JP3022518B2 - Coated cemented carbide tool - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cutting tool, and more particularly, to a cutting tool made of coated cemented carbide used for cutting steel and cast iron, which is excellent in wear resistance and fracture resistance at the same time. It is.

[0002]

2. Description of the Related Art Conventionally, as a tool material for cutting a metal material, a cemented carbide (WC-Co alloy or an alloy obtained by adding Ti, Ta, or Nb carbonitride to a WC-Co alloy) has been used. However, in recent years, as cutting conditions have become faster,
Periodic table IVa, Va,
Group VIa metals and carbides, nitrides, carbonitrides such as Al,
The use ratio of cemented carbide tools in which a coating film made of a carbonate, a boride, an oxide or a solid solution thereof is coated to a thickness of 3 to 15 μm is increasing. The coating thickness tends to be even greater, and CVD coated cemented carbides having a thickness of 20 μm or more have been proposed. In such a CVD-coated cemented carbide tool, a residual tensile stress is generated in the coating film in a cooling process after coating due to a difference in thermal expansion coefficient between the coating film and the base material, and the fracture resistance of the tool is reduced. The problem was pointed out.

[0003] On the other hand, a proposal has been made to improve the fracture resistance by applying a mechanical impact to the surface of the coated cemented carbide by blasting or the like, introducing cracks penetrating to the base metal in the coating film (patented). Japanese Patent Publication No. Hei 7-6066). It was confirmed that the proposed method improved the fracture resistance to some extent, but the crack that penetrated to the base material was introduced into the coating film in advance, so that the pre-crack length of Griffith became longer, and this longer crack However, there has been a problem that the chipping resistance is deteriorated or the wear of the coating film is disturbed, and the wear resistance is lowered.

[0004]

As described above, in the conventional surface-coated cemented carbide tool, when the thickness of the coating film is increased in order to increase the wear resistance, the fracture resistance of the tool decreases, Even when a crack is previously formed in a coating film having a relatively large thickness, there is a problem that the abrasion resistance is rather reduced depending on the state of the provided crack, which has not been solved yet. An object of the present invention is to provide a coated cemented carbide tool that improves both the fracture resistance and the wear resistance and extends the tool life in view of the conventional circumstances.

[0005]

Means for Solving the Problems In order to achieve the above object, the present inventors have conducted intensive studies and as a result, have determined that a base material is a cemented carbide having WC as a matrix and an iron group metal as a binder phase. After coating the surface with a ceramic film of a specific film quality and structure, by thermally or mechanically controlling the crack length and crack interval introduced into the coating film strictly,
It has been found that the tool life can be greatly extended by improving both the fracture resistance and the wear resistance. That is, the present invention consists of the specified inventions as summarized below.

(1) A coated cemented carbide cutting tool comprising a substrate made of a cemented carbide having WC as a matrix and an iron group metal as a binder phase and having a plurality of coating layers on the surface of the substrate, The innermost layer of the coating layer adjacent to the substrate has a thickness of 0.1 mm.
1 to 3 μm, preferably 0.3 to 1 μm titanium nitride, and (b) the average crack interval in the coating film at the ridge and / or rake face of the cutting edge is reduced on the mirror-polished cross-sectional structure of the tool. Smaller than the average crack interval in the surface coating film, (c)
50% or more of the cracks in the coating film on the ridge portion and / or the rake face of which the tip of the crack is in the innermost layer of titanium nitride or in the upper layer than titanium nitride or at the interface between these layers , Preferably at least 80%,
(D) A coated cemented carbide cutting tool, characterized in that the average length of cracks in the coating film at the cutting edge is shorter than the average value of the coating film thickness at the flank. (2) The coated cemented carbide cutting tool according to (1), wherein the interface between the layers is the interface between the innermost layer of titanium nitride and the layer immediately above it.

