JP5286619B2 - Surface coated cutting tool - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface coated cutting tool capable of reducing crater wear and exhibiting sophisticated wear resistance in cutting under high-speed condition. <P>SOLUTION: The surface coated cutting tool is provided with a substrate and a coating formed on the substrate. The coating comprises one or more layers. At least one layer of the coating is a hard oxide coating layer containing at least Al and Zr and has such a composition structure that the contents of Al and Zr are varied along the thickness direction of the hard oxide coating layer. This variation includes a maximum Al content point where an Al content becomes a maximum and a maximum Zr content point where a Zr content becomes a maximum. The maximum Al content point and the maximum Zr content point exist repeatedly. An Al content ratio Al/(Al+Zr) at the maximum Al content point is 0.99-0.9999 by an atomic ratio, and a Zr content ratio Zr/(Al+Zr) at the maximum Zr content point is 0.001-0.2 by an atomic ratio. Zirconium oxide is not contained in the hard oxide coating layer. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a surface-coated cutting tool comprising a substrate and a coating formed on the substrate.

  In recent years, the performance of machine tools has been remarkably improved, but on the other hand, there is an increasing demand for higher efficiency in cutting. Along with this, there is an increasing trend of high speed cutting. Further, there is a demand for further improvement in wear resistance in cutting tools for work materials such as Pb-free steel and ductile cast iron. Abrasion resistance and cutting edge strength are in a trade-off relationship, and it has been difficult to achieve both of them with conventional techniques. For this reason, the current situation is that the requirements for high-efficiency machining cannot be fully satisfied.

  As a conventional technique, attempts have been made to improve wear resistance by incorporating Zr into a coating, but cutting tools having physical properties that can cope with high-speed machining have not been obtained only by containing Zr (for example, Patent Document 1).

  In addition, in the layer containing Zr, the cutting tool is provided with a coating having a composition distribution in which the highest content points of the content of Zr and a specific element are alternately present, and the composition distribution is continuously changed. It has been proposed (for example, Patent Document 2).

However, the cutting tools proposed in Patent Documents 1 and 2 and the like have not been able to sufficiently improve both the wear resistance and the edge strength.
JP 59-222570 A JP 2004-42150 A

  The present invention has been made in view of the present situation as described above, and an object of the present invention is to provide a coating that can reduce crater wear and provide high wear resistance in cutting under high-speed conditions. It is to provide a surface-coated cutting tool provided.

  In order to achieve the above object, the present applicant has to form a coating film formed on a substrate with a composition in which the contents of Al and Zr are continuously changed within a specific range, and to have such a composition. It has been found that by not containing zirconium oxide in the layer, it is possible to improve the wear resistance especially in cutting of steel and cast iron, and the life is prolonged in cutting in a higher speed region.

  That is, the surface-coated cutting tool of the present invention is a surface-coated cutting tool comprising a substrate and a coating formed on the substrate, and the coating is composed of one layer or two or more layers. Of these, at least one layer is a hard oxide coating layer containing at least Al and Zr, and the content of Al and Zr varies along the thickness direction of the hard oxide coating layer. This change includes an Al maximum content point at which the Al content reaches a maximum and a Zr maximum content point at which the Zr content reaches a maximum. The Al maximum content point and the Zr maximum content point Al content ratio Al / (Al + Zr) at the Al maximum content point is repeatedly present, and the atomic ratio is 0.99 ≦ Al / (Al + Zr) ≦ 0.9999, and the Zr content ratio at the Zr maximum content point Zr / (Al + Zr) is the original A 0.001 ≦ Zr / (Al + Zr) ≦ 0.2 in a ratio, is characterized by not containing zirconium oxide hard oxide coating layer.

  The thickness of the hard oxide coating layer is preferably 0.05 μm or more and 20 μm or less.

  The distance between the adjacent Al maximum content point and the Zr maximum content point is preferably 0.005 μm or more and 1 μm or less.

  The coating film includes at least one element selected from the group consisting of Group IVa elements, Group Va elements, Group VIa elements, Al and Si, or Group IVa, Va and VIa elements in the Periodic Table And a coating layer X comprising at least one element selected from the group consisting of Al and Si and at least one compound selected from the group consisting of boron, carbon, nitrogen and oxygen. .

  Moreover, it is preferable that the said film further contains an Al oxide layer, and this Al oxide layer is formed directly under a hard oxide film layer.

The coating further includes a TiBN layer made of TiB _x N _y (x, y represents atomic% and satisfies 0.001 <x / (x + y) <0.2), and the TiBN layer is made of Al It is preferably formed immediately below the oxide layer.

Further, the coating film has TiB _a N _b O _c (a, b and c represent atomic%, 0.0005 <a / (a + b + c) <0.2, and 0 <c / (a + b + c) <0.5. It is preferable that the TiBNO layer is further formed directly under the Al oxide layer.

The Al oxide is preferably α-alumina.
It is preferable that the thickness d ₁ of the hard oxide coating layer and the thickness d ₂ of the Al oxide layer satisfy d ₁ / (d ₁ + d ₂ )> 0.05.

  The total thickness of the hard oxide coating layer and the Al oxide layer is preferably 0.5 μm or more and 20 μm or less.

  The surface-coated cutting tool has a cutting edge ridge line portion, in which at least one of the hard oxide coating layer, the Al oxide layer, and the coating layer X is exposed, and a portion other than the ridge line portion is The adjacent Al maximum content point and the Zr maximum content point are preferably present alternately and repeatedly, and the interval is preferably 0.005 μm or more and 1 μm or less.

  The coating film may be an embodiment in which at least one layer forming the layer has a compressive residual stress or no stress, and has the compressive residual stress or no stress. The layer is preferably at least one of the hard oxide coating layer and the Al oxide layer.

The coating is preferably formed by chemical vapor deposition.
One or more coating layers X are formed, and at least one layer is preferably a layer containing 50 mass% or more of TiCN formed by MT-CVD.

  It is preferable that a layer containing 50% by mass or more of the titanium compound is formed in the lowermost layer of the coating film.

The thickness of the coating is preferably 1 μm or more and 25 μm or less.
The substrate is preferably at least one of cemented carbide, cermet, aluminum oxide ceramics, and silicon nitride ceramics.

  By forming a layer having a composition in which the content of Al and Zr is continuously changed in a specific range in the coating formed on the base material, and by not including zirconium oxide in the layer, In the cutting of steel and cast iron, it is possible to improve the wear resistance and further extend the life.

<Surface coated cutting tool>
The surface-coated cutting tool of the present invention comprises a base material and a coating film formed on the base material. The surface-coated cutting tool of the present invention having such a configuration is, for example, a drill, end mill, milling or turning cutting edge replacement cutting tip, metal saw, gear cutting tool, reamer, tap, or pin shaft milling of a crankshaft. It can be used very effectively as an industrial chip. And the coated cutting tool of this invention can be used especially effectively as a blade-tip-exchange-type cutting tip for turning, such as steel and cast iron.

<Base material>
As the base material of the surface-coated cutting tool of the present invention, a conventionally known material known as such a cutting tool base material can be used without any particular limitation. For example, cemented carbide (for example, WC base cemented carbide, including WC, including Co, or further including carbonitride such as Ti, Ta, Nb, etc.), cermet (TiC, TiN, TiCN, etc.) High-speed steel, ceramics (titanium carbide, silicon carbide, silicon nitride, aluminum nitride, aluminum oxide, and mixtures thereof), cubic boron nitride sintered body, diamond sintered body Etc. can be mentioned as examples of such a substrate. When a cemented carbide is used as such a base material, the effect of the present invention is exhibited even if such a cemented carbide contains an abnormal phase called free carbon or η phase in the structure. In addition, these base materials may have a modified surface. For example, in the case of cemented carbide, a de-β layer may be formed on the surface, or in the case of cermet, a surface hardened layer may be formed. Even if the surface is modified in this way, the present invention The effect of is shown.

  Among these base materials, when it is at least one of cemented carbide, cermet, aluminum oxide ceramics, and silicon nitride ceramics, the wear resistance against steel and cast iron is further improved by forming the coating according to the present invention. can do.

