KR102663476B1 - 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, and 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 is Al _a Cr _b Me _(1-ab) N _x O _y (a, b, x, y is the atomic ratio, a+b≤1, 0.5≤x≤1, 0≤y≤0.5, x+y=1, Me is selected from group 4 elements, group 5 elements, group 6 elements, Si, B and S. At least one type), the point where the relief surface and the rake surface of the cutting tool meet is called the cutting edge R, and the first film is within a range of 50㎛ from the cutting tool R in the direction of the rake surface and the relief surface. When the Al atomic ratio of the film is R _a , 0.7<R _a ≤0.85 is satisfied, the central point of the relief surface is C, and the Al atomic ratio of the first film within 100㎛ around C is C. When _a , it is characterized by satisfying 0.55≤C _a≤0.7 .

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 the case of steel, it is a material that can realize various physical properties depending on the carbon content, heat treatment, etc., and the importance of lubrication and oxidation resistance as well as wear resistance is high for cutting tools used to process such steel. To this end, a technology for forming a hard film made of various ceramics on a cutting tool is being adopted to improve the lifespan of the cutting tool.

Among hard films for cutting tools, the composite nitride film of Al and Cr has excellent lubricity and heat resistance as well as excellent wear resistance, demonstrating excellent durability in cutting various types of steel. However, in the case of Al and Cr composite nitride, there is a problem that when the Al content increases, toughness improves but wear resistance rapidly decreases.

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.

Korean Patent Publication No. 20203-0102643

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 is Al _a Cr _b Me _(1-ab) N _x O _y (a, b, x, y are Atomic ratio, a+b≤1, 0.5≤x≤1, 0≤y≤0.5, x+y=1, Me is 1 selected from Group 4 elements, Group 5 elements, Group 6 elements, Si, B and S. The point where the relief surface and the rake surface of the cutting tool meet is called the cutting edge R, and the first film is formed within a range of 50㎛ from the cutting edge R in the direction of the rake surface and the relief surface. When the Al atomic ratio of R _a satisfies 0.7<R _a ≤0.85, the central point of the relief surface is C, and the Al atomic ratio of the first film within 50㎛ around C is C _a , a cutting tool that satisfies 0.55≤C _a≤0.7 is provided.

Additionally, in the first coating, R _a /C _a ≥1.03 can be satisfied.

Additionally, the hard film may have a thickness of 0.5 to 10㎛, and the first film may have a thickness of 0.1㎛ or more.

In addition, the hard film further includes a second film formed below the first film, and the second film is Al _(1-cde) Ti _c Cr _d Me _e N (c, d, e are atomic ratios, 0≤c≤0.8, 0≤d≤0.5, 0≤e≤0.15, c+d>0, c+d+e<1, Me is B, Si, Zr, V, Mn, Nb, Mo, Ta and It may consist of one or more types selected from W).

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 it is determined that a detailed description of a related known function or configuration may 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 excluding other components, but may 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” 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, a cutting tool includes a hard base material and a hard film formed on the hard base material, wherein the hard film is Al _a Cr _b Me _(1-ab) N _x O _y (a, b , x, y are atomic ratios, a+b≤1, 0.5≤x≤1, 0≤y≤0.5, x+y=1, Me is group 4 element, group 5 element, group 6 element, Si, B and It includes a first film made of (one or more types selected from S), and the point where the relief surface and the rake surface of the cutting tool meet is called the cutting edge R, and the cutting edge is within a range of 50㎛ from the cutting tool R in the direction of the rake surface and the relief surface. When the Al atomic ratio of the first film is R _a , 0.7<R _a ≤0.85 is satisfied, the central point of the relief surface is C, and the Al of the first film within 50㎛ around C is When the atomic ratio is C _a , it is characterized by satisfying 0.55≤C _a≤0.7 .

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 Al _a Cr _b Me _{(1-ab) N} The atomic ratio of Al contained in the film formed is relatively high at 0.7<R _a ≤0.85, thereby providing toughness that can cope with impacts continuously applied to the cutting edge, thereby improving the chipping resistance of the cutting edge.

