JP2005313242A - Surface coated cermet cutting tool with hard coating layer having excellent thermal shock resistance - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface coated cermet cutting tool with a hard coating layer having excellent thermal shock resistance. <P>SOLUTION: This cutting tool has the hard coating layer formed on a surface of a tool base body constituted of WC base cemented carbide alloy or TiCN base cermet. The hard coating layer is constituted of the following (a) to (c) layers: (a) a Ti compound layer as a lower layer composed of one or more layers of TiC layer, TiN layer, TiCN layer, TiCO layer and TiCNO layer formed by chemical deposition with a total average layer thickness of 3 to 20 μm, (b) a heat transformed α type Al<SB>2</SB>O<SB>3</SB>layer as an upper layer having a crystal structure transformed into an α type crystal structure by applying heat treatment to aluminum oxide having a κ type or θ type crystal structure in a chemically depositioned state, showing an X-ray diffraction chart with clear diffraction peak appearing on a (006) surface and a (018) surface by an X-ray diffraction measurement and having an average layer thickness of 1 to 15 μm, and (c) a CrN layer formed by chemical deposition as a surface layer and having an average layer thickness of 0.5 to 3 μm. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention exhibits excellent chipping resistance with respect to thermal shock that is repeatedly applied to the cutting edge portion at a very short pitch 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 a thermal shock resistance (hereinafter referred to as a coated cermet tool).

Conventionally, generally on the surface of a substrate (hereinafter collectively referred to as a tool substrate) made of 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, Ti carbide (hereinafter referred to as TiC) layer, nitride (hereinafter also referred to as TiN) layer, carbonitride (hereinafter referred to as TiCN) layer, carbonic acid layer formed by vapor deposition A compound layer (hereinafter referred to as TiCO) and a carbonitride oxide (hereinafter referred to as TiCNO) layer, or a Ti compound layer 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 the state of chemical vapor deposition and having an average layer thickness of 1 to 15 μm as an upper layer;
(C) As a surface layer, a chromium nitride (hereinafter referred to as CrN) layer formed by vapor deposition and having an average layer thickness of 0.5 to 3 μm,
A coated cermet tool formed by forming a hard coating layer composed of (a) to (c) 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 and the Al ₂ O ₃ layer constituting the hard coating layer of the above-mentioned coated cermet tool, and further the CrN layer has a granular crystal structure, and the TiCN layer constituting the Ti compound layer, For the purpose of improving the strength of the layer itself, chemical vapor deposition is performed at 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 that it has a vertically grown crystal structure.
JP 2003-266212 A 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, energy saving, and cost reduction for cutting, and along with this, cutting has been on the trend of higher speed. For coated cermet tools, there is no problem if this is used for continuous cutting and interrupted cutting under normal conditions such as steel and cast iron. When used for high-speed intermittent cutting in which repeated thermal shock is 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 The vapor-deposited α-type Al ₂ O ₃ layer that constitutes the material is hard and has excellent heat resistance, but it is extremely brittle against thermal shock, and this causes chipping (small chipping) in the hard coating layer. As a result, the service life is reached in a relatively short time.

Therefore, as a result of conducting 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 above coated cermet tool from the above viewpoint,
After the Ti compound layer is formed on the surface of the tool base as a lower layer in a normal chemical vapor deposition apparatus under normal conditions, the TiCN layer having the above vertically grown crystal structure (hereinafter referred to as l-TiCN) For example, an arc ion plating apparatus, which is a kind of physical vapor deposition apparatus, is used to form a Ti compound layer except for a metal Ti as a cathode electrode (evaporation source) and a reaction atmosphere such as methane decomposition gas, nitrogen Gas or a mixed gas of methane decomposition gas and nitrogen gas, or a mixed gas of methane decomposition gas and oxygen gas, or a mixed gas of methane decomposition gas, nitrogen gas and oxygen gas may be deposited] in conditions to form the Al ₂ O ₃ layer having a κ-type or θ-type crystal structure in a state of vapor deposited in an Ar atmosphere in this state, temperature: 900-960 ° C., held During: When subjected to heat treatment at 12 to 24 hours of conditions, the Ti compound layer while maintaining the current state, Al ₂ of the κ-type or θ-type of the Al ₂ O ₃ layer α-type crystal structure of the crystal structure As a result of the transformation to the O ₃ layer, the heat-transformed α-type Al ₂ O ₃ layer shows an X-ray diffraction chart in which clear diffraction peaks appear on the (006) plane and the (018) plane in X-ray diffraction measurement. Therefore, it has excellent thermal shock resistance. Therefore, a CrN layer is deposited as a surface layer on the heat-transformed α-type Al ₂ O ₃ layer. For example, in an arc ion plating apparatus that is one of the above physical vapor deposition apparatuses, metal Cr may be used as the cathode electrode (evaporation source) and the reaction atmosphere may be a nitrogen gas atmosphere.] Hard coating layer, i.e. Surface layer the CrN layer hard coating layer, the heating transformation α type the Al ₂ O ₃ layer is the top layer, in the coated cermet tool lower layer is composed of the Ti compound layer, the accompanying particularly severe thermal shock Excellent thermal shock resistance in combination with coexistence of the high-strength Ti compound layer and the CrN layer exhibiting excellent lubricity in the heat-transformed α-type Al ₂ O ₃ layer even in high-speed intermittent cutting As a result, it has been found that the occurrence of chipping in the hard coating layer is remarkably suppressed, and excellent wear resistance is exhibited over a long period of time.

