Patent Application
20240327956
The present disclosure relates to a cemented carbide for cutting tools and, more particularly, to a cemented carbide for cutting tools and a manufacturing method thereof, in which resistance to each of plastic deformation and crater wear is improved by controlling average particle diameters of a WC and a compound of the cemented carbide to appropriate levels.
Cemented carbide refers to an alloy manufactured by mixing hard tungsten carbide (WC) particles with a bonding phase provided by Co, Ni, and Fe. The cemented carbide has high hardness and strong toughness, so the cemented carbide is used as tool steel for cutting tools for processing metals or high-strength ceramics.
Typically, in order to improve the mechanical properties of a cemented carbide, methods to change the composition of the cemented carbide or to diversify the microstructure thereof are used. As a representative example, Korean Patent No. 10-1792534 discloses a method of strengthening hardness through controlling the microstructure of WC and controlling the composition of the hard coating layer, and Korean Patent No. 10-2050644 discloses a method of improving wear resistance and impact resistance by controlling the composition of Ti and the thickness of a cubic phase free (CFL) layer to appropriate ranges. In addition, Korean Patent No. 10-1302374 discloses a method of limiting the content of carbides excluding WC to a predetermined range.
However, in addition to the above methods, there is a constant need for a method of manufacturing cemented carbide that can enhance mechanical properties by controlling sintering conditions.
In order to solve the above problems, the present disclosure provides a cemented carbide for cutting tools and a manufacturing method thereof, in which sintering temperature and cooling rate are controlled to control the average particle diameter of the cemented carbide to an appropriate range, thereby improving resistance to plastic deformation and resistance to crater wear.
In order to accomplish the above objectives, one embodiment of the present disclosure relates to a cemented carbide for cutting tools including, by weight %, 4˜13% of Co, 1˜12% of a compound, and the remaining being WC and other unavoidable impurities, wherein an average particle diameter of the compound and an average particle diameter of the WC satisfy Relational expression 1 below.
(In Relational expression 1, A refers to the average particle diameter of a compound in a cemented carbide for cutting tools, and B refers to an average particle diameter of WC).
In the one embodiment, the compound may be provided as a carbide, a nitride, and a carbonitride formed by combining one or more elements selected from a group consisting of elements of group 4a, group 5a, or group 6a with carbon or nitrogen.
In the one embodiment, the compound may be provided as a carbide formed by combining one or more elements selected from a group consisting of elements of group 4a, group 5a, or group 6a with carbon.
In the one embodiment, the cemented carbide for cutting tools may have crack point A of 25% or less described below.
Crack point A=(the number of interfaces of compounds per unit area)/(the total number of compounds per unit area)×100. [Relational expression 2]
Another embodiment of the present disclosure relates to a cutting tool made of the cemented carbide for cutting tools described above and a hard film formed on a surface of the cemented carbide.
In the embodiment, the hard film may be formed by one or more methods selected from a chemical vapor deposition (CVD) method and a physical vapor deposition (PVD) method.
Still another embodiment of the present disclosure relates to a method for manufacturing a cemented carbide for cutting tools, the method including: a step of manufacturing a mixture by weighing raw material powder consisting of 4˜13% of Co, 1˜12% of a compound by weight % and the remaining being WC, and mixing the raw material powder; a step of manufacturing a molded body by putting the mixture into a mold and pressing the mixture; and a step of manufacturing a cemented carbide by sintering the mixture, wherein the sintering includes: a step of dewaxing the molded body at about 200 to 300° C. for one to three hours; a step of primarily sintering the molded body, which is dewaxed, at 1,000 to 1,250° C. for a predetermined period of time; a step of secondarily sintering the primarily-sintered molded body at 1,400 to 1,450° C. for a predetermined period of time; a step of thirdly sintering the secondarily-sintered molded body at 1,500 to 1,600° C. for a predetermined period of time; a step of primarily cooling the thirdly-sintered molded body down to 1000 to 1300° C.; and a step of secondarily cooling the primarily-cooled molded body down to a room temperature.
In the embodiment, the secondary sintering may be performed for 90 to 120 minutes.
In the embodiment, the second cooling step may be performed at a cooling rate of 120 to 150° C./min.
As described above, according to the manufacturing method of the cemented carbide for cutting tools according to the embodiment of the present disclosure, when the average particle diameter of the compound is 0.4 μm or less and the average particle diameter of the WC is 1.2 to 2.2 μm, the average particle diameter of the compound and the average particle diameter of the WC are controlled to appropriate levels, thereby improving resistance to plastic deformation and resistance to crater wear.
