Patent Publication Number: US-11390942-B2

Title: Cutting tool

Description:
TECHNICAL FIELD 
     The present disclosure relates to a cutting tool. 
     BACKGROUND ART 
     Conventionally, cutting tools made of cemented carbide or cubic boron nitride (cBN) sintered material have been used to cut steel, castings, and the like. When such a cutting tool is used to cut a workpiece the cutting tool has its cutting edge exposed to a severe environment such as high temperature and high stress, which invites wearing and chipping of the cutting edge. 
     Accordingly, suppressing wearing and chipping of the cutting edge is important in improving the cutting performance of the cutting tool and hence extending the life of the cutting tool. 
     For the purpose of improving a cutting tool&#39;s cutting performance (e.g., breaking resistance and wear resistance) a development of a coating for coating a surface of a substrate of cemented carbide, cBN sintered material and the like is underway. Inter alia, a coating composed of a compound of aluminum (Al), titanium (Ti), and nitrogen (N) (hereinafter also referred to as “AlTiN”) can have high hardness and also enhance oxidation resistance (for example, see Japanese Patent Laid-Open No. 10-330914 (PTL 1)). 
     CITATION LIST 
     Patent Literature 
     
         
         PTL 1: Japanese Patent Application Laid-Open No. 10-330914 
       
    
     SUMMARY OF INVENTION 
     The presently disclosed cutting tool is 
     a cutting tool comprising a substrate and an AlTiN layer disposed on the substrate, 
     the AlTiN layer including cubic Al x Ti (1-x) N crystal grains, 
     an atomic ratio x of Al in the Al x Ti (1-x) N being 0.7 or more and 0.95 or less, 
     the AlTiN layer including a first major surface on a side of a surface of the cutting tool and a second major surface on a side of the substrate, 
     the AlTiN layer including a first region having a distance of 0 nm or more and 100 nm or less from the first major surface, and a second region having a distance of more than 100 nm and 150 nm or less from the first major surface, 
     the first region having a maximum oxygen content ratio of 5 atomic % or more and 30 atomic % or less, 
     the second region having a maximum oxygen content ratio of less than 5 atomic %. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  illustrates an example of a cutting tool according to a first embodiment. 
         FIG. 2  illustrates another example of the cutting tool according to the first embodiment. 
         FIG. 3  illustrates still another example of the cutting tool according to the first embodiment. 
         FIG. 4  illustrates an AlTiN layer of the cutting tool according to the first embodiment. 
         FIG. 5  is a schematic cross section of a CVD apparatus used for manufacturing a cutting tool according to a second embodiment. 
         FIG. 6  is a schematic cross section of a gas introduction pipe of the CVD apparatus of  FIG. 5 . 
     
    
    
