JP5061392B2 - Surface coated cutting tool - Google Patents

Description

  The present invention relates to a surface-coated cutting tool in which a coating layer is formed on a substrate made of a cemented carbide.

  Conventionally, it has been demanded to improve the life of surface-coated cutting tools, and as one of countermeasures there have been proposed many attempts to improve the adhesion between a base material such as cemented carbide and a coating layer.

  For example, in Patent Document 1 and Patent Document 2, it is proposed to improve the adhesion between the substrate and the coating layer by diffusing components such as Co constituting the substrate into the coating layer. However, when the component of the base material diffuses into the coating layer in this way, or when the component of the base material reacts with the gas component for forming the coating layer, it is called the η layer on the outermost surface of the base material. An ultrathin layer is formed, or a thick diffusion layer is formed by the base material component in the interface region between the base material and the coating layer. And when such an ultra-thin layer or diffusion layer is formed, the phenomenon that the base material becomes brittle in the vicinity region thereof, thereby causing a problem that the adhesion between the base material and the coating layer decreases. was there.

  On the other hand, Patent Document 3 proposes that the lowermost layer of the coating layer in contact with the substrate is composed of an intermetallic compound of Co in order to improve the adhesion between the substrate and the coating layer. Although it is possible to improve the adhesion between the base material and the coating layer to some extent by this proposal, in recent cutting technology, extremely high performance is required for the surface-coated cutting tool. It is required to improve the tool life by further improving the adhesion between the coating layer and the coating layer.

  On the other hand, when the coating layer as described above is formed by a chemical vapor deposition method, an ultrathin layer called an η layer is formed on the outermost surface of the substrate as described above. Since the generation of this η layer has a problem of lowering the adhesion between the base material and the coating layer, various methods for not forming this η layer have been studied. It has been proposed that the adhesiveness between the substrate and the coating layer is improved by forming the η layer with a thickness of ˜2 μm (Patent Document 4).

However, even though this proposal is expected to improve the adhesion between the base material and the coating layer to some extent, the recent cutting technology demands extremely high performance for surface-coated cutting tools. It is required to improve the tool life by further improving the adhesion between the substrate and the coating layer.
JP 09-262705 A JP 2000-355777 A Japanese Patent Laid-Open No. 07-237011 Japanese Patent No. 3460565

  The present invention has been made in view of the above situation, and an object of the present invention is to provide a surface-coated cutting tool having improved adhesion between a substrate and a coating layer.

The surface-coated cutting tool of the present invention comprises a base material made of a cemented carbide and one or more coating layers covering the base material. The base material has W on the surface portion in contact with the coating layer. It has a substrate surface layer mainly composed of a double carbide with Co and a thickness of 0.005 μm or more and less than 0.1 μm, and the lowermost layer in contact with the substrate among the coating layers has a thickness of 0.005 μm or more. 0.1 μm or less and the chemical formula M _1-X Z _X (where M represents at least one element selected from the group consisting of Ti, Zr, Hf, Ni, Al, Cr, Co, and V; Z represents at least one element selected from the group consisting of carbon, nitrogen, oxygen, boron, and chlorine, X represents an atomic ratio, and 0 <X ≦ 0.5.) It is characterized by including.

  Here, the coating layer includes one or more hard layers formed on the lowermost layer, and the hard layers are composed of a group IVa element, a group Va element, a group VIa element, Al, and Si in the periodic table. Preferably, it is composed of a compound comprising at least one element selected from the group consisting of and at least one element selected from the group consisting of carbon, nitrogen, oxygen, boron, and chlorine.

  The hard layer preferably includes a layer mainly composed of TiCN formed by a chemical vapor deposition method, and preferably includes a layer including α-alumina or κ-alumina.

  In addition, a composition gradient layer is formed between the lowermost layer and the hard layer, and the composition gradient layer is a layer whose composition changes in the thickness direction from the composition of the lowermost layer to the composition of the hard layer. It is preferable that The base material is a cemented carbide containing tungsten carbide, an iron-based metal, and a third component, and the third component is a group IVa element, a group Va element, a group VIa element, an Al element in the periodic table. And a compound consisting of at least one element selected from the group consisting of Si and at least one element selected from the group consisting of carbon, nitrogen, oxygen and boron, and / or group IVa element of the periodic table , Va group element, VIa group element, Al, and Si are preferably at least one element selected from the group consisting of Si and Si.