<Coating>
The film formed on the base material of the surface-coated cutting tool of the present invention comprises one layer or two or more layers. At least one of these layers is a hard oxide coating layer formed by continuously changing the Al and Zr contents described in detail below within a specific range. The coating in the present invention may further include other layers as long as it includes this hard oxide coating layer. In addition, the film in this invention is not limited only to what coat | covers the whole surface on a base material, The aspect in which a film is partially formed, such as a corner part containing a cutting edge, is also included.

  The total thickness of such a coating (the total thickness when two or more layers are formed) is preferably 1 μm or more and 25 μm or less, more preferably the upper limit is 23 μm or less, and even more preferably 20 μm or less. The lower limit is 1.5 μm or more, more preferably 2 μm or more. When the thickness is less than 1 μm, the effect of improving various properties such as wear resistance may not be sufficiently exhibited. When the thickness exceeds 25 μm, the wear resistance is larger than that when the total thickness of the coating is within the above range. There is a tendency that the improvement effect of the property is not recognized, and the edge strength may be lowered, which is industrially disadvantageous. In addition, as a measuring method of a film thickness, a cutting tool can be cut | disconnected and the cross section can be observed with SEM (scanning electron microscope) or a metal microscope, and a cutting tool is similarly used as a measuring method of a film | membrane composition. It can cut | disconnect and the cross section can be performed by microanalysis using EPMA, ESCA, XPS, EDS, WDS, EELS, etc. Moreover, you may analyze using TEM as needed.

<Hard oxide coating layer>
The hard oxide coating layer in the present invention is a hard oxide coating layer formed by a composite coating composed of Al and Zr. This hard oxide coating layer has a composition structure in which the contents of Al and Zr change along the thickness direction of the hard oxide coating layer, and this change includes the maximum Al content that maximizes the Al content. Point and the Zr maximum content point where the Zr content becomes maximum, the Al maximum content point and the Zr maximum content point exist alternately, and the Al content ratio at the Al maximum content point Al / (Al + Zr) Is an atomic ratio of 0.99 ≦ Al / (Al + Zr) ≦ 0.9999, and the Zr content ratio Zr / (Al + Zr) at the Zr maximum content point is 0.001 ≦ Zr / (Al + Zr) ≦ 0.2. By including such a hard oxide coating layer, the hardness of the coating is increased and the heat insulation is improved, so that the wear resistance against steel and cast iron is improved. The hard oxide coating layer in the present invention includes inevitable impurities in addition to the oxide of Al and Zr. For example, Al oxides include α-alumina, κ-alumina, γ-alumina, θ-alumina, δ-alumina, η-alumina, χ-alumina, and amorphous alumina. Each hard oxide coating layer can be formed from one or more of these oxides. In the present invention, Zr is presumed to be present in the hard oxide coating layer as at least one of a substitutional atom and an interstitial atom.

  Between the adjacent Al or Zr maximum content points adjacent to each other, the content of Al and Zr may vary continuously along the thickness direction of the hard oxide coating layer, for example, 0.001 μm or more and 0.5 μm. Including those that change in stages with the following width. In this case, the inclination of the change in the content ratio of each of Al and Zr may be adjusted according to the interval between the maximum content points. In addition, there is a minimum content point where the content is the lowest between adjacent maximum content points, and changing means that the content decreases continuously between the maximum content point and the minimum content point. The content increases continuously between the minimum content point and the maximum content point. Further, the maximum content point only needs to be repeatedly present in the thickness direction of the hard oxide coating layer, and the number of repetitions is not particularly limited, but from the point that wear resistance and heat resistance can be further improved, The maximum content point is preferably 2 or more (the number of repetitions is 2 or more), more preferably 4 or more.

  The maximum content points of Al and Zr may be present at the same position in the thickness direction or at different positions, but from the point of increasing the hardness of the entire coating, It is desirable that the content points and the Zr maximum content points exist alternately. That is, this is a case where the Zr minimum content point exists at the same position in the thickness direction as the Al maximum content point, and the Al minimum content point exists at the same position in the thickness direction as the Zr maximum content point. The Al maximum content point has a relatively excellent wear resistance, in particular, an effect of suppressing chemical wear, but the heat insulation is insufficient, while the Zr maximum content point has a relatively excellent heat insulation property. Wearability may be insufficient. For this reason, in order to compensate the insufficient heat insulation of the Al maximum content point and the insufficient wear resistance of the Zr maximum content point by mutual inclusion, the maximum content points of Al and Zr are as described above. It is desirable to exist alternately. In addition, if it is possible to mutually complement the effects of wear resistance due to the inclusion of Al and heat insulation due to the inclusion of Zr, the alternating maximum points of Al and Zr are not necessarily the same position in the thickness direction. For example, they may be present at different positions in the thickness direction within the range of 0.001 μm to 0.5 μm.

  When the adjacent Al maximum content point and the Zr maximum content point are alternately and repeatedly present, the distance between the Al maximum content point and the Zr maximum content point is preferably 0.005 μm or more and 1 μm or less. More preferably, it is 0.03 μm or more and 0.6 μm or less. If this interval is less than 0.005 μm, it is difficult to clearly form the points (maximum content points) of the respective maximum contents in the above-mentioned atomic composition range, and if the interval exceeds 1 μm, the heat insulating property In addition, the point where the wear resistance is insufficient often appears locally in the hard oxide coating layer, so that the wear of the cutting edge of the cutting tool and the plastic deformation of the base material may easily proceed. The interval between the Al maximum content point and the Zr maximum content point may be constant in the thickness direction as described later, or may be different from each other within a range satisfying the above range. In addition, the maximum content point includes a case where there is a width in the thickness direction. In such a case, the central portion of the band where the atomic ratio is constant in the thickness direction is regarded as the maximum content point. .

  The Al content ratio Al / (Al + Zr) at the maximum content point is an atomic ratio of 0.99 ≦ Al / (Al + Zr) ≦ 0.9999, preferably 0.9995 or less, more preferably 0.999. It is as follows. When the Al content ratio exceeds 0.9999, the Zr content ratio decreases, and the effect of improving heat insulation is not sufficient. When the Al content ratio is less than 0.99, the chemical stability of the entire coating in the present invention is lowered.

  The Zr content ratio Zr / (Al + Zr) at the maximum content point is an atomic ratio, and is 0.001 ≦ Zr / (Al + Zr) ≦ 0.2, preferably 0.18 or less, more preferably 0.8. 15 or less. Further, the content ratio of Zr is preferably 0.0012 or more, more preferably 0.0015 or more. When the content ratio of Zr is less than 0.001, the effect of addition of Zr cannot be exerted, and when the content ratio of Zr exceeds 0.2, the hardness of the film becomes too high and the strength decreases. When cutting steel or cast iron, chipping or chipping may occur and the life may be shortened.

  The atomic ratio at each local maximum content point is not constant in the thickness direction, and the atomic ratio between adjacent Al maximum content points in the thickness direction may be different as long as the above range is satisfied.

In the present invention, the hard oxide coating layer does not contain zirconium oxide (ZrO ₂ ). Thus, when a hard oxide film layer does not contain zirconium oxide, it exhibits excellent wear resistance in dry high-speed cutting of steel and cast iron. The reason for this is unknown, but ZrO ₂ undergoes a phase transformation from monoclinic to tetragonal and from tetragonal to cubic as the temperature rises, and from monoclinic to tetragonal particularly in the temperature range of 1000 to 1200 ° C. It is known that volume change occurs during phase transformation to crystal, and when ZrO ₂ is included in the hard oxide coating layer, ZrO ₂ is used when dry cutting of steel or cast iron with high cutting edge temperature is performed. ₂ may self-destruct due to the volume change accompanying the above-mentioned phase transformation, but has high wear resistance in the dry high-speed cutting using the tip provided with the hard oxide coating layer not containing ZrO ₂ in the present invention. Presumed to show.

In the present invention, the fact that zirconium oxide (ZrO ₂ ) is not contained in the hard oxide coating layer means that XRD (X-ray diffraction) measurement is performed, and the X-ray diffraction angle and diffraction intensity of Al oxide and ZrO ₂ are measured. Data shall be collected and judged. Specifically, “the crystal structure of aluminum oxide, which is the main constituent of the hard oxide coating layer, in the standard diffraction intensity in the JCPDS (Join Committee on Powder Diffraction Standards) card, in descending order of diffraction intensity. Of the diffraction intensities at the eight interplanar spacings, the interfacial diffraction intensities with the lowest diffraction strength and the interplanar spacing d (Å) in the JCPDS card in the respective crystal structures of zirconium oxide (ZrO ₂ ) , ZrO ₂ monoclinic crystal: 3.164 Å, 2.840 Å, 2.606 Å (both are rounded down to the fourth decimal place), or ZrO ₂ tetragonal crystal: 2.950 Å, 1.810 Å, 1. Compared to the diffraction intensity with the highest diffraction intensity among the diffraction intensities at 535 mm (both digits are rounded down) These "oxide of zirconium if none of the diffraction intensity for (ZrO ₂₎ is smaller than the smallest of the diffraction intensity for the foregoing oxides of aluminum" hard oxide coating layer containing ZrO ₂ Suppose you don't.

