Surface coated cutting tools

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

Technical Field

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

Background Art

[0002] Coated tools in which a coating layer is formed on the surface of a substrate such as tungsten carbide (hereinafter referred to as WC) - based cemented carbide are known, and it is known that they exhibit excellent wear resistance. And various proposals have been made regarding the improvement of the coating layer in order to improve the durability of the coated tool.

[0003] For example, Patent Document 1 discloses a coated tool having a substrate and a coating layer on the substrate, wherein the coating layer has a face-centered cubic structure with a lattice constant of 0.403 to 0.455 nm (Ti , 1-y , 1-x , , x , , 1-x , y ,

[0004] , , Zr 1-x )(C y N 1-y )(0.4 < x < 0.95, 0.2 < y < 0.9) or 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 have wear resistance.

[0004] Also, for example, Patent Document 2 discloses a coated tool (insert) in which a nitride of Ti 1-x Me x having a lattice constant of 0.427 to 0.453 nm and an fcc structure is coated on a substrate (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.

Prior Art Documents

Patent Documents

[0005] [Patent Document 1] Patent No. 4028891 [Patent Document 2] US Patent Application Publication No. 2016 / 0298233 Summary of the Invention [Problem to be solved by the invention]

[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. [Means for solving the problem]

[0007] The 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 are included. the coating layer has a composite carbonitride layer, The composite carbonitride layer has an average thickness of 1.0 μm or more and 20.0 μm or less, When the total atomic ratio of the metal components is 1, the metal components Ti, V, Zr, and Nb are contained in atomic ratios a1, a2, a3, and a4, respectively, of the metal components; When the total atomic ratio of the nonmetallic components is 1, the nonmetallic components C and N are contained at atomic ratios b1 and b2, respectively, of the nonmetallic components; Furthermore, it contains unavoidable impurities, The a1, a2, a3, a4, b1, and b2 are 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 0.20≦b2≦0.80 and S expressed by Equation 1 (where ln is the natural logarithm) with n=4 and m=2. configis greater than or equal to 0.80R (where R is the gas constant), Contains crystal grains having a NaCl-type face-centered cubic structure, A surface-coated cutting tool characterized by:

number

[0008] Furthermore, the surface-coated cutting tool according to the 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. Contains Further contained in the atomic ratio a5 and a6, The a5 and a6 are a5<0.01 a6<0.01 and S expressed by Equation 1 with 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. [Effects of the Invention]

[0011] The surface-coated cutting tool has a coating layer that has high hardness and high toughness. [Brief explanation of the drawings]

[0012] [Figure 1] A schematic diagram of the crystal structure of TiN is shown. [Figure 2] A schematic diagram of the crystal structure of (TiVZrNb)(CN) or (TiVZrNbHfTa)(CN) is shown. DETAILED DESCRIPTION OF THE INVENTION

[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 goals at the same time according to conventional solid-solution strengthening theory. Meanwhile, in recent years, research has been conducted into solid solutions with increased entropy of mixing, including high-entropy alloys, which are alloys made by mixing five or more elements in roughly equal atomic proportions, and multi-principal element alloys, which are alloys composed of three or more elements with at least two or more principal elements. However, no research has been conducted into increasing the entropy of mixing for the coating layer of coated tools.

[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, 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. (ii) The thermal stability and oxidation resistance of the composite carbonitride layer at high temperatures are improved. We gained insight into the following.

[0016] A surface-coated cutting tool according to an embodiment of the present invention will be described below. 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 "greater than or equal to L and less than or equal to M," and the range includes an upper limit (M) and a lower limit (L). When a unit is stated only for the upper limit, the units for the upper limit (M) and the lower limit (L) are the same.

[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, this crystal lattice has each atom 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 in 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 of the formula :(Ti a1 V a2 Zr a3 Nb a4 )(C b1 N b2 ), a1, a2, a3, a4, b1, and b2 satisfy the following conditions: a1+a2+a3+a4=1, b1+b2=1, 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 0.20≦b2≦0.80 and S expressed by Equation 1 (where ln is the natural logarithm) with n=4 and m=2. config is preferably 0.80R (R is the gas constant) or more. Incidentally, the material may contain unintended, unavoidable impurities that are mixed in during the manufacturing process.