  Since the surface-coated cutting tool of the present invention has the above-described configuration, the adhesion between the base material and the coating layer is dramatically improved.

Hereinafter, the present invention will be described in more detail.
<Surface coated cutting tool>
The surface-coated cutting tool of the present invention comprises a substrate made of a cemented carbide and one or more coating layers that coat the substrate. The surface-coated cutting tool of the present invention having such a configuration is, for example, a drill, an end mill, a milling edge-changing cutting tip, a turning edge-changing cutting tip, a metal saw, a gear cutting tool, a reamer, a tap, or a crank. It is extremely useful as a cutting edge exchangeable cutting tip for shaft pin milling.

<Base material>
The base material of the present invention is made of a cemented carbide. As such a cemented carbide, a conventionally known one used as a base material for this type of surface-coated cutting tool can be used without any particular limitation. For example, a WC-based cemented carbide containing WC and Co as main components can be cited as such a cemented carbide. Such a WC-based cemented carbide can further include carbides such as Ti, Ta, Nb, V, Cr, and Zr, nitrides, carbonitrides, and the like.

  Such a base material of the present invention is a cemented carbide containing tungsten carbide, an iron-based metal, and a third component in particular, and the third component is a group IVa element (Ti, Zr) of the periodic table. , Hf, etc.), Group Va elements (V, Nb, Ta, etc.), Group VIa elements (Cr, Mo, W, etc.), Al, and Si, and at least one element selected from the group consisting of carbon, nitrogen, A compound comprising at least one element selected from the group consisting of oxygen and boron, and / or at least selected from the group consisting of Group IVa, Va, VIa, Al, and Si in the periodic table One element is preferred. By using the base material having such a composition, an effect that both wear resistance and chipping resistance can be obtained is obtained.

  Here, the iron-based metal (the total amount when two or more kinds are included) is preferably 3% by weight or more and 25% by weight or less with respect to the entire base material, and more preferably the upper limit is 14% by weight. The lower limit is 3.5% by weight. If it is less than 3% by weight, the fracture resistance may be lowered, and if it exceeds 25% by weight, the plastic deformation resistance may be lowered. In addition, when 2 or more types of elements are included as an iron-type metal, those compounding ratios are not specifically limited.

  Further, the third component (the total amount when two or more types are included) is preferably 0.5% by weight or more and 25% by weight or less, more preferably the upper limit is 10% by weight with respect to the whole substrate. %, The lower limit is 1% by weight. If it is less than 0.5% by weight, the plastic deformation resistance may be lowered, and if it exceeds 25% by weight, the toughness may be lowered. In the case where two or more elements are included as the third component, their blending ratio is not particularly limited.

  In the present invention, “iron-based metal” refers to at least one metal selected from the group consisting of iron (Fe), cobalt (Co), and nickel (Ni). Further, Cr, V, and Zr are treated as such iron-based metals when dissolved in Co or when present alone as a metal element. However, the content of Cr is preferably less than 0.3% by weight. If the Cr content exceeds this range, the wettability is deteriorated and voids are generated.

<Substrate surface layer>
The base material of the present invention is a base material surface having a thickness of 0.005 μm or more and less than 0.1 μm mainly composed of a double carbide of W and Co at the surface portion in contact with the coating layer (ie, the interface portion with the coating layer). Has a layer. By forming a base material surface layer having a specific thickness on the surface portion of the base material in this way, the strength as a cutting tool has been dramatically improved and a coating layer is laminated on the base material surface layer. The adhesion between the material and the coating layer is greatly improved.

  When the thickness of the substrate surface layer is less than 0.005 μm, the effect of improving the adhesion between the substrate and the coating layer is low, while when the thickness is 0.1 μm or more, the adhesion between the substrate and the coating layer is improved. In some cases, the effect is further reduced and the strength is further reduced. Although the detailed mechanism that shows a specific excellent effect only when a substrate surface layer having a specific range of thickness is formed in this way has not yet been fully elucidated, the thickness of the substrate surface layer is probably When it falls within this range, it is presumed that chemical interdiffusion occurs between the coating layer and the substrate surface layer, thereby improving the adhesion between them. That is, it is considered that this mutual diffusion does not effectively occur when the thickness of the substrate surface layer is 0.005 μm or less. On the other hand, when the thickness of the substrate surface layer exceeds 0.1 μm, the adhesion of the interface portion at the interface between the substrate surface layer and the portion other than the substrate surface layer in the substrate decreases, and as a result It is presumed that the adhesion between the substrate and the coating layer is lowered.

