Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23B—TURNING; BORING
  • B23B27/00—Tools for turning or boring machines; Tools of a similar kind in general; Accessories therefor
  • B23B27/14—Cutting tools of which the bits or tips or cutting inserts are of special material
  • B23B27/148—Composition of the cutting inserts
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
  • C23C14/06—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the coating material
  • C23C14/0641—Nitrides
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
  • C23C14/06—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the coating material
  • C23C14/14—Metallic material, boron or silicon
  • C23C14/16—Metallic material, boron or silicon on metallic substrates or on substrates of boron or silicon
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
  • C23C14/22—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the process of coating
  • C23C14/34—Sputtering
  • C23C14/3435—Applying energy to the substrate during sputtering
  • C23C14/345—Applying energy to the substrate during sputtering using substrate bias
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
  • C23C14/22—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the process of coating
  • C23C14/34—Sputtering
  • C23C14/3485—Sputtering using pulsed power to the target
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
  • C23C14/22—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the process of coating
  • C23C14/34—Sputtering
  • C23C14/35—Sputtering by application of a magnetic field, e.g. magnetron sputtering
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23B—TURNING; BORING
  • B23B2228/00—Properties of materials of tools or workpieces, materials of tools or workpieces applied in a specific manner
  • B23B2228/10—Coatings
  • B23B2228/105—Coatings with specified thickness

Definitions

• This disclosure relates to cutting tools.
• Cubic boron nitride (hereinafter referred to as "cBN”) is second only to diamond in hardness and has excellent thermal and chemical stability. Furthermore, because it is more stable than diamond when used with ferrous materials, cBN sintered compacts have been used as cutting tools for machining ferrous materials.
• the cutting tool comprises: 1.
• the number nR of voids per 50 ⁇ m length of the MAlN layer on the rake face is 3 or less;
• the cross-sectional area of the voids is 1.0 ⁇ 10 ⁇ 4 ⁇ m 2 or more and 0.5 ⁇ m 2 or less.
• FIG. 1 is a perspective view illustrating one embodiment of a cutting tool.
• FIG. 2 is a schematic cross-sectional view of a cutting tool according to one aspect of this embodiment.
• FIG. 3 is a schematic cross-sectional view of a cutting tool according to another aspect of the present embodiment.
• FIG. 4 is a schematic cross-sectional view of a cutting tool according to another aspect of the present embodiment.
• FIG. 5 is a schematic cross-sectional view of a cutting tool according to another aspect of the present embodiment.
• FIG. 6 is an enlarged BSE image of a cross section of the cutting tool according to this embodiment.
• FIG. 7 is an enlarged BSE image of a cross section of the cutting tool according to this embodiment.
• FIG. 1 is a perspective view illustrating one embodiment of a cutting tool.
• FIG. 2 is a schematic cross-sectional view of a cutting tool according to one aspect of this embodiment.
• FIG. 3 is a schematic cross-sectional view of a cutting tool according to another aspect of the present
• FIG. 8 is a BSE image showing an enlarged cross section of the cutting tool according to this embodiment.
• FIG. 9 is an enlarged BSE image of a cross section of the cutting tool according to this embodiment.
• FIG. 10 is an enlarged BSE image of a cross section of the cutting tool according to this embodiment.
• a cutting tool including a rake face and a flank face the cutting tool comprises a substrate made of a cubic boron nitride sintered body and a coating provided on the substrate;
• the cubic boron nitride sintered body contains cubic boron nitride
• the coating includes a MAlN layer;
• M in the MAlN layer represents a metal element including titanium, chromium, or both;
• the MAlN layer contains cubic M x Al 1-x N crystal grains, the atomic ratio x of the metal element M in the M x Al 1-x N is 0.3 or more and 0.7 or less;
• the content of the cubic boron nitride is 20% by volume or more relative to the cubic boron nitride sintered body,
• a cutting tool including a rake face and a flank face includes a substrate and a coating provided on the substrate, the coating includes a TiMAlN layer; the TiMAlN layer contains cubic Ti x M y Al z N crystal grains; the atomic ratio x of titanium element in the Ti x M y Al z N is 0.4 or more and 0.79 or less; the atomic ratio y of the element M in the Ti x M y Al z N is 0.01 or more and 0.1 or less; the atomic ratio z of aluminum element in Ti x M y Al z N is 0.2 or more and 0.5 or less; the sum of x, y, and z is 1; the element M is at least one of boron and silicon, or both; The number nF of voids per 100 ⁇ m length in the TiMAlN layer located on the flank in a cross section obtained by cutting the TiMAlN layer along
• the MAlN or TiMAlN layers in the cutting tools of Patent Documents 1 and 2 contain minute voids that are not counted in these patent documents, and these minute voids can cause damage to the coating and substrate during cutting. Therefore, when applying these tools to highly efficient cutting processes (such as cutting processes with high feed rates), further improvements in performance (e.g., chipping resistance) are required.
• This disclosure was made in consideration of the above circumstances, and aims to provide a cutting tool with excellent chipping resistance.
