JP2005138208A - Surface coated cutting tool and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface coated cutting tool with improved abrasion resistance in a cutting tool such as a drill, an end mill, a cutting edge replaceable tip for milling and turning, a metal saw, a gear cutting tool, a reamer, and a tap. <P>SOLUTION: The surface coated cutting tool includes a film formed in an atmosphere including an argon gas. The film is composed of an oxide including at least Al. An argon amount included in the film is limited to be in the range of < 3 at %. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  TECHNICAL FIELD The present invention relates to cutting tools such as drills, end mills, milling and turning cutting tips, metal saws, gear cutting tools, reamers, taps and the like, and their manufacturing methods, in particular, cutting with a wear-resistant coating formed on the surface thereof. It relates to the tool and its manufacturing method.

  Recent trends in cutting tools include the need for dry machining that does not require cutting fluids from the viewpoint of global environmental conservation, the diversification of work materials, and the cutting speed has been increased to further improve machining efficiency. The tool edge temperature tends to become higher and higher due to the high speed. As a result, the tool life is shortened, and the properties required for the tool material are becoming stricter.

Therefore, in order to improve the wear resistance and surface protection function, the surface of a hard substrate such as a cutting tool such as a WC-based cemented carbide, cermet, cubic boron nitride sintered body, high-speed steel, or wear-resistant tool. In addition, Al _x Ti _1-xy Si _y C _z N _1-z (where 0.05 ≦ x ≦ 0.75, 0.01 ≦ y ≦ 0.1, 0.003) is obtained by physical vapor deposition (PVD method). It is well known to form a single layer or multiple layers of AlTiSi nitrides or carbonitrides such as 6 ≦ z ≦ 1) as a hard coating layer (see Japanese Patent No. 2793773 of Patent Document 1). . However, even with an AlTiSi-based nitride or carbonitride film that is said to have higher heat resistance than conventional TiN or TiCN, the cutting point temperature is 900 for high-speed, high-efficiency cutting that is currently directed. Since the temperature reaches close to 0 ° C., there is a problem that the film is oxidized in such an environment and the hardness and strength deteriorate.

  In addition, European Patent Publication EP0693544B1 of Patent Document 2 discloses a tool in which α-type crystal alumina is coated on the surface of a substrate by a chemical vapor deposition method (CVD method). This α-type alumina has a feature that the crystal structure is stable even at a temperature of 1000 ° C. or higher. However, in the CVD method according to Patent Document 2, film formation is performed under a temperature environment close to 1000 ° C., so that damage to the base material (extreme deterioration of the strength of the base material) is large, and tensile residual stress remains in the film. There are problems such as low film strength and fracture toughness values, which tend to cause chipping and chipping, and the resulting coating is particularly unsuitable for intermittent cutting.

Japanese Patent No. 3159572 of Patent Document 3 discloses that an alumina coating containing a compressive residual stress can be formed by the PVD method with respect to the above-described problem. The point in the PVD method of Patent Document 3 is that the temperature at the time of film formation is increased, and according to the example, it is understood that a temperature of 780 ° C. or higher is required at the time of film formation. Although the temperature of 780 ° C. is lower than 1000 ° C. or higher by the CVD method of Patent Document 2, film formation at a further lower temperature is desired in consideration of damage to the substrate. In particular, film formation at 700 ° C. or lower is desired. Further, since the alumina coating is formed by sputtering using only Ar gas with alumina as a target, Ar remains in the coating, resulting in a decrease in film strength.
Japanese Patent No. 2793773 European Patent Publication EP0695744B1 Japanese Patent No. 3159572

  As described above, in order to meet various severe requirements for cutting tools in recent years, it has been attempted in the prior art to coat the surface of the tool with a hard coating. However, the surface-coated cutting tools according to the prior art have not yet fully satisfied various severe requirements for cutting tools in recent years.

  Therefore, an object of the present invention is to further improve the wear resistance and surface protection function of a surface-coated cutting tool.

