JP5898051B2 - Coated tool - Google Patents

Description

  The present invention relates to a coated tool having a coating layer.

Conventionally, a cutting tool widely used for metal cutting is widely used in which a multilayer coating layer such as a TiCN layer or an Al ₂ O ₃ layer is deposited on the surface of a substrate such as cemented carbide. Yes. Moreover, with the increase in demand for heat-resistant alloys such as Inconel and stainless steel, a cutting tool having excellent cutting performance in cutting heat-resistant alloys is required. However, with a conventional cutting tool, the temperature near the cutting edge becomes high during cutting. As a result, there has been a problem that a thermal crack occurs in the cutting blade or a crack develops from the generated thermal crack, thereby causing chipping or chipping in the cutting blade.

Therefore, in Patent Document 1, the total thickness is 1 on the surface of the cemented carbide substrate made of Co of 12.0 to 15.0 wt%, Cr of 0.52 to 0.64 wt%, and the balance of WC. A cutting tool milling insert coated with 1.9 to 3.6 μm first to third TiCNO layers and an outermost Al ₂ O ₃ layer with a thickness of 1.8 to 3.6 μm is described.

JP 2007-160504 A

  However, in the insert of Patent Document 1, the effect of suppressing the occurrence of thermal cracking is insufficient, and the coating layer may be peeled off.

  An object of the present invention is to provide a cutting tool capable of suppressing the generation of thermal cracks in the cutting blade and the occurrence of peeling of the coating layer even in a processing where the cutting blade is at a high temperature, such as a heat-resistant alloy cutting. It is to provide.

The coated tool of the present invention is mainly composed of a WC phase having an average particle size of 0.9 to 1.2 μm, and contains 10 to 15% by mass of Co and 0.2 to 0.6% by mass of Cr ₃ C _2. on the surface of the substrate made of cemented carbide, a TiCN layer having an average thickness of 1 to 3 [mu] m, and _{the Al} 2 _{O 3} layer having an average thickness of 0.3 to 0.7 [mu] m, but those obtained by laminating in this order.

According to the coated tool of the present invention, the average particle size and Co content of the WC phase are adjusted to an optimum range for processing difficult-to-cut materials, and thermal cracks and their progress are suppressed by heat generation during cutting. Moreover, even if the cutting edge becomes high temperature, the Al ₂ O ₃ layer suppresses the oxidation of the coating layer. Moreover, the thickness of _{the Al} 2 _{O 3} layer can suppress separation of 0.3~0.7μm So adhesion easily _{the Al} 2 _{O 3} layer be processed heat-resistant alloy.

It is a schematic sectional drawing of the cutting tool which is a suitable example of the coating tool of this invention. It is a scanning electron microscope (SEM) photograph about the surface of the outermost layer in the (a) cutting edge and (b) rake face of the cutting tool of FIG. Is a sectional view for explaining an example of a method of setting the sample at the time of forming the cutting tool of FIG 1, the the Al ₂ O ₃ layer thickness and the outermost surface layer of the crystal structure in (a) cutting and the rake face set how varied is a schematic diagram showing an example of a set of methods to differentiate the thickness of the Al ₂ O ₃ layer thickness and the other main surface side of the Al ₂ O ₃ layer on one main surface (b).

As shown in FIG. 1, a cutting tool 1 which is a preferred example of the coated tool of the present invention has a TiN layer 4, a TiCN layer 5, an intermediate layer 6, and an Al ₂ O ₃ layer 7 on the surface of a base 2. In addition, a coating layer 9 is provided in which the outermost layer 8 is formed in order from the base 2 side. Further, according to FIG. 1, a TiC _x N _y layer (0 <x, 0.5 ≦ y, x + y = 1, hereinafter simply referred to as the outermost layer) is formed on the surface of the Al ₂ O ₃ layer 7 as the outermost layer 8. Are stacked. The average thickness of each layer of the covering layer 9 is 0.3 to 0.7 μm for the TiN layer 4, 1 to 3 μm for the TiCN layer 5, 0.01 to 0.1 μm for the intermediate layer 6, and 0 for the Al ₂ O ₃ layer 7. 3 to 0.7 μm, and the outermost layer 8 is 0.3 to 0.7 μm. The average thickness of each layer is calculated by measuring the thickness at an interval of 1 μm over a width of 10 μm or more at an arbitrary position of each layer, and taking the average value.

