JP2008284636A - Coated cutting tool - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coated cutting tool and a manufacturing method for the coated cutting tool, which provides excellent abrasion resistance and toughness. <P>SOLUTION: The coated cutting tool includes: a base material 1 laminated with a fine grain layer 1p made of WC group cemented carbide using WC particles 10p of fine grain as a hard layer and a coarse grain layer 1g made of WC group cemented carbide using WC particles 10g of coarse grain as a hard layer; and a coated film 2 formed on the base material 1 surface. The mean particle diameter of WC particles 10p of the fine grain layer 1p is 1 μm or less, and the mean particle diameter of WC particles 10g of the coarse grain layer 1g is 3 μm or more. The fine grain layer 1p is disposed on the surface side of the base material, and the coated film 2 is formed on this layer 1p by means of physical vapor deposition. Crystal grain 20 developed by direct contact with the WC particles 10p of the fine grain layer 1p exists among the crystal grain 20 forming the coated film 2, and the grain diameter of the crystal grain 20 is the size approximately same as the WC particles 10p of the fine grain layer 1p. The coated cutting tool is manufactured by forming the coated film 2 after performing bombardment process on the base material 1 surface using dilute gas ion. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a coated cutting tool having a coating film on a substrate surface made of a cemented carbide, and a method for manufacturing the cutting tool. In particular, the present invention relates to a coated cutting tool having excellent wear resistance, fracture resistance, and toughness.

  Coated cutting tools with a coating film on the surface of a cemented carbide based on WC (tungsten carbide) and cemented carbide with iron group elements such as Co (cobalt) as a binder have been developed. (For example, see Patent Documents 1 and 2).

  Typical properties required for cutting tools include wear resistance (e.g., flank wear resistance, crater wear resistance), strength (e.g., bending strength), toughness (e.g., chipping resistance, chipping resistance, (Heat cracking resistance). The cutting tool described in Patent Document 1 is composed of a cemented carbide alloy having a different composition, a surface layer and an inner layer, and a substrate having a laminated structure in which the inner layer is sandwiched between two surface layers, thereby providing crater wear resistance. We are trying to improve. The cutting tool described in Patent Document 2 is a laminated structure in which a surface layer and an inner layer are composed of a WC-based cemented carbide having WC particles having different average particle diameters as a hard phase, and the inner layer is sandwiched between two surface layers. By using the base material, the strength and toughness are improved.

JP-A-58-52003 Japanese Unexamined Patent Publication No. Hei 7-197265

  However, conventionally, sufficient examination has not been made on both the base material and the coating film, and it is difficult for conventional coated cutting tools to improve the overall characteristics.

  The techniques described in Patent Documents 1 and 2 attempt to improve the properties of the base material so that they can be used to some extent even if the coating film is lost. However, it is not considered to improve the characteristics of the entire coated cutting tool including not only the substrate but also the coating film. Therefore, the coating film is merely present and cannot be fully utilized.

  In order to improve the properties of the coating film, for example, it is conceivable to adjust the composition of the coating film and the film formation conditions. However, there are many types of coating film compositions, and a great deal of research is required to select an optimal composition for obtaining desired characteristics. Accordingly, it is desired to develop a coated cutting tool having a coating film having excellent characteristics regardless of the composition.

  The present invention has been made in view of the above circumstances, and one of its purposes is to provide a coated cutting tool having excellent wear resistance, fracture resistance, and toughness. Moreover, the other object of this invention is to provide the manufacturing method of the said coated cutting tool.

  The present inventors have obtained the following knowledge in developing a coated cutting tool having a coating film on a substrate surface made of a WC-based cemented carbide.

  A base material excellent in both wear resistance and toughness can be obtained by forming the base material with a WC-based cemented carbide having WC particles having different average particle diameters as a hard phase.

  On the other hand, chemical vapor deposition (CVD) and physical vapor deposition (PVD) are known as coating film formation methods. The CVD method has a relatively high substrate temperature during film formation, so a film with excellent adhesion to the substrate can be obtained, but tensile stress remains due to thermal stress during film formation and cracks occur on the film surface. The crack propagates to the base material at the time of cutting and reduces the fracture resistance of the tool. In addition, the substrate itself may be damaged by heating during film formation. In contrast, the PVD method has a relatively low substrate temperature during film formation, so there is little risk of damage due to cracks in the film or damage to the substrate during film formation. Since stress is applied, it has excellent fracture resistance, high hardness and excellent wear resistance. However, since the PVD method has a low substrate temperature, the obtained film is inferior in adhesion to the substrate as compared with the film formed by the CVD method.

  Based on these facts, the present inventors have developed a coated cutting tool capable of exhibiting excellent properties of both the base material and the coating film, and as a base material, the WC group having fine WC particles as a hard phase is used. A layer having a laminated portion in which a fine particle layer made of a cemented carbide and a coarse particle layer made of a WC-based cemented carbide having coarse WC particles as a hard phase was adopted. As a result of research and development, the present inventors have nucleated a film on a bonded phase such as Co in the CVD method, whereas the PVD method nucleated a film on a hard phase such as WC. As a result, the PVD method was adopted as a method for forming a coating film formed directly on the substrate. Then, in the film formation by the PVD method, improvement in adhesion between a film formed by the PVD method (hereinafter referred to as a PVD film) and the substrate was examined.

