JP2004299021A - Surface coated cermet cutting tool having hard coated layer exhibiting superior heat and impact resistance - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface coated cermet cutting tool having a hard coated layer exhibiting superior heat and impact resistance. <P>SOLUTION: This cutting tool is so formed that (a) a Ti compound layer as a lower layer and (b) the hard coated layer as the upper layer are formed on the surface of a tool base body comprising WC-group cemented carbide or TiCN-group cermet. The Ti compound layer comprises a single layer or more layers out of TiC layer, TiN layer, TiCN layer, TiCO layer or TiCNO layer, which are formed by chemical vapor deposition, and has the mean total layer thickness of 3-20 μm. The hard coated layer is so formed that aluminium oxide having κ or θ crystal structure in a state formed by the chemical vapor deposition is heated to transform its crystal structure into α crystal structure, shows an X-ray diffraction chart with a clear diffraction peak on (006) surface and (018) surface in an X-ray diffractometry, and comprises an Al<SB>2</SB>O<SB>3</SB>layer transformed to α phase by heating and having the mean thickness of 1-15 μm. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００１８】
【表２】

【００１９】
【表３】

【００２０】
【表４】

【００２１】
【表５】

【００２２】
【表６】

【００２３】
【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、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、硬質被覆層の上部層を構成する加熱変態α型Ａｌ_２Ｏ_３層がすぐれた耐熱衝撃性を発揮することから、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示すのに対して、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, A Ti compound layer comprising one or more of a carbonate (hereinafter, referred to as TiCO) layer and a carbonitride (hereinafter, referred to as TiCNO) layer, and having a total average layer thickness of 3 to 20 μm. ,
(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 forming a hard coating layer composed of the above (a) and (b) is known, and this coated cermet tool is used for continuous cutting or intermittent cutting of, for example, various kinds of steel or cast iron. It is also known that this is performed (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, but on the other hand, there has been a strong demand for labor saving, energy saving, and further cost reduction for cutting work.Accordingly, cutting work has tended to be further accelerated. 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 for high-speed interrupted cutting, in which thermal shock is repeatedly applied at a very short pitch, the Ti compound layer, which is the lower layer of the hard coating layer, has high strength and excellent impact resistance, but the upper layer depositing α-type the Al ₂ O ₃ layer constituting the, although excellent in heat resistance in hard, because is extremely fragile against thermal shock, which is chipping in the hard coating layer because (small chipping) Easily without, for reach this result relatively short time service life at present.
[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 using a normal chemical vapor deposition apparatus, the κ-type or θ-type crystal structure is formed under the same normal conditions. forming a _{the Al} 2 _{O 3} layer having, in an Ar atmosphere in this state, temperature: nine hundred to nine hundred and sixty ° C., retention time: When subjected to heat treatment under conditions of 12 to 24 hours, the Ti compound layer holding the current situation while, _{the Al} 2 _{O 3} layer of the κ-type or θ-type crystal structure is transformed into _{the Al} 2 _{O 3} layer of α-type crystal structure, the heating transformation α type _{the Al} 2 _{O 3} layer of this result, X-rays diffraction The measurement shows an X-ray diffraction chart in which clear diffraction peaks appear on the (006) plane and the (018) plane, and has excellent thermal shock resistance. Therefore, the upper layer of the hard coating layer is heating transformation α type _{the Al} 2 _{O 3} layer, the lower In There coated cermet tool composed by the Ti compound layer, in particular the heating transformation α type the Al ₂ O ₃ layer in accompanying high speed intermittent cutting work with severe thermal shock, the coexistence of the Ti compound layer having a high strength In combination with the above, since the steel exhibits excellent thermal shock resistance, the occurrence of chipping in the hard coating layer is remarkably suppressed, and a study result showing that excellent wear resistance is exhibited over a long period of time was obtained. .
[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 heat treatment in a state of being formed by chemical vapor deposition to transform the crystal structure into an α-type crystal structure, and X-ray diffraction. FIG. 4 shows an X-ray diffraction chart in which clear diffraction peaks appear on the (006) and (018) planes by measurement, and has a heat-transformed α-type Al ₂ O ₃ layer having an average layer thickness of 1 to 15 μm;
The present invention is characterized in that the hard coating layer formed of the above (a) and (b) is formed, and the hard coating layer has excellent thermal shock resistance.
[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 a high strength, and the presence of the Ti compound layer makes the hard coating layer have a high strength. In addition, the Ti compound layer can be used for any of the tool substrate and the heat-transformed α-type Al ₂ O ₃ layer which is 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-mentioned effect cannot be sufficiently exerted. If the average layer 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 wear resistance of the hard coating layer due to the high hardness and excellent heat resistance of Al ₂ O ₃ itself, and also has the excellent thermal shock resistance of itself as described above. Has an effect of remarkably suppressing the occurrence of chipping in the hard coating layer. However, if the average layer thickness is less than 1 μm, the above effect cannot be sufficiently exerted, while the average layer thickness exceeds 15 μm. If the thickness is too large, chipping is likely to occur. Therefore, the average layer thickness is set to 1 to 15 μm.
[0010]
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.
[0011]
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.
[0012]
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 growing crystal structure, and the other conditions show the conditions for forming a normal granular crystal structure.) A compound layer was 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 was formed by vapor deposition under the same conditions as shown in Table 3, and the layer was formed in an Ar atmosphere at a temperature of: A heat treatment is performed at 940 ° C. for a predetermined time within a range of 12 to 24 hours to convert the κ-type or θ-type Al ₂ O ₃ layer into an α-type Al ₂ O ₃ layer. similarly Table heated transformation α type the Al ₂ O ₃ layer composed by transformation The present invention coated cermet tools 1 to 13 by forming a top layer of the hard coating layer at the target layer thickness shown in prepared respectively.
For the purpose of comparison, as shown in Table 5, the conventional coating cermet was formed under the same conditions except that the upper layer of the hard coating layer was an evaporated α-type Al ₂ O ₃ layer having an average layer thickness also shown in Table 5. Tools 1 to 13 were manufactured respectively.
[0013]
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.
[0014]
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.
[0015]
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, it was confirmed that both of the former consisted of a Ti compound layer and a heat-transformed α-type Al ₂ O ₃ layer, and that of the latter consisted of both a Ti compound and a vapor-deposited α-type Al ₂ O ₃ layer. Furthermore, the thickness of the constituent layers of the hard coating layer of these coated cermet tools was also measured using a scanning electron microscope (similarly, vertical section measurement), and the average layer thickness was substantially the same as the target layer thickness. (Average value of five-point measurements).
[0016]
Next, the above coated cermet tools 1 to 7 of the present invention and conventional coated cermet tools 1 to 13 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: 400m / min,
Notch: 1.6 mm,
Feed: 0.25 mm / rev,
Cutting time: 3 minutes,
Dry high-speed interrupted cutting test of alloy steel under the conditions of
Work material: JIS S45C lengthwise round bar with four equally spaced longitudinal grooves,
Cutting speed: 420m / min,
Cut: 1.5 mm,
Feed: 0.25 mm / rev,
Cutting time: 3 minutes,
A dry high-speed intermittent cutting test was performed on carbon steel 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.
[0017]
[Table 1]

