KR20200076964A - A hard layer for cutting tools and manufacturing method for the same - Google Patents

Abstract

The present invention relates to a hard film formed on a hard base material such as a cemented carbide or cermet used in a cutting tool. The hard film according to the present invention is formed on or close to the surface of the hard base material by a PVD method. The hard film includes an alternating and repeating layer in which layers A and B are alternately laminated one or more times. Inside the layer B, a plurality of particles made of materials of the layer A are dispersed. Accordingly, the hard film can extend the cutting life of the cutting tool.

Description

Hard coating for cutting tools and its manufacturing method {A HARD LAYER FOR CUTTING TOOLS AND MANUFACTURING METHOD FOR THE SAME}

The present invention relates to a hard film formed on a hard base material such as cemented carbide, cermet, ceramic, and cubic boron nitride used in cutting tools, and more specifically, to a composite multi-layer of a nitride film and an oxide film formed adjacent to the hard base material. , The nitride film is an AlTiN-based or AlCrN-based cubic structure, and the oxide film is made of γ-Al ₂ O ₃ having a cubic crystal structure, and relates to a technique for improving the bonding strength between the nitride film and the oxide film.

The cutting edge of the cutting tool is exposed to a high temperature environment of about 1000℃ during high-speed processing of high-hardness materials, and not only wear and tear due to friction and oxidation due to contact with the workpiece, but also mechanical impact such as interruption. Therefore, it is essential that the cutting tool has appropriate wear resistance and toughness.

In order to impart the required wear resistance and toughness to the cutting tool, chemical vapor deposition (hereinafter referred to as'CVD') or physical vapor deposition (hereinafter referred to as'PVD') is used on the surface of cemented carbide generally used as a cutting tool. ) To form a hard thin film.

The hard thin film is composed of a single-layer or multi-layered non-oxide thin film (for example, TiN, TiC, TiCN), or an oxide-based thin film having excellent oxidation resistance (for example, Al ₂ O ₃ ) or a mixed layer thereof. Examples of the cargo-based thin film include carbides, nitrides, and carbonitrides of Group 4, 5, and 6 metal elements on the periodic table, such as TiN, TiC, TiCN, and examples of the oxide-based thin film typically include α-Al ₂ O ₃ , κ- Al ₂ O ₃ , γ-Al ₂ O ₃ and the like.

However, when depositing an oxide film such as Al ₂ O ₃ , the stacking thickness and the number of times are limited due to the insulating properties of the oxide film, and the composition and physical properties of the nitride film and the oxide film are different. The hard film has limitations in securing good bonding strength between the thin films, and there is a problem in that the applied value as a hard film for cutting tools decreases due to a decrease in abrasion resistance and chipping resistance.

Republic of Korea Patent Publication No. 2000-0072535

The problem of the present invention is that the nitride film and the oxide film are made of a composite multi-layer structure, the formation of the oxide film is stably performed, the bonding force between the nitride film and the oxide film is improved, and when applied to a cutting tool, the cutting life of the cutting tool is extended. It is to provide a hard film and a method for manufacturing the same.

One aspect of the present invention for solving the above problem is a hard film formed by PVD method on the surface of a hard gas, wherein the hard film is an alternating repeating layer in which A and B layers are alternately stacked one or more times and repeatedly stacked. It is to provide a hard coating for cutting tools, a plurality of particles made of the material of the A layer is dispersed inside the B layer.

Another aspect of the present invention for solving the above problem is a method of forming a hard film by repeatedly stacking the A layer and the B layer one or more times alternately by a PVD method on the surface or an adjacent portion of the hard gas, (a ) Forming a layer A to form a plurality of droplets on the surface; (b) forming a layer B on the layer A; (c) etching the B layer to expose at least a portion of the plurality of droplets; (d) forming a layer A on the etched layer B so that a plurality of droplets are formed on the surface; And (a) to (d) alternately repeating the steps one or more times.

The hard coating for a cutting tool according to the present invention has a multi-layered structure which is alternately stacked alternately in the form of AB, so that a plurality of particles connected to the A layer are dispersed inside the B layer (especially the upper and lower portions inside the B layer) By forming a bridge structure connected to the layer A of), adhesion between the thin films is improved, and through dispersion strengthening, an effect of improving the physical properties of the hard film can be obtained.

