JP6169913B2 - Cutting tools - Google Patents

Description

  The present invention relates to a cutting tool in which the surface of a substrate made of a cemented carbide is coated with a coating layer.

  2. Description of the Related Art Conventionally, as a cutting tool that has been widely used for cutting metal or the like, a cemented carbide coated with a coating layer is preferably used. For example, Patent Document 1 discloses that a plasma CVD method is used to optimize the position on which a substrate is placed when forming a film, and a coating layer that covers the cutting blade and a coating layer that covers the rake and flank surfaces. The structure which varied the film quality is disclosed. Further, in Patent Document 2, after the coating layer is formed, the surface of the coating layer is polished so that the surface state of the coating layer coated on the rake face side and the coating layer coated on the flank face side are different. The configuration is disclosed. In either case, it is described that the cutting performance required for each part is optimized to provide a cutting tool that can be used for a long time.

Japanese Patent Laid-Open No. 7-80703 JP 2011-230286 A

  However, in the cutting tool described in Patent Documents 1 and 2, the film quality or surface state of the coating layer is different depending on each part, the adhesion between the substrate and the coating layer is not improved. Sometimes peeled off or chipped.

  An object of the present invention is to provide a cutting tool that can be used for a long time by improving the adhesion between the substrate and the coating layer, optimizing the cutting performance required for the rake face and the flank face.

The cutting tool of the present invention is such that the surface of the substrate made of a cemented carbide containing WC particles is coated with a coating layer, with the intersection ridge line between the rake face and the flank face as the cutting edge, and the rake face side The average particle diameter dr of the WC particles in a region 300 μm or more away from the cutting edge on the surface of the substrate is 0.5 to 2.5 μm, and the WC particles on the surface of the substrate on the flank side The average particle diameter df is 0.6 to 3.5 μm, and the df is larger than the dr.

  According to the cutting tool of the present invention, the average particle diameter dr of the WC particles on the base surface on the rake face side is within a predetermined range, and dr is larger than the average particle diameter df of the WC particles on the base surface on the flank face side. By being small, the hardness of the substrate surface on the rake face side is high and hardly deforms. This reduces the hardness difference between the substrate and the coating layer on the rake face where wear resistance is required, and the coating layer cannot follow the deformation when the substrate deforms, and the coating layer peels off. Suppress. As a result, the progress of wear of the coating layer required for the rake face can be suppressed. In addition, since df is within a predetermined range and larger than dr, the toughness of the base on the flank side is high, and in the flank coating layer on which impact is applied by intermittent cutting rather than the rake face, Even when an impact is applied, the base of the flank surface absorbs the impact and suppresses chipping and chipping.

About the suitable example of this invention, (a) It is a schematic perspective view, (b) It is XX sectional drawing.

  In the cutting tool 1 of this embodiment, as shown in FIGS. 1A and 1B, the intersecting ridge line between the rake face 2 and the flank face 3 is a cutting edge 4, and the surface of the base 5 is covered with a coating layer 6. ing. The substrate 5 is made of a cemented carbide having a hard phase containing WC particles and a binder phase that binds the hard phase. In addition, the hard phase in the cemented carbide of the present embodiment is composed of WC particles, or mainly composed of WC particles, and any one or more metal elements of the other periodic tables 4, 5, and 6 metals. It contains at least one B1 type solid solution phase of carbide, nitride and carbonitride. In addition, the binder phase in the cemented carbide according to the present embodiment is composed of Co as a main component and a metal element in the hard phase in solid solution.

  According to this embodiment, the average particle diameter dr of the WC particles on the surface of the substrate 5 on the rake face 2 side is 0.5 to 2.5 μm, and the WC particles on the surface of the substrate 5 on the flank 3 side are The average particle size df is 0.6 to 3.5 μm. Also, df is larger than dr. In the present invention, the average particle diameter of the WC particles on the surface of the substrate is calculated by measuring the average particle size of the WC particles existing in a region within 10 μm from the surface of the substrate 5 in the cross-sectional photograph of the cutting tool 1. Is done.

