JP2014121740A - Surface-coated cutting tool in which hard coating layer exhibits excellent peeling resistance in heavy cutting work - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface-coated cutting tool in which a hard coating layer exhibits excellent peeling resistance in heavy cutting work.SOLUTION: The surface-coated cutting tool is formed by coating a Ti compound layer as a lower layer and a Ti-including AlOlayer as an upper layer on a surface of a tool base body, and the Ti-including AlOlayer of the upper layer is constituted of a Ti-including α-AlOcolumnar crystal grain having a longitudinally long shape in the layer thickness direction and having an α type crystal structure oriented on a (11-20) surface and a Ti-including κ-AlOcrystal grain having a κ type crystal structure, and the Ti-including α-AlOcolumnar crystal grain contacts with a recess of a lower layer surface in its lower end, and while, the Ti-including κ-AlOcrystal grain contacts with a surface except for the recess of the lower layer surface in its lower end, and the Ti-including κ-AlOcrystal grain is formed in a crystal grain clearance in which the mutual Ti-including α-AlOcolumnar crystal grains are not adjacent just above the lower layer surface.

Description

  In particular, the present invention provides a hard coating layer even when cutting of various materials such as steel and cast iron is performed under heavy cutting conditions in which a high load such as high feed and high cutting acts on the cutting edge. The present invention relates to a surface-coated cutting tool (hereinafter referred to as a coated tool) that exhibits excellent cutting performance over a long period of use because it has excellent peeling resistance.

Conventionally, generally on the surface of a substrate (hereinafter collectively referred to as a tool substrate) composed of a tungsten carbide (hereinafter referred to as WC) -based cemented carbide or titanium carbonitride (hereinafter referred to as TiCN) -based cermet. ,
(A) As a lower layer, Ti carbide (hereinafter referred to as TiC) layer, nitride (hereinafter also referred to as TiN) layer, carbonitride (hereinafter referred to as TiCN) layer, carbon oxide (hereinafter referred to as TiCO) A Ti compound layer comprising one or more of a layer and a carbonitride oxide (hereinafter referred to as TiCNO) layer,
(B) As an upper layer, an aluminum oxide layer (Al ₂ O ₃ layer),
A coated tool formed by vapor-depositing a hard coating layer comprising the above (a) and (b) is well known.

In the conventional coated tool, various proposals have been made to improve the tool performance.
For example, as shown in Patent Document 1, in a coated tool in which a lower layer of TiC, TiCN, TiN or the like is provided on the surface of a tool base and an Al ₂ O ₃ layer is formed thereon as an upper layer, the lower layer side is κ rich in -al ₂ O _3, by the surface side covering forming _{the Al} 2 _{O 3} layer rich in _α-Al 2 _{O 3,} the cast iron, in cutting of steel, wear resistance, to improve the chipping resistance Has been proposed.

Further, as shown in Patent Document 2, instead of the upper Al ₂ O ₃ layer, a Ti-containing α-Al ₂ O ₃ layer is formed by coating, and further, the Ti-containing α-Al ₂ O ₃ layer is It has been proposed that when a constituent atom shared lattice point distribution graph is created, the highest peak exists in Σ3 and the distribution ratio of Σ3 is set to 60 to 80% to improve chipping resistance.

Further, for example, as shown in Patent Document 3, a Ti compound layer as a lower layer, an α-type Al ₂ O ₃ layer as an intermediate layer, and a flat plate-shaped polygonal and long crystal as an upper layer on the surface of a tool base. In a coated tool in which a Ti-containing α-type Al ₂ O ₃ layer having a grain structure is vapor-deposited, an intermediate layer and an upper layer of a flank and a rake face are respectively formed as α-type Al ₂ O having a high (0001) plane orientation ratio. ₃ layers of Ti-containing α-type Al ₂ O ₃ layers, and among the Ti-containing α-type Al ₂ O ₃ crystal grains in the upper layer of the flank and rake face, 60% or more of the crystal grains by area ratio It has been proposed to improve peeling resistance and wear resistance in high-speed heavy cutting by dividing the inside by a crystal lattice interface composed of at least one Σ3.

