KR20130060542A - Hard coating film for cutting tools - Google Patents

Abstract

PURPOSE: A hard coating layer for a cutting tool is provided to a monolayer of an AlCrN group formed as a lower layer on a base material and improve the abrasive resistance, shock resistance, chipping resistance, lubrication etc. by laminating a nano multilayer, which is formed by successively laminating AlTi(Si)N/TiAlN/AlCrN/TiAlN thin film group, alternately and repeatedly. CONSTITUTION: A hard coating layer for a cutting tool includes a structure in which the first and second layers are alternately laminated. The first layer is formed of Al_1-xCr_xN(0.3<=x<=0.7). The second layer is formed into a nano multilayer structure including a thin layer A where the average thickness is 3-20 nm, a thin layer B, a thin layer C, and a thin layer D or a structure in which the nano multiplayer structure is repeated more than twice. The thin layer A is formed of Al_1-a-bTi_aSi_bN(0.3<=a<=0.7, 0<=b<=0.1). The thin layer B and the thin layer D are formed of Ti_1-xAl_xN(0.3<=x<=0.7). The thin layer C is formed of Al_1-zCr_zN(0.3<=z<=0.7). The Al content of the thin layer A and B are different. [Reference numerals] (AA) Basic material; (BB) Layer D; (CC) Layer C; (DD) Layer B; (EE) Layer A; (FF) First layer; (GG) Second layer

Description

Hard film for cutting tools {HARD COATING FILM FOR CUTTING TOOLS}

The present invention relates to a hard coating formed on a hard base material such as cemented carbide or cermet used in cutting tools. More specifically, the lower layer formed adjacent to a hard base material such as cemented carbide and the upper layer formed on the lower layer are alternately laminated, and the upper layer again includes thin layer A, thin layer B, thin layer C and thin layer D. It is made of a nano multilayer structure or a repeating layer structure thereof, and relates to a hard film improved both toughness and wear resistance compared to the conventional multilayer thin film structure.

As the industry becomes increasingly precise, high speed, and mass produced, it is required to improve cutting performance and lifespan for cutting tools. Particularly, during high-speed cutting of high-hardness workpieces and cutting of low-heat-conducting materials, high heat of about 900 ° C or more locally occurs at the tip of the insert that rubs against the workpiece. By forming on the cutting surface of the insert, the life of the cutting tool can be increased.

Conventionally, it has abrasion resistance, oxidation resistance, or impact resistance such as TiN, Al ₂ O _3, TiAlN, AlTiN, AlCrN, etc. on a base material such as cemented carbide, cermet, end mill, and drills to improve cutting performance and life improvement. By forming a single layer hard film or a multilayer hard film in which two or more layers are laminated, there has been a response to the demand for a hard workpiece or a hard workpiece.

By the way, the workpieces are gradually becoming harder, and the demand for processing of hard materials with low thermal conductivity and severe welding is also increasing. Therefore, it is difficult to meet the above demands only by developing a thin film composition with simple physical properties or by simple multilayer structure. It's getting harder.

Accordingly, in recent years, many attempts have been made to increase cutting performance by regularly repeating lamination of two or more kinds of nano-level thin films having different physical properties.

For example, Korean Patent Publication No. 876366 discloses an underlayer for physical adhesion and the orientation of (200) planes on a cemented carbide tool insert, end mill, drill or cermet tool by physical vapor deposition (PVD). After depositing the (Ti, Al) N multilayer thin film in order to continuously improve the impact resistance and chipping resistance, the top layer is made of TiAlN or AlTiSiN, A layer, B layer, C having different compositions Through a structure consisting of a layer and a D layer and alternately stacked, a thin film structure having improved abrasion resistance and oxidation resistance of the uppermost layer is disclosed.

Wear resistance and oxidation resistance can be improved through the multilayer structure as described above, but in order to improve various characteristics required for cutting operations such as abrasion resistance, impact resistance (toughness) and chipping resistance, development of a hard film having a new structure is required. .

An object of the present invention is to provide a hard coating film for cutting tools in which toughness (impact resistance), abrasion resistance, chipping resistance, lubricity, and the like are generally improved.