  The cutting tool 1 according to this embodiment having this range is hard to be deformed because the base 5 has a high hardness. In addition, since dr is smaller than df, the difference in ease of deformation due to the difference in hardness between the base body 5 and the coating layer 6 is reduced on the rake face 2 where wear resistance is required. The peeling of the coating layer 6 due to the difference in the degree of deformation is suppressed. As a result, the progress of wear of the coating layer 6 required for the rake face 2 can be suppressed. Furthermore, since df is large, the toughness of the flank 3 of the substrate 5 is high. Therefore, in the coating layer 6 of the flank 3 that receives an impact by interrupted cutting rather than the rake face 2, the base 5 of the flank 3 can absorb the impact even when the impact is applied from the surface of the coating layer 6. . As a result, chipping and chipping of the coating layer 6 on the flank 3 can be suppressed.

  That is, when dr is smaller than 0.5 μm, the toughness of the surface of the substrate 5 on the rake face 3 side is lowered, and the fracture resistance is lowered. On the other hand, if dr is larger than 2.5 μm, the hardness of the substrate 5 is lowered and easily deformed, and the rake face 2 requiring wear resistance has a large hardness difference between the substrate 5 and the coating layer 6. The layer 6 is easily peeled off. A desirable range of dr is 0.7-2 μm.

  If df is smaller than 0.6 μm, when an impact is applied from the surface of the coating layer 6, the ability to absorb the impact of the substrate 5 on the flank 3 side is reduced, and defects and chipping are likely to occur. Become. Further, if df is larger than 3.5 μm, the hardness of the substrate 5 is lowered and easily deformed, and the coating layer 6 is easily peeled off. A desirable range of df is 0.8 to 2.5 μm.

  Furthermore, if dr is not less than df, the effect of suppressing the progress of wear of the coating layer 6 required for the rake face 2 and the impact absorbing ability of the coating layer 6 on the flank face 3 cannot be made compatible. The coating layer 6 on the second side peels off, or the coating layer 6 is easily damaged or chipped on the flank 3.

Here, in the present embodiment, df / dr (ratio of the average particle diameter df of the WC particles on the surface of the substrate 5 on the flank 3 side to the average particle diameter dr of the WC particles on the surface of the substrate 5 on the rake face 2 side). ) Is 1.05 to 1.2. Within this range, the wear resistance on the rake face 2 and the fracture resistance on the flank face 3 can be optimized. A desirable range of df / dr is 1.1 to 1.1.
5.

  Furthermore, in this embodiment, a region where the average particle diameter of the WC particles is larger than the average particle diameter of the WC particles inside the substrate 5 is present at a thickness of 100 to 300 μm from the surface of the substrate 5. Yes. As a result, the shock absorbing capacity of the substrate 5 is further increased. In the present invention, the inside of the substrate 5 refers to a region having a depth of 500 μm or more from the surface of the substrate 5.

  Moreover, in this embodiment, the content rate of the binder phase in the surface of the base | substrate 5 by the side of the flank 3 is larger than the content rate of the binder phase in the surface of the base | substrate 5 by the side of the rake face 2. FIG. Thereby, the deformation of the substrate 5 on the rake face 2 side can be suppressed, and the peel resistance of the coating layer 6 can be improved. Further, it is possible to increase the impact absorbing ability of the base body 5 on the flank 3 side and to improve the fracture resistance on the flank 3 side.

  Furthermore, according to this embodiment, tungsten (W) is dissolved in the binder phase, and the solid solution ratio of tungsten in the binder phase is increased from the surface to the inside in the vicinity of the surface of the base 5 on the flank 3 side. It consists of a concentration distribution that increases once, takes a maximum value, and decreases toward the inside of the substrate 5. As a result, there is an effect that heat generated during cutting is efficiently propagated. In this embodiment, the position where the solid solution ratio of tungsten in the binder phase takes the maximum value is 50 to 200 μm in depth from the surface of the substrate.

In the present embodiment, the coating layer 6 contains a TiCN layer made of columnar TiCN crystals extending in a direction perpendicular to the surface of the substrate 5. In this embodiment, the coating layer 6 is formed by a CVD method. As a result, the adhesion between the substrate 5 and the coating layer 6 is high, and the coating layer 6 has high wear resistance and chipping resistance. Furthermore, the covering layer 6 is any one of TiN layers having an average thickness of 0 to 0.7 μm, the TiCN layer having an average thickness of 3 to 15 μm, and TiCO, TiNO, and TiCNO having an average thickness of 0 to 0.1 μm. An intermediate layer composed of the above, an Al ₂ O ₃ layer having an average thickness of 2 to 8 μm, and a TiC _x N _y layer having an average thickness of 0 to 0.7 μm (0 ≦ x, 0.5 ≦ y, x + y = 1) The outermost layer is made of a structure in which the surface layer is sequentially laminated on the surface of the substrate. With this configuration, the wear resistance and fracture resistance of the coating layer 6 are high.

