cermets, as the earliest studied cermets, are widely used as cermet coatings in aerospace, metallurgy, petrochemical, machinery and other industries because of their high hardness (HV1200-1400) and extremely high compressive strength of 6000MPa (600kg·N / mm).

[0003] Currently, common spraying processes for metal ceramic coatings include plasma spraying, flame spraying, and supersonic flame spraying. Among them, supersonic flame spraying is particularly suitable for spraying metal ceramic materials. Supersonic flame spraying involves rapidly heating the binder phase in the powder to a melt in a flame flow. The powder is then rapidly sprayed onto the substrate surface along with the flame flow, where it cools to form a coating. The powder used for spraying is generally a composite powder, with each powder particle containing both a hard phase and a binder phase. The powder particle size is generally 22-53 microns, 15-45 microns, 10-38 microns, and 5-30 microns. Spraying powders with smaller particle sizes often result in better coating performance. However, the minimum particle size of metal ceramic powder produced by current processes can only reach 5-15 μm, making it impossible to achieve high-yield production of ultrafine metal ceramic powders of 2-10 μm.

[0004] Based on this, there is an urgent need to provide a 2-10 μm ultrafine tungsten carbide metal ceramic spherical powder and a preparation method thereof. Summary of the Invention

[0005] The embodiment of the present invention provides a 2-10 μm ultrafine tungsten carbide metal ceramic spherical powder and a preparation method thereof, which can solve the problem that traditional process methods cannot achieve high-yield preparation of 2-10 μm ultrafine metal ceramic powder.

[0006] In a first aspect, the present invention provides a method for preparing 2-10 μm ultrafine tungsten carbide cermet spherical powder, the preparation method comprising the following steps:

[0007] (1) adding a hard phase powder, a metal binder phase powder, a binder, and a wet grinding medium into a ball mill and performing ball milling to mix the hard phase powder, thereby obtaining a mixed powder slurry; wherein the hard phase powder is tungsten carbide, the metal binder phase powder is metal cobalt and metal chromium, and the binder is a cellulose derivative;

[0008] (2) spray drying and granulating the mixed powder slurry using a spray dryer to obtain a pre-sintered composite powder;

[0009] (3) placing the pre-sintered composite powder in a tubular furnace for sintering to obtain the ultrafine tungsten carbide metal ceramic spherical powder; wherein the particle size of the tungsten carbide metal ceramic spherical powder is 2-10 μm.

[0010] Preferably, in step (1), the mass ratio of the hard phase powder to the metal binder phase powder is (83-89):(11-17), and the mass ratio of metal cobalt to metal chromium in the metal binder phase powder is (8-12):(3-5).

[0011] Preferably, in step (1), the particle size of the hard phase powder and the metal binder phase powder is 300-1000 nm.

[0012] Preferably, in step (1), the binder is sodium carboxymethyl cellulose.

[0013] More preferably, the mass ratio of the binder to the total mass of the hard phase powder and the metal binder phase powder is (1.5-3):100.

[0014] Preferably, in step (1), the wet grinding medium is water or ethanol.

[0015] More preferably, the mass ratio of the wet grinding medium to the total mass of the hard phase powder and the metal binder phase powder is (2-9):1.

[0016] Preferably, in step (1), the grinding balls used in the ball mill are zirconia grinding balls, the ball milling speed is 230-260 r / min, and the time is 2-8 h.

[0017] Preferably, in step (1), the solid content of the mixed powder slurry is 10-15%.

[0018] Preferably, in step (2), during the spray drying and granulation process of the spray dryer, the inlet air temperature of the spray dryer is 190-210°C, the outlet air temperature is 100-120°C, and the speed of the peristaltic pump is 18-22 r / min.

[0019] Preferably, in step (3), during the sintering process, the sintering is first performed at 400-600° C. for 0.5-1.5 h, and then at 1100-1400° C. for 1-4 h.

[0020] In a second aspect, the present invention provides a 2-10 μm ultrafine tungsten carbide metal ceramic spherical powder prepared by the preparation method described in any one of the first aspects above.