     DETAILED DESCRIPTION 
     [Problem to be Solved by the Present Disclosure] 
     In recent years, a cutting tool having a long tool life has also been demanded for a more efficient cutting process. In high-speed continuous processing of carbon steel, in particular, there is a demand for a cutting tool excellent in heat resistance and wear resistance. 
     [Advantageous Effect of the Present Disclosure] 
     The presently disclosed cutting tool can also have a long tool life even in high-speed continuous processing of carbon steel in particular. 
     DESCRIPTION OF EMBODIMENTS OF THE PRESENT DISCLOSURE 
     Initially, embodiments of the present disclosure will be listed and described. 
     (1) The presently disclosed cutting tool is 
     a cutting tool comprising a substrate and an AlTiN layer disposed on the substrate, 
     the AlTiN layer including cubic Al x Ti (1-x) N crystal grains, 
     an atomic ratio x of Al in the Al x Ti (1-x) N being 0.7 or more and 0.95 or less, 
     the AlTiN layer including a first major surface on a side of a surface of the cutting tool and a second major surface on a side of the substrate, 
     the AlTiN layer including a first region having a distance of 0 nm or more and 100 nm or less from the first major surface, and a second region having a distance of more than 100 nm and 150 nm or less from the first major surface, 
     the first region having a maximum oxygen content ratio of 5 atomic % or more and 30 atomic % or less, 
     the second region having a maximum oxygen content ratio of less than 5 atomic %. 
     The presently disclosed cutting tool can also have a long tool life even in high-speed continuous processing of carbon steel in particular. 
     (2) The second region preferably has a maximum oxygen content ratio of 3 atomic % or more and less than 5 atomic %. The presently disclosed cutting tool can thus have a long tool life. 
     (3) The AlTiN layer preferably has a thickness of 0.1 μm or more and 20 μm or less. The presently disclosed cutting tool can thus have a longer tool life. 
     (4) Preferably, the cutting tool further comprises an underlying layer disposed between the substrate and the AlTiN layer, wherein 
     the underlying layer is composed of a first compound consisting of at least one element selected from the group consisting of a group 4 element, a group 5 element and a group 6 element of the periodic table and Al and at least one element selected from the group consisting of carbon, nitrogen, oxygen and boron. 
     This can enhance the AlTiN layer in peeling resistance. 
     (5) Preferably, the cutting tool further comprises a surface layer disposed on the AlTiN layer, wherein 
     the surface layer is composed of a second compound consisting of at least one element selected from the group consisting of a group 4 element, a group 5 element and a group 6 element of the periodic table and Al and at least one element selected from the group consisting of carbon, nitrogen, oxygen and boron. 
     The presently disclosed cutting tool can thus have a further longer tool life. 
     DETAILED DESCRIPTION OF EMBODIMENTS OF THE PRESENT DISCLOSURE 
     A specific example of the present disclosed cutting tool will now be described below with reference to the drawings. In the drawings of the present disclosure, like reference numerals denote like or equivalent components. Furthermore, in the drawings, length, width, thickness, depth and other similar dimensional relationships are changed as appropriate for clarification and simplification of the drawings, and may not represent actual dimensional relationships. 
     In the present specification, an expression in the form of “A to B” means a range&#39;s upper and lower limits (that is, A or more and B or less), and when A is not accompanied by any unit and B is alone accompanied by a unit, A has the same unit B. 
     In the present specification, when a compound or the like is represented by a chemical formula without specifying any specific atomic ratio, it shall include any conventionally known atomic ratio and should not necessarily be limited to what falls within a stoichiometric range. For example, “AlTiN” has a ratio in atomicity including any conventionally known atomic ratio. 
     First Embodiment: Cutting Tool 
     The presently disclosed cutting tool is 
     a cutting tool comprising a substrate and an AlTiN layer disposed on the substrate, 
     the AlTiN layer including cubic Al x Ti (1-x) N crystal grains, 
     an atomic ratio x of Al in the Al x Ti (1-x) N being 0.7 or more and 0.95 or less, 
     the AlTiN layer including a first major surface on a side of a surface of the cutting tool and a second major surface on a side of the substrate, 
     the AlTiN layer including a first region having a distance of 0 nm or more and 100 nm or less from the first major surface, and a second region having a distance of more than 100 nm and 150 nm or less from the first major surface, 
     the first region having a maximum oxygen content ratio of 5 atomic % or more and 30 atomic % or less, 
     the second region having a maximum oxygen content ratio of less than 5 atomic %. 
     The presently disclosed cutting tool can also have a long tool life even in high-speed continuous processing of carbon steel in particular. Although why it can do so is not known, it is inferred as indicated by items (i) and (ii) below: 
     (i) In the presently disclosed cutting tool, the AlTiN layer has a maximum oxygen content ratio of 5 atomic % or more and 30 atomic % or less in the first region located on a side of an outermost surface thereof. The first region thus has excellent heat resistance and excellent wear resistance. The cutting tool can thus have a long tool life. 
     (ii) in the presently disclosed cutting tool, the AlTiN layer has a maximum oxygen content ratio of less than 5 atomic in the second region. The second region thus has high hardness and excellent wear resistance. The cutting tool can thus have a long tool life. 
     &lt;Configuration of Cutting Tool&gt; 
     As shown in  FIG. 1 , a cutting tool  1  of the present embodiment comprises a substrate  10 , and an AlTiN layer  11  disposed on substrate  10  (hereinafter also simply referred to as a “cutting tool”). 
     As shown in  FIG. 2 , a cutting tool  21  may further comprise an underlying layer  12  disposed between substrate  10  and AlTiN layer  11 . 
     As shown in  FIG. 3 , a cutting tool  31  may further comprise a surface layer  13  disposed on AlTiN layer  11 . Other layers such as underlying layer  12  and surface layer  13  will be described hereinafter. 
     In the present specification, the above-described layers disposed on substrate  10  may be collectively referred to as a “coating.” That is, as shown in  FIGS. 1 to 3 , cutting tools  1 ,  21  and  31  comprise coatings  14 ,  24  and  34  disposed on substrate  10 , and the coatings include AlTiN layer  11 . Further, as shown in  FIGS. 2 and 3 , coatings  24  and  34  may further include underlying layer  12  and/or surface layer  13 . 
     &lt;Applications of Cutting Tool&gt; 
     The cutting tool can for example be a drill, an end mill (e.g., a ball end mill), an indexable cutting insert for a drill, an indexable cutting insert for an end mill, an indexable cutting insert for milling, an indexable cutting insert for turning, a metal saw, a gear cutting tool, a reamer, a tap, or the like. 
     &lt;Substrate&gt; 
     The substrate of the present embodiment can be any substrate conventionally known as a substrate of this type. For example, it preferably includes at least one selected from the group consisting of a cemented carbide (for example, a tungsten carbide (WC)-base cemented carbide, a cemented carbide containing WC and Co a cemented carbide containing WC and a carbonitride of Cr, Ti, Ta, Nb or the like, and the like), a cermet (mainly composed of TiC, TiN, TiCN, or the like), a high-speed steel, ceramics (titanium carbide, silicon carbide, silicon nitride, aluminum nitride, aluminum oxide, and the like), a cubic boron nitride (cBN) sintered material, and a diamond sintered material. 
     Of these various types of substrates, it is particularly preferable to select a cemented carbide (a WC-base cemented carbide, in particular) or a cermet (a TiCN-base cermet, in particular). This is because these substrates are particularly excellent in balance between hardness and strength at high temperature, in particular, and present excellent characteristics as a substrate for a cutting tool for the above-described applications. 
     When using a cemented carbide as a substrate, the effect of the present embodiment is exhibited even if the cemented carbide has a structure including free carbon or an extraordinary phase referred to as η phase, Note that the substrate used in the present embodiment may have its surface modified. For example, for the cemented carbide, the surface may be provided with a β-free layer, and for the cermet, the surface may be provided with a surface hardened layer, and even if the surface is modified in this way, the effect of the present embodiment is exhibited. 
     &lt;Coating&gt; 
     A coating according to the present embodiment includes an AlTiN layer disposed on the substrate. The “coating” coats at least a part of the substrate (for example, a rake face, a flank, and the like) to exhibit a function to improve the cutting tool&#39;s various characteristics such as breaking resistance, wear resistance, peeling resistance and the like. The coating is preferably applied not only to a part of the substrate but also to the entire surface of the substrate. However, even if the substrate is partially uncoated with the coating or the coating is partially different in configuration, such does not depart from the scope of the present embodiment. 
     The coating&#39;s thickness is preferably 2.5 μm or more and 30 μm or less, more preferably 3 μm or more and 25 μm or less. Note that the thickness of the coating means a total thickness of any layers constituting the coating. A “layer constituting the coating” for example includes an AlTiN layer, an underlying layer, a surface layer and the like, as will be described hereinafter. 
     Each layer configuring the coating is measured in thickness by observing with a scanning transmission electron microscope, (STEM) a sample in a cross section parallel to the direction of a normal to a surface of the substrate, for example. The scanning transmission electron microscope is JEM-2100F (trade name) manufactured by JEOL Ltd., for example. 
     As used herein, “thickness” means an average thickness, Specifically, a sample in cross section is observed with a magnification of 5,000 to 10,000 times in an area of 100 to 500 μm 2 , and in one field of view, 10 locations are subject to measurement in thickness in width and their average value is determined as “thickness.” 
     &lt;AITiN Layer&gt; 
     The AlTiN layer of the present embodiment includes cubic Al x Ti 1-x N crystal grains (hereinafter also simply referred to as “crystal grains”). That is, the AlTiN layer is a layer including polycrystalline Al x Ti 1-x N. In the present embodiment, “crystal grains of Al x Ti 1-x N” mean crystal grains each of a composite crystal formed of a layer made of AlN (hereinafter also referred to as an “AlN layer”) and a layer made of TiN (hereinafter also referred to as a “TiN layer”) alternately stacked. In the present embodiment, the AlN layer also includes a layer having a portion with Al substituted with Ti. Further, the TiN layer also includes a layer having a portion with Ti substituted with Al. 
     For cubic crystal grains, the AlN layer and the TiN layer both have an FCC structure (Face-Centered Cubic structure). 
     An atomic ratio x of Al in the Al x Ti 1-x N is 0.7 or more and 0.95 or less, preferably 0.8 or more and 0.9 or less. 
     The x is determined by analyzing crystal grains in the AlTiN layer appearing in a sample in a cross section parallel to the direction of a normal to a surface of the substrate with an energy dispersive X-ray (EDX) spectrometer accompanying a scanning electron microscope (SEM) or a TEM, The atomic ratio x of Al thus determined is a value determined as an average of all of the crystal grains of the Al x Ti 1-x N. Specifically, any 10 points in the AlTiN layer in a sample in the above-described cross section is each measured to obtain a value x, and an average value of such values obtained at the 10 points is defined as x in the Al x Ti 1-x N. Herein, “any 10 points” are selected from different crystal grains of the AlTiN layer. The EDX device is JED-2300 (trade name) manufactured by JEOL Ltd., for example. Not only the atomic ratio of Al but those of Ti and N can also be calculated in the above method. 
     In the present embodiment, being “disposed on the substrate” is not limited to being disposed directly on the substrate and also includes being disposed on the substrate via another layer. That is, the AlTiN layer may be disposed directly on the substrate or may be disposed on the substrate via another layer such as an underlying layer described hereinafter insofar as such does not impair an effect of the surface-coated cutting tool according to the present embodiment. 
     On the AlTiN layer, another layer such as a surface layer may be disposed. The AlTiN layer may be an outermost surface layer of the coating. 
     As shown in  FIG. 4 , AlTiN layer  11  includes a first major surface  11   a  on a side of a surface of cutting tool  1  and a second major surface  11   b  on a side of substrate  10 . AlTiN layer  11  includes a first region  11 A having a distance of 0 nm or more and 100 nm or less from first major surface  11   a , and a second region  11 B having a distance of more than 100 nm and 150 nm or less from first major surface  11   a.    
     In the AlTiN layer of the present embodiment, the first region has a maximum oxygen content ratio of 5 atomic % or more and 30 atomic % or less. The first region thus has excellent heat resistance and excellent wear resistance. The cutting tool can thus have a long tool life. 
     The first region can have the maximum oxygen content ratio with a lower limit of 5 atomic % or more, and the lower limit can be 6 atomic % or more, 7 atomic % or more. The first region can have the maximum oxygen content ratio with an upper limit of 30 atomic % or less, and the lower limit can be 29 atomic % or less, 27 atomic % or less. The first region can have a maximum oxygen content ratio of 5 atomic % or more and 30 atomic % or less, 6 atomic % or more and 29 atomic % or less, 7 atomic % or more and 27 atomic % or less. 
     In the present specification, the Al TiN layer&#39;s oxygen content ratio (as converted to SiO 2 ) is measured while etching a surface of a diamond layer using an Auger electron spectrometer (AES) (device: PHI 650® produced by Perkin-Elmer) in accordance with JIS K 0146:2002 (ISO 14606:2000) while etching the AlTiN layer in the direction of a normal to the first Major surface. 
     The etching is performed in a direction from the first major surface toward the second major surface (hereinafter also referred to as a “depthwise direction”) in the direction of a normal to the first major surface. The oxygen content ratio is measured at points at intervals of 1 nm in the depthwise direction of the AlTiN layer. Thus; the oxygen content ratio can be measured at intervals of 1 nm in the depthwise direction of the AlTiN layer. 
     The Auger electron spectroscopic measurement is conducted under the following conditions:
     Electron Energy: 10 kv   Electron beam current: 3 mA   Angle of incidence: 90°   (Detector: 55°)   Beam diameter: 1 nm   Sputter Ion: Ar   Mode: Depth Analysis (Depth Profile)   