A more preferable configuration of the coating layer of the above embodiment will be described in detail. The surface of the substrate made of the cemented carbide is coated, and from the substrate side, the TiN layer, the TiCN layer, the intermediate layer, and Al ₂ The O ₃ layer and the outermost layer are provided in this order. The intermediate layer is made of any one of TiCO, TiNO, and TiCNO. The outermost layer is composed of a TiC _x N _y layer (0 ≦ x, 0.5 ≦ y, x + y = 1). More preferable average thickness of each layer of the covering layer 6 is 0.1 to 0.7 μm for the TiN layer, 4 to 13 μm for the TiCN layer, 0.01 to 0.1 μm for the intermediate layer, ₃ to 3 for the Al ₂ O ₃ layer. 6 μm and the outermost layer is 0.3 to 0.7 μm. The average thickness of each layer is calculated by measuring the thickness at 10 or more measurement points at 1 μm intervals over a width of 10 μm or more at an arbitrary position of each layer, and taking the average value.

Here, if the TiCN layer is in the above range, sufficient wear resistance can be maintained and the fracture resistance is high. A more preferable range of the TiCN layer is 5 to 10 μm. When the Al ₂ O ₃ layer is in the above range, sufficient oxidation resistance is maintained, wear resistance is high, and chipping resistance is also high. A more preferable range of the Al ₂ O ₃ layer is 4 to 5 μm. The TiN layer, the intermediate layer, and the outermost layer can be omitted.

The TiN layer enhances the adhesion between the substrate 5 and the coating layer 6. When the average thickness of the TiN layer is 0.1 to 0.7 μm, the coating layer 6 has good adhesion with the substrate 5, and The coating layer 6 is difficult to chip. A more preferable range of the TiN layer is 0.4 to 0.5 μm. further,
An intermediate layer between the TiCN layer and _{the Al} 2 _{O 3} layer has an effect of enhancing the adhesion between the TiCN layer and _{the Al} 2 _{O 3} layer. When the average thickness of the intermediate layer is 0.01 to 0.1 μm, the Al ₂ O ₃ layer is difficult to peel and the Al ₂ O ₃ layer is difficult to chip. A more preferable range of the intermediate layer is 0.03 to 0.08 μm. The outermost layer consisting of TiC _x N _y layers (0 ≤ x, 0.5 ≤ y, x + y = 1) makes the cutting tool surface bright, such as gold, and determines whether the cutting blade is unused or used. It is provided for the sake of ease. If it is 0.3 to 0.7 μm, it can be visually identified. The outermost layer may contain oxygen at a ratio of 10% by mass or less based on the total amount.

  The combination of the substrate and the coating layer can enhance both the adhesion of the coating layer required for the rake face during cutting and the chipping resistance of the coating layer required for the flank surface.

(Production method)
A method for producing the coated tool of the present invention will be described.

First, a WC raw material powder having an average particle size of 0.2 to 10 μm by a microtrack method and a Cr ₃ C ₂ raw material powder having an average particle size of 0.2 to ₃ μm by a microtrack method are charged into a pulverizer and mixed with water. Alternatively, a solvent is added and stirred to prepare a slurry. Here, using the WC raw material powder having the above average particle diameter, the mixed powder is pulverized until the average particle diameter by the microtrack method becomes 0.2 to 3 μm while stirring the slurry. Further, the Co raw material powder is not added when the WC raw material powder and the Cr ₃ C ₂ raw material powder are added, and the average particle diameter of the mixed powder by the microtrack method becomes 0.2 to 2.5 μm while stirring the slurry. Then, the Co raw material powder is added to the slurry. That is, when the Co raw material powder is introduced from the beginning, the Co raw material powders are aggregated around the end of the pulverization time. If desired, metal powder and carbon powder are added to the slurry at the time of charging the WC raw material powder and Cr ₃ C ₂ raw material powder in order to adjust the saturation magnetization of the cemented carbide after firing. In the case of addition of VC material powder and TaC raw material powder is added at the time of turn-on of WC raw material powder and _Cr 3 _{C 2} raw powder. Moreover, an organic binder, a dispersing agent, etc. are added and adjusted to a slurry, and it is set as a granule by spray drying.