(3) On the uppermost layer of titanium nitride,
Titanium carbonitride having a thickness of 3 to 30 μm, preferably 5 to 15 μm, having an aspect ratio of 5 or more, preferably 10 to 50, and at least one alumina layer of 0.5 to 10 μm, preferably 1 to 8 μm in the upper layer The coated cemented carbide cutting tool according to the above (1) or (2), which is coated. (4) Of the cracks in the coating film on the cutting edge ridge and / or the rake face, the tip of the crack on the substrate side is in the innermost layer titanium nitride, in the columnar crystal titanium carbonitride, or in the nitriding. 50% or more, preferably 80 to 100% at the interface between titanium and titanium carbonitride comprising the columnar crystals
% Of the coated cemented carbide cutting tool according to the above (3). (The abundance at the tip of the crack on the substrate side means the total amount.) (5) Alumina having a thickness of 3 to 20 μm is formed on the innermost layer of titanium nitride, and an aspect ratio of 3 to 30 μm is formed on the uppermost layer. The coated cemented carbide cutting tool according to the above (1) or (2), wherein the columnar crystal is made of titanium carbonitride, and the upper layer is further coated with alumina of 0.5 to 10 μm.

(6) The method according to any of (1) to (5) above, wherein the average value of the crack interval in the coating film on the ridge portion and / or the rake face of the cutting edge is 10 μm or less. Coated cemented carbide cutting tool. (7) On the cross-sectional structure, among the crack intervals in the coating film at the ridge portion of the cutting edge or the rake face, the average value of the smaller crack interval is X, and the average value of the crack intervals in the coating film on the flank face is X. The coated cemented carbide cutting tool according to any one of (1) to (6), wherein when Y is set, the value of Y / X satisfies a relationship of 2 or more. (8) Of the cracks in the coating film on the ridge and / or rake face of the cutting edge, 50% or more, preferably 75%, of the cracks on the surface side of the coating film whose tips do not penetrate the surface of the coating film. ~ 1
The coated cemented carbide cutting tool according to any one of the above (1) to (7), wherein the content is 00%.

(9) Among the cracks in the coating film on the ridge portion and / or the rake face of the cutting edge, those present only in the titanium carbonitride film composed of the columnar crystals and not penetrating the coating layers above and below the titanium carbonitride film. Is 50% or more, preferably 70 to 100%. The coated cemented carbide cutting tool according to any one of the above (2) to (8). (10) The coated cemented carbide cutting tool according to any one of (1) to (9), wherein the surface of the cemented carbide has a β-removed layer.

(11) The coated cemented carbide according to any one of the above (1) to (10), wherein cracks in the coating film at the ridge portion of the cutting edge are mechanically introduced after coating. Cutting tools. (12) The titanium carbonitride composed of the columnar crystals is 800 ° C. or higher by a CVD method using an organic CN compound as a reaction gas.
The coated cemented carbide cutting tool according to any one of the above (3) to (11), wherein the coated cutting tool is coated at a temperature of 000 ° C or less, preferably 850 to 950 ° C. (13) The coated cemented carbide cutting tool according to any of (1) to (12) above, wherein the total thickness of the coating film is in the range of 3 to 50 μm. The adhesion between the titanium nitride coated on the innermost layer and the columnar crystal titanium carbonitride or the alumina layer of (5) and between the columnar crystal titanium carbonitride and the alumina layer are between the respective layers. An intermediate layer may be coated for improvement. Examples of the intermediate layer include titanium boronitride, titanium carbide, and titanium carbonitride having a thickness of about 0.1 to 5 μm.

