JP4895586B2 - Surface coated cutting tool - Google Patents

Description

  The present invention relates to a surface-coated cutting tool formed by forming a hard coating layer on the surface of a substrate.

  Currently, cutting tools are used to improve slidability, wear resistance, and fracture resistance by forming various hard coating layers on the surface of hard materials such as WC-based cemented carbide and TiCN-based cermet. In particular, a hard coating layer formed by a physical vapor synthesis method has high hardness and high wear resistance, and is widely used in various applications. Among such physical vapor phase synthesis methods, particularly in the arc ion plating method suitably used as a method for forming a hard coating layer, coarse molten particles called droplets are generated during film formation, It is known that macro particles flying over the surface and having a diameter of 1 μm or more are dispersed in the hard coating layer. Generation | occurrence | production of this macro particle becomes a factor of chipping of a cutting edge, and a defect | deletion, or the smoothness of a cutting surface is impaired and becomes a factor which reduces the lifetime of a cutting tool.

  Therefore, in Patent Document 1, for example, macro particles in a hard film (hard coating layer) formed by an arc ion plating method are chemically or mechanically removed, or are formed into fine holes by laser beam irradiation. It is disclosed that, by changing, the fine holes have a function of holding a machining fluid (cutting fluid), and friction and wear of the hard film can be reduced.

Further, in Patent Document 2, in the method of forming a hard film (hard coating layer) by an arc ion plating method, the droplets are removed by blasting to cause the presence of pores, acetylene at the time of film formation, The reaction of a reaction gas such as methane more than the stoichiometric ratio causes the free carbon to precipitate in the hard film, and then the free carbon is removed with phosphate to make the pores mist. It is disclosed that the holding force of the cutting fluid (cutting fluid) can be increased to suppress the friction and wear of the hard coating.
JP 2002-146515 A JP 2005-153072 A

  However, as in Patent Document 1 and Patent Document 2, in the method in which voids are present entirely on the surface of the hard coating layer, the lubricity between the hard coating layer and the chips is sufficient on the rake face where chips are discharged. However, in the cutting blade, there is a problem that the void tends to cause chipping and chipping, and the void portion remains without being cut and the processed surface becomes rough.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a surface-coated cutting tool that has excellent chip disposal, high fracture resistance, and good finished surface roughness.

  In the present invention, a cutting tool used for wet machining that uses a cutting fluid should have a void on the rake face to increase the retention of the cutting fluid. Further, it is based on the knowledge that it is better to eliminate voids on the surface of the hard coating layer as much as possible in order to smooth the roughness of the machined surface.

That is, the surface-coated cutting tool of the present invention is a surface-coated cutting tool in which the surface of a base is coated with a hard coating layer, and voids are dispersed on at least the surface of the hard coating layer, and the cutting blade on the surface of the hard coating layer is used. The area ratio of the void existing at the position is 5 area% or less, and the area ratio of the void existing at the rake face position of the surface of the hard coating layer is 8 to 30 area% It is.

Here, it an area ratio of the voids present in the cutting edge position of the surface of the hard coating layer is 5% by area or less, important in that it can further improve the wear resistance and chipping resistance of the cutting edge It is .

Moreover, it is important that the area ratio of the voids existing at the rake face position on the surface of the hard coating layer is 8 to 30 area% in that the frictional resistance during chip treatment on the rake face can be reduced. .

  Note that the film thickness at the cutting edge position of the hard coating layer is thinner than the film thickness at the rake face position is high in chipping resistance at the cutting edge, and the hard coating layer is also caused by rubbing wear due to chips on the rake face. It is desirable in that a good chip disposal can be achieved without wear.

  Furthermore, when the cutting edge has an R honing with a radius of curvature R = 0.005 to 0.1 mm, the distribution of the voids can be easily realized.

  According to the surface-coated cutting tool of the present invention, on the rake face, voids exist on the surface of the hard coating layer, the hard coating layer has a low coefficient of friction when discharging chips, and the chip discharge performance is good. The blade has a low void content ratio on the surface of the hard coating layer, has high fracture resistance, and can smooth the processed surface, and as a result, can exhibit excellent cutting performance.

  Here, when the area ratio of the voids existing at the cutting edge position on the surface of the hard coating layer is 5% by area or less, the occurrence of chipping or chipping due to the voids can be reduced, and the cutting blade The fracture resistance can be further improved.

Further, since the area ratio of voids existing at the rake face position on the surface of the hard coating layer is 8 to 30% by area, the wear resistance on the rake face and the holding power of the cutting fluid can be achieved at the same time. Frictional resistance can be reduced.

