KR102600871B1 - Cermet cutting tools - Google Patents

Abstract

The present invention relates to a cutting tool made of cermet mainly containing Ti carbide or Ti carbonitride.
The cutting tool according to the present invention includes a sintered body including an upper surface, a side surface intersecting the upper surface, and an edge formed at an intersection ridge portion of the upper surface and the side surface, the sintered body comprising carbonitride containing Ti, A hard phase containing carbides, carbonitrides, or mixtures thereof of one or more metals selected from metals in groups 4, 5, and 6 of the periodic table, and a bonding phase consisting of one or more metals selected from Fe, Co, and Ni, , the total carbon content of the sintered body is 7.5% by weight or more, and the sweating area of the non-ground surface of the sintered body is 5% or less.

Description

Cermet cutting tools {CERMET CUTTING TOOLS}

The present invention relates to a cutting tool made of cermet mainly containing titanium (Ti) carbide or titanium (Ti) carbonitride.

As base materials for wear-resistant tools or cutting tools used in metal cutting, WC-Co cemented carbide, cermet containing TiC or Ti(C,N), other ceramics, or high-speed steel are mainly used.

Among them, WC-Co cemented carbide alloy is made up of cobalt (Co) and tungsten (W), which have strong strategic material properties, and is widely used due to its excellent physical properties, but has the disadvantage of being expensive.

Cermet generally refers to a composite material composed of an inexpensive ceramic hard phase and a metal bonded phase. In the cutting tool field, hard ceramic powders such as WC, NbC, TaC, and Mo ₂ C are used in TiC or Ti(C,N) powder. Ceramic made by mixing partially mixed hard phase powder and bonded phase powder mainly containing metals such as nickel (Ni), cobalt (Co), and/or iron (Fe) and sintering in a vacuum, hydrogen, or argon gas atmosphere. It refers to a metal composite sintered material. These cermets have advantages such as high hardness, excellent chemical stability at high temperatures, low specific gravity, and low raw material prices.

Meanwhile, as a means of improving the wear resistance, fracture resistance, and thermal shock resistance of cermets, methods for controlling the microstructure or residual stress of cermets have been proposed, as shown in the following patent documents, but there is still much room for improvement in physical properties.

Republic of Korea Patent Publication No. 10-2008-0018189 Japanese Registered Patent Publication No. 5188578

The purpose of the present invention is to provide a cermet cutting tool with improved wear resistance and life stability.

In order to solve the above problem, the present invention includes a sintered body including an upper surface, a side surface intersecting the upper surface, and an edge portion formed at an intersection ridge portion of the upper surface and the side surface, wherein the sintered body includes carbonitride containing Ti and , a hard phase containing carbides, carbonitrides, or mixtures thereof of one or more metals selected from group 4, 5, and 6 metals of the periodic table, and a bonding phase consisting of one or more metals selected from Fe, Co, and Ni. It provides a cermet cutting tool, characterized in that the total carbon content of the sintered body is 7.5% by weight or more, and the sweating area of the non-ground surface of the sintered body is 5% or less.

The cermet cutting tool according to an embodiment of the present invention maintains the total carbon content of the cermet sintered body constituting the cutting tool as high as 7.5% by weight or more while maintaining the sweating area as low as 5% or less, thereby providing excellent wear resistance as an insert. When processed, the lifespan deviation for each corner is significantly reduced, resulting in good lifespan stability.

1 is a schematic diagram of a cermet cutting tool according to one embodiment of the present invention.
Figure 2 shows microstructure photographs and measured sweating areas of the non-ground surfaces of cermet cutting tools according to Examples and Comparative Examples 1 to 3.
Figure 3 is a photograph of the microstructure of a cermet cutting tool according to an example.
Figure 4 is a composition profile analyzed from the surface of the cermet cutting tool according to Comparative Example 1 to a depth of 30㎛.
Figure 5 is a composition profile analyzed from the surface of a cermet cutting tool according to an example to a depth of 30㎛.
Figure 6 is a photograph taken at the beginning and end of the cutting performance evaluation of the cermet cutting tool according to Example and Comparative Examples 1 to 3.
Figure 7 shows the cutting performance evaluation results of cermet cutting tools according to Examples and Comparative Examples 1 to 3.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the embodiments of the present invention illustrated below may be modified into various other forms, and the scope of the present invention is not limited to the embodiments detailed below. Examples of the present invention are provided to more completely explain the present invention to those with average knowledge in the art.

