JP5590335B2 - Surface coated cutting tool with excellent chipping resistance and chipping resistance with excellent hard coating layer - Google Patents

Description

  The present invention has high chipping resistance and chipping resistance with a hard coating layer in high-speed intermittent cutting of various steels and cast irons that are accompanied by high heat generation and intermittent and impact loads are applied to the cutting edge. Thus, the present invention relates to a surface-coated cutting tool (hereinafter referred to as a coated tool) that exhibits excellent cutting performance over a long period of use.

Conventionally, generally on the surface of a substrate (hereinafter collectively referred to as a tool substrate) composed of a tungsten carbide (hereinafter referred to as WC) -based cemented carbide or titanium carbonitride (hereinafter referred to as TiCN) -based cermet. ,
(A) Ti carbide (hereinafter referred to as TiC) layer, nitride (hereinafter also referred to as TiN) layer, carbonitride (hereinafter referred to as TiCN) layer formed by chemical vapor deposition of the lower layers. A Ti compound layer composed of one or more of a carbon oxide (hereinafter referred to as TiCO) layer and a carbonitride oxide (hereinafter referred to as TiCNO) layer,
(B) an aluminum oxide (hereinafter referred to as Al ₂ O ₃ ) layer in which the upper layer is formed by chemical vapor deposition;
A coated tool formed by forming a hard coating layer composed of (a) and (b) above is known, and this coated tool is known to be used for cutting various steels and cast irons. It has been.

  However, the above-mentioned coated tool has a problem that chipping, chipping, etc. are likely to occur under cutting conditions in which a heavy load is applied to the cutting edge, and the tool life is short-lived. Proposals have been made.

  For example, in Patent Document 1, in the lower layer in which the first layer in contact with the substrate is TiN and the second layer is TiCN, the thickness of the second layer is 60% or more of the total thickness, and the particles The average particle size in the horizontal direction is 0.3 to 1.2 μm, and the average particle size in the vertical direction is at least 2.5 times the average particle size in the horizontal direction. It has been proposed to increase chipping and wear resistance.

  In Patent Document 2, at least a columnar TiCN layer is formed as a Ti compound layer as a lower layer, and the TiCN columnar shape is located at a distance of 1/5 of the thickness of the TiCN layer from the upper end of the TiCN layer. The ratio between the horizontal average grain size d1 of the crystal grains and the horizontal average grain size d2 of the TiCN columnar crystal grains at a position 2/5 of the thickness of the TiCN layer from the lower end of the TiCN layer is 1 ≦ By setting d1 / d2 ≦ 1.3 and d1 = 0.2 to 1.5 μm, both wear resistance and fracture resistance are excellent, and fracture resistance in long-time cutting including intermittent cutting is achieved. It has been proposed to improve wear resistance.

Further, in Patent Document 3, in a coated tool having at least a TiCN layer and an Al ₂ O ₃ layer as a hard coating layer, the TiCN layer is composed of a lower TiCN layer and an upper TiCN layer, and the film thickness of the lower TiCN layer. t1 is 1 μm ≦ t1 ≦ 10 μm, the film thickness t2 of the upper TiCN layer is 0.5 μm ≦ t2 ≦ 5 μm, and satisfies the relationship of 1 <t1 / t2 ≦ 5. Further, TiCN particles of the upper TiCN layer The average crystal width w2 is 0.2 to 1.5 μm, and the average crystal width w1 of the TiCN particles of the lower TiCN layer is 0.7 times or less of w2, thereby improving the adhesion of the hard coating layer, It has been proposed to prevent delamination and improve fracture resistance and wear resistance in intermittent cutting and the like.

Japanese Patent Laid-Open No. 10-15711 JP-A-10-109206 JP 2005-186221 A

  In recent years, there is a strong demand for energy saving and energy saving in cutting, and with this, the coated tool has come to be used under more severe conditions. Even when a coated tool is used for high-speed interrupted cutting that is accompanied by high heat generation and more intermittent and impact loads are applied to the cutting edge, the mechanical impact resistance and thermal shock resistance of the lower layer Therefore, chipping and chipping are likely to occur on the cutting edge due to a high load during cutting, and as a result, the service life is reached in a relatively short time.

