JPH06108254A - Cutting tool made of surface-coated wc-base sintered hard alloy - Google Patents

Abstract

PURPOSE:To provide a cutting tool showing excellent cutting performance, on the surface of a WC-base sintered hard alloy substrate, by forming a specified titanium nitride internal layer and a specified titanium carbo-nitride external layer thereon. CONSTITUTION:A titanium nitride internal layer having 5 to 50nm thickness and whose crystalline grains have a granular structure is formed on the surface of a WC-base sintered hard alloy substrate. On the titanium nitride internal layer, a titanium carbo-nitride external layer having 1 to 8mum thickness and whose crystalline grains have a columnar structure is formed. On the surface of the cutting tool made of the surface coated WC-base sintered hard alloy, furthermore, a single layer or multi layers of one or two kinds among aluminum oxide, titanium carbonate and titanium carbo-nitride-oxide having a 0.1 to 2mum thickness. In this way, the surface coated cutting tool in which the peeling of the hard coated layer is hard to occur can be provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface-coated WC formed by using a tungsten carbide (hereinafter referred to as WC) -based superalloy as a substrate and forming a hard coating layer having excellent adhesion on the surface thereof.
The present invention relates to a base cemented carbide cutting tool, and even when used for intermittent cutting such as milling cutting under more severe conditions, the hard coating layer does not easily peel off and exhibits excellent cutting performance. The present invention relates to a cutting tool.

[0002]

2. Description of the Related Art Generally, on the surface of a WC-based cemented carbide substrate,
Surface-coated WC-based cemented carbide cutting tool coated with a Ti nitride (hereinafter referred to as TiN) layer and a Ti carbonitride (hereinafter referred to as TiCN) layer by a chemical vapor deposition method (hereinafter referred to as CVD method) , And the surface of the surface-coated WC-based cemented carbide cutting tool, titanium oxycarbonitride, titanium carbonate, and aluminum oxide (hereinafter, respectively TiC
NO, TiCO, and Al ₂ O ₃ )
Surface-coated WC-based cemented carbide cutting tool obtained by forming a hard coating layer consisting of two or more single-layer or two or more multi-layers with an average layer thickness within the range of 0.5 to 10 μm is an interrupted steel. It is known to be used for cutting.

However, the conventional CVD method uses 900 ° C.
Since it is carried out at a high temperature exceeding 100 ° C., WC-based cemented carbide substrate and T
A decarburization layer is formed at the boundary with the iN layer, and the crystal grains of the formed TiN layer grow abnormally, so that sufficient wear resistance and fracture resistance cannot be obtained. With carbide cutting tools, the service life under severe conditions was unsatisfactory.

For this reason, in recent years, there has been proposed a medium temperature chemical vapor deposition method (hereinafter referred to as MT-CVD method) in which an organic CN compound can be used for chemical vapor deposition at a temperature of 700 to 900 ° C. 62-44572 gazette).

[0005]

However, the above-mentioned MT-C
The VD method is effective in forming a decarburized substrate layer and preventing abnormal growth of crystal grains in the TiCN layer.
Since it is performed at a low temperature, it is inferior in adhesiveness to the TiCN layer formed by the conventional high temperature CVD method, so it is used for intermittent cutting such as high speed, high feed milling cutting and wet milling cutting under more severe conditions. If the TiCN layer is not sufficiently adhered to the WC-based superalloy substrate,
Therefore, peeling or chipping of the TiCN layer occurred, and the tool life could not be extended.

[0006]

Therefore, the present inventors have
While maintaining the advantages of the TiCN layer formed by the MT-CVD method,
As a result of research to improve the adhesion strength to the WC-based cemented carbide substrate, (a) the thickness: 5 formed on the surface of the WC-based cemented carbide substrate by the ordinary high temperature CVD method.
The TiN layer having a grain structure of ˜50 nm has a grain structure.
The adhesiveness is particularly excellent, and the thickness of the TiN layer formed by the high temperature CVD method by the MT-CVD method is:
A surface-coated WC-based cemented carbide cutting tool obtained by forming a TiCN layer having a columnar structure with crystal grains of 1 to 8 μm is a surface-coated WC obtained by a conventional MT-CVD method.
The adhesion of the TiCN layer is extremely superior to that of the base cemented carbide cutting tool. (B) The surface of the surface-coated WC-based cemented carbide cutting tool prepared in (a) above has a thickness of:
The inventors have found that a single layer of aluminum oxide, titanium carbonate, or titanium oxycarbonitride having a thickness of 0.1 to 2 μm may be formed, or two or more layers may be formed.

The present invention has been made on the basis of the above findings. (1) A TiN layer having a grain structure with a grain size of 5 to 50 nm on the surface of a WC-based cemented carbide substrate. (Hereinafter, referred to as TiN inner layer) and a TiCN layer formed on the TiN inner layer and having a thickness of 1 to 8 μm and a crystal grain having a columnar structure (hereinafter, referred to as TiCN outer layer).
A surface-coated WC-based cemented carbide cutting tool,
(2) One of aluminum oxide, titanium carbonate, and titanium oxycarbonitride having a thickness of 0.1 to 2 μm on the surface of the surface-coated WC-based cemented carbide cutting tool according to (1). The present invention is characterized by a surface-coated WC-based cemented carbide cutting tool formed by forming a single layer of one kind or a multi-layer of two or more kinds (hereinafter referred to as an outermost layer).