     Note that, as measured by the applicant, it has been confirmed that, as measured in the same sample, while the AlTiN layer&#39;s oxygen content ratio was measured a plurality of tunes while where it was measured was changed, measurement results were obtained without substantial variation and there was no arbitrariness even when where it was measured was set as desired. Where it is measured can for example be the cutting tool&#39;s rake face, cutting edge, or the like. 
     The second region has a maximum oxygen content ratio of less than 5 atomic % The second region thus has high hardness and excellent wear resistance. The cutting tool can thus have a long tool life. 
     The second region can have the maximum oxygen content ratio with an upper limit of less than 5 atomic %, and the upper limit can be 4.5 atomic % or less, 4 atomic % or less. The second region can have the maximum oxygen content ratio with a lower limit of 0 atomic % or more, 2.5 atomic % or inure, 3 atomic % or more. The second region can have a maximum oxygen content ratio of 0 atomic % or more and less than 5 atomic %, 2.5 atomic % or more and less than 5 atomic %, 3 atomic % or more and less than 5 atomic %, 2.5 atomic % or more and 4.5 atomic % or less. 3 atomic % or more and 4 atomic % or less. 
     The AlTiN layer preferably has a thickness of 0.1 μm or more and 20 μm or less. The cutting tool can thus have a longer tool life. 
     The AlTiN layer can have a lower limit in thickness of 0.1 μm or more, 1 μm or more. The AlTiN layer can have an upper limit in thickness of 20 μm or less, 10 μm or less. The AlTiN layer can be 0.1 μm or more and 20 μm or less, 1 μm or more and 10 μm or less in thickness. 
     The AlTiN layer&#39;s thickness can be determined by observing a sample in cross section of the cutting tool with a scanning transmission electron microscope (STEM) or the like, as has been described above. 
     &lt;Underlying Layer&gt; 
     As shown in  FIGS. 2 and 3 , cutting tools  21  and  31  comprise coatings  24  and  34 , respectively, which can further include underlying layer  12  disposed between substrate  10  and AlTiN layer  11 . Underlying layer  12  is preferably composed of a first compound consisting of at least one element selected from the group consisting of a group 4 element, a group 5 element and a group 6 element of the periodic table and Al and at least one element selected from the group consisting of carbon, nitrogen, oxygen and boron. Examples of the group 4 element of the periodic table include titanium (Ti), zirconium (Zr), hafnium (Hf), and the like. Examples of the group 5 element of the periodic table include vanadium (V), niobium (Nb), tantalum (Ta), and the like. Examples of the group 6 element of the periodic table include chromium (Cr), molybdenum (Mo), tungsten (W), and the like. 
     The first compound is different in composition from the AlTiN layer. That is, when the first compound is AlTiN, the first compound has a composition different from constituting the AlTiN layer. 
     The underlying layer is preferably composed of a first compound represented by TiCN. The underlying layer composed a TiCN exhibits strong adhesion to the AlTiN layer. As a result, the coating is enhanced in peeling resistance. 
     The underlying layer can have a lower limit in thickness of 0.1 μm or more, 1 μm or more, 1.5 μm or more. The underlying layer can have an upper limit in thickness of 20 μm or less, 15 μm or less, 10 μm or less. The underlying layer can be 0.1 μm or more and 20 μm or less, 1 μm or more and 15 μm or less, 1.5 μm or more and 10 μm or less in thickness. 
     The underlying layer&#39;s thickness can be determined by observing a sample in cross section of the cutting tool with a scanning transmission electron microscope (STEM) or the like, as has been described above. 
     &lt;Surface Layer&gt; 
     As shown in  FIG. 3 , cutting tool  31  comprises coating  34  which can further include surface layer  13  disposed on AlTiN layer  11 . Surface layer  13  is composed of a second compound consisting of at least one element selected from the group consisting of a group 4 element, a group 5 element and a group 6 element of the periodic table and Al and at least one element selected from the group consisting of carbon, nitrogen, oxygen and boron. 
     The second compound is different in composition from the AlTiN layer. That is, when the second compound is AlTiN, the second compound has a composition different from Al x Ti (1-x) N constituting the AlTiN layer. 
     Examples of the second compound include Al 2 O 3  and TiN. 
     The surface layer can have a lower limit in thickness of 0.1 μm or more, 0.2 μm or more. The surface layer can have an upper limit in thickness of 3 μm or less, 2 μm or less, 1 μm or less. The surface layer can be 0.1 μm or more and 3 μm or less, 0.2 μm or more and 2 μm or less, 0.2 μm or more and 1 μm or less in thickness. 
     The surface layer&#39;s thickness can be determined by observing a sample in cross section of the cutting tool with a scanning transmission electron microscope (STEM) or the like, as has been described above. 
     &lt;Another Layer&gt; 
     The coating of the cutting tool may further include another layer insofar as it does not impair an effect of the cutting tool according to the present embodiment. The other layer may have a composition different from or identical to that of the MEN laver, the underlying layer, or the surface layer. Examples of a compound included in the other layer include TiN, TiCN, TiBN, and Al 2 O 3 . The other layer is not limited, either, in in what order it is stacked. For example, an example of the other layer is an intermediate layer disposed between the underlying layer and the AlTiN layer. While the other layer is not particularly limited in thickness as long as it does not impair an effect of the present embodiment, it is for example 0.1 μm or more and 20 μm or less. 
     Second Embodiment: A Method for Manufacturing a Cutting Tool 
     While a method for manufacturing a cutting tool according to the first embodiment is not particularly limited, it for example comprises a first step of preparing the substrate (hereinafter also simply referred to as a “first step”), and a second step of depositing a coating including, the AlTiN layer on the substrate through chemical vapor deposition (CVD) (hereinafter also simply referred to as a “second step”). The method for manufacturing the cutting tool according to the present embodiment can further comprise a third step of blasting the coating (hereinafter also referred to as a “third step”). An example of the method for manufacturing the cutting tool according to the first embodiment will be described below. Note that the following manufacturing method is an example, and the method of manufacturing the cutting tool according to the first embodiment is not limited to the following method and the cutting tool may be manufactured in a different method. 
     &lt;First Step: Step of Preparing a Substrate&gt; 
     In the first step, a substrate is prepared. For example, a cemented carbide substrate, a cermet substrate or the like is prepared as the substrate. The cemented carbide substrate may be a commercially available product or may be manufactured in a typical powder metallurgy method. When the substrate is manufactured in a typical powder metallurgy method, for example, WC powder and Co powder or the like are mixed using a ball mill or the like to obtain a powdery mixture. After the powdery mixture is dried, it is shaped into a prescribed shape to obtain a shaped body. The shaped body is sintered to obtain a WC-Co based cemented carbide (a sintered material). 
     Subsequently, the sintered material can be honed or subjected to a prescribed cutting edge process to prepare a substrate made of the WC-Co based cemented carbide. In the first step, any other substrate may be prepared insofar as it is a substrate conventionally known as a substrate of this type. 
     &lt;Second Step: Step of Forming an AlTiN Layer&gt; 
     In the second step, a first gas, a second gas and a third gas are jetted onto the substrate in an atmosphere of 650° C. or higher and 800° C. or lower and 2 kPa or higher and 30 kPa or lower, the first gas including a gas of a halide of aluminum, a gas of a halide of titanium, carbon monoxide, carbon dioxide, and dehydrated ethanol, the second gas including a gas of a halide of aluminum, a gas of a halide of titanium and a gas of ammonia, the third gas including a gas of ammonia. The second step can be performed using, for example, a CVD apparatus described below. 
     (CVD Apparatus) 
       FIG. 5  is a schematic cross section of one example of a CVD apparatus used for manufacturing the cutting tool according to the present embodiment. As shown in  FIG. 5 , a CVD apparatus  50  includes a plurality of substrate setting jigs  52  for setting substrate  10 , and a reaction chamber  53  made of heat-resistant alloy steel and incorporating substrate setting jigs  52  therein. A temperature controller  54  is provided around reaction chamber  53  for controlling the temperature inside reaction chamber  53 . In the present embodiment, substrate  10  is set on a protrusion which substrate setting jig  52  is provided with. Such a setting allows deposition to be done on a rake face, a flank, and a cutting edge portion uniformly. 
     A gas introduction pipe  58  having a first gas introduction pipe  55 , a second gas introduction pipe  56  and a third gas introduction pipe  57  adjacently bonded together extends in the vertical direction through a space inside reaction chamber  53  rotatably about the vertical direction. Gas introduction pipe  58  is configured such that the first gas introduced into first gas introduction pipe  55 , the second gas introduced into second gas introduction pipe  56 , and the third gas introduced into third gas introduction pipe  57  are not mixed together inside gas introduction pipe  58  (see  FIG. 6 ). Further, first gas introduction pipe  55 , second gas introduction pipe  56 , and third gas introduction pipe  57  are each provided with a plurality of throughholes for jetting the gases respectively flowing through first, second and third gas introduction pipes  55 ,  56  and  57  onto substrate  10  set on substrate setting jig  52 . In the present embodiment, it is preferable that the gas jetting throughhole and substrate  10  be spaced by a sufficient distance. This allows the first gas, the second gas, and the third gas to flow uniformly and can thus prevent turbulence. 
     Further, reaction chamber  53  is provided with a gas exhaust pipe  59  for externally exhausting the gas inside reaction chamber  53 , and the gas in reaction chamber  53  passes through gas exhaust pipe  59  and is exhausted out of reaction chamber  53  via a gas exhaust port  60 . 
     More specifically, the first gas, the second gas and the third gas are introduced into first gas introduction pipe  55 , second gas introduction pipe  56  and third gas introduction pipe  57 , respectively. In doing so, the first, second and third gases in their respective gas introduction pipes may have any temperature that does not liquefy the gases. Subsequently, the first gas, the second gas and the third gas are jetted in this order repeatedly into reaction chamber  53  with an atmosphere set therein to have a temperature of 650° C. or higher and 800° C. or lower and a pressure of 2 kPa or higher and 30 kPa or lower. As gas introduction pipe  58  has the plurality of throughholes, the first, second, and third gases introduced are jetted into reaction chamber  53  through different throughholes, respectively. While the gases are thus jetted, gas introduction pipe  58  is rotating at a rotation speed for example of 2 to 4 rpm about the above-described axis, as indicated in  FIG. 5  by a rotating arrow. As a result, the first gas, the second gas, and the third gas can be jetted in this order repeatedly onto substrate  10 . 
     (First Gas) 
     The first gas includes a gas of a halide of aluminum, a gas of a halide of titanium, carbon monoxide, carbon dioxide, and dehydrated ethanol. 
     Examples of the gas of a halide of aluminum include a gas of aluminum chloride (a gas of AlCl 3  and a gas of Al 2 Cl 6 ). Preferably, a gas of AlCl 3  is used. The gas of a halide of aluminum preferably has a concentration (% by volume) of 0.1% by volume or more and 20% by volume or less with reference to the total volume of the first gas. 
     Examples of the gas of a halide of titanium include a gas of titanium (IV) chloride (a gas of TiCl 4 ), a gas of titanium (III) chloride (a gas of TiCl 3 ), and the like. Preferably a gas of titanium (IV) chloride is used. The gas of a halide of titanium preferably has a concentration (in % by volume) of 0.1% by volume or more and 20% by volume or less with reference to the total volume of the first gas. 
     In the first gas, the gas of a halide of aluminum has a molar ratio more preferably of 0.1 or more and 0.9 or less with reference to the total moles of the gas of a halide of aluminum and the gas of a halide of titanium. 
     Carbon monoxide, carbon dioxide, and dehydrated ethanol preferably have a concentration (in % by volume) of 0.1% by volume or more and 20% by volume or less with reference to the total volume of the first gas. 
     The first gas may include a gas of hydrogen and may include an inert gas such as a gas of argon. The inert gas preferably has a concentration (in % by volume) of 10% by volume or more and 60% by volume or less with reference to the total volume of the first gas. The gas of hydrogen typically occupies the balance of the first gas. 
     The first gas is jetted onto the substrate at a flow rate preferably of 5 to 60 L/min. 
     (Second Gas) 
     The second gas includes a gas of a halide of aluminum, a gas of a halide of titanium, and a gas of ammonia. The gas of a halide of aluminum and the gas of a halide of titanium can be the gases exemplified in the above (First Gas) section. The gas of a halide of aluminum and the gas of a halide of titanium that are used for the first gas may be identical to or different from the gas of a halide of aluminum and the gas of a halide of titanium that are used for the second gas, respectively. 
     The gas of a halide of aluminum preferably has a concentration (% by volume) of 2% by volume or more and 50% by volume or less with reference to the total volume of the second gas. 
     The gas of a halide of titanium preferably has a concentration (in % by volume) of 0.1% by volume or more and 20% by volume or less with reference to the total volume of the second gas. 
     In the second gas, the gas of a halide of aluminum has a molar ratio preferably of 0.1 or more and 0.9 or less with reference to the total moles of the gas of a halide of aluminum and the gas of a halide of titanium. 
     The gas of ammonia preferably has a concentration (in % by volume) of 0.1% by volume or more and 20% by volume or less with reference to the total volume of the second gas. 
     The second gas may include a gas of hydrogen and may include an inert gas such as a gas of argon. The inert gas preferably has a concentration (in % by volume) of 0.1% by volume or more and 20% by volume or less with reference to the total volume of the second gas. The gas of hydrogen typically occupies the balance of the second gas. 
     The second gas is jetted onto the substrate at a flow rate preferably of 5 to 60 L/min. 
     (Third Gas) 
     The third gas includes a gas of ammonia. The third gas may include a gas of hydrogen and may include an inert gas such as a gas of argon. 
     The gas of ammonia preferably has a concentration (in % by volume) of 0.1% by volume or more and 40% by volume or less with reference to the total volume of the third gas. The gas of hydrogen typically occupies the balance of the third gas. 
     The third gas is jetted onto the substrate at a flow rate preferably of 5 to 20 L/min. 
     &lt;Third Step: Blasting Step&gt; 
     In the present step, the coating is blasted. The blasting is performed for example under the following conditions. The blasting allows compressive residual stress to be imparted to the coating.
     Blasting conditions   Medium: 500 g of zirconia particles   Projection angle: 90°   Projection distance: 50 mm   Projection time: 3 seconds   

