JPH0623431B2 - Hard coating coated cutting tool parts - Google Patents

Description

TECHNICAL FIELD The present invention relates to a hard coating-coated cutting tool member that exhibits high wear resistance and welding resistance in cutting non-ferrous metals, ceramics and composite materials.

(Prior Art) Conventionally, as a cutting tool base material, a constraint degree tool steel, a tungsten carbide based cemented carbide, a cermet or a ceramic is generally used, and in recent years, to impart higher wear resistance to them, for example, As shown in JP-B-54-24914 or JP-B-62-56231, a cutting tool member whose surface is coated with a hard layer composed of a single layer or multiple layers of titanium nitride, carbide, carbonitride and aluminum oxide is also available. It is used.

However, these tool components are, for example, Al-Si alloys, FRP
When a material containing a hard substance is cut at high speed, such as, the tool life is short due to lack of wear resistance,
There has been a demand for cutting tools having higher wear resistance.

On the other hand, single crystal diamond or sintered diamond cutting tools are known to have extremely high wear resistance even when cutting the above work materials, because diamond has the highest altitude among existing substances. In addition, it also has the characteristic that there is little welding of the work material. However, these diamond cutting tools are expensive and difficult to machine into complicated shapes.

In recent years, the vapor phase synthesis technology of diamond has progressed, and diamond or a diamond-like hard carbon film (hereinafter collectively referred to as a diamond film) is synthesized by a hot filament method, a direct current discharge CVD method, a microwave discharge method or a high frequency discharge method. As a result, application to cutting tools has also been attempted. However, the diamond film lacks the adhesion to the base material as compared with the conventional ceramic hard coating, so that the film peels off from the base material when a strong stress is applied to the film during cutting. was there.

(Problems to be solved by the present invention) It is said that a diamond film has lower adhesion to a tool substrate and is more likely to be peeled off than a conventional ceramic film.
This is because it is difficult for diamond to form an interdiffusion layer with the base material for tools, and the coefficient of thermal expansion is significantly different from that of the base material. When the base material temperature during diamond synthesis is cooled from 700 ℃ to 1200 ℃ to room temperature. It is considered that a large compressive stress remains in the film.

The present inventors conducted a cutting test of an Al-Si alloy under various conditions using a cutting tool coated with diamond and examined the state of delamination of the diamond film. It was found that the peeling of the diamond film tends to occur under the condition that the welding of the material to the cutting tool cutting edge is likely to occur. Next, when the diamond film on the cutting tool used in this test was observed with an optical microscope, the diamond film was composed of polycrystals having a self-shaped surface and had a violent surface structure.

When observing the growth process of the diamond film, the diamond grains after nucleation grow with time and eventually come into contact with nearby diamond grains to form a film. Then, after the film is formed, selective growth of diamond particles occurs, the average particle size of the diamond particles observed from the surface of the film increases, and the surface roughness also increases. Nucleation occurs, and a sudden increase in surface roughness is suppressed. However, when synthesizing a film made of high-hardness diamond having a self-shaped surface, it is unavoidable that the surface of the film becomes rough to some extent.

The present inventors have found that the diamond film has a sharp undulation on its surface, so that the frictional resistance to the flow of the work material increases, the film is easily separated, and the welding of the work material is also facilitated. I decided that. Therefore, in order to reduce the surface roughness of the film surface, the cutting tool substrate was coated with diamond, and then the substrate surface was polished to a mirror surface by lapping fine diamond powder to perform a cutting test. As a result, it was found that the welding of the work material to the cutting edge of the cutting tool was almost the same as that of the sintered diamond, and the life of the cutting tool was remarkably extended. However, the method of mirror-polishing the surface of the cutting tool after coating the diamond film has a large risk of peeling off the diamond film during polishing, and there is a drawback that this method cannot be applied to tools with complicated shapes and is put to practical use. There are many problems above.

(Means for Solving the Problem) Since the welding of the work material to the cutting tool cutting edge is reduced and the peeling resistance is improved by reducing the surface roughness of the diamond film, the present inventors First, coat the surface of the substrate with a high-hardness polycrystalline diamond film having an automorphic surface,
Then, it was devised to make the surface smooth by coating the outer layer with an amorphous hard carbon film having no self-shaped surface.

While the Vickers hardness of diamond is 7,000 to 10,000 kg / mm ² , the hardness of the amorphous hard carbon film varies greatly depending on the synthesis conditions, and the Vickers hardness is 10
It is distributed from less than 00 kg / mm ² to about 7,000 kg / mm ² , and when hydrogen is contained in the synthesis atmosphere, the lower the synthesis temperature is, the more hydrogen is contained in the film. Also, when measured Raman spectrum with a Raman spectrometer, whereas with Shiyapu peak at least near 1330 cm ^-1 in the spectrum diamond or diamond-like hard carbon film, the amorphous hard carbon film 1450～1660Cm ^{- It} has a wide half-value peak with a maximum at ¹ . The amorphous hard carbon film aimed at by the present invention has a Vickers hardness of 2000 kg / mm ² or more and is called i-carbon or amorphous diamond, and shows sufficiently high wear resistance even when used for cutting tools. is there.

