JPH04261703A - Polycrystal diamond cutting tool - Google Patents

Abstract

PURPOSE:To increase defectresistance, wear resistance and heat resistance, by forming the growth face side of a poly-crystal diamond layer in 5mum to 20mum film thickness composed by a low pressure vapor phase method as the rake face of a tool. CONSTITUTION:A lamination body having a diamond sintered body 3 whose mean particle size is in 0.1-1.0mum and a polycrystal diamond layer 4 whose film thickness composed by a low pressure vapor phase method is in 5mum-20mum on the surface thereof, is used as a polycrystal diamond cutting tool raw material. And, the growth face side of the polycrystal diamond layer 4 is taken as the rake face 7 of the tool.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a polycrystalline diamond cutting tool having excellent wear resistance, chipping resistance and heat resistance, and having a sharp cutting edge.

0002

BACKGROUND OF THE INVENTION Diamond is used as cutting tools and wear-resistant tools because of its high hardness and high thermal conductivity. However, single-crystal diamond has the drawback of cleavage, and in order to suppress this drawback, diamonds have been sintered together using ultra-high pressure sintering technology, such as that described in Japanese Patent Publication No. 52-12126. Diamond sintered bodies have been developed.

Among commercially available diamond sintered bodies, those with particularly fine grains of several tens of micrometers or less have excellent wear resistance without causing the cleavage phenomenon seen in the above-mentioned single-crystal diamond. It is known to show gender.

However, since these diamond sintered bodies contain several percent to several tens of percent of binder, there is a problem in that chipping occurs in the particles constituting the sintered body. In particular, this chipping phenomenon becomes noticeable when the wedge angle of the cutting edge of the tool becomes small, and it is extremely difficult to manufacture a tool with a sharp cutting edge. In addition, especially when the wedge angle of the cutting edge of the tool becomes smaller than 80°, the current diamond sintered body lacks toughness, which not only causes chipping during cutting, but also makes it more likely to break when used as a tool. It has been known.

[0005] It is thought that such problems can be improved by using diamond as constituent particles, which have a small particle size and few internal defects, and by strengthening the bonds between these particles. From this point of view, attempts have been made to synthesize a strong sintered body by sintering only diamond without containing a binder. However, since diamond particles are difficult to deform, pressure is not transmitted to the gaps between the particles, resulting in graphitization, and the reality is that only a diamond-graphite composite can be obtained.

On the other hand, as a method for synthesizing diamond, in recent years, the technology of low-pressure gas phase method has made remarkable progress, and it has become possible to manufacture polycrystals made only of diamond. Part 1
One known tool type is one in which a base material made of cemented carbide or ceramic is coated with a polycrystalline diamond thin film. However, this type of diamond-coated tool has a problem with the adhesion between the diamond thin film and the base material, so its use is limited. Another type of polycrystalline diamond tool using the low pressure gas phase method is a polycrystalline diamond thin plate with a thickness of 0.1 to 3.0 mm, as disclosed in Japanese Patent Application No. 63-34033. is brazed directly to the tool base material. This tool does not suffer from the peeling phenomenon of polycrystalline diamond, which is a problem with diamond-coated tools, and can be used with performance equivalent to or better than conventional ultra-high pressure sintered diamond tools. For example, Japanese Patent Application No. 1-237534 discloses a high-toughness polycrystalline diamond tool having excellent strength, heat resistance, and wear resistance.

However, even when using polycrystalline diamond produced by the low-pressure vapor phase method, if the wedge angle of the cutting edge becomes smaller than 80°, it becomes difficult to form a sharp cutting edge, and there is a significant tendency for the cutting edge to break easily during cutting. It was not something that could be improved.

[0008] In this way, conventional diamond tools
When attempting to form a sharp cutting edge, chipping of the cutting edge has been a problem, regardless of whether a diamond sintered body or polycrystalline diamond synthesized by a low-pressure vapor phase method is used.

[0009] Therefore, the present invention was made to solve the above problems, and provides a polycrystalline diamond cutting tool that has a sharp cutting edge and has excellent chipping resistance, wear resistance, and heat resistance. The purpose is to provide.