[0018]
[Table 2]

[0019]
[Table 3]

[0020]
[Table 4]

[0021]
[Table 5]

[0022]
[Table 6]

[0023]
【The invention's effect】
From the results shown in Tables 4 to 6, the coated cermet tools 1 to 13 of the present invention have a very high thermal shock, and the high-temperature intermittent cutting of steel accompanied by high heat generation has the effect of forming the heating layer constituting the upper layer of the hard coating layer. Since the transformed α-type Al ₂ O ₃ layer exhibits excellent thermal shock resistance, the occurrence of chipping at the cutting edge is remarkably suppressed and excellent wear resistance is exhibited, whereas the upper layer of the hard coating layer has excellent wear resistance. In the conventional coated cermet tools 1 to 13 including the vapor-deposited α-type Al ₂ O ₃ layer, the high-speed intermittent cutting does not allow the vapor-deposited α-type Al ₂ O ₃ layer to withstand severe thermal shock, and chipping occurs at the cutting edge. It is clear that the service life can be reached 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 of being formed by chemical vapor deposition to transform the crystal structure into an α-type crystal structure, and X-ray diffraction measurement is performed. 9 shows an X-ray diffraction chart in which clear diffraction peaks appear on the (006) plane and the (018) plane, and has a heat-transformed α-type aluminum oxide layer having an average layer thickness of 1 to 15 μm;
A cutting tool made of a surface-coated cermet, wherein the hard coating layer formed by forming the hard coating layer constituted by (a) and (b) has excellent thermal shock resistance.

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