[0021] Compared with the prior art, the present invention has at least the following beneficial effects:

[0022] In the present invention, based on the process properties of the WC-Co-Cr metal ceramic system, a cellulose derivative is selected as a binder. First, tungsten carbide hard phase powder, metal cobalt and chromium bonding phase powder, the binder and a wet grinding medium are mixed in proportion to form a mixed powder slurry. The binder can evenly disperse the nanometer or submicron hard phase powder and bonding phase powder, and keep the powder particles evenly distributed in the mixed powder slurry. In this way, the droplets can be broken into small droplets in the subsequent spray granulation process. Finally, after sintering and densification, tungsten carbide metal ceramic spherical powder with regular morphology, uniform composition, high yield and ultrafine particle size (2-10μm) can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0024] Figure 1 This is a SEM image of the morphology of a 2-10 μm ultrafine tungsten carbide cermet spherical powder provided in Example 1 of the present invention; wherein the scale bar is 10 μm;

[0025] Figure 2 This is a SEM image of the cross-sectional morphology of a 2-10 μm ultrafine tungsten carbide cermet spherical powder provided in Example 1 of the present invention;

[0026] Figure 3 This is a SEM image of the morphology of a 2-10 μm ultrafine tungsten carbide cermet spherical powder provided in Example 1 of the present invention before sintering heat treatment; wherein the scale bar is 20 μm;

[0027] Figure 4 This is a laser particle size distribution diagram of a 2-10 μm ultrafine tungsten carbide cermet spherical powder provided in Example 1 of the present invention;

[0028] Figure 5 This is a SEM image of the morphology of a 2-10 μm ultrafine tungsten carbide cermet spherical powder provided in Example 3 of the present invention before sintering heat treatment; wherein the scale bar is 20 μm;

[0029] Figure 6 This is a SEM image of the morphology of a 2-10 μm ultrafine tungsten carbide cermet spherical powder provided in Example 4 of the present invention before sintering heat treatment; wherein the scale bar is 20 μm;

[0030] Figure 7 This is a SEM image of the morphology of a 2-10 μm ultrafine tungsten carbide cermet spherical powder provided in Example 5 of the present invention before sintering heat treatment; wherein the scale bar is 20 μm;

[0031] Figure 8 This is a SEM image of the morphology of a 2-10 μm ultrafine tungsten carbide cermet spherical powder provided in Example 6 of the present invention before sintering heat treatment; wherein the scale bar is 20 μm;

[0032] Figure 9 This is a SEM image of the morphology of a 2-10 μm ultrafine tungsten carbide cermet spherical powder provided in Example 7 of the present invention before sintering heat treatment; wherein the scale bar is 20 μm;

[0033] Figure 10 This is a SEM image of the morphology of a 2-10 μm ultrafine tungsten carbide cermet spherical powder provided in Example 8 of the present invention before sintering heat treatment; wherein the scale bar is 20 μm;

[0034] Figure 11 This is a SEM image of the morphology of a 2-10 μm ultrafine tungsten carbide cermet spherical powder provided in Example 9 of the present invention before sintering heat treatment; wherein the scale bar is 20 μm;

[0035] Figure 12 This is a SEM image of the morphology of the tungsten carbide cermet spherical powder provided in Comparative Example 1 of the present invention before sintering heat treatment; wherein the scale bar is 20 μm;

[0036] Figure 13 This is a SEM image of the morphology of the tungsten carbide cermet spherical powder provided in Comparative Example 2 of the present invention before sintering heat treatment; wherein the scale bar is 20 μm;

[0037] Figure 14 This is a SEM image of the morphology of the tungsten carbide cermet spherical powder provided in Example 10 of the present invention before sintering heat treatment; wherein the scale bar is 20 μm;

[0038] Figure 15 This is a SEM image of the morphology of the tungsten carbide cermet spherical powder provided in Example 11 of the present invention before sintering heat treatment; wherein the scale bar is 20 μm;

[0039] Figure 16This is a SEM image of the morphology of the tungsten carbide metal ceramic spherical powder provided in Comparative Example 3 of the present invention before sintering heat treatment; wherein the scale bar is 10 μm. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0041] At present, the production method of metal ceramic powder is generally carried out by mixing raw material powder, dispersant, wet grinding medium and binder to form a slurry, and forming it by spray drying method. Among them, the selection of binder has an important influence on the various properties of the powder obtained by spray drying. The binders commonly used in industry include polyethylene glycol, polyvinyl alcohol, compound resin, etc.; however, when the above-mentioned types of binders are used to mix the original powder slurry of 2-10μm ultrafine powder, it is impossible to obtain an ideal pre-spray slurry. Moreover, after spray granulation and sintering, the morphology of the obtained metal ceramic powder is irregular, and the particle size distribution of the obtained powder is too wide. The yield of the 2-10μm particle size ultrafine powder obtained by screening is extremely low, and it is impossible to obtain a 2-10μm particle size metal ceramic spherical powder that meets the requirements.