  In view of the above, the inventors of the present invention have an excellent hard coating layer even when used in high-speed intermittent cutting with high heat generation and intermittent and impact loads acting on the cutting edge. As a result of earnest research on coated tools that have excellent shock absorption and, as a result, excellent chipping resistance and fracture resistance over a long period of use, the following knowledge has been obtained.

  That is, the present inventors proceeded with studies on the pore distribution form of the hard coating layer of the coated tool, particularly the Ti carbonitride (hereinafter referred to as TiCN) layer of the Ti compound constituting the lower layer. However, the high-temperature strength of the TiCN layer is not achieved by uniformly forming the microvoids formed in the lower layer of the hard coating layer made of the TiCN layer in the TiCN layer, but by dispersing it in a regular and inhomogeneous manner. It was found that the mechanical and thermal impact resistance can be improved without causing a decrease in hardness at high temperature.

  And the TiCN layer (henceforth a modified TiCN layer) provided with the said void | hole distribution form can be formed into a film by the following chemical vapor deposition methods, for example.

For example, after depositing a TiN layer as one of the Ti compound layers constituting the lower layer on the tool base surface,
(A) A TiCN layer is deposited on the TiN layer using a TiCl ₄ —CH ₃ CN—N ₂ —H ₂ -based reactive gas,
(B) In the film forming process of (a), the introduction of the reactive gas is stopped, and at the same time, SF ₆ -based gas is introduced to perform SF ₆ etching,
(C) Next, the step (a) and the step (b) are repeated to form a TiCN layer having a target thickness.

  According to the above (a) to (c), a modified TiCN layer is formed as one of the Ti compound layers constituting the lower layer. When the surface texture of the modified TiCN layer is observed with a scanning electron microscope, It is confirmed that micropores having a pore diameter of 2 to 30 nm are formed, and the micropore density has a pore distribution form that periodically changes along the layer thickness direction.

  The coated tool of the present invention in which the modified TiCN layer having the pore distribution form is deposited as at least one of the Ti compound layers constituting the lower layer of the hard coating layer is accompanied by high heat generation, and Even when used for high-speed intermittent cutting of steel and cast iron where intermittent and impact loads are applied to the cutting edge, the hard coating layer has excellent chipping resistance and fracture resistance, and excellent wear resistance over a long period of use. It was found that it can be demonstrated.

The present invention has been made based on the above findings,
“(1) On the surface of a tool base made of tungsten carbide-based cemented carbide or titanium carbonitride-based cermet,
(A) The lower layer includes a Ti compound layer including at least a Ti carbonitride layer and having a total average layer thickness of 3 to 20 μm,
(B) the upper layer is an aluminum oxide layer having an average layer thickness of 1 to 25 μm;
In the surface-coated cutting tool obtained by chemical vapor deposition of the hard coating layer comprising the above (a) and (b),
Inside the at least one Ti carbonitride layer constituting the lower layer (a), micropores having a pore diameter of 2 to 30 nm are formed, and at least one constituting the lower layer (a) When the Ti carbonitride layer of the layer is divided into a thickness width region of 0.1 μm parallel to the tool substrate surface, and the micropore density existing in the thickness width region is measured,
A thickness width region having a micropore density of 200 to 500 / μm ² and a thickness width region having a micropore density of 0 to 20 / μm ² are alternately arranged along the thickness direction of the lower layer. A surface-coated cutting tool characterized by having a pore distribution form in which the fine pore density in the lower layer changes periodically along the layer thickness direction by forming at least a plurality of regions.
(2) The vacancy density in the at least one Ti carbonitride layer constituting the lower layer of (a) is periodically changed along the layer thickness direction with a period of 0.5 μm to 5 μm. The surface-coated cutting tool according to (1), which has a hole distribution form. "
It has the characteristics.

