JP4793629B2 - Surface-coated cermet cutting tool that exhibits excellent chipping resistance with a hard coating layer in high-speed cutting of difficult-to-cut materials - Google Patents

Description

  This invention has excellent lubricity of the hard coating layer, and therefore, even when used for high-speed cutting with high heat generation of difficult-to-cut materials with high viscosity such as mild steel, stainless steel, and even high manganese steel, The present invention relates to a surface-coated cermet cutting tool (hereinafter referred to as a coated cermet tool) that exhibits excellent chipping resistance over a long period of time without cutting chips adhering to the cutting edge during cutting.

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 titanium carbide (hereinafter referred to as TiC) layer, a titanium nitride (hereinafter also referred to as TiN) layer, a titanium carbonitride (hereinafter referred to as TiCN) layer, a titanium carbonate (hereinafter referred to as TiCO) A Ti compound layer consisting of one or two or more of the layers shown below and a titanium carbonitride oxide (hereinafter referred to as TiCNO) layer and having an overall average layer thickness of 3 to 20 μm,
(B) As an upper layer, an aluminum oxide (hereinafter referred to as α-type Al ₂ O ₃ layer) layer having an average layer thickness of 1 to 15 μm and having an α-type crystal structure in a chemical vapor deposited state;
There is known a coated cermet tool formed by vapor-depositing the hard coating layer constituted by the above (a) and (b) with a chemical vapor deposition apparatus, and this coated cermet tool is a continuous material such as various steels and cast irons. It is well known that it is used for cutting and intermittent cutting.

Further, in the above-described coated cermet tool, the constituent layer of the hard coating layer generally has a granular crystal structure, and further, the TiCN layer constituting the Ti compound layer as the lower layer is intended to improve the strength of the layer itself. In a normal chemical vapor deposition apparatus, a gas mixture containing organic carbonitrides is used as a reaction gas, and it is formed by chemical vapor deposition at an intermediate temperature range of 700 to 950 ° C. so that it has a vertically grown crystal structure. It is also known to do.
Japanese Unexamined Patent Publication No. 6-31503 Japanese Patent Laid-Open No. 6-8010

  In recent years, the performance of cutting devices has been dramatically improved, while on the other hand, there is a strong demand for labor saving, energy saving, and cost reduction for cutting, and with this, cutting tends to be faster. For coated cermet tools, when used for cutting carbon steel, low alloy steel, and ordinary cast iron under high-speed cutting conditions, there is no problem with normal cutting performance. Especially when cutting high viscosity difficult-to-cut materials such as stainless steel and high manganese steel under high-speed cutting conditions with high heat generation, the lubricity of the hard coating layer is insufficient. This makes it easier for chips to be welded to the cutting edge, which causes chipping (small chipping), resulting in a relatively short service life.

