JP2005131730A - Surface-coated cermet cutting tool with hard coating layer having superior chipping resistance - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface-coated cermet cutting tool with a hard coating layer having superior heat-impact resistance. <P>SOLUTION: This hard coating layer is composed of the following (a) and (b) : (a) a Ti compound layer having the total average layer thickness of 3 to 20 μm which are formed by chemical deposition as a lower layer on a surface of a tool base body composed of WC group cemented carbide or TiCN group cermet, and (b) a heating transformation α type Al<SB>2</SB>O<SB>3</SB>layer whose clear diffraction peak appearing on a (006) surface and a (018) surface by X-ray diffraction measurement, and which is formed by transforming a crystal structure of the Al<SB>2</SB>O<SB>3</SB>layer having a crystal structure of a κ type or a θ type into an α type crystal structure, by applying heat treatment in a state of dispersing and distributing oxide particulates having the composition formula : TiO<SB>X</SB>Ti formed by chemical deposition as a transformation generating crack starting point material, on a surface of the Al<SB>2</SB>O<SB>3</SB>layer having the crystal structure of the κ type or the θ type in a state of being formed by chemical deposition as an upper layer. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  This invention is made of a surface-coated cermet that exhibits excellent chipping resistance with a hard coating layer against mechanical thermal shock that is repeatedly applied to the cutting edge portion at a very short pitch, especially during high-speed intermittent cutting of steel and cast iron. The present invention relates to a cutting tool (hereinafter referred to as a coated cermet tool).

Conventionally, generally on the surface of a substrate (hereinafter collectively referred to as a tool substrate) composed of a tungsten carbide (hereinafter referred to as WC) -based cemented carbide or titanium carbonitride (hereinafter referred to as TiCN) -based cermet. ,
(A) As a lower layer, a Ti carbide (hereinafter referred to as TiC) layer, nitride (hereinafter also referred to as TiN) layer, carbonitride (hereinafter referred to as TiCN) layer formed by chemical vapor deposition, A Ti compound layer having a total average layer thickness of 3 to 20 μm, comprising one or more of a carbon oxide (hereinafter referred to as TiCO) layer and a carbonitride oxide (hereinafter referred to as TiCNO) 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 the state of 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 (a) and (b) above is known, and this coated cermet tool is used for continuous cutting and intermittent cutting of various steels and cast irons, for example. It is also known that

In general, the Ti compound layer or the Al ₂ O ₃ layer constituting the hard coating layer of the above-mentioned coated cermet tool has a granular crystal structure, and the TiCN layer constituting the Ti compound layer is further improved in the strength of the layer itself. For the purpose of improvement, it is formed by chemical vapor deposition in a medium temperature range of 700 to 950 ° C. using a mixed gas containing an organic carbonitride such as CH ₃ CN as a reaction gas in a normal chemical vapor deposition apparatus. It is also known to have a vertically elongated crystal structure.
Japanese Unexamined Patent Publication No. 6-31503 Japanese Patent Laid-Open No. 6-8010

In recent years, the performance of cutting machines has been remarkable. On the other hand, there is a strong demand for labor saving and energy saving and further cost reduction for cutting work. For coated cermet tools, there is no problem when this is used for continuous cutting and interrupted cutting under normal conditions such as steel and cast iron. The Ti compound layer, which is the lower layer of the hard coating layer, has high strength and excellent impact resistance when used for high-speed intermittent cutting in which mechanical thermal shock is repeatedly applied at a very short pitch. The deposited α-type Al ₂ O ₃ layer that forms the upper layer is hard and has excellent heat resistance, but it is extremely brittle to mechanical thermal shocks. ( As a result, the service life is reached in a relatively short time.