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) As a lower layer, all consist of one layer or two or more layers of TiC layer, TiN layer, TiCN layer, TiCO layer, and TiCNO layer formed by vapor deposition, and have a total average layer thickness of 3 to 20 μm. Having a Ti compound layer,
(B) As an upper layer, heat treatment is applied to Al ₂ O ₃ having a κ-type or θ-type crystal structure in a state where chemical vapor deposition is formed, and the crystal structure is transformed into an α-type crystal structure. A heat-transformed α-type Al ₂ O ₃ layer having an average layer thickness of 1 to 15 μm and showing an X-ray diffraction chart in which clear diffraction peaks appear on the (006) plane and the (018) plane by measurement,
(C) As a surface layer, a CrN layer formed by vapor deposition and having an average layer thickness of 0.5 to 3 μm,
The present invention is characterized by a coated cermet tool having a thermal shock resistance with an excellent hard coating layer formed by forming the hard coating layer configured as described above in (a) to (c).

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, and in addition to the tool base and the heat-transformed α-type Al ₂ O ₃ layer that is the upper layer. Also has an action that contributes to improving the adhesion of the hard coating layer to the tool substrate, but if the total average layer thickness is less than 3 μm, the above-mentioned action cannot be fully exerted, while the total When the average layer thickness exceeds 20 μm, it becomes easy to cause thermoplastic deformation particularly in high-speed intermittent cutting with high heat generation, and this causes uneven wear. Therefore, the total average layer thickness is set to 3 to 20 μm. .

(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 as described above, the excellent thermal shock resistance possessed by itself. However, if the average layer thickness is less than 1 μm, the above effect cannot be fully exerted, while the average layer thickness exceeds 15 μm. When the thickness is too thick, chipping is likely to occur. Therefore, the average layer thickness is set to 1 to 15 μm.

(C) Surface layer (CrN layer)
The CrN layer is interposed between the work material and the cutting edge surface, and has an effect of improving the lubricity between them, thereby contributing to the improvement of chipping resistance. If the thickness is less than 5 μm, a desired improvement effect cannot be obtained in the above action, while an average layer thickness of up to 3 μm is sufficient for the action. Therefore, the average layer thickness is set to 0.5 to 3 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 discriminating effect cannot be obtained, whereas the discriminating effect by the TiN layer is sufficient with an average layer thickness of up to 1 μm.

This invention-coated cermet tool has a high thermal shock, and even in high-speed intermittent cutting of steel with high heat generation, the heat-transformed α-type Al ₂ O ₃ layer constituting the upper layer of the hard coating layer has excellent thermal shock Since it exhibits the properties, the occurrence of chipping at the cutting edge is remarkably suppressed, and excellent wear resistance is exhibited 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 in a vacuum of 5 Pa at a predetermined temperature within a range of 1370 to 1470 ° C. for 1 hour, and 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, a normal chemical vapor deposition apparatus was 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 a vertically long shape described in JP-A-6-8010). TiCN having a target layer thickness shown in Table 4 under the conditions shown in Table 4 below, showing the conditions for forming a TiCN layer having a grown crystal structure. The compound layer is formed as a lower layer of the hard coating layer, and then an Al ₂ O ₃ layer having a crystal structure of κ type or θ type is formed by vapor deposition under the same conditions shown in Table 3, and this is performed in an Ar atmosphere at a temperature: Heat treatment is performed at 940 ° C. for 12 to 24 hours for a predetermined time, thereby converting the κ-type or θ-type crystal structure Al ₂ O ₃ layer into an α-type crystal structure Al ₂ O ₃ layer. also shown in Table 4 to heat transformation α type the Al ₂ O ₃ layer composed by transformation The present invention is formed by forming the upper layer of the hard coating layer with the target layer thickness and further depositing a CrN layer with the target layer thickness shown in Table 4 as the same surface layer under the conditions shown in Table 3. Cermet tools 1 to 13 were produced, respectively.
For comparison purposes, as shown in Table 5, a conventional coated cermet under the same conditions except that the upper layer of the hard coating layer is a vapor-deposited α-type Al ₂ O ₃ layer having the average layer thickness shown in Table 5 as well. Tools 1-13 were produced respectively.

