JP2017071044A - Surface cover cutting tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent roughly expansion of crystal grain and generation of crack on coat during cooling.SOLUTION: A surface cover cutting tool comprises a substrate and coat formed on the substrate. The coat comprises α-AlOlayer containing a plurality of α-AlOcrystal grains. The α-AlOlayer includes lower layer part arranged at substrate side, middle section part arranged on the lower layer part, and upper layer part arranged on the middle section. In crystal orientation mapping using an electron backscatter diffraction apparatus on to sectional polishing surface of the α-AlOlayer, the lower layer part has 35% or less of area ratio of α-AlOcrystal grain having (001) direction, the middle section has 35% or more of area ratio of α-AlOcrystal grain having (001) direction, and the upper layer part has 35% or less of area ratio of α-AlOcrystal grain having 001) direction. The thickness of the α-AlOlayer is 4 to 18 μm. The thickness of the middle section occupies 50% or more of thickness in the α-AlOlayer. The thickness of both of the lower layer part and the upper layer part is 1 μm or more.SELECTED DRAWING: None

Description

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

Conventionally, a surface-coated cutting tool in which a film is formed on a substrate has been used. For example, in JP2013-063504A (Patent Document 1), a Ti compound layer is used as a lower layer, and an upper layer made of an Al ₂ O ₃ layer having an α-type crystal structure is disposed on the lower layer. Surface-coated cutting tools having a coating have been proposed. In particular, this surface-coated cutting tool has a configuration in which the (11-20) orientation at the interface between the upper layer and the lower layer is 30 to 70 area%, and the (0001) orientation in the entire upper layer is 45 area% or more. Has been. On the other hand, there is no disclosure about the distribution of (001) orientation in the depth direction of the α-Al ₂ O ₃ layer.

Japanese Patent Application Laid-Open No. 10-204439 (Patent Document 2) is composed of two or more α-type aluminum oxide unit layers exhibiting different X-ray diffraction patterns, and the α-type aluminum oxide unit layer is 25.5 degrees at 2θ. , 35.5 degrees, 37.2 degrees, and 68.4 degrees, the strongest peak appears, and the second peak height (H ₂ ) in the same X-ray diffraction pattern as the strongest peak height (H ₁ ) Cutting tool made of surface-coated cemented carbide comprising a hard coating layer composed of an α-type aluminum oxide composite layer exhibiting an X-ray diffraction pattern with a ratio (H ₁ ) / (H ₂ ) of 1.5 to 2.7 Has been proposed.

  Japanese Patent Laid-Open No. 2000-218410 (Patent Document 3) is composed of a lower layer having a high crystal orientation and an upper layer having a low crystal orientation, and the thickness of the upper layer is 10 to 40 in a ratio to the total of the lower layer. A surface-coated cemented carbide cutting tool having a hard coating layer including an aluminum oxide layer having an α-type crystal structure with a layer thickness corresponding to% is proposed.

JP 2013-063504 A JP 10-204639 A JP 2000-218410 A

As proposed in Patent Documents 1 to 3 above, by improving the film quality of α-Al ₂ O ₃ , the performance of cutting tools made of cemented carbide is improved, particularly crater wear resistance and chipping resistance are improved. It is expected that. However, regarding film quality improvement, as long as attention is paid to the orientation of Al ₂ O ₃ crystal grains in a specific direction as in Patent Document 1, the effect of improving the film strength can be obtained, but various problems are included. Will be.

For example, the (001) orientation of α-Al ₂ O ₃ crystal grains tends to have a higher coefficient of thermal expansion in the direction parallel to the substrate surface, so that there are many cracks in the coating during cooling after film formation. May occur. In addition, (001) -oriented α-Al ₂ O ₃ crystal grains grow under high-speed conditions, so that the crystal grains may become coarse and wear resistance may be reduced. On the other hand, as long as the film including a plurality of crystal grains of Al ₂ O _{3 having} different orientations is focused as in Patent Documents 2 and ₃ , α oriented in a specific direction (for example, (001) plane direction) since the grain fraction of -al ₂ O ₃ decreases, it becomes difficult to obtain the effect of improving the film strength sufficiently.

  The present invention has been made in view of the above circumstances and is a surface-coated cutting tool capable of preventing the coarsening of crystal grains and preventing the occurrence of cracks in the coating during cooling after sufficiently obtaining the effect of improving the film strength. The purpose is to provide.

The surface-coated cutting tool according to an aspect of the present invention includes a base material and a coating formed on the base material, and the coating includes α-Al containing a plurality of α-Al ₂ O ₃ crystal grains. include ₂ O ₃ layer, said the alpha-Al ₂ O ₃ layer, a lower layer portion disposed on the substrate side, and an intermediate portion disposed on the lower layer portion on the upper layer disposed on the intermediate portion In the crystal orientation mapping using an electron beam backscattering diffractometer with respect to the cross-sectional polished surface of the α-Al ₂ O ₃ layer, the lower layer portion is a (001) -oriented α-Al ₂ O ₃ crystal The area ratio of the grains is less than 35%, and the intermediate portion has an area ratio of the (001) -oriented α-Al ₂ O ₃ crystal grains of 35% or more in the crystal orientation mapping, In the crystal orientation mapping, the area ratio of the (001) -oriented α-Al ₂ O ₃ crystal grains is less than 35%, The thickness of the α-Al ₂ O ₃ layer is 4 to 18 μm, the thickness of the intermediate portion occupies 50% or more of the thickness of the α-Al ₂ O ₃ layer, and the lower layer portion and the upper layer portion Each thickness is 1 μm or more.