Through this, wear resistance of a cutting tool can be improved and lifespan thereof can be increased.
Hereinafter, a cemented carbide for cutting tools according to the present disclosure will be described in detail. The drawings introduced below are provided as examples so that the idea of the present disclosure can be sufficiently conveyed to those skilled in the art. Accordingly, the present disclosure is not limited to the drawings presented below and may be embodied in other forms, and the drawings presented below may be exaggerated to clarify the idea of the present disclosure. In this case, unless otherwise defined, technical and scientific terms used have meanings commonly understood by those skilled in the art to which this invention pertains, and the description of well-known functions and configurations that may unnecessarily obscure the gist of the present disclosure in the following description and the accompanying drawings is omitted.
According to one aspect of the present disclosure, the present disclosure relates to the cemented carbide for cutting tools which includes 4˜13% of Co, 1˜12% of a compound, and the remaining being WC and other unavoidable impurities so that resistance to plastic deformation and resistance to crater wear are excellent.
In this specification, WC refers to a tungsten carbide formed by combining tungsten (W) powder and carbon (C) powder.
In this specification, the compound may refer to a carbide, a nitride, and a carbonitride formed by combining one or more elements selected from a group consisting of elements of group 4a, group 5a, or group 6a with carbon or nitrogen.
For example, the compound may refer to carbides, nitrides, and carbonitrides formed by combining one or more metals selected from a group consisting of Cr, Zr, Nb, Mo, Ti, Hf, Ta and V with 1 wt % or less of C or N. The compound may be more preferably provided as a metal carbide formed by combining one or more metals selected from a group consisting of Cr, Zr, Nb, Mo, Ti, Hf, Ta and V with 1 wt % or less of carbon. The compound may be more preferably provided as any one metal carbide selected from TiC, NbC, and TaC.
Hereinafter, in this specification, for convenience of explanation, the compound is, for example, a carbide in which one or more metals selected from a group consisting of Cr, Zr, Nb, Mo, Ti, Hf, Ta and V and 1 wt % or less of carbon are combined with each other but is not limited thereto, and it is obvious that the compound may be applied even to nitride and carbonitride.
According to the embodiment, in the process of manufacturing the cemented carbide of the present disclosure, by controlling a temperature increase rate and cooling rate, the particle diameters of the compound and the WC can be adjusted.
For example, according to the present disclosure, the cemented carbide for cutting tools may be manufactured by performing a step of dewaxing a molded body having a mixed raw material powder at about 200 to 300° C. for 1 to 3 hours, a step of primarily sintering the molded body, which is dewaxed, at 1,000 to 1,250° C. for a predetermined period of time, a step of secondarily sintering the primarily-sintered molded body at 1,400 to 1,450° C. for a predetermined period of time, a step of thirdly sintering the secondarily-sintered molded body at 1,500 to 1,600° C. for a predetermined period of time, a step of primarily cooling the thirdly-sintered molded body down to 1000 to 1300° C., and a step of secondarily cooling the primarily-cooled molded body down to a room temperature.
In this process, in the third sintering step, 1,500 to 1,600° C. is maintained for 90 to 120 minutes, and in the second cooling step, the particle diameters of the compound and the WC may be adjusted by cooling the compound and WC at cooling rates of 120 to 150° C./min.
As a result, the average particle diameter of the compound and the average particle diameter of the WC may be controlled to satisfy the following relational equation 1.
(In Relational expression 1, A refers to an average particle diameter of the compound in the cemented carbide for cutting tools, and B refers to an average particle diameter of the WC)
In addition, in the cemented carbide for cutting tools, the average particle diameter of the compound may be controlled to be 0.4 μm or less, and the average particle diameter of the WC may be controlled to be 1.2 to 2.2 μm.
In other words, in the manufacturing process of the present disclosure, by controlling a sintering period of time and cooling rate, the average particle diameter of the compound may be manufactured to be 0.4 μm or less, and the average particle diameter of the WC may be manufactured to be 1.2 to 2.2 μm. While the average particle diameters of the compound and the WC are provided within the ranges described above, resistance to plastic deformation and crater wear can be secured by additionally limiting the ratio of the average particle diameters of the compound and the WC.
