JP6050183B2 - Cutting tools - Google Patents

Description

  The present invention relates to a cutting tool that exhibits excellent wear resistance in, for example, cutting of steel or the like.

  As a cutting tool, a coating tool in which a coating layer is formed on the surface of a substrate such as cemented carbide or cermet to improve wear resistance, slidability, and fracture resistance is widely used.

For example, in Patent Document 1, a Ti compound layer of TiN or TiCN and an Al ₂ O ₃ layer are formed in a thickness of ₃ to 30 μm on the surface of a cemented carbide substrate, and then the outermost surface underlayer of the TiOx layer is set to a thickness of 0.03. 1 to 3 μm, and a cutting tool formed with a hard coating layer having a structure in which a TiCNO (O is oxygen diffused from the outermost surface underlayer) layer is laminated in the order of 0.05 to 2 μm, is disclosed. It is described that the workability of a highly viscous work material such as stainless steel or mild steel is low in affinity to chips and is excellent in welding resistance.

  Patent Documents 2 and 3 disclose a method of smoothing the surface of the coating layer by polishing the surface of the coating layer after forming a coating layer similar to the above configuration.

JP 2001-310203 A JP 2008-055581 A JP 2006-297585 A

  However, in the configuration of Patent Documents 1-3, since the surface of the coating layer has a TiCNO layer, although the welding resistance to chips is improved, it is insufficient, and the TiCNO layer has a low hardness and is relatively fast. There was a problem that it was worn out and the effect of suppressing welding hardly lasted.

  An object of the present invention is to provide a cutting tool that can maintain good welding resistance for a long time during cutting and has a long tool life.

The cutting tool of the present invention is provided with a coating layer composed of multiple layers on the surface of the substrate, and the outermost layer of the coating layer comprises at least one of a TiC phase, a TiN phase, and a TiCN phase, and a Ti ₃ O ₅ phase. In addition, the content ratio of the Ti ₃ O ₅ phase of the outermost layer is such that the substrate side is less than the surface side.

According to the present invention, since the outermost layer contains the Ti ₃ O ₅ phase together with at least one of the TiC phase, the TiN phase, and the TiCN phase, the affinity with the work material that contacts when cutting is low. High resistance to welding. Moreover, since the content of the Ti ₃ O ₅ phase in the outermost layer is less on the substrate side than on the surface side of the outermost layer, the hardness of the outermost layer is higher on the substrate side than on the surface side, and the surface of the outermost layer Then, high welding resistance can be exhibited. Therefore, the surface of the outermost layer that is most likely to be welded by first contacting the work material has excellent welding resistance, and T
The effect of preventing welding is maintained even on the substrate side of the outermost layer having a small content ratio of the i ₃ O ₅ phase. Furthermore, the progress of wear of the outermost layer is slow, and as a result, high wear resistance is sustained for a long time.

BRIEF DESCRIPTION OF THE DRAWINGS About an example of the insert which is a suitable embodiment of the cutting tool of this invention, (a) Schematic perspective view, (b) The principal part expanded sectional view containing a coating layer.

  An example of an insert which is an embodiment of the cutting tool of the present invention will be described based on the schematic perspective view of FIG.

In the insert 1, as shown in FIG. 1A, the intersecting ridge line portion of the rake face 2 and the flank 3 constitutes a cutting edge 4, and as shown in FIG. On the surface, one or more layers of Ti carbide, nitride, carbonitride, carbonate, nitride oxide and carbonitride (7 to 11 in FIG. 1 (b)) and Al of α-type crystal structure There is provided a coating layer in which a ₂ O ₃ layer (hereinafter simply referred to as an Al ₂ O ₃ layer) 12 and an outermost layer 14 containing a Ti ₃ O ₅ phase are sequentially laminated. Note that the insert 1 in FIG. 1A has a plate shape and a principal surface having a substantially square shape. In addition, the content ratio of the Ti ₃ O ₅ phase in the outermost layer 14 is configured to be less on the substrate side than on the surface side of the outermost layer 14.

