JP4921984B2 - Surface coated cutting tool - Google Patents

Description

  The present invention relates to a surface-coated cutting tool formed by forming a film on a substrate.

  A base material constituting a cutting tool has been coated with various coatings for the purpose of protecting the surface and further improving various properties such as wear resistance and toughness. Among them, aluminum oxide is used as a coating for covering the surface of the base material because it has a high hardness and exhibits particularly excellent wear resistance and is expected to prevent surface oxidation of the base material. Attempts have been made since ancient times. In recent years, various attempts have been made to add various elements to the aluminum oxide for the purpose of further increasing the hardness of the aluminum oxide and further improving the wear resistance.

  However, since there is a certain limit to improving the wear resistance by forming such aluminum oxide in a single layer, attempts have been made to improve the wear resistance by various further approaches.

  As one of such attempts, a conventional multilayer coating structure (Patent Document 1) is used to repeat a layer made of an oxide such as aluminum oxide and a layer made of another compound such as nitride or carbide. A multi-layered film is proposed (Patent Documents 2 to 4). However, since such a multi-layer structure is formed by laminating compounds of different types of chemical compositions, sufficient wear resistance could not be achieved as a result due to insufficient adhesion of each layer. .

On the other hand, a cutting tool having a multilayer coating in which a layer made of aluminum oxide containing S and a layer made of pure aluminum oxide not containing S has been proposed (Patent Document 5), but contains S. The layer made of aluminum oxide showed a tendency to become brittle and also lacked adhesion to the layer made of pure aluminum oxide, so that sufficient wear resistance could not be obtained.
Japanese Patent Laid-Open No. 07-205361 JP 2002-113604 A JP 2002-254228 A JP-T-2001-513708 Japanese Patent Laid-Open No. 09-141502

  This invention is made | formed in view of such a condition, The place made into the objective is to provide the surface coating cutting tool provided with the aluminum oxide multilayer coating with which abrasion resistance improved as a coating.

  The surface-coated cutting tool of the present invention comprises a substrate and one or more coatings formed on the substrate, and the coating includes at least an aluminum oxide multilayer coating, and the aluminum oxide multilayer coating Has a structure in which two or more unit layers composed of aluminum oxide containing an additive element are included, and the two or more unit layers are periodically and repeatedly laminated. The kind or combination of the additive elements is different, and the additive element is at least one selected from the group consisting of IVa group element, Va group element, VIa group element, Y, Ca, Mg, B, and Si in the periodic table. It is a seed element.

  Here, the unit layer preferably has a thickness of 0.5 nm to 50 nm, and the aluminum oxide containing the additive element preferably has a γ-type crystal structure.

  The aluminum oxide multilayer coating is preferably formed by physical vapor deposition, preferably has a stress of −4 GPa to 3 GPa, and preferably has a thickness of 0.1 μm to 10 μm.

  In addition to the aluminum oxide multilayer coating, the above-mentioned coating is at least one element selected from the group consisting of IVa group element, Va group element, VIa group element, Al, and Si in the periodic table, or at least one of the elements One or more hard coatings containing a compound composed of one kind and at least one element selected from the group consisting of carbon, nitrogen, oxygen, and boron can be included.

  The hard coating is at least one element selected from the group consisting of Ti, Cr, Al, and Si, or at least one selected from the group consisting of at least one element selected from the group consisting of carbon, nitrogen, oxygen, and boron. It is preferable to include a compound composed of a seed element, and at least one element selected from the group consisting of Ti, Cr, Al, and Si, or at least one of the elements, and carbon, nitrogen, oxygen, and boron It is preferable that two or more types of layers containing a compound consisting of at least one element selected from the group consisting of are laminated with each layer having a thickness of 1 nm or more and 100 nm or less periodically repeated.

  The base material is preferably composed of any one of cemented carbide, cermet, high speed steel, ceramics, cubic boron nitride sintered body, and diamond sintered body.

  The surface-coated cutting tool of the present invention is characterized by having the characteristics of improved wear resistance by having the above-described configuration.

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 base material and one or more coating films formed on the base material. The surface-coated cutting tool of the present invention having such a basic configuration is, for example, a drill, an end mill, a milling or turning cutting edge replacement type cutting tip, a metal saw, a gear cutting tool, a reamer, a tap, or a crankshaft pin. It can be used very effectively as a chip for milling.