According to the embodiment, when the ratio (A/B) of the average particle diameters of the compound and the average particle diameter of the WC is less than 18, it means that the particle of the compound are excessively finer than the particle of the WC.
Typically, the compound may be dissolved in the lattice formed by a Co-bonded phase in the cemented carbide alloy to form an interstitial solid solution. The compound included in the cemented carbide in the form of the interstitial solid solution can induce solid solution strengthening by interfering with the movement of dislocations in the cemented carbide. As a result, the mechanical properties of the cemented carbide can be improved.
However, in this process, when the particle size of the compound is excessively small, the interstitial solid solution cannot effectively impede the movement of dislocations, making it difficult to induce a sufficient solid solution strengthening effect. As a result, the mechanical strength of the cemented carbide may be reduced. That is, this means that the wear resistance and chipping resistance of the cemented carbide are reduced. This means that when a cutting tool is manufactured of the cemented carbide, resistance to plastic deformation of the cutting tool is reduced, and thus the deformation easily occurs, and crater wear may easily occur.
Conversely, when the ratio (A/B) of the average particle diameter of the compound and the average particle diameter of the WC exceeds 30, it means that a compound of a coarse size is formed. In this case, one compound may combine with one or more other compounds formed around the one compound to form one coarse-sized compound. This may also reduce the plastic deformation resistance and crater wear resistance of the cemented carbide by lowering the density of the compound.
That is, according to the present disclosure, it is possible to manufacture the cemented carbide for cutting tools, in which the cemented carbide realizes the most optimal solid solution strengthening effect by controlling a sintering period of time and a cooling rate, thereby having excellent resistance to each of plastic deformation and crater wear. The comparative results of the plastic deformation resistance and crater wear resistance according to the sintering period of time and cooling rate will be described later.
The cemented carbide for cutting tools has been described above according to the embodiment of the present disclosure. In this specification, the cemented carbide for cutting tools has been explained, but a cutting tool manufactured with the cemented carbide for cutting tools may also be applied in the same way.
According to an embodiment, the cutting tool may include the cemented carbide and a hard film for cutting tools described above.
According to an embodiment, the hard film, which is a film including one or more alumina layers, may be formed on a surface of a base material formed of the cemented carbide.
For example, the hard film may include a layer of TiCxNyOz (x+y+z=1) having a single-layer or multi-layer structure between the base material made of the cemented carbide and the alumina layer. In addition, the layer of Ti(C,N,O) includes additive elements such as aluminum (Al), zirconium (Zr), and boron (B), and thus the bonding characteristics of the alumina layer and the layer of TiCxNyOz (x+y+z=1) can be improved.
According to an embodiment, the hard film may be formed through one or more methods selected from a chemical vapor deposition (CVD) method and a physical vapor deposition (PVD) method.
Hereinafter, a method for manufacturing the cemented carbide for cutting tools will be described with reference to
The method for manufacturing the cemented carbide for cutting tools according to the embodiment of the present disclosure may include a step of manufacturing a mixture by weighing raw material powder consisting of 4˜13 wt % of Co, 1˜12 wt % of a compound and the remaining being WC, and mixing the raw material powder, a step of manufacturing a molded body by putting the mixture into a mold and pressing the mixture, and a step of manufacturing a cemented carbide by sintering the mixture.
First, Co powder, compound powder, and WC powder may be prepared. In this case, the compound powder refers to a powder composed of a carbide, a nitride, and a carbonitride containing one or more elements selected from a group consisting of elements of group 4a, group 5a, or group 6a.
The powder is weighed to have 4 to 13 wt % of Co, 1 to 12 wt % of a compound, and the remaining being WC, and then mixed to prepare a mixture. In this case, in order to uniformly mix the powder, a mixer may be operated at 40 to 60 rpm for primary mixing of the powder, and then, after the primary mixing, may be operated at 5 to 15 rpm for secondary mixing of the powder.
Next, the mixture is pressed to manufacture a molded body, and the molded body is sintered to manufacture a cemented carbide for cutting tools.
Referring to
The step a) is a process of removing unnecessary impurities in the sintering process by dewaxing the molded body at about 200 to 300° C. for 1 to 3 hours.
According to an embodiment, the dewaxing step may be performed by any one dewaxing of heat dewaxing, solvent dewaxing, and catalytic dewaxing.
Next, the molded body which is dewaxed may be primarily sintered through the step b) by maintaining a temperature at 1,000 to 1,250° C. for 30 to 120 minutes.
