JP5029099B2 - Surface coated cutting tool with excellent wear resistance with high hard coating layer in high speed cutting - Google Patents

Description

  The present invention relates to a surface-coated cutting tool (hereinafter referred to as a coated tool) that exhibits excellent wear resistance with a hard coating layer, particularly in high-speed cutting with high heat generation such as steel and cast iron.

Conventionally, on the surface of a base composed of tungsten carbide (hereinafter referred to as WC) base cemented carbide or titanium carbonitride (hereinafter referred to as TiCN) base cermet (hereinafter collectively referred to as a tool base),
(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 tool formed of a hard coating layer comprising: a coated tool that further improves wear resistance by replacing a part of Ti in the Ti compound layer with 10 atomic% or less of Cr or the like. Are known.
JP-A-6-31503 JP-A-10-244405

In recent years, the performance of cutting machines has been remarkable, while there has been a strong demand for labor saving and energy saving in cutting, as well as cost reduction, and along with this, the tendency to increase cutting speed for the purpose of improving cutting efficiency However, in the above-mentioned conventional coated tool, there is no problem when it is used for continuous cutting and intermittent cutting under normal conditions such as steel and cast iron, but especially when this is used under high-speed cutting conditions. The hard coating layer constituting this has high temperature strength due to the lower Ti compound layer and high temperature hardness due to the upper Al ₂ O ₃ layer, but the heat resistance due to the Ti compound layer is insufficient. Therefore, it is easy to cause thermoplastic deformation and uneven wear due to heat generated during cutting, so that the wear resistance is lowered and the service life is reached in a relatively short time.

In view of the above, the inventors of the present invention, from the above viewpoint, in order to improve the wear resistance of the hard coating layer of the above-mentioned coated tool, the TiCN layer constituting the Ti compound layer as the lower layer thereof, that is, the Ti compound As a result of conducting research by paying attention to a (Ti, Cr) CN layer in which a part of Ti having a relatively high high-temperature strength is replaced with Cr among the layers,
(A) In a hard coating layer of a conventional coated tool, a (Ti, Cr) CN layer (hereinafter referred to as “conventional Ti-based CN layer”) among the Ti compound layers constituting the lower layer is, for example, a normal chemical vapor deposition In the device
Reaction gas composition: by _{volume%, TiCl 4: 3~10%,} CrF 5: 0.1~0.4%, CH 3 CN: 0.5~3%, N 2: 20~40%, H 2: remaining,
Reaction atmosphere temperature: 800 to 900 ° C.
Reaction atmosphere pressure: 6-20 kPa,
It is formed by vapor deposition under the conditions (called normal conditions)
Reaction gas composition: by _{volume%, TiCl 4: 1~5%,} CrCl 3: 0.7~2.5%, CH 3 CN: 3~6%, N 2: 20~40%, HCl: 0.5 ~2%, H _2: remainder,
Reaction atmosphere temperature: 800 to 900 ° C.
Reaction atmosphere pressure: 5 to 20 kPa,
As compared with the above normal conditions, that is, the above-mentioned normal conditions, vapor deposition is performed under the condition that a small amount of CrCl ₃ and HCl are added instead of CrF ₅ which is one of the reaction gas components, and further the content ratio of CH ₃ CN is increased. Forming
Composition formula: (Ti _1-X Cr _X ) C _1-Y N _Y (however, in atomic ratio, X: 0.12 to 0.20, Y: 0.35 to 0.55),
When the Ti-based carbonitride layer satisfying the above conditions is formed, the resulting Ti-based carbonitride layer (hereinafter referred to as “modified Ti-based CN layer”) has the same crystal structure as that of the conventional Ti-based CN layer. That is, it has a NaCl type face centered cubic crystal structure in which constituent atoms composed of Ti, Cr, carbon (C), and nitrogen (N) are present at lattice points, respectively, but compared with the conventional Ti-based CN layer. Excellent heat resistance.