Therefore, as a result of conducting research to improve the chipping resistance of the Al ₂ O ₃ layer constituting the upper layer of the hard coating layer of the above coated cermet tool from the above viewpoint,
After forming the Ti compound layer under the normal conditions as a lower layer on the surface of the tool base with a normal chemical vapor deposition device, the crystal structure of κ type or θ type is also formed under the same normal conditions. forming a the Al ₂ O ₃ layer having, then the surface of the the Al ₂ O ₃ layer at same chemical vapor deposition apparatus,
Reaction gas composition: by _{volume%, TiCl 4: 0.2~3%,} CO 2: 0.2~10%, Ar: 5~50%, H 2: remainder,
Reaction atmosphere temperature: 900-1020 ° C.
Reaction atmosphere pressure: 7-30 kPa,
Time: 1-10 minutes
When the treatment is performed under the conditions, the surface of the Al ₂ O ₃ layer is
Composition formula: TiO _x ,
In this state, Ti oxide fine particles satisfying an X value of 1.2 to 1.9 in terms of atomic ratio with respect to Ti are dispersed and distributed, as measured by an Auger spectroscopic analyzer. Heat treatment, preferably heat treatment is performed in an Ar atmosphere at a pressure of 7 to 50 kPa at a temperature of 1000 to 1200 ° C. for 10 to 120 minutes to obtain Al ₂ O _{3 having the} κ-type or θ-type crystal structure. When the layer was transformed into an Al ₂ O ₃ layer having an α-type crystal structure, the resulting heat-transformed α-type Al ₂ O ₃ layer was uniformly distributed on the surface of the Al ₂ O ₃ layer before the transformation. Since the Ti oxide fine particles become the starting point of cracks that occur when the κ-type or θ-type crystal structure is transformed into the α-type crystal structure, the transformation-generated cracks are extremely fine and uniformly dispersed. It becomes a distributed state, regardless of the layer thickness That is, even when the layer thickness is changed, an X-ray diffraction chart in which a clear diffraction peak appears at a uniform intensity on the (006) plane and the (018) plane in the X-ray diffraction measurement. Therefore, the upper layer of the hard coating layer is the heat-transformed α-type Al ₂ O ₃ layer and the lower layer is the Ti compound layer (this Ti compound layer is subjected to the above conditions). In the coated cermet tool constituted by the above heat treatment, the heat-transformed α-type Al ₂ O ₃ layer is formed even in high-speed intermittent cutting with a severe mechanical thermal shock. Combined with the coexistence of the Ti compound layer having high strength, it exhibits excellent chipping resistance, so that chipping in the hard coating layer is remarkably suppressed, and excellent wear resistance is exhibited over a long period of time. Nina Than it was to obtain the results of a study that.

The present invention has been made based on the above research results, and on the surface of a tool base composed of a WC-based cemented carbide or TiCN-based cermet,
(A) The lower layer is composed of one or more of TiC layer, TiN layer, TiCN layer, TiCO layer, and TiCNO layer 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, on the surface of an Al ₂ O ₃ layer having a κ-type or θ-type crystal structure in a state of chemical vapor deposition,
As a transformation initiation crack starting material, chemical vapor deposition is formed, and
Composition formula: TiO _x ,
In the state where Ti oxide fine particles satisfying an X value of 1.2 to 1.9 in terms of atomic ratio with respect to Ti are dispersed and distributed as measured by an Auger spectroscopic analyzer, heat treatment is performed. The crystal structure of the Al ₂ O ₃ layer having the κ-type or θ-type crystal structure is transformed into an α-type crystal structure, and is clearly diffracted in the (006) plane and the (018) plane by X-ray diffraction measurement. A heat transformed α-type Al ₂ O ₃ layer showing an X-ray diffraction chart in which a peak appears and having an average layer thickness of 1 to 15 μm;
The present invention is characterized by a coated cermet tool having the chipping resistance with excellent hard coating layer formed by forming the hard coating layer constituted by (a) and (b) above.

Next, the reason why the constituent layers of the hard coating layer of the coated cermet tool of the present invention are numerically limited as described above will be described below.
(A) Average layer thickness of lower layer (Ti compound layer) The Ti compound layer itself has high strength, and the presence of the Ti compound layer makes the hard coating layer have high strength, and the tool base and upper layer. Is firmly adhered to any of the heat-transformed α-type Al ₂ O ₃ layers, and thus has an effect of improving the adhesion of the hard coating layer to the tool substrate. However, when the total average layer thickness is less than 3 μm, If the total average layer thickness exceeds 20 μm, it becomes easy to cause thermoplastic deformation, especially during high-speed intermittent cutting with high heat generation, which causes uneven wear. Therefore, the total average layer thickness was determined to be 3 to 20 μm.
(B) Composition of Ti oxide fine particles (X value)
Ti oxide fine, since it becomes a starting point of cracking which occurs upon heating transformation to heat transformation α type the Al ₂ O ₃ layer of the street deposited α-type the Al ₂ O ₃ layer described above, the heating transformation α-type Al ₂ O ₃ Transformation cracks in the layer are refined and uniformly distributed. As a result, the heat-transformed α-type Al ₂ O ₃ layer has excellent chipping resistance and X-ray diffraction measurement. In the (006) plane and (018) plane, regardless of the layer thickness, an X-ray diffraction chart in which a clear diffraction peak with uniform intensity appears is shown, that is, without the formation of dispersion of the Ti oxide fine particles. Although it is difficult to form a heat-transformed α-type Al ₂ O ₃ layer showing the X-ray diffraction chart, transformation occurs even when the X value is less than 1.2 or more than 1.9 in terms of atomic ratio to Ti. The crack refinement effect cannot be fully exhibited, One (006) plane and (018) from the formation of the heating transformation α type the Al ₂ O ₃ layer shows an X-ray diffraction chart appearing clear diffraction peaks can be difficult to face, the atomic ratio thereof X values for Ti in It was determined to be 1.2 to 1.9.
(C) Average layer thickness of the upper layer (heat-transformed α-type Al ₂ O ₃ layer) The heat-transformed α-type Al ₂ O ₃ layer is composed of a hard coating layer due to the high hardness and excellent heat resistance of Al ₂ O ₃ itself. While improving wear resistance, it has the effect of remarkably suppressing the occurrence of chipping in the hard coating layer due to its excellent chipping resistance as described above, but when the average layer thickness is less than 1 μm, On the other hand, when the average layer thickness exceeds 15 μm, the chipping tends to occur when the average layer thickness is too large. Therefore, the average layer thickness is set to 1 to 15 μm.

