Patent Publication Number: US-2021187623-A1

Title: Coated tool and cutting tool

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a national stage entry according to 35 U.S.C. § 371 of PCT Application No. PCT/JP2019/034600 filed on Sep. 3, 2019, which claims priority to Japanese Application No. 2018-166092 filed on Sep. 5, 2018, which are entirely incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to a coated tool for use in a cutting process. 
     BACKGROUND 
     As a coated tool for use in the cutting process, such as a turning process and a milling process, a coated tool is discussed in, for example, Patent Document 1 (Japanese Unexamined Patent Publication No. H8-300203). 
     In Patent Document 1, it is discussed that a titanium compound layer is oriented in a (220) surface, which may strengthen the adhesion of the layer to a substrate or the layer below, making it difficult for delamination to occur from an interface, and suppressing the occurrence of unusual damage and life degradation caused by delamination. 
     The coated tool discussed in Patent Document 2 (Japanese Unexamined Patent Publication No. 2015-182209) may include a configuration in which a coating layer is located on a surface of a base member composed of cemented carbide or the like. The coating layer may include a layer (titanium compound layer) including a compound of titanium (Ti) and a layer (aluminum oxide layer) including aluminum oxide (Al 2 O 3 ). Additionally, in the coated tool discussed in Patent Document 2, a plurality of voids may be formed at an interface between the titanium compound layer and the aluminum oxide layer. There is discussion that impact relaxation effect may be obtainable because of the plurality of voids. 
     SUMMARY 
     A coated tool of the present disclosure may include a base member including a first surface, and a coating layer located at least on the first surface of the base member. The coating layer may include a first layer and a second layer. The first layer may be located on the first surface and includes cubic titanium carbonitride. The second layer may be contactedly located on the first layer and includes aluminum oxide. The first layer may include an orientation coefficient Tc (220) of the titanium carbonitride by X-ray diffraction analysis of 3.0 or more. The coating layer may include a plurality of voids located side by side in the first layer, in a direction along a boundary between the first layer and the second layer in a cross section orthogonal to the first surface. An average value of widths of the voids in a direction along the interface may be less than an average value of distances between the voids adjacent to each other. 
     A cutting tool of the present disclosure may include a holder including a bar shape which extends from a first end to a second end and including a pocket located at a side of the first end, and the above coated tool which is located at the pocket. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view illustrating a coated tool of the present disclosure. 
         FIG. 2  is a sectional view taken along line A-A in the coated tool illustrated in  FIG. 1 . 
         FIG. 3  is an enlarged view in the vicinity of a coating layer in the coated tool illustrated in  FIG. 2 . 
         FIG. 4  is an enlarged view in a region B 1  illustrated in  FIG. 3 . 
         FIG. 5  is an enlarged view of another non-limiting embodiment in the region B 1  illustrated in  FIG. 3 . 
         FIG. 6  is a plan view illustrating a cutting tool of the present disclosure. 
         FIG. 7  is an enlarged view in a region B 2  illustrated in  FIG. 6 . 
     
    
    
     DETAILED DESCRIPTION 
     A coated tool of the present disclosure is described in detail below with reference to the drawings. For the sake of description, each of the drawings referred to in the following illustrates, in a simplified form, only main members necessary for the explanation. Hence, the coated tool is capable of including any structural member not illustrated in the drawings referred to. Dimensions of the members in each of the drawings are not ones which faithfully represent dimensions of actual structural members and dimension ratios of these members. 
     &lt;Coated Tool&gt; 
     The coated tool  1  of the present disclosure includes a base member  3  and a coating layer  5  as illustrated in  FIGS. 1 and 2 . The base member  3  includes a first surface  7  (an upper surface in  FIG. 2 ), a second surface  9  adjacent to the first surface  7  (a side surface in  FIG. 2 ), and a cutting edge  11  located at least on a part of a ridge line where the first surface  7  intersects with the second surface  9 . 
     The base member  3  has a quadrangular plate shape in the example shown in  FIG. 1 , and the first surface  7  has a quadrangular shape. The number of the second surfaces  9  is therefore four. At least a part of the first surface  7  is a rake surface region, and at least a part of the second surface  9  is a flank surface region. The shape of the base member  3  is not limited to the quadrangular plate shape, and for example, the first surface  7  may have a triangular, pentagonal, hexagon or circular shape. Alternatively, the base member  3  may have a columnar shape besides the plate shape. 
