KR102009687B1 - Cutting tools coated with hard film - Google Patents

Abstract

The present invention relates to a cutting tool having an improved service life, having high temperature oxidation resistance and resistance to thermal cracks, through controlling the composition and microstructure of the cemented carbide and controlling the microstructure of the hard coating.
The cutting tool according to the present invention includes a base material made of cemented carbide and a hard coating formed on at least a portion of the base material, wherein the base material is 5.5 to 10 wt% of Co and 4 to 15 wt% of carbide except WC. And, including the remaining WC and unavoidable impurities, the average particle size of the WC is 0.8 ~ 3㎛, the CFL (Cubic phase Free Layer) layer is formed on the surface of the base material to a thickness of less than 5㎛, the hard film Is composed of a single layer or a multilayer structure of two or more layers, and formed by PVD method, Ti _a Al _b Me _c C _1-x N _x O _y (0.3 ≦ a ≦ 0.6, 0.4 ≦ _b ≦ 0.7, 0 ≦ _c ≦ 0.1, 0.5≤x≤1, 0≤y≤0.5, Me includes at least one selected from 4a, 5a, 6a, Si, B, S), and 5 from the edge of the inclined surface of the cutting tool. It is characterized in that the proportion of particles having an aspect ratio of 1.5 or less is 50% or more among droplets having a particle size of 1 μm or more on the surface of the film located in the range of ˜50 μm. The.

Description

Hard Film Cutting Tools {CUTTING TOOLS COATED WITH HARD FILM}

The present invention relates to a cutting tool in which a hard film is formed on a base material made of cemented carbide, specifically, the composition and the microstructure of the cemented carbide and the control of the microstructure of the hard film, having high temperature oxidation resistance and resistance to heat cracking, A cutting tool having an improved lifespan.

Cemented carbide used in cutting tools is a composite material that combines a hard phase containing WC with a binder of a metal represented by Co, and is a representative dispersed alloy, and its mechanical properties are basically based on the particle size of the WC hard phase and the amount of Co-bonded metal phase. In particular, hardness and toughness are inversely related to each other. On the other hand, depending on the cutting method and the workpiece, the characteristics required for the cemented carbide for cutting tools also vary, and various attempts have been made to control the mechanical properties of cemented carbide.

In addition, a hard film is formed on the surface of the cemented carbide in order to prolong the life of the cutting tool in response to the above-described high temperature oxidation, thermal shock, abrasion, and the like.

Steel exhibits relatively good machinability compared to stainless steel or cast iron. However, since high-speed cutting is generally performed to improve productivity, the surface of the cutting tool is exposed to high heat, ending its life through chemical wear patterns caused by oxidation.

In addition, in the case of workpieces with severe interruptions, such as mechanical parts, since repeated thermal shock is applied to the cutting tool, the life of the cutting tool is mainly ended due to breakage due to thermal cracking.

In the patent literature, in order to improve the cutting performance of the Ti _a Al _b Nb _d Me (C _1-x N _x ) film, a fine droplet having a particle diameter of 300 nm or less is present on the clearance surface than the cutting surface, and the clearance surface The technique of improving the cutting life is disclosed by the fact that the average composition of the coarse droplets having a particle size of 1000 nm or more is higher than the average composition of the coarse droplets present on the cutting surface.

Republic of Korea Patent Publication No. 10-2013-0098861

An object of the present invention is to solve the problem of suppressing oxidation due to a high temperature oxidation environment, suppressing thermal cracking due to thermal shock generated during processing of a severely interrupted workpiece, and improving the life of a cutting tool.

In order to solve the above problems, the present invention is a cutting tool including a base material made of cemented carbide and a hard film formed on at least a portion of the base material, wherein the base material is 5.5 to 10% by weight of Co and 4 to excluding WC. 15 wt% of carbide, the remaining WC and inevitable impurities, the average particle size of the WC is 0.8 ~ 3㎛, CFL (Cubic phase Free Layer) layer is formed on the surface of the base material less than 5㎛ thickness The hard coating is formed of a single layer or a multilayer structure of two or more layers, and formed by PVD method, Ti _a Al _b Me _c C _1-x N _x O _y (0.3 ≦ a ≦ 0.6, 0.4 ≦ _b ≦ 0.7, 0 ≤ c ≤ 0.1, 0.5 ≤ x ≤ 1, 0 ≤ y ≤ 0.5, Me comprises at least one layer selected from 4a, 5a, 6a group, Si, B, S), the inclined surface of the cutting tool The proportion of particles having an aspect ratio of 1.5 or less in droplets having a particle size of 1 μm or more on the surface of the film located in the range of 5 to 50 μm from the edge of Provide cutting tools greater than 0%.