[0042] Therefore, based on the above problems, an embodiment of the present invention provides a method for preparing 2-10 μm ultrafine tungsten carbide cermet spherical powder, the preparation method comprising the following steps:

[0043] (1) adding a hard phase powder, a metal binder phase powder, a binder, and a wet grinding medium into a ball mill and performing ball milling to mix the hard phase powder, thereby obtaining a mixed powder slurry; wherein the hard phase powder is tungsten carbide, the metal binder phase powder is metal cobalt and metal chromium, and the binder is a cellulose derivative;

[0044] (2) spray drying and granulating the mixed powder slurry using a spray dryer to obtain a pre-sintered composite powder;

[0045] (3) placing the pre-sintered composite powder in a tubular furnace for sintering to obtain the ultrafine tungsten carbide metal ceramic spherical powder; wherein the particle size of the tungsten carbide metal ceramic spherical powder is 2-10 μm.

[0046] Considering that the binders commonly used in the prior art, such as polyethylene glycol and polyvinyl alcohol, are used in the preparation of ultrafine metal ceramic powders, they cannot make the different phases of nano or submicron raw powders evenly dispersed, and cannot keep the mixed powders evenly distributed in the slurry, resulting in the different phases of the original powder in the mixed slurry used for spray drying tending to aggregate and precipitate. During the spray feeding period, the powder in the slurry is prone to rapid precipitation, resulting in unstable changes in the concentration of the slurry, so that the final metal ceramic powder has uneven composition, irregular morphology and too wide a particle size distribution range. In the embodiment of the present invention, the process properties of the WC-Co-Cr metal ceramic system are explored, and cellulose derivatives are selected as binders through a large number of creative experiments. The refractory metal carbide tungsten carbide hard phase powder, metal cobalt and chromium bonding phase powder are first mixed with the binder and wet grinding medium in proportion to form a mixed powder slurry. The binder can evenly disperse the nano or submicron hard phase powder and bonding phase powder, and keep the powder particles uniformly distributed in the mixed powder slurry, so as to ensure that the droplets are broken into small droplets in the subsequent spray granulation process. Finally, after sintering, tungsten carbide metal ceramic spherical powder with regular morphology, uniform composition, high yield and ultrafine particle size (2-10μm) can be obtained.

[0047] According to some preferred embodiments, in step (1), the mass ratio of the hard phase powder to the metal binder phase powder is (83-89):(11-17) (for example, it can be 83:11, 86:11, 83:15, 86:15, 89:17 or 89:17), and the mass ratio of metal cobalt to metal chromium in the metal binder phase powder is (8-12):(3-5) (for example, it can be 8:3, 8:4, 8:5, 10:3, 10:4, 10:5, 12:3, 12:4 or 12:5).

[0048] According to some preferred embodiments, in step (1), the particle size of the hard phase powder and the metal binder phase powder is 300-1000 nm (for example, 300 nm, 500 nm, 800 nm or 1000 nm).

[0049] In an embodiment of the present invention, refractory metal tungsten carbide is used as hard phase powder, and a certain proportion of cobalt and chromium are added as metal binder phase powder for compounding. The particle size of the above powders is all at the submicron level. Based on the process performance of the above powders, by selecting a suitable binder and mixing it with the ball mill, not only can the powders be evenly dispersed, but also the sedimentation rate of the hard phase powder and the metal binder phase powder in the mixed powder slurry can be regulated, which is conducive to the formation of ultrafine metal ceramic spherical powders, in which each powder particle contains a hard phase and a metal binder phase.