     The coating layer  5  is located at least on the first surface  7  of the base member  3 . The coating layer  5  may be located only on the first surface  7  or on a surface other than the first surface  7  in the base member  3 . The coating layer  5  is also located on the second surface  9  in addition to the first surface  7  in the example shown in  FIG. 2 . The coating layer  5  is included for the purpose of improving characteristics of the coated tool  1  during a cutting process, such as wear resistance and chipping resistance. 
     The coating layer  5  includes a first layer  13  and a second layer  15  as illustrated in  FIG. 3 . The first layer  13  is located on the first surface  7  and includes cubic titanium carbonitride. The second layer  15  is contactedly located on the first layer  13 . The second layer  15  may include, for example, aluminum oxide (Al 2 O 3 ). 
     In addition, for example, a titanium nitride layer  17  may be included between the first layer  13  and the base member  3 . Bondability between the base member  3  and the first layer  13  becomes higher if such a configuration is included. 
     The first layer  13  includes a titanium carbonitride layer  19 . Other than the titanium carbonitride, the first layer  13  may include, for example, titanium carbide, nitride, oxide, carbon oxide and oxycarbonitride. The first layer  13  may be made into a single layer or, alternatively, may include a configuration in which a plurality of layers are laminated one on another as long as it includes cubic titanium carbonitride. 
     The titanium nitride layer  17  and the titanium carbonitride layer  19  include titanium nitride and titanium carbonitride as a main component, respectively, and may contain other components. The term “main component” denotes a component having the largest value in mass % among values of other components. 
     The coating layer  5  may be composed only of the first layer  13  and the second layer  15  or, alternatively, may include a layer other than these layers. For example, a different layer may be interposed between the base member  3  and the first layer  13  or, alternatively, a different layer may be located on the second layer  15 . 
     The titanium carbonitride layer  19  may include a configuration in which a plurality of regions different in composition are laminated one on another. For example, the titanium carbonitride layer  19  may include a configuration in which a so-called MT (moderate temperature) first region  19   a , and a so-called HT (high temperature) second region  19   b  are laminated one on another. 
     In cases where the first layer  13  includes the first region  19   a  and the second region  19   b , the first layer  13  may further include an intermediate region  19   c  between the first region  19   a  and the second region  19   b . A boundary between the layers and a boundary between the regions can be determined, for example, by observing an electron microscope photograph (a scanning electron microscope (SEM: Scanning Electron Microscope) photograph or a transmission electron microscope (TEM: Transmission Electron Microscope) photograph). Identification can be performed by the ratio of elements constituting each layer and differences in a size or an orientation of a crystal. 
     The first layer  13  includes the highest peak in a (220) surface among crystal surfaces of the cubic titanium carbonitride by X-ray diffraction (XRD) analysis and satisfies an orientation coefficient Tc (220) of 3.0 or more, which strengthens the adhesion of the layer to a substrate  3  or the layer below. This makes it difficult for delamination to occur from an interface, and suppresses the occurrence of unusual damage and life degradation caused by delamination. 
     The orientation coefficient Tc (hkl) can be calculated by the following formula. Tc(hkl)={I(hkl)/I 0 (hkl)}/[( 1/7)×Σ{I(HKL)/Io(HKL)}] Here, (HKL) is crystal surfaces of (111), (200), (220), (311), (331), (420), and (422). I(HKL) and I(hkl) are peak intensities of the peaks attributed to each crystal surface detected in the X-ray diffraction analysis of the cubic titanium carbonitride of the first layer. Io(HKL) and Io(hkl) are standard diffraction intensities of each crystal surface described in JCPDS card No. 00-042-1489. 
     The above orientation coefficient Tc (hkl) may be measured from the upper surface of the first layer  13 , for example, at a rake surface  9 . 
     If the second layer  15  includes aluminum oxide, examples include α-alumina(α-Al 2 O 3 ), γ-alumina(γ-Al 2 O 3 ) and κ-alumina(κ-Al 2 O 3 ). If the second layer  15  includes α-alumina of these, heat resistance of the coated tool  1  can be enhanced. The second layer  15  may be configured to include only one of the above compounds or, alternatively, may include a plurality of kinds of the above compounds. 
     Identification of the aluminum oxide included in the second layer  15  from among the above compounds can be evaluated, for example, by carrying out X-ray diffraction (XRD) analysis and by observing a distribution of peak values. 