     &lt;Another Step&gt; 
     In the manufacturing method according to the present embodiment, in addition to the steps described above, an additional step may be performed, as appropriate, within a range that does not impair an effect of the present embodiment. Examples of the additional step include the step of forming an underlying layer between the substrate and the AlTiN layer, and the step of forming a surface layer on the AlTiN layer. The underlying layer and the surface layer may be formed in any method, and the layers are formed for example through CVD. When the step of forming the surface layer on the AlTiN layer is performed, the third step is performed after the surface layer is funned. 
     In the method for manufacturing a surface-coated cutting tool according to the present embodiment, the AlTiN layer is formed through CVD. When this is compared with forming the coating through PVD, the former enhances the coating&#39;s adhesion to the substrate (or coating adhesion). 
     Examples 
     The present embodiment will be described more specifically with reference to examples. Note, however, that the present embodiment is not limited to these examples. 
     &lt;&lt;Manufacturing a Cutting Tool&gt;&gt; 
     &lt;Preparing the Substrate&gt; 
     Initially, as a substrate, a substrate composed of cemented carbide indicated in Table 1 below (hereinafter also simply referred to as a “substrate”) was prepared (i.e., a first step). Powdery raw materials of a blending composition (% by mass) shown in Table 1 were uniformly mixed to provide a powdery mixture. In Table 1, “balance” indicates that WC occupies the balance of the blending composition (% by mass). 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 substrate&#39;s blending composition (mass %) 
               
