KR102663475B1 - Cutting tools with hard coating - Google Patents

Abstract

The present invention relates to a cutting tool in which a hard film is formed on a hard base material such as cemented carbide, cermet, or CBN.
The cutting tool according to the present invention includes a hard base material and a hard film formed on the hard base material, and the hard film includes a first film made of Ti _(1-x) Si _x N (x is the atomic ratio), , the point where the relief surface and the rake surface of the cutting tool meet is called the cutting edge R, and the Si atomic ratio of the first film within a range of 50㎛ from the cutting tool R in the direction of the rake surface and the relief surface is called R _x , _When 0 _{< R} Characterized by satisfaction.

Description

Cutting tools with hard coating {CUTTING TOOLS WITH HARD COATING}

The present invention relates to a cutting tool in which a hard film is formed on a hard base material such as cemented carbide, cermet, and CBN.

In order to improve the lifespan of cutting tools when machining workpieces with high hardness, such as high-hardness steel of HRC 50 or higher, technology is being adopted to form a hard film made of various ceramics on the surface of the cutting tool.

Among these hard films, the TiSiN film, which is a composite nitride of Ti and Si, has excellent wear resistance and heat resistance, and thus demonstrates excellent durability in cutting high-hardness steel, etc. However, the TiSiN film has excellent wear resistance when the Si content is high, but chipping resistance is reduced, and when the Si content is low, the wear resistance is reduced.

Hard coating required for each area of the cutting tool, for example, the cutting edge where constant impact is applied, and the rake face or flank face where friction with chips occurs continuously. The characteristics may vary.

In the following patent document, when the atomic-based Si content on the flank surface within 500㎛ from the cutting edge center is F _Si , and the atomic-based Si content on the rake surface within 500㎛ from the cutting edge center is R _Si , 0.5 A technology has been disclosed that improves the wear resistance of a cutting tool and improves the chipping resistance by differently adjusting the Si content of the rake surface and the relief surface with the cutting edge as the boundary so that < _FSi / ( _FSi + R _Si ) ≤ 0.6.

Korean Patent Publication No. 2023-0102643

The object of the present invention is to provide a hard coating for cutting tools with improved wear resistance while maintaining chipping resistance at a certain level or higher.

The present invention is a cutting tool comprising a hard base material and a hard film formed on the hard base material, wherein the hard film includes a first film made of Ti _(1-x) Si _x N (x is the atomic ratio), , the point where the relief surface and the rake surface of the cutting tool meet is called the cutting edge R, and the Si atomic ratio of the first film within a range of 50㎛ from the cutting tool R in the direction of the rake surface and the relief surface is called R _x , _When 0 _{< R} We provide cutting tools that satisfy your needs.

Additionally, in the first coating, R _x /C _x <0.67 can be satisfied.

Additionally, the thickness of the first film may be 0.1 to 3㎛, and the hardness of the first film may be 40 GPa or more.

In addition, the hard film further includes a second film formed on the lower part of the first film, and the second film is Al _(1-abc) Ti _a Cr _b Me _c N (Me is B, Si, Zr, V , Mn, Nb, Mo, Ta, W, 0≤a≤0.8, 0≤b≤0.5, 0≤c≤0.15, 0<a+b, a+b+c<1, a, b, c can be made up of atomic ratio).

Additionally, the thickness of the second film may be 0.1 to 10 μm.

The cutting tool according to the present invention maintains the chipping resistance of the cutting edge where continuous impact is applied, while improving the wear resistance of the flank surface where chips and friction continuously occur, thereby providing locally optimal cutting performance tailored to the location area of the hard film. By exerting this, the lifespan of the cutting tool can be extended when machining workpieces with high hardness such as high-hardness steel.

Figure 1 is a view showing the center of the cutting edge, rake surface, relief surface, and relief surface of a cutting tool.
Figure 2 is a diagram showing the cutting edge and center of a cutting tool in the shape of a drill or end mill.
Figure 3 is a diagram showing the area within 50㎛ from the center of the cutting tool edge.
Figure 4 is a diagram schematically showing the cross-sectional structure of a cutting tool according to an embodiment of the present invention.

Hereinafter, in describing the present invention, if a detailed description of a related known function or configuration is judged to unnecessarily obscure the gist of the present invention, the detailed description will be omitted. In addition, when a part is said to 'include' a certain component, this does not mean that other components are excluded, but that it can further include other components, unless specifically stated to the contrary.

The present invention is a cutting tool comprising a hard base material and a hard film formed on the hard base material.

