JP2005297143A - Surface coated cutting tool - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface coated cutting tool which is excellent in the chipping resistance and the peeling resistance and has a long service life even under the service conditions that the cutting edge is exposed in the high temperature state, such as high speed cutting, heavy cutting, and dry cutting. <P>SOLUTION: The surface coated cutting tool has a coating layer composed of an outermost layer and an inner layer on the surface of a base material. The inner layer has a columnar structure having an aspect ratio of at least 3 to improve wear resistance, and has a Ti-containing layer composed of TiCN, in which any one of respective orientation indexes TC(220), TC(311), and TC(422) of crystal planes (220), (311), (422) becomes the maximum value of the orientation indexes. The outermost layer is composed of aluminum nitride to give the lubricity. Further, the inner layer is formed by the CVD method which can give excellent adhesiveness, and the outermost layer is formed by the PVD method which can give a compressive residual stress. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a cutting tool having a coating layer on a substrate surface. In particular, the present invention relates to a surface-coated cutting tool in which a coating layer hardly peels off, has excellent fracture resistance, and has a long tool life even in an environment where the cutting edge becomes high temperature, such as high-speed, high-efficiency machining, and dry machining.

  In recent years, at machining sites, due to reduction in machining costs and changes in demand, high-speed, high-efficiency machining, high accuracy, and high quality have been aimed at, and work materials have also diversified. Also, since the latter half of the 1990s, interest in environmental pollution such as global warming and dioxin issues has increased, and in machining, the use of cutting oil has been suppressed as much as possible from the viewpoint of global environmental conservation and work environment improvement. Is required to have a dry process that does not use any cutting oil and is a completely zero-emission process. Since dry machining does not use cutting oil, there is little cooling effect, and during cutting, the load on the cutting edge and the temperature of the cutting edge temperature are greatly increased. In the processing such as high speed and high efficiency machining, the load on the cutting edge and the cutting edge temperature are also increased. . Against this background, cutting tools are becoming more and more important for performance such as heat resistance (oxidation resistance) and wear resistance at high temperatures such as 800-900 ° C, and the characteristics required for tool materials become severe. On the other hand.

In order to meet the above requirements, the surface of the tool base is made of titanium-based ceramics such as titanium carbide (TiC), titanium nitride (TiN), titanium carbonitride (Ti (C, N)), alumina (Al ₂ O ₃ ), zirconia Cutting tools having a coating layer made of an oxide ceramic such as (ZrO ₂ ) are widely used. For example, Patent Document 1 discloses a cutting tool including a coating layer that defines an orientation index of X-ray diffraction. Further, a cutting tool including a coating layer made of aluminum nitride has been proposed in order to improve characteristics such as oxidation resistance (see Patent Documents 2 and 3).

Japanese Patent Laid-Open No. 11-124672 Japanese Patent Publication No.59-27302 JP 2002-273607 A

  However, conventional cutting tools do not have sufficient cutting performance to perform further high-speed, high-efficiency processing or dry processing that does not use any cutting oil. Even if a film having excellent cutting performance such as oxidation resistance and wear resistance is provided, if the film is peeled off at the initial stage of cutting or a defect occurs, the characteristics of the film cannot be fully exhibited. Therefore, it is desired to develop a cutting tool that can maintain the coating layer on the surface of the base material for a longer time without causing peeling or chipping.

  FIG. 1 is a schematic cross-sectional view showing the structure of a typical cutting edge portion of a cutting tool. In general, the cutting edge in the base material 10 is composed of a flank 11 and a rake face 12 as shown in FIG. 1 (A) .In many cases, the angle α formed by the flank 11 and the rake face 12 is an acute angle or Right angle. When the coating film 20 is formed on the blade edge having such a shape, the film thickness c of the tip of the blade edge becomes larger than the film thickness b of the surface 12 where the film thickness a of the flank 11 is easy to be a.

  In the cutting tool provided with the coating 20, the ideal wear progress of the cutting edge will be described. First, as shown in FIG. ), After reaching the base material 10, as shown in FIG. 1 (D), the base material 10 is worn with the coating 20 while being exposed.

  However, as a result of detailed investigation of the wear state of the cutting tool having the coating layer by the present inventors, in the conventional cutting tool, the wear does not proceed as shown in FIGS. In the initial stage, as shown in FIG. 1 (E), not only the coating 20, but also the tip of the blade tip of the substrate 10 has already disappeared, and the substrate 10 is exposed. Actually turned out to be deficient. Further, it was found that the exposed portion 13 in the substrate 10 was already oxidized. From these things, even if it has a coating layer excellent in oxidation resistance and abrasion resistance as described in the above-mentioned patent documents, the base material is exposed at the initial stage of cutting, and the tool life is significantly improved. It is considered difficult.

  Therefore, a main object of the present invention is to provide a surface-coated cutting tool that has a coating layer that is excellent in adhesion to a substrate and fracture resistance, and that can further extend the tool life.

  The present invention defines the composition of the outermost layer to impart lubricity, defines the composition, crystal structure and orientation of the inner layer in order to improve wear resistance, and adheres to the base material and provides fracture resistance. In order to improve the properties, the above-mentioned object is achieved by making the outermost layer deposition method different from the inner layer deposition method.