<Base material>
As the base material of the surface-coated cutting tool of the present invention, a conventionally known material known as such a cutting tool base material can be used without particular limitation. For example, cemented carbide (for example, WC base cemented carbide, including WC, including Co, or further including carbonitride such as Ti, Ta, Nb, etc.), cermet (TiC, TiN, TiCN, etc.) High-speed steel, ceramics (titanium carbide, silicon carbide, silicon nitride, aluminum nitride, aluminum oxide, and mixtures thereof), cubic boron nitride sintered body, diamond sintered body Etc. can be mentioned as examples of such a substrate. When a cemented carbide is used as such a base material, the effect of the present invention is exhibited even if such a cemented carbide contains an abnormal phase called free carbon or η phase in the structure.

  In addition, these base materials may have a modified surface. For example, in the case of cemented carbide, a de-β layer may be formed on the surface, or in the case of cermet, a surface hardened layer may be formed, and even if the surface is modified in this way, The effect is shown.

<Coating>
The film formed on the base material of the surface-coated cutting tool of the present invention is one in which one or more kinds of films are formed, and includes an aluminum oxide multilayer film as at least one of the films. In addition, such a film is not restricted only to what coat | covers the whole surface on a base material, The aspect in which the film is not formed partially is included, and also the lamination | stacking aspect of a part of film Also includes embodiments in which are different.

  In addition to the aluminum oxide multilayer coating, such a coating is at least one element selected from the group consisting of IVa group element, Va group element, VIa group element, Al, and Si in the periodic table, or the element One or more hard coatings containing a compound comprising at least one element selected from the group consisting of carbon, nitrogen, oxygen, and boron, and further including a coating of another composition You can also.

  The total thickness (total film thickness) of such a film is preferably 0.1 μm or more and 15 μm or less, more preferably the upper limit is 12 μm or less, still more preferably 10 μm or less, and the lower limit is 0.5 μm or more. More preferably, it is 1 μm or more. If the thickness is less than 0.1 μm, the effect of improving various properties such as wear resistance and oxidation resistance may not be sufficiently exhibited, and if it exceeds 15 μm, the chipping resistance may be lowered, which may be undesirable. The coating of the present invention includes a case where Mn, Fe, Co, Ni, Cu, Zn or the like is contained in an amount of 10 atomic% or less so as not to reduce the wear resistance. Hereinafter, these coating films will be described in more detail.

<Aluminum oxide multilayer coating>
The aluminum oxide multilayer coating of the present invention has a structure in which two or more unit layers composed of aluminum oxide containing an additive element are included, and the two or more unit layers are periodically laminated. Yes.

  By having such a structure, the wear resistance is remarkably improved as compared with a film made of a single layer of aluminum oxide. This is probably because the number of interfaces generated between the unit layers also increases in proportion to the number of unit layers stacked, and the progress of cracks occurring in the thickness direction of the coating during cutting is suppressed by any of these interfaces, thereby It is presumed that this is because it is possible to very effectively prevent the wear resistance reduction due to the progress of the above.

  In addition, since the unit layers of the present invention each include an additive element rather than a pure aluminum oxide layer containing only aluminum oxide, the unit layers between the unit layers are compared with the case where a pure aluminum oxide layer is included in the multilayer structure. Adhesion is drastically improved. This is because the inclusion of the additive element causes distortion in the crystal lattice in the crystal structure of the aluminum oxide, so that the adhesion to the pure aluminum oxide layer is considered to decrease, but the layer with distortion in the crystal lattice It is thought that it is because adhesion improves on the contrary.

  Therefore, in addition to the above reasons, the aluminum oxide multilayer coating of the present invention having the structure as described above has various characteristics such as hardness, high temperature stability and good slidability of the aluminum oxide itself due to the inclusion of the additive element. In addition, since the adhesion between the unit layers has been greatly improved, the synergistic action of these has achieved extremely high wear resistance. In addition, as described later, the aluminum oxide multilayer coating preferably has a γ-type crystal structure. However, the above-described laminated structure can stably maintain the γ-type crystal structure. This is considered to contribute to the improvement of wear resistance.

  Here, the unit layer in the present invention is a basic structural unit constituting the above-described aluminum oxide multilayer coating, and is composed of aluminum oxide containing an additive element. The aluminum oxide multilayer coating of the present invention has a structure in which two or more kinds of such unit layers are included and the two or more kinds of unit layers are periodically and repeatedly laminated.

  The “two or more types” of unit layers means that there are a plurality of unit layers having different compositions (that is, two or more types), and the type or combination of additive elements contained in the aluminum oxide is Different compositions shall be considered different. However, the concentration of the additive element in each unit layer may have a distribution in the thickness direction due to the manufacturing method as described later, and the boundary between each unit layer is not clearly shown if observed microscopically. However, even in such a case, it does not depart from the scope of the present invention. When specifying an individual unit layer or defining its thickness, if the boundary is not clearly indicated as such, the middle point in the thickness direction of the boundary region is regarded as the boundary.