  Using this granule, it is molded into a predetermined tool shape by a known molding method such as press molding, casting molding, extrusion molding, cold isostatic pressing. In this embodiment, a paste containing carbon powder is applied to the flank side surface of the molded body and dried. Then, the cemented carbide mentioned above is produced by baking at 1350-1550 degreeC in a vacuum or non-oxidizing atmosphere. At this time, since the portion where the carbon powder is applied is sintered more than the other portions, the average particle size of the WC particles in the cemented carbide on the base surface on the flank side is set to the base on the rake face 2 side. 5 can be made larger than the average particle diameter of the WC particles in the cemented carbide on the surface. In the present invention, the present invention is not limited to this production method. For example, a paste containing carbon powder is applied to the entire surface of the molded body, or by another method, in the cemented carbide on the entire surface of the substrate. After making the average particle diameter of the WC particles larger than the average particle diameter of the WC particles in the cemented carbide inside the substrate, the region where the average particle diameter of the surface WC particles is large is polished only on the rake face side. The method of doing can also be applied.

  Thereafter, the rake face or the rake face and the flank face are subjected to polishing or honing of the cutting edge while adjusting dr and df as desired.

Then, if desired, a coating layer is formed on the surface of the substrate made of the cemented carbide.
An example of a method for forming a coating layer by chemical vapor deposition (CVD) will be described.
First, as a reaction gas composition, titanium tetrachloride (TiCl ₄ ) gas is 0.5 to 10.0% by volume, nitrogen (N ₂ ) gas is 10 to 60% by volume, and the balance is hydrogen (H ₂ ) gas. Are introduced into the reaction chamber, and a TiN layer is formed in the chamber under conditions of 800 to 940 ° C. and 8 to 50 kPa.

Next, as a reaction gas composition, titanium tetrachloride (TiCl ₄ ) gas is 0.5 to 10.0 vol%, nitrogen (N ₂ ) gas is 10 to 60 vol%, and acetonitrile (CH ₃ CN) gas is vol%. A mixed gas consisting of 0.1 to 3.0% by volume and the remainder of hydrogen (H ₂ ) gas is prepared and introduced into the reaction chamber, and the TiCN layer is formed at a film forming temperature of 780 to 880 ° C. and 5 to 25 kPa. The lower part of the film is formed. Here, of the above film forming conditions, the ratio of acetonitrile gas in the reaction gas is adjusted to 0.1 to 0.4% by volume, and the film forming temperature is set to 780 ° C. to 880 ° C. In this case, the lower portion is desirable because a TiCN layer composed of fine columnar crystals (MT-TiCN) can be formed.

In addition, although the film-forming conditions of the lower part of a TiCN layer may be formed on a single condition, the film-forming conditions of a TiCN layer can be changed on the way and a structure state can also be changed. For example, the ratio of acetonitrile (CH ₃ CN) gas can be increased to make the upper crystal of the TiCN layer into a columnar crystal having a width wider than that of the lower crystal. Alternatively, during the film formation of the TiCN layer, the film formation conditions are as follows: titanium tetrachloride (TiCl ₄ ) gas is 1.0 to 5.0% by volume, and acetonitrile (CH ₃ CN) gas is 0.5 to 5.0. A mixed gas consisting of volume%, nitrogen (N ₂ ) gas of 10.0 to 30.0 volume% and the remainder of hydrogen (H ₂ ) gas is prepared and introduced into the reaction chamber, and the chamber is 950 to 1100 ° C. By changing the condition to 5 to 40 kPa, the upper crystal of the TiCN layer can be made columnar crystal wider than the lower crystal. Under this condition, a desired TiCN layer can be formed even under a condition in which a part of the mixed acetonitrile (CH ₃ CN) gas is changed to methane (CH ₄ ) gas and mixed. The mixing ratio of acetonitrile (CH ₃ CN) gas may be changed stepwise, but can also be changed continuously.

