JP2001062603A - Surface coated cutting tool made of tungsten cemented carbide super hard alloy whose hard coated layer displays excellent tipping resistance in interrupted heavy cutting - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface-coated cutting tool made of a tungsten cemented carbide super hard alloy whose hard coated layer can display excellent chipping resistance in interrupted heavy cutting. SOLUTION: This surface-coated cutting tool made of a tungsten cemented carbide super hard alloy is composed of (a) a Ti compound layer having the average layer thickness of 0.1 to 3 μm and a granular crystal structure on the surface of a tungsten cemented carbide super hard alloy base body and consisting of one kind or two kinds or more out of TiC layer, TiN layer, TiCO layer, TiNO layer and TiCNO layer in which a residual tensile stress is present (b) an upper part layer in which a residual compression stress is existed and a lower part layer in which the residual tensile stress is existed, having the average layer thickness of 2 to 10 μm, and the upper part layer and lower part layer have a mutually continuous vertically long growth crystal structure and the upper part layer is formed by chemical vapor depositing the hard coated layer constituted by TiCN layer having the layer thickness corresponding to 20 to 40% of the average layer thickness of 2 to 10 μm, and (c) Al2O3 layer having the average layer thickness of 0.5 to 10 μm and the granular crystal structure and in which the residual tensile stress is existed by the entire average layer thickness of 3 to 15 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface-coated tungsten carbide-based cemented carbide in which a hard coating layer exhibits excellent chipping resistance, especially when interrupted cutting is performed under heavy cutting conditions such as high feed and high cutting. The present invention relates to a cutting tool (hereinafter referred to as a coated carbide tool).

[0002]

2. Description of the Related Art Conventionally, a tungsten carbide-based cemented carbide substrate (hereinafter referred to as a cemented carbide substrate) generally has (a)
Each of which has an average layer thickness of 0.1 to 3 μm and a granular crystal structure, a titanium carbide (hereinafter, referred to as TiC) layer, a titanium nitride (hereinafter, also referred to as TiN) layer, and a titanium carbonitride (hereinafter, referred to as TiCN). ) Layer, titanium carbonate (hereinafter, T
(b) a Ti compound layer comprising one or more of an iCO) layer, a titanium oxynitride (hereinafter, shown as TiNO) layer, and a titanium carbonitride (hereinafter, shown as TiCNO) layer; A titanium carbonitride (hereinafter referred to as 1-TiCN) layer having an average layer thickness of 2 to 10 μm and a vertically grown crystal structure, and (c) an aluminum oxide having an average layer thickness of 0.5 to 5 μm and a granular crystal structure ( Hereinafter, Al ₂
O ₃ ) layer and a hard coating layer composed of ₃ to 15
A coated carbide tool formed by chemical vapor deposition with a total average layer thickness of μm is known, and it is also known that the coated carbide tool is used for continuous cutting or interrupted cutting of steel, cast iron, or the like.
It is also well known that, generally, those having an α-type crystal structure, those having a κ-type crystal structure, and the like are widely and practically used as the Al ₂ O ₃ layer constituting the hard coating layer of the coated carbide tool. Further, the l-TiCN layer is known, for example, from JP-A-6-8010 and JP-A-7-328808, and
Using a mixed gas containing organic carbonitride as the reaction gas,
It is formed by chemical vapor deposition in a medium temperature range of 700 to 950 ° C.

[0003]

On the other hand, in recent years, there is a strong demand for labor saving, energy saving, and further cost reduction in cutting, and accordingly, cutting is performed under heavy cutting conditions such as high feed and high cutting. Although it tends to be performed, in the above-mentioned conventional coated cemented carbide tool, chipping (minute chipping) occurs in the hard coating layer, especially when this is used for interrupted cutting under heavy cutting conditions such as high feed and high cutting. At present, it is easy to occur, and as a result, the service life is reached in a relatively short time.

[0004]

Means for Solving the Problems Accordingly, the present inventors have
From the above-mentioned viewpoints, as a result of conducting research to improve the chipping resistance of the hard coating layer in the conventional coated carbide tool, (a) in the hard coating layer of the conventional coated carbide tool, Is formed by a chemical vapor deposition method, a residual tensile stress of 30 to 70 kgf / mm ² exists in any of the constituent layers, which causes chipping in intermittent heavy cutting with high impact.

(B) As described above, when the Ti compound layer and the Al ₂ O ₃ layer constituting the hard coating layer of the coated cemented carbide tool are formed by a chemical vapor deposition method, tensile stress remains in each case,
This cannot be formed so that the compressive stress remains, but in the case of the same l-TiCN layer, after forming the l-TiCN layer (lower partial layer) in which the tensile stress remains, the deposition conditions are changed. As a result, a compressive stress of 5 to ²⁰ kgf / mm ² remains without damaging the vertically-grown crystal structure of the lower partial layer, that is, while maintaining the vertically-grown crystal structure of the lower partial layer. l-
A TiCN layer (upper partial layer) can be formed.