[0021]

number

[0022] When the values ​​of a1, a2, a3, a4, b1, and b2 satisfy the above relationships, the entropy of mixing of the (TiVZrNb)(CN) layer is increased, and the (TiVZrNb)(CN) layer has the physical properties (i) to (ii) obtained above. And a1, a2, a3, a4, b1, b2 are 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 CVD using chloride as a raw material gas, it inevitably contains trace amounts of Cl (an amount that 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 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 an NaCl-type face-centered cubic structure. However, crystal grains of a structure other than the NaCl-type face-centered cubic structure may also be contained, but the presence of crystal grains of a structure other than the NaCl-type face-centered cubic structure is unintended. In the claims and this specification, "having crystal grains of an NaCl-type face-centered cubic structure" means that in addition to crystal grains of an NaCl-type face-centered cubic structure, unintended crystal grains of a structure other than 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 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 is made of one or more Ti compounds (not limited to stoichiometric composition) selected from Ti nitride, carbide, carbonitride, and oxide layers, and / or aluminum oxide (not limited to stoichiometric composition), with 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 reactor becomes unstable, a layer different from the (TiVZrNb)(CN) layer, the lower layer, and the upper layer may be unintentionally formed.

[0028] 2.Base (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, such as 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), or 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 thicknesses of the layer are measured at multiple locations (e.g., five locations), 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, use the lower layer 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 the chlorine content of the (TiVZrNb)(CN) layer are determined as follows. The Ti, V, Zr, and Nb contents a1, a2, a3, and a4, the C and N contents b1 and b2, and the chlorine content are calculated by irradiating an electron beam from the surface side of a sample with a polished coating layer surface using an electron probe microanalyzer (EPMA), and averaging the results of 10 characteristic X-ray analyses.

[0037] (3) Identification of the crystal 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 had a NaCl-type face-centered cubic structure. X-ray diffraction was measured using CuKα radiation using the 2θ-θ method 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 method for producing the (TiVZrNb)(CN) layer of this embodiment uses, for example, TiCl4, ZrCl4, VCl4, NbCl 5 , HClThe deposition can be performed by the CVD method using N2, CH3CN, Ar, and H2 gases.

[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 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.

[0042] (3) Composition The (TiVZrNbHfTa)(CN) layer, which is a composite carbonitride layer, has a composition of the formula :(Ti a1 V a2 Zr a3 Nb a4 Hf a5 Ta a6 )(C b1 N b2 ), a1, a2, a3, a4, a5, a6, b1, and b2 satisfy the following conditions: a1+a2+a3+a4+a5+a6=1, b1+b2=1, 0.01≦a1≦0.60 0.01≦a2≦0.60 0.01≦a3≦0.60 0.01≦a4≦0.60 0.00≦a5<0.01 0.00≦a6<0.01 0.20≦b1≦0.80 0.20≦b2≦0.80 and S expressed by Equation 1 (where ln is the natural logarithm) with n=6 and m=2. config is preferably 0.80R (R is the gas constant) or more. Incidentally, the material may contain unintended, unavoidable impurities that are mixed in during the manufacturing process.

[0043]

number

[0044] where 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] When the values ​​of a1, a2, a3, a4, a5, a6, b1, and b2 satisfy the above relationships, the entropy of mixing of the (TiVZrNbHfTa)(CN) layer is increased, and the (TiVZrNbHfTa)(CN) layer has the physical properties (i) to (ii) obtained above. And a1, a2, a3, a4, a5, a6, b1, b2 are S config It is preferable to determine it so that Since the upper limits of a5 and a6 are both less than 0.01, S config The calculated upper limit is 1.08R.

[0046] (4) Cl content 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.