  Further, “repeatedly and periodically laminated” means that the unit layers are alternately stacked when there are two types of unit layers, and also when they are composed of three or more types with a certain period (for example, the A layer, In the case of being laminated by the B layer and the C layer, it is included that the layers are repeatedly laminated in the order of A layer / B layer / C layer (that is, the A layer is again laminated on the C layer). .

  The additive elements contained in the aluminum oxide include group IVa elements (Ti, Zr, Hf, etc.), group Va elements (V, Nb, Ta, etc.), group VIa elements (Cr, Mo, W, etc.) in the periodic table. ), At least one element selected from the group consisting of Y, Ca, Mg, B and Si. In other words, the aluminum oxide constituting the unit layer contains one or more kinds of additive elements. As described above, the composition of the unit layer differs depending on the type or combination of the additive elements. However, the combination is different here when each unit layer includes a plurality of additive elements. In addition to the case where the combination of elements is different, the case where the number of added elements included itself is different is also included.

  The additive elements as described above have characteristics that aluminum oxide further improves various properties such as hardness, high temperature stability and good slidability of aluminum oxide by being contained in aluminum oxide.

  The aspect in which aluminum oxide contains an additive element is preferably an aspect in which the additive element is contained as an interstitial type or a substitution type in the crystal structure of aluminum oxide. Even in the case where an additive element is included in such an embodiment, the expression “aluminum oxide” is simply used in the present invention for the compound unless otherwise specified. The content of the additive element is preferably such that the additive element is contained in an amount of 0.01 atomic% to 30 atomic% with respect to the aluminum in the aluminum oxide, more preferably the upper limit is 25 atomic%, and still more preferably. Is 20 atomic%, and the lower limit is 0.1 atomic%. If it is less than 0.01 atomic%, the hardness of the aluminum oxide may not be sufficiently improved, and if it exceeds 30 atomic%, the hardness of the aluminum oxide may be lowered. In addition, when two or more kinds of additive elements are included in the unit layer, the total amount is preferably within the above range, but the ratio between the additive elements is not particularly limited.

  In addition, the aluminum oxide constituting such a unit layer preferably has a γ-type crystal structure from the viewpoint of productivity and prevention of coarsening of crystal grains. There is no change in the crystal structure. Here, the γ-type crystal structure means a spinel crystal structure crystallographically, and can be identified by X-ray diffraction (XRD).

  The unit layer preferably has a thickness of 0.5 nm to 50 nm. This is because the γ-type crystal structure as described above may not be maintained when the thickness is less than 0.5 nm or exceeds 50 nm. The upper limit of the thickness of the unit layer is more preferably 30 nm or less, still more preferably 20 nm or less, and the lower limit is 1 nm or more.

  The aluminum oxide multilayer coating of the present invention preferably has a thickness of 0.1 μm or more and 10 μm or less. This is because if it is less than 0.1 μm, sufficient wear resistance may not be obtained, and if it exceeds 10 μm, the coating itself may be self-destructed. The upper limit of the thickness of such an aluminum oxide multilayer coating is more preferably 5 μm or less, further preferably 3 μm or less, and the lower limit is 0.3 μm or more, more preferably 0.5 μm or more. The number of unit layers can be determined from the thickness of the aluminum oxide multilayer coating and the thickness of each unit layer, and is not particularly limited.

  In addition, it is preferable that the aluminum oxide multilayer coating film of this invention has a stress of -4 GPa or more and 3 GPa or less. Thereby, favorable adhesiveness with a base material or another coating film is securable. Here, the stress is an internal stress (inherent strain) remaining in the coating, and is a concept including both compressive residual stress and tensile residual stress. In the present invention, the term “stress” includes both compressive residual stress and tensile residual stress (note that the state in which the stress is released to 0 GPa is also included for convenience).

  The compressive residual stress is a stress represented by a numerical value “−” (minus) (unit: “GPa” is used in the present invention). In addition, when expressing the magnitude of compressive residual stress without using numerical values, it expresses that the compressive residual stress increases as the absolute value of the numerical value increases, and the compressive residual stress decreases as the absolute value of the numerical value decreases. It shall be expressed that the stress is small. Generally, the higher the compressive residual stress, the higher the toughness. Further, the tensile residual stress refers to a stress represented by a numerical value “+” (plus) (unit: “GPa” is used in the present invention).

