JP6439201B2 - Method for manufacturing surface-coated cutting tool - Google Patents

Description

  The present invention relates to a surface-coated cutting tool.

Conventionally, a surface-coated cutting tool in which a coating is formed on a substrate has been used. For example, Japanese Patent Application Laid-Open No. 2006-198735 (Patent Document 1) discloses a coating film including an α-Al ₂ O ₃ layer in which the proportion of the Σ3 type crystal grain boundary to the Σ3-29 type crystal grain boundary is 60-80%. A surface-coated cutting tool is disclosed.

In addition, JP 2014-526391 A (Patent Document 2) includes an α-Al ₂ O ₃ layer in which the length of the Σ3-type grain boundary is more than 80% of the length of the Σ3-29-type grain boundary. A surface-coated cutting tool having a coating is disclosed.

JP 2006-198735 A Special table 2014-526391 gazette

In coatings containing α-Al ₂ O ₃ layer consisting of α-Al ₂ O ₃ polycrystal, the higher the mechanical properties ratio of Σ3 type crystal grain boundaries in a grain boundary contained in the α-Al ₂ O ₃ layer is higher It is expected that the life of the cutting tool will be extended because various characteristics such as the improvement are improved and the wear resistance and fracture resistance are improved.

  However, in recent cutting work, there has been a problem that speeding up and efficiency improvement have progressed, the load applied to the cutting tool has increased, and the life of the cutting tool has been shortened. For this reason, it is required to further improve the mechanical properties of the coating film of the cutting tool and further extend the life of the cutting tool.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a surface-coated cutting tool that improves the mechanical properties of the coating and further extends the life of the cutting tool. It is in.

The surface-coated cutting tool according to one aspect of the present invention includes a base material and a coating formed on the base material, and the coating includes an α-Al ₂ O ₃ layer, and the α-Al ₂ O _{The three} layers include a plurality of α-Al ₂ O ₃ crystal grains and exhibit (001) orientation, and the grain boundaries of the crystal grains include a CSL grain boundary and a general grain boundary. Of these, the length of the Σ3-type grain boundary is more than 80% of the length of the Σ3-29 type grain boundary, and is the sum of the length of the Σ3-29 type grain boundary and the length of the general grain boundary. It is 10% or more and 50% or less of the total length of all the grain boundaries.

  According to the above, the mechanical properties of the coating are improved, and the life of the cutting tool can be further extended.

[Description of Embodiment of the Present Invention]
First, embodiments of the present invention will be listed and described.

[1] A surface-coated cutting tool according to an aspect of the present invention is a surface-coated cutting tool including a base material and a coating film formed on the base material, and the coating film is α-Al ₂ O. _The α-Al ₂ O ₃ layer includes a plurality of α-Al ₂ O ₃ crystal grains and exhibits (001) orientation, and the grain boundaries of the crystal grains are generally CSL grain boundaries. The length of the Σ3-type grain boundary of the CSL grain boundary is more than 80% of the length of the Σ3-29-type grain boundary, and the length of the Σ3-29-type grain boundary. And the length of the general grain boundary is 10% or more and 50% or less of the total length of all grain boundaries. In this surface-coated cutting tool, the mechanical properties of the coating are improved and the life is extended.

  [2] The CSL grain boundaries are the Σ3-type grain boundaries, Σ7-type grain boundaries, Σ11-type grain boundaries, Σ17-type grain boundaries, Σ19-type grain boundaries, Σ21-type grain boundaries, and Σ23-type crystal grains. And the length of the Σ3-29 type crystal grain boundary is the Σ3 type crystal grain boundary, Σ7 type crystal grain boundary, Σ11 type crystal grain boundary constituting the CSL grain boundary, Σ17 The total length of each of the type grain boundaries, Σ19 type grain boundaries, Σ21 type crystal grain boundaries, Σ23 type crystal grain boundaries, and Σ29 type crystal grain boundaries is preferable. Thereby, said effect is fully exhibited.

[3] The α-Al ₂ O ₃ layer preferably has a thickness of 2 to 20 μm. Thereby, said characteristic is exhibited most effectively.

[4] The α-Al ₂ O ₃ layer preferably has a surface roughness Ra of less than 0.2 μm. As a result, adhesive wear between the work material and the tool edge is suppressed, and as a result, the chipping resistance of the edge is improved.

[5] The α-Al ₂ O ₃ layer includes a point where the absolute value of the compressive stress is maximum in a region within 2 μm from the surface side of the coating, and the absolute value of the compressive stress at the point is less than 1 GPa. It is preferable. Thereby, the chip | tip of the tool blade edge | tip by the mechanical and thermal fatigue which generate | occur | produces at the time of an intermittent cutting process is suppressed, As a result, the reliability of a blade edge | tip improves.

[6] The coating includes a TiC _x N _y layer between the base material and the α-Al ₂ O ₃ layer, and the TiC _x N _y layer is 0.6 ≦ x / (x + y) ≦ 0. It is preferable that TiC _x N _y satisfying the atomic ratio of .8 is included. This improves the adhesion between the substrate and the α-Al ₂ O ₃ layer.

[Details of the embodiment of the present invention]
Hereinafter, embodiments of the present invention (hereinafter also referred to as “present embodiments”) will be described in more detail.

<Surface coated cutting tool>
The surface-coated cutting tool of the present embodiment has a configuration including a base material and a film formed on the base material. Such a coating preferably covers the entire surface of the substrate. However, even if a part of the substrate is not covered with this coating or the configuration of the coating is partially different, this embodiment It does not deviate from the scope.

