JP2013006255A - Surface-coated cutting tool having hard coating layer exhibiting excellent chipping resistance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface coated cutting tool having a hard coating layer exhibiting excellent chipping resistance in high-speed intermittent cutting.SOLUTION: In the surface coated cutting tool in which the hard coating layer formed of a lower layer, a middle layer and an upper layer is formed on the surface of a tool substrate by vapor deposition, (a) the lower layer is formed of a Ti compound layer, (b) the middle layer is formed of a Zr-contained κ-type AlOlayer (lower middle layer) in which Zr is contained by 0.004-0.12% (ratio of Zr with respect to the total composition in terms of atomic percent) in an AlOlayer of κ-type crystal structure and a TiOthin layer (upper middle layer) formed partially on the grain boundary of the lower middle layer, and (c) the upper layer has an α-κ mixture structure of the κ-type AlOlayer and an α-type AlOlayer formed on the TiOthin layer when the vertical cross section thereof is observed, and when the polished surface thereof is observed, the AlOlayer has an α-κ mixture network structure in which the α-type AlOlayer surrounds the κ-type AlOlayer.

Description

  This invention is especially when cutting of various materials such as steel and cast iron is performed under high-speed intermittent cutting conditions with high heat generation and impact and intermittent high load acting on the cutting edge. In particular, the present invention relates to a surface-coated cutting tool (hereinafter referred to as a coated tool) in which a hard coating layer exhibits excellent chipping resistance over a long period of use.

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,
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, the aluminum oxide layer (b) described above is composed of a lower Al ₂ O ₃ layer made of fine κ-type Al ₂ O ₃ particles having an average particle size of 1 μm or less, and an average particle size. A coated tool formed as a multilayer structure with an upper Al ₂ O ₃ layer composed of coarse α-type Al ₂ O ₃ particles of ₂ μm or more is known. According to this coated tool, severe cutting conditions such as intermittent cutting are known. Also, it is known that peeling between the lower layer and the Al ₂ O ₃ layer is suppressed, and it is excellent in chipping resistance and wear resistance, thereby extending the life.

For example, as shown in Patent Document 2, when forming the aluminum oxide layer of (b) above, a Zr-containing κ-type Al ₂ O ₃ layer having high-temperature strength and excellent mechanical and thermal impact resistance; When the upper layer is formed by alternately laminating heat-transformed α-type Al ₂ O ₃ layers having excellent high-temperature hardness and heat resistance, chipping resistance in heavy cutting work in which a large load acts on the cutting edge, It is known that the wear resistance can be improved.

JP 2004-291162 A JP 2009-83008 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 in cutting work, and cost reduction. In conventional coated tools, there is no problem when this is used for continuous cutting under normal conditions such as steel and cast iron. However, this is accompanied by high heat generation and is intermittent and shocking to the cutting edge. When used in high-speed interrupted cutting conditions where a load is applied, the impact strength of the hard coating layer, especially the upper layer, is insufficient, so the service life is relatively short due to chipping and chipping. Is the current situation.

  Therefore, the present inventors have earnestly studied to improve the impact resistance of the hard coating layer from the above viewpoint, and as a result, obtained the following knowledge.

First, the present inventors aim to improve chipping resistance by reducing the impact and intermittent load acting on the hard coating layer, particularly the upper layer made of the Al ₂ O ₃ layer, in high-speed intermittent cutting. As a result of studying the layer structure of such a hard coating layer, a multilayer structure in which a κ-type Al ₂ O ₃ layer and an α-type Al ₂ O ₃ layer were sequentially laminated in the layer thickness direction was provided. Compared to the conventional coated tool, the coated tool provided with an Al ₂ O ₃ layer having an α-κ mixed structure structure as shown in FIGS. 1A and 1B is accompanied by higher heat generation. And when it was used under high-speed intermittent cutting conditions in which impact and intermittent high load act on the cutting edge, it was found that it exhibits excellent chipping resistance without causing a decrease in wear resistance. .