  As a result, when the fine particle layer of the laminated portion is set to the surface side of the base material, and the film is formed on the surface of the fine particle layer by the PVD method, fine crystal grains are formed on the fine WC particles. From the fact that is dispersed finely, it has been found that the adhesion between the substrate and the film is improved. However, the surface of the cemented carbide substrate as-sintered may have a binder phase such as Co, which has become a liquid phase during sintering, leached locally, and the binder phase may cover the WC particles. . Therefore, as described above, in order to improve the adhesion between the base material and the PVD film, it has been found that it is preferable to form a film after performing a specific pretreatment (cleaning). Specifically, when a bombardment treatment using rare gas ions is performed on the substrate surface, the binder phase present on the substrate surface side is removed, and the WC particles in the fine particle layer arranged on the substrate surface side are removed. Is likely to be exposed. When a film is formed by the PVD method in this state, crystal grains of the PVD film are formed and grown in contact with the WC particles of the fine particle layer existing on the substrate surface. That is, among the crystal grains of the PVD film that exist directly on the base material in the crystal grains constituting the coating film, there are many that grow directly in contact with the WC particles of the fine particle layer. In this way, in the crystal grains constituting the portion immediately above the base material in the coating film, there are crystal grains continuously formed with the WC particles on the surface side of the base material (particularly WC particles in the fine particle layer). Adequate adhesion can be obtained between the substrate and the coating film (particularly the PVD film).

  Here, as a pretreatment before forming the coating film on the substrate, there is a bombardment treatment using metal ions (for example, Ti ions). This process has a high etching rate and excellent cleaning workability. However, in this treatment, impurities used for cleaning such as Ti tend to remain on the substrate surface. If impurities are present on the surface of the base material, the crystal grains of the PVD film cannot be substantially formed continuously with the WC particles of the base material, so that the adhesion between the base material and the PVD film is lowered.

  As described above, the PVD film crystal grains are formed and grown continuously on the WC particles of the base material, so that the PVD film crystal grains present immediately above the base material in the coating film and the WC present on the base material surface. Particles are approximately the same size. That is, the crystal grains present in the vicinity of the boundary with the base material in the coating film are refined in the same manner as the WC particles in the fine particle layer. With this miniaturization, the coating film itself can also improve chipping resistance and wear resistance. Furthermore, when the crystal grains of the PVD film are grown in a columnar shape, it is easy to maintain excellent adhesion to the substrate, and in addition, the fine grains of the fine PVD film formed on the fine WC particles Sag is easily maintained from the substrate side to the surface side of the film.

  In this way, when a specific pretreatment is performed on a base material having a specific structure and then formed by the PVD method, a coating film having excellent adhesion to the base material can be obtained, and the characteristics of the film itself can be obtained. Can also be improved. That is, an effect more than that obtained by simply miniaturizing the film itself is obtained. Therefore, the obtained coated cutting tool can fully utilize a coating film having excellent characteristics, and can sufficiently utilize a base material having excellent characteristics even when the coating film disappears. . The present invention is based on these findings.

The method for producing a coated cutting tool of the present invention is a method for producing a coated cutting tool by forming a coating film on at least a part of a substrate surface made of a WC-based cemented carbide, and includes the following steps.
1. a fine-grained layer made of a WC-based cemented carbide with WC particles having an average particle size of 1 μm or less as a hard phase, and a coarse-grained layer made of a WC-based cemented carbide with WC particles having an average particle size of 3 μm or more as a hard phase; The process of preparing the base material which has the laminated part on which was laminated | stacked.
2. A step in which the fine particle layer of the laminated portion is set to the surface side of the base material, and at least a part of the surface of the laminated portion is subjected to bombardment treatment using rare gas ions.
3. A step of forming a film by physical vapor deposition on the fine particle layer subjected to the bombardment treatment.

  By the manufacturing method of the present invention, the coated cutting tool of the present invention can be obtained in which the base material and the coating film are sufficiently adhered and are excellent in wear resistance, chipping resistance, chipping resistance and toughness. The coated cutting tool of the present invention is formed by laminating a fine particle layer made of a WC-based cemented carbide having fine WC particles as a hard phase and a coarse particle layer made of a WC-based cemented carbide having coarse WC particles as a hard phase. A substrate having a laminated portion and a coating film formed on at least a part of the surface of the substrate. The fine particle layer has WC particles having an average particle size of 1 μm or less as a hard phase, and the coarse particle layer has WC particles having an average particle size of 3 μm or more as a hard phase. The coating film includes a film (hereinafter referred to as a PVD film) formed by a physical vapor deposition method on the fine particle layer of the laminated portion disposed on the surface side of the substrate. This PVD film includes crystal grains grown in direct contact with the WC particles present on the surface side of the fine particle layer. The coated cutting tool of the present invention satisfies d1 / d2 of 0.7 or more and 1.3 or less, where d1 is the average particle size of the WC particles in the fine particle layer and d2 is the average particle size of the crystal grains of the PVD film. Hereinafter, the present invention will be described in detail.

<Base material>
"composition"
The base material is composed of a WC-based cemented carbide composed of a hard phase mainly composed of WC and a binder phase mainly composed of an iron group metal such as Co or Ni. The base material is further composed of one or more elements selected from the group of metal elements of groups IVa, Va, VIa of the periodic table, one or more elements selected from the group of metal elements, and carbon, nitrogen, oxygen And a compound (solid solution) consisting of one or more elements selected from the group consisting of boron. Specifically, elements: Cr, Ta, V, Ti, compounds: (Ta, Nb) C, VC, Cr ₂ C ₃ , NbC, TiCN, etc., these elements and compounds are used during sintering. Many have the function of suppressing the grain growth of WC particles. If the amount of WC particles is too small, the wear resistance and toughness are reduced, and the crystal grains constituting the PVD film are difficult to be formed following the WC particles. Is preferably 70 to 98% by mass. A cemented carbide having a known composition may be used. The composition of the fine particle layer and the composition of the coarse particle layer may be the same or different.

