JP2006102834A - Surface coated cermet-made cutting tool, having hard coating layer exhibiting excellent chipping resistance in high-speed intermittent cutting - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface coated cermet-made cutting tool, having a hard coating layer exhibiting excellent chipping resistance in high-speed intermittent cutting. <P>SOLUTION: In this surface coated cutting tool, a hard coating layer composed of (a) a lower layer and (b) an upper layer is formed on the surface of a substrate. The lower layer (a) is formed of a Ti compound layer comprising two layers or more selected from a TiC layer, a TiN layer, a TiCN layer, a TiCO layer and a TiCNO layer which are chemically deposited and having a total average layer thickness of 3 to 20μm, and the upper layer (b) is formed of an Al<SB>2</SB>O<SB>3</SB>layer chemically deposited and has an average layer thickness of 1 to 15μm. One layer of the Ti compound layer comprises the TiCN layer having an average layer thickness of 2.5 to 15 μm, and having a measured inclined angle degree distribution graph obtained by applying an electron beam to individual crystal grains having a cubic crystal lattice existing in a measurement range of a surface polishing face using a field emission type scanning electron microscope and measuring an angle of inclination made by normal of [013] face which is a crystal face of crystal grain to the normal of the surface polishing face or a specific value. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a surface-coated cermet cutting tool (hereinafter referred to as a coated cermet tool) that exhibits excellent chipping resistance with a hard coating layer, particularly in high-speed intermittent cutting of steel or cast iron.

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) 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 of the lower layers. A Ti compound layer consisting of two or more of a carbon oxide (hereinafter referred to as TiCO) layer and a carbonitride oxide (hereinafter referred to as TiCNO) layer and having a total average layer thickness of 3 to 20 μm,
(B) an aluminum oxide (hereinafter referred to as Al ₂ O ₃ ) layer having an average layer thickness of 1 to 15 μm, wherein the upper layer is formed by chemical vapor deposition;
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
Japanese Unexamined Patent Publication No. 6-31503

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 work, and along with this, cutting work tends to be further accelerated. 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. When it is used for high-speed intermittent cutting with repeated mechanical impacts at extremely short pitches, the hard coating layer that composes this is the high-temperature strength of the lower Ti compound layer and the high-temperature hardness of the upper Al ₂ O ₃ layer. However, since the high-temperature strength of the Ti compound layer is insufficient, it cannot respond satisfactorily to mechanical impacts. Since the ping (small chipping) tends to occur, at present, leading to a relatively short time service life.

In view of the above, the present inventors conducted research by paying attention to the Ti compound layer, which is the lower layer, in order to improve the chipping resistance of the hard coating layer of the above-described coated cermet tool. result,
Of the Ti compound layer that is the lower layer of the hard coating layer of the above coated cermet tool, the TiCN layer (hereinafter referred to as the conventional TiCN layer) is a normal chemical vapor deposition apparatus.
Reaction gas composition - by _{volume%, TiCl 4: 2~10%,} CH 3 CN: 0.5~3%, N 2: 10~30%, H 2: remainder,
Reaction atmosphere temperature: 800 to 900 ° C.
Reaction atmosphere pressure: 6-20 kPa,
However, prior to the formation of the conventional TiCN layer,
Reaction gas composition - by _{volume%, TiCl 4: 0.2~1%,} CH 4: 1~5%, H 2: 20~40%, N 2: 5~15%, Ar: the remaining,
Reaction atmosphere temperature: 760 to 850 ° C.
Reaction atmosphere pressure: 4-8 kPa,
Deposition time: 0.8 to 2.0 hours
The TiCN thin film as a seed thin film (hereinafter referred to as a TiCN seed thin film) is preferably formed with an average layer thickness of 0.8 to 1.2 μm under the above conditions, and the above-mentioned conventional TiCN layer is formed on the TiCN seed thin film. When the TiCN layer is formed under the same conditions, the TiCN layer at the time of formation is significantly affected by the crystal arrangement of the TiCN seed thin film, and the TiCN layer is formed as a result. (Hereinafter referred to as a history TiCN layer) has a higher high-temperature strength and superior mechanical impact resistance compared to the above-described conventional TiCN layer. The coated cermet tool in which the Al ₂ O ₃ layer and the lower layer are composed of the Ti compound layer and one of the Ti compound layers is the hysteresis TiCN layer is accompanied by particularly severe mechanical impact. Even in high-speed intermittent cutting, the hard coating layer exhibits excellent chipping resistance and exhibits excellent wear resistance over a long period of time.