     A content ratio of the titanium carbonitride in the first layer  13  and a content ratio of the aluminum oxide in the second layer  15  are not limited to a specific value. A non-limiting embodiment thereof is a configuration in which the first layer  13  includes the titanium carbonitride as a main component, and the second layer  15  includes the aluminum oxide as a main component. The term “main component” denotes a component having the largest value in mass % among values of other components. 
     The first layer  13  may include a component other than the titanium carbonitride, and the second layer  15  may include a component other than the aluminum oxide. For example, bondability between the first layer  13  and the second layer  15  is improved if the first layer  13  includes the aluminum oxide and the second layer  15  includes the titanium compound such as the titanium carbonitride. 
     The coating layer  5  includes the voids  21  in an interior of the first layer  13  as illustrated in  FIG. 4 . Specifically, the coating layer  5  includes the plurality of voids  21  located side by side in the first layer  13 , in a direction along the boundary  16  between the first layer  13  and the second layer  15  in a cross section orthogonal to the first surface  7  of the base member  3 . 
     In the coated tool  1  of the present disclosure, an average value of widths w 1  of the voids  21  in a direction parallel to the first surface  7  in the cross section orthogonal to the first surface  7  is smaller than a distance between the voids  21  adjacent to each other, namely, an average value of widths w 2  at the first portion X. The coated tool  1  including such a configuration can obtain high impact resistance in the voids  21  while reducing degradation of strength of the first portion X. As a result, the coated tool  1  of the present disclosure includes high impact resistance and good bondability. 
     In evaluating the average value of the widths w 1  of the voids  21  in the direction parallel to the first surface  7 , it is unnecessary to evaluate the widths w 1  of all the voids  21  existing in the cross section orthogonal to the first surface  7 , but the average value may be evaluated by an average value of the widths w 1  of approximately 10 voids  21  located side by side in the cross section. For example, a 10 μm square region including the boundary between the first layer  13  and the second layer  15  may be extracted in the cross section orthogonal to the first surface  7 , and the widths w 1  of the voids  21  in the region may be measured. An average value of the widths w 2  of the first portion X may be evaluated by an average value of distances between approximately 5 voids  21  located side by side in the cross section. 
     The voids  21  may exist in the first layer  13 , and may include, for example, not only the configuration located in the first layer  13  as illustrated in  FIG. 4 , or a configuration located in each of the first layer  13  and the second layer  15  as illustrated in  FIG. 5 . An imaginary line segment along the boundary between the first layer  13  and the second layer  15  is indicated by a chain line in  FIG. 5 , and the voids  21  located in the second layer  15  may be located along the boundary between the first layer  13  and the second layer  15 . 
     The phrase that “the voids  21  are located along the boundary between the first layer  13  and the second layer  15 ” denotes that distances from the plurality of voids  21  to the boundary between the first layer  13  and the second layer  15  fall within a range of ±20% of an average value thereof. 
     In cases where the second layer  15  includes α-alumina as aluminum oxide from the viewpoint of heat resistance and durability of the coated tool  1 , the durability of the coated tool  1  can be further enhanced if the plurality of voids  21  are located in the first layer  13 . 
     The reason for this is as follows. Hardness of the titanium carbonitride is higher but impact resistance thereof is lower than that of α-alumina. Therefore, if the voids  21  are located in the first layer  13 , impact resistance because of the voids  21  can be enhanced in the first layer  13 , and the durability of the coated tool  1  can be further enhanced. 
     Although no particular limitations are imposed on size of the voids  21 , the size is settable to, for example, 20-200 nm. The impact relaxation effect because of the voids  21  can be enhanced if the size of the voids  21  is 20 nm or more. It is easy to maintain the strength of the first layer  13  if the size of the voids  21  is 200 nm or less. The term “size of the voids  21 ” denotes the maximum value of the widths w 1  of the voids  21  in the cross section orthogonal to the first surface  7 . 
     No particular limitations are imposed on shape of the voids  21 . The impact resistance can be further enhanced while reducing a ratio of the voids  21  if the width w 1  in the direction parallel to the first surface  7  is larger than a height h 1  in the direction orthogonal to the first surface  7 , in other words, if an average value of the widths w 1  of the voids  21  in the direction parallel to the first surface  7  is larger than an average value of the heights h 1  of the voids  21  in the direction orthogonal to the first surface  7  in the cross section orthogonal to the first surface  7 . The reason for this is as follows. 
