JP2013208698A - Surface coated cutting tool whose hard coating layer exhibits excellent chipping resistance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface coated cutting tool whose hard coating layer exhibits excellent chipping resistance and wear resistance in high-speed intermittent cutting of alloy tool steel or the like.SOLUTION: A surface coated cutting tool has a hard coating layer comprising (a), (b) and (c) formed by chemical vapor deposition on a surface of a tool base body, where (a) is a lower layer made of a Ti compound layer having a total average layer thickness of 3-20 μm, (b) is an intermediate layer made of an aluminum oxide layer having an average layer thickness of 1-15 μm, and (c) is an upper layer made of a modified Ti carbonitride layer having a vertically-long grown crystalline structure with an average layer thickness of 4-14 μm. (d) The modified Ti carbonitride layer constituting the upper layer includes at least one B-containing region with an average B content of 1.5-3.0 atom% at an interval within a range of a depth of 0.5-4.0 μm from a surface toward an inner part along a layer thickness direction.

Description

  The present invention is a surface-coated cutting tool that exhibits excellent chipping resistance and wear resistance with a hard coating layer in high-speed and strong intermittent cutting of alloy tool steel and the like, and exhibits excellent cutting performance over a long period of use. (Hereinafter referred to as a coated tool).

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 composed of two or more of a carbon oxide (hereinafter referred to as TiCO) layer and a carbonitride oxide (hereinafter referred to as TiCNO) layer,
(B) an aluminum oxide (hereinafter referred to as Al ₂ O ₃ ) layer in which the upper layer is formed by chemical vapor deposition;
A coated tool formed by forming a hard coating layer composed of (a) and (b) above is known. Furthermore, various methods for improving the cutting performance of the coated tool have been proposed.

  For example, in Patent Document 1, in a conventional coated tool, a TiCN layer constituting a Ti compound layer as a lower layer is used in a normal chemical vapor deposition apparatus, using a mixed gas containing organic carbonitride as a reaction gas, It is disclosed that the strength of the hard coating layer itself is improved by forming a TiCN layer having a vertically grown crystal structure by chemical vapor deposition in a medium temperature range of 700 to 950 ° C.

Patent Document 2 discloses that one or two or more of a Ti compound layer composed of a TiC layer, a TiN layer, a TiCN layer, a TiCO layer, a TiNO layer, and a TiCNO layer on the surface of a cemented carbide substrate is vertically long. Surface formed by forming a hard coating layer composed of a textured TiCN layer and, if necessary, an α-type Al ₂ O ₃ layer and / or a κ-type Al ₂ O ₃ layer with an overall average layer thickness of 8 to 30 μm In the coated cemented carbide slow-away cutting tip, the average layer thickness of the vertically structured TiCN layer is increased to 6 to 20 μm, and the vertically grown crystal structure is retained in the vertically structured TiCN layer while maintaining the thickness. Fine TiB ₂ grains divided in the direction are dispersed and distributed with an average thickness of 0.1 to 1 μm, and the distribution ratio is B (boron) in the 0.3 μm × 0.3 μm region using Auger electron spectroscopy Ingredient analysis value ( By providing the TiB ₂ grain distribution segment band layer exhibiting a 1-10 atomic% in concentration) one or more layers, the surface-coated cemented carbide Suroauei cutting which exhibits chipping resistance of the hard coating layer was thickened is excellent A chip is disclosed.

Japanese Patent Laid-Open No. 6-8010 JP 2000-54133 A

  In recent years, the performance of cutting equipment has been remarkable, while the demand for labor saving and energy saving and further cost reduction for cutting is strong, and with this, cutting has been on the trend of higher speed. In this case, there is no problem when it is used for continuous cutting and intermittent cutting under normal conditions such as alloy tool steel, but this is accompanied by high heat generation and intermittent / impact on the cutting edge. When it is used for high-speed hard interrupted cutting that requires a heavy load, chipping (minute chipping), chipping, etc. are likely to occur in the hard coating layer, and it cannot be said that the wear resistance is sufficient. The current situation is that the service life is reached in a short time.

  Therefore, the present inventors have high high-temperature hardness and high-temperature strength in the upper layer in order to improve the chipping resistance and wear resistance of the hard coating layer of the coated tool from the above viewpoint, and As shown schematically in FIG. 1 (a), the crystal structure of an NaCl type face centered cubic crystal in which constituent atoms consisting of Ti, carbon, and nitrogen are present at lattice points (FIG. 1 (b) is ( 011) shows a state of being cut at the plane), and researched with a focus on forming a TiCN layer having a vertically elongated crystal structure (hereinafter referred to as an l-TiCN layer).