In addition, the stress of such an aluminum oxide multilayer coating can be measured by the sin ² ψ method using an X-ray stress measuring apparatus, and can be any point located on a flat portion such as a rake face or a flank face of a cutting tool. Three or more stress points (preferably selected at a distance of 0.5 mm or more from each other so that each point can represent the stress of the part) are measured by the sin ² ψ method, and the average value is calculated. It can be measured by obtaining.

The sin ² ψ method using X-rays is widely used as a method for measuring the residual stress of a polycrystalline material. For example, “X-ray stress measurement method” (Japan Society of Materials Science, 1981 Corporation) The method described in detail on pages 54 to 67 of Yokendo) may be used.

  The stress of such an aluminum oxide multilayer coating is more preferably within the range of 2.5 GPa or less, more preferably 2 GPa or less, and the lower limit of −3.5 GPa or more, more preferably −3 GPa or more. It is. In addition, when it has a stress (tensile residual stress) exceeding 3 GPa, the adhesiveness (bonding force) with other coatings and base materials may be inferior, whereas when the stress is less than −4 GPa, it has a large compressive stress. For this reason, self-destruction of the film may occur.

<Hard coating>
In addition to the aluminum oxide multilayer coating, the coating of the present invention 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, or the element And at least one hard coating containing a compound comprising at least one element selected from the group consisting of carbon, nitrogen, oxygen, and boron (that is, a hard coating containing the element or compound). preferable.

  Such a hard coating is composed of at least one element selected from the group consisting of Ti, Cr, Al, and Si, or at least one of the elements, and carbon, nitrogen, oxygen, and boron. It is preferable to include a compound consisting of at least one element selected from the group, and at least one element selected from the group consisting of Ti, Cr, Al, and Si, or at least one of the elements, and carbon, Two or more layers containing a compound composed of at least one element selected from the group consisting of nitrogen, oxygen, and boron, and each layer is periodically and repeatedly stacked with a thickness of 1 nm to 100 nm. It is preferable that

  Such a hard coating is preferably one having high hardness and excellent wear resistance, and exhibiting extremely excellent toughness. In particular, at least one element selected from the group consisting of Ti, Cr, Al, and Si, or at least one element selected from the group consisting of at least one of the elements and carbon, nitrogen, oxygen, and boron A film containing a compound consisting of the above is extremely effective because it has excellent oxidation resistance and heat resistance, and exhibits particularly excellent wear resistance.

Here, as an element or a compound contained in such a hard film, for example, Cr, Ti, Al, Si, V, Zr, Hf, TiAl, TiSi, AlCr, TiN, TiON, TiCN, TiCNO, TiBN, TiCBN , TiAlCN, AlN, AlCN, AlCrCN , AlON, CrN, CrCN, TiSiN, TiSiCN, Ti 2 O 3, TiAlON, ZrN, ZrCN, AlZrN, TiAlN, TiAlSiN, TiAlCrSiN, AlCrN, AlCrSiN, TiZrN, TiAlMoN, TiAlNbN, TiSiN, _{TiSiCN, AlCrTaN, AlTiVN, TiB 2} , TiCrHfN, CrSiWN, TiAlCN, TiSiCN, AlZrON, AlCrCN, AlHfN, CrSiBON, TiA WN, mention may be made of AlCrMoCN, TiAlBN, the TiAlCrSiBCNO like.

  In particular, at least one element selected from the group consisting of Ti, Cr, Al, and Si, or at least one element selected from the group consisting of at least one of the elements and carbon, nitrogen, oxygen, and boron Examples of the compound consisting of Ti, Cr, Al, Si, TiN, TiCN, TiAlN, TiAlNO, TiAlCNO, TiBN, TiCBN, TiSiN, TiSiNO, TiSiCNO, CrTiN, CrTiNO, CrTiCNO, SiAlN, SiAlNO, SiAlCNO, CrSiN, CrSiNO, CrSiCNO, SiAlN, SiAlNO, SiAlCNO, CrSiN, CrSiNO, CrSiCNO, TiAlSiN, TiAlSiNO, TiAlSiCNO, TiAlCrN, TiAlCrNO, T AlCrCNO, TiCrSiN, TiCrSiNO, TiCrSiCNO, AlCrN, AlCrNO, AlCrSiNO, AlCrCNO, there may be mentioned AlCrSiBNO like, particularly AlCrN, AlCrNO, AlCrSiNO, AlCrSiBNO, AlCrCNO the like.

  In the above chemical formula, those in which the atomic ratio of each element is not particularly described are not necessarily equivalent, and all conventionally known atomic ratios are included. For example, when simply describing TiN, the atomic ratio of Ti and N includes 1: 1, and includes 2: 1, 1: 0.95, 1: 0.9, etc. (unless otherwise noted, the following) The same).