That is, the present invention is a surface-coated cutting tool having a coating layer on a substrate surface, the coating layer comprising an inner layer formed on the substrate and an outermost layer formed on the inner layer. The outermost layer and the inner layer satisfy the following.
<Inner layer>
I. Forming by chemical vapor deposition
II. Provide a titanium-containing layer made of TiCN that satisfies the following conditions (1) and (2)
(1) Has a columnar structure with an aspect ratio of 3 or more
(2) Any of the orientation indices TC (220), TC (311), and TC (422) on the (220), (311), and (422) planes of the crystal has the maximum value of the orientation index. <Outermost layer>
I. Forming by physical vapor deposition
II. Consists of a film made of an aluminum compound selected from Al nitride, carbonitride, oxynitride, and oxycarbonitride

  In order to extend the life of the cutting tool even under harsh conditions such as high speed, high efficiency machining, and dry machining that does not use any cutting oil, the present inventors have made it possible to improve the oxidation resistance and wear resistance of the coating layer. In addition to improving the properties, it has been found that it is effective to suppress the chipping and chipping of the cutting edge that occur in the early stage of cutting and the exposure of the base material due to film peeling. In order to improve fracture resistance, the outermost layer is formed by a physical vapor deposition method capable of imparting compressive residual stress, and is composed of nitride aluminum having a relatively low hardness. In order to improve the adhesiveness, it was found that it is preferable to form the inner layer by chemical vapor deposition. At this time, in particular, it was also found that the wear resistance can be improved by constituting the inner layer from a compound having a specific composition and structure. Based on these findings, the present invention is defined. Hereinafter, the present invention will be described in more detail.

(Coating layer)
<Outermost layer>
In the present invention, the outermost layer that first contacts the work material during cutting is made of any aluminum compound selected from Al nitride, carbonitride, nitride oxide, and carbonitride oxide. These nitride-based aluminums have a hexagonal crystal structure, have a relatively low hardness of 20 GPa or less, hardly oxidize even when the temperature exceeds 1000 ° C. (excellent oxidation resistance), and reactivity with steel materials Has the property of being low. As described above, since the hardness is relatively low, the wear of the coating proceeds without loss, and the loss of the inner layer can be suppressed. Also, since the reactivity with the work material is low, adhesion of the cutting edge is suppressed, so that the lubricity of the cutting edge surface can be improved, cutting resistance is reduced, and sudden chipping and chipping are suppressed. In addition, the effect that the surface quality of the work material can be improved is also obtained.

  In the present invention, the outermost layer made of nitride aluminum is formed by physical vapor deposition (hereinafter referred to as PVD method). In order to improve the fracture resistance, it is preferable to apply compressive residual stress to the coating. Normally, a film formed by chemical vapor deposition (hereinafter referred to as a CVD method) is formed at a high temperature and thus has excellent adhesion to the substrate, but tensile stress remains due to thermal stress during film formation. Cracks are likely to occur on the surface. This crack may propagate from the coating to the base material at the time of cutting to reduce the fracture resistance. Therefore, in the present invention, in order to improve the fracture resistance, the outermost layer is formed by the PVD method in order to impart compressive residual stress to the outermost layer.

  The residual compressive stress value is preferably -5 GPa or more and 0 GPa or less. When the residual stress value exceeds 0 GPa, tensile residual stress is applied to the coating, and cracking is likely to occur as in the case of a film formed by the CVD method, so that further improvement in fracture resistance cannot be expected. If it is less than -5 GPa, the compressive residual stress is too large, and the coating may peel off at the cutting edge before cutting or chipping may occur, which is not preferable. The residual stress can be adjusted by changing the film forming conditions. For example, it can be controlled by adjusting the film formation temperature, gas pressure, bias voltage, and the like.

  In the present invention, as described above, the PVD method is adopted as a film formation method of the outermost layer so that the outermost layer having high crystallinity and imparted with compressive residual stress can be formed. Examples of the PVD method include a balanced magnetron sputtering method, an unbalanced magnetron sputtering method, and an ion plating method. In particular, the arc ion plating method (cathode arc ion plating) in which the ionization rate of the raw material elements is high is optimal. When cathode arc ion plating is used, metal ion bombardment treatment can be performed on the surface of the inner layer before forming the outermost layer, so that the adhesion between the outermost layer and the inner layer is remarkably improved. This is a preferable process from the viewpoint of adhesion.

  The outermost layer may contain one or more additional elements selected from B, F, Mg, Si, Ca, V, Cr, Zn, Zr, and Ti. When at least one of B, Mg, Ca, V, Cr, Zn, and Zr is included, the oxides of these elements formed by the oxidation reaction occurring on the tool surface due to the temperature rise during cutting are the main components. It has the effect of densifying some Al oxides. Also, since the oxides of B and V have a low melting point, they act as a lubricant during cutting, and the oxides and F of Mg, Ca, Zn, and Zr have the effect of suppressing adhesion of the work material. is there. Furthermore, since nitrides, carbonitrides, nitrides, and carbonitrides of V, Cr, Zr, and Ti exhibit conductivity, the cathode discharge is stabilized during film formation and applied to the substrate. This is preferable because the DC bias voltage is effective, that is, the current easily flows. The content of the additional element is preferably more than 0 and less than 10 atomic%, with Al and the additional element being 100 atomic%.