The Al ₂ O ₃ layer consisting of the alpha-kappa mixed organizational structure of the present invention (upper layer), for example, such as the following, via an intermediate layer consisting of lower intermediate layer and the upper intermediate layer, Al ₂ thereon It can be formed by depositing an O ₃ layer.
That is, after forming a Ti compound layer as a lower layer on the surface of the tool base, first, a Zr-containing κ-type Al ₂ O ₃ layer with a predetermined Zr content ratio is deposited as a lower intermediate layer, and then as an upper intermediate layer The titanium oxide thin layer is partially formed at the grain boundary of the lower intermediate layer, and then an Al ₂ O ₃ layer is deposited on the intermediate layer composed of the lower intermediate layer and the upper intermediate layer, thereby the α- An Al ₂ O ₃ layer (upper layer) having a κ mixed structure can be formed.

When a vertical cross section of the Al ₂ O ₃ layer (upper layer) having the above α-κ mixed structure structure is observed, for example, as shown in FIG. 1A, a thin titanium oxide layer as an intermediate layer is not formed. A κ-type Al ₂ O ₃ phase formed continuously on the surface portion (that is, the intragranular portion of the Zr-containing κ-type Al ₂ O ₃ layer (lower intermediate layer) not covered with the titanium oxide thin layer); An α-κ mixed structure of α-type Al ₂ O ₃ phase continuously formed on the titanium oxide thin layer is observed, and further, when the outermost surface of the upper layer is observed, for example, as shown in FIG. Thus, an α-κ network mixed structure is observed as if the α-type Al ₂ O ₃ phase surrounds the κ-type Al ₂ O ₃ phase.

The upper layer of the present invention has a unique structure as described above, and by this structure, heat resistance and high hardness provided by α-type Al ₂ O ₃ and high toughness provided by κ-type Al ₂ O ₃ phase. Therefore, in high-speed intermittent cutting with high heat generation and impact and intermittent high load acting on the cutting edge, it exhibits superior chipping resistance compared to conventional coated tools, The present inventors have found that excellent wear resistance is exhibited throughout the use of the present invention.

This invention has been made based on the above findings,
“(1) In a surface-coated cutting tool in which a hard coating layer composed of a lower layer, an intermediate layer, and an upper layer is deposited on the surface of a tool base composed of a tungsten carbide-based cemented carbide or a titanium carbonitride-based cermet,
(A) The lower layer is composed of one or more of a Ti carbide layer, a nitride layer, a carbonitride layer, a carbonate layer, and a carbonitride layer, and a total layer of 3 to 20 μm A Ti compound layer having a thickness;
(B) The intermediate layer consists of a lower intermediate layer and an upper intermediate layer,
The lower intermediate layer has a layer thickness of 0.5 to 3 μm, and Zr is 0.004 to 0.12% in the Al ₂ O ₃ layer having a κ-type crystal structure (however, the ratio of Zr to the whole composition is atomic%) Zr-containing κ-type Al ₂ O ₃ layer
The upper intermediate layer is a thin titanium oxide layer having a layer thickness of 0.02 to 0.05 μm and partially formed at the grain boundary of the lower intermediate layer,
(C) The upper layer is composed of an Al ₂ O ₃ layer having a layer thickness of 1 to 15 μm, and the Al ₂ O ₃ layer has a κ-type Al ₂ O ₃ phase and the above when the vertical cross section of the upper layer is observed. When the α-κ mixed structure of α-type Al ₂ O ₃ phase formed on the titanium oxide thin layer is present and the surface polished surface of the upper layer is observed, the periphery of the κ-type Al ₂ O ₃ phase is α An α-κ network mixed structure surrounded by a type Al ₂ O ₃ phase,
A surface-coated cutting tool characterized by that.
(2) The titanium oxide thin layer partially formed at the grain boundary of the lower intermediate layer composed of the Zr-containing κ-type Al ₂ O ₃ layer is 20 to 60 in a vertical cross section at the interface between the lower intermediate layer and the upper intermediate layer. The surface-coated cutting tool according to (1), wherein the surface-coated cutting tool is formed at a line segment ratio of%.
(3) In the upper layer, the occupation ratio of the α-type Al ₂ O ₃ phase in the total amount with the κ-type Al ₂ O ₃ phase is 20 to 60 area% in the vertical section of the upper layer, The surface-coated cutting tool according to (1) or (2), wherein the surface-polished surface is 25 to 65 area%. "
It has the characteristics.