• the cutting tool according to the present disclosure comprises: 1. A cutting tool including a rake face and a flank face, The cutting tool includes a substrate and a coating provided on the substrate, the coating includes a MAlN layer; the MAlN layer contains cubic M x Al 1-x N crystal grains, the atomic ratio x of the metal element M in the M x Al 1-x N is 0.2 or more and 0.8 or less; M in the MAlN layer represents a metal element including titanium, chromium, or both; In a cross section of the MAlN layer cut along a plane including a normal to the rake face, the number nR of voids per 50 ⁇ m length of the MAlN layer on the rake face is 3 or less; The cross-sectional area of the voids is 1.0 ⁇ 10 ⁇ 4 ⁇ m 2 or more and 0.5 ⁇ m 2 or less.
• the cutting tool has excellent chipping resistance when the number nR of voids per 50 ⁇ m length of the MAlN layer on the rake face is 3 or less.
• chip resistance means resistance to chipping of the MAlN layer from the substrate.
• the number of voids nF per 50 ⁇ m length of the MAlN layer on the flank may be 3 or less.
• wear resistance means resistance to wear of the MAlN layer during cutting.
• the number of voids n C per 50 ⁇ m length of the MAlN layer on the cutting edge surface may be not more than 3.
• the nF may be 3 or less, the nR may be 3 or less, and the nC may be 3 or less. By specifying them in this way, the cutting tool has excellent wear resistance in addition to excellent fracture resistance.
• the metal element M may further contain at least one element selected from the group consisting of boron, silicon, vanadium, zirconium, niobium, molybdenum, hafnium, tantalum, and tungsten. By specifying it in this way, the cutting tool will have excellent heat resistance and lubricity in addition to excellent chipping resistance.
• the substrate may comprise at least one material selected from the group consisting of cemented carbide, cermet, high-speed steel, ceramics, cubic boron nitride sintered body, and diamond sintered body. By specifying it in this way, the cutting tool has excellent versatility in terms of machining conditions.
• the surface roughness Rmax of the substrate may be 1 ⁇ m or less. By specifying it in this way, the cutting tool has even better chipping resistance.
• the coating may further include an underlayer disposed between the substrate and the MAlN layer, and the composition of the underlayer may be different from the composition of the MAlN layer.
• the coating may further include a surface layer disposed on the MAlN layer, and the composition of the surface layer may be different from the composition of the MAlN layer.
• the thickness of the MAlN layer may be 0.1 ⁇ m or more and 2.0 ⁇ m or less. By specifying it in this way, the cutting tool will have even better chipping resistance.
• the thickness of the coating may be 0.1 ⁇ m or more and 2.5 ⁇ m or less. By specifying it in this way, the cutting tool will have even better chipping resistance.
• the present embodiment An embodiment of the present disclosure (hereinafter referred to as "the present embodiment") will be described below. However, the present embodiment is not limited thereto.
• the notation “A to Z” means the upper and lower limits of a range (i.e., A to Z). When no unit is specified for A and only a unit is specified for Z, the unit of A and the unit of Z are the same.
• the chemical formula when a compound is represented by a chemical formula in which the composition ratio of the constituent elements is not limited, such as "TiN,” the chemical formula is considered to include all conventionally known composition ratios (element ratios).
• the chemical formula is considered to include not only stoichiometric compositions but also non-stoichiometric compositions.
• the chemical formula "TiN” includes not only the stoichiometric composition “Ti 1 N 1 ,” but also non-stoichiometric compositions such as “Ti 1 N 0.8 .” This also applies to descriptions of compounds other than "TiN.”
• the cutting tool comprises: A cutting tool including a rake face and a flank face, the cutting tool comprises a substrate and a coating provided on the substrate; the coating includes a MAlN layer; the MAlN layer contains cubic M x Al 1-x N crystal grains, the atomic ratio x of the metal element M in the M x Al 1-x N is 0.2 or more and 0.8 or less; M in the MAlN layer represents a metal element including titanium, chromium, or both; In a cross section of the MAlN layer cut along a plane including a normal to the rake face, the number nR of voids per 50 ⁇ m length of the MAlN layer on the rake face is 3 or less; The cross-sectional area of the voids is 1.0 ⁇ 10 ⁇ 4 ⁇ m 2 or more and 0.5 ⁇ m 2 or less.
• the surface-coated cutting tool (hereinafter sometimes simply referred to as "cutting tool") according to this embodiment may be, for example, a drill, an end mill, an indexable cutting tip for a drill, an indexable cutting tip for an end mill, an indexable cutting tip for milling, an indexable cutting tip for turning, a metal saw, a gear cutting tool, a reamer, a tap, etc.
• FIG. 1 is a perspective view illustrating one embodiment of a cutting tool.
• a cutting tool 10 having this shape is used as an indexable cutting insert for turning.
• the cutting tool 10 shown in Figure 1 has a surface including an upper surface, a lower surface, and four side surfaces, and is shaped like a rectangular prism that is slightly thin in the vertical direction overall. Furthermore, the cutting tool 10 has a through-hole that penetrates the upper and lower surfaces, and at the boundaries between the four side surfaces, adjacent side surfaces are connected by arcuate surfaces.
• the top and bottom surfaces typically form the rake face 1a, the four side surfaces (and the arc surfaces connecting them) form the flank face 1b, and the surface connecting the rake face 1a and flank face 1b forms the cutting edge face 1c.
• rake face refers to the surface that scoops out chips removed from the workpiece.
• flank face refers to the surface that partly contacts the workpiece.
