Surface-coated cutting tool

Abstract

Provided is a surface-coated cutting tool having a coating layer containing crystal grains each having a NaCl-type face-centered cubic structure, in which the coating layer includes a composite carbonitride layer, the composite carbonitride layer has an average thickness of 1.0 μm to 20.0 μm inclusive, metal components Ti, V, Zr and Nb are contained respectively at atomic content ratios of a1, a2, a3 and a4 wherein the total of the atomic content ratios of the metal components is 1, non-metal components C and N are contained respectively at atomic content ratios of b1 and b2 wherein the total of the atomic content ratios of the non-metal components is 1, unavoidable impurities are further contained, the a1, the a2, the a3, the a4, the b1 and the b2 respectively satisfy the formulae 0.01 ≤ a1 ≤ 0.60, 0.01 ≤ a2 ≤ 0.60, 0.01 ≤ a3 ≤ 0.60, 0.01 ≤ a4 ≤ 0.60, 0.20 ≤ b1 ≤ 0.80 and 0.20 ≤ b2 ≤0.80, and the following formula Sconfig ≥ 0.80R (wherein R represents a gas constant; and ln represents a natural logarithm) is satisfied.

Description

surface coated cutting tools

[0001] The present invention relates to a surface-coated cutting tool (hereinafter sometimes referred to as a coated tool). This application claims priority to Japanese Patent Application No. 2022-55518, filed on March 30, 2022. The entire contents of said Japanese patent application are incorporated herein by reference.

[0002] Coated tools, which have a coating layer formed on the surface of a substrate such as a tungsten carbide (hereinafter referred to as WC)-based cemented carbide, are known to exhibit excellent wear resistance. Various proposals have been made to improve the coating layer in order to enhance the durability of coated tools.

[0003] For example, Patent Document 1 discloses a substrate and a coating layer on the substrate, the coating layer having a face-centered cubic structure with a lattice constant of 0.403 to 0.455 nm (Ti ｘ Zr １－ｘ ) (C ｙ N １－ｙ ) (0.4<x<0.95, 0.2<y<0.9) or has a face-centered cubic structure with a lattice constant of 0.430 to 0.450 nm (Ti ｘ Hf １－ｘ ) (C ｙ N １－ｙ ) (0.4<x<0.95, 0.2<y<0.9), and the coating layer is said to be hard and wear-resistant.

[0004] For example, Patent Document 2 discloses a method for forming a Ti film having an fcc structure with a lattice constant of 0.427 to 0.453 nm on a substrate. １－ｘ Me ｘ The patent describes a coated tool (insert) coated with a nitride of (Me) (0.1≦x≦0.9, Me is one or more of Zr and Hf), and the coating layer of the coated tool is said to be hard and suitable for dry cutting of stainless steel.

[0005] Patent No. 4028891 U.S. Patent Application Publication No. 2016 / 0298233

[0006] The present invention has been made in consideration of the above circumstances and proposals, and has an object to provide a coated tool having a coating layer that has high hardness and improved toughness.

[0007] A surface-coated cutting tool according to an embodiment of the present invention comprises a substrate and a coating layer on the surface of the substrate, the coating layer comprising a composite carbonitride layer, the composite carbonitride layer having an average thickness of 1.0 μm or more and 20.0 μm or less, and the metal components Ti, V, Zr, and Nb are each present in an atomic ratio of a when the total atomic ratio of the metal components is 1. １ , a ２ , a ３ , a ４ When the total atomic ratio of the nonmetallic components is 1, the nonmetallic components C and N are contained in an amount of b １ , b ２ and further containing unavoidable impurities, １ , a ２ , a ３ , a ４ , b １ , b ２ is 0.01≦a １ ≦0.60 0.01≦a ２ ≦0.60 0.01≦a ３ ≦0.60 0.01≦a ４ ≦0.60 0.20≦b １ ≦0.80 0.20≦b ２ ≦0.80, and S is expressed by Equation 1 (where ln is the natural logarithm) with n=4 and m=2. ｃｏｎｆｉｇ 1. A surface-coated cutting tool comprising: a surface-coated cutting tool having a crystal grain having a face-centered cubic NaCl structure; and a surface-coated cutting tool having a crystal grain having a face-centered cubic NaCl structure; wherein R is a gas constant and R is a gas constant.

