KR102165405B1 - Tungsten carbide powder and manufacturing thereof - Google Patents

Abstract

The present invention relates to a cemented carbide powder containing tungsten carbide, which can shape physical properties of a coating layer by mixing fine-grained carbide powders having different particle sizes to improve the filling rate, and a method of manufacturing the same. The present invention is a cemented carbide powder comprising 80 to 95 parts by weight of tungsten carbide powder, 1 to 7 parts by weight of chromium, and 4 to 13 parts by weight of cobalt, wherein the tungsten carbide is 10 to 20 parts by weight of tungsten carbide powder having a size of 0.1 to 1.0 μm ; It provides a cemented carbide powder comprising 20 to 30 parts by weight of tungsten carbide powder having a size of 2.5 to 3.5 µm and the balance of tungsten carbide powder having a size of 3.5 to 5.0 µm.

Description

Cemented carbide powder containing tungsten carbide and a method for manufacturing the same TECHNICAL FIELD

The present invention relates to a carbide powder containing tungsten carbide and a method for manufacturing the same, and more particularly, by mixing fine-grained carbide powder with different particle sizes to improve the filling rate, tungsten carbide capable of shaping the physical properties of the coating layer. It relates to a cemented carbide powder and a method for producing the same.

The thermal spraying method is a surface modification technology that forms a coating that can have properties suitable for use on an inexpensive base material. It uses a high-temperature heat source to melt or semi-melt the thermal spraying material and make it in a high-speed spraying collision. It is a process of forming a thick film. At this time, the thermal spraying material forming the coating layer includes most of the materials that can be melted, and with the development of thermal spraying process technology, almost all materials ranging from ceramics and carbide-based metals are currently used.

Using such a thermal spraying process, many studies are being conducted to improve the life of parts used under harsh conditions such as abrasion or corrosive environments, and this process is widely applied in various industrial fields such as automobiles, aircraft, ships, and military. have.

WC-based coatings manufactured by the HVOF spraying method are widely used in mechanical parts that require wear resistance and corrosion resistance. In particular, it is applied to turbine blades of construction equipment, plants, pistons, aircraft, etc., because it has excellent resistance to corrosion and abrasion in harsh environments.

Recently, WC-Co-Cr-based powder is used to improve abrasion resistance and corrosion resistance, and studies on WC-Co-Cr-based coatings so far have mainly been conducted on spraying distance, barrel length, powder size, binder, and addition. Research on the influence of thermal spraying process variables such as elements is ongoing.

In overseas advanced countries, medium-sized companies worth hundreds of billions of dollars are leading the development and application of thermal spray coatings around the world, while domestic companies have 50 companies worth billions of billions, and only a few companies have technology with sales of 1 to 300 billion won. It shows limitations in development and is in a hurry to follow advanced overseas companies.

The domestic utility industry developed mainly in the steel industry in the 1990s, and has since grown with the application of energy and IT industries.

Cr and Cd, which are used in the wet plating industry, are representative environmentally hazardous substances and are being developed to replace them worldwide. Representatively, HCAT (Hard Chromium Alternatives Team) in the United States and C-HCAT in Canada are composed of aviation A consortium has been formed to replace hard Cr and Cd plating applied to the military, military and steel industries, and is currently developing alternative coatings using high-speed thermal spray coatings.

In Europe, regulations on hexavalent chromium-plated products are being strengthened, so these parts are required to be developed by the HVOF coating method using WC-Co-Cr-based thermal spraying powder. However, 100% of the WC-Co-Cr-based thermal spraying powder used in Korea is imported from foreign countries, and it is almost impossible to manufacture when a special specification desired by the consumer occurs.

Therefore, it is necessary to develop a new type of thermal spray coating powder that can actively cope with the conditions of the consumer and is suitable for the environmental requirements of each country.

(0001) Korean Patent Application Publication No. 10-2003-0053780 (0002) Korean Patent Application Publication No. 10-2005-0095030

In order to solve the above-described problem, the present invention provides a cemented carbide powder including tungsten carbide that can shape the physical properties of a coating layer by mixing fine-grained carbide powder having different particle sizes to improve the filling rate, and a method for manufacturing the same. .