Here, if the TiCN layer 5 is thinner than 1 μm, sufficient wear resistance cannot be maintained. On the contrary, if the TiCN layer 5 is thicker than 3 μm, it is easily lost. A more preferable range of the TiCN layer 5 is 2 to 2.5 μm. If the Al ₂ O ₃ layer 7 is thinner than 0.3 μm, sufficient oxidation resistance cannot be maintained, and wear resistance decreases. On the contrary, if the Al ₂ O ₃ layer 7 is thicker than 0.7 μm, chipping is easy. A more preferable range of the Al ₂ O ₃ layer 7 is 0.4 to 0.6 μm.

The substrate 2 mainly contains a WC phase having an average particle size of 0.9 to 1.2 μm and contains 10 to 15% by mass of Co and 0.2 to 0.6% by mass of Cr ₃ C _2. Made of cemented carbide. Note that “mainly composed of the WC phase” means a state containing 50 mass% or more of WC, and a particularly preferable range is that containing 84.4 mass% or more of WC. The combination of the substrate 2 and the covering layer 9 suppresses thermal cracks and their progress even by heat generated during cutting. Moreover, even if the cutting edge becomes high temperature, the Al ₂ O ₃ layer 7 suppresses oxidation of the coating layer. Moreover, the average thickness of _{the Al} 2 _{O 3} layer 7 so 0.3 to 0.7 [mu] m, even working of adhesion tends to heat resistant alloys such as Ni-based alloys and Ti-based alloys of _{the Al} 2 _{O 3} layer 7 Peeling can be suppressed.

Here, if the average particle size of the WC phase is smaller than 0.9 μm, the toughness is low and sudden defects are likely to occur. On the other hand, if the average particle size of the WC phase is larger than 1.2 μm, the hardness decreases, so that sufficient wear resistance cannot be maintained. A more preferable range of the average particle diameter of the WC phase is 1.0 to 1.15 μm. If the Co content is less than 10% by mass, sufficient toughness and strength cannot be ensured, and defects are likely to occur. On the other hand, when the Co content is more than 15% by mass, there is a problem that the thermal conductivity is lowered and thermal cracks are easily generated and are lost. A more preferable range of the Co content is 11 to 13% by mass. When the content of Cr is less than 0.2% by mass in terms of Cr ₃ C ₂ , the substrate 2 is easily corroded and the coating is easily peeled off. On the other hand, when the Cr content is more than 0.6% by mass in terms of Cr ₃ C ₂ , the toughness is lowered and defects are likely to occur. More preferable range of _Cr 3 _{C 2} in terms of Cr is 0.4 to 0.5 mass%.

Further, the TiN layer 4 enhances the adhesion between the substrate 2 and the coating layer 9. When the average thickness of the TiN layer 4 is 0.3 to 0.7 μm, the coating layer 9 adheres to the substrate 2. The covering layer 9 is difficult to chip. A more preferable range of the TiN layer 4 is 0.4 to 0.5 μm. Further, an intermediate layer 6 made of any one of TiCO, TiNO and TiCNO is provided between the TiCN layer 5 and the Al ₂ O ₃ layer 7, and the intermediate layer 6 is composed of the TiCN layer 5 and the Al ₂ O ₃ layer. Adhesion with the layer 7 can be enhanced. When the average thickness of the intermediate layer 6 is 0.01 to 0.1 μm, the Al ₂ O ₃ layer 7 is difficult to peel off and the Al ₂ O ₃ layer 7 is difficult to chip. A more preferable range of the intermediate layer 6 is 0.03 to 0.08 μm.

