JP6736032B2 - Coated cutting tools - Google Patents

Description

The present invention relates to a coated cutting tool.

Conventionally, on the surface of a base material made of cemented carbide, for example, a single layer or two or more layers of Ti carbide, nitride, carbonitride, carbon oxide and carbonitride oxide, and aluminum oxide. It is well known that a coated cutting tool obtained by vapor-depositing a coating layer made of a layer to have a total film thickness of 3 to 20 μm by a chemical vapor deposition method is used for cutting steel or cast iron.

Usually, when a coating film is formed on the surface of a tungsten carbide based cemented carbide, tensile stress remains in the coating film, so that the fracture strength of the coated cutting tool is lowered and the coating cutting tool is likely to be broken. Up to now, it has been proposed to release tensile residual stress by performing shot peening or the like after film formation to generate cracks, and a considerable effect has been obtained (see, for example, Patent Document 1).

In a Ti compound layer, a cutting tool having a region surrounded by cracks and an intermittent crack that is not in contact with one end of the crack or a crack forming the region has been proposed inside the region (for example, see Patent Document 2). ).

JP-A-5-116003 International publication 2015/025903

In recent cutting processes, high speed, high feed and deep cutting have become remarkable, and tool life tends to be shorter than in the past. Against this background, even with the tool disclosed in Patent Document 1, if the number of cracks in the coating is simply increased, the chipping resistance is improved, but the peeling resistance and chipping resistance of the coating starting from the cracks are improved. And wear resistance are reduced. Further, the coated cutting tool disclosed in Patent Document 2 is required to have further improved wear resistance due to such a background. The present invention has been made to solve these problems, and by devising a crack generation mode of the coated cutting tool, it has excellent chipping resistance, wear resistance and chipping resistance, and has a tool life. An object of the present invention is to provide a long-length coated cutting tool.

The inventors of the present invention, from the above-mentioned viewpoint, have made repeated studies on the extension of the tool life of the coated cutting tool, and when the number density of the intermittent cracks in the flank is high, the work material and the coated cutting tool are rubbed during machining. It has been found that rubbing wear due to abrasion occurs. And, as a result of the particles of the Ti compound layer on the flank surface falling off due to the rubbing wear, it was found that the wear resistance is not sufficient. Based on this knowledge, the present inventors can improve wear resistance without impairing chipping resistance and chipping resistance and, as a result, prolong tool life by adopting the following configuration. I got the knowledge that I can.

That is, the gist of the present invention is as follows.
(1)
A coated cutting tool comprising a substrate and a coating layer formed on the surface of the substrate,
The coated cutting tool has a rake face, a flank face, and a cutting edge ridge portion between the rake face and the flank face,
The coating layer comprises at least one Ti compound layer,
The Ti compound layer is a compound layer containing Ti or Ti and Al and at least one element selected from the group consisting of C, N, O and B,
When the polishing surface of the Ti compound layer that is substantially parallel to the surface of the base material is viewed from above, the Ti compound layer has a region surrounded by cracks,
Inside the region, the crack surrounding the region, and has an intermittent crack that does not contact at one end or both ends,
Filled fraud and mitigating risk and mean number density A _r of the region and the average number density B _r of the intermittent cracks 1.2 <B _r / A _r ≦ 1.59 in the rake face,
Filled fraud and mitigating risk and mean number density A _f of the region and the average number density B _f of the intermittent cracks _{0.1 <B f / A f ≦} 0.93 in the flank,
And a coated cutting tool in which B _r /A _r >B _f /A _f .
(2)
The Ti compound layer is formed on the surface of the base material and has an average thickness of 2.0 μm or more and 20.0
The coated cutting tool according to (1), which has a thickness of μm or less.
(3)
The Ti compound layer includes at least one TiCN layer,
The average particle size of the TiCN layer is 0.3 μm or more and 2.0 μm or less, (1) or (
2) Coated cutting tool.
(4)
Atomic ratio of carbon [C/(C+N) to the total of carbon and nitrogen contained in the TiCN layer]
] Is 0.50 or more and 0.75 or less, The coated cutting tool of (3).
(5)
The coated cutting tool according to any one of (1) to (4), wherein the coating layer has an aluminum oxide layer having an average thickness of 1.0 μm or more and 15.0 μm or less on the surface of the Ti compound layer.
(6)
The average thickness of the entire coating layer is 3.0 μm or more and 30.0 μm or less, (1) to (5)
Any of the coated cutting tools.
(7)
The coated cutting tool according to any one of (1) to (6), wherein the base material is any of a cemented carbide, a cermet, a ceramics and a cubic boron nitride sintered body.