(B) About the conventional Ti-based CN layer and the modified Ti-based CN layer of (a),
Using a field emission scanning electron microscope, as illustrated in the schematic explanatory diagrams of FIGS. 1A and 1B, the electron beam is individually applied to each crystal grain having a cubic crystal lattice existing within the measurement range of the surface polished surface. Is measured with respect to the normal of the surface polished surface, and the tilt angle formed by the normal of the {111} plane that is the crystal plane of the crystal grain is measured. When the tilt angle distribution graph is created by dividing the measured tilt angles within the range of 0.25 degree pitches and summing up the frequencies existing in each section, the conventional Ti-based CN layer is 3, the distribution of the measured inclination angle of the {111} plane shows an unbiased inclination angle number distribution graph in the range of 0 to 45 degrees, whereas the modified Ti-based CN layer As shown in FIG. 2, a sharp peak appears at a specific position in the tilt angle section, In such a case, cooling cracks are uniformly dispersed in the modified Ti-based CN layer, thereby suppressing a decrease in high-temperature strength of the modified Ti-based CN layer due to an increase in Cr content. In addition, the sharp maximum peak can be changed by adjusting the Cr content in the modified Ti-based CN layer with respect to the height and the tilt angle segment position appearing in the tilt angle segment on the horizontal axis of the graph.

(C) As described above, when the modified Ti-based CN layer is formed, the Cr content ratio in the layer is set to 0.12 to 0.20 in the ratio (atomic ratio) to the total amount with Ti. In the tilt angle distribution graph of the modified Ti-based CN layer, the frequency at which the sharpest peak appears in the range of 1.25 to 10 degrees of the tilt angle section and exists in the range of 0 to 10 degrees. The inclination angle distribution graph occupies a ratio of 45% or more of the entire frequency in the inclination angle distribution graph, and accordingly, the Cr content ratio in the modified Ti-based CN layer is within the above range. The peak sharp peak in the tilt angle distribution graph is out of the range of 1.25 to 10 degrees of the tilt angle section and is in the range of 0 to 10 degrees. The frequency ratio that exists in In this case, the heat resistance cannot be expected to be further improved, and the decrease in high-temperature strength due to the increased Cr content cannot be suppressed by uniform distribution of cooling cracks.
That is, the Cr component of the modified Ti-based CN layer has a desired heat resistance improving effect when the ratio (atomic ratio) to the total amount with Ti is 0.12 (12 atomic%) or more, but the content ratio If it exceeds 0.20 (20 atomic%), in high-speed cutting with high heat generation, the modified Ti-based CN layer softens rapidly, and is susceptible to thermoplastic deformation and uneven wear. The ratio (atomic ratio) in the total amount with Ti needs to be 0.12 to 0.20.

(D) The upper layer of the hard coating layer is an Al ₂ O ₃ layer, the lower layer is an adhesive Ti compound layer and a modified Ti-based CN layer, and the modified Ti-based CN layer is 2.5 to has an average layer thickness of 15 [mu] m, within range of the highest peak appears, or one 0 - 10 degree tilt angle segment within the range distribution of 1.25 to 10 degrees measurement angle of inclination of the {111} plane In a coated tool with a frequency ratio of 45% or more, the modified Ti-based CN layer has a much higher heat resistance than the conventional Ti-based CN layer, and the Al ₂ O ₃ layer as the upper layer has a higher heat resistance. Combined with having excellent high-temperature hardness, especially in high-speed cutting with high heat generation, the hard coating layer exhibits excellent heat resistance, and does not cause thermoplastic deformation and uneven wear. To show excellent wear resistance over a long period of time.
The research results shown in (a) to (d) above were obtained.