Next, the molded body which is dewaxed may be secondarily sintered through the step c) by maintaining a temperature at 1,400 to 1,450° C. for 30 to 120 minutes.
A predetermined rigidity may be imparted to the molded body through the primary sintering and secondary sintering.
Next, the secondarily-sintered molded body may be thirdly sintered through the step d) at 1,500 to 1,600° C. for 90 to 120 minutes so as to remove pores formed in the molded body and improve strength.
According to an embodiment, when the third sintering period of time is less than 90 minutes, particles may not receive sufficient heat energy to grow in the sintering process, and thus the amount of carbide diffused into Co may be reduced. This may result in a decrease in the number of compound particles per unit area in the cemented carbide and a relative decrease in the average particle diameter of the compound particles. On the other hand, when the third sintering period of time exceeds 120 minutes, the WC and the compound may overgrow and the average particle diameters thereof may increase. For this reason, the third sintering period of time is preferably 90 to 120 minutes, and more preferably 90 to 100 minutes.
After the first to third sintering, the thirdly-sintered molded body may be primarily cooled down to 1000 to 1300° C. through the step e). In this case, the primary cooling may be performed at a cooling rate of 1 to 10° C./min.
Finally, the primarily-cooled molded body may be secondarily cooled down to a room temperature (25° C.) though the step f).
According to an embodiment, the primary cooling may be performed slowly at a cooling rate of 1 to 10° C./min, while the secondary cooling may be performed rapidly at a cooling rate of 120 to 150° C./min.
When the secondary cooling is performed at less than 120° C./min, a period of time required for complete cooling to a room temperature increases, resulting in an increase in the average particle diameter of the compound. This means that, as explained above, one compound may combine with one or more other compounds formed around the one compound to form one coarse-sized compound. For this reason, the wear resistance and plastic deformation resistance of the cemented carbide may be reduced.
Conversely, when the speed of the secondary cooling exceeds 150° C./min, the average particle diameter of the compound may excessively decrease. As explained earlier, this also causes a decrease in the wear resistance and plastic deformation resistance of the cemented carbide.
In addition, residual stress may occur inside the cemented carbide due to excessive rapid cooling. In this case, cracks or breaks may occur in some cemented carbide, which may reduce the yield of a product. For this reason, the secondary cooling is preferably performed at 120 to 150° C./min, and may more preferably be performed at 120 to 130° C./min.
Hereinafter, the cemented carbide for cutting tools according to the present disclosure will be described in more detail through an embodiment. However, the following embodiment is only a reference to explain the present disclosure in detail, and the present disclosure is not limited thereto, and may be implemented in various forms.
Additionally, unless otherwise defined, all technical and scientific terms have the same meaning as commonly understood by those skilled in the art to which the present disclosure pertains. Terms used in description herein are intended merely to effectively describe particular embodiments and are not intended to limit the present disclosure. Additionally, the unit of compounds not specifically described in the specification may be weight %.
Co powder, NbC powder (hereinafter, referred to as a compound), and WC powder are prepared. Afterwards, the metal powder is weighed to contain 8.3 wt % of Co, 4 wt % of NbC, and residual WC, then first mixed at 40 rpm by using a mixer, and then second mixed at 5 rpm to prepare a mixture. Next, the prepared mixture is placed in a mold and pressed to manufacture a molded body.
The manufactured molded body is dewaxed at 250° C. for 120 minutes, and then primarily sintered at 1200° C. for 30 minutes. The primarily-sintered molded body is immediately subjected to secondary sintering at 1,430° C. for 60 minutes, and after the secondary sintering, third sintering is performed at 1,550° C. for 90 minutes. All of the primary to third sinterings are performed in an Ar atmosphere.
The molded body that has completed the third sintering is then primarily cooled from 1500° C. to 1200° C. at a cooling rate of 5° C./min, and after stabilizing the sintered carbide, the carbide is secondarily cooled from 1200° C. to 25° C. at a cooling rate of 120° C./min, and accordingly a cemented carbide for cutting tools is manufactured.
All processes are performed in the same manner as Embodiment 1 except that third sintering is performed for 120 minutes.
All processes are performed in the same manner as Embodiment 1 except that secondary cooling is performed at a cooling rate of 150° C./min.
All processes are performed in the same manner as Embodiment 1 except that third sintering is performed for 150 minutes.