Since the coated cutting tool of the present invention can improve wear resistance without impairing chipping resistance and chipping resistance, it has an effect of prolonging tool life as compared with the conventional case.

It is a schematic cross section which shows one aspect of the coated cutting tool of this invention. It is a schematic diagram which shows one aspect of the area|region surrounded by the crack of this invention. It is a schematic diagram which shows another aspect of the area|region surrounded by the crack of this invention. It is an example of the photograph which looked at the polishing surface substantially parallel to the surface of the rake face of the base material in the Ti compound layer of the present invention from the top. It is an example of the photograph which looked at the grinding|polishing surface substantially parallel to the surface of the flank of a base material in the Ti compound layer of this invention from the upper surface.

Hereinafter, a mode for carrying out the present invention (hereinafter, simply referred to as “the present embodiment”) will be described in detail, but the present invention is not limited to the present embodiment described below. The present invention can be variously modified without departing from the gist thereof.

The coated cutting tool of the present embodiment includes a base material and a coating layer formed on the surface of the base material. The coated cutting tool has a rake face, a flank face, and a cutting edge ridge portion between the rake face and the flank face. Specific examples of the type of coated cutting tool include a cutting edge exchangeable cutting insert for milling or turning, a drill, and an end mill.

FIG. 1 is a schematic cross-sectional view showing one aspect of the coated cutting tool of the present embodiment. The coated cutting tool 100 includes a base material 1 and a coating layer 2 formed on the surface of the base material 1, and has a rake face 3, a flank face 4, and a cutting edge between the rake face 3 and the flank face 4. And a ridge portion 5. The coating layer 2 is a two-layer structure in which a Ti compound layer 11 and an aluminum oxide layer 12 described later are laminated on the surface of the base material 1 in this order.

The base material in the present embodiment is not particularly limited as long as it can be used as the base material of the coated cutting tool. Examples of the substrate include at least one selected from the group consisting of cemented carbide, cermet, ceramics, cubic boron nitride sintered body, diamond sintered body, and high speed steel. Among these, when the base material is at least one selected from the group consisting of cemented carbide, cermet, ceramics and cubic boron nitride sintered body, the wear resistance and fracture resistance of the coated cutting tool are more improved. It is more preferable because it is more excellent.

These base materials may have a modified surface. For example, when the base material is cemented carbide, a de-beta layer may be formed on the surface of the base material, and when the base material is cermet, a surface hardened layer may be formed. .. Even if the surface of the substrate is modified in this way, the effects of the present invention can be exhibited.

In the coated cutting tool of the present embodiment, when the average thickness of the entire coating layer is 3.0 μm or more, the wear resistance tends to be further improved. On the other hand, when the average thickness of the entire coating layer is 30.0 μm or less, the fracture resistance tends to be further improved. Therefore, the average thickness of the entire coating layer is preferably 3.0 μm or more and 30.0 μm or less from the viewpoint of further improving wear resistance and fracture resistance in a well-balanced manner, and from the same viewpoint, 3 The thickness is more preferably 0.2 μm or more and 25.0 μm or less, still more preferably 3.4 μm or more and 22.0 μm or less, and particularly preferably 3.5 μm or more and 18.0 μm or less.

In the coated cutting tool of the present embodiment, the coating layer includes at least one Ti compound layer. The Ti compound layer is a compound layer containing a Ti element or a Ti element and an Al element, and further containing at least one element selected from the group consisting of C, N, O and B. The Ti element or the Ti element And Al element, and preferably at least one element selected from the group consisting of C, N, and O. Examples of the Ti compound layer include a TiC layer, a TiN layer, a TiCN layer, a TiCO layer, a TiCNO layer, a TiAlCO layer and a TiAlCNO layer. The Ti compound layer may be composed of one layer or multiple layers (for example, two layers or three layers). When the Ti compound layer is composed of two layers, the TiC layer or the TiN layer is formed as the first layer on the surface of the base material, and the TiCN layer is formed as the second layer on the surface of the first layer. May be. When the Ti compound layer is composed of three layers, in addition to the first layer and the second layer, a TiCO layer, a TiCNO layer, a TiAlCONO layer, or a TiAlCNO layer is formed on the surface of the second layer as the third layer. You may form as.

In the coated cutting tool of the present embodiment, it is preferable that the Ti compound layer is formed on the surface of the base material because the adhesion between the base material and the coating layer is further improved. If the average thickness of the Ti compound layer is 2.0 μm or more, the abrasion resistance tends to be further improved. On the other hand, when the average thickness of the Ti compound layer is 20.0 μm or less, the fracture resistance tends to be further improved. Therefore, the average thickness of the Ti compound layer is preferably 2.0 μm or more and 20.0 μm or less, and from the same viewpoint, it is more preferably 3.0 μm or more and 15.0 μm or less, and 4.0 μm or more. It is more preferably 14.0 μm or less. The "average thickness of the Ti compound layer" as used herein means the average thickness of one layer when the Ti compound layer is composed of one layer, and the Ti compound layer is composed of multiple layers. In this case, it means the average thickness of the entire Ti compound layer.