[Hard base material]

The hard base material may be molded to the shape required for the cutting tool, for example, it may be molded into an insert shape, drill, or endmill shape.

As shown in FIG. 1, the cutting tool formed into an insert shape is formed in a substantially rectangular parallelepiped shape and has a fastening hole formed in the center. In the drawing, the upper surface forms a rake face, the side surface in the drawing forms a flank face, the boundary between the rake face and the flank face forms a cutting edge, and the four corners form a nose part. do.

In the case of an insert-shaped cutting tool, the "center part" of the relief surface refers to the point where the diagonals of the four corners constituting the relief surface intersect, as shown in FIG. 1.

As shown in Figure 2, the 'central part' of a cutting tool formed in the shape of a drill and an endmill is the cutting edge of the blade that is 2 mm or more away from the base edge and the next cutting edge that meets when drawn in the perpendicular direction. It refers to the central part of the street.

[Hard membrane]

A hard film is a film formed on the hard base material.

In one embodiment of the present invention, the hard film includes a first film made of Ti _{(1-x) Si} Let's _call it part R, and if the Si atomic ratio of the first film is _R When the central point is C and the Si atomic ratio of the first film within 50㎛ around C is C _x , it is characterized by satisfying 0.15≤C _x≤0.30 .

The first coating may preferably be located on the upper surface (outermost surface) of the hard coating. Additionally, the first coating may be composed of one layer or may be composed of a multi-layer structure in which two or more layers are stacked.

The present invention relates to the Ti _{(1-x) Si} The atomic ratio of Si included is relatively low _at 0<R

In addition, in the Ti _{(1-x ) Si} By increasing the wear resistance, it improves the wear resistance of the flank surface where chips and friction continuously occur.

In other words, by varying the atomic ratio of Si, which constitutes the first film, between the cutting edge and the relief surface, the life of the cutting tool is further extended, especially when machining workpieces with high hardness such as high hardness steel of HRC 50 or higher. You can achieve the desired effect.

Additionally, in the first coating, it is desirable to satisfy R _x /C _x <0.67. The difference between the Si atomic ratio of the cutting edge R and the Si atomic ratio of the flank center point C is at least greater than the above value range, which has the effect of improving the chipping resistance of the cutting edge and extending the overall cutting tool life by improving the wear resistance of the flanking surface. Because it is more desirable.

In addition, it is preferable that the thickness of the first coating is 0.1 to 3㎛. This means that if the thickness of the first coating is less than 0.1㎛, the wear resistance of the first coating cannot be sufficiently realized, and if the thickness is more than 3㎛, the internal stress increases, leading to chipping resistance. This is because performance can actually deteriorate. A more preferable thickness of the first coating is 0.2 to 1.5 μm.

Additionally, the hardness of the first film may preferably be 40 GPa or more.

In addition, as shown in FIG. 4, the hard film may further include a second film formed below the first film and having a multi-layer structure consisting of one layer or two or more layers.

The second film is Al _(1-abc) Ti _a Cr _b Me _c N (Me is a type selected from B, Si, Zr, V, Mn, Nb, Mo, Ta, W, 0≤a≤0.8, 0≤b≤0.5, 0≤c≤0.15, 0<a+b, a+b+c<1, a,b,c are atomic ratios).

The second film, which is a nitride thin film containing Al and Ti or Cr, is known to have excellent wear resistance as well as heat resistance and chipping resistance. By arranging the second film of this composition between the hard base material and the bottom of the first film, which has excellent wear resistance, it is possible to supplement the chipping resistance of the first film, which has excellent wear resistance but is relatively poor in chipping resistance.

The second film may have any one of the metal elements B, Si, Zr, V, Mn, Nb, Mo, Ta, and W in addition to Al, Ti, and Cr. By controlling these metal elements, the wear resistance, chipping resistance, heat resistance, etc. of the second film can be greatly improved.

In the second film, a, b, and c determine the composition ratio of the metal elements Al, Ti, Cr, and Me. If the Al composition is large, wear resistance, oxidation resistance, and lubricity are superior, but if the Al content is too high, chipping occurs. Since there is a problem of increased resistance, it is preferable that the contents of Ti and Cr are 0≤a≤0.8 and 0≤b≤0.5.

Other elements can improve the chipping resistance, heat resistance, and wear resistance of the second film by adding Zr, B, etc., but if the content is high, it can act as a cause of increased residual stress due to an increase in the amorphous phase, so the other elements, Me, are added. The content is preferably 0≤c≤0.15.