  The upper limit of the thickness of the substrate surface layer is more preferably 0.09 μm, still more preferably 0.08 μm, and the lower limit is 0.007 μm, more preferably 0.01 μm. The thickness of such a substrate surface layer can be determined by combining SEM (scanning electron microscope), TEM (transmission electron microscope), etc. with EDS (fluorescent X-ray elemental analysis), EPMA (electron beam microanalyzer), etc. After the interface between the coating layer and the substrate was exposed with a Calotest (simple precision film thickness measuring instrument), the etching process was performed with Mr. Murakami's reagent, and this can be measured by observing it with a metal microscope. Etc. can be identified by X-ray diffraction.

  In addition, it is preferable that such a base material surface layer is formed in the surface part of the whole surface of a base material (the whole surface which becomes an interface part when a coating layer is formed later). Even if the substrate surface layer is not partially formed in the part (at the interface part in contact with the coating layer), it does not depart from the scope of the present invention.

Here, the double carbide of W and Co refers to a compound represented by the general formula W _S Co _T C _U (wherein S, T, and U each independently represents an arbitrary positive number). . Examples thereof include W ₃ Co ₃ C, W ₆ Co ₆ C, W ₄ Co ₂ C, W ₂ Co ₄ C, W ₉ Co ₃ C ₄ , and W ₁₀ Co ₃ C _3.4 . However, since the same effect is exhibited regardless of these compositions, in the present invention, the expression “double carbide of W and Co” is simply adopted without specifying the composition. Such double carbides of W and Co have the same composition as the η layer formed in the cemented carbide substrate of this type of surface-coated cutting tool, and the substrate surface layer of the present invention has this η The thickness of the layer is specified.

  In addition, the main component being a double carbide of W and Co means that other components such as inevitable impurities can be contained in a small amount (0.3 wt% or less).

  Such a substrate surface layer of the present invention can be formed on the surface portion of the substrate as follows, for example. That is, the substrate is first cleaned for about 0.5 to 6 minutes for each cleaning solution using a cleaning solution (this processing step is called a cleaning step). Examples of the cleaning liquid include alcohol-based cleaning liquids such as ethyl alcohol, acid-based cleaning liquids such as hydrochloric acid and tartaric acid, and alkali-based cleaning liquids such as alkali ion water and sodium hydroxide. These cleaning liquids can be used alone or in combination of two or more. When an acid cleaning liquid is used as the cleaning liquid, the thickness of the substrate surface layer tends to increase, and when the other cleaning liquid is used, the thickness of the substrate surface layer tends to decrease. Further, when the cleaning time is lengthened, the thickness of the substrate surface layer tends to increase, and when the cleaning time is shortened, the thickness of the substrate surface layer tends to decrease.

  Next, the base material that has undergone the above-described cleaning process is subjected to a high-temperature heat treatment (such a treatment process is referred to as a high-temperature heating process). This high temperature heating step is performed, for example, by adding 1 or 2 or more gases to 4 to 50 l / min. Is used at a flow rate of 50 hPa to atmospheric pressure (1013 hPa), and refers to a treatment step of holding the substrate at 850 to 1300 ° C. for 0 to 25 minutes. By subjecting the substrate to high-temperature heat treatment in this way, a substrate surface layer having a predetermined thickness can be formed on the surface portion of the substrate.

Here, examples of the gas include Ar, H ₂ , CH ₄ , N ₂ , CH ₃ CN, TiCl ₄ , CO, and the like. When two or more kinds are used, any partial pressure ratio can be set. . On the other hand, when the pressure condition is lowered, the thickness of the substrate surface layer tends to increase, and when the pressure condition is increased (under atmospheric pressure), the thickness of the substrate surface layer tends to decrease. Further, if the holding time is too long, the thickness of the substrate surface layer tends to increase. The thickness of the substrate surface layer can be controlled by appropriately adjusting the above conditions.