Next, an HT-TiCN layer constituting the upper part of the TiCN layer is formed. Specific film forming conditions for the HT-TiCN layer include, for example, titanium tetrachloride (TiCl ₄ ) gas of 2.5 to 4.0% by volume and methane (CH ₄ ) gas of 0.1 to 10.0% by volume. Then, a mixed gas composed of 5.0 to 20.0% by volume of nitrogen (N ₂ ) gas and the remaining hydrogen (H ₂ ) gas is prepared and introduced into the reaction chamber, and the inside of the chamber is 900 to 1050 ° C., 5 ˜40 kPa.

Further, an intermediate layer is formed. Specific film forming conditions include, for example, titanium tetrachloride (TiCl ₄ ) gas of 1.0 to 4.0% by volume, methane (CH ₄ ) gas of 0 to 7.0% by volume, and nitrogen (N ₂ ) gas. 0 to 20.0% by volume, carbon dioxide (CO ₂ ) gas 1.0 to 5.0% by volume, and the remainder consisting of hydrogen (H ₂ ) gas. These mixed gases are adjusted and introduced into the reaction chamber, and the inside of the chamber is set to 900 to 1050 ° C. and 5 to 40 kPa.

Subsequently, an Al ₂ O ₃ layer is formed. As a method for forming the Al ₂ O ₃ layer, 0.5 to 5.0% by volume of aluminum trichloride (AlCl ₃ ) gas, 0.5 to 3.5% by volume of hydrogen chloride (HCl) gas, carbon dioxide Using a mixed gas composed of 0.5 to 5.0% by volume of (CO ₂ ) gas, 0.0 to 0.5% by volume of hydrogen sulfide (H ₂ S) gas, and the remainder consisting of hydrogen (H ₂ ) gas, It is desirable to set it as 950-1100 degreeC and 5-10kPa.

If desired, an outermost layer composed of a TiC _x N _y layer (0 ≦ x, 0.5 ≦ y, x + y = 1) is formed. Specific film forming conditions are as follows: titanium tetrachloride (TiCl ₄ ) gas is 0.1 to 10.0% by volume, nitrogen (N ₂ ) gas is 0 to 60.0% by volume, and the remainder is hydrogen (reaction gas composition). A mixed gas composed of H ₂ ) gas is adjusted and introduced into the reaction chamber, and the inside of the chamber may be set to 960 to 1100 ° C. and 10 to 85 kPa.

Tungsten carbide (WC) powder with an average particle size of 5 μm, metallic cobalt (Co) powder with an average particle size of 1.2 μm, Cr ₃ C ₂ powder with an average particle size of 2.5 μm, NbC powder with an average particle size of 2.0 μm, average A TaC powder having a particle diameter of 2.0 μm, a ZrC powder having an average particle diameter of 2.0 μm, and a TiC powder having an average particle diameter of 2.5 μm are added and mixed at a ratio shown in Table 1, and the average particle diameter of the mixed powder is 0.00. Grinding was carried out with a vibration mill until it was in the range of 9 to 1.1 μm. At this time, regarding the addition of Co, the Co powder was added when the average particle diameter of the mixed powder in the middle of pulverization was in the range of 1.0 to 2.0 μm.

  Thereafter, the mixed powder obtained by granulation by spray drying was formed into a cutting tool shape by press molding. On the other hand, a paste (C paste) containing 10% by mass of carbon powder having an average particle diameter of 0.05 μm was prepared, and the paste was applied to the surface of the part shown in Table 1 with an average thickness of 5.0 μm. And dried. In addition, the side surface of Table 1 indicates a flank, and the main surface indicates a rake face.

  Then, the molded body was subjected to binder removal treatment and fired at a temperature shown in Table 1 for 1 hour in a vacuum of 0.5 to 100 Pa. In addition, each metal content in the cemented carbide after baking was the same as a raw material preparation composition. Furthermore, the surface of the base on the rake face side was smoothed by double-head processing on the manufactured cemented carbide, and then the cutting edge portion was subjected to blade edge processing (R honing) by blast processing.