            
           
           
               
               
               
               
               
               
               
            
               
                   
                 Co 
                 TiC 
                 TiCN 
                 Cr 3 C 2   
                 TaC 
                 WC 
               
               
                   
                   
               
               
                   
                 8.0 
                 2.0 
                 2.0 
                 0.3 
                 0.5 
                 balance 
               
               
                   
                   
               
            
           
         
       
     
     Subsequently, the powdery mixture was pressure-formed into a prescribed shape and thereafter sintered for 1 to 2 hours at 1300 to 1500° C. to obtain a substrate (substrate shape: CNMG120408 N-GU). 
     &lt;Depositing the Coating&gt; 
     Subsequently, the CVD apparatus shown in  FIG. 5  was employed to deposit on the substrate a coating including an underlying layer, an AlTiN layer, and a surface layer. 
     (Depositing the Underlying Layer) 
     Under conditions indicated in Table 2 for deposition, a reactant gas having a composition indicated in Table 2 was jetted onto a surface of the substrate to deposit an underlying layer of TiCN. 
     
       
         
           
               
             
               
                 TABLE 2 
               
               
                   
               
               
                 conditions for depositing underlying layer 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
            
               
                 composition of reactant gas 
                 TiCl 4  = 2.0 vol %, CH 3 CN = 0.7 vol %, 
               
               
                   
                 H 2  = balance 
               
            
           
           
               
               
               
            
               
                 temperature 
                 860° 
                 C. 
               