  Although the substrate surface layer can be formed on the surface portion of the substrate as described above, the thickness of the substrate surface layer can also be controlled by the formation conditions of the coating layer (especially the lowermost layer) described later. It is.

<Coating layer>
The surface-coated cutting tool of the present invention includes one or more coating layers that coat the above-described base material. Here, the coating layer covering the base material may be formed so as to cover the entire surface of the base material, or may be formed so as to cover only a part of the base material. means. However, the purpose of forming the coating layer is to improve various characteristics of the cutting tool in the first place. Therefore, the coating layer is a part that contributes to the improvement of the cutting performance even when the entire surface of the substrate is coated or a part of it is coated. It is preferable to coat at least a part of.

  The thickness of the coating layer of the present invention (when the coating layer is formed by laminating two or more layers) is preferably 0.5 μm or more and 40 μm or less. When the thickness is less than 0.5 μm, the effect of improving various properties such as wear resistance may not be sufficiently exhibited. On the other hand, if the thickness exceeds 40 μm, no further improvement in various properties is observed. Is not advantageous. However, as long as economic efficiency is ignored, the thickness may be 40 μm or more, and the effect of the present invention is shown. As a method for measuring the thickness of such a coating layer, for example, it is possible to measure by cutting a surface-coated cutting tool and observing the cross section using an SEM (scanning electron microscope).

  Such a coating layer of the present invention includes at least a lowermost layer as described below, and can include a hard layer and a composition gradient layer.

<Lower layer>
In the present invention, the lowermost layer in contact with the substrate (substrate surface layer) in the coating layer has a thickness of 0.005 μm or more and 0.1 μm or less, and a chemical formula M _1-X Z _X (where M is Ti, Zr represents at least one element selected from the group consisting of Hf, Ni, Al, Cr, Co, and V, and Z represents at least one element selected from the group consisting of carbon, nitrogen, oxygen, boron, and chlorine. An element, X represents an atomic ratio, and 0 <X ≦ 0.5.) By forming such a lowermost layer, combined with the formation of the substrate surface layer, the entire coating layer has extremely strong adhesion to the substrate. This is probably because the chemical interdiffusion as described above occurs between the substrate surface layer and the lowermost layer, thereby improving the adhesion between them. The surface-coated cutting tool of the present invention thus has extremely high adhesion between the coating layer and the substrate, so that various properties such as wear resistance are improved, and the tool life is greatly extended. It has been done.

  Here, it is extremely important to define the thickness of the lowermost layer. When the thickness is less than 0.005 μm, strong adhesion cannot be obtained, and when the thickness exceeds 0.1 μm. Since the lowermost layer itself is brittle, the adhesion to the base material is lowered. More preferably, the upper limit of the thickness of the lowermost layer is 0.09 μm, and the lower limit is 0.006 μm. In addition, the thickness of such a lowermost layer can be measured by the same method as the method of measuring the thickness of the substrate surface layer, and the identification of the composition and the like is performed by EPMA-EDS (electron beam microanalyzer-energy dispersion). Type fluorescent X-ray analysis).

On the other hand, in the chemical formula M _1-X Z _X , M particularly preferably represents at least one element composed of Ti, Co, Zr, Hf, and Al, and X has an upper limit of 0.5, more preferably 0.8. 4, more preferably 0.3, and the lower limit thereof is more preferably 0.01, still more preferably 0.1. When two or more elements are contained as M, the total amount thereof represents “1-X” in the above formula (however, the atomic ratio between these two or more elements is not particularly limited), and Z When two or more elements are included, the total amount thereof represents “X” in the above formula (however, the atomic ratio between these two or more elements is not particularly limited). It is particularly preferable that Z in the above formula contains chlorine. By including chlorine, particularly excellent wear resistance can be obtained. Such a lowermost layer is preferably formed by chemical vapor deposition (CVD) as follows.

  That is, one or two or more reaction gases (source gases) and a carrier gas are added at 4 to 50 l / min. It can be formed by maintaining at 800-1300 ° C. for 3-25 minutes under a pressure condition of 40 hPa-600 hPa. The partial pressure ratio between the reaction gas and the carrier gas is not particularly limited, but the ratio of the reaction gas to the carrier gas is preferably 1% by volume to 95% by volume.