Next, a coating layer was formed on the cemented carbide by a CVD method. The film forming conditions were as follows. First, TiCl ₄ : 2.0% by volume, N ₂ : 33.0% by volume, and the remaining H ₂ was allowed to flow to a TiN layer of 0.1% at 880 ° C. and 16 kPa. The film was formed with a thickness of 1 μm. Next, under the film forming conditions of 825 ° C. and 9 kPa, a mixed gas of TiCl ₄ : 2.5% by volume, N ₂ : 23.0% by volume, CH ₃ CN: 0.4% by volume, and the remainder is H ₂ was flowed. A first TiCN layer having a columnar shape extending in a direction perpendicular to the surface of the substrate and having an average crystal width of 0.3 μm was formed to a thickness of 3.5 μm. Then, CH ₃ CN is changed to 0.8% by volume, and a second TiCN layer extending in a direction perpendicular to the surface of the substrate and having an average crystal width of 0.8 μm is formed to a thickness of 2.5 μm. The film was formed. After that, under film formation conditions of 950 ° C. and 10 kPa, mixing is performed with 3.0% by volume of TiCl ₄ gas, 3.0% by volume of CH ₄ gas, 10.0% by volume of N ₂ gas, and the remainder of H ₂ gas. Gas was allowed to flow to form a 0.3 μm thick HT-TiCN layer. And, under the film forming conditions of 1010 ° C. and 20 kPa, TiCl ₄ : 3.5% by volume, CH ₄ : 2.0% by volume, N ₂ : 5.0% by volume, CO ₂ : 2.0% by volume, and the rest An intermediate layer was formed to a thickness of 0.1 μm by flowing a mixed gas of H ₂ . Then, under the film forming conditions of 1005 ° C. and 9 kPa, AlCl ₃ : 1.5% by volume, HCl: 2.0% by volume, CO ₂ : 4.0% by volume, H ₂ S: 0.3% by volume, and the rest An αAl ₂ O ₃ layer was formed to a thickness of 5 μm by flowing a mixed gas of H ₂ . Finally, under the film forming conditions of 1010 ° C. and 30 Pa, the outermost layer made of TiN is 0.5 μm by flowing a mixed gas of TiCl ₄ : 3.0% by volume, N ₂ : 30.0% by volume, and the remaining H _2. The film was formed with a thickness of.

For the obtained cutting tool, the cut and polished surface was observed with a scanning electron microscope (SEM), and the average particle diameter of WC particles in the 10 μm thickness region from the surface of the rake face and flank face was measured with image analysis software SEMVIEW. The average particle diameter (dr, df) of the WC particles on the surface of the substrate on the rake face side and flank face side was measured. In Table 2, it described as dr and df. Further, when dr or df is larger than the average particle diameter of WC particles inside the substrate, the average particle diameter of WC particles in the region of 10 μm × 10 μm is measured in the vicinity of the surface of the substrate, and dr or df is A large area was identified and the thickness from the surface of the substrate was estimated. The thickness is shown in Table 2.

Further, the content of the binder phase in the vicinity of the surface of the substrate on the rake face side or the flank face side was measured by wavelength dispersion X-ray analysis (WDS) and listed in Table 2. Further, the composition analysis of the binder phase was performed by WDS, and the solid solution amount of tungsten in the binder phase was confirmed. Then, the solid solution amount of tungsten in each binder phase within a range of 500 μm to 600 μm in depth from the surface of the substrate is measured for each position of the binder phase scattered within this range, and the average value is calculated. The solid solution amount of tungsten in the binder phase of the cemented carbide at each position inside the substrate. Further, the solid solution amount of tungsten in each binder phase interspersed within the range from the surface of the substrate to the depth from the surface up to 300 μm was also measured. When there is a region where the solid solution amount of tungsten in the range of the surface to a depth of 300 μm is higher than the solid solution amount of tungsten in the substrate (within a depth of 500 μm to 600 μm from the surface). The depth at which the solid solution amount of tungsten was maximized was confirmed. Table 2 shows the depth at which the solid solution amount of tungsten is maximized as the W distribution depth. In addition, a sample in which the amount of tungsten does not change from the inside to the surface, that is, a region where the region higher than the solid solution amount of tungsten does not exist in the range of the surface to a depth of 300 μm is described as being constant in the table.

Then, using this cutting tool, a turning test was performed under the following conditions to evaluate the cutting performance. The results are shown in Table 2.
(Cutting conditions)
Work material: SCM440 φ200 × 400cm, with 4 grooves (for fracture resistance evaluation)
SCM435 φ200 × 400cm (for wear evaluation)
Tool shape: CNMG120408
Cutting speed: 250 m / min Feeding speed: 0.20 mm / rev
Cutting depth: 2.0mm
Others: Use of water-soluble cutting fluid Evaluation item: Evaluation of chipping resistance was performed by cutting six corners of each sample and measuring the number of impacts until chipping occurred. In the wear resistance evaluation, the flank wear amount at a cutting time of 15 minutes was measured.