All processes are performed in the same manner as Embodiment 1 except that third sintering is performed for 60 minutes.
All processes are performed in the same manner as Embodiment 1 except that secondary cooling is performed at a cooling rate of 60° C./min.
All processes are performed in the same manner as Embodiment 1 except that secondary cooling is performed at a cooling rate of 180° C./min.
Embodiments 1 to 3 and Comparative examples 1 to 4 are summarized in Table 1 below.
[Analysis and performance evaluation]
The cross-sections of cemented carbides for cutting tools manufactured according to Embodiments 1 to 3 and Comparative Examples 1 to 4 were mirror polished and microstructures thereof were observed by using an optical microscope.
Referring to
On the other hand, referring to
Through
The average atomic diameters of the WC and the compound on the microstructure were quantitatively measured by using an image analyzer, and a ratio between the average particle diameter of the compound and the average particle diameter of the WC was calculated on the basis of the measured atomic diameters. In this case, the ratio of the average particle diameter of the compound and the average particle diameter of the WC was calculated according to Relational expression 1 below.
(In Relational expression 1, A refers to an average particle diameter of a compound in a cemented carbide for cutting tools, and B refers to an average particle diameter of WC)
The average particle diameter of the WC, the average particle diameter of the compound, and the ratio of the average particle diameter of the compound and the average particle diameter of the WC are shown in Table 2 below.
Referring to Table 2, it can be seen that in a state in which in Embodiments 1 to 3, the average particle diameter of the compound satisfies 0.4 μm or less and the average particle diameter of the WC satisfies 1.2 to 2.2 μm, the average particle diameter of the compound and the average particle diameter of the WC are formed in a range of satisfying Relational expression 1.
On the other hand, in Comparative example 1, the sintering period of time was increased to 150 min during the third sintering, and as a result, the average diameter of the compound increased to 0.55 μm relative to Embodiment 3, in which WC has a similar average particle diameter. As a result, it can be checked that the ratio (A/B) of the average particle diameter of the compound and the average particle diameter of the WC exceeded 30%.
In Comparative example 2, the sintering period of time was reduced to 60 min during the third sintering, and as a result, the average particle diameter of a compound decreased relative to the average particle diameter of WC. As a result, it can be checked that the ratio (A/B) of the average particle diameter of the compound and the average particle diameter of the WC is less than 18%.
In Comparative example 3, a cooling rate during secondary cooling was decreased to 60° C./min, and as a result, the average particle diameter of a compound increased relative to the average particle diameter of WC. As a result, it can be checked that the ratio (A/B) of the average particle diameter of the compound and the average particle diameter of the WC exceeded 30%.
In Comparative example 2, a cooling rate was increased to 180° C./min during secondary cooling, and as a result, the average particle diameter of the compound decreased relative to the average particle diameter of the WC. As a result, it can be checked that the ratio (A/B) of the average particle diameter of the compound and the average particle diameter of the WC is less than 18%.
That is, in the above-described manufacturing process of the cemented carbide for cutting tools according to the embodiment of the present disclosure, the secondary sintering is performed for 90 to 120 minutes, and the secondary cooling is performed at a cooling rate of 120 to 150° C./min. Accordingly, the ratio (A/B) of the average particle diameter of the compound and the average particle diameter of the WC may be 18 to 30%.
Crack point comparison tests and wear resistance tests were performed to compare plastic deformation resistance and crater wear resistance of cemented carbide manufactured according to Embodiments 1 to 3 and Comparative examples 1 to 4.
In the present disclosure, a crack point refers to a point at which a crack easily occurs. Typically, a crack tends to occur at an interface between compounds and grow along the interface, causing destruction. For this reason, when the number of interfaces of compounds is smaller than the total number of the compounds, the occurrence of cracks can be suppressed and mechanical strength of the compounds can be improved. As a result, the plastic deformation and crater wear of cemented carbide and a cutting tool made of the cemented carbide can be prevented.
Hereinafter, the crack point may be divided into crack point A, which means the interface ratio of compounds among all of the compounds formed in a unit area, and crack point B, which is an average of interface ratios of compounds among the compounds formed in 20 small equal areas by dividing the unit area into the 20 small equal areas. The crack point A and crack point B may be defined as follows.
