JP2004181614A - Surface-coated cermet cutting tool with hard coating layer of excellent thermal shock resistance - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface-coated cermet cutting tool with hard coating layer of excellent thermal shock resistance. <P>SOLUTION: This surface-coated cermet cutting tool forms the hard coating layer constituted of the following (a) to (c) : (a) a Ti compound layer constituted one layer or more than two layers among a TiC layer, a TiN layer, a TiCN layer, a TiCO layer and a TiCNO layer which are all chemically evaporated and formes as a lower layer and having the total average layer thickness of 3 to 20 μm; (b) a heating transformed α type Al<SB>2</SB>O<SB>3</SB>layer for constituting an α type crystal structure of a crystal structure by applying heat treatment to aluminum oxide having a κ type or θ type crystal structure in a state of being chemically evaporated and formed as an upper layer and having a structure of dispersing-distributing a heating transformed crack and the average layer thickness of 1 to 15 μm; and (c) a TiN layer chemically evaporated and formed as a surface layer and having the average layer thickness of 0.1 to 2 μm. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【００２０】
【表２】

【００２１】
【表３】

【００２２】
【表４】

【００２３】
【表５】

【００２４】
【表６】

【００２５】
【発明の効果】
表４〜６に示される結果から、本発明被覆サーメット工具１〜１３は、硬質被覆層の上部層を構成する加熱変態α型Ａｌ_２Ｏ_３層中に分散分布する加熱変態生成クラックの作用で、熱衝撃がきわめて高く、かつ高い発熱を伴なう鋼の高速断続切削でも、硬質被覆層中に内蔵された状態で存在する前記加熱変態生成クラックの作用で、切刃部のチッピング発生が著しく抑制され、すぐれた耐摩耗性を発揮するのに対して、硬質被覆層の上部層が蒸着α型Ａｌ_２Ｏ_３層からなる従来被覆サーメット工具１〜１３においては、高速断続切削では前記蒸着α型Ａｌ_２Ｏ_３層が激しい熱衝撃に耐えられず、切刃部にチッピングが発生し、比較的短時間で使用寿命に至ることが明らかである。
上述のように、この発明の被覆サーメット工具は、各種鋼や鋳鉄などの通常の条件での連続切削や断続切削は勿論のこと、特に熱衝撃がきわめて高く、かつ高い発熱を伴なう切削条件の最も厳しい高速断続切削でもすぐれた耐チッピング性を示し、長期に亘ってすぐれた切削性能を発揮するものであるから、切削装置の高性能化並びに切削加工の省力化および省エネ化、さらに低コスト化に十分満足に対応できるものである。
【図面の簡単な説明】
【図１】本発明被覆サーメット工具３の硬質被覆層を構成する加熱変態α型Ａｌ_２Ｏ_３層（目標層厚：１５μｍ）のＸ線回折チャートを示す図である。
【図２】本発明被覆サーメット工具９の硬質被覆層を構成する加熱変態α型Ａｌ_２Ｏ_３層（目標層厚：１０μｍ）のＸ線回折チャートを示す図である。
【図３】本発明被覆サーメット工具１２の硬質被覆層を構成する加熱変態α型Ａｌ_２Ｏ_３層（目標層厚：５μｍ）のＸ線回折チャートを示す図である。
【図４】従来被覆サーメット工具３の硬質被覆層を構成する蒸着α型Ａｌ_２Ｏ_３層（目標層厚：１５μｍ）のＸ線回折チャートを示す図である。
【図５】従来被覆サーメット工具９の硬質被覆層を構成する蒸着α型Ａｌ_２Ｏ_３層（目標層厚：１０μｍ）のＸ線回折チャートを示す図である。
【図６】従来被覆サーメット工具１２の硬質被覆層を構成する蒸着α型Ａｌ_２Ｏ_３層（目標層厚：５μｍ）のＸ線回折チャートを示す図である。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention provides a hard coating layer that exhibits excellent chipping resistance against thermal shock repeatedly applied at a very short pitch to a cutting edge, particularly during high-speed intermittent cutting of steel or cast iron, that is, the hard coating layer is excellent. The present invention relates to a surface-coated cermet cutting tool having thermal shock resistance (hereinafter referred to as a coated cermet tool).
[0002]
[Prior art]
2. Description of the Related Art Conventionally, generally, a substrate (hereinafter, these are collectively referred to as a tool substrate) formed of a tungsten carbide (hereinafter, referred to as WC) -based cemented carbide or a titanium cermet (hereinafter, referred to as TiCN) -based cermet is generally provided on a surface of the substrate. ,
(A) As a lower layer, a Ti carbide (hereinafter, referred to as TiC) layer, a nitride (hereinafter, also referred to as TiN) layer, a carbonitride (hereinafter, referred to as TiCN) layer, all formed by chemical vapor deposition, Ti having a total average layer thickness of 3 to 20 μm, comprising one or two or more layers of a carbonate (hereinafter referred to as TiCO) layer and a carbonitride (hereinafter referred to as TiCNO) layer Compound layer,
(B) a vapor-deposited α-type aluminum oxide (hereinafter referred to as Al ₂ O ₃ ) layer having an α-type crystal structure in a state formed by chemical vapor deposition and having an average layer thickness of 1 to 15 μm as an upper layer;
A coated cermet tool formed by vapor-depositing a hard coating layer composed of (a) and (b) above is known, and this coated cermet tool can be used for continuous cutting or intermittent cutting of various types of steel or cast iron, for example. It is also known that it is used (for example, see Patent Document 1).