In order to solve the above problem, the present invention is a cemented carbide powder comprising 80 to 95 parts by weight of tungsten carbide powder, 1 to 7 parts by weight of chromium, and 4 to 13 parts by weight of cobalt, wherein the tungsten carbide has a size of 0.1 to 1.0 μm. 10 to 20 parts by weight of tungsten carbide powder; It provides a cemented carbide powder comprising 20 to 30 parts by weight of tungsten carbide powder having a size of 2.5 to 3.5 µm and the balance of tungsten carbide powder having a size of 3.5 to 5.0 µm.

The cemented carbide powder may have a porosity of less than 44%, a fluidity (50g) of 11.5 to 12.5 sec, and an apparent density of 4.0 to 5.0 g/cm 3.

The carbide powder may be a powder for thermal spray coating or a 3D printer.

The present invention also provides a joint pin for an excavator joint manufactured using the powder for spray coating.

The present invention also includes (a) mixing a raw material comprising tungsten carbide, cobalt and chromium; (b) forming raw material powder by introducing the mixed raw material into a spray dryer; (c) sintering the raw material powder; And (d) pulverizing and classifying the sintered metal, and then mixing the sintered metal in a size ratio to prepare a cemented carbide powder.

The raw material further comprises 20 to 40 parts by weight of alcohol and 1 to 5 parts by weight of wax, between steps (b) and (c); (b`) Injecting the raw material powder into a hydrogen furnace may further include a step of dewaxing.

The (a) mixing step uses atrition milling, and may be performed for 5 to 25 hours.

The spray drying apparatus of step (b) may have a rotational speed of 5,000 to 10,000 rpm and a hot air inlet temperature of 150 to 200°C.

The (c) sintering step may be performed for 150 to 200 minutes at a temperature of 1100 to 1300°C.

The (b`) dewaxing step may be performed for 2 to 5 hours in a hydrogen furnace at 400 to 500°C.

The cemented carbide powder containing tungsten carbide according to the present invention and the method of manufacturing the same improve the filling rate by mixing fine carbide powders with different particle sizes, thereby increasing the hardness and wear resistance due to the increase of the carbide component per unit area, It is used for thermal spray coating (HOVF) and can be used to manufacture high-density cemented carbide, and especially, it can be used for joint pins of construction equipment to greatly increase durability.

1 shows the change in porosity according to the size of tungsten carbide particles according to an embodiment of the present invention. (a) is a particle of 4 μm (porosity 48%), and (b) is a particle of 0.5 μm (porosity 48%) , (c) briefly shows the mixing (porosity of 44%) of 4㎛ and 0.5㎛ particles.
2 is a schematic diagram schematically showing a high-speed thermal spray coating according to an embodiment of the present invention.
Figure 3 is a schematic diagram showing the internal flow of the high-speed thermal spray coating apparatus according to an embodiment of the present invention.
Figure 4 shows a method and equipment for manufacturing a carbide powder according to an embodiment of the present invention.
5 shows a joint pin for an excavator joint manufactured using a thermal spray coating method using carbide powder according to an embodiment of the present invention and a location of use thereof.

Hereinafter, a preferred embodiment of the present invention will be described in detail. In describing the present invention, when it is determined that a detailed description of a related known technology may obscure the subject matter of the present invention, a detailed description thereof will be omitted. Throughout the specification, when a part "includes" a certain component, it means that other components may be further included rather than excluding other components, unless otherwise stated.

The present invention is intended to illustrate specific embodiments and to be described in detail in the detailed description, since various transformations can be applied and various embodiments can be provided. However, this is not intended to limit the present invention to a specific embodiment, it should be understood to include all conversions, equivalents, or substitutes included in the spirit and scope of the present invention.

