JP2010029980A - Cutting tool - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cutting tool having high chipping resistance and high wear resistance. <P>SOLUTION: The surface of a substrate 6 formed of a cubic boron nitride (cBN) sintered body containing at least 70 vol.% cBN is covered by a covering layer 7, the cBN sintered body is formed by bonding a bonded phase including the carbide of at least one element selected from a group of at least 4, 5, and 6 group metals of the periodic table and an iron group metal around cBN particles including cBN coarse particles with a particle size of 4 to 6 μm and fine particles with the particle size of 0.5 to 1.2 μm, and the covering layer 7 is composed of Ti<SB>1-a-b-c-d</SB>Al<SB>a</SB>W<SB>b</SB>Si<SB>c</SB>M<SB>d</SB>(C<SB>x</SB>N<SB>1-x</SB>) (where M is at least one selected from a group of Nb, Mo, Ta, Hf and Y, 0.45≤a≤0.55, 0.01≤b≤0.1, 0.01≤c≤0.05, 0.01≤d≤0.1, 0≤x≤1), thereby forming the cutting tool 1. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a cutting tool having a coating layer formed on the surface of a substrate.

  Currently, for members that require wear resistance, slidability, and fracture resistance, such as cutting tools, wear-resistant members, and sliding members, sintered alloys such as cemented carbide and cermet, diamond, and cBN (cubic boron nitride) A technique is used in which a coating layer is formed on the surface of a substrate made of a high-hardness sintered body such as a sintered body to improve wear resistance, slidability, and fracture resistance. Among them, cBN sintered bodies that have hardness next to diamond and are less likely to react with iron are used for high-speed machining and difficult-to-cut materials that are difficult to machine with cemented carbide and cermet, especially hardened steel. .

For example, Patent Document 1 discloses a cutting tool in which a coating layer of TiC, TiN, Al ₂ O ₃ or the like is formed on the surface of a cBN substrate, and an improvement in wear resistance is seen in cutting of general steel or cast iron. It is described. Further, Patent Document 2 discloses a cutting tool in which a TiAlN film is formed on the surface of a cBN substrate, and describes that the cutting tool has a long life in cutting a hard hard material such as hardened steel. Further, Patent Document 3 discloses a cutting tool in which a cBN substrate surface is coated with a hard coating layer having a TiAlSiN composition and a Ti / Al ratio continuously changing, and exhibits excellent chipping resistance in high-speed heavy cutting. Is described.
JP 59-8679 A JP-A-8-119774 JP 2004-345006 A

However, as the coating layer deposited on the surface of the cBN substrate, of TiC and TiN Patent Document 1, _Al 2 _{O 3} coating layer, TiAlN coated layer of Patent Document 2, in any of TiAlSiN coating layer of Patent Document 3, Cutting performance was insufficient, and further life extension was required. For example, it has been required to further extend the tool life even when used for cutting cast iron.

  Then, the cutting tool of this invention aims at providing the cutting tool with a still longer life in the cutting tool which formed the coating layer in the cBN sintered compact.

The cutting tool of the present invention is obtained by coating the surface of a cutting blade tip made of a cBN sintered body containing 70% by volume or more of cubic boron nitride (cBN) with a coating layer, and the cBN sintered body is A carbide of at least one element selected from Group 4, 5, and 6 metals and iron group metal around cBN particles of 4 to 6 μm cBN coarse particles and 0.5 to 1.2 μm cBN fine particles bound becomes in a binding phase containing the coating _{layer, Ti 1-a-b-} c-d Al a W b Si c M d (C x N 1-x) ( however, M is Nb, Mo, One or more selected from Ta, Hf, and Y, 0.45 ≦ a ≦ 0.55, 0.01 ≦ b ≦ 0.1, 0.01 ≦ c ≦ 0.05, 0.01 ≦ d ≦ 0. 1, 0 ≦ x ≦ 1).

  Here, the cutting edge tip is brazed to the pedestal via a backing plate, and the concentration of the iron group metal in the cBN sintered body decreases from the interface of the backing plate toward the rake face surface. It is desirable.