  In addition, this hard film can form these elements or compounds as a single layer or a multilayer, and in the case of a multilayer, the case where the layer which consists of these elements or compounds is laminated | stacked by the thickness of 1 nm-5 micrometers is also included. In particular, at least one element selected from the group consisting of Ti, Cr, Al, and Si, or at least one element selected from the group consisting of at least one of the elements and carbon, nitrogen, oxygen, and boron It is preferable that two or more types of layers containing a compound composed of an element constitute a hard coating in which the thickness of each layer is periodically repeated to a thickness of 1 nm to 100 nm. In this way, by periodically repeating the above layers, the oxidation resistance and heat resistance are further improved, and extremely excellent wear resistance is exhibited. Here, periodically laminating means laminating with a certain periodicity, for example, by laminating two kinds of layers alternately in the upper and lower directions, as in the case of the aluminum oxide multilayer coating. In addition, when the thickness of each layer is less than 1 nm or exceeds 100 nm, the effect of improving the abrasion resistance by lamination may not be shown, but even in that case, it is inherent to these elements and compounds. The effect of improving wear resistance is shown. The thickness of each layer is more preferably 2 nm or more and 60 nm or less.

  Further, such a hard coating preferably has a thickness of 0.3 μm or more and 10 μm or less (when it is formed of multiple layers, the total thickness thereof), more preferably the upper limit thereof is 7 μm or less, more preferably 5 μm or less. The lower limit is 0.5 μm or more, more preferably 1 μm or more. If the thickness is less than 0.3 μm, sufficient wear resistance may not be exhibited and sufficient toughness may not be exhibited. If the thickness exceeds 10 μm, the fracture resistance may decrease, which is not preferable.

  Moreover, it is preferable that such a hard film has the stress of -4 GPa or more and 3 GPa or less similarly to said aluminum oxide multilayer coating. Thereby, favorable adhesiveness with a base material or another coating film is securable.

  In addition, such a hard film can be formed between a base material and an aluminum oxide multilayer film, and can also be formed on an aluminum oxide multilayer film, The lamination | stacking arrangement | positioning is not specifically limited.

<Manufacturing method>
In the present invention, the film formed on the substrate is optimally formed by physical vapor deposition. This is because a film can be formed advantageously without deteriorating the substrate. Among these, the aluminum oxide multilayer coating is particularly preferably formed by physical vapor deposition. In addition to the above reasons, an additive element can be easily contained in aluminum oxide, a γ-type crystal structure can be easily formed, and a stress of −4 GPa to 3 GPa can be easily applied. This is because it can.

  As such a physical vapor deposition method, it is particularly preferable to employ an ion plating method or a sputtering method. Despite the fact that the ion plating method is a process at a relatively low temperature, it is possible to easily obtain a dense film. In particular, the arc ion plating method has an advantage that the film formation rate is further high and high production efficiency can be obtained. Have Further, the sputtering method has an advantage that a smooth coating film can be easily formed, and a coating film having excellent adhesion resistance to the work material is obtained, and at the same time, the finished surface roughness of the work material is improved. As such a physical vapor deposition method, any of various conventionally known conditions can be employed.

  Thus, although the manufacturing method of the coating of the present invention is not particularly limited, the above-described sputtering method is employed to form an aluminum oxide multilayer coating including aluminum oxide which is a non-conductive material. It is particularly preferred. Among these, it is preferable to employ a magnetron sputtering method using a pulse power source for the cathode. On the other hand, a combination of a sputtering method and an arc ion plating method, or a method of forming a film by an arc ion plating method by imparting conductivity by dispersing a conductive substance in aluminum oxide can be employed.

  And when forming an aluminum oxide multilayer film by sputtering method, as a concrete condition, conventionally known conditions can be employed without any particular limitation, but when employing an unbalanced magnetron sputtering method in particular, the following conditions Is preferably adopted.

  That is, as targets, first, a number of targets corresponding to the type of unit layer are prepared. Such a target is a mixture of Al powder and a compound (oxide, carbide, etc.) containing a desired additive element according to the composition of each unit layer (the mixing ratio is the inclusion of the additive element contained in aluminum oxide) It can be prepared by sintering the mixture).

  In the sputtering apparatus (film forming apparatus), the base material (substrate) temperature is set to 500 to 850 ° C., and the base material is opposed to a plurality of unbalanced magnetron sputtering sources including the target. Flow oxygen gas while rotating the holder (work table) equipped with. And while applying the discharge voltage (250-400V) of pulse DC to all the said unbalanced magnetron sputter sources, while controlling the pressure ratio of the oxygen gas with respect to an inert gas within the range of 1-50%, it is a base-material bias. An aluminum oxide multilayer coating film can be formed by reactive sputtering while controlling the voltage within a range of −500V to −25V.