With this configuration, the surface of the outermost layer 14 where the insert 1 first comes into contact with the work material and is most likely to be welded can exhibit high welding resistance, and the wear resistance of the outermost layer 14 is higher on the substrate side than on the surface side. It is high. As a result, the welding resistance is excellent and the effect of preventing welding is maintained for a long time. Moreover, since the Ti ₃ O ₅ phase exhibits a blue color, when the lower layer of the outermost layer 14 or the substrate 6 is black, it is visually confirmed that the outermost layer 14 is worn and used when the insert 1 is used. It can be easily confirmed, and when viewed later, it can be easily determined whether the insert 1 is unused or used, and the progress of wear can be easily confirmed.

Here, in this embodiment, the content ratio of the Ti ₃ O ₅ phase in the outermost layer 14 gradually decreases from the surface side of the outermost layer 14 toward the substrate side. With this configuration, the outermost layer 14 has high welding resistance, and wear resistance and fracture resistance are also high.

In the present invention, the content ratio of the Ti ₃ O ₅ phase of the outermost layer 14 can be confirmed by thin film X-ray diffraction measurement with respect to the surface of the outermost layer 14. Specifically, the peak intensities detected by the X-ray diffraction measurement are added together as a denominator, and the peak intensity of the peak due to the Ti ₃ O ₅ phase is added up and calculated as a numerator. The content ratio of Ti ₃ O ₅ phase can be determined. Incidentally, when the peak of the lower layer to the X-ray diffraction pattern (e.g., the Al ₂ O ₃ layer, etc.) is present, it not included in the above calculations. Further, if the outermost layer 14 is polished obliquely and X-ray diffraction measurement is performed in order from a region with a small amount of polishing, the content ratio of the Ti ₃ O ₅ phase with respect to the depth direction of the outermost layer 14 can be confirmed. In this embodiment, the content ratio of the Ti ₃ O ₅ phase on the surface of the outermost layer 14 is 20 to 40%. As a result, the effect of suppressing the welding to the work material can be sufficiently exhibited.

Here, when the outermost layer containing the Ti ₃ O ₅ phase is formed by film formation, the film tends to be concentrated on the cutting edge portion 4 of the insert 1. However, according to the film forming method of the insert 1 of this embodiment described later, the outermost layer 14 including the Ti ₃ O ₅ phase can be formed with a uniform thickness. As a result, the ratio (t _c / t _f ) between the average thickness t _c of the outermost layer 14 at the cutting edge portion 4 and the average thickness t _f of the outermost layer 14 at the flank 3 is 0.8 to 1.2, and the ratio of the average thickness _{t f} of the outermost layer 14 in the average thickness _{t r} and the flank 3 of the outermost layer 14 on the rake face 2 _(t r / t _f) may be 0.8 to 1.2. Ratio (t _c / t _f ) and ratio ( _tr
If / t _f ) is within this range, the balance between wear resistance and fracture resistance at the cutting edge portion 4, rake face 2 and flank face 3 is good. In addition, according to this method, the content ratio of the Ti ₃ O ₅ phase can be gradually reduced from the surface side of the outermost layer 14 toward the substrate 6 side.

In the present embodiment, the outermost layer 14 contains a Ti ₄ O ₇ phase in addition to the Ti ₃ O ₅ phase. As a result, the Ti ₄ O ₇ phase has a high welding resistance in the same manner as the Ti ₃ O ₅ phase, so that the welding resistance of the insert 1 can be increased. In this embodiment, the content ratio of the Ti ₄ O ₇ phase on the surface of the outermost layer 14 is 5 to 25%.