  According to the above, after sufficiently obtaining the effect of improving the film strength, it is possible to prevent the crystal grains from becoming coarse and to prevent the coating from cracking during cooling.

[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 includes a base material and a coating film formed on the base material, and the coating film includes a plurality of α-Al ₂ O ₃ crystal grains. an α-Al ₂ O ₃ layer, the α-Al ₂ O ₃ layer being disposed on the intermediate portion, a lower layer portion disposed on the substrate side, an intermediate portion disposed on the lower layer portion, and The lower layer portion is formed of (001) -oriented α-Al ₂ O in crystal orientation mapping using an electron beam backscattering diffractometer with respect to the cross-sectional polished surface of the α-Al ₂ O ₃ layer. ₃ is less than 35%, and the intermediate portion has an area ratio of (001) -oriented α-Al ₂ O ₃ crystal grains of 35% or more in the crystal orientation mapping. In the crystal orientation mapping, the area ratio of the (001) -oriented α-Al ₂ O ₃ crystal grains is less than 35%. The thickness of the α-Al ₂ O ₃ layer is 4 to 18 μm, the thickness of the intermediate portion occupies 50% or more of the thickness of the α-Al ₂ O ₃ layer, and the lower layer portion and the upper layer The thickness of each part is 1 μm or more. With such a configuration, the surface-coated cutting tool can sufficiently obtain the effect of improving the film strength, prevent coarsening of crystal grains, and prevent the coating from cracking during cooling.

[2] In the lower layer part, the area ratio of (110) -oriented α-Al ₂ O ₃ crystal grains is preferably 40% or more in the crystal orientation mapping. Thereby, the effect which suppresses the coarsening of a crystal grain can be heightened.

[3] In the above-mentioned crystal orientation mapping, the upper layer part preferably has an area ratio of (110) -oriented α-Al ₂ O ₃ crystal grains of 40% or more. Thereby, the effect which suppresses the crack generation of the film at the time of cooling can be heightened.

[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 this embodiment includes a base material and a coating film formed on the base material. The coating preferably covers the entire surface of the substrate. However, even if a part of the substrate is not coated with this coating or the configuration of the coating is partially different, it does not depart from the scope of the present invention.

  The surface-coated cutting tool of the present embodiment includes a drill, an end mill, a cutting edge replaceable cutting tip for a drill, a cutting edge replaceable cutting tip for an end mill, a cutting edge replaceable cutting tip for milling, a cutting edge replaceable cutting tip for turning, a metal saw, It can be suitably used as a cutting tool such as a gear cutting tool, reamer, or tap.

<Base material>
Any substrate can be used as long as it is conventionally known as this type of substrate. For example, cemented carbide (for example, WC-based cemented carbide, including WC, including Co or containing carbonitride such as Ti, Ta, Nb), cermet (TiC, TiN, TiCN, etc.) Main 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 Is preferred.

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

  When the surface-coated cutting tool is a blade-tip-exchangeable cutting tip or the like, the substrate includes those having a chip breaker and those having no chip breaker. The edge of the edge of the blade edge is sharp edge (the ridge where the rake face and flank face intersect), honing (the sharp edge is given a radius), negative land (the chamfered), honing and negative land. Any combination of these is included.

<Coating>
The coating includes an α-Al ₂ O ₃ layer containing crystal grains of a plurality of α-Al ₂ O ₃ (aluminum oxide whose crystal structure is α-type). For example, the coating film may be composed of a plurality of layers including one or more α-Al ₂ O ₃ layers including a plurality of α-Al ₂ O ₃ crystal grains and further including other layers. α-Al ₂ O ₃ layer contains the α-Al ₂ O ₃ of containing crystal grains of a plurality of α-Al ₂ O ₃ polycrystal. The crystal grains of α-Al ₂ O ₃ usually have a grain size of about 0.1 to 2 μm.

The coating has a thickness of 4 to 45 μm (4 μm or more and 45 μm or less, and in the present application, when the numerical range is expressed using “˜”, the range includes upper and lower numerical values). Furthermore, the thickness of the coating is preferably 5 to 35 μm. If this thickness is less than 4 μm, the wear resistance may be insufficient. When this thickness exceeds 45 μm, when a large stress is applied between the coating and the substrate in intermittent processing or the like, peeling or destruction of the coating may occur frequently. In the present specification, “thickness” of various films and layers such as a coating, an α-Al ₂ O ₃ layer and a TiCN layer described later mean “average thickness”.

  As the other layers, TiCNO layer, TiBN layer, TiC layer, TiN layer, TiAlN layer, TiSiN layer, AlCrN layer, TiAlSiN layer, TiAlNO layer, AlCrSiCN layer, TiCN layer, TiSiC layer, CrSiN layer, AlTiSiCO layer, TiSiCN layer Etc. can be illustrated. Here, in the present specification, when the compound is represented by a chemical formula as described above, when the atomic ratio is not particularly limited, any conventionally known atomic ratio is included, and is not necessarily limited to the stoichiometric range.

  For example, when “TiAlN” is described, the ratio of the number of atoms constituting TiAlN is not limited to Ti: Al: N = 0.5: 0.5: 1, and any conventionally known atomic ratio is included. The same applies to the description of compounds other than “TiAlN”. In the present embodiment, a metal element such as Ti, Al, Si, Zr, or Cr and a non-metal element such as N (nitrogen), O (oxygen), or C (carbon) are not necessarily stoichiometric. There is no need to constitute the composition.

