JP6853450B2 - Surface coating cutting tool - Google Patents

Description

According to the present invention, even when cutting various types of steel, cast iron, etc. are performed under high load and low speed conditions in which the hard coating layer is prone to plastic deformation, the hard coating layer has excellent plastic deformation resistance and is long-term. The present invention relates to a surface-coated cutting tool (hereinafter referred to as a coated tool) that exhibits excellent wear resistance over its use.

Conventionally, generally, on the surface of a substrate (hereinafter, collectively referred to as a tool substrate) composed of a tungsten carbide (hereinafter, WC) -based cemented carbide or a titanium nitride (hereinafter, TiCN) -based cermet. ,
(A) The lower layer is a Ti carbide (hereinafter referred to as TiC) layer, a nitride (hereinafter, also indicated by TiN) layer, a carbonitride (hereinafter, indicated by TiCN) layer, and a carbon oxide (hereinafter, TiCO). A Ti compound layer consisting of one layer or two or more of the (shown) layer and the carbonitride oxide (hereinafter referred to as TiCNO) layer.
(B) The upper layer is an aluminum oxide layer (hereinafter referred to as Al ₂ O ₃ layer),
A covering tool in which a hard coating layer composed of the above (a) and (b) is formed by vapor deposition is known, but chipping resistance, chipping resistance, and chipping resistance and chipping resistance are determined according to the type of work material and cutting conditions. Various proposals have been made to improve tool performance such as peelability and abrasion resistance.

For example, in Patent Document 1, the surface of a WC-based cemented carbide substrate is coated with a composite hard layer composed of an inner layer of a titanium compound including at least one carbonitride layer of titanium and an outer layer of aluminum oxide. The carbonitride layer of titanium, which is at least one layer constituting the inner layer of the titanium compound, is a TiCN layer in which the maximum peak due to X-ray diffraction appears on the (220) plane, and the outer layer of aluminum oxide is a κ type. Abnormal damage due to peeling, abrasion, etc. occurs by using an aluminum oxide layer that is mainly composed of crystals and in _{which the maximum peak appears on the surface defined as the surface of κ-Al 2} O _{3 with a surface spacing of 2.79 angstrom in ASTM.} It has been proposed to prevent this and improve the tool life.
That is, by orienting the TiCN layer on the (220) plane, the adhesion with the substrate or the lower layer is increased, and peeling from the interface is less likely to occur, so that the occurrence of abnormal damage and shortening of life due to peeling are suppressed. be able to. Further, on the TiCN layer oriented to the (220) plane, an oxidation in which a maximum peak appears on a plane defined as a plane having a plane spacing of 2.79 angstrom of _{κ-Al 2} O _{3 mainly composed of κ type crystals in ASTM.} When coating the aluminum layer, κ-Al ₂ O ₃ showing the orientation of the distance 2.79 Å between the surfaces for the coating layer surface is smooth, abnormal damage hardly occurs due to friction between the chip and the tool , This aluminum oxide layer is less likely to cause abnormal damage and exhibits stable wear resistance.

Further, in Patent Document 2, in a coated tool in which an inner layer and an outer layer are coated on the surface of a tool substrate, the inner layer has a multi-layer structure having a titanium nitride layer having a thickness of 10 μm or more and a columnar structure, and the outer layer is at least. The layer includes the α-type aluminum oxide layer, and the orientation indexes TC (422) and TC (311) of the (422) plane and the (311) plane of the titanium nitride layer are both 1.3 or more and 3 or less. Orientation, orientation index TC (422) and TC
It has been proposed to improve the peel resistance, wear resistance, crater resistance, and fracture strength of the coated tool by setting the orientation index TC (hkl) excluding (311) to 1.5 or less. ing.
Here, by setting the orientation indices TC (422) and TC (311) of the titanium carbide layer to 1.3 or more and forming the structure into a columnar structure, the fracture resistance of the film can be improved even with a film thickness of 10 μm or more. It is possible to greatly improve and improve wear resistance, and it is possible to suppress the progress of wear due to chipping during cutting, and welding of the work material during cutting is less likely to occur, and as a result, cutting applied to the film. It is said that the peel resistance is greatly improved because the increase in stress can be prevented.