  Below, the hard coating layer of the coated tool of this invention is demonstrated in detail.

Lower layer:
It is composed of one or more of Ti carbide (TiC) layer, nitride (TiN) layer, carbonitride (TiCN) layer, carbonate (TiCO) layer and carbonitride oxide (TiCNO) layer. The lower layer made of the Ti compound layer contributes to improving the high temperature strength of the hard coating layer by its excellent high temperature strength, and also comprises a tool base and an intermediate layer (particularly, a Zr-containing κ-type Al ₂ O ₃ layer). It firmly adheres to any of the lower intermediate layers) and has the effect of improving the adhesion of the hard coating layer to the tool substrate.
If the total layer thickness of the lower layer is less than 3 μm, the above-mentioned effect cannot be fully exerted. On the other hand, if the total layer thickness exceeds 20 μm, chipping and chipping occur particularly in high-speed intermittent cutting with high heat generation. Since it becomes easy, the total layer thickness was determined to be 3 to 20 μm.

Middle layer:
The intermediate layer composed of the lower intermediate layer (Zr-containing κ-type Al ₂ O ₃ layer) and the upper intermediate layer (titanium oxide thin layer) can be formed, for example, by the following method.

With an ordinary chemical vapor deposition device, the initial stage of 1 to 120 minutes
Reaction gas composition (volume%): AlCl ₃ : 2 to 5%, H ₂ : remaining reaction atmosphere temperature: 930 to 980 ° C.,
Reaction atmosphere pressure: 5 to 8 kPa,
The lower layer is processed in the atmosphere of
The lower intermediate layer (Zr-containing κ-type Al ₂ O ₃ layer) is formed on the surface of the lower layer (Ti compound layer) subjected to the above treatment,
Reaction gas composition (volume%): AlCl ₃ : 3 to 6%, ZrCl ₄ : 0.6 to 1.8%, CO ₂ : 6 to 10%, HCl: 1.0 to 3.0%, H ₂ S : 0.1~0.18%, H _2: remainder,
Reaction atmosphere temperature: 930-980 ° C.
Reaction atmosphere pressure: 5 to 8 kPa,
It can form by forming into a film on these conditions.
The Zr-containing κ-type Al ₂ O ₃ layer formed by the above-described deposition has a κ-type crystal (Zr-containing κ-type Al ₂ O ₃ crystal grain) structure in the state of chemical vapor deposition, and has excellent high-temperature strength. Has excellent mechanical and thermal shock resistance.

Here, in the formed lower intermediate layer (Zr-containing κ-type Al ₂ O ₃ layer), the content ratio of Zr in the entire composition (Zr / (Al + Zr + O) × 100% value) is 0% in atomic percent. It is necessary to satisfy 0.004% to 0.12%.
This is because when the content ratio of Zr is less than 0.004%, the κ-type Al ₂ O ₃ layer becomes an α-type Al ₂ O ₃ layer due to the high reaction temperature during the growth of the α-type Al ₂ O ₃ layer of the upper layer. On the other hand, when it is transformed by heating and exceeds 0.12%, ZrO ₂ is formed in the κ-type Al ₂ O ₃ layer, and there is a grain boundary formed by the ZrO ₂ phase, so that the κ-type Al ₂ O ₃ phase This is because the grain boundary strength as a whole is lowered.
Further, the layer thickness of the lower intermediate layer (Zr-containing κ-type Al ₂ O ₃ layer) needs to be 0.5 to 3 μm. This is because when the layer thickness is less than 0.5 μm, the excellent high-temperature strength as described above and the excellent mechanical and thermal impact resistance cannot be sufficiently exhibited. When the thickness exceeds 3 μm, thermoplastic deformation that causes uneven wear tends to occur, and wear accelerates. Therefore, the layer thickness is set to 0.5 to 3 μm.

