JP2001087907A - Machining tool of cemented carbide based on surface- covered tungsten carbide with its hard covering layer exhibiting excellent chipping resistance in intermittent heavy duty machining - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a machining tool made of surface-covered cemented carbide having a hard covering layer exhibiting an excellent chipping resistance in intermittent heavy-duty machining. SOLUTION: To the surface of the cemented carbide body based on tungsten carbide, a hard covering layer having a total mean thickness of 5-25 μm is formed by chemical evaporation, wherein the hard covering layer is composed of (a) a Ti-compound layer consisting of one or more of layers of TiC, TiN, TiCN, TiCO and TiCNO each of which has a mean thickness of 0.1-5 μm and has a granular crystalline structure and in which a residual tensile stress exists, (b) a TiCN layer having a mean thickness of 2-15 μm and composed of an upper layer where a residual compressive stress exists and a lower layer where a residual tensile stress exists, (c) a TiN layer having a mean thickness of 2-15 μm and composed of an upper layer where a residual compressive stress exists and a lower layer where a residual tensile stress exists, and (d) an Al2O3 layer which has a mean thickness of 0.5-10 μm and a granular crystalline structure and in which a residual tensile stress exists.

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 5 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
iCO) layer and titanium carbonitride (hereinafter referred to as Ti
(B) Titanium carbonitride (hereinafter referred to as l-type) having an average layer thickness of 2 to 15 μm and a vertically grown crystal structure.
A hard coating layer composed of an aluminum oxide (hereinafter, referred to as Al ₂ O ₃ ) layer having an average layer thickness of 0.5 to 10 μm and a granular crystal structure; A coated carbide tool formed by chemical vapor deposition with a total average layer thickness of 25 μm is known, and it is also known that this 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. And the above l-TiC
The N layer is formed, for example, in JP-A-6-8010 or JP-A-7-810.
It is known from, for example, 328808, and is formed by performing chemical vapor deposition in a normal chemical vapor deposition apparatus at a medium temperature range of 700 to 950 ° C. using a mixed gas containing an organic carbonitride as a reaction gas. It is.

[0003]

On the other hand, in recent years, the use of FA in cutting equipment has been remarkable, and there has been a strong demand for labor saving, energy saving, and further cost reduction in cutting work. In addition to continuous cutting and intermittent cutting under the conditions described above, versatility capable of performing cutting even in heavy cutting conditions such as high feed and high cutting is required, but in the conventional coated carbide tool described above, In particular, when this is used to perform intermittent cutting under heavy cutting conditions such as high feed and high cutting, chipping (small chipping) is likely to occur in the hard coating layer, which leads to a relatively short service life. Is the current situation.

[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 is present in any of the constituent layers, even if the crystal structure is a granular crystal or a vertically-grown crystal. Intermittent heavy cutting with impact may cause chipping.

(B) As described above, when a Ti compound layer, an Al ₂ O ₃ layer, and an l-TiCN layer constituting a hard coating layer of a coated carbide tool are formed by a chemical vapor deposition method, tensile stress remains in any case. However, this cannot be formed so that the compressive stress remains, but in the case of the 1-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 remains without impairing the vertically elongated crystal structure of the lower partial layer, that is, while maintaining the vertically elongated crystal structure of the lower partial layer. -The ability to form a TiCN layer (upper partial layer).

(C) The above-mentioned l-TiCN layer (upper partial layer) in which the compressive stress of 5 to 20 kgf / mm remains remains under normal conditions, that is, the reaction gas composition (% by volume, the same applies hereinafter) -TiCl ₄ : 1
_{~3%, N 2: 20~40%} , CH 3 CN: 0.1~1
%, H ₂ : remaining, ambient temperature: 800 to 920 ° C., atmospheric pressure: 50 to 150 Torr, and a predetermined thickness of the l-TiCN layer (lower partial layer) having a residual tensile stress of 30 to 70 kgf / mm. After the formation by chemical vapor deposition, the deposition conditions were as follows: reaction gas composition—TiCl ₄ : 0.1-1%, N ₂ : 30
_{~50%, CH 3 CN: 0.1~1} %, H 2: remainder, ambient temperature: from 940 to 1,000 ° C., atmospheric pressure: 50～200Torr, to change, can be formed by performing a predetermined time chemical vapor deposition.