  The film thickness of the outermost layer is preferably set to 1/2 or less of the total film thickness of the inner layers described later. At this time, the coating layer can have a good balance between fracture resistance, lubricity and wear resistance. If it exceeds 1/2, the outermost layer becomes thick, and although it is excellent in lubricity, it tends to be worn out, so there is a risk of shortening the tool life. In particular, the thickness of the outermost layer is preferably 0.03 μm or more and 10 μm or less. If it is less than 0.03 μm, it is difficult to obtain a sufficient fracture resistance function and lubrication function, and if it exceeds 10 μm, the outermost layer is thicker than the inner layer in the same manner as described above, and wear resistance tends to be lowered. The method for measuring the film thickness can be obtained, for example, by cutting a cutting tool having a coating layer and observing the cross section using an SEM (scanning electron microscope).

  In the outermost layer, the surface roughness of the portion in contact with the work material in the vicinity of the edge of the cutting edge is preferably 1.3 μm or less in terms of Rmax with respect to 5 μm measured by a method of observing from the cutting tool cross section. As a result of investigations by the present inventors, when the surface roughness of the contacted portion in the outermost layer becomes rougher than 1.3 μm, welding of the work material is likely to occur, and it becomes difficult to exert a defect suppressing effect or a lubricating effect. I found out. This surface roughness is the maximum surface when the cutting tool is cut and the cross section is wrapped after the outermost layer is formed, and the surface roughness of the coating surface is observed within a standard length of 5 μm with a metal microscope or electron microscope. Roughness (Rmax) is assumed, and macroscopic swells are excluded. Further, the surface roughness can be controlled to some extent by the film forming conditions. For example, the higher the film formation temperature, the rougher the crystal structure, so that the surface roughness of the film surface becomes rougher. Therefore, lowering the film formation temperature can be mentioned. Thus, after film formation, Rmax can be 1.3 μm or less in the film formation completion state without performing any special treatment, but after film formation, for example, polishing with a buff, a brush, a barrel, an elastic grindstone, or the like is performed. It is also possible to change the surface roughness by performing surface modification by microblasting, shot peening, or ion beam irradiation.

<Inner layer>
In the present invention, as an inner layer provided on the substrate side with respect to the outermost layer, a titanium-containing layer made of TiCN having a specific structure and orientation described later is coated on the substrate surface to provide wear resistance, and Provided is a cutting tool having wear resistance in addition to the characteristics of the outermost layer. In particular, by forming the inner layer by a CVD method, the adhesion between the coating layer and the substrate is improved, so that the characteristics of the coating layer can be effectively exhibited and the tool life can be extended. Examples of the CVD method include a thermal CVD method and a plasma CVD method.

<Titanium-containing layer>
In the present invention, the titanium-containing layer is a TiCN film having a columnar structure with an aspect ratio of 3 or more and a crystal plane having a specific crystal orientation, and wear resistance in a severe cutting environment where the cutting edge is at a high temperature. The crystal orientation is defined based on the knowledge that the tool life can be extended by extending the tool life. Specifically, each orientation index (orientation strength coefficient) TC (220), TC (311), or TC (422) on the (220) plane, (311) plane, or (422) plane of the crystal is one of The maximum value of the orientation index is assumed. The orientation index TC is defined as follows.

  In order for the orientation index (orientation strength coefficient) TC (220), TC (311), or TC (422) to reach the maximum value, the deposition conditions for the titanium-containing layer (deposition temperature, deposition pressure, gas composition) , Gas flow rate, gas flow rate, gas introduction procedure, and the like). Moreover, the method of changing suitably the surface state of the base material directly under or below a titanium containing layer, or the surface state of the coating film directly under or under a titanium containing layer is also mentioned. Specifically, for example, a titanium-containing layer is formed on the base material by appropriately changing the film formation conditions in a state where the surface roughness Zmax is controlled to 0.05 μm or more and 1.3 μm or less. May be. Alternatively, a titanium-containing layer may be formed on this film by appropriately changing the film formation conditions in a state in which the surface roughness of the film, the chemical state of the particles, the particle diameter, and the like are controlled.

  The diffraction intensity is preferably measured in a flat portion (smooth portion) of the base material so that reflection or the like is not caused by unevenness of the base material in the cross section of the base material. The identification of the X-ray diffraction intensity in the periodic table IVa, Va, VIa group metal carbonitride is not described in the JCPDS file (Powder Diffraction File Published by JCPDS International Center for Diffraction Data). Therefore, the identification of the diffraction intensity of the titanium-containing layer made of TiCN as the carbonitride is the diffraction data of the titanium (Ti) carbide as the metal, the diffraction data of the nitride, and the measured TiCN carbonitride It is preferable to obtain the surface index by comparing the diffraction data of the surface area, estimating each plane index, and measuring the diffraction intensity of the plane index.

  The titanium-containing layer has a columnar structure having an aspect ratio of 3 or more in order to improve wear resistance. This is because if the aspect ratio is less than 3, the wear resistance decreases under high-temperature cutting conditions, and the intended wear resistance cannot be improved.