As an example of another layer, for example, a TiCN layer is disposed between the α-Al ₂ O ₃ layer and the substrate. Since this TiCN layer is excellent in wear resistance, it is possible to impart suitable wear resistance to the coating. The TiCN layer is particularly preferably formed by MT-CVD (medium temperature CVD). The MT-CVD method can form a film at a relatively low temperature of about 850 to 900 ° C., and can reduce damage to the substrate due to heating during film formation.

  The TiCN layer desirably has a thickness of 2 to 20 μm. If this thickness is less than 2 μm, the wear may be likely to proceed. If this thickness exceeds 20 μm, chipping resistance may be reduced.

As other layers, an outermost surface layer, an intermediate layer, and the like can be included in the coating. The outermost surface layer is a layer disposed on the outermost surface side of the coating. The intermediate layer is a layer disposed between the outermost surface layer and the α-Al ₂ O ₃ layer, between the α-Al ₂ O ₃ layer and the TiCN layer, or between the TiCN layer and the substrate. For example, a TiN layer can be exemplified as the outermost surface layer. For example, a TiCNO layer can be exemplified as the intermediate layer.

<Α-Al ₂ O ₃ layer>
The α-Al ₂ O ₃ layer includes a lower layer portion disposed on the base material side, an intermediate portion disposed on the lower layer portion, and an upper layer portion disposed on the intermediate portion.

Lower section, electron backscatter diffraction to its section polishing surface of the α-Al ₂ O ₃ layer (EBSD: Electron Backscatter Diffraction) in the crystal orientation mapping using the apparatus, (001) crystal oriented α-Al ₂ O ₃ The area ratio of the grains is less than 35%.

In the intermediate part, the area ratio of the (001) -oriented α-Al ₂ O ₃ crystal grains is 35% or more in the crystal orientation mapping. In the upper layer portion, the area ratio of (001) -oriented α-Al ₂ O ₃ crystal grains is less than 35% in the above-described crystal orientation mapping.

The surface-coated cutting tool of the present embodiment has a specific direction of the α-Al ₂ O ₃ layer ((001) due to the intermediate portion in which the area ratio of the (001) -oriented α-Al ₂ O ₃ crystal grains is 35% or more. The effect of improving the film strength due to the orientation in the () -plane direction) can be sufficiently obtained. Furthermore, since the area ratio of the (001) -oriented α-Al ₂ O ₃ crystal grains in the lower layer is less than 35%, the α-Al ₂ O ₃ crystal grains can be prevented from becoming coarse and wear-resistant. Deterioration can be suppressed. In addition, since the area ratio of the (001) -oriented α-Al ₂ O ₃ crystal grains in the upper layer portion is less than 35%, it is possible to prevent cracking of the coating during cooling and to suppress a reduction in chipping resistance. can do. That is, by providing such a lower layer portion and an upper layer portion, the α-Al ₂ O ₃ crystal grains, which is a disadvantage that the orientation in the (001) plane direction of the α-Al ₂ O ₃ layer is too high, Generation of cracks in the coating during coarsening and cooling can be suppressed.

Here, “(001) -oriented α-Al ₂ O ₃ crystal grains” refers to the inclination angle of the (001) plane with respect to the normal of the substrate surface (the surface located on the coating surface side) ( An α-Al ₂ O ₃ crystal grain having an angle between the normal of the substrate surface and the (001) plane normal) of 0 to 10 °. Whether or not any α-Al ₂ O ₃ crystal grains are (001) -oriented in the α-Al ₂ O ₃ layer is determined by using a field emission scanning electron microscope (FE-SEM) equipped with an EBSD device. Can be confirmed. EBSD is based on automatic analysis of Kikuchi diffraction patterns generated by backscattered electrons.

For example, using FE-SEM equipped with the EBSD apparatus, a cut surface obtained by cutting the α-Al ₂ O ₃ layer a plane including the normal of the substrate surface (a vertical cross section of the α-Al ₂ O ₃ layer) section A polished surface (the cross-section polished surface is a surface obtained by polishing the cut surface will be described later) is photographed. Next, the normal direction of the (001) plane of each pixel of the photographed image and the normal direction of the substrate surface (that is, a linear direction parallel to the thickness direction of the α-Al ₂ O ₃ layer on the cross-section polished surface) The angle formed by is calculated. Then, a pixel whose angle is within 0 to 10 ° is selected. The selected pixel has α-Al ₂ O ₃ crystal grains with an inclination angle of (001) plane of 0 to 10 ° with respect to the substrate surface, that is, (001) -oriented α-Al ₂ O ₃ . Corresponds to crystal grains.

Then, the area ratio of the (001) -oriented α-Al ₂ O ₃ crystal grains in a predetermined region of the cross-sectional polished surface of the α-Al ₂ O ₃ layer is expressed as α-Al ₂ O of the cross-sectional polished surface as crystal orientation mapping. It is calculated based on a color map created by color-coding the selected pixels for the _three layers. In the crystal orientation mapping, since a predetermined color is given to the selected pixel, the area ratio of the (001) -oriented α-Al ₂ O ₃ crystal grains in a predetermined region is set to the given color. It can be calculated using as an index. Calculation of the angle formed above, selection of a pixel whose angle is within 0 to 10 °, and calculation of the area ratio are performed using commercially available software (trade name: “Orientation Imaging Microscopy Ver 6.2”, manufactured by EDAX). Can be used.