[0011]

DETAILED DESCRIPTION OF THE INVENTION According to the present invention, a cemented carbide having WC as a matrix and an iron group metal as a binder phase or an alloy further added with a carbonitride such as Ti, Ta, Nb, etc., is used as a substrate. A coated cemented carbide cutting tool having a plurality of coating layers on the surface of the substrate, wherein (a) the innermost layer of the coating layer adjacent to the substrate has a thickness of 0.1 to 3 μm, preferably 0.3
チ タ ン 1 μm titanium nitride. Preferably, the upper layer has a thickness of 3 to 30 μm, more preferably 5 to 15 μm, and an aspect ratio of 5 or more, more preferably 10 to 50 columnar crystals of titanium carbonitride, more preferably 0.5 to 10 μm, more preferably 1 to 10 μm. At least one layer of 8 μm alumina is coated. (B) On the mirror-polished cross-sectional structure of the tool, the average crack interval in the coating film on the cutting edge ridge and / or the rake face is made smaller than the average crack interval in the coating film on the flank face. (C) Among the cracks in the coating film on the cutting edge ridge and / or the rake face, the tip of the crack on the substrate side is in the innermost layer of titanium nitride;
Alternatively, 50% or more, preferably 80 to 10%, is present in the upper layer of titanium nitride or at the interface between the layers.
0%. When the titanium nitride of the columnar crystal is coated on the upper layer of the titanium nitride of the innermost layer, the titanium nitride of the innermost layer, the titanium carbonitride of the columnar crystal, or the titanium nitride and the columnar crystal. At the interface with titanium carbonitride consisting of at least 50%, preferably 80 to 100%. (D) It is important that the average length of the cracks in the coating film on the cutting edge ridge and / or the rake face is shorter than the average value of the coating film thickness on the flank face.

Hereinafter, (a) to (d) of the invention (1) will be described.
(D) and other reasons for limiting the invention will be described. (A) The innermost layer is made of titanium nitride because it has excellent adhesion to the cemented carbide material and is very excellent as a film quality for preventing cracks in the coating film from reaching the base material.
If the thickness is less than 0.1 μm, the effect cannot be expected,
When the thickness is more than 3 μm, the abrasion resistance is reduced. The upper layer of titanium carbonitride film is preferably coated from the viewpoint of abrasion resistance. Further, by forming a columnar crystal film having an aspect ratio of 5 or more, it is easy to introduce cracks and the film itself is tough. Limited.
If the aspect ratio is in the range of 10 to 50, particularly excellent performance can be expected. When the thickness is less than 5 μm, the effect of improving the wear resistance is small, and when the thickness is more than 30 μm, the decrease in fracture resistance becomes remarkable.
Further, the upper alumina film is necessary from the viewpoint of suppressing rake face wear when the steel is cut at a high speed.
If the thickness is less than 5 μm, the effect is small, and if it exceeds 10 μm, the fracture resistance is remarkably reduced.

(B) When the cross-sectional structure of the tool is mirror-finished and observed with an optical microscope or a scanning electron microscope, the average crack interval in the coating film on the ridge portion of the cutting edge and / or the rake face is a coating film on the flank. If the average crack interval is smaller than the average crack interval, the fracture resistance during intermittent cutting is improved, and the breakage, falling off, and peeling phenomena of the film due to excessive introduction of cracks at the flank which controls wear resistance can be suppressed. In particular, among the crack intervals in the coating film of the cutting edge ridge portion or the rake face on the cross-sectional structure,
Assuming that the average value of the narrower crack interval is X and the average value of the crack interval in the flank coating film is Y, if the relationship of Y / X is 2 or more is satisfied, in particular, these values are satisfied. Since the effect is remarkable, this is limited. In addition, the said cutting edge ridge line part is the center part of a cutting edge ridge line part (it says to the connecting part with a rake face or a flank), the said flank is a flank center part, and a rake face is a knives edge part. It refers to a position at 0-100 μm from the joint of the rake face to the rake face side (see FIGS. 1 and 2). In addition, the observation of the cross-sectional structure by the above-mentioned optical microscope or scanning electron microscope is performed by taking a photograph of the coating film at a designated place for a length of about 50 to 100 μm in distance and using the photograph to check the state of crack introduction. evaluate. However, when the number of cracks introduced in this observation field is small, the measurement field is extended. The term “crack” as used herein refers to a crack having a length equal to or more than １ ／ of the thickness of each coating layer and introduced in a direction perpendicular to the surface of the coating film (see FIG. 3). this is,
This is because when a crack having a crack length equal to or more than １ ／ of the thickness of each layer is introduced, the film of each layer becomes particularly tough and cutting performance is improved. When the average crack interval of each coating layer was different, the smallest average crack interval was defined as the average crack interval of the present invention.