That is, for example, when the oxide of aluminum is α-Al ₂ O ₃ , the eight interplanar spacings d (Å) arranged in order from the highest diffraction intensity in the JCPSD card at the standard diffraction intensity is 3.479Å. 552 Å, 2.379 Å, 2.085 Å, 1.740 Å, 1.601 Å, 1.404 い ず れ, 1.374 Å (both digits are rounded down after the decimal point). Among these diffraction intensities at the interplanar spacing, those having the lowest diffraction intensity, and 3.164Å, 2.840Å in the case where the interplanar spacing d (Å) due to the oxide of zirconium (ZrO ₂ ) is monoclinic, and Compared to the diffraction intensity at 2.606 、 and the diffraction strength at 2.950 Å, 1.810 Å, and 1.535 Å in the case of tetragonal crystals (all of which are rounded down to the fourth decimal place). When the latter diffraction intensity is low, it is determined that the hard oxide coating layer does not contain ZrO ₂ . In addition, the surface spacing of the α-Al ₂ O ₃ is determined according to JCPDS No. 46-1212 and No. 010-0173 (Huang, T., Parrish, W., Masciocchi, N., Wang, P., Adv. X-Ray Anal., 33, 295. (1990), Acta Crystallogr., Sec. B: Structural Science. 49, 973, (1993)).

Further, for example, when the aluminum oxide is κ-Al ₂ O ₃ , as in the case of α-Al ₂ O ₃ , as in the case of α-Al ₂ O ₃ , the eight-surface spacing d arranged in order from the highest diffraction intensity in the JCPSD card at the reference diffraction intensity d. (Å), 3.040 に お け る, 2.790Å, 2.570Å, 2.320Å, 2.110Å, 1.640Å, 1.430Å, 1.390Å (both are rounded down to the fourth decimal place) Among them, the diffraction intensity at 3.164Å, 2.840Å and 2.606Å in the case where the lowest diffraction intensity and the interplanar spacing d (Å) due to zirconium oxide (ZrO ₂ ) are monoclinic, In the case of tetragonal crystal, the diffraction intensity of 2.950Å, 1.810 に お け る and 1.535Å (all of which are rounded down to the fourth decimal place) is the highest. Base, if the latter diffraction intensity is low, ZrO ₂ is determined not to be contained in the hard oxide coating layer. The surface spacing of the κ-Al ₂ O ₃ is determined by JCPDS No.052-0803 and No.004-0878 (Halvarsson, M., Langer, V., Vuorinen, S., Powder Diffraction, 14, 61, (1999), Yourdshahyan, Y., Ruberto, C., Halvarsson, M., Bengtsson, L., Langer, V., Lundqvist, B., J. Am. Ceram. Soc., 82, 1365. (1999) Stumpf et al., Ind. Eng. Chem., 42, 1398, (1950)).

  The thickness of the hard oxide coating layer is preferably 0.05 μm or more, more preferably 0.1 μm or more, and further preferably 0.5 μm or more and 20 μm or less. When the thickness of the hard oxide coating layer is less than 0.05 μm, the effect of providing the hard oxide coating layer may not be sufficiently obtained.

<Coating layer X>
The coating film includes at least one element selected from the group consisting of Group IVa elements, Group Va elements, Group VIa elements, Al and Si, or Group IVa, Va and VIa elements in the Periodic Table And a coating layer X comprising at least one element selected from the group consisting of Al and Si and at least one compound selected from the group consisting of boron, carbon, nitrogen and oxygen. . By providing such a coating layer X, the balance between wear resistance and toughness can be further increased. When the element or compound which comprises the coating layer X is comprised by 2 or more types, the combination is not specifically limited. As the element or compound as described above, for example Cr, Ti, Al, Si, V, Zr, Hf, TiC, TiN, TiCN, TiNO, TiCNO, TiB 2, TiO 2, TiBN, TiBNO, TiCBN, ZrC, HfC , HfN, TiAlN, AlCrN, CrN , VN, TiSiN, TiSiCN, AlTiCrN, TiAlCN, ZrCN, ZrCNO, Al 2 O 3, AlN, AlCN, ZrN, TiAlC, NbC, NbN, NbCN, Mo 2 C, WC, W 2 C etc. can be mentioned. In the present invention, when the compound is represented by the chemical formula as described above, it is assumed that all the conventionally known atomic ratios are included unless the atomic ratio is particularly limited, and are not necessarily limited to those in the stoichiometric range. . For example, when simply describing “TiCN”, the atomic ratio of “Ti”, “C”, and “N” is not limited to 50:25:25, and also when “TiN” is described, “Ti” and “N” The atomic ratio is not limited to 50:50. These atomic ratios include all conventionally known atomic ratios (the same applies to the following chemical vapor deposition layer, physical vapor deposition layer, examples, etc.).

  The thickness of the coating layer X is not particularly limited, but is preferably 0.1 μm or more and 30 μm or less. When the thickness of the coating layer X is less than 0.1 μm, the above-mentioned balance improvement effect may not appear. When it exceeds 30 μm, no significant improvement in wear resistance is observed, and the fracture resistance deteriorates. There is.

  In the coating film, the position in the thickness direction for forming the coating layer X is not particularly limited. For example, when formed on the hard oxide coating layer, wear resistance, heat dissipation, welding resistance, It is possible to improve at least one of the recognition characteristics of the cutting edge used, and when formed under the hard oxide coating layer, the balance between wear resistance and toughness is improved, and Improvement in adhesion can be realized.

Further, the coating layer X may be formed by one layer or two or more layers. When a plurality of layers are formed, at least one layer is preferably a TiCN layer formed by MT-CVD. In this case, The balance between the wear resistance and the strength of the cutting edge of the cutting tool can be made favorable. The composition ratio of the TiCN layer is not particularly limited, and the TiCN layer may contain other elements such as oxygen, silicon, Zr, Hf, and Al. As the MT-CVD method, any of the conventionally known conditions can be adopted. However, in order to further reduce damage to the substrate due to heating during film formation, the film is formed at 800 ° C. or higher and 900 ° C. or lower. Is preferred. In this case, the gas used for film formation is preferably a nitrile gas, particularly acetonitrile (CH ₃ CN), because it is excellent in mass productivity.

<Al oxide layer>
The coating preferably includes an Al oxide layer, and the Al oxide layer is preferably formed immediately below the hard oxide coating layer. By including the Al oxide layer, the adhesion of the coating can be further improved. In this case, at the boundary between the hard oxide coating layer and the Al oxide layer, the composition of Al may change continuously, or may change intermittently or discontinuously. Even if it is this aspect, the improvement effect of the adhesive force by including an Al oxide layer is exhibited.

  Examples of the Al oxide include α-alumina, κ-alumina, γ-alumina, θ-alumina, δ-alumina, η-alumina, χ-alumina, and amorphous alumina, and two of these Al oxides. Although the state where the above is mixed can be mentioned, α-alumina is preferable from the viewpoint of chemical stability, and α-alumina is preferably contained in the Al oxide layer at a mass ratio of 50% or more. The more preferable content of α-alumina is 60% or more. By making the Al oxide layer containing α-alumina in such a range, excellent wear resistance and chemical stability can be obtained. it can.

The thickness of the Al oxide layer is not particularly limited, and the thickness d ₁ of the hard oxide coating layer and the thickness d ₂ of the Al oxide layer satisfy d ₁ / (d ₁ + d ₂ )> 0.05. It is preferable to satisfy. It is more preferable to satisfy 0.1 <d ₁ / (d ₁ + d ₂ ) <0.7. When d ₁ / (d ₁ + d ₂ ) is 0.05 or less, the content ratio of Zr in the entire coating becomes small, so that the effect of including Zr may be reduced.