Crack point A=(the number of interfaces of compounds per unit area)/(the total number of compounds per unit area)×100
Crack point B=2{(number of interfaces of compounds in each region)/(total number of compounds in each region)×100}/20
In order to compare the crack point A with crack point B, the cross section of the cemented carbide manufactured according to Embodiments 1 to 3 and Comparative examples 1 to 4 was mirror polished and an area of 5×4 mm2 was photographed by an optical microscope, and the crack point was calculated by measuring the total number of compounds observed in the corresponding area and the number of interfaces between the compounds.
In addition, as illustrated in
Referring to Table 3, it can be seen that crack points A of a cemented carbide manufactured according to Embodiments 1 to 3 are 18.27, 22.25, and 18.54%, respectively, which are less than 25%. The number of interfaces of compounds compared to the total number of the compounds may be adjusted to an appropriate level, thereby preventing the formation of cracks and improving plastic deformation resistance.
Crack points B were also measured to be 17.94, 21.22, and 17.62%, and thus it was checked that the compound was evenly formed without being excessively formed in a specific area.
On the other hand, it can be observed that a crack point of a cemented carbide manufactured according to Comparative examples 1 to 4 exceeds 25%.
Specifically, in Comparative example 1 and Comparative example 3, the average particle diameter of the compound increased, and the number of compound interfaces increased relatively, and as a result, the crack point exceeded 25%.
In Comparative example 2 and Comparative example 4, the average particle diameter of the compound decreased, but the total number of compounds decreased relatively, and as a result, the crack point exceeded 25%. However, the reason for which the number of compounds decreased in Comparative example 2 and Comparative example 3 is that the measuring of the number of compounds was performed for the compounds that can be distinguished by an optical microscope, that is, compounds with minimum diameters of 0.1 μm or more that can be distinguished by an optical microscope, and thus the number of the compounds appears to have decreased. However, in reality, it is preferable to determine that multiple compounds with minimum particle diameters of less than 0.1 μm were formed.
In order to verify a wear resistance effect according to the crack point A and crack point B, wear resistance evaluation was performed under the following conditions, and the results are shown in Table 4.
Cutting conditions for wear resistance evaluation
Referring to Table 4, in Embodiments 1 to 3 in which actual crack points A and crack points B are both 25% or less, plastic deformations have relatively reduced, and Comparative examples 1 to 4 in which the crack points A and crack points B both exceed 25%, plastic deformations increased. Through this, it can be seen that wear resistance is improved when the crack point is 25% or less.
In fact, in comparison of
In addition, in comparison of
That is, according to the present disclosure, it was experimentally confirmed that plastic deformation resistance and crater wear resistance were improved by mixing the compound and the WC having appropriate diameter sizes, and as a result, crack points decreased and actual wear resistance was improved.
As described above, the present disclosure may provide the cemented carbide for cutting tools which includes, by weight %, 4˜13% of Co, 1˜12% of a compound, and the remaining being WC and other unavoidable impurities.
In this case, the compound may be provided as a carbide, a nitride, and a carbonitride formed by combining one or more elements selected from a group consisting of elements of group 4a, group 5a, or group 6a with carbon or nitrogen.
According to an embodiment of the present disclosure, in a step of manufacturing the cemented carbide, a secondary sintering period of time and a secondary cooling temperature are controlled so that the average particle diameter of the compound can be controlled to be 0.4 μm or less, and the average particle diameter of the WC can be controlled to be 1.2 to 2.2 μm.
More preferably, while in the cemented carbide, the average particle diameter of the compound is 0.4 μm or less and the average particle diameter of the WC is 1.2 to 2.2 μm, the secondary sintering period of time and secondary cooling temperature of the cemented carbide may be controlled so that the average particle diameter of the compound and the average particle diameter of the WC satisfy Relational expression 1 below.
(In Relational expression 1, A refers to the average particle diameter of the compound in the cemented carbide for cutting tools, and B refers to the average particle diameter of the WC.)
Through this, the present disclosure can significantly improve plastic deformation resistance and crater wear resistance.
Although the present disclosure has been explained through specific matters and limited embodiments as described above, this is only provided to facilitate a more general understanding of the present disclosure, and the present disclosure is not limited to the above embodiments. Those skilled in the art to which the present disclosure pertains can make various modifications and variations from the descriptions.
Therefore, the idea of the present disclosure should not be limited to the described embodiments, and not only the claims to be described later, but also all things that are equivalent to the claims fall within the scope of the idea of the present disclosure.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2021-0120730 | Sep 2021 | KR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/KR2022/008458 | 6/15/2022 | WO |