(B) About the conventional TiCN layer and the history TiCN layer that constitute the lower layer of the hard coating layer of the above coated cermet tool,
Using a field emission scanning electron microscope, as shown in the schematic explanatory diagrams of FIGS. 1A and 1B, electron beams are individually applied to crystal grains having a cubic crystal lattice existing within the measurement range of the surface polished surface. Irradiation is performed to measure an inclination angle formed by a normal line of a {013} plane that is a crystal plane of the crystal grain with respect to a normal line of the surface-polished surface. When the measured inclination angle within the range is divided for each pitch of 0.25 degrees and the inclination angle number distribution graph is created by summing up the frequencies existing in each division, the conventional TiCN layer is formed as shown in FIG. As shown in FIG. 2, the distribution of measured tilt angles on the {013} plane shows an unbiased tilt angle number distribution graph in the range of 0 to 45 degrees, whereas the history TiCN layer is illustrated in FIG. As shown, a sharp peak appears at a specific position in the tilt angle section. The maximum peak that appears on the horizontal axis of the graph varies depending on the reaction atmosphere temperature and the pressure of the reaction atmosphere when the TiCN seed thin film is formed. Varies with TiCl ₄ content.

(C) As described above, when the TiCN seed thin film is formed, by setting the content of TiCl _{4 in} the reaction gas to 0.2 to 1%, the gradient angle distribution graph of the history TiCN layer has a sharp maximum. A peak appears in the range of 20 to 30 degrees of the tilt angle section, and exists in the range of 20 to 30 degrees by setting the reaction atmosphere temperature to 760 to 850 ° C. and the reaction atmosphere pressure to 4 to 8 kPa. An inclination angle distribution graph occupying a ratio of 60 to 85% of the entire frequency in the inclination angle distribution graph is shown in this case. In this case, according to the test results, the content of TiCl ₄ is 0. When it is less than 2%, the highest peak inclination angle section position appears in the above-mentioned history TiCN layer inclination angle number distribution graph, while its content is 1%. On the contrary, the inclination angle section position of the highest peak is less than 20 degrees, and in any case, the desired excellent high temperature strength cannot be obtained in the hysteresis TiCN layer, and the reaction atmosphere temperature and reaction atmosphere are not obtained. Regarding the pressure, when the temperature is less than 760 ° C. or the pressure is less than 4 kPa, the frequency ratio existing in the range of 20 to 30 degrees in the gradient angle distribution graph of the history TiCN layer exceeds 85%. When the temperature exceeds 850 ° C. or the pressure exceeds 8 kPa, the power ratio becomes less than 60%, which is the desired superiority. Inability to ensure high temperature strength.
The research results shown in (a) to (c) above were obtained.

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 two 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. Ti compound layer,
(B) Al ₂ O ₃ layer having an average layer thickness of 1 to 15 μm, wherein the upper layer is formed by chemical vapor deposition,
In the surface-coated cermet cutting tool formed by forming the hard coating layer composed of (a) and (b) above, one of the Ti compound layers of the above (a) is an average of 2.5 to 15 μm. Having a layer thickness, and
Using a field emission scanning electron microscope, each crystal grain having a cubic crystal lattice existing within the measurement range of the surface polished surface is irradiated with an electron beam, and the crystal grain is normal to the surface polished surface. The tilt angle formed by the normal line of the {013} plane, which is the crystal plane, is measured, and among the measured tilt angles, the measured tilt angles within the range of 0 to 45 degrees are classified for each pitch of 0.25 degrees. In addition, in the inclination angle number distribution graph obtained by summing up the frequencies existing in each section, the highest peak exists in the tilt angle section within the range of 20 to 30 degrees and also exists within the range of 20 to 30 degrees. A history TiCN layer showing an inclination angle frequency distribution graph in which the total frequency to be occupied accounts for 60 to 85% of the entire frequency in the inclination angle frequency distribution graph,
It is characterized by a coated cermet tool that exhibits excellent chipping resistance with a hard coating layer in high-speed intermittent cutting.