  According to the present invention, in a surface-coated cutting tool including a coating formed in an atmosphere containing argon, the coating is made of an oxide containing at least Al, and the amount of argon contained in the coating is less than 3 at%. It is characterized by being restricted within.

  The Al-containing oxide film may contain at least one of an alumina having an α-type crystal structure and a γ-type crystal structure, or may contain amorphous alumina. In addition, the Al-containing oxide film preferably also contains one or more elements of Zr, Si, Cr, Ti, and B additionally.

  The thickness of the Al-containing oxide film is preferably in the range of 0.5 to 5 μm. The nanoindentation hardness of the oxide film is preferably 18 GPa or more. Furthermore, a nitride, carbide, carbonitride, oxynitride, oxycarbide of any one or more elements of group IVa element, group Va element, group VIa element, Al, Si, and B in the periodic table, It is also preferable that one or more intermediate layers of oxycarbonitride are inserted between the base material and the Al-containing oxide film.

  The base material on which the Al-containing oxide film is coated includes WC-based cemented carbide, cermet, high-speed steel, ceramics, cubic boron nitride sintered body, diamond sintered body, silicon nitride sintered body, aluminum oxide, And can be formed of a shift in titanium carbide. Further, the surface-coated cutting tool can be any one of a drill, an end mill, a milling and turning cutting edge replaceable tip, a metal saw, a gear cutting tool, a reamer, and a tap.

  In the method for producing the surface-coated cutting tool as described above, the Al-containing oxide film is preferably coated by physical vapor deposition. The physical vapor deposition method may include at least one of an unbalanced magnetron sputtering method and an arc type ion plating method.

  Further, in the method for producing a surface-coated cutting tool according to the present invention, a base material is set in a reduced-pressure reaction chamber, a metal element is vaporized in the reaction chamber, the reaction chamber contains argon and oxygen, and the vaporized metal element And an oxygen gas are reacted to form a film made of an oxide containing at least Al on the base material, and the amount of argon contained in the film is suppressed within a range of less than 3 at%. In this case, the Al-containing oxide film can be formed at a temperature of 750 ° C. or lower.

  According to the present invention, it is possible to improve wear resistance and oxidation resistance characteristics in cutting tools such as drills, end mills, milling and turning cutting edge replaceable tips, metal saws, gear cutting tools, reamers, taps, In particular, it is possible to provide a surface-coated cutting tool having a long life in high-speed cutting.

  As a result of the study by the present inventors in view of the situation in the prior art as described above, if the amount of argon contained in the Al-containing oxide film formed in the atmosphere containing Ar is limited to less than a predetermined amount, it is high. As a result, a coating having a high strength and a high hardness was obtained, and as a result, the inventors have obtained the knowledge that cutting performance is improved even under severe cutting conditions such as high-speed dry processing, and have reached the present invention.

  That is, according to the present invention, in the surface-coated cutting tool including a coating formed in an atmosphere containing argon, the coating is made of an oxide containing at least Al, and the amount of argon contained in the coating is less than 3 at%. It is characterized by being limited within the range. The Al-containing oxide film whose Ar content is limited within this range has high hardness, and as a result, the wear resistance during the cutting test is improved.

  If the Ar content is 3 at% or more, the hardness of the Al-containing oxide film is lowered, the film strength is lowered, and the tool edge is easily chipped during cutting. On the other hand, there is no preferred lower limit for the Ar content, and it is preferable that the Ar content be zero if possible. However, when an Al-containing oxide film is formed by a method in which Ar gas is present in the film formation atmosphere, it is considered substantially impossible to completely reduce the Ar content in the film. However, in the current analyzer (Rutherford backscattering analysis method: RBS method), the Ar detection limit is up to 0.001 at%. Therefore, in the Al-containing oxide film according to the present invention, residual argon within a range of less than 3 at% is detected or undetectable by the RBS method.