<Hard layer>
The coating layer of the present invention preferably includes one or more hard layers formed on the lowermost layer, and this hard layer (each layer when two or more layers are formed) is a group IVa in the periodic table. At least one element selected from the group consisting of elements (Ti, Zr, Hf, etc.), group Va elements (V, Nb, Ta, etc.), group VIa elements (Cr, Mo, W, etc.), Al, and Si; It is preferably composed of a compound comprising at least one element selected from the group consisting of carbon, nitrogen, oxygen, boron, and chlorine.

The compounds as described above, for example TiC, TiN, TiCN, TiNO, TiCNO, TiB 2, TiO 2, TiBN, TiBNO, TiCBN, ZrC, ZrO 2, HfC, HfN, TiAlN, AlCrN, CrN, VN, TiSiN, TiSiCN, AlTiCrN, TiAlCN, ZrCN, ZrCNO, Al 2 O 3, AlN, AlCN, ZrN, ZrO 2, TiO 2, TiZrCN, TiAlC, NbC, NbN, NbCN, Mo 2 C, WC, W 2 C, HfO, HfO ₂ , TiCrC, ZrBN, AlHfN, TaN, TaCN, TaC, HfN and the like. In addition, when chlorine is contained in these compounds, chlorine may be contained as an interstitial type, may be contained as a substitution type, and may form a compound.

  In the present invention, when the compound is represented by the chemical formula as described above, it is assumed that all the conventionally known atomic ratios are included unless the atomic ratio is particularly limited, and are not necessarily limited to those in the stoichiometric range. . For example, when simply describing “TiCN”, the atomic ratio of “Ti”, “C”, and “N” is not limited to 50:25:25, and also when “TiN” is described, “Ti” and “N” The atomic ratio is not limited to 50:50. These atomic ratios include all conventionally known atomic ratios.

  Of the compounds constituting the hard layer as described above, more preferably, at least one element selected from the group consisting of Ti, Zr, and Hf, and a group consisting of carbon, nitrogen, oxygen, boron, and chlorine It is preferable to select a compound comprising at least one element selected. In particular, it is preferable to form a layer made of these compounds immediately above the lowermost layer. This is because the adhesion between the lowermost layer and the hard layer can be made particularly strong.

  The hard layer of the present invention preferably includes a layer containing α-alumina (alumina having a crystal structure of α type) or κ-alumina (alumina having a crystal structure of κ type) as the above compound. Thereby, the abrasion resistance of a coating layer can be improved further.

  Here, the layer containing α-alumina or κ-alumina means containing 50% by weight or more of such alumina, and more preferably composed of only such alumina excluding inevitable impurities. Say. The crystal structure of alumina can be identified by X-ray diffraction (XRD).

  The thickness of such a hard layer (thickness per hard layer) is preferably 0.3 μm or more and 20 μm or less, more preferably the lower limit is 0.5 μm or more, further preferably 1 μm or more, and the upper limit is It is suitable that it is 15 μm or less, more preferably 10 μm or less. When the thickness of the hard layer is less than 0.3 μm, various properties such as wear resistance may not be sufficiently improved, and even if the thickness exceeds 20 μm, the properties are not significantly improved. It may not be preferable.

  In addition, it is preferable that the hard layer of this invention is formed by CVD method. Thereby, a hard layer can be continuously formed with respect to the lowermost layer, and the adhesion can be improved. As such a CVD method, a conventionally known method can be used without any particular limitation, and the conditions and the like are not limited. For example, a film forming temperature of about 800 to 1050 ° C. can be adopted, and a conventionally known gas such as a nitrile gas such as acetonitrile can be used as the gas to be used without any particular limitation.

  And it is preferable that especially the coating layer of this invention contains the layer which has as a main component TiCN formed by a chemical vapor deposition method, more preferably MT-CVD method as a hard layer. This is because a layer mainly composed of titanium carbonitride (TiCN) having excellent wear resistance can be formed while reducing damage to the substrate based on the application of heat by the CVD method. Here, the layer containing TiCN as a main component means a layer containing 90% by weight or more of TiCN, and preferably includes only TiCN except for inevitable impurities. Further, the MT-CVD (moderate temperature CVD) method is generally performed at about 950 to 1050 ° C., while the normal CVD method as described above is often performed at about 950 to 1050 ° C. This is a method performed at a relatively low temperature.