  In addition, by making the film thickness at the cutting edge position of the hard coating layer thinner than the film thickness at the rake face position, the chipping edge has high chipping resistance, and the rake face is hard coated even by rubbing wear caused by chips. Good chip disposal without erosion of the layer.

  Further, when the cutting edge has an R honing with a radius of curvature R = 0.005 to 0.1 mm, the reason is unknown, but the void distribution tends to be easily realized.

  As for an example of the surface-coated cutting tool of the present invention, (a) a schematic perspective view of the surface-coated cutting tool of the present invention, (b) FIG. 1 which is a schematic sectional view, and a microscope showing an example of the surface-coated cutting tool of the present invention This will be described with reference to FIG.

  1 and 2, a surface-coated cutting tool (hereinafter simply referred to as a tool) 1 according to the present invention includes a rake face 3 on a main surface, a flank face 4 on a side face, a rake face 3 and a flank face 4. A cutting edge 5 is provided at the crossing ridge line, and a hard coating layer 6 is formed on the surface of the substrate 2.

  The hard coating layer 6 includes one or more metal elements selected from Group 4, 5 and 6 elements of the periodic table, Al and Si, and one or more non-metal elements selected from nitrogen, carbon, boron and oxygen. It is comprised by the at least 1 layer of these compounds.

  According to the present invention, the voids 8 are dispersed on at least the surface of the hard coating layer 6, and the area ratio of the voids 8 existing on the surface of the cutting edge 5 of the hard coating layer 6 is the rake face of the surface of the hard coating layer 6. It is characterized in that it is smaller than the area ratio of the voids 8 existing at the three positions.

  As a result, the cutting edge 5 has a high chipping resistance and a low machined surface roughness, and the rake face 3 has a low friction coefficient of the hard coating layer 6 when discharging chips due to the presence of the void 8. As an excellent cutting performance.

  That is, when the void 8 exists in the whole surface of the hard coating layer 6, the void 8 tends to become a starting point of a crack and the fracture resistance in the cutting blade 5 falls. On the contrary, when the void 8 does not exist on the entire surface of the hard coating layer 6, the frictional resistance of the chips on the rake face 3 is increased, and wear progresses or the chips are welded to the rake face 3. is there. That is, in any case, cutting performance cannot be improved.

  In addition, the area ratio of the void 8 existing on the surface of the hard coating layer 6 is the area of the void 8 observed in the region of the structure photograph 5 μm or more × 10 μm or more such as a scanning micrograph on the surface of the hard coating layer 6. The ratio can be determined by measuring by the Luzex image analysis method. In addition, about calculation of an area ratio, it measures about three or more places of arbitrary areas, and calculates from the average value.

  In addition, the void 8 has an average diameter of 0.2 to 10 μm and an average depth of 0.1 to 2 μm. The retention of the cutting fluid is high and the wear resistance of the hard coating layer does not deteriorate so much. Desirable in terms.

  Here, if the area ratio of the void 8 existing at the position of the cutting edge 5 on the surface of the hard coating layer 6 is 5% by area or less, the influence of the void 8 serving as the starting point of the crack in the cutting edge 5 to which the impact is the greatest. This is desirable in that it can be reduced and the fracture resistance of the cutting blade 5 can be further improved. Furthermore, since the arithmetic average roughness (Ra) at the position of the cutting edge 5 of the hard coating layer 6 is 0.12 μm or less, the cutting edge 5 has high chipping resistance, and the cutting resistance during cutting can be reduced. Is desirable. In addition, arithmetic mean roughness (Ra) in the position of the cutting edge 5 of the hard coating layer 6 is based on JIS B0601'01 using a stylus type surface roughness measuring device, cut-off value: 0.25 mm, It can be measured at a reference length of 0.8 mm and a scanning speed of 0.1 mm / second.

In addition, by setting the area ratio of the void 8 existing at the position of the cutting edge 5 on the surface of the hard coating layer 5 to 5 area% or less , the occurrence of chipping or chipping due to the void 8 can be reduced, and the cutting edge 5 can be reduced. It is possible to further improve the fracture resistance. A preferable range of the area ratio of the void 8 existing at the position of the cutting edge 5 on the surface of the hard coating layer 6 is 4 area% or less. Further, the area ratio of the voids 8 existing at the position of the rake face 3 on the surface of the hard coating layer 6 is 8 to 30 area%, which achieves both wear resistance on the rake face and holding power of the cutting fluid. It is important in that the frictional resistance at the time of chip treatment on the rake face 3 can be reduced. A preferable range of the area ratio of the void 8 existing at the position of the rake face 3 on the surface of the hard coating layer 6 is 8 to 20 area%.