In order to obtain a columnar structure, organic carbonitride such as CH ₃ CN, which can easily obtain a columnar structure, is used as the raw material gas, and the reaction atmosphere temperature (800 ° C to 950 ° C) and pressure (4.0 kPa to 80 kPa) are controlled. You can get it. In addition, when using a gas species other than organic carbonitrides, there are methods such as increasing the film formation rate, increasing the film formation temperature, and increasing the concentration of the source gas. In order to set the aspect ratio to 3 or more, for example, the average grain size of crystals is reduced (preferably 0.05 μm or more and 1.5 μm or less), and a film structure of a columnar structure is grown. Examples of the method include a method of appropriately changing the film formation conditions (film formation temperature, film formation pressure, gas composition, gas flow rate, gas flow rate, etc.) of the titanium-containing layer. Moreover, the method of changing suitably the surface state of the base material directly under or under a titanium content layer, or the surface state of the coating layer directly under or under a titanium content layer is also mentioned. Specifically, for example, a titanium-containing layer is formed on the base material by appropriately changing the film formation conditions in a state where the surface roughness Zmax is controlled to be 0.05 μm or more and 1.5 μm or less. May be. Alternatively, a titanium-containing layer may be formed by appropriately changing the film formation conditions on the film in a state in which the surface roughness of the film, the chemical state of the particles, the particle diameter (especially 0.01 μm or more and 1.0 μm or less) are controlled A film may be formed.

  The aspect ratio may be measured as follows, for example. That is, the cross section of the coating layer is mirror-finished to etch the grain boundaries of the film structure of TiCN having a columnar structure. Then, at a place corresponding to 1/2 of the thickness of the film made of TiCN, the width of each crystal in the horizontal direction with the base material is defined as the particle size, and the average value is obtained by measuring the particle size of each crystal (the average value is Average particle size). The film thickness is divided by the obtained average particle diameter to calculate the ratio of the average particle diameter to the film thickness, and this calculated value may be used as the aspect ratio.

<Compound layer>
When the inner layer is formed of a plurality of films, at least one film is the titanium-containing layer, and the other films are one or more selected from periodic table IVa, Va, VIa group metals, Al, Si, B It is preferable to be a compound layer composed of the first element and one or more second elements selected from B, C, N, O (However, when the first element is only B, the second element is Other than B). That is, when the inner layer is formed of a plurality of films, it is preferable that the inner layer is composed of the titanium-containing layer and the compound layer. This compound layer is different from the titanium-containing layer. That is, a film having a composition different from that of the titanium-containing layer may be used. When the compound layer is a film made of TiCN, the structure or orientation may be different. Further, this compound layer is formed by the CVD method in the same manner as the titanium-containing layer.

  Each of the titanium-containing layer and the compound layer may be a single film or a plurality of films. In the case where the titanium-containing layer is composed of a plurality of films, it may be a film having different orientation. In the case where the compound layer is composed of a plurality of films, the composition or structure of each film may be different. Moreover, when providing a compound layer, you may make any of a titanium content layer and a compound layer into the base-material side. That is, it is good also as a titanium content layer, a compound layer, and an outermost layer in order from a base material side, and it is good also as a compound layer, a titanium content layer, and an outermost layer in order from a base material side. When the compound layer is the innermost layer, it is preferably a film made of titanium nitride (TiN) having high adhesion to the substrate.

  The film thickness of the entire coating layer composed of the outermost layer and the inner layer is preferably 0.1 μm or more and 30.0 μm or less. When the film thickness of the entire coating layer is less than 0.1 μm, the wear resistance tends to be impaired. When the thickness exceeds 30.0 μm, the wear resistance can be improved by increasing the thickness of the coating layer, but the chipping tends to occur, and the life due to chipping often occurs, and stable processing tends to be difficult. Of course, after forming the coating layer, surface treatment such as polishing or laser treatment may be applied to the cutting edge ridge line portion as in the conventional case. The tool of the present invention does not significantly impair the properties of the coating layer by such surface treatment.

  The present invention uses both the PVD method and the CVD method as described above to form the coating layer, and there is an inner layer formed by the CVD method on the substrate surface. It is the structure which comprises the outermost layer formed into a film by the method. Further, in the present invention, since the outermost layer is formed by the PVD method, unlike the case of forming by the CVD method in which a chlorinated gas is often used, Cl which may cause deterioration of the coating film is the outermost layer. Not contained in.

(Base material)
In the present invention, the base material is a WC base cemented carbide, cermet, high speed steel, ceramics, cubic boron nitride sintered body, diamond sintered body, silicon nitride sintered body, and aluminum oxide and carbonized. It is preferable to use what is comprised from either of the sintered compacts containing titanium. In addition, when using a base material made of WC-based cemented carbide or cermet, the so-called de-β phase where the hard phase other than WC has disappeared, the binder-rich layer rich in the binder phase with the hard phase disappearing, and the binder phase reduced. The effect of the present invention is recognized even when a surface modification layer such as a cured surface layer is present on the surface of the substrate.

  The tool of the present invention may be any one of a drill, an end mill, a cutting edge exchangeable tip for milling, a cutting edge exchangeable tip for turning, a metal saw, a gear cutting tool, a reamer, and a tap.

  As described above, the present invention provides the coating layer with the outermost layer having excellent fracture resistance and lubricity and the inner layer having excellent wear resistance as a coating layer, and in order to sufficiently exhibit the functions of these coating layers. By prescribing, it is possible to have excellent cutting performance and prolong the tool life even in the use environment where the cutting edge is exposed to a high temperature state such as dry machining, high speed and high efficiency machining.