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) Ti compound layer (lower layer)
The Ti compound layer itself has high-temperature strength, and the presence of the Ti compound layer makes the hard coating layer have high-temperature strength, and firmly adheres to both the tool base and the upper Al ₂ O ₃ layer. Therefore, it has an effect of improving 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 exhibited, while the total average layer thickness is If it exceeds 20 μm, it becomes easy to cause thermoplastic deformation particularly by high-speed intermittent cutting accompanied by generation of high heat, which causes uneven wear. Therefore, the total average layer thickness is set to 3 to 20 μm.

(B) History TiCN layer (lower layer)
As described above, when the TiCN seed thin film is formed, by setting the content of TiCl _{4 in} the reaction gas to 0.2 to 1%, the sharpest peak in the tilt angle distribution graph is 20 to 20 in the tilt angle section. When the reaction atmosphere temperature is set to 760 to 850 ° C. and the reaction atmosphere pressure is set to 4 to 8 kPa, the sum of the frequencies existing in the range of 20 to 30 degrees is the inclination angle number. A hysteresis TiCN layer showing an inclination angle frequency distribution graph that occupies 60 to 85% of the total frequency in the distribution graph is formed, and as a result, the hysteresis TiCN layer has excellent high-temperature strength. However, if the average layer thickness is less than 2.5 μm, the hard coating layer cannot be provided with the desired excellent high-temperature strength, while if the average layer thickness exceeds 15 μm. Easily thermoplastic deformation which causes partial wear is generated, since it becomes worn accelerates, determined the average layer thickness and 2.5～15Myuemu.

(C) Al ₂ O ₃ layer (upper layer)
The Al ₂ O ₃ layer has excellent high-temperature hardness and heat resistance, and contributes to improving the wear resistance of the hard coating layer. However, if the average layer thickness is less than 1 μm, the hard coating layer has sufficient wear resistance. On the other hand, if the average layer thickness exceeds 15 μm and becomes too thick, chipping tends to occur. 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.

  This invention-coated cermet tool has a high-temperature strength in which the hysteresis TiCN layer, which is one of the lower layers of the hard coating layer, is excellent even in high-speed intermittent cutting such as steel and cast iron with extremely high mechanical and thermal shock, Since it exhibits excellent chipping resistance, the hard coating layer exhibits excellent wear resistance without occurrence of chipping.

  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, a Ti compound layer is formed as a lower layer of the hard coating layer on the surfaces of the tool bases A to F and the tool bases a to f using a normal chemical vapor deposition apparatus under the conditions shown in Table 3. In this case, when forming the history TiCN layer of the Ti compound layer, first, the conditions shown in Table 4, that is, the conditions of the seed thin film a to k for the target history TiCN layer determined based on the test results A TiCN seed thin film is formed, and subsequently, a history TiCN layer is formed by vapor deposition with the combination shown in Table 5 and the target layer thickness under the same conditions as those for forming the conventional TiCN layer shown in Table 3 as described above. also under the conditions shown in Table 3, the combination also shown in Table 5 the Al ₂ O ₃ layer as an upper layer, and the present invention coated cermet tools 1 to 13 by depositing formed at the target layer thickness it The manufactured.

For comparison purposes, as shown in Table 6, under the conditions shown in Table 3 as the lower and upper layers of the hard coating layer, the Ti compound layer and Al ₂ O having the target layer thickness shown in Table 6 are also used. Conventionally coated cermet tools 1 to 13 were produced by vapor deposition of _three layers, respectively.