The tool according to the present invention can prolong the life of the cutting tool by suppressing oxidation resistance and heat cracking.

1 is for explaining the aspect ratio of the droplets formed around the edge portion.
Figure 2 shows a method of measuring the thickness of the CFL of the cutting tool according to an embodiment of the present invention.
3 is a scanning electron microscope image of the hard film formed according to the Examples and Comparative Examples of the present invention.
Figure 4 shows the process of measuring the particle size and long-term ratio of the droplet using an image analyzer.
Figure 5 shows the results of measuring the reaction pressure and the particle size, hardness, and coating thickness (top / side) of the film.
6 and 7 show the results of XRD analysis of the hard coating according to the comparative example.
8 and 9 show the results of XRD analysis of the hard coating according to the embodiment.

Hereinafter, the configuration and operation of the present invention will be described with reference to the accompanying drawings. In the following description of the present invention, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted. In addition, when a part is said to "include" a certain component, this means that it may further include other components, except to exclude other components unless otherwise stated.

The cutting tool according to the present invention is a cutting tool including a base material made of cemented carbide and a hard coating formed on at least a portion of the base material, wherein the base material is 5.5 to 10% by weight of Co and 4 to 15 weight except WC. It contains% carbide, the remaining WC and unavoidable impurities, the average particle size of the WC is 0.8 ~ 3㎛, the CFL (Cubic phase Free Layer) layer is formed on the surface of the base material to a thickness of less than 5㎛, The hard coating is composed of a single layer or a multilayer structure of two or more layers, and formed by PVD method, Ti _a Al _b Me _c C _1-x N _x O _y (0.3 ≦ a ≦ 0.6, 0.4 ≦ _b ≦ 0.7, 0 ≦ c ≤ 0.1, 0.5 ≤ x ≤ 1, 0 ≤ y ≤ 0.5, Me includes at least one selected from 4a, 5a, 6a group, Si, B, S) edges of the inclined surface of the cutting tool The proportion of particles having an aspect ratio of 1.5 or less is 50% or more among droplets having a particle size of 1 μm or more on the surface of the film located in the range of 5 to 50 μm from the portion. The features.

Cemented carbide substrate

The base material constituting the cemented carbide cutting tool according to the present invention is made of cemented carbide sintered body, including Co 5.5 ~ 10% by weight, carbide 4 ~ 15% by weight except WC, and may contain the remaining WC and unavoidable impurities.

The Co serves as a binder to hold the hard phase WC, and the toughness increases as the Co content increases and the toughness decreases as the content decreases. If the Co content is less than 5.5% by weight, it is not preferable because the toughness is insufficient and the breakage frequency increases during intermittent processing, and if it exceeds 10% by weight, plastic deformation may be caused during high feed processing, which is not preferable.

The carbide contains a metal carbide, such as Cr ₃ C _2, and serves to inhibit the growth of WC particles during the sintering process, if the content is less than 4% by weight, it causes rapid wear of the cutting tool slope, 15% by weight If it exceeds the heat crack formation frequency is high, it is preferably included in 4 to 15% by weight.

The unavoidable impurities are raw materials for producing cemented carbide or impurities inevitably incorporated in the manufacturing process, and should be maintained at 1 wt% or less, preferably 0.1 wt% or less, and more preferably 0.01 wt% or less.

When the average particle size of the WC is less than 0.8㎛, it causes a fast wear of the surface during the cutting process (Crater wear), if it exceeds 3㎛ the base material hardness is lowered, so that the flank wear (Flank wear) is faster, 0.8 ~ 3㎛ range Is preferred.