The total film thickness d ₁ + d ₂ of the Al oxide layer and the hard oxide coating layer is preferably 0.5 μm or more and 20 μm or less, more preferably 1.0 μm or more, and further preferably 1.5 μm or more. Preferably there is. The upper limit is more preferably 18 μm or less, and further preferably 15 μm or less. When d ₁ + d ₂ is less than 0.5 μm, improvement in wear resistance may not be observed. When it exceeds 20 μm, there is a tendency that no significant improvement in wear resistance is observed compared to the above range. Moreover, since the strength of the blade edge may be lowered, it is industrially disadvantageous.

  The Al oxide layer is formed together with the coating layer X from the viewpoint that the adhesion between the coating and the cemented carbide as the base material and the balance between the strength of the cutting edge of the cutting tool and the wear resistance can be improved. It is preferable. Here, the coating layer and the Al oxide layer are relatively excellent in oxidation resistance. However, in the case where the coating layer X is provided together, in order to improve the adhesion between these layers, a TiBN layer described later or It is preferable to include a TiBNO layer.

When the coating includes an Al oxide layer, a layer (TiBN layer) composed of TiB _x N _y (x, y represents atomic% and satisfies 0.001 <x / (x + y) <0.2) is further added. It is preferable to include. More preferably, x / (x + y) is 0.002 <x / (x + y) <0.15. This TiBN layer is a layer formed immediately below the Al oxide layer. When x / (x + y) is 0.01 or less, the effect of improving the adhesion is low, and when it is 0.2 or more, the reactivity with the work material is increased and wear due to welding or the like easily proceeds. Sometimes. As long as B and N satisfy the above atomic ratio, the abundance ratio of Ti and BN is not particularly limited.

Further, when the coating includes an Al oxide layer, instead of the TiBN layer, TiB _a N _b O _c (a, b and c represent atomic%, and 0.0005 <a / (a + b + c) <0. 2 and 0 <c / (a + b + c) <0.5) is preferably further included (TiBNO layer). This TiBNO layer is a layer formed immediately below the Al oxide layer. When a / (a + b + c) is 0.0005 or less, the effect of improving the adhesion is low, and when it is 0.2 or more, the reactivity with the work material is increased, and wear due to welding or the like easily proceeds. Sometimes. By including oxygen element (O), the hardness of the entire film is increased, so that it is possible to further improve the wear resistance, but when c / (a + b + c) is 0.5 or more, the hardness of the film There is a risk that the TiBNO layer becomes the base point of fracture during cutting. As long as B, N, and O satisfy the above atomic ratio, the abundance ratio between Ti and BNO is not particularly limited.

<Lower layer>
It is preferable that a layer containing 50% by mass or more of the titanium compound as a lowermost layer (immediately above the base material) of the coating film is formed. By providing a layer containing a specific amount of such a titanium compound as the lowermost layer, the adhesion of the laminated film can be further improved.

  The titanium compound constituting the lowermost layer is preferably a compound of Ti and at least one of carbon, nitrogen, silicon and oxygen, and preferably TiN.

<Outermost surface layer>
From the viewpoint of improving the welding resistance, the outermost layer is preferably a layer made of an oxide. As the layer made of such an oxide, a layer mainly composed of the Al oxide or a layer mainly composed of an oxide such as Ti or Hf is preferably used. In addition, in order to clarify the state of use of the chip (recognition, ie, whether it is unused or used), at least one of the rake face and the flank face is a bright glossy layer as a surface layer. It is preferable that the surface-coated cutting tool has a structure having a cutting edge ridge line portion, and at least one of the hard oxide coating layer, the Al oxide layer, and the coating layer X is exposed in the ridge line portion. It is preferable that the portion other than the ridge line portion is constituted by a hard oxide coating layer.

  FIG. 4A is a cross-sectional view at the nose R bisector (a cross-sectional view in the thickness direction of the blade edge divided by a line that bisects the apex angle of the nose R). The ridge line portion 12 is preferably a layer made of an oxide as described above. Moreover, although the layer which comprises the surface layer part 10, 11, 13, and 14 of the ridgeline part shown to Fig.4 (a) is not specifically limited, It is a more preferable aspect that a use condition can be confirmed. The above-described exposure refers to a case where the exposure rate at the edge line 12 of the blade edge is, for example, 50% or more of the surface area when the hard oxide coating layer or the Al oxide layer is exposed. The exposure rate is a region including the center portion of the surface of the cutting edge ridge line portion 12, and the value in the case where the center of this region and the central portion of the cutting edge ridge line portion 12 are substantially at the same position. . As for the exposure rate in the blade edge line part 12, it is more desirable that it is 80% or more of the surface area. When the hard oxide layer or the Al oxide layer is exposed, the exposure rate of the surface layer portions 11 and 13 is preferably such that the surface region from the blade edge portion 12 is 50% or more of the surface area of each portion. However, there is no particular limitation as long as the corner can be identified. The exposure rate of the hard oxide layer or Al oxide layer in the surface layer portions 10 and 14 is desirably 50% or more, more preferably 80% or more of the surface area of each portion.

  Further, in order to improve the microchipping resistance of the cutting edge, the layer thickness of the oxide layer in the cutting edge ridge line portion 12 is reduced or shown in a sectional view taken along the nose R bisector of FIG. Thus, it is effective to expose the inner layer (blade edge ridge portion 12c) of the oxide layer. In FIG. 4 (b), for example, a cutting edge ridge line when a coating layer X is formed on a substrate, a hard oxide coating layer or an Al oxide layer is formed thereon, and an arbitrary surface layer is provided. Indicates the part. That is, in FIG. 4B, the surface layer portions 10 and 14 are arbitrary surface layers, and the surface layer portions 11, 12a, 12b and 13 are hard oxide coating layers or Al oxide layers. The cutting edge ridge line portion 12c is preferably exposed at an inner layer of 5% or more, and desirably has an inner layer exposed of 10% or more, thereby improving the microchipping resistance. Further, in the cutting edge ridges 12a and 12b, the hard oxide coating layer, the Al oxide layer or the coating layer X is preferably exposed by 50% or more, and desirably 80% or more. Further, the surface layer portions 11 and 13 are desirably exposed at 50% or more of the surface area as in FIG. 4A, but are not particularly limited as long as the corners can be identified.

  What is necessary is just to process the exposure of the said desired layer using an elastic grindstone barrel, a brush, a blast etc., for example.

  As described above, at least one of the hard oxide coating layer, the Al oxide layer, and the coating layer X is exposed in the ridge line portion, thereby improving the microchipping resistance in the ridge line portion of the blade edge. In addition, since the hard oxide coating layer of the present invention is provided, damage caused by friction of the coating layer caused by chipping can be effectively suppressed. As a result, the wear resistance and the like can be remarkably improved as a whole cutting tool.

<Residual stress>
The coating may be a layer in which at least one or more layers forming the coating have compressive residual stress or no stress, and these layers include the hard oxide coating layer and the Al oxide. It is preferably at least one of the layers.

As described above, in order to obtain a state having a compressive residual stress or a state having no stress, by processing the coating of the portion contributing to cutting using an elastic grindstone, a barrel, a brush, a blast, A layer in which such compressive residual stress is introduced or a layer without stress has improved toughness compared to the case where tensile residual stress exists in the layer. Although the compressive residual stress to introduce | transduce is not specifically limited, For example, if it introduce | transduces in 0.0MPa or more and the range of 5.0MPa or less, the improvement effect of toughness will become favorable. In the present invention, the residual stress can be measured by the sin ² ψ method using an X-ray stress measuring device.

  The introduction of the compressive residual stress and the formation of the layer having no stress can be performed on the coating after all the layers have been formed and the coating has been completed. In this case, the effect of the present invention is not reduced. In addition, as described later, even when a part of the laminate is removed by surface treatment in order to obtain a surface layer and a specific layer, the effect of the present invention is exhibited as long as the hard oxide film layer exists. Is.

<Other layers>
The coating in the present invention may further contain one or more layers other than the hard oxide coating layer as described above. The formation position of such other layers is not particularly limited, and by forming such other layers, for example, the effect of the present invention of further improving adhesion and providing high wear resistance can be further achieved. It is also possible to achieve the effect that it can be improved, lubricity can be imparted, or adhesion with the work material can be suppressed.