The cermet cutting tool according to the present invention includes a sintered body including an upper surface, a side surface intersecting the upper surface, and an edge portion formed at an intersection ridge portion of the upper surface and the side surface, the sintered body comprising carbonitride containing Ti, and a periodic table of elements. Includes a hard phase containing carbides, carbonitrides, or mixtures thereof of one or more metals selected from Group 4, 5, and 6 metals, and a bonding phase consisting of one or more metals selected from Fe, Co, and Ni. The total carbon content of the sintered body is 7.5% by weight or more, and the sweating area of the non-ground surface of the sintered body is 5% or less.

In the present invention, “total carbon content” refers to the content of all carbon present in the form of carbon or carbide in the sintered body.

As in the present invention, when the total carbon content of the cermet sintered body is kept high at 7.5% by weight or more and at the same time the sweating area of the non-ground surface is kept at 5% or less, excellent wear resistance and life stability can be obtained.

In addition, in the cermet cutting tool, the sintered body contains 40 to 80% by weight of carbonitride containing Ti, carbide, carbonitride, or at least one metal selected from group 4, 5, and 6 metals of the periodic table. It may contain 15 to 40% by weight of the mixture thereof and 5 to 25% by weight of the bonding phase.

If the content of carbonitride containing Ti is less than 40% by weight, the cutting tool may deform quickly due to lack of heat resistance when machining high-speed cutting conditions and high-hardness workpieces, and tungsten carbide (WC), cobalt (Co) and If Ti carbonitride, which is more brittle than nickel (Ni), exceeds 80% by weight, the cutting tool is likely to be damaged under interrupted conditions, so 40 to 80% by weight is preferable.

If the carbide, carbonitride, or mixture thereof of one or more metals selected from the 4th, 5th, and 6th group metals of the periodic table is less than 15% by weight, the grain growth inhibition effect and high temperature plastic deformation resistance are reduced, resulting in high-speed, continuous operation. It has the disadvantage of easily causing deformation of the cutting tool under certain conditions, and if it exceeds 40% by weight, it interferes with the bonding force between carbonitrides containing Ti and the metal bonding phases Co, Ni, and Fe, making Ti vulnerable to external shocks. Since cracks easily occur between the carbonitride contained and the metal bonding phases of Co, Ni, and Fe, tool life can be reduced. Therefore, the content of carbides, nitrides, or mixtures thereof is preferably in the range of 15 to 40% by weight.

If the content of the bonding phase is less than 5% by weight, the bonding force between the hard Ti-based carbonitrides becomes weak, which has the disadvantage of easily damaging the cutting tool even under weak intermittent conditions. If it exceeds 25% by weight, it has excellent characteristics under intermittent conditions. However, since the cutting tool is easily deformed under high-speed conditions, the range of 5 to 25% by weight is preferable.

Additionally, in the cermet cutting tool, compressive residual stress of 600 MPa to 800 MPa may be formed in an area from the surface of the sintered body to a depth of 50 μm. In this way, by forming a high compressive residual stress of 600 MPa to 800 MPa in the area from the surface to a depth of 50㎛, sufficient chipping resistance and wear resistance can be obtained.

In addition, in the cermet cutting tool, the difference between the Co content measured on the surface of the sintered body and the Co content measured at a depth of 10 μm, or the Ni content measured on the surface of the sintered body and the Ni content measured at a depth of 10 μm The difference may be 2% by weight or less. In this way, by reducing the difference between the Co and Ni contents on the surface and the Co and Ni contents at a depth of 10㎛, wear resistance and life stability can be further improved.

In addition, in the cermet cutting tool, the sintered body includes a core structure in which the core part is made of a carbonitride phase containing Ti, and the rim part is made of a composite carbonitride containing tungsten (W), , a rich phase of tungsten (W) may be formed in the rim portion.

Ti carbonitride appears as a solid-solution (Ti,M1,M2)(C,N) between a core of Ti(C,N) and other carbides added to surround the core. ) A core-rim structure with a rim formed is created. In the sintered body according to the present invention, a significant amount of tungsten rich (W-rich) phase is formed on the rim, thereby improving the chipping resistance of the core. It can be reinforced.

In addition, in the cermet cutting tool, at least one surface of the sintered body is hard having a single-layer or two- or more-layer multilayer structure made of nitride, carbide, carbonitride, oxide, oxynitride, diamond, etc. formed by the PVD method and/or CVD method. A film may form.

<Example>

The cermet according to the embodiment of the present invention was manufactured through the following process.

First, 53% by weight of Ti(C,N), 8% by weight of bonded Co, 8% by weight of Ni, 18% by weight of WC, and other carbides were weighed and mixed to obtain 8% by weight of TaNbC and 5% by weight of Mo ₂ C and sintered. Raw material powder was made. At this time, fine particles of Ti(C,N) with an average particle size of 1.2㎛ or less were used.