• the cutting edge face is included in the portion that makes up the cutting edge of the cutting tool.
• the cutting tool 10 may have a shape with or without a chip breaker.
• the shape of the cutting edge of the cutting tool is represented by a flat surface (cutting edge surface 1c), but the shape of the cutting edge is not limited to this.
• cutting edge shapes include sharp edges (ridges where the rake face and flank intersect) (e.g., Figure 3) and negative lands (chamfered shapes) (e.g., Figure 2).
• each part of cutting tool 10 has been explained above using Figure 1, but in the base material of the cutting tool according to this embodiment, the same terms as above will be used for the shape and names of each part corresponding to cutting tool 10. That is, the base material of the cutting tool has a rake face and a flank face. The base material may also have a cutting edge surface connecting the rake face and the flank face.
• the cutting tool 10 includes a substrate 11 and an MAlN layer 12 provided on the substrate 11 (FIG. 4).
• the cutting tool 10 may further include an underlayer 13 provided between the substrate 11 and the MAlN layer 12 (FIG. 5).
• the cutting tool 10 may further include a surface layer 14 provided on the MAlN layer 12 (FIG. 5).
• the underlayer 13, the surface layer 14, and other layers will be described later.
• the above-described layers provided on the substrate may be collectively referred to as a "coating.” That is, the cutting tool 10 includes a coating 20 that covers the substrate 11 (FIGS. 2 and 3).
• the coating 20 includes the MAlN layer 12 (FIG. 4).
• the coating 20 may further include the underlayer 13 or the surface layer 14 (FIG. 5).
• the substrate of this embodiment can be any known substrate of this kind.
• the substrate can be selected from the group consisting of cemented carbide (for example, tungsten carbide (WC)-based cemented carbide, cemented carbide containing Co in addition to WC, cemented carbide containing Cr, Ti, Ta, Nb, etc. carbonitride in addition to WC), cermet (mainly composed of TiC, TiN, TiCN, etc.), high-speed steel, ceramics (titanium carbide, silicon carbide, silicon nitride, aluminum nitride, aluminum oxide, etc.), cubic boron nitride sintered body (cBN sintered body) and diamond sintered body.
• cemented carbide for example, tungsten carbide (WC)-based cemented carbide, cemented carbide containing Co in addition to WC, cemented carbide containing Cr, Ti, Ta, Nb, etc. carbonitride in addition to WC
• cermet mainly composed of TiC, TiN, TiCN,
• cemented carbide particularly WC-based cemented carbide
• cermet particularly TiCN-based cermet
• cubic boron nitride sintered body may be selected. This is because these substrates have an excellent balance of hardness and strength, especially at high temperatures, and have excellent properties as substrates for cutting tools for the above-mentioned applications.
• the effects of this embodiment are still exhibited even if the cemented carbide contains free carbon or an abnormal phase known as the ⁇ phase in its structure.
• the substrate used in this embodiment may also have its surface modified.
• a de- ⁇ layer may be formed on the surface of a cemented carbide, or a surface-hardened layer may be formed on the surface of a cBN sintered compact. The effects of this embodiment are still exhibited even if the surface is modified in this way.
• the surface roughness Rmax of the substrate may be 1 ⁇ m or less, or may be 0.5 ⁇ m or less.
• the lower limit of the surface roughness Rmax of the substrate is not particularly limited, but may be, for example, 0.1 ⁇ m or more.
• the surface roughness can be measured in accordance with JIS B06012001 using a stylus surface roughness measuring instrument with a cutoff value of 0.3 mm, a reference length of 0.8 mm, and a scanning speed of 0.06 mm/sec.
• the substrate may be a cubic boron nitride sintered body (cBN sintered body).
• the cubic boron nitride sintered body contains cubic boron nitride.
• the cubic boron nitride sintered body may further contain a binder.
• cubic boron nitride refers to cubic boron nitride crystal grains. That is, the cubic boron nitride sintered body contains polycrystalline cubic boron nitride.
• the cubic boron nitride content may be 20% by volume or more, 20% to 97% by volume or less, or 20% to 80% by volume or less, relative to the cubic boron nitride sintered body.
• the cubic boron nitride content (volume %) and the binder (binding phase) content (volume %) described below in the cubic boron nitride sintered body can be confirmed by performing structural observation, elemental analysis, etc. on the cubic boron nitride sintered body using an energy dispersive X-ray analyzer (EDX) "Octane Elect EDS System” (trademark) attached to a scanning electron microscope (SEM) ("JEOL Ltd. JSM-7800F” (trademark)).
• EDX energy dispersive X-ray analyzer
• SEM scanning electron microscope
• the cubic boron nitride content (volume %) can be determined as follows. First, the cubic boron nitride sintered body is cut at an arbitrary position to prepare a sample containing a cross section of the cubic boron nitride sintered body. A focused ion beam device, cross-section polisher device, etc. can be used to prepare the cross section. Next, the cross section is observed at 5000x magnification using an SEM to obtain a backscattered electron image. In the backscattered electron image, cubic boron nitride particles appear black (dark field), and areas where the binder is present appear gray or white (bright field).
• the backscattered electron image is binarized using image analysis software (for example, "WinROOF” by Mitani Corporation).
• image analysis software for example, "WinROOF” by Mitani Corporation.
