JP4445815B2 - Surface coated cutting tool - Google Patents

Description

  The present invention relates to a cutting tool such as a drill, an end mill, a milling or turning cutting edge replaceable tip, a metal saw, a gear cutting tool, a reamer, and a tap, and more particularly, a surface-coated cutting tool having a wear-resistant coating formed on the surface thereof. It is about.

  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 ) (N _z C _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 to solve the above-mentioned problems, and the object of the present invention is to provide a drill, end mill, milling or turning cutting edge replaceable tip, metal saw, gear cutting tool, reamer, tap. It is a surface-coated cutting tool that is suitably used for the above-mentioned, and is to provide a surface-coated cutting tool having improved peeling resistance and wear resistance as compared with conventional ones.

  As a result of examining various tool surface coating films for the above-mentioned problems, the present inventors have found that on the base material, Al, at least one of Cr and V, nitrogen, carbon, and oxygen. An inner layer formed of a compound containing at least one selected element is coated. The inner layer mainly includes a cubic compound, and on the inner layer, at least one of Al, Cr, and V is formed. An outer layer formed of a nitride, carbonitride, or oxycarbonitride containing an element is coated, and the outer layer is mainly composed of a hexagonal compound, and the outer layer has a larger Al content than the inner layer. The present inventors have found that a surface-coated cutting tool can suppress film peeling and exhibits excellent wear resistance and chipping resistance, and has reached the present invention. That is, the present invention is as follows.

  The surface-coated cutting tool of the present invention is 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 on a substrate. The formed inner layer is coated, and the inner layer is mainly composed of a cubic compound, and further includes a nitride, carbonitride, or oxycarbonitride containing at least one element of Al, Cr, and V on the inner layer The outer layer is formed by coating, the outer layer is mainly composed of a hexagonal compound, and the outer layer has a larger Al content than 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 the nitride, carbonitride or oxycarbonitride forming the outer layer is preferably 1 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). And a compound containing at least one element selected from nitrogen, carbon and oxygen. Here, it is more preferable that the value a satisfies 0 <a <0.35 and the value 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 and / or B in atomic%.

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

  Furthermore, in the present invention, the inner layer is formed of a nitride made of a hexagonal compound containing at least one element of Al, Cr, and V, and has a larger Al content than the inner layer. Is preferably 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 peel resistance and wear resistance of drills, end mills, milling or turning cutting tips, metal saws, gear cutting tools, reamers, taps, etc. A coated cutting tool can be provided.

  The surface-coated cutting tool of the present invention is 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 on a substrate. The formed inner layer is coated, and the inner layer is mainly composed of a cubic compound, and further includes a nitride, carbonitride, or oxycarbonitride containing at least one element of Al, Cr, and V on the inner layer The outer layer is formed by coating, the outer layer is mainly composed of a hexagonal compound, and the outer layer has a larger Al content than 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 excellent in chemical stability and exhibits excellent wear resistance in cutting metal materials, at least one element of Cr and V, and nitrogen, carbon, and oxygen. One of the characteristics is that the base material is covered with an inner layer mainly composed of a cubic compound, which is formed of a compound containing at least one selected element. Here, mainly consisting of a cubic compound means that when such an inner layer is measured by X-ray diffraction, the X-ray peak intensity due to the cubic compound is higher than the X-ray peak intensity due to the compound having a crystal structure other than the cubic crystal. It means getting bigger.

  Further, the surface-coated cutting tool of the present invention has a low friction coefficient and lubricity with respect to a metal material, exhibits high chemical stability, Al, and at least one element of Cr and V, An inner layer formed of a compound containing at least one element selected from nitrogen, carbon and oxygen, and a nitride or charcoal containing at least one of Al, Cr and V having excellent adhesion Another feature is that an outer layer covering the inner layer is formed of nitride or oxycarbonitride. Such an outer layer is preferably mainly composed of a hexagonal compound. Here, mainly consisting of a hexagonal compound means that when such an outer layer is measured by X-ray diffraction, the X-ray peak intensity of the hexagonal compound is greater than the X-ray peak intensity of the compound having a crystal structure other than hexagonal crystal. It means getting bigger.