[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. Base material 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 method for manufacturing the (TiVZrNbHfTa)(CN) layer of this embodiment uses, for example, a gas in which HfCl4 and TaCl5 are added to the film-forming gas of the first embodiment, i.e., TiCl4, ZrCl4, VCl4, NbCl5, HfCl4, TaCl 5 , HCl The deposition can be performed by the CVD method using N2, CH3CN, Ar, and H2 gases.

[0052] The above description includes the following additional features. (Appendix 1) A surface-coated cutting tool having a substrate and a coating layer on a surface of the substrate, the coating layer has a composite carbonitride layer, The composite carbonitride layer has an average thickness of 1.0 μm or more and 20.0 μm or less, When the total atomic ratio of the metal components is 1, the metal components Ti, V, Zr, and Nb are contained in atomic ratios a1, a2, a3, and a4, respectively, of the metal components; When the total atomic ratio of the nonmetallic components is 1, the nonmetallic components C and N are contained at atomic ratios b1 and b2, respectively. Furthermore, it contains unavoidable impurities, The a1, a2, a3, a4, b1, and b2 are 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 0.20≦b2≦0.80 and S expressed by Equation 1 (where ln is the natural logarithm) with n=4 and m=2. config is greater than or equal to 0.80R (where R is the gas constant), Contains crystal grains having a NaCl-type face-centered cubic structure, A surface-coated cutting tool characterized by:

number

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

[0054] <Example of the first embodiment> 1. Manufacturing the substrate The raw material powders prepared were WC powder, TiC powder, ZrC powder, TaC powder, NbC powder, Cr3C2 powder, TiN powder, and Co powder. These raw material powders were blended according to the composition shown in Table 1, and wax was added. The mixture was ball milled in acetone for 24 hours, dried under reduced pressure, and then pressed into a green compact of the desired shape at a pressure of 98 MPa.

[0055] This green compact was then vacuum sintered, and after sintering, the cutting edge was honed to R: 0.05 mm to produce substrates A to C made of WC-based cemented carbide with 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 %): TiCl4: 0.02-0.10% ZrCl4: 0.10-0.50% VCl4: 0.02-0.10% NbCl5: 0.02-0.10% CH3CN: 0.10~0.50%, HCl: 0.10-0.50% N2: 0.0-12.0% Ar: 10.0 to 50.0% H2: 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 each of the substrates A to C under the film formation conditions shown in Table 2, and Comparative Examples 1 to 10 shown in Table 5 were obtained. In the manufacturing process of the comparative example, the composition of the raw material gas was changed from that of the example. 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 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] For Examples 1 to 10, Comparative Examples 1 to 10, and Conventional Examples 1 and 2, the average thickness of each layer, the content of each element, the chlorine content, and whether or not they have an NaCl-type face-centered cubic structure were measured using the methods described above. These results are summarized in Table 5.

[0062] [Table 1]

[0063] [Table 2]

[0064] [Table 3]

[0065] [Table 4]

[0066] [Table 5]

[0067] In Table 5, Conventional Examples 1 and 2 do not contain V, Zr, or Nb, so S config is the result calculated from -R / 2[b1ln(b1)+b2ln(b2)]. "**" indicates that the content was below the quantitative accuracy of the analytical equipment, so analysis was performed using single-element detection of chlorine only, confirming the peak in the characteristic X-ray spectrum of chlorine and confirming that a trace amount of chlorine was present. It was also confirmed that all of the examples, comparative examples, and conventional examples had crystal grains that substantially had an 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 carried out on a hollow round bar made of alloy steel SCM440 with two equally spaced grooves, with each of them being screwed to the tip of a tool steel bit with a fixing jig, and the flank wear width of the cutting edge was measured. This cutting test is suitable for evaluating hardness and toughness because it involves interrupted cutting and is prone to chipping, which requires both wear resistance and chipping resistance.

[0069] Cutting test Work material: JIS SCM440 Hollow round bar with two equally spaced grooves (width 20 mm) (Outer diameter Φ180, inner diameter Φ50) Cutting speed: 250m / min. Cut: 1.5mm Feed rate: 0.4mm / 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 criterion: flank wear width 0.4 mm), so the number of cutting passes until the lifespan was reached is shown.