[0008] Furthermore, the surface-coated cutting tool according to the above embodiment may satisfy at least one of the following items (1) and (2).

[0009] (1) The composite carbonitride layer contains at least one of Hf and Ta as the metal component in an atomic ratio of a ５ , a ６ and further comprising: ５ , a ６ is a ５ <0.01 a ６<0.01, and S represented by Formula 1 where n = 6 and m = 2 ｃｏｎｆｉｇ (However, a ｉ When (i=5 or 6) is zero (not included), a ｉ ln(a ｉ ) = 0) is 0.80R or more.

[0010] (2) The composite carbonitride layer contains 0.50 atomic % or less of Cl.

[0011] The surface-coated cutting tool has a coating layer that has high hardness and high toughness.

[0012] 1 shows a schematic diagram of the crystal structure of TiN, 2 shows a schematic diagram of the crystal structure of (TiVZrNb)(CN) or (TiVZrNbHfTa)(CN).

[0013] High hardness and high toughness in the coating layer of a surface-coated cutting tool are in a trade-off relationship, and it is considered difficult to achieve both at the same time under conventional solid-solution strengthening theory. Meanwhile, in recent years, research has been conducted on solid solutions with increased entropy of mixing, such as high-entropy alloys, which are alloys in which five or more elements are mixed in approximately equal atomic ratios, and multi-principal element alloys, which are alloys composed of three or more elements and at least two or more principal elements. However, no research has been conducted on increasing the entropy of mixing in the coating layer of a coated tool.

[0014] The present inventors have conducted extensive research into increasing the entropy of mixing in the solid solution (alloy) that constitutes the coating layer of a coated tool, in order to achieve both high hardness and high toughness, which are in a trade-off relationship and could not be achieved with conventional coating layers.

[0015] As a result, they discovered that when the entropy of mixing is increased in a composite carbonitride layer of a specific composition that constitutes the coating layer of a coated tool, (i) the composite carbonitride layer of a specific composition is composed of multiple types of atoms with different atomic radii, which causes strain within the crystal grains and improves hardness and toughness, and (ii) the thermal stability and oxidation resistance of the composite carbonitride layer at high temperatures are improved.

[0016] Hereinafter, a surface-coated cutting tool according to an embodiment of the present invention will be described. In this specification and claims, when a numerical range is expressed as "L to M" (where L and M are both numerical values), this is synonymous with "at least L and at most M," and the range includes an upper limit (M) and a lower limit (L). When a unit is specified for only the upper limit, the upper limit (M) and the lower limit (L) have the same unit.

[0017] I. First Embodiment The composite carbonitride of (TiVZrNb) (sometimes expressed as (TiVZrNb)(CN)) constituting the coating layer according to the first embodiment will be described.

[0018] 1. Coating Layer 1-1. (TiVZrNb)(CN) Layer (1) Crystal Structure (TiVZrNb)(CN) has an atomic arrangement as shown in Figure 2. That is, one of the Ti, V, Zr, or Nb atoms, each with a different atomic radius, resides at the cation site (4), and C and N atoms are randomly mixed at the anion sites (2, 3), forming a crystal lattice. Compared to the TiN crystal structure (Ti atom (1), N atom (2)) shown schematically in Figure 1, each atom in this crystal lattice is displaced from its ideal lattice point position. This causes distortion within the crystal lattice (shown by the deviation from the dotted line in Figure 2), which improves hardness and toughness. The amount of displacement of each atom is also shown schematically in Figure 2.

[0019] (2) Average Thickness The average thickness of the (TiVZrNb)(CN) layer, which is a composite carbonitride layer, is preferably 1.0 μm or more and 20.0 μm or less. This is because if the average thickness is less than 1.0 μm, the (TiVZrNb)(CN) layer is too thin to ensure sufficient durability, while if the average thickness exceeds 20.0 μm, the crystal grains of the (TiVZrNb)(CN) layer tend to coarsen, making chipping more likely to occur. The average thickness of the (TiVZrNb)(CN) layer is more preferably 3.0 μm or more and 16.0 μm or less.