  Examples of the compound that forms such another layer include AlN, AlCN, TiN, TiCN, VN, and ZrN. Note that such another layer has a thickness of 0.01 μm or more and 10 μm or less, preferably 0.1 μm or more and 5 μm or less.

<Manufacturing method>
The coating in the present invention can be formed by either chemical vapor deposition (CVD) or physical vapor deposition (PVD), but by chemical vapor deposition because of its adhesion to the substrate and chemical stability. It is preferable to do.

  Further, the hard oxide coating layer having a composition structure in which the contents of Al and Zr are continuously changed in the layer can be produced by, for example, a CVD furnace as shown in FIG. FIG. 1 is a diagram schematically showing a cross section of a CVD furnace 1. A plurality of base material setting jigs 3 holding the base material 2 can be installed in the CVD furnace 1. These are covered with a stainless steel reaction vessel 4 and heated with a heater 5. The coating layer can be formed by flowing a raw material gas. The jigs and the like in the reaction vessel 4 are usually made of graphite. The source gases 7 and 8 are configured to be exhausted from the exhaust port 9.

In the present invention, in order to change the raw material gas introduced into the reaction vessel 4 in a short time or continuously, it is desirable to make the gas in the reaction vessel uniform. FIG. 2 schematically shows the base material setting jig 3 and the base material 2 held thereon. As shown in FIG. 2, the base material setting jig 3 promotes the uniform gas dispersion in the reaction vessel 4 because the through holes are open. For example, when the raw material gas is introduced from an introduction nozzle 8 having a plurality of communication ports as shown in FIG. 1, the introduction nozzle 8 is preferably rotated. Further, in order to promote the gas circulation in the reaction vessel 4, it is desirable that the base material 2 is placed horizontally as shown in FIG. In addition, in FIG. 2, as an example of the installation method of such a base material, it is 12.7 mm square, the thickness is 4.76 mm, and the center has a hole. JIS standard B-4120 (1998) CNMA120408 shape The case where the base material 2 is installed is schematically shown and described. In order to reduce variations in the quality and thickness of the coating layer X of the base material 2, it is desirable to arrange the base materials so that the cutting edge position is on the through hole as shown in FIG. 2. In addition, by using a spacer or the like (not shown) between the base material setting jig 3 and the base material 2, it is possible to reduce the variation between the coating layer X on the upper surface and the lower surface of the base material. This is desirable. Further, according to various test results, when the raw material gas was introduced into the reaction vessel 4, when the ZrCl ₄ gas inlet 7 and the other raw gas inlet 8 were separated as shown in FIG. When forming the hard oxide coating layer of the present invention, it becomes possible to control the Zr content within the above range, that is, a more accurate composition in the coating layer in a situation where Zr is relatively less than Al. This is desirable because it allows control. The ZrCl ₄ introduction jig 6 for diffusing ZrCl ₄ introduced from the introduction port has a plurality of concentric holes as shown in FIG. 3, and gas is introduced into the reaction vessel 4. It is introduced uniformly.

Using the above-described CVD furnace, for example, the inside of the reaction vessel is heated to a predetermined temperature within the range of 750 ° C. to 1100 ° C., and the film can be formed by flowing the source gas into the reaction vessel. The source gas used is TiCl ₄ , ZrCl ₄ , ZrCl ₃ , AlCl ₃ , N ₂ , H ₂ , CH ₃ CN, CH ₄ , CO, CO ₂ , BCl ₃ , H ₂ S, Ar, etc. The pressure is preferably a predetermined pressure within a range of 3 kPa to 60 kPa. In the hard oxide coating layer according to the present invention, in order to precisely control the composition of elements constituting the coating layer along the thickness direction, the introduced gas type, the amount and the introduction time are automatically controlled using a computer, sequencer, etc. It is desirable to do.

  As described above, the hard oxide coating layer of the present invention in which the contents of Al and Zr are defined can be formed.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these. In addition, the chemical composition (composition of the compound) of each layer constituting each coating film was confirmed by an X-ray microanalyzer (EPMA), and the thickness of each layer was confirmed by observing a cross section of the coating film using an SEM or a metal microscope. .

The film formed on the substrate in this example was formed by the CVD method, MT (Moderate Temperature) -CVD method, or HT (High Temperature) -CVD method as follows. In this example, the temperature of the ZrCl ₄ gas generation container was set to 500 degrees.

(Examples 1 to 11: structure)
5.0 mass% TiC, 2.0 mass% TiCN, 0.8 mass% TaC, 0.6 mass% NbC, 0.3 mass% ZrC, 0.2 mass% Cr ₃ C ₂ , 7.8 mass% The raw material powder blended with the composition ratio of Co and the balance of WC was wet mixed in a ball mill for 48 hours, dried, and then pressed into a green compact at a pressure of 100 MPa, and this green compact was vacuumed at 2 Pa. Hold at 1450 ° C. for 1 hour. Thereafter, the green compact is taken out, and the seating surface is flattened, and then blade edge processing (0.6 mm honing as viewed from the rake face with a SiC brush) is performed, and is defined in JIS standard, B-4120 (1998). A cutting tip substrate made of WC cemented carbide having a CNMA120408 shape was prepared. It was confirmed by observing with a metal microscope that the surface cut in the thickness direction was lapped with a diamond paste and a 15 μm de-β layer was formed on the surface of the substrate.

  Next, according to the coating composition shown in Table 1, a coating film was formed on the surface of the substrate thus prepared using a known chemical vapor deposition method.

  The composition of the coating was formed such that the layer described on the left side of the column “Coating Layer Structure” in Table 1 was laminated on top in order as the lowest layer. Moreover, the description in parentheses in the column of “Coating layer structure” in Table 1 indicates the thickness (μm) of each layer, and the hard oxide coating layers A1 to A3 have the composition structure shown in Table 2 below.

From the measurement results of EPMA, it was confirmed that 0.23 atomic% of Zr element was contained in α-Al ₂ O ₃ (2.5) in Example 4 of Table 1. Moreover, for each film of Examples performs known XRD (X-ray diffraction) measurement confirmed ZrO ₂ of presence in the hard oxide coating layer. Specifically, the diffraction intensities of each of the eight peaks related to α-Al ₂ O ₃ or κ-Al ₂ O ₃ and the six peaks of monoclinic crystal and tetragonal crystal related to ZrO ₂ were compared. In all cases, the diffraction intensity of all the six peaks related to ZrO ₂ was smaller than the minimum value of the diffraction intensity of the eight peaks related to α-Al ₂ O ₃ or κ-. As a result, it was found that the hard oxide coating layer of Example 1 to 11 does not contain ZrO _2.

In Table 2, Zr / (Al + Zr) indicates a Zr maximum content point at a predetermined interval, and Al / (Al + Zr) indicates an Al maximum content point at a predetermined interval. D _Zr-Al represents the distance between the adjacent Zr maximum content point and the Al maximum content point. In addition, the description regarding this maximum content point is the same in the following tables.

  The hard oxide coating layers A1 to A3 in Table 2 were held for 5 minutes under the film formation conditions “A-Zr” shown in Table 3, and then alternately held for 5 minutes under the film formation conditions “A-Al”. It was formed repeatedly. In A1, each condition was alternately repeated 15 times, A2 was alternately repeated 40 times, and A3 was alternately repeated 130 times to form a hard oxide film layer having a predetermined film thickness.

(Cutting evaluation)
About the surface covering cutting tool of Examples 1-11 manufactured as mentioned above, the flank wear amount and the crater wear amount were measured by implementing a continuous turning test on the following cutting conditions. The smaller the flank wear amount, the better the wear resistance, and the smaller the crater wear amount, the lower the crater wear. The results are shown in Table 4 below.

(Abrasion resistance test of steel: cutting conditions)
Work material: SCM435 round bar Cutting speed: 320m / min
Feed: 0.34 mm / rev.
Cutting depth: 2.0mm
Cutting oil: None Cutting time: 8 minutes (Abrasion resistance test of cast iron: cutting conditions)
Work material: FCD450 round bar Cutting speed: 350m / min
Feed: 0.32 mm / rev.
Cutting depth: 2.0mm
Cutting oil: None Cutting time: 6 minutes (Toughness test: Cutting conditions)
The 20 corners were cut by cutting under the following cutting conditions, the damage rate was calculated, and the toughness of the obtained surface-coated cutting tool was evaluated.