  In addition, for the purpose of identification before and after the use of the cutting tool, a TiN layer having a golden color tone may be vapor-deposited as necessary, but the average layer thickness in this case may be 0.1 to 1 μm, This is because if the thickness is less than 0.1 μm, a sufficient discrimination effect cannot be obtained, while the discrimination effect by the TiN layer is sufficient with an average layer thickness of up to 1 μm.

The coated cermet tool of the present invention has an excellent heat-transformed α-type Al ₂ O ₃ layer that forms the upper layer of the hard coating layer even in high-speed intermittent cutting of steel with extremely high mechanical and thermal shock and high heat generation. Since it exhibits excellent chipping resistance, it exhibits excellent wear resistance over a long period of time.

  Next, the coated cermet tool of the present invention will be specifically described with reference to examples.

WC powder, TiC powder, ZrC powder, VC powder, TaC powder, NbC powder, Cr ₃ C ₂ powder, TiN powder, TaN powder, and Co powder all having an average particle diameter of 1 to 3 μm are prepared as raw material powders. These raw material powders were blended into the composition shown in Table 1, added with wax, ball milled in acetone for 24 hours, dried under reduced pressure, and pressed into a green compact with a predetermined shape at a pressure of 98 MPa. The green compact was vacuum sintered at a predetermined temperature in the range of 1370 to 1470 ° C. for 1 hour in a vacuum of 5 Pa. After sintering, the cutting edge portion was R: 0.07 mm honing By performing the processing, tool bases A to F made of a WC-base cemented carbide having a throwaway tip shape specified in ISO · CNMG120408 were manufactured.

In addition, as raw material powders, TiCN (mass ratio TiC / TiN = 50/50) powder, Mo ₂ C powder, ZrC powder, NbC powder, TaC powder, WC powder, all 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 by a ball mill for 24 hours, dried, and pressed into a 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 the sintering, the cutting edge portion was subjected to a honing process of R: 0.07 mm. Tool bases a to f made of TiCN-based cermet having a standard / CNMG12041 chip shape were formed.

Next, an ordinary chemical vapor deposition apparatus is used on the surfaces of the tool bases A to F and the tool bases a to f, and Table 3 (l-TiCN in Table 3 is described in JP-A-6-8010). Ti compound as a lower layer of the hard coating layer under the conditions shown in (1) shows the conditions for forming a TiCN layer having a vertically grown crystal structure, and (2) shows conditions for forming a normal granular crystal structure. The layers are formed by vapor deposition in the combinations shown in Table 5 and with the target layer thickness. Then, under the conditions shown in Table 3, Al ₂ O ₃ layers having a crystal structure of κ type or θ type are also shown in Table 5. The combinations shown in Table 5 were formed by vapor deposition with the target layer thickness and the target layer thickness, and then Ti oxide fine particles on the surface of the κ-type or θ-type Al ₂ O ₃ layer under the same conditions as shown in Table 4. In the state formed by vapor deposition, During r atmosphere temperature: 1100 ° C. and subjected to heat treatment at a predetermined time holding conditions in the range of 20 to 100 minutes, the the Al ₂ O ₃ layer of the κ-type or θ-type crystal structure α-type crystal structure the present invention coated cermet tools 1 to 13 were prepared respectively by forming was transformed into the the Al ₂ O ₃ layer heated transformed α-type the Al ₂ O ₃ layer formed by the upper layer of the hard coating layer.