(A) First, the hard coating layer of the conventional coated tool is, for example, an ordinary 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,
After forming a lower layer made of an l-TiCN layer under the above conditions (referred to as normal conditions), an Al ₂ O ₃ layer is deposited thereon.
(B) The present inventors, after depositing the the Al ₂ O ₃ layer, further thereon, was deposited top layer consisting of l-TiCN layer under normal conditions described above.
(C) At this time, in the middle of the film forming process for depositing the l-TiCN layer under normal conditions, the reaction atmosphere pressure is lowered, and at the same time, a small amount of BCl ₃ is added to the reaction gas for a short time. After film formation, an l-TiCN layer is formed according to normal conditions.
Further, by repeatedly performing the step (c), a plurality of B-containing regions at a predetermined interval in the l-TiCN layer, that is, regions where B that has not reached the formation of the TiB ₂ layer exists. It was confirmed that it was formed. And it discovered that the structure | tissue fine effect of the crystal grain of a 1-TiCN layer became remarkable by forming one or more of this B containing field.

(D) Further, the present inventors set the B content in the layer thickness direction of the l-TiCN layer in which the B-containing region is formed by Auger electron spectroscopy along the vertical cross-section polished surface. As a result of a line analysis, a B-containing region is formed on the inner side of the l-TiCN layer from the interface between the Al ₂ O ₃ layer (intermediate layer) and the l-TiCN layer (upper layer), as shown in FIG. Further, the crystal structure of the l-TiCN layer is refined, and further, an interval in the range of 0.5 to 4.0 μm is provided on the inner side along the layer thickness direction from the surface of the l-TiCN layer, A plurality of peaks of B content appear, and when the B content at the peak position is measured, one or more B-containing regions having an average B content of 1.5 to 3.0 atomic% are included. -TiCN layer (hereinafter referred to as "modified l-TiCN layer") is formed. It was heading.
(E) Then, an Al ₂ O ₃ layer (intermediate layer) is formed by vapor deposition, and a modified l-TiCN layer (upper layer) having the at least one B-containing region and having a refined structure is formed. The coated tool provided with the hard coating layer formed by vapor deposition improves the adhesion between the intermediate layer and the upper layer, and at the same time forms the l-TiCN layer (upper layer) on the Al ₂ O _3. Regardless of the fact that the grain growth of the upper layer is suppressed, it has excellent heat resistance even when it is used for high-speed hard interrupted cutting that involves high heat generation and intermittent and impact loads on the cutting edge. It has been found that it exhibits chipping properties and excellent wear resistance over a long period of use.

The present invention has been made based on the above knowledge,
In a surface-coated cutting tool in which a hard coating layer is formed on the surface of a tool base composed of tungsten carbide-based cemented carbide or titanium carbonitride-based cermet,
The hard coating layer has a total average layer thickness of (a) 3 to 20 μm from the tool base side, and is a Ti carbide layer, nitride layer, carbonitride layer, carbonate layer, or carbonitride oxide layer. A lower layer composed of one or two or more Ti compound layers,
(B) an intermediate layer comprising an aluminum oxide layer having an average layer thickness of 1 to 15 μm,
(C) an upper layer comprising a modified Ti carbonitride layer having a vertically grown crystal structure with an average layer thickness of 4 to 14 μm,
With a laminated structure of
(D) The modified Ti carbonitride layer having the vertically grown crystal structure that constitutes the upper layer has a vertical cross-section polished surface of the entire upper layer along the layer thickness direction from the upper layer surface by Auger electron spectroscopy. When the B content is subjected to AES line analysis over a B area, the B content region observed as a peak of the B content is at least spaced from the surface in the range of 0.5 to 4.0 μm in the depth direction on the inner side. One surface-covered cutting tool that appears and has an average B content in the B-containing region of 1.5 to 3.0 atomic%. "
It has the characteristics.

