JPH1015709A - Surface coating cutting tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce abrasion due to plastic deformation of a tip edge and obtain a favorablel life in high speed intermittent cutting by containing specified weight % Zr and/or Hf in a substrate. SOLUTION: A cemented carbide to be used is obtained by adding 0.05-0.5wt% Zr and/or Hf to a substrate. Thus, Zr and/or Hf is added to mostly penetrate into B-1 type solid solution phase and binder phase of the cemented carbide, thereby preventing plastic deformation of a tip edge especially affected by cutting heat during cutting. The surface part of the substrate has a Vickers hardness 70-90% of the Vickers hardness of the enough inner side of the substrate, Zr an/or Hf is dissolved and/or dispersed in the substrate surface layer part, and B-1 type solid solution phase is dispersed, decreased and/or made zero to compensate for the defective resistance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coated cemented carbide suitable for cutting tools, and more particularly to a surface-coated cemented carbide having excellent fracture resistance and wear resistance.

[0002]

2. Description of the Related Art Cemented carbide is used to improve cutting efficiency.
Tools coated with a hard coating by the VD method are widely used. A tool provided with a modified layer called a binder phase enriched layer, a surface softened layer, a β-removed layer, etc. on the substrate surface in order to improve the chipping resistance of the cutting edge of this type of tool is also disclosed in, for example, JP-A-8-141.
As shown in Japanese Patent Publication No. 1 (Kokai) No. 1 (Kokai), it is widely used practically.
In order to further improve the alloy strength at high temperatures, Zr or Hf
Can be added to the substrate, for example, as described in JP-A-6-9347.
No. 3 discloses this.

[0003]

The tool provided by the above technique has been adopted because it can withstand high-speed cutting including intermittent cutting for a long time, and is highly efficient and unmanned in cutting. However, due to recent advances in near-net-shape technology, the shapes of component materials have become increasingly complex. Therefore, the impact force and the number of impacts applied to the cutting tool are steadily increasing, and the loss of the tool is a serious problem. However, when a small amount of Zr and / or Hf is added to the substrate in order to improve the plastic deformation resistance of the substrate at high temperatures, chipping is more likely to occur in the cutting edge during high-speed intermittent cutting than when no Zr and / or Hf are added. SUMMARY OF THE INVENTION An object of the present invention is to provide a tool that further improves fracture resistance and plastic deformation resistance in view of the current situation.

[0004]

Means for Solving the Problems The inventors of the present invention have proposed a conventional tool, which has the first hardness and the first hard coating of the substrate which are in contact with the substrate.
As a result of examining the cutting test paying attention to the relationship between the layers, the following findings were obtained. By appropriately adjusting the hardness of the surface layer portion of the base material, further setting the first layer of the hard film to TiN, and appropriately setting the thickness of the TiN layer, the fracture resistance is improved, and Zr / Hf
The plastic deformation resistance of the cutting edge at a high temperature during cutting can be maintained by the addition of the like. The present invention has been made based on these findings, and has the following configuration. The substrate contains 0.05 to 0.5% by weight of Zr and / or Hf, and has a surface softening layer having a Vickers hardness of 70 to 90% of the Vickers hardness sufficiently inside the substrate in the surface layer portion of the substrate. Of the coating layers constituting the hard coating, the first layer which is in contact with the base is T
iN. Preferably, the first layer has a thickness of 0.2 to 1.2 μm.
m of TiN, and the thickness of the surface softening layer is 5 to 25 μm.

[0005]

The substrate has a Zr and / or Hf content of 0.05 to
A cemented carbide added with 0.5% by weight is used. Zr and / or
Or, by adding Hf, most of them dissolve into the B-1 type solid solution phase and cemented phase of cemented carbide, and are particularly effective in preventing plastic deformation of the cutting edge, which is affected by cutting heat during cutting. There is. If less than 0.05% by weight, the effect is thin,
If the content exceeds 0.5% by weight, the alloy becomes brittle. However, when Zr and / or Hf is added, the edge of the blade tends to be chipped by the impact during cutting, so that the surface layer portion of the base and the first layer must compensate for this as follows. The Vickers hardness of the surface layer of the substrate is 70 to 9 of the Vickers hardness sufficiently inside the substrate.
0%, and Zr and / or Hf are solid-solved and / or dispersed in the surface layer portion of the base material. Deficiency can be compensated. Furthermore, the thickness is 5
By setting the thickness to ２５25 μm, plastic deformation resistance and toughness are imparted to the cutting edge.