• the area ratio of pixels originating from the dark field pixels originating from cubic boron nitride
• the cubic boron nitride content volume percentage
• the ratio determined by the above method is the area ratio of cubic boron nitride in the field of view, but in this embodiment, this area ratio is treated as a volume ratio. In other words, if the area ratio of cubic boron nitride determined by the above method is 20%, the cubic boron nitride content will be considered to be 20 volume% relative to the cubic boron nitride sintered body.
• the median diameter D 50 of the cubic boron nitride may be 0.1 ⁇ m or more and 5 ⁇ m or less, or 0.2 ⁇ m or more and 3 ⁇ m or less.
• the D50 of cubic boron nitride can be determined as follows. First, a sample containing a cross section of a cubic boron nitride sintered body is prepared according to the method for determining the cubic boron nitride content described above, and a backscattered electron image is obtained. Next, image analysis software ("WinROOF (ver. 7.4.5)" by Mitani Corporation) is used to calculate the equivalent circle diameter of each dark field (equivalent to cBN) in the backscattered electron image. It is preferable to calculate the equivalent circle diameter of 100 or more cubic boron nitride particles by observing five or more fields of view.
• WinROOF ver. 7.4.5
• the equivalent circle diameters are arranged in ascending order from smallest to largest to determine the cumulative distribution.
• the particle size at which the cumulative area is 50% in the cumulative distribution is D50 .
• the equivalent circle diameter means the diameter of a circle having the same area as the measured area of a cubic boron nitride particle.
• binder refers to a substance that binds the crystal grains of the cubic boron nitride together.
• the binder may contain a compound consisting of at least one element selected from the group consisting of Group 4 elements, Group 5 elements, Group 6 elements, Al (aluminum), and Si (silicon) in the periodic table of the elements, and at least one element selected from the group consisting of C (carbon), N (nitrogen), B (boron), and O (oxygen).
• Examples of the Group 4 elements include Ti (titanium), Zr (zirconium), and Hf (hafnium).
• Examples of the Group 5 elements include V (vanadium), Nb (niobium), and Ta (tantalum).
• Examples of the Group 6 elements include Cr (chromium), Mo (molybdenum), and W (tungsten).
• the components contained in the binder can be determined by analyzing the area corresponding to the binder of a sample containing the cut surface of the cutting tool using energy dispersive X-ray spectroscopy (SEM-EDX) attached to an SEM. The observation magnification at this time is, for example, 10,000x.
• SEM-EDX energy dispersive X-ray spectroscopy
• Examples of compounds consisting of at least one element selected from the group consisting of Group 4 elements, Group 5 elements, Group 6 elements, Al and Si in the periodic table of the elements, and at least one element selected from the group consisting of C, N, B and O include nitrides such as TiN and AlN, carbides such as TiC and WC, borides such as TiB2 and AlB2 , oxides such as Al2O3 , and the like, as well as TiCN , AlON, SiAlON, SiTiAlON, etc.
• the cubic boron nitride sintered body may contain inevitable impurities to the extent that the effects of the present disclosure are not impaired.
• “Inevitable impurities” refers to elements and compounds that may be contained in trace amounts in the raw materials of the cubic boron nitride sintered body or during its production.
• the content (volume %) of each element and compound contained as an inevitable impurity may be 0% to 5% by volume, and the sum of these (i.e., the total content of trace impurities) may be 0% to 5% by volume. Therefore, inevitable impurities may or may not be contained in the cubic boron nitride sintered body.
• Examples of inevitable impurities include Li, Mg, Ca, Sr, Ba, Be, Si, Ga, La, Fe, and Cu.
• the coating according to this embodiment includes an MAlN layer.
• M in the MAlN layer represents a metal element including titanium, chromium, or both.
• the "coating" has the effect of improving various properties of the cutting tool, such as chipping resistance and wear resistance, by covering at least a portion of the substrate (e.g., a portion of the rake face and a portion of the flank face).
• the coating may cover the entire surface of the substrate. However, even if a portion of the substrate is not covered with the coating or the coating has a partially different configuration, this does not depart from the scope of this embodiment.
• the thickness of the coating may be 0.1 ⁇ m or more and 2.5 ⁇ m or less, 0.3 ⁇ m or more and 2.5 ⁇ m or less, or 0.5 ⁇ m or more and 1.5 ⁇ m or less.
• the thickness of the coating refers to the sum of the thicknesses of the layers that make up the coating.
• layers that make up the coating include the MAlN layer, the intermediate layer described below, and other layers such as the base layer and surface layer described above.
• the thickness of the coating can be determined, for example, by measuring 10 arbitrary points on a cross-sectional sample parallel to the normal direction of the substrate surface using an SEM and averaging the thicknesses at the 10 measured points. The measurement magnification is, for example, 10,000x. The same applies when measuring the thickness of the MAlN layer, the intermediate layer, the base layer, and the surface layer described above.
• SEMs include the JSM-7600F (product name) and JSM-7800 (product name) manufactured by JEOL Ltd.
• the MAlN layer contains crystal grains of cubic M x Al 1-x N. That is, the MAlN layer is a layer containing polycrystalline M x Al 1-x N.
• the crystal grains of cubic M x Al 1-x N can be identified by, for example, a diffraction peak pattern obtained by X-ray diffraction.
