KR20230030763A - Cvd film for cutting tool with excellent wear resistance - Google Patents

Abstract

A purpose of the present invention is to provide a hard film having excellent adhesiveness and improved wear resistance and toughness. In accordance with the present invention, a film for a cutting tool, which is a film formed through a CVD method, includes a first layer, and a second layer formed in an upper part of the first layer. The first layer includes a layer including TiC^x N^y (x+y=1, x＞0, y＞0) as a main phase, and oriented such that the peak intensity of a surface (311) and/or a surface (422) can be the greatest during X-ray diffraction analysis, and the second layer has a structure in which an A layer formed of Ti^1-x Al^x C^1-y N^y (0.6<=x<1.0, 0<=y<=1), and a B layer formed of TiN are alternately and repeatedly stacked at least twice in the form of A/B/A/B.

Description

Coating for CVD cutting tools with excellent wear resistance {CVD FILM FOR CUTTING TOOL WITH EXCELLENT WEAR RESISTANCE}

The present invention relates to a coating for a cutting tool, which is formed by chemical vapor deposition as a coating for a cutting tool, includes an AlTiN layer having a high Al content, and has excellent oxidation resistance, wear resistance, and peeling resistance.

In order to improve cutting performance and life, a method of depositing a thin film such as TiN, TiAlN, AlTiN, Al ₂ O ₃ which is a hard film on a hard substrate such as cemented carbide, cermet, end mill, drill, etc. is used.

Until the 1980s, cutting tools were coated with TiN to improve their cutting performance and lifespan. The coating technology was changed to TiAlN, and an AlTiN thin film with more Al was developed to further improve wear resistance and oxidation resistance. The AlTiN thin film has an effect of improving high-temperature oxidation resistance and wear resistance by forming an Al ₂ O ₃ oxide layer, but has a problem in that it has a weak bonding force with a hard substrate.

In recent years, workpiece materials have become increasingly hard, and there is an increasing demand for difficult-to-cut materials that have low thermal conductivity and severe adhesion to tools. It is important to have excellent oxidation resistance and wear resistance in order to obtain excellent cutting performance and lifespan during high-speed cutting for high-hardness workpieces and high-speed cutting for difficult-to-cut materials.

In response to this demand, an AlTiN thin film formed by a CVD method with excellent oxidation resistance and wear resistance by increasing the Al content by 0.7 or more in terms of molar ratio among Al and Ti has emerged as a new alternative, but low exfoliation resistance and toughness have become a problem. The scope of application is limited.

For example, the following patent literature discloses a hard film having improved wear resistance through an AlTiN thin film formed by a CVD method having a lamellar structure and a texture preferentially oriented in a specific crystal plane. However, the technology for improving the bonding force with the hard substrate, which is the most problematic for the application of the AlTiN thin film, is not disclosed.

Republic of Korea Patent Publication No. 2016-0130752

An object of the present invention is to provide a coating for a cutting tool having excellent peeling resistance and further improved abrasion resistance.

In order to achieve the above object, a film formed by the CVD method, the film includes a first layer and a second layer formed on top of the first layer, the first layer is TiC _x N _y ( x + y = 1, x>0, y>0) as a main phase and includes a layer oriented so that the peak intensity of the (311) plane and / or (422) plane is the largest in X-ray diffraction analysis In the second layer, an A layer made of Ti _1-x Al _x C _1-y N _y (0.6≤x<1.0, 0≤y≤1) and a B layer made of TiN are formed twice or more A / B It provides a coating for a cutting tool having a structure that is repeatedly laminated in an alternating / A / B form.

In the film according to an embodiment of the present invention, a TiCN layer having crystal growth is placed under the AlTiN layer to improve bonding strength with the AlTiN layer, and a multi-layered structure with a TiN layer interposed between the AlTiN layers is applied. , peeling resistance and abrasion resistance of coatings for cutting tools can be remarkably improved.

In addition, the wear resistance of the coating film according to an embodiment of the present invention can be further improved by applying a fine grain structure of the TiCN layer having a particle size of 0.9 μm or less.

In addition, in the film according to one embodiment of the present invention, during XRD analysis, AlTiN grown with the largest peak intensity of the (111) plane and AlTiN grown with the largest peak intensity of the (200) plane are disposed with a TiN layer interposed therebetween. Thus, more improved wear resistance can be obtained.