The outermost layer 8 is made of a TiC _x N _y layer (0 <x, 0.5 ≦ y, x + y = 1). The surface of the cutting tool 1 is gold, and the cutting blade is judged as unused or used. It is provided for the sake of ease. If it is 0.3 to 0.7 μm, it can be visually identified. Further, in this embodiment, as shown in FIG. 2, on the surface of the outermost layer 8, TiC _x N _y crystals (0 <x, 0.5 ≦ y, x + y = 1) are formed of granular particles at the cutting edge. The rake face consists of acicular particles. As a result, in the cutting edge, there are few voids on the surface of the coating layer 9, and wear of the coating layer 9 is small. On the other hand, since the acicular particles are deposited on the surface of the coating layer 9 on the rake face, there are many voids on the surface of the coating layer 9, so that the retention of cutting fluid on the surface of the coating layer 9 is improved. As a result, the flow of chips generated by machining becomes smooth, and the temperature rise at the cutting edge can be suppressed. The outermost layer 8 may contain oxygen at a ratio of 10% by mass or less in the total amount.

  Furthermore, in the present embodiment, the outermost layer 8 has a structure in which the carbon concentration on the substrate side is higher than the carbon concentration on the surface side. As a result, acicular particles are formed on the rake face, and the surface of the outermost layer 8 is gold, making it easy to identify the use.

Further, the overall shape of the cutting tool 1 of FIG. 1 is a substantially plate shape, the side surface is 90 ° with respect to the main surface, and a shape that uses the ends of both main surfaces as cutting edges, a so-called double-sided negative chip. A shape is mentioned as a suitable example. And although both main surfaces may consist of the same shape, as another embodiment, the average thickness of the Al ₂ O ₃ layer 7 on one main surface side and the Al ₂ O ₃ on the other main surface side. The structure from which the average thickness of the layer 7 differs may be sufficient. With this configuration, when cutting is performed under two processing conditions, a cutting tool is used by properly using one main surface side cutting blade and the other main surface side cutting blade under different processing conditions. Provides more optimal tool performance. At this time, the breaker shape on the one main surface side and the breaker shape on the other main surface side may be different in order to obtain a more optimal tool performance.

  Furthermore, although the said cutting tool 1 cuts by applying the cutting blade formed in the intersection of a rake face and a flank to a to-be-cut object, the coated tool of this invention is not limited to this. In addition to the cutting tool 1, it can be applied to various applications such as wear parts such as sliding parts and molds, tools such as excavation tools, blades, and impact resistant parts. It has sex.

(Production method)
A method for producing the coated tool of the present invention will be described.
First, metal powder, carbon powder, etc. are appropriately added to and mixed with inorganic powders such as metal carbides, nitrides, carbonitrides, oxides, etc. that can form a hard alloy to be the base 2 by firing, press molding, casting After forming into a predetermined tool shape by a known molding method such as molding, extrusion molding, cold isostatic pressing, etc., the substrate 2 made of the hard alloy described above is fired in a vacuum or non-oxidizing atmosphere. Make it. Then, the surface of the base 2 is subjected to polishing or honing of the cutting edge as desired.

Then, a surface coating layer is formed on the surface by chemical vapor deposition (CVD).
First, a mixed gas composed of 0.5 to 10% by volume of titanium tetrachloride (TiCl ₄ ) gas, 10 to 60% by volume of nitrogen (N ₂ ) gas, and the balance of hydrogen (H ₂ ) gas is prepared as a reaction gas composition. Then, it is introduced into the reaction chamber, and the TiN layer 4 is formed in the chamber under conditions of 800 to 940 ° C. and 8 to 50 kPa.