[0071] [Table 6]

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

[0073] <Example of the second embodiment> 1. Manufacturing the substrate Substrates A to C made of WC-based cemented carbide having the same insert shape as that of Mitsubishi Materials Corporation's CNMG120408-MA were manufactured.

[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 %): TiCl4: 0.02-0.10% VCl4: 0.02-0.10% ZrCl4: 0.10-0.50% NbCl5: 0.02-0.10% *HfCl4: 0.00~0.02% *TaCl5: 0.00-0.01% CH3CN: 0.10~0.50%, HCl: 0.10-0.50% N2: 0.0-12.0% Ar: 10.0 to 50.0% H2: remaining *HfCl4 and TaCl5 are 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 each of the substrates A to C under the film formation conditions shown in Table 7, and Comparative Examples 11 to 15 shown in Table 9 were obtained. In the manufacturing process of the comparative example, the composition of the raw material gas was changed from that of the example. In 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] [Table 7]

[0080] [Table 8]

[0081] [Table 9]

[0082] In Table 9, "**" indicates that the content was below the quantitative accuracy of the analytical equipment, so analysis was performed using single-element detection of chlorine only, and a peak in the characteristic X-ray spectrum of chlorine was confirmed, confirming that a trace amount of chlorine was present. Also, all examples, Comparative Example It was confirmed that all of them 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 carried out on a hollow round bar made of alloy steel SCM440 with two equally spaced grooves, with each being screwed to the tip of a tool steel bit with a fixing jig, and the flank wear width of the cutting edge was measured. This cutting test is suitable for evaluating hardness and toughness because it involves interrupted cutting and is prone to chipping, which requires both wear resistance and chipping resistance.

[0084] Cutting test Work material: JIS SCM440 Hollow round bar with two equally spaced grooves (width 20 mm) (Outer diameter Φ180, inner diameter Φ50) Cutting speed: 250m / min. Cut: 1.5mm Feed rate: 0.4mm / 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 tool life expired before the number of cutting passes reached 20 due to chipping or flank wear (life judgment standard: flank wear width 0.4 mm), so the number of cutting passes until the tool life expired is shown.

[0086] [Table 10]

[0087] As is clear from the results shown in Table 10, all of Examples 11 to 15 had little wear, no chipping, and improved hardness and toughness, and exhibited excellent cutting performance over a long period of time. In contrast to this, in all of Comparative Examples 11 to 15, the amount of wear was large or chipping occurred, and the service life was reached 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 any modifications equivalent to the claims and within the scope thereof. [Explanation of symbols]

[0089] 1 Ti atom 2 Anion site (N atom) 3 Anion site (C atom) 4 Cation site (Ti, V, Zr, or Nb atom, or 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 a surface of the substrate, the coating layer has a composite carbonitride layer, the composite carbonitride layer has an average thickness of 1.0 μm or more and 20.0 μm or less, When the total atomic ratio of the metal components is 1, the metal components Ti, V, Zr, and Nb are each expressed as a １ , a ２ , a ３ , a ４ Contains When the total atomic ratio of the nonmetallic components is 1, the nonmetallic components C and N are each expressed as b １ , b ２ Contains Furthermore, it contains unavoidable impurities, the aforesaid a １ a ２ a ３ a ４ b １ b ２ are 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 Sconfig, expressed by Equation 1 (where ln is the natural logarithm) with n = 4 and m = 2, is 0.80R (where R is the gas constant) or more; Contains crystal grains having a NaCl-type face-centered cubic structure, A surface-coated cutting tool characterized by: [Equation 5]

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 containing a ５ , a ６ teeth, a ５ <0.01 a ６ <0.01 where n=6, m=2, and S represented by Equation 1 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. 3. The surface-coated cutting tool according to claim 1, wherein the composite carbonitride layer contains 0.50 atomic % or less of Cl.

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