Further, Patent Document 3 describes an orientation index of the structure coefficient TC (hkl) of the titanium nitride layer in a coating tool in which a hard coating layer including at least one titanium nitride layer is formed on the surface of the substrate. When TC (220) is the maximum, the indentation hardness of the hardness reference piece is Hs, and the indentation hardness of the titanium nitride layer is Ht, (average value of Ht) / Hs ≧ 3, and the titanium nitride layer When the maximum value of the indentation hardness of is Htmax and the minimum value is Htmin, (Htmax-Htmin) / (average value of Ht) <0.5, the crystal orientation of the titanium nitride layer is controlled, and the charcoal is used. It has been proposed to improve the wear resistance and fracture resistance of the coated tool by eliminating the variation in the hardness of the titanium nitride layer.

Japanese Unexamined Patent Publication No. 8-300203 Japanese Patent No. 11-140647 Japanese Patent No. 5729777

In recent years, the performance of cutting equipment has been remarkably improved, while there is a strong demand for labor saving, energy saving, and cost reduction for cutting. Along with this, the cutting process becomes more efficient, and a high load tends to act on the cutting edge due to heavy cutting such as high cutting and high feed, intermittent cutting, and the like. There is no problem when the above-mentioned conventional covering tool is used for continuous cutting and high-speed cutting under normal conditions such as steel and cast iron, but the conventional covering tool is used as a hard coating layer due to the action of a high load. When used under high-load, low-speed cutting conditions that cause plastic deformation, the plastic deformation of the hard coating layer tends to cause the crystal grains that make up the hard coating layer to fall off, which is also the cause. Abnormal wear is likely to progress, which causes a problem that the tool life is reached in a relatively short time.

Therefore, from the above viewpoint, the present inventors consider that even when the hard coating layer is used under high load and low speed cutting conditions in which a high load acts on the cutting edge and the hard coating layer is likely to undergo plastic deformation. As a result of intensive research on the structure of the hard coating layer that is less likely to cause abnormal damage, the hard coating layer is composed of a lower layer made of a Ti compound layer and an upper layer made of an Al ₂ O ₃ layer, and the lower layer is formed. When at least one Ti carbonitride (hereinafter, also referred to as “TiCN”) layer is provided as the constituent Ti compound layer and the (200) orientation of the TiCN layer is enhanced, the height is high. Even if a load (particularly, a large shearing force on the surface of the TiCN layer) acts, the TiCN layer exhibits excellent plastic deformation resistance, and as a result, abnormal damage such as dropping of crystal grains constituting the TiCN layer occurs. It was found that it can be suppressed and that the wear resistance can be improved by this.
Further, when the TiCN layer is formed as a columnar vertically elongated structure having an aspect ratio of 5 or more, in addition to excellent plastic deformation resistance, it exhibits further excellent wear resistance brought about by the columnar vertically elongated structure. I found it.

The present invention has been made based on the above findings.
"(1) In a surface-coated cutting tool in which a hard coating layer is formed on the surface of a tool substrate composed of a tungsten carbide-based cemented carbide or a titanium nitride-based cermet.
(A) The hard coating layer is composed of at least a lower layer and an upper layer.
(B) The lower layer is composed of one layer or two or more layers selected from a carbide layer of Ti, a nitride layer, a carbonitride layer, a carbon oxide layer, a carbonitride oxide layer and a composite nitride layer of Ti and Al. It becomes, and at least one layer of which consists of Ti compound layer having a total average layer thickness of 2~15μm comprised of carbonitride layer of Ti having an average layer thickness of more than 1.7 [mu] m,
(C) The upper layer is composed of an aluminum oxide layer having an average layer thickness of 1 to 15 μm.
(D) At least one Ti carbonitride layer in the lower Ti compound layer has a maximum diffraction peak intensity due to X-ray diffraction on the (200) plane, and has an orientation index Tc (200). A surface coating cutting tool characterized by being 2.0 or more.
(2) In the vertical cross section of the Ti compound layer, the area ratio of the crystal grains made of Ti carbonitride having a columnar longitudinal structure having an aspect ratio of 5 or more is 70 area% or more. The surface coating cutting tool according to (1).
(3) The surface coating cutting tool according to (1) or (2), wherein in the Ti compound layer, the layer thickness of all Ti carbonitride layers is 1.7 to 13.5 μm. "

Next, the covering tool of the present invention will be described in detail.
Hard layer of the coated tool of the present invention includes at least a lower layer comprising a Ti compound layer, composed of an upper layer from the Al ₂ O ₃ layer.

