JPH0569204A - Hard layer coated tungsten carbide group cemented carbide made cutting tool - Google Patents

Abstract

PURPOSE:To provide a hard layer coated WC group cemented carbide cutting tool having excellent performance. CONSTITUTION:(1) A hard layer coated WC group cemented carbide cutting tool in which a surface of WC group cemented carbide base substance is coated by a hard layer made of a single layer of one kind or a duplex layer of two kinds of titanium carbide or carbonitride, and having mean grain size in the range of 0.01-0.5mum with coarser grains distributed in the inner surface and finer grains in the outer surface so as to vary monotonously from the inner surface to the outer surface, and having mean layer thickness of 5-20mum. (2) A hard layer coated WC group cemented carbide cutting tool in which the hard layer coated WC group cemented carbide cutting tool of (1) is coated additionally by an upper layer having mean layer thickness of 0.1-10mum made of a single layer or a duplex layer of TiCO, TiCNO, TiN and Al2O3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hard layer coated tungsten carbide based cemented carbide cutting showing excellent performance when used for high speed interrupted cutting and heavy cutting under severe conditions such as high feed and high depth of cut. It is about tools.

[0002]

2. Description of the Related Art In general, a surface of a tungsten carbide based cemented carbide substrate (hereinafter referred to as a WC based cemented carbide substrate) is formed of a single layer of TiC or TiCN or a multilayer thereof by a chemical vapor deposition method or a physical vapor deposition method. A hard layer-coated WC-based cemented carbide cutting tool formed by coating a hard layer (hereinafter, referred to as a hard layer) is known.

Further, the hard layer is used as a lower layer, and TiCO and TiCN formed on the lower layer and the lower layer.
Made of WC-based cemented carbide with a hard layer formed by forming a coating layer having an average layer thickness of 0.5 to 20 μm, which is composed of an upper layer consisting of a single layer of O, TiN, Al ₂ O ₃ or a plurality of layers thereof. Cutting tools are also known.

It is also known that refining the crystal grains of the hard layer is effective as a means for improving the characteristics of the hard layer of these hard layer-coated WC-based cemented carbide cutting tools.

[0005]

However, when the thickness of the hard layer is thin, the fineness of the crystal grains is maintained, but when the thickness becomes 5 μm or more, the thickness of the hard layer increases toward the surface as the layer thickness increases. And the crystal grain size increases, and the average grain size of the surface portion is 0.
The hard layer having a grain size of 5 μm or more and having a larger crystal grain size toward the surface is apt to be cracked from the surface and has a large amount of wear at the surface portion. It has been found that when an alloy cutting tool is used for high-speed intermittent cutting, sufficient wear resistance cannot be obtained, the hard layer peels off, and abnormal wear occurs at an early stage.

[0006]

Therefore, the present inventors have
Note that the larger the grain size of the hard layer, the better the adhesion strength to the ordinary WC-based cemented carbide substrate, while the finer the grain size of the hard layer, the higher the wear resistance and the more difficult it is to crack. However, when research was conducted to obtain a hard layer coated WC-based cemented carbide cutting tool that exhibits even longer life when used for high-speed intermittent cutting, (1) coating on a WC-based cemented carbide substrate The crystal grain size of the hard layer is kept as fine as possible within the range of 0.01 to 0.5 μm, and (2) the crystal grain size of the contact surface portion with the substrate is maximized in consideration of the adhesion to the substrate, A hard layer that monotonically decreases from the inner surface to the smallest grain size of the surface part and has the requirements of (1) and (2) above is excellent in adhesion to the substrate and is resistant to cracking and wear resistance. Is excellent Than it was to obtain a cormorant knowledge.

The present invention was made on the basis of the above findings, and it was found that Ti was formed on the surface of a WC-based cemented carbide substrate.
In a cutting tool formed by coating a hard layer having an average layer thickness of 5 to 20 μm consisting of one type of single layer or two types of multilayers of C and TiCN, the hard layer has an average grain size of 0 as a whole. A hard-layer-coated WC-based cemented carbide cutting tool that is in the range of 0.01 to 0.5 μm and monotonically decreases from the inner surface to the surface. As a lower layer, TiCO, T on the lower layer
Average layer thickness composed of a single layer of iCNO, TiN and Al ₂ O ₃ or an upper layer composed of a plurality of layers: 0.1
It is characterized by a hard layer-coated WC-based cemented carbide cutting tool formed by forming a coating layer of 10 μm.

To form the hard layer or the lower layer of the hard layer-coated WC-based cemented carbide cutting tool of the present invention, first, a WC-based cemented carbide substrate having a predetermined shape and composition is placed in a chemical vapor deposition apparatus. After charging, holding the substrate for a sufficient time to reach the temperature at which chemical vapor deposition is performed, or heating to that temperature and then performing chemical vapor deposition, a hard layer with a large grain size is formed on the substrate surface, A hard layer having excellent adhesion to the substrate is formed.