0010

[Means for Solving the Problems] The polycrystalline diamond cutting tool according to the present invention has an average grain size of 0 as a tool material.
．． It has a diamond sintered body of 1 μm or more and 10 μm or less, and a polycrystalline diamond layer with a film thickness of 5 μm or more and 20 μm or less synthesized by a low-pressure vapor phase method on at least one main surface of the diamond sintered body. . The growth surface side of the polycrystalline diamond layer is configured to be the rake face of the tool.

[0011] As for the form of the cutting tool, there are those in which a two-layer structure of this diamond sintered body and a polycrystalline diamond layer formed by a low-pressure vapor phase method is used as the tool body, and those in which this two-layer structure is used as a tool body.
Some use a layered structure bonded to a tool support.

Furthermore, the wedge angle of the cutting edge formed by the rake face and the flank face of the polycrystalline diamond cutting tool according to the present invention is formed to be 40° or more and 70° or less.

Furthermore, in the polycrystalline diamond cutting tool according to the present invention, the tool material containing the diamond sintered body and the polycrystalline diamond layer has a material of groups IVA and IVB of the periodic table on the side of the tool support that is joined to the tool support. Groups VA, VB, VIA, VIB, VII and VII
A thin film layer made of a metal included in Group B or a compound thereof is formed, and the tool material and tool support are further bonded with a brazing material.

[0014]

[Operations and Effects of the Invention] Here, the functions and effects of the polycrystalline diamond cutting tool according to the present invention will be explained with reference to the process leading up to the present invention.

[0015] For example, the inventor has
We analyzed the cause of the insufficient performance of cutting tools using polycrystalline diamond synthesized by the conventional low-pressure gas phase method as shown in No. 4. The polycrystalline diamond shown in this conventional example uses a base material such as molybdenum (Mo) or silicon (Si) that can be dissolved and separated by mechanical processing or chemical processing, and the surface of this base material is A polycrystalline diamond layer is formed using a low-pressure vapor phase method, and then the base material is separated from the polycrystalline diamond layer to take out the tool material. In such a method, the coefficient of thermal expansion of the base material and the coefficient of thermal expansion of the polycrystalline diamond synthesized on the surface thereof are different, so that a large residual stress is generated after the film is formed. It was also confirmed that when the base material was separated from the formed polycrystalline diamond layer, the polycrystalline body was deformed due to residual stress. It was also thought that this deformation may introduce microscopic cracks into the interior of the polycrystalline diamond, leading to a decrease in the strength of the tool.

[0016] From these analytical results, it was considered that it is extremely difficult to avoid the problem of residual stress and the occurrence of cracks caused by it as long as a material other than diamond is used for the base material.

[0017] Therefore, next, we investigated a method of using diamond as a base material and forming a polycrystalline diamond film on its surface by a low-pressure vapor phase method. In such a method, there are several similar known examples. For example, Japanese Patent Application Laid-Open No. 60-90884 discloses a cutting tool and a wear-resistant tool in which a diamond coating layer is formed on the surface of a diamond-based sintered material by vapor phase synthesis to an average thickness of 0.2 to 20 μm. Surface-coated diamond-based sintered materials are disclosed. In this conventional example, a diamond-based sintered material containing 5% by volume or more of an iron group metal as a binder is used. Using such a material as a base material, the conditions described in the example of the above publication (substrate surface temperature 500~
Attempts were made to coat polycrystalline diamond at temperatures (830°C), but there were problems such as difficulty in forming a coating layer due to the influence of the binder contained in the base material, or poor adhesion strength between the base material and the coating layer. occured. Another conventional example of a method for improving such problems is Japanese Patent Application Laid-open No. 63-69.
No. 971 discloses a method for manufacturing a diamond-coated sintered body using a base material from which an iron group metal binder has been removed. Further, Japanese Patent Application Laid-Open No. 185859/1983 discloses a method using sintered diamond containing a small amount of SiC as a binder as a base material, and a diamond-coated sintered diamond obtained thereby. By further studying the above-mentioned conventional examples, the present invention has made it possible to manufacture tool materials with excellent strength that could not be achieved with conventional materials, as well as cutting tools with sharp cutting edges.