  In the production of the cermet tools 1 to 13 according to the present invention, a test piece is prepared separately, and the test piece is loaded into the chemical vapor deposition apparatus, and Ti oxide fine particles are formed on the surface of the test piece. At that time, it was taken out from the apparatus, and the composition (X value) of the Ti oxide fine particles was measured with an Auger spectroscopic analyzer.

For comparison purposes, as shown in Table 6, an evaporated α-type Al ₂ O ₃ layer having the target layer thickness shown in Table 6 is also formed as the upper layer of the hard coating layer under the same conditions as shown in Table 3. And conventionally the coated cermet tools 1-13 were each manufactured on the same conditions except not performing formation of said Ti oxide fine particle, and heat processing on the said conditions.

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 above-mentioned present invention coated cermet tool and the conventional coated cermet tool obtained as a result, X Line diffraction was measured.

First, as a sample for X-ray diffraction measurement, a single crystal WC in which diffraction peaks appear only on the (001) plane and the (002) plane on the X-ray diffraction chart is used as a substrate sample, and the surface of the substrate sample is coated with the present invention. The target layer thicknesses of the cermet tools 3, 9, and 12 are 15 μm, 10 μm, and 5 μm in the heat-transformed α-type Al ₂ O ₃ layer, and the conventional coated cermet tools 3, 9, and 12 have the same target layer thicknesses of 15 μm, 10 μm. , And 5 μm of vapor-deposited α-type Al ₂ O ₃ layer under the same conditions as those for forming a heat-transformed α-type Al ₂ O ₃ layer and vapor-deposited α-type Al ₂ O ₃ with a target layer thickness of 15 μm, 10 μm, and 5 μm, respectively. Layers were formed directly to prepare inventive coated samples AC and conventional coated samples ac.

Next, X-ray diffraction measurement of the above-mentioned heat-transformed α-type Al ₂ O ₃ layer and vapor-deposited α-type Al ₂ O ₃ layer of these coated samples was performed using a normal X-ray diffractometer and Cu placed in the X-ray tube. By irradiating the anode (target) with thermionic electrons generated from the metal W filament under the conditions of voltage: 40 kV and current: 350 mA, the characteristic X-ray having a wavelength of 0.154 nm from the Cu anode surface A certain Cu-Kα ray is generated, the characteristic X-ray is irradiated onto the surface of the coated sample, and the X-ray diffracted 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 by measuring with an X-ray detector. The measurement results are shown in FIGS.

1 to 3 showing X-ray diffraction charts of the heat-transformed α-type Al ₂ O ₃ layers of the present coated samples A to C, and X-ray diffraction charts of the deposited α-type Al ₂ O ₃ layers of the conventional coated samples a to c 4 to 6 showing a clear diffraction peak with uniform intensity on the (006) plane and the (018) plane at any thickness in the heat-transformed α-type Al ₂ O ₃ layer. On the other hand, it is clear that there are no diffraction peaks in the (006) plane and the (018) plane in the deposited α-type Al ₂ O ₃ layer.

In addition, for 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 measured with an Auger spectrometer (observation of the longitudinal section of the layer). In the former case, the Ti oxide fine particles each comprising a Ti compound layer having substantially the same composition as the target composition and a heat-transformed α-type Al ₂ O ₃ layer and deposited on the surface before the heat treatment are also measured as described above. And showed substantially the same composition as the target composition. On the other hand, it was confirmed that the latter consisted of a Ti compound having the same composition as the target composition and a vapor-deposited α-type Al ₂ O ₃ layer. Furthermore, when the thicknesses of the constituent layers of the hard coating layer of these coated cermet tools were measured using a scanning electron microscope (same longitudinal section measurement), all of them had an average layer thickness substantially equal to the target layer thickness (5 The average value of point measurement) was shown.

Next, in the state where each of the various coated cermet tools is screwed to the tip of the tool steel tool with a fixing jig, the present coated cermet tools 1 to 13 and the conventional coated cermet tools 1 to 13 are as follows.
Work material: JIS · SCM440 lengthwise equidistant 4 vertical grooved round bar,
Cutting speed: 400 m / min,
Cutting depth: 1.6mm,
Feed: 0.25mm / rev,
Cutting time: 3 minutes
Dry high-speed intermittent cutting test of alloy steel under the conditions (normal cutting speed is 200 m / min),
Work material: JIS · S45C lengthwise equal 4 round grooved round bars,
Cutting speed: 420 m / min,
Incision: 1.5mm,
Feed: 0.25mm / rev,
Cutting time: 3 minutes
Dry high-speed intermittent cutting test of carbon steel under the conditions (normal cutting speed is 200 m / min),
Work material: JIS / FC300 lengthwise equidistant 4 bars with vertical grooves,
Cutting speed: 450 m / min,
Cutting depth: 1.0 mm,
Feed: 0.20mm / rev,
Cutting time: 5 minutes
The dry high speed intermittent cutting test (normal cutting speed is 250 m / min) was performed on cast iron under the above conditions, and the flank wear width of the cutting edge was measured in any cutting test. The measurement results are shown in Table 7.