According to the method of manufacturing a hard film of the present invention, after depositing a large amount of wedge-shaped droplets upon deposition of a nitride film, an oxide film is deposited to a thickness level of the droplet level, and then, through an etching process, the droplets of the nitride film are projected to the surface of the oxide film. By maintaining the electrical conductivity by improving the deposition, the deposition process is performed more stably (by reaching the set value immediately and maintaining stability) during the next nitride film deposition. In addition, by repeating the above process, it is possible to manufacture a hard film having a complex multi-layer structure to have a continuous microstructure or an oxide dispersion strengthening (ODS) effect.

Figure 1 shows the structure of the hard film according to an embodiment of the present invention.
Figure 2 shows the manufacturing process of the hard film according to an embodiment of the present invention.

Hereinafter, with reference to the accompanying drawings for the embodiment of the present invention will be described the configuration and operation. In the following description of the present invention, when it is determined that a detailed description of related known functions or configurations may unnecessarily obscure the subject matter of the present invention, the detailed description will be omitted. Also, when a part is said to'include' a certain component, this means that other components may be further included rather than excluding other components, unless otherwise stated.

The hard film according to the present invention is formed on the surface of a hard gas by PVD method, and the hard film includes an alternating repeating layer in which A and B layers are alternately stacked one or more times, and the inside of the B layer. E, characterized in that a plurality of particles made of the material of the A layer is dispersed.

According to one embodiment of the present invention, the A layer is Al _a Ti _1-ab Me _b N of cubic crystal (0.3≤a≤0.7, 0≤b≤0.1, Me is V, Zr, Nb, Mo, Hf, Ta , W, Y or one or more selected elements) or Al _x Cr _1-xy Me _y N (0.3≤x≤0.7, 0≤y≤0.1, Me is V, Zr, Nb, Mo, Hf, Ta, W, It is preferable to consist of one or more elements selected from Y) in terms of balance between abrasion resistance and chipping resistance and drop formation, and the B layer contains γ-Al ₂ O ₃ of cubic crystal to improve oxidation resistance, and is complex It is preferable in terms of the strengthening effect by the multilayer.

At least some of the plurality of particles may be integrally connected to the A layer formed under the B layer.

At least some of the plurality of particles are integrally connected with the A layer formed on the lower portion of the B layer, and when the A layer is formed on the upper portion of the B layer, a bridge structure integrally connected with the A layer on the upper portion can be formed. have.

The plurality of particles may have a wedge shape in which their size decreases as they move upward.

The hard gas may be made of cemented carbide containing tungsten carbide, cermet containing titanium carbonitride, ceramic, boron nitride or diamond.

When the overall thickness of the alternating repeating layer is less than 0.5 μm, it is difficult to exhibit the characteristics of the thin film, and when it exceeds 10 μm, the compressive stress accumulated in the thin film is proportional to the thickness and time of the thin film due to the manufacturing characteristics of the thin film by PVD method. Given that the risk of peeling increases, the thickness is preferably in the range of 0.5 to 10 µm, and more preferably 2 to 8 µm.

In addition, when the unit thickness of the A layer forming the alternating repetition layer is less than 5 nm, it is difficult to exhibit abrasion resistance characteristics of the thin film, and droplets of an appropriate size are not formed, and when it exceeds 5.0 μm, the compressive stress increases. As the hardness and elastic modulus increase, the peeling or bonding strength with the oxide film is significantly reduced, so a range of 5 nm to 5.0 μm is preferable.

In addition, if the unit thickness of the B layer forming the alternating repetition layer is less than 2 nm, it is difficult to exert the natural oxidation resistance of the thin film, and when it exceeds 1.5 μm, insulation due to oxidation (poisoning) occurs throughout the entire equipment with a coating. Since the deposition of the oxide layer becomes difficult as well, the droplet may not protrude to the surface even after the etching process exceeding the droplet size of the A layer, so a range of 2 nm to 1.5 μm is preferable.

In addition, the alternating repetition layer may include two layers of AB, three layers of ABA, four layers of ABAB and more micro-multilayers (when the unit layer has a thickness of 1 µm or more) or nano-multilayers (thickness of the unit layer is 1). Less than μm) structure.

In addition, the method of manufacturing a hard film according to the present invention is a method of forming a hard film by repeatedly stacking A layers and B layers one or more times by alternating one or more times on the surface of a hard gas by (PV) method, (a) on the surface. Forming a layer A to form a plurality of droplets; (b) forming a layer B on the layer A; (c) etching the B layer to expose at least a portion of the plurality of droplets; (d) forming a layer A on the etched layer B so that a plurality of droplets are formed on the surface; And alternately repeating steps (a) to (d) one or more times.