The terms used in the present invention are only used to describe specific embodiments, and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In the present invention, terms such as include or have are intended to designate the presence of features, numbers, steps, actions, components, parts, or a combination of them described in the specification, and one or more other features, numbers, and steps. It is to be understood that it does not preclude the possibility of the presence or addition of, operations, components, parts, or combinations thereof.

The present invention is a cemented carbide powder comprising 80 to 95 parts by weight of tungsten carbide powder, 1 to 7 parts by weight of chromium, and 4 to 13 parts by weight of cobalt, wherein the tungsten carbide is 10 to 20 parts by weight of tungsten carbide powder having a size of 0.1 to 1.0 μm ; It relates to a cemented carbide powder comprising 20 to 30 parts by weight of tungsten carbide powder having a size of 2.5 to 3.5 µm and the balance of tungsten carbide powder having a size of 3.5 to 5.0 µm.

The cemented carbide powder of the present invention may include 80 to 95 parts by weight of tungsten carbide powder, 1 to 7 parts by weight of chromium, and 4 to 13 parts by weight of cobalt.

Tungsten carbide is an alloy of tungsten and carbon, and has a very high strength and is used in the manufacture of machine tools, armored armor bullets for tanks, and ballpoint pen nibs. However, tungsten carbide has a high brittleness and a very high melting point, so it is almost impossible to manufacture it in a certain shape through a process such as casting or forging directly. Therefore, cobalt or chromium is used by sintering as a substrate. The tungsten carbide used in the present invention has a purity of 99% by weight or more, and has a powder particle size (FSSS) of 45 to 150 µm, a flow rate (50 g) of 9 to 10 sec, and an apparent density of 7.3 to 7.4 g/cm 3 It is preferable to use. When the purity of tungsten carbide is less than 99% by weight, the desired strength does not appear, and even when tungsten carbide that is out of the above properties is used, the strength of the cemented carbide layer produced using the cemented carbide particles may decrease.

Chromium is added in 1 to 7 parts by weight as a role of improving hardness and increasing corrosion resistance, and does not perform its role if it is out of the above range.

Cobalt is used as a substrate for the tungsten carbide, and may include 4 to 13 parts by weight. If it is contained in less than 4 parts by weight, it is difficult to process the cemented carbide powder because it cannot serve as a base material, and if it is included in more than 13 parts by weight, the strength of the carbide powder may decrease.

The tungsten carbide may include 10 to 20 parts by weight of tungsten carbide powder having a size of 0.1 to 1.0 μm; It may consist of 20 to 30 parts by weight of tungsten carbide powder having a size of 2.5 to 3.5 µm and the balance of tungsten carbide powder having a size of 3.5 to 5.0 µm. As shown in (a) and (b) of FIG. 1, when tungsten carbide powder having a certain size is used, the porosity exceeds 48% (filling rate 52%). Since such porosity is affected only by the shape and mixing of particles, there is little change in porosity even when particles having a small size are used. However, as shown in (c) of FIG. 1, when tungsten carbides having different sizes are mixed and used, the porosity may be lowered to less than 44%, and the bending of the bonding interface may also be maintained close to the assembly phase, thereby increasing toughness. Therefore, the tungsten carbide is 0.1 ~ 1.0㎛ size tungsten carbide powder 10 ~ 20 parts by weight; It is preferable to mix and use in a ratio of 20 to 30 parts by weight of tungsten carbide powder having a size of 2.5 to 3.5 µm and the remainder of tungsten carbide powder having a size of 3.5 to 5.0 µm. There is a change in the curvature of the interface, and it may become closer to the particulate phase, resulting in poor toughness.

The cemented carbide powder may have a fluidity (50 g) of 11.5 to 12.5 sec and an apparent density of 4.0 to 5.0 g/cm 3. Since the cemented carbide powder is composed of a mixture of tungsten carbide powder, chromium and cobalt powder having various sizes, it is preferable to have the above physical properties.