[0050] According to some preferred embodiments, in step (1), the binder is sodium carboxymethyl cellulose; the mass ratio of the binder to the total mass of the hard phase powder and the metal binder phase powder is (1.5-3):100 (for example, it can be 1.5:100, 2:100 or 3:100).

[0051] The experiments of the present invention have confirmed that when traditional binders such as polyethylene glycol are used in the submicron metal ceramic system of the present invention, the hard phase powder and metal bonding phase powder of different phases cannot be evenly distributed in the slurry, and may even cause agglomeration between the powder particles, thereby failing to obtain a metal ceramic powder with uniform composition, regular morphology and small particle size distribution. In the embodiment of the present invention, through extensive research on the powder properties and process performance of the above-mentioned metal ceramic system, it was found that when a certain amount of sodium carboxymethyl cellulose was added to the submicron hard phase powder and metal bonding phase powder to prepare a mixed slurry, a mixed slurry with uniform powder particle distribution and suitable viscosity could be prepared. When the mixed slurry was spray-dried and formed, the powder particles in the slurry could be evenly settled, thereby forming a metal ceramic spherical powder with regular morphology, uniform composition and a particle size distribution in the range of 2-10 μm. At the same time, the type of binder and the ratio of its hard phase powder and metal bonding phase powder have an important influence on the forming of metal ceramic spherical powder. The experimental verification of the present invention found that if the binder content is too low, it will be unfavorable for the uniform dispersion of the hard phase powder and the metal bonding phase powder, which will make it difficult to quickly form the composite powder during the spray drying process, and the powder formed after forming will have an irregular shape; if the binder content is too high, the porosity of the metal ceramic spherical powder formed after the final sintering will be higher, thereby reducing the performance of the metal ceramic spherical powder.

[0052] According to some preferred embodiments, in step (1), the wet grinding medium is water or ethanol; the mass ratio of the wet grinding medium to the total mass of the hard phase powder and the metal binder phase powder is (2-9):1 (for example, it can be 2:1, 3:1, 5:1, 6:1, 7:1, 8:1 or 9:1).

[0053] According to some preferred embodiments, in step (1), the solid content of the mixed powder slurry is 10-15% (for example, it can be 10%, 11%, 12%, 13%, 14% or 15%).

[0054] For metal ceramic powders with refractory metal tungsten carbide as the main hard phase, the solid content of spray drying granulation has a crucial influence on the results of spray granulation. According to previous experimental rules, when the other parameters do not change, the particle size of the powder obtained by spraying is positively correlated with the solid content of the mixed powder slurry, that is, the greater the solid content of the mixed powder slurry, the larger the overall particle size of the powder obtained by spraying. When preparing large-particle powder particles (above 15μm), the solid content of the mixed powder slurry only needs to be controlled at more than 50% to obtain large-particle powders with uniform particle size distribution, good morphology, and density. However, when preparing 2-10μm ultrafine powders, in order to obtain a higher proportion of ultrafine powders, it is necessary to significantly reduce the solid content of the mixed powder slurry. However, blindly reducing the solid content of the mixed powder slurry will cause the properties of the mixed powder slurry to change significantly, and the raw material powders in the slurry will be unevenly distributed and sedimented, which will ultimately still result in the obtained metal ceramic powder having a too wide particle size distribution and poor spherical morphology. Therefore, in the embodiment of the present invention, on the basis of the above-mentioned binder type and content, the solid content of the mixed powder slurry is further coordinated and regulated, which is conducive to obtaining 2-10μm ultrafine metal ceramic spherical powder with high yield and regular morphology. It has been verified by the experiment of the present invention that if the solid content of the mixed powder slurry is too low, the molding of metal ceramic spherical powder cannot be achieved, and if the solid content of the mixed powder slurry is too high, not only will the particle size of the metal ceramic powder be too large, but the yield of the metal ceramic powder will also be low.

[0055] According to some preferred embodiments, in step (1), the grinding balls used in the ball mill are zirconia grinding balls, the ball milling speed is 230-260 r / min (for example, it can be 230 r / min, 240 r / min, 250 r / min or 260 r / min), and the time is 2-8 h (for example, it can be 2 h, 4 h, 5 h or 8 h).

