JP6535922B2 - Method of manufacturing surface coated cutting tool - Google Patents

Description

  The present invention relates to a surface coated cutting tool.

Conventionally, surface-coated cutting tools having a coating formed on a substrate have been used. For example, JP-A-2006-198735 (Patent Document 1) has a film including an α-Al ₂ O ₃ layer in which the ratio of Σ3 type crystal grain boundaries to Σ3-29 type crystal grain boundaries is 60 to 80%. A surface coated cutting tool is disclosed.

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

JP, 2006-198735, A Japanese Patent Application Publication No. 2014-526391

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 due to the improvement of various characteristics including the above, and the wear resistance and fracture resistance.

  However, in recent cutting processing, speeding-up and high efficiency progressed, load on the cutting tool increased, and shortening of the life of the cutting tool became a problem. Therefore, there is a need to further improve the mechanical properties of the coating of the cutting tool and to further prolong the life of the cutting tool.

  The present disclosure has been made in view of such circumstances, and an object of the present disclosure is to provide a surface-coated cutting tool having improved mechanical properties of a coating and further extending the life of the cutting tool. It is in.

A surface-coated cutting tool according to an aspect of the present disclosure is a surface-coated cutting tool having a rake face and a flank face, and includes a substrate and a film formed on the substrate. The film 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 the grain boundaries of the crystal grains include CSL grain boundaries and general grain boundaries. . The α-Al ₂ O ₃ layer on the rake face side shows (001) orientation, and in the α-Al ₂ O ₃ layer on the rake face side, the length L _R3 of the Σ3 type grain boundary among CSL grain boundaries is Σ3 Total length L _R of the whole grain boundary which is 80% or more of the length L R _3-29 of the -29 type grain boundary and which is the sum of the length L _{R 3-29} and the length of the general grain boundary L _RG 10% or more and 50% or less. The α-Al ₂ O ₃ layer on the flank surface side shows (001) orientation, and in the α-Al ₂ O ₃ layer on the flank surface side, the length L _F3 of 33 type grain boundaries among CSL grain boundaries is Σ3 Total length L _F of the whole grain boundary which is 80% or more of the length L _{F 3-29} of the -29 type grain boundary and which is the sum of the length L _{F 3-29} and the length L _FG of the general grain boundary 10% or more and 50% or less of The ratio _L R3 _{/ LR 3-29} of the length _{L R3} and length _{LR 3-29} is smaller than the ratio _L F3 _{/ L F3-29} of the length _{L F3} and length _{L F3-29.}

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

FIG. 1 is a perspective view of a surface coated cutting tool according to an embodiment of the present disclosure. It is an II-II arrow directional cross-sectional view of FIG. It is sectional drawing which illustrates the surface coating cutting tool which has the honing edge line part.

Description of the embodiment of the present invention
First, embodiments of the present disclosure will be listed and described.

[1] A surface-coated cutting tool according to an aspect of the present disclosure is a surface-coated cutting tool having a rake surface and a flank surface, and includes a substrate and a film formed on the substrate. The film 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 the grain boundaries of the crystal grains include CSL grain boundaries and general grain boundaries. . The α-Al ₂ O ₃ layer on the rake face side shows (001) orientation, and in the α-Al ₂ O ₃ layer on the rake face side, the length L _R3 of the Σ3 type grain boundary among CSL grain boundaries is Σ3 Total length L _R of the whole grain boundary which is 80% or more of the length L R _3-29 of the -29 type grain boundary and which is the sum of the length L _{R 3-29} and the length of the general grain boundary L _RG 10% or more and 50% or less. The α-Al ₂ O ₃ layer on the flank surface side shows (001) orientation, and in the α-Al ₂ O ₃ layer on the flank surface side, the length L _F3 of 33 type grain boundaries among CSL grain boundaries is Σ3 Total length L _F of the whole grain boundary which is 80% or more of the length L _{F 3-29} of the -29 type grain boundary and which is the sum of the length L _{F 3-29} and the length L _FG of the general grain boundary 10% or more and 50% or less of The ratio _L R3 _{/ LR 3-29} of the length _{L R3} and length _{LR 3-29} is smaller than the ratio _L F3 _{/ L F3-29} of the length _{L F3} and length _{L F3-29.} This surface-coated cutting tool has improved mechanical properties of the coating and an extended life.

[2] In the surface-coated cutting tool described above, CSL grain boundaries are 33 type grain boundaries, 77 type grain boundaries, 1111 type grain boundaries, 1717 type grain boundaries, 1919 type grain boundaries, 2121 type grain boundaries , A 型 23 type grain boundary, and a 界 29 type grain boundary, and the length L _R3-29 is a 33 type grain boundary, Σ7 type grain boundary, Σ11 type in the α-Al ₂ O ₃ layer on the rake face side The sum of the lengths of the grain boundary, 型 17 type grain boundary, 1919 type grain boundary, 2121 type grain boundary, 2323 type grain boundary, and Σ29 type grain boundary, and the length L _F3-29は₃ type grain boundaries, 、 7 type grain boundaries, 1111 type grain boundaries, 1717 type grain boundaries, 1919 type grain boundaries, 2121 type grain boundaries in the α-Al ₂ O ₃ layer on the flank side It is the total of the lengths of Σ23 type grain boundaries and Σ29 type grain boundaries.

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

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

[5] The α-Al ₂ O ₃ layer includes a point where the absolute value of compressive stress is maximum in a region within 2 μm from the surface side of the coating, and the absolute value of compressive stress at this point is less than 1 GPa Is preferred. As a result, it is possible to suppress the chipping of the cutting edge of the tool due to mechanical and thermal fatigue occurring at the time of intermittent cutting, and as a result, the reliability of the cutting edge is improved.

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

Details of the Embodiment of the Present Invention
Hereinafter, a surface-coated cutting tool according to an embodiment of the present invention (hereinafter also referred to as “the present embodiment”) will be described in more detail using FIGS. 1 to 3.