In addition, in the method of manufacturing the hard film, the maximum height (H) of the droplets protruding from the thin film surface formed in the film forming process of the A layer is less than 0.02 μm, and electrical conduction is not smoothly performed with high electrical resistance. The thickness of the oxide film is also lowered below the appropriate range, and if it is more than 1.5 μm, electrical conduction cannot be made uniformly due to the diversification of the size of the droplet formed (increased size distribution). It is preferably 1.5 μm.

In addition, when the density of the droplet is less than 1.0×10 ⁴ ea/mm ² per unit area, the electrical conduction effect is low, and since the size or area of the oxide dispersed by the droplet increases, the dispersion strengthening effect is not large, and 5.0×10 ^{When it is more than 7} ea/mm 2, the size or area of the oxide dispersed by the droplet decreases, so the nature of the thin film decreases, so it is preferable that it is 1.0×10 ⁴ ea/mm 2 ~ 5.0×10 ⁷ ea/mm 2.

In addition, the ratio (T/H) of the thickness (T) of the B layer to the height (T) of the droplets formed on the surface of the thin film is preferably 0.1 to 0.9.

In addition, the formation and height of the droplet can be controlled through nitrogen content and cathode current during deposition of the A layer thin film.

In addition, in the step (b), the deposition of the layer B is performed at a thickness thinner than the highest height of the droplets of the layer A formed on the lower layer, a bridge made of a material of the layer A inside the layer B It is preferable because it is easy to form a structure.

[Example]

Preparation of hard film

In an embodiment of the present invention, a bipolar power supply frequency of 40 kHz or higher is achieved by using reactive pulse magnetron sputtering, which is physical vapor deposition (PVD), on a hard base material surface made of a sintered body containing cemented carbide, cermet, high-speed steel, cBN, or diamond. (supply frequency) is applied, and a process temperature of 450 to 600°C is applied to form a multilayer film having a structure as shown in FIG. 1.

In the multilayer film according to the embodiment of the present invention, a nitride layer is formed on the lowermost layer in contact with the hard base material, and oxides and nitrides are alternately repeatedly formed, and the number of repeated laminations formed as a whole is preferably 2 to 9 times. .

As the target used for the coating, an arc target of AlTi or AlCr and a sputter target of Al were used, and the initial vacuum pressure was reduced to 8.5×10 ^-5 Torr or less, and N ₂ and O ₂ were injected as a reaction gas. In addition, the gas pressure for coating was maintained at 50 mTorr or less, preferably at 40 mTorr or less, and the coating temperature was 400 to 600°C, and the substrate bias voltage during coating was -20 V to -100 V when coating a nitride film and -100 when coating an oxide film. ~ -150V was applied. The coating conditions may vary depending on equipment characteristics and conditions.

Specifically, as the base material, a cemented carbide composed of WC having an average particle size of 0.8 μm and a Co content of 10 wt.% was used. In addition, AlTiN or AlCrN thin film, using AlTi (60at.% / 40.at.%) or AlCr (64at.% / 36at.%) target, bias -40 V, arc current 100A, N2 pressure 2.66Pa It was formed on condition. In addition, Al ₂ O ₃ thin film, Al 99.9at.% using a target, bias -125V (single-pole pulse, 45kHz), sputter power 20KW, injecting O ₂ and Ar as a reaction gas, the film is formed under the condition of pressure 0.5Pa Did. In addition, etching was performed using tungsten filament as the electron emission source, under the conditions of bias -200V (monopole pulse, 40kHz), Ar flow rate 50sccm, time 10 minutes.

The thin film structure, the number of repeated laminations, the total thickness and the thin film hardness of the hard film prepared under the above conditions are shown in Table 1 below.