Next, the constituent layers of the hard coating layer of the coated tool of the present invention will be described in detail.
(A) Lower layer (Ti compound layer)
Ti compound layer consisting of one or more of TiC layer, TiN layer, TiCN layer (including 1-TiCN layer), TiCO layer, TiCNO layer itself has high temperature strength. In addition to the high temperature strength of the hard coating layer, the hard coating layer firmly adheres to both the tool base and the Al ₂ O ₃ layer, which is an intermediate layer, and thus contributes to improving the adhesion of the hard coating layer to the tool base. However, if the total average layer thickness is less than 3 μm, the above-mentioned effect cannot be sufficiently exerted. On the other hand, if the total average layer thickness exceeds 20 μm, chipping is particularly caused by high-speed, strong intermittent cutting with high heat generation. The total average layer thickness is determined to be 3 to 20 μm because it is easy to occur.

(B) Intermediate layer (Al ₂ O ₃ layer)
The intermediate layer composed of the Al ₂ O ₃ layer formed on the lower layer has excellent high-temperature hardness and heat resistance, and has an effect of improving the wear resistance of the hard coating layer, but the average layer thickness is If the thickness is less than 1 μm, the hard coating layer cannot exhibit sufficient wear resistance. On the other hand, if the average thickness exceeds 15 μm, chipping tends to occur. Was set to 1 to 15 μm.

(C) Upper-layer modified l-TiCN layer The upper layer composed of the modified l-TiCN layer formed on the intermediate layer is obtained by incorporating TiB ₂ that is hexagonal into the cubic TiCN crystal structure. From this point, TiCN nuclei are reformed to prevent coarsening of TiCN particles. In addition, since TiB ₂ is formed intermittently a plurality of times in a short time, a TiB ₂ layer is not formed, and a B-rich region exists, that is, a B-containing region. Therefore, since the cubic crystal structure of TiCN is not completely divided, the toughness of the TiCN crystal is not impaired.
Here, if the average layer thickness of the upper layer is less than 4 μm, the wear resistance cannot be ensured over a long period of use. On the other hand, if it exceeds 14 μm, the chipping resistance and chipping resistance are increased due to the thickening of the layer. Decreases. Therefore, the average layer thickness of the upper layer was set to 4 to 14 μm.
As described above, the modified l-TiCN layer is formed in the middle of a film forming process for depositing the l-TiCN layer under normal conditions, for example, the film formation of the l-TiCN layer having a predetermined target layer thickness is completed. The reaction atmosphere pressure was reduced to 3.0 to 3.5 kPa at a time before 30 minutes, and at the same time, BCl ₃ was reacted for 60 to 80 seconds so that the ratio of the reaction gas to the reaction gas was 0.8 to 2.2% by volume. A film is formed by adding it to the gas, and thereafter, an l-TiCN layer is formed until a predetermined target layer thickness is reached in accordance with normal conditions. It can be formed by repeating this step a predetermined number of times (at least once). As shown in FIG. 2, at least one B-containing region is formed at a predetermined interval inside the formed modified l-TiCN layer, and crystals of the modified l-TiCN layer in the B-containing region are formed. The grain becomes a refined structure.

When the B content is linearly analyzed along the layer thickness direction by Auger electron spectroscopy on the vertical cross-section polished surface of the modified l-TiCN layer, the inner surface extends along the layer thickness direction from the surface of the modified l-TiCN layer. There is at least one B-containing region in which a plurality of peaks of B content appear with an interval in the range of 0.5 to 4.0 μm on the side, and the average content of B in the B-containing region is 1.5 to 3.0 atomic%.
Here, since the B-containing region in the present invention does not form a continuous layer of TiB ₂ as described above, irradiation was performed along the layer thickness direction of the vertical cross-section polished surface by AES line analysis by Auger electron spectroscopy. At the beam position, as shown in FIG. 3, there is a problem that when TiB ₂ happens to be absent, B cannot be detected, and it cannot be detected even though the B-containing region exists. Therefore, in the present invention, AES line analysis was performed at five locations at equal intervals in the horizontal direction with respect to the modified l-TiCN layer, and the peak of the B content was detected. And when a peak is detected even at one place, it is set as a B-containing region, and the maximum peak of each B content detected by the AES line analysis at five places at that time is averaged, and the B content is obtained. The average content of B in the region (atomic%) was determined.

  When the interval between the B-containing regions is less than 0.5 μm, the strength of the modified l-TiCN layer grown by nucleation of new TiCN crystals is insufficient, and peeling due to in-layer fracture during processing occurs. On the other hand, when the interval between the B-containing regions is on the inner side exceeding 4.0 μm, the grain size of the modified l-TiCN layer grown by nucleation of new TiCN crystals becomes too large. Therefore, the interval between the B-containing regions is set to 0.5 to 4.0 μm.