(C) The above-mentioned l-TiCN layer (upper partial layer) in which the compressive stress of 5 to ²⁰ kgf / mm ² remains is formed under a normal condition, that is, a reaction gas composition (% by volume, the same applies hereinafter). TiCl ₄ : 1
_-3 %, N2: 20-40%, CH3CN: 0.1-1
%, H2: rest, ambient temperature: from 800 to 920 ° C., atmospheric pressure: 50～150Torr, conditions prescribed layer thickness l-TiCN layer residual tensile stresses are present 30~70kgf / mm ² (the lower portion layer) in the After the formation by chemical vapor deposition, the deposition conditions were changed to the reaction gas composition (% by volume, the same applies hereinafter) -TiCl ₄ :
_{0.1~1%, N 2: 30~50%} , CH 4: 0.1~1
%, H ₂ : remaining, ambient temperature: 940 to 1000 ° C., atmospheric pressure: 50 to 200 Torr, and chemical vapor deposition for a predetermined time. (D) As described above, in the l-TiCN layer of the hard coating layer, the residual tensile stress is present in the lower part and the residual compressive stress is present in the upper part. L-T where stress and residual compressive stress coexist
When the iCN layer is present as a constituent layer of the hard coating layer, the resulting coated carbide tool has excellent chipping resistance even in high impact applied cutting in which interrupted cutting is performed under heavy cutting conditions. The ability to exhibit excellent cutting performance over a long period of time. (D) The upper partial layer in which the residual compressive stress exists in the l-TiCN layer constituting the hard coating layer has a layer thickness corresponding to 20 to 40% of the average layer thickness of the l-TiCN layer for the reason described later. It is necessary to have (A) ~
The research results shown in (d) were obtained.

The present invention has been made based on the above research results, and (a) all have an average layer thickness of 0.1 to 3 μm and a granular crystal structure on the surface of a cemented carbide substrate, TiC layer, TiN with residual tensile stress
Layer, TiCN layer, TiCO layer, TiNO layer, and Ti
A Ti compound layer composed of one or more of CNO layers, (b) an upper partial layer having an average layer thickness of 2 to 10 μm and having a residual compressive stress and a lower partial layer having a residual tensile stress The upper partial layer and the lower partial layer have a mutually continuous vertically-grown crystal structure, and the upper partial layer has an average layer thickness of 20 to 4 μm of 3 to 10 μm.
An l-TiCN layer having a layer thickness corresponding to 0%, (c)
A hard coating layer composed of an Al ₂ O ₃ layer having an average layer thickness of 0.5 to 5 μm and a granular crystal structure and having a residual tensile stress, is chemically vapor-deposited at a total average layer thickness of 3 to 15 μm. Thus, the present invention is characterized in that a hard coated layer exhibits excellent chipping resistance in intermittent heavy cutting.

The thickness of the upper partial layer in the l-TiCN layer constituting the hard coating layer of the coated carbide tool of the present invention is set to a layer thickness corresponding to 20 to 40% of the l-TiCN layer. If the thickness of the layer is less than 20% of the l-TiCN layer, the residual compressive stress of the layer is relatively small, and it is not possible to secure a sufficiently satisfactory chipping resistance. Above 40% of the layer, the grain growth is incorporated into the longitudinally grown crystal structure and the excellent toughness provided by the vertically grown crystallographic structure is impaired.

Further, the average thickness of the constituent layers in the hard coating layer of the coated carbide tool of the present invention is determined for the following reasons. That is, each of the Ti compound layers has a function of improving interlayer adhesion between constituent layers as a common property, and therefore, the average layer thickness is 0.1%.
If the average thickness is less than 3 μm, chipping may occur on the cutting edge by high-speed cutting, especially when a TiC layer exists as a constituent layer. And also soft T
When the iN layer is present, the wear of the hard coating layer is promoted, so that the average layer thickness is 0.1 to 3 μm.
m.

The Al ₂ O ₃ layer has an effect of improving the abrasion resistance of the hard coating layer.
If the average layer thickness is less than 5 μm, the desired excellent wear resistance cannot be ensured. On the other hand, if the average layer thickness exceeds 5 μm, chipping tends to occur on the cutting edge. It was determined to be 5 μm.