The carbide powder may be a powder for thermal spray coating or a 3D printer. The cemented carbide powder is used for thermal spray coating, especially for high-speed thermal spray coating (HOVF), and can be used to form a cemented carbide layer on the surface of the base material (see FIGS. 2 and 3), and it is also used in metal 3D printers to provide high strength products. It is also possible to produce directly. In particular, when used for high-speed thermal spray coating, it is used for joint pins used for construction equipment, especially excavator pipes, and not only can significantly increase the durability of the joint pin (see Fig. 5), but also has a disk, flat, spherical, etc. Since it can be coated on the surface of the product, it is possible to form a carbide layer on the surface of various products that require high strength.

The present invention also includes (a) mixing a raw material comprising tungsten carbide, cobalt and chromium; (b) forming raw material powder by introducing the mixed raw material into a spray dryer; (c) sintering the raw material powder; And (d) pulverizing and classifying the sintered metal, and then mixing the sintered metal in a size ratio to prepare a cemented carbide powder (see FIG. 4).

The step (a) is a step of mixing the raw materials, preferably using attrition milling, and may be performed for 5 to 25 hours. If it is mixed for less than 5 hours, the mixing may not be complete and unevenness of the cemented carbide powder may occur. If it is mixed for more than 25 hours, the cemented carbide powder may be pulverized without any further mixing effect, resulting in deterioration of physical properties.

The step (b) is a step of forming raw material powder, and is preferably performed using a spray drying apparatus having a rotational speed of 5,000 to 10,000 rpm and a hot air inlet temperature of 150 to 200°C. When the spray drying apparatus is operated below the above range, it is difficult to form a powder having a desired size, and when the spray drying apparatus is operated under the above range, the amount of energy used increases, which is inefficient.

In addition, the raw material may further include 20 to 40 parts by weight of alcohol and 1 to 5 parts by weight of wax. Alcohol and wax are added to increase the agglomeration of the raw material powder, and are added to make the powder form a spherical shape, and if it is added below the above range, the powder may not be formed in a spherical shape and the strength may decrease, exceeding the above range. When mixed, voids may be generated in the powder and the strength may decrease. In addition, in the case of forming a powder using alcohol and wax as described above, between steps (b) and (c); (b`) It is preferable to additionally perform the step of dewaxing by adding the raw material powder to a hydrogen furnace to remove the wax and alcohol components. The (b`) dewaxing step may be performed for 2 to 5 hours in a hydrogen furnace at 400 to 500°C. If the dewaxing process is performed at less than 400℃ or less than 2 hours, the strength of the cemented carbide layer may decrease due to the remaining wax components, and if the dewaxing process exceeds 500℃ or for more than 5 hours, no more wax components are removed. It is inefficient because the dewaxing process is performed.

The step (c) is a step of sintering the raw material powder and may be performed for 150 to 200 minutes at a temperature of 1100 to 1300°C. If the sintering is performed within the above range, the sintering becomes incomplete and the density and fluidity of the powder decreases, so that the physical properties of the cemented carbide layer may deteriorate.If it exceeds the above range, the density and fluidity of the powder increases, making it difficult to process the cemented carbide layer.

In the step (d), the sintered metal is pulverized and classified, and then mixed at a size ratio to prepare a cemented carbide powder. The cemented carbide powder having each size is classified according to the size, and then mixed according to the ratio to produce a final carbide powder. Will be manufactured.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings so that those of ordinary skill in the art can easily implement them. In addition, in describing the present invention, when it is determined that a detailed description of a related known function or a known configuration may unnecessarily obscure the subject matter of the present invention, a detailed description thereof will be omitted. In addition, certain features presented in the drawings are enlarged or reduced or simplified for ease of description, and the drawings and their components are not necessarily drawn to scale. However, those skilled in the art will readily understand these details.

Example

Tungsten carbide having a purity of 99% by weight was prepared in the following ratio

17 parts by weight of tungsten carbide powder having a size of 0.1 to 1.0 μm;

25 parts by weight of tungsten carbide powder having a size of 3.0 μm and

43 parts by weight of tungsten carbide powder having a size of 4.0 μm;

In addition, 5 parts by weight of chromium and 10 parts by weight of cobalt were mixed to prepare a raw material powder.