[0020] (3) Composition The (TiVZrNb)(CN) layer, which is a composite carbonitride layer, has a composition represented by the formula: (Ti ａ１ V ａ２ Zrａ３ Nb ａ４ ) (C ｂ１ N ｂ２ ) when expressed by the above a １ , a ２ , a ３ , a ４ , b １ , b ２ is a １ +a ２ +a ３ +a ４ = 1, b １ +b ２ = 1, and 0.01≦a １ ≦0.60 0.01≦a ２ ≦0.60 0.01≦a ３ ≦0.60 0.01≦a ４ ≦0.60 0.20≦b １ ≦0.80 0.20≦b ２ ≦0.80, and S is expressed by Equation 1 (where ln is the natural logarithm) with n=4 and m=2. ｃｏｎｆｉｇ It is preferable that the ratio of the gas constant to the total gas is 0.80R or more (R is the gas constant). Note that the gas may contain unintentional impurities that are mixed in during the manufacturing process.

[0021]

[0022] a １ , a ２ , a ３ , a ４ , b １ and b ２ When the values ​​of satisfy the above relationship, the entropy of mixing of the (TiVZrNb)(CN) layer is increased, and the (TiVZrNb)(CN) layer has the physical properties (i) to (ii) obtained from the above findings. １ , a ２ , a ３ , a ４ , b １ , b ２ is S ｃｏｎｆｉｇ It is preferable to determine the value so that S is larger. ｃｏｎｆｉｇ The calculated upper limit is 1.04R.

[0023] (4) Cl Content When a film is formed by a CVD method using chlorides as a source gas, a very small amount of Cl is inevitably contained (an amount whose presence can be confirmed by single-element analysis of chlorine alone). If the Cl content is 0.50 atomic % or less, the Cl provides lubricity to the (TiVZrNb)(CN) layer. Here, the Cl content (atomic %) is the ratio of the Cl content to all atoms of Ti, V, Zr, Nb, C, N, and Cl.

[0024] (5) NaCl-type face-centered cubic structure The (TiVZrNb)(CN) layer preferably has crystal grains of the NaCl-type face-centered cubic structure. However, crystal grains other than those of the NaCl-type face-centered cubic structure may be contained, but the presence of crystal grains other than those of the NaCl-type face-centered cubic structure is unintended. In the claims and this specification, "having crystal grains of the NaCl-type face-centered cubic structure" means that in addition to crystal grains of the NaCl-type face-centered cubic structure, unintended crystal grains other than those of the NaCl-type face-centered cubic structure may also be present.

[0025] 1-2. Other Layers (1) Lower Layer A lower layer consisting of one or more Ti compound layers (not limited to stoichiometric compositions) selected from the group consisting of Ti nitride layers, carbide layers, and carbonitride layers, with a total average thickness of 0.1 to 20.0 μm, may be provided between the substrate and the (TiVZrNb)(CN) layer. The provision of the lower layer improves the adhesion between the substrate and the (TiVZrNb)(CN) layer.

[0026] (2) Upper Layer An upper layer may be provided on the (TiVZrNb)(CN) layer, which comprises one or more Ti compound layers (not limited to stoichiometric composition) selected from the group consisting of nitride layer, carbide layer, carbonitride layer, and oxide layer of Ti, and / or aluminum oxide layer (not limited to stoichiometric composition), and has a total average thickness of 0.1 to 25.0 μm. The provision of the upper layer improves chipping resistance and wear resistance.

[0027] (3) Unintentional Layers When the gas pressure or temperature in the CVD furnace becomes unstable, layers other than the (TiVZrNb)(CN) layer, lower layer, and upper layer may be unintentionally formed.

[0028] 2. Substrate (1) Material Any conventionally known substrate material can be used as long as it does not impede the achievement of the object of the present invention. Examples include WC-based cemented carbide (containing Co in addition to WC, and also containing carbides or nitrides of Ti, Zr, Ta, Nb, Cr, etc.), cermet (containing TiC, TiN, TiCN, etc. as its main component), ceramics (titanium carbide, silicon carbide, silicon nitride, aluminum nitride, aluminum oxide), and cBN sintered body.

[0029] (2) Shape The shape of the substrate is not particularly limited as long as it is a shape that can be used as a cutting tool, and examples thereof include the shape of an insert and the shape of a solid tool.

[0030] 3. Measurement Method The average thickness, the content of each element, and the average chlorine content of the (TiVZrNb)(CN) layer of this embodiment are determined as follows.