<Surface coated cutting tool>
Referring to FIG. 1, a surface-coated cutting tool 10 (hereinafter simply referred to as "tool 10") of the present embodiment has a cutting edge where a rake face 1, a flank face 2, a rake face 1 and a flank face 2 intersect. And the ridge line portion 3. That is, the rake face 1 and the flank face 2 are faces which are connected by sandwiching the blade edge 3. The cutting edge ridge line portion 3 constitutes a cutting edge of the tool 10. The shape of such a tool 10 depends on the shape of the substrate to be described later.

  FIG. 1 shows a tool 10 as an indexable cutting insert for turning, but the tool 10 is not limited to this, and a drill, an end mill, an indexable cutting insert for a drill, an indexable cutting insert for an end mill, a milling cutter The cutting tool according to the present invention can be suitably used as a cutting tool such as a cutting insert having a cutting edge, a metal saw, a gear cutting tool, a reamer, and a tap.

  In addition, when the tool 10 is a tip-exchange-type cutting tip or the like, the tool 10 may or may not have a chip breaker, and the shape of the cutting edge ridge portion 3 may be a sharp edge (rake surface (See Fig. 1), honing (with a sharp edge to the sharp edge) (see Fig. 3), negative land (chamfered), a combination of honing and negative land All things are included.

  Referring to FIG. 2, the tool 10 has a configuration including a substrate 11 and a film 12 formed on the substrate 11. In the tool 10, the film 12 preferably covers the entire surface of the substrate 11, but a part of the substrate 11 is not covered with the film 12, or the structure of the film 12 is partially different. Even if it does not deviate from the scope of this embodiment.

<Base material>
The base material 11 of the present embodiment has a rake face 11a, a flank 11b, and a cutting edge 11c where the rake face 11a and the flank 11b intersect. The rake face 11 a, the flank 11 b and the edge line 11 c constitute the face 1, the flank 2 and the edge 3 of the tool 10.

  As the base material 11, any base material can be used as long as it is conventionally known as this type of base material. For example, cemented carbide (for example, WC base cemented carbide, WC, Co containing, or addition of carbonitrides such as Ti, Ta, Nb etc. included), 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 base materials, it is particularly preferable to select WC-based cemented carbide and cermet (especially TiCN-based cermet). This is because these substrates have an excellent balance of hardness and strength particularly at high temperatures, and have excellent properties as a substrate of the surface-coated cutting tool for the above-mentioned applications.

<Coating>
The film 12 of the present embodiment may include other layers as long as it includes the α-Al ₂ O ₃ layer. Examples of other layers include TiN layer, TiCN layer, TiBNO layer, TiCNO layer, TiB ₂ layer, TiAlN layer, TiAlCN layer, TiAlON layer, TiAlONC layer and the like. The order of the lamination is not particularly limited.

In the present embodiment, in the chemical formulas such as “TiN”, “TiCN”, and “TiC _x N _y ”, the atomic ratio is not particularly specified, and the atomic ratio of each element is only “1”. Not shown, and all conventionally known atomic ratios are included.

  The film 12 of the present embodiment has an effect of improving various properties such as abrasion resistance and chipping resistance by coating the base material 11.

  The film 12 has a thickness of 3 to 30 μm (3 to 30 μm, where the range includes the upper limit and the lower limit when the numerical range is represented using “to” in the present application), more preferably 5 to 20 μm It is preferable to have. If the thickness is less than 3 μm, the abrasion resistance may be insufficient, and if it exceeds 30 μm, peeling or breakage of the coating 12 occurs when a large stress is applied between the coating 12 and the substrate 11 in intermittent processing. May occur frequently.

<Α-Al ₂ O ₃ Layer>
The film 12 of the present embodiment includes an α-Al ₂ O ₃ layer. The α-Al ₂ O ₃ layer can be contained in one or more layers in the film 12.

The α-Al ₂ O ₃ layer is a layer containing 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, the crystal grains have a particle size of about 100 to 2000 nm. A "grain boundary" exists between the crystal grains of a plurality of α-Al ₂ O ₃ .

  Grain boundaries have a great influence on material properties such as grain growth, creep properties, diffusion properties, electrical properties, optical properties, and mechanical properties. Important properties to be considered are, for example, the grain boundary density in the substance, the chemical composition of the interface, and the crystallographic structure, ie the grain interface orientation and the grain orientation deviation. In particular, the corresponding lattice (CSL) grain boundaries play a special role. CSL grain boundaries (also referred to simply as "CSL grain boundaries") are characterized by a multiplicity index Σ, which is the density of the crystal lattice sites of the two crystal grains in contact at the grain boundaries, and both crystals It is defined as the ratio to the density of the corresponding part when the grids are superimposed. It is generally accepted that for simple structures, grain boundaries with low 低 values tend to have low interfacial energy and special properties. Therefore, control of the proportion of special grain boundaries and the distribution of grain misorientation estimated from the CSL model is believed to be important for the properties of the ceramic coating and methods for improving these properties.

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

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

The grain boundaries in the α-Al ₂ O ₃ layer of the present embodiment include the above-described CSL grain boundaries and general grain boundaries. CSL grain boundaries are 33 type grain boundaries, 77 type grain boundaries, 1111 type grain boundaries, 1717 type grain boundaries, 1919 type grain boundaries, 2121 type grain boundaries, 2323 type grain boundaries, and Σ29 type grain boundaries It consists of grain boundaries. However, even when one or more grain boundaries other than Σ3 type grain boundaries are not observed when observed by the above-mentioned EBSD, it does not deviate from the scope of the present embodiment as long as the effect of the present embodiment is exhibited. . General grain boundaries are grain boundaries other than CSL grain boundaries. Therefore, the general grain boundary, the remaining portion except the CSL grain boundaries from whole grain boundary crystal grains of the α-Al ₂ O ₃ in the case of observation by EBSD.