The present invention will be described in detail below.
Lower Ti compound layer:
The lower layer composed of one or two or more Ti compound layers of Ti carbide layer, nitride layer, carbonitride layer, carbonate layer and carbonitride layer is formed under normal chemical vapor deposition conditions. In addition to having high-temperature strength, the hard coating layer has high-temperature strength by itself, and it adheres firmly to both the tool base and the upper layer made of Al ₂ O _3. Thus, it is already well known that the hard coating layer has an action that contributes to improving the adhesion to the tool substrate, but at least one modified TiCN layer constituting the lower layer of the present invention, that is, with a pore diameter of 2 to 2. The lower layer in which fine pores of 30 nm are dispersed and distributed in a predetermined distribution form in the modified TiCN layer has a cutting edge exposed to a high temperature, and in high-speed intermittent cutting that receives mechanical and thermal shock. Has excellent high-temperature strength, Comprising a temperature hardness, at the same time, excellent chipping resistance, exhibits chipping resistance. If the total average layer thickness is less than 3 μm, the above-mentioned effect cannot be sufficiently exhibited. On the other hand, if the total average layer thickness exceeds 20 μm, chipping tends to occur. It was determined to be 3 to 20 μm.
Upper layer Al ₂ O ₃ layer:
Al ₂ O ₃ layer constituting the upper layer is already well known to have high temperature hardness and heat resistance, but if the average layer thickness is less than 1 μm, it will ensure wear resistance over a long period of use. On the other hand, if the average layer thickness exceeds 25 μm, the Al ₂ O ₃ crystal grains are likely to be coarsened. As a result, in addition to a decrease in high-temperature hardness and high-temperature strength, resistance to high-speed intermittent cutting is also improved. Since the chipping property and chipping resistance are lowered, the average layer thickness is set to 1 to 25 μm.
Deposition of modified TiCN layer contained in lower layer:
The modified TiCN layer of the present invention can be formed as at least one lower layer composed of a Ti compound layer formed under normal chemical vapor deposition conditions.
For example, using normal chemical vapor deposition equipment,
Reaction gas composition (volume%):
TiCl ₄ : 4 to 5%,
N _2: 30~40%,
H ₂ : residual reaction atmosphere temperature: 850 to 950 ° C.,
Reaction atmosphere pressure: 10-30 kPa,
After depositing a TiN layer having a predetermined thickness under the conditions of
(A) On the surface of the TiN layer,
Reaction gas composition (volume%):
TiCl ₄ : 1-3%
CH ₃ CN: 0.5~1.5%,
N _2: 5~15%,
H ₂ : residual reaction atmosphere temperature: 850 to 930 ° C.,
Reaction atmosphere pressure: 5 to 20 kPa,
(B) Then, the introduction of the reaction gas was stopped, and instead, SF ₆ gas was added so that the gas composition was 5 to 10% by volume. ₂ gases are introduced, and this SF ₆ gas causes the following conditions:
Reaction gas composition (volume%):
SF ₆ : 5 to 10%,
H ₂ : residual reaction atmosphere temperature: 800 to 1050 ° C.
Reaction atmosphere pressure: 4 to 27 kPa,
The SF ₆ etching is performed for 5 to 30 minutes under the above conditions.
(C) Next, the introduction of the SF ₆ -based gas is stopped, the reaction gas (a) is introduced into the apparatus, and a TiCN layer is formed again by vapor deposition under the same conditions as (a).

  The above steps (b) and (c) are repeated, and finally a modified TiCN layer having a target layer thickness is formed by vapor deposition.

Thereafter, a Ti compound layer required as a lower layer is formed to form a lower layer having a target layer thickness, and an Al ₂ O ₃ layer, which is an upper layer, is deposited on the upper layer by vapor deposition. By doing so, a hard coating layer is formed.
Pore distribution form of modified TiCN layer contained in lower layer:
FIG. 1 shows a schematic diagram of the pore distribution form of the modified TiCN layer included in the lower layer of the present invention formed under the above chemical vapor deposition conditions.