When chemical vapor deposition is performed on a WC-based cemented carbide substrate without reaching the temperature at which chemical vapor deposition is performed, the grain size of the contact surface portion with the substrate becomes small, which results in W of the hard layer.
Sufficient adhesion to the C-based cemented carbide substrate cannot be obtained.

Then, the chemical vapor deposition is continued, but when the reaction temperature of the chemical vapor deposition is continuously lowered, the crystal grains of the hard layer formed become finer, and finally the crystal grains at the surface portion are the finest. A hardened layer is obtained.

The hardness and strength of the hard layer thus produced are not only improved as a whole, but also cracks from the surface and rapid wear are not progressed, and it is excellent for cutting under severe conditions. These characteristics can be exhibited over a long period of time. In this invention, the average grain size of the hard layer monotonically decreases from the inner surface to the surface means that the average grain size decreases from the inner surface to the surface in a macroscopic view. However, it is preferable that the decrease is continuous from a microscopic point of view, but it is unavoidable that the decrease is continuous from a microscopic point of view due to fluctuations in the reaction temperature of chemical vapor deposition, etc. However, the average grain size may decrease from the inner surface to the surface of the hard layer as a whole, and may be in any form.

The average grain size of the hard layer or the lower layer of the present invention is limited to be in the range of 0.01 to 0.5 μm so that the average grain size of the hard layer or the lower layer is 0. If it is less than 0.01 μm, the hard layer becomes amorphous and desired wear resistance cannot be obtained, which is not preferable. On the other hand, if it exceeds 0.5 μm, both wear resistance and crack resistance sharply decrease, which is not preferable. It is due to. Further, the average layer thickness of the hard layer or the lower layer is set to 5 to 20 μm, and it is not preferable that the average layer thickness of the hard layer is less than 5 μm because sufficient abrasion resistance cannot be obtained, while if it exceeds 20 μm. This is because the toughness is lowered and the chip is easily broken, which is not preferable. Also,
It is not preferable that the average layer thickness of the upper layer is 0.1 to 10 μm, if the average layer thickness of the hard layer is less than 0.1 μm, sufficient abrasion resistance cannot be obtained, while if it exceeds 10 μm, the toughness is reduced. This is due to the unfavorable reason for the decrease in the number and the tendency for defects to occur.

[0013]

EXAMPLES Next, the hard layer-coated WC-based cemented carbide cutting tool of the present invention will be specifically described based on Examples. Example 1 The composition is almost the same as the composition shown in Table 1, and
Prepare a throwaway tip having a shape corresponding to S standard SNG432, and use this throwaway tip as W
C-based cemented carbide substrates A to E were used.

[0014]

[Table 1]

WC-based cemented carbide substrates A to E shown in Table 1
On the surface of each, under pressure: 100 torr
While flowing the reaction gas having the component composition shown in Table 5 for the reaction time shown in Tables 2 to 5, the reaction temperature at the start of the reaction shown in Tables 2 to 5 is continuously lowered from the reaction temperature at the end of the reaction. Chemically vapor-deposited under the conditions to make the coated cutting tool of the present invention 1-8
Was manufactured.

[0016]

[Table 2]

[0017]

[Table 3]

[0018]

[Table 4]

[0019]

[Table 5]

The average layer thickness of the hard layers of the coated cutting tools 1 to 8 of the present invention formed by chemical vapor deposition under the conditions shown in Tables 2 to 5 and the average grain size of crystal grains near the substrate and near the surface were measured. The measurement results are shown in Tables 6 to 7. In addition,
The average grain size of the crystal grains is measured by the Heyn method, and a SEM photograph of the fractured surface of the hard layer is taken, and the average number of grains (N) cut by the diameter (L) of the circle drawn on the photograph is measured. Then, L / N was defined as the average diameter of particles = average particle size. However, in this case, if the particles at both ends are cut at the boundary, 1 /
Calculated as 2 pieces.

Further, using the above coated cutting tools 1 to 8 of the present invention, a work material: SNCM439 (Brinell hardness: 260) slit material, a cutting speed: 200 m / min, a feed: 0.3 m / rev. , Depth of cut: 2 mm, cutting time: 15 min. A high-speed intermittent cutting test was performed under the following conditions: cooling oil: none, the flank wear width of the cutting edge was measured, and the cutting edge condition was also observed. The results are shown in Tables 6 to 7.