The Ar content in the Al-containing oxide film is determined by the flow rate ratio of oxygen gas and argon gas introduced into the film forming chamber and the discharge conditions for ionizing the gas, for example, the operating conditions of the pulse sputtering power source and the pulse bias power source (pulse ON- OFF time, power, etc.). In addition to these condition adjustments, when Ar gas is introduced into the deposition chamber from the vicinity of the magnetron sputtering region and oxygen gas is introduced from the vicinity of the substrate surface, there is little mixing of Ar into the Al-containing oxide film. It was. By adjusting these film formation conditions, an alumina film can be formed even at 750 ° C. or lower. In order to form an Al-containing oxide film, there is a method using an Al ₂ O ₃ evaporation source. However, in this case, there is a problem that a film forming speed is slow, and it is preferable to use a metal evaporation source.

  The Al-containing oxide coating may include α-type crystals and / or γ-type crystals of alumina. The safer crystal structure of the alumina film at high temperatures is α-type, but cutting performance can be improved even with γ-type and amorphous alumina films compared to conventional nitride and carbonitride films. is there. This is because since the alumina coating is an oxide, it can suppress the diffusion of oxygen from the surface even when it becomes high temperature during cutting, and the intermediate layer between the substrate and the substrate and the oxide coating ( This is because, for example, the oxidation of the bonding layer) can be suppressed.

  If the Al-containing oxide coating additionally contains at least one of Zr, Si, Cr, Ti, and B, further performance improvement of the surface-coated cutting tool can be achieved. First, if the oxide coating contains an oxide of Zr, the thermal conductivity of the Zr oxide is poor, so that the thermal barrier property of the coating is improved, which is preferable from the viewpoint of suppressing deformation of the substrate in a high-temperature cutting environment. . If the oxide film contains Si and Ti oxides, the film hardness is improved and the wear resistance is improved. It is preferable that the oxide coating contains oxides of Cr and B because the welding resistance of the coating is improved and the peel resistance of the membrane is improved.

  The thickness of the Al-containing oxide film is preferably in the range of 0.5 to 5 μm. This is because when the thickness of the coating is less than 0.5 μm, no improvement in wear resistance is seen, and conversely, if it exceeds 5 μm, the residual stress in the surface coating film increases and the adhesion strength with the substrate decreases. It is.

  The nanoindentation hardness of the Al-containing oxide coating is preferably 18 GPa or more. Here, the Al-containing oxide film according to the present invention is a thin film having a thickness on the order of μm, and the indenter that is pushed in to the hardness measurement by so-called Vickers or Knoop reaches a depth where the influence of the hardness value of the substrate cannot be avoided. Therefore, it is preferable to measure by the nanoindentation method (see tribologist, Vol. 47, No. 3, (2002), pages 177-183). By the way, it is said that the hardness of the cutting tool is empirically required to be 2 to 5 times the hardness of the work material. Therefore, when cutting a hard material such as hardened steel, for example, a coating hardness of less than 18 GPa causes a problem in wear resistance, so a higher hardness is desired.

  The compressive residual stress value of the Al-containing oxide film obtained by the present invention was in the range of 0.1 GPa to 7 GPa (see Table 2). From the viewpoint of the strength of the coating that improves chipping and chipping properties, the residual compressive stress of the coating is more preferably in the range of about 0.5 to 5 GPa. The residual stress value in the coating was determined by X diffraction method.