[0031] (1) Average Thickness The average thickness of the (TiVZrNb)(CN) layer or the like can be determined as follows. A sample for observing the longitudinal cross section of the coating layer is prepared using a cross section polisher (CP) or the like, and the longitudinal cross section is observed using a scanning electron microscope (SEM). The layer thicknesses at multiple locations (e.g., five locations) are measured, and these are averaged to determine the average thickness of the (TiVZrNb)(CN) layer or the like. The definition of the surface of the substrate will be described later.

[0032] Here, the longitudinal section refers to a section perpendicular to the surface of the base body of the insert when the surface is treated as a flat surface, ignoring minute irregularities on the surface of the base body.

[0033] The surface of the substrate is defined as the average line (straight line) of the interface roughness between the substrate and the coating layer in an observed image of the longitudinal section.

[0034] That is, the interface between the coating layer (if a lower layer exists, the lower layer is used instead of the (TiVZrNb)(CN) layer) and the substrate is determined from the observed image of the longitudinal section, and an average line is drawn on the roughness curve of the obtained interface between the coating layer and the substrate, which is defined as the surface of the substrate. The direction perpendicular to this average line is defined as the direction perpendicular to the substrate (thickness direction of the layer).

[0035] Furthermore, even if the substrate has a curved surface, if the radius of curvature of the curved surface is sufficiently large compared to the thickness of the coating layer, the interface between the coating layer and the substrate in the measurement area will be approximately flat, and the surface of the substrate can be determined using a similar method.

[0036] (2) Content of each element and chlorine content of the coating layer The content of each element and chlorine content of the (TiVZrNb)(CN) layer are determined as follows: Contents of Ti, V, Zr, and Nb a １ , a ２ , a ３ , a ４ , and C, N content b １ , b ２ The content of chlorine is determined by irradiating a sample with a polished surface of the coating layer with an electron beam from the surface side of the sample using an electron probe microanalyzer (EPMA), and averaging the result of 10 characteristic X-ray analysis points.

[0037] (3) Identification of the crystalline structure of the (TiVZrNb)(CN) layer. X-ray diffraction tests were performed on the (TiVZrNb)(CN) layer using an X-ray diffractometer to confirm that it has a NaCl-type face-centered cubic structure. X-ray diffraction was measured using the 2θ-θ method with CuKα radiation under the following measurement conditions: measurement range (2θ): 15 to 135 degrees, X-ray output: 45 kV, 40 mA, divergence slit: 0.5 degrees, scan step: 0.013 degrees.

[0038] 4. Manufacturing Method The (TiVZrNb)(CN) layer of this embodiment can be manufactured by, for example, ４ , ZrCl ４ , VCl ４ , NbCl ５ , H ２ , HCl, N２ , C.H. ３ CN, Ar, H ２ The deposition can be carried out by the CVD method using the gases mentioned above.

[0039] II. Second Embodiment The composite carbonitride of (TiVZrNbHfTa) (sometimes expressed as (TiVZrNbHfTa)(CN)) constituting the coating layer according to the second embodiment will be described.

[0040] 1. Coating Layer 1-1. (TiVZrNbHfTa)(CN) Layer (1) Crystal Structure The crystal structure is obtained by replacing "(TiVZrNb)(CN)" and "Ti, V, Zr, Nb atoms" in the description of the first embodiment regarding the crystal structure described above with "(TiVZrNbHfTa)(CN)" and "Ti, V, Zr, Nb, Hf, Ta atoms (Hf and Ta are selected depending on the composition)," respectively.

[0041] (2) Average Thickness The average thickness is obtained by replacing "(TiVZrNb)" with "(TiVZrNbHfTa)" in the description of the first embodiment regarding the average thickness described above.