表５〜７に示される結果から、本発明被覆サーメット工具１〜１３は、機械的熱的衝撃がきわめて高く、かつ高い発熱を伴なう鋼や鋳鉄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Ａｌ₂Ｏ₃層がすぐれた耐チッピング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Ａｌ₂Ｏ₃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Ａｌ₂Ｏ₃層が激しい機械的熱的に耐えられず、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。

From the results shown in Tables 5 to 7, the coated cermet tools 1 to 13 of the present invention have an extremely high mechanical thermal shock and the upper part of the hard coating layer even in high-speed intermittent cutting of steel or cast iron with high heat generation. The heat-transformed α-type Al ₂ O ₃ layer that forms the layer exhibits excellent chipping resistance, so that chipping at the cutting edge is remarkably suppressed and excellent wear resistance is exhibited, while hard coating In the conventional coated cermet tools 1 to 13 in which the upper layer of the layer is a vapor-deposited α-type Al ₂ O ₃ layer, the vapor-deposited α-type Al ₂ O ₃ layer cannot withstand severe mechanical and thermal in high-speed intermittent cutting. It is clear that chipping occurs at the blade and the service life is reached in a relatively short time.

  As described above, the coated cermet tool of the present invention has extremely high mechanical thermal shock and high heat generation as well as continuous cutting and interrupted cutting under normal conditions such as various steels and cast iron. Because it exhibits excellent chipping resistance even in high-speed intermittent cutting with the most severe cutting conditions, and exhibits excellent cutting performance over a long period of time, it is possible to improve the performance of the cutting equipment and save labor and energy in cutting. Furthermore, it can cope with cost reduction sufficiently satisfactorily.

The present invention coated cermet heating transformation α type the Al ₂ O ₃ layer constituting the hard coating layer of the tool 3 (target layer thickness: 15 [mu] m) is a diagram showing an X-ray diffraction chart of. The present invention heat transformed α-type the Al ₂ O ₃ layer constituting the hard coating layer of the coated cermet tool 9 (target layer thickness: 10 [mu] m) is a diagram showing an X-ray diffraction chart of. The present invention coated heat transformed α-type the Al ₂ O ₃ layer constituting the hard layer of the cermet tool 12 (target layer thickness: 5 [mu] m) is a diagram showing an X-ray diffraction chart of. Conventional coated cermet tool 3 of the hard coating layer deposited α-type the Al ₂ O ₃ layer constituting the (target layer thickness: 15 [mu] m) is a diagram showing an X-ray diffraction chart of. Conventional coated cermet hard layer deposition α type the Al ₂ O ₃ layer constituting the tool 9 (target layer thickness: 10 [mu] m) is a diagram showing an X-ray diffraction chart of. Conventional coated cermet tool 12 hard layer deposition α type the Al ₂ O ₃ layer constituting the (target layer thickness: 5 [mu] m) is a diagram showing an X-ray diffraction chart of.

Claims (1)

On the surface of the tool base composed of tungsten carbide based cemented carbide or titanium carbonitride based cermet,
(A) As a lower layer, each consists of one or two or more of Ti carbide layer, nitride layer, carbonitride layer, carbonate layer, and carbonitride oxide layer 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, chemical vapor deposition is formed on the surface of an aluminum oxide layer having a κ-type or θ-type crystal structure in the state of chemical vapor deposition,
Composition formula: TiO _x ,
In the state where Ti oxide fine particles satisfying an X value of 1.2 to 1.9 in terms of atomic ratio with respect to Ti are dispersed and distributed as measured by an Auger spectroscopic analyzer, heat treatment is performed. The crystal structure of the aluminum oxide layer having the κ-type or θ-type crystal structure is transformed into an α-type crystal structure, and clear diffraction peaks are observed on the (006) plane and the (018) plane by X-ray diffraction measurement. A heat-transformed α-type aluminum oxide layer showing an X-ray diffraction chart appearing and having an average layer thickness of 1 to 15 μm;
A surface-coated cermet cutting tool having excellent chipping resistance due to the hard coating layer formed by the hard coating layer constituted of (a) and (b) above.

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