That is, in the polycrystalline diamond cutting tool of the present invention, the base material has an average particle diameter of 0.1 to
A 10 μm diamond sintered body is used. The reason why the average particle size of this diamond sintered body is specified within this range is that if the average particle size is larger than 10 μm, the polycrystalline diamond particles coated on the surface will also become coarser, and when the tool is manufactured or This is because chipping and breakage are likely to occur when used as a tool. Also, 0
．． If it is smaller than 1 μm, the current sintering technology cannot produce a diamond sintered body with a uniform composition, and as a result, the polycrystalline diamond particles coated on the surface become non-uniform. This is because a material with stable strength cannot be obtained.

[0019] Furthermore, this diamond sintered body is exposed to the temperature conditions (generally 700 to 1000°C in the current technology) during the low-pressure vapor phase synthesis of the polycrystalline diamond to be coated.
A material with high heat resistance that does not deteriorate in quality is used. Such a highly heat-resistant diamond sintered body is known, for example, from Japanese Patent Application Laid-open No. 53
-114589 publication or JP-A-61-3386
The one described in Publication No. 5 is known.

Further, in consideration of the balance of thermal expansion coefficient with the polycrystalline diamond layer synthesized on the surface thereof, the diamond content in the diamond sintered body is preferably 80% or more. In such a sintered body with a high diamond content, direct bonding between diamond particles generally occurs, and this bonding state also affects the particles of the polycrystalline diamond layer synthesized on the surface. Continued and maintained. Therefore, even in the polycrystalline diamond particles to be synthesized, a highly tough diamond layer in which each particle is directly bonded without having a clear grain boundary can be easily synthesized.

Further, in the polycrystalline diamond cutting tool according to the present invention, a polycrystalline diamond layer having a thickness of 5 to 200 μm is formed on the surface of the diamond sintered body, which is synthesized by a low-pressure vapor phase method. As mentioned above, this polycrystalline diamond layer has high toughness that reflects the direct bonding between the particles of the diamond sintered body, and has a predetermined film thickness that prevents chipping during tool manufacturing or use as a tool. It is possible to suppress the occurrence of defects.

[0022]

[Embodiments] Examples of the present invention will be described below. FIG. 1 is a partial cross-sectional structural view of the cutting edge portion of a polycrystalline diamond cutting tool according to the present invention. Note that the illustrated cutting tool has a tool form in which a tool material is joined to a tool support. Referring to FIG. 1, a brazed portion 6 is attached to a predetermined area of a tool support 1 made of cemented carbide or steel.
The tip 2 of the tool is fixed through the . The chip 2 includes a diamond sintered body 3, a polycrystalline diamond layer 4 synthesized by a low pressure vapor phase method, and a diamond sintered body 3.
A coating metal layer 5 is provided on the bonding surface side of the substrate. A rake face 7 of the tool is formed on the growth surface side of the polycrystalline diamond layer 4. Furthermore, a tool flank 8 is formed on the end face of the chip 2. Furthermore, the cutting edge portion formed at the intersection of the rake face 7 and flank face 8 of the tool is
The wedge angle θ of the cutting edge constituted by both surfaces is formed in a range of 40° or more and 70° or less.

The coating metal layer 5 is made of, for example, titanium (Ti).
and nickel (Ni), but also groups IVA, IVB, VA, VB, etc. of the periodic table.
Group VIA, Group VIB, Group VII and Group VIIB
A metal layer included in the group or a compound thereof may be used.

Various low pressure vapor phase methods can be applied to synthesize the polycrystalline diamond layer 4. For example, a method in which thermionic radiation or plasma discharge is used to decompose and excite the raw material gas, and a method in which a film is formed using a combustion flame are effective. In addition, raw material gases include, for example, methane, ethane,
It is common to use a mixed gas whose main components are hydrocarbons such as propane, alcohols such as methanol and ethanol, organic carbon compounds such as esters, and hydrogen. However, in addition to these, inert gases such as argon, oxygen, carbon monoxide, water, etc. may also be contained in the raw material as long as they do not interfere with the diamond synthesis reaction or its properties.

Next, a concrete example will be explained. Specific Examples Polycrystalline diamond was synthesized for 10 hours under the following conditions by thermal CVD using a linear tungsten filament with a diameter of 0.5 mm and a length of 100 mm as a thermionic emitting material. Note that the base material contains 2% by volume of Co as a binder.
was dissolved and extracted by acid treatment, with an average crystal grain size of 3μ
A diamond sintered body of m was used.