In the coated cutting tool of the present embodiment, the Ti compound layer has a region surrounded by cracks in the Ti compound layer when the polishing surface substantially parallel to the surface of the base material is viewed from above, and the Ti compound layer is provided inside the region. Have cracks that surround the region and intermittent cracks that do not touch at one or both ends. Here, “viewed from above” means that the polished surface of the Ti compound layer is viewed from the direction of the normal to the surface. In other words, when viewed from the surface side of the coating layer before polishing the surface of the coating layer, that is, when viewed from the opposite side of the substrate.

In coated cutting tool of the present embodiment, at least a portion of the rake face, and the average number density _{B r} of average number density _{A r} intermittent crack region satisfies _{0.7 <B r} / A r <4.0 As a result, the effect of stopping the progress of cracks generated in the coating layer during cutting by the intermittent cracks is obtained, and therefore chipping resistance and fracture resistance are excellent. When B _r /A _r exceeds 0.7, the intermittent cracks are sufficiently distributed, so that the effect of stopping the progress of cracks generated in the coating layer during cutting by the intermittent cracks can be obtained. This improves chipping resistance and chipping resistance. On the other hand, when B _r /A _r is less than 4.0, it is possible to prevent the cracks surrounding the region and the intermittent cracks from being easily connected. As a result, the coated cutting tool can suppress a decrease in fracture resistance. From the same viewpoint, B _r /A _r is more preferably 0.9<B _r /A _r <3.5, and further preferably 1.2<B _r /A _r <3.0. preferable.

In coated cutting tool of the present embodiment, at least a portion of the flank face, and the average number density _{A f} in the region and the average number density _{B f} intermittent crack satisfies _{0.1 <B f / A f <} 1.5 This can prevent the particles of the Ti compound layer on the flank from falling off. As a result, rubbing wear due to rubbing between the work material and the coated cutting tool during cutting can be suppressed, and thus the coated cutting tool has excellent wear resistance. When B _f /A _f exceeds 0.1, the effect of stopping the progress of cracks generated in the coating layer during cutting by the intermittent cracks is obtained due to the appropriate distribution of the intermittent cracks. This improves the chipping resistance and fracture resistance of the coated cutting tool. On the other hand, when B _f /A _f is less than 1.5, the abrasion resistance of the flank can be suppressed, and thus the coated cutting tool has excellent wear resistance. From the same viewpoint, B _f /A _f is more preferably 0.1<B _f /A _f <1.3, and further preferably 0.1<B _f /A _f <1.2. preferable.

In the coated cutting tool of the present embodiment, when B _r /A _r and B _f /A _f have a relation of B _r /A _r >B _f /A _f , cracks generated in the coating layer during cutting. It has an excellent balance between the effect of stopping with the intermittent crack and the effect of suppressing the rubbing wear of the flank. As a result, the coated cutting tool has excellent wear resistance, chipping resistance, and fracture resistance.

From the same viewpoint as above, in at least a portion of the rake face, and the average number density _{B r} of average number density _{A r} intermittent crack region satisfies _{1.2 <B r} / A r <3.0, escape at least a portion of the surface, and the average number density _{a f} in the region and the average number density _{B f} intermittent cracks preferably satisfies _{0.1 <B f / a f <} 1.2.

The polishing surface of the Ti compound layer is, for example, in a coated cutting tool, polishing is performed until the surface or the inside of the Ti compound layer is exposed in a direction substantially parallel to the surface of the base material in at least a part of the rake face or the flank face. It is the surface of the Ti compound layer thus obtained. At this time, it is preferable to obtain a polished surface at a position where a thickness of 50% or more of the average thickness of the Ti compound layer remains. In the case of a coated cutting tool in which Ti compound layers having a plurality of compositions are formed, it is preferable to measure the region of the layer having the largest average thickness and the intermittent crack.