The present invention as means for solving the aforementioned problems is a hard coating formed on the base material surface, the hard film is the first layer, and comprises a laminated in the first layer and the second layer is alternating Al _{1 - x} Cr _x N (0.3 ≦ _x ≦ 0.7), and the second layer has a nano multilayer structure or a nano multilayer structure including a thin layer A, a thin layer B, a thin layer C, and a thin layer D having an average thickness of 3 to 20 nm. It consists of a structure that is repeatedly laminated two or more times, the thin layer A is made of Al _{1 -a- b} Ti _a Si _b N (0.3≤a≤0.7, 0≤b≤0.1), the thin layer B and thin layer D Ti _{1 - x} Al _x N (0.3≤x≤0.7), the thin layer C is made of Al _{1 - z} Cr _z N (0.3≤z≤0.7), Al between the thin layer A and the thin layer B It provides a hard film for cutting tools, characterized in that the content of the different.

Further, in the hard coating according to the present invention, the ratio (T ₁ / T ₂ ) of the thickness of the first layer to the thickness of the second layer is 0.1 or more and less than 1.0, and alternating lamination of the first layer and the second layer is performed. It is preferable that the thickness of a structure is 1.0-20.0 micrometers.

In addition, in the hard coating according to the present invention, the nano multilayer structure is preferably laminated in the order of the thin layer A-B-C-D.

In addition, in the hard coating according to the present invention, the hardness of the hard coating is preferably 35 GPa or more.

In addition, in the hard film according to the present invention, the difference between the Al content of the thin layer A and thin layer B is preferably 0.1 or more.

The multi-layer hard film for cutting tools according to the present invention is an alternating repetition of an AlCrN-based single layer formed as a lower layer on a base material and a nano multilayer formed through a sequential stacking of AlTi (Si) N / TiAlN / AlCrN / TiAlN-based thin films. Through lamination, various characteristics required for the cutting tool coating, such as wear resistance, impact resistance, chipping resistance, and lubricity, can be improved evenly, and thus can be suitably used for the processing of difficult materials.

1 is a cross-sectional view schematically showing the structure of the hard film according to the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, embodiments of the present invention illustrated in the following may be modified in many different forms, the scope of the present invention is not limited to the embodiments described in the following. Embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art. In addition, the size or thickness of the film or regions in the accompanying drawings should be understood to be exaggerated for the understanding of the invention.

1 is a cross-sectional view schematically showing the structure of the PVD hard film for cutting tools according to the present invention. As shown, the hard coating according to the present invention has a structure in which a first layer (lower layer) formed on the base material and a second layer (wear-resistant layer) formed on the first layer are alternately stacked in two or more layers. It is characterized by.

The first layer is a thin film whose main purpose is to improve toughness (impact resistance), and the composition is made of Al _1-x Cr _x N (0.3 ≦ _x ≦ 0.7). If the Cr content (x) is less than 0.3, the insulation is increased, making it difficult to deposit DC due to the characteristics of the equipment, and the brittleness is increased by the formation of hcp-AlCrN rather than fcc-AlCrN, which lowers abrasion resistance and shortens the life of the tool. If exceeds, the coarse thin film structure is formed and Cr ₂ N segregation is formed during work involving high temperature such as cutting, which lowers the wear resistance and shortens the tool life. 0.3-0.7 are preferable. In addition, the unit thickness of the first layer is preferably 0.01 to 10㎛.

The second layer is a thin film mainly for improving wear resistance, and has a nano multilayer structure including thin layer A, thin layer B, thin layer C, and thin layer D having an average layer thickness of 3 to 20 nm, or the nano multilayer structure repeatedly stacked two or more times. It is characterized by consisting of a structure. In general, as the period of nanomultilayer decreases, the thin film is strengthened as the generation and movement of dislocations is suppressed. If the thickness of the thin layer is too thin, less than 3 nm, the boundary between nanolayers that suppress the generation and movement of dislocations becomes unclear. It is advisable not to be less than 3 nm because the mixing zone is formed by interdiffusion between layers and the hardness and elastic modulus are lowered. When it exceeds 20 nm, it is easy to generate dislocation and move dislocation easily. And a decrease in elastic modulus and a decrease in matching strain energy due to the formation of misfit dislocations, which are accompanied by a decrease in reinforcing effect, and therefore, 3 to 20 nm is preferable. The laminated structure of the thin layer may be stacked in various forms such as A / B / C / D, A / D / C / B, B / A / D / C, D / A / C / B, and the first layer The form which does not contact C layer and interposes B layer or D layer between A layer and C layer is the most preferable.