Japanese Patent No. 2775935 JP 2006-289556 A JP 2011-183487 A

In recent years, the performance of cutting equipment has been remarkable. On the other hand, there is a strong demand for labor saving and energy saving and further cost reduction for cutting, and with this, cutting tends to become more efficient. In the above-mentioned conventional coated tool, there is no problem when it is used for continuous cutting under normal conditions such as steel and cast iron. However, this is particularly difficult when high loads such as high feed and high cutting are applied to the cutting edge. When used for heavy cutting conditions that act, the coating strength of the hard coating layer, particularly the upper Al ₂ O ₃ layer and the lower Ti compound layer, is not sufficient, and the coating layer is likely to peel off. As a result, the service life is reached in a relatively short time.

  Therefore, the present inventors obtained the following knowledge from the above viewpoints, as a result of intensive studies to improve the peel resistance of the hard coating layer particularly in heavy cutting.

First, the present inventors constituted the upper layer from Ti-containing α-Al ₂ O ₃ columnar crystal grains and Ti-containing κ-Al ₂ O ₃ crystal grains, and in particular, in the vicinity immediately above the lower layer, the Ti-containing α -Stress generated due to high load applied to the cutting edge during heavy cutting by filling the crystal grain gap where the Al ₂ O ₃ columnar crystal grains are not adjacent to each other with Ti-containing κ-Al ₂ O ₃ crystal grains Has been found to be relaxed by Ti-containing κ-Al ₂ O ₃ crystal grains, and the generation and propagation of cracks can be suppressed, so that the occurrence of delamination of the upper layer due to grain boundary fracture of the crystal grains can be suppressed. It was.
Moreover, the present inventors can ensure the high temperature strength of the upper layer by increasing the area ratio of Ti-containing α-Al ₂ O ₃ columnar crystal grains oriented in the (11-20) plane in the upper layer. At the same time, it has been found that excellent wear resistance is exhibited by the heat shielding effect of the Ti-containing α-Al ₂ O ₃ columnar crystal grains.

  In other words, according to the coated tool of the present invention, even when used in heavy cutting conditions where a high load such as high feed and high cutting acts on the cutting edge, it exhibits excellent peeling resistance and long-term performance. It exhibits excellent wear resistance over use.

This invention has been made based on the above findings,
“On the surface of the tool base made of tungsten carbide base cemented carbide or titanium carbonitride base cermet,
(A) The lower layer is composed of one or more of Ti carbide layer, nitride layer, carbonitride layer, carbonate layer and carbonitride oxide layer having an overall average layer thickness of 3 to 20 μm. A Ti compound layer having uneven portions formed on the surface thereof,
(B) The upper layer has a Ti-containing Al ₂ O ₃ layer having an average layer thickness of 2 to 15 μm, and the Ti content in the total amount with Al being 0.01 to 0.2 atomic%,
In the surface-coated cutting tool in which the hard coating layer composed of the above (a) and (b) is formed by vapor deposition,
(C) The upper layer includes a Ti-containing α-Al ₂ O ₃ columnar crystal grain having a vertically elongated shape in the layer thickness direction and having an α-type crystal structure, and a Ti-containing κ-Al ₂ having a κ-type crystal structure. Composed of O ₃ crystal grains,
(D) In the upper layer, at least near the surface of the upper layer, Ti-containing α-Al ₂ O ₃ columnar crystal grains are formed adjacent to each other in the direction perpendicular to the layer thickness direction, while the lower layer The lower ends of the Ti-containing α-Al ₂ O ₃ crystal grains immediately above the surface are in contact with the recesses on the surface of the lower layer, and the Ti-containing α-Al ₂ O ₃ columnar crystal grains are adjacent to each other immediately above the lower layer surface. Ti-containing κ-Al ₂ O ₃ crystal grains grown from the surface of the lower layer surface other than the recesses are formed in the crystal grain gaps that are not,
(E) In the upper layer, the area ratio of the Ti-containing α-Al ₂ O ₃ columnar crystal grains oriented in the (11-20) plane is 50 of the total area of the Ti-containing Al ₂ O ₃ crystal grains in the upper layer. A surface-coated cutting tool characterized by occupying at least area%. "
It has the characteristics.

