JP2005271132A - Surface coated cutting tool - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface coated cutting tool, suitably used for a drill, an end mill, a knife edge replacement type tip for milling and lathe turning, a metal saw, a gear cutting tool, a reamer or a tap, and improved in stripping resistance and wear resistance more than before. <P>SOLUTION: This surface coated cutting tool is characterized in that an inner layer formed of a compound at least containing at least one element out of Al, Cr and V and one or more elements selected from nitrogen, carbon and oxygen is coated on a base material, further an outer layer formed of a carbonitride or acidic nitride containing at least one element out of Al, Cr and V is coated on the inner layer, and the outer layer has a larger carbon content than the inner layer. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to cutting tools such as drills, end mills, milling and turning cutting tips, metal saws, gear cutting tools, reamers, taps, etc., and more particularly to a cutting tool having a wear-resistant coating formed on its surface. is there.

  In recent years, in addition to the pursuit of high-speed, high-precision, and high-efficiency machining, dry machining is also aimed at as an environmental measure. In addition, with the advancement of industrial technology, industrial activities that use a lot of difficult-to-cut materials and new materials used in aircraft, space development, nuclear power generation, etc. are becoming increasingly active, qualitative diversification and quantitative It is expected that the expansion will be further advanced, and naturally there is a demand for these cutting processes. To date, many surface-coated cutting tools have been proposed and put to practical use for such problems.

For example, Patent Document 1 discloses a hard coating layer on the surface of a hard base material such as a cutting tool such as a WC-based cemented carbide, cermet, high-speed steel, or wear-resistant tool for improving wear resistance and surface protection function. (Al _x Ti _1-xy Si _y ) (C _z N _1-z ) (where 0.05 ≦ x ≦ 0.75, 0.01 ≦ y ≦ 0.1, 0.6 ≦ z ≦ 1) ) And a hard film coated tool and a hard film coated member are disclosed.

Further, Patent Document 2 discloses nitrides, carbonitrides, oxynitrides, oxycarbonitrides, and nitrides, carbonitrides, and acids containing Ti and Al as main components and containing Ti in an appropriate amount. Nitride, oxycarbonitride has a microstructure such as TiSi-based compounds, and Ti 3 as a main component is carbonitride, oxynitride, oxycarbonitride, and Si ₃ N ₄ and Si are independent phases. It is disclosed that when one or more layers are alternately coated so as to exist, the performance of the cutting tool is extremely good in dry high-speed cutting. According to Patent Document 2, although the alumina layer formed by surface oxidation that occurs in cutting in the conventional TiAlN film functions as an oxidation protective film against inward diffusion of oxygen, in dynamic cutting, the outermost surface The alumina layer peels off more easily than the porous Ti oxide layer directly below it, and is not sufficient for the progress of oxidation. However, the TiSi-based film of the invention described in Patent Document 2 has the oxidation resistance of the film itself. Not only is it extremely high, but a very dense composite oxide of Ti and Si containing Si is formed on the outermost surface, so the porous Ti oxide layer, which has been a problem in the past, is not formed. It is shown.

Patent Document 3 describes that by using AlCrV carbonitride and nitride, it is possible to form a film quality for a cutting tool that is higher in hardness and superior in wear resistance than a TiAlN film. Yes.
Japanese Patent No. 2793773 Japanese Patent No. 3347687 JP 2003-34859 A

  However, in order to perform high-speed, high-efficiency machining and dry machining that does not use a lubricant completely in the cutting process, the above-described coating stability at high temperatures is not sufficient. That is, it is a problem how to maintain a film having excellent characteristics on the surface of the base material for a long time with good adhesion without causing peeling or defects.

  In other words, when cutting a material that is easily welded to the cutting edge, such as low-carbon steel, stainless steel, or ductile cast iron, film peeling is likely to occur due to the welding of the work material. Likely to happen. For this reason, in order to prevent peeling, it is important how to prevent the welding of the work material, and at the same time, it is an important issue to make the film quality excellent in wear resistance.

  The present invention has been made in order to solve the above-mentioned problems, and the object of the present invention is to provide a drill, end mill, milling and turning cutting edge replaceable tip, metal saw, gear cutting tool, reamer, tap, etc. The present invention provides a surface-coated cutting tool that is preferably used for a surface-coated cutting tool that has improved peel resistance and wear resistance as compared with conventional ones.

  As a result of studying various tool surface coating films for the above-mentioned problems, the present inventors selected Al, at least one of Cr and V, and nitrogen, carbon, and oxygen on the base material. A carbonitride or oxycarbonitride which is coated with an inner layer formed of a compound containing at least one element selected from the group consisting of Al and at least one of Cr and V on the inner layer. It is found that the outer layer formed by coating a surface-coated cutting tool having an outer layer having a larger carbon content than the inner layer is capable of suppressing film peeling and exhibits excellent wear resistance. It came. That is, the present invention is as follows.