[0056] In the embodiment of the present invention, the binder is first mixed with water to prepare a binder aqueous solution with a certain mass concentration (2%), and then the binder is added to the ball mill together with the hard phase powder and the metal binder phase powder and crushed and refined at a certain rotation speed, so that the raw material powders are fully mixed, which is conducive to the subsequent uniform molding of the powder.

[0057] According to some preferred embodiments, in step (2), during the spray drying granulation process performed by the spray dryer, the inlet air temperature of the spray dryer is 190-210°C (for example, 190°C, 200°C or 210°C), the outlet air temperature is 100-120°C (for example, 100°C, 110°C or 120°C), and the speed of the peristaltic pump is 18-22 r / min (for example, 18 r / min, 20 r / min or 22 r / min).

[0058] In an embodiment of the present invention, a mixed powder slurry is formed by uniformly dispersing hard phase powder, metal binder phase powder, etc. in a solvent containing a binder. By coordinated control of the inlet air temperature, outlet air temperature and feed rate (rotation speed of the peristaltic pump) during the spray drying process, the mixed powder slurry is facilitated to become spherical droplets under the action of centrifugal force or pressure, the solvent in the droplets evaporates under the action of hot air, and the mixed powder, etc. agglomerates into spherical particles with a certain strength under the action of the binder, thereby forming an ultrafine metal ceramic spherical powder with uniform dispersion and regular morphology.

[0059] According to some preferred embodiments, in step (3), during the sintering process, the steel is first sintered at 400-600°C (for example, 400°C, 500°C or 600°C) for 0.5-1.5h (for example, 0.5h, 1h or 1.5h), and then sintered at 1100-1400°C (for example, 1100°C, 1200°C, 1300°C or 1400°C) for 1-4h (for example, 1h, 2h, 3h or 4h).

[0060] In the embodiment of the present invention, the pre-sintered composite powder formed by spray drying is further subjected to gradient temperature sintering, thereby effectively removing the binder in the composite powder, thereby obtaining a densified ultrafine metal ceramic spherical powder.

[0061] In summary, in the embodiments of the present invention, by strictly controlling the proportion of each powder raw material, the type and content of the binder, the solid content of the mixed powder slurry, and the process parameters in the preparation process of the metal ceramic spherical powder, the metal ceramic spherical powder with regular powder morphology, uniform raw material distribution, high yield and ultrafine particle size of 2-10μm is prepared in batches. The spherical powder can be used to form a metal ceramic coating on the surface of the base material through thermal spraying equipment, and is widely used in aerospace, metallurgy, petrochemical, machinery and other industries.

[0062] In order to more clearly illustrate the technical solutions and advantages of the present invention, a 2-10 μm ultrafine tungsten carbide cermet spherical powder and a preparation method thereof are described in detail through the following examples.

[0063] Example 1:

[0064] (1) Zirconia grinding balls and ball milling media (water) were placed in a ball mill jar in sequence, and then a binder aqueous solution (solute: sodium carboxymethyl cellulose) with a mass concentration of 2% was added and stirred, and then hard phase powder (tungsten carbide powder with a particle size of 300-1000nm) and metal binder phase powder (metal cobalt and metal chromium with a particle size of 300-1000nm) were added to the ball mill jar and ball milled at 250r / min for 2h to obtain a mixed powder slurry with a solid content of 12.5%; wherein the mass ratio of the hard phase powder to the metal binder phase powder metal cobalt and metal chromium was 86:10:4, the total mass ratio of the hard phase powder and the metal binder phase powder to the mass ratio of the zirconia balls was 1:1, the total mass ratio of the hard phase powder and the metal binder phase powder to the mass ratio of the ball milling media was 1.25:8.75, and the total mass ratio of the hard phase powder and the metal binder phase powder to the sodium carboxymethyl cellulose contained in the binder was 100:2;

[0065] (2) controlling the temperature of the mixed powder slurry to 50° C. and spray granulating the mixed powder slurry using a spray dryer to obtain a pre-sintered composite powder; wherein the process parameters of the spray granulation are: an inlet air temperature of 200° C., an outlet air temperature of 110° C., and a peristaltic pump speed of 20 r / min;

[0066] (3) The pre-sintered composite powder was placed in a corundum crucible and sintered in a tubular furnace with an argon protective atmosphere. The temperature was first raised from room temperature to 500°C at a rate of 5°C / min and kept warm for 1 hour. The temperature was then raised from 500°C to 1230°C at a rate of 5°C / min and kept warm for 2 hours. Finally, the powder was cooled to room temperature with the furnace and sieved through 1800 mesh and 6000 mesh sieves, respectively, to obtain ultrafine tungsten carbide metal ceramic spherical powder with a particle size between 1800 and 6000 mesh (2-10 μm).