As shown in Table 1 below, the Examples and Comparative Examples 2 to 3 of the present invention had the same contents of Ti(C,N), WC, TaNbC, Mo ₂ C, Co, and Ni, and had different carbon contents; For Example and Comparative Example 1, raw materials were prepared with the same carbon content.

division Composition (% by weight) Ti(C,N) WC TaNbC Mo ₂ C Co Ni carbon Comparative Example 1 53 18 8 5 8 8 2.0 Comparative Example 2 53 18 8 5 8 8 1.6 Comparative Example 3 53 18 8 5 8 8 0.8 Example 1 53 18 8 5 8 8 2.0

Carbide balls and an organic solvent were added to the raw material powder, mixed and pulverized for 10 hours, and then dried to obtain a mixed powder. The obtained mixed powder was pressed through a CNMG120408 shape mold at a pressure of 2 tons/cm2 to produce a molded body.

Next, the prepared molded body was sintered through the process conditions in Table 2 below to manufacture a cutting tool.

Degreasing temperature
(℃) Degreasing time
(hr) Sintering temperature
(℃) Sintering time
(hr) Cooling speed
(℃/min) Cooling method Comparative Example 1 600 One 1500 2 5 Low pressure Ar Comparative example 2 600 One 1500 2 5 Low pressure Ar Comparative example 3 600 One 1500 2 5 Low pressure Ar Example 600 One 1600 2 20 High pressure Ar

Surface and microstructure

1 is a schematic diagram of a cutting tool according to one embodiment of the present invention. As shown in FIG. 1, the sintered body manufactured according to an embodiment of the present invention has an upper surface 11, a side surface 12 that intersects the upper surface, and an intersection ridge portion of the upper surface 11 and the side surface 12. It is processed into the shape of the insert 10 including the cutting edge 13 to be formed. At this time, the top surface 11 and the side surfaces 12 are not ground, and the cutting edge 13 and its vicinity are ground to maintain the sintered surface texture.

Figure 2 shows microstructure photographs and measured sweating areas of the non-ground surfaces of cermet cutting tools according to Examples and Comparative Examples 1 to 3.

As can be seen in Figure 2, in the case of the example of the present invention, the sweating area on the non-grinding surface (top or side) is 2%, and there is virtually no sweating, whereas in the case of Comparative Example 1, the sweating area is 89%, In Comparative Example 2, sweating was formed over a very large area (76%), and in Comparative Example 3, sweating was formed over half of the area (54%).

Figure 3 is a photograph of the microstructure of a cermet cutting tool according to an example. In Figure 3, the phase that appears in dark gray is a core made of Ti(C,N), and the phase that appears in light gray around this core is the rim. ) The white part indicated by the arrow is the tungsten-rich (W-rich) phase. In this way, the tungsten rich phase formed on the rim can serve to reinforce the chipping resistance of the core. As shown in FIG. 3, the tungsten rich phase is formed on the rim of the sintered body according to an embodiment of the present invention. Many images have been formed.

Sintered body characteristics

Table 3 below shows the results of measuring the coercive force (Hc) and total carbon content (TC) of the sintered bodies manufactured according to Comparative Examples 1 to 3 and Examples.

division Comparative Example 1 Comparative Example 2 Comparative Example 3 Example sweating area
(%) 89 76 54 2 coercivity
(Hc, Oe) 120 93 30 108 Total carbon content
(weight%) 7.8 7.53 7.2 7.75

When the total carbon content (TC, Total Carbon) of cermet increases during the sintering process, high hardness non-magnetic precipitates appear, the coercive force (Hc) increases, and sweating increases due to the precipitates.

As confirmed in Table 3, in the case of Comparative Examples 1 to 3, Comparative Example 1, which had the largest sweating area, had the highest total carbon content and coercive force, and Comparative Example 3, which had the smallest sweating area, had a relatively low total carbon content. The content and coercivity were shown.

In contrast, in the case of the example of the present invention, the total carbon content and coercive force were 7.75% and 108 Oe, respectively, which were very high, about the same as Comparative Example 1, but the measured sweating area was 2%, meaning that sweating was not substantially possible. There is a difference in having no surface texture.

residual stress

Table 4 below shows the results of measuring the surface residual stress of the sintered bodies manufactured according to Comparative Examples 1 to 3 and Examples.

division Composition (% by weight) residual stress
(MPa) TiCN WC Ta
NbC Mo ₂ C Co Ni Comparative Example 1 53 17 8 5 9 8 -300 ~ -500 Comparative example 2 53 17 8 5 9 8 -300 ~ -500 Comparative example 3 53 17 8 5 9 8 -300 ~ -500 Example 53 17 8 5 9 8 -600 ~ -800

The surface residual stress in Table 4 is the residual stress in the area from the surface of the sintered body to a depth of 50 μm. As shown in Table 4, the sintered body according to the embodiment of the present invention shows a residual stress of -600 to -800 MPa, which is higher than the residual stress of -300 to -500 MPa in Comparative Example 1. The high residual stress on the surface serves to improve the wear resistance and chipping resistance of the sintered body of the present invention.

composition profile

Figure 4 is a composition profile analyzed from the surface of a cermet cutting tool according to Comparative Example 1 to a depth of 30㎛, and Figure 5 is a composition profile analyzed from the surface of a cermet cutting tool according to an example to a depth of 30㎛.