The thickness of the second film is preferably 0.1 to 10 ㎛, because if it is less than 1 ㎛, it is difficult to sufficiently compensate for wear resistance, and if it exceeds 10 ㎛, internal stress increases and chipping resistance may increase. A more preferable thickness is 1 ㎛. It is ~8㎛.

In addition, in the inclined surface area 200㎛ or more away from the cutting edge in the direction perpendicular to the cutting edge, the Si atomic ratio of the Ti _{(1-x) Si} You can.

<Example>

In an embodiment of the present invention, two types of surface treatments (ion bombardment) and an arc ion plating method (physical vapor deposition (PVD)) are used on the surface of the base material made of cemented carbide, Figure 4 As shown in , a hard film composed of the second film and the first film was formed.

Specifically, arc targets of TiAl, AlCr, and TiSi were used as targets for coating. After wet microblasting and washing with ultrapure water, the base material was dried and placed at a predetermined distance in the radial direction from the central axis on the rotary table in the coating furnace. It was installed along the circumference at a remote location, and the initial vacuum pressure in the coating furnace was reduced to below 8.5×10 ^-5 Torr.

After heating to a temperature of 400 to 600°C, a bias voltage of -400 to -200 V is applied to the rotating base material on the rotary table under an Ar gas atmosphere, and an Ar ion bombard is applied for 30 to 90 minutes. Ion bombardment was performed. The gas pressure for coating was maintained at 50 mTorr or less, preferably 40 mTorr or less, to form the second film as the lower layer and the first film as the upper layer.

The second film was formed using TiAl, AlCr, and TiSi targets at a bias voltage of -100 to -30V, an arc current of 100 to 150A, and N ₂ as a reaction gas injected at a pressure of 20 to 40 mtorr.

The first film was formed using a TiSi target by applying a bias voltage of -400 to -200V, using an arc current of 100 to 150A, and injecting N ₂ as a reaction gas at a pressure of 20 to 40 mtorr.

The examples and comparative examples of the present invention were manufactured under the above-described conditions, and basic information on the conditions and thickness of the corresponding hard film is shown in Table 1 below. Coating conditions may vary depending on equipment characteristics and conditions.

division second film first film target 1
(Composition fee) target 2
(Composition fee) thickness
(㎛) target
(Composition fee) bias voltage
(V) thickness
(㎛) Example 1 TiAl(50:50) - 2.2 TiSi (80:20) -300 1.0 Example 2 TiAl(50:50) - 2.5 TiSi (75:25) -300 1.2 Example 3 TiAl(50:50) AlCr(70:30) 2.5 TiSi (80:20) -250 0.8 Example 4 TiAl(50:50) AlCr(70:30) 2.6 TiSi (75:25) -400 1.3 Example 5 AlCr(70:30) - 2.8 TiSi (80:20) -200 1.5 Example 6 AlCr(70:30) - 2.0 TiSi(75:25) -200 1.3 Example 7 AlCr(70:30) TiSi (90:10) 1.9 TiSi (80:20) -300 1.2 Comparative Example 1 TiAl(50:50) - 2.3 TiSi (80:20) -30 1.2 Comparative Example 2 TiAl(50:50) - 2.6 TiSi (75:25) -70 1.0 Comparative Example 3 TiAl(50:50) AlCr(70:30) 2.5 TiSi (80:20) -70 1.0 Comparative Example 4 TiAl(50:50) AlCr(70:30) 2.8 TiSi (75:25) -50 1.5 Comparative Example 5 AlCr(70:30) - 2.6 TiSi (80:20) -40 1.6 Comparative Example 6 AlCr(70:30) - 2.0 TiSi(75:25) -40 1.2 Comparative Example 7 AlCr(70:30) TiSi (90:10) 2.0 TiSi (80:20) -50 1.3

The Si content of each part was measured for samples made according to the conditions in Table 1. The cross sections of the hard films of the examples and comparative examples according to Table 1 were analyzed at a magnification of 15,000 with a SEM (Scanning Electron Microscope) and the composition was analyzed with an EDS (Energy Dispersive Spectrometer), and the point where the relief surface of the cutting tool and the inclined surface meet as shown in Figure 1. is called the cutting edge R, and within a range of 50 ㎛ from the cutting edge R in the direction of the inclined surface and the relief surface, the Si atomic ratio of the first film _is R Table 2 shows the results when the Si atomic ratio of the first film within ㎛ _{is C} (Si content at this time excludes non-metals).