  Such a surface-coated cutting tool according to this embodiment includes a drill, an end mill, a cutting edge exchangeable cutting tip for a drill, a cutting edge exchangeable cutting tip for an end mill, a cutting edge exchangeable cutting tip for milling, and a cutting edge exchangeable cutting tip for turning. It can be suitably used as a cutting tool such as a metal saw, a gear cutting tool, a reamer, and a tap.

<Base material>
As the base material used in the surface-coated cutting tool of the present embodiment, any material can be used as long as it is conventionally known as this type of base material. For example, cemented carbide (for example, WC-based cemented carbide, including WC, including Co, or including carbonitrides such as Ti, Ta, Nb), cermet (TiC, TiN, TiCN, etc.) Component), high-speed steel, ceramics (titanium carbide, silicon carbide, silicon nitride, aluminum nitride, aluminum oxide, etc.), cubic boron nitride sintered body, or diamond sintered body preferable.

  Among these various substrates, it is particularly preferable to select a WC-based cemented carbide or cermet (particularly TiCN-based cermet). This is because these substrates are particularly excellent in the balance between hardness and strength at high temperatures, and have excellent characteristics as substrates for surface-coated cutting tools for the above applications.

  In addition, when the surface-coated cutting tool is a cutting edge replacement type cutting tip or the like, such a substrate includes those having a chip breaker and those having no chip breaker, and the cutting edge ridge line portion has a sharp shape. Included are edges (edges where the rake face and flank face intersect), honing (sharp edges are added to the edges), negative lands (chamfered), and combinations of honing and negative lands. .

<Coating>
The coating of this embodiment may contain other layers as long as it includes the α-Al ₂ O ₃ layer. Examples of the other layer include a TiN layer, a TiCN layer, a TiBNO layer, a TiCNO layer, a TiB ₂ layer, a TiAlN layer, a TiAlCN layer, a TiAlON layer, and a TiAlONC layer. Note that the order of stacking is not particularly limited.

In the present embodiment, those having no particular atomic ratio in the chemical formulas such as “TiN”, “TiCN”, and “TiC _x N _y ” indicate that the atomic ratio of each element is only “1”. It is not shown and all conventionally known atomic ratios are included.

  The coating film of this embodiment has an effect of improving various characteristics such as wear resistance and chipping resistance by coating the base material.

  Such a film of the present embodiment has a thickness of 3 to 30 μm (3 μm or more and 30 μm or less, and in the present application, when a numerical range is expressed using “to”, the range includes upper and lower numerical values), more preferably It is preferable to have a thickness of 5 to 20 μm. If the thickness is less than 3 μm, the wear resistance may be insufficient. If it exceeds 30 μm, peeling or breaking of the coating is frequently caused when a large stress is applied between the coating and the substrate in intermittent processing. May occur.

<Α-Al ₂ O ₃ layer>
The coating of this embodiment includes an α-Al ₂ O ₃ layer. This α-Al ₂ O ₃ layer can be included in the coating film in one layer or in two or more layers.

This α-Al ₂ O ₃ layer is a layer including crystal grains of a plurality of α-Al ₂ O ₃ (aluminum oxide whose crystal structure is α-type). That is, this layer is composed of polycrystalline α-Al ₂ O ₃ . Usually, this crystal grain has a grain size of about 100 to 2000 nm.

In addition, this α-Al ₂ O ₃ layer exhibits (001) orientation. Here, “shows (001) orientation” means that the normal direction to the (001) plane is ± with respect to the normal direction of the α-Al ₂ O ₃ layer surface (the surface located on the coating surface side). The case where the proportion of crystal grains (α-Al ₂ O ₃ ) within 20 ° is 50% or more in the α-Al ₂ O ₃ layer shall be said. Specifically, the law of the vertical cross section (the α-Al ₂ O ₃ layer surface of the α-Al ₂ O ₃ layer with a scanning electron microscope which is known as electron backscatter diffraction described below (EBSD) (SEM) When a cross section parallel to the line direction is observed and image processing is performed by color mapping, the area ratio of the crystal grains in the α-Al ₂ O ₃ layer is 50% or more. .

The plurality of α-Al ₂ O ₃ crystal grain boundaries (hereinafter, also simply referred to as “crystal grain boundaries”) include CSL grain boundaries and general grain boundaries, and among the CSL grain boundaries, Σ3-type crystals The length of the grain boundary is more than 80% of the length of the Σ3-29 type grain boundary, and the total of all grain boundaries, which is the sum of the length of the Σ3-29 type grain boundary and the length of the general grain boundary It is characterized by being 10% or more and 50% or less of the length. As a result, the coating film (α-Al ₂ O ₃ layer) of the present embodiment has improved mechanical properties, which can further extend the life of the cutting tool.

  Grain boundaries have a significant effect on material properties such as grain growth, creep properties, diffusion properties, electrical properties, optical properties, and mechanical properties. Important properties to consider are, for example, grain boundary density in the material, chemical composition of the interface, and crystallographic structure, ie, grain interface orientation and grain orientation difference. In particular, the corresponding lattice (CSL) grain boundaries play a special role. A CSL grain boundary (also referred to simply as “CSL grain boundary”) is characterized by a multiplicity index Σ, which is the density of crystal lattice sites of two grains in contact with the grain boundary, It is defined as the ratio with the density of the corresponding part when the lattices are overlapped. For simple structures, it is generally accepted that low Σ value grain boundaries tend to have low interfacial energy and special properties. Therefore, the control of the ratio of the special grain boundaries and the distribution of grain orientation difference estimated from the CSL model is considered to be important for the characteristics of the ceramic coating and the method for improving these characteristics.