Furthermore, in the present embodiment, the outermost layer 14 contains at least one of a TiC phase, a TiN phase, and a TiCN phase in addition to the Ti ₃ O ₅ phase, and by adjusting these content ratios, The wear resistance of the surface layer 14 can be increased, and the color of the insert 1 can be freely adjusted. That is, when a TiN phase and a Ti ₃ O ₅ phase coexist, it becomes light blue, and when a TiC phase or a TiCN phase and a Ti ₃ O ₅ phase coexist, it becomes a group blue. For example, it is possible to change the color between differently shaped inserts and visually distinguish the inserts.

Here, in the present embodiment, it is a ratio (longest length / average width) of the longest length of each particle constituting the outermost layer 14 when viewed in plan and the average width of particles in a direction perpendicular thereto. The average value of the aspect ratio is larger on the substrate 6 side than on the surface side. That is, the shape of the particles constituting the outermost layer 14 seen at the surface side position of the outermost layer 14 is granular, whereas the particles constituting the outermost layer 14 seen at the position of the outermost layer 14 on the substrate 6 side. The shape is needle-like. Thus, the outermost layer 14 has good adhesion with the Al ₂ O ₃ layer 12. As a result, chipping of the outermost layer 14 can be suppressed. In order to continuously confirm the shape viewed from the surface of the particles constituting the outermost layer 14 between the surface side and the substrate 6 side, the outermost layer 14 is polished obliquely and the polished surface is scanned. By observing with an electron microscope (SEM) and using electron backscatter diffraction (EBSD) color mapping, the orientation of each crystal surface of the coating layer is confirmed to identify the contour of each crystal, and the coating The average aspect ratio of the particles constituting the outermost layer 14 in plan view of the layer can be continuously confirmed from the surface side to the substrate side. In this embodiment, the average aspect ratio of the particles constituting the outermost layer 14 in plan view of the coating layer is gradually increased from the surface side toward the substrate 6 side.

  In the present embodiment, the ratio of nitrogen to carbon is larger on the surface side than on the substrate 6 side of the outermost layer 14. Thereby, the outermost layer 14 exhibits a bright color with higher brightness, and the use / non-use of the insert can be easily determined visually. In addition, in order to confirm the distribution of the ratio of nitrogen to carbon in the outermost layer 14, the outermost layer 14 is polished obliquely, and the content ratio of nitrogen and carbon is confirmed by an electron beam microanalyzer (EPMA) on the polished surface. Or X-ray photoelectron spectroscopy (XPS). In the present embodiment, the ratio of nitrogen to carbon gradually increases from the substrate 6 side to the surface side of the outermost layer 14.

  Moreover, in this embodiment, the average thickness of the outermost layer 14 in the rake face 2 is 0.2-1 micrometer, and surface roughness (Ra) is 0.05-2 micrometers. Thereby, the welding resistance of the outermost layer 14 can be further increased, and the wear resistance and chipping resistance are high.

Next, the Al ₂ O ₃ layer 12 formed below the outermost layer 14 (base 6) will be described. In this embodiment, _Al 2 _{O 3} crystals constituting the _{the Al} 2 _{O 3} layer 12 is α-type crystal structure. The average crystal width as viewed from the direction perpendicular to the surface of the substrate 6 is 0.05 to 0.7 μm. This increases the wear resistance of the insert 1. The average thickness of the Al ₂ O ₃ layer 12 in this embodiment is _{3 to} 10 μm. With this thickness, no lower peak than the Al ₂ O ₃ layer 12 is detected in the X-ray diffraction measurement.

In the present embodiment, one or more layers selected from the group of TiC, TiN, TiCN, TiCNO, TiCO, and TiNO are provided on the base 6 side of the Al ₂ O ₃ layer 12. Thus, the wear resistance and fracture resistance are improved by the Al ₂ O ₃ layer 12 and its lower layer. According to this embodiment, as a specific configuration, as shown in FIG. 1B, a TiN layer 7 is provided as a first layer and a TiCN layer 8-10 is provided as a second layer immediately above the base 6. Is provided. According to this embodiment, the average thickness of the TiN layer 7 is 0.05 to 2 μm, and the average thickness of the TiCN layer 8-10 is 3 to 15 μm in total.