division R _x (at.%) W _x (at.%) C _x (at.%) Rx/Cx Example 1 7.2 14.8 19.2 0.38 Example 2 9.2 18.6 24.3 0.38 Example 3 8.5 15.7 19.7 0.43 Example 4 6.7 17.4 23.9 0.28 Example 5 9.8 14.6 19.5 0.50 Example 6 9.5 19.1 24.4 0.39 Example 7 7.6 14.5 19.6 0.39 Comparative Example 1 17.7 19.1 19.8 0.89 Comparative Example 2 20.1 23.9 24.7 0.81 Comparative Example 3 15.6 18.9 19.5 0.80 Comparative Example 4 21.9 24.3 24.7 0.89 Comparative Example 5 17.2 19.4 20.1 0.86 Comparative Example 6 22.3 24.0 24.7 0.90 Comparative Example 7 17.1 19.0 19.9 0.86

In the case of the example, as a result of EDS analysis, the Si content of the first film satisfies 0<R _x ≤0.10, and as the distance from the cutting edge increases from W _x to C _x , the Si content of the first film gradually decreases to 0.15. It can be confirmed that the range of ≤C _x ≤0.30 is satisfied. In addition, it can be confirmed that R _x /C _x <0.67 is satisfied, and the wear resistance and chipping resistance of the hard film formed in this way were evaluated under the following conditions.

(1) Wear resistance evaluation

Work material: heat treated SKD61 (diameter: 100mm)

Sample model number: CNNMG120408-VP3

Cutting speed: 80 m/min

Cutting feed: 0.15 mm/rev

Cutting depth: 1.5mm

Coolant: Used

(2) Chipping resistance evaluation

Work material: Mold steel NAK80 (300mm×200mm×100mm)

Sample model number: ADKT170608PESR-MM

Cutting speed: 100 m/min

Cutting feed: 0.15 mm/tooth

Cutting depth: 5mm

Coolant: Not used

The processing results evaluated under the two conditions as described above are shown in Table 3 below.

division Heat treatment SKD61 processing results NAK80 machining results Chip removal amount
(cm3) Wear type Processing length
(mm) Wear type Example 1 250 normal wear 2600 Wear/chipping Example 2 258 normal wear 2000 Wear/chipping Example 3 238 normal wear 1800 Wear/chipping Example 4 250 normal wear 1400 Boundary chipping Example 5 238 normal wear 1200 Part R damaged Example 6 229 normal wear 1000 Boundary chipping Example 7 267 normal wear 1800 Wear/chipping Comparative Example 1 188 Excessive wear 2200 Wear/chipping Comparative Example 2 217 normal wear 1500 Wear/chipping Comparative Example 3 208 normal wear 1000 Boundary chipping Comparative Example 4 204 Excessive wear 1100 Boundary chipping Comparative Example 5 188 Excessive wear 900 Part R damaged Comparative Example 6 196 Excessive wear 800 Part R damaged Comparative Example 7 213 normal wear 1500 Boundary chipping

As shown in the cutting performance evaluation results, Examples 1 to 7 showed superior tool life than Comparative Examples 1 to 7. In particular, as the chip removal amount of heat-treated SKD61 workpiece machining increased significantly, the machining length of NAK80 workpiece also showed improved results. Through this, it was confirmed that the lifespan of the tool was improved by supplementing wear resistance and chipping resistance through the difference in Si content between the cutting edge and the relief surface.

Claims (5)

Hard base material,
A cutting tool comprising a hard film formed on the hard base material,
The hard film includes a first film made of Ti _(1-x) Si _x N (x is the atomic ratio),
The point where the relief surface and the rake surface of the cutting tool meet is called the cutting edge R, and when the Si atomic ratio of the first film _is R Satisfies <R _x ≤0.10,
When the central point of the relief surface is C, and the Si atomic ratio of the first film within 50㎛ around C is C _x , 0.15≤C _x ≤0.30 is satisfied,
A cutting tool that satisfies R _x /C _x ≤0.5.
delete According to claim 1,
The thickness of the first film is 0.1 to 3㎛,
A cutting tool wherein the first film has a hardness of 40 GPa or more.
According to claim 1,
The hard film further includes a second film formed below the first film,
The second coating is Al _(1-abc) Ti _a Cr _b Me _c N (Me is a type selected from B, Si, Zr, V, Mn, Nb, Mo, Ta, W, 0≤a≤0.8, A cutting tool consisting of 0≤b≤0.5, 0≤c≤0.15, 0<a+b, a+b+c<1, and a, b, and c are atomic ratios).
According to claim 4,
A cutting tool wherein the second film has a thickness of 0.1 to 10 μm.

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