JPH068009A - Cutting tool made of surface coating tungsten carbide group super hard alloy excellent in chipping resistance property - Google Patents

Abstract

(57) [Summary] [Purpose] To improve the chipping resistance of a surface-coated WC-based cemented carbide cutting tool. [Structure] The hard coating layer formed on the surface of the WC-based cemented carbide substrate is composed of a single layer or a laminate of two or more layers of TiCN, and one or more layers of these constituent layers are a) a crystal structure that changes from a granular crystal structure to a vertically grown crystal structure, (b) a granular crystal structure to a vertically grown crystal structure,
Furthermore, the crystal structure is changed from the vertically elongated crystal structure to the granular crystal structure, (c) the crystal structure is changed from the vertically elongated crystal structure to the granular crystal structure, or two or more kinds of crystal structures are formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention has excellent chipping resistance, and therefore has excellent resistance not only to continuous cutting of steel and cast iron, but also to milling and interrupted cutting thereof. The present invention relates to a surface-coated tungsten carbide (hereinafter referred to as WC) -based cemented carbide cutting tool that exhibits wear resistance.

[0002]

2. Description of the Related Art Conventionally, generally, for example, JP-A-59-52.
As described in Japanese Patent No. 703, a WC-based cemented carbide substrate, and a surface portion having a relatively high Co content as a binder phase forming component compared to the inside of the substrate, that is, a Co-rich surface portion, Titanium carbonitride (hereinafter referred to as TiCN) is formed on the surface of the WC-based cemented carbide substrate having the chemical vapor deposition method or physical vapor deposition method.
It is often the case that a surface-coated WC-based cemented carbide cutting tool formed by forming a hard coating layer consisting of (1) with an average layer thickness of 0.5 to 20 μm is used for continuous cutting of steel or cast iron, for example. It is known.

WC having the above Co-enriched surface portion
The base cemented carbide substrate is mixed with, for example, a nitride powder such as TiN or a carbonitride powder such as TaCN and (Ti, W) CN as a raw material powder, and the green compact is vacuum-sintered under normal conditions. It is also known to be manufactured by a method such as.

[0004]

On the other hand, in recent years, FA and diversification of cutting technology have been remarkable in recent years, and accordingly, excellent wear resistance is exhibited by cutting tools, for example, continuous cutting and interrupted cutting. However, when the above conventional surface-coated WC-based cemented carbide cutting tool is used for intermittent cutting, chipping is likely to occur in the cutting edge and the service life is relatively short. The current situation is that

[0005]

Therefore, the present inventors have
From the above viewpoints, the conventional surface-coated WC-based cemented carbide cutting tool was focused on, and as a result of research to improve the chipping resistance thereof, generally, for example, a hard coating layer by a chemical vapor deposition method. When forming a TiCN layer as the above, the reaction gas composition: volume%, TiCl ₄ : 1 to 5%, CH
_{4: 5~7%, N 2:} 20~30%, H 2: remainder, reaction temperature: 950 to 1050 ° C., atmospheric pressure: 50 to 200 Torr, is formed by the conditions, TiCN layer formed granular crystal Although it usually has a structure, the reaction gas composition is changed by setting the reaction temperature to a relatively low temperature under the conditions for forming the TiCN layer having the granular crystal structure in the latter half process, the intermediate process, or the first half process. Under different conditions, that is, reaction gas composition: volume%, TiCl ₄ : 1 to 4%, CH
_{Under the conditions of 3} CN: 0.1 to 1%, N _{2 to} 0 to 25%, H ₂ : remaining, reaction temperature: 800 to 900 ° C., atmospheric pressure: 30 to 200 torr, the resulting TiCN layer is , (A) a crystal structure that changes from a granular crystal structure to a vertically elongated crystal structure,
(B) a crystal structure that changes from a granular crystal structure to a vertically grown crystal structure, and further changes from this vertically grown crystal structure to a granular crystal structure; (c) a crystal structure that changes from a vertically grown crystal structure to a granular crystal structure; One or two or more layers of the hard coating layer having any one of the crystal structures of the above (c) and composed of a single layer or a laminate of two or more layers of TiCN, and the above (a) to (c). ), Or a surface-coated WC-based cemented carbide cutting tool having a crystal structure of two or more types, the chipping resistance of the cutting edge is further improved by the vertically elongated crystal structure in the TiCN layer. ,
We have obtained the research results that excellent wear resistance can be exhibited not only in continuous cutting of steel and cast iron but also in these intermittent cutting.