When the Cubic phase free layer (CFL) layer having no cubic carbide and carbonitride layer is formed on the surface of the base material with a thickness of 5 μm or more, the wear surface of the cutting tool may be rapidly worn, and therefore, less than 5 μm. It is preferable that the CFL layer is not formed.

Hard coating

The hard coating may be formed of a single layer or a multilayer structure of two or more layers, and Ti _a Al _b Me _c C _1-x N _x O _y (0.3 ≦ a ≦ 0.6, 0.4 formed by PVD method (physical vapor deposition)). ≤ b ≤ 0.7, 0 ≤ c ≤ 0.1, 0.5 ≤ x ≤ 1, 0 ≤ y ≤ 0.5, Me is a layer consisting of at least one selected from group 4a, 5a, 6a, Si, B, S) Hard film properties). In this case, other layers other than the main layer may be formed as necessary.

When forming the Ti _a Al _b Me _c C _1-x N _x O _y layer, a droplet is generated, as shown in Figure 1, 5 ~ 50㎛ from the edge of the inclined surface of the cutting tool If the aspect ratio (long-term ratio) of 50% or more of the droplet particles having a particle size of 1 μm or more in the range is more than 1.5, the frequency of chipping and peeling of the edge of the film becomes high, which may cause a rapid end of life during interrupted processing. Therefore, it is preferable that an aspect ratio (long ratio) of 50% or more of the droplet particles having a particle size of 1 µm or more is maintained at 1.5 or less.

In addition, when the total thickness of the hard film is less than 5㎛ is caused by the inclined surface wear is not suitable as a tool for steel (steel), if it is more than 20㎛ is preferably 5 ~ 20㎛ because peeling and chipping is likely to occur. .

In addition, the cutting tool may include an insert, and the Ti _a Al _b Me _c C _1-x N _x O _y layer formed by the PVD method has a (200) plane of 30 in the normal direction of the insert surface during XRD analysis. It is preferable to first grow in the direction of ° ~ 60 °. At this time, the angle means the internal angle formed by the (200) plane direction with the normal of the base material surface.

The Ti _a Al _b Me _c C _1-x N _x O _y layer formed by the PVD method is formed at _a reaction pressure of 2 to 5 Pa or less, and it is easy to implement a microstructure according to the present invention. As shown, the thin film thickness ratio of the top surface to the side of the insert is thinned to less than about 70%, causing rapid top surface wear during cutting and causing stress unevenness of the side and top surface, which may cause peeling at a thickness of less than 20 μm. When the reaction pressure exceeds 5Pa, the compressive stress on the surface of the thin film is lowered and the hardness and plastic deformation resistance (H ³ / E ² ) of the insert are lowered.

[Carbide alloy]

Starting materials prepared as shown in Table 1 below were blended for 8 hours using an attrition mill having a forced grinding effect because the compound cantilever is in a jar.

When mixing, 30 vol% of the total diameter ball of the starting material and the total volume of the vessel was used as a mixing / grinding medium, and 30 vol% of the ethanol was applied as a solvent to assist the ethanol. The blended slurry was granulated through a spray dryer, pressed into a CNMG120408-HM form (lozenge shape) to form a compact, and then sintered in a vacuum sintering furnace for 60 to 120 minutes at a temperature of 1350 to 1450 ° C.

After grinding the upper and lower surfaces of the sintered body manufactured through this process and honing, TiAlN (Al: Ti = 5: 5) having a thickness of about 4 μm as the first layer and AlTiN having a thickness of about 4 μm as the first layer were obtained by PVD. (Al: Ti = 67: 33) was coated and the coating was carried out under the conditions of the arc current plating method using a cathode current of 120A, Pulsed Bias -40V, duty cycle 70%, frequency 40kHz. .

In the analysis of the CFL layer, as shown in FIG. 2, the surface of the sintered body was mirror-polished (polished), and the thickness of the CFL layer was analyzed by an optical microscope, and the results are shown in Table 1 below.