  As shown in FIG. 1, in the modified TiCN layer included in the lower layer of the present invention, there are a plurality of regions each having a high density of pores having a pore diameter of 2 to 30 nm and a region having a low pore density. In addition, the plurality of high-density micro-hole regions and the low-density micro-hole regions have a hole distribution form in which the micro-hole density changes periodically along the layer thickness direction.

  This will be described in more detail with reference to FIG.

  FIG. 2 is a pore distribution pattern diagram showing the correlation between the position in the layer thickness direction and the minute hole density in the modified TiCN layer included in the lower layer having the hole distribution pattern of the present invention formed under the chemical vapor deposition conditions. Indicates.

  This hole distribution pattern can be obtained by the following method.

First, the lower layer is divided into thickness width regions of 0.1 μm parallel to the tool base surface (in FIG. 3, the sections partitioned by a plurality of parallel lines drawn parallel to the tool base surface are 0. This corresponds to a thickness width region of 1 μm.), The number of fine pores having a diameter of 2 to 30 nm existing in each divided thickness width region was measured over a total length of 10 μm, and a scanning electron microscope (magnification 50000 times) was measured. Measured to obtain the micropore density (pieces / μm ² ) existing in the thickness region of 0.1 μm, and graph the micropore density obtained in each thickness region along the layer thickness direction. By doing so, the hole distribution form figure of the layer thickness direction shown as FIG. 2 is created.

Then, according to the pore distribution pattern of the modified TiCN layer included in the lower layer of the present invention, in the layer thickness direction pore distribution pattern, the micropore density is a maximum value (200 to 500 / μm ² ). A thickness width region that is within the range) and a thickness width region in which the micropore density is a minimum value (within a range of 0 to 20 / μm ² ) are periodically and along the layer thickness direction of the lower layer. At least a plurality of regions are alternately formed.

For example, in FIG. 2, three thickness width regions in which the micropore density shows a maximum value (within 200 to 500 μm / μm ² ) are formed in the layer thickness direction, and the micropore density is minimal. Three thickness width regions showing values (in the range of 0 to 20 pieces / μm ² ) are formed in the layer thickness direction.

  And, from the pore distribution pattern in the layer thickness direction, in the modified TiCN layer included in the lower layer of the present invention, the distribution of minute pores having a pore diameter of 2 to 30 nm formed inside the modified TiCN layer is It can be seen that a hole distribution form periodically changing along the thickness direction is formed.

In the present invention, the maximum value of the micropore density is determined to be in the range of 200 to 500 / μm ^{2 because} the maximum value of the micropore density is less than 200 / μm ² and the difference from the minimum region. Becomes too small to fully exhibit the characteristics of the periodic structure. On the other hand, if it exceeds 500 / μm ² , the porosity becomes too high, and the wear resistance decreases as the modified TiCN layer becomes brittle. Because.

The minimum value of the micropore density is determined to be in the range of 0 to 20 / μm ² in order to maintain the high-temperature strength and high-temperature hardness of the modified TiCN layer as a whole in addition to impact resistance. This is because a region having a micropore density of 20 holes / μm ² or less is required in the modified TiCN layer. When the minimum value of the micropore density exceeds 20 holes / μm ² , Even if the impact resistance is excellent, the toughness and wear resistance of the modified TiCN layer are lowered.

  In the present invention, the pore diameter of the fine pores is determined to be 2 to 30 nm. If the pore diameter of the pores formed in the modified TiCN layer is less than 2 nm, the impact relaxation effect cannot be expected. If the thickness exceeds 30 nm, the toughness of the modified TiCN layer will decrease significantly, and the impact relaxation effect against intermittent and impact loads will be maintained while maintaining the high temperature strength and hardness of the modified TiCN layer. For this, the pore size of the micropores formed inside the modified TiCN layer must be 2 to 30 nm.