     During a cutting process of a workpiece for the purpose of manufacturing a cut product, the coating layer  5  is susceptible to a cutting load in the direction orthogonal to the first surface  7 . If the voids  21  have such a shape that the width w 1  in the direction parallel to the first surface  7  is larger than the height h 1  in the direction orthogonal to the first surface  7 , the cutting load can be absorbed in a wide range of the voids  21  without making the voids  21  larger than necessary. This makes it possible to further enhance the impact resistance while reducing the ratio of the voids  21 . 
     Specifically, the cutting load tends to be absorbed in a wide range of the voids  21  if a ratio of the average value of the widths w 1  of the voids  21  in the direction orthogonal to the first surface  7  to the average value of the heights h 1  of the voids  21  in the direction parallel to the first surface  7  is 1.2 or more. Additionally, if the above ratio is 2 or less, it is easy to ensure a deformation amount of the voids  21  in the direction orthogonal to the first surface  7 , thus leading to stable absorption of the cutting load in the voids  21 . 
     If the average value of the heights h 1  of the voids  21  in the direction orthogonal to the first surface  7  is smaller than Rz where Rz is a maximum height of the boundary between the first surface  7  and the second surface  9  in the cross section orthogonal to the first surface  7 , it is easy to reduce degradation of the durability of the coating layer  5 . 
     The coated tool  1  of the present disclosure has the enhanced impact resistance because of deformation of the first portion X located between the voids  21  adjacent to each other and because of deformation of the plurality of voids  21  in the first layer  13 . If an average value of widths of the voids  21  in the direction orthogonal to the first surface  7  is smaller than Rz, an imaginary line connecting the voids  21  adjacent to each other is indicated by a zigzag shape that is bent larger than the width of the void  21 . 
     In cases where the imaginary line is indicated by the above shape, even if a crack occurs at one of the first portions X, the crack is less likely to propagate to the first portion X located adjacent to the first portion X with the crack. The durability of the coating layer  5  is therefore less likely to degrade. 
     The durability of the coating layer  5  is also less likely to degrade if an average value of distances dl from the voids  21  to the boundary between the first layer  13  and the second layer  15  is larger than an average value of widths w 2  of the first portions X in the cross section orthogonal to the first surface  7 . 
     The reason for this is as follows. Because, in comparison with the first portions X, the above case ensures a sufficient distance from the voids  21  to the boundary between the first layer  13  and the second layer  15 , even if a crack occurs at one of the first portions X, the crack is less likely to reach the boundary between the first layer  13  and the second layer  15 . The bondability between the first layer  13  and the second layer  15  is less likely to degrade because the crack is less likely to reach the boundary between the first layer  13  and the second layer  15 . 
     The voids  21  are located in the first layer  13  and located away from the boundary between the first layer  13  and the second layer  15 . The bondability between the first layer  13  and the second layer  15  is less likely to degrade while achieving enhanced impact resistance in the coating layer  5  if an average value of the distances dl from the voids  21  to the boundary between the first layer  13  and the second layer  15  is larger than an average value of the heights h 1  of the voids  21  in the direction orthogonal to the first surface  7  in the cross section orthogonal to the first surface  7 . 
     The reason for this is as follows. Because, in comparison with the size of the voids  21 , the distance from the voids  21  to the boundary between the first layer  13  and the second layer  15  can be sufficiently ensured, even if the voids  21  are deformed due to absorption of the cutting load, the boundary between the first layer  13  and the second layer  15  is not deformed, or the deformation amount becomes sufficiently small. The bondability between the first layer  13  and the second layer  15  is less likely to degrade because the boundary between the first layer  13  and the second layer  15  is less subjected to large deformation. 
     Examples of material of the base member  3  include inorganic materials, such as cemented carbide, cermet, and ceramics. The material of the base member  3  is not limited to these materials. 
     Examples of composition of cemented carbide include WC (tungsten carbide)-Co, WC—TiC (titanium carbide)-Co and WC—TiC—TaC (tantalum carbide)-Co. Specifically, WC, TiC and TaC are hard particles, and Co is a binding phase. The cermet is a sintered composite material obtainable by compositing metal into a ceramic component. Specific examples of the cermet include compounds composed mainly of TiC or TiN (titanium nitride). 
     The base member  3  may include a through hole  23  that passes through the first surface  7  and a surface located on an opposite side of the first surface  7 . The through hole  23  is usable for inserting a fixing member that is intended to fix the coated tool  1  to a holder. Examples of the fixing member include a screw and a clamping member. 