  Here, the cutting edge 5 may be a sharp edge with a curvature radius R of less than 0.005 mm, but the reason is that the cutting edge 5 has an R honing with a curvature radius R = 0.005 to 0.1 mm. Is unknown, but the distribution of the specific void 8 tends to be easily realized. A preferable range of R honing of the cutting edge 5 is a curvature radius R = 0.02 to 0.05 mm.

  Furthermore, when the film thickness of the hard coating layer 6 is 0.2 to 5.0 μm, the hard coating layer 6 has high fracture resistance and can prevent film peeling, and the hard coating layer 6 has sufficient lubricity. Desirable because it has wear resistance. In addition, by making the film thickness at the position of the cutting edge 5 of the hard coating layer 6 smaller than the film thickness at the position of the rake face 3, the chipping resistance at the cutting edge 5 with the greatest impact of the work material is high, and Even on the rake face 3, even with rubbing wear caused by chips, the hard coating layer 6 is not worn away and good chip treatment can be performed. A preferable range of the film thickness at the position of the cutting edge 5 of the hard coating layer 6 is 0.5 to 2 μm, and a preferable range of the film thickness at the position of the rake face 3 of the hard coating layer 6 is 1.5 to 2.5 μm.

  In addition, as the substrate 2, cemented carbide, cermet, silicon nitride, and oxide composed of a hard phase mainly composed of tungsten carbide or titanium carbonitride and a binder phase mainly composed of an iron group metal such as cobalt or nickel. Hard materials such as ceramics mainly composed of aluminum, a hard phase made of polycrystalline diamond or cubic boron nitride and a binder phase such as ceramics or iron group metal are fired under an ultra-high pressure, etc. used.

(Production method)
Next, the manufacturing method of the surface coating cutting tool of this invention is demonstrated.

  First, a tool-shaped substrate is produced using a conventionally known method.

  Next, on the surface of the substrate, one or more metal elements selected from Group 4, 5, 6 elements of the periodic table, Al and Si, and one or more non-metal elements selected from nitrogen, carbon, and oxygen, A hard coating layer made of the above compound is formed.

Note that a physical vapor phase synthesis (PVD) method such as an ion plating method or a sputtering method is used as a film forming method. The details of several examples of the film formation method will be described. When a composite hard layer containing titanium (Ti) and aluminum (Al) is produced by an ion plating method, two types of metal targets, namely metal titanium and metal aluminum, are used. Are used independently, or a titanium aluminum (TiAl) alloy is used as a target, and a metal source is evaporated and ionized by arc discharge or glow discharge, and at the same time, nitrogen (N ₂ ) gas as a nitrogen source or methane (CH as a carbon source) ₄ ) Reacted with acetylene (C ₂ H ₂ ) gas to form a film. At this time, in order to increase the density of the hard coating layer and the adhesion to the substrate, and to disperse the predetermined macroparticles 10 in the hard coating layer 6, the film is formed while applying a bias voltage of 30 to 200V. It is desirable.

Here, as an example of a method for realizing the distribution state of the voids 8 in the hard coating layer 6 in the present invention, it can be realized by changing the distribution of the macro particles 10 in the formed hard coating layer 6. Specifically, a method of performing gas bombardment treatment during or at the end of film formation is preferable. According to this method, since the edge portion is selectively polished in the gas bombardment process, the macro particles 10 on the surface of the cutting edge 5 of the formed hard coating layer 6 can be selectively removed. After completion of the film, the area ratio of the macro particles 10 existing on the surface of the cutting edge 5 of the hard coating layer 6 is smaller than the area ratio of the macro particles 10 existing at the rake face 3 position on the surface of the hard coating layer 6. It can be configured.

  Thereafter, the macro particles 10 present on the surface of the hard coating layer 6 are removed from the hard coating layer 6 formed by mechanical polishing such as blasting or polishing using a brush and an abrasive. At this time, since the macro particles 10 are removed together with the portions embedded in the normal portions other than the macro particles 10 of the hard coating layer 6, voids 8 are formed in the portions where the macro particles 10 are removed. The distribution of voids 8 in the hard coating layer 6 that has been subjected to polishing reflects the distribution of macro particles 10 in the hard coating layer 6 that has not been subjected to polishing processing in order to reflect the distribution of the voids 8 in the hard coating layer 6 that has been subjected to polishing. Is configured such that the area ratio of the void 8 existing on the surface of the cutting edge 5 of the hard coating layer 6 is smaller than the area ratio of the void 8 existing at the position of the rake face 3 on the surface of the hard coating layer 6. it can.