[0042] (3) Composition The (TiVZrNbHfTa)(CN) layer, which is a composite carbonitride layer, has a composition represented by the formula: (Ti ａ１ V ａ２ Zr ａ３ Nb ａ４ Hf ａ５ Ta ａ６ ) (C ｂ１ N ｂ２ ) when expressed by the above a １ , a ２ , a ３ , a ４ , a ５ , a ６ , b １ , b ２ is a １ +a ２ +a ３ +a ４ +a ５ +a ６ = 1, b １ +b ２ = 1, and 0.01≦a １ ≦0.60 0.01≦a ２≦0.60 0.01≦a ３ ≦0.60 0.01≦a ４ ≦0.60 0.00≦a ５ <0.01 0.00≦a ６ <0.01 0.20≦b １ ≦0.80 0.20≦b ２ ≦0.80, and S is expressed by Equation 1 (where ln is the natural logarithm) with n=6 and m=2. ｃｏｎｆｉｇ It is preferable that the ratio of the gas constant to the total gas is 0.80R or more (R is the gas constant). Note that the gas may contain unintentional impurities that are mixed in during the manufacturing process.

[0043]

[0044] Here, a ｉ When (i=5 or 6) is 0.00 (when Hf or Ta is not contained), a ｉ ln(a ｉ ) is treated as 0 (zero).

[0045] a １ , a ２ , a ３ , a ４ , a ５ , a ６ , b １ and b ２ When the values ​​of satisfy the above relationship, the entropy of mixing of the (TiVZrNbHfTa)(CN) layer is increased, and the (TiVZrNbHfTa)(CN) layer has the physical properties (i) to (ii) obtained from the above findings. １ , a ２ , a ３ , a ４ , a ５ , a ６ , b １ , b ２ is S ｃｏｎｆｉｇ It is preferable to determine the value so that a is larger than a ５ , a ６ Since the upper limits of both are less than 0.01, S ｃｏｎｆｉｇ The calculated upper limit is 1.08R.

[0046] (4) Inclusion of Cl The inclusion of Cl is achieved by replacing "(TiVZrNb)(CN)" with "(TiVZrNbHfTa)(CN)" in the description of the first embodiment regarding the inclusion of Cl. That is, the Cl content (atomic %) is the ratio to all atoms of Ti, V, Zr, Nb, Hf, Ta, C, N, and Cl.

[0047] (5) NaCl-Type Face-Centered Cubic Structure The NaCl-type face-centered cubic structure is obtained by replacing "(TiVZrNb)" with "(TiVZrNbHfTa)" in the description of the first embodiment regarding the NaCl-type face-centered cubic structure described above.

[0048] 1-2. Other Layers The other layers are obtained by replacing "(TiVZrNb)" with "(TiVZrNbHfTa)" in the description of the first embodiment regarding the other layers.

[0049] 2. Substrate The substrate is the same as that described in the first embodiment.

[0050] 3. Measurement Method The measurement method is the same as that described in the first embodiment regarding the measurement method, except that "(TiVZrNb)" is replaced with "(TiVZrNbHfTa)." The contents of Hf and Ta are also measured by EPMA.

[0051] 4. Manufacturing Method The manufacturing method of the (TiVZrNbHfTa)(CN) layer of this embodiment is, for example, a method of manufacturing the (TiVZrNbHfTa)(CN) layer of this embodiment by adding HfCl ４ , TaCl ５ gas added, i.e., TiCl ４ , ZrCl ４ , VCl ４ , NbCl ５ , HfCl ４ , TaCl ５ , H ２ , HCl, N ２ , C.H. ３ CN, Ar, H ２ The deposition can be carried out by the CVD method using the gases mentioned above.

