JPH11140647A - Coated cemented carbide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an alloy having excellent peeling resistance, wear resistance, crater resistance and rupture strength and suitable for cutting tools by regulating the orientational properties of a carbon nitride titanium layer included in the internal layer of a ceramics coating layer to a specified range. SOLUTION: On the surface of a base material of a cemented carbide composed of the WC series hard phase contg. one or more kinds among the carbides, carbon nitrides and nitrides of the group IVa, Va and VIa metals and the Co series bonding phase, ceramics-coating layers as an internal layer and an external layer are formed. The external layer includes at least an aluminum oxide layer, and the crystal structure of the layer has the α type. The internal layer has a multilayer structure having a carbon nitride titanium layer, the layer is composed of a columnar structure having a thickness of >=10 μ, and, in the case the index of the orientational properties TC of the layer is defined as the formula, Both indexes of the orientational properties TC (422) and TC (311) expressed by the formula are regulated to 1.3 to 3. In the formula, I (hk1) denotes the measured diffraction intensity in the measured (hk1) plane, I0 (hk1) denotes the average value of the powder diffraction intensity of TiC and TiN in the (hk1) plane in accordance with the ASTM standard, and (hk1) denotes 8 planes such as (111) or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a coated cemented carbide, and more particularly to a coated cemented carbide used for cutting tools and the like, which is excellent in toughness and wear resistance.

[0002]

2. Description of the Related Art The life of a cutting tool has been improved by depositing a coating layer of titanium carbide, titanium nitride, titanium carbonitride or aluminum oxide on the surface of a cemented carbide. In general, chemical vapor deposition, plasma CVD (Chemical Vap
or a deposition layer formed by using a physical vapor deposition method or the like.

[0003] However, when machining is performed using these coated cutting tools, machining that requires wear resistance of the coating layer at high temperatures, such as high-speed cutting of steel or machining of ductile cast iron at high speeds, In addition, the wear resistance of the coating layer may be insufficient due to the large number of processes such as small component processing and the number of bites to the work material, or the tool life may be shortened due to damage or peeling of the coating layer. Had occurred.

[0004] In order to overcome these problems, a coating technique has heretofore been controlled by controlling the structure of a coating layer or disclosed in JP-A-8-132130 and JP-A-5-269606.
Many improvements have been attempted, such as the control of the orientation of the coating layer as disclosed in Japanese Patent Application Laid-Open Publication No. H11-163,036. However, the effect was not enough at present.

Accordingly, an object of the present invention is to provide a coated cemented carbide having excellent peel resistance, wear resistance, crater resistance and excellent breaking strength, and suitable for a cutting tool. .

[0006]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the inventors of the present invention have found that compared with conventional coated cemented carbides for coated cutting tools, peeling of the coating layer during cutting is more difficult. Has found a coated cemented carbide that can greatly improve the tool life by stably improving the tool life by greatly improving the wear resistance of the film itself and improving the breaking strength of the film. .

Therefore, the coated cemented carbide of the present invention has the following constitution. The coated cemented carbide of the present invention contains tungsten carbide as a main component, a hard phase containing at least one of carbides, nitrides, and carbonitrides of group IVa, Va, and VIa metals, and a binder phase containing Co as a main component. And a ceramic coating layer having an inner layer and an outer layer formed on the surface of the base material. The inner layer and the outer layer have the following characteristics.

The outer layer includes at least an aluminum oxide layer, and the aluminum oxide layer has an α-type crystal structure.

The inner layer has a multilayer structure having a titanium carbonitride layer. The titanium carbide layer has a columnar structure having a thickness of 10 μm or more, and has an orientation index TC of the titanium carbonitride layer.
To

[0010]

(Equation 3)

When defined as (4)
The orientation index TC (42) between the (22) plane and the (311) plane
2) and TC (311) are both 1.3 or more and 3 or less.

In the coated cemented carbide of the present invention, both the orientation index TC (422) and TC (311) of the titanium carbonitride layer are set to 1.3 or more, and the structure is made to be a columnar structure, so that it is 10 μm or more. Even with a film thickness, it is possible to improve the abrasion resistance while greatly improving the destruction resistance of the film.
However, if the orientation index TC (422) or TC (311) exceeds 3, the orientation in a certain direction becomes too strong, and conversely, the film has reduced fracture resistance.