  The hard layer of the present invention is composed only of at least one element selected from the group consisting of IVa group elements, Va group elements, VIa group elements, Al, and Si in addition to the above-described compounds. Layers can also be included.

  The identification of the composition of the hard layer of the present invention can be confirmed by EPMA-EDS (electron beam microanalyzer-energy dispersive X-ray fluorescence analysis).

<Composition gradient layer>
In the coating layer of the present invention, a composition gradient layer can be formed between the lowermost layer and the hard layer, and the composition gradient layer is formed from the composition of the lowermost layer to the hard layer (on the composition gradient layer). When a plurality of hard layers are formed, a layer whose composition changes in the thickness direction to the composition of the hard layer immediately above the composition gradient layer is preferable. By forming such a composition gradient layer, the adhesion between the lowermost layer and the hard layer can be enhanced. Such a composition gradient layer preferably has a thickness of 0.2 μm or more and 2 μm or less, more preferably a lower limit of 0.3 μm or more, an upper limit of 1 μm or less, and even more preferably 0.8 μm or less. Is preferred. If the thickness of the composition gradient layer is less than 0.2 μm, the adhesion may not be improved, and if it exceeds 2 μm, the characteristics are not significantly improved, which may be industrially undesirable.

  Such a composition gradient layer does not need to be formed independently of the lowermost layer and the hard layer, but usually, depending on the forming method, both layers are formed when the hard layer is formed after the lowermost layer is formed. It is inevitably formed in the middle stage. In other words, the composition gradient layer is observed or not observed depending on the observation conditions, and is usually observed when the observation magnification by a transmission electron microscope (TEM) or the like is set to 2 million times or more. It is what is done.

  In addition, since such a composition gradient layer is formed at the boundary between the lowermost layer and the hard layer, when the boundary between these two layers cannot be clearly defined, the thickness direction in such a composition gradient layer The intermediate point is regarded as the boundary between these layers, and the thickness of each layer is measured.

<Manufacturing method>
This invention also provides the manufacturing method of the surface coating cutting tool provided with the base material which consists of a cemented carbide, and the 1 or more coating layer which coat | covers it. Such a production method includes a step of preparing a base material (also referred to as “base material preparation step”), a step of forming the base material surface layer described above (also referred to as “base material surface layer forming step”), A step of forming a lowermost layer containing the first compound and having a thickness of 0.005 μm or more and 0.1 μm or less as a lowermost layer in contact with the base material of the coating layer (also referred to as “lowermost layer forming step”); Including at least. And this lowermost layer formation process is preferably performed by CVD method as already demonstrated above, and it is preferable to perform with the same apparatus as the apparatus used for a base-material surface layer formation process.

  In addition, as long as the manufacturing method of this invention includes the above processes, it does not interfere even if it includes another process. For example, the process etc. which form a hard layer are included. The step of forming such a hard layer (also referred to as “hard layer forming step”) is also preferably performed by a CVD method. Therefore, the coating layer of the present invention is particularly preferably formed by the CVD method.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these.

<Base material preparation process>
Substrates A to C were obtained by molding a cutting edge-exchangeable cutting tip having a shape of CNMA120408 (JIS B4120 1998) using the cemented carbide described in Table 1 below. The balance of the components listed in Table 1 is tungsten carbide (WC), i.e., these cemented carbides contain tungsten carbide, an iron-based metal, and a third component. For example, “(Ti, Ta, Nb, Cr, Zr) C” in the base material B indicates that 5.1% by weight of carbide whose metal component is Ti, Ta, Nb, Cr, Zr is contained. (Each notation also has the same meaning in other substrates).

<Base material surface layer forming step>
The cleaning process described in Table 2 was performed on each of the base materials A to C prepared above. In Table 2, “acid-based cleaning solution” refers to tartaric acid, hydrochloric acid, etc., “alkali-based cleaning solution” refers to sodium hydroxide, alkaline ionized water, etc., and “alkali-based + acid-based cleaning solution” refers to an alkaline cleaning solution. This indicates that the cleaning is performed with an acid cleaning solution after the cleaning, and “ethyl alcohol” indicates an alcohol cleaning solution.