In the coated cutting tool of the present embodiment, the region observed on the polished surface of the Ti compound layer in the rake face or the flank refers to cracks and dry blasting that occur in the coating layer during cooling after forming the coating layer, The area is surrounded by cracks generated in the coating layer by processing such as shot peening. The "number of areas" is, for example, "area surrounded by cracks", and a small unit in which the area surrounded by cracks is not formed is defined as one area. However, if there are n small areas that do not share cracks in the “area surrounded by cracks”, the area is defined as (n+1) areas. Specifically, in the case of the region 20 shown in FIG. 2, since there are three small units 21 to 23 surrounded by cracks in the region 20, the “number of regions” in this example is There are three. In this example, it can be said that the small units 21 and 22 (or 22 and 23, or 21, 22, and 23) form one region, but since these regions are not small units, It is not included in the “number of areas” in the embodiment. On the other hand, in the case of the region 30 shown in FIG. 3, since there are two small regions 31 and 32 that do not share the crack surrounding the region 30, the “number of regions” in this example is three.

In the coated cutting tool of the present embodiment, the average number density of regions on the rake face or the flank face can be obtained by the following method. That is, the number density of regions can be obtained by measuring the number of regions observed on the polished surface of the Ti compound layer and dividing the measured number of regions by the measured area of the Ti compound layer. Then, the average number density is obtained by summing the number densities of the measured fields of view and dividing the sum of the number densities of the regions by the number of fields of view measured. _Let Ar be the average number density of the regions observed on the polished surface of the Ti compound layer on the rake face, and A _f be the average number density of the regions observed on the polished surface of the Ti compound layer on the flank face. A _r and A _f are collectively referred to as A.

As used herein, the term "intermittent crack" refers to a crack that surrounds a region and a crack that does not contact at one end or both ends. The mode of the intermittent crack is, for example, a mode not in contact with any of the cracks in the region, the crack is progressing from the crack surrounding the region toward the inside of the region, but the progress does not proceed across the region but progresses in the middle. A mode in which it is stopped is included.

In the coated cutting tool of the present embodiment, the average number density of intermittent cracks on the rake face or the flank face can be obtained by the following method. That is, the number density of the intermittent cracks is obtained by measuring the number of the intermittent cracks observed on the polished surface of the Ti compound layer and dividing the measured number of the intermittent cracks by the measured area of the Ti compound layer. The average number density is determined by summing each number density of the measured visual fields and dividing the sum of each number density by the number of measured visual fields. The rake face, the average number density of intermittent cracks observed on the polished surface of the Ti compound layer and B _r, in the flank, the mean number density of the intermittent cracks observed on the polished surface of the Ti compound layer and B _{f, Br} and _Bf are collectively referred to as B.

In the coated cutting tool of the present embodiment, it is preferable that the Ti compound layer includes at least one TiCN layer because the wear resistance is further improved. If the average particle size of the TiCN layer is 0.3 μm or more, the fracture resistance tends to be further improved. On the other hand, when the average particle size of the TiCN layer is 2.0 μm or less, the wear resistance on the flank tends to be further improved. Therefore, the average particle size of the TiCN layer is preferably 0.3 μm or more and 2.0 μm or less from the viewpoint of further improving the balance between fracture resistance and wear resistance. From the same viewpoint, the average particle size of the TiCN layer is more preferably 0.3 μm or more and 1.5 μm or less.

In the coated cutting tool of the present embodiment, the average particle size of the TiCN layer can be obtained by the following method. That is, the coated cutting tool is held in vacuum at 1200° C. for 10 minutes to be heat-treated to diffuse the binder phase component of the cemented carbide base material into the crystal grain boundaries of the TiCN layer. Then, the mirror-polished surface of the cross section of the coated cutting tool in the orthogonal direction is observed with a scanning electron microscope (SEM), and a photograph is taken. At this time, it is advisable to observe a backscattered electron image of 5000 times to 20000 times. A straight line was drawn in a direction parallel to the interface between the cemented carbide base material and the coating layer in the central portion of the photograph of the TiCN layer taken, and the number of grain boundaries of the TiCN layer crossing this straight line was measured, The average grain size of the TiCN layer is calculated. The straight line may be drawn at a position of 40% or more and 60% of the average thickness of the TiCN layer.

In the coated cutting tool of the present embodiment, when the atomic ratio [C/(C+N)] of carbon to the total of carbon and nitrogen contained in the TiCN layer is 0.50 or more, wear resistance tends to be further improved. It is in. On the other hand, when the atomic ratio [C/(C+N)] is 0.75 or less, the fracture resistance tends to be further improved. Therefore, the atomic ratio [C/(C+N)] is preferably 0.50 or more and 0.75 or less from the viewpoint of further improving the wear resistance and the fracture resistance in a well-balanced manner. From the same viewpoint, the atomic ratio [C/(C+N)] is more preferably 0.50 or more and 0.70 or less.

In the coated cutting tool of the present embodiment, the atomic ratio [C/(C+N)] of carbon to the total of carbon and nitrogen contained in the TiCN layer is determined by, for example, the amount of C in the TiCN layer by an electron probe microanalyzer (EPMA). And N are quantified.