Below, the hard coating layer of the coated tool of this invention is demonstrated in detail.
Lower layer:
The lower Ti compound layer is one of Ti carbide (TiC) layer, nitride (TiN) layer, carbonitride (TiCN) layer, carbonate (TiCO) layer and carbonitride oxide (TiCNO) layer. It consists of two or more layers.
The lower layer exists as a lower layer of the Zr-containing Al ₂ O ₃ layer, and the hard coating layer contributes to the improvement of the high-temperature strength due to its excellent high-temperature strength. In addition, the tool base and the Zr-containing Al ₂ O ₃ It adheres firmly to any of the layers and has the effect of improving the adhesion of the hard coating layer to the tool substrate.
However, when the overall average layer thickness of the lower layer is less than 3 μm, the above-mentioned effect cannot be sufficiently exerted. On the other hand, when the overall average layer thickness exceeds 20 μm, a high feed at which a high load acts on the cutting edge, In heavy cutting such as high cutting, chipping and defects are likely to occur, so the average layer thickness is determined to be 3 to 20 μm.

Upper layer:
In the present invention, a Ti-containing Al ₂ O ₃ layer is formed by vapor deposition as an upper layer, and the upper layer has a vertically long shape in the layer thickness direction and has a α-type crystal structure and Ti-containing α-Al ₂ O _3. It consists of columnar crystal grains and Ti-containing κ-Al ₂ O ₃ crystal grains having a κ-type crystal structure, and the structure of the upper layer changes in the layer thickness direction.
In FIG. 1, the schematic longitudinal cross-sectional schematic diagram of the hard coating layer (lower layer and upper layer) of this invention is shown.
As shown in FIG. 1, in the upper layer of the present invention, at least in the vicinity of the upper layer surface, Ti-containing α-Al ₂ O ₃ columnar crystal grains are formed adjacent to each other in a direction perpendicular to the layer thickness direction. Yes. On the other hand, in the upper layer immediately above the surface of the lower layer, the lower end of the Ti-containing α-Al ₂ O ₃ columnar crystal grains is in contact with the concave portion on the surface of the lower layer, and other than the concave portion on the surface of the lower layer (hereinafter, this is convex). Ti-containing κ-Al ₂ O ₃ crystal grains are formed in contact with the surface of the portion), and in the vicinity of the lower layer surface, Ti-containing α-Al ₂ O ₃ columnar crystal grains are not adjacent to each other. Is formed in such a state that Ti-containing κ-Al ₂ O ₃ crystal grains are filled in the gap.

Here, the vicinity of the surface of the upper layer refers to a region from the surface of the upper layer to a depth of 0.5 μm, while the vicinity of the surface of the lower layer refers to the distance from the interface between the lower layer and the upper layer to the inner side of the upper layer. An area up to 5 μm.
In addition, the recesses on the surface of the lower layer and the surfaces other than the recesses are as follows.
That is, as shown in FIG. 1, the concave portion on the surface of the lower layer is a portion where the crystal grains of the adjacent Ti compound and the α-Al ₂ O ₃ crystal grain of the upper layer intersect, The uppermost surface portion of the lower layer layer included in the range of the triple-point radius 0.1 to 0.5 μm of crystal grains.
On the other hand, the surface other than the concave portion is the outermost surface of the lower layer and refers to a portion outside the range of the concave portion described above from the point of the apex angle of the crystal grain of the adjacent Ti compound.

In the vicinity of the surface of the lower layer, a preferred area ratio (Ti-containing κ-Al) occupied by Ti-containing κ-Al ₂ O ₃ crystal grains filling a crystal grain gap in which Ti-containing α-Al ₂ O ₃ columnar crystal grains are not adjacent to each other ₂ O ₃ measured area × 100 measurement area occupied / lower layer near the surface of the grains) is from 5 to 50 area%, also preferred area ratio of the Ti-containing _kappa-Al 2 _{O 3} crystal grains in the entire upper layer Is 5 to 30 area%.
Area ratio of Ti-containing _κ-Al 2 _{O 3} grains in the lower layers near the surface is less than 5 area%, or the area ratio of the Ti-containing _κ-Al 2 _{O 3} crystal grains in the entire top layer is less than 5 area% In some cases, the effect of relaxing the stress generated by the high load applied to the cutting edge by the Ti-containing κ-Al ₂ O ₃ crystal grains is insufficient, while the Ti-containing κ-Al ₂ O ₃ crystal in the vicinity of the surface of the lower layer When the area ratio of grains exceeds 50 area% or when the area ratio of Ti-containing κ-Al ₂ O ₃ crystal grains in the entire upper layer exceeds 30 area%, it occupies the upper layer (11-20) Since the area ratio of the Ti-containing α-Al ₂ O ₃ columnar crystal grains oriented in the plane is relatively reduced and the wear resistance is remarkably reduced, the Ti-containing κ-Al ₂ occupies the entire upper layer in the vicinity of the lower layer surface. The area ratio of O ₃ crystal grains is It is preferably 5 to 50 area% and 5 to 30 area%, respectively.