[0013] The wear resistance is improved only by 10 µm.
In addition to the effect of the columnar structure having the thick film, the improvement of the fracture resistance of the film is considered to have a great effect of suppressing the progress of wear due to chipping in the film during cutting. further,
Since chipping in the film is less likely to occur, welding of the workpiece during cutting due to this is less likely to occur, and an increase in cutting stress applied to the film can be prevented, so that peeling resistance can be significantly improved.

In the present structure, the titanium carbonitride layer is
The atmosphere during coating is TiCl_Four , CH _Three CN, N_Two and
H_Two The conditions for the first half and the second half were changed as follows.
Filmed. That is, for 120 minutes from the beginning of film formation,
(TiCl_Four + CH_Three CN) / Total gas volume ratio
N smaller than the second half, and N in the first half_Two / Total gas
By setting the ratio of the amount to twice or more of the latter half,
A layer is formed.

In the coated cemented carbide of the present invention, the inner layer has at least one layer of a titanium nitride layer and a titanium boronitride layer in addition to the titanium carbonitride layer, and the outer layer has a titanium carbide layer and a carbonitride layer other than the aluminum oxide layer. It is preferable to have at least one layer of a titanium layer and a titanium nitride layer.

In the coated cemented carbide of the present invention, the orientation index TC (hkl) except for the orientation index TC (422) and TC (311) is preferably 1.5 or less.

In the structure of the coated cemented carbide according to the present invention, the orientation of the titanium carbonitride layer is TC (422) and TC (31).
1) alone and strong, orientation index TC of crystal plane excluding these
By setting (hkl) to 1.5 or less, more remarkable effects can be obtained.

In the coated cemented carbide of the present invention, it is preferable that the layer immediately below the outer aluminum oxide layer is a titanium boronitride layer.

In the coated cemented carbide of the present invention, the orientation index TCa of the aluminum oxide layer having the α-type crystal structure is represented by

[0020]

(Equation 4)

When defined as (1)
The orientation index between the (10) plane and the (104) plane is TCa (1).
10) It is preferred that ≧ 1.2 and TCa (104) ≧ 1.2.

In the structure of the coated cemented carbide according to the present invention, an effect of further improving the performance can be obtained by coating the outer layer with an aluminum oxide layer mainly having an α-type crystal structure having the above-mentioned orientation.

From the viewpoint of further improving the performance, α
Index TCa of the aluminum oxide layer having the p-type crystal structure
Are TCa (104) ≧ 1.3 and TCa (116) ≧
It is preferably 1.3.

With this structure, the effect of suppressing crater wear occurring on the rake face is improved. This is because crater abrasion, which occurred in the conventional film quality, appeared as a combination of general chemical abrasion and mechanical damage such as film peeling and film destruction caused by cutting chips, whereas the structure of the present invention With the effect that the film strength and hardness of the base of the aluminum oxide layer are significantly improved, mechanical damage is suppressed,
In addition, chemical wear is suppressed by the effect of the aluminum oxide layer.

Here, the α-type aluminum oxide layer is made of A
It is manufactured by a normal CVD process using lCl ₃ and CO ₂ as source gases. Generally, CV using this source gas
In the D process, the crystal structure of aluminum oxide is α,
A κ or θ structure is obtained. In general, among aluminum oxides, among κ-type aluminum oxides, the finest aluminum oxide is easily obtained, and high strength and high adhesion are easily obtained. However, because κ-type aluminum oxide is a metastable phase that is stable at a relatively low temperature, the hardness, especially the high-temperature hardness, tends to be lower than that of α-type aluminum oxide, resulting in inferior wear resistance.

According to the combination of the orientation of the inner layer of the present invention and the combination of the α-type aluminum oxide layer, one of the conventional problems can be solved.
Thus, it has succeeded in suppressing the decrease in the adhesion strength. In addition, in the aluminum oxide layer of the present invention, by setting the orientation within the range of the present invention, despite being an α-type aluminum oxide, a high hardness similar to that of a κ-type can be realized while a high hardness of the aluminum oxide layer is achieved. And high wear resistance.