In addition, in the Al _a Cr _b Me _{(1-ab ) N} By improving wear resistance by making a relatively low at _≤0.7 , the wear resistance of the flank surface where chips and friction continuously occur is improved.

In other words, by forming the edge and flank surfaces with different atomic ratios of Al, which constitutes the first film, the durability of the cutting tool is improved even when used for cutting various types of steel, resulting in the effect of further extending the lifespan. You can get it.

Additionally, in the first coating, it is desirable to satisfy R _a /C _a ≥1.03. The difference between the Al atomic ratio of the cutting edge R and the Al atomic ratio of the flank center point C is at least greater than the above value range, which means that the overall cutting effect is achieved through the local optimization effect of improving the chipping resistance of the cutting edge and improving the wear resistance of the flank surface. This is because it is more desirable for extending tool life.

In addition, the thickness of the hard film is preferably 0.5 to 10㎛. If the thickness of the hard film is less than 0.5㎛, the effect of the hard film is not sufficient, and if it is more than 10㎛, the internal stress increases and the chipping resistance is rather poor. This is because it can deteriorate.

In addition, the thickness of the first coating is preferably 0.1㎛ or more, because if the thickness of the first coating is less than 0.1㎛, the effect of the first coating is not sufficient.

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-cde) Ti _c Cr _d Me _e N (c, d, e are atomic ratios, 0≤c≤0.8, 0≤d≤0.5, 0≤e≤0.15, c+d> 0, c+d+e<1, Me may be composed of one or more selected from B, Si, Zr, V, Mn, Nb, Mo, Ta and W).

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≤c≤0.8 and 0≤d≤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≤e≤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 more than 200㎛ away from the cutting edge in the direction perpendicular to the cutting edge, the atomic ratio of Al of the Al _a Cr _b Me _(1-ab) N _x O _y film constituting the first film is also 0.55 ~ It can be formed to be 0.7.

<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 AlCrSi 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 AlCrSi 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 AlCr and AlCrSi targets by applying a bias voltage of -400 to -200 V, arc current of 100 to 150 A, and N ₂ as a reaction gas injected at a pressure of 20 to 40 mtorr.

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) - 2.5 AlCr(70:30) -300 1.2 Example 2 TiAl(50:50) - 3.1 AlCrSi(70:20:10) -400 0.8 Example 3 TiAl(50:50) AlCr(70:30) 1.9 AlCr(70:30) -250 2.0 Example 4 TiAl(50:50) AlCr(70:30) 2.1 AlCr(75:35) -400 1.5 Example 5 AlCr(70:30) - 2.3 AlCr(70:30) -200 2.0 Example 6 AlCr(70:30) - 3.4 AlCrSi(70:20:10) -200 0.5 Example 7 AlCr(70:30) AlCrSi(60:30:10) 3.5 AlCr(70:30) -300 0.9 Comparative Example 1 TiAl(50:50) - 2.3 AlCr(70:30) -30 1.4 Comparative Example 2 TiAl(50:50) - 2.9 AlCrSi(70:20:10) -70 1.0 Comparative Example 3 TiAl(50:50) AlCr(70:30) 2.1 AlCr(70:30) -70 1.9 Comparative Example 4 TiAl(50:50) AlCr(70:30) 2.3 AlCr(75:35) -50 1.5 Comparative Example 5 AlCr(70:30) - 2.3 AlCr(70:30) -40 2.1 Comparative Example 6 AlCr(70:30) - 3.5 AlCrSi(70:20:10) -40 0.6 Comparative Example 7 AlCr(70:30) AlCrSi(60:30:10) 3.0 AlCr(70:30) -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 rake surface and the relief surface, the Al atomic ratio of the first film is Ra, the central point of the relief surface is C, and the periphery of C is 50 ㎛. Table 2 shows the results when the Al atomic ratio of the first film within 500㎛ of the first film located 500㎛ away from the cutting edge R in the C direction in _the direction of the flank surface is W _a. (Al content at this time excludes non-metals).

