JP5074772B2 - 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 for the purpose of further improving various properties of such aluminum oxide. For example, there has been proposed a cutting tool provided with a single-layer coating made of aluminum oxide composed of fine crystal grains having a γ-type crystal structure (Patent Document 1). As a result, the surface roughness of the coating is improved and the surface roughness of the machined surface of the work material is improved. However, the aluminum oxide having a γ-type crystal structure is harder than the aluminum oxide having an α-type crystal structure. Is low, and sufficient wear resistance is not exhibited, and thermal stability is also lacking, resulting in inferior tool life.

  On the other hand, aluminum oxide having an α-type crystal structure has advantages in comparison with those having a γ-type crystal structure in terms of the above points. However, since the crystal grains are usually large (for example, Patent Document 2). ), It is known that cracks tend to develop during cutting, and as a result, there is a tendency to lack wear resistance and fracture resistance.

  As described above, various attempts have been made to improve various characteristics of a film made of aluminum oxide. However, there are some limits to improving various characteristics by forming aluminum oxide in a single layer. Attempts have been made to improve various properties through further approaches.

  As one of such attempts, a conventional multilayer coating structure (Patent Document 3) 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 4 to 6). 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 7), 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.
JP-T-2001-522725 JP 07-216549 A 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

  The present invention has been made in view of such a situation, and an object of the present invention is to provide a surface-coated cutting tool provided with an aluminum oxide multilayer coating having improved characteristics such as wear resistance and fracture resistance as a coating. Is to provide.

  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 Includes a first unit layer containing aluminum oxide having an α-type crystal structure, and a second unit layer containing aluminum oxide having a γ-type crystal structure, and the first unit layer and the second unit layer, The first unit layer and the second unit layer each have a thickness of 0.5 nm or more and 50 nm or less.

  Here, either one or both of the first unit layer and the second unit layer is a group consisting of IVa group element, Va group element, VIa group element, Y, Ca, Mg, B and Si in the periodic table. It is preferable that the additive element which is an at least 1 sort (s) element chosen from is included.

  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 in that characteristics such as wear resistance and fracture resistance are improved 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 replaceable cutting tip, a metal saw, a 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 partially formed is included, and also the lamination | stacking aspect of a part of film is also partially 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 includes a first unit layer containing aluminum oxide having an α-type crystal structure, and a second unit layer containing aluminum oxide having a γ-type crystal structure, and the first unit. The first unit layer and the second unit layer have a thickness of 0.5 nm or more and 50 nm or less, respectively. .

By having such a structure, various characteristics such as wear resistance and fracture resistance are dramatically improved as compared with a film composed of a single layer of aluminum oxide. This is because aluminum oxide having an α-type crystal structure (the aluminum oxide having such a crystal structure may be simply referred to as α-Al ₂ O ₃ hereinafter) and aluminum oxide having a γ-type crystal structure (such as (Hereinafter sometimes referred to simply as γ-Al ₂ O ₃ ) with a specific thickness, the crystal grains of the α-type crystal structure are transformed into γ-type crystals. The crystal can be made as fine as a crystal grain, and thus retains good characteristics (ie, high hardness and good oxidation resistance (high temperature stability)) due to the α-type crystal structure. Disadvantages (absence of wear resistance and fracture resistance) caused by the growth of grains can be eliminated, and as a result of these effects acting synergistically, extremely good wear resistance and fracture resistance are shown. Is It is considered that.

  In addition, the first unit layer and the second unit layer are different from the crystal orientation and the crystal orientation of the crystal grains at the interface (the crystal orientation represented by the Miller index such as (100) or (110)). (Indicating the direction of the grain arrangement), the layers are laminated with extremely high adhesion, which contributes to the improvement of wear resistance and fracture resistance.

  Furthermore, since the smoothness of the coating surface is improved at the same time by the above configuration, the smoothness of the processed surface of the work material can be made extremely good.

  Here, in the above, each unit layer includes aluminum oxide having the crystal structure as described above includes the case where the unit layer is substantially composed of only such aluminum oxide, and the unit layer. Indicates that it may contain unavoidable impurities and other components. The α-type crystal structure is a crystallographically corundum-type crystal structure, and the γ-type crystal structure is crystallographically a spinel-type crystal structure. All of these can be identified by X-ray diffraction (XRD) or TEM diffraction patterns. In addition, due to a manufacturing method as described later, an α-type crystal structure and a γ-type crystal structure may be mixed in the boundary region between the first unit layer and the second unit layer, which is extremely microscopic. If observed, the boundary between both unit layers may not be clearly shown, but even such a case 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.

The first unit layer and the second unit layer must each have a thickness of 0.5 nm to 50 nm. This is because if the thickness is less than 0.5 nm, the crystallinity may decrease and the hardness may be insufficient, and if it exceeds 50 nm, the crystal size of the α-Al ₂ O ₃ of the first unit layer may become coarse. is there. The upper limit of the thickness of each unit layer is more preferably 30 nm or less, still more preferably 20 nm or less, and the lower limit thereof is 1 nm or more.