  Moreover, it is desirable that the period in the layer thickness direction in the distribution form of the minute holes is 0.5 μm to 5 μm. If this period is less than 0.5 μm, the toughness and wear resistance of the lower layer including the modified TiCN layer tend to decrease, while if the period exceeds 5 μm, the modified TiCN layer against intermittent and impact loads The impact resistance of the will decrease.

  In the present invention, there is provided a pore distribution form in which the thickness width region in which the micropore density of the modified TiCN layer in the lower layer of the hard coating layer shows the above-mentioned maximum value and minimum value alternately appears periodically. Therefore, even in high-speed intermittent cutting with high heat generation and intermittent / impact high load acting on the cutting edge, without impairing the original high temperature hardness and heat resistance of the modified TiCN layer, Exhibits excellent chipping resistance and chipping resistance.

In the coated tool of the present invention, as a hard coating layer, a lower layer made of a Ti compound layer including at least one modified TiCN layer and an upper layer made of an Al ₂ O ₃ layer are formed by coating, and in the lower layer The modified TiCN layer has a pore distribution pattern in which the micropore density changes periodically along the layer thickness direction, resulting in high heat generation of steel, cast iron, etc., and intermittently on the cutting edge. Even when used for high-speed interrupted cutting where high loads and impacts are applied, it has excellent chipping resistance and fracture resistance. As a result, it has excellent wear resistance over a long period of use and has a long tool life. Is achieved.

The schematic diagram of the lower layer (modified TiCN layer) of the coating tool of the present invention having the pore distribution form of the present invention is shown. FIG. 5 shows a micro-vacancy density distribution diagram in the layer thickness direction of a lower layer (modified TiCN layer) having a pore distribution form of the present invention. FIG. 2 is a schematic view showing a state in which the lower layer (modified TiCN layer) of the present invention is partitioned by a plurality of (virtual) parallel lines drawn parallel to the tool base surface into a 0.1 μm thick width region and partitioned.

  Next, the coated tool of the present invention will be specifically described with reference to examples.

WC powder, TiC powder, ZrC powder, VC powder, TaC powder, NbC powder, Cr ₃ C ₂ powder, TiN powder, TaN powder, and Co powder all having an average particle diameter of 1 to 3 μm are prepared as raw material powders. These raw material powders were blended into the composition shown in Table 1, added with wax, ball milled in acetone for 24 hours, dried under reduced pressure, and pressed into a green compact with a predetermined shape at a pressure of 98 MPa. The green compact was vacuum sintered at a predetermined temperature in the range of 1370 to 1470 ° C. for 1 hour in a vacuum of 5 Pa. After sintering, the cutting edge portion was R: 0.07 mm honing By performing the processing, tool bases A to E made of WC-based cemented carbide having an insert shape specified in ISO · CNMG120408 were manufactured.

In addition, as raw material powders, TiCN (mass ratio TiC / TiN = 50/50) powder, Mo ₂ C powder, ZrC powder, NbC powder, TaC powder, WC powder, all having an average particle diameter of 0.5 to 2 μm. Co powder and Ni powder are prepared, and these raw material powders are blended in the blending composition shown in Table 2, wet mixed by a ball mill for 24 hours, dried, and pressed into a compact at a pressure of 98 MPa. The green compact was sintered in a nitrogen atmosphere of 1.3 kPa at a temperature of 1540 ° C. for 1 hour, and after the sintering, the cutting edge portion was subjected to a honing process of R: 0.07 mm. Tool bases a to e made of TiCN-based cermet having an insert shape of standard / CNMG120408 were formed.

Next, a normal chemical vapor deposition apparatus is used on the surfaces of these tool bases A to E and tool bases a to e,
As a lower layer of the hard coating layer, a Ti compound layer is formed by vapor deposition under the conditions shown in Table 3 and the target layer thickness shown in Table 5.

  However, in forming the Ti compound layer, at least one of them is formed by vapor deposition of the modified TiCN layer under the conditions shown in Table 4.