     The size of the base member  3  is not particularly limited. For example, a length of one side of the first surface  7  may be settable to approximately 3-20 mm. A height from the first surface  7  to the surface located on the opposite side of the first surface  7  may be settable to approximately 5-20 mm. 
     &lt;Manufacturing Method&gt; 
     A non-limiting embodiment of a method for manufacturing the coated tool  1  of the present disclosure is described below. 
     Firstly, a mixed powder is manufactured by suitably adding metal powder, carbon powder or the like to inorganic powder selected from carbide, nitride, carbonitride and oxide or the like, which are capable of forming a hard alloy constituting a base member  3  by sintering, and then by mixing them together. 
     Subsequently, a molded body is manufactured by molding the mixed powder into a predetermined tool shape with the use of a known molding method. Examples of the molding method include press molding, casting molding, extrusion molding and cold isostatic pressing. The base member  3  is manufactured by sintering the molded body in vacuum or a non-oxidizing atmosphere. A surface of the base member  3  may be then subjected to polishing process and honing process as needed. 
     Subsequently, a coating layer  5  is deposited on the surface of the base member  3  by chemical vapor deposition (CVD) method. 
     The first step is to deposit a titanium nitride layer  17  (underlayer) on the surface of the base member  3 . A first mixed gas used as a reaction gas is manufactured by mixing 0.5-10 vol % of titanium tetrachloride gas and 10-60 vol % of nitrogen gas into hydrogen (H 2 ) gas. The titanium nitride layer  17  is deposited in a temperature range of 830-870° C. by introducing the first mixed gas at a gas partial pressure of 10-20 kPa into a chamber. 
     The next step is to deposit a first region  19   a  in the first layer  13 . A second mixed gas is manufactured by blending 0.5-10 vol % of titanium tetrachloride gas, 1-50 vol % of nitrogen gas, 0.1-5.0 vol % of acetonitrile gas, and 0.01-0.5 vol % of methane gas into hydrogen gas. The MT-first region  19   a  is deposited by introducing the second mixed gas into the chamber. 
     The next step is to deposit an intermediate layer  19   c . A third mixed gas is manufactured by blending 3-30 vol % of titanium tetrachloride gas, 3-15 vol % of methane gas, 5-10 vol % of nitrogen gas and 0.5-5 vol % of carbon dioxide (CO 2 ) gas into hydrogen gas. The intermediate region  19   c  having a thickness of approximately 50-300 nm is deposited in a temperature range of 980-1050° C. by introducing the third mixed gas at a gas partial pressure of 6-12 kPa into the chamber. Voids  21  are formable in the intermediate region  19   c  because the third mixed gas includes carbon dioxide gas. With the above conditions, a coated tool  1  in which an average value of widths w 1  of the voids  21  in a direction parallel to the first surface  7  is smaller than an average value of distances w 2  between the voids  21  adjacent to each other in a cross section orthogonal to the first surface  7  can be manufactured. 
     Additionally, since the thickness of the intermediate region  19   c  is as small as approximately 50-300 nm, it becomes possible to align the voids  21  formed in the intermediate region  19   c  in a direction along the boundary between the first layer  13  and the second layer  15 . 
     The next step is to deposit a second region  19   b  in the first layer  13 . A fourth mixed gas is manufactured by blending 1-4 vol % of titanium tetrachloride gas, 5-20 vol % of nitrogen gas, 0.1-10 vol % of methane gas and 0.5-10 vol % of carbon dioxide gas into hydrogen gas. The HT-second region  19   b  having a thickness of approximately 0.3-3 μm is deposited in a temperature range of 950-1050° C. by introducing the fourth mixed gas at a gas partial pressure of 5-45 kPa into the chamber. 
     The next step is to deposit a second layer  15 . A deposition temperature is set to 950-1100° C., and a gas pressure is set to 5-20 kPa. A reaction gas composition is as follows. A fifth mixed gas is manufactured by blending 5-15 vol % of aluminum trichloride (AlCl 3 ) gas, 0.5-2.5 vol % of hydrogen chloride (HCl) gas, 0.5-5.0 vol % of carbon dioxide gas and 0-1 vol % of hydrogen sulfide (H 2 S) gas into hydrogen gas. The second layer  15  is deposited by introducing the fifth mixed gas into the chamber. 