  In addition, the surface-coated cutting tool of the present invention comprises an inner layer having the above composition and an outer layer having the above composition, and the outer layer has a larger Al content than the inner layer, thereby obtaining particularly excellent lubricity. Therefore, it is also characterized by the effect that a very excellent film peeling resistance can be obtained. With the present invention that combines these features, it is possible to improve the peeling resistance and wear resistance in drills, end mills, milling or turning edge inserts, metal saws, gear cutting tools, reamers, taps, etc. It becomes possible to provide a surface-coated cutting tool having a long life.

  As described above, the surface-coated cutting tool of the present invention is 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, An inner layer mainly composed of a cubic compound 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.

The nitride, carbonitride, oxynitride, oxycarbonitride, and the like that form the inner layer in the present invention have an amount of Cr and V excluding Al (Al _1-ab Cr _a V _b ) (where 0 ≦ (a ≦ 0.5, 0 ≦ b ≦ 0.5, 0 ≠ a + b ≦ 0.5), preferably a nitride, carbonitride, oxynitride or oxycarbonitride of the compound. 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 0.2 <a + b <0.4. When the value of a + b is within this range, the adhesion with the outer layer is improved, and excellent film peeling resistance is obtained. Since it is obtained, it is particularly preferable. Furthermore, in (Al _1-ab Cr _a V _b ), the value of a is preferably 0 <a <0.35, and the value of b is more preferably 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 believed 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 surface-coated cutting tools, the composition of the nitride, carbonitride, oxynitride, oxycarbonitride, etc. that form the inner layer should be confirmed using an X-ray photoelectron spectrometer (XPS) or an Auger electron spectrometer (AES). Can do. The crystal structure can be confirmed by X-ray analysis.

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, oxycarbonitride, or the like of a suitable compound represented by, for example, a cathode arc ion plating method as described later In the case of manufacturing a surface-coated cutting tool, for example, it can be realized by forming the inner layer under the condition that the substrate bias voltage is in the range of −300 to −20V. 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 −150 to −50 V when manufacturing the surface-coated cutting tool. it can.

The inner layer in the present invention is preferably formed of a nitride containing Al and at least one of Cr and V. When the inner layer is formed from the nitride of the above compound, the film has higher toughness and excellent fracture resistance than the case where the inner layer is formed from the carbonitride of the same compound. This is because there are significant advantages. Among them, a suitable compound in 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) More preferably, the compound is formed of a nitride of the above, 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 an outer layer is formed of nitride, carbonitride, or oxycarbonitride containing at least one element of Al, Cr, and V. The The nitride, carbonitride, or oxycarbonitride forming the outer layer may contain elements other than those described above (for example, Si, Ti, B) as long as the effects of the present invention are not impaired.

In the nitride, 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 <0.5 , 0 ≦ d <0.5, preferably 0 ≦ c <0.35, 0 ≦ d <0.35), preferably a nitride, carbonitride or oxycarbonitride of a compound . The outer layer is preferably mainly a hexagonal compound. This is because when the outer layer is a hexagonal compound, the hardness is lower than that of the inner layer, chipping resistance is improved, and lubricity is improved. Moreover, it is preferable that both the inner layer and the outer layer of the tool of the present invention contain 50 atomic% or more of Al as a metal element, and this provides excellent oxidation resistance and extremely excellent adhesion between both layers. Become. The composition of the nitride, carbonitride or oxycarbonitride forming the outer layer can be confirmed by XPS, and the crystal structure can be confirmed by X-ray analysis.