  In recent years, a technique based on a scanning electron microscope (SEM) known as electron backscatter diffraction (EBSD) has emerged and is used to study grain boundaries in ceramic materials. The EBSD technique is based on automatic analysis of the Kikuchi diffraction pattern generated by backscattered electrons.

  For each crystal grain of the material of interest, the crystallographic orientation is determined after indexing the corresponding diffraction pattern. With commercially available software, structure analysis and determination of grain boundary character distribution (GBCD) are made relatively easily by using EBSD. By applying EBSD to the interface, it is possible to determine the grain boundary orientation difference for a sample population with a large interface. Usually, the misorientation distribution is associated with the processing conditions of the substance. Grain boundary orientation differences can be obtained by conventional orientation parameters such as Euler angles, angle / axis pairs, or Rodriguez vectors. The CSL model is widely used as a characterization tool.

  The CSL grain boundaries of the present embodiment are usually Σ7 type crystal grain boundaries, Σ7 type crystal grain boundaries, Σ11 type crystal grain boundaries, Σ17 type crystal grain boundaries, Σ19 type crystal grain boundaries, Σ21 type crystal grain boundaries, It consists of a Σ23 type crystal grain boundary and a Σ29 type crystal grain boundary. However, even when one or more grain boundaries other than the Σ3-type grain boundary are not observed when observed using a scanning electron microscope (SEM) known as electron beam backscatter diffraction (EBSD), As long as the effect of this embodiment is shown, it does not depart from the scope of this embodiment.

The Σ3-type grain boundary of this embodiment is considered to have the lowest grain boundary energy among the CSL grain boundaries of α-Al ₂ O ₃ , and thus the proportion of all CSL grain boundaries is high. By doing so, it is considered that mechanical properties (particularly plastic deformation resistance) can be improved. For this reason, in this embodiment, all the CSL crystal grain boundaries are represented by the notation of Σ3-29 type crystal grain boundary, and the length of this Σ3 type crystal grain boundary is more than 80% of the length of the Σ3-29 type crystal grain boundary. Is defined as The length of the Σ3-type grain boundary is more preferably 83% or more, and still more preferably 85% or more of the length of the Σ3-29 type grain boundary. Thus, the higher the value, the better. It is not necessary to define the upper limit, but the upper limit is 99% or less from the viewpoint of a polycrystalline thin film.

  Here, the length of the Σ3-type grain boundary indicates the total length of the Σ3-type grain boundary in the field of view observed by EBSD, and the length of the Σ3-29 type grain boundary is observed by EBSD. The total length of the Σ3-29 type grain boundary defined below in the visual field is shown. That is, the lengths of the Σ3-29 type grain boundaries are the Σ3-type grain boundaries, Σ7-type grain boundaries, Σ11-type crystal grain boundaries, Σ17-type crystal grain boundaries, and Σ19-type crystal grains respectively constituting the CSL grain boundaries. The total length of each of the boundary, the Σ21-type grain boundary, the Σ23-type crystal grain boundary, and the Σ29-type crystal grain boundary.

  On the other hand, since this Σ3 type grain boundary is a crystal grain boundary having high consistency as is clear from having a low grain boundary energy, the Σ3 type crystal grain boundary is 2 One crystal grain behaves like a single crystal or twin crystal and tends to coarsen. When the crystal grains are coarsened, film characteristics such as chipping resistance are deteriorated, so that it is necessary to suppress the coarsening. Therefore, in this embodiment, the length of the Σ3-type grain boundary is defined as 10% or more and 50% or less of the total length of all the grain boundaries, and the above-described suppression effect is ensured.

  Accordingly, if the length of the Σ3-type grain boundary exceeds 50% of the total length of all the grain boundaries, the crystal grains become undesirably coarse, and if it is less than 10%, the above excellent mechanical properties cannot be obtained. . A more preferable range is 20 to 45%, and a further preferable range is 30 to 40%.

Here, the total grain boundary is a sum of a grain boundary other than the CSL grain boundary and the CSL grain boundary. Note that crystal grain boundaries other than CSL crystal grain boundaries are referred to as general grain boundaries for convenience. Therefore, the general grain boundary is a remaining part obtained by removing the Σ3-29 type crystal grain boundary from the whole grain boundary of the α-Al ₂ O ₃ crystal grain when observed by EBSD. Therefore, the “total length of all grain boundaries” can be expressed as “the sum of the length of the Σ3-29 type grain boundary and the length of the general grain boundary”.

  In this embodiment, whether the length of the Σ3-type grain boundary is more than 80% of the length of the Σ3-29 type grain boundary, and the length of the Σ3-type grain boundary is the sum of all the grain boundaries. Whether it is 10% or more and 50% or less of the length can be confirmed as follows.

That is, an α-Al ₂ O ₃ layer is first formed based on the manufacturing method described later. Then, the formed α-Al ₂ O ₃ layer (including the base material) is cut so that a cross section perpendicular to the α-Al ₂ O ₃ layer is obtained (that is, the surface of the α-Al ₂ O ₃ layer). And cut so that the cut surface obtained by cutting the α-Al ₂ O ₃ layer at a plane including the normal line to is exposed). Thereafter, the cut surface is polished with water-resistant abrasive paper (containing a SiC abrasive abrasive as an abrasive).