  The surface-coated cutting tool of the present invention is formed on a substrate with a compound containing at least one element selected from Al, at least one of Cr and V, and one or more elements selected from nitrogen, carbon, and oxygen. And the outer layer formed of carbonitride or oxycarbonitride containing Al and at least one element of Cr and V is coated on the inner layer. It has a carbon content higher than that of the inner layer.

  In the surface-coated cutting tool of the present invention, the thickness of the outer layer is preferably 0.1 to 2 μm.

  The average crystal grain size of carbonitride or oxycarbonitride forming the outer layer is preferably 0.2 μm or less.

The inner layer in the surface-coated cutting tool of the present invention is (Al _1-ab Cr _a V _b ) (where 0 ≦ a ≦ 0.5, 0 ≦ b ≦ 0.5, 0 ≠ a + b ≦ 0.5). It is preferably formed of a compound containing at least one element selected from nitrogen, carbon, and oxygen. Here, it is more preferable that the value of a satisfies 0 <a <0.35 and the value of b satisfies 0 <b <0.35. More preferably, the values of a and b satisfy 20 <a / b <100.

  The inner layer and / or the outer layer in the surface-coated cutting tool of the present invention preferably contains 20% or less of Si in atomic percent.

  The inner layer in the present invention is preferably formed of a nitride containing Al and at least one of Cr and V.

  Furthermore, in the present invention, a layer formed of carbonitride containing Al and at least one element of Cr and V, and having a higher carbon content than the inner layer, It is preferable that the inner layer is divided.

  In the surface-coated cutting tool of the present invention, the total thickness of the layer covering the substrate is preferably 0.5 to 8 μm.

  According to the present invention, it is possible to improve the peeling resistance and wear resistance of drills, end mills, milling and turning cutting tips, metal saws, gear cutting tools, reamers, taps, etc. A cutting tool can be provided.

  The surface-coated cutting tool of the present invention is formed on a substrate with a compound containing at least one element selected from Al, at least one of Cr and V, and one or more elements selected from nitrogen, carbon, and oxygen. And the outer layer formed of carbonitride or oxycarbonitride containing Al and at least one element of Cr and V is coated on the inner layer. It has a carbon content higher than that of the inner layer. Here, the inner layer may be formed so as to directly cover the surface of the base material, or may be formed so as to cover the base material with another layer interposed therebetween. Similarly, the outer layer may be formed so as to directly cover the inner layer, or may be formed so as to cover the inner layer with another layer interposed therebetween.

  The surface-coated cutting tool of the present invention is selected from Al having excellent chemical stability and excellent wear resistance in cutting metal materials, and at least one of Cr and V, and nitrogen, carbon, and oxygen. One of the characteristics is that the base material is coated with an inner layer formed of a compound containing at least one kind of element. Further, the surface-coated cutting tool of the present invention has a low coefficient of friction and lubricity with respect to a metal material, exhibits high chemical stability, Al, at least one of Cr and V, and nitrogen. Carbon nitride containing an inner layer formed of a compound containing at least one element selected from carbon, oxygen, Al having excellent adhesion, and at least one of Cr and V Alternatively, the outer layer is formed by coating the inner layer with oxycarbonitride. In addition, the surface-coated cutting tool of the present invention includes an inner layer having the above composition and an outer layer having the above composition, and the outer layer has a carbon content larger than that of the inner layer, and thereby can obtain particularly excellent lubricity. It is also characterized by the effect that a very excellent film peel resistance can be obtained. With this feature that combines these features, it is possible to improve the peel resistance and wear resistance of drills, end mills, milling and turning blade inserts, metal saws, cutting tools, reamers, taps, etc. It is possible to provide a long surface-coated cutting tool.

  As described above, the surface-coated cutting tool of the present invention has an inner layer made of a compound containing at least one of Al, at least one of Cr and V, and one or more elements selected from nitrogen, carbon, and oxygen. It is formed. The compound forming the inner layer may contain elements other than those described above (for example, Si and B described later) within a range that does not impair the effects of the present invention. In the present invention, when the inner layer contains Al, the oxidation resistance is improved, the thermal conductivity is increased, and heat generated during cutting can be released from the tool surface.