Thus, the amount of Cr and V excluding Al is (Al _{1 -cd} Cr _c V _d ) (where 0 ≦ c <0.5, 0 ≦ d <0.5, 0 ≦ c + d <0.5). A surface-coated cutting tool having an outer layer formed of a nitride, carbonitride, or oxycarbonitride of a suitable compound represented by, for example, a surface-coated cutting tool by a cathode arc ion plating method as described later. In the case of manufacturing, for example, it can be realized by forming the outer layer under the condition that the substrate bias voltage is in the range of −300 to −20V.

  Here, in the surface-coated cutting tool of the present invention, the outer layer has a larger Al content than the inner layer. Here, the difference in Al 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 Al content between the outer layer and the inner layer is less than 5%, the above-described effect due to the outer layer having a larger Al content than the inner layer is not sufficiently exhibited.

  In the surface-coated cutting tool of the present invention, if the outer layer has a larger Al content than the inner layer, for example, the Al content increases continuously or stepwise from the inner layer to the outer layer. It may be realized. The structure in which the Al content continuously increases from the inner layer to the outer layer is, for example, a target for forming the outer layer when a surface-coated cutting tool is manufactured by, for example, the cathode arc ion plating method as described later. This can be realized by using a material having a higher Al content than the target for forming the inner layer. In addition, the structure in which the Al content is gradually increased 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 realized by gradually increasing the film formation time by the target and the arc current.

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

  Moreover, the outer layer uses a target having a higher Al content than the target used when forming the inner layer in the process of manufacturing the surface-coated cutting tool of the present invention, which will be described later, so that the Al 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 large Al content is not particularly limited, but is preferably 0.1 to 2 μm, and more preferably 0.2 to 1 μm. . This is because when the thickness of the outer layer is less than 0.1 μm, the excellent effect as the outer layer may not be exhibited, and when the thickness of the outer layer exceeds 2 μm, the wear resistance may be easily lowered. Because there 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 nitride, carbonitride, or oxycarbonitride having an average crystal grain size of 1 μm or less, more preferably 0.7 μm or less. Thereby, an outer layer having particularly excellent lubricity and adhesion strength with the inner layer can be realized. From the viewpoint of wear resistance, the average crystal grain size of the nitride, 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 nitride, carbonitride, or oxycarbonitride containing at least one element of Al, Cr, and V in the outer layer of the surface-coated cutting tool is, for example, SEM or It can be observed and measured using a TEM.

  A surface-coated cutting tool having an outer layer formed of a nitride, carbonitride, or oxycarbonitride containing at least one of Al, Cr, and V having such a suitable average crystal grain size is provided. As will be described later, for example, when a surface-coated cutting tool is manufactured by the cathode arc ion plating method, it is preferable to form the outer layer under the condition that the base material bias voltage is in the range of −150 to −50V.

  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 preferably contain Si in atomic%, preferably 20% or less, more preferably 15%. % Or less may be included. This is because 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% in atomic% because the inner layer and / or the outer layer tend to become brittle and conversely promote wear. Further, when the inner layer and / or the outer layer contains Si, in order to obtain the effect of refining the structure, it is preferable that Si is contained at 1% or more in atomic%, and it is contained at 5% or more. Is more preferable. 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.

  The inner layer and / or the outer layer may contain B in an atomic% of 20% or less, preferably 15% or less, more preferably 10% or less. When B is present in the inner layer and / or the outer layer, a highly hard coating 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 amount of more than 20% in terms of atomic%, since 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, B is preferably contained at 1% or more in atomic%, and contained at 5% or more. More preferably. In particular, when B is contained in the outer layer, BN, which is a hexagonal compound, is generated, which improves lubricity and improves the chipping resistance by forming a low hardness film, which is preferable. 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 of Al, at least one of Cr and V, and at least one element selected from nitrogen, carbon, and oxygen, You may form so that it may divide | segment in the layer (partition layer) which has Al content larger than this inner layer. An excellent peelability can be realized by dividing the inner layer into multiple layers by such a divided layer. Here, the division of the inner layer means that each of the divided inner layers is divided into a state in which the inner layer exists in a state substantially parallel to the substrate surface.