Lower layer:
The lower layer composed of the Ti compound layer (for example, TiC layer, TiN layer, TiCN layer, TiCO layer , TiCNO layer and TiAlN layer ) imparts high temperature strength to the hard coating layer by its own excellent high temperature strength. .. Further, the Ti compound layer adheres to both the surface of the tool substrate and the _{upper layer composed of the Al 2} O ₃ layer, and has an effect of maintaining the adhesion of the hard coating layer to the tool substrate.
However, when the total average layer thickness of the Ti compound layer is less than 2 μm, the above-mentioned action cannot be sufficiently exerted.
On the other hand, the lower layer of the present invention has excellent plastic deformation resistance as described later, but when the total average layer thickness of the lower layer exceeds 15 μm, plastic deformation is caused by a high load acting during cutting. As a result, it causes the occurrence of falling off of crystal grains, the occurrence of chipping, chipping, peeling, or the occurrence of abnormal damage such as the progress of uneven wear.
Therefore, in the present invention, the total average layer thickness of the lower layer composed of the Ti compound layer is set to 2 to 15 μm.

Lower TiCN layer:
As described above, the lower layer of the hard coating layer of the coating tool of the present invention is composed of a Ti compound layer, and the lower layer contains at least one TiCN layer, and the layer has (200) orientation. It is configured as a TiCN layer having.
That is, when the diffraction peak intensities from each crystal lattice plane are measured by X-ray diffraction for the crystal grains constituting the TiCN layer of at least one of the lower layers, the maximum diffraction peak intensity appears on the (200) plane (200). 200) Has orientation.
FIG. 1 shows an example of a chart of diffraction peak intensities from each crystal lattice surface measured by X-ray diffraction for the TiCN layer of the coating tool of the present invention.
As is clear from FIG. 1, it can be seen that the TiCN layer of the coating tool of the present invention has the maximum diffraction peak intensity for the (200) plane as compared with the peak strength of the other crystal lattice planes.
The X-ray diffraction was measured by the 2θ-θ method using CuKα rays using PANalytical Empyrene of Spectris as an X-ray diffractometer, and the measurement conditions were: measurement range (2θ): 30 to 130 degrees, X-ray output: The measurement was performed under the conditions of 45 kV, 40 mA, divergence slit: 0.5 degrees, scan step: 0.013 degrees, and measurement time per step: 0.48 sec / step.

上記式中、Ｉ（ｈｋｌ）は測定された（ｈｋｌ）面のピーク強度（回折強度）を示し、Ｉ_０（ｈｋｌ）はＪＣＰＤＳカード（Ｊｏｉｎｔ Ｃｏｍｍｉｔｔｅｅ ｏｎ Ｐｏｗｄｅｒ Ｄｉｆｆｒａｃｔｉｏｎ Ｓｔａｎｄａｒｄｓ（粉末Ｘ線回折標準））で表される（ｈｋｌ）面を構成するＴｉＣとＴｉＮの粉末回折強度の平均値を示す。また、（ｈｋｌ）は、（１１１）、（２００）、（２２０）、（３１１）、（２２２）、（３３１）、（４２０）、（４２２）の８面であり、上記式の中括弧内は８面の平均値を示す。 Further, when the orientation index Tc (hkl) is determined for at least one TiCN layer, the coating tool of the present invention shows a Tc (200) value of 2.0 or more, preferably 3.0 or more. (200) Has orientation.
The orientation index Tc (hkl) is defined by the following equation.

In the above formula, I (hkl) indicates the peak intensity (diffraction intensity) of the measured (hkl) plane, and I ₀ (hkl) is a JCPDS card (Joint Committee on Power Diffraction Standards). The average value of the powder diffraction intensities of TiC and TiN constituting the represented (hkl) plane is shown. Further, (hkl) is the eight surfaces of (111), (200), (220), (311), (222), (331), (420), and (422), and is in the curly braces of the above equation. Indicates the average value of 8 planes.