[0052] The above description includes the following additional features: (Additional Note 1) A surface-coated cutting tool having a substrate and a coating layer on the surface of the substrate, wherein the coating layer has a composite carbonitride layer, and the composite carbonitride layer has an average thickness of 1.0 μm or more and 20.0 μm or less, and when the total atomic ratio of the metal components is 1, the metal components Ti, V, Zr, and Nb are each present in an atomic ratio of the metal components a １ , a ２ , a ３ , a ４ When the total atomic ratio of the nonmetallic components is 1, the nonmetallic components C and N are contained in an amount of b １ , b ２ and further containing inevitable impurities, １ , a ２ , a ３ , a ４ , b １ , b ２ is 0.01≦a １ ≦0.60 0.01≦a ２ ≦0.60 0.01≦a ３ ≦0.60 0.01≦a ４ ≦0.60 0.20≦b １ ≦0.80 0.20≦b ２ ≦0.80, and S is expressed by Equation 1 (where ln is the natural logarithm) with n=4 and m=2. ｃｏｎｆｉｇ 1. A surface-coated cutting tool comprising: a surface-coated cutting tool having a crystal grain having a face-centered cubic NaCl structure; and a surface-coated cutting tool having a crystal grain having a face-centered cubic NaCl structure; wherein R is a gas constant and R is a gas constant. (Note 2) The composite carbonitride layer contains at least one of Hf and Ta as the metal component in an atomic ratio of a ５ , a ６ and further comprising: ５ , a ６ is a ５ <0.01 a ６ <0.01, and S represented by Formula 1 where n = 6 and m = 2 ｃｏｎｆｉｇ (However, a ｉ When (i=5 or 6) is zero (not included), a ｉ ln(a ｉ) = 0) is 0.80R or more. (Appendix 3) The surface-coated cutting tool according to Appendices 1 or 2, wherein the composite carbonitride layer contains 0.50 atomic % or less of Cl. (Appendix 4) The surface-coated cutting tool according to any of Appendices 1 to 3, wherein a lower layer is provided between the base and the composite carbonitride layer, the lower layer consisting of one or more Ti compound layers selected from a Ti nitride layer, a Ti carbide layer, and a Ti carbonitride layer, and having a total average thickness of 0.1 to 20.0 μm. (Appendix 5) The surface-coated cutting tool according to any of Appendices 1 to 4, wherein an upper layer is provided on top of the composite carbonitride layer, the upper layer consisting of one or more Ti compound layers selected from a Ti nitride layer, a Ti carbide layer, a Ti carbonitride layer, and an Ti oxide layer, and having a total average thickness of 0.1 to 25.0 μm.

[0053] The present invention will be described below with reference to examples, but is not limited to these examples. That is, an insert cutting tool using a WC-based cemented carbide as the substrate will be described, but the substrate may be made of any of the materials described above, and the shape may be other shapes such as a solid tool, as described above.

[0054] <Example of the First Embodiment> 1. Manufacturing of the Base Body As raw material powders, WC powder, TiC powder, ZrC powder, TaC powder, NbC powder, Cr ３ C ２ These raw material powders were blended to the composition shown in Table 1, and wax was added thereto. The mixture was ball milled in acetone for 24 hours, dried under reduced pressure, and then pressed into a powder compact of a predetermined shape at a pressure of 98 MPa.

[0055] Thereafter, this green compact was vacuum sintered, and after sintering, the cutting edge was subjected to honing with a radius of 0.05 mm to produce substrates A to C made of WC-based cemented carbide having the insert shape of CNMG120408-MA manufactured by Mitsubishi Materials Corporation.

[0056] 2. Film Formation A (TiVZrNb)(CN) layer was formed on the surface of each of the substrates A to C using a CVD apparatus, to obtain Examples 1 to 10 shown in Table 5. The film formation conditions were as shown in Table 2, and were roughly as follows:

[0057] Reaction gas composition (content of gas components is in volume %): TiCl ４ :0.02~0.10% ZrCl ４ :0.10~0.50% VCl ４ :0.02~0.10% NbCl ５ :0.02~0.10% CH ３ CN: 0.10-0.50%, HCl: 0.10-0.50% N ２ : 0.0~12.0% Ar: 10.0~50.0% H ２ : Remaining Reaction atmosphere pressure: 4.5 to 12.0 kPa Reaction atmosphere temperature: 800 to 950°C

[0058] In Examples 3 to 10, the lower layer and / or upper layer shown in Table 4 was formed under the conditions shown in Table 3.

[0059] For comparison, a (TiVZrNb)(CN) layer was formed on the surface of substrates A to C under the film formation conditions shown in Table 2, to obtain Comparative Examples 1 to 10 shown in Table 5. In the manufacturing process of the Comparative Examples, the composition of the raw material gas was changed from that of the Examples. In Comparative Examples 3 to 10, the lower layer and / or upper layer shown in Table 4 was formed under the conditions shown in Table 3.

[0060] Furthermore, for comparison with the conventional technology, a TiCN layer and the lower layer, lower layer and upper layer shown in Table 4 were formed on the surfaces of substrates A and C under the conditions shown in Table 3, and Conventional Examples 1 and 2 shown in Table 5 were produced.

[0061] The average thickness of each layer, the content of each element, the chlorine content, and whether or not the layer has an NaCl-type face-centered cubic structure were measured using the methods described above for Examples 1 to 10, Comparative Examples 1 to 10, and Conventional Examples 1 and 2. The results are summarized in Table 5.