The above cleavage is, for example alpha-Al ₂ O ₃ layer surface (alpha-Al if other layers are formed on the ₂ O ₃ layer on the film surface) on a plate for a sufficiently large hold And fixed in close contact with wax or the like, and then cut in a direction perpendicular to the flat plate with a rotary blade cutter (cut so that the rotary blade and the flat plate are as vertical as possible) To do. This cutting can be performed at any part of the α-Al ₂ O ₃ layer as long as it is performed in such a vertical direction. However, the cutting may be performed so as to include a cutting edge tip as described later. preferable.

  In addition, the above polishing is performed using the water-resistant abrasive papers # 400, # 800, and # 1500 in order (the number (#) of the water-resistant abrasive paper means a difference in the particle size of the abrasive, and the number is The larger the particle size, the smaller the particle size of the abrasive).

Subsequently, the polished surface is further smoothed by ion milling with Ar ions. The conditions for the ion milling treatment are as follows.
Acceleration voltage: 6 kV
Irradiation angle: 0 ° from the normal direction of the surface of the α-Al ₂ O ₃ layer (that is, the linear direction parallel to the thickness direction of the α-Al ₂ O ₃ layer at the cut surface)
Irradiation time: 6 hours.

  Thereafter, the smoothed polished surface is observed with an SEM equipped with EBSD. The observation location is not particularly limited, but it is preferable to observe the tip of the cutting edge in consideration of the relationship with the cutting characteristics. The cutting edge tip usually means the edge of the cutting edge where the rake face and flank intersect, but if the edge of the cutting edge is honing or chamfered, observe any part within the machining range. It shall be.

  The SEM uses a Zeiss Supra 35 VP (CARL ZEISS) equipped with an HKL NL02 EBSD detector. EBSD data is collected sequentially by placing a focused electron beam onto each pixel individually.

The normal of the sample surface (smoothed α-Al ₂ O ₃ layer) is tilted by 70 ° with respect to the incident beam, and analysis is performed at 15 kV. In order to avoid the charging effect, a pressure of 10 Pa is applied. The high current mode is used in combination with the opening diameter of 60 μm or 120 μm. Data collection is performed at a step of 0.1 μm / step for 500 × 300 points corresponding to a surface area of 50 × 30 μm on the polished surface.

Data processing is performed with and without noise filtering. Noise filtering and grain boundary character distribution are determined using commercially available software (trade name: “orientation Imaging microscopy Ver 6.2”, manufactured by EDAX). Analysis of grain boundary character distribution is based on data available from Grimmer (H. Grimmer, R. Bonnet, Philosophical Magazine A 61 (1990), 493-509). The Brandon criterion (ΔΘ <Θ ₀ (Σ) ^−0.5 , where Θ ₀ = 15 °) is used to take into account the tolerance of the experimental value from the theoretical value (D. Brandon Acta metall 14 (1966), 1479-1484). This can be confirmed by counting the special grain boundaries corresponding to arbitrary Σ values and expressing them as a ratio to the total grain boundaries. That is, the length of the Σ3-type grain boundary, the length of the Σ3-29 type grain boundary, and the total length of all the grain boundaries can be obtained as described above.

On the other hand, whether or not the α-Al ₂ O ₃ layer exhibits (001) orientation can be confirmed as follows. That is, after the α-Al ₂ O ₃ layer is cut so that a cross section perpendicular to the α-Al ₂ O ₃ layer can be obtained in the same manner as described above, the polishing and smoothing treatment is similarly performed.

Then, the treated cut surface thus, the the α-Al ₂ O ₃ layer using SEM with similar EBSD (001) checks whether showing the orientation. Specifically, using the same software as above, the normal direction of the (001) plane of each measurement pixel and the normal direction of the α-Al ₂ O ₃ layer surface (the surface located on the coating surface side) ( In other words, the angle formed with the α-Al ₂ O ₃ layer in the cut plane and a straight line direction parallel to the thickness direction of the α-Al ₂ O ₃ layer is calculated, and a color map is created so that pixels whose angle is within ± 20 ° are selected. To do. In this case, the color map is created over the entire cut surface (that is, the α-Al ₂ O ₃ layer).

Specifically, using the method of “Cristal Direction MAP” included in the above software, the Tolerance of 20 ° between the normal direction of the surface of the α-Al ₂ O ₃ layer and the normal direction of the (001) plane of each measurement pixel A color map (with a direction difference within ± 20 °) is created. Then, by calculating the area ratio of the pixels based on this color map, when the area ratio is 50% or more, it is assumed that “α-Al ₂ O ₃ layer exhibits (001) orientation”.

<Thickness of α-Al ₂ O ₃ layer>
The α-Al ₂ O ₃ layer preferably has a thickness of 2 to 20 μm. Thereby, the above excellent effects can be exhibited. The thickness is more preferably 3 to 15 μm, still more preferably 5 to 10 μm.

When the thickness is less than 2 μm, the above excellent effects may not be sufficiently exhibited. When the thickness exceeds 20 μm, the linear expansion coefficient between the α-Al ₂ O ₃ layer and another layer such as an underlayer The interfacial stress due to the difference between the _two increases, and the α-Al ₂ O ₃ crystal grains may fall off. Such a thickness can be confirmed by observation of a vertical cross section of the substrate and the coating using a scanning electron microscope (SEM) or the like.

<Surface roughness of α-Al ₂ O ₃ layer>
The α-Al ₂ O ₃ layer preferably has a surface roughness Ra of less than 0.2 μm. As a result, the coefficient of friction between the chips and the tool cutting edge is reduced, and not only chipping resistance is improved, but also stable chip discharge performance can be exhibited. The surface roughness Ra is more preferably less than 0.15 μm, and even more preferably less than 0.10 μm. Thus, the lower the surface roughness Ra, the better. It is not necessary to define the lower limit, but the lower limit is 0.05 μm or more from the viewpoint that the coating is affected by the surface properties of the substrate.