1 is a schematic view of the structure of a hard coating according to an embodiment of the present invention.
FIG. 2 is a result of X-ray diffraction analysis of a film prepared according to an embodiment of the present invention, and shows a peak (red box) of a crystal plane having high intensity among peaks of a TiCN layer.
FIG. 3 is a result of X-ray diffraction analysis of a film prepared according to an embodiment of the present invention, and shows a crystal plane peak (red box) with the highest intensity among peaks of an AlTiN layer.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

However, the embodiments of the present invention exemplified below may be modified in many different forms, and the scope of the present invention is not limited to the embodiments described below. The embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art.

A film for a cutting tool according to the present invention is formed by the CVD method, and the film includes a first layer and a second layer formed on top of the first layer, and the first layer is TiC _x N _y (x +y = 1, x>0, y>0) as a main phase, including a layer oriented so that the peak intensity of the (311) plane and / or (422) plane is the largest in X-ray diffraction analysis And, in the second layer, an A layer made of Ti _1-x Al _x C _1-y N _y (0.6≤x<1.0, 0≤y≤1) and a B layer made of TiN are formed at least twice or more by A/ It is characterized in that it has a structure that is alternately and repeatedly laminated in the form of B / A / B.

In the present invention, 'main phase' means a phase that makes up 80% or more, preferably 90% or more, more preferably 95% or more, and most preferably 99% or more in terms of volume fraction in the corresponding layer.

As shown in FIG. 1, the film according to an embodiment of the present invention is formed and used on a base material 100 used for a cutting tool such as cemented carbide or cermet, and largely underlayer 200 ), the first layer 300 and the second layer 400 are included.

The base layer 200 can be selectively formed to improve bonding strength between the base material 100 and the first layer 300, and a layer made of TiN can be used. The thickness of the base layer 200 is preferably less than 2 μm, and more preferably less than 1 μm.

The first layer 300 includes a TiCN layer having TiC _x N _y (x + y = 1, x > 0, y > 0, hereinafter referred to as 'TiCN') formed in contact with or adjacent to the base material as a main phase. It is done by

In the film according to the present invention, the TiCN layer is disposed on the lower side in contact with the AlTiN layer of the second layer 300, and together with this, the strongest peaks on the (311) plane and / or (422) plane during X-ray diffraction analysis By applying a TiCN layer oriented to appear, the bonding strength between the TiCN layer as the first layer 300 and the AlTiN layer forming a part of the second layer 400 is improved (ie, peeling resistance of the film) while improving, The wear resistance of the entire film can also be improved through the TiCN layer having excellent wear resistance.

In the TiCN layer, when the (311) plane is the strongest peak in X-ray diffraction analysis, the (422) plane is in the second strongest peak state, or if the (422) plane is the strongest peak, the (311) plane is the strongest peak. The second strongest peak state is more preferable in terms of bonding strength with the AlTiN layer.

When the thickness of the first layer 300 is less than 0.5 μm, it is difficult to obtain the above effect, and when the thickness exceeds 15 μm, the bonding force between the TiCN layer and the AlTiN layer of the second layer 400 decreases. It is preferable to form a range.

The TiCN layer is preferably formed of fine grains having an average grain size of 0.9 μm or less in microstructure to improve bonding strength with the AlTiN layer formed thereon and to improve wear resistance of the entire film.

The second layer 400 is formed in a stacked structure in A/B/A/B form with a TiN layer 420 functioning as a buffer layer interposed between AlTiN layers 410.

The A layer has Al content of 0.6 or more in molar ratio, and AlTiN, which is contained more than Ti, as a main phase. AlTiN has excellent oxidation resistance, but has a problem of low exfoliation resistance. In order to improve the low exfoliation resistance of the AlTiN layer in the film according to the present invention, as described above, a TiCN layer oriented in a specific crystal direction was disposed below the AlTiN layer. Further, in the coating film according to the present invention, by disposing the TiN layer between the AlTiN layers constituting the second layer 400, peeling resistance of the coating film can be further improved.