• M represents a metal element.
• the metal element M includes titanium, chromium, or both.
• the metal element M may further include at least one element (hereinafter sometimes referred to as a "third element") selected from the group consisting of boron, silicon, vanadium, zirconium, niobium, molybdenum, hafnium, tantalum, and tungsten.
• boron is generally considered to be a semimetal that exhibits properties intermediate between metallic elements and non-metallic elements, but in the MAlN layer of this embodiment, elements that have free electrons are considered to be metals, and boron is included in the range of metallic elements.
• the metal element M may be titanium. That is, the coating may include a TiAlN layer as the MAlN layer, and the TiAlN layer may include cubic Ti x Al 1-x N crystal grains.
• the TiAlN layer is a layer including polycrystalline Ti x Al 1-x N.
• the cubic Ti x Al 1 -x N crystal grains can be identified by, for example, a diffraction peak pattern obtained by X-ray diffraction.
• the atomic ratio x of the metal element M in the M x Al 1-x N is 0.2 or more and 0.8 or less, and may be 0.4 or more and 0.65 or less.
• the x can be determined by performing elemental analysis of the entire MAlN layer on the cross-sectional sample using energy dispersive X-ray spectroscopy (SEM-EDX) attached to a SEM.
• SEM-EDX energy dispersive X-ray spectroscopy
• the observation magnification is, for example, 5000x.
• the x value is determined by measuring 10 arbitrary points on the MAlN layer of the cross-sectional sample, and the average value of the determined 10 points is defined as the x value in the MAlN layer.
• the metal element M includes multiple metal elements
• the sum of the atomic ratios of the respective metal elements is the atomic ratio x of the metal element M.
• the "arbitrary 10 points" are selected from different crystal grains in the MAlN layer.
• An example of the EDX device is the JED-2300 (product name) manufactured by JEOL Ltd.
• the atomic ratio w of titanium in the M x Al 1-x N may be more than 0 and not more than 0.8, or may be 0.4 or more and not more than 0.65. It goes without saying that when the metal atom M is titanium only, the atomic ratio x of the metal element M and the atomic ratio w of titanium will be the same.
• the atomic ratio y of chromium in the M x Al 1-x N may be more than 0 and not more than 0.8, or may be 0.25 or more and not more than 0.5. Needless to say, when the metal atom M is only chromium, the atomic ratio x of the metal element M and the atomic ratio y of chromium will be the same.
• the atomic ratio z of the third element in the M x Al 1-x N may be more than 0 and not more than 0.8, or may be 0.01 or more and 0.4 or less.
• the sum of the atomic ratios of the respective metal elements becomes the atomic ratio z of the third element.
• the thickness of the MAlN layer may be 0.1 ⁇ m or more and 2.0 ⁇ m or less, or 0.3 ⁇ m or more and 1.4 ⁇ m or less. If the MAlN layer forms a multilayer structure as described below, the thickness of the MAlN layer refers to the thickness per layer. This thickness can be measured, for example, by observing the cross section of the cutting tool as described above using an SEM at a magnification of 10,000x.
• the coating may contain one or more MAlN layers (e.g., 2 to 50 layers).
• the MAlN layers may be alternately stacked with other layers, such as intermediate layers, to form a multilayer structure.
• the MAlN layers themselves may form a multilayer structure.
• the number of voids nR per 50 ⁇ m length of the MAlN layer on the cutting face is not more than 3.
• the number of voids nF per 50 ⁇ m length of the MAlN layer on the flank may be not more than 3.
• voids refers to gaps having a cross-sectional area of 1.0 ⁇ 10 ⁇ 4 ⁇ m 2 or more and 0.5 ⁇ m 2 or less when the MAlN layer is cut.
• the voids may extend in the thickness direction of the coating.
• the inventors have confirmed that voids having a cross-sectional area of less than 1.0 ⁇ 10 ⁇ 4 ⁇ m 2 are not generated by the cutting tool manufacturing method described below, or that even if they are generated, the number of voids is very small. In other words, voids having a cross-sectional area of less than 1.0 ⁇ 10 ⁇ 4 ⁇ m 2 may exist.
• voids having a cross-sectional area of less than 1.0 ⁇ 10 ⁇ 4 ⁇ m 2 exist, the inventors believe that they cannot become the origin of chipping when repeatedly subjected to impacts during cutting. Furthermore, in this embodiment, the inventors have confirmed that voids having a cross-sectional area exceeding 0.5 ⁇ m 2 are not generated by the cutting tool manufacturing method described below. In other words, the number of voids having a cross-sectional area exceeding 0.5 ⁇ m 2 may be zero.
• the number of voids is counted using the following procedure.
• a cross section of the cutting tool as described above is observed at a magnification of 30,000 times using an SEM to obtain an SEM image.
• a backscattered electron composition image (BSE image) is obtained so that the MAlN layer is continuously included within a length of 50 ⁇ m (the length in the direction perpendicular to the thickness direction of the MAlN layer) (e.g., Figure 6).
• the number of BSE images obtained is not particularly limited as long as the MAlN layer is included within the above-mentioned 50 ⁇ m length range, and may be one field of view or multiple fields of view.
• the BSE images may be stitched together (e.g., Figures 8 and 9) and the number of voids, as described below, may be counted.