In view of the above, the present inventors have developed the above-described coated cermet tool that exhibits excellent chipping resistance with a hard coating layer excellent in high-speed cutting of highly viscous difficult-to-cut materials. As a result of conducting research by focusing on the hard coating layer of conventional coated cermet tools,
(A) Conventionally, in general, a chromium oxide (hereinafter referred to as Cr ₂ O ₃ ) layer (hereinafter referred to as a conventional Cr ₂ O ₃ layer) is a normal chemical vapor deposition apparatus.
Reaction gas composition: volume%, CrCl ₃ : 2 to 4%, CO ₂ : 4.5 to 7%, HCl: 2.5 to 5%, H ₂ : remaining,
Reaction atmosphere temperature: 950-1020 ° C.
Reaction atmosphere pressure: 6 to 10 kPa,
And a crystal structure of a corundum hexagonal close-packed crystal in which constituent atoms composed of Cr and oxygen are present at lattice points, that is, atoms of a unit cell of Cr ₂ O _{3 in} FIG. The arrangement is composed of crystal grains having a crystal structure shown in a schematic diagram [(a) is a perspective view, (b) is a plan view of a cross section 1 to 9], but has lubricity equivalent to that of a graphite material. However, since it is a brittle material, when it is applied as a surface layer of a hard coating layer of a coated cermet tool and used for high-speed cutting, the wear progress is extremely fast and cannot be put to practical use.
(B) On the other hand, the Cr ₂ O ₃ layer is also a normal chemical vapor deposition device,
Reaction gas composition: volume%, CrCl ₃ : 2 to 4%, CO ₂ : 4.5 to 7%, HCl: 2.5 to 5%, H ₂ : remaining,
Reaction atmosphere temperature: 850 to 920 ° C.
Reaction atmosphere pressure: 12-20 kPa,
In other words, the resulting Cr ₂ O ₃ layer (hereinafter referred to as a modified Cr ₂ O ₃ layer) is formed by a field emission scanning electron microscope. As shown in the schematic explanatory diagrams in FIGS. 2 (a) and 2 (b), each crystal grain having a hexagonal crystal lattice existing within the measurement range of the surface polished surface is irradiated with an electron beam, and electron backscattering is performed. Using a diffraction image apparatus, the inclination angle formed by the normal of the (0001) plane, which is the crystal plane of the crystal grain, is measured with respect to the normal of the surface-polished surface at an interval of 0.1 μm / step in a predetermined region. And, among the measured tilt angles, the measured tilt angles within a range of 45 to 90 degrees are divided into pitches of 0.25 degrees, and the tilt angle number distribution is obtained by counting the frequencies existing in each section. when you create a graph, the conventional Cr ₂ O ₃ layer, in FIG. 4 As shown, whereas show the unbiased inclination angle frequency distribution graph in the range of distribution of 45 to 90 degrees measured tilt angle of the (0001) plane, the reforming Cr ₂ O ₃ layer, FIG. 3 As shown in Fig. 4, a sharp maximum peak appears at a specific position of the tilt angle section, and this sharp maximum peak is changed by changing the formation conditions of the modified Cr ₂ O ₃ layer. The position of appearing in changes.
(C) The above-mentioned modified Cr ₂ O ₃ layer has a further improved high-temperature strength in a state of having excellent lubricity equivalent to that of the conventional Cr ₂ O ₃ layer, and therefore In the coated cermet tool formed by vapor deposition as the surface layer of the hard coating layer, the chips adhere to the cutting edge portion even in the high-speed cutting with high heat generation of the highly viscous difficult-to-cut material. As a result, there is no occurrence of chipping, and since the progress of wear is remarkably suppressed by the excellent high-temperature strength provided, excellent wear resistance can be exhibited over a long period of time.
(D) According to the test results, by adjusting the formation conditions of the modified Cr ₂ O ₃ layer, the sharp maximum peak appears in the range of 80.00 to 89.25 degrees of the tilt angle section. When the inclination angle distribution graph in which the total of the frequencies existing in the range of 80 to 90 degrees occupies a ratio of 45 to 80% of the entire frequency in the inclination angle distribution distribution graph is shown, the resulting inclination angle number In the distribution graph, the modified Cr _{2 in} which the highest peak of the inclination angle section appears in the range of 80.00 to 89.25 degrees and the frequency ratio existing in the range of 80 to 90 degrees accounts for 45 to 80%. The coated cermet tool formed by vapor-depositing the O ₃ layer as the surface layer of the hard coating layer does not cause chips to be deposited on the cutting edge portion even in high-speed cutting of the above difficult-to-cut material with high heat generation. No chipping results Excellent I cooperation with and be provided with a high-temperature strength, to become to exert over the superior wear resistance to long term.
The research results shown in (a) to (d) 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) As a lower layer, a Ti compound layer composed of two or more of a TiC layer, a TiN layer, a TiCN layer, a TiCO layer, and a TiCNO layer and having an overall average layer thickness of 3 to 20 μm,
(B) an α-type Al ₂ O ₃ layer having an average layer thickness of 1 to 15 μm as an upper layer;
In the coated cermet tool formed by vapor- depositing the hard coating layer constituted by (a) and (b) using a chemical vapor deposition apparatus ,
The surface layer of the hard coating layer has an average layer thickness of 2 to 5 μm, and using a field emission scanning electron microscope, each crystal grain having a hexagonal crystal lattice existing within the measurement range of the surface polished surface has electrons. A predetermined region is irradiated at an interval of 0.1 μm / step with respect to the normal line of the surface-polished surface, and the crystal plane of the (0001) plane is the crystal plane of the crystal grain. The inclination angle formed by the normal is measured, and among the measurement inclination angles, the measurement inclination angle within the range of 45 to 90 degrees is divided for each pitch of 0.25 degrees, and the frequency existing in each division is determined. In the inclination angle number distribution graph obtained by aggregation, the highest peak is present in the inclination angle section within the range of 80.00 to 89.25 degrees, and the total of the frequencies existing within the range of 80 to 90 degrees is the inclination. Of the whole frequency in the angle distribution graph 5-80% modifiers Cr ₂ O ₃ layer shows an inclination angle frequency distribution graph in a proportion of,
This is characterized by a coated cermet tool which is formed by vapor deposition using a chemical vapor deposition apparatus and exhibits excellent chipping resistance with a hard coating layer in high-speed cutting of difficult-to-cut materials.