The specific control of the orientation of the α-type aluminum oxide is carried out by the following method. First, after coating the layer immediately below the aluminum oxide layer, before starting the film formation of the aluminum oxide layer, an atmosphere containing only CO ₂ and H ₂ as a carrier is used, and the CO ₂ partial pressure P _CO2 at this time is changed to P _CO2 = 0.3
０．６0.6 torr and slightly oxidize the surface of the layer directly underneath for 5 to 10 minutes.
An aluminum oxide layer is formed at a temperature of ° C. This makes it possible to form an α-type aluminum oxide layer irrespective of the film formation temperature of the aluminum oxide layer. However, by controlling the oxidation conditions on the surface immediately below the α-type aluminum oxide layer, the orientation of the aluminum oxide layer can be controlled. Is possible. The orientation can also be changed by changing the thickness of the aluminum oxide layer using the same oxidation conditions.

The use of a TiBN layer obtained by adding a small amount of boron to TiN as the immediately lower layer is effective for improving the adhesion of the upper aluminum oxide layer.

In the coated cemented carbide of the present invention, it is preferable that the aluminum oxide layer does not exist only in the vicinity of the ridge of the cutting edge.

After the coating layer is coated, the surface of the coating layer is treated by mechanical treatment such as blasting or brushing until the aluminum oxide layer is removed only at the cutting edge ridge portion, whereby the surface is treated. The above effect is greater. The degree of treatment at this time is required to ensure that the aluminum oxide layer is surely removed at the cutting edge portion of the cutting edge ridge line with which the cutting powder actually contacts during cutting. However, depending on the degree of treatment, there is no problem even if the aluminum oxide layer remains without being partially removed at the ridge portion at a position away from the cutting edge, and the effects of the present invention can be obtained. Also, in the present invention, the aluminum oxide layer does not exist only at the cutting edge ridge portion, but depending on the processing method, it may be removed even at an angular location unrelated to cutting, such as around the seating surface of the chip, This does not substantially affect the effects of the present invention.

[0031] In the coated cemented carbide of the present invention, the tensile residual stress of the inner titanium carbonitride layer at the cutting edge ridge portion is 1
It is preferably 0 kg / mm ² or less.

After coating by the film surface treatment as described above,
By reducing the residual tensile stress existing in the coating layer to 10 kg / mm ² or less in the TiCN layer as the inner layer, it is possible to improve the effect on the breakdown resistance of the film.

The coated cemented carbide according to the present invention has a layer in which the hard phase other than tungsten carbide is reduced or disappears on the surface of the substrate of the cemented carbide, and the thickness of the layer is 50 μm or less in the flat part. Is preferred.

The surface of the cemented carbide substrate has a layer in which the hard phase other than tungsten carbide has been reduced or disappeared, and the thickness of the flat layer is 50 μm or less. The combination of the coating layer and the surface treatment according to the present invention is very effective against damage such that the coating layer falls off near the surface layer of the cemented carbide part.

The reason why the thickness of the substrate surface layer region is set to 50 μm or less is that if the thickness exceeds 50 μm, a slight plastic deformation or elastic deformation tends to occur in the surface layer during cutting.
m or less is more effective.

The surface layer is formed by a known method using a nitrogen-containing hard phase raw material, or a nitriding atmosphere during the heating process during sintering. It can be manufactured by a method of setting a charcoal atmosphere.

[0037]

Embodiments of the present invention will be described below.

Example 1 CNMG120408 was used as a substrate with the following compositions A to D.
A WC-based cemented carbide substrate having the following shape was prepared.

A: WC-10% Co-3% ZrCN-6% NbC B: WC-6% Co-3% ZrCN-2% TiCN C: WC-10% Co-5% TiCN-3% NbC D: WC-6% Co-2% ZrC-3% TiC A coating film having the structure of the inner layer and the outer layer shown in Table 1 was formed on the surface of the substrate.

[0040]

[Table 1]

Samples A to C have a layer consisting of WC and Co only on the surface layer of the base material. The thickness of each layer in each sample is a flat part thickness, A: 25 μm, B:
50 μm, C: 55 μm. No surface layer region was present on the substrate surface of Sample D. The coating conditions of each layer of the product of the present invention are shown below.