               
                 pressure 
                 9 
                 kPa 
               
               
                 gas flow rate 
                 50.5 
                 L/min 
               
               
                   
               
            
           
         
       
     
     (Depositing the AlTiN layer) 
     Subsequently, for Samples 1 to 10, an AlTiN layer was deposited on the underlying layer. Depositing the AlTiN layer was divided into a first half and a second half by changing the first gas in type (i.e., the second step). 
     In the first half, under the conditions for deposition as indicated in Table 3 at the “conditions for depositing the AlTiN layer” column, the first gas specified in Table 8 at the “conditions for depositing the AlTiN layer,” “1st half” and “1st gas (table 4)” column (see table 4 for the composition of the gas), the second gas having the composition indicated in Table 5, and the third gas having the composition indicated in Table 6 were jetted in this order repeatedly onto a surface of the underlying layer to deposit an AlTiN layer. The first half&#39;s deposition time is as indicated in Table 8 at the “conditions for depositing the AlTiN layer,” “1st half” and “time (min.)” column. 
     Subsequently, in the second half, under the conditions for deposition as indicated in Table 3 at the “conditions for depositing the AlTiN layer” column, the first gas specified in Table 8 at the “conditions for depositing the AITiN layer,” “2nd half” and “1st gas (table 4)” column (see table 4 for the composition of the gas), the second gas having the composition indicated in Table 5, and the third gas having the composition indicated in Table 6 were jetted in this order repeatedly onto a surface of the underlying layer to deposit an AlTiN layer. The second half&#39;s deposition time is as indicated in Table 8 at the “conditions for depositing the AlTiN layer,” “2nd half” and “time (min.)” column. 
     The substrate was set on a protrusion which the substrate setting jig was provided with. Furthermore, the gas jetting throughhole and the substrate were spaced by a sufficient distance (for example of 5 cm). 
     
       
         
           
               
             
               
                 TABLE 3 
               
               
                   
               
               
                 conditions for depositing AlTiN layer 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
            
               
                   
                 temperature 
                 780° 
                 C. 
               
               
                   
                 pressure 
                 3 
                 kPa 
               
               
                   
                 rotational speed 
                 2 
                 rpm 
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 4 
               
             
            
               
                   
               
               
                 composition of 1st gas 
               
            
           
           
               
               
               
               
               
               
               
            
               
                 ID no. 
                 b 
                 c 
                 d 
                 e 
                 f 
                 g 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 AlCl 3  (vol %) 
                 0.83 
                 0.83 
                 0.83 
                 0.83 
                 1.00 
                 0.83 
               
               
                 TiCl 4  (vol %) 
                 0.17 
                 0.17 
                 0.17 
                 0.17 
                 0.00 
                 0.17 
               
               
                 AlCl 3 /(AlCl 3  + 
                 0.83 
                 0.83 
                 0.83 
                 0.83 
                 1.00 
                 0.83 
               
               
                 TiCl 4 ) (molar 
               
               
                 ratio) 
               
               
                 Ar (vol %) 
                 38 
                 38 
                 38 
                 38 
                 40 
                 60 
               
               
                 CO (vol %) 
                 8.6 
                 9 
                 9.4 
                 9.85 
                 10 
                 0 
               
               
                 CO 2  (vol %) 
                 8.6 
                 9 
                 9.4 
                 9.85 
                 10 
                 0 
               
               
                 C 2 H 5 OH (vol 
                 4.8 
                 4 
                 3.2 
                 2.3 
                 0 
                 0 
               
               
                 %) 
               
               
                 H 2  (vol %) 
                 balance 
                 balance 
                 balance 
                 balance 
                 balance 
                 balance 
               
               
                 gas flow rate 
                 30 
                 30 
                 30 
                 30 
                 30 
                 20 
               
               
                 (L/min) 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 5 
               
               
                   
               
               
                 composition of 2nd gas 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                   
                 AlCl 3  (vol %) 
                 4.2 
               
               
                   
                 TiCl 4  (vol %) 
                 0.7 
               
               
                   
                 AlCl 3 /(AlCl 3  + TiCl 4 ) (molar ratio) 
                 0.86 
               
               
                   
                 NH 3  (vol %) 
                 11 
               
               
                   
                 Ar (vol %) 
                 16 
               
               
                   
                 H 2  (vol %) 
                 balance 
               
               
                   
                 gas flow rate (L/min) 
                 40 
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 6 
               
               
                   
               
               
                 composition of 3rd gas 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                   
                 NH 3  (vol %) 
                  2 
               
               
                   
                 H 2  (vol %) 
                 balance 
               
               
                   
                 gas flow rate (L/min) 
                 10 
               
               
                   
                   
               
            
           
         
       
     
     For example, for Sample 1 shown in Table 8, in the first half, with a temperature of 780° C., a pressure of 3 kPa, and the gas introduction pipe having a rotational speed of 2 rpm set as conditions for deposition (see Table 3), the first gas indicated in Table 4 by an identification number g (AlCl 3 : 0.83% by volume, TiCl 4 : 0.17% by volume; Ar: 60% by volume, H 2 : balance, and gas flow rate: 20 L/min.), the second gas indicated in Table 5 (AlCl 3 : 4.2% by volume, TiCl 4 : 0.7% by volume, NH 3 : 11% by volume, Ar: 16% by volume, H 2 : balance, and gas flow rate: 40 L/min.), and the third gas indicated in Table 6 (NH 3 : 2% by volume, H 2 : balance, and gas flow rate: 10 L./min.) were jetted in this order repeatedly onto a surface of the substrate to deposit an AlTiN layer. The first halfs deposition time was 592 minutes. 
     Subsequently, in the second half, with a temperature of 780° C., a pressure of 3 kPa, and the gas introduction pipe having a rotational speed of 2 rpm set as conditions for deposition (see Table 3), the first gas indicated in Table 4 by an identification number c (AlCl 3 : 0.83% by volume, TiCl 4 : 0.17% by volume, Ar: 38% by volume, CO: 9% by volume, CO 2: 9 % by volume, C 2 H 5 OH: 4% by volume, H 2 : balance, and gas flow rate: 30 L/min.), the second gas indicated in Table 5 (AlCl 3 : 4.2% by volume, TiCl 4 : 0.7% by volume, NH 3 : 11% by volume, Ar: 16% by volume, H 2 : balance, and gas flow rate: 40 L/min.), and the third gas indicated in Table 6 (NH 3 : 2% by volume, H 2 : balance, and gas flow rate: 10 L/min.) were jetted in this order repeatedly onto a surface of the substrate to deposit an AlTiN layer. The second half&#39;s deposition time was 8 minutes. 
     For sample 11, under the conditions for deposition as indicated in Table 3 at the “conditions for depositing the AlTiN layer” column, the first gas having the composition specified in table 4 by identification number g, the second gas having the composition specified in Table 5, and the third gas having the composition specified in Table 6 were jetted in this order repeatedly onto a surface of the underlying layer to deposit an Al 2 O 3  layer. The deposition was done for 600 minutes. 
     For sample 12, under the conditions for deposition as indicated in Table 3 at the “conditions for depositing the AlTiN layer” column, the first gas having the composition specified in table 4 by an identification number f, the second gas having the composition specified in Table 5, and the third gas having the composition specified in Table 6 were jetted in this order repeatedly onto a surface of the underlying layer to deposit an Al 2 O 3  layer. The deposition was done for 10 minutes. 
     (Depositing the Surface Layer) 
     Subsequently, under conditions indicated in Table 7 for deposition, a reactant gas having a composition indicated in Table 7 was jetted onto a surface of the AlTiN layer to deposit a surface layer of TiN. 
     