Hereinafter, 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.
(A) Ti compound layer of the lower layer The Ti compound layer exists as a lower layer of the α-type Al ₂ O ₃ layer, and contributes to improving the high temperature strength of the hard coating layer by its excellent high temperature strength. The substrate and the α-type Al ₂ O ₃ layer are firmly adhered to each other, thereby improving the adhesion of the hard coating layer to the tool substrate. However, when the average layer thickness is less than 3 μm, the above-described operation is sufficiently achieved. On the other hand, if the average layer thickness exceeds 20 μm, it becomes easy to cause thermoplastic deformation especially in high-speed cutting with high heat generation, which causes uneven wear. Was determined to be 3 to 20 μm.
(B) an upper layer α type the Al ₂ O ₃ layer α type the Al ₂ O ₃ layer of, by Al ₂ O ₃ hot hardness excellent with itself and heat resistance and contributes to improvement in wear resistance of the hard coating layer If the average layer thickness is less than 1 μm, the desired excellent wear resistance cannot be fully exhibited. On the other hand, if the average layer thickness exceeds 15 μm, chipping is likely to occur. The average layer thickness was determined to be 1 to 15 μm.
(C) a surface layer modification Cr ₂ O ₃ layer reforming Cr ₂ O ₃ layer, as described above, by adjusting its forming conditions, the highest peak of sharp inclination angle segment from 80.00 to 89.25 An inclination angle frequency distribution graph that appears in the range of degrees and in which the sum of the frequencies existing in the range of 80 to 90 degrees accounts for 45 to 80% of the entire frequency in the inclination angle frequency distribution graph is shown. In the state, when it is vapor-deposited as the surface layer of the hard coating layer of the coated cermet tool, it has high strength, exhibits excellent lubricity, and high-speed cutting of the above difficult-to-cut materials with high heat generation However, no chips were welded to the cutting edge, and as a result, no chipping occurred, which was superior to the conventional coated cermet tool in which a Cr ₂ O ₃ layer was formed as the surface layer of the hard coating layer. Demonstrate wear resistance over a long period of time If the average layer thickness is less than 2 μm, the desired excellent lubricity cannot be sufficiently exhibited. On the other hand, if the average layer thickness exceeds 5 μm, the chipping may occur. The average layer thickness was set to 2 to 5 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 the outermost surface layer of the hard coating layer as necessary, but the average layer thickness in this case is It may be 0.1 to 1 μm, and 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 for an average layer thickness of up to 1 μm.