The cutting test of the cutting tool finally made in this way uses a square shaped workpiece made of SM45 material, cutting speed 300m / min, 200m / min, feed rate 0.25mm / rev and cutting depth 1.5mm. Section processing was carried out, and the evaluation was made by comparing the number of times until excessive wear and damage occurred.

division Starting material CFL
(Μm) Cutting frequency WC Carbon Nitride (wt%) Co
(wt%) Vc =
150 Vc =
250 wt% Granularity
(Μm) TaC TaNbC Cr ₃ C ₂ WTiC WTiCN Comparative Example 1 94 0.8 0 0 1.0 0 0 5.0 Less than 1 40 40 Comparative Example 2 93 0.8 1.5 0 0 0 0 5.5 Less than 1 110 55 Example 1 90.5 0.8 4.0 0 0 0 0 5.5 Less than 1 140 65 Example 2 86.5 0.8 8.0 0 0 0 0 5.5 Less than 1 140 65 Comparative Example 3 92.5 1.3 0 1.5 0 0 0 6.0 Less than 1 110 65 Comparative Example 4 89 0.8 0 0 1.0 0 0 10.0 Less than 1 70 70 Example 3 90 2.0 0 4.0 0 0 0 6.0 Less than 1 140 70 Example 4 84 2.0 0 5.0 0 5.0 0 6.0 Less than 1 140 65 Example 5 80 2.0 0 7.0 0 7.0 0 6.0 Less than 1 125 65 Comparative Example 5 74 2.0 0 10.0 0 10.0 0 6.0 Less than 1 100 65 Example 6 83 2.0 0 5.0 0 5.0 0 7.0 Less than 1 140 70 Example 7 82 2.0 0 5.0 0 5.0 0 8.0 Less than 1 140 70 Comparative Example 6 72 2.0 0 10.0 0 10.0 0 8.0 Less than 1 70 65 Example 8 77 2.0 0 7.0 0 7.0 0 9.0 Less than 1 140 80 Comparative Example 7 89 2.0 0 0 1.0 0 0 10.0 Less than 1 85 80 Example 9 76 2.0 0 7.0 0 7.0 0 10.0 Less than 1 125 80 Comparative Example 8 69 2.0 0 10.0 1.0 10.0 0 10.0 Less than 1 85 70 Comparative Example 9 71 2.0 5.0 12.0 0 0 0 12.0 Less than 1 55 65 Comparative Example 10 71 3.6 5.0 7.0 0 7.0 0 10.0 2 100 80 Example 10 89 2.0 0 4.0 0 0 1.0 6.0 4 125 70 Comparative Example 11 86 2.0 0 4.0 0 0 3.0 7.0 15 105 65 Comparative Example 12 84 2.0 0 4.0 0 0 4.0 8.0 24 75 70

As confirmed in Table 1, 5.5 to 10% by weight of Co and 4 to 15% by weight of carbides excluding WC, the average particle size of WC is 0.8 to 3㎛, CFL layer is less than 5㎛ thickness When the physical properties of the cutting tool (Examples 1 to 10) made of a cemented carbide having a TiAlN-based or AlTiN-based hard film were formed, they were superior to those of the cutting tools (Comparative Examples 1 to 12) not belonging to the embodiment range of the present invention. It can be seen that the cutting performance.

[Hard film]

Based on the results of Table 1 above, a film forming test for each thin film condition was performed using a cemented carbide material of CNMG120408-HM type (lozenge shape) manufactured from a raw material having a blending ratio of Example 8.

The main layer was produced by alternately laminating thin layer A, single layer, or thin layer A and thin layer B. Thin layer A was fabricated by arc ion plating, and thin layer B was produced by sputtering.

Each deposition condition is shown in Table 2 below. The analysis results and cutting performance evaluation results of the thin films manufactured under the conditions of Table 2 are shown in Table 3 below.

At this time, the thickness of the thin film was measured by analyzing the fracture surface through SEM, and the short and short ratios of the droplets were determined by filtering the droplets of 1 μm or more using image analysis software as shown in FIG. 4. Danbi was measured by analyzing.

In addition, through the XRD analysis, the change in the orientation according to the change in the reaction pressure (0.5Pa ~ 5Pa) of the thin film was measured, the results are shown in Figures 6 to 9.