Next, as a reaction gas composition, titanium tetrachloride (TiCl ₄ ) gas is 0.5 to 10% by volume, nitrogen (N ₂ ) gas is 10 to 60% by volume, and acetonitrile (CH ₃ CN) gas is 0% by volume. A mixed gas composed of 0.1 to 3.0% by volume and the remainder consisting of hydrogen (H ₂ ) gas was prepared and introduced into the reaction chamber, and the TiCN layer 5 was formed at a film formation temperature of 780 to 880 ° C. and 5 to 25 kPa. The lower part is deposited. Here, of the above film forming conditions, the ratio of acetonitrile gas in the reaction gas is adjusted to 0.1 to 0.4% by volume, and the film forming temperature is set to 780 ° C. to 880 ° C. In this case, the lower portion is desirable because the TiCN layer 5 made of fine streaks (MT-TiCN) can be formed.

In addition, although the film-forming conditions of the lower part of the TiCN layer 5 may be formed under a single condition, the film-forming conditions of the TiCN layer can be changed in the middle to change the structure state. For example, the ratio of acetonitrile (CH ₃ CN) gas can be increased to make the upper crystal of the TiCN layer 5 into a columnar crystal having a width wider than that of the lower crystal. Alternatively, during the film formation of the TiCN layer 5, the film formation conditions are as follows: titanium tetrachloride (TiCl ₄ ) gas is 1 to 5% by volume, methane (CH ₄ ) gas is 4 to 10% by volume, and nitrogen (N ₂ ). By adjusting a mixed gas consisting of 10 to 30% by volume of gas and the remainder consisting of hydrogen (H ₂ ) gas into the reaction chamber and changing the inside of the chamber to 950 to 1100 ° C. and 5 to 40 kPa, The upper crystal of the TiCN layer 5 can be a columnar crystal that is wider than the lower crystal. Under this condition, the desired TiCN layer 5 can be formed even if acetonitrile (CH ₃ CN) gas is used in a proportion of 0.5 to 5% by volume instead of methane (CH ₄ ) gas.

Next, an HT-TiCN layer constituting the upper part of the TiCN layer 5 is formed. The specific film formation conditions of the HT-TiCN layer are as follows: titanium tetrachloride (TiCl ₄ ) gas is 2.5 to ₄ % by volume, methane (CH ₄ ) gas is 0.1 to 10% by volume, and nitrogen (N ₂ ). A gas mixture of 5 to 20% by volume and the remainder consisting of hydrogen (H ₂ ) gas was prepared and introduced into the reaction chamber, the inside of the chamber was set to 900 to 1050 ° C. and 5 to 40 kPa, and the film formation time was 20 to 20%. 60 minutes is desirable.

Further, the intermediate layer 6 is produced. Specific film forming conditions, titanium tetrachloride (TiCl ₄₎ 1 to 4% by volume of the gas, methane (CH ₄₎ gas 0-7% by volume, nitrogen _{(N 2)} 0 to 20% by volume of the gas, dioxide A mixed gas composed of 1 to 5% by volume of carbon (CO ₂ ) gas and the remaining hydrogen (H ₂ ) gas is prepared. These mixed gases are adjusted and introduced into the reaction chamber, and the film is formed under the conditions of 900 to 1050 ° C., 5 to 40 kPa, and a film formation time of 20 to 60 minutes.

Subsequently, an Al ₂ O ₃ layer 7 is formed. As a method of forming the Al ₂ O ₃ layer 7, aluminum trichloride (AlCl ₃ ) gas is 0.5 to 5.0% by volume, hydrogen chloride (HCl) gas is 0.5 to 3.5% by volume, dioxide dioxide. A mixed gas composed of 0.5 to 5.0% by volume of carbon (CO ₂ ) gas, 0.0 to 0.5% by volume of hydrogen sulfide (H ₂ S) gas, and the remaining hydrogen (H ₂ ) gas is used. 950-1100 ° C., 5-10 kPa is desirable.

Further, the outermost layer 8 is formed as desired. Specific film forming conditions are as follows: titanium tetrachloride (TiCl ₄ ) gas is 0.1 to 10% by volume, nitrogen (N ₂ ) gas is 0 to 60% by volume, and the remainder is hydrogen (H ₂ ) gas. The mixed gas consisting of the above may be adjusted and introduced into the reaction chamber, and the inside of the chamber may be set to 960 to 1100 ° C. and 10 to 85 kPa.