In addition, the thin layer A is preferably made of Al _{1 -a- b} Ti _a Si _b N (0.3≤a≤0.7, 0≤b≤0.1), which is hexagonal B4 when the Ti content (a) is less than 0.3 Due to the phase formation of the structure, brittleness increases, wear resistance decreases, and the life of the tool is shortened.If the Al exceeds 0.7, the amount of solid solution is reduced by substituting Al in which the atomic radius is smaller than that of Ti, thereby reducing the hardness and wear resistance of the thin film. This is because the TiO ₂ oxide is easily formed in a high temperature environment during cutting, and the Ti element inside the thin film is diffused to the outside, resulting in a high temperature hardness due to Ti element depletion. In addition, the thin layer A may optionally contain less than 0.1 Si. When a small amount of Si (less than 0.1) is added, an amorphous Si ₃ N ₄ phase is formed along the grain boundaries of the crystalline AlTiN phase to form particles of the crystalline phase. Since it is made finer, hardness and wear resistance are improved. In addition, an amorphous Si ₃ N ₄ phase forms SiO ₂ oxide during high temperature cutting to prevent external diffusion of internal elements, thereby improving the life of the cutting tool. However, if the content (b) of Si exceeds 0.1, the amorphous Si ₃ N ₄ phase is increased, thereby lowering its own hardness and lowering the particle refining effect of the crystalline AlTiN phase, which may cause deterioration in wear resistance.

In addition, the thin layer B and the thin layer D is preferably made of Ti _{1 - x} Al _x N (0.3 ≤ _x ≤ 0.7), when the Al content (x) is less than 0.3 is replaced by Al having a smaller atomic radius than Ti As the amount of solid solution decreases, the hardness and abrasion resistance of the thin film are reduced, and TiO ₂ oxide is easily formed in a high temperature environment during cutting, and the Ti element inside the thin film is diffused to the outside, which may cause high temperature hardness due to Ti element depletion. In the case of more than 0.7, the phase formation of the hexagonal B4 structure increases brittleness, thereby lowering the wear resistance and shortening the life of the tool.

In addition, the thin layer C is preferably made of Al _{1 - z} Cr _z N (0.3≤z≤0.7), for the same reason as the first layer.

As described above, the present invention has an AlCrN layer as a lower layer (first layer) adjacent to the base material for improving toughness (impact resistance), and a nano-multi layer including thin layers A, B, C, and D for improving the wear resistance layer ( Second layer) structure, and the lower layer and the wear-resistant layer are alternately laminated, so that the entire hard film can be improved in toughness, wear resistance, chipping resistance and lubricity.

The nano-layer (second layer) is a combination of TiAlN, AlTiN, and AlCrN-based coatings, and is characterized in that the wear resistance is improved through composition control between the layers.

On the other hand, the Al content between the thin layer A and the thin layer B should be different, and the difference in Al content is preferably maintained at 0.1 or more, which is when the Al content difference is less than 0.1, the elastic modulus according to the composition change between the nano-multi-layer This is because the difference is not so large that the effect of reducing the strengthening effect of the thin film, considering the reason for the numerical limitation on the composition of the thin layer A and the thin layer B, it is good to maintain the difference in the Al content of 0.1 ~ 0.2.

Incidentally, the ratio (T ₁ / T ₂₎ of the first layer thickness to the thickness of the second layer is preferably maintained to less than 0.1 to 1.0. The reason is that when a crack is generated due to impact on the thin film, it is effective to delay propagation of cracks to deep layers by repeated alternating layers of the second layer, which is a hard layer, and the first layer, which is a soft layer. If the thickness of the second layer is too thin (less than 0.1), the crack propagation delay effect is reduced, and if the thickness of the first layer is thicker than the thickness of the second layer (more than 1.0), the crack propagates deeply. The delaying effect is because the wear resistance of the entire thin film may decrease as the first layer, which is a large soft layer, becomes thicker.

Moreover, it is preferable that the thickness of the hard film laminated | stacked alternately of a 1st layer and a 2nd layer is 1.0-20.0 micrometers.

[Example]

Hard having the cross-sectional structure shown in FIG. 1 using the arc ion plating method, which is physical vapor deposition (PVD), on hard substrate surfaces including cemented carbide, cermet, high speed steel, end mills, drills, etc. A film was formed.

Specifically, in the embodiment of the present invention, AlTi (or AlTiSi), TiAl, and AlCr arc targets were commonly used on the cemented carbide substrate composed of WC-10wt% Co, and the initial vacuum pressure was 8.5 × 10. N- ₂ was injected into the reaction gas at ^-5 Torr or less. And the reaction gas pressure is 30 mTorr or less (preferably 20 m Torr or less), the coating temperature was set to 400 ~ 550 ℃, the substrate bias voltage at the time of coating was used to apply a -20 ~ -150V. Coating conditions can vary from embodiments of the present invention depending on the equipment characteristics and conditions used.