Next, the core growth of TiO _X for forming a thin layer of titanium oxide (hereinafter referred to as “TiO _X ”) of the upper intermediate layer is specifically performed by, for example, an ordinary chemical vapor deposition apparatus.
Reaction gas composition (volume%): TiCl ₄ : 0.5 to 1.5%, CO ₂ : 3 to 10%, Ar: 25.0 to 35.0%, H ₂ : remaining,
Reaction atmosphere temperature: 880-980 ° C.,
Reaction atmosphere pressure: 3 to 15 kPa,
Reaction time: 1-30 min
It can be formed by performing the process under the conditions.

By the above nucleus growth treatment, an upper intermediate layer made of a thin TiO _X layer is partially formed at the grain boundary of the lower intermediate layer (Zr-containing κ-type Al ₂ O ₃ layer).
The layer thickness of the TiO _X thin layer (upper intermediate layer) needs to be 0.02 to 0.5 μm.
When the layer thickness of the TiO _X thin layer (upper intermediate layer) is less than 0.02 μm, the total area of the lower intermediate layer (Zr-containing κ-type Al ₂ O ₃ layer) is up to the target area ratio. The occupying ratio of the α-type Al ₂ O ₃ phase in the total amount of the κ-type Al ₂ O ₃ phase in the upper layer is reduced, the hardness of the upper layer is reduced, and the wear resistance is reduced. descend. On the other hand, when the layer thickness exceeds 0.5 μm, the entire surface area of the lower intermediate layer (Zr-containing κ-type Al ₂ O ₃ layer) covers more than a desired area ratio. toughness of Al ₂ O ₃ phase and occupying the total amount κ-type Al ₂ O ₃ phase occupancy is less and less top layer of the impact resistance, by reason that the chipping resistance is lowered.
The TiO _X thin layer (upper intermediate layer) is not precipitated uniformly at the grain boundaries and within the grains of the lower intermediate layer (Zr-containing κ-type Al ₂ O ₃ layer), but preferentially formed at the grain boundaries. However, it is preferably formed at a line segment ratio of 20 to 60% in the vertical cross section of the interface between the lower intermediate layer and the upper intermediate layer.
This is in the upper layer composed of a mixed structure of κ-type _Al 2 _{O 3} phase and the α-type _Al 2 _{O 3} phase, production ratio of κ-type _Al 2 _{O 3} phase and the α-type _Al 2 _{O 3} phase, the This is because it is influenced by the generation ratio (line segment ratio) of the TiO _X thin layer (upper intermediate layer).
For example, when the generation ratio (line segment ratio) of the TiO _X thin layer (upper intermediate layer) is relatively large, the generation ratio of the κ-type Al ₂ O ₃ phase in the upper layer decreases, and as a result, Lower toughness, impact resistance and chipping resistance of the upper layer. On the other hand, when the generation ratio (line segment ratio) of the TiO _X thin layer (upper intermediate layer) is relatively small, the generation ratio of the α-type Al ₂ O ₃ phase in the upper layer decreases, and as a result, This is because the hardness of the upper layer is reduced and the wear resistance is reduced.

The layer thickness and ratio (line segment ratio) of the TiO _X thin layer (upper intermediate layer) can be adjusted by, for example, the content ratio of TiCl ₄ in the reaction time and reaction gas composition in the nucleus growth process, When the reaction time is shortened, or when the content ratio of TiCl ₄ in the reaction gas composition is decreased, the TiO _X thin layer (upper intermediate layer) with a small layer thickness or a small generation ratio (line segment ratio) Is formed.