From the above crystal orientation mapping, in this embodiment, the α-Al ₂ O ₃ layer is disposed on the substrate side in the cross-sectional polished surface, and the (001) -oriented α-Al ₂ O ₃ crystal grain area ratio is 35. It is specified that the lower layer part which becomes less than% is included. Further, it is specified to include an intermediate portion that is disposed on this lower layer portion and has an area ratio of (001) -oriented α-Al ₂ O ₃ crystal grains of 35% or more. Furthermore, it is specified that the area ratio of the (001) -oriented α-Al ₂ O ₃ crystal grains disposed on the intermediate portion includes an upper layer portion of less than 35%. In calculating the area ratio of the (001) -oriented α-Al ₂ O ₃ crystal grains, the FE-SEM observation magnification can be appropriately selected from the range of 2000 to 20000 times. In addition, the number of fields of view (about 1 to 10) can be adjusted so that the observation area is 200 to 10,000 μm ² , for example, 250 μm ² .

The lower layer portion preferably has an area ratio of (001) -oriented α-Al ₂ O ₃ crystal grains of 30% or less in the crystal orientation mapping. This is because the coarsening of α-Al ₂ O ₃ crystal grains can be effectively prevented. The intermediate portion preferably has an area ratio of (001) -oriented α-Al ₂ O ₃ crystal grains of 40% or more in the crystal orientation mapping. This is because the effect of improving the film strength can be obtained sufficiently advantageously by orienting in the (001) plane direction. In the above crystal orientation mapping, the upper layer portion preferably has an area ratio of (001) -oriented α-Al ₂ O ₃ crystal grains of 30% or less. This is because cracks in the coating during cooling and use can be effectively prevented.

In the crystal orientation mapping, the lower limit of the area ratio of the (001) -oriented α-Al ₂ O ₃ crystal grains in the lower layer is preferably 0%. The upper limit of the area ratio of the (001) -oriented α-Al ₂ O ₃ crystal grains in the middle is preferably 100%. The lower limit of the area ratio of the (001) -oriented α-Al ₂ O ₃ crystal grains in the upper layer portion is preferably 0%. Each layer portion can obtain the above-described effects within such an area ratio range.

<Thickness of α-Al ₂ O ₃ layer>
The α-Al ₂ O ₃ layer has a thickness of 4 to 18 μm. By setting it as such thickness, abrasion resistance and chipping resistance can be improved. An effect of suppressing welding of the work material can also be obtained. In particular, the thickness of the α-Al ₂ O ₃ layer is preferably 5 to 15 μm. If the thickness of the α-Al ₂ O ₃ layer is less than 4 μm, it is too thin, and there is a possibility that the effect of improving the wear resistance and the effect of suppressing the welding of the work material cannot be obtained. If the thickness of the α-Al ₂ O ₃ layer exceeds 18 μm, the coating is easily peeled off and the chipping resistance may be lowered.

<Ratio of the thickness of the intermediate portion in the thickness of the α-Al ₂ O ₃ layer>
The thickness of the intermediate portion occupies 50% or more of the thickness of the α-Al ₂ O ₃ layer. Thereby, the area ratio of the (001) -oriented α-Al ₂ O ₃ crystal grains in the entire α-Al ₂ O ₃ layer is increased, and the effect of improving the film strength can be sufficiently obtained. The upper limit of the ratio occupied by the thickness of the intermediate portion is 80%. When the upper limit of 80% is exceeded, the thickness of the upper layer portion or the lower layer portion is too thin, and the effect of suppressing the coarsening of the α-Al ₂ O ₃ crystal grains or the effect of suppressing crack generation is sufficiently obtained. There is a risk of being lost. The optimum thickness of the intermediate part is 55 to 65% of the thickness of the α-Al ₂ O ₃ layer.

Here, the thickness of the lower layer portion, the middle portion, and the upper layer portion can be calculated as follows. That is, the EBSD device sequentially from the surface of the α-Al ₂ O ₃ layer (the surface located on the coating surface side) to the substrate along the normal direction of the substrate surface with respect to the cross-section polished surface. The area of 1 × 1 μm is photographed with an FE-SEM equipped with a (001) -oriented α-Al ₂ O ₃ crystal grain area ratio. First, a region where the area ratio of (001) -oriented α-Al ₂ O ₃ crystal grains is less than 35% is specified as an upper layer portion. Subsequently, when a region that is 35% or more appears, the intermediate portion is specified, and when a region that is less than 35% appears again, the lower portion is specified. When the lower layer portion, the middle portion, and the upper layer portion are specified, each of the specified layers on the cross-sectional polished surface is continuously imaged in the 1 × 1 μm range by the above-mentioned FE-SEM at five locations where the specified portions are not biased. The thickness of the part can be determined.

As a result, in the present embodiment, the thickness of the intermediate portion occupies 50% or more of the thickness of the α-Al ₂ O ₃ layer. Furthermore, the thickness of both the lower layer part and the upper layer part is 1 μm or more.

Further, the thickness of the α-Al ₂ O ₃ layer can be measured by observing the cross-section polished surface. For example, the thickness of the α-Al ₂ O ₃ layer is determined using a field emission scanning electron microscope (FE-SEM) equipped with an energy dispersive X-ray spectroscopy (EDS). It can be measured by observing the cross-section polished surface of the ₂ O ₃ layer. Observing the cross section polishing surface of the α-Al ₂ O ₃ layer at a plurality of locations may be determined by calculating the average value of the thickness. In the present embodiment, the α-Al ₂ O ₃ layer has a thickness of 4 to 18 μm.