division R _a (at.%) W _a (at.%) C _a (at.%) R _a /C _a Example 1 75.3 72.5 68.5 1.10 Example 2 82.5 78.1 69.3 1.19 Example 3 73.4 69.9 69.7 1.05 Example 4 80.3 76.4 74.1 1.08 Example 5 73.3 69.1 69.9 1.05 Example 6 79.3 75.3 70.2 1.13 Example 7 76.4 71.8 69.7 1.10 Comparative Example 1 67.2 68.5 69.9 0.96 Comparative Example 2 68.2 69.0 69.5 0.98 Comparative Example 3 66.5 68.9 69.8 0.95 Comparative Example 4 73.5 74.1 74.5 0.99 Comparative Example 5 68.5 69.0 69.3 0.99 Comparative Example 6 69.1 69.7 69.8 0.99 Comparative Example 7 68.7 69.1 70.1 0.98

In the case of the example, as a result of analysis by EDS, the Al content of the first film satisfies 0.7<R _a ≤0.85, and the Al content of the first film gradually increases as the distance from the cutting edge increases from W _a to C _a and is 0.55. It can be confirmed that the range of ≤C _a ≤0.7 is satisfied. In addition, it can be confirmed that R _a /C _a ≥ 1.03 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: Carbon steel SM45C (300mm×200mm×100mm)

Sample model number: SNMX1206ANN-MM

Cutting speed: 250 m/min

Cutting feed: 0.2 mm/rev

Cutting depth: 2.0 mm

Coolant: Not 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 SM45C machining results NAK80 machining results Processing length
(mm) Wear type Processing length
(mm) Wear type Example 1 7500 normal wear 2100 Wear/chipping Example 2 7900 normal wear 1900 Wear/chipping Example 3 6900 normal wear 1500 Wear/chipping Example 4 7100 normal wear 1400 Boundary chipping Example 5 7300 normal wear 1900 Wear/chipping Example 6 7900 normal wear 1500 Wear/chipping Example 7 8200 normal wear 2200 Wear/chipping Comparative Example 1 6100 Excessive wear 1900 Wear/chipping Comparative Example 2 6500 Excessive wear 1400 Wear/chipping Comparative Example 3 5900 Excessive wear 1000 R-butchipping Comparative Example 4 5300 Excessive wear 1100 Boundary chipping Comparative Example 5 5700 Excessive wear 1000 Boundary chipping Comparative Example 6 4500 Excessive wear 800 R-butchipping Comparative Example 7 6500 normal wear 1300 Wear/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 SM45C workpiece machining length increased significantly, the NAK80 workpiece machining length 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 Al content between the cutting edge and the relief surface.

Claims (4)

Hard base material,
A cutting tool comprising a hard film formed on the hard base material,
The hard film is Al _a Cr _b Me _(1-ab) N _x O _y (a, b, x, y are atomic ratios, a+b≤1, 0.5≤x≤1, 0≤y≤0.5, x+ y = 1, Me is one or more selected from Group 4 elements, Group 5 elements, Group 6 elements, Si, B and S) and a first film made of
The point where the relief surface and the rake surface of the cutting tool meet is called the cutting edge R, and when the Al 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 R _a , 0.7 <R _a ≤0.85 is satisfied,
When the central point of the relief surface is C and the Al atomic ratio of the first film within 50㎛ around C is C _a , a cutting tool that satisfies 0.55≤C _a≤0.7 .
According to claim 1,
In the first film, a cutting tool satisfying R _a /C _a ≥1.03.
According to claim 1,
The thickness of the hard film is 0.5 to 10㎛,
A cutting tool wherein the first film has a thickness of 0.1 μm or more.
According to claim 1,
The hard film further includes a second film formed below the first film,
The second film is Al _(1-cde) Ti _c Cr _d Me _e N (c, d, e are atomic ratios, 0≤c≤0.8, 0≤d≤0.5, 0≤e≤0.15, c+d> 0, c+d+e<1, Me is one or more selected from B, Si, Zr, V, Mn, Nb, Mo, Ta and W). A cutting tool.