  In addition, in this application, surface roughness Ra shall mean arithmetic mean roughness Ra of JISB0601 (2001).

<Compressive stress of α-Al ₂ O ₃ layer>
The α-Al ₂ O ₃ layer includes a point where the absolute value of the compressive stress is maximum in a region within 2 μm from the surface side of the coating, and the absolute value of the compressive stress at the point is preferably less than 1 GPa. Thereby, the sudden chipping | deletion defect | deletion of the blade edge accompanying the mechanical and thermal fatigue of the tool blade edge which generate | occur | produces at the time of an intermittent cutting process is suppressed, and a labor-saving / energy-saving effect can be exhibited. The absolute value is more preferably less than 0.9 GPa, and still more preferably less than 0.8 GPa. The lower limit of the absolute value is not particularly limited, but the lower limit is 0.2 GPa or more from the viewpoint of a balance between wear resistance and fracture resistance.

Here, the "surface side of the film", in the thickness direction of the α-Al ₂ O ₃ layer, means a side opposite the side from the substrate side, another layer α-Al ₂ O ₃ layer on the When it is not formed, it means the surface of the α-Al ₂ O ₃ layer.

In addition, the compressive stress in this embodiment can be measured by the conventionally known sin ² ψ method using X-rays, the penetration depth constant method, or the like.

<TiC _x N _y layer>
The coating of this embodiment can include a TiC _x N _y layer between the substrate and the α-Al ₂ O ₃ layer. This TiC _x N _y layer preferably contains TiC _x N _y that satisfies an atomic ratio of 0.6 ≦ x / (x + y) ≦ 0.8. This improves the adhesion between the substrate and the α-Al ₂ O ₃ layer.

  The atomic ratio is more preferably 0.65 ≦ x / (x + y) ≦ 0.75, and further preferably 0.67 ≦ x / (x + y) ≦ 0.72. When x / (x + y) is less than 0.6, the wear resistance may be insufficient, and when it exceeds 0.8, the chipping resistance may be insufficient.

<Manufacturing method>
The surface-coated cutting tool of this embodiment can be manufactured by forming a film on a substrate by a chemical vapor deposition method. When a film other than the α-Al ₂ O ₃ layer is formed, these films can be formed under conventionally known conditions. On the other hand, the α-Al ₂ O ₃ layer can be formed as follows.

That is, first, AlCl ₃ , HCl, CO ₂ , CO, H ₂ S, O ₂ , and H ₂ are used as source gases. The blending amounts are 3-5% by volume of AlCl ₃ , 4-6% by volume of HCl, 0.5-2% by volume of CO ₂ , 0.1-1% by volume of CO, and 1-5% of H ₂ S. %, O ₂ is 0.0001 to 0.01% by volume, and the balance is H ₂ . Further, volume ratios of 0.1 ≦ CO / CO ₂ ≦ 1, 0.1 ≦ CO ₂ / H ₂ S ≦ 1, 0.1 ≦ CO ₂ / AlCl ₃ ≦ 1, 0.5 ≦ AlCl ₃ / HCl ≦ 1 Is preferably adopted.

  Moreover, as for the various conditions of a chemical vapor deposition method, temperature is 950-1050 degreeC, a pressure is 1-5 kPa, and a gas flow rate (total gas amount) is 50-100 L / min.

Then, after the α-Al ₂ O ₃ layer is once formed by chemical vapor deposition in this way, annealing is performed. The annealing conditions are a temperature of 1050 to 1080 ° C., a pressure of 50 to 100 kPa, and a time of 120 to 300 minutes. The annealing atmosphere is performed by flowing H ₂ and Ar (argon) at a flow rate of ₂₀ to 30 L / min.

In this way, the α-Al ₂ O ₃ layer of the present embodiment having a desired thickness can be formed. In particular, by setting the volume ratio of O ₂ in the source gas within the above range, it is possible to ensure a sufficient film formation rate while reducing the risk of explosion and the like, and annealing as described above after film formation. it is possible to prevent the impurities such as sulfur remains on α-Al ₂ O ₃ layer in by performing particularly outstanding as a method for producing α-Al ₂ O ₃ layer of the present embodiment.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these.

<Preparation of substrate>
Two types of base materials P and P described in Table 1 below were prepared. Specifically, the raw material powder having the composition shown in Table 1 is uniformly mixed, pressed into a predetermined shape, and then sintered at 1300-1500 ° C. for 1-2 hours, so that the shape is CNMG120408NUX A cemented carbide base material (Sumitomo Electric Industries, JIS B4120 (2013)) was obtained.

<Formation of coating>
A film was formed on the surface of each substrate obtained above. Specifically, the base material was set in a chemical vapor deposition apparatus to form a film on the base material by chemical vapor deposition. The film formation conditions are as described in Table 2 and Table 3 below. Table 2 shows the formation conditions of each layer other than the α-Al ₂ O ₃ layer, and Table 3 shows the formation conditions of the α-Al ₂ O ₃ layer. Note that TiBNO and TiCNO in Table 2 are intermediate layers in Table 5 described later, and the other layers correspond to the layers other than the α-Al ₂ O ₃ layer in Table 5. Further, TiC _x N _y layers are those atomic ratio x / (x + y) consists of TiC _x N _y is 0.7.

In addition, as shown in Table 3, the α-Al ₂ O ₃ layer has 10 formation conditions of A to G and X to Z, among which A to G are the conditions of the examples, and X to Z are It is conditions of a comparative example (prior art).