Through the above-described coating method, a monolayer (first layer), which is a toughness layer, and a nanomultilayer (second layer), which is a wear resistant layer, were alternately laminated. Here, the single layer is an Al _1-x Cr _x N film, and the nano multilayer is a unit layer (A) Al _y Ti _1-y (Si) N film and the unit layer (B) Ti _z Al _1-z N film and unit A multilayer thin film structure in which a layer (C) Al _1-x Cr _x N film and a unit layer (D) Ti _z Al _1-z N film were sequentially stacked was applied.

The single layer was formed in a unit thickness of 0.06 ~ 0.18㎛, the nano-multi-layer is laminated 7 to 10 times each unit layer to a thickness of 18 ~ 20nm to form a thickness of 0.14 ~ 0.18㎛, then single layer and nano multilayer By alternately laminating 15 to 20 times again, the hard coating according to the embodiment of the present invention was completed.

On the other hand, if necessary, a variety of thin films may be additionally formed on the hard film formed according to the embodiment of the present invention. In addition, since the hard film according to the embodiment of the present invention uses physical vapor deposition (PVD), a thin film thickness may be formed up to about 20 μm.

Table 1 below shows the composition, thin film structure, alternating lamination cycle and total film thickness of the hard film formed according to the embodiment of the present invention.

Composition, Thin Film Structure, Alternating Lamination Cycle, and Total Thin Film Thickness of Hard Film According to an Embodiment of the Present Invention Example
No. Thin film structure film
Total thickness
(Μm) The first layer Second layer Furtherance thickness
(Μm) Furtherance thickness
(Μm) Lamination
Cycle
(nm) One AlCrN (5: 5) 0.06 AlTiSiN (57: 38: 5) / TiAlN (5: 5) / AlCrN (5: 5) / TiAlN (5: 5) 0.18 18 4.3 2 AlCrN (7: 3) 0.07 AlTiSiN (57: 38: 5) / TiAlN (5: 5)
AlCrN (7: 3) / TiAlN (5: 5) 0.17 20 4.2 3 AlCrN (5: 5) 0.16 AlTiN (67:33) / TiAlN (5: 5) /
AlCrN (5: 5) / TiAlN (5: 5) 0.17 20 4.3 4 AlCrN (7: 3) 0.14 AlTiN (67:33) / TiAlN (5: 5) /
AlCrN (7: 3) / TiAlN (5: 5) 0.18 19 4.1 5 AlCrN (5: 5) 0.06 AlTiN (67:33) / TiAlN (5: 5) /
AlCrN (5: 5) / TiAlN (5: 5) 0.16 19 4.0 6 AlCrN (7: 3) 0.06 AlTiN (67:33) / TiAlN (5: 5) /
AlCrN (7: 3) / TiAlN (5: 5) 0.17 20 4.1

In addition, in order to evaluate the characteristics of the hard film formed in accordance with an embodiment of the present invention, the surface of the base material consisting of the same WC-10wt% Co as the embodiment of the present invention in a thin film structure as shown in Table 2 below A hard film of about the same thickness as the hard film according to the embodiment was formed.

Composition, Thin Film Structure, and Total Thickness of Hard Film According to Comparative Example Comparative Example
No. Thin film structure Monolayer
Multilayer
Lamination
Cycle pellicle
Total thickness
(Μm) Single layer Nano multilayer Furtherance thickness
(Μm) Furtherance thickness
(Μm) Lamination
Cycle
(nm) One TiAlN (5: 5) 4.2 - - - - 4.2 2 AlTiN (67:33) 4.1 - - - - 4.2 3 AlCrN (5: 5) 4.2 - - - - 4.3 4 AlCrN (7: 3) 4.2 - - - - 4.2 5 - - TiAlN (5: 5) / AlCrN (7: 3) 20 - 4.3 6 - - AlTiN (67:33) / AlCrN (7: 3) 19 - 4.2 7 - - TiAlN (5: 5) / AlCrN (5: 5) 18 - 4.2 8 - - AlTiN (67:33) / AlCrN (5: 5) 19 - 4.3 9 - - AlTiN (67:33) / TiAlN (5: 5)
/ AlCrN (5: 5) / TiAlN (5: 5) 18 - 4.0 10 - - AlTiN (67:33) / TiAlN (5: 5)
/ AlCrN (7: 3) / TiAlN (5: 5) 19 - 4.2 11 AlCrN (5: 5) 0.07 AlTiN (67:33) / AlCrN (5: 5)
/ TiAlN (5: 5) 0.16 - 20 4.1 12 AlCrN (7: 3) 0.07 AlTiN (67:33) / AlCrN (7: 3)
/ TiAlN (5: 5) 0.17 - 19 4.3 13 AlCrN (5: 5) 0.08 AlTiSiN (57: 38: 5) / AlCrN (5: 5)
/ TiAlN (5: 5) 0.15 - 20 4.4 14 AlCrN (7: 3) 0.07 AlTiSiN (57: 38: 5) / AlCrN (7: 3)
/ TiAlN (5: 5) 0.16 - 19 4.1

As confirmed in Table 2, Comparative Examples 1 to 4 are hard films having a single layer structure made of TiAlN or AlCrN formed with a thickness of about 4.2 to 4.3 μm, and these hard films are compared with hard films having a nano multilayer structure. It is to.