  Furthermore, it is desirable that the coating layer has a thickness of 0.5 to 5 μm.

According to the cutting tool of the present invention, the circumference of the cBN particles of the cBN coarse particles having a particle diameter of 4 to 6 μm and the cBN fine particles having a particle diameter of 0.5 to 1.2 μm is at least from the periodic tables 4, 5, and 6 metals. and one or more elements of the carbide and iron group cBN sintered body bound constituted by bonded phase containing a metal _{selected, Ti 1-a-b-} c-d Al a W b Si c M d (C x N _1-x ) (where M is at least one selected from Nb, Mo, Ta, Hf, and Y, 0.45 ≦ a ≦ 0.55, 0.01 ≦ b ≦ 0.1, 0.01 ≦ c) ≦ 0.05, 0.01 ≦ d ≦ 0.1, 0 ≦ x ≦ 1) is combined to extend the life as a cutting tool, and exhibits excellent cutting performance especially in the intermittent processing of cast iron did.

  Here, the cutting edge tip is brazed to the pedestal via the backing plate, and the concentration of the iron group metal in the cBN sintered body decreases from the interface of the backing plate toward the rake face surface. In some cases, generation of residual stress due to difference in thermal expansion coefficient between the iron group metal and the coating layer, abnormal grain growth of the coating layer, etc. while maintaining the adhesion with the backing cemented carbide and the high strength of the cBN sintered body This has the effect of suppressing defects in the coating layer.

  Further, it is desirable that the thickness of the coating layer is 0.5 to 5 μm because the balance between wear and chipping is good and the tool life is extended.

  An example of the cutting tool of the present invention will be described on the basis of (a) a schematic perspective view and (b) a schematic sectional view of FIG.

  As shown in FIG. 1 (a), a cutting tool (hereinafter simply referred to as a tool) 1 of the present invention has a shape in which a crossing edge line between a rake face 2 and a flank 3 is a cutting edge 4, and FIG. As shown in (b), a coating layer 7 is formed on the surface of a base body (hereinafter simply referred to as a base body) 6 made of a cBN sintered body. Further, according to FIG. 1A, the base 6 has a structure in which the tip body 10 is brazed to the tip of the chip body 10 via a backing plate 11.

  The cBN (cubic boron nitride) sintered body forming the substrate 6 has at least a periodic table 4 around the cBN particles of cBN coarse particles having a particle diameter of 4 to 6 μm and cBN fine particles having a particle diameter of 0.5 to 1.2 μm. It comprises a structure in which a carbide of one or more elements selected from Group 5 and 6 metals and a bonded phase containing an iron group metal are combined.

  Here, when the cubic boron nitride is less than 70% by volume, the wear proceeds remarkably. In addition, when the binder phase does not contain TiC and is only an iron group metal, the wear of the binder phase remarkably proceeds. On the other hand, if only TiC and no iron group metal is contained, the holding power of the cBN particles is reduced, and the cBN particles fall off.

  The carbide of one or more elements selected from the group of metals of Group 4, 5 and 6 of the periodic table constituting the binder phase (hereinafter abbreviated as carbide) is highly TiC-containing. It is desirable to improve the hardness and bonding strength with cBN, and it is desirable to contain Co as an iron group metal in order to satisfy the interface between the carbide layer and cBN and reduce defects.

  The cBN particles are composed of coarse and fine mixed particles of cBN coarse particles having a particle size of 4 to 6 μm and cBN fine particles having a particle size of 0.5 to 1.2 μm. The method for determining whether or not the mixture is coarse and fine is as follows. First, a micrograph is taken of the cross section of the sintered body, and the area of each of 20 or more cBN particles is determined from the photograph by an image analysis method. Next, the particle size of cBN is calculated according to the measuring method of the average particle size of the cemented carbide specified in CIS-019D-2005. Then, the particle size distribution of the cBN particles is taken to determine whether the distribution has two peaks. Of the two peaks, when the larger peak is in the range of 4 to 6 μm and the smaller peak is in the range of 0.5 to 1.2 μm, It is defined that cBN particles of 6 μm cBN coarse particles and cBN fine particles having a particle size of 0.5 to 1.2 μm exist.