  Between the base material and the Al-containing oxide coating, nitride, carbide, carbonitriding of one or more elements of group IVa element, group Va element, group VIa element, Al, Si, and B in the periodic table More preferably, an intermediate layer (for example, a bonding layer) of at least one of a metal, an oxynitride, an oxycarbide, and an oxycarbonitride is inserted. The thickness of such an intermediate layer is also preferably in the range of 0.5 to 5 μm for the same reason as the Al-containing oxide film. Although these intermediate layers have high hardness, they have poor oxidation resistance properties at high temperatures compared to oxides. However, since the Al-containing oxide coating according to the present invention suppresses the diffusion of oxygen from the surface, The layer can also maintain excellent wear resistance. Moreover, since these intermediate | middle layers can improve the adhesiveness of a board | substrate and an Al containing oxide film, it is preferable also from a viewpoint of improving the peeling resistance of a film. In addition, it is preferable that the nanoindentation hardness of these intermediate | middle layers is 23 GPa or more.

  The base material of the cutting tool coated with the Al-containing oxide film is WC-based cemented carbide, cermet, high-speed steel, ceramics (silicon carbide, silicon nitride, aluminum nitride, aluminum oxide, etc.), cubic boron nitride firing It is preferably formed of any one of a sintered body, a diamond sintered body, a silicon nitride sintered body, aluminum oxide, and titanium carbide. The surface-coated cutting tool can be a drill, an end mill, a milling and turning cutting edge replaceable tip, a metal saw, a gear cutting tool, a reamer, a tap, or the like.

  In order to coat the substrate surface with the wear-resistant coating according to the present invention, a film forming process capable of forming a high-strength Al-containing oxide coating is indispensable. Therefore, as a result of examining various film forming methods, it is preferable to use a physical vapor deposition method to form an Al-containing oxide film. The physical vapor deposition method includes a sputtering method and an ion plating method, and in particular, an unbalanced magnetron sputtering method (Kobe Steel Works Technical Report, Vol. 50, 2000, pp. 58-61), dual magnetron sputtering, or cathodic arc ion plating has been found suitable.

  In the following various embodiments according to the present invention, the improvement of the wear resistance of a surface-coated cutting tool coated with an Al-containing oxide coating is specifically illustrated. In these examples, the crystallinity and residual stress of the film were measured by X-ray diffraction method, and the composition and Ar content of the film were confirmed and measured by RBS method. Note that a method other than the unbalanced magnetron sputtering method can be used for forming the surface coating film.

(Example 1)
In Example 1 of the present invention, a cemented carbide cutting tip having a composition of JIS standard P30 and a shape of JIS standard SNG432 is prepared as a base material for a surface-coated cutting tool, and cold cathode arc type ion plating is provided on the surface thereof. A wear-resistant coating was formed using unbalanced magnetron sputtering or dual magnetron sputtering.

  For film formation, a film forming apparatus as schematically illustrated in the plan perspective view of FIG. 1 was used. In the film forming apparatus 5, there is provided a substantially disk-shaped base material holder 8 which can be rotated around its center point. A plurality of arc evaporation sources 1 and 2, sputter evaporation sources 3 and 4, and a heater 6 are arranged facing the peripheral surface of the disk-shaped holder 8. And the base material 9 of the cutting tip was mounted | worn on the surrounding surface of the disk shaped holder 8. FIG.

  A predetermined metal material is set in the arc evaporation sources 1 and 2, another predetermined metal material is set in the unbalanced sputter source 3, and Al (aluminum) is set in the unbalanced sputter source 4. It was.

First, the inside of the film forming apparatus 5 is evacuated to a vacuum degree of 1 × 10 ⁻³ Pa or less while heating the substrate 9 to 500 ° C. using the heater 6, and then a gas inlet near the sputter evaporation sources 3 and 4. Ar (argon) gas was introduced from 7a. Then, a glow discharge is generated in Ar gas while applying a bias voltage of −1000 V to the cutting tip 9 while maintaining a vacuum of 3 Pa, and after cleaning the substrate surface with Ar ions, the Ar gas is exhausted. did.

