JPH0456768A - diamond coated cutting tools - Google Patents

Abstract

PURPOSE:To provide a diamond-coated cutting tool with the diamond coating layer firmly attached and having wear resistance by using a hard material having a specified linear expansion coefficient as the base material and forming the diamond coating layer in a specified thickness. CONSTITUTION:A hard material such as an Si3N4-based sintered body having <=4.0X10<-6>/deg linear expansion coefficient is used as the base material, a diamond coating layer having 20-150 mum thickness is formed on the base material surface by the vapor-phase synthesis using a microwave plasma CVD device, etc., and the cutting tool is produced. The roughness of at least the face and/or flank of the tool close to the edge is preferably controlled to <=0.2 s. Consequently, the tool with the diamond coating layer firmly attached and having wear resistance is obtained, and the surface roughness of the cut material is improved.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a diamond-coated cutting tool that enables cutting of various light alloys including Al-8t alloy at high speed and for a long time. This invention relates to a diamond-coated cutting tool in which the surface of a base material made of a hard material is coated with diamond by precipitation.

[Prior art] As a surface-coated cutting tool, PVD (Physical
sical Vapor Deposition)
Law and CVD (Chemical Vapor De
position) method.

Surface cutting tools in which a single layer or multiple layers of carbides, nitrides, carbonitrides of Hf, Zr, and oxides of AL are formed are widely used in practice. In addition, diamond has extremely high hardness and is chemically stable, so AI, C
It hardly reacts with u or other light metal alloys. Therefore, when diamond is used to cut such light metals at high speed, the surface of the workpiece is extremely well finished, so single-crystal diamond, sintered diamond, or diamond-coated cutting tools are widely used as cutting tools. has been done. Conventionally, cemented carbide has been mainly used as the base material for diamond-coated cutting tools.

[Problems to be Solved by the Invention] However, when cemented carbide is used as the base material as in the conventional diamond-coated cutting tool described above, there is a large difference in the coefficient of thermal expansion between the cemented carbide and diamond. Large thermal residual stresses are generated in the diamond coating layer. The linear expansion coefficient of cemented carbide is generally 5 to 6X10-6/
de g, and the coefficient of linear expansion of diamond is 3X10
-6/deg is well known. For this reason, the diamond coating layer spontaneously peels off when it exceeds a certain layer thickness that can provide sufficient adhesion strength to the base material. Therefore, it is not possible to form a thick coating layer, and it has not been possible to significantly improve wear resistance.

In order to solve these problems, attempts have been made to form an intermediate layer between the base material and the diamond coating layer, but the linear expansion coefficient of the material considered as this intermediate layer has Since it is the same or larger than cemented carbide, it does not lead to an improvement in adhesion strength.

Cutting tools and wear-resistant tools have high adhesive strength with the base material,
Sufficient layer thickness is required. However, for the reasons mentioned above, it has not been possible to obtain a diamond coating layer that has sufficient adhesion strength to the base material.
Also, regarding the layer thickness of the diamond coating layer, it has not been realized to form a layer thickness of 20 μm or more. In addition, the surface roughness of the diamond coating layer is generally as rough as 1 to 10s, and when flattening treatment such as lapping is performed on it, the layer thickness becomes thinner, which significantly reduces the wear resistance. It will be reduced to Therefore, there was a problem in that the diamond coating layer had to be used with its rough surface as it was.

[Means for Solving the Problems] The present invention provides a diamond-coated cutting tool in which diamond is deposited and coated on part or all of the rake face and flank face of a cutting tool made of a hard material by vapor phase synthesis. It is related to. This diamond-coated cutting tool has a linear expansion coefficient of the hard material that is the base material of 4. oxlo-
'deg-' or less, and the layer thickness of the diamond coating layer is 20 μm to 150 μm.

Another feature of the present invention is that the surface roughness of the rake face and/or flank face at the rear of the diamond coating layer is 0.2S or less at least in the vicinity of the cutting edge.

[Function] In the present invention, the linear expansion coefficient of the hard material serving as the base material is set to 4.
．． The reason why it is limited to 0 This is because a diamond coating layer of a certain thickness cannot be formed. The reason why we discovered that the range of linear expansion coefficient is limited in this way is that as a hard material covering diamond,
Based on the assumption that using a material with a coefficient of linear expansion close to that of the diamond coating layer would suppress the peeling of the diamond coating layer due to thermal residual stress, we conducted experiments with various linear expansion coefficients of the base material. The expansion coefficient is 4. oxlo-'
This is because it was concluded that sufficient adhesion strength to the diamond coating layer can be obtained by using a hard material of deg-1 or less as the base material.

Purpose A of the diamond-coated cutting tool of the present invention
In cutting light metal alloys such as L and Cu alloys, the temperature of the tool cutting edge only rises to a low temperature of 500 to 600°C even under various conditions.

Therefore, diffusion wear due to chemical reaction between the tool and the workpiece material is not a problem. For the same reason, thermal cracking, which is a disadvantage of ceramic tools, does not occur.