Then, α-Al ₂ O ₃ layer of the present embodiment satisfy the following (1) to (4).
(1) The r-side α-Al ₂ O ₃ layer and the flank-side α-Al ₂ O ₃ layer each exhibit (001) orientation;
(2) In the α-Al ₂ O ₃ layer on the rake face side, the length L _R3 of the 33 type grain boundary is more than 80% of the length L _R3-29 of the 3−3-29 type grain boundary, and 10% or more and 50% or less of the total length L _R of the whole grain boundary which is the sum of L _{R 3-29} and the length L _RG of the general grain boundary;
(3) In the α-Al ₂ O ₃ layer on the flank side, the length L _F3 of the 33 type grain boundary is more than 80% of the length L _F3-29 of the 3−3-29 type grain boundary, and 10% or more and 50% or less of the total length L _F of the whole grain boundary which is the sum of L _{F 3-29} and the length L _FG of the general grain boundary;
(4) the length _{L R3} and the ratio _L R3 _{/ L R3-29} of the length _{L R3-29} is smaller than the ratio _L F3 _{/ L F3-29} of the length _{L F3} and length _{L F3-29} .

The above (1) will be described. In the present specification, when the α-Al ₂ O ₃ layer on each surface side indicates “(001) orientation”, the normal direction to the (001) surface is the α-Al ₂ O ₃ layer surface (on the surface side of the film The ratio (area ratio) of crystal grains (α-Al ₂ O ₃ ) within ± 20 ° with respect to the normal direction of the surface to be located is 50% or more in the α-Al ₂ O ₃ layer I shall say the case. Specifically, a vertical cross section (a cross section parallel to the normal direction of the surface of the above α-Al ₂ O ₃ layer) of each of the α-Al ₂ O ₃ layers on the rake surface side and the flank surface side using a SEM equipped with EBSD C) when the image processing by color mapping is performed, the area ratio of the crystal grains in the α-Al ₂ O ₃ layer is 50% or more in each observed image after the image processing. It shall be.

The area to be color mapped in α-Al ₂ O ₃ layer, in the thickness direction are all in the range of α-Al ₂ O ₃ layer. That is, for all the regions of the surface located on the coated surface side of the α-Al ₂ O ₃ layer, to the surface located on the substrate side of the α-Al ₂ O ₃ layer, it is color mapped. For an α-Al ₂ O ₃ layer having a thickness on the micro order, one observation image can confirm the entire range in the thickness direction. On the other hand, in the in-plane direction (direction orthogonal to the thickness direction) of the α-Al ₂ O ₃ layer, an arbitrary range may be color mapped.

Generally, alpha-Al ₂ O about _three layers of (001) orientation is increased, alpha-Al since the hardness of the ₂ O ₃ layer is increased, the (1) of the present embodiment to satisfy the alpha-Al ₂ According to the O ₃ layer, the occurrence of cracks due to impact during processing can be suppressed, the toughness of the cutting tool can be greatly improved, and thus high wear resistance can be provided.

Note that "surface side of the film" in the thickness direction of the α-Al ₂ O ₃ layer, the substrate side means the opposite side, another layer α-Al ₂ O ₃ layer on is not formed In the case, it means the surface of the α-Al ₂ O ₃ layer.

The above (2) and (3) will be described. The 33 type grain boundary is considered to have the lowest grain boundary energy among the CSL grain boundaries of α-Al ₂ O ₃ , and thus, by increasing the proportion of all CSL grain boundaries, mechanical It is believed that the properties (especially plastic deformation resistance) can be enhanced. Therefore, in the present embodiment, all CSL grain boundaries are represented by Σ3-29 type grain boundaries, and the length L _R3 of Σ3 type grain boundaries in the α-Al ₂ O ₃ layer on the rake face side is The length L of the _界 3-29 type grain boundary in the α-Al ₂ O ₃ layer on the rake face side is defined as more than 80% of R _{3-29 and} the _{Σ 3} type grain in the α-Al ₂ O ₃ layer on the flank side The length L _F3 of the field is defined as more than 80% of the length L _R3-29 of the 3−3-29 type grain boundary in the α-Al ₂ O ₃ layer on the flank side.

The length L _R3 indicates the total length of Σ3 type grain boundaries in the field of view observed when observing the α-Al ₂ O ₃ layer on the rake face side with an EBSD-provided SEM, and the length L _R3-29 is a Σ3 type grain boundary, a 77 type grain boundary, Σ11 in a field of view observed when the α-Al ₂ O ₃ layer on the rake surface side is observed using an EBSD-provided SEM. It shows the total length of the respective types of crystal grain boundary, 1717 crystal grain boundary, 1919 crystal grain boundary, 2121 crystal grain boundary, Σ23 crystal grain boundary, and Σ29 crystal grain boundary. Similarly, the length L _F3 indicates the total length of Σ3 type grain boundaries in the observed field of view when the α-Al ₂ O ₃ layer on the flank side is observed with an EBSD-provided SEM. In the case of _observing the α-Al ₂ O ₃ layer on the flank side with the EBSD, the L ₃ type crystal grain boundary, Σ 7 type crystal in the field of view, when the length L _{F 3-29} is the _observation on the _flank surface side The total lengths of the grain boundary, 、 11 type crystal grain boundary, Σ17 type crystal grain boundary, Σ19 type crystal grain boundary, Σ21 type crystal grain boundary, Σ23 type crystal grain boundary, and Σ29 type crystal grain boundary are shown.

The length L _R3 is more preferably 83% or more of the length L _R3-29 , and still more preferably 85% or more. The same applies to the length L _F3 , more preferably 83% or more of the length L _F3-29 , and still more preferably 85% or more. Thus, the higher the numerical value, the better. The upper limit need not be defined, but the upper limit is 99% or less from the viewpoint of being a polycrystalline thin film.

On the other hand, since this 33 type grain boundary is a grain boundary having high consistency as apparent from the fact that it has low grain boundary energy, the 界 3 type grain boundary is a grain boundary 2 One grain has a single crystal or twin-like behavior and tends to be coarsened. When the crystal grains are coarsened, the film characteristics such as chipping resistance deteriorate, so it is necessary to suppress the coarsening. Therefore, in the present embodiment, the lengths L _R3 and L _F3 of Σ3 type crystal grain boundaries are the total of all grain boundaries in the α-Al ₂ O ₃ layer positioned on any of the rake face and the flank face. The length L _R , L _F is defined to be 10% or more and 50% or less, and the above-described suppression effect is secured.