"Construction"
A base material shall have the laminated part formed by laminating | stacking the multiple types of cemented carbide alloy from which the average particle diameter of WC particle | grains differs. A structure in which at least a part of the substrate, in particular, the blade edge and the vicinity thereof is composed of a laminated portion and the fine particle layer is disposed on the rake face side is preferable. The whole base material may have a laminated structure, or only the blade edge and its vicinity may be constituted by a laminated portion, and the blade edge such as a breaker portion and other portions in the vicinity thereof may be constituted only by a coarse particle layer or a fine particle layer. If the entire base material has a laminated structure, the manufacturability of the base material is good. Specific laminated structures include, for example, a cross-sectional two-layer structure in which a fine particle layer having fine WC particles as a hard phase and a coarse particle layer having coarse WC particles as a hard phase are laminated, or two fine particle layers And a cross-sectional three-layer structure sandwiching one coarse layer. In addition, when the coarse particle layer is formed in a polygonal column shape such as a rectangular parallelepiped shape, a structure in which the fine particle layer is arranged on at least two sides adjacent to the surface constituting the coarse particle layer, or the entire surface constituting the coarse particle layer is covered. An encapsulated structure in which a fine particle layer is arranged. The fine particle layer of the laminated portion is arranged on the surface side of the substrate, that is, the side on which the coating film is formed.

<Fine particle layer>
[WC particle size]
The WC particles in the fine particle layer have an average particle size of 1 μm or less. The smaller the average particle size, the more easily the substrate becomes harder and the wear resistance can be improved. 0.8 μm or less is more preferable. Conversely, when it exceeds 1 μm, the progress of wear is accelerated. In order to set the average particle size of the WC particles in the fine particle layer to 1 μm or less, it is possible to use fine WC particles having an average particle size of 1 μm or less as a raw material. The fine WC particles used as a raw material may be a commercially available product or a commercially available product may be pulverized and used finely. Moreover, you may utilize what contains a grain growth inhibitor as a raw material.

[Thickness of fine particle layer]
The fine particle layer contributes to increasing the hardness and wear resistance of the substrate itself, and is arranged on the surface side of the substrate to improve the adhesion between the substrate and the coating film (particularly the PVD film). And it contributes to improving the characteristics of the coating film. In order to sufficiently obtain such an effect, it is preferable that the thickness of the fine particle layer is relatively thin. On the other hand, if the fine particle layer is too thick, crater wear resistance and toughness tend to decrease. Therefore, the thickness of the fine particle layer is preferably 100 μm or less, particularly preferably 10 μm or less. In order to suppress the deterioration of crater wear resistance, there is ultimately a configuration in which one WC particle in the fine particle layer exists in the thickness direction, that is, a constitution in which the thickness of the fine particle layer is equivalent to the maximum diameter of the WC particles. preferable.

<< Coarse Grain Layer >>
The WC particles in the coarse layer have an average particle size of 3 μm or more. The larger the average particle size, the more easily the base material becomes tough, and if it is less than 3 μm, the effect of improving toughness cannot be sufficiently obtained. A more preferable average particle diameter is 3 μm or more and 10 μm or less. As the raw material for the WC particles of the coarse layer, a commercially available product or a product obtained by pulverizing a commercially available product to have a predetermined size can be used.

<Formation of substrate>
The base material having a laminated portion in which a fine particle layer and a coarse particle layer are laminated is formed, for example, by separately forming a press-formed product for a fine particle layer and a press-formed product for a coarse particle layer, and a desired portion is a laminated portion These materials are stacked and sintered so as to be integrated, or a raw material for a fine particle layer and a raw material for a coarse particle layer are prepared, and both raw materials are formed into a mold so that a desired portion becomes a laminated portion. It can be manufactured by laminating and forming an integrated press-formed body and sintering. In particular, it is preferable to form an integrated press-molded body because it is easy to sufficiently bond the fine particle layer and the coarse particle layer.

<Coating film>
"Preprocessing"
A coating film is formed on at least a part of the substrate. The formation location of the coating film can be appropriately selected, and the coating film may be formed only on a part of the surface of the base material, particularly the blade edge and the vicinity thereof, or the coating film is formed over the entire surface of the base material. May be formed. And before forming the coating film on the base material, the bombardment treatment using rare gas ions is performed at the position where the coating film is formed at least on the surface of the base material, particularly in the laminated portion arranged on the base material surface side. Apply to the fine particle layer to clean the substrate surface, and among the plurality of WC particles present on the surface side of the fine particle layer, at least a part of the WC particles should expose the substrate surface side portion. . Various rare gases such as Ar, Kr, and Xe can be used. In particular, when this treatment is performed by generating noble gas ions while emitting thermionic electrons from the electron source to the rare gas, the surface of the WC particles can be cleaned with high quality. In addition to improving the adhesion, the etching rate can be improved and the productivity is excellent. As the electron source, a hot filament capable of emitting thermal electrons such as a tungsten filament can be used. If the treatment time is increased or the bias voltage is increased, the number of WC particles exposed on the substrate surface side of the WC particles can be increased, and the crystal grains formed in direct contact with the WC particles can be increased. You can increase the number.

<Formation method>
The coating film includes a film (PVD film) formed by the PVD method. It is preferable that the PVD film is present at least directly on the base material, particularly on the fine particle layer arranged on the base material surface side, and may be all PVD films from the base material side to the surface side, or the base material side is a PVD film, A CVD film may be combined such that the surface side is a film formed by a CVD method (CVD film). Specific 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 (cathode arc ion plating) method in which the ionization rate of the raw material elements is high is suitable. If the substrate temperature during film formation is too high or too low, the crystal grains of the PVD film become larger or smaller, making it difficult to form crystal grains following the WC particles of the base material. The part where the coating film is not formed on the substrate is formed after masking or the like.

"composition"
The composition of the coating film is not particularly limited. Any composition that can be formed by the PVD method can be applied to the PVD film. In particular, the coating film is composed of one or more elements selected from the group consisting of group IVa, Va and VIa metal elements, Al, Si and B, and a group consisting of carbon, nitrogen, oxygen and boron. It is preferable to have at least one compound film made of a compound with one or more selected elements. Specific examples include TiCN, Al ₂ O ₃ , TiAlN, TiN, and AlCrN. The coating film may be a single film having a single composition or a multilayer structure having a plurality of types of films having different compositions. The thickness (total thickness in the case of a multilayer structure) is preferably 1 to 10 μm. The thickness can be changed by adjusting the film formation time.