Raw material gas (flow rate): H2
300 sccm
C2 H2
15 sccm gas pressure
:80 Torr
Filament temperature: 2250℃
filament
Distance between boards: 5mm Board temperature
: After synthesis at 900°C, the recovered diamond mass was cut into pieces and the structure was observed, and it was found that the base diamond sintered body was covered with polycrystalline diamond with an average crystal grain size of 3 μm and a thickness of 100 μm. was observed. After mirror-polishing the growth surface of the polycrystalline diamond layer of this diamond mass (A), Ti with a thickness of 1 μm and Ni with a thickness of 2 μm are laminated and coated on the base material side. Brazing was performed using a cemented carbide shank and silver solder having a melting point of 730° C. using the coated surface as the joining surface. Next, this joined body was subjected to cutting edge processing by grinding using a diamond grindstone to produce indexable tips with different wedge angle sizes.

For comparison, the tool material was a single polycrystalline diamond with a thickness of 0.1 mm synthesized on a Si base material under the same conditions as above (B), and the Co-extracted tool used as the base material in the above experiment. The diamond sintered body used as the base material in the above experiment was used as the tool material (C), and the tool material was the diamond sintered body used as the base material in the above experiment before Co was extracted (D
) was made into a throw-away tip.

Table 1 shows the amount of chipping on the cutting edge of these various tools.

[0029]

[Table 1] As shown in the results in Table 1, it has become clear that according to the present invention, it is possible to easily produce a tool with good edge sharpness, which was difficult to produce by conventional grinding.

Furthermore, in order to evaluate the performance of these tools, cutting tests were conducted under the following conditions.

(Cutting conditions) Work material: A390-T6 (Al-
17%Si) A round bar with four V-shaped grooves formed in the axial direction.
Cutting speed: 600m/min Depth of cut: 0.3mm Feed rate: 0.12mm/rev.
Coolant: Water-soluble oil As a result, the tools of the present invention did not suffer from chipping of the cutting edge even after cutting for 90 minutes, and good work surface roughness was obtained. However, when the wedge angle of the comparative tools (B), (C), and (D) was less than 70°, the cutting edge was damaged within 10 minutes from the start of cutting, making them unusable.

[Brief explanation of the drawing]

FIG. 1 is a partial sectional view of the cutting edge portion of a polycrystalline diamond cutting tool according to the present invention.

[Explanation of symbols]

1 Tool support 2 Chip 3 Diamond sintered body 4 Polycrystalline diamond layer 5 Coating metal layer 6 Brazing part 7 Rake face 8 Relief surface

Claims (5)

[Claims] [Claim 1] As a tool material, the average grain size is 0.1μ.
m or more and 10 μm or less, and a polycrystalline diamond layer having a thickness of 5 μm or more and 20 μm or less synthesized by a low-pressure vapor phase method on at least one main surface of the diamond sintered body, A polycrystalline diamond cutting tool with the growing surface of the diamond layer serving as the rake face of the tool. 2. The polycrystalline diamond cutting tool further includes a tool support, and the tool material including the diamond sintered body and the polycrystalline diamond layer is such that the growth surface side of the polycrystalline diamond layer faces the rake of the tool. The polycrystalline diamond cutting tool of claim 1, wherein the polycrystalline diamond cutting tool is joined to the tool support in a plane manner. 3. A flank face of the tool that intersects with the rake face of the polycrystalline diamond layer is formed on the end face of the tool material, and the wedge angle of the cutting edge portion sandwiched between the rake face and the flank face is 40. Claim 1, wherein the angle is between 70° and 70°.
Or the polycrystalline diamond cutting tool according to 2. 4. On the side of the joint surface of the tool material with the tool support, there is formed a metal material of Group IVA, Group IVB, and VA of the periodic table.
A thin film layer made of a metal included in Group VB, Group VIA, Group VIB, Group VIIA, or Group VIIB, or a compound thereof, is formed between the tool material and the tool support. 4. The polycrystalline diamond cutting tool according to claim 2, wherein the cutting tool is joined to the body using a brazing material. 5. The brazing material has a melting point of 700° C. or higher.
The polycrystalline diamond cutting tool according to claim 4, wherein a material having a temperature of 300° C. or less is used.