In the coated cutting tool of the present embodiment, when the coating layer includes an aluminum oxide layer (hereinafter referred to as “Al ₂ O ₃ layer”) on the surface of the Ti compound layer, the progress of wear due to the reaction with the work material is promoted. It is preferable because it can be suppressed. The crystal type of the Al ₂ O ₃ layer is not particularly limited, and examples thereof include α type, β type, δ type, γ type, κ type, χ type, pseudo τ type, η type, and ρ type. Among these, the crystal type of the Al ₂ O ₃ layer is preferably α type from the viewpoint of being more stable even at high temperature, and from the viewpoint of further excellent adhesiveness between the Ti compound layer and the Al ₂ O ₃ layer. It is preferably kappa type. In particular, when the region involved in cutting, such as high-speed cutting, has a high temperature, it is preferable that the Al ₂ O ₃ layer is an α-type Al ₂ O ₃ layer because chipping and chipping are less likely to occur. When the average thickness of the Al ₂ O ₃ layer is 1.0 μm or more, the crater wear resistance on the rake face tends to be further improved. On the other hand, when the average thickness of the Al ₂ O ₃ layer is 15.0 μm or less, the fracture resistance tends to be further improved. Therefore, from the viewpoint of further improving the crater wear resistance and fracture resistance in a well-balanced manner, the average thickness of the Al ₂ O ₃ layer is preferably 1.0 μm or more and 15.0 μm or less, and from the same viewpoint. , 3.0 μm or more and 12.0 μm or less, more preferably 5.0 μm or more and 12.0 μm or less.

An example of a photograph of the polishing surface of the Ti compound layer of the present embodiment that is substantially parallel to the rake face of the base material is shown in FIG. 4, and the flank surface of the base material of the Ti compound layer of the present embodiment is shown. FIG. 5 shows an example of a photograph of a polished surface that is substantially parallel to the surface as seen from above.

As a method of forming each layer constituting the coating layer in the coated cutting tool of the present embodiment, for example, the following method can be mentioned.

If the TiN layer is included in the Ti compound layer, TiN layer, for example, the feed gas _{composition, TiCl 4: 3.0~10.0mol%, N} 2: 20~60mol%, H 2: the balance, Temperature: It can be formed by a chemical vapor deposition method at 850 to 920° C. and a pressure of 100 to 350 hPa.

When the TiCN layer is included in the Ti compound layer, the TiCN layer has, for example, a raw material gas composition of TiCl ₄ :10 to 15 mol%, CH ₃ CN :1 to ₃ mol%, N ₂ :0 to ₂₀ mol%, and H ₂ : The balance can be formed by a chemical vapor deposition method in which the temperature is 850 to 920° C. and the pressure is 60 to 80 hPa.

In the above method, C/(C+N) in the TiCN layer can be adjusted only to less than 0.65. C / the TiCN layer (C + N) in order to 0.65 to 0.75, for example, the raw material gas composition _{TiCl 4: 1.0~8.0mol%, CH 3} CN: 1.0~2.0mol _{%, C 3 H 6: 1.0~2.0mol} %, N 2: 10~50mol%, H 2: the balance, temperature: 700 to 900 ° C., a pressure: formed by chemical vapor deposition to 50~100hPa be able to.

In this case, reducing the feed gas composition ratio of _CH 3 CN for _{TiCl 4 [CH 3 CN / TiCl} 4], it is possible to reduce the average particle size of the TiCN layer. Further, if the temperature is lowered, the average grain size of the TiCN layer can be reduced.

When the TiC layer is included in the Ti compound layer, the TiC layer may have, for example, a raw material gas composition of TiCl ₄ : 1.0 to 3.0 mol%, CH ₄ : 4.0 to 6.0 mol%, and H ₂ : balance. And the temperature is 990 to 1030° C. and the pressure is 50 to 100 hPa.

When the Al ₂ O ₃ layer is an α-type Al ₂ O ₃ layer, the α-type Al ₂ O ₃ layer has, for example, a source gas composition of AlCl ₃ : 2.1 to 5.0 mol% and CO ₂ : 2. 5 to 4.0 mol%, HCl: 2.0 to 3.0 mol%, H ₂ S: 0.28 to 0.45 mol%, H ₂ : balance, temperature: 900 to 1000° C., pressure: 60 to 80 hPa. Can be formed by a chemical vapor deposition method.