Further, as described above, the 1-TiCN layer imparts excellent toughness to the hard coating layer due to the vertically grown crystal structure, and the compressive stress is formed only on the lower partial layer where residual tensile stress exists. Has an effect of improving the chipping resistance of the hard coating layer, but if the average layer thickness is less than 2 μm, the desired effect cannot be obtained. 10μ thick
If it exceeds m, chipping or chipping is likely to occur in the cutting edge, so the average layer thickness is set to 2 to 10 μm. Further, the reason why the total average layer thickness of the hard coating layer is set to 3 to 15 μm is that if the average layer thickness is less than 3 μm, the desired wear resistance cannot be secured, while the average layer thickness exceeds 15 μm. This is because the chipping and chipping of the cutting edge are likely to occur.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the coated carbide tool of the present invention will be specifically described with reference to examples. As raw material powder, fine-grained WC powder having an average particle size of 1.5 μm, medium-grained WC powder of 3.0 μm, and (Ti, W) CN of 1.2 μm (the same in weight ratio, hereinafter, TiC / TiN / WC) = 24/20/5
6) Powder, (Ti, W) C (TiC / W) of 1.2 μm
C = 50/50) powder, 1.3 μm (Ta, Nb)
C (TaC / NbC = 90/10) powder, 1.2 μm
Cr ₃ C ₂ powder and Co powder of 1.2 μm were prepared, and these raw material powders were blended in the blending composition shown in Table 1, wet-mixed for 72 hours in a ball mill, dried, and then mixed. The compact is formed into a compact with a shape of a throw-away chip in accordance with ISO standard CNMG120412, and this compact is placed in a vacuum atmosphere of 10 ^-3 torr at 1400 to 1400.
Carbide substrates A to E were respectively manufactured by vacuum sintering at a predetermined temperature in the range of 1460 ° C. for one hour. Further, 100 torr is applied to the super hard substrate E.
After holding for 1 hour at a temperature of 1400 ° C. in a CH ₄ gas atmosphere of r, carburizing treatment is performed under slow cooling conditions, and carbon and Co adhering to the surface of the carbide substrate after the treatment are removed by acid and barrel polishing. , The maximum Co at 11 μm from the surface
A Co-enriched zone having a content of 15.9% by weight and a depth of 42 μm was formed on the surface of the substrate. In addition, the sintered body was kept sintered, and the surface of the cemented carbide substrate C had a maximum Co content of 10.5% by weight and a depth of 23 μm at a position 17 μm from the surface.
m Co-enriched zone, the super-hard substrate D has a maximum Co content of 14.5% by weight at a position of 22 μm from the surface on the surface portion,
A Co-enriched zone having a depth of 29 μm was formed, and the remaining carbide substrates A and B did not have the Co-enriched zone and had a uniform structure as a whole.
Further, Table 1 shows the internal hardness (Rockwell hardness A scale) of each of the carbide substrates A to E.

[0013] Then, in a state where these super-hard substrates A to E are processed and honed into a predetermined shape, the surfaces thereof are formed on a surface thereof by using an ordinary chemical vapor deposition apparatus under the conditions shown in Table 2. By forming the hard coating layer having the target composition and the target layer thickness (the flank of the cutting edge) shown in FIG. 4, the 1-TiCN layer among the constituent layers of the hard coating layer is an upper partial layer in which residual compressive stress exists. The present invention provides a coated super hard tool 1 to 10 comprising a lower partial layer having a residual tensile stress and a conventional coated super hard tool 1 to 10 wherein only a residual tensile stress exists in the 1-TiCN layer. did. For each of the resulting coated carbide tools, the composition and average thickness of the constituent layers of the hard coating layer were measured using an electron probe microanalyzer and an optical microscope, and the residual stress of each constituent layer was measured. Calculated based on the measurement results of X-ray diffraction, each of them shows substantially the same composition and average layer thickness as the target composition and target layer thickness shown in Tables 3 and 4, and substantially the same as the target residual stress. Residual stress was indicated.

Next, the coated carbide tools 1 to 10 according to the present invention will be described.
And the conventional coated carbide tools 1 to 10; Work material: JIS SCM440, longitudinally-elongated round bar with four longitudinal grooves, cutting speed: 200 m / min. Infeed: 4 mm Feed: 0.3 mm / rev. , Cutting time: 10 minutes, Dry intermittent high-incision cutting test of alloy steel under the following conditions: Work material: JIS SCr420H, a longitudinally-elongated round bar with four longitudinal grooves, Cutting speed: 200 m / min . Infeed: 1.5 mm Feed: 0.6 mm / rev. The cutting time: 10 minutes, a dry intermittent high feed cutting test of the alloy steel was performed under the following conditions, and the maximum flank wear width of the cutting edge was measured in each cutting test. Table 5 shows the measurement results.