《Organization》
By forming a film by PVD method after a specific pretreatment as described above, among the crystal grains constituting the coating film, the crystal grains of the PVD film existing directly above the substrate (hereinafter referred to as crystal grains immediately above) Some of them are formed and grown directly in contact with WC particles (hereinafter referred to as surface WC particles) existing on the surface side of the fine particle layer (hereinafter referred to as continuous crystal grains). In particular, when the surface WC particles are densely dispersed on the substrate surface side, the crystal grains directly above are mainly composed of continuous crystal grains. The continuous crystal grains are approximately the same size as the surface WC particles. Specifically, when the average particle diameter of WC particles (including surface WC particles) in the fine particle layer is d1, and the average particle diameter of continuous crystal grains of the PVD film is d2, d1 / d2 is 0.7 or more and 1.3 or less. Fulfill.

  As described above, when impurities are present on the surface of the base material due to the pretreatment, the crystal grains of the PVD film immediately above the base material cannot be formed in direct contact with the surface WC particles, so that the adhesion is deteriorated. Also, when the crystal grain of the PVD film directly above the substrate is larger than the surface WC particles and d1 / d2 is less than 0.7, the film is easy to peel off, smaller than the surface WC particles, and d1 / d2 exceeds 1.3. , Wear resistance decreases. In particular, d1 / d2 is preferably 0.8 or more and 1.2 or less. The size of d1 / d2 can be changed depending on the cleaning conditions, film forming conditions, and the like. To set d1 / d2 to 0.7 or more and 1.3 or less, cleaning processing time: 10 to 60 minutes, bias voltage during processing: -500 to -1500V, substrate temperature during film formation: 400 to 600 ° C, film formation Preferably, the bias voltage at the time is −10 to −200 V, and the pressure of the atmosphere during film formation is 0.5 to 5 Pa.

  When the surface WC particles are densely dispersed in the fine particle layer arranged on the surface side of the base material, the crystal grains that are not continuously formed on the surface WC particles are sandwiched between the continuous crystal grains. Thus, it can be as large as continuous crystal grains. At this time, the average particle diameter of the crystal grains immediately above can be taken as d2.

  The crystal grains constituting the PVD film are preferably columnar. In particular, when the crystal grains directly above are formed and grown to follow the surface WC grains and are atomized, and the aspect ratio is large, specifically a columnar structure of 5 or more, improvement in wear resistance and toughness due to high hardness Further improvement is preferable. The columnar structure can be formed by adjusting the film forming conditions. Specifically, the substrate temperature is 400 to 600 ° C., the bias voltage is −10 to −200 V, and the atmospheric pressure is 0.5 to 5 Pa. In addition to the above film forming conditions, a columnar structure is easily obtained when the film forming speed is increased, specifically, 0.6 to 3 μm / h. The aspect ratio can be changed, for example, by changing the bias voltage. To increase the aspect ratio to 5 or more, the bias voltage is increased (to the −200 V side).

<Roughness>
Since the crystal grains immediately above the PVD film are formed following the surface WC particles, the film growth is stabilized and the surface of the PVD film becomes smooth. Specifically, the surface roughness satisfies Ra of 0.1 μm or less. By providing such a smooth PVD film on the tool surface, the coated cutting tool of the present invention can improve machining accuracy. The surface roughness Ra tends to decrease as the average particle diameter d1 of the WC particles in the fine particle layer decreases.

<Application>
The coated cutting tool of the present invention having the above configuration is excellent in wear resistance, fracture resistance, and toughness, and is therefore suitable, for example, as a steel milling tool that is prone to thermal cracking. The tool of the present invention is also excellent in chipping resistance. Therefore, the tool of the present invention is suitable for a tool that performs intermittent cutting where high toughness is desired since chipping is likely to occur, that is, an intermittent turning tool.

  The coated cutting tool of the present invention is excellent in wear resistance and toughness, and the base material and the coating film are sufficiently in close contact with each other, so that both the base material and the coating film can be fully utilized. The manufacturing method of this invention coated cutting tool can manufacture the said this invention coated cutting tool.

(Test Example 1)
PVD is formed on the surface of a substrate formed by laminating a fine particle layer made of WC-based cemented carbide with fine WC particles as a hard phase and a coarse particle layer made of WC-based cemented carbide with coarse WC particles as a hard phase. A coated cutting tool having a coating film formed thereon was prepared, and the wear resistance and the peeling resistance of the coating film were examined.

A base material is produced as follows. Raw material powders having the composition (mass%) shown in Table 1 are prepared and wet-mixed and pulverized to produce powder types I and II. Powder type I containing coarse WC particles (average particle size 3.5 μm) is fed into a mold and press-molded at a pressure of 0.5 t / cm ² and then contains fine WC particles (0.8 μm). Powder type II is further fed into a mold and press-molded at a pressure of 1.5 t / cm ² to produce a laminated press-molded body. A commercially available powder was used as the raw material powder.

  By subjecting the above-mentioned laminated press-formed body to vacuum sintering at 1400 ° C., a base material (throw away tip) of JIS standard shape SNGN120408 in which the coarse layer and the fine layer are laminated so as to have a two-layer structure is obtained. . Powder types I and II were used so that the coarse layer after sintering had a thickness of 4750 μm and the fine layer had a thickness of 10 μm.