Upper layer:
The upper layer formed of the Al ₂ O ₃ layer is formed on the surface of the intermediate layer formed of the lower intermediate layer and the upper intermediate layer, for example, using a normal chemical vapor deposition apparatus.
Reaction gas composition: by _{volume%, AlCl 3: 6~10%,} CO 2: 10~15%, HCl: 3~5%, H 2 S: 0.05~0.2%, H 2: remainder,
Reaction atmosphere temperature: 960 to 1000 ° C.
Reaction atmosphere pressure: 3 to 5 kPa,
It can be formed by vapor deposition under the following conditions.
When the Al ₂ O ₃ layer is formed under these conditions, the surface portion where the TiO _X thin layer of the intermediate layer is not formed (that is, the Zr-containing κ-type Al ₂ O ₃ not covered by the TiO _X thin layer). From the intragranular portion where the layer (lower intermediate layer) is exposed, the κ-type Al ₂ O ₃ phase grows, while the upper intermediate layer (that is, the TiO _X thin film) on which the TiO _X thin layer of the intermediate layer is formed. When the α-type Al ₂ O ₃ phase grows from the Zr-containing κ-type Al ₂ O ₃ layer (lower intermediate layer) covered with the layer (when the vertical cross section of the upper layer structure is observed) An α-κ mixed tissue as shown in FIG. 1 (a) is observed.
Furthermore, when the outermost surface of the upper layer is observed, as shown in FIG. 1 (b), the α-type Al ₂ O ₃ phase appears to surround the κ-type Al ₂ O ₃ phase, as shown in FIG. A kappa network mixed structure is observed.

The generation ratio of α-type Al ₂ O ₃ phase and κ-type Al ₂ O ₃ phase in the upper layer structure is influenced by the generation ratio (line segment ratio) of the TiO _X thin layer (upper intermediate layer) and the layer thickness of the upper layer. In response, when the generation ratio (line segment ratio) of the TiO _X thin layer (upper intermediate layer) is relatively large, the initial generation ratio of the α-type Al ₂ O ₃ phase increases, and as the layer thickness of the upper layer increases, The occupation ratio of the α-type Al ₂ O ₃ phase in the upper layer increases.
On the other hand, when the generation ratio (line segment ratio) of the TiO _X thin layer (upper intermediate layer) is relatively small, the initial generation ratio of the κ-type Al ₂ O ₃ phase becomes dominant. As the increase, the occupation ratio of the α-type Al ₂ O ₃ phase increases, and as a result, the occupation ratio of the κ-type Al ₂ O ₃ phase in the upper layer decreases.
In the upper layer, the occupation ratio of the α-type Al ₂ O ₃ phase in the total amount with the κ-type Al ₂ O ₃ phase is 20 to 60 area% in the vertical cross section of the upper layer, and the surface polishing surface of the upper layer It is desirable that it is 25-65 area%. This occupation ratio of alpha-type _Al 2 _{O 3} phase, in the vertical cross section of the upper layer, less than 20 area%, or, in the surface polishing surface of the upper layer is less than 25 area%, alpha-type _Al 2 O _{This is because} the occupation ratio of the _three phases is reduced, the hardness of the upper layer is reduced, and the wear resistance is lowered. On the other hand, the occupation ratio of the α-type Al ₂ O ₃ phase is 60 areas in the vertical section of the upper layer. % Or when the surface polished surface of the upper layer exceeds 65 area%, the occupancy ratio of the κ-type Al ₂ O ₃ phase in the total amount with the α-type Al ₂ O ₃ phase of the upper layer This is because the toughness, impact resistance and chipping resistance of the upper layer are reduced.