<Crystal grains of (110) -oriented α-Al ₂ O _{3 in} the lower layer and the upper layer>
In the lower layer portion of the α-Al ₂ O ₃ layer, the area ratio of (110) -oriented α-Al ₂ O ₃ crystal grains is preferably 40% or more in the crystal orientation mapping. The coefficient of thermal expansion of α-Al ₂ O ₃ is high in the normal direction of the (110) plane and low in the parallel direction. For this reason, by making the coefficient of thermal expansion of the lower layer portion relatively low, it is possible to effectively prevent cracking of the coating during cooling, and to advantageously suppress a reduction in chipping resistance. Further, since the α-Al ₂ O ₃ crystal grains are likely to be coarsened under the film forming conditions for obtaining the (001) orientation, an α-Al ₂ O ₃ layer not having the (001) orientation is disposed. It is because it tries to suppress. Thus, the hardness decreases due to crystal grain coarsening of α-Al ₂ O ₃ it is possible to effectively prevent, can be advantageously suppress a decrease in wear resistance.

The upper layer part of the α-Al ₂ O ₃ layer preferably has an area ratio of (110) -oriented α-Al ₂ O ₃ crystal grains of 40% or more in the crystal orientation mapping. Thereby, the crack generation | occurrence | production of the film at the time of use can be prevented effectively, and the fall of chipping resistance can be suppressed advantageously.

  It is considered that as the angle (orientation difference) formed between the crystal planes to be oriented is larger, the crack is less likely to progress and the effect of suppressing chipping of the blade edge can be obtained. Therefore, when crystal grains having an angle between oriented crystal planes of around 90 ° coexist in the layer, there is a possibility that the effect of suppressing crack generation and propagation can be effectively obtained.

The angle formed between the (110) plane of the α-Al ₂ O ₃ crystal grains and the (001) plane is 90 °. Therefore, in the present embodiment, (001) in the lower portion and an upper portion having a grain oriented α-Al ₂ O _3, controlled to have a crystal grain of α-Al ₂ O ₃ oriented (110) Thus, it is possible to obtain the effect of suppressing the generation of cracks and the effect of suppressing the coarsening of crystal grains.

On the other hand, in the middle part of the α-Al ₂ O ₃ layer, the area ratio of the (001) -oriented α-Al ₂ O ₃ crystal grains is 35% or more. The surface-coated cutting tool of this embodiment can sufficiently obtain the effect of improving the film strength due to the orientation of the intermediate portion in the (001) plane direction.

It should be noted that the fact that the area ratio of the (110) -oriented α-Al ₂ O ₃ crystal grains in the lower layer portion and the upper layer portion is 40% or more also indicates that the electrons with respect to the cross-sectional polished surface of the α-Al ₂ O ₃ layer described above It can be measured from crystal orientation mapping using a line backscattering diffractometer. “(110) -oriented α-Al ₂ O ₃ crystal grains” refers to the inclination angle of the (110) plane relative to the normal of the substrate surface (the normal of the substrate surface and the normal of the (110) plane) Α-Al ₂ O ₃ crystal grains having an angle between 0 and 10 °.

That is, using a FE-SEM equipped with an EBSD device, the cross-sectional polished surface of the α-Al ₂ O ₃ layer was photographed, and the normal direction of the (110) plane of each pixel of the photographed image using the above-mentioned commercially available software And calculation of an angle formed by the normal direction of the substrate surface and selection of a pixel whose angle is within 0 to 10 °. Subsequently, as a crystal orientation mapping, the selected pixel is color-coded to create a color map. By using the color of the color map as an index, the area ratio of the (110) -oriented α-Al ₂ O ₃ crystal grains in the lower layer portion and the upper layer portion of the α-Al ₂ O ₃ layer can be calculated.

From the crystal orientation mapping, the area ratio of the (110) -oriented α-Al ₂ O ₃ crystal grains in the lower layer portion and the upper layer portion is specified to be 40% or more, respectively. In calculating the area ratio of (110) -oriented α-Al ₂ O ₃ crystal grains, it is preferable to appropriately select the observation magnification of the FE-SEM as described above so that the observation area is appropriate. It is preferable to adjust the number of fields of view.

Note that the area ratio of the (110) -oriented α-Al ₂ O ₃ crystal grains in the lower layer and the upper layer is preferably as high as possible, and the upper limit is ideally 100%. As the area ratio of the (110) oriented α-Al ₂ O ₃ crystal grains is higher, the effect of suppressing the coarsening of the crystal grains can be obtained in the lower layer portion, and the effect of suppressing the occurrence of cracks can be obtained in the upper layer portion. it can.

<Polishing of cut surface of α-Al ₂ O ₃ layer>
Hereinafter, it is necessary to calculate the area ratio between the (001) -oriented α-Al ₂ O ₃ crystal grains and the (110) -oriented α-Al ₂ O ₃ crystal grains, or α-Al ₂ O ₃ A polishing method for preparing a cut surface (cross-sectional polished surface) of the α-Al ₂ O ₃ layer necessary for measuring the thickness of the layer and the intermediate portion will be described.