  After the substrate is cleaned by a gas bombardment process, a film is formed by an arc ion plating method. For example, Sample No. 1-2 is produced as follows. The base material is disposed in the chamber of the film forming apparatus so that the fine particle layer is on the surface side of the base material. Next, argon gas is introduced into the chamber, the pressure in the chamber is maintained at 3.0 Pa, the substrate bias voltage is gradually increased to -1000 V, and thermoelectrons are emitted using a tungsten (W) filament. While releasing, argon ions are generated to clean the substrate surface for 30 minutes. Thereafter, argon gas is exhausted from the chamber, and film formation is subsequently performed. Film formation is carried out by setting the substrate temperature to a predetermined temperature, in a vacuum state, or by arc discharge between the evaporation source and the chamber while introducing at least one of nitrogen, methane and oxygen as the reaction gas. This is done by partially melting the evaporation source and evaporating the cathode material. In this test, a TiAlN film (thickness 4 μm) was formed as a coating film. Film formation was performed at a substrate temperature of 450 ° C., a bias voltage of −150 V, and an atmospheric pressure of 4 Pa. By this step, a coated cutting tool (coated chip) is obtained.

  In this test, a plurality of coated chips with different average grain sizes of the crystal grains constituting the coating film were prepared by changing the cleaning conditions and film formation conditions (Sample Nos. 1-1 to 1-5). . Sample Nos. 1-3 and 1-4 have cleaning processing time: 10 to 60 minutes, bias voltage during processing: -500 to -1500 V, substrate temperature during film formation: 450 to 550 ° C, during film formation Cleaning and film formation were performed at a bias voltage of −10 to −200 V and an atmospheric pressure during film formation of 0.5 to 5 Pa.

  When the cut surface of the obtained coated chip was observed with a microscope, as shown in FIG. 1, the surface of the base material 1 had a part of the binder phase 11 removed, and the WC particles 10p existing on the surface side of the fine particle layer 1p. The WC particles 10p in a state where the substrate surface side portion is exposed are present. The coating film 2 formed on the surface of the substrate 1 by the PVD method has a large number of crystal grains 20p grown in direct contact with the WC particles 10p existing on the surface side of the fine particle layer 1p. The size of the crystal grain 20p varies depending on the coated chip, and there are those having the same size as the contacting WC particles 10p and those smaller or larger than the WC particles 10p. The coating film shown in FIG. 1 has a columnar shape in which one crystal grain is continuous from the substrate side to the surface side. And the crystal grains on the surface side may be different particles that are not continuous, a mixed structure of granular crystal grains and columnar crystal grains, or only granular crystal grains. Samples Nos. 1-2 to 1-4 all have a columnar structure. For example, the aspect ratio of the crystal grains of sample No. 1-2 was 5 or more. Further, by sufficiently applying pressure when forming the press-molded body as described above, the WC particles of the fine particle layer 1p are between the WC particles 10g of the coarse particle layer 1g at the boundary between the fine particle layer 1p and the coarse particle layer 1g. It can be used as a base material in which fine WC particles that appear to be 10p are present.

  For each coated chip, the average particle diameter d1 (μm) of the WC particles 10p of the fine particle layer 1p and the average particle diameter d2 of the crystal grains 20p grown in direct contact with the WC particles 10p of the fine particle layer 1p in the coating film 2 (μm) was measured to determine d1 / d2. Further, the average particle diameter d3 (μm) of 10 g of WC particles in 1 g of the coarse layer was determined. As a result, in each sample, the average particle diameter d1 of the WC particles in the fine particle layer was 0.8 μm, and the average particle diameter d3 of the WC particles in the coarse particle layer was 3.5 μm.

The average particle diameters d1 and d2 were measured as follows. Cut the coated chip, wrap the cut surface, perform crystal analysis by SEM (scanning electron microscope), import the analysis image into the image analyzer and analyze it, and analyze the WC particles and coating film (PVD film) on the cut surface The grain size (μm) of the crystal grains is measured, and the average value of these is taken as the average grain size. The average particle diameter d1 of the WC particles is an average value obtained by measuring a plurality (30 in this case) of arbitrary WC particles existing in the vicinity of the boundary with the coating film on the substrate. The average particle diameter d2 of the crystal grains of the coating film is an average value obtained by arbitrarily measuring a plurality (30 in this case) of crystal grains growing directly in contact with the WC particles. Crystal analysis can be performed using, for example, ECP (Electron channeling pattern) method, EBSD (Electron Back
Scatter Diffraction Patterns) method. Here, we analyzed by EBSD method.

  The average particle diameter d3 is the average value obtained by measuring the particle diameters of all WC particles existing within a certain range of the cut surface (here, within a 100 μm square inside the substrate sufficiently away from the fine particle layer). . For the average particle diameters d1 and d3, the above average value may be appropriately modified by the Fullman equation.

  A cutting test was performed using the obtained coated tip under the following cutting conditions. Table 2 shows cutting conditions and evaluation methods. Table 3 shows the results of the cutting test.

  As shown in Table 3, the WC particles present on the surface side of the fine particle layer and the crystal grains present in the vicinity of the boundary with the base material in the coating film are comparable, that is, d1 / d2 is 0.7 to 1.3. When it exists, it turns out that the adhesiveness of a coating film can be improved. A sample having d1 / d2 of 0.7 to 1.3 is also excellent in wear resistance. This is considered to be because the coating film can be fully utilized because the coating film is sufficiently adhered, and the wear resistance of the entire coated cutting tool can be improved. Further, when the surface roughness of the coating film was examined for samples having d1 / d2 of 0.7 to 1.3, the Ra was 0.1 μm or less in all samples, and the coating film surface was very smooth.

(Test Example 2)
Instead of the base material prepared in Test Example 1, a base material in which the size of the WC particles in the fine layer and the size of the WC particles in the coarse layer was changed was prepared, and the coated cutting tool including the base material was resistant to the coating. Abrasion and fracture resistance were investigated.

  The base material was prepared under the same conditions as in Example 1 using raw material powder having the same composition as in Test Example 1 except that the average particle diameter of WC particles was different (thickness of fine particle layer: 10 μm, coarse particle layer) Thickness: 4750 μm).