[0003]
In general, the Ti compound layer and the Al ₂ O ₃ layer constituting the hard coating layer of the above-mentioned coated cermet tool have a granular crystal structure, and further, the TiCN layer constituting the Ti compound layer is provided with the strength of the layer itself. For the purpose of improvement, by using a mixed gas containing an organic carbonitride, for example, CH ₃ CN, as a reaction gas in a normal chemical vapor deposition apparatus, the mixture is formed by chemical vapor deposition at a medium temperature range of 700 to 950 ° C. It is also known to have a vertically elongated crystal structure (for example, see Patent Document 2).
[0004]
[Patent Document 1]
JP-A-6-31503 [Patent Document 2]
JP-A-6-8010 [0005]
[Problems to be solved by the invention]
In recent years, the performance of cutting equipment has been remarkably improved, and on the other hand, there is a strong demand for labor saving, energy saving, and further cost reduction for cutting work.Accordingly, cutting work tends to be even faster, In the case of coated cermet tools, there is no problem if this is used for continuous cutting or interrupted cutting under ordinary conditions such as steel or cast iron. When used in high-speed interrupted cutting in which thermal shock is repeatedly applied at a very short pitch to the surface, the deposited α-type Al ₂ O ₃ layer constituting the upper layer of the hard coating layer is hard and has excellent heat resistance, Because of its brittleness, chipping (small chipping) easily occurs in the hard coating layer, and as a result, the service life of the hard coating layer is relatively short in the present situation.
[0006]
[Means for Solving the Problems]
In view of the above, the present inventors have conducted research to improve the thermal shock resistance of the Al ₂ O ₃ layer constituting the upper layer of the hard coating layer of the coated cermet tool from the above-described viewpoint.
After the Ti compound layer is formed on the surface of the tool base as a lower layer under a normal condition by a normal chemical vapor deposition apparatus, Al ₂ O ₃ having a κ-type or θ-type crystal structure is also formed under a normal condition. When a layer is formed by vapor deposition and subjected to heat treatment in this state in a hydrogen atmosphere at a temperature of 1000 to 1100 ° C. and a holding time of 2 to 10 hours, a κ-type or θ-type crystal of the Al ₂ O ₃ layer is obtained. The structure is transformed into an α-type crystal structure, and a crack formed by heat transformation is distributed and distributed in the layer. The resulting heat-transformed α-type Al ₂ O ₃ layer is used as an upper layer. When a relatively thin titanium nitride (hereinafter, referred to as TiN) layer is formed as a surface layer by vapor deposition on the surface under the same ordinary conditions, this TiN layer forms an interface with the heat-transformed α-type Al ₂ O ₃ layer. With heat transformation cracks Since crowded in so holding the heating transformation product cracks remarkably stabilized state, the lower layer of the hard coating layer is composed of the Ti compound layer, the upper layer and the surface layer is above the heating transformation α-type Al _In the coated cermet tool composed of the ₂ O ₃ layer and the TiN layer, the thermal transformation generation cracks distributed and distributed in the thermal transformation α-type Al ₂ O ₃ layer constituting the upper layer are particularly severe during high-speed interrupted cutting. A study result was obtained that the thermal shock is absorbed and alleviated, thereby significantly suppressing the occurrence of chipping in the hard coating layer.
[0007]
The present invention has been made on the basis of the above research results, and has a tool base formed of a WC-based cemented carbide or a TiCN-based cermet,
(A) The lower layer is composed of one or more of a TiC layer, a TiN layer, a TiCN layer, a TiCO layer, and a TiCNO layer all formed by chemical vapor deposition, and has a total average layer thickness of 3 to 20 μm. A Ti compound layer having