The coated cermet tool of the present invention is a modified material that constitutes the surface layer of a hard coating layer even when used for high-speed cutting with high heat generation of difficult-to-cut materials with high viscosity such as mild steel, stainless steel, and high manganese steel. The high quality Cr ₂ O ₃ layer has excellent high temperature strength in addition to the excellent lubricity of Cr ₂ O ₃ itself, so it maintains excellent lubricity for a long period of time. It contributes to the improvement of chipping resistance and enables further extension of the service life.

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

As raw material powders, WC powder, TiC powder, ZrC powder, VC powder, TaC powder, NbC powder, Cr ₃ C ₂ powder, TiN powder, TaN powder, all having a predetermined average particle diameter in the range of 1 to 3 μm, And Co powders, these raw material powders are blended in the blending composition shown in Table 1, further added with wax, ball mill mixed in acetone for 32 hours, dried under reduced pressure, and then pressed to a predetermined shape at a pressure of 98 MPa. The green compact is press-molded, and this green compact is 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, R: By performing a honing process of 0.07 mm, tool bases A to F made of a WC-base cemented carbide having a throwaway tip shape defined in ISO · CNMG120212 were manufactured.

Further, as raw material powders, TiCN (mass ratio TiC / TiN = 50/50) powder, Mo ₂ C powder, ZrC powder, NbC powder, all having a predetermined average particle diameter in the range of 0.5 to 2 μm, TaC powder, WC powder, Co powder, and Ni powder are prepared. These raw material powders are blended in the blending composition shown in Table 2, wet mixed by a ball mill for 32 hours, dried, and then compacted at a pressure of 98 MPa. The green compact is pressed into a body, and the green compact is sintered in a nitrogen atmosphere of 1.3 kPa at a temperature of 1540 ° C. for 1 hour. After sintering, the cutting edge portion is subjected to a honing process of R: 0.07 mm. The tool bases a and c to f made of TiCN base cermet having a chip shape of ISO standard / CNMG120212 were formed.

Next, each of the tool bases A to F and the tool bases a and c to f was charged into a normal chemical vapor deposition apparatus. First, Table 3 (l-TiCN in Table 3 is JP-A-6-8010). Table 6 shows the conditions for forming a TiCN layer having a vertically elongated crystal structure described in the publication, and other conditions for forming a normal granular crystal structure. The Ti compound layer and the α-type Al ₂ O ₃ layer having the target layer thicknesses shown are vapor-deposited as lower and upper layers of the hard coating layer in the same combination shown in Table 6, and then the conditions shown in Table 4 Thus, the coated cermet tools 1 to 12 of the present invention are formed by vapor-depositing the modified Cr ₂ O ₃ layer having the target layer thickness shown in Table 6 as the surface layer of the hard coating layer in the same combination shown in Table 6. Manufactured.

For comparison purposes, instead of the modified Cr ₂ O ₃ layer, the conventional Cr ₂ O ₃ layer having the target layer thickness shown in Table 7 under the conditions shown in Table 5 is also combined as shown in Table 7. Thus, comparative coated cermet tools 1 to 12 were produced under the same conditions except that vapor deposition was performed as the surface layer of the hard coating layer.

Next, the modified Cr ₂ O ₃ layer and the conventional Cr ₂ O ₃ layer constituting the surface layer of the hard coating layer of the above-described coated cermet tool of the present invention and the comparative coated cermet tool, using a field emission scanning electron microscope, Each inclination angle number distribution graph was created.

That is, the tilt angle number distribution graph is set in a lens barrel of a field emission scanning electron microscope with the surface of the Cr ₂ O ₃ layer as a polished surface, and incident at 70 degrees on the polished surface. Using an electron backscatter diffraction image apparatus, an electron beam with an acceleration voltage of 15 kV at an angle is irradiated to each crystal grain having a hexagonal crystal lattice existing within the measurement range of the surface polished surface with an irradiation current of 1 nA, A 30 × 50 μm region is measured at an interval of 0.1 μm / step, and an inclination angle formed by a normal line of the (0001) plane that is a crystal plane of the crystal grain is measured with respect to a normal line of the polished surface. Based on the measurement results, by dividing the measurement inclination angle within the range of 45 to 90 degrees among the measurement inclination nuclei for each pitch of 0.25 degrees, and by counting the frequencies existing in each division Created.