The present invention was made based on the above-mentioned research results, and is based on the WC-based cemented carbide substrate or C
o On the surface of a WC-based cemented carbide substrate having an enriched surface portion, T
A surface-coated WC-based cemented carbide cutting tool comprising a hard coating layer composed of a single layer of iCN or a laminate of two or more layers and having an average layer thickness of 0.5 to 20 μm. One or two or more of the constituent layers consisting of more than one layer are (a) a crystal structure that changes from a granular crystal structure to a vertically grown crystal structure, (b) a grain structure from a vertically grown crystal structure, and A crystal structure that changes from a vertically grown crystal structure to a granular crystal structure, (c) A crystal structure that changes from a vertically grown crystal structure to a granular crystal structure, (a) to (c) above
Of the above, or a surface-coated WC having an improved chipping resistance by having a crystal structure of two or more kinds.
It is characterized by a cutting tool made of base cemented carbide.

In the surface-coated WC-based cemented carbide cutting tool of the present invention, the hard coating layer has an average layer thickness of 0.5 to 0.5.
20 μm means that when the layer thickness is less than 0.5 μm,
This is because it is not possible to ensure the desired excellent wear resistance provided by the hard coating layer, while if the layer thickness exceeds 20 μm, the cutting edge is likely to be chipped.

[0008]

EXAMPLES Next, the surface-coated WC-based cemented carbide cutting tool of the present invention will be specifically described by way of examples. As a raw material powder, WC powder having an average particle size of 3 μm, 1.5
μm (Ti, W) C powder (TiC / WC = 3 by weight ratio)
0/70) and 1.2 μm of (Ti, W) CN powder (T
iC / TiN / WC = 24/20/56 by weight ratio, 1.3 μm of (Ta, Nb) C powder (TaC / NbC =
Weight ratio 90/10) and the same 1.2 μm Co powder were prepared, these raw material powders were compounded to the compounding composition shown in Table 1, wet-mixed for 72 hours in a ball mill, and dried,
Press molding into a green compact, and then press this green compact into 1 × 10 ^-2
ISO-CNMG120408 is obtained by vacuum sintering under the conditions of a temperature of 1450 ° C. for 1 hour in a torr vacuum.
WC-based cemented carbide substrates A to C and Co having the shape of
Enriched surface (maximum Co content: 13% by weight, thickness: 20
WC-based cemented carbide substrates D each having a (μm) were produced. Also, for the WC-based cemented carbide substrate C, in a methane gas atmosphere of 100 Torr, a temperature of 1400 ° C.
Was subjected to a carburizing treatment under the condition of holding for 1 hour.
m) was formed.

Next, these WC-based cemented carbide substrates A to
On the surface of D, an ordinary chemical vapor deposition apparatus was used, and the formation conditions of the granular crystal structure of TiCN were as follows: reaction gas composition: volume%, TiCl ₄ : 3%, CH ₄ :
5%, N ₂ : 25%, H ₂ : remaining, reaction temperature: 1020 ° C., atmospheric pressure: 100 torr, and the conditions for forming the TiCN longitudinal growth crystal structure are: reaction gas composition: volume% TiCl ₄ : 1.5%, CH
₃ CN: 0.5%, N ₂ : 25%, H ₂ : remaining, reaction temperature: 860 ° C., atmospheric pressure: 50 torr, and these formation conditions are appropriately converted for each constituent layer during formation, The surface-coated WC-based cemented carbide of the present invention is formed by forming a TiCN constituent layer consisting of a single layer or a laminate of two or more layers having the crystal structure shown in Tables 2 and 3 with the average layer thickness also shown in Table 2. Cutting tools (hereinafter referred to as the coated cutting tools of the present invention) 1 to 16 were manufactured.

For the purpose of comparison, a conventional surface-coated WC-based cemented carbide cutting tool (hereinafter referred to as conventional coated cutting) is used under the same conditions except that the crystal structure of the TiCN layer has a granular crystal structure as shown in Table 3. 1 to 4).