(B) As an upper layer, Al ₂ O ₃ having a κ-type or θ-type crystal structure is subjected to a heat treatment in a state of being formed by chemical vapor deposition to transform the crystal structure into an α-type crystal structure and to generate heat transformation. A heat-transformed α-type Al ₂ O ₃ layer having a structure in which cracks are dispersed and distributed and an average layer thickness of 1 to 15 μm;
(C) as a surface layer, a TiN layer formed by chemical vapor deposition and having an average layer thickness of 0.1 to 2 μm;
The present invention is characterized by a coated cermet tool having a hard coating layer having excellent thermal shock resistance, formed by forming a hard coating layer composed of (a) to (c) above.
[0008]
The reason why the average layer thickness of the constituent layers of the hard coating layer of the coated cermet tool of the present invention is limited as described above is as follows.
(A) Lower layer (Ti compound layer)
The Ti compound layer itself has strength, and the presence of the Ti compound layer allows the hard coating layer to have strength. In addition, the Ti compound layer is firmly attached to both the tool base and the heating-transformed α-type Al ₂ O ₃ layer as the upper layer. Has a function of contributing to the improvement of the adhesion of the hard coating layer to the tool base, but if the total average layer thickness is less than 3 μm, the above effect cannot be sufficiently exerted. If the thickness exceeds 20 μm, it becomes easy to cause thermoplastic deformation, especially in high-speed interrupted cutting accompanied by high heat generation, and this causes uneven wear. Therefore, the total average layer thickness is set to 3 to 20 μm.
[0009]
(B) Upper layer (heat-transformed α-type Al ₂ O ₃ layer)
The heat-transformed α-type Al ₂ O ₃ layer improves the abrasion resistance of the hard coating layer due to the high hardness and excellent heat resistance of Al ₂ O ₃ itself, and as described above, the heat transformed dispersed and distributed in the layer. It has a function of absorbing thermal shock by the action of generated cracks and remarkably suppressing the occurrence of chipping in the hard coating layer. However, if the average layer thickness is less than 1 μm, the above action cannot be sufficiently exerted. On the other hand, if the average layer thickness exceeds 15 μm and becomes too large, the cracks generated by the heat transformation may cause chipping. Therefore, the average layer thickness is set to 1 to 15 μm.
[0010]
(C) Surface layer (TiN layer)
As described above, the TiN layer sufficiently penetrates into the heat transformation generation cracks at the interface with the heat transformation α-type Al ₂ O ₃ layer to maintain the heat transformation formation cracks in a significantly stabilized state. The heat-transformed α-type Al ₂ O ₃ layer has an effect of sufficiently exhibiting the improvement in thermal shock resistance provided by the layer. However, if the average layer thickness is less than 0.1 μm, the heat-transformed α-type Al ₂ O _{3 layer is not used.} Due to insufficient stabilization of the heat transformation cracks in the layer, chipping due to the heat transformation cracks is likely to occur, while the effect of the TiN layer is sufficient for an average layer thickness of up to 2 μm. The average layer thickness is determined to be 0.1 to 2 μm in consideration of economy.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, the coated cermet tool of the present invention will be specifically described with reference to examples.