  Hereinafter, the surface-coated cutting tool of the present invention will be specifically described using examples. In each sample, the composition of the coating layer was XPS, the residual stress was measured by X-ray diffraction, the film hardness was measured by a nano indenter (MTS Nano Indenter XP), and the seizure property was SUJ2 as a counterpart material in the atmosphere at 800 ° C. The condition was confirmed by a high-temperature pin-on-disk tribo tester (TRIBOMETER / HT-800 manufactured by SCM). Among the coating layers, the outermost layer is a PVD method other than the cathode arc ion plating method shown below, for example, a balanced sputtering method or an unbalanced sputtering method, and the inner layer is other than the thermal CVD method shown below. A film can also be formed by a CVD method, for example, a plasma CVD method.

(Test Example 1)
After blending material powders with a composition of WC: 86% by mass, Co: 8.0% by mass, TiC: 2.0% by mass, NbC: 2.0% by mass, ZrC: 2.0% by mass, wet-mixed for 72 hours in a ball mill and dried Then, it was press-molded into a green compact with a breaker shape. The green compact was sintered in a sintering furnace in a vacuum atmosphere at 1420 ° C. for 1 hour to obtain a sintered body. The edge of the edge of the obtained sintered body was subjected to SiC brush honing and chamfered to obtain a throw-away tip base material made of WC-based cemented carbide of ISO · SNMG120408.

An inner layer was formed on the surface of the substrate using a thermal CVD method which is a kind of CVD method. In this example, TiN (0.5 μm), columnar structure TiCN (6 μm), TiBN (0.5 μm), and κ-Al ₂ O ₃ (2 μm) were sequentially formed from the substrate side. Table 1 shows the film formation conditions of each film, specifically, the composition (volume%) of the reaction gas, the pressure (kPa) during film formation, and the film formation temperature (° C.). The film thickness was adjusted by the film formation time. In this test, the TiCN film was formed such that it had a columnar structure with an aspect ratio of 4.2 and the (311) plane of the orientation index TC had the maximum value. Specifically, the reaction gas is CH ₃ CN, the temperature is set to 900 ° C., the pressure is set to 8 kPa, and the surface roughness of the TiN film formed in the lower layer of the TiCN film is set to about 0.1 μm at Zmax. The film formation conditions (gas composition, pressure, temperature) were determined.

Next, a method for forming the outermost layer will be described. A base material with an inner layer formed is mounted on the base material holder of a known cathode arc ion plating device, and the pressure in the chamber is reduced by a vacuum pump, and the base material holder is rotated and installed in the device. The substrate was heated to a temperature of 650 ° C. with the heater and vacuuming was performed until the pressure in the chamber became 1.0 × 10 ⁻⁴ Pa. Next, argon gas is introduced into the chamber, the pressure in the chamber is maintained at 3.0 Pa, the substrate bias power supply voltage is gradually increased to -2000 V, and the tool surface is cleaned for 15 minutes. It was. Thereafter, the argon gas in the chamber was exhausted.

Next, an alloy target, which is a metal evaporation source of the coating component constituting the outermost layer, is arranged, and a substrate temperature of 650 is introduced while introducing a gas for obtaining a desired coating among nitrogen, methane, and oxygen as reaction gases. While maintaining 100 ° C, reaction gas pressure 2.0Pa, substrate bias voltage at 200V, supply 100A arc current to the cathode electrode, and metal ion (aluminum ion) from arc evaporation source (metal whose main component is Al) Was generated to form the outermost layer. Then, when the predetermined film thickness (2 μm) was reached, the current supplied to the evaporation source was stopped to obtain cutting tips having the outermost layer having the composition shown in Table 2 (Samples 1-1 to 1-4). . In these cutting tips, when the surface roughness of the outermost layer in contact with the work material in the vicinity of the edge of the edge of the cutting edge was examined, all samples were compared with a reference length of 5 μm measured by the method of observing from the tool cross section. Thus, Rmax was 1.3 μm or less. Specifically, for example, in Sample 1-2, Rmax was 0.6 μm. In addition, as a conventional product, a cutting tool having no outermost layer by the PVD method, that is, a sample 1-5 having only a coating layer by the CVD method (the composition of the coating layer is the same composition as the inner layer) was also prepared. . In the cutting tip having these coating layers, the Cl content (atomic%) of the outermost layer, the residual stress of the outermost layer, the nanoindentation hardness (GPa) of the coating layer, and the seizure state were examined. The results are shown in Table 2. Note that the Cl content of the outermost layer (κ-Al ₂ O ₃ film by CVD method) in Sample No. 1-5 was about 0.1 atomic%. In Table 2, the Cl content expressed as “ND” indicates the detection limit or less in the XPS analysis. The nanoindentation hardness was measured by controlling the indentation load so that the indentation depth of the indenter was 1/10 or less of the film thickness of the entire coating layer.

  Using a cutting tip having the coating layer, cutting was performed under the conditions shown in Table 3, and the processing time until the tool life was reached was measured. In the peel resistance test, the tool life was defined as the time when film peeling occurred. In the wear resistance test, the tool life was determined when the flank wear amount reached 300 μm. The test results are shown in Table 4.