  In the above, the thickness of each unit layer can be adjusted by controlling the rotation speed of the work table. Further, the thickness of the aluminum oxide multilayer coating can be adjusted by controlling the total number of hours required for film formation.

  In addition, the crystal structure of aluminum oxide may be γ-type by controlling the discharge voltage of the unbalanced magnetron sputtering source and the substrate bias voltage so that the surface of the target is in a so-called transition mode. it can. The stress of the aluminum oxide multilayer coating can be adjusted by controlling the substrate bias voltage.

EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these. The chemical composition of each film below is XPS (X-ray photoelectron spectrometer) or SEM (TEM) -EDX (energy dispersive fluorescence X-ray spectrometer attached to a scanning electron microscope (transmission electron microscope)). Confirmed by. The thickness of each coating and each unit layer is measured by observing a cross section perpendicular to the surface of the coating with a TEM (transmission electron microscope), and the stress of each coating is measured using an X-ray stress measuring device. Then, it was measured by the aforementioned sin ² ψ method. Further, the crystal structure of aluminum oxide contained in the aluminum oxide multilayer coating was confirmed by XRD, and the mode in which aluminum oxide contained an additive element was confirmed by using TEM and TEM-EDX in combination.

  In the following, the coating is formed by a combination of an unbalanced magnetron sputtering method and a cathodic arc ion plating method, which are physical vapor deposition methods, but includes cases where the film is formed by other known physical vapor deposition methods.

<Production of surface-coated cutting tool>
First, the following two types were prepared as base materials. That is, the grade is a WC standard cemented carbide of JIS standard M20, and the shape as a cutting tip is JIS standard CNMG120408 (used for wear resistance test 1 and wear resistance test 2 described later) and grade Is a WC standard cemented carbide of JIS standard P20 and the shape as a cutting tip is JIS standard SDEX42MT (used for intermittent cutting test described later) (the above JIS standard is a 1998 version) is there). And the film was similarly formed with respect to each base material by the following method.

  That is, first, the substrate was mounted on an unbalanced magnetron sputtering apparatus (film forming apparatus) using a pulsed DC power source as a cathode. In this film forming apparatus, a plurality of arc evaporation sources and a plurality of unbalanced magnetron sputtering evaporation sources (hereinafter referred to as UBM sputtering sources) are arranged, with the center point as the center and facing each of these evaporation sources. The base material was mounted on a rotating holder (work table). The necessary gas is introduced from the gas inlet into the film forming apparatus. In addition, a heater is provided in the film forming apparatus.

  Next, raw materials (that is, targets) were set in the evaporation source so that the chemical composition of the coating film formed on the substrate surface was as shown in Table 1 below. That is, a predetermined raw material (for example, TiAl, Ti, AlCr, etc.) is set in a plurality of arc evaporation sources, and a predetermined raw material (aluminum oxide multilayer coating contains a desired additive element) in a plurality of UBM sputtering sources The target obtained by mixing and sintering the Al powder and the compound containing the desired additive element was set. An aluminum oxide multilayer coating is formed by a UBM sputtering source, and a hard coating is formed by an arc evaporation source.

Subsequently, the inside of the chamber of the apparatus was depressurized to 1 × 10 ⁻³ Pa or less by a vacuum pump, and the temperature of the base material was heated to 650 ° C. by a heater installed in the apparatus and held for 1 hour.

  Next, argon gas was introduced to maintain the pressure in the chamber at 3.0 Pa, the substrate bias power supply voltage was gradually increased to −1000 V, and the surface of the substrate was cleaned for 15 minutes. Thereafter, argon gas was exhausted.

  Subsequently, in order to form a hard coating, the following conditions were adopted to form a hard coating with a desired thickness. That is, the substrate (substrate) temperature is set to 400 to 600 ° C., and one or more gases of nitrogen, methane (carbon source), and oxygen are introduced as a vacuum or a reaction gas, and the above-mentioned base is used by the arc ion plating method. A hard film of each constitution was formed on the material surface.