Work Material: S55C Grooved Round Bar Cutting Speed: 110m / min
Feed: 0.45 mm / rev.
Cutting depth: 2.0mm
Cutting oil: None Cutting time: 1 minute

(Examples 12-21, Comparative Examples 1-3: Composition)
A surface-coated cutting tool was obtained in the same manner as in Example 1 except that the coating composition was set to Table 5 and each hard oxide coating layer X shown in Table 6 was used.

The composition of the coating was formed such that the layer described on the left side of the column “Coating Layer Structure” in Table 5 was laminated on top in order as the lowest layer. Moreover, the description in parentheses in the column of “Coating layer structure” in Table 5 indicates the thickness (μm) of each layer. Incidentally, with respect to each film shown in Table 6 performs known XRD (X-ray diffraction) measurement confirmed ZrO ₂ of presence in the hard oxide coating layer. Specifically, the diffraction intensities of each of the eight peaks related to α-Al ₂ O ₃ or κ-Al ₂ O ₃ and the six peaks of monoclinic crystal and tetragonal crystal related to ZrO ₂ were compared. In all cases, the diffraction intensity of all the six peaks related to ZrO ₂ was smaller than the minimum value of the diffraction intensity of the eight peaks related to α-Al ₂ O ₃ or κ-. As a result, it was found that the hard oxide coating layers B to N do not contain ZrO ₂ .

  The above-mentioned cutting evaluation was performed on the surface-coated cutting tools obtained in Examples 12 to 21 and Comparative Examples 1 to 3. The results are shown in Table 6.

  The hard oxide coating layers B to D shown in Table 6 were held for 5.5 minutes under the film formation conditions “X-Zr” shown in Table 7, and then held for 5.5 minutes under the film formation conditions “X-Al”. The conditions were alternately repeated nine times to form a film having a predetermined film thickness. In addition, the hard oxide coating layers E to N were alternately held under the conditions of holding the film formation condition “X-Zr” shown in Table 7 for 3.75 minutes and then holding the film with “X-Al” for 3.75 minutes. The film having a predetermined film thickness was formed by repeating 9 times. Note that X in the film formation conditions is the same as X in each hard oxide coating layer.

(Examples 22-30, Comparative Examples 4-5: Period)
A surface-coated cutting tool was obtained in the same manner as in Example 1 except that the coating composition was set as Table 8, and each hard oxide coating layer X was used as shown in Table 9.

The composition of the coating was formed so that the layer described on the left side of the column of “Coating Layer Structure” in Table 8 was laminated on top in order as the lowest layer. Moreover, the description in parentheses in the column of “Coating layer structure” in Table 8 indicates the thickness (μm) of each layer. Incidentally, with respect to each film shown in Table 9, subjected to known XRD (X-ray diffraction) measurement confirmed ZrO ₂ of presence in the hard oxide coating layer. Specifically, the diffraction intensities of each of the eight peaks related to α-Al ₂ O ₃ or κ-Al ₂ O ₃ and the six peaks of monoclinic crystal and tetragonal crystal related to ZrO ₂ were compared. In all cases, the diffraction intensity of all the six peaks related to ZrO ₂ was smaller than the minimum value of the diffraction intensity of the eight peaks related to α-Al ₂ O ₃ or κ-. As a result, it was found that the hard oxide coating layers O to T6 do not contain ZrO ₂ .

In Table 9, each hard oxide film layer OS was formed on the following conditions.
Hard oxide coating layer O: The process of holding for 14.5 seconds under the film formation condition “C-Zr” and then holding for 14.5 seconds under the film formation condition “C-Al” is repeated 500 times.
Hard oxide coating layer P: The process of holding for 19 seconds under the film formation condition “C-Zr” and then holding for 19 seconds under the film formation condition “C-Al” is repeated 350 times.
Hard oxide coating layer Q: The process of holding for 75 seconds under the film formation condition “C-Zr” and then holding for 75 seconds under the film formation condition “C-Al” is repeated 90 times.
Hard oxide coating layer R: The process of holding for 24 minutes under the deposition condition “C-Zr” and then holding for 24 minutes under the deposition condition “C-Al” is repeated five times.
Hard oxide coating layer S: The process of holding for 57.5 minutes under the film formation condition “C-Zr” and then holding for 57.5 minutes under the film formation condition “C-Al” is repeated twice.

Further, the hard oxide coating layers T1 to T6 were formed under the following conditions. The distance d _Zr-Al “0.12-0.25” between the maximum contained points of Zr and Al in the hard oxide coating layer T5 of Example 29 is 0.12 μm and 0 depending on the following film forming conditions. The value is between 25 μm. Further, the ratio of the maximum content point of Zr and Al in the hard oxide coating layer T6 of Example 30 is a value between 0.053 and 0.013 for Zr and 0 for Al according to the following film formation conditions. Indicates a value between .996 and 0.990.

Hard oxide coating layer T1: after holding for 4 minutes under film formation condition “E-Zr”, continuously gas mixing ratio from film formation condition “E-Zr” to film formation condition “E-Al” over 330 seconds And changing the gas mixture ratio continuously from the film formation condition “E-Al” to the film formation condition “E-Zr” over 330 seconds is repeated eight times, and finally the film formation condition “E- Hold at "Zr" for 4 minutes. The step of changing the gas mixing ratio at T1 is, for example, ZrCl ₄ gas, from 0.90 vol% to 0.01 vol% shown in Table 7 over 330 seconds, that is, 0.091 vol% / min. After changing the mixed gas ratio at a speed of 9.5, changing the mixed gas ratio from 0.01 volume% to 0.90 volume% at a speed of 0.091 volume% / min was repeated nine times. The same applies to other source gases.

  Hard oxide film layer T2: After holding for 330 seconds under the film formation condition “E-Zr”, only hydrogen gas was allowed to flow for 330 seconds (hydrogen gas volume fraction 100%), and then under the film formation condition “E-Al” After holding for 330 seconds, only hydrogen gas is allowed to flow for 330 seconds (hydrogen gas volume fraction 100%) and the change is repeated 8 times. If there is a zone where the concentration analysis value of Al and / or Zr is almost constant (specifically, within ± 1% of the analysis value) between the Zr maximum content point and the Al maximum content point, It was regarded as the maximum content point of the band.

  Hard oxide coating layer T3: Hold for 4 minutes under film-forming conditions “E-Zr”. Thereafter, the gas mixing ratio is continuously changed over 290 seconds from the film formation condition “E-Zr” to the film formation condition “E-Al”, and then the film formation condition “E-Al” is maintained for 290 seconds, and again. The process of continuously changing the gas mixture ratio from the film formation condition “E-Al” to the film formation condition “E-Zr” over 5 minutes and then holding the film formation condition “E-Zr” for 290 seconds 8 times Repeated. Subsequently, the hard oxide film layer was formed by maintaining the film formation condition “E-Zr” for 230 seconds. Regarding the interval between the Zr maximum content point and the Al maximum content point, if there is a band in which the concentration analysis value of Al and / or Zr is almost constant (specifically, within ± 1% of the analysis value), the center point is determined. It was regarded as the maximum content point of the band. The continuous gas ratio was changed in proportion to the gas supply time in the same manner as T1.

  Hard oxide coating layer T4: The process of holding for 5 minutes under the film formation condition “E-Zr” and then holding for 290 seconds under the film formation condition “E-Al” was repeated four times. Thereafter, the process of holding for 330 seconds under the film forming condition “E-Zr” and then holding for 330 seconds under the film forming condition “E-Al” was repeated six times. Next, the process of holding the film formation condition “E-Zr” for 5 minutes and then holding the film formation condition “E-Al” for 5 minutes was repeated four times.

  Hard oxide coating layer T5: The process of holding for 330 seconds under the film formation condition “E-Zr” and then holding for 330 seconds under the film formation condition “E-Al” was repeated twice. Thereafter, the process of holding for 330 seconds under the film-forming condition “K-Zr” and then holding for 330 seconds under the film-forming condition “K-Al” was repeated four times. Next, the process of holding for 330 seconds under the film formation condition “E-Zr” and then holding for 330 seconds under the film formation condition “E-Al” were repeated twice.

  Hard oxide coating layer T6: The process of holding for 290 seconds under the deposition condition “E-Zr” and then holding for 290 seconds under “E-Al” was repeated four times. Thereafter, the process of holding for 330 seconds under the film forming condition “K-Zr” and then holding for 330 seconds under the film forming condition “K-Al” was repeated six times. Next, the process of holding the film formation condition “E-Zr” for 290 seconds and then holding the film formation condition “E-Al” for 290 seconds was repeated four times.