  As shown in Table 4, samples 1-1 to 1-4 having a nitrided aluminum film formed by the PVD method as the outermost layer have a long tool life even in dry processing. This is considered to be because the nitride-based aluminum film is less likely to be chipped or chipped, and the lubricity is imparted to reduce the cutting resistance to make the film difficult to peel off. In particular, it is considered that the fracture resistance could be improved by forming by the PVD method. In addition, because the inner layer with excellent wear resistance was formed by the CVD method with excellent adhesion, the adhesion between the coating layer and the base material was improved, and the functions of the coating layer were fully demonstrated. It is believed that there is. Further, as shown in Table 2, these samples 1-1 to 1-4 show little seizure even under a high temperature environment and are excellent in heat resistance.

(Test Example 2)
A cutting tip substrate similar to the cemented carbide substrate used in Test Example 1 was produced, and the film formation conditions (gas composition, pressure, temperature) shown in Table 1 using the thermal CVD method on the obtained substrate surface The inner layer was formed at In this example, TiN (0.5 μm), columnar structure TiCN (4 μm) or granular structure TiCN (4 μm), TiBN (0.5 μm), and Al ₂ O ₃ —ZrO ₂ (1.5 μm) were sequentially formed from the substrate side. On this inner layer, AlN (Table 2 Sample 1-1; 2 μm) was formed as the outermost layer under the same conditions as in Test Example 1 (cathode arc ion plating). The film thickness was adjusted by the film formation time. In this example, TiCN films each having a columnar structure or a granular structure were formed by changing the film forming conditions. As shown in Table 1, the columnar texture TiCN film changes the pressure during film formation and the film formation temperature, and also changes the surface roughness and gas conditions of the film formed in the lower layer of the TiCN film. The surface taking the maximum value of the orientation index was changed. Specifically, CH ₃ CN is used as the reaction gas, the gas temperature is 920 ° C., the pressure is 6 kPa, and the aspect ratio of the TiCN film is set to 3 or more by gradually introducing CH ₃ CN (corresponding to the titanium-containing layer). . In addition, the surface roughness of the base material is controlled to 0.09 μm in Zmax, and the TiCN film is formed while controlling the aspect ratio on the outside (the side away from the base material) of this base material. The maximum value of the orientation index was TC (422). In addition, all the surface roughness of the part that contacts the work material near the edge of the edge of the outermost layer is 0.4 μm in Rmax with respect to the reference length of 5 μm measured by the method of observing from the tool cross section. In the sample, after forming the outermost layer, the surface of the outermost layer was polished. Table 5 shows the surface of the TiCN film having the maximum morphology, aspect ratio, and orientation index TC.

  Using each sample having the TiCN film shown in Table 5 as an inner layer, continuous cutting was performed under the following cutting conditions, and the processing time until the tool life was measured. The tool life was determined when the flank wear amount reached 300 μm. The test results are also shown in Table 5.

Work material: SUS material Wear resistance test with round bar Speed: V = 200m / min
Feed: f = 0.2mm / rev.
Cutting depth: d = 1.5mm
Cutting oil: None

  As a result, as shown in Table 5, a sample having a columnar structure TiCN film in which the inner layer has an aspect ratio of 3 or more and the orientation index TC (311), TC (220), or TC (422) has the maximum value. 2-1 to 2-3 can maintain wear resistance even in dry processing, and can extend the life of cutting tools together with the lubrication effect and chipping suppression effect of the outermost AlN film I understand that. In particular, it is considered that the inner layer was formed by the CVD method, so that the adhesiveness of the coating layer to the substrate was excellent, and the characteristics such as wear resistance, lubricity, and fracture resistance were sufficiently exhibited.

(Test Example 3)
A cutting tip substrate similar to the cemented carbide substrate used in Test Example 1 was produced, and the film formation conditions (gas composition, pressure, temperature) shown in Table 1 using the thermal CVD method on the obtained substrate surface The inner layer was formed at Then, an outermost layer was formed on the inner layer under the same conditions as in Test Example 1 (cathode arc ion plating) to obtain a cutting tip having a coating layer (Sample Nos. 3-1 to 3-19, 3-21). In addition, a cutting tip in which the outermost layer was formed by the CVD method was obtained (Sample No. 3-20). Table 6 shows the composition of each coating film constituting the coating layer and the film thickness of each coating film. Each film shown in Table 6 is a first film, a second film, etc. in order from the side closer to the substrate. The film thickness was adjusted by the film formation time. In this example, the columnar TiCN film has an aspect ratio of 3 or more, and the film formation conditions are controlled so that one of the orientation indices TC (311), TC (220), and TC (422) takes the maximum value. (Corresponding to a titanium-containing layer).

  Using a cutting tip having a coating layer shown in Table 6, continuous cutting was performed under the following cutting conditions, and the processing time until the tool life was measured. The tool life was determined when the flank wear amount reached 300 μm. The results of the test are shown in Table 7.

Work material: SCM435 Round wear resistance test with a round bar for 10 seconds Speed: V = 180 m / min
Feed: f = 0.2mm / rev.
Cutting depth: d = 1.5mm
Cutting oil: None

  As a result, as shown in Table 7, samples 3-1 to 3-12, in which a nitrided aluminum film by PVD method is used as the outermost layer, and a specific TiCN film and a compound film having a specific composition by CVD method are provided in the inner layer. It can be seen that 16 to 3-19 and 3-21 have longer tool life. This is considered to be because it has excellent adhesion and is excellent in fracture resistance, lubricity, and wear resistance.