If the lengths L _R3 and L _F3 of the 33 type grain boundaries exceed 50% of the total length L _R and L _F of the entire grain boundaries on each side, the grains are coarsened, which is not preferable. If it is less than 10%, the above excellent mechanical properties can not be obtained. A more preferable range of the lengths L _R3 and L _F3 of Σ3 type crystal grain boundaries is 20 to 45%, and a further preferable range is 30 to 40%.

The term "whole grain boundary" refers to the sum of general grain boundaries other than CSL grain boundaries and CSL grain boundaries. Thus, "total length L _R of Zentsubukai" on the rake face side, be expressed as "Σ3-29 type sum of grain boundary length L _R3-29 and general grain boundary length L _RG" can, "total length L _F of Zentsubukai" on the flank face side, be expressed as "the sum of Σ3-29 type crystal grain boundary length L _F3-29 and general grain boundary length L _FG" it can.

The above (4) will be described. Above _{(4) α-Al 2 O} 3 layer satisfying, in α-Al ₂ O ₃ layer on the rake face side, a relatively large proportion of Σ3 type crystal grain boundaries of the CSL grain boundaries, the flank side In the α-Al ₂ O ₃ layer, the proportion of Σ 3 -type grain boundaries among CSL grain boundaries is relatively small. Therefore, the α-Al ₂ O ₃ layer satisfying the above (2) and (3) and further satisfying the above (4) is particularly excellent in plastic deformation resistance on the flank side and Σ3 type crystal on the rake side It is possible to sufficiently suppress the deterioration of film properties such as chipping resistance caused by too many grain boundaries.

In cutting under high-speed conditions and low-feed conditions (hereinafter also referred to as "high-speed low-feed cutting"), the heat load on the flank side is large, and wear on the flank tends to increase. On the other hand, if it is an α-Al ₂ O ₃ layer satisfying the above (2) to (4), it can withstand the load applied to the flank side, and severe cutting conditions are particularly encountered on the flank side. Long life can be maintained even in high speed / low feed cutting.

The difference {(L _R3 / L _{R3 -29} )-(L _F3 / L _{F3 -29} )} between the ratio L _R3 / L _R3-29 and the ratio L _F3 / L _F3-29 is -1 to _-10. Is preferred. In this case, the balance between the improvement of the chipping resistance on the rake surface side and the improvement of the plastic deformation resistance on the flank surface side is excellent. The difference is more preferably -4 to -9. In order to satisfy such a difference, the length L _R3 of the 33 type grain boundary is preferably ₈₀ to 95% of the length L _R3-29 of the 3−3-29 type grain boundary, and 83 to 95. % Is more preferable, and 80 to 90% is particularly preferable. The length L _F3 of the 33 type crystal grain boundary is 90 to 99% of the length L _F3-29 of the Σ3-29 type crystal grain boundary Is preferably, and more preferably 91 to 99%.

In the present embodiment, whether or not the α-Al ₂ O ₃ layer satisfies the above (1) can be confirmed as follows.

First, an α-Al ₂ O ₃ layer is formed on a substrate based on a manufacturing method described later. Then, the formed rake face side α-Al ₂ O ₃ layer (including the base and the like) is cut so as to obtain a cross section perpendicular to the α-Al ₂ O ₃ layer (ie, α-Al ₂ O cut surface obtained by cutting the alpha-Al ₂ O ₃ layer in the plane is cut to expose containing normal to the surface of the _three layers). Thereafter, the cut surface is polished with a water-resistant polishing paper (containing a SiC abrasive abrasive as an abrasive).

Note that the above-mentioned cutting is carried out, for example, on the surface of the α-Al ₂ O ₃ layer surface (when the other layer is formed on the α-Al ₂ O ₃ layer, the film surface is made large) on the holding flat plate. Fixed closely using wax etc., and then cutting in a direction perpendicular to the flat plate with a rotary blade cutter (cutting so that the rotary blade and the flat plate are as vertical as possible) 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.

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

Subsequently, the above-mentioned polished surface is further smoothed by ion milling with Ar ions. The conditions for the ion milling treatment are as follows.
Acceleration voltage: 6kV
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 in the cut surface)
Irradiation time: 6 hours.

Further, the position of the cutting is set so as to avoid at least the vicinity of the blade edge 3. Specifically, with reference to FIG. 3, the outer edge A ₁ of the area and the rake face 1 is in contact (indicated by a dotted line extending in the FIG. 3, left and right) surfaces in contact with the rake face 1, in contact with the flank 2 faces ( A region connecting the upper and lower dotted lines in FIG. 3 and the outer edge A _{2 of the} region in contact with the flank 2 is regarded as the cutting edge ridge portion 3, and at least from the outer edge A ₁ which is the end portion of the cutting edge ridge portion 3 0.2mm or more away position (position away from the outer edge a ₁ to the left in FIG. 3), applied as making the position of the cross section. Similarly, in the cross section on the flank 2 side of the α-Al ₂ O ₃ layer, a position spaced 0.2 mm or more from the outer edge A ₂ which is the end of the cutting edge 3 (from the outer edge A ₂ to the lower side in FIG. The remote position) is applied as a cross-sectional production position.

  The smoothed polished surface is then observed with a SEM equipped with EBSD. The SEM uses a Zeiss Supra 35 VP (made by CARL ZEISS) equipped with a HKL NL02 EBSD detector. EBSD data is collected in turn by placing focused electron beams individually on each pixel.

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

Then, using a commercially available software (trade name: “orientation imaging microscopy Ver 6.2”, manufactured by EDAX), the normal direction of the (001) plane of each measurement pixel and the α-Al ₂ O ₃ layer surface (coated surface side calculating an angle between a straight line direction) is parallel to the thickness direction of the normal direction (i.e. α-Al ₂ O ₃ layer in the該切section of the surface) which is located, and the angle is within ± 20 ° Create a color map so that the selected pixels are selected.