  In Table 1, No. No. 5 hard coating directly under the aluminum oxide multilayer coating and 7 indicates that the hard film on the aluminum oxide multilayer film is a film in which two kinds of layers are periodically laminated. For example, no. 5 is a 1.5 μm-thickness film (−5 μm thick), a layer containing AlCrN having a thickness of 5.0 nm and a layer containing AlCrNO having a thickness of 4.0 nm are periodically laminated (stacked alternately). (Having a stress of 1.4 GPa) is formed (indicating that a layer containing AlCrN is first formed on the TiAlN layer). No. No. 7 for the hard coating. The same content as 5 is shown. Such a periodic lamination of the hard coating can be formed by adjusting the rotation speed of the holder in the film forming apparatus or by adjusting the kind and flow rate of the reaction gas every half rotation.

  On the other hand, in order to form a desired aluminum oxide multilayer coating, the following conditions were employed. That is, the base material (substrate) temperature is set to 500 to 850 ° C., and the holder with the base material is rotated in the film forming apparatus so as to face a plurality of UBM sputtering sources. While applying a pulsed DC discharge voltage (300V) to the UBM sputtering source, the pressure ratio of the oxygen gas to the inert gas is controlled within the range of 2 to 20% and the substrate bias voltage is within the range of -500V to -50V. The aluminum oxide multilayer coating film was formed by the reactive sputtering method under control.

  Thus, No. 1 shown in Table 1 was obtained. Surface-coated cutting tools in which 1 to 12 coatings were formed on each substrate were prepared. No. 1 to 8 are examples of the present invention. 9 to 12 are comparative examples. The comparative example is the same as the above example except that a predetermined raw material is set on the target of the UBM sputtering source so that a film different from the structure of the aluminum oxide multilayer film of the present invention is formed. These were prepared (these conditions were conventionally known conditions). The film of the comparative example thus formed was described in the column of the aluminum oxide multilayer film for convenience in Table 1 (the film having the composition described in the unit layer column of Nos. 9 and 10 is not a multilayer but a single film). In addition, the numerical values described together with the unit “at%” and the unit “nm” shall be based on the description of the examples described later for convenience).

  In Table 1 above, the laminated structure of the film indicates that the film is laminated on the base material in order from the left (the blank in Table 1 indicates that the corresponding film is not formed). ing). In Table 1, the chemical composition indicates the composition of the compound constituting each hard coating, the thickness indicates the thickness of the coating, and the stress indicates the stress of the coating. In addition, the description of the unit layer in the column of the aluminum oxide multilayer coating indicates that the unit layer composed of the additive element-containing aluminum oxide represented by each chemical formula is periodically and repeatedly stacked (two types). The description indicates that the unit layer described in the upper part and the unit layer described in the lower part are alternately stacked up and down, and the three types indicate that the middle unit layer is provided on the upper unit layer. It is formed and periodically laminated in the order of forming the lower unit layer thereon (in each case, the lamination is started from the unit layer described in the upper part)). In each chemical formula in the unit layer column, elements other than “Al” and “O” are additive elements, and the numerical value in parentheses is the unit “at%” (atomic%) on the left side. The numerical value indicated is the content of the additive element (two types are described in the chemical formula order), and the numerical value indicated by the unit “nm” on the right is the thickness of the unit layer. The notation “γ” indicates that the crystal structure is γ type. It was confirmed that the additive element was contained as an interstitial type or a substitution type in the crystal structure of aluminum oxide.

  That is, for example, No. The surface-coated cutting tool 1 includes a base material and four kinds of coatings formed on the base material, and the coating has a stress composed of TiN having a thickness of 0.5 μm on the base material − A hard coating having a thickness of 1.0 GPa is formed, a hard coating having a stress of -3.0 GPa composed of TiAlN having a thickness of 1.0 μm is formed thereon, and a stress having a thickness of 1.5 μm and a stress of −0. A 6 GPa aluminum oxide multilayer coating is formed, and a hard coating having a stress of -0.5 GPa composed of TiN having a thickness of 0.5 μm is formed on the aluminum oxide multilayer coating. A unit layer of 3.5 nm thickness composed of aluminum oxide containing 2.4 atomic% of Cr (having a γ-type crystal structure), and aluminum oxide containing 5.6 atomic% of Ti as an additive element It shows a structure in which unit layers having a thickness of 3.0 nm composed of um (having a γ-type crystal structure) are alternately stacked.

  The surface-coated cutting tool thus produced was subjected to three types of cutting tests (abrasion resistance test 1, wear resistance test 2, and intermittent cutting test) under the following conditions. The results are shown in Table 2 below. In the wear resistance test 1 and the wear resistance test 2, the time for the flank wear amount to be 0.15 mm is measured, and the longer the time is, the better the wear resistance is. In the intermittent cutting test, the time until the tool is broken is measured, and the longer the time, the better the fracture resistance (toughness).