Mainly composed of tungsten carbide (WC) powder having an average particle diameter of 0.8 μm, 10% by mass of metallic cobalt (Co) powder having an average particle diameter of 1.2 μm, and vanadium carbide (VC) powder having an average particle diameter of 1.0 μm. Add 0.2% by mass of chromium carbide (Cr ₃ C ₂ ) powder with an average particle size of 1.0 μm at a ratio of 0.6% by mass and mix it into a grooved cutting tool shape (GBA43R300NY) by press molding. After that, a binder removal treatment was performed, and firing was performed at 1500 ° C. for 1 hour in a vacuum of 0.01 Pa to produce a cemented carbide. Further, the prepared cemented carbide was subjected to blade edge processing (honing) by brushing.

  Hard coating layers having various compositions shown in Table 1 were formed on the substrate thus prepared by arc ion plating. Further, for some samples, bombardment using a mixed gas of nitrogen gas and argon gas was performed in the middle or at the end of film formation under the conditions shown in Table 1, and on the surface of the cutting edge of the formed hard coating layer Macro particles were removed.

  Thereafter, the surface of the formed hard coating layer was blasted under the conditions shown in Table 1 using a wet microblast method using alumina abrasive grains having an average particle diameter of 5 μm.

  With respect to the obtained sample, the surface of the hard coating layer at the land position of the cutting edge and the rake face was observed with a scanning electron microscope (SEM), and the void area ratio was measured. In addition, the area ratio of the void in Table 1 is the area ratio of the void in the region of 5 μm in the direction perpendicular to the ridgeline of the cutting edge 100 μm × the cutting edge in the direction parallel to the ridgeline of the cutting edge. Table 1 shows an average value at three arbitrary locations as a void area ratio. Moreover, the film thickness of the hard coating layer was calculated | required from the cross-sectional SEM photograph of the cutting tool. Further, the arithmetic average roughness Ra at the cutting edge position on the surface of the hard coating layer was measured at three arbitrary positions with a contact-type surface roughness meter, and obtained from the average value. A specific measuring method is based on JIS B0601'01 using a stylus type surface roughness measuring device, cut-off value: 0.25 mm, reference length: 0.8 mm, scanning speed: 0.1 mm / Measured in seconds.

  Next, a cutting test was performed under the following cutting conditions using the obtained grooved cutting tool-shaped throw-away tip (cutting tool). The results are shown in Table 2.

Cutting method: Intermittent turning work material: SCM440, four 5 mm wide grooved cutting speed: 100 m / min
Feeding: 0.2mm / rev
Cutting depth: 2mm
Cutting state: Wet evaluation method: State of cutting edge and rake face at the stage where 2000 impacts were applied, and the number of impacts until failure

  From Table 1 and Table 2, sample No. 1 in which a lot of voids were generated on the entire surface of the hard coating layer without performing the bombarding process during or at the end of film formation. In No. 9, chipping occurred early and the tool life was short. In addition, sample No. 1 with a uniform void on the entire surface of the hard coating layer without performing bombarding during or after the film formation was formed by sputtering. Even with the tool No. 10, chipping occurred early and the tool life was short. Further, in place of the bombarding process during or at the end of the film formation, a blasting process was performed after the film formation to uniformly reduce the voids on the entire surface of the hard coating layer. No. 11, chip welding occurred on the rake face and the tool life was short.

  On the other hand, the sample area No. in which the void area ratio at the rake face position on the surface of the hard coating layer within the scope of the present invention is larger than that at the cutting edge position. Nos. 1 to 8 exhibited good cutting performance with low frictional resistance and good chip disposal and excellent chipping resistance at the cutting edge. Among them, a sample in which the area ratio of voids existing at the cutting edge position on the surface of the hard coating layer is 5 area% or less and the area ratio of voids existing at the rake face position on the surface of the hard coating layer is 10 to 30 area%. No. 1 to 3 and 7 can extend the number of impacts in particular and have a long tool life.

It is (a) schematic perspective view which shows the suitable example of the surface covering cutting tool of this invention, (b) principal part expanded sectional drawing. It is a drawing substitute photograph which shows an example of the surface coating cutting tool of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Surface coating cutting tool 2 Base | substrate 3 Rake face 4 Flank 5 Cutting edge 6 Hard coating layer 8 Void 10 Macro particle

Claims (3)

In the surface-coated cutting tool in which the surface of the base is coated with the hard coating layer, voids are dispersed on at least the surface of the hard coating layer, and the area ratio of the voids existing at the cutting edge position on the surface of the hard coating layer is 5 with at most area%, the surface-coated cutting tool, wherein the area ratio of the voids present in the rake face position of the surface of the hard layer is 8 to 30 area%. 2. The surface-coated cutting tool according to claim 1 , wherein a film thickness at the cutting edge position of the hard coating layer is thinner than a film thickness at the rake face position. The surface-coated cutting tool according to claim 1 or 2 wherein the cutting edge and having a R honing radius of curvature R = 0.005~0.1mm.

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