In general, AlTiN films have low impact resistance due to weak toughness, but AlTiN films having a lamellar structure can improve toughness. And, in order to obtain the effect of improving toughness, the average thickness of the lamellar region (average spacing between fine layers constituting the lamella) is preferably 150 nm or less, more preferably 100 nm or less, and most preferably 50 nm or less. The lamellar structure may be an alternating repetition of regions having different compositions and different crystal structures, such as a face-centered cubic (fcc) structure and a hexagonal structure (hcp) structure, or the same crystal structure, for example, a face-centered cubic (fcc) structure. While having, different composition regions may be alternately repeated. The lamellar structure is effective in extending the life of the cutting tool by increasing resistance to load when using it. In particular, it may be preferable that the two alternating regions have the same face-centered cubic (fcc) structure and have different compositional regions.

In addition, the AlTiN Considering bonding force and wear resistance, the aluminum content (x) is preferably 0.6 or more and less than 0.95, and more preferably 0.7 or more and 0.93 or less in a rich range.

In addition, the AlTiN layer may have a volume fraction of tissue having a face centered cubic structure (fcc) of 90 vol% or more. AlTiN The film with a main phase may have a face-centered cubic structure (fcc) and a dense hexagonal structure (hcp) depending on the film formation conditions, but a face-centered cubic structure is more advantageous in terms of abrasion resistance and impact resistance. In addition, since the characteristics of the face-centered cubic structure can be sufficiently expressed only when the face-centered cubic structure is 90 vol% or more, the crystal structure of the AlTiN layer preferably has a face-centered cubic structure of 90 vol% or more.

In addition, in the film according to an embodiment of the present invention, the second layer 400 is an AlTiN layer (layer A in FIG. ), and an AlTiN layer (C layer in FIG. 1) oriented so that the peak intensity of the (111) plane is the highest in X-ray diffraction analysis may have a structure in which the TiN layer is interposed. By alternately and repeatedly arranging AlTiN layers having different orientations in this way, it is possible to further improve peeling resistance by preventing stress from being concentrated in a specific direction in the AlTiN layer.

In addition, the thickness of the second layer 200 is preferably 2 to 6 μm, which means that when the thickness of the second layer is less than 2 μm, wear resistance and oxidation resistance may not be sufficient, and when the thickness exceeds 6 μm, internal stress This is because peeling resistance may be lowered by

Hereinafter, in order to explain the present invention in more detail, a preferred embodiment according to the present invention will be described in more detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments described herein.

[Example 1]

First, the cemented carbide base material is mixed for 13 hours by adding 10% by weight of Co, which acts as a binder of cemented carbide, and 2% by weight of carbides or carbonitrides containing elements of Groups 4, 5, or 6. After pulverization, a mixed powder is obtained using a spray drying method. With the obtained mixed powder, a molded article was manufactured by performing a press at a pressure of 2 ton/cm 2 to manufacture the SNMX1206ANN-MM model.

Subsequently, a dewaxing process is performed at 600 ° C to remove the organic binder component introduced in the molded product manufacturing process, and then sintering is performed in an inert gas atmosphere for 1 to 2 hours, followed by predetermined cooling in an inert gas atmosphere up to 600 ° C. After the rate cooling, a sintering process was performed by a natural cooling method to prepare a base material for forming a hard film.

A film was formed on the prepared base material using a thermal CVD method.

First, a method of introducing 8ml/min of TiCl ₄ , 12ml/min of N ₂ , and 100ml/min of H ₂ gas at 850° C. under a pressure of 5 mbar using a hot-wall CVD reactor Through this, a TiN layer having a thickness of 1 μm or less was formed as an underlayer.

Next, at 800° C., under a pressure of 50 mbar, a mixed gas of 4 ml/min TiCl ₄ , 0.5 ml/min CH ₃ CN, 15 ml/min N ₂ , and 2000 ml/min H ₂ was introduced to obtain a thickness of about 9 μm. An MT-TiCN layer (first layer) was formed.

Then, at 800° C., under a pressure of 5 mbar, 5 ml/min of TiCl ₄ , 18 ml/min of AlCl ₃ , and 1200 ml/min of H ₂ mixed gas were introduced, and 65 ml/min of NH ₃ and 140 ml/min of N ₂ , 0.5 ml /min of the CH ₃ CN mixture was passed into the reactor as the second gas feed. After a coating time of 20 minutes, a black gray AlTiN layer having a thickness of 2 μm was formed. The aluminum content (x) of the resulting AlTiN layer was 0.93.