As described above, at least one TiCN layer of the coating tool of the present invention shows the maximum peak intensity by X-ray diffraction on the (200) plane, and the orientation index Tc (200) ≥ 2.0 (200) orientation. Due to its properties, even when a large shearing force acts on the TiCN layer during cutting, the TiCN layer has plastic deformation resistance, so that the crystal grains constituting the layer fall off, resulting in chipping, chipping, and so on. It is possible to suppress the occurrence of peeling or the occurrence of abnormal damage such as the progress of uneven wear, and thereby the wear resistance can be improved.
However, when the X-ray diffraction peak intensity for the (200) plane cannot be said to be the maximum as compared with the diffraction peak intensity from other lattice planes, or the orientation index Tc (200) is less than 2.0. In such a case, (200) the plane orientation is not sufficient, so that the effect of improving the plastic deformation resistance is not sufficient, and as a result, the particles are prevented from falling off when a high load (high shear force) is applied. It is not possible to suppress the occurrence of chipping / chipping and uneven wear.
Therefore, in the present invention, the X-ray diffraction peak intensity of the (200) plane measured for at least one TiCN layer of the lower layer is the maximum as compared with the peak intensity of the other crystal lattice planes. The orientation index Tc (200) was determined to be 2.0 or more, preferably 3.0 or more.

At least one TiCN layer in the lower layer preferably has a columnar longitudinal structure.
In particular, the area ratio of the columnar vertically elongated TiCN crystal grains having an aspect ratio of 5 or more obtained from the maximum particle width W of the TiCN crystal grains and the maximum particle length L in the layer thickness direction is 70 of the vertical cross-sectional area of the TiCN layer. When it occupies an area% or more, it can be expected to have an excellent effect of improving wear resistance, which is a characteristic of columnar vertically long structures.
The maximum particle width W and the maximum particle length L are the crystal grains in the direction perpendicular to the layer thickness direction when one crystal grain in the vertical cross section of the TiCN layer is measured for the columnar vertically elongated TiCN crystal grains. The largest value in the width (short side) is called the maximum grain width W, while the largest value in the height (long side) of the crystal grains in the layer thickness direction is called the maximum particle length L.
Further, the layer thickness of the TiCN layer is not particularly limited, but it is desirable that the layer thickness of all the TiCN layers constituting the Ti compound layer is 1.7 to 13.5 μm.
This is because when the thickness of the TiCN layer is 1.7 μm or more, the value of Tc (200) tends to increase, the plastic deformation resistance in high-load cutting is improved, and the amount of flank wear is also reduced. This is because the wear resistance is improved, and on the other hand, when the layer thickness of the TiCN layer exceeds 13.5 μm, plastic deformation is likely to occur, and abnormal damage due to the progress of uneven wear occurs.

Film formation of TiCN layer:
The lower Ti compound layer in the present invention is formed, for example, as follows.
That is, various Ti compound layers including one or more of the TiC layer, the TiN layer, the TiCN layer, the TiCO layer, the TiCNO layer and the TiAlN layer are vapor-deposited and formed by using a normal chemical vapor deposition apparatus.
Among them, (200) a TiCN layer having high orientation or a TiCN layer in which crystal grains having a columnar longitudinal structure having an aspect ratio of 5 or more occupy 70 area% or more of the vertical cross section of the lower layer is, for example, the following. It can be formed by the vapor deposition method of.
Reaction gas composition (% by volume): TiCl ₄ 1-5%, CH ₃ CN 0.5-1.5%, N ₂ 25-40%, balance H ₂ ,
Reaction atmosphere temperature: 750 to 850 ° C,
Reaction atmosphere pressure: 5-10 kPa
By lowering the reaction atmosphere temperature and lowering the gas concentration ratio that is the raw material of the TiCN layer, (200) a highly oriented crystal structure is likely to be formed, and the structure is likely to have a columnar vertically elongated structure.
Also, when forming the TiN layer, for example,
Reaction gas composition (volume%): NH ₃ 0.5 to 2.0%, TiCl ₄ 0.1 to 0.3%, N _{20 to} 10%, balance H ₂ ,
Reaction atmosphere temperature: 750 to 850 ° C,
Reaction atmosphere pressure: 5-8 kPa
By producing under the above conditions, it becomes easy to form crystal grains having a columnar vertically long structure having an aspect ratio of 5 or more.