[0067] Example 2:

[0068] (1) Zirconia grinding balls and ball milling media (water) are placed in a ball mill jar in sequence, and then a binder aqueous solution (solute is sodium carboxymethyl cellulose) with a mass concentration of 2% is added and stirred, and then hard phase powder (tungsten carbide powder with a particle size of 300-1000nm) and metal binder phase powder (metal cobalt and metal chromium with a particle size of 300-1000nm) are added to the ball mill jar and ball milled at 250r / min for 2h to obtain a mixed powder slurry with a solid content of 12.5%; wherein the mass ratio of the hard phase powder to the metal binder phase powder metal cobalt and metal chromium is 89:8:3, the total mass ratio of the hard phase powder and the metal binder phase powder to the mass ratio of the zirconia balls is 1:1, the total mass ratio of the hard phase powder and the metal binder phase powder to the mass ratio of the wet grinding media is 1.25:8.75, and the total mass ratio of the hard phase powder and the metal binder phase powder to the sodium carboxymethyl cellulose contained in the binder is 100:2;

[0069] (2) controlling the temperature of the mixed powder slurry to 50° C. and spray granulating the mixed powder slurry using a spray dryer to obtain a pre-sintered composite powder; wherein the process parameters of the spray granulation are: an inlet air temperature of 200° C., an outlet air temperature of 110° C., and a peristaltic pump speed of 20 r / min;

[0070] (3) The pre-sintered composite powder was placed in a corundum crucible and sintered in a tubular furnace with an argon protective atmosphere. The temperature was first raised from room temperature to 500°C at a rate of 5°C / min and kept warm for 1 hour. The temperature was then raised from 500°C to 1230°C at a rate of 5°C / min and kept warm for 2 hours. Finally, the powder was cooled to room temperature with the furnace and sieved through 1800 mesh and 6000 mesh sieves, respectively, to obtain ultrafine tungsten carbide metal ceramic spherical powder with a particle size between 1800 and 6000 mesh (2-10 μm).

[0071] Example 3:

[0072] Example 3 is basically the same as Example 1, except that: in step (1), the ratio of the total mass of the hard phase powder and the metal binder phase powder to the mass of the wet grinding medium is 1.5:8.5, and the solid content of the mixed powder slurry is 15%.

[0073] Example 4:

[0074] Example 4 is basically the same as Example 1, except that in step (1), the ratio of the total mass of the hard phase powder and the metal binder phase powder to the mass of the wet grinding medium is 1:9, and the solid content of the mixed powder slurry is 10%.

[0075] Example 5:

[0076] Example 5 is basically the same as Example 1, except that in step (1), the ratio of the total mass of the hard phase powder and the metal binder phase powder to the mass of the wet grinding medium is 2:8, and the solid content of the mixed powder slurry is 20%.

[0077] Example 6

[0078] Example 6 is basically the same as Example 1, except that: in step (1), the ratio of the total mass of the hard phase powder and the metal binder phase powder to the mass of the wet grinding medium is 0.8:9.2, and the solid content of the mixed powder slurry is 8%.

[0079] Example 7

[0080] Example 7 is basically the same as Example 1, except that: in step (1), the ratio of the total mass of the hard phase powder and the metal binder phase powder to the mass of the ball milling medium is 5:5, and the solid content of the mixed powder slurry is 50%.

[0081] Example 8

[0082] Example 8 is basically the same as Example 1, except that in step (1), the binder is carboxymethyl cellulose with a mass concentration of 2%.

[0083] Example 9

[0084] Example 9 is basically the same as Example 1, except that in step (1), the binder is hydroxyethyl cellulose with a mass concentration of 2%.