In the nitride, carbonitride, oxynitride or oxycarbonitride forming the inner layer in the present invention, the amount of Cr and V excluding Al is (Al _1-ab Cr _a V _b ) (where 0 ≦ a Preferably, it is a nitride, carbonitride, oxynitride or oxycarbonitride of a compound defined by ≦ 0.5, 0 ≦ b ≦ 0.5, 0 ≠ a + b ≦ 0.5). That is, the inner layer in the surface-coated cutting tool of the present invention is (Al _1-ab Cr _a V _b ) (where 0 ≦ a ≦ 0.5, 0 ≦ b ≦ 0.5, 0 ≠ a + b ≦ 0.5). ) -Containing nitrides, carbonitrides, oxynitrides, or oxycarbonitrides. This is because in (Al _1-ab Cr _a V _b ), if at least one of a and b exceeds 0.5, the hardness of the inner layer is lowered and sufficient wear resistance may not be exhibited. . Particularly preferable wear resistance is obtained when a + b> 0.3, and when the value of a + b is within this range, adhesion with the outer layer is improved, and excellent film peeling resistance is obtained. Particularly preferred. Further, in (Al _1-ab Cr _a V _b ), it is more preferable that the value of a is 0 <a <0.35 and the value of b is 0 <b <0.35. This is because excellent peeling resistance can be expected when both Cr and V are contained at the same time and the values of a and b are both less than 0.35. The reason for this is not clear, but it is thought that Cr can improve lubricity at low temperatures, V can improve lubricity at relatively high temperatures, and exhibits excellent peeling resistance under a wide range of cutting conditions by being simultaneously present. . Further, it is particularly preferable that the values of a and b have a relationship of 20 <a / b <100. In the surface-coated cutting tool, the composition of the nitride, carbonitride, oxynitride or oxycarbonitride forming the inner layer can be confirmed by an X-ray photoelectron spectrometer (XPS) or an Auger electron spectrometer (AES). it can.

Thus, the amount of Cr and V excluding Al is (Al _1-ab Cr _a V _b ) (where 0 ≦ a ≦ 0.5, 0 ≦ b ≦ 0.5, 0 ≠ a + b ≦ 0.5). A surface-coated cutting tool having an inner layer formed of nitride, carbonitride, oxynitride or oxycarbonitride of a suitable compound represented by When manufacturing a coated cutting tool, it is realizable by forming an inner layer on the conditions which make a substrate bias voltage into the range of -300--50V, for example. Among them, preferred a, b values are nitrides, carbonitrides, oxynitrides of suitable compounds represented by (Al _1-ab Cr _a V _b ) having a relationship of 20 <a / b <100 Alternatively, a surface-coated cutting tool having an inner layer formed of oxycarbonitride can be realized by setting the substrate bias voltage within a range of −300 to −150 V when manufacturing the surface-coated cutting tool. it can.

The inner layer in the present invention is preferably formed of a nitride containing at least one element of Cr and V. When the inner layer is formed of the compound nitride, the advantage is that the film has higher toughness and excellent fracture resistance compared to the case where the inner layer is formed of the compound carbonitride. Because there is. Among them, preferred compounds of which the inner layer is represented by (Al _1-ab Cr _a V _b ) (where 0 ≦ a ≦ 0.5, 0 ≦ b ≦ 0.5, 0 ≠ a + b ≦ 0.5) It is preferable that it is formed of nitride, and a suitable compound represented by (Al _1-ab Cr _a V _b ) in which the values of a and b have a relationship of 20 <a / b <100 It is particularly preferable that it is formed of the nitride.

  In the surface-coated cutting tool of the present invention, the above-described inner layer is coated, and the outer layer is formed of carbonitride or oxycarbonitride containing Al and at least one element of Cr and V. . The carbonitride or oxycarbonitride that forms this outer layer may contain elements other than those described above (for example, Si, Ti, B) within a range that does not impair the effects of the present invention.

In the carbonitride or oxycarbonitride forming the outer layer in the present invention, the amount of Cr and V excluding Al is (Al ₁ -cd Cr _c V _d ) (where 0 ≦ c <1.0, 0 ≦ A carbonitride or oxycarbonitride of a compound defined by d <1.0, 0.3 <c + d <1.0) is preferable. That is, the outer layer in the surface-coated cutting tool of the present invention is (Al _1-cd Cr _c V _d ) (where 0 ≦ c <1.0, 0 ≦ d <1.0, 0.3 <c + d <1 0.0) is preferably formed of carbonitrides or oxycarbonitrides. In (Al _{1 -cd} Cr _c V _d ), the value of c + d is set to be greater than 0.3 because wear resistance may be lowered when the value is 0.3 or less. Further, in (Al _{1 -cd} Cr _c V _d ), it is more preferable that the value of c is 0 <c <0.5, and the value of d is 0 <d <0.5. This is because excellent peeling resistance can be expected when both Cr and V are contained at the same time and the values of c and d are both 0.5 or less. The reason for this is not clear, but it is thought that Cr can improve lubricity at low temperatures, V can improve lubricity at relatively high temperatures, and exhibits excellent peeling resistance under a wide range of cutting conditions by being simultaneously present. . Further, it is particularly preferable that the values of c and d have a relationship of 20 <c / d <100. In the surface-coated cutting tool, the composition of carbonitride or oxycarbonitride forming the outer layer can be confirmed by XPS.