Next, an inclination angle number distribution graph was created for each of the hysteresis TiCN layer and the conventional TiCN layer constituting the hard coating layer of the present invention coated cermet tool and the conventional coated cermet tool using a field emission scanning electron microscope.
That is, the inclination angle number distribution graph is set in a lens barrel of a field emission scanning electron microscope in a state where the surfaces of the hysteresis TiCN layer and the conventional TiCN layer are polished surfaces, and 70 ° An electron backscatter diffraction image apparatus is used by irradiating an electron beam with an acceleration voltage of 15 kV at an incident angle with an irradiation current of 1 nA on each crystal grain having a cubic crystal lattice existing within the measurement range of the surface polished surface. , Measuring the inclination angle formed by the normal of the {013} plane, which is the crystal plane of the crystal grain, with respect to the normal of the polished surface at an interval of 0.1 μm / step in a region of 30 × 50 μm, Based on the measurement results, the measurement inclination angles within the range of 0 to 45 degrees out of the measurement inclination angles are divided for each pitch of 0.25 degrees, and the frequencies existing in each division are tabulated. Created by.

  In the graphs showing the distribution of tilt angles of various modified TiCN layers and conventional TiCN obtained as a result, the {013} plane is present in the tilt angle section where the peak is the highest, and in the tilt angle section within the range of 20 to 30 degrees. Tables 5 and 6 show the ratios of the tilt angle numbers to the tilt angle number distribution graph as a whole.

In each of the above-mentioned various inclination angle number distribution graphs, as shown in Tables 5 and 6, the history TiCN layer of the coated cermet tool of the present invention has a measured inclination angle distribution on the {013} plane of 20 to 30 degrees. In contrast to the inclination angle distribution graph, the highest peak appears in the inclination angle section within the range, and the ratio of the inclination angle numbers existing in the inclination angle section within the range of 20 to 30 degrees is 60 to 85%. In the conventional TiCN layer of the conventional coated cermet tool, the distribution of the measured inclination angle of the {013} plane is unbiased within the range of 0 to 45 degrees, the highest peak does not exist, and the range of 20 to 30 degrees. The inclination angle number distribution graph in which the ratio of the inclination angle numbers existing in the inclination angle section is 30% or less was also shown.
FIG. 2 is a graph showing the inclination angle number distribution of the history TiCN layer of the coated cermet tool 9 of the present invention, and FIG. 3 is a graph showing the inclination angle number distribution graph of the conventional TiCN layer of the conventional coated cermet tool 9.

Further, for the above-described coated cermet tools 1 to 13 and the conventional coated cermet tools 1 to 13, the constituent layers of the hard coating layer were observed using an electron beam microanalyzer (EPMA) and an Auger spectroscopic analysis device (layer When the longitudinal section was observed), it was confirmed that both the former and the latter were composed of a Ti compound layer and an Al ₂ O ₃ layer having substantially the same composition as the target composition. Moreover, when the thickness of the constituent layer of the hard coating layer of these coated cermet tools was measured using a scanning electron microscope (same longitudinal section measurement), the average layer thickness (substantially the same as the target layer thickness) Average value of 5-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: 360 m / min,
Incision: 1.5mm,
Feed: 0.20mm / rev,
Cutting time: minutes,
Dry high-speed intermittent cutting test (normal cutting speed is 220 m / min) of alloy steel under the above conditions (cutting condition A),
Work material: JIS / S50C lengthwise equal 4 round bars with vertical grooves,
Cutting speed: 360 m / min,
Cutting depth: 2.0 mm
Feed: 0.25mm / rev,
Cutting time: 10 minutes,
Dry high-speed intermittent cutting test of carbon steel under the conditions (cutting condition B) (normal cutting speed is 250 m / min),
Work material: JIS / FCD450 lengthwise equidistant round bars with 4 vertical grooves,
Cutting speed: 360 m / min,
Cutting depth: 2.0 mm
Feed: 0.40mm / rev,
Cutting time: 10 minutes,
The dry high-speed intermittent cutting test (normal cutting speed is 220 m / min) of ductile cast iron under the above conditions (cutting condition C), and the flank wear width of the cutting edge was measured in any cutting test. The measurement results are shown in Table 7.