In addition, only about the α-Al ₂ O ₃ layer of the example formed under the conditions of A to G, the flow rate of 1050 ° C., 50 kPa, H ₂ was 20 L / min, and the flow rate of Ar during the annealing time described in Table 4. Was annealed under the condition of 30 L / min.

For example, the formation condition A is 3.2 volume% AlCl ₃ , 4.0 volume% HCl, 1.0 volume% CO ₂ , 0.5 volume% CO, 2 volume% H ₂ S, 0 A material gas having a composition is supplied from 0.003 volume% O ₂ and the balance H ₂ to a chemical vapor deposition apparatus under conditions of a pressure of 3.5 kPa and a temperature of 1000 ° C., and a flow rate (total gas amount) of 70 L / min. It is shown that an α-Al ₂ O ₃ layer is formed by performing a chemical vapor deposition method and then annealing for 180 minutes under the above conditions.

In addition, each layer other than the α-Al ₂ O ₃ layer described in Table 2 was similarly formed by a chemical vapor deposition method, except that annealing was not performed. “Remaining” in Table 2 indicates that H ₂ occupies the remainder of the source gas. The “total gas amount” indicates the total volume flow rate introduced into the chemical vapor deposition apparatus per unit time, assuming that the gas in the standard state (0 ° C., 1 atm) is an ideal gas (α− in Table 3). The same applies to the Al ₂ O ₃ layer).

The composition and thickness of each coating were confirmed by SEM-EDX (scanning electron microscope-energy dispersive X-ray spectroscopy), and the length of the Σ3-type grain boundary of the α-Al ₂ O ₃ layer, Σ3-29 The length of the type grain boundary and the total length of all the grain boundaries were confirmed by the method described above. The presence or absence of (001) orientation of the α-Al ₂ O ₃ layer was also confirmed by the above-described method.

As a result, the composition and thickness of each coating are as shown in Table 5, and the length of the Σ3 type grain boundary of the α-Al ₂ O ₃ layer is what percentage of the length of the Σ3-29 type grain boundary, The percentage of the total length of all grain boundaries is shown in the sections of “Σ3 / Σ3-29” and “Σ3 / total grain boundaries” in Table 4, respectively. Further, crystal grains (α-Al ₂ ) whose normal direction to the (001) plane is within ± 20 ° with respect to the normal direction of the surface of the α-Al ₂ O ₃ layer (the surface located on the coating surface side). The ratio (%) of O ₃ ) is also shown in the section “(001) orientation ratio” in Table 4.

<Production of surface-coated cutting tool>
Surface-coated cutting tools of Examples 1 to 15 and Comparative Examples 1 to 6 shown in Table 5 below were produced by forming a film on the substrate under the conditions of Tables 2 to 4 above. The thickness of each layer was adjusted by appropriately adjusting the film formation time (the film formation speed of each layer is about 0.5 to 2.0 μm / hour).

For example, the surface-coated cutting tool of Example 4 employs the base material P described in Table 1 as the base material, and a TiN layer having a thickness of 0.5 μm is formed on the surface of the base material P under the conditions of Table 2. Then, a TiC _x N _y layer having a thickness of 5.0 μm is formed on the underlayer under the conditions of Table 2, and a TiBNO layer having a thickness of 0.5 μm is formed on the TiC _x N _y layer as an intermediate layer under the conditions of Table 2. An α-Al ₂ O ₃ layer having a thickness of 5.0 μm is formed on the intermediate layer under the formation conditions B in Table 3 and Table 4, and then a TiN layer having a thickness of 1.0 μm is formed as an outermost layer in Table 2. By forming under conditions, it is shown that a film having a total thickness of 12.0 μm is formed on the substrate. In the α-Al ₂ O ₃ layer of the surface-coated cutting tool of Example 4, the length of the Σ3-type grain boundary is 88% of the length of the Σ3-29-type grain boundary, and the total of all the grain boundaries. 30% of the length. The α-Al ₂ O ₃ layer has a (001) orientation (that is, a crystal whose normal direction to the (001) plane is within ± 20 ° with respect to the normal direction of the α-Al ₂ O ₃ layer surface. The proportion of grains (α-Al ₂ O ₃ ) is 57% in the α-Al ₂ O ₃ layer).

Since the α-Al ₂ O ₃ layers of Comparative Examples 1 to 6 are all formed under the conditions of the prior art that do not follow the method of the present invention, these α-Al ₂ O ₃ layers are as in the present invention. (See Table 3 and Table 4).

  A blank in Table 5 indicates that the corresponding layer is not formed.

<Cutting test>
The following five types of cutting tests were performed using the surface-coated cutting tool obtained above.

<Cutting test 1>
For the surface-coated cutting tools of Examples and Comparative Examples described in Table 6 below, the cutting time until the flank wear amount (Vb) becomes 0.20 mm under the following cutting conditions is measured, and the final damage form of the blade edge Was observed. The results are shown in Table 6. The longer the cutting time, the better the wear resistance and the longer the tool life. In addition, when the final damage form is wear, the chipping resistance is excellent and the tool life is also prolonged.

<Cutting conditions>
Work material: SUJ2 round bar peripheral cutting speed: 350 m / min
Feeding speed: 0.2mm / rev
Cutting depth: 2.0mm
Cutting fluid: Yes.

  As is apparent from Table 6, the surface-coated cutting tool of the example is superior in both wear resistance and chipping resistance to the surface-coated cutting tool of the comparative example, and the tool life is prolonged. it is obvious. That is, it was confirmed that the mechanical properties of the coating of the surface-coated cutting tool of the example were improved.