This invention was made based on the above research results, and in the surface-coated cutting tool in which a hard coating layer composed of an upper layer and a lower layer is formed on the surface of the tool base by vapor deposition,
(A) The upper layer is made of an aluminum oxide layer having an average layer thickness of 1 to 15 μm formed by chemical vapor deposition,
(B) The lower layer has a total average layer thickness of 3 to 20 μm, and each consists of an adhesive Ti compound layer and a modified Ti carbonitride layer formed by chemical vapor deposition,
(C) The adhesion Ti compound layer is composed of a Ti carbide layer, a nitride layer, a carbonitride layer, a carbonate layer, and a carbonitride oxide layer having a total average layer thickness of 0.5 to 5 μm. It consists of one or more layers,
(D) The modified Ti carbonitride layer has an average layer thickness of 2.5 to 15 μm, and
Composition formula: (Ti _1-X Cr _X ) C _1-Y N _Y (however, in atomic ratio, X: 0.12 to 0.20, Y: 0.35 to 0.55),
Further, the modified Ti-based carbonitride layer is a cubic crystal lattice existing within the measurement range of the surface polished surface using a field emission scanning electron microscope. Irradiating the individual crystal grains with an electron beam, and measuring the tilt angle formed by the normal of the {111} plane, which is the crystal plane of the crystal grain, with respect to the normal of the surface polished surface, of corners, as well as dividing the measured tilt angle within a range of 0 to 45 degrees for each pitch of 0.25 degrees, the inclination angle frequency distribution graph obtained by aggregating the frequencies present in each segment, 1. The highest peak exists in the inclination angle section in the range of 25 to 10 degrees, and the total of the frequencies existing in the range of 0 to 10 degrees occupies a ratio of 45% or more of the entire degrees in the inclination angle distribution graph. Showing an inclination angle number distribution graph,
It is characterized by a surface-coated cutting tool (coated tool) that exhibits excellent wear resistance with a hard coating layer in high-speed cutting characterized by the above.

Next, the reason why the constituent layers of the hard coating layer of the coated tool of the present invention are numerically limited as described above will be described below.
(A) Adhesive Ti compound layer of lower layer Adhesive Ti compound layer adheres firmly to both the tool base and the upper layer Al ₂ O ₃ layer and the modified Ti-based CN layer, and thus a hard coating layer However, if the total average layer thickness is less than 0.5 μm, the desired excellent adhesion cannot be ensured, while the adhesion is a total up to 5 μm. Since the average layer thickness is sufficient, the total average layer thickness was determined to be 0.5 to 5 μm.

(B) power ratio present in highest peak position Oyo beauty plants constant inclination angle in Sector in inclination angle segment of the inclined angle frequency distribution graph of the reformed Ti-based CN layer above modified Ti-based CN layer of the lower layer As described above, by setting the Cr content ratio (X value) in the layer to 0.12 to 0.20 in terms of the atomic ratio of the total amount with Ti, an inclination angle in the range of 1.25 to 10 degrees. It classified the presence of the highest peak, or one 0 - 10 ° degrees proportion present in the range of, which can be at least 45% of the total power at the inclination angle frequency distribution graph, therefore, its content ratio frequency but be less than 0.12, even beyond 0.20, which deviate from the range of the maximum peak position of appearing inclination indicator from 1.25 to 10 degrees, it exists within the range of 0 - 10 degrees further The proportion will be less than 45%, so it will be hot Not only can the deterioration of the temperature be suppressed by the uniform distribution of cooling cracks, but it will also be impossible to ensure an excellent heat resistance improvement effect in high-speed cutting, resulting in wear resistance due to the occurrence of thermoplastic deformation or uneven wear. Is inferior.
In addition, the C component in the modified Ti-based CN layer improves the hardness of the layer, while the N component has the effect of improving the high-temperature strength. By coexisting both these components, high hardness and excellent strength are achieved. Therefore, when the content ratio (Y value) of the N component in the layer is less than 0.35 in terms of the atomic ratio to the total amount with the C component, the desired strength can be ensured. On the other hand, if the content ratio (Y value) similarly exceeds 0.55, the content ratio of the C component becomes relatively small and the desired high hardness cannot be obtained. It was set as 0.35-0.55.
As described above, the modified Ti-based CN layer has higher heat resistance than the conventional Ti-based CN layer as described above. However, when the average layer thickness is less than 2.5 μm, the desired superiority is obtained. However, if the average layer thickness exceeds 15 μm, chipping is likely to occur, so that the average layer thickness is 2.5 to 15 μm. Determined.