The crystal grains of the present invention have a granular structure T
In order to form the iN inner layer, a gas such as TiCl ₄ , N ₂ and H ₂ used in a normal CVD reaction is reacted for a short time in a high vacuum at a reaction temperature of over 900 ° C. and a pressure of 150 torr or less. Is formed by. The short time is 1
10 minutes. Further, the TiCN outer layer of the present invention having a columnar structure of crystal grains is formed by a usual MT-CVD method.

The thickness of the TiN inner layer is set to 5 to 50 nm because if the thickness is smaller than 5 nm, the effect of sufficiently improving the adhesive force of the TiCN outer layer cannot be obtained. On the other hand, the thickness of the TiN inner layer is more than 50 nm. If it is made large, the crystal grains will not become granular, and the strength of the substrate will be reduced by performing high temperature CVD for a long time, and a decarburized layer will be formed between the substrate and the TiN inner layer, and the adhesion will be reduced, which is not preferable. is there.

The thickness of the TiCN outer layer is set to 1 to 8 μm because if it is less than 1 μm, sufficient wear resistance cannot be obtained because columnar crystal grains of the TiCN outer layer cannot be obtained.
If it is larger than μm, defects and chipping are likely to occur.

The thickness of the outermost layer is set to 0.1 to 2 μm because when it is less than 0.1 μm, there is no effect of improving crater resistance and welding resistance, while when it is more than 2 μm, defects occur.
This is because chipping is likely to occur.

[0012]

EXAMPLES Next, the surface-coated WC-based cemented carbide cutting tool of the present invention will be specifically described by way of examples.

A throw-away tip having the same composition as that shown in Table 1 and having a shape defined by ISO standard SNG432 is prepared, and the throw-away tip is used as a WC-based cemented carbide substrate AE. And

[0014]

[Table 1]

On the surfaces of these WC-based cemented carbide substrates A to E shown in Table 1, the TiN inner layer and MT-CVD by the ordinary CVD method under the conditions shown in Tables 2 to 7, respectively.
Forming an outer layer of TiCN by the method, and the coated cutting tools of the present invention (hereinafter referred to as the inventive tools) 1 to 9 shown in Tables 8 to 9
And comparative coated cutting tools (hereinafter, comparative tools) 1 to 4 are prepared, and for comparison, conventional coated cutting tools (hereinafter, conventional tools) 1 to 2 are prepared only by a normal CVD method or MT-CVD method. It was made. In addition, the comparison tools 1 to 4 are T
The thickness of the iN inner layer and the TiCN outer layer is outside the scope of the present invention.

[0016]

[Table 2]

[0017]

[Table 3]

[0018]

[Table 4]

[0019]

[Table 5]

[0020]

[Table 6]

[0021]

[Table 7]

[0022] The present invention tools 1-9, Comparative tools 1 to 4 and conventional tools 1-2, Workpiece: SNCM439 (Hardness: H _B 260) Cutting speed: 200 meters / min feed Ri: 0.3 mm / Blade depth: 2.0 mm Cutting time: 15 min A milling test of steel was conducted under the condition of no cooling oil: not only to measure the flank wear width of the cutting edge, but also to observe the cutting edge condition. These results are also shown in Table 8. ~ Shown in Table 9.

[0023]

[Table 8]

[0024]

[Table 9]

From the results shown in Tables 8 to 9, when milling under the above conditions, all of the tools 1 to 9 of the present invention have a small flank wear width of the cutting edge, and further the cutting edge condition. It can be seen that, while normal wear is exhibited, the comparative tools 1 to 4 cause abnormal wear or initial chipping, and the conventional tools 1 to 2 cause initial chipping or initial peeling.

[0026]

As described above, according to the present invention, it is possible to provide a surface-coated WC-based cemented carbide cutting tool exhibiting superior cutting performance to the prior art, which can greatly contribute to industrial development. Is.

Claims (2)

[Claims] 1. A titanium nitride inner layer having a thickness of 5 to 50 nm and a crystal grain having a granular structure on the surface of a WC-based cemented carbide substrate, and a titanium nitride inner layer formed on the titanium nitride inner layer and having a thickness of 1 to 8 μm.
m, a surface-coated WC-based cemented carbide cutting tool formed by forming an outer layer of titanium carbonitride having a columnar structure of crystal grains. 2. The surface-coated WC-based cemented carbide cutting tool according to claim 1, further comprising: aluminum oxide, titanium carbonate, titanium oxycarbonitride having a thickness of 0.1 to 2 μm. A surface-coated WC-based cemented carbide cutting tool, which is formed by forming one type of single layer or two or more types of multiple layers.