In general, when a surface-coated carbide tool is used, the grade of the cemented carbide substrate is changed depending on the purpose of use. Therefore, in the present invention, the hardness of the surface softening layer is defined by a relative value to the hardness sufficiently inside the substrate. However, the Vickers hardness inside the substrate is usually about 1400 to 1700. If the Vickers hardness of the surface softened layer is less than 70% or if the thickness exceeds 25 μm, the cutting edge is plastically deformed during cutting and the tool has a long life. When the Vickers hardness exceeds 90% and when the thickness is less than 5 μm, the toughness is insufficient and chipping easily occurs. The above Vickers hardness values are all measured at room temperature.

Next, the first layer in contact with the base of the coating layer constituting the hard coating is made of TiN. When each titanium compound is compared by Vickers hardness, TiC is 3300 to 380.
0, TiCN is 2300-2800, whereas TiCN
N is as soft as 1800 to 2200, has an appropriate buffering action against impact, and makes up for the drawbacks of adding Zr and Hf. Also,
Since the film can be formed at a relatively low temperature, the diffusion of the base component is small, the decarburized layer is prevented from being generated at the interface between the base and the first layer, and the stress generated due to the difference in the coefficient of thermal expansion between the base and the coating is small. , Etc. The thickness of the first layer is 0.2 to 1.2 μm
m is good, and with this thickness, deformation of the first layer does not pose a problem. If the thickness is less than 0.2 μm, not only does the buffering effect become insufficient, but also because of the diffusion of iron group metals from the substrate,
The quality of the second and subsequent layers may be degraded. 1.2 μm
If it exceeds, the TiN particles may become coarse and adversely affect the crystal morphology of the second and subsequent layers.

As a second layer that is in contact with the first layer, TiCN is particularly recommended. This TiCN layer is made of MT-C
The columnar crystal is grown using the VD method. TiCN has an intermediate hardness between TiN and TiC among titanium compounds,
It has the same crystal structure and is preferred as a coating in contact with TiN. In the columnar crystal of TiCN film, the force during cutting is 1
Since it is transmitted to two particles without passing through a grain boundary, it is very strong against vertical force. Regarding abrasion, in the case of granular crystals having no direction, abrasion progresses due to the crystal grains falling off from the grain boundaries, but in the case of columnar crystals that are long in the vertical direction, they do not fall off and have excellent wear resistance. ing. Third
Regarding the layer structure after the layer, TiC,
TiN, Al ₂ O ₃ or the like may be used as appropriate. Hereinafter, the present invention will be described in detail based on examples.

[0009]

EXAMPLE As Example 1 of the present invention, Zr was contained in an amount of 2.0% by weight, and the Vickers hardness was 155 in a sufficient inside of the substrate.
0, a first layer TiN of 0.3 μm was formed on the surface of a CNMG120408 shaped cemented carbide having a surface softening layer of 1350 and a surface softening layer thickness of 15 μm by a known CVD method.
m, a second layer TiCN of 6.0 μm by MT-CVD using acetonitrile, a third layer of 1.0 μm of TiC by CVD, and 1.5 μm of alumina by a fourth layer CVD. 0.5 μm of TiN is deposited on the outermost layer by CVD.
m was formed. As Comparative Example 2, the same coating was applied using the same superhard substrate as in Example 1 of the present invention except that there was no surface softening layer. Inventive Example 3 containing 0.25% by weight of Zr, Vickers hardness of 1530 sufficiently inside the substrate, 1220 of the surface softened layer, and 15 μm of the surface softened layer
The first layer TiN is formed to a thickness of 0.3 μm on the surface of a cemented carbide having a shape of CNMG120408 by a known CVD method.
Second layer T by MT-CVD using acetonitrile
iCN is deposited to a thickness of 10.0 μm, and TiC is deposited on the third layer by CVD.
Was formed in a thickness of 1.0 μm, and alumina was applied to the fourth layer by CVD method.
A 0 μm film was formed, and a 0.5 μm TiN film was formed on the outermost layer by a CVD method. Comparative Example 4 has the same composition as that of Inventive Example 3 except that it does not contain Zr, and has Vickers hardness of 1520 sufficiently inside the substrate and 120 Vickers hardness in the surface softened layer.
0, CNMG120 having a surface softening layer thickness of 15 μm
A 408-shaped super-hard substrate was coated with the same coating as in Example 1 of the present invention. Comparative Example 5 was the same as Inventive Example 3 except that there was no surface softening layer. Comparative Example 6 was the same as Example 3 of the present invention except that TiN in the first layer was changed to TiC.