  Further, the results shown in Table 7 indicate that the outermost layer preferably has a thickness of 0.03 μm to 10 μm, and the overall thickness is preferably 0.1 μm to 30 μm. Further, it is understood that the outermost layer is preferably 1/2 or less of the total thickness of the inner layer.

  As a result of cutting all the chips of Samples 3-1 to 3-21 and measuring the surface roughness of the outermost layer in contact with the work material in the vicinity of the edge of the cutting edge at a reference length of 5 μm, Sample 3- All the chips except 21 had a Rmax of 1.3 μm or less, but Sample 3-21 had a Rmax of 1.9 μm. Therefore, when polishing the surface roughness of the outermost layer of sample 3-21 with the # 1500 diamond paste in the vicinity of the edge of the edge of the cutting edge, the surface roughness after polishing was measured by the same method. It was 0.52 μm. As a result of a cutting test using the polished tip under the same cutting conditions, the tool life was 28 min. This is considered to be because the unevenness of the portion in contact with the work material in the vicinity of the edge of the edge of the cutting edge is reduced and the cutting resistance is lowered. In addition, when the surface roughness was measured in the same manner for Sample 3-3, the Rmax was 0.78 μm, but when the edge was polished and cut again in the same manner as above, the machining time was 51 min, which was greatly improved. It was.

Prepare a plurality of drill base materials made of cemented carbide of JIS standard K10 with an outer diameter of 8 mm, and form a coating layer on each base material in the same manner as in Example 1, and then drill with a coating layer. Obtained. Of the coating layers, the inner layer was the same as in Test Example 1, and the outermost layer was the same as Sample 1-1. In addition, as a conventional product, a sample similar to Sample 1-5 (comprising only a coating layer formed by the CVD method) having no outermost layer formed by the PVD method was prepared. Perform drilling of SCM440 (H _R C30) using a drill comprising these coating layers, tried to evaluate the tool lifetime.

  Cutting conditions were a cutting speed of 90 m / min, a feed rate of 0.2 mm / rev., No cutting oil (using air blow), and a blind hole with a depth of 24 mm. The tool life was determined when the dimensional accuracy of the work material was out of the specified range, and the evaluation was performed based on the number of holes drilled until the life reached. As a result, the drill having the same coating layer as Sample 1-1 was able to machine 6,500 holes, but the drill having the same coating layer as Sample 1-5 could only process 610 holes. From this, it was confirmed that the present invention greatly improved the tool life even in the dry processing.

Prepare multiple 6-blade end mill bases made of JIS standard K10 cemented carbide with an outer diameter of 8 mm, and form coating layers on each base in the same manner as in Example 1 to provide coating layers. An end mill was obtained. Of the coating layers, the inner layer was the same as in Test Example 1, and the outermost layer was the same as Sample 1-2. In addition, as a conventional product, a sample similar to Sample 1-5 (comprising only a coating layer formed by the CVD method) having no outermost layer formed by the PVD method was prepared. Using an end mill with these coating layers, SKD11 (H _R C60) end mill side milling was performed and the tool life was evaluated.

  Cutting conditions were a cutting speed of 200 m / min, a feed of 0.03 mm / blade, a cutting amount Ad = 12 mm; Rd = 0.2 mm, and no cutting oil (using air blow). The tool life was determined when the dimensional accuracy of the work material was outside the specified range, and the evaluation was performed based on the machining length until the end of the life. As a result, the end mill having the same coating layer as Sample 1-2 could cut 195 m, but the end mill having the same coating layer as Sample 1-5 could only process 15 m. From this, it was confirmed that the present invention greatly improved the tool life even in the dry processing.

A cutting chip base material using a cBN sintered body as a base material was prepared, and a cutting layer was formed on the cutting chip base material, and cutting was performed to evaluate the tool life. The cBN sintered body is made of cemented carbide pot and ball, and mixed with a binder powder consisting of 40% TiN: 10% by mass and 50% cBN powder with an average particle size of 2.5μm. It was obtained by filling a cemented carbide container and sintering at a pressure of 5 GPa and a temperature of 1400 ° C. for 60 minutes. This cBN sintered body was processed to obtain a cutting tip base material having the shape of ISO standard SNGN120408. A plurality of such chip base materials were prepared. Then, a coating layer was formed on each chip substrate by the same method as in Example 1 to obtain a cutting chip having the coating layer. As an example, the coating layer is a sample having a coating layer similar to that of Sample 3-1, and, as a conventional product, Sample 1-5 having no outermost layer by PVD method (only having a coating layer by CVD method) The thing provided with the same coating layer was prepared. Using a cutting tip comprising these coating layers, subjected to peripheral cutting machining of round bar of SCM415 (H _R C62), tried to evaluate the tool lifetime.