[0022]

[Table 6]

[0023]

[Table 7]

Example 2 The hard layer of the coated cutting tools 1 to 8 of the present invention obtained in Example 1 was used as a lower layer, and on the lower layer, TiCO having the thickness shown in Tables 8 to 9 was further added. TiN, TiCNO and A
An upper layer consisting of one single layer of l ₂ O ₃ or two or more multi-layers was formed by a chemical vapor deposition method to prepare coated cutting tools 9 to 16 of the present invention.

The conditions for forming the upper layer by the chemical vapor deposition method are as follows. (A) In the case of TiN layer Temperature: 980 ° C., pressure: 100 torr, Reaction gas composition: 4% TiCl ₄ -8% N ₂ -88% H ₂ (b) In case of TiCN layer Temperature: 1000 ° C., pressure: 100 torr, Reaction gas composition: 4% TiCl ₄ -3% CH ₄ -4% N ₂
-89% H ₂ (c) TiCO layer Temperature: 1000 ° C., pressure: 100 torr, reaction gas composition: 4% TiCl ₄ -6% CO-90% H ₂ (d) TiCNO layer Temperature: 1000 ° C. Pressure: 100 torr, Reaction gas composition: 4% TiCl ₄ -3% CO-3% N _2-
In the case of 90% H ₂ (e) Al ₂ O ₃ layer Temperature: 1000 ° C., pressure: 100 torr, reaction gas composition: 3% AlCl ₃ -5% CO ₂ -92% H
₂

The coated cutting tools 9 to 16 of the present invention thus produced were also subjected to a high-speed interrupted cutting test under the same conditions as those of the high-speed interrupted cutting test conducted in Example 1,
The results are shown in Tables 8-9.

[0027]

[Table 8]

[0028]

[Table 9]

Conventional Example Conventionally coated cutting tools 1 to 6 were prepared by coating the surface of a normal WC-based cemented carbide substrate with a hard layer having the average grain size and the average layer thickness shown in Table 10 under predetermined conditions. ..

In the conventional coated cutting tools 1 and 2, the average grain size of the coated hard layer is within the range of 0.01 to 0.5 μm of the present invention, but the average grain size increases from near the substrate to near the surface. Does not satisfy the conditions of the present invention,
The conventional coated cutting tools 3 and 4 do not satisfy the conditions of the present invention in that the average grain size of the coated hard layer does not change from the vicinity of the substrate to the vicinity of the surface, and the conventional coated cutting tool 5
In Nos. 6 and 6, the average grain size of the coated hard layer is 0.
The point of exceeding 5 μm does not satisfy the condition of the present invention.

Conventional coated cutting tools 1 to 6 shown in Table 10
Was subjected to a high-speed interrupted cutting test under the same conditions as those of the high-speed interrupted cutting test conducted in Example 1. Abnormal wear occurred 15 minutes before the cutting time, and the abnormal wear occurred. The times are shown in Table 10.

[0032]

[Table 10]

[0033]

From the results shown in Tables 1 to 10, it can be seen that the average grain size of the crystal grains is in the range of 0.01 to 0.5 μm and the grain size decreases monotonically from the inner surface to the surface. The present invention coated cutting tool coated with a hard layer does not cause abnormal wear over a long period of time, and exhibits excellent cutting performance, but conventional coated cutting tools that do not satisfy the conditions of the present invention are both short You can see that it will reach the end of its life.

Therefore, by using the hard layer-coated WC-based cemented carbide cutting tool of the present invention, the number of times of exchanging the cutting tool can be reduced as compared with the conventional case, and the industrially excellent effect is achieved.

Claims (2)

[Claims] 1. A hard layer having an average layer thickness of 5 to 20 μm, which is composed of one type of single layer or two types of multiple layers of Ti carbide and carbonitride, on the surface of a tungsten carbide based cemented carbide substrate. In the coated cutting tool, the average grain size of the crystal grains of the hard layer is 0.01 to 0.5 μm.
A hard-layer-coated tungsten carbide-based cemented carbide cutting tool characterized by being in the range of m and decreasing monotonically from the inner surface to the surface. 2. A lower layer having an average layer thickness of 5 to 20 μm, which is composed of one type of single layer or two types of multiple layers of Ti carbide and carbonitride on the surface of a tungsten carbide based cemented carbide substrate. Cutting consisting of coating an upper layer with an average layer thickness of 0.1 to 10 μm consisting of one single layer or two or more multiple layers of titanium carbonate, titanium oxycarbonitride, titanium nitride and aluminum oxide. In the tool, the average grain size of the crystal grains of the lower layer is 0.01 to 0.5 μ.
A hard-layer-coated tungsten carbide-based cemented carbide cutting tool characterized by being in the range of m and decreasing monotonically from the inner surface to the surface.