(C) Among the cracks in the coating film on the ridge portion and / or the rake face of the cutting edge, the tips of the cracks on the base metal side are in the innermost layer titanium nitride, in the columnar crystal titanium carbonitride,
Alternatively, if 50% or more is stopped at the interface between the titanium nitride and the titanium carbonitride composed of the columnar crystal, the rate of cracks penetrating to the base material decreases, so that the cracks penetrating the base material during intermittent cutting are reduced. It is preferable because a phenomenon in which the cemented carbide base material is broken and broken as a source of stress concentration or the cemented carbide immediately below the coating film is broken, whereby the coating film is peeled off and the wear resistance is reduced can be suppressed. Especially preferred is 80%
That is the time.

(D) If the average length of the cracks in the coating film on the ridge and / or the rake face is shorter than the average value of the coating film thickness on the flank, the penetration from the surface to the base metal is made. This is preferable because the number of cracks can be reduced, and the fracture of the cemented carbide base material due to oxidation of the cemented carbide base material at the tip of the crack penetrating the base material during high-speed cutting and an increase in wear due to peeling of the film can be suppressed.

[0016] Further, 3
２０20 μm alumina, and furthermore, a thickness of 3 to 30
It is preferable that titanium carbide nitride having a columnar crystal having an aspect ratio of 5 μm or more and alumina having a thickness of 0.5 to 5 μm be further coated thereon because both high-speed and low-speed wear resistance are compatible. Here, the inner 3 to 20 μm alumina is 3 μm.
When the thickness is smaller than m, the effect is small, and when the thickness is larger than 20 μm, the fracture resistance is significantly reduced.
Also, the outer 0.5-10 μm alumina is 0.5 μm
When the thickness is thinner, the effect is small. When the thickness is larger than 10 μm, the wear resistance is reduced. Further, by setting the average value of the crack interval in the coating film of the cutting edge ridge portion and / or the rake face to 10 μm or less, the cutting stress applied to the cutting edge ridge portion is prevented from being concentrated on a specific crack tip. In other words, stress can be dispersed, so that fracture resistance is improved, and abnormal wear is suppressed.

[0017] Further, among the cracks in the coating film on the ridge line portion and / or the rake face of the cutting edge, if not more than 50% of the cracks on the coating film surface side do not penetrate the coating film surface, The high heat generated during high-speed cutting is preferable because deterioration of the film quality due to oxidation of the coating film, breakage of the film, and a rapid increase in wear due to peeling can be suppressed. In particular, at this time, if cracks in the coating film at the ridge portion of the cutting edge exist only in the titanium carbonitride film made of the columnar crystals, and 50% or more of the cracks do not penetrate through the coating layers above and below, Since the crystal grains of the titanium carbonitride film composed of the columnar crystals are columnar, even in cutting in which an impact is repeatedly applied, such as during intermittent cutting, cracks develop parallel to the film surface or cracks coalesce. This is preferable because it can suppress the occurrence of welding defects due to chipping of the film and a rapid increase in wear due to peeling of the film. In the coated cemented carbide of the present invention, the total coating thickness range is 3 to 50.
It is preferably set to μm.

Next, on the surface of the cemented carbide, a β-free layer (WC
And a layer having no precipitates other than the binder phase metal), since the toughness on the surface of the cemented carbide base material is improved when the crack propagates into the base material due to the cutting stress, Cracks do not easily propagate, and fracture resistance can be further improved. In addition, β
When there is a portion having a higher hardness than the inside of the alloy immediately below the layer, the balance between fracture resistance and wear resistance is improved. The de-β layer can be obtained by sintering a cemented carbide composition powder containing nitride and / or carbonitride in a denitrification atmosphere such as vacuum, and its thickness is preferably 5 to 50 μm. In addition,
The crack in the coating film at the edge of the cutting edge can be mechanically introduced after coating, and the coated cemented carbide cutting tool of the present invention can be manufactured by controlling the degree of mechanical impact. As a method of applying a mechanical impact, there can be mentioned, for example, a method of polishing with a brush or an elastic whetstone to which abrasive grains are adhered, a method of barrel processing, and the like, in addition to the blast processing.

