JP2006231433A - Surface-coated cermet cutting tool with hard coating layer exerting excellent chipping resistance in high-speed intermittent cutting - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface-coated cermet cutting tool with a hard coating layer exerting excellent chipping resistance in high-speed intermittent cutting. <P>SOLUTION: The surface-coated cermet cutting tool is composed by forming the hard coating layer on the surface of a tool base body. The hard coating layer is composed of the following lower and upper layers (a) and (b), namely, (a) as the lower layer is a Ti compound layer composed of two or more layers of a TiC layer, a TiN layer, a TiCN layer, a TiCO layer, and a TiCNO layer that are all formed by chemical vapor deposition and having a total average layer thickness of 3-20 μm, and (b) as the upper layer is an Al<SB>2</SB>O<SB>3</SB>layer having a total average layer thickness of 1-15 μm and formed by chemical vapor deposition. One of two or more layers in the Ti compound layer (a) is the TiCN layer having an average layer thickness of 2.5-15 μm and showing a specific inclination angle frequency distribution graph. <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, all of which are formed by chemical vapor deposition as the lower layer, A Ti compound layer composed of two or more layers 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 formed by chemical vapor deposition in which the upper layer has an average layer thickness of 1 to 15 μm;
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 have focused on the TiCN layer of the Ti compound layer, which is the lower layer, in order to improve the chipping resistance of the hard coating layer of the coated cermet tool. , As a result of research,
(A) Usually, the TiCN layer (hereinafter referred to as “conventional TiCN layer”) constituting the Ti compound layer, which is the lower layer of the hard coating layer of the conventional coated cermet tool, 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,
The TiCN layer constituting the Ti compound layer, which is the lower layer of the hard coating layer of the coated cermet tool, is also formed by the same chemical vapor deposition apparatus.
Reaction gas composition - by _{volume%, TiCl 4: 0.2~1%,} CH 3 CN: 0.3~2%, C 2 H 4: 1~3%, N 2: 10~30%, H 2: remaining,
Reaction atmosphere temperature: 700-780 ° C.
Reaction atmosphere pressure: 25-40 kPa,
The resulting TiCN layer (hereinafter referred to as “modified TiCN layer”) has excellent high temperature strength and excellent mechanical impact resistance. The coated cermet tool in which the upper layer of the hard coating layer is composed of the Al ₂ O ₃ layer, the lower layer is composed of the Ti compound layer, and one of the Ti compound layers is composed of the modified TiCN layer is particularly severe. Even in high-speed intermittent cutting with mechanical impact, the hard coating layer exhibits excellent chipping resistance and exhibits excellent wear resistance over a long period of time.

(B) Using the field emission scanning electron microscope, the conventional TiCN layer and the modified TiCN layer are within the measurement range of the surface polished surface as shown in the schematic explanatory diagrams of FIGS. 1 (a) and 1 (b). The crystal grains having an existing cubic crystal lattice are irradiated with an electron beam, and the inclination angle formed by the normal of the {110} plane, which is the crystal plane of the crystal grain, is made with respect to the normal of the surface polished surface. Measured and divided the measured inclination angle within the range of 0 to 45 degrees among the measured inclination angles for each pitch of 0.25 degrees, and the number of inclination angles obtained by totalizing the frequencies existing in each section When the distribution graph is created, the conventional TiCN layer shows an unbiased inclination angle number distribution graph within the range of the measured inclination angle of the {110} plane within the range of 0 to 45 degrees as illustrated in FIG. In contrast, the modified TiCN layer is inclined as illustrated in FIG. Appear sharp highest peak in a specific position of the segment, the sharp highest peak, the added C ₂ H ₄ of the content changes that position appears at the inclination angle section of the graph the horizontal axis by a component in the reaction gas.