As raw material powders, WC powder, TiC powder both having an average particle size of 1 to 3 [mu] m, ZrC powder, VC powder, TaC powder, NbC powder, _Cr 3 _{C 2} powder, TiN powder, prepared TaN powder and Co powder, Then, these raw material powders were blended into the blending composition shown in Table 1, further added with wax, ball-milled in acetone for 24 hours, dried under reduced pressure, and then pressed into a green compact of a predetermined shape at a pressure of 98 MPa. Then, this green compact is vacuum-sintered in a vacuum of 5 Pa at a predetermined temperature in the range of 1370 to 1470 ° C. for 1 hour, and after sintering, the cutting edge is honed with R: 0.07 mm. By processing, tool bases A to F made of a WC-based cemented carbide having a throw-away tip shape specified in ISO-CNMG120408 were manufactured, respectively.
[0012]
Further, as raw material powders, TiCN (TiC / TiN = 50/50 by mass ratio) powder, Mo ₂ C powder, ZrC powder, NbC powder, TaC powder, WC powder each having an average particle diameter of 0.5 to 2 μm , Co powder, and Ni powder are prepared, and these raw material powders are blended in the blending composition shown in Table 2, wet-mixed in a ball mill for 24 hours, dried, and pressed into a green compact at a pressure of 98 MPa. The green compact was sintered in a nitrogen atmosphere of 1.3 kPa at a temperature of 1540 ° C. for 1 hour, and after sintering, the cutting edge was subjected to a honing process of R: 0.07 mm to obtain an ISO. Tool bases a to f made of TiCN-based cermet having a tip shape of standard CNMG120412 were formed.
[0013]
Then, on the surfaces of the tool bases A to F and the tool bases a to f, a conventional chemical vapor deposition apparatus was used, and Table 3 (l-TiCN in Table 3 is a vertically long sheet described in JP-A-6-8010). It shows the conditions for forming a TiCN layer having a growth crystal structure, and the other conditions show the conditions for forming a normal granular crystal structure.) A compound layer is formed by vapor deposition as a lower layer of the hard coating layer, and then a κ-type or θ-type Al ₂ O ₃ layer is formed by vapor deposition under the same conditions as shown in Table 3, and the layer is formed in a hydrogen atmosphere at a temperature of: Heat treatment is performed at 1050 ° C. for a predetermined time within a range of 2 to 10 hours to transform the κ-type or θ-type crystal structure into α-type, and the heat-transformed cracks are dispersed and distributed in the layer. similarly Table heated transformation α-type _Al 2 _{O 3} layer and In the present invention, the TiN layer is formed as the upper layer of the hard coating layer with the target layer thickness shown in Table 3 and the TiN layer having the target layer thickness shown in Table 4 is formed on the same surface layer under the same conditions as shown in Table 3. Coated cermet tools 1 to 13 were respectively manufactured.
For the purpose of comparison, as shown in Table 5, except that the upper layer of the hard coating layer was a vapor-deposited α-type Al ₂ O ₃ layer having an average layer thickness also shown in Table 5, and the surface layer was not formed. Manufactured the conventional coated cermet tools 1 to 13 under the same conditions.
[0014]
For the purpose of observing the difference between the heat-transformed α-type Al ₂ O ₃ layer and the vapor-deposited α-type Al ₂ O ₃ layer constituting the hard coating layer of the coated cermet tool of the present invention and the conventional coated cermet tool obtained as described above, X was used. Line diffraction was measured.
First, as a sample for X-ray diffraction measurement, a single crystal WC having a diffraction peak only on the (001) plane and the (002) plane on the X-ray diffraction chart was used as a substrate sample. The target layer thickness of the cermet tools 3, 9, and 12 is 15 μm, 10 μm, and 5 μm, and the heat-transformed α-type Al ₂ O ₃ layer, and the target layer thickness of the conventional coated cermet tools 3, 9, and 12 are also 15 μm, 10 μm. , and under the same conditions as the conditions for forming the deposited α-type _Al 2 _{O 3} layer of 5 [mu] m, the target layer thickness each 15 [mu] m, 10 [mu] m, and 5 [mu] m heating transformation α-type _Al of 2 _{O 3} layer and deposition α-type _Al 2 _{O 3} Layers were formed directly to prepare coating samples A to C of the present invention and conventional coating samples a to c.