Since the amorphous carbon film is also synthesized without having a self-shaped surface, it has the effect of smoothing the origin of the diamond film on the self-shaped surface coated on the inner layer of the cutting tool, reducing the welding of the work material and A reduction in frictional resistance between the work material and the hard coating is expected.

The effect of extending the life of the cutting tool by coating the cutting tool made of cemented carbide substrate with the diamond film is when the film thickness is 0.5 μm or more, but try to coat the diamond film beyond 100 μm. Then, since the cemented carbide and the diamond have different thermal expansion coefficients, the film peels off from the substrate during cooling of the member after coating the diamond film to room temperature.

Therefore, the inventors of the present invention synthesized and observed a diamond film having a self-shaped surface on a cutting tool made of a cemented carbide base material with a thickness within this range by a DC antistatic CVD method and a microwave discharge method. As a result, the size of diamond grains and the roughness of the film surface change depending on the synthesis conditions, the position on the substrate, and the synthesis time, that is, the film thickness. Is 0.1 to 1 μm near 2 μm, and 0.5 to 2 μ near film thickness 10 μm.
m, and the film thickness was 2 to 5 μm in the vicinity of 50 μm. Next, when an amorphous hard carbon film was coated on the outer layer of these diamond films by a high frequency CVD method with the target of 1/2 the thickness of the diamond film, the surface roughness of the film before the amorphous hard carbon film was coated. It decreased to less than 1/3.

The thickness of the amorphous hard carbon film coated on the outer layer of the diamond film should be changed according to the surface roughness of the diamond film.
If the thickness is m, the thickness of the amorphous hard carbon film is 0.5 μm and the surface of the substrate is sufficiently smooth. However, when the thickness of the diamond film is around 100 μm, the surface roughness is about 5 μm. It is necessary to coat an amorphous hard carbon film of 25 μm.

Specific examples of the present invention will be shown below.

(Example) A mixed gas of methane and hydrogen was introduced into a vacuum chamber, and DC discharge plasma was generated between a filament and an anode provided in the vacuum chamber. A diamond film was coated on a SNGA120408 type cutting tip made of WC-Co based cemented carbide placed on the anode. The conditions for synthesizing diamond at this time are as follows: flow rate of methane is 10 SCCM, flow rate of hydrogen is 500 SCCM, distance between filament and substrate is 3 cm, and filament temperature is about 2100.
Synthesis was carried out for 3 hours at a current of 3 A between filament and anode. When this sample was examined by an optical microscope, diamond was composed of polycrystals having an automorphic surface, and its surface roughness was about 1 μm.

Next, using methane as a raw material on this substrate and coating the amorphous hard carbon film at a power of 150 W for 3 hours using a capacitively coupled high-frequency plasma CVD apparatus, and observing, the origin difference was 0.
A smooth surface of 5 μm or less was obtained.

A cutting test was conducted under the following conditions using the cutting tip of the present invention and the cutting tip coated only with the diamond film under the above conditions.

Work material Al-Si alloy (containing 13% of Si) Cutting speed 800m / min Depth of cut 0.2mm Feed rate 0.15mm / rev Cutting method Dry continuous cutting As a result, carbide tip coated with diamond film is for 1 hour While the diamond film of the cutting edge was peeled off after cutting and flank wear was progressing, the cutting tip of the present invention still has a hard coating on the cutting edge even after cutting for 3 hours, and welding of the work material to the cutting edge is also possible. It was less than the cutting tip coated with only the diamond film.

After the cutting test, these cutting chips were cut and the thicknesses of the diamond film and the amorphous hard carbon film were examined.
8 μm, the thickness of the amorphous hard carbon film is 3 μm,
The thickness of the comparative chip coated with diamond film is about
It was 8 μm.

In this example, the coating of the diamond film was performed by the direct current discharge plasma method, which is a CVD method using a hot filament.
Method, a known method such as a CVD method using microwave or high frequency, and the coating of the amorphous hard carbon film by a known method such as a direct current discharge method and a microwave discharge method in addition to this embodiment. It can be carried out.

(Effect) The hard coating-coated cutting tool according to the present invention has a diamond film having high wear resistance coated on the inner layer and an amorphous hard carbon film coated on the outer layer to make the surface smooth, thereby providing welding resistance and peeling resistance. It is possible to maintain excellent cutting performance for a long time in cutting non-ferrous metals, sintered ceramics, composite materials such as FRP.

Claims (3)

[Claims] 1. A cutting tool member coated with a hard coating, wherein the coating of the innermost layer in contact with the base material is a polycrystalline diamond or diamond-like carbon film having a self-shaped surface, and the outer layer of the coating has a self-shaped surface. A hard film-coated cutting tool member characterized by being coated with a non-crystalline hard carbon film. 2. The diamond or diamond-like carbon film having a self-shaped surface has a thickness of 0.5 to 100 μm, and the amorphous hard carbon film has a thickness of 0.5 to 25 μm. Hard coating coated cutting tool parts. 3. The hard coating-coated cutting tool according to claim 1, wherein the base body of the cutting tool member is a cemented carbide containing tungsten carbide as a main component.