The upper layer composed of the mixed structure (vertical cross section) of the κ-type Al ₂ O ₃ phase and the α-type Al ₂ O ₃ phase and the network-like mixed structure (the surface of the upper layer) has a heat resistance that the α-type Al ₂ O ₃ phase has. Κ-type Al ₂ O ₃ phase has high strength, high toughness, and impact resistance without sacrificing properties and hardness, and is accompanied by high heat generation and high-speed intermittent operation with intermittent and high impact loads. Exhibits excellent chipping resistance over long-term use in cutting.
However, if the average layer thickness of the upper layer is less than 1 μm, the desired excellent wear resistance cannot be sufficiently exerted over a long period of use, while if the average layer thickness exceeds 15 μm, the chipping will occur. Therefore, the average layer thickness is determined to be 1 to 15 μm.

  Even when the coated tool of the present invention performs cutting of various steels, cast irons, etc., with high heat generation, and even when performed under high-speed intermittent cutting conditions where intermittent and impact high loads act on the cutting edge, In addition to high hardness and heat resistance, the hard coating layer, especially the upper layer, has excellent toughness and impact resistance, so it exhibits excellent chipping resistance over a long period of use, further extending the service life. It is possible.

It is a schematic diagram of the hard coating layer of this invention coated tool, (a) shows (alpha) -kappa mixed structure in the vertical cross section of an upper layer, (b) is (alpha) -kappa network shape in the surface polishing surface of an upper layer. A mixed tissue is shown.

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

  As raw material powders, the powders shown in Table 1 each having an average particle diameter of 1 to 3 μm were prepared. These raw material powders were blended into the blending composition shown in Table 1, and further wax was added in acetone. 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 base having a throwaway tip shape defined in ISO / CNMG120408 by performing vacuum sintering under the conditions of the above, and performing a honing process of R: 0.07 mm on the cutting edge after sintering A to D were prepared.

  Also, as the raw material powder, the powders shown in Table 2 each having an average particle diameter of 0.5 to 2 μm are prepared, and these raw material powders are blended in 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 base a to d made of TiCN base cermet having a chip shape of ISO standard / CNMG120408 was manufactured by performing a honing process of R: 0.07 mm on the cutting edge portion.

Next, each of the tool bases A to D and the tool bases a to d 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 conditions for forming a TiCN layer having a vertically elongated crystal structure are shown, and the other conditions are the conditions for forming a normal granular crystal structure). The Ti compound layer is deposited as a lower layer of the hard coating layer,
Then, under the vapor deposition conditions shown in Table 4, the layer thickness shown in Table 7 and the Zr-containing κ-type Al ₂ O ₃ layer having a Zr content ratio are vapor-deposited as a lower intermediate layer,
Next, the Zr-containing κ-type Al ₂ O ₃ layer was subjected to TiO _X nucleus growth treatment under the conditions shown in Table 5, and the TiO _X thin layer having the layer thickness and generation ratio (line segment ratio) shown in Table 7 was obtained. (Upper middle layer)
Subsequently, the coated tools 1 to 12 of the present invention shown in Table 7 were produced by forming an Al ₂ O ₃ layer having a predetermined layer thickness as an upper layer under the conditions shown in Table 3.