In forming the coating layer 9, the state of setting the sample is controlled. As shown in FIG. 3 (a), a substantially rod-like column 11 is erected on the set plate 17, a substantially conical or cylindrical spacer 14 is inserted into the column 11, and then the sample 12 that is the base 2 is inserted into the column 11. The screw hole 13 of (12a) is penetrated and the spacer 14 is also penetrated. Next, the spacer 14 is inserted, the next sample 12 (12b) is inserted, and the two samples 12 (12b) are placed with the spacer 14 interposed. At this time, the rake faces of the two samples facing each other are generally parallel to each other, and the distance d between the rake faces of the two samples is adjusted to be 0.5 to 1 mm. In this way, a plurality of samples are set. A dummy sample 16 is placed on the uppermost sample. Further, the distance between the lower sample and the set plate 17 is also controlled to 0.5 to 1.0 mm. By forming the film in this state, the thickness of the Al ₂ O ₃ layer and the crystal structure of the outermost layer on the cutting edge and the rake face can be varied.

Further, in order different from the one main surface side of the thickness of the Al ₂ O ₃ layer 7 thickness and the other main surface side the Al ₂ O ₃ layer 7, as shown in FIG. 3 (b), lower While the interval between the sample 12 and the set plate is made wider than 1.0 mm, only two samples 12 are set on the column 11, and no dummy sample is placed on the uppermost sample. By forming the film in this state, the thickness of the Al ₂ O ₃ layer 7 on one main surface side can be made different from the thickness of the Al ₂ O ₃ layer 7 on the other main surface side. At this time, by making the shape of the breaker provided on the opposing rake face different from the shape of the breaker provided on the non-facing rake face, the obtained cutting tool can be used on both sides under different cutting conditions.

To tungsten carbide (WC) powder, metal cobalt (Co) powder with an average particle diameter of 1.2 μm and Cr ₃ C ₂ powder with an average particle diameter of 2.5 μm are added and mixed, and then the cutting tool shape is formed by press molding. After being molded, the binder removal treatment was performed, and firing was performed at 1400 ° C. for 1 hour in a vacuum of 0.5 to 100 Pa to produce cemented carbides shown in Table 1. Furthermore, the cutting edge processing (R honing) was given to the rake face side by blasting to the manufactured cemented carbide.

  Next, a coating layer was formed on the cemented carbide by a CVD method. As shown in FIG. 3A, the sample is placed on the spacer through the screw hole of the sample in a state where the spacer is inserted into a substantially rod-like column that stands on the set plate. The next sample was placed therewith, and the sample was set on a set plate. At this time, the rake faces of the two samples facing each other were adjusted to be parallel to each other, and the distance between the rake faces of the two samples was adjusted to the distance shown in Table 1. A dummy sample was placed on the uppermost sample. In addition, the distance between the lower sample and the set plate was adjusted to the distance shown in Table 1.

The film formation conditions were as follows. First, a TiN layer was formed by flowing a mixed gas of TiCl ₄ : 2.0% by volume, N ₂ : 33% by volume, and the remainder H _{2 under} the conditions of 880 ° C. and 16 kPa. Next, under film formation conditions of 825 ° C. and 9 kPa, a mixed gas of TiCl ₄ : 2.5% by volume, N ₂ : 23% by volume, CH ₃ CN: 0.4% by volume, and the balance is H ₂ is averaged. After the first TiCN layer having a crystal width of 0.3 μm was formed, the mixed gas was TiCl ₄ : 2.5% by volume, N ₂ : 10% by volume, CH ₃ CN: 0.9% by volume, and the rest was H _{Then, a second} TiCN layer having an average crystal width of 0.7 μm was formed. Subsequently, under the film forming conditions of 1010 ° C. and 20 kPa, a third TiCN was supplied by flowing a mixed gas of TiCl ₄ : 3.5% by volume, CH ₄ : 7% by volume, N ₂ : 10% by volume, and the remaining H _2. A layer was formed. In the table, the total thickness of the first to third TiCN layers is shown as the average thickness of the TiCN layer.