Thus, the amount of Cr and V excluding Al is (Al ₁ -cd Cr _c V _d ) (where 0 ≦ c <1.0, 0 ≦ d <1.0, 0.3 <c + d <1. A surface-coated cutting tool having an outer layer formed of a carbonitride or oxycarbonitride of a suitable compound represented by 0) is produced by, for example, a cathode arc ion plating method as described later. In this case, for example, the inner layer can be formed under the condition that the substrate bias voltage is in the range of −300 to −50V. Further, among them, carbonitride or oxycarbonitride of a suitable compound represented by (Al ₁ -cd Cr _c V _d ) having a relationship in which the values of c and d are preferably 20 <c / d <100 The surface-coated cutting tool including the formed outer layer can be realized by setting the substrate bias voltage within the range of −300 to −150 V when manufacturing the surface-coated cutting tool.

  Here, the surface-coated cutting tool of the present invention is characterized in that the outer layer has a larger carbon content than the inner layer. Here, the difference in carbon content between the outer layer and the inner layer is preferably 5% or more, and more preferably 10% or more. This is because if the difference in carbon content between the outer layer and the inner layer is less than 5%, the above-described effects due to the outer layer having a larger carbon content than the inner layer are not sufficiently exhibited.

  In the surface-coated cutting tool of the present invention, if the outer layer has a larger carbon content than the inner layer, for example, the carbon content is realized to increase continuously or stepwise from the inner layer to the outer layer. May be. The structure in which the carbon content continuously increases from the inner layer to the outer layer is, for example, as described later, when the surface-coated cutting tool is manufactured by, for example, the cathode arc ion plating method, the methane gas introduction amount is continuously increased. It can be realized by increasing it. In addition, the configuration in which the carbon content gradually increases from the inner layer to the outer layer is, for example, as described later, when manufacturing a surface-coated cutting tool by, for example, the cathode arc ion plating method, This can be achieved by increasing it step by step.

  In addition, each carbon content of an inner layer and an outer layer can be measured using AES, for example.

  In addition, in the process of manufacturing the surface-coated cutting tool of the present invention to be described later, the outer layer increases its methane gas introduction amount (flow rate, pressure, etc.) more than the inner layer formation so that the carbon content becomes larger than the inner layer. Can be formed.

  In the surface-coated cutting tool of the present invention, the thickness of the outer layer having a high carbon content is not particularly limited, but is preferably 0.1 to 2 μm, more preferably 0.2 to 1 μm. . This is because if the thickness of the outer layer is less than 0.1 μm, the excellent effect as the outer layer may not be exhibited, and if the thickness of the outer layer exceeds 2 μm, the film may be easily peeled off. It is. The thickness of the outer layer can be measured by cutting the surface-coated cutting tool and using AES from the cross section.

  The outer layer in the surface-coated cutting tool of the present invention is preferably formed of the carbonitride or oxycarbonitride having an average crystal grain size of 0.2 μm or less, more preferably 0.1 μm or less. Thereby, an outer layer having particularly excellent lubricity and adhesion strength with the inner layer can be realized. Further, from the viewpoint of wear resistance, the average crystal grain size of the carbonitride or oxycarbonitride forming the outer layer is preferably 1 nm or more, and more preferably 3 nm or more. The average crystal grain size of carbonitride or oxycarbonitride containing Al and at least one element of Cr and V in the outer layer of the surface-coated cutting tool is, for example, a film cross section or a fracture surface using SEM Can be observed and measured.

  A surface-coated cutting tool comprising an outer layer formed of carbonitride or oxycarbonitride containing Al having such a suitable average crystal grain size and at least one element of Cr and V, As will be described later, when manufacturing a surface-coated cutting tool by, for example, the cathode arc ion plating method, it is preferable to form the outer layer under the condition that the substrate bias voltage is in the range of -300 to -150V.