The titanium carbonitride composed of the columnar crystals is produced by CVD using an organic CN compound such as acetonitrile (CH ₃ CN), succinonitrile, tolunitrile, acrylonitrile or butyronitrile as a reaction gas.
The coating at a temperature of 0 ° C. or more and 1000 ° C. or less is preferable because the titanium carbonitride film easily becomes columnar crystals having an aspect ratio of 5 or more and the cracks described in the present invention are easily introduced.

[0020]

Hereinafter, the present invention will be described with reference to examples.
This does not limit the present invention. Example 1 86% WC-3% TaC-1% N by weight
A cemented carbide powder having a composition of bC-2% TiC-1% ZrC-7% Co is pressed at 1400.degree.
Sintering under the condition of holding time, flattening, cutting edge treatment, IS
A cemented carbide chip having a shape of O model number CNMG120408 was produced. The chip was coated with the following three types of coating films in order from the bottom by a CVD method. Film quality: 0.5 μm TiC-10 μm TiCN (aspect ratio 3) -0.5 μm TiBN-2 μm α-alumina (total film thickness 13 μm) Film quality: 0.5 μm TiN-10 μm TiCN (aspect ratio 3) -0.5 μm TiBN-2 μm α-alumina (total film thickness) 13 μm) Film quality: 0.5 μm TiN-10 μm TiCN (aspect ratio 7) -0.5 μm TiBN-2 μm α-alumina (total film thickness 13 μm)

When coating a TiCN film of a quality, acetonitrile is used as a raw material as an organic CN compound.
Columnar TiCN coated at 00 ° C with an aspect ratio of about 7
A film was formed. In addition, H ₂ S gas was used as an additive gas when coating the alumina film, and the film was coated so that the film thickness was uniform at the ridge of the cutting edge and at the center of the flank. For this reason, the coating film thickness was about 13 μm for each of the rake face, the ridge line of the cutting edge, and the center of the flank face in any film quality.

Further, the surface of the coated cemented carbide is changed in the crack state in the coating film shown in Table 1 by changing the size, the projection speed, the projection angle, and the projection time of the iron ball using the iron ball. A chip was prepared. The state of cracks in the coating film is
After cutting each coated cemented carbide with a diamond wheel and embedding it in resin so that the cut surface can be seen, the cut surface is ground at a grinding speed of 30 m / s using a # 140 diamond wheel with a grinder.
ec, feed rate 20 cm / sec, depth of cut 4 μm
(Initial), 2 μm (middle), 1 μm (late), about 300 μm thick surface ground, and # 15 with a polishing machine
Rough polishing with a diamond paste having a mean particle size of 1 00 to 11.5 to 8.9 μm, followed by # 3000 (average particle size of 5.
The surface polished and finished with a diamond paste of 9 to 4.7 μm, JIS R6001) was x1 using an optical microscope.
Observed at 500 and quantified.

[0023]

[Table 1]

Next, using these chips, a work material made of SCM435 shown in FIG. 4 (a round bar material having four grooves on the outer periphery and being intermittently cut) was cut under the following conditions, and the fracture resistance of each tool was determined. Abrasion resistance test 1 was carried out under the following conditions using a work material made of SCM435.

[0025] The life was determined at the time of occurrence of chipping, and the life was averaged over four corners.