  Furthermore, on the outer periphery of the cBN particles, an intermetallic compound of one or more elements selected from the group consisting of Group 4, 5 and 6 metals of the periodic table, iron group metal and Al, carbide, nitride, carbonitride The presence of an intermediate phase composed of a compound, boride, borocarbide, boronitride, or oxide is desirable because cBN particles can be held firmly.

Coating layer _{7, Ti 1-a-b-} c-d Al a W b Si c M d (C x N 1-x) ( where one M is selected Nb, Mo, Ta, Hf, from Y It is above, 0.45 ≦ a ≦ 0.55, 0.01 ≦ b ≦ 0.1, 0.01 ≦ c ≦ 0.05, 0.01 ≦ d ≦ 0.1, 0 ≦ x ≦ 1 The hard coating layer 8 comprised by this is comprised.

  The cutting tool in which the base 6 and the hard coating layer 8 are combined is particularly excellent in chipping resistance and cutting performance in intermittent machining of castings.

  In this composition region of the hard coating layer 8, the oxidation start temperature is increased, the oxidation resistance is increased, and the wear resistance during cutting of the tool 1 is improved. In particular, a crater when processing difficult-to-cut materials such as hardened steel The progress of wear can be suppressed. In addition, since the internal stress inherent in the hard coating layer 8 can be reduced, chipping that tends to occur at the tip of the cutting edge 4 can be suppressed, and the chipping resistance is high.

  That is, if a (Al composition ratio) is less than 0.45, the oxidation resistance of the hard coating layer 8 is lowered, and if a (Al composition ratio) is more than 0.55, the crystals of the hard coating layer 8 are reduced. The structure tends to change from cubic to hexagonal and hardness decreases. A particularly desirable range of a is 0.48 ≦ a ≦ 0.52. On the other hand, if b (W composition ratio) is less than 0.01, the internal stress of the hard coating layer 8 is high and the fracture resistance is lowered, and the adhesiveness between the base 6 and the hard coating layer 8 is lowered and cutting is performed. Chipping and peeling of the coating layer 7 are likely to occur inside, and if b (W composition ratio) is more than 0.1, the hardness of the hard coating layer 8 decreases. A particularly desirable range of b is 0.01 ≦ b ≦ 0.08. Furthermore, when c (Si composition ratio) is more than 0.05, the hardness of the hard coating layer 8 is lowered. A particularly desirable range for c is 0.01 ≦ c ≦ 0.04. Further, when d (M composition ratio) is less than 0.01, the oxidation start temperature becomes low, and when d (M composition ratio) is more than 0.1, a part of the metal M is different from the cubic crystal. As a low hardness phase, the hardness of the hard coating layer 8 decreases. A particularly desirable range of d is 0.01 ≦ d ≦ 0.08.

  The metal M is at least one selected from Nb, Mo, Ta, Hf, and Y. Among them, the inclusion of Nb or Mo is desirable because it has the most excellent wear resistance and oxidation resistance.

  Further, C and N which are non-metallic components of the hard coating layer 8 are excellent in hardness and toughness required for the cutting tool, and suppress droplets (coarse particles) generated on the surface of the hard coating layer 8. Therefore, a particularly desirable range of x (C composition ratio) is 0 ≦ x ≦ 0.5. Here, according to the present invention, the composition of the hard coating layer 8 can be measured by energy dispersive X-ray analysis (EDX) or X-ray photoelectron spectroscopy (XPS).

  Further, since the hard coating layer 8 has a high internal stress, the coating layer 7 is difficult to chip even if it is thickened, and even if the thickness of the hard coating layer 8 is 0.5 to 6 μm, the hard coating layer 8 It is possible to prevent peeling and chipping due to the internal stress of 8 itself, and to maintain sufficient wear resistance.