division number Thin film structure 1 time thickness
(㎛) Repeat stacking times
(time) Total thickness
(㎛) Thin film hardness
(GPa) Comparative example One AlTiN-based single layer structure 1-1 AlTiN(60:40) 4.1 - 4.1 34.2 1-2 AlTiVZrN(54:36:5:5) 4.3 - 4.3 34.8 1-3 AlTiNbMoN(54:36:5:5) 4.0 - 4.0 35.5 1-4 AlTiHfTaN(56.4:37.6:3:3) 3.8 - 3.8 34.8 1-5 AlTiWYN(56.4:37.6:3:3) 3.8 - 3.8 35.9 2 AlCrN-based single layer structure 2-1 AlCrN(64:36) 3.9 - 3.9 31.1 2-2 AlCrVZrN(57.6:32.4:5:5) 4.0 - 4.0 32.0 2-3 AlCrNbMoN(57.6:32.4:5:5) 4.1 - 4.1 32.4 2-4 AlCrHfTaN(60.2:33.8:3:3) 3.9 - 3.9 32.0 2-5 AlCrWYN(60.2:33.8:3:3) 4.0 - 4.0 33.0 3 AlTiN/Al ₂ O ₃ alternating repeating multi-bridge structure 3-1 AlTiN(60:40)/Al ₂ O ₃ 1.0 4 4.0 31.5 3-2 AlTiVZrN(54:36:5:5)/Al ₂ O ₃ 0.9 4 3.7 32.3 3-3 AlTiNbMoN(54:36:5:5)/Al ₂ O ₃ 0.8 4 3.6 32.4 3-4 AlTiHfTaN(56.4:37.6:3:3)/Al ₂ O ₃ 0.9 4 3.8 31.9 3-5 AlTiWYN(56.4:37.6:3:3)/Al ₂ O ₃ 0.9 4 3.8 33.8 4 AlCrN/Al ₂ O ₃ alternating multi-layer non-bridge structure 4-1 AlCrN(64:36)/Al ₂ O ₃ 0.9 4 3.7 30.3 4-2 AlCrVZrN(57.6:32.4:5:5)/Al ₂ O ₃ 1.0 4 4.0 32.5 4-3 AlCrNbMoN(57.6:32.4:5:5)/Al ₂ O ₃ 0.9 4 3.9 31.0 4-4 AlCrHfTaN(60.2:33.8:3:3)/Al ₂ O ₃ 0.9 4 3.6 31.9 4-5 AlCrWYN(60.2:33.8:3:3)/Al ₂ O ₃ 0.8 4 3.8 31.8 Example 5, 6 AlTiN/Al ₂ O ₃ alternating repeating multi-layer bridge structure 5-1 AlTiN(60:40)/Al ₂ O ₃ 1.8 2 3.6 32.4 5-2 AlTiVZrN(54:36:5:5)/Al ₂ O ₃ 1.8 2 3.8 32.3 5-3 AlTiNbMoN(54:36:5:5)/Al ₂ O ₃ 2.0 2 4.0 32.9 5-4 AlTiHfTaN(56.4:37.6:3:3)/Al ₂ O ₃ 1.9 2 3.8 33.5 5-5 AlTiWYN(56.4:37.6:3:3)/Al ₂ O ₃ 1.9 2 3.9 33.0 6-1 AlTiN(60:40)/Al ₂ O ₃ 0.9 4 3.7 33.4 6-2 AlTiVZrN(54:36:5:5)/Al ₂ O ₃ 1.0 4 4.0 34.0 6-3 AlTiNbMoN(54:36:5:5)/Al ₂ O ₃ 1.0 4 4.0 33.9 6-4 AlTiHfTaN(56.4:37.6:3:3)/Al ₂ O ₃ 0.9 4 3.8 33.1 6-5 AlTiWYN(56.4:37.6:3:3)/Al ₂ O ₃ 0.9 4 4.0 34.2 7, 8 AlCrN/Al ₂ O ₃ alternating repeating multi-layer bridge structure 7-1 AlCrN(64:36)/Al ₂ O ₃ 1.9 2 3.9 29.9 7-2 AlCrVZrN(57.6:32.4:5:5)/Al ₂ O ₃ 1.9 2 3.8 30.8 7-3 AlCrNbMoN(57.6:32.4:5:5)/Al ₂ O ₃ 2.2 2 4.3 31.2 7-4 AlCrHfTaN(60.2:33.8:3:3)/Al ₂ O ₃ 2.1 2 4.2 31.8 7-5 AlCrWYN(60.2:33.8:3:3)/Al ₂ O ₃ 1.9 2 4.0 32.0 8-1 AlCrN(64:36)/Al ₂ O ₃ 0.9 4 3.7 31.5 8-2 AlCrVZrN(57.6:32.4:5:5)/Al ₂ O ₃ 0.9 4 3.8 32.5 8-3 AlCrNbMoN(57.6:32.4:5:5)/Al ₂ O ₃ 0.8 4 3.8 32.1 8-4 AlCrHfTaN(60.2:33.8:3:3)/Al ₂ O ₃ 0.9 4 3.9 31.9 8-5 AlCrWYN(60.2:33.8:3:3)/Al ₂ O ₃ 0.8 4 3.7 32.0

Evaluation of hard film properties

The peeling resistance, abrasion resistance and chipping resistance of the composite multilayer film constituted of the structure of Table 1 were evaluated under the following evaluation conditions.