(D) Further, regarding the TiN layer of the Ti compound layer constituting the hard coating layer of the coated cemented carbide tool, the TiN layer having a granular crystal structure has a reaction gas composition of -TiCl ₄ : 2 10%, N _2: 20~
40%, H ₂ : remaining, ambient temperature: 900 to 1050 ° C., atmospheric pressure: 50 to 300 Torr. Compared to the chemical vapor deposition conditions, the concentration of the TiN forming component in the reaction gas is relatively small. to depressed, and reaction atmosphere pressure raised condition, i.e., the reaction gas composition _{-TiCl 4: 0.2~1%, N 2} : 5~
When the TiN layer is subjected to chemical vapor deposition under the following conditions: 10%, H ₂ : remaining, ambient temperature: 900 to 1050 ° C., atmospheric pressure: 400 to 600 Torr, the above l-
A TiN layer having a vertically grown crystal structure having substantially the same fracture structure and light microscopic structure as the TiCN layer is formed.

(E) Further, the TiN (hereinafter referred to as 1-TiN) layer having the vertically elongated crystal structure formed in (d) also has a residual tensile stress of 30 to 70 kgf / mm. Similarly to the l-TiCN layer described in the above (c), first, the l-TiN layer (lower partial layer) having a residual tensile stress of 30 to 70 kgf / mm under the above condition (d) has a predetermined layer thickness. after chemical vapor deposited up to the deposition conditions, the reaction gas composition _{-TiCl 4: 0.2~1%, N 2} : 5~
10%, H ₂ : remaining, ambient temperature: 950 to 1150 ° C., atmospheric pressure: 50 to 300 Torr, and performing chemical vapor deposition for a predetermined time, without impairing the vertically elongated crystal structure of the lower partial layer, ie, An l-TiN layer (upper partial layer) in which a compressive stress of 5 to 20 kgf / mm remains can be formed with a vertically elongated crystal structure continuous with the vertically elongated crystal structure of the lower partial layer.

(F) As shown in (c) and (e) above, l-Ti having a stress distribution in which a residual tensile stress exists in a lower portion and a residual compressive stress exists in an upper portion.
When the CN layer and the 1-TiN layer are present as constituent layers of the hard coating layer, the resulting coated carbide tool can be used for the high impact applied cutting in which the interrupted cutting is performed under heavy cutting conditions. Has excellent chipping resistance, and exhibits excellent cutting performance over a long period of time.

(G) l-Ti constituting the hard coating layer
The upper partial layer where the residual compressive stress exists in the CN layer and the l-TiN layer is formed by the above-mentioned l-T for the reason described later.
20 to 40% of the average layer thickness of the iCN layer and the 1-TiN layer
It is necessary to have a layer thickness corresponding to. The research results shown in (a) to (g) above 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 5 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
(B) an upper partial layer having an average layer thickness of 2 to 15 μm and having a residual compressive stress and a lower part 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 2 to 15 μm.
An l-TiCN layer having a layer thickness corresponding to 0%, (c)
An upper partial layer having an average layer thickness of 2 to 15 μm and having a residual compressive stress and a lower partial layer having a residual tensile stress, wherein the upper partial layer and the lower partial layer are mutually continuous vertically grown crystals. Having tissue and the upper partial layer comprises:
An l-TiN layer having a layer thickness corresponding to 20 to 40% of the average layer thickness of 2 to 15 μm, and (d) 0.5 to 10 μm.
An Al ₂ O ₃ layer having an average layer thickness and a granular crystal structure of m, and having a residual tensile stress, and a hard coating layer constituted by chemical vapor deposition with a total average layer thickness of 5 to 25 μm.
The present invention is characterized by a coated carbide tool in which a hard coating layer exhibits excellent chipping resistance in intermittent heavy cutting.

The thickness of the upper partial layer of the 1-TiCN layer and the 1-TiN layer constituting the hard coating layer of the coated carbide tool of the present invention is determined by any one of the upper partial layers. If the thickness is less than 20% of the average layer thickness,
Not only the relative ratio of the residual compressive stress to the residual tensile stress in the hard coating layer becomes lower, but also the balance of the residual stress distribution in the entire hard coating layer is lost, and as a result, chipping easily occurs on the cutting edge. Is 40 times the average layer thickness of the l-TiCN layer and the l-TiN layer.
%, The average thickness is determined to be 20 to 40% of the average layer thickness because the grain structure is mixed with the vertically-grown crystal structure and the excellent toughness provided by the vertically-grown crystal structure is impaired. is there.

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 reason. 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 it is less than μm, it is not possible to secure the desired excellent interlayer adhesion. On the other hand, if the average layer thickness exceeds 5 μm, the chipping is likely to occur on the cutting edge. It was determined as 0.1 to 5 μm.

The Al ₂ O ₃ layer has an effect of improving the abrasion resistance of the hard coating layer.
When the average layer thickness is less than 5 μm, the desired excellent wear resistance cannot be secured. On the other hand, when the average layer thickness exceeds 10 μm, chipping easily occurs on the cutting edge. It was determined to be 10 μm.