And under film-forming conditions of 1010 ° C. and 20 kPa, TiCl ₄ : 3.5% by volume, CH ₄ : 0 to 3% by volume, N ₂ : 0 to 10% by volume, CO ₂ : 2% by volume, and the rest is H _2. Then, an intermediate layer was formed. Thereafter, a mixture of AlCl ₃ : 1.5% by volume, HCl: 2% by volume, CO ₂ : 4% by volume, H ₂ S: 0.3% by volume, and the remaining H ₂ under the film forming conditions of 1005 ° C. and 9 kPa. An αAl ₂ O ₃ layer was formed by flowing a gas. Finally, under the film forming conditions of 1010 ° C. and 30 Pa, the outermost layer was formed by flowing a mixed gas of TiCl ₄ : 3.0% by volume, N ₂ : 30% by volume, and the remaining H ₂ . The outermost layer had a composition based on TiN. However, since it was mixed due to carbon (C) diffusion or the like, it was represented as Ti (CN) in the table.

About the obtained cutting tool, the grinding | polishing process by mechanical grinding | polishing and ion milling was implemented so that the coating layer described in Table 1, 2 could be observed, and the cross section was exposed. The microstructural state of each layer viewed from the direction substantially perpendicular to the cross section of each layer was observed, and the average thickness was measured. Then, confirmation of the atomic species existing in the outermost layer, composition, and the like were also observed by energy dispersive X-ray spectroscopy (EDS), electron energy loss spectroscopy (EELS), and the like. The results are shown in Tables 1 and 2.

Then, using this cutting tool, a cutting test was performed under the following conditions to evaluate fracture resistance. The results are shown in Table 2.
(Cutting conditions)
Work material: Inconel 718 Square tool shape: PNMU1205ANER-SM (Kyocera Corporation insert)
Cutting speed: 40 m / min Feed rate: 0.15 mm / blade cutting: 2.0 mm (axial direction) × 10 mm (radial direction)
Others: Use of water-soluble cutting fluid Evaluation items: Time to failure and state of cutting edge

From Tables 1 and 2, Sample No. with an average particle diameter of WC phase smaller than 0.9 μm. In No. 12, the toughness was low and sudden loss occurred. Sample No. with an average particle size of WC phase larger than 1.2 μm. In No. 13, wear increased. Sample No. with a Co content of less than 10% by mass 14 was deficient. Conversely, Sample No. with a Co content of more than 15% by mass was obtained. In 15, defects due to thermal cracks occurred. Sample No. with a Cr ₃ C ₂ content of less than 0.2% by mass. In No. 16, the coating layer peeled from the substrate. Sample No. with a Cr ₃ C ₂ content of more than 0.6 mass%. In No. 17, the toughness was reduced and lost. Sample No. with an average thickness of TiCN layer less than 1 μm In 18, the wear increased. Sample No. in which the average thickness of the TiCN layer is thicker than 3 μm In 19, a defect occurred. Sample No. _{2 in which} the average thickness of the Al ₂ O ₃ layer is thinner than 0.3 μm. In No. 20, the wear was large. Sample No. _{2 in which} the average thickness of the Al ₂ O ₃ layer is thicker than 0.7 μm. In No. 21, chipping occurred.

  On the other hand, sample No. consisting of a substrate and a coating layer within the scope of the present invention. In Nos. 1 to 11, chipping and chipping were suppressed, and progress of wear was also suppressed.