Further, when the average content of B in the B-containing region is less than 1.5 atomic%, nucleation of new TiCN crystals is not sufficient, and therefore in the modified l-TiCN layer on the upper layer side from the B-containing region. On the other hand, when the average content of B in the B-containing region exceeds 3.0 atomic%, TiB ₂ having a different crystal structure is formed as a layer, which causes peeling. The B content at the peak position needs to be 1.5 to 3.0 atomic%.

Furthermore, in the present invention, in the modified l-TiCN layer formed on the intermediate layer (Al ₂ O ₃ layer), at least one B-containing region where a peak of B content exists at the predetermined interval is formed. As a result, the crystal grains of the modified l-TiCN layer in this B-containing region become finer, the adhesion with the Al ₂ O ₃ layer of the intermediate layer is improved, and usually on the Al ₂ O ₃ layer When the Ti compound layer is formed, the crystal grains become coarse. However, in the present invention, the crystal grains of the modified l-TiCN layer are refined, and the deterioration of chipping resistance and wear resistance due to the coarsening of the crystal grains is suppressed. can do. Further, since oxygen atoms are not added when forming the modified l-TiCN layer, the toughness of the TiCN layer is not reduced and chipping during cutting is reduced.

The coated tool of the present invention deposits a modified l-TiCN layer (upper layer) having at least one B-containing region and having a refined structure on an Al ₂ O ₃ layer (intermediate layer). As a result, the adhesion between the intermediate layer and the upper layer is improved, and at the same time, coarsening of crystal grains of the modified l-TiCN layer of the upper layer is suppressed, and oxygen is substantially contained in the upper layer. Since the reduction in toughness is suppressed, it exhibits excellent chipping resistance even when used for high-speed, heavy-duty cutting with high heat generation and intermittent / impact loads on the cutting edge. It exhibits excellent wear resistance over a long period of use.

It is a schematic diagram which shows the crystal structure of the NaCl type face centered cubic crystal which the modified l-TiCN layer which comprises the upper layer of a hard coating layer has. It is a schematic longitudinal cross-sectional schematic diagram which shows an example of the longitudinal cross-section structure | tissue structure of a hard coating layer. It is a conceptual diagram of the identification method of the B containing area | region by Auger electron spectroscopy of the modified l-TiCN layer in this invention.

  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 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 WC-based cemented carbide having an insert 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, 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 then pressed into a compact at a pressure of 98 MPa, This green compact is sintered in a nitrogen atmosphere of 1.3 kPa at a temperature of 1540 ° C. for 1 hour, and after sintering, the cutting edge portion is subjected to a honing process of R: 0.07 mm. -Tool bases a to f made of TiCN-based cermet having the insert shape of CNMG12041 were formed.

Next, on the surfaces of these tool bases A to F and tool bases a to f, the combination shown in Table 5 is used as a lower layer of the hard coating layer using a normal chemical vapor deposition apparatus under the conditions shown in Table 3. A Ti compound layer (however, excluding the modified l-TiCN layer) is formed by vapor deposition.
Subsequently, an Al ₂ O ₃ layer as an intermediate layer is formed by vapor deposition under the conditions shown in Table 3 and with the target layer thickness shown in Table 5 again, and then the upper layer is formed under the conditions shown in Table 4. The coated tools 1 to 13 of the present invention were produced by vapor-depositing the modified l-TiCN layers as layers in the combinations shown in Table 5 and with the target layer thickness.
Further, for reference purposes, the same tool base and lower layer as those of the present coated tool 1, 3, 8, 9 are formed on the intermediate layer, and the upper layer is formed by changing the forming conditions from the present invention. Coated tools 1, 3, 8, and 9 were produced.

Further, for the purpose of comparison, as a lower layer of the hard coating layer, a Ti compound layer is formed by vapor deposition with the combination shown in Table 6 and the target layer thickness also shown in Table 6 under the conditions shown in Table 3. Thereafter, an Al ₂ O ₃ layer as an intermediate layer is formed by vapor deposition at the target layer thickness shown in Table 6 under the conditions shown in Table 3, and then as an upper layer under the conditions shown in Table 3. Conventional coated tools 1 to 13 were manufactured by vapor-depositing normal l-TiCN layers with the target layer thicknesses shown in Table 6 as well.