  Note that the first unit layer and the second unit layer may have the same thickness or different thicknesses. Further, these unit layers may have the same thickness in the entire region in the thickness direction of the aluminum oxide multilayer coating, or may have different thicknesses within the above range.

  In addition, either one or both of the first unit layer and the second unit layer is composed of a group IVa element (Ti, Zr, Hf, etc.) and a group Va element (V, Nb, Ta, etc.) in the periodic table. , VIa group elements (Cr, Mo, W, etc.), Y, Ca, Mg, B, and an additive element that is at least one element selected from the group consisting of Si can be included. That is, such an additive element is included only in either the first unit layer or the second unit layer (in this case, a unit layer containing aluminum oxide, a unit layer containing aluminum oxide and the additive element, and May be repeated alternately and vertically), or may be included in both. When both the first unit layer and the second unit layer contain such an additive element, the type or combination of the additive elements may be the same or different in both unit layers. Here, the combination being different includes the case where each unit layer includes a plurality of additive elements, in addition to the case where the combination of the additive elements is different, as well as the case where the number of additive elements included is different. By including such an additive element in aluminum oxide, it has characteristics that the various characteristics such as hardness, high temperature stability and good slidability of aluminum oxide are further improved. Moreover, when both unit layers contain an additive element, the effect that the adhesiveness between each unit layer is further improved can be exhibited, thereby further improving the wear resistance.

  Here, the aspect in which the additive element is contained in the unit layer 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 the additive element is contained in such a manner, the expression “aluminum oxide” is simply used in the present invention for the compound. Note that the crystal structure of aluminum oxide as described above in each unit layer is maintained even when such an additive element is contained.

  Further, the content ratio 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 aluminum in the aluminum oxide of each unit layer, and more preferably the upper limit is 25 atoms. %, More preferably 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.

  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. In addition, the number of lamination | stacking of each unit layer can be determined from the thickness of said aluminum oxide multilayer film and the thickness of each unit layer, and is not specifically limited. In addition, when the first unit layer and the second unit layer are alternately and repeatedly stacked, the layer closest to the base material (layer for starting the stacking) may be the first unit layer or the second unit layer. It may be a unit layer.

  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, for example, laminating with a certain periodicity such as alternately laminating two kinds of layers. 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 and defect resistance can be ensured.

  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. This is because, in addition to the above reasons, α-type and γ-type crystal structures can be easily formed and stress of −4 GPa or more and 3 GPa or less can be easily applied. Further, according to the physical vapor deposition method, when the additive element is contained in the aluminum oxide, there is an advantage that it can be easily contained.

  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, when a plurality of base materials are set on a circular holder (work table) that rotates so as to face each evaporation source (target) in the sputtering apparatus, it is within 1/4 of the holder. All base materials are set in an area (area where the central angle is within 90 °). The target is disposed so that the target for forming the first unit layer and the target for forming the second unit layer are opposed to each other with the holder interposed therebetween.

In this case, as a target for forming the first unit layer (unit layer containing α-Al ₂ O ₃ ), aluminum is used, and the discharge voltage is set so that the surface is completely oxide (so-called poisoning mode) ( 100-250V). Further, as a target for forming the second unit layer (unit layer containing γ-Al ₂ O ₃ ), aluminum is used, and the surface thereof is an intermediate transition state between metal aluminum and oxide (so-called poisoning mode and metal mode). The discharge voltage is set high (250 to 400 V) so as to achieve an intermediate transition mode.

  Then, the base material (substrate) temperature is set to 500 to 850 ° C. while adjusting the flow rate ratio of oxygen and argon (1 to 50% as oxygen / argon) to be constant and sending these gases into the apparatus. The holder (work table) on which the base material is set is adjusted and rotated. Next, the frequency of the pulse voltage applied to the substrate is changed every time the holder rotates halfway. That is, in the region where the base material is subjected to vapor deposition by the target forming the first unit layer, the frequency is set to 350 to 500 kHz, while the base material is subjected to vapor deposition by the target forming the second unit layer. Sets the frequency to 30-200 kHz.

  By adopting such conditions, an aluminum oxide multilayer coating can be suitably formed by a reactive sputtering method. In the above, the thickness of each unit layer can be adjusted by controlling the rotation speed of the work table. The thickness of the aluminum oxide multilayer coating can be adjusted by controlling the total number of hours required for film formation. The stress of the aluminum oxide multilayer coating can be adjusted by controlling the substrate bias voltage.

  In addition, when each unit layer contains the above additive element, when preparing the target, Al powder and a compound (oxide, carbide, etc.) containing the desired additive element are mixed (mixing ratio is aluminum oxide) It is adjusted according to the content ratio of the additive element contained in), and can be prepared by sintering the mixture.

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. Moreover, the crystal structure of the aluminum oxide contained in the aluminum oxide multilayer coating was confirmed by a TEM diffraction pattern, and the mode in which the 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 methods.