Subsequently, while applying a bias voltage of −60 V to the base material 9, a reaction gas such as N ₂ (nitrogen gas) or / and CH ₄ (methane) gas or / and oxygen gas is held in a disk shape from the gas inlet 7 b. In a state of being introduced in the vicinity of the peripheral surface of the tool 8, a vacuum arc discharge is generated at the arc evaporation sources 1 and 2 with an arc current of 100 A to ionize a predetermined metal material. An intermediate layer having bondability and wear resistance was formed on the surface of the material 9. Examples of these intermediate layers are shown in Table 1. As will be understood from Table 1, the formation of these intermediate layers can be omitted.

  Next, an Al oxide film was formed under the film formation temperature environment shown in Table 2. That is, 50 SCCM oxygen gas and 350 SCCM Ar gas were introduced into the film forming apparatus 5 in the state where a −100 V pulse DC (pulse frequency 250 kHz, ON time and OFF time 2 μsec.) Was applied as the substrate bias. And 7b, and with the pressure in the apparatus 5 set to 1 Pa, the unbalanced magnetron sputtering source 3 (aluminum) and / or the unbalanced magnetron sputtering source 4 (metal other than aluminum) is discharged to contain Al. An oxide film was formed. At this time, pulse DC (pulse frequency 100 kHz, ON time 8 μsec., OFF time 2 μsec.) Was used as the discharge power source, and the sputtering power was set to 3 kW. Each Al-containing oxide film was formed in a predetermined film thickness by adjusting the discharge time. Examples (samples 1 to 14) according to the present invention formed in this way are shown in Tables 1 and 2. Tables 1 and 2 also show comparative examples (samples 15 to 18) formed similarly to the product of the present invention. In Table 2, the symbol ND in the column indicating the amount of residual Ar indicates that the amount of residual Ar was below the detection limit of the RBS method.

  Each of the SNG432 cemented carbide cutting tips having the coatings of the present invention and the comparative products shown in Tables 1 and 2 was actually subjected to a dry continuous cutting test and an intermittent cutting test under the conditions shown in Table 3, and the cutting edge of the cutting edge The results of measuring the flank wear width are shown in Table 2. As is clear from Table 2, it can be confirmed that the cutting tool life is greatly improved in the product of the present invention compared to the comparative product.

(Example 2)
In Example 2, the reamer (JISK10 cemented carbide) was coated by the same method as in Example 1 to obtain the reamer of sample 1 and comparative products 15-18. These reamers were used to actually drill cast iron (FC250) and evaluate the lifespan of the cast iron (FC250). Cutting conditions were set to a reamer diameter of 20 mm, a cutting speed of 5 m / min, a feed of 0.4 mm / blade, and a cutting depth of 0.15 mm, and cutting was performed under wet conditions (wet conditions). Note that the tool life was determined as the number of workpieces to be processed in which the dimensional accuracy of the machining began to deviate from the specified range. The life evaluation results are shown in Table 4. From Table 4, it can be confirmed that the lifetime of the reamer according to the present invention is greatly improved.

(Example 3)
In Example 3, the end mill (JISK10 cemented carbide) was coated by the same method as in Example 1 to obtain Sample 3 and the end mills of conventional products 15-18. Then, using these end mills, cast iron (FCD450) was actually subjected to side cutting (cutting width: 15 mm), and the life evaluation was performed. As cutting conditions, the cutting speed was set to 100 m / min, the feed was set to 0.05 mm / blade, the cutting was set to 2 mm, and cutting was performed under wet conditions (wet conditions). Note that the tool life was determined as the machining length at which the dimensional accuracy of the workpiece began to deviate from the specified range. The life evaluation results are also shown in Table 4. From Table 4, it can be confirmed that the life of the end mill of the present invention is greatly improved.

Example 4
In Example 4, first, a cemented carbide pot and a ball are used to mix a binder powder composed of 40 mass% TiN and 10 mass% Al and a 50 mass% cBN powder having an average particle diameter of 2.5 μm. In addition, the mixed powder was filled in a cemented carbide container and sintered at a temperature of 1400 ° C. for 60 minutes under a pressure of 5 GPa. The obtained cBN sintered body was processed to obtain a cutting tip having a shape of ISO standard SNGA120408.