(C) As described above, the modified TiCN layer is newly added with C ₂ H ₄ at a ratio of 1 to 3% in the reaction gas, while the content ratio of TiCl _{4 in} the reaction gas is 0.2%. The reforming was formed under the conditions that the reaction atmosphere temperature was relatively low as 700 to 780 ° C. and the reaction atmosphere pressure was relatively high as 25 to 40 kPa. In the TiCN layer, the sharpest peak appears in the range of 0 to 10 degrees of the tilt angle section in the above tilt angle distribution graph, and the sum of the frequencies existing in the range of 0 to 10 degrees is the tilt angle. An inclination angle frequency distribution graph occupying a ratio of 50 to 75% of the entire frequency in the number distribution graph is shown. In this case, according to the test result, the content ratio of C ₂ H ₄ in the reaction gas is 1%. Even if less than 3% is high However, if the inclination angle section where the highest peak appears is out of the range of 0 to 10 degrees, the reaction atmosphere temperature exceeds 780 ° C., or the reaction atmosphere pressure is less than 25 kPa, 0 to 10 degrees. The total ratio of the frequencies existing in the range is less than 50% of the entire frequencies in the tilt angle frequency distribution graph, and in any case, the high-temperature strength superior to the TiCN layer cannot be ensured, and further the reaction If the atmospheric temperature is less than 700 ° C. or the reaction atmospheric pressure exceeds 40 kPa, the deposition rate of the layer is significantly reduced, which is undesirable in terms of cost, while the frequency existing in the range of 0 to 10 degrees. It is difficult to make the TiCN layer higher than 75%.
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) Ti having a total average layer thickness of 3 to 20 μm, wherein 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 formed by chemical vapor deposition. Compound layer,
(B) Al ₂ O ₃ layer formed by chemical vapor deposition with an upper layer having an average layer thickness of 1 to 15 μm,
In the surface-coated cermet cutting tool formed by forming the hard coating layer composed of (a) and (b) above, one of the two or more Ti compound layers of (a) above is 2.5. Having an average layer thickness of ˜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 {110} 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 within the range of 0 to 10 degrees and also exists within the range of 0 to 10 degrees. A modified TiCN layer showing a tilt angle frequency distribution graph in which the total frequency to be accounted for 50 to 75% of the total frequency in the tilt 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) Modified TiCN layer As described above, by setting the content ratio of C ₂ H ₄ which is a component of the reaction gas to 1 to 3%, the measured inclination angle is within the inclination angle range of 0 to 10 degrees. When the highest peak appears, the reaction atmosphere temperature is 700 to 780 ° C., and the reaction atmosphere pressure is 25 to 40 kPa, the total ratio of frequencies existing in the inclination angle section of 0 to 10 degrees is the inclination angle number distribution. A modified TiCN layer showing an inclination angle distribution graph that is 50 to 75% of the total frequency in the graph is formed, and as a result, the modified TiCN layer has excellent high-temperature strength. If the average layer thickness is less than 2.5 μm, the hard coating layer cannot be provided with the desired high-temperature strength. On the other hand, if the average layer thickness exceeds 15 μm, thermoplastic deformation that causes uneven wear occurs. No longer, since the so wear is accelerated, it 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.

  The coated cermet tool according to the present invention has a high-temperature strength in which the modified 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, it exhibits excellent wear resistance without occurrence of chipping in the hard coating layer.

  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 defined in ISO · CNMG12041 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, on the surfaces of these tool bases A to F and tool bases a to f, modified TiCN is used as a lower layer of the hard coating layer under the conditions shown in Tables 3 and 4 using a normal chemical vapor deposition apparatus. The Ti compound layer including the layers is formed by vapor deposition in the combination shown in Table 6 with the target layer thickness, and the Al ₂ O ₃ layer is also shown in Table 6 as the upper layer under the same conditions as shown in Table 3. The coated cermet tools 1 to 13 according to the present invention were manufactured by vapor deposition with a target layer thickness in combination.

For comparison purposes, as shown in Table 7, the hard coating layer includes the conventional TiCN layer having the target layer thickness shown in Table 7 under the conditions shown in Tables 3 and 5 as the lower layer and the upper layer. Conventionally coated cermet tools 1 to 13 were produced by depositing a Ti compound layer and an Al ₂ O ₃ layer, respectively.

Next, an inclination angle number distribution graph was prepared for each of the modified TiCN layer and the conventional TiCN layer constituting the hard coating layer of the above-described coated cermet tool of the present invention and the conventional coated cermet tool using a field emission scanning electron microscope. .
That is, the tilt angle number distribution graph is set in a lens barrel of a field emission scanning electron microscope with the surfaces of the modified TiCN layer and the conventional TiCN layer being polished surfaces, and 70 ° on the polished surface. An electron backscatter diffraction imaging apparatus is irradiated by irradiating an electron beam with an acceleration voltage of 15 kV at an incident angle of 1 nA 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. Using a 30 × 50 μm region at an interval of 0.1 μm / step, the inclination angle formed by the normal of the {110} plane, which is the crystal plane of the crystal grain, is measured with respect to the normal of the polished surface. Based on this measurement result, among the measured tilt angles, the measured tilt angles within the range of 0 to 45 degrees are divided for each pitch of 0.25 degrees, and the frequencies existing in each section are tabulated. Created by.