A cutting test was performed using the above chips.
First, the wear resistance was evaluated by turning in Tests 1 and 2.
The time until the flank wear of the tool reached 0.3 mm was evaluated. Test 1 conditions were: work material: S45C, cutting speed: 200 m / min, feed: 0.3 mm / rev,
Cut: 2.0 mm, wet cutting. The results were as follows: Inventive Example 1 was 55 minutes, Comparative Example 2 was 48 minutes, and Inventive Example 3 was 65 minutes.
Minutes, Comparative Example 4 is 47 minutes, Comparative Example 5 is 67 minutes, Comparative Example 6
Was 66 minutes. In the case of S45C cutting, there is no significant difference in the life between Example 1 of the present invention and Comparative Example 2 to which Zr was added. No deterioration of wear resistance and deterioration of plastic deformation resistance were observed by the surface softened layer, and the effect of Zr addition was confirmed. On the other hand, the comparative example 4 without the addition of Zr has a shorter life.

The conditions of test 2 were as follows: work material: FCD70,
Cutting speed: 150m / min, feed: 0.3mm / re
v, depth of cut: 2.0 mm, wet cutting. Result is,
Invention Example 1 was 22 minutes, Comparative Example 2 was 20 minutes, Invention Example 3
Was 27 minutes, Comparative Example 4 was 21 minutes, Comparative Example 5 was 28 minutes, and Comparative Example 6 was 28 minutes. S4 also when cutting FCD70
A tendency similar to that of 5C was observed. In particular, the effect of Zr addition was confirmed in Inventive Example 1.

Next, the fracture resistance was evaluated by interrupted cutting in tests 3 and 4. The evaluation was made by the number of impacts until the tool was broken. However, the upper limit of the number of impacts was 1,000. Each tool was tested for four corners. Test 3 conditions were as follows: Work material: SCM435 round bar with four grooves, cutting speed: 150 m / min, feed: 0.2 mm / rev,
Cut: 2.0 mm, dry cutting. As a result, in the present invention example 1, 1000 times or more, 1000 times or more, 800
Times, 1000 times or more. Comparative Example 2 was 630 times,
820, 770 and 670 times. Test 4 conditions were as follows: Work material: SCM435 with four grooves, Cutting speed: 15
0 m / min, feed: 0.3 mm / rev, cut:
2.0 mm, dry cutting. As a result, the product 3 of the present invention was 1
000 times or more, 1000 times or more, 800 times, 1000 times or more, Comparative Example 4 is 1000 times or more, 1000 times or more, 1
000 times or more, 920 times, Comparative Example 5 230 times, 540 times
Times, 310 times, 720 times, Comparative Example 6 was 900 times, 740 times
Times, 150 times and 720 times. It can be seen that Examples 1 and 3 of the present invention have more reliably improved fracture resistance than Comparative Examples 2, 4 and 5 having no surface softening layer. Further, Comparative Example 6 was different from Comparative Examples 4 and 5 in that the variation in the number of endurance impacts was large and the defect state was minute.

[0013]

According to the present invention, the fracture resistance is further improved as compared with the conventional tool, the wear caused by plastic deformation is small, and a good life is exhibited in high-speed interrupted cutting. It is suitable for high efficiency and unmanned cutting of cutting materials.

Claims (3)

[Claims] 1. A surface-coated cutting tool in which a hard coating composed of two or more layers is coated on the surface of a cemented carbide substrate.
The substrate comprises a surface softening layer containing 0.05 to 0.5% by weight of Zr and / or Hf, wherein the surface layer of the substrate has a Vickers hardness of 70 to 90% of the Vickers hardness sufficiently inside the substrate. And the Zr and / or Hf is B
A surface-coated cutting tool, wherein the first layer of the hard coating that is dissolved in the type-1 solid solution phase and / or the binder phase and that is in contact with the substrate is TiN. 2. The surface-coated cutting tool according to claim 1, wherein the thickness of the first layer is 0.2 to 1.2 μm. 3. The surface-coated cutting tool according to claim 1, wherein the thickness of the surface softening layer is 5 to 25 μm.