First, an α-Al ₂ O ₃ layer is formed based on the manufacturing method described later. The formed α-Al ₂ O ₃ layer is cut so as to obtain a cross section perpendicular to the α-Al ₂ O ₃ layer (that is, the α-Al ₂ O ₃ layer in a plane including the normal of the substrate surface) To expose the cut surface). Thereafter, the cut surface is polished with water-resistant abrasive paper (containing a SiC abrasive abrasive as an abrasive).

For example, the above-described cutting may be performed by using the α-Al ₂ O ₃ layer surface (if another layer is formed on the α-Al ₂ O ₃ layer, the coating surface) on a sufficiently large holding plate. After being fixed in close contact with wax or the like, it is 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). 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.

  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 larger the number, the more abrasive The particle size of the agent is small).

  Subsequently, the above-mentioned cross-section polished surface is further smoothed by ion milling with Ar ions. The conditions for the ion milling treatment are as follows.

Accelerating voltage: 6kV
Irradiation angle: 0 ° from the normal direction of the substrate surface
Irradiation time: 6 hours.

Thereafter, the cross-section polished surface of the smoothed α-Al ₂ O ₃ layer, may be observed by FE-SEM equipped with the EBSD apparatus. For example, a Zeiss Supra 35 VP (manufactured by CARL ZEISS) equipped with an HKL NL02 EBSD detector can be used. EBSD data can be collected sequentially by placing the focused electron beam on each pixel individually.

<Method for manufacturing surface-coated cutting tool>
The surface-coated cutting tool of this embodiment can be manufactured as follows.

  First, by sintering the raw material, for example, a base material made of a cemented carbide is prepared. Subsequently, a honing process is performed on a region in the vicinity of the edge portion of the edge of the base material using a general method such as a brush or a plastic medium as necessary.

Subsequently, it can manufacture suitably by forming a film by said chemical vapor deposition (CVD) method on said base material. When the CVD method is used, the film forming temperature becomes 800 to 1200 ° C. This temperature is higher than that of physical vapor deposition, which improves the adhesion to the substrate. When each layer as a layer other than the Al ₂ O ₃ layer is formed, these layers can be formed under conventionally known conditions.

In order to form the α-Al ₂ O ₃ layer, for example, AlCl ₃ , HCl, CO ₂ , H ₂ S and H ₂ may be used as the source gas. The blending amount is 0.5 to 5% by volume of AlCl ₃ , 1 to 5% by volume of HCl, 0.3 to ₃ % by volume of CO ₂ , 0.05 to 1.5% by volume of H ₂ S, and the balance Is H ₂ . Furthermore, various conditions of the CVD apparatus are a temperature of 950 to 1050 ° C., a pressure of 1 to 20 kPa, and a gas flow rate (total gas amount) of 10 to 150 L / min.

The thickness of each layer other than the α-Al ₂ O ₃ layer and the α-Al ₂ O ₃ layer can be adjusted by appropriately adjusting the film formation time (the film formation rate of each layer is about 0.5 ˜2.0 μm / hour).

  After the coating is formed, surface treatment can be performed using various methods such as brush treatment, blast treatment such as sand blast treatment, wet blast treatment, and shot peening treatment, or PVD bombard treatment as necessary. Thereby, compressive stress can be applied to the coating.

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

<Preparation of substrate>
Attritor (wet media agitation type pulverizer) was prepared by mixing a raw material powder composed of 6.5% by mass of Co, 1.2% by mass of TaC, 0.5% by mass of ZrC and the balance of WC. , Trade name (model number): “wet attritor 100S” (manufactured by Nippon Coke Kogyo Co., Ltd.) for 10 hours and then dried. Thereafter, the green compact was press-molded into a green compact at a pressure of 100 MPa, and the green compact was put in a vacuum container and held at 1440 ° C. in a vacuum of 2 Pa for 1 hour.

Next, the green compact is taken out from the vacuum container, and the bottom surface is flat-polished, and then 0.6 mm honing is performed as a cutting edge treatment when viewed from the scooping surface with a SiC brush, and JIS (Japan Industrial Standard) B 4120 (2013) A base material (manufactured by Sumitomo Electric Industries, Ltd.) made of WC cemented carbide having the shape of CNMA120408 defined in the above. A plurality of prepared substrates were prepared in order to correspond to combinations of formation conditions of an α-Al ₂ O ₃ layer described later.

<Formation of coating>
A film was formed on the surface of each substrate obtained above. Specifically, a film was formed on the base material by the CVD method by setting the base material in a CVD apparatus. The film forming conditions are as described in Table 1, Table 2, Table 3, and Table 4 below. Table 1 shows conditions (temperature conditions, pressure conditions, and thickness) for forming each layer other than the α-Al ₂ O ₃ layer. Table 2 shows the composition ratio (unit: volume%) of the source gas for forming each layer other than the α-Al ₂ O ₃ layer. In addition, the conditions for forming each layer other than the α-Al ₂ O ₃ layer and the composition ratio of the source gas are common to the respective base materials.

Table 3 shows the composition ratio (unit: volume%) of the raw material gas for forming the α-Al ₂ O ₃ layer, and the temperature condition and pressure condition of the raw material gas. As shown in Table 3, there are four gas conditions a to d for the raw material gas for forming the α-Al ₂ O ₃ layer. In this example, when creating each layer part of the lower layer part, the middle part and the upper layer part, a total of 15 (samples 1 to 15) α-Al ₂ are applied by combining these four gas conditions. An O ₃ layer was formed. Table 4 shows the gas conditions (a to d) of the raw material gas applied to form each layer part of the lower layer part, the middle part and the upper layer part for each sample, and the thickness of each layer part. The method for measuring the thickness of the α-Al ₂ O ₃ layer described in Table 1 and Table 4 and the thickness of each of the other layer portions is as described above, and the average values of the measured thicknesses at the five locations are respectively displayed. ing.