The Al ₂ O ₃ layer the Al ₂ O ₃ layer (c), the upper layer has excellent high-temperature hardness, contributes to improvement in wear resistance of the hard coating layer, the average layer thickness is less than 1 [mu] m, hard Since the coating layer cannot exhibit sufficient wear resistance, on the other hand, if the average layer thickness exceeds 15 μm, chipping tends to occur. Therefore, the average layer thickness is set to 1 to 15 μm. It was.

  In addition, for the purpose of identification before and after the use of the cutting tool, the TiN layer having a golden color tone may be vapor-deposited as necessary, but the average layer thickness in this case is 0.1 to 1 μm may be sufficient, 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 tool of the present invention has excellent heat resistance and high temperature strength in the modified Ti-based CN layer in the lower layer of the hard coating layer even in high-speed cutting processing such as steel and cast iron with high heat generation, and is thermoplastic. By suppressing the occurrence of deformation and uneven wear, the hard coating layer exhibits excellent wear resistance.

  Next, the coated 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 are blended in the blending composition shown in Table 1, added with wax, ball milled in acetone for 20 hours, dried under reduced pressure, and pressed into a compact of a predetermined shape at a pressure of 98 MPa. The green compact was vacuum-sintered at a predetermined temperature within a range of 1370 to 1470 ° C. for 1 hour in a vacuum of 5 Pa, and after sintering, the cutting edge portion was R: 0.05 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 , NbC powder, TaC powder, WC powder, Co, all having an average particle diameter of 0.5 to 2 μm. 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 20 hours, dried, and then pressed into a compact at a pressure of 98 MPa. 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 is subjected to a honing process of R: 0.07 mm. Tool bases a to e made of TiCN base cermet having a chip shape of CNMG120212 were formed.

Next, on the surfaces of these tool bases A to F and tool bases a to e , an ordinary chemical vapor deposition apparatus is used, and an adhesive Ti compound layer and a modified Ti-based CN layer are formed as a lower layer of the hard coating layer. The lower layer was formed by vapor deposition under the conditions shown in Table 3 with the combinations and target layer thicknesses shown in Table 4, and then the Al ₂ O ₃ layer as the upper layer was also formed under the conditions shown in Table 3. The coated tools 1 to 11 of the present invention were manufactured by vapor deposition with the combination shown in FIG.

Further, for the purpose of comparison, as a lower layer of the hard coating layer, an adhesive Ti compound layer and a conventional Ti-based CN layer are formed by vapor deposition with the combinations and target layer thicknesses shown in Table 5 under the conditions shown in Table 3. Furthermore, conventional coated tools 1 to 11 were manufactured by vapor-depositing Al ₂ O ₃ layers as upper layers under the conditions shown in Table 3 and with the target layer thicknesses also shown in Table 5.

Next, with respect to the modified Ti-based CN layer and the conventional Ti-based CN layer constituting the hard coating layer of the above-described coated tool of the present invention and the conventional coated tool, a gradient angle number distribution graph is respectively obtained using a field emission scanning electron microscope. Created.
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 modified TiCN layer and the conventional Ti-based CN layer are polished surfaces. An electron backscatter diffraction image is obtained by irradiating an electron beam with an acceleration voltage of 15 kV at an incident angle of 70 degrees 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. The inclination angle formed by the normal of the {111} plane, which is the crystal plane of the crystal grain, with respect to the normal of the surface polished surface in a 30 × 50 μm region at an interval of 0.1 μm / step using an apparatus. Based on the measurement results, among the measured tilt angles, the measured tilt angles within the range of 0 to 45 degrees are divided into pitches of 0.25 degrees, and the frequency existing in each section is determined. Created by counting.