  Since such an inner layer is divided into divided layers, when a large stress is suddenly applied during cutting, film breakage occurs at the multilayer film interface where the bonding force is slightly reduced. Since the number of fracture units can be reduced by multilayering, and the sudden large-breaking phenomenon of the film can be suppressed, a stable long-life surface-coated cutting tool can be realized as a result.

Such a divided layer is formed of a nitride made of a hexagonal compound containing at least one element of Al, Cr, and V, and is formed of a layer having a larger Al content than the inner layer. While acceptable as long as the amount of Cr and V except for Al are _{(Al 1-ef Cr e V} f) ( where, 0 ≦ e <0.35,0 ≦ f <0.35,0 ≦ e + f < 0.5) is preferable. That is, split layer in the surface-coated cutting tool of the present _{invention, (Al 1-ef Cr e} V f) ( where, 0 ≦ e <0.35,0 ≦ f <0.35,0 ≦ e + f <0. 5) is preferably formed of nitride. In _{(Al 1-ef Cr e V} f), when at least one of e and f is more than 0.35, because the abrasion resistance may deteriorate. In yet _{(Al 1-ef Cr e V} f), the value of e is 0, the value of the f is more preferably 0. This is because splitting with low hardness AlN can improve chipping resistance and can be expected to have excellent peeling resistance. In the surface-coated cutting tool, the composition of the nitride 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 <0.35,0 ≦ f <0.35,0 ≦ e + f <0.5) A surface-coated cutting tool comprising a split layer formed of a nitride of a suitable compound represented by the following formula can be used, for example, in the case of manufacturing a surface-coated cutting tool by, for example, the cathodic arc ion plating method, as described later. This can be realized by forming the dividing layer under the condition that the bias voltage is in the range of −300 to −20V.

  Such a divided layer is characterized by having an Al content larger than that of the inner layer. Here, the difference in Al 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 Al content between the divided layer and the inner layer is less than 5%, the above-described effect due to the divided layer having an Al content larger than that of the inner layer is not sufficiently exhibited.

  In addition, the Al content of the divided layer can be measured using AES, for example.

  In addition, in the process of manufacturing the surface-coated cutting tool of the present invention, which will be described later, the divided layer uses a target having a higher Al content than the target for forming the inner layer as the target, so that the Al content is larger than that of the inner layer. Can be formed.

  When the inner layer is divided into multiple layers by the divided layer, there is no particular limitation on the number of divisions of the inner layer, and each portion of the divided inner layer may have an equal thickness or non-uniformity. Thickness may be sufficient. 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 of the divided parts of the inner layer are in the range of 0.001 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 0.001 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 TEM, or using AES.

  Moreover, when an inner layer is divided | segmented into multiple layers by the said division layer, it is preferable that the thickness of a division | segmentation layer (when multiple layers are formed, any thickness) is 1-200 nm, 10-100 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. The thickness of the divided layer can also be measured by cutting the surface-coated cutting tool and observing the cross section using SEM or TEM, as in the case of the outer layer described above.

  Furthermore, in the surface-coated cutting tool of the present invention, when the inner layer is formed of Al, nitride, carbonitride, oxynitride or oxycarbonitride containing at least one element of Cr and V In addition, a layer (innermost layer) formed of at least one of Al, Cr, and V and / or a nitride thereof 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 above-mentioned adhesion may not be sufficiently exerted, 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 −10 to 0 GPa, and more preferably −6 to −1 GPa. When the residual stress is less than −10 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 is liable to crack, and the chipping and chipping properties may be reduced. The residual stress can be measured by the sin ² ψ method using, for example, an X-ray residual stress measuring device.

  The surface-coated cutting tool having such a suitable residual stress is, for example, a substrate bias voltage in the range of −300 to −20 V when the surface-coated cutting tool is manufactured 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.