[0085] Example 10

[0086] Example 10 is substantially the same as Example 1, except that in step (1), the mass ratio of the total mass of the hard phase powder and the metal binder phase powder to the mass ratio of the sodium carboxymethyl cellulose contained in the binder is 100:1.5.

[0087] Example 11

[0088] Example 11 is basically the same as Example 1, except that in step (1), the mass ratio of the total mass of the hard phase powder and the metal binder phase powder to the mass ratio of the sodium carboxymethyl cellulose contained in the binder is 100:2.5.

[0089] Comparative Example 1

[0090] (1) Zirconia grinding balls and ball milling media (water) are placed in a ball mill jar in sequence, and then a binder aqueous solution (solute is polyvinyl alcohol) with a mass concentration of 10% is added and stirred, and then hard phase powder (tungsten carbide powder with a particle size of 300-1000nm) and metal binder phase powder (metal cobalt and metal chromium with a particle size of 300-1000nm) are added to the ball mill jar and ball milled at 250r / min for 2h to obtain a mixed powder slurry with a solid content of 30%; wherein the mass ratio of the hard phase powder to the metal binder phase powder metal cobalt and metal chromium is 86:10:4, the total mass ratio of the hard phase powder and the metal binder phase powder to the mass ratio of the zirconia balls is 1:1, the total mass ratio of the hard phase powder and the metal binder phase powder to the mass ratio of the ball milling media is 3:7, and the total mass ratio of the hard phase powder and the metal binder phase powder to the mass ratio of the polyvinyl alcohol contained in the binder is 100:2;

[0091] (2) controlling the temperature of the mixed powder slurry to 50° C. and spray granulating the mixed powder slurry using a spray dryer to obtain a pre-sintered composite powder; wherein the process parameters of the spray granulation are: an inlet air temperature of 200° C., an outlet air temperature of 110° C., and a peristaltic pump speed of 20 r / min;

[0092] (3) The pre-sintered composite powder was placed in a corundum crucible and sintered in a tubular furnace with an argon protective atmosphere. The temperature was first raised from room temperature to 500°C at a rate of 5°C / min and kept warm for 1 hour. The temperature was then raised from 500°C to 1230°C at a rate of 5°C / min and kept warm for 2 hours. Finally, the powder was cooled to room temperature with the furnace and sieved through 1800 mesh and 6000 mesh sieves, respectively, to obtain ultrafine tungsten carbide metal ceramic spherical powder with a particle size between 1800 and 6000 mesh (2-10 μm).

[0093] Comparative Example 2

[0094] Comparative Example 2 is basically the same as Comparative Example 1, except that: in step (1), the ratio of the total mass of the hard phase powder and the metal binder phase powder to the mass of the ball milling medium is 1.25:8.75, and the solid content of the mixed powder slurry is 12.5%.

[0095] Comparative Example 3

[0096] Comparative Example 3 is basically the same as Comparative Example 1, except that: in step (1), the binder is polyethylene glycol of the same mass concentration and proportion, the ratio of the total mass of the hard phase powder and the metal binder phase powder to the mass of the ball milling medium is 5:5, and the solid content of the mixed powder slurry is 30%.

[0097] The yield calculation, morphology analysis and laser particle size test of the tungsten carbide cermet spherical powder in Examples 1 to 11 and Comparative Examples 1 to 3 are shown in Tables 1 and Figures 1 to 10 shown.

[0098] Table 1

[0099] Example Powder output rate in the particle size distribution range of 2-10μm (%) Example 1 72.12 Example 2 69.64 Example 3 50.61 Example 4 45.57 Example 5 19.51 Example 6 / Example 7 6.56 Example 8 40.16 Example 9 52.91 Example 10 9.08 Example 11 26.72 Comparative Example 1 17.59 Comparative Example 2 / Comparative Example 3 /