  In the surface-coated cutting tool of the present invention, from the viewpoint of improving oxidation resistance, wear resistance, and peel resistance, the inner layer and / or the outer layer are preferably 20% or less, more preferably 15% or less of Si in atomic%. May be included. When Si is present in the inner layer and / or the outer layer, the structure of the inner layer and / or the outer layer is refined and the hardness of the inner layer and / or the outer layer is improved. However, it is not preferable that the inner layer and / or the outer layer contain Si exceeding 20% by atomic% because the inner layer and / or the outer layer tend to become brittle and wear is accelerated. Further, when the inner layer and / or the outer layer contain Si, in order to obtain the effect of refining the structure, Si is preferably contained at 1% or more in atomic%, and is preferably contained at 5% or more. More preferred. Here, the Si content in the inner layer and / or the outer layer of the surface-coated cutting tool can be measured using XPS, AES, or the like, for example.

  Further, the inner layer and / or the outer layer may contain B in atomic%, preferably 15% or less, more preferably 10% or less. When B exists in the inner layer and / or the outer layer, a high hardness film is obtained, and there is an advantage that the oxide of B formed by surface oxidation during cutting particularly densifies the oxide of Al. Further, since the oxide of B has a low melting point, it acts as a lubricating oil at the time of cutting, and has an advantage of exhibiting excellent peeling resistance. However, it is not preferable that the inner layer and / or the outer layer contain B in an atomic percent exceeding 15% because the wear resistance tends to decrease. Further, when the inner layer and / or the outer layer contains B, in order to improve wear resistance and peel resistance, it is preferable that B is contained at 1% or more in atomic%, and it is contained at 5% or more. More preferably. Here, the B content in the inner layer of the surface-coated cutting tool can be measured using, for example, XPS, AES, or the like.

  The inner layer in the surface-coated cutting tool of the present invention is formed of a compound containing at least one element selected from Al, at least one of Cr and V, and one or more elements selected from nitrogen, carbon, and oxygen. It may be formed so as to be divided in a layer (divided layer) having a larger carbon content. An excellent peelability can be realized by dividing the inner layer into multiple layers by such a divided layer. In addition, because the inner layer is divided by the divided layers, when a large stress is suddenly applied during cutting, film breakage occurs at the multilayer film interface where the bond strength is slightly reduced. Since the unit can be reduced by multilayering, and the sudden large-breaking phenomenon of the film can be suppressed, as a result, a surface-coated cutting tool having a stable and long life can be realized.

The divided layer may be formed of carbonitride containing Al and at least one of Cr and V, and may have a carbon content larger than that of the inner layer. V amount _{(Al 1-ef Cr e V} f) ( where, 0 ≦ e ≦ 0.5,0 ≦ f ≦ 0.5,0 ≠ e + f ≦ 0.5) of the defined in the compound coal Nitride is preferred. That is, split layer in the surface-coated cutting tool of the present _{invention, (Al 1-ef Cr e} V f) ( where, 0 ≦ e ≦ 0.5,0 ≦ f ≦ 0.5,0 ≠ e + f ≦ 0. 5) is preferably formed of carbonitride. In _{(Al 1-ef Cr e V} f), when at least one of e and f is more than 0.5, because the abrasion resistance may deteriorate. In yet _{(Al 1-ef Cr e V} f), the value of e is 0 <e <0.35, the value of the f is more preferably 0 <f <0.35. This is because excellent peeling resistance can be expected when both Cr and V are contained at the same time and the values of e and f are both less than 0.35. The reason for this is not clear, but it is thought that Cr can improve lubricity at low temperatures, V can improve lubricity at relatively high temperatures, and exhibits excellent peeling resistance under a wide range of cutting conditions by being simultaneously present. . Further, it is particularly preferable that the values of e and f have a relationship of 20 <e / f <100. In the surface-coated cutting tool, the composition of the carbonitride forming the divided layer can be confirmed by AES or the like.

The amount of Cr and V in this way except for Al are _{(Al 1-ef Cr e V} f) ( where, 0 ≦ e ≦ 0.5,0 ≦ f ≦ 0.5,0 ≠ e + f ≦ 0.5) In the case of manufacturing a surface-coated cutting tool by a cathodic arc ion plating method, for example, as described later, a surface-coated cutting tool having a divided layer formed of carbonitride of a suitable compound represented by This can be realized by forming the dividing layer under the condition that the substrate bias voltage is in the range of −300 to −50V.

  The dividing layer is characterized by having a larger carbon content than the inner layer. Here, the difference in carbon content between the divided layer and the inner layer is preferably 5% or more, and more preferably 10% or more. This is because if the difference in carbon content between the divided layer and the inner layer is less than 5%, the above-described effects due to the divided layer having a larger carbon content than the inner layer are not sufficiently exhibited.

  The carbon content of the divided layer can be measured using, for example, AES.