  Furthermore, the surface-coated cutting tool of the present invention includes a layer covering the substrate (an inner layer, an outer layer, a divided layer and an innermost layer, and the layer when another layer is formed between the inner layer and the outer layer). ) Is preferably 0.5 to 8 [mu] m, more preferably 1.0 to 6.0 [mu] m. 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, as with 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 cemented carbide, 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 or 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 surface-coated cutting tool is improved will be specifically described using examples, but the present invention is not limited thereto. The compositions of the inner layer, outer layer, innermost layer, etc. of each example and each comparative example were measured by XPS (X-ray photoelectron spectrometer) and AES (Auger electron spectrometer), and the crystal structure was confirmed by an X-ray diffractometer. .

<Examples 1-5, Comparative Examples 1-4>
As the base material, a cemented carbide alloy having a grade of JIS standard M20 and a chip shape having a SPGN120308 chip having a JIS standard were used and mounted on a cathode arc ion plating apparatus.

First, 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 inner layer compound formed on the base material with 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 As a composition, an alloy target as a metal evaporation source was set so as to be the compounds shown in Table 1, and among the reaction gases, nitrogen, methane, and oxygen were used to obtain the gas from which the inner layer of each example of the present invention was obtained. While being introduced, while maintaining a substrate temperature of 650 ° C., a reaction gas pressure of 2.0 Pa, and a substrate bias voltage of −150 V, an arc current of 100 A is supplied to the cathode electrode to generate metal ions from the arc evaporation source, (Inner layer) was formed. When the inner layers reached the predetermined thicknesses shown in Table 1, the current supplied to the evaporation source was stopped.

  Subsequently, a nitride, carbonitride, or oxycarbonitride film containing at least one of Al, Cr, and V was formed as an outer layer on the inner layer formed as described above. Specifically, an alloy target that is a metal evaporation source is set, and a reaction temperature of nitrogen, methane, and oxygen is introduced while introducing a gas for obtaining the coating (outer layer) of the present invention, while the substrate temperature is 650 ° C. The gas pressure was increased to 2.0 Pa, the substrate bias voltage was increased to −75 V, an arc current of 100 A was supplied to the cathode electrode, metal ions were generated from the arc evaporation source, and an outer layer having an average crystal grain size of 0.7 μm was formed. . However, since the outer layer of Example 4 further contained Si, the average crystal grain size was refined to 0.5 μm. When the outer layer had a predetermined thickness, the current supplied to the evaporation source was stopped and gradually cooled.

Of these examples, for Example 2, an Al _0.65 Cr _0.35 N film was formed on the substrate as the innermost layer before the inner layer was formed. Specifically, a target that is a metal evaporation source is set so that such an innermost layer is formed, and a substrate temperature of 650 ° C. and a substrate bias voltage are set while introducing nitrogen as a reaction gas at a gas pressure of 2.0 Pa. While maintaining at −150 V, 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. Thereafter, an inner layer was formed on the innermost layer in the same manner as described above.

In Example 3 as well, a Cr film was formed as the innermost layer on the substrate before the inner layer was formed. Specifically, a Cr target as a metal evaporation source was set, and a cathode temperature of 100 A was applied to the cathode electrode while maintaining a substrate temperature of 650 ° C. and a substrate bias voltage of −150 V in a vacuum of 1.0 × 10 ⁻⁴ Pa. The innermost layer was formed by generating metal ions from an arc evaporation source. When the innermost layer reached a predetermined thickness, the current supplied to the evaporation source was stopped. Thereafter, an inner layer was formed on the innermost layer in the same manner as described above.

  Further, in Example 5, when forming the outer layer, the substrate bias voltage was set to −50 V, and the outer layer was made of Al and B nitrides having an average crystal grain size of 1.3 μm.

  In addition, about each comparative example, although the film of the compound composition described in Table 1 was formed like the above, the comparative example 4 was made into the base material, without coating.