Various measurements were performed on the lower intermediate layer (Zr-containing κ-type Al ₂ O ₃ layer), the upper intermediate layer (TiO _X thin layer), and the upper layer (Al ₂ O ₃ layer) of the inventive coated tool 1-12. . That is,
Lower intermediate layer: For the Zr content ratio in the layer, a secondary ion mass spectrometer is used to measure a mirror-polished cross section, and an average value of five different fields of view at an observation magnification of 10,000 times is actually measured. It was.
Upper intermediate layer: Mirror-polished vertical section was subjected to element mapping at an observation magnification of 20,000 using an Auger electron spectrometer, and the length of the TiO _X thin layer occupying in a 1 μm line segment was measured. The average value of the five line segments was calculated as the line segment ratio of the TiO _X thin layer.
Upper layer: The occupancy ratio of the α-type Al ₂ O ₃ phase in the total amount of the κ-type Al ₂ O ₃ phase in the vertical section of the upper layer is determined by using an electron beam backscattering diffractometer on the mirror-polished cross section. At an observation magnification of 2,000, horizontal direction: 20 μm × longitudinal direction: a region corresponding to the film thickness of the upper layer was measured, and regions of α-type Al ₂ O ₃ phase and κ-type Al ₂ O ₃ phase were defined respectively. The area of was calculated.
The α-κ network mixed structure on the surface polished surface of the upper layer is mirror-polished on the surface and measured with an electron beam backscatter diffractometer at an observation magnification of 5,000 times. The regions of the Al ₂ O ₃ phase and the κ-type Al ₂ O ₃ phase were defined, and an α-κ network mixed structure was confirmed. The occupancy ratio of the α-type Al ₂ O ₃ phase in the total amount with the κ-type Al ₂ O ₃ phase is the same as the measurement of the network-like mixed structure, and the measurement range is 10 μm square in all directions. The average value was taken as the actual measurement value.
In addition, about the layer thickness of said each layer, it measured by the longitudinal cross-section measurement using the scanning electron microscope. The upper intermediate layer (TiO _X thin layer) was observed at an observation magnification of 20,000 times, and the other layers were observed at an observation magnification of 2,000 times, and the average value of these five points was taken as the layer thickness.
Table 7 summarizes these values.

For the purpose of comparison, a Ti compound layer having a layer thickness shown in Table 6 was deposited on the tool bases A to D and a to d as a lower layer of the hard coating layer under the conditions shown in Table 3. ,
Next, under the vapor deposition conditions shown in Table 8, a Zr-containing κ-type Al ₂ O ₃ layer having a layer thickness and a Zr-containing ratio shown in Table 10 was formed as a lower intermediate layer (for some, Zr-free) Κ-type Al ₂ O ₃ layer)
Next, under the conditions shown in Table 9, the Zr-containing κ-type Al ₂ O ₃ layer was subjected to TiO _X nuclear growth treatment (some of which were not subjected to nuclear growth treatment), and the layer thicknesses shown in Table 10 were obtained. , Forming a TiO _X thin layer (upper intermediate layer) with an area ratio (for some, the TiO _X thin layer is not formed)
Subsequently, comparative coated tools 1 to 12 shown in Table 10 were produced by forming an Al ₂ O ₃ layer having a predetermined thickness as an upper layer under the conditions shown in Table 3.

Next, for the above-mentioned comparative coated tools 1-12, as in the case of the present coated tools 1-12, the Zr content ratio of the lower intermediate layer, the line segment ratio of the TiO _X thin layer (upper intermediate layer), the upper layer The measurement was performed on the vertical cross section and the surface polished surface of the upper layer.
In addition, about the layer thickness of said each layer, it measured by the longitudinal cross-section measurement using a scanning electron microscope, measured using those 5 points | pieces, and made those average values the layer thickness.
Table 10 summarizes these values.

Next, for the above-described inventive coated tools 1-12 and comparative coated tools 1-12, both are screwed to the tip of the tool steel tool with a fixing jig,
Work material: JIS / S30C lengthwise equal 8 round grooves
Cutting speed: 370 m / min,
Cutting depth: 1.6mm,
Feed: 0.27mm / rev,
Cutting time: 5 minutes
A dry wet high speed intermittent cutting test of carbon steel under the above conditions (referred to as cutting condition A) (normal cutting speed is 250 m / min),
Work material: JIS / SCM415 lengthwise equal 8 round grooved round bars,
Cutting speed: 350 m / min,
Incision: 2.5mm,
Feed: 0.23mm / rev,
Cutting time: 5 minutes
Wet high-speed intermittent cutting test (normal cutting speed is 200 m / min) of alloy steel under the above conditions (referred to as cutting condition B),
Work material: JIS / FCD450 lengthwise equidistant round bars with 8 vertical grooves,
Cutting speed: 350 m / min,
Incision: 2.7 mm,
Feed: 0.3mm / rev,
Cutting time: 5 minutes
Wet high-speed intermittent cutting test (normal cutting speed is 180 m / min) of ductile cast iron under the above conditions (referred to as cutting condition C),
In each cutting test, the flank wear width of the cutting edge was measured.
The measurement results are shown in Table 11.