[0015]
Next, the X-ray diffraction measurement of the above-mentioned heat-transformed α-type Al ₂ O ₃ layer and the vapor-deposited α-type Al ₂ O ₃ layer of these coated samples was carried out by using a usual X-ray diffractometer, and Cu was placed in an X-ray tube. By irradiating the anode (target) with thermoelectrons generated from the metal W filament under the conditions of voltage: 40 kV and current: 350 mA, characteristic X-rays having a wavelength of 0.154 nm from the Cu anode surface are obtained. X-rays that generate a certain Cu-Kα ray, irradiate the characteristic X-ray to the surface of the coated sample, and diffract at an angle equal to the X-ray incident angle θ with respect to the coated sample surface among the X-rays scattered from the coated sample Was measured with an X-ray detector. The measurement results are shown in FIGS.
FIGS. 1 to 3 show X-ray diffraction charts of the heat-transformed α-type Al ₂ O ₃ layers of coating samples A to C of the present invention, and X-ray diffraction charts of vapor-deposited α-type Al ₂ O ₃ layers of conventional coating samples a to c. 4 to 6, the heating-transformed α-type Al ₂ O ₃ layer shows clear diffraction peaks on the (006) plane and the (018) plane, whereas the vapor-deposited α-type Al ₂ the O ₃ layer is clear that these (006) plane and (018) diffraction peak at a surface are not present.
[0016]
Further, with respect to the coated cermet tools 1 to 13 of the present invention and the conventional coated cermet tools 1 to 13 obtained as a result, the constituent layers of the hard coating layer were observed using a scanning electron microscope (observing the longitudinal section of the layers). As a result, in the former, all consisted of a Ti compound layer, a heat-transformed α-type Al ₂ O ₃ layer in which cracks generated by heat transformation were dispersed and distributed in the layer, and in the latter, a Ti compound and vapor-deposited α-type Al It was confirmed to consist of a ₂ O ₃ layer. Furthermore, when the thickness of the constituent layers of the hard coating layer of these coated cermet tools was measured using a scanning electron microscope (also in the longitudinal section), the average layer thickness was substantially the same as the target layer thickness in all cases. (Average value of five-point measurements).
[0017]
Next, the above coated cermet tools 1 to 7 according to the present invention and the conventional coated cermet tools 1 to 7 in a state where all of the above various coated cermet tools were screwed to the tip of a tool steel tool with a fixing jig. ,
Work material: JIS SCM440 4 rods with longitudinal grooves at regular intervals in the longitudinal direction,
Cutting speed: 380m / min,
Cut: 1.5 mm,
Feed: 0.22 mm / rev,
Cutting time: 3 minutes,
Dry high-speed interrupted cutting test of alloy steel under the conditions of
Work material: Round bar with four vertical grooves at equal intervals in the length direction of JIS / SUS304,
Cutting speed: 330m / min,
Cut: 1.5 mm,
Feed: 0.22 mm / rev,
Cutting time: 3 minutes,
A dry high-speed interrupted cutting test of stainless steel was performed under the following conditions.
[0018]
Further, for the coated cermet tools 8 to 13 of the present invention and the conventional coated cermet tools 8 to 13,
Work material: JIS SCM440 4 rods with longitudinal grooves at regular intervals in the longitudinal direction,
Cutting speed: 380m / min,
Cut: 1.0 mm,
Feed: 0.18 mm / rev,
Cutting time: 3 minutes,
Dry high-speed interrupted cutting test of alloy steel under the conditions of
Work material: Round bar with four vertical grooves at equal intervals in the length direction of JIS / SUS304,
Cutting speed: 330m / min,
Cut: 1.0 mm,
Feed: 0.18 mm / rev,
Cutting time: 3 minutes,
A dry high-speed intermittent cutting test of stainless steel was performed under the following conditions, and the flank wear width of the cutting edge was measured in each cutting test. Table 6 shows the measurement results.
[0019]
[Table 1]