Upper layer consisting of Al ₂ O _{3 layers:}
The upper layer of the coating tool of the present invention is a lower layer including a TiCN layer having a maximum peak intensity by X-ray diffraction on the (200) plane and having an orientation index Tc (200) of 2.0 or more. on the surface by conventional chemical vapor deposition, is formed by depositing the _{the Al} 2 _{O 3} layer having an average layer thickness of 1 to 15 m.
Al ₂ O ₃ has various crystal structures such as α-type, κ-type, and γ-type, but it has excellent high-temperature hardness, oxidation resistance, and excellent thermal stability. From the above points, the _{α-type Al 2} O ₃ layer having an α-type crystal structure is desirable _{as the Al 2} O _{3 layer constituting the upper layer.}
For example, when forming an α-type Al ₂ O _{3 layer,}
Reaction gas composition (% by volume): AlCl ₃ 2-5%, CO ₂ 10-20%, HCl 1-3%, H ₂ S 0-0.15%, balance H ₂ ,
Reaction atmosphere temperature: 850-950 ° C,
Reaction atmosphere pressure: 5-10 kPa
It is manufactured under the following conditions.
Further, if the average layer thickness of the upper layer is less than 1 μm, wear resistance over a long period of use cannot be ensured, while if the average layer thickness exceeds 15 μm, Al ₂ O ₃ crystal grains are coarse. As a result, in addition to the decrease in high-temperature hardness and high-temperature strength, the chipping resistance and fracture resistance during high-load cutting, in which a large shearing force acts on the cutting edge, are reduced, so that the average layer thickness is reduced. Was set to 1 to 15 μm.

According to coated tool of the present invention, the hard coating layer formed on the surface of the tool substrate comprises an upper layer comprising a lower layer and the Al ₂ O ₃ layer consisting of at least a Ti compound layer, at least one of the lower layer The layer is composed of a TiCN layer, and the TiCN layer has a maximum diffraction peak intensity due to X-ray diffraction on the (200) plane and an orientation index Tc (200) of 2.0 or more. The layer has excellent plastic deformation resistance.
As a result, even when used under high load and low speed cutting conditions in which a large shearing force acts on the surface of the TiCN layer, the coating tool of the present invention has the excellent plastic deformation resistance of the TiCN layer, so that the crystal grains fall off. It is possible to suppress the occurrence of abnormal damage such as chipping, chipping, and peeling, and in combination with the excellent high-temperature hardness, oxidation resistance, and thermal stability of the upper layer composed of _{Al 2} O _{3 layers,} It exhibits excellent wear resistance over a long period of use, and is particularly effective for work materials such as carbon steel and alloy steel, which are easily affected by the progress of wear on the rake face.
Further, the wear resistance can be further improved by setting the area ratio of the crystal grains having a columnar longitudinal structure having an aspect ratio of 5 or more in the lower layer to 70 area% or more of the vertical cross section of the lower layer. , The life of the cutting tool can be extended.

An example of the diffraction peak intensity obtained from each crystal lattice plane measured by X-ray diffraction is shown for the TiCN layer of the coating tool of the present invention.

Embodiments of the covering tool of the present invention will be specifically described based on examples.

As raw material powders, both WC powder having an average particle size of 1 to 3 [mu] m, TiC powder, ZrC powder, NbC powder, _Cr 3 _{C 2} powder, TiN powder, and Co powder was prepared, these raw powders, Table 1 After blending to the compounding composition shown in (1), wax is further added, the mixture is ball-mill mixed in acetone for 24 hours, dried under reduced pressure, and then press-molded into a green compact having a predetermined shape at a pressure of 98 MPa, and the green compact is 5 Pa. Vacuum sintered in vacuum at a predetermined temperature within the range of 1370 to 1470 ° C. under the condition of holding for 1 hour, and after sintering, a tool base a to WC-based superhard alloy having an insert shape of ISO standard CNMG120408. d was manufactured respectively.