In the present invention, when the upper layer has the above-described structure in the layer thickness direction, in heavy cutting processing in which a high load is applied to the cutting edge such as high feed and high cutting, the interface with the upper layer, particularly the lower layer. Ti-containing κ-Al ₂ O ₃ crystal grains relieve stress generated in the vicinity. As a result, crack initiation and growth are suppressed, and grain boundary fracture of the crystal grains is suppressed, and peeling of the upper layer occurs. Can be prevented.
However, if the average layer thickness of the upper layer is less than 2 μm, the desired excellent wear resistance cannot be sufficiently exhibited. On the other hand, if the average layer thickness exceeds 15 μm, chipping is likely to occur. Therefore, the average layer thickness was determined to be 2 to 15 μm.

  Further, the upper layer of the present invention improves the heat shielding effect by containing the Ti component, which contributes to the improvement of wear resistance, but the content ratio (atomic ratio) of the Ti component in the total amount with the Al component. When Ti / (Al + Ti) × 100) is less than 0.01 atomic%, the desired wear resistance due to the heat shielding effect cannot be exhibited, while the content ratio of the Ti component is 0.2. If it exceeds atomic%, Ti oxide is generated in the upper layer, and the presence of the Ti layer lowers the heat shielding effect of the upper layer. Therefore, the Ti content (Ti / (Al + Ti) × 100 value by atomic ratio) Was determined to be 0.01 to 0.2 atomic%.

Further, the upper layer of the present invention increases the (11-20) orientation degree of the Ti-containing α-Al ₂ O ₃ columnar crystal grains of the upper layer, thereby improving the high-temperature strength and contributing to improved wear resistance.
When the area ratio of the Ti-containing α-Al ₂ O ₃ columnar crystal grains oriented in (11-20) is less than 50% by area of the total area of the Ti-containing Al ₂ O ₃ crystal grains in the upper layer, the high-temperature strength of the upper layer Since the wear resistance also decreases, the area ratio of the Ti-containing α-Al ₂ O ₃ columnar crystal grains oriented to (11-20) in the upper layer is determined to be 50% or more. It was.
Here, the area ratio of the Ti-containing α-Al ₂ O ₃ columnar crystal grains oriented to (11-20) is a hexagonal crystal existing in the measurement range of the upper layer cross section using a field emission scanning electron microscope. Each crystal grain having a lattice is irradiated with an electron beam, and the angle difference formed by the normal of the (11-20) plane that is the crystal plane of the crystal grain is within 10 ° with respect to the normal of the surface of the tool base. The crystal grains are mapped, and the mapping area is calculated as a ratio to the measurement area.

The upper layer of the present invention composed of the Ti-containing Al ₂ O ₃ crystal grains described above can be deposited by, for example, the following two-stage film formation process.