When the Al ₂ O ₃ layer is a κ-type Al ₂ O ₃ layer, the κ-type Al ₂ O ₃ layer has, for example, a source gas composition of AlCl ₃ : 2.1 to 5.0 mol% and CO ₂ : 2. _{0~6.0mol%, CO: 3.0~5.5mol%,} HCl: 3.0~5.0mol%, H 2 S: 0.3~0.5mol%, H 2: the balance, temperature: It can be formed by a chemical vapor deposition method at 900 to 1000° C. and a pressure of 60 to 80 hPa.

When the TiAlCNO layer is included in the Ti compound layer, the TiAlCNO layer has, for example, a source gas composition of TiCl ₄ : 3.0 to 5.0 mol%, AlCl ₃ : 1.0 to 2.0 mol%, and CO: 0. 4 to 1.0 mol %, N ₂ :30 to 40 mol %, H ₂ : balance, and temperature: 975 to 1025° C., pressure: 90 to 120 hPa can be formed by a chemical vapor deposition method.

When the TiAlCO layer is included in the Ti compound layer, the TiAlCO layer has, for example, a raw material gas composition of TiCl ₄ : 0.5 to 1.5 mol%, AlCl ₃ : 3.0 to 5.0 mol%, and CO: 2. It can be formed by a chemical vapor deposition method in which 0 to 4.0 mol%, H ₂ : balance, and temperature: 975 to 1025° C. and pressure: 60 to 100 hPa.

If it contains TiCNO layer of Ti compound layer, TiCNO layer, for example, the feed gas _{composition, TiCl 4: 3.0~5.0mol%, CO} : 0.4~1.0mol%, N 2: 30~ 40 mol%, H ₂ : balance, temperature: 975 to 1025° C., pressure: 90 to 110 hPa can be formed by a chemical vapor deposition method.

When the TiCO layer is included in the Ti compound layer, the TiCO layer has, for example, a raw material gas composition of TiCl ₄ : 0.5 to 1.5 mol%, CO: 2.0 to 4.0 mol%, and H ₂ : balance. , Temperature: 975 to 1025° C., pressure: 60 to 100 hPa.

A coated cutting tool that satisfies the relationship between the average number density of regions and the average number density of intermittent cracks in each Ti compound layer on the rake face and the flank face can be obtained, for example, by the following method.

After forming the coating layer, if dry shot blasting is performed using a shot material having a shape with a larger aspect ratio than in the past, the average number density B of the intermittent cracks in the Ti compound layer can be easily controlled. The aspect ratio of the shot material is preferably 1.5 or more and 3.0 or less, and more preferably the shape of the shot material has a sharp convex portion. When controlling the morphology of cracks in the Ti compound layer on the rake face, the dry shot blasting conditions are such that the projection angle is 80° to 90° with respect to the surface of the coating layer on the rake face, and the projection material is 80 m/sec It is recommended to project at a projection speed of 100 m/sec and a projection time of 0.5 minutes to 1.0 minutes. In this case, the shot material for dry shot blasting is preferably a material such as Al ₂ O ₃ or ZrO ₂ having an average particle diameter of 160 μm to 200 μm. When controlling the crack morphology in the Ti compound layer on the flank, the dry shot blasting conditions are such that the projection angle is 80° to 90° with respect to the surface of the coating layer on the flank, and the projection material is 40 to 60 m/sec. It is recommended that the projection is performed at a projection speed of 0.5 to 1.0 minute. In this case, the shot material for dry shot blasting is preferably a material such as Al ₂ O ₃ or ZrO ₂ having an average particle size of 100 to 140 μm. At this time, the form of cracks can be easily controlled by masking the surface that is not dry shot blasted.

Here, the aspect ratio of the shot material is a value obtained by dividing the value of the maximum diameter in the shot material by the value of the minimum diameter. The average particle size of the shot material is the average value of the maximum diameter value and the minimum diameter value of the shot material. The projection angle is an angle formed by the surface of the coating layer and the projection angle of the projection material. Therefore, when performing dry shot blasting on the rake face, it refers to the angle between the surface of the coating layer on the rake face and the angle at which the projection material is projected, and when performing dry shot blasting on the flank face, It refers to the angle formed by the surface of the coating layer and the angle at which the projection material is projected.

The thickness of each layer can be measured from the sectional structure of the coated cutting tool using an optical microscope, SEM, field emission scanning electron microscope (FE-SEM), or the like. As for the thickness of the coated cutting tool, it is preferable to measure the thickness of each layer at three or more locations at a position in the vicinity of 50 μm from the cutting edge toward the rake face of the coated cutting tool, and obtain the average value thereof. The composition of each layer can be measured from the sectional structure of the coated cutting tool of the present embodiment using an energy dispersive X-ray spectrometer (EDS), a wavelength dispersive X-ray spectrometer (WDS), or the like.