  From the results shown in Tables 5 to 7, in the coated cermet tools 1 to 13 of the present invention, one of the lower layers of the hard coating layer is within the range where the inclination angle of the {013} plane is 20 to 30 degrees. And a history TiCN layer showing an inclination angle number distribution graph in which the total ratio of the frequencies existing in the inclination angle division range of 20 to 30 degrees occupies 60 to 85%. Even in high-speed intermittent cutting of steel and cast iron with extremely high mechanical impact, the history TiCN layer has excellent high-temperature strength and exhibits excellent chipping resistance, so that the occurrence of chipping at the cutting edge is remarkably suppressed, While exhibiting excellent wear resistance, one of the lower layers of the hard coating layer is unbiased in the distribution of the measured inclination angle of the {013} plane within the range of 0 to 45 degrees, the highest peak Inclination angle distribution graph In the conventional coated cermet tools 1 to 13 constituted by the conventional TiCN layer, the mechanical impact resistance of the hard coating layer is insufficient in high-speed intermittent cutting, so that 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 of the present invention has excellent chipping resistance not only for continuous cutting and interrupted cutting under normal conditions such as various steels and cast iron, but also for high-speed interrupted cutting particularly requiring high-temperature strength. Since it exhibits excellent cutting performance over a long period of time, it can sufficiently satisfy the high performance of the cutting device, the labor saving and energy saving of the cutting work, and the cost reduction.

It is a schematic explanatory drawing which shows the measurement range of the inclination angle of the {013} plane of the crystal grain in the various TiCN layers which comprise a hard coating layer. It is an inclination angle number distribution graph of the {013} plane of the history TiCN layer which constitutes the lower layer of the hard coating layer of the present coated cermet tool 9. 6 is a graph showing the inclination angle distribution of the {013} plane of the conventional TiCN layer constituting the lower hard coating layer of the conventional coated cermet tool 9.

Claims (1)

On the surface of the tool base composed of tungsten carbide based cemented carbide or titanium carbonitride based cermet,
(A) The lower layer is composed of two or more of Ti carbide layer, nitride layer, carbonitride layer, carbonate layer, and carbonitride layer, all formed by chemical vapor deposition, and 3 A Ti compound layer having a total average layer thickness of ˜20 μm,
(B) an aluminum oxide layer having an average layer thickness of 1 to 15 μm, wherein the upper layer is formed by chemical vapor deposition;
In the cutting tool made of surface-coated cermet formed by forming the hard coating layer composed of (a) and (b) above,
One of the Ti compound layers of (a) above has an average layer thickness of 2.5 to 15 μm, and
Using a field emission scanning electron microscope, each crystal grain having a cubic crystal lattice existing within the measurement range of the surface polishing surface is irradiated with an electron beam, and the crystal grain is compared with the normal line of the surface polishing surface. The tilt angle formed by the normal of the {013} plane, which is the crystal plane, is measured, and among the measured tilt angles, the measured tilt angles within the range of 0 to 45 degrees are classified for each pitch of 0.25 degrees. In addition, in the inclination angle number distribution graph obtained by summing up the frequencies existing in each section, the highest peak exists in the inclination angle section in the range of 20 to 30 degrees and also exists in the range of 20 to 30 degrees. A titanium carbonitride layer showing a tilt angle frequency distribution graph in which the total frequency to be occupied accounts for 60 to 85% of the total power in the tilt angle frequency distribution graph,
A surface-coated cermet cutting tool that exhibits excellent chipping resistance with a hard coating layer in high-speed intermittent cutting characterized by comprising

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