Next, at 850° C. under a pressure of 5 mbar, TiCl ₄ at 8 ml/min, N ₂ at 12 ml/min, and H ₂ at 100 ml/min were supplied through the reactor. After 10 minutes of coating time, a TiN layer with a thickness of 1 μm or less was formed, and then, at 800° C., under a pressure of 5 mbar, 4 ml/min of TiCl ₄ , 20 ml/min of AlCl ₃ , and 1200 ml/min of H ₂ were mixed. A gas was introduced and a mixture of NH ₃ at 80 ml/min and N ₂ at 160 ml/min and CH ₃ CN at 0.5 ml/min was passed through the reactor as a second gas supply. After a coating time of 20 minutes, a black gray AlTiN layer having a thickness of 2 μm was formed. The aluminum content (x) of the resulting AlTiN layer was 0.89.

Finally, at 850° C. under a pressure of 5 mbar, 8 ml/min of TiCl ₄ , 12 ml/min of N ₂ , and 100 ml/min of H ₂ were passed through the reactor. After a coating time of 20 minutes, a TiN layer having a thickness of 2 μm or less was formed.

2 and 3 show the results of X-ray diffraction analysis of the hard coating according to Example 1 of the present invention. As confirmed in FIG. 2, the peak representing the maximum intensity of the TiCN layer of the hard film prepared according to Example 1 is the (311) plane, and the second strongest (422) peak is formed.

In addition, as confirmed in FIG. 3, the peaks showing the maximum intensity of the AlTiN layer of the hard film prepared according to Example 1 are the (111) plane and the (200) plane.

That is, in the hard film according to Example 1 of the present invention, a TiCN layer oriented in the (311) and (422) planes is formed on the surface of the hard substrate (base material), and then the TiCN layer is oriented in the (111) and (200) planes. By forming the AlTiN layer, the bonding force between the two layers is improved due to the similarity of the crystal structure.

[Comparative Example 1]

After fabricating the MT-TiCN layer on the same cemented carbide base material as in Example 1 by the same process, a single AlTiN layer oriented in a (111) plane was formed.

[Comparative Example 2]

After the MT-TiCN layer was prepared on the same cemented carbide base material as in Example 1 by the same process, a single AlTiN layer oriented in a (200) plane was formed.

[Comparative Example 3]

After fabricating the MT-TiCN layer on the same cemented carbide base material as in Example 1 by the same process, a single AlTiN layer oriented in the (111) plane was formed to a thickness similar to that of Example 1.

[Comparative Example 4]

After manufacturing the MT-TiCN layer on the same cemented carbide base material as in Example 1 by the same process, a single AlTiN layer oriented in the (200) plane was formed to a thickness similar to that of Example 1.

Table 1 below shows conditions for forming each layer when the films of Example 1 and Comparative Examples 1 to 4 were formed by the CVD method.

Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 TiCN
(1st floor) hour min 50 50 50 50 50 TiCN temperature ℃ 800 800 800 800 800 TiCN enter mbar 50 50 50 50 50 TiCN TiCl ₄ ml/min 4 4 4 4 4 TiCN N ₂ ml/min 15 15 15 15 15 TiCN _H2 ml/min bal. bal. bal. bal. bal. TiCN CH ₃ CN ml/min 0.5 0.5 0.5 0.5 0.5 AlTiN (second layer) hour min 30 30 30 40 40 AlTiN temperature ℃ 800 800 800 800 800 AlTiN enter mbar 5 5 5 5 5 AlTiN TiCl ₄ ml/min 3 4 3 4 3 AlTiN N ₂ ml/min 140 160 140 160 140 AlTiN _H2 ml/min Bal bal Bal bal Bal AlTiN CH ₃ CN ml/min 0.5 0.5 0.5 0.5 0.5 AlTiN AlCl ₃ ml/min 18 20 18 20 18 AlTiN NH ₃ ml/min 65 80 65 80 65 TiN hour min 10 TiN temperature ℃ 850 TiN enter mbar 5 TiN TiCl ₄ ml/min 8 TiN N ₂ ml/min 12 TiN _H2 ml/min 100 AlTiN hour min 7 AlTiN temperature ℃ 800 AlTiN enter mbar 5 AlTiN TiCl ₄ ml/min 4 AlTiN N ₂ ml/min 160 AlTiN _H2 ml/min bal AlTiN CH ₃ CN ml/min 0.5 AlTiN AlCl ₃ ml/min 20 AlTiN NH ₃ ml/min 80 TiN hour min 20 TiN temperature ℃ 850 TiN enter mbar 5 TiN TiCl ₄ ml/min 8 TiN N ₂ ml/min 12 TiN _H2 ml/min 100