  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, predetermined raw materials (for example, TiAl, Ti, AlCr, etc.) were set in a plurality of arc evaporation sources, and predetermined raw materials were also set in two types of UBM sputtering sources. The two types of UBM sputtering sources were arranged so as to face each other with the holder interposed therebetween. 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.

  One of the two UBM sputtering sources is for forming the first unit layer (hereinafter referred to as the first UBM sputtering source), and the other UBM sputtering source is the second UBM sputtering source. This is for forming a unit layer (hereinafter referred to as a second UBM sputtering source). Each of the targets was configured as described above. In addition, when each unit layer described in Table 1 contains an additive element, as described above, a target obtained by mixing and sintering an Al powder and a compound containing the additive element was used.

  Thus, in order to form a hard film, the following conditions were employ | adopted and the hard film of desired thickness was formed. 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 TiAlN layer is a film formed by periodically repeating two layers. 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 oxygen gas is allowed to flow while rotating the holder on which the base material is mounted in the film forming apparatus so as to face two types of UBM sputtering sources. A pulse DC discharge voltage was applied to both UBM sputtering sources (the discharge voltage of the first UBM sputtering source was controlled to 180V, and the discharge voltage of the second UBM sputtering source was controlled to 340V). In the region where the substrate is subjected to vapor deposition by the first UBM sputtering source (that is, the period during which the holder on which the substrate is set rotates the region), the frequency of the pulse DC power supply is set to 400 kHz, while the substrate In the region subjected to vapor deposition by the second UBM sputtering source (that is, the period during which the holder on which the substrate is set rotates the region), the frequency of the pulse DC power source was set to 45 kHz. At this time, the flow rate ratio of oxygen to argon (oxygen / argon) is controlled to a constant value of 6.7%, and the substrate bias voltage is controlled within the range of −500 V to −50 V to oxidize by reactive sputtering. An aluminum multilayer coating was formed.

  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 examples are all the above 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, and a predetermined condition is adopted. These were prepared in the same manner as in Example 1 (the conditions known in the art were used). The film of the comparative example formed in this way is described in the column of the aluminum oxide multilayer film for convenience in Table 1. (The film of the composition described in the unit layer column of No. 9 to 11 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 the description of the unit layer in the column of the aluminum oxide multilayer coating, the unit with the notation “α-” indicates the configuration of the first unit layer, and the unit with the notation “γ-” indicates the configuration of the second unit layer. The unit layer described in the upper part and the unit layer described in the lower part are alternately stacked vertically (in each case, starting from the unit layer described in the upper part) Show. In addition, in each chemical formula in the column of the unit layer, when there is an element other than “Al” and “O”, the element is an additive element, and the numerical value in parentheses is the unit “at%” ( The numerical value represented by (atomic%) is the content of the additive element (two types are described according to the chemical formula order), and the numerical value represented by the unit “nm” is the thickness of each unit layer. In addition, when an additive element was contained in the crystal structure of aluminum oxide, it was confirmed that it was contained as an interstitial type or a substitution type.

  That is, for example, No. The surface-coated cutting tool 2 includes a base material and four kinds of coatings formed on the base material. The coating first 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 -2.6 GPa composed of TiAlBN having a thickness of 1.5 μm is formed thereon, and a stress having a thickness of 2.0 μm and a stress of −2. A 5 GPa aluminum oxide multi-layer coating is formed, and a hard coating with a stress of -1.0 GPa composed of TiN having a thickness of 0.5 μm is formed on the aluminum oxide multi-layer coating. And a first unit layer having a thickness of 24 nm composed of aluminum oxide having a crystal structure of γ, and an aluminum oxide having a γ-type crystal structure containing 5.6 atomic% of Ti as an additive element. Indicating that the second unit layer of Ruatsumi 37nm has a laminated structure repeatedly up and down alternately.

  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, it is considered that such excellent wear resistance and fracture resistance (toughness) are exhibited. .

  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 (9)

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 includes a first unit layer including aluminum oxide having an α-type crystal structure, and a second unit layer including aluminum oxide having a γ-type crystal structure, and the first unit layer includes: It has a structure in which the second unit layer is alternately and repeatedly stacked,
The surface-coated cutting tool, wherein the first unit layer and the second unit layer each have a thickness of 0.5 nm to 50 nm.   Either one or both of the first unit layer and the second unit layer is 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. The surface-coated cutting tool according to claim 1, further comprising an additive element which is at least one kind of element.   The surface-coated cutting tool according to claim 1, wherein the aluminum oxide multilayer coating is formed by physical vapor deposition.   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 any one of claims 1 to 4, wherein the aluminum oxide multilayer coating has a thickness of 0.1 µm or more and 10 µm or less.   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 containing one or more hard coatings containing a seed and at least one element selected from the group consisting of carbon, nitrogen, oxygen, and boron is included. 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 6, 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 to 100 nm 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 1-8 characterized by the above-mentioned. A surface-coated cutting tool according to claim 1.