As the TiCN layer 8-10, so-called MT-TiCN layers 8 and 9 made of columnar crystals formed at a relatively low film formation temperature of 780 to 900 ° C. containing acetonitrile (CH ₃ CN) gas as a raw material, It has a configuration in which a so-called HT-TiCN layer 10 formed at a high film formation temperature of 950 to 1100 ° C. is formed in order. Further, the MT-TiCN layers 8 and 9 are composed of a fine MT-TiCN layer 8 made of fine fine columnar crystals having an average crystal width of less than 0.5 μm, and a coarse columnar shape having a relatively large average crystal width of 0.5 to 2 μm. It consists of a lamination with a coarse MT-TiCN layer 9 made of crystals. Thereby, the adhesive force with the Al ₂ O ₃ layer 12 is increased, and peeling and chipping of the coating layer can be suppressed.

In this embodiment, an intermediate layer 11 made of TiCNO having an average thickness of 0.05 to 0.5 μm is provided on the surface of the HT-TiCN layer 10. As a result, the α-type Al ₂ O ₃ layer 12 made of Al ₂ O ₃ crystals having an α-type crystal structure with an average particle size of 0.05 to 0.7 μm can be more easily produced on the surface of the intermediate layer 11 described later. it can.

  The thickness of each layer and the properties of the crystals constituting each layer should be measured by observing an electron micrograph (scanning electron microscope (SEM) photograph or transmission electron microscope (TEM) photograph) in the cross section of the insert 1. Is possible. In the present invention, the crystal form of the crystals constituting each layer of the coating layer is columnar. The average ratio of the average crystal width to the length of the coating layer in the thickness direction is 0.3 or less on average. Refers to the state. On the other hand, when the ratio of the average crystal width to the length in the thickness direction of the coating layer of each crystal exceeds 0.3 on average, the crystal form is defined as granular.

On the other hand, the base 6 of the insert 1 is a hard material composed of tungsten carbide (WC) and, if desired, at least one selected from the group consisting of carbides, nitrides, and carbonitrides of Group 4, 5, and 6 metals of the periodic table. Cemented carbide, Ti-based cermet, or Si ₃ N ₄ , Al ₂ O ₃ , diamond, cubic nitridation in which phases are bonded with a binder phase composed of an iron group metal such as cobalt (Co) or nickel (Ni) Ceramics such as boron (cBN) can be used. In particular, when the insert 1 is used as a cutting tool, the base 6 may be made of cemented carbide or cermet in terms of fracture resistance and wear resistance. Depending on the application, the substrate 6 may be made of a metal such as carbon steel, high-speed steel, or alloy steel.

(Production method)
A method for manufacturing the insert of this embodiment will be described.

  First, metal powder, carbon powder, etc. are appropriately added to and mixed with inorganic powders such as metal carbides, nitrides, carbonitrides, and oxides that can be formed by firing the hard alloy described above, press molding, cast molding, A predetermined tool shape is formed by a known forming method such as extrusion molding or cold isostatic pressing. Then, the base body 6 mentioned above is produced by baking the obtained molded object in a vacuum or non-oxidizing atmosphere. Then, polishing or honing of the cutting edge portion is performed on the surface of the base as desired.

Next, a coating layer is formed on the surface of the obtained substrate 6 by chemical vapor deposition (CVD). First, a TiN layer is formed as a first layer directly on the substrate. The conditions for forming the TiN layer include, as a mixed gas composition, titanium tetrachloride (TiCl ₄ ) gas in a ratio of 0.5 to 10% by volume and nitrogen (N ₂ ) gas in a ratio of 10 to 60% by volume, with the remainder being hydrogen. Using a mixed gas composed of (H ₂ ) gas, the film is formed at a film forming temperature of 800 to 940 ° C. (in the chamber) and a pressure of 8 to 50 kPa.