<Abrasion resistance test 1>
Work material: SCM435 round bar Cutting speed: 350m / min
Cutting depth: 2.0mm
Feed: 0.2 mm / rev.
Dry / Wet: Dry <Abrasion resistance test 2>
Work material: FCD450 round bar Cutting speed: 260m / min
Cutting depth: 2.0mm
Feed: 0.3 mm / rev.
Dry / Wet: Dry <Intermittent cutting test>
Work material: SCM440
Cutting speed: 380 m / min
Cutting depth: 2.0mm
Feed: 0.2 mm / rev.
Dry / Wet: Dry

  As can be seen from Table 2, no. 1-No. Each of the surface-coated cutting tools according to Example 8 of the present invention has excellent wear resistance and also has fracture resistance (toughness). That is, since the surface-coated cutting tools of these examples have the aluminum oxide multilayer coating film having the structure of the present invention as the coating film, such excellent wear resistance is exhibited and the chipping resistance (toughness) is also excellent. It is thought that it showed.

  In addition, a compound comprising at least one element selected from the group consisting of Ti, Cr, Al, and Si and at least one element selected from the group consisting of carbon, nitrogen, oxygen, and boron as the hard coating. No. including a film in which two or more kinds of layers including layers are periodically and repeatedly laminated. In 5 and 7, it was confirmed that these coatings had excellent oxidation resistance and heat resistance by showing particularly excellent wear resistance.

  In contrast, no. 9-No. The surface-coated cutting tools of 12 comparative examples were inferior in wear resistance and toughness (breakage resistance) as compared with those in the above examples. That is, when an aluminum oxide multilayer coating having the requirements of the present invention is not formed, the wear resistance and fracture resistance are inferior.

  In the present embodiment, a material having a chip breaker is used as a base material. However, the present embodiment is also applicable to a tool (chip) having no chip breaker or a tool (chip) whose upper and lower surfaces are entirely polished. The same effect can be obtained. In addition, although the cemented carbide is adopted as the composition of the base material, it is possible to use cermet, high speed steel, ceramics, cubic boron nitride sintered body, or diamond sintered body instead of the cemented carbide. The same effect as the embodiment can be obtained.

  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 (10)

A surface-coated cutting tool comprising a substrate and one or more coatings formed on the substrate,
The coating comprises at least an aluminum oxide multilayer coating;
The aluminum oxide multilayer coating has a structure in which two or more unit layers composed of aluminum oxide containing an additive element are included, and the two or more unit layers are periodically laminated.
Each of the unit layers is different in type or combination of the additive elements,
The surface coating is characterized in that the additive element is at least one element selected from the group consisting of group IVa element, group Va element, group VIa element, Y, Ca, Mg, B and Si in the periodic table Cutting tools.   The surface-coated cutting tool according to claim 1, wherein the unit layer has a thickness of 0.5 nm to 50 nm.   The surface-coated cutting tool according to claim 1, wherein the aluminum oxide containing the additive element has a γ-type crystal structure.   The surface-coated cutting tool according to claim 1, wherein the aluminum oxide multilayer coating is formed by a physical vapor deposition method.   The surface-coated cutting tool according to claim 1, wherein the aluminum oxide multilayer coating has a stress of −4 GPa to 3 GPa.   The surface-coated cutting tool according to claim 1, wherein the aluminum oxide multilayer coating has a thickness of 0.1 μm to 10 μm.   In addition to the aluminum oxide multilayer coating, the coating is at least one element selected from the group consisting of IVa group element, Va group element, VIa group element, Al, and Si in the periodic table, or at least one of the elements The hard coating film according to any one of claims 1 to 6, comprising one or more hard coatings containing a compound consisting of a seed and at least one element selected from the group consisting of carbon, nitrogen, oxygen, and boron. Surface coated cutting tool.   The hard coating is at least one element selected from the group consisting of Ti, Cr, Al, and Si, or at least one selected from the group consisting of at least one element and carbon, nitrogen, oxygen, and boron. The surface-coated cutting tool according to claim 7, comprising a compound comprising a seed element.   The hard coating is at least one element selected from the group consisting of Ti, Cr, Al, and Si, or at least one selected from the group consisting of at least one element and carbon, nitrogen, oxygen, and boron. The two or more kinds of layers containing a compound composed of a seed element are laminated in such a manner that each layer has a thickness of 1 nm or more and 100 nm or less and is periodically repeated. Surface coated cutting tool.   The said base material is comprised with either a cemented carbide alloy, a cermet, high speed steel, ceramics, a cubic boron nitride sintered compact, or a diamond sintered compact, The any one of Claims 1-9 characterized by the above-mentioned. A surface-coated cutting tool according to claim 1.