[0062]

[0063]

[0064]

[0065]

[0066]

[0067] In Table 5, Conventional Examples 1 and 2 do not contain V, Zr, or Nb, and therefore, ｃｏｎｆｉｇ is -R / 2[b １ ln(b １ ) + b ２ ln(b ２ ) ]. "**" indicates that the content was below the quantitative accuracy of the analytical equipment, so that a trace amount of chlorine was confirmed by detecting a peak in the characteristic X-ray spectrum of chlorine through single element detection of chlorine alone. It was also confirmed that all of the examples, comparative examples, and conventional examples had crystal grains with a substantially NaCl-type face-centered cubic structure.

[0068] Next, for Examples 1 to 10, Comparative Examples 1 to 10, and Conventional Examples 1 and 2, a wet end face cutting test was conducted on a hollow round bar made of alloy steel SCM440 with two equally spaced grooves, with each bar screwed to the tip of a tool steel bit with a fixture, and the flank wear width of the cutting edge was measured. This cutting test is a process in which flank wear is likely to progress, and the cutting edge is prone to chipping because it includes intermittent cutting. Therefore, since this process requires both wear resistance and chipping resistance, it is suitable for evaluating hardness and toughness.

[0069] Cutting test Workpiece: JIS SCM440 hollow round bar (outer diameter Φ180, inner diameter Φ50) with two equally spaced grooves (width 20 mm) Cutting speed: 250 m / min. Cutting depth: 1.5 mm Feed rate: 0.4 mm / rev. Number of cuts: 20 passes

[0070] The results of the cutting tests are shown in Table 6. Note that for Comparative Examples 1 to 10 and Conventional Examples 1 and 2, the lifespan expired before the number of cutting passes reached 20 due to chipping or flank wear (lifespan judgment standard: flank wear width 0.4 mm), so the number of cutting passes until the lifespan was reached is shown.

[0071]

[0072] As is clear from the results shown in Table 6, Examples 1 to 10 all had low wear, no chipping, and improved hardness and toughness, demonstrating excellent cutting performance over a long period of time. In contrast, Comparative Examples 1 to 10 and Conventional Examples 1 and 2 all had high wear or chipping, reaching the end of their service life in a short period of time.

[0073] <Example of the Second Embodiment> 1. Manufacturing of the Substrate Substrates A to C were manufactured from WC-based cemented carbide, each having the same insert shape as that of Mitsubishi Materials Corporation's CNMG120408-MA, as in the first embodiment.

[0074] 2. Film Formation A (TiVZrNbHfTa)(CN) layer was formed on the surface of each of the substrates A to C using a CVD apparatus, to obtain Examples 11 to 15 shown in Table 9. The film formation conditions were as shown in Table 7, and were roughly as follows:

[0075] Reaction gas composition (content of gas components is in volume %): TiCl ４ :0.02~0.10% VCl ４ :0.02~0.10% ZrCl ４ :0.10~0.50% NbCl ５ :0.02~0.10% *HfCl ４ :0.00~0.02% *TaCl ５ :0.00~0.01% CH ３ CN: 0.10-0.50%, HCl: 0.10-0.50% N ２ : 0.0~12.0% Ar: 10.0~50.0% H ２ :Remaining *HfCl ４ , TaCl ５ is selected depending on the composition of the (TiVZrNbHfTa)(CN) layer. Reaction atmosphere pressure: 4.5 to 12.0 kPa Reaction atmosphere temperature: 800 to 950°C

[0076] In Examples 13 to 15, the lower layer and / or upper layer shown in Table 8 was formed under the conditions shown in Table 3.

[0077] For comparison, a (TiVZrNbHfTa)(CN) layer was formed on the surface of substrates A to C under the film formation conditions shown in Table 7, to obtain Comparative Examples 11 to 15 shown in Table 9. In the manufacturing process of the Comparative Examples, the composition of the source gas was changed from that of the Examples. For Comparative Examples 13 to 15, the lower layer and / or upper layer shown in Table 8 was formed under the conditions shown in Table 3.