  For Examples 1 to 5 and Comparative Examples 1 to 4 manufactured in the above steps, a dry milling test is performed under the following conditions, and a time when the flank wear width of the cutting edge exceeds 0.15 mm (time that can be cut) is measured. did. That is, the cutting conditions were such that the work material was SCM415, the cutting speed was 300 m / min, the feed amount was 0.05 mm / blade, and the cut was 1 mm. The results and the crystal structure of each layer are shown together in Table 1.

In the above table, a / b represents a / b values of a and b in the chemical formula (Al _1-ab Cr _a V _b ) showing a part of the compound composition of the inner layer.

  As is apparent from Table 1, the surface-coated cutting tools of Examples 1 to 5 in the present invention all have a longer cutting time than those of Comparative Examples 1 to 4, It was confirmed that the lifetime was greatly improved as compared with Comparative Examples 1 to 4.

  In particular, the surface-coated cutting tool of Example 3 was confirmed to have excellent wear resistance in the cutting of SCM415, which is likely to cause film peeling. This is presumably because the outer layer was AlN, which is an Al-rich hexagonal compound, and because it had a thin Cr metal layer as the innermost layer, it exhibited very excellent peel resistance.

<Examples 6 to 8>
A surface-coated cutting tool of the present invention was prepared in the same manner as in Examples 1 to 5 described above except that the innermost layer, inner layer, and outer layer having the compositions shown in Table 2 were formed. And as above, as a result of conducting a cutting test (dry milling test) on Examples 6 to 8, the performance shown in Table 2 was obtained.

In the above table, a / b represents a / b values of a and b in the chemical formula (Al _1-ab Cr _a V _b ) showing a part of the compound composition of the inner layer.

As is apparent 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 composition (Al _1-ab Cr _a V _b ) forming the inner layer are as follows: The possible cutting time was longer than in Examples 1 to 5, and a particularly excellent cutting tool life could be obtained.

<Example 9>
In Example 7, when an inner layer having the same compound composition as in Example 7 was formed, the inner layer and the divided layer having the same composition as the outer layer were alternately formed, so that the inner layer was divided by the divided layers. A surface-coated cutting tool was produced in the same manner as in Example 7 except that the inner layer was formed. In the surface-coated cutting tool thus obtained, the inner layer (cubic Al _0.713 Cr _0.28 V _0.007 N) is uniformly divided every 60 nm in a divided layer made of hexagonal AlN with a thickness of 30 nm, and the total as the inner layer The thickness was 3 μm. About Example 9 obtained in this way, as a result of conducting a cutting test (dry milling test) in the same manner as described above, the performance shown in Table 3 was obtained.

  As can be seen from Table 3, in Example 9 in which the inner layer was divided by the divided layer, the possible cutting time was longer than those in Examples 1 to 8, and the cutting tool life was very excellent. It could be confirmed.

  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 (9)

An inner layer formed of a compound containing at least one element selected from Al, at least one of Cr and V, and at least one element selected from nitrogen, carbon, and oxygen is coated on the substrate, The inner layer is mainly composed of a cubic compound, and the outer layer formed of nitride, carbonitride, or oxycarbonitride containing at least one of Al, Cr, and V is coated on the inner layer. The outer layer is mainly composed of a hexagonal compound, the outer layer has a higher Al content than the inner layer, and the inner layer includes a hexagonal crystal containing at least one element of Al, Cr, and V. A surface-coated cutting tool characterized by being divided by a layer having a larger Al content than the inner layer, which is formed of a nitride made of a compound .   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 nitride, carbonitride, or oxycarbonitride forming the outer layer is 1 µm or less. The inner layer is made of (Al _1-ab Cr _a V _b ) (where 0 ≦ a ≦ 0.5, 0 ≦ b ≦ 0.5, 0
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 ≠ a + b ≦ 0.5) and at least one element selected from nitrogen, carbon, and oxygen. .   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 and / or B in atomic percent.   The surface-coated 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 surface-coated cutting tool according to any one of claims 1 to 8 , wherein the total thickness of the layer covering the substrate is 0.5 to 8 µm.