Specifically, using the “Cristal Direction MAP” method included in the above software, the Tolerance 20 ° between the normal direction of the α-Al ₂ O ₃ layer surface and the normal direction of the (001) plane of each measurement pixel Create a color map (where the direction difference is within ± 20 °). Then, by calculating the area ratio of the above-mentioned pixels based on this color map, when the area ratio becomes 50% or more, “the α-Al ₂ O ₃ layer on the rake surface shows (001) orientation” It shall be.

Likewise, α-Al ₂ O ₃ layer of flank side (001) checks whether showing the orientation. And (001) orientation is shown in the α-Al ₂ O ₃ layer on either side, that is, the normal direction to the (001) plane is located on the surface of the α-Al ₂ O ₃ layer (the surface side of the film When it is confirmed that the ratio of crystal grains (α-Al ₂ O ₃ ) within ± 20 ° with respect to the normal direction of the surface) is 50% or more, the α-Al ₂ O ₃ layer is It will satisfy the above (1).

Further, in the present embodiment, each of the r-side α-Al ₂ O ₃ layer and the flank-side α-Al ₂ O ₃ layer satisfies the above (2) and (3), and further, these satisfy the above (4) It can be confirmed as follows whether it is filled or not.

First, as described above with a cross-section perpendicular to the α-Al ₂ O ₃ layer in the same manner to obtain, after cutting the α-Al ₂ O ₃ layer on the rake face side, the polishing and smoothing processing also in the same manner Do. Then, the section processed in this way is observed with a SEM equipped with the same EBSD as described above.

The normal to the sample plane (cross section of the smoothed α-Al ₂ O ₃ layer) is inclined 70 ° with respect to the incident beam and the analysis is performed at 15 kV. A pressure of 10 Pa is applied to avoid the charging effect. The high current mode is used in combination with the aperture diameter of 60 μm or 120 μm. Data collection is performed in steps of 0.1 μm / step on 500 × 300 points corresponding to a surface area of 50 × 30 μm on the polishing 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). Taking into account the tolerances from the theoretical values of the experimental values (D. Brandon Acta metall), using the Brandon criterion (ΔΘ <Θ ₀ ()) ^-0.5 , where Θ ₀ = 15 °) .14 (1966), 1479-1484). It can be confirmed by counting special grain boundaries corresponding to any Σ value and expressing it as a ratio to all grain boundaries.

By the above, the α-Al ₂ O ₃ layer on the rake face side, the length of the Σ3 type crystal grain boundary _{L R3, Σ3-29} type crystal grain boundary length _{L R3-29,} and the sum of Zentsubukai _{L R} You can determine the length. Similarly, the length of the Σ3 type crystal grain boundaries in α-Al ₂ O ₃ layer of flank side _{L F3, Σ3-29} type crystal grain boundary length _{L F3-29,} and the sum of Zentsubukai _{L F} You can determine the length. From the determined values, it can be confirmed whether the rake face side α-Al ₂ O ₃ layer and the flank side α-Al ₂ O ₃ layer satisfy the above (2) and (3), and further It can be confirmed whether or not the α-Al ₂ O ₃ layer satisfies the above (4).

<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-mentioned excellent effects can be exhibited. The thickness is more preferably 2 to 15 μm, and further preferably 2 to 10 μm.

When the thickness is less than 2 μm, the above-mentioned excellent effects may not be exhibited sufficiently, and when it exceeds 20 μm, the coefficient of linear expansion between the α-Al ₂ O ₃ layer and other layers such as the underlayer. interfacial stress increases due to the difference, the crystal grains of α-Al ₂ O ₃ is sometimes fall off. Such thickness can be confirmed by observation of the vertical cross section of the substrate and the film 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 cutting edge of the tool is reduced, and not only chipping resistance is improved, but also stable chip discharging performance can be exhibited. The surface roughness Ra is more preferably less than 0.15 μm, and still more preferably less than 0.10 μm. Thus, the surface roughness Ra is preferably as low as possible, and it is not necessary to define the lower limit, but the lower limit is 0.05 μm or more from the viewpoint that the film is affected by the surface properties of the substrate.

  In the present application, surface roughness Ra means arithmetic mean roughness Ra in accordance with JIS B 0601 (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 compressive stress is maximum in a region within 2 μm from the surface side of the coating, and the absolute value of compressive stress at this point is preferably less than 1 GPa. Thereby, the sudden loss of the cutting edge accompanying mechanical and thermal fatigue of the tool cutting edge which occurs at the time of intermittent cutting is suppressed, and the labor saving / energy saving effect can be exhibited. The absolute value is more preferably less than 0.9 GPa, 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 the balance between wear resistance and chipping resistance.

The compressive stress in the present embodiment can be measured by a conventionally known method such as a sin ² ψ method using an X-ray, a constant penetration depth method, or the like.

<TiC _x N _y layer>
Coatings of the present embodiment may include TiC _x N _y layer between the substrate and the α-Al ₂ O ₃ layer. The TiC _x N _y layer preferably contains TiC _x N _y satisfying 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 still more preferably 0.67 ≦ x / (x + y) ≦ 0.72. If x / (x + y) is less than 0.6, the abrasion resistance may be insufficient, and if 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 (CVD) method. When a layer other than the α-Al ₂ O ₃ layer is formed among the films, those layers can be formed using a chemical vapor deposition apparatus under conventionally known conditions. On the other hand, the α-Al ₂ O ₃ layer can be formed as follows.

AlCl ₃ , HCl, CO ₂ , H ₂ S, O ₂ and H ₂ are used as source gases. The compounding amount is ₃ to 5% by volume of AlCl ₃ , 4 to 6% by volume of HCl, 0.5 to 2% by volume of CO ₂ , 1 to 5% by volume of H ₂ S, 0.0001 to 0 of O ₂ .01 volume%, and the remainder is H ₂ . Furthermore, a volume ratio of 0.1 ≦ CO ₂ / H ₂ S ≦ 1, 0.1 ≦ CO ₂ / AlCl ₃ ≦ 1, 0.5 ≦ AlCl ₃ / HCl ≦ 1 is adopted.