[0078] For Examples 11 to 15 and Comparative Examples 11 to 15, the average thickness of each layer, the content of each element, the chlorine content, and whether or not the layer has an NaCl-type face-centered cubic structure were measured using the methods described above. These results are summarized in Table 9.

[0079]

[0080]

[0081]

[0082] In Table 9, "**" indicates that the content was below the quantitative accuracy of the analytical equipment, and therefore a trace amount of chlorine was confirmed by single-element detection analysis of chlorine alone, confirming a peak in the characteristic X-ray spectrum of chlorine. It was also confirmed that all of the Examples, Comparative Examples, and Conventional Examples had crystal grains with a NaCl-type face-centered cubic structure.

[0083] Next, for Examples 11 to 15 and Comparative Examples 11 to 15, a wet end face cutting test was conducted on a hollow round bar made of alloy steel SCM440 with two equally spaced grooves, with each bar screwed to the tip of a tool steel bit using a fixture, and the flank wear width of the cutting edge was measured. This cutting test is a process in which flank wear is likely to progress, and the cutting edge is prone to chipping due to the interrupted cutting. Therefore, since this process requires both wear resistance and chipping resistance, it is suitable for evaluating hardness and toughness.

[0084] Cutting test Workpiece: JIS SCM440 hollow round bar (outer diameter Φ180, inner diameter Φ50) with two equally spaced grooves (width 20 mm) Cutting speed: 250 m / min. Cutting depth: 1.5 mm Feed rate: 0.4 mm / rev. Number of cuts: 20 passes

[0085] The results of the cutting test are shown in Table 10. For Comparative Examples 11 to 15, the lifespan expired before the number of cutting passes reached 20 due to chipping or flank wear (lifespan judgment standard: flank wear width 0.4 mm), so the number of cutting passes until the lifespan was reached is shown.

[0086]

[0087] As is clear from the results shown in Table 10, Examples 11 to 15 all had low wear, no chipping, and improved hardness and toughness, demonstrating excellent cutting performance over a long period of time. In contrast, Comparative Examples 11 to 15 all had high wear or chipping, reaching the end of their service life in a short period of time.

[0088] The above-disclosed embodiments are merely illustrative in all respects and are not restrictive. The scope of the present invention is defined by the claims, not by the above-disclosed embodiments, and is intended to include meanings equivalent to the claims and all modifications within the scope of the claims.

[0089] 1 Ti atom 2 Anion site (N atom) 3 Anion site (C atom) 4 Cation site (any atom of Ti, V, Zr, or Nb, or any atom of Ti, V, Zr, Nb, Hf, or Ta (Hf and Ta are selected depending on the composition))

Claims

1. A surface-coated cutting tool having a substrate and a coating layer on the surface of the substrate, wherein the coating layer has a composite carbonitride layer, and the composite carbonitride layer has an average thickness of 1.0 μm or more and 20.0 μm or less, and when the total atomic ratio of the metal components is 1, the metal components Ti, V, Zr, and Nb are each in an atomic ratio of a １ , a ２ , a ３ , a ４ When the total atomic ratio of the nonmetallic components is 1, the nonmetallic components C and N are contained in an amount of b １ , b ２ and further containing unavoidable impurities, １ , a ２ , a ３ , a ４ , b １ , b ２ is 0.01≦a １ ≦0.60 0.01≦a ２ ≦0.60 0.01≦a ３ ≦0.60 0.01≦a ４ ≦0.60 0.20≦b １ ≦0.80 0.20≦b ２ ≦0.80, Sconfig expressed by Equation 1 where n = 4 and m = 2 (where ln is the natural logarithm) is 0.80R or more (where R is the gas constant), and the surface-coated cutting tool contains crystal grains having a NaCl-type face-centered cubic structure.

2. The composite carbonitride layer contains at least one of Hf and Ta as the metal component in an atomic ratio of a ５ , a ６ and further comprising: ５ , a ６ is a ５ <0.01 a ６ <0.01, and S represented by Formula 1 where n = 6 and m = 2 ｃｏｎｆｉｇ (However, a ｉ When (i=5 or 6) is zero (not included), a ｉ ln(a ｉ 2. The surface-coated cutting tool according to claim 1, wherein the value of R is 0.80R or more.

3. A surface-coated cutting tool according to claim 1 or 2, characterized in that the composite carbonitride layer contains 0.50 atomic % or less of Cl.