In addition, Comparative Examples 5 to 8 are nano-layered hard films obtained by alternately stacking TiAlN / AlCrN about 18 to 20 nm in thickness approximately 200 times. Formed differently from the example, it is for confirming the difference in cutting performance according to the difference between the single layer and nano multilayer structure.

In addition, Comparative Examples 9 and 10 do not form a single layer, and alternately stacked in a structure of AlTiN / TiAlN / AlCrN / TiAlN in the same manner as in the embodiment of the present invention. It is for.

In addition, Comparative Examples 11 to 14 are hard film structures in which monolayers and nanomultilayers are alternately and repeatedly stacked, as in the embodiment of the present invention, except that the nanomultilayer structure is formed of three layers of AlTi (Si) N / AlCrN / TiAlN. By doing so, it is to confirm the difference in cutting performance according to the difference with the nano-multilayer structure according to the embodiment of the present invention.

Table 3 below shows the results of measuring the actual composition of the thin film constituting each layer through an energy diffraction X-ray spectrometer (EDX) after the hard film was formed according to Examples and Comparative Examples. .

Composition of each layer constituting the hard film according to Examples 1 to 6 and Comparative Examples 1 to 14 division No. Thin film composition (EDX, at%) Single layer Nano multilayer Al Ti Cr N Al Ti Cr Si N Comparative example One 27.1 28.9 - 44 - - - - - 2 37.4 19.4 - 43.2 - - - - - 3 26.6 - 28.9 44.5 - - - - - 4 35.8 - 18.5 45.7 - - - - - 5 - - - - 32.4 14 9.5 - 44.1 6 - - - - 35.2 9.5 9.4 - 45.9 7 - - - - 26.6 13.8 13.9 - 45.7 8 - - - - 30.7 8.6 14.6 - 46.1 9 - - - - 28 18.3 7.2 - 46.5 10 - - - - 32.1 18 4.1 - 45.8 11 26.1 - 28.1 45.8 29.3 10.7 14 - 46 12 37 - 17.6 45.4 34.4 11.1 8.1 - 46.4 13 26 - 28.2 45.8 23.3 13 7.4 0.8 45.5 14 37.1 - 17.5 45.4 26.4 13.1 4.5 0.8 45.3 Example One 26.3 - 27.9 45.8 23.3 15.5 5.6 0.6 45.1 2 36.8 - 17.8 45.4 23.2 15.7 5.9 0.6 45.5 3 25.9 - 28.3 45.8 29.2 17.1 7.1 - 46.6 4 37.1 - 17.5 45.4 30.9 17.8 5 - 46.3 5 25.5 - 27.7 46.8 29.6 18.1 6.8 - 45.5 6 37.8 - 17.1 45.1 31.7 18.5 4.4 - 45.4

As confirmed in Table 3 above, the actual composition of the formed film is somewhat different from the target composition, but shows a nearly similar composition.

Evaluation of Hardness, Friction Coefficient, and Crack Length of Hard Film

In order to evaluate the hardness of the hard film formed as described above, a microscopic hardness test was carried out using a Fisherscope (model name HP100C-XYP; German HELMUT FISCHER GMBH). The hardness (degradation hardness) after the high temperature deterioration process at 900 degreeC for 30 minutes was measured.

In addition, in order to evaluate the friction characteristics of the hard coating, using a CETR UMT-2 micro-tribometer using a ball-on-disc test of the sliding distance (ball (Si ₃ N ₄ , diameter 4mm, hardness HV _50g 1600) 60 revolutions) was measured. At this time, the evaluation of the friction characteristics was carried out under the conditions of 50 ~ 60% relative humidity, rotation speed 318rpm (10m / min) at a temperature of 20 ~ 25 ℃.

In addition, in order to evaluate the crack resistance (toughness) of the hard coating was applied to the diamond indentation of 30kgf load was measured the length of the cracks generated in the thin film, the results are shown in Table 4 below.