  The raw material gas is sprayed to the base material disposed in the reaction vessel of the chemical vapor deposition apparatus, and the ejection direction of the raw material gas at this time is that the flank of the base material is against the ejection direction of the raw material gas It becomes substantially vertical, and it adjusts so that the rake face of a substrate may become substantially parallel to the ejection direction of source gas. Further, conditions of the chemical vapor deposition method are a temperature of 950 to 1050 ° C., a pressure of 1 to 5 kPa, and a gas flow rate (total gas amount) of 50 to 100 L / min. Further, the introduction rate of the source gas into the reaction container is set to 1.7 to 3.5 m / sec.

Then, after an α-Al ₂ O ₃ layer is once formed by a chemical vapor deposition method under the conditions described above, 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. Further, the atmosphere for this annealing is performed by flowing H ₂ and Ar (argon) at a flow rate of ₂₀ to 30 L / min.

Thus, the α-Al ₂ O ₃ layer of the present embodiment having a desired thickness can be formed. In particular, the compounding amount of O _{2 in} the source gas is in the above range, and the flank surface of the substrate is substantially perpendicular to the ejection direction of the source gas, and the rake surface of the substrate is substantially parallel to the ejection direction of the source gas By adjusting the ejection direction of the source gas so as to satisfy the above, it is possible to form an α-Al ₂ O ₃ layer satisfying the above (2) to (4). The reason is presumed as follows.

O ₂ is highly reactive as compared with other gases such as CO ₂ , and has the functions of increasing the number of nuclei of α-Al ₂ O ₃ and increasing the deposition rate. In addition, O ₂ can also have the function of reducing the proportion of Σ 3 -type grain boundaries in CSL grain boundaries. This is because, if the deposition rate is too fast, Σ3 type crystal grain boundaries, which are crystal grain boundaries having high consistency, are not easily generated.

  By the way, on the rake surface side which is substantially parallel to the ejection direction of the source gas, the flow velocity density of the source gas tends to be relatively high, and on the flank side which is substantially perpendicular to the ejection direction of the source gas. The flow velocity density of the source gas tends to be relatively low. That is, on the rake face side, the residence time of the raw material gas becomes shorter, and on the flank side, the residence time of the source gas tends to be longer, in other words, the rake face side is compared with the flank side. The source gas tends to be supplied more frequently.

Therefore, apparently, adsorption and diffusion of O ₂ on the rake surface side occur more frequently than adsorption and diffusion of O _{2 on} the flank surface side, which causes the action of O ₂ on the rake surface side. The reduction of Σ3 type crystal grain boundaries is caused, and as a result, the ratio of Σ3 type crystal grain boundaries on the flank side becomes larger than that on the rake face side.

Also it is possible to prevent the impurities such as sulfur in α-Al ₂ O ₃ layer in by annealing as described above after film formation remains, as a manufacturing method of α-Al ₂ O ₃ layer of the present embodiment It is particularly excellent.

  Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited thereto.

<Preparation of base material>
Two types of substrates, substrate P and substrate K described in Table 1 below, were prepared. Specifically, the raw material powder having the composition described in Table 1 is uniformly mixed, pressure-formed into a predetermined shape, and sintered at 1300 to 1500 ° C. for 1 to 2 hours to obtain a shape of CNMG 120408 NUX. A base material made of cemented carbide (made by Sumitomo Electric Industries, Ltd.) was obtained.

<Formation of film>
A film was formed on the surface of each of the substrates obtained above. Specifically, a film was formed on a substrate by a chemical vapor deposition method by setting the substrate in a chemical vapor deposition apparatus. The substrate was placed in the reaction vessel so that the rake face was substantially parallel to the gas ejection direction and the flank face was substantially orthogonal to the gas ejection direction.

The conditions for forming the film are as described in Tables 2 and 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 ones correspond to the respective layers in Table 5 excluding the α-Al ₂ O ₃ layer. Further, TiC _x N _y layers are those atomic ratio x / (x + y) consists of TiC _x N _y is 0.7.

Further, as shown in Table 3, the formation conditions of the α-Al ₂ O ₃ layer are ten ways of A to G and X to Z, among which A to G are the conditions of the example, and X to Z are It is the conditions of a comparative example (prior art). In the formation of the α-Al ₂ O ₃ layer, the introduction rate of the source gas was 2 m / sec, and while fixing the substrate, the gas pipe for emitting the source gas was rotated at 2 rpm. Note that only the α-Al ₂ O ₃ layer of the embodiment are formed under the conditions of A-G, while the annealing time as described in Table 3, 1050 ° C., 50 kPa, flow rate 20L / min of H _2, the flow rate of Ar Annealing was performed under the conditions of 30 L / min.

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

Each layer other than the α-Al ₂ O ₃ layer described in Table 2 was similarly formed by the chemical vapor deposition except that annealing was not performed. The “remaining” in Table 2 indicates that H ₂ occupies the remaining portion of the source gas. Further, “total gas amount” refers to the total volume flow rate introduced into the chemical vapor deposition apparatus per unit time with the gas in the standard state (0 ° C., 1 atm) as an ideal gas (α − in Table 3) The same applies to the Al ₂ O ₃ layer). In addition, the thickness of each layer was adjusted by appropriately adjusting the film formation time (the film formation rate of each layer is about 0.5 to 2.0 μm / hour).

<Preparation of surface-coated cutting tools>
By forming a film on the substrate under the conditions of Table 2 and Table 3 above, surface-coated cutting tools of Examples 1 to 15 and Comparative Examples 1 to 6 shown in Table 4 and Table 5 below were produced. .