  Further, the coating layer 7 includes two layers, that is, a hard coating layer 8 and another coating layer 9 selected from one of AlN, carbides, nitrides, and carbonitrides of Periodic Tables 4, 5, and 6 metals. In some cases, the chipping resistance can be improved by using the above multilayer. The film thickness of the coating layer 7 (total film thickness of the hard coating layer 8 and the other coating layer 9) is 0.5 to 5.0 μm to prevent film peeling and chipping of the hard coating layer 8. This is desirable because sufficient wear resistance can be maintained. In addition, when using as a cutting tool for cast iron processing, it is desirable that the thickness of the coating layer 7 is 1 μm to 3 μm. Moreover, when using as a cutting tool for hardening steel processing, it is desirable that the thickness of the coating layer 7 is 0.5 micrometer-5 micrometers.

The base 6 is brazed to the pedestal via the backing plate 11, and the concentration of the iron group metal in the cBN sintered body decreases from the interface of the backing plate 11 toward the rake face 10 surface. Has the effect of preventing the deterioration of performance due to abnormal grain growth of the coating layer 7 or heat shock.
(Production method)
Next, the manufacturing method of the tool mentioned above is demonstrated.

  For example, coarse cBN raw material powder having an average particle diameter of 4 to 6 μm, fine cBN raw material powder having an average particle diameter of 0.1 to 1.5 μm, and periodic tables 4 and 5 having an average particle diameter of 0.2 to 3 μm as the raw material powder. And carbide powder of one or more elements selected from Group 6 metals and, if necessary, at least one raw material of Al having an average particle size of 0.5 to 5 μm or iron group metals of 0.5 to 3 μm The powder is weighed to a specific composition and pulverized and mixed in a ball mill for 16 to 72 hours.

  Thereafter, if necessary, it is molded into a predetermined shape. For molding, known molding means such as press molding, injection molding, cast molding, and extrusion molding can be used.

  Next, this is loaded together with a separately prepared cemented carbide backing support into an ultra-high pressure sintering apparatus and held at a predetermined temperature in the range of 1200 to 1600 ° C. under a pressure of 4 to 6 GPa for 10 to 30 minutes. Thus, the cubic boron nitride sintered body of the present invention is obtained. At this time, in order to have a structure in which the carbides of Group 4, 5, and 6 metals and the nitrides of Groups 4, 5, and 6 of the periodic table existed individually, the temperature rising and cooling rate was 30 to 30 minutes per minute. The heating and holding time is preferably 10 to 15 minutes under a pressure of 5 GPa at a predetermined temperature in the range of 1400 to 1600 ° C.

Next, the coating layer 7 is formed on the surface of the substrate 6. A physical vapor deposition (PVD) method such as an ion plating method or a sputtering method can be suitably applied as a method for forming the hard coating layer 8. As a detailed example of the film forming method, a case where the hard coating layer 8 is produced by an ion plating method will be described. Metal titanium (Ti), metal aluminum (Al), metal tungsten (W), metal silicon (Si) , Metal M (where M is one or more selected from Nb, Mo, Ta, Hf, and Y) is used as a metal target or a composite alloy target, and the metal source is evaporated by arc discharge or glow discharge. At the same time, the film is formed by reacting with nitrogen (N ₂ ) gas as a nitrogen source or methane (CH ₄ ) / acetylene (C ₂ H ₂ ) gas as a carbon source. In addition, by introducing nitrogen (N ₂ ) gas or argon (Ar) gas at a rate of 1 to 10 Pa as a film formation atmosphere, the adhesion and hardness of the hard coating layer 8 to the base 6 are improved.

  When the hard coating layer 8 is formed by an ion plating method or a sputtering method, a hard coating layer can be produced by controlling the crystal structure and orientation of the hard coating layer 8, and the adhesion to the substrate 6 can be achieved. In order to enhance the properties, it is preferable to apply a bias voltage of 30 to 200 V during film formation.