  Next, a TiCN layer is formed as a second layer. Here, the TiCN layer is composed of three layers of an MT-TiCN layer of a fine columnar crystal layer having a small average crystal width, a coarse columnar crystal layer having a larger average crystal width than this layer, and an HT-TiCN layer. The film forming conditions for this will be described.

The film formation conditions of the fine columnar crystal layer in the MT-TiCN layer are as follows: titanium tetrachloride (TiCl ₄ ) gas is 0.5 to 10% by volume, nitrogen (N ₂ ) gas is 10 to 60% by volume, acetonitrile (CH ₃ CN) gas in a ratio of 0.1 to 0.4% by volume, and the remaining gas is a hydrogen (H ₂ ) gas, the film forming temperature is 780 to 900 ° C., and the pressure is 5 to 25 kPa. . The film formation conditions of the coarse columnar crystal layer in the MT-TiCN layer are as follows: titanium tetrachloride (TiCl ₄ ) gas is 0.5 to 4.0 vol%, nitrogen (N ₂ ) gas is 10 to 40 vol%, acetonitrile (CH ₃ CN) gas is contained at a ratio of 0.4 to 2.0% by volume, and the remaining gas is a hydrogen (H ₂ ) gas mixed gas, the film forming temperature is 780 to 900 ° C., and the pressure is 5 to 25 kPa. And

The HT-TiCN layer comprises titanium tetrachloride (TiCl ₄ ) gas in an amount of 0.1 to 4% by volume, methane (CH ₄ ) gas in an amount of 0.1 to 10% by volume, and nitrogen (N ₂ ) gas in an amount of 5 to 25% by volume. The film is formed at a film forming temperature of 950 to 1100 ° C. and a pressure of 5 to 40 kPa, using a mixed gas comprising the hydrogen (H ₂ ) gas.

The intermediate layer made of TiCNO is 950 to 1100 ° C. and 5 to 40 kPa in the chamber, 1 to 5% by volume of titanium tetrachloride (TiCl ₄ ) gas, ₄ to 10% by volume of methane (CH ₄ ) gas, nitrogen ( N ₂ ) gas is mixed in a volume of 10 to 30% by volume, carbon monoxide (CO) gas is 4 to 8% by volume, and the remainder is hydrogen (H ₂ ) gas, and introduced into the chamber for 10 to 60 minutes. To form a film. Note that the intermediate layer can be formed without passing the mixed gas containing CO gas, but in order to make the crystals constituting the α-type Al ₂ O ₃ layer fine, the CO gas is used. It is desirable to go through a process of flowing the mixed gas containing.

The film formation conditions for the Al ₂ O ₃ layer are as follows: aluminum trichloride (AlCl ₃ ) gas is 0.5 to 5.0% by volume, hydrogen chloride (HCl) gas is 0.5 to 3.5% by volume, carbon dioxide ( A mixed gas composed of 0.5 to 5.0% by volume of CO ₂ ) gas, 0 to 0.5% by volume of hydrogen sulfide (H ₂ S) gas, and the remaining hydrogen (H ₂ ) gas was introduced into the chamber. The film is formed at a film formation temperature of 950 to 1100 ° C. and a pressure of 5 to 10 kPa.

Further, an outermost layer is formed on the α-type Al ₂ O ₃ layer. For example, titanium tetrachloride (TiCl ₄ ) gas is 1 to 5% by volume, nitrogen (N ₂ ) gas is 0 to 30% by volume, acetonitrile (CH ₃ CN) gas or methane (CH ₄ ) gas is 0 to 1% by volume. Then, using the mixed gas of hydrogen (H ₂ ) gas as the remainder, the film forming temperature is 900 to 1100 ° C., the pressure is 5 to 10 Pa, and any one of the TiC layer, the TiN layer, and the TiCN layer is formed. At this time, a TiC layer is generated if nitrogen (N ₂ ) gas is not included. If acetonitrile (CH ₃ CN) gas or methane (CH ₄ ) gas is not included, a TiN layer is formed. Otherwise, a TiCN layer is generated. Any of these TiC layers, TiN layers or TiCN layers is formed with a uniform thickness within 20% of the rake face, flank face and cutting edge.