  Cutting conditions were a cutting speed of 160 m / min, a cutting depth of 0.1 mm, a feed of 0.08 mm / rev., And no cutting oil. Judgment of the tool life was made when the surface roughness of the work material reached 3.2 μm in Rz, and the evaluation was performed based on the cutting time until the life reached. The surface roughness Rz of the work material after cutting for 1 minute under the above cutting conditions was defined as the initial surface roughness. The surface roughness Rz is a 10-point average roughness defined in JIS B0601. As a result, the cutting tip having the same coating layer as Sample 3-1 had an initial surface roughness of 1.2 μm in Rz and could be processed for 80 minutes until it reached 3.2 μm in Rz. The cutting tip having the same coating layer as 1-5 had an initial surface roughness Rz of 3.4 μm and could only be processed for 7 minutes before reaching Rz of 3.2 μm. From this, it was confirmed that the present invention greatly improved the tool life even in the dry processing.

  The grade is made of cemented carbide of JIS standard P10, and chip shape: Prepare multiple cutting chip base materials of SNMG120408 of ISO standard, and form coating layers on each base material in the same way as in Example 1. A cutting tip having a coating layer was obtained. Of the coating layers, the inner layer was the same as in Test Example 1, and the outermost layer was the same as in Sample 1-3. In addition, as a conventional product, a sample similar to Sample 1-5 (comprising only a coating layer formed by the CVD method) having no outermost layer formed by the PVD method was prepared. Using a cutting tip having these coating layers, the outer periphery of a round bar of SCM415 was cut and the surface quality of the work material was examined.

  Cutting conditions were a cutting speed of 100 m / min, a cutting depth of 2 mm, a feed of 0.3 mm / rev., A cutting time of 20 minutes, and a cutting oil used. As a result, the work material cut with the cutting tip having the same coating layer as Sample 1-3 had a iridescent gloss, but the cutting material having the same coating layer as Sample 1-5 was used. The work material that had been cut with the insert had a white finish and had no gloss. Therefore, by providing a nitride-based aluminum film in the outermost layer, the lubricity of the film surface contributes and the chipping of the cutting edge is suppressed, and the generation of the constituent cutting edge is also suppressed and the sharpness can be maintained. It was confirmed that the surface quality was remarkably improved.

  The surface-coated cutting tool of the present invention is particularly suitable for cutting under cutting conditions such as dry machining, high speed, high feed machining, and the like where the cutting edge temperature is high.

It is a cross-sectional schematic diagram showing the structure of a typical cutting edge part of a cutting tool, (A) is the state before cutting, (B) ~ (D) is the initial stage of cutting when ideal wear is performed , The middle stage of cutting and the latter stage of cutting are shown, respectively, and (E) shows the wear state at the beginning of cutting in the conventional cutting tool.

Explanation of symbols

  10 Substrate 11 Flank 12 Rake face 13 Exposed part 20 Coating film

Claims (10)

In a surface-coated cutting tool having a coating layer on the substrate surface,
The coating layer comprises an inner layer formed by chemical vapor deposition on the substrate and an outermost layer formed by physical vapor deposition on the inner layer,
The inner layer is
It has a columnar structure with an aspect ratio of 3 or more, and any one of the orientation indices TC (220), TC (311), and TC (422) of the (220) plane, (311) plane, and (422) plane of the crystal is It has a titanium-containing layer made of TiCN that takes the maximum value of the orientation index,
The outermost layer is
A surface-coated cutting tool comprising an aluminum compound selected from Al nitride, carbonitride, nitrogen oxide, and carbonitride. The outermost layer contains one or more additional elements selected from B, F, Mg, Si, Ca, V, Cr, Zn, Zr, Ti,
2. The surface-coated cutting tool according to claim 1, wherein the content of the additional element is more than 0 and less than 10 atomic% when Al and the additional element are 100 atomic%.   3. The surface-coated cutting tool according to claim 1, wherein the outermost layer does not contain chlorine. Further, the inner layer includes one or more first elements selected from periodic table IVa, Va, VIa group metals, Al, Si, and B, and one or more second elements selected from B, C, N, and O. 4. The surface-coated cutting tool according to claim 1, further comprising a compound layer made of an element.
However, the compound layer is a layer different from the titanium-containing layer. When the first element is only B, the second element is other than B.   5. The surface-coated cutting tool according to claim 1, wherein the film thickness of the outermost layer is 1/2 or less of the total film thickness of the inner layer.   6. The surface-coated cutting tool according to claim 1, wherein a film thickness of the outermost layer is 0.03 μm or more and 10 μm or less, and a film thickness of the entire coating layer is 0.1 μm or more and 30 μm or less.   In the outermost layer, the surface roughness of the portion in contact with the work material in the vicinity of the edge portion of the cutting edge is 1.3 μm or less in Rmax with respect to 5 μm measured by a method of observing from the cutting tool cross section. Item 7. A surface-coated cutting tool according to any one of Items 1 to 6.   The base material is a WC base cemented carbide, cermet, high speed steel, ceramics, cubic boron nitride sintered body, diamond sintered body, silicon nitride sintered body, and sintered body containing aluminum oxide and titanium carbide. The surface-coated cutting tool according to any one of claims 1 to 7, wherein the surface-coated cutting tool is formed of any one of the following.   The surface-coated cutting tool is any one of a drill, an end mill, a milling blade tip, a turning tip, a metal saw, a cutting tool, a reamer, and a tap. The surface coating cutting tool in any one.   The surface-coated cutting tool according to any one of claims 1 to 9, wherein the physical vapor deposition method is an arc ion plating method or a magnetron sputtering method.

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