The modified TiCN layer is
(A) First, a TiCN layer is formed under the film forming conditions shown in Table 4,
(B) Next, under the etching conditions shown in Table 4, the formed TiCN layer was subjected to SF ₆ etching for a predetermined time,
(C) The above steps (a) and (b) are repeated until a modified TiCN layer having a predetermined thickness as shown in Table 6 is obtained.
After forming a lower layer having a predetermined thickness by vapor deposition, an Al ₂ O ₃ layer, which is an upper layer of the hard coating layer, is formed by vapor deposition with a target layer thickness shown in Table 5 under the formation conditions shown in Table 3.

The lower layer shown in Table 5 including the modified TiCN layer shown in Table 6 having a pore distribution form in which the micropore density changes periodically along the layer thickness direction by the deposition, and Al ₂ The coated tools 1 to 15 of the present invention were manufactured by vapor-depositing a hard coating layer consisting of an O ₃ layer and the upper layer shown in Table 5 as well.

  The modified TiCN layer contained in the lower layer of the inventive coated tools 1 to 15 is observed over a plurality of fields of view using a scanning electron microscope (magnification 50000 times), and is shown in the schematic diagram of FIG. The pore distribution morphology was observed.

Similarly, using a scanning electron microscope (magnification 50000 times), the modified TiCN layer contained in the lower layer of the inventive coated tool 1 to 15 is 0.1 μm in the layer thickness direction as shown in FIG. , And the number of micropores having a pore diameter of 2 to 30 nm existing in the thickness width region is measured to obtain the micropore density (pieces / μm ² ). The horizontal axis represents the micropore density ( 2 / μm ² ), and the vertical axis is the depth in the layer thickness direction, the pore distribution pattern shown in FIG. 2 was created.

In FIG. 2, the maximum value of the micropore density when the micropore density is between 200 and 500 / μm ² is the maximum value Dmax, while the micropore density is 0 to 20 / μm. ² is defined as the minimum value Dmin, and Dmax and Dmin are obtained from the hole distribution pattern created as FIG. 2, and the period along the layer thickness direction is determined. The distance between Dmax that appears on the fly was determined as the period C at which the micropore density changes.

  Table 6 shows values of the maximum value Dmax, the minimum value Dmin, and the period C.

For comparison purposes, a Ti compound layer as a lower layer of the hard coating layer on the surfaces of the tool bases A to E and the tool bases a to e under the conditions shown in Table 3 and the target layer thickness shown in Table 7 Comparative coating tools 1 to 10 having TiCN layers shown in Table 7 were prepared by vapor-depositing Al ₂ O ₃ layers as upper layers. (The comparative coated tools 1 to 10 do not form a modified TiCN layer.)
Further, the Ti compound layer as the lower layer of the hard coating layer and the Al ₂ O ₃ layer as the upper layer are formed by vapor deposition under the conditions shown in Table 3 and the target layer thickness shown in Table 7. By forming a modified TiCN layer in which the micropore density of TiCN changes under the conditions shown in Table 4, the lower layer shown in Table 7 including the modified TiCN layer shown in Table 8 and Al ₂ Comparative coated tools 11-15 having an upper layer composed of an O ₃ layer were produced.

  About the TiCN layer of the comparative coating tool 1-10, and the modified TiCN layer of the comparative coating tool 11-15, the micropore density of the TiCN layer was measured using the scanning electron microscope (50000 times magnification).

For the comparative coated tools 1 to 10, there is no significant difference in the pore density of the TiCN layer in the layer thickness direction, and pores having a pore diameter of 40 to 100 nm are in the layer at a density of about 0 to 3 / μm ² . Were evenly distributed.

  Table 8 shows the value of the pore density of the fine pores uniformly distributed over the entire layer thickness direction for the comparative coated tools 1 to 10.

  For the comparative coated tools 11 to 15, the pore distribution form in the layer thickness direction was obtained in the same manner as the coated tools 1 to 15 of the present invention.

  Table 8 shows values of the maximum value Dmax, the minimum value Dmin, and the period C obtained for the comparative coated tools 11 to 15.