22 parts by weight of alcohol and 3.2 parts by weight of wax were mixed with the raw material powder, and then added to an attrition mill for 10 hours to mix.

Then, the mixed powder was spray-dried by putting it into a spray drying apparatus maintained at a disk rotation speed of 9000 rpm and a hot air inlet temperature of 170°C.

After spray drying was completed, it was added to a hydrogen furnace at 450° C. for 3 hours to perform a dewaxing process, and sintered in a sintering furnace at 1270° C. for 170 minutes to obtain a carbide powder.

The obtained carbide powder was introduced into a classifier having a crushing blade rotation speed of 3000 rpm, a vibrating body size of 200 to 320 mesh, and a classifier rotation speed of 5000 rpm to obtain carbide particles having an appropriate size (see FIG. 4).

Experimental example

The carbide powder prepared in the above example was supplied to the HVOF shown in FIG. 3 to perform thermal spray coating, and then the physical properties of the formed film are described in Table 1 below.

unit Conventional powder Example powder Coating layer hardness Hv 1200 1300 Wear mg 1.2 0.65

Existing powder shown in Table 1 had the same ratio as in Example (85 parts by weight of tungsten carbide powder, 5 parts by weight of chromium, and 10 parts by weight of cobalt), but was carried out using tungsten carbide having the same size (4.0 μm). .

As shown in Table 1, when using the powder according to the embodiment of the present invention was confirmed to have a higher hardness.

As described above, specific parts of the present invention have been described in detail, and it will be apparent to those of ordinary skill in the art that these specific techniques are only preferred embodiments, and the scope of the present invention is not limited thereby. will be. Accordingly, it will be said that the substantial scope of the present invention is defined by the appended claims and their equivalents.

Claims (10)

In the carbide powder containing 80 to 95 parts by weight of tungsten carbide powder, 1 to 7 parts by weight of chromium and 4 to 13 parts by weight of cobalt,
The tungsten carbide is
10 to 20 parts by weight of tungsten carbide powder having a size of 0.1 to 1.0 μm;
20 to 30 parts by weight of tungsten carbide powder of 2.5 to 3.5 μm and
The balance of tungsten carbide powder of 3.5-5.0 μm;
Is composed of,
The cemented carbide powder has a porosity of less than 44%, a fluidity (50g) of 11.5 to 12.5 sec, and an apparent density of 4.0 to 5.0 g/cm 3.
delete The method of claim 1,
The cemented carbide powder, characterized in that the powder for thermal spray coating or 3D printer.
A joint pin for an excavator joint manufactured using the carbide powder of claim 1.
(a) mixing a raw material containing tungsten carbide, cobalt and chromium;
(b) forming a raw material powder by introducing the mixed raw material into a spray dryer;
(c) sintering the raw material powder; And
(d) pulverizing and classifying the sintered metal, and then mixing the sintered metal at a size ratio to prepare a cemented carbide powder;
The method of manufacturing the carbide powder of claim 1 comprising a.
The method of claim 5,
The raw material further comprises 20 to 40 parts by weight of alcohol and 1 to 5 parts by weight of wax,
Between steps (b) and (c);
(b`) adding the raw material powder to a hydrogen furnace and dewaxing;
Carbide powder manufacturing method, characterized in that it further comprises.
The method of claim 5,
The (a) mixing step uses attrition milling, and is carried out for 5 to 25 hours.
The method of claim 5,
In the spray drying apparatus of step (b), the rotational speed of the disc is 5,000 to 10,000 rpm, and the hot air inlet temperature is 150 to 200°C.
The method of claim 5,
The (c) sintering step is a method for producing carbide powder, characterized in that carried out for 150 to 200 minutes at a temperature of 1100 to 1300 ℃.
The method of claim 6,
The (b`) dewaxing step is a method for producing carbide powder, characterized in that it is carried out for 2 to 5 hours in a hydrogen furnace of 400 ~ 500 ℃.

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