From Table 7, Table 10, and Table 11, this invention coated tools 1-12 are the mixed structure (vertical cross section) of κ-type Al ₂ O ₃ phase and α-type Al ₂ O ₃ phase, and the reticulated mixed structure (upper layer Top surface), κ-type Al ₂ O ₃ phase has excellent strength, toughness, and impact resistance, and α-type Al ₂ O ₃ phase has excellent heat resistance and hardness. Therefore, it exhibits excellent chipping resistance over a long period of use in high-speed intermittent cutting with high heat generation and intermittent / impact high loads.
On the other hand, the comparative coated tools 1 to 12 may cause chipping due to intermittent / impact high loads under high heat generation, or lack of wear resistance, resulting in a short life. it is obvious.

  As described above, the coated tool of the present invention is not only for continuous cutting and intermittent cutting under normal conditions such as various steels and cast irons, but particularly with high heat generation, the cutting blade is intermittently / impactly loaded. Even in high-speed interrupted cutting with high resistance, it exhibits excellent chipping resistance and exhibits excellent cutting performance over a long period of time. It can cope with cost reduction sufficiently satisfactorily.

Claims (3)

In a surface-coated cutting tool in which a hard coating layer composed of a lower layer, an intermediate layer, and an upper layer is deposited on the surface of a tool base composed of a tungsten carbide-based cemented carbide or a titanium carbonitride-based cermet,
(A) The lower layer is composed of one or more of a Ti carbide layer, a nitride layer, a carbonitride layer, a carbonate layer, and a carbonitride layer, and a total layer of 3 to 20 μm A Ti compound layer having a thickness;
(B) The intermediate layer consists of a lower intermediate layer and an upper intermediate layer,
The lower intermediate layer has a layer thickness of 0.5 to 3 μm, and Zr is 0.004 to 0.12% in the Al ₂ O ₃ layer having a κ-type crystal structure (however, the ratio of Zr to the whole composition is atomic%) Zr-containing κ-type Al ₂ O ₃ layer
The upper intermediate layer is a thin titanium oxide layer having a layer thickness of 0.02 to 0.5 μm and partially formed at the grain boundary of the lower intermediate layer,
(C) The upper layer is composed of an Al ₂ O ₃ layer having a layer thickness of 1 to 15 μm, and the Al ₂ O ₃ layer has a κ-type Al ₂ O ₃ phase and the above when the vertical cross section of the upper layer is observed. When the α-κ mixed structure of α-type Al ₂ O ₃ phase formed on the titanium oxide thin layer is present and the surface polished surface of the upper layer is observed, the periphery of the κ-type Al ₂ O ₃ phase is α An α-κ network mixed structure surrounded by a type Al ₂ O ₃ phase,
A surface-coated cutting tool characterized by that. The titanium oxide thin layer partially formed at the grain boundary of the lower intermediate layer composed of the Zr-containing κ-type Al ₂ O ₃ layer has a line of 20 to 60% in the vertical cross section at the interface between the lower intermediate layer and the upper intermediate layer. The surface-coated cutting tool according to claim 1, wherein the surface-coated cutting tool is formed in a fraction. In the upper layer, the occupation ratio of the α-type Al ₂ O ₃ phase in the total amount with the κ-type Al ₂ O ₃ phase is 20 to 60 area% in the vertical cross section of the upper layer, and the surface polishing surface of the upper layer The surface-coated cutting tool according to claim 1, wherein the surface-coated cutting tool is 25 to 65 area%.

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