Hardness, coefficient of friction, and crack length of Examples 1 to 6 and Comparative Examples 1 to 14 division No. Thin film structure Room temperature
(GPa) Deterioration Hardness
(GPa) Coefficient of friction
(COF) Crack length
(30kg _f , μm) Single layer Nano multilayer Comparative example One TiAlN - 32.4 24 0.7 64 2 AlTiN - 35.5 29 0.72 65 3 AlCrN - 31.1 27 0.3 46 4 AlCrN - 29.5 25.5 0.33 46 5 - TiAlN / AlCrN 35.4 32.4 0.5 58 6 - AlTiN / AlCrN 36.7 34.3 0.48 59 7 - TiAlN / AlCrN 34.8 32.1 0.41 58 8 - AlTiN / AlCrN 36 34.1 0.44 58 9 - AlTiN / TiAlN / AlCrN / TiAlN 38.5 36.5 0.6 60 10 - AlTiN / TiAlN / AlCrN / TiAlN 38.8 36.8 0.65 64 11 AlCrN AlTiN / AlCrN / TiAlN 36.3 34.7 0.4 51 12 AlCrN AlTiN / AlCrN / TiAlN 35.9 33.7 0.44 53 13 AlCrN AlTiSiN / AlCrN / TiAlN 36.9 34.1 0.46 53 14 AlCrN AlTiSiN / AlCrN / TiAlN 37 35.9 0.47 54 Example One AlCrN AlTiSiN / TiAlN / AlCrN / TiAlN 38.3 38 0.39 49 2 AlCrN AlTiSiN / TiAlN / AlCrN / TiAlN 38.4 37.9 0.41 50 3 AlCrN AlTiN / TiAlN / AlCrN / TiAlN 37.3 36.1 0.35 51 4 AlCrN AlTiN / TiAlN / AlCrN / TiAlN 37.5 36.1 0.36 51 5 AlCrN AlTiN / TiAlN / AlCrN / TiAlN 37.9 36.4 0.41 48 6 AlCrN AlTiN / TiAlN / AlCrN / TiAlN 38.1 36.7 0.43 49

As confirmed in Table 4, the coatings of Comparative Examples 1 to 4 consisting of only a single layer have a room temperature hardness of 29.5 to 35.5 GPa, not only in terms of hardness, but also in terms of high temperature degradation environment. It turns out that it is high compared with a multilayer film. In addition, TiAlN-based coatings have low frictional properties and crack resistance, but relatively high hardness, while AlCrN-based coatings have low hardness but excellent frictional and cracking resistance. In other words, the monolayer coating tends to have a pronounced deficiency in some physical properties compared to the hard coating of the nano multilayer structure.

Comparative Examples 5 to 8 are nanomultilayers in which TiAlN / AlCrN nanolayers are alternately laminated without a single layer, but hardness and friction characteristics are improved compared to a single layer coating, but show poor crack resistance.

Comparative Examples 9 and 10 have a structure in which the AlTiSiN / AlCrN / TiAlN nanolayers are alternately laminated without a single layer. Although the hardness is improved compared to Comparative Examples 1 to 8, the friction characteristics and the crack resistance are compared with Comparative Examples 5 to 8. The sex tends to be inferior.

In Comparative Examples 11 to 14 having a structure substantially similar to those of the present invention, compared to Comparative Examples 1 to 10, hardness, friction characteristics, and crack resistance were improved in a balanced form.

Examples 1 to 6 of the present invention after the high temperature deterioration test hardness is 36.1 ~ 38GPa is equal to or more than when compared to the room temperature hardness of Comparative Examples 1 to 10, the coefficient of friction is 0.35 ~ 0.43 All Comparative films except AlCrN single layer It shows excellent properties compared to the crack length is 48 ~ 51㎛ level shows excellent properties compared to all the hard film.

From the evaluation of the hard film properties as described above, the hard film of Examples 1 to 6 of the present invention shows that the hardness, friction resistance, crack resistance, and the like are evenly improved compared to Comparative Examples 1 to 14.

Wear Resistance Rating

In order to evaluate the cutting performance when the hard coatings of Examples 1 to 6 and Comparative Examples 1 to 14 of the present invention were used particularly for cutting operations requiring wear resistance, a workpiece: carbon steel (SM45C, carbon steel milling), sample model number : SPKN1504EDSR (ISO), cutting speed: 200m / min, cutting feed: 0.3mm / tooth, cutting depth: 2mm under the conditions of the cutting test, the results are shown in Table 5 below.