  For example, in the case of the sample 5, the film formation method for each layer part is that the lower layer part is formed for a certain period of time under the gas condition “d”, and then the gas condition (mixing ratio) is switched to “a” to form the intermediate part. Then, the gas condition is changed to “d” and the upper layer is formed.

In Table 4, Sample 12 has one α-Al ₂ O ₃ layer, and as will be described later, the area ratio of (001) -oriented α-Al ₂ O ₃ crystal grains is 80. %, The gas conditions under which the α-Al ₂ O ₃ layer was formed and the thickness of the layer were described in the middle column of the sample 12. Sample 13 is composed of two α-Al ₂ O ₃ layers, and as will be described later, the area ratio of the (001) -oriented α-Al ₂ O ₃ crystal grains from the substrate side is 15%. One layer is a layer in which the area ratio of (001) -oriented α-Al ₂ O ₃ crystal grains is 75%. For this reason, the gas conditions and the layer thicknesses are described in the lower and middle columns of the sample 13, respectively.

The thickness of each layer other than the α-Al ₂ O ₃ layer and the α-Al ₂ O ₃ layer can be adjusted by appropriately adjusting the film formation time. In Tables 1 and 2, MT-TiCN means a TiCN layer formed by MT-CVD, and HT-TiCN means a TiCN layer formed by HT-CVD (High temperature CVD). To do. TiN (first layer) means that a TiN layer is first formed on a substrate. In the present example, the configuration of the coating is in the order of the TiN layer, MT-TiCN layer, HT-TiCN layer, TiCNO layer, and α-Al ₂ O ₃ layer from the substrate side. The α-Al ₂ O ₃ layer is composed of the base layer side, the lower layer part, the intermediate part, and the upper layer part in this order. In this embodiment, the upper layer portion of the Al ₂ O ₃ layer is disposed on the outermost surface of the coating.

<Surface treatment>
Blasting was performed on each sample on which a film was formed, and compressive stress was applied.

<Measurement of orientation of α-Al ₂ O ₃ layer>
Regarding each sample obtained from the above, the α-Al ₂ O ₃ layer was cut along a plane including the normal line of the base material surface, and the cut surface (vertical cross section of the α-Al ₂ O ₃ layer) was described above. Polishing processing was performed. Further, for the cross-sectional polished surface of the obtained α-Al ₂ O ₃ layer, an FE-SEM (trade name (model number): “SU6600”, manufactured by Hitachi High-Technologies Corporation) equipped with an EBSD device as described above was used. The crystal orientation of the α-Al ₂ O ₃ crystal grains was measured. Specifically, the crystal orientation mapping described above, alpha-Al ₂ lower part of the O ₃ layer, an intermediate portion and (001) of the upper part oriented alpha-Al ₂ O ₃ crystal grains of area ratio, and (110 ) The area ratio of oriented α-Al ₂ O ₃ was calculated. Whether or not it is a (001) -oriented α-Al ₂ O ₃ crystal grain and whether or not it is a (110) -oriented α-Al ₂ O ₃ crystal grain are as defined above. I did it. The observation magnification for the calculation of the area ratio of the (001) -oriented α-Al ₂ O ₃ crystal grains and the area ratio of the (110) -oriented α-Al ₂ O ₃ crystal grains was 20000, and the observation area was The number of fields of view was adjusted to 200 μm ² .

The area ratio of the (001) -oriented α-Al ₂ O ₃ crystal grains and the area ratio of the (110) -oriented α-Al ₂ O ₃ crystal grains obtained from the orientation measurement are shown in Table 5 below. Shown in Table 5, α-Al ₂ O ₃ layer thickness ([mu] m), and α-Al ₂ O ₃ layer thickness / α-Al ₂ O ₃ layer ratio (middle portion occupied by the thickness of the intermediate portion of the thickness of (Thickness) (%).

<Cutting test>
Each sample was subjected to a cutting test under the following conditions.

Work material: FCD450 round bar Cutting speed: 250m / min
Feeding: 0.30mm / rev
Cutting depth: 1.5mm
Cutting oil: Wet (water-soluble oil)
Evaluation: Measured with the flank wear width ≧ 0.3 mm as the life.

  In the cutting test, the cutting tool was set on a cutting machine and cut. The cutting tool was removed from the cutting machine every 30 seconds, the amount of flank wear was measured, and the time until this exceeded 0.3 mm was evaluated as the life. The longer this time, the longer the life, and it can be evaluated that the cutting tool can prevent the coarsening of crystal grains and the occurrence of cracks as well as the effect of improving the film strength. The results are also shown in Table 5 below.

  In the remarks column in Table 5, the shape change of the tool observed by observing each sample during the cutting test and after the cutting test is described. In the remarks column of Table 5, “Performance is good” means that the service life is 8 minutes or more, and there is no shape change that can be recognized as the occurrence of chipping or wear has greatly advanced until this service life is reached. Means that.

  Further, “chipping” means that chipping has occurred during the cutting test and the lifetime has come. “Large wear” means that wear has greatly advanced during the cutting test and the life has come. “Occurrence of film peeling” means that the film has peeled off during the cutting test and has reached its end of life.