[0100] Combined with Table 1 and Figures 1 to 6 It can be seen that in the embodiment of the present invention, by selecting a suitable binder and regulating parameters such as solid content, the morphology of the obtained tungsten carbide cermet spherical powder meets the spherical requirements, the particle distribution is uniform, the output rate of 2-10μm powder is high, and the particle size distribution of the powder is sufficiently concentrated to meet the particle size requirement of 2-10μm; Figures 7 and 8 It can be seen from the figure that when the total mass of the hard phase powder and the metal binder phase powder is too high or too low relative to the mass of the sodium carboxymethyl cellulose contained in the binder, the particle size of the metal ceramic powder will be too large and it will not be possible to form a regular spherical powder. Figure 9 It can be seen from the figure that when the solid content of the mixed slurry is too high, the viscosity of the binder is too strong, resulting in excessive viscosity of the slurry, making the particles obtained by spray granulation too large; Figure 10 and Figure 11It can be seen from the results that when other types of binders (such as carboxymethyl cellulose or carboxyethyl cellulose) are used, it is also not conducive to obtaining spherical powders with uniform morphology and small particle size; further combined with Figure 12 It can be seen that when the same mass concentration of polyvinyl alcohol is used as the binder, the prepared ceramic metal powder has almost no spherical particles, and the raw material powder is almost entirely dispersed; Figure 13 and Figure 14 It can be seen from the figure that when the total mass of the hard phase powder and the metal binder phase powder is too high or too low relative to the mass of the sodium carboxymethyl cellulose contained in the binder, the proportion of small particle size powder is relatively small, which is not conducive to improving the production efficiency of small particle size powder production. Figure 12 、 Figure 13 and 15 As can be seen from the figure, when using traditional polyvinyl alcohol as a binder, spray granulation cannot be performed at low solids contents. At a solids content of 30%, the spray granulation effect is poor, and the yield of ceramic spherical powder is low. When using traditional polyethylene glycol as a binder at a solids content of 30%, the slurry stability is too poor, resulting in the spray granulation of broken particles with hollow interiors.

[0101] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for preparing 2-10 μm ultrafine tungsten carbide cermet spherical powder, characterized in that: The preparation method comprises the following steps: (1) adding a hard phase powder, a metal binder phase powder, a binder, and a wet grinding medium into a ball mill and performing ball milling to mix the hard phase powder, thereby obtaining a mixed powder slurry; wherein the hard phase powder is tungsten carbide, the metal binder phase powder is metal cobalt and metal chromium, and the binder is a cellulose derivative; (2) spray drying and granulating the mixed powder slurry using a spray dryer to obtain a pre-sintered composite powder; (3) placing the pre-sintered composite powder in a tubular furnace for sintering to obtain the ultrafine tungsten carbide metal ceramic spherical powder; wherein the particle size of the tungsten carbide metal ceramic spherical powder is 2-10 μm.

2. The preparation method according to claim 1, characterized in that In step (1), the mass ratio of the hard phase powder to the metal binder phase powder is (83-89):(11-17), and the mass ratio of metal cobalt to metal chromium in the metal binder phase powder is (8-12):(3-5).

3. The preparation method according to claim 1, characterized in that In step (1), the particle size of the hard phase powder and the metal binder phase powder is 300-1000 nm.

4. The preparation method according to claim 1, characterized in that In step (1), the binder is sodium carboxymethyl cellulose; Preferably, the mass ratio of the binder to the total mass of the hard phase powder and the metal binder phase powder is (1.5-3):

100.

5. The preparation method according to claim 1, characterized in that In step (1), the wet grinding medium is water or ethanol; Preferably, the mass ratio of the wet grinding medium to the total mass of the hard phase powder and the metal binder phase powder is (2-9):

1.

6. The preparation method according to claim 5, characterized in that In step (1), the grinding balls used in the ball mill are zirconia grinding balls, the ball milling speed is 230-260 r / min, and the time is 2-8 h.

7. The preparation method according to claim 1, characterized in that In step (1), the solid content of the mixed powder slurry is 10-15%.

8. The preparation method according to claim 1, characterized in that In step (2), during the spray drying and granulation process of the spray dryer, the inlet air temperature of the spray dryer is 190-210°C, the outlet air temperature is 100-120°C, and the speed of the peristaltic pump is 18-22r / min.

9. The preparation method according to claim 1, characterized in that In step (3), during the sintering process, the steel is first sintered at 400-600°C for 0.5-1.5 hours, and then sintered at 1100-1400°C for 1-4 hours.

10. A 2-10 μm ultrafine tungsten carbide cermet spherical powder, characterized in that: The preparation method according to any one of claims 1 to 9 is used for preparation.

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