       
         
           
               
             
               
                 TABLE 7 
               
               
                   
               
               
                 conditions for depositing surface layer 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
            
               
                 composition of reactant gas 
                 TiCl 4  = 0.5 vol %, N 2  = 41.2 vol %, 
               
               
                   
                 H 2  = balance 
               
            
           
           
               
               
               
            
               
                 temperature 
                 780° 
                 C. 
               
               
                 pressure 
                 79.8 
                 kPa 
               
               
                 gas flow rate 
                 45.9 
                 L/min 
               
               
                   
               
            
           
         
       
     
     &lt;Blasting&gt; 
     The coating deposited on the substrate was blasted under the following conditions (a third step):
     Blasting conditions   Medium: 500 g of zirconia particles   Projection angle: 90°   Projection distance: 50 mm   Projection time: 3 seconds   

     Through the above process, cutting tools were produced for samples 1 to 12 indicated in table 8. 
     
       
         
           
               
               
               
             
               
                 TABLE 8 
               
               
                   
               
             
            
               
                   
                   
                 coating&#39;s composition &amp; 
               
               
                   
                 conditions for depositing 
                 each layers thickness 
               
            
           
           
               
               
               
               
               
               
            
               
                   
                 AlTiN layer 
                 underlying 
                   
                 surface 
                   
               
            
           
           
               
               
               
               
               
            
               
                   
                 layer 
                 AlTiN layer 
                 layer 
                   
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                   
                 1st half 
                 2nd half 
                 composition 
                 atomic 
                   
                 composition 
                 total 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                 sample 
                 1st gas 
                 time 
                 1st gas 
                 time 
                 (thickness: 
                 ratio x 
                   
                 (thickness: 
                 coating 
               
               
                 nos. 
                 (table 4) 
                 (min.) 
                 (table 4) 
                 (min.) 
                 μm) 
                 of Al 
                 (μm) 
                 μm) 
                 (μm) 
               
               
                   
               
               
                 1 
                 g 
                 592 
                 c 
                 8 
                 TiCN(4.8) 
                 0.82 
                 5.0 
                 TiN(0.2) 
                 10.0 
               
               
                 2 
                 g 
                 588 
                 c 
                 12 
                 TiCN(4.8) 
                 0.82 
                 5.0 
                 TiN(0.2) 
                 10.0 
               
               
                 3 
                 g 
                 560 
                 c 
                 40 
                 TiCN(4.8) 
                 0.81 
                 5.0 
                 TiN(0.2) 
                 10.0 
               
               
                 4 
                 g 
                 530 
                 e 
                 70 
                 TiCN(4.8) 
                 0.81 
                 5.0 
                 TiN(0.2) 
                 10.0 
               
               
                 5 
                 g 
                 590 
                 b 
                 10 
                 TiCN(4.8) 
                 0.82 
                 5.0 
                 TiN(0.2) 
                 10.0 
               
               
                 6 
                 g 
                 560 
                 b 
                 40 
                 TiCN(4.8) 
                 0.81 
                 5.0 
                 TiN(0.2) 
                 10.0 
               
               
                 7 
                 g 
                 562 
                 c 
                 38 
                 TICN(4.8) 
                 0.81 
                 5 0 
                 TIN(0.2) 
                 10.0 
               
               
                 8 
                 g 
                 580 
                 e 
                 20 
                 TICN(4.8) 
                 0.82 
                 5.0 
                 TiN(0.2) 
                 10.0 
               
               
                 9 
                 g 
                 540 
                 e 
                 60 
                 TiCN(4.8) 
                 0.80 
                 5.0 
                 TiN(0.2) 
                 10.0 
               
               
                 10 
                 g 
                 532 
                 d 
                 68 
                 TiCN(4.8) 
                 0.80 
                 5.0 
                 TiN(0.2) 
                 10.0 
               
               
                 11 
                 g 
                 600 
                 — 
                 — 
                 TiCN(4.8) 
                 0.82 
                 5.0 
                 TiN(0 2) 
                 10.0 
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 12 
                 (f) 
                  (10) 
                 — 
                 — 
                 TiCN(4.8) 
                 no AlTiN layer 
                 TiN(0.2) 
                 10.0 
               
               
                   
                   
                   
                   
                   
                   
                 (Al 2 O 3  layer (5.0)) 
               
               
                   
               
            
           
           
               
               
               
            
               
                   
                 AlTiN layer&#39;s 
                   
               
               
                   
                 oxygen content ratio 
                   
               
            
           
           
               
               
               
               
            
               
                   
                 1st region 
                 2nd region 
                   
               
            
           
           
               
               
               
               
               
               
            
               
                   
                   
                 distance 
                   
                 distance 
                   
               
               
                   
                   
                 from 1st 
                   
                 from 1st 
               
            
           
           
               
               
               
               
               
               
            
               
                   
                 major 
                   
                 major 
                   
                 cutting test 
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                   
                 sample 
                 surface 
                 max. value 
                 surface 
                 max. value 
                 distance 
                   
               
               
                   
                 nos. 
                 (nm) 
                 (atom %) 
                 (nm) 
                 (atom %) 
                 (km) 
                 damaged state 
               
               
                   
                   
               
               
                   
                 1 
                 27 
                 27 
                 103 
                 3 
                 4.8 
                 normally worn 
               
               
                   
                 2 
                 32 
                 17 
                 103 
                 4 
                 4.2 
                 normally worn 
               
               
                   
                 3 
                 96 
                 7 
                 103 
                 3 
                 4.0 
                 normally worn 
               
               
                   
                 4 
                 92 
                 8 
                 103 
                 4 
                 3.8 
                 normally worn 
               
               
                   
                 5 
                 31 
                 33 
                 104 
                 3 
                 1.4 
                 rake face 
               
               
                   
                   
                   
                   
                   
                   
                   
                 worn/broken 
               
               
                   
                 6 
                 97 
                 31 
                 104 
                 4 
                 1.0 
                 rake face 
               
               
                   
                   
                   
                   
                   
                   
                   
                 worn/broken 
               
               
                   
                 7 
                 95 
                 8 
                 102 
                 6 
                 1.2 
                 rake face 
               
               
                   
                   
                   
                   
                   
                   
                   
                 worn/broken 
               
               
                   
                 8 
                 29 
                 3 
                 103 
                 3 
                 1.0 
                 rake face 
               
               
                   
                   
                   
                   
                   
                   
                   
                 worn/broken 
               
               
                   
                 9 
                 98 
                 4 
                 104 
                 3 
                 1.3 
                 rake face 
               