Examples of the method for measuring the average number density in the region of the Ti compound layer and the intermittent cracks include the following methods. The coated cutting tool is polished in a direction substantially parallel to the surface of the base material until the surface or the inside of the Ti compound layer is exposed to obtain a polished surface of the Ti compound layer. If the polished surface is etched with hydrofluoric nitric acid, cracks can be easily observed. The polished surface is observed with an optical microscope at 300 times to 750 times, and a photograph of the polished surface is taken. Using the photograph of the polished surface, the number of regions of the Ti compound layer and the number of intermittent cracks are measured. By dividing the measured number of regions and the number of interrupted cracks by the measured area, the number density of regions and interrupted cracks can be obtained. The average number density A of the regions and the average number density B of the interrupted cracks can be obtained by summing the measured region densities of the respective visual fields and the number densities of the interrupted cracks and dividing each by the number of the measured visual fields. It is preferable to measure a range of 0.2 mm ² or more using a photograph of the polished surface, more preferably to measure a range of 0.25 mm ² or more, and further to measure a range of 0.3 mm ² or more. preferable. When the number of regions is measured using a photograph of the polished surface, the range in which it is not possible to confirm whether a region is formed due to cracks at the edges of the photograph is 0.5. By the above-described measuring method, the average number density A of regions and the average number density B of intermittent cracks on the rake face and the flank face can be obtained.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

As a base material, a cemented carbide cutting insert having a JIS standard CNMG1201212 shape of 86.0WC-1.0TiCN-1.0TaC-0.5NbC-0.5ZrC-11.0Co (above mass%) was prepared. After round honing was performed on the ridge line of the cutting edge of this substrate with a SiC brush, the surface of the substrate was washed. Next, the base material was placed in an external heating type chemical vapor deposition apparatus, and a coating layer was formed on the surface of the base material under the film forming conditions shown in Table 1 so that the composition and the average thickness of the coating layer shown in Table 3 would be obtained. Formed. At this time, the TiCN layer of each sample was formed under the film forming conditions shown in Table 2. The conditions for forming the TiCN layer shown in Table 2 correspond to the types of coating layers shown in Table 1. Ten samples were prepared for each. In the crystal type of the aluminum oxide layer (Al ₂ O ₃ layer) shown in Table 3, α represents an α-type Al ₂ O ₃ layer, and κ represents a κ-type Al ₂ O ₃ layer.

After the coating layer was formed, the obtained sample was subjected to dry shot blasting or wet shot blasting under the conditions shown in Table 4. At this time, in the invention products 1 to 10 and the comparative products 4, 5, and _{7 to 9} , particles of Al ₂ O ₃ or ZrO ₂ having an aspect ratio of 1.5 were used as the projection material. For Comparative Products 3 and 6, steel or Al ₂ O ₃ particles having an aspect ratio of 1.0 was used as the shot material.

For the thickness of each layer of the obtained sample, the cross section near the position of 50 μm from the cutting edge of the coated cutting tool toward the center of the rake face was measured at three locations by SEM, and the average value (arithmetic mean value) was calculated. I asked.

In order to measure the area of the Ti compound layer and the intermittent cracks, the obtained sample was polished in a direction substantially parallel to the surface of the base material until the Ti compound layer was exposed. At this time, polishing surfaces of the rake face and the flank face were prepared. The polished surface of the Ti compound layer was adjusted so that 70% of the average thickness of the Ti compound layer remained, and the polished surface of the Ti compound layer was etched with hydrofluoric acid. The polished surface of the Ti compound layer was observed with an optical microscope at 300 times, and a photograph of the polished surface in the range of 0.33 mm ² was taken. For each sample, three inserts were prepared, the number of Ti compound layer regions and the number of intermittent cracks were determined using photographs of the polished surface, and the average number density A of the Ti compound layer regions was calculated from these values. And the average number density B of the intermittent crack was calculated. The average number density on the rake face was A _r, and the average number density of intermittent cracks was B _r . The average number density on the flank was A _f, and the average number density of the intermittent cracks was B _f . The results are shown in Table 5.

Regarding the atomic ratio [C/(C+N)] of C with respect to the total of C and N contained in the TiCN layer of the obtained sample, the value in the vicinity of the position of 50 μm from the cutting edge of the coated cutting tool toward the center of the rake face was measured. It was measured from the cross section using EPMA. The obtained results are shown in Table 6.

The following cutting test was performed and evaluated using the obtained sample. The results are shown in Table 8.

[Cutting test 1: Wear resistance test]
Work Material: S45C Round Bar,
Cutting speed: 260m/min,
Feed: 0.30 mm/rev,
Notch: 2.0 mm,
Coolant: Yes,
Evaluation item: When the maximum flank wear width reached 0.2 mm without causing defects (defects in the table) or chipping and chipping (indicated as "normal wear" in the table). Was defined as the tool life, and the processing time until the tool life was measured.