Thereafter, using a mixed gas of ₂ to 20% by volume of carbon dioxide (CO ₂ ) gas and 80 to 95% by volume of nitrogen (N ₂ ) gas, the temperature in the chamber is 900 to 1100 ° C., and the pressure is 5 to 10 Pa.
As described above, the surface of any one of the TiC layer, TiN layer, and TiCN layer on the surface is oxidized to change a part of the TiCN layer into a Ti ₃ O ₅ phase. According to this method, the content ratio of the Ti ₃ O ₅ phase in the outermost layer 14 can be reduced from the surface side of the outermost layer 14 toward the substrate side, and the average thickness t of the outermost layer in the cutting edge portion. the ratio of the outermost layer with an average thickness _{t f} in _c and a flank _(t c / t _f) the 0.8 to 1.2, and the outermost layer in the average thickness _{t r} and the flank of the outermost layer on the rake face The ratio (t _r / t _f ) to the average thickness t _f can be controlled to 0.8 to 1.2. As a result, the occurrence of color unevenness on the surface of the cutting tool can be suppressed, and a good appearance can be maintained.

  Then, if desired, polishing is performed from the surface of the outermost layer of the formed cutting tool. Thereby, the surface roughness of the outermost surface can be reduced, and the welding resistance of the outermost layer can be further improved.

  A metal cobalt (Co) powder with an average particle diameter of 1.2 μm is added to and mixed with tungsten carbide (WC) powder with an average particle diameter of 1.5 μm at a ratio of 6% by mass, and the cutting tool shape ( CNMG120412). The obtained compact was subjected to a binder removal treatment and fired at 1400 ° C. for 1 hour in a vacuum of 0.5 to 100 Pa to produce a cemented carbide. Furthermore, the cutting edge processing (R honing) was performed on the rake face side by brush processing on the manufactured cemented carbide.

  Next, various coating layers were formed on the cemented carbide by the CVD method under the film forming conditions shown in Table 1 and the layer configuration shown in Table 2. The surface of the coating layer, that is, the surface of the outermost layer was brushed.

With respect to the obtained insert, the coating layer on the rake face was observed with a scanning electron microscope, and the shape, average particle diameter (or average crystal width), and average thickness of crystals constituting each layer were estimated. In Table 2, that the crystal form of the crystals constituting each layer of the coating layer is columnar means that the ratio of the average crystal width to the length in the thickness direction of the coating layer of each crystal (average crystal width / thickness direction). (Length) is 0.3 or less on average, and the ratio of the average crystal width to the length in the thickness direction of the coating layer of each crystal (average crystal width / length in the thickness direction) is 0.00 on average. Those exceeding 3 indicate that the crystal form is granular. For example, sample no. 1, the crystal constituting the first layer has an average ratio of the average crystal width to the length in the thickness direction of the coating layer exceeding 0.3 on average.
A plurality of granular crystals exist in the thickness direction of the first layer. Further, the crystals constituting the second layer indicate that the ratio of the average crystal width to the length in the thickness direction of the coating layer is 0.3 or less on average.