               
                   
                   
                   
                   
                   
                   
                   
                 worn/broken 
               
               
                   
                 10 
                 95 
                 7 
                 104 
                 6 
                 1.1 
                 rake face 
               
               
                   
                   
                   
                   
                   
                   
                   
                 worn/broken 
               
               
                   
                 11 
                 — 
                 0 
                 — 
                 0 
                 1.2 
                 rake face 
               
               
                   
                   
                   
                   
                   
                   
                   
                 worn/broken 
               
            
           
           
               
               
               
               
               
            
               
                   
                 12 
                 no AlTiN layer 
                 1.5 
                 flank 
               
               
                   
                   
                   
                   
                 significantly 
               
               
                   
                   
                   
                   
                 worn 
               
               
                   
                   
               
            
           
         
       
     
     &lt;Evaluating Characteristics of Cutting Tools&gt;&gt; 
     The cutting tools of samples 1 to 12 each underwent measurement of the thickness of each layer of the coating, the composition of the AlTiN layer, and the oxygen content ratio of the AlTiN layer. 
     &lt;Thickness of Each Layer of Coating&gt; 
     The underlying layer, the AlTiN layer, the surface layer, and the entire coating were measured in thickness with a scanning, transmission electron microscope (STEM) (trade name: JEM-2100F, manufactured by JEOL Ltd.). How this measurement was specifically done will not be described as it has been described in the first embodiment. A result is shown in table 8, the “coating&#39;s composition and each layer&#39;s thickness” column, the “underlying layer,” “AlTiN layer,” “surface layer,” and “total coating” subcolumns. 
     For example, Sample 1 had an underlying layer which was a 4.8 μm-thick TiCN layer, art AlTiN layer which was a 5.0 μm-thick layer, a surface layer which was a 0.2 μm-thick TIN layer, and a coating having a total thickness of 10.0 μm. 
     &lt;Composition of AlTiN Layer&gt; 
     The AlTiN layer was subjected to measurement of an atomic ratio x of Al in Al x Ti 1-x N with an energy-dispersive-X-ray-analysis (EDX) device (SU9000® produced by Hitachi High-Tech Corporation) accompanying a scanning electron microscope (SEM). How this measurement was specifically done will not be described as it has been described in the first embodiment. A result is shown in table 8, the “coating&#39;s composition and each layer&#39;s thickness” column, the “atomic ratio x of Al” subcolumn. 
     &lt;Oxygen Content Ratio of AlTiN Layer&gt; 
     The AlTiN layer&#39;s oxygen content ratio was measured with an Auger electron spectrometer (device: PHI 650® produced by Perkin-Elmer). How this measurement was specifically done will not be described as it has been described in the first embodiment. A maximum oxygen content ratio in each of the first and second regions of the AlTiN layer and where it is measured (or a distance front a major surface) are indicated in Table 8 at the “AlTiN layer&#39;s oxygen content ratio” column. 
     For example, sample is AlTiN layer was measured, as follows: the first region had a maximum oxygen content ratio of 27 atomic % at a point having a distance of 27 nm from a major surface, and the second region had a maximum oxygen content ratio of 3 atomic at a point having a distance of 103 inn from the major surface. 
     &lt;&lt;Cutting Test&gt;&gt; 
     (Cutting Evaluation: Continuous Processing Test) 
     The cutting tools of samples 1 to 12 were used to continuously turn an external shape of carbon steel under the following cutting conditions. The conditions correspond to high-speed continuous processing of carbon steel. A cutting distance (in meters) reached when the flank was worn by an amount of 0.25 mm or the cutting edge portion was broken was measured. Moreover, how the cutting tools were damaged after cutting (i.e., a final damaged state) was observed. A result thereof is shown in table 8. A longer cutting distance indicates a longer tool life. 
     &lt;Cutting Conditions&gt;
     Workpiece: S45C round bar   Cutting speed: 400 m/min.   Feed rate: 0.3 mm/t   Cutting amount: 2 mm   Cutting oil: DIN type   

     &lt;Discussions&gt; 
     The cutting tools of samples 1 to 4 correspond to examples. The cutting tools of samples 5 to 12 correspond to comparative examples. It has been confirmed that the cutting tools of samples 1 to 4 (examples) had longer tool life than those of samples 5 to 12 (comparative examples). 
     It is believed that Samples 1 to 4 provided increased tool life as the AlTiN layer had the first region with a maximum oxygen content ratio of 5 atomic % or more and 30 atomic or less and hence excellent heat resistance, and the second region with a maximum oxygen content ratio of less than 5 atomic % and hence high hardness and excellent wear resistance. 
     Samples 5 and 6 had a rake face worn and broken. It is believed that this is because in samples 5 and 6 the AlTiN layer had the first region with a maximum oxygen content ratio exceeding 30 atomic %, and while the first region had excellent heat resistance, it was reduced in hardness. 
     Sample 7 had a rake face worn and broken. It is believed that this is because in sample 7 the AlTiN layer had the second region with a maximum oxygen content ratio of 6 atomic % and hence reduced hardness. 
     Samples 8 and 9 had a rake face worn and broken. It is believed that this is because in samples 8 and 9 the AlTiN layer had the first region with a maximum oxygen content ratio of less than 5 atomic % and hence reduced heat resistance. 
     Sample 10 had a rake face worn and broken. It is believed that this is because in sample 10 the AlTiN layer had the second region with a maximum oxygen content ratio of 6 atomic % and hence reduced hardness. 
     Sample 11 had a rake face worn and broken. Itis believed that this is because in sample 11 the AlTiN layer had the first region with a maximum oxygen content of 0 atomic. % and hence reduced heat resistance, and the second region with a maximum oxygen content of 0 atomic % and hence reduced hardness. 
     Sample 12 had a flank significantly worn and thus had a short tool life. It is believed that this is because in sample 12 no AlTiN layer exists and an Al 2 O 3  layer having low hardness exists. 
     While embodiments and examples of the present disclosure have been described as above, it is also planned from the beginning that the configurations of the above-described embodiments and examples are appropriately combined and variously modified. 
     The embodiments and examples disclosed herein are illustrative in any respects and should not be construed as being restrictive. The scope of the present invention is defined by the terms of the claims, rather than the above-described embodiments and examples, and is intended to include any modifications within the scope and meaning equivalent to the claims. 
     REFERENCE SIGNS LIST 
       1 ,  21 ,  31  cutting tool,  10  substrate,  11  AlTiN layer,  11   a  first major surface,  11   b  second major surface,  11 A first region,  11 B second region,  12  underlying layer,  13  surface layer,  14 ,  24 ,  34  coating,  50  CVD apparatus,  52  substrate setting jig,  53  reaction chamber,  54  temperature controller,  55  first gas introduction pipe,  56  second gas introduction pipe,  57  third gas introduction pipe,  58  gas introduction pipe,  59  gas exhaust pipe,  60  gas exhaust port