<Cutting test 2>
For the surface-coated cutting tools of Examples and Comparative Examples described in Table 7 below, the cutting time until the flank wear amount (Vb) becomes 0.20 mm under the following cutting conditions is measured and the final damage form of the blade edge Was observed. The results are shown in Table 7. The longer the cutting time, the better the wear resistance and the longer the tool life. In addition, when the final damage form is wear, the chipping resistance is excellent and the tool life is also prolonged.

<Cutting conditions>
Work material: S50C round bar peripheral cutting speed: 300 m / min
Feeding speed: 0.5mm / rev
Cutting depth: 2.0mm
Cutting fluid: Yes.

  As is apparent from Table 7, the surface-coated cutting tool of the example is superior in wear resistance and has a longer tool life than the surface-coated cutting tool of the comparative example. That is, it was confirmed that the mechanical properties of the coating of the surface-coated cutting tool of the example were improved.

<Cutting test 3>
For the surface-coated cutting tools of Examples and Comparative Examples described in Table 8 below, the cutting time until the flank wear amount (Vb) becomes 0.20 mm under the following cutting conditions is measured, and the final damage form of the blade edge Was observed. The results are shown in Table 8. The longer the cutting time, the better the wear resistance and the longer the tool life. In addition, when the final damage form is wear, the chipping resistance is excellent and the tool life is also prolonged.

<Cutting conditions>
Work material: FCD600 round bar peripheral cutting speed: 300 m / min
Feeding speed: 0.3mm / rev
Cutting depth: 1.5mm
Cutting fluid: Yes.

  As is apparent from Table 8, the surface-coated cutting tool of the example is superior to both the surface-coated cutting tool of the comparative example in both wear resistance and chipping resistance, and the tool life is prolonged. it is obvious. That is, it was confirmed that the mechanical properties of the coating of the surface-coated cutting tool of the example were improved.

<Cutting test 4>
For the surface-coated cutting tools of Examples and Comparative Examples described in Table 9 below, the cutting time until the flank wear amount (Vb) becomes 0.20 mm under the following cutting conditions is measured, and the final damage form of the blade edge Was observed. The results are shown in Table 9. The longer the cutting time, the better the wear resistance and the longer the tool life. In addition, when the final damage form is wear, the chipping resistance is excellent and the tool life is also prolonged.

<Cutting conditions>
Work material: FC200 round bar peripheral cutting speed: 500 m / min
Feeding speed: 0.25mm / rev
Cutting depth: 1.5mm
Cutting fluid: Yes.

  As is apparent from Table 9, the surface-coated cutting tool of the example is superior in wear resistance and has a longer tool life than the surface-coated cutting tool of the comparative example. That is, it was confirmed that the mechanical properties of the coating of the surface-coated cutting tool of the example were improved.

<Cutting test 5>
With respect to the surface-coated cutting tools of Examples and Comparative Examples described in Table 10 below, the cutting time until the tool was lost under the following cutting conditions was measured. The results are shown in Table 10. The longer the cutting time, the better the fracture resistance and the longer the tool life.

<Cutting conditions>
Work material: SCM440 (90 ° × 4 groove outer periphery cutting)
Peripheral speed: 200m / min
Feeding speed: 0.2mm / rev
Cutting depth: 1.5mm
Cutting fluid: Yes.

  As is apparent from Table 10, the surface-coated cutting tool of the example is superior in fracture resistance to the surface-coated cutting tool of the comparative example, and it is clear that the tool life is prolonged. That is, it was confirmed that the mechanical properties of the coating of the surface-coated cutting tool of the example were improved.

<Confirmation of effect of surface roughness Ra of α-Al ₂ O ₃ layer>
For the surface-coated cutting tools of Example 1, Example 2, and Example 11, the surface roughness Ra of the α-Al ₂ O ₃ layer was measured in accordance with JIS B 0601 (2001). The results are shown in Table 11.

Subsequently, the surface-coated cutting tools of Example 1A, Example 2A, and Example 11A were respectively obtained by subjecting the α-Al ₂ O ₃ layer of each surface-coated cutting tool to an aero lapping process under the following conditions. Was made. Then, for each of these surface-coated cutting tools, the surface roughness Ra of the α-Al ₂ O ₃ layer was measured in the same manner as described above. The results are shown in Table 11.

<Aero wrap conditions>
Media: Elastic rubber media with a diameter of about 1 mm containing diamond abrasive grains with an average particle size of 0.1 μm (trade name: “Multicone”, manufactured by Yamashita Towers)
Projection pressure: 0.5 bar
Projection time: 30 seconds wet / dry: dry.

  And about these surface-coated cutting tools of Examples 1, 1A, 2, 2A, 11, and 11A, the cutting time until the flank wear amount (Vb) was 0.20 mm was measured under the following cutting conditions. . The results are shown in Table 11. It shows that the longer the cutting time, the lower the coefficient of friction between the chip and the tool edge, and the more stable chip discharge performance can be exhibited.

<Cutting conditions>
Work material: SS400 round bar peripheral cutting speed: 100 m / min
Feeding speed: 0.1mm / rev
Cutting depth: 1.0mm
Cutting fluid: None.

As is apparent from Table 11, the surface-coated cutting tools of Examples 1A, 2A, and 11A having the α-Al ₂ O ₃ layer having a surface roughness Ra of less than 0.2 μm have a surface roughness of 0.2 μm or more. Compared to the surface-coated cutting tools of Examples 1, 2, and 11 having an α-Al ₂ O ₃ layer having a thickness Ra, the coefficient of friction between the chip and the tool edge is reduced, and stable chip discharge is achieved. It was confirmed that it was possible to demonstrate the properties.