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 on 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. The intensity was measured by 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 inventive 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 show that, in the heat-transformed α-type Al ₂ O ₃ layer, clear diffraction peaks appear on the (006) plane and the (018) plane, whereas the evaporated α-type Al ₂ In the O ₃ layer, it is clear that there are no diffraction peaks on these (006) plane and (018) plane.

Moreover, about this invention coated cermet tool 1-13 obtained as a result, and the conventional coated cermet tool 1-13, the structural layer of this hard coating layer is observed using a scanning electron microscope (the longitudinal section of a layer is observed). As a result, the former is composed of a Ti compound layer, a heat-transformed α-type Al ₂ O ₃ layer, and a CrN layer, and the latter is composed of a Ti compound, a vapor-deposited α-type Al ₂ O ₃ layer, and a CrN layer. confirmed. Furthermore, when the thickness of the constituent layer of the hard coating layer of these coated cermet tools was measured using the same scanning electron microscope (also measured in the longitudinal section), the average layer thickness was substantially the same as the target layer thickness. (Average value of 5-point measurement) was shown.

Next, with respect to the present invention coated cermet tools 1 to 7 and the conventional coated cermet tools 1 to 13 in a state where any of the above various coated cermet tools is screwed to the tip of the tool steel tool with a fixing jig. ,
Work material: JIS / SCM415 lengthwise equal 4 round grooved round bars,
Cutting speed: 450 m / min,
Cutting depth: 2.0 mm
Feed: 0.35mm / rev,
Cutting time: 4 minutes
Dry high-speed intermittent cutting test (normal cutting speed is 200 m / min) of alloy steel under the above conditions (referred to as cutting condition A),
Work material: JIS / FC350 lengthwise equidistant round bars with 4 vertical grooves,
Cutting speed: 350 m / min,
Cutting depth: 1.0 mm,
Feed: 0.15mm / rev,
Cutting time: 5 minutes
Dry high-speed intermittent cutting test (normal cutting speed is 200 m / min) of normal cast iron under the conditions (cutting condition B)
Work material: JIS-S35C lengthwise equal length 4 round fluted round bars,
Cutting speed: 380 m / min,
Incision: 1.5mm,
Feed: 0.25m / rev,
Cutting time: 10 minutes,
The dry high-speed intermittent cutting test (normal cutting speed is 200 m / min) of carbon steel under the above conditions (referred to as cutting condition C), the flank wear width of the cutting edge was measured in any cutting test. The measurement results are shown in Table 6.

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 heating constituting the upper layer of the hard coating layer even in high-speed intermittent cutting of steel accompanied by high heat generation. 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 is In the conventional coated cermet tools 1 to 13 consisting of a vapor-deposited α-type Al ₂ O ₃ layer, the vapor-deposited α-type Al ₂ O ₃ layer cannot withstand severe thermal shock in high-speed intermittent cutting, and chipping occurs at the cutting edge. It is clear that the service life is reached in a relatively short time.

  As described above, the coated cermet tool according to the present invention has not only continuous cutting and intermittent cutting under normal conditions such as various steels and cast iron, but also cutting conditions with extremely high thermal shock and high heat generation. Even the most severe high-speed intermittent cutting shows excellent chipping resistance and demonstrates excellent cutting performance over a long period of time. It is possible to cope with the transformation sufficiently.

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 more of Ti carbide layer, nitride layer, carbonitride layer, carbonate layer, and carbonitride layer formed by vapor deposition, and A Ti compound layer having a total average layer thickness of 3 to 20 μm,
(B) As an upper layer, heat treatment is applied to aluminum oxide having a κ-type or θ-type crystal structure in the state of chemical vapor deposition, and the crystal structure is transformed into an α-type crystal structure. A heat-transformed α-type aluminum oxide layer showing an X-ray diffraction chart in which clear diffraction peaks appear on the (006) plane and the (018) plane, and having an average layer thickness of 1 to 15 μm;
(C) a chromium nitride layer formed by vapor deposition and having an average layer thickness of 0.5 to 3 μm as a surface layer;
A surface-coated cermet cutting tool having excellent thermal shock resistance with a hard coating layer formed by forming the hard coating layer composed of (a) to (c) above.

Images