Further, an l-TiCN layer and an l-TiN
Both layers give the hard coating layer excellent toughness due to the elongated growth crystal structure as described above, and the residual compressive stress of each upper partial layer causes the relative tensile stress and residual compressive stress in the hard coating layer to be relatively high. There is an effect of maintaining the stress distribution in a good state, and as a result, the chipping resistance of the hard coating layer is improved. However, if the average layer thickness is less than 2 μm, the desired effect cannot be obtained. ,
On the other hand, if the average layer thickness exceeds 15 μm, chipping and chipping easily occur in the cutting edge. Therefore, the average layer thickness is set to 2 to 15 μm. In addition, the reason why the total average layer thickness of the hard coating layer is set to 5 to 25 μm is that if the average layer thickness is less than 5 μm, the desired wear resistance cannot be secured, while the average layer thickness exceeds 25 μm. This is because the chipping and chipping of the cutting edge are likely to occur.

[0016]

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 cemented carbide substrate E was kept in a 100 Torr CH4 gas atmosphere at a temperature of 1400 ° C. for 1 hour, and then carburized under slow cooling conditions. After the treatment, carbon and Co adhering to the cemented carbide substrate surface were converted into an acid. And by removing by barrel polishing, the maximum Co content at a position 11 μm from the surface: 15.
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: 10.0% by weight, Depth: 23 μm, Co-enriched zone. The above-mentioned carbide substrate D has a maximum Co content of 14.5% by weight, depth: 29 μm on the surface at a position 22 μm from the surface.
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).

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 l-TiCN layer and the l-Ti of the constituent layers of the hard coating layer are formed.
The residual tensile stress is applied to any of the coated cemented carbide tools 1 to 10 of the present invention in which the N layer is composed of an upper partial layer having a residual compressive stress and a lower partial layer having a residual tensile stress, and the constituent layers of the hard coating layer. Were produced, respectively. 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 spaced round bar with four longitudinal grooves, cutting speed: 180 m / min. Infeed: 3.5 mm Feed: 0.35 mm / rev. Cutting time: 10 minutes, dry intermittent high-cut cutting test of alloy steel under the following conditions: Work material: JIS SCr420H Round bar with four longitudinal grooves at equal intervals in the longitudinal direction, Cutting speed: 210 m / min. Infeed: 1.3 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.

[0019]

[Table 1]

[0020]

[Table 2]

[0021]

[Table 3]

[0022]

[Table 4]

[0023]

[Table 5]

[0024]

According to the results shown in Tables 2 to 5, the l-TiCN layer and the l-TiCN layer existing as constituent layers in the hard coating layer are shown.
The coated carbide tool 1 according to the present invention, in which the TiN layer comprises an upper partial layer having a residual compressive stress and a lower partial layer having a residual tensile stress.
10 to 10, since the hard coating layer has excellent chipping resistance, even without performing cutting or chipping on the cutting edge, even when performing intermittent cutting under heavy cutting conditions such as high feed or high cutting. The conventional coated carbide tools 1 to 10 exhibit excellent wear resistance over a long period of time, whereas the constituent layers of the hard coating layer have residual tensile stress. It is clear that intermittent heavy cutting causes chipping, which leads to a shorter 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 is possible to satisfactorily cope with the FA of the cutting device, the labor saving and energy saving of the cutting process, and the cost reduction.

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Masayuki Miichi 1511 Furamagi, Ishishita-cho, Yuki-gun, Ibaraki Pref. F-term in Mitsubishi Materials Corporation Tsukuba Works (reference)

Claims (1)

[Claims] 1. A titanium carbide layer comprising: (a) a titanium carbide layer having an average layer thickness of 0.1 to 5 μm and a granular crystal structure, and having a residual tensile stress, on a 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 layer; and (b) having an average layer thickness of 2 to 15 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 15 μm, and (c) an upper partial layer having an average layer thickness of 2 to 15 μm and having a residual compressive stress. And the lower sublayer with residual tensile stress? The upper partial layer and the lower partial layer have a vertically elongated crystal structure continuous with each other, and the upper partial layer has a layer thickness corresponding to 20 to 40% of the average layer thickness of 2 to 15 μm. And (d) an aluminum oxide layer having an average layer thickness of 0.5 to 10 μm and a granular crystal structure, and a hard coating layer formed by chemical vapor deposition with an overall average layer thickness of 5 to 25 μm. A cutting tool made of a surface-coated tungsten carbide-based cemented carbide that exhibits excellent chipping resistance with a hard coating layer in intermittent heavy cutting.