20% by volume of coarse cBN raw material powder with an average particle diameter of 5 μm as raw material powder, 60% by volume of fine cBN raw material powder with 0.8 μm, and 80% by volume of cBN raw material powder, and TiC raw material with an average particle diameter of 1.2 μm 17% by volume of powder and 3% by volume of 1.5 μm metallic Al raw material powder were prepared, and this powder was mixed for 15 hours by a ball mill using alumina balls.
Next, the mixed powder was pressure-molded at a pressure of 98 MPa. The molded body was fired by heating at 50 ° C./min using an ultra-high pressure apparatus, holding at 1500 ° C. for 15 minutes at a pressure of 5.0 GPa, and then firing by lowering the temperature at 50 ° C./min. As a result, a cBN sintered body was obtained. Moreover, it cut out to the predetermined dimension from the produced sintered compact by wire electric discharge machining, and brazed to the cutting step part formed in the cutting-blade front-end | tip part of a cemented carbide base. Then, the cutting edge of the cBN sintered body was subjected to blade edge processing (changing honing) using a diamond wheel.

  A coating layer was formed on the thus-prepared substrate (JIS / CNGA120408 throwaway tip shape) by arc ion plating. A specific film formation method is as follows. After the substrate is set in an arc ion plating apparatus and heated to 500 ° C., an arc current of 100 A, a bias voltage of 50 V, and a heating temperature of 500 ° C. are set in an atmosphere into which nitrogen gas is introduced at 2.5 Pa. A coating layer having the composition shown in Table 1 was formed. The composition of the coating layer was observed at a magnification of 500 using a scanning electron microscope (VE8800) manufactured by Keyence, and at an acceleration voltage of 15 kV using an EDAX analyzer (AMETEK EDAX-VE9800) attached to the apparatus. The composition was quantitatively analyzed by the ZAF method, which is a type of energy dispersive X-ray spectroscopy (EDX) method. For elements that could not be measured by this method, an X-ray photoelectron spectrometer (Quantum 2000) manufactured by PHI was used, and the X-ray source was irradiated with monochrome AlK (200 μm, 35 W, 15 kV) to a measurement region of about 200 μm. Measurements were made. The measurement results are shown in Table 1 as the composition of the coating layer.

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 1.
Cutting method: Outside diameter processed work material: FC250, 4-groove cutting speed: 500 m / min
Feeding: 0.2mm / rev
Cut: Shoulder cut 0.2mm, depth cut 0.4mm
Cutting state: Dry evaluation method: Can be processed until wear width is 0.1mm or chipping occurs and processing becomes impossible
Processing quantity.

  From the results shown in Table 1, a sample No. with a (Al composition ratio) larger than 0.55 was obtained. In No. 13, the crystal structure of the coating layer partially changed from cubic to hexagonal, resulting in poor wear resistance of the tool and crater wear. On the contrary, the sample No. a (Al composition ratio) is smaller than 0.45. No. 18, the oxidation start temperature of the coating layer was low and the wear resistance of the tool was poor, and crater wear progressed. Further, Sample No. No. that does not contain W and b (W composition ratio) is 0. In Nos. 11 and 12, chipping occurred in the tool, and conversely, sample Nos. With b (W composition ratio) exceeding 0.1. In No. 14, the wear resistance of the tool was poor, and all of them had a short tool life. Further, sample No. c with a c (Si composition ratio) exceeding 0.05 Also in 12, 15, and 17, crater wear progressed due to poor wear resistance of the tool. In addition, Sample No. containing no M (one or more selected from Nb, Mo, Ta, Hf, Y) was used. In Nos. 12 and 18, the amount of wear of the tool was large when the oxidation start temperature was lowered and cutting was performed, and conversely, sample Nos. With d (M composition ratio) exceeding 0.1. No. 16, the wear resistance was lowered, crater wear progressed, and the tool life was short.

  On the other hand, the composition of the hard layer is within the range of the present invention. In Nos. 1 to 10, the oxidation resistance was improved and excellent wear resistance was exhibited, and the fracture resistance was also good. As a result, the tool life was long.