Further, the surface roughness of the outermost layer, which is the surface of the coating layer, was measured with a stylus type surface roughness meter. Furthermore, the constituent component and the content ratio of the outermost layer were calculated by X-ray diffraction measurement of the outermost layer. Moreover, the coating layer was grind | polished diagonally and the change of the content rate of each structural component with respect to the depth direction of outermost layer was measured. The content ratio of Ti ₃ O ₅ at the position where the surface of the outermost layer is not polished and the thickness of 1/3 of the surface of the outermost layer on the obliquely polished surface is the surface side Ti ₃ O ₅ , the substrate side Ti ₃ O _5, the content of Ti ₄ O _7, surface _Ti 4 _{O 7,} was referred to as substrate-side _Ti 4 _{O 7.} Sample No. Regarding 1 to 4, it was confirmed that the content ratio of Ti ₃ O ₅ gradually decreased from the surface side to the substrate side. Moreover, the average thickness at the rake face, flank face and cutting edge of the outermost layer was measured. In the table, the rake face thickness, the flank face thickness, and the cutting edge thickness were respectively indicated. Further, the outermost layer 14 is polished obliquely, the polished surface is observed with a scanning electron microscope (SEM), and the surface of each crystal of the coating layer is subjected to electron backscatter diffraction (EBSD) color mapping. By confirming the orientation state, the contour of each crystal was specified, and the change from the surface side to the substrate side was confirmed with respect to the average aspect ratio of the particles constituting the outermost layer when the coating layer was viewed in plan. Further, an electron beam microanalyzer (EPMA) was used to confirm a change in the ratio of nitrogen to carbon from the substrate side to the surface side of the outermost layer. The change of the average aspect ratio from the surface side to the substrate side was expressed as the substrate side aspect ratio, and the change in the ratio of nitrogen to carbon was expressed as the surface side CN ratio. The results are shown in Tables 2-4.

Next, a cutting test was performed using the insert under the following two cutting conditions. The results are shown in Table 4.
(Abrasion evaluation)
Cutting method: Turning work material: SCM415
Cutting speed: 300 m / min Feed: 0.35 mm / rev
Cutting depth: 2.0mm
Cutting state: Wet evaluation method: Time for flank wear to be 0.3 mm or more (indicated in the table as wear evaluation life) and the state of the cutting edge at that time (intermittent evaluation)
Cutting method: Turning work material: SCM440 (with 4 grooves)
Cutting speed: 300 m / min Feed: 0.35 mm / rev
Cutting: 1.5 minutes Cutting state: Wet evaluation method: Number of impacts until the cutting edge is broken (in the table, described as intermittent evaluation life)

From the results shown in Tables 1 to 4, Sample No. having no Ti ₃ O ₅ phase on the outermost layer was obtained. In No. 5, the welding resistance of the outermost layer was insufficient. In addition, a Ti ₃ O ₅ phase was generated in the outermost layer by film formation, and the content ratio of the Ti ₃ O ₅ phase in the outermost layer was the same on the surface side and the substrate side. In No. 6, the outermost layer was worn quickly and the tool life was short. On the other hand, sample No. which is within the scope of the present invention. In 1-4 and 7, the welding resistance was high and the tool life tended to be long.

1 insert 2 rake face 3 flank face 4 the cutting edge 6 base 7 TiN layer 8, 9 MT-TiCN layer 10 HT-TiCN layer 11 intermediate layer 12 _Al 2 _{O 3} layer 14 outermost layer

Claims (5)

A coating layer composed of multiple layers is provided on the surface of the substrate, and the outermost layer of the coating layer contains at least one of a TiC phase, a TiN phase and a TiCN phase, and a Ti ₃ O ₅ phase, and the outermost layer A cutting tool in which the content of the Ti ₃ O ₅ phase is less on the substrate side than on the surface side. The ratio (t _c / t _f ) between the average thickness t _{c of the} outermost layer at the cutting edge part and the average thickness t _f of the outermost layer at the flank is 0.8 to 1.2, and the ratio at the rake face is the cutting tool of claim 1 wherein the ratio of the outermost layer of average thickness _{t f (t r / t f} ) is 0.8 to 1.2 in the flank face and the average thickness _{t r} of the outermost layer. The cutting tool according to claim 1, wherein the outermost layer contains a Ti ₄ O ₇ phase in addition to the Ti ₃ O ₅ phase.   The cutting tool according to any one of claims 1 to 3, wherein an average aspect ratio of particles constituting the outermost layer in a plan view of the coating layer is larger on the base side than on the surface side.   The cutting tool according to any one of claims 1 to 4, wherein the surface side of the outermost layer has a larger proportion of nitrogen to carbon on the surface side.