  After cleaning the obtained substrate under the same conditions as Sample No. 1-2 in Test Example 1, the TiAlN film (thickness) was obtained by arc ion plating under the same conditions as Sample No. 1-2. 4 μm) was formed. By this step, a coated chip is obtained.

  For the coated chip obtained, the average particle diameter d1, d3 (μm) of the WC particles and the average particle diameter d2 (μm) of the crystal grains of the coating film were measured in the same manner as in Test Example 1, and d1 / d2 was calculated. Asked. As a result, all the samples satisfied d1 / d2 = 0.7 to 1.3 (for example, sample No. 2-3 has d1 / d2 = 0.9). Therefore, it is considered that the coating film is sufficiently adhered to the substrate in any sample.

  A cutting test was performed using the obtained coated tip under the following cutting conditions. Table 4 shows cutting conditions and evaluation methods. Table 5 shows the results of the cutting test. Furthermore, the surface roughness Ra (μm) of the coating film was also measured. The results are shown in Table 5.

  As shown in Table 5, it can be seen that the smaller the average particle diameter d1 of the WC particles in the fine particle layer, the better the wear resistance. It can also be seen that the larger the average particle diameter d3 of the WC particles in the coarse-grained layer, the better the fracture resistance. From these facts, it can be seen that by setting d1 to 1 μm or less and d3 to 3 μm or more, a coated cutting tool having high hardness and high toughness and excellent in both wear resistance and fracture resistance can be obtained. In particular, this coated cutting tool is expected to be useful for steel cutting, which has a high cutting resistance, and whose surface is desired to have high hardness, and for intermittent cutting, which is desired to have high toughness.

(Test Example 3)
Instead of the base material prepared in Test Example 1, a base material having a changed fine particle layer thickness was prepared, and the coated cutting tool including the base material was examined for wear resistance and fracture resistance.

The base material was prepared under the same conditions as in Example 1, using raw material powder having the same composition as in Test Example 1, except that the amount of powder type II was changed so that the thickness of the fine particle layer was different. did. The pressure during molding may be changed according to the thickness of the fine particle layer. In addition, a base material (sample No. 3-1) using only coarse powder type I and a base material (sample No. 3-9) using only fine powder type II were also prepared. The pressure during molding was 1.5 t / cm ² for both Sample Nos. 3-1 and 3-9, and the sintering conditions were the same as in Test Example 1.

  After cleaning the obtained substrate under the same conditions as Sample No. 1-2 in Test Example 1, the TiAlN film (thickness) was obtained by arc ion plating under the same conditions as Sample No. 1-2. 4 μm) was formed. By this step, a coated chip is obtained.

  For the coated chip obtained, the average particle diameter d1, d3 (μm) of the WC particles and the average particle diameter d2 (μm) of the crystal grains of the coating film were measured in the same manner as in Test Example 1, and d1 / d2 was calculated. Asked. As a result, all the samples having both the fine particle layer and the coarse particle layer have d1 of 0.8 μm, d3 of 3.5 μm, and satisfy d1 / d2 = 0.7 to 1.3 (for example, sample No. 3-3 Is d1 / d2 = 0.9), and it is considered that the coating film is sufficiently adhered to the substrate. Further, when the surface roughness of the coating film was examined for the sample having both the fine particle layer and the coarse particle layer, Ra was 0.1 μm or less in all samples.

  A cutting test was performed using the obtained coated tip under the following cutting conditions. Table 6 shows cutting conditions and evaluation methods. Table 7 shows the results of the cutting test.

  As shown in Table 7, compared to the case of only the coarse particle layer, if the coarse particle layer and the fine particle layer are provided, the flank wear amount can be reduced and the fracture resistance can be improved, but the fine particle layer becomes thicker. The amount of crater wear increases. However, if the thickness of the fine particle layer is 100 μm or less, the amount of crater wear can be reduced, and if it is particularly 10 μm or less, the crater wear amount can be the same as when the fine particle layer is not provided.

(Test Example 4)
When the coating film has a columnar structure, the film forming conditions of the coating film were changed to change the aspect ratio of the crystal grains, and the wear resistance of the coated cutting tool having this coating film was examined.

  A substrate produced in the same manner as in Test Example 1 was cleaned under the same conditions as Sample No. 1-2 in Test Example 1, and then a TiAlN film (thickness 4 μm) was formed by arc ion plating. During film formation, the substrate bias voltage was changed and r1 (described later) was changed with respect to the film formation conditions of Sample No. 1-2 in Test Example 1 to form coating films with different aspect ratios. (For example, the substrate bias voltage of sample No. 4-3 is -180V). By this step, a coated chip is obtained.

  For the coated chip obtained, the average particle diameter d1, d3 (μm) of the WC particles and the average particle diameter d2 (μm) of the crystal grains of the coating film were measured in the same manner as in Test Example 1, and d1 / d2 was calculated. Asked. As a result, in all samples, d1 was 0.8 μm, d3 was 3.5 μm, and d1 / d2 = 0.9. In all samples, the surface roughness of the coating film was Ra of 0.1 μm or less.