Sample No. 1 of Example 1 Two samples were prepared using the same material as the base of 1 and provided with a PNMU1205ANER-GM breaker manufactured by Kyocera Corporation on one main surface and a PNMU1205ANER-SM breaker manufactured by Kyocera Corporation on the other main surface. . Then, the main surfaces of one of the two samples are opposed to each other with an interval of 0.8 mm and set in the state as shown in FIG. 1 CVD film was formed. When the cross section of the obtained cutting tool was observed with a scanning electron microscope, the average thickness of the Al ₂ O ₃ layer on one main surface was 0.6 μm, and the average thickness of the Al ₂ O ₃ layer on the other main surface was It was 0.5 μm. When both surfaces of this sample were used for cutting evaluation under the following cutting conditions that required oxidation resistance, the cutting edge formed with the GM breaker had a cutting time of 14 minutes, and the cutting with the SM breaker formed. The cutting time was 10 minutes with the blade, and it was found that the cutting blade specifications on the GM breaker side showed better cutting performance under this cutting condition.
(Cutting conditions)
Work material: Inconel 718 Square tool shape: PNMU1205ANER-GM / SM (Kyocera Corporation insert)
Cutting speed: 40 m / min Feed rate: 0.25 mm / blade cutting: 2.0 mm (axial direction) × 10 mm (radial direction)
Other: Uses water-soluble cutting fluid

1 cutting tool 2 base 4 TiN layer 5 TiCN layer 6 intermediate layer 7 _Al 2 _{O 3} layer 8 outermost layer 9 covering layer

Claims (6)

A substrate made of a cemented carbide containing, as a main component, a WC phase having an average particle size of 0.9 to 1.2 μm and containing 10 to 15% by mass of Co and 0.2 to 0.6% by mass of Cr ₃ C ₂ on the surface of a TiCN layer having an average thickness of 1 to 3 [mu] m, average thickness and _{the Al} 2 _{O 3} layer of 0.3 to 0.7 [mu] m, with the you turn position from the base side, wherein _{the Al} 2 _{O 3} layer The outermost layer consisting of a TiC _x N _y layer (0 <x, 0.5 ≦ y, x + y = 1) having an average thickness of 0.3 to 0.7 μm is located on the surface of the outermost layer, A coated tool consisting of granular particles on the cutting edge and needle-like particles on the rake face . A substrate made of a cemented carbide containing , as a main component, a WC phase having an average particle size of 0.9 to 1.2 μm and containing 10 to 15% by mass of Co and 0.2 to 0.6% by mass of Cr ₃ C ₂ A TiCN layer having an average thickness of 1 to ₃ μm and an Al ₂ O ₃ layer having an average thickness of 0.3 to 0.7 μm are sequentially located on the surface of the substrate, and the Al ₂ O ₃ layer on the surface, the average thickness of _TiC x _{N y} layer of 0.3~0.7μm (0 <x, 0.5 ≦ y, x + y = 1) the outermost layer is located consisting of the outermost layer, the rake face , base side high have to be covered tool than the carbon concentration of the carbon concentration of the surface side of the. A substrate made of a cemented carbide containing , as a main component, a WC phase having an average particle size of 0.9 to 1.2 μm and containing 10 to 15% by mass of Co and 0.2 to 0.6% by mass of Cr ₃ C ₂ A TiCN layer having an average thickness of 1 to ₃ μm and an Al ₂ O ₃ layer having an average thickness of 0.3 to 0.7 μm are sequentially disposed on the surface of the substrate, and the both sides of the substantially plate-like surface are used. a cutting tool, one main surface side the the Al ₂ O ₃ layer thickness and the other main surface side the the Al ₂ O ₃ layer of the covering tool and is that different thicknesses of the. The coated tool according to claim 3 , wherein the shape of the breaker on the one main surface side and the shape of the breaker on the other main surface side are different. The coated tool according to any one of claims 1 to 4, wherein a TiN layer having an average thickness of 0.3 to 0.7 µm is laminated between the substrate and the TiCN layer. Between the _{the Al} 2 _{O 3} layer and the TiCN layer, the average thickness of 0.01 to 0.1 m TiCO, intermediate layer made of any one of TiNO and TiCNO is laminated claims 1 to 5 A coated tool according to any one of the above.