Wear resistance evaluation result division No. Thin film structure Cutting life
(Processing
Distance, m) End of life
cause Single layer Nano multilayer Comparative example One TiAlN - 7.8 damage 2 AlTiN - 8 Chipping 3 AlCrN - 2.5 Chipping 4 AlCrN - 2.5 Chipping 5 - TiAlN / AlCrN 10 Chipping 6 - AlTiN / AlCrN 10 damage 7 - TiAlN / AlCrN 10 damage 8 - AlTiN / AlCrN 10 damage 9 - AlTiN / TiAlN / AlCrN / TiAlN 13.6 Chipping 10 - AlTiN / TiAlN / AlCrN / TiAlN 14.1 damage 11 AlCrN AlTiN / AlCrN / TiAlN 11.1 Excessive wear 12 AlCrN AlTiN / AlCrN / TiAlN 11.2 Excessive wear 13 AlCrN AlTiSiN / AlCrN / TiAlN 11.8 Excessive wear 14 AlCrN AlTiSiN / AlCrN / TiAlN 12 Excessive wear Example One AlCrN AlTiSiN / TiAlN / AlCrN / TiAlN 17 Normal wear 2 AlCrN AlTiSiN / TiAlN / AlCrN / TiAlN 17.8 Normal wear 3 AlCrN AlTiN / TiAlN / AlCrN / TiAlN 14.8 Normal wear 4 AlCrN AlTiN / TiAlN / AlCrN / TiAlN 15 Normal wear 5 AlCrN AlTiN / TiAlN / AlCrN / TiAlN 16.8 Normal wear 6 AlCrN AlTiN / TiAlN / AlCrN / TiAlN 17 Normal wear

As confirmed in Table 5, the hard film according to Examples 1 to 6 of the present invention has a cutting life of 14.8 to 17m, and it can be seen that the causes of end of life are all caused by normal wear. On the other hand, Comparative Examples 1 to 10, as well as Comparative Examples 11 to 14 having a thin film structure similar to the embodiments of the present invention not only significantly lower wear resistance than the Examples 1 to 6 of the present invention, but also life through normal wear It is not terminated and its life ends through excessive wear. Therefore, it is confirmed that the hard film according to Examples 1 to 6 of the present invention has excellent wear resistance.

Toughness Evaluation

In order to evaluate the cutting performance when the hard films of Examples 1 to 6 and Comparative Examples 1 to 14 of the present invention were used especially for cutting conditions requiring toughness (impact resistance), the impact resistance performance of milling processing evaluation Evaluation) was performed under the following conditions: workpiece: alloy steel (SCM440, three-piece plate milling of alloy steel), sample part number: SPKN1504EDSR (ISO), cutting speed: 200 m / min, cutting feed rate: 0.2 mm / tooth, cutting depth: 2 mm. , Evaluation was performed until the hard coating coated insert breakage, the results are shown in Table 6 below.

Toughness (impact resistance) evaluation result division No. Thin film structure Cutting life
(Processing distance, m) Single layer Nano multilayer Comparative example One TiAlN - 2.9 2 AlTiN - 2.8 3 AlCrN - 0.8 4 AlCrN - One 5 - TiAlN / AlCrN 3.2 6 - AlTiN / AlCrN 3 7 - TiAlN / AlCrN 3.2 8 - AlTiN / AlCrN 3.5 9 - AlTiN / TiAlN / AlCrN / TiAlN 4.1 10 - AlTiN / TiAlN / AlCrN / TiAlN 3.2 11 AlCrN AlTiN / AlCrN / TiAlN 6.5 12 AlCrN AlTiSiN / AlCrN / TiAlN 6.1 13 AlCrN AlTiSiN / AlCrN / TiAlN 6.5 14 AlCrN AlTiSiN / AlCrN / TiAlN 6.9 Example One AlCrN AlTiSiN / TiAlN / AlCrN / TiAlN 8.1 2 AlCrN AlTiSiN / TiAlN / AlCrN / TiAlN 9.3 3 AlCrN AlTiN / TiAlN / AlCrN / TiAlN 8.6 4 AlCrN AlTiN / TiAlN / AlCrN / TiAlN 8.1 5 AlCrN AlTiN / TiAlN / AlCrN / TiAlN 8.6 6 AlCrN AlTiN / TiAlN / AlCrN / TiAlN 9.3

As confirmed in Table 6, the hard coating according to Examples 1 to 6 of the present invention not only shows excellent impact resistance compared to Comparative Examples 1 to 10, but also has a thin film structure similar to the embodiment of the present invention. Compared with Comparative Examples 11 to 14 also shows excellent impact resistance.