As can be seen in Figures 4 and 5, in the case of Comparative Example 1 in which sweating was strongly formed, the content of Co and Ni, which are bonding metals, appears high on the surface, and the content of Co and Ni decreases from the surface layer to 3 to 4㎛. It showed a composition profile that gradually increased toward the inside to a point of about 30㎛ and then became constant.

In contrast, in the case of the example, not only did the content of Co and Ni, which are bonding metals, appear on the surface to be very low, but the content of Co and Ni decreased within 0.5㎛ in the surface layer, then gradually increased toward the inside to a point of about 30㎛, and then decreased to a constant level. The composition profile is shown. That is, in the case of the embodiment of the present invention, the difference between the contents of Co and Ni, which are bonding metals on the surface, and the contents of Co and Ni within the interior is less than 2%, so there is almost no composition deviation.

Cutting performance evaluation

An insert was processed using the sintered body manufactured according to Examples and Comparative Examples 1 to 3 of the present invention, and then cut under the following cutting conditions. Cutting performance was evaluated for each of the three corners of the machined insert, and wear resistance and life stability were evaluated through average values and deviations.

- Work material: SCM440-4 groove (cross-section/outer diameter interrupted machining)

- Vc (cutting speed): 250mm/min

- fn (feed speed): 0.2mm/min

- ap (depth of cut): 1.5mm

- Dry/Wet: Wet

Figure 6 is a photograph taken at the beginning and end of the cutting performance evaluation of the cermet cutting tool according to Example and Comparative Examples 1 to 3.

As can be seen in Figure 6, in Comparative Examples 1 to 3, wear of the inserts was significantly advanced at the end of processing due to sweating existing on the surface. In contrast, in the case of Examples, the initial processing stage is similar to Comparative Examples 1 to 3, but the wear state at the end stage shows that almost no wear has progressed compared to Comparative Examples 1 to 3.

Figure 7 shows the cutting performance evaluation results of cermet cutting tools according to Examples and Comparative Examples 1 to 3.

As can be seen in Figure 7, in the case of Comparative Examples 1 to 3, the difference in processing life for each corner is very large, but in the Example of the present invention, the average of the three corners is 30.3, an improved result compared to Comparative Examples 1 to 3. and showed excellent processing life with little deviation. That is, the insert according to the embodiment of the present invention has improved life stability compared to Comparative Examples 1 to 3.

Claims (6)

Comprising a sintered body including an upper surface, a side surface intersecting the upper surface, and an edge formed at an intersection ridge portion of the upper surface and the side surface,
The sintered body includes carbonitride containing Ti, a hard phase containing carbide, carbonitride, or a mixture thereof of one or more metals selected from metals in groups 4, 5, and 6 of the periodic table, and Fe, Co, and Ni. Comprising a bonding phase consisting of one or more selected metals,
The total carbon content of the sintered body is 7.5% by weight or more,
A cermet cutting tool, characterized in that the sweating area of the non-ground surface of the sintered body is 5% or less. According to claim 1,
The sintered body,
40 to 80% by weight of carbonitride containing Ti,
15 to 40% by weight of carbide, carbonitride, or a mixture thereof of one or more metals selected from group 4, 5, and 6 metals of the periodic table,
A cermet cutting tool, characterized in that it contains 5 to 25% by weight of the bonding phase. The method of claim 1 or 2,
A cermet cutting tool, characterized in that a compressive residual stress of 600 MPa to 800 MPa is formed in an area from the surface of the sintered body to a depth of 50㎛. The method of claim 1 or 2,
The difference between the Co content measured on the surface of the sintered body and the Co content measured at a depth of 10 μm, or the difference between the Ni content measured on the surface of the sintered body and the Ni content measured at a depth of 10 μm is 2% by weight or less. Made with cermet cutting tools. The method of claim 1 or 2,
The sintered body is a cermet cutting tool, characterized in that the core part is made of a carbonitride phase containing Ti, and the rim part includes a core structure made of a composite carbonitride containing tungsten (W). The method of claim 1 or 2,
A cermet cutting tool, characterized in that one or two or more layers of hard coating are formed on at least one surface of the sintered body.

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