That is, for example, after the lower layer is coated by a normal chemical vapor deposition apparatus, the surface of the lower layer is also formed by the same normal chemical vapor deposition apparatus.
≪First stage≫
Reaction gas composition (volume%): AlCl ₃ : 1 to 5%, TiCl ₄ : 0.1 to 0.5%, CO ₂ : 0.01 to 0.5%, CO: 0.1 to 1.0% , H ₂ : remaining,
(However, the CO gas and the CO ₂ gas are alternately introduced at intervals of 1 to 5 minutes. The CO gas and the CO ₂ gas are introduced first at least twice. Repeat above.)
Reaction atmosphere temperature: 900-950 ° C.
Reaction atmosphere pressure: 6 to 10 kPa,
Vapor deposition is performed under the conditions.
That is, in the first stage vapor deposition, a low oxidizing CO gas is first introduced, then a highly oxidizing CO ₂ gas is introduced, and then these gases are alternately introduced to form the lower layer. Ti-containing α-Al ₂ O ₃ nuclei are formed in the recesses on the surface, and Ti-containing κ-Al ₂ O ₃ nuclei are formed in addition to the recesses on the surface of the lower layer.
As shown in FIG. 1, the concave portion on the surface of the lower layer is a portion where _three crystal grains of the adjacent Ti compound crystal grains and the α-Al ₂ O ₃ crystal grains of the upper layer intersect with each other. The portion of the outermost surface of the lower layer layer included in the range of the triple-point radius 0.1 to 0.5 μm of the crystal particles, and the portion other than the concave portion on the surface of the lower layer is the uppermost surface of the lower layer and is an adjacent Ti compound From the point of the apex angle of the crystal grains, it is called a portion outside the range of the above-mentioned recess.

After completion of the first stage, vapor deposition is performed under the following second stage conditions until a desired target layer thickness is obtained.
≪Second stage≫
Reaction gas composition (volume%): AlCl ₃ : 6 to 10%, TiCl ₄ : 0.6 to ₂ %, CO ₂ : 5 to 15%, HCl: 3 to 6%, H ₂ S: 0.1 to 0 .5%, H ₂ : remaining,
Reaction atmosphere temperature: 960 to 1000 ° C.
Reaction atmosphere pressure: 6 to 10 kPa,
By performing the first-stage and second-stage vapor deposition, the upper layer composed of the Ti-containing Al ₂ O ₃ layer defined in the present invention can be formed by coating.

The crystal structure and structure of the Ti-containing Al ₂ O ₃ layer near the lower layer surface or near the upper layer surface are as described above, and the lower end of the Ti-containing α-Al ₂ O ₃ crystal grains immediately above the lower layer surface is The surface of the lower layer surface other than the recesses is in contact with the recesses on the surface of the lower layer, and the crystal grain gap immediately adjacent to the Ti layer-containing α-Al ₂ O ₃ columnar crystal grains is just above the surface of the lower layer. Ti-containing κ-Al ₂ O ₃ crystal grains grown from the above are formed, and in the vicinity of the upper layer surface, Ti-containing α-Al ₂ O ₃ columnar crystal grains are adjacent to each other in a direction perpendicular to the layer thickness direction. Is formed.
The upper layer having the above-described structure structure has improved thermal shielding properties by containing Ti, and Ti-containing κ-Al ₂ O ₃ crystal grains relieve stress generated near the interface with the lower layer. As a result, the generation / progress of cracks is suppressed, the grain boundary fracture of the crystal grains is suppressed, and the peeling of the upper layer is prevented.

Further, for the Ti-containing α-Al ₂ O ₃ columnar crystal grains constituting the upper layer of the present invention, a crystal having a hexagonal crystal lattice existing within the measurement range of the cross-sectional polished surface using a field emission scanning electron microscope Each grain is irradiated with an electron beam, and a crystal grain within an angle difference of 10 ° formed by a normal of the (11-20) plane, which is the crystal plane of the crystal grain, is mapped to the normal of the tool base surface. When the mapping area is calculated as a ratio to the measurement area, the area ratio of the Ti-containing α-Al ₂ O ₃ columnar crystal grains oriented in (11-20) is the total Ti-containing Al ₂ O ₃ crystal grains in the upper layer. As a result, the upper layer exhibits excellent high temperature strength.

The peeling resistance of the upper layer in the present invention is mainly brought about by Ti-containing κ-Al ₂ O ₃ crystal grains formed near the surface of the lower layer, and the high-temperature strength and wear resistance are mainly (11-20). This is brought about by the Ti-containing α-Al ₂ O ₃ columnar crystal grains having a high degree of orientation to the surface and excellent heat shielding effect.