The aspect ratio is measured as follows. Corrosive solution such as a mixed solution of boiling acid, nitric acid and distilled water, polished parallel or at an angle (preferably 10 ° or less) to the longitudinal section of the coated chip (cross section in the thickness direction of the coating film) The crystal grain boundary is lifted up using, and a photograph taken at a high magnification (preferably 5000 to 20000 times) is observed with an SEM. As shown in FIG. 1, in the coating film 2, a straight line L ₁ passing through a point 15% (0.15 × W ₂ ) of the thickness W ₂ of the coating film 2 is drawn from the surface, and the coating film 2 is covered from the boundary with the base material 1. A straight line L ₂ passing through a point of 15% (0.15 × W ₂ ) of the thickness W ₂ of the covering film 2 is drawn. The straight lines L ₁ and L ₂ are straight lines orthogonal to the thickness direction of the coating film, in other words, straight lines parallel to the surface of the coating film 2. The particle size r _1, r ₂ on the straight line L _1, L ₂ measured in each crystal grain 20, the average value of the particle size _{((r 1 + r 2)} / 2). An average value ((r ₁ + r ₂ ) / 2) of a plurality of (here 10) crystal grains 20 is obtained, and an average value ave.CS (here, {Σ A ratio (W ₂ /ave.CS) between ((r ₁ + r ₂ ) / 2)} / 10) and the thickness W ₂ is defined as an aspect ratio. Here, a case is considered where the columnar crystal grains 20 are continuous from the substrate side to the surface side of the coating film. When the columnar crystal grains are continuous only from the substrate side to the middle part of the coating film, that is, when the crystal grains on the substrate side and the crystal grains on the film surface side are different particles, the substrate side The aspect ratio is defined as the ratio between the average grain size of the columnar crystal grains present in the column and the average thickness at points continuous from the substrate side.

  Using the obtained coated tip, a cutting test was performed under the cutting conditions shown in Table 6 (wear resistance (flank wear amount)). Table 8 shows the results of the cutting test.

  As shown in Table 8, it can be seen that when the aspect ratio is large, the wear resistance is excellent. This is considered to be because the hardness of the coating film was improved.

(Test Example 5)
A coated cutting tool in which the cleaning conditions before forming the coating film were changed was produced for the substrate produced in Test Example 1, and the relationship between the cleaning conditions and the surface roughness of the coating film was examined.

  Sample Nos. 5-1 and 5-2 were prepared by cleaning the base material prepared in the same manner as in Test Example 1 by gas bombardment treatment under the same conditions as Sample No. 1-2 in Test Example 1. A TiAlN film (thickness 4 μm) was formed by arc ion plating under the same conditions as in No. 1-2. However, the cleaning time was the time shown in Table 9. By this step, a coated chip is obtained.

  Sample No. 5-3 was cleaned by bombardment treatment using metal ions (metal bombardment treatment) on the base material prepared in the same manner as in Test Example 1, and then the same conditions as Sample No. 1-2 Then, a TiAlN film (thickness 4 μm) was formed by arc ion plating. This treatment was performed by generating Ti ions in an argon atmosphere (cleaning time: 10 minutes). By this step, a coated chip is obtained.

  For the coated chip obtained, the average particle diameter d1, d3 (μm) of the WC particles and the average particle diameter d2 (μm) of the crystal grains of the coating film were measured in the same manner as in Test Example 1, and d1 / d2 was calculated. Asked. As a result, all samples had d1 of 0.8 μm and d3 of 3.5 μm. Sample Nos. 5-1 and 5-2 satisfy d1 / d2 = 0.7 to 1.3 (for example, sample No. 5-1 has d1 / d2 = 0.9), and the coating film is a base material. It is thought that it is closely attached to On the other hand, Sample No. 5-3, when the cut surface was observed with a microscope, was formed and grown in direct contact with the WC particles of the base material in the coating film, and the crystal grains having the same size as the WC particles were substantially formed. Did not exist.

  Using the obtained coated tip, a cutting test was performed under the cutting conditions shown in Table 6 (wear resistance (flank wear amount)). Table 9 shows the results of the cutting test. Further, the surface roughness Ra of the coating film and the surface roughness Ra of the processed surface of the work material were measured. The results are also shown in Table 9. The surface roughness Ra of the processed surface was measured at the beginning of cutting.

  As shown in Table 9, it can be seen that by performing the gas bombardment treatment, the surface of the coating film can be smoothed and a good processed surface can be obtained. In particular, it is possible to further smooth the coating film and improve the accuracy of the processed surface by sufficiently cleaning the gas bombardment process for a long time. Furthermore, it turns out that the coated cutting tool which is excellent also in abrasion resistance is obtained by performing a gas bombardment process. This is probably because the impurities accompanying the cleaning are not present on the surface of the base material, so that the coating film and the base material can be sufficiently adhered to each other and the characteristics of the coating film can be improved.

(Test Example 6)
Furthermore, in order to confirm the effect of the gas bombardment process, the case where the gas bombardment process was performed, the case where the metal bombardment process was performed, and the case where the bombardment process was not performed were compared.

  Prepare a substrate having a fine particle layer and a coarse particle layer prepared in Test Example 1 and a substrate having only a coarse particle layer produced in Test Example 3, that is, a substrate having no fine particle layer, and coat After pre-treatment by changing the cleaning conditions before film formation, a TiAlN film (thickness 4 μm) was formed by arc ion plating under the same conditions as Sample No. 1-2. By this step, a coated chip is obtained.

  Samples Nos. 6-1 and 6-2 were cleaned by gas bombardment treatment under the same conditions as Sample No. 1-2 of Test Example 1. Samples Nos. 6-3 and 6-4 were cleaned under the same conditions as the metal bombardment treatment applied to Sample No. 5-3 of Test Example 5. Samples Nos. 6-5 and 6-6 were not subjected to any treatment and were not cleaned.

  Among the obtained coated chips, for sample No. 6-2 having both a fine particle layer and a coarse particle layer, the average particle diameter d1, d3 (μm) of WC particles was coated in the same manner as in Test Example 1. The average grain size d2 (μm) of the crystal grains of the film was measured, and d1 / d2 was determined. As a result, d1 is 0.8 μm, d3 is 3.5 μm, d1 / d2 = 0.9, and it is considered that the coating film is sufficiently adhered to the substrate. The surface roughness of the coating film of Sample No. 6-2 was 0.1 μm or less in terms of Ra.

  Using the obtained coated tip, a cutting test was performed under the cutting conditions shown in Table 6 (wear resistance (flank wear amount)). Table 10 shows the results of the cutting test.