     Thereafter, as needed, a polishing process is carried out on a part of the surface of the deposited coating layer  5  at which the cutting edge  11  is located. If the polishing process is carried out, a workpiece is less likely to be welded onto the cutting edge  11 , thus leading to the coated tool  1  having more excellent fracture resistance. 
     The above manufacturing method is a non-limiting embodiment of the method for manufacturing the coated tool  1  of the present disclosure. Hence, the coated tools  1  are not limited to ones which are manufactured by the above manufacturing method. For example, a third layer may be deposited separately on the second layer  15 . 
     In order to manufacture the coated tool  1  in which the average value of the widths w 1  of the voids  21  in the direction parallel to the first surface  7  is larger than an average value of the heights h 1  of the voids  21  in the direction orthogonal to the first surface  7  in the cross section orthogonal to the first surface  7 , time adjustment may be carried out during the deposition of the intermediate region  19   c  so that the intermediate region  19   c  is deposited in a thickness of approximately 50-150 nm. 
     In order to manufacture the coated tool  1  in which an average value of the distances dl from the voids  21  to the boundary  16  is larger than an average value of the heights h 1  of the voids  21  in the direction orthogonal to the first surface  7  in the cross section orthogonal to the first surface  7 , time adjustment may be carried out during the deposition of the intermediate region  19   c  so as to be deposited in a thickness of approximately 50-150 nm, and thereafter time adjustment may be carried out during the deposition of the second region  19   b  in the first layer  13  so as to be deposited in a thickness of approximately 0.5-3 μm. 
     In order to manufacture the coated tool  1  in which an average value of the distances dl from the voids  21  to the boundary  16  is larger than an average value of the distances w 2  of the voids  21  adjacent to each other in the cross section orthogonal to the first surface, time adjustment may be carried out during the deposition of the second region  19   b  in the first layer  13  so as to be deposited in a thickness of approximately 0.5-3 μm. 
     &lt;Cutting Tool&gt; 
     A cutting tool  101  of the present disclosure is described below with reference to the drawings. 
     As illustrated in  FIGS. 6 and 7 , the cutting tool  101  includes a holder  105  having a bar-shaped body that extends from a first end (an upper side in  FIG. 6 ) to a second end (a lower side in  FIG. 6 ) with a pocket  103  located at a side of the first end, and the coated tool  1  located at the pocket  103 . In the cutting tool  101 , the coated tool  1  is attached so that a part of the ridge line which is usable as a cutting edge is protruded from a front end of the holder  105 . 
     The pocket  103  is a part that permits attachment of the coated tool  1 . The pocket  103  includes a seating surface parallel to a lower surface of the holder  105 , and a constraining side surface inclined relative to the seating surface. The pocket  103  opens into a side of the first end of the holder  105 . 
     The coated tool  1  is located at the pocket  103 . A lower surface of the coated tool  1  may be in a direct contact with the pocket  103 . Alternatively, a sheet may be held between the coated tool  1  and the pocket  103 . 
     The coated tool  1  is attached so that the part of the ridge line which is usable as the cutting edge is protruded outward from the holder  105 . The coated tool  1  is attached to the holder  105  by a screw  107 . 
     Specifically, the coated tool  1  is attached to the holder  105  in such a manner that screw parts are engaged with each other by inserting the screw  107  into the through hole of the coated tool  1 , and by inserting a front end of the screw  107  into a screw hole (not illustrated) formed in the pocket  103 . 
     For example, steel and cast iron are usable as the holder  105 . High toughness steel may be used in a non-limiting embodiment. 
     Examples illustrated in  FIGS. 6 and 7  have illustrated and described the cutting tools for use in the so-called turning process. Examples of the turning process include inner diameter processing, outer diameter processing and grooving process. The cutting tools are not limited to ones which are used for the turning process. For example, the coated tools  1  of the above non-limiting embodiment are applicable to the cutting tools for use in the milling process. 
     DESCRIPTION OF THE REFERENCE NUMERALS 
     
         
         
           
               1  coated tool 
               3  base member 
               5  coating layer 
               7  first surface 
               9  second surface 
               11  cutting edge 
               13  first layer 
               15  second layer 
               16  boundary between first layer and second layer 
               17  titanium nitride layer 
               19  titanium carbonitride layer 
               19   a  first region 
               19   b  second region 
               19   c  intermediate region 
               21  void 
               23  through hole 
               101  cutting tool 
               103  pocket 
               105  holder 
               107  fixing screw