  The coated tool of the present invention has a hard coating layer, particularly the upper layer, even when cutting various steels and cast irons, etc., under heavy cutting conditions such as high feed and high cutting in which a high load acts on the cutting edge. However, since it has an action of suppressing the progress of cracks and exhibits a high temperature strength and an excellent heat shielding effect, it exhibits excellent peel resistance and wear resistance over a long period of use.

The longitudinal cross-sectional schematic diagram of the hard coating layer of this invention coated tool is shown.

  Next, the coated tool of the present invention will be specifically described with reference to examples.

  As the raw material powders, the powders shown in Table 1 each having an average particle diameter of 1 to 3 μm were prepared. After ball mill mixing for a period of time and drying under reduced pressure, the green compact was press-molded into a green compact of a predetermined shape at a pressure of 98 MPa, and this green compact was held at a predetermined temperature in the range of 1370 to 1470 ° C. for 1 hour in a vacuum of 5 Pa. WC-based cemented carbide tool substrate A having an insert shape defined in ISO / CNMG120408 by performing a sintering process under vacuum conditions and performing a honing process of R: 0.07 mm on the cutting edge after sintering. Each E was produced.

  In addition, as the raw material powder, the powders shown in Table 2 each having an average particle diameter of 0.5 to 2 μm were prepared, and these raw material powders were blended into the blending composition shown in Table 2 and wetted by a ball mill for 24 hours. After mixing and drying, the green compact was press-molded into a green compact at a pressure of 98 MPa, and the green compact was sintered in a nitrogen atmosphere of 1.3 kPa at a temperature of 1540 ° C. for 1 hour and after sintering. Then, the tool bases a to e made of TiCN-based cermet having an ISO standard / CNMG120212 insert shape were prepared by performing honing of R: 0.07 mm on the cutting edge portion.

Next, each of these tool bases A to E and tool bases a to e was charged into a normal chemical vapor deposition apparatus, and Table 3 (l-TiCN in Table 3 is described in JP-A-6-8010). The target layer thicknesses shown in Table 6 under the conditions shown in Table 6 are the conditions for forming a TiCN layer having a vertically grown crystal structure. Of the Ti compound layer as a lower layer of the hard coating layer,
Subsequently, the present coated tools 1 to 10 shown in Table 7 are formed by vapor-depositing the Ti-containing Al ₂ O ₃ layer having the target layer thickness shown in Table 7 as an upper layer under the evaporation conditions shown in Table 4. Were manufactured respectively.

The area ratio of the Ti-containing α-Al ₂ O ₃ columnar crystal grains oriented in (11-20) in the upper layer of the present coated tools 1 to 10 is in a state where the cross section of the upper layer is a polished surface.
It is set in a lens barrel of a field emission scanning electron microscope, and an electron beam with an acceleration voltage of 15 kV is incident on the polished surface at an incident angle of 70 degrees with an irradiation current of 1 nA and exists within the measurement range of each polished surface. Irradiate each crystal grain, and use an electron backscatter diffraction image apparatus to measure a distance of 50 μm in the direction parallel to the tool base surface and the same distance as the thickness of the upper layer in the normal direction to the tool base surface. Measured at an interval of 1 μm / step, the crystal structure of the measured crystal grain is identified as a hexagonal crystal structure, and is the crystal plane of the crystal grain with respect to the normal of the tool substrate surface (11-20) ) Measure the inclination angle formed by the normal of the surface, and map the crystal grains whose angle difference is within 10 ° to the normal of the surface of the tool base based on the measurement result. (1) Was determined area ratio of oriented Ti-containing _α-Al 2 _{O 3} columnar grains to -20).
These values are shown in Table 7.