  Next, with respect to the modified l-TiCN layer of the coated tool of the present invention, the B content along five lines arranged at equal intervals in the horizontal direction in the layer thickness direction by Auger electron spectroscopy on the vertical cross-section polished surface The line analysis is performed to obtain each peak position where the peak of the B content appears, and when any one of the five lines appears, the position is set as the B-containing region, and further, the five lines at that time The average value of B content calculated | required from each upper peak of the top was calculated | required, and it was defined as the average content of B of the B content area | region.

  Table 5 shows the value of the average content of B in each B-containing region of the present coated tool and the reference coated tool.

  Similarly, the B content of the l-TiCN layer of the conventional coated tool was linearly analyzed, but B was not contained.

Further, for the modified l-TiCN layer of the coated tool of the present invention, grains per unit area of the modified l-TiCN crystal grains in each B-containing region using a field emission scanning electron microscope and an electron backscatter diffraction image apparatus. The boundary length is obtained, and the grain boundary length per unit area of the crystal grains on the inner side from each B-containing region is obtained, and the crystal refinement ratio R _{TiCN of} each B-containing region (where R = (B containing The grain boundary length per unit area of the modified l-TiCN crystal grains in the region / (grain boundary length per unit area of the modified l-TiCN crystal grains on the inner side from the B-containing region) was calculated.

  Here, the grain boundary length per unit area of the modified l-TiCN crystal grains can be measured and calculated as follows.

That is, the modified l-TiCN layer is set in a lens barrel of a field emission scanning electron microscope in a state where the vertical cross section of the modified l-TiCN layer is a polished surface. A line is irradiated at an irradiation current of 1 nA to individual crystal grains existing within the measurement range of the vertical cross-section polished surface, and an electron backscatter diffraction image apparatus is used, and a predetermined measurement region is spaced at an interval of 0.1 μm / step. The inclination angle formed by the normal lines of the (001) plane and the (011) plane, which are the crystal planes of the crystal grains, is measured with respect to the normal line of the vertical cross-section polished surface. Then, the angles at which the (001) plane normal lines and the (011) plane normal lines cross each other at the interface between adjacent crystal grains are obtained, and the (001) plane normal lines and ( 011) The angle at which the surface normals intersect is 2 degrees After setting the above case as a grain boundary, a field emission scanning electron microscope is used to scan the longitudinal cross-section measurement region in the B-containing region of the modified l-TiCN layer and identify it as a grain boundary in the measurement region The length GB _LO (μm) of the portion to be measured was determined, and the value GB _LO / G _AO of the ratio to the measured area G _AO (μm ² ) of the vertical cross-section polished surface was determined.

Similarly, the longitudinal cross-sectional measurement region on the inner side from the B-containing region of the modified l-TiCN layer is scanned, and the length GB _LI (μm) of the portion identified as the grain boundary in the measurement region is obtained, then, to determine the value _GB LI _{/ G AI} ratio between the area _{G AI} of the measured longitudinal sectional polished surface (μm ^2).

Next, GB _LO / G _AO (corresponding to the grain boundary length per unit area in the B-containing region) and GB _LI / G _AI (corresponding to the grain boundary length per unit area on the inner side from the B-containing region) ) Was determined and this was defined as the crystal refinement rate R _TiCN of the modified l-TiCN layer.

That is, the crystal refinement ratio R _TiCN
= (Grain boundary length per unit area of modified l-TiCN crystal grains in the B-containing region) / (grain boundary length per unit area of modified l-TiCN crystal grains inside the B-containing region)
= (GB _LO / G _AO ) / (GB _LI / G _AI )
It is.

Table 5 shows the value of the crystal refining rate R _TiCN of each B-containing region for the modified l-TiCN layer of the coated tool of the present invention.

As shown in Table 5, it can be seen that the modified l-TiCN layer of the coated tool of the present invention has a crystal refinement ratio R _TiCN larger than 15.8, and crystal grains are refined in the B-containing region. .

  In addition, when the thickness of the lower layer, the intermediate layer, and the upper layer of the coated tool of the present invention and the conventional coated tool was measured using the scanning electron microscope (same longitudinal section measurement), all were substantially equal to the target layer thickness. The same average layer thickness (average value of 5-point measurement) was shown.