  Subsequently, by performing the high-temperature heating process shown in Table 2 on each base material that has undergone the cleaning process, the surface portion of each base material (the portion that becomes the interface when a coating layer is formed later) ) To form a substrate surface layer mainly composed of double carbide of W and Co. The thickness is shown in Table 6. In Table 2, in the column of “type” of the gas used in the high-temperature heating process, for those described to introduce a different gas from a certain temperature, after the different gas is introduced The partial pressure ratio is shown in the “Partial pressure ratio” column. In addition, “holding time” indicates the time for holding at the temperature described in Table 2, but “0” indicates that the lowermost layer below when the temperature reaches the temperature described in Table 2. Indicates that formation begins.

<Lower layer formation process>
For each base material on which the base material surface layer was formed as described above, the lowermost layer was formed on the base material surface layer by the CVD method under the conditions described in Table 3. Table 6 shows the thickness and composition (M _1-X Z _X ) of the lowermost layer thus formed.

<Hard layer forming process>
With respect to the precursor of the surface-coated cutting tool in which the lowermost layer is formed on the base material (on the base material surface layer) as described above, each of the hard layers a and b described in Table 4 below is changed to the lowermost layer. It formed continuously on the entire upper surface. For example, in the hard layer a in Table 4, a layer made of TiN having a thickness of 0.3 μm is formed as the second layer on the lowermost layer, and a layer made of TiCN having a thickness of 2.5 μm is formed thereon as the third layer. And a layer made of TiZrCN with a thickness of 1.5 μm is formed as a fourth layer thereon, a layer made of TiCNO with a thickness of 1.0 μm is formed thereon as a fifth layer, and a layer as a sixth layer is formed thereon. It shows that a layer made of κ-alumina having a thickness of 1.0 μm was formed, and a layer made of TiN having a thickness of 0.5 μm was formed thereon as the seventh layer. The same applies to the hard layer b. In Table 4, “TiCN” indicates a layer made of TiCN formed by MT-CVD (that is, a layer mainly composed of TiCN), and “α-Al ₂ O ₃ ” indicates a layer made of α-alumina. (Ie, a layer containing α-alumina), and “κ-Al ₂ O ₃ ” indicates a layer made of κ-alumina (ie, a layer containing κ-alumina). Moreover, it shows that the 6th layer of the hard layer b is comprised with the mixture (zirconium: 0.3 weight%) of (alpha) -alumina and zirconium.

  And each layer of such a hard layer was formed by CVD method which employ | adopted the conditions shown in the following Table 5. FIG. In addition, it is preferable to perform continuously the said base material surface layer formation process, the lowest layer formation process, and a hard layer formation process in the same apparatus.

<Surface coated cutting tool>
As described above, No. 1 shown in Table 6 below. 1 to 24 surface-coated cutting tools of the examples of the present invention were produced. Similarly, No. 1 shown in Table 6 below. Surface-coated cutting tools of 1 to 6 comparative examples were manufactured. For example, in No. 6 of Table 6, The surface-coated cutting tool No. 1 uses “Substrate A” shown in Table 1 as a base material, and forms a base material surface layer having a thickness of 0.013 μm on the base material according to the forming conditions shown in Table 2. A lowermost layer having a composition of TiC having a thickness of 0.005 μm was formed on the surface layer of the base material according to the formation conditions described in Table 3, and “hard layer a” described in Table 4 was formed as a hard layer on the lowermost layer. (That is, the second layer of the hard layer a is formed on the lowermost layer, and the seventh layer is sequentially formed thereon). In addition, No. In the surface-coated cutting tools of Comparative Examples 1 to 6, the thickness of the substrate surface layer or the thickness of the lowermost layer is outside the scope of the present invention.

<Performance evaluation>
The surface-coated cutting tool obtained as described above was subjected to a continuous cutting test and an intermittent cutting test under the following conditions to evaluate the degree of adhesion between the substrate and the coating layer. The results are shown in Table 7 below.

<Conditions for continuous cutting test>
Holder used: PCLNR2525-43 (Sumitomo Electric Hardmetal)
Work material: SCM435 (HB = 246) round bar Cutting speed: 240 m / min.
Feed: 0.26 mm / rev.
Cutting depth: 2.0mm
Wet / dry: wet (water-soluble oil)
Evaluation: The time (minutes) until the cutting edge was broken due to the progress of wear on the rake face side was determined. The longer the time, the better the wear resistance, and the stronger the adhesion between the substrate and the coating layer.