Regarding Table 4 and Table 5, the composition and thickness of each film are confirmed by SEM-EDX (scanning electron microscope-energy dispersive X-ray spectroscopy), and the length of Σ3 type grain boundary of α-Al ₂ O ₃ layer The length of the Σ3-29 type grain boundary and the total length of the whole grain boundary were confirmed by the method described above. Further, regarding the α-Al ₂ O ₃ layer on the rake surface side and the flank surface side, the normal direction to the (001) surface is the surface of the α-Al ₂ O ₃ layer (the surface located on the coating surface side) The ratio (%) of crystal grains (α-Al ₂ O ₃ ) within ± 20 ° with respect to the normal direction of

For example, referring to Table 4, the surface-coated cutting tool of Example 1 employs the base material P described in Table 1 as a base material, and a 1.2 μm thick TiN layer as a base layer on the surface of the base material P A TiC _x N _y layer of 13.0 μm in thickness is formed on the underlayer under the conditions of Table 2 and a Ti BNO layer of 0.7 μm in thickness as an intermediate layer on the TiC _x N _y layer. Is formed under the conditions of Table 2, and an α-Al ₂ O ₃ layer having a thickness of 8.6 μm is formed on the intermediate layer under the forming conditions of Table 3. Thereafter, a TiN layer having a thickness of 0.9 μm is formed as the outermost layer. It shows that it is the structure which formed the film with a total thickness of 24.3 micrometers on the base material by forming on 2 conditions. In addition, the blank in Table 4 shows that the corresponding layer is not formed.

Further, referring to Table 5 relates to Example 1, the α-Al ₂ O ₃ layer on the rake face side, the length of the Σ3 type crystal grain boundary _{L R3,} the length of Σ3-29 type crystal grain boundary _{L R3} 89% of ₋₂₉ , and 17% of the total length L _R of the whole grain boundary. Further, in the α-Al ₂ O ₃ layer on the flank side, the length L _F3 of the 33 type grain boundary is 94% of the length L _F3-29 of the 3−3-29 type grain boundary, and the whole grain boundary Total length L _F of 20%. Also, the ratio (%) of the ratio (L _R3 / L _R3-29 ) to the ratio (%) of (L _F3 / L _F3-29 ) is “(L _R3 / L _{R3 −29} )-(L _F3 Although it is shown in the column of "/ L _F3-29 )", it is understood that the ratio L _R3 / L _R3-29 is smaller than the ratio L _F3 / L _F3-29 because this value is "-". Furthermore, this α-Al ₂ O ₃ layer exhibits (001) orientation on the rake face side and the flank face side.

Incidentally, since the all α-Al ₂ O ₃ layers of Comparative Examples 1 to 6 are formed in the prior art conditions that do not comply with the method of the present invention, those α-Al ₂ O ₃ layer, as in the present invention Of the crystalline structure which does not show any characteristic (see Table 5).

<Cutting test>
The following two types of cutting tests were performed using the surface-coated cutting tool obtained above. The following cutting tests are similar to high speed low feed cutting.

<Cutting test 1>
With respect to 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 is measured according to the following cutting conditions and the final damage form of the cutting edge Observed. The results are shown in Table 6. The longer the cutting time, the better the wear resistance and the longer the tool life.

<Cutting conditions>
Work material: SCM 435 round bar peripheral cutting speed: 400 m / min
Feeding speed: 0.1 mm / rev
Depth of cut: 1.0 mm
Cutting fluid: Yes.

  As apparent from Table 6, the surface-coated cutting tool of the example is superior to both of the wear resistance and chipping resistance as compared with the surface-coated cutting tool of the comparative example, and the tool life is prolonged it is obvious. That is, it has been confirmed that the mechanical properties of the film of the surface-coated cutting tool of the example are improved.

<Cutting test 2>
With respect to the surface-coated cutting tools of the examples and comparative examples described in Table 7 below, the cutting time until the crater wear amount (Kt) reaches 0.20 mm was measured according to the following cutting conditions. The results are shown in Table 7. The longer the cutting time, the better the wear resistance and the longer the tool life.

<Cutting conditions>
Work material: S55C round bar peripheral cutting speed: 300m / min
Feeding speed: 0.05 mm / rev
Depth of cut: 2.0 mm
Cutting fluid: Yes.

  As apparent from Table 7, the surface-coated cutting tool of the example is excellent in fracture resistance as compared with the surface-coated cutting tool of the comparative example, and it is clear that the tool life is prolonged. That is, it has been confirmed that the mechanical properties of the film of the surface-coated cutting tool of the example are improved.

<Confirmation of Effect of Surface Roughness Ra of α-Al ₂ O ₃ Layer>
The surface roughness Ra of the α-Al ₂ O ₃ layer was measured according to JIS B 0601 (2001) for the surface-coated cutting tools of Example 1, Example 2, and Example 11. The results are shown in Table 10.

Subsequently, the surface-coated cutting tools of Example 1A, Example 2A, and Example 11A are obtained by performing the aerowrap treatment of the following conditions on the α-Al ₂ O ₃ layer of each of the above-described surface-coated cutting tools. Was produced. Then, for each of these surface-coated cutting tool, 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 10.

<Conditions for aero wrap processing>
Media: Elastic rubber media with a diameter of about 1 mm containing diamond abrasive grains with an average particle diameter of 0.1 μm (trade name: "Multicon", manufactured by Yamashita Works Inc.)
Projection pressure: 0.5 bar
Projection time: 30 seconds wet / dry: dry.

  And about the surface covering cutting tool of these Examples 1, 1A, 2, 2A, 11, and 11A, the cutting time until the flank wear amount (Vb) becomes 0.20 mm was measured according to the following cutting conditions . The results are shown in Table 8. The longer the cutting time, the lower the coefficient of friction between the chips and the cutting edge of the tool, which indicates that stable chip discharging performance can be exhibited.

<Cutting conditions>
Work material: SS400 round bar peripheral cutting speed: 300 m / min
Feeding speed: 0.1 mm / rev
Depth of cut: 1.0 mm
Cutting fluid: None.

As apparent from Table 8, the surface-coated cutting tools of Examples 1A, 2A, and 11A provided with an α-Al ₂ O ₃ layer having a surface roughness Ra of less than 0.2 μm exhibited a surface roughness of 0.2 μm or more. As compared with the surface-coated cutting tools of Examples 1, 2 and 11 provided with an α-Al ₂ O ₃ layer having a thickness Ra, the coefficient of friction between chips and the cutting edge of the tool is reduced, and chip discharge is stable. It has been confirmed that it is possible to demonstrate the nature.