• the size of one field of view may be, for example, 3.7 ⁇ m x 2.6 ⁇ m.
• the obtained BSE image is converted into a monochrome image of 256 levels within a range excluding the vicinity of the substrate and 30 nm from the film surface (hereinafter, sometimes referred to as the "evaluation range").
• the 80th level counted from black is used as a threshold, and binarization processing is performed using image analysis software (e.g., "WinROOF” manufactured by Mitani Shoji Co., Ltd.). Shape analysis is then performed on the portions that emerge through the binarization, and portions with a cross-sectional area of 1.0 ⁇ 10 ⁇ 4 ⁇ m 2 or more and 0.5 ⁇ m 2 or less are counted as voids (e.g., Figure 7 ).
• a void is counted as one whether it penetrates the target MAlN layer or not.
• the number of voids is counted as 3 ( Figure 7).
• voids are generated starting from the surface of the substrate, while others are generated independently within the film structure.
• the inventors believe that the voids observed in the MAlN layer in the SEM image of the cross-sectional sample are one of these types of voids.
• the number of such voids is counted at least three "continuous ranges of 50 ⁇ m in length," and the average value is taken as the number of voids.
• the above-mentioned method of counting voids applies to all surfaces, including the flank, rake face, and cutting edge (see Figures 2 and 3, for example).
• the number of voids is counted within the maximum length range that can be ensured and converted to the number of voids per 50 ⁇ m length to determine the number of voids. For example, if the maximum length range that can be ensured is 20 ⁇ m, the number of voids is counted within a 20 ⁇ m long range and the number of counted voids is multiplied by 2.5 to calculate the number of voids per 50 ⁇ m length.
• nC when the cutting tool further includes a cutting edge surface connecting the cutting face and the flank, when the cross section of the MAlN layer is cut along a plane including a normal to the cutting edge surface, nC may be 3 or less, where nC is the number of voids per 50 ⁇ m length of the MAlN layer on the cutting edge surface.
• the nR may be 3 or less, 2 or less, or 1 or less.
• Voids present on the rake face act as chipping origins when repeatedly subjected to impacts during cutting. In other words, reducing the number of voids in the MAlN layer on the rake face improves chipping resistance.
• the nF may be 3 or less, 2 or less, or 1 or less.
• the presence of voids on the flank face may reduce wear resistance against abrasive wear during cutting, and may accelerate flank wear. In other words, reducing the number of voids in the MAlN layer on the flank face improves wear resistance.
• the nC may be 3 or less, 2 or less, or 1 or less.
• Voids present on the cutting edge surface act as chipping origins when repeatedly subjected to impacts during cutting. In other words, reducing the number of voids in the MAlN layer on the cutting edge surface further improves chipping resistance.
• nF may be 3 or less, nR may be 3 or less, and nC may be 3 or less. In another aspect of this embodiment, nF may be 2 or less, nR may be 2 or less, and nC may be 2 or less. In another aspect of this embodiment, nF may be 1 or less, nR may be 1 or less, and nC may be 1 or less.
• the coating contains multiple MAlN layers, it is sufficient that at least one of the multiple MAlN layers meets the above-mentioned condition regarding the number of voids. This is because it is believed that the effects of this disclosure will be achieved in such MAlN layers.
• the number nD of droplets per 50 ⁇ m length of the MAlN layer on the flank may be 1 or less, or may be 0.
• the term "droplet" refers to a metal particle present in a layer constituting the coating (e.g., an MAlN layer such as a TiAlN layer) and having a predetermined size, as described below.
• the number of droplets is determined as follows: The cross section of the cutting tool is observed at a magnification of 30,000 times using an SEM to obtain an SEM image. The SEM image is acquired so that the MAlN layer is continuously included within a 50 ⁇ m length range. The obtained SEM image is visually inspected, and a white, approximately circular portion present in the MAlN layer (e.g., in the layer shown in light gray in FIG. 10 ) is noted.
• the length L a ( ⁇ m) of the long side and the length L b ( ⁇ m) of the short side of a rectangle circumscribing this approximately circular portion are determined.
• the rectangle is set so that the long side or the short side is parallel to the main surface of the substrate.
• "parallel” is not limited to geometric parallelism but also encompasses approximately parallelism. If the determined L a and L b satisfy the following conditions, the approximately circular portion is counted as a droplet. 0.25 ⁇ L b /L a ⁇ 1 and 0.1 ⁇ L a The number of droplets is counted in at least three "continuous ranges of 50 ⁇ m length," and the average value is taken as the number of droplets.
• the coating may further include other layers as long as the effects of this embodiment are not impaired.
• examples of such other layers include a base layer provided between the substrate and the MAlN layer, a surface layer provided on the MAlN layer, and an intermediate layer provided between the base layer and the MAlN layer or between the MAlN layer and the surface layer.
• the compositions of the base layer, surface layer, and intermediate layer may be the same or different from those of the MAlN layer, as long as they are distinguishable from the MAlN layer.
• the base layer may be, for example, a layer made of a compound represented by TiN.
• the surface layer may be, for example, a layer made of a compound represented by AlCrN.
• the intermediate layer may be, for example, a layer made of a compound represented by CrN.
• the thickness of the other layers is not particularly limited as long as the effects of this embodiment are not impaired, and examples include 0.1 ⁇ m to 2 ⁇ m.