[Cutting test 2: fracture resistance test]
Work Material: Two round bars with grooves at equal intervals in the length direction of S45C,
Cutting speed: 220m/min,
Feed: 0.35 mm/rev,
Notch: 1.5 mm,
Coolant: Yes,
Evaluation item: The tool life was defined as the time when the sample was damaged, and the number of impacts until the tool life was measured. The number of impacts was the number of times the sample and the work material contacted each other, and the test was terminated when the maximum number of contacts reached 20,000. Five inserts were prepared for each sample, the number of impacts was measured for each, and the average value (arithmetic mean value) was calculated from the values of the number of impacts, which was taken as the tool life.

The machining time until the tool life in the wear resistance test was evaluated as A for 35 minutes or more, B for 25 minutes or more and less than 35 minutes, and C for less than 25 minutes. In addition, the number of impacts up to the tool life in the fracture resistance test was evaluated as 20,000 times as A, 10,000 times or more and less than 20,000 times as B, and less than 10,000 times as C. In this evaluation, the rank is (excellent) A>B>C (inferior), and the higher A or B, the better the cutting performance.

From the results in Table 8, both the abrasion resistance test and the fracture resistance test of the invention products were evaluated as B or higher. On the other hand, the comparative product was evaluated as C in either of the abrasion resistance test and the fracture resistance test. Further, the evaluation of the fracture resistance test of Comparative Product 5 and Comparative Product 9 was A, but the evaluation of the abrasion resistance test was C. Therefore, it can be seen that the invention product has improved wear resistance without lowering chipping resistance and chipping resistance.

From the above results, it is understood that the tool life of the invention product is extended by improving the wear resistance without lowering the chipping resistance and the chipping resistance.

This application is based on the Japanese patent application filed on May 24, 2016 (Japanese Patent Application No. 2016-103027), the contents of which are incorporated herein by reference.

The coated cutting tool of the present invention can improve wear resistance without impairing chipping resistance and chipping resistance, and can prolong the tool life as compared with conventional ones, and therefore, in the field where such a demand exists, Highly available on.

DESCRIPTION OF SYMBOLS 1... Base material, 2... Coating layer, 3... Rake surface, 4... Relief surface, 5... Cutting edge ridge portion, 11... Ti compound layer, 12... Aluminum oxide layer, 20, 30... Region, 21-23... Small Unit, 31, 32... Small area, 100... Coated cutting tool.

Claims (7)

A coated cutting tool comprising a substrate and a coating layer formed on the surface of the substrate,
The coated cutting tool has a rake face, a flank face, and a cutting edge ridge portion between the rake face and the flank face,
The coating layer comprises at least one Ti compound layer,
The Ti compound layer is a compound layer containing Ti or Ti and Al and at least one element selected from the group consisting of C, N, O and B,
When the polishing surface of the Ti compound layer that is substantially parallel to the surface of the base material is viewed from above, the Ti compound layer has a region surrounded by cracks,
Inside the region, the crack surrounding the region, and has an intermittent crack that does not contact at one end or both ends,
Filled fraud and mitigating risk and mean number density A _r of the region and the average number density B _r of the intermittent cracks 1.2 <B _r / A _r ≦ 1.59 in the rake face,
Filled fraud and mitigating risk and mean number density A _f of the region and the average number density B _f of the intermittent cracks _{0.1 <B f / A f ≦} 0.93 in the flank,
And a coated cutting tool in which B _r /A _r >B _f /A _f . The coated cutting tool according to claim 1, wherein the Ti compound layer is formed on the surface of the base material and has an average thickness of 2.0 μm or more and 20.0 μm or less. The Ti compound layer includes at least one TiCN layer,
The coated cutting tool according to claim 1, wherein the TiCN layer has an average particle size of 0.3 μm or more and 2.0 μm or less. The coated cutting tool according to claim 3, wherein the atomic ratio [C/(C+N)] of carbon to the total of carbon and nitrogen contained in the TiCN layer is 0.50 or more and 0.75 or less. The coated cutting tool according to claim 1, wherein the coating layer has an aluminum oxide layer having an average thickness of 1.0 μm or more and 15.0 μm or less on the surface of the Ti compound layer. The coated cutting tool according to claim 1, wherein the entire average thickness of the coating layer is 3.0 μm or more and 30.0 μm or less. The coated cutting tool according to any one of claims 1 to 6, wherein the base material is one of a cemented carbide, cermet, ceramics and a cubic boron nitride sintered body.