[0011]

[Table 1]

[0012]

[Table 2]

[0013]

[Table 3]

Next, regarding the various coated cutting tools obtained as a result, a work material: a square material of SCM440 (hardness: H _B 220), a cutting speed: 200 m / min., And a feed: 0.25 mm / rev. Cutting depth: 3 mm, cutting time: 30 minutes, dry milling test of steel is performed, flank wear width of cutting edge is measured, and further, work material: SNCM439 (hardness: H _B 280) A dry interrupted cutting test of steel was carried out under the conditions of square bar, cutting speed: 100 m / min., Feed: 0.4 mm / rev., Depth of cut: 3 mm, and the cutting time until the end of its service life was measured. The results of these measurements are shown in Tables 2 and 3.

Further, FIGS. 1 and 2 show photographs of discontinuous surface structures (magnification: 5000 times) of the surfaces of the coated cutting tool 1 of the present invention and the conventional coated cutting tool 2 by a scanning electron microscope. As shown in FIG. 1, in FIG. 1 (the cutting tool 1 coated with the present invention), the crystal structure T is changed from a granular crystal structure to a vertically elongated crystal structure, and further from this vertically grown crystal structure to a granular crystal structure.
The iCN layer (the lower part of FIG. 1 shows the substrate) is shown, and FIG. 2 (conventional coated cutting tool 1) shows the TiCN layer (the lower part of FIG. 2 also shows the substrate) consisting only of the grain structure. Has been done.

[0016]

From the results shown in Tables 2 and 3 and FIGS. 1 and 2, at least one of the constituent layers consisting of a single layer of TiCN or a laminate of two or more layers has a grainy crystal structure to a vertically elongated crystal structure. Inventive coated cutting having a crystal structure that changes to a crystal structure that changes to a grain structure from a grain structure to a crystal structure that changes from a grain structure to a grain structure, or a crystal structure that changes from a grain structure to a grain structure All of the tools 1 to 16 show excellent wear resistance in continuous cutting of steel as compared with the conventional coated cutting tools 1 to 4 in which a hard coating layer made of a TiCN layer having a granular crystal structure is formed, and Conventionally coated cutting tools 1 to 4 for intermittent cutting of steel
It is clear that while it reaches the service life in a relatively short time due to chipping generated on the cutting edge, it exhibits excellent chipping resistance as compared with general and excellent wear resistance over a long period of time. .

As described above, since the surface-coated WC-based cemented carbide cutting tool of the present invention has excellent chipping resistance, for example, continuous cutting of steel and cast iron, as well as chipping resistance is required. It also exhibits excellent wear resistance in these interrupted cuts and exhibits excellent cutting performance over a remarkably long period of time.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional structure photograph of a surface portion of a coated cutting tool 1 of the present invention, taken by a scanning electron microscope.

FIG. 2 is a vertical cross-sectional structure photograph of a surface portion of a conventional coated cutting tool 1 by a scanning electron microscope.

Claims (2)

[Claims] 1. A surface-coated tungsten carbide-based cemented carbide cutting tool comprising a tungsten carbide-based cemented carbide substrate having a hard coating layer formed on the surface thereof with an average layer thickness of 0.5 to 20 μm. The layer is composed of a single layer of titanium carbonitride or a laminated layer of two or more layers, and one or more layers of these constituent layers are (a) a crystal structure that changes from a granular crystal structure to a vertically elongated crystal structure, (B) a crystal structure that changes from a granular crystal structure to a vertically grown crystal structure, and further changes from this vertically grown crystal structure to a granular crystal structure, (c) a crystal structure that changes from a vertically grown crystal structure to a granular crystal structure, above (a) to ( any of c), or 2
A surface-coated tungsten carbide-based cemented carbide cutting tool with excellent chipping resistance, characterized by having a crystal structure of at least one kind. 2. A hard coating layer is formed on the surface of a tungsten carbide based cemented carbide substrate having a surface portion in which the content of Co as a binder phase forming component is relatively large compared to the inside of the substrate.
In a surface-coated tungsten carbide-based cemented carbide cutting tool formed with an average layer thickness of ˜20 μm, the hard coating layer is composed of a single layer of titanium carbonitride or a laminate of two or more layers, and these constituent layers (A) a crystal structure that changes from a granular crystal structure to a vertically elongated crystal structure; and (b) a granular crystal structure to a vertically grown crystal structure, and further from this vertically grown crystal structure to a granular crystal structure. (C) a crystal structure that changes from a vertically elongated crystal structure to a granular crystal structure, any of the above (a) to (c), or 2
A surface-coated tungsten carbide-based cemented carbide cutting tool with excellent chipping resistance, characterized by having a crystal structure of at least one kind.