• the method for manufacturing a cutting tool includes the steps of: A step of preparing the substrate (hereinafter sometimes referred to as the "first step”); and forming the MAlN layer on the substrate by high-power pulse sputtering (hereinafter, sometimes referred to as the "second step”).
• HiPIMS High-power pulse sputtering
• HiPIMS is a type of sputtering method. Unlike conventional sputtering, HiPIMS is a film-forming method in which pulsed power is applied, and atoms from the target (raw material) are ejected by discharge and deposited onto a substrate or other surface.
• the HiPIMS method a substrate and a target are placed inside the device as a cathode, and then a negative voltage is applied to the target to generate a discharge.
• the device is filled with an inert gas (e.g., Ar gas) under reduced pressure.
• the discharge ionizes the inert gas inside the device, and the inert gas ions collide with the surface of the target at high speed. This collision ejects atoms from the target, which are then deposited on the substrate to form a coating. Because the HiPIMS method forms films based on the above-described principle, droplets are less likely to be generated compared to the arc cathode ion plating method.
• an MAlN layer such as a TiAlN layer
• a substrate made of cubic boron nitride sintered body using the HiPIMS method, some of the voids are generated from the surface of the substrate, while others are generated independently within the film structure. Because the voids are considered to be due to the film formation method, the inventors believe that the voids are also generated when forming layers other than the MAlN layer (e.g., an underlayer, an intermediate layer, etc.).
• a substrate is prepared.
• the substrate include cemented carbide, cermet, and cubic boron nitride sintered body.
• Commercially available substrates may be used.
• the substrate may be manufactured by a general powder metallurgy method.
• WC powder and Co powder are first mixed using a ball mill or the like to obtain a mixed powder.
• the mixed powder is then dried and molded into a predetermined shape to obtain a compact.
• the compact is then sintered to obtain a WC-Co cemented carbide (sintered body).
• the sintered body is then subjected to a predetermined cutting edge processing, such as honing, to produce a substrate made of a WC-Co cemented carbide.
• a substrate with a cutting edge surface FIG. 2
• a substrate without a cutting edge surface FIG. 3
• any substrate other than those described above can be prepared as long as it is a conventionally known substrate of this type.
• ⁇ Second step step of forming MAlN layer>
• the MAlN layer is formed on the substrate by high-power pulse sputtering, using a target containing metal elements M (e.g., Ti, Cr, etc.) and Al in amounts adjusted according to the composition of the MAlN layer to be formed.
• M metal elements
• the second step can be performed as follows: First, a chip of any shape is mounted as a substrate in the chamber of the film-forming device.
• the substrate is positioned so that its relief surface faces the target.
• the substrate is attached to a substrate holder on a rotating table that is rotatably installed in the center of the chamber of the film-forming device.
• a bias power supply is connected to the substrate holder. With the rotating table rotating in the center of the chamber, Ar gas and nitrogen gas are introduced.
• sputtering power (e.g., average power 10 kW, frequency 2000-4000 Hz, pulse width 50-100 ⁇ s) is applied to the target for forming the MAlN layer. This causes metal atoms to be ejected from the target for forming the MAlN layer. After a predetermined time has elapsed, the application of the sputtering power is stopped, forming an MAlN layer on the surface of the substrate.
• the deposition time is adjusted to ensure the thickness of the MAlN layer falls within a predetermined range.
• the MAlN layer may be formed on the surface of the substrate other than the portion involved in the cutting process (e.g., the rake face and flank near the cutting edge) as well as on the surface of the substrate other than the portion involved in the cutting process.
• the raw material of the MAlN layer contains metal elements M and Al.
• the raw material of the TiAlN layer contains Ti and Al.
• the raw material of the TiAlN layer is a powder sintered alloy of Ti and Al.
• the raw material of the CrAlN layer contains Cr and Al.
• the raw material of the CrAlN layer is a powder sintered alloy of Cr and Al.
• the above-mentioned reactive gas is appropriately set depending on the composition of the MAlN layer.
• the reactive gas may be a mixture of nitrogen gas and an inert gas.
• the surface of the substrate may be etched before the MAlN layer is formed.
• the etching conditions may be, for example, as follows. Etching conditions: Inert gas: Ar gas Temperature: 500°C Pressure: 350 mPa Voltage: Pulse DC voltage (500V, frequency 200kHz) Processing time: 5 minutes
• the manufacturing method according to this embodiment may also include other steps such as forming a base layer on the substrate, forming an intermediate layer on the base layer or the MAlN layer, forming a surface layer on the MAlN layer, and performing a surface treatment.
• the other layers may be formed by conventional methods. Specifically, for example, the other layers may be formed by a physical vapor deposition (PVD) method other than the HiPIMS method.
• PVD physical vapor deposition
• surface treatment steps include surface treatment using a medium in which diamond powder is supported on an elastic material.
• ⁇ Cutting tool manufacturing> ⁇ Step 1: Preparation of substrate> Substrates of cemented carbide, cermet, or cubic boron nitride sintered body were prepared according to the following procedure. The substrates used for each sample are shown in Tables 1 and 2. In Tables 1 and 2, items listed across multiple samples mean that the items are the same for those multiple samples. For example, with regard to the composition of the substrate in Table 1, samples 1 to 4 all indicate that they are cBN.