Comprehensive Cutting Performance Evaluation

In general, the drilling process is slower than the milling process and is performed under wet conditions, so the lubricity (welding resistance) and chipping resistance of the machining insert are very important. The present inventors, in order to comprehensively evaluate the lubricity, chipping resistance, wear resistance and toughness of the hard coating according to Examples 1 to 6 and Comparative Examples 1 to 14 of the present invention, the workpiece: carbon steel (SM45C, carbon steel drilling), samples Part number SPMT07T208 / XOMT07T205 (indexable drill insert, 20-5D), cutting speed: 150m / min, cutting feed rate: 0.1mm / rev, cutting depth: 90mm (penetration). The results are shown in Table 7 below.

Drilling Machining Cutting Performance Evaluation Result division No. Thin film structure Cutting life
(hole: 20-90mm) End of life
cause Single layer Nano multilayer ratio
School
Yes One TiAlN - 52 Welding / Excessive Wear 2 AlTiN - 52 Welding / Chipping 3 AlCrN - 16 Excessive wear 4 AlCrN - 10 Excessive wear 5 - TiAlN / AlCrN 80 Chipping 6 - AlTiN / AlCrN 80 Welding / Chipping 7 - TiAlN / AlCrN 80 Excessive wear 8 - AlTiN / AlCrN 82 Excessive wear 9 - AlTiN / TiAlN / AlCrN / TiAlN 104 Chipping 10 - AlTiN / TiAlN / AlCrN / TiAlN 104 Welding / Chipping 11 AlCrN AlTiN / AlCrN / TiAlN 208 Excessive wear 12 AlCrN AlTiN / AlCrN / TiAlN 208 Excessive wear 13 AlCrN AlTiSiN / AlCrN / TiAlN 208 Excessive wear 14 AlCrN AlTiSiN / AlCrN / TiAlN 208 Excessive wear room
city
Yes One AlCrN AlTiSiN / TiAlN / AlCrN / TiAlN 256 Normal wear 2 AlCrN AlTiSiN / TiAlN / AlCrN / TiAlN 256 Normal wear 3 AlCrN AlTiN / TiAlN / AlCrN / TiAlN 230 Normal wear 4 AlCrN AlTiN / TiAlN / AlCrN / TiAlN 230 Normal wear 5 AlCrN AlTiN / TiAlN / AlCrN / TiAlN 256 Normal wear 6 AlCrN AlTiN / TiAlN / AlCrN / TiAlN 256 Normal wear

In the same manner as the abrasion resistance and toughness (impact resistance) evaluation results described above, it exhibits a significantly higher level than the comparative examples 1 to 14, which are the lifespan of the inserts forming the hard coating according to Examples 1 to 6 of the present invention. Since the cutting life is longer than that of Comparative Examples 11 to 14 having a thin film structure similar to that of Example 1, a single layer based on AlCrN and AlTi (Si) N / It has been confirmed that the repeated alternating lamination structure of the nano-multilayer based on TiAlN / AlCrN / TiAlN can evenly improve characteristics such as wear resistance and toughness, and thus can be suitably used for cutting tools for difficult materials.

Claims (5)

Hard film formed on the surface of the base material,
The hard coating includes a structure in which the first layer and the second layer are alternately stacked,
The first layer is made of Al _{1 - x} Cr _x N (0.3≤x≤0.7),
The second layer is composed of a nano multilayer structure including a thin layer A, thin layer B, thin layer C, thin layer D having an average thickness of 3 to 20 nm, or a structure in which the nano multilayer structure is repeatedly laminated two or more times.
The thin layer A is made of Al _{1 -a- b} Ti _a Si _b N (0.3≤a≤0.7, 0≤b≤0.1),
The thin layer B and the thin layer D is made of Ti _{1 - x} Al _x N (0.3≤x≤0.7),
The thin layer C is made of Al _{1 - z} Cr _z N (0.3≤z≤0.7),
The thin layer A and the thin layer B is a hard coating for a cutting tool, characterized in that the content of Al different. The method of claim 1,
The ratio (T ₁ / T ₂ ) of the thickness of the first layer to the thickness of the second layer is 0.1 or more and less than 1.0, and the thickness of the alternating laminated structure of the first layer and the second layer is 1.0 to 20.0 μm. Hard film for cutting tools. The method of claim 1,
The nano multilayer structure is a hard film for a cutting tool, characterized in that laminated in the order of the thin layer ABCD. The method of claim 1,
Hard coating for a cutting tool, characterized in that the hardness of the hard film is 35GPa or more. The method of claim 1,
Hard film for a cutting tool, characterized in that the difference between the Al content of the thin layer A and thin layer B is 0.1 or more.

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