Next, the coated tools of the present invention 1 to 13, the conventional coated tools 1 to 13, and the reference coated tool 1 in the state in which each of the various coated tools is screwed to the tip of the tool steel tool with a fixing jig. 3, 8, 9
Work material: JIS / SKD12 lengthwise equidistant four round grooved round bars,
Cutting speed: 280 m / min. ,
Incision: 2.5mm,
Feed: 0.3 mm / rev. ,
Cutting time: 18 minutes
Wet high-speed strong interrupted cutting test of alloy tool steel under the conditions (cutting condition A) (normal cutting speed is 200 m / min.),
Work material: JIS · SKD62 lengthwise equidistant four round grooved round bars,
Cutting speed: 300 m / min. ,
Incision: 2.5mm,
Feed: 0.5 mm / rev. ,
Cutting time: 15 minutes,
Dry high-speed strong interrupted cutting test of alloy tool steel under the conditions (cutting condition B) (normal cutting speed is 180 m / min.),
Work material: JIS / SKD4 lengthwise equidistant four round grooved round bars,
Cutting speed: 320 m / min. ,
Incision: 1.5mm,
Feed: 0.6 mm / rev. ,
Cutting time: 18 minutes
Dry high-speed continuous cutting test of alloy tool steel under the following conditions (cutting condition C) (normal cutting speed is 200 m / min.),
In each cutting test, the flank wear width of the cutting edge was measured.
The measurement results are shown in Table 7.

From the results shown in Tables 5 to 7, the coated tools 1 to 13 of the present invention have a B-containing region and a modified l-TiCN layer (upper layer) having a refined structure is formed. As a result, the adhesion between the intermediate layer and the upper layer is improved, and at the same time, the coarsening of crystal grains of the modified l-TiCN layer of the upper layer is suppressed. Even when used for high-speed, heavy-duty cutting that requires an impact load, it exhibits excellent chipping resistance and excellent wear resistance over a long period of use.

  On the other hand, as the upper layer of the hard coating layer, in the conventional coated tools 1 to 13 having the B-containing region and the modified l-TiCN layer having a refined structure is not formed, the upper layer In this case, the crystal grains are likely to be coarsened, and therefore, the adhesion and wear resistance between the intermediate layer and the upper layer are not sufficient, resulting in high heat generation and high-speed strong force that causes intermittent and impact loads on the cutting edge. In intermittent cutting, it is clear that chipping, chipping, peeling, etc. occur and the service life is reached in a relatively short time.

  In addition, the reference coated tools 1, 3, 8, and 9, which have a B-containing region but whose B average content is not in the range of 1.5 to 3.0 atomic%, have a service life as compared with the conventional coated tools. However, it is clear that the modified layer of the upper layer 1-TiCN layer is not sufficient in suppressing the grain coarsening and reaches the service life in a relatively short time.

  As described above, the coated tool of the present invention exhibits excellent chipping resistance and wear resistance in high-speed hard interrupted cutting such as alloy tool steel, and exhibits excellent cutting performance over a long period of time. It can cope with high performance of cutting equipment, labor saving and energy saving of cutting, and cost reduction.

Claims (1)

In a surface-coated cutting tool in which a hard coating layer is formed on the surface of a tool base composed of a tungsten carbide-based cemented carbide or a titanium carbonitride-based cermet,
The hard coating layer has a total average layer thickness of (a) 3 to 20 μm from the tool base side, and is a Ti carbide layer, nitride layer, carbonitride layer, carbonate layer, or carbonitride oxide layer. A lower layer composed of one or two or more Ti compound layers,
(B) an intermediate layer comprising an aluminum oxide layer having an average layer thickness of 1 to 15 μm,
(C) an upper layer comprising a modified Ti carbonitride layer having a vertically grown crystal structure with an average layer thickness of 4 to 14 μm,
With a laminated structure of
(D) The modified Ti carbonitride layer having the vertically grown crystal structure that constitutes the upper layer has a vertical cross-section polished surface of the entire upper layer along the layer thickness direction from the upper layer surface by Auger electron spectroscopy. When the B content is subjected to AES line analysis over a B area, the B content region observed as a peak of the B content is at least spaced from the surface in the range of 0.5 to 4.0 μm in the depth direction on the inner side. One surface-covered cutting tool that appears and has an average B content in the B-containing region of 1.5 to 3.0 atomic%.