  The above-mentioned cutting evaluation was performed on the surface-coated cutting tools obtained in Examples 22 to 30 and Comparative Examples 4 to 5. The results are shown in Table 9.

(Examples 31-35: thickness)
A surface-coated cutting tool was obtained in the same manner as in Example 1 except that the coating composition was set as Table 10 and each hard oxide coating layer X shown in Table 11 was used.

The composition of the coating was formed such that the layer described on the left side of the column “Coating Layer Structure” in Table 10 was laminated on top in order. Further, the description in parentheses in the column of “Coating layer structure” in Table 10 indicates the thickness (μm) of each layer. Note that for each coating according to Table 11, performs a known XRD (X-ray diffraction) measurement confirmed ZrO ₂ of presence in the hard oxide coating layer. Specifically, the diffraction intensities of each of the eight peaks related to α-Al ₂ O ₃ or κ-Al ₂ O ₃ and the six peaks of monoclinic crystal and tetragonal crystal related to ZrO ₂ were compared. In all cases, the diffraction intensity of all the six peaks related to ZrO ₂ was smaller than the minimum value of the diffraction intensity of the eight peaks related to α-Al ₂ O ₃ or κ-. As a result, the hard oxide coating layer U1~U5 was found not contain ZrO _2.

In Table 11, each hard oxide coating layer was formed under the following conditions.
Hard oxide film layer U1: The process of holding for 290 seconds under the film formation condition “A-Zr” and then holding for 290 seconds under the film formation condition “A-Al” was repeated five times.
Hard oxide coating layer U2: The process of holding for 290 seconds under the film formation condition “A-Zr” and then holding for 290 seconds under the film formation condition “A-Al” was repeated seven times.
Hard oxide coating layer U3: The process of holding for 330 seconds under the deposition condition “A-Zr” and then holding for 330 seconds under the deposition condition “A-Al” is repeated 15 times.
Hard oxide coating layer U4: The process of holding for 12.75 minutes under film formation condition “A-Zr” and then holding for 12.75 minutes under film formation condition “A-Al” is repeated 18 times.
Hard oxide coating layer U5: The process of holding for 27 seconds under the film formation condition “C-Zr” and then holding for 27 seconds under the film formation condition “C-Al” were repeated twice.

  The above-described cutting evaluation was performed on the surface-coated cutting tools obtained in Examples 31 to 35. The results are shown in Table 11.

(Examples 36 to 45: composition of TiBN layer and TiBNO layer)
Surface coating cutting tools were obtained in the same manner as in Example 1 except that the coating composition was set to Table 12 and the hard oxide coating layers B and A1 were used.

  The composition of the coating was formed such that the layers listed on the left side of the column “Coating Layer Structure” in Table 12 were laminated on top in order as the lowest layer. Further, the description in parentheses in the column of “Coating layer structure” in Table 12 indicates the thickness (μm) of each layer.

  The above-mentioned cutting evaluation was performed on the surface-coated cutting tools obtained in Examples 36 to 45. The results are shown in Table 12.

(Comparative Examples 6-11)
A surface-coated cutting tool was obtained in the same manner as in Example 1 except that the coating composition was changed to Table 13.

  The composition of the coating was formed such that the layer described on the left side of the column “Coating Layer Structure” in Table 13 was laminated on top in order as the lowest layer. Moreover, the description in parentheses in the column of “Coating layer structure” in Table 13 indicates the thickness (μm) of each layer. The above-mentioned cutting evaluation was performed on the surface-coated cutting tools obtained in Comparative Examples 6 to 11. The results are shown in Table 14.

(Inner layer exposure 1)
For the surface-coated cutting tools obtained in Examples 2, 6, and 12 and Comparative Examples 7, 9, and 10, as shown in Table 15 or Table 16, respectively, a # 320 SiC brush, a vibration barrel machine, or a # 320 elastic grindstone was used. Then, a coating layer removing process was performed on the edge of the blade edge, and a chip having the structure of each part described in Table 15 or Table 16 was prepared.

  In Table 15 and Table 16, for example, “0.02 mmHT-TiCN removal” in the column of the surface layer portion 11 means that the surface layer portion 11 is a boundary line portion with the cutting edge ridge line portion 12 (broken line in FIG. 4A). Part) in the direction of the surface layer region 10, indicating that it has been removed with a maximum width of 0.02 mm. The “maximum 0.02 mm” means the widest value of the width removed while observing the surface state of the surface layer portion 11 in various cross sections, and the surface layer actually removed in various cross sections. The width of the part 11 is in the range of 0-0.02 mm. Similarly, “0.03 mm TiN removal” in the column of the surface layer portion 13 means that the surface layer portion 13 extends from the boundary line portion (broken line portion in FIG. 4A) to the cutting edge ridge line portion 12. In the direction, it indicates that it has been removed with a maximum width of 0.03 mm. Further, for example, “TiCN is exposed to 10%” in the column of the surface layer portion 12 means that the unit length (0) along the edge line portion of the cutting edge of the cutting tool centered on the bisector of the nose R .2 mm), the exposed area of TiCN is 10% or more. This exposure can be determined by observing using a reflection electron image of an electron microscope, an optical microscope, a video microscope, or the like. From the examples shown in Table 15 and Table 16, the surface-coated cutting tool provided with the hard oxide coating layer having a structure whose composition changes in the thickness direction as in the present invention removes the oxide layer at the edge portion of the cutting edge. In this case, it can be seen that the effect of improving the microchipping resistance is great, and as a result, the wear resistance and toughness are improved.

  In Table 15 and Table 16, for example, the damage rate data of Example 2 and Example 2 c, and Comparative Example 7 and Comparative Example 7a are compared. In Comparative Example 7a, even if TiCN is exposed, the failure rate However, in the case of Example 2 where TiCN was exposed in Example 2, it was found that the breakage rate was drastically improved. Moreover, also when Example 2 is compared with Comparative Example 9 and Comparative Example 10, respectively, the improvement effect of the damage rate when TiCN is exposed in Example 2 is also shown. The reason for this is not clear, but when the hard oxide coating layer of the present invention is included as a coating, it is presumed that it is difficult to cause breakage at the joint between the layers.

(Inner layer exposure 2)
The surface-coated cutting tools obtained in Examples 2, 6, and 12 and Comparative Examples 7, 9, and 10 were subjected to a wet blasting treatment with alumina with abrasive grains of 50 μm and a discharge pressure of 0.1 MPa. The inner layer was exposed to, and compressive residual stress was introduced. The compressive residual stress was measured by the sin ² ψ method using an X-ray stress measurement apparatus.

  The surface layer portions 11 to 13 in Table 17 correspond to the respective portions in the cross-sectional view of the nose R bisector shown in FIG. Moreover, the cutting test similar to Example 1 was done about the cutting tool which performed these processes. The results are shown in Table 17. In addition, the ridgeline part of the actual cutting tool corresponding to the cutting edge ridgeline part 12 in FIG. 4A has an inscribed circle of 12.7 mm and a nose R of 0.8 mm. Further, when the gloss of the cutting edge of each cutting tool and the processed surface of the work material was visually confirmed within 1 minute after the start of the cutting test, 2a and 2b show that the cutting edge is welded compared to 2 in Table 17. The gloss of the work surface of the work material was excellent. Also, the evaluation of 6a and 6b was better than 6 in Table 17, and the cutting edges of 12a to 12f and the processing surface of the work material were excellent in comparison with 12 in Table 17.

(Inner layer exposure 3)
For the surface-coated cutting tools obtained in Examples 2A to 2E, Examples 6A to 6E, and Examples 12A to 12A in Table 15 or Table 16, the method described above (inner layer exposure 2) was used. When blasting was performed and a compressive stress of -0.1 to -0.2 MPa was introduced, the improvement in wear resistance of the test, that is, the flank wear amount decreased by 0.001 to 0.002 mm. The toughness improvement, that is, the breakage rate, was reduced by 5-15%.

(Examples 46 to 49, Comparative Examples 12 to 15: base materials)
A surface-coated cutting tool was produced by the same procedure as in Example 1 except that the materials having the respective composition shown in Table 18 were used as the substrate. Table 19 shows the combinations of the base material and the coating layer. In addition, as a coating layer, the thing of the Example shown in Table 1 and Table 6 and the comparative example shown in Table 13 was applied.