The cutting test of the cutting tool formed with the main layer was made using SCM45 square shaped workpiece, cutting speed 200m / min, 300m / min, feed speed 0.25mm / rev, cutting depth 1.5mm. Section processing was carried out and evaluated by comparing the number of processing until excessive wear and damage occurred.

division Main floor Thin layer A Thin Floor B rescue reaction
pressure
(Pa) Puls bias target CH ₄ : N A (I) target N: O kW V Duty kHz Comparative Example 2-1 Ti 2: 1 120 - - - Monolayer 0.5 40 One 40 Example 2-1 Ti 2: 1 120 - - - Monolayer 2.5 30 0.7 40 Example 2-2 Ti 2: 1 120 - - - Monolayer 5 30 0.7 40 Comparative Example 2-2 Ti 2: 1 120 - - - Monolayer 8 30 0.7 40 Comparative Example 2-3 Ti: Al = 5: 5 0: 1 120 - - - Monolayer 2 50 One 20 Comparative Example 2-4 Ti: Al = 5: 5 0: 1 120 - - - Monolayer 3 50 One 20 Comparative Example 2-5 Ti: Al = 5: 5 0: 1 120 - - - Monolayer 4 50 One 20 Example 2-3 Ti: Al = 5: 5 0: 1 120 - - - Monolayer 4 50 0.7 40 Comparative Example 2-6 Ti: Al = 6.7: 3.3 0: 1 120 - - - Monolayer 0.5 40 One 40 Comparative Example 2-7 Ti: Al = 6.7: 3.3 0: 1 120 - - - Monolayer 1.5 40 One 40 Example 2-4 Ti: Al = 6.7: 3.3 0: 1 120 - - - Monolayer 2.5 30 One 40 Example 2-5 Ti: Al = 6.7: 3.3 0: 1 120 - - - Monolayer 5 30 One 40 Comparative Example 2-8 Ti: Al = 6.7: 3.3 0: 1 120 - - - Monolayer 8 30 One 40 Example 2-6 Ti: Al: Cr = 4: 5: 1 0: 1 120 - - - Monolayer 5 40 0.7 40 Example 2-7 Ti: Al: Nb = 4: 5: 1 0: 1 120 - - - Monolayer 5 40 0.7 40 Example 2-7 Ti: Al: Ta = 4: 5: 1 0: 1 120 - - - Monolayer 5 40 0.7 40 Example 2-9 Ti: Al: Y = 4: 5.5: 5 0: 1 120 - - - Monolayer 5 40 0.7 40 Example 2-10 Ti: Al: Si = 4: 5.5: 0.5 0: 1 120 - - - Monolayer 5 30 0.7 40 Example 2-11 Ti: Al = 5: 5 0: 1 120 Al 0: 1 10 Shift stack 5 40 0.7 40 Example 2-12 Ti: Al = 6.7: 3.3 0: 1 120 Al 0: 1 10 Shift stack 5 40 0.7 40 Example 2-13 Ti: Al: Cr = 4: 5: 1 0: 1 120 Al 0: 1 10 Shift stack 5 40 0.7 40 Example 2-14 Ti: Al: Nb = 4: 5: 1 0: 1 120 Al 0: 1 10 Shift stack 5 40 0.7 40 Example 2-15 Ti: Al: Ta = 4: 5: 1 0: 1 120 Al 0: 1 10 Shift stack 5 40 0.7 40 Example 2-16 Ti: Al: Y = 4: 5.5: 5 0: 1 120 Al 0: 1 10 Shift stack 5 40 0.7 40 Example 2-17 Ti: Al: Si = 4: 5.5: 0.5 0: 1 120 Al 0: 1 10 Shift stack 5 30 0.7 40

Figure 5 shows the results of measuring the reaction pressure and the particle size, hardness, coating thickness (top / side) of the film. As shown in FIG. 5, when the process pressure is less than 2 Pa, the ratio of the thickness of the upper surface to the side of the insert is thinned to less than about 70%, causing rapid wear of the upper surface during cutting and causing stress unevenness on the side and the upper surface of 20 μm When the reaction pressure exceeds 5 Pa, the compressive stress on the surface of the thin film is lowered, and the hardness and plastic deformation resistance (H ³ / E ² ) of the insert are lowered. It can be seen that it is preferable.