[0020]
[Table 2]

[0021]
[Table 3]

[0022]
[Table 4]

[0023]
[Table 5]

[0024]
[Table 6]

[0025]
【The invention's effect】
From the results shown in Tables 4 to 6, the coated cermet tools 1 to 13 of the present invention showed that the heating transformation generated cracks dispersed and distributed in the heating transformation α-type Al ₂ O ₃ layer constituting the upper layer of the hard coating layer. Even in high-speed interrupted cutting of steel with extremely high thermal shock and high heat generation, chipping of the cutting edge portion is remarkably generated due to the action of the above-mentioned heat transformation generation crack existing in a state embedded in the hard coating layer. The conventional coated cermet tools 1 to 13 in which the upper layer of the hard coating layer is formed of a vapor-deposited α-type Al ₂ O ₃ layer, while exhibiting excellent wear resistance are suppressed, and the vapor-deposited α It is evident that the mold Al ₂ O ₃ layer cannot withstand severe thermal shock, chipping occurs at the cutting edge, and reaches a service life in a relatively short time.
As described above, the coated cermet tool of the present invention can be used not only for continuous cutting or interrupted cutting under ordinary conditions such as various types of steel and cast iron, but also for cutting conditions involving extremely high thermal shock and high heat generation. It shows excellent chipping resistance even in the most severe high-speed interrupted cutting, and exhibits excellent cutting performance over a long period of time. It can respond satisfactorily to the conversion.
[Brief description of the drawings]
FIG. 1 is a view showing an X-ray diffraction chart of a heat-transformed α-type Al ₂ O ₃ layer (target layer thickness: 15 μm) constituting a hard coating layer of the coated cermet tool 3 of the present invention.
FIG. 2 is an X-ray diffraction chart of a heat-transformed α-type Al ₂ O ₃ layer (target layer thickness: 10 μm) constituting a hard coating layer of the coated cermet tool 9 of the present invention.
FIG. 3 is a diagram showing an X-ray diffraction chart of a heat-transformed α-type Al ₂ O ₃ layer (target layer thickness: 5 μm) constituting a hard coating layer of the coated cermet tool 12 of the present invention.
FIG. 4 is an X-ray diffraction chart of a vapor-deposited α-type Al ₂ O ₃ layer (target layer thickness: 15 μm) constituting a hard coating layer of the conventional coated cermet tool 3.
FIG. 5 is an X-ray diffraction chart of a vapor-deposited α-type Al ₂ O ₃ layer (target layer thickness: 10 μm) constituting a hard coating layer of the conventional coated cermet tool 9.
6 is a diagram showing an X-ray diffraction chart of a vapor-deposited α-type Al ₂ O ₃ layer (target layer thickness: 5 μm) constituting a hard coating layer of the conventional coated cermet tool 12. FIG.

Claims (1)

On the surface of a tool substrate composed of tungsten carbide-based cemented carbide or titanium carbonitride-based cermet,
(A) the lower layer is composed of one or more of a carbide layer, a nitride layer, a carbonitride layer, a carbonate layer, and a carbonitride layer of Ti, all of which are formed by chemical vapor deposition; And a Ti compound layer having a total average layer thickness of 3 to 20 μm,
(B) As an upper layer, aluminum oxide having a κ-type or θ-type crystal structure is subjected to heat treatment in a state formed by chemical vapor deposition to transform the crystal structure into an α-type crystal structure, and cracks generated by heat transformation are formed. A heat-transformed α-type aluminum oxide layer having a dispersedly distributed structure and an average layer thickness of 1 to 15 μm,
(C) as a surface layer, a titanium nitride layer formed by chemical vapor deposition and having an average layer thickness of 0.1 to 2 μm;
A cutting tool made of a surface-coated cermet, in which the hard coating layer formed of the above (a) to (c) has excellent thermal shock resistance.

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