In the gradient angle distribution graphs of the various Cr ₂ O ₃ layers obtained as a result, the tilt existing in the tilt angle section where the (0001) plane shows the highest peak and the tilt angle section within the range of 45 to 90 degrees. The ratio of the number of angles to the number of inclination angles in the entire inclination angle distribution graph is shown in Tables 6 and 7, respectively.

In the gradient angle distribution graphs of the various Cr ₂ O ₃ layers described above, as shown in Tables 6 and 7, all of the modified Cr ₂ O ₃ layers of the coated cermet tool of the present invention were measured on the (0001) plane. The highest peak appears in the inclination angle section where the inclination angle distribution is in the range of 80.00 to 89.25 degrees, and the ratio of the number of inclination angles existing in the inclination angle section in the range of 80 to 90 degrees is 45 to While the inclination angle number distribution graph is 80% , the conventional Cr ₂ O ₃ layer of the comparative coated cermet tool has a distribution of measured inclination angles on the (0001) plane within a range of 45 to 90 degrees. An inclination angle distribution graph in which the ratio of the inclination angle existing in the inclination angle section in the range of 80 to 90 degrees is not more than 30% is unbiased.

3 is a graph showing the distribution of the number of inclination angles of the modified Cr ₂ O ₃ layer, which is the surface layer of the hard coating layer of the coated cermet tool 6 of the present invention, and FIG. 4 is the surface of the hard coating layer of the comparative coated cermet tool 6. ₂ shows an inclination angle number distribution graph of a conventional Cr ₂ O ₃ layer as a layer.

Further, when the thickness of the resulting present invention coated cermet tools 1 to 12 and Comparative coated cermet tool 1-12 layers constituting the hard layer of the, was measured using a scanning electron microscope (longitudinal sectional measurement) , Each showed an average layer thickness (average value of 5-point measurement) substantially the same as the target layer thickness.

Next, for the various coated cermet tools of the present invention coated cermet tools 1 to 12 and comparative coated cermet tools 1 to 12 , all of which are screwed to the tip of the tool steel tool with a fixing jig,
Work material: JIS / SS400 lengthwise equidistant 4 round bars with flutes,
Cutting speed: 330 m / min,
Incision: 3mm,
Feed: 0.35mm / rev,
Cutting time: 10 minutes,
Dry interrupted high-speed cutting test (normal cutting speed is 200 m / min) of mild steel under the following conditions (referred to as cutting condition A),
Work material: JIS / SUS316 round bar,
Cutting speed: 280 m / min,
Incision: 1.5mm,
Feed: 0.25mm / rev,
Cutting time: 10 minutes,
In a dry continuous high-speed cutting test (normal cutting speed is 150 m / min) of stainless steel under the following conditions (referred to as cutting condition B),
Work material: JIS / SMn438 round bar,
Cutting speed: 360 m / min,
Cutting depth: 2mm,
Feed: 0.4mm / rev,
Cutting time: 10 minutes,
The dry continuous high-speed cutting test (normal cutting speed is 200 m / min) of high manganese 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 8.