<Confirmation of effect of applying compressive stress to α-Al ₂ O ₃ layer>
For the surface-coated cutting tools of Example 1, Example 2, and Example 11, there is a point where the absolute value of the stress is maximum in the region within 2 μm from the surface side of the coating in the α-Al ₂ O ₃ layer. The absolute value of the stress at that point was measured. The results are shown in Table 12 (“Stress Value” section). The stress is measured by the sin ² ψ method using X-rays. In the section of “Stress Value” in Table 12, the numerical value indicates an absolute value, the tensile stress is “tensile”, and the compressive stress is “compressed”. It was written.

Next, by subjecting the α-Al ₂ O ₃ layer of each of the above surface-coated cutting tools to wet blasting under the following conditions, Example 1B, Example 1C, Example 2B, Example 2C, and A surface-coated cutting tool of Example 11B was produced. Then, for each of these surface-coated cutting tools, in the same manner as above, it was confirmed that there was a point where the absolute value of the stress was maximum in a region within 2 μm from the surface side of the coating in the α-Al ₂ O ₃ layer. The absolute value of stress at that point was measured. The results are shown in Table 12 (“Stress Value” section). The difference in stress between Example 1B and Example 1C, and Example 2B and Example 2C is due to the difference in the projection pressure of the wet blasting process.

<Conditions for wet blasting>
Media: Alumina media (φ50μm)
Projection pressure: 1-2 bar
Projection time: 10 seconds wet / dry: wet.

  And about these surface-coated cutting tools of Examples 1, 1B, 1C, 2, 2B, 2C, 11 and 11B, the cutting time until the tool was lost under the following cutting conditions was measured. The results are shown in Table 12. It shows that the longer the cutting time is, the more the cutting edge of the tool edge caused by mechanical and thermal fatigue generated during intermittent cutting is suppressed, and the reliability of the edge is improved as a result.

<Cutting conditions>
Work material: SUS304 (60 ° × 3 groove outer periphery cutting)
Peripheral speed: 150m / min
Feeding speed: 0.25mm / rev
Cutting depth: 1.0mm
Cutting fluid: None.

As apparent from Table 12, the α-Al ₂ O ₃ layer includes a point where the absolute value of the stress is maximum in a region within 2 μm from the surface side of the coating, and the stress at that point is a tensile stress. When the absolute value of the compressive stress is less than 1 GPa, chipping of the tool edge due to mechanical and thermal fatigue that occurs during intermittent cutting is suppressed, and as a result, the reliability of the edge is improved. Was confirmed.

  Although the embodiments and examples of the present invention have been described as described above, it is also planned from the beginning that the configurations of the above-described embodiments and examples may be appropriately combined and variously modified.

  The embodiment disclosed this time is to be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above-described embodiment but by the scope of claims, and is intended to include meanings equivalent to the scope of claims and all modifications within the scope.

Claims (4)

A surface-coated cutting tool comprising a base material and a coating formed on the base material,
The coating includes an α-Al ₂ O ₃ layer,
The α-Al ₂ O ₃ layer includes a plurality of α-Al ₂ O ₃ crystal grains and exhibits a (001) orientation;
The grain boundaries of the crystal grains include CSL grain boundaries and general grain boundaries,
Of the CSL grain boundaries, the length of the Σ3-type grain boundary is more than 80% of the length of the Σ3-29-type grain boundary, and the length of the Σ3-29-type grain boundary and the length of the general grain boundary Ri 50% der less than 10% of the total length of all the grain boundaries is the sum of the length,
The (001) orientation means that the α-Al ₂ O ₃ crystal has a normal direction with respect to the (001) plane within ± 20 ° with respect to the normal direction of the surface of the α-Al ₂ O ₃ layer. A method for producing a surface-coated cutting tool , which refers to a case where the proportion of grains is 50% or more in the α-Al ₂ O ₃ layer ,
A first step of forming the α-Al ₂ O ₃ layer by chemical vapor deposition;
Annealing the formed α-Al ₂ O ₃ layer,
In the first step, AlCl ₃ , HCl, CO ₂ , CO, H ₂ S, O ₂ , and H ₂ are used as source gases , the temperature is 950 to 1050 ° C., the pressure is 1 to 5 kPa, Executed under the condition that the gas flow rate is 50 to 100 L / min,
The said 2nd process is a manufacturing method of the surface covering cutting tool performed on the conditions whose temperature is 1050-1080 degreeC, a pressure is 50-100 kPa, and time is 120-300 minutes. The source gas is AlCl _Three 3-5% by volume, HCl 4-6% by volume, CO ₂ 0.5-2% by volume, CO 0.1-1% by volume, H ₂ 1 to 5% by volume of S, O ₂ 0.0001 to 0.01% by volume, the balance being H ₂ The method for producing a surface-coated cutting tool according to claim 1, which is used in an amount of The source gas is 0.1 ≦ CO / CO ₂ ≦ 1, 0.1 ≦ CO ₂ / H ₂ S ≦ 1, 0.1 ≦ CO ₂ / AlCl _Three ≦ 1, 0.5 ≦ AlCl _Three The method for producing a surface-coated cutting tool according to claim 1 or 2, which is used at a volume ratio of / HCl ≦ 1. The second step is H at a flow rate of 20-30 L / min. ₂ The manufacturing method of the surface-coated cutting tool of any one of Claims 1-3 performed by the atmosphere which flows Ar and Ar.