[0026]

Table 2 shows the results.
film thickness of 10 μm coated with a columnar crystal TiCN film having an aspect ratio of 3 or 7,
[Satisfies the constituent requirement (a) of the invention (1)], and the crack state is (b), (c), or
Sample No. satisfying the constitutional requirements of (d). 1-6, 1-8 ~
The sample No. 1-13 (the product of the present invention) has the lowermost layer which is not TiN. 1-1 to 1-3 and film quality,
Sample No. which does not satisfy any of the constituent requirements (b), (c) and (d) 1-4, 1-5, 1-7 and 1-14 to 1-
As compared with No. 16, excellent fracture resistance and wear resistance were exhibited. Above all, the average value of the crack interval in the coating film at the edge line of the cutting edge is 10 μm.
Inventive product No. 1-9 to 1-12 showed particularly excellent fracture resistance and wear resistance. Further, the invention product 1 in which the value of Y / X (the average value of the crack interval at the edge of the cutting edge X, the average value of the crack interval in the flank coating film Y) is 2 or more.
10, 1-11 and 1-12 exhibited particularly excellent fracture resistance and abrasion resistance.

[0028]

[Table 2]

(Example 2) The same cemented carbide as in Example 1 was used.
A cemented carbide tip having the shape of SO model number CNMG120408 was produced. This chip was coated with the coating film quality described in Example 1, and the surface of the coated cemented carbide was blasted from the rake face side using an iron powder of about 100 μm while changing the projection speed variously, as shown in Table 3. Chips with different crack states in the coating film were produced. Using these chips, the same cutting test as in Example 1 was performed.

[0030]

[Table 3]

The results are shown in Table 4. No. 1 of the present invention. Each of the tips 2-3 to 2-7 exhibited excellent chipping resistance and wear resistance. In particular, the tip of the crack in the coating film on the edge line of the cutting edge on the base metal side was formed of the innermost layer of titanium nitride or carbon. The sample No. in which the ratio stopped in the titanium nitride was 80% or more. 2-5, 2-6, and 2-7 exhibited particularly excellent fracture resistance and wear resistance.

[0032]

[Table 4]

Example 3 The same cemented carbide as in Example 1 was used.
A cemented carbide tip having the shape of SO model number CNMG120408 was produced. Film quality: 1 μm TiN-7 μm TiCN (aspect 5)
２０20) -2 μm TiC-5 μm κ-alumina (total film thickness 15 μm). The TiCN film uses acetonitrile, nitrogen gas, TiCl ₄ , and hydrogen gas as a source gas or a carrier gas, changes the coating temperature during coating in the range of 800 to 1000 ° C., and further changes the furnace pressure and the gas composition ratio. By covering by covering, an object having an aspect ratio in a range of 5 to 20 was produced. Further, after flank surfaces of these tools were masked, iron powder was blasted from the rake surface side while changing the projection speed, and chips having different crack states in the coating film shown in Table 5 were produced. Using these chips, the same cutting test as in Example 1 and the wear resistance test 2 shown below were performed.

[0034]

[Table 5]

[0035]

The results are shown in Table 6. No. 1 of the present invention. All of the chips 3-3 to 3-9 exhibited excellent fracture resistance and wear resistance. Among the cracks in the coating film on the ridge of the cutting edge, the tip of the crack on the surface of the coating film was particularly high. Sample N in which 50% or more do not penetrate the coating film surface
o. The chips 3-5 to 3-9 showed particularly excellent wear resistance in the wear resistance test 1, which is a high-speed cutting test. Further, among the cracks in the coating film at the edge of the cutting edge, 50% or more of the cracks were present only in the titanium carbonitride film formed of columnar crystals and did not penetrate the coating layers above and below. 3
The chips of -7 to 3-9 showed excellent performance in the fracture resistance test 1 and the abrasion resistance test 2 in which the film was easily peeled off by the impact of intermittent cutting.