  Moreover, when the layer thickness of each component layer of this invention coated tool 1-15 and comparative coated tool 1-15 was measured using the scanning electron microscope, all are the target layer thickness shown in Table 5-Table 8, and It showed substantially the same average layer thickness.

つぎに、前記本発明被覆工具１〜１５及び比較被覆工具１〜１５について、表９に示す条件で切削加工試験を実施し、いずれの切削試験でも切刃の逃げ面摩耗幅を測定した。

Next, a cutting test was carried out on the present invention coated tools 1 to 15 and comparative coated tools 1 to 15 under the conditions shown in Table 9, and the flank wear width of the cutting edge was measured in any cutting test.

  Table 10 shows the measurement results.

表５〜１０に示される結果から、本発明の被覆工具は、硬質被覆層の下部層として、改質ＴｉＣＮ層内部に形成された微小空孔の微小空孔密度が層厚方向に沿って周期的に変化する空孔分布形態を有していることにより、鋼や鋳鉄等の高熱発生を伴い、しかも、切れ刃に断続的・衝撃的高負荷が作用する高速断続切削加工に用いた場合でも、耐チッピング性、耐欠損性にすぐれ、その結果、長期の使用にわたってすぐれた耐摩耗性を発揮することが明らかである。

From the results shown in Tables 5 to 10, in the coated tool of the present invention, as the lower layer of the hard coating layer, the micropore density of micropores formed inside the modified TiCN layer is periodic along the layer thickness direction. Even if it is used for high-speed intermittent cutting with high heat generation of steel, cast iron, etc., and intermittent / impact high loads acting on the cutting edge. It is clear that it has excellent chipping resistance and chipping resistance, and as a result, exhibits excellent wear resistance over a long period of use.

  On the other hand, the comparative coated tools 1 to 10 in which the pore distribution in the TiCN layer of the lower layer is substantially uniform are accompanied by high heat generation, and the intermittent high-speed intermittent load is applied to the cutting edge. When used in cutting, it is clear that chipping, chipping, etc. will lead to a short life, and the void density outside the scope of the present invention periodically varies along the layer thickness direction. It is clear that the comparative coated tools 11 to 15 having the hole distribution form are inferior in wear resistance as compared with the coated tool of the present invention.

  As described above, the coated tool of the present invention has excellent chipping resistance in high-speed intermittent cutting with high heat generation such as steel and cast iron and intermittent and impact high load acting on the cutting edge. Demonstrate fracture resistance and extend the service life, but it is used not only for high-speed interrupted cutting conditions but also for high-speed cutting conditions, high cutting depths, high feeds, high-speed heavy cutting conditions, etc. Of course, it is also possible.

Claims (2)

On the surface of the tool base composed of tungsten carbide based cemented carbide or titanium carbonitride based cermet,
(A) The lower layer includes a Ti compound layer including at least a Ti carbonitride layer and having a total average layer thickness of 3 to 20 μm,
(B) the upper layer is an aluminum oxide layer having an average layer thickness of 1 to 25 μm;
In the surface-coated cutting tool obtained by chemical vapor deposition of the hard coating layer comprising the above (a) and (b),
Inside the at least one Ti carbonitride layer constituting the lower layer (a), micropores having a pore diameter of 2 to 30 nm are formed, and at least one constituting the lower layer (a) When the Ti carbonitride layer of the layer is divided into a thickness width region of 0.1 μm parallel to the tool substrate surface, and the micropore density existing in the thickness width region is measured,
A thickness width region having a micropore density of 200 to 500 / μm ² and a thickness width region having a micropore density of 0 to 20 / μm ² are alternately arranged along the thickness direction of the lower layer. A surface-coated cutting tool characterized by having a pore distribution form in which the fine pore density in the lower layer changes periodically along the layer thickness direction by forming at least a plurality of regions.   The pore distribution form in which the micropore density in at least one Ti carbonitride layer constituting the lower layer of (a) changes periodically along the layer thickness direction at a cycle of 0.5 μm to 5 μm The surface-coated cutting tool according to claim 1, comprising:

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