[0015]

[Table 1]

[0016]

[Table 2]

[0017]

[Table 3]

[0018]

[Table 4]

[0019]

[Table 5]

[0020]

From the results shown in Tables 2 to 5, it can be seen from the results that the l-TiCN layer existing as a constituent layer in the hard coating layer is composed of an upper partial layer having a residual compressive stress and a lower partial layer having a residual tensile stress. Invented coated carbide tools 1 to 10 have chipping edges even when performing intermittent cutting under heavy cutting conditions such as high feed and high cutting, since the hard coating layer has excellent chipping resistance. And no chipping
While exhibiting excellent wear resistance over a long period of time,
In the conventional coated carbide tools 1 to 10 in which only the residual tensile stress exists in the l-TiCN layer,
It is apparent that the constituent layers other than the TiCN layer also have residual tensile stress and, in the intermittent heavy cutting in which a high impact is applied, chipping occurs, which leads to a short service life in a relatively short time. As described above, the coated cemented carbide tool of the present invention exhibits excellent chipping resistance not only in continuous cutting and interrupted cutting of steel or cast iron, but also in interrupted heavy cutting in which high impact is applied, for a long time. Since it shows excellent cutting performance over a long period of time, it can sufficiently cope with labor saving and energy saving of the cutting process, and further, cost reduction.

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[Procedure amendment]

[Submission date] August 3, 1999 (1999.8.3)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0012

[Correction method] Change

[Correction contents]

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the coated carbide tool of the present invention will be specifically described with reference to examples. As raw material powder, fine-grained WC powder having an average particle size of 1.5 μm, medium-grained WC powder of 3.0 μm, and (Ti, W) CN of 1.2 μm (the same in weight ratio, hereinafter, TiC / TiN / WC) = 24/20/5
6) Powder (1.3 μm) of (Ta, Nb) C (TaC /
NbC = 90/10) powder, a 1.2 μm Cr ₃ C ₂ powder, and a 1.2 μm Co powder were prepared, and these raw material powders were blended into the blending composition shown in Table 1 and then subjected to ball milling for 72 hours. After wet mixing and drying, the mixed powder is mixed with I
It is press-formed into a green compact in the form of a throw-away tip in accordance with SO standard CNMG120412, and this green compact is
Carbide substrates A to E were manufactured by vacuum sintering in a vacuum atmosphere of ^-3 torr at a predetermined temperature in the range of 1400 to 1460 ° C. for 1 hour. further,
The above-mentioned cemented carbide substrate E is kept in a 100 Torr CH ₄ gas atmosphere at a temperature of 1400 ° C. for 1 hour, and then subjected to carburizing treatment under slow cooling conditions. After the treatment, carbon and Co adhering to the cemented carbide substrate surface are removed. 14. maximum Co content at a position 11 μm from the surface by removing with acid and barrel polishing;
A Co-enriched zone of 9% by weight and a depth of 42 μm was formed on the surface of the substrate. In addition, the sintered body was kept sintered and the surface of the cemented carbide substrate C had a maximum Co at a position 17 μm from the surface.
Content: 10.5% by weight, depth: Co-enriched zone with a depth of 23 μm. On the surface of the cemented carbide substrate D, the maximum Co content at a position 22 μm from the surface: 14.5% by weight, depth: 29 μm
Were formed, and the remaining carbide substrates A and B did not have the Co-enriched zone, and had a uniform structure as a whole. Further, Table 1 shows the internal hardness (Rockwell hardness A) of the above-mentioned carbide substrates A to E.
Scale).

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Masayuki Miichi 1511 Furamagi, Ishishita-cho, Yuki-gun, Ibaraki Pref. F-term in Mitsubishi Materials Corporation Tsukuba Works (reference) AA18 BA18 BA35 BA36 BA38 BA41 BA43 BB03 BB12 CA03 JA01 LA01 LA22

Claims (1)

[Claims] 1. A titanium carbide layer comprising: (a) a titanium carbide layer having an average layer thickness of 0.1 to 3 μm and a granular crystal structure, and having a residual tensile stress, on the surface of a tungsten carbide-based cemented carbide substrate; A titanium compound layer composed of one or more of a titanium nitride layer, a titanium carbonitride layer, a titanium carbonate layer, and a titanium carbonitride oxide layer; and (b) an average layer thickness of 2 to 10 μm, An upper partial layer in which residual compressive stress exists and a lower partial layer in which residual tensile stress exists, wherein the upper partial layer and the lower partial layer have a vertically-elongated crystal structure continuous with each other, and the upper partial layer is A titanium carbonitride layer having a layer thickness corresponding to 20 to 40% of the average layer thickness of 2 to 10 μm, and (c) an aluminum oxide layer having an average layer thickness of 0.5 to 5 μm and a granular crystal structure; Hard coating layer composed of 3 Formed by chemical vapor deposition in overall average layer thickness of 15 [mu] m,
Surface-coated tungsten carbide-based cemented carbide cutting tool with a hard coating layer that exhibits excellent chipping resistance in intermittent heavy cutting.