(TiN layer) Temperature: 880 ° C., pressure: 120 torr, reaction gas composition: 46% H ₂ -4% TiCl ₄ -50% N in volume%
₂ (TiCN layer of present invention products 1 to 5) TiCN layer (first half 120 minutes): temperature: 880 ° C., pressure: 68 torr, reaction gas composition:
By _{volume%, 68.6% H 2 -1.2%} TiCl 4 -0.
2% CH ₃ CN-30% N ₂ TiCN layer (remaining in the latter half): temperature: 880 ° C., pressure: 68 torr, reaction gas composition:
By _{volume%, 76.6% H 2 -7.2%} TiCl 4 -1.
2% CH ₃ CN-15% N ₂ (TiBN layer) Temperature: 990 ° C., pressure: 150 torr, reaction gas composition: 45.5% H ₂ -4% TiCl ₄ -49 by volume%
% N ₂ -1.5% BCl ₃ (Al ₂ O ₃ layer) Temperature: 1030 ° C., Pressure: 68 torr, Reaction gas composition: 85% H ₂ -9% AlCl ₃ -6% CO by volume%
₂ (TiC layer) Temperature: 1030 ° C., pressure: 68 torr, reaction gas composition: 90% H ₂ -3% TiCl ₄ -7% CH by volume%
₄ Here, the orientation index of the inner TiCN layer was determined from a diffraction peak by X-ray diffraction. At this time, (31) of TiCN
1) The diffraction peak of the plane overlaps the peak of the (111) plane of the WC of the substrate, and the peak intensity of the (111) plane is (the intensity of the (101) plane, which is the strongest peak of the WC) × 0.25. This was subtracted from the strength of the (311) plane of TiCN to subtract the strength of the WC (111) plane.

Table 2 shows the orientation of the TiCN layer of each sample.
Shown in Table 3 shows the orientation of alumina.

[0044]

[Table 2]

[0045]

[Table 3]

Here, by changing the oxidation state of the surface of the TiBN film before the formation of the alumina, a sample in which the orientation of the alumina was changed was simultaneously produced.
These are shown in the table as b, 1c. here,
The sample of a, P _CO2 = 0.3 torr, 5 minutes, the sample of b, P _CO2 = 0.4 torr, 10 minutes, the sample of c, P _CO2 =
Oxidation conditions of 0.6 torr and 10 minutes are used.

The TiCN layer of the present invention was broken after coating, and it was confirmed by SEM (scanning electron microscope) observation of the fractured surface that it had a columnar structure.

Tables 1 and 2 also show comparative products for comparison. The TiCN films of Comparative Products 6 and 7 were formed as follows.
The test was performed under the following conditions.

(TiCN layer (Comparative product 6)) Temperature: 880 ° C., Pressure: 68 torr, Reaction gas composition:
76.6% H in volume%_Two -7.2% TiCl_Four -1.
2% CH_Three CN-15% N_Two (TiCN layer (Comparative product 7)) Temperature: 1000 ° C, pressure: 150 torr, reaction gas set
Composition: 90% H by volume%_Two -4% TiCl_Four -4% CH
_Four -2% N _Two The alumina layer of the comparative product 8 was formed under the following film forming conditions.
A κ-type alumina was produced. In comparison product 8,
Except for the alumina layer, a film was formed under the conditions of the product of the present invention.

(Alumina layer (comparative product 8)) Temperature: 980 ° C., pressure: 68 torr, reaction gas composition:
A sample with a volume percentage of 85% H ₂ -9% AlCl ₃ -6% CO ₂ (oxidation of the surface of the TiBN layer before alumina formation is not performed, and alumina formation is started simultaneously with the reaction gas composition of alumina) is used. The cutting evaluation was performed under the following cutting conditions 1 and 2.

(Cutting condition 1) Work material: SCM415 (4-groove material) Cutting speed: 250 m / min Feeding: 0.20 mm / rev Cutting depth: 1.5 mm Number of impacts: 500 times Cutting oil: water soluble (Cutting condition 2) ) Work material: FCD70 Cutting speed: 250 m / min Feed: 0.3 mm / rev Cutting depth: 1.5 mm Cutting time: 10 minutes Cutting oil: Water-soluble The evaluation results are shown in Tables 4 and 5.

[0052]

[Table 4]

[0053]

[Table 5]

From these results, it can be seen that the product of the present invention is superior to the conventional product in all of the abrasion resistance, chipping resistance and crater resistance of the film.