Therefore, Si3N4 and StC, which are not normally suitable for cutting steel due to defects due to thermal diffusion or thermal cracking, can be used as the base material for the diamond coating. The coefficient of linear expansion of these substances varies depending on the raw materials and manufacturing method, but is approximately 4.
．． When a sintered body having a coefficient of linear expansion of oxlo-'/deg or less is used as a base material and is actually coated with diamond, a diamond coating layer with significantly higher adhesion strength than conventional ones can be obtained. When using these base materials, 2.
It becomes possible to obtain a diamond coating layer with a thickness of 0 μm or more. Therefore, when a diamond surface-coated cutting tool or wear-resistant tool with a layer thickness of 20 μm or more is manufactured using these base materials, its life will be dramatically longer than that of a conventional tool with a layer thickness of 20 μm or less.

In addition, the lower limit of the layer thickness of the diamond surface coating layer is 20 μm.
Another reason for limiting the thickness to 20 .mu.m is that if the surface planarization treatment is performed with a thickness of 20 .mu.m or less, the layer thickness becomes too thin, resulting in insufficient wear resistance. Also, the upper limit is 150 μm.
This is because a layer thickness exceeding 150 μm is unnecessary and uneconomical for cutting tools and wear-resistant tools.

Examples carried out to demonstrate the effects of the present invention will be described below.

[Example: The linear expansion coefficient is 2.0XIO-'/deg, and 3wt
%Y2O3-2wt%A1203 ZrO2-1wt
%AtN and the rest is Si3N4
3N4 base sintered body and linear expansion coefficient of 4.0XIO-'
/deg, 0.5wt%B/2wt%C-
A SiC-based sintered body containing 2wt% At203 and the remaining portion consisting of SiC was prepared, and this was processed into a throw-away tip with model number 5PG422 specified by JIS.

As a commonly performed surface treatment, the surfaces of these indexable chips are roughly polished using a No. 200 resin bonded diamond grinding wheel, and then final polishing is performed to a thickness of 20 μm using a No. 800 resin bonded diamond grinding wheel. Ta.

The present invention is carried out by forming a diamond coating layer with a layer thickness of 20 to 100 μm on the surface of these hard substrates by placing them in a mixed plasma of hydrogen and methane using a 2.45 GHz microwave plasma CVD device. Examples 1-4
We have manufactured diamond-coated cutting tips for use in This hard base material had been heated to 950°C. Furthermore, the coating layer deposited on the surface of this base material was confirmed to be diamond by reflection electron beam diffraction. Furthermore, regarding the diamond-coated cutting tips used in Examples 3 and 4, using No. 600 diamond abrasive grains,
Surface flattening treatment was performed by lapping the flank and rake faces near the cutting edge for about 3 hours. In this way, diamond-coated cutting tips used in Examples 1 to 4 of the present invention shown in Table 1 were manufactured.

For comparison, ISOK10 cemented carbide (specifically WC-8wt%CO: linear expansion coefficient 5゜0XIO-'/
DEG) with the same shape (Comparative Example 1), and a comparative chip (Comparative Example 1) in which this chip was subjected to the same surface treatment as in Examples 1 to 4, and a diamond coating layer was formed with a layer thickness of 5 μm using the same equipment. Example 2), a chip made of Si3N4-based sintered body without forming a diamond coating layer (comparative example 3), and
A chip made of C-based sintered body (Comparative Example 4) was prepared.

These are also shown in Table 1.

(Left below) Using these materials, perform intermittent cutting under the conditions shown in Table 2, measure the amount of flank wear and the surface roughness of the workpiece after 2 minutes and 10 minutes, and calculate the cutting edge. The state of wear was observed.

Table 2 Note) Items marked with * have lapping treatment near the cutting edge.

Examples 1 to 4 described above. The intermittent cutting test results of Comparative Examples 1 to 4 are shown in Table 3.

In Table 3, the data after 10 minutes for Comparative Examples 1 to 4 is not shown because all of Comparative Examples 1 to 4 had already reached the end of their lifespans after 2 minutes. be.

(Left below) As is clear from the interrupted cutting test results shown in Table 3,
In Examples 1 to 4 of the diamond-coated cutting tip of the present invention, Comparative Example 1 which is a conventional cutting tip
-4 have better adhesion and abrasion resistance with the base material, and the surfaces were flattened by lapping (Example 3 and Example 4). The surface roughness becomes better.

[Effects of the Invention] As described above, according to the present invention, the coefficient of linear expansion is 4. o
By forming a diamond coating layer with a thickness of 20 μm to 150 μm on a hard material of xio-'deg-' or less as a base material, diamond coated cutting has good adhesion and wear resistance of the diamond coating layer. You can get tools.

Furthermore, by flattening the surface roughness of the coating layer of such a diamond-coated cutting tool to 0.2s at least near the cutting edge of the rake face and flank face of the tool, the surface roughness of the workpiece can be improved. can be significantly improved.

Claims (2)

[Claims] (1) In a diamond-coated cutting tool in which part or all of the rake and flank surfaces of a cutting tool made of a hard material are coated with diamond by vapor phase synthesis, the linear expansion of the hard material that serves as the base material The coefficient is 4.0×10^-^
6 deg^-^1 or less, and the diamond coating layer has a layer thickness of 20 μm to 150 μm. (2) The diamond-coated cutting tool according to claim 1, wherein the surface roughness of the diamond-coated layer at least near the cutting edge of the rake face and/or flank face of the tool is 0.2 s or less. .