[0037]

[Table 6]

Example 4 86% WC-1% T by weight
aC-1% NbC-3% TiC-2% ZrCN-7% C
o and pressed in a vacuum atmosphere.
Sintering was performed under the condition of holding at 00 ° C. for 1 hour, and flattening and cutting edge treatment were performed to produce a cemented carbide chip having a shape of ISO model number CNMG120408. The cross section of this cemented carbide was mirror-polished and the structure was observed with an optical microscope.
It could be confirmed that a 5 μm de-β layer was formed, and a portion having a higher hardness than the inside of the alloy was formed immediately below the β-layer. This chip and the chip produced in Example 1 having no β-removed layer on the alloy surface were coated with the film quality coated in Example 1. Furthermore, the surface of this coated cemented carbide is
The size of the iron ball, the projection speed, the projection angle, and the projection time were changed using an iron ball in the same manner as in Example 1 and blasting was performed to produce chips having different crack states in the coating film shown in Table 7. did.

[0039]

[Table 7]

Next, a chip resistance test 1 and a wear resistance test 1 were carried out using these chips in the same manner as in Example 1. The results are shown in Table 8. N which is the product of the present invention
o. All of the chips 4-1 to 4-4 exhibited excellent fracture resistance and wear resistance. Sample Nos. 4-3 and 4-4 have no β-removed layer. Compared to 4-1 and 4-2, it was confirmed that they had particularly excellent fracture resistance and wear resistance.

[0041]

[Table 8]

(Example 5) The surface of the cemented carbide prepared in Example 4 was coated with the following film quality. Further, the surface of the coated cemented carbide was polished from the rake face side with a brush having diamond # 400 adhered thereto, and the brush rotation speed, the brush cutting amount, the amount of the grinding oil, etc. were changed to change the coating speed shown in Table 9 below. Chips with different crack states in the coating were produced. Using these chips, the same chipping resistance test and SCM415 as in Example 1 were subjected to wear resistance tests 3 and 4 under cutting conditions shown in Table 10 below. Film quality: 0.3 μm TiN-0.4 μm TiBN-6 μ
mα-Al ₂ O ₃ −0.3 μm TiCNO-10 μmT
iCN (aspect ratio 10) -0.5 μm AlON-
1.5 μm κ-Al ₂ O ₃ (total film thickness 19 μm)

[0043]

[Table 9]

[0044]

[Table 10]

The results are shown in Table 11. From the results in Table 11, Samples 5-3 to 5-8 of the present invention were Samples 5-1, 5-
It can be seen that it has excellent wear resistance and chipping resistance as compared with Comparative Example 2. Among them, samples 5-6, 5-7, and 5-8 in which the ratio of the presence of cracks only in the TiCN film exceeded 50% showed particularly excellent performance in high-speed cutting.

[0046]

[Table 11]

As described above, the present invention has been described by way of examples. However, the scope of the present invention is limited by the contents described in the claims, and the scope of the claims can be limited by the above examples. is not.

[0048]

According to the present invention, the distance between cracks in the coating layer of a cemented carbide, the position of the tip thereof, and the like are quantitatively specified.
Excellent fracture resistance and wear resistance can be obtained.

[Brief description of the drawings]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory view showing a cutting edge ridge, a flank, a rake face, and the like of a tip according to the present invention.

FIG. 2 is a schematic view of the chip of FIG. 1 as viewed from above.

FIG. 3 is an explanatory view showing a positional relationship between a tip of a crack and a substrate in a coating layer of a cemented carbide according to the present invention.

FIG. 4 is a cross-sectional view of a work material (round bar) made of SCM435 used for a cutting test of an example.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-11-99405 (JP, A) JP-A-10-15711 (JP, A) JP-A 9-1403 (JP, A) JP-A-7-107 26366 (JP, A) JP-A-6-246512 (JP, A) JP-A-6-108258 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B23B 27/14 C23C 16 / 36 C23C 28/04

Claims (14)