From the results shown in Tables 6 to 8, in the coated cermet tools 1 to 12 of the present invention, the surface layer of the hard coating layer is in the range of the inclination angle of the (0001) plane of 80.00 to 89.25 degrees. It is composed of a modified Cr ₂ O ₃ layer showing the highest peak in the inclination angle section and showing an inclination angle distribution graph in which the total ratio of the frequencies existing in the inclination angle section range of 80 to 90 degrees occupies 45 to 80%. Since the modified Cr ₂ O ₃ layer has excellent lubricity and high temperature strength, even in high-speed cutting with high heat generation of the above highly viscous difficult-to-cut material, chips are generated on the cutting edge. Excellent lubricity without welding is maintained over a long period of time, and as a result, chipping of the hard coating layer is prevented, and excellent wear resistance is exhibited over a long period of time. , (0001) plane measurement inclination angle distribution is 45-9 Every unbiased manner in within, in a conventional Cr ₂ O ₃ layer compared coated cermet tool 1-12 constituted by showing the inclination angle frequency distribution graph in which the highest peak does not exist, both in high-speed cutting above, Although the conventional Cr ₂ O ₃ layer of the surface layer has lubricity, due to insufficient high-temperature strength, it wears out early, and cutting is performed in the absence of the conventional Cr ₂ O ₃ layer. Therefore, it is clear that chipping occurs in the hard coating layer in a short time after the start of cutting, which leads to the service life.

  As described above, the coated cermet tool of the present invention is not only continuous cutting and intermittent cutting under normal conditions such as various steels and cast irons, but particularly high-speed cutting with high heat generation of highly viscous difficult-to-cut materials. However, since it exhibits excellent chipping resistance and excellent wear resistance over a long period of time, it is fully satisfied with high performance of cutting equipment, labor saving and energy saving of cutting work, and further cost reduction It can cope with.

FIG. 2 is a schematic diagram showing an atomic arrangement of a unit cell of a corundum type hexagonal close-packed crystal constituting a Cr ₂ O ₃ layer, where (a) is a perspective view and (b) is a plan view of cross sections 1 to 9. It is a schematic diagram illustrating a measurement range of the inclination angle of the crystal grains (0001) plane in Cr ₂ O ₃ layer constituting the surface layer of the hard coating layer. It is an inclination angle number distribution graph of the (0001) plane of the modified Cr ₂ O ₃ layer constituting the surface layer of the hard coating layer of the coated cermet tool 6 of the present invention. It is an inclination angle number distribution graph of the (0001) plane of the conventional Cr ₂ O ₃ layer constituting the surface layer of the hard coating layer of the comparative coated cermet tool 6 .

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, it is composed of two or more of a titanium carbide layer, a titanium nitride layer, a titanium carbonitride layer, a titanium carbonate layer, and a titanium carbonitride oxide layer, and has an overall average layer thickness of 3 to 20 μm. Having a Ti compound layer,
(B) As an upper layer, an aluminum oxide layer having an average layer thickness of 1 to 15 μm and having an α-type crystal structure in a state of chemical vapor deposition,
In the surface-coated cermet cutting tool formed by vapor- depositing the hard coating layer composed of (a) and (b) above using a chemical vapor deposition apparatus ,
The surface layer of the hard coating layer has an average layer thickness of 2 to 5 μm, and using a field emission scanning electron microscope, each crystal grain having a hexagonal crystal lattice existing within the measurement range of the surface polished surface has electrons. A predetermined region is irradiated at an interval of 0.1 μm / step with respect to the normal line of the surface-polished surface, and the crystal plane of the (0001) plane is the crystal plane of the crystal grain. The inclination angle formed by the normal is measured, and among the measurement inclination angles, the measurement inclination angle within the range of 45 to 90 degrees is divided for each pitch of 0.25 degrees, and the frequency existing in each division is determined. In the inclination angle number distribution graph obtained by aggregation, the highest peak is present in the inclination angle section within the range of 80.00 to 89.25 degrees, and the total of the frequencies existing within the range of 80 to 90 degrees is the inclination. Of the whole frequency in the angle distribution graph 5-80% modified chromium oxide layer exhibiting a tilt angle frequency distribution graph in a proportion of,
A surface-coated cermet cutting tool that exhibits excellent chipping resistance in high-speed cutting of difficult-to-cut materials, formed by vapor deposition using the same chemical vapor deposition equipment .

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