  The obtained surface-coated cutting tool was subjected to cutting evaluation under the following conditions. The results are shown in Table 19.

(Abrasion resistance test of steel and cast iron: cutting conditions)
Work material: SCM415 round bar Cutting speed: 370 m / min
Feed: 0.35 mm / rev.
Cutting depth: 2.0mm
Cutting oil: None Cutting time: 7 minutes (Toughness test: Cutting conditions)
The 20 corners were cut by cutting under the following cutting conditions, the damage rate was calculated, and the toughness of the obtained surface-coated cutting tool was evaluated.

Work material: SCM435 grooved round bar Cutting speed: 95m / min
Feed: 0.46 mm / rev.
Cutting depth: 2.0mm
Cutting oil: None Cutting time: 1 minute

(Examples 50 to 53, Comparative Examples 16 to 19)
A surface-coated cutting tool was produced by the same procedure as in Example 1 except that the materials having the respective composition shown in Table 20 were used as the substrate. Table 21 shows combinations of base materials and coating layers. In addition, as a coating layer, the thing of the Example shown in Table 1 or Table 6 and the comparative example shown in Table 13 was applied. Moreover, about the obtained surface coating cutting tool, cutting evaluation was performed on the following conditions. The results are shown in Table 21.

(Abrasion resistance test of steel and cast iron: cutting conditions)
Work material: S35C round bar Cutting speed: 260m / min
Feed: 0.33 mm / rev.
Cutting depth: 2.0mm
Cutting oil: None Cutting time: 6 minutes (Toughness test: Cutting conditions)
The 20 corners were cut by cutting under the following cutting conditions, the damage rate was calculated, and the toughness of the obtained surface-coated cutting tool was evaluated.

Work material: SCM435 grooved round bar Cutting speed: 105m / min
Feed: 0.45 mm / rev.
Cutting depth: 2.0mm
Cutting oil: None Cutting time: 1 minute

The layers other than the hard oxide coating layer in each of the examples and the comparative examples were stopped in accordance with the film forming conditions shown in Table 22 below when the coating of the desired thickness was formed. In Table 22, “residue” of H ₂ gas indicates the remaining part of 100% volume. Moreover, TiN (lowermost layer) indicates the formation conditions when the lowermost layer of the coating is a TiN layer, and when forming a TiN layer other than the lowermost layer of the coating, the conditions described in “TiN” are used. A film was formed. In Table 20, α-Al ₂ O ₃ (*) indicates the formation conditions in the case of α-Al ₂ O _{3 in} Example 4.

  As is clear from the above examples, the surface-coated cutting tools of the examples of the present invention show excellent results both in improving wear resistance and reducing crater wear in cutting under high speed conditions. Is clear. Therefore, the surface-coated cutting tool of the present invention has excellent cutting performance.

  Although the embodiments and examples of the present invention have been described as described above, it is also planned from the beginning to appropriately combine the configurations of the above-described embodiments and examples.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a schematic diagram which shows the cross section of a CVD furnace. It is a schematic diagram which shows a base material and a base material setting jig. It is a schematic diagram showing a ZrCl ₄ introducing jig. (A) It is a schematic diagram which shows the cross section of the bisector of the nose R of a cutting tool, (b) It is a schematic diagram which shows the cross section of the bisector of the nose R of the cutting tool in the state where the inner layer was exposed.

Explanation of symbols

1 CVD reactor, 2 base material, 3 base material setting jig, 4 reaction vessel, 5 heater, 6 ZrCl ₄ introduction jig, 7, 8 source gas, 9 exhaust port, 10, 11, 13, 14 surface layer Part, 12 edge of ridgeline.

Claims (21)

A surface-coated cutting tool comprising a substrate and a coating formed on the substrate,
The coating consists of one or more layers,
At least one layer of the coating is a hard oxide coating layer containing at least Al and Zr,
The hard oxide coating layer has a composition structure in which the contents of Al and Zr change along the thickness direction of the hard oxide coating layer, and the change includes an Al maximum that maximizes the Al content. A point and a Zr maximum content point where the Zr content is a maximum, the Al maximum content point and the Zr maximum content point are repeatedly present,
The Al content ratio Al / (Al + Zr) at the Al maximum content point is 0.99 ≦ Al / (Al + Zr) ≦ 0.9999 in atomic ratio,
The Zr content ratio Zr / (Al + Zr) at the Zr maximum content point is 0.001 ≦ Zr / (Al + Zr) ≦ 0.2 in atomic ratio,
The hard oxide coating layer is a surface-coated cutting tool that does not contain zirconium oxide.   The surface-coated cutting tool according to claim 1, wherein the hard oxide coating layer has a thickness of 0.05 μm or more and 20 μm or less.   The surface-coated cutting tool according to claim 1 or 2, wherein the adjacent Al maximum content point and the Zr maximum content point are present alternately and repeatedly, and the interval is 0.005 µm or more and 1 µm or less. The surface-coated cutting tool has a cutting edge ridge line portion,
The surface-coated cutting tool according to any one of claims 1 to 3, wherein the hard oxide coating layer is exposed at the edge of the cutting edge.   The coating is at least one element selected from the group consisting of Group IVa elements, Group Va elements, Group VIa elements, Al and Si, or Group IVa, Group Va and Group VIa elements in the Periodic Table And a coating layer X comprising at least one element selected from the group consisting of Al and Si and a compound consisting of at least one element selected from the group consisting of boron, carbon, nitrogen and oxygen. The surface-coated cutting tool according to any one of 4. The surface-coated cutting tool has a cutting edge ridge line portion,
The surface-coated cutting tool according to claim 5, wherein the coating layer X is exposed at the edge of the cutting edge.   The surface-coated cutting tool according to claim 5 or 6, wherein at least one coating layer X is formed, and at least one layer is a layer containing TiCN formed by an MT-CVD method. The coating further includes an Al oxide layer,
The surface-coated cutting tool according to claim 1, wherein the Al oxide layer is formed immediately below the hard oxide coating layer. The surface-coated cutting tool has a cutting edge ridge line portion,
The surface-coated cutting tool according to claim 8, wherein the Al oxide layer is exposed at the edge of the cutting edge. The coating further includes a TiBN layer made of TiB _x N _y (x, y represents atomic% and satisfies 0.001 <x / (x + y) <0.2),
The surface-coated cutting tool according to claim 8 or 9, wherein the TiBN layer is formed immediately below the Al oxide layer. The coating has TiB _a N _b O _c (a, b and c represent atomic%, and satisfies 0.0005 <a / (a + b + c) <0.2 and 0 <c / (a + b + c) <0.5. A TiBNO layer comprising
The surface-coated cutting tool according to claim 8 or 9, wherein the TiBNO layer is formed immediately below the Al oxide layer.   The surface-coated cutting tool according to claim 8, wherein the Al oxide layer is made of α-alumina. 13. The surface according to claim 8, wherein the thickness d ₁ of the hard oxide coating layer and the thickness d ₂ of the Al oxide layer satisfy d ₁ / (d ₁ + d ₂ )> 0.05. Coated cutting tool.   The surface-coated cutting tool according to any one of claims 8 to 13, wherein the hard oxide coating layer and the Al oxide layer have a total thickness of 0.5 µm to 20 µm.   The surface-coated cutting tool according to any one of claims 1 to 14, wherein the coating is a layer in which at least one layer forming the coating has a compressive residual stress or no stress. The surface-coated cutting tool according to any of the hard oxide target film layer, or has a compressive residual stress, or a layer having no stress claims 1-14. The surface-coated cutting tool according to any one of claims 8 to 14 , wherein the Al oxide layer is a layer having compressive residual stress or no stress.   The surface-coated cutting tool according to claim 1, wherein the coating is formed by a chemical vapor deposition method.   The surface-coated cutting tool according to claim 1, wherein a layer containing a titanium compound is formed in the lowermost layer of the coating.   The surface-coated cutting tool according to claim 1, wherein the coating has a thickness of 1 μm or more and 25 μm or less.   The surface-coated cutting tool according to any one of claims 1 to 20, wherein the base material is at least one of cemented carbide, cermet, aluminum oxide ceramics, and silicon nitride ceramics.

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