<Test results and discussion>
As shown in Table 5, the α-Al ₂ O ₃ layers of the examples (Samples 1, 2, 5, 6, 7, 8, 10, and 14) were formed of (001) -oriented α-Al ₂ O ₃ crystals. It consisted of a lower layer portion and an upper layer portion having an area ratio of grains of less than 35%, and an intermediate section having an area ratio of (001) -oriented α-Al ₂ O ₃ crystal grains of 35% or more. The thickness of the α-Al ₂ O ₃ layer is 4～18Myuemu, ratio of thickness of the intermediate portion occupies in the thickness of the α-Al ₂ O ₃ layer, was more than 50%. Note that the thickness of each of the lower layer portion and the upper layer portion is 1 μm or more. These samples could be evaluated as “good performance”.

In particular, Samples 5, 6, and 7 have (110) at least in the upper layer portion or the lower layer portion in addition to the above-described characteristics of the (001) -oriented α-Al ₂ O ₃ crystal grains in the lower layer portion, the middle portion, and the upper layer portion. The area ratio of the oriented α-Al ₂ O ₃ crystal grains was 40% or more. These samples had a lifespan of 11 minutes or longer and had better performance.

On the other hand, the α-Al ₂ O ₃ layer of Comparative Examples (Samples 3, 4, 9, 11, 12, 13 and 15) will be considered. In the sample 3, the area ratio of the (001) -oriented α-Al ₂ O ₃ crystal grains in the upper layer portion was 40%, which was evaluated as “chipping”, and the lifetime was 6 minutes. It is thought that cracks occurred in the coating during cooling of the tool. In Sample 4, the area ratio of the (001) -oriented α-Al ₂ O ₃ crystal grains in the upper layer portion was 40%, which was evaluated as “large wear”, and the lifetime was 6 minutes. It is considered that the coarsening of the α-Al ₂ O ₃ crystal grains occurred during the film formation process.

In Sample 9, the ratio of the thickness of the middle portion to the thickness of the α-Al ₂ O ₃ layer was less than 50%, which was evaluated as “high wear”, and the lifetime was 5 minutes. α-Al ₂ O ₃ layer in the (001) -oriented α-Al ₂ O ₃ crystal grains of area ratio is low is considered that the effect of improving the film strength is not obtained sufficiently. In Sample 11, the thickness of the α-Al ₂ O ₃ layer was 20 μm, and it was evaluated that “film peeling occurred”, and the lifetime was 3 minutes. It is considered that the thickness of the α-Al ₂ O ₃ layer was too thick.

In Samples 12 and 13, the α-Al ₂ O ₃ layer was composed of one or two layers, and it was evaluated as “chipping” and “wearing out” in some cases. Lifespan was 5 or 6 minutes. It is considered that inconvenience occurred due to the absence of any of the lower layer portion, the middle portion, and the upper layer portion in the α-Al ₂ O ₃ layer. In the sample 15, the area ratio of the (001) -oriented α-Al ₂ O ₃ crystal grains in the middle part was 30%, and it was evaluated as “high wear” on the rake face, and the lifetime was 6 minutes. It is considered that the area ratio of the (001) -oriented α-Al ₂ O ₃ crystal grains in the α-Al ₂ O ₃ layer was low, and the effect of improving the film strength was not sufficiently obtained.

  Therefore, the surface-coated cutting tool of the example obtained the effect of improving the film strength by being oriented in the (001) plane direction as compared with the surface-coated cutting tool of the comparative example, and then the (001) plane direction. It can be said that it is excellent in that it can suppress the coarsening of crystal grains, which are disadvantages of being too high in orientation, and the occurrence of cracks in the coating during cooling.

  Although the embodiments and examples of the present invention have been 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 (3)

A surface-coated cutting tool comprising a substrate and a coating formed on the substrate,
The coating includes an α-Al ₂ O ₃ layer including a plurality of α-Al ₂ O ₃ crystal grains,
The α-Al ₂ O ₃ layer includes a lower layer portion disposed on the substrate side, an intermediate portion disposed on the lower layer portion, and an upper layer portion disposed on the intermediate portion,
In the lower layer portion, in the crystal orientation mapping using an electron beam backscattering diffractometer with respect to the cross-sectional polished surface of the α-Al ₂ O ₃ layer, the area ratio of (001) -oriented α-Al ₂ O ₃ crystal grains is Less than 35%,
The intermediate portion has an area ratio of (001) -oriented α-Al ₂ O ₃ crystal grains of 35% or more in the crystal orientation mapping,
The upper layer portion has a (001) -oriented α-Al ₂ O ₃ crystal grain area ratio of less than 35% in the crystal orientation mapping,
The α-Al ₂ O ₃ layer has a thickness of 4 to 18 μm,
The thickness of the intermediate portion occupies 50% or more of the thickness of the α-Al ₂ O ₃ layer,
The surface-coated cutting tool, wherein the lower layer part and the upper layer part each have a thickness of 1 μm or more. _2. The surface-coated cutting tool according to claim 1, wherein the lower layer portion has an area ratio of (110) -oriented α-Al ₂ O ₃ crystal grains of 40% or more in the crystal orientation mapping. The surface-coated cutting tool according to claim 1, wherein the upper layer portion has an area ratio of (110) -oriented α-Al ₂ O ₃ crystal grains of 40% or more in the crystal orientation mapping.