Further, as the raw material powder, both (TiC / TiN = 50/50 in mass ratio) TiCN having an average particle diameter of 0.5~2μm powder, ZrC powder, TaC powder, Mo ₂ C powder, WC powder, Co powder And Ni powder are prepared, these raw material powders are blended into the compounding composition shown in Table 2, wet-mixed with a ball mill for 24 hours, dried, and then press-molded into a green compact at a pressure of 98 MPa. The body was sintered in a nitrogen atmosphere of 1.3 kPa at a temperature of 1500 ° C. for 1 hour, and after sintering, a tool base e made of TiCN-based cermet having an insert shape of ISO standard CNMG120412 was prepared.

Then, each of these tool substrates a to d and the tool substrate e is charged into a normal chemical vapor deposition apparatus, and under the conditions shown in Tables 3 and 4, as a lower layer of the target layer thickness shown in Table 6. the Ti compound layer is vapor deposited, and then, under the conditions shown in Table 3, by depositing form the Al ₂ O ₃ layer as an upper layer of the target layer thicknesses shown in Table 6, the present as shown in Table 6 Invention covering tools 1 to 13 were manufactured, respectively.
The HT-TiCN layer shown in Table 3 shows a TiCN layer prepared at a reaction atmosphere temperature higher than that of the TiCN layer shown in paragraph 0016.
Further, in Table 3, the film forming conditions of the Ti compound layer in which crystal grains having a columnar longitudinal structure having an aspect ratio of 5 or more are likely to be formed are TiN layer-1 (first layer) and TiAlN layer.

Further, for the purpose of comparison, each of the tool substrates a to d and the tool substrate e is charged into a normal chemical vapor deposition apparatus, and the target layer thickness shown in Table 7 is obtained under the conditions shown in Tables 3 and 5. the Ti compound layer as a lower layer was vapor deposited and then, under the conditions shown in Table 3, the the Al ₂ O ₃ layer as an upper layer of the target layer thicknesses shown in Table 7 by depositing formed, in Table 7 The shown comparative examples covering tools 1 to 13 were manufactured, respectively.

The diffraction peak intensities from each lattice surface were measured by X-ray diffraction for the TiCN layer of the lower layer of the covering tools 1 to 13 of the present invention and the comparative covering tools 1 to 13.
FIG. 1 shows a chart obtained for the covering tool 1 of the present invention.
The X-ray diffraction was measured by the 2θ-θ method using CuKα rays using PANalytical Empylean manufactured by Spectris as an apparatus.
The measurement conditions are measurement range (2θ): 30 to 130 degrees, X-ray output: 45 kV, 40 mA, divergence slit: 0.5 degrees, scan step: 0.013 degrees, measurement time per step: 0.48 sec / step. Is.
From the chart obtained above, it was determined whether or not the diffraction peak intensity from the (200) plane was the maximum with respect to the diffraction peak intensity from the other lattice planes.
Tables 6 and 7 show the determination results.

の式によって算出した。
ここで、Ｉ（ｈｋｌ）は測定された（ｈｋｌ）面の回折ピーク強度を示し、Ｉ_０（ｈｋｌ）はＪＣＰＤＳカード（Ｊｏｉｎｔ Ｃｏｍｍｉｔｔｅｅ ｏｎ Ｐｏｗｄｅｒ Ｄｉｆｆｒａｃｔｉｏｎ Ｓｔａｎｄａｒｄｓ（粉末Ｘ線回折標準））で表される（ｈｋｌ）面を構成するＴｉＣとＴｉＮの粉末回折強度の平均値を示す。また、（ｈｋｌ）は、（１１１）、（２００）、（２２０）、（３１１）、（２２２）、（３３１）、（４２０）、（４２２）の８面である。
表６、表７に、上記で算出した配向性指数Ｔｃ（２００）の値を示す。 Further, the orientation index Tc (200) was determined based on the measurement result of the diffraction peak intensity.
The orientation index Tc (200) is

It was calculated by the formula of.
Here, I (hkl) indicates the diffraction peak intensity of the measured (hkl) plane, and I ₀ (hkl) is represented by a JCPDS card (Joint Committee on Powder Diffraction Standards) (powder X-ray diffraction standard). The average value of the powder diffraction intensities of TiC and TiN constituting the hkl) plane is shown. Further, (hkl) has eight surfaces of (111), (200), (220), (311), (222), (331), (420), and (422).
Tables 6 and 7 show the values of the orientation index Tc (200) calculated above.