Further, for the Ti-containing Al ₂ O ₃ layers of the coated tools 1 to 10 of the present invention, Ti-containing κ− in the vicinity of the lower layer surface (region from the interface between the lower layer and the upper layer to the inner side of the upper layer to 0.5 μm). Al ₂ O ₃ with determining the area ratio of crystal grains (Ti-containing _κ-Al 2 _{O 3} measured area × 100 measurement area occupied / lower layer near the surface of the grains), Ti-containing kappa-Al ₂ in the entire upper layer O ₃ area ratio of crystal grains (Ti-containing _kappa-Al 2 _{O 3} crystal grains measuring the occupied area / upper layer entire measurement area × 100), were determined by the following measurement method.
Area ratio of Ti-containing κ-Al ₂ O ₃ crystal grains (Ti-containing κ-Al ₂ O ₃ crystal) in the vicinity of the lower layer surface (region from the interface between the lower layer and the upper layer to the inner side of the upper layer to 0.5 μm) Grain measurement area / measurement area in the vicinity of the lower layer surface × 100) is 0.5 μm from the interface between the lower layer and the upper layer to the inner side of the upper layer, and 50 μm in the direction parallel to the tool substrate surface. Measurement range (0.5 μm × 50 μm) is set in a lens barrel of a field emission scanning electron microscope, an electron beam with an acceleration voltage of 15 kV at an incident angle of 70 degrees is applied to the polished surface with an irradiation current of 1 nA, Irradiate each crystal grain within the measurement range of each polished surface, and measure an area of 0.5 × 50 μm at an interval of 0.1 μm / step using an electron backscatter diffraction image apparatus. The crystal structure of the crystal grains The κ-Al ₂ O ₃ crystal grains having a crystal structure maps were calculated as a percentage of the measurement range area of the area.
Area ratio of Ti-containing _κ-Al 2 _{O 3} crystal grains in the entire upper layer (Ti-containing _κ-Al 2 _{O 3} measured area × 100 of total grain measurement area occupied / upper layer) of the lower layer and the upper layer The measurement area (upper layer film thickness x 50 μm) of the distance from the interface to the uppermost surface of the upper layer (upper layer film thickness) and the distance of the cross-sectional polished surface of 50 μm in the direction parallel to the tool substrate surface is measured by the field emission scanning electron microscope. Set in a lens barrel, and irradiate the polishing surface with an electron beam with an acceleration voltage of 15 kV at an incident angle of 70 degrees with an irradiation current of 1 nA on each crystal grain existing in the measurement range of each polishing surface. Using an electron backscatter diffraction image apparatus, the measurement region of the upper layer thickness × 50 μm is measured at an interval of 0.1 μm / step, the crystal structure of the measured crystal grain is specified, and the crystal structure of the orthorhombic crystal mapping the _κ-Al 2 _{O 3} crystal grains, the area that It was calculated from the ratio of the measurement range area. These values are shown in Table 7.

For the purpose of comparison, with respect to the tool bases A to E and the tool bases a to e, a Ti compound layer having a target layer thickness shown in Table 6 is used as a lower layer of the hard coating layer under the conditions shown in Table 3. Vapor deposition,
Subsequently, the comparative coating tools 1 to 10 shown in Table 8 are manufactured by forming the Ti-containing Al ₂ O ₃ layer having the target layer thickness shown in Table 8 as an upper layer under the evaporation conditions shown in Table 5. did.

Next, with respect to the above-mentioned comparative coated tools 1 to 10, in the same manner as in the case of the coated tools 1 to 10 of the present invention, using a field emission scanning electron microscope and an electron backscatter diffraction image device, On the other hand, the inclination angle formed by the normal of the (11-20) plane, which is the crystal plane of the crystal grain, is measured, and based on this measurement result, the angle difference is 10 with respect to the normal of the surface of the tool base. The area ratio of Ti-containing α-Al ₂ O ₃ columnar crystal grains oriented in (11-20) was determined by mapping the crystal grains within the range of ° and calculating the mapping area as a ratio to the measurement area.

Moreover, about said comparison coated tools 1-10, it is the same as the case of this invention coated tools 1-10, the lower layer surface vicinity (from the interface of a lower layer and an upper layer to the inner side of an upper layer to 0.5 micrometer. Area) of Ti-containing κ-Al ₂ O ₃ crystal grains in the region) (measured occupied area of Ti-containing κ-Al ₂ O ₃ crystal grains / measured area in the vicinity of the lower layer surface × 100) and Ti content in the entire upper layer _κ-Al 2 _{O 3} was determined area ratio of crystal grains (Ti-containing _κ-Al 2 _{O 3} crystal grains measuring the occupied area / upper layer entire measurement area × 100).
These values are shown in Table 8.