    In the gradient angle distribution graphs of the various modified Ti-based CN layers and the conventional Ti-based CN layers obtained as a result, the tilt angle segment where the {111} plane shows the highest peak, and the tilt within the range of 0 to 10 degrees Tables 4 and 5 show the ratio of the number of tilt angles existing in the angle section to the number of tilt angles in the entire tilt angle distribution graph.

In the above-mentioned various inclination angle number distribution graphs, as shown in Table 4, all of the modified Ti-based CN layers of the present coated tools 1 to 11 have a distribution of measured inclination angles of {111} planes of 1.25. An inclination angle number distribution graph in which the highest peak appears in the inclination angle section within the range of -10 degrees and the ratio of the inclination angle numbers existing in the inclination angle section within the range of 0 to 10 degrees is 45% or more is shown. On the other hand, as shown in Table 5, the conventional Ti-based CN layers of the conventional coated tools 1 to 11 are all unbiased in the range of the measured inclination angle of the {111} plane within the range of 0 to 45 degrees. The inclination angle number distribution graph in which the highest peak does not exist and the ratio of the inclination angle number existing in the inclination angle section within the range of 0 to 10 degrees is 30% or less is also shown.
2 shows an inclination angle number distribution graph of the modified Ti-based CN layer of the coated tool 5 of the present invention, and FIG. 3 shows an inclination angle number distribution graph of the conventional Ti-based CN layer of the conventional coated tool 5. is there.

Further, regarding the above-described coated tools 1 to 11 of the present invention and the conventional coated tools 1 to 11 , the constituent layers of the hard coating layer were observed using an electron beam microanalyzer (EPMA) and an Auger spectroscopic analyzer (longitudinal section of the layer). Observed) confirmed that the former and the latter consisted of an adhesive Ti compound layer, a modified Ti-based CN layer and a conventional Ti-based CN layer having substantially the same composition as the target composition, and an Al ₂ O ₃ layer. It was done. Moreover, when the thickness of the constituent layer of the hard coating layer of these coated tools was measured using a scanning electron microscope (similarly longitudinal section measurement), the average layer thickness (5 The average value of point measurement) was shown.

Then, with the set screw at the distal end portion to the fixing jig of the various either tool steel byte coated cermet tool, the present invention coated tools 1 to 11 and conventional coated tools 1 to 11,
Work material: JIS / SNCM439 round bar,
Cutting speed: 380 m / min,
Cutting depth: 1.5 mm,
Feed: 0.25 mm / rev,
Cutting time: 7 minutes,
Wet continuous high-speed cutting test (normal cutting speed is 200 m / min) of alloy steel under the conditions (referred to as cutting condition A),
Work material: JIS / FC350 lengthwise equidistant round bars with 4 vertical grooves,
Cutting speed: 400 m / min,
Cutting depth: 2.0 mm,
Feed: 0.30 mm / rev,
Cutting time: 7 minutes,
Wet intermittent high-speed cutting test of cast iron under the conditions (cutting condition B) (normal cutting speed is 250 m / min),
Work material: JIS / S50C lengthwise equal 4 round grooved round bars,
Cutting speed: 360 m / min,
Cutting depth: 1.3 mm,
Feed: 0.35 mm / rev,
Cutting time: 7 minutes,
The carbon steel was subjected to a wet intermittent high speed cutting test (normal cutting speed is 250 m / min) under the above conditions (referred to as cutting conditions C),
In any cutting test (using water-soluble cutting oil), the flank wear width of the cutting edge was measured. The measurement results are shown in Table 6.