(1) Peel resistance evaluation: Absence of abnormal wear due to tearing of thin film

Workpiece: SM45C

Sample model number: SNMX1206ANN-MM

Cutting speed: 200m/min

Cutting feed: 0.2mm/tooth

Cutting depth: 2mm

(2) Wear resistance evaluation: insert wear surface and inclined surface wear

Workpiece: SCM440

Sample model number: SNMX1206ANN-MM

Cutting speed: 250m/min

Cutting feed: 0.2mm/tooth

Cutting depth: 2mm

(3) Evaluation of chipping resistance: chipping of nose and R of the cutting edge of the insert

Workpiece: STS316L

Sample model number: APMT1604PDSR-MM

Cutting speed: 150m/min

Cutting feed: 0.2mm/tooth

Cutting depth: 10mm

Table 2 shows the results of evaluation under the above conditions.

number Peel resistance Abrasion resistance Chipping resistance Remark number Processing length
(mm) Wear type Processing length
(mm) Wear type Processing length
(mm) Wear type Remark 1-1 1300 Thin Film,
Excessive wear 2200 Excess Wear,
damage 300 R-Bopping Comparative example 1-2 1000 Thin Film,
Excessive wear 2200 Excess Wear,
Chipping 300 R-Bopping Comparative example 1-3 1100 Thin Film,
Excessive wear 2200 Excess Wear,
Chipping 350 Border chipping Comparative example 1-4 1050 Thin Film,
Chipping 1800 Excess Wear,
damage 250 R-Bopping Comparative example 1-5 1200 Thin Film,
Excessive wear 1800 Excess Wear,
damage 250 R-Bopping Comparative example 2-1 1500 Thin Film,
Excessive wear 1000 Excess Wear,
damage 200 Border chipping Comparative example 2-2 1500 Thin Film,
Excessive wear 1200 Excess Wear,
Chipping 200 Border chipping Comparative example 2-3 1450 Thin Film,
Excessive wear 1200 Excess Wear,
Chipping 200 Border chipping Comparative example 2-4 1600 Thin Film,
Excessive wear 1000 Excess Wear,
damage 250 R-Bopping Comparative example 2-5 1300 Thin Film,
Chipping 1050 Excess Wear,
damage 200 Border chipping Comparative example 3-1 800 Thin film tearing 2900 Excessive wear 400 R-Bopping Comparative example 3-2 850 Thin film tearing 2900 Excessive wear 400 R-Bopping Comparative example 3-3 650 Thin film tearing 2950 Excessive wear 350 R-Bopping Comparative example 3-4 700 Thin film tearing 2400 Chipping 350 R-Bopping Comparative example 3-5 800 Thin film tearing 2250 Chipping 400 R-Bopping Comparative example 4-1 1100 Thin film tearing 1500 Excessive wear 350 Border chipping Comparative example 4-2 1000 Thin film tearing 1500 Excessive wear 350 Border chipping Comparative example 4-3 1100 Thin film tearing 1500 Excessive wear 350 Border chipping Comparative example 4-4 900 Thin film tearing 1450 Chipping 400 R-Bopping Comparative example 4-5 950 Thin film tearing 1450 Chipping 350 R-Bopping Comparative example 5-1 2400 Normal wear 4800 Normal wear 900 Border chipping Example 5-2 2550 Normal wear 4600 Normal wear 800 Border chipping Example 5-3 2400 Normal wear 4800 Normal wear 900 Border chipping Example 5-4 2100 Normal wear 4850 Normal wear 900 Border chipping Example 5-5 2400 Normal wear 4500 Normal wear 950 Border chipping Example 6-1 2900 Normal wear 5200 Normal wear 1200 Normal wear Example 6-2 2850 Normal wear 5100 Normal wear 1100 Normal wear Example 6-3 3000 Normal wear 5300 Normal wear 1100 Normal wear Example 6-4 2900 Chipping 5000 Normal wear 1300 Normal wear Example 6-5 2950 Normal wear 5000 Normal wear 1200 Normal wear Example 7-1 2000 Normal wear 3400 Excessive wear 750 Border chipping Example 7-2 2100 Normal wear 3450 Excessive wear 750 Border chipping Example 7-3 2050 Normal wear 3700 Normal wear 750 Border chipping Example 7-4 1700 Normal wear 3300 Excessive wear 850 Border chipping Example 7-5 1950 Normal wear 3550 Normal wear 850 Border chipping Example 8-1 2800 Normal wear 3900 Normal wear 1000 Normal wear Example 8-2 2600 Normal wear 3900 Normal wear 1100 Normal wear Example 8-3 2550 Normal wear 3550 Excessive wear 1050 Normal wear Example 8-4 2400 Normal wear 3800 Normal wear 900 Border chipping Example 8-5 2600 Normal wear 3900 Normal wear 1000 Normal wear Example