Further, the vertical cross section of the TiCN layer in the lower layer of the covering tools 1 to 13 of the present invention and the comparative covering tools 1 to 13 is 10 μm in the direction parallel to the tool substrate using a scanning electron microscope (magnification: 5000 times). The maximum particle width W and the maximum particle length L are measured for each of the TiCN crystal grains existing in the region at the height of the layer thickness of the TiCN layer in the direction perpendicular to the substrate, and the values of the aspect ratio L / W are measured. The area ratio of the crystal grains having an aspect ratio L / W of 5 or more to the vertical cross section of the TiCN layer was determined.
Tables 6 and 7 show the area ratios obtained above.

Further, when the thickness of each constituent layer of the hard coating layer of the coating tools 1 to 13 of the present invention and the coating tools 1 to 13 of the comparative example was measured using a scanning electron microscope (longitudinal cross-sectional measurement), all of them were the target layers. The average layer thickness (average value of 5-point measurement) substantially the same as the thickness was shown.

Next, with respect to the various covering tools of the covering tools 1 to 13 of the present invention and the covering tools 1 to 13 of the comparative example, the following cutting conditions are obtained while all of them are screwed to the tip of the tool steel cutting tool with a fixing jig. A cutting test was carried out under A and cutting condition B.
≪Cutting condition A≫
Work material: S45C
Cutting speed: 200 m / min,
Notch: 3.0 mm,
Feed: 0.4 mm / rev,
Cutting time: Dry continuous high depth cutting test of carbon steel round bar under the condition of 5 minutes,
≪Cutting condition B≫
Work Material: SCM440
Cutting speed: 250 m / min,
Notch: 2.0 mm,
Feed: 0.3mm / rev,
Cutting time: Wet intermittent cutting test of alloy steel 4-slit material under the condition of 5 minutes,
The flank wear width of the cutting edge in the above cutting test was measured, and the occurrence of abnormal damage such as chipping, chipping, and peeling was observed with the naked eye.
Tables 8 and 9 show the test results.

From the results shown in Tables 8 and 9, in the coating tools 1 to 13 of the present invention, since the TiCN layer having excellent plastic deformation resistance is present in the lower layer, the TiCN crystal grains fall off, and the chipping caused by this, Demonstrates excellent wear resistance without occurrence of chipping or peeling.
On the other hand, the covering tools 1 to 13 of Comparative Examples have a relatively short service life due to abnormal damage such as falling off of TiCN crystal grains, chipping, chipping, and peeling in high-load / low-speed cutting. It is clear that it will reach.

As described above, the covering tool of the present invention exhibits particularly excellent cutting performance in high-load and low-speed cutting in which a high load (large shear force) acts on the cutting edge, but under normal conditions such as various steels and cast iron. Of course, it can also be used for continuous cutting and intermittent cutting.

Claims (3)

In a surface-coated cutting tool in which a hard coating layer is formed on the surface of a tool substrate composed of a tungsten carbide-based cemented carbide or a titanium nitride-based cermet.
(A) The hard coating layer is composed of at least a lower layer and an upper layer.
(B) The lower layer is composed of one layer or two or more layers selected from a carbide layer of Ti, a nitride layer, a carbonitride layer, a carbon oxide layer, a carbonitride oxide layer and a composite nitride layer of Ti and Al. It becomes, and at least one layer of which consists of Ti compound layer having a total average layer thickness of 2~15μm comprised of carbonitride layer of Ti having an average layer thickness of more than 1.7 [mu] m,
(C) The upper layer is composed of an aluminum oxide layer having an average layer thickness of 1 to 15 μm.
(D) At least one Ti carbonitride layer in the lower Ti compound layer has a maximum diffraction peak intensity due to X-ray diffraction on the (200) plane, and has an orientation index Tc (200). A surface coating cutting tool characterized by being 2.0 or more. Claim 1 is characterized in that, in the vertical cross section of the Ti compound layer, the area ratio of the crystal grains made of Ti carbonitride having a columnar longitudinal structure having an aspect ratio of 5 or more is 70 area% or more. Surface coating cutting tool described in. The surface coating cutting tool according to claim 1 or 2, wherein in the Ti compound layer, the layer thickness of all Ti carbonitride layers is 1.7 to 13.5 μm.

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