From the results shown in Tables 4 to 6, the present invention coated tools 1 to 11 are all modified Ti-based CN layers of the lower layer of the hard coating layer, and the inclination angle of the {111} plane is 1.25 to Inclination angle distribution graph showing the highest peak in the inclination angle section within the range of 10 degrees and the total ratio of the frequencies existing in the inclination angle section range of 0 to 10 degrees occupying 45% or more, and high heat generation Even in high-speed cutting of steel and cast iron with high temperature, the modified Ti-based CN layer has excellent heat resistance and high-temperature strength, and prevents the occurrence of thermoplastic deformation and uneven wear. The conventional Ti-based CN layer of the lower layer of the hard coating layer is non-biased within the range of the measured inclination angle of the {111} plane within the range of 0 to 45 degrees, while exhibiting wear resistance. It is composed of a conventional Ti-based CN layer showing an inclination angle number distribution graph with no peak. In the conventional coated tools 1 to 11 are all the generation of thermoplastic deformation or uneven wear of the hard layer in high-speed cutting, the wear resistance of the hard coating layer are those very poor, a relatively short time using It is clear that it reaches the end of its life.

  As described above, the coated tool of the present invention has excellent resistance to hard coating even in high-speed cutting with high heat generation, as well as continuous cutting and intermittent cutting under normal conditions such as various steels and cast iron. Since it exhibits wearability and exhibits excellent cutting performance over a long period of time, it can sufficiently satisfy the high performance of cutting equipment, labor saving and energy saving of cutting, and cost reduction. .

It is a schematic explanatory drawing which shows the measurement range of the inclination angle of the {111} plane of the crystal grain in the modified Ti type | system | group CN layer which comprises the lower layer of a hard coating layer, and the conventional Ti type | system | group CN layer. It is an inclination angle number distribution graph of the {111} plane of the modified Ti-based CN layer constituting the lower layer of the hard coating layer of the present coated tool 5. 7 is a graph showing the inclination angle number distribution of the {111} plane of a conventional Ti-based CN layer constituting the lower layer of the hard coating layer of the conventional coating tool 5.

Claims (1)

In a surface-coated cutting tool in which a hard coating layer composed of an upper layer and a lower layer is vapor-deposited on the surface of a tool base composed of a tungsten carbide-based cemented carbide or a titanium carbonitride-based cermet,
(A) The upper layer is made of an aluminum oxide layer having an average layer thickness of 1 to 15 μm formed by chemical vapor deposition,
(B) The lower layer has a total average layer thickness of 3 to 20 μm, and each consists of an adhesive Ti compound layer and a modified Ti carbonitride layer formed by chemical vapor deposition,
(C) The adhesion Ti compound layer is composed of a Ti carbide layer, a nitride layer, a carbonitride layer, a carbonate layer, and a carbonitride oxide layer having a total average layer thickness of 0.5 to 5 μm. It consists of one or more layers,
(D) The modified Ti carbonitride layer has an average layer thickness of 2.5 to 15 μm, and
Composition formula: (Ti _1-X Cr _X ) C _1-Y N _Y (however, in atomic ratio, X: 0.12 to 0.20, Y: 0.35 to 0.55),
Further, the modified Ti-based carbonitride layer is a cubic crystal lattice existing within the measurement range of the surface polished surface using a field emission scanning electron microscope. Irradiating the individual crystal grains with an electron beam, and measuring the tilt angle formed by the normal of the {111} plane, which is the crystal plane of the crystal grain, with respect to the normal of the surface polished surface, of corners, as well as dividing the measured tilt angle within a range of 0 to 45 degrees for each pitch of 0.25 degrees, the inclination angle frequency distribution graph obtained by aggregating the frequencies present in each segment, 1. The highest peak exists in the inclination angle section in the range of 25 to 10 degrees, and the total of the frequencies existing in the range of 0 to 10 degrees occupies a ratio of 45% or more of the entire degrees in the inclination angle distribution graph. Showing an inclination angle number distribution graph,
A surface-coated cutting tool that exhibits excellent wear resistance with a hard coating layer in high-speed cutting.