As can be seen from Table 2, Sample Nos. 5 to 8 corresponding to Examples have excellent peeling resistance, abrasion resistance, and chipping resistance compared to Comparative Examples.

In particular, although Comparative Examples Samples No. 3 and 4 had the same layered structure as Example Samples No. 6 and 8, they showed significant differences in peeling resistance, abrasion resistance, and chipping resistance only by not applying a bridge structure. , It can be seen that the bridge structure according to the present invention has the effect of improving the bonding strength between the nitride film and the oxide film, and improving the hardness and toughness.

Among the examples, the sample No. of which the number of repetitive laminations was four was repeated. Compared to Sample Nos. 5 and 7 in which 6 and 8 were repeated two times, the peeling resistance, abrasion resistance, and chipping resistance were slightly better overall. Is inferred.

On the other hand, it can be seen that in the same thin film structure, the difference in the processing length according to the type and content of the metal (Me) element is not large, and shows a different trend in terms of wear type.

That is, the hard film having the composition, hardness and lamination structure according to the present invention can realize improved peeling resistance, abrasion resistance and chipping resistance compared to a hard film obtained by combining a conventional nitride film and an oxide film.

Claims (8)

A hard film formed by PVD on the surface of a hard gas,
The hard film includes an alternating repeating layer in which A and B layers are alternately stacked one or more times, and repeatedly stacked.
A hard film for a cutting tool in which a plurality of particles made of the material of the A layer are dispersed inside the B layer. According to claim 1,
The A layer is cubic Al _a Ti _1-ab Me _b N (0.3≤a≤0.7, 0≤b≤0.1, Me is one or more selected from V, Zr, Nb, Mo, Hf, Ta, W, Y Element) or Al _x Cr _1-xy Me _y N (0.3≤x≤0.7, 0≤y≤0.1, Me is one or more elements selected from V, Zr, Nb, Mo, Hf, Ta, W, Y) Done,
The layer B comprises a cubic γ-Al ₂ O ₃ , a hard coating for cutting tools. According to claim 1,
At least a part of the plurality of particles is connected to the A layer formed in the lower portion of the B layer, a hard coating for cutting tools. According to claim 1,
At least some of the plurality of particles are integrally connected with the A layer formed on the lower portion of the B layer, and when the A layer is formed on the upper portion of the B layer, a bridge structure is formed integrally connected with the A layer on the upper portion, Hard coating for cutting tools. According to claim 1,
The hard gas is a hard film for a cutting tool, made of a cemented carbide containing tungsten carbide, cermet containing titanium carbonitride, ceramic, boron nitride or diamond. A method of forming a hard film by repeatedly stacking the A layer and the B layer one or more times by alternating one or more times on the surface or adjacent portion of the hard gas,
(a) forming a layer A to form a plurality of droplets on the surface;
(b) forming a layer B on the layer A;
(c) etching the B layer to expose at least a portion of the plurality of droplets;
(d) forming a layer A on the etched layer B so that a plurality of droplets are formed on the surface; And
The steps of (a) ~ (d) alternately repeated one or more times; including, the method of manufacturing a hard film. The method of claim 6,
The A layer is cubic Al _a Ti _1-ab Me _b N (0.3≤a≤0.7, 0≤b≤0.1, Me is one or more selected from V, Zr, Nb, Mo, Hf, Ta, W, Y Element) or Al _x Cr _1-xy Me _y N (0.3≤x≤0.7, 0≤y≤0.1, Me is one or more elements selected from V, Zr, Nb, Mo, Hf, Ta, W, Y) Done,
The B layer comprises a cubic γ-Al ₂ O ₃ , a method for producing a hard film. The method of claim 6,
In the step (b), the film formation of the B layer is performed to a thickness thinner than the highest height of the drop of the A layer formed on the lower layer, a method for manufacturing a hard coating for cutting tools.

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