  From Tables 1 and 2, sample no. 5 and dr No. df larger than df In No. 6, the number of impacts leading to the chip was short and the amount of wear was large. On the other hand, sample No. which is within the scope of the present invention. In 1-4, chipping and chipping were suppressed, and the progress of wear was also suppressed.

  The raw material powder of Example 1 was used to prepare the composition shown in Table 3 and molded in the same manner as in Table 1. A paste containing the same carbon powder as in Example 1 was applied to the surface of the part shown in Table 3 and dried. Next, firing was performed in the same manner as in Example 1 at the firing temperature shown in Table 3, and the prepared cemented carbide was subjected to blade edge processing (R honing) on the rake face side by blasting. In addition, each metal content in the cemented carbide after baking was the same as a raw material preparation composition. Then, a coating layer was formed on the above cemented carbide under the same conditions as in Example 1.

The obtained cutting tool was evaluated in the same manner as in Example 1. Further, a turning test was performed using the cutting tool under the following conditions to evaluate the cutting performance. The results are shown in Table 3.
(Cutting conditions)
Work material: FCD450 φ125 × 80 × 300mm, with 4 holes (for fracture resistance evaluation)
Tool shape: CNMG120408
Cutting speed: 300 m / min Feeding speed: 0.20 mm / blade cutting: 2.0 mm
Others: Use of water-soluble cutting fluid Evaluation item: Cutting time until cutting becomes impossible

  From Table 3, the sample Nos. With the same dr and df. In No. 8, the number of impacts leading to the breakage was short and the amount of wear was large. On the other hand, sample No. which is within the scope of the present invention. In No. 7, chipping and chipping were suppressed, and progress of wear was also suppressed.

DESCRIPTION OF SYMBOLS 1 Cutting tool 2 Rake face 3 Relief face 4 Cutting edge 5 Base body 6 Coating layer

Claims (8)

A cutting tool in which the surface of the substrate made of a cemented carbide containing WC particles is coated with a coating layer, with the intersection ridge line between the rake surface and the flank as a cutting edge, and the surface of the substrate on the rake surface side The average particle diameter dr of the WC particles in the region 300 μm or more away from the cutting edge is 0.5 to 2.5 μm, and the average particle diameter df of the WC particles on the surface of the base on the flank side is 0. A cutting tool having a diameter of 6 to 3.5 μm and a larger df than the dr.   The cutting tool according to claim 1, wherein a ratio of the df to the dr (df / dr) is 1.05 to 1.2.   The cutting tool according to claim 1 or 2, wherein the coating layer includes a TiCN layer made of columnar TiCN crystals extending in a direction perpendicular to the surface of the substrate.   The coating layer is any one of a TiN layer having an average thickness of 0 to 0.7 μm, a TiCN layer having an average thickness of 3 to 15 μm, and TiCO, TiNO, and TiCNO having an average thickness of 0 to 0.1 μm. An intermediate layer, an Al 2 O 3 layer having an average thickness of 2 to 8 μm, and an outermost layer made of a TiCxNy layer (0 ≦ x, 0.5 ≦ y, x + y = 1) having an average thickness of 0 to 0.7 μm are sequentially stacked. The cutting tool according to claim 3, wherein the cutting tool is configured as described above.   A region where the average particle diameter of the WC particles on the surface side of the base on the flank side is larger than the average particle diameter of the WC particles inside the base is present in a thickness of 100 to 300 μm from the surface of the base. The cutting tool according to any one of claims 1 to 4.   The cutting tool according to any one of claims 1 to 5, wherein a content ratio of the binder phase on the surface of the base on the flank side is larger than a content ratio of the binder phase on the surface of the base on the rake face side.   Tungsten (W) is dissolved in the binder phase, and the solid solution ratio of tungsten in the binder phase once increases from the surface of the substrate toward the inside on the surface side of the substrate on the flank side. The cutting tool according to claim 6, comprising a concentration distribution that decreases toward the inside of the substrate after taking a maximum value.   The cutting tool according to claim 7, wherein the position where the solid solution ratio of tungsten in the binder phase takes a maximum value exists at a depth of 50 to 200 μm from the surface of the base on the flank side.

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