[0055]Example 2 Using samples 1a and 2a produced in Example 1,
After coating the coating layer, the alumina layer at the ridge was removed.
Until it is coated with a nylon brush containing SiC abrasive grains.
The surface was treated. Prepare a surface-treated sample,
These were 1aH and 2aH. In addition, iron
Samples 1aHB and 2 blasted using powder
aHB was prepared, and these were measured using an X-ray diffractometer.
And sin ^Two The residual stress of the inner TiCN layer is reduced by the ψ method.
It was measured. Table 6 shows the stress measurement results, and the cutting conditions of Example 1.
Tables 7 and 8 show the results of cutting evaluation under the conditions 1 and 2.
Shown in

[0056]

[Table 6]

[0057]

[Table 7]

[0058]

[Table 8]

From these results, it was found that the samples 1aH and 2aH not subjected to the blast treatment all had a tensile residual stress of more than 10 kg / mm ² , whereas the samples 1aHB and 2aHB subjected to the blast treatment had a residual tensile stress of 10 kg / mm ^2. mm ² or less. In the samples 1aHB and 2aHB subjected to the blast treatment,
It was found that both the flank wear and the chipping were improved as compared with the samples 1aH and 2aH which were not subjected to the blast treatment under both the cutting conditions 1 and 2.

The embodiments disclosed this time are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

[0061]

As described above, in the coated cemented carbide of the present invention, by setting the orientation of the titanium carbonitride layer contained in the inner layer of the ceramic coating layer to a predetermined range,
A coated cemented carbide having excellent exfoliation resistance, abrasion resistance, crater resistance and excellent breaking strength, and suitable for a cutting tool can be obtained. This makes it possible to stably and dramatically improve the life of the cutting tool.

Claims (9)

[Claims] 1. The method according to claim 1, wherein the main component is tungsten carbide.
a, Va, a cemented carbide composed of a hard phase containing at least one of carbides, nitrides, and carbonitrides of Group VIa metals and a binder phase containing Co as a main component; A ceramic coating layer comprising an inner layer and an outer layer formed, wherein the inner layer has a multilayer structure having a titanium carbonitride layer, the outer layer includes at least an aluminum oxide layer, and the crystal structure of the aluminum oxide layer is The titanium carbonitride layer of the inner layer has an α-type, and has a columnar structure having a thickness of 10 μm or more. In the orientation of the titanium carbonitride layer, the (422) plane represented by the following formula and the (311) plane A coated cemented carbide, wherein both the orientation index TC (422) and the TC (311) with the surface are 1.3 or more and 3 or less. (Equation 1) 2. The inner layer, other than the titanium carbonitride layer,
At least one of a titanium nitride layer and a titanium boronitride layer, wherein the outer layer is at least one of a titanium carbide layer, a titanium carbonitride layer, and a titanium nitride layer in addition to the aluminum oxide layer.
The coated cemented carbide of claim 1 having a layer. 3. The orientation index TC (422) and TC
3. The orientation index TC (hkl) except for (311) is 1.5 or less.
2. The coated cemented carbide according to item 1. 4. The coated cemented carbide according to claim 1, wherein a layer of the outer layer immediately below the aluminum oxide layer is a titanium boronitride layer. 5. An orientation index TCa between the (110) plane and the (104) plane of the aluminum oxide layer having an α-type crystal structure represented by the following formula: TCa (110) ≧ 1.2 and TCa (104) 5. The coated cemented carbide according to claim 1, wherein ≧ 1.2. (Equation 2) 6. The orientation index TC between the (104) plane and the (116) plane of the aluminum oxide layer having an α-type crystal structure.
a is TCa (104) ≧ 1.3 and TCa (116)
The coated cemented carbide according to any one of claims 1 to 4, wherein ≥ 1.3. 7. The method according to claim 1, wherein the aluminum oxide layer does not exist only near the edge of the cutting edge.
7. The coated cemented carbide according to any one of items 1 to 6. 8. At least at the cutting edge ridge portion, a tensile residual stress of the inner layer of the titanium carbonitride layer is 10 k.
and characterized in that g / mm ² or less, Cemented carbide according to claim 7. 9. A layer in which the hard phase excluding the tungsten carbide is reduced or disappears on a surface portion of the base material of the cemented carbide, wherein the thickness of the layer is 50 μm or less in a flat portion. The coated cemented carbide according to any one of claims 1 to 8,