  As shown in Table 10, the sample with the fine particle layer has less flank wear than the sample without the fine particle layer. However, a sample not subjected to gas bombardment treatment has a small degree of improvement in wear resistance. Therefore, it is considered that when a film having a coarse particle layer and a fine particle layer is subjected to gas bombardment treatment, a coated cutting tool having a high degree of improvement in wear resistance and excellent wear resistance can be obtained.

(Test Example 7)
A coated cutting tool in which the composition of the coating film and the formation method were changed was produced from the substrate produced in Test Example 1, and the wear resistance was examined.

  Prepare a substrate having a fine particle layer and a coarse particle layer prepared in Test Example 1 and a substrate having only a coarse particle layer prepared in Test Example 3, that is, a substrate having no fine particle layer. The substrate was also cleaned under the same conditions as Sample No. 1-2 in Test Example 1, and then a coating film having the composition shown in Table 11 was formed by the forming method shown in Table 11. The film formation conditions for the PVD method in Table 11 were the same as those for Sample No. 1-3 in Test Example 1, and the film formation conditions for the CVD method were known conditions. The number in parentheses attached to the side of the composition of the coating film is the thickness (μm) of the coating film of each composition.

  Among the obtained coated chips, WC particles were prepared in the same manner as in Test Example 1 for sample Nos. 7-2 and 7-4 that had both a coarse layer and a fine layer and formed a coating film by the PVD method. The average particle diameters d1, d3 (μm) and the average particle diameter d2 (μm) of the crystal grains of the coating film were measured, and d1 / d2 was determined. As a result, in all samples, d1: 0.8 μm, d3: 3.5 μm, d1 / d2 = 0.9, and it is considered that the coating film is sufficiently adhered to the substrate. Further, the surface roughness of the coating films of Sample Nos. 7-2 and 7-4 were both Ra and 0.1 μm or less.

  Using the obtained coated tip, a cutting test was performed under the cutting conditions shown in Table 6 (wear resistance (flank wear amount)). Table 11 shows the results of the cutting test.

  As shown in Table 11, the sample with a coarse layer and a fine particle layer on the base material, and after the gas bombardment treatment was performed, the coating film was formed by the PVD method, regardless of the composition of the coating film. It can be seen that the wear resistance is excellent. In particular, the sample in which the coating film is formed by the PVD method has a higher degree of improvement in wear resistance due to the fine particle layer than the sample in which the coating film having the same composition is formed by the CVD method. Therefore, a coated cutting tool with excellent wear resistance can be obtained by forming a coating film by the PVD method after cleaning by gas bombardment treatment on a substrate having a coarse particle layer and a fine particle layer. it is conceivable that.

  Note that the above-described coated cutting tool can be appropriately changed without departing from the gist of the present invention, and is not limited to the above-described configuration. For example, the composition of the base material, the arrangement of the laminated portions, and the composition and thickness of the coating film can be appropriately changed.

  The coated cutting tool of the present invention can be suitably used for steel milling and intermittent cutting. The manufacturing method of this invention coated cutting tool can be utilized suitably for manufacture of the said this invention coated cutting tool.

It is a partial explanatory view showing the section of the present coated cutting tool typically.

Explanation of symbols

1 Substrate 1p Fine particle layer 1g Coarse particle layer 10p, 10g WC particles 11 Bonded phase
2 Coated film 20 Coated crystal grains 20p Crystal grains grown directly in contact with WC particles

Claims (9)

A base material having a laminated portion in which a fine particle layer made of a WC-based cemented carbide alloy having fine WC particles as a hard phase and a coarse particle layer made of a WC-based cemented carbide alloy having coarse WC particles as a hard phase are laminated. And a coated cutting tool comprising a coating film formed on at least a part of the surface of the substrate,
The fine particle layer has WC particles having an average particle size of 1 μm or less as a hard phase,
The coarse layer has WC particles having an average particle size of 3 μm or more as a hard phase,
The coating film includes a film formed by physical vapor deposition on the fine particle layer of the laminated portion disposed on the surface side of the substrate, and this film is directly applied to the WC particles existing on the surface side of the fine particle layer. With crystal grains grown in contact,
A coated cutting tool, wherein d1 / d2 is 0.7 or more and 1.3 or less, where d1 is an average particle diameter of WC particles of the fine particle layer and d2 is an average particle diameter of the crystal grains.   2. The coated cutting tool according to claim 1, wherein the fine particle layer has a thickness of 100 μm or less.   2. The coated cutting tool according to claim 1, wherein the fine particle layer has a thickness of 10 μm or less.   2. The coated cutting tool according to claim 1, wherein among the crystal grains constituting the film formed by the physical vapor deposition method, the crystal grains immediately above the base material have a columnar structure.   5. The coated cutting tool according to claim 4, wherein the crystal grains constituting the columnar structure have an aspect ratio of 5 or more.   2. The coated cutting tool according to claim 1, wherein the surface roughness of the film formed by the physical vapor deposition method is Ra of 0.1 μm or less.   2. The coated cutting tool according to claim 1, wherein the coated cutting tool is a steel milling tool or an intermittent turning tool. A method for producing a coated cutting tool for producing a coated cutting tool by forming a coated film on at least a part of a substrate surface made of a WC-based cemented carbide,
A fine particle layer made of WC-base cemented carbide with WC particles having an average particle size of 1 μm or less as a hard phase and a coarse particle layer made of WC-base cemented carbide with WC particles having an average particle size of 3 μm or more as a hard phase are laminated. Preparing a base material having a laminated portion formed;
A step of performing a bombardment process using ions of a rare gas on at least a part of the surface of the laminated part, with the fine particle layer of the laminated part being a surface side of the substrate;
A method of manufacturing a coated cutting tool comprising: forming a film by physical vapor deposition on the fine particle layer subjected to the bombardment treatment.   9. The method of manufacturing a coated cutting tool according to claim 8, wherein the bombardment process is performed by generating ions of a rare gas while emitting thermal electrons from an electron source to the rare gas.

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