<Confirmation of the effect of compressive stress application of 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 It confirmed that the absolute value of the stress at that point was measured. The results are shown in Table 11 ("stress value" section). The stress measurement is carried out by the sin ² ψ method using X-rays, and in the “stress value” section of Table 11, the numerical values indicate absolute values, tensile stress is “tensile”, compressive stress is “compression”. And written.

Next, wet blasting is performed on the α-Al ₂ O ₃ layer of each surface-coated cutting tool described above to obtain Example 1B, Example 1C, Example 2B, Example 2C, and Example 2C, respectively. A surface-coated cutting tool of Example 11B was produced. Then, for each of these surface-coated cutting tools, it is confirmed that there is a point where the absolute value of stress is maximum in the region within 2 μm from the surface side of the coating in the α-Al ₂ O ₃ layer in the same manner as above. And the absolute value of the stress at that point was measured. The results are shown in Table 11 ("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 blast treatment.

<Conditions of wet blasting treatment>
Media: Alumina Media (φ 50 μm)
Projection pressure: 1 to 2 bar
Projection time: 10 seconds wet / dry: wet.

  And about the surface covering cutting tool of these Examples 1, 1B, 1C, 2, 2B, 2C, 11, and 11B, the cutting time until a tool loses was measured by the following cutting conditions. The results are shown in Table 9. It indicates that the longer the cutting time, the smaller the loss of the cutting edge of the tool due to mechanical and thermal fatigue occurring during the intermittent cutting, and as a result, the reliability of the cutting edge is improved.

<Cutting conditions>
Work material: SUS304 (60 ° × 3 groove outer periphery cutting)
Speed: 250 m / min
Feeding speed: 0.05 mm / rev
Depth of cut: 1.0 mm
Cutting fluid: None.

As is apparent from Table 9, in the α-Al ₂ O ₃ layer, the region within 2 μm from the surface side of the film includes a point where the absolute value of stress is maximum, and the stress at that point is tensile stress, If the absolute value is less than 1 GPa compressive stress, chipping of the cutting edge of the tool due to mechanical and thermal fatigue caused during intermittent cutting is suppressed, and as a result, the reliability of the cutting edge is improved. Was confirmed.

  Although the embodiments and examples of the present invention have been described above, it is also originally intended from the beginning that the configurations of the above-described embodiments and examples are appropriately combined or variously modified.

  It should be understood that the embodiments disclosed herein are illustrative in all respects and not restrictive. The scope of the present invention is shown not by the embodiments described above but by the scope of claims, and is intended to include meanings equivalent to the scope of claims and all modifications within the scope.

  1 rake face, 2 flank face, 3 edge ridge, 10 tools, 11 base materials, 11a scoop face, 11b flank, 11c edge ridge, 12 coating.

Claims (4)

A surface coated cutting tool having a rake face and a flank face, wherein
A substrate, and a film formed on the substrate,
The coating comprises an α-Al ₂ O ₃ layer,
The α-Al ₂ O ₃ layer includes a plurality of crystal grains of α-Al ₂ O ₃ ,
The grain boundaries of the crystal grains include CSL grain boundaries and general grain boundaries,
The α-Al ₂ O ₃ layer on the rake face side shows (001) orientation,
In α-Al ₂ O ₃ layer of the rake face side, the length LR3 of Σ3 type crystal grain boundaries of the CSL grain boundaries is 80% of the length LR3-29 of Σ3-29 type crystal grain boundaries, And 10% or more and 50% or less of the total length LR of the whole grain boundary which is the sum of the length LR3-29 and the length of the general grain boundary LRG,
The flank side α-Al ₂ O ₃ layer exhibits a (001) orientation,
In the α-Al ₂ O ₃ layer on the flank side, the length LF3 of Σ3 type crystal grain boundaries among CSL grain boundaries is more than 80% of the length LF3-29 of Σ3-29 type crystal grain boundaries, And 10% or more and 50% or less of the total length LF of the whole grain boundary which is the sum of the length LF3-29 and the length LFG of the general grain boundary,
A ratio LR3 / LR3-29 between the length LR3 and the length LR3-29 is smaller than a ratio LF3 / LF3-29 between the length LF3 and the length LF3-29,
The (001) orientation indicates that the crystal of the α-Al ₂ O _{3 has} a direction normal to the (001) plane within ± 20 ° with respect to the direction normal to the surface of the α-Al ₂ O ₃ layer. It is a manufacturing method of a surface covering cutting tool which says the case where the ratio of a grain becomes 50% or more in the above-mentioned alpha-Al ₂ O ₃ layer,
A first step of forming the α-Al ₂ O ₃ layer by a chemical vapor deposition method;
And _b) annealing the formed α-Al ₂ O ₃ layer.
In the first step, AlCl ₃ , HCl, CO ₂ , 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, and the gas flow rate Is performed under the condition of 50 to 100 L / min.
The method of producing a surface-coated cutting tool, wherein the second step is performed under the conditions of a temperature of 1050 to 1080 ° C., a pressure of 50 to 100 kPa, and a time of 120 to 300 minutes. The raw material gas, the AlCl ₃ 3 to 5% by volume, HCl 4-6% by volume, the CO ₂ 0.5 to 2 vol%, the H ₂ S 1 to 5 vol%, 0.0001 to O ₂ The method for producing a surface-coated cutting tool according to claim 1, wherein the amount is 0.01% by volume, and the balance is H ₂ . The raw material gas is used at a volume ratio of 0.1 ≦ CO ₂ / H ₂ S ≦ 1, 0.1 ≦ CO ₂ / AlCl ₃ ≦ 1, 0.5 ≦ AlCl ₃ / HCl ≦ 1. method for manufacturing a surface-coated cutting tool according to. The method for manufacturing a surface-coated cutting tool according to any one of claims 1 to 3, wherein the second step is performed in an atmosphere in which H ₂ and Ar flow at a flow rate of ₂₀ to 30 L / min.

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