Table 2 below shows the C content of the TiCN layer and preferentially grown crystal planes among the films of Example 1 and Comparative Examples 1 to 4. In Table 2, two preferentially grown crystal planes are described when the intensity of peaks appearing in X-ray diffraction analysis is similar.

1st floor Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 C content 0.7 or higher 0.7 or higher 0.7 or higher 0.7 or higher 0.7 or higher Preferential Growth Decision Plane (311),
(422) (311),
(422) (311),
(422) (311),
(422) (311),
(422)

Table 3 below shows the Al content (molar ratio) of the TiAlN layer among the films of Example 1 and Comparative Examples 1 to 4, preferentially grown crystal plane and thickness.

Table 3 below shows the Al content (molar ratio) of the TiAlN layer among the films of Example 1 and Comparative Examples 1 to 4, preferentially grown crystal plane and thickness. 2nd floor Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Al content 0.95, 0.92 0.94 0.92 0.93 0.92 Preferential Growth Decision Plane (111),
(200) (111) (200) (111) (200) Thickness (㎛) 6 5 5 6 6

Cutting performance evaluation

The wear resistance and chipping resistance of cutting tools having coatings prepared according to Example 1 and Comparative Examples 1 to 4 of the present invention were evaluated under the following evaluation conditions.

(1) Evaluation of wear resistance: wear on the insert flank, rake and crater

Work material: SCM440

Sample model number: SNMX1206ANN-MM

Cutting speed: 250m/min

Cutting feed: 0.15mm/tooth

Cutting Depth: 1.5mm

Coolant: none (dry)

(2) Evaluation of chipping resistance: Breakage of the cutting edge of the insert

Work material: SCM440

Sample model number: SNMX1206ANN-MM

Cutting speed: 180m/min

Cutting feed: 0.15mm/tooth

Cutting Depth: 2.0mm

Coolant: none (dry)

Table 4 below shows the samples and results evaluated for wear resistance and chipping resistance under the above conditions.

Example Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Wear resistance Machining time 35 minutes 25 minutes 20 minutes 30 minutes 27 minutes Chipping resistance Machining time 40 minutes 42 minutes 47 minutes 30 minutes 35 minutes

As confirmed in Table 4 above, the film according to Example 1 of the present invention has improved bonding strength through crystal orientation and thickness control between the AlTiN (111) and (200) plane layers, and the tool life is longer than that of comparative examples. Significantly improved.

100: parent material
200: lower layer
300: first layer
400: second layer

Claims (5)

As a film formed by the CVD method,
The film includes a first layer and a second layer formed on top of the first layer,
The first layer includes TiC _x N _y (x + y = 1, x>0, y>0) as a main phase, and has a peak of (311) plane and/or (422) plane in X-ray diffraction analysis Including a layer oriented so that the strength is greatest,
In the second layer, an A layer made of Ti _1-x Al _x C _1-y N _y (0.6≤x<1.0, 0≤y≤1) and a B layer made of TiN are formed by A/B/ Coating for cutting tools having a structure in which layers are alternately and repeatedly layered in A/B form. According to claim 1,
The A-layer is oriented so that the peak intensity of the (111) plane is the highest during X-ray diffraction analysis, and the peak intensity of the (200) plane is the highest during X-ray diffraction analysis. A coating for a cutting tool in which an oriented A-2 layer is disposed with the TiN layer interposed therebetween. According to claim 1,
The TiC _x N _y (x + y = 1, x>0, y>0) has an average particle size of 0.9 μm or less, a coating for a cutting tool. According to claim 1,
The layer A has a volume fraction of tissue having a face centered cubic structure (fcc) of 90 vol% or more, a coating for a cutting tool. According to claim 1,
A base layer is further included under the first layer, and the base layer includes TiN as a main phase.

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