(57) [Claims] 1. A coated cemented carbide cutting tool comprising a substrate made of a cemented carbide with WC as a matrix and an iron group metal as a binder phase, and a plurality of coating layers provided on the surface of the substrate.
(A) the innermost layer of the coating layer adjacent to the substrate has a thickness of 0.1 to
(B) the average crack interval in the coating film on the ridge and / or the rake face of the cutting edge on the mirror-polished cross-sectional structure of the tool, the average crack interval in the coating film on the flank face; (C) Among the cracks in the coating film on the cutting edge ridge and / or the rake face, the tip of the crack on the substrate side is in the innermost layer of titanium nitride or in the upper layer than titanium nitride or between the layers. (D) the average length of the cracks in the coating film at the cutting edge ridge and / or the rake face is shorter than the average value of the coating film thickness at the flank face. A coated hard metal cutting tool characterized by the above-mentioned. 2. The coated cemented carbide cutting tool according to claim 1, wherein the interface between the layers is the interface between the innermost layer of titanium nitride and the layer immediately above it. 3. An upper layer of the innermost layer of titanium nitride is coated with titanium carbonitride having a thickness of 3 to 30 μm and comprising columnar crystals having an aspect ratio of 5 or more, and at least one layer of alumina of 0.5 to 10 μm is further coated thereon. The coated cemented carbide cutting tool according to claim 1 or 2, wherein 4. Among the cracks in the coating film on the ridge portion and / or rake face of the cutting edge, the tip of the crack on the substrate side is in the innermost layer titanium nitride, in the columnar crystal titanium carbonitride, 4. The coated cemented carbide cutting tool according to claim 3, wherein an amount at an interface between the titanium nitride and the titanium carbonitride composed of the columnar crystal is 50% or more. 5. 5. A crack in the coating film on the ridge portion and / or the rake face of the cutting edge, wherein the tip of the crack on the substrate side is in the innermost layer titanium nitride, in the columnar crystal titanium carbonitride, The coated cemented carbide cutting tool according to any one of claims 1 to 4, wherein an amount at an interface between the titanium nitride and the titanium carbonitride composed of the columnar crystal is 80% or more. 6. An upper layer of titanium nitride of 3 to 2
0 μm alumina, 3 to 30 μm thick on top
A titanium carbonitride comprising columnar crystals having an aspect ratio of 5 or more,
3. The coated cemented carbide cutting tool according to claim 1, wherein the upper layer is further coated with alumina of 0.5 to 10 [mu] m. 7. The coated cemented carbide according to claim 1, wherein an average value of a crack interval in the coating film on the ridge portion and / or the rake face of the cutting edge is 10 μm or less. Cutting tools. 8. The average value of the smaller of the crack intervals among the crack intervals in the coating film on the cutting edge ridge portion or the rake face on the sectional structure is X, and the average value of the crack intervals in the coating film on the flank face. The coated cemented carbide cutting tool according to any one of claims 1 to 7, wherein when the value is Y, the value of Y / X satisfies a relationship of 2 or more. 9. Of the cracks in the coating film on the ridge and / or the rake face, at least 50% of the cracks on the surface side of the coating film do not penetrate the surface of the coating film. The coated cemented carbide cutting tool according to any one of claims 1 to 8, wherein: 10. Among the cracks in the coating film on the ridge portion and / or the rake face of the cutting edge, there are cracks that exist only in the titanium carbonitride film made of the columnar crystals and do not penetrate the coating layers above and below. It is at least 50%.
The coated cemented carbide cutting tool according to any one of the above. 11. The coated cemented carbide cutting tool according to claim 1, wherein a surface of said cemented carbide has a β-removed layer. 12. A coated cemented carbide cutting tool according to claim 1, wherein cracks in the coating film at the edge of the cutting edge are mechanically introduced after coating. 13. The titanium carbonitride comprising columnar crystals is formed at a temperature of 800 ° C. by a CVD method using an organic CN compound as a reaction gas.
The coated cemented carbide cutting tool according to any one of claims 3 to 12, wherein the coated tool is coated at a temperature of at least 1000 ° C. 14. The coated cemented carbide cutting tool according to claim 1, wherein the total thickness of the coating film is in the range of 3 to 50 μm.