  Further, in the process of manufacturing the surface-coated cutting tool of the present invention to be described later, the divided layer can be formed such that the carbon content is larger than that of the inner layer by increasing the methane gas introduction amount (flow rate, pressure, etc.). .

  When the inner layer is divided into multiple layers by the divided layer, the number of divisions of the inner layer is not particularly limited, and each portion of the divided inner layer may have an equal thickness or an uneven thickness. It may be. In addition, when it divides | segments into uneven thickness, there exists an advantage that it becomes possible to respond | correspond to various fracture stress. The thickness of each part of the inner layer is not particularly limited, but all the parts of the divided inner layer are in the range of 0.01 to 0.5 μm, and the total thickness of each part of the inner layer However, it is preferable that it exists in the range of the suitable thickness of the inner layer mentioned later. If the thickness of any part of the inner layer is less than 0.01 μm, the wear resistance may be insufficient, and if the thickness of any part of the inner layer exceeds 0.5 μm. This is because the effect of dividing the inner layer into multiple layers may be reduced. Similarly to the case of the outer layer described above, the thickness of each part of the inner layer can be measured by cutting the surface-coated cutting tool and observing the cross section using SEM or using AES.

  When the inner layer is divided into multiple layers by the divided layer, the thickness of the divided layer (when multiple layers are formed, any thickness thereof) is preferably 1 to 200 nm, preferably 10 to 100 nm. More preferably. If the thickness of the divided layer is less than 1 nm, the effect of dividing the inner layer into multiple layers may be reduced, and if the thickness of the divided layer exceeds 200 nm, the wear resistance may be reduced. Because. Similarly to the case of the outer layer described above, the thickness of the divided layer can also be measured by cutting the surface-coated cutting tool and observing the cross section using an SEM.

  Furthermore, in the surface-coated cutting tool of the present invention, when the inner layer is formed of Al, and carbonitride, oxynitride, or oxycarbonitride containing at least one of Cr and V, A layer (innermost layer) formed of nitride containing Al and at least one of Cr and V may be formed between the inner layer and the base material. By interposing such an innermost layer between the base material and the inner layer, the adhesion between the inner layer and the base material is improved.

  The thickness of the innermost layer is not particularly limited, but is preferably 0.05 to 1.0 μm, and more preferably 0.1 to 0.5 μm. This is because if the innermost layer thickness is less than 0.05 μm, the effect of improving the adhesion may not be sufficiently exhibited, and if the innermost layer thickness exceeds 1.0 μm, This is because the wearability may be reduced. As in the case of the outermost layer described above, the thickness of the innermost layer can be measured by cutting the surface-coated cutting tool and observing the cross section using SEM or analyzing it using AES.

In the surface-coated cutting tool of the present invention, the residual stress of the inner layer is preferably −6 to 0 GPa, and more preferably −4 to −1 GPa. When the residual stress is less than −6 GPa, the compressive residual stress in the surface coating film becomes too large, and the adhesion strength with the base material tends to decrease. On the other hand, if the residual stress exceeds 0 GPa, tensile stress remains in the coating, and the film tends to crack, and the chipping property and chipping property may be reduced. The residual stress can be measured using, for example, an X-ray residual stress measuring apparatus or by the Sin ² ψ method.

  The surface-coated cutting tool having such a suitable residual stress is, for example, a substrate bias voltage in the range of −250 to −100 V when the surface-coated cutting tool is produced by, for example, the cathode arc ion plating method as described later. This can be realized by forming the inner layer under the inner condition.

  In the surface-coated cutting tool of the present invention, the thickness of the inner layer is not particularly limited, but is preferably 0.4 to 8 μm, and more preferably 1 to 6 μm. This is because if the inner layer thickness is less than 0.4 μm, the wear resistance may be insufficient, and if the inner layer thickness exceeds 8 μm, the fracture resistance may decrease. Because there is. The thickness of the inner layer can be measured by cutting the surface-coated cutting tool and observing the cross section using an SEM, as in the case of the outer layer described above.

  Further, in the surface-coated cutting tool of the present invention, the total thickness of the layers covering the substrate (including the inner layer and the outer layer, and other layers when the other layer is formed between the inner layer and the outer layer) is 0. The thickness is preferably 5 to 8 μm, and more preferably 1.0 to 6.0 μm. If the total thickness is less than 0.5 μm, sufficient wear resistance may not be improved. If the total thickness exceeds 8 μm, the residual stress in the layer covering the substrate increases. This is because the adhesion strength with the substrate may be reduced. The total thickness can also be measured by cutting the surface-coated cutting tool and observing the cross section using an SEM, similarly to the thicknesses of the inner layer and the outer layer described above.