In addition, as confirmed in FIGS. 8 and 9, as a result of XRD analysis, unlike the comparative example (see FIGS. 6 and 7), in the case of the hard coating of Table 2 formed according to the embodiment of the present invention, the (200) plane The state of growth in the direction of 30 ° to 60 ° from the normal direction of the insert surface is shown.

division Droplet
Aspect ratio 1.5
Fraction below Thin film thickness
(Μm) Cutting frequency vc: 200 vc: 300 Comparative Example 2-1 0 9.4 145 55 Example 2-1 62 8.7 130 60 Example 2-2 90 7.6 125 60 Comparative Example 2-2 100 6.9 65 50 Comparative Example 2-3 13 6.3 105 70 Comparative Example 2-4 45 6.6 115 60 Comparative Example 2-5 37 7.8 50 55 Example 2-3 100 9.2 115 105 Comparative Example 2-6 43 11.7 100 95 Comparative Example 2-7 57 10.4 90 90 Example 2-4 85 8.9 130 110 Example 2-5 90 8.7 130 110 Comparative Example 2-8 90 7.4 90 75 Example 2-6 100 15.6 155 145 Example 2-7 100 12.3 150 130 Example 2-7 100 12.6 145 120 Example 2-9 100 9.1 130 100 Example 2-10 100 8.4 115 105 Example 2-11 100 9.3 165 110 Example 2-12 100 10.2 115 110 Example 2-13 100 8.2 155 115 Example 2-14 100 7.3 155 100 Example 2-15 100 7.7 145 120 Example 2-16 100 8.2 115 100 Example 2-17 100 9.3 145 145

As confirmed in Table 3 above, the aspect ratio of the droplets of 1 μm or more in particle size of 1.5 μm or more, such as the hard coating according to Examples 2-1 to 2-17, is 50% or more (that is, the aspect ratio of large droplets of 1.5 is 1.5). Maximizing the fraction to be kept below) showed improved cutting performance compared to the other (Comparative Examples 2-1 to 2-8).

That is, the ratio of particles having an aspect ratio of 1.5 or less among droplets having a particle size of 1 μm or more on the surface of the coating film positioned in the range of 5 to 50 μm from the edge of the inclined surface of the cutting tool to the cemented carbide base material according to the embodiment of the present invention. When the hard film formed with this 50% or more is formed, it is possible to implement improved cutting performance compared to the other.

Claims (4)

Cutting tool comprising a base material made of cemented carbide and a hard film formed on at least a portion of the base material,
The base material contains 5.5 to 10% by weight of Co, 4 to 15% by weight of carbides, excluding WC, and the remaining WC and unavoidable impurities,
The average particle size of the WC is 0.8 ~ 3㎛,
The CFL (Cubic phase Free Layer) layer is formed on the surface of the base material to a thickness of less than 5㎛,
The hard coating is made of a single layer or a multilayer structure of two or more layers,
Ti _a Al _b Me _c C _1-x N _x O _y formed by PVD (0.3≤a≤0.6, 0.4≤b≤0.7, 0≤c≤0.1, 0.5≤x≤1, 0≤y≤0.5, Me Comprises a layer consisting of at least one selected from Groups 4a, 5a, 6a, Si, B, and S),
And a hard film having a hard film having a proportion of 1.5 or less of an aspect ratio of 1.5 or less among droplets having a particle size of 1 μm or more on the surface of the film positioned in the range of 5 to 50 μm from the edge of the inclined surface of the cutting tool. The method of claim 1,
The total thickness of the hard film is 5 ~ 20㎛, cutting tool formed hard film. The method of claim 2,
The cutting tool comprises an insert,
The Ti _a Al _b Me _c C _1-x N _x O _y layer formed by the PVD method has a hard film-cutting in which (200) planes are preferentially grown in the direction of 30 ° to 60 ° from the normal direction of the insert surface during XRD analysis. tool. The method of claim 3,
The Ti _a Al _b Me _c C _1-x N _x O _y layer formed by the PVD method is formed at a reaction pressure of 2Pa or more and 5Pa or less.

Images