Next, for the above-described inventive coated tools 1 to 10 and comparative coated tools 1 to 10, both are screwed with a fixing jig to the tip of the tool steel tool,
Work material: JIS / S45C round bar,
Cutting speed: 120 m / min,
Incision: 3mm,
Feed: 0.7 mm / rev.
Cutting time: 5 minutes
Under the conditions (referred to as cutting condition A), dry high feed cutting test of carbon steel (normal feed is 0.3 mm / rev.),
Work material: JIS / SCM420 round bar,
Cutting speed: 120 m / min,
Cutting depth: 3.5mm,
Feed: 0.6mm / rev.
Cutting time: 5 minutes
In the above condition (referred to as cutting condition B), dry high feed cutting test of nickel chromium molybdenum alloy steel (normal cutting depth is 1.5 mm),
Work material: JIS / FC300 round bar,
Cutting speed: 150 m / min,
Incision: 4mm,
Feed: 0.7 mm / rev.
Cutting time: 5 minutes
Wet high-cut cutting test of gray cast iron under the conditions (cutting condition C) (normal cutting is 1.5 mm),
In each cutting test, the flank wear width of the cutting edge was measured.
The measurement results are shown in Table 9.

From Table 7-9, the present invention coated tool 1-10, Ti-containing κ-Al ₂ O ₃ crystal grains formed in the vicinity of the lower layer surface of the top layer, the cracks caused by high load acting on the cutting edge As the Ti-containing α-Al ₂ O ₃ crystal grains have excellent high-temperature strength and heat shielding properties, the load is high on the cutting edge. It can be seen that excellent peeling resistance and wear resistance are exhibited over a long period of use under heavy cutting conditions such as high feed and high cutting.

  On the other hand, it is clear that the comparative coated tools 1 to 10 are inferior in the peel resistance or wear resistance of the hard coating layer, and reach the service life in a short period due to the occurrence of peeling or a decrease in wear resistance.

As described above, the coated tool of the present invention is excellent in resistance to peeling not only in continuous cutting and intermittent cutting under normal conditions such as various steels and cast iron, but also in heavy cutting in which a high load acts on the cutting edge. It exhibits excellent cutting performance over a long period of time and exhibits excellent cutting performance, so that it can sufficiently satisfy the high performance of cutting equipment, labor saving and energy saving of cutting work, and cost reduction. Is.

Claims (1)

On the surface of the tool base composed of tungsten carbide based cemented carbide or titanium carbonitride based cermet,
(A) The lower layer is composed of one or more of Ti carbide layer, nitride layer, carbonitride layer, carbonate layer and carbonitride oxide layer having an overall average layer thickness of 3 to 20 μm. A Ti compound layer having uneven portions formed on the surface thereof,
(B) The upper layer has a Ti-containing Al ₂ O ₃ layer having an average layer thickness of 2 to 15 μm, and the Ti content in the total amount with Al being 0.01 to 0.2 atomic%,
In the surface-coated cutting tool in which the hard coating layer composed of the above (a) and (b) is formed by vapor deposition,
(C) The upper layer includes a Ti-containing α-Al ₂ O ₃ columnar crystal grain having a vertically elongated shape in the layer thickness direction and having an α-type crystal structure, and a Ti-containing κ-Al ₂ having a κ-type crystal structure. Composed of O ₃ crystal grains,
(D) In the upper layer, at least near the surface of the upper layer, Ti-containing α-Al ₂ O ₃ columnar crystal grains are formed adjacent to each other in the direction perpendicular to the layer thickness direction, while the lower layer The lower ends of the Ti-containing α-Al ₂ O ₃ crystal grains immediately above the surface are in contact with the recesses on the surface of the lower layer, and the Ti-containing α-Al ₂ O ₃ columnar crystal grains are adjacent to each other immediately above the lower layer surface. Ti-containing κ-Al ₂ O ₃ crystal grains grown from the surface of the lower layer surface other than the recesses are formed in the crystal grain gaps that are not,
(E) In the upper layer, the area ratio of the Ti-containing α-Al ₂ O ₃ columnar crystal grains oriented in the (11-20) plane is 50 of the total area of the Ti-containing Al ₂ O ₃ crystal grains in the upper layer. A surface-coated cutting tool characterized by occupying at least area%.