• the cemented carbide substrate was manufactured by a general powder metallurgy method. That is, WC powder, Co powder, and the like were mixed using a ball mill or the like to obtain a mixed powder. After drying the mixed powder, it was molded into a predetermined shape (the shape specified in ISO standard CNGA120408) to obtain a green body. The green body was then sintered to obtain a WC-Co based cemented carbide (sintered body) substrate.
• the cermet substrate was manufactured by a general powder metallurgy method. Specifically, cermet raw material powders such as TiC powder were mixed in a ball mill or the like to obtain a mixed powder. The mixed powder was dried and then molded into a predetermined shape (the shape specified in ISO standard CNGA120408) to obtain a green body. The green body was then sintered to obtain a cermet (sintered body) substrate.
• the surface roughness Rmax of the obtained substrate was measured using a stylus surface roughness measuring instrument in accordance with JIS B06012001, with a cutoff value of 0.3 mm, a reference length of 0.8 mm, and a scanning speed of 0.06 mm/sec. The results are shown in Tables 1 and 2.
• an MAlN layer was formed by HiPIMS so as to have the composition shown in Table 1 or 2. That is, multiple targets were placed in a film-forming apparatus, and the substrate was attached to a rotary substrate auxiliary jig provided at the center of these targets, and film formation was carried out in the following manner. At this time, the substrate was placed so that the flank of the substrate faced the target.
• the interior of the film-forming apparatus was first reduced in pressure to 3 mPa and then heated to approximately 500°C. Ar gas was then introduced. A 500 V pulsed DC voltage (frequency 200 kHz) was then applied to the substrate in an atmosphere of 350 mPa to generate Ar plasma, which etched the surface of the substrate (for 5 minutes).
• Samples 1 to 6 and 21 were formed under the same conditions as described above, except that the voltage and pulse width of the bias power supply were changed as follows: In this way, cutting tools for Samples 1 to 6 and 21 were fabricated.
• the cubic boron nitride content in the cubic boron nitride sintered bodies of Samples 1 to 4, Samples 7 to 21, and Samples 24 to 34 was determined by the method described above. Specifically, cross-sectional samples of the cubic boron nitride sintered bodies were photographed with an SEM, and the photographed images were subjected to image analysis to determine the content. As a result, the cubic boron nitride content in the cubic boron nitride sintered bodies of Samples 1 to 4, Samples 7 to 21, and Samples 24 to 34 was 65% by volume.
• the binder content in the cubic boron nitride sintered bodies was also measured by the same method. The binder content in the cubic boron nitride sintered bodies of Samples 1 to 4, Samples 7 to 21, and Samples 24 to 34 was 35% by volume.
• the thickness of each layer constituting the coating (i.e., the thickness of each of the underlayer, MAlN layer, and surface layer) was determined by measuring 10 arbitrary points on a cross-sectional sample parallel to the normal direction of the substrate surface using an SEM (manufactured by JEOL Ltd., product name: JEM-2100F) and calculating the average value of the thicknesses measured at the 10 points. The observation magnification was 10,000 times. The results are shown in Tables 1 and 2.
• compositions of the base layer and surface layer were determined by analyzing the entire layer of the cross-sectional sample described above using an SEM-EDX device. The results are shown in Table 2.
• the number of voids per 50 ⁇ m length of the MAlN layer was determined using the method described above. Specifically, the cross-sectional sample was observed using an SEM at 30,000x magnification to obtain an SEM image. A backscattered electron image (BSE image) was obtained so that the MAlN layer was continuously included within a 50 ⁇ m length range (see Figures 6 and 8 ). The obtained BSE image was converted into a 256-level monochrome image within a range excluding the substrate and the first 30 nm near the film surface (hereinafter referred to as the "evaluation range").
• binarization was performed using image analysis software ("WinROOF” manufactured by Mitani Shoji Co., Ltd.), with the 80th level counting from black as the threshold. Shape analysis was then performed on the portions that emerged after binarization, and portions with a cross-sectional area of 1.0 ⁇ 10 ⁇ 4 ⁇ m 2 or more and 0.5 ⁇ m 2 or less were counted as voids (see Figure 7 ). Here, if some of the voids were outside the evaluation range, they were not counted. The number of voids was counted on the flank, rake face, and cutting edge. The results are shown in Tables 3 and 4.
• the number of droplets per 50 ⁇ m length of the MAlN layer was determined by the method described above. Specifically, the cross-sectional sample was observed at 30,000x magnification using an SEM to obtain an SEM image (e.g., Figure 10). The SEM image was acquired so that the MAlN layer was included within a continuous 50 ⁇ m length range. The obtained SEM image was visually inspected, and the number of droplets within a continuous 50 ⁇ m length range was counted. The results are shown in Tables 3 and 4.
• Samples 1, 2, 8 to 10, 13 to 15, and 17 to 34 correspond to Examples. Samples 3 to 7, 11, 12, and 16 correspond to Comparative Examples.
• Conditions for heavy interrupted cutting test Workpiece SCr420H U-groove end face round bar Cutting speed (Vc): 100 m/min Feed rate (f): 0.1 mm/rev Cutting depth (ap): 0.2 mm Cutting oil: dry type

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