  As the base material used in the surface-coated cutting tool of the present invention, those that have been widely used in the art can be appropriately used, and are not particularly limited, but have high hardness even at high temperatures. , WC-based cemented carbide, cermet, high speed steel, ceramics (silicon carbide, silicon nitride, aluminum nitride, aluminum oxide, silicon carbide, titanium carbide and their composite materials), cubic boron nitride sintered body, diamond It is preferably any one of base materials made of a sintered body. Among them, it is particularly preferable to use a WC-based hard superalloy, cermet, or cubic boron nitride sintered body as a base material.

  The surface-coated cutting tool of the present invention can be applied to various conventionally known cutting tools used for cutting. In particular, the coated cutting tool of the present invention is preferably a drill, an end mill, a milling and turning cutting edge replaceable tip, a metal saw, a gear cutting tool, a reamer, or a tap.

  The surface-coated cutting tool of the present invention is manufactured by coating a base material with an inner layer and an outer layer (in some cases, an innermost layer or the like in some cases) by a known film forming process capable of forming a highly crystalline compound. be able to. As such a film forming process, a physical vapor deposition method is preferable because compressive stress can be applied to the film. Examples of the physical vapor deposition method include an ion plating method, a sputtering method, and an electron beam vapor deposition method. When the ion plating method is employed in manufacturing the surface-coated cutting tool of the present invention, The arc type ion plating method is preferable because it is easy to ensure adhesion with the substrate. When the sputtering method is adopted, the magnetron sputtering method (balanced and unbalanced magnetron sputtering method) is used. It is preferable to use it because it is excellent for coating a non-conductive material. Among these, it is particularly preferable to use the cathode arc ion plating method in which the ion ratio of the raw material elements is high. This is because, when the cathode arc ion plating method is used, a metal ion bombardment treatment can be performed on the surface of the base material before forming the inner layer, so that the adhesion of the inner layer is remarkably improved.

  Next, how the wear resistance of the coated cutting tool is improved will be described in detail using examples. The composition of the examples was confirmed by XPS (X-ray photoelectron spectrometer) and AES (Auger electron spectrometer).

<Examples 1-5, Comparative Examples 1-4>
As the base material, a cemented carbide alloy with a grade of JIS standard K10 and a chip shape with SPGN120308 of a JIS standard were used and mounted on a cathode arc ion plating apparatus.

First, the inside of the chamber is depressurized by a vacuum pump, and the substrate is heated to a temperature of 650 ° C. by a heater installed in the apparatus, and evacuation is performed until the pressure in the chamber reaches 1.0 × 10 ⁻⁴ Pa. It was. Next, argon gas was introduced to maintain the pressure in the chamber at 3.0 Pa, and while gradually increasing the voltage of the substrate bias power source, the surface of the substrate was cleaned for 15 minutes while being set to −1500 V. Thereafter, argon gas was exhausted.

  Next, an alloy target as a metal evaporation source is set so that the compound composition of the inner layer is the compound shown in Table 1, and the coating of the present invention is obtained among nitrogen, methane, and oxygen as reaction gases. While the gas is introduced, the substrate temperature is maintained at 650 ° C., the reaction gas pressure is 2.0 Pa, the substrate bias voltage is maintained at −150 V, and an arc current of 100 A is supplied to the cathode electrode to generate metal ions from the arc evaporation source. To form a coating (inner layer). When the inner layers reached the predetermined thicknesses shown in Table 1, the current supplied to the evaporation source was stopped.

  Subsequently, a carbonitride film containing Al and at least one element of Cr and V was formed as an outer layer on the inner layer. Specifically, an alloy target which is a metal evaporation source is set, and a substrate gas of 650 ° C. and a reaction gas is introduced as a reaction gas while introducing a gas from which nitrogen, methane, and oxygen can be obtained. The pressure was increased to 2.0 Pa, the substrate bias voltage was increased to −300 V, an arc current of 100 A was supplied to the cathode electrode, metal ions were generated from an arc evaporation source, Al having an average crystal grain size of 0.15 μm, Cr and An outer layer made of carbonitride containing at least one element of V was formed. When the outer layer had a predetermined thickness, the current supplied to the evaporation source was stopped and the cooling was performed.

  In Example 3, before forming the inner layer, a nitride film including Al and at least one of Cr and V was formed as the innermost layer on the base material. Specifically, an alloy target as a metal evaporation source is set, and nitrogen and oxygen are introduced as reaction gases, and the substrate temperature is maintained at 650 ° C., the reaction gas pressure is 2.0 Pa, and the substrate bias voltage is maintained at −150 V. As it was, an arc current of 100 A was supplied to the cathode electrode, and metal ions were generated from the arc evaporation source to form the innermost layer. When the innermost layer reached a predetermined thickness, the current supplied to the evaporation source was stopped.