<Conditions for intermittent cutting test>
Holder used: PCLNR2525-43 (Sumitomo Electric Hardmetal)
Work material: SCM435 (HB = 246) Square material Cutting speed: 220 m / min.
Feed: 0.21 mm / rev.
Cutting depth: 1.5mm
Cutting time: 2 minutes Wet / dry: Dry Evaluation: A test was performed with 10 cutting edges, and the number of missing cutting edges was determined. The smaller the number of missing cutting edges, the stronger the adhesion between the substrate and the coating layer.

As is clear from Table 7, it was confirmed that the surface-coated cutting tool of the example of the present invention had stronger adhesion between the base material and the coating layer than the surface-coated cutting tool of the comparative example. That is, all of the surface-coated cutting tools of Comparative Examples 1 to 6 in which the thickness of the substrate surface layer or the thickness of the lowermost layer is outside the definition of the present invention were inferior in adhesion between the substrate and the coating layer. Therefore, in the surface-coated cutting tool of the example, such an excellent effect is shown in that the thickness mainly composed of double carbides of W and Co is 0.005 μm or more in the surface portion of the substrate in contact with the coating layer. A chemical formula M _1-X Z _X (where M is Ti) having a thickness of 0.005 μm or more and 0.1 μm or less as the lowermost layer in contact with the base material of the coating layer, forming a base material surface layer of less than 0.1 μm , Zr, Hf, Ni, Al, Cr, Co, and V represents at least one element selected from the group consisting of V, Z is at least one selected from the group consisting of carbon, nitrogen, oxygen, boron, and chlorine It is apparent that X is an atomic ratio, and 0 <X ≦ 0.5.) This is caused by forming a layer containing the first compound represented by the following formula.

  Although the embodiments and examples of the present invention have been described as described above, it is also planned from the beginning to appropriately combine the configurations of the above-described embodiments and examples.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

Claims (6)

A surface-coated cutting tool comprising a substrate made of a cemented carbide and one or more coating layers covering the substrate,
The base material has a base material surface layer having a thickness of 0.005 μm or more and less than 0.1 μm mainly composed of a double carbide of W and Co on a surface portion in contact with the coating layer;
The lowermost layer in contact with the substrate of the coating layer has a thickness of 0.005 μm or more and 0.1 μm or less, and a chemical formula M _1-X Z _X (where M is Ti, Zr, Hf, Ni, Al, At least one element selected from the group consisting of Cr, Co and V; Z represents at least one element selected from the group consisting of carbon, nitrogen, oxygen, boron and chlorine; and X represents an atomic ratio. And a surface-coated cutting tool comprising a first compound represented by 0 <X ≦ 0.5. The coating layer includes one or more hard layers formed on the lowermost layer,
The hard layer is composed of at least one element selected from the group consisting of group IVa elements, group Va elements, group VIa elements, Al, and Si in the periodic table, and carbon, nitrogen, oxygen, boron, and chlorine. The surface-coated cutting tool according to claim 1, wherein the surface-coated cutting tool is composed of a compound composed of at least one element selected from the group.   The surface-coated cutting tool according to claim 2, wherein the hard layer includes a layer mainly composed of TiCN formed by chemical vapor deposition.   The surface-coated cutting tool according to claim 2, wherein the hard layer includes a layer containing α-alumina or κ-alumina. A composition gradient layer is formed between the lowermost layer and the hard layer,
The surface-coated cutting tool according to any one of claims 1 to 4, wherein the composition gradient layer is a layer whose composition changes in a thickness direction from the composition of the lowermost layer to the composition of the hard layer. The base material is a cemented carbide containing tungsten carbide, an iron-based metal, and a third component,
The third component includes at least one element selected from the group consisting of group IVa elements, group Va elements, group VIa elements, Al, and Si in the periodic table, and a group consisting of carbon, nitrogen, oxygen, and boron. A compound comprising at least one element selected from the group consisting of at least one element and / or at least one element selected from the group consisting of group IVa element, group Va element, group VIa element, Al and Si in the periodic table. Item 6. The surface-coated cutting tool according to any one of Items 1 to 5.