  A film of sample 10 was formed on the surface of the cutting tip by the same method as in Example 1. Using this surface-coated cutting tip, outer peripheral cutting of SUJ2 round bar (HRC62), which is a kind of hardened steel, was performed. As cutting conditions, the cutting speed was 100 m / min, the cutting depth was 0.2 mm, and the feed was 0.1 mm / rev. And cutting for 40 minutes under dry conditions to examine the flank wear amount. As a result, the wear amount of the cBN sintered compact cutting tip having the coating film of Sample 10 was 0.068 mm, whereas the wear amount of the cBN sintered compact tip not coated with the hard film was 0. It was 255 mm. Further, the determination of the tool life in Example 4 was determined as the length of the processing time when the dimensional accuracy of the workpiece began to deviate from the specified range. The life evaluation results are also shown in Table 4.

It is a plane perspective view which illustrates typically the film-forming apparatus which can be utilized for preparation of the surface covering cutting tool by this invention.

Explanation of symbols

  1, 2 arc evaporation source, 3, 4 unbalanced magnetron sputtering source, 5 film forming apparatus, 6 heater, 7a Ar gas inlet, 7b gas inlet such as oxygen, nitrogen and / or methane, 8 base material holder 9 Substrate.

Claims (13)

  A surface-coated cutting tool including a coating formed in an atmosphere containing argon, wherein the coating is made of an oxide containing at least Al, and the amount of argon contained in the coating is limited to a range of less than 3 at%. A surface-coated cutting tool characterized by comprising:   2. The surface-coated cutting tool according to claim 1, wherein the oxide film includes alumina having at least one of an α-type crystal structure and a γ-type crystal structure.     The surface-coated cutting tool according to claim 1, wherein the oxide film contains amorphous alumina.   The surface-coated cutting tool according to any one of claims 1 to 3, wherein the oxide film also contains one or more elements selected from Zr, Si, Cr, Ti, and B.   The surface-coated cutting tool according to any one of claims 1 to 4, wherein the oxide film has a thickness in a range of 0.5 to 5 µm.   The surface-coated cutting tool according to any one of claims 1 to 5, wherein the oxide coating has a nanoindentation hardness of 18 GPa or more.   Nitrides, carbides, carbonitrides, oxynitrides, oxycarbides of one or more elements selected from group IVa elements, group Va elements, group VIa elements, Al, Si, and B in the periodic table; and The surface-coated cutting according to any one of claims 1 to 6, wherein one or more intermediate layers selected from oxycarbonitrides are inserted between the base material and the oxide film. tool.   The substrate is selected from WC-based cemented carbide, cermet, high-speed steel, ceramics, cubic boron nitride sintered body, diamond sintered body, silicon nitride sintered body, aluminum oxide, and titanium carbide. The surface-coated cutting tool according to claim 1, wherein the surface-coated cutting tool is formed by:   The surface-coated cutting tool is any one of a drill, an end mill, a milling and turning cutting edge replaceable tip, a metal saw, a gear cutting tool, a reamer, and a tap. The surface-coated cutting tool according to 1.   A method for producing the surface-coated cutting tool according to claim 1, wherein the oxide film is coated by a physical vapor deposition method.   The manufacturing method according to claim 10, wherein the physical vapor deposition method includes at least one of an unbalanced magnetron sputtering method and an arc type ion plating method.   A method for producing a surface-coated cutting tool, wherein a base material is set in a reduced-pressure reaction chamber, a metal element is vaporized in the reaction chamber, the reaction chamber contains argon and oxygen, and the vaporized metal element and oxygen gas To form a coating film made of an oxide containing at least Al on the base material, and the amount of argon contained in the coating film is suppressed within a range of less than 3 at%. Tool production method.   The manufacturing method according to claim 12, wherein the Al-containing oxide film is formed at a temperature of 750 ° C. or less.

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