  Coarse cBN raw material powder having an average particle size of 5 μm, fine cBN raw material powder having an average particle size of 0.8 μm, TiC raw material powder having an average particle size of 1.0 μm, TiN raw material powder having an average particle size of 1.2 μm, an average particle size of 1. 5 μm TiCN raw material powder, ZrC raw material powder with an average particle size of 1.2 μm, ZrN raw material powder with an average particle size of 1.2 μm, WC raw material powder with an average particle size of 0.9 μm, HfC raw material powder with an average particle size of 1.0 μm A metal Al raw material powder having a particle size of 1.5 μm and a metal Co raw material powder having an average particle size of 0.8 μm were prepared so as to have the composition shown in Table 2, and this powder was ball milled using alumina balls. For 15 hours. Next, the mixed powder was press-molded at a pressure of 98 MPa. This molded body was heated at a temperature rising rate shown in Table 2 using an ultrahigh pressure and high temperature apparatus, fired at a pressure of 5.0 GPa at a firing temperature and time shown in Table 2, and then cooled down as shown in Table 2. CBN sintered body was obtained by firing at a reduced temperature. Sample No. 1 in Example 1 except that the cutting tool was used in the same process as Example 1 and the thickness of the coating layer was 3.0 μm. 7 was formed under the same conditions as in Sample 7 (Sample Nos. 22 to 31). Using this sample, cutting evaluation was performed in the same manner as described above. The results are shown in Table 3.

  As for the particle size of the cBN particles, first, a scanning electron micrograph was taken of a cross section of the cBN sintered body, and the area of each of 20 or more cBN particles was determined from the photograph by an image analysis method. Next, the particle size of cBN was calculated according to the measuring method of the average particle size of the cemented carbide specified in CIS-019D-2005. And the particle size distribution of cBN particle | grains was taken and it was confirmed whether distribution had two peaks. When there are two peaks, Table 2 shows the particle size of the peak top on the coarse particle side and the particle size of the peak top on the fine particle side.

  As is apparent from Tables 2 and 3, Sample No. containing no carbide of one or more elements selected from Group 4, 5, and 6 metals. In No. 26, the wear resistance was poor and the number of processing was small. Sample No. containing no iron group metal was used. In 28, chipping occurred frequently and the number of processing was small. Furthermore, sample No. with a content ratio of cBN particles less than 70% by volume. In No. 27, the wear resistance was poor and the number of processing was small. Further, the sample No. 2 in which the distribution of cBN particles in the sintered body does not have two peaks of coarse particles and fine particles. In 29-31, the chipping resistance was poor and the number of processing was small.

  On the other hand, at least one element selected from Group 4, 5, and 6 metals on the periphery of cBN particles of 4-6 μm cBN coarse particles and 0.5-1.2 μm cBN fine particles. Sample No. 1 was bonded with a binder phase containing carbide and an iron group metal and formed with a specific coating layer. In 22-25, all had a long tool life compared with the comparative example.

An example of the cutting tool of this invention is shown, (a) schematic perspective view and (b) schematic sectional drawing.

Explanation of symbols

1 Cutting tool
2 rake face 3 flank face 4 cutting edge 6 substrate (cBN sintered body)
7 Hard coating layer 8 Coating layer 9 Other coating layer 10 Chip body 11 Backing plate

Claims (3)

A cutting tool in which the surface of a cutting edge tip made of a cBN sintered body containing 70% by volume or more of cubic boron nitride (cBN) is coated with a coating layer, the cBN sintered body having a particle size of 4 to 6 μm. The surrounding of the cBN particles of the cBN coarse particles and the cBN fine particles having a particle diameter of 0.5 to 1.2 μm includes at least one element carbide selected from Group 4, 5, and 6 metals and an iron group metal. It will bind to a binding phase, wherein the coating _{layer, Ti 1-a-b-} c-d Al a W b Si c M d (C x N 1-x) ( however, M is Nb, Mo, Ta, One or more selected from Hf and Y, 0.45 ≦ a ≦ 0.55, 0.01 ≦ b ≦ 0.1, 0.01 ≦ c ≦ 0.05, 0.01 ≦ d ≦ 0.1, A cutting tool comprising 0 ≦ x ≦ 1).   The cutting edge chip is brazed to a pedestal via a backing plate, and the concentration of the iron group metal in the cBN sintered body decreases from the interface of the backing plate toward the rake face surface. The cutting tool according to claim 1.   The thickness of the said coating layer is 0.5-5 micrometers, The cutting tool of Claim 1 or 2 characterized by the above-mentioned.

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