  In the gradient angle distribution graphs of the various modified TiCN layers and conventional TiCN layers obtained as a result, the {110} plane has the highest peak, and the tilt angle within the range of 0 to 10 degrees. Tables 6 and 7 show the ratios of the existing tilt angle numbers to the tilt angle number distribution graph as a whole.

In each of the various inclination angle distribution graphs described above, as shown in Tables 6 and 7, all of the modified TiCN layers of the coated cermet tool of the present invention have a measured inclination angle distribution on the {110} plane of 0 to 10 degrees. An inclination angle number distribution graph in which the highest peak appears in the inclination angle section in the range of 0 and the ratio of the inclination angle numbers existing in the inclination angle section in the range of 0 to 10 degrees is 50 to 75%. On the other hand, the conventional TiCN layers of the conventional coated cermet tools are all unbiased in the distribution of the measured inclination angle of the {110} plane within the range of 0 to 45 degrees, the highest peak does not exist, and 0 to 10 degrees. The inclination angle number distribution graph in which the ratio of the inclination angle number existing in the inclination angle section within the range is 30% or less was also shown.
FIG. 2 is a graph showing the inclination angle distribution of the modified TiCN layer of the coated cermet tool 8 of the present invention, and FIG. 3 is a graph showing the inclination angle distribution of the conventional TiCN layer of the conventional coated cermet tool 8.

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, with the various coated cermet tools described above, the present coated cermet tools 1 to 13 and the conventional coated cermet tools 1 to 13 in the state where all the above-mentioned various coated cermet tools are screwed to the tip of the tool steel tool with a fixing jig.
Work material: JIS / S30C lengthwise equal length 4 round bar with round groove,
Cutting speed: 440 m / min,
Cutting depth: 1.0 mm,
Feed: 0.20mm / rev,
Cutting time: 8 minutes
Wet high-speed intermittent cutting test of carbon steel under the above conditions (cutting condition A) (normal cutting speed is 300 m / min),
Work material: JIS / SCM415 lengthwise equidistant 4 round grooved round bars,
Cutting speed: 400 m / min,
Cutting depth: 1.2mm,
Feed: 0.20mm / rev,
Cutting time: 8 minutes
Wet high-speed intermittent cutting test (normal cutting speed is 250 m / min) of alloy steel under the above conditions (cutting condition B),
Work material: JIS / FCD450 lengthwise equidistant round bars with 4 vertical grooves,
Cutting speed: 370 m / min,
Incision: 1.5mm,
Feed: 0.15mm / rev,
Cutting time: 8 minutes
Wet high-speed intermittent cutting test (normal cutting speed is 250 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 8.

  From the results shown in Tables 6 to 8, 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 {110} plane is 0 to 10 degrees. And a modified TiCN layer showing an inclination angle distribution graph in which the total ratio of the frequencies existing in the inclination angle division range of 0 to 10 degrees occupies 50 to 75%. Even in high-speed intermittent cutting of steel and cast iron with extremely high mechanical impact, the modified TiCN layer has excellent high-temperature strength and excellent chipping resistance, so that chipping at the cutting edge is significantly suppressed. In contrast to the excellent wear resistance, one of the lower layers of the hard coating layer is unbiased within the range of the measured inclination angle of the {110} plane in the range of 0 to 45 degrees, Inclination angle number distribution graph without the highest peak In the conventional coated cermet tools 1 to 13 composed of the conventional TiCN layer, since the mechanical impact resistance of the hard coating layer is insufficient in high-speed interrupted cutting, chipping occurs at the cutting edge portion. 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 {110} 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 {110} plane of the modified TiCN layer constituting the lower layer of the hard coating layer of the coated cermet tool 8 of the present invention. 6 is a graph showing the inclination angle number distribution of the {110} plane of conventional TiCN constituting the hard coating layer lower layer of the conventional coated cermet tool 8.

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 oxide layer formed by chemical vapor deposition, A Ti compound layer having a total average layer thickness of 20 μm,
(B) an aluminum oxide layer formed by chemical vapor deposition in which the upper layer has an average layer thickness of 1 to 15 μm;
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 two or more 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 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 of the {110} 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 within the range of 0 to 10 degrees and also exists within the range of 0 to 10 degrees. A titanium carbonitride layer showing an inclination angle frequency distribution graph in which the total frequency to be occupied accounts for 50 to 75% of the entire frequency in the inclination 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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