  Further, in Example 5, when forming the outer layer, carbonitriding containing Al having an average crystal grain size of 0.4 μm and at least one element of Cr and V at a substrate bias voltage of −50 V It was set as the outer layer which consists of things.

  In Comparative Example 4, the coating was not performed and the substrate was left as it was.

  With respect to Examples 1 to 5 and Comparative Examples 1 to 4 manufactured in the above process, a dry turning test was performed under the following conditions, and a time when the flank wear width of the blade edge exceeded 0.2 mm was measured. The cutting conditions were such that the work material was a Ti-6Al-4V alloy, the cutting speed was 60 m / min, the feed amount was 0.2 mm / rev, and the cut was 1 mm. The results are shown in Table 1.

  As is clear from Table 1, in the present invention, it was confirmed that the cutting tool life of Examples 1 to 5 was greatly improved as compared with Comparative Examples 1 to 4.

  In the cutting of titanium alloy, as can be seen by comparing Comparative Examples 1, 2, and 4, the conventional coating film did not contribute to the improvement of wear resistance, but is a surface-coated cutting tool of the present invention. Examples 1 to 5 do not contain a Ti component in the coating film, and use a film quality excellent in lubricity as an outer layer. Therefore, the coating film has very excellent wear resistance and is excellent in cutting a titanium alloy. It can be seen that it shows performance.

<Examples 6 to 8>
A surface-coated cutting tool of the present invention was produced in the same manner as in Example 1 except that the inner layer and the outer layer having the compositions shown in Table 2 were formed. As described above, the performance shown in Table 2 was obtained as a result of performing the cutting test on Examples 6 to 8.

From Table 2, Examples 6 to 8 in which the values of a and b are in the range of 20 <a / b <100 in the compound forming the inner layer (Al _1-ab Cr _a V _b ) are particularly excellent cutting tools. I was able to get a lifetime.

<Example 9>
When the inner layer having the same composition as in Example 7 was formed, the inner layer was formed in the same manner except that the inner layer forming step and the dividing layer forming step similar to the outer layer were alternately performed. The inner layer was a divided layer having a thickness of 0.05 μm. A surface-coated cutting tool divided into 15 layers was produced. Each portion of the divided inner layer had a uniform thickness of 0.2 μm. About Example 9 obtained in this way, as a result of performing the cutting test similarly to the above-mentioned, the performance shown in Table 3 was obtained.

  From Table 3, it was confirmed that Example 9 in which the inner layer was divided by the divided layer had a very excellent cutting tool life.

Claims (10)

  An inner layer formed of a compound containing at least one element selected from Al, Cr and V, and at least one element selected from nitrogen, carbon, and oxygen is coated on the substrate. An outer layer formed of carbonitride or oxycarbonitride containing Al and at least one of Cr and V is coated on the outer layer, and the outer layer has a larger carbon content than the inner layer. A surface-coated cutting tool characterized by that.   The surface-coated cutting tool according to claim 1, wherein the outer layer has a thickness of 0.1 to 2 μm.   The surface-coated cutting tool according to claim 1 or 2, wherein an average crystal grain size of carbonitride or oxycarbonitride forming the outer layer is 0.2 µm or less. The inner layer is selected from (Al _1-ab Cr _a V _b ) (where 0 ≦ a ≦ 0.5, 0 ≦ b ≦ 0.5, 0 ≠ a + b ≦ 0.5), nitrogen, carbon, and oxygen. The surface-coated cutting tool according to any one of claims 1 to 3, wherein the surface-coated cutting tool is formed of a compound containing at least one kind of element.   The surface-coated cutting tool according to claim 4, wherein the value of a satisfies 0 <a <0.35 and the value of b satisfies 0 <b <0.35.   The surface-coated cutting tool according to claim 4 or 5, wherein the values of a and b satisfy 20 <a / b <100.   The surface-coated cutting tool according to any one of claims 1 to 6, wherein the inner layer and / or the outer layer contains 20% or less of Si in atomic percent.   The surface cutting tool according to any one of claims 1 to 7, wherein the inner layer is formed of a nitride containing Al and at least one element of Cr and V.   The inner layer is divided by a layer formed of carbonitride containing Al and at least one element of Cr and V, and having a larger carbon content than the inner layer. The surface-coated cutting tool according to claim 8. The surface-coated cutting tool according to any one of claims 1 to 9, wherein the total thickness of the layer covering the substrate is 0.5 to 8 µm.